Ingeteam recently introduced its “crowbarless” solution, a modular fault ride through (FRT) system for power converters that will strengthen the grid compliance of doubly fed induction generators (DFIG). Thanks to the modular FRT system, the crowbarless solution offers superior capabilities compared to the active crowbar system traditionally used to protect the power converter from grid voltage transient.
Until recently, most grid codes allowed wind turbines to disconnect from the grid when transients in grid voltage could jeopardize the integrity of their elements, especially the power converter. Due to the ever-increasing wind power penetration around the world, this is no longer the case. Ingeteam has come up with a new way to deal with low capacity transmission lines, or weak grids, and FRT events to remain fully grid compliant.
“The traditional crowbar solution used in DFIG topology presents a poor response to the voltage sags,” said Ingeteam’s director of research and development, Carlos Gironés. “This is because the machine side converter is disabled when a voltage sag appears in the stator terminal until the inductor generator flux is stabilized. Thanks to new software and hardware implemented in our crowbarless solution, the machine side converter is available at all times during the voltage sag, achieving injection times required by the most restrictive grid codes.”
To date, the most widely used system to protect the power converters from voltage spikes is the so-called “active crowbar,” a shunt circuit composed of actively controlled switches and dissipation elements that are connected to shunt the high currents, avoiding damages to the converter. However, this system presents the limitation that, while the active crowbar is connected, the power converter is not in operation, the active and reactive power set points cannot be tracked, therefore, the wind turbine is not being controlled. Ingeteam’s crowbarless power converter, designed to operate in DFIG topology, uses a modular FRT system that removes the need for the active crowbar.
The crowbarless solution presents behavioral advantages in issues related to weak grids or grid fault events, allowing doubly fed induction generators to overcome previous technical constraints and comply with the strictest grid codes. Coupled to a suitable selection of grid filter and control loops tuning, it is able to keep the control of the wind turbine during these transients, achieving the controllability required in order to operate in weak grids.
In addition, the modularity concept of the FRT system allows for a cost optimization for each application. The solution is flexible and offers a cost-optimal power converter option for each wind farm scenario.
For more information, go to www.ingeteam.com.