A power converter and a control method thereof

Abstract

The present invention provides a power converter and a control method thereof. In the power converter, the output side of the DC converter is respectively connected to the DC sides of two motor controllers, and the AC side of each motor controller is connected to a corresponding motor in a power system; the motors and motor controllers connected to each other are regarded as a subsystem, and the energy conversion efficiency of the subsystem is the subsystem efficiency. Since the output side voltage of the DC converter is set according to the relationship between the system efficiency and the efficiency of the first subsystem, the efficiency of the second subsystem, and the two optimal values ​​of the output side voltage of the DC converter, the system efficiency is optimized when the two motors reach their respective preset working states, that is, the optimization of the system efficiency is achieved; in addition, since the relationship between the system efficiency and the efficiencies of the two subsystems is related to the current working mode of the power system, the control method can achieve the optimization of the system efficiency of the power system in all working modes of the vehicle.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a power converter and a control method thereof. Background Art

[0002] Typically, in a power converter of a power system, the output side of a boost converter is connected to a power supply terminal of a first motor via a first motor controller, and the output side of the boost converter is also connected to a power supply terminal of a second motor via a second motor controller, wherein the first motor is mechanically connected to an engine in the power system, and the second motor is mechanically connected to an axle of a vehicle in which the power system is located.

[0003] Currently, there is a solution as follows: it optimizes the system efficiency of the power system by optimizing the overall efficiency of the second motor controller and the second motor; however, in certain operating modes of the power system, such as the series drive mode, when the overall efficiency of the second motor controller and the second motor reaches the optimal level, the system efficiency does not reach the optimal level.

[0004] Therefore, how to optimize the system efficiency of the power system in all working modes of the power system is a technical problem that needs to be solved urgently. Summary of the invention

[0005] In view of this, the present invention provides a power converter and a control method thereof, so as to optimize the system efficiency of the power system in all working modes of the power system.

[0006] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0007] On one hand, the present application provides a control method for a power converter, in which the output side of a DC converter is respectively connected to the DC sides of two motor controllers, and the AC side of each motor controller is connected to a corresponding motor in a power system; the interconnected motors and motor controllers are used as a subsystem, and the energy conversion efficiency of the subsystem is the subsystem efficiency; the control method for the power converter includes:

[0008] determining a current operating mode of the power system;

[0009] According to the current working mode, determining the relationship between the system efficiency and the first subsystem efficiency and the second subsystem efficiency;

[0010] Determine two optimal values ​​of the output side voltage of the DC converter respectively; the optimal value is the value of the output side voltage when the motor in the subsystem reaches a preset working state and the subsystem efficiency reaches an optimal state;

[0011] The output side voltage of the DC converter is set according to the relationship and the two optimal values.

[0012] Optionally, the first subsystem is mechanically connected to an engine in a power system, and the second subsystem is mechanically connected to an axle in a vehicle in which the power system is located; and determining the relationship between the system efficiency and the efficiency of the first subsystem and the efficiency of the second subsystem according to the current working mode includes:

[0013] If the current working mode is the pure electric driving mode or the first parallel driving mode, the power system is running in the first state, and the system efficiency is only related to the efficiency of the second subsystem;

[0014] If the current working mode is the series drive mode, the second parallel drive mode or the regenerative braking mode, then the power system is running in the second state, and the system efficiency is related to both the first subsystem efficiency and the second subsystem efficiency;

[0015] If the current working mode is the parking power generation mode or the third parallel drive mode, the power system is running in the third state at this time, and the system efficiency is only related to the efficiency of the first subsystem.

[0016] Optionally, the first parallel driving mode is a parallel driving mode in which the first subsystem is in a standby state and the second subsystem is in an electric state;

[0017] The second parallel driving mode is a parallel driving mode in which the first subsystem is in a power generation state and the second subsystem is in a motoring state;

[0018] The third parallel driving mode is a parallel driving mode in which the first subsystem is in a power generation state and the second subsystem is in a standby state.

[0019] Optionally, setting the output side voltage of the DC converter according to the relationship and the two optimal values ​​includes:

[0020] If the power system operates in the first state, the output side voltage is set to: the optimal value corresponding to the second subsystem;

[0021] If the power system operates in the third state, the output side voltage is set to: the optimal value corresponding to the first subsystem;

[0022] If the power system operates in the second state, the output side voltage is set by optimizing the system efficiency between the two optimal values ​​by utilizing the relationship.

[0023] Optionally, the output side voltage is set by optimizing the system efficiency between the two optimal values ​​by utilizing the relationship, including:

[0024] Determine whether the two optimal values ​​are equal;

[0025] If the two optimal values ​​are equal, setting the output side voltage to the optimal value;

[0026] If the two optimal values ​​are not equal, the following steps are performed in sequence:

[0027] Selecting an intermediate voltage value between the two optimal values;

[0028] According to the relationship, at the two optimal values ​​and each of the intermediate voltage values, the system efficiency when the two subsystems reach their respective preset working states is determined, and the output side voltage of the DC converter is set to the voltage value corresponding to the maximum system efficiency.

