Power grid simulator control method based on sliding mode weighted fusion

Abstract

The invention discloses a power grid simulator control method based on sliding mode weighted fusion, and belongs to the field of power grid simulator control, and the method comprises the steps: 1, the whole power grid simulator employs a three-phase four-wire system, and each phase is independently controlled; 2, voltage and current double-closed-loop control is adopted for each phase, a voltage loop is subjected to quasi-proportional resonance control so as to realize zero static error adjustment, and a current loop is subjected to proportional-integral control so as to improve the dynamic adjustment capability; and 3, sliding mode control is embedded in a voltage loop, and weighted fusion is carried out on the output of the controller to enhance the robustness of the system. According to the invention, through a weighted fusion control mode of sliding mode control and quasi-proportional resonance control, the dynamic adjustment process of the power grid simulator is improved and the robust performance of the system is enhanced on the premise of ensuring the steady-state precision of normal operation of the power grid simulator.

Description

TECHNICAL FIELD

[0001] The application is suitable for the field of grid simulator control and relates to a grid simulator control method based on sliding mode weighted fusion. BACKGROUND

[0002] With the promotion of the global "double carbon" goal and the large-scale grid connection of new energy power generation, the form of the power system is undergoing profound changes: the traditional synchronous generator dominated "large unit, high inertia" grid is gradually transitioning to a new type of power system with "low inertia and high penetration rate of power electronic devices". Under this background, as a core tool for supporting new energy equipment research and development, grid planning verification and operation control strategy optimization, the technical requirements of the grid simulator have been upgraded from the early "steady-state characteristic reproduction" to "high-fidelity simulation of full dynamic scenarios", and higher requirements are faced in terms of control method, especially in terms of control accuracy and disturbance rejection capability.

[0003] The commonly used voltage control methods of the grid simulator include proportional integral (PI), droop, VSG, proportional resonance (PR), etc. Different control strategies have their own advantages and disadvantages, but it is difficult to simultaneously consider voltage control accuracy and dynamic requirements. PI control has poor adaptability to nonlinear scenarios and weak disturbance rejection capability; the disturbance rejection capability of droop and VSG is improved, but three-phase independent control cannot be achieved; PR can be controlled in three phases, but the dynamic regulation capability is slow and the disturbance rejection capability is poor. SUMMARY

[0004] In view of the above deficiencies of the grid simulator voltage control in terms of steady-state accuracy and disturbance rejection capability, the application provides a grid simulator control method based on sliding mode weighted fusion, so as to improve the accuracy of the grid simulator and the disturbance rejection performance of the system while ensuring the steady-state accuracy, thereby ensuring the reliability of the grid simulation.

[0005] To achieve the above application purposes, the following technical solutions are adopted: The grid simulator control method based on sliding mode weighted fusion is applied to a grid simulator adopting three-phase four-wire system, and voltage-current double-loop control is adopted for phase A, phase B and phase C, which are independent of each other. The grid simulator control method comprises the following steps: Step S1: Collecting the phase output voltage and phase inductance current of the inverter side of the grid simulator k Step S2: Subtracting the phase voltage reference signal from the phase output voltage to obtain the phase error signal k k k k e k ; wherein, k represents any phase, and k = A, B, C ​​​​Step S2: The quasi-proportional resonant controller uses equation (2) to... k Phase error signal e k of Laplace expression After processing, the quasi-proportional resonant controller is obtained. k Phase output : (2) In equation (2), s express Laplace Transformation, for of Laplace expression, , These are the proportional gain coefficient and resonant gain coefficient of the quasi-proportional resonant controller, respectively. The resonant frequency of the quasi-proportional resonant controller. The cutoff frequency of the quasi-proportional resonant controller; Step S3: Use equation (3) to obtain the sliding mode controller. k Smooth mold surface s k : (3) In equation (3), c >0 indicates the parameter of the sliding surface. for e k The first derivative; Step S4: Design a sliding mode controller using equation (4): (4) In equation (4), For sliding mode controllers k Phase output, K This is the disturbance gain coefficient. It is a saturation function. The thickness of the boundary layer, For power grid simulator k Phase output voltage, For power grid simulator k Phase inductor current, for The second derivative, V dc This is the DC bus voltage. L For the filter inductor on the inverter side of the power grid simulator, C These are the filter capacitors on the inverter side of the power grid simulator. R For the load on the inverter side of the power grid simulator; Step S5: Obtain the current loop using equation (13). k Phase reference signal : (13) In equation (13), Indicates the weighting coefficient; Step S6: From With the power grid simulator k Phase sampling inductor current By doing the difference, we get k The phase difference value is then input into the proportional-integral controller for processing, and the output is... k Phase-modulated waves are superimposed on the feedforward wave. k In the phase voltage reference signal, it is compared with a triangular wave to generate k The phase SPWM signal drives the switching transistors on the inverter side of the power grid simulator to turn on and off.

