Five-phase motor fast pulse width modulation method based on multi-vector model predictive current control

Abstract

The application provides a kind of five-phase motor fast pulse width modulation method based on multi-vector model prediction current control, to solve the problem that higher control accuracy and lower algorithm complexity cannot be achieved simultaneously in the existing five-phase permanent magnet synchronous motor model prediction current control strategy.The method comprises: establishing motor model and model prediction value evaluation function;combining current error and coordinate transformation theory, updating the expression of value evaluation function;the value evaluation function is subjected to partial differentiation with respect to duty cycle to obtain the minimum value, and the virtual duty cycle is obtained;the virtual duty cycle is reconstructed, and then acts on the inverter to drive the five-phase motor to run.The application adopts model prediction current control theory, combines fast pulse width modulation strategy, can actively and in advance calculate the optimal control duty cycle, so as to obtain faster dynamic response and lower overshoot than traditional model prediction control strategy.

Description

Technical Field

[0001] This invention relates to the field of high-performance control of permanent magnet synchronous motors, specifically a fast pulse width modulation method for a five-phase motor based on multi-vector model predictive current control. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) have become core power components in high-end industrial servo systems and new energy vehicles due to their high power density and efficiency. Continuous improvement in their control performance is key to driving development in these fields. To achieve high-performance control of PMSMs, in addition to traditional control methods (such as PI control), model predictive control (MMC) has become a research hotspot in academia and industry due to its advantages such as fast dynamic response, intuitive concepts, and ease of handling multiple variables. It is widely considered one of the mainstream technologies for next-generation motor control.

[0003] Currently, various modulation methods based on model predictive current control can be broadly categorized into single-vector and multi-vector methods. Single-vector modulation methods have a lower computational burden, but because only one basic voltage vector can be selected per cycle, their output is inherently discontinuous. This leads to errors between the selected optimal vector and the ideal target vector, resulting in significant current distortion and severely limited control accuracy. Multi-vector modulation methods analyze voltage vector space through geometric relationships, thus achieving higher control accuracy. However, their geometric solution process typically involves complex trigonometric function calculations or piecewise function judgments, resulting in high computational complexity and posing a significant challenge to the real-time computing capabilities of the controller. Summary of the Invention

[0004] The present invention aims to solve the major technical contradiction in the existing model predictive current control strategy for five-phase permanent magnet synchronous motors, which is that high control accuracy and low algorithm complexity cannot be achieved at the same time.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a fast pulse width modulation method for a five-phase motor based on multi-vector model predictive current control, comprising:

[0006] S1: Collect the phase current and angle signals of the motor at the current moment, transform the phase current from the five-phase stationary coordinate system to the two-phase rotating coordinate system, and obtain the dq axis current signal;

[0007] S2: Based on the current time shaft and The duty cycle of the axis determines the current time. shaft and The voltage signal of the dq axis is obtained by combining it with the angle signal at the current moment;

[0008] S3: Based on the dq-axis current signal and the dq-axis voltage signal, the predicted value of the dq-axis current at the next moment is obtained by using the first-order Euler discretization equation of the permanent magnet synchronous motor.

[0009] S4: Determine the actual mechanical angular velocity based on the collected angle signal of the motor at the current moment;

[0010] S5: Determine the target value of the dq axis current;

[0011] S6: Calculate the current error on the dq axis at the next moment when the zero vector in the basic voltage vector is used as the input of the inverter switch, based on the predicted value of the dq axis current and the target value of the dq axis current.

[0012] S7: Construct a value assessment function based on the current dq-axis voltage signal and the current error caused on the dq-axis at the next moment;

[0013] S8: The value assessment function is extended based on the principle of one-time delay compensation for discrete systems, as well as the PWM modulation formula and the Parker transform formula;

[0014] S9: Apply the expanded value assessment function to the theoretically optimal value assessment function at the current moment. shaft duty cycle and Differentiate the duty cycles of each axis and set them to zero to obtain the theoretical optimum for the next time step. shaft and Axis duty cycle;

[0015] S10: Theoretically optimal for the next time step shaft and The axis duty cycle is converted to obtain a virtual duty cycle, and then the duty cycle is reconstructed to obtain the final duty cycle;

[0016] S11: The modulation pulse width is generated based on the final duty cycle, and the five-phase motor is driven to run through the inverter.

[0017] Compared with existing technologies, the significant advantages of this invention are as follows: This invention employs model predictive current control theory, enabling proactive and advance calculation of the optimal control duty cycle, thereby achieving a faster dynamic response and lower overshoot than traditional PI controllers. More importantly, thanks to the lightweight computation and nonlinear fitting characteristics of the ReLU function, this invention combines the lower algorithmic complexity of traditional single-vector model predictive current control with the higher control accuracy of traditional multi-vector model predictive current control, demonstrating promising application prospects in the field of low-cost, high-performance motor control. Attached Figure Description

[0018] Figure 1 This is a circuit topology diagram of the object of implementation of the present invention.

