Control method of three-level inverter, motor driver and vehicle

Abstract

The invention relates to a control method of a three-level inverter, a motor driver and a vehicle. The control method comprises the following steps: acquiring a first voltage at two ends of a first bus capacitor, a second voltage at two ends of a second bus capacitor, a reference current of the three-level inverter and a modulation voltage corresponding to each phase line on the alternating current side of the three-level inverter; determining an initial accumulated charge based on the first voltage and the second voltage; determining a zero-sequence injection voltage based on the reference current, the modulation voltage corresponding to each phase line and the initial accumulated charge; determining a target modulation voltage corresponding to each phase line according to the modulation voltage corresponding to each phase line and the zero-sequence injection voltage; and outputting a target modulation signal to the three-level inverter according to the target modulation voltage. Obviously, the probability of midpoint voltage deviation can be effectively reduced through the zero-sequence injection voltage, interference in the control process of the three-level inverter is reduced, the output quality of the target modulation signal is improved, and the control efficiency of the three-level inverter is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic control, and particularly relates to a control method of a three-level inverter, a motor driver and a vehicle. BACKGROUND

[0002] At present, automobiles are evolving towards high voltage and high power acceleration. The three-level inverter provides a solid guarantee for long endurance and high performance of vehicles due to its large output capacity, high output voltage and small current harmonic content. However, in the related art, the three-level inverter often has a midpoint voltage deviation due to differences in circuit parameters and inherent defects of three-phase modulation strategies, introduces more harmonics to cause a poor output current waveform, and thus causes damage to capacitor devices and affects the robustness of the three-level inverter. SUMMARY

[0003] Therefore, the present application provides a control method of a three-level inverter, a motor driver and a vehicle to solve the problem of midpoint voltage deviation of the three-level inverter, introduction of more harmonics to cause a poor output current waveform, and thus damage to capacitor devices and affect the robustness of the three-level inverter.

[0004] In a first aspect, an embodiment of the present application provides a control method of a three-level inverter. The direct current side of the three-level inverter includes a positive direct current bus, a negative direct current bus, a first bus capacitor and a second bus capacitor connected in series between the positive direct current bus and the negative direct current bus. The method comprises: obtaining a first voltage across the first bus capacitor, a second voltage across the second bus capacitor, a reference current of the three-level inverter, and a modulation voltage corresponding to each phase line of an alternating current side of the three-level inverter. Determining an initial cumulative charge based on the first voltage and the second voltage. Determining a zero sequence injection voltage based on the reference current, the modulation voltage corresponding to each phase line, and the initial cumulative charge. Determining a target modulation voltage corresponding to each phase line according to the modulation voltage corresponding to each phase line and the zero sequence injection voltage. Outputting a target modulation signal to the three-level inverter according to the target modulation voltage.

[0005] In a possible design, the target modulation voltage corresponding to each phase line is determined according to the modulation voltage corresponding to each phase line and the zero sequence injection voltage, comprising: arranging the modulation voltage corresponding to each phase line in descending order to obtain a first modulation voltage, a second modulation voltage and a third modulation voltage. Obtaining a first target modulation voltage, a second target modulation voltage and a third target modulation voltage according to the first modulation voltage, the second modulation voltage, the third modulation voltage and the zero sequence injection voltage.

[0006] In a possible design, before outputting the target modulation signals according to the target modulation voltages to the three-level inverter, the method further includes: when the second modulation voltage is consistent with the sign of the second target modulation voltage, performing the step of outputting the target modulation signals according to the target modulation voltages to the three-level inverter; and when the second modulation voltage is inconsistent with the sign of the second target modulation voltage, updating the sign of the second modulation voltage to the sign of the second target modulation voltage, and re-performing the step of determining the zero sequence injection voltage based on the reference current, the modulation voltages corresponding to the respective phase lines, and the initial accumulated charge.

[0007] In a possible design, the method further includes: when the third target modulation voltage is greater than or equal to a first threshold value and the first target modulation voltage is less than or equal to a second threshold value, maintaining the zero sequence injection voltage unchanged, where the first threshold value is less than the second threshold value; when the third target modulation voltage is less than the first threshold value, updating the zero sequence injection voltage to a difference between the first threshold value and the third modulation voltage, and updating the first target modulation voltage, the second target modulation voltage, and the third target modulation voltage according to the updated zero sequence injection voltage; and when the first target modulation voltage is greater than the second threshold value, updating the zero sequence injection voltage to a difference between the second threshold value and the first modulation voltage, and updating the first target modulation voltage, the second target modulation voltage, and the third target modulation voltage according to the updated zero sequence injection voltage.

[0008] In a possible design, the zero sequence injection voltage is a sum of a feedforward regulation voltage and a feedback regulation voltage, and before obtaining the first target modulation voltage, the second target modulation voltage, and the third target modulation voltage according to the first modulation voltage, the second modulation voltage, the third modulation voltage, and the zero sequence injection voltage, the method further includes: taking a sum of the first modulation voltage and the feedforward regulation voltage as a first limiting voltage, and taking a sum of the third modulation voltage and the feedforward regulation voltage as a second limiting voltage; when the second limiting voltage is greater than or equal to a first threshold value and the first limiting voltage is less than or equal to a second threshold value, maintaining the feedforward regulation voltage unchanged, where the first threshold value is less than the second threshold value; when the second limiting voltage is less than the first threshold value, updating the feedforward regulation voltage to a difference between the first threshold value and the third modulation voltage; and when the first limiting voltage is greater than the second threshold value, updating the feedforward regulation voltage to a difference between the second threshold value and the first modulation voltage.

