Analysis of four working methods of UPS power supply

UPS is a constant voltage and constant frequency uninterruptible power supply with the energy storage device and inverter as the main component. Its main function is to supply power to electronic equipment reliably and uninterruptedly through the UPS system. Depending on the usage, the UPS can be converted into four different modes of operation: normal operation, battery operation, bypass operation, and bypass maintenance.

1. Normal operation mode

The power supply principle of the uninterruptible power system is that when the mains is normal, the machine will convert the alternating current of the mains into direct current, and then charge the battery for use when the power is interrupted; here I emphasize that the uninterruptible power system is not only when the power is cut off. When the voltage is too low or too high, instantaneous surge, etc., which is enough to affect the power quality of the normal operation of the equipment, the uninterruptible power supply system will operate to provide stable and clean power for the equipment.

When the main supply is normally supplied, the mains is divided into two loops to act simultaneously after the filter circuit. One is to charge the battery pack through the charging circuit, and the other is to pass through the rectifier circuit as the input of the inverter, and then pass through the rectifier circuit. The conversion of the inverter provides power to the load; it can be seen that the output of the online uninterruptible power system is completely supplied by the inverter, so regardless of the quality of the mains power, the output is stable and not affected.

2. How the battery works

Once the mains is abnormal, the DC power stored in the battery is converted into AC power. At this time, the input of the inverter is supplied by the battery pack, and the inverter continues to provide power for the load to continue to use, so as to achieve the function of uninterrupted power supply. The power source of the uninterruptible power system is the battery, and the capacity of the battery is limited, so the uninterruptible power system will not supply unlimited power like the mains. The power supply time must be limited. To prolong the discharge time, a long-term UPS must be purchased.

3. Bypass operation mode

When the online UPS is overloaded, the bypass command (manual or automatic), the inverter is overheated or the machine is faulty, the UPS generally converts the inverter output to the bypass output, that is, directly powered by the mains. Since the phase of the output frequency of the UPS needs to be the same as the phase of the mains frequency during bypass, the phase-locked synchronization technology is adopted to ensure that the UPS output is synchronized with the mains. The bypass switch bidirectional thyristor works in parallel, which solves the problem of bypass switching time, truly achieves uninterrupted switching, and the control circuit is complex. It is generally used in medium and high-power UPS. If it is overloaded, the load must be artificially reduced, otherwise, the bypass circuit breaker will automatically cut off the output.

4. Bypass maintenance method

When the UPS is being repaired, the normal power supply of the load equipment is ensured by manual bypass. When the maintenance operation is completed, the UPS is restarted and the UPS is turned into a normal operation. Extremely low maintenance rate, MTTR of 150,000 hours, greatly improves UPS availability.