A voltage stabilization control method for a variable speed permanent magnet synchronous generator

Abstract

The present invention discloses a variable-speed permanent magnet synchronous generator voltage stabilization control method for flywheel energy storage, comprising the following steps: S1, collecting the DC bus voltage, the three-phase stator current of the generator, and the generator rotor speed, and performing coordinate transformation on the three-phase current to obtain dq current feedback; S2, using the difference between the bus voltage reference and the feedback value to obtain a q-axis current command via a voltage outer loop controller; S3, using the q-axis current command to obtain a d-axis current command via a constant voltage control calculation module, and using the difference between the dq current command value and the feedback value to obtain a voltage command via a current loop controller; S4, after coordinate transformation, the voltage command passes through an SVPWM module to generate a pulse signal for rectifier control. This method overcomes the problem of rapid motor speed drop during discharge in a flywheel energy storage system, which causes unstable motor terminal voltage and directly affects bus voltage stability. The method can maintain terminal voltage stability even in a wide range of speed fluctuations, and has the advantages of simple calculation and strong robustness.

Description

Technical Field

[0001] The present invention relates to the technical field of permanent magnet synchronous generator control, and in particular to a variable speed permanent magnet synchronous generator voltage stabilization control method applied to flywheel energy storage. Background Art

[0002] With the rapid development of permanent magnet materials and power electronics technology, the performance of permanent magnet synchronous generators (PMSGs) has significantly improved. Compared with traditional electrically excited synchronous generators and doubly fed induction generators, permanent magnet synchronous generators (PMSGs) offer advantages such as simple structure, high power density, and high operating efficiency. However, there is also the problem of unadjustable permanent magnet excitation. When PMSGs are used in flywheel energy storage systems with a wide speed range, the terminal voltage of the variable-speed permanent magnet synchronous generator and the DC side voltage of the rectifier fluctuate significantly, affecting voltage regulation.

[0003] Traditional control strategies are mostly based on permanent magnet synchronous motor control strategies. However, these traditional rectifier schemes only stabilize the DC terminal voltage and do not regulate the generator terminal voltage, which is considered single-port voltage regulation. Simultaneously controlling the generator terminal voltage and the rectifier DC terminal voltage is considered dual-port voltage regulation. This means that while maintaining the generator terminal voltage stable, the rectifier also regulates the DC bus voltage. Generator terminal voltage regulation strategies can employ mechanical excitation adjustment or feeding magnetizing or field weakening currents into the armature windings, but the former is more complex.

[0004] Through the above analysis, the present invention proposes a variable speed permanent magnet synchronous generator voltage stabilization discharge control strategy to perform voltage stabilization control on the generator terminal voltage. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention proposes a method for voltage stabilization control of a variable-speed permanent magnet synchronous generator, which controls the stator flux linkage under speed fluctuations, keeps the motor terminal voltage stable, realizes dual-port voltage stabilization, and ensures the stability of the flywheel energy storage system during discharge operation. The method has the advantages of fast dynamic response and strong robustness.

[0006] In order to solve the above technical problems, the technical solution of the present invention is:

[0007] A method for controlling voltage stabilization of a variable speed permanent magnet synchronous generator comprises the following steps:

[0008] S1, collects DC bus voltage, generator three-phase stator current and generator rotor speed, and performs coordinate transformation on the three-phase current to obtain dq current feedback;

[0009] S2, the difference between the bus voltage setting and the feedback value is obtained through the voltage outer loop controller to obtain the q-axis current command;

[0010] S3, the q-axis current command is obtained by the constant voltage control calculation module to obtain the d-axis current command, and the difference between the dq current command value and the feedback value is obtained by the current loop controller to obtain the voltage command;

[0011] S4. After the voltage command coordinates are transformed, it passes through the SVPWM module to generate a pulse signal to control the rectifier.

[0012] Preferably, the step S1 includes.

[0013] S1-1, use the speed encoder to obtain the rotor speed ω and position signal θ;

[0014] S1-2, use the voltage / current sensor to collect the DC bus voltage signal U dc , and the three-phase current signal I a , I b , I c ;

[0015] S1-3, transform the three-phase current on the left side through the three-phase / two-phase coordinate transformation module to obtain the current component I in the two-phase static αβ coordinate system α , I β ;

[0016] S1-4, then through the two-phase stationary / rotating coordinate transformation, the current component I in the d and q axis rotating coordinate system is obtained d , I q .

[0017] Preferably, the step S1 further includes S1-5: multiplying the rotor speed ω by the number of motor pole pairs p to obtain the electrical angular velocity ω. e .

[0018] Preferably, in step S2, the feedback value is the DC bus voltage signal U collected by the voltage sensor in step S1-2. dc .

