Copper Loss Research Articles

Electromagnetic–Thermal Characteristics Analysis of a Tubular Permanent Magnet Linear Generator for Free-Piston Engines

Temperature rise of the tubular permanent magnet linear generator (TPMLG) might lead to insulation failure and demagnetization of permanent magnets, affecting the safe and stable operation of other equipment and the entire system. Herein, a bidirectional electromagnetic–thermal coupling method for analyzing the electromagnetic loss and thermal characteristics of a TPMLG considering the effect of increased temperature on the permanent magnet was proposed. To study the electromagnetic–thermal characteristics of the TPMLG under stable power generation, a two-dimensional electromagnetic field model and a three-dimensional temperature field model were established and coupled. The temperature field of the TPMLG was numerically calculated using computational fluid dynamics over finite volume method under natural air cooling and forced air cooling conditions. Effects of loss and air flow velocity on the steady temperature field were investigated. Results indicated that copper loss increased by 24.5% considering the influence of temperature rise. The windings’ top central position in the TPMLG was the spot with the highest temperature of 127.8 °C and there was a potential demagnetization risk for the permanent magnets. Some reference for future research of clarifying thermal characteristics and cooling design was provided.

Dynamic simulation of a space lithium-cooled reactor system coupled with a He–Xe closed Brayton cycle

The lithium-cooled reactor with Brayton conversion power system mainly consists of fast reactor, intermediate heat exchanger, closed Brayton cycle (CBC) loops filled with Helium–Xenon (He–Xe) binary gas mixtures and heat rejection loop which radiate residual heat through heat pipes to outer space. In this study, a dynamic model of 100-kWe lithium-cooled reactor with Brayton conversion power system was established based on RESYS code, which include reactor core thermal-hydraulic model, six-group neutron kinetics model and decay heat model, heat exchanger model, Closed Brayton cycle model including turbine, compressor and rotating shaft, heat pipe radiator model etc. The nominal steady-state simulation is carried out to verify the correctness and accuracy of individual component model the integrated system model. Four typical transient conditions including accidental reactivity insertion, loss of coolant flow of primary loop, partial and total external load loss and a step reduction in the mass flow rate of heat rejection loop are simulated to analysis the transient characteristics and prove the safety features for those simulated scenarios. The results are helpful for the design, evaluation and operation of space liquid-lithium-cooled reactor power system with He–Xe closed Brayton cycle.

The capacity planning method for a hydro-wind-PV-battery complementary system considering the characteristics of multi-energy integration into power grid

The hydro-wind-PV-battery complementary operation has the potential to increase the integration of renewable energy sources into power grid. Nevertheless, the determination of the optimal capacity configuration mode and size for a hydro-wind-PV-battery complementary system (HWPBS) remains a persistent challenge. This study proposes a capacity planning framework for the HWPBS considering the characteristics of multi-energy integration to power grid. First, the centralized (CCP) and distributed (DCP) configuration patterns considering the ways of multi-energy integration into power grid are proposed to explore the optimal capacity configuration mode. Second, considering the randomness of incoming water of hydropower stations, a scenario analysis technique is proposed to obtain the typical inflow scenarios. Then, with the objectives of maximizing expected renewable generation and minimizing expected power abandonment and load loss, the capacity configuration models for the HWPBS under the CCP and DCP are developed. A load reconstruction method is proposed to reduce the computational burden. The parallelogram method is implemented to linearize the hydropower production model. Additionally, a set of indicators are proposed to evaluate the economy and reliability of the HWPBS. The proposed framework is applied to the Yalong River Basin. The results show that: the wind-PV configuration capacity is affected by load demand, battery storage and configuration patterns. The load demand process with better correlation to wind-PV output is advantageous for integrating wind and solar resources. Battery storage can effectively reduce power abandonment and load loss, and the configuration pattern has a significant impact on the final capacity of wind-PV power.