[0009] In a possible design, before the first target modulation voltage, the second target modulation voltage and the third target modulation voltage are obtained according to the first modulation voltage, the second modulation voltage, the third modulation voltage and the zero sequence injection voltage, the method further includes: taking a sum of the first modulation voltage and the feedback adjustment voltage as the third limit voltage, and taking a sum of the third modulation voltage and the feedback adjustment voltage as the fourth limit voltage. When the fourth limit voltage is greater than or equal to the first threshold value and the fourth limit voltage is less than or equal to the second threshold value, the feedback adjustment voltage is maintained unchanged. When the fourth limit voltage is less than the first threshold value, the feedback adjustment voltage is updated as a difference between the first threshold value and the third modulation voltage. When the third limit voltage is greater than the second threshold value, the feedback adjustment voltage is updated as a difference between the second threshold value and the first modulation voltage.

[0010] In a possible design, determining the initial accumulated charge based on the first voltage and the second voltage includes: calculating a voltage difference between the first voltage and the second voltage. The initial accumulated charge is determined according to the voltage difference and a preset feedback control model.

[0011] In a possible design, the reference current includes a given d-axis current and a given q-axis current, and determining the zero sequence injection voltage based on the reference current, the modulation voltage corresponding to each phase line and the initial accumulated charge includes: determining a reference current corresponding to each phase line according to the given d-axis current and the given q-axis current. The zero sequence injection voltage is determined according to the reference current corresponding to each phase line, the modulation voltage corresponding to each phase line and the initial accumulated charge.

[0012] In a second aspect, an embodiment of the present application provides a motor driver, including a three-level inverter, a motor and a controller, the three-level inverter is connected with the motor, the controller is connected with the three-level inverter and the motor, and the controller is configured to execute the control method of the three-level inverter in any of the above embodiments.

[0013] In a third aspect, an embodiment of the present application provides a vehicle, including the motor driver in any of the above embodiments.

[0014] The control method of the three-level inverter and the vehicle provided by the embodiments of the present application can determine the initial accumulated charge according to the first voltage between the first bus capacitor and the second voltage between the second bus capacitor, determine the zero sequence injection voltage according to the reference current, the modulation voltage corresponding to each phase line and the initial accumulated charge, and then determine the target modulation voltage corresponding to each phase line according to the modulation voltage corresponding to each phase line and the zero sequence injection voltage to output the target modulation signal to the three-level inverter. In this way, the present application can effectively reduce the probability of the midpoint voltage deviation through the zero sequence injection voltage, improve the output quality of the target modulation signal, effectively reduce the interference in the current sampling process based on the analysis of the reference current, improve the control accuracy of the three-level inverter, and ensure the robustness of the three-level inverter. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced. Obviously, the accompanying drawings in the following description only represent some of the embodiments of the present application, and other drawings can be obtained by those of ordinary skill in the art without any creative effort.

[0016] Figure 1 A structural block diagram of a vehicle is provided for an embodiment of the present application.

[0017] Figure 2 A structural schematic diagram of a three-level inverter is provided for an embodiment of the present application.

[0018] Figure 3 A flow chart of a control method of a three-level inverter is provided for an embodiment of the present application.

[0019] Figure 4 A waveform diagram of a midpoint potential is provided for an embodiment of the present application.

[0020] Figure 5 A control block diagram of a midpoint potential balancing strategy is provided for an embodiment of the present application.

[0021] Figure 6 A control block diagram of a control method of a three-level inverter is provided for an embodiment of the present application.

[0022] Figure 7 Another waveform diagram of a midpoint potential is provided for an embodiment of the present application. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be described below with reference to the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments only represent some of the embodiments of the present application, rather than all the embodiments.

[0024] The terminology used in the following description merely for the purpose of describing particular embodiments and is not intended to limit the application. As used in this description and the accompanying claims, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term "at least one" or "one or more" means one, two, three, or more, unless the context clearly indicates otherwise. The term "and / or" used in the context of describing associated objects means that there are three possibilities: either there is one object alone, both objects are present together, or there is one object alone, unless the context clearly indicates otherwise. The character " / " generally represents an "or" relationship between the associated objects.

[0025] Reference in the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the application. The appearances of the phrase "in one embodiment" or "in some embodiments" in various places in the specification are not necessarily all referring to the same embodiment, although it can. The terms "including," "comprising," "having" and variations thereof are meant to encompass the terms "including but not limited to," unless otherwise indicated.

[0026] At the moment when automobiles are evolving towards high-voltage and high-power acceleration, three-level inverters provide a solid guarantee for long endurance and high performance of vehicles due to their large output capacity, high output voltage, and small current harmonic content. However, in the related art, the three-level inverter often has a midpoint voltage deviation due to differences in circuit parameters and inherent defects in three-phase modulation strategies, introduces more harmonics to cause poor output current waveform, and thus causes damage to capacitor devices, affecting the robustness of the three-level inverter.

[0027] Based on this, the application provides a control method of a three-level inverter and a vehicle, which can effectively reduce the probability of midpoint voltage deviation, reduce interference in the control process of the three-level inverter, and improve the efficiency and accuracy of the control of the three-level inverter.

