Energy storage converter control integral type fast nonsingular self-adaptive super-spiral sliding mode control method

Abstract

The invention discloses an integral type fast nonsingular self-adaptive super-spiral sliding mode control method for an energy storage converter, provides a solution for the problem of low accuracy of a traditional interference state observer, and designs a super-spiral interference observer. A superhelix algorithm is adopted to accurately estimate disturbance and uncertainty information of external changes and internal parameters of the energy storage converter system. Secondly, a finite time observer is adopted to accurately observe the output current of an inverter system, an integral type fast nonsingular self-adaptive super-spiral sliding mode control method is adopted, the controller weakens the buffeting problem, the control gain parameter design of the super-spiral sliding mode control algorithm depends on interference and uncertain boundary information, and the control gain parameter design of the super-spiral sliding mode control algorithm depends on the uncertain boundary information. The information is relatively difficult to obtain in the actual situation, and the adaptive gain can enable the control gain to be adaptively adjusted so as to ensure the stability and robustness of the system.

Description

Technical Field

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

[0002] With the development of economy, the demand and consumption of energy are increasing day by day, and the traditional energy reserves are gradually decreasing. The development of renewable energy has become a research consensus in China. Renewable energy such as wind power and photovoltaic has been rapidly developed. New power supply methods such as distributed power supply system, microgrid, DC grid have become research hotspots. With the increasingly serious environmental pollution caused by traditional energy, the development of low-carbon and environmentally friendly projects such as new energy vehicles has been strongly supported by the country, and the development of new energy utilization is facing unprecedented opportunities and challenges.

[0003] Among many new energy fields, energy storage technology is a very important technical link. In renewable energy power generation systems such as photovoltaic and wind power, the power generation system has great instability and randomness. In order to ensure the stability and reliability of power supply, the energy storage converter, as an important link between the energy storage power station and the power grid, has the characteristics of multi-input and multi-output, strong coupling, and nonlinearity. The nonlinear control method for the energy storage converter has become a key issue in current research. The control effect of the energy storage converter is easily affected by various multi-source interference and uncertainty. For example, many forms of external interference such as electromagnetic interference and harmonic interference have a great impact on the voltage regulation performance of the system and even affect the stability of the system. Due to various uncertainties and external disturbances in the working conditions, complex uncertainties have a great impact on the normal operation of the inverter. At the same time, some special application scenarios put forward higher requirements on the dynamic response and stability error of the inverter. Therefore, how to ensure the robustness of the inverter and improve the system performance indicators in the presence of multiple nonlinear interferences in the system has become a research hotspot for scholars.

[0004] As the most common control strategy in engineering, the traditional PID control method has a simple structure and is easy to implement, but its parameter setting is complex and its robustness is poor. Using the feedback linear method, a linear signal model in a small area of ​​the equilibrium point is established to achieve the closed-loop stability of the system. However, this method is relatively sensitive to interference, and the linearization method cannot effectively suppress non-matching interference. Summary of the invention

[0005] The purpose of the present invention is to provide an integral 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 influence between the d and q axes inside the system in the existing traditional control methods.

[0006] The technical solution adopted by the present invention is an integral fast non-singular adaptive super-helical 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 a state space averaging method, and the coupled part of the converter is included in the lumped disturbance based on ADRC. The disturbance is quickly and accurately estimated by a finite time observer and a super-helical disturbance observer, and the output of the observer is combined with an output feedback control method as a feedforward compensation, and an integral fast non-singular adaptive super-helical sliding mode controller based on a super-helical disturbance observer and a 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] Follow the steps below to implement it:

[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: Design a super-helical disturbance observer and a finite-time observer based on the equivalent model of the grid-connected three-phase inverter. 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. The 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 surface;

[0013] Step 5: According to 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, the duty cycle is obtained by SPWM modulation, and 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 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 inverter AC side 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 They represent the components of the inverter's AC voltage on the d and q axes, respectively. Ld 、i Lq Respectively 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] Based on this three-phase inverter, PQ control is used. PQ control includes a power outer loop and a current inner loop. The outer loop calculates the current inner loop reference value i through 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 disturbed model is obtained by mathematically transforming equation (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 the 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 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 grid-side current i of d and q axes be d ,i q The deviation from the grid-side current reference value is d 、e q for:

[0045]

[0046] In formula (12), i dref for i d The reference value of 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 simplified equation (14) yields:

