Loss Of Power Supply Research Articles

Thermal hydraulic simulation of the steam generator under fast transient events

A multidomain computational procedure was applied to model the RD-14M steam generator. It was based on the two-fluid Eulerian approach to model the water–steam flow, the blending method for interfacial force terms, the wall heat partition model (RPI) for wall boiling, and the conjugate heat transfer (CHT) method for thermal coupling between the primary and secondary circuits. The computational model of the overall steam generator is achieved by combining full 3D simulation in the riser and 0D modeling with ad hoc Dynamic Boundary Conditions (DBC) in separator/dryer, downcomer, and pre-heater regions. The implementation was carried out in the OpenFOAM(R) environment. Both steady state nominal conditions as well as transient events, such as loss of power supply and reactor shutdown, were studied. The results were compared with previous RELAP5 and full-3D models getting quite good agreement. The information obtained was very useful to understand the overall thermal-hydraulic behavior of steam generators but also local phenomena around the tubes and baffles inside the riser, which are unavailable in system-code models.

Numerical Calculation Model and Efficiency Analysis of Distributed-Energy-Store Railgun

In order to study the factors affecting the launch efficiency of the distributed-energy-store (DES) railgun, a numerical calculation model of the DES railgun is established in this article. Taking the six-stage equidistant DES railgun with 4-MJ initial energy storage as an example, the simulation results show that the launch efficiency of DES railgun is 21.14%, and the resistance loss and the residual magnetic energy of rail account for a small proportion of 6.47% and 3.77%, respectively. The resistance loss of power supply and other energy losses (the losses caused by the equivalent resistance produced by the armature and its related physical effects) accounted for the highest proportions, respectively, 23.91% and 37.52%. Therefore, these two parts of losses should be reduced to further improve the system launch efficiency. The influence of system parameters on launch efficiency was analyzed, and the parameters include capacitance, charging voltage, inductance, equivalent internal resistance, rail length, interval of current feed point, armature mass, inductance gradient, and rail height. Among them, inductance gradient has the most significant impression on launch efficiency, followed by equivalent internal resistance, rail length, and interval of current feed point. The conclusions can guide the selection of the feeding mode of the electromagnetic launch system and provide reference to the further optimization of the DES railgun launch system.

Integration of RES-based Power Plants into the Unified Energy System of Russia: Problematic Issues and Approaches to Solving Them

Recent years have seen mass-scale integration of wind (WPP) and solar (SPP) power plants for capacities ranging from a few to several hundred megawatts into the Unified Energy System (UES) of Russia. Wind and solar power plants for a total capacity of 5.28 GW are to be commissioned by the end of 2024, and around 6.7 GW else are to be commissioned within the next decade. WPPs and SPPs are constructed in the framework of capacity supply agreements, which guarantee the return of investments in the wholesale electricity and capacity market. The aim of the study is to analyze problematic matters concerned with integrating RES into the UES of Russia and to outline a list of first-priority and further steps to be taken for securing the optimal control of power system operation modes under the conditions of a growing share of RES in the mix of generating capacities. In view of the fact that certain power districts operating within the UES of Russia have been islanded for various reasons, the problematic matters of RES integration are analyzed also for these power system operation conditions. Experience gained around the world with integrating RES into power systems is considered, and the RES introduction scales for which certain organizational and technical measures must be developed and taken are ranked. Statistical data from Russian and foreign sources on the reliability indicators of wind farms and photovoltaic systems for various capacities are given. The equipment of modern WPPs and SPPs features high availability indicators; however, it is quite frequently disconnected, which leads to load surges on the adjacent grids and the need to cover the emergency active power shortage by conventional power plants. The article suggests a list of first-priority steps to be taken for correctly integrating RES into distribution grids that will make it possible to avoid grid equipment failures and incidents involving mass-scale loss of power supply to consumers in the course of power system operation. The implementation of the plans that have been set forth will facilitate smooth integration of the growing RES capacities into the UES of Russia, while keeping the ability to control the power systems operation modes. The article substantiates the need of introducing certain amendments to the legislation, statutory, regulatory and technical documents that set out technical requirements for RES equipment, its technological connection to and operation as part of power systems. If implemented in a goal-seeking and stage-by-stage manner, the suggested measures will help rule out excessive disconnections of RES, engage them in control of power system operation modes, guarantee reliable power supply to consumers, and secure safe and reliable performance of the UES of Russia.

