Effective Controller Design for the Cascaded H-bridge Multilevel DSTATCOM for Reactive Compensation in Distribution Utilities

The Static Synchronous Compensators (STATCOMs) have been recoginzed as the most effective solution for dynamic reactive power compensation, voltage stability enhancement and subsynchronous resonance damping purposes in the electric power systems. The STATCOMs in the distribution utilites (DSTATCOMs) are increasingly investigated for dynamic reactive power compensation and power quality improvement in the distribution utilites. This paper presents a novel control scheme for the cascaded H-bridge (CHB) DSTATCOM. The principle of the carrier phase-shifted pulse-width modulation (CPS-PWM) and the mathematical model of the CHB-DSTATCOM are presented. The power balancing mechanism and the stable control region are analyzed. The current loop controller and the dc-link voltage balancing controller are synthesized and the design guidelines are provided. The simulation results obtained from the Electromagnetic Transient Program / Alternative Transient Program (EMTP/ATP) are presented and evaluated, which verifies the validity and effectiveness of the devised control scheme.