[0006] The characteristic of the sliding mode weighted fusion power grid simulator control method described in this invention is that the sliding mode controller in step S4 is designed according to the following steps: Step S4.1: When s k When = 0, calculate using equation (6). s k first derivative : (6) In equation (6), for k Phase error signal e k The second derivative, for The first derivative; Step S4.2: Design the sliding mode controller according to equation (9). k Equivalent control output ; (9) Step S4.3: Design the sliding mode controller according to equation (11). k Phase switching control output : (11) Step S4.4: Obtain the sliding mode controller according to equation (12). k Phase output : (12) The electronic device comprises a memory and a processor, and the memory is used for storing a program supporting the processor to execute the power grid simulator control method, and the processor is configured to execute the program stored in the memory.

[0007] The computer readable storage medium stores a computer program, and when the computer program is run by a processor, the steps of the power grid simulator control method are executed.

[0008] Compared with the prior art, the present application has the following advantages: 1、The present application adopts a weighted fusion algorithm of quasi-proportional-resonant control and sliding mode control output, which can quickly adapt to different degrees of environmental changes according to the system state adjustment of the weighted fusion output, so that the present application can guarantee the steady-state accuracy and also consider the dynamic adjustment performance.

[0009] 2、The present application uses a weighted fusion algorithm of quasi-proportional-resonant control and sliding mode control to control the output voltage characteristics of the power grid simulator, which solves the problem of output voltage waveform distortion and excessive overshoot of the power grid simulator when it is disturbed, so that it can quickly adjust and reduce the output voltage overshoot and harmonic distortion rate, improve the system robustness, and guarantee the reliability of the power grid simulation. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 It is a control block diagram of the power grid simulator based on sliding mode weighted fusion. Figure 2 It is a flowchart used in the present application based on sliding mode weighted fusion. Figure 3a It is an output voltage waveform diagram when the sliding mode weighted fusion is adopted under normal working conditions. Figure 3b It is an output voltage Fourier analysis diagram when the sliding mode weighted fusion is adopted under normal working conditions. Figure 4a It is an output voltage waveform diagram when the sliding mode weighted fusion is not adopted under zero voltage ride-through working conditions. Figure 4b It is an output voltage waveform diagram when the sliding mode weighted fusion is adopted under zero voltage ride-through working conditions. DETAILED DESCRIPTION

[0011] Since the steady-state accuracy directly affects the equipment evaluation and power quality, such as voltage / frequency deviation exceeding the limit will lead to control failure; the disturbance rejection capability is related to the stability of the system in response to new energy fluctuations, low voltage ride through and other disturbances. Therefore, in the embodiment, a power grid simulator control method based on sliding mode weighted fusion is proposed, which is based on a three-phase four-wire topology of a power grid simulator that can be independently controlled in three phases. By detecting the instantaneous value of each phase output voltage and inductor current, the weighted fusion output of the proportional resonant control and sliding mode control is used as the voltage loop, and the proportional integral is used as the current loop output modulation wave. According to the weighted fusion output of the voltage loop of the two control modes, the disturbance rejection capability and robustness of the system are enhanced. Specifically, as shown in Figure 1 , the method comprises: Step S1: collecting the phase output voltage and phase inductor current of the inverter side of the power grid simulator, and obtaining the phase error signal after the phase voltage reference signal and the phase output voltage are subtracted. k k k k k e k ; wherein, k represents any phase, and k = A, B, C; (1) In formula (1), is the phase voltage reference signal of the inverter side of the power grid simulator, k is the phase output voltage of the inverter side of the power grid simulator. k

[0012] Step S2: the proportional resonant controller processes the expression of the phase error signal k e k to obtain the phase output of the proportional resonant controller: Laplace k (2) In formula (2), represents a transformation, Laplace is the expression of , , Laplace , , are the proportional gain coefficient and the resonant gain coefficient of the proportional resonant controller, is the resonant frequency of the proportional resonant controller, ​​​​​​​​​​​​The cutoff frequency of the PR controller represents the response speed of the PR controller to track the reference signal.

