Research On Key Techniques Of Active Power Filters Applied For Aircraft AC Power Utility

With the increasing requirements of performance for the modern aircraft, more and more electronic equipments are applied. The AC power utility in aircraft is affected seriously by harmonics, reactive and unbalanced component. The power quality, the performance of the generators and equipments degrade obviously.As an advanced technique for improving power quality and refining the utility pollution, active power filter is researched widely and developed in recent years. The key techniques of active power filters applied for aircraft AC power utility is researched in this thesis.There are some characteristics in the aircraft AC power utility: independent lower capacity system, larger inner impedance, higher power frequency, higher nonlinear load ratio, three-phase four-wire system, unbalanced loads, etc. The APF techniques for aircraft AC power utility are unique.Based on the analysis of the traditional harmonics elimination methods, the APF applied for aircraft is presented to compensate the harmonics, reactive and unbalanced components in the thesis. APF applied in aircraft utility has advantages compared to the traditional harmonic elimination strategies.The typical current detection approaches for the three-phase four-wire system are researched under the power theory system. The improved synchronized rotation frame method and the improved crossing vector method are proposed respectively. According with the universal instantaneous power theory, the improved synchronized rotation frame method can calculate the current reference easily and rapidly using the source voltage information without the phase-locked-loop and sinusoidal function calculation. In improved crossing vector algorithm, the harmonics, reactive and the imbalance current can be detected totally under the constant active power rule even if the source voltage is imbalanced. Considering the characteristics of the aircraft utility, the improved crossing vector algorithm is preferred to apply in the APF for aircraft utility.The circuit topology and current track method of the APF in three-phase four-wire system are analyzed in detail. The three dimension space vector modulation for current control strategy is deduced and implemented by DSP+FPGA in a three-phase four-leg APF. Because of the higher power frequency in aircraft, the good current track performance of APF is required. According with the comparison of the topologies and current controllers, the split-capacitor three-phase full-bridge topology and hysterisis current controller are used in the APF for aircraft utility.The equivalent circuit of the shunt APF is obtained and the mathematical model is built up. The transfer functions of current detection, current track control and DC side voltage control are deduced in detail. The design method of APF for aircraft utility is educed. The key parameters of the APF are confirmed and the APF design is implementation.Based on the academic analysis and simulation, the prototype of APF for 400Hz aircraft utility is built up. The experimental results are received under the different condition. The feasibility and validity of the APF are proved and the active power filter theory can be enriched.