Distributed Power Electronics for Second-Life Batteries
Author
Suarez Porras, Jorge
Term
4. term
Education
Publication year
2022
Submitted on
2022-06-02
Pages
110
Abstract
As the electric vehicle market grows, used car batteries are becoming attractive second-life options for stationary battery energy storage to support the power grid. These batteries are not uniform: they differ in state of health (SOH, how worn they are) and state of charge (SOC, how full they are), which makes control, efficiency, and safe operation more complex. This work analyzes control methods for connecting second-life batteries to the grid using a cascaded H-bridge (CHB) topology. This architecture allows more independent, flexible control of many battery modules. We present and compare alternative switching techniques based on pulse-width modulation (PWM) for multilevel inverters (MLI), which convert the batteries’ direct current into alternating current at multiple voltage levels. We also propose strategies for a battery energy management system (BEMS) to allocate power and protect the batteries. Finally, we introduce an active balancing technique to equalize the state of energy (SOE) among cells. The results show that these strategies are applicable in practice and expand the control capabilities of battery storage systems.
Efterhånden som markedet for elbiler vokser, bliver brugte batterier fra biler attraktive som second-life energilagre til at støtte elnettet. Disse batterier er dog ikke ens: de varierer i sundhedstilstand (SOH, hvor slidte de er) og i ladetilstand (SOC, hvor fyldte de er). Det gør styring, effektivitet og sikker drift mere kompleks. Dette arbejde analyserer forskellige styremetoder til at tilslutte second-life batterier via en kaskadekoblet H-bro-topologi (CHB). Denne opbygning gør det muligt at styre mange batterimoduler mere uafhængigt og fleksibelt. Vi viser og sammenligner alternative koblingsmetoder baseret på pulsbredde-modulation (PWM) for flerniveaus-invertere (MLI), som omdanner batteriets jævnstrøm til vekselstrøm med flere spændingstrin. Der foreslås desuden strategier for et batteri-energistyringssystem (BEMS), der fordeler belastning og beskytter batterierne. Endelig præsenteres en aktiv balanceringsteknik, der udligner energitilstanden (SOE) mellem cellerne. Resultaterne viser, at strategierne kan anvendes i praksis og udvider mulighederne for styring af batterilagringssystemer.
[This apstract has been rewritten with the help of AI based on the project's original abstract]