Uninterruptible Power Supply (UPS)

High-frequency uninterruptible power supply is an important device used to protect electronic equipment from power failures. It provides stable power to ensure that the equipment continues to operate normally during power outages or power fluctuations. It is widely used in various fields, including data centers, medical facilities, communication base stations, industrial automation, and office environments. They protect important electronic equipment such as key equipment, servers, network equipment, and telecommunication systems from damage caused by power failures.

Compared with traditional low-frequency UPS, high-frequency UPS uses a higher operating frequency, usually above 10kHz. This high-frequency technology makes UPS more compact and efficient, and provides faster response time and better power quality.

A. Basic working principle of high-frequency uninterruptible power supply (UPS):

1. Rectification and inversion process:

High-frequency uninterruptible power supply (UPS) first converts the input AC power into DC power through a rectifier. This process uses semiconductor rectifier devices, such as diodes or thyristors, to rectify the sine wave of the AC power supply to obtain a relatively stable DC voltage. For example, in a common three-phase input high-frequency uninterruptible power supply (UPS), after the three-phase AC passes through the rectifier bridge, it will output a DC bus voltage, which is generally around 380V400V.

Then, the inverter converts the DC power into AC power and outputs it to the load. The inverter uses high-frequency switching technology to switch the DC voltage at a very high frequency (usually 10kHz100kHz or even higher) by controlling the on and off of the power switch tube (such as the IGBT module), thereby synthesizing an AC power that is close to a sine wave. This high-frequency switching enables the inverter to more accurately control the amplitude, frequency and phase of the output voltage to meet the load's demand for high-quality electricity. For example, for some sophisticated electronic equipment, such as servers, communication base station equipment, etc., the total harmonic distortion (THD) of the output voltage is required to be very low. The inverter of the high-frequency uninterruptible power supply (UPS) can control the THD within 3% through high-frequency switching control, which is much lower than the harmonic distortion level of the traditional power frequency uninterruptible power supply (UPS).

2. Energy storage and energy conversion:

High-frequency uninterruptible power supplies (UPS) are usually equipped with battery packs as energy storage units. When the mains power is normal, the rectifier will charge the battery pack while supplying power to the load, storing the electrical energy in the form of chemical energy. For example, in the high-frequency uninterruptible power supply (UPS) using lead-acid batteries, during the charging process, the battery gradually stores electrical energy by controlling the charging current and voltage. The charging voltage is generally around 2.3V2.4V per cell (taking a 12V battery as an example, it consists of 6 cells).

Once the mains power is interrupted, the battery pack immediately discharges to provide DC power to the inverter, which then converts it into AC power to continue to power the load. This energy conversion process ensures that the load will not experience power outages during a mains power failure, ensuring the continuous operation of key equipment. Taking the data center as an example, if the city power is cut off, the battery pack of the high-frequency uninterruptible power supply (UPS) can maintain the normal operation of servers and other equipment in a short time (generally designed to be 1015 minutes, which can be extended according to demand), avoiding data loss and business interruption, and also buying time for the subsequent backup generator to start and connect to the power supply system.

B. Advantages of high-frequency uninterruptible power supply (UPS) compared to industrial frequency uninterruptible power supply (UPS):

1. Volume and weight advantages:

The volume and weight of the transformer of the high-frequency uninterruptible power supply (UPS) are greatly reduced due to the use of high-frequency switching technology and high-frequency transformers (compared with the industrial frequency transformer of the industrial frequency uninterruptible power supply (UPS)). For example, for an uninterruptible power supply (UPS) with the same power of 100kVA, the transformer of the industrial frequency uninterruptible power supply (UPS) may weigh hundreds of kilograms and be bulky, while the high-frequency transformer of the high-frequency uninterruptible power supply (UPS) may weigh only tens of kilograms, and the volume is also much smaller accordingly. This makes the high-frequency uninterruptible power supply (UPS) have obvious advantages in places with limited installation space, such as some small computer rooms or distributed base stations, and is easier to install and layout.

The overall structure of a high-frequency uninterruptible power supply (UPS) is more compact, and its internal electronic components can use smaller and more integrated devices due to the high-frequency design. This not only reduces the physical volume of the equipment, but also reduces transportation costs and installation difficulties, and improves installation flexibility. For example, in some floor distribution rooms, the space is relatively cramped, and the high-frequency uninterruptible power supply (UPS) can be placed more conveniently without occupying too much space, leaving enough space for other power equipment.

2. Efficiency and energy-saving characteristics:

The efficiency of a high-frequency uninterruptible power supply (UPS) is relatively high during normal operation. Due to the low conduction loss and fast switching characteristics of its high-frequency switching devices, its efficiency can reach more than 95% in the mains power supply mode, while the efficiency of the power frequency uninterruptible power supply (UPS) is generally around 90%. For example, in a data center with a load power of 50kW, if a high-frequency uninterruptible power supply (UPS) is used, a large amount of power consumption can be saved every year compared to the power frequency uninterruptible power supply (UPS).

