Applicability improvement and hysteresis current control method simplification in shunt active filters

Hysteresis current control method is widely used in Pulse Width Modulation (PWM) inverters because of simplicity in performance, fast control response and good ability in limiting peak current. However, switching frequency in hysteresis current control method with fixed bandwidth has large variation during a cycle and therefore causes nonoptimal current ripple generation in output current. One of basic problems in implementing hysteresis current control is its variable switching frequency that causes sound noise and increase in inverter losses and also high frequency current components injection to the source current. In this paper, a fixed frequency hysteresis current controller is proposed for grid connected inverters. In the proposed approach, the required bandwidth of the controller is calculated according to system parameters. Also, the derivative of the reference current is eliminated to solve the problems associated with practical implementation of the converter. Finally, a shunt active filter has been used for removing the current harmonic components generated by non-linear loads. Proposed method is simple to perform and reliable, and also has been simulated in MATLAB software environment.