Light storage converter backstepping complementary control method based on finite time observer

Abstract

The invention discloses an optical storage converter backstepping complementary control method based on a finite time observer. A sliding mode item is introduced in backstepping control to ensure the robustness of a system; a finite time observer is introduced to estimate a state signal which cannot be directly measured by the system according to a measurable output signal of the system, so that the system performance is improved, and the sampling delay is reduced; an improved reaching law is introduced to reduce the chattering phenomenon which always exists in a sliding mode controller, and finally, a backstepping method is combined with a complementary sliding mode, so that the system has higher precision and better robustness, and has better dynamic response capability.

Description

Technical Field

[0001] The invention belongs to the technical field of power electronics, and in particular relates to a backstepping complementary control method for a photovoltaic storage converter based on a finite time observer. Background Art

[0002] In recent years, China has put forward new requirements for environmental protection and sustainable development, and distributed energy, microgrids and related industries have developed rapidly. Photovoltaic energy storage technology has important functions such as improving the reliability of power supply of power grids and promoting the consumption of new energy. It is a key technology for distributed energy, microgrids and related industries. DC grid systems usually use batteries with energy storage functions to store and release energy. In the process of charging and discharging energy storage batteries, energy storage converters are very important devices. Energy storage converters, also known as bidirectional energy storage inverters, can control the charging and discharging of energy storage equipment and realize the conversion of AC and DC power. They are the core components of photovoltaic energy storage systems.

[0003] In the photovoltaic and energy storage grid-connected system, the photovoltaic and energy storage converter coupled by the DC bus is an important part of the energy storage system. Traditional PI control is difficult to control due to its nonlinearity, strong coupling and multi-input and multi-output characteristics, making it difficult to meet the control requirements. In the face of the high-precision and fast-response control requirements of photovoltaic and energy storage converters, domestic and foreign researchers have proposed control methods such as sliding mode control, anti-disturbance control, fuzzy control and model predictive control. Although fuzzy control is simple to control and does not require a mathematical model of the controlled object, its lack of systematicity and difficulty in parameter adjustment have some impact on the stable control of photovoltaic and energy storage converters. Although model predictive control is good at handling multi-input and multi-output systems, it cannot have sufficient control over photovoltaic and energy storage converters due to its complex calculations and the influence of model errors. Summary of the invention

[0004] The purpose of the present invention is to provide a backstepping complementary control method for a photovoltaic storage converter based on a finite time observer, so as to solve the jitter problem of the existing photovoltaic storage converter and realize stable control of the photovoltaic storage converter.

[0005] The technical solution adopted by the present invention is a back-stepping complementary control method of a photovoltaic storage converter based on a finite time observer, which is used to control a subsequent converter of the photovoltaic storage converter, wherein the subsequent converter includes a three-phase full-bridge inverter, LC The filtering part, the grid-connected part and the load part are implemented according to the following steps: Step 1: Construct an equivalent mathematical model of a three-phase full-bridge inverter; Step 2: Based on the equivalent mathematical model constructed in step 1, a mathematical model in the dq axis rotation coordinate system is constructed through dq transformation; Step 3: Construct the ADRC paradigm and design the finite-time observer; Step 4: The given active power and reactive power are passed through the power outer loop to obtain the current reference value of the dq axis of the current inner loop; Step 5: Design a sliding mode controller and introduce a complementary structure to apply it to sliding mode control; Step 6: Design an improved reaching law and apply it to the complementary sliding mode obtained in step 5; Step 7: Obtain the control output through the sliding mode controller constructed in step 6, use SPWM modulation to get the duty cycle, and apply the duty cycle to the control of the three-phase full-bridge inverter switch tube, thereby realizing signal control of the full-bridge switch.

[0006] The present invention is also characterized in that: Step 1 is as follows: The mathematical model of the three-phase full-bridge inverter in the photovoltaic storage converter in the three-phase coordinate system is: (1) In formula (1), U ao , U bo , U co They are the sum of the voltage of the filter part of the three-phase inverter a, b, c phases and the voltage on the distribution network side. R is the equivalent resistance, i a , i b , i c They are the three-phase output currents of a, b, and c of the three-phase full-bridge inverter, L For the three-phase full-bridge inverter AC measurement filter inductor, e a , e b , e c They are the three-phase voltages a, b, and c on the grid-connected side respectively.

