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An overview of uninterruptible power supplies
Abstract
An uninterruptible power supply (UPS) can range from a 9 volt battery all the way to an extremely large and costly battery system. The UPS sits between a power supply such as a wall outlet and a device like a computer to prevent undesired features that can occur within the power source such as outages, sags, surges, and bad harmonics from the supply to avoid a negative impact on the device. There are several types of UPSes as they strictly relate to computers. The standby UPS is a battery backup to fill in the void of power loss, while the ferroresonant stand by couples the battery back up with the power supply by a transformer, where the transformer acts as a buffer from the power supply to the stand by supply. The line interactive UPS uses an inverter converter only, with a power supply the stand by battery is charged up, and with a loss of the primary power supply, the inverter converter switches over to the battery back up with a much quicker switching time that the stand by UPS.
... e increase in nonlinear load has exponentially caused power quality problems such as high harmonics of current and voltage and low power factor, especially when connected to the grid in a distributed generation system. ese loads generate a variety of PQ issues, including harmonics in source/load voltages and currents, which have a negative impact on system security, efficiency, and dependability [1]. As a result, many studies have been conducted employing various custom power devices (CPD) to improve the system's PQ. ...
... In such a system, power interruption can be a serious problem for sensitive equipment. In 2005, conventional uninterruptible power supply (UPS) systems were summarized [1]. In the case of an input power failure from the national grid, the UPS is employed as a backup power supply for the load (usually mains). ...
... It examines the relationship between current harmonics and output power and outlines the causes of current harmonics. Both modelling and experimental evaluation support theoretical conclusions and analysis [1,2]. A general model, adapted from the classic control block diagram, was developed to investigate the harmonic production process induced by a single-phase UPS system. ...
UPS Uninterruptible power supply) is used as backup when the input source, usually the national grid, fails to give power to a load. In addition to the growing use of electronic power devices in industrial and residential systems, such as UPS, controlled rectifiers, SMPS (Switch Mode Power Supplies), and DC Converters, there is a serious problem caused by harmonics in AC mains, which lowers the power quality. Harmonics can cause a variety of problems, including sensitive equipment failure, resonance issues, heated wires, power loss, and inefficient distribution systems. A passive or active power filter could be used to reduce harmonics. However, passive filters are more difficult to design and are bulkier. With the advancement of power electronics, active power filters were developed, and the best combination of both was supplied in the form of hybrid active power filters (HAPF). This study shows an approach to minimizing the harmonics contained in the output of a UPS connected to a nonlinear load. Experiments with several UPS types have been conducted under various nonlinear loads, as well as charging and discharging of batteries, and the proposed technique significantly reduces harmonics in a system with a HAPFs (hybrid active power filter) based on a unique FLCC (fuzzy logic current controller). In this paper, we use a fuzzy logic controller to generate pulse width modulation (PWM) switching signals in a single-phase half-bridge HAPF. The operation of the proposed PWM-FLCC will be studied in a steady and transient state. Based on a connection between the uninterrupted power supply (UPS) supplying a single-phase power to a nonlinear load, different power filter topologies and a brief review of reference current extraction (RCE) methods used in this study were also included and the most common configurations have been compared with their advantages and disadvantages to ensure the right selection of the power filter for UPS connected with the nonlinear load. The results of the investigation demonstrate that the HAPF with the fuzzy logic current controller has reasonable performance, with a significant reduction in current THD down to 1.09%, as per IEEE-519 standard.
... Line-interactive UPSs can cope with continuous undervoltages, brownouts and overvoltage surges without consuming the limited reserve battery power. It is achieved by selecting automatically different power taps on the built-in autotransformer [7,8]. VFI (Voltage and Frequency Independent) called online topology is meant for devices requiring protection against frequency distortions, noise and harmonic distortion. ...