Isolation‐based bidirectional generalized step‐up multilevel converter with optimized device count

SummaryThis article describes a generalized single‐phase multiwinding step‐up transformer‐based multilevel converter with optimized device count. The proposed topology comprises of a single dc source, eight switches (four unidirectional and four bidirectional) and a single high‐frequency multiwinding transformer. Phase disposition pulse width modulation (PDPWM) is used for the level creation. The proposed converter is examined qualitatively and quantitatively using the total number of transformers, PWM control method, switch count, voltage stress, and the number of gate drivers, all of which are favorable. All elements of transformer selection, winding requirements, and comparative study have been thoroughly examined. A thorough Lagrange multiplier method has been applied to minimize the copper losses and optimize the multiwinding transformer (MWT) winding. The proposed converter simulations are performed using the MATLAB/SIMULINK environment. Further, the validation of the result is confirmed by a hardware setup of 0.9 kW.

Venturi Injector Optimization for Precise Powder Transport for Directed Energy Deposition Manufacturing Using the Discrete Element Method and Genetic Algorithms.

Additive manufacturing technologies such as directed energy deposition use powder as their raw material, and it must be deposited in a precise and controlled manner. Venturi injectors could be a solution for the highly precise transport of particulate material. They have been studied from different perspectives, but they are always under high-pressure conditions and mostly fed by gravity. In the present study, an optimization of the different dimensional parameters needed for the manufacturing of a Venturi injector in relation to a particle has been carried out to maximize the amount of powder capable of being sucked and transported for a specific flow in a low-pressure system with high precision in transport. For this optimization, simulations of Venturi usage were performed using the discrete element method, generating different variations proposed by a genetic algorithm based on a preliminary design of experiments. Statistical analysis was also performed to determine the most influential design variables on the objective, with these being the suction diameter (D3), the throat diameter (d2), and the nozzle diameter (d1). The optimal dimensional relationships were as follows: a D3 34 times the particle diameter, a d2 26.5 times the particle diameter, a d1 40% the d2, a contraction angle alpha of 18.73°, and an expansion angle beta of 8.28°. With these proportions, an 85% improvement in powder suction compared to the initial attempts was achieved, with a maximum 2% loss of load.

Analysis of the Possibility of Copper Recovery from Flotation Stratiform Copper Ore Tailings

ABSTRACT Flotation tailings produced at three concentrator plants operated by KGHM Polska Miedz SA (SW Poland) are all continuously deposited in the Zelazny Most Tailings Storage Facility. The aim of this study was to analyze the possibility of recovering copper from the stream of final tailings continually produced by the largest of the three KGHM concentrator plants. The tailings sample contained 0.25% of Cu and was characterized by a relatively fine grain size. The tests were performed for three narrow-range size fractions of the tailings sample: −0.040, 0.040–0.160 and +0.160 mm. The findings demonstrate that the coarse and fine fractions are the main carriers of copper-bearing minerals which can be recovered with satisfactory results, if the fractions are processed separately. The coarse grain fraction was milled and then floated in the presence of standard flotation reagents with satisfactory results. The fine fraction was floated in the presence of NaHS with a relatively good efficiency which requires further research. The presented results prove that copper losses in this material can be partially reduced already at the stage of the upgrading processes performed in the concentrator plant.

A tri-level Typhoon-DAD robust optimization framework to enhance distribution network resilience

Extreme natural disasters such as typhoon often cause failures in distribution networks within a short time, and even lead to large area blackouts. We propose a tri-level robust optimization framework that combines pre-disaster, in-disaster and post-disaster strategy comprehensively to enhance distribution network resilience. The typhoons are regarded as attackers, and a tri-level Defender-Attacker-Defender model for typhoon disaster is used to integrate multiple resilience resources. In the first level, line hardening and distributed generation unit commitment are used to improve resilience in pre-disaster. The second level contains attack budget, attack time, hardening budget, repair time and load loss. It couples with the third level iteratively to generate the worst failure scenario under typhoon. In the third level, the Nested Column-and-Constraint Generation algorithm is used to solve distribution network reconfiguration and intentional islanding. Simulation time is spanned to the entire 24-hour disaster day. In the end, the proposed framework is tested through a case study using real data from super typhoon “Mangkhut” (2018) in Yangjiang, China. The result shows that it can effectively reduce load loss under the worst typhoon scenario and enhance distribution network resilience with limited resources.

