A photovoltaic system active reserve power point tracking control method and tracking control system based on a composite parameter mathematical model

Abstract

This invention proposes a photovoltaic (PV) system active power reserve point tracking (EPP) control method and tracking control system based on a composite parameter mathematical model. The method includes: establishing a composite parameter mathematical model of the PV system; constructing an analytical equation set based on the composite parameter mathematical model; solving the analytical equation set using currently measured PV operating parameters to obtain real-time parameters such as current environmental irradiance and temperature; determining the maximum power point of the PV system under the current environment; and evaluating the current real-time active power reserve rate of the PV system based on this, thus achieving EPP tracking. This method overcomes the problems of high cost for multi-point, large-scale measurements of irradiance and temperature, and low accuracy for single-point measurements of irradiance and temperature.

Description

Technical Field

[0001] This invention belongs to the field of power automation technology, and in particular relates to a method and control system for active power reserve point tracking control of photovoltaic systems based on a composite parameter mathematical model. Background Technology

[0002] Photovoltaic active power reserve control transforms photovoltaic power plants from "passive power generation" to a flexible resource that "actively supports the power grid," and is a key technology for solving the stability problem of high proportion of new energy connected to the power grid.

[0003] In traditional photovoltaic (PV) active power reserve control, when there are rapid changes in irradiance or temperature fluctuations, the maximum power point (MPPT) is found, and then the PV system is calculated and operated at the desired active power reserve operating point. However, this requires repeated searches for the maximum power point, which reduces the effective time and effectiveness of the active power reserve. Furthermore, maximum power point estimation (MPPE) has emerged, which obtains irradiance G and temperature T directly from sensors or through empirical models, and then substitutes them into a mathematical model to estimate the current maximum power point power and calculate the reserve rate. However, this method suffers from high costs associated with multi-point, large-scale measurements of irradiance G and temperature T, and low accuracy with single-point measurements of irradiance G and temperature T.

[0004] Therefore, this paper proposes a novel mathematical model for online estimation of the maximum power point (MPP) of a photovoltaic (PV) system, along with its Reserve Power Point Tracking (RPPT) control method. This model utilizes the current PV system output power Ppv, output voltage Vpv, and output power Ppv. pv Relative output voltage V pv The rate of change dPpv / dVpv is used to achieve online estimation of the maximum power point Pmppe, and based on this, the irradiance G and temperature T of the photovoltaic system are evaluated, and then the current real-time active power reserve rate is calculated. This enables real-time tracking of active power reserve points, ensuring a stable active power reserve rate for photovoltaic systems under varying light intensity and temperature conditions. Summary of the Invention

[0005] The purpose of this invention is to propose a photovoltaic system active power reserve point tracking control method and tracking control system based on a composite parameter mathematical model, so as to overcome the problems of high cost of multi-point large-scale measurement of light intensity and temperature and low accuracy of single-point measurement of light intensity and temperature.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for online estimation of the maximum power point (MPP) and active power reserve tracking control of a photovoltaic (PV) system based on a composite parameter mathematical model is proposed. Specifically, after the PV system enters active power reserve operation, the output power of the PV system and the rate of change of output power relative to output voltage are acquired and substituted into a pre-constructed set of analytical equations based on the composite parameter mathematical model to solve for the real-time irradiance and temperature received by the PV panel. Based on the real-time irradiance and temperature, the MPP of the PV system under the current environment is calculated, and the current real-time active power reserve rate of the PV system is evaluated based on the MPP under the current environment, thereby achieving active power reserve tracking and control.

[0008] Preferably, the photovoltaic system enters the active power reserve working state in the following specific manner:

[0009] When the photovoltaic system starts up, the initial maximum power point Pmax is obtained through the maximum power point tracking algorithm MPPT.

[0010] Based on the set target active power reserve rate Based on the initial maximum power point Pmax, determine the initial active power reserve operating point, enabling the photovoltaic system to enter the active power reserve operating state.

