Power Conditioner For Voltage Sag/Swell and Harmonic Mitigation

Electrical traction is as environmental friendly, pollution-free and energy efficient mode of transport and offers an excellent alternative to fossil fuels as a source of energy. Indian Railways are the world's largest transportation sector. Presently 37.65 percentage (Indian Railway statistical Publication 2016-17) of total route kilometers have been electrified by Indian Railways. Under heavy traffic, overloading on a finite section of transmission line with multiple locomotive loads yields to a dip in transmission voltage below the rated voltage of locomotive load and an inefficient operation of motor takes place if the system is operated with this under voltages. AC railway traction systems are also susceptible to harmonic distortion. A compensation scheme to improve voltage profile and current harmonic mitigation of Indian Railway traction system is proposed in this paper. The power conditioner is used for effective switching can control the harmonics too. A novel power conditioner is introduced which functions both as a DVR and APF to effectively control the voltage sag/swell and harmonic in the 25 kV traction line. In this paper, the unit vector generation control strategy is used to generate current and voltage references for compensation and control. The unit vector generation strategy utilizes low pass filters to separate the reactive and harmonic content in the load current. The simulation studies showed good results with the voltage sag/swell compensation and reactive current compensation giving almost ideal result of near unity power factor and harmonic currents getting compensated. Thus this will offer a solution to the problems faced with traction loads.