Integral-type fast non-singular adaptive super-helical sliding mode control method for energy storage converters

Abstract

The present invention discloses an integral-type fast non-singular adaptive super-helical sliding mode control method for energy storage converters. This method addresses the low accuracy of traditional interference state observers and designs a super-helical interference observer. This method uses a super-helical algorithm to accurately estimate external changes in the energy storage converter system and disturbances and uncertainty information about internal parameters. A finite-time observer is then used to precisely observe the output current of the inverter system. An integral-type fast non-singular adaptive super-helical sliding mode control method is employed. This controller mitigates the chattering problem. The control gain parameter design of the super-helical sliding mode control algorithm relies on boundary information about interference and uncertainty, which is relatively difficult to obtain in actual situations. Adaptive gain allows for adaptive adjustment of the control gain to ensure system stability and robustness.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and in particular relates to an integral-type fast non-singular adaptive super-spiral sliding mode control method for an energy storage converter. Background Art

[0002] With economic development, energy demand and consumption are increasing, while traditional energy reserves are gradually decreasing. The development of renewable energy has become a consensus in China. Renewable energy sources such as wind and photovoltaic power have experienced rapid development, and new power supply methods such as distributed power systems, microgrids, and DC grids have become research hotspots. As traditional energy sources increasingly pollute the environment, the development of low-carbon and environmentally friendly projects such as new energy vehicles has received strong national support. The development of new energy utilization faces unprecedented opportunities and challenges.

[0003] Energy storage technology is a crucial component in many new energy sectors. Renewable energy generation systems, such as photovoltaic and wind power, are characterized by significant instability and randomness. To ensure stable and reliable power supply, energy storage converters, a crucial link between energy storage power stations and the grid, feature multiple inputs and multiple outputs, strong coupling, and nonlinearity. Nonlinear control methods for energy storage converters have become a key research topic. Their control is highly susceptible to various sources of interference and uncertainty, such as electromagnetic interference (EMI) and harmonic interference. These interferences significantly impact the system's voltage regulation performance and even stability. The presence of various uncertainties and external disturbances in operating conditions significantly impacts the normal operation of the inverter. Furthermore, some specialized application scenarios place higher demands on the inverter's dynamic response and stability error. Therefore, ensuring inverter robustness and improving system performance in the presence of multiple nonlinear interferences has become a hot topic of research.

[0004] Traditional PID control, the most common control strategy in engineering, is simple and easy to implement, but its parameter tuning is complex and robustness is poor. Using feedback linearization, a linear signal model is established within a small region of the equilibrium point to achieve closed-loop stability. However, this method is relatively sensitive to interference, and linearization methods cannot effectively suppress mismatched interference. Summary of the Invention

[0005] The purpose of the present invention is to provide an integral-type fast non-singular adaptive super-helical sliding mode control method for an energy storage converter, which solves the problems of insufficient accuracy in estimating the total external disturbance of the energy storage converter and the coupling effect between the d and q axes within the system in existing traditional control methods.

[0006] The technical solution adopted by the present invention is an integral fast non-singular adaptive super-spiral sliding mode control method for energy storage converter control, which is used to control the subsequent converter of the photovoltaic converter. The subsequent converter is a three-phase grid-connected inverter, including a current reference value obtained by PQ control from a given power reference value. A disturbed state space average model of the three-phase full-bridge inverter is established by the state space averaging method. Based on ADRC, the coupling part of the converter is included in the lumped disturbance. The disturbance is quickly and accurately estimated by a finite-time observer and a super-spiral disturbance observer. The output of the observer is combined with the output feedback control method as a feedforward compensation. An integral fast non-singular adaptive super-spiral sliding mode controller based on the super-spiral disturbance observer and the finite-time state observer is designed to realize the control of the inverter output current.

[0007] The present invention is also characterized in that:

[0008] Please follow the steps below to implement:

[0009] Step 1: Construct a mathematical model of the three-phase grid-connected inverter in the dq coordinate system;

[0010] Step 2: Convert the mathematical model established in step 1 into a spatial state model, expand the total disturbance into the spatial state model, and construct an equivalent model of the grid-connected three-phase inverter;

[0011] Step 3: Based on the equivalent model of the grid-connected three-phase inverter, a super-helical disturbance observer and a finite-time observer are designed. The super-helical disturbance observer is used to observe the total disturbance of the system. The observed total disturbance is fed back to the finite-time observer to estimate the state variables. A second-order disturbance estimation is introduced to improve the observation accuracy of the disturbance and state variables.

