Research On Single-Phase Unified Power Quality Conditioner

With the development of science and technology, the demand of modern intelligent electrical equipment on power quality is becoming higher and higher. Composed of series and parallel double converter unified power quality conditioner (UPQC) has the comprehensive ability of power quality regulation. It can improve the power quality of the grid side, compensate system harmonic current and reactive current, to achieve high power factor. It can also improve the load side of the power quality, to stabilize the load voltage. In this paper, the single-phase UPQC system has been researched.Firstly, the topology and working principle of the main circuit of the single-phase UPQC system has been researched. The main circuit structure was established. The harmonic detection methods had been studied in this paper. The detection method of instantaneous reactive power theory for construction of single-phase system is determined. The modulation strategy has been studied on. the bipolar SPWM method was applied in this paper.Secondly, based on the concept of modular control, the series converter is functionally equivalent to a dynamic voltage regulator (DVR); the series converter is controlled as a harmonic voltage source. The structure, function and mathematical model of series compensation part are analyzed.The calculation of the parameters of each device is given. A control method based on PI is derived for the series compensation part. The UPQC simulation results demonstrate the effectiveness of the control method.Moreover, the parallel converter is functionally equivalent to an active power filter (APF). The parallel converter is controlled as a harmonic current source. The structure, function and mathematical model of parallel compensation part are analyzed. The calculation of the parameters of each device is given. The double closed loop control method based on PI is deduced for the parallel compensation part. The UPQC simulation results demonstrate the effectiveness of the control method.Finally, combined control strategy of outer loop proportional resonant (PR) control and proportional (P) control of inner loop current is introduced in series. Combined control strategy of proportional (P) control and repetitive control is introduced in parallel. The single-phase UPQC simulation results demonstrate that:the addition of compound control technology improves the effect of compensation voltage and current of UPQC system; the function of UPQC system is improved. Finally, the experimental platform is set up, and the parallel compensation part of single-phase UPQC system is tested and verified, and the corresponding experimental waveforms and conclusions are given. Experimental results show that the proposed parallel part design method of the parameters of the main circuit, harmonic detection method and composite controller design method is reasonable and feasible. It can achieve better harmonic current suppression and voltage compensation effect.