Improved single‐layer powder core inductor design procedure for DC‐DC converters

AbstractOne of the early design decisions for DC‐DC converters is the choice of an appropriate magnetic core material. Powder cores in particular are suitable due to their saturation flux density of up to 1.5 T. However, high DC currents constitutes a significant problem since the winding cross‐section rises with the current, which consequently increases AC losses due to skin effects. Another challenge is the reduction of winding layers to decrease proximity losses. This paper presents an improved single‐layer winding design procedure for DC‐DC converter powder cores. The procedure determines the optimum number of parallel cores and stacks. This way, the procedure enables a predefined maximum wire cross‐section for copper loss optimisation and single‐layer winding. The introduced approach defines the optimum switching frequency as a trade‐off between core loss and core volume. Finally, experimental tests with two setups validate 27 kW DC‐DC converters and hence the design procedure using Si‐IGBTs and SiC‐MOSFETs. The results demonstrate that SiC‐MOSFETs reduce core volume by a factor of 3 compared to Si‐IGBTs. Further, the SiC setup reaches high efficiencies of up to 98.53% compared to 98.17% for the Si‐based converter.

Robust resilience enhancement strategy for gas‐electricity integrated energy system considering multiple reinforcement levels

AbstractNatural disasters are extreme events with low probability but strong destructive ability, which have a serious impact on the power system. The gas‐electricity integrated energy system is more likely to be affected by natural disasters due to its complex multi‐energy coupling characteristic. In order to improve the resilience of the gas‐electricity integrated energy system under natural disasters, this paper proposes a three‐layer defence‐attack‐defence robust resilience improvement model with the objective of minimizing the load loss in the gas‐electricity integrated energy system. Firstly, in order to cope with various levels of disaster and improve the economy of line/pipeline reinforcement in the gas‐electricity integrated energy system, a multi‐level line/pipeline reinforcement model is proposed on the basis of load weight in the upper layer. Then, information entropy is introduced to represent the impact of natural disasters in the middle layer. Based on the operation constraints of the gas‐electricity integrated energy system, the optimal allocation of the mobile electricity storage and liquefied gas storage is established in the lower layer. The three‐layer resilience improvement model is solved by the nested column and constraint generation algorithm. Finally, the case study proves the feasibility of the model and the effectiveness of the solution method.

Efficiency Improvement of Permanent Magnet Synchronous Motors Using Model Predictive Control Considering Core Loss

The highway cycle is an important consideration in the EV’s new European driving cycles (NEDCs) range, as the steady-state efficiency improvement in such conditions can be greatly beneficial. In the model predictive control (MPC) of the permanent magnet synchronous motors (PMSMs), the predicted next-step feedback reference generated by the equivalent circuit model (ECM) will contribute directly to the voltage vector selection, therefore influencing the performance of the motor control. In the current MPC scheme, when the conventional ECM is applied, it only considers copper loss, and the core loss is usually disregarded. In some circumstances, such as the highway cycle of EVs, the motors are at high speed, the torque is low, and the core loss can be significant in the losses, thus affecting the accuracy of control and the efficiency of the system; hence, the introduction of core loss ECM into the MPC would be beneficial. This paper aims to investigate the steady-state efficiency improvement of a novel ECM of PMSM considering core loss ECM, and the comparison will be based on model predictive direct torque control (MPDTC) using the core loss ECM, which will be compared to MPDTC with the conventional ECM of the PMSM. The results demonstrate the proposed ECM’s efficiency improvement in various conditions, the limitations of the model and the simulation are discussed, and future work is proposed.

