IEEE Power & Energy Magazine - November/December 2019 - 81

Standards developers should ensure that the intent of codes and
requirements remains neutral in terms of technology while still
providing clarity and consistency regarding specific technologies.
focused on mechanical parts and the performance of wind
turbines, the first standard dealing with electrical testing of
grid connection of wind turbines addressed power-quality
aspects. This was IEC 61400-21, published in 2001. This standard was based on several national guidelines in the 1990s,
mainly those of Denmark and Germany. Due to the expansion
of grid-connection requirements, the second edition published
in 2008 includes guidelines for testing and measuring fault
ride-through capability and control performance of wind turbines. The third edition, expected in 2019, will also include
such guidelines.
In response to increased grid-connection requirements, the
new standards IEC 61400-21-2 for testing wind power plants
and IEC 61400-21-4 for testing electrical components and subsystems are under development. These test standards are driven
by the rapidly growing share of wind in power systems. Even so,
significant parts of the standards are generally valuable for other
converter-connected generation, such as solar photovoltaics
(PVs, covered by IEC TC82). The same can be said about the
development of modeling standards.
In 2015, TC88 published IEC 61400-27-1, the first standard
that identifies generic models for wind turbines and a procedure to validate a wind turbine model based on tests according
to IEC 61400-21-1. The next edition is expected in 2019 with

IEC 61400-27-1 designating models and IEC 61400-27-2 indicating procedures for model validation. The IEC 61400-27-1
models are included in IEC 61970-302, which describes how
to exchange data for dynamic power system simulations using
generic models. A technical report, IEC 61400-21-3, which is
about wind turbine harmonic models, is scheduled to be published in 2019. An overview of the different IEC TC88 standards
and their interaction with the grid-connection requirements are
shown in Figure 1.

Challenges for Distributed Energy Resource
Standards and Grid Codes
Standards and grid codes covering distributed energy resources
(DERs) need to consider a very wide variety of requirements. In
the past, low DER penetration allowed for a clear distinction
between large transmission-connected plants and small units
connected to the distribution grid. Big plants were responsible
for system security and provided functions such as frequency
control and fault ride through. Dedicated communication
links to these plants also enabled fast and reliable two-way
communication so system operators could regulate these resources from a control room.
Historically, smaller DER units have acted autonomously as
communication to the control room is very challenging due to

TC8/SC8A

TC88: Wind Energy Generation Systems

Wind Turbine Components

Measurement
and Test

61400-21-4: Test Bench Test
Components and Subsystems

Wind Turbine

Wind Power Plant

61400-21-1:
Wind Turbines

61400-21-2:
Wind Power Plants

61400-21: Series-Measurement and Assessment of Electrical Capabilities
Validation

System

Grid: Requirements
Grid Codes

61400-27-2: Electrical Simulation Models; Model Validation
61400-21-3: Wind Turbine Harmonic Model

Modeling

Power

61400-27-1: Electrical Simulation Models; Generic Models

Validation of Grid
Requirements, System
Operation, and
System Protection

figure 1. An overview of TC88 standards related to grid connections.
november/december 2019

ieee power & energy magazine

IEEE Power & Energy Magazine - November/December 2019

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - November/December 2019