Passive–Active Co-Design for Robust LCL-Filtered Grid-Connected Photovoltaic Inverters

Efficient operation of LCL-filtered grid-connected photovoltaic inverters under uncertain grid conditions requires coordinated treatment of passive-filter and current-controller interactions. This study addresses the interaction mechanism between passive LCL network parameters and active controller parameters through a systematic simultaneous passive–active co-design framework for a 10 kW inverter. A controlled five-strategy M1–M5 comparison separates conventional, control-only, passive-network-only, sequential, and simultaneous designs under a common plant, delay, modulation, switching, FFT, and uncertainty-validation protocol. Multi-objective search is supported by fast physical indicators, while leakage-free Gaussian process regression is used only as a candidate-screening accelerator before direct switching verification. The selected M5 design achieves a switching-model current total harmonic distortion of 0.8004%, passive damping loss of 8.236 W, and nominal phase and gain margins of 59.13° and 8.13 dB, respectively. Across 1000 shared Monte Carlo samples, its strict acceptance ratio is 98.3%, with zero true discrete-pole instability; rejected samples are conservative all-crossover margin anomalies. These simulation-based results indicate that M5 provides a balanced engineering compromise among harmonic performance, damping loss, dynamic response, and robustness rather than a design that dominates every individual metric. Gaussian process regression reduces screening cost but neither defines the objective nor replaces high-fidelity validation. Hardware-in-the-loop and experimental validation remain future work.