DE102011050719B4 - Emergency operable three-phase motor drive circuit - Google Patents

Abstract

Emergency operable drive circuit (50, 54, 100) for a three-phase motor (38) with contactable motor strings (30) comprising two inverter units (16a, 16b) each connected to a contact side (76a, 76b) of the motor strings (30), wherein each inverter unit (16a, 16b) is included in a separate converter unit (13a, 13b) with intermediate circuit (18a, 18b), characterized in that the first inverter unit (16a) is replaced by a DC bus (12) fed by a supply network (12). 18a), and the second inverter unit (16b) is powered by a DC energy storage device (110) such that the motor (38) operates in a first normal mode by concatenated line voltages of the inverter units (16a, 16b) in a dual inverter operation through the utility grid (12) and the energy storage device (110) can be energized, and in parallel or independently thereof, the energy storage device (11 0) is chargeable, and in a second emergency mode, the motor (38) alone by the energy storage device (110) or solely by the supply network (12) can be energized, for which at least two Y-switching elements (40, 44) are provided to one each the two contact sides (76a, 76b) of the motor strands (30) short circuit to form a Y-circuit for the emergency mode, wherein emergency operation control lines (58a, 58b) of the two converter means (13a, 13b) are provided to the respective opposite contact side (76a, 76b) of the motor strands (30) via the Y-switching elements (40, 44) shorted.

Description

STATE OF THE ART

The present invention relates to a non-operational motor drive circuit for a three-phase motor with mutually contactable motor strands. The circuit comprises two inverter units, which are each connected to a contact side of the motor strands according to the teaching of claim 1. Furthermore, the invention relates to a method for operating such a circuit.

Generic motor drive circuit are used for example in pitch drives of wind or hydroelectric power plants for adjusting the pitch (pitch) of a rotor or turbine against a Anströmmedium such as wind or water. To adjust the angle of attack, a three-phase motor is used in many cases, which is energized by means of a converter. The converter device consists in principle of a rectifier, which produces a DC-DC voltage for a DC voltage intermediate circuit from an AC mains voltage, this intermediate circuit feeding an inverter. The rectification can be uncontrolled or controlled, for example with a phase control. Also conceivable are active feed units, which can be capable of being regenerated. The concrete embodiment of the rectifier corresponds to the prior art, in the following, therefore, this unit, which supplies a DC link, always described as a rectifier. The inverter is used to convert the DC DC voltage of the DC link into an AC voltage for energizing the three-phase motor. The inverters operate on the basis of power electronic switches, for example by means of three half-bridges, which are designed, for example, as MOSFET, IGBT transistors or IGCT transistors. These generate a variable voltage by pulse width modulation, wherein the height of the output voltage and the frequency can be controlled within wide limits in order to drive both asynchronous and synchronous motors. As a result, any rotational speeds or torques of the three-phase motors can be adjusted. The motor strings of the motor are connected to each other in a star or delta connection at least on one side of the contact.

To increase reliability and reduce downtimes such drive circuits may include a Notenergiespeicher that can provide based on an auxiliary power source, usually battery or accumulator, a DC power supply. This results in the problem that an AC drive device is supplied with DC voltage during emergency operation. This problem is solved in that a three-phase drive motor is operable by supplying a direct current into the DC link of an inverter. However, the problem arises here that in the event of a defect of the inverter unit, the drive completely fails and the motor and thus the switched-on mechanical system fail.

The invention relates to a Notbetriebsfähigkeit a motor drive circuit based on a double inverter structure in which redundancy of the inverter unit and a DC emergency power supply increased reliability during operation of the three-phase motor can be ensured. Various concepts are known from the prior art, for example, the redundant design of the entire drive system, wherein two or more inverter devices and two or more three-phase motors are used. In addition, there are drive circuits in which a single motor can be controlled by two inverter devices that can be switched in parallel. As a result, in the first operating mode (normal operation), a redundantly held drive branch is maintained for a second operating mode (emergency operation), whereby manufacturing and maintenance costs are increased without additional benefit for normal operation.

Double inverters drive circuits are known from the prior art, which is a prerequisite for a three-phase motor with motor chains accessible on both sides, ie a motor in which the motor strands, ie individual connected stator but also rotor windings, are accessible from the outside by two contact sides. The motor strings of a first contact side are usually connected to a first converter means and the second contact side to a second converter means. By coordinated control of the inverters, which are included in the converter devices, higher motor powers can be achieved by this double converter operation. Such double converter circuits achieve higher performance from the fact that at the same intermediate circuit voltage, a higher voltage can be applied to the three-phase motor than in a conventional converter device; The motor can thus be designed for a given power with a higher rated voltage but a smaller rated current. The maximum line voltage that a servo drive inverter can apply to a star-configured motor is the DC link voltage. In a conventional converter, this voltage acts as a chained voltage across one (Δ circuit) or two motor strings (Y circuit). For a double inverter, this maximum voltage can be a string voltage act while at the same time the winding strands can be acted upon with the same currents and thus identical torques can be achieved. The increase of the voltage by a factor of 3 leads to an increase of the rated speed and thus of the motor power. Alternatively, with an adapted motor selection, the rated current can be reduced by a factor of 3 from the outset so that low-power converters can be used.

For a double inverter operation it is necessary that the two inverters work synchronously with each other. Such synchronization can be achieved, for example, by a communication control line which allows synchronization and adjustment of important parameters. In this case, it may be advantageous for the two intermediate circuits of the two converter devices, which energize the two sides of the motor strands of the three-phase motor, to be connected to one another in order to enable an energy exchange between the two intermediate circuits of the converter devices.

However, in particular in safety-relevant drive systems, such as a pitch drive, it has been found that converter devices, especially in the case of overvoltage, lightning or overload, are significantly more susceptible to breakdown than the electromechanical drive motors. Such safety-related applications can be in addition to a pitch control of a wind or hydroelectric power plant, in which the failure can lead to the destruction of the power plant, for example, drive circuits for elevator drives, door drives, vehicle drives, pump or compressor drives or other safety-related drive systems.

Therefore, from the prior art, the problem of extending a motor drive circuit such that it has a high redundancy and reliability in double inverter operation, with the arrangement of two inverter devices reduces an increased risk of failure while the advantages of a double judge circuit can be exploited for a safety-related drive system ,

From the generic document US 8 058 830 B2 is a dual inverter topology for the operation of a three-phase vehicle engine, in which a first electrical energy source via a first inverter with a first contact side of the motor strands and a rectifier via a second inverter for supplying the motor with a second contact side of the motor strands are connected. The rectifier is powered by a generator driven by an internal combustion engine. The circuit arrangement is used to drive a hybrid vehicle, wherein the first power source can operate the motor, and at low charge capacity, a range-extender function can be produced by means of energization by the rectifier.

The DE 10 2008 037 064 A1 describes a circuit arrangement for the redundant supply of a three-phase motor connected in star connection by means of at least two electrical energy sources and two inverters, wherein at least one electrical energy source by means of a switch of the electric drive is separable.

In the WO 2009/070089 A1 For example, there is proposed a method and system for controlling a three-phase motor for a vehicle drive, wherein it is possible to switch between a star and a delta connection for operation at high or low speed.

