A Current Control Strategy for a Permanent Magnet Synchronous Motor Simulator Based on Pole Reconstruction

Abstract

The present invention provides a current control strategy for a permanent magnet synchronous motor simulator based on pole reconstruction. It uses complex vectors for modeling and analysis, simplifies the d-axis and q-axis voltage equations of a conventional interface circuit into a complex vector voltage equation model; the delay link of the system is considered in the modeling, making the obtained discrete complex vector model more in line with the actual digital control requirements; the control strategy obtained after pole reconstruction has the advantages of flexible parameter selection, good robustness, no steady-state error, etc., and can achieve the required control effect through parameter configuration. In particular, it can achieve deadbeat control without static error, overcomes the problem of steady-state error existing in traditional deadbeat current predictive control under parameter perturbation, and at the same time expands the parameter mismatch stability range of traditional deadbeat current predictive control.

Description

Technical Field

[0001] The present invention belongs to the technical field of hardware-in-the-loop testing of permanent magnet synchronous motors, and particularly relates to a current control strategy for a permanent magnet synchronous motor simulator based on pole reconstruction. Background Art

[0002] For testing vehicle drive motors using a power hardware-in-the-loop (PHIL) motor emulator (EME), it is a relatively good solution at the present stage. In the test, the real motor terminal current and voltage characteristics are simulated through power electronic devices and control algorithms, and the load demand and fault injection are changed through software. Compared with the traditional motor mechanical load bench test method, it can significantly improve the test efficiency of the motor control unit, shorten the development cycle of the motor controller, and reduce the R & D cost. During the operation of the motor emulator, its current control strategy is the core link to ensure the simulation accuracy of the motor voltage and current terminal characteristics, and determines the response speed and steady-state accuracy of the current loop of the motor emulator. However, the existing PI-based control strategy has a low-pass filtering characteristic, which limits the simulation bandwidth of the motor emulator and is only applicable to medium and low-speed motor emulators; although open-loop control can avoid current loop control conflicts, it has poor robustness, is easily affected by parameter perturbations, and its differential calculation will introduce a certain amount of high-frequency noise, and the simulation accuracy is not high enough; although some existing technologies are designed based on a continuous-domain mathematical model and are discretized and then applied to a digital control system, due to factors such as control delay in the digital control system, after the control strategy designed based on the continuous system is applied to the digital system, the control performance will change. Therefore, how to provide a new current control strategy for a permanent magnet synchronous motor emulator, while overcoming the above deficiencies of the existing technologies and providing better control effects, is an urgent technical problem in this field. Summary of the Invention

[0003] In view of this, in response to the technical problems existing in this field, the present invention provides a current control strategy for a permanent magnet synchronous motor emulator based on pole reconstruction, specifically including the following steps:

[0004] Step 1: Establish a continuous complex vector transfer function in the dq coordinate system for the interface circuit of the permanent magnet synchronous motor emulator;

[0005] Step 2: Equivalent the three-phase inverter on the permanent magnet synchronous motor emulator side to a zero-order hold, and considering the delay link of the digital controller, establish the corresponding continuous complex vector transfer functions respectively, and perform discretization processing in combination with the continuous complex vector transfer function established in Step 1 to obtain the discrete complex vector transfer function of the interface circuit;

[0006] Step 3: Reconstruct the poles of the discrete complex vector transfer function of the interface circuit, convert the complex poles into two real poles, and achieve complete decoupling between the dq axes;

[0007] Step 4: For the discrete complex vector transfer function of the interface circuit after pole reconstruction, design a discrete current control strategy and the corresponding controller parameters based on the required control effect.

[0008] Furthermore, the specific establishment process of the continuous complex vector transfer function in Step 1 includes:

[0009] First, establish the voltage equation of the L-type interface circuit in the three-phase coordinate system, and after Clark coordinate transformation, obtain the following voltage equation in the two-phase stationary coordinate system:

[0010]

[0011] where respectively represent the complex vectors of the voltage on the motor drive unit side, the voltage on the motor simulator side, and the current of the interface circuit in the stationary coordinate system, satisfying R f is the actual value of the phase resistance of the interface circuit; L f is the actual value of the phase inductance of the interface circuit;

[0012] Perform a complex vector Park transformation on the above formula to obtain the following complex vector voltage equation in the synchronous rotating coordinate system:

[0013]

