UPS power supply can be divided into two categories based on its working mode: backup and online, with two types of output waveforms: square wave output and sine wave output. When the backup type U source is powered normally by the mains power, the mains power directly provides power to the load through the AC bypass channel and then through the conversion switch, and the inverter inside the machine is in a stopped working state. This UPS power supply is essentially equivalent to a commercial voltage regulator with extremely poor voltage stability. In addition to improving the amplitude fluctuation of the mains voltage, it has basically no adverse effects on the frequency instability, waveform distortion, and interference from the power grid. When the mains power supply is interrupted or below 170V, the battery only supplies power to the inverter and provides stable and frequency stable AC power to the load. The advantages of backup UPS power supply are high operating efficiency, low noise, and relatively cheap price. It is mainly suitable for situations where there is little fluctuation in the power supply and there is no high demand for power quality. When the power supply is normal, the online UPS power supply first converts the AC power supply of the power supply into a DC power supply, then performs pulse modulation and filtering, and then converts the DC power supply back into an AC power supply. After rectification, the AC power supply is provided to the load through an inverter. Once the mains power is interrupted, the battery will provide AC power to the load through an inverter. Therefore, for online UPS power supply, under normal circumstances, regardless of the presence or absence of mains power, it is always powered by the inverter of the UPS power supply to the load, thus avoiding all impacts caused by voltage fluctuations and interference in the mains power grid. It is obvious that the power supply quality of online UPS power supply is significantly superior to backup UPS power supply, as it can achieve stable frequency and voltage supply to the load. Moreover, when switching from mains power supply to battery power supply, the conversion time is zero wave output. The load capacity difference of UPS power supply is only 4060% of the rated load, and it cannot be charged with inductive loads. If the load carried is too large, the third harmonic component contained in the square wave transmission voltage will increase the capacitive current flowing into the load, and in severe cases, it will damage the power filter capacitor of the load. The relationship between the distortion of the sine wave voltage waveform and the load is not as obvious as that of the square wave output UPS power supply. The load capacity is relatively strong and can carry micro inductive loads. When UPS power supplies of different types are in the inverter power supply state, unless absolutely necessary, they are generally not allowed to operate at full load or overload, otherwise it will significantly increase the number of UPS power supply faults.