In this paper, it is reported that energy capacitor system (ECS), which combines power electronic devices and electric double-layer capacitor, can significantly decrease voltage and power fluctuations of grid-connected fixed-speed wind generator. The proper selection of wind farm output power reference is still a problem for smoothing the wind farm output power. This paper proposes exponential moving average to generate the reference output power of a grid-connected wind farm. The objective of the control system is to follow the line power reference by absorbing or providing real power to or from the ECS. Moreover, the necessary reactive power can also be supplied to keep the wind farm terminal voltage at the desired reference level. Real wind speed data were used in the simulation analyses, which validate the effectiveness of the proposed control strategy. Simulation results clearly show that our proposed ECS can be suitable for wind power application.

The spread of wind power generation is progressed hugely in recent year from viewpoint of environmental problems including global warming. Though wind power is considered as a very prospective energy source, wind power fluctuation due to the random fluctuation of wind speed has still created some problems. Therefore, research is going on how to smooth this wind power fluctuation. This paper presents energy capacitor system (ECS) which consists of electric double-layer capacitor (EDLC) and power electronics devices and works as an electric power storage system for generated output leveling the output power. Moreover, hydrogen is paid to attention in recent year from viewpoint of exhaustion problem of fossil fuel. Therefore the hydrogen generator (HHOG) is also installed at the wind farm to generate hydrogen. In this paper, the effectiveness of the proposed system is verified by the simulation analyses using PSCAD/EMTDC. Figure 1 shows the model system used for the simulation analyses of the proposed system. The output of the squirrel-cage induction generator, which works as wind generator (50 [MVA] power rating) is smoothed with ECS (20 [MVA] power rating), and hydrogen gas is produced constantly from the hydrogen generator(10 [MVA] power rating). In this paper, to verify the effectiveness of the proposed system, the real wind speed data is used which was obtained Fig. 1. Model system in Hokkaido Island, JAPAN. As rigid conditions, −4 [m/s] and +4 [m/s]of real wind speed was used as Case 1 and Case 2.The simulation result is shown in Fig. 2. In a low wind speed of Fig. 2(a), it is clear that when ECS is used, the line power can be smoothed well. In a high wind speed of Fig. 2(b), since the pitch controller is used to maintain the IG real power at the rated level, the fluctuation of the line power is small. In this case, when ECS is used the line power can be smoothed. In hydrogen generator, it can be confirmed the constant hydrogen generation by constant power consumption as shown in Fig. 2(c). The amount of the hydrogen gas generation is 254 [Nm 3 ] in 600 sec simulation time. From these results, it can be concluded that the proposed system can operate effectively in power systems to generate constant hydrogen as well as generate high quality electrical power from the natural fluctuating wind. (a) Line Power (Case 1 [low wind speed]) (b) Line power (Case 2 [high wind speed]) (c) Amount of hydrogen gas generation Fig. 2. Simulation result -2 -

The spread of wind power generation has progressed hugely in recent years from the viewpoint of environmental problems including global warming. Though wind power is considered as a very prospective energy source, wind power fluctuation due to the random fluctuation of wind speed has still created some problems. Therefore, research has been performed on how to smooth the wind power fluctuation. This paper proposes Energy Capacitor System (ECS) for the smoothing of wind power which consists of Electric Double‐Layer Capacitor (EDLC) and power electronics devices and works as an electric power storage system. Moreover, hydrogen has received much attention in recent years from the viewpoint of the problem of exhaustion of fossil fuel. Therefore, it is also proposed that a hydrogen generator be installed at the wind farm to generate hydrogen. In this paper, the effectiveness of the proposed system is verified by simulation analyses using PSCAD/EMTDC. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(3): 10–18, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20864

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