Network construction type optical storage grid-connected system control method, device and equipment and storage medium

Abstract

The invention provides a network construction type optical storage grid-connected system control method, device and equipment and a storage medium, the method is applied to a VSC converter, and the converter comprises a three-phase inverter bridge and an LC type filter. The method mainly comprises the following steps: acquiring electric power information of an input end and an output end of the LC type filter; calculating the phase and the virtual potential of the reference voltage by using the information; generating a reference voltage according to the parameters; calculating a current required for adjusting to the reference voltage as a reference current; generating a current regulation and control parameter; setting an S-type function as a switching function; and finally, performing commutation control on the VSC converter according to the switching function and the current regulation and control parameters. The method aims to cope with the nonlinear characteristic of the network-forming type current converter, and the influence of disturbance and parameter change is resisted through the reference value.

Description

Technical Field

[0001] The present application belongs to the field of photovoltaic-storage grid-connected control, and in particular, relates to a control method, device, equipment and storage medium for a grid-connected photovoltaic-storage system. Background Art

[0002] The high proportion of new energy grid-connected based on inverters has made the power system's power electronics characteristics obvious. The system's low inertia and weak damping problems have become increasingly prominent, weakening the system's anti-interference ability and worsening the system's frequency stability, seriously threatening the system's safe and stable operation. The grid-connected inverter can provide voltage and frequency support for the power grid, and has gradually become a key equipment for solving the problem of new energy grid-connected.

[0003] Among many grid-connecting technologies, the virtual synchronous generator (VSG) technology enables the grid-connected converter to have external characteristics similar to those of a synchronous generator (SG), which has good effects and has therefore been widely studied.

[0004] The traditional grid-connected system based on VSG control already has good grid support capabilities, but most previous grid-connected studies did not consider the nonlinear characteristics of the grid-connected converter, or only studied its nonlinearity separately. Obviously, the converter is a typical power electronic device. If the nonlinear characteristics of its variable structure are ignored, the established mathematical model will be inaccurate.

[0005] In traditional VSG-based converter control, voltage and current dual closed-loop control based on proportional integral (PI) is widely used. Although this control method is simple in structure and easy to implement, it has great limitations in situations such as strong coupling and high-precision control, and is prone to phase lag, limiting the bandwidth of the VSG power loop, and causing VSG control performance to deteriorate and the system response time to lengthen. Summary of the invention

[0006] The purpose of the present application is to overcome the problems existing in the above-mentioned prior art and to provide a control method, device, equipment and storage medium for a grid-connected photovoltaic energy storage system.

[0007] The present application provides a control method for a grid-connected photovoltaic storage grid-connected system, which is applied to a VSC converter of a photovoltaic storage grid-connected system, including a three-phase inverter bridge and an LC filter connected front and back. The method includes:

[0008] Acquire first power information and second power information corresponding to the input end and the output end of the LC filter respectively;

[0009] Inputting the first power information into the rotor mechanical equation to calculate the phase information of the reference voltage;

[0010] Inputting the second power information into a reactive excitation equation to calculate a virtual potential;

[0011] generating a reference voltage according to the phase information and the virtual potential;

[0012] calculating a current when the voltage in the first power information is adjusted to the reference voltage as a reference current;

[0013] Subtracting the reference current from the current in the first power information to generate a current control parameter;

[0014] Setting an S-type function as a switching function on the slope of the current control parameter;

[0015] The VSC converter is controlled according to the switching function and the current control parameter.

[0016] Optionally, the reference current is subtracted from the current in the first power information to generate a current control parameter, and the reference current is subtracted from the current in the first power information to generate a control parameter, and the expression is as follows:

[0017]

[0018] Among them, i d is the current on the d-axis of the synchronously rotating coordinate system, i d,ref is i d Reference value of i q is the current in the q-axis of the synchronous rotating coordinate system, i q,ref is i q reference value.

[0019] Optionally, an S-type function is set as a switching function on the slope of the current control parameter, and the steps are as follows:

[0020] The expression for calculating the current control parameter is derived as follows:

[0021]

[0022] Set the S-type function as the switching function, the expression is as follows:

[0023]

[0024] Among them, ε d , ε q , k d , k q are control parameters, all greater than 0, and is the control parameter S of the current in the d-axis and q-axis d and S q The derivative of I d -i d，ref 、i q -i q，ref The derivative of .

