CN113595374B

CN113595374B - Active discharge method and controller of power converter

Info

Publication number: CN113595374B
Application number: CN202110908064.1A
Authority: CN
Inventors: 杜恩利; 张震
Original assignee: Hefei Yangguang Electric Power Technology Co ltd
Current assignee: Hefei Yangguang Electric Power Technology Co ltd
Priority date: 2021-08-09
Filing date: 2021-08-09
Publication date: 2023-04-07
Anticipated expiration: 2041-08-09
Also published as: CN113595374A

Abstract

The invention provides an active discharge method and a controller of a power converter, wherein in the method, after an active discharge instruction is received, at least two conversion circuits in the power converter are controlled to work in a matching way, so that a capacitor in the power converter is discharged through a discharge circuit; namely, the energy consumption on the capacitor is realized through the matching work of at least two conversion circuits, so that the maintenance electric shock is avoided; and no hardware circuit is needed to be added, so that the device has the advantages of volume and cost. In addition, the redundant discharge mode and the conversion circuit discharge mode are executed at the same time or mutually stand-by, so that the redundant processing of active discharge can be realized, the discharge failure caused by the failure of any discharge mode can be avoided, the discharge function of the capacitor can be still completed after the failure of any discharge mode is ensured, the high-voltage safety is realized, and the reliability of active discharge is improved.

Description

Active discharge method and controller of power converter

Technical Field

The present invention relates to the field of power electronics technologies, and in particular, to an active discharging method and a controller for a power converter.

Background

A high-voltage battery-powered power converter, such as a power converter in an electric vehicle, has a high-voltage energy storage device, i.e., a high-voltage capacitor, such as capacitor Cbk shown in fig. 1, between the positive and negative poles of the dc bus, and further includes a capacitor CBUS at the output terminal of each boost circuit because the boost circuit is provided in the power converter. When the high-voltage battery is powered off, if the two capacitors Cbk and CBUS are not discharged, the corresponding voltage lasts for a certain time. If the power converter is maintained, the electric shock danger exists for the working personnel. Therefore, after the high-voltage battery of the whole vehicle is powered off, the capacitor of the whole vehicle should be discharged in time.

Disclosure of Invention

In view of this, the present invention provides an active discharging method and a controller for a power converter, so as to discharge a capacitor in time after a high voltage battery of a vehicle is powered off.

In order to achieve the above purpose, the embodiments of the present invention provide the following technical solutions:

the invention provides an active discharge method of a power converter, wherein the preceding stage of an inverter circuit in the power converter is provided with at least two conversion circuits, and each conversion circuit comprises a switching tube bridge arm and an inductor; the active discharge method comprises the following steps:

judging whether an active discharging instruction is received or not;

and if the active discharge instruction is received, controlling at least two conversion circuits to work cooperatively so as to discharge the capacitor in the power converter through the discharge circuit until the voltage on the capacitor is less than a preset safe voltage.

Optionally, the capacitor includes: the first capacitor is arranged between the input end of each conversion circuit and the positive and negative electrodes of the parallel buses, and the second capacitor is arranged between the output end of each conversion circuit and the positive and negative electrodes of the parallel buses;

in the active discharging method, controlling at least two of the conversion circuits to work cooperatively so as to discharge a capacitor in the power converter through a discharging circuit, includes:

and controlling a loop of a conversion circuit discharge mode formed by the corresponding conversion circuit and the second capacitor, and discharging the first capacitor and the second capacitor by taking the inductor in the corresponding conversion circuit as the discharge circuit.

Optionally, the controlling the corresponding conversion circuit and the second capacitor to form a loop of a conversion circuit discharging manner, and discharging the first capacitor and the second capacitor by using an inductor in the corresponding conversion circuit as the discharging circuit includes repeatedly performing:

controlling at least two conversion circuits and the second capacitor to form a first loop so as to discharge the second capacitor through the inductor in the corresponding conversion circuit until the voltage on the second capacitor is equal to the voltage on the first capacitor;

and controlling at least one conversion circuit, the first capacitor and the second capacitor to form a second loop, and charging the second capacitor by using the voltage on the first capacitor until a charging stop condition is met.

