A maximum torque current ratio control method and system for a dual three-phase permanent magnet synchronous motor based on virtual signal injection

Abstract

The application discloses a maximum torque current ratio control method and system for a dual three-phase permanent magnet synchronous motor based on virtual signal injection, injects a bipolar square wave signal into a current vector angle, calculates d-q axis currents after the injection of the bipolar square wave signal by using the current vector angle of the injected bipolar square wave signal, substitutes the d-q axis currents after the injection of the bipolar square wave signal into a modified torque equation, calculates positive polarity torque T e up and negative polarity torque T e down of the dual three-phase permanent magnet synchronous motor, and according to Taylor series expansion, when the difference between T e up and T e down is equal to 0, T e up and T e down are superposed with an initial current vector angle β after PI controller control, an optimal current vector angle is obtained, and the required d-q axis reference currents of the dual three-phase permanent magnet synchronous motor are calculated. The application realizes accurate control of the maximum torque current ratio.

Description

Technical Field

[0001] This invention belongs to the field of multiphase permanent magnet synchronous motor drive control application, and in particular relates to a method and system for controlling the maximum torque-to-current ratio of a dual three-phase permanent magnet synchronous motor based on virtual signal injection. Background Technology

[0002] With the rapid development of high-end fields such as transportation, aerospace, and national defense, the performance requirements for motors and their control systems, as core components of equipment, are further increasing. Multiphase permanent magnet synchronous motors (PMSMs) consist of two key components: a multi-polarized permanent magnet rotor and a stator with windings. Due to their advantages such as high efficiency, large torque, and small size, they play an important role in the operation and control of industrial automation. Compared with surface-mounted PMSMs, a significant characteristic of built-in PMSMs is the larger difference in inductance, specifically, the q-axis inductance is significantly greater than the d-axis inductance. This difference between the q-axis and d-axis inductances helps generate additional torque, known as reluctance torque. Therefore, the torque generated in a built-in PMSM consists of the permanent magnet torque from the permanent magnets and the reluctance torque. The maximum torque-to-current ratio (MTPA) control method is a way to maximize torque utilization. It achieves the smallest current vector amplitude among various current vectors for a specific torque, effectively reducing copper losses.

[0003] Chinese patent CN118842365A discloses an MTPA control method using an extreme value search algorithm. This method uses the amplitude of the motor's feedback current vector to search for an appropriate direct-axis current value, minimizing the current amplitude and ultimately achieving MTPA control. Chinese patent CN118801747A discloses an improved MTPA control method. This method uses the extreme value principle in the electromagnetic torque formula of a permanent magnet synchronous motor to make the rate of change of electromagnetic torque with the current angle zero, determining the extreme point of the electromagnetic torque. The corresponding current angle is the MTPA operating point, thus achieving maximum torque-to-current ratio control. Chinese patent CN117978030A discloses a constant-parameter MTPA control method. This method simplifies the calculation method compared to traditional piecewise solutions by adding an error term between the real-time operating MTPA curve and the set MTPA curve value to the established value function. It also provides a system model for solving the predictive value function of the permanent magnet synchronous motor model. However, these methods mainly consider the implementation of MTPA control and do not further analyze dynamic response capability and current angle error. To further improve the control performance of multiphase permanent magnet synchronous motors, it is of great significance to develop MTPA control with fast speed and accuracy. Summary of the Invention

[0004] In view of this, the present invention provides a method and system for controlling the maximum torque-current ratio of a dual three-phase permanent magnet synchronous motor based on virtual signal injection. Unlike the traditional method based on sinusoidal signal injection, this method uses bipolar square wave signal injection, which can increase the injection frequency, accelerate the dynamic response capability, and correct the torque equation, thereby further reducing the current vector angle error and improving the accuracy of the maximum torque-current ratio control.

[0005] The present invention achieves the above-mentioned technical objectives through the following technical means.