Research on the Influence of Different Winding Forms on the Performance of Induction Motor

Background: As a component of the motor’s electromechanical energy conversion, the winding is very important. When the winding design is improper, the harmonic content is increased, which leads to an increase in the motor loss and torque ripple. Therefore, winding design is very important for motor design. Objective: The effect of winding forms on the induction motor is analysed in this paper. The variation in performance parameters of different winding forms is invesitgated. Methods: This paper takes an 11 kW, 1500 r/min induction motor as the research object; the two- dimensional transient field finite element model has been established to calculate the basic parameters, which are then compared with the experimental data to verify the correctness of the model. Finally, the magnetizing reactance, starting performance, stator leakage reactance, various losses, and efficiency under different winding forms are calculated and compared. Results: When the motor adopts double-layer winding, the magnetizing reactance, stator slot leakage reactance, and harmonic leakage reactance are less than those of the motor with single-layer winding by 13.47%, 25.37% and 20.97%, respectively, while the end-leakage reactance, starting torque, and starting current rotor copper loss are higher than those of the motor with single-layer winding by 7.14%, 9.52%, 18.54%, and 15.23%, respectively. The core loss and stator copper loss of motors with different winding forms are almost unchanged. The efficiency of the motor with single-layer winding is higher than that of the motor with double-layer winding by 1.22%. Conclusion: When the winding form is different, the magnetizing reactance, stator slot leakage reactance, harmonic leakage reactance, and end-leakage reactance are different. Leakage reactance is the main factor that causes a difference in starting torque and starting current between the two winding forms. The core loss and stator copper loss of motor with different winding forms are almost unchanged, while the difference in the rotor copper loss is obvious. In addition, the efficiency of the motor with single-layer winding is higher than that of the motor with double-layer winding.

Influence of bond thermal and mechanical properties on the additively manufactured grinding wheels performance: Mechanical, wear, surface integrity, and topography analysis

It is always a great challenge to fabricate customized grinding wheels using diverse bonding materials to determine their impacts on the cutting ability and grinding performance. Additive Manufacturing methods offer tremendous advantages for customized and prototype production to reduce the cost as well as increase speed to market. This work aims to extend the grinding operation knowledge by examining acrylate base resin bonds with different mechanical and thermal characteristics to print the grinding wheels. Extensive experiments are conducted to investigate their performance in metal grinding, with hardness ranging from soft to super hard. A remarkable improvement in grinding performance has been established by using high-temperature resistance bond material, which was more prominent in the case of aluminium and hardened steel. It was discovered that utilizing the bond material with a higher mechanical and thermal characteristic could provide high grain retention under elevated temperatures, which participated in less grinding force (up to 58 % and 18 % in the case of soft and hard metals, respectively). Employing bond material with improved mechanical and thermal properties to fabricate grinding wheels significantly prolonged the tool life, for example, by up to 80 % for hardened steel at maximum, along with promoting dimensional accuracy. Nevertheless, however, using high-temperature resistance resin brought slight improvement in tool life for the hard metals grinding due to the intensely aggressive grinding condition, which could not be largely compensated by using modified resin. The surface roughness of the ground part represented considerable improvements through using high-temperature resistance resin by representing 33 % and 30 % roughness values reduction for Al and hard metal, respectively, compared to those ground with lower temperature resistance resin. Moreover, the ground surface's microhardness examination indicated meaningful surface microstructure change by applying different grinding parameters and bond material types. Furthermore, the microtopography of the grinding wheels before and after the grinding operation revealed that employing the higher temperature resistance resin could bring about notably less chip loading and grain loss.

