This study suggests a novel ultra-step-up dc–dc converter with low normalised voltage stress across the power devices. The proposed converter incorporates the conventional boost converter with a self-lift circuit and charge pump concept and utilises a voltage multiplier cell at the output side. In the input side, two inductors are magnetised during the switch on-time. During the switch off-time, the stored energy in these inductors, charge pump capacitor and input source, is delivered to the load. Accordingly, the proposed converter is capable of providing high voltage gains with a small duty cycle. Besides, the voltage stress across the power devices is low. Therefore, the MOSFET switch with low R _DS-on and devices with reduced nominal voltage can be used which in turn reduces the conduction and turn-on losses. The analysis of the voltage and current stresses is accomplished. The circuit performance is compared with other solutions in the literature in terms of voltage gain and normalised voltage stress of the semiconductors. Eventually, to validate the theoretical analysis, the experimental results are given.

Flexible interconnection switch (FIS) is a power electronic device applied to electrical distribution system to realise the flexible control of power flow. Due to the fact that the reliability of FIS tends to be influenced by its operating conditions and dynamic characteristics during its actual operation, it is of significance to characterise the effects of loadings on reliability of FIS. Therefore, an improved reliability model of FIS is proposed, considering the state uncertainty of current and voltage loadings. First, the structural reliability model of modular multilevel converter (MMC) is established. Next, in view of the uncertainty of source and load in distribution network, Monte Carlo simulation is used to deal with the random current loadings, thus the equivalent reliability model of insulated gate bipolar transistor module is built. Then, considering the arm's voltage loading sharing mechanism, a state-dependent arm reliability model is built. Finally, an eight-state reliability model for the entire FIS is developed, and Markov-based analytical method is used to solve it. With the standard test system as well as the actual project in Hangzhou are taken as the testing systems, the reliability indices of FIS are calculated and compared with the field data. The numerical results validate the validity of the proposed model.

In this study, a quadratic-based transformerless high step-down DC-DC buck converter is presented. There are two switching patterns applied to the switches. Through the first switching pattern, the proposed converter provides a constant step-down voltage conversion ratio for the whole ranges of duty cycles. On the other hand, by using an interleaved switching pattern for the proposed converter the input voltage will be divided equally between the primary capacitors, as a result, low voltage stress will be across the semiconductor components. This feature allows the designer to select switches and diodes with lower voltage ratings. However, with the interleaved switching pattern, the converter will have two different voltage conversion ratios for duty cycles larger and less than 0.5. Furthermore, the proposed converter is capable of providing a high range of currents without applying extremely narrow duty ratios. Theoretical analysis is provided in this study. To show the merits of the proposed converter, it is compared with other similar recently presented converters. A 430 W prototype of the proposed converter with 600 V/20 V is implemented and experimental results are presented and compared with the theoretical ones.

This document studies torque degradation of an internal permanent magnet motor due to an incorrect rotor angle measurement when low rotor angle resolution sensors are used. The performance of the control with different rotor angle resolution is also analysed to determine the torque error due to the use of an incorrect synchronous rotating reference system. To address torque degradation due to the low resolution of Hall sensors, a new method of estimating the rotor angle is proposed that incorporates the information from Hall sensors. In this way, good resolution is achieved, allowing the machine to be controlled over a wide speed range even with rated torque. This method is validated through simulations and real experiments.

This study proposes a practical control strategy of passivity based control (PBC) of the power conversion system (PCS) used in the energy storage system. First, the differential equations based on the Kirchhoff voltage and current laws are listed in the study, and the mathematical model in Euler–Lagrange form is also given. On the basis of the PBC theory, the system passivity of the PCS is demonstrated, the implementation of differential equations based on the damping injection principle is deduced, and simulation results in SIMULINK are also given. The PBC strategy has the advantages of high stability globally in a nonlinear system, and strong robustness to the system parameters deviation and external interference. Finally, a PCS prototype of 10 kW, which is made up of ac–dc converter and dc–dc converter, is built and the experimental results verify the correctness and effectivity of the proposed solution.