An Investigation of the Performance of Single- and Double-Converter Parallel Active Power Filters under Various Modulation Modes

Active power filters are considered to be an efficient solution for compensating the disturbances of current and reactive power in three-phase power distribution networks with non-linear loads. In this article, a parallel active power filter composed of two three-level converters connected in parallel is presented. The active power filter is intended to be part of a three-phase power distribution network with a nonlinear load. The dependences of the total harmonics distortion of the phase currents on the power consumed by the load in the case of converters working under the scalar or space vector pulse width modulation are investigated. In addition, the power losses in the elements of the converters are estimated. At medium power, a double-converter active power filter is beneficial over a single-converter active power filter, providing lower total harmonic distortion values. The space vector pulse width modulation ensures better compensation of harmonics than the scalar one. At high power, single-converter active power filters cannot compensate the current harmonics. With a double-converter active power filter, compensation is successful, and the total harmonics distortion is only 5%. Importantly, at high power, the total losses in the components of a single-converter active power filter are nearly twice the losses in the components of a double-converter filter.