DE102020111576B4 - Circuit arrangement for a power converter, power converter, electrical machine and method for operating an electrical machine - Google Patents

Abstract

Circuit arrangement (300, 400, 500) for a power converter (150) for an electrical machine (100), having: - a power half-bridge (160) with a high-side power switch (161) and a low-side power switch (162) ,- a driver unit (210), which is set up to switch at least one first power switch, selected from high-side power switch (161) and low-side power switch (162), conducting and blocking,- a switch-off path (220) and a supply path (240), which is designed in such a way that when the switch-off path (220) is activated, a supply voltage (V2) is applied via the supply path (240) to a control terminal of the first power switch (162), so that the latter is switched on, and - a redundant supply path (250, 250'), which is designed in such a way that a supply voltage (V2, V3) can be applied to the control terminal of the first power switch (162), so that the latter is switched on when the switch-off path (220) is activated, and which is designed in such a way that the supply voltage is permanently connected to the control terminal of the first circuit breaker (162).

Description

The present invention relates to a circuit arrangement for a power converter for an electrical machine, a power converter, an electrical machine and a method for operating an electrical machine.

State of the art

Electrical machines, such as those used in vehicles or motor vehicles, can be operated using a power converter (also referred to as an inverter), usually both as a generator and as a motor. For this purpose, such a power converter generally has a power half-bridge with a high-side power switch and a low-side power switch (both e.g. MOSFETs or IGBTs) for each phase of the electrical machine, in order to be able to energize the phase windings accordingly. Separately excited machines also have the option of energizing a rotor or field winding.

Furthermore, such a power converter typically has what is known as a switch-off path, which makes it possible to short-circuit all phases to ground or to the supply voltage. This procedure is also referred to as an active phase short circuit. This means that if the switch-off path is activated, e.g. in the event of a fault, no more torque is generated by the electric machine and no more electrical energy is delivered to the vehicle electrical system. A safe state is assumed.

Another way of assuming a safe state is, in the case of an externally excited electrical machine, to reduce the excitation current. However, this procedure requires significantly more time to reduce the excitation field, which in many cases is unacceptable for safety reasons.

From the DE 11 2017 000 253 T5 (E1) a circuit arrangement is known in which a switch-off path and a supply path are provided in order to turn on a circuit breaker if required, for example in order to bring about a phase short-circuit. the JP 2014-158 399 A also discloses a shutdown path.

Disclosure of Invention

According to the invention, a circuit arrangement for a power converter, a power converter, an electrical machine and a method for operating an electrical machine with the features of the independent patent claims are proposed. Advantageous configurations are the subject of the dependent claims and the following description.

The invention is based on a circuit arrangement for a power converter which has a power half-bridge with a high-side power switch and a low-side power switch and a driver unit which is set up to have at least a first power switch selected from high-side power switches and Low-side power switch (i.e. the high-side power switch or the low-side power switch or both), conducting and blocking, i.e. switching on and off. The power switches can be MOSFETs or IGBTs, for example, and the driver unit can be a gate driver.

In addition, such a circuit arrangement, as already mentioned, has a switch-off path and a supply path, which are designed in such a way that when the switch-off path is activated, a supply voltage is applied via the supply path to a control terminal (e.g. a gate terminal) of the first power switch (i.e. the high-side or the low-side power switch, depending on which one is controlled via the driver unit; if both are controlled, one of them) is applied so that it is turned on.

It is expedient here if the driver unit is connected to the control connection of the first circuit breaker, the switch-off path being designed in such a way that when it is activated, the driver unit is separated from the control connection of the first circuit breaker. In this case, the switch-off path can be designed in such a way that it is activated by changing a voltage level present thereon. It is also usual that in such a case, i.e. when the driver unit is disconnected or switched off, the other circuit breaker is first switched to blocking or opened before the relevant circuit breaker is switched to conducting. A separate, suitable circuit can be provided for this purpose.

At this point it should be mentioned that a switch-off path can also be understood to mean those circuit components which—when a certain voltage level is applied at a point of the switch-off path—lead to the first circuit breaker being switched on. In this respect, the supply path can also be counted as part of the switch-off path, but this is irrelevant to the way it works.

By means of such a switch-off path, the circuit breaker in question can be switched on if required or in the event of a fault. it ver It is clear that one power half-bridge is to be provided for each phase in the circuit arrangement or in the power converter for an electrical machine, ie three power half-bridges in the case of a three-phase electrical machine. A drive unit and also a switch-off path and a supply path can then be provided for each power half-bridge.

