Design of FPGA-based real-time Hardware-In-the-Loop simulator of a battery energy storage

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Debreceni Tibor
Department of Automation and Applied Informatics

In the ground, air and water transportation the electric drive is gaining more and more ground. For these electric drive systems we need safe and efficient power supply, which are usually modern battery packs. These battery systems reach even higher power levels with new topologies and technologies.

For such high power battery systems in the range of kilo- and megawatts, we need complex control and management systems. In this power range a small mistake in the control system can cause serious damages and injuries, which can be lethal. In worst case, a fault in the management system can cause an explosion in the battery system, which is extremely dangerous. In a modern battery pack, there are usually Li-ion batteries. This type of battery is sensitive for over or under temperatures and overload, which results explosion by massive gas production, which van cause several damages.

Therefore to prevent these failures it is important to test the control and Battery-Management-System (BMS) units before it it tested with the real battery pack. In the power electronics, engineers often use simulations for testing new control units. One of the most popular testing method is the Hardware-In-the-Loop (HIL) simulation. In this method the power converter is simulated in a HIL simulator, which is connected to the control unit, so it can be tested safely. The same method can be used in the testing of BMS units, but here the simulator runs the models of the battery pack and the main circuit of the battery system.

With a battery HIL simulator we can model the behavior of the system in real time, with 10-100 nsec of simulation time-step. With this method, we can manipulate the controllers of the BMS in real time and we can observe the signals of the batteries in the pack or the signals of the main circuit. Another advantage of the HIL simulator is the error injection, which means we can generate failures in the main circuit, or the battery pack. We can generate short circuits or open circuit, over or under voltages. By these failure injections, we can prepare the BMS unit to handle these failures. These tests cannot be done safely with the real battery packs.

In my bachelor thesis my task was to design an FPGA based HIL simulator capable of simulating a general battery pack with a specific active balancing topology. With this simulator a new BMS unit will be tested. The goal was to achieve the 100 nsec simulation time-step with the simulator. The FPGA developer kit a used was a Nexys 4 board with a Xilinx Artix-7 FPGA on board. I generated the verilog files using MATLAB HDL coder from Simulink models.

To test the BMS unit we need an interface board between the FPGA kit and the BMS module. This interface board generates the analog signals to the BMS unit, and it receives the digital control signals to the balancing stage. Together with a colleague of the Siemens Zrt. we made the specification of the hardware of the interface board, and the block diagrams are designed and reviewed for further realization steps.


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