An investigation of innovative voltage control approaches to increase Rooftop PV penetration

Yiqing Wang

In Western Australia, steady increases in rooftop photovoltaic (PV) systems are mainly caused by the continued decrease in the cost of solar PV systems. The high penetration of PV systems will cause increasing reverse power to be injected into grids. As a result, the distribution network will face major voltage rise challenges. This issue has a negative influence on the reliability and security of the power network operation. Therefore, it is necessary to investigate methods to mitigate voltage rise to enhance the penetration of rooftop PV systems. This study evaluates the effectiveness of feasible solutions for voltage management through simulation studies using the DIgSILENT PowerFactory software. These solutions draw on control means provided by utility operated equipment only or in combination with utility and prosumer operated equipment. In this project, the primary strategy used to mitigate voltage rise was the use of on-load voltage regulation transformers (OL-VRDTs) with and without the application of the line drop compensation (LDC) on a 22kV/415V distribution network. This study also examined the combination methods between the OL-VRDTs with and without LDC and prosumers’ reactive power controls in their PV inverters (fixed power factor controller or volt-var response control Q(V)). The results showed that the implementation of the OL-VRDTs with LDC was the best utility approach to mitigate voltage rise. However, the success of this method depends on the selection of the set-point voltage of the OLTCs and the line drop compensation parameters. Furthermore, the voltage rise mitigation capability of the sole OL-VRDTs-based methods can be improved when combined with the reactive power controls of PV inverters. This is because reactive power controllers absorb additional reactive power from the grid to reduce voltage rise. However, this may require additional investment by utilities to inject more reactive power into their grids. The Q(V) controller has a lower Q demand than the fixed power factor controller and is hence the preferred prosumer method. However, the most advanced prosumer method is fulltime Q(V) control, which is independent of solar PV generation. In addition, it was shown that both OL-VRDT-based voltage control and fulltime Q(V) control can reduce voltage variations and increase the load carrying capacity of the LV feeder.

An investigation of innovative voltage control approaches to increase Rooftop PV penetration

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