[0025] Optionally, performing commutation control on the VSC converter according to the switching function and the current control parameter includes:

[0026] Adding a feedforward coupling term in the switching function, the expression is as follows:

[0027]

[0028] Among them, the ε d , ε q , k d , k q is the control parameter, R s is the resistance value of the LC filter, L s is the inductance value of the LC filter.

[0029] Optionally, before inputting the first power information into the rotor mechanical equation to calculate the phase information of the reference voltage, the method includes:

[0030] The converter mathematical model of the stationary coordinate system is transformed into the synchronous rotating coordinate system, and the expression is as follows:

[0031]

[0032] Among them, the u d and u q is the voltage of d-axis and q-axis in the synchronous rotating coordinate system, i d and i q is the current of the d-axis and q-axis in the synchronously rotating coordinate system, R s is the resistance value of the LC filter, L s is the inductance of the LC filter, and ω is the reference angular velocity of the VSC converter.

[0033] The present application also provides a control device for a grid-connected photovoltaic energy storage system, comprising:

[0034] A VSC converter applied to a photovoltaic energy storage grid-connected system, wherein the VSC converter comprises a three-phase inverter bridge and an LC filter connected in front and behind;

[0035] An acquisition module, for acquiring first power information and second power information corresponding to an input end and an output end of the LC filter respectively;

[0036] A phase module, inputting the first power information into a rotor mechanical equation to calculate phase information of a reference voltage;

[0037] A potential module, inputting the second power information into a reactive excitation equation to calculate a virtual potential;

[0038] A reference voltage module, generating a reference voltage according to the phase information and the virtual potential;

[0039] A reference current module, which calculates a current when the voltage in the first power information is adjusted to the reference voltage, as a reference current;

[0040] a parameter module, subtracting the reference current from the current in the first power information to generate a current control parameter;

[0041] A function module, setting an S-type function as a switching function on the slope of the current control parameter;

[0042] A control module performs commutation control on the VSC converter according to the switching function and the current control parameter.

[0043] Optionally, the control module performs commutation control on the VSC converter according to the switching function and the current control parameter, including:

[0044] Adding a feedforward coupling term in the switching function, the expression is as follows:

[0045]

[0046] Among them, the ε d , ε q , k d , k q is the control parameter, R s is the resistance value of the LC filter, L s is the inductance value of the LC filter.

[0047] Optionally, before the phase module inputs the first power information into the rotor mechanical equation to calculate the phase information of the reference voltage, the method includes:

[0048] The converter mathematical model of the stationary coordinate system is transformed into the synchronous rotating coordinate system, and the expression is as follows:

[0049]

[0050] Among them, the u d and uq is the voltage of the d-axis and q-axis in the synchronously rotating coordinate system, i d and i q is the current of the d-axis and q-axis in the synchronously rotating coordinate system, R s is the resistance value of the LC filter, L s is the inductance of the LC filter, and ω is the reference angular velocity of the VSC converter.

[0051] The present application also provides a grid-connected photovoltaic energy storage system control device, including:

[0052] A memory for storing a computer executable program of the control method of the above-mentioned grid-connected photovoltaic energy storage system;

[0053] A processor is used to call the computer executable program to execute: obtaining the first power information and the second power information of the input and output ends of the LC filter in the VSC converter of the photovoltaic energy storage grid-connected system; inputting the first power information into the rotor mechanical equation to calculate the phase information of the reference voltage; inputting the second power information into the reactive excitation equation to calculate the virtual potential; generating a reference voltage according to the phase information and the virtual potential; calculating the current when the voltage in the first power information is adjusted to the reference voltage as the reference current; subtracting the reference current from the current in the first power information to generate a current control parameter; setting an S-type function as a switching function on the slope of the current control parameter; and performing commutation control on the VSC converter according to the switching function and the current control parameter.

[0054] The present application also provides a storage medium, including: a computer executable program stored therein, wherein the computer executable program is used to be called by a processor to execute the steps of the above-mentioned grid-connected photovoltaic energy storage system control method.

