Optimal Control Of Hith-permeability Distributed Photovoltaic Low-voltage Distribution Network With The Energy Storage System

In recent years,under the severe situation of increasing primary energy consumption and increasing environmental pressure in China,distributed renewable clean energy power generation technology has developed rapidly,especially the development of distributed photovoltaics under the encouragement of relevant national policies Especially fast.However,distributed photovoltaic output is easily affected by meteorological conditions,showing significant intermittency and randomness,causing great interference and uncertainty after access to the distribution network,affecting the quality of voltage and the reliability of power supply of the system.With its unique advantages of fast power control and flexible energy management,energy storage provides an effective way for the safe absorption of high-permeability distributed photovoltaics and the solution of the voltage over-limit problem of low-voltage distribution networks.This article studies the optimal control of high-permeability photovoltaic low-voltage distribution network energy storage system.The specific contents are as follows:Firstly,in view of the relatively large R/X characteristics of the low-voltage distribution network,the basic principle of the voltage generation of the low-voltage distribution network is analyzed,and the corresponding characteristic of the active voltage of the low-voltage distribution network is obtained through simplification.It is proposed to solve the problem of voltage over-limit of low-voltage distribution network by adding energy storage and coordinating the active power of the optical storage unit into the system.A mathematical model of each unit of the photovoltaic low-voltage distribution network with energy storage is established,in which photovoltaic power generation uses maximum power tracking control,and energy storage charging and discharging control uses constant power control.And the simulation and analysis of the system are carried out in Matlab/SimulinkSecondly,in view of the imbalance of the energy storage system participating in the voltage control process,a distributed coordinated control strategy for the charging and discharging of each energy storage unit of the energy storage system is proposed.The control strategy consists of three parts.First,the active voltage of the low-voltage distribution network exceeds the limit,and the local exchange control is used to determine the initial exchange power of the energy storage according to the system voltage limit.Then the weighted uniform control strategy is adopted to modify the initial exchange power considering the capacity of the energy storage unit,so that each energy storage unit is proportional to its rated capacity when participating in the voltage adjustment.Finally,for the different initial charging states of energy storage units,a distributed dynamic consistent control strategy is proposed to coordinate the state of charge of each energy storage unitFinally,in order to verify the correctness and effectiveness of the proposed control strategy,the proposed distributed coordinated control strategy was added to the optical storage low-voltage distribution network for example analysis.After the three control strategies of energy storage are gradually added,the effectiveness of the proposed control strategy is verified by analyzing the system voltage and the results of the change curve of the state of charge of each energy storage unit.It can be seen that the local droop control can participate in the control in time when the bus voltage connected to the energy storage exceeds the limit,but because there is no coordinated control with other energy storage units,the control effect mainly depends on the capacity of a single energy storage unit.After adding distributed coordinated and consistent control,through the coordinated control of each energy storage unit,under the premise of ensuring that the voltage does not exceed the limit,the capacity and state of charge of each energy storage unit of the energy storage system are also considered.From the simulation results,this The control strategy makes the most effective use of the capacity of the entire energy storage system.