A wind power generation has an inherent problem with fluctuation of generation power depending on wind velocity change. The power fluctuation induces problems with power quality，then generation power leveling is required. A battery energy storage system is one of countermeasures for suppressing power fluctuation. Several controls have been reported，but there are relatively complex. This paper proposes a control for power leveling that is simple and reliable with regard to keeping state of charge of the battery. Simulation studies are carried out and effectiveness of the proposed control is reported.

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By the movement towards formation of standard international adjustment and the viewpoint of lightning protection，buildings using TN grounding systems are increasing. And there are many studies about the evaluation of grounding systems from viewpoints of lightning protection and earth fault protection. However there have been only a few studies of grounding systems from a viewpoint of the common-mode noise， which are induced to grounding system from inverter devices and disturb stable operation of electrical devises.For the present study，the author evaluated grounding system from the viewpoint of common-mode noises. The present paper shows the route of common-mode current in the power and grounding system with a PWM inverter and an induction motor，and describes the features of each grounding system，i. e. TT，TN，and IT grounding system.

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