Permanent magnet synchronous generator control system and control method

Abstract

The invention discloses a permanent magnet synchronous generator control system and control method, and relates to the field of motor voltage stabilization control. A control system is divided into a slow subsystem unit and a fast subsystem unit, and the slow subsystem unit takes direct-axis current id, quadrature-axis current iq and rotating speed omega of a motor as input; and obtaining an optimal direct-axis reference current i * d and an optimal quadrature-axis reference current i * q through a prediction model under optimal constraint, and observing the optimal direct-axis reference current i * d and the optimal quadrature-axis reference current i * q through self-coupling PI control by the sub-system unit to obtain control signals ud and uq. According to the method, the influence of reasons such as system parameter change and external interference on system control characteristics is solved, meanwhile, the robustness and the anti-interference capability of the system can be improved, and the dynamic characteristics of the system are improved.

Description

Technical Field

[0001] The present invention relates to the field of motor voltage stabilization control, and in particular to a permanent magnet synchronous generator control system and a control method. Background Art

[0002] With the development of permanent magnet materials, permanent magnet synchronous generators using permanent magnet excitation have gained wide attention due to their simple mechanical structure, high efficiency, and high power density. They are widely used in electric vehicles, aerospace, new energy power generation and other industries. The working speed of the generator depends on the speed of the prime mover. In some applications, the speed of the prime mover is very high (more than 50,000 rpm), and the speed variation range is very wide, which causes the frequency and amplitude of the output voltage of the permanent magnet generator to vary widely, causing the output voltage amplitude of the rectifier DC side to vary greatly, which has a very adverse effect on the stability of the output voltage of the power generation system, and the voltage level requirements for power switching devices and filter capacitors will be very high, which brings difficulties to the selection of devices. Therefore, it is necessary to perform current conversion control on the output voltage of the permanent magnet generator operating in a wide speed range to provide stable AC and DC power output. At the same time, the AC voltage at the generator end and the DC voltage at the rectifier end are adjusted, which belongs to dual-port voltage regulation control. Dual-port voltage regulation can maintain the output voltage stability of the power generation system under a wide speed range.

[0003] The output voltage of the permanent magnet generator can be adjusted by mechanically adjusting the excitation, hybrid excitation, or injecting direct-axis current into the armature winding to adjust the air gap magnetic field. Since the former two have problems such as complex structure, high cost and manufacturing difficulty, the latter is generally used to achieve voltage regulation. The method of adjusting the air gap magnetic field with a PWM rectifier can accurately achieve dual-port voltage regulation, which can not only ensure that the DC side has a higher output voltage accuracy and smaller voltage ripple, but also reduce the current harmonic content on the AC side of the motor, and significantly improve the high-speed operation area of ​​the generator system. In the PWM rectifier system of the permanent magnet synchronous generator, various controls on the permanent magnet synchronous generator can be attributed to the control of the motor current vector. When the motor parameters are determined, the output voltage of the permanent magnet synchronous generator is only related to the component i of the stator current vector in the d and q coordinates. d 、i q The vector control of permanent magnet synchronous generator is essentially through the i d 、i q The control of i can realize the control of the amplitude and phase of the stator current vector. Therefore, under the premise that the permanent magnet flux cannot be changed, in order to overcome the voltage instability problem caused by speed and load changes, it is necessary to control i d 、i q The output voltage is stabilized by the control. Summary of the invention

[0004] In view of the above-mentioned defects of the prior art, the present invention provides a permanent magnet synchronous generator control system, comprising:

[0005] Slow subsystem unit, with the direct axis current of the motor , quadrature axis current and speed As input, the optimal direct axis reference current is obtained through the prediction model under the optimal constraint and the optimal quadrature-axis reference current ;

[0006] The fast subsystem unit uses auto-coupling PI control to observe the optimal direct axis reference current and the optimal quadrature-axis reference current , get the control signal and .

[0007] Furthermore, the optimal direct-axis reference current and the optimal quadrature-axis reference current For the prediction model The optimal solution of the prediction model is:

[0008] .

