Voltage stability control method and system for photovoltaic power generation system

Abstract

The invention discloses a photovoltaic power generation system voltage stability control method and system, and relates to the field of photovoltaic power generation system stability control. The method comprises the following steps: acquiring a real-time storage energy state parameter by using a dynamic model according to a real-time operation parameter of a nonlinear boost converter system; determining real-time mismatching interference and matching interference by using an extended disturbance observer; determining a real-time sliding mode variable in a sliding mode controller by using a new sliding mode function according to the real-time mismatching interference; mismatching interference estimation and exponential function terms are introduced into the new sliding mode function; according to the real-time sliding mode variable and the matching interference, the duty ratio of PWM is adjusted through the control law, the conduction time of a switch device in the nonlinear boost converter system is changed, and the output voltage of a capacitor in the nonlinear boost converter system is made to track the reference voltage of the nonlinear boost converter system. According to the invention, the voltage transient response rate and stability of the nonlinear boost converter system can be improved.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic power generation system stability control, and in particular to a photovoltaic power generation system voltage stability control method and system. Background Art

[0002] Solar energy resources have attracted extensive attention due to their clean, pollution-free and abundant reserves. How to control the output voltage of photovoltaic power generation systems has become an important issue that needs to be solved urgently. In order to overcome the problems of slow response speed and low control accuracy of traditional control methods, sliding mode control technology can effectively cope with the fluctuation of internal system parameters and external interference, showing excellent robustness. It is suitable for handling the coordinated control tasks of complex systems with uncertainty and fuzziness, but due to the generation of jitter, the system performance will be seriously affected. To solve this problem, scholars are committed to designing improved sliding mode functions and reaching laws to effectively deal with jitter and improve system dynamics. Among them, the commonly used exponential reaching law achieves fast dynamic response and robustness of the system by setting appropriate control gains. However, due to the asymptotic convergence of state variables, it is necessary to improve the convergence speed of state variables, and the control gain in the exponential reaching law is usually designed to be quite large, which may lead to higher jitter, thereby exacerbating the instability of the system. Summary of the invention

[0003] The purpose of the present application is to provide a method and system for voltage stability control of a photovoltaic power generation system, which can improve the voltage transient response rate and stability of a nonlinear boost converter system.

[0004] To achieve the above objectives, this application provides the following solutions:

[0005] In a first aspect, the present application provides a method for voltage stability control of a photovoltaic power generation system, comprising: constructing a dynamic model of a nonlinear boost converter system in the photovoltaic power generation system; establishing a sliding mode function that introduces mismatched interference estimation; adding an exponential function term on the basis of the sliding mode function to obtain a new sliding mode function; establishing an extended disturbance observer for mismatched interference and matched interference; determining a control law of the nonlinear boost converter system according to the new sliding mode function, the dynamic model, and the extended disturbance observer for mismatched interference and matched interference; obtaining a real-time storage energy state parameter of the nonlinear boost converter system using the dynamic model according to the real-time operating parameters of the nonlinear boost converter system; determining real-time mismatched interference and matched interference according to the real-time storage energy state parameter using the extended disturbance observer; determining real-time sliding mode variables using the new sliding mode function in the sliding mode controller according to the real-time mismatched interference; and adjusting PWM (Pulse Width Modulation) according to the real-time sliding mode variables and the real-time matching interference using the control law. Modulation, pulse width modulation) duty cycle; according to the adjusted PWM duty cycle, changing the on-time of the switching device in the nonlinear boost converter system so that the output voltage of the capacitor in the nonlinear boost converter system tracks the reference voltage of the nonlinear boost converter system.

[0006] In the second aspect, the present application provides a photovoltaic power generation system voltage stability control system, which is used to execute the above-mentioned photovoltaic power generation system voltage stability control method, and the photovoltaic power generation system voltage stability control system includes: an operating status module, a sliding mode controller, an extended disturbance observer, a control module and a PWM module.

[0007] The operating state module is connected to the sliding mode controller and the extended disturbance observer respectively, the extended disturbance observer is connected to the sliding mode controller, the sliding mode controller is connected to the control module, the control module is connected to the PWM module, and the PWM module is connected to the switching device in the nonlinear boost converter system.