[0029] Optionally, determining a current operating mode of the power system includes:

[0030] Obtaining the issued mode instruction, and determining the current working mode according to the mode instruction; or,

[0031] The current operating mode is determined according to the current power flow direction in the power converter.

[0032] Optionally, determining the current operating mode according to a current power flow direction in the DC converter includes:

[0033] If the power of the DC converter flows only to the second subsystem, the current working mode is a pure electric drive mode or a first parallel drive mode; the first parallel drive mode is a parallel drive mode in which the first subsystem is in a standby state and the second subsystem is in an electric state;

[0034] If there is power flowing from the first subsystem to the second subsystem, the current working mode is a series drive mode or a second parallel drive mode; the second parallel drive mode is a parallel drive mode in which the first subsystem is in a power generation state and the second subsystem is in a motoring state;

[0035] If the power of the first subsystem flows to the DC converter but does not flow to the second subsystem, the current working mode is the parking power generation mode or the third parallel driving mode; the third parallel driving mode is a parallel driving mode in which the first subsystem is in a power generation state and the second subsystem is in a standby state;

[0036] If power flows from the second subsystem to the DC converter, the current operating mode is a regenerative braking mode.

[0037] Optionally, determining the optimal value includes:

[0038] According to the preset working state, the optimal value is found in a pre-stored optimal value distribution map.

[0039] Optionally, the preset working state includes: a preset output torque and a preset speed of the motor.

[0040] Optionally, after setting the output side voltage of the DC converter, the method further includes:

[0041] Determining whether the output side voltage is greater than or equal to a preset upper limit value;

[0042] If the output side voltage is greater than or equal to the preset upper limit value, setting the output side voltage to the preset upper limit value;

[0043] If the output side voltage is less than the preset upper limit value, determining whether the output side voltage is less than or equal to a preset lower limit value;

[0044] If the output side voltage is less than or equal to the preset lower limit value, setting the output side voltage to the preset lower limit value;

[0045] If the output side voltage is greater than the preset lower limit value, the output side voltage is maintained.

[0046] A second aspect of the present application provides a power converter, comprising: a DC converter and two motor controllers; wherein:

[0047] The input side of the DC converter is connected to the high-voltage battery;

[0048] The AC side of each motor controller is connected to a corresponding motor in the power system; the motor mechanically connected to the output shaft of the engine in the power system is a first motor, and the motor mechanically connected to the wheel axle in the vehicle in which the power system is located is a second motor;

[0049] The controller in the DC converter is respectively connected to the controller in each motor controller for communication;

[0050] The controller in the DC converter or the controller in the motor controller is used to execute the control method of the power converter as described in any one of the first aspects of the present application.

[0051] Optionally, the DC converter is a boost converter.

[0052] A third aspect of the present application provides a power system, comprising: an engine, two motors and a power converter as described in any one of the second aspect of the present application.

[0053] Optionally, it also includes: a power separation device; wherein:

[0054] The output shaft of the engine is mechanically connected to the wheel axle through the power separation device.

[0055] A fourth aspect of the present application provides a vehicle, comprising: a power system as described in any one of the third aspects of the present application.

[0056] It can be seen from the above technical solution that the present invention provides a control method for a power converter, in which the output side of the DC converter is connected to the DC side of two motor controllers respectively, and the AC side of each motor controller is connected to a corresponding motor in the power system; the interconnected motor and motor controller are regarded as a subsystem, and the energy conversion efficiency of the subsystem is the subsystem efficiency. In the control method, since the output side voltage of the DC converter is set according to the relationship between the system efficiency and the efficiency of the first subsystem, the efficiency of the second subsystem, and the two optimal values ​​of the output side voltage of the DC converter, the system efficiency can be optimized when the two motors reach their respective preset working states, that is, the system efficiency can be optimized; in addition, since the relationship between the system efficiency and the efficiencies of the two subsystems is related to the current working mode of the power system, the control method can optimize the system efficiency of the power system in all working modes of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0058] Figure 1 and Figure 2 They are structural schematic diagrams of two implementation modes of the power system;

[0059] Figure 3 for Figure 2 A schematic diagram showing the power flow of the power system in pure electric driving mode;

[0060] Figure 4a and Figure 4b They are Figure 2 Schematic diagram of two power flows of the power system in series drive mode;

[0061] Figure 5a for Figure 2 A schematic diagram showing the power flow of the power system in the first parallel drive mode;

[0062] Figure 5b and Figure 5c They are Figure 2 Schematic diagram of two power flows of the power system in the second parallel drive mode;

[0063] Figure 6a for Figure 2 A schematic diagram of the power flow of the power system in the third parallel drive mode;

[0064] Figure 6b for Figure 2 A schematic diagram of the power flow of the power system in the fourth parallel drive mode;

[0065] Figure 7a and Figure 7b They are Figure 2 Schematic diagram of two power flows of the power system in regenerative braking mode;

[0066] Figure 8 for Figure 2 A schematic diagram showing the power flow of the power system in the parking power generation mode;

