Research Of Voltage Stability And Control Strategy With Wind Power And Photovoltaic Power Integration

In recent years, with the rapid development of new energy power generation, the scale of wind power and photovoltaic power integration is increasing. The influence on voltage stability of power system caused by the randomness of wind power and photovoltaic power output is more and more serious. Therefore, to study the effect on voltage stability of the system cased by wind farms and solar power station and the corresponding reactive voltage control strategy has been the important topic. This paper analyzes the power system voltage stability of the grid connected with wind farm and photovoltaic power station based on the probability analysis method. In view of the voltage fluctuation and voltage stability problem of grid connected with wind farm and photovoltaic power station, this paper puts forward a kind of two-tier reactive power and voltage control strategy. The main research content is as follows:(1) This paper summarizes the research status of wind power and photovoltaic power generation at home and abroad, and then analyzes the static voltage instability mechanism and the static voltage stability analysis method. The mathods of static voltage stability include deterministic voltage stability analysis method and the probability analysis method mainly. The deterministic analysis method includes PV curve and VQ curve method, sensitivity analysis, characteristic value analysis and modal analysis. The probability analysis method includes the Monte Carlo(MC) simulation method and the Stochastic Response Surface Method(SRSM) mainly. Finally, the indicators to masure the voltage stability are introduced.(2) A probability distribution model of wind farm and photovoltaic power station is established based on Copula theory and Kernel Density Estimation(KDE), and then we analyze the system voltage stability cased by the correlation between wind farm and photovoltaic power station. Fistly, the knowledge of the probability theory is introduced. Then, a joint probability distribution model of wind farm and photovoltaic power station is established. Continuous Power Flow(CPF) calculation is used in different discrete segments and the discrete probability distribution of the node voltage, system load margin and critical voltage is established. The probability distribution function of the node voltage, load margin and critical voltage are obtained by using Gramm-Charlier series expansion method. Lastly, program is written in matlab R2014 a and simulation is performed to study the system voltage stability cased by the correlation between wind farm and photovoltaic power station.(3) To solve the impact of wind power and photovoltaic power station on power system voltage stability, a two-tier reactive power and voltage control strategy is put forward. Firstly, discrete equipment is pre-performed according to the optimization result based on the prediction information of wind power and photovoltaic power station. And then, the static voltage stability index is proposed, according to the measured data, a multi-objective optimization model is put forward. Lastly, the particle swarm optimization(PSO) is used to solve the problem. The reactive power coordinative control strategy among wind farm, photovoltaic power station and dynamic equipment can meet the requirements of voltage, at the same time, the static voltage stability of system can be improved.