Feasibility study and performance analysis of microgrid with 100% hybrid renewables for a real agricultural irrigation application

Recently, wide attention has been paid to the techno-economic viability for electrifying rural and remote areas while less awareness for agricultural irrigation pumps is given. Diesel generators are still utilized for agricultural facilities, causing ecological issues and energy price growth. In this paper, an integrative techno-economic design optimization framework for adequate planning of fully renewable energy system including photovoltaic units, wind turbines and batteries fed a real case-study of an agricultural load of 240 kWh/day in Al-Sadat city, Egypt, is proposed using HOMER Pro. The project site is favorably chosen since Egypt holds great potential for renewables; manipulating these resources becomes crucial for achieving national sustainability as per Egypt 2030 vision. The feasibility and performance of the proposed energy system are evaluated and analyzed regarding its technical and economic dimensions and compared with four different energy alternatives, including the existing real system and the standalone diesel system, for fair comparisons. The design optimization is followed by parametric and reliability analyses to uncover the impacts of uncertainty in seven key input parameters and power generation shortage on optimal economic behavior. The achieved outcomes reveal that the fully renewable solar/wind/batteries/converter system is of optimal behaviours over other alternatives to fulfil the load demand. The proposed system acquires the minimum net present cost ($194,017) and cost of energy (0.119 $/kWh) and efficiently attains a negligible ratio in both capacity shortage and unserved load with only 0.098%. Besides, a productive amount of surplus energy (61.7%) is achieved for further deferable loads supplying. Moreover, the parametric analysis proves the great reliance of system cost on the uncertainty of discount rate, project lifetime and components’ capital costs while the uncertainty in renewable resources has a slight impact on the system performance. In addition, the reliability analysis indicates that a small and tolerable loss of power supply by 2% results in considerable financial benefits while optimizing the microgrid design. The study is expected to raise the awareness of exploiting renewable energy in Egypt and provide a valuable proposal for replacing the existing energy system of the addressed case-study.

A mission-driven two-step virtual machine commitment for energy saving of modern data centers through UPS and server coordinated optimizations

Recent years witness a rapid increasing of data center energy consumption, among which the power losses of uninterruptible power supply (UPS) and server dominate. This paper proposes a mission-driven two-step virtual machine (VM) commitment by considering the characteristics of UPS power losses in virtual machine allocation. To formulate the optimization problem, a power model of data center is built by combining server power with power losses of rack level UPSs. Further, a two-step virtual machine allocation method is proposed, in which the best fit decreasing algorithm first groups the VMs and then the genetic algorithm searches for the optimal allocation of servers equipped with the grouped VMs. A data center with 100 servers and 100 VMs is simulated using the public data collected from PlanetLab platform. Results have verified that the total power consumption is reduced by up to 2.47%. In parallel, possible combinations need to be searched decrease by 3.35 × 10182 times in the VM allocation problem in the case with 100 servers and 100 VMs.

Equivalent magnetic circuit method of estimating iron losses in induction motor spindles

The iron losses in the motor of motorized spindles have a significant effect on their heat generation, thermal deformation, and machining accuracy. The equivalent magnetic circuit (EMC) method for estimating iron losses in the spindle motor is proposed, where the magnetic flux density distribution of any cross section inside the spindle motor is assumed as a uniform one. A mechanical loss separation method of no load running combined with a sudden loss of power supply is also proposed. The EMC method is verified by prototype experiment and a different analysis method comparison. The EMC does not need to solve complex electromagnetic fields, and to do 2D or 3D eddy current analysis and the corresponding post-processing. There is only need to perform a simple magnetic circuit calculation. Therefore, it can realize a fast analysis and prediction. The proposed mechanical loss separation method requires only one prototype during a whole testing process. There is no need for any other same prototype and a coupling device. It is simpler, and can eliminate the braking torque and electromagnetic losses of the spindle motor.

