Dual-loop geometric-based control of full-bridge inverters for stand-alone distributed generation systems

Buck-derived topologies are a popular alternative for the inverter stage of distributed generation systems. The lack of a grid connection places high reliability demands on the inverter controller. Dual-loop linear schemes are traditionally employed for the control of single-phase full-bridge inverters because of their simple implementation. However, the voltage loop dynamics are usually sluggish due to the requirement of making the outer loop's bandwidth much lower than the inner loop one. On the other hand, state-plane-based controllers offer fast and stable response against large signal disturbances, but constant switching frequency can only be achieved at the expense of a high computational cost. This work introduces a hybrid dual-loop control technique for inverters that combines the advantages of linear and state-plane-based controllers. The proposed dual loop scheme features a geometric-based voltage outer loop that provides fast and robust performance. The outer loop controller is complemented with a linear inner loop that ensures constant switching frequency and simple implementation. The derivation of the geometric controller is performed in the normalized state plane. Simulation and experimental results are provided in order to validate the proposed control scheme.