[0009] Furthermore, the direct axis control signal of the autocoupled PI control The control law is:

[0010] ;

[0011] Among them, xd is the state variable, id is the direct axis current, ud is the control variable, yes The estimated value of , .

[0012] Furthermore, the quadrature axis control signal of the auto-coupling PI control The control law is:

[0013] .

[0014] A second aspect of the present invention provides a control method for a permanent magnet synchronous generator control system, which is implemented based on the permanent magnet synchronous generator control system and includes the following steps:

[0015] S1, the direct axis current of the motor , quadrature axis current and speed As input, the optimal direct axis reference current is obtained through the prediction model under the optimal constraint and the optimal quadrature-axis reference current ;

[0016] S2. Observe the optimal direct-axis reference current using auto-coupling PI control and the optimal quadrature-axis reference current , get the control signal and ;

[0017] S3, the control signal and After coordinate transformation, it is modulated by SVPWM and finally acts on the power converter.

[0018] Furthermore, the control signal The methods for obtaining include:

[0019] Construct the equation of state:

[0020] ;

[0021] in, is the state variable, ; is the expected variable, ;e d is the tracking error;

[0022] Get control signal for: ;

[0023] in, for An estimated value of is the feedback matrix, which satisfies ; is the feedforward gain, satisfying: .

[0024] Furthermore, the control signal The methods for obtaining include:

[0025] Construct the equation of state:

[0026] ;

[0027] in, is the state variable, ; is the expected variable, ;e q is the tracking error;

[0028] Get control signal for: ;

[0029] in, is the current Observed value of is the feedback matrix, satisfying ; is the feedforward gain, satisfying:

[0030] .

[0031] Compared with the prior art, the present invention has the following technical effects:

[0032] The present invention uses singular perturbation theory to analyze the dynamic process of the system, divides the control system into a fast subsystem and a slow subsystem, and jointly controls the motor. The voltage slow subsystem adopts the constrained optimal model prediction method, and observes the total disturbance by designing an extended state observer, taking into account multiple control performances such as variable constraints, anti-interference and set value tracking. Compared with the traditional model predictive control, it is more suitable for nonlinear systems, can achieve online optimization, and has greater flexibility. The current fast subsystem adopts the SC-PI control strategy. Compared with the traditional PI control, a convergence factor is introduced, and the convergence factor is used to centrally control the proportional integral link, which can solve the influence of system parameter changes and external interference on the system control characteristics, and at the same time improve the system change robustness and anti-interference ability, and improve the system dynamic characteristics.

[0033] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a block diagram of dual-port voltage stabilization control of a permanent magnet generator with a wide speed range based on singular perturbation theory according to an embodiment of the present invention;

[0035] Figure 2 This is a diagram showing the simulation result of the DC bus voltage obtained under the dual-port voltage stabilization control method of a wide speed range permanent magnet generator based on singular perturbation theory in a specific embodiment of the present invention;

[0036] Figure 3 It is a simulation diagram of the voltage waveform at the motor terminal under the dual-port voltage stabilization control method of a permanent magnet generator in a wide speed range based on singular perturbation theory in a specific embodiment of the present invention;

[0037] Figure 4 This is a diagram of the air gap flux simulation results under a dual-port voltage stabilization control method for a wide speed range permanent magnet generator based on singular perturbation theory in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0038] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0039] The voltage slow subsystem can obtain the optimal direct-axis reference current and quadrature-axis reference current by observing the changes in load-side parameters. The current fast subsystem can effectively track the changes in reference current by observing the motor-side parameters, thus achieving efficient regulation of the direct-axis and quadrature-axis currents on the motor side. d The motor magnetization or weakening magnetic regulation is realized as the speed of the prime mover changes. q The motor active power is adjusted as the load changes. The output voltage of the three-phase PWM rectifier is stabilized through coordinate transformation theory and SVPWM algorithm modulation.

