Uninterruptible Power System Research Articles

FEATURES OF ENSURING ELECTROMAGNETIC COMPATIBILITY OF UNINTERRUPTIBLE POWER SYSTEMS

An overview of the main structures of uninterruptible power systems is provided. The impact on internal-system and external-system electromagnetic compatibility of these devices is determined. Contemporary standards and requirements for ensuring electromagnetic compatibility of uninterruptible power systems are analyzed. Features of the structures of uninterrupted power systems such as online, offline and line interactive by the conductive path of propagation of interference are given. The main advantages of eco uninterrupted power supply are summarized. A generalized approach is proposed for the application of radiofrequency interference filters depending on the electromagnetic environment and features of uninterruptible power systems. Refined limitations on the possibilities of adjusting the basic and influence parasitic parameters of the filter links by symmetric and asymmetric propagation of conductive disturbances. The possibility of using remote control of the effectiveness of means of reducing conductive disturbances was assessed. The expediency of localization of control parameters of smart radiofrequency interference filters with the use of artificial intelligence is determined. References 10, figures 6, tables 2.

Preparation of Pb-Ca Master Alloy by Molten Salt Electrolysis

Lead-acid batteries (LABs) are commonly utilized in various applications such as electric motorcycles, uninterruptible power systems, and stationary energy storage devices. Calcium (Ca) is an essential element being added to Pb grid alloys to increase their mechanical strength. In this paper, molten salt electrolysis is used to prepare Pb-Ca master alloy in molten CaCl2-NaCl at 700 °C. The Ca concentration reaches 2.51 wt%, and the current efficiency reaches 85.0% for the 1 A-scale electrolyzer and 75.8% for the 50 A-scale cell. Compared with the traditional physical mixing ways, Ca is selectively and gradually deposited in the liquid Pb cathode without worrying about the immense heat generated by mixing Ca and Pb. In addition, molten salt serves as a media to avoid the oxidation of Ca. Through thermodynamic calculations and electrochemical measurements, the Pb-Ca formation prefers to happen rather than Pb-Na alloy in molten CaCl2-NaCl because of the stronger interaction of Ca and Pb than Na and Pb. Overall, this paper provides a straightforward strategy to prepare Pb-Ca master alloys, which can be expanded to prepare various liquid semimetal alloys containing reactive metals.

Effect of SPWM Inverter in Combination with Solar Uninterruptible Induction Motor Drive

The increase in the popularity of uninterruptible induction motor drives has prompted industrial applications to be interested in this technology. Each of these drives has a rectifier at the input that charges batteries. When there is a power outage, an inverter powered by the batteries supplies the motor with electricity. In addition, a separate system of uninterruptible power supplies is regularly installed on the industrial site. The study highlights the advantages of combining the two systems and demonstrates them with simulation and measurement results. This paper will consider connecting solar panels to combined uninterruptible power systems. Solar panels can be used to charge batteries with high efficiency, requiring only MPPT controllers. Hence, if solar panels are installed on the roofs of industrial facilities, they can be integrated into the uninterruptible power supply. The paper describes the effects of combining an uninterruptible motor drive with a single-phase inverter that mainly affects the DC bus voltage. In turn, the DC bus voltage ripple and fluctuation also affects the quality parameters of the motor and single-phase load such as the Total Harmonic Distortion. Furthermore, the paper presents the solar-assisted combined system components used for the measurement, and the results derived from them.

Partial Discharge Localization Techniques: A Review of Recent Progress

Monitoring the partial discharge (PD) activity of power equipment insulation is crucial to ensure uninterrupted power system operation. PD occurrence is highly correlated to weakened insulation strength. If PD occurrences are left unchecked, unexpected insulation breakdowns may occur. The comprehensive PD diagnostic process includes the detection, localization, and classification of PD. Accurate PD source localization is necessary to locate the weakened insulation segment. As a result, rapid and precise PD localization has become the primary focus of PD diagnosis for power equipment insulation. This paper presents a review of different approaches to PD localization, including conventional, machine learning (ML), and deep learning (DL) as a subset of ML approaches. The review focuses on the ML and DL approaches developed in the past five years, which have shown promising results over conventional approaches. Additionally, PD detection using conventional, unconventional, and a PCB antenna designed based on UHF techniques is presented and discussed. Important benchmarks, such as the sensors used, algorithms employed, algorithms compared, and performances, are summarized in detail. Finally, the suitability of different localization techniques for different power equipment applications is discussed based on their strengths and limitations.

