WO2020120312A1

WO2020120312A1 - Discharging an inverter intermediate circuit capacitor by means of bridge short-circuit pulses

Info

Publication number: WO2020120312A1
Application number: PCT/EP2019/083967
Authority: WO
Inventors: Martin Trunk; Manfred Kirschner
Original assignee: Robert Bosch Gmbh
Priority date: 2018-12-13
Filing date: 2019-12-06
Publication date: 2020-06-18
Also published as: DE102018221593A1

Abstract

The invention relates to an inverter arrangement (10), comprising a bridge circuit (20) comprising at least one high-side power semiconductor (T1) and a low-side power semiconductor (T2), which are connected to one another in series, an intermediate circuit capacitor (CZK), which is connected in parallel with the high-side power semiconductor (T1) and the low-side power semiconductor (T2), a control apparatus (30), which is designed to control the high-side power semiconductor (T1) and the low-side power semiconductor (T2), wherein the low-side power semiconductor (T2) has an inflow connection (SL) and a short-circuit current measurement apparatus (40) is arranged at the inflow connection (SL), which short-circuit current measurement apparatus is designed to measure a short-circuit current of the bridge circuit (20) and wherein the control apparatus (30) is designed to detect a short circuit in the bridge circuit (20) based on the measured short-circuit current and to discharge the intermediate circuit capacitor (CZK) by activating the high-side power semiconductor (T1) based on the detection of the short circuit.

Description

description

title

DISCHARGE A INVERTER BETWEEN CIRCUIT CAPACITOR BY BRIDGE SHORT CIRCUIT

The present invention relates to an inverter arrangement

Drive system for an electrical machine comprising one

Inverter arrangement, a vehicle with such

Inverter arrangement, and a control method for a

Inverter arrangement for discharging an intermediate circuit capacitor.

State of the art

Electrical drive systems, such as those used in electrical and

Hybrid vehicles are used, can include inverters that generate voltage signals from an electrical DC voltage, which are used for

Driving an electrical machine are suitable. A DC intermediate circuit with an intermediate circuit capacitor is provided at the input of such an inverter.

The inverters can be designed, for example, as a bridge circuit with a predetermined number of bridge branches, each with two power semiconductors. The bridge circuit is supplied with an intermediate circuit voltage, i.e. a DC voltage with a high potential, which is referred to as a high DC voltage potential, and a low potential, which is referred to as a low DC voltage potential, and with a load, in particular an electrical machine. Each bridge branch has two power semiconductors, which are connected in series to each other.

The load is connected to the bridge arm between the two power semiconductors. One of the power semiconductors is therefore a so-called highside Power semiconductors and the other power semiconductor is a so-called low-side power semiconductor. Parallel to the two power semiconductors is one

Intermediate circuit capacitor arranged.

There may be various conditions where the

Inverter arrangement must quickly and reliably discharge the intermediate circuit capacitor.

Discharge of the intermediate circuit capacitor is usually implemented by means of a discharge resistor or by means of a so-called contacting.

A power semiconductor comprises an inflow electrode, an outflow electrode and a gate electrode, via which the connection between the inflow electrode and the outflow electrode is controlled. When you turn on the

Power semiconductor is the application of a gate voltage

Power semiconductors switched from a stop region to a saturation region over a linear region. The connection between the inflow electrode and the outflow electrode conducts in the saturation region. Does that fall

Gate voltage, the power semiconductor changes from the saturation area back to the blocking area and between the inflow electrode and

Drain electrode is idling.

When switching on, the gate voltage is now applied to one of the power semiconductors (for example the low-side power semiconductor) of the bridge circuit only very briefly, while the other power semiconductor (for example the high-side power semiconductor) is switched on, the power semiconductor not reaching the saturation range. Nevertheless, a short-circuit current builds up through the power semiconductor. The very brief application of the gate voltage is repeated quickly in succession. This allows the

DC link capacitor are discharged without the power semiconductor ever reaching the saturation range.

To control the starting, the switch-off overvoltage is usually measured and the short-circuit current is determined therefrom in order to determine the switch-on time of the subsequent switching pulse. This function needs one Information storage and high-resolution processing, especially by a microprocessor. The entire PEU (Power Electronics Unit) must be active so that the starting can be implemented. If terminal 30 supply is omitted, this means, for example, a significant effort for the voltage supply, since the low voltage side must be supplied from the high voltage.

It is therefore the task of simplifying the contacting function.

