Research On Multi-Input DC-DC Converter For Medium Voltage DC Distribution Network

With the increase of distributed energy penetration,the traditional AC power distribution system should respond to the shortage of energy and load fluctuation.The hybrid power distribution technology with high power converter as the core can realize the functions of multi energy access,fast load response,flexible energy supply and so on.In this paper,the idea of centralized DC distribution is proposed,the output of wind turbines is rectified and conveyed to short-distance converter stations,and a multi-input DC-DC converter is used in the converter station to converge and boost the power input of multiple fans to transfer the energy to the medium voltage DC distribution network.A multi-input DC-DC converter is proposed for medium voltage DC distribution network.The low frequency full-bridge inverter is adopted in the DC side of the multi-input,and the energy is transferred to the high voltage side through the low frequency transformer coupling.The high voltage side uses the modular multi-level topology of the rectifier to multi-channel power transmission to the medium voltage DC bus.The topological structure and working principle of the proposed converter are analyzed in detail.The carrier stacking modulation strategy is selected and the voltage balance modulation is realized.A phase-shifted power modulation method based on fundamental wave is proposed.The reasonable system parameters are designed according to the performance requirements,and the simulation model is built by using SIMULINK simulation platform.The simulation results verify the effectiveness of the proposed converter modulation strategy and the phase shift power modulation method.The corresponding hardware experimental platform is designed and built,and the modulating and equalizing functions of the modular multilevel rectifier and the measured results of the power transmission modulation in the single input and multi-input conditions.Experimental results show that the proposed converter can achieve multi-DC input,with multi-channel power transmission capacity,suitable for wind power generation and other multi-energy DC distribution network applications.