[0008] The operation state module is used to obtain the real-time operation parameters of the nonlinear boost converter system, and obtain the real-time storage energy state parameters according to the real-time operation parameters by using the dynamic model of the nonlinear boost converter system; the extended disturbance observer is used to determine the real-time mismatch interference and matching interference according to the real-time storage energy state parameters; the sliding mode controller is used to determine the real-time sliding mode variable according to the real-time mismatch interference by using a new sliding mode function; the sliding mode function introduces mismatch interference estimation and exponential function terms; the control module is used to adjust the duty cycle of the PWM module according to the real-time sliding mode variable and the real-time matching interference by using a control law; the control law is determined according to the new sliding mode function, the dynamic model, the mismatch interference and the extended disturbance observer of the matching interference; the PWM module is used to drive the switching device in the nonlinear boost converter system according to the adjusted duty cycle, change the conduction time, and make the output voltage of the capacitor in the nonlinear boost converter system track the reference voltage of the nonlinear boost converter system.

[0009] According to the specific embodiments provided in this application, this application has the following technical effects:

[0010] The present application provides a method and system for controlling the voltage stability of a photovoltaic power generation system. An exponential function term is added to the sliding mode function, which accelerates the convergence speed when the system state deviates from the sliding mode function, so that the output voltage of the capacitor in the nonlinear boost converter system adjusted by the control law can quickly track the reference voltage; and a sliding function for introducing mismatched interference estimation is designed, and the uncertainty caused by the mismatched interference is offset by a disturbance observer, thereby ensuring that the system state can remain stable even in the presence of mismatched interference. The present application demonstrates excellent tracking and anti-interference capabilities when the reference voltage changes, and improves the voltage transient response rate and stability of the nonlinear boost converter system. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0012] Figure 1 A schematic diagram of a flow chart of a method for controlling voltage stability of a photovoltaic power generation system provided in one embodiment of the present application;

[0013] Figure 2 A schematic diagram of the overall working principle of a photovoltaic power generation system voltage stabilization control method provided in one embodiment of the present application;

[0014] Figure 3A schematic diagram of output voltage waveforms under different reference voltages provided by another embodiment of the present application;

[0015] Figure 4 A schematic diagram of an inductor current waveform under different reference voltages provided by another embodiment of the present application;

[0016] Figure 5 Estimated error under different reference voltages provided by another embodiment of the present application Schematic diagram;

[0017] Figure 6 Estimated error under different reference voltages provided by another embodiment of the present application Schematic diagram. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0019] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0020] In an exemplary embodiment, Figure 1 As shown, a method for controlling voltage stability of a photovoltaic power generation system is provided, comprising the following steps 101 to 110. Among them:

[0021] Step 101: Construct a dynamic model of a nonlinear boost converter system in a photovoltaic power generation system.

[0022] Step 102: Establish a sliding mode function for introducing mismatched interference estimation.

[0023] Step 103: adding an exponential function term on the basis of the sliding mode function to obtain a new sliding mode function.

[0024] Step 104: Establish an extended disturbance observer for mismatched disturbance and matched disturbance.

[0025] Step 105: Determine the control law of the nonlinear boost converter system according to the new sliding mode function, the dynamic model, the extended disturbance observer of the mismatched disturbance and the matched disturbance.

[0026] Step 106: According to the real-time operating parameters of the nonlinear boost converter system, the real-time storage energy state parameters of the nonlinear boost converter system are obtained using the dynamic model.

[0027] Step 107: Determine the real-time mismatch disturbance and match disturbance using the extended disturbance observer according to the real-time storage energy state parameter.

[0028] Step 108: According to the real-time mismatch disturbance, a new sliding mode function is used in the sliding mode controller to determine the real-time sliding mode variable.

[0029] Step 109: According to the real-time sliding mode variable and the real-time matching disturbance, the duty cycle of the PWM is adjusted by using the control law.

[0030] Step 110: changing the on-time of the switch device in the nonlinear boost converter system according to the adjusted PWM duty cycle, so that the output voltage of the capacitor in the nonlinear boost converter system tracks the reference voltage of the nonlinear boost converter system.

