Advanced Decoupling Techniques for Grid-Connected Inverters With Multiple Inputs

Abstract

The parallel connection of multiple distributed energy resources with a common DC-link structure is typically used in grid-connected applications which enables flexible operation maximizing power production of the inverter system under various operation conditions. However, it has brought drawbacks for DC-link power decoupling with the requirement of a larger capacitor bank, faster voltage regulation, etc., to maintain a constant DC-link voltage which increases the overall size and cost. In this paper, a DC-link decoupling technique using a nonlinear control algorithm is proposed to perform rapid DC-link voltage regulation for multi-input grid-connected inverters. With the implementation of a nonlinear observer, the power fed into the DC-link from multiple inputs is estimated by the proposed control algorithm and can be rapidly compensated by the inverter minimizing the DC-link voltage fluctuation. The effectiveness of the proposed nonlinear power decoupling control algorithm is verified by comparing the DC-link performance with a conventional control algorithm through both simulation results on a MATLAB platform and experimental verification on a grid-connected inverter prototype.

Keywords

• DC-AC power converters
• observers
• nonlinear control systems
• feedforward systems