Uninterruptible Power Supply System Research Articles

A Comparative Analysis of Support Vector Machine and Decision Tree Algorithm for Predicting Fault in Uninterruptible Power Supply Systems

Power supply systems can have problems, and Ghana Gas Limited is not an exception. Ghana Gas Limited uses an intricate Uninterruptible Power Supply (UPS) system which is made up of several parts such as electromechanical components, PCB boards, and electrolytic capacitors. The majority of components have technical lifespans that are governed by usage, operational environment, and working conditions, such as electrical stress, working hours, and working cycles. Most of the time, these errors affect the integrity and power supply after manufacture. The issue is that it takes longer for the professionals who operate on this machine to recognize these flaws, which makes it difficult for them to predict errors quickly or anticipate the likelihood of faults happening in the system components at an early stage for effective corrective action to be performed. Support vector machines (SVM) and decision trees were used in this study to anticipate faults for technical data scheduling of uninterruptible power supply systems for Ghana Gas Limited in an efficient manner. Based on a comparative analysis using these two techniques, faults in Ghana Gas Limited's power supply system were predicted using a four-hour daily interval dataset on UPS recordings, including input voltage, battery voltage, battery current, and alarm, spanning from August 2017 to October 2023. The findings depicted that the support vector machine was more efficient in detecting the fault locations in the power supply system with an accuracy of 96.80%, recall of 99.80%, precision of 100 %, F1-score of 93.15%. The results from the error metrics also validate the measures in assessing the predictive ability of the model with MAE of 0.42%, MSE of 1.18%, RMSE of 4.45%, R2 of 99.97%, RMSLE of 0.036%, and MAPE of 0.21%.

Vienna Rectifier Modeling and Harmonic Coupling Analysis Based on Harmonic State-Space

Due to the high permeability characteristics of power electronic devices connected to the distribution grid, the potential harmonic coupling problem cannot be ignored. The Vienna rectifier is widely utilized in electric vehicle charging stations and uninterruptible power supply (UPS) systems due to its high power factor, adaptable control strategies, and low voltage stress on power switches. In this paper, the three-level Vienna rectifier is studied, and the harmonic state-space (HSS) method is used to model the rectifier. The proposed model can reflect the harmonic transfer characteristics between the AC current and the DC output voltage at various frequencies. Finally, the model’s accuracy and the corresponding harmonic characteristics analysis are further verified by simulation and experimental test results. The results show that the harmonic state-space modeling used for Vienna rectifiers can reflect the harmonic dynamics of the AC and DC sides, which can be used in stability analysis, control parameter design, and other related fields.

Current Sensorless Pole-Zero Cancellation Output Voltage Control for Uninterruptible Power Supply Systems with a Three-Phase Inverter

This article presents a proportional–derivative (PD) type output voltage regulator without the current feedback, taking into account system parameter and load variations. The main advantages are given as follows: First, the first-order output voltage derivative observer is developed without the requirement of system parameter information, which makes it possible to stabilize the system without current sensing. Second, a simple self-tuner implements the feedback-loop adaptation by updating the desired dynamics accordingly. Third, the observer-based active damping injection for the PD-type controller results in the closed-loop system order reduction to 1 by the pole-zero cancellation, including the disturbance observer as a feed-forward term. The prototype uninterruptible power supply system comprised of a 3 kW three-phase inverter, inductors, and capacitors verifies the practical merits of the proposed technique for linear and nonlinear loads.

Design and management of photovoltaic energy in uninterruptible power supplies

The growing demand for sustainable systems due to climate change has led to increased reliance on renewable energy sources. However, this transition has raised concerns about power quality in power systems due to climate variations and the intermittent nature of renewables, photovoltaic energy generation in particular. In this context, uninterruptible power supply systems play a crucial role in ensuring reliable and high-quality energy supply. As an added benefit, photovoltaic energy generation may be integrated into uninterruptible power supply systems by sharing the inverter already present and storing generated energy in the batteries. In this paper, it is presented the design and management of photovoltaic energy, integrated into double-conversion uninterruptible power supplies. A method for selecting the suitable number of panels to be used in series in a given application is developed, considering the panel model used, and the environmental mission profile. A management algorithm for tracking the maximum power point of the photovoltaic generation while ensuring the hold-up time is proposed, introducing the dynamic hold-up time concept. Using the point for maximum power instead of the dynamic hold-up time at two different locations leads to voltage sags of 12.6% in the first and 24.3% in the second. Using the method to select the number of panels in series, 13 panels are selected for the first location, resulting in an annual generation that is only 2.3% smaller than the maximum power point. The results are validated using a hardware-in-the-loop platform and the dSpace Microlabbox 1202.

