Optical storage system sliding mode active-disturbance-rejection control method considering source load power fluctuation

Abstract

The invention belongs to the technical field of photovoltaic energy storage system control, and particularly relates to an optical storage system sliding mode active-disturbance-rejection control method considering source load power fluctuation. The method comprises the following steps: S1, considering the fluctuation of source load power in a light storage system, analyzing the charge and discharge behaviors of a storage battery, constructing a mathematical model of a storage battery-photovoltaic system, and obtaining a corresponding state equation; s2, designing a controller structure according to the mathematical model constructed in the step S1 based on sliding mode control and active disturbance rejection control principles, and designing a current loop; and S3, designing each part of a voltage loop, and introducing the parts into the controller structure designed in the step S2. By adopting the technical means, when the source / load power fluctuates, the stable control of the bus voltage of the optical storage system and the reasonable distribution of the power are realized, so that the optical storage system operates safely and stably.

Description

Technical Field

[0001] The present invention belongs to the technical field of photovoltaic energy storage system control, and in particular relates to a sliding mode self-disturbance rejection control method for a photovoltaic energy storage system taking into account source-load power fluctuations. Background Art

[0002] The advantage of photovoltaic power generation is that it can directly convert solar energy into electrical energy, and the operation process is pollution-free, so it is regarded as an important direction for future energy development. However, as the "source" side of the photovoltaic power generation system, the output power of the photovoltaic module will be affected by the intensity of light and temperature, which is uncertain. As the "load" side of the photovoltaic power supply system, the user load has a large uncertainty in the amount of power consumption due to the variety of load types and user electricity usage habits. The introduction of energy storage systems provides important technical support for the application of photovoltaic power generation. Through energy storage equipment, the system can store electrical energy when there is excess power generation and release electrical energy when there is insufficient power generation, thereby balancing the mismatch between power generation and power consumption. Therefore, it is very important to control the photovoltaic storage system.

[0003] At present, the control methods for photovoltaic storage systems mainly include PI control, sliding mode control, linear anti-disturbance control, etc. If sliding mode control is used alone, although it is suitable for systems with strong uncertainty and disturbance, the problem of chattering needs to be solved; the response speed of traditional PI control depends on parameter setting. Although the response speed can be adjusted within a certain range, it is difficult to adjust quickly when the system state and external disturbances change greatly. At the same time, when sudden disturbances occur externally, the controller needs a certain amount of time to adjust the output to restore to the set point; linear anti-disturbance control has good anti-disturbance performance and robustness, and is suitable for processing complex nonlinear or time-varying systems. However, its traditional differential link usually assumes that the input signal is smooth, so there will be problems of poor accuracy and sensitivity to signals; at the same time, the anti-disturbance ability mainly depends on the observer (ESO), and its coefficient is too large, which will increase the impact of high-frequency noise on the system, thereby limiting the upper limit of the anti-disturbance ability of the photovoltaic storage system. Therefore, in view of the defects in the current existing technology, it is necessary to conduct research and analysis to provide a composite control scheme to make the photovoltaic storage system have higher robustness when the source and load power fluctuates. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a sliding mode anti-disturbance control method for a photovoltaic storage system taking into account source-load power fluctuations.

[0005] To achieve the above object, the present invention adopts the following technical solution:

[0006] A sliding mode anti-disturbance control method for a photovoltaic storage system considering source-load power fluctuations comprises the following steps:

[0007] Step S1, considering the power fluctuation of the source and load in the photovoltaic storage system, analyzing the charging and discharging behavior of the battery, constructing a mathematical model of the battery-photovoltaic system, and obtaining the corresponding state equation;

[0008] Step S2, based on the sliding mode control and active disturbance rejection control principles, design the controller structure and the current loop according to the mathematical model constructed in step S1;

[0009] Step S3, designing various parts of the voltage loop and introducing them into the controller structure designed in step S2, so as to achieve stable control of the bus voltage of the light storage system and reasonable distribution of power when the source load power fluctuates.

[0010] Furthermore, in step S1, the source-load power volatility in the photovoltaic storage system is considered, the charging and discharging behavior of the battery is analyzed, a mathematical model of the battery-photovoltaic system is constructed, and the corresponding state equation is obtained, specifically: the charging and discharging behavior of the lithium battery is analyzed, and the topology of the half-bridge bidirectional Buck / Boost converter of the photovoltaic system is analyzed, a mathematical model of the battery-photovoltaic system is constructed, and the corresponding state equation is obtained.

