Multi-source energy power compensation control method based on super-torque double sliding modes

Abstract

The invention relates to a multi-source energy power compensation control method based on super-torsion double sliding modes, which comprises the following steps of: firstly, modeling by adopting a Kalman filtering control method through an active power filter and a phase locking loop, and accurately extracting a fundamental frequency positive sequence component in unbalanced three-phase power grid voltage and load current signals; secondly, determining power flow among the power grid, the load and the EV by using static reactive power compensation of an electric energy quality problem processing method according to the sampling signal; controlling the photovoltaic system by using a maximum power point tracking control technology, judging and selecting a grid-connected mode or an island mode in real time according to parameter conditions, and sending corresponding on and off signals to the system; then, a super-torque double-sliding-mode control method is adopted to calculate compensation current outside power balance, and the system control rate is determined; finally, generation of compensation current with reactive power flow is considered, harmonic suppression and elimination are completed through a proportional resonance controller, and the purpose of improving the stability of a power grid in the charging process of the electric vehicle is achieved.

Description

Technical Field

[0001] The invention belongs to the field of sliding mode control theory and power system control technology, and relates to a multi-source energy power compensation control method based on super-torsion double sliding modes. Background Art

[0002] With the popularity of electric vehicles and the increase in charging facilities, electric vehicle charging stations play an increasingly important role in distribution networks. However, the nonlinear current generated during the charging process of electric vehicles will cause a series of problems in the distribution network, including current imbalance and distortion of power quality. These problems may lead to challenges in the safety, reliability and efficiency of the power supply system. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a multi-source energy power compensation control method based on super-torsion dual sliding mode to achieve the purpose of improving the power quality.

[0004] The present invention provides a multi-source energy power compensation control method based on super-torsion dual sliding mode, comprising:

[0005] Step 1: Through the active power filter and the phase-locked loop, the Kalman filter control method is used to model and extract the fundamental frequency positive sequence component in the unbalanced three-phase grid voltage and load current signals;

[0006] Step 2: Based on the sampled signal, the static reactive power compensation of the power quality problem processing method is used to determine the power flow between the grid, the load and the electric vehicle;

[0007] Step 3: Apply the maximum power point tracking control technology to control the photovoltaic system. By tracking the maximum output power of the photovoltaic cells, the energy conversion efficiency of the photovoltaic cells is improved. The system judges and selects the grid-connected mode or the island mode in real time according to the parameter conditions, and sends the corresponding on and off signals to the system.

[0008] Step 4: Use the super-torque dual sliding mode control method to calculate the compensation current that satisfies the power balance. Select the appropriate switching function S(X) according to the state equation to determine the sliding mode surface to ensure that the system can move stably on the switch surface. Determine the system control rate to ensure that the system can reach the switch surface within a limited time from any initial point to meet the accessibility conditions of the sliding mode.

[0009] Step 5: Calculate the reference current based on the positive sequence component estimated by the linear Kalman filter in step 1, consider that the compensation current with reactive power flow is generated by the static reactive power compensation, and use the proportional resonant controller to suppress and eliminate harmonics.

[0010] The invention discloses a multi-source energy power compensation control method based on super-torsion dual sliding mode, which can accurately estimate and optimize the nonlinear current in the electric vehicle charging station by comprehensively using Kalman filtering and sliding mode control technology. Kalman filtering can provide accurate current estimation values, while sliding mode control can achieve robust tracking and control of current. This comprehensive application helps to reduce power quality problems and improve the stability and efficiency of the distribution network. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a flow chart of a multi-source energy power compensation control method based on super-torsion dual sliding mode of the present invention;

[0012] Figure 2 is a relationship diagram between a three-phase stationary coordinate system and a dq synchronous rotating coordinate system in an embodiment of the present invention;

[0013] Figure 3 It is a system structure block diagram containing SAPF and MPPT in an embodiment of the present invention;

[0014] Figure 4 This is a schematic diagram of MPPT control in an embodiment of the present invention;

[0015] Figure 5 Schematic diagram of a control method in an embodiment of the present invention. DETAILED DESCRIPTION

