Although FRT capability is claimed in Japanese grid code for RE, DVS capability is not. In some European countries, not only FRT but also DVS is claimed. Whether this choice of our grid code is pragmatically adequate or not? To answer the question, it is necessary to evaluate FRT and DVS capabilities. But the past studies only evaluated qualitative merit of FRT and DVS, or evaluated quantitative merit on fictional system models. Since the authors intend to evaluate FRT and DVS capabilities in existing power system of Japan, some method for the evaluation must be invented. For the evaluation, values of FRT and DVS capabilities are evaluated by reduction amount of stabilizing equipment (i.e. SVC in the paper). The evaluation based on strict optimal SVC disposition is quite difficult, because existing power system must be adequately modeled, because number of SVCs is large and because every power flow conditions must be considered. However, semi‐optimal SVC disposition can be calculated as shown in the paper. As the result, value of FRT is quite larger than value of DVS. And then, our grid code is proved as pragmatically adequate, except some flaw in claimed FRT design that is introduced in the paper.
Although FRT capability is claimed in Japanese grid code for RE, DVS capability is not. In some European countries, not only FRT but also DVS is claimed. Whether this choice of our grid code is pragmatically adequate or not? To answer the question, it is necessary to evaluate FRT and DVS capabilities. But the past studies only evaluated qualitative merit of FRT and DVS, or evaluated quantitative merit on fictional system models. Since the authors intend to evaluate FRT and DVS capabilities in existing power system of Japan, some method for the evaluation must be invented. For the evaluation, values of FRT and DVS capabilities are evaluated by reduction amount of stabilizing equipment (i.e. SVC in the paper). The evaluation based on strict optimal SVC disposition is quite difficult, because existing power system must be adequately modeled, because number of SVCs is large and because every power flow conditions must be considered. However, semi-optimal SVC disposition can be calculated as shown in the paper. As the result, value of FRT is quite larger than value of DVS. And then, our grid code is proved as pragmatically adequate, except some flaw in claimed FRT design that is introduced in the paper. K E Y W O R D SDVS, FRT, grid code, induction motor load, power system, renewable energy 1. Evaluation must be applied not to just a simple system model, but to one that appropriately describes real systems. 2.Optimal SVC allocation to maintain system stability must be determined for faults that may occur anywhere in the Electr Eng Jpn. 2018;205:33-40.
Although output of individual RE (Renewable Energy) such as PV (Photovoltaic Generation) severely varies, total output of many REs locate with geographical diversity is considerably smoothed out. The phenomenon is well known and is called as (mutual) smoothing effect. To quantitatively and mathematically express it, a theory named "Transfer Hypothesis" using "Transfer Swing Period Tx" as an important parameter is presented. Since the theory regards the effect as a kind of low pass filter, the theory can be applied to not only spectrum on frequency axis but also time sequential data.However, whole view of factors that affect Tx is not made clear yet. Therefore, it is questionable that once identified Tx in the studied area can be always adequate for practical use. The paper verifies the adequacy. Seasonal factors such as month and week, impact by number of sites in the studied area, and geographical factors such as distance between neighboring sites and studied area's size are examined. It has been demonstrated that Tx of two sites strongly depends on their distance, that number of sites does not affect Tx, and that Tx of the studied area is equal to that of two sites separated a distance 1/3 the length of the studied area. Therefore, it has been found that long time measurement on many sites is not necessary to identify Tx. K E Y W O R D Sirradiance, mutual smoothing effect, photovoltaic generation, renewable energy, transfer hypothesis, transfer swing period 10
Although output of individual RE (Renewable Energy) such as PV (Photovoltaic Generation) severely varies, total output of many REs locate with geographical diversity is considerably smoothed out. The phenomenon is well known and is called as (mutual) smoothing effect. To quantitatively and mathematically express it, a theory named "Transfer Hypothesis" using "Transfer Swing Period Tx" as an important parameter is presented. Since the theory regards the effect as a kind of low pass filter, the theory can be applied to not only spectrum on frequency axis but also time sequential data.However, whole view of factors that affect Tx is not made clear yet. Therefore, it is questionable that once identified Tx in the studied area can be always adequate for practical use. The paper verifies the adequacy. Seasonal factors such as month and week, impact by number of sites in the studied area, and geographical factors such as distance between neighboring sites and studied area's size are examined. It has been demonstrated that Tx of two sites strongly depends on their distance, that number of sites does not affect Tx, and that Tx of the studied area is equal to that of two sites separated a distance 1/3 the length of the studied area. Therefore, it has been found that long time measurement on many sites is not necessary to identify Tx. K E Y W O R D Sirradiance, mutual smoothing effect, photovoltaic generation, renewable energy, transfer hypothesis, transfer swing period 10
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