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Conventional methods to schedule power generators maintenance aim to secure enough supply reserve margin to the power system when its power generators have to go under maintenance. However, the use of such methods in scenarios of large penetration of VRE, might be problematic. This is because in such scenarios conventional scheduling methods might inadvertently concentrate maintenance operations when residual demand is particularly low, creating situations in which there is insufficient supply‐demand balancing capability and inertia to operate the power system properly. In this study, we present the development of a new method to schedule generator maintenance that ensure inertia and balancing capability constraints, and show its effectiveness. [ABSTRACT FROM AUTHOR]

Abstract: The growth of renewable energy penetration on power grids is reaching high levels in many countries around the world. In such high‐penetration scenarios, the proper characterisation of the intermittency of renewable power generation becomes important to the operation of power grids. In this study, using the most recent high‐resolution global horizontal irradiance data in Japan, we characterise short‐term fluctuations of photovoltaic (PV) power in regional scale, in a scenario of high penetration of PV. We analysed 1 year of data with a resolution of 10 seconds for the Kanto area in Japan. The results show that the distribution of the short‐term fluctuations is non‐Gaussian, presenting a shape similar to a Laplacian distribution. In addition to statistical aspects, a methodology is presented to evaluate the fluctuations considering aspects relevant to power grid operators. Applying this methodology, we show that the highest fluctuations within the time frame of secondary regulation control of frequency reached 5% of the hourly power demand. Fluctuations of PV power within the primary regulation control time frame were within 3% of hourly power demand, and the 99th percentile of the fluctuations was within 1% of it. With the proposed methodology, which can be generally applied, we go beyond the description of statistical properties of short‐term fluctuations of PV, showing also the importance to evaluate them in a context relevant to power grid operators. [ABSTRACT FROM AUTHOR]

SUMMARY The high penetration of variable sources of renewable power generation will lead to operational difficulties in supply/demand balancing in the entire power system. The mass deployment of electric vehicles (EVs) and plug-in hybrid vehicles (PHEVs) will also cause significant changes in electricity demand. Therefore, controlling and managing the charging time of EVs/PHEVs are effective approaches that are imperative for improving balancing in power system operation. We assumed travel patterns for EVs in a model of the future Tokyo power system and analyzed the power system loads, including the charging load of the EVs, under several charging control scenarios. We verified that charging time controls are substantially effective for reducing the fuel costs in the power system. Further, we found that load leveling under a multicar charging management scenario gave the best results in terms of the fuel costs in all cases. [ABSTRACT FROM AUTHOR]

SUMMARY To assure power system stability when variable photovoltaic (PV) power generation is deployed on a large scale, accurate irradiance forecasting will be important in the near future. A substantial amount of PVs will be generating power at numerous locations in the power service area, and it will be necessary to predict the total PV output for supply/demand balancing control. Therefore, irradiance forecasting accuracy should be verified using the total irradiance at numbers of sites equivalent to areas with large-scale PV deployment. This paper reports an investigation of the accuracy of an approach to area total irradiance prediction based on regional numerical weather prediction data from the Japan Meteorological Agency. The forecast area total irradiance is compared to the assumed total area irradiance for numbers of sites equivalent to large-scale PV deployment. [ABSTRACT FROM AUTHOR]

The development of methods to forecast photovoltaic (PV) power generation regionally is of utmost importance to support the spread of such power systems in current power grids. The objective of this study is to propose and to evaluate methods to forecast regional PV power 1 day ahead of time and to compare their performances. Four forecast methods were regarded, of which two are new ones proposed in this study. Together, they characterize a set of forecast methods that can be applied in different scenarios regarding availability of data and infrastructure to make the forecasts. The forecast methods were based on the use of support vector regression and weather prediction data. Evaluations were performed for 1 year of hourly forecasts using data of 273 PV systems installed in two adjacent regions in Japan, Kanto, and Chubu. The results show the importance of selecting the proper forecast method regarding the region characteristics. For Chubu, the region with a variety of weather conditions, the forecast methods based on single systems' forecasts and the one based on stratified sampling provided the best results. In this case, the best annual normalized root mean square error (RMSE) and mean absolute error (MAE) were 0.25 and 0.15 kWh/kWhavg, respectively. For Kanto, with homogeneous weather conditions, the four methods performed similarly. In this case, the lowest annual forecast errors were 0.33 kWh/kWhavg for the normalized RMSE and 0.202 kWh/kWhavg for the normalized MAE. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Under the anticipated high penetration of variable renewable energy generation such as photovoltaics and higher share of nuclear generation, the issue of supply-demand balancing capability should be evaluated and fixed in a future power system. Improvement of existing balancing measures and new technologies such as demand activation and energy storage are expected to solve the issue. In this situation, a long-range power system supply-demand analysis should have the capability to evaluate the balancing capability and balancing countermeasures. This paper presents a new analysis methodology of activated demand model and evaluation of supply-demand balancing capability for a long-range power system demand-supply analysis model, ESPRIT. Model analysis was made to verify the new methodology of the tool including day-ahead scheduling of a heat pump water heater, an EV/PHEV, and a battery. [ABSTRACT FROM AUTHOR]

