A modulation method and device for suppressing common mode voltage in a new energy electric drive system

Abstract

The present invention discloses a modulation method and device for suppressing the common mode voltage in a new energy electric drive system, and relates to the technical field of voltage modulation. The method mainly includes: based on a common mode voltage suppression modulation algorithm, four non-zero voltage vectors for synthesizing a reference voltage vector are determined according to the sector where the reference voltage vector is located; based on the volt-second balance principle, a mathematical expression of the action time of the four non-zero voltage vectors with respect to the reference voltage vector is determined; based on the harmonic flux minimization principle, an action time optimization model is established according to the mathematical expression of the action time of the four non-zero voltage vectors with respect to the reference voltage vector; the action time optimization model is solved to obtain the action time of the four non-zero voltage vectors, thereby calculating the common mode injection voltage to realize modulation. The present invention can reduce current harmonics while suppressing the common mode voltage, and eliminate the common mode voltage spikes and line voltage mutations caused by the traditional modulation algorithm.

Description

Technical Field

[0001] The present invention relates to the field of voltage modulation technology, and in particular to a modulation method and device for suppressing common-mode voltage in a new energy electric drive system. Background Art

[0002] In recent years, the rapid development of new energy technologies has fueled the rapid advancement of inverter-related technologies, while also placing higher demands on the stable and safe operation of inverters. Permanent magnet synchronous motors (PMSMs), with their small size, simple structure, and high efficiency and energy saving, are widely used in new energy vehicles. Two-level voltage source inverters, due to their high reliability, mature technology, and low cost, are widely used to drive PMSMs. Traditional space vector pulse width modulation and discontinuous pulse width modulation are the standard modulation methods for two-level voltage source inverters. However, these traditional modulation methods introduce significant common-mode voltage in new energy electric drive systems.

[0003] Common-mode voltage can cause numerous engineering application problems, such as electromagnetic interference, sensor failure, and even physical damage. In new energy electric drive systems, common-mode voltage transmitted to the motor can cause shaft current and voltage issues. Excessive shaft current can damage the motor bearings, while shaft voltage can be transmitted to the external space through parasitic capacitance, causing electromagnetic interference. Common-mode voltage can also couple into the battery via the DC bus, affecting the operation of the battery's internal controller and voltage diagnostics.

[0004] Currently, the main algorithms for suppressing common-mode voltage in two-level inverters include active zero-vector modulation, far-vector modulation, and near-vector modulation. Active zero-vector modulation effectively reduces the common-mode voltage amplitude, and its linear modulation range is unconstrained. However, it can lead to large current harmonics and, when considering dead-band effects, common-mode voltage spikes and excessive line voltage variation. While far-vector modulation and near-vector modulation can reduce common-mode voltage, their modulation range is limited compared to traditional space vector modulation, and they are also associated with significant current distortion. Summary of the Invention

[0005] The purpose of the present invention is to provide a modulation method and device for suppressing the common-mode voltage in a new energy electric drive system, which can reduce current harmonics while suppressing the common-mode voltage and eliminate the common-mode voltage spikes and line voltage mutations caused by traditional modulation algorithms.

[0006] To achieve the above objectives, the present invention provides the following solutions.

[0007] A modulation method for suppressing common mode voltage in a new energy electric drive system, comprising:

[0008] Obtaining a reference voltage vector and determining the sector in which the reference voltage vector is located based on the phase angle of the reference voltage vector; the reference voltage vector is obtained by coordinate transformation of a three-phase reference voltage; the three-phase reference voltage is obtained by inverting a DC voltage through an inverter;

[0009] Based on the suppression common mode voltage modulation algorithm, four non-zero voltage vectors for synthesizing the reference voltage vector are determined according to the sector where the reference voltage vector is located;

[0010] Based on the volt-second balance principle, determine the mathematical expression of the action time of the four non-zero voltage vectors with respect to the reference voltage vector;

[0011] Based on the harmonic flux minimization principle, an action time optimization model is established according to the mathematical expression of the action time of four non-zero voltage vectors with respect to the reference voltage vector.

[0012] Solve the action time optimization model to obtain the action times of four non-zero voltage vectors;

[0013] The common-mode injection voltage is calculated according to the action time of the four non-zero voltage vectors, and the common-mode injection voltage is added to the three-phase reference voltage to obtain the modulated wave;

[0014] The three-phase carrier is determined according to the sector where the reference voltage vector is located, and the three-phase carrier is compared with the modulation wave to generate PWM pulses; the PWM pulses are used to drive the motor to rotate.

[0015] Optionally, the coordinate transformation formula of the reference voltage vector and the three-phase reference voltage is:

[0016] ;

[0017] in, is the reference voltage vector of Axis component, is the reference voltage vector of Axis component, is the reference voltage of phase A, is the B-phase reference voltage, is the C-phase reference voltage.

