Bilateral Power Supply In Electrified Railway And Its Influence And Countermeasure Analysis To Power System

Electrified railway is a single load which is a unbalanced load to electric power system.To decrease the negative-sequence influence to electric power system,both normal railway and high-speed railway set up neutral section at each traction substation and section post to change the phase at each segmentation.Neutral section goes against to high-speed and heavy-haul transportation because of the weakness both in mechanics and electrics.Setting the co-phase power supply device at traction substation can solve the power quality problems such as harmonic and negative sequence and reduce the neutral section of traction substation.Combine with co-phase power supply system and bilateral power supply technique can achieve continuous co-phase power supply and improve power supply reliability.but bilateral AC electrified railway makes traction networks be a parallel line of electric power system which is similar to Electromagnetic Loop Network.Bilateral AC electrified railway is a single phase loop which is different to Electromagnetic Loop Network.Some researches show that Electromagnetic Loop Network can bring bad influence to the safety of electric power system,so it’s necessary to study the relationship between bilateral AC electrified railway and electric power system combining with their facts.First of all,this paper has researched the factor of electric power system which can influence the equalizing current and the result shows that equalizing current ratio is decided by equivalent impedance of electric power system and traction power supply system.The key to decrease the equalizing current is reduce the ratio.Then this paper deduce the expression of equalizing current of transfixion power supply mode Also,the influence on relay protection equipment and problems of flow transferring overload has been analyzed on theory and simulation.To solve this problem,put forward a protection scheme based on segmentation power supply technique and measurement and control technique.Secondly,this paper has analyzed transient process of loop closing operation at section post and calculated the limit value of the voltage value amplitude and phase angle difference.Then the paper research the influence of bilateral AC electrified railway in the term of harmonic,it has analyzed harmonic resonance and permeability characteristics of traction network.According to the theory of harmonic resonance,put forward that add wave-trap high-pass filter can solve the problem of harmonic.At last,this paper use PSD analyze the influence of bilateral power supply system based on the actual data of ChuXiong power grid.The result proves that the mode of outside power supply will influence the Equalizing Current.Compare to the one way feeding system,Bilateral Power Supply won’t threaten the safety of electric power system in steady condition.