[0012] Step 4: Apply the observation value obtained in step 3 to the integral fast non-singular self-superhelical sliding mode controller and introduce the integral term in the sliding mode surface;

[0013] Step 5: Based on the sliding mode controller obtained in step 4, add the adaptive superhelical reaching law;

[0014] Step 6: According to the above steps, the output of the grid-connected inverter control method based on the fast integral terminal sliding mode of the super-helical disturbance observer and the finite-time state observer is constructed, and the duty cycle is obtained by SPWM modulation. The duty cycle is applied to the control of the three-phase inverter switch tube to realize the control of the three-phase inverter.

[0015] Step 1 is specifically as follows:

[0016] According to Kirchhoff's law, the variable relationship of the grid-connected inverter in the abc coordinate system is derived:

[0017]

[0018] In formula (1), u a 、u b 、u c is the three-phase voltage on the three-phase inverter side, i La 、i Lb 、i Lc is the three-phase current flowing through the inductor, L and C are the filter inductor and capacitor parameters respectively, R is the circuit equivalent resistance parameter, u ga 、u gb 、u gc is the AC grid voltage, i a 、i b 、i c is the three-phase current on the grid side;

[0019] The mathematical model of the AC side of the inverter in dq coordinates is obtained by transforming equation (1) into:

[0020]

[0021] In formula (2), ω is the grid voltage angular frequency, u d 、u q Represents the components of the inverter's AC voltage on the d and q axes, i Ld 、i Lq Represent the components of the inductor current on the d and q axes, i d 、i q They represent the components of the grid-side current on the d and q axes, respectively, and u dr =s d u dc ,u qr =s q u dc , s d 、s q They are the d-axis and q-axis switching functions respectively. The switching function is defined as:

[0022]

[0023] Step 2 is as follows:

[0024] On the basis of the three-phase balance of the grid voltage, the d-axis direction of the grid voltage is taken as the direction of the voltage vector. According to the instantaneous power theory, the power equation is obtained as follows:

[0025]

[0026] In formula (4), P ref , Q ref are the reference values ​​of active power and reactive power respectively, i dref 、i qrefThey are the current reference values ​​of the set active power and reactive power respectively;

[0027] The active power and reactive power in the circuit are calculated by formula (4):

[0028]

[0029] PQ control is used on the basis of this three-phase inverter. PQ control includes a power outer loop and a current inner loop. The outer loop calculates the current inner loop reference value i by formula (5). dref 、i qref , and then the current inner loop control law is designed by the differential equation (2) to control the output;

[0030] The internal and external disturbances and parameter perturbations of the system are uniformly expressed as lumped disturbances, and the following disturbance model is obtained by mathematical transformation of formula (2):

[0031]

[0032] In formula (6), b d 、b q are the d-axis and q-axis control gain, respectively, and f d 、f q are the equivalent lumped disturbances of d and q axes, and the lumped disturbance f d 、f q Including the unmodeled part of the system, the coupled part, and the internal and external disturbances of the system, its expression is:

[0033]

[0034] Step 3 is as follows:

[0035] Let the state variable x d1 =i d , x d3 =f d , x q1 =i q , x q3 =f q , then formula (7) can be written as follows:

[0036]

[0037] Define z d1 、z d2 、z d3 、z q1 、z q2 、z q3 x d1 、x d2 、x d3 、xq1 、x q2 、x q3 The observation value of is, according to the disturbance model of formula (6), the following finite time observer is designed:

[0038]

[0039] In formula (9), sgn(.) is the sign function, k d1 、k d2 、k q1 、k q2 is the observer gain and is a positive number; α1∈(1-ε,1), ε>0, α2=2α1;

[0040] Design the following superhelical interference observer:

[0041]

[0042] In formula (10), sgn(.) is the sign function; k 1,2,3,4 is the observer gain; x Where the disturbance x d3 , x q3 The calculation is as follows:

[0043]

[0044] Let the d and q axis grid side current i d ,i q The deviation from the grid-side current reference value e d 、e q for:

[0045]

[0046] In formula (12), i dref for i d Reference value, i qref for i q Reference value of

[0047] The integral sliding surface is combined with the non-singular terminal sliding mode, and the dq-axis integral fast non-singular terminal sliding surface is selected as S d 、S q :

