Despite increasing levels of solar-PV penetration in electrical distribution networks, to date the inverters of these PV systems have not been significantly utilized for distribution network control. One particular area of interest for these inverters is their potential to inject/absorb reactive power to/from grid to help manage the voltage profile of their distribution feeder. Various reactive power management strategies have been proposed to address this issue using different voltage-reactive power relationships, but their effectiveness can be limited by competing performance objectives, or simply because the higher resistance characteristics of a typical LV feeder constrain the range of voltage regulation that can be achieved by reactive power injection.
This paper addresses this issue by proposing a combined strategy, where an electronic tap-changer is incorporated into the feeder distribution transformer to provide the feeder voltage regulation function, and the PV DG systems at each feeder bus are then used to minimize feeder losses by providing local load reactive power support. The investigation takes into account a variety of issues such as feeder impedance, dynamic transformer tap changing, different load types and levels of PV penetration. The results obtained from a detailed distribution feeder simulation model show that the combined strategy can very effectively regulate the distribution feeder voltage throughout an entire 24 hour period even with high solar irradiance fluctuations, while still significantly reducing feeder losses.