A Study On Synchronization Signal Detection Method Based On Adaptive Notch Filter For Aircraft Power System

With the proposed of "More electric Aircraft" in aviation industry in the nineties ofthe20th century, aircraft power system is also facing profound changes. Traditional400Hz constant frequency power supply changes to the variable frequency powersupply, the operating frequency is varied over a range on the order of360Hz to800Hz.And harmonic currents produced by the increasing nonlinear load will seriously affectthe aircraft power quality. With the application of a large number of electronic devicessuch as converters and active power filter in the air power system, the modified aeropower standard means that quickly and accurately extract the synchronous signals is thepremise of control. Compare with the current methods, adaptive notch filter has itssuperiority.Adaptive notch filter is mainly composed of the notch filter and adaptive algorithm.On the basis of introducting principles respectively, the paper mathematical analysis forthe differential equations of single-phase ANF structure firstly, which is used to extractthe signal. The theoretical analysis results that the dynamic response has an inverserelationship with the fundamental frequency. The higher the frequency, the lower theresponse speed of extraction. In addition, the use of different reference coordinatesystem in three-phase power supply, the update equations have some differences. Whenset to the same parameters, the different structure of the ANF has a different dynamicresponse speed, and there is a fixed ratio of6:3:2. When it’s need to extract harmonis,the multi-channel adaptive notch filter can achieve the harmonic components of thesignal. By modifying the notch filter’s parameter, it’s not only able to get the integerharmonic, but also can successfully extracted out the inter-harmonic component. Forparallel structure, all channels work in parallel will not bring additional delay.For dynamic response speed of ANF is great impacted by the fundamentalfrequency, this paper proposes two new structure of ANF. One is constant time responseANF(CT－ANF). By introducing the measured frequency to the feedback part of ANF,it can eliminate the influence caused by frequency. The other structure is constant cycleresponse ANF(CC－ANF).It feeded the square of measured frequency back to thefrequency detection unit. It can accelerate the ANF response speed in a fixed cycle time.After the theoretical conclusions, there made a simulation. The results show that, thetwo methods presented in this paper can effectively improve the dynamic response speed.Later, DDSRF-PLL compared with the proposed CT-ANF in simulation underfrequency hopping, the voltage asymmetry, the existence of distortion and otherworking conditions. The simulation results show that both methods can successfullyextract the synchronous signals in the aircraft power system. But CT-ANF has optimumperformance in accuracy and rapidity.Experiments verified full-text research. The experimental results verified thefollowing points:1) The dynamic response of ANF is related with the fundamentalfrequency and structure.2) CT-ANF and CC-ANF can effectively improve the dynamicresponse speed.3) CT-ANF can extract the synchronization signal in aircraft powersystem. It fully proved the correctness of theoretical analysis and simulation.