Power Quality Enhancement in Grid-connected Renewable Energy Systems Using APF Integrated with Fuel Cell Technology: A Hybrid Control and Optimization Approach

Grid-connected renewable energy systems often suffer from power quality (PQ) issues such as harmonic distortion and poor voltage regulation due to the integration of power electronic interfaces and non-linear loads. This paper proposes a hybrid control and optimization approach to enhance PQ in a grid-tied renewable system using an Active Power Filter (APF) integrated with fuel cell technology. A Proton Exchange Membrane Fuel Cell (PEMFC) provides a clean DC source to support the APF, supplying real power for harmonic and reactive compensation. The APF is controlled via a two-level hybrid strategy: an intelligent controller (adaptive neuro-fuzzy or fuzzy-PI) maintains the DC-link voltage and coordinates fuel cell output, while a fast inner-loop current control (based on synchronous reference frame theory and hysteresis PWM) injects compensating currents. A Particle Swarm Optimization (PSO) algorithm is employed offline to fine-tune controller parameters for optimal Total Harmonic Distortion (THD) reduction and dynamic response. Simulation case studies demonstrate that the proposed system significantly improves PQ: source current THD is reduced from about 25% (without compensation) to under 3% with the hybrid APF, complying with IEEE-519 standards. The fuel cell-integrated APF also corrects power factor to ~0.99 and provides voltage support during disturbances. The results highlight the effectiveness of combining fuel cell distributed generation with advanced control and optimization techniques for maintaining high power quality in renewable-rich grids.