The US Pat. No. 7,800,331 B2 teaches one with the US 8 058 830 B2 related dual inverter topology for operating a three-phase motor for an electric vehicle drive, wherein the provision of electrical energy of a first and a second energy source depends on the requested torque.

In addition, the concerns DE 199 57 064 A1 a lid with mechanical and electrical interface for other such parts, wherein the cover is provided for a motor terminal box with electronic circuit for electrically influencing an asynchronous motor. The asynchronous motor is operated in star connection.

The JP 2009-273348 A describes a dual inverter circuit connected to a common DC power supply. Between a second inverter unit and the motor strings, a short-circuit switching element is arranged, which can connect the motor strings for one-sided inverter operation by means of a first inverter unit with each other, so as to provide a single inverter operation can.

The above-mentioned disadvantages are solved by a drive circuit and a drive method for operating a drive circuit according to the independent claims.

DISCLOSURE OF THE INVENTION

In a first inventive aspect, a non-operational drive circuit for a three-phase motor with contactable motor strands on both sides is proposed, which comprises two inverter units, which are each connected to a contact side of the motor strands. Each inverter unit is included in a separate DC link converter. The first inverter unit can be supplied by a DC link fed by a supply network, and the second inverter unit can be supplied by a DC energy storage device, so that the motor in a first normal mode by linked phase voltages of the inverter units in a double inverter operation through the supply network and through the energy storage device can be energized and parallel or independently thereof, the energy storage device is chargeable and in a second emergency mode alone powered by the DC energy storage device or by the supply network, for which at least two Y-switching elements are provided to each one of the two contact side of the motor strands to form a Y- Short circuit for the emergency mode, wherein emergency operation control lines of the two inverter devices are provided to the respective opposite contact side of the motor strands on the Y- Short circuiting of switching elements.

In other words, the invention proposes a double inverter drive circuit in which a three-phase motor which can have contactable motor strands on both sides, in particular three motor strands, but also several motor strands, can be supplied with current by means of two inverter units. In the connection between each inverter unit and a contact side of the motor strings, a decoupling switching element can be arranged for switchable connection or in the event of a fault for decoupling. At least one contact side, but also conceivable on both contact sides, at least one switching element, such as an electromechanical contactor element or an electronic switching element is arranged, which can switch to a second switching position in case of failure of an inverter unit, so that in the second mode of energization by the remaining active inverter unit is possible by means of the energy storage device. In the second operating mode, the motor current can be supplied via the first or the second inverter unit, preferably via the second inverter unit, since it is preferably separable via a switching element and therefore connected substantially directly to the energy storage device. The first inverter unit is connected to a DC link fed by a supply network, and the second inverter unit is connected at least indirectly via a DC link to a DC energy storage device. The DC energy storage device may comprise, for example, one or more double-layer capacitors, accumulators or comparable rechargeable DC energy storage means. It can store DC voltage and can be supplied with charging energy via the motor strings of the motor in a first operating mode (normal operation). In addition, it is advantageously conceivable that the DC energy storage device can be charged by an independent charging device through the supply network. In the second operating mode (emergency operation), a supply of the motor by means of energy of the energy storage device and the second inverter device can be ensured by means of one or more switching elements.

Thus, a normal operation can be realized, in which the motor can be energized by means of both inverter units and a mains and battery power, so that, if about the same DC link voltages can be provided, by about 70 percent higher drive power of the engine can be achieved. In such a case, for example, can be used in a 400-volt three-phase network motors, which are provided in star connection for 690-volt networks. The power range can thus be increased by a factor of 1.73. This results in lower current ripple in motor operation, i. a lower level of THD harmonics (Total Harmonic Distortions), so that disturbing network feedback is reduced. Furthermore, lower inductance motors, e.g. HS motors (high-speed motors), used to achieve a comparable drive power or torque and speed.

As a motor, a standard three-phase motor can be used in which all six coil ends are led out, as is the case typically with asynchronous motors. In synchronous motors, especially permanent synchronous motors, access to all six coil ends is usually possible without much effort. The emergency operable motor drive circuit combines the advantages of a double inverter operation with a high degree of redundancy, ie interference immunity, so that in a safety-relevant drive, eg adjustment of the rotor blade of a wind or hydroelectric power plant, but also in a Vehicle drive, a lift or door drive, a pump or compressor drive high reliability can be guaranteed.

Since in safety-relevant drives the use of double inverter units can lead to an increased risk of failure of the semiconductor components, according to the invention at least one switching element in the motor string lines arranged such that in case of failure of at least one inverter unit, in particular the mains powered inverter, energization of the three-phase motor by the remaining second, energy storage powered Inverter unit is possible. In this case, it is provided according to the invention that the switching element short-circuits the motor strands of a contact side in order to realize a star connection (Y circuit). It may furthermore be possible to connect corresponding motor strands of both contact sides to one another such that a triangular circuit (Δ circuit) can be realized.

Thus, according to the invention, at least one switching element is provided in order, if necessary, for example in the second operating mode, to short-circuit at least one contact side of the motor strings to form a Y-circuit and preferably to disconnect it from the connected inverter unit. The switching element short-circuits all contacts of the motor strings of a contact side, so that when the motor strings of the opposite contact side are energized, a star operation of the motor is possible. Thus, at least one, advantageously both, inverter units perform a Y energization of the motor, provided on each contact page, a Y-switching element is provided. As part of a star connection, a high starting torque can be generated, the speed is limited. In particular, in the case of high starting load star connection can be advantageously used when starting the engine. Subsequently, it is possible, for example, to switch over in the first operating mode with inverter units supplying current to both sides.

Alternatively or additionally, at least one switching element may be provided in order to connect the contact sides of the motor strands to form a Δ-circuit in emergency operation. The switching element can each short-circuited by 120 ° motor strands of the two contact sides in the second mode, so that a triangular circuit of the motor strands can be realized, with an energization of one and the other inverter unit side, preferably from the second, energy storage powered inverter unit is possible. In this case, a single switching element is sufficient to integrate the motor in an emergency operable circuit, so that a two-sided Bestromungsbetrieb means of an inverter unit is possible. In all cases, however, it must be prevented that in the second switching state of the switching element both inverter units continue to work actively, since otherwise a short circuit of the inverter units may occur. As part of a triangle circuit of the motor strands, the motor can be operated at full speed but a reduced torque. Thus, depending on the arrangement in star connection or delta connection of the switching elements, a star connection or delta connection can be realized in order to be able to ensure either a high torque or a high speed in the second operating mode.

