The Development Of The AC Power Redundancy Switching Device

With the development of the economy, requirements of sustainable and reliable power supplies become more and more important. There are usually two independent power supplies to ensure the normal operation of some important electric equipment, one of which is a frequently-used power supply, and the other is a stand-by power. The switch of the two power supplies is carried out by an AC power redundancy switching device.Based on the investigation of the domestic and foreign AC power redundancy switching device, this article compares the common dual power supply switching scheme and analyses common types and detection methods of power quality. In view of the faults existing in present redundancy switching device, such as not very high electrical energy detection accuracy, not very fast switching speed, and the poor switching device reliability, we develop a high accuracy and high reliability AC power redundancy switching device based on DSP platform using electromagnetic relay. Aiming at improving the accuracy of power detection, the paper designs voltage sampling circuits based on Hall voltage sensors as well as current transformation circuits based on the true RMS convention by the log and anti-log electronic circuits. We use the half wave RMS detection algorithm to detect power quality, and furthermore, rectify it on the occasion of even harmonic interference. By using this method, the accuracy of power quality detection has been highly improved, which provides accurate basis for switching action. In order to speeding up switching action, this paper designs accelerating circuits to speed up the electromagnetic relay switching rather than adopting SCR commonly used in STS device based on reliability consideration and at the same time puts forward some methods to prolong the life of the relays. To improve reliability of the device, redundant circuits with reducing complexity are applied in the design. Meanwhile, the break-before-switch operating mode of the switches has also greatly raised the reliability.Finally, a prototype system of the AC power redundancy switching device has been developed which realized fast switching between dual power supplies. The tests have shown that the AC power redundancy switching device has fast switching speed, and high reliability, which realized the design requirements.