To achieve carbon neutrality, variable renewable energy penetration will be desired. But installing the variable renewable energy invites decrease in the ratio of synchronous machines, because variable renewable energy is mainly consists of inverter based resources. The power system stability is maintained with the inertia energy of conventional synchronous machines. At the same time of synchronous machines decrease, the stability of the power system will decrease. To keep the stability of the power system, we will try to develop inverters with virtual inertia. The basic development policy is described in this paper.

It is necessary to understand the situation in Western balancing service markets where they established them ahead of Japan to extract future issues and suggestions for Japan's balancing service market. We took up PJM in the U. S., Regelleistung in Germany, and National Grid ESO in the U. K., where DSR market participation is advanced, and surveyed the following three research perspectives. (1) regulation of balancing service markets, (2) DSR participation and price trends in the markets, and (3) business cases of DR and virtual power plants (VPP).

Aged CVTs have been often used in substations, but the expected lifetime of CVTs is unclear, so that it is difficult to determine the appropriate renewal time. Therefore, in this paper, we focus on oil-impregnated paper capacitors inside CVTs and propose a concept to evaluate their expected lifetime based on the partial discharge (PD) progress characteristics. By using a fundamental oil-impregnated paper capacitor model, the PD progress characteristics were measured and discussed from electrical and optical aspects.

This study proposes a new method to estimate the concentration of the furfural contained in the insulating oil of oil-filled transformer based on infrared spectroscopic spectrum of the insulating oil. In this study, first, spectrometry is carried out on the insulating oil collected and prepared by on-site sampling, accelerated aging test, and mixing and stirring. Second, selected explanatory variable from correlation coefficient between absorbance and furfural content in the oil. Finally, furfural content was estimated by PLS regression using various wavenumber patterns, and the results were compared to verify what kind of wavenumber pattern is useful.