[0018] Optionally, based on the common mode voltage suppression modulation algorithm, four non-zero voltage vectors for synthesizing the reference voltage vector are determined according to the sector where the reference voltage vector is located, specifically including:

[0019] When the sector where the reference voltage vector is located is the S1 sector, the four non-zero voltage vectors used to synthesize the reference voltage vector are V6, V1, V2, and V3, and the order of action of the four non-zero voltage vectors is V6-V1-V2-V3-V2-V1-V6;

[0020] When the sector where the reference voltage vector is located is the S2 sector, the four non-zero voltage vectors used to synthesize the reference voltage vector are V1, V2, V3 and V4, and the order of action of the four non-zero voltage vectors is V1-V2-V3-V4-V3-V2-V1;

[0021] When the sector where the reference voltage vector is located is the S3 sector, the four non-zero voltage vectors used to synthesize the reference voltage vector are V2, V3, V4, and V5, and the order of action of the four non-zero voltage vectors is V2-V3-V4-V5-V4-V3-V2;

[0022] When the sector where the reference voltage vector is located is the S4 sector, the four non-zero voltage vectors used to synthesize the reference voltage vector are V3, V4, V5 and V6, and the order of action of the four non-zero voltage vectors is V3-V4-V5-V6-V5-V4-V3;

[0023] When the sector where the reference voltage vector is located is the S5 sector, the four non-zero voltage vectors used to synthesize the reference voltage vector are V4, V5, V6 and V1, and the order of action of the four non-zero voltage vectors is V4-V5-V6-V1-V6-V5-V4;

[0024] When the sector where the reference voltage vector is located is the S6 sector, the four non-zero voltage vectors used to synthesize the reference voltage vector are V5, V6, V1 and V2, and the action order of the four non-zero voltage vectors is V5-V6-V1-V2-V1-V6-V5.

[0025] Optionally, the mathematical expression of the action time of the four non-zero voltage vectors with respect to the reference voltage vector is:

[0026] ;

[0027] ;

[0028] in, is the reference voltage vector, is the switching period, is a non-zero voltage vector The action time, is a non-zero voltage vector The action time, is a non-zero voltage vector The action time, is a non-zero voltage vector The action time, 、 、 and The value of is 1 to 6.

[0029] Optionally, the action time optimization model includes an objective function and constraints, and the optimization goal is to minimize the objective function under the constraints;

[0030] The mathematical expression of the objective function is:

[0031] ;

[0032] ;

[0033] ;

[0034] ;

[0035] ;

[0036] in, is the objective function value, and are all intermediate parameters. is a constant, is a non-zero voltage vector The duty cycle of the action, is the reference voltage vector, is the reference voltage vector After switching to the first sector Axis component, is the reference voltage vector After switching to the first sector Axis component, is the reference voltage vector The phase angle, is the reference voltage vector The sector number;

[0037] The mathematical expression of the constraint condition is:

[0038] ;

[0039] in, is a non-zero voltage vector The duty cycle of the action, is the sequence number of the non-zero voltage vector, is the minimum duty cycle allowed for a non-zero voltage vector, 、 、 and The value of is 1 to 6.

[0040] Optionally, the common-mode injection voltage is calculated according to the action time of the four non-zero voltage vectors, specifically including:

[0041] Calculate the average common-mode voltage based on the action time of four non-zero voltage vectors;

[0042] The common-mode injection voltage is determined according to the average common-mode voltage and the sector where the reference voltage vector is located.

[0043] Optionally, the calculation formula for the average common-mode voltage is:

[0044] ;

[0045] in, is the average common-mode voltage, is the DC voltage, is a non-zero voltage vector The duty cycle of the action, is a non-zero voltage vector The duty cycle of the action, is a non-zero voltage vector The duty cycle of the action, is a non-zero voltage vector Duty cycle is the reference voltage vector After switching to the first sector Axis component, is the reference voltage vector After switching to the first sector Axis component, 、 、 and The value of is 1 to 6.

[0046] Optionally, determining the common-mode injection voltage according to the average common-mode voltage and the sector in which the reference voltage vector is located specifically includes:

[0047] When the sector where the reference voltage vector is located is the S1 sector, the common mode injection voltage is ;

[0048] When the sector where the reference voltage vector is located is the S2 sector, the common mode injection voltage is ;

[0049] When the sector where the reference voltage vector is located is the S3 sector, the common mode injection voltage is ;

[0050] When the sector where the reference voltage vector is located is the S4 sector, the common mode injection voltage is ;

[0051] When the sector where the reference voltage vector is located is the S5 sector, the common mode injection voltage is ;

[0052] When the sector where the reference voltage vector is located is the S6 sector, the common mode injection voltage is .

