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

Abstract

The invention discloses a dual three-phase permanent magnet synchronous motor maximum torque current ratio control method and system based on virtual signal injection, and the method comprises the steps: injecting a bipolar square wave signal into a current vector angle, and calculating the d-q axis current after the bipolar square wave signal is injected through the current vector angle of the bipolar square wave signal; the d-q axis current after the bipolar square wave signal is injected is substituted into the corrected torque equation, the positive polarity torque Tup and the negative polarity torque Tdown of the dual three-phase permanent magnet synchronous motor are calculated and are expanded according to the Taylor series, when the difference between the Tup and the Tdown expanded according to the Taylor series is equal to 0, the difference between the Tup and the Tdown passes through a PI controller and then is superposed with an initial current vector angle beta, and the initial current vector angle beta is obtained. And obtaining a current optimal current vector angle, and calculating a d-q axis reference current required by the dual three-phase permanent magnet synchronous motor. According to the invention, accurate control of the maximum torque current ratio is realized.

Description

Technical Field

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

[0002] With the rapid development of high-end fields such as transportation, aerospace, and national defense, the motor and its control system, as the core components of the equipment, have further improved their operating performance requirements. The multi-phase permanent magnet synchronous motor consists of two key components: a multi-polar permanent magnet rotor and a stator with windings. Due to its advantages such as high efficiency, high torque, and small size, it plays an important role in the operation control of the industrial automation field. Compared with the surface-mounted permanent magnet synchronous motor, the significant feature of the built-in permanent magnet synchronous motor is the large inductance difference, that is, the q-axis inductance is significantly greater than the d-axis inductance. This difference between the q-axis inductance and the d-axis inductance helps to generate additional torque, which is called reluctance torque. Therefore, the torque generated in the built-in permanent magnet synchronous motor is composed of the permanent magnet torque from the permanent magnet and the reluctance torque. The maximum torque to current ratio (MTPA) control method is a way to maximize the use of torque. It can have the smallest amplitude current vector among various current vectors for a specific torque, which can effectively reduce copper loss.

[0003] Chinese patent CN118842365A discloses an MTPA control method using an extreme value search algorithm. This method uses the extreme value search algorithm and the feedback current vector amplitude of the motor to search for an appropriate motor direct axis current value, so that the current amplitude reaches the minimum value, and finally realizes MTPA control. Chinese patent CN118801747A discloses an improved MTPA control method. In the electromagnetic torque formula of the permanent magnet synchronous motor, this method uses the extreme value principle to make the rate of change of the electromagnetic torque with the current angle zero, determine the extreme value point of the electromagnetic torque, and the corresponding current angle is the MTPA working point, thereby realizing the maximum torque current ratio control. Chinese patent CN117978030A discloses a constant parameter MTPA control method. This method adds the error term between the real-time MTPA curve of the motor and the set MTPA curve value in the established value function, simplifies the calculation method compared with the traditional segmented solution, and at the same time, provides a system model for solving the value function of the permanent magnet synchronous motor model prediction. However, these methods mainly consider the realization of MTPA control, and do not further analyze the dynamic response capability and current angle error. In order to further improve the control performance of multi-phase permanent magnet synchronous motors, it is of great significance to carry out MTPA control with rapidity and accuracy. Summary of the invention

[0004] In view of this, the present invention provides a maximum torque-to-current ratio control method and system for a dual three-phase permanent magnet synchronous motor based on virtual signal injection. Different from the traditional method based on sinusoidal signal injection, this method utilizes 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 maximum torque-to-current ratio control.

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

[0006] A maximum torque-current ratio control method for 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 by 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 e Substitute the corrected torque equation to calculate the positive polarity torque T of the dual three-phase permanent magnet synchronous motor. e up and negative polarity torque T e down , and expand it according to the Taylor series; the Taylor series expansion of T e up With T e down The difference is used as the criterion for the maximum torque current ratio; when the Taylor series expansion of T e up With T e down When the difference is equal to 0, T e up With T e down The difference is superimposed with the initial current vector angle β after passing through the PI controller to obtain the current optimal current vector angle, and the dq-axis reference current required by the dual three-phase permanent magnet synchronous motor is calculated to achieve overall closed-loop control.

[0010] According to a further technical solution, the torque equation is corrected using a mathematical model of a dual three-phase permanent magnet synchronous motor.

[0011] In a further technical solution, the corrected torque equation is:

[0012]

[0013] in, They represent the d-axis current and q-axis current after the positive square wave signal is injected, They represent the d-axis current and q-axis current after the negative square wave signal is injected, respectively. p Indicates the number of motor pole pairs, u d and u q Respectively represent the d and q axis voltages, i d and i q They represent the d-axis and q-axis currents before injecting the bipolar square wave signal, R is the stator resistance, ω e is the electrical angular velocity, L d represents the d-axis stator inductance, and δ represents the amplitude of the injected signal.

