Copper loss optimization method and device of permanent magnet synchronous motor, and medium

Abstract

The invention discloses a copper loss optimization method and device and a medium, and the method comprises the steps: constructing a motor model which comprises an electromagnetic torque equation and a copper loss equation; setting a plurality of RLS estimators for executing parameter updating of the motor; constructing a cost function based on exploration and utilization of a dual-control mechanism; performing single-step prediction on the motor state, calculating a cost function gradient, and determining a current increment; generating an optimal current state based on gradient descent; converting the optimal current state into a control voltage instruction; the voltage instruction is converted into an inverter driving signal, the inverter driving signal adjusts the phase current of the motor, and copper loss optimization of the motor is achieved. According to the method, through precise optimal energy consumption point control, the phase current amplitude is reduced compared with traditional control, copper loss is synchronously reduced, the cost function based on exploration and utilization dual control is constructed, the problem that an existing algorithm excessively depends on a single model is avoided, and the control precision is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of permanent magnet synchronous motor control, and particularly to a copper loss optimization method, device and medium for a permanent magnet synchronous motor. Background Art

[0002] Permanent magnet synchronous motors (PMSMs) are widely used in electric vehicles due to advantages such as high efficiency and high power density. However, under high-power operating conditions, the copper loss in the stator windings of the motor increases significantly, leading to a decrease in energy efficiency and temperature rise problems. To achieve minimum copper loss, control strategies are commonly used to control the current vector under different load conditions.

[0003] Interior permanent magnet synchronous motors (IPMSMs) have become core components of electric vehicles due to their high power density, and their copper loss optimization depends on precise control. However, the motor parameters are prone to change due to magnetic saturation and temperature effects, resulting in the following problems with traditional methods: 1) Parameter time-varying problem: The permanent magnet flux linkage and inductance difference are significantly affected by magnetic saturation and temperature, and it is difficult for traditional offline parameter tables or single estimators to accurately identify them in real time; 2) Insufficient dynamic performance: Online methods based on extremum search need to inject high-frequency signals, resulting in torque ripple, and the speed of tracking the optimal operating point is slow when the load / speed changes suddenly; 3) Signal dependence problem: Existing methods rely on ideal torque observation, and the observation error in actual applications will significantly reduce the control accuracy.

[0004] In summary, there is an urgent need for a copper loss optimization method that does not require signal injection, adapts to parameter changes, and has strong robustness. Summary of the Invention

[0005] The purpose of the present invention is to provide a copper loss optimization method, device and medium for a permanent magnet synchronous motor to reduce the copper loss of the permanent magnet synchronous motor.

[0006] To solve the above technical problems, the present invention provides a copper loss optimization method for a permanent magnet synchronous motor, including: A copper loss optimization method for a permanent magnet synchronous motor, including: Construct a motor model, where the motor model includes an electromagnetic torque equation and a copper loss equation; Set multiple RLS estimators for performing parameter update of the motor and transforming the electromagnetic torque equation into a torque linear model; Construct a cost function based on an exploration and exploitation dual control mechanism; Perform a single-step prediction of the motor state, calculate the gradient of the cost function, and determine the current increment; Generate an optimal current state based on gradient descent; Convert the optimal current state into a control voltage command; Convert the voltage command into an inverter drive signal, and the inverter drive signal adjusts the motor phase current to achieve copper loss optimization of the motor.

[0007] Optionally, the electromagnetic torque equation calculates the electromagnetic torque of the motor using the number of pole pairs, permanent magnet flux linkage, d-axis inductance, q-axis inductance, d-axis current, and q-axis current.

[0008] Optionally, the copper loss equation calculates the copper loss of the motor using the phase current.

[0009] Optionally, convert the electromagnetic torque equation into a torque linear model as follows: Set and initialize the sampling time, permanent magnet flux linkage, d-axis inductance, and q-axis inductance, and construct an RLS estimator; Update the parameters through the RLS estimator based on the measured torque and current; Convert the electromagnetic torque equation into a torque linear model.

