Grid code requirements and advanced power electronics solutions [Part 1/8: Overview]

As the electricity generation capacity continues to increase globally, including a higher share of renewable generation, and more nonlinear and other challenging loads are connected to the electrical grids, stricter requirements regarding grid connection, grid operation and balancing of generation (renewable or non-renewable) and consumption are introduced by transmission system operators (TSO for short) and distribution system operators (DSO for short). These requirements are compiled into grid codes (also known as network codes) and ensure that electric power systems remain reliable and robust while supplying continuous high-quality power.

Grid codes define the requirements that facilities (generators, consumers, prosumers and electrical grids) have to comply with in order to achieve grid code compliance.

Compliance can be fulfilled by using several methods including network planning, controllable generators, controllable loads, conventional mechanically switched compensation devices or modern power electronics solutions like power electronics-based compensation devices and power electronics-based energy storage devices.

Grid codes

A grid code is a technical specification that defines the parameters a facility connected to an electrical grid has to meet to ensure safe, secure, efficient and economic proper functioning of the electric power system. The facility can be an electricity generator (renewable or non-renewable), a consumer (load), a prosumer or another electrical grid (transmission grid, distribution grid, minigrid or microgrid). 

The contents of a grid code may vary depending on the country, the TSO or the DSO requirements. The grid code regulates the general conditions pertaining to how facilities connect to the electrical grid. The grid code also covers grid usage, system services, grid expansion, general grid operation and requirements for power quality and energy efficiency improvement.

Regarding generators, the rules of the grid code apply to all facilities that feed into the electrical grid, from large power plants to independent power producers (IPP for short). Among other things, the grid code defines specific conditions that must be met for these generation facilities to participate in providing ancillary services. The grid code will also specify the required behaviour of these facilities during system disturbances. These requirements include for example voltage control, power factor control, reactive power supply, response to a system fault (e.g., short-circuit), response to frequency changes on the grid, and requirement to ride through short interruptions.

Types of grid codes

Unbundling of electric power systems and the increasing shares of decentralised generation are major drivers of grid code development. Different stakeholders are involved with the development of grid codes including policy makers, owners and operators of generators, system operators and regulators, generator and grid asset manufacturers and consumers.

The different types of grid codes facilitate operational flexibility, operational stability, security and quality of supply as well as the proper operation of wholesale markets. Grid codes can be divided broadly into three groups following the classification of the European Network of Transmission System Operators for Electricity:

• Connection codes: Aimed to deliver greener power and adopt smarter consumption patterns.
• Operation codes: Aimed to reinforce the security of supply.
• Market codes: Aimed to allow a wider integration of the electrical market.

Grid code requirements

Technical requirements in grid codes are determined by the need to maintain the reliability, security and quality of the power supply and fulfil the following objectives:

• The electrical power needs of all consumers must be met reliably.
• Voltage and frequency must be maintained within set limits to avoid damaging equipment connected to the electrical grid.
• The electric power system must be able to recover quickly from system disturbances.
• At all times, the electric power system must operate without endangering the public or operating staff.

Technical requirements for services and capabilities for generators, consumers, prosumers or electrical grids are presented in grid codes. These services and capabilities can be used also to support the electric power system when needed. They are usually not available all the time but depend on whether the generator or the load is on-line and operating at a level where a service or capability can be provided. They are usually only called upon when needed, some services and capabilities are used during normal operation (continuous) and some are provided for abnormal/emergency situations (event driven).

Grid code requirements can be divided into two groups:

• Ancillary services: Services required by the TSO or DSO to maintain the integrity and stability of the electric power system.
• Power quality improvement capabilities: They are capabilities required for the mitigation of different power quality problems of the electric power system.

Typical grid code requirements - Ancillary services

Typical grid code requirements - Power quality improvement capabilities

The next article of this series will discuss grid code compliance.

If you would like to receive any of my publications on the topic or to explore how #PowerElectronics solutions can help your installation to achieve grid code compliance, feel free to reach me at pedro.esteban@meruspower.com. 

You are also welcome to join my running series of weekly #FreeWebinars for Asia-Pacific region on cutting edge #PowerElectronics solutions and their applications.

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About the author:

Pedro Esteban is a versatile, multicultural and highly accomplished marketing, communications, sales and business development leader who holds since 2002 a broad global experience in sustainable energy transition including renewable energy, energy efficiency and energy storage. Author of over a hundred technical publications, he delivers numerous presentations each year at major international trade shows and conferences. He has been a leading expert at several management positions at General Electric, Alstom Grid and Areva T&D, and he is currently working at Merus Power Plc.