[0031] By implementing the above steps 101 to 110, an exponential function term is added to the sliding mode function, which speeds up the convergence speed when the system state deviates from the sliding mode function, so that the output voltage of the capacitor in the nonlinear boost converter system adjusted by the control law can quickly track the reference voltage; and a sliding function for introducing mismatched interference estimation is designed, and the uncertainty of mismatched interference in the nonlinear boost converter system is offset by an extended disturbance observer, so that the system state can remain stable even in the presence of mismatched interference. The present application shows excellent tracking ability and anti-interference ability when the reference voltage changes, and improves the voltage transient response rate and stability of the nonlinear boost converter system.

[0032] The nonlinear boost converter system specifically refers to a typical DC-DC boost converter in a photovoltaic power generation system. Since photovoltaic power generation is intermittent and uncertain, the DC-DC boost converter system has time-varying interference.

[0033] In another exemplary embodiment of the present application, Figure 2 As shown, the nonlinear boost converter system includes: a photovoltaic voltage source, a switching device, a diode, a filter inductor, a capacitor and a load resistor. The positive electrode of the photovoltaic voltage source is connected to one end of the filter inductor, and the other end of the filter inductor is respectively connected to the anode of the diode and the source of the switching device; the negative electrode of the photovoltaic voltage source is respectively connected to the drain of the switching device, one end of the capacitor and one end of the load resistor; the gate of the switching device is used to input a control input signal; the cathode of the diode is respectively connected to the other end of the capacitor and the other end of the load resistor.

[0034] Figure 2 The photovoltaic power generation position in refers to the photovoltaic voltage source. K is a switching device driven by PWM. D is a diode.

[0035] In another exemplary embodiment of the present application, due to the intermittent and uncertain nature of photovoltaic power generation, inevitable uncertainty and interference will occur, and the voltage regulation performance will be seriously affected. Considering the influence of time-varying disturbances, disturbance estimation is introduced. Then the above step 101 can be replaced by the following steps 201 to 203:

[0036] Step 201: Considering the influence of time-varying disturbances, an initial dynamic model of the nonlinear boost converter system is established as:

[0037]

[0038] Where i1(t) is the inductor current at time t, u is the control input signal, which will generate the drive signal, and u∈[0,1]. v1(t) is the output voltage of the capacitor in the nonlinear boost converter system at time t, L is the inductance of the filter inductor in the nonlinear boost converter system, and v 2f (t) is the nominal value of the power supply voltage in the nonlinear boost converter system at time t; C0 is the capacitance of the capacitor in the nonlinear boost converter system, R f is the nominal value of the load resistance; D1(t) and D2(t) are both time-varying disturbances at time t, v2(t) is the output voltage of the PV array at time t, and R is the load resistance in the nonlinear boost converter system.

[0039] Step 202: The nonlinear boost converter system is a typical bilinear system with multiple disturbances. Considering the system operation state, the state variables are defined as:

[0040]

[0041] Where x1 is the total energy stored in the nonlinear boost converter system and x2 is the rate of change of the stored energy.

[0042] Step 203: Since all variables in the system can be parameterized in principle, all system variables can be written as functions of x1 and its finite-order derivatives. Therefore, the initial dynamic model of the nonlinear boost converter system is transformed according to the defined state variables, and the final dynamic model of the nonlinear boost converter system is obtained as:

[0043]

[0044] In the formula, is the first-order derivative of x1, is the first-order derivative of x2, u avis the intermediate control signal, D3(t) is the mismatch interference at time t, D3(t)=Li1(t)D1(t)+C0v1(t)D2(t); D4(t) is the matching interference at time t,

[0045] In another exemplary embodiment of the present application, the sliding mode function of the mismatched interference estimation introduced in step 102 is:

[0046]

[0047] Where s is the sliding mode variable, x2 is the rate of change of stored energy, c1 is a constant greater than 0, x1 is the total energy stored in the nonlinear boost converter system, and x 1ref is the reference energy, is the estimated value of D3(t), and D3(t) is the mismatch interference at time t.

[0048] In another exemplary embodiment of the present application, an exponential function term is added to the original sliding mode function to accelerate the convergence speed when the system state deviates from the sliding mode function. Then the new sliding mode function in step 103 is:

[0049]

[0050] In the formula, s * is the new sliding mode variable, x2 is the rate of change of stored energy, c1 is a constant greater than 0, and x 1ref is the reference energy, is the estimated value of D3(t), D3(t) is the mismatch interference at time t, α is a constant greater than 0, and s(0) is the initial value of the sliding mode function.