[0010] Optionally, the cost function includes at least an exploitation term and an exploration term. The exploitation term is used to provide the current optimal tracking, and the exploration term is used to provide the parameter estimation error.

[0011] Optionally, the process of determining the current increment is as follows: Calculate the motor state at a certain moment, and the motor state includes the current current state; Calculate the estimated electromagnetic torque of the motor at this moment through the RLS estimator; Calculate the optimal current reference value through the estimated electromagnetic torque, and calculate the cost according to the current current state and the optimal current reference value; Calculate the gradient of the cost with respect to the current increment to obtain the cost function gradient, and the cost function gradient is used to determine the current increment.

[0012] Optionally, the process of converting the optimal current state into a control voltage command is as follows: Construct the motor d-axis voltage equation and the motor q-axis voltage equation, and convert the optimal current state into a control voltage command according to the motor d-axis voltage equation and the motor q-axis voltage equation.

[0013] Optionally, convert the voltage command into an inverter drive signal through pulse width modulation.

[0014] The present invention also provides a copper loss optimization device for a permanent magnet synchronous motor, and the device includes: A memory for storing a computer program; A processor for executing the computer program to implement the copper loss optimization method as described above.

[0015] The present invention also provides a non - transitory computer - readable storage medium storing instructions, which, when executed by a processor, perform the above - mentioned copper loss optimization method.

[0016] The copper loss optimization method for a permanent - magnet synchronous motor provided by the present invention reduces the phase - current amplitude compared with the traditional control through precise optimal energy - consumption point control, and synchronously reduces the copper loss. In addition, the present invention also constructs a cost function based on dual control of exploration and exploitation, avoiding the problem that the existing algorithms overly rely on a single model and improving the control accuracy. The copper loss optimization method provided by the present invention does not require signal injection, adapts to parameter changes, and has strong robustness. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following - described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0018] Figure 1 It is a flowchart of a copper loss optimization method provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The core of the present invention is to provide a copper loss optimization method for a permanent - magnet synchronous motor. In the prior art, traditional copper loss optimization methods have problems such as parameter time - variation, insufficient dynamic performance, and signal dependence.

[0020] A copper loss optimization method provided by the present invention includes constructing a motor model, where the motor model includes an electromagnetic torque equation and a copper loss equation; setting a plurality of RLS estimators for performing parameter update of the motor; constructing a cost function based on a dual - control mechanism of exploration and exploitation; performing a single - step prediction on the motor state, calculating the cost - function gradient, and determining the current increment; generating an optimal current state based on gradient descent; converting the optimal current state into a control voltage command; and converting the voltage command into an inverter drive signal, where the inverter drive signal adjusts the motor phase current to achieve copper loss optimization of the motor.

[0021] The method of the present invention reduces the phase - current amplitude compared with the traditional control through optimal energy - consumption point control, synchronously reduces the copper loss, and constructs a cost function based on dual control of exploration and exploitation, avoiding the problem that the existing algorithms overly rely on a single model and improving the control accuracy.

[0022] To enable those skilled in the art to better understand the solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0023] Please refer to Figure 1 , Figure 1 which is a flowchart of the copper loss optimization method provided by the embodiment of the present invention.

[0024] See Figure 1 , in the embodiment of the present invention, the copper loss optimization method includes: A copper loss optimization method for a permanent magnet synchronous motor includes: S1: Construct a motor model, where the motor model includes an electromagnetic torque equation and a copper loss equation.

[0025] In this embodiment, the electromagnetic torque equation calculates the electromagnetic torque of the motor using the number of pole pairs, permanent magnet flux linkage, d-axis inductance, q-axis inductance, d-axis current, and q-axis current. The expression is as follows: ; where T represents the electromagnetic torque, p, , and are the motor parameters determined during motor design, representing the number of pole pairs, permanent magnet flux linkage, d-axis inductance, and q-axis inductance, and are the d-axis current and q-axis current.

[0026] It should be noted that in this embodiment, the copper loss equation calculates the copper loss of the motor using the phase current. The expression of the copper loss in this embodiment is as follows: ; where R is the winding resistance, and the amplitude of the phase current .

