A NEW ADVANCED CONTROL STRATEGY FOR A SERIES ACTIVE POWER QUALITY CONDITIONER UNDER NETWORK DISTURBANCES.

Harmonic current and/or voltage pollution of three phase supply electrical networks is becoming a very serious problem due to the wide use of non-linear loads such as arc furnace, industrial high power thyristor converters and adjustable speed drives. These non-linear loads draw current, with high harmonic content which produces a variety of undesirable phenomena on the power system such as power losses, decrease of power factor, over- voltages, voltage drop... Theses disturbances affects can be minimised with the use of active power quality converters connected directly to the mains network. The authors in this paper propose a new advanced control strategy for a series active power quality conditioner connected to a three-phase electrical power network with sinusoidal or non-sinusoidal means voltages. A new definition of residual instantaneous active and reactive power based on the a,b transformation of instantaneous voltages and currents of the AC system are introduced to extract the voltage harmonic references to control the active power conditioner.The introduction of these components in the new control algorithm of the active power quality conditioner are investigated and compared under non-sinusoidal mains voltage conditions. The main advantage of this new advanced control method validated by simulations shows that the mains line currents constitute always a balanced sinusoidal system when operating under disturbances like flicker, sags, under-voltage...Simulations have been performed to verify steady and dynamic compensation characteristics in case we have many disturbances in the electrical power system.The introduction of these new residual power components lead also to the definition of an advanced THD power factor that is compared to the classical one