[0011] Furthermore, the charging and discharging behavior of the lithium battery is analyzed, and the topology of the half-bridge bidirectional Buck / Boost converter of the photovoltaic system is analyzed, a mathematical model of the battery-photovoltaic system is constructed, and the corresponding state equation is obtained. The specific steps are as follows:

[0012] Step S11, analyzing the charging and discharging behavior of the battery, establishing its equivalent circuit model, and obtaining the output characteristic equation:

[0013]

[0014] Where U oc is the open circuit voltage of the battery, U p and U B are the terminal voltages of the RC circuit and the battery, respectively; I is the battery current; R1, R2 and C are the internal resistance, polarization resistance and polarization capacitance of the battery, respectively;

[0015] The battery state of charge is calculated using the ampere-hour integration method, and the following formula is obtained:

[0016]

[0017] In the formula, SOC(t s ) indicates the state of charge of the battery, E Bmax represents the total energy of the battery, t0 and t s are the start time and end time of the integration process, I bIndicates the output current of the battery. When it is a positive number, the battery is in a discharging state, otherwise the battery is in a charging state;

[0018] Step S12: Analyze the charging and discharging states of the half-bridge bidirectional Buck / Boost converter interface circuit of the photovoltaic system, and obtain the equivalent state equation:

[0019]

[0020] Where L is the inductance, C B and C dc is the filter capacitor, U B and U dc are the energy storage side voltage and the DC bus voltage respectively, I B and I L are the energy storage side current and the inductor current, R eq is the equivalent load on the bus side, which can be expressed as:

[0021]

[0022] Where U dc is the DC bus voltage, R is the load, P CPL It is the sum of the photovoltaic power output power and the power consumed on the DC bus.

[0023] Furthermore, in step S2, based on the sliding mode control and active disturbance rejection control principles, the controller structure is designed according to the mathematical model constructed in step S1, and the current loop is designed. The current loop design is specifically as follows:

[0024] The current loop adopts sliding mode control, and the mathematical model of sliding mode control is:

[0025]

[0026] Where U dc is the DC bus voltage, I L is the inductor current, f(U dc ,I L ) is the nonlinear relationship between the DC bus voltage and the inductor current, ω1 is the effect of the photovoltaic storage system on the current;

[0027] Set the sliding surface s to:

[0028] s=I L -I Lref (6)

[0029] In the formula, I L is the inductor current, I Lref is its reference value;

[0030] Design u1 so that the system state tends to the sliding surface and remains on it, which can be specifically expressed as:

[0031]

[0032] Where u1 is the corresponding sliding mode control law, b i is the compensation coefficient, k i is the main control parameter, sgn(e) is Symbolic function.

[0033] Furthermore, in step S3, the designing of each part of the voltage loop specifically includes the following steps:

[0034] Step S31, designing a sliding mode differential estimator;

[0035] Step S32, designing a sliding mode extended state observer;

[0036] Step S33: design an error feedback controller.

[0037] Further, in step S31, the design of the sliding mode differential estimator is specifically:

[0038] The sliding mode differential estimator model is described by the following differential equation:

[0039]

[0040] Where x1 is the output signal of the sliding mode differential estimator, x2 is the derivative estimate of the output signal, k is the switching gain used to adjust the strength of the sliding mode differential, sgn(e) is the sign function, and U dref is the DC bus voltage reference value;

[0041] Define the sliding surface:

[0042] s=x1-U dcref (9)

[0043] When s = 0, the system moves on the sliding surface so that x1 tracks U dref ;

[0044] By discretizing the above continuous system, we can obtain:

[0045]

[0046] Where k is the switching gain, T s is the sampling period.

[0047] Further, in step S32, the designing of the sliding mode extended state observer specifically includes the following steps:

[0048] Step S321: The nonlinear function expression of the DC bus voltage input and output is:

[0049]

[0050] Where L is the inductance, C dc is the filter capacitor, U dc is the DC bus voltage, I L is the inductor current, R eq is the equivalent load on the bus side, ω represents the disturbance to the system;

[0051] Define the perturbation function f1(U dc ,ω,t) and control quantity gain b, which is expressed as:

[0052]

[0053] In formula (12), f1(U dc ,ω,t) is the disturbance function, b is the control gain;

[0054] Arrange formula (11) and (12) to obtain the system input U dc and system output I L The linear combination expression is:

[0055]

[0056] The control gain b is an inherent parameter of the system and it is difficult to obtain its actual value. Therefore, let b0 be the estimated value of b, and we get:

[0057]

[0058] Where b0 is the estimated value of b;

[0059] Step S322, take state variable x1=U dc , x2=f, let vector x=[x1,x2], and the state space equation of the system is:

[0060]

[0061] in C=

[10] ,D=[0],

[0062] Let the state vector z = [z1, z2], where the state variable z1 is used to track the DC bus voltage U dc , the state variable z2 is used to track the total disturbance; the linear extended state observer is expressed in the following state space equation form:

[0063]

[0064] where F = [β1, β2] T , β1 and β2 are the gains of error feedback;

[0065] Using the pole placement method and performing a Laplace transform, we get:

[0066]

[0067] Where ω0 is the bandwidth parameter;

[0068] Step S323: The state space equation of the sliding mode extended state observer is:

[0069]

[0070] In the formula, k1 and k2 are sliding mode gain parameters, and L is the controller gain. Adjust k1 and k2 to make the sliding mode extended state observer characteristics match formula (17);

[0071] According to the error state, u2 is designed to make the system state tend to the sliding surface and remain on it, which is specifically expressed as:

[0072]

[0073] Where: u2 is the corresponding sliding mode control law, represents the compensation for the total disturbance, k u is the error compensation coefficient, and sgn(e) is the sign function.

