In this paper, a novel high step-up interleaved DC-DC converter is presented, which is composed of an interleaved structure, an asymmetric voltage multiplier cell (AVMC) and a passive lossless clamped circuit. Compared to the classical interleaved boost converter, the proposed converter has higher voltage gain owing to the employment of the AVMC and the coupled inductor. Besides, the input current ripple is limited at low values with the help of the interleaved structure, which gives more life time of the input power source. The voltage stresses of main switches are substantially low so that the MOSFETs with low-voltagerated and on-resistance ( DS (ON) R ) can be used. In addition, the voltage stresses and the reverse recovery problems of diodes are improved dramatically. Moreover, the zero-current-switching (ZCS) turn-on of switches and the ZCS turn-off of the clamp diodes are realized to reduce the switching losses. The leakage inductor energy is recycled and the voltage spikes are improved greatly by the passive lossless clamped circuit so that the efficiency can be upgraded further. Finally, a 400W 40V-input 400V-output prototype is established to demonstrate the performance of this converter. The highest efficiency is about 97.3% and the full-load efficiency is approximate 97%.

In this article, a novel passive lossless clamped circuit composed of two capacitors and one diode is proposed. One of the two capacitors is used to construct a flowing path for the energy of leakage inductor and the other is used to store the leakage energy. Compared with a classical passive lossless clamped circuit, the novel circuit structure is more flexible and versatile, and the number of the extra capacitor and diode is consistent to the classical circuit for recycling the energy. Moreover, an idea of using more capacitors in series instead of a single output capacitor to reduce voltage stress and volume is presented. In order to extend their application scope and demonstrate their practical value, the novel clamped circuits and the idea are integrated into a family of cascade dc–dc converters based on the popular boosting cell, such as voltage-lift cell, symmetric voltage multiplier cell and asymmetric voltage multiplier cell. As a representative, a novel cascade converter, which integrates the novel passive lossless clamped circuit and the idea is analyzed in detail. The proposed converter has a high voltage gain and low ripple input current. The voltage stresses of an output diode and output capacitor can be effectively reduced. Its output capacitor adopts a 20-uF polypropylene (CBB) capacitor rated at 250 V to replace the higher rated electrolytic capacitor. A prototype circuit in the laboratory is established to verify its performances.

Reduction of the cogging torque is preferred during the design process of a permanent magnet (PM) synchronous machine (PMSM), especially in the low-speed traction applications. This article presents a dual-skew magnet technique to minimize the cogging torque in the axial-flux permanent-magnet (AFPM) motor with a yokeless and segmented armature (YASA). The theoretical expression of the cogging torque of the AFPM machine is deduced, and the advantages of the dual-skew magnet are verified by comparing with a sector shape magnet and a conventional skew magnet using the 3-D finite-element method (FEM). The simulation results show that, compared with the other two magnet topologies, the machine equipped with the dual-skew magnet shows its advantages in the reduction of cogging torque, torque ripple, and magnet eddy current loss.

A voltage sensorless control of low-complexity model predictive direct power control (LC-MPDPC) for pulse width modulation (PWM) rectifier is proposed. The conventional LCMPDPC adopts one or two voltage vectors during one control period, which achieve good steady-state performance and quick dynamic response. Besides, based on the mathematical model of the real system, the conventional method only requires one prediction to find the optimal voltage vector, which reduces the control complexity and computational burden. However, the use of one or two vectors during one sampling interval present abundant current harmonics and high power ripples. In order to solve these problems, whilst preserving all the advantages of conventional LC-MPDPC, this paper presents a novel control scheme, with the aim of operating at a constant-switching frequency and obtaining an excellent steady-state performance at a low switching frequency. The proposed method is based on an optimal application of three voltage vectors in a symmetrical way, which takes advantage of advanced pulse width modulation techniques. Furthermore, the virtual flux based control scheme is introduced to achieve voltage sensorless control. The proposed strategy is compared with the conventional MPDPC methods and its effectiveness is confirmed by both simulation and experimental results from a three-phase PMW rectifier under 1000-W operation condition.

A rotor structure of Permanent Magnet (PM)-assisted synchronous Reluctance Machine (PMa-synRM) with ferrite PM is presented in this paper, in which the irreversible demagnetization of PM and torque ripple are reduced. The bypass rib is proposed and added to the flux barrier of the rotor. The path for the demagnetizing field of armature windings is provided and the torque ripple can also be reduced by the bypass rib. Based on the 2-D finite-element analysis (FEA), the location and dimensions of the bypass rib are investigated and improved. A PMa-synRM with the proposed rotor structure is designed and compared with that using a conventional rotor. The field distributions for different currents are studied to explain the principle of the bypass rib. The results show that the PMa-synRM with the proposed rotor achieves higher antidemagnetization ability and lower torque ripple.

Halbach array-based permanent magnet (PM) brushless machines exhibit attractive features when compared with conventional PM brushless machines with normal segmented magnets, including the flux-concentration effect, essentially sinusoidal air-gap flux density due to PMs, and negligible cogging torque. However, as for a motor/generator used in flywheel, an external rotor composed of Halbach array and rotor back-iron is necessary to increase the inertia of flywheel system, which is different from the conventional external-rotor machines. In this paper, a Halbach array PM motor is studied compared with the radial magnet array. The relationship between the air-gap field distribution and the magnet array is discussed. Finally, the eddy current loss in PMs of the external-rotor ironless brushless dc motor is analyzed between the Halbach PM motor and the conventional PM motor.