Control of thyristor-based commutation cells

The growing share of photovoltaic generators connected to low-voltage grids leads to increased and more frequent load changes in these grids. Transfer switches are often applied to control the resulting voltage fluctuations. As mechanical transfer switches are not suitable for frequent switching due to the degeneration of the switching contacts, it is essential to develop new apparatus that are capable of frequent switching of high currents. This paper presents a pulse generator for thyristor-based commutation cells that are capable of fulfilling the function of transfer switches. The control is described for different operating points and is developed in a generalized manner in order to minimize the implementation effort. The control successfully avoids short circuits of the windings and minimizes the voltage stress of the thyristors.