N − 1 Security Criteria Based Integrated Deterministic and Probabilistic Framework for Composite Power System Reliability

Unpredictable variations in load demand and unanticipated component failures are progressively impacting the operation of modern power systems, making system evaluation more stochastic in nature. Although deterministic approaches were formerly the norm for determining system status, probabilistic approaches have greatly improved the capacity to capture the stochastic behavior characteristic of power system operations. The presented work in the paper recommends the use of probabilistic modelling approaches with deterministic approaches, highlighting their crucial function in augmenting the reliability and security of contemporary power systems to unanticipated failures. In this paper, N − 1 security criteria based reliability of the composite power system (CPS) is proposed using an integrated deterministic and probabilistic framework (D-P) considering outage of the transmission line. For the deterministic approach (DA), line overloading on available lines is determined using the static security index (SSI). For the probabilistic approach (PA), reliability indices such as expected loss of power (ELOP), expected frequency of contingency (EFOC), expected loss of load (ELOL), probability of load curtailment (PLC), and expected duration of load curtailments (EDLC) are calculated. Further, for each contingency, a performance index is determined using both approaches to assess the severity of the contingency that occurred on the power system. Based on the N − 1 security criteria based reliability analysis using an integrated D-P framework, a credible critical set of transmission lines is obtained, which can serve as important information to system operators. The proposed techniques have been tested on IEEE 24 bus reliability test system (RTS).

A Novel Pumping Principle for a Total Artificial Heart.

Total artificial hearts (TAH) serve as a temporary treatment for severe biventricular heart failure. The limited durability and complication rates of current devices hamper long-term cardiac replacement. The aim of this study was to assess the feasibility of a novel valveless pumping principle for a durable pulsatile TAH (ShuttlePump). The pump features a rotating and linearly shuttling piston within a cylindrical housing with two in- and outlets. With a single moving piston, the ShuttlePump delivers pulsatile flow to both systemic and pulmonary circulation. The pump and actuation system were designed iteratively based on analytical and in silico methods, utilizing finite element methods (FEM) and computational fluid dynamics (CFD). Pump characteristics were evaluated experimentally in a mock circulation loop mimicking the cardiovascular system, while hemocompatibility-related parameters were calculated numerically. Pump characteristics cover the entire required operating range for a TAH, providing 2.5-9 L/min of flow rate against 50-160 mmHg arterial pressures at stroke frequencies of 1.5-5 Hz while balancing left and right atrial pressures. FEM analysis showed mean overall copper losses of 8.84 W, resulting in a local maximum blood temperature rise of <2 K. The CFD results of the normalized index of hemolysis were 3.57 mg/100 L, and 95% of the pump's blood volume was exchanged after 1.42 s. This study indicates the feasibility of a novel pumping system for a TAH with numerical and experimental results substantiating further development of the ShuttlePump.

Analysis of Partial Load Loss of the PCS and Internal Storage Battery Loss in Residential PV Power Generation and Storage Battery Systems

Analysis of Partial Load Loss of the PCS and Internal Storage Battery Loss in Residential PV Power Generation and Storage Battery Systems

Fault-Tolerant Control of Dual Three-Phase PMSM Based on Minimum Copper Loss Under Multi-Phase Open and Open-Switch Faults

Fault-Tolerant Control of Dual Three-Phase PMSM Based on Minimum Copper Loss Under Multi-Phase Open and Open-Switch Faults

Attack–Defense Confrontation Analysis and Optimal Defense Strategy Selection Using Hybrid Game Theoretic Methods

False data injection attacks are executed in the electricity markets of smart grid systems for financial benefits. The attackers can maximize their profits through modifying the estimated transmission power and changing the prices of market electricity. As a response, defenders need to minimize expected load losses and generator trips through load and power generation adjustments. The selection of strategies of the attacking and defending sides turns out to be a symmetric game process. This article proposes a hybrid game theory method for analyzing the attack–defense confrontation: firstly, a micro-grid-based power market model considering false data injection attacks is established using the Nash equilibrium method; secondly, the attack–defense game function is constructed and solved via the Stackelberg equilibrium algorithm. The Markov game algorithm and distributed learning algorithm are used to update equilibrium function; finally, a dynamic game behavior model of the two players is constructed through simulating the attack–defense probability. The evolutionary game method is used to select the optimal defense strategy for dynamic probability changes. Modified IEEE standard bus systems are illustrated to certify the effectiveness of the proposed model.

