Control of shunt unbalanced power active compensators for reactive and asymmetry elimination in four wire electrical systems using symmetrical components

The paper presents a new method for obtaining the reference currents for a shunt unbalanced power active compensator (SUPAC), working under unbalanced voltages and asymmetrical linear loads. The reference currents are obtained using the unifying theory of electrical power (UTEP), UTEP has been successfully applied to the control of power converters for improving electric quality and optimizes the balance of the current supplied by the three-phase generator. This system improves efficiency. For the implementation of the unit efficiency control (UEC) the currents in the load and the voltages at the point of common connection (PCC) are transformed to the respective direct, inverse and homopolar symmetrical components. The developed system compensates the power losses in the inverter bridge and in the AC and DC buses with three currents in phase with the respective direct phase voltages or using photovoltaic panels connected to the DC bus. The system efficiently improves the electrical quality in three-phase systems when single-phase linear loads from line to neutral point are connected. The digital control is achieved with a digital signal processor (DSP) and the power section consists of a commercial three-phase power inverter bridge and some interface cards.