Design method for rotating speed self-adaptive flux weakening controller of permanent magnet synchronous motor

Abstract

The invention relates to a design method, in particular to a design method for a rotating speed self-adaptive flux weakening controller of a permanent magnet synchronous motor. The invention aims to solve the problem that the parameter setting of the existing flux-weakening controller needs trial and error. The method comprises the following steps: step 1, calculating a q-axis voltage reference value and constructing a q-axis voltage closed loop; 2, designing different types of rotating speed self-adaptive voltage regulators according to different current loop decoupling methods; and step 3, flux weakening control is realized through the adjusting effect of the rotating speed self-adaptive voltage closed loop. The invention belongs to the technical field of field weakening control of a permanent magnet synchronous motor.

Description

Technical Field

[0001] The invention relates to a design method and belongs to the technical field of permanent magnet synchronous motor weak magnetic control. Background Art

[0002] Dual closed-loop control is the basic control framework of permanent magnet synchronous motors. It consists of an outer speed loop and an inner current loop. Its core is to transform the three-phase sinusoidal current into a two-phase rotating current for control through coordinate transformation, and finally output the inverter switching signal through space vector pulse width modulation (SVPWM). For permanent magnet synchronous motors that require weak magnetic field control, it is often necessary to introduce a voltage loop on the basis of a dual closed-loop system, that is, to perform weak magnetic field control by means of voltage vector amplitude feedback. For the current loop and speed loop, since their closed-loop systems are linear systems, the transfer function can be directly written and then the parameter setting method of the corresponding controller can be derived, but for the voltage closed loop, the situation is completely different. Figure 1 The schematic diagram of the voltage amplitude feedback weak magnetic control loop, where the reference value u of the voltage regulator is s,ref is the radius of the inscribed circle of the SVPWM hexagonal voltage constraint. d and u q represents the d and q axis voltages, then the feedback value u of the voltage vector amplitude is s Written as:

[0003]

[0004] The voltage closed-loop method is an effective way to achieve weak magnetic field operation of permanent magnet synchronous motors, and has strong parameter robustness and feasibility. However, the nonlinearity of the voltage closed-loop worsens the proportional integral (PI) tuning problem, resulting in the lack of PI tuning standards for voltage regulators. Summary of the invention

[0005] The present invention aims to solve the problem that the existing weak magnetic controller parameter setting needs to be tried and true, and further proposes a method for designing a permanent magnet synchronous motor speed adaptive weak magnetic controller.

[0006] The technical solution adopted by the present invention to solve the above-mentioned problem is: the steps of the present invention include:

[0007] Step 1, calculate the q-axis voltage reference value and construct the q-axis voltage closed loop;

[0008] Step 2, designing different types of speed adaptive voltage regulators according to different current loop decoupling methods;

[0009] Step 3: Implement magnetic field weakening control through the regulation of the speed adaptive voltage closed loop.

[0010] Furthermore, in step 1, the q-axis voltage u q is used as feedback for the proposed voltage closed loop instead of the voltage vector magnitude u s The purpose is to put the nonlinear calculation in advance, and its reference value u q,ref for:

[0011]

[0012] In formula (2), u dc Indicates the inverter DC bus voltage, u d represents the d-axis voltage.

[0013] Furthermore, step 2 specifically includes:

[0014] Step 201, designing a speed adaptive voltage closed-loop regulator for non-integral decoupling;

[0015] Step 202: Design a speed adaptive voltage closed-loop regulator for integral decoupling.

[0016] Further, for the non-integral decoupling structure in step 201, it is assumed that the actual d-axis current can well follow its reference value, that is, i d =i d,ref ; The q-axis voltage u output by the current PI regulator q,PI and back EMF are regarded as disturbance terms. In the analysis of the voltage closed loop, feedforward decoupling and feedback decoupling are treated equally. The open-loop transfer function of the voltage loop with non-integral decoupling is H v,1 (s) is written as:

[0017]

[0018] In formula (3), K p,v Represents the proportionality factor of the voltage regulator, K i,v represents the integral coefficient of the voltage regulator, ω e Indicates the electrical angular velocity of the motor, L d represents the d-axis inductance of the permanent magnet synchronous motor;

[0019] If the proportionality factor K p,v is zero, then formula (3) is simplified to a pure integral link, and the voltage closed-loop transfer function G v,1 (s) is written in the form of a first-order inertia link:

[0020]

[0021] In formula (4), ω v Represents the bandwidth of the voltage loop;

