METHOD AND DEVICE FOR RAPIDLY DETERMINING A REFERENCE VOLTAGE SYNCHRONOUS WITH THE NETWORK FOR A NETWORK CONTROLLED CONVERTER AFTER A NETWORK DISTURBANCE

摘要

The orthogonal components of the voltage vector of an a-c voltage network are transformed by means of a vector rotator, smoothed and transformed back. The frequency of the transformation elements required for the transformation in the vector rotator is set during a network disturbance under controlled conditions in accordance with a stored frequency value. After the end of the network disturbance, the direction given by the smoothed transformed orthogonal components is controlled to a reference value in that the frequency of the transformation elements is readjusted according to the direction deviation. The phase of the transformation elements determines the phase of the co-system fundamental of the network. A counter system fundamental can also be taken into consideration. Also if the returning power network contains asymmetrical and harmonic containing transients, a reference voltage synchronous with the fundamental can be obtained thereby within a few milliseconds for synchronizing network controlled converters.