Improved Design Optimization for High-Efficiency Matching Networks
TL;DR: In this article, an improved design optimization approach for multistage matching networks comprising L-section stages was proposed to explore the possibility of improvement in efficiency of the network by allowing the Lsection stages to have complex input and load impedances.
Abstract: Multistage matching networks are often utilized to provide voltage or current gains in resonant conversion applications, such as large conversion ratio power converters and wireless power transfer. In the conventional approach, each stage of a multistage matching network is designed to have a purely resistive input impedance and assumed to be loaded by a purely resistive load. This paper introduces an improved design optimization approach for multistage matching networks comprising L-section stages. The proposed design optimization approach explores the possibility of improvement in efficiency of the network by allowing the L-section stages to have complex input and load impedances. A new analytical framework is developed to determine the effective transformation ratio and efficiency of each stage for the case when input and load impedances may be complex. The method of Lagrange multipliers is used to determine the gain and impedance characteristics of each stage in the matching network that maximize overall efficiency. Compared with the conventional design approach for matching networks, the proposed approach achieves higher efficiency, resulting in loss reduction of up to 35% for a three-stage L-section matching network. The theoretical predictions are validated experimentally using a three-stage matching network designed for 1 MHz and 100 W operation.
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TL;DR: In this article, the authors reviewed the latest developments in capacitive power transfer (CPT) technology, focusing on two key technologies: the compensation circuit topology and the capacitive coupler structure.
Abstract: Capacitive power transfer (CPT) technology is an effective and important alternative to the conventional inductive power transfer (IPT). It utilizes high-frequency electric fields to transfer electric power, which has three distinguishing advantages: negligible eddy-current loss, relatively low cost and weight, and excellent misalignment performance. In recent years, the power level and efficiency of CPT systems has been significantly improved and has reached the power level suitable for electric vehicle charging applications. This paper reviews the latest developments in CPT technology, focusing on two key technologies: the compensation circuit topology and the capacitive coupler structure. The comparison with the IPT system and some critical issues in practical applications are also discussed. Based on these analyses, the future research direction can be developed and the applications of the CPT technology can be promoted.
201 citations
Cites background from "Improved Design Optimization for Hi..."
...The number of LC cells determines the system power and efficiency, which needs to be optimized according to practical requirements [78]....
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22 Jun 2017
TL;DR: In this paper, a large air-gap capacitive wireless power transfer (WPT) module is introduced as part of a multi-modular capacitive WPT system for electric vehicle charging.
Abstract: This paper introduces a high-performance large air-gap capacitive wireless power transfer (WPT) module as part of a multi-modular capacitive WPT system for electric vehicle charging. This WPT module utilizes two pairs of metal plates separated by an air-gap as the capacitive coupler, incorporates L-section matching networks to provide gain and reactive compensation, and is driven by a GaN-based inverter operating at 6.78 MHz. The system achieves high efficiency and simplicity by eliminating the need for high-voltage capacitors, and instead utilizes the parasitic capacitances formed between the coupling plates and the vehicle chassis and roadway as part of the matching networks. This paper also presents a comprehensive design methodology for the capacitive WPT system that guarantees high performance by ensuring zero-voltage switching of the inverter transistors, and by selecting matching network component values to maximize efficiency under practical constraints on inductor quality factor and self-resonant frequency. Two prototype 6.78-MHz 12-cm air-gap capacitive WPT systems have been designed, built and tested. The first prototype with 625 cm2 coupling plate area transfers up to 193 W of power and achieves an efficiency greater than 90%, with a power transfer density of 3 kW/m2. The second prototype with 300 cm2 coupling plate area transfers up to 557 W of power and achieves an efficiency of 82%, with a power transfer density of 18.5 kW/m2, which exceeds the state-of-the-art for capacitive WPT systems by more than a factor of four.
64 citations
Cites background or methods from "Improved Design Optimization for Hi..."
...4(c) are dominated by the losses in the inductors, the efficiency of the two networks can be well-approximated in terms of their current gains and impedance characteristics as [6], [13]: ≈ 1 − , , , , , (1a) ≈ 1 − , , , ,...
