EP2499729A2

EP2499729A2 - Inverter with voltage clamping device

Info

Publication number: EP2499729A2
Application number: EP10771741A
Authority: EP
Inventors: Robert Januschevski; Kai Borntraeger
Original assignee: ZF Friedrichshafen AG
Current assignee: ZF Friedrichshafen AG
Priority date: 2009-11-11
Filing date: 2010-10-29
Publication date: 2012-09-19
Also published as: US20120217918A1; WO2011057901A3; JP2013511248A; DE102009046616A1; CN102612800A; WO2011057901A2

Abstract

The invention relates to an inverter, in particular for supplying energy to a three-phase motor (3) of a motor vehicle. Said inverter comprises a half-bridge (1a, 1b, 1c) for electrically connecting to the three-phase motor (3), characterised in that said half-bridge (1a, 1b, 1c) comprises a voltage limiting element (8) which is electrically connected to an inlet (6b) and an outlet (6c) of a power semi-conductor switch (5a; 5b) of the half bridge (1a, 1b, 1c), said voltage limiting element establishing a high-resistance or low resistance connection in a defined manner between the inlet (6b) and the outlet (6c) of the power semi-conductor switch (5a, 5b) in accordance with the voltage value of the voltage applied between the inlet (6b) and the outlet (6c) of the power semi-conductor switch (5a; 5b).

Description

inverter

The present invention relates to an inverter according to the preamble of claim 1.

For driving electric machines, inter alia converters are used, the machines being used e.g. by means of a DC source, e.g. a battery, but require one or more AC phases to operate. Such machines, particularly in the automotive driveline art, e.g. Three-phase motors, e.g. permanently or externally excited synchronous motors.

An inverter has e.g. a motor-side inverter or a drive inverter, the DC voltage from e.g. a DC link of the inverter, in particular a DC link with DC link capacitor, converts into an AC voltage of the desired frequency for controlling the direction of rotation and the rotational speed of the three-phase motor to be driven. Such drive inverters are used in particular in motor vehicles, e.g. in electrically powered vehicles or in hybrid-powered vehicles, the three-phase motor e.g. is designed as a vehicle drive motor.

Such vehicle drive motors, in particular permanently excited synchronous motors, usually show the design-related behavior that during operation an increasing with increasing speed counter voltage or internal voltage is induced (pole wheel), at very high speeds in the DC link, in particular by means of freewheeling diodes of (drive) Inverter, is fed or fed back and can cause damage in the inverter or the inverter, the battery, and other components (voltage feedback). In order to avoid this, but still be able to operate the engine at high speeds, in the prior art, therefore, a field weakening is made above the rated speed to avoid such a harmful voltage feedback. Nevertheless, damage to the converter or other components is also possible when using the field weakening, in particular when a motor is operated above the rated speed (field weakening operation), and, for example, a field Weak current can no longer be sustained. The cause may be, for example, a failure of the control electronics.

In order to protect the inverter against harmful voltage feedback in the case of an unintended AC-side (ie emanating from the motor) voltage increase, various protective circuits are proposed in the prior art. Usually, e.g. Power semiconductor switch of the inverter or its motor-side inverter and thus the associated respective motor terminals shorted in case of failure. By short-circuiting via the bridge circuit, it can be prevented that e.g. the DC link capacitor, a battery, the circuit breaker, etc., and thus the inverter are damaged by the induced voltage due to the rotor rotation. However, a weak point of the known arrangements is usually that the short circuit must be actively carried out by a control electronics of the inverter. When the drive electronics fail, there is no protection mechanism against damage caused by the voltage induced in the synchronous machine or motor.

DE 102 51 977 A1 discloses a synchronous motor with inverter, wherein a complex protection device against voltage feedback is connected to the winding phases, wherein the protection device cooperates with the control logic of the inverter for detecting a fault or to protect against voltage feedback. DE 298 13 080 U1 shows a further, connected to the windings of a motor protection against voltage feedback, wherein the protection device in turn has an associated with the control logic electronics for producing the protective function. This system is also complex and expensive to manufacture. DE 198 35 576 A1 discloses a drive system for a permanent-magnet electric motor which contains an operating state detection unit in order to generate a short circuit of the power semiconductor switches by means of a drive arrangement of the inverter as required. Like the preceding, this arrangement is likewise complex, cost-intensive and can not be realized without the use of control logic.

