Abstract : This paper introduces the experience gained in the design process of UPS systems, and, based on specific engineering projects, puts forward the author's views on the system's wiring methods, microcomputer monitoring, and the application of harmonic regulators, providing a reference for engineering design. Keywords: UPS system; signal acquisition; redundancy design; harmonic regulator With the continuous improvement of the automatic control level of power plants, DCS systems are widely used in power plants. At the same time, UPS (Uninterruptible Power Supply) systems, which provide reliable power protection for DCS systems, have become an important component for the safe and reliable operation of power plants. A UPS system mainly consists of rectifiers, inverters, static switches, bypass devices, and other major components, as shown in Figure 1. Working principle: The poor-quality plant power supply is first converted into DC power by the rectifier, and then the DC power is converted back into a pure, high-quality sine wave power supply in the inverter using the high-frequency pulse width modulation (SPWM) method. When the AC power supply is lost or components such as the rectifier fail, the inverter is powered by the DC system or its own battery pack via a latching diode. When the inverter fails and the output voltage is abnormal or overloaded, the static switch switches to bypass. In the design of the UPS system for Unit 3 of Ansteel's Second Power Plant, considering the inconvenience of maintaining the UPS's own batteries, a backup DC power supply from the power plant's DC power supply panel was adopted. Furthermore, isolation transformers were added before the rectifier and bypass devices and after the inverter in the UPS system design to achieve complete electrical isolation between the load and the power supply, eliminating interference from plant power noise and surges. Figure 2 shows the single-unit electrical schematic diagram of the UPS system for Unit 3 of Ansteel's Second Power Plant. 1. Protection and Signal Acquisition a. A qualified UPS system should provide stable frequency power and have protection against voltage decay, surges, and short-term interruptions. The UPS system in this project is from the American brand BEST, and it features a choke before the rectifier to protect its power components from damage. Some brands (such as APC) offer chokes as a special option in their UPS systems. Furthermore, the system itself has overvoltage, undervoltage, overcurrent, and phase loss protection functions. b. Signal acquisition includes analog quantities such as current, voltage, and frequency, as well as operating status quantities. In the design of the UPS system for the Ansteel Unit 3 project, each cabinet's digital analog control panel has a flowchart that displays the single-unit operating status, single-unit output voltage, single-unit output current, single-unit output frequency, rectifier fault signals, inverter fault signals, static transfer switch status signals, overload or output short-circuit shutdown signals, load percentage, plant power supply changes, rectifier filter status, and protection action signals. Additionally, the acquired signals are sent to the back-end computer via an RS2232 interface and printed out. The signals displayed on the back-end system include operating status indicators, output voltage, output current, output frequency, rectifier status, inverter status, static transfer switch status signal, overload or output short circuit shutdown signal, load percentage, etc. Furthermore, the manufacturer provides dedicated SMARTMON software for operators to perform microcomputer monitoring. (Full text available for download: Discussion on Power Plant UPS System Design Scheme)