Purification of Copper Concentrate from Arsenic under Autoclave Conditions

This study presents the results of a two-stage autoclave processing of a copper–arsenic concentrate. Copper concentrate is an important raw material to produce copper and other metals. However, in some cases, the concentrate may contain increased amounts of arsenic, which makes further processing difficult. Therefore, the development of modern hydrometallurgical methods for processing copper concentrate with a high arsenic content is an urgent task, which could lead to the optimization of the raw material processing process and the improvement of the quality of the concentrate. It has been established that the optimal conditions for the sequential two-stage autoclave processing of copper–arsenic concentrate are: t = 220–225 °C, τoxidation = 20 min, τtot = 90 min, Po2 = 0.4 MPa, and L:S = 10:1, [H2SO4]initial = 40 g/dm3; in this case, 85% of zinc, 44% of iron, and 78% of arsenic, respectively, are extracted into the solution during both stages and the loss of copper was about 0.01%. This is explained by the fact that at the first stage (oxidation) of the autoclave processing of the copper–arsenic concentrate, copper, together with iron, leaches into the solution, and at the second stage (reduction), copper precipitates out of the solution in the form of chalcocite. Copper in the residue after autoclave leaching is in the form of Cu2S, iron is in the form of pyrite (FeS2), and lead is in the form of anglesite (PbSO4), respectively. The obtained micrographs and EDX mappings clearly show no iron arsenates. This confirms that at the oxidative stage of the developed process, arsenic, removed by 78%, remains in the solution. The remaining arsenic is associated with tennantite, indicating the effectiveness of the treatment process in removing arsenic from the copper–arsenic concentrate. A second important observation is the presence of pronounced areas of copper sulfides in the microphotos without iron and arsenic impurities. This confirms that copper is deposited as chalcocite during the reduction phase of the process, which is the desired result.

Optimized robust control for improving frequency response of delay dependent AC microgrid with uncertainties

Converter-interface-based renewable energy incorporated into modern power systems causes deterioration in power system stability and it is proving to be a main challenge for operators using sluggish traditional generation with a growing share of converter-interface generation, and there is a need for an alternative means to deliver rapid frequency control. This paper proposes two control loops as secondary frequency control, first is an improved optimized delay-dependent frequency control to ensure robust frequency control under daily changes in system parameters that may occur in prospective, renewable-rich future AC microgrids. For a variety of operating conditions, the design process employs a mixed H2/H∞ robust control based on linear matrix inequality (LMI). In second, a speedy-acting improved power stability control loop is utilized as the proposed secondary frequency control, because demand response aggregators can be beneficial for frequency control. Robustness is evaluated against several perturbations and communication delay attacks through dynamic simulation and stability is evaluated by small-signal analysis. Different case studies subject to generation\\load loss, multiple time delay and parameter uncertainties are demonstrated on an interconnected AC microgrid system to verify the performance of the proposed control technique.

Determining total cost of ownership and peak efficiency index of dynamically rated transformer at the PV-power plant

Dynamic rating of the transformer is a promising technology, which is suitable for various applications. Using dynamic rating for connecting renewable energy is believed to be beneficial for the economy and flexibility of the power system. However, to safely deploy such operation strategies, it is important to have more precise estimates for the total costs of owning such units and determine how effective such operation method is for a solar power plant. This study proposes a method for calculating total ownership costs (TOC) of dynamically rated transformers used for the connection of the solar power plant to the grid as well as analyzes its efficiency. The sensitivity analysis looks into the change in TOC and peak efficiency index (PEI) after considering reactive power dispatch. Results of this study also show how TOC, PEI, and load and no-load losses change depending on the transformer size.