... This solution provides an impenetrable barrier between the incoming power from a grid and sensitive electronic equipment. It is also called a double-conversion UPS due to the rectifier directly driving the inverter, even when powered from the standard AC current [8,9,11,12]. Moreover, UPSs in the double conversion topology are equipped with a static bypass that can increase UPS efficiency. ...
Along with the increase in the use of nonlinear electronic devices, e.g. personal
computers, power tools and other electrical appliances, the requirements for uninterruptible
power supplies are constantly growing. This paper proposes a method and deep analysis of
results viable for checking how single-phase uninterruptible power supplies (UPSs) cope
with nonlinear circuits under varying power loads in terms of electric energy quality.Various
classes of single-phase UPS systems with different topologies were tested, for instance
line-interactive and double conversion (online) single-phase UPS devices. Furthermore,
measurements were carried out in view of a power source – loads were supplied both
from a power grid and UPS built-in battery. Juxtaposition of the obtained results such as
a THDU, THDI (Total Harmonic Distortion) percentage ratio of input/output voltage and
current, a power factor and crest factor volume etc. of the tested UPS systems indicated
major differences in their performance during laboratory tests.
... UPS systems can be mainly classified as rotary and static based on [18], [23] and [24]. A classic example for rotary UPS systems would be fly wheels where the energy will be stored as mechanical inertia as illustrated in the figure below. ...
... Schematic view of a 2-pole, single phase synchronous generator, Source:[34] ..23 ...
This dissertation presents an analytical study on virtual synchronous machine-based power
control in active rectifiers for micro grids supported by prototype modelling, simulation
results and discussions.
Popularity and demand of the distributed energy resources and renewable energy sources
are increasing due to their economic and environmental friendliness. Concept of micro grid
with an active rectifier (AR) interface has been found to be promising for smart integration
of such distributed generation units.
Having the presence of a synchronous generator (SG) in a micro grid introduces several
advantages in terms of stability and reliability in the power system. This is mainly owed to
the inertia, damping and load sharing properties of SG. This in return, gives rise to the
question if an AR of a micro grid can imitate the behaviour of a synchronous generator, can
the stability and reliability introduced by SG be replicated in a micro grid.
A research on the state-of-the-art for uninterruptible power supplies (UPS) has been carried
out to identify the implementation and the control strategies of redundancy and parallel
operation as UPS has been an established technology over the last decades. The theoretical
study on virtual synchronous machine (VSM) concept in the fall, 2011, has been extended in
developing a model with classical inner current control and outer voltage control loops
based on the synchronous reference frame.
The complete active rectifier model has been able to emulate the inertia, damping and load
sharing properties of a SG and redundancy and expandability of parallel UPS systems. It
must be emphasized that due to the flexibility of the virtual machine parameters and the
absence of magnetic saturation and eddy current losses, a much improved performance
have been achieved with a VSM compared to a synchronous generator.
Simulations have been carried out for single and parallel operation of active rectifiers in
island and grid-tied modes with satisfactory stability, damping and power sharing features.
... Uninterrupted power supply (UPS) has become a popular solution in the industry, like enterprise IT, commercial telecom, data center, cloud computing area, and so on. Meanwhile, there is a strong demand for the UPS system to provide more reliable and secure electrical power supply for the critical devises [1] [2]. ...
... Besides, such controller can confirm fault-detection within 5ms, and the forced commutation mechanism can accelerate the overall transfer process. ) are sensed, and transformed to derive their synchronous-reference frame components ( , ), and these synchronous-reference-frame transformation is defined in (2). Note that represents for the line frequency of grid. ...
... Last few years have witnessed the widespread application of Uninterruptible Power Supply (UPS) system in the network center, financial institution and hospital [1]. Meanwhile, the strong need for UPS system to provide more reliable, efficient and secure electrical power supply for the modern digital equipment [2] propels the growing attention of UPS technology by the engineers and academic researchers. ...