[0011] Preferably, the specific method for obtaining the photovoltaic system output power and the rate of change of output power relative to output voltage is as follows: detect the current output current and voltage of the photovoltaic system to calculate the output power of the photovoltaic system; and use the square wave perturbation method to obtain the rate of change of photovoltaic system output power relative to output voltage.

[0012] Preferably, the analytical equations based on the composite parameter mathematical model are expressed as follows:

[0013]

[0014] In the formula, P pv V represents the output power of the photovoltaic system. pv Output DC voltage for the photovoltaic system; dP pv / dV pv The output power P of the photovoltaic system pv Relative output voltage V pv The rate of change; C1 and C2 are the fitting coefficients, respectively. , , where I mpp and V mpp These represent the maximum output current and maximum output voltage under standard temperature and illumination conditions, respectively; I sc This is the short-circuit current. V oc Open circuit voltage, , where Isc0 and V oc0 G represents the short-circuit current and open-circuit voltage under standard temperature and illumination conditions, respectively; G is the real-time illumination intensity received by the photovoltaic panel, T is the real-time photovoltaic panel temperature, G0 is the standard illumination intensity, and T0 is the standard temperature. The difference between the real-time photovoltaic panel temperature T and the standard temperature T0, i.e. ; For the corrected ideal factor, , where A is the diode ideality factor, k is the Boltzmann constant, q is the electron charge; β and γ are correction coefficients.

[0015] Preferably, the analytical equations based on the composite parameter mathematical model are solved using the multi-starting point Newton-Raphson method to obtain the optimal solutions for real-time light intensity and real-time photovoltaic panel temperature.

[0016] Preferably, the calculation of the maximum power point of the photovoltaic system under the current environment based on real-time light intensity and real-time photovoltaic panel temperature is specifically as follows:

[0017]

[0018] In the formula, P mppe This represents the maximum power point of the photovoltaic system under the current environment. , These represent the current and voltage corresponding to the maximum power point under standard temperature and illumination conditions, respectively.

[0019] Preferably, the assessment of the current real-time active power reserve of the photovoltaic system based on the maximum power point of the photovoltaic system under the current environment is specifically calculated as follows: Assessing the current real-time active power reserve of the photovoltaic system. , can be represented as:

[0020]

[0021] In the formula, This represents the current real-time active power reserve rate of the photovoltaic system.

[0022] The preferred control of the active power reserve point is as follows:

[0023] Target active power reserve rate Compared with the current real-time active power reserve rate The comparison is performed, and the active power output of the photovoltaic system is adjusted in real time through a PI controller; when > At that time, adjust the output power P of the photovoltaic system. pv Rise, control Decrease; when < At that time, adjust the output power P of the photovoltaic system. pvDecrease, control rise.

[0024] Preferably, the control of the active power reserve point also includes:

[0025] Real-time monitoring of the maximum power point P of the photovoltaic system under the current environment mppe The change in the amount of power; if the change exceeds a set threshold, it is determined that the environment has changed, the output power of the photovoltaic system and the rate of change of the output power relative to the output voltage are obtained, and the current real-time active power reserve of the photovoltaic system is reassessed. According to the reassessment and target active power reserve rate Adjust the active power reserve status; if the threshold is not exceeded, maintain the current status.

[0026] A photovoltaic system active power reserve point tracking control system based on a composite parameter mathematical model includes a processor, a memory, and a computer program stored in the memory. When the processor executes the computer program, it specifically executes any of the steps in the above-mentioned photovoltaic system active power reserve point tracking control method.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] This invention discloses a principle and control flow for active power point tracking (RPPT) based on a composite parameter mathematical model of the maximum power point online estimation of a photovoltaic system. It directly calculates the estimated maximum operating power by tracking the slope corresponding to the current power level on the PV curve, eliminating the need to directly measure real-time irradiance G and real-time photovoltaic panel temperature T. The active power reserve operating point is calculated using the estimated maximum operating power, making the active power reserve control system more accurate and flexible. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the PV curve of a photovoltaic cell in an example of the present invention;

[0030] Figure 2 The photovoltaic system P in the example of this invention pv -V pv curve;

[0031] Figure 3 The photovoltaic system dP in the example of this invention pv / dV pv -V pv curve;