Optionally, controlling at least two of the conversion circuits and the second capacitor to form a first loop includes:

and controlling a switching tube in one half bridge arm in at least one conversion circuit to work in a chopping mode, controlling a switching tube in the other half bridge arm in at least one conversion circuit to be switched on, and switching tubes to be switched off so as to enable the current flowing through the corresponding inductor to be a preset calibration current.

Optionally, the current directions of the inductors in the conversion circuit are opposite in the two operation modes.

Optionally, controlling at least one of the conversion circuits to form a second loop with the first capacitor and the second capacitor includes:

and controlling at least one conversion circuit to work in a boosting mode, so that the corresponding conversion circuit, the first capacitor and the second capacitor form a second loop.

Optionally, the charging stop condition is: the voltage on the first capacitor drops by half.

Optionally, controlling at least two of the converter circuits to work cooperatively to discharge a capacitor in the power converter through a discharge circuit, further includes:

and discharging the capacitor in a manner of matching at least one redundant discharge manner with the discharge manner of the conversion circuit.

Optionally, at least two discharging modes are executed sequentially or simultaneously.

Optionally, when at least two discharging modes are executed successively:

executing the redundant discharge mode, and executing the discharge mode of the conversion circuit if the redundant discharge mode fails to meet a first preset discharge requirement; alternatively, the first and second electrodes may be,

after the conversion circuit discharge mode is executed, if a second preset discharge requirement is not met, the redundancy discharge mode is executed.

Optionally, the redundant discharge mode is:

and controlling the inverter circuit to output reactive power according to the position of the motor rotor, and discharging the capacitor by taking a motor stator winding as the discharge circuit in the redundant discharge mode.

Optionally, the redundant discharge mode is:

and controlling a switching tube in the inverter circuit to directly discharge and serve as the discharge circuit in the redundant discharge mode, and converting the energy on the capacitor into desaturation energy of the switching tube.

Optionally, when an additional discharge circuit is arranged between the positive electrode and the negative electrode of the parallel bus at the output end of each conversion circuit, the redundant discharge mode is as follows:

and controlling the extra discharge circuit to be conducted, and taking a discharge resistor in the extra discharge circuit as the discharge circuit in the redundant discharge mode to discharge the capacitor.

Optionally, the first preset discharge requirement includes: after the first preset duration, the voltage between the anode and the cathode of the output parallel bus of each conversion circuit is smaller than the first preset voltage.

Optionally, the second preset discharge requirement is the same as the first preset discharge requirement, or the second preset discharge requirement includes: and the voltage on the first capacitor and the voltage on the second capacitor are both smaller than a preset safety voltage.

The second aspect of the invention also provides a controller of the power converter, which is in communication connection with a vehicle control unit of an electric vehicle to receive an active discharge instruction; and for performing the method of active discharging of a power converter as described in any of the paragraphs above with respect to the first aspect.

Optionally, the controller is further configured to control a power system of the electric vehicle.

The active discharging method of the power converter provided by the invention controls at least two converting circuits in the power converter to work in a matching way after receiving an active discharging instruction, so that a capacitor in the power converter is discharged through a discharging circuit; namely, the energy consumption on the capacitor is realized through the matching work of at least two conversion circuits, so that the maintenance electric shock is avoided; and no hardware circuit is needed to be added, so that the device has the advantages of volume and cost.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings to be used in the description of the embodiments or the prior art will be briefly introduced below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a power converter according to an embodiment of the present invention;

FIG. 2 is a flow chart of an active discharging method of a power converter according to an embodiment of the present invention;

FIG. 3 is a partial flow chart of an active discharging method of a power converter according to an embodiment of the present invention;

fig. 4a and fig. 4b are schematic diagrams of two current paths when the conversion circuit of the power converter provided by the embodiment of the invention discharges;

fig. 5a and 5b are two other flowcharts of an active discharging method of a power converter according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of a power converter with additional discharge circuits according to an embodiment of the present invention;

fig. 7 is a schematic diagram of a current path when the converter circuit of the power converter according to the embodiment of the present invention performs a boost operation.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In this application, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a component of' 8230; \8230;" does not exclude the presence of additional identical elements in the process, method, article, or apparatus that comprises the element.

The invention provides an active discharging method of a power converter, which is used for discharging a capacitor in time after a high-voltage battery of a whole vehicle is powered off.

