Calculating approach and implementation for active filters in unbalanced three-phase system using synchronous detection method

The authors present calculation approaches for obtaining compensating components for a reactive and harmonic current compensator in unbalanced three-phase power systems. The synchronous detection method is applied to calculate proper compensating components by monitoring the line currents and voltages. The per-phase calculation algorithm is implemented to share and distribute the compensating power using approaches of equal power, equal current, and equal resistance. The proposed algorithm and the implementation circuit are presented with their test results. The merits of the proposed methods are the capabilities to operate under an unbalanced three-phase system by per-phase calculation, to avoid conversion error by force waveform calculation, and to implement the hardware in a simple manner. it can be widely used in active filter designs for current compensation and load balancing