[0016] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0017] like Figure 1 As shown, a multi-source energy power compensation control method based on super-torsion dual sliding mode of the present invention comprises:

[0018] Step 1: Through the active power filter and phase-locked loop, the Kalman filter control method is used to model and extract the fundamental frequency positive sequence component in the unbalanced three-phase grid voltage and load current signals, specifically:

[0019] Step 1.1: Assume that the system three-phase voltage expression is:

[0020]

[0021] The three-phase grid voltage is converted into a stationary reference system through Clark (3-2 transformation), and V in the α-β coordinate system is obtained. α With V β :

[0022]

[0023] Among them, Va 、V b 、V c is the system three-phase voltage, V is the voltage amplitude, and the spatial angle between the three phases is 120°. a 、V b 、V c The relationship between the ABC three-phase stationary coordinate system and the dq synchronous rotating coordinate system is as follows Figure 2 shown.

[0024] Step 1.2: According to the V in the stationary coordinate system obtained in step 1.1 α 、V β The α-β model is obtained, and the state vector is considered as: ξ=[ξ 1 ξ 2 ξ 3 ξ 4 ] T ; Then use triangular expansion to rewrite the model expression as:

[0025]

[0026] State vector ξ 1 , 2 , 3 , 4 for:

[0027] ξ 1 =V - cos(φ - )+V + cos(φ + )

[0028] ξ 2 =-(V - sin(φ - )+V + sin(φ + ))

[0029] ξ 3 =-(V - cos(φ - )-V + cos(φ + ))

[0030] ξ 4 =V - sin(φ - )-V + sin(φ + )

[0031] Where, ω is the grid angular frequency, φ + is the positive sequence component of the initial phase angle, φ - is the negative sequence component of the initial phase angle; V+ is the positive sequence component of the amplitude, V - is the amplitude of the negative positive sequence component; the instantaneous phase is defined by the following formula:

[0032]

[0033] Step 1.3: According to step 1.2, the obtained model is rewritten using trigonometric transformation to obtain the dynamic model of the grid voltage after Clarke transformation:

[0034] in, is the state matrix, As the output matrix, and Applying exact discretization yields:

[0035]

[0036] Among them, the output vector y ξ =[v α (t); v β (t)], I 4 is the 4×4 identity matrix.

[0037] Step 1.4: Taking into account the special properties of the state transfer matrix, the recursive process of the conventional Kalman filter is obtained based on the discrete time model of the process and measurement noise:

[0038] The discrete-time model is:

[0039]

[0040] The recursive process of the conventional Kalman filter is:

[0041]

[0042] In this implementation, it is assumed that the frequencies in the output matrix are known, and a phase-locked loop is used to estimate the unknown frequencies, and then the output matrix is ​​fed back for calculation. Based on a discrete-time model that considers process and measurement noise, a conventional Kalman filter is recursively used to obtain the estimated state Among them, process and measurement noise is unrelated to ν(n), n|n-1 and n|n represent the prior estimate and the posterior estimate respectively. is the covariance matrix, Kalman gain matrix

[0043]

[0044] Step 1.5: Step 1.4 based on the estimated state The fundamental frequency positive sequence DC component can be estimated as:

[0045]

[0046] Then, using the estimated instantaneous phase and amplitude, the positive sequence component is obtained as:

[0047]

[0048] Wherein, the grid parameters are estimated based on the estimated signal as:

[0049]

[0050] According to the phase-locked loop, the instantaneous phase is It is obtained recursively by a conventional Kalman filter taking into account the special properties of the state transfer matrix.

[0051] Step 2: Based on the sampled signals, the static reactive power compensation of the power quality problem treatment method is used to determine the power flow between the grid, the load and the electric vehicle.

