An active parallel power decoupling circuit with a dual loop control scheme for micro‐inverters

Abstract

AbstractAn important challenge in single‐stage single‐phase micro‐inverters is reducing required capacitance by various active power decoupling (APD) techniques in order to use film capacitors with a longer lifetime instead of electrolytic capacitors. In this paper, a photovoltaic (PV)‐side parallel APD circuit based on a bidirectional flyback converter is proposed. This topology is able to increase the average and ripple voltages for the capacitor due to having a transformer and thus can reduce the required capacitance. In the control scheme, dual control loops on the main and decoupling circuits manage the micro‐inverter operation. The primary control loop is based on the instantaneous active and reactive power theory and a proportional resonant (PR) controller that is responsible for delivering the PV panel energy to the grid. The secondary control loop regulates the pulsation power on the dc‐link capacitor through the PR controller. Simulation results demonstrated that the proposed APD circuit and the control method could properly damp the pulsation power in the normal and reference tracking operations. Furthermore, the good robustness of the micro‐inverter was confirmed in shutdown and start‐up. Finally, the experimental results with a 180‐W single‐phase micro‐inverter prototype are presented, which validates the advantages of the proposed configuration.