[0055] The beneficial effects of this application are:

[0056] The present application provides a control method for a grid-type photovoltaic energy storage grid-connected system, which is applied to the VSC converter of the photovoltaic energy storage grid-connected system, including a three-phase inverter bridge and an LC filter connected front and back, and the method includes: obtaining first power information and second power information corresponding to the input and output ends of the LC filter respectively; inputting the first power information into the rotor mechanical equation to calculate the phase information of the reference voltage; inputting the second power information into the reactive excitation equation to calculate the virtual potential; generating a reference voltage according to the phase information and the virtual potential; calculating the current when the voltage in the first power information is adjusted to the reference voltage as the reference current; subtracting the reference current from the current in the first power information to generate a current control parameter; setting an S-type function as a switching function on the slope of the current control parameter; and controlling the commutation of the VSC converter according to the switching function and the current control parameter. The present application targets the nonlinear characteristics of the grid-type converter and uses reference values ​​to control the influence of disturbances and parameter changes.

[0057] Furthermore, the chattering phenomenon in SMC control is weakened by improving the sigmoid function, thereby further enhancing the system's anti-disturbance ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is a schematic diagram of the control flow of the grid-connected photovoltaic storage system in this application;

[0059] Figure 2 It is a schematic diagram of the thermostat dial image in this application;

[0060] Figure 3 It is a schematic diagram of the rotor mechanical control frame in this application;

[0061] Figure 4 It is a schematic diagram of the reactive excitation control box in this application;

[0062] Figure 5 It is a schematic diagram of the d-axis current inner loop SMC control frame in this application;

[0063] Figure 6 It is a schematic diagram of the improved grid-connected photovoltaic storage system in this application;

[0064] Figure 7 It is a schematic diagram of the improved sigmoid function image in this application;

[0065] Figure 8 It is a schematic diagram of the active power waveform output by the VSG system in this application;

[0066] Fig. 9 It is a schematic diagram of the reactive power waveform output by the VSG system in this application. DETAILED DESCRIPTION

[0067] The present application is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present application and implement it.

[0068] The present application provides a control method for a grid-connected photovoltaic and energy storage system, which is applied to a VSC converter of the photovoltaic and energy storage grid-connected system.

[0069] Please refer to Figure 1 As shown, the VSC converter includes a three-phase inverter bridge and an LC filter connected in series. The three-phase inverter bridge includes a switch element T1, a switch element T2, a switch element T3, a switch element T4, a switch element T5 and a switch element T6. The LC filter includes a filter parasitic resistor R s , filter inductance L s And filter capacitor C f The LC filter is located between the photovoltaic hybrid energy storage and the grid interface, and is used to filter out the harmonics generated by the power electronic converter and improve the quality of grid-connected power.

[0070] Please refer to Figure 2 to Figure 6 As shown, the control method of a grid-connected photovoltaic energy storage system comprises the following steps:

[0071] S101 , obtaining first power information and second power information corresponding to an input end and an output end of the LC filter, respectively.

[0072] The LC filter is composed of a filter inductor L s And filter capacitor C f The filter circuit composed of the inductor and the capacitor realizes the filtering function of the specific frequency signal through the interaction of the inductor and the capacitor.

[0073] In this application, power information includes various parameters such as voltage, current, power factor, phase angle, harmonic content, etc.

[0074] The first power information or the second power information includes: voltage, current, power factor, harmonic content, and other information describing power characteristics.

[0075] S102: Input the first power information into a rotor mechanical equation to calculate phase information of a reference voltage.

[0076] exist Figure 1 In the grid-connected converter model shown in the figure, the VSC converter model is connected by the inductor L through the filter. s and parasitic resistance R s The components are used to smooth the AC voltage and current output by the converter to reduce harmonics and meet the power quality requirements of the power grid.

[0077] The main function of the inductor Ls is to limit the rate of change of the current, thereby smoothing the AC current waveform. The size of the inductor will affect the filtering effect and the dynamic response of the system.

[0078] In actual inductors, there is always a certain resistance, which is called parasitic resistance. It will cause energy loss, and its influence should be considered during modeling to ensure the accuracy of the model. The model expression is as follows:

[0079]

[0080] Among them, L s is the filter inductance, i a 、i b and i c is the three-phase current of the filter inductor, R s is the parasitic resistance of the filter, u aN 、u bN and u cN is the converter output voltage, u ga 、u gb and u gc is the grid voltage, U dc is the DC side voltage, S ak , S bk and S ck is the switch function.

