A paradigm change in wind power station control through emulation of conventional power plant behaviour

With a new control concept presented in this paper, wind power stations with inverter-coupled synchronous generators (SG-WPS) behave to a great extent like the turbine-generator sets of conventional thermal power plants including the ability of the release of active- and reactive reserve power. This allows every single SG-WPS to improve its contribution to power grid stability. The new control concept consists of three main subsystems: The control of the grid-side inverter, the control of the generator-side inverter and the control of the rotor speed with the pitch angle. This paper points to all named subsystems, but the main focus is on the control of the dc-link voltage of the frequency inverter. In contrast to conventional control concepts of SG-WPS, where the dc-link voltage is regulated with the grid-side inverter, here it is controlled with the generator-side inverter. This is a paradigm change in wind power station control. Without the task of dc-link voltage control, the grid-side inverter of the SG-WPS is operated with droop based virtual synchronous machine emulation. It allows the SG-WPS to immediately react to grid disturbances by the release of active- and reactive reserve power. This is an important step in the conversion of a WPS from a “negative consumer” to a voltage source. Simulation results show the dynamic behaviour of the SG-WPS with the new control concept as a whole. A test bench and experimental results for the dc-link voltage control with the generator-side inverter will be presented.