Compensation in Nonsinusoidal, Unbalanced Three-Phase Four-Wire Systems With Active Power-Line Conditioner

Abstract

For three-phase four-wire circuits, two compensation criteria have been established: one based on the instantaneous value concept and the other on the average value concept. Thus, according to the instantaneous value concept the non instantaneous power current is reduced, without altering the instantaneous active power. According to the average value concept, the nonactive average-current is reduced, without altering the average power. When the zero-sequence voltage component exists, both compensation types would not enable the zero-sequence (neutral) source current elimination. Then, two approaches are marked in this paper. The first one is for eliminating the non instantaneous power current or the nonactive average-current but the neutral current can still flow. The second one for eliminating the modified non instantaneous power current or the modified nonactive average-current, thus the neutral current component is compensated. According to recent recommendations in this work three-phase systems are considered as four-conductor systems. Experimental results are obtained to confirm the theoretical properties and to show the compensator performance.Index Terms-Active power-line conditioner, compensation, instantaneous power theory.

Three-Phase Four-Wire Active Power Conditioners for Weak Grids

“…The use of a three-phase three-wire shunt active power filter cannot effectively reduce or eliminate line harmonics in this case [5]. An effective solution to this problem is to use a three-phase four-wire active power filter [6], [7]. If the system requires a neutral point connection, a simple approach is to use an APC with two capacitors to split the DC link and tie the neutral point to the mid-point of the two capacitors.…”

Critical analysis of different current decomposition and compensation schemes

“…In practice for systems with m − 1 phases and a neutral conductor, it is often desirable to require zero neutral current [13], [14]. For the three cases considered in Section II the decomposition technique can be modified to obtain the smallest active current, the smallest instantaneous power current or the smallest constant instantaneous power current under the additional constraint of zero neutral current.…”

Assessment of unbalance and distortion in power systems that include active power line conditioners

“…This lack is more accentuated when modern compensation equipment is used. Actually, it is possible to dispose of compensation systems with active power filter, APFs, with parallel connection; and combined systems of series -parallel compensation with the use of APF in series and shunt connection, [3][4][5][6]. In this last case, with an appropriated control strategy, it is possible to eliminate the harmonics and unbalance of the current, as well as to obtain a conditioned voltage at the load terminals.…”