[0081] By controlling the switch function S ak , S bk and S ck To generate u aN 、u bN and u cN These voltages.

[0082] u ga 、u gb and u gc It is the voltage of the three phases a, b, and c on the grid side at the grid connection point. These voltages are fixed and determined by the grid, and the converter needs to adapt to these voltages for stable power transmission.

[0083] U dc It is the voltage on the DC side of the converter and is the DC source of the photovoltaic storage system.

[0084] S ak , S bk and S ck It is used to control the on and off of the switching elements (such as IGBT or MOSFET) in the converter. By changing the value of these switching functions, the waveform and amplitude of the converter output voltage can be controlled, thereby achieving control of the AC side current and power.

[0085] Through Kirchhoff's voltage law and Kirchhoff's current law, the relationship between the inductor current and the converter output voltage, the grid connection point voltage and the DC side voltage is established.

[0086] Before performing relevant calculations, the stationary coordinate system of the three currents is first converted into a synchronous rotating coordinate system. The expressions are as follows:

[0087]

[0088] Among them, u d and u q are the transformed d-axis and q-axis voltages.

[0089] like Figure 3 As shown in the figure, the speed regulator is used in VSG control to simulate the frequency regulation characteristics of the synchronous generator, that is, the droop characteristics between active power and frequency, and the expression is as follows:

[0090] P m =P ref +k q (ω0-ω)

[0091] Among them, P ref is the reference active power, k q is the active power-frequency droop coefficient.

[0092] In order to optimize the external characteristics of the converter, virtual inertia and damping are further added, that is, the rotor mechanical motion equation of the synchronous generator is simulated, and the expression is as follows:

[0093]

[0094] Where J is the moment of inertia, D is the damping torque, Pm is the mechanical power of the synchronous generator, Pe is the electromagnetic power, ω and ω g They represent the reference angular velocity of VSG control and the grid synchronization angular velocity respectively.

[0095] In general, ω g It can be replaced by the grid reference angular velocity ω0.

[0096] Substitute the expression of the droop characteristic between active power and frequency into the rotor mechanical motion equation, and let ω g =ω0, Δω=ω-ω0, we can get:

[0097]

[0098] Among them, k pIt is equivalent to the adjustment ratio of the synchronous motor speed regulator, which indicates the change in mechanical torque caused by a certain frequency offset. D represents the damping coefficient of the system, which can ensure that the frequency changes within a reasonable range during the adjustment process. The inertia time constant J indicates that the VSG has virtual mechanical inertia, which can control the size of the inertia during the entire adjustment process.

[0099] This control can obtain the phase information ω of the reference voltage.

[0100] S103: Input the second power information into a reactive excitation equation to calculate a virtual potential.

[0101] Please refer to Figure 4 As shown in the figure, the excitation system, as an important part of the synchronous motor, can adjust the excitation electromotive force of the motor, thereby adjusting the output reactive power, and finally ensuring the stability of the terminal voltage. When simulating the method of adjusting reactive power and voltage of synchronous motors, the adjustment of the virtual potential Em in the virtual synchronous generator (VSG) is the key link. This process usually includes three parts: reactive power adjustment, terminal voltage adjustment, and setting of no-load potential.

[0102] By adjusting the reactive power output of VSG to respond to the system's demand for reactive power, the reactive balance of the power system is maintained. VSG adopts a closed-loop control strategy to monitor the reactive power demand of the system in real time, and adjusts the excitation current of VSG accordingly, thereby changing its virtual potential E m , in order to achieve the purpose of regulating reactive power.

[0103] Specifically, the VSG performs constant reactive power regulation or reactive power regulation that changes according to a certain rule. For example, in the constant reactive power regulation mode, the VSG maintains its output reactive power near the set value to cope with the fluctuation of the system reactive power.

[0104] Keep the VSG terminal voltage within the allowable range to ensure the voltage stability of the power system. Monitor the VSG terminal voltage in real time through the voltage transformer (PT).

