Design and fully digital control of parallel active filters for thyristor rectifiers

The paper presents the implementation of a digitally controlled parallel active filter for a thyristor rectifier with inductive load. Using a state-of-the-art DSP platform (ADSP21020 and ADMC200), a fully digital control of the system, based on the dead-beat control of inverter currents and space vector modulation, is implemented. The intrinsic calculation delay of the dead-beat algorithm is shown to represent a serious hurdle for the achievement of a satisfactory compensation quality. In particular, meeting the IEC 1000-3-2 standards for class A equipment appears to be quite difficult especially in the high frequency range. The paper investigates the effects of the input passive filters and power converter design on the system´s performance and describes the implementation of the digital control by means of the specified hardware. Experimental results are finally given to evaluate the achieved performance