• 전기학회논문지
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• 제60권8호
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• pp.1515-1522
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• 2011

This paper proposes the algorithm for the output AC voltage control of Z-source inverter by the detection of the input DC voltage and Z-network capacitor voltage. The actual modulation index of the proposed method is detected by the capacitor voltage in Z-network and input DC voltage of three-phase Z-source inverter. Control modulation index for the output voltage control is calculated by the detected actual modulation index and reference modulation index. And, calculated control modulation index is applied to the modified space vector modulation (SVM) for control the output voltage of Z-source inverter. To verify the validity of the proposed method, PSIM simulation was achieved and a DSP controlled 1[kW] three-phase Z-source inverter was producted. The simulation and experiment were performed under the condition that the load was changed in case of the constant input DC voltage and the input DC voltage was changed in case of the load was constant. As a result, we could know that the output phase voltage of Z-source inverter followed to the reference voltage 70[VRMS] despite the load or the input DC voltage were suddenly changed.

• 전기학회논문지
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• 제62권7호
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• pp.950-955
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• 2013

This paper proposes a new low-cost current detection method to implement vector-controlled inverter of 3-phase induction motor or permanent-magnet synchronous motor using 2 shunt resistors instead of expensive Hall current sensors. The proposed method can detect perfect phase currents without current-immeasurable area in all operating conditions of motor. This method uses 2 shunt resistors in Hall current sensor positions conventionally used to detect phase currents. Therefore, it requires accurate analog differential amplifiers to detect voltages across shunt resistors at high electric potential to ground. We show the good solutions which are implemented by voltage-divider resistors networks and the instrumentation amplifiers using several Op Amps at cheap price. Computer simulations and experiments were performed to confirm the effectiveness of proposed method. These results show that proposed method can perfectly detect phase currents without current-immeasurable area in all operating conditions of motor.

• 전기학회논문지
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• 제65권10호
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• pp.1648-1654
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• 2016

This paper analyzes complex vector current control for the enhanced cross-coupling compensation in accordance with parameter variation in grid-connected inverter system, and verifies through simulation and experiment. Complex vector current control is performed in the synchronous reference frame through d-q transformation. It generates cross-coupling components with rotating nominal angular frequency. In general, cross-coupling elements are compensated by decoupling terms added to output of conventional decoupling PI controller. But, it is impossible to compensate them perfectly which transient response is especially deteriorated such as large overshoot and slow tracking, when variation of grid impedance or measurement error occurs. However, complex vector current control can improve stability and response characteristic of current control regardless of the situation as before. Decoupling controller and complex vector controller are represented through complex forms, and these controllers are analyzed by using frequency response in s-domain, respectively. It is verified that complex vector controller has more superior response characteristic than decoupling controller through MATALB, PSIM and experimental in 5kW grid-connected inverter when L filter parameter is varied from 1.1mH to increase double, 2.2mH.

• 전기학회논문지
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• 제67권7호
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• pp.846-853
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• 2018

In this paper, an improved model predictive control (MPC) method is proposed, which reduces the amount of calculations caused by the increased number of candidate voltage vectors with the increased voltage level in multi-level inverters. When the conventional MPC method is used for multi-level inverters, all candidate voltage vectors are considered to predict the next-step current value. However, in the case that the sampling time is short, increased voltage level makes it difficult to consider the all candidate voltage vectors. In this paper, the improved MPC method which can get a fast transient response is proposed with a small amount of the computation by adding new candidate voltage vectors that are set to find the optimal vector. As a result, the proposed method shows faster transient response than the method that considers the adjacent vectors and reduces the computational burden compared to the method that considers the whole voltage vector. the performance of the proposed method is verified through simulations and experiments.

• 조명전기설비학회논문지
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• 제29권9호
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• pp.71-80
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• 2015

This paper proposes a convenient thermal modeling method for loss distribution control method of 3-level Active NPC(Neutral Point Clamped) inverter. In the drawback of conventional 3-level NPC, the generated losses can occur unbalance in each switching device, as a result, thermal utilization of designed system has been decreased. In order to compensate unbalanced losses, Active NPC inverter performed loss balancing control with thermal modeling during operation of each switching device. Therefore, this paper deals with a convenient thermal modeling method based on newton's law of cooling rather than conventional thermal modeling method. Both simulation and experimental results based on 10kW 3-level Active NPC inverter confirm the validity of the analysis performed in the study.