[0028] Next, the control method of the three-level inverter and the vehicle provided by the embodiments of the present application are further introduced. Understandably, the three-level inverter involved in the present application has the advantages of multi-level output, low harmonic distortion, high efficiency and low switching loss, and is widely used in various fields. For example, the three-level inverter can be used for automobile motor drive, industrial motor drive and photovoltaic power generation, and the present application does not limit the specific application scenarios of the three-level inverter. In the following embodiments, the three-level inverter is taken as an example for illustration.

[0029] The three-level inverter can include a T-type three-level inverter, a diode clamped three-level inverter (Neutral Point Clamped, NPC) or other three-level inverters with midpoint voltage deviation, and the present application does not limit the specific type of the three-level inverter. In the following embodiments, the three-level inverter is taken as a T-type three-level inverter for illustration.

[0030] Please refer to Figure 1 , which shows a structural schematic diagram of a vehicle provided by an embodiment of the present application. As shown in Figure 1 , the vehicle 10 includes a motor driver 100 and a power battery 200. The motor driver 10 includes a controller 101, a three-level inverter 102 and a motor 103, the controller 101 is connected with the three-level inverter 102 and the motor 103 respectively, and the three-level inverter 102 is connected with the motor 103. The motor driver 100 is used to convert the direct current output by the power battery 200 into alternating current, to provide a stable and controllable power source for the operation of the motor 103, and to realize dynamic control of torque, speed and position.

[0031] The controller 101 is used to output a control signal to the three-level inverter 102, to control the three-level inverter 102 to output a voltage corresponding to the control signal. The controller 101 is also used to detect the running state of the motor 103. The three-level inverter 102 is used to output a corresponding voltage to drive the motor 103 to operate according to the received control signal. The motor 103 can include a permanent magnet but is not limited to a synchronous motor , which can include an interior permanent magnet synchronous motor (IPMSM) and a surface permanent magnet synchronous motor . The present application does not limit the specific type of the motor 103.

[0032] In an embodiment of the present application, as shown in Figure 2 , the direct current side of the three-level inverter 102 includes a positive direct current bus , a negative direct current bus and a second bus capacitor 1023 connected in series between the positive DC bus BUS+ and the negative DC bus The DC side of the three-level inverter 102 is connected with the power battery 200 through the positive DC bus BUS+ and the negative DC bus The first bus capacitor 1022 and the second bus capacitor 1023 divide the DC voltage Udc output by the power battery 200, the voltage across the first bus capacitor 1022 is the first voltage Udc1, and the voltage across the second bus capacitor 1023 is the second voltage Udc2. The midpoint O between the first bus capacitor 1022 and the second bus capacitor 1023 is a reference potential point, and the midpoint voltage is measured at the midpoint potential O, which provides the basis for three-level output. The three-level inverter 102 further includes three bridge arms, for example, the first bridge arm includes the switch tube and the switch tube , the second bridge arm includes the switch tube and the switch tube , and the third bridge arm includes the switch tube and the switch tube . The connection point between the switch tube and the switch tube of the first bridge arm leads to the first phase line, which includes the switch tube and the switch tube . The connection point between the switch tube and the switch tube of the second bridge arm leads to the second phase line, which includes the switch tube and the switch tube . The connection point between the switch tube and the switch tube of the third bridge arm leads to the third phase line, which includes the switch tube and the switch tube . By controlling the switching logic and duty cycle of the four switch tubes on each bridge arm, the output voltage and output current of the corresponding bridge arm can be controlled. The midpoint O is connected with the switch tube. In other embodiments, the number of switch tubes can be set according to the specific structure of the three-level inverter 102, and more or fewer switch devices can be included in other types of three-level inverters 102, and the specific number of switch devices is not limited by the present application.

[0033] It can be understood that the vehicle 10 can be a pure electric vehicle, a hybrid vehicle, or a fuel cell vehicle, and the specific type of the vehicle 10 is not limited by the present application.

[0034] Please refer to Figure 3This document illustrates a flowchart of a control method for a three-level inverter 102 according to an embodiment of this application. The control method for the three-level inverter 102 provided in this application can be applied to a motor driver 100 and executed by the controller 101 of the motor driver 100. The control method for the three-level inverter 102 provided in this application includes the following steps S1 to S5.

[0035] Step S1: Obtain the first voltage across the first bus capacitor, the second voltage across the second bus capacitor, the reference current of the three-level inverter, and the modulation voltage corresponding to each phase line on the AC side of the three-level inverter.

[0036] For example, the reference current includes a given d-axis current and a given q-axis current. The reference current corresponding to each phase line is determined based on the given d-axis current and the given q-axis current, thereby determining the zero-sequence injection voltage based on the reference current corresponding to each phase line, the modulation voltage corresponding to each phase line, and the initial accumulated charge.

[0037] Understandably, in order to reduce glitches during the current sampling process, a two-phase rotating coordinate system (i.e., The reference current in the two-phase coordinate system is converted into a three-phase reference current in the three-phase stationary coordinate system, and the three-phase modulation voltage is calculated based on the converted three-phase reference current. In this way, controlling the three-level inverter 102 based on the two-phase reference current can effectively reduce the coupling path caused by interference and improve the accuracy of controlling the three-level inverter 102.

[0038] In one embodiment of this application, the reference current corresponding to each phase line can be determined based on the given d-axis current and the given q-axis current using formulas (1) and (2).

[0039] (1); (2); in, This is expressed as the electrical angle of the motor rotor. I A Represented as the reference current corresponding to the first phase line, I B Represented as the reference current corresponding to the second phase line, I C It is represented as the reference current corresponding to the third phase line. Formula (1) converts the two-phase reference current in the rotating coordinate system to the two-phase current in the stationary coordinate system; Formula (2) converts the two-phase current in the stationary coordinate system to the three-phase current in the stationary coordinate system.