[0019] Figure 2 Flow chart of the five-phase motor fast pulse width modulation method based on the multi-vector model predictive current control of the present application.

[0020] Figure 3 Comparison chart of experimental results of the method proposed in the present application and other three methods in the industry, with the comparison dimensions being current circle, rotating speed and torque. Figure 3 (a) and Figure 3 (b) is a traditional single-vector model predictive current control method, Figure 3 (c) is a traditional multi-vector model predictive current control method, Figure 3 (d) is the method proposed in the present application.

[0021] Figure 4 Comparison chart of experimental results of the method proposed in the present application and other three methods in the industry, with the comparison dimension being MCU processing required clock cycle. Figure 4 (a) and Figure 4 (b) is a traditional single-vector model predictive current control method, Figure 4 (c) is a traditional multi-vector model predictive current control method, Figure 4 (d) is the method proposed in the present application. DETAILED DESCRIPTION

[0022] In order to better explain the present application and facilitate understanding, the present application is described in detail below through specific embodiments in combination with the accompanying drawings.

[0023] The present application provides a five-phase motor fast pulse width modulation method based on multi-vector model predictive current control, Figure 1 The circuit topology structure diagram of the implementation object applied in the verification of the present application is that a two-level voltage source five-phase inverter drives a five-phase permanent magnet synchronous motor. The parameters of the five-phase motor are shown in Table 1.

[0024] Table 1

[0025]

[0026] Figure 2 Flow chart of the five-phase motor fast pulse width modulation method based on the multi-vector model predictive current control of the present application. The specific process includes the following steps:

[0027] S1: Collecting the phase current of the motor at the current time and the angle signal , through the following coordinate change theory formula, the phase current is transformed from the five-phase stationary coordinate system to the two-phase rotating coordinate system, to obtain the dq-axis current signal .

[0028]

[0029]

[0030] in , , , , , These represent the currents of phases A, B, C, D, and E at the current moment. , The fundamental space at the current time is respectively shaft current and shaft current, , The third harmonic space at the current time shaft current and shaft current, This is the zero-sequence current component. , These are the d-axis current and q-axis current at the current moment, respectively.

[0031] S2: Set the current time shaft and Duty cycle of the shaft Multiply by gain Get the current time shaft and shaft voltage signal The specific formula is as follows:

[0032]

[0033] Combined with the current angle signal The d-axis and q-axis voltage signals at the current moment are calculated. The specific formula is as follows:

[0034]

[0035] in, The magnitude of the basic voltage vector. , The result of finding the extremum of the partial derivative of the value assessment function at the current moment changes with each iteration. Initially, take... , In this embodiment, To account for the vector magnitude in the virtual voltage vector after the third spatial harmonic elimination method, its value is 0.5528. ,in It is 110V.

[0036] S3: Based on the fundamental theory of model prediction, the result obtained in S1... , and S2 , Substitute into the first-order Euler discretization equation of the permanent magnet synchronous motor, the d-axis and q-axis current prediction values at the next time are obtained , , the specific formula is as follows:

[0037] ,

[0038] In the formula, are the dq-axis current prediction values at the next time, are the dq-axis currents at the current time, are the dq-axis voltages at the current time, , respectively represent the dq-axis inductances, is the electrical angular velocity at the current time, represents the phase resistance, represents the sampling period, represents the permanent magnet flux linkage.

[0039] S4: The motor angle signal collected in step S1 is calculated as follows to obtain the actual mechanical angular velocity .

[0040]

[0041]

[0042] wherein is the electrical angular velocity at the current time, is the mechanical angular velocity at the current time, is the number of pole pairs of the motor, in the embodiment .

[0043] S5: For the q-axis: the target mechanical speed is subtracted from the actual mechanical speed , and the difference value is input to the PI controller, and the current target value output by the PI controller is used. For the d-axis: the strategy is adopted.

[0044] S6: The d-axis and q-axis current prediction values , obtained in S3 and the d-axis and q-axis current target values and obtained in S5 are calculated as follows:

[0045]

[0046] wherein, , Ld and Lq represent d-axis and q-axis inductance respectively, R represents phase resistance, Ts represents sampling period, Ψf represents permanent magnet flux linkage. and and represent current error on d-axis and q-axis at next time instant when zero vector in basic voltage vector is used as input. In this embodiment, zero vector is zero vector in virtual voltage vector after considering third harmonic elimination method, mH, mH, , , .

