Abstract: An electrolyte solution containing a compound represented by the following formula (1).

Abstract: An electrolyte solution containing a compound (1) represented by the formula (1), (wherein R101 and R102 are each individually a substituent such as a C1-C7 alkyl group, and the substituent optionally contains at least one divalent to hexavalent hetero atom in a structure or optionally has a structure obtained by replacing at least one hydrogen atom by a fluorine atom or a C0-C7 functional group) and at least one compound (11) selected from compounds such as a compound represented by formula (11-1) (wherein R111 and R112 are the same as or different from each other and are each a hydrogen atom or the like, and R113 is an alkyl group free from a fluorine atom or the like):

Abstract: A variable-speed pumped-storage power generating system includes a variable-speed generator/motor, a frequency converter connected to an electric power system, and a pump/turbine driven by the generator/motor.

Abstract: There is disclosed a protecting apparatus for a secondary excitation type variable speed AC generator/motor having a primary winding connected to an electric power system and a secondary winding each phase of which is AC excited by an independent power converter unit. The protecting apparatus is arranged to detect an electrical event which includes at least one of an overvoltage and overcurrent appearing at each phase of the secondary winding of the AC generator/motor, to decide whether the detected electrical event meets a predetermined condition and to close, when the electrical event detected in respect to any of phases of the secondary winding is decided as meeting the predetermined condition, a switch circuit connected in the corresponding phase of the secondary winding.

Abstract: Disclosed in a variable speed pumping-up electrical power system comprising a variable speed generator/motor, a frequency converter connected between the generator/motor and an a.c. power system, a controller controlling an effective power input to the generator/motor by controlling the frequency converter on the basis of the difference between an actual effective power input from the a.c. power system and an externally-applied effective power command, and a correction circuit correcting the effective power command on the basis of the difference between the frequency of the a.c. power system and a frequency setting.