... According to the European Standard EN 62040-3 [2], the UPS system is divided into on-line, off-line and line-interactive UPS in compliance with the power delivery to the critical load predominantly coming from the grid or inverters in the normal mode of operation. On-line UPS system is mostly popular and widely configured for sensitive load, as it provides excellent characteristic in being immune to grid frequency variation, voltage irregularity, and other power issues [3]. ...
... It is often necessary to raise the output voltage of the inverter to the AC output voltage using a low frequency transformer [8,9,11,12]. These topologies are known as ferroresonantbased UPSs [13][14][15][16]. Due to the use of the step-up transformer, the current drawn from the batteries and flowing through the inverter is higher than the load current, which causes high current stress on the inverter [12]. ...
This work presents a design for uninterruptible power supply inverters using Pareto front optimization for improved cost and efficiency. Three PWM modulation techniques applied to the full-bridge inverter are analyzed. As a result, the best MOSFET design solution in terms of the cost and efficiency of the inverter is evaluated based on a database with 47 power MOSFETs. Using the Pareto front, the optimal and sub-optimal solutions are compared, considering the three modulation techniques and the characteristics of MOSFETs manufactured for different voltage levels. Thermal and electrical measurements are used to validate the models.
... The inverter for SOHO UPSs generally operates from a battery voltage of 12 V or 24 V [17], making it necessary to raise the voltage at the output of the inverter using a low-frequency transformer [16,17,23,24]. Topologies that employ a low-frequency transformer are known as ferroresonant-based UPSs [29][30][31][32][33]. ...
This paper presents a comparative analysis of electrical losses and subsequent thermal limits of the inverter of UPSs for small office and home office (SOHO) applications. For this, three PWM modulation techniques applied to the full-bridge converter are considered, with power levels of 100–1000 W and switching frequencies of 30–120 kHz. To validate the electrical and thermal models, a dSapce MicroLabBox equipment was used to implement modulation techniques on a commercial 1000 W UPS, and a Keysight DAQ970A data logger was used for temperature measurements. As a result, the MOSFET temperatures and losses are obtained for the three modulation techniques evaluated, indicating the best scenario for use and its influence on the UPS autonomy time.
... In order to facilitate users to select the power quality control equipment suitable for the actual situation, the prevention and control capabilities of the main voltage sag control equipment are summarized in Table 1. DVR [41] SSTS [29] STATCOM [42] SVC [43] UPQC [44] UPS [45] and [46] Voltage sag/rise ...
In recent years, voltage sags are one of the most critical research issues in the field of power quality. With the all-embracing study of voltage sag mitigation measures and equipment, the classification of voltage sag mitigation measures and equipment is becoming more and more necessary. Reasonable classification methods not only can guide users to choose appropriate control measures and equipment, but also provide basis and research direction for new voltage sag control measures and equipment. Firstly, this study performs a detailed analysis of the current stage of voltage sag control measures and equipment, and proposes a classification method that divides the voltage sag control measures into three categories: the power supply side, the customer side and the equipment manufacturing company. Secondly, due to the difference between single power supply and dual power supply in voltage sag control equipment, this study proposes a classification method for voltage sag control equipment based on the number and type of power supply. Finally, in order to help users to select the voltage sag control equipment suitable for the actual situation, this paper summarizes the prevention and control ability of the main voltage sag control equipment.
... However, fulfilling these requirements is insufficient to prevent negative effects. To mitigate them, different types of low-power uninterruptible power supplies (UPSs) [10], or utilization of PQ conditioning devices, such as Ferroresonant transformers [11], Dynamic Voltage Restorers (DVRs) [12], Unified Power Quality Conditioners (UPQCs) [13], Universal Power Quality Conditioning Systems (UPQCSs) [14], distribution static compensators (DSTATCOM) [15], or others have been proposed. It is important to emphasize that for their proper operation voltage sag detection, voltage reference generation (synchronization) and adequate control are essential [16]. ...