[0013] Step S3: Obtain the sliding mode controller by using formula (3) k Phase sliding surface s k : (3) In formula (3), c >0 represents the parameter of the sliding surface, which determines the convergence speed, c The larger the convergence speed is faster; For e k The first derivative of , The first derivative of s k The first derivative of , which is a negative real number s k Exponential convergence to 0, then the system is asymptotically stable.

[0014] Step S4: Design the sliding mode controller by using formula (4): (4) In formula (4), is the k phase output of the sliding mode controller, K is the disturbance gain coefficient, is the saturation function, is the thickness of the boundary layer, is the k phase output voltage of the grid simulator, is the k phase inductor current of the grid simulator, is the second derivative of , V dc is the DC bus voltage, L is the filter inductance on the inverter side of the grid simulator, C is the filter capacitance on the inverter side of the grid simulator, R is the load on the inverter side of the grid simulator.

[0015] The sliding mode controller in step S4 is implemented as follows: Step S4.1: Based on the circuit parameters on the inverter side of the grid simulator, the output voltage dynamic equation is as shown in formula (5): (5) In formula (5), is the the first derivative of is the first derivative of M denotes the modulation degree of the inverter side of the grid simulator.

[0016] When s k = 0, in combination with equation (5), the second derivative of s k the first derivative of : (6) In equation (6), is k the phase error signal e k the second derivative of

[0017] Step S4.2: Substitute equation (6) into the state equation (7): (7) Substitute into and rearrange to obtain the expression: (8) Finally, when k , the equivalent control output of the sliding mode controller is designed according to equation (9); : (9) Step S4.3: To ensure that the system state can reach the sliding mode surface in a finite time, the reachability condition needs to be satisfied: (10) In equation (10) , denotes the minimum convergence rate of the system state approaching the sliding mode surface.

[0018] The tangent switching control output of the sliding mode controller is designed according to equation (11): k : (11) Step S4.4: The output of the sliding mode controller is obtained according to equation (12): : k (12) Step S5: The phase reference signal of the current loop is obtained using equation (13): : k (13) Step S6: The phase reference signal of the voltage loop is obtained using equation (14): : ​(13) In equation (13), This represents the weighting coefficient.

[0019] Step S6: From With the power grid simulator k Phase sampling inductor current By doing the difference, we get k The phase difference value is then input into the proportional-integral controller for processing, and the output is... k Phase-modulated waves are superimposed on the feedforward wave. k In the phase voltage reference signal, it is compared with a triangular wave to generate k The phase SPWM signal drives the switching transistors on the inverter side of the power grid simulator to control the output voltage characteristics of the power grid simulator, thereby improving the steady-state accuracy and transient robustness of the power grid simulator.

[0020] In this embodiment, an electronic device includes a memory and a processor. The memory stores a program that supports the processor in executing the above-described method, and the processor is configured to execute the program stored in the memory.

[0021] In this embodiment, a computer-readable storage medium stores a computer program, which is executed by a processor to perform the steps of the above method.

[0022] The flowchart of the implementation of this invention is as follows: Figure 2 As shown, based on the analysis in steps S1 to S6, the effectiveness of the sliding mode weighted fusion proposed in this invention is further verified by using the normal operating conditions and low voltage ride-through operating conditions of the power grid simulator.

[0023] For a three-phase four-wire power grid simulator, the DC side voltage parameters are: U dc =700V, modulation wave frequency f o =50Hz, carrier frequency f c =10kHz, rated power is 50kW, rated output voltage RMS value per phase is 220V, and the output voltage under normal operating conditions when the voltage loop adopts sliding mode weighted fusion is as follows: Figure 3a and Figure 3b As shown. Among them, Figure 3a This is the output voltage waveform when using sliding mode weighted fusion under normal operating conditions. Figure 3b This is a Fourier analysis diagram of the output voltage under normal operating conditions when using sliding mode weighted fusion.

