The Study Of Reactive Power Compensation Method For The Electrified Railway Load

In this paper, the load characteristics and structure of the traction system are introduced firstly for the electrified railways. The current characteristics of ports are analyzed when various traction transformers are connected with the grid in traction power supply of railway in our country. Meanwhile, taking SS4 locomotive as typical load, its harmonics are analyzed. Thereby, the necessity of reactive power compensation is illustrated for traction power supply system, and its features are harmonic current compensation and negative sequence current compensation. It is introduced briefly that the system structure and basic principle of TCR+FC type Static Var Compensator (SVC). For the electrified railway load characteristics, the symmetrical component method which can compensate the negative sequence current is introduced, reactive power compensation formula is derived, and SVC control system which adopts the symmetrical component method and combines traditional PID control is designed. To filtering the harmonics of inductive load, an approach to design the filter of SVC is presented. In order to verify the feasibility of symmetrical component method, in MATLAB SIMULINK the model of svc which the load is SS4 electromotive is built, parameters of filter is designed, The simulation results show that this solution is feasible and efficien.Finally, experimental system, which adopted DSP as the control core, was built, and the program was written for this system. In this experimental platform, experiment was completed, and the results were shown. Experimental results shows that SVC controller with the symmetric component method can compensate reactive power fast and accurately, make the voltage and the current in phase, and possess good steady-state and dynamic performances. Experiments about varying load characteristics are done, and the result proves the controller can be available for different loads, has good robustness and that the method is a very effective strategy for reactive compensation.