An Intentional Islanded Mode of Operation for a Four-Leg Converter Under Rapid and Asymmetrical Load Changes

The intentional islanded mode of operation is becoming critical for power electronics converters since small energy storages are developed for residential applications. It provides an uninterruptable power supply for the local loads and creates an opportunity to disconnect from the grid if needed. In order to provide the full functionality of the islanding mode, the four-leg power electronics converters are required to work with unpredictable, asymmetrical loads. Maintaining desired voltage levels at the point of common coupling during high power demand is challenging. Moreover, rapid load changes, mainly resistive in residential solutions, can cause a voltage stability problem. The load change study must also focus on the converter’s start of operation without load or total load disconnection, which are crucial for voltage stability. This paper presents control enhancements for the islanded mode of operation. It identifies the issue of rapid asymmetrical load changes and presents a solution based on simulation research.