Based on this, the object of the present invention is to solve the above-described problems and to provide an inverter. strike, which provides a corresponding protection against voltage feedback of a three-phase motor easily and conveniently without the inclusion of the control logic of the inverter available.

This object is achieved by the features of claim 1.

According to the invention, an inverter is provided, in particular for supplying energy to a three-phase motor of a motor vehicle, the inverter having a half bridge for electrical connection to the three-phase motor, the half bridge having a voltage limiting element which is electrically conductively connected to an input and an output of a power semiconductor switch of the half bridge depending on the voltage value (magnitude and sign) of a voltage applied between the input and output of the power semiconductor switch voltage defines a high-impedance or low-impedance connection between the input and output of the power semiconductor switch creates.

Furthermore, an inventive inverter is proposed, in which each half-bridge of the inverter is provided with an input and an output of a power semiconductor switch of the half-bridge electrically connected voltage limiting element which depends on the voltage value (magnitude and sign) of an applied voltage between the input and output of the power semiconductor switch defines a high-impedance or low-resistance connection between the input and output of the power semiconductor switch of the respective half-bridge creates.

In one embodiment of the invention, the inverter is designed such that the low-resistance connection in each case creates a current flow possibility through the respective voltage limiting element in the direction from input to output of the respective power semiconductor switch. In one embodiment, in particular, the low-resistance connection in each case creates a current flow possibility through the respective voltage-limiting element in antiparallel or in opposite directions. set to the current flow direction by a freewheeling diode connected to the input and the output of the respective power semiconductor switch.

According to a further embodiment of the inverter according to the invention, the voltage limiting element is arranged in the reverse direction between the input and the output, wherein the voltage limiting element is conductive in the reverse direction from reaching a defined voltage value between input and output.

In yet another embodiment of the inverter, the voltage limiting element comprises an active and / or a passive element. The voltage limiting element may comprise a comparator and / or a controlled power switch, in particular a semiconductor switch or a mechanical switch. The voltage limiting element may comprise a Zener diode and / or a suppressor diode and / or a varistor. In particular, the voltage limiting element can be formed from exactly one component or have exactly such a component.

Also proposed is a drive arrangement, in particular of a motor vehicle, which has a three-phase motor, wherein a phase winding of the three-phase motor is electrically conductively connected to the half-bridge of an inverter according to the invention for supplying electrical energy.

In a further embodiment of the drive arrangement according to the invention, in each case one winding strand of the rotary current motor is electrically conductively connected to one half-bridge of the inverter each. The three-phase motor can be a synchronous motor, in particular a permanent or third-excited synchronous motor.

Further features and advantages of the invention will become apparent from the following description of embodiments of the invention, with reference to the figures of the drawings, which show details essential to the invention, and from the claims. The individual characteristics can be individually or individually to be realized in several in any combination in a variant of the invention.

Preferred embodiments of the invention are explained below with reference to the accompanying drawings. It shows:

1 shows by way of example a bridge circuit of an inverter according to a possible embodiment of the invention.

In the following description and the drawing same reference numerals correspond to elements of the same or comparable function.

Fig. 1 shows a bridge circuit 1 of a drive inverter according to the invention or inverter with a Spannungsbegrenzungsanord- tion 2, in particular for protection against voltage feedback of a motor, e.g. a three-phase motor 3, in particular a separately excited or permanently excited synchronous motor. The (drive) inverter is for example part of a converter known in the art.

A converter has, for example, in a known manner a rectifier unit (not shown), which feeds a DC link in which, for example, an intermediate circuit capacitor is arranged. The intermediate circuit supplies, for example, an intermediate circuit voltage U _Z K, in particular as a DC voltage to the input 1 'of the inverter 2, for example for the bridge circuit 1 of the inverter, for generating the provided for motor operation AC voltage. The inverter generates, for example, an alternating voltage as an output voltage with variable voltage and frequency, for example to control the direction of rotation and speed of the three-phase motor 3 connected or connected thereto.

