Low voltage ride through at 1-line fault using real time symmetrical coordinate transformation

This paper proposes a real time symmetrical coordinate transformation applied for the fault-ride-through when the imbalanced fault occurs in the 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. This fault causes the imbalance voltages and currents in the utility system. To have better fault ride through ability, it is indispensable quick and precise detection of the imbalanced voltages and phases. This paper presents the novel fault-ride-through control using the real time symmetrical coordinate transform from the memorized 3-phase voltage data. Simulation results show the effectiveness of the proposed method when the dc side voltage is constant and the 1 Line-Low Voltage fault. Simulation results certify that the proper change of the controller of the dc-dc converter from the MPPT control to the constant dc voltage control can perform the good FRT operation. Extended discussion about the role of the dc energy storage and the dc circuit breaker for the future dc system is also shown.