Self-balanced Symmetric Source Configuration of Nine Level Switched Capacitor-Based Grid Connected Inverter with LCL Filter

This paper presents a single-phase self-balanced symmetric source configuration of nine level switched capacitor (SC)-based grid connected inverter with LCL filter. It comprises two DC sources, two switched capacitors and ten unidirectional switches with less per unit Total Standing Voltage (TSV). Out of ten switches, eight switches have been faced the stress of 0.5Vdc only and rest of the switches have been faced the stress of 2Vdc individually. By changing input DC voltage ratios, it is possible to get more number of levels also. For both symmetric and asymmetric source configurations, a Unified Rounding Control Scheme (URCS) has been applied with RL load. In grid connection point of view, to achieve UPF operation, a dq frame current control strategy along with Unipolar Level Shifted Phase Disposition Pulse Width Modulation (ULSPD-PWM) scheme has been elucidated clearly. While considering resonant peak problems and grid stability, the LCL filter has been designed carefully. In this topology, the capacitors are self-balanced without the need of auxiliary circuits and separate complex control schemes. Lastly, to corroborate the proposed concept of nine level grid connected inverter with LCL filter and other source configurations have been elucidated with MATLAB/Simulink platform.