Uninterruptible power supplies management

Dejan Pojbič (2011) Uninterruptible power supplies management. EngD thesis.

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Abstract

The thesis focuses on the equipment for uninterruptible power supply (hereinafter referred to as UPS) and defines their security component. It carefully describes the three most widely used UPS units: waiting, corrective and linear. The device equipped with a waiting UPS unit filters power and loads it, thus charging batteries. Very similar to a waiting UPS is the corrective UPS, except that the latter regulates voltage fluctuations to the required value in the range of – 15 % + 20 % and therefore excludes work in battery mode. The linear UPS unit first of all converts AC power to DC. When necessary it charges batteries, but most of the power gets converted back to AC power. If the equipment for uninterruptible power supply fails and the system is not protected against possible problems in the electrical network, we need control over the UPS unit. That is why the thesis presents the CS121 card and the UNMS program, which enable us to control the UPS unit, allowing us to monitor, configure and warn it. CS121 cards can be integrated or external; both versions can be found in standard or truncated form. The CS121 card is a microcomputer that allows monitoring and management of the UPS unit, transmission and management of the sensor (temperature, smoke, etc...), web server, mail server and allows connection to other Generex’s products. UNMS 2 (which stands for Universal Network Management System) is a program for Windows, which allows online monitoring and management of the UPS unit and other devices. UNMS's website is dynamic, the data gets refreshed in real time. The program works with operating systems Windows XP, 2003, 2008 and 7. The free version allows connection of up to ten devices, the payable of up to 1500. Events initiated by the UPS unit, the CS121 card or any other device connected to the UNMS program can be configured. Basic events are pre-prepared and can be modified to specific needs. A device, such as BACS, Sensor Manager, etc..., has to be added. Since UNMS does not allow sending SMS messages in the last part of the thesis presents the development of the application PosljiSMS, written in the Python programming language, which can send SMS alerts. Python is a free, object-oriented programming language that works with most operating systems. This program was developed with the Eclipse development environment [6] and the PyDev plug-in [7]. Python requires the Python database [8]. PySerial [9] has to be installed to allow connection to the GSM module. Both are free online. SMS messages can be sent using a mobile phone or a GSM module (which stands for Global System for Mobile Communications). For this thesis the GSM module TC31i Cinterion has been chosen since it is reliable and supports AT commands. The RS232 serial port enabled connection to the computer. DezurniSMS is a Java based program that determines which person on duty will receive the SMS message. The program DezurniSMS requires the Java Runtime Environment [4], which is free online. The user interface was developed with the NetBeans software [5]. The program selects the candidates that can receive SMS messages from a specific station. From the list of candidates for a particular station it opts for those who are currently on duty. If the SMS messages would get sent to everybody on duty it would cost a lot, it would test people’s patience and disturb their private lives. The goal of this study was to develop an application for sending SMS messages that with the UNMS program and the CS121 card informs on the UPS unit.

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