• Journal of Electrical Engineering and Technology
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• 제9권1호
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• pp.162-169
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• 2014

The analysis and comparation of the half-coiled short-pitch windings with different phase belt are presented in the paper. The half-coiled short-pitch windings can supply the odd and even harmonics simultaneously, which can be applied in multiphase bearingless motor (MBLM). The space harmonic distribution of the half-coiled short-pitch windings with two kinds of phase belt is studied wi th respect to different coil pitch, and the suitable coil pitch can be selected from the analysis results to reduce the additional radial force and torque pulse. The two kinds of half-coiled short-pitch windings are applied to the five- and six-phase bearingless motor, and the comparation from the Finite Element Method (FEM) results shows that the winding with $2{\pi}/m$ phase belt is fit for the five phase bearingless motor and the winding with ${\pi}/m$ phase belt is suitable for the six phase bearingless motor. Finally, a five phase surface-mounted permanent magnet (PM) bearingless motor is built and the experimental results are presented to verify the validity and feasibility of the analysis. The results presented in this paper will give useful guidelines for design optimization of the MBLM.

• Journal of international Conference on Electrical Machines and Systems
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• 제3권4호
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• pp.379-382
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• 2014

In this paper, the cogging torques were calculated for 1kw double-sided axial flux permanent magnet (AFPM) generator with different stator core pole arrangements. The generator is composed of 18 stator pole and 24 rotating field magnets on each side. The cogging torques of the generator with three types of arrangements of stator poles were calculated using 3D finite element method and the optimum core shape was determined to minimize the cogging torque.

• Journal of international Conference on Electrical Machines and Systems
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• 제1권2호
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• pp.116-124
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• 2012

Wind is an abundant source of natural energy which can be utilized to generate power. Wind velocity does not remain constant, and as a result the output power of wind turbine generators (WTGs) fluctuates. To reduce the fluctuation, different approaches are already being proposed, such as energy storage devices, electric double layer capacitors, flywheels, and so on. These methods are effective but require a significant extra cost to installation and maintenance. This paper proposes to reduce output power fluctuation by controlling kinetic energy of a WTG system. A MW-class pitch-regulated permanent magnet synchronous generator (PMSG) is introduced to apply a power fluctuation reducing method. The major advantage of this proposed method is that, an additional energy storage system is not required to control the power fluctuation. Additionally, the proposed method can mitigate shaft stress of a WTG system. Which is reflected in an enhanced reliability of the wind turbine. Moreover, the proposed method can be changed to the maximum power point tracking (MPPT) control method by adjusting an averaging time. The proposed power smoothing control is compared with the MPPT control method and verified by using the MATLAB SIMULINK environment.

• Journal of Electrical Engineering and Technology
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• 제11권6호
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• pp.1556-1570
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• 2016

In the process of virtual inertia control (VIC), the frequency regulation capability of the directly-driven wind turbine with permanent-magnet synchronous generator (D-PMSG) on wind farm is related to its rotor kinetic energy and capacity margin. This paper proposes the method for assessing the D-PMSG frequency regulation capability and defining its coefficient according to the operating state of wind power generators. In addition, the calculating method of parameters in VIC is also discussed according to the principles of primary frequency regulation and inertia response of synchronous generators. Then, by introducing the capability coefficient into the proportion-differential virtual inertia control (PD-VIC) for power coordination, a coordinated virtual inertia control (C-VIC) strategy is developed, with the consideration of the difference in frequency regulation capability between wind power generators. The proposed control method can not only give full play to the frequency regulation capability of wind power generators, decrease the movements of the pitch angle control system but also bring some self-coordination capability to different wind power generators thus to avoid a secondary drop in system frequency. The simulations and experiments prove the proposed method to be effective and practicable.

• 에너지공학
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• 제12권4호
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• pp.309-319
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• 2003

본 논문의 목적은 가변속 풍력터빈이 배전망에 미치는 영향을 평가하기 위한 모의해석 모델을 제시하고 제시된 모델을 사용하여 배전망에서의 전력품질에 대한 모의해석을 수행하는 것이다. 모델링된 풍력발전 시스템은 고정피치각을 갖는 풍력터빈과 영구자석형 동기발전기로 구성되며 전력전자 인버터에 의해 가변속 운전 및 무효전력 출력제어가 이루어진다. 풍력터빈 연계에 의한 전압변동 및 고조파 문제를 언급하며, 그 영향에 대하여 제시한 모델을 사용하여 정상상태 및 동특성 해석을 수행한다. 다양한 용량과 다른 출력제어방식의 가변속 풍력터빈을 이용하여 모의하고 평가한다. 사례연구들을 통해 각기 다른 계통상태에서 풍속의 변동 및 다른 출력제어방식에 따른 배전망의 전압변동에 미치는 영향과 고조파 문제를 보여준다. 모델링 및 모의는 PSCAD/EMTDC 프로그램을 기반으로 하여 수행한다.

• Journal of Electrical Engineering and Technology
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• 제10권5호
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• pp.1950-1957
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• 2015

Modern wind generators (WGs) are forced or encouraged to participate in frequency control in the form of inertial and/or primary control to improve the frequency stability of power systems. To participate in primary control, WGs should perform deloaded operation that maintains reserve power using speed and/or pitch-angle control. This paper proposes an optimization formulation that allocates the required reserve to WGs to maximize the kinetic energy (KE) stored in a wind power plant (WPP). The proposed optimization formulation considers the rotor speed margin of each WG to the maximum speed limit, which is different from each other because of the wake effects in a WPP. As a result, the proposed formulation allows a WG with a lower rotor speed to retain more KE in the WPP. The performance of the proposed formulation was investigated in a 100-MW WPP consisting of 20 units of 5-MW permanent magnet synchronous generators using an EMTP-RV simulator. The results show that the proposed formulation retains the maximum amount of KE with the same reserve and successfully increases the frequency nadir in a power system by releasing the stored KE in a WPP in the case of a disturbance.