Improved active-disturbance-rejection control method for network-building type optical storage system based on timing convergence sliding mode

Abstract

The invention discloses an improved active-disturbance-rejection control method for a network construction type optical storage system based on a timing convergence sliding mode, and provides an improved sliding mode active-disturbance-rejection control strategy combining a fractional order expansion state observer and fixed time convergence sliding mode control, and the improved sliding mode active-disturbance-rejection control strategy is applied to the design of a network construction type optical storage converter. According to the invention, the transient voltage fluctuation of the system is effectively reduced, the response speed of the system is accelerated, and the positive effect on the improvement of the performance of the system is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and in particular relates to an improved self-disturbance rejection control method for a grid-type photovoltaic storage system based on a timing convergent sliding mode. Background Art

[0002] In the photovoltaic and energy storage grid-connected system, photovoltaic and energy storage units are connected to the grid through power electronic interfaces. However, the introduction of a large number of power electronic devices in the actual grid will lead to a reduction in system inertia and damping, as well as a reduction in overcurrent capacity. These factors pose a serious challenge to the stable operation of the grid. In order to deal with such problems, Virtual Synchronous Generators (VSG) technology has been proposed and applied to grid-connected systems. VSG can simulate the second-order equation of synchronous generator rotor motion, so that the inertial support capacity and damping characteristics in the grid-connected system can reach a level comparable to that of synchronous generators, which makes VSG control play a significant role in stabilizing voltage and balancing power.

[0003] In order to solve the problems of voltage fluctuations and weakened frequency support caused by the increase in power electronic devices during the grid transformation process, scholars have done a lot of work and produced two research directions. One is the improvement of VSG algorithm parameters, and the other is to improve the control performance of the inverter.

[0004] At present, most of the articles on improving VSG control performance are devoted to improving VSG algorithm parameters. There are few studies on inverter control performance. Given that the photovoltaic energy storage grid-connected system presents strong coupling and nonlinear characteristics, nonlinear control methods have received great attention due to their good fit with nonlinear systems and their positive impact on system stability and dynamic performance.

[0005] As large-scale distributed power generation equipment gradually replaces traditional synchronous generators, grid-connected systems face a series of challenges such as lack of inertia, decreased voltage and frequency stability. The introduction of grid-connected control technology has endowed distributed power generation equipment with the necessary inertia and frequency support capabilities. In the field of grid-connected control technology, virtual synchronous generator technology has been widely used, but the traditional PI control strategy it relies on has problems such as weak anti-interference ability and insufficient transient stability. Summary of the invention

[0006] The purpose of the present invention is to provide an improved self-disturbance rejection control method for a grid-type photovoltaic storage system based on a timed convergent sliding mode, which effectively reduces the transient voltage fluctuation of the system and speeds up the response speed of the system.

[0007] The technical solution adopted by the present invention is to improve the active disturbance rejection control method of the grid-type photovoltaic storage system based on the timing convergent sliding mode, which is specifically implemented according to the following steps: Step 1: Use VSG control on the grid-type photovoltaic storage converter; Step 1.1: Active frequency control; Step 1.2: Reactive voltage regulation control; Step 1.3: Virtual impedance control; Step 1.4: Voltage and current double closed loop; Step 2: Inverter controller design; Step 2.1: Observer design; Step 2.2: Improved design of state error feedback law; Step 3: DC-DC converter controller design.

[0008] The present invention is also characterized in that: Step 1.1 is as follows: Active frequency control simulates the primary frequency regulation process of a synchronous generator, and its expression is: (1) In formula (1), P m The mechanical power provided to the prime mover, P ref is the specified power of VSG, and are the rotor rated angular frequency and the actual output angular frequency, K p is the droop coefficient of active frequency modulation; The damping and inertia links of the synchronous generator are supplemented into the control strategy of the grid-connected inverter through the control algorithm, and the rotor motion equation of the VSG is expressed as: (2) In formula (2), J is the moment of inertia, D is the damping coefficient, P e is the VSG output active power, θ The initial phase.

[0009] Step 1.2 is as follows: Power regulation control is achieved by adjusting the virtual electromotive force of the VSG model E m To adjust the reactive power and terminal voltage, the equation for reactive power voltage regulation is: (3) In formula (3), K i is the integrator gain, Q ref is the reactive power reference value of the inverter, Q eis the actual value of reactive power output by the inverter, K q is the droop coefficient of the reactive voltage regulation link, U n is the rated value of the inverter terminal voltage, U m is the actual value of the inverter terminal voltage.

