The integration of renewable energy sources into microgrids demands advanced power electronic solutions to maintain power quality and stability amidst variable generation and dynamic load conditions. This study focuses on improving a five-level cascaded H-bridge (CHB) inverter to suppress harmonics and regulate voltage in renewable-integrated microgrids. By using a hybrid control strategy that integrates variable frequency pulse width modulation (VFPWM) with proportional-integral (PI) controllers (Kp = 7, Ki = −4), systematically tuned via the Ziegler–Nichols method. An LCL filter (L1 = 16.8 mH, L2 = 5.05 mH, C = 104.9 μF) attenuates harmonics. Performance is validated in MATLAB/Simulink under resistive/nonlinear loads, carrier frequencies (900–1200 Hz), and dynamic microgrid conditions. The significance lies in achieving IEEE 519-compliant 2.64% THDI (under standardized conditions: 10 Ω resistive load, 100 V per module, 1050 Hz carrier, VFPWM), facilitating 40% smaller passive filters and scalable renewable integration for tropical climates like Malaysia. The system achieves 2.64% grid current THDI (10 Ω resistive load, 100 V per H-bridge module, 1050 Hz carrier frequency, VFPWM modulation), reducing total harmonic distortion (THD) by 50%–70% vs conventional three-level inverters. The combination of VFPWM and phase disposition yields optimal voltage THDU (26.50%–26.75%). Optimized PI tuning lowers grid current THDI from 12.54% to 2.64%, complying with IEEE 519. The five-level CHB enhances scalability, fault tolerance, and power quality, enabling cost-effective integration, making it a preferable choice for renewable integration.
Rahman et al. (Thu,) studied this question.
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