In this paper, a novel method for real-time prediction of voltage sag duration is proposed. It is based on the recently introduced new characteristic of voltage sag, named harmonic footprint, and is formulated using a logistic regression model. The concept is mathematically formulated and statistically analyzed using an extensive set of real grid measurement data which are recorded in distribution grids. Furthermore, the proposed method is applied as a part of an advanced grid-tie converter control. It is included in previously developed methods for fast sag detection and magnitude of voltage sag prediction. The algorithm is applied to the control of grid-tie converters used in distributed generators and tested with real/grid measurement data in the IEEE 13-bus test grid by simulations and in the IEEE 33-bus test grid using a hardware-in-the-loop (HIL) microgrid laboratory testbed. It is shown that this method can prevent unnecessary tripping of distributed generators (DG) and improve low-voltage ride-through (LVRT) support. In addition, the model has the potential to be applied to a wide range of devices or algorithms for the protection, monitoring, and control systems of distribution grids.
... The static systems use converter and inverter with power electronics to store, process, and deliver the power at grid-failure, in contrast, Rotary systems use generator and motor to perform the same functions. Another type, [2,3]. Most BPSs available in the markets according to their power ratings, starting from only 300VA to provide backup power to one computer, to the bigger units that may provide backup power to a complete building with a number of a megawatt. ...
For a portable backup power system, there is an essential need to contribute to increasing the energy conversion efficiency between the source and the electrical household appliances to overcome the recent issues of global warming. This paper proposes a Backup power system (BPS) compatible with the capability to match with two primary power sources; Grid-Connected power as an AC and solar-PV as a DC power source. This system composes of a rechargeable battery bank of about 300V, while the voltage matching concept keeps maintaining the battery fully charged as long as the source power is available. MATLAB-based simulation has performed to prove the concept of the adopted voltage-matching. A relay switch circuit controlled by the main power source is used to changeover the load/appliances between direct link through bypassing the main power and the storage battery power when both options of main power are unavailable. The result shows the excellent utilization of the traditional BPS losses, the proposed topology can achieve about 99% power efficiency as compared with the traditional one.
... Albert Marzàbal received the B.S. degree in telecommunications engineering, the M.S. degree in electronics engineering (with the highest distinction), and the diploma of advanced studies (DEA) in the Ph.D. program of Vision, Control, and Robotics from the Technical University of Catalonia, Barcelona, Catalonia, in 2000, 2005, and 2009, respectively. He now works in the research laboratory of Salicru, S.A., a company that has designed, manufactured and commercialized power electronics products for the key sectors of the energy market since 1965. ...
To enhance the robustness and disturbance rejection ability of an on-line uninterruptible power supply (UPS) system, an Internal Model Control (IMC)-based DC-link voltage regulation method is proposed in this paper. Furthermore, the multi-mode operations of the on-line UPS system are investigated and their corresponding control strategies are proposed. The proposed control strategies are capable of achieving the seamless transition in traditional normal mode, PV-aided normal mode, enhanced eco-mode and burn-in test mode. Meanwhile, the uninterruptible load voltage is promised during the mode transition. The small signal analysis is also conducted to investigate the stability of enhanced eco-mode and burn-in test mode. Finally, extensive experimental results are provided to validate the effectiveness of the proposed methods.
... Over the last few years, Uninterruptible Power Supply (UPS) system has been widely installed in the communication systems, network centers, financial institution and medical equipment to provide conditioned and reliable power [1,2]. According to the IEC Standard 62040-3 [3], the UPS system is categorized as on-line, off-line, and line-interactive UPS systems in the normal mode of operation. ...
... De modo geral, o carregador de baterias para aplicações em UPS é baseado em um conversor abaixador conectado diretamente ao barramento CC [3], [24], [25], como mostrado na Figura 1(a). A utilização de um conversor bidirecional exclusivo em comparação a conexão de um banco de baterias diretamente ao barramento da UPS pode reduzir o número de baterias conectadas em série, além de proporcionar um melhor controle da tensão do barramento CC no caso de falta de energia por parte da rede ou mesmo distúrbios de entrada ou de carga. ...