• – Batterieladefunktionalität: Der Ladezustand der an der zweiten Wechselrichtereinheit angeschlossenen Energiespeichereinrichtung kann über den Leistungsfluss der ersten Wechselrichtereinheit in den Motor gesteuert werden. Es können sehr hohe Ladeströme bis zum Maximalstrom der ersten Wechselrichtereinheit zur Verfügung gestellt werden, die klassischerweise nur aufwendig realisierbar sind.
• – Bremsenergie bzw. generatorische Energie des Motors kann von der zweiten Wechselrichtereinheit aufgenommen und in der Energiespeichereinrichtung gespeichert werden. Durch diese Rekuperation kann die mittlere Verlustleistung der Antriebsschaltung verringert und ein Brems-Chopper und Bremswiderstand verkleinert ausgeführt bzw. nicht mehr benötigt werden. Besonders vorteilhaft ist diese Betriebsart, falls der Energiespeicher auch einen dynamischen Energiefluss erlaubt, z.B. wenn Kondensatoren oder Ultracaps anstelle von oder ergänzend zu typischen wiederaufladbaren Batterien eingesetzt werden.
• – Die von der ersten Wechselrichtereinheit dem Versorgungsnetz entzogene Leistung kann durch das Zusammenspiel mit der Energiespeichereinrichtung geglättet und Leistungsspitzen der Netzbelastung unterdrückt werden. Glättungskondensatoren, Induktivitätsdrosseln oder andere Glättungsbauelemente können geringer dimensioniert, weggelassen oder geschont werden. So werden beispielsweise bei Übertragung von Energie über Schleifringe in den drehenden Teil eines Rotors (z.B. Windkraftanlage), die Schleifringe des Pitchsystems geschont.
• – Boost-Funktion mittels Energiespeichereinrichtung, so dass kurzfristig Energie zur Abfederung von Leistungsspitzen aus der Energiespeichereinrichtung entnommen werden kann – beispielsweise für eine Schnell- oder Notfahrt. Hierdurch wird das Versorgungsnetz entlastet und hohe Stromspitzen vermieden.

According to an advantageous further development, in the first operating mode by a coordinated activation, for example a tuned or synchronized PWM voltage specification of the two inverter units, the energy storage device can be charged both via the first inverter unit and the motor strings, as well as by regenerative energy of the motor ( 38 ) be rechargeable. For this purpose, phase sequences and amplitudes of the drive voltages of the inverter units can be set and a predefinable phase offset can be impressed. Hereby, by means of a suitable inverter regulator method, the voltage and current phasors of the two inverters can be related to each other in such a way that the transfer of supercharging energy from the first inverter unit to the second inverter unit can be achieved. For this purpose, synchronization information such as phase position, voltage and current amplitude values, height of the DC link voltage, etc., can be transmitted in an analog or digital manner. A central control device or a controller integrated in a converter device can carry out a synchronization of the two inverter control systems. Thus, the power flow between the two inverter units can be set freely, ignoring parasitic energy stores, which include the inductances of the motor windings, with P ₁ , P ₂ power of the first and second inverter unit and P _{M of} the motor power applies: P ₁ = P _M + P ₂ . P ₂ indicates the power consumption (P ₂ > 0) and power output (P ₂ <0) of the energy storage device to the motor via the second inverter unit, and may arbitrarily within the limits P _M - P _1max ≤ P ₂ ≤ P _M + P _1max be set. Here, P _{1max is} the maximum power that the first inverter unit can deliver on the basis of the currently flowing current - without considering the reactive power of the motor. The PWM synchronization provides a charge management of the energy storage device, which ensures that always sufficient energy is stored in the energy storage device for the second mode. The charge management can be integrated in one of the two inverter units. So can one Power flow in both directions, can be achieved from first to second inverter unit across the motor strands or vice versa. Various control mechanisms and advantages can be included:

• Battery charging functionality: The state of charge of the energy storage device connected to the second inverter unit can be controlled via the power flow of the first inverter unit into the motor. Very high charging currents up to the maximum current of the first inverter unit can be made available, which are classically only expensive to implement.
• - Braking energy or regenerative energy of the engine can be picked up by the second inverter unit and stored in the energy storage device. As a result of this recuperation, the average power loss of the drive circuit can be reduced and a brake chopper and braking resistor can be made smaller or no longer needed. This operating mode is particularly advantageous if the energy store also allows dynamic energy flow, for example if capacitors or ultracaps are used instead of or in addition to typical rechargeable batteries.
• The power withdrawn from the supply network by the first inverter unit can be smoothed by the interaction with the energy storage device and power peaks of the network load can be suppressed. Smoothing capacitors, inductance chokes or other smoothing devices can be made smaller, omitted or conserved. For example, when transferring energy via slip rings in the rotating part of a rotor (eg wind turbine), the slip rings of the pitch system are spared.
• - Boost function by means of energy storage device, so that energy can be removed for cushioning power peaks from the energy storage device in the short term - for example, for a quick or emergency drive. As a result, the supply network is relieved and high current peaks avoided.

According to an advantageous further development, each inverter unit may be included in a converter device, wherein the two converter devices are connected to a communication control line for synchronization purposes, and / or at least one rotation angle of the motor can be determined by at least one converter device, preferably both converter devices via at least one rotation angle sensor , In the first operating mode, a converter device as the master converter device and a second converter device as a slave converter device can be connected by the communication control line, which, for example, implements a fieldbus system, which, as already illustrated above, enables a clocking of the master converter device to produce tuned PWM signals. Signals of the slave inverter device for a phase-correct operation of the engine provides. For example, PWM switching data, switching frequency, switching phase data for switching frequency synchronization, rotor rotation angle, field-oriented control parameters, such as field alignment, vector control data and space vector alignment of rotor and / or stator magnetic field, phase and frequency information, etc. can be transmitted between the inverter units and their control means via the communication control line become. Furthermore, the supply voltages can be parameterized or braking resistor switch-on thresholds can be set synchronously. The communication control line can be implemented digitally as a field bus, and signal an emergency operating case, for example, if the intermediate circuit voltage of the first or second converter unit or other faults fails and, alternatively or also additively, determine a rotational angle and / or a rotational speed or comparable rotational angle of the motor. On the basis of the rotation angle sensor, for example, the field orientation can be adjusted. If rotational angle sensors are connected to both converter devices, if the rotational angle sensor of a first converter device fails, the data of the rotational angle sensor of the first converter device can be used to control the second converter device, wherein the corresponding sensor data can likewise be exchanged via the communication control line. This results in an increase in the redundancy in the sensor determination of the state variables of the three-phase motor.

According to an advantageous further development, at least one switching element can be provided in order to separate at least one contact side of the motor strings from an inverter unit in the second operating mode. Thus, the half bridges of an inverter unit, in particular the first inverter unit, in the second mode of operation can be separated from the contact side of the three-phase motor. As a result, internal short circuits of an inverter unit or the power inverter unit in the second mode have no influence. Furthermore, in order to protect the motor and the power semiconductor components of the inverter units, decoupling of the non-energized contact side of the motor from the inactive inverter unit can be achieved in order to avoid further damage.

Furthermore, and independently of this, according to a further advantageous development, at least one switching element may be a semiconductor switching element. This switching element may for example be a semiconductor star point switching element. In principle, the switching elements can be constructed as desired and designed, for example, as a three-pole or multi-pole electromechanical contactor. Especially For example, the switching elements in the second operating mode can separate the respective inactive or failed inverter unit, in particular the grid-fed converter unit, from the motor strings and thus have at least six switch contacts. However, in particular in the case of a Y-switching element, which has the task of short-circuiting the motor strands of a contact side, but also for a Δ-switching element or a disconnecting element or decoupling switching element, the possibility to perform this as a maintenance-free semiconductor switching element. Thus, the semiconductor switching element may comprise a bridge rectifier unit, which can rectify the currents of the individual motor strings, and have a thyristor switching element which short-circuits the rectified DC voltage between the motor strings of a contact side by igniting the thyristor, and thus realizes a short circuit of the motor strings , Alternatively, a combination of bridge rectifier and transistor switching element, an anti-parallel circuit of a diode-Tranistor series circuit or a triac switching element or similar semiconductor switching elements can be used. By using a semiconductor switching element, a mechanical wear of the switching element can be avoided, and a high mechanical strength, switching spark suppression and a long service life can be ensured with low maintenance and costs.

