Research On Relay Protection Of Virtual Flexible Cophase Power Supply Device

Electrified railways adopting single-phase power frequency 27.5kV power supply system will inevitably have the neutral section.In the past,due to the presence of the dead zone of neutral power supply,the speed of the electric locomotive will inevitably cause speed loss,increase of energy consumption,overvoltage,bow net arc and other issues.The virtual flexible cophase power supply technology uses the virtual flexible cophase power supply equipment to supply power in the neutral section of the existing line,which can better solve a series of problems caused by the dead zone of the power supply,and has a wide application prospect.Relay protection is the premise and guarantee of the safe and reliable operation of the power supply system.The introduction of new types of equipment will inevitably require corresponding protection schemes.Therefore,it is of great significance to research the relay protection scheme of the virtual flexible cophase power supply device.This paper firstly analyzes the whole process of the electric locomotive passing through the neutral section of the virtual flexible and cophase power supply device,and gives the topological map of the train at each stage.Combined with the topological diagram,it illustrates the working principle of the virtual flexible cophase power supply device.For the traction power supply system,the characteristics of voltage on the left and right sides of the power neutral section power supply arm,the virtual flexible cophase power supply device adopts the amplitude modulation phase shift and power control technology to achieve continuous passing neutral section.This paper analyzes the amplitude-modulated phase-shifting algorithm and power control algorithm used in the virtual flexible in-phase power supply device,and builds a simulation model of the passing neutral section system of the corresponding virtual flexible cophase power supply device.Furthermore,since the virtual flexible cophase power supply technology does not cancel the neutral section,a virtual flexible cophase power supply device is added to the existing line.There is a complicated coupling relationship between the virtual flexible cophase power supply device and the out-phasing power supply arms and the over-phased power trains on both sides.This paper uses the topological diagram of the virtual flexible cophase power supply device to analyze the short circuit or open circuit of the contact network that may appear on the line,faults such as short-circuit in the segment,virtual and flexible power supply unit and neutral segment disconnection,phase separation between locomotive energized phases,or phase-to-phase short circuit across the power supply arm,and corresponding protection schemes are proposed.Finally,the RTDS simulation platform is used to simulate the entire process of the train passing the virtual flexible cophase power supply device and various fault modes to verify the feasibility of the proposed protection scheme.