The object is achieved by an inverter arrangement according to claim 1, a drive system for an electrical machine according to claim 6, a vehicle with an inverter arrangement according to claim 7 and a control method for an inverter arrangement according to claim 8.

Disclosure of the invention

The invention relates to an inverter arrangement, comprising an

Bridge circuit comprising at least a first power semiconductor, preferably a highside power semiconductor, and a second

Power semiconductors, preferably a low-side power semiconductor, which are connected in series with one another, an intermediate circuit capacitor which is connected in parallel with the first power semiconductor and the second power semiconductor, and a control device which is set up to control the first power semiconductor and the second power semiconductor. The second power semiconductor has a connection, preferably an inflow connection or outflow connection, on which a short-circuit current measuring device is arranged, which is set up to measure a short-circuit current of the bridge circuit. The control device is set up based on the measured

Short-circuit current to detect a short circuit in the bridge circuit and to discharge the intermediate circuit capacitor by contacting the first power semiconductor based on the detection of the short circuit.

In the context of these explanations, the first power semiconductor is referred to below as a highside power semiconductor and the second power semiconductor as a low-side power semiconductor for better understanding designated. The highside power semiconductor is the one with the high one

Power semiconductors connected to direct voltage potential and the low-side power semiconductor is the power semiconductor connected to the low direct voltage potential. Nevertheless, this assignment can also be interchanged, so that the first power semiconductor is a low-side power semiconductor and the second power semiconductor is a high-side power semiconductor. Likewise, if the assignment of the first and second power semiconductors is interchanged, the assignment of the

Make short-circuit current measuring device from the second to the first power semiconductor.

In this way, the control device is able to implement the clocking in such a way that the clocking power semiconductor, the high-side power semiconductor, by measuring and evaluating what flows in the power path, ie the path through one or more power semiconductors

Short-circuit current is switched off.

The term "power semiconductor" includes the terms power switch and semiconductor switch.

The power semiconductors are preferably IGBT transistors or metal oxide field-effect transistors (MOSFETs) or silicon carbide field-effect transistors (SiC-FETs).

By measuring the short-circuit current between the inflow connection of the low-side power semiconductor and the negative connection of the

The intermediate circuit voltage, the control device can control the starting directly based on the measured short-circuit current. Indirect

Control methods, such as indirect readjustment of the short-circuit current, can be avoided.

The contacting preferably comprises more than 1000 pulses (switch-on and switch-off processes of the power semiconductor, in particular the highside power semiconductor), more preferably more than 10,000 pulses in a period of 0.2 to 2 seconds. The length of a pulse is preferably between 1 and 20 nanoseconds. The number of pulses, the length of the pulse, and the time period depend on several factors such as the DC link voltage, the switching behavior or the

Commutation inductance, which also allows further value ranges.

The short-circuit current measuring device preferably comprises one

Measuring resistor, especially a shunt. With comparatively small ones

Currents, measurement is possible via a measuring resistor. However, the greater the current to be measured that runs through the shunt, the greater are the power losses, for example heat losses.

The control device advantageously has a microcontroller. Due to the particularly simple design of the inverter arrangement and the particularly simple type of implementation of the contacting, a less complex microcontroller can be used.

In a preferred embodiment, the short-circuit current measuring device is advantageously set up to measure the short-circuit current with a time resolution of less than 1 microsecond.

Measuring the short-circuit current with a time resolution of less than 1

Microsecond is referred to as a highly dynamic current measurement.

In a preferred embodiment, the

Short-circuit current measuring device advantageously an inductance and the short-circuit current measuring device is advantageously set up to measure a change in the short-circuit current via the inductance.

The inductance is advantageously a parasitic inductance in the power path, that is to say in the path through one or more power semiconductors.

In a preferred embodiment, the control device

advantageously set up, the short circuit in the bridge circuit based on a gate voltage of the first power semiconductor, preferably of the highside power semiconductor, and the change in the short-circuit current.

The change in the short-circuit current (di / dt) alone is not sufficient for the control device to be able to detect a short-circuit. However, during a normal switch-on process or during the operation of the power semiconductor in the saturation range, there is never a dynamic positive current change simultaneously with a high gate voltage unless it occurs

Short circuit case. In this way, the control device can

provide comparatively fast short-circuit detection.

The switching on and switching off, that is to say the switching on of the first power semiconductor, preferably of the highside power semiconductor, is advantageously implemented by a set / reset flip-flop which is controlled by the control device.