[0024] In addition, to verify the dynamics and robustness of the control system under transient conditions, a zero-voltage ride-through test was conducted. The output voltage results of the power grid simulator obtained under zero-voltage ride-through are as follows: Figure 4aand Figure 4b As shown in the figure. Among them, Figure 4a The output voltage waveform result when the voltage ring does not adopt the sliding mode weighted fusion, only adopts the PR controller, Figure 4b The output voltage waveform result when the voltage ring adopts the sliding mode weighted fusion. It can be seen that the output voltage has a large degree of overshoot under the zero voltage ride-through working condition when the sliding mode weighted fusion is not adopted, and the adjustment time is slow, while the overshoot of the output voltage under the zero voltage ride-through working condition is greatly improved when the sliding mode weighted fusion is adopted, and the adjustment time is reduced, and the dynamic adjustment ability and robustness of the system are significantly enhanced.

[0025] In summary, the present application proposes a power grid simulator control method based on sliding mode weighted fusion, which has obvious improvement compared with the original control strategy. The present application can improve the dynamic adjustment ability and robustness of the power grid simulator under abnormal working conditions under the premise of ensuring the steady-state accuracy, thereby providing method guidance for improving the anti-disturbance ability and dynamic performance of the power grid simulation system. The above is only an embodiment of the present application and does not limit the present application. Any modification, synonymous replacement and improvement within the accuracy and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A power grid simulator control method based on sliding mode weighted fusion, applied to a power grid simulator adopting three-phase four-wire system, and the A-phase, B-phase and C-phase all adopt voltage-current double-loop control, each phase is independent of each other, characterized in that, The power grid simulator control method comprises the following steps: Step S1: Collecting the inverter side of the grid simulator k phase output voltage and k phase inductor current, will k phase voltage reference signal and k phase output voltage difference, get k phase error signal e k ; wherein k represents any one phase, and k = A, B, C; Step S2: The proportional-resonant controller processes the phase error signal using formula (2) to obtain the phase output of the proportional-resonant controller k phase error signal e k of Laplace expression k phase output the proportional-resonant controller​ (2) In formula (2), s denotes Laplace transformed, is of Laplace expression, , are a proportional gain coefficient and a resonant gain coefficient of a proportional-resonant controller, respectively, is a resonant frequency of the proportional-resonant controller, is a cut-off frequency of the proportional-resonant controller; Step S3: obtaining the sliding mode controller using formula (3) k phase sliding surface s k : (3) in formula (3), c > 0 denotes a parameter of the sliding surface, is e k the first derivative; Step S4: design a sliding mode controller by using formula (4): (4) in formula (4), is a sliding mode controller k is a phase output, K is a disturbance gain coefficient, is a saturation function, is a thickness of a boundary layer, is a grid simulator k is a phase output voltage, is a grid simulator k is a phase inductance current, is a second derivative of V dc is a DC bus voltage, L is a filter inductance on the inverter side of the grid simulator, C is a filter capacitance on the inverter side of the grid simulator, R is a load on the inverter side of the grid simulator;​ Step S5: obtaining the current loop with formula (13) k phase reference signal : (13) In formula (13), denotes a weighting factor; Step S6: from the grid simulator k the sampled inductor current the difference, the resulting k phase difference is input into a proportional-integral controller for processing, outputting k a phase modulation wave and superimposed on the feedforward k phase voltage reference signal, and compared with a triangular wave, thereby generating k a phase SPWM signal to drive the switching tube of the inverter side of the grid simulator.

2. The sliding mode weighted fusion power grid simulator control method of claim 1, wherein, The sliding mode controller in step S4 is designed by the following steps: Step S4.1 : When s k = 0, the first derivative of s k :​ (6) In formula (6), is k phase error signal e k second derivative of is first derivative of Step S4.2: Designing the sliding mode controller according to formula (9) k Equivalent control output ; (9) Step S4.3: Designing the sliding mode controller according to formula (11) k Phase switching control output : (11) Step S4.4: Obtain the sliding mode controller according to formula (12) k phase output : (12)。 3. An electronic device comprising a memory and a processor, characterized in that The memory is configured to store a program supporting the processor to execute the power grid simulator control method of claim 1 or 2.

4. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is configured to execute the steps of the power grid simulator control method of claim 1 or 2 when the computer program is run by the processor.

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