[0048]

[0049] In formula (13), λ1 and λ2 are greater than 0,

[0050] When the system enters the sliding mode, Right now:

[0051]

[0052] Step 5 is specifically as follows:

[0053] Derivative and simplify equation (14) to obtain:

[0054]

[0055] From equation (15), we can get the equivalent control law u of the current inner loop d and q axes: dreq 、u qreq for:

[0056]

[0057] The improved super-helical sliding mode reaching law is used as the switching control law of the sliding mode surface. The d-axis switching control law is as follows:

[0058]

[0059] In formula (17), m a is the integral of the switching term, k2=2εk1+β+4ε 2 ,in γ1,μ,ε,β,k m All are positive numbers;

[0060] The q-axis switching control law is as follows:

[0061]

[0062] In formula (18), m b is the integral of the switching term, k5=2εk4+β+4ε 2 ,in γ1,μ,ε,β,k m All are positive numbers;

[0063] Combining equations (16), (17) and (18), we can obtain the complete integrated control law u for the d and q axes: d 、u q for:

[0064]

[0065] The beneficial effects of the present invention are:

[0066] The present invention proposes an integral-type fast non-singular adaptive super-helical sliding mode control method for energy storage converters. This method addresses the low accuracy of traditional interference state observers by designing a super-helical interference observer and employing a super-helical algorithm to accurately estimate external changes in the energy storage converter system and disturbances and uncertainties in its internal parameters. A finite-time observer is then used to precisely observe the output current of the inverter system. An integral-type fast non-singular adaptive super-helical sliding mode control method is employed to mitigate chattering. The control gain parameter design of the super-helical sliding mode control algorithm relies on boundary information about interference and uncertainty, which is relatively difficult to obtain in real-world situations. Adaptive gain allows for adaptive adjustment of the control gain to ensure system stability and robustness. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 This is a control block diagram of the energy storage converter control integral type fast non-singular adaptive super spiral sliding mode control method of the present invention;

[0068] Figure 2 This is the main circuit topology diagram of the three-phase grid-connected inverter;

[0069] Figure 3 It is a control block diagram of the energy storage converter of the present invention;

[0070] Figure 4 This is the transient simulation waveform of the dq axis current under PI control;

[0071] Figure 5 This is a transient simulation waveform diagram of the dq axis current controlled by the control method of the present invention;

[0072] Figure 6 This is the transient waveform of the grid-side current under PI control when the active power suddenly increases from 35kW to 75kW;

[0073] Figure 7 This is a transient waveform diagram of the grid-side current controlled by the control method of the present invention when the active power suddenly increases from 35kW to 75kW;

[0074] Figure 8 This is the transient waveform of the grid-side current under PI control when the active power suddenly drops from 75kW to 35kW;

[0075] Figure 9 This is a transient waveform diagram of the grid-side current controlled by the control method of the present invention when the active power suddenly drops from 75kW to 35kw;

[0076] Figure 10 This is the grid current harmonic analysis diagram of PI control;

[0077] Figure 11 This is a harmonic analysis diagram of the grid current controlled by the control method of the present invention. DETAILED DESCRIPTION

[0078] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0079] Example 1

[0080] This embodiment provides a fast non-singular adaptive super-spiral sliding mode control method for an energy storage converter, which is used to control a subsequent converter of a photovoltaic converter, wherein the subsequent converter is a three-phase grid-connected inverter, such as Figure 1 As shown, the current reference value is obtained by PQ control from a given power reference value, the state space averaging method is used to establish a disturbed state space average model of the three-phase full-bridge inverter, and the coupled part of the converter is included in the lumped disturbance based on ADRC. The disturbance is quickly and accurately estimated through a finite time observer and a super helical disturbance observer, and the output of the observer is combined with the output feedback control method as a feedforward compensation. An integral fast non-singular adaptive super helical sliding mode controller based on the super helical disturbance observer and the finite time state observer is designed to realize the control of the inverter output current.