Vanadium Redox Flow Battery Stack Balancing to Increase Depth of Discharge Using Forced Flow Attenuation

Vanadium redox flow batteries are gaining great popularity in the world due to their long service life, simple (from a technological point of view) capacity increase and overload resistance, which hardly affects the service life. However, these batteries have technical problems, namely in balancing stacks with each other in terms of volumetric flow rate of electrolyte. Stack power depends on the speed of the electrolyte flow through the stack. Stacks are connected in parallel by electrolytes to increase battery power. If one of the stacks has a lower hydrodynamic resistance, the volume of electrolytes passing through it increases, which leads to a decrease in the efficiency of the remaining stacks in the system. This experimental study was conducted on a 10 kW uninterruptible power supply system based on two 5 kW stacks of all-vanadium redox flow batteries. It was demonstrated that forced flow attenuation in a circuit with low hydrodynamic resistance leads to an overall improvement in the system operation.

Research on Calendar Aging for Lithium-Ion Batteries Used in Uninterruptible Power Supply System Based on Particle Filtering

The aging process of lithium-ion batteries is an extremely complex process, and the prediction of the calendar life of the lithium-ion battery is important to further guide battery maintenance, extend the battery life and reduce the risk of battery use. In the uninterruptible power supply (UPS) system, the battery is in a floating state for a long time, so the aging of the battery is approximated by calendar aging, and its decay rate is slow and difficult to estimate accurately. This paper proposes a particle filtering-based algorithm for battery state-of-health (SOH) and remaining useful life (RUL) predictions. First, the calendar aging modeling for the batteries used in the UPS system for the Shanghai rail transportation energy storage power station is presented. Then, the particle filtering algorithm is employed for the SOH estimation and RUL prediction for the single-cell battery calendar aging model. Finally, the single-cell SOH and RUL estimation algorithm is expanded to the pack and group scales estimation. The experimental results indicate that the proposed method can achieve accurate SOH estimation and RUL prediction results.

Evaluation and Improvement of Backup Capacity for Household Electric Vehicle Uninterruptible Power Supply (EV-UPS) Systems

The use of electric vehicles (EVs) for household uninterruptible power supplies (UPSs), particularly in rural areas, can greatly improve household power reliability. However, because EVs are mobile, the evaluation of backup capacity for EV-UPS systems is completely different when compared to traditional UPSs. As a result, the focus of this paper is on the evaluation and improvement of backup capacity for EV-UPS systems. The architectures for EV-UPS systems are presented first. The methodology for calculating backup capacity for EV-UPS systems is then presented, followed by four detailed cases based on different grid failure times. Furthermore, the impact of system operating parameters on backup capacity, such as different load power, EV mobility pattern parameters, and grid outage durations, is investigated. The results of backup capacity in cases of different operating parameters are detailed using an EV mobility model. An improved strategy for increasing backup capacity is proposed, in which more backup energy can be released during a power outage. Meanwhile, the next trip requirement is unaffected. The backup capacity with the improved strategy is then calculated and compared to the results with the traditional strategy. Finally, a 5 kW EV-UPS experimental platform is constructed, and the experimental results are presented to validate the proposed method.

Study of the influence of the type of pores present in the electrodes on the behaviour of a SWAGELOK-type supercapacitor