An Integrated Cooperative Control Strategy for EVs Accessed Community Uninterruptible Power System

The energy storage capacity of electric vehicles (EVs) enables them to have the potential to form an uninterruptible power system (UPS) when the power supply is interrupted in the community. To solve the problems related to the reasonable power distribution and accurate voltage tracking control for EVs accessed community UPS, an integrated cooperative control strategy based on the multi-agent system is proposed in this paper. First, an improved power distribution strategy based on the P-f droop control is developed to realize the state-ofcharge balancing of EVs having different capacities and voltages. Then, a cooperative voltage tracking control strategy for EV energy storage units is developed to realize the accurate voltage tracking control, and a second-order sliding mode differentiator is designed to estimate the derivative of the virtual control law. Besides, the unknown part of the model is approximated by the fuzzy logic system, and the neighborhood synchronization error is upper-bounded by the prescribed performance control. The integrated cooperative control strategy designed is completely distributed. Results show the effectiveness of the proposed integrated cooperative control strategy.

Enabling stable cycling performance with rice husk silica positive additive in lead-acid battery

Lead-acid battery has been widely used in stationary energy storages, such as photovoltaic application, grid service and uninterrupted power system due to the advantages of high safety, recyclability, and low cost. However, the low cyclic performance limits its further applications in emerging functions. One of the main failure modes is caused by the high polarization on the PbO2 positive plate. Herein, the rice husk silica with hierarchical porous structure was used as the positive additive for preventing from the high polarization of the PbO2 positive plate. Nitrogen adsorption-desorption isothermal and X-ray diffraction confirmed that the hierarchical porous rice husk silica enlarged the electrochemical surface area of the PbO2 positive plate, endowing a high rate of active material utilization and low polarization during the charging process. Compared with the blank plate, the PbO2 plate with rice husk silica showed improved Coulombic efficiency and a prolonged cycle life. These notable features verify that the porous rice husk silica is a cost-effective positive additive for sustained lead-acid batteries.

Separation of antimony from lead-antimony alloy by molten salt electrolysis

Lead-acid batteries (LABs) are widely used in electric motorcycles, uninterruptible power systems, and stationary energy storage devices. However, spent LABs should be recycled to reuse lead (Pb) and thereby close the Pb cycle and avoid Pb contamination. In order to reuse the recovered Pb, the purity of recovered Pb should meet the required standard. Since antimony (Sb) is a common alloying element in Pb alloy grid such as the Pb-Sb alloy, separating Sb from the recovered Pb is necessary. In this paper, we proposed a molten salt electrolysis method to separate Sb from liquid Pb-Sb alloys in terms of forming a solid Ca-Sb intermetallic at the top of the liquid Pb-Sb cathode. The electrochemical separation process was performed in molten NaCl-CaCl2. The content of Sb (atomic percent) in the Pb-Sb alloy was reduced from 1% to less than 0.01% (atomic ratio). The recovery principle lies in the different alloying potentials between Ca-Sb and Ca-Pb. Hence, molten salt electrolysis is a promising separation method to recover pure Pb from spent Sb-containing Pb alloys.

Source for Autonomous Power Supply System Based on Flow Battery

The article deals with the urgent task of creating a technological and production basis for the development and serial production of energy storage systems with flow batteries and uninterruptible power systems based on them. Flow batteries are a highly efficient solution for long-term energy storage in critical and alternative energy facilities. The main advantage of the flow batteries is the ability to create a system with the required power and capacity without redundant parameters due to the fact that the characteristics of the system are regulated by independent blocks, as in a fuel cell. Among flow batteries, vanadium redox flow batteries (VRFB) are of particular interest, as they have a long service life. The main elements of a flow battery are the stack, which determines the power of the battery and its efficiency, and the electrolyte, which determines the energy capacity of the battery and its service life. A stand for testing the operating modes of the flow battery stack has been developed. A 5 kW flow battery operating on an electrolyte with the addition of hydrochloric acid, which is a stabilizer in new generation electrolytes, has been tested.

