FPGA-synthesizable Electrical Battery Cell Model for High Performance Real-time Algorithms
Periodica Polytechnica Electrical Engineering and Computer Science
Modern battery management systems (BMS) for advanced battery energy storages are expected to provide sufficient and reliable State-of-Charge (SoC) and State-of-Health (SoH) information. Focusing also on mid-and long-term maintenance purposes, health monitoring can be realized only by using high performance real-time estimation algorithms involving online electrical battery cell model. Due to the nonlinear I-V characteristics of cells and multivariable nonlinear functions describing the model
... ameters, a real-time model synthesized to FPGA seems to be the best solution to fulfill also the strongest requirements of energy management and e-mobility applications in respect of scalability, modularity, accuracy and effectiveness. In this paper, an FPGA-synthesizable battery cell model is presented and proposed. The design approach is discussed from offline to online model design including the model considerations using MATLAB/Simulink ® . The performance analysis and evaluation referenced to the offline model are presented and discussed. Introduction E-mobility and large-scale stationary energy storages specify even more specific and safety-critical requirements on advanced battery systems, hereby boosting the development need of special purpose electrical battery cell models. In opposite to this, applied research focuses more on the scalability and modularity. In technical point of view, developing electrical battery cell models has two main driving forces. One is the offline (continuous-time with floating-point number representation) circuit simulation of battery systems providing I-V characteristics for electrical system design purpose  . In applications, where the battery pack is connected to nonlinear systems (especially high power motor drives, or grid-connected energy storages), it is crucial to verify the designed battery system behavior  . The other is the online simulation, where the goal is to create a real-time electrical battery cell model, which can be run in real-time simulations and in online, i.e. model-based SoC and SoH estimation algorithms, as well [3, 4] . Such online model is essential in advanced battery energy storages. Expected modularity allows extra functions to be attached easily, and the required scalability enables level-to-pack extensions within certain error tolerances and additional dependencies of parameters [5, 6] . All these complex requirements lead the developers to switch rather to FPGA from MCU in the BMS for running high performance, online SoC and SoH estimation algorithms. Next to this, if the battery cell model is available in synthesizable form, then one more great advantage is that it can be used also in modern FPGA-based Hardware-In-the-Loop (HIL) simulators. HIL is a test approach, where, in this case, the BMS is tested involving the original BMS electronics and the real-time simulator of the battery on the expected cell-or pack level solving the state equations numerically step by step  . By using battery HIL simulator, also the extreme failure cases are reproducible, which is not possible in the real system . In this paper, an FPGA-synthesizable electrical battery cell model is introduced using fixed-point number representation, which is designed and verified in MATLAB/Simulink. This online Simulink model can be used in FPGA or in processorbased BMS and also in real-time HIL simulators.