Research On System Software Of Stability Control Device For Photovoltaic Power Station

Benefited from the rapid progress of photovoltaic power generation technology as well as national policy support for renewable energy,China’s photovoltaic power generation industry flourished over the years.Compared to traditional power generation methods,photovoltaic power generation is advantaged with no pollution,large reserves and short construction period.However,due to the volatility and uncertainty of photovoltaic power generation,the voltage at the point of interconnection between distributed photovoltaic power generation and grid fluctuates sharply,which seriously affects the stability of grid voltage and frequency.Therefore,it is of great practical significance to study the control strategy as well as characteristics of reactive voltage and active frequency when connecting distributed photovoltaic power generation to grid.In this paper,except for describing the status of researches on photovoltaic power station voltage and frequency control technology and power protocol communication,the basic principles and characteristics of voltage and frequency control measures are analyzed.Meanwhile,combined the research results and actual engineering requirements,a strategy for controlling the voltage and frequency of photovoltaic power station is proposed,which has two modes of reactive power control and active power control.In reactive power control mode,three strategies,namely reactive powercontrol voltage,reactive power-control power factor and reactive power direct control,are adopted to stably control the voltage at grid-connected point.In active control mode,three methods including direct active control,primary frequency modulation control and system oscillation suppression are used to suppress frequency fluctuations.Based on the traditional incremental PID algorithm,the integral separation,dead zone characteristics and segmented fixed coefficients are integrated,so that an improved incremental PID algorithm is realized to speed up the regulation voltage stability.In this paper,based on the research of above-mentioned control methods,the distributed photovoltaic power station coordination monitoring is designed,including the overall structure of this device software system.Meanwhile,the functional requirement analysis,non-functional requirement analysis and functional design are introduced in detail.In this software,the above-mentioned improved incremental PID algorithm and two control modes are realized,and most of the functions of IEC104 protocol master and slave stations are accomplished.Besides,by means of various blocking modules,the device safety is protected,and the stable communication of “four remote” data between the device and other related equipment is completed.According to the results of voltage stability and frequency fluctuation test of the Electric Power Research Institute of Zhejiang Electric Power Company,as well as long-term testing and operation in two photovoltaic power stations in Ningbo and Jinhua,the designed control system works well in actual projects,which fully proves the effectiveness of above-mentioned control strategy and device system software.Thus,this system has important engineering and economic value in application.