Power Electronics Help to Control Electrical Grids

An anonymous reader writes: "IEEE Spectrum magazine has a timely article about how power electronics are proving necessary for the widespread connection of wind turbines to the electric power grid. It explains many issues that currently make it difficult to utilize wind power. Older articles discuss other issues affecting the nation's power grid."

Comments

Doesn't quite ring true

[Willard B. Trophy]

As someone who built wind farms for four years, and is now a director of Canada's first urban wind power co-op, WindShare, I'm not convinced that this article really accounts for much.

While it's true that most wind turbines use induction generators, they do so for several reasons, including:

• safety: as the wind can blow at any time, an alternator could energize a powerline that's down for maintenance. Induction generators need line (excitation) current to get them going, and thus they won't frazzle an unsuspecting worker.
• stability: an induction generator's torque/speed curve matches that of a stall-regulated wind turbine. Thus a wind turbine of this type will tend to run at a constant speed.

All the turbines I have worked with have either had modest capacitor banks to correct for reactive power, or used insanely cool AC/AC back-to-back inverters to produce line quality AC.

I'm also concerned about the article's allegations of power intermittence. Wind turbine rotors have a fair amount of rotational inertia, so they're not capable of passing every flutter of the wind to the generator. It seems that this part of the article is a sales pitch for a new product that the vast majority of installations won't need.

I was also amused at the requirement of wind turbines to "ride through" grid frequency variations. This is basically a nice way of spinning the fact that wind turbine controllers are often far more picky about the frequency they'll accept or put out, than the rather poor regulation that applies to our power grids.

An finally, that picture. Where on earth did they get it? Apart from the fact that it's a contravention of every safety code to climb the tower of a running turbine, the climber must be a human sloth. To get that kind of motion blur on wind turbine blades, you'd have to have several minutes' exposure. Thus our perfectly sharp climber (and their horse) must be moving incredibly slowly ...

Wind is only part of the answer.

[Zebra_X]

GE manufactures a turbine rated for 3.6MW output. Ge is currently an industry leader in these types of turbines though, they are desiged primarily for offshore use. Smaller MW ratings between 1.5 and 2.8 are more common. Unfortunately, even with wind turbines producing @ 3MW it would require approximately 1.26 Million of them to meet the U.S.'s current power demands. Currently Coal plants are responsible for the majority of our power capacity in the U.S.

While the *idea* of wind power is certainly a nice one, and the notion of helping the environmement is well intentioned, the reality is that wind is insufficient as a power source and as a result - it's ability to displace the most polluting source, coal, will be ineffective. Other solutions will be required to truly solve the pollution/capacity problem that we face.

A potentially viable start to "solving" some fo these problems would be to distribute residential power generation, especially in dense urban areas. Technologies such as fuel cells, and compact turbines could be used for this. An added benefit of this strategy would be zero emissions and heat reclemation in the case of fuel cells, and better regulatory control over the emissions of compact gas fired turbines.

My two cents.