• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.146-150
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• 2001

A new three-phase soft-switching active front-end inverter is presented. The topology consists of a quasi-resonant PWM boost converter with an additional resonant branch, which provides low loss at high frequency operation. This leads to a high conversion efficiency and a remarkable reduction in the size of the input inductor. To synchronise the PWM pattern with the resonance cycle, a modified space vector modulation with asymmetrical PWM pattern is used. A high power factor can be achieved for both power flow directions. Due to a new control strategy the converter features a low content of harmonics in the line currents even for distorted line voltages.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.980-981
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• 2015

A quasi-resonant flyback converter using a simple 8-bit microcontroller for a LED lighting is proposed in this paper. The proposed converter is easily and precisely controlled by the simple controller using a low-cost 8-bit microcontroller. Also, in order to operate the 8-bit microcontroller, the proposed converter system does not require any additional power supply for the controller. A prototype power supply is developed to supply a 270[W] LED lighting with the wide input voltage ranges ($175[V_{ac}]-265[V_{ac}]$). Experimental results will be show the practicality and validity of the proposed circuit.

• Proceedings of the KIEE Conference
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• 2001.10a
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• pp.258-261
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• 2001

High Power factor Active Filter converter is used for Inverter Air conditioner power supply to meet IEC standard. In the active filter topology for power factor, extra switch just control the input current indirectly to meet the IEC standard for reducing the cost and size. In this paper, low cost converter was suggested by simulation using extra switch which auxiliary pulse is inserted and quasi resonant soft switching topology control is adapted for panel's inverter air conditioner converter Inserting auxiliary Pulse method to the extra switch has the benefit of reducing THD by low cost input control circuit. And also quasi resonant soft switching topology can reduce switching loss. So both technical is suitable for Panel's Air conditioner.

• Journal of Electrical Engineering and Technology
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• v.2 no.1
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• pp.89-97
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• 2007

This paper presents a new circuit topology of active edge resonant snubbers assisted half-bridge soft switching PWM inverter type DC-DC high power converter for DC bus feeding power plants. The proposed DC-DC power converter is composed of a typical voltage source-fed half-bridge high frequency PWM inverter with a high frequency planar transformer link in addition to input DC busline side power semiconductor switching devices for PWM control scheme and parallel capacitive lossless snubbers. The operating principle of the new DC-DC converter treated here is described by using switching mode equivalent circuits, together with its unique features. All the active power switches in the half-bridge arms and input DC buslines can achieve ZCS turn-on and ZVS turn-off commutation transitions. The total turn-off switching losses of the power switches can be significantly reduced. As a result, a high switching frequency IGBTs can be actually selected in the frequency range of 60 kHz under the principle of soft switching. The performance evaluations of the experimental setup are illustrated practically. The effectiveness of this new converter topology is proved for such low voltage and large current DC-DC power supplies as DC bus feeding from a practical point of view.

• Journal of Power Electronics
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• v.16 no.3
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• pp.1176-1189
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• 2016

In this paper, a novel quasi-direct power control (Q-DPC) scheme based on a resonant frequency adaptive proportional-resonant (PR) current controller with a variable frequency resonant phase locked loop (RPLL) is proposed, which can achieve a fast power response with a unity power factor. It can also adapt to variations of the generator frequency in T-type Three-level shaft synchronous generator (SSG) converters. The PR controller under the static α-β frame is designed to track ac signals and to avert the strong cross coupling under the rotating d-q frame. The fundamental frequency can be precisely acquired by a RPLL from the generator terminal voltage which is distorted by harmonics. Thus, the resonant frequency of the PR controller can be confirmed exactly with optimized performance. Based on an instantaneous power balance, the load power feed-forward is added to the power command to improve the anti-disturbance performance of the dc-link. Simulations based on MATLAB/Simulink and experimental results obtained from a 75kW prototype validate the correctness and effectiveness of the proposed control scheme.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1322-1333
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• 2014

