The Develop Of Power Lithium-ion Battery Simulator

As the traditional non-renewable fossil fuel continue to consume and the citiesfacing to a more and more serious environmental pollution problem, the new energyand clean energy is getting more attention and investment. The traffic field is alsodeveloping towards non-polluting and energy saving. But electric vehicle has someshortcomings such as the cost of using the battery pack is very high and the cycle lifeof battery pack is not long. So a battery manage system is needed to monitor andmanage the battery pack, reduce the cost of using batteries, improve the cycle life ofbattery and forecast the current temperature of battery pack and remaining mileage.If we use battery packs to debug electric vehicles and battery manage systems, thenwe have to facing problems such as the long debug time, high cost, low efficiencyand low accuracy. Therefore, there should be a high accuracy battery simulator as analternate.In order to establish an accurate battery model, this paper is focused on the mostwidely used Lithium-ion battery in electric vehicles, studies it’s technical parameters,charge and discharge performance characteristics, the relationship between OCV andSOC and second-order equivalent model of the battery internal resistance. Accordingto the characteristic relationship among SOC, OCV, ohm resistance and polarizationresistance, SOC as a variable to control OCV and the second-order equivalentmodel of the battery internal resistance, based on which establishing the batteryequivalent model. And then a Simulink simulating model is established in the paper.An accurate model for the development of the battery simulator is established.Facing the inherent requirements of dynamic battery terminal voltage and theparameters needed to simulate, a hardware circuit design is proposed. There are twovoltage simulating channels and one temperature simulating channel in the design.Both these channels are controlled by a controller. The controller control the circuitoutput the needed voltage according to the established battery equivalent model, thevoltage of a battery is simulated through this way. Well the equivalent resistor of thePt100simulator channel is determined by the temperature input by the user. In order to simulate the complex dynamic characteristics of battery, thecontroller is performed in two steps. The first, the user set the nominal capacity andinitial capacity, and then the controller calculates the SOC using ampere hour methodand the OCV according to the SOC-OCV formula. The second, the controllercalculates internal ohm resistance, polarization resistance and polarizationcapacitance, detects the sudden change of battery current through ADC, calculatesthe voltage drop on internal resistance, and then the output terminal voltage isdetermined.Finally, some experiments were done to verify the accuracy and function of thebattery simulator. It proved that the battery simulation designed is totally correct, andit also has a high accuracy.