Method and device for operating power electronic component, power electronic component

Abstract

The invention relates to a method for operating a power electronics system (1), in particular an inverter or rectifier, comprising at least one half-bridge (2) having two semiconductor switches (3, 4) connected in series and at least one intermediate circuit capacitor (6) connected in parallel to the series of semiconductor switches (3, 4), in order to carry out a discharge process for discharging the at least one intermediate circuit capacitor (6), the two semiconductor switches (3, 4) are actuated in order to generate a plurality of discharge pulses in such a way that the two semiconductor switches are switched simultaneously for a predetermined duration (ton) for each discharge pulse. The semiconductor switches (3, 4) are actuated as a function of an intermediate circuit voltage of the power electronics (1) applied to the intermediate circuit capacitor (6) in such a way that the pulse energies (E) of the discharge pulses of the discharge process are the same or almost the same.

Description

Technical Field

[0001] The invention relates to a method for operating a power electronic device, in particular an inverter or a rectifier, which has at least one half-bridge, which has two semiconductor switches connected in series and at least one intermediate circuit capacitor connected in parallel with the series circuit of the semiconductor switches, wherein, in order to carry out a discharge process for discharging the at least one intermediate circuit capacitor, the two semiconductor switches are controlled in such a way as to generate a plurality of discharge pulses that the two semiconductor switches are simultaneously turned on for a predetermined duration for each discharge pulse.

[0002] Furthermore, the invention relates to a device for operating such a power electronic component, which is distinguished by a control unit which is specially designed to carry out the above-mentioned method.

[0003] Furthermore, the invention relates to a power electronic component, in particular as described above, which has the above-mentioned device.

[0004] Furthermore, the invention relates to a computer program, a machine-readable storage medium, a drive train and a vehicle. Background Art

[0005] Methods and devices of the type mentioned at the outset are known from the prior art. It is known to switch a half-bridge into a short circuit in order to discharge an intermediate circuit capacitor or an intermediate circuit, in which two semiconductor switches, in particular a semiconductor switch for a positive high voltage potential and a semiconductor switch for a negative high voltage potential, are switched on simultaneously. It is particularly known to switch on a so-called soft short circuit, in which one of the semiconductor switches is fully switched on and the other of the semiconductor switches is switched on slowly by means of an increased gate series resistance. A half-bridge transverse current is set depending on the gate voltage of the other semiconductor switch, which discharges the capacitance of the intermediate circuit, in particular the intermediate circuit capacitor. This transverse current is converted into short pulses, so-called discharge pulses, which have been repeatedly converted with a fixed clock frequency. The power loss formed in this way is reduced by the semiconductor switch, which is controlled slowly and therefore has a full intermediate circuit voltage at this point in time of the discharge pulse. Summary of the invention

[0006] The method according to the invention having the features of claim 1 has the advantage that the intermediate circuit or the intermediate circuit capacitor is discharged more quickly than before. To this end, it is provided according to the invention that the semiconductor switch is controlled in accordance with the intermediate circuit voltage of the power electronic device applied to the intermediate circuit capacitor in such a way that the corresponding pulse energies of the discharge pulses of the discharge process are identical or almost identical. It is then provided that within the discharge process, the discharge pulses have identical or almost identical pulse energies, at least within the discharge process. Each discharge pulse within the discharge process thus causes the same or almost identical pulse energy. The advantage resulting from this is that the pulse energy fully utilizes the full potential of the power electronic device even at low intermediate circuit voltages and thus accelerates the discharge, and in the case of high voltages, overloading of the power electronic device is prevented.

[0007] According to a preferred embodiment of the present invention, the duration of the corresponding discharge pulse is predetermined according to the current intermediate circuit voltage. Therefore, the pulse energy of the corresponding discharge pulse is set according to the current intermediate circuit voltage. As a result, the corresponding discharge pulse obtains the same discharge energy or almost the same energy as the previous or subsequent discharge pulse.

[0008] Furthermore, it is preferably provided that the duration is predetermined by a pre-stored characteristic curve as a function of the intermediate circuit voltage. The characteristic curve is stored in particular in a non-volatile memory of a control unit or controller, for example a power electronics device. The characteristic curve pre-determines the duration for the respective discharge pulse as a function of the currently applied intermediate circuit voltage. This ensures that a discharge pulse with an optimized discharge energy is reliably set until the intermediate circuit voltage is discharged.