Centralized fusion robust filtering for networked uncertain systems with colored noises, one-step random delay, and packet dropouts

This paper studies the estimation problem for multisensor networked systems with mixed uncertainties, which include colored noises, same multiplicative noises in system parameter matrices, uncertain noise variances, as well as the one-step random delay (OSRD) and packet dropouts (PDs). This study utilizes the centralized fusion (CF) algorithm to combing all information received by each sensor, which improve the accuracy of the estimation. By using the augmentation method, de-randomization method and fictitious noise techniques, the original uncertain system is transformed into an augment model with only uncertain noise variances. Then, for all uncertainties within the allowable range, the robust CF steady-state Kalman estimators (predictor, filter, and smoother) are presented based on the worst-case CF system, in light of the minimax robust estimation principle. To demonstrate the robustness of the proposed CF estimators, the non-negative definite matrix decomposition method and Lyapunov equation approach are employed. It is proved that the robust accuracy of CF estimator is higher than that of each local estimator. Finally, the simulation example applied to the uninterruptible power system (UPS) with colored noises and multiple uncertainties illustrates the effectiveness of the proposed CF robust estimation algorithm.

Analysis and design of a wide range ZVS/ZCS push–pull DC/DC converter with voltage clamped

A new isolated zero-voltage switching (ZVS)/zero-current switching (ZCS) push–pull (PP) DC/DC converter is presented. One auxiliary switch S3 and a clamping capacitor Cc are introduced at the primary of the conventional push–pull converter and a voltage doubler-rectifier is adopted on the secondary side. This proposed converter has the features: (1) Switching losses are reduced significantly owing to zero-voltage switching of primary switches and zero-current switching of secondary diodes over a wide load range variation. (2) The voltage spike across all of the power devices can be clamped that enable the use of low-voltage, low-performance, and lower-cost devices. (3) The energy stored in the transformer leakage inductance is used for the soft-switching action and no additional resonant inductor is required. (4) A voltage doubler-rectifier is employed to remove the problem of the diode reverse-recovery effect and reduce the duty cycle loss that provides a much higher voltage conversion ratio. These merits make this simple converter provide an attractive solution for a distributed power system, uninterruptible power system, or battery charge/discharge system. The detailed operation, analysis, design, comparative study, and experimental results for the proposed converter are presented and a 600 W prototype was developed to verify the discussed theoretical analysis.

Control technology and development status of flywheel energy storage system

Flywheel energy storage technology has attracted more and more attention in the energy storage industry due to its high energy density, fast charge and discharge speed, long service life, clean and pollution-free characteristics. It is wwidely used in uninterruptible power system, grid frequency modulation, energy recovery and reuse and other fields. With the development of flywheel rotor materials, motors, bearings and control technology, flywheel energy storage technology has been greatly developed. Introducing the basic structure of the flywheel energy storage system in the above three applications. Typical charge-discharge control strategies are given for the three sensor-less algorithms of model reference adaptive control, sliding mode observer andextended Kalman filter, which are suitable for flywheel energy storage devices.

ИССЛЕДОВАНИЕ ЗАВИСИМОСТИ ВНУТРЕННЕГО СОПРОТИВЛЕНИЯ СВИНЦОВО-КИСЛОТНОЙ АККУМУЛЯТОРНОЙ БАТАРЕИ ОТ ВЕЛИЧИНЫ ОСТАТОЧНОГО ЗАРЯДА

Currently, lead-acid batteries are widely used in uninterruptible and emergency power systems, which may include dozens or even hundreds of individual batteries. In order to increase the reliability and simplify the process of diagnostics of such systems, it is proposed to use the method of monitoring the internal impedance of batteries in a certain frequency band in conjunction with the control of open circuit voltage. The pa-per presents the results of experimental studies of the dependence of the total resistance of lead-acid batteries on the degree of residual charge, as well as the conclusions obtained in the analysis of experimental data.

