Master-slave parallel control method for energy storage converters of photovoltaic/battery micro grid system

Abstract

Provided is a master-slave parallel control method for energy storage converters of a photovoltaic / battery micro grid system. When the grid works normally, the maser energy storage converter and the slave energy storage converters of the photovoltaic / battery micro grid system both work in a grid-connected mode, and a three-stage charging strategy including constant-current charging, constant-voltage charging and floating charging is implemented according to the battery state of the energy storage systems. When the grid fails, the master energy storage system is switched to an off-grid mode to establish a voltage and a frequency for the bus of the photovoltaic / battery micro grid system, and the slave energy storage systems continue to work in a grid-connected mode. An energy management system adjusts the output power of the energy storage converters in the slave energy storage systems in real time according to the load power, the state of the master energy storage system and the power of a photovoltaic power generation system, in order to maintain the power balance in the micro grid system. In order to meet the power allocation requirement of each energy storage system in the photovoltaic / battery micro grid system, the energy management system issues power dispatching instructions to the slave energy storage converters according to the battery state, the generation power of the photovoltaic system and the load power.

Description

technical field [0001] The invention relates to a control method for master-slave parallel operation of multiple energy storage converters in an optical storage microgrid system. Background technique [0002] With the rapid development of distributed new energy, microgrid systems that can be flexibly switched between grid-connected and off-grid are becoming more and more widely used. The microgrid system is a small power generation and distribution system consisting of distributed power sources, power loads, power distribution facilities, monitoring and protection devices, and energy storage devices when necessary. When the power grid is normal, the optical storage microgrid system operates in the grid-connected mode, and the energy storage converters in the optical storage microgrid system achieve the set operation goals according to the preset operation management strategy. When the power grid fails, the photovoltaic storage microgrid system switches to the off-grid mode,...

AI Technical Summary

Problems solved by technology

However, droop control is suitable for high-voltage transmission lines with large reactance and low resistance. At present, the photovoltaic storage microgrid system is generally connected to the low-voltage distribution network, and the transmission line parameters are just the opposite, which makes it difficult for droop control to operate in the actual photovoltaic storage microgrid system.

[0004] The commonly used master-slave parallel control is to send power scheduling instructions from the master energy storage converter to schedule the power of the slave energy storage converters. However, when the number of slave energy storage converters in the microgrid system changes, it needs to Modify the program of the main energy storage converter, and the expansion of the microgrid system is more complicated

In addition, the commonly used master-slave parallel control does not protect the main energy storage converter. When the load in the microgrid system is too large or too small, the battery of the main energy storage system will exceed the threshold, resulting in the shutdown of the main energy storage converter. This leads to the "paralysis" of the entire microgrid system

Images