A Model of a Lithium Iron Phosphate Battery Using PSCAD.

摘要

Presently, internal combustion engine vehicles (ICEV) are very harmful to humans and the environment. This issue yields a large problem for our society and has helped revolutionize the study of electric vehicles. Although electric vehicles are pollution free, there are two main concerns in their development; the first being the charging and discharging characteristics of the total battery performance and the second being the range. Due to this, battery development is a crucial aspect to improving the performance of electric vehicles.;This progress requires dependable computer aided designs to model the battery accurately and reliably. Using Power Systems Computer Aided Design (PSCAD) the qualities of a constant discharging Lithium Iron Phosphate battery was observed by creating an equivalent runtime circuit model. This model demonstrates the performance effects of the lithium iron phosphate battery given varying temperatures and battery state of charge (SOC). The runtime model constitutes of two circuits. The first circuit represents the change in SOC over a period of time by implementing a dependent current source and a resistor in series. In addition to this, the runtime model includes a second circuit that mimics the Thevenin model using multiple parallel R-C networks that are in series with the dependent voltage source. All the parameters are based on the SOC.;In order to find the fixed parameters of the circuit, MATLAB was used to implement basic current voltage characteristics. The collected data for various temperatures was inserted into MATLAB and organized with the intent to find a model of the terminal voltage (Vt) of the battery. Given the varying SOC multiple equations were determined for the variable battery voltage, and were the deciding factors in obtaining the component values of the modeled circuit. Once these parameters were found, the circuit was simulated in PSCAD.;In order for the PSCAD simulator to function properly it was necessary that the SOC varied with time. Given a 160 Ah Lithium Iron Phosphate battery, a circuit was created that showed a graphical output of a varying SOC for 7200 seconds or 2 hours. The second circuit was created using mathematical simulators in PSCAD. These mathematical components included integrators, adders and XYZ look up tables. The second circuit was driven by two input terminals. The X input which was the temperature and the Y input which was the SOC. Throughout the simulation the X input varied because of the data in the lookup tables and the Y input varied because of the SOC in the first circuit. Once the simulations for all temperatures were completed the average marginal error came to be 2.1% therefore making PSCAD an accurate simulation tool for modeling circuits. Therefore this justifies that PSCAD is a precisemodeling tool. After comparing the measured and simulated plots, the results revealed that PSCAD is a useful resource for depicting the functionality of batteries under constant discharge and numerous temperatures. For future industries, this determines that PSCAD can be used as a sufficient tool to analyze and evaluate the characteristics of batteries for the use of electric vehicle technology.