[0053] Optionally, determining the three-phase carrier according to the sector where the reference voltage vector is located specifically includes:

[0054] When the sector where the reference voltage vector is located is the S1 sector, the three-phase carriers are 、 and ;

[0055] When the sector where the reference voltage vector is located is the S2 sector, the three-phase carriers are 、 and ;

[0056] When the sector where the reference voltage vector is located is the S3 sector, the three-phase carriers are 、 and ;

[0057] When the sector where the reference voltage vector is located is the S4 sector, the three-phase carriers are 、 and ;

[0058] When the sector where the reference voltage vector is located is the S5 sector, the three-phase carriers are 、 and ;

[0059] When the sector where the reference voltage vector is located is the S6 sector, the three-phase carriers are 、 and .

[0060] A computer device includes: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the modulation method for suppressing the common-mode voltage in a new energy electric drive system.

[0061] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0062] The modulation method for suppressing common-mode voltage in a new energy electric drive system, provided by the present invention, uses four non-zero voltage vectors to synthesize a reference voltage vector, eliminating the large common-mode voltage caused by using a zero vector. A time optimization model is established and solved based on the mathematical expression of the action time of the four non-zero voltage vectors with respect to the reference voltage vector. This optimally distributes the action time of the four non-zero voltage vectors, eliminating common-mode voltage spikes, avoiding excessive line voltage variation, and minimizing current harmonics. Furthermore, the modulation method for suppressing common-mode voltage in a new energy electric drive system, provided by the present invention, can be optimized online and implemented based on a carrier wave, eliminating the need to change the hardware structure and simplifying implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0064] Figure 1 This is a structural block diagram of the new energy electric drive system provided by the present invention.

[0065] Figure 2 This is a schematic diagram of a two-level inverter driving a permanent magnet synchronous motor provided by the present invention.

[0066] Figure 3 This is a flow chart of the modulation method for suppressing common-mode voltage in a new energy electric drive system provided by the present invention.

[0067] Figure 4 This is the space vector diagram of the two-level inverter provided by the present invention.

[0068] Figure 5 Harmonic flux trajectory diagrams of the three modulation algorithms provided by the present invention.

[0069] Figure 6 This is a schematic diagram of a carrier implementation using the modulation algorithm provided by the present invention.

[0070] Figure 7 This is a diagram of the common-mode voltage simulation results when the active zero vector modulation algorithm provided by the present invention is adopted.

[0071] Figure 8 This is a diagram of the common-mode voltage simulation results using the SVPWM algorithm provided by the present invention.

[0072] Figure 9 This is a diagram of the common-mode voltage simulation results using the modulation algorithm provided by the present invention.

[0073] Figure 10This is a diagram of the A-phase current simulation results using the active zero vector modulation algorithm provided by the present invention.

[0074] Figure 11 This is a diagram of the simulation results of phase A current using the SVPWM algorithm provided by the present invention.

[0075] Figure 12 This is a diagram of the simulation results of phase A current using the modulation algorithm provided by the present invention.

[0076] Figure 13 The present invention provides a line voltage modulation algorithm using active zero vector modulation Simulation result diagram.

[0077] Figure 14 The line voltage using the SVPWM algorithm provided by the present invention Simulation result diagram.

[0078] Figure 15 The line voltage modulation algorithm provided by the present invention is Simulation result diagram. DETAILED DESCRIPTION

[0079] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0080] In response to the problems existing in the existing technology, the present invention proposes a modulation method and device for suppressing the common-mode voltage in the new energy electric drive system based on the traditional active zero-vector modulation algorithm. The method and device can suppress the common-mode voltage while reducing current harmonics and eliminating the common-mode voltage spikes and line voltage mutations caused by the traditional modulation algorithm.

[0081] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0082] The modulation method for suppressing the common mode voltage in the new energy electric drive system proposed in the present invention is applied to the new energy electric drive system. The structure of the new energy electric drive system is shown in FIG. Figure 1 ,in, Represents the reference voltage vector of Axis component, Represents the reference voltage vector of Axis component, represents the A-phase modulation voltage, represents the B-phase modulation voltage, represents the C-phase modulation voltage, represents the common-mode injection voltage, Indicates the carrier wave, Represents DC voltage. New energy electric drive systems generally consist of an energy storage system, an inverter, a motor, and a transmission mechanism. The energy storage system provides stable DC power, which is converted into three-phase AC power by the inverter to drive the motor, and the transmission mechanism is omitted. The process of a two-level inverter driving a permanent magnet synchronous motor (PMSM) is shown in Figure 2 ,in, Indicates DC voltage, Indicates the DC voltage midpoint, 、 and They are the marking points on the three bridge arms of the two-level inverter. Indicates the place, Indicates the neutral point of the load, Represents common-mode voltage. The present invention suppresses common-mode voltage modulation in new energy electric drive systems by providing an online optimizer and selector. The online optimizer collects a reference voltage vector and calculates the common-mode injection voltage used to reduce current harmonics. The common-mode injection voltage is added to the three-phase reference voltage and compared with a set of three-phase carriers selected by the selector to generate PWM pulses.

