Reduced Switch Single DC Source Cascaded H-bridge Multilevel Inverter based DSTATCOM

The application of multilevel inverters (MLIs) for the realization of Distribution Static Compensator (DSTATCOM) overcomes the requirement of higher power rating of switches. However, the high component count and multiple DC-link capacitors in conventional MLIs make the inverter design complicated. These inverters also require additional controls and circuits for DC-link capacitor voltage balancing for its satisfactory multi-level output. This paper proposes a reduced switch single DC source cascaded H-bridge multilevel inverter (RSDCHBMLI) for DSTATCOM operation. The RSDCHBMLI uses a single DC-link capacitor and hence eliminates the problem of capacitor voltage balancing. The topology also leads to reduction in component count along with inherent isolation. FCS-MPC current control is implemented to perform load compensation in presence of feeder impedance along with maintaining sinusoidal voltages at the point of common coupling (PCC). This paper also implements a current based DC-bus voltage controller which allows easier calculation of the controller gain parameters. The performance of the current based controller is found to be better than the conventional DC-bus controllers under the test conditions and results are presented for a 11-kV distribution system simulated in PSCAD/EMTDC environment.