A novel digital hysteresis current controller for an active power filter

An active power filter is used to eliminate current harmonics produced by nonlinear loads. This paper discusses a novel method of controlling a power inverter used to inject compensating currents into the power system. A digital signal processor performs the harmonic isolation and generates a digital reference current. A hysteresis current controller has been implemented in a field programmable gate array and generates the switching signals from this reference. This reduces the analogue circuitry and enhances the system´s immunity to noise. This paper presents the results and discusses the performance of a small scale inverter under completely digital control