The bridge circuit 1 of the inverter, at the input terminals 1 ', for example, the intermediate circuit voltage U _Z K is applied, for example, a half-bridge 1 a and 1 b, 1 c, which each with a winding strand 3a and 3b, 3c of the three-phase motor electrically, for example via a respective center tap 4a and 4b, 4c in a known manner connectable or connected. In the present case, the three-phase motor 3 is designed, for example, as a three-phase motor whose three winding phases 3a, 3b, 3c are each fed by a half-bridge 1 a, 1 b, 1 c. The respective strand 3a, 3b, 3c of the three-phase motor 3 is thereby by the respective half-bridge 1 a, 1 b, I c delivered a voltage or a potential of predetermined polarity for a certain period of time. For this purpose, the respective power semiconductor switch 5a, 5b of the half-bridges 1 a, 1 b, 1 c are respectively controlled, for example by means of a control logic, in a known manner accordingly.

A half bridge 1 a, 1 b, 1 c has e.g. a first power semiconductor switch 5a and a second power semiconductor switch 5b, e.g. as an insulated gate bipolar transistor (IG BT) or as a field effect transistor (FET), e.g. are formed as a metal-oxide-semiconductor field effect transistor (MOSFET). The power semiconductor switches 5a, 5b are e.g. in particular designed or correspondingly dimensioned for the voltages occurring in the converter or in the drive inverter. Other power semiconductor switch types are also conceivable.

The power semiconductor switches 5a, 5b each have a control input 6a, e.g. in the form of a gate electrode and an input 6b in e.g. Form of a collector electrode (IGBT) or drain electrode (MOSFET) and an output 6c in e.g. Shape of an emitter electrode (IGBT) or source electrode (MOSFET). Between input 6b and output 6c, a free-wheeling diode 7, for example, is connected in parallel in a conventional manner, in particular in parallel in the reverse direction.

The power semiconductor switches 5a (lower row), 5b (upper row) are, as mentioned above, e.g. controlled via their respective control input 6a or control terminal in a known manner, e.g. from control electronics (not shown), between input 6b and output 6c due to the control e.g. a short circuit can be generated, i.e. the power semiconductor switch 5a and 5b turns on.

The inverter according to the invention has a voltage limiting arrangement 2, which is formed by, for example, a voltage limiting element 8, in particular, for example, is formed by one voltage limiting element 8 per half bridge 1 a or 1 b, 1 c. In the present case, the voltage limiting element 8 is connected in each case in the associated half bridge 1 a, 1 b, 1 c to the input 6 b of the power semiconductor switch 5 a and to the output 6 c thereof, and thus suitable for bridging in the intended current flow direction with low resistance. The entrance 6b is also For example, with the center tap 4a and 4b, 4c of the associated half-bridge 1 a, or

1 b, 1 c electrically connected. The voltage limiting element 8 is so far in each case arranged in parallel or parallel to input 6b and output 6c of the respective power semiconductor switch 5a and arranged so far parallel to the respective freewheeling diode 7 of the power semiconductor switch 5a, wherein the freewheeling diode also with the input 6b and 6c output the power semiconductor switch 5a and 5b is connected.

According to the invention is also provided, a voltage limiting element 8 parallel to a freewheeling diode 7 and to an input 6b and a

To arrange output 6c of a power semiconductor switch 5b of the upper row, in particular for each half-bridge 1 a, 1 b, 1 c. With such an arrangement, the arrangement on the power semiconductor switches 5a of the lower row can be dispensed with.

The voltage limiting element 8 of the Spannungsbegrenzungsanord- tion 2 is inventively provided to the induced terminal voltage or voltage of the three-phase motor 3 in the example. To set or limit the case of a voltage feedback from the motor to a defined (threshold) value. The defined value or the predetermined threshold voltage is in this case e.g. chosen to be harmless to the inverter and other components to be protected, e.g. no danger can be expected. The voltage limitation from a defined threshold voltage can be determined solely by the voltage limiting element 8 in the form of one or more suitably selected components and in particular without e.g. Interaction, e.g. be achieved with the control logic of the inverter, insofar as self-sufficient.

