The Single-phase Unified Power Qulity Controller

Unified Power Quality Controller comb ines the function of the voltagecompensator and current compensator, which can control the multiple powerquality problems. UPQC has become the emphasis of power control field for it’sexcellent compensation performance. The single-phase UPQC has beenresearched in this paper.Firstly, the topology and working principle of UPQC has been researched,the main circuit structure and mathematical model was established. The LCLfilter was introduced into the parallel section of UPQC, and the ma in deviceparameters had been designed.Secondly, the single-phase power detection methods had been studied in thispaper. Based on the research on single-phase voltage and current detections onthe basis of the instantaneous reactive power theory, the single-phase voltagedetection method which can detect voltage sags and swells of single-phasesystem was proposed. For reducing the calculation of the single-phase currentdetection, the detection based on the trigono metric function was proposed, and itsmodified detection method improved the detection accuracy.Moreover, the modulation strategy for single-phase has been studied on, thesingle-phase SVPWM method was applied in the paper. The switching mode wasoptimized, which can reduce the switching losses.Finally, the UPQC control strategies had been studied. The double-loopcurrent control strategy based on PR outer loop was proposed, with comparingthe traditional control strategies applied in UPQC. However the compoundcontrol which combined the PI control and repetitive control can overcome theshortcomings of PI control method, its calculation is much huge and system ismuch complex. Then the PR control was proposed, which can achieve good effectwith sma ll amount of work. The PR control method had been improved byintroducing the inner feedback current of the capacitive. The double-loop currentcontrol strategy based on PR outer loop can achieve better control effect than thesingle loop PR control method. The single-phase UPQC designed in the paperwas simulated in the Simulink, the results of simulation illustrate the correctnessand feasib ility of the proposing methods.