Analysis on Relay Coordination in IEEE 9 bus PV integrated Hybrid Power System using ETAP software: A case study

The modern power system of the country like India, there is an important need to design an uninterrupted electrical power system network having adequate security, stability and reliability. In this present paper an IEEE 9-Bus hybrid system is considered for a short circuit analysis and protection relying coordination for designing of overcurrent relaying scheme to operate the relay efficiently and disconnect the fault section from healthy section instantly. It also compares the differences between existing systems with PV connected hybrid system. Now days, when Electrical Power System adopts the Renewable Energy source with existing power source of the network, the main challenge is to design a protection scheme to protect the hybrid system where different intermittent sources make a great impact. To design such a power system the behavior of the existing protection scheme need to be analyzed. In this paper authors simulate an IEEE 9-Bus system using ETAP simulation and analysis is made through Load Flow Study and Short Circuit Analysis. The study reveals that the behavior of the protection system changes with variation of the renewable energy sources integrated with in the bus system. Also set point of the protection relays varies with percentage sharing of the load by PV sources compared to the existing scheme. Observation of the behavior of existing protection system with PV connected hybrid system generates a road map to design an accurate protection scheme for hybrid system.

Analysis of Power Quality parameters at comparing UPS of different Technologies

Commercial and industrial consumers are vulnerable to disturbances in distribution networks. One solution to this is using the Uninterruptible Power Systems (UPS). However, this may have other impacts on the power system. This document describes the main principles of UPS system operation. In addition, the paper presents tests on two UPS to verify the quality of power supplied to the system that the UPS feeds. For this purpose, the power factor, the voltage unbalance factor, the frequency variation and the voltage and current waveform were recorded due to the presence of harmonics. This paper also shows the importance of implementing a UPS labeling program.

Uninterruptible power supply for renewable energy sources

Scientific and technological advance results in a constantly increasing number of first category customers that in the event of input power failures can entail significant economic losses. A promising direction is the development of uninterruptible power systems that rely on renewable energy sources and, above all, photovoltaic arrays and wind power turbines. If energy customers are located near foothill and mountain rivers, it seems economically viable to apply mini or micro-hydro power plants. The paper examines different approaches to UPS topology based on renewable energy sources. Besides renewable energy sources, power supply encompasses some traditional autonomous sources including diesel, gas piston or gas power plants. In addition, the systems provide inputs for connecting an external power system. The paper shows that agrarian production finds it relevant to develop mobile uninterruptible power systems. The authors propose some modes of operation that improve the economic performance of uninterruptible power supply by using rechargeable batteries solely during power conversion from one power source to another. The paper contains proposals developed to improve operational and technical features of uninterruptible power systems through a new topology, modular character of main functional elements and optimization of system structure.

Symmetric Dual-Switch Converter

High step-up dc/dc converters are widely used in many industrial applications, especially in green energy power generation and uninterruptible power systems. The circuit configuration of a dual-switch high step-up dc/dc converter is very simple and the converter can achieve a high step-up voltage gain by operating in parallel charge and series discharge. However, this converter has a strict requirement of the parameter's consistency or it will lead to the high voltage stress of switches due to parasitic capacitance and inductor's resonance. Although passive lossless clamp circuit can be adopted to realize the voltage balance of switches in steady state, unbalance voltage still exists in dynamic state owing to an unsymmetrical structure. Therefore, this article proposed a dual-switch converter with symmetric topology, which can realize the voltage balance of switches and capacitors in both steady and dynamic states. According to the proposed converter, a prototype rated at 200 W has been established in the lab and the experimental results verify the accuracy of the analysis.

Can the dexamethasone intravitreal implant Ozurdex be safely administered in an out-of-operating room setting?

Purpose To describe a standardized protocol of the dexamethasone intravitreal (DEX) implant Ozurdex (Allergan, Dublin, Ireland) performed in a controlled environment surgical cabin (CESC). Methods Retrospective and observational study conducted on patients who underwent a DEX implant between May 2011 and June 2019, in a third level University Hospital. The controlled environment surgical cabin (ArcSterile, Imex, Valencia, Spain) used in this study was the MB 20 (2 m width, 1.60 m depth, and 2 m height) with an uninterrupted power system (ARSSAI1) to keep the cabin working for 20 min. The cabin was used in the open mode. A standardized protocol of intravitreal injections in controlled environment surgical cabin was designed. Results From May 2011 to February 2015, a total of 454 DEX implants were performed in the operating room, whereas from March 2015 to June 2019, 1054 DEX devices were implanted using the CESC. The mean number of DEX implants/per week was significantly lower in the operating room than in the CESC [2.3 (2.1 to 2.5) versus 3.8 (3.6 to 4.1), mean difference 1.5 (1.2 to 1.8), p < 0.0001]. The incidence of endophthalmitis was similar in the two populations, 0/454 (0.0%; 95% CI 0.0 to 0.81%) and 0/1054 (0.0%; 95% CI 0.0 to 0.35%) in the operating room and in the CESC, respectively. Conclusions The CESC may be a good alternative to the conventional operating room for the administration of the intravitreal DEX implant.

