Extended-range electric drive system based on double neutral point series power supply and control method thereof

Abstract

The application provides a range-extending electric drive system based on double neutral point series power supply and a control method thereof. The system comprises a first motor, a second motor, a power battery, a power coupler, a first clutch, a second clutch, an engine and a control unit connected in a double neutral point series power supply topology. The first power input end of the power coupler is in driving connection with the first motor, and the power output end is in driving connection with the drive shaft of the vehicle. The first clutch is used for engaging or separating the driving connection between the engine and the second motor. The second clutch is used for engaging or separating the driving connection between the second motor and the second power input end of the power coupler. The control unit is used for controlling the first clutch, the second clutch, and the inverters of the first motor and the second motor. The scheme of the application can fully exert the driving / generating performance of the double neutral point series power supply topology.

Description

Technical Field

[0001] This application belongs to the field of new energy vehicle drive control technology, specifically, it relates to a range-extended electric drive system based on dual neutral point series power supply and its control method. Background Technology

[0002] Improving power performance and driving range are the key research and development directions for electric drive systems in new energy vehicles. Currently, dual-motor drive systems have gradually become the mainstream solution for high-performance new energy vehicles. For example, there are range-extended topologies that simultaneously configure generators and electric motors, as well as pure electric topologies that configure dual motors on the front and rear axles and dual motors in the center.

[0003] In Chinese Invention Patent CN119628466A, the applicant proposed a control system for a dual-neutral-point series-powered dual permanent magnet synchronous motor (PMSM). This system tracks the target DC bus voltage through a boost controller to output an equivalent duty cycle that modulates and controls the inverters of the two motors. Compared to a single-neutral-point boost structure, this dual-neutral-point series-powered topology can achieve a wider boost range. The applicant also proposed a feasible average duty cycle allocation strategy for using this topology in dual-motor pure electric drive of new energy vehicles: symmetrically allocating the equivalent duty cycle to the inverters of the two motors with 0.5 as the center.

[0004] This power supply topology can be further applied to range-extended drive systems. By working in conjunction with the engine, it can improve the power and range of pure electric drive systems, thereby adapting to more complex and varied driving scenarios. To this end, based on the boost characteristics of the dual-neutral-point series power supply topology, it is necessary to rationally determine the average duty cycle of the two motors for different vehicle operating conditions to fully utilize the driving performance of this power supply topology. Summary of the Invention

[0005] This application provides a range-extended electric drive system based on dual neutral point series power supply through embodiments. This system can flexibly select the scheme for adjusting and controlling the two motors according to the actual working conditions of the vehicle, so as to ensure that the system has a high voltage utilization rate under different working conditions.

[0006] The system includes a first motor, a second motor, and a power battery. The positive terminal of the power battery is electrically connected to the neutral point of the first motor, and the negative terminal is electrically connected to the neutral point of the second motor. The first motor and the second motor have the same DC bus voltage.

[0007] The system also includes a power coupler, a first clutch, a second clutch, an engine, and a control unit. The first power input terminal of the power coupler is connected to a first motor, and the power output terminal is connected to the vehicle's drive shaft. The first clutch engages or disengages the transmission connection between the engine and the second motor. The second clutch engages or disengages the transmission connection between the second motor and the second power input terminal of the power coupler. The control unit controls the engagement / disengagement states of the first and second clutches, the on / off state of the power coupler, and modulates the inverters of the first and second motors.

[0008] Furthermore, the control unit controls the engagement state of the first clutch and the second clutch, as well as the switching state of the power coupler, based on the vehicle operating conditions; and determines the average duty cycle of the modulation signals of the inverters of the first motor and the second motor based on the dual-motor voltage comprehensive utilization rate model, and performs switching control on each power device in the inverter based on the modulation signals.

[0009] Furthermore, the comprehensive utilization model of the dual-motor voltage is as follows:

[0010]

[0011] Where DCSUR1 and DCSUR2 are the voltage utilization rates of the first motor and the second motor, respectively, and α h1 α h1 Average duty cycle, Average_α, for the modulation signals of the inverters of the first and second motors, respectively. h For α h1 and α h2 The mean, Δα h For α h1 and α h2 The difference.

[0012] Furthermore, the control unit includes: a working mode switching module, which switches the working mode based on a preset switching strategy or in response to manual operation; a transmission state control module, which controls the engagement state of the first clutch and the second clutch, as well as the switching state of the power coupler, based on the working mode; and a duty cycle determination module, which, based on the working mode, searches for the optimal value of r and Average_α that satisfy the constraints in the dual-motor voltage comprehensive utilization rate model, with the target voltage utilization rate of at least one motor as a constraint. h and determining α based on search results h1 and / or α h2 Where r = 1 / Δα h ; Modulation control module, based on α h1 α h2Modulation signals are generated for the inverters of the first motor and the second motor, and the modulation signals are used to modulate and control the inverters of the first motor and the second motor.

[0013] Furthermore, in the dual-motor voltage utilization model, with the target voltage utilization rate of at least one motor as a constraint, the optimal value of r and Average_α that satisfy the constraint are searched. h Specifically, this includes the following operations:

[0014] Based on the dual-motor voltage comprehensive utilization rate model, a three-dimensional constraint surface for the voltage utilization rate of the first motor and a three-dimensional constraint surface for the voltage utilization rate of the second motor are generated.

[0015] Based on the operating mode and the real-time speed and target torque of at least one motor, determine the target voltage utilization rate of at least one motor.

