To execute higher harmonic measurement by injecting dispersedly an in-phase current synchronized by a non-integer-fold frequency of a system fundamental frequency from each low rank system to the high rank system side, regardless of the load state of each low rank system or the like.
One of plural injection devices 8a-8d is used as a standard device, and only the standard device 8a among the devices 8a-8d is driven before measurement, and an output current of an injection frequency by the device 8a is injected from a low rank system 6a to which the device 8a is connected, through a high rank system 1, to low rank systems 6b-6d to which residual devices 8b-8d are connected, and phases of the currents of injection frequencies of each system 6b-6d are detected. On measurement, the device 8a is driven, and simultaneously the devices 8b-8d are driven with output current phases shifted by 180° from the detected phases of the currents of the injection frequencies before measurement at each low rank system 6b-6d, and the same phase currents synchronized by the injection frequencies based on the output current phase of the device 8a are injected simultaneously from the system 6b-6d to the high rank system side.
TSUKAMOTO MASAKAZU
NATSUDA YASUKAZU
SHIKATA TOSHIHIKO
NISSIN ELECTRIC CO LTD
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