Coordinated voltage control of distributed PV inverters for voltage regulation in low voltage distribution networks

Abstract

This paper reviews and analyzes the existing voltage control methods of distributed solar PV inverters to improve the voltage regulation and thereby the hosting capacity of a low-voltage distribution network. A novel coordinated voltage control method is proposed based on voltage sensitivity analysis. The proposed method is simple for computation and does not require closed loop communication if the network infrastructure does not change. This method is suitable for a hierarchical control structure where a supervisory controller has the provision to adapt the settings of local PV inverter controllers for overall system optimization. In the proposed method, the voltage bands and droop settings of PV inverters are calculated by the supervisory control, assuming equal power rating of inverters at each node. The local controllers of each PV inverter implement the volt/var control and if necessary, the active power curtailment based on measured local voltages and the predetermined settings calculated by the supervisory control. Advantage of the proposed method is that the calculated reactive power and active power droop settings enable fair contribution of PV inverters at each node to the voltage regulation. Simulation studies are conducted using DigSilent Power factory software on a simplified form of the benchmark LV network provided by CIGRE. The simulation results show that the proposed control method is effective for overvoltage prevention compared to the conventional volt/var method, which uses identical droop settings for all the PV inverters.