Droop speed control
Encyclopedia
In electricity generation, droop speed control is the primary instantaneous system using net frequency deviations to distribute with stability load changes over generating plants.
For stable operation of the electrical grid of North America, power plants operate with a five percent speed droop. This means the full-load speed is 100% and the no-load speed is 105%. This is required for the stable operation of the net without hunting and dropouts of power plants. Normally the changes in speed are minor due to inertia
of the total rotating mass of all generators and motors running in the net. Adjustments in power output are made by slowly raising the droop curve by increasing the spring pressure on a centrifugal governor
or engine control unit
adjustment. Generally this is a basic system requirement for all power plants because the older and newer plants have to be compatible in response to the instantaneous changes in frequency without depending on outside communication. Voltage control of several power sources is not practical because there would not be any independent feedback, resulting in the total load being put on one power plant.
It can be mathematically shown that if all machines synchronized to a system have the same droop speed control, they will share load proportionate to the machine ratings.
The thousands of AC generators are running synchronously with the power grid which acts like an infinite sink. Next to the inertia given by the parallel operation of synchronous generators, the frequency speed droop is the primary instantaneous parameter in control of an individual power plant's power output (KW
).
S is the ratio of frequency deviation when comparing the load versus the nominal frequency.
For stable operation of the electrical grid of North America, power plants operate with a five percent speed droop. This means the full-load speed is 100% and the no-load speed is 105%. This is required for the stable operation of the net without hunting and dropouts of power plants. Normally the changes in speed are minor due to inertia
Inertia
Inertia is the resistance of any physical object to a change in its state of motion or rest, or the tendency of an object to resist any change in its motion. It is proportional to an object's mass. The principle of inertia is one of the fundamental principles of classical physics which are used to...
of the total rotating mass of all generators and motors running in the net. Adjustments in power output are made by slowly raising the droop curve by increasing the spring pressure on a centrifugal governor
Centrifugal governor
A centrifugal governor is a specific type of governor that controls the speed of an engine by regulating the amount of fuel admitted, so as to maintain a near constant speed whatever the load or fuel supply conditions...
or engine control unit
Engine control unit
An engine control unit is a type of electronic control unit that determines the amount of fuel, ignition timing and other parameters an internal combustion engine needs to keep running...
adjustment. Generally this is a basic system requirement for all power plants because the older and newer plants have to be compatible in response to the instantaneous changes in frequency without depending on outside communication. Voltage control of several power sources is not practical because there would not be any independent feedback, resulting in the total load being put on one power plant.
It can be mathematically shown that if all machines synchronized to a system have the same droop speed control, they will share load proportionate to the machine ratings.
The thousands of AC generators are running synchronously with the power grid which acts like an infinite sink. Next to the inertia given by the parallel operation of synchronous generators, the frequency speed droop is the primary instantaneous parameter in control of an individual power plant's power output (KW
Kw
kw or KW may refer to:* Kuwait, ISO 3166-1 country code** .kw, the country code top level domain for Kuwait* Kilowatt* Self-ionization of water Kw* Cornish language's ISO 639 code* Kitchener–Waterloo, Ontario, Canada...
).
S is the ratio of frequency deviation when comparing the load versus the nominal frequency.
See also
- Electric power transmissionElectric power transmissionElectric-power transmission is the bulk transfer of electrical energy, from generating power plants to Electrical substations located near demand centers...
- Wide area synchronous gridWide area synchronous gridA wide area synchronous grid, also called an "interconnection" in North America, is a power grid at a regional scale or greater that operates at a synchronized frequency and is electrically tied together during normal system conditions...
- Dynamic demand (electric power)Dynamic demand (electric power)Dynamic Demand is the name of a semi-passive technology for adjusting load demands on an electrical power grid. The concept is that by monitoring the frequency of the power grid, as well as their own...
Further reading
- Alfred Engler: Applicability of droops in low voltage grids. International Journal of Distributed Energy Resources, Vol 1, No 1, 2005.