A pre-control method and device for preventing overvoltage in subway trains

Abstract

The invention discloses a method and a device for pre-controlling overvoltage protection in a subway train. The method comprises the following steps: 1) in the operational process of a target train, detecting input current in a variable-frequency speed control system in real time, and calculating current change rate di / dt according to the detected input current; and 2) judging whether precontrol needs to be carried out according to the state of the current change rate di / dt so as to control a chipping unit to conduct depressurization before overvoltage is generated by current or voltage leap. The device comprises a data detection and processing unit and a precontrol unit. The device has the advantages that the implementation method is simple, the required cost is low, overvoltage and overcurrent caused by current or voltage leap due to a jumping bow can be prevented and the control efficiency and precision are high.

Description

technical field [0001] The invention relates to the technical field of subway trains, in particular to a pre-control method and device for preventing overvoltage in subway trains. Background technique [0002] Subway trains have the advantages of large passenger capacity, fast travel speed, and high comfort, and are one of the important means to solve urban traffic problems. Subway trains are composed of multiple trains, generally 6 trains (4 trains and 2 trailers), and each train has an independent frequency control system (VVVF). During the operation of the subway train, due to the fluctuation of the pantograph and catenary, bow jumping phenomenon often occurs, especially in high-speed subway trains, the instantaneous change of network voltage often exceeds a certain range (such as 300V) and bow jumping occurs, resulting in Net voltage and intermediate voltage jump. [0003] At present, a line reactor is usually installed in each VVVF main circuit of a subway train to su...

AI Technical Summary

Problems solved by technology

However, during the actual operation of the subway train, there will still be overvoltage and overcurrent caused by sudden changes in current and voltage caused by jumping bows. For example, the fluctuation of the pantograph and catenary will cause jumping bows. Make the network voltage and intermediate voltage change suddenly, and once the jumping bow is restored, there will be a certain voltage difference between the network voltage and the intermediate voltage, resulting in an excessive current change rate di / dt, which passes through the line reactor in the circuit (L) After freewheeling, an instantaneous induction voltage will be generated, which will cause intermediate voltage overvoltage protection, or the inverter current will overcurrent due to the instantaneous increase of intermediate voltage, and overvoltage and overcurrent will cause VVVF to trip the high-speed circuit breaker device, so that the train has no power, affecting the normal operation of the train

[0004] The above-mentioned VVVF main circuit adopts line reactors and filter capacitors, which can only suppress sudden changes in voltage and current under normal conditions, and realize overvoltage control based on the threshold judgment of the intermediate voltage. Due to the limitation of chopping bandwidth and chopping frequency, etc., when chopping is turned on , when the intermediate voltage is greater than a certain value, the chopper is controlled to be turned on, and the energy cannot be absorbed quickly when an overvoltage occurs, so it is only suitable for controlling the problem that the intermediate voltage is too high during braking or traction under normal circumstances. For such The overvoltage caused by di / dt current mutation and du / dt voltage mutation caused by jumping bow can not be well suppressed, so that there will be fault protections such as overvoltage and inverter overcurrent.

Some practitioners have proposed to reduce the du / dt and di / dt of power devices by using an overlapping motherboard structure, but it is only suitable for controlling the sudden changes in the voltage and current of the power device itself, and it is still impossible to avoid the above-mentioned current and voltage caused by jumping bows. Overvoltage and overcurrent problems caused by sudden changes

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