[0105] The measured value of the machine-end voltage is compared with the given value, and the control deviation is calculated by the PID controller. The excitation current of the VSG is adjusted accordingly, thereby changing the virtual potential Em and realizing the regulation of the machine-end voltage.

[0106] Through closed-loop control, VSG can quickly respond to changes in terminal voltage and take corresponding regulatory measures to maintain voltage stability.

[0107] Set a suitable no-load potential value for the VSG as a reference for regulating reactive power and voltage. The no-load potential is the virtual potential value of the VSG in the no-load state (i.e. no current passing through). It determines the excitation level and reactive power output capacity of the VSG.

[0108] The setting of no-load potential should comprehensively consider the rated capacity, voltage level, reactive power demand and stability requirements of the power system of the VSG. In the control system of the VSG, the no-load potential value can be set by adjusting the initial value of the excitation current or setting the corresponding control parameters. Once the setting is completed, the VSG will adjust the reactive power and voltage on this basis.

[0109] S104: Generate a reference voltage according to the phase information and the virtual potential.

[0110] The phase information and virtual potential are obtained, and the reference voltage of the VSG is generated using this information. The reference voltage is the instruction output by the VSG controller to the inverter to generate the desired voltage waveform.

[0111] The specific steps to generate the reference voltage are as follows:

[0112] According to the virtual potential E m and phase information ω, and use the sine or cosine function to calculate the instantaneous voltage value.

[0113] In some cases, the voltage amplitude needs to be fine-tuned according to system requirements. This is achieved by multiplying the virtual potential by an adjustment factor.

[0114] S105. Calculate the current when the voltage in the first power information is adjusted to the reference voltage, and use the current as the reference current.

[0115] The main function of the voltage outer loop is to ensure that the output voltage remains consistent with the set value to cope with external interference such as input voltage fluctuations and load changes. The output voltage is indirectly controlled by sampling the output voltage and comparing it with the set reference voltage, and adjusting the reference value of the current inner loop according to the comparison result.

[0116] The voltage sampler samples the output voltage in real time and compares the sampled value with the set reference voltage. The error value is calculated based on the comparison result, which reflects the deviation between the current output voltage and the set value.

[0117] The reference value of the current inner loop is adjusted according to the error value to guide the current inner loop to perform more precise current control. By adjusting the output of the current inner loop, the output voltage can be indirectly affected to make it closer to the set value.

[0118] On this basis, when the voltage is the same as the voltage reference value, or is within a preset difference range, the reference current can be determined according to a formula for calculating power.

[0119] S106. Subtract the reference current from the current in the first power information to generate a current control parameter.

[0120] Sliding Mode Control (SMC) is a variable structure control method. Its core idea is to design a specific sliding surface so that the system's state trajectory reaches the sliding surface within a finite time, and then slides along the sliding surface to enter the so-called "sliding mode". In the sliding mode, the dynamic performance of the system is robust to parameter changes and external disturbances, that is, the system can run on the predetermined path without being affected by these factors until it reaches a steady state.

[0121] Please refer to Figure 5 As shown in the figure, in the current inner loop control, the basic goal of applying SMC is to make the currents of the d-axis and q-axis (i d and i q ) can quickly and accurately track its reference value (i d,ref and i q,ref ). This goal can be achieved by designing appropriate sliding surfaces and control laws.

[0122] For the current inner loop control of VSC, the sliding surface is designed as a linear combination of current errors, that is:

[0123]

[0124] Among them, S d and S q They represent the sliding surface of the d-axis and q-axis currents, respectively, i d and i q is the actual current value, i d,ref and i q,ref is the corresponding reference value. d and S q When both are equal to 0, it means that the instantaneous value of the current completely tracks the given reference value, and the system enters the sliding mode motion state.

[0125] S107: Setting an S-type function as a switching function on the slope of the current control parameter.

[0126] In order to make the system trajectory quickly reach and remain on the sliding surface, it is necessary to design an appropriate control law (switching function).

[0127] Traditional sliding mode control laws often contain sign functions, but sign functions may cause chattering problems and affect system performance.

