Electric power generation that relies on various sources as the primary sources of energy is expected to bring down CO2 emissions levels to support the overall strategy to curb global warming. Accordingly, utilities are moving towards integrating more renewable sources for generation, mostly dispersed, and adopting Smart Grid Technologies for system control. In order to construct, operate, and maintain power systems stably and economically in such background, thorough understanding about the characteristics of power systems and their components is essential. This paper presents modeling and simulation techniques available for the analysis of critical aspects such as thermal capacity, stability, voltage stability, and frequency dynamics, vital for the stable operation of power systems.
The report modeled an electricity interchange trade between a PPS (Power Producer and Supplier) and a cogeneration user, and evaluated the trade using the optimizing simulation. In this simulation model, cogeneration user and PPS behave economically optimizing independently. The aim of this report was to evaluate the energy consumption under the economical electricity interchange. The computed estimations answered that the primary energy consumption was reduced in proportion to electricity interchange amount, even if the electricity efficiency of cogeneration was low than the grid's efficiency. From the comparison with energy formula and the computed estimation, the operation of cogeneration was shown to choose the heat-load-following mode and to utilize the waste heat. This was the reason to reduce the primary energy consumption and the energy cost, by interchange of CGS surplus electricity.
In the transport sector, Plug-in Hybrid Electric Vehicle (PHEV) is being developed as an environmentally friendly vehicle. PHEV is a kind of hybrid electric vehicle, which can be charged from power grid. Therefore, when analyzing reduction effect of CO2 emission by PHEVs, we need to count the emission from the power sector. In addition, the emission from the power sector is greatly influenced by charge pattern, i.e. timing of charge. For example, we can realize the load leveling by bottom charge, which charges late at night. If nuclear power plants were introduced by load leveling, we could expect substantial CO2 reduction. This study proposes an algorithm for bottom charge based on load-duration curve of charging. By adjusting the amplitude of charging power, we can bring the shape of curve close to that of ideal bottom charge. We evaluated the algorithm by using optimal generation planning model. The evaluation index is a difference between Target case, in which PHEVs ideally charge to raise the bottom demand, and Proposal case, in which PHEVs charge using the proposed algorithm. Annual CO2 emissions of Target case and Proposal case are 20.0% and 17.5% less than that of Reference case. Percentage of the reduction effect of Proposal case to that of Target case results in 87.5%. These results show that the proposed algorithm is effective in bottom-up of daily load curve.
Time dependent three-dimensional numerical analysis is carried out in order to clarify causes of voltage loss occurring near power takeoff regions and to suggest how to reduce the voltage loss for the scramjet engine driven MHD generator which was developed under the hypersonic vehicle electric power system program in USA. The numerical results under the experimental condition show that the local positive electric field is induced near the power takeoff electrodes. The phenomenon is due to the electric field loss by the high electric current through the weakly ionized plasma with low temperature and also by the low electromotive force near the power takeoff electrodes. When the configuration of power takeoff electrodes is modified, the current density near the power takeoff electrodes becomes small and the electromotive force becomes strong. The electric power output under the optimum electrode configuration of power takeoff is improved by 22 percent, compared with the value under the experimental condition.
There are many PWM control apparatuses, which are higher harmonics current sources, in distribution systems. And higher harmonics causes over current by parallel resonance. To avoid the over current, it is necessary to predict frequency characteristics of resonance. In this paper, a new prediction method is proposed. Firstly the line model, in which frequency characteristics of line inductance and resistance are taken account, are approximated by R-L parallel circuits. And then, using eigen value and eigenvector, the problem is decomposed to each eigen mode problem. Moreover, to get a bird's-eye view of phenomenon, a variable separate type approximate is introduced. Finally a new index matrix, which gives the distribution of over current, is introduced.
On constructing a microgrid, it is essential to design capacity of photovoltaic power generation (PV) systems and storage batteries in accordance with a control target. In this study, we constructed a simulation model of energy control system in the microgrid used in the demonstration project. By using this model, we investigated the minimum capacity of NaS battery for different PV system capacities for keeping the target power imbalance within ±3% over 30 min. The main results are as follows. The microgrid involving 330-kW PV systems (corresponding to the actual system) needs a NaS battery capacity of at least approximately ±20kW, and PV systems with a capacity up to about 890kW can be integrated in the microgrid with a NaS battery capacity of ±500kW (corresponding to the actual system). We estimated the minimum capacity of NaS battery for different PV system capacities and clarified that the output behavior of the NaS battery and PAFC when supply and demand power imbalance over 30 min. exceeds the ±3% limit. We suggested the improved control model and showed that it is effective in decreasing the minimum capacity of NaS battery, although it has negative effects on the reduction of short-period power flow fluctuation at the grid-connection point.
The IEEJ has published useful papers for electric power and energy systems. These papers published in IEEJ transactions contribute to special engineers to receive the doctor degree or understand newly developed technologies etc. But, it is very important to know the impression of young students about IEEJ transactions papers considering the technology transfer. This paper describes reaction comments of next generation university students under learning engineering of design and drawing of power equipments in 2009 after the Lehman Shock (the Lehman Brothers' worldwide economical collapse dated Sept. 15 2008).
In this technical note, fundamental characteristics of lightning to tall structures are described, and recent researches related to lightning to tall structures are reviewed. In Section 2, the relationship between the incidence of lightning to a tall structure and the structure height, and that between the incidence of upward lightning initiated from a tall structure and the structure height, both of which were obtained by Eriksson empirically, are shown. Also, winter lightning strikes to tall structures and to wind-turbine-generator towers located on the coastal area of the Sea of Japan are described. In Section 3, characteristics of a current wave propagating along a tall structure hit by lightning are discussed. Also, simplified transmission-line representations for lightning strikes to a tall structure and to flat ground are shown, and dependences of the peak current on the observation height (top or bottom of the structure) and on the current risetime, obtained from the analysis using the simplified representations, are shown. In Section 4, median values of lightning currents measured on tall structures are shown. In Section 5, the electromagnetic field environment in the vicinity of a tall structure hit by lightning is discussed. Also, the far-field enhancement factor and the far-field-to-current conversion factor for lightning strikes to tall structures are shown.