According to an advantageous further development, the first inverter unit can be connected to a rectifier unit with DC link connected to a supply network to form a first converter device and preferably wegschaltbar of the motor strands, and the second inverter unit substantially directly with the energy storage device via a second DC link to Forming a second converter device to be connected. Thus, the first inverter means may be of conventional construction and substantially directly connected to a utility grid. It is also conceivable that a connection between the two intermediate circuits of the first and second converter means can be made switchable, so that in case of failure of the mains supply a double inverter operation by the energy storage device upright can be obtained. Due to the switchability of the first converter device, the motor can be operated by the second converter device in an emergency, without disturbing electrical defects within the first converter device. In addition, for example, given a switchable connection of energy storage device to the DC link of the first and second inverter unit conceivable that in the second mode in case of failure of the second inverter unit, the energy storage can energize the DC link of the first inverter unit, so that an emergency operation by means of the energy storage device and the first inverter unit is feasible. For this purpose, the second inverter unit can be decoupled by means of one or more switching elements and the motor strings are connected to form a Y or Δ circuit.

In principle, the energy storage device can be embodied as a rechargeable electrical energy store which is based for example on an electrochemical active principle (capacitor, accumulator or the like), magnetic operating principle (superconducting coils) or on a mechanical operating principle (flywheel storage, etc.). According to an advantageous further development, the energy storage device may comprise capacitors, ultracapacitors, rechargeable batteries or a combination thereof. For this purpose, low-cost, high-capacity and often rechargeable energy storage can be used and used for example in combination with the power supply. Such electrochemical energy stores are mechanically robust and relatively insensitive to high temperature fluctuations.

According to an advantageous further development, a zero current regulator unit can be connected to both inverter units in order to regulate a zero current through the motor strings for charging the energy storage device in the first operating mode. Thus, with the two converter devices, a regulation of the zero-current component for charging the energy storage device and for compensation in the first operating mode can be carried out. A zero current is present when the sum of the three motor currents is not zero. This zero-current component is undesirable in the first mode of operation apart from the case of charging, since it leads to undesirable losses in the motor and the converter units and can also cause torque fluctuations. The cause of the zero current is, inter alia, parasitic asymmetries of the two inverters, e.g. in different forward voltages, different switching times of the semiconductors or measurement errors of the current sensors, which affect the current values via the current control. In order to reduce the current flow and the energy consumption, the zero current in the first operating mode can be minimized outside of the charging case and selectively adjusted in the charging case for charging the energy storage device, wherein a corresponding control method can be used.

According to an advantageous further development, the energy storage device in the second operating mode can be connected to the intermediate circuits of both inverter units by means of a switching element be, so that a double inverter operation is feasible. The coupling can be produced by an electromechanical contactor or an electronic switching element, so that the DC intermediate circuits of both inverter units are switchably connectable. If, for example, the mains supply fails, or if a defect occurs in the rectifier unit of the first inverter device, it is possible to switch to the second operating mode and to supply the intermediate circuits of both inverter units with energy from the energy storage device so that dual-directional operation is maintained even in the second operating mode and thus the advantages of the double straightening operation are retained even in emergency operation.

According to an advantageous further development, the energy storage device in the second operating mode can be decoupled from the second inverter unit and connectable to the intermediate circuit of the first inverter unit by means of one or more switching elements, so that a current supply of the motor via the first inverter unit can be performed. Thus, in the second mode, i. Motor energization alone by the energy storage device, a control of the motor via the first inverter unit, for example, in a defect occurring the second inverter unit. This increases the redundancy and fault tolerance of the circuit.

According to an advantageous further development, the energy storage device in the first operating mode can be disconnected from the intermediate circuit of the second inverter unit and the second intermediate circuit can be connected by means of one or more switching elements to a DC voltage provided by the supply network. Thus, in the event of a defect or failure of the energy storage device, double inverter operation can be ensured with sole mains supply. This increases the redundancy and fault tolerance of the circuit.

Thus, in the second operating mode, the motor is energized by the second inverter unit, by the first inverter unit, or in a coordinated double inverter operation by both inverter units, whereby a failure probability in the case of a defect of a power semiconductor module is greatly reduced.

In a further aspect of the invention, a method for operating a drive circuit is proposed in which in a first normal mode a double inverter operation of the motor is performed by energization by means of the supply network and the energy storage device, in particular at low engine load, the energy storage device is charged, and in a second Notbetriebsart, in particular failure of the supply network, an inverter or double inverter operation of the engine is carried out in case of care alone by the energy storage device or the supply network. By this operating method, a high error robustness and availability of the drive, in particular a safety-related drive such as pitch actuator, lift drive or the like can be achieved. The energy storage device is used in normal operation and charged continuously, so that a failure of the energy storage can be detected immediately. In emergency mode, the benefits of dual inverter operation can be maintained or normal inverter operation can be maintained. As a result, a high redundancy of the control electronics, a low probability of failure and increased power output can be achieved.

The above operating method has a first mode, which corresponds to a double-inverter operation known per se and has its advantages, wherein a first inverter side is supplied by a supply network and a second inverter side with the DC energy storage device. In case of failure of a converter device, for example in case of power failure of the first inverter device in case of failure of the rectifier unit, the first inverter unit or the first DC link can be switched by means of a switching element or by short circuit of the opposite inverter unit in the second mode in which advantageously the defective inverter unit or Converter device is decoupled or short-circuited, and with the remaining intact inverter unit or inverter an emergency operation under supply by the energy storage device is feasible. The second operating mode can basically realize a triangular circuit or a star connection of the motor, it being possible to switch between star and delta connection, for example in a start-up phase, so that emergency operation can be maintained at reduced speed or reduced torque.

In an advantageous embodiment of the method, a switchover between the first and second operating modes in dependence on a power loss of the three-phase motor, a failure or reducing the DC link voltage of the first inverter unit ( 16a ) or in the case of non-tuned inverter output voltages, preferably in the first operating mode when an inverter output voltage is exceeded predeterminable power value of the motor, the additional energy demand from the energy storage device is made available and / or in the second mode, the energy storage device is coupled to the first, the second or both intermediate circuits to allow an inverter or a double inverter operation. For the detection of an emergency operating case, an indirect determination of the drive power or the rotational speed of the three-phase motor can be used, but in addition electrical variables, for example by monitoring the DC link voltage preferably the first inverter, the synchronized complementary PWM voltages of the two converter devices or monitoring the mains voltage In case of deviating from a setpoint, an emergency operation case can be detected, and the second mode can be initiated by disconnecting the first converter means and interconnecting the motor strings in a Y or Δ circuit. Thus, an automated switching between the first and second mode, with a fault message when switching to the second mode can be sent to a higher-level control center. In the context of the first operating mode, drive energy that is above a predefinable power value of the motor can be retrieved from the energy storage device, so that power peaks can be cushioned by the energy storage device without affecting the supply network. In the second mode of operation, by connecting the DC link circuits of both inverter units, for example by a switchable contactor or the like, dual inverter operation can be maintained with all the advantages in which the drive power is provided by the energy storage device. This is particularly suitable in case of failure of the power supply.