[0128] In this application, the linear combination of the current errors is derived:

[0129]

[0130] Please refer to Figure 7 As shown, the exponential reaching law with improved sigmoid function is used to suppress chattering:

[0131]

[0132] Among them, among them, ε d , ε q , k d , k q are control parameters, all greater than 0, and is the control parameter S of the current in the d-axis and q-axis d and S q The derivative of I d -i d，ref 、i q -i q，ref The derivative of .

[0133] Furthermore, due to the existence of cross-coupling terms in the mathematical model of the LC grid-connected converter in the dq coordinate system, the current i d and i q No direct independent control.

[0134] Therefore, a feedforward decoupling control strategy is designed to eliminate the influence of these coupling terms. Based on SMC control, the following feedforward decoupling control law is designed:

[0135]

[0136] The closed loop obtained according to the above formula is as follows:

[0137]

[0138] Among them, the ε d , ε q , k d , k q is the control parameter, R s is the resistance value of the LC filter, L s is the inductance value of the LC filter.

[0139] Combining the above three current stationary coordinate system conversion to synchronous rotating coordinate system expression, feedforward decoupling control law and closed-loop expression, we can get:

[0140]

[0141] By introducing the decoupling term, independent control of id and iq can be achieved and the closed-loop system can be stabilized.

[0142] S108. Perform commutation control on the VSC converter according to the switching function and the current control parameter.

[0143] Through such a design, the grid-connected photovoltaic energy storage system can achieve stable and accurate current control in a complex power grid environment, improving the overall performance and robustness of the system.

[0144] To prove the stability, the robustness of the technical solution of the present application is analyzed below.

[0145] Constructing Lyapunov functions

[0146]

[0147] Derivative the above formula:

[0148]

[0149] in:

[0150]

[0151] In the neighborhood of the sliding surface, S d , S q is not equal to 0, so V is positive definite, and from the above formula we know Less than 0, that is is negative definite. According to Lyapunov's second method, the system is asymptotically stable.

[0152] The present invention applies an improved sliding mode control strategy to a grid-type photovoltaic storage system. Compared with traditional PI control, it takes into account the nonlinear characteristics of the converter and adopts the exponential reaching law of the improved sigmoid function. A sliding mode controller is built in the current inner loop, which enables the system to gain in sliding surface movement and suppress uncertainty disturbances, and reduce output voltage jitter, thereby effectively improving the control performance and control accuracy of the grid-type control strategy.

[0153] In order to verify the correctness and effectiveness of the control strategy proposed in this paper, the following simulation software is built in Matlab / Simulink: Figure 5 The grid-connected photovoltaic energy storage system shown in the figure is to verify the effectiveness of the control strategy proposed in this paper when the system is running. Among them, the DC side of the converter is photovoltaic plus hybrid energy storage, and the hybrid energy storage is composed of batteries and supercapacitors. The battery adopts power control to ensure that the current is not overloaded during battery charging and discharging, and the supercapacitor adopts constant voltage control to maintain a constant DC bus voltage. The system simulation parameters are shown in Table 1:

[0154] Table 1 System simulation parameters

[0155]

[0156] like Figure 8 As shown, in order to verify the effect of the improved system when it is disturbed by a fault, the simulation time is set to 3s, and the grid voltage drop is set to 0.6pu at 1-2s, and the comparison diagram of the active power output of the VSG system is obtained.

[0157] Depend on Figure 8 It can be seen that when the grid voltage drops by 0.6pu, the active power output of the original system has fluctuated to a large extent, while the system improved by sliding mode control can output stable active power.

[0158] like Fig. 9 As shown in the figure, when the grid voltage drops by 0.6pu, the reactive power overshoot emitted by the improved system is smaller and the time to reach stability is shorter. The original system cannot maintain stability after reaching stability, and gradually experiences large-scale power oscillations.

[0159] The main reason is that sliding mode control is more robust than traditional PI control, making the current Id and Iq waveforms of the current inner loop output smoother, thereby making the power output more stable, and has obvious advantages over PI control in resisting fault disturbances.