[0010] Step 1.3 is as follows: Combining active frequency regulation control and reactive voltage regulation control, the voltage vector output by VSG is: (4) In formula (4), E ma 、E mb 、E mc are the VSG output voltage vectors of a, b and c axes in the three-phase coordinate system respectively; The voltage vector output by VSG E ma 、E mb 、E mc After Park transformation, the three-phase coordinates are transformed into the dq coordinate system. E d , E q And participate in the virtual impedance control, which simulates the synchronous reactance and stator resistance of the synchronous generator. The specific state equation is: (5) In formula (5) V odref , V oqref is the rated value of the voltage outer loop, R f is the inductor parasitic resistance, I Ld , I Lq It is the component of the AC output current on the d and q axes.

[0011] Step 1.4 is as follows: In the main circuit of the grid-type photovoltaic storage converter, according to KVL, the circuit equation of the bidirectional DC / AC converter in the abc three-phase stationary coordinate system is: (6) In formula (6), I oa , I ob ,I oc is the grid-side current of phases a, b, and c, V oa , V ob , V oc is the grid-side voltage of phases a, b, and c, I La , I Lb , I Lc is the AC output current of phases a, b, and c, V La , V Lb , V Lc is the AC output side phase voltage of phases a, b, and c, L f is the filter inductor; According to KCL, the state equation at the grid connection point is: (7) According to equations (4) and (5), there is coupling in the output voltage and current dq components, and the coupling term is ωL f I oq ,- ω L f I od , ωV oq ,- ωV od ; Perform Park transformation on equations (6) and (7) to convert the three-phase abc coordinate system into the dq rotating coordinate system, and obtain the differential equations of loop voltage and node current in the dq coordinate system. Convert them to obtain the double closed-loop control equation: (8) (9) In formula (8) and formula (9), K dp1 , K dp2 , K qp1 , K qp2 is the proportional adjustment coefficient of the PI control used in the voltage and current double closed loop link, K di1 , K di2 ,K qi1 , K qi2 is the integral adjustment parameter.

[0012] Step 2.1 is as follows: Transform equations (6) and (7) and perform secondary derivative to obtain: (10) Transform equation (10) into the traditional ADRC paradigm: (11) In formula (11), y =[ y 1 y 2] T , y 1, y 2 is the output of the system V od , V oq ; b =[ b d b q ] T , b d , b q That is, the control amount of the d and q axes u d , u q Gain of u =[ u d u q ] T , u d , u q are the input controls of the system on d and q respectively; F =[ F d F q ] T , F d , F q is the disturbance part of d and q axis; Since the control structures of the output voltages on the d and q axes are the same, a second-order active disturbance rejection controller is constructed with the output voltage of the d axis as the control object; make x d1 = Vod , x d2 = , x d3 = F d , establish the spatial state equation: (12) In formula (12), , ; The introduced fractional derivative term transforms equation (11) into: (13) In formula (13), , F deq is the lumped disturbance on the d-axis, is the fractional derivative term, where ; Redefine state variables x d1 = V od , x d2 = , x d3 = F d The spatial state equation is established as: (14) The form of the process design fractional-order extended state observer established according to equation (14) and the state observer in linear system theory is: (15) In formula (15), z d1 , z d2 , z d3 They are x d1 , x d2 , x d3 Observed values ​​of . Parameters β d1 , β d2 , β d3 is the gain coefficient of the observer.

[0013] Step 2.2 is as follows: The voltage loop voltage error is defined as , The designed timed convergence integral sliding surface is: (16) In formula (16), , is the integral coefficient of FTCSMC, , , ; make , and connect it with formula (12) to obtain the equivalent control law: (17) The fixed-time convergence integral sliding mode surface in formula (16) can only ensure that the system converges within a fixed time during the sliding process. Therefore, the fixed-time theory is applied to the system, and the fixed-time convergence sliding mode reaching law is designed as: (18) In formula (18), , , , , is the switching gain of FTCSMC and ; Combining equation (17) and equation (18), we get the input control u d for: (19) The FTCSMC of the system is time-stable, and its upper stability bound is: (20) In formula (20), T d is the total settling time, T d1 is the settling time of the sliding process, T d2 is the settling time of the arrival process, T d1 , T d2 The specific relationship is: (twenty one).