[0006] A method for controlling the maximum torque-to-current ratio of a dual three-phase permanent magnet synchronous motor based on virtual signal injection:

[0007] Inject a bipolar square wave signal into the current vector angle;

[0008] The dq-axis current after the bipolar square wave signal is injected is calculated using the current vector angle of the injected bipolar square wave signal.

[0009] The dq-axis voltage, the dq-axis current before the bipolar square wave signal is injected, the dq-axis current after the bipolar square wave signal is injected, and the electrical angular velocity ω are calculated. e Substituting the corrected torque equation, the positive polarity torque T of the dual three-phase permanent magnet synchronous motor is calculated. e up and negative polarity torque T e down And expand it according to the Taylor series; the Taylor series expansion T e up With T e down The difference is used as a criterion for determining the maximum torque-to-current ratio; when the Taylor series expansion of T... e up With T e down When the difference is 0, T e up With T e down The difference is superimposed on the initial current vector angle β after passing through the PI controller to obtain the current optimal current vector angle. The required dq axis reference current of the dual three-phase permanent magnet synchronous motor is then calculated, thereby realizing the overall closed-loop control.

[0010] A further technical solution involves modifying the torque equation using a mathematical model of a dual three-phase permanent magnet synchronous motor.

[0011] A further technical solution is that the modified torque equation is:

[0012]

[0013] in, These represent the d-axis current and q-axis current after a positive square wave signal is injected, respectively. These represent the d-axis current and q-axis current after the injection of a negative square wave signal, respectively. p U represents the number of pole pairs of the motor. d and u q Representing the d-axis and q-axis voltages respectively, i d and i q These represent the d-axis and q-axis currents before the bipolar square wave signal is injected, respectively, where R is the stator resistance and ω is the d-axis current. e L is the electric angular velocity. d δ represents the d-axis stator inductance, and δ represents the amplitude of the injected signal.

[0014] A further technical solution is that the bipolar square wave signal is:

[0015]

[0016] Where δ represents the amplitude of the injected signal, T s This represents one signal period, and N represents the set of natural numbers.

[0017] A further advanced technical solution involves injecting a bipolar square wave signal, resulting in the following current vector angle:

[0018]

[0019] A further technical solution is that the dq-axis current after the injection of the bipolar square wave signal is:

[0020]

[0021] Among them, I s This indicates the amplitude of the stator current.

[0022] A further advanced technical solution is that the difference between the positive and negative torques, as expressed in the Taylor series expansion, is...

[0023] A further technical solution is that the required dq-axis reference current for the dual three-phase permanent magnet synchronous motor is:

[0024]

[0025] Where β' is the optimal current vector angle, I s This indicates the amplitude of the stator current.

[0026] In a further technical solution, the bipolar square wave signal includes a positive square wave and a negative square wave, and the duty cycle of both the positive and negative square waves is 50%.

[0027] A maximum torque-to-current ratio control system for a dual three-phase permanent magnet synchronous motor includes:

[0028] The virtual signal injection module enables the injection of bipolar virtual square wave signals.

[0029] The signal demodulation module is used to obtain the optimal current vector angle;

[0030] The speed controller is used to obtain the required dq axis reference current for the dual three-phase permanent magnet synchronous motor.

[0031] The beneficial effects of this invention are as follows:

[0032] 1) The maximum torque-current ratio control method based on virtual bipolar square wave signal injection proposed in this invention can effectively utilize the advantage of high injection frequency of square wave signal to improve dynamic response capability, and improve control accuracy through torque equation correction.

[0033] 2) This invention analyzes the injection method and demodulation principle of virtual bipolar square wave signal injection, and extends the principle accordingly;

[0034] 3) This invention uses a torque correction method, which reduces the dependence on motor parameters and improves the accuracy of torque calculation. Attached Figure Description

[0035] Figure 1 This is a structural diagram of the maximum torque-to-current ratio of the dual three-phase permanent magnet synchronous motor based on virtual square wave signal injection according to the present invention;

[0036] Figure 2 This is a schematic diagram of the square wave signal demodulation principle of the present invention;

[0037] Figure 3 This is a flowchart of the maximum torque-to-current ratio control of the present invention;

