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

Abstract

Abstract This paper describes the operation of reduced-switch single DC source cascaded H-bridge multilevel inverter (RSDCHBMLI). Compared to conventional multilevel inverters, RSDCHBMLI offers a number of advantages such as lower component count, inherent isolation and requirement of single DC source. The paper proposes application of RSDCHBMLI as DSTATCOM in a weak distribution system. The usage of single DC-link capacitor in this topology eliminates the problem of capacitor voltage balancing in DSTATCOM operation. The DSTATCOM is operated in current controlled mode (CCM) using Finite control set-Model predictive control (FCS-MPC). FCS-MPC is successful in independently performing load compensation in presence of feeder impedance along with maintaining sinusoidal voltages at the point of common coupling (PCC), without the need of any modulator or supplementary control techniques. This paper also explores different control schemes used for maintaining the DC-bus voltage. A current based proportional-integral (PI) DC-bus voltage controller is implemented in this paper, which allows easier calculation of the controller gain parameters. The performance of the current based controller is also compared with conventional power based DC-bus controllers in terms of steady state error and settling time. The results are presented for a 11-kV distribution system with RSDCHBMLI based DSTATCOM simulated in PSCAD/EMTDC environment.