[0074] Further, in step S33, the design error feedback controller is specifically:

[0075] The error feedback controller consists of two parts: the disturbance compensation unit and the proportional control unit. Let u0 be the output of the error feedback controller, then the realization form of the disturbance compensation unit is:

[0076]

[0077] In the formula, I Lref is the inductor current reference value; u0 is the output of the error feedback controller, b0 is the estimated value of the control quantity gain b, u0 / b L represents the ideal control signal before disturbance compensation; z2 is the state variable used to track the total disturbance, and -z2 / b L The role of is to reduce the total disturbance effect estimated by the sliding mode extended state observer;

[0078] Substituting equation (20) into (14), taking the limit, we get:

[0079]

[0080] The system is simplified to a single integral system, so the following proportional controller is designed:

[0081] u0=ω c (x1-z1) (22)

[0082] In equations (21) and (22), z1 is used to track the DC bus voltage U dc The state variable, f1(U dc ,ω,t) is the perturbation function, ω c is the controller gain.

[0083] The present invention also provides a computer storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the sliding mode anti-disturbance control method of the photovoltaic storage system considering the power fluctuation of the source and load are implemented.

[0084] Compared with the prior art, the present invention has the following beneficial technical effects:

[0085] (1) Different from the traditional approach of directly adopting a single battery or photovoltaic system model, this patent truly considers the power fluctuations on the "source" side and the load side, utilizes the power interaction between the energy storage module and the DC bus, and uses a bidirectional interface converter as an interface to study the charging and discharging behavior of the battery from a mechanism perspective, thereby establishing a battery-photovoltaic system joint model to improve the modeling accuracy of the photovoltaic storage system.

[0086] (2) In actual solar energy storage control systems, the traditional differential link is very sensitive to noise and easily amplifies high-frequency noise in the signal, resulting in a decrease in the performance of the control system. The present invention innovatively proposes a differential solution method based on sliding mode control, which not only solves the sensitivity problem of the differential link, but also enhances the robustness and anti-noise ability of the system.

[0087] (3) Based on the self-disturbance rejection control, the present invention introduces a sliding mode control method, specifically a sliding mode differential estimator and a sliding mode extended state observer, which improves the parameter setting of the control system. Therefore, compared with the traditional PI control method, the sliding mode self-disturbance rejection control method of the present invention can improve the energy utilization rate, response speed and robustness of the photovoltaic storage system, so that it can cope with the power fluctuations of the source and load. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] Figure 1 is a typical structural diagram of the optical storage system of the present invention;

[0089] Figure 2 A model diagram of a lithium-ion battery of the present invention;

[0090] Figure 3 This is a topological diagram of the energy storage side interface of the half-bridge bidirectional charge / discharge converter used in the present invention;

[0091] Figure 4 is a circuit structure diagram of different switch states under the charge / discharge state of the present invention,

[0092] Figure 4 (a) is Buck mode, VT1 is turned on, VT2 is turned off,

[0093] Figure 4 (b) Buck mode, VT1 is turned off, VT2 is turned off,

[0094] Figure 4 (c) is the Boost mode, VT1 is turned off, VT2 is turned on,

[0095] Figure 4 (d) Boost mode, VT1 is turned off, VT2 is turned off;

[0096] Figure 5 The design block diagram of the optical storage system controller of the present invention;

[0097] Figure 6 is the photovoltaic array output power P in the embodiment PV The simulation result diagram is

[0098] Figure 6 (a) is the external environment change curve, Figure 6 (b) is the photovoltaic panel output power P PV changes;

[0099] Figure 7 is the power P of the energy storage battery under different control strategies in the embodiment B The SOC change diagram,

[0100] Figure 7 (a) is the power P of the energy storage battery B changes, Figure 7 (b) The change of SoC of energy storage battery;

[0101] Figure 8 is the DC bus voltage U under different control strategies in the embodiment dc The simulation result diagram of

[0102] Fig. 9 is a constant power load power variation curve in the embodiment;

[0103] Fig.10 is the power P of the energy storage battery under different load powers in the embodiment B The simulation results of SOC are shown in Figure 2.

[0104] Fig.10 (a) is the power P of the battery B changes, Fig.10 (b) is the change of battery SoC;

[0105] Fig.11 is the DC bus voltage U under different load powers in the embodiment dc 's change graph. DETAILED DESCRIPTION

[0106] The present invention is further explained below in detail with reference to the accompanying drawings so that those skilled in the art can have a deeper understanding of the present invention and be able to implement it.