[0047] S7: constructing value evaluation function according to current time instant dq-axis voltage signal and current error on dq-axis at next time instant:

[0048]

[0049] wherein is value evaluation function symbol in model predictive current control of this scheme.

[0050] S8: extending value evaluation function according to one-shot delay compensation principle of discrete system, PWM modulation formula and Park transformation formula:

[0051]

[0052]

[0053]

[0054] S9: partial differentiating value evaluation function in S8 with respect to and respectively, and setting partial differential to zero to obtain expression of optimal and , which are specifically shown as follows:

[0055]

[0056]

[0057] wherein is electrical angle at next time instant, and represent duty cycle of optimal axis and axis at next time instant respectively. ​

[0058] S10: the duty cycle expression obtained in S9 is converted to obtain a virtual duty cycle and S11: the virtual duty cycle obtained in S10 is converted to obtain a final duty cycle :

[0059]

[0060] S12: the final duty cycle obtained in S11 is reconstructed to obtain a final duty cycle .

[0061]

[0062]

[0063] wherein represents a virtual duty cycle obtained only by duty cycle conversion without duty cycle reconstruction, represents a final duty cycle obtained after reconstruction and used for final pulse width modulation. represents a zero vector duty cycle. the function is a maximum value taking function, the function is a minimum value taking function. the function is a rectification function, which truncates all negative input values to zero while keeping positive input values unchanged. The core idea is to introduce nonlinearity while maintaining the simplicity of calculation. The specific expression of the function is as follows:

[0064]

[0065] S11: according to the final duty cycle modulation pulse width is generated, and then the five-phase motor is driven to run through the inverter.

[0066] The present application reduces the current distortion degree from 4.11% to 1.48% by analyzing the mathematical theory to solve the accurate duty cycle predicted by the multi-vector model, and reduces the algorithm time cost from 17.23 microseconds to 3.01 microseconds, which has good application prospect in the field of low-cost and high-performance five-phase motor control.

[0067] Embodiment

[0068] In the case that the motor working conditions are completely consistent, Figure 3 The experimental results of four different model predictive current control methods are shown in the comparison chart, and the comparison dimensions are the fundamental and harmonic current circles, the speed and the torque in turn. Among them Figure 3 (a) and Figure 3 (b) are the traditional single-vector model predictive current control modulation method, Figure 3 (c) is the traditional multi-vector model predictive current control modulation method, Figure 3(d) is the fast pulse width modulation method proposed in the application. It can be concluded from the figure that the effects of methods (a), (b), (c) and (d) are improved to different degrees in turn, and methods (a) and (b) have the worst performance, because the single-vector modulation strategy can only select one vector in a control cycle, and cannot synthesize vectors in any direction, resulting in high current ripple and torque ripple. Method (c) is a traditional multi-vector modulation strategy based on the geometric approximation method, which is slightly better than methods (a) and (b), because this method uses multiple basic voltage vectors in the voltage vector space for vector synthesis, thereby having higher freedom to approximate the target required voltage vector. Method (d) has the best performance, because the fast pulse width modulation method for five-phase motor based on multi-vector model predictive current control proposed in the application is essentially an exact solution method for duty cycle expression by analytical method, which has a natural advantage over the geometric approximation method, thereby being able to exhibit the optimal output characteristics under the same working conditions.

[0069] Figure 4 The experimental results of the four methods in the actual deployment process are compared in the time cost comparison chart. The hardware scheme MCU is TMS320F28379D, and the working clock frequency is 200MHz. Methods (a) and (b) have small computing power requirements due to the calculation characteristics of single vector, method (c) adopts the traditional multi-vector modulation strategy of geometric approximation method, and its deployment process involves complex trigonometric function operations and multiple branch loop judgment statements, so it has extremely high computing power requirements. Method (d) benefits from the simple duty cycle analytical expression, and still has the lowest computing power requirement under the condition that the output characteristics are better than methods (a), (b) and (c). In particular, method (d) has only 17.47% of the code running time cost of method (c), which is also a multi-vector model predictive current control modulation method.

[0070] Therefore, the fast pulse width modulation method for five-phase motor based on multi-vector model predictive current control proposed in the application can greatly reduce the algorithm complexity under the premise of improving the existing motor control effect, has good industrial application prospect, and is suitable for popularization.