Referring to fig. 1, at least two conversion circuits are arranged at a front stage of an inverter circuit in the power converter; the inverter circuit is composed of S1 to S6, and the conversion circuit at least includes a switching tube bridge arm and an inductor, such as a boost circuit, specifically referring to fig. 1, wherein L1, Q1 and Q2 constitute one conversion circuit, and L2, Q3 and Q4 constitute another conversion circuit; in addition, two conversion circuits are shown in fig. 1 as an example, and in practical application, more conversion circuits may be provided, and input ends and output ends of the conversion circuits are connected in parallel to form a preceding stage conversion module. A first capacitor Cbk is arranged between the anode and the cathode of the input-end parallel bus of each conversion circuit, a second capacitor CBUS is arranged between the anode and the cathode of the output-end parallel bus of each conversion circuit, both capacitors belong to the power converter, and after the UDC of the high-voltage battery is powered off, very high voltage exists, which brings electric shock danger to maintenance work.

Referring to fig. 2, the active discharge method of the power converter includes:

s101, judging whether an active discharging instruction is received.

In general, after the power of the high-voltage battery of the electric vehicle is lost, the vehicle control unit detects the situation, and sends an active discharge instruction to the controller of the power system, and the controller receives the active discharge instruction, and then executes step S102.

And S102, controlling at least two conversion circuits to work cooperatively so as to discharge the capacitor in the power converter through the discharge circuit until the voltage on the capacitor is less than the preset safe voltage.

Each conversion circuit comprises an inductor which can be used as a discharge circuit. Specifically, if the on-off control is performed on the switching tubes in the at least two conversion circuits through the controller, the corresponding inductors and the second capacitor CBUS can form a loop due to the parallel connection relationship of the corresponding conversion circuits, and then the energy on the second capacitor CBUS can be consumed by taking the corresponding inductors as the discharge circuit, so that the discharge of the second capacitor CBUS is realized; since the energy on the first capacitor Cbk can be transmitted to the second capacitor CBUS through the conversion circuit, the first capacitor Cbk can also be indirectly discharged through the above process; therefore, the discharge of the capacitor in the power converter is realized, and the maintenance electric shock is avoided.

According to the active discharging method of the power converter, through the principle, at least two conversion circuits work in a matching mode, energy consumption on a capacitor is achieved, and further maintenance electric shock is avoided; and no hardware circuit is needed to be added, so that the device has the advantages of volume and cost.

On the basis of the above embodiment, step S102 includes: and controlling the corresponding conversion circuit and the second capacitor to form a loop of the conversion circuit discharging mode, and discharging the first capacitor and the second capacitor by taking the inductor in the corresponding conversion circuit as a discharging circuit.

Referring to fig. 3, this step specifically includes the loop execution:

s201, controlling at least two conversion circuits and a second capacitor to form a first loop so as to discharge the second capacitor through inductors in the corresponding conversion circuits until the voltage on the second capacitor is equal to the voltage on the first capacitor.

Since the second capacitance CBUS is located after each conversion circuit, the voltage on the second capacitance CBUS will be higher than the voltage on the first capacitance Cbk; after the power of the high-voltage battery is lost, the voltage on the second capacitor CBUS may be directly discharged until the voltages of the two are equal, the discharging operation at this time may be stopped, and step S202 is executed.

S202, controlling at least one conversion circuit, the first capacitor and the second capacitor to form a second loop, and charging the second capacitor by using the voltage on the first capacitor until the charging stop condition is met.

When the voltage of the second capacitor CBUS is equal to the voltage of the first capacitor Cbk, the at least one conversion circuit may be controlled to operate in the boost mode, so that the at least one conversion circuit, the first capacitor Cbk and the second capacitor CBUS form a second loop, the second capacitor CBUS is charged by the voltage of the first capacitor Cbk, and step S201 is executed again after the charging is stopped.

As the second capacitor CBUS is charged by the voltage on the first capacitor Cbk, the voltage on the first capacitor Cbk is decreased, and the voltage on the second capacitor CBUS is increased; the charge stop condition may specifically be: the voltage on the first capacitor Cbk is reduced by half, namely the voltage on the first capacitor Cbk is reduced to 1/2 of the voltage of the conversion circuit before the conversion circuit works; of course, other values, such as 1/3, etc., are also possible, and are merely exemplary and not limiting; depending on the specific application environment, are all within the scope of the present application.