Este artigo propõe um controlador robusto para um carregador de baterias de uma fonte ininterrupta de energia considerando a incerteza paramétrica da resistência interna da bateria. O modelo dinâmico do carregador de baterias é obtido pela abordagem de espaço de estados, possibilitando a utilização de uma estratégia de controle por retroação de estados. O projeto do controlador a partir de um regulador quadrático linear proporciona um desempenho ótimo para o sistema. A estabilidade robusta com incertezas paramétricas é provada por meio de desigualdades matriciais lineares. A viabilidade prática dos controladores é confirmada com resultados obtidos em hardware-in-the-loop Typhoon HIL402.
... The Uninterruptible Power Supply (UPS) systems have recently experienced a large demand as the investment on the critical loads, such as: data center, financial institution, personal computers and healthcare facilities, is dramatically increased. These critical loads, which require reliable, secure and efficient power supply, are usually connected to the grid by the UPSs, since the UPSs are able to protect the critical loads from the power outages, surges and other issues from the grid [1]. ...
... RIVEN by the increasing importance of the Uninterruptible Power Supply (UPS) in the industry including enterprise IT, commercial telecom, data center and cloud computing area [1], the global market for the UPS system is projected to soar dramatically in the next few years. Meanwhile, the strong need for the UPS system to provide more reliable, efficient and secure electrical power supply for the modern digital equipment propels the UPS technology advancement by engineers and academic researchers [2]. ...
In this paper, a DC-link voltage protection (DCVP) control method is proposed to address the DC-link overvoltage issue due to power back-feeding in parallel Uninterruptible Power Supply (UPS) system. The proposed control method is able to protect the inverter against the excessive DC-link voltage, which increases the system reliability and robustness. Moreover, a current sharing control strategy is proposed by online regulating the virtual resistance of each UPS module. The proposed current sharing control strategy is able to address the circulating fundamental and harmonic current caused by the line impedance mismatching or power back-feeding issue in the UPS system. In addition, an improved consensus-based distributed controller is proposed to alleviate the overshoot issue during the transient process in voltage amplitude and frequency restoration. Finally, the feasibility of the proposed methods is verified by experimental results from the parallel UPS prototypes.
... is a simplified block diagram of the online UPS with low frequency isolating transformer. "Ref.[6]" ...
This paper addressed the design of online uninterruptible power supply (UPS) system with a low frequency
transformer for isolation, based on given specifications which include bypass switch and battery and taken into account
the concentrated on open loop operation. Depending on the application, the online UPS system is composed by two stage
conversions of AC/DC and DC/AC, the enclosure of these freeloading effects of all components and devices is very
important to design the UPS system for acceptable performance. The initial stage of the design is based on the theoretical
calculations and few assumptions have been made throughout the design. Simulation work has been carried out by
MATLAB/Simulink program to validate the operation of the online UPS system with low frequency transformer isolation. The
analysis of the results are presented and the justifications with regards to performance evaluation parameters which some are
not satisfied the design specifications are discussed in details.
Synchronization and power-sharing control are essential for islanded parallel inverters. Traditionally, droop control and other grid-forming control are the typical methods with voltage-supporting abilities. However, those methods only apply to systems with a certain line impedance. For the application of uninterruptible power supply (UPS) systems with near-zero line impedance, droop-controlled inverters are prone to loss of stability. To address this issue, this letter introduces a new first-order phase-lock-loop (PLL)-synchronized voltagesupporting control method for the islanded operation of parallel inverters in UPS systems. It is found that the first-order PLL is employed for frequency synchronization in islanded operation. Meanwhile, voltage support and power sharing can be guaranteed with modified current control. Experimental results validate the feasibility of the proposed method
Dynamic voltage restorer (DVR) is considered as one of the best and cost-effective solution in addressing the power quality concerns in distribution systems. The integration of DVR with the reliable grid eliminates the need for external energy storage unit and can address the issue of compensating long/deep voltage sags. In this paper, a new topology, wherein the DVR taps in energy through a three-winding transformer connected to the grid is proposed. As different configurations are available for three-winding transformer, detailed analysis is conducted to find the best possible configuration of the three-winding transformer for a DVR integrated system. The studies are carried out in MATLAB/Simulink platform and the results are presented.
