Control Method Reserach Of Novel Traction Power Supply System Based MTDC

The electric railway has many advantages such as strong traction force,low noise,small environment pollution,high energy efficiency,large volume.It is a very important means of transportation that promote the development of national economy.In the electric railway power supply system,it also has many problems exist,such as the power quality,excessive phase,capacity utilization and so on.In order to solve the existing problems,this paper put forward a kind of novel traction power supply system based MTDC(modular multilevel converter multi-terminal DC,MMC-MTDC).The novel traction power supply system using power electronic converter technology,out the power with in phase.eliminate the locomotive "electricity split-phase" problem,improve the utility grid and traction network power quality greatly.In this paper,the multi-terminal HVDC technology is applied to railway traction power supply system,using the MMC construction of dc network between the traction network and utility grid.Taken the novel traction power supply system based MTDC as the research object.Research on the theoretical analysis,mathematical modeling,control strategy design,simulation,etc.The main content of the thesis are as follows:1)Analysis of the MMC-MTDC basic structure and control principle.The MMC converter be introduced which is composed of traction power supply system.This paper discusses on the basic structure of MMC,MMC module running state,expounds the mathematical model of the MMC,two kinds of modulation strategies of MMC are studied.The mathematical model of MMC-MTDC system is introduced in detail,and the power transmission principle of MMC converter and AC system are analyzed.The three level control structure is designed for MTDC system.Analysis of the converter level control strategy.2)Research on MMC-MTDC system level coordination control strategy.The master-slave control,DC voltage margin control,DC voltage slope control,are comparative analysis,this paper discusses their respective advantages and disadvantages,and aiming at the shortages put forward relevant optimization control strategy.A hybrid control strategy is designed,this strategy used the multi-terminal system converter station between station and inside the station hybrid control scheme for configuration.At the phase of voltage margin,introduction of droop control,suppress the transient over-voltage;Avoid multiple converter station power synchronous changes when the system disturbance.3)Control method research of novel traction power supply system based MTDC.Thefive terminal model of traction power supply system is constructed,introduces the single-phase H bridge converter(single phase H-bridge,SPH-MMC)mathematical model and principle.Based on the analysis of instantaneous power of SPH-MMC,designed circulation suppressor.In order to control the DC voltage and active power of the system,an improved droop control strategy based on DC voltage square is proposed,establish the simplified model of electric locomotive,and simulate the control strategy of the system in PSCAD/EMTDC.