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...An analytical framework for designing L-section matching networks that provide both gain and compensation was introduced in [6], [13]....
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27 Jun 2016
TL;DR: In this article, an analytical optimization approach for the design of multistage matching networks for capacitive WPT systems was proposed to maximize the matching network efficiency and identify the optimal distribution of gains and compensations among the L-section stages.
Abstract: High-power large air-gap capacitive wireless power transfer (WPT) systems require matching networks that provide large voltage or current gain and reactive compensation. This paper introduces an analytical optimization approach for the design of L-section multistage matching networks for capacitive WPT systems. The proposed approach maximizes the matching network efficiency and identifies the optimal distribution of gains and compensations among the L-section stages. The results of the proposed approach are validated using an exhaustive-search based numerical optimization for a 12-cm air-gap, 6.78-MHz, 125-W capacitive WPT system. A 6.78-MHz, 15-W prototype comprising a two-stage matching network is also designed using the proposed analytical approach and the theoretical predictions are validated experimentally.
57 citations
Cites methods from "Improved Design Optimization for Hi..."
...A new analytical framework is introduced in [13] for the design of Lsection stages that can have complex load and input impedances, and hence, can provide both gain and compensation....
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...An analytical framework is developed in [13] to characterize L-section stages of multistage networks that can have complex input and load impedances....
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TL;DR: A unified resonant tuning configuration with minimum passive component counts is proposed to achieve CC and CV outputs at two ZPA operating frequencies and, according to the proposed configuration, all the possible inductive power transfer and capacitive power transfer topologies are analogized.
Abstract: In both normal and fast wireless electric vehicle charging systems, constant current/constant voltage (CC/CV) charging profile, regardless of the variation of the battery state of charge, is one of the most essential characteristics to ensure the battery performance and reliability. The input zero phase angle (ZPA) is able to minimize the system volt-ampere rating, enhance the power transfer capability, and make it easy to achieve soft-switching operation over the full range of battery charging profile. Therefore, the load-independent CC and CV output characteristics with ZPA conditions are necessary for wireless charging systems. However, the existing methods that can achieve these functions either add power switches or need a large number of compensation components, which make the system inefficient, uneconomical, and bulky. In this paper, a unified resonant tuning configuration with minimum passive component counts is proposed to achieve CC and CV outputs at two ZPA operating frequencies. According to the proposed configuration, all the possible inductive power transfer (IPT) and capacitive power transfer (CPT) topologies are analogized. With these topologies, both CC and CV outputs with ZPA are achieved using a minimum number of compensation components and no additional power switches. Among all the simplest IPT topologies, a primary Series-secondary Series and Parallel (S-SP) compensation topology is illustrated to demonstrate the analysis.
54 citations
Cites background from "Improved Design Optimization for Hi..."
...two lumped components: a parallel reactance and a series reactance, are the two types of the most basic resonant circuit [41], [42]....
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01 Oct 2017
TL;DR: In this paper, a large air-gap capacitive wireless power transfer (WPT) system for electric vehicle charging that achieves a power transfer density exceeding the state-of-the-art by more than a factor of four is presented.
Abstract: This paper introduces a large air-gap capacitive wireless power transfer (WPT) system for electric vehicle charging that achieves a power transfer density exceeding the state-of-the-art by more than a factor of four. This high power transfer density is achieved by operating at a high switching frequency (6.78 MHz), combined with an innovative approach to designing matching networks that enable effective power transfer at this high frequency. In this approach, the matching networks are designed such that the parasitic capacitances present in a vehicle charging environment are absorbed and utilized as part of the wireless power transfer mechanism. A new modeling approach is developed to simplify the complex network of parasitic capacitances into equivalent capacitances that are directly utilized as the matching network capacitors. A systematic procedure to accurately measure these equivalent capacitances is also presented. A prototype capacitive WPT system with 150 cm2 coupling plates, operating at 6.78 MHz and incorporating matching networks designed using the proposed approach, is built and tested. The prototype system transfers 589 W of power across a 12-cm air gap, achieving a power transfer density of 19.6 kW/m2.
51 citations
Cites methods from "Improved Design Optimization for Hi..."