[0107] Different from the traditional practice of directly using a single battery or photovoltaic system model, the present invention truly considers the power fluctuations on the "source" side and the "load" side, uses the power interaction between the energy storage module and the DC bus, and uses a bidirectional interface converter as an interface to study the charging and discharging behavior of the battery from a mechanism perspective, thereby establishing a battery-photovoltaic system joint model. Based on the principle of self-disturbance rejection control, a corresponding self-disturbance rejection controller is designed according to the established mathematical model; the sliding mode differential estimator and the sliding mode extended state observer are introduced into the self-disturbance rejection controller to achieve stable control of the bus voltage of the photovoltaic storage system and reasonable power distribution when the source and load power fluctuates, so that the photovoltaic storage system can operate safely and stably.

[0108] The present invention provides a sliding mode anti-disturbance control method for a photovoltaic storage system considering source-load power fluctuations. Figures 1 to 5 , including the following steps:

[0109] Step S1: Considering the power fluctuation of the source and load in the photovoltaic storage system, the charging and discharging behavior of the battery is analyzed, a mathematical model of the battery-photovoltaic system is constructed, and the corresponding state equation is obtained.

[0110] See also Figure 1 The photovoltaic storage system mainly includes photovoltaic, energy storage and load modules; the main body of the energy storage module is a battery pack, which transmits electric energy bidirectionally with the DC bus through a DC-DC converter; at the same time, the "source" side (photovoltaic module) and the "load" side (user load) are also connected to the DC bus through the converter.

[0111] In the photovoltaic storage system, lithium batteries are mostly used as storage batteries. Their working principle is based on the movement of lithium ions between the positive and negative electrodes of the battery through the electrolyte to achieve energy storage and release; the power interaction control between the energy storage module and the DC bus often uses a half-bridge bidirectional Buck / Boost converter. Therefore, in the present invention, the charging and discharging behavior of the lithium battery is analyzed, and the topological structure of the half-bridge bidirectional Buck / Boost converter of the photovoltaic system is analyzed, a mathematical model of the battery-photovoltaic system is constructed, and the corresponding state equation is obtained.

[0112] The specific steps of step S1 are as follows:

[0113] Step S11, see Figure 2 The modeling of lithium batteries includes electrochemical models and equivalent circuit models. The battery charging and discharging behavior is analyzed, and its equivalent circuit model is established to obtain the output characteristic equation:

[0114]

[0115] Where U oc is the open circuit voltage of the battery, U p and U B are the terminal voltages of the RC circuit and the battery, I is the battery current, R1, R2 and C are the internal resistance, polarization resistance and polarization capacitance of the battery, respectively.

[0116] In order to accurately estimate the battery's state of charge (SOC), the ampere-hour integration method is used for calculation:

[0117]

[0118] Where E Bmax represents the total energy of the battery, t0 and t s are the start time and end time of the integration process respectively; I b Indicates the output current of the battery. When it is a positive number, the battery is in a discharging state, otherwise the battery is in a charging state.

[0119] Step S12: Analyze the charging and discharging states of the half-bridge bidirectional Buck / Boost converter interface circuit of the photovoltaic system to obtain an equivalent state equation, see Figure 3 .

[0120] The energy storage side interface circuit is analyzed in two states: charging and discharging. For the specific analysis process, please refer to Figure 4 , the equivalent state equation can be obtained as:

[0121]

[0122] Where L is the inductance, C B and C dc is the filter capacitor, U B and U dc are the energy storage side voltage and the DC bus voltage respectively, I B and I L are the energy storage side current and the inductor current respectively. eq is the equivalent load on the bus side, which can be expressed as:

[0123]

[0124] Where Udc is the DC bus voltage, R is the load, P CPL P S (Photovoltaic power output) and P L (power consumption on the DC bus). eq When it is greater than zero, it means that the bus side is consuming power. At this time, the photovoltaic storage system is mainly affected by the "source" side; otherwise, it is affected by the "load" side.

[0125] Step S2: Based on the principles of sliding mode control and active disturbance rejection control, the controller structure is designed according to the mathematical model constructed in step S1, and the current loop is designed.

[0126] See also Figure 5 , is a design block diagram of the photovoltaic storage system controller. The controller structure includes two parts: voltage loop and current loop. The current loop adopts sliding mode control and the voltage loop adopts active disturbance rejection control structure. The specific design steps of the voltage loop are described in step S3.

[0127] The current loop design is specifically as follows:

[0128] Different from the traditional PI control, the current loop adopts sliding mode control to achieve fast tracking and response to the inductor current. The mathematical model of sliding mode control is:

[0129]

[0130] Where U dc is the DC bus voltage, I L is the inductor current, f(U dc ,I L ) is the nonlinear relationship between the DC bus voltage and the inductor current, and ω1 is the impact of the photovoltaic storage system on the current.