[0051] If the designed control law can satisfy the sliding condition of the sliding mode function, then within a finite time, the sliding mode variable s * It will approach 0, which means the system state is stable.

[0052] In another exemplary embodiment of the present application, for matched and unmatched interferences, a corresponding disturbance observer is designed to suppress system disturbances and ensure stable operation of the system so that the system output is not affected by matched and unmatched interferences. Then the above step 104 can be replaced by the following steps 301 to 305:

[0053] Step 301: Establish a disturbance observer for mismatched disturbances:

[0054]

[0055] In the formula, is the estimated value of D3, D3 is the mismatch interference, for The estimated value of is the first-order derivative of D3, w 11 and w 12 are auxiliary variables of mismatched interference, w 11 The first derivative of w 12 The first derivative of 11 and h 12 are all constants greater than 0, x1 is the total energy stored in the nonlinear boost converter system, and x2 is the rate of change of the stored energy.

[0056] Step 302: Establish a disturbance observer matching the disturbance as:

[0057]

[0058] In the formula, is the estimated value of D4, D4 is the matching interference, for The estimated value of is the first-order derivative of D4, w 21 and w 22 are auxiliary variables matching interference, w 21 The first derivative of w 22 The first derivative of 21 and h 22 are all constants greater than 0, u av It is the intermediate control signal.

[0059] Step 303: Define the estimated error as: and In the formula, D i The estimation error of for Estimation error of , i=3,4.

[0060] Among them, the estimated error Defined as:

[0061]

[0062]

[0063] Step 304: According to the estimation error, the disturbance observer of the unmatched disturbance and the disturbance observer of the matched disturbance, the expression of the first-order derivative of the estimation error is determined as follows: In the formula, for The first-order derivative of , H is a positive definite matrix.

[0064] The expression of the first derivative of the estimation error is It can also be expressed as:

[0065] Step 305: Deriving the first-order derivative of the estimation error, the extended disturbance observer of the mismatched disturbance and the matched disturbance is obtained as: In the formula, for The second-order derivative of D i The second derivative of H * is a positive definite matrix.

[0066] Extended Disturbance Observer It can also be expressed as: is bounded. To ensure that the designed disturbance observer can accurately estimate the matching and mismatching disturbances, the matrices H and H are selected * is a positive definite matrix.

[0067] This application uses a disturbance observer to estimate the disturbance and designs a suitable control gain of the high-frequency switching function, which can further suppress the jitter and ensure its strong robustness. The nonlinear disturbance observer is used to offset the uncertainty of the mismatch in the system, and a sliding function based on disturbance estimation is designed, so that the system state can remain stable even in the presence of mismatched disturbances.

[0068] In another exemplary embodiment of the present application, the above step 105 can be replaced by the following steps 401 to 404:

[0069] Step 401: The controller is designed to ensure sliding along the sliding surface. Then the new sliding function is derived as follows:

[0070]

[0071] In the formula, For * The first derivative of , s * is the new sliding mode variable, is the second-order derivative of x2, x2 is the rate of change of stored energy, c1 is a constant greater than 0, is the first-order derivative of x1, x1 is the total energy stored in the nonlinear boost converter system, for The first derivative of is the estimated value of D3, D3 is the mismatch interference, α is a constant greater than 0, s(0) is the initial value of the sliding mode function, and t is the time.

[0072] Step 402: Substitute the dynamic model of the nonlinear boost converter system into the derived sliding mode function to obtain the deformed sliding mode function:

[0073]

[0074] In the formula, u av is the intermediate control signal and D4 is the matching interference.

[0075] Step 403: According to the deformed sliding mode function and the hyperbolic tangent function, the expression of the intermediate control signal is determined as follows:

[0076]

[0077] In the formula, is the estimated value of D4, k1 and k2 are both constants greater than 0.

