On the applications of active filters to generic loads

The paper discusses the application of parallel active filters to the compensation of generic loads. In particular, attention is focused on the potential instability which can occur in the compensating system in the presence of a capacitive load impedance. This problem is illustrated in the case of a typical active filter implementation but the analysis is extended also to other control strategies discussed in the literature. Some of these are shown to improve the system's stability, although at the expense of an increased interaction with the utility grid. The modulation technique of the power converter implementing the active filter also plays a key role in determining the system's robustness and the quality of the compensation. The last part of the paper discusses the effectiveness of the more common current control strategies both from the stability and from the compensation quality standpoint.