Reduced-Order Controllers Using Integrated Controller-Plant Dynamics Approach for Grid-Connected Inverters

This article presents a new way to achieve reduced-order controllers using an integrated controller-plant dynamics approach. The proposed method combines the controller and plant dynamics to achieve specific overall control functionalities. The method is applied to a grid-connected inverter that conventionally uses second-order proportional-resonant (PR) and proportional-integrating (PI) transfer functions. The proposed approach replaces a third-order PR+PI function with a first-order PI function without compromising its features. The approach is to integrate the dynamics of the inverter and its output filter with the PI function to achieve a PR functionality. The proposed approach not only obviates the computational and digital implementation challenges pertaining to the PR compensators, it also results in a generally more robust and stable operation of the inverter in practical grid conditions. Detailed theoretical analysis, simulations, comparisons, and laboratory experiments are presented to elucidate various aspects of the proposed method.