[0007] Step 2 is specifically as follows: Convert equation (1) from the three-phase coordinate system to the two-phase rotating dq coordinate system, and the mathematical model in the dq two-phase coordinate system is: (2) In formula (2), R is the filter resistor of the three-phase full-bridge inverter, ω is the grid voltage angular frequency; u d , u q are the output voltages on the d and q axes respectively, u d =s du dc , u q =s q u dc ;s d 、s q They are the d and q axis switching functions respectively; u dc is the bus voltage on the DC side; e d , e q is the component of the grid voltage on the d and q axes; i Ld , i Lq is the component of the grid-side current in the d and q axes; Deriving equation (2) transforms it into a paradigm that satisfies the second-order auto-disturbance rejection: (3).

[0008] Step 3 is as follows: Define the control object: (4) In formula (4), y is the output of the three-phase inverter system, u is the input control of the system, b For control u The gain, b d , b q That is, the control amount of the d and q axes u d , u q The gain, F is the sum of all disturbances in the system, where y =[ y 1 y 2 ] T ; b =[ b d b q ] T ; u =[ u d u q ] T ; F =[ F d F q] T ,definition F d , F q is the lumped disturbance of d and q axes; definition y 1 =i Ld , y 2 =i Lq , y ref is the output target value, and the output target values ​​on the d and q axes are defined as i Ldref , i Lqref ; Express equation (4) in matrix form: (5) In formula (5), b d , b q , F d , F q It is expressed as: (6) Define the d-axis state variable , , , the q-axis state variable is , , , then the spatial state equation of the system shown in formula (4) is: (7) According to the spatial state expression of formula (7), the form of designing the finite time observer is: (8) In formula (9), k 1 , k 2 , k 3 , k 4 , k 5 , k 6 is the observer gain, , ,in i= 1,2,3,4…; z d1 , z d2 , z d3 , zq1 , z q2 , z q3 They are x d1 , x d2 , x d3 , x q1 , x q2 , x q3 Observed value of .

[0009] Step 4 is as follows: Assume that the active power and reactive power reference values ​​of the photovoltaic power converter are P ref , Q ref When the solar storage converter is running, the inner ring d and q axis current reference values ​​are i Ldref , i Lqref Respectively expressed as: (9).

[0010] Step 5 is specifically as follows: According to the basic recursive idea of ​​backstepping, a virtual control quantity is designed p for: (10) In formula (10), is a constant, virtual control quantity p =[ p 1 , p 2 ], i L =[ i Ld , i Lq ] T .

[0011] Select the Lyapunov function V for: (11) In formula (11), V =[ V 1 , V 2 ] T , e =[ e1 , e 2 ] T , d-axis error e 1 =i Ld i Ldref ， Q-axis error e 2 =i Lq i Lqref。

[0012] Deriving equation (11) and substituting equation (8) and equation (10) into it, we can obtain: (12) make , ,in , is a constant, then: (13) Combining equation (13) with equation (12), we get: (14) From formula (14), we know that when p 1 , p 2 When it converges to 0, the system is stable according to the Lyapunov stability criterion. At this time, the design of the state error feedback rate is simplified to the virtual control quantity p 1 , p 2 The control of s dg , s qg for: (15) In formula (15), λ 1 , λ 2 is a constant, and the design is s dg , s qg Orthogonal complementary sliding surfaces s dc , s qc for: (16) The sliding surface s d , s q It is expressed as: (17) Based on the equivalent control method, the equivalent control law of d and q axes is designed. u deq , u qeq for: (18).

[0013] Step 6 is specifically as follows: The improved reaching law is used as the switching control law of sliding mode ADRC, that is, u dsw , u qsw for: (19) Combining equation (18) and equation (19) gives the control law of the sliding mode controller d and q axes: u d , u q for: (20).

[0014] In formula (19), .

