OPTIMIZED CONTROL STRATEGY IN GRID CONNECTED CASCADED MULTI LEVEL INVERTER TO IMPROVE GRID STABILITY

Abstract

This paper proposes an optimized control strategy for a grid-connected cascaded multilevel inverter designed to enhance the grid stability and power quality in smart grid environments. The novelty of this work lies in the implementation of independently regulated low-voltage DC links for each H-bridge cell, which enables modular control, fault tolerance, and improved dynamic performance. In addition, the control scheme operates without the need for reference frame transformation, significantly reducing the computational complexity. The main objective is to achieve selective and flexible compensation of disturbing currents caused by nonlinear, unbalanced, or reactive loads using current decomposition based on the conservative power theory (CPT). This decomposition allows the system to isolate specific current components and apply targeted compensation strategies in real time. Experimental validation under both ideal and degraded grid conditions demonstrates the effectiveness of the proposed control method. Key performance outcomes include the Total Harmonic Distortion (THD) reduction in the source current from 13.2% to 3.1%. The voltage regulation accuracy 1.5% of the reference value across the variable load conditions. Improved dynamic response time, with compensation settling achieved within 20 ms during load transients. Stable operation under voltage sag conditions up to 30% depth, with maintained power compensation functionality using the MATLAB Simulink environment.

Keywords

• Cascaded Multilevel Inverter
• Grid Stability
• Conservative Power Theory
• Optimized Control Strategy
• Total Harmonic Distortion
• Power Quality

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