Research On Assembled DC Transformer Applied To DC Distribution Tail Power Conversion

Existing AC distribution network has been unable to meet diversified demand and a large number of new energy,and DC distribution network has incomparable advantages,such as improving the quality of power and the electric capacity,fast independent control of active power,access to renewable energy flexibly and conveniently and etc.DC distribution network will undoubtedly become the main direction of future distribution network research.A novel high-frequency isolation Assembled DC Transformer(ADCT),which includes using standardized modules to assemble the desired system structure and neighbor control to realize the global coordination control,is proposed in this paper for future DC distribution power conversion.The LLC resonant converter was be used as standardized module of Assembled DC Transformer to form a DC transform system through the series-parallel structure.LLC resonant converter can realize completely soft-switching,high conversion efficiency,and its voltage clamping characteristics can achieve Input-Voltage-Sharing(IVS)of the Input-Series Output-Parallel(ISOP)system naturally.Chapter 2 has a detailed derivation the voltage gain of the LLC resonant conversion module,and mapped the gain curve to prove the feasibility of achieving voltage balance using voltage clamping characteristics in ISOP system.Using voltage clamping characteristics and Magnetic-Coupling Current-Balancing(MC-CB)unit,the neighbor control was proposed and introduced in detail,and the MC-CB unit has carried on the detailed theoretical derivation and simulation analysis to prove that the feasibility of achieving current sharing in Input-Parallel Output-Parallel(IPOP)system by MC-CB unit.Later,a new IS-IPOP structure was proposed,combined with neighbor control,can realize independent open-loop control of voltage and current.Assembled DC Transformer proposed in this paper has superior transient performance and stable and reliable control.It also can realize cutting and adding modules on load and redundant backup,which is convenient for spot operation and has great application prospect.At last,an ADCT hardware prototype is designed and built up to verify the validity of the proposed solution.