And repeatedly executing the steps S201 and S202 until the voltage of the Cbk on the first capacitor and the voltage of the second capacitor CBUS both decrease to be less than the preset safe voltage, so that the electric shock hazard can be avoided in the maintenance work.

In the above embodiment, the step S201 specifically includes: and controlling a switching tube in one half bridge arm in at least one conversion circuit to work in a chopping mode, controlling a switching tube in the other half bridge arm in at least one conversion circuit to be switched on, and switching tubes to be switched off so as to enable the current flowing through the corresponding inductor to be a preset calibration current.

In practical application, the lower tube in one conversion circuit can be controlled to work in a chopping mode, and the upper tube in the other conversion circuit is controlled to be conducted, and the upper tube in one conversion circuit can also be controlled to work in the chopping mode, and the lower tube in the other conversion circuit is controlled to be conducted, which depends on the specific application environment, and the control method and the control device are all within the protection scope of the application.

Taking the two-level DCDC conversion module formed by two parallel conversion circuits shown in fig. 1 as an example, if the lower tube in one conversion circuit is controlled to operate in the chopping mode and the upper tube in the other conversion circuit is controlled to be on, in practical application, the switching tubes Q1 and Q4 may be controlled to be off, the switching tube Q2 is controlled to be on, and the switching tube Q3 operates in the chopping mode, at this time, the current path is as shown in fig. 4 a; alternatively, the switching tubes Q2 and Q3 may be controlled to be turned off, the switching tube Q4 is turned on, and the switching tube Q1 operates in the chopping mode, in which case the current path is as shown in fig. 4 b. In both modes, the controller controls the current flowing through the inductors L1 and L2 to be the preset calibration current I, and the value of the preset calibration current I can be calibrated in an off-line state. And the current flowing through the inductors L1 and L2 is in the opposite direction. The specific situation that the upper tube in one conversion circuit is controlled to work in a chopping mode and the lower tube in the other conversion circuit is conducted is similar to the above situation and is not shown one by one.

In either way, the second capacitor CBUS may be discharged.

In this embodiment, two conversion circuits are connected in parallel for explanation, but in practical application, there may be 3 or more conversion circuits, and the discharge processing is performed in a similar manner, and details are not repeated.

In the above embodiment, in order to increase the reliability of the active discharge, another discharge method may be set as a redundancy (hereinafter, referred to as a redundant discharge method) and the two discharge methods are set as backup for each other in practical application, that is, on the basis of the above embodiment, in step S102, the method further includes: and discharging the capacitor in a manner of at least one redundant discharge in cooperation with the discharge manner of the conversion circuit.

Moreover, the two discharging modes can be executed simultaneously, can also be executed successively and are mutually standby; when the execution is performed successively, the specific execution sequence can be two types:

(1) As shown in fig. 5a, the redundancy discharging method is performed first, and if the redundancy discharging method fails to satisfy the first preset discharging requirement, the converting circuit discharging method is performed. The first preset discharge requirement may specifically be: after the first preset time period T1, the voltage between the anode and the cathode of the output parallel bus of each conversion circuit is smaller than a first preset voltage U1. That is, if the discharge effect of the redundant discharge mode fails to make the voltage between the positive and negative electrodes of the parallel bus at the output end of each conversion circuit smaller than the first preset voltage U1 after the first preset time period T1, step S102 is executed.

(2) As shown in fig. 5b, the conversion circuit discharge mode is executed first, and if the second preset discharge requirement is not satisfied, the redundancy discharge mode is executed. The second preset discharge requirement may be the same as the first preset discharge requirement, or the second preset discharge requirement may also include: the voltage on the first capacitor Cbk and the voltage on the second capacitor CBUS are both smaller than a preset safety voltage U2; depending on the specific application environment, are all within the scope of the present application.

In practical applications, the redundant discharge mode may be any one of the following modes:

(1) And controlling the inverter circuit to output reactive power according to the position of the motor rotor, and discharging the capacitor by taking the motor stator winding as a discharge circuit in a redundant discharge mode.

(2) And the switch tube in the inverter circuit is controlled to directly discharge and is used as a discharge circuit in a redundant discharge mode, and the energy on the capacitor is converted into the desaturation energy of the switch tube.

(3) When an extra discharge circuit (including R1 and Q5 shown in fig. 6) is arranged between the output end of each conversion circuit and the positive and negative electrodes of the parallel bus, the extra discharge circuit is controlled to be turned on, and a discharge resistor (such as R1 shown in fig. 6) in the extra discharge circuit is used as a discharge circuit in a redundant discharge mode to discharge the capacitor.

