Motor control optimization method based on segmented carrier and common-mode voltage injection

Abstract

The invention belongs to the technical field of motor control, and discloses a motor control optimization method based on segmented carrier and common-mode voltage injection, which comprises the following steps: S1, dividing a low-speed operation interval, a medium-speed operation interval and a high-speed operation interval according to the operation speed of a motor; s2, under the condition of ensuring the harmonic performance of the output current, determining the optimal carrier frequency f of all-condition motor operation; s3, dividing the low-speed operation interval and the medium-speed operation interval of the motor into N equal parts, and determining the lowest carrier frequency fN of the operation of the motor in each equal part; s4, determining a reference rotating speed nref, if the reference rotating speed is greater than the maximum rotating speed nmax of the motor, injecting a frequency tripling common-mode voltage Vcom, and if the reference rotating speed does not exceed the maximum rotating speed nmax of the motor, not performing common-mode voltage injection; and S5, selecting a corresponding carrier frequency according to the speed interval corresponding to the reference rotating speed to generate a three-phase switching signal. The control method is simple, the application range is wide, the maximum rotating speed of the motor can be increased, the switching loss of the inverter can be reduced, and the system efficiency is remarkably improved under the condition that the current harmonic performance is not reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of motor control, and in particular relates to a motor control optimization method based on segmented carrier and common mode voltage injection. Background Art

[0002] As an important energy conversion device, motors are widely used in daily life. Traditional motors use commutators and other devices for commutation operation, which has problems such as high noise and high maintenance costs. With the development of power electronics and motor control technology, motors controlled by power electronic devices and inverters have gradually developed, and motor control methods are an indispensable part of motor application systems such as electric bicycles, balance cars and robots. The optimization of motor control methods plays an important role in the rapid response, smooth operation, high efficiency and energy saving of motors.

[0003] Traditional motor control methods mainly include Vf control, If control and magnetic field orientation control, but Vf control is an open-loop control without feedback mechanism, which is easy to cause motor out-of-step problems; If control method loses the word adjustment ability of torque, so magnetic field orientation control is used in most applications. Traditional motor modulation methods include PWM modulation, SPWM modulation and SVPWM modulation. The DC bus voltage utilization rate of ordinary SPWM modulation method is low, and the SVPWM modulation method fully utilizes the DC bus voltage, but the control method is relatively complex, especially when used on multi-level converters. Most of these modulation methods use fixed carrier frequency. Higher carrier frequency has larger switching loss when the motor is running at low speed, which reduces the efficiency of the controller; lower carrier frequency has poor current harmonic performance when the motor is running at high speed. Variable frequency carrier technology mainly includes motor speed following control and segmented carrier frequency control. The speed following control method generates switching signals by randomly changing the frequency period of the carrier through the speed, which may have current distortion problems. Segmented carrier frequency control has problems such as large carrier interval span, poor current harmonic performance and high system loss. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a motor control optimization method based on segmented carrier and common-mode voltage injection. While ensuring the output current harmonic performance, the carrier frequency is appropriately reduced to reduce switching losses, and the DC bus voltage utilization rate is improved through the method of triple frequency common-mode voltage injection, thereby increasing the motor operating speed.

[0005] The present invention provides a motor control optimization method based on segmented carrier and common mode voltage injection, comprising the following steps:

[0006] S1. According to the motor running speed, the speed range is divided into the low speed running range [0,n L ], medium speed operation range [nL ,n M ] and high-speed operation range [n M ,n H ];

[0007] S2. Under the condition of ensuring the output current harmonic performance, determine the optimal carrier frequency f for the motor under all working conditions;

[0008] S3. Divide the motor low-speed operation range and medium-speed operation range into N equal parts, and determine the minimum carrier frequency f of the motor in each part. N ;

[0009] S4. Determine the reference speed n ref , if the reference speed is greater than the maximum motor speed n max And the voltage reaches saturation, then the triple frequency common mode voltage V is injected com , if the voltage does not reach saturation, no common-mode voltage injection is performed;

[0010] S5. Select a corresponding carrier frequency according to the speed range corresponding to the reference speed to generate a three-phase switching signal.

[0011] Furthermore, in step S1, the maximum value n of the high-speed operation interval H is the rated speed n of the motor, the maximum value in the low-speed operation range is ≤30%n, and the maximum value in the medium-speed speed range is around 60%n.

[0012] Furthermore, in step S2, the optimal carrier frequency f is the lowest carrier frequency of the motor when the output current of the motor is not distorted under all operating conditions.

[0013] Furthermore, in step S3, the minimum carrier frequency f N It is the lowest carrier frequency in each equal interval where the current output harmonics do not exceed the set value.

