Grid oper­a­tors, faced with a pro­fu­sion of local renew­able ener­gy elec­tric pow­er pro­duc­ers, are now devel­op­ing so-called “smart” grids to ensure sta­bil­i­ty in the over­all pow­er sup­plied to the end-users. With a view to help­ing the oper­a­tors in their task to bal­ance the grid, while pro­mot­ing the devel­op­ment of renew­able ener­gy sources pro­duced local­ly, the UTC-Avenues Lab. is propos­ing the devel­op­ment of local micro-grids to gen­er­ate, store and con­trol pow­er exchanges with the nation­al grid system. 

Enabling any­one to become a renew­able ener­gy pro­duc­er with the pos­si­bil­i­ty to inject sur­plus pro­duc­tion into the nation­al grid is indeed an attrac­tive con­cept but it brings with it a set of tech­ni­cal issues and problems.“Today’s nation­al grid in France is not designed to accept a bi-direc­tion­al pow­er flow”, under­lines Manuela Sechi­lar­iu and Fab­rice Loc­ment, both of whom are research sci­en­tists at the UTC-Avenues Lab. 

When there is excess demand, pow­er gen­er­a­tion sta­tions must be start­ed and brought on line to meet the demand, while excess pow­er gen­er­a­tion, in reverse, leads to volt­age and fre­quen­cy vari­a­tions of the pow­er deliv­ered to the grid and the users. Today the net­work oper­a­tors want to be able to adapt their grids not only to accept decen­tralised pow­er pro­duc­tion nut also the inter­mit­tent ran­dom inputs as pro­duced by pho­to­volta­ic (PV) arrays and wind tur­bine generators. 

Grid stability is a problem

One solu­tion, when faced with the prob­lem of ‘dif­fuse’ pro­duc­tion means, and the essen­tial need to bal­ance pro­duc­tion with demand, is to devel­op so-called “smart grids”. In prac­ti­cal terms, this con­sists of imple­ment­ing a communications/information net­work that is super­im­posed on the nation­al grid and allows you to reg­u­late the lat­ter as a func­tion of the infor­ma­tion col­lect­ed an exchanged. A smart grid of this nature will have the capac­i­ty to exchange infor­ma­tion as need­ed to bal­ance the whole pow­er sys­tem. “It is nonethe­less a dif­fi­cult task and nec­es­sar­i­ly calls for par­tic­i­pa­tion of a large num­ber of pro­duc­ers to help the bal­anc­ing over­ar­ch­ing objec­tive”, details Manuela Sechilariu. 

Local micro-networks communicating with a ‘smart’ national grid

Local micro-net­works com­mu­ni­cat­ing with a ‘smart’ nation­al gridThe solu­tion advo­cat­ed by the research sci­en­tists and their team depends on the devel­op­ment of local micro-grids. The lat­ter use local renew­able ener­gy sources, while opti­miz­ing pro­duc­tion, con­sump­tion and stor­age so as to con­tribute active­ly to bal­anc­ing the nation­al grid per­for­mance. A micro-grid sys­tem, devel­oped at the UTC-Avenues Lab. includes pro­duc­tion facil­i­ties (PV arrays or wind tur­bine gen­er­a­tors), stor­age and grid reg­u­la­tion sys­tems. The main device is a sys­tem con­troller which acts as an inter­face with the nation­al dis­tri­b­u­tion grid and ensures a con­stant­ly- reg­u­lat­ed pow­er flow. “We have devel­oped algo­rithms that help pre­dict pow­er demand lev­els, pow­er pro­duc­tion to be brought on-line and there­by ensure sta­bil­i­ty for the nation­al grid as a whole”, under­lines Manuela Sechi­lar­iu. The research engi­neers are also sat­is­fied that they can “ensure opti­mal pow­er pro­duc­tion, both in terms of oper­a­tional cost and the appro­pri­ate use made of renew­able ener­gy sources”. 

UTC’s Avenues Lab­o­ra­to­ry already has an exper­i­men­tal rig with pho­to­volta­ic (PV) pan­els up and run­ning on the cam­pus, with asso­ciate pow­er stor­age units and algo­rith­mic con­trol sys­tems. The next step will be to build and equip a scale one charg­ing sta­tion for all-elec­tric vehi­cles, the pow­er com­ing from PV shel­ters, which con­nects into the French nation­al grid. “The demand for fast charg­ing elec­tric vehi­cles could rise rapid­ly and leads to a sharp upturn of pow­er demands on the grid”, explains Fab­rice Loc­ment. One solu­tion con­sists of devel­op­ing micro-grids to recharge the vehi­cles and there­by decrease the nation­al demand while enhanc­ing and encour­ag­ing use of renew­able ener­gy sources.