[0067] Fig. 9 A schematic diagram of a flow chart of an implementation of a method for controlling a power converter provided in an embodiment of the present application;

[0068] Fig.10a is a first subsystem efficiency distribution diagram obtained when the output side voltage of the DC converter is equal to 220V;

[0069] Fig.10b is a first subsystem efficiency distribution diagram obtained when the output side voltage of the DC converter is equal to 450V;

[0070] Fig.11 is the optimal value distribution diagram corresponding to the efficiency of the first subsystem;

[0071] Fig.12 is the optimal value distribution diagram corresponding to the efficiency of the second subsystem;

[0072] Fig.13 and Fig.14 They are flow charts of two other implementation modes of the power converter control method provided in the embodiments of the present application. DETAILED DESCRIPTION

[0073] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0074] In this application, relational terms such as first and second, etc. are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0075] In order to optimize the system efficiency of the power system in all operating modes of the power system, an embodiment of the present application provides a control method for a power converter.

[0076] In the power converter 10, see Figure 1 or Figure 2 The input side of the DC converter 11 is connected to the high-voltage battery 20, and the output side of the DC converter 11 is respectively connected to the DC side of the first motor controller 12 and the DC side of the second motor controller 13; the AC side of the first motor controller 12 is connected to the power supply end of the first motor 40 in the power system, and the AC side of the second motor controller 13 is connected to the power supply end of the second motor 50 in the power system; the first motor 40 is mechanically connected to the engine 30 in the power system, and the second motor 50 is mechanically connected to the wheel axle 60 in the vehicle in which the power system is located.

[0077] Among them, the first motor 40 and the first motor controller 12 serve as the first subsystem 100, and the energy conversion efficiency of the first subsystem 100 is the first subsystem efficiency; the second motor 50 and the second motor controller 13 serve as the second subsystem 200, and the energy conversion efficiency of the second subsystem 200 is the second subsystem efficiency.

[0078] It can be seen that the power converter 10 can be used to form two power systems: Figure 1 and Figure 2 shown in Figure 1 In the power system shown, the output shaft of the engine 30 is not connected to the wheel axle 60; Figure 2 In the power system shown, the output shaft of the engine 30 is mechanically connected to the axle 60 via a power separation device 70 .

[0079] Below Figure 2 The various working modes of the power system shown are described in detail, specifically including the following working modes:

[0080] 1. Pure electric driving mode

[0081] engine First Motor Power separation device Second motor High voltage battery Standby Standby disconnect electric Discharge

[0082] From the above table, we can see that Figure 3 As shown, in the pure electric drive mode, the power flows as follows: high-voltage battery 20 → DC converter 11 → second motor controller 13 → second motor 50 → axle 60 , that is, high-voltage battery 20 → DC converter 11 → second subsystem 200 → axle 60 .

[0083] 2. Series drive mode

[0084] engine First Motor Power separation device Second motor High voltage battery run Power Generation disconnect electric Discharge or charge

[0085] From the above table, we can see that Figure 4a or Figure 4b As shown, in the series drive mode, the power flow is divided into two directions. The first direction is: engine 30→first motor 40→first motor controller 12→second motor controller 13→second motor 50→axle 60, that is, engine 30→first subsystem 100→second subsystem 200→axle 60; the second direction is: high-voltage battery 20→DC converter 11→second motor controller 13→second motor 50→axle 60, that is, high-voltage battery 20→DC converter 11→second subsystem 200→axle 60, or, engine 30→first motor 40→first motor controller 12→DC converter 11→high-voltage battery 20, that is, engine 30→first subsystem 100→DC converter 11→high-voltage battery 20.

[0086] 3. Four parallel drive modes

[0087]

[0088]

[0089] From the above table, we can see that Figure 5a As shown, in the first parallel drive mode, the power flow is divided into two directions. The first direction is: high-voltage battery 20→DC converter 11→second motor controller 13→second motor 50→axle 60, that is, high-voltage battery 20→DC converter 11→second subsystem 200→axle 60, and the second direction is: engine 30→power separation device 70→axle 60.

[0090] like Figure 5b or Figure 5c As shown, in the second parallel drive mode, the power flow is divided into three directions, the first direction is: engine 30→first motor 40→first motor controller 12→second motor controller 13→second motor 50→axle 60, that is: engine 30→first subsystem 100→second subsystem 200→axle 60; the second direction is: high-voltage battery 20→DC converter 11→second motor controller 13→second motor 50→axle 60, that is, high-voltage battery 20→DC converter 11→second subsystem 200→axle 60, or, engine 30→first motor 40→first motor controller 12→DC converter 11→high-voltage battery 20, that is: engine 30→first subsystem 100→DC converter 11→high-voltage battery 20; the third direction is: engine 30→power separation device 70→axle 60.

[0091] like Figure 6a As shown, in the third parallel drive mode, power flows in two directions. The first direction is: engine 30 → first motor 40 → first motor controller 12 → DC converter 11 → high-voltage battery 20, that is, engine 30 → first subsystem 100 → DC converter 11 → high-voltage battery 20, and the second direction is: engine 30 → power separation device 70 → wheel axle 60.