DRAWINGS

Further advantages result from the present description of the drawing. In the drawings, embodiments of the invention are shown. The drawing, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into meaningful further combinations.

Show it:

1 an inverter drive circuit of the prior art;

2 two variants of redundantly designed drives of the prior art;

3 a first embodiment of a drive circuit according to the invention;

4 a second schematically illustrated embodiment of a drive circuit according to the invention;

5 a schematic relationship in the dq coordinate system of the two-sided power supply of an engine;

6 Current space pointer representation of various modes of an embodiment of the invention;

7 a further embodiment of a drive circuit according to the invention;

8th a further embodiment of a drive circuit according to the invention;

In the figures, the same or similar components are numbered with the same reference numerals. In the following, the first operating mode is to be understood as a "normal operating mode" and the second operating mode as an "emergency operating mode"

The 1 shows a converter 10 of the prior art for energizing a drive-three-phase motor 38 whose motor strands 30 are connected in star connection. The converter device 10 is connected to a supply network 12 (Power Grid) connected in three phases, the three mains phases by means of one in the inverter device 10 included rectifier unit 14 by means of bridge rectifier diodes 22 is converted into a DC voltage by means of a DC link 18 an inverter unit 16 supplied with DC voltage. To stabilize the DC-DC voltage, one or more DC link capacitances 24 in the intermediate circuit 18 arranged to store a DC energy or can absorb regenerative energy of the motor and smooth the harmonics of the DC DC voltage. in the Case of power failure of the supply network 12 can be a DC energy storage device 110 be provided, with contactors K ₁ , K ₂ 40 as emergency operation switching elements 102 the network DC voltage off and the emergency mode can switch on. The inverter unit 16 includes three power semiconductor switching bridges, in each of which two power semiconductor switching elements 26 , For example, IGBT, MOSFET or IGCT transistors to form a pulse width modulated output voltage (PWM voltage) are arranged. The power semiconductor switching elements 26 The DC bridge rectifier voltage feeds the motor strings of the three-phase motor as PWM voltage 20 one. As freewheel are the inverter switching elements 26 diodes 28 connected in parallel, so that an increased life and protection against inductive voltage peaks can be achieved. Drive control logic (not shown) actuates the six inverter switching elements 26 such that a desired rated speed or a desired rated torque of the three-phase motor 20 can be achieved by commutation of the strand currents. The drive control may include current / voltage sensors and / or mechanical speed, rotation angle and torque sensors for generating demand-responsive PWM signals to a desired drive behavior of the three-phase motor 20 provide. The three-phase motor 20 in Y-circuit has a single contact side, where the three motor strings 30 can be contacted on one side from the outside. The failure of the supply network 12 , the bridge rectifier unit 14 , a short circuit of the DC link capacity 24 of the DC link 18 or the failure of an inverter switching element 26 the inverter unit 16 leads to a total failure of the drive system, whereas in case of failure of the three-phase system 12 or the rectifier unit 14 a short-term operation by the switchable energy storage device 110 can be maintained. Because three-phase motors 20 are designed to be robust, the probability of failure of the drive circuit 10 much higher than a mechanical failure of the engine 38 , In particular in safety-relevant drive trains a redundancy is therefore provided, as described in the 2 are shown by way of example.

2a shows a fully redundant constructed motor drive system 34 comprising two electrically separate drive units, each drive unit consisting of a three-phase motor 38 and a converter device 13 consists. The converter device 13 again comprises a rectifier unit 14 and an inverter unit 16 , Starting from the supply network 12 the two drive units are electrically connected in parallel, the motors 38 via a mechanical coupling 42 mechanically coupled together and together drive a mechanical load. In case of failure of a drive unit, the drive task can be met by the remaining second engine line with 50% drive power. The cost of such a drive train redundancy is twice as high as the cost of a single drive units, so that such a redundant system is used only in rare cases, in which high availability is required.

Alternatively shows 2 B another redundant drive system 36 in which only the drive circuit is designed to be redundant, and the two sub-drive circuits to a single AC motor 38 connected. Each partial drive circuit comprises a converter device 13 , wherein the two converter devices 13 between supply network 12 and three-phase motor 38 connected in parallel, and via two associated switching elements 40 K11, K12 or K21, K22 to the supply network 12 and the three-phase motor 38 can be coupled. In case of failure of a converter 13 can this from the utility grid 12 and three-phase motor 38 decoupled, and the second converter device 13 be coupled to allow trouble-free redundant operation. Here, the cost of the electronic system are doubled, but the mechanical components of the three-phase motor can 38 just be interpreted, compared to the in 2a illustrated fully redundant drive systems. In both cases, only a drive behavior as in the in 1 can be achieved, so that in principle only a simple converter operation is made possible, and a redundancy is kept available only for emergency operation.

3 shows a first embodiment of a drive circuit according to the invention. The motor drive circuit 100 comprises a first converter device 13a connected to a utility network 12 connected. The converter device 13a includes a rectifier unit 14 , a DC link 18a and an inverter unit 16a , The rectifier unit 14 consists essentially of a bridge rectifier, in which individual rectifier diodes 24 the supply three-phase current of the supply network 12 in a DC voltage for the DC link 18a transforms. The DC potential of the DC link 18a is done by means of a DC link capacity 24 smoothed, which minimizes the ripple of the DC _{link voltage} U _1max . The inverter unit 16a includes six inverter switching elements 26 in three half-bridges, for example IGBTs, each with a freewheeling diode 28 are connected in parallel to protect against overvoltage. The inverter unit 16 serves to turn the DC link voltage by means of a PWM switching method, a three-phase voltage with adjustable amplitude, frequency and phase to be able to produce. Not shown is a higher-level control device, the PW modulation of the inverter unit 16 controls. The output of the inverter unit 16a is to a first contact page 76a the three engine lines 30 the three-phase motor 38 connected. The motor strands 30 the opposite contact side 76b are connected to a complementary inverter unit 16b a second converter device 13b connected, so that a double change operation of the engine 38 is possible. The for the operation of the inverter unit 16b required DC DC voltage is from an energy storage device 110 provided the DC link 18b the converter device 13b provided. The energy storage device 110 may be an electrochemical energy storage, for example, accumulator assembly (Pb battery, NiMh battery, Lithium ion rechargeable battery or the like), capacitor assembly, or any other rechargeable DC energy storage device, such as mechanical flywheel, compressed air storage or the like. Between the first inverter device 13a and the engine 38 is an emergency mode switching element 102 in the form of a Y-switching element 44 K ₃ interposed. In normal operation, the motor strings 30 via the two converter devices 13a . 13b energized. In case of failure of the mains supply 12 or a defect within the inverter device 13a can the emergency operation switching element 102 Switch K ₃ and the first contact side 76a the motor strands 30 connect in star connection. In this case, at least at short notice in emergency operation, the engine by means of the energy storage device and the second converter device 13b be energized. In normal operation can via a higher-level control device or the respective controller of the inverter devices 13a . 13b a tuned PWM control of the inverter switching elements 26 be made so that on the one hand, a speed and torque control of the engine 38 on the other hand, a required charging or compensation charge of the energy storage device 110 is possible. In braking mode of the engine 38 can generate regenerative energy through the second inverter unit 16b in the energy storage device 110 be directed. For fast load changes or high starting currents, the supply network 12 be relieved that in the short term energy from the energy storage device 110 can be provided or recorded.

