Copper Loss Analysis of a Multiwinding High-Frequency Transformer for a Magnetically-Coupled Residential Microgrid

Abstract

Improvements in characteristics of magnetic materials and switching devices have provided the feasibility of replacing the electrical buses with high-frequency magnetic links in small-scale micro-grids. This can effectively reduce the number of voltage conversion stages, size and cost of the microgrid, and isolate the sources and loads. To optimally design the magnetic link, an accurate evaluation of copper loss of the windings considering both the current waveforms and parasitic effects are required. This paper studies the copper loss analysis of a three-winding high-frequency magnetic link for residential micro-grid applications. Due to the non-sinusoidal nature of the voltages and currents, the loss analysis is carried out on a harmonic basis taking into account the variations of phase shift, duty ratio and amplitude of the waveforms. The high-frequency parasitic phenomena including the skin and proximity effects are taken into account. The maximum and minimum copper loss operating conditions of the magnetic link and their dependency on the phase shift angle and the duty ratio of the connected waveforms are studied. A prototype of the micro-grid including the magnetic link is developed to validate the theoretical analysis, evaluate the micro-grid efficiency and perform the loss breakdown.

A Topology of DC-DC Converter Based on Multi-Winding Transformer for Grid Integration of Multiple Renewable Energy Resources

“…The H-bridge converter in port one is connected to a PV generation system, port two to a wind turbine generator, port three to a battery and port four to a high-voltage DC bus, followed by a single-phase inverter. In this structure, the transformer core is used as a magnetic coupling bus to transfer the power between the converter ports in a magnetic form [20,21]. The main advantage of the system is that the power ports having different operating voltages is easily matched by the transformer turns ratios, and also they are electrically isolated and their relation is only in the magnetic form [16].…”

“…For the magnetic core, a toroidal core made from amorphous alloy 2605SA1 has been selected in this paper. To find the proper dimensions of the transformer, reluctance network modeling (RNM) is used for field analysis, as is explained in [18,21,24]. As a result, the number of turns for the windings and the core dimension were determined based on the required inductances, considering maximum flux density in the core.…”

“…A complete study on the magnetically coupled multi-port converters has been presented in [16][17][18][19][20]. It should be noted that the system operation and design of the multi-winding high-frequency transformer become very complex in the case of a large number of windings [21][22][23][24]. A magnetically coupled converter with two inputs and one output is presented in [25], where instead of combining input DC sources in electric form, they are combined in magnetic form by adding the produced magnetic fluxes together using the magnetic core of the multi-winding transformer.…”

A Grid-connected Hybrid Renewable Energy System Using High-frequency Multi-winding Transformer and Phase Shift Modulation Technique

“…The H-bridge converter in port one is connected to a PV generation system, port two to a wind turbine generator, port three to a battery and port four to a high-voltage dc bus followed by a single phase inverter. In this structure, the transformer core is used as a magnetic coupling bus to transfer the power between the converter ports in a magnetic form [20], [21]. The main advantage of the system that power ports having different operating voltages are easily matched by transformer turns ratios and also are electrically isolated and their relation is only in the magnetic form [16].…”

“…A complete study on the magnetically coupled multi-port converters have been presented in [16]- [20]. It should be noted that the system operation and design of multi-winding high-frequency transformer become very complex in the case of large number windings [21]- [24]. A magnetically coupled converter with two input and one output is presented in [25] where instead of combining input dc sources in electric form, they are combined in magnetic form by adding up the produced magnetic fluxes together using the magnetic core of the multiwinding transformer.…”