[0014] In a further technical solution, the bipolar square wave signal is:

[0015]

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

[0017] A further technical solution is that the current vector angle after injecting the bipolar square wave signal is:

[0018]

[0019] In a further technical solution, the dq axis current after the injection of the bipolar square wave signal is:

[0020]

[0021] Among them, I s Indicates the stator current amplitude.

[0022] Further technical solution, the difference between the positive polarity torque and the negative polarity torque of Taylor series expansion is

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

[0024]

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

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

[0027] A dual three-phase permanent magnet synchronous motor maximum torque current ratio control system, comprising:

[0028] Virtual signal injection module, realizing bipolar virtual square wave signal injection;

[0029] A signal demodulation module for obtaining an optimal current vector angle;

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

[0031] The beneficial effects of the present invention are:

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

[0033] 2) The present invention analyzes the injection mode and demodulation principle of the virtual bipolar square wave signal injection and expands it in principle;

[0034] 3) The present invention adopts a torque correction method, which reduces the dependence on motor parameters and improves the calculation accuracy of torque. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a structural diagram of the maximum torque-current ratio of a 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 maximum torque current ratio control flow chart of the present invention;

[0038] FIG4( a ) is a d-axis current waveform diagram of the maximum torque current ratio control result of the present invention;

[0039] FIG4( b ) is a waveform diagram of the electromagnetic torque of the maximum torque current ratio control result of the present invention;

[0040] FIG4( c ) is a current vector angle diagram of the maximum torque current ratio control result of the present invention. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0042] The present invention implements a method for controlling the maximum torque current ratio of a dual three-phase permanent magnet synchronous motor based on virtual bipolar square wave signal injection, based on the following control system, the control system includes system hardware and system software, the system hardware includes a 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. Figure 1 , where i d * and i q * Indicates the dq axis reference current, u d and u q represents the dq axis voltage, i x * and i y * Indicates the given current on the xy axis, i x and i y Indicates the actual current on the xy axis, i α and i β represents the α-β axis current, u α and u β represents the α-β axis voltage, u x and u y represents the xy axis voltage, i A-F Represents the six-phase current of the motor, ω m Represents the mechanical angular velocity, θ e Indicates the electrical angle, n ref It indicates the given speed of the motor, and n indicates 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 spaced 30° apart; the inverter input is connected to a DC power supply, and the inverter signal end is connected to an SVPWM module; the inverter is a six-phase two-level topology structure, 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 alternating current required to drive the motor; the position sensor adopts a rotary transformer and is coaxially connected to the dual three-phase permanent magnet motor for measuring the mechanical angular velocity of the motor; the current sensor is connected to the inverter, 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 PI to obtain the dq axis reference current required by the dual three-phase permanent magnet synchronous motor; the current controller is controlled by PI to obtain the dq axis voltage and the xy axis reference voltage; the coordinate conversion module is used to convert the six-phase current in the natural coordinate system into the current in the rotating coordinate system to achieve decoupling control.

[0045] The specific control process 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 demodulating the virtual signal injection module, and the optimal current vector angle is compared with the stator current amplitude (I s ) to obtain the required dq axis reference current (i d * and i q * ), and then the dq axis voltage (u d and u q ), converting the dq axis voltage into the voltage under the α-β axis (u α and u β ); and the collected six-phase current can be transformed into the actual current under the dq axis (i d and i q ) and the actual current (i x and i y ), the current in the harmonic space is given (i x * and i y * ) is set to zero to reduce the impact of current harmonics on the system. The given current is subtracted from the actual current and the PI controller outputs the xy axis voltage (u x and u y ), together with the dq axis voltage, acts on the SVPWM module to generate a PWM signal, thereby controlling the inverter to turn on and off, thereby achieving control of the motor.

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

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

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

[0049]

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

[0051]

[0052] Among them, u d and u q They refer to the voltage components of the dq subspace respectively, R is the stator resistance, i d 、i q They are the current in the dq coordinate system (the current sensor collects the six-phase current of the dual three-phase permanent magnet synchronous motor and obtains it through the coordinate conversion module), L d , L q They represent the d-axis stator inductance and the q-axis stator inductance, respectively, f is the permanent magnet stator flux, ω e is the electrical angular velocity (the mechanical angular velocity of the motor ω m and the number of motor pole pairs n p After multiplication, we get: p represents the differential symbol, n p Represents the number of motor pole pairs, T e is the electromagnetic torque;

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

[0054]

[0055] Where δ represents the amplitude of the injected signal, T s represents a signal cycle, and N represents a natural number set;

[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, Represent the d-axis current and q-axis current after the signal is injected;

[0059] Taking into account the nonlinear changes of permanent magnet flux, d-axis inductance and q-axis inductance with the operation of the motor, which causes the estimated torque value to deviate from the actual torque value, the initial torque equation is corrected:

[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] Since the amplitude δ of the injected signal is very small, It can be expressed as:

[0065]

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

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

[0068]

[0069] in, They respectively represent the electromagnetic torque, d-axis current and q-axis current after the negative polarity square wave signal is injected.

