Impact of Component Losses on the Efficiency of a New Quasi-Z-Source-Based Dual Active Bridge

Part 16: Optimization Techniques in EnergyInternational audienceThe paper analyzes the impact of the component losses on the efficiency of the novel DC/DC converter. The converter is a combination of the quazi-Z-source (qZS) network and dual active bridge (DAB). In the analysis the mathematical loss models of the proposed DC/DC converter are derived and efficiency is estimated. Eventually the efficiency is verified experimentally

A Fluxgate-Based Current Sensor for DC Bias Elimination in a Dual Active Bridge Converter

A concern with the isolation transformer in a dual active bridge (DAB) dc-dc converter is the dc bias in magnetization. This article proposes a fluxgate-based current sensor to measure the dc component mixed with a large, high-frequency ac current. Compared with a commercial Hall effect current sensor, the proposed sensor significantly reduces measurement error. This article presents the working principle and design considerations. A prototype is demonstrated for dc bias elimination control in a DAB converter

Analytical modelling and power density optimisation of a single phase dual active bridge for aircraft application

A design procedure for the Dual Active Bridge (DAB) converter is presented, which aims to optimized power density and computational effort. When designing a DAB, the selection of circuit design parameters such as switching frequency, leakage inductance and semiconductor technologies is a complex question when targeting losses and weight minimization of the final design. In this paper, analytical models of the operating waveforms, the losses and the weight of all DAB components are developed. The proposed design algorithm is used for designing a 3kW high frequency DAB for an aircraft DC power system

Design Optimization of High Frequency Transformer for Dual Active Bridge DC-DC Converter

This paper presents a design optimization procedure for high frequency transformer (HFT) employed in bidirectional dual active bridge (DAB) isolated DC-DC converter. It is shown that leakage inductance, phase-shifted angle, skin and proximity effects have to be taken into account together with the HFT voltage-ampere rating to minimize total losses. It is also demonstrated that the leakage inductance required for zero voltage switching operation can be realized under the proposed design procedure without employing extra inductor. The proposed design methodology is experimentally validated by measurements on a prototype HFT

Triple-Phase Shift Modulation for Dual Active Bridge based on Simplified Switching Loss Model

In this paper the dual active bridge (DAB) is analyzed and three modulation approaches are proposed and tested to improve the converter's efficiency. Zero-voltage switching maps are reported to show the most favorable operating conditions to reduce switching and conduction losses contributions. The results are validated considering an experimental DAB converter prototype. It is shown that accounting ZVS with the characterization of switching behavior of the devices allows significant improvements with respect to simply give a constraint on the instantaneous current switching values, at the reported operating conditions

Reactive power minimization of dual active bridge DC/DC converter with triple phase shift control using neural network

Reactive power flow increases dual active bridge (DAB) converter RMS current leading to an increase in conduction losses especially in high power applications. This paper proposes a new optimized triple phase shift (TPS) switching algorithm that minimizes the total reactive power of the converter. The algorithm iteratively searches for TPS control variables that satisfy the desired active power flow while selecting the operating mode with minimum reactive power consumption. This is valid for the whole range of converter operation. The iterative algorithm is run offline for the entire active power range (-1pu to 1pu) and the resulting data is used to train an open loop artificial neural network controller to reduce computational time and memory allocation necessary to store the data generated. To validate the accuracy of the proposed controller, a 500-MW 300kV/100kV DAB model is simulated in Matlab/Simulink, as a potential application for DAB in DC grids

Loss Estimation of a Dual Active Bridge as part of a Solid State Transformer using Frequency Domain Modelling

This paper proposes an improved method for the loss estimation of a Dual Active Bridge (DAB) using frequency domain modelling. The method uses a detailed, frequency depending transformer model to describe even highly utilized DABs. The model is used to estimate the occurring losses of a DAB as part of an modular Solid State Transformer (SST). The influence of the SST\u27s phase power ripple is considered for the loss estimation. The results of the frequency domain model and the loss calculation are validated using measurement data of an SST-cell prototype

A Bidirectional Soft-Switched DAB-Based Single-Stage Three-Phase AC–DC Converter for V2G Application

In vehicle-to-grid applications, the battery charger of the electric vehicle (EV) needs to have a bidirectional power flow capability. Galvanic isolation is necessary for safety. An ac-dc bidirectional power converter with high-frequency isolation results in high power density, a key requirement for an on-board charger of an EV. Dual-active-bridge (DAB) converters are preferred in medium power and high voltage isolated dc-dc converters due to high power density and better efficiency. This paper presents a DAB-based three-phase ac-dc isolated converter with a novel modulation strategy that results in: 1) single-stage power conversion with no electrolytic capacitor, improving the reliability and power density; 2) open-loop power factor correction; 3) soft-switching of all semiconductor devices; and 4) a simple linear relationship between the control variable and the transferred active power. This paper presents a detailed analysis of the proposed operation, along with simulation results and experimental verification

Analysis of AC link topologies in non-isolated DC/DC triple active bridge converter for current stress minimization

This paper presents analysis of the non-isolated DC/DC triple active bridge (TAB) converter under various purely inductor-based AC link topologies. The objective of the analysis is to find the topology that incorporates the least value of the AC link inductors which leads to reduced converter footprint in addition to minimum internal current stresses. Modelling of the TAB under each of the different topologies is presented in per unit expressions of power transfer and reactive power assuming fundamental harmonic analysis. The power expressions are used to calculate the inductor values necessary to achieve same rated power transfer of Dual Active Bridge (DAB) converter for the sake of standardizing comparison. On this basis, the topology requiring the least value of interface inductors, hence lowest footprint, is identified. Furthermore, based on phase shift control, particle swarm optimization (PSO) is used to calculate optimal phase shift ratios in each of the proposed topologies to minimize reactive power loss (hence current stress). The topology with minimum stresses is therefore identified and the results are substantiated using a Matlab-Simulink model to verify the theoretical analysis