Online Monitoring of Battery Degradation for Enhanced Power Smoothing of PV Power Plants

Abstract

In pursuit of a carbon-neutral future, the integration of photovoltaic (PV) power plants into the electrical power grid is expanding. Although beneficial, this expansion presents challenges due to weather-induced variability, which destabilizes the grid and causes voltage and frequency deviations. A viable solution is the use of Battery Energy Storage Systems (BESS) alongside PV power plants. However, conventional controllers, which lead to uniform and frequent charging cycles, accelerate degradation and reduce efficiency in BESS. To address this, this paper proposes segmenting the BESS units into distinct charging and discharging groups, effectively minimizing battery cycling and enhancing their lifespan. The controller dynamically assigns batteries to each group based on power fluctuation forecasts using a power-sharing model. This model manages battery activation, enables inter-group support, and balances degradation by monitoring BESS charge levels and assessing battery health through an online system. This controller, coupled with a degradation balancing layer, strategically prioritizes units based on their cycling age. The proposed technique was rigorously tested and experimentally validated, demonstrating that it significantly reduces battery degradation to a maximum of 0.099%, in stark contrast to the up to 4.41% observed with conventional controllers.