[0083] like Figure 3 As shown, the specific implementation process of the above modulation method is as follows.

[0084] Step 1: Obtain a reference voltage vector and determine the sector in which the reference voltage vector is located based on its phase angle. The reference voltage vector is obtained by coordinate transformation of a three-phase reference voltage; the three-phase reference voltage is obtained by inverting a DC voltage through an inverter and can be directly acquired by the controller.

[0085] Specifically, the coordinate transformation formula of the reference voltage vector and the three-phase reference voltage is:

[0086] ;

[0087] in, is the reference voltage vector of Axis component, is the reference voltage vector of Axis component, is the reference voltage of phase A, is the B-phase reference voltage, is the C-phase reference voltage.

[0088] like Figure 4As shown in FIG, the space vector diagram of the two-level inverter is evenly divided into six sectors S1 to S6. When the phase angle of the reference voltage vector is 0-60°, it is in the S1 sector; when the phase angle is 60°-120°, it is in the S2 sector, and so on.

[0089] Step 2: Based on a suppressed common mode voltage modulation algorithm, four non-zero voltage vectors for synthesizing a reference voltage vector are determined according to the sector in which the reference voltage vector is located. Preferably, the suppressed common mode voltage modulation algorithm is an active zero vector pulse width modulation (AZSPWM) algorithm.

[0090] The selected non-zero voltage vectors and their action sequence when the reference voltage vector is in different sectors are shown in Table 1.

[0091] Table 1 Action sequence of non-zero voltage vectors

[0092]

[0093] Among them, V1-V6 represent the six switching vectors of the space vector diagram. The action order represents the order in which the switching state of the inverter changes over time in each switching cycle, corresponding to the switching state 100-101. 1 indicates that the upper bridge arm is turned on and the lower bridge arm is turned off, and 0 indicates that the upper bridge arm is turned off and the lower bridge arm is turned on.

[0094] When the sector where the reference voltage vector is located is the S1 sector, the four non-zero voltage vectors used to synthesize the reference voltage vector are V6, V1, V2 and V3, and the action order of the four non-zero voltage vectors is V6-V1-V2-V3-V2-V1-V6.

[0095] When the sector where the reference voltage vector is located is the S2 sector, the four non-zero voltage vectors used to synthesize the reference voltage vector are V1, V2, V3 and V4, and the action order of the four non-zero voltage vectors is V1-V2-V3-V4-V3-V2-V1.

[0096] When the sector where the reference voltage vector is located is the S3 sector, the four non-zero voltage vectors used to synthesize the reference voltage vector are V2, V3, V4 and V5, and the action order of the four non-zero voltage vectors is V2-V3-V4-V5-V4-V3-V2.

[0097] When the sector where the reference voltage vector is located is the S4 sector, the four non-zero voltage vectors used to synthesize the reference voltage vector are V3, V4, V5 and V6, and the action order of the four non-zero voltage vectors is V3-V4-V5-V6-V5-V4-V3.

[0098] When the sector where the reference voltage vector is located is the S5 sector, the four non-zero voltage vectors used to synthesize the reference voltage vector are V4, V5, V6 and V1, and the action order of the four non-zero voltage vectors is V4-V5-V6-V1-V6-V5-V4.

[0099] When the sector where the reference voltage vector is located is the S6 sector, the four non-zero voltage vectors used to synthesize the reference voltage vector are V5, V6, V1 and V2, and the action order of the four non-zero voltage vectors is V5-V6-V1-V2-V1-V6-V5.

[0100] Step 3: Based on the volt-second balance principle, determine the mathematical expression of the action time of the four non-zero voltage vectors with respect to the reference voltage vector.

[0101] The mathematical expression is as follows:

[0102] ;

[0103] ;

[0104] in, is the reference voltage vector, is the switching period, is a non-zero voltage vector The action time, is a non-zero voltage vector The action time, is a non-zero voltage vector The action time, is a non-zero voltage vector The action time, subscript 、 、 and They represent the serial numbers of the four non-zero voltage vectors respectively. For the specific relationship between them and the sectors, please refer to the 2nd to 5th columns in Table 1.

