Windmill Synchronization

If two of them are out of phase then you will probably have a very impressive display of power output. The important part is to have someone elses name handy to give to the nice people with badges that show up to put the fire out and arrest the responsible party if someone was hurt or killed.

Your posting suggests that you are not involved in this project in any manner (other than possibly a homework assignment). Thus, I'll give you assistance and not the best answer. Take a few moments to make a block diagram of the system. Label the blocks from your posting. Consider the pros and cons of trying to force synchronization at or within each block. I think you will find two options. One is difficult and dangerous to the point where you might as well call it impossible. The other will look very easy at the block diagram level. It is not that easy to do in real life, but it is not only possible but it is "the way".

Work on it. The CR4 people that provide answers don't do it based upon a life of having other people think for them.

If all of them produce DC, Keep all of them DC until you convert them all to AC using the same converter. Hence no need to sync them all! All depends on the topography I suppose! That's only my view so it may not be a viable solution without looking at the financial aspect of it!

It's not a homework assignment...lol. I'm not "that" involved with this site it's just curiosity. I was questioning the people who do run/work at the site. I had several ideas of how to accomplish this, but all of them were shot down. No the buses are not DC they are inverted in each windmill (I asked). Again the responses I got yesterday were I don't know, but that's a good question. My responsibilities at this place end at the transmission side of the switchyard. I'm sure there is some standard way of doing this, but I couldn't get an answer. Now Guest you don't need to be so condescending I am a professional in the power industry, but that doesn't mean that I know everything about everything related to my industry. I'm a fossil guy not a wind guy. Also just because I can think of different theoretical ways to accomplish this doesn't mean it's the standard way it's done. Otherwise I appreciate the responses.

It''s not that difficult, funny that no one involved in the project could answer.

Assuming it is NOT a grid-connected system, the first one on-line would establish an output, then every one connected after that would synchronize to the mini-grid you have established. The inverters do that in their own software/firmware, they measure the line phase angles to establish their output to synchronize to it.

If however it is a grid connected system, i.e it is feeding into the local power utility, then the grid is the established frequency / phase angle that the inverters synchronize to.

They are connected to the grid. This windfarm is existing it's past the contruction phase. Each of these circuits (turbine busses) have there own breaker that is then stepped up again in the switchyard for transmission levels. I believe the busses coming from the turbines run at 34.5kV if I remember correctly. It's then connected to one of our 500 lines. I asked if there were switches or if the inverters were networked to time them, and I was told no. Now it is very possible that the people I was talking to didn't know. They were operations people. JRaef you did change my thinking a bit. I kept thinking in terms of the turbines sync'ing with each other, but they would have to be looking down the line and each would sync to the line. I'm still not sure which device they use for it though.

You also have self excited (capacitor excited) Induction generators.

Just as a side note to the "typical" aspect, you could check out the german's Enercon wind mills. Those have a direct drive (no gear reduction) multi-pole alternator. I believe the 2 MW models are at the lower end of their products line. I also believe that they were held off the North American market by a patent dispute with a "big" american alternator producer who had wound their initial products, about 20 years ago. That issue is obviously over now as they are getting locally involved. Googling them will provide some insight into their interconnection scheme.

"The ENERCON annular generator is a low-speed synchronous generator with no direct grid coupling. The output voltage and frequency vary with the speed and are converted for output to the grid by a DC link and inverter. This achieves a high degree of speed variability"

I'm familiar with induction motors/generators, but not in this application so thank you. But these particular turbines are DC generators. I half have an answer now. Still don't know exactly what they use, but good enough. It's still an interesting setup that is not the way I would of imagined. Also these have pitch (blade rotation) and yaw (base rotation) control just to throw that out there. Anyways the windmill starts to turn, they soft start them by using the blade pitch. The blade rotation is speed up through a gear box at a ratio of 120/1. A DC generator is rotated and it's output is inverted, then it passes through a phase converter to supply the three phase power, it is then stepped up to 34.5kV. This all happens at each windmill in the dang mast, head, or whatever the industry lingo is. At the base of the windmill is a circuit switcher. That is where the sync-check is. It is a permissive for the switch that checks the line. Each circuit of how ever many windmills (some of the circuits have different quantities) then goes to the switchyard where it's connected to another bus and stepped up to transmission levels. I was just curious, and I appreciate the help JRaef.

Now the synchronous generator you mentioned like my steam generators...now that's more my cup of tea.

Consider how an inverter works. It is essentially a very large low frequency audio amplifier. It takes a 60Hz (for North America, 50Hz for elsewhere) sinewave and uses the DC input as the power rails of the amplifier and it amplifies that 60 hz sine wave to output AC. the 60hz sinewave can either be generated by an onboard oscillator or it can come from an external source (such as the grid itself), or in the case of standby inverter systems a combination of both.

There are a lot of ways to skin a cat as they say.

So there is an inverter there somewhere, just "inside" the wind mill. Most likely the circuit switcher switches on first, THEN the inverter is energized once it can establish the firing pattern to match the line. That's how I would do it anyway. Switching an already energized inverter into a line, even with a very fast switch, is a disaster waiting to happen IMHO.

In general, the use of DC and an inverter allows for less stringent speed control and more output in a wider wind speed range, something worth considering for sure. But unless they have permanent magnet (translate: expensive) DC generators, they have brushes and commutators to maintain instead of the speed control. Still a detriment to long-term operating cost and reliability, just a different one. I would hazard to guess that someone did a thorough analysis of all of these factors before rushing headlong into that design, but lately, I have seen a lot of "gotta have it at any cost" mentality on these sort of things for political reasons and it servers as a dis-justice to the industry sometimes.

I agree.

Wvengineer,

You said: connected in a delta configuration. Each individual mill is producing its power with a 3-phase delta output. Not separate single-phase mills connected three at a time in a delta arrangement. I suspect you already meant this but your post was somewhat ambiguous.

--JMM

Jmueller: Sorry about that I don't personally know anyone that would of assumed I meant they could possibly be using three separate single phase windmills timed so that they were producing three phase power. That gave me a bit of a chuckle though. If you read post #7 it's not so ambiguous. But I will admit that in the first post I should of said "each windmill's output is connected in a delta configuration".