Are you stuck with DFIG?


Let’s assume that if one given turbine drive train technology was clearly superior to others, everyone would be using it already. When it comes to generator technology selection, multiple inputs influence the final decision: engineers’ conclusions, production’s preference, customer’s needs and top management’s decisions.

In recent years, we have seen a clear trend towards permanent magnet generators (PMG). For direct-drive and medium-speed drive trains, PMG has become the obvious choice. This is no longer a subject of debate. However, when it comes to high-speed solutions, more options tend to emerge.

Historically, high-speed drive train was mainstream in traditional wind turbines: first came stall control and then double-fed induction generator (DFIG) technology, which offered more controllability. However, in the past few years, a few forward-looking companies have built their turbines using high-speed PMGs, to reach higher energy yield, better grid side control and less maintenance. One of the drawbacks is the need for a bigger converter, which can increase the overall system cost.

But the bottom line is this: Turbine makers who start from the scratch, without being burden by outdated strategic choices, are selecting PMG as their technology of choice. We have observed this many times, even when the topology is high speed with a traditional gearbox. The latest example was the Chongqing Haizhuang Windpower Equipment 5 MW offshore turbine.

The reality is that many companies are in effect “stuck” with their existing turbine portfolio, and they need to defend their DFIG selection of 10 to 15 years ago. In parallel, at a time where business is tough, R&D efforts are often reduced.

During this autumn, The Switch will open a generator technology selection debate to hear your opinions: PMG or DFIG?

We feel that such an open discussion will help make our entire industry stronger. I warmly welcome you to join the debate. And I hope to convince you that switching to better technology is not as risky and difficult as one might think. PMG is just a generator – and we have done this many times.

Jussi Vanhanen
Director, Sales and Marketing