4 schematically shows a representation of a notbetriebsfähigen drive circuit 110 , The basic structure of the representation corresponds to the drive circuit of 3 , so includes the drive circuit 100 a supply network 12 , a first converter device 13a and a second converter device 13b , each to the two contact pages 76a and 76b a three-phase motor 38 are connected. The converter device 13a includes a rectifier unit 14 and an inverter unit 16a , The second converter device 13b includes an inverter unit 16b , wherein the DC link to an energy storage device 110 , For example, a battery or a capacitor arrangements is connected. In addition, for example, regenerative hydrogen cells, electromechanical flywheels that can store mechanical energy and deliver electrical energy or similar electrical energy storage devices are conceivable. The three-phase motor 38 includes separately contactable motor strands 30 , In the case of synchronous motors and the DC-powered rotor windings can be connected via a rectifier to an external power supply. The concatenated phase voltages U _A , U _B and U _C can be represented in the complex dq coordinate system as a rotating voltage U or current vector I. Thus, the drive circuit 100 of the 4 be shown unipolar, since the three-phase AC phases U _A , U _B and U _C can be displayed in a complex plane to form a rotating voltage and current, and thus a single-pole complex representation of the drive circuit 100 allows.

In 5 is shown schematically in the single-pole complex representation with respect to the two feeding voltage and current pointers a simplified equivalent circuit diagram of the notbetriebsfähigen drive circuit according to the invention. In the dq coordinate system, ie, a coordinate system oriented at the direction of the motor current vector as the d axis, so that the d axis corresponds to the motor current vector direction and the q axis is disposed at right angles therewith, the in 4 to interpret the equivalent circuit diagram shown. The two converter devices are represented by complex voltage sources U ₁ and U ₂ . In double inverter operation, the engine becomes 38 with the outside through the contact pages 76a . 76b accessible motor strands 30 by the two arbitrarily adjustable, in the complex dq plane rotating voltage vectors U _{1 of} the first inverter device 13a and U _{2 of} the second converter device 13b provided.

The ratio and orientation of the two voltage vectors U ₁ and U ₂ results in a complex motor voltage U _M and a motor current I _M due to the ohmic and inductive behavior of the motor 38 ,

für die q-Komponente als vorteilhaft erweisen. U_M und I_M bezeichnen den Motor-Spannungsraumzeiger und -Stromzeiger. Für die Leistungsübertragung ist lediglich die d-Komponente des Spannungsraumzeigers U_2d der zweiten Wechselrichtereinheit 16b relevant, die für eine motorregelungsoptimierte Ansteuerung den folgenden Bedingungen genügen sollte:
|U₁| ≤ 1/√3U_1max , |U₂| ≤ 1/√3U_2max und U_M = U₁ – U₂. Für eine Ladespannung U_2d ergibt sich dann

sowie U_1d = U_2d + U_Md. Die für die Blindleistung relevanten q-Komponenten können gemäß dem oben angegebenen Verhältnis der Zwischenkreisspannungen aufgeteilt werden. Des weiteren kann in der ersten Betriebsart die beiden Wechselrichtereinheiten 16 an ihren Aussteuergrenzen U_max derart geregelt werden, dass sich

für die d-Komponente und

für die q-Komponente ergeben. In the first operating mode, each of the two inverters 16a . 16b To the output side, turn on the voltage space hand, which is inside a hexagon with the side length 1 / √ 3 U _max to 2 / 3U _{max of} the maximum intermediate circuit voltage U _{max of} the first or second inverter unit 16a . 16b Otherwise, unwanted harmonics in the motor currents occur that cause torque fluctuations. The following is in the 6 a complex current / voltage space vector diagram considers that a d- and a q-axis, wherein the d-axis corresponds to the orientation of the current space pointer, and is not to be confused with a runner-fixed space vector diagram. With a restriction to the inner circle, ie hexagons with the side length 1 / √ 3 U _max , wherein the current space pointer in the direction of the d-axis of the motor 38 is aligned and the voltage space vector can be divided into a d and q component can, in a rule, in which the current space pointer alone on the basis of the desired engine behavior is adjustable (control priority of the engine behavior) and the state of charge of the energy storage device 110 does not take into account the engine 38 be operated optimally. Depending on the set torque, however, only a limited power transmission to the energy storage device 110 possible, since the necessary for power transmission portion of the current space pointer is limited. At a control priority of the engine behavior and in the case of charging the energy storage device 110 can the two inverter units 16 be controlled below their control limits such that a charging power of the energy storage device 110 with P _bat = 3 / 2U _2d · │I _M │ and the voltages U _Md = U _1d - U _2d for the d component and

prove advantageous for the q component. U _M and I _M denote the motor voltage space pointer and current pointer. For the power transmission is only the d-component of the voltage _space vector U _{2d of} the second inverter unit 16b relevant, which should satisfy the following conditions for a motor control optimized drive:
| U ₁ | ≤ 1 / √ 3 U _1max . | U ₂ | ≤ 1 / √ 3 U _2max and U _M = U ₁ - U ₂ . For a charging voltage U _2d then arises

and U _1d = U _2d + U _Md . The q components relevant for the reactive power can be divided according to the ratio of the DC link voltages given above. Furthermore, in the first operating mode, the two inverter units 16 be controlled at their control limits U _max such that

for the d component and

for the q component.

If the drive limits of the maximum DC link voltages have been reached, the power flow to the energy storage device 110 no longer be chosen freely, so he is to choose with regard to the limitation. Thus, it is possible to choose the d components analogous to the q components and aligned with the desired motor voltage space vector.

6a shows the case of operation by means of two inverter devices 13 , wherein the first power supply unit supplied on the network side 13a a rotating voltage vector U ₁ and the second energy storage supplied converter 13b can generate a rotating voltage vector of amplitude U ₂ . The resulting motor voltage results after 5 as vector difference U _M = U ₁ - U ₂ . The two DC intermediate circuits 18 allow the maximum generation of an inverter _voltage U _1max or U _2max . Considering one for the operation of the engine 38 optimized motor current I _m , the motor voltage U _{M can be} specified by selecting U ₁ and U ₂ , wherein the phase position and amplitude of the second voltage U ₂ statement about whether energy from the energy storage device 110 withdrawn or stored in energy. The targeted tuning of the motor current or the two double-directional voltage U ₁ and U ₂ can be an optimally controlled adjustment of speed and torque of the motor 38 achieved and a charge of the energy storage device 110 to be controlled. In the case of 6a in which the Voltage space pointer U ₂ includes a positive d-component with respect to the motor current I _M , the energy storage device 110 loaded.

6b shows a further constellation of the voltage space pointer, wherein the d-component of the voltage space vector U _{2 has} a negative component with respect to the motor current I _M. Thus, energy from the energy storage device 110 taken, and the energy storage device 110 actively drives the engine 38 at. If the two maximum _voltages U _1max and U _2max are approximately the same, a motor power higher by 3 than in single inverter operation can be achieved.