[0105] Taking the reference voltage vector in the S1 sector as an example, the relationship between each non-zero voltage vector and the reference voltage vector is as follows:

[0106] ;

[0107] ;

[0108] in, is a non-zero voltage vector The action time, is a non-zero voltage vector The action time, is a non-zero voltage vector The action time, is a non-zero voltage vector action time.

[0109] When the reference voltage vector is in the remaining five sectors S2-S6, it can be converted to the first sector S1 through a simple coordinate transformation, so the calculation is consistent with that when the reference voltage vector is in the first sector S1. The principle of coordinate transformation is that the phase angle changes and the amplitude remains unchanged. The formula is ,in Represents the reference voltage vector The phase angle after conversion to the first sector, Represents the reference voltage vector The phase angle, Represents the reference voltage vector The sector number.

[0110] Step 4: Based on the harmonic flux minimization principle, establish an action time optimization model based on the mathematical expression of the action time of the four non-zero voltage vectors with respect to the reference voltage vector. Preferably, the action time optimization model includes an objective function and constraints, and the optimization goal is to minimize the objective function under the constraints.

[0111] In one switching cycle, the harmonic flux can be expressed as follows:

[0112] ;

[0113] in, is the harmonic flux linkage, is the actual voltage vector, For the switching cycles, For time.

[0114] Its root mean square value is:

[0115] ;

[0116] in, is the RMS value of the harmonic flux linkage.

[0117] For the above voltage vector selection method, It can be further expressed as:

[0118] ;

[0119] ;

[0120] ;

[0121] ;

[0122] ;

[0123] in, and are all intermediate parameters. is a constant, is a non-zero voltage vector The duty cycle of the action, that is , is the reference voltage vector After switching to the first sector Axis component, is the reference voltage vector After switching to the first sector Axis component.

[0124] Therefore, the established action time optimization model can be expressed as:

[0125] Objective function: ;

[0126] Constraints: ;

[0127] in, is a non-zero voltage vector The duty cycle of the action, that is , is the sequence number of the non-zero voltage vector, The minimum duty cycle allowed for a non-zero voltage vector. Setting the minimum duty cycle can avoid common-mode voltage peaks and line voltage mutations caused by the dead zone effect.

[0128] Specifically, taking the reference voltage vector in the first sector as an example, 、 、 and The values ​​of are 6, 1, 2 and 3 respectively. The value of is 1, then , .

[0129] Step 5: Solve the action time optimization model to obtain the action time of the four non-zero voltage vectors.

[0130] The harmonic flux linkage within a switching cycle is minimized to reduce current harmonics. The principle is that within a switching cycle, the integral of the deviation of the actual voltage vector from the reference voltage vector can be defined as the harmonic flux linkage. When the actual voltage vector acts continuously in time in the defined vector action sequence, its harmonic flux linkage can be represented as a closed geometric figure, such as Figure 5As shown, the distance of the geometric figure's center of gravity from the origin represents the magnitude of the harmonics. The traditional space vector pulse width modulation (SVPWM) algorithm minimizes harmonics, but its common-mode voltage is large. The active zero vector modulation algorithm reduces the common-mode voltage, but its harmonic components increase. The modulation algorithm of the present invention redistributes the action time of the non-zero voltage vector in the active zero vector modulation algorithm, minimizing the root mean square value of the harmonic flux linkage, thereby reducing harmonics. The above-mentioned action time optimization model is essentially a constrained quadratic equation problem for finding the extreme value. The solution does not require a large amount of computation time and can therefore be calculated online.

[0131] By setting the action time of the minimum non-zero voltage vector, the common mode voltage spike and line voltage mutation problems can be effectively improved. The principle is: Figure 4 As shown in the traditional active zero vector modulation algorithm, when the reference voltage vector is close to the voltage vector V1, according to the above volt-second balance calculation formula, the action time of the voltage vector V2 will be very short, which will cause the switch state to suddenly change from 100 to 010, causing the line voltage to change from arrive And when considering the dead zone effect, the state of the switch during the dead zone depends only on the direction of the current, which may lead to the appearance of the switch state 000, and the switch state 000 corresponds to In the present invention, by setting the action time of the minimum non-zero voltage vector, direct switching of non-adjacent non-zero switching vectors can be effectively prevented, thus avoiding sudden changes in line voltage and common-mode voltage spikes.

[0132] Step 6: Calculate the common-mode injection voltage based on the duration of the four non-zero voltage vectors, and add the common-mode injection voltage to the three-phase reference voltage to obtain a modulated wave. Preferably, first, calculate the average common-mode voltage based on the duration of the four non-zero voltage vectors; then determine the common-mode injection voltage based on the average common-mode voltage and the sector in which the reference voltage vector is located. This common-mode injection voltage is then sent to the inverter via the modulation module.