[0014] Furthermore, in step S4, when the reference speed is greater than the maximum speed of the motor and the voltage reaches saturation, the amplitude of the injected sinusoidal common mode voltage is 15% to 30% of the maximum amplitude of the reference wave, and the frequency is three times the frequency of the reference wave, wherein the maximum speed of the motor n max is the rated speed n of the motor.

[0015] Furthermore, the reference wave is a sine wave in the range of [-0.5, 0.5], the maximum amplitude of the reference wave is 0.5, and the reference wave frequency is the fundamental frequency f ac , the relationship between the reference wave, the rotation speed n and the injected triple frequency common mode voltage is as follows:

[0016]

[0017] V com=A com ×0.5·sin(3f ac t)

[0018] Where, P is the number of motor poles; V com is the injected triple frequency common mode voltage; A com is the injected triple frequency common mode voltage amplitude.

[0019] The present invention also discloses the application of a motor control optimization method based on segmented carrier and common mode voltage injection in a motor control system. The motor control system includes a DC power supply, an inverter and a load motor.

[0020] Beneficial effects:

[0021] 1. The motor control optimization method based on segmented carrier and common-mode voltage injection proposed in the present invention selects the motor speed n and the optimal carrier frequency under all working conditions in segments according to percentage, matches the low-speed operation segment of the motor with the lowest carrier frequency, reduces the system switching loss when the motor runs at low speed, and improves the controller efficiency.

[0022] 2. The motor control optimization method based on segmented carrier and common-mode voltage injection proposed in the present invention has a simple control method and a wide range of applications. When the voltage of the motor reaches a saturation state during high-speed operation, triple frequency common-mode voltage injection is performed, which improves the utilization rate of the bus DC voltage and thus increases the speed of the motor.

[0023] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flow chart of a motor control optimization method based on segmented carrier and common mode voltage injection of the present invention;

[0025] Figure 2 This is a structural topology diagram of the motor control system corresponding to the control optimization method of the present invention. DETAILED DESCRIPTION

[0026] In order to make the technical solutions, advantages and purposes of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of this application.

[0027] The method of the present invention is mainly applicable to a motor control system, which mainly includes a DC power supply, an inverter and a load motor. Figure 2 shown.

[0028] like Figure 1 As shown, the present invention provides a motor control optimization method based on segmented carrier and common mode voltage injection, comprising the following steps:

[0029] S1. According to the motor running speed, the speed range is divided into the low speed running range [0,n L ], medium speed operation range [n L ,n M ] and high-speed operation range [n M ,n H ];

[0030] The maximum value n of the high-speed operation range H is the rated speed n of the motor, the maximum value of the low-speed operation range is 20% n, and the maximum value of the medium-speed speed range is 40% n;

[0031] S2. Under the condition of ensuring the output current harmonic performance, determine the optimal carrier frequency f for the motor under all working conditions;

[0032] The optimal carrier frequency f is the lowest carrier frequency of the motor when the harmonics of the motor output current under all working conditions is not greater than 4%;

[0033] S3. Divide the motor low-speed operation range and medium-speed operation range into N equal parts, and determine the minimum carrier frequency f of the motor in each part. N ;

[0034] N can be any positive integer, the minimum carrier frequency f N The lowest carrier frequency at which the harmonic performance of the current output in each equal interval does not exceed 4%;

[0035] S4. Determine the reference speed n ref , if the reference speed is greater than the maximum motor speed n max , then the triple frequency common mode voltage V com , if the reference speed does not exceed the maximum motor speed n max , then no common-mode voltage injection is performed;

[0036] When the reference speed is greater than the maximum speed of the motor and the voltage reaches saturation, the amplitude of the injected sinusoidal common-mode voltage is 15% to 30% of the maximum amplitude of the reference wave, and the frequency is three times the reference wave frequency. max is the rated speed of the motor n;

[0037] The reference wave is a sine wave in the range of [-0.5, 0.5], the maximum amplitude of the reference wave is 0.5, and the reference wave frequency is the fundamental frequency f ac , the relationship between the reference wave, the rotation speed n and the injected triple frequency common mode voltage is as follows:

[0038]

[0039] V com =A com ×0.5·sin(3f ac t)

[0040] Where, P is the number of motor poles; V com is the injected triple frequency common mode voltage; A com is the injected triple frequency common mode voltage amplitude.

[0041] S5. According to the reference speed n ref The corresponding speed interval selects the corresponding carrier frequency to generate a three-phase switching signal.

[0042] Under the premise of ensuring that the current harmonic performance does not exceed 4%, the present invention appropriately reduces the carrier frequency when the motor speed is low, and injects a triple frequency common mode voltage when the motor speed is high to improve the DC bus voltage utilization rate, significantly reduce the system switching loss and improve the system efficiency.

