A Method for Presuming Total Output Fluctuation of Highly Penetrated Photovoltaic Generation Considering Mutual Smoothing Effect

Abstract

SUMMARYMutual smoothing effect of renewable energy (RE) is quite important because the amount and cost of countermeasures for maintaining soundness of power systems highly depend on evaluation of the effect. In spite of its importance, there is as yet no established method to evaluate the effect. The authors present a method for presuming the total output fluctuations of highly penetrated RE from a few measured data considering the effect. By analyzing the measured data, existing photovoltaic (PV) output fluctuations are revealed to be coherent at slower swing periods and random at faster swing periods. To represent the PV's output fluctuation tendencies, a "Transfer Hypothesis" is introduced. A "Constant Transfer Swing Period Hypothesis" and "-20 dB/dec Slope Hypothesis" are also introduced. These hypotheses are verified by direct and indirect methods using the measured data. Only 3 sites' data are able to presume total fluctuation of 15 sites successfully. The relationship between distance and the transfer swing period for every 2 sites out of the 15 sites agrees with these hypotheses. Finally, the authors show the total fluctuation presumption of highly penetrated PV deployment in the Hokuriku region using the proposed methods.

Development of Estimation Method of Spatial Average Irradiance Fluctuation Characteristics Considering Smoothing Effect around Observation Point

“…First, we verify the validity of the transfer hypothesis [7] in case of ensemble irradiance fluctuations at N points, and estimate the size of an area in which ensemble irradiance fluctuations can be represented by fluctuations at a single point. First, we verify the validity of the transfer hypothesis [7] in case of ensemble irradiance fluctuations at N points, and estimate the size of an area in which ensemble irradiance fluctuations can be represented by fluctuations at a single point.…”

“…The frequency characteristic S mea ( f ) of the spatial-average irradiance fluctuations is defined using S coh ( f ), S ran ( f ), and the period T x at which the synchronism collapses [7]. The frequency characteristic S mea ( f ) of the spatial-average irradiance fluctuations is defined using S coh ( f ), S ran ( f ), and the period T x at which the synchronism collapses [7].…”

“…In addition, the idea of the 1∕ √ N rule was extended to estimate the output fluctuations of PVS groups with periods below 100 min by varying N according to the fluctuation period [5]. On the other hand, regarding fluctuations with periods from several tens of minutes to several hours, it was shown, based on irradiance data observed in Hokuriku Region, that the smoothing effect according to the observation point density can be expressed by using the transfer hypothesis [7]. We calculated the weighted average irradiance at 61 observation points and found that there are several days in a year when the maximum fluctuation width estimated by a 120-min window is as large as 400 W/m 2 [6].…”

“…However, the independence of long-period fluctuations among different observation points was not confirmed, and such fluctuations are assumed to be synchronous in a certain area around the observation point. [7], irradiance fluctuation parameters observed at multiple locations are used to express the frequency characteristics of actual spatial-average irradiance fluctuations through assumedly synchronous and independent components. However, the smoothing effect around the observation points was not taken into account, and the maximum fluctuation width of the short-period fluctuation could be overestimated.…”

Evaluation Method for Real-Time Dynamic Line Ratings Based on Line Current Variation Model for Representing Forecast Error of Intermittent Renewable Generation

“…Actual monitored solar irradiation data (minute by minute) for Osaka, Japan, were used to generate the fluctuation in the output power of the PV system. We considered the spatial smoothing effect of the solar irradiation data based on the transfer hypothesis [31,32]. Moreover, based on this hypothesis, we have analyzed the effect of spatial smoothing on the variation in line temperature; this paper adopted Case B (where the area is 100 km 2 ) in [33].…”