However, it is also expedient if, for example, several or all power switches are controlled by means of the driver unit (then with separate control lines each), so that the switch-off path and the supply path can also be branched to these power switches, so that ultimately all or all of the high-side power switches Low-side power switches can be turned on at the same time in order to bring about the active phase short circuit mentioned at the outset.

Although an active phase short-circuit can now be brought about in principle in this way if necessary or in the event of an error, errors can still occur, e.g. an interruption or a short-circuit to ground can occur in the supply path, or the supply voltage can fail. This would result in the circuit breaker in question not (any longer) being able to be switched on despite activation of the switch-off path.

Against this background, it is now proposed within the scope of the invention that the circuit arrangement also has a redundant supply path, which is designed in such a way that when the switch-off path is activated, a supply voltage can be applied to the control terminal of the first circuit breaker, so that it is switched on.

If, for example, an interruption or a ground short-circuit occurs in the (primary) supply path, a necessary supply voltage is still present at the control terminal of the first power switch via the redundant supply path in order to ultimately bring about the desired active phase short-circuit.

For example, different supply voltages can be used for the (primary) supply path and the redundant supply path, which are then respectively applied to the control connection of the first circuit breaker. Different supply voltages are then to be understood, for example, as different tapping points with, for example, also different voltage levels within the circuit arrangement or also different connection pins on the power converter.

In principle, however, it is also possible for the (primary) supply path and the redundant supply path to use the same supply voltage, i.e. e.g. the same tap point within the circuit arrangement. The necessary redundancy is achieved through the separate supply paths.

Not according to the invention, the redundant supply path can be designed in such a way that the supply voltage can be applied actively to the control terminal of the first power switch, in particular by means of a switch (e.g. a MOSFET or other transistor) in the redundant supply path. A microcontroller can then be provided here, for example, which is set up to actively apply the supply voltage, in particular by means of the switch, to the control connection of the first circuit breaker. This makes it possible to switch on the redundant supply path only when required.

According to the invention, the redundant supply path is designed in such a way that the supply voltage is permanently connected to the control terminal of the first circuit breaker. A diode or what is known as a flyback converter (or flyback converter) can then be used here in order to avoid unwanted compensating currents.

As an alternative to the variant according to which the redundant supply path and the (primary) supply path are of identical design, it is also particularly preferred if the circuit arrangement has an electrical energy store such as a capacitor, which is arranged in the redundant supply path.

The energy store can be charged from the supply path, for example. This causes the electrical energy store to be charged by the supply voltage present on the supply path during regular operation of the circuit arrangement. As long as there is no interruption in the supply path, the supply voltage can be applied to the control terminal of the first power switch in the manner described above by activating the switch-off path, so that the latter is turned on. However, if there is an interruption in the supply path or the supply voltage fails, the (then charged) electrical energy store takes over the function of the supply voltage and, when the switch-off path is activated, causes a supply voltage (namely from the electrical energy store) to be applied to the control terminal of the first circuit breaker , so that it is switched on.

With this variant, an active phase short-circuit can also be brought about in the event of an interruption in the supply path or a failure of the (actual) supply voltage. It goes without saying that due to a limited capacity of the electrical energy store, the first circuit breaker can only be switched on for a limited time. However, suitable dimensioning can ensure that the active phase short circuit is maintained at least until—in the case of a separately excited electrical machine—the excitation current has been (sufficiently) reduced. Compared to the variant described above, however, fewer additional components are required in the circuit arrangement.

The invention also relates to a power converter with a circuit arrangement according to the invention, in particular with one power half-bridge per phase for the electrical machine to be controlled, as explained above.

The subject of the invention is also an electric machine with a rotor and a stator as well as a power converter according to the invention. Accordingly, the stator then has phase windings. It is also preferred if the electrical machine is designed as an externally excited electrical machine.

Furthermore, the invention relates to a method for operating an electrical machine according to the invention, in which, in the event of a fault, a phase short circuit is actively brought about by activating the switch-off path.

With regard to the further advantages and preferred configurations of the power converter, the electrical machine and the method, to avoid repetition, reference is made to the above statements, which apply here accordingly.

Further advantages and refinements of the invention result from the description and the attached drawing.

The invention is shown schematically in the drawing using exemplary embodiments and is described below with reference to the drawing.

character list

• 1 shows schematically an electrical machine according to the invention in a preferred embodiment.
• 2 shows schematically a power converter in a preferred embodiment.
• 3 shows schematically a circuit arrangement not according to the invention.
• 4 shows a circuit arrangement according to the invention in a preferred embodiment.
• 5 shows a circuit arrangement not according to the invention.
• 6 shows a circuit arrangement according to the invention in a further preferred embodiment.

embodiment(s) of the invention

In 1 is a roughly schematic representation of an electrical machine 100 according to the invention in a preferred embodiment, which also has a power converter 150 according to the invention in a preferred embodiment.

