• 대한전기학회논문지
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• 제41권5호
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• pp.474-482
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• 1992

This paper describes the speed control system of an induction type ac servomotor drive on the vector control basis of slip frequency and constant secondary flux control for a quick torque response. The system is composed of a digital controller using a SCB-V50 microprocessor and a PWM inverter with power MOSFETs for high speed switching. And, for the measurement of actual instantaneous currents, MDCS A070-051 hall sensors are employed. The rising time of step responce by this system through the test of a 600[W] ac servomotor is 30[ms]. Overall experimental result shows that the drive performance of the system is similar to that of a separately excited armature current control of a dc motior.

• Journal of Power Electronics
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• 제17권6호
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• pp.1658-1671
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• 2017

To address the inaccurate load demand sharing problems among parallel inverter-interfaced voltage-controlled distributed generation (DG) units in islanded microgrids (MGs) with different DG power ratings and mismatched feeder impedances, an enhanced voltage control scheme based on the active compensation of circulating voltage drops is proposed in this paper. Using the proposed strategy, reactive power and harmonic currents are shared accurately and proportionally without knowledge of the feeder impedances. Since the proposed local controller consists of two well-separated fundamental and harmonic voltage control branches, the reactive power and harmonic currents can be independently shared without having a remarkable effect on the amplitude or quality of the DGs voltage, even if nonlinear (harmonic) loads are directly connected at the output terminals of the units. In addition, accurate load sharing can also be attained when the plug-and-play performance of DGs and various loading conditions are applied to MGs. The effects of communication failures and latency on the performance of the proposed strategy are also explored. The design process of the proposed control system is presented in detail and comprehensive simulation studies on a three-phase MG are provided to validate the effectiveness of the proposed control method.

• Journal of Power Electronics
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• 제13권5호
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• pp.877-883
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• 2013

This paper discussed a transformer-less shunt static synchronous compensator (STATCOM) with consideration of the following aspects: fast compensation of the reactive power, harmonic cancelation and reducing the unbalancing of the 3-phase source side currents. The STATCOM control algorithm is based on the theory of instantaneous reactive power (P-Q theory). A self charging technique is proposed to regulate the dc capacitor voltage at a desired level with the use of a PI controller. In order to regulate the DC link voltage, an off-line Genetic Algorithm (GA) is used to tune the coefficients of the PI controller. This algorithm arranged these coefficients while considering the importance of three factors in the DC link voltage response: overshoot, settling time and rising time. For this investigation, the entire system including the STATCOM, network, harmonics and unbalancing load are simulated in MATLAB/SIMULINK. After that, a 35KVA STATCOM laboratory setup test including two parallel converter modules is designed and the control algorithm is executed on a TMS320F2812 controller platform.

• 전기학회논문지P
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• 제60권4호
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• pp.227-235
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• 2011

This paper describes a PMSM control algorithm for realizing a low-cost motor drive system using a general purpose microcontroller. The proposed sensorless algorithm consists of the current observer and the sensorless scheme based on instantaneous reactive power. Also the control board system is not the high-cost DSP(digital signal processor) system but the general purpose microcontroller and it allows to reduce the unit cost of the motor system. However the clock frequency of the proposed microcontroller is one-fifths for the clock frequency of the DSP. In addition, the switching frequency must be selected as the lower frequency because of complex mathematic modeling of the sensorless algorithm. the low switching frequency augments the noise of the motor and might make accurate speed control impossible. Thus this paper proposes the optimization method to supplement the drawback of the general purpose microcontroller and the usefulness of the proposed method is verified through the experiment.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1537-1539
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• 2005

This paper proposes 210[kVA] rated SIV(Static Inverter) system for the TTX(Tilting Train eXpress). The SIV provides power of a fluorescent light in the car, Air-conditioner, and other equipments. To control output voltage it is used voltage control loop for constant voltage control and simultaneously used current control loop for instantaneous control at load changing. The performance of SIV system will be verified by simulation and experimental results.