[0016] Search for contour lines corresponding to the target voltage utilization of the at least one motor on the three-dimensional constraint surface of the voltage utilization of the at least one motor, and search for the optimal r and the corresponding Average_α based on the contour lines. h .

[0017] Optionally, the operating modes include single-motor drive mode, dual-motor drive mode, single-generator single-drive mode, and pure power generation mode.

[0018] Furthermore, when the operating mode is a single-motor drive mode: both the first clutch and the second clutch are in the disengaged state, and the power coupler is in the open state; the duty cycle determination module uses a preset α... h1 Given the value of r and the target voltage utilization rate of the first motor as constraints, search for the minimum value of r that simultaneously satisfies these constraints and its corresponding Average_α. h Then, α is determined based on the search results. h2 .

[0019] Furthermore, when the operating mode is a dual-motor drive mode: the first clutch is in a disengaged state, the second clutch is in a engaged state, and the power coupler is in an open state; the duty cycle determination module searches for the minimum value of r and the corresponding Average_α that simultaneously satisfy the target voltage utilization rate of the first motor and the second motor, using this as a constraint. h Then, α is determined based on the search results. h1 and α h2 .

[0020] Furthermore, when the operating mode is a single-generator single-drive mode: the first clutch is engaged, the second clutch is disengaged, and the power coupler is activated; the duty cycle determination module searches for the minimum value of r that simultaneously satisfies the target voltage utilization rate of the first motor and the second motor, along with the corresponding Average_α, under the constraint of the target voltage utilization rate of the first motor and the second motor. h Then, α is determined based on the search results. h1 and α h2 .

[0021] Furthermore, when the operating mode is pure power generation mode: the first clutch is engaged, the second clutch is disengaged, and the power coupler is closed; the duty cycle determination module uses a preset α... h2 Given the target voltage utilization rate of the second motor as a constraint, search for the minimum value of r that satisfies this constraint and its corresponding Average_α. h Then, α is determined based on the search results. h1 .

[0022] Optionally, the first motor and the second motor are permanent magnet synchronous motors, excitation synchronous motors, or hybrid excitation synchronous motors.

[0023] This application also provides a control method through embodiments for controlling the aforementioned range-extended electric drive system based on dual neutral point series power supply, including the following operations:

[0024] Depending on the vehicle's operating conditions, the operating mode is switched based on a preset switching strategy or in response to manual operation.

[0025] The operating mode controls the engagement state of the first clutch and the second clutch, as well as the switching state of the power coupler.

[0026] Based on the aforementioned operating mode, in the dual-motor voltage comprehensive utilization rate model, with the target voltage utilization rate of at least one motor as a constraint, we search for r and Average_α that satisfy the constraint. h and determining α based on search results h1 and / or α h2 , where α h1 α is the average duty cycle of the modulation signal of the inverter of the first motor. h2 The average duty cycle of the modulation signal of the inverter of the first motor is r = 1 / (α). h1 -α h2 ),Average_α h =(α h1 +α h2 ) / 2;

[0027] Based on α h1α h2 Modulation signals are generated for the inverters of the first motor and the second motor, and the modulation signals are used to modulate and control the inverters of the first motor and the second motor.

[0028] The range-extended electric drive system and its control method based on dual neutral point series power supply provided in this application automatically or manually switch different working modes according to various operating conditions of the vehicle. A dual-motor voltage comprehensive utilization rate model is established with the goal of improving the comprehensive voltage utilization rate. According to the specific performance requirements of the two motors under different working modes, the dual-motor voltage comprehensive utilization rate model is used to search for the optimal average duty cycle for modulation control of the two motors, thereby fully utilizing the driving / generating performance of the dual motors under the dual neutral point series power supply topology. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the architecture of an existing dual-motor drive system.

[0030] Figure 2 This is a schematic diagram of the architecture of another existing dual-motor drive system.

[0031] Figure 3 A schematic diagram of the architecture of a dual-motor drive system with a dual-neutral-point series power supply topology;

[0032] Figure 4 This is a schematic diagram of the architecture of a range-extended electric drive system based on dual neutral point series power supply and its system state in single motor drive mode, according to an embodiment of this application.

[0033] Figure 5 This is a schematic diagram of the control unit architecture of a range-extended electric drive system based on dual neutral point series power supply according to an embodiment of this application;

[0034] Figure 6 This is a schematic diagram of the system state of a range-extended electric drive system based on dual neutral point series power supply provided in the embodiments of this application under dual motor drive mode;

[0035] Figure 7 This is a schematic diagram of the system state of the range-extended electric drive system based on dual neutral point series power supply provided in the embodiments of this application in single generator single drive mode;

[0036] Figure 8 This is a schematic diagram of the system state of a range-extended electric drive system based on dual neutral point series power supply provided in the embodiments of this application in pure power generation mode.

[0037] Figure 9 This is a schematic diagram illustrating the working mode switching process of a range-extended electric drive system based on dual neutral point series power supply according to an embodiment of this application.

[0038] Figure 10 This is a schematic diagram of the three-dimensional constraint surface for the voltage utilization of the first motor and the second motor according to an embodiment of this application;

[0039] Figure 11A This is a schematic diagram illustrating the determination of the optimal boost ratio based on the voltage utilization of two motors, according to an embodiment of this application.

[0040] Figure 11B This is a schematic diagram illustrating the determination of the optimal boost ratio based on the voltage utilization rate of a motor, according to an embodiment of this application.