[0078] Step 404: According to the expression of the intermediate control signal and the dynamic model, the control law of the nonlinear boost converter system is determined as:

[0079]

[0080] Where u is the control input signal, v 2f is the nominal value of the power supply voltage in the nonlinear boost converter system, L is the inductance of the filter inductor in the nonlinear boost converter system, v1 is the output voltage of the capacitor in the nonlinear boost converter system, R f is the nominal value of the load resistance, C0 is the capacitance of the capacitor in the nonlinear boost converter system, v2 is the PV array output voltage, and i1 is the inductor current.

[0081] Due to interference D i The n-th order derivative of (t) is continuous and bounded, and its higher-order derivatives can be written as:

[0082]

[0083] Wherein, j = 1, 2, 3 ... n, i = 3, 4, γ represents a positive integer. When time approaches infinity, the first-order derivative of the interference can be regarded as 0, and the specific value of the interference limit γ is not required here. Indicates D i (t) Take the j-th derivative with respect to time t.

[0084] will u av Substitute into get:

[0085]

[0086] In another exemplary embodiment of the present application, an exponential function term is added to the original sliding mode function to accelerate the convergence speed when the system state deviates from the sliding mode function, and the stability of the sliding mode controller is analyzed based on the new sliding mode function. After the above step 103, the method may also include:

[0087] The error dynamics equation of the disturbance observer can be expressed as follows:

[0088]

[0089] in, for The derivative of is the estimation error, d (2) is the actual disturbance to the system,

[0090] To ensure the stable operation of the system, if there is a feasible solution to the following equation, it means that the system is asymptotically stable:

[0091]

[0092] Among them, L i is a positive definite matrix, and Q is a positive definite matrix.

[0093] Choose a Lyapunov function:

[0094]

[0095] Among them, in Lyapunov stability theory, is a Lyapunov function, which is a function of the variable The function of Used to determine the stability of the system. It will eventually converge to a negative value, It means that the system state is stable.

[0096] Taking the derivative of the Lyapunov function we get:

[0097]

[0098] Among them, λ m Yes D f The minimum eigenvalue of , so when time tends to infinity, the norm of the estimation error is bounded by:

[0099]

[0100] Next, the stability of the sliding mode controller is analyzed. The derivative of the sliding mode function can be transformed into the following form:

[0101]

[0102] Select the Lyapunov function and take the derivative:

[0103]

[0104] According to the above estimation error norm boundedness, it can be seen that the estimation error of the disturbance is bounded, so:

[0105]

[0106] In summary, it can be verified that the Lyapunov function is less than 0, which means that the designed sliding mode control strategy can ensure the stable voltage operation of the photovoltaic power generation system.

[0107] In order to verify the superiority of the sliding mode disturbance observer control strategy proposed in this application over the traditional sliding mode control strategy in the voltage control of photovoltaic power generation system, MATLAB modeling was used for simulation testing.

[0108] In the actual operation process, since the power system contains multiple distributed power generation devices, there may be power exchange between the power generation units. Therefore, for the reference voltage v of the DC-DC boost converter, ref1 It is not constant either, so changing the reference voltage verifies the effectiveness of this application when facing different reference voltage values, which is more in line with the actual operation of the microgrid.

[0109] The reference voltages are selected as 12V, 24V and 48V after 0s, 0.5s and 2.5s respectively. Figure 3 It can be seen that after the reference voltage changes, the voltage can rise to the reference voltage and remain stable after experiencing a small fluctuation. The adjustment time is within 0.2s, indicating that the application has the ability to quickly converge the voltage. At the same time, the jitter generated in the process of the voltage reaching a stable state is small, which verifies the strong interference suppression ability of the application. After the reference voltage changes, the traditional sliding mode controller takes a long time to reach a stable state due to the influence of external disturbances, and it is impossible to track the reference value. The change of current can be seen by Figure 4 It can be seen that in the control strategy designed by the present application, the current reaches stability within 0.2s and the jitter is also small. Under the traditional sliding mode control, due to the existence of mismatch interference, although the current finally reaches stability, it takes a long time and fluctuates greatly. The present application can better adapt to the change of reference voltage and greatly improve the voltage regulation performance. Figure 5 and Figure 6It can be seen that the sliding mode control scheme with disturbance observation has a good processing effect on the matching and mismatching interference in the system. The disturbance error can converge to 0 quickly, and the disturbance observer can offset the interference. This application shows excellent tracking ability and anti-interference ability when the reference voltage changes.