[0014] where represents the complex vector of the voltage on the permanent magnet synchronous motor simulator side; represents the complex vector of the voltage output by the motor drive unit side; represents the complex vector of the current of the interface circuit; ω e is the electrical angular velocity;

[0015] From the above complex vector voltage equation, obtain the following continuous complex vector transfer function:

[0016]

[0017] Furthermore, in Step 2, for the delay link and the zero-order hold, they are first described in the continuous domain as G d (s) = e -sT , GZOH(s) = (1 - e -sT ) / s, and accordingly, substitute the Laplace operator in the complex domain s → s + jω e , to obtain the continuous complex vector transfer functions of the delay link and the zero-order hold respectively as:

[0018]

[0019]

[0020] The continuous complex vector transfer function formed by the two is converted into a discrete complex vector transfer function:

[0021]

[0022] In the formula, T is the discrete step size.

[0023] Furthermore, when performing pole reconstruction in step three, first represent the discrete complex vector transfer function of the interface circuit in the following form:

[0024]

[0025] Select the coefficients k1 to k3 in the formula as k1 = α1 + α2, k2 = α1α2, k2 = b -1 , where α1 and α2 are undetermined real coefficients, that is, the reconstructed poles. The discrete complex vector transfer function after pole reconstruction can be obtained as:

[0026]

[0027] Furthermore, for the discrete complex vector transfer function after the above pole reconstruction in step four, design the following controller discrete complex vector transfer function:

[0028]

[0029] In the formula, k4 is an undetermined coefficient, and α1 is the same as above, which is the reconstructed pole;

[0030] Then the control closed-loop transfer function can be determined as:

[0031]

[0032] In actual control, the required control performance is specifically obtained by selecting different k4 and α2.

[0033] Furthermore, for the need of deadbeat control, select k4 = 1 and α2 = -1 to achieve it.

[0034] The current control strategy of the permanent magnet synchronous motor simulator based on pole reconstruction provided by the present invention uses complex vectors for modeling and analysis, simplifies the d-axis and q-axis voltage equations of a conventional interface circuit into a complex vector voltage equation model; considers the delay link of the system in the modeling, making the obtained discrete complex vector model more in line with the actual digital control requirements; the control strategy obtained through pole reconstruction has the advantages of flexible parameter selection, good robustness, no steady-state error, etc., and can achieve the required control effect through parameter configuration, especially can achieve deadbeat control without static error, overcomes the problem of steady-state error existing in the traditional deadbeat current predictive control under parameter perturbation, and at the same time expands the parameter mismatch stability range of the traditional deadbeat current predictive control. Brief Description of the Drawings

[0035] Figure 1 is the topological structure of the motor simulator system applicable to the present invention;

[0036] Figure 2 is the equivalent model of the three-phase L-type interface circuit of the permanent magnet synchronous motor simulator applicable to the present invention;

[0037] Figure 3 is the block diagram of pole reconstruction and control strategy in the method provided by the present invention;

[0038] Figure 4 is the relationship between the controller parameter α1 of the present invention and the minimum inductance mismatch multiple m of the motor simulator system;

[0039] Figure 5 is the amplitude-frequency characteristic curve of the cross-coupling term of the motor simulator system based on the controller of the present invention. Specific Embodiments

[0040] The technical solutions of the present invention will be described clearly and completely below with reference to the accompanying drawings. Obviously, the described embodiments are some but not all of the embodiments of the present invention. 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 protection scope of the present invention.

[0041] The current control strategy of the permanent magnet synchronous motor simulator based on pole reconstruction provided by the present invention specifically includes the following steps:

[0042] Step 1: Establish a continuous complex vector transfer function in the dq coordinate system for the interface circuit in the permanent magnet synchronous motor simulator as shown in Figure 1 ;

[0043] Step 2: Equivalent the three-phase inverter on the permanent magnet synchronous motor simulator side to a zero-order hold, and consider the delay link of the digital controller. Establish the corresponding continuous complex vector transfer functions respectively, and perform discretization processing in combination with the continuous complex vector transfer function established in Step 1 to obtain the discrete complex vector transfer function of the interface circuit;

[0044] Step 3: Reconstruct the poles of the discrete complex vector transfer function of the interface circuit, convert the complex poles into two real poles, and achieve complete decoupling between the dq axes;

[0045] Step 4: For the discrete complex vector transfer function of the interface circuit after pole reconstruction, design the discrete current control strategy and the corresponding controller parameters based on the required control effect.