[0160] The present application also provides a control device for a grid-connected photovoltaic energy storage system, comprising:

[0161] A VSC converter applied to a photovoltaic energy storage grid-connected system, wherein the VSC converter comprises a three-phase inverter bridge and an LC filter connected in front and behind;

[0162] An acquisition module, for acquiring first power information and second power information corresponding to an input end and an output end of the LC filter respectively;

[0163] A phase module, inputting the first power information into a rotor mechanical equation to calculate phase information of a reference voltage;

[0164] A potential module, inputting the second power information into a reactive excitation equation to calculate a virtual potential;

[0165] A reference voltage module, generating a reference voltage according to the phase information and the virtual potential;

[0166] A reference current module, which calculates a current when the voltage in the first power information is adjusted to the reference voltage, as a reference current;

[0167] a parameter module, subtracting the reference current from the current in the first power information to generate a current control parameter;

[0168] A function module, setting an S-type function as a switching function on the slope of the current control parameter;

[0169] A control module performs commutation control on the VSC converter according to the switching function and the current control parameter.

[0170] Furthermore, the control module performs commutation control on the VSC converter according to the switching function and the current control parameter, including:

[0171] Adding a feedforward coupling term in the switching function, the expression is as follows:

[0172]

[0173] Among them, the ε d , ε q , k d , k q is the control parameter, R s is the resistance value of the LC filter, L s is the inductance value of the LC filter.

[0174] Furthermore, before the phase module inputs the first power information into the rotor mechanical equation to calculate the phase information of the reference voltage, the phase module includes:

[0175] The converter mathematical model of the stationary coordinate system is transformed into the synchronous rotating coordinate system, and the expression is as follows:

[0176]

[0177] Among them, the u d and u q is the voltage of d-axis and q-axis in the synchronous rotating coordinate system, i d and i q is the current of the d-axis and q-axis in the synchronously rotating coordinate system, R s is the resistance value of the LC filter, L s is the inductance of the LC filter, and ω is the reference angular velocity of the VSC converter.

[0178] The embodiments and / or implementation methods described above are only used to illustrate the preferred embodiments and / or implementation methods for realizing the technology of the present invention, and are not intended to limit the implementation methods of the technology of the present invention in any form. Any technical personnel in this field may make slight changes or modifications to other equivalent embodiments without departing from the scope of the technical means disclosed in the content of the present invention, but they should still be regarded as technologies or embodiments that are essentially the same as the present invention.

[0179] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and its core ideas of this application. The above is only the preferred implementation method of this application. It should be pointed out that due to the limitations of textual expression and the objective existence of infinite specific structures, ordinary technicians in this technical field can make some improvements, modifications or changes without departing from the principles of this application, and combine the above technical features in an appropriate manner; the improvements, modifications, changes or combinations, or the direct application of the concept and technical solution of the invention to other occasions without improvement, should be regarded as the scope of protection of this application.

Claims

1. A control method for a grid-connected photovoltaic energy storage system, characterized in that: In a VSC converter applied to a photovoltaic energy storage grid-connected system, the VSC converter includes a three-phase inverter bridge and an LC filter connected in series, and the method includes: Acquire first power information and second power information corresponding to the input end and the output end of the LC filter respectively; Inputting the first power information into the rotor mechanical equation to calculate the phase information of the reference voltage; Inputting the second power information into a reactive excitation equation to calculate a virtual potential; generating a reference voltage according to the phase information and the virtual potential; calculating a current when the voltage in the first power information is adjusted to the reference voltage as a reference current; Subtracting the reference current from the current in the first power information to generate a current control parameter; Setting an S-type function as a switching function on the slope of the current control parameter; The VSC converter is controlled according to the switching function and the current control parameter.

2. The control method of the grid-connected photovoltaic energy storage system according to claim 1 is characterized in that: Subtract the reference current from the current in the first power information to generate a current control parameter, which is expressed as follows: Among them, i d is the current in the d-axis of the synchronous rotating coordinate system, i d,ref is i d Reference value of i q is the current in the q-axis of the synchronous rotating coordinate system, i q,ref is i q reference value.

3. The control method of the grid-connected photovoltaic energy storage system according to claim 2 is characterized in that: An S-type function is set as a switching function on the slope of the current control parameter, and the steps are as follows: The expression for calculating the current control parameter is derived, and the derived expression is as follows: Set the S-type function as the switching function, the expression is as follows: Among them, ε d , ε q , k d , k q are control parameters, all greater than 0, and is the control parameter S of the current in the d-axis and q-axis d and S q The derivative of I d -i d，ref 、i q -i q，ref The derivative of .