Further advantageously, the control device can switch off the first power semiconductor, preferably the highside power semiconductor, after a predetermined time has elapsed, even if there is still no short circuit in the

Bridge circuit was detected.

In a preferred embodiment, the short-circuit current measuring device is advantageously set up to integrate and / or filter the change in the short-circuit current, preferably low-pass filters.

In this way, the performance of the contact function can be increased further, as this eliminates the dependency of the DC link voltage.

The invention further relates to a drive system for an electrical machine, comprising an inverter arrangement of the type described above.

The invention further relates to a vehicle comprising a

Inverter arrangement of the type described above. The invention further relates to a control method for an inverter arrangement for discharging an intermediate circuit capacitor, comprising the steps:

a) closing a first power semiconductor, preferably a high-side power semiconductor, a bridge circuit by a

Control device;

b) measuring a short-circuit current at a connection, preferably an inflow connection, of a second power semiconductor, preferably a low-side power semiconductor of the bridge circuit by means of a

Short-circuit current measuring device;

c) detecting a short circuit in the bridge circuit by the control device based on the measured short circuit current; d) opening of the first power semiconductor, preferably the highside power semiconductor, by the control device based on the detected short circuit; and

e) repeating steps 1) to d) in order to provide the function of contacting the first power semiconductor, preferably the highside power semiconductor, until the intermediate circuit capacitor is discharged.

In a preferred embodiment, a change in the short-circuit current at an inductance is advantageously carried out in step b)

Short-circuit current measuring device measured, wherein

the control device in step c) detects the short circuit in the bridge circuit based on a gate voltage of the highside power semiconductor and the change in the short circuit current.

In a preferred embodiment, the change in the short-circuit current is advantageously integrated and / or filtered, preferably low-pass filtered, in step b).

Further measures improving the invention are shown below together with the description of the preferred exemplary embodiments of the invention with reference to figures.

Embodiments It shows:

1 shows a circuit diagram of an inverter arrangement;

2 shows a diagram of various measured values over time when the intermediate circuit capacitor is discharged;

3 shows a diagram of various measured values over time in the case of a

Starting pulse;

Fig. 4 is a flowchart of the control method for a

Inverter arrangement for discharging a

Intermediate circuit capacitor; and

5 shows a vehicle with an inverter arrangement.

1 shows an inverter arrangement 10 comprising a bridge circuit 20. The bridge circuit 20 is designed as a half-bridge and comprises a high-side power semiconductor TI and a low-side power semiconductor T2, which are connected in series with one another. An electric drive M, preferably a phase connection of a multi-phase electrical machine, is connected to the inverter arrangement 10 between the highside power semiconductor TI and the low-side power semiconductor T2.

An intermediate circuit capacitor CZK is arranged in parallel with the bridge circuit 20.

The inverter arrangement 10 further comprises a control device 30 with a microprocessor 31, which is set up to control the high-side power semiconductor TI and the low-side power semiconductor T2. The control device 30 controls the highside power semiconductor TI via a first gate driver GTH and the lowside power semiconductor T2 via a second gate driver GTL. The first gate driver GTH has a first capacitance CI and the second gate driver GTL has a second capacitance C2. The first capacity CI and the second capacitance C2 are backup capacitors that support the voltage supply of the respective gate drivers GTH, GTL. The second gate driver GTL also has a low-side gate driver supply VI, which supplies the second gate driver GTL with voltage. The second gate driver GTL is connected to the first gate driver GTH via a high-voltage diode D1. The first gate driver GTH is supplied from the low-side gate driver supply VI via the high-voltage diode D1. Such a method is referred to as a bootstrap method.

The inverter arrangement 10 further comprises a high-voltage battery HV, which supplies the inverter arrangement 10 with a high potential HV + and a low potential HV-.

The highside power semiconductor TI has a first inflow electrode SH, a first outflow electrode DH and a first gate electrode GH. The low-side power semiconductor T2 has a second inflow electrode SL, a second one

Drain electrode DL and a second gate electrode GL. The first

Inlet electrode SH has the same potential as the second one

Drain electrode DL. The electric drive M has the same potential. The first drain electrode DH is connected to the high potential HV +. A short-circuit current measuring device 40 is arranged between the second inflow electrode SL and the low potential HV-.