[0022] The PI tuning method of the speed adaptive voltage closed-loop regulator with non-integral decoupling is obtained, which is as follows:

[0023]

[0024] Furthermore, the open-loop transfer function H of the voltage loop of the integral decoupling in step 202 is v,2 (s) is written as:

[0025]

[0026] In formula (6), ω c represents the bandwidth of the current loop, and s represents the complex frequency;

[0027] Get its closed-loop transfer function G v,2 (s) is:

[0028]

[0029] G v,2 (s) has two poles. The two poles are equally arranged on the negative real axis and the stability is strictly guaranteed. K p,v and K i,v The relationship between them is expressed as:

[0030]

[0031] Assumptions:

[0032]

[0033] Closed loop transfer function G v,2 (s) is written as:

[0034]

[0035] In formula (10), ω v ′ represents the closed-loop pole frequency, and the actual bandwidth of the voltage closed loop ω v Calculated by the following formula:

[0036]

[0037] In formula (11), j represents an imaginary unit. Solving the above formula, we can obtain the real voltage closed-loop bandwidth:

[0038]

[0039] The PI tuning method of the speed adaptive voltage closed-loop regulator with integral decoupling is obtained:

[0040]

[0041] The beneficial effects of the present invention are:

[0042] 1. The present invention solves the problem of difficult controller parameter setting caused by voltage closed-loop nonlinearity in traditional weak magnetic control;

[0043] 2. On the one hand, the present invention provides a clear design theory that the voltage regulator parameters should have speed adaptive properties; on the other hand, it simplifies the parameter setting process, and the voltage regulator parameter setting can be completed by manually selecting the closed-loop bandwidth;

[0044] 3. The present invention replaces the traditional voltage vector amplitude closed-loop feedback with q-axis voltage closed-loop feedback, so that the nonlinear calculation of the voltage closed-loop is pre-placed;

[0045] 4. The present invention constructs different voltage closed-loop control block diagrams according to different current loop decoupling branches, thereby designing different speed adaptive parameter setting rules;

[0046] 5. The permanent magnet synchronous motor speed adaptive weak magnetic controller designed by the present invention can realize online PI parameter setting by only inputting the expected bandwidth, solving the problem of difficult parameter setting caused by the nonlinearity of the traditional voltage closed loop. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a schematic diagram of the voltage amplitude feedback weak magnetic control loop;

[0048] Figure 2 It is a schematic diagram of the adaptive flux weakening control of the speed of a permanent magnet synchronous motor;

[0049] Figure 3 It is a classification diagram of the classic decoupling method;

[0050] Figure 4 It is a speed adaptive voltage closed loop block diagram for non-integral decoupling;

[0051] Figure 5 It is a closed-loop block diagram of speed adaptive voltage for integral decoupling

[0052] Figure 6 It is the Bode plot of the voltage closed-loop transfer function of the integral type decoupling;

[0053] Figure 7 This is a schematic diagram of the speed step experiment results when the voltage loop bandwidth is 50Hz;

[0054] Figure 7 a is a schematic diagram of feedforward decoupling, Figure 7 b is a schematic diagram of feedback decoupling, Figure 7 c is internal model decoupling, Figure 7 d is a schematic diagram of deviation decoupling;

[0055] Figure 8This is a schematic diagram of the speed step experiment results when the voltage loop bandwidth is 30Hz;

[0056] Figure 8 a is a schematic diagram of feedforward decoupling, Figure 8 b is a schematic diagram of feedback decoupling, Figure 8 c is the schematic diagram of internal model decoupling, Figure 8 d is a schematic diagram of deviation decoupling;

[0057] Fig. 9 This is the result of the sudden load test when the voltage loop bandwidth is 50Hz;

[0058] Fig. 9 a is a schematic diagram of feedforward decoupling, Fig. 9 b is a schematic diagram of feedback decoupling, Fig. 9 c is the schematic diagram of internal model decoupling, Fig. 9 d is a schematic diagram of deviation decoupling;

[0059] Fig.10 This is the result of the sudden load test when the voltage loop bandwidth is 30Hz;

[0060] Fig.10 a is a schematic diagram of feedforward decoupling, Fig.10 b is a schematic diagram of feedback decoupling, Fig.10 c is the schematic diagram of internal model decoupling, Fig.10 d is a schematic diagram of deviation decoupling. DETAILED DESCRIPTION

[0061] Specific implementation method 1: Figure 2 As shown, a method for designing a permanent magnet synchronous motor speed adaptive field weakening controller comprises the following specific steps:

[0062] Step 1: Calculate the q-axis voltage reference value and construct the q-axis voltage closed loop; q-axis voltage u q is used as feedback for the proposed voltage closed loop instead of the voltage vector magnitude u s The purpose is to put the nonlinear calculation in advance, and its reference value u q,ref for:

[0063]

[0064] In formula (2), u dc Indicates the inverter DC bus voltage, u d represents the d-axis voltage;

[0065] Step 2, designing different types of speed adaptive voltage regulators according to different current loop decoupling methods;

[0066] Step 201, design of a speed adaptive voltage closed-loop regulator for non-integral decoupling; for the non-integral decoupling structure, it is assumed that: the actual d-axis current can well follow its reference value, i.e., i d =i d,ref ; The q-axis voltage u output by the current PI regulator q,PI and back EMF are regarded as disturbance terms. In the analysis of the voltage closed loop, feedforward decoupling and feedback decoupling are treated equally. The open-loop transfer function of the voltage loop with non-integral decoupling is H v,1 (s) is written as:

[0067]

[0068] In formula (3), K p,v Represents the proportionality factor of the voltage regulator, K i,v represents the integral coefficient of the voltage regulator, ω e Indicates the electrical angular velocity of the motor, L d represents the d-axis inductance of the permanent magnet synchronous motor;

[0069] If the proportionality factor K p,v is zero, then formula (3) is simplified to a pure integral link, and the voltage closed-loop transfer function G v,1 (s) is written in the form of a first-order inertia link:

[0070]

[0071] In formula (4), ω v Represents the bandwidth of the voltage loop;

[0072] The PI tuning method of the speed adaptive voltage closed-loop regulator with non-integral decoupling is obtained, which is as follows:

[0073]

[0074] Step 202: Design of a speed adaptive voltage closed-loop regulator for integral type decoupling; the open-loop transfer function H of the integral type decoupling voltage loop v,2 (s) is written as:

[0075]

[0076] In formula (6), ω c represents the bandwidth of the current loop, and s represents the complex frequency;

[0077] Get its closed-loop transfer function G v,2 (s) is:

[0078]

[0079] G v,2(s) has two poles. The two poles are equally arranged on the negative real axis and the stability is strictly guaranteed. K p,v and K i,v The relationship between them is expressed as:

[0080]

[0081] Assumptions:

[0082]

[0083] Closed loop transfer function G v,2 (s) is written as:

[0084]

[0085] In formula (10), ω v ′ represents the closed-loop pole frequency, and the actual bandwidth of the voltage closed loop ω v Calculated by the following formula:

[0086]

[0087] In formula (11), j represents an imaginary unit. Solving the above formula, we can obtain the real voltage closed-loop bandwidth:

[0088]

[0089] The PI tuning method of the speed adaptive voltage closed-loop regulator with integral decoupling is obtained:

[0090]

[0091] Step 3: Implementing magnetic field weakening control through the regulation of the speed adaptive voltage closed loop;

[0092] The function of the voltage closed loop is: when the voltage vector amplitude reaches the voltage limit, if the speed is to be further increased, the d-axis current needs to be reduced. The principle of magnetic weakening is as shown in formula (14):

[0093]

[0094] Among them, Figure 3 As shown in the figure, the four classic decoupling methods are divided into two categories according to whether the decoupling branch contains integrals: the first category is that the decoupling branch does not contain integral operations, including feedforward decoupling and feedback decoupling; the second category is that the decoupling branch contains integral operations, including internal model decoupling and deviation decoupling;

[0095] The reason for this classification is that the same type of decoupling method has the same structure in the analysis and design of the voltage closed loop, so the same type of current decoupling can adopt the same speed adaptive voltage regulator parameter setting method; different speed adaptive voltage regulators are designed for different decoupling types. According to the frequency domain analysis, it can be deduced that the PI parameters of the proposed method have speed adaptive characteristics, which is in line with common sense, because as the motor speed increases, the d-axis current change rate of the weak magnetic controller output will decrease.

[0096] In step 201, for the non-integral decoupling structure, it is assumed that the actual d-axis current can well follow its reference value, i.e. d =i d,ref ; The q-axis voltage u output by the current PI regulator q,PI and back EMF are considered as disturbance terms. Then, in the analysis of the voltage closed loop, feedforward decoupling and feedback decoupling are treated equally.

