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Advanced Energy and Decarbonisation Office (AEDO)

Method for Online Monitoring of Batteries in Multilevel Stationary Energy Storage Systems Without Affecting the Electrical Network

19 October 2026

Affiliation

NTU

Focus topic

Energy Storage

Live grid-battery health checks without disturbing the grid

Summary

A control method and system for determining battery states (e.g., state of charge and health) in multilevel battery energy storage systems (BESS) while they operate on the grid, without degrading grid power quality.

Achievements: validated on a 3.84 kW / 3.46 kWh lab prototype with four cascaded battery strings connected to a 220 V grid, across active, mixed and reactive power injection modes. Battery model parameters were identified accurately in real time, converging rapidly, and the method flagged one module with higher internal resistance, consistent with aging. Grid current harmonic content was identical with and without monitoring (THD ~2.88%), well within IEEE 1547-2018 limits, with fast transients and no overshoot. No additional hardware is needed; the approach covers series- and parallel-connected configurations and can extend to multiport EV charging stations.

Carbon abatement potential is indirect: safer, longer-lived and better-utilized grid batteries support renewable integration and grid services such as frequency regulation and peak shaving.

What makes this novel compared to best-in-class technology?

Existing online monitoring methods distort grid current, need extra hardware such as supercapacitors, or only work in DC systems. This method gives continuous battery diagnostics in AC grid-connected multilevel BESS with no measurable impact on power quality and no added components.

TRL Level

4-6

Relevant for

  • Utility-scale BESS operators and integrators

  • Power-conversion and inverter manufacturers

  • Battery management system suppliers

  • EV charging station operators

About

NTU logo

Inventors: Ezequiel Rodriguez Ramos, Enrique Alejandro Nunes-Di-Pierri, Liang Gaowen, Josep Pou, Ramon Leyva-Grasa

Affiliation: Nanyang Technological University, Singapore (NTU), Energy Research Institute @ NTU (ERI@N); Universitat Rovira i Virgili

Contact NTU for licensing opportunities and more information.

Please quote ID ref [2024-461] in your email.