Single-phase single-stage photovoltaic grid-connected power generation system control method, device, equipment and medium

Abstract

The invention discloses a single-phase single-stage photovoltaic grid-connected power generation system control method, device and equipment and a medium, and relates to the technical field of photovoltaic grid-connected power generation, and the method comprises the steps: estimating the output current of a photovoltaic cell panel based on a photovoltaic cell panel current estimator, performing maximum power tracking based on a perturbation and observation method according to the output voltage and current of the photovoltaic cell panel to obtain a reference value of the output voltage of the photovoltaic cell panel; calculating the optimal direct current bus current applied to the current control loop; the reference value of the power grid current is calculated by multiplying the optimal direct-current bus current by the difference between the sine of the power grid voltage angle and the capacitive current; calculating to obtain a grid-connected current estimation value by subtracting the output current of the inverter from the capacitance current estimation value; calculating the power grid voltage according to the product of the parameter of the PI regulator, the output current of the inverter and the estimated value difference thereof; and further determining a driving signal for switching on and switching off an optimal switch of the grid-connected current controller based on model predictive control.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic grid-connected power generation, and in particular to a control method, device, equipment and medium for a single-phase single-stage photovoltaic grid-connected power generation system. Background Art

[0002] In order to popularize and apply photovoltaic grid-connected power generation systems more quickly, it is particularly important to optimize system control methods to reduce system costs and improve system efficiency. To achieve this goal, reducing the number of power conversion stages and the number of system components are effective solutions. Single-stage inverters are 4-10% more efficient than two-stage configurations. In addition, if the number of sensors used can be reduced, the previous goal can also be achieved.

[0003] At present, five sensors are usually required in single-phase single-stage photovoltaic grid-connected power generation systems, namely, grid voltage sensor, grid current sensor, capacitor current sensor, photovoltaic panel voltage sensor and current sensor. The traditional control strategy requires sampling the voltage and current of the photovoltaic panel through the photovoltaic panel voltage sensor and current sensor to realize the maximum power point tracking (MPPT) of photovoltaic; sampling the capacitor current through the capacitor current sensor to realize the active damping of the LCL filter; sampling the grid voltage through the grid voltage sensor to realize the phase-locked loop to track the grid voltage phase; sampling the grid current through the grid current sensor to realize the control of the grid current through the current closed loop.

[0004] However, the current method is to control the system by sampling the voltage and current of the photovoltaic panels, the capacitor current, the grid voltage and the grid-connected current through multiple sensors, which increases the system cost and the complexity of the control of the grid-connected power generation system. Summary of the invention

[0005] In view of the shortcomings of the prior art that the use of multiple sensors increases the system cost and the complexity of control, the present invention proposes a single-phase single-stage photovoltaic grid-connected power generation system control method, device, equipment and medium, which calculates the estimated values ​​of the photovoltaic panel output current, the LCL filter capacitor current and the grid voltage through a constructed estimator, and then obtains the grid current, the grid voltage, the estimated value of the photovoltaic panel output voltage and the reference value of the grid current to control the single-phase single-stage photovoltaic grid-connected power generation system, thereby solving the problems existing in the prior art.

[0006] A control method for a single-phase single-stage photovoltaic grid-connected power generation system, the single-phase single-stage photovoltaic grid-connected power generation system comprising a single-phase single-stage photovoltaic grid-connected inverter, a photovoltaic panel connected in parallel to a DC input terminal of the inverter, and a power grid connected to an output terminal of the inverter through an LCL filter, the control method comprising the following steps:

[0007] An estimator is constructed based on a reference model, an adaptive model and a PI regulator, and the estimated values ​​of the photovoltaic panel output current, the LCL filter capacitor current and the grid voltage are calculated by the estimator; the reference model is used to obtain the output current of the inverter and the output voltage of the photovoltaic panel in the single-phase single-stage photovoltaic grid-connected power generation system; the adaptive model is used to generate an estimated value of the inverter output current and an estimated value of the photovoltaic panel output voltage; the PI regulator is used to adjust the output of the adaptive model to the value of the reference model;

