Loss and efficiency estimation method for six-phase permanent magnet synchronous motor

Abstract

The application discloses a six-phase permanent magnet synchronous motor loss and efficiency estimation method, and belongs to the technical field of motor loss estimation. Specifically, the loss power of the motor is divided, and the loss power is composed of copper loss power, iron loss power and additional loss power; the expression of the copper loss power, the iron loss power and the additional loss power under each working condition is modeled respectively; the power of the three types of losses is added, and the total loss power of the motor is calculated; and finally, the efficiency of the motor is calculated. The additional loss power is obtained by dividing the speed interval and using an adaptive algorithm. The application can obtain a relatively accurate additional loss power value, and the six-phase permanent magnet synchronous motor loss and efficiency estimation will be more accurate, and the application also provides a certain reference for the motor loss and efficiency estimation method.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of motor loss estimation, more specifically to a six-phase permanent magnet synchronous motor loss and efficiency estimation method. BACKGROUND

[0002] Permanent magnet synchronous motor is mainly driven by the rotating magnetic field generated by the stator current, which interacts with the rotor permanent magnet magnetic field to produce electromagnetic torque to drive the motor to rotate. Permanent magnet synchronous motor has the characteristics of high efficiency, energy saving, compact structure, strong reliability, low noise and environmental protection, and is widely used in new energy vehicles, industrial automation, household appliances, energy, rail transportation and other fields. At present, the estimation method of motor loss and efficiency is mostly the same, and the calculation deviation is large, which is difficult to accurately calculate the motor loss and efficiency under various working conditions, and the obtained efficiency data is seriously distorted, which cannot accurately draw the efficiency MAP.

[0003] The Chinese invention patent with the application publication number CN 114465537A discloses a permanent magnet synchronous motor high-precision modeling method, device and storage medium. In the modeling method, step S2 is based on the thermal characteristics of the vehicle permanent magnet synchronous motor to derive a thermal model of the motor internal loss and temperature change. The motor internal loss includes copper loss and iron loss, and the iron loss includes hysteresis loss, eddy current loss, additional loss and high-frequency loss, i.e. the motor stator iron loss is represented as: P Fe = P h + P c + P e + P f , P h is the hysteresis loss, P c is the eddy current loss, P e is the additional loss, and P f is the high-frequency loss. The patent does not consider the influence of motor speed on the calculation of additional loss, resulting in insufficient accuracy of motor loss calculation. SUMMARY

[0004] The present application provides a six-phase permanent magnet synchronous motor loss and efficiency estimation method, which aims to solve the problem that the existing permanent magnet synchronous motor does not consider the influence of motor speed on the calculation of additional loss, resulting in insufficient accuracy of motor loss calculation.

[0005] The present application adopts the following technical solutions:

[0006] A six-phase permanent magnet synchronous motor loss and efficiency estimation method, comprising the following steps:

[0007] Step 1, dividing the loss power of the motor by the copper loss power of the motor, the iron loss power and additional power loss Composition, namely: ;

[0008] Step 2: Model the copper power loss expression for each operating condition, as shown in the following formula: ,in, The number of phases of the motor is taken here. ; For each phase current, The impedance of each phase of the motor, The impedance of the motor controller;

[0009] Step 3: Model the iron loss power expression for each operating condition, as shown in the following formula: ,in, and For material coefficients, For the current frequency, This refers to the magnetic flux density amplitude.

[0010] Step 4: Calculate the additional power loss under each operating condition. The expression is modeled and obtained using an adaptive algorithm: ① Divide the speed range into 3 speed ranges. , , Their corresponding power is respectively , and ;in, This refers to the instantaneous speed of the motor. ① Set the rated speed of the motor; ② Set the initial additional power loss value to... The convergence region parameter is Calculate the impact factor and ③ Calculate the theoretical additional loss value for the first generation. offset from the first generation ④ Calculate the theoretical additional loss value for the Nth generation. offset of the Nth generation ⑤ Determine if it exists If so, output the theoretical additional loss value. ⑥ Similarly, output the additional loss value. and ⑦ Write the piecewise function for the additional power loss: ;

[0011] Step 5: Add up the power losses of the above three categories and calculate the total power loss of the motor. Then we have: ;

[0012] Step 6: Calculate the motor efficiency , then wherein, is the bus voltage, is the bus current.

