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In recent years, with the progress of new energy conversion technology, especially an increasing number of gas turbine units applied to the market, the connection between the natural gas system and the electric system has become increasingly close. Initially the gas and electricity markets operated relatively independently. Therefore, it is necessary to establish the coupling architecture of natural gas market and electricity market to meet the energy demand of users. This paper attempts to propose a power and gas coupling system based on clearing market structure. Firstly, the difference between natural gas–electricity coupling market and joint settlement market is discussed. The combined market considered in this paper is somewhat different from the associated electricity market and natural gas market. The calculations are easier and the results more reliable than those of the traditional linked gas markets and electric power market. Then, a mathematical model of joint clearing market is established based on bilateral energy contracts. Then, the piecewise linearization approximation (PLA) algorithm is proposed to solve the nonlinear problem. The locational piecewise price (LMEP) and locational marginal gas price (LMGP) are identified respectively, and the bilateral contracts are processed. The solution proposed in this paper guarantees strong duality and clear meaning of dual variables, making PLA easy to apply and solve market clearing problems based on dual variables or Lagrange multiplier pricing, as well as easy to deal with bilateral contract problems. Finally, the proposed joint clearing market is verified by an improved 3-electric bus and 6-gas node system.

In recent years China has committed to energy saving and emission reduction. Chinese Government has proposed a strategic policy of carbon neutrality. In the context of energy shortage, the development of sustainable cities and green buildings is a major trend. An important part of energy consumption in cities is the energy consumed by temperature regulation in buildings, and reducing this part of energy consumption can be of great help to the development of sustainable cities. In this paper, our team propose a scheme for temperature regulation with large permanent magnet direct drive fans system and air conditioners. Compare the conventional room temperature regulation scheme which only uses air conditioners with the new room temperature regulation scheme which uses the large permanent magnet direct drive fan and air conditioners by simulating the indoor temperature regulation process. The results of simulation show that the new scheme’s temperature regulation effects are more uniform than the conventional scheme. The new scheme can reach the target Comfort Index of Human Body faster than the conventional scheme, and the energy consumption can be reduced by more than 8%. The paper concludes that the new room temperature control solution is more energy efficient, reduces carbon emissions and helps to achieve the carbon neutrality target.

Due to its better power density and efficiency, permanent magnet linear synchronous motor (PMLSM) is ideal for generating electricity with wave power device (WPD). Nevertheless, when the PMLSM for the WPD control system is impacted by changes in motor characteristics and interference from the outside environment, it typically is unable to deliver high-quality dynamic performance on schedule. Although sliding mode control (SMC) has been introduced to improve the robustness of the system greatly in recent decades, traditional methods still have problems such as slow dynamic response, poor anti-disturbance performance, large chattering amplitude, and phase delay. To solve the above defects in SMC, an improved global fast terminal high-order SMC strategy based on novel reaching law for improving PMLSM dynamic performance is proposed in this paper, as well as the sliding mode surface and control law of the speed controller is designed based on this control strategy. The proposed strategy would not only shorten the dynamic response time but also weaken the chattering magnitude in the sliding mode stage, improving the dynamic performance of both speed and current. The simulation results demonstrate that in comparison to the traditional PI and SMC control methods, the improved strategy proposed in this paper can further enhance the control performance of the linear motor, demonstrating the method’s enormous potential in the double closed-loop vector control system of PMLSM for WPD.

IntroductionThe diversity of freshwater fishes is threatened by multiple environmental stressors, including climate change, alterations in land use, and introduction of non-native species. However, the quantification of temporal biodiversity in freshwater communities is limited. Here, we asked: i) how has alpha (species richness), beta (changes in freshwater species composition), and gamma diversity (total species diversity in a landscape) changed over time for lakes over a 50 year period?; and ii) What are the climatic, land use, and lake morphological drivers associated with higher diversity?MethodsWe assembled a database of fish species occurrence from 20 lakes across subalpine and alpine regions in Alberta from 1970-2019, in addition to lake morphological, climatic, and land use characteristics of the watersheds. ResultsWe observed an overall increase in alpha, beta, and gamma diversity from the 1970s to 2009s. However, all measures of diversity declined from 2010-2019. We found that more lakes and species assemblages were influenced by species gains, rather than species losses (with the exception of the last decade of sampling). DiscussionGenerally, we found that coolwater species were expanding and coldwater fishes were being lost throughout our study lakes. We highlight temporal heterogeneity in fish biodiversity responses to substantial environmental pressures in this region.