[0052] Static VAR compensation (SAPF) ensures the power flow between the grid, loads and EVs and is usually designed to handle power quality (PQ) issues and support the grid. Assuming that the SAPF operates in a well-controlled manner and neglects switching losses, e.g. Figure 3 , the system equation on the DC side is expressed as follows according to the power balance theory:

[0053]

[0054] In the equilibrium equation, the unknown load power P is obtained by using the Luenberger observer L ; Based on the system state space: The design of the linear observer is completed as:

[0055]

[0056] Among them, c and v dc are the DC link capacitor and voltage, P * is the reference active power, ζ 1 for ζ 2 is the load power P L ; Output power P of photovoltaic cells pv =U pv I pv , P ＊ is the DC link control signal of the reference power, ζ=[ζ 1 ζ 2 ] T, u=P ＊ +P PV , A=[0-2 / c;00],B=[2 / c;0],C=

[10] The error matrix of the closed-loop observer The Routh-Hurwitz criterion is satisfied to ensure the asymptotic stability of the observer.

[0057] Step 3: Apply the maximum power point tracking control technology to control the photovoltaic system. By tracking the maximum output power of the photovoltaic cells, the energy conversion efficiency of the photovoltaic cells is improved. The system judges and selects the grid-connected mode or the island mode in real time according to the parameter conditions, and sends the corresponding on and off signals to the system. Specifically:

[0058] Step 3.1: Change the duty cycle of the DC / DC converter circuit in series between the PV array and the load to ensure that the PV array outputs at maximum power. The duty cycle of the boost converter is calculated by the following formula:

[0059]

[0060] The duty cycle is compared with a sine wave to generate the switching pulses for the boost converter, such as Figure 4 As shown. Among them, is the photovoltaic array current at the maximum power point, V dc is the DC link voltage.

[0061] Step 3.2: Grid voltage amplitude V m and Δθ are the parameters that determine whether the system should operate in grid-connected mode or independent mode. The change in the system phase angle is: Δθ = θ s -θ g , when the coupling V m >1.1pu or V m <0.88pu、Phase angle θ s <θ g When the parameter becomes abnormally out of range, the system changes to island mode; conversely, when the parameter value returns to the normal range, the system returns to grid-connected mode.

[0062] Step 3.3: Synchronous control provides the system with on / off signals to obtain the system equations:

[0063]

[0064] Taking s as the control quantity of on-off, the state equation of the system is:

[0065]

[0066] Step 4: Use the super-torque dual sliding mode control method to calculate the compensation current that satisfies the power balance. Select the appropriate switching function S(X) according to the state equation to determine the sliding mode surface to ensure that the system can move stably on the switch surface. Determine the system control rate to ensure that the system can reach the switch surface within a limited time from any initial point and meet the accessibility conditions of the sliding mode, which are as follows:

[0067] Step 4.1: The general form of the system state equation is:

[0068]

[0069] The power state equation obtained based on the power balance equation in step 2 is:

[0070]

[0071] The power state equation is transformed with the state equation of the system in step 3.3 to obtain the transformed system state equation:

[0072]

[0073] in, s 1 Indicates the MPPT duty cycle, s 2 Indicates the reference active power P * cs 3 Indicates u PV .

[0074] Step 4.2: * is used to represent the target value to design the dual sliding membrane super torque control based on the transformed system state equation in step 4.1 and the stability condition on the sliding surface: S(X,t)=0 and the accessibility condition: Select the two sliding surfaces as: Complete the design of DC link voltage and photovoltaic regulator, such as Figure 5 As shown; where X∈R n , u∈R.

[0075] Step 4.3: Determine the control law expression as: u = u eq +U σ , based on steps 4.1 and 4.2, we get:

[0076]

[0077] You can set Get the equivalent control u eq , and is determined according to the super-helical sliding mode controller STA: The DC link control signal P is used as the reference power ★ By uσ and The control signal is obtained:

[0078]

[0079] According to the Luenberger observer in step 2, the load power is estimated as follows:

[0080]

[0081] The problem that the load power status is not available in practice is solved.

