UPS technology and its development trends

    Abstract: This article introduces the working principle, purchase method and maintenance technology of USB, and explains the development trend of UPS, which has strong practicality.

    Keywords: UPS purchase and maintenance development trends

Computers have been widely used in all walks of life. As an important factor directly related to the safe operation of computer software and hardware, the reliability of power quality should be the primary consideration for small and medium-sized enterprises. UPS (Uninterruptable Power System), which appeared with the birth of computers, has now been accepted by the majority of computer users. UPS is mainly used to provide uninterrupted power supply to a single computer, computer network system or other power electronic equipment. At present, UPS is being widely used in computers, transportation, banking, securities, communications, medical, industrial control and other industries.

1 How UPS works

UPS is a power protection device that contains an energy storage device, uses an inverter as the main component, and stabilizes voltage and frequency output. When the mains power is input normally, the UPS stabilizes the mains power and supplies it to the load. At the same time, it charges the battery inside the machine and stores the energy in the battery. When the mains power is interrupted (accidental power outage) or the input fails, the UPS will supply the power to the load. The energy of the battery is converted into 220V AC and continues to be used by the load, allowing the load to maintain normal operation and protect the load software and hardware from damage.

Currently, there are many types of UPS power equipment on the market, with output power ranging from 500VA to 3000kVA. UPS can be divided into three categories according to the working mode: backup type, online type and online interactive type. According to its output waveform, it can be divided into square wave output and sine wave output.

1.1 Backup UPS power supply

When the mains power supply is normal, the mains power supplies power directly to the load through the AC bypass channel and the transfer switch. The inverter in the machine is in a stopped working state. At this time, the UPS power supply is essentially equivalent to a poor-performance UPS. Mains voltage regulator. In addition to improving the amplitude fluctuation of the mains voltage, it basically does not improve the adverse effects such as voltage instability, waveform distortion, and interference from the power grid. Only when the mains power supply is interrupted or lower than 170V, the battery will supply power to the UPS inverter and provide stable voltage and frequency square wave AC power to the load.

1.2 Online UPS power supply

When the city power supply is normal, it first rectifies the city AC power into DC power, then performs pulse width modulation and filtering, and then converts the DC power back into sine wave AC power through the inverter to supply power to the load. Once the mains power is interrupted, the DC power provided by the battery is immediately replaced to provide sine wave AC power to the load through the inverter. Therefore, for online UPS power supply, under normal circumstances, regardless of whether there is mains power, the inverter of the UPS power supply supplies power to the load, thus avoiding all voltage fluctuations and interference caused by the mains power grid. coming impact. Obviously, the power supply quality of online UPS power supply is significantly better than that of backup UPS power supply. Because it can achieve stable frequency and voltage supply to the load, and when switching from mains power supply to battery power supply, the conversion time is zero. It truly provides users with high-quality pure sine wave power supply with stable voltage and frequency, thereby providing power protection that meets the needs of network systems.

1.2 Online interactive UPS power supply

When the mains power supply is normal, it first rectifies the mains AC power into DC power, then performs pulse width modulation and filtering, and then converts the DC power back into sine wave AC power through the inverter to supply power to the load. Once the mains power is interrupted, the DC power provided by the storage battery is immediately replaced to provide sine wave AC power to the load through the inverter. Therefore, for online UPS power supply, under normal circumstances, regardless of whether there is mains power, the inverter of the UPS power supply supplies power to the load, thus avoiding all voltage fluctuations and interference caused by the mains power grid. coming impact. Obviously, the power supply quality of online UPS power supply is significantly better than that of backup UPS power supply. Because it can achieve stable frequency and voltage supply to the load, and when switching from mains power supply to battery power supply, the conversion time is zero. It truly provides users with high-quality pure sine wave power supply with stable voltage and frequency, thereby providing power protection that meets the needs of network systems.

1.2 Online interactive UPS power supply

Online interactive UPS power supply is also called 3-port UPS power supply and uses a power frequency transformer. From the perspective of energy transfer, the transformer has three ports for energy flow: Port 1 is connected to the mains input; Port 2 is connected to the battery through a bidirectional converter; Port 3 is the output. When the mains power is supplied, the alternating current flows into the transformer through port 1. Under the control of the voltage stabilizing circuit, the appropriate transformer tap is selected and connected. At the same time, under the action of the bidirectional converter at port 2, the output voltage at port 3 is jointly adjusted with the help of the energy conversion of the battery. , in order to achieve better voltage stabilization effect. When the mains power fails, the battery supplies power to the transformer through port 2 through the bidirectional converter to maintain the AC output on port 3. In the process of transformer tap switching of the online interactive UPS power supply, the bidirectional converter works as an inverter. It is powered by the battery, so it can achieve uninterrupted output voltage, and there can also be no conversion time during the switching process from mains power supply to battery power supply. The online interactive UPS battery circuit is simple to implement and does not require a separate charger, which reduces production costs and improves reliability. This type of product does not have AC/DC or DC/AC conversion when working on mains power supply, which improves the efficiency of the whole machine. Online interactive UPS combines many advantages of backup UPS and online UPS, and is a very good form of transformation. However, since it uses a power frequency transformer, it also has problems of being bulky and large in size.