[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, and 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 normal 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 normal 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 energy storage converter control integral fast non-singular adaptive super-helical sliding mode control method of the present invention proposes a solution to the problem of low accuracy of traditional interference state observers, designs a super-helical interference observer, and uses a super-helical algorithm to accurately estimate the external changes of the energy storage converter system and the disturbance and uncertainty information of the internal parameters. Secondly, a finite time observer is used to accurately observe the output current of the inverter system, and an integral fast non-singular adaptive super-helical sliding mode control method is used. The controller weakens the jitter problem. The control gain parameter design of the super-helical sliding mode control algorithm depends on the boundary information of interference and uncertainty. It is relatively difficult to obtain this information in actual situations. The adaptive gain can make the control gain adaptively adjusted to ensure the stability and robustness of the system. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0068] Figure 2 It 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 It is a transient simulation waveform diagram of 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 The transient waveform diagram of the current on the grid side 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] Fig. 9 The transient waveform diagram of the current on the grid side controlled by the control method of the present invention when the active power suddenly drops from 75kW to 35kw;

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

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

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

[0079] Example 1

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

[0081] Example 2

[0082] This embodiment provides an energy storage converter control integral type fast non-singular adaptive super spiral sliding mode control method, based on Example 1, specifically implemented according to the following steps:

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

[0084] Three-phase grid-connected inverter circuit topology 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 value across the DC side voltage 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 inverter AC side 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 They represent the components of the inverter's AC voltage on the d and q axes, respectively. Ld 、i Lq Respectively 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] Based on this three-phase inverter, PQ control is used. PQ control includes a power outer loop and a current inner loop. The outer loop calculates the current inner loop reference value i through 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 disturbed model is obtained by mathematically transforming equation (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 the 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: Design a super-helical disturbance observer and a finite-time observer based on the equivalent model of the grid-connected three-phase inverter. 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. The 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 surface;

[0104] Step 5: According to 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, the duty cycle is obtained by SPWM modulation, and 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 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 grid-side current i of d and q axes be d ,i q The deviation from the grid-side current reference value is d 、e q for:

[0119]

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

[0121] Integral sliding mode is a special way to construct 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, so that the system can be located on the sliding mode surface in the initial stage, ensuring 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 simplified equation (14) yields:

[0129]

[0130] From the analysis of formula (15), it can be seen 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 are no differential terms, 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, and 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 k1 and k2 adaptive control laws do not require disturbances and the boundary values ​​of the derivatives can realize 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 of them are positive numbers, and the adaptive control laws k4 and k5 do not require disturbances and the boundary values ​​of the derivatives can realize 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 voltage and current dual-loop control is adopted for the front-stage DC / DC converter of the energy storage converter to improve the control accuracy and anti-interference ability of the system. The voltage outer loop adopts the improved sliding mode anti-disturbance control, and estimates the DC bus voltage and disturbance through the finite time observer. In the feedback control, an integral fast non-singular terminal sliding mode controller is adopted; the voltage outer loop provides a reference value for the inductor current inner loop, so the control quantity of the voltage outer 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 value of .

[0151] The bidirectional DC / DC reference value 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 equation (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 used in the present invention can estimate low-frequency and high-frequency disturbances without establishing an accurate mathematical model of the inverter system, and the first-order derivative of the disturbance of the observed object does not need to be zero, which is particularly suitable for inverters with large internal parameter changes and uncertain information such as external changes. The observer uses the superhelical algorithm to improve the accuracy and speed of the observer's observation of external and internal parameter disturbances.

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

[0162] 3) The superhelical function adopted by the present invention has a fast and stable convergence speed, so that the interference error converges to zero in a limited time, thereby achieving the expected performance. It consists of two parts. First, a continuous function of the error variable can be obtained, so that the error signal also appears to be a continuous state; second, the integral of the discontinuous time derivative exists in the error, which avoids the occurrence of 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 integral fast non-singular adaptive super-helical sliding mode control method for the energy storage converter of the present invention, in the grid-connected inverter model built in the Matlab / Simulink platform, under 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 amplitude of the three-phase current suddenly increases from 51.3A to 150.2A; it suddenly drops from 75kW to 35kW at 0.3s, and the corresponding amplitude of the three-phase current suddenly drops from 150.2A to 51.3A, thereby causing 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 of the 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, and 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 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.