4. The control method of the grid-connected photovoltaic energy storage system according to claim 3 is characterized in that: The method further comprises: performing commutation control on the VSC converter according to the switching function and the current control parameter, comprising: Adding a feedforward coupling term in the switching function, the expression is as follows: Among them, the ε d , ε q , k d , k q is the control parameter, R s is the resistance value of the LC filter, L s is the inductance value of the LC filter, are respectively d and i q The derivation of .

5. The control method of the grid-connected photovoltaic energy storage system according to claim 1, characterized in that: Before inputting the first power information into the rotor mechanical equation to calculate the phase information of the reference voltage, the method comprises: The converter mathematical model of the stationary coordinate system is transformed into the synchronous rotating coordinate system, and the expression is as follows: Among them, the u d and u q is the voltage of d-axis and q-axis in the synchronous rotating coordinate system, i d and i q is the current of the d-axis and q-axis in the synchronously rotating coordinate system, R s is the resistance value of the LC filter, L s is the inductance of the LC filter, ω is the reference angular velocity of the VSC converter, are respectively d and i q The derivation of .

6. A network construction characterized by: include: A VSC converter applied to a photovoltaic energy storage grid-connected system, wherein the VSC converter comprises a three-phase inverter bridge and an LC filter connected in front and behind; An acquisition module, for acquiring first power information and second power information corresponding to an input end and an output end of the LC filter respectively; A phase module, inputting the first power information into a rotor mechanical equation to calculate phase information of a reference voltage; A potential module, inputting the second power information into a reactive excitation equation to calculate a virtual potential; A reference voltage module, generating a reference voltage according to the phase information and the virtual potential; A reference current module, which calculates a current when the voltage in the first power information is adjusted to the reference voltage, as a reference current; a parameter module, subtracting the reference current from the current in the first power information to generate a current control parameter; A function module, setting an S-type function as a switching function on the slope of the current control parameter; A control module performs commutation control on the VSC converter according to the switching function and the current control parameter.

7. The control device for the grid-connected photovoltaic energy storage system according to claim 6, characterized in that: The control module performs commutation control on the VSC converter according to the switching function and the current control parameter, including: Adding a feedforward coupling term in the switching function, the expression is as follows: Among them, the ε d , ε q , k d , k q is the control parameter, R s is the resistance value of the LC filter, L s is the inductance value of the LC filter.

8. The control device for the grid-connected photovoltaic energy storage system according to claim 6, characterized in that: Before the phase module inputs the first power information into the rotor mechanical equation to calculate the phase information of the reference voltage, the phase module includes: The converter mathematical model of the stationary coordinate system is transformed into the synchronous rotating coordinate system, and the expression is as follows: Among them, the u d and u q is the voltage of d-axis and q-axis in the synchronous rotating coordinate system, i d and i q is the current of the d-axis and q-axis in the synchronously rotating coordinate system, R s is the resistance value of the LC filter, L s is the inductance of the LC filter, and ω is the reference angular velocity of the VSC converter.

9. A grid-connected photovoltaic energy storage system control device, characterized in that: include: A memory for storing a computer executable program of the control method of the grid-connected photovoltaic energy storage system according to any one of claims 1 to 5; The processor is used to call the computer executable program to execute: obtaining first power information and second power information of an input end and an output end of an LC filter in a VSC converter of a photovoltaic energy storage grid-connected system; Inputting the first power information into the rotor mechanical equation to calculate the phase information of the reference voltage; Inputting the second power information into a reactive excitation equation to calculate a virtual potential; generating a reference voltage according to the phase information and the virtual potential; calculating a current when the voltage in the first power information is adjusted to the reference voltage as a reference current; Subtracting the reference current from the current in the first power information to generate a current control parameter; An S-type function is set as a switching function on the slope of the current control parameter; and commutation control is performed on the VSC converter according to the switching function and the current control parameter.

10. A storage medium, characterized in that: include: A computer executable program is stored, and the computer executable program is used to be called by a processor to execute the steps of the control method of the grid-connected photovoltaic energy storage system according to any one of claims 1 to 5.

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