[0041] Figure 12 This is an equivalent circuit diagram of a range-extended electric drive system based on dual neutral point series power supply provided in the embodiments of this application in single motor drive mode;

[0042] Figure 13 This is a flowchart illustrating the process of determining the average duty cycle of a motor in a single-motor drive mode for a range-extended electric drive system based on dual neutral point series power supply according to an embodiment of this application.

[0043] Figure 14 This is a flowchart illustrating the process of determining the average duty cycle of a motor in a dual-motor drive mode for a range-extended electric drive system based on dual neutral point series power supply, according to an embodiment of this application.

[0044] Figure 15 This is a flowchart illustrating the process of determining the average duty cycle of a motor in a single generator single drive mode for a range-extended electric drive system based on dual neutral point series power supply according to an embodiment of this application.

[0045] Figure 16 This is an equivalent circuit diagram of a range-extended electric drive system based on dual neutral point series power supply provided in the embodiments of this application in pure power generation mode;

[0046] Figure 17 This is a schematic diagram illustrating the process of determining the average duty cycle of a motor in pure power generation mode for a range-extended electric drive system based on dual neutral point series power supply according to an embodiment of this application. Detailed Implementation

[0047] The present application will now be further described based on preferred embodiments and with reference to the accompanying drawings.

[0048] The vocabulary used in this specification is for illustrative purposes and is not intended to limit the scope of this application. It should also be noted that, unless otherwise expressly specified and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a direct connection, or an indirect connection via an intermediate medium; or they can refer to the internal communication between two components. Those skilled in the art will understand the specific meaning of these terms in this application.

[0049] <I. Introduction to Existing Dual-Motor Drive Solutions for New Energy Vehicles>

[0050] Currently, dual-motor systems are gradually becoming the mainstream solution for high-performance new energy vehicles, for example, Figure 1 This paper illustrates a classic dual-motor drive system, which mainly comprises two three-phase AC motors, namely motor 1 and motor 2. Each motor is connected to the power battery via a corresponding inverter, namely inverter 1 and inverter 2, for DC-AC conversion. Generally, for ease of description, motor 1 and its corresponding inverter 1 can be collectively referred to as motor 1, and motor 2 and its corresponding inverter 2 can be collectively referred to as motor 2.

[0051] like Figure 1 As shown, the two inverters are connected in parallel and are relatively independent. Without an additional voltage regulation device, the DC bus voltage is equal to the battery voltage and cannot be actively adjusted, which undoubtedly limits the application of this dual-motor drive scheme in the field of new energy vehicle drive. Figure 2 The dual-motor drive topology shown, which integrates a front-end DC-DC regulating bus voltage, actively regulates the DC bus voltage through additional power devices S0, S'0, and inductor L. While this increases the bus voltage and expands the speed range, it undoubtedly increases the size and cost of the control system. Furthermore, neither of the two dual-motor drive systems using parallel topologies can be integrated with an engine to achieve range-extended drive.

[0052] In its earlier Chinese invention patent application CN119628466A, the applicant disclosed a dual-motor drive system employing a dual-neutral-point series power supply topology, such as... Figure 3 As shown, the control system includes two permanent magnet synchronous motors (PMSMs). The positive and negative terminals of the power supply (i.e., the power battery) are connected to the neutral points of the two motors, respectively, and the two motors have the same DC bus voltage. This invention patent also proposes a scheme for controlling this dual-neutral-point series power supply topology: a boost controller tracks the target DC bus voltage to output an equivalent duty cycle (Δα). hThen, the boost distributor uses a preset distribution strategy, centering on 0.5, to distribute Δα... h The duty cycle α of the two motors is distributed evenly to obtain an average duty cycle α. h1 α h2 Finally, through the corresponding modulator, using α-based... h1 α h2 The generated modulation signal is used to modulate and control both motors. This control strategy, when applied to a dual-motor drive mode, can achieve a wider boost range.

[0053] <II. Overall Architecture of Range-Extended Electric Drive System Based on Dual Neutral Point Series Power Supply>

[0054] Because a series power supply architecture is used, therefore, Figure 3 The dual neutral point series power supply topology shown can also be applied to the range-extended electric drive system of new energy vehicles, thereby greatly expanding the scope of application of this architecture. However, the average duty cycle allocation strategy described above is only applicable to the dual-motor drive condition and is difficult to adapt to more complex and variable driving scenarios and drive conditions. Therefore, it is necessary to improve the above power supply architecture based on the boost characteristics of the dual neutral point series power supply topology and reasonably determine the average duty cycle of the two motors for different vehicle conditions in order to give full play to the drive / generation performance of this power supply topology.

[0055] To achieve the above objectives, embodiments of this application provide a range-extended electric drive system based on dual neutral point series power supply. Figure 4 A schematic diagram of the architecture of the range-extended electric drive system in a specific embodiment is shown. As shown, the system includes a dual-motor architecture with a neutral point series power supply topology, as well as a power coupler, a first clutch (i.e., clutch 1 in the figure), a second clutch (i.e., clutch 2 in the figure), an engine, and a control unit.

[0056] Specifically, such as Figure 4 As shown, the dual-motor architecture includes a first motor (i.e., motor 1 and inverter 1 in the figure), a second motor (i.e., motor 2 and inverter 2 in the figure), and a power battery. The positive terminal of the power battery is electrically connected to the neutral point N1 of the first motor, and the negative terminal is electrically connected to the neutral point N2 of the second motor. The voltage between its positive and negative terminals is u. in The inverters of the first and second motors are connected in parallel with the DC bus capacitor C, and have the same DC bus voltage u. bus .

