Distributed type photovoltaic on-grid and off-grid energy storage inversion system

Abstract

The invention provides a distributed type photovoltaic on-grid and off-grid energy storage inversion system, which comprises a photovoltaic array, a BOOST one-way conversion circuit, a maximum power point tracking MPPT device, an energy storage system, a direct current bus, an on-grid and off-grid controller, an on-grid and off-grid inverter and a micro-grid, wherein the output energy of the photovoltaic array sequentially passes through the BOOST one-way conversion circuit and the maximum power point tracking MPPT device and is connected to the direct current bus; the energy storage system isconnected into the direct current bus in parallel, the direct-current bus is connected with the micro-grid through an on-grid and off-grid inverter, and the micro-grid is connected with the main gridto form a grid-connected mode, and the micro-grid is disconnected with the main grid to form an off-grid mode; the on-grid and off-grid controller is connected with the on-grid and off-grid inverter,an on-grid and off-grid controller is used for carrying out island detection on the micro-grid, and automatic switching is carried out on the grid-connected mode and the off-grid mode according to the detection result. Coordination and unification of grid connection, grid disconnection and energy storage are realized, and system cost is reduced.

Description

technical field [0001] The invention relates to the field of grid-connected solar cells, in particular to a distributed photovoltaic and off-grid energy storage inverter system. Background technique [0002] With the continuous increase of the installed capacity of photovoltaic power plants, the current capacity of general photovoltaic power plants has reached the MW level. If small-capacity inverters are still used, the number of inverters in the entire photovoltaic power plant will be too large, which will not only increase the construction of the power plant cost, and will affect the power generation efficiency of the entire power station. In order to improve the power, reliability and efficiency of power stations and reduce costs, large-scale photovoltaic power stations currently use high-power photovoltaic grid-connected inverters. Most of the high-power photovoltaic grid-connected inverters in the industry use multiple low-power inverters to operate in parallel. Howe...

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Problems solved by technology

[0004] 1) The output of the photovoltaic power generation system is affected by environmental factors such as light and temperature, and the output power will show large changes, especially when the weather is changeable, its power generation will show obvious randomness and uncontrollability;

[0005] 2) From the perspective of hybrid energy storage photovoltaic grid-connected power generation system design, the system power imbalance caused by this fluctuation needs to be supplemented or absorbed by the energy storage unit.

The capacity and life of lead-acid batteries that work frequently in this situation will be affected, which is determined by the characteristics of lead-acid batteries. There are three main reasons: frequent high-power charging and discharging will cause the temperature inside the lead-acid battery to rise. The active material of the high and positive and negative plates will fall off in large quantities, causing irreversible capacity loss of the battery; high current charging and discharging will cause the plate of the lead-acid battery to bend and deform, and if there is a large voltage drop, it will also cause the self-protection of the battery to shut down; frequent Charging and discharging will make the lead-acid battery work in a small cycle of charging and discharging, which will accelerate the aging and capacity loss of the lead-acid battery, and reduce the cycle life of the battery

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