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

In this paper, a contactless charging system for laptop battery is proposed. The system consists of three parts: a high frequency power supply from a full-bridge inverter with frequency modulation, a LLC resonant tank that incorporates a loosely coupled transformer (LCT) and a resonant capacitor series connected with the primary winding, and a rectification output circuits that uses a full-bridge diode rectifier. Due to the characteristics of the LCT, the design of proposed contactless charging system is different from traditional LLC converter. Several design considerations are studied thoroughly to help improve the system efficiency. With carefully designed system parameters, the LLC converter could operate at or slightly before the series resonant point within the full load range. Therefore, zero-voltage-switching (ZVS) can be ensured for all the primary switches, and zero-current-switching (ZCS) can be achieved by all the secondary diodes. The design considerations based on the effect of the LCT turns number to the winding and core loss are analyzed and verified by experimental results. For a 100-W hardware prototype employing secondary synchronous rectification, the peak DC-DC efficiency reaches 92%, and from 20% load to full load the efficiency maintains higher than 88.5%.

Design considerations of LLC resonant converter for contactless laptop charger

This paper presents a comprehensive digital control strategy for a single-switch bridgeless SEPIC PFC converter which employs the damping circuit to improve the stability of the converter. To do this, first, the 5th order control-to-inductor current model and control-to-output model are derived mathematically in both the s- and the z-domains, in where the digital delay effects are included. After that, it is confirmed that the damping circuit assists to stabilize the control loops from the loop-gain analysis of the derived models. The design procedures of the digital voltage and the current feedback controllers and the current feed-forward controller are explained in detail. The experimental results show that the designed controller is very well adopted for a 150 W LED drive application. The experimental results show that the input current THD meets EC61000 standard as well as verifying the designed digital controller under the given specification.

Z-domain modeling and control design of single-switch bridgeless SEPIC PFC converter with damping circuit

A novel single-switch three-level (TL) converter is proposed for dimmable LED lighting. Compared with standard TL converters, the proposed topology not only maintains the advantage of using a lower voltage rating power switch that is rated half the input voltage, but also eliminates one active switch and its associated driving circuit. Moreover, it can naturally solve the voltage stress imbalance issue because of the resonant flying capacitor. The operation principle and dimming scheme of the proposed TL converters have been described. A prototype of 46-W dimmable LED driving converter has been implemented to verify the designs and analyses. The experimental result shows that single-switch TL buck converter can regulate the LED current from zero to the desired 1 A with fast slew rate. A peak efficiency of 98% was achieved with 400 kHz switching frequency.

Single-switch three-level DC-DC converters for dimmable LED lighting

Multi-objective robust optimization allocation for energy storage using a novel confidence gap decision method

The proposed inductive power transfer (IPT) system for laptop charging consists of three parts: a high frequency power supply from a full-bridge inverter with frequency modulation, a LLC resonant tank that incorporates a loosely coupled transformer (LCT) and a resonant capacitor series connected with the primary winding, and a rectification output circuits that uses a full-bridge diode rectifier. Due to the relatively large air gap, the magnetic coupling coefficient of the IPT system is significantly lower than that with tightly coupled transformer. As a result, the efficiency of the IPT system is always a major concern for applications with possible misalignment variation condition. To ensure high power transfer efficiency, the IPT system should have high tolerance for different misalignment conditions. In this paper, the effect of coupling coefficient deviation to compensation network efficiency is analyzed, and asymmetrical LCT which has significant higher misalignment tolerance is proposed. By using finite element analysis (FEA) simulation method, the performance of different transmitter and receiver coil dimensions are compared. In order to validate the performance of the proposed design, a 100-W hardware prototype with two sets of LCT is built and the corresponding experiments are carried out. As compared to the symmetrical LCT architecture, the proposed asymmetrical LCT prototype improves the coupling coefficient reduction from 70% to 12.5% when the misalignment ranges from 0 to 40 mm. Therefore, the efficiency deviation for the asymmetrical LCT is maintained nearly constant over the entire tested misalignment variation ranges.

Cong Zheng

Papers

Design considerations of LLC resonant converter for contactless laptop charger

Z-domain modeling and control design of single-switch bridgeless SEPIC PFC converter with damping circuit

Single-switch three-level DC-DC converters for dimmable LED lighting

Multi-objective robust optimization allocation for energy storage using a novel confidence gap decision method

Asymmetrical loosely coupled transformer for wireless laptop charger with higher misalignment tolerance