For the sake of increasing the energy efficiency of the city’s energy supply, it is an effective approach to adopt the joint planning of the integrated energy system employing a group of cooling heat and power. However, the coupling matrix in the integrated energy system is quite difficult to formulate. In this paper, a standardized construction method for modeling Energy Hub is proposed. The construction of the model is divided into several steps. In addition, the difficult of solving the coupling matrix of integrated energy system can be availably reduced through this method. Considering the nonlinear problem caused by dispatch factors, this paper proposes a comprehensive energy system optimization strategy by using improved particle swarm optimization algorithm. Finally, using an example of a residential area with cooling, heating and electricity system to verify the effectiveness of the proposed modeling and calculation method . At the same time, the influence of demand response and energy storage on economy during operation is analyzed.

The paper aims at the phenomenon of the magnetic field between phases of magneto-optical current transducer, studies the magnetic field interference distribution characteristics and proposes the orthogonal optical path optimization scheme to improve the ability of the magneto-optic current transducer to resist the external magnetic field interference. The mathematical model of magnetic field interference degree of magneto-optic current transducer is established, and the distribution characteristics of magnetic field interference degree of magneto-optical current transducer under the effect of interfering current are studied. The research shows that the position of interfering current has a specific law on the magnetic field interference degree of the magneto-optic current transducer, and the interfering current at a specific position has no interference effect on magneto-optic current transducer. It is pointed out that magnetic field interference degree is larger when the magneto-optic current transducer is arranged in the conventional way, and the error caused by the magnetic field interference between phases cannot be ignored. The orthogonal optical path optimization scheme of magneto-optic current transducer is put forward, which can improve the anti-interference ability from external magnetic field of magneto-optic current transducer without changing its body structure and installation condition. The experimental results show that the relative error of magneto-optic current transducer caused by the interfering current is less than 0. 1% when the orthogonal optical path optimization scheme is adopted, which proves the correctness and practicability of the orthogonal optical path optimization scheme.

For the purpose of studying the influence of high frequency PWM harmonics on the losses of induction motor, this paper first introduces the latest international standard IEC/TS 60034-2-3 for the separation of the losses and the measurement of the efficiency of induction motor under PWM power supply. Then, considering that the skin effect of windings in induction motors under the condition of PWM power supply more apparent, this paper uses the stator AC resistance to replace the stator DC resistance in the IEC/TS 60034-2-3 standard to obtain more accurate separation results. On this basis, an improved method of loss separation for converter-fed induction motor is proposed by using the accurate time-step finite element method to calculate the rotor copper loss under no-load condition which cannot be considered in IEC/TS 60034-2-3 standard. Finally, this method is used to measure and separate the losses of a 5.5 kW converter-fed motor under different operating conditions. The results show that the loss of induction motor which is driven by PWM converter is obviously greater than that of sinusoidal drive, especially under light load or no load condition. The whole no-load losses of the motor driven by PWM converter increases by more than 20.0% compared with that of the sinusoidal driving condition.

The MEMS sensor converts the physical signal of nature into an electrical signal. The output signal of the MEMS sensor is so weak and basically in the low-frequency band that the MEMS sensor interface circuit has a rigorous requirement for the noise/offset and temperature coefficient, especially in the bandgap reference block. However, the traditional amplifier has low-frequency noise and offset voltage, which will decrease the precision of the bandgap reference. In order to satisfy the need of the MEMS sensor interface circuit, a high-precision and low-noise bandgap reference is proposed in this paper. A novel operational amplifier with a chopper-stabilization technique is adopted to reduce offset and low-frequency noise. At the same time, the V-curve compensation circuit is used to realize the second-order curvature compensation. The circuit is implemented under the 0.18 μm standard of the CMOS process. The test result shows that the temperature coefficient of the bandgap is 2.31 ppm/°C in the range of −40–140 °C, while the output voltage noise is only 616 nV/sqrt(Hz)@1 Hz and the power-supply rejection ratio is 73 dB@10 kHz. The linear adjustment rate is 0.33 mV/V for supply voltages of 1.2–1.8 V at room temperature, the power consumption is only 107 μW at 1.8 V power supply voltage, and the chip active area is 0.21 × 0.28 mm2.

Abstract By collecting and sorting the energy demand data of developing and developed countries, this paper makes a comprehensive analysis of their energy demand, including the change of energy demand and the change trend of energy load in various sectors. The survey scope of the article includes the overall change trend of energy supply, natural gas, oil, electricity, coal, renewable energy (such as wind energy, solar energy, geothermal energy, tidal energy, etc.), and the data change of global carbon dioxide emission. Besides, this paper selects a variety of energy sources for comprehensive analysis to analyze the existing change trend in chronological order. The analysis methods include data statistics of primary energy production and consumption, energy intensity analysis of gross domestic product (GDP), production, and demand balance of oil, natural gas, and coal, and study the trade balance between different types of energy in different countries and regions. The regions examined in this review include the organization for economic cooperation and development (OECD); the group of seven (G7); Brazil, Russia, India, China and South Africa (BRICs); the European Union; Europe; North America; the Commonwealth of Independent States (CIS); Asia; Latin America; the Pacific Ocean; the Middle East and Africa. By studying these data, we can make a better summary of the current energy use, so as to conveniently grasp the context of energy development and have a general understanding of the current energy structure. Therefore, individuals and policymakers in the fields of energy trade can think more deeply about the future situation and draw conclusions.