[0040] like Figure 1 As shown, in a specific embodiment, a permanent magnet synchronous generator control system is provided, including a permanent magnet synchronous motor module, a power converter module and a sampling module, wherein the permanent magnet synchronous motor module adopts a three-phase permanent magnet synchronous motor; the power converter module adopts a three-phase fully controlled bridge power converter, and the three phases are independent of each other and do not affect each other; the sampling module is used to sample the current, voltage and rotor position angle at the current moment; the control part of the permanent magnet synchronous generator includes a speed outer loop and a current inner loop, wherein the speed outer loop is realized by a slow subsystem unit, and the current inner loop is realized by a fast subsystem, and the slow subsystem unit uses the direct axis current of the motor , quadrature axis current and speed As input, the optimal direct axis reference current is obtained through the prediction model under the optimal constraint and the optimal quadrature-axis reference current The fast subsystem unit uses auto-coupling PI control to observe the optimal direct axis reference current and the optimal quadrature-axis reference current , get the control signal and .

[0041] Based on the permanent magnet synchronous generator control system, in a specific embodiment, a permanent magnet synchronous generator control system control method is provided, comprising the following steps:

[0042] S1, speed outer loop control, based on the direct axis current of the motor , quadrature axis current and speed As input, the optimal direct axis reference current is obtained through the prediction model under the optimal constraint and the optimal quadrature-axis reference current .

[0043] The specific control process includes:

[0044] S11, estimate the total disturbance d through the extended state observer;

[0045] S12, detect the direct axis current of the motor , quadrature axis current and speed Value, and then get the electric power on the AC side ;

[0046] S13. Build prediction model:

[0047] ;

[0048] The constraints of the prediction model are:

[0049] .

[0050] Under the above constraints, the prediction model is solved and the solution obtained is the optimal direct axis reference current. and the optimal quadrature-axis reference current , the solution of the prediction model is contained in the following set:

[0051] ;

[0052] When the inequalities in the constraints are not binding, in this case, only active power can be provided so that the AC current is minimized.

[0053] S2, current inner loop control, using auto-coupling PI control to observe the optimal direct axis reference current and the optimal quadrature-axis reference current , get the control signal and .

[0054] S21, adopts auto-coupling PI control method to achieve current i d track .

[0055] According to the mathematical model of permanent magnet synchronous generator, we get:

[0056] ;

[0057] Then the state equation is constructed as:

[0058] ;

[0059] in, is the state variable, ; is the expected variable, ;e d is the tracking error;

[0060] Get control signal for: ;

[0061] in, for An estimated value of is the feedback matrix, which satisfies ; is the feedforward gain, satisfying: .

[0062] S22, adopts auto-coupling PI control method to achieve current i q track . .

[0063] According to the mathematical model of permanent magnet synchronous generator, we get:

[0064] ;

[0065] Then the state equation is constructed as:

[0066] ;

[0067] in, is the state variable, ; is the expected variable, ;e q is the tracking error;

[0068] Get control signal for: ;

[0069] in, is the current Observed value of is the feedback matrix, satisfying ; is the feedforward gain, satisfying:

[0070] .

[0071] S3, the control signal and After coordinate transformation, it is modulated by SVPWM and finally acts on the power converter.

[0072] In order to verify the effectiveness of the control method of the wide speed range permanent magnet synchronous generator control system based on singular perturbation theory, a simulation verification was carried out. The motor parameters are shown in Table 1.

[0073] Table 1 Motor simulation parameter settings

[0074]

[0075] This paper simulates a built-in three-phase permanent magnet synchronous generator with a rated speed of 36000rpm, five pole pairs, a rated power of 65kW, and a rated current of 120A.

[0076] Figure 2 The figure shows the simulation result of the DC bus voltage. It can be seen from the figure that at 1.1s, the speed is set to decrease from 41400rpm. Under the singular perturbation control strategy, the DC voltage also decreases slightly. The speed reaches 23400rpm at 1.4s, and the discharge process ends. The DC bus voltage drops to a minimum value of 27.357V at around 1.412s. But then it quickly recovers to 28.5V. Under the id=0 control strategy, at the simulation time of 1.1s, the DC bus voltage also decreases with the speed, drops to a minimum value of 26.689V at around 1.225s, and then slowly rises, and rises to a maximum value of 31.534V at around 1.334s, and then decreases again, gradually recovering to 28.5V. It can be clearly seen that when the speed range fluctuates greatly (23400rpm-41400rpm), the bus fluctuation under the id=0 control strategy is more obvious than that under the dual-port voltage-stabilized flux control, and the maximum and minimum values ​​differ by 4.845V; while the maximum and minimum values ​​of the bus voltage under the singular perturbation voltage-stabilized control differ by 2.527V during the large speed fluctuation. It can be seen that when the speed fluctuation range is large, the singular perturbation control strategy has better voltage stabilization performance than the traditional id=0 control strategy.

