What is it about?
DC-DC converter is main key blocks in electric vehicles (EVs) traction system to process the energy deliver to the load. Bulky passive components and cooling device volume in conventional circuit structure DC-DC converter cause the conventional DC-DC converter required more size and space where lead to the low power density converter. By proposing an optimum level of multilevel converter structure with soft-switching technique, the DC-DC converter can be designed smaller as compared to the conventional circuit structure. The performance of the proposed converter is evaluated by using Pareto-Front method to determine the maximum power density of the converter by considering several crucial parameters.
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Why is it important?
The improvement circuit structure of DC-DC converter is required for high power applications in order to increase the power density and the efficiency of the overall system. Thus, by proposing the optimum level of multilevel capacitor-clamped DC-DC boost converter with soft-switching technique implementation, and several comparison has been made among the other proposed converter, it has been confirm 4-level capacitor-clamped DC-DC boost converter with passive lossless snubber circuit have the highest power density and maximum efficiency characteristics. The proposed converter also has been evaluated by using a comprehensive method which is Pareto-Front method.
Perspectives
I hope this article can realize the importance of high power density converter regarding to the application. As we heading to future of transportation such as EV, power density will be considered in design the power source, power converter and electric motor. Thus, this paper can be very useful in designing high power density converter and may add some ideas to the other researcher.
MOHD AMIRUL NAIM KASIRAN
Universiti Tun Hussein Onn Malaysia
Read the Original
This page is a summary of: Evaluation of high power density achievement of optimum 4-level capacitor-clamped DC-DC boost converter with passive lossless snubber circuit by using Pareto-Front method, IET Power Electronics, October 2019, the Institution of Engineering and Technology (the IET),
DOI: 10.1049/iet-pel.2019.0604.
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Resources
A Study of 4-level DC-DC Boost Inverter with Passive Component Reduction Consideration
This study is to analyze design principles of boost inductor and capacitor used in the 4-level DC-DC boost converter to realize size reduction of passive component referring to their attributes. The important feature of this circuit is that most of the boost-up energy is transferred from the capacitor-clamped to the output side which the small inductance can be used at the input side. The inductance of the boost inductor is designed by referring the inductor current ripple. On the other hand, the capacitance of the capacitor-clamped is designed by considering voltage stress on semiconductor devices and also the used switching frequency. Besides that, according to the design specifications, the required inductance in 4-level DC-DC boost converter is decreased compared to a conventional conventional DC-DC boost converter. Meanwhile, voltage stress on semiconductor device is depending on the maximum voltage ripple of the capacitor-clamped. A 50 W 4-level DC-DC boost converter prototype has been constructed. The results show that the inductor current ripple was 1.15 A when the inductors, 1 mH and 0.11 mH were used in the conventional and 4-level DC-DC boost converters, respectively. Thus, based on the experimental results, it shows that the reduction of passive components by referring to their attributes in 4-level DC-DC boost converter is achieved. Moreover, the decreasing of voltage stress on the semiconductor devices is an advantage for the selection of low ON-resistance of the devices which will contribute to the reduction of the semiconductor conduction loss. The integration result of boost converter and H-bridge inverter is also shown.
Parameters design evaluation in 3-level flying capacitor boost converter
Flying capacitor boost converter (FCBC) is one of the possible power converter for high power applications such as solar systems and electric vehicles system and so on. The aim of this paper is to establish relationship between the capacitance of the flying capacitor and output voltage ripple. 3-level FCBC prototype has been constructed for parameters design confirmation. Experimental result shows that the input current ripple is within design value. By identifying the input current ripple, the inductance of the boost inductor is estimated and it needs approximately only 25% compared to the 2-level conventional boost converter. Besides, 3-level FCBC only requires inductor core volume of 35% compared to the 2-level conventional boost converter. Moreover, it is confirmed that the relationship between the capacitance of the flying capacitor and output voltage ripple is independent. This finding is concretely proven by the simulation and experimental results. Therefore, the boost inductor and capacitance of the flying capacitor can be designed independently without considering output voltage ripple.
4-level capacitor-clamped boost converter with hard-switching and soft-switching implementations
This paper presents parameters analysis of 4-level capacitor-clamped boost converter with hard-switching and soft-switching implementation. Principally, by considering the selected circuit structure of the 4-level capacitor-clamped boost converter and appropriate pulse width modulation (PWM) switching strategy, the overall converter volume able to be reduced. Specifically, phase-shifted of 120° of each switching signal is applied in the 4-level capacitor-clamped boost converter in order to increase the inductor current ripple frequency, thus the charging and discharging times of the inductor is reduced. Besides, volume of converters is greatly reduced if very high switching frequency is considered. However, it causes increasing of semiconductor losses and consequently the converter efficiency is affected. The results show that the efficiency of 2-level conventional boost converter and 4-level capacitor-clamped boost converter are 98.59% and 97.67%, respectively in hard-switching technique, and 99.31% and 98.15%, respectively in soft-switching technique. Therefore, by applying soft-switching technique, switching loss of the semiconductor devices is greatly minimized although high switching frequency is applied. In this study, passive lossless snubber circuit is selected for the soft-switching implementation in the 4-level capacitor-clamped boost converter. Based on the simulation results, the switching loss is approximately eliminated by applying soft-switching technique compared to the hard-switching technique implementation.
Implementation of Resonant and Passive Lossless Snubber Circuits for DC-DC Boost Converter
This paper presents the comparison of resonant and passive lossless snubber circuits implementation for DC-DC boost converter to achieve soft-switching condition. By applying high switching frequency, the volume reduction of passive component can be achieved. However, the required of high switching frequency cause the switching loss during turn-ON and turn-OFF condition. In order to reduce the switching loss, soft-switching technique is required in order to reduce or eliminate the losses at switching devices. There are various of soft-switching techniques can be considered, either to reduce the switching loss during turn-ON only, or turn-OFF only, or both. This paper discusses comparative analyses of resonant and passive lossless snubber circuits which applied in the DC-DC boost converter structure. Based on the simulation results, the switching loss is approximately eliminated by applying soft-switching technique compared to the hard-switching technique implementation. The results show that the efficiency of resonant circuit and passive lossless snubber circuit are 82.99% and 99.24%, respectively. Therefore, by applying passive lossless snubber circuit in the DC-DC boost converter, the efficiency of the converter is greatly increased. Due to the existing of an additional capacitor in soft-switching circuit, it realizes lossless operation of DC-DC boost converter.
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