Applying an HIL Simulation Platform for Energy Systems in Hybrid Electric Vehicles
"Using LabVIEW for data acquisition, simulation, and control with an NI USB DAQ device resulted in a straightforward solution that helped set up a simple and lower-cost test bench."
- Lucía Gauchía,
Universidad Carlos III
Setting up a flexible, safe, and low-cost test bench for simulating hybrid power sources such as fuel cells and batteries.
Applying hardware-in-the-loop (HIL) simulation using NI LabVIEW and the LabVIEW Control Design and Simulation Module to simulate fuel cell behavior in a hybrid system with a real battery and determine how to integrate an actual fuel cell into an acquisition and control program.
Lucía Gauchía - Universidad Carlos III
Javier Sanz - Universidad Carlos III
Hybrid electric vehicles have raised interest in the automotive industry due to the uncertain future of fossil fuel reserves and the effect of greenhouse gas emissions. We needed an experimental setup to evaluate the performance of a hybrid power train. Most experimental test benches are assembled to work with a specific power train, which usually requires less-flexible, high-cost hardware. We simulated part of the test bench to achieve lower costs and greater flexibility.
Test Bench Configuration
Our test bench is suitable for the setup of different power trains for transportation and stationary applications. We acquired this flexibility using a simulated fuel cell, load, and real battery (or other energy storage devices such as supercapacitors), as shown in Figure 1.
The advantage of using a simulated fuel cell is that we can program different types of fuel cells, such as proton exchange membrane (PEM), SOCF, and molten-carbonate fuel cells (MCFC), without investing in each of these devices and installing hydrogen. With a real battery, we can make future comparisons between different battery technologies, such as nickel-metal hydride (NiMh) and lithium (Li) ion, which we can easily change in the test bench.
We carried out test bench data acquisition and control with an NI USB-6215 data acquisition (DAQ) device, which we could use with either a desktop computer or laptop programmed with LabVIEW. Choosing the programming language for the fuel-cell model was critical in the setup because we needed it to interact easily with the rest of the test bench. The most straightforward solution was to program the dynamic fuel-cell model with LabVIEW to incorporate the fuel cell into the data acquisition program. This solution required only one programming language for the whole test bench.
We developed the model with the LabVIEW Control Design and Simulation Module to create a fast and easy way to describe equations. The block panel in Figure 2 shows where we can choose simulation parameters such as initial time, final time, and solver method. For our fuel cell model, we selected the Runge-Kutta 1 solver method with a step time of 1e-8 s.
The fuel cell dynamic model outputs were the fuel cell voltage and current limitation. These outputs were sent through the analog outputs of the USB-6215 DAQ device to a direct current programmable power source, the Sorensen DCS 20-150E, which operated as a fuel cell. Therefore, we needed only a DC power source, DAQ device, and computer to simulate a fuel cell.
We needed the simulated fuel cell to interact with the Maxxima Tudor-Exide VRLA batteries (12 V, 50 Ah) shown in Figure 3. They interacted electrically by connecting in parallel with the DC power source, which simulated the fuel cell with the real battery. The simulated fuel cell and the real battery supply the power for a direct current electronic load (Chroma 63201). We previously calculated the current requested by the electronic load, taking into account the electric machine, transmission, and vehicle dynamics. We loaded the current profile we obtained to the Chroma 63201 driver in LabVIEW and sent it to the electronic load through an RS232 serial connection.
We controlled the test bench using two current sensors that measured the battery and load current, and one voltage sensor that measured the DC bus voltage. Also, we continuously monitored the battery state of charge (SOC), taking into account the previous SOC and the current charged or discharged during each time step.
With this test bench, we can test different degrees of hybridization because the percentage of current supplied by the batteries affects battery life, fuel cell efficiency, hydrogen costs, and vehicle range.
Successful Development of an HIL Test Bench
Developing the HIL test bench proved to be a practical method to study each of the power sources present in a hybrid electric vehicle because we could examine the experimental test of hybridization degree and consequences on the whole system. Using LabVIEW for data acquisition, simulation, and control with an NI USB DAQ device resulted in a straightforward solution that helped set up a simple and lower-cost test bench.
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