Two of the main challenges for electric vehicle (EV) adoption include limited range and long recharge times. Ultra-fast charging can help to mitigate both of these concerns. However, for typical 400 V battery EVs, the charging rate is limited by the practical cable size required to carry the charging current. To reach ultra-high charge rates of 350 or 400 kW, 800 V battery EVs are a promising alternative. However, the design of an 800 V EV requires careful new considerations for all electrical systems. This paper reviews the current state of 800 V vehicle powertrain electrical design, and performs an analysis of benefits, challenges, and future trends regarding multiple vehicle powertrain components. Specifically, detailed benefits and challenges related to the battery, propulsion motor, inverter, auxiliary power unit, and on- and off-board chargers are discussed.

Geared devices are commonly used to match the operating speed and torque of the power source with the second-mover. Such geared devices are usually mechanical gears. As counterparts of the conventional mechanical gears, magnetic gears are becoming promising devices, mainly due to the merits of physical isolation between moving parts, no gear lubrication, no mechanical fatigue, inherent overload protection and reduced maintenance, etc. Recently, several new topologies have been proposed to achieve better performances. In this paper, a general review of magnetic gears is presented, including a discussion of the most common and upcoming topologies and a description of the working principle. A comparison of different topologies is carried out, in terms of gear ratio and torque density. The main computational techniques generally adopted for coaxial magnetic gears are listed and described. Some key aspects concerning the design, the existed challenges and potential applications are also discussed. This paper aims to provide a comprehensive overview of the magnetic gear for readers working in this field.

Recently, non-rare-earth motors are attracting more and more attention due to the booming of the electric vehicle (EV) market and, more importantly, the increasing price of the rare-earth magnet material. This paper focuses on the performance comparison among a commercial interior permanent magnet (IPM) motor and two non-rare-earth motors, including a synchronous reluctance motor (SynRM) and a permanent-magnet-assisted synchronous reluctance motor (PMaSynRM). The design procedure to develop a high-torque-density, low-torque-ripple and high-efficiency SynRM is presented. Combined with a developed automatic modeling and simulation procedure, the finite element analysis (FEA)-based differential evolution (DE) algorithm is introduced for the SynRM rotor optimization. In order to fully inspire the potential of the SynRM, a novel method to optimize the motor split ratio is proposed under the constraint of the copper loss. In addition, different slot–pole combinations are investigated to maximize the motor torque, and the rotor structure is also dealt with towards the centrifugal stress at the maximum operating speed. Finally, the motor performance comparison is carried out, and the results show that although the SynRM achieves almost 61% cost savings, its poor torque capability, power factor and flux weakening (FW) capability are non-negligible defects. On the contrary, the PMaSynRM exhibits excellent features for the EV applications in terms of cost, torque density, efficiency and FW capability. This paper presents a novel split ratio optimization method for the optimal SynRM/PMaSynRM design and demonstrates the characteristics of the IPM motors, SynRMs and PMaSynRMs for EV applications.

In this paper, an analytical model in the $dq$ reference frame is developed to recognize the steady-state of the self-excited reluctance generator, considering no-load and resistive load conditions. A fast method to estimate the minimum capacitance requirement is proposed. Experiments have been carried out to verify the analytical results. After that, attention is paid on the capability of self-excitation in reluctance generator with different residual magnetisms in the rotor. Different levels of residual rotor magnetism are achieved by different magnetizing DC currents. An indicative value of phase current is defined to determine the self-excitation, and the required minimum residual rotor magnetism for self-excitation in the reluctance generator connected with different capacitances are discussed. At last, the capability of self-excitation in the reluctance generator by connecting charged capacitors is investigated.

In this paper, a fast evaluation of efficiency map and driving cycle efficiency of interior permanent magnet synchronous machines (IPMSMs) for electric vehicles (EVs) is proposed. Several techniques are applied to speed up the simulation process, including the iron loss and AC Joule loss calculations via static and time-harmonic magnetic simulation, efficiency map building via surface-fit and driving cycle efficiency via finite element interpolation. Moreover, an equivalent phase current angle technique is used to imitate the step-skewed simulation. As a result, compared to the commercial software, the calculation time consumption of the efficiency map and driving cycle efficiency can be reduced by 99.4% and 98.1%, respectively. It shows a great potential for the fast evaluation of the IPMSM performances. Furthermore, this fast evaluation method is combined with differential evolution algorithm to carry out a multi-mode and multi-objective optimization on an IPMSM, which will be of great benefit for the determination of the optimal traction motors for EVs. Finally, a prototype of the optimal machine is manufactured and tested to validate the precision of proposed method. The experimental results show good agreement with the results obtained by the proposed method.

In the last few years, wind energy conversion systems have been increasingly installed worldwide. The self-excited reluctance generators (SERGs) are found to be potential candidates as isolated wind turbine generators, especially for low- and medium-power applications. This paper focuses on the characteristics of SERG for wind turbine generation system. A simplified dynamic model of the generation system is developed, discretized by backward Euler formula and simulated. With this model, the process of self-excitation and operation characteristic of SERG are investigated. Regarding to the varying generated voltage at different speeds, variable capacitances allow suitable regulation of the voltage. The variation of capacitance with speed is obtained by the active and reactive power (PQ) balances method. Combining the power speed characteristics of wind turbine and SERG, the PQ balances method is also used to determine the “optimal capacitor and resistor combination” that achieves the highest usage of wind power. This paper exhibits the performance of SERG for wind applications, and most importantly, makes the prediction of the highest energy conversion efficiency of the system.