[0110] In view of the shortcomings of traditional sliding mode control methods, this application proposes a voltage stability control method for photovoltaic power generation systems based on a sliding mode disturbance observer. For a typical DC-DC boost converter in a photovoltaic power generation system, a system model is established considering the system operation state, disturbance estimation is introduced in the design of the sliding mode function, and the system control law is designed; for matching and mismatching interference, a corresponding disturbance observer is designed to suppress system disturbances and ensure stable operation of the system; an exponential function term is added to accelerate the convergence speed when the system state deviates from the sliding mode function, and the final control law of the system is designed based on the new sliding mode function, so that the stability performance of the photovoltaic system is further improved, and both the disturbance estimation error and the output voltage are guaranteed. This application has good adaptability to changes in reference voltage, can obtain better voltage transient response, stronger time-varying interference suppression capability, avoid excessive overshoot, and can reduce jitter, so that the system can operate safely and reliably.

[0111] Based on the same inventive concept, the embodiment of the present application also provides a photovoltaic power generation system voltage stability control system for implementing the photovoltaic power generation system voltage stability control method involved above. The implementation scheme for solving the problem provided by the system is similar to the implementation scheme recorded in the above method, so the specific limitations in one or more photovoltaic power generation system voltage stability control system embodiments provided below can refer to the limitations of the photovoltaic power generation system voltage stability control method above, and will not be repeated here.

[0112] In an exemplary embodiment, a photovoltaic power generation system voltage stability control system is provided, wherein the photovoltaic power generation system voltage stability control system is used to execute the above-mentioned photovoltaic power generation system voltage stability control method, and the photovoltaic power generation system voltage stability control system includes: an operating state module, a sliding mode controller, an extended disturbance observer, a control module and a PWM module.

[0113] The operating state module is connected to the sliding mode controller and the extended disturbance observer respectively, the extended disturbance observer is connected to the sliding mode controller, the sliding mode controller is connected to the control module, the control module is connected to the PWM module, and the PWM module is connected to the switching device in the nonlinear boost converter system.

[0114] The operation state module is used to obtain the real-time operation parameters of the nonlinear boost converter system, and obtain the real-time storage energy state parameters according to the real-time operation parameters by using the dynamic model of the nonlinear boost converter system; the extended disturbance observer is used to determine the real-time mismatch interference and matching interference according to the real-time storage energy state parameters; the sliding mode controller is used to determine the real-time sliding mode variable according to the real-time mismatch interference by using a new sliding mode function; the sliding mode function introduces mismatch interference estimation and exponential function terms; the control module is used to adjust the duty cycle of the PWM module according to the real-time sliding mode variable and the real-time matching interference by using a control law; the control law is determined according to the new sliding mode function, the dynamic model, the mismatch interference and the extended disturbance observer of the matching interference; the PWM module is used to drive the switching device in the nonlinear boost converter system according to the adjusted duty cycle, change the conduction time, and make the output voltage of the capacitor in the nonlinear boost converter system track the reference voltage of the nonlinear boost converter system.

[0115] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0116] 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 core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A method for controlling voltage stability of a photovoltaic power generation system, characterized in that: include: Construct a dynamic model of a nonlinear boost converter system in a photovoltaic power generation system; Establishing a sliding mode function that introduces mismatched disturbance estimation; Adding an exponential function term on the basis of the sliding mode function to obtain a new sliding mode function; Establish the extended disturbance observer for mismatched disturbance and matched disturbance; Determine the control law for a nonlinear boost converter system based on a new sliding mode function, dynamic model, and extended disturbance observers for mismatched and matched disturbances. According to the real-time operating parameters of the nonlinear boost converter system, the dynamic model is used to obtain the real-time storage energy state parameters of the nonlinear boost converter system; According to the real-time storage energy state parameter, using the extended disturbance observer, determining the real-time mismatch disturbance and matching disturbance; According to the real-time mismatch disturbance, a new sliding mode function is used in the sliding mode controller to determine the real-time sliding mode variable; According to the real-time sliding mode variable and the real-time matching disturbance, the duty cycle of the PWM is adjusted by using the control law; According to the adjusted PWM duty cycle, the conduction time of the switch device in the nonlinear boost converter system is changed so that the output voltage of the capacitor in the nonlinear boost converter system tracks the reference voltage of the nonlinear boost converter system.

