| With the energy sources and environment problem becomes increasingly prominent, photovoltaic and other renewable clean energy are more and more get the favour of all countries in the world. In the photovoltaic(PV) industry, distribution photovoltaic system is dominant. Affected by the environment, photovoltaic system output has typical characteristics of intermittent and uncertainty, which leads to the low utilization rate of PV gird inverter and increased out-of-limit voltage risk. With the improvement of photovoltaic permeability in grid, photovoltaic system will be more and more influential to grid voltage. So the study of PV systems interconnection performance and how to make more friendly coordination between photovoltaic power supply and power grid operation has important theoretical significance and practical value.This paper introduces the comparison of several mature distribution network voltage regulation methods, discusses their respective principle and applicable occasions, then systematically analyses the working principle of distribution photovoltaic system and inverter PQ control strategy. On this basis, this paper analyzes distribution photovoltaic system voltage control strategy of reactive power regulation.In order to improve the situation of out-of-limit voltage and low power factor at grid-connected point caused by grid-connection of photovoltaic system and change of load, this article analyzes the voltage characteristic of grid-connected point, demonstrates the possibility of out-of-limit voltage in low voltage power grid, researches the methods to meet the needs of regulating voltage and power factor, then proposes a voltage-power factor control strategy. According to the specific control requirements, this control strategy sets the operation of the PV inverter to voltage adjustment work mode and power factor adjustment work mode. According to the seven different states, the inverter is switched to operate in the two work modes. Under this control strategy, the PV system real-time responses the change of the voltage and power factor at grid-connected point and distributes the active and reactive power output of the PV inverter dynamically. It ensures the voltage fluctuates within the permitted range and maximizes the improvement of the line power factor levels. The effectiveness of the proposed control strategy is verified by case study results. |