The selected components, whose properties allow a corresponding threshold setting, thus specify the voltage from which a limitation occurs. For example, by means of the voltage limiting element or elements 8, the potentially damaging voltage peaks of the induced voltage are cut off or suppressed. In this case, the three-phase motor is braked, for example, until the voltage drops to a harmless voltage value. For this purpose, for example, the voltage limiting elements 8 are each of high resistance for a long time, in particular in their intended blocking direction, until they are connected to or between them. see input 6b and output 6c respectively applied voltage reaches the intended threshold voltage. From the threshold voltage or from exceeding the threshold voltage, for example due to voltage feedback from the motor 3, the voltage limiting elements 8, for example, each low impedance, in particular in the intended current flow direction of input 6b to 6c low impedance. They become conductive in their blocking direction. In this respect, a voltage limiting element 8 connects input 6b and output 6c of a respective power semiconductor switch 5a or 5b as a function of the voltage value of the voltage applied between input 6b and output 6c in a high-impedance or low-impedance manner, ie essentially nonconductive or conductive.

The inverter is designed such that the low-resistance connection by the voltage limiting element 8 from reaching the threshold each creates a Stromflussmöglichkeit by the respective voltage limiting element 8 in the direction of input 6b to output 6c of the respective power semiconductor switch 5a and 5b. In other words, the voltage limiting element 8 in the case of reaching the threshold voltage, ie in the case of the low-resistance connection, in its reverse direction conductive. The reverse direction of the voltage limiting element 8 arranged between the input 6b and the output 6c corresponds in this case to e.g. in particular the reverse direction of the freewheeling diode 7.

The low-resistance connection provides e.g. In particular, in each case a current flow possibility through the respective voltage limiting element 8 opposite or antiparallel to the intended or intended current flow direction through the connected to the input 6b and the output 6c of the respective power semiconductor switch freewheeling diode 7. Thus, a current 9 of e.g. a winding strand 3a of the motor 3 via the low-impedance voltage limiting element 8 and a e.g. Freewheeling diode 7 e.g. to another winding strand 3b of the motor 3 flow.

In order to ensure this functionality, various components can be used as a voltage limiting element 8, for example from au- auf switchable elements or elements integrated in the inverter. A voltage limiting element 8 can be an active (construction) element which, for example, permits control or has a passive (construction) element or can be designed as such.

For example, the voltage limiting element 8 may have an arrangement of several components, e.g. a device with e.g. a comparator, which causes an overvoltage or an exceeding of the threshold voltage due to e.g. Voltage feedback detected and subsequently actuated a circuit breaker whose permeability (on / off) can be controlled in dependence on the detected voltage value. The power switch may comprise a semiconductor switch, e.g. a transistor switch or a e.g. mechanical switch, e.g. a relay, his. It is also conceivable, as voltage limiting element 8 e.g. use a power zener diode (essentially zener diode circuit with transistor, e.g., a complementary Darlington stage) or a so-called known thyristor crowbar.

The voltage limiting element 8 can be a passive element, for example a Zener diode, which becomes conductive or low resistance as soon as it reaches its breakdown voltage selected as eg threshold voltage, a suppressor diode or eg a varistor, ie a voltage-dependent resistor. It is conceivable within an inverter, for example, different types of voltage limiting elements 8, for example, each half bridge 1 a, 1 b, 1 c different types, to provide a voltage limiting arrangement 2. All of the voltage limiting elements 8 according to the invention or the voltage limiting arrangement 2 limit the voltage independently or independently, ie solely as a function of the voltage applied to the voltage limiting element 8, eg as a result of a voltage feedback. In that regard, a voltage limiting element 8 according to the invention or the voltage limiting arrangement 2 is independent of a control of or through the inverter (s), converter (s) or motor (s), etc. Other components, in particular a wiring with external signal sources such as those of a control logic of the inverter or inverter, which controls, for example, the power semiconductors are not provided for voltage limitation according to the invention next. The voltage limitation according to the invention, in which a respective conductive connection between two terminals of the motor 3 is created by a voltage limiting element 8, in each case at least from potentially damaging voltage feedback or from overshooting a threshold value, in each case in conjunction with one freewheeling diode 7 causes, for example, a braking torque, which may cause the motor to be decelerated in a motor decoupled from the drive train, ie the speed will decrease until the voltage drops to a safe level. In an engine connected to the drive train, for example, the entire drive train is braked, but the resulting braking torque is substantially lower than a short-circuit braking torque.