[0077] Figure 3 For this control method, the voltage waveform at the motor end has almost no change in voltage amplitude at 41400rpm and 23400rpm, and the voltage at the end remains constant in the operating speed range, which is consistent with the theoretical analysis. The voltage stabilization effect is better, and the adverse effects of voltage fluctuations over a large range with speed on voltage stabilization control and device selection are reduced.

[0078] Figure 4The figure is the air gap flux simulation result. When the motor runs in the high-speed stage, the machine-end voltage is large. At this time, the control strategy feeds a negative d-axis current to the motor to weaken the permanent magnet magnetic field. The air gap flux is small, smaller than the permanent magnet flux. At this time, the weak magnetic operation keeps the machine-end voltage at the set value; when the speed decreases and the motor runs in the low-speed stage, the machine-end voltage is small. The control strategy feeds a positive d-axis current to the motor to enhance the permanent magnet magnetic field, increase the air gap flux, and maintain voltage stability.

[0079] In summary, by analyzing the curves of voltage and current when the speed changes in a wide range, it can be obtained that the control method of the wide-speed range permanent magnet synchronous generator control system based on singular perturbation theory has a better voltage stabilization effect for voltage stabilization control under fluctuations in the rated speed range of 0.65 to 1.15 times.

[0080] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A permanent magnet synchronous generator control system, characterized in that: include: Slow subsystem unit, with the direct axis current of the motor , quadrature axis current and speed As input, the optimal direct axis reference current is obtained through the prediction model under the optimal constraint and the optimal quadrature-axis reference current ; The fast subsystem unit uses auto-coupling PI control to observe the optimal direct axis reference current and the optimal quadrature-axis reference current , get the control signal and .

2. A permanent magnet synchronous power generation system control system according to claim 1, characterized in that: The optimal direct-axis reference current and the optimal quadrature-axis reference current For the prediction model The optimal solution of the prediction model is: 。 3. A permanent magnet synchronous generator control system according to claim 1, characterized in that: Direct axis control signal of autocoupled PI control The control law is: ； Among them, xd is the state variable, id is the direct axis current, ud is the control variable, yes The estimated value of , .

4. A permanent magnet synchronous generator control system according to claim 1, characterized in that: Quadrature axis control signal of auto-coupling PI control The control law is: 。 5. A control method for a permanent magnet synchronous generator control system, characterized in that: The permanent magnet synchronous generator control system according to any one of claims 1 to 4 is implemented, comprising the following steps: S1, the direct axis current of the motor , quadrature axis current and speed As input, the optimal direct axis reference current is obtained through the prediction model under the optimal constraint and the optimal quadrature-axis reference current ; S2. Observe the optimal direct-axis reference current using auto-coupling PI control and the optimal quadrature-axis reference current , get the control signal and ; S3, the control signal and After coordinate transformation, it is modulated by SVPWM and finally acts on the power converter.

6. A permanent magnet synchronous generator system control method according to claim 5, characterized in that: The control signal The methods for obtaining include: Construct the equation of state: ； in, is the state variable, ; is the expected variable, ;e d is the tracking error; Get control signal for: ; in, for An estimated value of is the feedback matrix, which satisfies ; is the feedforward gain, satisfying: .

7. A control method for a permanent magnet synchronous generator control system according to claim 5, characterized in that: The control signal The methods for obtaining include: Construct the equation of state: ； in, is the state variable, ; is the expected variable, ;e q is the tracking error; Get control signal for: ; in, is the current Observed value of is the feedback matrix, satisfying ; is the feedforward gain, satisfying: 。

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