The short-circuit current measuring device 40 comprises a parasitic inductance LI in the power path, that is to say in the path through at least one

Power semiconductor runs. A change in the short-circuit current di / dt, that is to say the change in the current through the

Power path to be measured. In FIG. 1, the inductance is arranged between the low-side power semiconductor and the low DC voltage potential. The inductance can, however, in principle at any point in the

Power path may be arranged, in particular between the phase connection of a multi-phase electrical machine and the high-side power semiconductor or the low-side power semiconductor. An arrangement between the high DC voltage potential and the highside power semiconductor is also possible. The short-circuit current measuring device 40 also includes one Low pass filter 41, which is the measured signal of the change in

Short-circuit current di / dt low-pass filtered. Furthermore, the

Short-circuit current measuring device 40 an integrator 42, which is set up to integrate the low-pass filtered signal. The integrated signal is forwarded to the control device 30.

The control device 30 comprises a comparator 32 for processing the integrated signal of the short-circuit current device 40

Comparator 32 can detect control device 30 whether there is a high highside gate voltage VGH, which preferably exceeds a predefinable first threshold value, and a large change, which preferably exceeds a predeterminable second threshold value, of short-circuit current di / dt. If this is the case, the control device 30 detects a short circuit.

The control device 30 is assigned a set-reset flip-flop 33 in order to implement the control of the first gate driver GT _H.

For switching on, the control device 30 controls the second gate driver GTL in such a way that a low-side gate voltage VGL is applied to the second gate electrode GL, which turns on the low-side power semiconductor T2. The low-side power semiconductor T2 remains switched on for the duration of the starting. As soon as the control device 30 additionally controls the first gate driver GTH in such a way that a high-side gate voltage VGH, which switches on the high-side power semiconductor TI, is present at the first gate electrode GH, a short-circuit current builds up in the power path. This short circuit is detected by the control device 30 as described above, and the control device 30 controls the first gate driver GTH in such a way that the first

Gate electrode GH no longer has a high-side gate voltage VGH.

This process is repeated several times and thus implements the described function of starting in order to discharge the intermediate circuit capacitor CZK.

The control device 30 switches off the highside power semiconductor TI not only when a short circuit has been detected, but also after a predetermined time has elapsed. Therefore, the output of the

Comparator 32 connected to the set-reset flip-flop 33, but the Output of the comparator 32, which indicates whether a short circuit has been detected or is linked to the signal of the control device 30 for switching off the highside power semiconductor TI due to the expiry of a predetermined time.

Fig. 2 shows a diagram during the complete discharge of the

DC link capacitor by clocking over time. The flip-flop output voltage VQ of the set-reset flip-flop 33 is shown

Short circuit current II through the inductance LI in the power path and

DC link capacitor voltage VZK across the DC link capacitor CZK. The pinning is carried out for about 0.37 seconds until the

DC link capacitor CZK is discharged.

During the starting process, the flip-flop output voltage VQ moves between a “high level”, in this example IV, for switching on the highside power semiconductor TI and a “low level”, in this example 0V, for switching off the highside power semiconductor TI. Due to a lack of resolution, the more than 1000 switching steps here turn out to be

continuous block.

The same applies to the short-circuit current II, it being evident from the diagram that the maximum value of the short-circuit current II is approximately the same for each pulse of the starting.

Figure 3 shows a diagram during only a single pulse of starting. The DC link capacitor voltage VZK, the

Short-circuit current II, the high-side gate voltage VGH and the inputs and the output of the set-reset flip-flop 33. The set-reset flip-flop 33 has a set input, a reset input and an output, with the set voltage VFFS being present at the set input and the reset input at the

Reset voltage VFFR is present and the flip-flop output voltage VFFQ is present at the output. As can be seen, the time window is approximately 30 nanoseconds wide. The DC link capacitor voltage VZK remains almost constant with such a short time window. A single pulse of starting does not have a major influence on the intermediate circuit capacitor voltage VZK. After about 10 Nanoseconds, the controller 30 controls the set voltage VFFS to IV, whereby the set-reset flip-flop 33 sets a flip-flop output voltage VFFQ - high output level from IV. This leads to a high-side gate voltage VGH depending on the gate driver supply, in this example of 16V. The high-side power semiconductor TI is thus switched on and moves from the blocking area into the saturation area. As a result, a short-circuit current II begins to build up in the power path. This leads over the

Short-circuit current measuring device 40 to a rising reset voltage VFFR. In this example, the short circuit is detected after a few nanoseconds and the reset voltage VFFR exceeds a limit value. The set voltage VFFS and the flip-flop output voltage VFFQ fall back to the low level, in this example to 0V. The high-side gate voltage VGH drops to 0V in this example. the highside power semiconductor TI is now switched on. The short-circuit current II then drops back to 0A. In this way, the intermediate circuit capacitor VZK is gradually discharged.

