Battery Management System (BMS) Test Stand Utilizing a Hardware-in-the-Loop (HIL) Emulated Battery

Most people rely on lithium-ion batteries to power one or more of their portable devices every day. Though most portable devices operate at low voltage, there are many emerging applications that may rely on batteries with voltages up to 1 kVDC. As battery voltage increases, so does the number of series connected, individual cells used to construct it. Battery management systems (BMSs) are used to maintain safe operation, ensuring that no cell is ever charged too high or discharged too low. It also bleeds off excess energy from high cells to bring all the cells down to the same state of charge (SoC). There are countless BMS systems on the market and many more that are being designed and introduced for sale every day. While most BMSs share some common features, there is no single standard that defines BMS architecture, operation, or communication. Evaluation of the short- and long-term performance of a BMS is difficult; requiring it to be either connected to a physical high voltage battery, which is expensive and potentially unsafe, or to some other device that can accurately emulate the battery. In the work presented here, a battery emulator has been assembled and validated using a power-hardware-in-the-Loop (PHIL) system. Using this method, any type of battery can be emulated so long as a validated MATLAB simulation model at the cell level is available. A 264-cell battery model has been created and simulated. Though the eventual plan is to emulate all 264 cells, only six of those cells have been emulated using a PHIL system and interfaced with a BMS to date. The options considered for emulation of the real-time cell model are discussed along with the rationale for the emulator design choices made so far. Some initial results from the 6-cell emulation experiment are also presented.