[0038] Figure 4(a) shows the d-axis current waveform of the maximum torque-current ratio control result of the present invention;

[0039] Figure 4(b) is an electromagnetic torque waveform diagram showing the maximum torque-current ratio control result of the present invention;

[0040] Figure 4(c) is a current vector angle diagram of the maximum torque-current ratio control result of the present invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0042] This invention discloses a method for controlling the maximum torque-to-current ratio of a dual three-phase permanent magnet synchronous motor based on virtual bipolar square wave signal injection. The method is based on a control system comprising system hardware and system software. The system hardware includes the dual three-phase permanent magnet synchronous motor, a DC power supply, an SVPWM module, an inverter, a position sensor, and a current sensor. The system software includes a virtual signal injection module, a signal demodulation module, a speed controller, a current controller, and a coordinate transformation module. See also... Figure 1 , where i d * and i q * U represents the dq-axis reference current. d and u q Represents the dq axis voltage, i x * and i y * Indicates the given current along the x and y axes, i x and i y i represents the actual current along the x and y axes. α and i β U represents the α-β axis current. α and u β Represents the α-β axis voltage, u x and u y Represents the voltage along the x and y axes, i A-F ω represents the six-phase current of the motor. m θ represents the mechanical angular velocity. e Represents electrical angle, n ref represents the given speed of the motor, and n represents the actual speed of the motor.

[0043] The two sets of three-phase windings of the dual three-phase permanent magnet synchronous motor are spatially 30° apart; the inverter input is connected to a DC power supply, and the inverter signal is connected to an SVPWM module; the inverter has a six-phase two-level topology, and the inverter output is connected to phases A, B, C, D, E, and F of the dual three-phase permanent magnet synchronous motor, responsible for converting the PWM signal into the six-phase sinusoidal AC power required to drive the motor; the position sensor uses a rotary transformer and is coaxially connected to the dual three-phase permanent magnet motor to measure the motor's mechanical angular velocity; the current sensor is connected to the inverter and is responsible for sampling the six-phase current of the dual three-phase permanent magnet synchronous motor.

[0044] The virtual signal injection module is responsible for injecting bipolar virtual square wave signals; the signal demodulation module is used to obtain the optimal current vector angle; the speed controller is controlled by a PI controller to obtain the dq axis reference current required by the dual three-phase permanent magnet synchronous motor; the current controller is controlled by a PI controller to obtain the dq axis voltage and the xy axis reference voltage; the coordinate transformation module is used to convert the six-phase current in the natural coordinate system into the current in the rotating coordinate system to achieve decoupled control.

[0045] The specific control flow of the closed-loop control of the dual three-phase permanent magnet synchronous motor is as follows: the optimal current vector angle (β') is obtained by demodulation by the virtual signal injection module, and the optimal current vector angle is compared with the stator current amplitude (I) output by the speed regulator. s The required dq-axis reference current (i) is obtained by combining these parameters. d * and i q * The dq-axis voltage (u) is then obtained via two current controllers. d and u q This transforms the dq-axis voltage into the α-β axis voltage (u). α and u β The collected six-phase currents, after coordinate transformation, can yield the actual current (i) under the dq axis. d and i q ) and the actual current (i) under the xy axis x and i y ), giving the current in the harmonic space (i x * and i y * The current is set to zero to reduce the impact of current harmonics on the system. The difference between the given current and the actual current is used to output the x and y axis voltages (u) via the PI controller. x and u y Together with the dq axis voltage, it acts on the SVPWM module to generate a PWM signal, thereby controlling the inverter to turn on and off, and realizing the control of the motor.

