Grid Codes for Renewable Powered Systems

By International Renewable Energy Agency IRENA

This report contains the latest developments and good practices to develop grid connection codes for power systems with high shares of variable renewable energy – solar photovoltaic and wind.

• Language: English
• Publisher: IRENA
• Release date: Apr 1, 2022
• ISBN: 9789292605100

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© IRENA 2022

Unless otherwise stated, material in this publication may be freely used, shared, copied, reproduced, printed and/or stored, provided that appropriate acknowledgement is given of IRENA as the source and copyright holder. Material in this publication that is attributed to third parties may be subject to separate terms of use and restrictions, and appropriate permissions from these third parties may need to be secured before any use of such material.

Citation: IRENA (2022), Grid codes for renewable powered systems, International Renewable Energy Agency, Abu Dhabi.

ISBN: 978-92-9260-427-1

eBook ISBN: 978-92-9260-510-0

Acknowledgements

This report benefited from input and review of experts: Eckard Quitmann (Enercon), Feng Shuanglei (China Electric Power Research Institute), Hazril Izan Bahari (SEDA), Ioannis Theologitis (ENTSO-E), João Peças Lopes (INESC TEC. Portugal), Jorge Nuñez (Planning Manager, System Operator Honduras), Juan Carlos Montero (ICE Costa Rica), Julia Matevosyan (ERCOT, USA), Leonardo Meeus (FSR), Lina Marcela Ramirez Arbelaez (XM Colombia), Narasimhan S.R. (Power System Operation Corporation Limited [POSOCO] India), Nicholas Miller (HickoryLedge), Ralph Pfeiffer (Amprion), Ronnie Belmans (KU Leuven), Soonee Sushil Kumar (Power System Operation Corporation Limited [POSOCO] India), Virginia Echinope (Ministry of Energy Uruguay), Carlos Fernandez, Emanuele Bianco, Emanuele Taibi, Raul Miranda and Rabia Ferroukhi (IRENA).

IRENA is grateful for the support of the China Electric Power Research Institute (CEPRI) in the preparation of this report.

The report was developed by IRENA’s Innovation and Technology Centre (IITC), directed by Dolf Gielen, and led by the Innovation Team, managed by Roland Roesch. The report was prepared under the guidance of Francisco Boshell and was authored by Arina Anisie, Gayathri Nair, Huiming Zhang and Daniel Gutierrez-Navarro (IRENA), and Nis Martensen, Peter-Philipp Schierhorn and Natalia Escobosa Pineda (Energynautics).

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This report is available for download: www.irena.org/publications

Disclaimer

This publication and the material herein are provided as is. All reasonable precautions have been taken by IRENA to verify the reliability of the material in this publication. However, neither IRENA nor any of its officials, agents, data or other third-party content providers provides a warranty of any kind, either expressed or implied, and they accept no responsibility or liability for any consequence of use of the publication or material herein.

The information contained herein does not necessarily represent the views of all Members of IRENA. The mention of specific companies or certain projects or products does not imply that they are endorsed or recommended by IRENA in preference to others of a similar nature that are not mentioned. The designations employed and the presentation of material herein do not imply the expression of any opinion on the part of IRENA concerning the legal status of any region, country, territory, city or area or of its authorities, or concerning the delimitation of frontiers or boundaries.

Cover photos: engel.ac/Shutterstock, Iren Moroz/Shutterstock, Alexandru Chiriac/Shutterstock, Ralf Geithe/Shutterstock, foxbat/Shutterstock.

