Voltage Control Algorithm of Fault Study in Inverter-based Distribution Networks

The“Guarantee of Grid Connection System for Renewable Energy Projects under 1MW,” implemented in October 2016, aimed to promote small-scale renewable energy projects by ensuring grid connection and covering grid reinforcement costs by Korea Electric Power Corporation. Following this policy, applications and connections for small-scale renewable energy projects surged, with a total of 20.1GW of applications, of which 17.3GW were connected. However, indiscriminate connections have led to issues such as reverse power flow and over voltage, raising grid stability concerns. Consequently, the small-scale renewable energy grid connection system is scheduled to end in December 2023. Traditional equipment like Tap and SVR has limitations in addressing these issues, leading to the adoption of autonomous control function of the inverter for voltage control. The control function of the inverter control reactive power to adjust the point of common coupling (PCC) voltage without requiring additional equipment. This paper proposes an advanced algorithm to precisely control voltage fluctuations during line switching using the control function of the inverter. This algorithm prevents blackout caused by line outage through line switching and accurately controls voltage fluctuations using Volt-Var and DVEC functions. By modelling the inverter with Matlab/Simulink and validating voltage control results in the domestic distribution networks, the paper demonstrates how the proposed algorithm can autonomously adjust PCC voltage and maintain grid stability even during network faults.