Standards Development

Scope

The proposal focuses on the test items, test devices, test procedures, and test reports of wind turbine grid adaptability test. The grid adaptability of wind turbine mainly refers to its endurance capacity and response characteristics under severe conditions of the power grid.

The specified test items in the proposal include: voltage deviation adaptability, frequency deviation adaptability, three-phase voltage unbalance adaptability, voltage fluctuation and flicker adaptability, and harmonic voltage adaptability. Corresponding to each test item, the technical requirements are respectively proposed. The specified test devices include the operation conditions of the equipment in the field test and the main technical specifications, and the accuracy requirements of the test equipment are also given. The specified test procedures include the no-load tests and on- load tests, where different test items and test methods are implemented. The specified test reports include the date which needs to be recorded, the parameters which need to be calculated, and the uncertainty of the test.

The proposal is applicable to the grid-connected wind turbine.

Purpose

The wind turbines show different response characteristics under different grid conditions. Especially, when the power grid is operating under severe conditions (however, still within the requirements of the grid codes), the wind turbine may not be able to endure the corresponding voltage deviations, frequency deviations, three-phase voltage unbalances, flickers, harmonics, etc, which would eventually lead to the unplanned disconnection of wind turbines or even wind farms.

For example, a regional power grid in China was once affected by the locomotive traction substation of electrified railway, resulting in local wind farm shutdown for many times when the output three-phase current unbalance exceeding the protection limit (however, three-phase voltage unbalance still within the requirements of the grid codes). On August 9, 2019, Great Britain power grid suffered a massive blackout, and the grid adaptability of Hornsea Wind Farm fill a key role during the accident development process.

Thus, the g rid adaptability and operation characteristics of wind turbine under different grid conditions should be emphasized on. To tackle the above problems, the common requirements and test/evaluation methods of grid adaptability should be specified in an international technical specification.

Purpose:

Based on this technical specification, the grid adaptability test results of wind turbines are consistent and could be accepted all over the world.

It would be applied by:

1. the wind turbine manufacturer, striving to meet well-defined grid adaptability;

2. the wind turbine purchaser, in specifying such grid adaptability;

3. the wind turbine operator, who may be required to verify that stated, or required grid adaptability are met;

4. the wind turbine planner or regulator, who has to be able to accurately and fairly determine the behaviours of a wind turbine under the voltage and frequency variations to ensure that the installation is designed so that grid codes are respected;

5. the wind turbine certification authority or testing organization, in evaluating the grid adaptability of the wind turbine type;

6. the planner or regulator of the electric network, who has to be able to determine the grid connection required for a wind turbine.

Prior to the proposal, the most similar IEC standards include IEC 61400-21-1 (Wind energy generation systems – measurement and assessment of electrical characteristics – wind turbines) and IEC TS 63102 (Grid code compliance assessment methods for grid connection of wind and PV power plants). Besides, the ongoing project IEC TS 61400-21-4 (Wind energy generation systems – measurement and assessment of electrical characteristics – wind turbine components and subsystems) also presents some tests to validate the capability of the DUT to operate within a defined range.

IEC 61400-21-1 was proposed from the perspective of the wind turbine itself, which specified the measurement and assessment methods of its electrical characteristics. However, it did not require the endurance capability of the wind turbine under severe conditions of the power grid. Therefore, the proposal will specify the capability and response of wind turbines from a different angle. IEC TS 63102 was drafted from the perspective of the power plant level, which specified the grid code compliance assessment methods of wind and PV power plants. However, the specific test items and procedures were not given regarding the grid adaptability of the wind turbine, such as voltage and frequency deviations, three-phase voltage unbalances, flickers, harmonics, etc.

IEC TS 61400-21-4 is prepared currently where additional measurement and test of electrical characteristics are considered. Some similar ideas close to this proposal are discussed in IEC TS 61400-21-4 in the component and subsystem level, such as the voltage capability and frequency capability. By contrast, this proposal will focus on the topic of grid adaptability, which aims to comprehensively discuss the endurance capability of the wind turbine and prescribe the test procedures, considering the requirments and experience globally.Except for these documents, no other appropriate international standard has been found in the field. It is the right time to draft an IEC specification to standardize and promote the test procedures of grid adaptability of the wind turbine.