[0133] After solving a constrained binary linear equation to obtain the optimal non-zero voltage vector action time, in order to further reduce the calculation time of the system, a carrier-based implementation method can be used to calculate the corresponding common-mode injection voltage when the carrier-based implementation is based on the following principle: Figure 6 As shown, is a positive carrier, is the result of a 180° phase shift of the positive carrier, They are three-phase modulation voltage (i.e. modulation wave), They are the ABC three-phase switch states, is the line voltage, is the common mode voltage (i.e. By adjusting the magnitude of the common-mode injection voltage, any non-zero voltage vector action time can be achieved. By following the principle of equal average common-mode voltage, the common-mode injection voltage can be obtained from the action time of four non-zero switching vectors.

[0134] The average common-mode voltage is given by:

[0135] ;

[0136] in, is the average common-mode voltage, is the DC voltage, is a non-zero voltage vector The duty cycle of the action, is a non-zero voltage vector The duty cycle of the action, is a non-zero voltage vector The duty cycle of the action, is a non-zero voltage vector The duty cycle of the action.

[0137] Taking the reference voltage vector in the S1 sector as an example, the formula can be written as:

[0138] .

[0139] Specifically, the common mode injection voltage is determined according to the average common mode voltage and the sector where the reference voltage vector is located in the following manner: when the sector where the reference voltage vector is located is the S1 sector, the common mode injection voltage is When the reference voltage vector is located in the S2 sector, the common mode injection voltage is When the reference voltage vector is located in the S3 sector, the common mode injection voltage is When the reference voltage vector is located in the S4 sector, the common mode injection voltage is When the reference voltage vector is located in the S5 sector, the common mode injection voltage is When the reference voltage vector is located in the S6 sector, the common mode injection voltage is .

[0140] Step 7: Determine the three-phase carrier wave according to the sector where the reference voltage vector is located, and compare the three-phase carrier wave with the modulation wave to generate PWM pulses. The PWM pulses are used to drive the motor to rotate.

[0141] Compared with the traditional SPWM single carrier modulation algorithm, the present invention adopts a 180 degree difference Dual Carrier The common-mode injection voltage of each sector and the relationship between each sector and each phase carrier are shown in Table 2.

[0142] Table 2 Common-mode injection voltage of each sector and the relationship between each sector and each phase carrier

[0143]

[0144] in, 、 and Represent the carriers of phases A, B and C respectively, express , express , that is: when the sector where the reference voltage vector is located is the S1 sector, the three-phase carriers are 、 and When the reference voltage vector is located in the S2 sector, the three-phase carriers are 、 and When the sector where the reference voltage vector is located is the S3 sector, the three-phase carriers are 、 and When the sector where the reference voltage vector is located is S4 sector, the three-phase carriers are 、 and When the reference voltage vector is located in the S5 sector, the three-phase carriers are 、 and When the reference voltage vector is located in the S6 sector, the three-phase carriers are 、 and .

[0145] Taking the reference voltage vector in the S1 sector as an example, the A phase modulation voltage is compared with By comparison, the B-phase modulation voltage and the C-phase modulation voltage are both Compare; if the comparison result is greater than, the corresponding switch state is 1, indicating that the upper bridge arm is turned on and the lower bridge arm is turned off. If the comparison result is less than, the corresponding switch state is 0, indicating that the upper bridge arm is turned off and the lower bridge arm is turned on.

[0146] Under the same working conditions, the active zero vector modulation algorithm, SVPWM algorithm and the modulation method for suppressing the common mode voltage in the new energy electric drive system provided by the present invention (hereinafter referred to as the modulation algorithm of the present invention) are respectively used to perform simulations using simulation software such as MATLAB and SIMULINK. The simulation results are shown in Figures 7 to 15 .

[0147] Figure 7 、 Figure 8 and Figure 9The common-mode voltage simulation results when using the active zero-vector modulation algorithm, SVPWM algorithm and the modulation algorithm of the present invention are shown respectively. It can be seen that the common-mode voltage of the SVPWM algorithm is the largest. Although the active zero-vector modulation algorithm can reduce the common-mode voltage, it will cause the occurrence of common-mode voltage spikes. Common-mode voltage spikes will also cause electromagnetic interference to equipment and systems. The modulation algorithm of the present invention suppresses the occurrence of common-mode voltage spikes while reducing the common-mode voltage.

[0148] Figure 10 、 Figure 11 and Figure 12 The following are the simulation results of phase A current when using the active zero vector modulation algorithm, SVPWM algorithm, and the modulation algorithm of the present invention, respectively. THD stands for Total Harmonics Distortion. It can be seen that the current harmonics of the SVPWM algorithm are the smallest, and the current harmonics of the active zero vector modulation algorithm are the largest. The modulation algorithm of the present invention reduces the current harmonics while reducing the common-mode voltage.