[0057] A power coupler is disposed between the shafts of two motors and the drive shaft of the vehicle. It is used to transmit the power output from the shaft of motor 1 to the drive shaft of the vehicle independently, or to transmit the power output from the shafts of motor 1 and motor 2 to the drive shaft of the vehicle in a coupled manner. The first power input end of the power coupler is directly connected to the shaft of motor 1, and its power output end is connected to the drive shaft of the vehicle. A clutch 2 is disposed between the second power input end of the power coupler and the shaft of motor 2, allowing the transmission connection between motor 2 and the second power input end of the power coupler to be engaged or disengaged. A clutch 1 is disposed between the shaft of the engine and the shaft of motor 2, allowing the transmission connection between the engine and motor 2 to be engaged or disengaged. In the embodiments of this application, the clutch 1, clutch 2, and the power coupler connecting the two motors and the drive shaft can all be implemented in a manner known to those skilled in the art.

[0058] The control unit is used to control the engagement and disengagement of the two clutches and the switching state of the power coupler, and to modulate and control the inverters of the two motors. Figure 5 A schematic diagram of the control unit architecture is shown in one specific embodiment, with reference to... Figure 4 , Figure 5 The control unit includes a working mode switching module, a transmission state control module, a duty cycle determination module, and a modulation control module. The specific implementation of the control unit will be described in detail below with reference to the accompanying drawings.

[0059] <III. Determining and Switching Operating Modes Based on Vehicle Operating Conditions>

[0060] Because different vehicle operating conditions place different demands on the driving performance of the two motors and the charging and discharging performance of the power battery, the control unit needs to switch the engagement state of clutch 1 and clutch 2, as well as the on / off state of the power coupler, according to the different operating conditions of the vehicle, thereby putting the system in different operating modes. The above switching operation is mainly achieved through the cooperation of the operating mode switching module and the transmission state control module. Specifically, the operating mode switching module switches the operating mode based on a preset switching strategy or in response to manual operation, according to the specific operating conditions of the vehicle. The transmission state control module, based on the switched operating mode, controls the engagement state of clutch 1 and clutch 2 and the on / off state of the power coupler by sending control signals (such as switching signals or start / stop signals) to clutch 1, clutch 2, and the power coupler.

[0061] For example, in Figure 4In the illustrated embodiment, the power coupler is in the open state under the control of the control unit, and both clutch 1 and clutch 2 are in the disengaged state. At this time, the power battery is the only power source, and only the shaft of motor 1 is connected to the drive shaft of the vehicle through the power coupler. That is, it is in the working mode of motor 1 driving the vehicle alone. In this application, this working mode is called single motor drive mode or working mode ①. This working mode is applicable to all low power range working conditions, as well as to a wider range of speed ranges, i.e. high speed and low torque working conditions.

[0062] remove Figure 4 The operating mode shown can also be controlled by the control unit, allowing the range-extended electric drive system to operate in any of the following modes: Figures 6 to 8 (The control unit is not shown in the figure) shows the different operating modes.

[0063] exist Figure 6 In the operating mode shown, clutch 1 is in the disengaged state, clutch 2 is in the engaged state, and the power coupler is in the open state. At this time, the power battery also serves as the sole power source to supply power to the two motors. The torque output by the two motors drives the vehicle after being coupled through the power coupler. In this application, this operating mode is referred to as the dual-motor drive mode or operating mode ②. In this operating mode, the two motors can couple to output a larger torque, but the power supply current will also increase accordingly, resulting in a significant increase in winding copper losses. Therefore, it is suitable for operating conditions where a large torque output is expected in a short period of time, such as getting out of trouble or climbing hills.

[0064] exist Figure 7 In the operating mode shown, clutch 1 is engaged, clutch 2 is disengaged, and the power coupler is open. At this time, motor 2 acts as a generator, and the engine and power battery jointly drive motor 1. Motor 1 drives the vehicle independently through the power coupler. In this application, this operating mode is called single generator single drive mode or operating mode ③. This operating mode is suitable for high-power conditions. Because if the power battery alone provides power under high power conditions, the battery output current, i.e., the neutral line current, will be too large, and excessive copper losses will be generated when flowing through the winding. Therefore, when the power is large, the generator can charge the capacitor, thereby reducing the power battery output current. When the generator power is greater than the operating condition requirements, the remaining power can flow into the battery, i.e., charge the power battery.

[0065] exist Figure 8In the operating mode shown, clutch 1 is engaged, clutch 2 is disengaged, and the power coupler is closed. At this time, motor 2 acts as a generator, using the torque output from the engine to charge the power battery. Motor 1 does not output torque to the vehicle's drive shaft; it only acts as a boost inductor. In this application, this operating mode is referred to as the pure power generation mode or operating mode ④. This operating mode is suitable for situations where the vehicle is parked and the power battery charge is low.

[0066] Figure 9 The figure shows a flowchart of a working mode switching module switching between different working modes according to vehicle operating conditions in a specific embodiment. As shown, when the power battery charge is too low (e.g., SOC is below SOC...), the module switches between different working modes. min When the power battery's power P is 0, it can automatically enter working mode ③ or working mode ④.

[0067] If the power battery's charge exceeds the state of charge (SOC) min Furthermore, in situations such as getting out of trouble or rapid acceleration, it can enter working mode ② to output high torque by receiving instructions manually set by the driver. Otherwise, it can automatically switch between working modes ②, ③, and ④ according to the preset switching strategy and information such as the power battery power P, speed, and torque.