[0014] Step 3 is as follows: The energy storage is performed by the DC-DC converter to step up and down the voltage, so the mathematical state equation obtained according to the state space averaging method is: (twenty two) In formula (22), d ais the duty cycle of the DC-DC converter switch, F v ( t ), F c ( t ) are the voltage and current disturbance values ​​generated when the DC-DC converter is running; Convert the bus voltage equation in equation (22) into the second-order auto-disturbance rejection paradigm: (twenty three) In formula (23), , , y 0 is the output of the system u dc ; b 0 is the control amount u A gain of 0; u 0 is the output duty cycle of the DC-DC converter d a ; F 0 is the disturbance part; Improve formula (23): (twenty four) In formula (24), , is the total disturbance excluding the control input, b 1 is the control gain after improvement; Defining state variables x c1 = u dc , , x c3 = F 1, then the observer form is: (25) In formula (25), z c1 , z c2 , z c3 They are x c1 , x c2 , x c3 The observed value of parameter β c1 , β c2 , β c3 is the gain coefficient of the observer; First, define the voltage error of the voltage loop of the DC-DC converter as , , the designed timed convergence integral sliding surface is: (26) make , and connect it with formula (25) to obtain the equivalent control law: (27) The fixed-time convergence sliding mode reaching law is designed as: (28) Combining equations (27) and (28), the voltage outer loop control law of the DC-DC converter is: (29).

[0015] The beneficial effects of the present invention are: The present invention improves the active disturbance rejection control method of a grid-type photovoltaic storage system based on a timed convergent sliding mode, proposes an improved sliding mode active disturbance rejection control (Sliding Mode Active Disturbance Rejection Control, SM-ADRC) strategy combining a fractional-order extended state observer (Fractional-order Extended State Observer, FOESO) with a fixed-time convergent sliding mode control (Fixed-time Convergent Sliding Mode Control, FTCSMC), and applies it to the design of a grid-type photovoltaic storage converter; the traditional extended state observer is combined with the fractional order to design a fractional-order extended state observer to improve its observation accuracy, enhance the system's observation ability of the internal state, and this observer is suitable for more systems because of its higher degree of freedom. The improved SMC effectively suppresses the chattering phenomenon in the traditional sliding mode control by virtue of its ability to converge to the equilibrium point in a fixed time, improves its convergence characteristics and robustness, and further attenuates the chattering phenomenon of the sliding mode; the entire control method effectively reduces the transient voltage fluctuation of the system and accelerates the system response speed, playing a positive role in improving the system performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a topological structure and a network control strategy diagram of a network-building type photovoltaic storage converter of the present invention; Figure 2 This is the block diagram of VSG active frequency modulation control; Figure 3 This is the VSG reactive voltage regulation control block diagram; Figure 4 It is the block diagram of virtual impedance control; Figure 5 This is a block diagram of the SM-ADRC improvement ideas; Figure 6 It is the variation diagram of sliding mode surface under different convergence laws; Figure 7 This is the block diagram of FTCSMC active disturbance rejection control based on FOESO; Figure 8 It is the block diagram of the voltage loop control of the DC-DC converter; Fig. 9 It is the output active power response diagram when the power command changes; Fig.10 It is the output reactive power response diagram when the power command changes; Figure 11 is a diagram showing the bus voltage output response when the light intensity and temperature change. Figure 11 (a) is u dc Output response diagram, FIG11( b ) is an enlarged view of point A in FIG11( a ), and FIG11( c ) is an enlarged view of point B in FIG11( a ). 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 an improved active disturbance rejection control method for a grid-type photovoltaic storage system based on a timing convergent sliding mode. Figure 1 The topological structure and control strategy of the grid-connected photovoltaic storage converter are shown in Figure 2. I oa , I ob , I oc is the grid-side current, V oa , V ob , V oc is the grid-side voltage, I La , I Lb , I Lc is the AC output current, V La , V Lb , V Lc is the phase voltage at the AC output side, L f , C f constitutes LC The capacitors and inductors of the filter part,R f is the inductor parasitic resistance, C dc is the DC side stabilizing capacitor, u dc is the DC bus voltage, and the total DC side current output is i out , the output current of photovoltaic and battery is i pv , i L , the output voltage is u pv , u bat The battery is connected to the subsequent converter through a buck-boost converter, the photovoltaic module is connected to the subsequent converter through a boost converter, and is controlled by the conductance increment method in the maximum power point tracking (MPPT) algorithm. The control method is specifically implemented in the following steps: Step 1: Use VSG control on the grid-type photovoltaic storage converter; The control strategy adopted by the grid-type photovoltaic storage converter is VSG control, which is based on the mathematical model of the synchronous generator and simulates the damping characteristics, frequency and voltage regulation characteristics and inertia characteristics of the synchronous generator. VSG control includes active frequency regulation control, reactive voltage regulation control, virtual impedance control and voltage and current double closed loop parts; Step 1.1: Active frequency control; Step 1.2: Reactive voltage regulation control; Step 1.3: Virtual impedance control; Step 1.4: Voltage and current double closed loop; Step 2: Inverter controller design; Step 2.1: Observer design; The voltage outer loop controller is improved and designed by combining fractional order theory with ADRC to observe the internal and external disturbances of the system. The nonlinear feedback error control law can be replaced by FTCSMC, which makes the controller have the characteristics of fast response speed, high control accuracy and excellent robust performance. Step 2.2: Improved design of state error feedback law; The state error feedback rate can be used to estimate and compensate the state error of the system in real time. In order to improve the convergence speed and robustness of the system, the ordinary sliding mode is improved to FTCSMC (Fixed-time Convergent Sliding Mode Control). Step 3: DC-DC converter controller design.