[0149] Figure 13 、 Figure 14 and Figure 15 The line voltages when using active zero vector modulation algorithm, SVPWM algorithm and modulation algorithm of the present invention are respectively From the simulation results, we can see that the line voltage of the SVPWM algorithm will not change from arrive The active zero vector modulation algorithm will cause the line voltage to change from arrive The sudden change in line voltage can damage the insulation of the motor in some applications, such as motors with long leads. The modulation algorithm of the present invention reduces the common-mode voltage while adding a relatively long zero level as a transition, eliminating the direct sudden change in line voltage.

[0150] In summary, the modulation method for suppressing the common mode voltage in the new energy electric drive system provided by the present invention is simple to implement and can be realized based on carrier modulation. The common mode voltage is effectively suppressed and its amplitude is reduced from Reduced to , common-mode voltage spikes and line voltage mutations are effectively eliminated, current quality is improved, and the performance and stability of the system are effectively increased.

[0151] In one embodiment, a computer program product is further provided, including a computer program, which implements the steps in the above method embodiments when executed by a processor.

[0152] In one embodiment, a computer-readable storage medium is further provided, on which a computer program is stored. When the computer program is executed by a processor, the steps in the above-mentioned method embodiments are implemented.

[0153] In one embodiment, a computer device is further provided, including a memory and a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps in the above-mentioned method embodiments are implemented.

[0154] Furthermore, the computer device also includes an input / output (I / O) interface and a communication interface. The processor, memory, and I / O interface are connected via a system bus, and the communication interface is connected to the system bus via the I / O interface. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and computer program in the non-volatile storage medium. The database of the computer device is used to store pending transactions. The I / O interface of the computer device is used to exchange information between the processor and external devices. The communication interface of the computer device is used to communicate with external terminals via a network connection. When the computer program is executed by the processor, the steps of the above-mentioned method embodiments are implemented.

[0155] It should be noted that the object information (including but not limited to object device information, object personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the object or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant laws, regulations and standards.

[0156] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the above-mentioned embodiments. In particular, any reference to memory, database, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The databases involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processors involved in the various embodiments provided herein may be, but are not limited to, general-purpose processors, central processing units (CPUs), graphics processing units (GPUs), digital signal processors (DSPs), programmable logic devices (PLDs), data processing logic devices based on quantum computing, and the like.

[0157] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0158] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A modulation method for suppressing common mode voltage in a new energy electric drive system, characterized in that: include: Obtaining a reference voltage vector, and determining a sector where the reference voltage vector is located according to a phase angle of the reference voltage vector; The reference voltage vector is obtained by coordinate transformation of the three-phase reference voltage; The three-phase reference voltage is obtained by inverting the DC voltage through an inverter; Based on the suppression common mode voltage modulation algorithm, four non-zero voltage vectors for synthesizing the reference voltage vector are determined according to the sector where the reference voltage vector is located; Based on the volt-second balance principle, the mathematical expressions of the action times of the four non-zero voltage vectors with respect to the reference voltage vector are determined; Based on the harmonic flux minimization principle, an action time optimization model is established according to the mathematical expression of the action time of four non-zero voltage vectors with respect to the reference voltage vector. The action time optimization model is solved to obtain the action times of four non-zero voltage vectors; The common-mode injection voltage is calculated according to the action time of four non-zero voltage vectors, and the common-mode injection voltage is added to the three-phase reference voltage to obtain a modulated wave; Determine the three-phase carrier according to the sector where the reference voltage vector is located, and compare the three-phase carrier with the modulation wave to generate a PWM pulse; the PWM pulse is used to drive the motor to rotate; The action time optimization model includes an objective function and constraints, and the optimization goal is to minimize the objective function under the constraints. The mathematical expression of the objective function is: ； ； ； ； ； in, is the objective function value, and All are intermediate parameters. is a constant, is a non-zero voltage vector The duty cycle of the action, is the reference voltage vector, is the reference voltage vector After switching to the first sector Axis component, is the reference voltage vector After switching to the first sector Axis component, is the reference voltage vector The phase angle, is the reference voltage vector The sector number; The mathematical expression of the constraint condition is: ； in, is a non-zero voltage vector The duty cycle of the action, is the sequence number of the non-zero voltage vector, is the minimum duty cycle allowed for a non-zero voltage vector, , , and The value of is 1 to 6.

2. The modulation method for suppressing the common mode voltage in the new energy electric drive system according to claim 1 is characterized in that: The coordinate transformation formula of the reference voltage vector and the three-phase reference voltage is: ； in, is the reference voltage vector of Axis component, is the reference voltage vector of Axis component, is the A phase reference voltage, is the B phase reference voltage, is the C phase reference voltage.

