THIS paper explores opportunities and challenges in power conversion in the VHF frequency range of 30-300 MHz. The scaling of magnetic component size with frequency is investigated, and it is shown that substantial miniaturization is possible with increased frequencies even considering material and heat transfer limitations. Likewise, dramatic frequency increases are possible with existing and emerging semiconductor devices, but necessitate circuit designs that either compensate for or utilize device parasitics. We outline the characteristics of topologies and control methods that can meet the requirements of VHF power conversion, and present supporting examples from power converters operating at frequencies of up to 110 MHz.

/pdf/opportunities-and-challenges-in-very-high-frequency-power-2j4vslax8q.pdf

Opportunities and Challenges in Very High Frequency Power Conversion

https://research.chalmers.se/publication/503205/file/503205_Fulltext.pdf

A review of fractional-order techniques applied to lithium-ion batteries, lead-acid batteries, and supercapacitors

Batteries have been widely applied in many high-power applications, such as electric vehicles (EVs) and hybrid electric vehicles, where a suitable battery management system (BMS) is vital in ensuring safe and reliable operation of batteries. This paper aims to give a brief review on several key technologies of BMS, including battery modelling, state estimation and battery charging. First, popular battery types used in EVs are surveyed, followed by the introduction of key technologies used in BMS. Various battery models, including the electric model, thermal model and coupled electro-thermal model are reviewed. Then, battery state estimations for the state of charge, state of health and internal temperature are comprehensively surveyed. Finally, several key and traditional battery charging approaches with associated optimization methods are discussed.

/pdf/a-brief-review-on-key-technologies-in-the-battery-management-epnx1tchkf.pdf

A brief review on key technologies in the battery management system of electric vehicles

Embodiments of the subject invention pertain to a method and apparatus for contactless power transfer. A specific embodiment relates to an impedance transformation network, a new class of load network for application to a contactless power system. Embodiments of the impedance transformation network enable a contactless power system to operate without encountering the common problems of: 1) over-voltage and/or under-voltage conditions; 2) over-power and/or under-power conditions; 3) power oscillations; and 4) high heat dissipation.

Method and apparatus for contactless power transfer

A novel six-band dual circular polarization (CP) rectenna for ambient radio frequency (RF) energy harvesting is presented. Due to the nonlinearity and complex input impedance of the rectifying circuit, the design of a multiband and/or broadband rectenna is always challenging and its performance can be easily affected by variation in the input power level and load. Therefore, an improved impedance matching technique is introduced, which is aimed to improve the performance of the rectifier with a varying condition. A broadband dual CP receiving antenna is proposed, which has a very wide bandwidth (from 550 to 2.5 GHz) and a compact size. An annular ring structure and a novel feeding technique are employed in order to reduce the size and improve the antenna performance. As a result, the proposed rectenna is the first design that covers six frequency bands, including part of the digital TV and most cellular mobile and WLAN bands in the U.K., while the optimal load range for a constant conversion efficiency is from 10 to 75 $\text{k}\Omega $ . The measured results show that the maximum harvested dc power of the rectenna in typical outdoor and indoor environments are 26 and 8 $\mu \text{W}$ , respectively; it can therefore be applied to a range of low-power wireless applications.

A Novel Six-Band Dual CP Rectenna Using Improved Impedance Matching Technique for Ambient RF Energy Harvesting

This paper presents a design of module-integrated converters (MICs) for photovoltaic (PV) modules connected in series in PV strings. The proposed concept enables a range of independent maximum power point tracking (MPPT) for each module, and dramatically decreases the requirements of power rating and efficiency for power converters with the trade-off of limited regulation ability. In this paper, different concepts of MICs are presented and evaluated, possible structures of MICs handling partial power are proposed, analyzed, realized, and verified. Simulation and experimental results are presented to validate the analysis. It is anticipated that the proposed approach will be a low-cost and high-efficiency solution for future photovoltaic power systems where PV modules mismatches are not significant.

Design of module-integrated converters for photovoltaic strings

Battery equalizers are widely used in multi-battery systems to maintain balanced charge among individual battery cells. While research on the hardware realization of battery equalizers has received significant attention, rigorous analysis of battery equalization process from the system's point of view remains largely unexplored. In this paper, we study two types of battery equalization system structures: series connection-based and module-based. Specifically, we develop mathematical models that describe the system-level behavior of the battery equalization processes under these equalization structures. Then, based on the mathematical models, analytical methods are derived to evaluate the performance of the equalization processes. In addition, we carry out statistical analysis to compare the performance of the two equalization structures considered.

Mathematical modeling and performance analysis of battery equalization systems

This paper investigates a new reconfigurable switched-capacitor (SC) based partial power architecture which enhances the performance of radio frequency (RF) resonant DC/DC converters with gallium nitride (GaN) power devices. The proposed architecture has a comprehensive compatibility with existing RF and SC topologies and improves the performance of RF converters through partitioning of energy conversion stage and output regulation stage. Emerging new wide bandgap devices like GaN FETs enable a higher power density DC/DC converter design. A wider input range, larger voltage conversion ratio, smaller size, and excellent transient performance are expected. The prototype of the proposed GaN reconfigurable SC-based partial power RF converter comprises of a 20 MHz resonant single-ended-primary-inductor-converter (SEPIC) as a regulated stage and a high-efficiency 2 MHz reconfigurable SC as an unregulated stage. The GaN RF resonant SEPIC regulates the output using a robust ON/OFF control scheme, which enables fast transient responses. The high-efficiency GaN reconfigurable SC provides 1:1, 2:1 and 3:1 voltage conversion ratio which widens the input voltage range. The power stage of the prototype achieves a peak efficiency of 93 % and a power density of 963 W/in3 at 91.5 W.

A GaN-based partial power converter with MHz reconfigurable switched-capacitor and RF SEPIC

This paper proposes a DC-DC converter that can be used in battery equalization and charging and discharging applications. The proposed topology is a high frequency (≥ 5 MHz) resonant bidirectional SEPIC DC-DC converter. The resonant technology and high frequency operation will allow the size and cost of a battery equalizer to be reduced because of the ability to reduce the size of the magnetic components. The topology of the DC-DC converter is proposed, analyzed, and realized, and then verified by simulation and experimental results. It is shown that this converter can obtain an efficiency that is greater than 81%.

High frequency resonant bidirectional SEPIC converter suitable for battery equalization and charger applications

This chapter deals with each of three components of battery health management (BHM): battery state estimation, battery prognostics, and decision making. The state‐of‐health (SOH) of batteries is a measurement that reflects the general condition of a battery and its ability to deliver the specified performance compared to a fresh battery. The chapter discusses how to determine the remaining useful life (RUL) of a battery. State estimation techniques, like the extended Kalman filter (EKF), have been applied for real‐time prediction of state‐of‐charge (SOC) and SOH of automotive batteries. A decision‐level fusion of data‐driven algorithms, like Autoregressive Integrated Moving Average (ARIMA) and neural networks, have been investigated for both diagnostics and prognostics. Particle filters (PFs) are a novel class of nonlinear filters that combine Bayesian learning techniques with importance sampling to provide good state tracking performance while keeping the computational load tractable.

Yehui Han

Papers

Design of module-integrated converters for photovoltaic strings

Mathematical modeling and performance analysis of battery equalization systems

A GaN-based partial power converter with MHz reconfigurable switched-capacitor and RF SEPIC

High frequency resonant bidirectional SEPIC converter suitable for battery equalization and charger applications

A bayesian approach to battery prognostics and health management