The authors discuss high-voltage power conversion. Conventional series connection and three-level voltage source inverter techniques are reviewed and compared. A novel versatile multilevel commutation cell is introduced: it is shown that this topology is safer and more simple to control, and delivers purer output waveforms. The authors show how this technique can be applied to either choppers or voltage-source inverters and generalized to any number of switches.<<ETX>>

Multi-level conversion : high voltage choppers and voltage-source inverters

Due to limitations of low power density, high cost, heavy weight, etc., the development and application of battery-powered devices are facing with unprecedented technical challenges. As a novel pattern of energization, the wireless power transfer (WPT) offers a band new way to the energy acquisition for electric-driven devices, thus alleviating the over-dependence on the battery. This paper presents an overview of WPT techniques with emphasis on working mechanisms, technical challenges, metamaterials, and classical applications. Focusing on WPT systems, this paper elaborates on current major research topics and discusses about future development trends. This novel energy transmission mechanism shows significant meanings on the pervasive application of renewable energies in our daily life.

Wireless Power Transfer—An Overview

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Power Electronics Converters Applications And Design

Electrifying transportation is a promising approach to alleviate the climate change issue. The adoption of electric vehicle into market has introduced significant impacts on various fields, especially the power grid. Various policies have been implemented to foster the electric vehicle deployment and the increasing trend of electric vehicle adoption in the recent years has been satisfying. The continual development of electric vehicle power train, battery and charger technologies have further improved the electric vehicle technologies for wider uptake. Despite the environmental and economical benefits, electric vehicles charging introduce negative impacts on the existing network operation. Appropriate charging management strategies can be implemented to cater for this issue. Furthermore, electric vehicle integration in the smart grid can bring many potential opportunities, especially from the perspective of vehicle-to-grid technology and as the solution for the renewable energy intermittency issue. This paper reviews the latest development in electric vehicle technologies, impacts of electric vehicle roll out and opportunities brought by electric vehicle deployment.

A review on the state-of-the-art technologies of electric vehicle, its impacts and prospects

Energy harvesting: State-of-the-art

330V high-voltage direct current (HVDC) power system is a preferred option of the magnetic train power supply system. The power supply for magnetic levitation control system is used to provide stable operation voltage to the suspension control circuits, which is the key part of magnetic train. The suspension control power supply is typically the converter with high input voltage and low multiple output voltages. The traditional solutions have these problems, such as uncontrolled duty ratio, poor cross-regulation rate, and low reliability. In order to solve these limits, a novel two-stage solution employing the double resonant tank LLC-DCX is proposed and developed in this paper, which can overcome the problems in traditional design. The proposed solution not only can increase the overall conversion efficiency significantly because of the achieving soft-switching over the entire operation range, but also can achieve the low input current ripple and high reliability owing to the uniform thermal distribution. A 210-W, 220-380V input prototype with four outputs, is fabricated and tested in the lab, and the results are presented in this paper. The declared features are demonstrated well by the experimental results.

Two-stage power supply based on double resonant tank LLC-DCX for magnetic levitation control system applications

In order to match the main features of LED lighting source and further save power, the power supply for LEDs also requires long life while maintaining high efficiency, high power factor, PWM dimming and low cost. However, a typical power supply for LEDs exist the following drawbacks: (1) utilize bulky electrolytic capacitor as storage capacitor with short lifetime; (2) employ a low frequency diode bridge as the rectifier cell; (3) engage multiple stages cascade structure for multiple LED strings. To overcome the aforementioned shortages, a novel LED lighting driver is proposed in this paper. In this design, the non-cascade Twin-Bus configuration and bridgeless technology are utilized to increase the efficiency of LED power supply, while special DCM operation mode and valley fill circuit are introduced to eliminate electrolytic capacitors and reduce capacitor size. A 50-W prototype has been designed and tested in the laboratory, and the experimental results under universal input voltage operation show the effectiveness and advantages of the proposed circuit.

Bridgeless electrolytic capacitor-less valley fill AC/DC converter for twin-bus type LED lighting applications

The state-of-the-art transformerless inverters can use MOSFET to achieve high efficiency, but difficult to do reactive power generation for upcoming standards. This paper proposed a MOSFET based transformerless inverter and a novel PWM modulation method for reactive power generation. PWM modulation and circuit operation are then detailed under reactive power generation condition. Ground loop voltage is derived with common mode and differential model circuit analysis. The hardware prototype of a two-stage micro-inverter with the proposed MOSFET inverter as the secondary stage has been designed. The experiment results demonstrate the reactive power capability, high efficiency, and high-frequency component free of the ground loop voltage of the proposed transformerless inverter.

A MOSFET transformerless inverter with reactive power capability for micro-inverter applications

Parabolic current control is an attractive current control method with fast transient response and constant switching frequency. Due to the good dynamics of parabolic current control, it can be employed in voltage source inverters to improve the system performance such as minimizing the distortion of current waveforms or voltage waveforms. To implement parabolic current control, a current sensor is required, associated with the current conditioning circuit and parabolic carrier generators. Since parabolic current control is based on the real-time information of the inductor current, any phase delay or propagation delay of the sensor itself and the conditioning circuitry, or limited resolution of parabolic carrier generators, could impact the current control performance. Since the parabolic current control compares analog signals to generate the required control signals, noise from the control board impacts the control precision as well. This paper will explore solutions to these problems. First, the inductor current of voltage source inverter is analyzed and the parabolic current control strategy is studied, then a sensorless parabolic current control method is proposed. The new sensorless parabolic control method utilizes a current emulator to rebuild the inductor current on a micro-controller. To avoid a dc offset on the ac-side output voltage caused by the current emulator, an additional control loop in the current emulator is added. The effectiveness of the proposed methods are experimentally verified by the use of an H-bridge voltage source inverter.

Cong Zheng

Papers

Two-stage power supply based on double resonant tank LLC-DCX for magnetic levitation control system applications

Bridgeless electrolytic capacitor-less valley fill AC/DC converter for twin-bus type LED lighting applications

A MOSFET transformerless inverter with reactive power capability for micro-inverter applications

A sensorless parabolic current control method for single phase standalone inverters