3. The modulation method for suppressing common mode voltage in a new energy electric drive system according to claim 1, characterized in that: Based on the suppression common mode voltage modulation algorithm, four non-zero voltage vectors for synthesizing the reference voltage vector are determined according to the sector where the reference voltage vector is located, specifically including: When the sector where the reference voltage vector is located is the S1 sector, the four non-zero voltage vectors used to synthesize the reference voltage vector are V6, V1, V2 and V3, and the action order of the four non-zero voltage vectors is V6-V1-V2-V3-V2-V1-V6; When the sector where the reference voltage vector is located is the S2 sector, the four non-zero voltage vectors used to synthesize the reference voltage vector are V1, V2, V3 and V4, and the action order of the four non-zero voltage vectors is V1-V2-V3-V4-V3-V2-V1; When the sector where the reference voltage vector is located is the S3 sector, the four non-zero voltage vectors used to synthesize the reference voltage vector are V2, V3, V4 and V5, and the action order of the four non-zero voltage vectors is V2-V3-V4-V5-V4-V3-V2; When the sector where the reference voltage vector is located is the S4 sector, the four non-zero voltage vectors used to synthesize the reference voltage vector are V3, V4, V5 and V6, and the action order of the four non-zero voltage vectors is V3-V4-V5-V6-V5-V4-V3; When the sector where the reference voltage vector is located is the S5 sector, the four non-zero voltage vectors used to synthesize the reference voltage vector are V4, V5, V6 and V1, and the action order of the four non-zero voltage vectors is V4-V5-V6-V1-V6-V5-V4; When the sector where the reference voltage vector is located is the S6 sector, the four non-zero voltage vectors used to synthesize the reference voltage vector are V5, V6, V1 and V2, and the action order of the four non-zero voltage vectors is V5-V6-V1-V2-V1-V6-V5.

4. The modulation method for suppressing common mode voltage in a new energy electric drive system according to claim 1, characterized in that: The mathematical expression of the action time of the four non-zero voltage vectors with respect to the reference voltage vector is: ； ； in, is the switching cycle, is a non-zero voltage vector The action time, is a non-zero voltage vector The action time, is a non-zero voltage vector The action time, is a non-zero voltage vector action time.

5. The modulation method for suppressing common mode voltage in a new energy electric drive system according to claim 1, characterized in that: The common-mode injection voltage is calculated based on the action time of the four non-zero voltage vectors, including: Calculate the average common-mode voltage based on the action time of four non-zero voltage vectors; The common-mode injection voltage is determined according to the average common-mode voltage and the sector where the reference voltage vector is located.

6. The modulation method for suppressing common mode voltage in a new energy electric drive system according to claim 5, characterized in that: The calculation formula of the average common mode voltage is: ； in, is the average common-mode voltage, is the DC voltage, is a non-zero voltage vector The duty cycle of the action, is a non-zero voltage vector The duty cycle of the action, is a non-zero voltage vector The duty cycle of the action.

7. The modulation method for suppressing common mode voltage in a new energy electric drive system according to claim 6, characterized in that: The common mode injection voltage is determined according to the average common mode voltage and the sector where the reference voltage vector is located, specifically including: When the sector where the reference voltage vector is located is the S1 sector, the common-mode injection voltage is ; When the sector where the reference voltage vector is located is the S2 sector, the common-mode injection voltage is ; When the sector where the reference voltage vector is located is the S3 sector, the common-mode injection voltage is ; When the sector where the reference voltage vector is located is the S4 sector, the common-mode injection voltage is ; When the sector where the reference voltage vector is located is the S5 sector, the common mode injection voltage is ; When the sector where the reference voltage vector is located is the S6 sector, the common mode injection voltage is .

8. The modulation method for suppressing common mode voltage in a new energy electric drive system according to claim 7, characterized in that: The three-phase carrier is determined according to the sector where the reference voltage vector is located, specifically including: When the sector where the reference voltage vector is located is the S1 sector, the three-phase carriers are , and ; When the sector where the reference voltage vector is located is the S2 sector, the three-phase carriers are , and ; When the sector where the reference voltage vector is located is the S3 sector, the three-phase carriers are , and ; When the sector where the reference voltage vector is located is the S4 sector, the three-phase carriers are , and ; When the sector where the reference voltage vector is located is the S5 sector, the three-phase carriers are , and ; When the sector where the reference voltage vector is located is the S6 sector, the three-phase carriers are , and .

9. A computer device comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement a modulation method for suppressing common-mode voltage in a new energy electric drive system as described in any one of claims 1-8.

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