[0068] It should be known that Figure 9 The illustrated embodiment is only one optional operating mode switching process. Those skilled in the art can reasonably select the SOC that triggers the operating mode switching based on data such as the specific vehicle model, motor, power battery, and engine specifications. min The values ​​of parameters such as P, speed, and torque, or the values ​​of... Figure 9 The work mode switching process shown should be adjusted appropriately.

[0069] <IV. Controlling the Dual Motors with the Goal of Improving Overall Voltage Utilization>

[0070] As can be seen from the above analysis of the working modes of the electric drive system under different operating conditions, the power transmission direction and the coordination relationship between the two motors and the power battery are different when they are working in different modes. Obviously, using only the same control strategy cannot meet the high performance and high efficiency requirements under different working modes.

[0071] Therefore, this application proposes a control strategy aimed at improving the overall voltage utilization rate of the dual motors under various operating conditions, and establishes a novel dual-motor voltage utilization rate model based on this control strategy, such as... Figure 4As shown, the control unit's modulation control of inverter 1 and inverter 2 is based on the dual-motor voltage comprehensive utilization rate model to determine the average duty cycle of the modulation signals of inverter 1 and inverter 2, thereby generating the corresponding modulation signals, and using the generated modulation signals to control the switching of each power device in inverter 1 and inverter 2.

[0072] 4.1 Establishing a model for the comprehensive utilization rate of voltage between two motors

[0073] The following section first introduces the process of establishing the dual-motor voltage comprehensive utilization rate model.

[0074] For the range-extended electric drive system provided in this application, under the dual neutral point series power supply topology, the relationship between the DC bus voltage and the power battery voltage is as follows:

[0075]

[0076] Where, α h1 α h2 Let α be the average duty cycle of the modulation signal for inverter 1 and inverter 2, respectively, and 0 < α. h2 <α h1 <1. In this application, the difference between the two is Δα h This is called the equivalent duty cycle, and r is called the boost ratio, in the subsequent α h1 α h2 During the determination process, for ease of processing, it can be done according to r = 1 / (α) h1 -α h2 ) to perform calculations.

[0077] Because a dual-neutral-point series power supply topology is adopted, the neutral points of motor 1 and motor 2 are connected to the positive and negative terminals of the power battery, respectively. The significant difference from the parallel topology is that the voltage ranges of the two motors are not the same, and the changes are more complex under different operating modes. It is not possible to fully utilize the performance of both motors by simply increasing the DC bus voltage using equation (1). A more feasible strategy is to establish a dual-motor voltage comprehensive utilization model based on the analysis of the voltage utilization rate of the two motors (generally, the voltage utilization rate of a motor is the ratio of its d-axis and q-axis moduli to the voltage of the power battery) as a basis for determining a reasonable modulation signal.

[0078] Taking motor 1 as an example, under steady state, its voltage utilization rate is analyzed. Ignoring the voltage drop across the zero-axis inductance and stator resistance, based on the dual neutral point series power supply topology, equation (2) can be derived:

[0079]

[0080] in, This is the neutral point voltage to ground of motor 1.

[0081] Phase voltages of the three phases A1, B1, and C1 of motor 1 The output range can be expressed as equation (3):

[0082]

[0083] Substituting equations (1) and (2) into equation (3) yields equation (4):

[0084]

[0085] Due to α h1 -α h2 =Δα h Therefore, the usable voltage range of motor 1, as shown in equation (5), can be derived. Similarly, the usable voltage range of motor 2, as shown in equation (6), can be derived:

[0086]

[0087] Although Δα increases with the increase of the boost ratio h It will gradually decrease, α h1 With α h2 The voltages will become increasingly similar, so the sum of the voltage utilization rates of the two motors will become larger and larger, and the overall usable voltage range of the motors will become wider and theoretically can be infinitely large. However, the specific voltage utilization rate needs to be determined based on the actual average duty cycle allocation.

[0088] To study the specific voltage utilization of the two motors, the average duty cycle value Average_α is defined. h =1 / 2(α) h1 +α h2 Therefore, the average duty cycle can be distributed to both motors using equation (7):

[0089]

[0090] Equations (5)-(6) can be rewritten as:

[0091]

[0092] Let both sides of the inequality be u in Therefore, the voltage utilization rate DCSUR1 of motor 1 and the voltage utilization rate DCSUR2 of motor 2 can be determined according to equation (9):

[0093]

[0094] 4.2 Draw the three-dimensional constraint surface for the voltage utilization of the two motors and search for the optimal α. h1 α h2

[0095] According to equation (9), Average_α h With the boost ratio r as the independent variable and DCSUR1 and DCSUR2 as function values ​​respectively, a graph can be plotted as follows: Figure 10 , Figure 11A and Figure 11B The voltage utilization three-dimensional constraint surface of motor 1 and motor 2 is shown.

[0096] Clearly, since the values ​​of DCSUR1 and DCSUR2 represent any set of r and Average_α... h The value corresponds to the voltage utilization rate that motors 1 and 2 can achieve. Therefore, in order to meet the performance requirements of the drive system, after determining the operating mode, the target voltage utilization rate of motors 1 and / or 2 should be determined according to different operating modes. Then, in the region on the above three-dimensional constraint surface that is not less than the target voltage utilization rate (indicating that the voltage utilization rate of motors 1 and / or 2 is greater than or equal to the target voltage utilization rate), the minimum value of r is searched (this value represents the target voltage utilization rate that can be achieved with the minimum boost ratio; in this application, this value is taken as the optimal value of r), thereby determining Average_α. h The values ​​are selected to ultimately determine the average duty cycle α of motor 1 and motor 2. h1 α h2 .