[0092] like Figure 6b As shown, in the fourth parallel drive mode, the power flow is: engine 30 →power separation device 70 →wheel axle 60.

[0093] From this, it can be inferred that: the parallel drive mode in which the first motor is in standby state and the second motor is in electric state is the first parallel drive mode, the parallel drive mode in which the second motor is in electric state is the second parallel drive mode, the parallel drive mode in which the first motor is in generating state and the second motor is in standby state is the third parallel drive mode, and the parallel drive mode in which the first motor is in standby state and the second motor is in standby state is the fourth parallel drive mode.

[0094] 4. Regenerative braking mode

[0095] engine First Motor Power separation device Second motor High voltage battery Run or Standby Standby or power generation Close or open Power Generation Charge

[0096] From the above table, we can see that Figure 7a As shown, in the regenerative braking mode, if the first motor 40 is in standby mode and the power separation device 70 is disconnected, the power flows in one direction, specifically: the axle 60 → the second motor 50 → the second motor controller 13 → the DC converter 11 → the high-voltage battery 20, that is, the axle 60 → the second subsystem 200 → the DC converter 11 → the high-voltage battery 20; Figure 7bAs shown, if the first motor 40 generates electricity and the power separation device 70 is closed, the power flow direction also includes another direction based on the above, specifically: axle 60→power separation device 70→first motor 40→first motor controller 12→DC converter 11→high-voltage battery 20, that is, axle 60→power separation device 70→first subsystem 100→DC converter 11→high-voltage battery 20.

[0097] 5. Parking power generation mode

[0098] engine First Motor Power separation device Second motor High voltage battery run Power Generation disconnect Standby Charge

[0099] From the above table, we can see that Figure 8 As shown, in the parking power generation mode, the power flow is: engine 30 → first motor 40 → first motor controller 12 → DC converter 11 → high-voltage battery 20, that is, engine 30 → first subsystem 100 → DC converter 11 → high-voltage battery 20.

[0100] In addition, the system efficiency of the power system includes the energy conversion efficiency of the DC converter and the efficiencies of the two subsystems. In practical applications, since the energy conversion efficiency of the DC converter does not change much with the change of the output side voltage of the DC converter, the change of the energy conversion efficiency of the DC converter is no longer considered when the control method optimizes the system efficiency.

[0101] In practical applications, due to Figure 2 When the power separation device 70 in the power system shown is disconnected, Figure 2 The mechanical structure of the power system shown is similar to Figure 1 The powertrain shown is the same, so Figure 1 The power flow direction in each operating mode of the power system shown is basically the same as the corresponding operating mode described above, and will not be repeated here.

[0102] See also Fig. 9 , the control method specifically comprises the following steps:

[0103] S110: Determine the current working mode of the power system.

[0104] In practical applications, there are two ways to determine the current working mode of the power system. The first way is to obtain a mode instruction issued, and determine the current working mode of the power system according to the mode instruction.

[0105] It should be noted that the mode instruction is issued by the vehicle controller, which includes information representing the current working mode of the power system. Therefore, the current working mode of the power system can be determined based on the mode instruction.

[0106] The second determination method is to determine the current working mode of the power system according to the current power flow direction in the power converter.

[0107] The following conclusions can be derived from the power flow under each working mode introduced above:

[0108] If the power of the DC converter only flows to the second subsystem, the current operating mode of the power system is a pure electric drive mode or a first parallel drive mode, and the power system operates in a first state; wherein, the first parallel drive mode is a parallel drive mode in which the first subsystem is in a standby state and the second subsystem is in an electric state.

[0109] If power flows from the first subsystem to the second subsystem, the current operating mode of the power system is the series drive mode or the second parallel drive mode, and the power system operates in the second state; wherein the second parallel drive mode is a parallel drive mode in which the first subsystem is in a power generation state and the second subsystem is in an electric state.

[0110] If the power of the first subsystem flows to the DC converter but not to the second subsystem, the current operating mode of the power system is the parking power generation mode or the third parallel drive mode, and the power system operates in the third state; wherein the third parallel drive mode is a parallel drive mode in which the first subsystem is in the power generation state and the second subsystem is in the standby state.

[0111] If there is power flowing from the second subsystem to the DC converter, the current working mode of the power system is the regenerative braking mode, and the power system operates in the second state.

[0112] It should be noted that in actual applications, when the motor is in standby state, the corresponding motor controller is also in standby state. When the motor is in generating state, the power flow of the corresponding motor controller is from its own AC side to its own DC side. When the motor is in electric state, the power flow of the corresponding motor controller is from its own DC side to its own AC side. Therefore, when the motor is in standby state, the corresponding subsystem is also in standby state. When the motor is in generating state, the corresponding subsystem is also in generating state. When the motor is in electric state, the corresponding subsystem is also in electric state.