[0019] Example 2 This embodiment provides an improved active disturbance rejection control method for a grid-type photovoltaic storage system based on a timing convergent sliding mode. Based on Embodiment 1, step 1.1 is specifically as follows: Figure 2 This is the block diagram of active frequency modulation control of VSG control. Active frequency modulation control simulates the primary frequency modulation process of synchronous generators. Its expression is: (1) In formula (1), P m The mechanical power provided to the prime mover, P ref is the specified power of VSG, and are the rotor rated angular frequency and the actual output angular frequency, K p is the droop coefficient of active frequency modulation; The damping and inertia links of the synchronous generator are supplemented into the control strategy of the grid-connected inverter through the control algorithm, and the rotor motion equation of the VSG is expressed as: (2) In formula (2), J is the moment of inertia, D is the damping coefficient, P e is the VSG output active power, θ The initial phase.

[0020] Example 3 This embodiment provides an improved anti-disturbance control method for a grid-type photovoltaic storage system based on a timing convergent sliding mode. Based on Embodiment 1-2, step 1.2 is specifically as follows: Figure 3 This is the block diagram of reactive voltage regulation control of VSG control. The reactive voltage regulation control is achieved by adjusting the virtual electromotive force of the VSG model. E m To adjust the reactive power and terminal voltage, the equation for reactive power voltage regulation is: (3) In formula (3), K i is the integrator gain, Q ref is the reactive power reference value of the inverter, Q e is the actual value of reactive power output by the inverter, K q is the droop coefficient of the reactive voltage regulation link, Un is the rated value of the inverter terminal voltage, U m is the actual value of the inverter terminal voltage.

[0021] Example 4 This embodiment provides an improved anti-disturbance control method for a grid-type photovoltaic storage system based on a timing convergent sliding mode. Based on Embodiments 1-3, step 1.3 is specifically as follows: Combining active frequency regulation control and reactive voltage regulation control, the voltage vector output by VSG is: (4) In formula (4), E ma 、E mb 、E mc are the VSG output voltage vectors of the a, b, and c axes of the three-phase coordinate system; The voltage vector output by VSG E ma , E mb , E mc After Park transformation, the three-phase coordinates are transformed into the dq coordinate system. E d , E q and participate in virtual impedance control, Figure 4 The virtual impedance control in simulates the synchronous reactance and stator resistance of the synchronous generator. The specific state equation is: (5) In formula (5) V odref , V oqref is the rated value of the voltage outer loop, R f is the inductor parasitic resistance, I Ld , I Lq It is the component of the AC output current on the d and q axes.

