Research On Series Converter Of The Single-phase UPQC

UPQC (Unified Power Quality Conditioner) is one of the most up-to-date development trends of Custom Power, which combines the function of voltage compensator, current compensator and energy storage device. Multiple power quality regulation function is implemented in UPQC simultaneously. UPQC is a more effective way to regulate the power quality of distribution system systematically and improve the reliability of power supply than others. Therefore, UPQC is becoming the emphasis of related research.The working theory and control technique of the single-phase UPQC is analyzed. By an optimistic method, the series converter is controlled as a sinusoidal current source and makes the input current sinusoidal, while the shunt converter is controlled as a sinusoidal voltage source and keeps the load voltage in the normal value. In this thesis, the series converter is placed emphasis on.In this thesis, for the series converter, direct current control scheme are selected; because of the good performance of the multiple-loop of voltage and current control scheme. Through analysis, simulations and experiments, the control scheme is proved to be highly effective.This paper analyses the cause and the expressions of the third harmonic in the supply current, then two methods are present to improve the supply current. The first one is to adopt a low-pass filter; the second one is to compensate the 100Hz harmonic of the output DC voltage. All of these two methods could improve the supply current, but the dynamic performance of the rectifier was deteriorated when the low-pass filter was adopted. However, when the dynamic compensator of VDC was adopted, the dynamic performance of the rectifier was not deteriorated. The theoretical analysis is verified by simulation and experiment.With the analysis above, the hardware and software of the experiment system are designed. The DSP controller TMS320F240 and its related circuits,such as signal adjustment, switch drive and its phase-locked loop are introduced. The software design contains: the software realization of control scheme, digital PI controller and phase-locked loop.A platform based on DSP is constructed to verify the feasibility of the controller and the topology. Finally the experimental result proves that it is accorded the proposed method and it is satisfied with the waveform.