[0131] Set the sliding surface s to:

[0132] s=I L -I Lref (6)

[0133] In the formula, I L is the inductor current, I Lref For I L Reference value.

[0134] Design u1 so that the system state tends to the sliding surface and remains on it, which can be specifically expressed as:

[0135]

[0136] Where u1 is the corresponding sliding mode control law, b i is the compensation coefficient, which is used to offset the interference of the system itself; k iis the main control parameter, which determines the effect of sliding mode control; sgn(e) is Symbolic function.

[0137] Step S3, designing various parts of the voltage loop and introducing them into the controller structure designed in step S2, so as to achieve stable control of the bus voltage of the light storage system and reasonable distribution of power when the source and load power fluctuates.

[0138] Design the voltage loop and adopt the anti-disturbance control structure. The controlled object is the DC bus voltage U dc , smoothed by a sliding mode differential estimator, which is mainly used to extract the true dynamics of the system from the noise. After smoothing, the sliding mode extended state observer is used to estimate the external disturbance and the uncertainty of the system. The sliding mode extended state observer is a technology that combines the sliding mode control idea with the extended state observer. It can not only estimate the system state, but also predict the impact of disturbances on the system. Finally, the control quantity is compensated by the error feedback controller. The error feedback controller is adjusted according to the system error (i.e., the deviation between the target and the actual state), and the compensation mechanism is used to correct the output of the system.

[0139] Designing the various parts of the voltage loop includes the following steps:

[0140] Step S31: design a sliding mode differential estimator, specifically:

[0141] The sliding mode differential estimator model can be described by the following differential equation:

[0142]

[0143] Where x1 is the output signal of the sliding mode differential estimator, x2 is the derivative estimate of the output signal, k is the switching gain used to adjust the strength of the sliding mode differential, sgn(e) is the sign function, and U dref is the DC bus voltage reference value.

[0144] Define the sliding surface:

[0145] s=x1-U dcref (9)

[0146] When s = 0, the system moves on the sliding surface so that x1 tracks U dref .

[0147] The sliding mode differential estimator is usually implemented in a discretized form. By discretizing the above continuous system, we can obtain:

[0148]

[0149] In the formula, k is the switching gain. Increasing the k value can improve the response speed and accuracy of the differential estimation.s is the sampling period, which determines the discretization accuracy.

[0150] Step S32: design a sliding mode extended state observer. The design of the sliding mode extended state observer is improved based on a general linear extended state observer. The specific improvement includes the following steps:

[0151] Step S321: Since the outer loop controlled variable is the DC bus voltage U dc The controlled variable of the inner loop is the inductor current I L The speed of change is slower and the amplitude of change is smaller. Therefore, the interface converter model expressed by formula (3) can derive the nonlinear function expression of the DC bus voltage input and output as follows:

[0152]

[0153] Where L is the inductance, C dc is the filter capacitor, U dc is the DC bus voltage, I L is the inductor current, R eq is the equivalent load on the bus side, and ω represents the disturbance suffered by the system.

[0154] Define the perturbation function f1(U dc ,ω,t) and control quantity gain b, which is expressed as

[0155]

[0156] In formula (12), f1(U dc ,ω,t) is the disturbance function, and b is the control gain.

[0157] By rearranging formulas (11) and (12), we can obtain the system input U dc and system output I L The linear combination expression is:

[0158]

[0159] Since the control gain b is an inherent parameter of the system and it is difficult to obtain its actual value, we can let b0 be the estimated value of b and obtain:

[0160]

[0161] Where b0 is the estimated value of b.

[0162] Step S322, take state variable x1=U dc , x2=f, let the vector x=[x1,x2], and then we can get the state space equation of the system in the form of:

[0163]

[0164] in C=

[10] ,D=[0],

[0165] Let the state vector z = [z1, z2], where the state variable z1 is used to track the DC bus voltage U dc , the state variable z2 is used to track the total disturbance. Therefore, the linear extended state observer can be expressed in the form of the following state space equation:

[0166]

[0167] where F = [β1, β2] T , β1 and β2 are the gains of error feedback.

[0168] Using the pole placement method and performing a Laplace transform we can get:

[0169]

[0170] Where ω0 is the bandwidth parameter.

[0171] Step S323: The state space equation of the sliding mode extended state observer is:

[0172]

[0173] In the formula, k1 and k2 are sliding mode gain parameters, and L is the controller gain; k1 and k2 are adjusted so that the characteristics of the sliding mode extended state observer match formula (17).

[0174] Similarly, according to the error state, u2 is designed to make the system state tend to the sliding surface and remain on it, which is specifically expressed as:

[0175]

[0176] Where: u2 is the corresponding sliding mode control law, represents the compensation for the total disturbance, k u is the error compensation coefficient, and sgn(e) is the sign function.

