External Power voltages are provided in sinusoidal waveforms to indoors of, for example, homes and factories. In places such as factories where the consequential loss due to power failure might be great, they may be equipped with uninterruptable power supply (UPS) in anticipation of unexpected power failures so that they can use the energy storage device instead when the power does not become available from the electric power grid. UPS can provide AC electricity in the event external electric power supply from the grid has failed, but supply of sinusoidal AC electricity that is not synchronized in phase can cause damages or fire to high precision equipment and instruments. Therefore, it needs to be known at what phase the AC power supply from the grid has failed in order to synchronize the phase of the replacement AC electricity. An UPS recreates the AC voltage magnitude and the phase, which correspond to those of the power from the grid at the time of the power failure, so that it can avoid damaging equipment.
In general, PID control sensors are used for AC voltage synchronization, or analog to digital converters (ADC) are used to perform the synchronization by converting the grid power electricity and predicting ahead.
A PID control sensor measures two values, passes through the controller based on the difference of the two values, and calculates the next responsive operation. A PID control sensor is highly complex, and resulting value of the PID control sensor is based on the measured value of the ADC, but since the error in the measured value of ADC cannot be ignored, PID has a shortfall of providing lower results for the cost of providing a PID.