Digital Signal Controller Based Automatic Transfer Switch

摘要

An automatic transfer switch (ATS) enables backup generators, DC to AC inverters,redundant UPS or other AC power sources to be used for a single load. An ATS is recommendedwhen no downtime from a power outage can be tolerated. Traditionally, an ATS used a hardwarezero cross detector coupled with a microcontroller to achieve synchronization between powersources. While this approach works when the power is clean, the presence of noise andharmonics in the power sources can trigger spurious zero cross detection. This leads to impropersynchronization resulting in a phase discontinuous transfer. The large loop currents that circulatecan destroy not only the ATS but also expensive equipment.This paper will explore notch filtering and correlation based techniques and the merits ofimplementing it in low cost Digital Signal Controllers (DSC) that will enable seamless transferbetween power sources. Such techniques were not possible to implement in low costmicrocontrollers as they are not designed to execute numeric intensive algorithms. Furthermore,with DSCs a hardware zero cross detector is not required. A DSC based solution improvesreliability, functionality, maintainability and fault tolerance while reducing system cost.