Protection Scheme Of Subway Virtual Co-phase Flexible Power Supply System

With the vigorous development of urban rail transit,the DC traction power supply system commonly used in subways has gradually failed to meet the power supply requirements of long lines and high speeds.Therefore,the traction power supply system of a subway test line uses rigid catenary in AC25 k V,and the power supply method is a direct power supply method with a return line;in order to ensure the balance on the primary high voltage side,the in-phase power supply device is adopted;The flexible passing neutral section device is used at the neutral section near the switch station to assist the train to pass through the neutral section at high speed to meet the demand for long lines and high speed.For such a traction power supply system,there is currently no corresponding relay protection scheme to ensure the safe and stable operation of the system,so it is meaningful to study its corresponding relay protection and emergency power supply scheme.Through the research on the current situation of flexible passing neutral section technology,in-phase power supply technology and relay protection at home and abroad,this paper finds that it is impossible to effectively protect the subway virtual in-phase flexible power supply system.Therefore,according to the structure of the traction network of the virtual in-phase flexible power supply system,the fault and protection needs of the virtual in-phase flexible power supply system are analyzed when system works in normal and over-zone power supply conditions.The direction and the position signal of the train are used as auxiliary signals.According to the fault characteristics in different situations,the protection requirements of traction network,in-phase power supply device and flexible passing neutral section device are discussed respectively when different auxiliary signals are occurred.Afterwards,a set of systematic protection schemes were proposed combined with wide area domain protection.At the same time,an emergency power supply scheme for over-zone power supply was also proposed;Then,according to the actual situation of a certain subway test line,the protection scheme of the test line was configured according to the protection requirements.On the basis of the proposed protection configuration,combined with the protection requirements and the actual situation of the test line,a complete protection setting calculation method is proposed when system works in normal and over-zone power supply conditions.The calculation method has been discussed about the transformer protection,traction substation bus protection,the switch station protection protection,flexible passing neutral section device,wide area domain protection.In order to verify the correctness of the protection scheme and the calculation method,a virtual in-phase flexible power supply system simulation model was built on RTDS for simulation verification,including in-phase power supply device,flexible passing neutral section device,traction substation,feeder line and other models.At the same time,the control algorithm of the in-phase power supply device,the flexible over-phase device and the the wide-area measurement and control system are given.Simulations on RTDS verify the correctness of the traction network and each device model.Finally,according to the traction network model of the virtual in-phase flexible power supply system built on RTDS,the system neutral section failure,supply arm failure,substation bus failure,in-phase power supply device failure,and over-zone power supply failure are simulated respectively to examine protection actions.After carrying out the analysis of the protection operation sequence,this paper obtain the voltage and current waveform at the time of the fault occurred,and the sequence diagram of the circuit breaker operation.The simulation results verify the correctness of the protection scheme,the rationality of the protection setting method,and the correctness of the short-circuit voltage and current calculation model.Finally,the protection scheme and emergency power supply scheme which are suitable for the subway virtual in-phase flexible traction power supply system are put forward.