[0097] Experimental results

[0098] The proposed control method is experimentally verified by using the present invention to conduct experimental verification on an actual three-phase permanent magnet synchronous motor towing test platform, where the rated voltage of the motor is 380V, the rated power is 2.2kW, and the current loop bandwidth is 300Hz.

[0099] Figure 7 and Figure 8 The speed step experimental results under different bandwidths and decoupling structures are shown. The speed is expressed in per-unit value with a base value of 2000r / min (1.0pu). The experiment is carried out in the weak magnetic field area. The experimental results verify the feasibility of the proposed voltage regulator PI tuning method. As the bandwidth decreases, the current rapidity and overshoot of the dynamic process will decrease simultaneously.

[0100] Fig. 9 and Fig.10 The sudden load test results under different bandwidths and decoupling structures are shown. The initial speed of the load test is 2400r / min (1.2pu). The experiment is also carried out in the weak magnetic region. According to the experimental results, as the bandwidth decreases, the rapidity and overshoot will decrease. The larger the bandwidth, the better the dynamic response to sudden load. The experimental results are consistent with theoretical expectations.

[0101] The feasibility of the proposed voltage loop PI regulator design method can be easily verified through speed step and sudden load experiments.

[0102] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement made to the above embodiments without departing from the content of the technical solution of the present invention, based on the technical essence of the present invention, within the spirit and principles of the present invention, still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for designing a permanent magnet synchronous motor speed adaptive field weakening controller, characterized in that: The specific steps include: Step 1, calculate the q-axis voltage reference value and construct the q-axis voltage closed loop; Step 2, designing different types of speed adaptive voltage regulators according to different current loop decoupling methods; Step 3: Implement magnetic field weakening control through the regulation of the speed adaptive voltage closed loop.

2. The method for designing a permanent magnet synchronous motor speed adaptive flux weakening controller according to claim 1, characterized in that: The q-axis voltage u in step 1 q is used as feedback for the proposed voltage closed loop instead of the voltage vector magnitude u s The purpose is to put the nonlinear calculation in advance, and its reference value u q,ref for: In formula (2), u dc Indicates the inverter DC bus voltage, u d represents the d-axis voltage.

3. The method for designing a permanent magnet synchronous motor speed adaptive flux weakening controller according to claim 1, characterized in that: Step 2 specifically includes: Step 201, designing a speed adaptive voltage closed-loop regulator for non-integral decoupling; Step 202: Design a speed adaptive voltage closed-loop regulator for integral decoupling.

4. The method for designing a permanent magnet synchronous motor speed adaptive flux weakening controller according to claim 3, characterized in that: In step 201, for the non-integral decoupling structure, it is assumed that the actual d-axis current can well follow its reference value, i.e. d =i d,ref ; The q-axis voltage u output by the current PI regulator q,PI and back EMF are regarded as disturbance terms. In the analysis of the voltage closed loop, feedforward decoupling and feedback decoupling are treated equally. The open-loop transfer function of the voltage loop with non-integral decoupling is H v,1 (s) is written as: In formula (3), K p,v Represents the proportionality factor of the voltage regulator, K i,v represents the integral coefficient of the voltage regulator, ω e Indicates the electrical angular velocity of the motor, L d represents the d-axis inductance of the permanent magnet synchronous motor; If the proportionality factor K p,v is zero, then formula (3) is simplified to a pure integral link, and the voltage closed-loop transfer function G v,1 (s) is written in the form of a first-order inertia link: In formula (4), ω v Represents the bandwidth of the voltage loop; The PI tuning method of the speed adaptive voltage closed-loop regulator with non-integral decoupling is obtained, which is as follows:

5. The method for designing a permanent magnet synchronous motor speed adaptive flux weakening controller according to claim 3, characterized in that: The open-loop transfer function H of the voltage loop of the integral decoupling in step 202 is v,2 (s) is written as: In formula (6), ω c represents the bandwidth of the current loop, and s represents the complex frequency; Get its closed-loop transfer function G v,2 (s) is: G v,2 (s) has two poles. The two poles are equally arranged on the negative real axis and the stability is strictly guaranteed. K p,v and K i,v The relationship between them is expressed as: Assumptions: Closed loop transfer function G v,2 (s) is written as: In formula (10), ω v ′ represents the closed-loop pole frequency, and the actual bandwidth of the voltage closed loop ω v Calculated by the following formula: In formula (11), j represents an imaginary unit. Solving the above formula, we can obtain the real voltage closed-loop bandwidth: The PI tuning method of the speed adaptive voltage closed-loop regulator with integral decoupling is obtained:

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