[0113] In practical applications, the power flow in the power converter can be represented by the power of the DC converter and the two subsystems. However, since the subsystem power is approximately equal to the power of its own motor, the power flow in the power converter can be represented by the power of the DC converter and the power of the two motors. If the positive directions of the three powers are specified as Figure 1 or Figure 2 As shown, the directions and magnitudes of the three powers in each working mode are described in the following table:

[0114]

[0115]

[0116] Among them, P1 is the power of the first motor, P2 is the power of the second motor, and P3 is the power of the DC converter.

[0117] S120. Determine the relationship between the system efficiency and the efficiencies of the two subsystems according to the current working mode.

[0118] If the current working mode is the pure electric driving mode or the first parallel driving mode, the power system is running in the first state, and the system efficiency is only related to the efficiency of the second subsystem. The specific relationship is: η sys =η2, where η sys is the system efficiency, and η2 is the efficiency of the second subsystem.

[0119] If the current working mode of the power system is the parking power generation mode or the third parallel drive mode, the power system is running in the second state, and the system efficiency is only related to the efficiency of the first subsystem. The specific relationship is: η sys =η1, where η1 is the efficiency of the first subsystem.

[0120] If the current working mode of the power system is the series drive mode, the second parallel drive mode or the regenerative braking mode, the power system is running in the third state, and the system efficiency is related to the first subsystem efficiency and the second subsystem efficiency; at this time, the specific relationship is as follows:

[0121] If the current working mode of the power system is the series drive mode or the second parallel drive mode, and the power of the second motor is greater than the power of the first motor, the specific relationship is: η sys =η2×(a1×η1+b1), a1=P1 / P2, b1=(P2-P1) / P2, where P1 is the power of the first motor and P2 is the power of the second motor.

[0122] If the current working mode of the power system is the series drive mode or the second parallel drive mode, and the power of the second motor is less than the power of the first motor, the specific relationship is: η sys =η1×(a2×η2+b2), a2=P2 / P1, b2=(P1-P2) / P1, where P1 is the power of the first motor and P2 is the power of the second motor.

[0123] If the current working mode of the power system is the regenerative braking mode, the specific relationship is: η sys =c×η1+d×η2, c=P1 / (P1+P2), d=P2 / (P1+P2).

[0124] It should be noted that the first parallel driving mode, the second parallel driving mode, and the third parallel driving mode are all described in detail above and will not be repeated here.

[0125] In summary, the relationship between the system efficiency and the efficiency of the two subsystems in each working mode is as described in the following table:

[0126]

[0127]

[0128] It should be noted that in actual applications, the relationship between the system efficiency and the efficiency of the two subsystems in each working mode is obtained based on the analysis of the power flow between the devices in each working mode, and is pre-stored in the power converter; in addition, the power of the first motor and the power of the second motor can be determined based on their respective current output torque and current angular velocity, which will not be elaborated here.

[0129] S130, respectively determine two optimal values ​​of the output side voltage of the DC converter.

[0130] Among them, the optimal value is the value of the output side voltage of the DC converter when the motor in the subsystem reaches the preset working state and the subsystem efficiency reaches the optimal state; in actual applications, the preset working state of the motor includes: the preset output torque and preset speed of the motor; wherein the preset speed can also be replaced by the preset angular velocity, which is not specifically limited here and is within the protection scope of this application.

[0131] In practical applications, the optimal value is obtained from a pre-stored optimal value distribution map according to the preset working state of the motor; and the optimal value distribution map is obtained through simulation testing and optimization. Taking the optimal value distribution map corresponding to the efficiency of the first subsystem as an example, the specific process is as follows:

[0132] First, through simulation tests, multiple first efficiency distribution diagrams are obtained under different output side voltages of the DC converter, for example, Fig.10a The first subsystem efficiency distribution diagram shown is obtained when the output side voltage of the DC converter is equal to 220V. Fig.10b The first subsystem efficiency distribution diagram shown is obtained when the output side voltage of the DC converter is equal to 450V.

[0133] It should be noted that the number of values ​​of the output side voltage of the DC converter when obtaining the subsystem efficiency distribution diagram can be set according to the specific situation. No specific limitation is made here and all are within the protection scope of this application.

[0134] Afterwards, in the multiple first subsystem efficiency distribution diagrams, power optimization is performed for the same preset working state, and the output side voltage of the DC converter corresponding to the maximum first subsystem efficiency is selected for each preset working state, so as to obtain the optimal value distribution diagram corresponding to the first subsystem efficiency, such as Fig.11 ( Fig.11 Only five values ​​of the output side voltage of the DC converter are shown as an example).

[0135] It should be noted that the process of obtaining the optimal value distribution diagram corresponding to the efficiency of the second subsystem is the same as the above process, which will not be repeated here; taking the five values ​​of the output side voltage of the DC converter as an example, the optimal value distribution diagram corresponding to the efficiency of the second subsystem is obtained as follows: Fig.12 shown.

[0136] S140: setting the output side voltage of the DC converter according to the above relationship and the two obtained optimal values.