[0022] Example 5 This embodiment provides an improved active disturbance rejection control method for a grid-type photovoltaic storage system based on a timing convergent sliding mode. Based on Embodiments 1-4, step 1.4 is specifically as follows: exist Figure 1 In the main circuit of the grid-type photovoltaic storage converter, according to KVL, the circuit equation of the bidirectional DC / AC converter in the abc three-phase stationary coordinate system is: (6) In formula (6), I oa , I ob , I oc is the grid-side current of phases a, b, and c, V oa , V ob , V oc is the grid-side voltage of phases a, b, and c, I La , I Lb , I Lc is the AC output current of phases a, b, and c, V La , V Lb , V Lc is the AC output side phase voltage of phases a, b, and c, L f is the filter inductor; According to KCL, the state equation at the grid connection point is: (7) According to equations (4) and (5), there is coupling in the output voltage and current dq components, and the coupling term is ωL f I oq ,- ω L f I od , ωV oq ,- ωV od ; Perform Park transformation on equations (6) and (7) to convert the three-phase abc coordinate system into the dq rotating coordinate system, and obtain the differential equations of loop voltage and node current in the dq coordinate system. Convert them to obtain the double closed-loop control equation: (8) (9) In formula (8) and formula (9), K dp1 , K dp2 , K qp1 , Kqp2 is the proportional adjustment coefficient of the PI control used in the voltage and current double closed loop link, K di1 , K di2 , K qi1 , K qi2 is the integral adjustment parameter.

[0023] Example 6 This embodiment provides an improved anti-disturbance control method for a grid-type photovoltaic storage system based on a timing convergent sliding mode. Based on embodiments 1-5, the design idea of ​​step 2 is as follows: Figure 5 As shown, step 2.1 is specifically as follows: Transform equations (6) and (7) and perform secondary derivative to obtain: (10) Transform equation (10) into the traditional ADRC paradigm: (11) In formula (11), y =[ y 1 y 2] T , y 1, y 2 is the output of the system V od , V oq ; b =[ b d b q ] T , b d , b q That is, the control amount of the d and q axes u d , u q Gain of u =[ u d u q ] T , u d , u q are the input controls of the system on d and q respectively; F =[ F d F q ] T, F d , F q is the disturbance part of d and q axis; Since the control structures of the output voltages on the d and q axes are the same, a second-order active disturbance rejection controller is constructed with the output voltage of the d axis as the control object; make x d1 = V od , x d2 = , x d3 = F d , establish the spatial state equation: (12) In formula (12), , ; The introduced fractional derivative term transforms equation (11) into: (13) In formula (13), , F deq is the lumped disturbance on the d-axis, is the fractional derivative term, where ; Redefine state variables x d1 = V od , x d2 = , x d3 = F d The spatial state equation is established as: (14) The form of the process design fractional-order extended state observer established according to equation (14) and the state observer in linear system theory is: (15) In formula (15), z d1 , z d2 , z d3 They are x d1 , x d2 ,x d3 Observed values ​​of . Parameters β d1 , β d2 , β d3 is the gain coefficient of the observer.

[0024] Step 2.2 is as follows: The voltage loop voltage error is defined as , The designed timed convergence integral sliding surface is: (16) In formula (16), , is the integral coefficient of FTCSMC, , , ; make , and connect it with formula (12) to obtain the equivalent control law: (17) The fixed-time convergence integral sliding mode surface in formula (16) can only ensure that the system converges within a fixed time during the sliding process. Therefore, the fixed-time theory is applied to the system, and the fixed-time convergence sliding mode reaching law is designed as: (18) In formula (18), , , , , is the switching gain of FTCSMC and ; Combining equation (17) and equation (18), we get the input control u d for: (19) The FTCSMC of the system is time-stable, and its upper stability bound is: (20) In formula (20), T d is the total settling time, T d1 is the settling time of the sliding process, T d2 is the settling time of the arrival process, T d1 , T d2 The specific relationship is: (twenty one); Based on the constructed sliding surface formula (16), the performance of the sliding mode reaching law is deeply analyzed. Through simulation, the performance comparison of the traditional exponential reaching law, the power reaching law and the fixed time convergence reaching law adopted in this embodiment is carried out on the jitter and reaching speed. The traditional exponential reaching law is , the power reaching law is .like Figure 6 As shown, under the sliding surface condition of this embodiment, the fixed time convergence approach law adopted not only shows a faster approach speed, but also performs more prominently in suppressing the chattering phenomenon.

[0025] In summary, the block diagram of FTCSMC active disturbance rejection control based on FOESO (Fractional-order Extended State Observer) is as follows: Figure 7 shown.

[0026] Example 7 This embodiment provides an improved active disturbance rejection control method for a grid-type photovoltaic storage system based on a timing convergent sliding mode. Based on embodiments 1-6, step 3 is specifically as follows: The energy storage is performed by the DC-DC converter to step up and down the voltage, so the mathematical state equation obtained according to the state space averaging method is: (twenty two) In formula (22), d a is the duty cycle of the DC-DC converter switch, F v ( t ), F c ( t ) are the voltage and current disturbance values ​​generated when the DC-DC converter is running; In this embodiment, the DC-DC converter adopts a voltage loop for control. The traditional PI control has a good effect in the static control process, but its dynamic response process is poor, which will affect the rapidity and accuracy of the system. Therefore, the control of the voltage loop is improved, and the improved SM-ADRC (Improved Sliding Mode Active Disturbance Rejection Control) control is adopted to improve the response speed and anti-disturbance ability of the system.