Optimization and techno-economic analysis of PV/Battery system for street lighting using genetic algorithm – A case study in Oman

Optimal sizing is necessary in hybrid renewable energy systems for the system to work with highest reliability and minimum cost. The street light system inside Sultan Qaboos University in Oman is considered as a case study for optimal sizing of PV/battery system for three different types of lamps, HPS, LED and discrete LED. The life cycle cost analysis and cost per kWh for two different configurations of panel and battery, the first with larger sized panel/battery and the second, smaller sized panel/battery with and without considering the number of autonomous days(NAD) is compared to investigate the economic feasibility of implementing the system in Oman. Genetic algorithm tool in MATLAB is used for optimal sizing, adopting loss of power supply(LPS) to gauge the reliability using actual data existing in Oman. The cost per kWh of generated energy with large panel/battery system was found to be 0.08 $/kWh while it was 19.9 $/kWh considering the same case for small panel/battery system proving the economic feasibility of implementing the large panel/battery system in Oman. Results also prove that higher the energy requirement, higher the LCC but lesser the cost per kWh. The conversion of the grid connected street light system extending a stretch of 8.6 km with 285 HPS lamps of 400 W to PV/battery system with LED lamp of 80W is expected to reduce the CO2 emissions by 133.595 tonnes annually. The results can be applied to practical systems worldwide to save millions of dollars and CO2 emissions.

Energy management strategy of hybrid solar-hydro system with various probabilities of power supply loss

An optimal energy management strategy is difficult for an efficient operation of hybrid renewable energy systems due to the instability of energy resources. The present study analyzes a hybrid PV-battery integrated with the pump-hydro-storage system (PHSS) utilizing the rainfall potential at various probabilities of power supply loss (PPSL). Two configurations have been studied. Configuration-1 is a PV-battery system, and Configuration-2 is a hybrid PV-battery-PHSS. PPSL are varied between 0.00 and 0.10 in steps of 0.02. The particle swarm optimization technique is used for size optimization based on the Levelized Cost of energy minimization. Configuration-1 and Configuration-2 at PPSL of 0.00 are highly oversized. Configuration-2, compared to Configuration-1, has less excess power due to the integration of PHSS. A decrease in the power supply reliability by just 2% has caused the decrease in the Levelized Cost of energy by about 31.3% for Configuration-1 and 28.8% for Configuration-2. The power system efficiency for Configuration-1 at PPSL of 0.00, 0.02, 0.04, 0.06, 0.08, and 0.10 is 34%, 71%, 77%, 79%, 80%, and 80%, respectively. However, for the Configuration-2, the power system efficiency compared to Configuration-1 at PPSL of 0.02, 0.04, 0.06, 0.08, and 0.10 has increased by about 11.8%, 2.8%, 0.0%, 1.3%, 1.3%, and 1.3%, respectively.

Converter Design for High Temperature Superconductive Degaussing Coils

Detection of the magnetic signature of ships can be avoided by using a degaussing system; a set of on-board copper coils that compensates for the magnetic signature. High temperature superconductors (HTS) are currently investigated as a replacement for copper degaussing coils. By using HTS, we have to deal with higher currents and therefore with higher power supply losses. Also, large current leads are needed which introduces extra losses. This paper investigates different possible solutions to minimize these losses. Four H-bridge-based MOSFET topologies are presented that were designed to reduce the power supply and current lead losses. The first topology uses an H-bridge configuration so that the degaussing current can freewheel through the low-resistance MOSFETs. The second topology places the H-bridge inside the cryostat so that the current leads can be made smaller. The third topology includes a smoothing capacitor in the cryostat so that the current leads and input current are even smaller. The fourth topology uses a transformer so that the current leads can be eliminated. Measurements were done to determine the MOSFETs and capacitor performance in liquid nitrogen. The simulated losses of the four topologies are compared to determine the most energy-efficient option for supplying current to the HTS coils. It was found that by submerging multiple parallel MOSFETs in liquid nitrogen, the on-state resistance is decreased and the current supply can be made more efficient. Also, by placing a smoothing capacitor inside the cryostat, the current lead losses can be minimized significantly. The benefits of using a transformer do not outweigh the transformer losses.