[0013] The motor impedance in step two is obtained by using the following formula: wherein, is the temperature, is the motor phase resistance at 25℃, is the motor line resistance at 25℃, is the motor resistance at the temperature . The controller impedance in step two is calculated in the following manner:

[0014] wherein, is the influence factor of the controller, is the equivalent capacitance of the controller, is the switching frequency of the controller, is the bus voltage of the controller, is the on-time of the controller. The controller is an SIC controller, and is taken; for the controller being an IGBT controller,

[0015] is taken. The influence factors in step four are calculated in the following manner: when ,

[0016] then ; when , then ; when , then ; when , then . The first generation of theoretical additional loss values in step four are calculated in the following formula:

[0017] . The first generation of offset values are calculated in the following formula: .

[0018] From the above description of the present application, compared with the prior art, the present application has the following advantages:

[0019] The present application is based on dividing the speed interval, and three theoretical additional loss power values , ,are calculated by using the adaptive algorithm.​ , get more accurate additional loss power value, six-phase permanent magnet synchronous motor loss and its efficiency estimation will be more accurate, and also provide certain reference for motor loss and its efficiency estimation method. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Flowchart of the present application.

[0021] Figure 2 Flowchart of the additional loss power obtaining method of the present application. DETAILED DESCRIPTION

[0022] The specific embodiments of the present application will be described below with reference to the accompanying drawings. In order to fully understand the present application, many details are described below, but the present application can be implemented without these details for those skilled in the art. For well-known components, methods and processes, the following will not be described in detail.

[0023] The present embodiment provides a six-phase permanent magnet synchronous motor loss and its efficiency estimation method, with reference to Figure 1 , specifically comprising the following steps:

[0024] Step one, divide the motor loss and model respectively.

[0025] Motor loss power Mainly by motor copper loss power , iron loss power and additional loss power , that is: .

[0026] Step two, model the copper loss power expression under each working condition, the formula is as follows:

[0027]

[0028] Among them, is the number of motor phases, here ; is the current of each phase, is the impedance of each phase motor, is the impedance of the motor controller.

[0029] ①Obtaining of motor impedance :

[0030] The above phase current can be obtained by real-time measurement, and the most important thing is to consider value will change with temperature, the approximate change rule is as follows:

[0031]

[0032]

[0033] in, For temperature, The resistance of the motor phase at 25℃. The resistance of the motor line at 25℃ For temperature The motor resistance below.

[0034] ② Controller impedance The acquisition

[0035] The impedance of a controller typically varies slightly between different controllers. The impedance primarily considers switching losses and conduction losses. It is calculated as follows:

[0036]

[0037] in, For the controller, the influence factor is taken as follows: (The value is missing from the original text). For controllers that are IGBT controllers, take... ; This is the equivalent capacitance of the controller; This refers to the switching frequency of the controller; This refers to the bus voltage of the controller; This refers to the on-time of the controller.

[0038] Step 3: Model the iron loss power expression for each operating condition, as shown in the following formula:

[0039]

[0040] in, and For material coefficients, For the current frequency, This represents the magnetic flux density amplitude.

[0041] Step 4: Calculate the additional power loss under each operating condition. Modeling is done using expressions.

[0042] Additional power loss This is mainly due to stray losses, which account for a relatively small proportion, but to improve data accuracy, an adaptive algorithm-based calculation method is used. (See reference...) Figure 2 The details are as follows:

[0043] ①Additional power loss The calculation is divided into multiple segments, mainly into three segments, namely, the additional loss segment ( ), additional loss 2 segment ( ) and additional loss 3 segment ( ), the corresponding power is , and . Wherein, is the instantaneous speed of the motor, is the rated speed of the motor.

[0044] ② For seven-segment SVPWM wave mode, in the additional loss 1 segment ( ), considering the additional loss caused by the change of motor magnetic field due to switching, in a complete PWM wave cycle, the PWM actually changes 6 times, so the average time of each time is about , so assuming the rated voltage is , therefore:

[0045] Assuming that in the 0th generation (initial state) setting, the initial additional loss power value is set to , the convergence domain parameter is , and the calculation of the influence factor is set to and , the calculation method is as follows:

[0046] When , , then ;

[0047] When , , then ;

[0048] When , , then .