[0046] In a preferred embodiment of the present invention, the specific establishment process of the continuous complex vector transfer function in Step 1 includes:

[0047] First, establish the voltage equation in the three-phase coordinate system for the L-type interface circuit as shown in Figure 2 , and obtain the following voltage equation in the two-phase stationary coordinate system after Clark coordinate transformation:

[0048]

[0049] In the formula, respectively represent the complex vectors of the voltage on the motor drive unit side, the voltage on the motor simulator side, and the current of the interface circuit in the stationary coordinate system, satisfying R f is the actual value of the phase resistance of the interface circuit; L f is the actual value of the phase inductance of the interface circuit; it should be noted that the actual inductance value and resistance value of the interface circuit will change during operation.

[0050] Perform complex vector Park transformation on the above formula to obtain the following complex vector voltage equation in the synchronous rotating coordinate system:

[0051]

[0052] In the formula, represents the complex vector of the voltage on the permanent magnet synchronous motor simulator side; represents the complex vector of the voltage output by the motor drive unit; represents the complex vector of the current of the interface circuit; ω e is the electrical angular velocity; it should be noted that for the application of variable synchronous rotating angular frequency, ω e is time-varying, but can be regarded as a constant within one control period.

[0053] The following continuous complex vector transfer function is obtained from the above complex vector voltage equation:

[0054]

[0055] In a preferred embodiment of the present invention, in step two, the delay link and the zero-order hold are first described in the continuous domain as G d (s) = e -sT , G ZOH (s) = (1 - e -sT ) / s, and accordingly, the Laplace operator is substituted in the complex domain as s → s + jω e . The continuous complex vector transfer functions of the delay link and the zero-order hold are respectively:

[0056]

[0057]

[0058] The continuous complex vector transfer function composed of the two is converted into a discrete complex vector transfer function:

[0059]

[0060] In the formula, T is the discrete step size.

[0061] In a preferred embodiment of the present invention, when performing pole reconstruction in step three, the discrete complex vector transfer function of the interface circuit is first expressed in the following form:

[0062]

[0063] Select the coefficients k1 to k3 in the formula as k1 = α1 + α2, k2 = α1α2, k2 = b -1 , where α1 and α2 are undetermined real coefficients, that is, the reconstructed poles. The discrete complex vector transfer function after pole reconstruction can be obtained as:

[0064]

[0065] In a preferred embodiment of the present invention, for the discrete complex vector transfer function after the above pole reconstruction in step four, the following controller discrete complex vector transfer function is designed:

[0066]

[0067] In the formula, k4 is an undetermined coefficient, and α1 is the reconstructed pole as above;

[0068] Then the control closed-loop transfer function can be determined as:

[0069]

[0070] In actual control, the required control performance is obtained by specifically selecting different k4 and α2. The above pole reconstruction and controller block diagram are as Figure 3 shown.

[0071] In a preferred embodiment of the present invention, for the need of deadbeat control, k4 = 1 and α2 = -1 are selected to achieve it. Of course, other values can also be selected for k4 and α2 to obtain the actual required control performance.

[0072] For the real coefficient α1, on the one hand, it determines the system stability range, and on the other hand, it affects the decoupling performance of the system under parameter perturbation conditions. The influence of α1 on the system stability is specifically illustrated by examples below. During the actual operation process, due to the influence of temperature and the saturation of the inductor coil core, etc., the actual circuit parameters change. Assume that there is a relationship L d = mL f , R d = nR f , correspondingly, At this time, the system closed-loop transfer function is:

[0073]

[0074] In the formula,

[0075] c1 = k1 + a d + 1

[0076] c2 = k1a d +(k2 + k4)k3b d + k1 + a d

[0077] c3 = k1a d +(k2 + k4α1)k3b d +(k2 + k4)ak3b d

[0078] c4 = (k2 + k4α1)ak3b d

[0079] According to the stability theorem, the necessary and sufficient condition for the system to be stable is that the poles are located inside the unit circle, that is, f(m) = max(|roots(z 4 - c1z 3 + c2z 2 - c3z + c4)|) < 1. Set the synchronous rotation frequency ω e = 2π50rad / s, and the discrete step size T = 1 / 10000, and the following can be obtained as Figure 4From the relationship between the minimum inductance mismatch multiple m and the coefficient α1 shown, it can be seen that as α1 increases, the allowable parameter mismatch range of the system becomes larger, and the robustness and stability are better. It should be noted that since the degree of resistance mismatch has no effect on the system stability, it is not included in the consideration range.