Improvement of technology of production of compensation copper and copper steel current ducts

The article describes the technology of manufacturing conductors for power supply systems for cranes, railway vehicles, powerful critical electric motors and power systems. The results of studies for copper-steel samples are shown; in these systems there is a decrease in material losses due to an increase in the strength and durability of products. The proposed technology can be used to use steel-copper wires in power supply loss compensation systems.

Dynamic Reliability Evaluation of Diesel Generator System of One Chinese 1000MWe NPP Considering Temporal Failure Effects

Loss of power supply from the diesel generator system (DGS) after loss of offsite power (LOOP) will pose great threat to the safety of GEN-II pressurized water reactors (PWR). Therefore, it is very desirable to evaluate the DGS’s reliability. The traditional analyzing tools are limited to static approaches neglecting the dynamic sequence failure behaviors, such as reliability block diagram (RBD), static fault tree (SFT). Static reliability modeling techniques are not capable of capturing the dynamic sequence-dependent failure behaviors typically existing in NPP safety systems such as DGS, and thus often overestimate the unreliability of systems. In this paper, motivated to study the effects of sequence failure behaviors, dynamic fault tree (DFT) is applied to evaluate the reliability of the DGS of one Chinese 1000MWe Nuclear Power Plant (NPP), and an integrated two-phased Markov Chain model is also developed, which can be considered as a contribution of this article. Comparative study of DGS reliability between DFT and SFT is carried out. The results indicate that compared with the result derived from the DFT model, the unreliability of DGS calculated by SFT is greatly overestimated by about one to two orders of magnitude. Therefore, DFT has a potential to improve the economy of NPP by relaxing the overestimated unreliability of nuclear power systems.

An embedded VFAF in DFIG-based wind farms for SSCI mitigation

Due to the increasing penetration of wind generations, a new type of sub-synchronous interactions, the so called sub-synchronous control interaction (SSCI), has emerged in power systems in the past decade. Incidents of this type have caused severe consequences in real-life power systems, including equipment damage and loss of power supply. To overcome the impacts and minimize the adverse influences of such phenomenon, this paper proposes a novel varying-frequency adaptive filter (VFAF) in doubly fed induction generators-based wind farms for SSCI mitigation. The proposed VFAF utilizes a linear prediction model and coefficient-based polynomials to analyse the spectral components of the controller signals. In addition, singular value decomposition is used to identify the number of signal components in the controllers. Then, based on the analysis, the VFAF produces compensation signals to modulate the distorted controller signals and thus mitigates the oscillations during SSCI. Based on this mechanism, the VFAF is auto-adaptive to various oscillation frequencies, including those that are time-varying. The above feature is of particularly importance in modern power systems. Testing cases of the VFAF have been conducted in the Power Factory software, and the results verify the effectiveness of the proposed VFAF under relevant system conditions.

Identifying and assessing power system vulnerabilities to transmission asset outages via cascading failure analysis

Power systems as critical infrastructure are an integral part of human society and are therefore of paramount importance to modern life. Vulnerabilities in the system, that are revealed either by accidental or deliberate events, can cause large losses of power supply with sever social and economic consequences. A tool that identifies the vulnerabilities in a power system can provide the operators the means to support reliable power system operations. This paper presents a methodology for power system vulnerability assessment that couples an AC based cascading failure simulation model and a meta-heuristic optimization procedure. The objectives of the assessment are to (1) rank the most important branches in the transmission grid, and (2) identify sets of branches if simultaneously tripped will cause the cascade with highest intensity. The first objective is achieved by ranking the criticality of the branches using two criteria (i) the impact that each branch failure has on the DNS and (ii) the frequency of line overload. The second objective is achieved by hard linking an AC based cascading failure simulation model and a meta-heuristic based optimization procedure. The methodology allows the generation and the identification of vulnerability scenarios, and therefore, provides insights that can be used by operators in developing strategies to minimize the effects of accidental and deliberate events. The algorithm developed for the purpose of this study is applied to the IEEE 118-bus test system and the Swiss power grid. The results demonstrate the capability of the proposed methodology for assessing power system vulnerability.

