An Improved Three-Level Cascaded Control for LCL-Filtered Grid-Connected Inverter in Complex Grid Impedance Condition

The passivity-based control (PBC) with Euler–Lagrange (EL) model has been used for LCL-filtered grid-connected converter. However, the impacts of delay and interaction resonances under capacitive grid impedance are rarely considered PBC method. Nonlinear Lyapunov’s stability theory is hard to estimate system accurately design controller parameters considering delay. This paper derived inverter current based on passive zero-pole maps applied reveal influence digital differential item loop. A new three-level cascaded method then proposed traditional achieve high robustness in complex grid. Furthermore, designed maintain passivity within switching frequency ranges parameter variations LCL filter investigated. Final validation effectiveness performance structure performed by simulation experimentation.