[0097] In the embodiments of this application, such as Figure 5 As shown, the above-mentioned three-dimensional constraint surface based on the voltage utilization of the two motors and the search for the optimal α h1 α h2 This is achieved through a duty cycle determination module. For example, in a certain operating mode, both motors need to output power, or one motor outputs power while the other generates electricity. After obtaining information such as the accelerator pedal depth or the engine's high-efficiency power generation range, and combining this with real-time speed information, the target torque that motor 1 and motor 2 should achieve can be determined. Then, the real-time speed and target torque of each motor are substituted into their respective voltage equations to determine the target voltage utilization rate of the two motors. Figure 11A On the three-dimensional constraint surface of the voltage utilization rates of the two motors shown, contour lines corresponding to the target voltage utilization rates of each motor are intercepted. These two contour lines are then projected onto the plane where DCSUR = 0, resulting in two parabolic projection lines. These two projection lines respectively enclose... Figure 11A The intersection of the blue and orange areas in the diagram corresponds to the region where the voltage utilization rates of both motors are simultaneously satisfied (i.e., Figure 11A(The red area in the image) Search for the point corresponding to the minimum value of r within this red area. This point is the optimal point for achieving the minimum boost ratio while simultaneously maximizing the voltage utilization of both motors. Use a set of r and Average_α corresponding to this point... h The value of can be used as the optimal r and Average_α for this working mode. h Then, α can be determined using equation (7). h1 α h2 .

[0098] For example, in certain operating modes, a single motor is used as a single drive or generator; for instance, motor 1 drives the vehicle alone. In this case, α h1 It can be determined in advance, and α h2 The value of has little impact on system performance. Therefore, the target voltage utilization rate can be determined solely based on the real-time speed and target torque of motor 1. Furthermore, the contour line corresponding to the target voltage utilization rate can be extracted from the three-dimensional constraint surface of motor 1's voltage utilization rate. Projecting this contour line onto the plane where DCSUR = 0 yields the region satisfying the voltage utilization rate of motor 1 (i.e.,...). Figure 11B (The blue area) In this case, the area can be drawn with a preset α. h1 The constraint r ~ Average_α h Curves, for example Figure 11B The red dashed line on the right side represents α. h1 =0.5 corresponds to r ~ Average_α h The curve, with the red dashed line to its left corresponding to α. h1 r ~ Average_α less than 0.5 h From the curve, we can know that α h1 r ~ Average_α greater than 0.5 h The curve is located at α h1 =0.5 corresponds to r ~ Average_α h The right side of the curve.

[0099] Furthermore, the point in the blue region where the curve has the smallest r can be found, satisfying α. h1 Given the given values, the target voltage utilization rate of motor 1 is achieved with the minimum boost ratio, using a set of r and Average_α values ​​corresponding to that point. h The value of can be used as the optimal r and Average_α for this working mode. h Then, α can be determined using equation (7). h2 The value of .

[0100] α was obtained from the search. h1 α h2 Then, the modulation control module uses αh1 α h2 Modulation signals are generated for inverter 1 and inverter 2 respectively, and modulation control is performed on inverter 1 and inverter 2 to fully utilize the driving or power generation performance of the two motors under various vehicle operating conditions. The generation of modulation signals and the modulation control method of the inverters are known to those skilled in the art and will not be described in detail here.

[0101] 4.3 α under different working modes h1 α h2 Search Strategy

[0102] The following section, in conjunction with the accompanying drawings, discusses α under each working mode. h1 α h2 The search strategy will be explained.

[0103] a. Single motor drive mode

[0104] like Figure 4 As shown, in this operating mode, both clutches 1 and 2 are disengaged, motor 1 drives the vehicle alone, and the three-phase windings of motor 2 are used only as part of the boost inductor to regulate the bus voltage and voltage utilization. Its equivalent circuit diagram is shown below. Figure 12 As shown, the average duty cycle of motor 1 can be preset to a value that puts it in a more ideal working state, for example, preset to its optimal average duty cycle (α). h1 =0.5), the control strategy for this working mode can be adopted. Figure 13 The process shown is as follows:

[0105] First, the average duty cycle of motor 1 is preset (for example, α is set). h1 =0.5,) and then calculate the required voltage u according to the motor voltage equation shown in equation (10). d1 u q1 Among them, i d1 i q1 The current distribution strategy can be used to determine the target torque required by the vehicle.

[0106]

[0107] In the above formula, u d u q u0 represents the voltages along the d, q, and 0 axes, respectively; i d i q i0 represents the d-axis current, q-axis current, and 0-axis current, respectively; R s L is the stator resistance. d L q L0 represents the d-axis, q-axis, and 0-axis inductances, respectively; ω e Let ψ be the electric angular velocity. f It is a permanent magnet flux linkage.

[0108] The motor voltage equation shown in equation (10) is applicable to the voltage calculation of permanent magnet synchronous motors. That is, in the embodiments of this application, motor 1 and motor 2 can be permanent magnet synchronous motors. In addition, in some other optional embodiments, motor 1 and motor 2 can also be three-phase motors that can realize power output and power generation, such as excitation synchronous motors or hybrid excitation synchronous motors. Accordingly, their motor voltage equations can be replaced by equation (10).

