CN-116720047-B - Temperature rise distribution analysis method and system for parallel photovoltaic modules

CN116720047BCN 116720047 BCN116720047 BCN 116720047BCN-116720047-B

Abstract

The invention discloses a temperature rise distribution analysis method and system of parallel photovoltaic modules, wherein the analysis method comprises the steps of obtaining appearance states of all batteries in the parallel photovoltaic modules, determining performance states of all batteries according to the appearance states of the batteries, and determining additional temperature rises of all batteries in the parallel photovoltaic modules by using an equivalent circuit model of the parallel photovoltaic modules according to the performance states of all batteries. The method and the device can evaluate the extra temperature rise of each battery in the parallel photovoltaic module.

Inventors

WANG LEI
Cao xinyue
SHI KAIXIN
Zhang Binshi
XU YIFAN
Zhao Zengruixue

Assignees

河海大学

Dates

Publication Date: 20260512
Application Date: 20230506

Claims (7)

1. The temperature rise distribution analysis method of the parallel photovoltaic modules is characterized by comprising the following steps of: Obtaining the appearance state of each battery in the parallel photovoltaic module; determining the performance state of each battery according to the appearance state of the battery; determining the extra temperature rise of each battery in the parallel photovoltaic assembly by using an equivalent circuit model of the parallel photovoltaic assembly according to the performance state of each battery; The method for determining the additional temperature rise of each battery in the parallel photovoltaic module by using the equivalent circuit model of the parallel photovoltaic module according to the performance state of each battery comprises the following steps: If the performance of part of the batteries in the branch circuit of the parallel photovoltaic module is reduced, determining the additional temperature rise of each battery in the branch circuit according to the volt-ampere characteristics of the main circuit, the branch circuit and the batteries; If the performance of part of the batteries in the branch circuit of the parallel photovoltaic module is reduced, determining the additional temperature rise of each battery in the branch circuit according to the volt-ampere characteristics of the main circuit, the branch circuit and the batteries comprises: When the performance of part of batteries in a branch of the parallel photovoltaic module is reduced, taking a preset voltage value of the parallel photovoltaic module as the voltage of the branch; Determining the voltage and current of each battery based on the volt-ampere characteristics of a main circuit, a branch circuit and the batteries, and when the current of the batteries is smaller than 0, reducing the performance of the batteries to make the absolute value of the current of the batteries with reduced performance be the reverse current of the batteries with reduced performance; The extra temperature rise of the battery with good performance is set to be 0, and the extra temperature rise of each battery with reduced performance is determined according to the voltage, the reverse current and the appearance state of the battery with reduced performance based on a preset temperature rise strategy; Wherein determining the voltage and current of each cell based on the volt-ampere characteristics of the main, branch and cell comprises: Determining the voltage and the current of each battery based on the fact that the voltage and the current of the battery accord with the volt-ampere characteristics of the battery, and according to the fact that the current of a main circuit is the sum of the currents of each branch circuit, the voltage of the branch circuit is the sum of the voltages of each battery, and the currents of the branch circuit are equal to the currents of each battery in the branch circuit; Wherein, the temperature rise strategy includes: acquiring environmental parameters and battery parameters of parallel photovoltaic module operation; determining the heat flow received by each battery by using the product of the voltage of the battery, the reverse current and the coefficient of converting the preset reverse current into heat energy; determining the temperature of each battery by using the environmental parameters, the battery parameters and the heat flow received by the battery; subtracting the temperature of the battery with good performance from the temperature of the battery with reduced performance to obtain additional temperature rise of each battery with reduced performance; Wherein, the batteries with different appearance states have different coefficients for converting reverse current into heat energy.
2. The method for analyzing temperature rise distribution of parallel photovoltaic modules according to claim 1, wherein the equivalent circuit model is built according to linear source characteristics of the parallel photovoltaic modules in a working state; each branch of the parallel photovoltaic module comprises a plurality of batteries which are connected in series.
3. The method for analyzing temperature rise distribution of parallel photovoltaic modules according to claim 1 or 2, wherein the determining the performance state of each cell according to the appearance state of the cell comprises: When the appearance of the battery is not damaged, the battery performance is good; And/or, when the appearance of the battery has micro-crack defects, the performance of the battery is reduced, and the heat distribution is uneven; and/or when the appearance of the battery has surface defects, the performance of the battery is reduced, and the heat distribution is uniform; and/or when the appearance of the battery has surface shielding, the battery performance is reduced, and the heat distribution is uniform.
4. The method for analyzing temperature rise distribution of parallel photovoltaic modules according to claim 1, wherein the battery performance state comprises good and degraded; According to the performance state of each battery, determining the extra temperature rise of each battery in the parallel photovoltaic module by using an equivalent circuit model of the parallel photovoltaic module, and further comprising: if the performances of all the batteries in the branch circuit of the parallel photovoltaic module are good, the extra temperature rise of all the batteries in the branch circuit is 0; if the performance of each battery in a branch of the parallel photovoltaic module is reduced, determining the additional temperature rise of each battery in the branch according to the volt-ampere characteristics of the batteries.