[0070] The revised torque equation only includes one parameter, the d-axis inductance. The finite element method is used to simulate the nonlinear changes of the dq-axis inductance and the permanent magnet flux. It can be found that the nonlinear change of the d-axis inductance is the smallest. Therefore, the revised torque equation can reduce the dependence on parameters. At the same time, the small-amplitude vibration of δ can further improve the accuracy of the torque calculation.

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

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

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

[0074]

[0075] A bipolar square wave signal is injected on the basis of the initial current vector angle. The current vector angle after the bipolar square wave signal is injected can be expressed as:

[0076]

[0077] Step 3) Calculating the optimal current vector angle through a signal demodulation module;

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

[0079]

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

[0081] Expand the torque equation according to the Taylor series:

[0082]

[0083] According to the difference between the positive polarity torque and the negative polarity torque after Taylor series expansion, we can get

[0084]

[0085] When outputting the MTPA judgment condition MTPA control can be realized when After passing through the PI controller, it is superimposed with the initial current vector angle β to obtain the current optimal current vector angle β'. Then, using formula (15), the dq axis reference current required by the dual three-phase permanent magnet synchronous motor is calculated.

[0086]

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

[0088] The above embodiments are only used to illustrate the design ideas 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, any equivalent changes or modifications made based on the principles and design ideas disclosed by the present invention are within the protection scope of the present invention.

Claims

1. A method for controlling the maximum torque-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 by 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 e Substitute the corrected torque equation to calculate the positive polarity torque T of the dual three-phase permanent magnet synchronous motor. e up and negative polarity torque T e down , and expand it according to the Taylor series; the Taylor series expansion of T e up With T e down The difference is used as the criterion for the maximum torque current ratio; when the Taylor series expansion of T e up With T e down When the difference is equal to 0, T e up With T e down The difference is superimposed with the initial current vector angle β after passing through the PI controller to obtain the current optimal current vector angle, and the dq-axis reference current required by the dual three-phase permanent magnet synchronous motor is calculated to achieve overall closed-loop control.

2. The maximum torque current ratio control method of a dual three-phase permanent magnet synchronous motor according to claim 1, characterized in that: The torque equation is corrected using the mathematical model of a dual three-phase permanent magnet synchronous motor.

3. The maximum torque current ratio control method of a dual three-phase permanent magnet synchronous motor according to claim 2 is characterized in that: The modified torque equation is: in, They represent the d-axis current and q-axis current after the positive square wave signal is injected, They represent the d-axis current and q-axis current after the negative square wave signal is injected, respectively. p Indicates the number of motor pole pairs, u d and u q Respectively represent the d and q axis voltages, i d and i q They represent the d-axis and q-axis currents before injecting the bipolar square wave signal, R is the stator resistance, ω e is the electrical angular velocity, L d represents the d-axis stator inductance, and δ represents the amplitude of the injected signal.

4. The maximum torque current ratio control method of a dual three-phase permanent magnet synchronous motor according to claim 1, characterized in that: The bipolar square wave signal is: Where δ represents the amplitude of the injected signal, T s represents a signal cycle, and N represents a set of natural numbers.

5. The maximum torque current ratio control method of a dual three-phase permanent magnet synchronous motor according to claim 4, characterized in that: The current vector angle after injecting the bipolar square wave signal is:

6. The maximum torque current ratio control method of a dual three-phase permanent magnet synchronous motor according to claim 5, characterized in that: The dq axis current after the injection of the bipolar square wave signal is: Among them, I s Indicates the stator current amplitude.

7. The maximum torque current ratio control method of a dual three-phase permanent magnet synchronous motor according to claim 3, characterized in that: The difference between the positive polarity torque and the negative polarity torque of the Taylor series expansion is 8. The maximum torque current ratio control method of a dual three-phase permanent magnet synchronous motor according to claim 1, characterized in that: The dq axis reference current required by the dual three-phase permanent magnet synchronous motor is: Where β' is the optimal current vector angle, I s Indicates the stator current amplitude.

9. The maximum torque current ratio control method of 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 cycles of the positive square wave and the negative square wave are both 50%.

10. A system for implementing the maximum torque current ratio control method of a dual three-phase permanent magnet synchronous motor according to any one of claims 1 to 9, characterized in that: include: Virtual signal injection module, realizing bipolar virtual square wave signal injection; A signal demodulation module for obtaining an optimal current vector angle; The speed controller is used to obtain the dq axis reference current required by the dual three-phase permanent magnet synchronous motor.

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