Research On Parallel Technology And Start Control Strategy Of Auxiliary Inverter

With the acceleration of the construction process of urban agglomeration and the increasing demand for inter-city rail,EMU has become the first choice for people to travel by virtue of its comfort,convenience and rapidity.As an important power supply equipment on the EMU,the quality and reliability of the auxiliary inverter power supply directly affects the passenger's ride experience.In order to improve the reliability and redundancy of the traditional medium voltage power supply system of EMU,this dissertation focuses on the parallel control technology and startup strategy of the auxiliary inverter.In the parallel control technology of auxiliary inverters,firstly,the single inverter control technology is studied,A new auxiliary toilet structure model of EMU with power frequency transformer is introduced,and the mathematical model of the inverter in different coordinate systems is constructed.Based on the analysis of three-phase rectifier load characteristics,the quasi-PIR resonant control strategy in dq coordinate system is introduced.The resonant frequency offset of different discrete methods is compared and analyzed.Pretortuous bilinear transform(PRE)is selected as the discrete method of the controller.Secondly,the parallel technology of wireless auxiliary inverters is studied.The causes of switching secondary circulating current in parallel system of auxiliary inverters with power frequency transformer are analyzed.A zero-crossing detection method of modulation wave is proposed to realize carrier synchronization.In order to solve the inherent contradiction between the voltage regulation ability of traditional droop control and the load power sharing performance of inverters,an improved resistance droop control method is proposed to improve the current sharing effect of parallel systems with linear loads.To solve the problem of output voltage drop caused by droop control coefficient,a voltage compensation strategy is introduced to increase the output voltage intelligently.Aiming at the problem of power sharing of non-linear load,a virtual impedance strategy combined with a specific sub-band-pass filter is adopted to increase the corresponding sub-harmonic impedance and enhance the harmonic current sharing ability.For startup of wireless inverters parallel system,the random startup strategy of dice-throwing method is studied in depth,and the mathematical model of dice-throwing method is constructed.For different number of inverters,the method of selecting the optimal base of throwing with the greatest startup probability and the fastest speed is given.Three common stochastic algorithms are compared and analyzed.Linear congruence stochastic algorithm is chosen as the starting stochastic algorithm of wireless inverters.In order to guarantee the randomness of the start-up time of the inverters in parallel system,this dissertation presents a seed mimber extraction method,and designs the start-up logic of the inverters in parallel system without interconnection lines.The system simulation platform is built,and the accurate model of parallel system is built by using S-Function module written in C language,and the simulation verification is carried out..Finally,the experimental verification is carried out by experimental platforms of parallel system with two wireless inverters.The simulation and experimental results prove that the parallel control and start-up control strategy of auxiliary inverters proposed in this dissertation are feasible.75 Figures,5 tables,72 references.