5. The method for analyzing temperature rise distribution of parallel photovoltaic modules according to claim 4, wherein if the performance of each battery in a branch of a parallel photovoltaic module is reduced, determining the additional temperature rise of each battery in the branch according to the volt-ampere characteristics of the battery comprises: When the performance of each battery in the branch is reduced, taking a preset voltage value of the parallel photovoltaic modules as the voltage of the branch, and determining the voltage of each battery according to the voltage of the branch; Determining the current of the battery according to the voltage of the battery based on the volt-ampere characteristic of the battery, and enabling the absolute value of the current of the battery to be the reverse current of the battery; And determining the additional temperature rise of each performance-reduced battery according to the voltage, the reverse current and the appearance state of the performance-reduced battery based on a preset temperature rise strategy.
6. The method of claim 1, wherein determining the temperature of each cell using the environmental parameter, the cell parameter, and the thermal flow of the cell comprises: In the formula, For the heat flux to which the battery is subjected, For the absorption rate of the battery, For the photoelectric conversion efficiency of the battery, For the intensity of the radiation to which the cell is subjected during operation, k is the coefficient of conversion of the reverse current into thermal energy, For the reverse current of the battery, For the voltage of the battery cell, 、、 Are all the temperature coefficients of the materials, For the stefin-boltzmann constant, The emissivity of the front and back sides of the cell respectively, The convective heat transfer coefficients of the front and back surfaces of the battery and air respectively, For the heat flux to which the battery is subjected, For the area of the battery, In order to be at the temperature of the environment, Is the temperature of the sky and is the temperature of the sky, Is the temperature of the ground surface, For the emissivity of the sky, For the ground-based emissivity, Is the temperature of the battery.
7. The utility model provides a temperature rise distribution analysis system of parallelly connected photovoltaic module which characterized in that includes: the acquisition module is used for acquiring the appearance state of each battery in the parallel photovoltaic module; the determining module is used for determining the performance state of each battery according to the appearance state of the battery; The evaluation module is used for determining the extra temperature rise of each battery in the parallel photovoltaic module by using an equivalent circuit model of the parallel photovoltaic module according to the performance state of each battery; The method for determining the additional temperature rise of each battery in the parallel photovoltaic module by using the equivalent circuit model of the parallel photovoltaic module according to the performance state of each battery comprises the following steps: If the performance of part of the batteries in the branch circuit of the parallel photovoltaic module is reduced, determining the additional temperature rise of each battery in the branch circuit according to the volt-ampere characteristics of the main circuit, the branch circuit and the batteries; If the performance of part of the batteries in the branch circuit of the parallel photovoltaic module is reduced, determining the additional temperature rise of each battery in the branch circuit according to the volt-ampere characteristics of the main circuit, the branch circuit and the batteries comprises: When the performance of part of batteries in a branch of the parallel photovoltaic module is reduced, taking a preset voltage value of the parallel photovoltaic module as the voltage of the branch; Determining the voltage and current of each battery based on the volt-ampere characteristics of a main circuit, a branch circuit and the batteries, and when the current of the batteries is smaller than 0, reducing the performance of the batteries to make the absolute value of the current of the batteries with reduced performance be the reverse current of the batteries with reduced performance; The extra temperature rise of the battery with good performance is set to be 0, and the extra temperature rise of each battery with reduced performance is determined according to the voltage, the reverse current and the appearance state of the battery with reduced performance based on a preset temperature rise strategy; Wherein determining the voltage and current of each cell based on the volt-ampere characteristics of the main, branch and cell comprises: Determining the voltage and the current of each battery based on the fact that the voltage and the current of the battery accord with the volt-ampere characteristics of the battery, and according to the fact that the current of a main circuit is the sum of the currents of each branch circuit, the voltage of the branch circuit is the sum of the voltages of each battery, and the currents of the branch circuit are equal to the currents of each battery in the branch circuit; Wherein, the temperature rise strategy includes: acquiring environmental parameters and battery parameters of parallel photovoltaic module operation; determining the heat flow received by each battery by using the product of the voltage of the battery, the reverse current and the coefficient of converting the preset reverse current into heat energy; determining the temperature of each battery by using the environmental parameters, the battery parameters and the heat flow received by the battery; subtracting the temperature of the battery with good performance from the temperature of the battery with reduced performance to obtain additional temperature rise of each battery with reduced performance; Wherein, the batteries with different appearance states have different coefficients for converting reverse current into heat energy.

