Grid tie synchronous generator rotating forward and reverse directions
Grid tie synchronous generator rotating forward and reverse directions
(OP)
Hi all,
Is it possible for a sync generator generates continuous power if it rotates forward and reverse (clockwise and counter clockwise) directions? The generator can be connected to power converter and grid tie inverter. The application drive the generator in forward rotation for a fixed amount of time, then reverse for some amount of time and cycle repeated. The time could be could be random. Regardless of the directions, the generator needs to generate power to the grid, is this possible?
Thank you
Is it possible for a sync generator generates continuous power if it rotates forward and reverse (clockwise and counter clockwise) directions? The generator can be connected to power converter and grid tie inverter. The application drive the generator in forward rotation for a fixed amount of time, then reverse for some amount of time and cycle repeated. The time could be could be random. Regardless of the directions, the generator needs to generate power to the grid, is this possible?
Thank you





RE: Grid tie synchronous generator rotating forward and reverse directions
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Grid tie synchronous generator rotating forward and reverse directions
RE: Grid tie synchronous generator rotating forward and reverse directions
I have seen brush gear that was not suitable for either direction, but most exciter brush gear is suitable for either direction and many generators use brushless excitation. The chances of brush issues are vanishingly small. But, if you have brush gear and the brushes are not perpendicular to the shaft, you may have issues.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Grid tie synchronous generator rotating forward and reverse directions
Assuming buoy movement cause the generator's shaft to move clockwise and counterclockwise e.g. 0-30rpm clockwise and then 0-30rpm counterclockwise for every 10 seconds. Would the power converter (inverter) connected to the generator be able to generate power to the grid regardless of the direction?
RE: Grid tie synchronous generator rotating forward and reverse directions
But if you are going to an inverter anyway, why an AC synchro us alternator? Why not use DC and skip the step of rectifying the aC to DC? You can get permanent magnet (brushless) DC genertaors in fairly large sizes now. How big are you thinking?
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
RE: Grid tie synchronous generator rotating forward and reverse directions
In most instances yes. Induction motors, synchronous motors and large generators are inherently bi-directional. Any limitations are due to occasional construction issues.
You are using a brushless exciter, so if the fan is bi-directional you should be good to go.
You may want to consider rectifiers before the invertor.
Consider also permanent magnet excitation. You may find less losses. The savings in losses may not be an issue and not worth the price for a large scale installation.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Grid tie synchronous generator rotating forward and reverse directions
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Grid tie synchronous generator rotating forward and reverse directions
A "DC brushless motor" is a synchronous AC motor, albeit one with a permanent-magnet rotor field. The stator waveforms would be rectified to DC in the same manner as a classic synchronous generator.
But with a permanent magnet motor, you don't really have independent control of the voltage and frequency -- with simple methods for rectification such as a basic diode bridge, the voltage and frequency will be directly proportional, which could be less than ideal.
But you are correct that with a conversion to DC, the direction sense of the generated AC waveforms do not matter.
Curt Wilson
Delta Tau Data Systems
RE: Grid tie synchronous generator rotating forward and reverse directions
RE: Grid tie synchronous generator rotating forward and reverse directions
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Grid tie synchronous generator rotating forward and reverse directions
My understanding based on earlier posts is that the AC generator connected to the rectifier can rotates forward or backwards. The change of phase sequence due to change of rotation is 'handled' by the rectifier and converted into DC. This DC amplitude is proportional to the generated AC regardless of the direction. The DC is then fed into inverter converting it to AC which is controlled to match the grid. Correct me if I am wrong.
Thanks
RE: Grid tie synchronous generator rotating forward and reverse directions
The title of your OP is "Grid tie synchronous generator rotating forward and reverse directions..."
Lest there be any misunderstanding:
If a polyphase AC machine's power output is routed through a rectifier and inverter and thence onto the grid, the AC machine in question is not "grid tied," if by grid tied you mean "synchronously grid tied." In this case it for sure exports power onto the grid but the exporting is via an asynchronous tie.
If on the other hand a machine is truly "synchronously grid tied," its phase rotation is that of the system to which it is connected. Our province's main generation company uses AC machines as pump-generating units; these are equipped with Kaplan runners, so to change from pumping mode to generating mode the machine must be taken off line and its rotation reversed by swapping connections to two of the machine's terminals by means of permanently-installed reversing switches.
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]