Research On Electrified Railway Power Quality Problems And Their Management Schemes

As an important infrastructure in transportation system, the electrified railway isa strong guarantee of the national economic development and social progress.However, because of the unique power supply mode and electric locomotive loadcharacteristics, the electrified railway brings about power quality problems such asnegative sequence current, harmonics, voltage fluctuations and flicker, etc. to thepower system, which reduces power supply quality of higher level power system aswell as traction power supply system itself, and influences the security and economicoperation of power system. Therefore, it is necessary to take practical and effectiveremedies to carry out electrified railway power quality management to ensure thestability of the traction power supply system. In this paper, the existing ordinaryelectrified railway and rapidly developing high-speed electrified railway powerquality problems are discussed, the corresponding governance program is proposedand the simulation is carried out, the simulation results confirm the effectiveness ofthe proposed method.In the study of ordinary electrified railway power quality control program, thispaper investigates the power quality management program of two different tractionelectric networks that respectively adopts balancing transformer and imbalancetransformer. Firstly, the characteristics of two typical traction transformers, that is,V/v transformer and Scott transformer are analyzed, on this basis, considering thesystem cost and equipment capacity, two different power quality compensationprograms are presented, and the compensation principle as well as structuraladvantages are introduced minutely, in the end, simulation is carried out. Thesimulation results show that two kinds of control programs can achieve good negativesequence and harmonic compensation.According to power quality governance of high-speed electrified railway, thispaper proposes a novel railway power compensation structure based on thehalf-bridge inverter, comparing to traditional railway power regulator, this newstructure can save a pair of switching bridge arm (four power switches) in thecircumstances to achieve the same functionality, which can effectively reduce the costof the device’s active capacity. This paper analyzes the electrical model, workingprinciple as well as DC voltage imbalances issue of this new compensation system. Combining the work principle of new compensation system, this paper presents asimple real-time reference instruction signal detection methods. In addition, thesystem synthesized control method, that is, the voltage outer loop current inner loop’sdual closed-loop control method is analyzed. Voltage outer loop includes DC-side busvoltage balance and capacitance voltage-sharing and guarantees the stability ofDC-side voltage. The current inner loop detects system output and reference quantityin real-time and adopts hysteresis control method to realize closed-loop control of thereference command current, ultimately, the balance of DC-side voltage and thetracking control of reference current are achieved, and the system realizescomprehensive compensation of negative sequence current, harmonics and reactivepower.Taking into account of the development trend of electrified railway as well as thestructural advantages of the new railway power compensation system based on thehalf-bridge inverter, the paper builds a small capacity experimental platform forhigh-speed electrified railway compensation structure. The text firstly studies themain circuit parameters design, the parameters design of the AC-side inductor, theDC-side capacitor and the choice of the power module are explored, then digitalcontrol system based on DSP2812is developed, the article briefly describes thehardware and software design of the control system. The small-capacity prototypeexperimental results verify the validity of the proposed new compensation system.