[0009] According to a preferred embodiment of the present invention, the duration of the respective discharge pulse is predetermined as a function of the target current flowing through the half-bridge during each discharge pulse. The pulse energy of the respective discharge pulse is therefore set as a function of the target current and the current intermediate circuit voltage. As a result, the respective discharge pulse obtains the same discharge energy or approximately the same energy as the preceding or succeeding discharge pulse.

[0010] Furthermore, it is preferably provided that the target current is predetermined as a function of the intermediate circuit voltage by means of a pre-stored characteristic curve. The characteristic curve is stored in particular in a non-volatile memory of a control unit or a controller, for example a power electronics device. The characteristic curve pre-determines the target current for the respective discharge pulse as a function of the currently applied intermediate circuit voltage. This ensures that the discharge pulse with the optimum discharge energy is reliably set until the intermediate circuit voltage is discharged.

[0011] Particularly preferably, the characteristic curve is determined by previous experiments and / or calculations and is then stored as described above. The characteristic curve can also be implemented in the form of a lookup table.

[0012] According to another embodiment of the invention, it is preferably provided that the actual current is detected by feedback. It is thereby possible to compare and adjust the set current with respect to a target current. For this purpose, the duration of the discharge pulse is again taken into account as a control variable. If the target current has already been programmed via a characteristic curve according to the previously advantageous embodiments, it is thereby possible to set the pulse energy significantly more precisely.

[0013] In addition, it is preferably provided that the corresponding pulse width or duration is determined according to the pre-charge duration of the gate driver of the corresponding semiconductor switch. Each semiconductor switch is usually assigned a device driver, by which the corresponding semiconductor switch is switched in a conductive or non-conductive manner. Since the conduction switching itself requires a certain duration until the threshold voltage of the semiconductor switch is exceeded and the semiconductor switch begins to receive current (here the so-called pre-charge duration is mentioned), this pre-charge duration is taken into account when determining the pulse width, so as to approximately obtain the pulse width or current pulse width actually set. In particular, for this purpose, a particularly determined or fixed time value corresponding to the pre-charge duration is added to the theoretical pulse width required to achieve the discharge energy. It is thereby ensured that the total pulse width includes not only the required pulse width but also the pre-charge duration, so that the desired discharge energy is reliably ensured. The pulse width then corresponds to the total pulse width minus the pre-charge duration.

[0014] Furthermore, it is preferably provided that the respectively converted pulse energy of the discharge pulse is approximately calculated, in particular assuming a triangular current signal, and that the set pulse width of the charging pulse following the discharge pulse is predetermined as a function of the converted pulse energy. The duration or pulse width of the discharge pulse is thus set or predetermined as a function of the pulse energy converted with the preceding, in particular immediately preceding, discharge pulse, in order to achieve the best results with regard to the accuracy of the pulse energy by varying the semiconductor parameters. In particular, the following formula is used for the preferred approximate calculation with the aid of a triangular signal:

[0015]

[0016] Here, E p corresponds to the pulse energy of the discharge pulse, I^ corresponds to the measured or approximated current peak value, V DC corresponds to the current intermediate circuit voltage, and t ist corresponds to the pulse width.

[0017] Preferably, the actually achieved charging pulse width or actual duration is detected, in particular measured by means of a sensor device suitable for this purpose, and used for predefining the duration for the discharge pulse or a subsequent discharge pulse. The duration for the discharge pulse or a subsequent discharge pulse is thus set as a function of the actually achieved pulse width of the discharge pulse in order to ensure the same or approximately the same pulse energy.

[0018] Preferably, in order to generate the discharge process, one of the semiconductor switches is switched permanently conductive and the other of the semiconductor switches is actuated repeatedly or in a pulsed manner. In particular, the semiconductor switch for the positive high voltage potential is actuated permanently and the semiconductor switch for the negative high voltage potential is actuated in a pulsed manner, or vice versa.

[0019] The device according to the invention having the features of claim 9 is distinguished in that the control unit is specially designed to carry out the method according to the invention. This results in the advantages already mentioned.

[0020] The power electronics device according to the invention having the features of claim 10 is distinguished in that the device is designed according to the invention. This results in the advantages already mentioned.