• 전력전자학회논문지
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• 제4권3호
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• pp.275-284
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• 1999

3산 전력 시스템에서 불평형 전원의 전압은 대칭좌표법에 의하여 정상, 역상, 영상성분으로 각각 분해 될 수 있고 또한 전력 시스템에 중성선이 없는 경우 영상성분은 부하측에 나타나지 않게 된다. 따라서 중성선이 없는 불평형 시스템에서는 전원측의 역상성분만을 검출하여 보상함으로써 부하측에 평형된 전압을 공급할 수 있을 뿐만 아니라 정상성분의 크기를 제어함으로써 부하에 인가되는 전압의 크기를 조정하는 것이 가능하다. 아울러 이러한 불평형 전압에 의한 각 대칭분은 3상 2상 변환을 통한 동기좌표축상에서의 효율적인 검출이 가능한데, 본 논문에서는 전원의 불평형 성분을 동기좌표축 상에서 순시적으로 검출하여 이를 보상하고 부하의 전압조정 기능 역시 수행하는 순간전압보상기의 보상 알고리즘 및 이때 좌표변환시 필요한 전원의 위상각 정보를 전원의 정상성분에 일치시키는 새로운 위상각 검출 알고리즘을 제안한다. 제안된 보상 시스템의 성능 및 특성을 시뮬레이션을 통하여 해석하고 실험으로써 검증하였다.

• 전력전자학회논문지
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• 제5권5호
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• pp.484-492
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• 2000

본 논문에서는 고조파전류 보상기능을 갖는 전압 보상기에 관한 연구를 수행하고 그 보상 특성을 해석하였다. 제안된 보상시스템은 하이브리드형 능동전력필터에서와 같이 LC로 구성되어 전력선에 병렬로 연결되는 수동필터와 직렬 변압기를 사용하여 전력선에 직렬로 연결되는 PWM 컨버터를 동시에 사용하는 회로구조를 갖는다. 제안된 보상시스템을 통해 다이오드 정류기와 같은 비선형 부하로 인해 발생되는 고조파 전류의 보상 및 전원 이상 현상으로 발생되는 전원측 이상 전압의 보상을 모두 수행한다. 단상 등가회로를 통해 보상시스템의 동작 원리를 설명하고 d-q 동기좌표계 축 상에서 보상시스템의 모든 제어를 수행하는 제어 알고리즘의 개발을 수행하였으며 실험을 통해 제안된 보상시스템의 보상특성을 확인하였다.

• 전기학회논문지
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• 제64권1호
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• pp.182-187
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• 2015

In the three-phase power system, when any one-phase or two-phases is open-phase, the unbalanced current flows and the single-phase power supplies to three-phase loads. Specially, motor coil and transformer coil receive over-current. As a result, great damage as well as electrical fire can occur to the power system. In order to improve these problems, this paper proposes that an open-phase detection device is designed by a new algorithm using electric potential difference between the resultant voltage of neutral point and ground, and a control circuit topology of open-phase protector is composed of highly efficient semiconductor devices. It improves response speed and reliability. The control algorithm circuit also operates the cut-off of a conventional residual current protective device (RCD) which flows an enforced leakage current to ground wire at open-phase accident. Furthermore, time delay circuit is added to prevent the incapable operation of open-phase protector about instantaneous open-phase not open-phase fault. The time delay circuit improves more reliability.

• Journal of Power Electronics
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• 제8권4호
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• pp.345-353
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• 2008

In this paper, a novel loss minimization of an induction generator in wind energy generation systems is presented. The proposed algorithm is based on the flux level reduction, for which the generator d-axis current reference is estimated using support vector regression (SVR). Wind speed is employed as an input of the SVR and the samples of the generator d-axis current reference are used as output to train the SVR algorithm off-line. Data samples for wind speed and d-axis current are collected for the training process, which plots a relation of input and output. The predicted off-line function and the instantaneous wind speed are then used to determine the d-axis current reference. It is shown that the effect of loss minimization is more significant at low wind speed and the loss reduction is about to 40% at 4[m/s] wind speed. The validity of the proposed scheme has been verified by experimental results.

• 전기학회논문지P
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• 제52권4호
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• pp.172-178
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• 2003

This paper examines the application of high voltage static var compensator(SVC) with cascade multilevel inverter which employs H-bridge inverter(HBI). This method has the primary advantage that the number of voltage levels can be increased for a given number of semiconductor devices when compared to the conventional control methods. The SVC system is modeled using the d-q transform which calculates the instantaneous reactive power. This model is used to design a controller and analyze the SVC system. From the mathematical model of the system, the design procedures of the circuit parameters L and C are presented in this thesis. To meet the specific total harmonic distortion(THD) and ripple factor of the capacitor voltage, the circuit parameters L and C are designed. Simulated and experimental results are also presented and discussed to validate the proposed schemes.