[0015] The beneficial effects of the present invention are: The present invention is based on a backstepping complementary control method for a photovoltaic energy storage converter based on a finite-time observer. A sliding mode term is introduced in the backstepping control to ensure the robustness of the system. A finite-time observer is introduced to estimate a state signal of the system that cannot be directly measured based on the measurable output signal of the system, thereby improving system performance and reducing sampling delay. An improved reaching law is introduced to reduce the chattering phenomenon that has always existed in the sliding mode controller. Finally, the backstepping method is combined with a complementary sliding mode, so that the system has higher accuracy and better robustness, and has better dynamic response capability. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is the overall structure diagram of the photovoltaic storage converter; Figure 2 It is a control block diagram of the backstepping complementary control method of the photovoltaic storage converter based on the finite time observer of the present invention; Figure 3 This is a control diagram of the backstepping complementary control method of the photovoltaic storage converter based on the finite time observer of the present invention; Figure 4This is the transient response diagram of the three-phase current a, b, c and DC bus voltage under the PI control strategy when the load power suddenly increases from 35kw to 85kw; Figure 5 It is a transient response diagram of three-phase current a, b, c and DC bus voltage under the control method of the present invention when the load power suddenly increases from 35kw to 85kw; Figure 6 This is the transient response diagram of the three-phase current a, b, c and DC bus voltage under the PI control strategy when the load power drops from 85kw to -35kw; Figure 7 It is a transient response diagram of three-phase current a, b, c and DC bus voltage under the control method of the present invention when the load power is suddenly reduced from 85kw to -35kw; Figure 8 It is the transient response diagram of three-phase current a, b, c and DC bus voltage under the PI control strategy of load power increasing suddenly, decreasing suddenly and increasing suddenly in sequence; Fig. 9 It is a transient response diagram of the three-phase current a, b, c phases and the DC bus voltage under the control method of the present invention when the load power increases suddenly, decreases suddenly, and increases suddenly in sequence; Fig.10 This is the harmonic analysis diagram of grid-connected current under PI control strategy; Fig.11 This is a harmonic analysis diagram of the grid-connected current under the control method of the present invention. DETAILED DESCRIPTION

[0017] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] Example 1 This embodiment provides a back-stepping complementary control method for a photovoltaic storage converter based on a finite time observer, which is used to control a subsequent converter of the photovoltaic storage converter, wherein the subsequent converter includes a three-phase full-bridge inverter, LC The overall structure of the photovoltaic storage converter is as follows: filtering part, grid-connected part and load part. Figure 1 As shown in the figure, it is mainly composed of a bidirectional DC-DC converter, a photovoltaic array, a storage battery, a three-phase full-bridge inverter, a filter, an AC load and a distribution network. The MPPT is a maximum power tracking technology. It is connected to the bus through the MPPT algorithm to achieve maximum power tracking of the bus voltage. The energy storage system can generate a bidirectional flow of energy with the bus through a DC converter. The back-stage converter is composed of a three-phase full-bridge inverter, a filter and a distribution network. The photovoltaic storage converter is composed of a bidirectional chopper and a three-phase full-bridge inverter. The S 1 ~S 6 is the switch tube of the three-phase converter; S 7 , S 8 is the switch tube of the DC chopper,e a , e b , e c is the grid side phase voltage; C dc is the DC side capacitance; L bat It is the filter inductor of DC chopper; u bat is the battery output voltage; i L The battery output current flows through the inductor L bat The current; i out is the current input into the converter by the DC bus; i pv It is the current output by the photovoltaic array after MPPT; S j Indicates the on / off status of the switch tubes in each bridge arm of the converter:

[0019] like Figure 2 As shown, the specific implementation steps are as follows: Step 1: Construct an equivalent mathematical model of a three-phase full-bridge inverter; The mathematical model of the three-phase full-bridge inverter in the photovoltaic storage converter in the three-phase coordinate system is: (1) In formula (1), U ao , U bo , U co They are the sum of the voltage of the filter part of the three-phase inverter a, b, c phases and the voltage on the distribution network side. R is the equivalent resistance, i a , i b , i c They are the three-phase output currents of a, b, and c of the three-phase full-bridge inverter, L For the three-phase full-bridge inverter AC measurement filter inductor, e a , e b , e c They are the three-phase voltages a, b, and c on the grid-connected side respectively.

