Bifurcation Analysis Of Photovoltaic System Grid Connection Node Voltage Stability

The solar energy has been one of the best choice that can take the place of the traditional fossil energy. So the photovoltaic power generation has grown so quickly, but as more and more photovoltaic power generation will be connected to grid,the stability of the entire power system will be influenced significantly, especially the voltage stability of power system,with the heavy random fluctuations and the poor control performance of grid connection electricity,it will produce great impact current when grid connection, which can cause the power grid voltage fluctuation and flicker, thus affecting the steady state voltage distribution and reactive power characteristics,and the grid connection node will be the first one that be influenced severely as an important node.So we try to know the fundamental mechanism of the photovoltaic power system voltage stability better so as to restrain instability, this paper analyzed the voltage stability and bifurcation phenomenons of photovoltaic power system grid connection node based on the bifurcation theory with the model of grid-connected photovoltaic system. The research contents and conclusions of this paper are as follows:1. The bifurcation phenomenons of photovoltaic power system grid connection node’s voltage stability were studied by the bifurcation theory based on the photovoltaic power system’s grid-connected model,afier a mathematical deduction,then chose active power of photovoltaic system injection power system and the sunlight intensity parameter as bifurcation parameters.The simulation results showed thatrwhen the active power continue to increase, the grid connection node’s voltage will cut down quickly, and dynamic bifurcation phenomenon may happen at the same time, which may bring sustain oscillation or occur instability phenomenon to the power system’s voltage; When the sunlight intensity continue to increase,the critical operation point was moved ahead,and the hopf bifurcation that appeared before grid connection node achieving it’s limit point will be delayed,that’s to say, it will increase the grid connection node’s stability domain.2. Install static var compensatorsVC) in photovoltaic system, observe the impact on voltage stability and bifurcation phenomenon of SVC. The simulation results show thatmear the photovoltaic system output limit, the reactive power loss at transmission line will increase, and it will reduce the grid connection node voltage stability, so using static var compensator (SVC) can delay or even reduce the bifurcation points, thereby it can improve the grid connection node voltage stability efficiently;Under the weaker sunshine intensity,although loading capacity of the grid connection node had a small decline, but the operation stability domain and voltage quality of grid connection node has improved to a great extent.