[0008] According to the output current estimation value and output voltage of the photovoltaic panel, the maximum power tracking based on the perturbation observation method is performed to obtain the reference value of the output voltage of the photovoltaic panel;

[0009] The optimal DC bus current applied to the current control loop is calculated based on the output voltage of the photovoltaic panel and its reference value, the output current of the photovoltaic panel and the DC bus capacitance; the reference value of the grid current is calculated by multiplying the optimal DC bus current by the difference between the sine value of the grid voltage angle and the LCL filter capacitor current;

[0010] The grid-connected current estimate is obtained by calculating the difference between the inverter output current and the estimated value of the LCL filter capacitor current;

[0011] According to the estimated values ​​of the grid-connected current, grid voltage, photovoltaic panel output voltage and the reference value of the grid current, the optimal switch on and off drive signal of the grid-connected current controller is determined, and then the single-phase single-stage photovoltaic grid-connected power generation system is controlled.

[0012] Furthermore, the single-phase single-stage photovoltaic grid-connected power generation system model is expressed as:

[0013]

[0014] Among them, u g is the grid voltage; u inv is the inverter output voltage; u pv is the output voltage of the photovoltaic panel; u c is the voltage across the LCL filter capacitor; i g is the grid-connected current; i cf is the LCL filter capacitor current; i inv is the inverter output current; i dc is the DC bus current; i pv is the output current of the photovoltaic panel; i c is the DC bus capacitor current; L inv is the inductance on the inverter side; L g is the grid side inductance; R inv is the equivalent resistance of the inductor on the inverter side; R gis the equivalent resistance of the grid-side inductor; S1 and S2 are the binary switch control signals of the two bridge arms, respectively. dc is the DC bus capacitance; C f is the LCL filter capacitor.

[0015] Furthermore, the optimal DC bus current applied to the current control loop is calculated based on the output voltage of the photovoltaic panel and its reference value, the DC bus capacitance and the output current of the photovoltaic panel, and specifically includes the following steps:

[0016] For sampling time T s Using the Euler approximation, we get:

[0017]

[0018] According to get:

[0019]

[0020] Among them, u pv (k+1) is the (k+1)th sampling period T s The predicted voltage of

[0021] Define u pv (k+1) is its reference value Right now

[0022] Then we get:

[0023]

[0024] in is the optimum DC bus current applied to the current control loop.

[0025] Further, the reference value of the grid current is calculated by multiplying the optimal DC bus current by the sine value of the grid voltage angle and the difference between the LCL filter capacitor current, and specifically includes the following steps:

[0026] According to the single-phase single-stage photovoltaic grid-connected power generation system model, we get:

[0027]

[0028] in:

[0029] Assume that the inverter operates at a fixed switching frequency and fixed sampling time T s , applying the Euler approximation we get:

[0030]

[0031] When the system control bandwidth is kept below the LCL resonant frequency, the behavior of the LCL filter is similar to that of the L filter:

[0032] i inv (k)≈i g (k), i inv (k+1)=i g (k+1)

[0033] Then we get:

[0034]

[0035] Where: u g (k) and u inv (k) are the grid voltage and inverter output voltage at the switching cycle k, respectively. g (k) and i inv (k) are the grid-side current and inverter current at the switching cycle k moment respectively;

[0036] Inverter voltage u inv (k) depends on the PV voltage, giving:

[0037]

[0038] The grid current error of the next sampling period is predicted and defined as:

[0039]

[0040] The cost function g is defined as:

[0041]

[0042] where i g *(k) is the grid current reference value at time k, expressed as:

[0043]

[0044] Furthermore, the grid voltage angle θ is obtained based on a single-phase phase-locked loop of a second-order generalized integral; specifically comprising the following steps:

[0045] According to the estimated grid angle u gα 、u gβ Perform synchronous rotation transformation to obtain u gd 、u gq ;

[0046] Through feedback control, u gq =0, perform integration operation on the accumulated value of the PI regulator output Δω and the initial grid angular frequency to obtain the estimated synchronous rotation angle θ.

