The so-called UPS power supply, that is, uninterruptible power supply, is a combination of battery energy storage inside and a combination of rectifier and inverter as the main part. It is used to turn mains electricity into uninterrupted, high-quality communication required for stable computer operation. A kind of constant voltage and constant frequency static power electronic power supply equipment for electric energy. At the same time, this power supply device also has protection and monitoring functions. It is mainly used to provide uninterrupted, high-quality AC power to computers and their network systems. When the mains input is normal, the UPS converts the mains power into high-quality AC power to the computer through the rectifier and inverter, or directly stabilizes the voltage and supplies it to the computer. At this time, the UPS is equivalent to an AC voltage stabilizer. In addition to the computer’s power supply, it also charges the battery in the machine; when the mains fails, the UPS immediately converts the DC power of the battery into high-quality AC power through the inverter, and continues to supply power to the computer to protect the computing software and hardware. Damaged, continue to work stably and normally.
UPS power supply can not only be directly used in computers, but also in equipment equipped with computers (such as medical CT, instrumentation in supply stations, etc.), radar stations, military, communication systems, program-controlled telephone systems, surgical operating rooms, etc. Use UPS instead of diesel generator set as a backup power source.
With the development of power electronic devices, computers, automatic control, electrochemistry, electromechanical integration, communication and network technologies, UPS products are continuously upgraded, and now the circuit structure has been modularized, integrated, and fully digital control. , Centralized environmental monitoring and remote intelligent management, etc. Based on this, nowadays, wherever it is applied to a computer, UPS must be used as its power supply. At present, UPS is mainly used in the power supply of computer and its network, communications, finance, electric power, transportation, national defense, universities and scientific research institutions, hospitals, public security and other departments, and plays a vital role.
There are five commonly used UPSs, namely
(1) Backup UPS;
(2) Online interactive UPS;
(3) Double conversion online UPS;
(4) Double-conversion voltage compensation online UPS;
(5) Three-port UPS.
The characteristics of various UPSs are described below.
①Backup UPS: It is the original circuit form of static UPS. Its characteristics are mature technology, simple circuit, low price and wide application. When the mains power is interrupted, the conversion time is 4 10ms. The output conversion switch is limited by the switching current capacity and the action time, and the output voltage stability is poor. It is only suitable for 2kV. A small UPS applications.
②On-line interactive UPS: On-line means that the inverter is working online, but does not output power, and is in a hot standby state. At the same time, it also takes into account the charging of the battery, which increases the power capacity when the mains is normal, and reduces The conversion time when the mains power is interrupted improves the filtering effect of the output voltage and belongs to the parallel full power adjustment method. Its output voltage stability is poor, the circuit is simple, and the cost is low. It is suitable for small-capacity UPS applications around 5kV. A.
③Double-conversion online UPS: It is especially suitable for high-power UPS applications. It is a series full-power conversion method, and the conversion time between mains power supply and battery power supply is 0, and the output power quality is high. When the SCR phase-controlled rectifier is used, the mains input power factor can only reach about 0.90: When the ICBT high-frequency SPWM rectifier is used, the mains input power factor can be increased to close to 1.
④ Double-conversion voltage compensation online UPS: This technology was proposed in the early 1990s, and it mainly applies the voltage compensation principle in AC voltage stabilization technology and the reactive power compensation technology in power active filter to UPS In the main circuit, a parallel-compensated UrS (Dela converter UPS) is formed. The conversion time of this kind of UPS is 0, the quality of the output electric energy is high, and it is suitable for high-power UPS applications.
⑤Three-port UPS: On-line UPS undergoes two power conversions from DC to AC and AC to DC, so the efficiency of the whole machine is low and the reliability is reduced. Three-port UPS strives to improve efficiency and reliability by changing the structure of UP’S. Its basic working principle is: When the mains power is normal, the mains power is sent to the winding I of the three-winding transformer through the AC voltage regulator, and the load is supplied to the load through the secondary winding I of the transformer and the transfer switch. At the same time, the city power supplies power to the bidirectional converter through the voltage regulator and winding 1. The bidirectional converter works in the rectification state at this time, and charges the battery after rectifying the city power into direct current: when the city power is abnormal, the control circuit switches immediately The battery continues to supply power to the load after the DC power is inverted into AC power by the bidirectional converter, which ensures that the power supply of the load is not interrupted. This kind of UPS is characterized by high efficiency and high reliability. The disadvantages are large size, high quality, high noise, and high price.