<p>This article proposes and validates a passivity-based co-design framework for grid current control and voltage feedforward in LCL-filtered grid-connected inverters to ensure both internal and external stability. First, an active damping scheme utilizing grid current feedback is developed via a high-pass filter (HPF). The cutoff frequency and gain of the HPF are systematically tuned to maintain a phase margin for the inner loop, effectively suppressing LCL resonance while significantly extending the achievable control bandwidth. Furthermore, the proposed scheme implements a point of common coupling (PCC) voltage feedforward via a low-pass filter (LPF) to promote the passivity of the inverter output admittance until the Nyquist frequency, thereby enhancing stability under various grid conditions. The effectiveness of the proposed approach is validated through comprehensive frequency-domain analysis and experimental results. Compared to the conventional methods, the proposed co-design approach demonstrates superior performance, increasing the current control bandwidth from 300 Hz to 436 Hz and reducing the current overshoot from 16.2% to 12.8%.</p>