UPS uninterruptible power supply technology explanation

When there is mains power, the mains power charges the battery and the load is powered by the mains power; After power failure, the energy stored in the battery is supplied to the load through the inverter.   
When the mains power input is normal, the UPS uninterruptible power supply does not do any processing and directly delivers the mains power to the user's equipment for use, while the charger (charging circuit) charges the battery. When the mains power is cut off, the backup UPS power supply will switch to the battery inverter state, and the battery will provide backup energy to continue supplying power to the load. Due to the backup working mode of the inverter, the backup UPS power supply has no purification function for the mains power, and the output voltage stabilization characteristics are poor, mostly using quasi square wave output. Moreover, the backup UPS power supply will have a conversion time of about a few milliseconds when switching from mains power to battery inverter operation, which is not suitable for some situations where switching time is not allowed. The advantages are cheap price and simple structure. Its capacity range is generally small, mostly below 1kVA. Due to its ability to handle power outages, it is only suitable for relatively simple and less important environments, such as office or home PCs, and unimportant online terminals.   
    
2. Online interactive: Online interactive UPS power supplies are generally equipped with AC voltage regulation circuits that use transformer tap voltage regulation in the AC path. The charger and inverter are integrated without rectification, and the output voltage is adjusted in segments, working in backup mode. When the input transformer tap changes, the power unit works as an inverter for a period of time to compensate for the interruption of output power supply during the relay jump process. When the input mains power is normal, the AC voltage regulator circuit with tap voltage regulation provides the output voltage.   
    
The UPS inverter is in reverse operation to charge the battery pack. When the mains power is abnormal, the inverter is put into reverse operation to convert the battery pack voltage into AC power output. Therefore, the online interactive UPS power supply has poor purification ability for the power grid, and there is intermittent time for battery switching during power failure. The current online interactive products are equipped with simple EMI filters at the input end, which have a certain suppression effect on electromagnetic interference. Due to the presence of an output voltage regulator, it can solve problems such as surges and voltage fluctuations in the mains power grid, but is powerless to address issues such as frequency instability, waveform distortion, and high voltage spikes that may occur in the grid. The advantages are high operating efficiency, compact structure, low cost, and can adapt to most situations where power outage requirements are not very strict, but it is not suitable for large data network centers and other critical power consumption areas. At present, the market products are mostly below 5kVA.   
There is currently a three port UPS technology on the market, which has a basic structure similar to online interactive systems. The inverter is responsible for output voltage regulation, charging, and inversion functions.   
The disadvantages of the three port technology are similar to those of online interaction, such as poor purification ability of the mains power, existence of switching time, inability to completely solve power quality problems, poor stability of working with diesel engines, and narrow input range of mains power. The advantages are compact structure, strong resistance to impact surges, high efficiency at rated voltage, and relatively low price.