[0137] The following is a detailed description of how to set the output voltage of the DC converter in different working modes, as follows:

[0138] If the power system operates in the first state, that is, the system efficiency is only related to the efficiency of the second subsystem, the output side voltage of the DC converter is set to: the optimal value corresponding to the second subsystem.

[0139] If the power system operates in the third state, that is, the system efficiency is only related to the efficiency of the first subsystem, the output side voltage of the DC converter is set to: the optimal value corresponding to the first subsystem.

[0140] If the power system operates in the second state, that is, the system efficiency is related to both the first subsystem efficiency and the second subsystem efficiency, the output side voltage of the DC converter is set by optimizing the system efficiency between two optimal values ​​using the above relationship.

[0141] The following is a detailed description of how to set the output voltage of the DC converter by optimizing the system efficiency between two optimal values ​​using the above relationship. The specific process is as follows: Fig.13 As shown, the specific steps include:

[0142] S210: Determine whether two optimal values ​​are equal.

[0143] If the two optimal values ​​are equal, step S220 is executed; if the two optimal values ​​are not equal, step S230 and step S240 are executed in sequence.

[0144] S220, setting the output side voltage of the DC converter to an optimal value.

[0145] S230: Select an intermediate voltage value between two optimal values.

[0146] In practical applications, the number of intermediate voltage values ​​selected between two optimal values ​​is limited and may be determined according to specific circumstances. No specific limitation is made here and all are within the protection scope of this application.

[0147] S240. According to the above relationship, at two optimal values ​​and each intermediate voltage value, determine the system efficiency when the two subsystems reach their respective preset working states, and set the output side voltage of the DC converter to the voltage value corresponding to the maximum system efficiency.

[0148] Take the current working mode of the power system as the series drive mode or the second parallel drive mode, and the power of the second motor is greater than the power of the first motor as an example, that is, η sys =η2×(a1×η1+b1) as an example, how to set the output side voltage of the DC converter is described as follows:

[0149] According to the preset working state of the first motor, that is, its preset output torque and preset angular velocity, the optimal value corresponding to the efficiency of the first subsystem is found from the optimal value distribution map corresponding to the efficiency of the first subsystem, and is recorded as the first optimal value V dcop1 According to the preset working state of the second motor, that is, its preset output torque and preset angular velocity, the optimal value corresponding to the efficiency of the second subsystem is found from the optimal value distribution map corresponding to the efficiency of the second subsystem, which is recorded as the second optimal value V dcop2 .

[0150] If V dcop1 =V dcop2 , then the output voltage V of the DC converter dcop =V dcop1 =V dcop2 .

[0151] If V dcop1 ≠V dcop2 , then assume that V dcop1 and V dcop2 Select n intermediate voltage values ​​between, namely V dcopn1 、V dcopn2 ...V dcopnn ; If V dcop1 <V dcop2 , then V dcop1 <V dcopn1 <V dcopn2 <... <V dcopnn <V dcop2 , if V dcop1 >V dcop2 , then V dcop1 >Vdcopn1 >V dcopn2 >..>V dcopnn >V dcop2 .

[0152] Afterwards, according to η sys =η2×(a1×η1+b1), at each of the n+2 voltage values, the system efficiency under the preset working state of the two motors is determined, that is:

[0153] η sys1 (V dcop1 ,Te1,ω1,Te2,ω2)=η2(V dcop1 ,Te2,ω2)·(a1·η1(V dcop1 ,Te1,ω1)+b1)

[0154] η sys2 (V dcop2 ,Te1,ω1,Te2,ω2)=η2(V dcop2 ,Te2,ω2)·(a1·η1(V dcop2 ,Te1,ω1)+b1)

[0155] …

[0156] η sysn (V dcopn ,Te1,ω1,Te2,ω2)=η2(V dcopn ,Te2,ω2)·(a1·η1(V dcopn ,Te1,ω1)+b1)

[0157] Among them, Te1 is the preset output torque of the first motor, ω1 is the preset angular velocity of the first motor, Te2 is the current output torque of the second motor, and ω2 is the preset angular velocity of the second motor.

[0158] Finally, the obtained n+2 system efficiencies are compared to select the maximum system efficiency, and the voltage value corresponding to the maximum system efficiency is set as the output side voltage of the DC converter.

[0159] It should be noted that when the current operating mode of the power system is the series drive mode or the second parallel drive mode, and the power of the second motor is greater than the power of the first motor, or when the current operating mode of the power system is the regenerative braking mode, the method for setting the output side voltage of the DC converter is the same as above and will not be repeated here.

[0160] Since the output side voltage of the DC converter is set according to the relationship between the system efficiency and the efficiencies of the two subsystems and the two optimal values ​​of the output side voltage of the DC converter, the system efficiency can be optimized when the two motors reach their respective preset working states, that is, the system efficiency can be optimized; in addition, since the relationship between the system efficiency and the efficiencies of the two subsystems is related to the current working mode of the power system, the control method can optimize the system efficiency of the power system in all working modes of the vehicle.