[0027] Convert the bus voltage equation in equation (22) into the second-order auto-disturbance rejection paradigm: (twenty three) In formula (23), , , y 0 is the output of the system u dc ; b 0 is the control amount u A gain of 0; u 0 is the output duty cycle of the DC-DC converter d a ; F 0 is the disturbance part; Improve formula (23): (twenty four) In formula (24), , is the total disturbance excluding the control input, b 1 is the control gain after improvement; Defining state variables x c1 = u dc , , x c3 = F 1, then the observer form is: (25) In formula (25), z c1 , z c2 , z c3 They are x c1 , x c2 , x c3 The observed value of parameter β c1 , β c2 , β c3 is the gain coefficient of the observer; First, define the voltage error of the voltage loop of the DC-DC converter as , , the designed timed convergence integral sliding surface is: (26) make , and connect it with formula (25) to obtain the equivalent control law: (27) The fixed-time convergence sliding mode reaching law is designed as: (28) Combining equations (27) and (28), the voltage outer loop control law of the DC-DC converter is: (29); The voltage loop control block diagram of the DC-DC converter is as follows: Figure 8 shown.

[0028] Simulation Analysis In order to verify the control performance of the improved anti-disturbance control method of the grid-type photovoltaic storage system based on the timing convergence sliding mode of the present invention, the system model was built using the Matlab / Simulink (R2018b) platform, and the traditional PI control, traditional SM-ADRC control and the improved SM-ADRC control of the present invention were compared to verify the superiority of the control method of the present invention. The parameters of the circuit are given in Table 1, and the parameters of the controller are given in Table 2.

[0029] Table 1 Circuit model parameters

[0030] Table 2 Controller parameters

[0031] 1) Output power dynamic response Initially given P e is 20kW, by giving P e The jump is performed to analyze the anti-disturbance performance of the three control strategies. P e The jump instruction is: at 0s-0.25s, P e The simulation results are shown in Figure 2. Fig. 9 shown.

[0032] go through P e The jump command process shows different control performances of the three different control strategies. The improved SM-ADRC control has great advantages over the other two control strategies in terms of anti-disturbance performance. Its advantages of fast response speed and small overshoot can make the system more stable and reliable during operation. The specific advantage data are shown in Table 3.

[0033] Table 3 Transient changes in output active power when power command changes

[0034] The initial setting value of reactive power is 0.P e Jump command will also affect the output of reactive power. The simulation results are as follows Fig.10 shown.

[0035] The simulation results show that the improved SM-ADRC has the advantages of small ripple, small overshoot and fast response speed in the comparison of the three control strategies. The specific advantage data are shown in Table 4.

[0036] Table 4 Transient changes in output reactive power when power command changes

[0037] 2) DC bus voltage dynamic response The initial given light intensity is 1000W / m 2 , the temperature is 25℃, and the VSG anti-interference performance of PI control, traditional SM-ADRC control and the improved SM-ADRC control strategy of this paper is analyzed by the jump of light intensity and temperature. The light intensity jump instruction is: the light intensity is 1000W / m at 0s-0.2s. 2 , and suddenly becomes 800W / m at 0.2s 2 And it lasts until 0.3s, and then suddenly increases to 1200W / m at 0.3s 2 And continue until the end; the temperature instruction is: the temperature is 25℃ at 0s-0.4s, increases to 35℃ at 0.4s and continues to 0.5s, and drops to 15℃ at 0.5s and continues until the end.

[0038] According to the instruction process of light intensity and temperature, the effects of changes in light intensity and temperature on the DC bus voltage under three different control strategies are compared. u dc The impact of u dc The transient simulation results under changes in light intensity and temperature are shown in Figure 11 (a)-(c).

[0039] Comparing the simulation results in Figure 11, it can be seen that the control performance of the PI control strategy is limited. u dc The results obtained by traditional SM-ADRC control and PI control are in sharp contrast. The overshoot, convergence speed and ripple of ADRC are much stronger than those under PI control. Compared with the traditional SM-ADRC, the improved SM-ADRC control strategy proposed in this paper has a better effect on the changes of light intensity and temperature. u dc The specific advantage data are shown in Table 5.