[0027] In this embodiment, the optimization goal is to minimize the copper loss as much as possible, which can be achieved by finding the minimum value of the amplitude of the motor phase current, that is, the optimal energy consumption point.

[0028] S2: Set multiple RLS estimators for performing parameter update of the motor and convert the electromagnetic torque equation into a torque linear model. The number of RLS estimators in this embodiment is N.

[0029] Furthermore, converting the electromagnetic torque equation into a torque linear model is specifically as follows: Set and initialize the sampling time, permanent magnet flux linkage, d-axis inductance, and q-axis inductance, construct an RLS estimator, and initialize the RLS estimator The expression is as follows: ; Among them, represents the jth initialized estimator, and T is the sampling time; Based on the measured torque and current, update the parameters through the RLS estimator, and the expression is as follows: ; Among them, B(k) represents the basis function, , represents the forgetting factor, , C(k) is the error covariance matrix, V is the gain vector, is the basic recurrence formula of the estimator, j is the estimator number, is the current, is the previous round, and k = 0 means initialization.

[0030] Convert the electromagnetic torque equation into a torque linear model, and the expression is as follows: ; Among them, R represents the RLS estimator.

[0031] S3: Construct a cost function based on the exploration and exploitation dual control mechanism. The cost function includes at least an exploitation term and an exploration term. The exploitation term is used to provide the current optimal tracking, and the exploration term is used to provide the parameter estimation error. The cost function The expression is as follows: ; Among them, represents the exploitation term, , represents the exploration term, represents the current current state, , is the mean value of the optimal current states of each estimator.

[0032] S4: Perform a single-step prediction on the motor state, calculate the cost function gradient, and determine the current increment. The process of determining the current increment is as follows: Calculate the motor state at a certain moment. The motor state includes the current current state. The state at a certain moment is expressed as follows: ; Among them, represents the current increment, Calculate the estimated electromagnetic torque of the motor at this moment through the RLS estimator. The electromagnetic torque estimated by the j-th estimator at time is expressed as follows: ; Since the measured torque at time is not available, the mean value of the electromagnetic torque estimated by N RLS estimators is used to calculate the estimated electromagnetic torque , and the expression is as follows: ; Calculate the optimal current reference value through the estimated electromagnetic torque, and calculate the cost according to the current current state and the optimal current reference value; Calculate the gradient of the cost with respect to the current increment to obtain the cost function gradient. The cost function gradient is used to determine the current increment, and the expression of the cost function gradient is as follows: ; where represents the gradient of the cost function, represents the value of the cost function at time , represents the value of the cost function at time .

[0033] S5: Generate the optimal current state based on gradient descent, and the expression is as follows: ; where is the adaptive gain, , driving the current vector to move towards the minimum point of the cost function.

[0034] S6: Convert the optimal current state into a control voltage command, and the process is as follows: Construct the motor d-axis voltage equation and the motor q-axis voltage equation, and convert the optimal current state into a control voltage command according to the motor d-axis voltage equation and the motor q-axis voltage equation.

[0035] The motor d-axis voltage equation and the motor q-axis voltage equation are expressed as follows: ; Through the above equations, this embodiment can convert the optimal current state into a control voltage command .

[0036] S7: Convert the voltage command into an inverter drive signal, and the inverter drive signal adjusts the motor phase current to achieve copper loss optimization of the motor.

[0037] In this embodiment, the voltage command is converted into an inverter drive signal through pulse width modulation.

[0038] A copper loss optimization method provided by an embodiment of the present invention reduces the phase current amplitude compared with the traditional control through precise optimal energy consumption point control, and synchronously reduces the copper loss. In addition, the method of this embodiment also constructs a cost function based on dual control of exploration and exploitation, avoiding the problem that the existing algorithms overly rely on a single model, and improving the control accuracy. The copper loss optimization method provided by this embodiment does not require high-frequency current / angle injection, fundamentally eliminates torque ripple, improves control smoothness, and the method of this embodiment is based on the forgetting factor RLS and gradient descent, quickly responds to load / speed changes. The method of this embodiment works in parallel with multiple RLS estimators with different initial parameters to cover the parameter uncertainty space and improve the identification robustness. Compared with the existing copper loss optimization algorithms, the method of the embodiment of the present invention reduces copper loss, improves dynamic performance, enhances robustness, and optimizes control accuracy.