[0161] Another embodiment of the present application provides another implementation of a control method for a power converter. The process of this implementation is as follows: Fig.14 As shown, based on the above implementation, after step S140, the following steps are further included:

[0162] S310: Determine whether the output side voltage of the DC converter is greater than or equal to a preset upper limit value.

[0163] If the output side voltage of the DC converter is greater than or equal to the preset upper limit value, step S320 is executed; if the output side voltage of the DC converter is less than the preset upper limit value, step S330 is executed.

[0164] Among them, the preset upper limit value is a voltage value set according to the actual situation of the DC converter, which is not specifically limited here and is within the protection scope of this application.

[0165] S320, setting the output side voltage of the DC converter to a preset upper limit value.

[0166] S330: Determine whether the output side voltage of the DC converter is less than or equal to a preset lower limit value.

[0167] If the output side voltage of the DC converter is less than or equal to the preset lower limit value, step S340 is executed; if the output side voltage of the DC converter is greater than the preset lower limit value, step S350 is executed.

[0168] Among them, the preset lower limit value is a voltage value set according to the actual situation of the DC converter, which is not specifically limited here and is within the protection scope of this application.

[0169] S340, setting the output side voltage of the DC converter to a preset lower limit value.

[0170] S350, maintaining the output side voltage of the DC converter.

[0171] In this implementation, by setting a preset upper limit value and a preset lower limit value, damage to the DC converter due to over-regulation is avoided, thereby improving the safety of the power converter.

[0172] Another embodiment of the present application provides a power converter for a power system, and its specific structure can be found in Figure 1 or Figure 2 , specifically including: a DC converter and two motor controllers; the connection relationship between the components is as follows:

[0173] The input side of the DC converter is connected to the high-voltage battery 20 ; the AC side of each motor controller is connected to a corresponding motor in the power system.

[0174] The motor mechanically connected to the engine 30 in the power system is the first motor 40 , and the motor controller connected to the first motor 40 is the first motor controller 12 . Therefore, the subsystem including the first motor 40 and the first motor controller 12 is the first subsystem 100 .

[0175] The motor mechanically connected to the wheel axle 60 in the vehicle where the power system is located is the second motor 50, and the motor controller connected to the second motor 50 is the second motor controller 13. Therefore, the subsystem including the second motor 50 and the second motor controller 13 is the second subsystem 200.

[0176] The controller in the DC converter is respectively connected to the controller in each motor controller for communication. The controller in the DC converter or the controller in any motor controller is used to execute the control method of the power converter provided in the above embodiment.

[0177] Optionally, the DC converter may be a boost converter or a buck converter, which is not specifically limited here and is within the protection scope of the present application.

[0178] In practical applications, the controller in the DC converter and the controller in each motor controller can also be integrated into an independent controller in the power converter. The two implementation methods can be determined according to the specific situation and are both within the protection scope of this application.

[0179] Another embodiment of the present application provides a power system, the specific structure of which can be seen in Figure 1 , specifically including: an engine 30, two motors and a power converter 10 of the power system provided in the above embodiment; the connection relationship between the various components has been described in detail in the above embodiment and will not be repeated here.

[0180] Another embodiment of the present application provides another implementation of the power system, see Figure 2 This embodiment is specifically based on the above embodiment and further includes: a power separation device 70; the output shaft of the engine 30 is mechanically connected to the wheel axle 60 through the power separation device 70.

[0181] Another embodiment of the present application provides a vehicle, which specifically includes: a main structure and a power system provided in the above embodiment; wherein the axle belongs to the main structure.

[0182] For the above description of the disclosed embodiments, the features recorded in each embodiment in this specification can be replaced or combined with each other, so that professionals in the field can implement or use the present application. The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as above with a preferred embodiment, it is not used to limit the present invention. Any technician familiar with the field can make many possible changes and modifications to the technical solution of the present invention using the methods and technical contents disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. A control method for a power converter, characterized in that: In the power converter, the input side of the DC converter is connected to the high-voltage battery, the output side of the DC converter is connected to the DC sides of two motor controllers respectively, and the AC side of each motor controller is connected to a corresponding motor in the power system; the interconnected motors and motor controllers are regarded as a subsystem, and the energy conversion efficiency of the subsystem is the subsystem efficiency; The control method of the power converter comprises: determining a current operating mode of the power system; According to the current working mode, determining the relationship between the system efficiency and the first subsystem efficiency and the second subsystem efficiency; Determine two optimal values ​​of the output side voltage of the DC converter respectively; the optimal value is the value of the output side voltage when the motor in the subsystem reaches a preset working state and the subsystem efficiency reaches an optimal state; The output side voltage of the DC converter is set according to the relationship and the two optimal values.

2. The control method of the power converter according to claim 1, characterized in that: The first subsystem is mechanically connected to an engine in a power system, and the second subsystem is mechanically connected to an axle in a vehicle in which the power system is located; and according to the current working mode, determining the relationship between the system efficiency and the efficiency of the first subsystem and the efficiency of the second subsystem includes: If the current working mode is the pure electric driving mode or the first parallel driving mode, the power system is running in the first state, and the system efficiency is only related to the efficiency of the second subsystem; If the current working mode is the series drive mode, the second parallel drive mode or the regenerative braking mode, then the power system is running in the second state, and the system efficiency is related to both the first subsystem efficiency and the second subsystem efficiency; If the current working mode is the parking power generation mode or the third parallel drive mode, the power system is running in the third state at this time, and the system efficiency is only related to the efficiency of the first subsystem.

