Technology for Highly Dependable Large Capacity UPS System.

This paper presents a simplified sinusoidal uninterruptible power supply (UPS) system. The proposed scheme includes features such as high power factor, low total harmonic distortion and good dynamic response at the AC output voltage. In addition, the scheme has the desirable characteristics, of high efficiency, simple circuit and low cost compared with a traditional standalone multiple stages UPS with power factor correction. The paper also presents the circuit operation, the analysis and, experimental results of the proposed UPS scheme. The proposed UPS approach is a good solution in low. power applications (/spl les/500 W).

In the modern world, when there is a power outage or a power failure, telecommunication systems, computer systems, and many other critical equipment, such as medical equipment, require uninterrupted power to support their operation. Uninterruptible power supply (UPS) systems are used for this purpose. Over the years, research on UPS systems and related publications have increased. Also, new opportunities for UPS systems have emerged with the development of novel storage technologies, power electronic topologies, rapid electronic devices, high-performance digital apps, and other technological advances. Servers and storage systems, personal computers, medical equipment, telecommunication systems, and industrial equipment all require clean, stable, and uninterrupted power supply from UPS systems. Several recent studies have focused on the design of UPS systems to provide continuous power under normal or abnormal power conditions, including power outages. Such UPS systems use energy storage technologies such as batteries or flywheels to provide power to loads in the absence of applied power. Typically, static power electronics such as fast-switching high-current insulated gate bipolar transistors (IGBTs) are used to convert power. This article discusses the most typical power line issues and how they relate to the various types of UPS systems available today.

The paper highlights the reliability estimation tool for power system's reliability estimation study. The reliability estimation tool was applied to the different configurations of Uninterruptible Power Supply (UPS) systems Capacity, Isolated Redundant, Parallel Redundant, Distributed Redundant, and System plus System Redundant configurations. UPS reliability parameters such as failure rates, Mean Time Between Failures, and Availability can be estimated from the proposed system's reliability estimation methods. The suggested reliability estimation methods in this paper are the Reliability Block Diagram (RBD) and the Monte-Carlo simulation methods. The UPS system reliability estimation study found that the System plus System Redundant configuration gives the highest reliability and availability values compared to all other configurations. Studies has been conducted to investigate the effects of the reliability level of every component in the UPS system onto the overall system's reliability, thus making it possible to rank their contribution to system's reliability and thereby useful in establishing the area of improvement in the design of the highest UPS system's reliability.

This paper is concerned with the control of a line interactive Uninterruptable Power Supply (UPS) system in a Microgrid. In grid connected mode, power can be imported from the grid to charge the battery or it can be injected into the grid to boost the power supplied by the Microgrid. In island mode, the UPS supplies local critical load in parallel with other sources. Power flow is controlled using the frequency and voltage drooping technique to ensure seamless transfer between grid connected and parallel islanding modes of operation. When the power is imported from the grid, an outer voltage controller that regulates the DC link voltage sets the power demand for an inner power flow controller. The outer voltage loop is designed with the aid of small signal analysis which has been used to model the dynamics of the inner power flow controller. Due to the limited DC link capacitance, the drooping coefficients are chosen carefully to limit transient circulating active power from the grid to the UPS module or from one UPS module to another. The traditional way of measuring active and reactive power which is based on using a low pass filter is replaced by a real time integration method which is shown to improve the response of the controller. A virtual impedance is utilized in grid-connected mode to improve output current THD. Experimental results of two 60kW line interactive UPS modules are provided to validate the design.

This paper presents the reactive power compensation with UPS. The most effective power quality improvement solution is analyzed in an uninterruptible power supply systems. The conventional UPS has three stages i.e rectifier converts AC to DC, Battery to store DC and Inverter to convert DC to AC. A novel technique has implemented in off-line UPS. The power is delivered to load via by-pass switch when main supply is available. Inverter does not operate during this period. So inverter function is same as conventional inverter. To overcome this problem, static change over switches has proposed. Hence it will get better voltage regulation and loss less in distribution system. The performance of simulation result is analyzed using MATLAB/SIMULINK.

In this paper, a regeneration protection solution is proposed to address the dc-link overvoltage issue and the unequal power sharing in the parallel uninterruptible power supply (UPS) systems. First, a dc-link voltage protection control strategy is proposed to protect the inverter against the excessive dc-link voltage that may trigger the protection mechanism of the UPS system. In addition, an active power-sharing control strategy by regulating the virtual resistance is proposed to solve the circulating current caused by UPS regeneration issue. Finally, the feasibility of the proposed regeneration protection solution is verified by experimental results from the parallel UPS system prototype.

Intelligent uninterruptible power supply system with back-up fuel cell/battery hybrid power source

A current sharing method considering battery state of charge(SOC) for multi-module uninterruptable power supply(UPS) system is proposed. Modularized UPS system consists of a single master module and multi slave modules. A master module performs output voltage control and distributes current commands to slave modules. The current commands are generated by using the proposed current sharing algorithm to balance the SOC of each UPS module. Moreover, the UPS mode transfer time can be significantly reduced by using the predictive current control. The predictive current control method is mathematically verified by analyzing the UPS system. The validity of proposed balancing method and predictive control is verified by simulation results.

