Reliable and affordable power supply with new microgrid solutions

Auteurs : Britta Buchholz
Publication REE REE 2017-2 Dossier Les microgrids
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Reliable and affordable power supply with new microgrid solutions


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48 Z REE N°2/2017 LES MICROGRIDSDOSSIER 1 Introduction: advancements in microgrid solutions over 25 years Microgrids include several genera- tors and loads that are operated in a controlled, coordinated way and are either connected to the main grid or operate off-grid. The first pioneering microgrids were taken into operation in the 1990´s. They started to stabilize the grid with adequate control systems when connecting wind turbines to existing Diesel generators on islands – at that time with a focus on Greek islands in Europe and in remote areas in Australia. Microgrid control systems Australian pioneers – then at the PowerCorp company that has become part of ABB in 2011 – developed micro- grid control systems to add high shares of the wind and solar energy to Diesel gene- rators and keep high power quality. First applications were islands and remote off- grid communities all over the world. Since then, in the last 25 years, the team has further developed sophistica- ted microgrid control algorithms, mostly with centralized control algorithms at that time. Based on technology development, the team partnered with power conver- sion system providers to develop the “PowerStore” product together with flywheel technology. The first microgrid where 600 kW wind generator, 2 240 kW Diesel generator and a 500 kW flywheel operated under one control system was installed in 2007 in the touristic remote community Coral Bay in Western Australia. One major milestone was reached in 2009, when the first decentralized Microgrid Plus Control System was developed – at that time for an R&D community on Ross Island, Antarctica. A 500 kW flywheel stabilizes 1000 kW of wind generators along with 1125 kW Diesel generators. Reliable and affordable power supply with new microgrid solutions Britta Buchholz Vice President, Global Product Manager Microgrids & Distributed Generation, ABB Having been a niche technology for more than 25 years, Microgrid solutions are now on their way to become the preferred technology to provide reliable and affordable power supply to locations with no or weak distribution grids. They also contribute to make existing rural, urban or industrial distribution systems stronger, smarter and greener. They serve to integrate a high penetration of renewables up to 100% and thus contribute to high power quality in the energy transition. This paper describes advan- cement in Microgrid solutions over the last 25 years, based on the experience of the installed base of over 40 microgrids all over the world. Then it highlights recent installations and a current project under development, including two islands in Alaska, USA, an urban microgrid in Melbourne, Austra- lia, the Longmeadow industrial site in Johannesburg, South Africa, and the Logistic Center of the International Commit- tee of the Red Cross in Nairobi, Kenya. It will show how the industrialized and standardized solution PowerStore with the Microgrid Plus Control System supports to make microgrids even more affordable [1]. ABSTRACT Technologies de niche depuis plus de 25 ans, les solutions microgrids sont en passe de deve- nir les technologies de référence pour la fourniture d’une énergie fiable et économique destinée aux consommateurs connectés à des réseaux faibles ou opérant indépendam- ment du réseau. Les solutions microgrids contribuent aussi à renforcer les réseaux ruraux, urbains et industriels et per- mettent leur transformation vers des réseaux intelligents et respectueux de l’environnement. Au-delà de leur capacité à améliorer la qualité de l’approvisionnement électrique, les microgrids permettent aussi d’intégrer de très hautes péné- trations d’énergies renouvelables, jusqu’à 100 %, s’inscri- vant donc dans une démarche de transition énergique. Cet article décrit l’évolution des solutions microgrids au cours des 25 dernières années grâce à l’expérience acquise de 40 microgrids installés à travers le monde. L’article met en avant les projets les plus récents ainsi que ceux en cours de réalisation notamment les projets sur deux îles en Alaska (Etats Unis), un microgrid en zone urbaine à Melbourne (Australie), le site industriel Longmeadow à Johannesburg (Afrique du Sud) ainsi que le projet du centre logistique du Comité International de la Croix Rouge à Nairobi (Kenya). L’article décrira aussi comment l’usage de solutions indus- trialisées et standardisées PowerStore et Microgrid Plus Sys- tem aident à rendre les solutions microgrids encore plus accessibles [1]. RÉSUMÉ KEYWORDS AND ABBREVIATIONS: Microgrid; PowerStore; Control System; Battery Energy Storage Systems, renewables, wind, solar, Austra- lia; America; Africa; Islands; Remote Communities; Industry. REE N°2/2017 Z 49 Reliable and affordable power supply with new microgrid solutions In general, the control system ma- nages the energy flow within the power network to ensure there is enough spin- ning reserve, and balances between supply and demand in the power grid. It also optimizes the average use of re- newable energy, even when sources are intermittent. PowerStore with flywheels and lithium-ion batteries Several systems were installed based on PowerStore with flywheels between 2007 and 2014. In the meantime, li- thium-ion batteries have become state of the art for most microgrid applica- tions that need power for 15 min up to several hours. The PowerStore product based on ABB´s PCS100 power conversion sys- tem has been continuously further developed to provide highest power quality to the customers. The first PowerStore using lithium- ion batteries was installed at the urban distribution system of AusNet Services in Melbourne, Australia, in 2014. With rated power of 1 MW, energy capacity of 1 MWh and in combination with a 1 MW