| 摘要 |
Current and voltage space vectors of the positive sequence system are formed from phase current and phase voltage sampling values of an electric power supply system, and power quantities of the positive sequence system are derived from them. System frequency components are eliminated from these power quantities by a least squares estimate, thus forming a measured active power quantity of the positive sequence system and a measured reactive power quantity of the positive sequence system. By forming quotients with a measured current quantity of the positive sequence system, also obtained using the least squares estimate, impedance values of the positive sequence system are also obtained. These are tested for monotony and abrupt changes and a suspected oscillation signal is formed, if applicable. In addition, to obtain an oscillation confirmation signal, the respective center point of the circle of the trajectory formed by the impedance values of the positive sequence system is determined and compared with the reactance value of the positive sequence system with regard to its imaginary part. If a suspected oscillation signal and an oscillation confirmation signal occur simultaneously, the oscillation signal is formed.
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