[0040] like Figure 4As shown in the figure, box J represents the fluctuation of the midpoint potential after the three-phase current in the three-phase stationary coordinate system is modulated. Box K represents the fluctuation of the midpoint potential after the reference current in the two-phase rotating coordinate system is converted into a three-phase reference current for modulation. Understandably, due to sensor measurement errors, the acquisition of three-phase current for modulation suffers from low signal-to-noise ratio and significant interference. Compared to the midpoint potential in box J, the midpoint potential in box K has the advantages of smaller fluctuations and less interference. Thus, by using the method of converting the reference current into a three-phase reference current in this scheme, interference can be effectively reduced, and the accuracy and efficiency of subsequent modulation can be improved.

[0041] In one embodiment of this application, the modulation voltage corresponding to each phase line on the AC side of the three-level inverter 102 can be determined based on the reference current. For example... Figure 5 As shown, the motor driver 100 also includes a current loop proportional-integral (PI) control module 105, a conversion modulation module 106, and a first conversion module 107. The controller 101 acquires the actual output current corresponding to each phase line of the AC terminal of the three-level inverter 102 obtained from sampling, for example... Figure 5 The I shown A '、I B 'and I C Then, the first conversion module 107 converts the actual d-axis current I based on the actual output current corresponding to each phase line. d and the actual q-axis current I q Next, the current loop proportional-integral control module 105 determines the current based on the reference current (e.g., ...). Figure 5 I in d and I q ) and the actual d-axis current I d and the actual q-axis current I q 'Perform calculations to obtain the two-phase reference voltage in a two-phase rotating coordinate system, such as...' Figure 5 Reference d-axis voltage U d and reference q-axis voltage U q The two-phase reference voltage is input to the conversion modulation module 106 to be converted into the modulation voltage corresponding to each phase line in the three-phase stationary coordinate system (e.g., ...). Figure 5 U in AT U BT and U CT). The first conversion module 107 can include a conversion model based on Clarke transformation and Park transformation. Clarke transformation can convert physical quantities in three-phase stationary coordinate system to two-phase stationary coordinate system. Park transformation, also known as Park's Transformation, projects the stator a, b, c three-phase currents to the direct axis (d-axis), the quadrature axis (q-axis) and the zero axis (0-axis) which rotates with the rotor, thereby diagonalizing the stator inductance matrix and simplifying the operation analysis of the synchronous motor. The current loop proportional integral control module 105 is configured to perform proportional integral operation on the current between the reference current and the two-phase feedback current to obtain two-phase modulation voltage. The conversion modulation module 106 can include a conversion model based on inverse Park transformation and inverse Clarke transformation. Inverse Park transformation is the inverse process of Park transformation, which is used to convert physical quantities (such as voltage and current) from two-phase rotating coordinate system to two-phase stationary coordinate system. Inverse Clarke transformation is the inverse process of Clarke transformation, which is used to convert physical quantities from two-phase stationary coordinate system to three-phase stationary coordinate system.

[0042] It can be understood that the conversion of the three-phase feedback current in the three-phase stationary coordinate system to the two-phase feedback current in the rotating coordinate system can be the inverse operation of formula (1) and formula (2), which will not be described here.

[0043] In an embodiment of the present application, as shown in Figure 6 , based on the two-phase reference voltage in the two-phase rotating coordinate system and the preset modulation model, the modulation voltage corresponding to each phase line in the three-phase stationary coordinate system is determined. It can be understood that the modulation conversion module 106 can include a second conversion module 1061 and a modulation module 1062. The second conversion module 1061 converts the two-phase reference voltage to three-phase reference voltage, such as Figure 6 U A , U B and U CThe conversion process is similar to that described in the above embodiments and will not be repeated here. The modulation module 1062 may include a preset modulation model. A three-phase reference voltage is input to the modulation module 1062, and the modulation voltage is calculated. The modulation model may include a model based on Space Vector Pulse Width Modulation (SVPWM) technology. The main idea of ​​SVPWM is to use the ideal flux linkage circle of the three-phase symmetrical motor stator as a reference standard when powered by a three-phase symmetrical sinusoidal voltage, and to appropriately switch different switching modes of the three-phase inverter 102 to form a PWM wave, using the formed actual flux linkage vector to track its accurate flux linkage circle. The modulation module 1062 may also include other modulation models; this application does not limit the specific style of the modulation model. In other embodiments, the modulation conversion module 106 may also include other units or modules; this application does not limit the specific style of the modulation conversion module 106.

[0044] For example, during the calculation process, the conversion modulation module 106 and the first conversion module 107 acquire and maintain the electrical angle θ of the motor rotor in real time. This effectively ensures that the two-phase feedback current and the two-phase reference current are in the same rotating coordinate system, improving the accuracy and reliability of the conversion.

[0045] Understandably, by acquiring physical quantities in the rotating coordinate system to calculate physical quantities in the stationary coordinate system, the interference of high-frequency oscillation terms can be reduced. The proportional-integral control module can reduce steady-state error, reduce the complexity of calculation, and reduce glitches in the current data during the acquisition process.

[0046] In other embodiments, the conversion modulation module 106 and the first conversion module 107 may also convert current and voltage using other models. This application does not limit the specific way in which physical quantities in a rotating coordinate system are converted into physical quantities in a stationary coordinate system.