The electrical machine 100, which can be used in particular in motor and generator operation, particularly preferably also in a so-called. Boost recuperation system (ie for energy recovery and drive support), has a rotor or rotor 110, for example, or excitation winding 111 or permanent magnets for generating a magnetic field. Correspondingly, a stand or stator 120 is also shown, which has stand or phase windings 121 shown only schematically here.

In 2 a power converter 150 according to the invention is shown schematically in a preferred embodiment, as is also the case with the electrical machine 100 according to FIG 1 can be used.

The power converter 150 has, for example, three power half-bridges 160 which are provided for three phases U, V, W of an electrical machine and are to be connected accordingly. Each of the three power half-bridges has a high-side power switch 161 and a low-side power switch 162, which are embodied here as MOSFETs and each of which has a gate or control connection with G, a drain connection with D and a source connection are marked with S.

A control unit 210 embodied as a gate driver and a switch-off path 220 are also indicated roughly schematically, the gate or control terminals G of high-side power switch 161 and low-side power switch 162 of at least one of power half-bridges 160 are controllable, so that they can be selectively switched on and off. The control unit can be deactivated by means of the switch-off path and, for example, the low-side power switches 162 can be turned on in order to actively bring about a phase short circuit.

Drive unit 210 and switch-off path 220 are here, for example, together with one of the power half-bridges 160, part of a circuit arrangement 300, which can be a circuit arrangement according to the invention in a preferred embodiment. For a more detailed view and description, reference is made to the following figures and the associated description, in particular also with regard to the redundant supply path, which is shown in 2 is not shown explicitly.

In 3 a circuit arrangement 200 not according to the invention is shown schematically, on the basis of which the basic structure and the basic mode of operation of a circuit arrangement, as they are also relevant to the invention, are to be explained.

As in 2 The high-side power switch 161 and the low-side power switch 162 are also shown here, as well as the control unit 210, whereby only the low-side power switch 162 can be controlled here by way of example, i.e. it can be switched on and off, for which purpose its gate or The control connection G is connected to the control unit 210 via a control line 211 and a switch 222 . Switching takes place by changing the potential at G, with the switch 162 conducting in the present case if the gate-source voltage U _GS is greater than the threshold voltage. As long as switch 222 is conducting, switch 162 follows the specifications of control unit 210.

The switch-off path 220 now has a switch 221, for example a MOSFET, which in the present case is designed to be normally blocking and only conducts when a negative gate-source voltage is applied. In the normal case, a supply voltage V ₂ , which can be obtained by means of a DC-DC or DC voltage converter from an on-board power supply voltage V ₁ of 48 V, for example, and is 15 V, for example, is present at a gate or driver connection of switch 222, so that this directs.

If the switch-off path is now activated by applying a negative gate-source voltage to the switch 221, the switch 221 is turned on or closed, as a result of which the supply voltage present at the gate or control terminal of the switch 222 is grounded is pulled. The switch 222 is thus turned off or opened, so that it is no longer possible to control the low-side power switch 161 by means of the control unit 210 .

Rather, the supply voltage V ₂ is now present via the supply path 240 at the gate or control connection of the low-side power switch 162, as a result of which the latter is switched on. This means that - with appropriate control of the other low-side power switches (cf 2 ) - an active phase short circuit can be brought about by activating the switch-off path 220 .

The (electrical) resistances R1, R2 and R3 can have values of 5 kOhm, 50 kOhm and 200 Ohm, for example, so that the desired functionality of the circuit arrangement 200 is achieved. However, it is understood that this is purely exemplary and other suitable values can also be used. The same applies to the voltage levels V ₁ and V ₂ here.

In the circuit arrangement 200 shown, however, the low-side power switch 162 can no longer be switched on if the supply voltage V ₂ fails or if the supply path 240 is interrupted or short-circuited.

In 4 a circuit arrangement 300 according to the invention is now shown in a preferred embodiment. The basic structure corresponds to the circuit arrangement 200 according to FIG 3 , so that reference is made to the description there. Identical components are provided with the same reference symbols.

In addition to a diode 241 in the supply path 240, a redundant supply path 250 is provided with a diode 251 provided therein, with which a supply voltage V ₃ of, for example, 12 V can be applied to the gate or control terminal of the low-side power switch 162 in order to Low-side power switch 162 to turn on when the shutdown path 220 is activated. The redundant supply path 250 is thus configured in the same way as the (primary) supply path 240 .

If the supply voltage V ₂ fails or if the supply path 240 is interrupted or short-circuited, the low-side power switch 162 can thus continue to be turned on. The diodes 241, 251 prevent unwanted compensating currents.