The sharp increase in energy consumption in recent years has increased the demand for new energy storage systems or the improvement of existing ones. Supercapacitors are the answer to this great challenge needed by any industrialized society. In this work, to improve the storage system of these supercapacitors, the composition of carbon-based electrodes has been modified by adding carbon carbonaceous materials and the influence of porous texture (porosity and porosity distribution) on carbonaceous electrodes. Thus, a commercial activated carbon-based electrode PCO-1000 was modified by adding structured carbons TEG, TEG-B92, and carbon black V3. For this purpose, three PCO-1000 (commercial activated carbon) base electrodes were prepared, to which 5 % Teflon was added as a binder and 5 % TEG (structured carbon), TEG-B92 (92 h heat-treated structured carbon) and V3 (carbon black), to provide the electrodes with carbon porous structures, as well as graphitic structures with carbon separation between lamellar layers. The structured carbons (TEG and TEG-B92) have carbon structures formed by interlamellar layers at carbon spacing distances and micro, macroporous pore distributions versus V3 carbon black with meso-macroporous distributions. Furthermore, carbon black V3 was selected as it has a pore distribution (meso-macroporous) greater than 50 Å which is electrochemically accessible by aqueous solutions of H2SO4, in an organic medium large solvated ions are not accessible to small pores. The supercapacitor prepared on the PCO-1000 basis with V3 (E-V3), is the best performing, with capacity, power, and energy parameters far superior to the other samples. This seems to indicate that E-V3 supercapacitors with a varied pore structure perform better than those with a predominantly micropore distribution. It seems to be deduced that it is the wide mesopores present in V3 that favour the diffusion of ions inside the carbons.In conclusion, the resistance of the supercapacitor cell is strongly dependent on the resistance of the electrolyte used, the size of the electrolyte ions in which it diffuses, and the size of the electrode pores, so the characteristics of the electrode material and the electrolyte must be considered together and not separately.Finally, this study could be of great importance in the fabrication of electrodes with a certain porosity distribution and predominance of wide mesopores and macropores to achieve important energy storage capacities in this type of supercapacitors and their application to hybrid electric vehicles, computers, uninterruptible power supply systems (UPS), motor starters, etc.

Sensorless Model Predictive Control of Single-Phase Inverter for UPS Applications via Accurate Load Current Estimation.

Single-phase inverters with an output LC filter, can generate low distortion output voltages, which are suitable for uninterruptible power supply (UPS) systems. The UPS system provides emergency power in the case of utility power failure, requiring high reliability and clean power. The sensorless control method is actually a soft-sensing technique, that reduces system cost, measurement-related losses, and, especially important for UPS systems, enhances the system reliability. This paper proposes a load current sensorless finite control set model predictive control (FCS-MPC) scheme for a single-phase UPS inverter. A time varying observer is proposed, which offers the accurate estimation for individual components simultaneously in periodic load current signal, without subsequent complex calculations. Compared with another two typical sensorless methods (the low-pass filter and the Kalman filter), the proposed observer-based FCS-MPC strategy has smaller load current estimation error and lower output voltage distortion, under both linear and nonlinear loads. The theoretical analysis is verified through simulation and experiment. A single-phase inverter rapid control prototype (RCP) is set up with the Speedgoat real-time target machine, to confirm the effectiveness of the system.

Life cycle assessment-based environmental impact analysis of a tier 4 data center: A case study in Turkey

Data centers are responsible for 1% of the global electricity consumption, leading to significant greenhouse gas emissions. This study is considered to be the first in the literature which uses life cycle assessment to investigate the environmental impacts of a tier-4 data center operation. The impacts were calculated via CCaLC software with Ecoinvent2 database by using CML2001 method. Office supplies, electricity, water and fuel consumption, direct emissions, and end-of-life treatment where applicable were considered in the system boundaries. The results show that more than 98% of the environmental impacts are caused by the electricity consumption in the data center. It was found out that improvements made in cooling and uninterrupted power supply systems have the potential to reduce the annual impacts by approximately 15% on average. Compared to the average data center in the United States, the data center analyzed in this study was found to have approximately 20% higher impact scores. The main conclusion of this study is that it is evident that governments should provide incentives such as tax deductions to promote energy efficiency and/or renewable energy utilization in the data centers for better impact mitigation.

Hibridno neprekidno napajanje sistema za navodnjavanje povrtarskih kultura

The paper presents the realization of a hybrid and uninterruptible power supply system based on green or renewable energy sources (solar and wind) which is used for irrigation of vegetable crops on the "smart land" at the location of the town Belegiš, which is located in the immediate vicinity of Belgrade and on the side of the Danube River. Within the power system are realized the photovoltaic power plant with an output AC power of 8 kW, the wind generator with a power of 0.5 kW and battery bank 48Vdc/720Ah. This three of power supplies are as primary power sources, while a diesel electric generator (DEG) with a power of 7.5 kW, is one auxiliary power source. In addition to this hybrid and uninterruptible power supply, a system for smart management for irrigation has been implemented. At the end of the paper will be present the experimental results obtained during the exploitation.

An overview of Uninterruptible Power Supply Systems

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.

