Grid code requirements and advanced power electronics solutions [Part 5/8: Power quality improvement capabilities]

After the introduction of grid codes, this fifth article will discuss power quality improvement capabilities.

Power quality related issues are of most concern nowadays. The widespread use of nonlinear, non-balanced and variable loads and generators led to a complete change in the electric power system. These generators and loads such as electronic equipment including information technology equipment, variable speed drives (VSD for short), programmable logic controllers (PLC for short) and LED lighting, renewable generation sources, electric vehicle charging stations and railway electrification systems, to name a few, are simultaneously the major creators and victims of power quality problems.

The increased sensitivity of facilities and processes to power quality problems turns the availability of electric power with high quality a crucial factor for the development of modern electric power systems. The mitigation of power quality problems it is also part of the requirements of most grid codes nowadays. 

Power quality problems

Poor power quality can cause innumerable problems in any facility connected to an electrical grid. The facility can be an electricity generating plant (renewable or non-renewable), a consumer (load) or another electrical grid (transmission grid, distribution grid, minigrid or microgrid). Typical sources of power quality problems include:

• End user equipment.
• End user electric power system and earthing.
• Weather phenomena (lightning, wind, rain, ice, etc.).
• Electric transmission and distribution system.
• Electric power generation system.

Types of power quality problems

Power quality problems (events or disturbances) can be classified according to the nature of the waveform distortion. They can be steady-state or non-steady-state. Steady-state problems can be described further by the amplitude, frequency, spectrum, modulation, source impedance, notch depth and notch area attributes. Non-steady state problems can be described further by other attributes such as rate of rise, rate of occurrence and energy potential.

International power quality standards

Power quality standards define the requirements that generators and loads have to comply with at their respective connection point (low or high voltage) with the electric power system. The standards ensure that electrical equipment can operate with the expected performance without degrading the operation of other equipment connected to the electric power system.

Active involvement in standards making efforts on the part of international organizations like IEC, IEEE, UIE, CIGRE and CIRED has impacted the stability and performance of electric power systems. There are many international standards on power quality, some of the most known are IEC 61000, IEEE 519, IEEE 1453, EN 50160, G5/4, GOST 13109 and D-A-CH-CZ. 

Besides international standards, many countries have also their own local standards and engineering recommendations on power quality.

Power quality and grid codes

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, operation and balancing of generation (renewable or non-renewable) and consumption (loads) are introduced by transmission system operators and distribution system operators to ensure that electric power systems remain reliable and robust. These requirements are compiled into grid codes. 

Grid codes typically include the necessary power quality improvement capabilities that facilities have to comply with in order to achieve grid code compliance.

Power quality monitoring

Electrical power quality is an important contributing factor in electrical supply security and reliability. Power quality problems can affect and cause significant losses to end users, electricity generators and distributors, and equipment and system manufacturers. In modern electric power systems, there are several parties who should monitor power quality.

• Suppliers of electric power: For fulfilling contractual obligations and for improving the performance of the electric power system.
• Regulators: To ensure compliance and to formulate standards.
• Consumers: For being able to select power quality improvement measures, for compliance and for monitoring the performance of new installations.
• Manufacturers of equipment: For being able to give performance guarantees and for the design and development of new equipment.

Traditionally, power quality monitoring has been performed on a case-to-case basis using portable devices to measure key parameters affecting power quality. With advanced power quality monitoring devices and cloud-based data storage, it is nowadays possible to monitor and assess power quality on a continual basis. Continuous power quality monitoring can help detect, record and prevent problems and losses. Some of the benefits of conducting frequent power quality assessments in installations include:

• Identification of the source and the frequency of power quality problems.
• Preventive and predictive maintenance assistance.
• Assessment of the sensitivity of process equipment to disturbances.
• Evaluation of equipment performance against specifications.

The next article of this series will discuss possible solutions for grid code requirements.

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 [email protected]. 

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.