• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.981-982
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• 2011

This paper discusses design aspects of slotless permanent magnet generator for high performance and low speed applications. The airgap flux density in was obtained from finite element analysis and the design of a PM generator. The relatively large diameter stator laminations of such machines tend, therefore, to have a very thin back of core and narrow teeth, which make them expensive and difficult to manufacture. this thesis proposes an alternative PM generator topology featuring a slotless stator whose laminations are manufactured from a split core. The test results with a resistive load confirm the satisfactory operation of generator.

• 조명전기설비학회논문지
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• 제28권4호
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• pp.49-55
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• 2014

In this paper, we propose the cogging toque reduction technique of the dual stator radial flux permanent magnet generator. The cogging toque is caused by the torque ripple increase and vibration and noise of the generator. And it is important factor determining cut-in speed of the small wind generator. To reduce cogging torque, permanent magnet displacement was studied. And the theory of the permanent magnet displacement was formulated and the cogging torque reduction according to the permanent magnet displacement was confirmed through the finite element method.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2013년도 전력전자학술대회 논문집
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• pp.238-239
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• 2013

It is a crucial requirement to utilize an economical battery capacity for the wind energy conversion system. In this paper, the optimal BESS capacity is determined for the wind farm whose dispatched power is assigned by the min-max dispatching method. Based on a lifetime cost function that indicates the BESS cost spent to dispatch 1kWh wind energy into grid, the battery capacity can be optimized so as to obtain the minimum system operation cost. Moreover, the battery state of charge (SOC) is also managed to be in a safe operating range to ensure the system undamaged. In order to clarify the proposed optimizing method, a 3MW permanent magnet synchronous generator (PMSG) wind turbine model and real wind speed data measured each minute are investigated.

• 한국지능시스템학회논문지
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• 제26권5호
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• pp.351-360
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• 2016

Rapid population growth with high living standards and high electronics use for personal comfort has raised the electricity demand exponentially. To fulfill this elevated demand, conventional energy sources are shifting towards low production cost and long term usable alternative energy sources. Hybrid renewable energy systems (HRES) are becoming popular as stand-alone power systems for providing electricity in remote areas due to advancement in renewable energy technologies and subsequent rise in prices of petroleum products. Wind and solar power are considered feasible replacement to fossil fuels as the prediction of the fuel shortage in the near future, forced all operators involved in energy production to explore this new and clean source of power. Presented paper proposes fuzzy logic based Energy Management System (EMS) for Wind Turbine (WT), Photo Voltaic (PV) and Diesel Generator (DG) hybrid micro-grid configuration. Battery backup system is introduced for worst environmental conditions or high load demands. Dump load along with dump load controller is implemented for over voltage and over speed protection. Fuzzy logic based supervisory control system performs the power flow control between different scenarios such as battery charging, battery backup, dump load activation and DG backup in most intellectual way.

• Journal of Electrical Engineering and Technology
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• 제8권5호
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• pp.1021-1028
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• 2013

The frequency of a power system should be kept within limits to produce high-quality electricity. For a power system with a high penetration of wind generators (WGs), difficulties might arise in maintaining the frequency, because modern variable speed WGs operate based on the maximum power point tracking control scheme. On the other hand, the wind speed that arrives at a downstream WG is decreased after having passed one WG due to the wake effect. The rotor speed of each WG may be different from others. This paper proposes an algorithm for assigning the droop of each WG in a wind power plant (WPP) based on the rotor speed for the virtual inertial control considering the wake effect. It assumes that each WG in the WPP has two auxiliary loops for the virtual inertial control, i.e. the frequency deviation loop and the rate of change of frequency (ROCOF) loop. To release more kinetic energy, the proposed algorithm assigns the droop of each WG, which is the gain of the frequency deviation loop, depending on the rotor speed of each WG, while the gains for the ROCOF loop of all WGs are set to be equal. The performance of the algorithm is investigated for a model system with five synchronous generators and a WPP, which consists of 15 doubly-fed induction generators, by varying the wind direction as well as the wind speed. The results clearly indicate that the algorithm successfully reduces the frequency nadir as a WG with high wind speed releases more kinetic energy for the virtual inertial control. The algorithm might help maximize the contribution of the WPP to the frequency support.