[0047] Step S2: Determine the initial accumulated charge based on the first voltage and the second voltage.

[0048] For example, in the three-level inverter 102, the DC-side capacitor has accuracy and parameter calibration errors. For instance, the nominal capacitance of the DC-side capacitor may change abruptly with impedance at high frequencies. Therefore, directly using the DC-side capacitor value to determine the initial accumulated charge results in a large error. This application determines the initial accumulated charge using the first voltage Udc1 and the second voltage Udc2 of the three-level inverter 102, which can effectively adapt to various dynamic environments, improve anti-interference capability, and improve the control efficiency of the three-level inverter 102. Understandably, determining the initial accumulated charge includes the following steps S201 to S202.

[0049] Step S201: Calculate the voltage difference between the first voltage and the second voltage.

[0050] For example, the voltage difference U can be calculated using formula (3). 差 : (3); During the operation of the three-level inverter 102, calculating the voltage difference between the two capacitors can effectively reduce the tolerance of the capacitor values ​​and reduce the influence of parameter dispersion. Through the dynamic change of the voltage difference, it is convenient to adjust the switching devices in real time and improve the anti-interference capability of the three-level inverter.

[0051] Step S202: Determine the initial accumulated charge based on the voltage difference and the preset feedback control model.

[0052] In one embodiment of this application, the feedback control model may include a proportional-integral (PI) control model, for example, the initial accumulated charge can be calculated using formula (4). : (4); Where, k p k is a proportional parameter. i T is the integration parameter. s The modulation period is used. The feedback control model can compensate for circuit errors such as capacitor accuracy, reduce control disturbances caused by capacitor parameter calibration errors, and ensure the control stability of the midpoint potential.

[0053] like Figure 7 As shown in the figure, the box L section represents the initial accumulated charge calculated directly from the capacitance value. The fluctuation of the midpoint potential is shown in the figure. The box M represents the initial accumulated charge calculated using the feedback control model. The fluctuation of the midpoint potential after the capacitor is applied. Under ideal conditions, the capacitor voltage is the bus voltage, and the initial accumulated charge can be calculated directly from the capacitance value. The midpoint potential fluctuates significantly, resulting in poor anti-interference capability. Therefore, this scheme calculates the initial accumulated charge based on the capacitor voltage and the feedback control model. This method can effectively reduce interference in parameter calibration. In other embodiments, the feedback control model may also include other computational models; this application does not limit the specific style of the feedback control model.

[0054] Step S3: Determine the zero-sequence injection voltage based on the reference current, the modulation voltage corresponding to each phase line, and the initial accumulated charge.

[0055] Specifically, according to the data obtained in steps S1 to S2, the zero sequence injection voltage is calculated, which can effectively reduce the interference in the calculation process, improve the accuracy of the zero sequence injection voltage, and improve the control efficiency of the three-level inverter 102.

[0056] In an embodiment of the present application, as shown in Figure 6 The motor driver 100 further includes a feedforward feedback module 104, which determines the zero sequence injection voltage U0 based on the joint action of feedforward control and feedback proportional integral control. The feedforward control is based on the measurement or prediction of system disturbance, and produces a control action in advance to offset the influence of the disturbance. The feedback proportional integral control is to measure the output of the system, compare it with the set value, and adjust the control quantity according to the error and the integral value, so as to reduce the error. The combination of the two can more comprehensively cope with various disturbances, greatly enhance the anti-interference ability of the system, facilitate the response to various disturbances, and improve the stability and flexibility of the three-level inverter 102 operation. Determining the zero sequence injection voltage U0 can include steps S301 to S302.

[0057] Step S301, according to the three-phase current, the three-phase modulation voltage, the zero sequence injection voltage and the modulation period, a first charge accumulation value is obtained.

[0058] Exemplarily, in each modulation period T s , the time Tx0 that each phase current flows through the midpoint O can be calculated by formula (5): (5); Wherein, x represents any one of the three-phase output by the three-level inverter 102, ,and Ux represents any one of the three-phase modulation voltage.

[0059] Then, according to the time Tx0 that each phase current flows through the midpoint O, the basic charge accumulation value of the three-phase current flowing through the midpoint O in each modulation period T s can be calculated by formula (6) : (6); Then, according to the basic charge accumulation value , the first charge accumulation value of the three-phase current flowing through the midpoint O in each modulation period T s after the three-phase modulation voltage is superimposed with the zero sequence injection voltage U0 can be calculated by formula (7) : (7); Since the three-phase modulation voltage does not change the sign of the three-phase modulation voltage after the zero-sequence injection voltage U0 is superimposed, a sign function sign can be introduced, which is used to return the corresponding sign representation according to the positive and negative of the input value. Then the voltage value of any item in the three-phase modulation voltage in formula (7) can be calculated by formula (8): (8) ; Then, formula (7) can be simplified to formula (9) according to formula (8) to determine the first charge accumulation value : (9) ; S302, the sum of the first charge accumulation value and the initial accumulated charge is taken as the second charge accumulation value, and when the second charge accumulation value is 0, the zero-sequence injection voltage is determined.

[0060] Exemplarily, the zero-sequence injection voltage U0 is determined according to the reference current corresponding to each phase line and the modulation voltage corresponding to each phase line. The initial accumulated charge determined according to formula (4) and the first charge accumulation value determined according to formula (9), the second charge accumulation value can be calculated according to formula (10): (10) ; When the second charge accumulation value is 0, the midpoint charge accumulation offset in one modulation period T s is 0, then the zero-sequence injection voltage U0 can be obtained by formula (11): wherein, is the feedforward regulation voltage, is the feedback regulation voltage, and the zero-sequence injection voltage U0 is the sum of the feedforward regulation voltage and the feedback regulation voltage .