[0021] The computer program according to the invention having the features of claim 11 is distinguished in that, when it is executed, it carries out the method according to the invention. This results in the advantages already mentioned.

[0022] The storage medium according to the invention having the features of claim 12 is distinguished by a computer program according to the invention which can be executed on a computer, for example a computing unit of a control unit.

[0023] The drive train according to the invention having the features of claim 13 has a power electronics device as described above and in particular an electric machine and / or an electrical energy storage device for supplying electrical energy to the electric machine. The drive train is operated by the power electronics device according to the method according to the invention. The advantages mentioned above are thus obtained.

[0024] A vehicle according to the invention, in particular a motor vehicle, having the features of claim 14 is distinguished by a drive train according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Further advantages and preferred features and feature combinations are obtained in particular from the preceding description and from the claims. The invention will be explained in more detail below with reference to the accompanying drawings. For this purpose, it is shown:

[0026] Figure 1 A half-bridge of a power electronics device is shown in a simplified diagram,

[0027] Figure 2A A diagram is shown for explaining an advantageous method for operating a power electronic device, and

[0028] Figure 2B A diagram is shown for explaining the time course of the discharge pulses,

[0029] Figure 3A A method is shown in which energy precontrol is performed as a function of the current.

[0030] Figure 3B An embodiment of an energy regulation is shown for which the converted pulse energy is calculated, and

[0031] Figure 3C An energy control is shown in which the discharge pulse width is measured. DETAILED DESCRIPTION

[0032] Figure 1 A power electronic device 1 is shown in a simplified diagram, which is designed, for example, as an inverter for an electric motor of an electric vehicle. The power electronic device 1 has a half-bridge 2, which has a first semiconductor switch 3 and a second semiconductor switch 4 connected in series with each other. The first semiconductor switch 3 is electrically connected to a positive potential of a supply voltage (+), in particular a high voltage, for example, and the second semiconductor switch 4 is electrically connected to a ground connection or to a negative potential of a supply voltage (-), in particular a high voltage. A phase 5 of the motor, for example U, V or W, is connected between the two semiconductor switches 3, 4. By controlling the semiconductor switches 3, 4, the phase 5 of the motor can be loaded with an operating current in a targeted manner. In addition, an intermediate circuit capacitor 6 is connected in parallel to the series circuit of the semiconductor switches 3, 4, and the supply voltage V DC The voltage drops via the intermediate circuit capacitor.

[0033] A so-called gate driver 7 is connected upstream of each semiconductor switch 3 , 4 , which switches the respective semiconductor switch 3 , 4 in a conducting or non-conducting manner. In this context, only the gate driver 7 is shown for the semiconductor switch 3 .

[0034] In order to discharge the intermediate circuit capacitor 6, one of the semiconductor switches, hitherto semiconductor switch 4, i.e., the low-side semiconductor switch, is fully turned on, and the other semiconductor switch of the semiconductor switches, i.e., semiconductor switch 3 or the high-side semiconductor switch, is pulsed or repeatedly operated by a gate driver 7 for a predetermined duration in order to achieve a soft short circuit.

[0035] According to a further embodiment, the low-side semiconductor switch is pulsed and the high-side semiconductor switch is permanently switched on in order to carry out the discharge process. By means of the increased gate series resistor 8, it is achieved that the semiconductor switch 3 is switched on only slowly. Depending on the gate voltage, a half-bridge cross-current is set which discharges the capacitance of the intermediate circuit capacitor 6 or the entire intermediate circuit. This cross-current is converted into short pulses by actuating the semiconductor switch 3, such as in Figure 1 , as indicated by the corresponding symbols in . The pulses are pulsed at a fixed clock frequency. The power loss that occurs is reduced via the first semiconductor switch 3, which has the full intermediate circuit voltage at the time of the pulse and is operated in particular in linear mode. The energy obtained from the intermediate circuit capacitor 6 is converted into heat in the semiconductor switch 3 and is preferably discharged via the cooling system of the power electronic device 1. The problem that arises here is that in the case of constant current control, when a lower voltage of the intermediate circuit is reached, the pulse energy no longer fully utilizes the full potential of the power electronic device 1 and tends to overload the power module 1 in the case of high voltages.

[0036] Figure 2B The time course of the gate voltage signal and the current I of the discharge pulse are shown.