[0047] Further, the estimator calculates the estimated values ​​of the photovoltaic panel output current, the capacitor current and the grid voltage, and specifically comprises the following steps:

[0048] Generates inverter output current estimate Adaptive model to calculate grid voltage estimate It is expressed as:

[0049]

[0050]

[0051]

[0052] Generate photovoltaic panel output voltage Adaptive model to calculate the estimated output current of photovoltaic panels It is expressed as:

[0053]

[0054]

[0055]

[0056] Generates inverter output current estimate The adaptive model is used to calculate the estimated value of the LCL filter capacitor current, which is expressed as:

[0057]

[0058]

[0059]

[0060]

[0061] Among them, K pg , K ig , K pipv , K iipv , K pc and K ic are the parameters of the PI regulator, is the reference value of the inverter output voltage, is the estimated value of the voltage across the LCL filter capacitor, s is the complex frequency, is the reference value of DC bus current.

[0062] The present invention also includes a single-phase single-stage photovoltaic grid-connected power generation system control device, the single-phase single-stage photovoltaic grid-connected power generation system includes a single-phase single-stage photovoltaic grid-connected inverter, a photovoltaic panel connected in parallel to the DC input end of the inverter, and a power grid connected to the output end of the inverter through an LCL filter, including:

[0063] An estimator construction module is used to construct an estimator based on a reference model, an adaptive model and a PI regulator, and the estimated values ​​of the photovoltaic panel output current, the LCL filter capacitor current and the grid voltage are calculated by the estimator; the reference model is used to obtain the output current of the inverter and the output voltage of the photovoltaic panel in the single-phase single-stage photovoltaic grid-connected power generation system; the adaptive model is used to generate an estimated value of the inverter output current and an estimated value of the photovoltaic panel output voltage; the PI regulator is used to adjust the output of the adaptive model to the value of the reference model;

[0064] A reference value calculation module for the output voltage of the photovoltaic panel, used for performing maximum power tracking based on the perturbation observation method according to the output current estimation value and output voltage of the photovoltaic panel to obtain a reference value of the output voltage of the photovoltaic panel;

[0065] The grid current reference value calculation module is used to calculate the optimal DC bus current applied to the current control loop according to the output voltage of the photovoltaic panel and its reference value, the output current of the photovoltaic panel and the DC bus capacitance; the grid current reference value is calculated by multiplying the optimal DC bus current by the difference between the sine value of the grid voltage angle and the LCL filter capacitor current;

[0066] A grid-connected current estimated value calculation module, used for calculating the difference between the inverter output current and the LCL filter capacitor current estimated value to obtain the grid-connected current estimated value;

[0067] The control module is used to determine the optimal switch on and off drive signal of the grid-connected current controller according to the grid-connected current, grid voltage, estimated value of the photovoltaic panel output voltage and reference value of the grid current, and then control the single-phase single-stage photovoltaic grid-connected power generation system.

[0068] The present invention also includes a single-phase single-stage photovoltaic grid-connected power generation system control computer device, including: a memory, a processor and a computer program stored in the memory, and when the processor executes the computer program, the steps of the control method of the single-phase single-stage photovoltaic grid-connected power generation system are implemented.

[0069] The present invention also includes a readable storage medium, which stores a computer program. The computer program includes program instructions. When the program instructions are executed by a processor, they are used to execute the steps of the control method of the single-phase single-stage photovoltaic grid-connected power generation system.

[0070] The present invention provides a single-phase single-stage photovoltaic grid-connected power generation system control method, device, equipment and medium, which have the following beneficial effects:

