Research On Power Quality Comprehensive Treatment Technology Of Vv Traction Power System

Affected by the rapid development of electrified railways,the power quality problems of the surrounding power grids have become increasingly prominent,which will cause problems in efficiency and safety for residential electricity and factory production.Therefore,the problem of power pollution to control electric traction is an important issue.In this thesis,various methods and principles for controlling the negative sequence,reactive power and harmonics of electric iron power quality are introduced and analyzed,and the railway power conditioner(RPC)is the main research object.The details are as follows:This thesis firstly describes the basic structure of railway electric traction.It describes the current power pollution situation of traction system,and analyzes the AC-DC and AC-DC-AC locomotive's characteristics of power quality,detailing the characteristics of several transformers like Vv transformer,compare different kinds of control measures at home and abroad,such as improving power grid,installing railway power conditioner(RPC),etc.Then,the research focus of this thesis is on the railway power conditioner with the Vv transformer.The principle,characteristics and application methods are studied and analyzed,including the electrical characteristic formula for deriving Vv transformer,angle analysis of RPC governing reactive power and negative sequence,establish a mathematical model of the complete compensation model and the degree of quantitative compensation when incomplete compensation;analyze the scheme of mixing active and passive devices to reduce negative sequence,reactive power and harmonic problems;expounding the general design ideas of passive LC filters,and demonstrating them with a PQMS engineering prototype.The practical application of RPC improves the power quality.Then,after introducing the modulation and control method of VSC,this thesis proposes a carrier-phase-shift modulation(CPS-SPWM)based on multi-winding transformer coupling multiplexed RPC,which demonstrates that it can be equivalent to multiple switching frequencies and the characteristics of multi-level converter,and the mathematical formula of Bessel function based on bilateral Fourier transform are used to describe the harmonics of SPWM and CPS-SPWM.It is analyzed that CPS-SPWM can suppress a lot of harmonics compared with SPWM.The principle of the wave is verified by simulation.Mathematical analysis of the power variation law of RPC's amplitude-phase control strategy,considering the VSC AC side reactance and internal resistance,establishing a rigorous mathematical relationship between the device's transmit and receive active,reactive power and the SPWM modulated wave parameters,revealing the law of power variation with parameters and its active and reactive coupling conditions using amplitude-phase control.Then,after analyzing and introducing several common control strategies,a full RPC system simulation model based on PI controller for amplitude-phase control is established.The model includes real-time calculation of compensation power reference value based on measurement of railway load.The model also includes RPC,it's active and reactive power PI control loop,BTBC's DC capacitor control loop.The author of this thesis found that the RPC compensation did not reach the complete treatment of negative sequence and reactive power,so the qualitative analysis of the Vv-RPC governance power quality error was made,and the imperfections of the traditional compensation strategy were also analyzed.The traditional control method has some defects.This thesis proposes an improved control scheme based on amplitude-phase control for the solution.A RPC two phases' symmetrical control method is designed,and the power quality of the grid side is introduced for compensation fine adjustment.Finally,a prototype of Vv-RPQMS based on RPC is proposed.The parameters of it's circuit components are designed.The simulink model is built and the whole system simulation is carried out.The simulation verifies the feasibility of various control techniques for RPC,such as CPS-SPWM modulation,PI controller and amplitude-phase control,and demonstrates the effectiveness of Vv-RPQMS devices.It also verifies the effectiveness and feasibility of the proposed new symmetrical control method and introducing grid side information to further improve the negative sequence and reactive power problems in power quality.