基于超级电容的交直交牵引供电系统及控制策略

AC-DC-AC Traction Power Supply System Based on Super Capacitor and Control Strategy

针对传统电气化铁路中无功、谐波、负序等电能质量问题和电分相问题,并考虑牵引负荷的冲击性,提出一种由多端口交直交(AC/DC/AC)变流器、牵引变压器及超级电容储能构成的牵引供电系统及控制策略。牵引变压器的二次侧分别通过两个整流端口与变流器中的单相整流器相连,将整流器的直流母线并联引出,变流器的逆变端口连接在牵引网上;超级电容通过Buck/Boost变换器并联至直流母线。整流器采用直流电压外环、网侧电流内环的双环控制,在稳定直流母线电压的同时解决电网侧电能质量问题。输出侧逆变器采用电压有效值外环,瞬时值内环控制输出电压的幅值和相位,可以彻底取消电分相。根据系统容量和牵引负荷的功率确定超级电容的充、放电阈值,计算得到充放电参考电流值,控制超级电容充放电以平抑电网输出功率的波动。最后在MATLAB/Simulink进行了仿真分析,验证了该方案的可行性。

Aiming at power quality problems such as reactive power,harmonics,negative sequence current,and the problems of neutral sections in traditional electrified railways,and considering the impact of traction load,a traction power supply system and control strategy composed of multi-port AC-DC-AC converters,traction transformers and super capacitor energy storage were proposed.The secondary side of the traction transformer was respectively connected to the single-phase rectifier in the converter through two rectification ports,the DC bus of the rectifier was led out in parallel,and the inverter port of the converter was connected to the traction network.The super capacitor was connected in parallel to the DC bus through the Buck/Boost converter.The dual-loop control of DC voltage outer loop and grid-side current inner loop were adopted in the rectifier,which can stabilize the DC bus voltage while solving power quality problems.The voltage effective value outer loop was adopted in the output-side inverter,and the instantaneous value inner loop was used to control the amplitude and phase of the output voltage,which can completely eliminate the electrical phase separation.According to the system capacity and the power of the traction load,the charging and discharging thresholds of the super capacitor were determined,the reference current value of charging and discharging was calculated,and the charging and discharging of the super capacitor were controlled to stabilize the fluctuation of the output power of the grid.A simulation analysis was carried out in MATLAB/Simulink to verify the feasibility of the scheme.