[0177] Step S33, design an error feedback controller, which consists of an interference compensation unit and a proportional control unit. Let u0 be the output of the error feedback controller, and the implementation form of the interference compensation unit is:

[0178]

[0179] In the formula, I Lrefis the inductor current reference value; u0 is the output of the error feedback controller, b0 is the estimated value of the control quantity gain b, u0 / b L represents the ideal control signal before disturbance compensation; z2 is the state variable used to track the total disturbance, and -z2 / b L The role of is to reduce the total disturbance effect estimated by the sliding mode extended state observer.

[0180] Substituting equation (20) into (14), taking the limit, we get:

[0181]

[0182] It can be seen that the system is simplified to a single integral system, so the following proportional controller can be designed:

[0183] u0=ω c (x1-z1) (22)

[0184] In equations (21) and (22), z1 is used to track the DC bus voltage U dc The state variable, f1(U dc ,ω,t) is the perturbation function, ω c is the controller gain.

[0185] The present invention also provides a computer storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the sliding mode anti-disturbance control method of the photovoltaic storage system considering the power fluctuation of the source and load are implemented.

[0186] Example:

[0187] The specific implementation is further described below in conjunction with the examples. The present invention uses corresponding simulation software to perform simulation verification according to the above implementation to evaluate the control effect of the control method of the present invention, wherein: the photovoltaic module, i.e., the "source" side parameter settings are shown in Table 1, and the energy storage side circuit parameters are shown in Table 2. Figure 1 , which is the typical structure of the photovoltaic storage system, a simulation model of the photovoltaic storage system is built, and the power fluctuations on the "source" side and the "load" side under the influence of light and temperature are considered respectively, and simulation analysis is carried out.

[0188] Table 1 Photovoltaic panel parameters

[0189]

[0190] Table 2 Energy storage module circuit parameters

[0191]

[0192] According to the voltage and power requirements, the photovoltaic panels are combined into a 2×4 photovoltaic array. The photovoltaic array receives uniform light, and the power consumed by the constant power load is fixed at 250W. The simulation time is set to 1.5s, and the changes in the external environment refer to Figure 6 As shown in (a), the temperature is reduced from 25°C to 10°C at the simulation time t = 0.5s, and the light intensity is increased from 1000W / m 2 Reduced to 300W / m 2 .

[0193] It is worth noting that the switching gain k of the sliding mode differential estimator in S3 of the present invention is set to 10, and the sampling period T s Take 5ms; the bandwidth parameter ω0 in the sliding mode extended state observer is 20Hz; the sliding mode gain parameter k1 is 40, k2 is 400; the controller gain L is 2; the error compensation coefficient k u Take 2. In the proportional controller, ω c Take 15.

[0194] The simulation results can be found in Figure 6 to Figure 8 , where the output power of the photovoltaic array changes as Figure 6 (b), the battery output power and SOC change as Figure 7 , DC bus voltage U dc Changes such as Figure 8 .

[0195] See also Figure 6 (b) is the change of the output power of the photovoltaic array. It can be seen that the temperature change at t = 0.5s has little effect on the maximum power point of the photovoltaic array. The temperature reduction causes a slight increase in the maximum photovoltaic power. As the light intensity decreases significantly at t = 1s, the output power of the photovoltaic array also decreases significantly. In addition, under the control of the present invention, the maximum power of the photovoltaic array after t = 1s is slightly higher than that under the traditional control.

[0196] See also Figure 7 , is the change of battery output power and SOC. The output power of the photovoltaic array and the output power of the battery under the control method of the present invention have smaller fluctuations than those under the PI double closed-loop control strategy. From t=0 to t=1s, the power provided by the photovoltaic array is greater than the power consumed by the load, so the power on the battery side is less than zero, it is in a charging state, and the SOC rises steadily; after t=1s, the power provided by the photovoltaic array is less than the power consumed by the load, the power on the battery side is greater than zero, it is in a discharging state, and the SOC decreases steadily. In addition, Figure 7 It can be seen from (b) that the battery SOC loss under the control method of the present invention is smaller than that under the traditional control.

[0197] See also Figure 8 , is the DC bus voltage Udc Under the control method of the present invention, when the external environment suddenly changes at t=0.5s and t=1s, the DC bus voltage of the system has a smaller overshoot and a shorter steady-state time. The detailed control performance data of the two are shown in Table 3.

[0198] Table 3 Performance comparison of two control methods considering environmental changes

[0199]

[0200] See also Fig. 9 , is the power change curve of constant power load. That is, the power on the "load" side fluctuates, and the power P of the constant power load Load according to Fig. 9 The curve shown in the figure is changed, that is, at t = 0.5s, P Load The power increases from 100W to 300W, and a sinusoidal disturbance with an amplitude of 30W is introduced at t=1s.