[0049] ③ When there is an additional loss power value , then the deviation of the additional loss power value calculated by the first generation is called "1 generation offset ", which is set to .

[0050] ④ Further calculate the additional loss power value of the first generation and the offset of the first generation , that is:

[0051]

[0052] ⑤ Continue the above steps by analogy, when N after , if there is , then is The value of

[0053] The value of and can be calculated.

[0054] The segment function for solving is written as follows:

[0055]

[0056] The judgment logic of the segment function is as follows: (1) the rotating speed of the motor is collected, and the interval is determined according to the rotating speed value; (2) the theoretical value is calculated according to the calculation function of the additional loss power value after the rotating speed interval is obtained.

[0057] Step five, the power of the above three kinds of losses is added to calculate the total loss power of the motor , and

[0058]

[0059] Step six, the efficiency of the motor is calculated , and

[0060]

[0061] wherein, is the bus voltage, is the bus current.

[0062] The above is only a specific embodiment of the present application, but the design concept of the present application is not limited to this, and any non-essential modification of the present application using this concept shall belong to the act of infringing the protection scope of the present application.

Claims

1. A method for estimating the losses and efficiency of a six-phase permanent magnet synchronous machine, characterized in that, comprising the steps of: Step one, the loss power of the motor is divided into copper loss power , iron loss power and additional loss power , namely: ; Step two, modeling the copper loss power expression under each working condition, the formula is as follows: Wherein, is the number of motor phases, here ; is the current of each phase, is the impedance of each phase motor, is the impedance of the motor controller; Step three, the iron loss power expression of each working condition is modeled, and the formula is as follows: Wherein, And is a material coefficient, is a current frequency, is a magnetic flux density amplitude; Step four, additional loss power under each working condition The expression is modeled by using the calculation method based on adaptive algorithm: ①Divide the three speed intervals , , , and the corresponding power is , and ; wherein, is the instantaneous speed of the motor, is the rated speed of the motor; ②Set the initial additional loss power value as , the convergence domain parameter as , and calculate the influence factors and ; ③Calculate the first generation of theoretical additional loss value and the first generation of offset ; ④Calculate the Nth generation of theoretical additional loss value and the Nth generation of offset erro n , that is: , wherein: P add(n-1) represents the (N-1)th generation of theoretical additional loss power value, erro (n-1) represents the (N-1)th generation of offset; ⑤Judge whether there is , if yes, output the additional loss value ; ⑥Similarly, output the additional loss values and ; ⑦Write the segmented function of the additional loss power: ; Step five, calculate the efficiency of the motor Then we have: Where, Vbus is the bus voltage of the controller, Ibus is the bus current.

2. A method of estimating the losses and efficiency of a six-phase permanent magnet synchronous machine as claimed in claim 1, characterized by, Motor impedance in step two is obtained using the following equation: , ; where, is temperature, is motor phase resistance at 25 °C, resistance is motor wire resistance at 25 °C, is motor resistance at temperature .

3. A method of estimating the losses and efficiency of a six-phase permanent magnet synchronous machine as claimed in claim 1, characterized by, Controller impedance in step two The calculation is performed in the following way: ; where, is the controller's influence factor, is the controller's equivalent capacitance, is the controller's switching frequency, is the controller's bus voltage, is the controller's on-time.

4. A method of estimating the losses and efficiency of a six-phase permanent magnet synchronous machine as claimed in claim 3, characterized in that: The controller is an IGBT controller, take ; for the controller is an IGBT controller, take .

5. The method of estimating the losses and efficiency of a six-phase permanent magnet synchronous machine as claimed in claim 1, wherein, The impact factor in step four and The calculation method is as follows: when , , then ; when , , then ; when , , then ; wherein U base is the rated voltage.

6. The method of estimating the losses and efficiency of a six-phase permanent magnet synchronous machine as claimed in claim 1, wherein, Theoretical additional loss value of the 1st generation in the step four And the offset of the 1st generation The following formula is used for calculation: .

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