Electric traction machines have been applied to both industrial variable speed applications and electric vehicles. The induction machine (IM) is a potential candidate for traction machines due to the established industrial base. However, most of the existing studies on traction IM design rely on optimization algorithms or iterative calculation programs that subsequently give no clear understanding of the design requirements for field-weakening or extended speed operation. Hence, published procedures to guide IM design for traction applications are somewhat ad hoc to-date. This paper identifies the key IM design parameters required to achieve a traction characteristic within power supply constraints. As an example, a 120 kW electric vehicle traction machine is studied as a benchmark machine and then the proposed design procedure is employed to re-design the machine to improve its extended speed performance. Improvements in terms of efficiency and field-weakening capability are presented. Experimental results from the benchmark machine are used for validation of the subsequent simulation studies reported in this paper. Finally, the identified parameters are shown to be similar with brushless permanent magnet machines. Thus, a generalized machine design philosophy can be concluded.

The modelling, control, switching schemes, novel applications, etc. of multi‐phase voltage source inverters (VSIs) have been studied in recent years. While some DC‐link capacitor considerations have been reported and ripple current assessments presented, the impact of these analyses on system design has not previously been quantified. These knowledge boundaries are expanded via this research. Meanwhile, a hypothesis is proposed that under the equitable operating conditions, the increase in the phase number decreases the DC‐link capacitor requirements compared with the representative conventional three‐phase VSIs. The analytical study shows the results corresponding to the hypothesis. Moreover, another hypothesis is made that other factors, e.g. switching strategies, carrier waveforms, and interleaving techniques also determine the DC‐link capacitor requirements, and some strategies can further decrease the DC‐link capacitor requirements. The presented analytical study supports this hypothesis. The study is partially validated via experiments on a brushless permanent magnet synchronous motor (PMSM) drive system designed for the equitable comparison of three‐ and nine‐phase VSIs driving PMSMs. Finally, the DC‐link capacitor design procedure is proposed for two level multi‐phase VSIs.

In order to improve the energy efficiency and economic effect of conventional diesel-powered rubber-tired gantry (RTG) cranes in container terminals, various hybrid RTG cranes were studied. However, these current hybrid RTG cranes have several disadvantages, such as high initial investment cost and poor versatility of energy management methods. In this paper, a hybrid RTG crane consisting of a small-sized diesel generator (DG), a ternary material lithium battery, and a supercapacitor (SC) is studied, and a hybrid RTG crane energy management method based on game theory is proposed. The DG, lithium battery, and SC are modeled as three independent agents to participate in the game, and a multi-agent system (MAS) is established. During the RTG crane work process, agents achieve a coordinated and stable working state through the game, i.e., the Nash equilibrium. Three typical crane operation scenarios, the rated load, continuous work, and intermittent work, are simulated and studied. According to the results, combinations of the three devices can meet the power demand and system performance. The power of the DG in the hybrid system is small (only 20 kW), reducing fuel consumption and overall emissions during RTG crane operation.

Fuel cell hybrid vehicles represent an alternative to battery electric vehicles and will gain importance in the future as they do not need large battery capacities and thus require less critical raw materials. Depending on the electric architecture, the voltage of the fuel cell stack and traction battery may overlap. Accordingly, it is necessary to use a bidirectional DC–DC converter that connects the battery to the DC bus, which supports overlapping input and output voltages. Furthermore, these converters should be non-isolating in terms of compact design. Concerning complexity and controllability, the bidirectional cascaded buck and boost converter is preferable and is the subject of this study. Published literature presents the bidirectional cascaded buck and boost converter with high losses for overlapping input and output voltages, introducing two methods for this operation mode. The method selected for this study, namely buck + boost, uses two switches, whereby one switch has a fixed duty cycle. However, there is no appropriate investigation to determine the impact of this fixed duty cycle on converter efficiency to date. Furthermore, efficiency improvement is possible by switching frequency modulation, but current literature does not address this modulation method for overlapping input and output voltages. Therefore, this paper investigates a non-isolated hard-switched bidirectional cascaded buck and boost converter for fuel cell hybrid vehicles operating with up to 19.8 kW. The study focuses on determining the optimum fixed duty cycle and efficiency optimisation through a novel critical conduction mode with adapted switching frequency by utilising the load-dependent inductance of the inductor with powder cores. Measurements with an experimental setup validate the proposed modulation method with Si-IGBT half-bridge modules. The results demonstrate that a loss reduction of 39% is possible with switching frequency modulation and the optimum duty cycle compared to fixed switching frequency. As a result, the converter achieves high efficiencies of up to 99% and low device junction temperatures.

Literature compares DC-DC converters with Si and SiC power semiconductors without optimum switching frequency in terms of efficiency, volume, and costs for the respective application and operating point. Typical switching frequencies, such as 25 kHz for Si-IGBTs and 100 kHz for SiC-MOSFETs, are chosen with unconditional statements. A design with optimum switching frequency is crucial for a meaningful conclusion about the best-suited semiconductor technology for the respective application. This paper uses a novel iterative design procedure to determine the optimum switching frequency considering a trade-off between efficiency, volume, and costs for bidirectional DC-DC converters based on Si-IGBTs and SiC-MOSFETs with ferrite cores. Due to the importance of fuel cell hybrid vehicles as the long-term alternative to conventional vehicles, the application analyzed is the bidirectional DC-DC converter connecting the traction battery to the DC-bus. Both converters are evaluated and compared in the simulation environment PSIM, and their parameters are according to available fuel cell hybrid vehicles on the market. This paper proves in PSIM that the optimum switching frequency in both cases is below the standard values. Furthermore, it presents that Si-IGBTs have efficiency losses of less than 2 % for the operating point of interest than SiC-MOSFETs, reducing semiconductor costs by 68 % while increasing core volume by 344 %.