[0020] Step 2: Based on the equivalent mathematical model constructed in step 1, a mathematical model in the dq axis rotation coordinate system is constructed through dq transformation; Step 3: Construct the ADRC paradigm and design the finite-time observer; Step 4: The given active power and reactive power are passed through the power outer loop to obtain the current reference value of the dq axis of the current inner loop; Step 5: Design a sliding mode controller and introduce a complementary structure to apply it to sliding mode control; Step 6: Design an improved reaching law and apply it to the complementary sliding mode obtained in step 5; Step 7: Obtain the control output through the sliding mode controller constructed in step 6, use SPWM modulation to get the duty cycle, and apply the duty cycle to the control of the three-phase full-bridge inverter switch tube, thereby realizing signal control of the full-bridge switch.

[0021] Example 2 This embodiment provides a backstepping complementary control method for a photovoltaic storage converter based on a finite time observer. Based on Embodiment 1, equation (1) is converted from a three-phase coordinate system to a two-phase rotating dq coordinate system, and its mathematical model in the dq two-phase coordinate system is obtained as follows: (2) In formula (2), R is the filter resistor of the three-phase full-bridge inverter, ω is the grid voltage angular frequency; u d , u q are the output voltages on the d and q axes respectively, u d =s d u dc , u q =s q u dc ;s d 、s q They are the d and q axis switching functions respectively; u dc is the bus voltage on the DC side; e d , e q is the component of the grid voltage on the d and q axes; i Ld , i Lq is the component of the grid-side current in the d and q axes; Deriving equation (2) transforms it into a paradigm that satisfies the second-order auto-disturbance rejection: (3).

[0022] Example 3 This embodiment provides a backstepping complementary control method for a photovoltaic storage converter based on a finite time observer. Based on Embodiment 1-2, step 3 is specifically as follows: Define the control object: (4) In formula (4), y is the output of the three-phase inverter system, u is the input control of the system, b For control u The gain, b d , b q That is, the control amount of the d and q axes u d , u q The gain, F is the sum of all disturbances in the system, where y =[ y 1 y 2 ] T ; b =[ b d b q ] T ; u =[ u d u q ] T ; F =[ F d F q ] T ,definition F d , F q is the lumped disturbance of d and q axes; definition y 1 =i Ld , y 2 =i Lq , y ref is the output target value, and the output target values ​​on the d and q axes are defined as i Ldref , i Lqref ; Express equation (4) in matrix form: (5) In formula (5), b d , b q , F d , F q It is expressed as: (6) Define the d-axis state variable , , , the q-axis state variable is , , , then the spatial state equation of the system shown in formula (4) is: (7) According to the spatial state expression of formula (7), the form of designing the finite time observer is: (8) In formula (9), k 1 , k 2 , k 3 , k 4 , k 5 , k 6 is the observer gain, , ,in i= 1,2,3,4…; z d1 , z d2 , z d3 , z q1 , z q2 , z q3 They are x d1 , x d2 , x d3 , x q1 , x q2 , x q3 Observed value of .

[0023] Example 4 This embodiment provides a back-stepping complementary control method for a photovoltaic storage converter based on a finite time observer. Based on Embodiments 1-3, step 4 is specifically as follows: Assume that the active power and reactive power reference values ​​of the photovoltaic power converter are P ref , Q ref When the solar storage converter is running, the inner ring d and q axis current reference values ​​are i Ldref , i Lqref Respectively expressed as: (9).

[0024] Example 5 This embodiment provides a back-stepping complementary control method for a photovoltaic storage converter based on a finite time observer. Based on embodiments 1-4, step 5 is specifically as follows: According to the basic recursive idea of ​​backstepping, a virtual control quantity is designed p for: (10) In formula (10), is a constant, virtual control quantity p =[ p 1 , p 2 ], i L =[ i Ld , i Lq ] T .

