Autonomous scheduling of heat-pump water heaters for mitigating voltage rise caused by photovoltaic power generation systems

Abstract For mitigating negative impacts of high-penetration photovoltaic power generation system (PVS) on electric power system, sufficient capability for adjusting the apparent load fluctuation including PVS power supply as negative load is needed. The increase in the daytime electricity consumption, which follows the change in the aggregated power supply of high-penetration PVS, would be essential measure against negative impacts. In this study, we focus on the daytime operation of a heat-pump water heater (HPWH) as one of measures, and introduce a brief idea for autonomously scheduling the daytime operation of individual HPWH so that the change in the aggregated electricity consumption by a number of HPWHs follows the irradiance change in a day. By using the electricity and hot-water consumption data for a year, we demonstrate the effect of daytime operation in terms of the voltage rise mitigation in a power distribution network caused by the reverse power flow from high-penetration PVS. The result shows that the voltage rise can be mitigated by applying the daytime operation to HPWH of a household with PVS, while the under-voltage condition due to the unnecessary daytime operation can be avoided based on the next day weather forecast.