2. The photovoltaic power generation system voltage stabilization control method according to claim 1, characterized in that: Construct a dynamic model of a nonlinear boost converter system in a photovoltaic power generation system, including: Considering the influence of time-varying disturbances, the initial dynamic model of the nonlinear boost converter system is established as: Where i1(t) is the inductor current at time t, u is the control input signal, v1(t) is the output voltage of the capacitor in the nonlinear boost converter system at time t, L is the inductance of the filter inductor in the nonlinear boost converter system, and v 2f (t) is the nominal value of the power supply voltage in the nonlinear boost converter system at time t; C0 is the capacitance of the capacitor in the nonlinear boost converter system, R f is the nominal value of the load resistance; D1(t) and D2(t) are both time-varying disturbances at time t, v2(t) is the output voltage of the photovoltaic array at time t, and R is the load resistance in the nonlinear boost converter system; Define the state variables as: Where x1 is the total energy stored in the nonlinear boost converter system, and x2 is the rate of change of stored energy; The initial dynamic model of the nonlinear boost converter system is transformed according to the defined state variables, and the final dynamic model of the nonlinear boost converter system is obtained as: In the formula, is the first-order derivative of x1, is the first-order derivative of x2, uav is the intermediate control signal, D3(t) is the mismatch interference at time t, D3(t)=Li1(t)D1(t)+C0v1(t)D2(t); D4(t) is the matching interference at time t, 3. The photovoltaic power generation system voltage stabilization control method according to claim 1, characterized in that: The sliding mode function for introducing mismatched interference estimation is: Where s is the sliding mode variable, x2 is the rate of change of stored energy, c1 is a constant greater than 0, x1 is the total energy stored in the nonlinear boost converter system, x1ref is the reference energy, is the estimated value of D3(t), and D3(t) is the mismatch interference at time t.

4. The photovoltaic power generation system voltage stabilization control method according to claim 1, characterized in that: The new sliding mode function is: In the formula, s * is the new sliding mode variable, x2 is the rate of change of stored energy, c1 is a constant greater than 0, x 1ref is the reference energy, is the estimated value of D3(t), D3(t) is the mismatch interference at time t, α is a constant greater than 0, and s(0) is the initial value of the sliding mode function.

5. The photovoltaic power generation system voltage stabilization control method according to claim 1, characterized in that: The extended disturbance observer for mismatched disturbance and matched disturbance is established, including: The disturbance observer for mismatched disturbance is established as: In the formula, is the estimated value of D3, D3 is the mismatch interference, for The estimated value of is the first-order derivative of D3, w 11 and w 12 are auxiliary variables of mismatched interference, w 11 The first derivative of w 12 The first derivative of 11 and h 12 are all constants greater than 0, x1 is the total energy stored in the nonlinear boost converter system, and x2 is the rate of change of the stored energy; The disturbance observer matching the disturbance is established as: In the formula, is the estimated value of D4, D4 is the matching interference, for The estimated value of is the first-order derivative of D4, w 21 and w 22 are auxiliary variables matching interference, w 21 The first derivative of w 22 The first derivative of 21 and h 22 are all constants greater than 0, u av is the intermediate control signal; The estimation error is defined as: and In the formula, D i The estimation error of for Estimation error of , i = 3, 4; According to the estimation error, the disturbance observer of the mismatched disturbance and the disturbance observer of the matched disturbance, the expression of the first-order derivative of the estimation error is determined as: In the formula, for The first-order derivative of , H is a positive definite matrix; By taking the derivative of the first-order derivative of the estimation error, the extended disturbance observer of the mismatched disturbance and the matched disturbance is obtained as: In the formula, for The second-order derivative of D i The second derivative of H * is a positive definite matrix.