[0109] Get u d1 u q1 Then, the target voltage utilization rate of motor 1 can be obtained. Then, in Figure 11B The contour line corresponding to the target voltage utilization rate is intercepted on the three-dimensional constraint surface of the voltage utilization rate of motor 1 shown. This contour line is then projected onto the plane where DCSUR = 0. α is then searched within the area enclosed by the projected line. h1 When the value is the default value, the corresponding value is r ~ Average_α h The minimum value of r on the curve (i.e., the optimal value of r under this working condition) and its corresponding Average_α h Finally, α is determined by equation (7). h2 .

[0110] b. Dual-motor drive mode

[0111] like Figure 6 As shown, in this working mode, both motors output torque, while only the power battery outputs torque. The DC bus voltage and the voltage utilization rate of the two motors can be adjusted according to the parameters of the two motors to maximize the overall voltage utilization rate.

[0112] Specifically, see Figure 14 Based on the torque and speed requirements of the two motors, the target voltage utilization rate of motor 1 can be calculated separately. And the target voltage utilization rate of motor 2 Then, contour lines corresponding to the target voltage utilization rates are intercepted on the three-dimensional constraint surfaces of the voltage utilization rates of the two motors respectively. After projecting the two contour lines onto the plane where DCSUR=0, the optimal r and Average_α are obtained within the intersection of the regions enclosed by the two projection lines, with the minimum r as the search objective. h α can then be calculated. h1 α h2 .

[0113] c. Single generator single drive mode

[0114] like Figure 7As shown, in this working mode, clutch 1 is working and clutch 2 is not working. Motor 2 is used as a generator. The engine and the power battery jointly drive motor 1. At this time, the operating conditions of inverters 1 and 2 should be considered in order to determine the DC bus voltage and the effective modulation range of the inverter.

[0115] Specifically, see Figure 15 The target torque of motor 1 and the target torque of motor 2 (i.e., the target torque for power generation) can be determined by the accelerator pedal depth and the high-efficiency operating range of the engine, respectively. After determining the target torques of the two motors, similar to the dual-motor drive mode, the target voltage utilization rate of motor 1 can be calculated by equation (10). And the target voltage utilization rate of motor 2 Then, calculate α using the same method as in the dual-motor drive mode. h1 α h2 .

[0116] d. Pure motor mode

[0117] like Figure 8 As shown, in this operating mode, clutches 1 and 2, the power coupler, and motor 1 do not output power externally; they only function as a boost inductor. See the equivalent circuit diagram below. Figure 16 At this time, it is possible to do as Figure 17 As shown, the effective modulation range of inverter 2 is first optimized (e.g., α). h2 The value is preset to 0.5). Similarly, the target torque (power generation) of motor 2 is determined based on the engine's efficient operating range, and the target voltage utilization rate of motor 2 can be calculated. Then, using a process similar to that of the single-motor drive mode, α is finally obtained through searching. h1 .

[0118] The range-extended electric drive system based on dual neutral point series power supply provided in this application aims to improve the overall voltage utilization rate by establishing a dual-motor voltage comprehensive utilization rate model based on the boost characteristics of the dual-motor neutral point series topology. According to the specific performance requirements of the two motors under different working modes, the dual-motor voltage comprehensive utilization rate model is used to search for the optimal average duty cycle for modulation control of the two motors, thereby fully leveraging the driving / generating performance of the dual motors under the dual neutral point series power supply topology.

[0119] Some embodiments of this application also provide a control method for controlling the aforementioned range-extended electric drive system based on dual neutral point series power supply. This control method includes the following operations:

[0120] Operation 1: Based on the vehicle's operating conditions, switch the working mode according to a preset switching strategy or in response to manual operation;

[0121] Operation 2: Based on the aforementioned working mode, control the engagement state of the first clutch and the second clutch, as well as the switching state of the power coupler;

[0122] Operation 3: Based on the aforementioned working mode, in the dual-motor voltage comprehensive utilization rate model, with the target voltage utilization rate of at least one motor as a constraint, search for r and Average_α that satisfy the constraint. h and determining α based on search results h1 and / or α h2 , where α h1 α is the average duty cycle of the modulation signal of the inverter of the first motor. h2 The average duty cycle of the modulation signal of the inverter of the first motor is r = 1 / (α). h1 -α h2 ),Average_α h =(α h1 +α h2 ) / 2;

[0123] Operation 4, based on α h1 α h2 Modulation signals are generated for the inverters of the first motor and the second motor, and the modulation signals are used to modulate and control the inverters of the first motor and the second motor.

[0124] The specific implementation methods of the above operations have been explained in detail in the introduction of the range-extended electric drive system based on dual neutral point series power supply, and will not be repeated here.

[0125] The specific embodiments of this application have been described in detail above. For those skilled in the art, several improvements and modifications can be made to this application without departing from the principle of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A range-extended electric drive system based on dual neutral point series power supply, comprising a first motor, a second motor, and a power battery, wherein, The positive terminal of the power battery is electrically connected to the neutral point of the first motor, and the negative terminal is electrically connected to the neutral point of the second motor. The first motor and the second motor have the same DC bus voltage. The feature is that it further includes: Power coupler, first clutch, second clutch, engine, and control unit; The first power input end of the power coupler is connected to the first motor via transmission, and the power output end is connected to the drive shaft of the vehicle via transmission. The first clutch is used to engage or disengage the transmission connection between the engine and the second motor; The second clutch is used to engage or disengage the transmission connection between the second motor and the second power input terminal of the power coupler; The control unit is used to control the engagement state of the first clutch and the second clutch, the switching state of the power coupler, and to perform modulation control on the inverters of the first motor and the second motor. The control unit controls the engagement state of the first clutch and the second clutch, as well as the on / off state of the power coupler, based on the vehicle's operating conditions. Furthermore, the average duty cycle of the modulation signals of the inverters of the first and second motors is determined based on the dual-motor voltage comprehensive utilization rate model, and the switching control of each power device in the inverter is performed based on the modulation signals. The comprehensive voltage utilization rate model for the dual-motor system is as follows: Where DCSUR1 and DCSUR2 are the voltage utilization rates of the first motor and the second motor, respectively, and α h1 α h1 Average duty cycle, Average_α, for the modulation signals of the inverters of the first and second motors, respectively. h For α h1 and α h2 The mean, Δα h For α h1 and α h2 The difference.

