| It’s necessary to supply airplane with three-phase400Hz,115V AC voltages which constituteground power unit (GPU) when maintainance is taken on ground or board. However, the presentpower supply of beeline can’t comply with the relevant requirements. Considering the extremelyadvantages of coping with voltage fluction and improving power quality, a study of dynamic voltagerestorer (DVR) applied in400Hz utility is presented in this thesis, which includes its key technologiesand implementation of improving power quality of power supply of beeline.400Hz utility is characterized with higher power frequency, larger inner impedance and easilyaffected by load when compared with50Hz utlity, thus the research on400Hz DVR is distinctive.Based on the analysis of present approaches of power supply of GPU, a new scheme adopting DVR isintroduced.The research of this thesis includes:1. The distribution schemes of GPU of airport are introduced, among which the power supply ofbeeline is taken as the main power supply due to its advantages such as stability, economy,environmental conservation, etc.. The feasibility and virtues of adoption of DVR to steabilize the loadvoltage are also analyzed.2. Based on detailed demonstration of whole technical scheme of mid-frequency DVR, theschematic diagram is given. Singe phase full-bridge circuit is adopted as the inverter power stage ofDVR after the comparison of circuit topology of three-phase four-wire system. To simplify systemcontrol, an unidirectional power-supply scheme is put forward to ensure that DVR only supply activepower to avoid voltage rise of DC capacitor caused by returning of active power. To realize thecontinous compensation and simply the system control, as well as to decline the harmics as possible,the18-pulse uncontrolled rectifier is adapted as the power supply circuit. The voltage compensationcapacity of several connection schemes for the rectifier is analyzed and the design rule of DCcapacitor is given. Meanwhile, the design of LC filter, step-down transformer, series transformer andpower circuit are analyzed in detail.3. A general research on voltage detection is carried out. To obtain the accurate compensationvoltage and promote the DVR’s performance, the detection of fundamental component andparameters of load voltage is necessary. Based on the analysis of traditional detection approaches, anew voltage detection method with easy implementation based on period phase is introduced, fromwhich the amplitude and phase of voltage, as well as the start and end of voltage sag can be judged correctly and quickly, and thus can meet the dynamic requirements of DVR. To extract thefundamental component from voltage, a voltage detection method based on2nd-order serial resonantfilter is presented, which can detect the fundamental voltage quickly with less calculations.4. Research on system control of DVR is introduced. Firstly, the circuit model of DVR along withthe control model of RMS feedback of load are built up, morever, the comparison of several voltagecontrol strategies is carried out. Through therotical analysis and simulation, the feasibility of RMScontrol stategy applied in mid-frequency is validated. After the analysis of voltage compensationstrategies, the mathematical model of minimum energy compensation is given. Considering the higherfrequency and a big variation of frequency of400Hz utility which easily leads to phase-locking error,a new phase locking method with zero crossing based on PI adjustment is proposed. The analysis ofvoltage compensation procedure indicates the composition of steady and dynamic stages, as well asdetection delay and switching period delay acts as the two main factors to affect the compensationperformance of DVR. To eliminate the effect of switching period delay, a new voltage compensationscheme based on phase compensation is put forward.5. Based on the therotical analysis and simulation, a DVR protype is built up and experimental testsare carried out when ultility voltage or load varies, which leads to the application of DVR in practicalengineering project. The experimental results validate the feasibility and correctness of research ofDVR in this thesis and enrich the theory of DVR as well as its practical application. |
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