[0043] Example 1

[0044] This embodiment discloses a motor control optimization method based on segmented carrier and common mode voltage injection, comprising the following steps:

[0045] S1. According to the motor running speed, the speed range is divided into a low speed running range [0, 100rpm], a medium speed running range [100rpm, 200rpm] and a high speed running range [200rpm, 500rpm];

[0046] S2. Determine that the optimal carrier frequency for the motor under full-operation conditions is 15k while ensuring that the output current harmonics do not exceed 4%;

[0047] S3. Divide the motor low-speed operation range into two equal parts [0, 50rpm] and [50rpm, 100rpm], and keep the medium-speed range unchanged. When the motor speed is in the range [0, 50rpm], select the carrier frequency as 4k; when the motor speed is in the range [50rpm, 100rpm], select the carrier frequency as 6k; when the motor speed is in the range [100rpm, 200rpm], select the carrier frequency as 10k; when the motor speed is in the range [200rpm, 500rpm], select the carrier frequency as 15k;

[0048] S4. Set reference speed n ref , if the motor reference speed n ref When the motor speed exceeds the maximum speed and the voltage reaches saturation, a triple frequency common mode voltage is injected. The injected triple frequency common mode voltage has an amplitude of 1 / 6 and a frequency that is three times the frequency of the generated reference wave. The reference wave frequency is the base frequency f ac , which has the following relationship with the rotation speed n and the injected triple frequency common mode voltage:

[0049]

[0050] S5. According to the reference speed n ref The corresponding carrier frequency is selected in the corresponding interval to generate a three-phase switching signal.

[0051] By adopting this control method, the maximum speed of the motor can be increased to 550rpm, which is 5% higher than the method without common-mode voltage injection. Compared with the control method with fixed carrier frequency, the device loss of this control method is reduced by 3.6%, 2.4% and 1.1% respectively when the speed is lower than 50rpm, 100rpm and 200rpm, thus improving the control efficiency.

[0052] It is hereby declared that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should be included in the scope of the claims of the present invention.

Claims

1. A motor control optimization method based on segmented carrier and common mode voltage injection, characterized in that: The following steps are involved: S1. According to the motor running speed, the speed range is divided into the low speed running range [0,n L ], medium speed operation range [n L ,n M ] and high-speed operation range [n M ,n H ]; S2. Under the condition of ensuring the output current harmonic performance, determine the optimal carrier frequency f for the motor under all working conditions; S3. Divide the motor low-speed operation range and medium-speed operation range into N equal parts, and determine the minimum carrier frequency f of the motor in each part. N ; S4. Set reference speed n ref , if the reference speed is greater than the maximum motor speed n max , and the voltage reaches saturation, then the triple frequency common mode voltage V com , if the voltage does not reach saturation, no common-mode voltage injection is performed; S5. Select a corresponding carrier frequency according to the speed range corresponding to the reference speed to generate a three-phase switching signal.

2. The motor control optimization method based on segmented carrier and common mode voltage injection according to claim 1, characterized in that: In step S1, the maximum value n of the high-speed operation range H is the rated speed n of the motor, the maximum value in the low-speed operation range is ≤30%n, and the maximum value in the medium-speed speed range is around 60%n.

3. The motor control optimization method based on segmented carrier and common mode voltage injection according to claim 1, characterized in that: In step S2, the optimal carrier frequency f is the lowest carrier frequency of the motor when the output current of the motor is not distorted under all operating conditions.

4. The motor control optimization method based on segmented carrier and common mode voltage injection according to claim 1, characterized in that: In step S3, the minimum carrier frequency f N It is the lowest carrier frequency in each equal interval where the current output harmonics do not exceed the set value.

5. The motor control optimization method based on segmented carrier and common mode voltage injection according to claim 1, characterized in that: In step S4, when the reference speed is greater than the maximum speed of the motor and the voltage reaches saturation, the amplitude of the injected sinusoidal common mode voltage is 15% to 30% of the maximum amplitude of the reference wave, and the frequency is three times the reference wave frequency, wherein the maximum speed of the motor n max is the rated speed n of the motor.

6. The motor control optimization method based on segmented carrier and common mode voltage injection according to claim 5, characterized in that: The reference wave is a sine wave in the range of [-0.5, 0.5], the maximum amplitude of the reference wave is 0.5, and the reference wave frequency is the fundamental frequency f ac , the relationship between the reference wave, the rotation speed n and the injected triple frequency common mode voltage is as follows: V com =A com ×0.5·sin(3f ac t) Where, P is the number of motor pole pairs; V com is the injected triple frequency common mode voltage; A com is the injected triple frequency common mode voltage amplitude.

7. Application of the motor control optimization method based on segmented carrier and common mode voltage injection as claimed in any one of claims 1 to 6 in a motor control system, wherein the motor control system comprises a DC power supply, an inverter and a load motor.

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