It is generally believed that large battery systems will be needed to store surplus electric energy due to the high penetration of renewable energy (RE) such as photovoltaic generation (PV). Since the main objective of high penetra-tion of RE is to reduce C02 emissions, reducing kWh output of thermal generation that emits large amounts of C02 in power systems should be sufficiently considered. However, thermal generation plays an important role in load fre-quency control (LFC) of power systems. Therefore, if LFC could be performed with batteries and hydropower genera-tion, the kWh output of thermal generation could be re-duced significantly. This paper presents a method of LFC using batteries in a power system with highly penetrated PVs. An assessment of the effect of the proposed method considering mutual smoothing effect of highly penetrated PVs is made. [ABSTRACT FROM AUTHOR]

ABSTRACT The development of a methodology to forecast accurately the power produced by photovoltaic systems can be an important tool for the dissemination and integration of such systems on the public electricity grids. Thus, the objective of this study was to forecast the power production of a 1-MW photovoltaic power plant in Kitakyushu, Japan, using a new methodology based on support vector machines and on the use of several numerically predicted weather variables, including cloudiness. Hourly forecasts of the power produced for 1 year were carried out. Moreover, the effect of the use of numerically predicted cloudiness on the quality of the forecasts was also investigated. The forecasts of power production obtained with the proposed methodology had a root mean square error of 0.0948 MW h and a mean absolute error of 0.058 MW h. It was also found that the forecast and measured values of power production had a good level of correlation varying from 0.8 to 0.88 according to the season of the year. Finally, the use of numerically predicted cloudiness had an important role in the accuracy of the forecasts, and when cloudiness was not used, the root mean square error of the forecasts increased more than 32%, and the mean absolute error increased more than 42%. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT The installed capacity of photovoltaic (PV) systems has recently increased at a much faster rate than the development of grid codes to effectively and efficiently manage high penetrations of PV within the distribution system. In a number of countries, PV penetrations in some regions are now raising growing concerns regarding integration. Management strategies vary considerably by country-some still have an approach that PV systems should behave as passive as possible, whereas others demand an active participation in grid control. This variety of grid codes also causes challenges in learning from 'best practice.' This paper provides a review of current grid codes in some countries with high PV penetrations. In addition, the paper presents a number of country-specific case studies on different approaches for improved integration of PV systems in the distribution grid. In particular, we consider integration approaches using active and reactive power control that can reduce or defer expensive grid reinforcement while supporting higher PV penetrations. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

With the increase in the size and capacity of electric power systems and the growth of widespread interconnections, the problem of power oscillations due to the reduced system damping has become increasingly serious. Since a Superconducting Magnetic Energy Storage (SMES) unit with a self-commutated convener is capable of controlling both the active (P) and reactive (Q) power simultaneously and quickly, increasing attention has been focused recently on power system stabilization by SMES control. This paper describes the effects of SMES control on" the damping of power oscillations. By examining the case of a single generator connected to an infinite bus through both theoretical analyses and experimental tests (performed with a SMES unit with maximum stored energy of 16 kJ and an artificial model system), the difference in the effects between P and Q control of SMES is clarified as follows: (1) In the case of P control, as the SMBS unit is placed closer to the terminal of the generator, the power oscillations will decay more rapidly. (2) In the case of Q control, it is most effective to install the SMES unit near the midpoint of the system. (3) By comparing the P control with Q control, the former is more effective than the latter based on the conditions that the SMES unit location and the control gain are the same. [ABSTRACT FROM AUTHOR]

SUMMARY: Mutual 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. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(3): 31–42, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com). DOI 10.1002/eej.22327 [ABSTRACT FROM AUTHOR]