[0025] Select the Lyapunov function V for: (11) In formula (11), V =[ V 1 , V 2 ] T , e =[ e 1 , e 2 ] T , d-axis error e 1 =i Ld i Ldref， Q-axis error e 2 =i Lq i Lqref。

[0026] Deriving equation (11) and substituting equation (8) and equation (10) into it, we can obtain: (12) make , ,in , is a constant, then: (13) Combining equation (13) with equation (12), we get: (14) From formula (14), we know that when p 1 , p 2 When it converges to 0, the system is stable according to the Lyapunov stability criterion. At this time, the design of the state error feedback rate is simplified to the virtual control quantity p 1 , p 2 The control of s dg , s qg for: (15) In formula (15), λ 1 , λ 2 is a constant, and the design is s dg , s qg Orthogonal complementary sliding surfaces s dc , s qc for: (16) The sliding surface s d , s q It is expressed as: (17) Based on the equivalent control method, the equivalent control law of d and q axes is designed.u deq , u qeq for: (18).

[0027] Example 6 This embodiment provides a back-stepping complementary control method for a photovoltaic storage converter based on a finite time observer. Based on embodiments 1-5, step 6 is specifically as follows: The improved reaching law is used as the switching control law of sliding mode ADRC, that is, u dsw , u qsw for: (19) In formula (19), ; when | s d |、| s q |When it is relatively large, the speed change item Close to , greater than , can speed up the approach speed, when | s d |、| s q |Compared to small, variable speed items Close to , which can reduce the chattering and at the same time make sgn( s d ) is replaced by tanh( s q ) function to achieve smoothing; Combining equation (18) and equation (19) gives the control law of the sliding mode controller d and q axes: u d , u q for: (20).

[0028] like Figure 3 The control diagram of the backstepping complementary control method of the photovoltaic storage converter based on the finite time observer of the present invention is shown. The control method of the present invention has the following advantages: 1) The finite-time observer used in the present invention is an improved version of the traditional extended state observer. The traditional extended state observer can estimate the system state in real time without measuring all the state variables of the system. At the same time, it has a certain robustness to model errors and measurement noise, and can improve the accuracy and stability of state estimation. The finite-time observer not only has the characteristics of the extended state observer, but also has the finite-time convergence characteristics of the finite-time observer, that is, the observer parameters are designed to ensure the homogeneity of the observation error system.

[0029] 2) The present invention adopts a backstepping complementary sliding mode method that combines backstepping and complementary sliding mode to achieve system control. Backstepping control has the characteristics of good global stability, excellent dynamic and static performance, and can effectively suppress the disturbance caused by load changes. Complementary sliding mode adds a generalized error sliding mode surface on the basis of conventional sliding mode control, which can not only reduce the time for the system state to reach the sliding mode surface, but also ensure the tracking accuracy of the system.

[0030] 3) In the present invention, the backstepping method and the sliding mode controller can suppress a series of disturbances generated by the photovoltaic storage converter, overcome the problem of uncertainty of the system's nonlinear parameters, and smooth the output to reduce the inherent jitter problem generated by the sliding mode controller.

[0031] 4) The convergence law in the present invention has a faster convergence speed and makes the system more stable than the traditional convergence rate. The traditional sign function is replaced by the hyperbolic tangent function, which solves the problem that the traditional sign function does not output with 0 as the center, so that the sliding mode controller can achieve a smoothing effect. The improved convergence law is affected by the sliding surface. When the system state approaches the sliding surface, the reduction of the speed change term can achieve the effect of reducing the vibration, making the system more stable.

[0032] Experimental analysis In order to verify the effectiveness of the backstepping complementary control method of the photovoltaic storage converter based on the finite time observer of the present invention, a simulation circuit is built in a hardware-in-the-loop (HIL) experimental platform, and a comparative analysis is performed with the traditional PI control strategy. It is defined that the power is positive when the voltage and current directions are consistent. The simulation parameter settings are shown in Table 1.

[0033] Table 1 Circuit parameters

[0034] The present invention uses a finite time observer to replace the traditional extended state observer, which can achieve a more accurate estimation of the lumped disturbance and a faster compensation effect of the estimation error, improve the ability to suppress the cross-effect of the d and q axes, and the observer has a simple structure, no additional parameters, and is easy to implement in engineering. The backstepping complementary sliding mode replaces the traditional sliding mode control, and the backstepping method is used to ensure the global stability of the system, thereby enhancing the stability and robustness of the system; like Figure 4-5 As shown in the figure, under the two control modes, when the load power suddenly changes from the stable output of 35kw to 85kw, the output power of the three-phase inverter AC side will respond dynamically. Figure 4 It can be seen that the transition time under PI control is 24ms, which is Figure 5 The transition time of the control strategy used in this paper is 8ms, and the convergence speed is improved compared with PI control.

