Optimized design of state variable feedback of grid-connected inverter with LCL-filter based on state observer

LCL-filter in grid-connected inverter has a better attenuation on switching ripples. But as a three order system, its resonance is difficult to be suppressed using traditional control strategy. This paper, based on an improved discrete state space model and improved discrete state space observer, proposes a method using optimized pole placement theory to achieve the best damping effect of the whole system, which improves the dynamic response of the system without additional sensors. Furthermore, the influence of closed-loop poles on the placement of observer's poles, as well as the range within which the observation feedback is stable and the impact of system parameters are discussed. A 10 kW grid-connected inverter with LCL-filter prototype is set up to verify the effectiveness and robustness of the proposed control strategy and observer configuration.