2. Selection of UPS

A UPS can be used for at least 3 years. When selecting a UPS power supply, users should determine the selection criteria based on their own requirements and choose the UPS that best suits their business needs, not the cheapest or the highest grade. Before purchasing a UPS, users should comprehensively consider factors such as the importance of the data processed by the load equipment, the power quality requirements of various electrical equipment, installation and space requirements, and economic budget. In addition, whether the weight and size of the UPS are appropriate are also key issues we should pay attention to when purchasing.

Next, users should understand the capacity of the UPS required and consider the total capacity when expanding the equipment in the future. Choosing reputable brands and manufacturers is also essential. Of course, when purchasing a UPS, you should also pay attention to its output power, length of power supply, output voltage waveform, instantaneous response characteristics, output frequency stability, waveform distortion coefficient, output voltage stability, safety performance, maintainability performance, price, etc. question. In short, users should choose appropriate UPS products based on their business needs and consider three aspects: technical performance, service guarantee and product price.

Network users can consider choosing online interactive UPS power supply. There are many types of online interactive UPS, but the quality varies. When purchasing, you must look for a good brand.

Computing centers and network management centers that have high requirements on power supply quality (such as banks, securities, air traffic control centers), etc., often need to use the following redundant power supply systems with "fault tolerance" function to ensure the safety of power supply to the load. .

Host-slave model "hot backup" redundant power supply system: Its structure is to connect the AC bypass of the host UPS to the inverter power output of the slave UPS. In case of failure of the host UPS, the slave UPS can be switched to With load. This redundant working method has limited application scope due to the lack of "capacity expansion" function and the possibility of 4 millisecond power interruption.

"1+1" type direct start-up redundant power supply system: It is directly connected in parallel by placing the outputs of two UPSs with the same power in the same amplitude, phase and frequency. During normal operation, the two UPSs each bear 1/2 of the load current. If one of the UPSs fails, the remaining UPS will bear the entire load. The mean time between failures (MTBF) of this parallel system is 7 to 8 times that of a single UPS, thus greatly improving the reliability of the system.

3 Routine maintenance of UPS

With the increasing popularity of computers, UPS, the protector of computers, has also been widely used. UPS is a simple-to-use but delicate device. Scientific use and maintenance will extend the life of UPS.

(1) Try not to connect inductive loads. Because the starting current of inductive loads often exceeds 3 to 4 times the rated current, this will cause an instant overload of the UPS and affect the life of the UPS. Inductive loads include electric fans and refrigerators commonly used in summer.

(2) It should not be fully loaded or overly lightly loaded. Do not use the UPS according to its rated power, and do not think that the empty interface should not be left idle to connect other electrical appliances. Long-term full load status will directly affect the life of the UPS. Under normal circumstances, the load capacity of online UPS should be controlled at 70% to 80%, while the load capacity of backup UPS should be controlled at 60% to 70%.

(3) Protect the battery. A very important component of UPS is the battery. At present, most small and medium-sized UPS use sealed lead-acid batteries that require no maintenance. Although it does not require maintenance on the surface, it can still break down if it is not taken care of properly, not to mention that the battery is very expensive. Batteries are relatively delicate and are required to work in an environment of 0 to 30°C, with the highest efficiency at 25°C.

(4) Regular maintenance. Usually, the terminal voltage of the UPS battery should be measured every six months. If the voltage exceeds 1V, you should use balanced constant voltage and current limiting (0.5A) charging; if it doesn't work, you can only replace the battery with a new one. If there is no power outage in the local area for a long time, the power supply must be artificially interrupted regularly (three months) to allow the UPS to discharge with load.

(5) Pay attention to lightning protection. Be sure to ensure effective shielding and grounding protection of the UPS.

4 Development Trends of UPS

With the continuous development of new technologies and their gradual application in practice, it can be predicted that UPS will develop in the direction of high frequency, intelligence, networking and large-capacity stand-alone redundancy in the future.

High frequency: Although the technology of traditional online UPS is very mature, it has many problems that cannot be overcome, which limits its development prospects. The introduction of the concept of high frequency has brought many new ideas and space to the development of UPS. With the development of high-frequency technology and devices, the technology and products of high-frequency online UPS of 3kVA and below have become familiar, and their functions and reliability should be higher than traditional UPS. High frequency plays an important role in reducing size, cost and better response to curved loads.

Intelligentization: The application of microprocessors in UPS used to be only used in large and medium-sized UPS, but in recent years it has gradually developed into small and micro UPS. The result is the intelligent development of UPS, including control, detection and communication. UPS is gradually managed by computers, and computers and peripherals can "autonomously" cope with some foreseeable problems, and can automatically manage and adjust, such as automatically shutting down the host computer's operating system and turning off its power, switching the UPS itself on and off regularly, etc. , and can pass relevant signals to the operating system or network administrator through the network to facilitate remote management.

Networking: The requirement to regard UPS as a member of the network family is becoming more and more urgent, because it is the basis for the normal operation of the network. The UPS is required to have larger storage capacity, be able to serve multiple computers or other peripherals at the same time, and be able to achieve dynamic configuration between loads through some mechanism.

Large-capacity stand-alone redundancy: As the network has increasingly higher requirements for UPS reliability, the way to solve reliability is to use redundancy methods in addition to requiring high reliability of the components themselves. Redundancy within a single machine of small-capacity UPS has emerged. Large-capacity UPS must still be implemented through parallel methods, but this requires too much investment for the user. There is no doubt that using Internet technology to monitor UPS systems will become one of the mainstream UPS technologies in the future.