Rsearch Of Phase Lock Method Applied On The Pulse Rectifier Power Supply System

High Magnetic Field has been developed into an important tool for scientific research.There are continuous magnetic fields and pulsed magnetic fields. Wuhan National HighMagnetic Field Center had built the pulse rectifier power supply system in order to realize50T/100ms high-stability flat-top of the long-pulse magnetic field. The pulse generatorsupply power to the system. The converter uses thyristors which could flow high current tomeet the requirements.The control precision of pulse rectifier system depends on the accuracy of pulserectifier firing angle. And the zero crossing signal of synchronization decides the accuracyof the firing angle. In order to realize50T/100ms high-stability flat-top of the long-pulsemagnetic field, we have to use the circuit of phase synchronization to track the frequencyand phase of the synchronization signal. Moreover, the pulse generator’s characteristicsinevitably make the frequency of the input voltage changes in a nonlinear order. Meanwhilethe input voltage has a high harmonic distortion. This requires us to solve the problem ofthe pulse rectifier system synchronization signal, so that the accuracy of long-pulsemagnetic field could be enhanced.The phase-locked loop’s brilliant characteristic of phase synchronization makes it amuch more popular circuit among various phase synchronous methods. Especially with thedevelopment of digital technology, the soft phase-locked loop which has high stability, easyachieving and flexible operation has more and more attracted people’s attention. Therefore,use high-performance software phase locked loop to obtain accurate phase synchronizationsignal of pulse rectifier system has become the focus of this study.By analyzing the synchronization signal of pulse rectifier systems, the author foundthat the synchronizing signal has three-phase voltage unbalance, frequency variationsvoltage dips and harmonic distortion and the causes of these problems. The author madetheoretical studies and simulation of zero-crossing PLL, reference frame transformationPLL and their applicability in the pulse rectifier system.According to the drawback of the traditional zero-based phase-locked loop, the authorproposes another kind of filter namely the bandpass filter used in the PLL. Add all-pass filter algorithm to reduce the effects of high order harmonics. And then put the twoimproved methods in the simulation of pulse rectifier system, finding that both of them canachieve50T/100ms high-stability flat-top of the long-pulse magnetic field. Eventually putthe improved zero-crossing method into the actual experiment, we found out that thesimulation results could be achieved.