[0082] Step 5: Calculate the reference current based on the positive sequence component estimated by the linear Kalman filter in step 1, consider that the compensation current with reactive power flow is generated by the static reactive power compensation, and use the proportional resonant controller to suppress and eliminate harmonics, specifically:

[0083] Step 5.1: The current compensated by static reactive power compensation is expressed as:

[0084]

[0085] The compensation current I fα,comp with I fβ,comp Obtained by comparing the inductive load with the fundamental load current component:

[0086]

[0087] Active current I fα,dc with I fβ,dc Through active power and get:

[0088]

[0089] Step 5.2: Proportional resonant control divides the control signal into two parts: proportional and resonant:

[0090]

[0091] Based on the reference active current and other parameters obtained in step 5.1, the estimated current error is:

[0092]

[0093] Finally, the switching signal of the static reactive power compensation (SAPF) is obtained by calculating the current error and Clark's inverse transformation. ip With K ir They are expressed as proportional gain and resonant gain, respectively, and the damping factor ζ r The value is 0.707.

[0094] The above description is only a preferred embodiment of the present invention and is not intended to limit the concept of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A multi-source energy power compensation control method based on super-torsion double sliding mode, characterized in that: include: Step 1: Through the active power filter and the phase-locked loop, the Kalman filter control method is used to model and extract the fundamental frequency positive sequence component in the unbalanced three-phase grid voltage and load current signals; Step 2: Based on the sampled signal, the static reactive power compensation of the power quality problem processing method is used to determine the power flow between the grid, the load and the electric vehicle; Step 3: Apply the maximum power point tracking control technology to control the photovoltaic system. By tracking the maximum output power of the photovoltaic cells, the energy conversion efficiency of the photovoltaic cells is improved. The system judges and selects the grid-connected mode or the island mode in real time according to the parameter conditions, and sends the corresponding on and off signals to the system. Step 4: Use the super-torque dual sliding mode control method to calculate the compensation current that satisfies the power balance. Select the appropriate switching function S(X) according to the state equation to determine the sliding mode surface to ensure that the system can move stably on the switch surface. Determine the system control rate to ensure that the system can reach the switch surface within a limited time from any initial point to meet the accessibility conditions of the sliding mode. Step 5: Calculate the reference current based on the positive sequence component estimated by the linear Kalman filter in step 1, consider that the compensation current with reactive power flow is generated by the static reactive power compensation, and use the proportional resonant controller to suppress and eliminate harmonics.

2. The multi-source energy power compensation control method based on super-torsion dual sliding mode according to claim 1 is characterized in that: The step 1 comprises the following steps: Step 1.1: Assume that the system three-phase voltage expression is: The three-phase grid voltage is converted to the stationary reference system through Clark transformation, and V in the α-β coordinate system is obtained. α With V β : Among them, V a 、V b 、V c is the system three-phase voltage, V is the voltage amplitude, and the spatial angle between the three phases is 120°; Step 1.2: According to the V in the stationary coordinate system obtained in step 1.1 α 、V β We get the α-β model and consider the state vector as: ξ=[ξ1ξ2ξ3ξ4] T ; Then use triangular expansion to rewrite the model expression as: The state vectors ξ1, ξ2, ξ3, ξ4 are: ξ1=V - cos(φ - )+V + cos(φ + ) ξ2=-(V - sin(φ - )+V + sin(φ + )) ξ3=-(V - cos(φ - )-V + cos(φ + )) ξ4=V - sin(φ - )-V + sin(φ + ) Where, ω is the grid angular frequency, φ + is the positive sequence component of the initial phase angle, φ - is the negative sequence component of the initial phase angle; V + is the positive sequence component of the amplitude, V - is the amplitude of the negative positive sequence component; the instantaneous phase is defined by the following formula: Step 1.3: According to step 1.2, the obtained model is rewritten using trigonometric transformation to obtain the dynamic model of the grid voltage after Clarke transformation: in, is the state matrix, As the output matrix, and Applying exact discretization yields: A(n)=exp(AT s )≈I4 Among them, the output vector y ξ =[v α (t); v β (t)], I4 is a 4×4 identity matrix; Step 1.4: Taking into account the special properties of the state transfer matrix, the recursive process of the conventional Kalman filter is obtained based on the discrete time model of the process and measurement noise: The discrete-time model is: The recursive process of the conventional Kalman filter is: Among them, process and measurement noise is unrelated to ν(n), n|n-1 and n|n represent the prior estimate and the posterior estimate respectively. is the covariance matrix, p>0, Kalman gain matrix Step 1.5: Step 1.4 based on the estimated state The fundamental frequency positive sequence DC component can be estimated as: Then, using the estimated instantaneous phase and amplitude, the positive sequence component is obtained as: Wherein, the grid parameters are estimated based on the estimated signal as: According to the phase-locked loop, the instantaneous phase is It is obtained recursively by a conventional Kalman filter taking into account the special properties of the state transfer matrix.

