• Journal of Power Electronics
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• v.18 no.6
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• pp.1708-1719
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• 2018

A complete current loop decoupling control strategy based on a sliding mode observer (SMO) is proposed to eliminate the influence of current dynamic coupling and back electromotive force (EMF) in the vector control of permanent magnet synchronous motors. With this strategy, current dynamic decoupling and back EMF compensation can be simultaneously achieved. Unlike conventional methods, the proposed strategy can avoid the disturbances caused by the parametric variations of motor systems and maintain the advantages of proportional integral (PI) controllers, which are robust and easy to operate. An improved SMO, which uses a special PI regulator other than a linear saturation function as the equivalent control law in the boundary layer of a sliding surface, is proposed to eliminate the estimated errors caused by the quasi-sliding mode and obtain a satisfactory decoupling performance. The stability and parameter robustness of the proposed strategy are also analyzed. Physical experimental results are presented to verify the validity of the method.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.4
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• pp.327-334
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• 2010

This paper deals with a single-phase dynamic voltage restorer(DVR) with a quasi Z-source topology. The proposed system based on a single-phase quasi Z-source PWM ac-ac converter which have features such as the input voltage and output voltage are sharing ground, and input current operates in continuous current mode(CCM). For the detection of voltage sag-swell, peak voltage detection method is applied. Also, the circuit principles of the proposed system are described. During the 60% severe voltage sag and 30% voltage swell, the proposed system controls the adding or missing voltage and maintains the rated voltage of sinusoidal waveform at the terminals of the critical loads. Finally, PSIM simulation and experimental results are presented to verify the proposed concept and theoretical analysis.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.2B no.3
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• pp.133-139
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• 2002

In this paper, a prototype of an active auxiliary quasi-resonant DC link (QRDCL) snubber assisted voltage source bidirectional power converter (AC to DC and DC to AC) operating at zero voltage soft-switching (BVS) PWM nlode is presented for a Battery Energy Storage System (BESS). The operating principle of this QRDCL circuit and multifunctional control-based converter system, including PWM inverter mode in which energy flows from the battery bank to the three-phase utility-grid in addition to an active PWM converter mode in which energy flows from the utility-grid to the battery banks are described respectively by the control implementation on the basis of d-q coordinate plane transformation. The multifunctional operation characteristics of this three-phase ZVS PWM bi-directional converter with QRDCL is demonstrated fer a BESS under the power conditioning and processing schemes of energy supply mode and energy storage mode, and compared with a conventional three-phase hard switching PWM bi-directional converter for a BESS. The effectiveness of the three-phase ZVS PWM hi-directional converter with QRDCL is proven via the simulation analysis.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.1 s.34
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• pp.17-20
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• 2005

In this paper, we presented the quasi-static characteristics of novel microstrip lines with anisotropic grooved dielectric in finite metal. A quasi-static mode-matching method has been used to analyze this new structure and the simulation results are validated through comparison with other available results. The results in this paper show that it is possible to control the propagation characteristics of microstrip lines with the use of anisotropic grooved dielectric in finite metal. Also anisotropic grooved dielectric in microstrip line can be newly added to the design parameters of high performance three dimensional monolithic microwave circuits and other microwave applications.

• Journal of Electrical Engineering and Technology
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• v.5 no.3
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• pp.477-483
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• 2010

This paper is studied on a novel buck-boost isolated converter for high efficiency and high power factor. The switching devices in the proposed converter are operated by soft switching technique using a new quasi-resonant circuit, and are driven with discontinuous conduction mode (DCM) according to pulse width modulation (PWM). The quasi-resonant circuit makes use of a step up-down inductor and a loss-less snubber capacitor. The proposed converter with DCM also simplifies the requirement of control circuit and reduces a number of control components. The input ac current waveform in the proposed converter becomes a quasi sinusoidal waveform in proportion to the magnitude of input ac voltage under constant switching frequency. As a result, it is obtained by the proposed converter that the switching power losses are low, the efficiency of the converter is high, and the input power factor is nearly unity. The validity of analytical results is confirmed by some simulation results on computer and experimental results.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.514-515
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• 2012

