Full Grid Voltage Feedforward for Critical Mode LCL-Type Single-Phase Grid-Tied Inverters With Physical Interpretations

Full grid voltage feedforward (GVF) is an effective strategy to suppress the current distortion caused by grid voltage harmonics. However, for critical conduction mode (CRM) grid-tied inverters, the time-varying parts of its control scheme make it impossible to derive its full GVF strategy from the point of view of the transfer function. Hence, this study first analyzes the physical interpretation of the full GVF of conventional LCL-type grid-tied inverters, and then reveals the role of each term from the perspective of the circuit. Then, a full GVF strategy for CRM grid-tied inverters is proposed. The design guidelines, parameter sensitivity, and application limitations of the proposed scheme are analyzed in detail. Finally, a 1-kW single-phase three-level grid-tied inverter was built. Experimental results show that the proposed full GVF can significantly suppress the current distortion caused by the grid voltage harmonics and lower the current total harmonic distortion value by 55% within the full power range.