• – durch Erhöhung des Leistungsflusses der ersten Wechselrichtereinheit kann eine erhöhte Aufladeleistung der Energiespeichereinrichtung bereitgestellt wird; und/oder
• – eine Feldstärkung oder -schwächung des Magnetfeldes des Motors erreicht wird, so dass eine Ladeleistungsübertragung und gleichzeitige Drehzahlregelung erfolgt; und/oder
• – durch Einkopplung einer Stromnullkomponente eine Ladeleistungsübertragung durch die Motorstränge durchgeführt wird. In diesem Regelfall kann der Stromraumzeiger verändert werden und es wird auf eine optimierte Motorregelung verzichtet. Somit kann das Drehmoment des Motors verändert werden, so dass beispielsweise durch Erhöhung des Drehmoments mehr Leistung zur Energiespeichereinrichtung übertragen werden kann. Allerdings kann hierbei die Drehzahl des Motors nicht mehr geregelt werden. Alternativ oder zusätzlich kann mittels einer Feldschwächung oder -stärkung die Stromzeigerlänge verändert und somit der Wirkungsgrad der Maschine beeinflusst werden. Eine Drehzahlregelung ist weiterhin möglich. Zusätzlich oder alternativ kann eine Nullstromkomponente oder ein überlagerter Gleichstrom in den Strom eingekoppelt werden, der zusätzlich eine Leistungsübertragung ermöglicht, allerdings ein pulsierendes Drehmoment hervorrufen kann. Gängige Regler können die vorgenannten Regelbedingungen erfüllen und entsprechend angepasst werden.

Due to the independent setting of the two voltage indicators in the first mode, especially in the case of control priority disregard of the motor behavior, the two inverter units 16 their resulting current space pointers by influencing the voltage amplitudes, PWM signal sequences, phase offsets etc. regulate such that:

• By increasing the power flow of the first inverter unit, an increased charging power of the energy storage device can be provided; and or
• - A field strengthening or weakening of the magnetic field of the motor is achieved, so that a charging power transmission and simultaneous speed control takes place; and or
• - By charging a current zero component, a charging power transmission is performed by the motor strands. In this case, the current space pointer can be changed and it is dispensed with an optimized engine control. Thus, the torque of the engine can be changed, so that more power can be transmitted to the energy storage device, for example by increasing the torque. However, in this case the speed of the motor can no longer be regulated. Alternatively or additionally, by means of a field weakening or strengthening the current pointer length can be changed and thus the efficiency of the machine can be influenced. A speed control is still possible. Additionally or alternatively, a zero-current component or a superimposed direct current can be coupled into the current, which additionally enables a power transmission, but can cause a pulsating torque. Common regulators can meet the aforementioned control conditions and be adapted accordingly.

7 schematically shows another embodiment of an emergency operable drive circuit 100 in which a star emergency operation (Y emergency operation) of the engine 38 is possible. A first converter device 13a is switchable via a decoupling switching element 40 . 48 K _1, for example, an electromechanical contactor, to a supply network 12 connected. The converter device 13a includes a rectifier unit 14 and an inverter unit 16a , The inverter unit 16a is to a first contact page 76a the motor strands 30 the three-phase motor 38 connected. To the opposite second contact page 76b is another inverter device 13b with inverter unit 16b connected. Its DC link is powered by an energy storage device 110 supplied with voltage, which also has a decoupling switching element 48 K ₂ from the converter device 13b can be decoupled. By the two decoupling switching elements 48 can the two inverter devices 13 from their voltage-supplying networks (supply network 12 or energy storage device 110 ) be decoupled in case of error. As a result, there is the possibility of unilateral operation of the engine 38 with the still intact inverter device 13 , The two converter devices 13 are via a communication control line 60 interconnected, via the synchronization information, such as phase angle, DC link voltage level, position and amplitude of the d and q components of the voltage and / or the motor current and similar information can be exchanged. A control device, not shown, one or both inverter devices 13a . 13b in coordination with each other. If one of the two converter devices fails, then it is possible by means of an emergency operating control line 58a respectively. 58b the two converter devices 13a . 13b the respective opposite contact side 76 the motor strands 30 via Y-switching elements 40 . 44 be shorted. In this case, the switching elements 40 as semiconductor switching elements 56 each comprising a thyristor and a bridge rectifier circuit to the rectified neutral point of the respective contact sides 76 short circuit. For example, falls the energy storage device 110 out, so can a normal converter operation with the help of the supply network 12 be maintained. In this case, the decoupling switching element K ₂ triggers 48 off and the contact page 76b is via the switching element 44a short-circuited .. If, however, the mains supply fails 12 from, then releases the decoupling element K ₁ 48 off and the contact page 76a is via the Y-switching element 44b shorted. Thus, at least in the short term emergency operation using the energy storage device 110 stored electrical energy can be maintained.

Finally shows 8th a further embodiment of a notbetriebsfähigen drive circuit 100 in emergency operation as a star-delta circuit 54 is designed. Basically, the in 8th illustrated circuit on a combination of in 3 and 7 executed circuits, so can the two contact pages 76a . 76b of the motor 38 via Y-switching elements 44a . 44b to be short-circuited for emergency operation as Y-circuit. Furthermore, via the triangle switching element K ₅ 46 the motor strands 30 be coupled in delta connection to one side via one of the two converter devices 13a . 13b to be energized. The two converter devices 13a . 13b can via decoupling switching elements K ₁ , K ₂ 48 in each case from the contact sides of the motor strands 30 be separated. The supply network 12 is indirectly via the decoupling switching elements K ₈ and K ₉ 102 to the two converter devices 13a . 13b connected. Both converter devices 13a . 13b include rectifier units 14a . 4b as well as DC link capacities 24 , An energy storage device 110 is physically in the second inverter device 13b arranged and can via emergency operation switching elements 102 K ₆ or K ₇ optionally with the DC intermediate circuits of the first and second converter device 13a . 13b be switched.

By means of in 8th shown flexible topology can be a network-based double inverter operation by mains supply of the two inverter devices 13a . 13b be guaranteed. For this purpose, switching element K ₆ and K _{7 are} to be opened, so that the energy storage device is decoupled, and the two switching elements K ₈ , K ₉ to close, so that both converter devices 13a . 13b be supplied with mains voltage. An inventive inverter operation, in which a converter 13a mains powered, the second converter device 13b battery powered or vice versa can be operated, as well as a pure energy storage supported inverter and Einzelumrichterbetrieb can be initiated in the one or both switching elements K ₈ , K. ₉ 102 be opened and one or both DC-DC circuits 18a respectively. 18b with the energy storage device 110 by closing one of the two switching elements K ₆ or K _{7 is} connected, so that the or the inverter units 16a respectively. 16b the motor strands 30 can be energized. It is both a star operation, as well as a triangle operation or when starting an initial star operation with subsequent triangle switching by respective activation of the switching elements 44 . 48 possible. Thus, a variety of switching variants and operating modes by the in 8th covered switching topology, wherein a higher-level control device, not shown, for example, one or both controllers of the inverter 16 can be the coordination between the switching operations of the two inverter units 16 can coordinate.