[0035] like Figure 6-7 As shown in the figure, under the two control modes, when the load power changes suddenly, the output power of the three-phase inverter AC side drops sharply from 85kw in stable operation to -35kw, which causes the dynamic response of the output power. Figure 6 It can be seen that the transition time under PI control is 32ms, which is Figure 7 The transition time of the control strategy used in this paper is 13ms, and the convergence speed is improved compared with PI control.

[0036] Figure 8-9 The current waveform on the grid side under the control strategy of the present invention is when the system load power suddenly increases from 40kw to 90kw, then suddenly decreases from 90kw to -20kw, and suddenly increases from -20kw to 40kw under the traditional PI control strategy and the control strategy of this paper. It can be seen that the current waveform of the control strategy of this paper is more stable than that of the PI control strategy, the current mutation when the power changes suddenly is also smaller, and the time to reach the AC current at the desired power is also shorter, which verifies the feasibility of the control of the present invention.

[0037] In order to verify the influence of the control in this paper on the power quality of the output current of the three-phase inverter, the grid-connected current of the three-phase inverter was analyzed by Fourier analysis for two steady-state cycles in Matlab / Simulink software. Fig.10 As shown, it is the harmonic analysis of the grid-connected current of the energy storage converter under traditional PI control, and the THD is 4.74%. Fig.11 The figure shows the harmonic analysis of the grid-connected current of the photovoltaic storage converter under the control of the present invention, and the THD is 0.98%. By comparison, it can be seen that the control of the present invention has a stronger harmonic suppression capability and improves the quality of grid-connected power.

[0038] In summary, the control strategy of the backstepping complementary sliding mode based on the finite time observer of the present invention effectively solves the problem that when the photovoltaic storage inverter is subjected to external time-varying disturbances in the grid-connected working mode, the three-phase current on the grid-connected side can be quickly restored to a stable state, thereby improving the convergence speed and control accuracy of the grid-connected inverter and effectively improving the power quality of the power grid.

Claims

1. A backstepping complementary control method for a photovoltaic storage converter based on a finite time observer is used to control a subsequent converter of the photovoltaic storage converter, which includes a three-phase full-bridge inverter, LC The filter part, the grid-connected part and the load part are characterized in that: Follow the steps below to implement it: Step 1: Construct an equivalent mathematical model of a three-phase full-bridge inverter; Step 2: Based on the equivalent mathematical model constructed in step 1, a mathematical model in the dq axis rotation coordinate system is constructed through dq transformation; Step 3: Construct the ADRC paradigm and design the finite-time observer; Step 4: The given active power and reactive power are passed through the power outer loop to obtain the current reference value of the dq axis of the current inner loop; Step 5: Design a sliding mode controller and introduce a complementary structure to apply it to sliding mode control; Step 6: Design an improved reaching law and apply it to the complementary sliding mode obtained in step 5; Step 7: Obtain the control output through the sliding mode controller constructed in step 6, use SPWM modulation to get the duty cycle, and apply the duty cycle to the control of the three-phase full-bridge inverter switch tube, thereby realizing signal control of the full-bridge switch.

2. The backstepping complementary control method of a photovoltaic storage converter based on a finite time observer according to claim 1 is characterized in that: The step 1 is specifically as follows: The mathematical model of the three-phase full-bridge inverter in the photovoltaic storage converter in the three-phase coordinate system is: （1） In formula (1), U ao , U bo , U co They are the sum of the voltage of the filter part of the three-phase inverter a, b, c phases and the voltage on the distribution network side. R is the equivalent resistance, i a , i b , i c They are the three-phase output currents of a, b, and c of the three-phase full-bridge inverter, L For the three-phase full-bridge inverter AC measurement filter inductor, e a , e b , e c They are the three-phase voltages a, b, and c on the grid-connected side respectively.

