Wind turbines – Part 21: Measurement and assessment of power quality characteristics of grid connected wind turbines
|Publication Date:||1 August 2008|
|ICS Code (Wind turbine energy systems):||27.180|
This part of IEC 61400 includes:
• definition and specification of the quantities to be determined for characterizing the power quality of a grid connected wind turbine;
• measurement procedures for quantifying the characteristics;
• procedures for assessing compliance with power quality requirements, including estimation of the power quality expected from the wind turbine type when deployed at a specific site, possibly in groups.
The measurement procedures are valid for single wind turbines with a three-phase grid connection, and as long as the wind turbine is not operated to actively control the frequency or voltage at any location in the network. The measurement procedures are valid for any size of wind turbine, though this standard only requires wind turbine types intended for PCC at MV or HV to be tested and characterized as specified in this standard.
The measured characteristics are valid for the specific configuration of the assessed wind turbine only. Other configurations, including altered control parameters that cause the wind turbine to behave differently with respect to power quality, require separate assessment.
The measurement procedures are designed to be as non-site-specific as possible, so that power quality characteristics measured at for example a test site can be considered valid also at other sites.
The procedures for assessing compliance with power quality requirements are valid for wind turbines with PCC at MV or HV in power systems with fixed frequency within ±1 Hz, and sufficient active and reactive power regulation capabilities and sufficient load to absorb the wind power production. In other cases, the principles for assessing compliance with power quality requirements may still be used as a guide.
NOTE 1 This standard uses the following terms for system voltage:
- low voltage (LV) refers to Un ≤ 1 kV;
- medium voltage (MV) refers to 1 kV < Un ≤ 35 kV;
- high voltage (HV) refers to Un > 35 kV.
NOTE 2 The issue of interharmonics is not addressed in this standard, though it is under consideration awaiting proper measurement and assessment procedures to be established by the appropriate IEC committee.