Performance Evaluation &amp;amp; Operation of DSP Control UPS System

An uninterruptible power supply (UPS) is a power conditioner that provides emergency power to a load when the supply power fails. In on-line UPS, the load is always connected to the inverter through the UPS static switch. Specialized expertise was required for collection, analysis, and dissemination of technical information relating to high quality uninterruptible power systems. Inherent in these responsibilities is the coordination of technical and contractual matters relating to the procurement and installation of uninterruptible power supply (UPS) systems which were required to support these facilities. The proposed circuit incorporates an AC/DC & DC & AC converter, which provided power factor correction and to assure feedback control. In our project when the AC main is available, the rectifier circuit will supply the power to the inverter as well as to the battery and battery will be charged. If the supply power fails suddenly, the battery will supply power to the inverter without any interruption and delay. In the constant current charging technique, a digital charger was designed and controlled through PIC12F675 microcontroller. In the realized system, The PIC16C73B was used as microcontroller. It was used to generate sinusoidal PWM (Pulse Width Modulation) signals that are connected to drive n-channel MOSFETs in inverter to assure feedback control and display units. The power circuit of the proposed UPS system was presented and analyzed. Circuit models were derived and a UPS digital control system using a digital signal processing (DSP) with microcontroller has been developed. The uninterruptible Power Supplies (UPS) are widely used by power supply during interruption of regular power supply due to load shedding, power failure, power fluctuations including telecommunication systems, medical systems, industrial control systems etc.

Design and implementation of state-of-charge estimation based on back-propagation neural network for smart uninterruptible power system

In this article, a method for estimating the state of charge of lithium battery based on back-propagation neural network is proposed and implemented for uninterruptible power system. First, back-propagation neural network model is established with voltage, temperature, and charge–discharge current as input parameters, and state of charge of lithium battery as output parameter. Then, the back-propagation neural network is trained by Levenberg–Marquardt algorithm and gradient descent method; and the state of charge of batteries in uninterruptible power system is estimated by the trained back-propagation neural network. Finally, we build a state-of-charge estimation test platform and connect it to host computer by Ethernet. The performance of state-of-charge estimation based on back-propagation neural network is tested by connecting to uninterruptible power system and compared with the ampere-hour counting method and the actual test data. The results show that the state-of-charge estimation based on back-propagation neural network can achieve high accuracy in estimating state of charge of uninterruptible power system and can reduce the error accumulation caused in long-term operation.

Robust Weighted Fusion Kalman Estimators for Networked Multisensor Mixed Uncertain Systems With Random One-Step Sensor Delays, Uncertain-Variance Multiplicative, and Additive White Noises

For networked multisensor systems with mixed uncertainties, including random one-step sensor delays, multiplicative noises and uncertain noise variances, a new augmented state approach with the fictitious noises is presented, by which the original system model is transformed into one without sensor delays and only with white noises. An extended Lyapunov equation approach with two Lyapunov equations is presented, which is applied to prove the robustness of the estimators. According to the minimax robust estimation principle, based on the worst-case system with conservative upper bounds of uncertain noise variances, the four weighted fusion robust time-varying and steady-state Kalman estimators (predictor, filter and smoother) are presented in the sense that their actual estimation error variances are guaranteed to have the corresponding minimal upper bounds for all admissible uncertainties. Their robustness and accuracy relations are proved, and their convergence in a realization is proved by the dynamic error system analysis (DESA) method. Specially, the presented modified robust covariance intersection (CI) fuser has higher robust accuracy than the original one. A simulation example applied to the uninterruptible power system (UPS) shows the effectiveness of the proposed approaches and results.