Research On Reactive Voltage Control Of Grid - Connected Photovoltaic Power Station

The development and utilization of large-scale photovoltaic (PV) power station can effectively relieve the energy crisis and reduce the environmental costs caused by energy exploitation. However, with the increase of the capacity of grid-connected PV power station, the negative influence on the power system reliability due to its output random fluctuating nature should be not ignored. Amongst, the most noteworthy problem is the voltage stability for the power system. Therefore, it is necessary to study the reactive voltage control policy of grid-connected PV power station.Firstly, the core component and structure of PV power station is introduced and simulation model is built up, in which the influence of irradiance, ambient temperature on the output capacity of PV module is analyzed by establishing the PV module model, and the decoupling control policy of active power/reactive power is proposed, upon the established inverter model. Furthermore, the equivalent model of grid-connected PV power station is built up and the dynamic response characteristics of PV power station are investigated, which provides a theoretical basis for further research.Secondly, the influence of PV power station on power flow, voltage profile and network loss is analyzed, by concerning the condition of PV power station connecting to the distribution network. By modeling the IEEE33 node, the variations of power flow, voltage profile and network loss are analyzed, on basis of the different interconnected positions, capacity and operating states. As a result, an engineering method about siting of PV power station is proposed, which can meet the requirements of voltage regulation.Finally, a reactive power control strategy for PV power station is proposed, by considering the influence of irradiance on output capacity of PV power station. The proposed strategy can select proper reactive voltage control mode, according to the control point voltage. The reactive power requirement of PV power station is determined, according to the sensitivity index of control point voltage. The actual output reactive power of PV inverter is calculated, according to the influence of irradiance on the output capacity of PV power station. Furthermore, the output reactive power reference for the PV power station is also calculated by setting reactive power link and then distributed to each PV inverter. The above simulation results show that the reactive power output ability of PV inverter is fully utilized and can realize precise control on output reactive power of PV power station, which can effectively improve voltage stability of the power system.