On the Limitations of Volt-var Control in PV-Rich Residential LV Networks: A UK Case Study

Abstract

Residential-scale photovoltaic (PV) inverters available in the market are embedded with two key functions designed to help mitigating voltage rise issues: Volt-Watt and Volt-var. Volt-var has attracted significant attention as it does not involve generation curtailment. However, residential-scale PV inverters are sized (kVA) to meet the peak active power generation of the panels (kW). Since active power generation is typically prioritized, their capabilities to absorb reactive power (kvar) during high generation periods will be limited. Using a real UK LV network, this work provides a comprehensive analysis to understand the extent to which the adoption of Volt-var control helps managing voltage rise issues. Considering different Volt-var curves and PV penetrations, results demonstrate that Volt-var control is ineffective when reactive power is needed the most. Furthermore, reactive power increases currents and, therefore, asset utilization. This highlights the importance of considering the kVA rating of inverters when adopting solutions involving reactive power.