[0201] See also Fig.10 , is the power P of the energy storage battery under different load powers B Simulation results of SOC. It can be seen that the control method of the present invention has a better control effect on the energy storage side when the load side changes compared to the traditional control. Under the control method of the present invention, the battery power has less jitter, making the battery charging and discharging process more stable. In addition, the battery charging power reaches a larger value after reaching a steady state, and the battery SOC gradually increases, which improves the energy utilization rate. Under the same situation, under traditional control, the battery SOC gradually decreases.

[0202] See also Fig.11 , is the DC bus voltage U under different load powers dc It can be seen that under the control method of the present invention, when the load suddenly changes at t = 0.5s and t = 1s, the DC bus voltage U dc Both have smaller overshoot and shorter steady-state time. The detailed control performance data of the two are shown in Table 4.

[0203] Table 4 Comparison of simulation performance of two control methods under load changes

[0204]

[0205] In summary, when the source load power fluctuates, the control method of the present invention significantly reduces the overshoot and adjustment time of the photovoltaic storage system compared with the traditional method, and can quickly restore the stability of the bus voltage and power in the photovoltaic storage system. Thus, the stable control of the bus voltage of the photovoltaic storage system and the reasonable distribution of power are achieved, so that the photovoltaic storage system can operate safely and stably.

[0206] It should be noted that the embodiments of the present invention are preferred implementations rather than limiting the present invention. It should be noted that, for those skilled in the art, without departing from the principles of the present invention, the specific implementations may be modified or some technical features may be replaced by equivalents, which shall all be deemed to be within the scope of the present invention.

Claims

1. A sliding mode anti-disturbance control method for a photovoltaic storage system considering source-load power fluctuations, characterized in that: The following steps are involved: Step S1, considering the power fluctuation of the source and load in the photovoltaic storage system, analyzing the charging and discharging behavior of the battery, constructing a mathematical model of the battery-photovoltaic system, and obtaining the corresponding state equation; Step S2, based on the sliding mode control and active disturbance rejection control principles, design the controller structure and the current loop according to the mathematical model constructed in step S1; Step S3, designing various parts of the voltage loop and introducing them into the controller structure designed in step S2, so as to achieve stable control of the bus voltage of the light storage system and reasonable distribution of power when the source load power fluctuates.

2. The sliding mode anti-disturbance control method for a photovoltaic storage system considering source-load power fluctuation according to claim 1 is characterized in that: In step S1, the source-load power fluctuation in the photovoltaic storage system is considered, the battery charging and discharging behavior is analyzed, a mathematical model of the battery-photovoltaic system is constructed, and the corresponding state equation is obtained, specifically: the charging and discharging behavior of the lithium battery is analyzed, and the topology of the photovoltaic system half-bridge bidirectional Buck / Boost converter is analyzed, a mathematical model of the battery-photovoltaic system is constructed, and the corresponding state equation is obtained.

3. The sliding mode anti-disturbance control method for a photovoltaic storage system considering source-load power fluctuation according to claim 2 is characterized in that: The charging and discharging behavior of the lithium battery is analyzed, and the topology of the half-bridge bidirectional Buck / Boost converter of the photovoltaic system is analyzed, a mathematical model of the battery-photovoltaic system is constructed, and the corresponding state equation is obtained. The specific steps are as follows: Step S11, analyzing the charging and discharging behavior of the battery, establishing its equivalent circuit model, and obtaining the output characteristic equation: Where U oc is the open circuit voltage of the battery, U p and U B are the terminal voltages of the RC circuit and the battery, respectively; I is the battery current; R1, R2 and C are the internal resistance, polarization resistance and polarization capacitance of the battery, respectively; The battery state of charge is calculated using the ampere-hour integration method, and the following formula is obtained: In the formula, SOC(t s ) indicates the state of charge of the battery, E Bmax represents the total energy of the battery, t0 and t s are the start time and end time of the integration process, I b Indicates the output current of the battery. When it is a positive number, the battery is in a discharging state, otherwise the battery is in a charging state; Step S12: Analyze the charging and discharging states of the half-bridge bidirectional Buck / Boost converter interface circuit of the photovoltaic system, and obtain the equivalent state equation: Where L is the inductance, C B and C dc is the filter capacitor, U B and U dc are the energy storage side voltage and the DC bus voltage respectively, I B and I L are the energy storage side current and the inductor current, R eq is the equivalent load on the bus side, which is specifically expressed as: Where U dc is the DC bus voltage, R is the load, P CPL It is the sum of the photovoltaic power output power and the power consumed on the DC bus.

