In the case of frequent fluctuations or occurrences of power supply, UPS systems may be necessary, because they can provide backup power circuits, and maintain important system operation when the power supply is cut off. In the case of voltage interruption due to transient fluctuation fire, UPS can maintain constant power to maintain load operation. In case of electrical failure, it will activate standby power supply to maintain system operation until it can be safely shut down. In addition, HIA of these UPS systems can reduce the risk of harmonic interruption and line transient.