Analysis and control of dual-output LCLC resonant converters with significant leakage inductance

The analysis, design and control of fourth-order LCLC voltage-output series-parallel resonant converters for the provision of multiple regulated outputs, is described. Specifically, state-variable concepts are developed to establish operating mode boundaries with which to describe the internal behavior and the impact of output leakage inductance. The resulting models are compared with those obtained from SPICE simulations and measurements from a prototype power supply under closed loop control to verify the analysis, modeling, and control predictions

Performance evaluation of SiC MOSFET in 5-level single phase converter

The use of silicon carbide (SiC) semiconductor power devices has been studied and evaluated in a wide variety of converters. The work presented in this paper shows the performance of C2M SiC MOSFETs compared to Si devices operating as switching elements in a 5-level, single phase, multilevel converter. The paper describes the multilevel converter platform used to undertake the evaluation study and experimental results for the operating temperature of the MOSFETs, and conversion efficiency are shown for frequencies ranging from 20 kHz to 80 kHz. Finally, a discussion of the results obtained to highlight the differences in the performance of the Si and SiC devices and the feasibility of using SiC in MLC

On the impact of current generation commercial gallium nitride power transistors on power converter loss

The enormous potential benefits of gallium nitride based power switching devices, only commercially available very recently, in terms of power switching device loss are highlighted. This is first demonstrated through a simulated prediction of loss in multilevel converters, followed by experimental validation. While the simulations focus on losses in multilevel converters, the observations made are relevant in a broad range of applications

Real-Time Prediction of Power Electronic Device Temperatures Using PRBS-Generated Frequency-Domain Thermal Cross Coupling Characteristics

This paper presents a technique to predict the temperature response of a multielement thermal system based on the thermal cross coupling between elements. The complex frequency-domain cross coupling of devices is first characterized using a pseudorandom binary sequence technique. The characteristics are then used to predict device temperatures for a known input power waveform using a discrete Fourier transform-based technique. The resulting prediction shows good agreement with an example practical system used for evaluation. To reduce the computational complexity of the initial method, a digital infinite impedance response (IIR) filter is fitted to each cross coupling characteristic. A high correlation fit is demonstrated that produces a near-identical temperature response compared to the initial procedure while requiring fewer mathematical operations. Experimental validation on the practical system shows good agreement between IIR filter predictions and practical results. It is further demonstrated that this agreement can be substantially improved by taking feedback from an internal reference temperature. Additionally, the proposed IIR filter technique allows the efficient calculation of future device temperatures based on simulated input, facilitating future temperature predictions

Methodologies for the design of LCC voltage-output resonant converters

Abstract: The paper presents five structured design methodologies for third-order LCC voltage output resonant converters. The underlying principle of each technique is based on an adaptation of a FMA equivalent circuit that accommodates the nonlinear behaviour of the converter. In contrast to previously published methods, the proposed methodologies explicitly incorporate the effects of the transformer magnetising inductance. Furthermore, a number of the methodologies allow the resonant-tank components to be specified at the design phase, thereby facilitating the use of standard off-the-shelf components. A procedure for sizing the filter capacitor is derived, and the use of error mapping, to identify parameter boundaries and provide the designer with a qualitative feel for the accuracy of a proposed converter design, is explored

Imaging of nuclear magnetic resonance spin–lattice relaxation activation energy in cartilage

Samples of human and bovine cartilage have been examined using magnetic resonance imaging to determine the proton nuclear magnetic resonance spin–lattice relaxation time, T1, as a function of depth within through the cartilage tissue. T1 was measured at five to seven temperatures between 8 and 38°C. From this, it is shown that the T1 relaxation time is well described by Arrhenius-type behaviour and the activation energy of the relaxation process is quantified. The activation energy within the cartilage is approximately 11 ± 2 kJ mol−1 with this notably being less than that for both pure water (16.6 ± 0.4 kJ mol−1) and the phosphate-buffered solution in which the cartilage was immersed (14.7 ± 1.0 kJ mol−1). It is shown that this activation energy increases as a function of depth in the cartilage. It is known that cartilage composition varies with depth, and hence, these results have been interpreted in terms of the structure within the cartilage tissue and the association of the water with the macromolecular constituents of the cartilage

Real-time temperature estimation in a multiple device power electronics system subject to dynamic cooling

This paper presents a technique to estimate the temperature of each power electronic device in a thermally coupled, multiple device system subject to dynamic cooling. Using a demonstrator system, the thermal transfer impedance between pairs of devices is determined in the frequency domain for a quantised range of active cooling levels using a technique based on pseudorandom binary sequences. The technique is illustrated by application to the case temperatures of power devices. For each cooling level and pair of devices, a sixth order digital IIR filter is produced which can be used to directly estimate temperature from device input power. When the cooling level changes, the filters in use are substituted and the internal states of the old filters are converted for use in the new filter. Two methods for filter state conversion are developed—a computationally efficient method which is suited to infrequent changes in power dissipation and cooling, and a more accurate method which requires increased memory and processing capacity. Results show that the temperature can be estimated with low error using a system which is suitable for integration on an embedded processor

A low cost, rapid impedance measurement technique suitable for Li-ion health diagnosis in battery energy storage systems

Battery energy storage is becoming a vital part of green energy systems. Prediction of the state of health of energy storage systems is difficult as it relies on a number of parameters. Pseudo Random Binary Sequence (PRBS) excitation of energy storage batteries has been shown to be a valid method of battery parameter identification for lead acid batteries [1]. The purpose of this work is to validate PRBS test data from a 3Ah LiFePO4 cell forming part of an EV battery-pack cell against Electrochemical Impedance Spectroscopy (EIS) data obtained from an industry-standard potentiostat (Solartron 1480). PRBS results are obtained in under 200 seconds on easily reproducible equipment which can be built into a green energy battery management system, while the EIS process takes over two hours on prohibitively expensive laboratory equipment. This work validates PRBS as a fast and portable method of obtaining the impedance spectrum of Lithium Ion cells, which can then be used to obtain information about SoH of the BESS

Repurposing ATX Power Supply for Battery Charging Applications

ICT equipment is usually replaced at regular intervals, usually before the equipment has failed, opening up the opportunity of providing a second-life through repurposing. In this paper we investigate the technical feasibility of repurposing the standard ATX power supply found in many desktop computers into a 12V battery charger. We provide an overview of the ATX power supply before describing how the power supply may be modified into a battery charger alongside experimental results

Critical Design Criterion for Achieving Zero Voltage Switching in Inductorless Half-Bridge-Driven Piezoelectric-Transformer-Based Power Supplies

A methodology for predicting the ability of inductor-less driven piezoelectric transformer (PT) based power supplies to achieve zero voltage switching (ZVS) is presented. A describing function approach is used to derive an equivalent circuit model of the PT operating in the vicinity of ZVS and the subsequent application of the model provides a quantitative measure of a PT's ability to achieve ZVS when driven by an inductor-less half-bridge inverter. Through detailed analysis of the analytical model, the limitations of the inductor-less half-bridge driven PT are exposed from which guidelines for designing both the PT and inverter are derived