CONTENTS

Figures, Tables and Boxes

Abbreviations

Executive summary

01 Grid code development

1.1 The role of grid codes in electricity system regulation

1.2 Relevance of grid codes in energy policies

1.3 Electricity sector transformation

1.4 Grid code development and revision planning

02 Grid code technical requirements

2.1 Requirements overview

2.2 Determination of technical parameters

2.3 Determining frequency ranges

2.4 Determining RoCoF limits

2.5 Determining FRT envelopes

03 Evolution of technical requirements

3.1 Controllability

3.2 Communication interfaces and integration

3.3 LVRT requirements in low-voltage distribution grids

3.4 HVRT requirements

3.5 Requirements for storage and other consumer-producer connections

3.6 Requirements for EV charging

3.7 Grid-forming capabilities of inverters

04 Ancillary services

4.1 Ancillary services and grid codes

4.2 Inertia management

4.3 Fast Frequency Response

4.4 Grid-forming inverters

4.5 Black-start capability

4.6 Leveraging flexibility from small-scale grid users

05 Grid code compliance management

5.1 Basic compliance enforcement approaches

5.2 Strategic verification management concepts

5.3 Application of new requirements to existing grid users

5.4 Recommendations on compliance enforcement and verification

06 Regional grid codes and international co-operation

6.1 The EU Network Codes

6.2 Co-ordination efforts in North America

6.3 Co-ordination efforts in Central America

6.4 Other co-ordination efforts

6.5 The role of international standards in VRE integration into power systems

6.6 Recommendations on formulating regional grid codes

07 Guidance for designing grid codes

7.1 Power system archetypes

7.2 Starting the VRE integration process

7.3 Stepping up VRE integration

7.4 Grid code requirements for high VRE shares

7.5 Country grid codes for multiple systems

7.6 Regulatory measures to support national policies and legislation

References

Glossary

FIGURES

Figure i Innovations of the power system

Figure ii Categories of grid codes in Europe, functionality and main actors

Figure iii Grid code parameter development and revision process

Figure iv Grid codes and innovation trends

Figure v Grid code formulation guidance according to grid size and VRE integration level

Figure 1 Categories of grid codes in Europe, functionality and main actors

Figure 2 Technological transformation trends in the power system

Figure 3 Application of high-level requirements according to system needs

Figure 4 Frequency control curve for a PV power plant

Figure 5 IEEE 519 informative interharmonic voltage limits based on flicker for frequencies up to 120 Hz for 60 Hz systems

Figure 6 Parameter development and revision process

Figure 7 IEEE C50.13 and IEC60034-3 limits on voltage and frequency

Figure 8 Frequency ranges required in grid codes in different synchronous areas of different sizes

Figure 9 The impact of total system inertia (TSI) constant on the frequency response of an interconnected system

Figure 10 RoCoF vs. system inertia projection for the Irish system, 2012

Figure 11 Voltage ride-through boundaries for wind-powered generation resources in ERCOT

Figure 12 The current (non-exhaustive) trends of technical requirements in grid connection codes

Figure 13 CIA triad

Figure 14 HVRT curves in selected grid codes

Figure 15 Distinction of capabilities, behaviour and provision of ancillary services

Figure 16 Overview of ancillary services and other services

Figure 17 Impact of system inertia on frequency response after an event

Figure 18 Impact of 140 MW of FFR (from battery units) on system frequency in the Irish power system

Figure 19 Wind turbine FFR provision and recovery period

Figure 20 Grid-following vs. grid-forming inverters

Figure 21 Grid code compliance testing in the project lifecycle

Figure 22 General scheme of conformity assessment

Figure 23 Stages of international co-operation in power systems

Figure 24 The Regional Electric System interconnecting Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua and Panama

Figure 25 Minimum requirement for reactive power capacity for all generation plants connected to the RTR

Figure 26 Steps in developing grid integration in SAARC

Figure 27 Grid code formulation guidance according to grid size and VRE integration level

TABLES

Table 1 Steps for developing, maintaining and revising a grid code

Table 2 Current harmonics distortion limits of the PV systems

Table 3 Voltage harmonics distortion limits of the PV systems

Table 4 HVRT requirements in selected countries

Table 5 Inertia-based FFR and other FFR requirement examples

Table 6 EU Network Codes

Table 7 Capacity thresholds for power-generating modules of four types, depending on the synchronous system they are connected to

Table 8 Main requirements in the EU NC RfG and where they apply

Table 9 EU NC RfG parameterisation of non-exhaustive requirements

Table 10 Applicable NERC standards for RTOs/ISOs

Table 11 Frequency range requirements and minimum operation times for generators connected to different synchronous systems as an example of regional variance in the NERC Reliability Standards

Table 12 IEC and IEEE product specification standards relevant to power systems and VRE integration

Table 13 International communication and power system design standards commonly referenced in grid codes

Table 14 International interconnection standards

Table 15 VRE shares in selected systems

Table 16 Selection of power system archetypes

BOXES

Box 1 What is the purpose of grid codes?