• Journal of Power Electronics
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• 제9권4호
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• pp.612-622
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• 2009

The short circuit ratio (SCR) of a given grid is able to show the stability of the system in the case of unwanted elements, such as wind turbulence. This paper presents the simulation of a model of the doubly fed induction generator in the simulation software PSCAD/EMTDC. This model has been used to study flicker during continuous operation and the effect of SCR and grid impedance angle on flicker emission. Simulation results show that compensation of the stator reactive power is an effective method to considerably reduce the flicker levels, irrespective of the grid conditions.

• 전기학회논문지
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• 제58권3호
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• pp.531-538
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• 2009

The paper deals with an operation scheme to improve the forecasting of output range and to regulate the active power output of the hybrid system consisting of a doubly fed induction generator (DFIG) and a fuel-cell. The power output of the wind turbine fluctuates as the wind speed varies and the slip power between the rotor circuit and power converter varies as the rotor speed change. The power fluctuation of a DFIG makes its operation difficult when a DFIG is connected to grid. A fuel cell system can be individually operated and adjusted output power, hence the wind turbine and fuel cell hybrid system can overcome power fluctuation by using a fuel-cell power control. In this paper, a fuel-cell is performed to regulate the active power output in comparison with the regulated active power output of a DFIG. And it also improves the forecasting of output range. Based on PSCAD/EMTDC tools, a DFIG and a proton exchange membrane fuel cell(PEMFC) is simulated and the dynamics of the output power in hybrid system are investigated.

• 태양에너지
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• 제20권1호
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• pp.1-9
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• 2000

Wind turbine system converts wind energy into electric energy. Since the velocity of wind is random in nature, control of the angular velocity of the blade is necessary in order to generate high quality electric power. The control of a blade can be divided into a stall regulation and a pitch control types. The stall regulation type which is based on the characteristics of an aerodynamic stall of the blades is simple and cheap, but it suffers from fluctuation of the resulting power. Or the contrary, pitch control type is based on the fact that the torque of the blade can be changed by varying the pitch angle of the blade. It is mechanically and mathematically complicated, but the control performance is better than that of the stall regulation type. This paper suggests a method of denying a mathematical modeling of the wind turbine system, and develops a speed control algorithm by pitch control. The validity of the algorithm is demonstrated with the results produced through sets of simulation.

• Journal of Electrical Engineering and Technology
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• 제9권3호
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• pp.1096-1103
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• 2014

This paper proposes a novel strategy for attenuating the output power fluctuation of the wind farm (WF) in a range of tens of seconds delivered to the grid, where the kinetic energy caused by the large inertia of the wind turbine systems is utilized. A control scheme of the two-level structure is applied to control the wind farm, which consists of a supervisory control of the wind farm and individual wind turbine controls. The supervisory control generates the output power reference of the wind farm, which is filtered out from the available power extracted from the wind by a low-pass filter (LPF). A lead-lag compensator is used for compensating for the phase delay of the output power reference compared with the available power. By this control strategy, when the reference power is lower than the maximum available power, some of individual wind turbines are operated in the storing mode of the kinetic energy by increasing the turbine speeds. Then, these individual wind turbines release the kinetic power by reducing the turbine speed, when the power command is higher than the available power. In addition, the pitch angle control systems of the wind turbines are also employed to limit the turbine speed not higher than the limitation value during the storing mode of kinetic energy. For coordinating the de-rated operation of the WT and the storing or releasing modes of the kinetic energy, the output power fluctuations are reduced by about 20%. The PSCAD/EMTDC simulations have been carried out for a 10-MW wind farm equipped with the permanent-magnet synchronous generator (PMSG) to verify the validity of the proposed method.

• 한국정밀공학회지
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• 제29권6호
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• pp.693-701
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• 2012

In this study, a small wind turbine airfoil specialized for national wind condition was designed in order to develop the furling control type HAWT. And then a flow analysis was carried out based on the blade drawing which was designed to characterize of the developed airfoil. The result of the flow analysis showed that the torque on the 3 blades was 180.23N.m. This is equivalent to an output power of 5.66kw and an output efficiency of 0.44. Then we produced and constructed a 3kW - furling control type HAWT by getting the system unit design technology such as the specialized furling control device. By operating this turbine, we could get 3kW of the rated power at a wind speed of 10.5m/s through the ability test. Cut-in wind speed was 2m/s, generator efficiency was 92% at the rated power output. Sound power level was 87.2dB(A). Also we observed that the output power was limited to 10.5m/s with furling system operation.