Dynamic Four-Quadrant Converter Control for Grid Connection of Renewable Energy Sources

Connecting renewable energy sources to the grid requires stable and reliable control algorithms. Especially in case of solar-energy systems, single-phase connection is often used at low power levels. This can be achieved by using a four-quadrant converter. For optimal reaction to variations of infeed (e.g. by shading by clouds) and grid disturbances, a fast reaction of the control is advantageous. Reaching such properties under the conditions of single-phase grid connection is challenging: The power pulsation and the inability to exchange energy around zero grid voltage require specialized control schemes for dynamic control. This paper presents the control scheme and measurement results for a four-quadrant converter control basing on the 'Pole Restraining` concept which allows fast instantaneous-value-based control even for four-quadrant converters connected to a single-phase grid.