3. The multi-source energy power compensation control method based on super-torsion dual sliding mode according to claim 1 is characterized in that: The step 2 is specifically as follows: The system equation on the DC side is expressed as follows according to the power balance theory: In the equilibrium equation, the unknown load power P is obtained by using the Luenberger observer L ; Based on the system state space: The design of the linear observer is completed as: Among them, c and v dc are the DC link capacitor and voltage, P * is the reference active power, ζ1 is ζ2 is the load power P L ; Output power P of photovoltaic cells pv =U pv I pv , P ＊ is the DC link control signal of the reference power, ζ=[ζ1 ζ2] T , u=P ＊ +P PV , A=[0 -2 / c;0 0],B=[2 / c;0],C=[1 0], the error matrix of the closed-loop observer The Routh-Hurwitz criterion is satisfied to ensure the asymptotic stability of the observer.

4. The multi-source energy power compensation control method based on super-torsion dual sliding mode according to claim 3 is characterized in that: The step 3 is specifically as follows: Step 3.1: Change the duty cycle of the DC / DC converter circuit in series between the PV array and the load to ensure that the PV array outputs at maximum power. The duty cycle of the boost converter is calculated by the following formula: in, is the photovoltaic array current at the maximum power point, V dc is the DC link voltage; Step 3.2: Grid voltage amplitude V m and Δθ are parameters that determine whether the system should operate in grid-connected mode or independent mode. The change in system phase angle is: Δθ = θ s -θ g , when the coupling V m >1.1pu or V m <0.88pu、Phase angle θ s <θ g When the parameter becomes abnormal and out of range, the system changes to island mode; conversely, when the parameter value returns to the normal range, the system returns to grid-connected mode; Step 3.3: Synchronous control provides the system with on / off signals to obtain the system equations: Taking s as the control quantity of on-off, the state equation of the system is:

5. The multi-source energy power compensation control method based on super-torsion dual sliding mode according to claim 3 is characterized in that: The step 4 is specifically as follows: Step 4.1: The general form of the system state equation is: The power state equation obtained based on the power balance equation in step 2 is: The power state equation is transformed with the state equation of the system in step 3.3 to obtain the transformed system state equation: in, s1 represents the MPPT duty cycle, s2 represents the reference active power P * cs3 means u PV ; Step 4.2: * is used to represent the target value to design the dual sliding membrane super torque control based on the transformed system state equation in step 4.1 and the stability condition on the sliding surface: S(X,t)=0 and the accessibility condition: Select the two sliding surfaces as: Complete the design of DC link voltage and photovoltaic regulator; where X∈R n , u∈R; Step 4.3: Determine the control law expression as: u = u eq +U σ , based on steps 4.1 and 4.2, we get: You can set Get the equivalent control u eq , and is determined according to the super-helical sliding mode controller STA: The DC link control signal P is used as the reference power ＊ By u σ and The control signal is obtained: According to the Luenberger observer in step 2, the load power is estimated as follows:

6. The multi-source energy power compensation control method based on super-torsion dual sliding mode according to claim 1 is characterized in that: The step 5 is specifically as follows: Step 5.1: The current compensated by static reactive power compensation is expressed as: The compensation current I fα,comp with I fβ,comp Obtained by comparing the inductive load with the fundamental load current component: Active current I fα,dc with I fβ,dc Through active power and get: Step 5.2: Proportional resonant control divides the control signal into two parts: proportional and resonant: Based on the reference active current and other parameters obtained in step 5.1, the estimated current error is: Finally, the switching signal of static reactive power compensation is obtained by calculating the current error and Clark's inverse transform.

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