Under light load conditions, the efficiency advantage of a high-frequency uninterruptible power supply (UPS) is more obvious. When the load rate is lower than 50%, the high-frequency uninterruptible power supply (UPS) can still maintain a high efficiency, while the efficiency of the industrial frequency uninterruptible power supply (UPS) will drop significantly as the load rate decreases. For some application scenarios with large load fluctuations, such as power supply for office equipment in commercial office buildings, the high-frequency uninterruptible power supply (UPS) can better adapt to different load levels, reduce energy waste, and meet the requirements of modern energy conservation.

3. Improvement of input power factor and harmonic distortion:

The input power factor of the high-frequency uninterruptible power supply (UPS) is usually high, which can reach 0.99 or even higher. This is due to the active power factor correction (PFC) technology it adopts, which can make the input current and input voltage in phase, reduce the reactive power demand on the power grid, and improve the power supply quality of the power grid. For example, in an industrial production workshop, when multiple high-frequency uninterruptible power supply (UPS) devices are connected to the power grid, due to their high power factor, they will not cause voltage fluctuations, flicker and other adverse effects on other electrical equipment in the workshop, ensuring the stable operation of the entire power grid system.

High-frequency uninterruptible power supply (UPS) also has excellent control over input current harmonic distortion. By adopting advanced filtering technology and high-frequency switching control strategy, its input current harmonic distortion can be controlled at a low level, which can generally meet the strict requirements of international standards (such as IEEE519 standard) for harmonic distortion. This can effectively avoid the interference of harmonic pollution on other sensitive equipment for some places with high requirements on power grid quality, such as hospitals and communication hubs, and ensure the electromagnetic compatibility of the entire power system.

C. Application scenarios and selection points of high-frequency uninterruptible power supply (UPS):

1. Data center and communication base station:

In data center, a large number of servers, storage devices, etc. have extremely high requirements on the stability and quality of power supply. High-frequency uninterruptible power supply (UPS) can provide reliable uninterruptible power supply for data center to prevent serious consequences such as data loss and system crash caused by power failure. For example, in large cloud data centers, hundreds or even thousands of servers need continuous and stable power supply. High-frequency uninterruptible power supply (UPS) can work with backup power supply systems such as diesel generators to ensure that the normal operation of the data center can be maintained under any circumstances.

Communication base stations are also important application sites for high-frequency uninterruptible power supplies (UPS). Communication equipment in base stations needs to run 24 hours a day to ensure the smooth operation of the communication network. High-frequency uninterruptible power supplies (UPS) can provide power to base station equipment in time when the city power is cut off. At the same time, its good input power factor and harmonic distortion characteristics also meet the strict requirements of the communication industry for the quality of the power grid, avoiding interference with communication signals. For example, in communication base stations in mountainous areas, the city power supply may be unstable. High-frequency uninterruptible power supplies (UPS) combined with renewable energy such as solar power generation systems can build a stable and reliable hybrid power supply system to ensure the normal operation of base stations.

2. Industrial automation and medical equipment:

In the field of industrial automation, various automation equipment and control systems on the production line do not allow power interruptions. High-frequency uninterruptible power supplies (UPS) can provide uninterruptible power for industrial robots, PLC control systems, automated testing equipment, etc. For example, in automobile manufacturing production lines, welding robots, assembly robots and other equipment may cause product quality problems or even damage the equipment if they suddenly lose power. High-frequency uninterruptible power supplies (UPS) can ensure that these devices can still operate normally for a period of time when the mains fails, so as to carry out orderly shutdown operations or switch to backup power.

Medical equipment has equally strict requirements on power supply. CT scanners, magnetic resonance imaging devices, life monitoring equipment, etc. in hospitals all require stable and reliable power. High-frequency uninterruptible power supplies (UPS) can ensure that these medical devices can operate normally when the mains fluctuates or fails, avoiding power problems that affect the diagnosis and treatment of patients. For example, in the operating room, the life support system relies on high-frequency uninterruptible power supplies (UPS) to continue to operate when the mains fails, providing protection for the patient's life safety. When selecting, for data centers and communication base stations, it is necessary to select a high-frequency uninterruptible power supply (UPS) of appropriate capacity based on the total load power and backup time requirements of the equipment. For example, if the total load of the data center is 200kW and the backup time is required to be 30 minutes, it is necessary to select a high-frequency uninterruptible power supply (UPS) model that can meet this power and time requirement, and consider its redundant configuration, such as using N+1 or 2N redundant systems to improve the reliability of power supply.

For industrial automation and medical equipment, in addition to considering power and backup time, it is also necessary to pay attention to the output voltage quality and dynamic response characteristics of the uninterruptible power supply (UPS). For example, some sophisticated medical equipment may require the output voltage transient response time of the uninterruptible power supply (UPS) to be very short, within a few milliseconds, to ensure the normal operation of the equipment, so when selecting, it is necessary to select a high-frequency uninterruptible power supply (UPS) product with fast dynamic response capabilities.

High-frequency uninterruptible power supply (UPS) has become an indispensable and important part of the modern power security system due to its unique working principle, obvious advantages over industrial frequency uninterruptible power supply (UPS), and outstanding performance in many key application scenarios. Understanding its principles, advantages and selection points is of great significance to ensure the stable operation of various key equipment and the reliability of power supply.