Research On Supporting Effect Of Photovoltaic Inverter To Network Voltage When Network Voltage Dips

As the scale of power network construction is growing with the increasing number of all kinds of connected electrical equipment,a higher request on the voltage quality is also proposed.In this paper,PVDG is equipped with reactive power compensation capability through improving the control mode of photovoltaic inverters.Reactive power is injected into the grid-connected point to boost the voltage of the grid-connected point and to improve the voltage quality of the distribution network during the voltage fault and sag of the distribution network.The change rule of transmission of the amplitude and type of the voltage sag induced by the short circuit in the power transmission line is firstly analyzed in this paper.Also,the trend of positive/ negative sequence voltage and unbalance factor changing along with the length of the power transmission line is also obtained via decomposing the fault voltage.It's clear that the grid-connected point of PVDG in the power distribution network will be affected when voltage sag occurs in the power distribution network according to the analysis on the transmission of the voltage sag.In order to reduce the impact of voltage sag of the grid-connected point,PVDG is provided with the reactive power compensation ability by means of superimposed control of positive and negative sequence voltage;meanwhile,reactive power is injected when the voltage sag occurs in the grid-connected grid to improve the voltage of the grid-connected point and to eliminate the unbalance factor of the grid-connected point.At last,the raising effect of the control strategy is verified through simulation.The node voltage of the power distribution network will be changed when the PVDG is connected to the power distribution network.At the same time,the IEEE33 node simulation of the power distribution network is established to verify the influence of PVDG connecting on the node voltage of the power distribution network and to calculate the optimal connecting point for the stability index of the node voltage of the power distribution network.PVDG with the reactive power compensation ability is connected to the power distribution network,so as to lift the regulating ability of the PV on the voltage of the power distribution network.Therefore,the supporting role of node voltage of the power distribution network can be tested through simulation when the power distribution network is in a short-circuit fault.