Voltage Coordinated Control Strategy For Distributed Photovoltaic-Energy Storage System In Low-Voltage Distribution Networks

With the rapid development of economy,energy shortage has become a serious problem faced by all countries,which greatly promotes the research and development of renewable energy power generation.Among them,photovoltaic power generation,because solar energy has the characteristics of simple energy conversion process and renewable solar energy,plays a very significant role in many renewable energy power generation.Because of the advantages of household distributed photovoltaic : local development and construction,local consumption and utilization,so household distributed photovoltaic is an important direction for the development of photovoltaic power generation under the background of double carbon.It can not only solve the problem of land use constraints and help achieve the goal of double carbon,but also fully mobilize personal enthusiasm and help rural revitalization.However,after the large-scale household distributed photovoltaic is incorporated into the low-voltage distribution network,it brings many adverse effects to the distribution network voltage,and the problem of voltage over-limit needs to be solved urgently.Aiming at the problem of voltage over-limit caused by household distributed photovoltaic grid-connected,it is significant to study and analyze the voltage control requirements of low-voltage distribution network.In this paper,the output specificities of photovoltaic and the load specificities of residents are compared and analyzed,and the mechanism of voltage change caused by household photovoltaic grid connection is analyzed.Considering that the access location,capacity and number of photovoltaic power supply will affect the distribution network voltage to varying degrees,the example conditions are set to analyze the examples in different scenarios.Due to the mismatch between household photovoltaic output and residential load characteristics in time,there will be a problem of voltage exceeding the upper limit in the case of excess photovoltaic output at noon and light load.And the problem of voltage lower limit when the photovoltaic output is 0 at night and the load is heavy.Therefore,it can be concluded that the large-scale household distributed photovoltaic grid-connected will indeed bring the problem of voltage over-limit to the distribution network voltage to varying degrees,laying a foundation for the design of subsequent voltage control strategies.Taking full account of the economy of voltage regulation,in the face of the problem of voltage exceeding the limit,the first consideration is to use the remaining capacity of the photovoltaic inverter incorporated into the household photovoltaic itself for voltage regulation.This paper proposes a voltage control strategy based on the remaining capacity of the photovoltaic inverter.When the voltage exceeds the upper limit,the photovoltaic inverter outputs inductive reactive power to reduce the voltage,and does not attenuate the active power voltage regulation when not necessary;when the voltage is lower,the active power always works in MPPT mode,and the photovoltaic inverter outputs capacitive reactive power.After determining the grid-connected topology of the photovoltaic system,Simulink is used to build the model.Finally,the example conditions are set for example analysis,and the effectiveness and superiority of the voltage control strategy proposed in this paper are obtained.At the same time,in the example results,the problem of whether the remaining capacity of the inverter is sufficient is involved.If the remaining capacity of the inverter is exhausted and the problem of voltage over-limit still exists,it is necessary to consider what means to continue voltage regulation.In the current context of dual carbon,the combination of ’ new energy + energy storage ’ is developing rapidly.Therefore,it is considered that after the distributed energy storage is introduced on the user side to continue remaining capacity of the photovoltaic inverter,the voltage has not yet solved the problem of over-limit.In this paper,a voltage control strategy based on photovoltaic inverter and energy storage coordination is proposed,that is,the voltage control is divided into two stages: when the voltage exceeds the limit,it takes the lead in entering the residual capacity voltage regulation stage of photovoltaic inverter;if the remaining capacity is exhausted,and the voltage over-limit problem still exists,the voltage regulation stage based on the consistency algorithm of energy storage is entered,and the two are coordinated to control the voltage.Based on the above grid-connected model of photovoltaic system,Simulink is used to build the model of distributed optical storage system.Finally,the example conditions are set for example analysis,and the effectiveness of the coordination voltage control strategy proposed in this paper is obtained.