Voltage sags have emerged as major problems in power quality in the recent years and the categorization of methods and tools available for reducing voltage sag is becoming increasingly crucial. Modern approaches and tools for minimizing voltage sag are based on an extensive research, aimed at developing effective categorization techniques to assist end users in selecting the most suitable tools and settings. To begin, this research provides a comprehensive assessment of the existing voltage sag control methods and equipment. Furthermore, it presents a classification scheme that divides voltage sag control strategies into three groups: those implemented by the power provider, the customer, and the equipment manufacturer. A classification system for voltage sag control equipment based on the number and type of power supply, taking into account the variations between single and dual power supply voltage sag control devices is also proposed. Additionally, to assist consumers in selecting the optimal device, this research demonstrates how primary voltage sag control equipment utilizes the preventive measures and an integrated software.
This paper presents describes about a unique DC Discharge System for Offline UPS. Whenever an offline mode UPS is connected to a motor load, as the motor decelerates either through the change of torque or due to the Dynamic braking there will be a regenerative energy produced. If this regenerative energy flows back into the UPS, then over-voltage condition takes place and causes damage to the UPS. This regenerative energy can bypass through the battery in online mode. But online mode operation of UPS needs high cost as large heat sinks are required. So, offline mode of operation is preferred in most of the cases. The proposed system dissipates the regenerative energy through the connected resistors and the remaining energy is used for the gating of semiconductor switches inside the UPS. The detailed principle of the proposed method is discussed in this project. The entire Discharge System and Gate pulse generating System are simulated in Proteus Software and the results are provided.
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.
An uninterruptible power supply (UPS) is a device that can continuously supply power for a certain period when a power outage occurs. UPS devices are used by national institutions, hospitals, and servers, and are located in numerous public places that require continuous power. However, maintaining such devices in good condition requires periodic maintenance at specific time points. Efficient monitoring can currently be achieved using a battery management system (BMS). However, most BMSs are administrator-centered. If the administrator is not careful, it becomes difficult to accurately grasp the data trend of each battery cell, which in turn can lead to a leakage or heat explosion of the cell. In this study, a deep-learning-based intelligent model that can predict battery life, known as the state of health (SoH), is investigated for the efficient operation of a BMS applied to a lithium-based UPS device.
In order to ensure the uninterrupted power supply, it is necessary for microgrid to operate in both grid-connected mode and islanded mode. To address this concern, this chapter introduces a unified decentralized control strategy for both grid-connected and islanded operation of the series-type microgrid (CMG). It can realize the smooth mode switching without the need of changing controllers. In terms of the scheme, the system always holds a unique equilibrium point regardless of the grid-connected or islanded operation. Since the CMG is performed in decentralized manner without any communication, it is a reliable and cost-effective solution. Moreover, the self-synchronization of each DG is obtained under both the resistance-inductance (RL) and resistance-capacitance (RC) loads. The small-signal stability is proved and the design of control parameters is given. Finally, the feasibility of the method is verified by simulation and OPAL-RT based real-time simulation results.KeywordsUnified decentralized controlGrid-connectedIslanded operationSeamless transitionUnique equilibrium pointSynchronizationSeries-type microgridCost-effectivePower balanceWithout communication
In the modular on-line uninterruptible power supply (UPS) system, the unequal power sharing may exist in the system due to the mismatched line resistance, leading to the circulating current, overloading, and even tripping the system. This chapter introduces a dynamic consensus algorithm (DCA)-based virtual resistance control strategy to share the active power and harmonic power. This approach does not require a central controller, and the communication links are only required between the neighboring UPS modules, which enhances system’s reliability and flexibility. Simulation results and experimental results are provided to verify the effectiveness of the control strategy.KeywordsAdaptive virtual resistanceModular uninterruptible power supply (UPS)Power sharingConsensusAC/DC rectifiersDC/AC invertersDroop controlHarmonic decouplingFrequency locked-loopHierarchical control
This paper focuses on the relationship between the controller and the control delay of the low switching frequency converter with active power filtering function. This paper also investigates the effect of the current transformer (CT) probe on the measured signals for a long-distance compensation of the non-linear loads. An one step deadbeat controller under consideration of the CT model is presented to meet the demands with the control delay compensation and the correction of the distorted measured signals. Finally, the laboratory test results will be used to support the aforementioned analysis.