In practical applications, there is a possibility of failure in all three modes, for example, failure of the switching tube Q5 may cause failure in the mode (3), and failure of any switching tube in the inverter circuit may also cause failure in the modes (1) and (2); in the inverter circuit discharge system, a failure of any switching tube also causes a failure of the system. The redundant discharge mode and the conversion circuit discharge mode are executed simultaneously or are mutually standby, so that the redundant processing of active discharge can be realized, the discharge failure caused by the failure of any discharge mode is avoided, the discharge function of the capacitor can be still completed after the failure of any discharge mode is ensured, the high-voltage safety is realized, and the reliability of active discharge is improved.

It should be noted that the method (3) is applicable to the case where the power converter originally has an additional discharge circuit, and can provide a software redundant discharge path for the power converter, so as to improve the discharge reliability. And modes (1) and (2) do not involve the addition of hardware circuits, so that the size and the cost are reduced. In addition, in the mode (2), since the through discharge of the switching tubes in the inverter circuit causes impact on the switching tubes, and the service life is reduced, the mode (1) is a preferred selection of the redundant discharge mode.

The following describes the active discharging method by taking the redundant discharging method (1) as an example, and then performing the discharging method of the conversion circuit:

1) As a controller of an electric automobile power system, after the controller receives an active discharge command of a whole automobile controller, the controller firstly adopts a mode (1) to discharge through a motor stator winding. The specific way of discharging through the motor stator winding is as follows: the controller controls the torque current to be zero and only outputs the exciting current to achieve the purpose of discharging.

2) During the discharging process of the stator winding of the motor, the controller monitors the voltage on the second capacitor CBUS, and if the voltage on the second capacitor CBUS is smaller than the first preset voltage U1 when the specified first preset time period T1 is reached, the discharging process is maintained until the discharging process is finished.

3) And if the voltage on the second capacitor CBUS is still greater than the first preset voltage U1 when the first preset time T1 is reached, stopping the discharging process of the motor stator winding. And closing the switching tubes S1 to S6 of the inverter circuit. And 4) executing the step 4), and starting the inductive discharge function of the conversion circuit.

4) And (3) judging whether the voltage U _ CBUS input to the second capacitor CBUS is lower than a safety voltage limit value, namely the preset safety voltage U2 in the above, if the voltage U _ CBUS is higher than the preset safety voltage U2, carrying out step (3), controlling the switching tubes Q1 and Q4 to be closed, switching the switching tube Q2 to be switched on, and operating the switching tube Q3 in a chopping mode (as shown in fig. 4 a), or controlling the switching tubes Q2 and Q3 to be closed, switching the switching tube Q4 to be switched on, and operating the switching tube Q1 in the chopping mode (as shown in fig. 4 b), so that the current flowing through the inductors L1 and L2 is the preset calibration current I.

5) And 4), stopping discharging when the voltage U _ CBUS on the second capacitor CBUS is equal to the voltage U _ Cbk on the first capacitor Cbk. At this time, if U _ Cbk > U2, the switching tubes Q2 and Q4 are controlled to modulate, while Q1 and Q3 are turned off, and the full bridges Q1 to Q4 operate in the boost mode, with the energy flow direction as shown in fig. 7.

6) And 5) continuing the step, and stopping the boosting mode until the voltage U _ Cbk on the first capacitor Cbk is 1/2 of the initial value of the voltage of the first capacitor Cbk before boosting. And repeating the step 4) and the step 5 until the voltage U _ Cbk on the first capacitor Cbk and the voltage U _ CBUS on the second capacitor CBUS are both lower than the preset safety voltage U2, and finishing the active discharging process.

The method can realize the mutual redundancy of the discharge mode of the motor stator winding and the discharge mode of the conversion circuit, ensure that the voltage of the capacitor is released to the safe voltage within the specified time, and realize the high-voltage safety; and any additional hardware circuit is not required to be added, the size of the power converter is reduced, and the cost is reduced.

The coordination forms and execution sequences of other circuit structures and other redundant discharge modes can be analogized and are not described in detail.