[0081] Example 2

[0082] This embodiment provides an integral-type fast non-singular adaptive super-helical sliding mode control method for an energy storage converter. Based on Example 1, the method is implemented in the following steps:

[0083] Step 1: Construct a mathematical model of the three-phase grid-connected inverter in the dq coordinate system;

[0084] The circuit topology of the three-phase grid-connected inverter is as follows: Figure 2 As shown, the DC side voltage is u in The DC voltage source is provided by controlling the inverter to output a certain power to supply the AC load. dc is the DC side voltage stabilizing capacitor, u dc is the voltage across the DC side stabilizing capacitor, i o Represents the DC bus current. According to Kirchhoff's law, the variable relationship of the grid-connected inverter in the abc coordinate system is derived:

[0085]

[0086] In formula (1), u a 、u b 、u c is the three-phase voltage on the three-phase inverter side, i La 、i Lb 、i Lc is the three-phase current flowing through the inductor, L and C are the filter inductor and capacitor parameters respectively, R is the circuit equivalent resistance parameter, uga 、u gb 、u gc is the AC grid voltage, i a 、i b 、i c is the three-phase current on the grid side;

[0087] The mathematical model of the AC side of the inverter in dq coordinates is obtained by transforming equation (1) into:

[0088]

[0089] In formula (2), ω is the grid voltage angular frequency, u d 、u q Represents the components of the inverter's AC voltage on the d and q axes, i Ld 、i Lq Represent the components of the inductor current on the d and q axes, i d 、i q They represent the components of the grid-side current on the d and q axes, respectively, and u dr =S d u dc ,u qr =S q u dc , S d 、S q They are the d-axis and q-axis switching functions respectively. The switching function is defined as:

[0090]

[0091] Step 2: Convert the mathematical model established in step 1 into a spatial state model, expand the total disturbance into the spatial state model, and construct an equivalent model of the grid-connected three-phase inverter;

[0092] On the basis of the three-phase balance of the grid voltage, the d-axis direction of the grid voltage is taken as the direction of the voltage vector. According to the instantaneous power theory, the power equation is obtained as follows:

[0093]

[0094] In formula (4), P ref , Q ref are the reference values ​​of active power and reactive power respectively, i dref 、i qref They are the current reference values ​​of the set active power and reactive power respectively;

[0095] The active power and reactive power in the circuit are calculated by formula (4):

[0096]

[0097] PQ control is used on the basis of this three-phase inverter. PQ control includes a power outer loop and a current inner loop. The outer loop calculates the current inner loop reference value i by formula (5). dref 、i qref , and then the current inner loop control law is designed by the differential equation (2) to control the output;

[0098] The internal and external disturbances and parameter perturbations of the system are uniformly expressed as lumped disturbances, and the following disturbance model is obtained by mathematical transformation of formula (2):

[0099]

[0100] In formula (6), b d 、b q are the d-axis and q-axis control gain, respectively, and f d 、f q are the equivalent lumped disturbances of d and q axes, and the lumped disturbance f d 、f q Including the unmodeled part of the system, the coupled part, and the internal and external disturbances of the system, its expression is:

[0101]

[0102] Step 3: Based on the equivalent model of the grid-connected three-phase inverter, a super-helical disturbance observer and a finite-time observer are designed. The super-helical disturbance observer is used to observe the total disturbance of the system. The observed total disturbance is fed back to the finite-time observer to estimate the state variables. A second-order disturbance estimation is introduced to improve the observation accuracy of the disturbance and state variables.

[0103] Step 4: Apply the observation value obtained in step 3 to the integral fast non-singular self-superhelical sliding mode controller and introduce the integral term in the sliding mode surface;

[0104] Step 5: Based on the sliding mode controller obtained in step 4, add the adaptive superhelical reaching law;

[0105] Step 6: According to the above steps, the output of the grid-connected inverter control method based on the fast integral terminal sliding mode of the super-helical disturbance observer and the finite-time state observer is constructed, and the duty cycle is obtained by SPWM modulation. The duty cycle is applied to the control of the three-phase inverter switch tube to realize the control of the three-phase inverter.

[0106] Example 3

[0107] This embodiment provides an energy storage converter control integral type fast non-singular adaptive super spiral sliding mode control method. Based on the embodiment 1-2, step 3 is specifically as follows:

[0108] Let the state variable x q3 =fq , then formula (7) can be written as follows:

[0109]

[0110] Define z d1 、z d2 、z d3 、z q1 、z q2 、z q3 x d1 、x d2 、x d3 、x q1 、x q2 、x q3 The observation value of is, according to the disturbance model of formula (6), the following finite time observer is designed:

[0111]

[0112] In formula (9), sgn(.) is the sign function, k d1 、k d2 、k q1 、k q2 is the observer gain and is a positive number; α1∈(1-ε,1), ε>0, α2=2α1;

