Direct current control by constant frequency hysteresis controller in active filtering systems

The aim of this paper is the conversion of the classical hysteresis controller into a constant frequency hysteresis current controller. The classical alternative to the hysteresis controller is the proportional-integrative controller which gives constant switching frequency and overall better performances with a cost of comprehensive parameter tuning and sensitivity at driven system change. The hysteresis controller main advantage is the simplicity and robustness with the cost of variable switching frequency. The compromise between these two solutions is the constant switching frequency hysteresis controller. This goal can be achieved with a combination of the hysteresis comparator and the PWM modulator. The performances are somewhat less good and depend on the compensating capacitor voltage and PI voltage controller parameter adjustment but with the advantage of constant switching frequency. The regulator implementation was validated on a complete active filtering system implemented in Matlab Simulink.