Continuous Operation of GFM Inverter with Carrier Frequency Reduction and One-Pulse Modulation Under Overcurrent Condition

Grid-forming (GFM) inverters, which provide inertia to the grid, are attracting attention as a solution to the problem of insufficient inertia caused by mass deployment of renewable energy using inverters. However, GFM inverters are prone to output overcurrent when power disturbances occur in the grid, and the solid-state switching devices cannot withstand the heat generated by the overcurrent. As a result, the GFM inverter either stops operation or limits the output current, which does not provide sufficient inertia. The objective of this study is to continue operation even under overcurrent conditions by suppressing heat generation due to solid-state switching device losses, and to supply sufficient inertia to the power grid. Two loss reduction methods are proposed to enable GFM inverters to continue operation under overcurrent for short periods duration: the first is carrier frequency reduction, which reduces the carrier frequency of PWM during overcurrent, and the other is one-pulse modulation, which outputs only one pulse per half cycle of the fundamental wave. The effectiveness of the proposed method was demonstrated through experiments.