Aiming at the low efficiency of vector control system caused by unreasonable current allocation, an improved energy saving control strategy based on weighted average current method is proposed in this paper, and the research is carried out on the background of interior permanent magnet synchronous motor vector control system. This method does not add new parameters, but achieves the goal of reducing motor loss and improving current utilization rate. Firstly, according to the mathematical model of permanent magnet synchronous motor considering iron loss resistance, the relationship between motor torque and d-q axis current is deduced. Then, by introducing the weighted average current factor, the minimum copper loss current and the minimum iron loss current are calculated analytically. Finally, the simulation analysis shows that the energy saving strategy proposed in this paper can further reduce the electrical loss of permanent magnet motor compared with the traditional energy saving control method, which proves the feasibility of this method in improving the energy efficiency of the vector control system of permanent magnet motor.

Power systems operate under energy and climate policies with the targets of carbon neutrality and CO2emissions reduction in recent years. To mitigate environmental problems, it is important to promote the accommodation of renewable energy with strong fluctuations through hosting capacity evaluation of the distribution network. A feasible region evaluation method is proposed to characterize an accurate region of renewable energy accommodation capacity in the distribution network on short-time scales. The evaluation model based on the optimal power flow model is established with the objective of minimizing the operating cost of the distribution network, satisfying the operational constraints. Through multi-parametric programming, the constraints of the optimal power flow model are projected onto the boundary of the feasible region. Each operation point (the renewable generator output) in the feasible region can be directly obtained, which can serve for real-time dispatch with safety. Simulation results show that the proposed method can accurately obtain the feasible region of renewable energy accommodation capacity and the computational efficiency has been greatly improved compared with the Monte Carlo method.

As a representative new energy source, solar energy has the advantages of easy access to resources and low pollution. However, due to the uncertainty of the external environment, photovoltaic (PV) modules that collect solar energy are often covered by foreign objects in the environment such as leaves and bird droppings, resulting in a decrease in photoelectric conversion efficiency, power losses, and even the “hot spot” phenomenon, resulting in damage to the modules. Existing methods mostly inspect foreign objects manually, which not only incurs high labor costs but also hinders real-time monitoring. To address these problems, this paper proposes an IDETR deep learning target detection model based on Deformable DETR combined with transfer learning and a convolutional block attention module, which can identify foreign object shading on the surfaces of PV modules in actual operating environments. This study contributes to the optimal operation and maintenance of PV systems. In addition, this paper collects data in the field and constructs a dataset of foreign objects of PV modules. The results show that the advanced model can significantly improve the target detection AP values.

This paper introduces a new method of estimating the variation interval and the expected value of optimal economic operation cost for the energy hub (EH) model considering load and renewable energy uncertainties in the residential district. Firstly, renewable energy and load uncertainties are defined as uncertain sets of historical data. Due to dispatch factors, the traditional EH model is non-linear and difficult to calculate and analyze. In this paper, a multi-step modeling method is developed for the breakdown of a complex EH model (CEH) into several simple EH (SEH) models and variable substitutions in each SEH, to eliminate the non-linearity of CEH. The upper and lower bound of the operating costs are then obtained based on the duality theorem and the expected value is calculated by expected value model. Finally, the case study in Beijing residential district is carried out to confirm the efficiency of the proposed method.

Chemical compounds dissolved in insulating oil, as indicators can excellently monitor the paper aging condition, which has attracted increasing interest in areas of transformer condition monitoring and fault diagnosis. Because of their outstanding features, such as good correlation with the degree of polymerization of cellulose paper and the aid of non-destructive online monitoring, chemical indicators have been effectively used for transformer condition assessment. In this study, a comprehensive, in-depth insight into the indicators of the aging of insulating paper from aging characteristics, physico-chemical characteristics, shortcomings of various compounds, generation pathways and mechanisms, and monitoring technologies are provided. It is expected that these chemical indicators can provide better guidance for the evaluation of paper insulation performance and transformer aging. In addition, the latest research progress, as well as current challenges and future prospects are also outlined. This study provides a theoretical basis and reference for chemical indicators in the fields of microscopic formation mechanism, diffusion equilibrium phenomenon, and insulation aging state assessment.