The authors discuss the duties of batteries in DC uninterruptible power supply (UPS) or telecommunications power systems. They show how the battery system affects the DC UPS system reliability and availability performance, discuss the impact of public power and engine alternators on battery sizing, and determine the essential parameters to be monitored. Also discussed are the issues of battery fault detection and the temperature compensation of battery voltage. >

In the article, based on the concept of increasing the reliability of the formed image of the complex of technical means for ensuring the operation of an unsolicited measuring station of the network of stations of the ground control complex, a solution is proposed for choosing the general scheme of an uninterruptible power supply as part of a complex of technical means of unsolicited measuring systems. The uninterrupted power supply system is designed to automatically provide a set of technical means for ensuring the operation of a non-demand measuring station with a guaranteed and uninterrupted power supply in accordance with the indicators of reliability, autonomy and quality of electricity specified in the terms of reference. A procedure for selecting the constituent elements of an uninterruptible power supply is proposed, the main stages and composition of the protection means for the power supply network are considered. A block diagram of protection over the power supply network is presented. It is noted that structurally, the uninterruptible power supply should be able to be placed both in a stationary room and in a block container.

Unlike the past, modern urban intersections have dramatic growth in size and utilizations. As a result, continual traffic signal control is essential. Hence the individual or regional electrical blackout may bring about uncontrollable traffic congestion. Late summer of 2011 a regional blackout brought about traffic nightmare not including time and revenue loss associated with this disaster. Due to this disaster our national police agency and other government agencies are in process of introducing an UPS (uninterruptible power supply) system into essential intersections. This study estimates the power consumption necessary to sustain at least 2 continuous hours for a standard four-legged intersection. Prototype was studied using these standards. The field experiment of prototype showed positive results and was able to meet standard guidelines set forth. Prototype tested was able to meet standards in medium to large capacity of traffic size..Key words : Traffic Signal System, Uninterruptible Power Supply, Material Standards, Traffic Device, Battery Back-up * 주저자 : 도로교통공단 교통공학연구실 선임연구원 ** 공저자 및 교신저자 : 아주대학교 건설교통학부 교수 *** 공저자 : 도로교통공단 교통공학연구실 연구원 **** 공저자 : 도로교통공단 교통공학연구실 연구원***** 공저자 : 도로교통공단 교통공학연구실 실장†논문접수일 : 2012년 8월 8일†논문심사일 : 2012년 8월 20일†게재확정일 : 2012년 8월 22일

1 - Introduction and basics

The purpose of this paper is to describe and discuss an approach to estimate the Reliability and Availability values of the Uninterruptible Power Supply (UPS) systems using Monte-Carlo simulation method. In this method, the failure rates (), and availability (A) of the major components in the UPS are simulated by the use of random number generators that produces deterministic reliability parameters that try to mimic results that would be obtained from field trials. Reliability parameters such as the system's Failure Rates (), Mean Time Between Failures (MTBF), System Availability (A), and System Unavailability (W), can be achieved and thus can be used as an indication of the reliability level of the UPS systems. In this paper, the method are applied to five UPS configurations (online with and without bypass, offline, line-interactive with buck/boost transformer and line-interactive with ferroresonant transformer), and comparisons on the results obtained from this method were made to the results from other reliability estimation method such as the Reliability Block Diagram (RBD), Boolean Truth Table and Field Data estimation method.

Standard uninterruptible power supply (UPS) systems for radio base stations use lead acid batteries stacks as energy storage device; the fairly short life cycle of such systems, not more than 3 years, together with the presence of highly polluting components make it costly in terms of money and environmental aspects. From these considerations originate the idea to develop an alternative UPS system based on compressed air storage able to replace the battery stacks and to satisfy more restrictive environmental requirements. This work is developed within the European project PNEUMA (PNEumatic Uninterruptible Machine - LIFE 04 ENV/IT/00595) with the final aim to develop some UPS demonstrators for an on site experimentation. In this paper it is described the way followed to set up an air turboalternator with a maximum power of 10.0 kW. Starting from the selection of the turbine, we decided to extract it from an ICE turbocharger because its size and its low cost matches our requirements. First of all, an experimental survey has been realized to test two turbines of different size: expansion ratio, corrected mass flow and efficiency have been measured varying inlet pressure and temperature. This activity led us to select the smaller turbine to develop the first pilot demonstrator; the turbine has been coupled to an high speed alternator (max. 60’000 rpm) by means of an elastic coupling. Some shakedown testing have been performed to verify the mechanical resistance and to test the power conversion system and the control system.

Paper presents a novel topology of a grid-connected back-up uninterruptible power supply (UPS) system with multilevel converters. The star-configuration three-phase "back-to-back" topology with a five-level diode-clamped rectifier (5LDCR) and a five-level diode-clamped inverter (5LDCI) supplies a three phase output load. The proposed multi-level current mode control techniques in both converters provide an effective solution to an imbalance problem with the capacitor voltages in a DC link network. The interfaced battery energy storage (BES), which constitutes an integral part of the entire UPS system, supplies the DC link capacitor voltages to the 5LDCI in a standby emergency mode because the proposed balancing method is constrained to the "back-to-back" operation only. Importantly, the UPS system is able to operate with an asymmetrical, a nonlinear and an impact loads in three phases and it provides the power factor correction on the grid side