Optimum sizing and simulation of hybrid renewable energy system for remote area

In current scenario, people tend to move towards outskirts and like to settle in places that are close to nature. But, due to urban lifestyle and to fulfill the basic needs, demand of electricity remains the same as in urban areas. This demand of electricity can be only fulfilled by using hybrid renewable energy resources, which is easily available in outskirts. Renewable energy resources are unreliable and more expensive. Researchers are working to make, it more reliable and economic in terms of utilization. This article proposes a metaheuristic grasshopper optimization algorithm (GOA) for the optimal sizing of hybrid PV/wind/battery energy system located in remote areas. The proposed algorithm finds the optimal sizing and configuration of remote village load demand that includes house electricity and agriculture. The optimization problem is solved by minimization of total system cost at a desirable level of loss of power supply’s reliability index (LPSRI). The results of GOA are compared with particle swarm optimization (PSO), genetic algorithm (GA) and hybrid optimization of multiple energy resources (HOMER) software. In addition, results are also validated by modeling and simulation of the hybrid energy system and its configurations at different weather conditions-based results. Hybrid PV/wind/battery is found as an optimal system at remote areas and sizing are[Formula: see text] with cost of energy (COE) (0.3473$/kWh) and loss of power supplies reliability index (LPSRI) (0%). It is clear from the results that GOA based methods are more efficient for selection of optimal energy system configuration as compared to others algorithms.

A Bayesian Approach to the Reliability Analysis of Renewables-Dominated Islanded DC Microgrids

The DC microgrid (DC MG) concept enables the hosting of DC-type renewable energy resources. However, their intermittent nature means that a high penetration of renewables can jeopardize supply adequacy and voltage provision during islanding. The work presented in this paper was therefore directed at developing a probabilistic graphical approach based on Bayesian networks (BNs) for the reliability analysis of renewables-dominated DC MGs. The proposed BN model incorporates a family of novel reliability indices for quantifying the impact of a high penetration of renewables on MG reliability, including loss of renewable power supply, rise in voltage, and reversal of power flow. The model is supported by a newly formulated fast and accurate linearized power flow algorithm for probability calculations. The accuracy of the BN model has been verified against a Monte-Carlo simulation (MCS). The effective application of the new BN model for reasoning and impact assessment reveals that a high penetration of renewables affects reliability indices differently. Case study results suggest that the proposed BN model shows promise as a valuable tool for the reliability analysis of renewables-dominated MGs that feature islanding capability.

Constraint multi-objective optimal design of hybrid renewable energy system considering load characteristics

Finding the optimal size of a hybrid renewable energy system is certainly important. The problem is often modelled as an multi-objective optimization problem (MOP) in which objectives such as annualized system cost, loss of power supply probability etc. are minimized. However, the MOP model rarely takes the load characteristics into account. We argue that ignoring load characteristics may be inappropriate when designing HRES for a place with intermittent high load demand. For example, in a training base the load demand is high when there are training tasks while the demand decreases to a low level when there is no training task. This results in an interesting issue, that is, when the loss of power supply probability is determined at a specific value, say 15%, then it is very likely that most of loss of power supply would occur right in the training period which is unexpected. Therefore, this study proposes a constraint multi-objective model to deal with this issue—in addition to the general multi-objective optimization model, the loss of power supply probability over a critical period is set as a constraint. Correspondingly, the non-dominated sorting genetic algorithm II with a relaxed epsilon constraint handling strategy is proposed to address the constraint MOP. Experimental results on a real world application demonstrate that the proposed model and algorithm are both effective and efficient.