6. The photovoltaic power generation system voltage stabilization control method according to claim 1, characterized in that: Based on the new sliding mode function, dynamic model, extended disturbance observer for mismatched disturbance and matched disturbance, the control law of the nonlinear boost converter system is determined, including: Derivative of the new sliding mode function: In the formula, For * The first derivative of , s * is the new sliding mode variable, is the second-order derivative of x2, x2 is the rate of change of stored energy, c1 is a constant greater than 0, is the first-order derivative of x1, x1 is the total energy stored in the nonlinear boost converter system, for The first derivative of is the estimated value of D3, D3 is the mismatch interference, α is a constant greater than 0, s(0) is the initial value of the sliding mode function, and t is the time; Substituting the dynamic model of the nonlinear boost converter system into the derived sliding mode function, the deformed sliding mode function is obtained as follows: In the formula, u av is the intermediate control signal, and D4 is the matching interference; According to the deformed sliding mode function and hyperbolic tangent function, the expression of the intermediate control signal is determined as follows: In the formula, is the estimated value of D4, k1 and k2 are both constants greater than 0; According to the expression of the intermediate control signal and the dynamic model, the control law of the nonlinear boost converter system is determined as: Where u is the control input signal, v 2f is the nominal value of the power supply voltage in the nonlinear boost converter system, L is the inductance of the filter inductor in the nonlinear boost converter system, v1 is the output voltage of the capacitor in the nonlinear boost converter system, R f is the nominal value of the load resistance, C0 is the capacitance of the capacitor in the nonlinear boost converter system, v2 is the PV array output voltage, and i1 is the inductor current.

7. The photovoltaic power generation system voltage stabilization control method according to claim 1, characterized in that: The operating parameters include: an inductor current and an output voltage of a capacitor in a nonlinear boost converter system; The stored energy state parameters include: total energy stored in the nonlinear boost converter system and a rate of change of stored energy.

8. The photovoltaic power generation system voltage stabilization control method according to claim 6, characterized in that: According to the real-time sliding mode variable and the real-time matching disturbance, the duty cycle of the PWM is adjusted by using the control law, specifically including: According to the real-time sliding mode variable and the real-time matching disturbance, the real-time intermediate control signal is calculated by using the expression of the intermediate control signal; According to the real-time intermediate control signal, the control input signal is obtained by using the control law; The duty cycle of the PWM is adjusted according to the control input signal.

9. The photovoltaic power generation system voltage stabilization control method according to claim 1, characterized in that: The nonlinear boost converter system includes: a photovoltaic voltage source, a switching device, a diode, a filter inductor, a capacitor and a load resistor; The positive electrode of the photovoltaic voltage source is connected to one end of the filter inductor, and the other end of the filter inductor is respectively connected to the anode of the diode and the source of the switch device; the negative electrode of the photovoltaic voltage source is respectively connected to the drain of the switch device, one end of the capacitor and one end of the load resistor; the gate of the switch device is used to input a control input signal; The cathode of the diode is connected to the other end of the capacitor and the other end of the load resistor, respectively.

10. A photovoltaic power generation system voltage stability control system, characterized in that: The photovoltaic power generation system voltage stability control system is used to execute the photovoltaic power generation system voltage stability control method according to any one of claims 1 to 9, and the photovoltaic power generation system voltage stability control system comprises: an operation state module, a sliding mode controller, an extended disturbance observer, a control module and a PWM module; The operating state module is connected to the sliding mode controller and the extended disturbance observer respectively; the operating state module is used to obtain the real-time operating parameters of the nonlinear boost converter system, and obtain the real-time storage energy state parameters according to the real-time operating parameters by using the dynamic model of the nonlinear boost converter system; An extended disturbance observer is connected to the sliding mode controller, and the extended disturbance observer is used to determine the real-time mismatch disturbance and matching disturbance according to the real-time storage energy state parameter; The sliding mode controller is connected to the control module; the sliding mode controller is used to determine the real-time sliding mode variable according to the real-time mismatch disturbance using a new sliding mode function; the sliding mode function introduces a mismatch disturbance estimation and an exponential function term; The control module is connected to the PWM module; the control module is used to adjust the duty cycle of the PWM module using a control law according to the real-time sliding mode variable and the real-time matching interference; the control law is determined according to the new sliding mode function, the dynamic model, the extended disturbance observer of the mismatching interference and the matching interference; The PWM module is connected to the switching device in the nonlinear boost converter system; the PWM module is used to drive the switching device in the nonlinear boost converter system according to the adjusted duty cycle, change the conduction time, and make the output voltage of the capacitor in the nonlinear boost converter system track to the reference voltage of the nonlinear boost converter system.

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