Lightning strikes affect wind power operations not only when accidents occur. If a wind turbine in the winter lightning area along the Sea of Japan is struck by lightning, the operator must promptly shut down the wind turbine. The wind turbines will be restarted after confirming that restarting them will not cause any major accidents. If the environment allows for quick inspections and restarting of wind turbines after shutdown, the impact of lightning shutdowns on the availability can be minimized. In this paper. the soundness monitoring for wind turbines is explained.

The AC tie-line model in power supply-demand and frequency analysis generally calculates the tie-line power flow only by the rotor angle deviation between control areas and the synchronizing torque coefficient. However, this model does not consider the damping of inter-area oscillation and instantaneous changes in tie-line power flow due to power supply-demand imbalance. Therefore, we propose an improved AC tie-line model considering these factors in this study.

Grid forming inverters are expected to be installed in the utility grid in the near future, because they can provide inertia and short circuit capacity that are likely to decrease due to abolishment of thermal power plants. Also, these inverters have the advantage of enabling stand-alone operation for microgrid or business continuity plan. Since a conventional grid following inverter controls its output current directly, it is easy to prevent overcurrent in an event of a grid fault. On the other hand, a grid forming inverter works as a voltage source, therefore it is a challenge to limit its output current. This paper provides a low voltage ride through control method for a grid forming inverter, which is based on a virtual impedance. It realizes reliable current limitation and stable operation. The effectiveness of the proposed control method is verified by EMT simulation.

In recent years, lightning strokes affects not only industrial facilities but also common households. In order to reduce the damage by lightning strokes, lightning observation have been actively conducted in various places. Japan Sea coast in Hokuriku is known as a rare region in the world where lightning discharges occur in winter season. Winter thunderstorm tends to be different from summer one, with a higher percentage of positive stroke and lower multiplicity of lightning flash. We have installed LF band receiver that can observe electromagnetic wave from the return stroke and the lightning processes of both cloud-to-ground (CG) and cloud-to-cloud (CC) discharge. From the received LF pulses, their radiation source locations are estimated using time of arrival method. As the result, lightning discharge with the length of over 100km are detected in winter thunderstorm season. These discharges are unlike general lightning discharge in winter thunderstorm season.

The pumped storage power station has a promising future and attention should be paid to maximize its economic benefits. Life cycle theory is an advanced method used to measure economics, the adoption of evaporative cooling systems will improve the stability and operational life of power generator-motor theoretically, resulting in the change of its life cycle cost. This paper investigates and summarises the existing research on cooling methods of generator-motor and the application of life cycle theory in the electric field. Then the paper makes a discussion on the impact of cooling methods of generator-motor on its life cycle cost, hoping to provide research ideas and references for the subsequent optimization of the life cycle economics of generator-motor.