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Connecting variable renewable energy power plants to weak grids can present additional challenges that are not seen in robust power systems, where the grid can maintain voltage without issues when reactive power is injected into the system. However, variable-power electronics controlled renewable energy connected to a weak grid may result in transient over voltages, voltage oscillations and system instability. Grid studies, such as power flow analyses, short circuit analyses, electro mechanic and electromagnetic transients, and power quality studies, can be especially important to maintain or increase the quality of supply, and avoid curtailment in the case a significant part of the generation comes from VRE in a relatively weak electricity network. Real case studies from several countries that combine big wind power plants and microgrids—were presented.

We also discussed how the grid studies and simulations are used to mitigate the instability risks, as well as the different measurements for proving grid code compatibility, such as the power quality and low voltage ride through (LVRT) tests.

Finally, the presentation showed how important grid codes are for Transmission System Operators (TSOs) to be able to maintain grid stability, particularly in weak systems.

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Silvia Martinez Romero, Senior Renewable Energy Specialist | ESMAP, The World Bank Group
 

Carlos Alvarez is the technical director of Energy to Quality since 2012. Energy to Quality is an electrical laboratory accredited for measuring power quality in wind turbines and member of the Measuring Network of Wind Energy Institute (MEASNET). He received his PhD in 2011 on Double Fed Induction Generator (DFIG) wind turbines and voltage dips in the Carlos III University of Madrid, Spain, and Lund University, Sweden. His main interests are power quality measurements and studies of grid integration of renewable power plants. Carlos is the convener of the Spanish group of the International Electrotechnical Commission (IEC) 61400-21, member of the Maintenance Group of the IEC 61400-21, and of the Working Group IEC 61400-27. Besides power quality in wind turbines and Photovoltaic (PV) units measuring projects, Carlos is also involved in several consultancy projects for grid integration of renewable power plants all over the world--such as wind power plants in South Africa, in Brazil, Egypt, Mexico, and Bolivia; solar power plants in Uganda, Mexico, Jordan, and Chile; and micro grids wind/diesel in Argentina. Carlos was also involved in the development of testing equipment, such as Under Voltage Ride through Test Units (UVRT) test units, in Spain and Brazil.

Contact: Carlos Alvarez | Technical Director | Barlovento | calvarez@energytoquality.com