Distributed Dynamic Event-Triggered Control for Accurate Active and Harmonic Power Sharing in Modular On-Line UPS Systems

Due to the mismatched line resistance in the modular online uninterruptible power supply (UPS) systems, accurate active power and harmonic power sharing is an arduous work. To tackle this issue, this article proposes a distributed dynamic event-triggered control for the power sharing to accurately compensate the effect of mismatch among the line resistances. Benefiting from the proposed control strategy, the UPS modules adaptively regulate the virtual resistance at the fundamental and harmonic frequencies, and hence, the accurate active power and harmonic power sharing are achieved. In addition, the suggested technique allows the UPS modules to exchange information at only the event-triggered times, which greatly reduces the number of communication among the neighboring units. Furthermore, the system's stability is analyzed using a Lyapunov function. Finally, experimental case studies are provided to evaluate the performance of the proposed control strategy, showing its effectiveness in achieving the accurate power sharing, and plug-and-play capability.

Design and analysis of robust backstepping controller for DC suppression of parallel UPS inverter system

AbstractHere, an improved control strategy is proposed, which adopts a non‐linear robust backstepping controller to eliminate DC circulating current in a parallel uninterruptible power supply (UPS) system. The traditional active and reactive power sharing control can ideally suppress the AC circulating current, but cannot effectively restrict the DC circulating current. Based on the traditional active power and reactive power sharing control (TAPRPSC) of the parallel UPS system, the proposed control strategy is used in each parallel inverter module to suppress the DC component disturbance in the inverter output voltage, which varies within a certain range. Hence the desirable steady‐state and dynamic performance of the system can be obtained. Moreover, the Lyapunov method is utilized to ensure the stability and robustness of the system. A parallel system of two UPS inverters with the proposed control strategy is built by Matlab/Simulink, and further experiments are carried out on the semi‐physical simulation platform of the Modelling Tech. Both the simulation and experimental results verify the effectiveness of the proposed control strategy for DC circulating current suppression and ideal output voltage tracking.

From Triboelectric Nanogenerator to Uninterrupted Power Supply System: The Key Role of Electrochemical Batteries and Supercapacitors

Currently, significant advances have been made in the field of high-performance energy storage technologies, such as Li-ion batteries and supercapacitors. However, the limited lifespans, as well as the frequent charging or replacement requirements, pose a set of challenges for their application in the Internet of things (IoTs), because the full power of the IoTs can only be realized by the sustainable operation of physical objects, especially embedded sensors, for the purpose of connecting and exchanging data with other devices and systems continually in real-time. A viable option for achieving the sustainability of the IoTs may be the combination of renewable energy harvesting technologies such as triboelectric nanogenerators (TENGs) with electrochemical energy storage technologies, where TENGs can harvest mechanical energies from ambient environments and transform them into electricity for charging electrochemical batteries and supercapacitors (SCs) conveniently, thus developing a new type of TENG-based uninterrupted power supply (TENG-UPS). In this review, we begin from a brief description of the operating mode of TENG and the integration strategy of TENG-UPS. The latest advances in the TENG-UPS are then thoroughly discussed from the perspective of structural design and system integration. Cutting edge developments of the as-designed self-powered sensing systems are then concisely illustrated to disclose the application potential in the IoTs. The main obstacles and future prospects for developing TENG-UPS-based intelligent systems are also highlighted in terms of design and manufacture at the conclusion. We expect this review will appropriately shine a light on the understanding of the key role of electrochemical energy storage devices in the development of TENG-based energy harvesting technology as well as the self-powered intelligent systems.

The Potential Role of Hybrid Renewable Energy System for Grid Intermittency Problem: A Techno-Economic Optimisation and Comparative Analysis

The renewed interest for power generation using renewables due to global trends provides an opportunity to rethink the approach to address the old yet existing load shedding problem. In the literature, limited studies are available that address the load shedding problem using a hybrid renewable energy system. This paper aims to fill this gap by proposing a techno-economic optimisation of a hybrid renewable energy system to mitigate the effect of load shedding at the distribution level. The proposed system in this work is configured using a photovoltaic array, wind turbines, an energy storage unit (of batteries), and a diesel generator system. The proposed system is equipped with a rule-based energy management scheme to ensure efficient utilisation and scheduling of the sources. The sizes of the photovoltaic array, wind turbine unit, and the batteries are optimised via the grasshopper optimisation algorithm based on the multi-criterion decision that includes loss of power supply probability, levelised cost of electricity, and payback period. The results for the actual case study in Quetta, Pakistan, show that the optimum sizes of the photovoltaic array, wind turbines, and the batteries are 35.75 kW, 10 kW, and 28.8 kWh, respectively. The sizes are based on the minimum values of levelised cost of electricity (6.64 cents/kWh), loss of power supply probability (0.0092), and payback period (7.4 years). These results are compared with conventional methods (generators, uninterruptible power supply, and a combined system of generator and uninterruptible power supply system) commonly used to deal with the load shedding problem. The results show that the renewable based hybrid system is a reliable and cost-effective option to address grid intermittency problem.

