Simulate a generic battery model charge-discharge using UDDS drive cycle data

Aim - Simulate a generic battery model charge-discharge using UDDS drive cycle data.

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UDDS stands for Urban Dynamometer Driving Schedule and refers to the United States Environmental Protection Agency mandated dynamometer test on fuel economy that represents city driving conditions which are used for vehicle testing. The UDDS drive cycle is shown in the following plot:

UDDS Current Profile- It is the charge and discharges data or the current profile data obtained for a particular vehicle running on battery following the UDDS drive cycle. Following plot represents the current profile:

This current profile is used as the input signal in the dynamic model which is discussed below.

Battery - The data for modelling the battery is derived from the Panasonic 18650 Li-Ion Cells. This battery is being used in the Tesla Model S X P100 with the following general cell specifications:

Battery Block - It implements a generic battery model for most popular battery types and can also model the temperature and ageing effects. It can be accessed from the Simulink block library: Electrical / Specialized Power Systems / Electrical Drives / Extra Sources.

Here, we have used lithium-ion battery types, whose specifications are specified above.

Following are the block parameters of the generic battery block as per the Panasonic 18650 Li-Ion Cell battery:

The first curve below shows the nominal current discharge characteristics and the second plot shoes the discharge time for different discharge current values.

The first curve shows the nominal current discharge characteristics and the second plot shoes the discharge time for different discharge current values.

Simulink Model:

The Simulink model consists of an input signal which is derived from the UDDS drive cycle, a controlled current source, a generic battery model, a bus selector and a scope to visualize the data.

Based on the input signal, two types of model can be created:

1. Static Model - The input signal in this model is a constant i.e. a constant amount of current is being drawn from the battery throughout the simulation. This constant current value can be changed by changing the value in the constant block.

2. Dynamic Model - In this model, the input signal is the current data obtained from the UDDS drive cycle which has a total duration of 1369 seconds. This signal is provided by the signal builder block in which the current profile data is imported from this datasheet: UDDS Current PROFILE

For both static and dynamic models, the simulation time is 1369 seconds. The input signal goes into the controlled current source which regulated the current flow from the battery with the help of user-provided input signal.

The output data of the battery are separated by the bus selector block into SOC, Current and Voltage. This separated data is visualized in a scope.

Result:

1. Static Model

SOC (State of Charge %)

The SOC is reducing linearly with the curve having a negative slope. The reason for this linear fall in SOC is due to the constant current discharge. 

Voltage

Again, due to the constant current discharge, the voltage is reducing almost linearly.

2. Dynamic Model:

SOC

Here, the battery is discharging with a varying curve and the effect of regenerative braking can also be seen where the SOC curve is rising. In 1369 seconds of simulation, it merely falls to 99.9% because of very high battery capacity.

Voltage:

The battery voltage is also reducing according to the current profile and drops to 26.418V from 26.49 V which is merely a difference of 0.07V.

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