Model-based generation of low distortion currents in grid-coupled PWM-inverters using an LCL output filter

In this work, a single phase LCL output stage for grid coupled applications is built and evaluated. An accurate model and observer of the output filter and the distorted grid voltage is implemented. This paper deals with the construction of a 14-state model, and the feedback control loop to obtain good closed loop response. Simulations indicate a good performance of the controller, with a total harmonic current distortion (THD) below 1%. Experimental results confirm the simulations, and illustrate the good operation of the Kalman observer to estimate the distorted grid voltage (THD 3%). The output filter effectively reduces the PWM harmonics in the grid current.