Three-phase Power System Power Quality Regulator

With the rapid development of power electronics, power electronic technologies have been widely used in all sorts of power systems and electric equipments. It makes switch devices and nonlinear loads more and more in the power lines systems. Harmonic distortions and reactive currents , three-phase voltage imbalance and flicker in power lines are geting more serious, this power quality problems are not only pollute the power supply performance,and impact running orders of electric equipments in power lines,but also bring much more line loss and overload fault.In order to restrain harmonic and compensate reactive power, foreign and domestic scholars have been successfully developed many new-style reactive compensation devices and active power filter systems. LC passive filters have become one of the assistant devices in active power filters system; shunt active power filters and static state realactive compensation technology have almostly popularized, and being applied in practice; series active power filters are becoming ripeness; unified power quality conditioner is a high performance-price rate ideal seting to solve power quality, has been paid much attention and research.This paper studies mainly on the realization of unified power quality conditioner in triphase power system, it consists of small rated passive filters and shunt APFand series APF system. Thereinto, passive filters and shunt APF are connected in parallel with loads, and compensate the adjustable current. Series APF are connected in series with loads, and compensate the adjustable voltage. Unified power quality conditioner in triphase power system is not only counteracting non positive order active basic-frequency waves and all distortion waves, but also compensating three-phase voltage imbalance and three-phase current imbalance and realactive power.The article analyses the composes and classfies of UPQC; it researches the effections of low-frequence pass filter in detecting power quality problems; it gives compares of three different detecting ways based on the arithmetic of the theory of instantaneous reactive power, and proposes a new synchronization test ways suited to three-phase imbalance power system; it researches the effections of power impedance and transforms connected in series with the power lines; it researches the adjusting effections of rated realactive of DC side; it compares the difference results with differ control approaches.Using MATLAB software, we design and realize the UQPC, simulation studies are made in a three-phase power system with sudden change load and three-pgase imbalance load, we contrast the experiment's results in distortion restrain and realactive compensation, and the simulation result validates the theoretical analysis is correct, it shows that the UPQC system is obviously improved in the power lines supply quality, and availably filter power distortion and compensate realactive power.