Based On Active Damping Oscillation Suppression Strategy To Solve The DC Voltage Of Traction Converter Oscillation Problem

All modern subway train traction drive system will support reactor and filtering capacitor installation in the traction inverter dc network circuit,the dc side capacitor voltage fluctuation limit within the scope of the permit,can make the system stable operation,at the same time,the dc side filter link to filter out higher harmonic,inhibition of short circuit current in traction inverter short-circuit and satisfies the requirement of converter inverter switch components.Because traction inverter dc negative impedance characteristics of the system damping is reduced,eas y to roughly reactor,capacitor in traction converters in low and middle frequency resonance,lead to the dc voltage,electric current sustained oscillation,serious when frequently lead to inverter over-current and blockade,loss of traction,caused by subway line big events later.Therefore,how to suppress dc side voltage oscillation of traction converter and improve system stability is the research content of this paper.The main work of this paper includes:Based on the analysis of inverter overcurrent in the operation of guangzhou metro train traction system,the fault mode and influence of dc side voltage oscillation in current train are studied and analyzed.This paper briefly introduces the mathematical model of asynchronous motor and the basic principle of vector control,on this basis,the inverter and motor for the more accurate mathematical modeling,the derivation and validation of the inverter input admittance expressions of transfer function,and use the Nyquist stability criterion,the negative impedance instability led to the mechanism of dc side voltage current oscillation are analyzed in detail.A common modeling method in literature is to consider the inverter as an ideal constant power source and analyze the error caused by the simplified approximation.Through analysis,it can be seen that the input admittance of the traction system not only depends on the physical characteristics of the motor itself,but also has a great relationship with the control method and the current steady-state condition.Based on the traction converter-asynchronous motor system modeling reference literature in the extraction of dc side capacitor voltage oscillation signal real-time correction or a given torque converters active damping of slip stability oscillation suppression strategy,set up a simulation model of MATLAB simulation tools for dc traction converters lateral oscillation instability phenomenon and the stability of active damping control strategy simulation verification.