[0113] Design the following superhelical interference observer:

[0114]

[0115] In formula (10), sgn(.) is the sign function; k 1,2,3,4 is the observer gain; Where the disturbance x d3 , x q3 The calculation is as follows:

[0116]

[0117] Step 4 is as follows:

[0118] Let the d and q axis grid side current i d ,i q The deviation from the grid-side current reference value e d 、e q for:

[0119]

[0120] In formula (12), i dref for i d Reference value, i qref for i q Reference value of

[0121] Integral sliding mode is a special construction method of sliding mode surface. On the basis of linear sliding mode surface, an integral term is added to make the order of switching function of system sliding mode consistent with the order of system sliding mode, which can make the system located on the sliding mode surface in the initial stage and ensure the global robustness of the system. Therefore, the integral sliding mode surface is combined with the non-singular terminal sliding mode, and the dq-axis integral fast non-singular terminal sliding mode surface S is selected. d 、S q for:

[0122]

[0123] In formula (13), λ1 and λ2 are greater than 0,

[0124] When the system enters the sliding mode, Right now:

[0125]

[0126] Example 4

[0127] This embodiment provides an energy storage converter control integral type fast non-singular adaptive super spiral sliding mode control method. Based on embodiments 1-3, step 5 is specifically as follows:

[0128] Derivative and simplify equation (14) to obtain:

[0129]

[0130] From the analysis of formula (15), we can see that the linear terms and play different leading roles in different motion stages of the system, which can achieve global rapid convergence, and the integral terms are introduced when constructing the sliding surface, and there is no differential term, which avoids singular phenomena;

[0131] From equation (15), we can get the equivalent control law u of the current inner loop d and q axes: dreq 、u qreq for:

[0132]

[0133] The improved super-helical sliding mode reaching law is used as the switching control law of the sliding mode surface. The d-axis switching control law is as follows:

[0134]

[0135] In formula (17), m a is the integral of the switching term, k2=2εk1+β+4ε 2 ,in γ1,μ,ε,β,km All are positive numbers, and the adaptive control laws of k1 and k2 do not require disturbances and the boundary values ​​of the derivatives can realize the adaptive adjustment of the coefficients;

[0136] The q-axis switching control law is as follows:

[0137]

[0138] In formula (18), m b is the integral of the switching term, k5=2εk4+β+4ε 2 ,in γ1,μ,ε,β,k m All are positive numbers, and the adaptive control laws k4 and k5 do not require disturbances and the boundary values ​​of the derivatives can realize the adaptive adjustment of the coefficients;

[0139] Combining equations (16), (17) and (18), we can obtain the complete integrated control law u for the d and q axes: d 、u q for:

[0140]

[0141] The present invention controls the energy storage converter as follows Figure 3 shown.

[0142] The DC / DC converter preceding the energy storage converter adopts dual-loop control of voltage and current to improve the system's control accuracy and anti-interference capability. The outer voltage loop adopts an improved sliding-mode active disturbance rejection control, estimating the DC bus voltage and disturbances through a finite-time observer. An integral fast non-singular terminal sliding-mode controller is used in the feedback control. The outer voltage loop provides a reference value for the inner inductor current loop, so the control variable of the outer voltage loop is the inductor current.

[0143]

[0144] In formula (20), f v (t), f c (t) are the unknown disturbances of voltage and current respectively;

[0145] Derivative of formula (20) yields:

[0146]

[0147] In formula (21) b v is the gain of the control quantity, f v is the equivalent lumped disturbance excluding the control input.

[0148] Let the state variable xv1 =u dc ,x v2 =f v , then the voltage outer loop observer is in the form of:

[0149]

[0150] Where, the voltage outer loop observer gain l v1,v2 >0;z v1 、z v2 x v1 、x v2 Observed values.

[0151] The reference value of bidirectional DC / DC is u dcref , the error between the output voltage and the reference voltage is e dc :

[0152] e dc =u dc -u dcref (twenty three)

[0153] The designed integral fast non-singular terminal sliding surface is:

[0154]

[0155] The derivative of the sliding surface of formula (24) is:

[0156]

[0157] Combining equations (21) and (25), the outer loop control law is:

[0158]

[0159] From the above content, it can be seen that the energy storage converter control integral type fast non-singular adaptive super-helical sliding mode control method of the present invention has the following advantages:

[0160] 1) The superhelical disturbance observer and fixed-time observer employed in this invention eliminate the need for a precise mathematical model of the inverter system and can estimate both low- and high-frequency disturbances. The first-order derivative of the observed disturbance does not need to be zero, making it particularly suitable for inverters with large internal parameter variations and uncertain external information. This observer utilizes a superhelical algorithm to improve the accuracy and speed of observing external and internal parameter disturbances.

