Magnetomechanical coupling is introduced in the assembled domain structure model, which is an energy-based multiscale magnetization model. The magnetoelastic interaction between mesoscopic particles was taken into account. The magnetization processes of grain-oriented and non-oriented steel were simulated. Magnetization curves in the rolling and transverse directions of a grain-oriented electrical steel were reconstructed. The degradation of non-oriented electrical steel by an external stress is also represented.
We are developing the power trading support system for judgement on making contract of negotiation transaction. About this system, fast derivation method of revenue distribution is developed. Calculation amount of deriving revenue is very large, because risk factors take a various value. Revenue is derived using “cost function” which represents the price against the amount of electricity generation. The total number is same as combination of risk factors. So in developed method, risk factors are considered sequentially in calculation, and temporary cost function is assembled on each step. We evaluated the trade-off of between effect of acceleration and error amount by example. We got the prospects that cumulative probability error is within 2% and calculation time is within 1 minute.
Since it has become obvious that half or more electricity is used by induction motors, modeling of induction motor load has become regarded as essential in power system stability analyses even in Japan, because power system stability can be extremely spoiled by motor's stall phenomenon. Therefore, for understanding and explanation of motor's stall phenomenon, some theory has also become recognized as essential. The authors had demonstrated that motor's stall can be well explained by “torque-speed curve” considering impedance of power system side by analysis, simulation, and experiment. By the way, stall can be regarded as “fast voltage instability” making a pair with “slow voltage instability” caused by run-away of on-load tap changer. Since “slow voltage instability” has been well explained by “P-V curve”, it seems desirable that “fast voltage instability” (i.e. stall phenomenon) is also explained by “P-V curve”. In P-V curve for explaining motor's stall, it becomes an issue how mechanical output torque that depends on only motor speed can be considered. On one hand, T-ω curve can be successfully translated onto P-V plane. On the other hand, “stability boundary curve” is introduced from past studies. These two theories, which seem different at a glance, are demonstrated as equivalent and well agree with simulation result.
An operation planning model of power generation system with high renewable energy penetration is presented, taking into account renewable-forecasting error distribution and the required flexibility capabilities. By using the model, we can analyze the production cost impact of flexibility-supplying technologies such battery energy storage and controllable heat pump water heaters. A supposed power system with high renewable energy penetration is taken as an example. The analysis results show that the introduction of battery storage systems and demand responsive heat pump water heaters could make lower the on-line capacity of partial-load gas-fired power generation units and make base load power generation units more utilized, which leads to the yearly production cost reduction.
Recently, advanced “smart meters” have been introduced widely to electric power distribution lines. Since smart meters consist of many low-voltage electronic devices, their vulnerability to disturbances such as lightning surges is a matter of concern. Therefore, to establish an effective lightning protection countermeasure against these disturbances, we have been investigating the lightning failure aspects of electronic watt-hour meters (WHMs), which have a function similar to that of a watt-meter section in smart meters. In this paper, we explored countermeasures for improving the performance of WHMs against the lightning transient magnetic fields. At first, we examined the performance of WHMs by lightning impulse current tests. As a result, it has become clear that the increase in distance between a bus conductor and a processing unit and magnetic shield of a processing unit are effective in reducing the probability of failures caused by the transient magnetic fields. Next, we proposed a calculation method of the lightning failure rate of WHMs based on a lightning surge analysis. The calculation results indicate that the failure occurs more frequently by subsequent strokes than by first strokes or if the grounding resistance of a pole transformer is higher.
This paper presents development results of a five-stage DC-1MV Ultrahigh Voltage Generator for ITER. Each generator outputs -200kV, and the total 5 generators are connected in series and outputs -1MV. In order to realize the DC-1MV output and 1-hour continuous operation, a feasibility of both gas insulation and gas cooling for semiconductor devices was validated. A simplified structure with stud-type diodes and heatsinks resulted in the compatibility of enough insulation distance and wide cooling surface. Withstand voltage tests and a temperature rise test were performed for the actual equipment of the rectifier and the step-up transformer. These test results verified the validity of the proposed design.
This paper discusses multiphase flashover in a Japanese 6.6kV medium voltage line. The multiphase flashover causes a short circuit in the line, and sometimes causes serious damages in power apparatuses and cables. Insulator voltage shows short-tail and stairwise waveform due to traveling waves reflected from neighbor poles and flashovers on the other insulators. A flashover on an insulator is determined using an integration method, which can consider an influence of voltage waveform on the flashover and can be used in the EMTP. Parameters such as grounding resistance, wavefront duration, power-frequency voltage and line configuration are examined to investigate the multiphase flashover in a medium voltage line. The simulation results suggest the insulator waveform significantly affect the multiphase flashover, and the integration method is an important tool for accurate lightning surge analysis with special reference to the multiphase flashover. This paper proposes an unbalanced insulation in power distribution line to reduce the multiphase flashover.
The Editorial Committee is working in planning and editing of the publication of Power and Energy Society. In this article, activities of the committee of the last term are reported, and recent trend and future problems are also discussed. The process of planning and editing of the publication, and the challenges to reduce the necessary months for reviewing papers and to increase the number of submitted papers are shown.