[0032] Figure 4 This is a schematic diagram of the active power reserve point tracking control principle in an example of the present invention;

[0033] Figure 5 This is a flowchart of the active power reserve point tracking algorithm in an example of the present invention;

[0034] Figure 6 This is a simulation model diagram of the active power reserve control of the photovoltaic system in an example of the present invention;

[0035] Figure 7 This is a simulation waveform diagram of the sudden change in reserve rate in an example of the present invention;

[0036] Figure 8 The simulated PV curve for the standby rate mutation in the example of this invention;

[0037] Figure 9 This is a simulation waveform diagram of light intensity change in an example of the present invention;

[0038] Figure 10 This is the PV curve of sudden change in light intensity in an example of the present invention;

[0039] Figure 11 This is a flowchart of the method of the present invention. Detailed Implementation

[0040] This invention proposes a principle and control method for active power point tracking (RPPT) in photovoltaic systems. It aims to avoid the problems of high cost of multi-point, large-scale measurement of G and T and low accuracy of single-point measurement of G and T by estimating the maximum power point online, and to quickly and stably adjust the active power reserve rate.

[0041] To better understand the above technical solution, the following will refer to the appendix to the instruction manual. Figures 1-11 The present invention provides a detailed description of the above technical solutions and specific implementation methods, but the implementation methods of the present invention are not limited thereto.

[0042] Example:

[0043] like Figure 5 The flowchart shown illustrates an active power reserve point tracking (RPPT) process for a photovoltaic system. The specific implementation steps are as follows:

[0044] S1: System startup, the calculation module enables the maximum power point tracking (MPPT) algorithm to find the initial maximum photovoltaic output power P under the current environment. max .

[0045] S2: Based on the set target active power reserve rate The maximum power P obtained from the initial scan max The initial active power reserve operating point is determined, enabling the photovoltaic system to enter active power reserve state.

[0046] S3: Detect the current output current I of the photovoltaic system. pv and output voltage V pvCalculate the current actual output power P pv Simultaneously, by injecting a square wave disturbance into the circuit, the current power-voltage slope dP is calculated. pv / dV pv Theoretical power-voltage P pv / dV pv Based on the mathematical model of photovoltaic cells and the power-voltage slope dP pv / dV pv The mathematical model based on photovoltaic cells can be expressed as follows:

[0047] (2.1)

[0048] In the formula, P pv V represents the output power of the photovoltaic system. pv Output DC voltage for the photovoltaic system; dP pv / dV pv The output power P of the photovoltaic system pv Relative output voltage V pv The rate of change; C1 is C2 is , where I mpp and V mpp The temperatures were 25℃ and the light intensity was 1000W / m², respectively. 2 Maximum output current and maximum output voltage under the specified conditions; I sc The short-circuit current can be expressed as V oc The open-circuit voltage can be expressed as , where I sc0 and V oc0 The temperatures were 25℃ and the light intensity was 1000W / m², respectively. 2 Short-circuit current and open-circuit voltage under the given conditions; G is the real-time irradiance received by the photovoltaic panel, T is the real-time temperature of the photovoltaic panel, and G0 is the standard irradiance of 1000 W / m². 2 T0 is the standard temperature of 25℃. The difference between the real-time photovoltaic panel temperature T and the standard temperature T0, i.e. ; For the corrected ideal factor, Where A is the diode ideality factor, k is the Boltzmann constant, and q is the electron charge; β and γ are correction coefficients, respectively: β = 0.5, γ = 0.00288 / ℃.

[0049] S4: After the slope calculation stabilizes, based on the five-parameter model of photovoltaic cells, construct the analytical equation set of the composite parameter mathematical model for online estimation of the maximum power point of the photovoltaic system, which includes irradiance G and temperature T:

[0050] (2.2)

[0051] In the formula, I sc and V oc as follows

[0052] (2.3)

[0053] The above equations were solved using the multi-starting-point Newton-Raphson method to obtain the optimal solutions for real-time illuminance G and temperature T. Based on the obtained real-time illuminance G and temperature T, the maximum power point P of the photovoltaic system under the current environment was calculated. mppe :

[0054] (2.4)

[0055] In the formula, , Temperature 25 o C. Illumination 1000W / m 2 The current and voltage corresponding to the maximum power point.