Diesel generator, the system provides active and reactive power sup- port during high demand periods of an industrial feeder in the urban distribu- tion system. Further it can switch into isolated/off-grid operation on com- mand or in emergency cases without supply interruption. In this case, the microgrid solution has delayed a power line investment that would have been necessary due to growing demand. The system is mobile and transportable [2]. Flywheels remain important for cer- tain applications, e.g. to provide frequen- cy support for loads with high peaks in harbors. This is the case at the installation at Kodiak Electric Association on Kodiak island in Alaska [3]. A 2 MW flywheel was added to stabilize the grid against fluctu- ations from the 9 MW wind generators and to provide frequency support for the new crane in the harbour. At the same time, it saves fuel by reducing the reli- ance on diesel generators. As a next step, flywheel and lithium- Ion technologies are currently being combined as a hybrid storage for Fire Island, 4 km off the coast of Anchorage, Alaska. In the system that has been deve- loped for Chugach Electric Association, the flywheel absorbs most short term wind fluctuations, whereas the lithium ion battery is used less frequently as storage for longer term events. The bat- tery has a capacity of 500 kWh with a maximum performance of 2 MW. PowerStore productization with standardized, modular and safe design Altogether, more than 40 micro- grids have been developed by the PowerCorp and then ABB team. So far, most microgrids were realized as indivi- dual projects and the PowerStore was designed to each special requirement. In order to make the PowerStore solu- tion even more affordable at high safety standards, a new set of productized, standardized PowerStore variants were developed and the products released in Figure 1: PowerStore Battery at AusNet Services facilities in Melbourne, Australia (left) and wind park stabilized by PowerStore Flywheel at Kodiak Island, Alaska, USA (right). Figure 2 : Productized and standardized PowerStore™ battery system. 50 Z REE N°2/2017 LES MICROGRIDSDOSSIER 1 October 2016. Ranged between 50 kW and 2 800 kW power and based on a modular and scalable concept, econo- mies of scale help to reduce cost and provide reliable, affordable and safe power to any place in the world. As shown in figure 2, power conversion system, microgrid automation and bat- teries are integrated into one standar- dized container of 10 feet, 20 feet or 40 feet. All PowerStore variants come with remote access. The product has several variants to serve different appli- cations, such as islands, remote areas on-grid or off-grid, urban grids, industry and commerce or institutions. Typical microgrid system set-up A typical microgrid includes several generators and loads that are operated in a controlled, coordinated way and are either connected to the main grid or operate off-grid. In most cases, new generators and storage are added to an existing energy supply infrastructure. Typically, Diesel generators supply power to islands or remote communities, and they serve as back-up and peak shaving power supply for industrial, commercial or residential sites. As renewable energies like solar photovoltaic systems and wind genera- tors have significantly decreased in cost, they become a viable option for cost efficient power supply. Especially when demand is gradually growing and new generation capacity must be added to the electricity system quickly, modular renewable energy and storage provide an economic solution. Integrating solar PV and wind ener- gy into the electricity system comes along with two major challenges: on the one hand, fluctuations in wind and solar resources result in fluctuations of voltage and frequency that need to be absorbed in order to keep power qua- lity stable. The second challenge is that wind generators and solar PV systems are connected to the electricity system via power electronics, with no inertia. When increasing the generators with power electronic and decreasing the contribution of Diesel generators, i.e. synchronous rotating machines with inertia, the system needs to be stabi- lized with artificial inertia. PowerStore™ resolves both of these challenges. The high performance Power Conversion System PCS100 is combined with either flywheel or lithium-ion batteries and the micro- grid controller. It stabilizes the grid by injecting active or reactive power as a quick absorption of fluctuations in frequency and voltage respectively that are caused by wind and solar PV gene- ration. Further in the “Virtual Generator Mode”, it behaves as a synchronous rotating machine and provides an arti- ficial inertia. Further, it shares the load with other Diesel generators in the microgrid if there are any, and it pro- vides frequency signals and the voltage reference to form the grid if there is no main grid available, be it planned or unplanned. In the Microgrid Plus Control System, each generator type or feeder type is equipped with at least one microgrid controller from the MGC600 family. The architecture is explained in figure 3. All generators and loads in the sys- tem communicate with each other via individual microgrid controllers, the MGC600 family. Based on the same hardware, they have different firmware dedicated to the type of the device, e.g. PV system, wind generator, hydro, Diesel generator, battery energy sto- rage, main grid or diverse loads. Each controller broadcasts its status to the microgrid system and decides indivi- dually to act according to the informa- tion available from other controllers. Adding further controllers to a larger generator, e.g. to each inverter of a so- lar PV system, to each wind turbine or to each Diesel generator, increases the robustness of the system. In case one of the generators or controllers fails, the rest of the system keeps operating. This system is flexible and scalable, because it is easy to add further gene- rators or loads without additional engi- neering efforts. This