3. The backstepping complementary control method of a photovoltaic storage converter based on a finite time observer according to claim 2 is characterized in that: The step 2 is specifically as follows: Convert equation (1) from the three-phase coordinate system to the two-phase rotating dq coordinate system, and the mathematical model in the dq two-phase coordinate system is: （2） In formula (2), R is the filter resistor of the three-phase full-bridge inverter, ω is the grid voltage angular frequency; u d , u q are the output voltages on the d and q axes respectively, u d =s d u dc , u q =s q u dc ;s d 、s q They are the d and q axis switching functions respectively; u dc is the bus voltage on the DC side; e d , e q is the component of the grid voltage on the d and q axes; i Ld , i Lq is the component of the grid-side current in the d and q axes; Deriving equation (2) transforms it into a paradigm that satisfies the second-order auto-disturbance rejection: （3）。 4. The backstepping complementary control method of a photovoltaic storage converter based on a finite time observer according to claim 3 is characterized in that: The step 3 is specifically as follows: Define the control object: （4） In formula (4), y is the output of the three-phase inverter system, u is the input control of the system, b For control u The gain, b d , b q That is, the control amount of the d and q axes u d , u q The gain, F is the sum of all disturbances in the system, where y =[ y 1 y 2] T ; b =[ b d b q ] T ; u =[ u d u q ] T ; F =[ F d F q ] T ,definition F d , F q is the lumped disturbance of d and q axes; definition y 1 =i Ld , y 2 =i Lq , y ref is the output target value, and the output target values ​​on the d and q axes are defined as i Ldref , i Lqref ; Express equation (4) in matrix form: （5） In formula (5), b d , b q , F d , F q It is expressed as: （6） Define the d-axis state variable , , , the q-axis state variable is , , , then the spatial state equation of the system shown in formula (4) is: （7） According to the spatial state expression of formula (7), the form of designing the finite time observer is: （8） In formula (9), k1, k2, k3, k4, k5, k6 are observer gains, , ,in i = 1,2,3,4…; z d1 , z d2 , z d3 , z q1 , z q2 , z q3 They are x d1 , x d2 , x d3 , x q1 , x q2 , x q3 Observed value of .

5. The backstepping complementary control method of a photovoltaic storage converter based on a finite time observer according to claim 4 is characterized in that: The step 4 is specifically as follows: Assume that the active power and reactive power reference values ​​of the photovoltaic power converter are P ref , Q ref When the solar storage converter is running, the inner ring d and q axis current reference values ​​are i Ldref , i Lqref Respectively expressed as: （9）。 6. The backstepping complementary control method of a photovoltaic storage converter based on a finite time observer according to claim 5 is characterized in that: The step 5 is specifically as follows: According to the basic recursive idea of ​​backstepping, a virtual control quantity is designed p for: （10） In formula (10), is a constant, virtual control quantity p =[ p 1, p 2], i L =[ i Ld , i Lq ] T . Select the Lyapunov function V for: （11） In formula (11), V =[ V 1, V 2] T , e =[ e 1, e 2] T , d-axis error e 1 =i Ld i Ldref ， Q-axis error e 2 =i Lq i Lqref ; Deriving equation (11) and substituting equation (8) and equation (10) into it, we can obtain: （12） make , ,in , is a constant, then: （13） Combining equation (13) with equation (12), we get: （14） From formula (14), we know that when p 1, p 2 converges to 0, the system is stable according to the Lyapunov stability criterion. At this time, the design of the state error feedback rate is simplified to the virtual control quantity p 1, p 2 control, define the generalized sliding surface s dg , s qg for: （15） In formula (15), λ 1. λ 2 is a constant, and the design is s dg , s qg Orthogonal complementary sliding surfaces s dc , s qc for: （16） The sliding surface s d , s q It is expressed as: （17） Based on the equivalent control method, the equivalent control law of d and q axes is designed. u deq , u qeq for: (18)。 7. The backstepping complementary control method of a photovoltaic storage converter based on a finite time observer according to claim 6 is characterized in that: The step 6 is specifically as follows: The improved reaching law is used as the switching control law of sliding mode ADRC, that is, u dsw , u qsw for: （19） Combining equation (18) and equation (19) gives the control law of the sliding mode controller d and q axes: u d , u q for: （20）。 8. The backstepping complementary control method of a photovoltaic storage converter based on a finite time observer according to claim 7 is characterized in that: In the formula (19), .

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