[0161] 2) The fast integral terminal sliding mode controller adopted in the present invention uses the three-phase output current to obtain the current in the two-phase rotating coordinate system through dq coordinate transformation, and obtains the current tracking error as input. Then, the integral term is introduced to correct the system layer by layer, so that the system has higher accuracy and robustness, ensuring the global stability of the system when subjected to internal and external disturbances.

[0162] 3) The superhelical function employed in this invention converges quickly and stably, allowing the interference error to converge to zero within a finite time, thus achieving the desired performance. It consists of two components: first, a continuous function of the error variable is obtained, thus making the error signal appear continuous; second, the integral of the discontinuous time derivative of the error avoids chattering.

[0163] 4) The present invention introduces a parameter adaptive law to further improve the generalized super-helical sliding mode controller, so that the generalized super-helical sliding mode controller has better steady-state and transient performance, and further improves the convergence speed and anti-disturbance ability of the controller.

[0164] Simulation analysis

[0165] In order to verify the feasibility of the integrated fast non-singular adaptive super-spiral sliding mode control method for the energy storage converter of the present invention, in a grid-connected inverter model built in the Matlab / Simulink platform, under both the control method of the present invention and the traditional PI control, when the active power suddenly changes, the output of 35kW in stable operation suddenly increases to 75kW at 0.2s, and the corresponding three-phase current amplitude suddenly increases from 51.3A to 150.2A; at 0.3s, it suddenly drops from 75kW to 35kW, and the corresponding three-phase current amplitude suddenly drops from 150.2A to 51.3A, resulting in the dynamic response of the three-phase current output on the AC side of the three-phase inverter.

[0166] like Figure 4 As shown in the traditional PI control, when i d When a mutation occurs, q The cross-coupling effect simulation. It can be seen that at 0.2s i d A sudden increase occurs due to the coupling effect i q There is an overshoot of 27.5A; at 0.3s i d A sudden decrease occurs, i q There is an overshoot of 29.5A. Figure 5 As shown, under the control of the present invention, when i d When a mutation occurs, q The cross-coupling effect. It can be seen from the figure that at 0.2s i d A sudden increase occurs, i qThere is only an overshoot of 8.5A, and the stabilization speed is very fast. By comparison, it can be seen that the control of the present invention has an obvious decoupling effect on the d-axis and q-axis currents, can control the disturbance more quickly, and finally achieve stability.

[0167] In order to verify the effectiveness of the control method designed in the present invention, a simulation circuit was built in a hardware-in-the-loop (HIL) experimental platform, and a comparative analysis was performed with the traditional PI control strategy. The power is defined as positive when the voltage and current directions are consistent. The simulation parameter settings are shown in Table 1.

[0168] Table 1 Circuit parameters

[0169] parameter Numerical Grid voltage amplitude e 311V <![CDATA[DC bus voltage U dc > 800V Filter inductor L 0.5mH Filter capacitor C 50μF Inductor parasitic resistance R 0.01Ω <![CDATA[DC regulated voltage capacitor C dc > 2.2mF Load power 35kW-75kW <![CDATA[Battery terminal voltage v bat > 400V

[0170] This invention addresses the low accuracy of traditional disturbance state observers by designing a superhelical disturbance observer. This algorithm uses a superhelical algorithm to accurately estimate external variations and internal parameter disturbances and uncertainties in a three-phase inverter system. This controller mitigates chattering by employing an integral-type fast nonsingular adaptive superhelical sliding mode control method. The design of the control gain parameters for the superhelical sliding mode control algorithm relies on boundary information about disturbances and uncertainties, which is relatively difficult to obtain in real-world situations. Adaptive gain allows for adaptive adjustment of control gain, ensuring system stability and robustness.