[0037] It is proposed that the current I of the discharge pulse is approximately calculated as I^ by means of a triangular signal according to the following equation by the method described below:

[0038]

[0039] Here, E p represents pulse energy, I^ represents current peak value, V DC represents the intermediate circuit voltage, and t ist represents the duration of the discharge pulse. It is shown that, with constant peak current and pulse width, the intermediate circuit voltage V DC Decline, pulse energy E p Linear decrease. Due to the DIBL effect, a slightly wider charging pulse must be set in order to achieve the same current, but this does not have a particularly large impact on the method.

[0040] With the voltage-dependent adaptation of the current and therefore also of the pulse width, a constant pulse energy is advantageously set for the discharge pulse of the discharge process, whereby the discharge rate of the intermediate circuit is significantly increased also in the region of lower voltages of the intermediate circuit, as for example in Figure 2A As shown in . The voltage curve decreases exponentially rapidly by the advantageous method.

[0041] Figure 2AIn order to explain an advantageous method for discharging the intermediate circuit, a diagram is shown which shows the current I and the voltage U over the time t. The previous voltage curve VD0 and the advantageous voltage curve produced by the method described below are shown, which has VD1 and an exponential drop. The diagram also shows a constant discharge current i0 and a charging current i1 adapted by the advantageous method, which at a maximum charging current i max With the minimum charging current i min Stretching in a stepped manner.

[0042] According to a first embodiment of the advantageous method, the pulse energy is pre-controlled by tracking the charging current i1 as a function of the currently applied intermediate circuit voltage VD1. For this purpose, a characteristic curve is stored in a non-volatile memory of a control unit 9, which controls the power electronic device 1 and in particular a part of the power electronic device 1. The characteristic curve is selected such that it predetermines a target current or a target current range (i min -i max ), and therefore with a higher peak current for a smaller intermediate circuit voltage V DC The pulse energy E of the discharge pulse is kept constant or approximately constant. The current is therefore tracked in such a way that the same pulse energy is always obtained from the intermediate circuit for each discharge pulse. DC The voltage drops in a quadratic manner, so an exponential discharge characteristic of the half bridge 2 appears, as shown by the curve VD1.

[0043] According to the second embodiment, the converted pulse energy E is adjusted to a target value according to the above-mentioned approximation formula. For this purpose, the pulse width of the corresponding discharge pulse, that is, the predetermined duration, is used as a control variable, and the current level of the corresponding discharge pulse is thus changed accordingly. In this case, the intermediate circuit voltage V is acquired, in particular in the controller 9, in particular in the calculation unit of the controller 9. DC The current voltage value and the current peak value I peak And the current pulse width t ist For pulse width t ist , predetermining that the control time of the output discharge pulse is reduced by a fixed time value t fix , which corresponds to the time elapsed for precharging the gate of the semiconductor switch 3 in the absence of a through current through the semiconductor switch 3. Thus, considering the precharging duration t fix , in order to obtain the actual pulse width: t ist =t on -t fix .

[0044] Since different batches of power semiconductors 3 , 4 may have different transfer characteristics, these deviations are compensated by taking the pulse width into account by setting a constant or identical pulse energy E. As a result, all components achieve approximately the same discharge time despite the different transfer characteristics of the individual semiconductor switches.

[0045] FIG. 3A to FIG. 3C A control loop is shown to explain and summarize the method described above.

[0046] according to Figure 3A In the embodiment, according to the target current I soll To adjust the actual current I ist First, measure the current intermediate circuit voltage V DC , and with I min and I max The target current I is determined in the form of a control window as described above. Soll =f(V DC ). At least if the actual current leaves the minimum current I min With the maximum current I max The adjustment window between the two is based on the adjustment difference I ist -I soll To adapt the new target pulse width or duration t on Then, it is preferred to reduce or increase the duration t on Subsequently, a discharge pulse is set by means of a controller, in particular by actuating the semiconductor switch 3. Ist Take measurements (I mess ) and feeds it back to the control loop for the subsequent pulse or the subsequent discharge pulse. In particular, the target current is compared with the actual current by the comparator 10 of the controller 9 and the pulse duration t for the subsequent discharge pulse is determined. on .