[0080] Regarding the influence of α1 on the system decoupling performance under parameter mismatch conditions, the closed-loop transfer function can be decomposed into the real part and the imaginary part, satisfying the following equations:

[0081]

[0082] Among them, the imaginary part reflects the cross-coupling characteristics of the system. Assuming that the system inductance undergoes parameter perturbation and the mismatch degree is m = 0.5, by selecting different α1, the frequency characteristic curves as shown in Figure 5 can be obtained. It can be seen from the figure that under parameter mismatch conditions, as the coefficient α1 increases, the high-frequency cross-coupling effect is significantly suppressed; however, its low-frequency coupling effect increases. Therefore, when selecting α1, the requirements of the system for parameter mismatch stability and decoupling performance should be weighed.

[0083] It should be understood that the magnitudes of the sequence numbers of the steps in the embodiments of the present invention do not mean the order of execution is prior or subsequent, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0084] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A current control method for a permanent magnet synchronous motor simulator based on pole reconstruction, characterized in that: Specifically, it includes the following steps: Step 1: Establish a continuous complex vector transfer function in the dq coordinate system for the interface circuit of the permanent magnet synchronous motor simulator; Step 2: Equivalent the three-phase inverter on the permanent magnet synchronous motor simulator side to a zero-order hold, and considering the delay link of the digital controller, establish the corresponding continuous complex vector transfer functions respectively, and perform discretization processing in combination with the continuous complex vector transfer function established in Step 1 to obtain the discrete complex vector transfer function of the interface circuit; Step 3: Reconstruct the poles of the discrete complex vector transfer function of the interface circuit, convert the complex poles into two real poles, and achieve complete decoupling between the dq axes; Step 4: For the discrete complex vector transfer function of the interface circuit after pole reconstruction, design a discrete current control strategy and the corresponding controller parameters based on the required control effect.

2. The current control method of the permanent magnet synchronous motor simulator according to claim 1, characterized in that: The specific establishment process of the continuous complex vector transfer function in Step 1 includes: First, establish the voltage equation in the three-phase coordinate system for the L-type interface circuit, and obtain the following voltage equation in the two-phase stationary coordinate system after Clark coordinate transformation: Wherein, respectively represent the complex vectors of the voltage on the motor drive unit side, the voltage on the motor simulator side, and the interface circuit current in the stationary coordinate system, and satisfy R f is the actual value of the phase resistance of the interface circuit; L f is the actual value of the phase inductance of the interface circuit; Perform the complex vector Park transformation on the above equation The following complex vector voltage equation in the synchronous rotating coordinate system is obtained: In the formula, represents the complex voltage vector on the side of the permanent magnet synchronous motor simulator; represents the complex voltage vector output on the side of the motor drive unit; represents the complex current vector of the interface circuit; ω e is the electrical angular velocity; From the above complex vector voltage equation, the following continuous complex vector transfer function is obtained:

3. The current control method of the permanent magnet synchronous motor simulator according to claim 2, characterized in that: In Step 2, for the delay link and the zero-order hold, they are first described in the continuous domain as and the Laplace operator is substituted accordingly in the complex domain The continuous complex vector transfer functions of the delay link and the zero-order hold are respectively: Based on these two continuous complex vector transfer functions, the discrete complex vector transfer function of the interface circuit is obtained: In the formula, T is the discrete step size.

4. The current control method of the permanent magnet synchronous motor simulator according to claim 3, wherein: When performing pole reconstruction in Step 3, first represent the discrete complex vector transfer function of the interface circuit in the following form: The coefficients k1 to k3 in the selection formula are k1 = α1 + α2, k2 = α1α2, and k3 = b respectively -1 , where α1 and α2 are undetermined real coefficients, that is, the reconstructed poles. The discrete complex vector transfer function after pole reconstruction can be obtained as follows:

5. The current control method of the permanent magnet synchronous motor simulator according to claim 4, wherein: In Step 4, for the discrete complex vector transfer function after the above pole reconstruction, design the following controller discrete complex vector transfer function: In the formula, k4 is a to-be-determined coefficient, and α1 is the reconstructed pole as above; Then the control closed-loop transfer function can be determined as: In actual control, the required control performance is specifically obtained by selecting different k4 and α2.

6. The current control method of the permanent magnet synchronous motor simulator according to claim 5, characterized in that: For the need of deadbeat control, select k4 = 1 and α2 = -1 to achieve.

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