[0056] Then calculate the current actual active power reserve rate. :

[0057] (2.5)

[0058] S5: Target active power reserve rate Compared with the current active power reserve rate A comparison is made, and the active power output of the photovoltaic system is adjusted in real time via a PI controller. When > At that time, adjust P pv Rise, control Decrease; when < At that time, adjust P pv Decrease, control Increase; ultimately guarantee the current active power reserve rate. Real-time tracking of target active power reserve rate

[0059] S6: Real-time monitoring of P mppe If the change exceeds a set threshold, it is determined that the environment has changed, and the process returns to execute S4 for reassessment. It also adjusts the active power reserve status; if the threshold is not exceeded, it maintains the current status.

[0060] The following are specific examples.

[0061] To verify the active power point tracking (APPT) of the photovoltaic system proposed in this paper, a simulation model of the active power reserve control of the photovoltaic system was built in Matlab / Simulink as follows: Figure 6 As shown in Table 1, the main parameters are as follows.

[0062] Table 1. Parameters of the Photovoltaic Active Power Reserve Control Simulation Model

[0063]

[0064] Simulation Scenario I: Illumination intensity G and ambient temperature T remain constant, active power reserve ratio... mutation

[0065] Simulation as Figure 7 As shown, the simulation duration is 3 seconds. Figure 7 In the middle, 1 second ago, P pv Stable at 112.7W, V pv Stable at 36.5V; Active power reserve rate At 1 second, P mutated from 0.1 to 0.2. pv and V pv All mutations occurred at 1 second and stabilized after fluctuating for a period of time. P pv Stable at 100.2W, V pv It stabilized at 37.6V, that is... Figure 8 The working point changed from point A to point B, which is in line with expectations.

[0066] Simulation Scenario II: Sudden change in light intensity G, ambient temperature T, and active power reserve ratio. constant

[0067] Simulation as Figure 9 As shown, the simulation duration is 3 seconds. Figure 9 In the meantime, 1 second prior, the active power reserve ratio is 0.1, P pv Stable at 112.7W, V pv Stable at 36.5V; light intensity abruptly changes from 850W / ㎡ to 1200W / ㎡ in 1 second, P pv and V pv All mutations occurred at 1 second and stabilized after fluctuating for a period of time. P pv Stable at 169.6W, V pv It stabilized at 38.9V, that is... Figure 10 The working point changed from point A to point B, which is in line with expectations.

[0068] The above are preferred embodiments of the present invention. Any changes made to the technical solution of the present invention that do not exceed the scope of the technical solution of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for active power reserve point tracking control of a photovoltaic system based on a composite parameter mathematical model, characterized in that, After the photovoltaic system enters the active power reserve working state, the output power of the photovoltaic system and the rate of change of the output power relative to the output voltage are acquired and substituted into the pre-constructed analytical equation system based on the composite parameter mathematical model to solve for the real-time irradiance received by the photovoltaic panel and the real-time photovoltaic panel temperature. Based on the real-time irradiance and the real-time photovoltaic panel temperature, the maximum power point of the photovoltaic system under the current environment is calculated, and the current real-time active power reserve rate of the photovoltaic system is evaluated based on the maximum power point of the photovoltaic system under the current environment, so as to realize the tracking and control of the active power reserve power point.

2. The photovoltaic system active power reserve point tracking control method based on a composite parameter mathematical model according to claim 1, characterized in that, The specific method by which the photovoltaic system enters the active power reserve working state is as follows: When the photovoltaic system starts up, the initial maximum power point Pmax is obtained through the maximum power point tracking algorithm MPPT. Based on the set target active power reserve rate Based on the initial maximum power point Pmax, determine the initial active power reserve operating point, enabling the photovoltaic system to enter the active power reserve operating state.

