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A permanent magnet synchronous generator is a generator where the excitation field is provided by a permanent magnet instead of a coil. The term synchronous refers here to the fact that the rotor and magnetic field rotate with the same speed, because the magnetic field is generated through a shaft-mounted permanent magnet mechanism, and current is induced into the stationary armature.
The generator is brought up to approximate synchronous speed by supplying more energy to its shaft - for example, opening the valves on a steam turbine, opening the gates on a hydraulic turbine, or increasing the fuel rack setting on a diesel engine. The field of the generator is energized and the voltage at the terminals of the generator is ...
A less stiff machine with lower SCR (a typical situation for modern h=generators) will follow the grid faster. [3] Stiffness is a ratio of the change in power output to the change of power angle. For example, if the system frequency decreases, the stiffer generator provides more power thus contributing to the system stability. [8]
This is useful for large variable speed wind turbines, because wind speed can change suddenly. When a gust of wind hits a wind turbine, the blades try to speed up, but a synchronous generator is locked to the speed of the power grid and cannot speed up. So large forces are developed in the hub, gearbox, and generator as the power grid pushes back.
All grid-connected wind turbines, from the first one in 1939 until the development of variable-speed grid-connected wind turbines in the 1970s, were fixed-speed wind turbines. As of 2003, nearly all grid-connected wind turbines operate at an exactly constant speed (synchronous generators) or within a few percents of constant speed (induction ...
Capability curves for generators with full converters: D-shape (red), rectangular (green), triangular (blue) The inverter-based resources (like solar photovoltaic (PV) generators, doubly-fed induction generators and full-converter wind generators, also known as "Type 3" and "Type 4" turbines [5]) need to have reactive capabilities in order to contribute to the grid stability, yet their ...