РАСЧЕТНЫЙ АНАЛИЗ ОДНОВРЕМЕННО ВОЗНИКАЮЩИХ ЗАПРОЕКТНЫХ АВАРИЙ НА ЭНЕРГОБЛОКАХ № 3 И 4 БАЭС

The paper presents the results of a computational analysis of simultaneously occurring beyond design basis accidents at power generating units No. 3 (BN-600) and No. 4 (BN-800) of the BNPP. Safety analysis for operating power generating units at the same time occurring beyond design basis accidents is carried out in accordance with the requirements of NP-001-15. Computational studies were performed with the SOCRAT-BN, ANSYS, ORIGEN2, and VIBROS 2.2 codes. There are considered beyond design basis accidents caused by seismic impact with intensity of 7 points on MSK-64 scale (exceeding the maximum allowed earthquake (MAE) for the site of power unit No. 3 and the corresponding MAE for the site of power unit No. 4). As a result of seismic impact at all the power generating units of the BNPP, a loss of system power supply occurs, which, together with additional failures of the main equipment, leads to beyond design basis accidents. The paper presents the results of computational studies of beyond design basis accidents in terms of reactor plant, assembly cooling pond and holding pond and radiation effects assessment. The results of a computation analysis of the beyond design basis accident showed that the release of radioactivity occurs only for the BN-600 reactor facility (where are breaking of the fuel elements cladding). At the same time, the predicted radiation doses for the first years after the accident are lower than the NRB-99/2009 criteria for making a decision on the evacuation and resettlement of inhabitants.

Knowledge gained from a 31-h power outage in Berlin Köpenick-medical problems and challenges

Am 19.02.2019 kam es nach Durchtrennung eines 110-kV-Kabels zu einem großflächigen Stromausfall im Berliner Bezirk Treptow-Köpenick. Nachfolgend waren ca. 30.000 Haushalte ohne Strom; betroffen waren ca. 70.000 Menschen. Der Stromausfall dauerte mehr als 24 h an und stellte alle Beteiligten vor eine Vielzahl von Herausforderungen. Es wurde der Führungsstab (operativ-taktisch) einberufen, in dem auch medizinische Schwerpunkte fortlaufend identifiziert und reevaluiert werden mussten. Hierbei handelte es sich mitunter um die Identifikation von besonders gefährdeten Patienten wie beispielsweise heimbeatmeten Patienten oder Patienten mit Kunstherz. Weiterhin mussten einzelne Pflegeheime evakuiert werden. Im Verlauf war es notwendig, aufgrund des Ausfalls der Stromversorgung im Schadensgebiet, eine Intensivstation bzw. „Intermediate-care“-Station mit 23 Patienten zu evakuieren. Krankenhäuser müssen sich im Rahmen von Vorplanungen auf derartige Szenarien einstellen. Weiterhin müssen seitens der zuständigen Behörden Vorplanungen erfolgen, die die besonderen Bedürfnisse von vulnerablen Gruppen beinhalten.

Smart system management and techno‐environmental optimal sizing of a desalination plant powered by renewables with energy storage

The present study assessed the performances of a brackish water reverse osmosis desalination unit powered by (PV/Wind/Battery) system with hydraulic storage. The hybrid renewable energy system and the reverse osmosis desalination plant were modeled for a specific site in southern Tunisia using real meteorological and water consumption data for 1 year. A total of 8760 simulations were treated under a dynamic simulator coupled to a smart energy management strategy to reach the hourly water load demand. Although the recognized reliability of the hybrid renewable sources compared to one- power source, their design may still critical. Therefore, in this paper, the authors suggest applying the methodology of optimizing the presented unit using an integrated systemic meta-modeling which is built through the design of experiments tool and defined by an equation involving the decision variables of the optimization as its parameters. This equation outlines the objects of the optimum sizing. The selected optimal design of the proposed unit is predicted by the genetic algorithm NSGA-II based on minimizing two objectives in conflict: Embodied energy and hydraulic loss of power supply. The CPU time of the NSGA-II optimization via the meta-model reached only 15 minutes of treatment (with one day to build the design of experiments) compared to the classic optimization via dynamic simulation. The results of the optimum sizing show that it is possible to consider a low water shortage rate (0% ⩽ LPSP-H < 5%) for a marginal variation of embodied energy rate which does not exceed (7%).

Research on switching loss reduction technology for missileborne DC-DC power supply

With the development of power electronics technology, DC-DC power supply is widely used in secondary power supply system on missile. How to restrain the loss caused by the periodical on-off of the switch tube plays an important role in ensuring the normal operation of the missile-borne power supply system. In this paper, the switching-tube Absorption Circuit and ZCT PWM soft-switching circuit are taken as the research objects, and the effects of the two circuits on the switching-tube loss suppression in the dual-pulse-width modulation mode are analysed, and a more effective method to reduce the switching loss of high frequency DC-DC power supply is obtained, it provides a reference for the further research of switching loss reduction technology in high frequency DC-DC power supply.