Modeling and Control of Power Converters for Grid-Connected Li-ion Batteries
In the transition to renewable energy sources, battery energy storage is becoming more important due to varying production from windmills and PV. Lithium Ion batteries have become the dominant technology in this field due to their high energy density, and high efficiency in large-scale grid applications. For the transfer of energy from the batteries to the consumers, DC-AC inverters are essential, as they directly convert the DC voltage of the battery into AC voltage for the grid. To feed the grid using batteries it is necessary to match characteristics of the grid such as phase, amplitude and frequency. To achieve this, a theoretical solution is proposed consisting of a control system using droop control and a phase locked loop. Additionally, LCL filter is implemented to mitigate harmonics. This method allows the battery system to automatically adjust its power output based on grid parameters, ensuring stable operation and contributing to grid reliability. A digital twin of the system is developed in SIMULINK and validated in OPAL RT. Here it is found that the digital twin closely resembles reality and the proposed controller functioned sufficiently. The results of this project demonstrate the feasibility of implementing Lithium Ion batteries as a energy storage solution for the electrical grid. This project mostly deals with the concept of creating the power flow from the battery system to the grid. In the future, more concrete solutions for high voltage systems should be developed.