2. The range-extended electric drive system based on dual neutral point series power supply according to claim 1, characterized in that, The control unit includes: The working mode switching module switches the working mode according to the vehicle's operating conditions based on a preset switching strategy or in response to manual operation. The transmission state control module controls the engagement state of the first clutch and the second clutch, as well as the switching state of the power coupler, based on the aforementioned working mode. The duty cycle determination module, based on the aforementioned operating mode, searches for the optimal value of r and Average_α that satisfy the constraints in the dual-motor voltage comprehensive utilization rate model, with the target voltage utilization rate of at least one motor as a constraint. h and determining α based on search results h1 and / or α h2 Where r = 1 / Δα h ; Modulation control module, based on α h1 α h2 Modulation signals are generated for the inverters of the first motor and the second motor, and the modulation signals are used to modulate and control the inverters of the first motor and the second motor.

3. The range-extended electric drive system based on dual neutral point series power supply according to claim 2, characterized in that, In the dual-motor voltage utilization model, with the target voltage utilization rate of at least one motor as a constraint, the optimal value of r and Average_α that satisfy the constraint are searched. h Specifically, this includes the following operations: Based on the dual-motor voltage comprehensive utilization rate model, a three-dimensional constraint surface for the voltage utilization rate of the first motor and a three-dimensional constraint surface for the voltage utilization rate of the second motor are generated. Based on the operating mode and the real-time speed and target torque of at least one motor, determine the target voltage utilization rate of at least one motor. Search for contour lines corresponding to the target voltage utilization of the at least one motor on the three-dimensional constraint surface of the voltage utilization of the at least one motor, and search for the optimal r and the corresponding Average_α based on the contour lines. h .

4. The range-extended electric drive system based on dual neutral point series power supply according to claim 2, characterized in that, The operating modes include single-motor drive mode, dual-motor drive mode, single-generator single-drive mode, and pure generator mode.

5. The range-extended electric drive system based on dual neutral point series power supply according to claim 4, characterized in that, When the operating mode is a single motor drive mode: Both the first clutch and the second clutch are in the disengaged state, and the power coupler is in the open state; The duty cycle determination module uses a preset α h1 Given the value of r and the target voltage utilization rate of the first motor as constraints, search for the minimum value of r that simultaneously satisfies these constraints and its corresponding Average_α. h Then, α is determined based on the search results. h2 .

6. The range-extended electric drive system based on dual neutral point series power supply according to claim 4, characterized in that, When the operating mode is the dual-motor drive mode: The first clutch is in the disengaged state, the second clutch is in the engaged state, and the power coupler is in the open state. The duty cycle determination module uses the target voltage utilization rate of the first motor and the second motor as constraints to search for the minimum value of r that simultaneously satisfies the constraints and the corresponding Average_α. h Then, α is determined based on the search results. h1 and α h2 .

7. The range-extended electric drive system based on dual neutral point series power supply according to claim 4, characterized in that, When the operating mode is single-generator single-drive mode: The first clutch is engaged, the second clutch is disengaged, and the power coupler is open. The duty cycle determination module uses the target voltage utilization rate of the first motor and the second motor as constraints to search for the minimum value of r that simultaneously satisfies the constraints and the corresponding Average_α. h Then, α is determined based on the search results. h1 and α h2 .

8. The range-extended electric drive system based on dual neutral point series power supply according to claim 4, characterized in that, When the operating mode is pure power generation mode: The first clutch is engaged, the second clutch is disengaged, and the power coupler is closed. The duty cycle determination module uses a preset α h2 Given the target voltage utilization rate of the second motor as a constraint, search for the minimum value of r that simultaneously satisfies this constraint and its corresponding Average_α. h Then, α is determined based on the search results. h1 .

9. The range-extended electric drive system based on dual neutral point series power supply according to claim 1, characterized in that, The first motor and the second motor are permanent magnet synchronous motors, excitation synchronous motors, or hybrid excitation synchronous motors.

10. A control method for controlling a range-extended electric drive system based on dual neutral point series power supply as described in claim 1, characterized in that, Includes the following operations: Depending on the vehicle's operating conditions, the operating mode is switched based on a preset switching strategy or in response to manual operation. The operating mode controls the engagement state of the first clutch and the second clutch, as well as the switching state of the power coupler. Based on the aforementioned operating mode, in the dual-motor voltage comprehensive utilization rate model, with the target voltage utilization rate of at least one motor as a constraint, we search for r and Average_α that satisfy the constraint. h and determining α based on search results h1 and / or α h2 , where α h1 α is the average duty cycle of the modulation signal of the inverter of the first motor. h2 The average duty cycle of the modulation signal of the inverter of the first motor is r = 1 / (α). h1 -α h2 ),Average_α h =(α h1 +α h2 ) / 2; Based on α h1 α h2 Modulation signals are generated for the inverters of the first motor and the second motor, and the modulation signals are used to modulate and control the inverters of the first motor and the second motor.

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