1) Normal operating mode

The power supply principle of the uninterruptible power supply system is that when the mains power is normal, the machine will convert the AC power of the mains power into DC power, and then charge the battery for use in case of power interruption; What I want to emphasize here is that the uninterruptible power system does not only operate when there is a power outage. For example, when the voltage is too low or too high, or when there is a sudden surge that can affect the power quality of the equipment's normal operation, the uninterruptible power system will operate to provide stable and clean power to the equipment. When the mains power is supplied normally, after passing through the filtering circuit, it is divided into two circuits that operate simultaneously. One is to charge the battery pack through the charging circuit, and the other is to use the rectifier circuit as the input of the inverter, and then provide power to the load through the inverter's conversion; From this, 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, its output is stable and not affected in any way.

2) Battery working mode

Once there is an abnormality in the mains power supply, 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 to the load for continued use, achieving the function of uninterrupted power supply. The power source of UPS uninterruptible power supply system is the battery, and the capacity of the battery is limited. Therefore, the uninterruptible power supply system will not have unlimited supply like the mains power. Therefore, no matter how large the capacity of the uninterruptible power supply system is, its power supply time will be limited when it is fully loaded. To extend the discharge time, it is necessary to purchase a long-term uninterruptible power supply system.

3) Bypass operation mode

When the online UPS is overloaded, the bypass command (manual or automatic), the inverter overheats, or the machine fails, the UPS generally converts the inverter output to a bypass output, that is, directly supplied by the mains power. Due to the need for the UPS output frequency phase to be the same as the mains frequency phase during bypass, phase-locked synchronization technology is used to ensure that the UPS output is synchronized with the mains. The bidirectional thyristor parallel working mode of the bypass switch solves the problem of bypass switching time and truly achieves uninterrupted switching. The control circuit is complex and is generally used in medium to high power UPS. If the load must be manually reduced during overload, otherwise the bypass circuit breaker will automatically cut off the output.

4) Bypass maintenance method

When the UPS is undergoing maintenance, the normal power supply to the load equipment is ensured through manual bypass. After the maintenance operation is completed, the UPS is restarted and returns to normal operation. Extremely low maintenance rate, MTTR of 150000 hours, greatly improving the availability of UPS uninterruptible power supply.

From an application perspective, the changes in UPS functionality have gone through three stages. The first stage is hardware protection, which protects the hardware system of the load device from damage due to abnormal power or sudden power interruption; The second stage is data protection, which protects the data of load devices from being damaged or lost due to sudden power outages when the mains power is interrupted; The third stage is system availability protection, which ensures high-quality power supply to critical loads in the event of normal, abnormal, or even interrupted mains power. The changes in these three stages are all driven by the continuous increase in demand for production systems due to social development and technological progress. The first stage was highlighted in the 1970s and 1980s, shortly after the birth of UPS. The second stage was prevalent in the mid-1990s, and the third stage became increasingly important from the late 1990s. Even today, system availability remains one of the most important indicators required for UPS power supply systems in data centers, factories, hospitals, rail transit and other electric fields.