[0171] Depend on Figure 6 It can be seen that when the output active power of the energy storage converter increases suddenly from 35kW to 75kw, i d The jump from 60A to 152A. The transition time from 35kW to 75kW under the PI control strategy is 14.3ms. The jump caused by the sudden increase in power produces a certain amount of overshoot. In addition, due to the coupling between powers, the transient process of reactive power is also caused when the active power suddenly changes, such as Figure 6 The framed part. Figure 7 It can be seen that under the control method of the present invention, when the converter output active power jumps from 30kW to 75kW, the transition time of the jump caused by the sudden power increase is 10.6ms, and the fluctuation of the current value during steady-state operation is smaller than that of PI control.

[0172] Depend on Figure 8 It can be seen that when the output active power of the energy storage converter jumps from 75kW to 35kW, i d The jump from 152A to 60A. The transition time from 75kW to 35kW under the PI control strategy is 28ms. The jump caused by the sudden power reduction produces a certain amount of overshoot. In addition, due to the coupling between the powers, the transient process of reactive power is also caused when the active power suddenly changes, such as Figure 8 The framed part. Figure 9 It can be seen that under the control method of the present invention, when the converter output active power jumps from 75kW to 35kW, the transition time of the jump caused by the sudden power reduction is 9.8ms, and the fluctuation of the current value during steady-state operation is smaller than that of PI control.

[0173] In order to verify the influence of the control method of the present invention on the power quality of the inverter output current, a Fourier analysis of two steady-state cycles was performed on the grid-connected current when the inverter output active power was 30kW in Matlab / Simulink software. Figure 10 As shown in Figure 1, the harmonic analysis of the grid-connected current of the energy storage converter under traditional PI control is shown, and the THD is 4.18%. Figure 11 The figure shows the harmonic analysis of the grid-connected current of the energy storage converter under the control of the present invention, with a THD of 1.59%. The comparison shows that the control of the present invention has a stronger harmonic suppression capability, improving the quality of the grid-connected power.

[0174] In summary, the energy storage converter control integral type fast non-singular adaptive super-spiral sliding mode control method of the present invention effectively solves the coupling effects of external disturbances and the current inner loop on the converter in the working mode, improves the control accuracy and convergence speed of the inverter during interference reception, and has good robustness, which can effectively improve the power quality of the power grid.

Claims

1. An integral-type fast non-singular adaptive super-spiral sliding mode control method for energy storage converter is used to control the subsequent converter of the photovoltaic converter, which is a three-phase grid-connected inverter. The method is characterized in that: This includes obtaining a current reference value through PQ control from a given power reference value, establishing a disturbed state space average model of a three-phase full-bridge inverter using the state space averaging method, incorporating the coupled part of the converter into the lumped disturbance based on ADRC, quickly and accurately estimating the disturbance through a finite time observer and a super helical disturbance observer, combining the observer's output as feedforward compensation with an output feedback control method, and designing an integral fast non-singular adaptive super helical sliding mode controller based on a super helical disturbance observer and a finite time state observer to achieve inverter output current control. Please follow the steps below to implement it: Step 1: Construct a mathematical model of the three-phase grid-connected inverter in the dq coordinate system; Step 2: Convert the mathematical model established in step 1 into a spatial state model, expand the total disturbance into the spatial state model, and construct an equivalent model of the grid-connected three-phase inverter; Step 3: Based on the equivalent model of the grid-connected three-phase inverter, a super-helical disturbance observer and a finite-time observer are designed. The super-helical disturbance observer is used to observe the total disturbance of the system. The observed total disturbance is fed back to the finite-time observer to estimate the state variables. A second-order disturbance estimation is introduced to improve the observation accuracy of the disturbance and state variables. Step 4: Apply the observation value obtained in step 3 to the integral fast non-singular self-superhelical sliding mode controller and introduce the integral term in the sliding mode surface; Step 5: Based on the sliding mode controller obtained in step 4, add the adaptive superhelical reaching law; Step 6: According to the above steps, the output of the grid-connected inverter control method based on the fast integral terminal sliding mode of the super-helical disturbance observer and the finite-time state observer is constructed, and the duty cycle is obtained by SPWM modulation. The duty cycle is applied to the control of the three-phase inverter switch tube to realize the control of the three-phase inverter.

