• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.42-45
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• 1997

A synchronous solid-state var compensator(SSVC) system which employs a three-phase neutral-point-darned (NPC) inverter is presented and analyzed for high voltage and high power applications. The proposed SSVC system can compensate for leading and lagging displacement factor. An optimal pulse-width-modulation (PWM) is used as a means of reducing the size of reactive components. A equivalent model is obtained using DQ-transform, and the characteristic of open-loop system are archived from DC and AC analyzes. A $\alpha$ phase-shift control is suggested using a self-controlled dc bus.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.7-11
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• 2017

This paper describes a design concept of NPC1 power stack for 1500VDC megawatt level solar inverter. This stack uses three latest half-bridge IGBT modules with highest power density and operation junction temperature, which enable realization of power level beyond 1MW without paralleling. Critical design concept on loop inductance is explained. Dynamic characteristics are verified by double-pulse test. Thermal characteristics and output power limits are verified by thermal test. Temperature-sensitive component on PCB as output power constraint is identified. Different PCB repositioning solutions are tested to give the overall output power thermal derating curves, which enable output power of 1.15MW at $T_A=55^{\circ}C$ with $15^{\circ}C$ thermal margin. The power stack characteristic and performance change under different thermal environment is further analyzed.

• Journal of Power Electronics
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• v.18 no.2
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• pp.432-444
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• 2018

This paper presents a capacitor voltage balancing topology using a three-level boost converter (TLBC) for a neutral point clamped (NPC) three-level inverter fed surface permanent magnet synchronous motor drive (SPMSM). It enhanced the performance of the drive in terms of its voltage THD and torque pulsation. The main attracting feature of the proposed control is the boosting of the input voltage and at the same time the balancing of the capacitor voltages. This control also reduces the computational complexity. For the purpose of close loop vector control, a software based cost effective resolver to digital converter RDC-less estimation is implemented to calculate the speed and position. The proposed drive is simulated in the MATLAB/SIMULINK environment and an experimental investigation using dSPACE DS1104 validates the proposed drive system at different operating condition.

• Journal of Electrical Engineering and Technology
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• v.6 no.5
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• pp.595-604
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• 2011

A three-phase three-level shunt active filter controlled by fuzzy logic current controller which can compensate current harmonics generated by nonlinear loads is presented. Three-level inverters and fuzzy controllers have been successfully employed in several power electronic applications these past years. To improve the conventional pwm controller performance, a new control scheme based on fuzzy current controller is adopted for three-level (NPC) shunt active filter. The scheme is designed to improve compensation capability of APF by adjusting the current error using a fuzzy rule. The inverter current reference signals required to compensate harmonic currents use the synchronous reference detection method. This technique is easy to implement and achieves good results. To maintain the dc voltage across capacitor constant and reduce inverter losses, a proportional integral voltage controller is used. The simulation of global system control and power circuits is performed using Matlab-Simulink and SimPowerSystem toolbox. The results obtained in transient and steady states under various operating conditions show the effectiveness of the proposed shunt active filter based on fuzzy current controller compared to the conventional scheme.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1500-1511
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• 2017

The purpose of this paper is to study a high-performance control scheme for neutral-point-clamping three-level (NPC-3L) inverter fed dual three-phase permanent magnet synchronous motor (PMSM) drives by considering some asymmetric factors such as the non-identical parameters in phase windings. To implement this, the system model is analyzed for dual three-phase PMSM drives with asymmetric factors based on the vector space decomposition (VSD) principle. Based on the equivalent circuits, PI controllers with feedforward compensation are used in the d-q subspace for regulating torque, where the cut-off frequency of the PI controllers are set at the twice the fundamental frequency for compensating both the additional DC component and the second order component caused by asymmetry. Meanwhile, proportional resonant (PR) controllers are proposed in the x-y subspace for suppressing the possible unbalanced currents in the phase windings. A dual three-phase space vector modulation (DT-SVM) is designed for the drive, and the balancing factor is designed based on the numerical fitting surface for balancing the DC link capacitor voltages. Experimental results are given to demonstrate the validity of the theoretical analysis and the proposed control scheme.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.630-634
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• 2004

A new three phase three-level Pulse Width Modulation (PWM) Switched Voltage Source (SVS) inverter with zero neutral point potential is proposed. The major advantage is that the peak value of the phase output voltage is twice as high as that of the conventional neutral-point-clamped (NPC) PWM inverter. Furthermore, three-level waveforms of the proposed inverter can be achieved without switch voltage unbalance problem. Since the average neutral point potential of the proposed inverter is zero, the common ground between input stage and output stage is possible. The proposed inverter is verified by experimental results based on a laboratory prototype.

• Proceedings of the KIPE Conference
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• 2013.11a
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• pp.107-108
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• 2013

본 논문에서는 3-레벨 NPC(Neutral Point Clamped) 인버터에서 사용되는 SVPWM(Space Vector Pluse Width Modulation)기법들 중 옵셋전압을 이용한 대칭 SVPWM과 효율을 높이기 위한 전압 지령 벡터를 계산한 $120^{\circ}$ DPWM(Discontinuous PWM)과 $60^{\circ}(+30^{\circ})$ DPWM을 비교 분석하였다. 각 SVPWM간의 효율 및 THD를 비교 분석 하였고 이를 통해 시뮬레이션으로 스위칭 방식에 따라 비교하여 효율 및 THD 결과를 도출하였다.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.209-210
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• 2011

본 논문은 3레벨 NPC 인버터의 중성점 전위 변동 시 퍼지제어기를 이용한 중성점 전위 제어 방법을 제안한다. 오프셋 전압을 퍼지제어기의 입력으로 하여 공간벡터의 스위칭 타이밍의 조절변수를 출력함으로써 기존의 오프셋 전압의 복잡한 수학적 모델링 없이 쉽고 간단하게 중성점 전압을 제어한다. 제안하는 제어기법의 우수성을 보이기 위하여 10kW급 계통연계 3-레벨 NPC인버터 모델을 기반으로 시뮬레이션을 수행하였다.

• Proceedings of the KIPE Conference
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• 2014.11a
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• pp.113-114
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• 2014

대용량 분산 발전원이 증가하면서 이러한 대용량 분산 발전을 효율적으로 운전하기 위한 많은 연구가 진행되고 있다. 본 논문에서는 멀티레벨 인버터 토폴로지 중 3L-NPC와 3L-T-type 인버터에 DSVPWMx(DSVPWMP, DSVPWMN, DSVPWMPN0, DSVPWMPN1, DSVPWMPN2, DSVPWMPN3)를 적용하였을 때 두 개의 멀티레벨 인버터에서 발생하는 효율의 차이를 비교하였다. 이를 검증하기 위한 방법으로 Psim Thermal Module을 활용하여 회로를 구성하고 각 PWM방식에서 전압변조비에 따른 효율을 비교 분석하였다.

• Proceedings of the KIPE Conference
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• 2014.11a
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• pp.187-188
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• 2014

본 논문에서는 3-레벨 NPC(Neutral Point Clamped) 인버터에서 상단 커패시터 전압과 하단 커패시터의 전압의 불균형 시 나타나는 출력 상전류 왜곡에 대한 보상기법에 대하여 제안한다. 스위칭 기법은 SVPWM(Space Vector Pulse Width Modulation)을 사용하였고 상단 커패시터 전압과 하단 커패시터 전압의 불균형이 DC-Link 전압의 0% 15% 35%일 때의 보상 전과 보상 후를 비교 분석 하여 시뮬레이션으로 출력 상전류 보상기법을 검증하였다.