Description

Temperature rise distribution analysis method and system for parallel photovoltaic modules Technical Field The invention relates to a temperature rise distribution analysis method and system for parallel photovoltaic modules, and belongs to the technical field of photovoltaic power generation. Background With the development of new energy, more and more photovoltaic modules are applied to actual life, and the reliability research of the photovoltaic modules is increasingly important. When cells are interconnected to form a module, there is a mismatch loss due to the difference in cell performance, and the loss of the photovoltaic module due to mismatch is not negligible. Wherein the parallel mismatch is caused by voltage mismatch between the parallel components, which can cause current reverse-sinking. Researches on the temperature of the photovoltaic module show that the temperature of the battery is further increased due to the mismatching of the photovoltaic array caused by various factors such as battery defects, faults and the like. The high temperature not only can reduce the output of the battery, but also can cause irreversible damage to the battery when serious, thereby greatly damaging the safety and efficient operation and maintenance of the photovoltaic module. For the influence of parallel mismatch of photovoltaic modules, the common mismatch causes that voltages among the parallel connections are different, so that forward bias voltage and reverse current flow into a branch circuit to raise the temperature, and the overall generated power is influenced. Therefore, it is necessary to calculate the temperature rise due to the parallel mismatch. Disclosure of Invention The invention aims to overcome the defects in the prior art and provides a temperature rise distribution analysis method and system for parallel photovoltaic modules, which can evaluate the additional temperature rise of each battery in the parallel photovoltaic modules. In order to achieve the above purpose, the invention is realized by adopting the following technical scheme: in one aspect, the invention provides a temperature rise distribution analysis method of parallel photovoltaic modules, which comprises the following steps: Obtaining the appearance state of each battery in the parallel photovoltaic module; determining the performance state of each battery according to the appearance state of the battery; and determining the extra temperature rise of each battery in the parallel photovoltaic assembly by using an equivalent circuit model of the parallel photovoltaic assembly according to the performance state of each battery. Further, the equivalent circuit model is built according to the linear source characteristics of the parallel photovoltaic modules in the working state; each branch of the parallel photovoltaic module comprises a plurality of batteries which are connected in series. Further, the determining the performance state of each battery according to the appearance state of the battery includes: When the appearance of the battery is not damaged, the battery performance is good; A preferred embodiment of the method for determining each battery performance state according to the appearance state of the battery comprises the steps of reducing the battery performance and non-uniform heat distribution when the appearance of the battery has micro-crack defects; A preferred embodiment of the method for determining each battery performance state according to the appearance state of the battery comprises the steps of reducing the battery performance and uniformly distributing heat when the appearance of the battery has surface defects; in a preferred embodiment, the determining the performance state of each battery according to the appearance state of the battery comprises the steps that when the appearance of the battery has surface shielding, the battery performance is reduced, and the heat distribution is uniform. Further, the battery performance states include good and degraded; further, determining the additional temperature rise of each battery in the parallel photovoltaic module by using the equivalent circuit model of the parallel photovoltaic module according to the performance state of each battery comprises: if the performances of all the batteries in the branch circuit of the parallel photovoltaic module are good, the extra temperature rise of all the batteries in the branch circuit is 0; In a preferred embodiment, if the performance of each battery in a branch of the parallel photovoltaic module is reduced, determining the additional temperature rise of each battery in the branch according to the volt-ampere characteristic of the battery; in a preferred embodiment, if the performance of a part of the cells in the branch of the parallel photovoltaic module is reduced, determining the additional temperature rise of each cell in the branch according to the volt-ampere characteristics of the main, branch and cell.