2. The energy storage converter control integral type fast non-singular adaptive super spiral sliding mode control method according to claim 1 is characterized in that: The step 1 is specifically as follows: According to Kirchhoff's law, the grid-connected inverter is derived abc Variable relationship in the coordinate system: （1） In formula (1), u a 、 u b 、 u c is the three-phase voltage on the three-phase inverter side, i La 、 i Lb 、 i Lc is the three-phase current flowing through the inductor, L 、 C are the filter inductance and capacitance parameters respectively, R is the circuit equivalent resistance parameter, u ga 、 u gb 、 u gc is the AC grid voltage, i a 、 i b 、 i c is the three-phase current on the grid side; The mathematical model of the AC side of the inverter in dq coordinates is obtained by transforming equation (1) into: （2） In formula (2), ω is the grid voltage angular frequency, u d 、u q Respectively represent the components of the inverter's AC voltage on the d and q axes, i Ld 、 i Lq Represent the components of the inductor current on the d and q axes, respectively. i d 、 i q Represent the components of the grid-side current on the d and q axes, respectively. u dr = s d u dc , u qr = s q u dc , s d 、 s q They are the d-axis and q-axis switching functions respectively. The switching function is defined as: （3）。 3. The energy storage converter control integral type fast non-singular adaptive super spiral sliding mode control method according to claim 2 is characterized in that: The step 2 is specifically as follows: On the basis of the three-phase balance of the grid voltage, the d-axis direction of the grid voltage is taken as the direction of the voltage vector. According to the instantaneous power theory, the power equation is obtained as follows: （4） In formula (4), P ref 、 Q ref are the reference values ​​of active power and reactive power respectively. i dref 、 i qref They are the current reference values ​​of the set active power and reactive power respectively; The active power and reactive power in the circuit are calculated by formula (4): （5） PQ control is used on the basis of this three-phase inverter. PQ control includes a power outer loop and a current inner loop. The outer loop uses the current inner loop reference value calculated by formula (5) i dref 、 i qref , and then the current inner loop control law is designed by the differential equation (2) to control the output; The internal and external disturbances and parameter perturbations of the system are uniformly expressed as lumped disturbances, and the following disturbed model is obtained by mathematical transformation of Equation (2): （6） In formula (6), b d 、 b q are the d-axis and q-axis control quantity gains respectively, f d 、 f q They are the equivalent d and q axis lumped disturbances, lumped disturbances f d 、 f q Including the unmodeled part of the system, the coupled part, and the internal and external disturbances of the system, its expression is: （7）。 4. The energy storage converter control integral type fast non-singular adaptive super spiral sliding mode control method according to claim 3 is characterized in that: The step 3 is specifically as follows: Let the state variable x d1 = i d , x d2 = , x d3 = f d , x q1 =i q , x q2 = , x q3 = f q , then formula (7) can be written as follows: （8） definition 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 The observation value of is, according to the disturbance model of formula (6), the following finite time observer is designed: （9） In formula (9), sgn(.) is the sign function, k d1 、 k d2 、 k q1 、 k q2 is the observer gain and is a positive number; , , ; Design the following superhelical interference observer: （10） In formula (10), sgn(.) is the sign function; k 1,2,3,4 is the observer gain; = z d3 - x d3 ; = z q3 - x q3 , where the disturbance x d3 , x q3 The calculation is as follows: （11）。 5. The energy storage converter control integral type fast non-singular adaptive super spiral sliding mode control method according to claim 4 is characterized in that: The step 4 is specifically as follows: Let the d and q axis grid side currents be i d , i q Deviation from the grid-side current reference value e d 、 e q for: （12） In formula (12), i dref for i d The reference value, i qref for i q Reference value of Combining the integral sliding mode surface with the non-singular terminal sliding mode, the dq-axis integral fast non-singular terminal sliding mode surface is selected as: （13） In formula (13), and greater than 0, ; When the system enters the sliding mode, ,Right now: （14）。 6. The energy storage converter control integral type fast non-singular adaptive super spiral sliding mode control method according to claim 5, characterized in that: The step 5 is specifically as follows: Derivative and simplify equation (14) to obtain: （15） From Equation (15), we can get the equivalent control law u of the current inner loop d and q axes: dreq 、u qreq for: （16） The improved super-helical sliding mode reaching law is used as the switching control law of the sliding mode surface. The d-axis switching control law is as follows: （17） In formula (17), m a is the integral of the switching term, , ,in , , , , , k m All are positive numbers; The q-axis switching control law is as follows: （18） In formula (18), m b is the integral of the switching term, , ,in , , , , , k m All are positive numbers; Combining equations (16), (17) and (18) we can obtain the complete integrated control law for the d and q axes: u d 、 u q for: （19）。

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