Simple unipolar maximum switching frequency limited hysteresis current control for grid-connected inverter

This study proposes a simple unipolar maximum switching frequency limited hysteresis current control (UMSFL-HCC) strategy without band suitable for the single-phase grid-connected inverter. At the starting moment of each sampling cycle, the actual grid-connected current is sampled and compared with the sine reference one without band offset and the control signals of various power switches are obtained directly according to the comparison results. The distribution law of the switching period corresponding to the phase angle of the current and other system parameters within one line cycle is derived. The design rule of the filter inductor considering the various requirements is presented as well. By selecting proper sampling period and filter value, the UMSFL-HCC achieves excellent control performance. At the same time, the ripple of the switching frequency is limited within a controllable range. The proposed strategy is very compact and the switching loss is lower. The simulation and experimental results verify its accuracy and feasibility.