[0039] This embodiment also provides a copper loss optimization device for a permanent magnet synchronous motor. The device includes: A memory for storing a computer program; A processor for executing the computer program to implement the copper loss optimization method as described above.

[0040] This embodiment also provides a non-transitory computer-readable storage medium storing instructions, and when the instructions are executed by a processor, the copper loss optimization method as described above is executed.

[0041] In this specification, the various embodiments are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the description of the method part.

[0042] Those skilled in the art can further realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of the two. To clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described according to functions in the above description. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0043] The steps of the methods or algorithms described in connection with the embodiments disclosed herein may be implemented directly in hardware, in software modules executed by a processor, or in a combination thereof. The software modules may be disposed in a random access memory (RAM), internal memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0044] Finally, it should also be noted that in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variation thereof is intended to cover a non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the phrase "comprising a..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0045] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for optimizing copper loss of a permanent magnet synchronous motor, characterized in that Including: Construct a motor model, where the motor model includes an electromagnetic torque equation and a copper loss equation; Set multiple RLS estimators for performing parameter updates of the motor and transforming the electromagnetic torque equation into a torque linear model; Construct a cost function based on an exploration and exploitation dual control mechanism; Perform a single-step prediction of the motor state, calculate the cost function gradient, and determine the current increment; Generate an optimal current state based on gradient descent; Convert the optimal current state into a control voltage command; Convert the voltage command into an inverter drive signal, and the inverter drive signal adjusts the motor phase current to achieve copper loss optimization of the motor.

2. The copper loss optimization method according to claim 1, characterized in that The electromagnetic torque equation calculates the electromagnetic torque of the motor using the number of pole pairs, permanent magnet flux linkage, d-axis inductance, q-axis inductance, d-axis current, and q-axis current.

3. The copper loss optimization method according to claim 1, wherein The copper loss equation calculates the copper loss of the motor using the phase current.

4. The copper loss optimization method according to claim 1, wherein Transform the electromagnetic torque equation into a torque linear model as follows: Set and initialize the sampling time, permanent magnet flux linkage, d-axis inductance, and q-axis inductance, and construct an RLS estimator; Update the parameters through the RLS estimator based on the measured torque and current; Convert the electromagnetic torque equation into a torque linear model.

5. The copper loss optimization method according to claim 1, wherein The cost function includes at least an exploitation term and an exploration term. The exploitation term is used to provide the current optimal tracking, and the exploration term is used to provide the parameter estimation error.

6. The copper loss optimization method according to claim 1, characterized in that The process of determining the current increment is as follows: Calculate the motor state at a certain moment, where the motor state includes the current current state; Calculate the estimated electromagnetic torque of the motor at this moment through the RLS estimator; Calculate the optimal current reference value through the estimated electromagnetic torque, and calculate the cost according to the current current state and the optimal current reference value; Calculate the gradient of the cost with respect to the current increment to obtain the cost function gradient, and the cost function gradient is used to determine the current increment.

7. The copper loss optimization method according to claim 1, characterized in that The process of converting the optimal current state into a control voltage command is as follows: Construct a motor d-axis voltage equation and a motor q-axis voltage equation, and convert the optimal current state into a control voltage command according to the motor d-axis voltage equation and the motor q-axis voltage equation.

8. The copper loss optimization method according to claim 1, wherein Convert the voltage command into an inverter drive signal through pulse width modulation.

9. A copper loss optimization device for a permanent magnet synchronous motor, characterized in that, The device includes: A memory for storing a computer program; A processor for executing the computer program to implement the copper loss optimization method according to any one of claims 1 to 8.

10. A non-transitory computer-readable storage medium storing instructions, characterized in that, When the instruction is executed by the processor, execute the copper loss optimization method according to any one of claims 1 to 8.

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