An Efficient Grid Interface for Permanent Magnet Generators Using Series Compensation
Nowadays, power electronics is an essential technology for enabling variable speed operation of wind turbines with increased energy capture and reduced mechanical stress. The commonly used doubly-fed induction generator only needs a small rated converter to enable variable speed operation and has a correspondingly low cost. On the other hand, permanent magnet (PM) generators have advantages such as no slip rings, high efficiency and the possibility of gearless operation. Their drawback is the need for a large power electronics converter, as the full power must be converted into voltage of fixed frequency suitable for the connection to the grid. This drawback motivates the search for new configurations with reduced losses, costs and space requirements. In this article, a new configuration using a variable series capacitor is investigated. The configuration shows simple control, low losses and a reduced need for semiconductor rating, and thus contributes to the technology shift towards permanent magnet generator solutions.