[0168] Table 1 Circuit parameters

[0169] parameter Numeric 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 capacitor C dc > 2.2mF Load power 35kW-75kW <![CDATA[Battery terminal voltage v bat > 400V

[0170] The present invention proposes a solution to the problem that the traditional interference state observer has low accuracy, designs a super-helical interference observer, and uses a super-helical algorithm to accurately estimate the external changes of the three-phase inverter system and the disturbance and uncertainty information of the internal parameters. The integral fast non-singular adaptive super-helical sliding mode control method is adopted. The controller weakens the chattering problem. The control gain parameter design of the super-helical sliding mode control algorithm depends on the boundary information of interference and uncertainty, and it is relatively difficult to obtain this information in actual situations. The adaptive gain can make the control gain adaptively adjusted to ensure the stability and robustness of the system.

[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 changes suddenly, such as Figure 6 The framed part. Figure 7 It can be seen that under the control method of the present invention, when the output active power of the converter jumps from 30kW to 75kw, the transition time of the jump caused by the sudden increase in power 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 changes suddenly, such as Figure 8 Framed part. Fig. 9 It can be seen that under the control method of the present invention, when the output active power of the converter 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, the grid-connected current of the inverter output active power of 30kW was subjected to Fourier analysis of 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 the traditional PI control, and the THD is 4.18%. Fig.11 The figure shows the harmonic analysis of the grid-connected current of the energy storage converter under the control of the present invention, and the THD is 1.59%. 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.

[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 when receiving interference, and the present invention has good robustness and can effectively improve the power quality of the power grid.

Claims

1. An energy storage converter control integral type fast non-singular adaptive super-helical sliding mode control method is used to control the subsequent converter of the photovoltaic converter, the subsequent converter is a three-phase grid-connected inverter, and is characterized in that: It includes obtaining the reference value of current through PQ control from a given power reference value, establishing the disturbed state space average model of the three-phase full-bridge inverter by the state space averaging method, and classifying the coupled part of the converter into 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 feedforward compensation. An integral fast non-singular adaptive super helical sliding mode controller based on a super helical disturbance observer and a finite time state observer is designed to realize the control of the inverter output current.

2. The energy storage converter control integral type fast non-singular adaptive super-helical sliding mode control method according to claim 1 is characterized in that: 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: Design a super-helical disturbance observer and a finite-time observer based on the equivalent model of the grid-connected three-phase inverter. 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. The 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 surface; Step 5: According to 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, the duty cycle is obtained by SPWM modulation, and the duty cycle is applied to the control of the three-phase inverter switch tube to realize the control of the three-phase inverter.

3. The energy storage converter control integral type fast non-singular adaptive super-helical sliding mode control method according to claim 2 is characterized in that: The step 1 specifically comprises: According to Kirchhoff's law, the variable relationship of the grid-connected inverter in the abc coordinate system is derived: 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; The mathematical model of the inverter AC side in dq coordinates is obtained by transforming equation (1) into: In formula (2), ω is the grid voltage angular frequency, u d 、u q They represent the components of the inverter's AC voltage on the d and q axes, respectively. Ld 、i Lq Respectively 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:

4. The energy storage converter control integral type fast non-singular adaptive super-helical sliding mode control method according to claim 3 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: 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): Based on this three-phase inverter, PQ control is used. PQ control includes a power outer loop and a current inner loop. The outer loop calculates the current inner loop reference value i through formula (5): 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 mathematically transforming equation (2): 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:

5. The energy storage converter control integral type fast non-singular adaptive super-helical sliding mode control method according to claim 4 is characterized in that: The step 3 is specifically as follows: 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: 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 According to the disturbance model of formula (6), the following finite time observer is designed: 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; Design the following superhelical interference observer: 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:

6. The energy storage converter control integral type fast non-singular adaptive super-helical sliding mode control method according to claim 5 is characterized in that: The step 4 is specifically as follows: Let the grid-side current i of d and q axes be d ,i q The deviation from the grid-side current reference value is d 、e q for: In formula (12), i dref for i d The reference value of i qref for i q Reference value of 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: In formula (13), λ1 and λ2 are greater than 0, When the system enters the sliding mode, Right now:

7. The energy storage converter control integral type fast non-singular adaptive super-helical sliding mode control method according to claim 6 is characterized in that: The step 5 is specifically as follows: Derivative and simplified equation (14) yields: From equation (15), we can get the equivalent control law u of the current inner loop d and q axes: dreq 、u qreq for: The improved super-helical sliding mode reaching law is used as the switching control law of the sliding mode surface, and the d-axis switching control law is as follows: 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 normal numbers; The q-axis switching control law is as follows: 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 normal numbers; 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:

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