is very important for areas where the electricity demand changes quickly or is not known at all. M+ Operations serves as a data acquisition system and hosts the local Human Machine Interface (HMI) with remote access options. Figure 3: Microgrid Plus Control System coordinating several generators and loads. REE N°2/2017 Z 51 Reliable and affordable power supply with new microgrid solutions Reliable and affordable power for Africa Africa´s demand for electricity is growing at high pace, and so is the need for reliable, safe and sustainable solutions. The high growth of electricity demand and lack of generation capaci- ties have led to planned or unplanned power cuts and load shedding mea- sures. Many industrial and commercial sites therefore have Diesel generators on site to reduce peak load and provide back-up power in case of loss of the main grid. Industrial microgrid for factory and offices at ABB´s South African headquarters in Johannesburg The industrial site located in Johan- nesburg includes a 96 000 m² area and hosts both a factory and offices with around 1 000 employees. It has faced load shedding measures and power cuts in the past. Electricity cost was rising even if the demand on site kept stable due to increasing peak demand charges. Diesel generators on site provi- ded back-up power supply and reduced peak load. In order to stabilize the grid and enable seamless transition from grid connected to islanding mode in case of a power cut, a PowerStore battery with capacity of 1 MW/380 kWh based on lithium-ion battery was installed. Further, as solar PV systems have experienced significant cost reductions and consi- dering the excellent solar resource in Johannesburg, a 750 kWp solar PV sys- tem was installed. The Microgrid Plus Control System balances the solar PV system with the PowerStore and the already existing Diesel generators to serve the load at all times. In case of loss of the main grid, PowerStore takes over seamlessly and forms the grid by providing a reference voltage and a frequency signal. In such a case, both solar PV system and Diesel generators share the load to reach optimal energy cost at highest possible use of energy from the PV system. M+ Operations monitors and logs all data locally on site and is equipped with remote monitoring. With this micro- grid, the owner expects to reduce CO2 by over 1 000 tons per year. The sys- tem can handle up to 100% renewable energy [4]. Commercial microgrid for logistic center of International Committee of Red Cross in Nairobi, Kenya As in many places in Africa, the Inter- national Committee of the Red Cross has powered its largest logistic hub in Nairobi, Kenya, with Diesel generators so far. The logistic hub hosts 170 employees. It deli- vers essential items such as food, medi- cines and relief supplies across Africa. In 2017, ABB will power this site through a state-of-the-art microgrid including a solar PV system and PowerStore Battery in ad- Figure 4: View of the Longmeadow site, Johannesburg. Figure 5: Views of the Nairobi Logistic Center. 52 Z REE N°2/2017 LES MICROGRIDSDOSSIER 1 dition to the Diesel generator. Thus, the logistic hub will be supplied with reliable power based on renewables in a region exposed to frequent outages and power quality issues. The system maximizes the use of solar energy and saves fuel cost, reducing carbon emissions at the same time. This kind of application for humani- tarian institutions has broad applications all over Africa to provide affordable power supply to areas without reliable power infrastructure. Concluding remark Time has come for microgrid solu- tions to play a significant role in the transition of the energy supply system. Grid connected, they provide flexibi- lity services to the main grid. Off-grid, they provide affordable reliable power anywhere. Based on broad experience with over 40 microgrid installations on islands, remote communities, urban, industrial and commercial grids, hard- ware and software have continuously been improved to serve the needs of the customers. With the reliable and scalable Microgrid Plus Control System and the productized and standardized PowerStore, solutions are ready to scale up and serve any place in the world with excellent power quality with safe devices and at economic conditions. As a consequence of the expected re- duction of cost due to lithium-ion battery storage and renewable energy, econo- mics will become even better over time. References to projects and techno- logies described in this paper can be found at the ABB web page, including video clips, images, brochures and scientific papers [1]. References [1] [2] N. Chander et al. “Battery/diesel grid- connected microgrids: a large-scale, industry-based case study of future microgrid capabilities”, Melbourne, 2015 [3] “Microgrid to run Alaskan island on renewables “, Zurich, 2016 http:// seitp202.nsf/0/a8e4440bce767e47c12 57d51003729ef/$file/Kodiak_Alaska_ microgrid.pdf [4] “Microgrid solution in Johannesburg, South Africa: Providing uninterrupted power supply” com/public/22a8e853540248209 d1054ca295206be/Data_sheet_ Longmeadow_FINAL.pdf [5] “State-of-the-art microgrid to power African hub of the International Committee of the Red Cross”, Zurich, September 2016 com/cawp/seitp202/5DB53B3A98839 397C125803D002C7953.asp Zurich L'AUTEUR Dr. Britta Buchholz is Global Pro- duct Manager for the Product Group Microgrids and Distributed Gene- ration within the business unit Grid Automation at ABB Power Grids. She joined ABB in 2011. Prior to that, she had several roles in R&D and as head of engineering at the regional energy company MVV Ener- gie in Mannheim, Germany. She holds a Master´s degree in Industrial Engineering from Karlsruhe Insti- tute of Technology (KIT), Germany, and a Doctor´s degree in Electrical Engineering from Kassel University, Germany, with a focus on PV-Diesel Hybrid Systems. In CIGRE, she has been holding several key positions including chairing the Study Com- mittee C6 “Distribution Systems and Dispersed Generation” from 2014 to 2016.