Combined start-stop device and control method for emergency direct current lubricating oil pump of steam turbine

Abstract

The present disclosure provides a composite start-stop device and a control method for a critical DC lubricating oil pump of a steam turbine, comprising a main contact module, a buck circuit and a current limiting module connected in sequence, and the main contact module is configured to cut off or connect two DC The buck circuit includes three parts, the first part is the parallel structure of the DC contactor and the power electronic switch, and the parallel structure is connected to a certain DC bus, and the second part is the fuse and the power electronic switch. Freewheeling diode series structure, the series structure is located on one side of the parallel structure, and is connected between two DC bus bars; the third part is the bus capacitor, which is arranged on the other side of the parallel structure and connected to the Between two DC buses; the current limiting module is set on one of the DC buses to limit the current for the load to be connected. The present disclosure not only has the advantages of smooth start-stop of the buck conversion DC motor start-stop device, but also greatly improves the anti-overload capability of the IGBT and the freewheeling diode.

Description

technical field [0001] The disclosure relates to a composite start-stop device and a control method of a steam turbine emergency direct current lubricating oil pump. Background technique [0002] The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art. [0003] The steam turbine unit of the power plant is designed with a complete lubricating oil system. When the plant AC or AC oil pump fails, the plant DC power supply system will drive the critical DC lubricating oil pump to run to maintain the oil pressure of the lubricating oil system to prevent the turbine from burning out. ACCIDENT. [0004] As the last emergency oil supply equipment for steam turbine bearings, the reliable start and stop of the DC lubricating oil pump is extremely important in the crisis of power supply from the battery pack. Due to the existence of the DC motor commutator, the failure rate of the DC motor itself...

AI Technical Summary

Problems solved by technology

However, power electronic components (whether it is IGBT or freewheeling diode) have limited resistance to voltage / current overload, and are prone to short-circuit faults due to overvoltage or overcurrent (most high-power power electronic devices fail with internal poles) Two serious problems can be derived from this: first, if the freewheeling diode is short-circuited, the entire DC power supply circuit will be short-circuited, which will lead to tripping and power failure, which will lead to oil-burning accidents in steam turbine bearings ; Second, when the IGBT is short-circuited, the DC oil pump will be hard-started, and the DC motor cannot be shut down

This solution still has the following problems: First, if the BUCK conversion fails and causes the circuit fuse to blow, the parallel resistive motor start-stop device will start automatically and immediately. The delay in this process is generally at least a few hundred milliseconds. For the lubricating oil system of the steam turbine (such as Westinghouse), the delay is still too long; second, if the BUCK conversion fails and does not cause the circuit fuse to blow, the DC motor will be directly hard-started. At this time, the parallel resistive start The input of the stop device has lost its meaning, and in this case, it often leads to the failure of the two parallel start-stop devices to power off normally

In addition, this solution does not improve the power electronic switch is relatively fragile, easy to burn short circuit problems due to overvoltage or overcurrent

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