Driven by global concerns about the climate and the environment, the world is opting for renewable energy sources (RESs), such as wind and solar. However, RESs suffer from the discredit of intermittency, for which energy storage systems (ESSs) are gaining popularity worldwide. Surplus energy obtained from RESs can be stored in several ways, and later utilized during periods of intermittencies or shortages. The idea of storing excess energy is not new, and numerous researches have been conducted to adorn this idea with innovations and improvements. This review is a humble attempt to assemble all the available knowledge on ESSs to benefit novice researchers in this field. This paper covers all core concepts of ESSs, including its evolution, elaborate classification, their comparison, the current scenario, applications, business models, environmental impacts, policies, barriers and probable solutions, and future prospects. This elaborate discussion on energy storage systems will act as a reliable reference and a framework for future developments in this field. Any future progress regarding ESSs will find this paper a helpful document wherein all necessary information has been assembled.
The eco-mode operation provides a high-efficiency operation for the double-conversion uninterrupted power supplies (UPSs), which utilizes the solid-state transfer switches (STS) path to power the loads and relies on the converter as alternate resources when the power quality degrades. For this operation, the commutation issue is a key point to confirm the protection of susceptible loads. Conventional thyristor-based STS system has the advantages of low cost and low conduction losses, but the natural commutation often prolongs the transfer process. Consequently, the susceptible loads suffer from severe grid faults for a long time. This paper investigates the commutation mechanism between the thyristor-based STS system and the double-conversion UPS. A forced commutation control is presented to accelerate the transfer process through the back-to-back neutral-point clamped (BTBNPC) converter. Besides, the waveform quality and dynamics of both AC end and DC end are considered for the BTBNPC converter. Finally, the laboratory test results are provided to validate the effectiveness of the proposed approach.
With the increasingly widespread use of modern communication systems, advanced medical equipment, advanced living facilities, and emergency systems requiring high-quality energy, there is an increasing need for reliable, efficient, and uninterrupted electricity supplies. Consequently, Uninterruptible Power Supplies (UPS) have recently experienced growing demand. However, because the stored energy of a UPS battery is only used in emergency situations, the battery utilization rate of a UPS is very low. Therefore, a hybrid UPS that integrates an Energy Storage System (ESS) with a UPS has recently been developed. Unlike the conventional UPS, this hybrid UPS can increase the battery utilization rate by using the stored energy of the battery when the grid is under normal operation. However, when a grid fault occurs, the hybrid UPS has to supply emergency power to critical loads. Therefore, transient voltage across the DC-link that could affect the power quality of critical loads can occur during mode transition. This paper proposes the operation method of a hybrid UPS with ESS function to minimize the transient voltage across the DC-link. PSCAD/EMTDC software is used to verify the validity of the proposed operation method.
