• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.5
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• pp.379-387
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• 2019

A bidirectional flyback converter is a suitable topology for use in a PV-to-bus differential power processing (DPP) module for PV applications due to its electrical isolation capability, bidirectional power transfer, high step-up ratio, and simple circuit structure. However, the bidirectional flyback converter design should consider the effect of the output-side power switch utilized for bidirectional operation compared with that of the conventional flyback converter. This study presents the structure and design methodology of the bidirectional flyback converter for a PV DPP module. Magnetizing inductance is designed by calculating the power loss of converter components within the rated load range under the discontinuous conduction mode, which is unaffected by the reverse recovery characteristics of the anti-parallel diode of the output-side power switch. The validity of the proposed design methodology is verified using a 25 W bidirectional flyback converter prototype. The operational principles and the performance of the DPP operation are verified using practical DPP modules consisting of bidirectional flyback converters implemented according to the proposed design methodology.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.2
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• pp.75-82
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• 1999

A compensation method of the motor parameters using zero sequence third harmonic voltage is presented for the speed sensorless vector control of the induction motor considering saturation of the flux. Generally, the air-gap flux of the saturated induction motor contains the space harmonic components rotating with the synchronous frequency of the motor. Because the EMF of the saturated induction motor contains the zero sequence harmonic voltages at the neutral point of the motor, those harmonic voltages can be used as a saturation index. In this work, the rotor flux observer is firstly designed for the speed sensorless vector control of induction motor. And a novel measurement method of the space harmonic voltage and a compensation method of th LPF(Low Pass Filter) are proposed. For compensating the non-linear variations of the magnetizing inductance depending on the saturation level of the motor, the dominant third harmonic voltage of the motor is used as a saturation function of the air-gap flux. And the variation of the stator resistance owing to the motor temperature can also be measured with the phase angle between the impressed voltage vector and the zero sequence voltage. The validity of the proposed parameter compensation scheme in the speed sensorless vector control using rotor flux observer is verified by the result of the simulations and the experiments.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.6
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• pp.551-554
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• 2017

This paper proposes a three-level LLC resonant converter using integrated magnetics (IM). Given that the switch voltage stress of the proposed converter is guaranteed to be half of the input voltage, the switching losses can be greatly reduced, thereby benefitting the high-frequency operation. To reduce the volume of reactive components such as transformers, high-frequency driving and planar core are applied. However, two resonant inductors and one transformer are required because of the three-level structure and the limited leakage inductance of the planar transformer for the resonant operation. Therefore, the effect of volume reduction is not very large. In order to solve these drawbacks, this paper proposes a new IM that integrates all magnetic elements used in the proposed three-level resonant converter by using the magnetizing inductor as a resonant inductor. The experimental results are presented by conducting a theoretical analysis of a prototype with 350 W to 800 kHz.