[0046] like Figure 3 As shown, a method for controlling the maximum torque-to-current ratio of a dual three-phase permanent magnet synchronous motor based on virtual bipolar square wave signal injection includes the following specific implementation steps:

[0047] Step 1) Use the mathematical model of the dual three-phase motor to correct the torque equation and obtain the accurate torque calculation equation;

[0048] The voltage and torque equations of a dual three-phase permanent magnet synchronous motor can be expressed as follows:

[0049]

[0050] When a dual three-phase permanent magnet synchronous motor is in steady-state operation, the voltage equation can be expressed as:

[0051]

[0052] Among them, u d and u q These refer to the voltage components in the dq subspace, where R is the stator resistance and i d i q These are the currents in the dq coordinate system (the current sensors collect the six-phase currents of the dual three-phase permanent magnet synchronous motor, which are then transformed by the coordinate transformation module), and L. d L q λ represents the d-axis stator inductance and the q-axis stator inductance, respectively. f For permanent magnet stator flux linkage, ω e Electric angular velocity (the mechanical angular velocity ω of the motor) m and the number of pole pairs n of the motor p After multiplication, we get (p represents the differential symbol, n) p T represents the number of pole pairs of the motor. e Electromagnetic torque;

[0053] The bipolar square wave signal in the injected current vector angle can be represented as:

[0054]

[0055] Where δ represents the amplitude of the injected signal, T s This represents one signal cycle, and N represents the set of natural numbers.

[0056] After injecting a positive square wave signal into the initial current vector angle, the initial torque equation can be expressed as:

[0057]

[0058] in, These represent the d-axis current and q-axis current after the injected signal, respectively;

[0059] Considering the nonlinear changes in permanent magnet flux linkage, d-axis inductance, and q-axis inductance during motor operation, which cause the estimated torque value to deviate from the actual torque value, the initial torque equation is corrected as follows:

[0060] The voltage equation under the dq axis (i.e., equation (3)) can be rewritten as:

[0061]

[0062] Substituting into equation (5), the initial torque equation can be rewritten as:

[0063]

[0064] Because the amplitude δ of the injected signal is very small, It can be represented as:

[0065]

[0066] Among them, I s This represents the stator current amplitude (derived from the motor's mechanical angular velocity ω). m After conversion, the actual motor speed n is obtained, and then compared with the given motor speed n. ref (The difference is obtained by passing the PI controller), where β represents the initial current vector angle;

[0067] Therefore, the corrected torque equation can be obtained as follows:

[0068]

[0069] in, These represent the electromagnetic torque, d-axis current, and q-axis current after the injection of a negative polarity square wave signal, respectively.

[0070] The revised torque equation includes only one parameter, the d-axis inductance. By simulating the nonlinear changes of the d-q axis inductance and the permanent magnet flux linkage using the finite element method, it can be found that the nonlinear change of the d-axis inductance is minimal. Therefore, the revised torque equation can reduce the dependence on the parameter. At the same time, the small amplitude vibration of δ can further improve the accuracy of torque calculation.

[0071] Step 2) Implement bipolar square wave signal injection using a virtual signal injection module;

[0072] The bipolar square wave signal required for the current vector angle is generated by the virtual signal injection module, where the duty cycle of both the positive and negative square waves is 50%, achieving effective injection throughout the entire cycle.

[0073] First, the initial current vector angle is solved using the actual d-axis current and q current:

[0074]

[0075] Injecting a bipolar square wave signal based on the initial current vector angle, the current vector angle after injecting the bipolar square wave signal can be expressed as:

[0076]

[0077] Step 3) Calculate the optimal current vector angle using the signal demodulation module;

[0078] The dq-axis current after injecting the bipolar square wave signal is calculated using the current vector angle obtained in step 2):

[0079]

[0080] Through the dq axis voltage (u) d and u q ), the dq-axis current (i) before injecting the bipolar square wave signal d and i q ), the dq-axis current after injecting a bipolar square wave signal (at this time, in formula (12) When calculating the injection of positive and negative polarity square wave signals, they respectively represent and and and electric angular velocity ω e Calculate the torque (Equation (9)), see [reference] Figure 2 Positive polarity torque With negative polarity torque The difference is the MTPA determination criterion.