A current flowing in the three-phase motor 3 and the inverter as a result of voltage feedback current 9 flows with active voltage limitation, for example by the voltage limiting element 8 (as soon as the voltage limiting element 8 due to, for example, an excessive terminal voltage, for example, between the center tap 4a and 4b, low impedance or permeable or electrically conductive ) Thus, for example, from a first, connected to the center tap 4a terminal of the three-phase motor 3 through the voltage limiting element 8 of the voltage limiting arrangement 2 via the freewheeling diode 7 back to another, connected to the center tap 4b terminal of the motor third

REFERENCE CHARACTERS

bridge circuit

'Input terminals

a, 1 b, 1 c half-bridge

Voltage limiting arrangement motor

a, 3b, 3c winding strand

a, 4b, 4c center tap

a Power semiconductor switch (lower row) b Power semiconductor switch (upper row) a Control input Power semiconductor switchb Input Power semiconductor switchc Output Power semiconductor switch

Freewheeling diode

Voltage limiting element

electricity

Claims

claims

1 . Inverter, in particular for supplying energy to a three-phase motor (3) of a motor vehicle, the inverter having a half-bridge (1 a, 1 b, 1 c) for electrical connection to the three-phase motor (3), characterized in that the half-bridge (1 a, 1 b) has a voltage limiting element (8) electrically conductively connected to an input (6b) and an output (6c) of a power semiconductor switch (5a, 5b) of the half bridge (1a, 1b, 1c) Voltage value of a voltage applied between input (6b) and output (6c) of the power semiconductor switch (5a; 5b) defines a high-resistance or low-resistance connection between input (6b) and output (6c) of the power semiconductor switch (5a; 5b).

2. Inverter according to claim 1, characterized in that each half-bridge (1 a, 1 b, 1 c) of the inverter with an input (6 b) and an output (6 c) of a power semiconductor switch (5 a, 5 b) of the half-bridge (1 a , 1 b, 1 c) electrically conductively connected voltage limiting element (8) is provided which defines a high-impedance or low-resistance connection as a function of the voltage value of a voltage present between input (6b) and output (6c) of the power semiconductor switch (5a; 5b) between input (6b) and output (6c) of the power semiconductor switch (5a, 5b) of the respective half-bridge (1a,

1 b, 1 c) creates.

3. Inverter according to claim 1 or 2, characterized in that the low-resistance connection in each case creates a current flow possibility through the respective voltage limiting element (8) in the direction from input (6b) to output (6c) of the respective power semiconductor switch (5a; 5b).

4. Inverter according to one of the preceding claims, characterized in that the low-resistance connection in each case a Stromflussmöglichkeit by the respective voltage limiting element (8) opposite to the current flux direction by a with the input (6b) and the output (6c) of the respective power semiconductor switch (5a, 5b) connected freewheeling diode (7) creates.

5. Inverter according to one of the preceding claims, characterized in that the voltage limiting element is arranged in the reverse direction between the input and the output, wherein the voltage limiting element is conductive from reaching a defined voltage applied between input and output voltage in the reverse direction.

6. Inverter according to one of the preceding claims, characterized in that the voltage limiting element (8) has an active and / or a passive element.

7. Inverter according to one of the preceding claims, characterized in that the voltage limiting element (8) comprises a comparator and / or a power switch, in particular a semiconductor switch or a mechanical switch.

8. Inverter according to one of the preceding claims, characterized in that the voltage limiting element (8) comprises a Zener diode and / or a suppressor diode and / or a varistor.

9. Inverter according to one of the preceding claims, characterized in that the voltage limiting element (8) has exactly one component.

10. Drive arrangement, in particular of a motor vehicle, comprising a three-phase motor (3), characterized in that a winding strand (3a, 3b, 3c) of the three-phase motor (3) with the half-bridge (1 a, 1 b, 1 c) of an inverter after a of claims 1 to 9 is electrically conductively connected to the supply of electrical energy.

1 1. Drive arrangement according to claim 10, characterized in that each one winding strand (3a, 3b, 3c) of the rotary current motor (3) is electrically conductively connected to a respective half-bridge (1 a, 1 b, 1 c) of the inverter.

12. Drive arrangement according to claim 10 or 1 1, characterized in that the three-phase motor (3) is a synchronous motor, in particular a permanent or third-excited synchronous motor.