[0061] Understandably, the second charge accumulation value is calculated by the initial accumulated charge and the first charge accumulation value , so as to deduce the zero-sequence injection voltage U0, which can effectively reduce the interference in the process of determining the zero-sequence injection voltage U0, improve the accuracy of the zero-sequence injection voltage U0, and guarantee the control efficiency of the three-level inverter 102.

[0062] Step S4, determine the target modulation voltage corresponding to each phase line according to the modulation voltage corresponding to each phase line and the zero-sequence injection voltage.

[0063] In some embodiments, the modulation voltage corresponding to each phase line can be superimposed with the zero sequence injection voltage U0 respectively to obtain the target modulation voltage corresponding to each phase line, as shown in the following formula: Figure 6 A B C

[0064] Step S5, output the target modulation signal according to the target modulation voltage to the three-level inverter.

[0065] It can be understood that the modulation voltage corresponding to each phase line is arranged in descending order to obtain the first modulation voltage Umax, the second modulation voltage Umid and the third modulation voltage Umin. The first target modulation voltage, the second target modulation voltage and the third target modulation voltage are obtained according to the first modulation voltage Umax, the second modulation voltage Umid, the third modulation voltage Umin and the zero sequence injection voltage U0. The motor driver 100 further comprises a wave generation calculation module 108. The wave generation calculation module 108 is configured to output a control signal to the three-level inverter 102 according to the received target modulation voltage, so as to drive the switch tube as shown in the following formula: Figure 2

[0066] In an embodiment of the present application, before outputting the target modulation signal according to the target modulation voltage to the three-level inverter, the present application also needs to verify and / or limit the superposition of the three-phase modulation voltage and the zero sequence injection voltage. The verification and limiting method provided by the embodiment of the present application comprises the following steps S501 to S504. It can be understood that the order of the following steps S501 to S504 can be changed according to different requirements, and some steps can be omitted.

[0067] S501, verify the target modulation voltage.

[0068] It can be understood that since the modulation voltage superimposed with the zero sequence injection voltage U0 changes the sign of the second modulation voltage Umid, it is necessary to verify the second modulation voltage Umid to ensure the accuracy of the control signal sent by the wave generation calculation module 108 to the three-level inverter 102.

[0069] In an embodiment of the present application, the second modulation voltage Umid and the zero sequence injection voltage U0 are superimposed to obtain the second target modulation voltage, i.e. Umid+U0, and the signs of the second modulation voltage and the second target modulation voltage are compared. When the signs of the second modulation voltage Umid and the second target modulation voltage are consistent, i.e. , it is determined that the zero sequence injection voltage U0 is calculated correctly, and the step of outputting the target modulation signal according to the target modulation voltage to the three-level inverter is executed.

[0070] ​​​​​When the second modulation voltage Umid is inconsistent with the sign of the second target modulation voltage, i.e. , it is determined that the zero sequence injection voltage U0 is calculated incorrectly. The sign of the second modulation voltage Umid is updated to the sign of the second target modulation voltage, i.e. , and step S3 is re-executed to recalculate the zero sequence injection voltage U0.

[0071] S502, clipping the target modulation voltage.

[0072] Understandably, when the target modulation voltage amplitude is too large, the three-level inverter 102 in operation exists the case that the pressure borne by the device exceeds the rated voltage and / or the current suddenly changes, thereby causing the device to be damaged; when the target modulation voltage amplitude is too small, the three-level inverter 102 exists the case that the output power is insufficient, the motor 103 cannot be driven, or the speed of the motor 103 cannot meet the requirements, thereby affecting the use effect of the motor 103. Therefore, by clipping the target modulation voltage, the operation efficiency of the three-level inverter 102 can be effectively improved.

[0073] In an embodiment of the present application, the first modulation voltage Umax and the zero sequence injection voltage U0 are superimposed to obtain the first target modulation voltage. The third modulation voltage Umin and the zero sequence injection voltage U0 are superimposed to obtain the third target modulation voltage. The first threshold is smaller than the second threshold. For example, the first threshold is , and the second threshold is 1. When the third target modulation voltage is greater than or equal to the first threshold and the first target modulation voltage is less than or equal to the second threshold, such as and , the zero sequence injection voltage U0 is maintained unchanged. When the third target modulation voltage is less than the first threshold, the zero sequence injection voltage U0 is updated to the difference between the first threshold and the third modulation voltage, and the first target modulation voltage, the second target modulation voltage and the third target modulation voltage are updated according to the updated zero sequence injection voltage U0. For example, , the zero sequence injection voltage is updated. When the first target modulation voltage Umax is greater than the second threshold, the zero sequence injection voltage U0 is updated to the difference between the second threshold and the first modulation voltage, and the first target modulation voltage, the second target modulation voltage and the third target modulation voltage are updated according to the updated zero sequence injection voltage U0. For example, , the zero sequence injection voltage is updated. In this way, by clipping the zero sequence injection voltage U0, the interference received by the three-level inverter 102 can be effectively reduced, and the efficiency of the three-level inverter 102 driving the motor 103 can be improved.

[0074] In other embodiments, the first threshold and the second threshold can be set according to actual needs, and the present application does not limit the specific values of the first threshold and the second threshold.

[0075] S503, clipping the feed-forward regulation voltage.

