Discretized Discontinuous Modulation Strategy for Cascaded H-Bridge StatCom

Abstract

This paper proposes a discontinuous modulation (DM) scheme for cascaded H-bridge (CHB) static compensators (StatComs) with star configuration. The proposed DM scheme guarantees zero steady-state active power in each converter phase-arm, even in the presence of severe grid imbalance conditions, thus remaining decoupled from the inter-phase capacitor voltage balancing controller. Moreover, the proposed DM scheme exploits the possibility of clamping to the zero-voltage level, thus providing a more flexible discontinuous operation than conventional DM methods. This involves lower zero-sequence-voltage injection requirements and lower switching losses. The proposed modulation scheme is experimentally corroborated and its performance under different grid voltage conditions is compared with traditional modulation schemes.