[0019] Preferably, step S3 includes the following sub-steps:

[0020] S3-1, the q-axis current instruction I q * , rotor electrical angular velocity ω e , DC bus voltage given value U dc * , the d-axis current command I is calculated by the flux calculation module d * ;

[0021] S3-2, q-axis current command I q * The current component I obtained in step S1-4 qThe difference is obtained by the q-axis PI controller to obtain the q-axis voltage command V q * ;

[0022] S3-3, d-axis current command I d * The current component I obtained in step S1-4 d The difference is obtained by the d-axis PI controller to obtain the d-axis voltage command V d * .

[0023] Preferably, in step S3-1, the calculation method of the magnetic flux calculation module is:

[0024] S3-1-1, calculate the stator flux ψ of the corresponding speed by the flux calculation module using the speed ω collected in step S1-1 c , where the calculation formula of the magnetic flux calculation module is in

[0025] S3-1-2, and the size of the stator flux can also be expressed by Eq. Calculate and combine the two equations and bring them into the q-axis current command I in step S2 q * , calculate the current command I of the d-axis d * ;

[0026] S3-1-3, the obtained d and q axis instructions I d * , I q * , and the current components I of the d and q axes in step S1-4 d , I q , respectively, and the difference is passed through the PI controller of the d and q axes to obtain the voltage command V in the rotating coordinate system. d * 、V q * .

[0027] As an example, in step S4, the pulse control signal is generated by: according to the d and q axis voltage instructions V d * 、V q * After coordinate transformation, we get the αβ axis reference voltage V α 、V β , the rectifier is controlled by generating a PWM signal through the SVPWM module.

[0028] The present invention has the following characteristics and beneficial effects:

[0029] The control method of the present invention is a dual-port voltage stabilization control strategy that controls the stator flux size to vary with speed, thereby maintaining a stable motor terminal voltage. Compared to the id = 0 control method used by traditional permanent magnet generators, the present invention improves the set value of the d-axis current. Based on the set value of the DC bus voltage and the feedback value of the rotor's electrical angular velocity, the stator flux size is calculated, thereby calculating the set value of the d-axis current, maintaining the stability of the motor terminal voltage, and achieving dual-port voltage stabilization of the permanent magnet synchronous generator. This overcomes the problem of a flywheel energy storage system in which the motor speed drops rapidly during discharge, resulting in unstable motor terminal voltage and directly affecting the stability of the bus voltage. The system can maintain terminal voltage stability even under a wide range of speed fluctuations, and has the advantages of simple calculation and strong robustness. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 Flowchart of a method according to an embodiment of the present invention.

[0032] Figure 2 Schematic diagram of a constant voltage control structure according to an embodiment of the present invention.

[0033] Figure 3 This is the bus voltage waveform under traditional id=0 control and speed fluctuation in an embodiment of the invention.

[0034] Figure 4 This is a bus voltage waveform diagram under constant voltage control under speed fluctuation in an embodiment of the invention.

[0035] Figure 5 1 is a waveform diagram of the generator terminal voltage during constant voltage control in an embodiment of the invention. DETAILED DESCRIPTION

[0036] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0037] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0038] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0039] The present invention provides a method for controlling voltage stabilization of a variable speed permanent magnet synchronous generator. Figure 1 and Figure 2 As shown, the following steps are included:

[0040] S1. Collect voltage, current and speed signals and perform coordinate transformation

[0041] Specifically, the current sensor is used to collect the three-phase current I of the motor a , I b , I c , use the voltage sensor to collect the DC bus voltage signal U dc The speed encoder is used to collect the motor rotor speed ω and rotor position signal θ.

[0042] The collected three-phase stator current signal I a , I b , I c , after the coordinate transformation module 8 performs coordinate transformation, the current component I in the two-phase rotation d and q coordinate systems is obtained. d , I q A constant amplitude transform is used.

[0043] The coordinate transformation module formula is:

[0044]

[0045]

[0046] S2, calculate the q-axis current given value by bus voltage control

[0047] According to the bus voltage given value U dc * , and the DC bus voltage signal U collected in step S1 dc The difference is obtained by the voltage outer loop PI controller to obtain the q-axis current command I q * .

[0048] S3, calculate the d-axis current command by controlling the stator flux

[0049] According to the q-axis current command I calculated in step S2 q * , and the speed ω collected in step S1, and the bus voltage given value U dc * , the d-axis current command I is calculated by calculation module 2 d * .

[0050] The purpose is to control the stator flux size to change with the speed, so as to maintain the stability of the motor terminal voltage. The specific steps are as follows:

[0051] a. Calculate the stator flux size in It can be seen that the magnitude of the stator flux changes with the speed. e =ω·p, where p is the number of motor pole pairs.

[0052] b. At the same time, the stator flux can be expressed by the formula: Calculated, where:

[0053]

[0054] Among them L d , L q are the motor d-axis and q-axis inductances, ψ f is the permanent magnet flux.