[0071] The present invention uses a maximum power tracking algorithm to track the maximum power point of a photovoltaic panel to achieve maximum power tracking. Compared with the traditional control method, the present invention only needs to collect the output voltage of the photovoltaic panel, and the output current of the photovoltaic panel is obtained through a constructed estimator. At the same time, in a single-phase single-stage photovoltaic grid-connected power generation system, the output electric energy of the photovoltaic panel is transmitted to the power grid. The traditional method requires a grid voltage sensor, a grid current sensor or an inverter output current sensor, and a capacitor current sensor to respectively detect the grid voltage, the grid current or the inverter output current, and the capacitor current. The present invention only needs to collect the output current of the inverter, and the grid voltage, the grid current, and the capacitor current can be obtained through the constructed estimator. The optimal switch conduction and shutdown drive signal of the grid current controller are controlled by the calculated grid current reference value, the grid current estimated value, the grid voltage estimated value, and the estimated value of the photovoltaic panel output voltage, which significantly reduces the cost of the single-phase single-stage photovoltaic grid-connected power generation system and the complexity of its control. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 This is a schematic diagram of a single-phase single-stage photovoltaic grid-connected power generation system in an embodiment of the present invention;

[0073] Figure 2 A maximum power point tracking flow chart based on the disturbance observation method in an embodiment of the present invention;

[0074] Figure 3 It is a second-order generalized integral structure diagram in an embodiment of the present invention;

[0075] Figure 4 1 is a structural diagram of a phase-locked loop based on second-order generalized integral in an embodiment of the present invention;

[0076] Figure 5 This is a schematic diagram of an estimator in an embodiment of the present invention;

[0077] Figure 6 The flowchart of the control method of the single-phase single-stage photovoltaic grid-connected power generation system in the embodiment of the present invention. DETAILED DESCRIPTION

[0078] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0079] A single-phase single-stage photovoltaic grid-connected power generation system such as Figure 1As shown, the single-phase inverter is connected to the grid through an LCL filter and the system is modeled using the following equation:

[0080]

[0081] Among them, u g is the grid voltage; u inv is the inverter output voltage; u pv is the output voltage of the photovoltaic panel; u c is the voltage across the LCL filter capacitor; i g is the grid-connected current; i cf is the LCL filter capacitor current; i inv is the inverter output current; i dc is the DC bus current; i pv is the output current of the photovoltaic panel; i c is the DC bus capacitor current; L inv is the inductance on the inverter side; L g is the grid side inductance; R inv is the equivalent resistance of the inductor on the inverter side; R g is the equivalent resistance of the grid-side inductor; S1 and S2 are binary switch control signals of the two bridge arms, respectively, and their values ​​are 1 or 0 (1 when the upper tube of the bridge arm is turned on, and 0 when the lower tube is turned on). When T1 is turned on and T2 is turned off, S1=1; when T1 is turned off and T2 is turned on, S1=0; when T3 is turned on and T4 is turned off, S2=1; when T3 is turned off and T4 is turned on, S2=0; C dc , DC bus capacitance; C f , LCL filter capacitor.

[0082] Depend on Figure 2 It can be seen that there are four possible situations in which the switching devices of the single-phase bridge inverter circuit are turned on:

[0083] Ⅰ. When T1 is on and T2 is off, T3 is on and T4 is off; S1 = 1, S2 = 1;

[0084] Ⅱ. When T1 is on and T2 is off, T3 is off and T4 is on; S1 = 1, S2 = 0

[0085] Ⅲ. When T1 is off and T2 is on, T3 is on and T4 is off; S1 = 0, S2 = 1

[0086] IV. When T1 is off and T2 is on, T3 is off and T4 is on. S1 = 0, S2 = 0

[0087] DC bus current control based on MPPT-MPC: The main concept of Model Predictive Control (MPC) technology is to select the next optimal driving signal of the switching device in a way that minimizes the cost function based on the prediction of the future behavior of the system. This is achieved through the following steps:

[0088] 1) Photovoltaic output reference voltage generation: In order to make the photovoltaic panel output maximum power, the perturbation observation algorithm is used to generate the photovoltaic reference voltage. Figure 2 ) is based on applying disturbances to the system and detecting changes in the output power of the photovoltaic panels.

[0089] 2) DC bus current control based on MPC:

[0090] For sampling time T s Use the Euler approximation as follows:

[0091]

[0092] Can be written as

[0093]

[0094] where u pv (k+1) is the (k+1)th sampling period T s The predicted voltage.