The drive circuit according to the invention is based on a double converter circuit in which an energy storage device is connected on the side of the second inverter unit in order to ensure a star or delta connection with the second converter device in the event of failure of the mains-powered converter branch. In normal operation, the energy storage device can be charged by the first inverter device through the motor currents, pick up regenerative energy of the motor and smooth out power peaks. In emergency operation, the motor can be operated both in a star connection, in which a full torque at reduced maximum speed is possible, as well as in a delta circuit, which allows a maximum speed with reduced torque. For the delta connection only a single switching element for emergency operation is necessary. As a three-phase motor, a standard motor can be used, in which all motor string ends are led out, which is a standard in asynchronous motors and is basically possible with synchronous machines. Since two inverter devices can be used whose encoders or encoder evaluations are used for redundancy purposes. An alternative supply of the intermediate circuit of the first converter device via a Notenergiespeicher is possible. The intermediate circuits of the two converter devices can be coupled together in order to continue to enable a continuous double inverter operation in case of failure of the network rectifier unit. Instead of the double inverter normal operation can operate in emergency operation alternately for a certain period of time a converter and for another period a second converter in star or delta connection the motor, whereby the life of the drive circuit can be extended. In certain phases, in which high power must be provided, can be switched to the double converter operation, and operated in a low load case, the engine in a Einrichterbetrieb. This is particularly advantageous in wind turbines, since in normal pitch operation typically no high speeds and rotational power are necessary, so that day or week, the inverter devices can be operated alternately or one-sided. By data communication of the two converter devices, a minimization control or charge control with respect to the zero-current components can be made possible. If both switching elements for the star and the triangular circuit provided, it can be switched in emergency mode between these two types of base circuit. It is sufficient even in an emergency operation star connection, a single switching element, if it can be ensured that the energy storage powered converter device will remain operable, especially if it is designed to be more robust, or set up redundant. By means of a communication control line between the two converter devices, error messages, charge control information, zero current control information and synchronization information can be exchanged, whereby an efficient double inverter operation can be enabled.

Claims (12)

Emergency operable drive circuit ( 50 . 54 . 100 ) for a three-phase motor ( 38 ) with mutually contactable motor strands ( 30 ), comprising two inverter units ( 16a . 16b ), each with a contact page ( 76a . 76b ) of the motor strands ( 30 ), each inverter unit ( 16a . 16b ) in a separate converter device ( 13a . 13b ) with DC link ( 18a . 18b ), characterized in that the first inverter unit ( 16a ) by one of a supply network ( 12 ) DC bus ( 18a ), and the second inverter unit ( 16b ) by a DC energy storage device ( 110 ) is power supply, so that the engine ( 38 ) in a first normal operating mode by means of linked phase voltages of the inverter units ( 16a . 16b ) in a double inverter operation through the utility grid ( 12 ) and the energy storage device ( 110 ) is energized, and in parallel or independently thereof, the energy storage device ( 110 ) is chargeable, and in a second emergency mode the engine ( 38 ) alone by the energy storage device ( 110 ) or alone through the supply network ( 12 ) is energized, for which at least two Y-switching elements ( 40 . 44 ) are provided to each one of the two contact pages ( 76a . 76b ) of the motor strands ( 30 ) to short circuit to form a Y-circuit for the emergency mode, wherein emergency operation control lines ( 58a . 58b ) of the two converter devices ( 13a . 13b ) are provided to the respective opposite contact side ( 76a . 76b ) of the motor strands ( 30 ) via the Y-switching elements ( 40 . 44 ) short circuit. Drive circuit according to claim 1, characterized in that in the first operating mode by a coordinated control of the two inverter units ( 16 ) the energy storage device ( 110 ) both via the first inverter unit ( 16a ) and the motor strands ( 30 ) as well as by regenerative energy of the engine ( 38 ) is rechargeable. Circuit according to Claim 2, characterized in that the two converter devices ( 13 ) for synchronization purposes with a communication control line ( 60 ), wherein at least one rotation angle of the motor ( 38 ) by at least one converter device ( 13a . 13b ), preferably by both converter devices ( 13 ) via at least one rotation angle sensor ( 64 ) is determinable. Circuit according to one of the preceding claims, characterized in that at least one switching element ( 40 . 48 ) is provided in order in the second operating mode at least one contact side ( 76 ) of the motor strands ( 30 ) from an inverter unit ( 16 ) to separate. Circuit according to one of the preceding claims, characterized in that at least one switching element ( 40 . 44 . 46 . 48 ) a semiconductor switching element ( 56 ). Circuit according to one of the preceding claims, characterized in that the first inverter unit ( 16a ) with one on a supply network ( 12 ) connected rectifier unit ( 14 ) with DC link ( 18a ) for forming the first converter device ( 13a ) and preferably connected switchable from the motor strands, and the second inverter unit ( 16b ) substantially directly with the energy storage device ( 110 ) via a second DC link ( 18b ) for forming a second converter device ( 13b ) connected is. Circuit according to one of the preceding claims, characterized in that the energy storage device ( 110 ) Capacitors, ultracapacitors, rechargeable batteries or a combination thereof. Circuit according to one of the preceding claims, characterized in that the energy storage device ( 110 ) in the second operating mode with the intermediate circuits ( 18a . 18b ) of both inverter units ( 16a . 16b ) by means of a switching element ( 102 ) Is connectable, so that a double inverter operation is feasible. Circuit according to one of the preceding claims, characterized in that the energy storage device ( 110 ) in the second mode of operation of the second inverter unit ( 16b ) and with the intermediate circuit ( 18a ) of the first inverter unit ( 16a ) by means of one or more switching elements ( 102 ) is connectable, so that an energization of the motor ( 38 ) via the first inverter unit ( 16a ) is feasible. Circuit according to one of the preceding claims, characterized in that the energy storage device ( 110 ) in the first mode of operation of the intermediate circuit ( 18b ) of the second inverter unit ( 16b ) and the second intermediate circuit ( 18b ) by means of one or more switching elements ( 102 ) with one through the supply network ( 12 ) provided DC DC voltage is connectable. Method for operating a drive circuit ( 50 . 54 . 100 ) according to one of the preceding claims 1 to 10, characterized in that in a first normal operating mode a double inverter operation of the motor ( 38 ) by energization by means of the supply network ( 12 ) and the energy storage device ( 110 ) is carried out, wherein in particular at low engine load, the energy storage device ( 110 ) is charged, and in a second emergency mode, in particular failure of the supply network ( 12 ), an inverter operation of the engine ( 38 ) in case of supply alone by the energy storage device ( 110 ) or the supply network ( 12 ) is carried out. Method according to Claim 11, characterized in that a changeover between the first and second operating modes is dependent on a power loss of the three-phase motor ( 38 ), a failure or reduction of the DC link voltage of the first inverter unit ( 16a ) or a non-tuned inverter output voltage, preferably in the first operating mode when a predefinable power value of the motor is exceeded ( 38 ) the additional energy demand from the energy storage device ( 110 ) and / or in the second mode the energy storage device ( 110 ) with the first, the second or both intermediate circuits ( 18a . 18b ) to enable inverter or dual inverter operation.

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