[0055] c. Combine the two equations and substitute them into I q * , then the d-axis current command I can be solved d * ,

[0056]

[0057] d. The calculated d and q axis current instructions I d * , I q * After limiting, the difference between the d-axis and q-axis current feedback values ​​obtained after coordinate transformation in step S1 passes through the d-axis PI controller 3 and the q-axis PI controller 4 respectively to obtain the d-axis and q-axis voltage reference values ​​V d * 、V q *

[0058] S4. Generation of rectifier control signal

[0059] V calculated in step S3 d * 、V q * , and then the voltage reference value in the two-phase stationary coordinate system is obtained through coordinate transformation, which is input into the SVPWM module 5 to generate a PWM control signal to control the rectifier.

[0060] from Figure 3-Figure 4 As can be seen, the above technical solution controls the stator flux magnitude to vary with speed, thereby maintaining a stable motor terminal voltage through a dual-port voltage regulation control strategy. Compared to the id = 0 control method used by traditional permanent magnet generators, the present invention improves the set value of the d-axis current (d-axis current command). Based on the set value of the DC bus voltage and the feedback value of the rotor's electrical angular velocity, the stator flux magnitude, and thus the set value of the d-axis current, is calculated. This maintains the stability of the motor terminal voltage and achieves dual-port voltage regulation for the permanent magnet synchronous generator.

[0061] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. It will be apparent to those skilled in the art that various changes, modifications, substitutions, and variations of these embodiments, including components, without departing from the principles and spirit of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for controlling voltage stabilization of a variable speed permanent magnet synchronous generator, characterized in that: The steps include: S1, collects DC bus voltage, generator three-phase stator current and generator rotor speed, and performs coordinate transformation on the three-phase current to obtain dq current feedback; The step S1 comprises: S1-1, use the speed encoder to obtain the rotor speed ω and position signal θ; S1-2, use the voltage / current sensor to collect the DC bus voltage signal U dc , and the three-phase current signal I a , I b , I c ; S1-3, transform the three-phase current on the left side through the three-phase / two-phase coordinate transformation module to obtain the current component I in the two-phase static αβ coordinate system α , I β ; S1-4, then through the two-phase stationary / rotating coordinate transformation, the current component I in the d and q axis rotating coordinate system is obtained d , I q ; S2, the difference between the bus voltage setting and the feedback value is obtained through the voltage outer loop controller to obtain the q-axis current command; S3, the q-axis current command is obtained by the constant voltage control calculation module to obtain the d-axis current command, and the difference between the dq current command value and the feedback value is obtained by the current loop controller to obtain the voltage command; S3-1, the q-axis current instruction I q * , rotor electrical angular velocity ω e , DC bus voltage given value U dc * , the d-axis current command I is calculated by the flux calculation module d * ; The calculation method of the magnetic flux calculation module is: S3-1-1, calculate the stator flux ψ of the corresponding speed by the flux calculation module using the speed ω collected in step S1-1 c , where the calculation formula of the magnetic flux calculation module is in S3-1-2, and the size of the stator flux can also be expressed by Eq. Calculate and combine the two equations and bring them into the q-axis current command I in step S2 q * , calculate the current command I of the d-axis d * ; S3-1-3, the obtained d and q axis instructions I d * , I q * , and the current components I of the d and q axes in step S1-4 d , I q , respectively, and the difference is passed through the PI controller of the d and q axes to obtain the voltage command V in the rotating coordinate system. d * 、V q * ; S3-2, q-axis current command I q * The current component I obtained in step S1-4 q The difference is obtained by the q-axis PI controller to obtain the q-axis voltage command V q * ; S3-3, d-axis current command I d * The current component I obtained in step S1-4 d The difference is obtained by the d-axis PI controller to obtain the d-axis voltage command V d * ; S4. After the voltage command coordinates are transformed, it passes through the SVPWM module to generate a pulse signal to control the rectifier.

2. The voltage stabilization control method for a variable speed permanent magnet synchronous generator according to claim 1, characterized in that: The step S1 also includes S1-5: multiplying the rotor speed ω by the number of motor pole pairs p to obtain the electrical angular velocity ω e .

3. The voltage stabilization control method for a variable speed permanent magnet synchronous generator according to claim 1, characterized in that: In step S2, the feedback value is the DC bus voltage signal U collected by the voltage sensor in step S1-2. dc .

4. The method for controlling voltage stabilization of a variable speed permanent magnet synchronous generator according to claim 2, characterized in that: In step S4, the pulse control signal is generated by: according to the d and q axis voltage instructions V d * 、V q * After coordinate transformation, we get the αβ axis reference voltage V α 、V β , the rectifier is controlled by generating a PWM signal through the SVPWM module.

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