Box 2 Legal status of the grid code in India

Box 3 VRE forecasting requirements in China

Box 4 Grid codes for remote control in China and Germany and the IEEE Standard

Box 5 Cybersecurity

Box 6 Cybersecurity for wind power plants

Box 7 European grid code for demand side flexibility

Box 8 Island nation examples: Indonesia and the Philippines

ABBREVIATIONS

AC Alternating current

AEMO Australian Energy Market Operator

AGC Automatic generation control

AGIR Authorities governing interconnecting requirements

CCT Critical clearing time

CEA Central Electricity Authority

CHP Combined heat and power

CIP Critical Infrastructure Protection

CNC Connection Network Code

CRIE Comisión Regional de Interconexion Eléctrica

DC Direct current

DER Distributed energy resources

DSO Distribution system operator

ENTSO-E European Network of Transmission System Operators for Electricity

ERC Electricity Regulatory Commission

ERCOT Electric Reliability Council of Texas

EU European Union

EU NC RfG EU Network Code Requirements for Generators

EV Electric vehicle

FFR Fast frequency response

FRT Fault ride through

FSM Frequency sensitive mode

GMS Greater Mekong Subregion

HVDC High voltage direct current

HVRT High voltage ride through

Hz Hertz

IBR Inverter-based resource

IEC International Electrotechnical Commission

IEEE Institute of Electrical and Electronics Engineers

IPP Independent power producer

IRENA International Renewable Energy Agency

ISO Independent system operator

kHz Kilohertz

kV Kilovolt

kW Kilowatt

LFSM-O Limited frequency sensitive mode for overfrequency

LFSM-U Limited frequency sensitive mode for underfrequency

LOM Loss-of-mains

LVRT Low voltage ride through

MER Mercado Eléctrico Regional

MW Megawatt

MWh Megawatt hour

MW-s Megawatt second

NERC North American Electric Reliability Corporation

PFR Primary frequency response

p.u. Per unit

PV Photovoltaic

RfG Requirement for generators

RMER Reglamento del Mercado Eléctrico Regional

RoCoF Rate of change of frequency

RTO Regional transmission operator

RTR Red de Transmisión Regional

SAARC South Asian Association for Regional Cooperation

SADC Southern African Development Community

SAPP Southern African Power Pool

SCADA Supervisory control and data acquisition

SIR Synchronous inertial response

SMGW Smart meter gateway

SNSP System non-synchronous penetration

THD Total harmonic distortion

TSI Total system inertia

TSO Transmission system operator

UFLS Under frequency load shedding

VRE Variable renewable energy

WECC Western Electricity Coordinating Council

EXECUTIVE SUMMARY

This report contains the latest developments and good practices to develop grid connection codes for power systems with high shares of variable renewable energy (VRE) – solar photovoltaic (PV) and wind. The analysis is an update of the 2016 International Renewable Energy Agency (IRENA) report Scaling up variable renewable power: The role of grid codes and elaborates on the latest developments and experiences related to technical requirements for connecting VRE generators and enabling technologies such as storage, electric vehicles (EVs) or flexible demand and their incorporation in grid connection codes.

There is an urgent need to adopt clean energy solutions to cope with growing demand and replace existing polluting generators. Utility-scale solar PV and wind farms are already operational in many countries with high shares of instantaneous demand being covered by VRE generation. An increasing number of countries aim to replace fossil fuel-based generation with more VRE generation,¹ which would lead to almost 100% renewable power in those countries before mid-century. An advantage, especially for solar PV, is that renewable energy can be deployed at lower voltage levels for direct consumption, with high demand correlation. Renewable energy is also inexpensive in the long run, producing affordable electricity. Wind power, though deployed at sites away from load centres, can be transported using transmission lines. Alternatively, it can be stored at site using energy storage solutions that could cover for peak loads or as required by the system operator.

VRE impacts the way power systems are operated

Traditional power systems are composed of largely conventional generators. These are synchronous generators: large, centralised dispatchable assets, contributing to system’s inertia and feeding large amounts of power into the transmission grid, from where power is transported to load centres. Electricity systems are changing, however, and the optimal generation mix in a power system now comprises diverse generation assets that can be distributed, located closer to consumers and decentralised in operation. Renewable generation technologies, most of which can only generate when the primary resource is available, are sustainable and cost-effective. Solar PV and wind power generators, which are VRE sources, are now mature technologies that are expected to grow exponentially in installed capacity in the future. Favourable ecosystems for the growth of renewables have ensured that this continues. The nature of VREs introduces challenges to system operation. VREs are variable,² uncertain,³ location constrained⁴ and inverter-based,⁵ replacing conventional synchronous generation technologies. This changes the dynamic behaviour of the power system to events.

Furthermore, three trends being observed in power systems are decentralisation, digitalisation and electrification of end users, which are driving the growth of the power system in a new and different direction. All of this comes at a cost to the system. The system operator has to ensure that the system is both flexible (able to accommodate the frequent imbalances between demand and supply) and stable (able to recover in event of any contingency).

With the power system evolving in operation, structure and organisation, there is a need for better monitoring, controllability and co-ordinated control of the different assets, assigning their roles and contribution to the system at different times of the day. Different assets also mean multiple stakeholders. With independent power producers (IPPs) owning and operating renewable projects, regulators performing regulatory overview, and planners looking at how the system can develop in the future. The real-time monitoring control and operation of the power