[0040] Table 5 Transient changes in output reactive power when power command changes

[0041] From the above content, we can know that 1) in terms of power mutation, the PI control, traditional SM-ADRC and the improved SM-ADRC control in this paper are compared. The results show that the control method of the present invention has a good improvement on the transient performance of the system compared with the other two control methods, making the power system more stable in the face of power mutation problems; 2) The control method of the present invention reduces the fluctuation and stabilization time of the DC bus voltage under external interference, and can improve the reliability of the photovoltaic energy storage grid-connected system.

Claims

1. An improved active disturbance rejection control method for a grid-type photovoltaic storage system based on a timed convergent sliding mode, characterized in that: Follow the steps below to implement it: Step 1: Use VSG control on the grid-type photovoltaic storage converter; Step 1.1: Active frequency control; Step 1.2: Reactive voltage regulation control; Step 1.3: Virtual impedance control; Step 1.4: Voltage and current double closed loop; Step 2: Inverter controller design; Step 2.1: Observer design; Step 2.2: Improved design of state error feedback law; Step 3: DC-DC converter controller design.

2. According to claim 1, the improved active disturbance rejection control method for a grid-type photovoltaic storage system based on a timing convergent sliding mode is characterized in that: The step 1.1 is specifically as follows: Active frequency control simulates the primary frequency regulation process of a synchronous generator, and its expression is: (1) In formula (1), P m The mechanical power provided to the prime mover, P ref is the specified power of VSG, and are the rotor rated angular frequency and the actual output angular frequency, K p is the droop coefficient of active frequency modulation; The damping and inertia links of the synchronous generator are supplemented into the control strategy of the grid-connected inverter through the control algorithm, and the rotor motion equation of the VSG is expressed as: (2) In formula (2), J is the moment of inertia, D is the damping coefficient, P e is the VSG output active power, θ The initial phase.

3. The improved active disturbance rejection control method for a grid-type photovoltaic storage system based on a timing convergent sliding mode according to claim 2 is characterized in that: The step 1.2 is specifically as follows: Reactive voltage regulation control is achieved by adjusting the virtual electromotive force of the VSG model. E m To adjust the reactive power and terminal voltage, the equation for reactive power voltage regulation is: (3) In formula (3), K i is the integrator gain, Q ref is the reactive power reference value of the inverter, Q e is the actual value of reactive power output by the inverter, K q is the droop coefficient of the reactive voltage regulation link, U n is the rated voltage of the inverter terminal, U m is the actual value of the inverter terminal voltage.

4. According to claim 3, the improved active disturbance rejection control method for a grid-type photovoltaic storage system based on a timing convergent sliding mode is characterized in that: The step 1.3 is specifically as follows: Combining active frequency regulation control and reactive voltage regulation control, the voltage vector output by VSG is: (4) In formula (4), E ma 、E mb 、E mc are the VSG output voltage vectors of a, b and c axes in the three-phase coordinate system respectively; The voltage vector output by VSG E ma , E mb , E mc After Park transformation, the three-phase coordinates are transformed into the dq coordinate system. E d , E q And participate in the virtual impedance control, which simulates the synchronous reactance and stator resistance of the synchronous generator. The specific state equation is: (5) In formula (5) V odref , V oqref is the rated value of the voltage outer loop, R f is the inductor parasitic resistance, I Ld , I Lq It is the component of the AC output current on the d and q axes.

5. According to claim 4, the improved active disturbance rejection control method for a grid-type photovoltaic storage system based on a timing convergent sliding mode is characterized in that: The step 1.4 is specifically as follows: In the main circuit of the grid-type photovoltaic storage converter, according to KVL, the circuit equation of the bidirectional DC / AC converter in the abc three-phase stationary coordinate system is: (6) In formula (6), I oa , I ob , I oc is the grid-side current of phases a, b, and c, V oa , V ob , V oc is the grid-side voltage of phases a, b, and c, I La , I Lb , I Lc is the AC output current of phases a, b, and c, V La , V Lb , V Lc is the AC output side phase voltage of phases a, b, and c, L f is the filter inductor; According to KCL, the state equation at the grid connection point is: (7) According to equations (4) and (5), there is coupling in the output voltage and current dq components, and the coupling term is ωL f I oq ,- ωL f I od , ωV oq ,- ωV od ; Perform Park transformation on equations (6) and (7) to convert the three-phase abc coordinate system into the dq rotating coordinate system, and obtain the differential equations of loop voltage and node current in the dq coordinate system. Convert them to obtain the double closed-loop control equation: (8) (9) In formula (8) and formula (9), K dp1 , K dp2 , K qp1 , K qp2 is the proportional adjustment coefficient of the PI control used in the voltage and current double closed loop link, K di1 , K di2 , K qi1 , K qi2 is the integral adjustment parameter.

