Permanent magnet synchronous motor (PMSM) provides a very competitive technology for electric vehicle (EV) traction drive with its higher power density and higher efficiency. When the control system of PMSM for EV is affected by the change of motor parameters and the interference from the external environment, the motor system cannot provide high-quality dynamic performance in time. In the paper, an EV motor control strategy based on improved sliding mode and proportional resonance theory is proposed, in which a speed controller is designed based on the improved exponential reaching law. The improved exponential approximation law overcomes chattering in traditional sliding mode control without increasing parameters and improves the anti-interference performance of the EV. In addition, the improved proportional resonance method is used to design the current controller of the PMSM control system, and the combination of the two has been successfully applied to EV for the first time. Finally, the experiment and urban road condition test are carried out to verify. The results show that the proposed scheme can effectively improve the dynamic performance and robustness of the PMSM system for EVs.

Traditional moving-magnet transversal-flux linear oscillatory machines (MTLOM) suffer from high fabrication difficulty and cost, low robustness and reliability, and low material utilization ratio, etc. In this paper, a novel stator-magnet moving-iron transversal-flux linear machine (SMTLOM) is proposed, with magnets inserted into the stator yoke (rather than mounted on stator poles) and mover composed of iron core only. First, the topology of proposed SMTLOM is described, as well as its operation principle. Then, the comparison rules are built to make fair comparison between the conventional MTLOM and the novel SMTLOM, from the perspective of practical application, including the same maximum size limitation, output thrust, and thermal source. By using a three-dimensional finite-element analysis (3-D FEA), comparisons of some key performance indexes, such as back electromotive force, thrust per coil length, thrust per magnets volume, thrust per machine volume, temperature distribution, material cost and structure reliability, etc., are made between these two types of machines. The results from 3-D FEA demonstrate that the novel SMTLOM has enjoyed merits of lower fabrication cost and weight, much higher reliability, thrust density, material utilization ratio, etc., which indicate that the novel SMTLOM is more suitable for driving compressor and easier for mass production.

In this article, a stator-magnet transverse-flux linear oscillatory machine is proposed for direct compressor drive. The robust transverse-flux structure with permanent magnets (PMs) embedded in the stator yoke and a moving-iron translator can yield high reliability and is relatively simple to fabricate. For electromagnetic performance analysis, a linear model under the no-load condition and a nonlinear model under the loaded condition are developed by taking into account the axial leakage flux and saturation effects of iron core, respectively. The effectiveness and accuracy of the proposed analytical models are verified by comparing the results with those of the finite-element analysis and the static experimental tests. Based on the measured static characteristics and damping coefficient, a system kinetic model is developed in the form of coupled equivalent electromechanical circuit, and validated by the results of dynamic test on a prototype. The key indices of the new machine are compared with those of an existing moving-magnet linear oscillatory machine, including the amount of PM usage, efficiency, and thrust density, etc. The case study results show that the proposed linear oscillatory machine is suitable for linear compressor drives.

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.

In order to estimate the core loss resistance of converter-fed induction motor accurately and efficiently, an analytical piecewise variable-coefficient core loss model is proposed. By introducing two voltage harmonics related coefficients, the influence of converter harmonics on core loss is simply and effectively considered. In addition, the surface and pulse loss caused by slot harmonics and the additional harmonic core loss caused by harmonic magnetic potential of stator winding under load condition are also considered. Based on the proposed model, an advanced core loss equivalent resistance model of converter-fed induction motor considering supply and spatial harmonics is proposed. The effectiveness of the proposed model is validated by comparisons with the measured core losses of 5.5 kW induction motor under no-load condition. In addition, compared with the finite-element method under load condition, the proposed analytical model reduces the computational time significantly while maintaining high accuracy.

While having various desired merits of high structural robustness and thus reliability, high thrust density, low fabrication cost, and so on, the stator-magnet moving-iron transverse-flux linear oscillatory machine suffers from high consumption of rare-earth magnetic material (high material cost) and heavy flux leakage at the stator outer region (underutilization of permanent magnets). To mitigate the demerits, a novel stator-magnet moving-iron transversal-flux hybrid-flux-path linear oscillatory machine (SMTHLOM), with additional back iron and auxiliary radially magnetized ferrite magnets, is proposed in this paper. The topology and operational principle of the proposed SMTHLOM are explained in detail. The 3-D finite-element analysis is introduced to investigate the sensitivities of main structural parameters, which enables the selection of optimal dimensions. Based on a set of comparison rules, a comprehensive comparison was conducted between these two topologies on various key indicators, such as the back electromotive force, thrust, and thermal distribution. The simulation results show that the SMTHLOM is low cost and small stator outer flux leakage, and thus is more suitable for some applications, e.g., fridge compressors, requiring low cost and high thrust density.