Power quality measurements of wind energy converters with full-scale converter according to IEC 61400-21

Abstract

Wind energy has reached remarkable shares in the electrical energy production in many countries worldwide. However, the connection of multi-megawatt wind farms leads to the necessity to examine the impact on the grid closely. The International Electrotechnical Commission (IEC) developed and released the IEC-standard 61400-21 as part of the IEC 61400 standards for testing and assessing power quality characteristics of grid-connected wind energy converters (WECs) in a consistent and accurate way. To easily compare WECs of different types it defines a measurement excerpt that states the key power quality characteristics: wind turbine specifications, active and reactive power output, flicker, harmonics, control of active and reactive power, protection, voltage dip response and reconnection time. Based on the measurement results in that excerpt the maximum grid connection capacity can be determined for a chosen connection point in order to fulfil the given national or international power quality requirements. Different wind turbine types have different power quality characteristics. As a pioneer in advanced WEC technology and grid integration, ENERCON has developed a range of certified WEC types to address the most demanding international grid codes. In recent years the power quality characteristics of all these types were tested and certified according to IEC 61400-21 by independent testing institutes. Reasons for the good power quality characteristics can be found in the design of these WECs based on an annular generator, injecting power via full-scale power electronics and associated control systems. Additional control features like soft-start without inrush currents, Storm Control and wind farm control systems to control the voltage, power factor or reactive power can, to a certain extent, even improve power quality in power systems.