An active power filter implemented with three single-phase Neutral Point Clamped (NPC) converters is presented and analyzed. The proposed active power filter is aimed to compensate current harmonics and reactive power in three-phase medium voltage power distribution systems. A predictive control algorithm provides the switching states that ensure fast current tracking capability. To take advantage of the predictive control implementation simplicity, this paper includes useful information to replicate this implementation on similar topologies of multilevel converters. The proposed scheme presents lower line to line voltage harmonic distortion as well as an independent control in each phase, compared with the conventional three-phase NPC topology. Simulated results confirm the implementation viability of the proposed active power filter topology and associated control strategy.

A predictive control algorithm specially developed for shunt active power filters aimed to compensate reactive power and current harmonics components is presented and analyzed. The proposed predictive control algorithm is implemented in a three-phase four-leg voltage-source inverter (4L-VSI). The use of a 4L-VSI allows the compensation of current harmonics, reactive power and neutral current harmonics generated by single-phase non-linear loads. A detailed mathematical model of the filter, including the effect of the power system equivalent impedance is derived and used to design the proposed predictive control algorithm. The proposed active power filter and associated control scheme performance and compensation effectiveness are demonstrated by simulation and with experimental results.

This paper presents an overview of the state of the art in reactive power compensation technologies. The principles of operation, design characteristics and application examples of Var compensators implemented with thyristors and self-commutated converters are presented. Static Var generators are used to improve voltage regulation, stability, and power factor in ac transmission and distribution systems. Examples obtained from relevant applications describing the use of reactive power compensators implemented with new static Var technologies are also described.