[0095] To successfully eliminate the voltage error of the (k+1)th sampling period, define u pv (k+1) is its reference value u pv (k)*, that is

[0096] Therefore, formula (3) can be rewritten as:

[0097]

[0098] in is the optimum DC bus current applied to the current control loop.

[0099] Grid-connected current control based on MPC:

[0100] According to the second equation of the mathematical model (1) of the single-phase single-stage photovoltaic grid-connected system:

[0101]

[0102] in:

[0103]

[0104] Substituting equation (6) into equation (5), we get

[0105]

[0106] Assume that the inverter operates at a fixed switching frequency and fixed sampling time T s , using the Euler approximation, equation (7) can be rewritten as:

[0107]

[0108] If the system control bandwidth is kept below the LCL resonant frequency, the behavior of the LCL filter is similar to that of the L filter:

[0109] i inv (k)≈i g (k), i inv (k+1)=i g (k+1) (9)

[0110] Therefore, formula (8) can be written as:

[0111]

[0112] Where: u g (k) and u inv (k) are the grid voltage and inverter output voltage at the switching cycle k, respectively. g (k) and i inv (k) are the grid-side current and inverter current at time k respectively.

[0113] The inverter voltage u used in the prediction process inv (k) also depends on the PV voltage as follows:

[0114]

[0115] For simplicity, the photovoltaic voltage can be considered equal to its reference voltage.

[0116] The main purpose of MPC control is to minimize the grid current error in the next sampling period. Therefore, the grid current error is first predicted and defined as follows:

[0117]

[0118] The cost function g is defined as follows:

[0119]

[0120] where i g*(k) is the grid current reference value at time k, which can be expressed as the optimal DC side current multiplied by the sine of the grid voltage angle and the difference between the capacitor current, as shown in formula (14).

[0121]

[0122] The optimal switching signal T applied to the inverter opt (i=1-4) is the switch state that minimizes the cost function value.

[0123] In formula (14), Obtained by a phase-locked loop based on second-order generalized integration.

[0124] Figure 3 It represents the second-order generalized integral structure diagram, where k represents the damping coefficient; ω is the resonant frequency of the second-order integrator, which is taken as the grid voltage angular frequency ω1; ug represents the input grid voltage signal; u gα Indicates u g The voltage signal after filtering; u gβ Denotes the hysteresis u gα 90° voltage signal.

[0125] A software phase-locked loop (PLL) is used to obtain the angle of the grid voltage synthesis vector (such as Figure 4 According to the estimated grid angle, u gα 、u gβ Perform synchronous rotation transformation to obtain u gd 、u gq Through feedback control, u gq =0, the PI regulator output Δω and the accumulated value of the initial grid angular frequency are integrated to obtain the estimated synchronous rotation angle θ.

[0126] Estimator Design: To estimate the PV panel current, capacitor current and grid voltage, three model reference adaptive estimators are designed.

[0127] The main design concept of the estimator is based on the use of a reference model and an adaptive model, with a correction / adaptation mechanism to adjust the output of the adaptive model to the reference model. Figure 5 shown.

[0128] 1) Grid voltage estimation

[0129] This estimator is designed to estimate the grid voltage, with: A = u pv ,

[0130] To generate an estimate of the inverter output current The adaptive model can be expressed as follows:

[0131]

[0132] The estimated error is given by:

[0133]

[0134] Then the adaptive mechanism can be expressed as:

[0135]

[0136] Properly select the parameter K of the PI regulator pg and K ig To ensure the error e i1 stability, thereby adjusting the voltage estimation effect.

[0137] 2) Photovoltaic panel output current estimation

[0138] The PV current is estimated by the estimator:

[0139]

[0140] The adaptive model designed to generate an estimate of the PV voltage can be expressed as:

[0141]

[0142] The estimated error is given by:

[0143]

[0144] Then the adaptive mechanism can be expressed as:

[0145]

[0146] Properly select the parameter K of the PI regulator pipv and K iipv To ensure the error e v2 stability, thereby adjusting the estimated effect of the current.

