New real time symmetrical coordinate transformation using complex number calculation to detect imbalanced fault in utility power system

This paper proposes a real time symmetrical coordinate transformation applied for detection of imbalanced fault in utility power system. The power conditioner of the photovoltaic system in Japan is required to remain connected when the utility power system fault occurs under certain condition. The most popular fault is 1 line-to-ground fault. The next is 2 line-short fault. Both cause the imbalance voltages and currents in 3-phase power system. To optimize the output from the power conditioner of the photovoltaic system, the detection of the imbalanced condition is important factor. In this paper, new development of the signal processing method by using the complex number algebra in real time system is shown. The fast detection of the imbalanced condition is verified by the computer simulations. It is also verified by the experiments that the calculation of proposed method can be done fast enough by using the digital signal processor.