Enhancing Inter-Phase Energy Balancing in Y-Connected Cascaded H-Bridge STATCOM via Common-Mode Voltage Feed-Forward without Complex Inverse Mapping

The Y-connected cascaded H-bridge (CHB) static compensator (STATCOM) is a widely used solution for reactive power compensation. However, maintaining inter-phase energy balance presents a significant challenge, especially during severe power imbalances. Closed-loop controllers, frequently referred to as inter-phase controllers, generate a common-mode voltage to maintain the energy balance. However, during rapid transients, an additional feed-forward term of common-mode voltage is used in conjunction with the closed-loop controller to prevent phase energies (or capacitor voltages) from deviating beyond their stipulated limits. Existing cutting-edge solutions frequently use a computation-intensive inverse mapping procedure based on positive and negative sequence components to determine the feed-forward term. In contrast, the article proposes a novel technique that determines the common-mode voltage feed-forward term from the instantaneous α-β components. The proposed work improves the dynamic response and reliability of Y-connected CHB-based STATCOM technology by eliminating the need for complex computations. The viability of this approach is validated by the experimental results obtained from a laboratory prototype.