[0147] 3) Capacitor current estimation

[0148] To estimate the capacitor current, we have:

[0149]

[0150] To generate an estimate of the inverter output current The adaptive model can be expressed as follows:

[0151]

[0152] The estimated error is given by:

[0153]

[0154] Then the adaptive mechanism can be expressed as:

[0155]

[0156] Properly select the parameter K of the PI regulator pc and K ic To ensure the error e i2 stability, thereby adjusting the estimated effect of the capacitor current.

[0157] For the estimated grid current It can be obtained by the following formula:

[0158]

[0159] In summary, the flow chart of the proposed control method for a single-phase single-stage grid-connected photovoltaic power generation system based on model predictive control is as follows: Figure 6 shown.

[0160] Depend on Figure 6 It can be seen that the output current of the photovoltaic panel is estimated according to the PV current estimator proposed above, and the maximum power tracking based on the perturbation observation method is performed on the output voltage and current of the photovoltaic panel to obtain the reference value of the output voltage of the photovoltaic panel. The optimal DC bus current value is obtained by the DC bus current controller based on model predictive control; the capacitor current estimate is obtained by the capacitor current estimator, and the grid current estimate is calculated according to formula (24). The grid voltage is estimated by the grid voltage estimator, and the angle of the grid voltage vector is obtained by a single-phase phase-locked loop based on second-order generalized integral. The value obtained by multiplying the optimal DC bus current value by the sine of the angle of the voltage vector minus the capacitor current estimate is obtained to obtain the grid current reference value. Finally, the optimal switch on and off drive signal is obtained by the grid current controller based on model predictive control.

[0161] Based on the same inventive concept, the present invention also proposes a control device for a single-phase single-stage photovoltaic grid-connected power generation system, the single-phase single-stage photovoltaic grid-connected power generation system comprising a single-phase single-stage photovoltaic grid-connected inverter, a photovoltaic panel connected in parallel to the DC input end of the inverter, and a power grid connected to the output end of the inverter through an LCL filter, including:

[0162] The estimator building module is used to build an estimator based on a reference model, an adaptive model and a PI regulator, and the estimated values ​​of the photovoltaic panel output voltage, the LCL filter capacitor current and the grid voltage are calculated by the estimator; the reference model is used to obtain the output current of the inverter and the output voltage of the photovoltaic panel in the single-phase single-stage photovoltaic grid-connected power generation system; the adaptive model is used to generate the estimated value of the inverter output current and the estimated value of the photovoltaic panel output voltage; the PI regulator is used to adjust the output of the adaptive model to the value of the reference model.

[0163] The reference value calculation module of the photovoltaic panel output voltage is used to perform maximum power tracking based on the perturbation observation method according to the output voltage and current of the photovoltaic panel to obtain the reference value of the photovoltaic panel output voltage.

[0164] The grid current reference value calculation module is used to calculate the optimal DC bus current applied to the current control loop according to the output voltage of the photovoltaic panel and its reference value, the output current of the photovoltaic panel and the DC bus capacitance; the reference value of the grid current is calculated by multiplying the optimal DC bus current by the difference between the sine value of the grid voltage angle and the LCL filter capacitor current.

[0165] The grid-connected current estimated value calculation module is used to obtain the grid-connected current estimated value by calculating the difference between the inverter output current and the LCL filter capacitor current estimated value.

[0166] The control module is used to determine the optimal switch on and off drive signal of the grid-connected current controller according to the grid-connected current, grid voltage, estimated value of the photovoltaic panel output voltage and reference value of the grid current, and then control the single-phase single-stage photovoltaic grid-connected power generation system.

[0167] Based on the same inventive concept, the present invention also proposes a control computer device for a single-phase single-stage photovoltaic grid-connected power generation system, comprising: a memory, a processor, and a computer program stored in the memory. When the processor executes the computer program, the steps of the control method of the single-phase single-stage photovoltaic grid-connected power generation system are implemented.

[0168] Based on the same inventive concept, the present invention also proposes a readable storage medium, which stores a computer program. The computer program includes program instructions. When the program instructions are executed by a processor, they are used to execute the steps of a control method for a single-phase single-stage photovoltaic grid-connected power generation system.

