Low voltage ride through
Encyclopedia
In electricity supply and generation
,
low voltage ride through (LVRT), or fault ride through (FRT), is what an electric device, especially wind generator
, may be required to be capable of when the voltage in the grid
is temporarily reduced due to a fault or load change in the grid. The voltage may be reduced in one, two or all the three phases
of the AC grid. The severity of the voltage dip
is defined by the voltage level during the dip (may go down to zero) and the duration of the dip.
Depending on the application the device may, during and after the dip, be required to:
For generating units such as wind turbines
and solar power stations, the required LVRT behaviour is defined in grid codes issued by the grid operator. Examples of the such grid codes are the German E.On grid code and UK National Grid code
For critical loads such as power supplies for computer centers and industrial processes the required LVRT performance is defined by the application. Often a special device called uninterruptible power supply
(UPS) is used to provide power to the critical load during the voltage dip.
Testing of the devices with less than 16 Amp rated current is described in the standard IEC
61000-4-11 and for higher current devices in IEC 61000-4-34
For wind turbines the LVRT testing is described in the standard IEC 61400-21 (2nd edition August 2008)
More detailled testing procedures are stated in the German guideline FGW TR3 (Rev.22).
Electrical power industry
The electric power industry provides the production and delivery of electric energy, often known as power, or electricity, in sufficient quantities to areas that need electricity through a grid connection. The grid distributes electrical energy to customers...
,
low voltage ride through (LVRT), or fault ride through (FRT), is what an electric device, especially wind generator
Wind generator
A wind generator is a device that generates electrical power from wind energy.Wind generators have traditionally been wind turbines, i.e. a propeller attached to an electric generator attached to appropriate electronics to attach it to the electrical grid or to charge batteries.Recently, however, a...
, may be required to be capable of when the voltage in the grid
Electric power transmission
Electric-power transmission is the bulk transfer of electrical energy, from generating power plants to Electrical substations located near demand centers...
is temporarily reduced due to a fault or load change in the grid. The voltage may be reduced in one, two or all the three phases
Three-phase electric power
Three-phase electric power is a common method of alternating-current electric power generation, transmission, and distribution. It is a type of polyphase system and is the most common method used by grids worldwide to transfer power. It is also used to power large motors and other heavy loads...
of the AC grid. The severity of the voltage dip
Power dips
A power dip is a very short drop in voltage in a system . It is most commonly observed when a high-current device is switched on and lights in the same system will dim momentarily...
is defined by the voltage level during the dip (may go down to zero) and the duration of the dip.
Depending on the application the device may, during and after the dip, be required to:
- disconnect temporarily from the grid, but reconnect and continue operation after the dip
- stay operational and not disconnect from the grid
- stay connected and support the grid with reactive power (defined as the reactive current of the positive sequence of the fundamental)
For generating units such as wind turbines
Wind turbine
A wind turbine is a device that converts kinetic energy from the wind into mechanical energy. If the mechanical energy is used to produce electricity, the device may be called a wind generator or wind charger. If the mechanical energy is used to drive machinery, such as for grinding grain or...
and solar power stations, the required LVRT behaviour is defined in grid codes issued by the grid operator. Examples of the such grid codes are the German E.On grid code and UK National Grid code
For critical loads such as power supplies for computer centers and industrial processes the required LVRT performance is defined by the application. Often a special device called uninterruptible power supply
Uninterruptible power supply
An uninterruptible power supply, also uninterruptible power source, UPS or battery/flywheel backup, is an electrical apparatus that provides emergency power to a load when the input power source, typically mains power, fails...
(UPS) is used to provide power to the critical load during the voltage dip.
Testing of the devices with less than 16 Amp rated current is described in the standard IEC
International Electrotechnical Commission
The International Electrotechnical Commission is a non-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies – collectively known as "electrotechnology"...
61000-4-11 and for higher current devices in IEC 61000-4-34
For wind turbines the LVRT testing is described in the standard IEC 61400-21 (2nd edition August 2008)
More detailled testing procedures are stated in the German guideline FGW TR3 (Rev.22).