What is the future of UPS power supply
Since the advent of UPS power supply, it has developed from the original dynamic, static UPS using SCR to the present intelligent UPS products using fully controlled power devices. The reason why UPS power supply develops so fast is mainly due to the rapid development of electronic technology, component manufacturing technology and control technology.
Benefited from the power supply technicians to the electric energy transformation mode and method of continuous in-depth research; The rapid development of information industry has provided a wide range of applications for UPS power supply products.
With the development of modern communication, electronic instruments, computers, industrial automation, electronic engineering, national defense and other high and new technologies,the requirements for the quality and reliability of power supply are becoming higher and higher, especially the continuity of power supply must be guaranteed.
Therefore, as an AC uninterruptible power supply system, UPS power supply will be developed continuously in the future.
At present, the research of power supply technicians on topological structure, devices and materials used, control methods and means used of UPS power supply is still going deep, aiming at improving the performance of UPS power supply, broadening its application field, improving its reliability and enhancing its adaptability.
According to the current research results, it can be expected that the future development of UPS products mainly revolves around the following aspects.
Switch to UPS lithium battery for UPS power supply
With the advantages of lithium battery in environmental protection, safety, light weight, small size, wide temperature range, high energy storage and low self-discharge, more and more UPS power supply manufacturers will follow the trend “Lithium Battery Replacement Lead Acid’, replace the traditional lead acid battery with UPS lithium battery.
At present, 10% of data centers have adopted lithium battery UPS power supply, and the trend of UPS power supply switching to lithium battery will be more rapid in the future.
UPS power supply has been widely and deeply applied in the industrial field, communication base station and other fields, and a variety of high-end and precision equipment has also increased greatly.
Therefore, the demand for high performance UPS lithium battery is also increasing. Lithium batteries have a number of advantages over ordinary lead batteries, but their price is relatively high.
However, the energy storage system composed of lithium batteries and UPS power supply system can better coordinate with the power grid and reduce electricity costs. Many developed countries are now using UPS lithium battery solutions, mainly for several reasons:
① Lithium batteries have high energy density, so they are light in weight and small in size. This dramatically reduces the footprintof the UPS power supply. In general, data centers take up a lot of space.
And in some of the land gold developed cities, such as London, Singapore, Hong Kong, cover an area of large battery will affect the benefit. Therefore, in terms of overall return on investment, using lithium batteries is beneficial to greatly reduce the footprint.
② Lithium-ion battery has good charging and discharging capacity, which will produce economic benefits, such as peak and valley electricity price cutting and valley filling. In addition, in the peak load, if the power grid is not enough, the lithiumbattery in UPS power supply can carry out collaborative power supply, reduce the input of municipal power, reduce the initial investment.
③ The cycle life of lithium batteryis longer than lead-acid battery. In terms of life-cycle cost,lithium-ion batteries already cost less than lead acid batteries because they are replaced less frequently. In a future where the price of lithium batteries is falling and the cost of lead acid is rising, UPS power supply can add value to its customers by switching to lithium batteries.
High frequency of UPS power supply
The high-frequency of UPS power supply on the one hand refers to the improvement of inverter switching frequency, which can effectively reduce the volume and weight of the device, and can eliminate the audio noise of the transformer and inductor, while improving the dynamic response capacity of the output voltage.
Due to the wide use of the new switching device IGBT, The switching frequency of small and medium capacity UPS inverter can be more than 20kHz. Using high frequency SPWM inverter to improve the inverter switching frequency is now a very mature technology.
In small and medium capacity UPS power supply, in order to further reduce the volume and weight of the device, it is necessary to remove the bulky power frequency isolation transformer, and the use of high frequency isolation is the real significance of the high-frequency of UPS power supply.
High frequency isolation can be realized in two ways: one is to add a DC/DC converter with high frequency isolation between the rectifier and the inverter; the other is to use the high frequency chain inverter technology, as shown in Figure.
As shown in Figure(a), a high-frequency isolation UPS power supply composed of a one-stage HIGH-FREQUENCY DC/DC isolation transform is inserted into a general (dual-transform) on-line UPS. The UPS power supply is characterized by simple structure and convenient control.
The disadvantage is that there are two stages of high frequency transformation in the system, resulting in the increase of the loss of the whole device, the efficiency is significantly reduced.
The form of high-frequency chain inverter which is shown in Figure(b) solves this problem. It combines high frequency isolation with sine wave inverter, obtains 100Hz pulsating DC through first-level high-frequency transformation, and then obtains the required sine wave voltage through first-level power-frequency inverter.
Compared with the high frequency DC isolation, the high frequency chain inverter adopts only one high frequency transform, which improves the efficiency of the system. However, this form of control is relatively complex, and only a small number of UPS power supplys currently use this technology.
Greening of UPS power supply
With the development of modern power electronics technology, many modern electric devices with high performance, low pollution and efficient use of electric energy are emerging.
For example, the network side current is very close to sine programmable switching power supply, UPS power supply with high power factor, IGBT device frequency conversion governor, high-frequency inverter rectifier welder and MHZ level DC/DC converter, etc.
These modern power supply devices and systems based on high frequency conversion technology have one outstanding characteristic: high efficiency, energy saving and no pollution. This is the goal of green power products.
To realize the greening of UPS power supply products, the most important work is to improve the power factor of the network side to reduce power pollution.
Secondly, the advanced transformation technology is used to improve the working state of power switching devices, so as to reduce the loss of power switching devices and the interference generated in the process of switching devices on and off. For small UPS power supply, active power factor correction (APFC) can be used to improve the network side power factor.
The most mature method is Boost power factor correction (PFC). In order to improve the working state of power switching devices, improve conversion efficiency and reduce interference, soft switching technology can be used to make power switching devices work in soft switching state.
Intellectualization of UPS power supply
Most UPS power supply, especially large capacity UPS power supply, operate on a continuous basis. It is one of the goals of UPS power supply development and production and the most concerned of UPS users to detect the status of UPS power supply in operation, find and deal with the faults of UPS in time, reduce UPS discontinuity time caused by faults or maintenance, and make UPS truly become uninterruptable power supply.
In order to achieve these functions, it is difficult to use common hardware circuit, only with the help of computer technology, give full play to the respective characteristics of hardware and software, make UPS power supply intelligent, to achieve the above requirements.
The hardware part of intelligent UPS power supply is basically composed of ordinary UPS power supply plus microcomputer system. By analyzing and synthesizing all kinds of information, the microcomputer system should complete the following functions in addition to the control function of UPS power supply normal operation.
① Monitor the UPS power supply in operation, and send the information of sampling points to the computer for processing at any time. On the one hand, the relevant parameters of power supply are obtained, and on the other hand, the working state of each part of the circuit is monitored to analyze whether each part of the circuit works normally.
② When the UPS power supply fails, according to the detection results, the fault diagnosis is carried out, the fault location is pointed out, and the method and way to deal with the fault is given.
③ Complete part of the control work, in the case of UPS power supply failure, according to the site needs to take the necessary emergency protection control action in time, to prevent the expansion of the fault affected surface. In addition, through the control of the rectifier part, according to the different requirements of different batteries, the battery can be automatically charged in stages of constant current.
④ Automatically display the detected data information, in the abnormal operation or failure of the equipment, can automatically record the relevant information in real time, and form a file for engineering and technical personnel to refer to.
⑤ According to the indicators given in the technical manual, automatic and regular self-inspection, and form a self-inspection record file.
⑥ Can use the program to control the UPS power supply start or stop, realize unattended.
⑦ With exchange information function, can be at any time to the computer input information or get information from the computer.