4. The sliding mode auto-disturbance rejection control method for a photovoltaic storage system considering source-load power fluctuation according to claim 1, characterized in that: In step S2, based on the sliding mode control and active disturbance rejection control principles, the controller structure is designed according to the mathematical model constructed in step S1, and the current loop is designed. The current loop design is specifically as follows: The current loop adopts sliding mode control, and the mathematical model of sliding mode control is: Where U dc is the DC bus voltage, I L is the inductor current, f(U dc ,I L ) is the nonlinear relationship between the DC bus voltage and the inductor current, ω1 is the effect of the photovoltaic storage system on the current; Set the sliding surface s to: s=I L -I Lref (6) In the formula, I L is the inductor current, I Lref is its reference value; Design u1 so that the system state tends to the sliding surface and remains on it, which can be specifically expressed as: Where u1 is the corresponding sliding mode control law, b i is the compensation coefficient, k i is the main control parameter, sgn(e) is Symbolic function.

5. The sliding mode auto-disturbance rejection control method for a photovoltaic storage system considering source-load power fluctuation according to claim 1, characterized in that: In step S3, the design of each part of the voltage loop specifically includes the following steps: Step S31, designing a sliding mode differential estimator; Step S32, designing a sliding mode extended state observer; Step S33: design an error feedback controller.

6. The sliding mode anti-disturbance control method for a photovoltaic storage system considering source-load power fluctuation according to claim 5, characterized in that: In step S31, the design of the sliding mode differential estimator is specifically as follows: The sliding mode differential estimator model is described by the following differential equation: Where x1 is the output signal of the sliding mode differential estimator, x2 is the derivative estimate of the output signal, k is the switching gain used to adjust the strength of the sliding mode differential, sgn(e) is the sign function, and U dref is the DC bus voltage reference value; Define the sliding surface: s=x1-U dcref (9) When s = 0, the system moves on the sliding surface so that x1 tracks U dref ; Discretize the above continuous system and get: Where k is the switching gain, T s is the sampling period.

7. The sliding mode anti-disturbance control method for a photovoltaic storage system considering source-load power fluctuation according to claim 5, characterized in that: In step S32, the design of the sliding mode extended state observer specifically includes the following steps: Step S321: The nonlinear function expression of the DC bus voltage input and output is: Where L is the inductance, C dc is the filter capacitor, U dc is the DC bus voltage, I L is the inductor current, R eq is the equivalent load on the bus side, ω represents the disturbance to the system; Define the perturbation function f1(U dc ,ω,t) and control quantity gain b, which is expressed as: In formula (12), f1(U dc ,ω,t) is the disturbance function, b is the control gain; Arrange formula (11) and (12) to obtain the system input U dc and system output I L The linear combination expression is: The control gain b is an inherent parameter of the system and it is difficult to obtain its actual value. Therefore, let b0 be the estimated value of b, and we get: Where b0 is the estimated value of b; Step S322, take state variable x1=U dc , x2=f, let vector x=[x1,x2], and the state space equation of the system is: in Let the state vector z = [z1, z2], where the state variable z1 is used to track the DC bus voltage U dc , the state variable z2 is used to track the total disturbance; the linear extended state observer is expressed in the following state space equation form: where F = [β1, β2] T , β1 and β2 are the gains of error feedback; Using the pole placement method and performing a Laplace transform, we get: Where ω0 is the bandwidth parameter; Step S323: The state space equation of the sliding mode extended state observer is: In the formula, k1 and k2 are sliding mode gain parameters, and L is the controller gain. Adjust k1 and k2 to make the sliding mode extended state observer characteristics match formula (17); According to the error state, u2 is designed to make the system state tend to the sliding surface and remain on it, which is specifically expressed as: Where: u2 is the corresponding sliding mode control law, represents the compensation for the total disturbance, k u is the error compensation coefficient, and sgn(e) is the sign function.

8. The sliding mode anti-disturbance control method for a photovoltaic storage system considering source-load power fluctuation according to claim 5, characterized in that: In step S33, the design of the error feedback controller is specifically as follows: The error feedback controller consists of two parts: the disturbance compensation unit and the proportional control unit. Let u0 be the output of the error feedback controller, then the realization form of the disturbance compensation unit is: In the formula, I Lref is the inductor current reference value; u0 is the output of the error feedback controller, b0 is the estimated value of the control quantity gain b, u0 / b L represents the ideal control signal before disturbance compensation; z2 is the state variable used to track the total disturbance, and -z2 / b L The role of is to reduce the total disturbance effect estimated by the sliding mode extended state observer; Substituting equation (20) into (14), taking the limit, we get: The system is simplified to a single integral system, so the following proportional controller is designed: u0=ω c (x1-z1) (22) In equations (21) and (22), z1 is used to track the DC bus voltage U dc The state variable f1(U dc ,ω,t) is the perturbation function, ω c is the controller gain.

9. A computer storage medium, characterized in that A computer program is stored on the medium, and when the computer program is executed by the processor, the steps of the sliding mode anti-disturbance control method of the photovoltaic storage system considering the source-load power fluctuation as described in any one of claims 1 to 8 are implemented.

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