• 조명전기설비학회논문지
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• 제29권9호
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• pp.33-41
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• 2015

To improve the power quality of distributed generation (DG) systems even in the presence of distorted grid condition, dual current control scheme of a grid-connected inverter is proposed. The proposed current control scheme is achieved by decomposing the inverter state equations into the fundamental and harmonic components. The derived models are employed to design dual current controllers. The conventional PI decoupling current controller is used in the fundamental model to control the main power flow in DG systems. At the same time, the predictive control is applied in the harmonic model to suppress undesired harmonic currents to zero quickly. To decompose the voltage inputs and state variables into the fundamental and harmonic components, the fourth order band pass filter (BPF) is designed in the discrete-time domain for a digital implementation. For experimental verification, 2kVA prototype of a grid-connected inverter has been constructed using digital signal processor (DSP) TMS320F28335. The effectiveness of the proposed strategy is demonstrated through comparative simulation and experimental results.

• 전력전자학회논문지
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• 제6권3호
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• pp.223-230
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• 2001

구형파 브러시리스 직류전동기를 구동시키기 위해서는 전동기의 회전자 위치에 대한 정보를 아는 것이 필수적이다. 본 논문에서는 회전자 위치를 검출하기 위해 일반적으로 사용되는 홀센서나 엔코더를 이용하지 않고, 각 상을 저항으로 Y결선하여 만들어지는 단자의 전압에 포함되어 있는 비여자상의 역기전력을 이용하여 전동기의 회전자 위치를 검출하는 구형파 브러시리스 직류전동기용 센서리스 드라이브 시스템을 제안한다. 이를 위해 3상 2여자 선단부 유니폴라 PWM을 수행할 결우에 대한 각상의 단자전압 분석을 수행하고, 분석된 단자전압 파형으로부터 회전자 위치를 검출하는 방법을 제안한다. 그리고 이를 실제로 간단한 회로로 구현하였다. 실험에 사용된 전동기는 100W급이며 Power MOSFET으호 인버터를 구성하였으며 87c196mc 컨트롤러를 사용하여 제어기를 구성하였다.

• 전력전자학회논문지
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• 제7권3호
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• pp.262-271
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• 2002

견인전동기 구동시스템에 사용되는 PWM 인버터는 전력용량이 크기 때문에 스위칭주파수가 제한되며, 따라서 전자기적 가청소음이 발생한다. 이러한 가청소음을 줄이기 위하여 새로운 MRSF-PWM 방식을 제안한다. 제안한 MRSF-PWM 방식에서는 고조파를 확산시키기 위해 삼각파와 톱니파를 함께 운송파로 사용하며, 출력전압의 선형제어범위를 넓히기 위해 정현파에 3차 고조파를 주입한 파형을 기준파로 사용한다. MRSF-PWM 방식의 타당성을 검증하기 위하여 컴퓨터 시뮬레이션을 수행하였다. 그 결과, MRSF-PWM 방식이 선형성 및 고조파 확산면에서 다른 RPWM 방식보다 우수하며 가청소음 저감면에서 SPWM 방식보다 효과적임을 확인하였다.

• 전력전자학회논문지
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• 제7권6호
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• pp.587-595
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• 2002

최근 배터리, 태양전지, 연료전지 등의 전원으로 구동되는 전기자동차에 대한 관심이 커지고 있다. 그런데, 이와 같은 전원들의 단위전지 전압은 자동차의 인버터를 구동하기에는 너무 낮기 때문에 수많은 단위전지를 직렬로 연결하여 사용해야하며, 이로 인해 전원의 구조가 복잡해지는 문제가 있다. 본 논문에서는 전기자동차의 응용을 위해 비교적 낮은 전원전압을 충분히 높은 안정된 직류 링크전압으로 바꾸어주는 고효율 대용량 승압 컨버터를 제안하고 그 설계기준과 실험결과를 제시한다.

• 전력전자학회논문지
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• 제7권6호
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• pp.596-603
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• 2002

본 논문에서는 영상고조파 주입법을 사용하여 3상 다이오드 정류기의 입력전류를 개선하는 새로운 방식의 고조파 저감기술을 제안한다. 3고조파 주입을 근간으로 하는 본 방식은 다이오드 정류기의 상측과 하측의 전류를 독립적으로 제어하기 위하여 두 대의 단상 반파 인버터와 두 대의 단상 변압기로 구성되어져 있다. 이렇게 만들어진 영상전류는 zigzag 변압기에 의해서 다이오드 정류기의 상측과 하측으로 주입이 되어진다. 이 결과 3상 다이오드 정류기의 입력전류는 순수한 정현파 전류가 된다. 본 방식의 타당성을 1.5kVA 시작품의 실험을 통하여 입증하였다.