This paper presents an analytical method to design the high-efficiency surface permanent magnet synchronous motor (SPMSM) or generator (SPMSG). The air-gap and permanent magnet size can be approximately determined based on our mathematics model, which is the most important part of SPMSM design. From our method, we can know that motor's power out torque is related to the torque angle that we selected in our design and it affects the air-gap and permanent magnet size. If we choose a low torque angle, the motor or generator's overload power handing capability will increase. The embrace value has a vital place in designing a motor or generator due to its effects on air gap flux density, cogging torque, efficiency and so on. In order to avoid the knee effect, the working point of the permanent magnet we selected in the design should be bigger than 0.5. The developed 36 slots, 4 poles, surface mound permanent generator is proposed. The corresponding finite element analysis (FEA) model is built based on our design method. Structure optimization includes stator and rotor structure size, permanent magnet size, magnetic bridge and air gap length which are analyzed and simulated by ANSYS Maxwell 2D FEA. Thermal analysis is conducted, and the housing of the alternator is designed. The alternator prototype is fabricated and tested based on our design.

Voltage sag is one of the most common power quality disturbances in industry, which causes huge inrush current in the windings of induction motors, and adversely impacts the motor's secure operation. For better understanding of the operation and protection of induction motors, there is a need for a detailed research of the transient characteristics of induction motors during sag events. In this paper, we first proposed a novel 2-D multi-slice field-circuit-motion coupling time-stepping finite element method (2-D multi-slice FCM coupling T-S FEM) for calculating the transient performance of the induction motor with skewed rotor bars. In the proposed method, the equations of field, circuit, and motion are expressed in a nodal matrix and coupled together. Based on this method, we have analyzed the electromagnetic properties of a 5.5-kW induction motor with skewed rotor bars under symmetrical voltage sag conditions. Then, the influences of voltage sag's sag magnitude, phase-angle jump, and initial phase angle on the stator inrush peak currents of the 5.5 kW and a 55-kW induction motors is studied. Finally, the proposed method is compared with 3-D FEM, the traditional 2-D multi-slice FEM and the measured data. The results show that the proposed method can reduce the computation time significantly with high precision.

A new method for on-chip random telegraph noise (RTN) characteristic time constant extraction using the double sampling circuit in an 8.3 Mpixel CMOS image sensor is described. The dependence of the measured RTN on the time difference between the double sampling and the key equation used for time constant extraction are derived from the continuous time RTN model and the discrete event RTN model. Both approaches lead to the same result and describe the data reasonably well. From the detailed study of the noisiest 1000 pixels, we find that about 75% to 85% of them show the signature of a single-trap RTN behavior with three distinct signal levels, and about 96% of the characteristic time constants fall between 1 μs and 500 μs with the median around 10 μs at room temperature.

This paper presents an analytical method to design an interior permanent magnet brushless DC electric motor (IPMBLDC motor) for a kind of electric impact wrench used for loading and unloading car bolts. It takes into account magnet assembly gap, rotor saturation webs, and bridges. Assumed flux leakage coefficient and selected working point of a permanent magnet were used in the initial design. An advanced equivalent magnetic circuit was developed to verify the total flux leakage and the quiescent operating point based on initial design parameters. Key design method points are considered and analyzed. Thermal analysis is given to simulate the temperature rise of all parts of the motor. The new impact wrench mechanical structure is designed, and its working principle analyzed. An electromagnetic field analysis based on MATLAB and the MAXWELL 2D finite element method (FEM) were used in the design to verify the equivalent magnetic circuit and optimize the IPMBLDC motor parameters. Experimental results are obtained to verify the design. The electrical and mechanical designs are combined and an analytical IPMBLDC motor design method is provided. We also show an innovative and reasonable mechanical dynamical calculation method for the impact wrench system, which can be used in whole system design of other functional electric tools.

Abstract In Wuerzburg, Germany, a terrorist attack and a killing rampage occurred five years apart (2016 and 2021). Following a structured evaluation of the rescue mission in 2016, a bundle of quality indicators and ten “lessons learned” were defined. Aim of the presented study was to compare the two rescue missions and to critically review the lessons learned from 2016 for their implementation and feasibility. An interdisciplinary and inter-professional group of experts analyzed the data using predefined quality indicators. All lessons defined in 2016 were critically reviewed and qualified as either lessons learned or lessons identified. While seven out of ten lessons were successfully implemented after 2016 (lessons learned), three lessons didn´t work and were recategorized as lessons identified (communication, zoning and the mutual exchange of different tactical approaches). Our results demonstrate that the conclusions drawn in 2016 have helped to improve the performance of the rescue forces in 2021. In addition, the identified lessons are now the basis for further improving emergency and disaster preparedness. It is important to understand, that the process of preparedness improvement is not completed with the definition of lessons identified. These must first be integrated into response plans and then trained intensively. A lesson identified only becomes a lesson learned once it has been successfully applied.