Design and Simulation of a 10kW High-Efficiency Dual Active Bridge Converter

Sammanfattning: The EU has proposed an ambitious goal to achieve widespread E-mobility in both the electrical and commercial sectors. To accomplish this, a substantial number of DC fast-charging stations must be built. These power converters, installed in the DC fast-charging stations (DCFC), differ from traditional DCDC converters as they exhibit high power density, reaching tens of kilowatts. In contrast to traditional non-isolated power converters, isolated power converters offer ideal galvanic isolation, providing protection to both the local power grid and electric vehicles. Among the DC power converters designed for industrial applications, the LLC resonant converters and DAB converters (Dual Active Bridge) have gained significant popularity. When compared to LLC converters, DAB converters demonstrate a more flexible input and output power range, as well as a higher power density. Considering these advantages, a 10kW bidirectional DAB power converter has been designed for the purpose of fulfilling the requirements of this thesis project. The thesis is organized into four distinct parts. The first part focuses on conducting a comprehensive literature review to explore the challenges prevalent in the current electrical field. Various DC-DC topologies are compared based on different factors, including component analysis, controllability, safety considerations, and cost-effectiveness. By examining these aspects, potential solutions for Electric Vehicles (EVs) are identified. In the second part, a specific DC-DC converter with a power rating of 10kW is chosen, utilizing the DAB (Dual Active Bridge) topology. The selection is based on the analysis conducted in the literature review. The thesis delves into the issues and technical challenges associated with this choice, such as reactive power, peak current, zero-voltage switching (ZVS), and phase shift modulation. These topics are thoroughly explored and discussed within the literature study. The second part of the thesis involves the establishment of a DAB model, incorporating mathematical equations and physical derivations. This modeling and design section discusses the energy conversion process, starting from fundamental physical formulas and extending to the overall system setup. Utilizing the proposed model, a control method called SPS (Single Phase Shift) modulation is implemented in the circuit to achieve closed-loop control. Within this part, the relationship between current, voltage, and output power is derived and utilized for the design of a PI closed controller. To address challenges associated with SPS control, such as reactive power elimination and peak current suppression, an EPS (Enhanced Phase Shift) control scheme is introduced. The EPS control scheme not only fulfills the basic requirement of power transfer but also optimizes the system’s overall efficiency. In the third part of the thesis, a simulation is developed to validate the accuracy of the proposed DAB model and control methods. Simulations are implemented using Simulink, a widely used software for dynamic system modeling and simulation. Various aspects of the system are evaluated through the simulation, including the leakage inductor current, voltage waveforms on both the primary and secondary sides and output power. These parameters are plotted and analyzed to assess the performance of the DAB model and control methods. Additionally, loss and efficiency analyses are conducted using PLECS, a simulation platform that specializes in power electronics systems. By inputting the datasheet information of the switches and transformer, PLECS enables the evaluation of losses and efficiency within the system. This analysis provides valuable insights into the performance and energy efficiency of the proposed DAB-based converter. In the final part of the thesis, conclusions are drawn based on the theoretical findings and simulation results obtained throughout the study. These conclusions reflect the overall outcomes and implications of the research conducted. Furthermore, the future work section outlines the tasks that remain unfinished or areas that can be explored in subsequent studies. This section serves as a guide for future researchers, highlighting potential directions for further investigation and improvement in the field of DAB-based DC-DC converters for E-mobility applications. By presenting the conclusions and future work, the thesis provides a comprehensive summary of the research conducted, its contributions, and potential avenues for future research and development.