Device for parallel supply into an AC or three-phase network

TLDR: In this paper, a vector rotator is used to form the angle between the vectors, which angle can be controlled to zero by a phase controller acting on the frequency control input of the final control element.

Abstract: In order to synchronise a final control element (an invertor (2) supplied, for example, from a solar generator (1) or an externally driven synchronous machine) to a network (11) to be supplied, both the magnitudes (¦Uw¦, ¦Un¦) and the directions of the corresponding voltage vectors are determined by means of coordinate converters (21, 31) and vector analysers (22, 32) from the final control element output voltage (Uw) and the network voltage (Un). The difference (¦Un¦-¦Uw¦) of the magnitudes is supplied via a magnitude controller (30) to the amplitude control input (3) of the final control element. A vector rotator (25) forms the angle between the vectors, which angle can be controlled to zero by a phase controller (33) acting on the frequency control input (4) of the final control element (2). In order to keep the final control element in synchronism with the network after closing the synchronising switch (14), and to control the exchange of real power and reactive power at the fundamental frequency between the mains and the final control element, the real component and the reactive component are determined from the measured current value (Iw) by means of a coordinate converter (41) and a vector rotator (42) and are each supplied to a controller (43, 44). The output signal of the real current controller is also connected to the phase controller input, and the output signal of the reactive power controller (43) is additionally connected to the magnitude controller input. This results in a universal apparatus which facilitates both network synchronisation and maintenance of a network-synchronous parallel operation of the final control element, while also facilitating the transition to an externally synchronised supply into a passive consumer network (isolated operation).