Research On Bus Voltage Stability Control Strategy For Photovoltaic Microgrid

As is well known,energy is indispensable for human production,life,and future development,as it deeply affects a country’s livelihood and competitiveness.However,with the rapid development of the economy,energy consumption is also constantly increasing.In order to deal with the upcoming energy crisis in today’s society,countries have made extensive and in-depth exploration in the field of new energy utilization.Among them,the research on photovoltaic micro grid that converts solar energy into electric energy is particularly attractive.To ensure the normal,safe,and efficient operation of photovoltaic microgrids,the research on voltage stability control of microgrid buses is of great significance.To address this issue,this dissertation concerns the following research work from: maximum power point tracking control of photovoltaic cells and coordinated control of hybrid energy storage.(1)Study on the composition and working principle of photovoltaic microgrid systems.By analyzing the working principle of photovoltaic cells,a simulation model of photovoltaic cells is established,and the output characteristic curve of photovoltaic cells is also obtained.It lays the foundation for the research on maximum power point tracking of photovoltaic cells.By Analyzing the mathematical models of batteries and supercapacitors,a simulation model of a hybrid energy storage photovoltaic microgrid system is established.This provides theoretical and model support for the research of bus voltage stability control.(2)The maximum power point tracking(MPPT)problem of photovoltaic cells is studied.Based on the idea of active disturbance rejection control,an active disturbance rejection control strategy with model compensation is proposed,which makes full use of the known information of the model to design the extended state observer.On the basis of the original bandwidth tuning method,an improved parameter design method is developed.It improves the estimation ability and control effect of the observer for low-frequency disturbances.It makes the goal of fast and accurate tracking control to be achieved.Through simulation results,it verifies that the stability and antiinterference ability of the system have been significantly improved.(3)To address the issue of the stability of microgrid bus voltage being affected by intermittent photovoltaic power generation and random switching of various loads,this dissertation presents a multi-mode droop control method for bus voltage based on the idea of hierarchical control of bus voltage.This method inputs the control signal of the converter into the switch tube and operates according to the set strategy based on the sag coefficient of the system and the charge level of the supercapacitor and battery when there is a fluctuation in the bus voltage.This control method achieves real-time tracking of load changes in the energy storage system.Inaddition,It also improves the accuracy of power allocation and provides a good solution for achieving stable control of bus voltage.