Design And Research Of Three-Phase Auxiliary Inverter Based On The High-Frequency Isolation

Besides the locomotive traction system,auxiliary converter system assumes the power supply of a variety of other devices, such as lighting systems, video detection, and signal lights. It is an important component of electric locomotives. Therefore,the study of the auxiliary converters has indispensable significance for the development of electric locomotives. Based on the technical parameters of the subject required auxiliary inverter, this paper designed one three-phase auxiliary inverter based on the high-frequency isolation.Firstly, according to the technical parameters of the auxiliary inverter, the topology structure of the three-phase auxiliary inverter is analyzed. The auxiliary inverter system is divided into two parts, DC/DC converter and DC/AC inverter. The main circuit of DC/DC converter with ISOP structure can be divided into two identical modules, each module is divided into two parts by the high frequency isolation transformer. The primary side of the transformer is half bridge inverter. As each transformer has two secondary side winding, the secondary side is two series of the full bridge rectifier circuit. The DC/AC inverter is a traditional two level inverter.Secondly, the main circuit is divided into the front stage circuit, half bridge inverter circuit, a high frequency isolation transformer, non controlled full bridge rectifier circuit and DC/AC three-phase inverter circuit, and calculates the value of the each main components.Thirdly, since the main circuit of DC/DC converter using Input-Series-Output-Parallel (ISOP) structure, the paper uses a centralized control strategy which is composed by output voltage regulating loop, input voltage sharing regulating loop and inductor current regulating loop to solve the problem of input voltage sharing and output current sharing between modules. And it has a detailed analysis of the strategy. The paper uses the double-loop control strategy and SVPWM modulation to control the DC/AC inverter. Then, the matlab/simulink software is used to simulate the control strategy, and the simulation results are carried out under the stable input voltage and the maximum fluctuating input voltage.Finally, this paper describes the overall framework of the control unit of the three-phase auxiliary inverter system, and the power circuit, sampling circuit, protection circuit and drive circuit are designed in detail. At the end of the paper, assembled a three-phase auxiliary inverter prototype and a experimental platform. Through the system of light load experiment and no-load switching overload experiment to test the function parameters for the design of the auxiliary inverter can meet the design requirements.The auxiliary inverter’s waveform simulation, experimental results and theoretical analysis, proved the feasibility of the design.