[0081] Expanding the torque equation using Taylor series:

[0082]

[0083] Subtracting the positive and negative torques from the Taylor series expansion yields the following:

[0084]

[0085] When the output MTPA is determined At that time, MTPA control can be achieved, that is After passing through the PI controller, the current vector angle β is superimposed with the initial current vector angle β to obtain the current optimal current vector angle β'. Then, using formula (15), the required dq axis reference current of the dual three-phase permanent magnet synchronous motor is calculated.

[0086]

[0087] The waveforms of the maximum torque-to-current ratio of the dual three-phase permanent magnet synchronous motor based on the virtual bipolar square wave signal injection are shown in Figures 4(a), (b), and (c). As can be seen from the figures, its dynamic response speed and control effect are both good.

[0088] The above embodiments are only used to illustrate the design concept and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. Therefore, all equivalent changes or modifications made based on the principles and design ideas disclosed in the present invention are within the protection scope of the present invention.

Claims

1. A method for controlling the maximum torque-to-current ratio of a dual three-phase permanent magnet synchronous motor based on virtual signal injection, characterized in that: Inject a bipolar square wave signal into the current vector angle; The dq-axis current after the bipolar square wave signal is injected is calculated using the current vector angle of the injected bipolar square wave signal. The dq-axis voltage, the dq-axis current before the bipolar square wave signal is injected, the dq-axis current after the bipolar square wave signal is injected, and the electrical angular velocity ω are calculated. e Substituting the corrected torque equation, the positive polarity torque T of the dual three-phase permanent magnet synchronous motor is calculated. e up and negative polarity torque T e down And expand it according to the Taylor series; the Taylor series expansion T e up With T e down The difference is used as a criterion for determining the maximum torque-to-current ratio; when the Taylor series expansion of T... e up With T e down When the difference is 0, T e up With T e down The difference is superimposed on the initial current vector angle β after passing through the PI controller to obtain the current optimal current vector angle, and the required dq axis reference current of the dual three-phase permanent magnet synchronous motor is calculated, thereby realizing the overall closed-loop control; The bipolar square wave signal is: Where δ represents the amplitude of the injected signal, T s This represents a signal period, and N represents the set of natural numbers. The current vector angle after the injection of the bipolar square wave signal is: The dq-axis current after the injection of the bipolar square wave signal is: Among them, I s Indicates the stator current amplitude; The revised torque equation is obtained by modifying the torque equation using a mathematical model of a dual three-phase permanent magnet synchronous motor, specifically as follows: Among them, i d up i q up These represent the d-axis current and q-axis current after a positive square wave signal is injected, respectively. d down i q down These represent the d-axis current and q-axis current after the injection of a negative square wave signal, respectively. p U represents the number of pole pairs of the motor. d and u q Representing the d-axis and q-axis voltages respectively, i d and i q These represent the d-axis and q-axis currents before the bipolar square wave signal is injected, respectively, where R is the stator resistance and ω is the d-axis current. e L is the electric angular velocity. d δ represents the d-axis stator inductance, and δ represents the amplitude of the injected signal.

2. The maximum torque-to-current ratio control method for a dual three-phase permanent magnet synchronous motor according to claim 1, characterized in that, The difference between the positive and negative torques in the Taylor series expansion is: .

3. The maximum torque-to-current ratio control method for a dual three-phase permanent magnet synchronous motor according to claim 1, characterized in that, The required dq axis reference current for the dual three-phase permanent magnet synchronous motor is: Where β' is the optimal current vector angle.

4. The maximum torque-to-current ratio control method for a dual three-phase permanent magnet synchronous motor according to claim 1, characterized in that, The bipolar square wave signal includes a positive square wave and a negative square wave, and the duty cycle of both the positive and negative square waves is 50%.

5. A system for implementing the maximum torque-to-current ratio control method for a dual three-phase permanent magnet synchronous motor according to any one of claims 1-4, characterized in that, include: The virtual signal injection module enables the injection of bipolar virtual square wave signals. The signal demodulation module is used to obtain the optimal current vector angle; The speed controller is used to obtain the required dq axis reference current for the dual three-phase permanent magnet synchronous motor.

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