4 shows the control method for an inverter arrangement 10 for discharging an intermediate circuit capacitor CZK. In a first step a), a high-side power semiconductor TI of a bridge circuit 20 is closed by a control device 30. Then in step b)

Short-circuit current at an inflow connection SL of a low-side power semiconductor T2 of the bridge circuit 20 through a

Short-circuit current measuring device 40 measured. In the subsequent step c), a short circuit in the bridge circuit 20 is detected by the control device 30 based on the measured short circuit current II. Finally, the highside power semiconductor TI is opened by the control device 30 based on the detected short circuit. Steps a) to d) represent a contact pulse. Steps a) to d) are thus repeated via loop e) until the function of contacting the highside power semiconductor TI is available until the intermediate circuit capacitor CZK is discharged .

5 shows a vehicle 50 with an inverter arrangement 10.

Claims

Expectations

1. Inverter arrangement (10) comprising:

a bridge circuit (20) comprising at least a first one

Power semiconductors (TI) and a second power semiconductor (T2), which are connected in series to one another;

an intermediate circuit capacitor (CZK) which is connected in parallel with the first power semiconductor (TI) and the second power semiconductor (T2); a control device (30) which is set up the first

Control power semiconductors (TI) and the second power semiconductor (T2); in which

the second power semiconductor (T2) has a connection (Si_) and a short-circuit current measuring device (40), which is set up to measure a short-circuit current of the bridge circuit (20), is arranged on the connection (Si_), and wherein

the control device (30) is set up based on the

measured short-circuit current to detect a short circuit in the bridge circuit (20) and to discharge the intermediate circuit capacitor (CZK) by contacting the first power semiconductor (TI) based on the detection of the short circuit.

2. Inverter arrangement (10) according to claim 1, wherein

the short-circuit current measuring device (40) is set up, the

Measure short-circuit current with a time resolution of less than 1 microsecond.

3. Inverter arrangement (10) according to one of claims 1 or 2, wherein

the short-circuit current measuring device (40) comprises an inductance (LI) and

the short-circuit current measuring device (40) is set up to measure a change in the short-circuit current via the inductance (LI).

4. Inverter arrangement (10) according to claim 3, wherein

the control device (30) is set up to short-circuit in the bridge circuit (20) based on a gate voltage (VGH) of the first Power semiconductor (TI) and the change in short-circuit current (di / dt) to detect.

5. Inverter arrangement (10) according to one of claims 3 or 4, wherein

the short-circuit current measuring device (40) is set up, the

To integrate and / or filter changes in the short-circuit current (di / dt), preferably to low-pass filters.

6. Drive system for an electrical machine (M), comprising a

Inverter arrangement (10) according to one of Claims 1 to 5.

7. Vehicle comprising an inverter arrangement (10) according to one of claims 1 to 5.

8. Control method for an inverter arrangement (10) for

Discharging an intermediate circuit capacitor (CZK), comprising the steps of: a) closing a first power semiconductor (TI) of a bridge circuit (20) by a control device (30);

b) measuring a short-circuit current at a connection (Si_) of a second power semiconductor (T2) of the bridge circuit (20) through a

Short-circuit current measuring device (40);

c) Detecting a short circuit in the bridge circuit (20) by the control device (30) based on the measured

Short-circuit current;

d) opening the first power semiconductor (TI) by the control device (30) based on the detected short circuit; and

e) repeating steps a) to d) in order to provide the function of contacting the first power semiconductor (TI) until the

DC link capacitor (CZK) is discharged.

9. The control method according to claim 8, wherein

in step b) a change in the short-circuit current (di / dt) at an inductance (LI) is measured by the short-circuit current measuring device (40), wherein the control device in step c) the short circuit in the

Bridge circuit (20) based on a gate voltage (VGH) of the high-side power semiconductor (TI) and the change in the short-circuit current (di / dt) detected.

10. The control method according to claim 9, wherein

in step b) the change in the short-circuit current (di / dt) at the inductance (LI) is integrated and / or filtered, preferably low-pass filtered.