| Due to energy crisis and environment pollution issues, the renewable energy power generation technology represented by the photovoltaic (PV) power generation has received extensive attention and developed rapidly in recent years. Distributed PV power generation system generally connects to low-voltage distribution network, traditional distribution network is generally a radial network with a single power source, and its voltage regulation is designed according to the radial network. Grid-connected PV power generation system changes the structure of distribution network, which makes the distribution system change from single supply radial network to multi-source network. The power flow is no longer one way flowing from substation to the load. And distribution network voltage and the voltage regulation effect of traditional voltage regulators are likely to be affected. Considering the impact of grid-connected PV power generation system on the distribution network, traditional voltage regulators can no longer meet the requirement of safe and economic operation of the power grid. Therefore, it’s necessary to study the voltage control strategy of distribution network with distributed PV power generation systems.Firstly, a three-phase single-stage grid-connected PV power generation system has been built in power system simulation software DIgSILENT/PowerFactory including the PV array model, maximum power point tracking (MPPT) model, inverter and its control model and simulation results show the effectiveness of the model.Then, impacts caused by grid-connected PV power generation system on distribution network voltage and its regulation are analyzed and the working principle of traditional voltage regulators are introduced.After that, a voltage control strategy based on battery energy storage system (BESS) is proposed to solve voltage violation problem caused by distributed photovoltaic (PV) power generation systems connected to distribution network. This strategy set the reference value of charge and discharge power according to the voltage amplitude and voltage sensitivity, in order to solve voltage violation problem. The validity of the proposed control strategy is verified by case study results.Finally, a voltage control strategy based on grid-connected PV inverter and on-load tap changing transformer (OLTC) is proposed to eliminate the influence of 6grid-connected PV power generation system on the grid voltage and its regulation. PV inverter is involved in grid voltage regulation by controlling the reactive power according to the voltage amplitude. If the PV inverter itself can not make the grid voltage return to normal, automatic voltage control (AVC) relay changes the tap of OLTC according to the maximum and minimum value of grid voltage estimated by feeder terminal units (FTUs) placed at key nodes of the grid. The validity of the proposed control strategy is verified by case study results. |
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