Research On Grid-Train Coupling Simulation And Resonance Suppression Strategy Based On Digital Real-Time Simulation System

Since the 1990s,China has vigorously developed railway technology.As a modern mode of railway transportation,it has the advantages of improving transportation capacity,saving energy,reducing transportation costs,helping to protect the environment,and increasing safety and reliability.The actual operation shows that,under normal operating conditions,the AC locomotive mainly injects relatively small harmonic currents into the grid through the pantograph.However,it still causes some pollution to the power grid environment.In a specific environment,it will cause grid-train coupling resonance.In China,there have been more than 10 resonance accidents in more than 10 lines,which has had a serious impact on the safe and stable operation of the railway system.The research contents of this thesis will be introduced from three aspects:the mechanism of grid-train coupling resonance and modeling of traction grid,the real-time simulation platform of traction power supply system,and the grid-train coupling resonance suppression.The thesis first introduces the grid-train coupling resonance mechanism and the modeling method of traction grid.It includes the parallel resonance mechanism and the series resonance mechanism,and then introduced the traction grid mathematical modeling method based on the complex depth theory and the multi-conductor chain geid model.And it builds traction grid off-line simulation modeling with different power supply modes such as direct power supply with return line,AT power supply,and BT power supply.At the same time,according to the model established above,the impedance characteristics of the traction grid and the sensitivity of the parameters were analyzed,and the impedance characteristics of the traction network were obtained.Secondly,with the help of real-time simulation,the development of a traction power supply system platform based on a real-time simulation system was carried out.The real-time operation of traction grid with different lengths is completed by using the core decoupling method..The traction drive system was connected to the actual train controller(TCU)for simulation.Finally,communication was established between different simulation systems,real-time traction power supply simulation system development was completed and experimental analysis was conducted.Then,the grid-train coupling resonance suppression algorithm of is introduced.As a harmonic source in the grid-train coupling system,the harmonic characteristics of the train mainly depend on the modulation algorithm of the multiple single-phase four quadrant converter in the train traction drive system.Therefore,in the study of resonance suppression methods,this thesis will focus on improving four quadrant converter harmonic characteristics optimization control and modulation algorithm as the starting point.The coupling resonance suppression of thegrid-train is carried out by the combination of the specific harmonic elimination(SHE-PWM)technology and the existing transient direct current control algorithm.Finally,this thesis introduces the digital realization method of SHE-PWM.By using the hardware in the loop method of real-time simulator,the algorithm of resonant suppression is verified and debugged,and the feasibility of the algorithm is proved.