Input-Admittance Passivity Compliance for Grid-Connected Converters With an LCL Filter

This work presents a design methodology and its experimental validation for the input-admittance passivity compliance of LCL grid-connected converters. The designs of the LCL filter parameters and discrete controller are addressed systematically, and suitable design guidelines are provided. The controller design is developed in the z-domain, with capacitor voltage based active damping used as degree of freedom to compensate for system delay effects. The role of resistive components in the circuit, which have inherent dissipative properties, is also discussed. As an outcome of the design, a passive input admittance shaping is obtained. The theoretical development is further verified in a low-scale prototype supplied from a controllable grid simulator. For the sake of generality, different combinations of resonant to sampling frequency are tested. Experimental results fully prove the input-admittance passivity compliance.