Backup power system (BPS) compatible with two options of primary power sources; grid-connected power (AC) or solar PV-power (DC), to provide power to household appliances that comprises; a rechargeable battery bank, a charging-balancing circuit to keep the battery fully charged when power from the utility grid is available, a battery management circuit to optimize a voltage output of the system and protect individual batteries from overcharging thereby prolonging the operating lifetime of batteries, a relay switch circuit controlled by the main power source to changeover the load/appliances between direct link through bypassing the main power and the storage battery power when both options of main power are unavailable, three led indicators to display the battery status. Short circuit protection is provided to protect the backup power system from appliance short circuits, and to protect the batteries in the event of a short circuit within the system. The result shows the excellent utilization of the traditional BPS losses, wherein some appliances, the proposed topology can achieve about 99% power efficiency as compared with the traditional one.
Backup power system (BPS) compatible with two options of primary power sources; grid-connected power (AC) or solar PV -power (DC), to provide power to household appliances that comprises; a rechargeable battery bank, a charging-balancing circuit to keep the battery fully charged when power from the utility grid is available, a battery management circuit to optimize a voltage output of the system and protect individual batteries from overcharging thereby prolonging the operating lifetime of batteries, a relay switch circuit controlled by the main power source to change-over the load/appliances between direct link through bypassing the main power and the storage battery power when both options of main power are unavailable, three led indicators to display the battery status. Short circuit protection is provided to protect the backup power system from appliance short circuits, and to protect the batteries in the event of a short circuit within the system. The result shows the excellent utilization of the traditional BPS losses, wherein some appliances, the proposed topology can achieve about 99% power efficiency as compared with the traditional one.
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 (DCVP) 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.
Traditional Uninterruptible Power Supplies (UPS) only provide stable power to critical loads in emergency situations, while Energy Storage Systems (ESS) perform functions such as generator output stabilization, frequency control, peak shaving, and load leveling. As the global ESS market expands, various ESS supply policies are being implemented in a number of countries. Accordingly, research and development of a hybrid UPS-ESS system combining the advantages of UPS and ESS are underway in order to ensure critical load stability in case of emergency. For such a situation, we propose the development of a system with a customer load management function by simply adding a converter and battery pack to a widely used conventional UPS. The proposed system in this paper is more economical than a hybrid UPS-ESS system or an ESS. In addition, the proposed system performs peak-clipping and load-shifting according to time-based rates, and has a longer power outage time in case of emergency without needing to communicate with the existing UPS.
In this paper we provide an implementation, evaluation, and analysis of PowerHammer, a malware (bridgeware [1]) that uses power lines to exfiltrate data from air-gapped computers. In this case, a malicious code running on a compromised computer can control the power consumption of the system by intentionally regulating the CPU utilization. Data is modulated, encoded, and transmitted on top of the current flow fluctuations, and then it is conducted and propagated through the power lines. This phenomena is known as a 'conducted emission'. We present two versions of the attack. Line level powerhammering: In this attack, the attacker taps the in-home power lines1 that are directly attached to the electrical outlet. Phase level power-hammering: In this attack, the attacker taps the power lines at the phase level, in the main electrical service panel. In both versions of the attack, the attacker measures the emission conducted and then decodes the exfiltrated data. We describe the adversarial attack model and present modulations and encoding schemes along with a transmission protocol. We evaluate the covert channel in different scenarios and discuss signal-to-noise (SNR), signal processing, and forms of interference. We also present a set of defensive countermeasures. Our results show that binary data can be covertly exfiltrated from air-gapped computers through the power lines at bit rates of 1000 bit/sec for the line level power-hammering attack and 10 bit/sec for the phase level power-hammering attack.
Contenido: Introducción; Diodos semiconductores de potencia; Circuitos con diodos y circuitos rectificadores; Tiristores; Rectificadores controlados; Controladores de voltaje CA; Técnicas de conmutación de tiristores; Transistores de potencia; Pulsadores de CD; Inversores de modulación de ancho de pulso; Convertidores de pulso resonante; Interruptores estáticos; Fuentes de poder; Propulsores de CD; Propulsores de CA; Protección de dispositivos y circuitos; Apéndices.
Uninterruptible Power Supplies (UPS) FAQ version 2.3
- N Christenson