6. The improved active disturbance rejection control method for a grid-type photovoltaic storage system based on a timing convergent sliding mode according to claim 5 is characterized in that: The step 2.1 is specifically as follows: Transform equations (6) and (7) and perform secondary derivative to obtain: （10） Transform equation (10) into the traditional ADRC paradigm: (11) In formula (11), y =[ y 1 y 2] T , y 1 , y 2 is the output of the system V od , V oq ; b =[ b d b q ] T , b d , b q That is, the control amount of the d and q axes u d , u q Gain of u =[ u d u q ] T , u d , u q are the input controls of the system on d and q respectively; F =[ F d F q ] T , F d , F q is the disturbance part of d and q axis; Since the control structures of the output voltages on the d and q axes are the same, a second-order active disturbance rejection controller is constructed with the output voltage of the d axis as the control object; make x d1 = V od , x d2 = , x d3 = F d , establish the spatial state equation: (12) In formula (12), , ; The introduced fractional derivative term transforms equation (11) into: (13) In formula (13), , F deq is the lumped disturbance on the d-axis, is the fractional derivative term, where ; Redefine state variables x d1 = V od , x d2 = , x d3 = F d The spatial state equation is established as: (14) The form of the process design fractional-order extended state observer established according to equation (14) and the state observer in linear system theory is: (15) In formula (15), z d1 , z d2 , z d3 They are x d1 , x d2 , x d3 The observed value of parameter β d1 , β d2 , β d3 is the gain coefficient of the observer.

7. The improved active disturbance rejection control method for a grid-type photovoltaic storage system based on a timing convergent sliding mode according to claim 6 is characterized in that: The step 2.2 is specifically as follows: The voltage loop voltage error is defined as , , the designed timed convergence integral sliding surface is: (16) In formula (16), , is the integral coefficient of FTCSMC, , , ; make , and connect it with formula (12) to obtain the equivalent control law: (17) The fixed-time convergence integral sliding mode surface in formula (16) can only ensure that the system converges within a fixed time during the sliding process. Therefore, the fixed-time theory is applied to the system, and the fixed-time convergence sliding mode reaching law is designed as: (18) In formula (18), , , , , is the switching gain of FTCSMC and ; Combining equation (17) and equation (18), we get the input control u d for: (19) The FTCSMC of the system is time-stable, and its upper stability bound is: (20) In formula (20), T d is the total settling time, T d1 is the settling time of the sliding process, T d2 is the settling time of the arrival process, T d1 , T d2 The specific relationship is: (21)。 8. The improved active disturbance rejection control method for a grid-type photovoltaic storage system based on a timing convergent sliding mode according to claim 7 is characterized in that: The step 3 is specifically as follows: The energy storage is performed by the DC-DC converter to step up and down the voltage, so the mathematical state equation obtained according to the state space averaging method is: (22) In formula (22), d a is the duty cycle of the DC-DC converter switch, F v ( t ), F c ( t ) are the voltage and current disturbance values ​​generated when the DC-DC converter is running; Convert the bus voltage equation in equation (22) into the second-order auto-disturbance rejection paradigm: (23) In formula (23), , , y 0 is the output of the system u dc ; b 0 is the control amount u A gain of 0; u 0 is the output duty cycle of the system in the DC-DC converter d a ; F 0 is the disturbance part; Improve formula (23): (24) In formula (24), , is the total disturbance excluding the control input, b 1 is the control gain after improvement; Defining state variables x c1 = u dc , , x c3 = F 1, then the observer form is: (25) In formula (25), z c1 , z c2 , z c3 They are x c1 , x c2 , x c3 The observed value of parameter β c1 , β c2 , β c3 is the gain coefficient of the observer; First, define the voltage error of the voltage loop of the DC-DC converter as , , the designed timed convergence integral sliding surface is: (26) make , and connect it with formula (25) to obtain the equivalent control law: (27) The fixed-time convergence sliding mode reaching law is designed as: (28) Combining equations (27) and (28), the voltage outer loop control law of the DC-DC converter is: (29)。

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