Editing Distributed generation (section)

== Integration with the grid ==

For reasons of reliability, distributed generation resources would be interconnected to the same transmission grid as central stations. Various technical and economic issues occur in the integration of these resources into a grid. Technical problems arise in the areas of [[power quality]], voltage stability, harmonics, reliability, protection, and control.<ref>{{cite web |title=Contribution to Bulk System Control and Stability by Distributed Energy Resources connected at Distribution Network |url=http://resourcecenter.ieee-pes.org/pes/product/technical-publications/PESTRPDFMRH0022 |publisher=IEEE PES Technical Report|date=15 January 2017}}</ref><ref>Tomoiagă, B.; Chindriş, M.; Sumper, A.; Sudria-Andreu, A.; Villafafila-Robles, R. [http://www.mdpi.com/1996-1073/6/3/1439/pdf Pareto Optimal Reconfiguration of Power Distribution Systems Using a Genetic Algorithm Based on NSGA-II.] Energies 2013, 6, 1439-1455.</ref> Behavior of protective devices on the grid must be examined for all combinations of distributed and central station generation.<ref>P. Mazidi, G. N. Sreenivas; ''Reliability Assessment of A Distributed Generation Connected Distribution System''; International Journal of Power System Operation and Energy Management(IJPSOEM), Nov. 2011</ref> A large scale deployment of distributed generation may affect grid-wide functions such as frequency control and allocation of reserves.<ref>Math H. Bollen, Fainan Hassan ''Integration of Distributed Generation in the Power System'', John Wiley & Sons, 2011
{{ISBN|1-118-02901-1}}, pages v-x</ref> As a result, [[smart grid]] functions, [[virtual power plant]]s<ref>[https://www.researchgate.net/publication/270821401_Decision_Making_Tool_for_Virtual_Power_Plants_Considering_Midterm_Bilateral_Contracts/ Decision Making Tool for Virtual Power Plants Considering Midterm Bilateral Contracts]</ref><ref>[https://www.researchgate.net/publication/279849005_The_Design_of_a_Risk-hedging_Tool_for_Virtual_Power_Plants_via_Robust_Optimization_Approach/ The Design of a Risk-hedging Tool for Virtual Power Plants via Robust Optimization Approach]</ref><ref>[https://www.researchgate.net/publication/296307377_A_Medium-Term_Coalition-Forming_Model_of_Heterogeneous_DERs_for_a_Commercial_Virtual_Power_Plant/ A Medium-Term Coalition-Forming Model of Heterogeneous DERs for a Commercial Virtual Power Plant]</ref> and [[grid energy storage]] such as [[power to gas]] stations are added to the grid. Conflicts occur between utilities and resource managing organizations.<ref>{{cite web |last1=Bandyk |first1=Matthew |title=Propelling the transition: The battle for control of virtual power plants is just beginning |url=https://www.utilitydive.com/news/propelling-the-transition-the-battle-for-control-of-virtual-power-plants-i/581875/ |website=Utility Dive |archive-url=https://web.archive.org/web/20200819022737/https://www.utilitydive.com/news/propelling-the-transition-the-battle-for-control-of-virtual-power-plants-i/581875/ |archive-date=19 August 2020 |date=18 August 2020 |url-status=live}}</ref>

Each distributed generation resource has its own integration issues. Solar PV and wind power both have intermittent and unpredictable generation, so they create many stability issues for voltage and frequency. These voltage issues affect mechanical grid equipment, such as load tap changers, which respond too often and wear out much more quickly than utilities anticipated.<ref>{{cite journal|last1=Agalgaonkar|first1=Y.P. |display-authors=etal |title=Distribution Voltage Control Considering the Impact of PV Generation on Tap Changers and Autonomous Regulators|journal=IEEE Transactions on Power Systems|date=16 September 2013|volume=29|issue=1|pages=182–192|doi=10.1109/TPWRS.2013.2279721|hdl=10044/1/12201 |s2cid=16686085 |hdl-access=free}}</ref> Also, without any form of energy storage during times of high solar generation, companies must rapidly increase generation around the time of sunset to compensate for the loss of solar generation. This high ramp rate produces what the industry terms the ''[[duck curve]]'' that is a major concern for grid operators in the future.<ref>{{cite web|title=What the Duck Curve Tells Us About Managing A Green Grid|url=https://www.caiso.com/Documents/FlexibleResourcesHelpRenewables_FastFacts.pdf |website=caiso.com|publisher=California ISO|access-date=29 April 2015}}</ref> Storage can fix these issues if it can be implemented. Flywheels have shown to provide excellent frequency regulation.<ref>{{cite book|last1=Lazarewicz|first1=Matthew |last2=Rojas|first2=Alex |title=IEEE Power Engineering Society General Meeting, 2004 |chapter=Grid frequency regulation by recycling electrical energy in flywheels |journal=Power Engineering Society General Meeting|volume=2|date=10 June 2004|pages=2038–2042 |doi=10.1109/PES.2004.1373235|isbn=0-7803-8465-2|s2cid=20032334 }}</ref> Also, flywheels are highly cyclable compared to batteries, meaning they maintain the same energy and power after a significant amount of cycles( on the order of 10,000 cycles).<ref>{{cite web |title=Flywheels |url=http://energystorage.org/energy-storage/technologies/flywheels |publisher=Energy Storage Association |access-date= }}</ref> Short term use batteries, at a large enough scale of use, can help to flatten the duck curve and prevent generator use fluctuation and can help to maintain voltage profile.<ref>{{cite web|last1=Lazar|first1=Jim |title=Teaching the "Duck" to Fly|url=http://www.ripuc.ri.gov/eventsactions/docket/4443-EERMC-Presentation2_5-8-14.pdf |publisher=RAP|access-date=29 April 2015}}</ref> However, cost is a major limiting factor for energy storage as each technique is prohibitively expensive to produce at scale and comparatively not energy dense compared to liquid fossil fuels. 
Finally, another method of aiding in integration is in the use of [[intelligent hybrid inverter|intelligent inverter]]s that have the capability to also store the energy when there is more energy production than consumption.<ref>{{cite web|title=Smart Grid, Smart Inverters for a Smart Energy Future|url=https://www.nrel.gov/state-local-tribal/blog/posts/smart-grid-smart-inverters-for-a-smart-energy-future.html |publisher=National Renewable Energy Labortatory }}</ref>