Claims

1. A fast pulse width modulation method for a five-phase motor based on multi-vector model predictive current control, characterized in that, include: S1: Collect the phase current and angle signals of the motor at the current moment, transform the phase current from the five-phase stationary coordinate system to the two-phase rotating coordinate system, and obtain the dq axis current signal; S2: Based on the current time shaft and The duty cycle of the axis determines the current time. shaft and The voltage signal of the dq axis is obtained by combining it with the angle signal at the current moment; S3: Based on the dq-axis current and voltage signals, the predicted value of the dq-axis current at the next moment is obtained using the first-order Euler discretization equation of the permanent magnet synchronous motor. The specific formula is as follows: ， In the formula, These are the predicted values ​​of the dq-axis current at the next time step. These are the dq-axis currents at the current time. These are the dq-axis voltages at the current time. , These represent the d-axis and q-axis inductances, respectively. Let be the electric angular velocity at the current moment. Indicates phase resistance. Indicates the sampling period. Indicates permanent magnet flux linkage; S4: Determine the actual mechanical angular velocity based on the collected angle signal of the motor at the current moment; S5: Determine the target value of the dq axis current; S6: Based on the predicted and target values ​​of the dq-axis current, calculate the current error on the dq-axis at the next moment when the zero vector in the basic voltage vector is used as the input to the inverter switch. The specific formula is as follows: ， in, , These represent the d-axis and q-axis inductance, respectively. Indicates phase resistance. Indicates the sampling period. Indicates permanent magnet flux linkage. and These represent the current errors on the d-axis and q-axis at the next moment when the zero vector from the basic voltage vector is used as the input to the inverter switch. The target value for the q-axis current. The target value for the d-axis current. Let be the electric angular velocity at the current moment. These are the predicted current values ​​for the d-axis and q-axis at the next time step, respectively. S7: Construct a value assessment function based on the current dq-axis voltage signal and the current error caused on the dq-axis at the next moment, specifically: ， In the formula, , These are the d-axis and q-axis voltage signals at the current moment, respectively. S8: Based on the principle of one-beat delay compensation for discrete systems, as well as the PWM modulation formula and the Parker transform formula, the value evaluation function is extended. The extended value evaluation function is as follows: ； In the formula, and They represent the theoretical optimal values ​​at the next time step, respectively. shaft and Axis duty cycle, For the electrical angle signal at the next moment, The magnitude of the basic voltage vector; S9: Apply the expanded value assessment function to the current moment. shaft duty cycle and Differentiate the duty cycles of each axis and set them to zero to obtain the theoretical optimum for the next time step. shaft and Axis duty cycle; S10: Theoretically optimal for the next time step shaft and The axis duty cycle is converted to obtain a virtual duty cycle, and then the duty cycle is reconstructed to obtain the final duty cycle. S11: The modulation pulse width is generated based on the final duty cycle, and the five-phase motor is driven to run through the inverter.

2. The fast pulse width modulation method for a five-phase motor based on multi-vector model predictive current control according to claim 1, characterized in that, The specific formula for transforming the phase current from the five-phase stationary coordinate system to the two-phase rotating coordinate system to obtain the dq-axis current signal is as follows: ， ， in , , , , , These represent the currents of phases A, B, C, D, and E at the current moment. , The fundamental space at the current time is respectively shaft current and shaft current, , The third harmonic space at the current time shaft current and shaft current, This is the zero-sequence current component. , These are the d-axis current and q-axis current at the current moment, respectively. angle signal.

3. The fast pulse width modulation method for a five-phase motor based on multi-vector model predictive current control according to claim 1, characterized in that, According to the current time shaft and The duty cycle of the axis determines the current time. shaft and The specific formula for the voltage signal of the shaft is: ， The specific formula for obtaining the dq-axis voltage signal at the current moment, combining the angle signal at the current moment, is as follows: ， in, The magnitude of the basic voltage vector. , , Theoretically optimal at the current time shaft duty cycle and Axis duty cycle, , These are the d-axis and q-axis voltage signals at the current moment, respectively. The current electrical angle signal is given at the initial moment. , .

4. The fast pulse width modulation method for a five-phase motor based on multi-vector model predictive current control according to claim 1, characterized in that, The specific formula for determining the actual mechanical angular velocity based on the collected angle signal of the motor at the current moment is as follows: ， ， in, Let be the electric angular velocity at the current moment. Let be the mechanical angular velocity at the current moment. The electric angle at the current moment, This represents the number of pole pairs of the motor.

5. The fast pulse width modulation method for a five-phase motor based on multi-vector model predictive current control according to claim 1, characterized in that, The method for determining the target value of the q-axis current is as follows: target mechanical speed With actual mechanical speed The difference is calculated and input to the PI controller, which then outputs the target q-axis current value. ; d-axis current target value .

6. The fast pulse width modulation method for a five-phase motor based on multi-vector model predictive current control according to claim 1, characterized in that, The extended value assessment function is theoretically optimal for the current moment. shaft duty cycle and Differentiate the duty cycles of each axis and set them to zero to obtain the theoretical optimum for the next time step. shaft and The specific formula for the shaft duty cycle is: ， 。

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