What is an uninterruptible power supply

UPS Definition

It is a kind of energy storage device, with rectifier and inverter as the main components, which provides constant voltage and constant frequency uninterruptible power supply for the load in the substation.

UPS Structure

The UPS system in the substation is generally composed of three parts: the main engine, the bypass voltage stabilizing cabinet, and the output feeder cabinet (small power can also be three-in-one), as the picture shows

Rectifier:

- Convert alternating current (AC) into direct current (DC), which is filtered and supplied to the inverter

-Provide charging voltage to the battery and act as a charger

Inverter:

Convert direct current (DC) to alternating current (AC) for load use

Battery:

UPS is used as a device for storing electrical energy, so that when the mains power fails, it can invert the DC power and provide uninterrupted power for the load. Its capacity determines its maintenance discharge (power supply) time

Static switch:

Also known as a static switch, it is an AC switch composed of two thyristors (SCR) connected in reverse parallel, and its closing and opening are controlled by a logic controller.

Isolation transformers, voltage regulators:

In the input or output part, the AC and DC are isolated, and the voltage stabilizer has the function of stabilizing the voltage in addition to isolation

UPS classification

1. Backup type
   With automatic voltage regulation, power failure protection and other functions, the conversion time is about 10ms

2. Interactive
   With filtering function, strong ability to resist mains interference, conversion time is less than 4ms

3. Online

The structure is relatively complex, the performance is perfect, and it can solve power problems such as spikes, surges, and frequency drift

UPS function

1. As the AC power supply of important equipment, it can prevent the sudden power failure of the mains from affecting the work and causing harm to the equipment

2. Eliminate "power pollution" such as power surges in the mains, instantaneous high/low voltage, wire noise and frequency deviation, improve power quality, and provide high-quality power for computers, etc.

UPS operating mode

1. Normal operation mode
   Under normal AC power supply, the rectifier converts AC to DC, eliminates "power pollution" in the mains, and simultaneously charges the battery. It is then supplied to the inverter to convert the DC power into AC power to provide a more stable power supply to the load. as the picture shows
   

2. Blackout mode
   When the AC power supply is abnormal or the rectifier or reactor fails, the battery pack will provide DC power to the inverter, so that the AC output will not be interrupted, thereby achieving the function of protecting the load. as the picture shows
   

3. Backup power mode
   When the inverter has abnormal conditions such as inverter fuse blown, short circuit and other faults, the inverter will automatically cut off to prevent damage. If the bypass AC power supply is normal at this time, the static switch will transfer the power supply to the bypass backup The power output is used by the load. as the picture shows
   

4. Maintenance bypass mode

When the UPS needs to be repaired or replaced and the load power supply cannot be interrupted, the inverter switch can be cut off first, then the maintenance bypass switch can be activated, and then the rectifier and bypass switch can be cut off. The AC power supply continues to supply AC power to the load through the maintenance bypass switch. At this time, maintenance personnel can safely maintain the UPS. as the picture shows