...The required matching network inductance and capacitance values are determined using the optimization approach presented in [10] and [16]....
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References
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01 Apr 1988
TL;DR: In this paper, the half-bridge series-resonant, parallel-reonant and combination series-parallel resonant converters are compared for low-output-voltage power supply applications.
Abstract: The half-bridge series-resonant, parallel-resonant, and combination series-parallel resonant converters are compared for use in low-output-voltage power supply applications. It is shown that the combination series-parallel converter, which takes on the desirable characteristics of the pure series and the pure parallel converter, avoids the main disadvantages of each of them. Analyses and breadboard results show that the combination converter can run over a large input voltage range and a large load range (no load to full load) while maintaining excellent efficiency. A useful analysis technique based on classical AC complex analysis is introduced. >
1,795 citations
02 Mar 1987
TL;DR: In this paper, the half-bridge series resonant, parallel resonant and combination series-parallel resonant converters are compared for use in low output voltage power supply applications, and it is shown that the combination seriesparallel converter, which takes on the desirable characteristics of the pure series and the pure parallel converters, removes the main disadvantages of those two converters.
Abstract: The half-bridge series resonant, parallel resonant and combination series-parallel resonant converters are compared for use in low output voltage power supply applications. It is shown that the combination series-parallel converter, which takes on the desirable characteristics of the pure series and the pure parallel converter, removes the main disadvantages of those two converters. Analyses and breadboard results show that the combination series-parallel converter can run over a large input voltage range and a large load range (no-load to full-load) while while maintaining excellent efficiency. A useful analysis technique based on classical ac complex analysis is also introduced.
860 citations
"Improved Design Optimization for Hi..." refers background in this paper
...Imposing these resistive constraints is appropriate for many applications, such as when the matching network is loaded by a class-D rectifier (which looks resistive under fundamental frequency approximation [24]), and driven by an inverter requiring near-resistive impedance for zero voltage and near-zero current switching....
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TL;DR: In this paper, a double-sided LCLC -compensated capacitive power transfer (CPT) system is proposed for the electric vehicle charging application, where two pairs of metal plates are utilized to form two coupling capacitors to transfer power wirelessly.
Abstract: A double-sided LCLC -compensated capacitive power transfer (CPT) system is proposed for the electric vehicle charging application. Two pairs of metal plates are utilized to form two coupling capacitors to transfer power wirelessly. The LCLC -compensated structure can dramatically reduce the voltage stress on the coupling capacitors and maintain unity power factor at both the input and output. A 2.4-kW CPT system is designed with four 610-mm × 610-mm copper plates and an air gap distance of 150 mm. The experimental prototype reaches a dc–dc efficiency of 90.8% at 2.4-kW output power. At 300-mm misalignment case, the output power drops to 2.1 kW with 90.7% efficiency. With a 300-mm air gap distance, the output power drops to 1.6 kW with 89.1% efficiency.
320 citations
TL;DR: In this paper, a four-plate compact capacitive coupler and its circuit model for large air gap distance capacitive power transfer (CPT) is presented, where two plates that are on the same side are placed close to each other to maintain a large coupling capacitance, and they are of different sizes to maintain the coupling between the primary and secondary sides.
Abstract: This paper proposes a four-plate compact capacitive coupler and its circuit model for large air-gap distance capacitive power transfer (CPT). The four plates are arranged vertically, instead of horizontally, to save space in the electric vehicle charging application. The two plates that are on the same side are placed close to each other to maintain a large coupling capacitance, and they are of different sizes to maintain the coupling between the primary and secondary sides. The circuit model of the coupler is presented, considering all six coupling capacitors. The LCL compensation topology is used to resonate with the coupler and provide high voltage on the plates to transfer high power. The circuit model of the coupler is simplified to design the parameters of the compensation circuit. Finite-element analysis is employed to simulate the coupling capacitance and design the dimensions of the coupler. The circuit performance is simulated in LTspice to design the specific parameter values. A prototype of the CPT system was designed and constructed with the proposed vertical plate structure. The prototype achieved an efficiency of 85.87% at 1.88-kW output power with a 150-mm air-gap distance.
269 citations