Another embodiment of the present invention further provides a controller of a power converter, which is in communication connection with a vehicle controller of an electric vehicle to receive an active discharge instruction issued by the vehicle controller; and for performing the method of active discharge of a power converter as described in any of the above embodiments.

In practical application, the controller can also be used for controlling a power system of an electric automobile, that is, the controller is a controller in the power system, and can realize the active discharge method in addition to the control of each device in the power system such as a power converter.

The specific process and principle of the active discharging method can be referred to the above embodiments, and are not described in detail herein.

All the embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, the system or system embodiments, which are substantially similar to the method embodiments, are described in a relatively simple manner, and reference may be made to some descriptions of the method embodiments for relevant points. The above-described system and system embodiments are only illustrative, wherein the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.

Those of skill would further appreciate that the various illustrative components and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the components and steps of the various examples have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

In the above description of the disclosed embodiments, the features described in the embodiments in this specification may be replaced or combined with each other to enable those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. The active discharging method of the power converter is characterized in that at least two conversion circuits are arranged at the front stage of an inverter circuit in the power converter, the conversion circuits comprise a switching tube bridge arm and an inductor, and a capacitor in the power converter comprises a first capacitor and a second capacitor; the active discharge method includes:

judging whether an active discharging instruction is received or not;

if the active discharge instruction is received, repeatedly executing the following steps until the voltage of the capacitor in the power converter is smaller than a preset safe voltage: controlling at least two conversion circuits and the second capacitor to form a first loop so as to discharge the second capacitor through the inductor in the corresponding conversion circuit until the voltage on the second capacitor is equal to the voltage on the first capacitor; and controlling at least one conversion circuit, the first capacitor and the second capacitor to form a second loop, and charging the second capacitor by using the voltage on the first capacitor until a charging stop condition is met.

2. The active discharge method of a power converter of claim 1, wherein the capacitor comprises: the first capacitor is arranged between the input end of each conversion circuit and the anode and the cathode of the parallel bus, and the second capacitor is arranged between the output end of each conversion circuit and the anode and the cathode of the parallel bus.

3. The active discharge method of power converter according to claim 1, wherein controlling at least two of said converting circuits and said second capacitor to form a first loop comprises:

4. The method of claim 3, wherein the inductors in the converter circuit have opposite current directions in the two operating modes.

5. The active discharging method of claim 1, wherein controlling at least one of the converting circuits to form a second loop with the first capacitor and the second capacitor comprises:

6. The active discharging method of a power converter according to claim 5, wherein the charge stop condition is: the voltage on the first capacitor drops by half.

7. The active discharge method of a power converter according to any of claims 2-6, wherein at least two of said converter circuits are controlled to cooperate to discharge a capacitor in said power converter through a discharge circuit, further comprising:

and discharging the capacitor in a manner of matching at least one redundant discharge mode with the discharge mode of the conversion circuit.

8. The active discharge method of a power converter according to claim 7, wherein at least two discharge modes are performed sequentially or simultaneously.

9. The active discharge method of a power converter according to claim 8, wherein at least two discharge modes are performed sequentially:

10. The active discharging method of the power converter according to claim 7, wherein the redundant discharging manner is:

11. The active discharge method of the power converter according to claim 7, wherein the redundant discharge manner is:

and controlling a switching tube in the inverter circuit to directly discharge, and converting the energy on the capacitor into desaturation energy of the switching tube as the discharge circuit in the redundant discharge mode.

12. The active discharge method of the power converter according to claim 7, wherein when an additional discharge circuit is provided between the positive and negative electrodes of the parallel bus at the output end of each of the conversion circuits, the redundant discharge mode is as follows:

13. The active discharge method of a power converter according to claim 9, wherein the first predetermined discharge requirement comprises: after the first preset duration, the voltage between the anode and the cathode of the output parallel bus of each conversion circuit is smaller than the first preset voltage.

14. The active discharge method of the power converter according to claim 9, wherein the second preset discharge requirement is the same as the first preset discharge requirement, or the second preset discharge requirement comprises: and the voltage on the first capacitor and the voltage on the second capacitor are both smaller than a preset safety voltage.

15. The controller of the power converter is characterized by being in communication connection with a vehicle control unit of an electric vehicle to receive an active discharge command; and for performing the method of active discharge of a power converter according to any of claims 1-9.

16. The controller for a power converter according to claim 15, wherein said controller is further configured to control a powertrain of said electric vehicle.