3. The control method of the power converter according to claim 2, characterized in that: The first parallel driving mode is a parallel driving mode in which the first subsystem is in a standby state and the second subsystem is in an electric state; The second parallel driving mode is a parallel driving mode in which the first subsystem is in a power generation state and the second subsystem is in a motoring state; The third parallel driving mode is a parallel driving mode in which the first subsystem is in a power generation state and the second subsystem is in a standby state.

4. The control method of the power converter according to claim 2, characterized in that: According to the relationship and the two optimal values, setting the output side voltage of the DC converter comprises: If the power system operates in the first state, the output side voltage is set to: the optimal value corresponding to the second subsystem; If the power system operates in the third state, the output side voltage is set to: the optimal value corresponding to the first subsystem; If the power system operates in the second state, the output side voltage is set by optimizing the system efficiency between the two optimal values ​​by utilizing the relationship.

5. The control method of the power converter according to claim 4, characterized in that: By using the relationship, optimizing the system efficiency between the two optimal values ​​to set the output side voltage, including: Determine whether the two optimal values ​​are equal; If the two optimal values ​​are equal, setting the output side voltage to the optimal value; If the two optimal values ​​are not equal, the following steps are performed in sequence: Selecting an intermediate voltage value between the two optimal values; According to the relationship, at the two optimal values ​​and each of the intermediate voltage values, the system efficiency when the two subsystems reach their respective preset working states is determined, and the output side voltage of the DC converter is set to the voltage value corresponding to the maximum system efficiency.

6. The control method of a power converter according to any one of claims 1 to 5, characterized in that: Determining a current operating mode of the power system includes: Obtaining the issued mode instruction, and determining the current working mode according to the mode instruction; or, The current operating mode is determined according to the current power flow direction in the power converter.

7. The control method of the power converter according to claim 6, characterized in that: Determining the current working mode according to the current power flow direction in the DC converter includes: If the power of the DC converter flows only to the second subsystem, the current working mode is a pure electric drive mode or a first parallel drive mode; the first parallel drive mode is a parallel drive mode in which the first subsystem is in a standby state and the second subsystem is in an electric state; If there is power flowing from the first subsystem to the second subsystem, the current working mode is a series drive mode or a second parallel drive mode; the second parallel drive mode is a parallel drive mode in which the first subsystem is in a power generation state and the second subsystem is in a motoring state; If the power of the first subsystem flows to the DC converter but does not flow to the second subsystem, the current working mode is the parking power generation mode or the third parallel driving mode; the third parallel driving mode is a parallel driving mode in which the first subsystem is in a power generation state and the second subsystem is in a standby state; If power flows from the second subsystem to the DC converter, the current operating mode is a regenerative braking mode.

8. The control method of a power converter according to any one of claims 1 to 5, characterized in that: Determining the optimal value includes: According to the preset working state, the optimal value is found in a pre-stored optimal value distribution map.

9. The control method of a power converter according to any one of claims 1 to 5, characterized in that: The preset working state includes: a preset output torque and a preset rotation speed of the motor.

10. The control method of a power converter according to any one of claims 1 to 5, characterized in that: After setting the output side voltage of the DC converter, the method further comprises: Determining whether the output side voltage is greater than or equal to a preset upper limit value; If the output side voltage is greater than or equal to the preset upper limit value, setting the output side voltage to the preset upper limit value; If the output side voltage is less than the preset upper limit value, determining whether the output side voltage is less than or equal to a preset lower limit value; If the output side voltage is less than or equal to the preset lower limit value, setting the output side voltage to the preset lower limit value; If the output side voltage is greater than the preset lower limit value, the output side voltage is maintained.

11. A power converter, characterized in that: include: DC converter and two motor controllers; including: The input side of the DC converter is connected to the high-voltage battery; The AC side of each motor controller is connected to a corresponding motor in the power system; the motor mechanically connected to the output shaft of the engine in the power system is a first motor, and the motor mechanically connected to the wheel axle in the vehicle in which the power system is located is a second motor; The controller in the DC converter is respectively connected to the controller in each motor controller for communication; The controller in the DC converter or the controller in the motor controller is used to execute the control method of the power converter according to any one of claims 1 to 10.

12. The power converter according to claim 10, characterized in that: The DC converter is a boost converter.

13. A power system, characterized in that: include: An engine, two electric machines and a power converter as claimed in claim 11 or 12.

14. The power system according to claim 13, characterized in that: Also includes: Power separation device; wherein: The output shaft of the engine is mechanically connected to the wheel axle through the power separation device.

15. A vehicle, characterized in that: include: A power system as claimed in claim 13 or 14.

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