[0076] It can be understood that the calculation of the feed-forward regulation voltage involves the three-phase modulation voltage and the corresponding symbol. To ensure the stable operation of the three-level inverter 102, reduce the probability of device damage, and ensure the stable operation of the motor 103, it is necessary to clip the feed-forward regulation voltage before obtaining the first target modulation voltage, the second target modulation voltage, and the third target modulation voltage according to the first modulation voltage Umax, the second modulation voltage Umid, the third modulation voltage Umin, and the zero sequence injection voltage U0.

[0077] In an embodiment of the present application, the sum of the first modulation voltage Umax and the feed-forward regulation voltage is taken as the first limiting voltage, and the sum of the third modulation voltage Umin and the feed-forward regulation voltage is taken as the second limiting voltage. When the second limiting voltage is greater than or equal to a first threshold value and the first limiting voltage is less than or equal to a second threshold value, the feed-forward regulation voltage is maintained unchanged, and the feed-forward regulation voltage is updated to the difference between the first threshold value and the third modulation voltage. For example, the feed-forward regulation voltage is updated. When the first limiting voltage is greater than the second threshold value, the feed-forward regulation voltage is updated to the difference between the second threshold value and the first modulation voltage. For example, the feed-forward regulation voltage is updated.

[0078] In this way, by clipping the feed-forward regulation voltage , the probability of the feed-forward regulation voltage exceeding the amplitude range due to abnormal three-phase modulation voltage can be effectively reduced, and the stable operation of the three-level inverter 102 is ensured.

[0079] S504, clipping the feedback regulation voltage.

[0080] It can be understood that the calculation of the feedback regulation voltage involves the initial accumulated charge and the symbol of the three-phase modulation voltage. By clipping the feedback regulation voltage before obtaining the first target modulation voltage, the second target modulation voltage, and the third target modulation voltage according to the first modulation voltage Umax, the second modulation voltage Umid, the third modulation voltage Umin, and the zero sequence injection voltage U0.The limiting can effectively reduce the circuit error and ensure the control stability of the neutral point potential of the three-level inverter 102.

[0081] In an embodiment of the present application, the sum of the first modulation voltage Umax and the feedback adjustment voltage Vfb is taken as a third limiting voltage, and the sum of the third modulation voltage Umin and the feedback adjustment voltage Vfb is taken as a fourth limiting voltage. When the fourth limiting voltage is greater than or equal to a first threshold and the fourth limiting voltage is less than or equal to a second threshold, the feedback adjustment voltage Vfb is maintained unchanged. When the fourth limiting voltage is less than the first threshold, the feedback adjustment voltage Vfb is updated to be the difference between the first threshold and the third modulation voltage. When the third limiting voltage is greater than the second threshold, the feedback adjustment voltage Vfb is updated to be the difference between the second threshold and the first modulation voltage. When the third limiting voltage is greater than the second threshold, the feedback adjustment voltage Vfb is updated to be the difference between the second threshold and the first modulation voltage. When the third limiting voltage is greater than the second threshold, the feedback adjustment voltage Vfb is updated to be the difference between the second threshold and the first modulation voltage. When the third limiting voltage is greater than the second threshold, the feedback adjustment voltage Vfb is updated to be the difference between the second threshold and the first modulation voltage. When the third limiting voltage is greater than the second threshold, the feedback adjustment voltage Vfb is updated to be the difference between the second threshold and the first modulation voltage. When the third limiting voltage is greater than the second threshold, the feedback adjustment voltage Vfb is updated to be the difference between the second threshold and the first modulation voltage. When the third limiting voltage is greater than the second threshold, the feedback adjustment voltage Vfb is updated to be the difference between the second threshold and the first modulation voltage. When the third limiting voltage is greater than the second threshold, the feedback adjustment voltage Vfb is updated to be the difference between the second threshold and the first modulation voltage. .

[0082] Thus, by limiting the feedback adjustment voltage Vfb, the circuit error and interference received by the three-level inverter 102 can be effectively reduced, the control stability of the neutral point potential is ensured, and the quality of the output voltage of the three-level inverter 102 is further improved.

[0083] Referring back to Figure 1 The present application also provides a motor driver 100, which comprises a three-level inverter 102, a motor 103, and a controller 101. The three-level inverter 102 is connected to the motor 103, and the controller 101 is connected to the three-level inverter 102 and the motor 103. The controller 101 is configured to implement the control method of the three-level inverter according to any one of the above embodiments.

[0084] It can be understood that the controller 101 implements the above control method through a computer program. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or some intermediate forms. The computer readable medium can include any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), and other memories.

[0085] ​​The embodiments of the present application also provide a vehicle 10, which comprises the motor driver 100 according to any one of the above embodiments. It can be understood by those skilled in the art that the schematic diagram is only an example of the vehicle 10, and does not constitute a limitation on the vehicle 10, which can comprise more or less components than the diagram, or combine certain components, or different components, for example, the vehicle 10 can also comprise a power system, an electrical system and the like.

[0086] It should be understood that the embodiments of the present application can be combined in any manner, for example, can be used alone, or can be used in combination with each other to achieve different technical effects, and the present application is not limited in this regard.

