It is well known that Transient Energy Function (TEF) method is useful for the efficient transient stability assessment represented by the estimation of critical clearing time (CCT). However, there still remains an issue for the practical use that most of the TEF methods adopt the classical model of a synchronous machine where an internal generated voltage is assumed to be constant. Besides, critical generated output can be more practical stability index instead of CCT used in the conventional TEF methods. In this paper, a conventional hybrid TEF method is developed for the estimation of the transient stable critical generated power by application of improved hybrid simulation. The proposed method can deal with the detailed model for the synchronous machine, and estimate the critical generated power with higher accuracy. Demonstrative result is presented for large network model in order to verify the practicability of the proposed method.
In this paper, we propose three applications evaluating the N-1 security quantitatively with increased uncertainties. By using Robust Dynamic Security region (RDS), which is based on the concept of Robust Power System Security (RS), the key region for judging the security and a new evaluation index for quantitative analysis, we can evaluate power system security as follows. (1) The calculation of RDS at the time of yearly peak load demand can be recognized as the benchmark of the N-1 security at present and this method can be applied to the future power system with increased renewable energy sources (RES) such as PV. (2) We show the yearly declining trend of the N-1 security owing to the increased PV penetration year by year. (3) We calculate the necessary amount of additional power supply capacity, including conventional electric power generators or storage batteries, needed for maintaining the N-1 security same as the present level. The effectiveness of the proposed method is demonstrated through simulations using a three machines model system.
The Japanese government has set the target amount of PV penetration 53GW by 2030. However, a large penetration of PV will cause several problems in power systems. One of these problems is the voltage increase due to decreased load demands associated with large PV active power output. Another problem is voltage variation caused by PV system output variation. In this paper, we focus our attention on voltage and reactive power control for large PV penetration and propose voltage control using PF (PV Power Factor), SC (Static Capacitor) and TAP (Transformer Tap). In the proposed method, the SC and TAP controls consider voltage stability by the use of VMPI-i and VMPI-i Sensitivity, and the PF control suppresses voltage variation and voltage increase. Finally, we simulate the controls with the Ward-Hale system to verify the validity of the proposed method.
Generally, Static Capacitors (SCs) for improving the power factor are installed in high voltage consumers and they are controlled by Automatic Power Factor Controller (APFC). However, the optimal capacity of SC can reduce the loss of the transformer and suppress the harmonic currents. Therefore, this paper proposes the novel control method of the SC for improving plural power quality, such as power factor, voltage and the harmonic currents comprehensively. The proposed method is implemented to the DSP board as the controller. The effectiveness of the method is confirmed by using Real-Time Simulator (RTS) and the experimental setup.
We compare the electrical performance and fluid phenomena of a liquid metal magnetohydrodynamic (LMMHD) power generator equipping electrodes with a finite electrical conductivity by using four different working fluids: mercury, NaK78, Galinstan and U-alloy47. Three-dimensional unsteady numerical simulations of turbulent duct flows under a non-uniform magnetic field are carried out. The profiles of the Hartmann layer and the wall-jet flows with M-shaped mean streamwise velocity are varied in accordance with the interaction parameter, which differs for each working fluid. A large interaction parameter decreases the wall friction loss and improves electrical efficiency. The finite electrical conductivity of electrode causes Joule loss and leads to a deterioration of efficiency. These results lead to the conclusion that a liquid metal with a high interaction parameter and a low electrical conductivity for reducing the electrical conductivity ratio of the fluid to electrodes will yield high electrical efficiency.
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.