Development and research of uninterruptible power supply system for networks with supply voltage up to 24 V

Objectives. Due to the continuous rapid development of renewable energy sources, requirements for secondary power supply systems keep increasing from year to year. Productive uptime for end users is dependent on the efficiency and stability of the power supply system. Such systems should be able to distribute and store energy from renewable sources having various parameters and configurations. Therefore, the present work is aimed at developing technical solutions for efficient uninterruptible secondary power supply systems in low voltage DC networks.Methods. Advanced circuitry solutions are used for performing pulse conversions with high efficiency. The flexible hardware-software system is used for implementing the parameter control system.Results. An uninterruptible power supply for low-voltage DC networks is developed. The description of subsystems and calculations for all main elements including the power ones are given. Using a contemporary component base, the system prototype is assembled, configured, and measured by parameters. The presented solutions allow achieving the universality of the system in terms of the input and output voltage range. Support for the fast-charging Power Delivery protocol is integrated. As well as regulating the battery charging current and voltage, the Li+ battery charging controller permits changes in the number of chargeable cells. The monitoring and control unit monitors network parameters and controls the system automation. Using a microcontroller as the control device, it is possible to easily change control parameters by changing software settings. Dual redundancy of the module monitoring the built-in battery parameters is used to ensure the reliability and safety of system functioning. Support for the standardized I2C communication protocol with a separate power bus allows any necessary sensors to be connected for monitoring system parameters. External high-power devices controlled by a PWM signal may be added, if required. In the paper, the Li+ battery charging profile recommended by the manufacturer is provided.Conclusions. The designed system provides stable power supply to end users at a power consumption up to 40 W for at least 45 min. The automation demonstrates reliable operation.

Comparative Analysis of Modulation Techniques on the Losses and Thermal Limits of Uninterruptible Power Supply Systems.

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.

Neural network-based control for RRP-based networked systems under DoS attacks with power interval

This paper is concerned with the optimal control problem for networked systems with the round-robin protocol (RRP) under the denial-of-service (DoS) attacker with power interval. In the literature, the control design is studied for the linear networked system subject to the DoS attacks with a known constant power or a known constant probability of data-packet dropouts. In this paper, the objective is to control the unknown nonlinear system in the communication network subject to the DoS attacks with a power interval and a time-varying probability of data-packet dropouts. The effects of the DoS attacks with power interval on a networked system under RRP are modeled accurately. A neural network (NN) -based observer is designed for the nonlinear system under the DoS attacks with power interval, and the relationship between the DoS attacker power interval and state estimation error is obtained. The NN actor–critic policy for the optimal control of the RRP-based networked system under the DoS attacks with power interval is found with adaptive dynamical programming, and stability of the resulting control system is analyzed. The proposed control method is demonstrated by a networked uninterruptible power supply system.

Determining the dynamics of electromagnetic fields, air ionization, low-frequency sound and their normalization in premises for computer equipment

This paper reports a study into the quantitative values and dynamics of physical factors in premises and workplaces of stationary and portable computers. The factors that are practically not perceived by the senses of operators were investigated. It is established that modern monitors do not generate electromagnetic fields of hygienically significant levels. System units generate electric fields (18‒22 V/m) and magnetic fields (220‒245 nT) that are approaching the maximum permissible. Sources of uninterruptible power supply and fluorescent lighting systems generate excess magnetic fields (up to 2250 nT and 2300 nT), respectively. The main excessive factor for portable computers is electric fields (up to 9 kV/m), which is the cause of air deionization in the user's zone of stay. It is shown that one system unit in the normative volume of the room (20 m3) deionizes air (into 100 cm-3 positive and 200 cm-3 negative). The generation of ions by modernized laser printers and photocopiers of various models (up to 1500 cm-3 and 2800 cm-3, respectively) was investigated. The distances at which the ionic composition of the air corresponds to the background values (1.0‒1.5 m) were determined. That requires the introduction of artificial air ionization in workplaces of users and a decrease in the levels of electrostatic fields. The spectral composition and amplitudes of magnetic fields of external power supplies of laptop computers were determined. It is shown that the difference in sound levels measured on the scales "Lin" and "A" reaches 24 dB, which indicates a significant impact of infrasound on users. Membrane-type protective panels configured for maximum resonant frequencies of low-frequency sound and infrasound have been proposed