[0087] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any change or replacement within the technical scope disclosed in the present application should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A control method for a three-level inverter, wherein the DC side of the three-level inverter includes a positive DC bus, a negative DC bus, and a first bus capacitor and a second bus capacitor connected in series between the positive DC bus and the negative DC bus, characterized in that: The method includes: Obtain the first voltage across the first bus capacitor, the second voltage across the second bus capacitor, the reference current of the three-level inverter, and the modulation voltage corresponding to each phase line on the AC side of the three-level inverter; The initial accumulated charge is determined based on the first voltage and the second voltage; The zero-sequence injection voltage is determined based on the reference current, the modulation voltage corresponding to each phase line, and the initial accumulated charge. The target modulation voltage corresponding to each phase line is determined based on the modulation voltage and the zero-sequence injection voltage corresponding to each phase line. The target modulation signal is output to the three-level inverter according to the target modulation voltage.

2. The control method as described in claim 1, characterized in that: The step of determining the target modulation voltage corresponding to each phase line based on the modulation voltage corresponding to each phase line and the zero-sequence injection voltage includes: The modulation voltages corresponding to each phase line are arranged in descending order to obtain the first modulation voltage, the second modulation voltage, and the third modulation voltage; The first target modulation voltage, the second target modulation voltage, and the third target modulation voltage are obtained based on the first modulation voltage, the second modulation voltage, the third modulation voltage, and the zero-sequence injection voltage.

3. The control method as described in claim 2, characterized in that: Before outputting the target modulation signal to the three-level inverter according to the target modulation voltage, the method further includes: When the sign of the second modulation voltage is consistent with that of the second target modulation voltage, the step of outputting the target modulation signal to the three-level inverter according to the target modulation voltage is executed; When the sign of the second modulation voltage is inconsistent with that of the second target modulation voltage, the sign of the second modulation voltage is updated to that of the second target modulation voltage, and the step of determining the zero-sequence injection voltage based on the reference current, the modulation voltage corresponding to each phase line, and the initial accumulated charge is re-executed.

4. The control method as described in claim 2, characterized in that: The method further includes: When the third target modulation voltage is greater than or equal to the first threshold and the first target modulation voltage is less than or equal to the second threshold, the zero-sequence injection voltage is kept unchanged, wherein the first threshold is less than the second threshold; When the third target modulation voltage is less than the first threshold, the zero-sequence injection voltage is updated to the difference between the first threshold and the third modulation voltage, and the first target modulation voltage, the second target modulation voltage, and the third target modulation voltage are updated according to the updated zero-sequence injection voltage; When the first target modulation voltage is greater than the second threshold, the zero-sequence injection voltage is updated to the difference between the second threshold and the first modulation voltage, and the first target modulation voltage, the second target modulation voltage, and the third target modulation voltage are updated according to the updated zero-sequence injection voltage.

5. The control method as described in claim 2, characterized in that: The zero-sequence injection voltage is the sum of the feedforward regulation voltage and the feedback regulation voltage. Before obtaining the first target modulation voltage, the second target modulation voltage, and the third target modulation voltage based on the first modulation voltage, the second modulation voltage, the third modulation voltage, and the zero-sequence injection voltage, the method further includes: The sum of the first modulation voltage and the feedforward adjustment voltage is used as the first limiting voltage, and the sum of the third modulation voltage and the feedforward adjustment voltage is used as the second limiting voltage. When the second limiting voltage is greater than or equal to the first threshold and the first limiting voltage is less than or equal to the second threshold, the feedforward adjustment voltage is kept constant, wherein the first threshold is less than the second threshold; When the second limiting voltage is less than the first threshold, the feedforward adjustment voltage is updated to the difference between the first threshold and the third modulation voltage; When the first limiting voltage is greater than the second threshold, the feedforward adjustment voltage is updated to the difference between the second threshold and the first modulation voltage.

6. The control method as described in claim 5, characterized in that: Before obtaining the first target modulation voltage, the second target modulation voltage, and the third target modulation voltage based on the first modulation voltage, the second modulation voltage, the third modulation voltage, and the zero-sequence injection voltage, the method further includes: The sum of the first modulation voltage and the feedback adjustment voltage is used as the third limiting voltage, and the sum of the third modulation voltage and the feedback adjustment voltage is used as the fourth limiting voltage. When the fourth limiting voltage is greater than or equal to the first threshold and the fourth limiting voltage is less than or equal to the second threshold, the feedback adjustment voltage remains unchanged; When the fourth limiting voltage is less than the first threshold, the feedback adjustment voltage is updated to the difference between the first threshold and the third modulation voltage; When the third limiting voltage is greater than the second threshold, the feedback adjustment voltage is updated to the difference between the second threshold and the first modulation voltage.

7. The control method as described in claim 1, characterized in that: The determination of the initial accumulated charge based on the first voltage and the second voltage includes: Calculate the voltage difference between the first voltage and the second voltage; The initial accumulated charge is determined based on the voltage difference and the preset feedback control model.

8. The control method as described in claim 1, characterized in that: The reference current includes a given d-axis current and a given q-axis current. The determination of the zero-sequence injection voltage based on the reference current, the modulation voltage corresponding to each phase line, and the initial accumulated charge includes: The reference current corresponding to each phase line is determined based on the given d-axis current and the given q-axis current. The zero-sequence injection voltage is determined based on the reference current corresponding to each phase line, the modulation voltage corresponding to each phase line, and the initial accumulated charge.

9. A motor driver, characterized in that, The device includes a three-level inverter, a motor, and a controller. The three-level inverter is connected to the motor, and the controller is connected to both the three-level inverter and the motor. The controller is used to execute the control method of the three-level inverter as described in any one of claims 1 to 8.

10. A vehicle, characterized in that, The vehicle includes the motor drive as described in claim 9.

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