Comparison of Volt–VAR Control and Power Factor Control of PV Inverters on the Voltage Profile of Low Voltage Distribution Networks

Abstract

The rapid increase of photovoltaic generation in low-voltage distribution networks can trigger voltage rise and overvoltage, particularly on feeders with a high resistance-to-reactance ratio. This study compares two smart-inverter voltage regulation strategies—volt–var control and power-factor control—to mitigate overvoltage and to increase the voltage-constrained photovoltaic penetration limit. A detailed low-voltage feeder model was developed, and steady-state power-flow simulations were performed in PowerFactory under two operating scenarios representing overvoltage and undervoltage conditions. Performance was evaluated using maximum bus voltage and network power losses while the photovoltaic penetration level was increased gradually. Without inverter control, the voltage limit was exceeded at a higher penetration level, limiting acceptable penetration to 125%. With volt–var control, reactive power is exchanged only when the local voltage deviates from a normal-voltage band, so overvoltage is mitigated effectively with a smaller increase in losses, extending the acceptable penetration to 140%. Power-factor control provides stronger voltage reduction because many inverters respond simultaneously following active power output, enabling the highest acceptable penetration of 150%, but it tends to drive larger reactive power flow and higher losses. Overall, both strategies improve voltage compliance and hosting capacity, but the trade-off between voltage reduction and increased losses indicates that the preferred method should be selected based on feeder operating conditions and the utility objective.