A Novel Reconfigurable Cross-connected Cascaded H-bridge based Multilevel Inverter for Virtual Inertia Emulation

This paper introduces a cross-connected cascaded H-bridge (CHB) based photovoltaic (PV) multilevel inverter with ability to reconfigure its structure for inertia injection to power electronics dominated grid under any frequency event. The inverter requires only one PV source along with closed-loop voltage controlled floating capacitors in each phase for synthesizing the multiple voltage levels at its output. To emulate virtual inertia, the inverter utilizes the stored energies from two of its floating capacitors connected in parallel under any contingency situation. A simulation study in MATLAB/Simulink environment reveals that the individual floating capacitor voltages can be restored back to their desired levels rapidly after the contingency event is cleared which ensures quick transition of the inverter into its normal mode of operation. The performance of the proposed reconfigurable inverter is also compared with a conventional cross-connected CHB inverter under similar contingency events to establish the improvement in grid frequency profile due to this reconfigurable operation.