Research on Current Control Strategy of the LCL-Type Grid-Connected Inverter Based on State Reconfiguration With Quasi Resonant-Extended State Observer

Abstract

The LCL-type grid-connected inverter (GCI) is a critical device for realizing energy transmission between distributed generation and the power grid. The current control of the GCI typically requires multiple sensors to enable active damping and grid-side current control, which increases the system cost. A full-state observation system based on state reconfiguration with quasi resonant-extended state observer was proposed, in which just a signal inverter-side inductor current sensor was required to realize real-time observation of the desired state variables. Meanwhile, the constraint of high observer bandwidth required for conventional extended state observer to track sinusoidal signals was solved by adding a quasi resonant link to the observation channel of each state variable of extended state observer. Moreover, the active disturbance rejection control current controller was designed in the dq frame, which simplified the complicated decoupling process of conventional methods by treating the coupling as part of the total disturbance. The software numerical simulation illustrates that the control strategy show excellent observation results and current tracking performance.

Keywords

• lcl-type grid-connected inverter
• state reconfiguration
• quasi resonant-extended state observer
• active damping
• current decoupling control