Voltage Sensorless Model Predictive Control for a Grid-Connected Inverter With <i>LCL</i> Filter
Nguyen Ngoc Nam, Ngoc-Duc Nguyen, Changwoo Yoon, Minho Choi, Young Il Lee
Abstract
This article introduces a sensorless model predictive control (MPC) scheme for a grid-connected inverter with an inductive–capacitive–inductive ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> ) filter using only the grid-side current measurement. A state estimator and a disturbance observer are designed based on the Lyapunov stability theory to reduce the number of sensors and to eliminate the steady-state error. A cost function penalizing the state tracking error is used for the MPC design, and the optimal weights of the cost function are systematically obtained by solving a linear matrix inequality (LMI)-based optimization problem. The variation in grid impedance is taken into account in the LMI optimization. The stability analysis of the overall system is presented, and the frequency responses of the closed-loop and open-loop systems are presented to verify suppression of the filter resonance frequency component. The effectiveness and feasibility of the proposed controller are validated through frequency response analysis and comparative simulation results. Experimental results are also presented to demonstrate the efficacy of the proposed control scheme compared to the linear quadratic regulator method.