Application of ups in urban rail transit (2)

Power supply mode of redundant backup

The ups of rail transit electromechanical system works in redundant backup mode. From the perspective of redundancy configuration scheme, there are the following modes: master-slave hot standby power supply mode; direct parallel redundant power supply mode.

Master slave hot backup power supply mode

The hot standby redundancy mode is two UPS series switching. During normal operation, only the main UPS supplies power to the critical load, while the other UPS is in no-load state. If the main UPS fails to operate, it will switch to the bypass, and the standby ups will automatically take over after about 2-8 Ms. This structure is economical in price, but there are many single points of failure. If the main UPS fails, the other one must take over the whole load, which means that the other must increase the power supply from 0 to 100% within about 8 ms. the defect of this method is that the standby UPS is in no-load state for a long time, its battery life will be shortened and its capacity will be reduced, and the standby UPS must have step load carrying capacity without capacity expansion. Because it is very difficult for people to know whether there are faults or hidden dangers in each part of the standby UPS in real time, when the standby machine is to be started, it may not work normally.

Direct parallel redundant power supply mode

N + 1 type UPS redundant parallel power supply scheme is to ensure that the output voltage amplitude of each single UPS is the same, and the output frequency and phase are the same, the output terminals of N + 1 ups with the same output power are connected in parallel to supply power to the load with output power of n single ups. In normal operation, N + 1 UPS share the load current averagely. When a UPS fails, the remaining N ups will continue to supply power while automatically offline under the control of parallel control signal.

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