본 논문에서는 인버터 모드 기능을 가지는 Quasi Z-소스 AC-AC 컨버터를 제안하였다. 제안된 시스템은 Quasi Z-소스 AC-AC 컨버터의 암단락 스위치 단에 PI제어가 된 양 방향 벅-부스트 컨버터를 연결하였다. 양방향 벅-부스트 컨버터에서 직류를 입력하는 모드를 인버터 모드라고 하고, 양방향 벅-부스트 컨버터에서 직류를 출력하는 모드는 컨버터 모드라고 한다. PSIM시뮬레이션에 의하여 인버터 모드 동작 시에는 직류 12V를 암단락 스위치단에 입력하여 AC_Load에 교류 전압를 출력하고, 컨버터 모드 동작 시에는 AC_Load에 교류 전압를 출력함과 동시에 암단락 스위치단에 연결된 DC_Load에 직류 전압을 일정하게 출력할 수 있음을 확인하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.4
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• pp.322-332
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• 2013

Conventional single-phase series quasi Z-source voltage compensator can not compensate for voltage sag less than 50% that frequently occurs in the industrial field. In this study, single-phase series quasi Z-source voltage sag-swell compensator which can compensate the voltage variation of entire range is proposed. The proposed system is composed of two quasi Z-source AC-AC converters connected in series with output terminal stage. Voltage sag less than 50% could be compensated by the intersection switching control of the upper converter duty ratio and of the upper converter duty ratio. Also the compensation voltage and its flowchart for each compensation mode are presented for entire sag-swell region. To confirm the validity of the proposed system, a DSP(DSP28335) controlled experimental system was manufactured. As a result, the proposed system could compensate for the voltage sag/swell of 20% and 60%. Finally, voltage compensation factor and THD(Total Harmonic Distortion) according to voltage variation and load change were measured, and voltage quality shows a good results.

• Journal of Satellite, Information and Communications
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• v.12 no.2
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• pp.28-32
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• 2017

In this paper, a quasi-resonant PWM converter, which is controlled by constant frequency, has been suggested. As quasi-resonant converter, the switches of the suggested converter has soft switching characteristics, which can operate to high frequency with high efficiency. Comparing with varied controlled frequency of quasi-resonant converter for controlling output voltage, the suggested converter has advantages which optimize filter and EMI filter design at constant switching frequency. The converter has been analyzed by switch mode analysis which verified soft switching operation. Also, the PWM operation and characteristics of the converter are verified by simulation and experiment of 100 kHz DC-DC converter.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.4
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• pp.588-592
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• 2012

This study concentrates the effect of hybridisation on the collapse mode and energy absorption for composite cylinders. The static collapse behavior of laminated(Al/CFRP/GFRP) circular-cylindrical composite shell under quasi-static axial compressive load has been investigated experimentally. Eight different hybrids of laminated(Al/CFRP/GFRP) circular-cylindrical composite shell were fabricated by autoclave. Eight types of composites were tested, namely, Al/carbon fiber/epoxy, Al/glass fiber/epoxy, Al/carbon-carbon-glass/epoxy, Al/carbon-glass-carbon/epoxy, Al/carbon-glass-glass/epoxy, Al/glass-glass-carbon/epoxy, Al/glass-carbon-glass/epoxy and Al/glass-carbon-carbon/epoxy. Collpase modes were highly dominated by the effect of hybridisation. The results also showed that the hybrid member with material sequence of Al-glass-carbon-carbon/epoxy exhibited good energy absorption capability.

• Journal of Mechanical Science and Technology
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• v.18 no.6
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• pp.924-932
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• 2004

In this study, the axial collapse tests were performed under either static (or quasi-static) or impact loads with several collapse velocities based on the expectation that para-closed sections of the front-end side members (spot welded hat and double hat shaped section members) would show quite different collapse characteristics from those for seamless section. The test results showed that both of the hat and double hat shaped section members failed in the stable sequential collapse mode in the static or quasi-static collapse tests, while the double hat shaped section members underwent the unstable collapse mode especially when the impact velocity is high. The mean collapse loads in the hat shaped section members increase with collapse velocity for all the cases of the static, quasi-static, and impact collapse tests. In the double hat shaped section members, however, the mean collapse loads decrease with increase in collapse velocity in the impact tests.