[0169] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A control method for a single-phase single-stage photovoltaic grid-connected power generation system, wherein the single-phase single-stage photovoltaic grid-connected power generation system comprises a single-phase single-stage photovoltaic grid-connected inverter and a photovoltaic battery panel connected in parallel to the DC input terminal of the inverter, wherein the output terminal of the inverter is connected to the power grid through an LCL filter, wherein: The control method comprises the following steps: An estimator is constructed based on a reference model, an adaptive model and a PI regulator; wherein the reference model is used to obtain the output current of the inverter and the output voltage of the photovoltaic panel in a single-phase single-stage photovoltaic grid-connected power generation system; the adaptive model is used to generate an estimated value of the inverter output current and an estimated value of the photovoltaic panel output voltage; the PI regulator is used to adjust the output of the adaptive model to the value of the reference model; and the estimated values ​​of the photovoltaic panel output current, the LCL filter capacitor current and the grid voltage are calculated by the estimator; According to the output current estimation value and output voltage of the photovoltaic panel, the maximum power tracking based on the perturbation observation method is performed to obtain the reference value of the output voltage of the photovoltaic panel; The optimal DC bus current applied to the current control loop is calculated based on the output voltage of the photovoltaic panel and its reference value, the output current of the photovoltaic panel and the DC bus capacitance; the grid current reference value is calculated by multiplying the optimal DC bus current by the difference between the sine value of the grid voltage angle and the LCL filter capacitor current; The estimated value of the grid-connected current is obtained by calculating the difference between the inverter output current and the estimated value of the LCL filter capacitor current; According to the estimated values ​​of the grid-connected current, grid voltage, photovoltaic panel output voltage and grid current reference value, the optimal switch on and off drive signal of the grid-connected current controller is determined, thereby controlling the single-phase single-stage photovoltaic grid-connected power generation system.

2. A single-phase single-stage photovoltaic grid-connected power generation system control method according to claim 1, characterized in that: The single-phase single-stage photovoltaic grid-connected power generation system model is expressed as: Among them, u g is the grid voltage; u inv is the inverter output voltage; u pv is the output voltage of the photovoltaic panel; u c is the voltage across the LCL filter capacitor; i g is the grid-connected current; i cf is the LCL filter capacitor current; i inv is the inverter output current; i dc is the DC bus current; i pv is the output current of the photovoltaic panel; i c is the DC bus capacitor current; L inv is the inductance on the inverter side; L g is the grid side inductance; R inv is the equivalent resistance of the inductor on the inverter side; R g is the equivalent resistance of the grid-side inductor; S1 and S2 are the binary switch control signals of the two bridge arms, respectively. dc is the DC bus capacitance; C f is the LCL filter capacitor.

3. A single-phase single-stage photovoltaic grid-connected power generation system control method according to claim 2, characterized in that: The method of calculating the optimal DC bus current applied to the current control loop according to the output voltage of the photovoltaic panel and its reference value, the DC bus capacitance and the output current of the photovoltaic panel specifically includes the following steps: For sampling time T s Using the Euler approximation, we get: According to get: Among them, u pv (k+1) is the (k+1)th sampling period T s The predicted voltage of Define u pv (k+1) is its reference value Right now Then we get: in is the optimum DC bus current applied to the current control loop.

4. A single-phase single-stage photovoltaic grid-connected power generation system control method according to claim 3, characterized in that: The reference value of the grid current is obtained by calculating the difference between the optimal DC bus current multiplied by the sine value of the grid voltage angle and the LCL filter capacitor current, and specifically includes the following steps: According to the single-phase single-stage photovoltaic grid-connected power generation system model, we get: in: but Assume that the inverter operates at a fixed switching frequency and fixed sampling time T s , applying the Euler approximation we get: When the system control bandwidth is kept below the LCL resonant frequency, the behavior of the LCL filter is similar to that of the L filter: i inv (k)≈i g (k),i inv (k+1)=i g (k+1) Then we get: Where: u g (k) and u inv (k) are the grid voltage and inverter output voltage at the switching cycle k, respectively. g (k) and i inv (k) are the grid-side current and inverter current at the switching cycle k moment respectively; Inverter voltage u inv (k) depends on the PV voltage, giving: The grid current error of the next sampling period is predicted and defined as: The cost function g is defined as: where i g *(k) is the grid current reference value at time k, expressed as:

5. A single-phase single-stage photovoltaic grid-connected power generation system control method according to claim 4, characterized in that: The grid voltage angle θ is obtained based on a single-phase phase-locked loop of a second-order generalized integral; specifically, the following steps are included: According to the estimated grid angle, u gα 、u gβ Perform synchronous rotation transformation to obtain u gd 、u gq ; Through feedback control, u gq =0, perform integration operation on the accumulated value of the PI regulator output Δω and the initial grid angular frequency to obtain the estimated synchronous rotation angle θ.

6. A single-phase single-stage photovoltaic grid-connected power generation system control method according to claim 4, characterized in that: The estimator is used to calculate the estimated values ​​of the photovoltaic panel output current, the capacitor current and the grid voltage, and specifically comprises the following steps: Generates inverter output current estimate Adaptive model to calculate grid voltage estimate It is expressed as: Generate photovoltaic panel output voltage Adaptive model to calculate the estimated output current of photovoltaic panels It is expressed as: Generates inverter output current estimate The adaptive model is used to calculate the estimated value of the LCL filter capacitor current, which is expressed as: Among them, K pg , K ig , K pipv , K iipv , K pc and K ic are the parameters of the PI regulator, is the reference value of the inverter output voltage, is the estimated value of the voltage across the LCL filter capacitor, s is the complex frequency, is the reference value of DC bus current.

7. A single-phase single-stage photovoltaic grid-connected power generation system control device, the single-phase single-stage photovoltaic grid-connected power generation system comprises a single-phase single-stage photovoltaic grid-connected inverter and a photovoltaic battery panel connected in parallel with the DC input end of the inverter, the inverter output end is connected to the power grid through an LCL filter, characterized in that: include: An estimator construction module is used to construct an estimator based on a reference model, an adaptive model and a PI regulator; wherein the reference model is used to obtain the output current of the inverter and the output voltage of the photovoltaic panel in a single-phase single-stage photovoltaic grid-connected power generation system; the adaptive model is used to generate an estimated value of the inverter output current and an estimated value of the photovoltaic panel output voltage; the PI regulator is used to adjust the output of the adaptive model to the value of the reference model; and the estimated values ​​of the photovoltaic panel output current, the LCL filter capacitor current and the grid voltage are calculated by the estimator; A photovoltaic panel output voltage reference value calculation module is used to perform maximum power tracking based on a perturbation observation method according to an estimated output current and output voltage of the photovoltaic panel to obtain a reference value of the photovoltaic panel output voltage; A grid current reference value calculation module is used to calculate the optimal DC bus current applied to the current control loop according to the output voltage of the photovoltaic panel and its reference value, the output current of the photovoltaic panel and the DC bus capacitance; and to calculate the reference value of the grid current by multiplying the optimal DC bus current by the difference between the sine value of the grid voltage angle and the LCL filter capacitor current; A grid-connected current estimated value calculation module, used for calculating the difference between the inverter output current and the LCL filter capacitor current estimated value to obtain the grid-connected current estimated value; The control module is used to determine the optimal switch on and off drive signal of the grid-connected current controller according to the grid-connected current, grid voltage, estimated value of the photovoltaic panel output voltage and reference value of the grid current, and then control the single-phase single-stage photovoltaic grid-connected power generation system.

8. A single-phase single-stage photovoltaic grid-connected power generation system control computer device, characterized in that: include: A memory, a processor and a computer program stored in the memory, wherein the processor implements the steps of the control method of the single-phase single-stage photovoltaic grid-connected power generation system according to any one of claims 1 to 6 when executing the computer program.

9. A readable storage medium, characterized in that: The readable storage medium stores a computer program, which includes program instructions. When the program instructions are executed by a processor, they are used to execute the steps of the control method of the single-phase single-stage photovoltaic grid-connected power generation system according to any one of claims 1 to 6.

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