[0047] according to Figure 3B The target pulse energy E Soll As a basis for energy regulation, the actual duration or the actual pulse width t Ist In this case, the duration t is determined or predetermined for the subsequent pulses as a function of the pulse energy. on , and is set by the regulator or controller 9 and in particular the semiconductor switch 3. As in the above exemplary embodiment, the actual current I flowing through the semiconductor bridge 2 is measured. Ist In addition, the actual pulse width or actual duration t of the discharge pulse is also calculated. IstIn particular, for this purpose, the pulse width t of the actual entire setting is determined by means of the equation described above. on and precharge duration t fix To calculate the actual set pulse width. According to the actual current and the actual duration t Ist , especially according to the intermediate circuit voltage V DC The controller 9 calculates the final set pulse energy E Ist , and feeds it back to the control unit. Ist , now considering the minimum energy E min and the maximum energy E max The duration t of the next discharge pulse is determined under the condition on Here, it is preferred to set the pulse width to the energy adjustment window. If the calculated energy value is not at the minimum energy E min With the maximum energy E max If the pulse duration t on .

[0048] Figure 3C A further exemplary embodiment is shown which differs from the above exemplary embodiment in that the actual pulse duration t ist Not calculated, but measured mess For this purpose, a sensor device 11 is used, for example, which monitors or measures the pulse duration t of the provided discharge pulse. ist_mess And as the converted pulse energy E Ist This makes it possible to adjust the pulse energy even more precisely and to compensate for unknown influences occurring due to semiconductor properties or unknown semiconductor parameters.

Claims

1. A method for operating a power electronic device (1), in particular an inverter or a rectifier, the power electronic device having at least one half-bridge (2) with two semiconductor switches (3, 4) connected in series and at least one intermediate circuit capacitor (6) connected in parallel with the series connection of the semiconductor switches (3, 4), wherein: In order to carry out a discharging process for discharging the at least one intermediate circuit capacitor (6), the two semiconductor switches (3, 4) are controlled to generate a plurality of discharge pulses in such a way that the two semiconductor switches are switched for each discharge pulse for a predetermined duration (t on ) are switched simultaneously and are conductive, characterized in that the semiconductor switches (3, 4) are controlled in accordance with an intermediate circuit voltage applied to an intermediate circuit capacitor (6) of the power electronic device (1) in such a way that the pulse energy (E) of the discharge pulses of the discharge process is the same or almost the same.

2. The method according to claim 1, characterized in that According to the intermediate circuit voltage or the target current (I soll ) to predetermine the duration (t on ).

3. The method according to claim 2, characterized in that According to the intermediate circuit voltage (V DC ) to predetermine the duration or the target current (I soll ).

4. The method according to claim 3, characterized in that The characteristic curve is acquired in advance by experiments and / or calculations and is stored in particular in a non-volatile memory of the power electronic component (1).

5. The method according to any one of the preceding claims, characterized in that According to the actual current (I ist ) to predetermine the target current (I soll ).

6. The method according to claim 5, characterized in that Depending on the pre-charging duration (t fix ) to predetermine the corresponding duration (t on ).

7. The method according to any one of the preceding claims, characterized in that In particular, the respectively converted pulse energy (E ist ), and according to the converted pulse energy (E ist ) to predetermine the predetermined duration (t on ).

8. The method according to any one of the preceding claims, characterized in that The actual discharge pulse width (t ist ) is detected, in particular measured, and used for predefining the duration (t on ).

9. A device for operating a power electronic component (1), in particular an inverter or a rectifier, wherein: The power electronic device (1) has at least one half-bridge (2) with two semiconductor switches (3, 4) connected in series and at least one intermediate circuit capacitor (6) connected in parallel with the series circuit of the semiconductor switches (3, 4), and is characterized by a controller (9) which is specially designed to implement the method according to any one of claims 1 to 8.

10. A power electronic device (1), in particular an inverter or a rectifier, comprising at least one half-bridge (2) having two series-connected semiconductor switches (3, 4) and at least one intermediate circuit capacitor (6), characterized in that The device according to claim 9. 11 . Computer program comprising instructions which, when the computer program is executed, in particular by a device according to claim 9 , carry out the method according to claim 1 .

12. A machine-readable storage medium having stored thereon a computer program according to claim 11. 13 . A drive train having a power electronic device according to claim 10 and in particular an electric machine and / or an electric energy store for supplying the electric machine with electrical energy.

14. A vehicle, in particular a motor vehicle, having a drive train according to claim 13.

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