To track the sinusoidal current under stationary frame and suppress the effects of low-order grid harmonics, the multi-resonant quasi-proportional plus resonant (PR) controller has been extensively used for digitally controlled LCL-type pulse-width modulation (PWM) converters with capacitor-current-feedback active damping. However, designing the controller is difficult because of its high order and large number of parameters. Moreover, the computation and PWM delays of the digitally controlled system significantly affect damping performance. In this study, the delay effect is analyzed by using the Nyquist diagrams and the system stability constraint condition can be obtained based on the Nyquist stability criterion. Moreover, impact analysis of the control parameters on the current loop performance, that is, steady-state error and stability margin, identifies that different control parameters play different decisive roles in current loop performance. Based on the analysis, a simplified controller design method based on the system specifications is proposed. Following the method, two design examples are given, and the experimental results verify the practicability and feasibility of the proposed design method.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.64 no.3
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• pp.143-145
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• 2015

One of the many problems besetting the converter designer is being able to design a switching power supply that can operate in the range of very wide input voltage. Specially, in an emergency diesel generator system, the AVR(Automatic Voltage Regulator) is a regulator which regulates the output voltage of the generator at a nominal constant voltage level. In addition, the AVR must be operated in very wide input voltage. Therefore, a power supply for the AVR must be operated at the very wide input voltage range. In this paper, a quasi-resonant flyback power supply with very wide input voltage range is proposed. Also, the performance of the proposed power supply is demonstrated through experiments.

• Journal of Power Electronics
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• v.18 no.6
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• pp.1659-1669
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• 2018

An improved circulating current suppression control method is proposed in this paper. In the proposed controller, an outer loop of the average capacitor voltage control model is used to balance the sub-module capacitor voltage. Meanwhile, an individual voltage balance controller and an arm voltage balance controller are also used. The DC and harmonic components of the circulating current are separated using a low pass filter. Therefore, a multiple quasi-proportional-resonant (multi-quasi-PR) controller is introduced in the inner loop to eliminate the circulating harmonic current, which mainly contains second-order harmonic but also contains other high-order harmonics. In addition, the parameters of the multi-quasi-PR controller are designed in the discrete domain and an analysis of the stability characteristic is given in this paper. In addition, a simulation model of a three-phase MMC system is built in order to confirm the correctness and superiority of the proposed controller. Finally, experiment results are presented and compared. These results illustrate that the improved control method has good performance in suppressing circulating harmonic current and in balancing the capacitor voltage.

• Journal of Power Electronics
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• v.15 no.3
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• pp.587-601
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• 2015

A high step-up dc-dc converter is proposed for photovoltaic power systems in this paper. The proposed converter consists of an input current doubler, a symmetrical switched-capacitor doubler and an active-clamp circuit. The input current doubler minimizes the input current ripple. The symmetrical switched-capacitor doubler is composed of two symmetrical quasi-resonant switched-capacitor circuits, which share the leakage inductance of the transformer as a resonant inductor. The rectifier diodes (switched-capacitor circuit) are turned off at the zero current switching (ZCS) condition, so that the reverse-recovery problem of the diodes is removed. In addition, the symmetrical structure results in an output voltage ripple reduction because the voltage ripples of the charge/pump capacitors cancel each other out. Meanwhile, the voltage stress of the rectifier diodes is clamped at half of the output voltage. In addition, the active-clamp circuit clamps the voltage surges of the switches and recycles the energy of the transformer leakage inductance. Furthermore, pulse-width modulation plus phase angle shift (PPAS) is employed to control the output voltage. The operation principle of the converter is analyzed and experimental results obtained from a 400W prototype are presented to validate the performance of the proposed converter.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.394-395
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• 2011

In order to increase the power conversion efficiency and improve the power factor, a modified forward converter is proposed, which adopts a capacitive output filter instead of the inductive output filter of the conventional forward converter. Therefore, the proposed converter has wide input voltage range in opposite to that of the conventional forward converters. Moreover, the proposed converter uses the critical conduction mode for automatic current shaping to improve the power factor. As a result, the proposed converter can achieve quasi-resonant zero-voltage-switching, which can minimize the switching loss of main MOSFET. In addition, the operational principle of the proposed converter is analyzed and the characteristic of the proposed converter is investigated in this paper. To validate the effectiveness of the proposed converter, a prototype of 13W is implemented and the experimental results are discussed in more detail.