Research Keyword: Power Converters

Jul 26

HIGH FREQUENCY INTERACTIONS BETWEEN POWER CONVERTERS IN DC NETWORKS

This article discusses the occurrence of high frequency interactions between power electronics converters in dc microgrids. Such interactions occur around the switching frequencies of the converters and are dependent on the filters connected between the converters and the dc network. The resulting resonances, under certain conditions, may coincide with some of the converters switching frequencies. In such a situation there is an expressive amplification of voltage or current, polluting the voltage along the feeder, resulting in large circulation of current at high frequency. This is an issue that can affect loads and converters connected to the microgrid and that is difficult to identify, since it occurs in frequencies beyond the frequency range usually identifies by the power quality analyzers. Simulation and experimental results are shown, based on typical converter values used in low voltage dc microgrids.

Jul 24

3D Printed Heat Sinks in GaN-based power converters

A proposal to use additive manufacturing is presented in this paper to overcome such issues. A comparison of materials, shapes, and conventional vs. 3D printed heat sinks is presented in this paper.

Jul 24

State-of-the-Art Wireless Charging Systems for e-Bikes: Technologies and Applications

Several advancements were made in wireless charging for e-transportation however, the knowledge acquired in the context of wireless charging of electric cars are not sufficient to apply to electric bicycle (e-bikes). Therefore, this paper reviewed state-of-the-art wireless charging technologies with a special emphasis on e-bike charging. A comparative analysis of different kinds of wireless charging techniques is also presented to provide a clear understanding and guidelines to choose the best suitable technology for implementation. In addition, current issues, challenges, and future research scopes are identified where necessary modifications need to be done before implementing the technology for e-bikes.

Jul 23

NON-ISOLATED HIGH VOLTAGE GAIN BOOST DC-DC CONVERTER WITH CAPABILITY OF CANCELING INPUT CURRENT RIPPLE

This paper proposes a non-isolated high voltage gain boost dc-dc converter with the feature of canceling input current ripple. At the input port of the proposed converter, there are two coupled inductors are used in an interleaved configuration and the input current passes through the primary winding of coupled inductors. Interleaving helps to solve the problem of high current stress of switches in high voltage gain converters. The proposed converter has two switches in its structure. In the proposed converter, the voltage stress of the switches is less than the peak output voltage. In this paper, the proposed topology is analyzed in all operating modes. The value of current and voltage stresses of switches, input current ripple, and voltage gain are calculated. Finally, the accuracy performance of the proposed converter is reconfirmed through simulation and experimental results.

Jul 23

ZERO VOLTAGE SWITCHING HIGH STEP UP/DOWN BIDIRECTIONAL DC-DC CONVERTER UTILIZING THREE-WINDING COUPLED INDUCTORS

In this paper, a new zero voltage switching (ZVS) bidirectional dc-dc converter is proposed. The proposed converter has the capability of operating as a high step-up and high step-down converter because of having bidirectional power flow. The proposed converter is suitable for battery energy storage systems and hybrid electric vehicles. Moreover, in the proposed converter the current ripple at the low voltage and high voltage DC ports is cancelled by using an small inductance filter which causes increasing the lifetime of battery source. The proposed converter is analyzed, and the theoretical results are obtained. The obtained theoretical results are verified by using the experimental results.

Jul 23

Bi-directional Three Phase Zero Voltage Soft-Switching Converter

This digest proposes a DC side active clamping branch with a clamping capacitor in series with two switches in a common source connection to realize zero voltage soft-switching (ZVS) for a bi-directional two level three phase converter. Moreover, conventional space vector modulation technique is modified to realize ZVS for a bi-directional two level three phase converter. Utilizing the modified space vector modulation (MSVM) technique, bi-directional converter can achieve ZVS for all switching devices in both inverter and rectifier modes of operation. The MSVM technique allows all the switches including in; main converter and auxiliary circuit operate at the same switching frequency. Moreover, simulation results are presented in this digest. Furthermore, laboratory scaled prototype of the bi-directional ZVS converter is assembled rated for 20-kW to experimentally verify the theoretical analysis.

Jul 23

THREE-PORT HIGH VOLTAGE CONVERSION RATIO DC-DC CONVERTER

In this paper, a new three-port DC-DC converter with high voltage conversion ratio is proposed. The proposed converter is useful for photovoltaic (PV) systems, which have a PV source integrated with an extra battery source to supply the output load. The voltage conversion ratio of the high dc voltage port over the low voltage dc port can be more increased by increasing the turns ratio of the coupled inductors for the whole range of duty cycles. The main advantage of the proposed converter comparing to other conventional three-port converters, is achieving higher voltage gain and higher ratio of voltage gain over components’ number. The proposed converter has also the leased normalized voltage stresses on switches for duty cycles higher than 0.3 among the conventional converters of the same type. Moreover, two output voltages of the proposed converter can be simultaneously regulated on different constant levels with a proper precision. In this study, the proposed converter is analyzed and the voltage conversion ratios, the inductors’ average currents, the voltage and current stress on switches are calculated theoretically. Finally, to verify the operation of the proposed converter, the experimental and simulation results of 20V/40V/400V prototype are extracted.

Jul 23

MODELING AND ANALYSIS OF TRANSVERSE-TYPE PIEZOELECTRIC TRANSFORMER BY MEANS OF A POLYNOMIAL APPROACH

The micro-fabrication technology requires high force, high displacement, low mass actuators low step frequencies, high power and energy density. Upon this point, piezoelectric transformer (PT) are promising and have some advantages compared with the usual electromagnetic ones operating at resonance. Besides, their electromechanical behaviors depend several parameters such as the operating frequency, load located to the output electrodes as well as the gap. Recently, for a transverse-type PT, Hamilton’s principle or the equivalent circuit model have been used but the gap (distance between the primary and secondary electrodes) is neglected. Now, the polynomial approach (PA) which a semi-analytical method is applied in this manuscript to develop and illustrate the 2D modeling of this type PT taking into account the gap.

Jul 22

Control Method for LLC Converter Based on Power Factor with High Robustness Against Variation of Output Voltage and Load Impedance

The LLC converter is a very effective topology for miniaturization of power supplies. However, its application is currently limited. That is because of the problem of degraded system stability when the load condition changes. This paper proposed a control system that controls the output voltage by adjusting the power factor cosθ of the LLC converter to address this problem. As a result, simulations confirm that the proposed control method can significantly improve the frequency characteristics of the LLC converter and shows stable control characteristics regardless of the operating frequency. We also designed an experimental control circuit that can realize the proposed control.

Jul 22

PQ MEASUREMENT ERRORS DUE TO HIGH FREQUENCY DISTORTION PRODUCED BY POWER ELECTRONICS CONVERTERS

The interactions of the low-pass filters, or output filters, present in multiple power electronics converters (PEC) connected to an electric grid create conditions to the circulation of high-frequency current among the passive elements of the filters. It is verified by simulation and field measurements that such current can achieve significant values if the converters are connected in the same feeder or next to the other. Power quality analyzers (PQA) may not record the high-frequency component, which is related to the switching frequency. At some cases, however, PQA records incorrect harmonics measurements as a side effect due to the electrical variables contain high frequency spectral components and the sampling rate designed for the PQA. The conclusion is that existing PQAs may be not prepared to correctly identify and quantify the high-frequency components that are most probably present in the modern electric networks, and in microgrids, with many PEC-based distribution energy resources.