In 5 a circuit arrangement 400 not according to the invention is shown. The basic structure corresponds to the circuit arrangement 300 according to FIG 4 , so that in this respect on the dor term description is referenced. Identical components are provided with the same reference symbols.

However, a PMIC (“Power Management Integrated Circuit”) 215 and a microcontroller 216 for controlling the driver unit 210 are also shown here. In addition, not only the low-side power switch 162 can be controlled, but also the high-side power switch 161. The switch-off path 220 and the (primary) supply path 240 are shown here together, so that only the functionality, but not the specific Wiring is shown. In the event of a fault, the low-side power switches 162 are preferably closed after the high-side power switches 161 have opened.

In addition, a switch 252, e.g. a MOSFET, is now provided in the redundant supply path 250, which can be closed by means of the microcontroller 216 if required, e.g. if an error is detected in the (primary) supply path 240, so that the supply voltage V ₃ is then applied to the Gate or control terminal of the low-side power switch 162 can be applied.

The redundant supply path 250 can alternatively be connected--then as preferred embodiments of the invention--using a diode or what is known as a flyback converter; a permanent connection is also conceivable.

In 6 a circuit arrangement 500 according to the invention is shown in a further preferred embodiment. The basic structure corresponds to the circuit arrangement 300 according to FIG 4 , so that reference is made to the description there. Identical components are provided with the same reference symbols.

However, here the redundant supply path 250' is not configured in the same way as the (primary) supply path 240; instead, an electrical energy store C configured as a capacitor is provided, which is arranged in a region in the redundant supply path 250' in which the redundant supply path 250' separate from the supply path 240 runs. The capacitor C is then connected to the supply path 240 via part of the redundant supply path 250′ and via this to the supply voltage V ₂ present thereon. In other words, the capacitor C is connected to the supply path 240 and to the supply voltage V ₂ present thereabove and connected or arranged in parallel with the gate-source path of the low-side power switch 162 (and here also with the resistor R ₃ ).

In regular operation, the capacitor C is initially charged by means of the supply voltage V ₂ . If the supply voltage V ₂ fails or if the supply path 240 is interrupted or short-circuited, the capacitor then provides a voltage or supply voltage, whereby the low-side power switch 162 continues to be switched on, at least for a certain time. The diode 241 prevents the capacitor C from discharging into the supply path 240.

It goes without saying that a redundant supply path 250' with capacitor C can also be used as an additional redundant switch-off path in the embodiment according to FIG 4 can be present.

Claims (10)

Circuit arrangement (300, 400, 500) for a power converter (150) for an electrical machine (100), having: - a power half-bridge (160) with a high-side power switch (161) and a low-side power switch (162) , - a driver unit (210) which is set up to switch on and off at least one first power switch, selected from the high-side power switch (161) and low-side power switch (162), - a switch-off path (220) and a supply path (240), which is designed in such a way that when the switch-off path (220) is activated, a supply voltage (V ₂ ) is applied via the supply path (240) to a control terminal of the first power switch (162), so that the latter is switched on , and - a redundant supply path (250, 250'), which is designed in such a way that a supply voltage (V ₂ , V ₃ ) can be applied to the control terminal of the first power switch (162), so that it is conductively switched is altered when the switch-off path (220) is activated, and is designed in such a way that the supply voltage is permanently connected to the control terminal of the first circuit breaker (162). Circuit arrangement (500) after claim 1 , further comprising an electrical energy store (C) in the redundant supply path (250 '). Circuit arrangement (500) after claim 2 , Wherein the electrical energy store (C) in the redundant supply path (250 ') charged with the supply path (240) and about it with the applied supply voltage (V ₂ ) is connected. Circuit arrangement (500) after claim 2 or 3 , wherein the electrical energy store (C) is designed as a capacitor. Circuit arrangement (300, 400, 500) according to one of the preceding claims, wherein the driver unit (210) is connected to the control terminal of the first power switch (162), and wherein the switch-off path (220) is designed in such a way that, when it is activated, the driver unit (210) is separated from the control terminal of the first power switch (162). Circuit arrangement (300, 400, 500) according to one of the preceding claims, wherein the switch-off path (220) is designed in such a way that it is activated by changing a voltage level present thereon. Power converter (150) for an electrical machine, with a circuit arrangement (300, 400, 500) according to one of the preceding claims. Electrical machine (100) with a rotor (110), a stator (120) and a power converter (150). claim 7 . Electrical (100) machine after claim 8 , which is designed as a separately excited electrical machine. Method for operating an electrical machine (100). claim 8 or 9 , In the event of a fault, a phase short circuit is actively brought about by the shutdown path (220) being activated.

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