3. The photovoltaic system active power reserve point tracking control method based on a composite parameter mathematical model according to claim 1, characterized in that, The specific method for obtaining the output power of the photovoltaic system and the rate of change of the output power relative to the output voltage is as follows: detect the current output current and voltage of the photovoltaic system to calculate the output power of the photovoltaic system; and use the square wave perturbation method to obtain the rate of change of the output power of the photovoltaic system relative to the output voltage.

4. The photovoltaic system active power reserve point tracking control method based on a composite parameter mathematical model according to claim 1, characterized in that, The analytical equations based on the composite parameter mathematical model are expressed as follows: In the formula, P pv V represents the output power of the photovoltaic system. pv Output DC voltage for the photovoltaic system; dP pv / dV pv The output power P of the photovoltaic system pv Relative output voltage V pv The rate of change; C1 and C2 are the fitting coefficients, respectively. , , where I mpp and V mpp These represent the maximum output current and maximum output voltage under standard temperature and illumination conditions, respectively; I sc This is the short-circuit current. V oc Open circuit voltage, , where I sc0 and V oc0 G represents the short-circuit current and open-circuit voltage under standard temperature and illumination conditions, respectively; G is the real-time illumination intensity received by the photovoltaic panel, T is the real-time photovoltaic panel temperature, G0 is the standard illumination intensity, and T0 is the standard temperature. The difference between the real-time photovoltaic panel temperature T and the standard temperature T0, i.e. ; For the corrected ideal factor, , where A is the diode ideality factor, k is the Boltzmann constant, q is the electron charge; β and γ are correction coefficients.

5. The photovoltaic system active power reserve point tracking control method based on a composite parameter mathematical model according to claim 4, characterized in that, The analytical equations based on the composite parameter mathematical model were solved using the multi-starting point Newton-Raphson method to obtain the optimal solutions for real-time light intensity and real-time photovoltaic panel temperature.

6. The photovoltaic system active power reserve point tracking control method based on a composite parameter mathematical model according to claim 4, characterized in that, The calculation of the maximum power point of the photovoltaic system under the current environment is based on real-time light intensity and real-time photovoltaic panel temperature, and the specific calculation is as follows: In the formula, P mppe This represents the maximum power point of the photovoltaic system under the current environment. , These represent the current and voltage corresponding to the maximum power point under standard temperature and illumination conditions, respectively.

7. The photovoltaic system active power reserve point tracking control method based on a composite parameter mathematical model according to claim 5, characterized in that, The method for assessing the current real-time active power reserve of the photovoltaic system based on its maximum power point under the current environment is as follows: The specific calculation for assessing the current real-time active power reserve of the photovoltaic system is as follows. , can be represented as: In the formula, This represents the current real-time active power reserve rate of the photovoltaic system.

8. The photovoltaic system active power reserve point tracking control method based on a composite parameter mathematical model according to claim 1, characterized in that, The control of the active power reserve point is as follows: Target active power reserve rate Compared with the current real-time active power reserve rate The comparison is performed, and the active power output of the photovoltaic system is adjusted in real time through a PI controller; when > At that time, adjust the output power P of the photovoltaic system. pv Rise, control Decrease; when < At that time, adjust the output power P of the photovoltaic system. pv Decrease, control rise.

9. The photovoltaic system active power reserve point tracking control method based on a composite parameter mathematical model according to claim 1, characterized in that, The control of active power reserve points also includes: Real-time monitoring of the maximum power point P of the photovoltaic system under the current environment mppe The change in the amount of power; if the change exceeds a set threshold, it is determined that the environment has changed, the output power of the photovoltaic system and the rate of change of the output power relative to the output voltage are obtained, and the current real-time active power reserve of the photovoltaic system is reassessed. According to the reassessment and target active power reserve rate Adjust the active power reserve status; if the threshold is not exceeded, maintain the current status.

10. A photovoltaic system active power reserve point tracking control system based on a composite parameter mathematical model, characterized in that, It includes a processor, a memory, and a computer program stored in the memory. When the processor executes the computer program, it specifically performs the steps in the photovoltaic system active power reserve point tracking control method as described in any one of claims 1-9.

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