Week 5 Battery characteristics using drive cycle
Aim:
To simulate generic battery model charge-discharge using UDDS data
Theory:
Driving Cycle:
A driving cycle is a series of data points representing the speed of a vehicle versus time.
Driving cycles are produced by different countries and organizations to assess the performance of vehicles in various ways, as for example fuel consumption and polluting emissions.
The driving cycle plays a very important role in vehicle simulation. In this project, UDDS driving cycle is being used for simulation of generic battery.
Generic Battery:
Here generic battery of the following parameters is simulated for UDDS drive cycle.
Signal Builder:
Here signal builder is used for creating a current signal for the battery to simulate. The signal builder accepts the signal in a form of the current profile, but the UDDS cycle is in a form of data which is speed vs. time. So this data is converted into a current profile with respect to time and is given as an input to the signal builder.
Controlled current source:
The Controlled Current Source block converts the Simulink input signal into an equivalent current source. The generated current is driven by the input signal of the block. The positive current direction is as shown by the arrow in the block icon.
The output of the signal builder is in the form of a current signal which is converted into the current source by using the block 'Controlled current source' and then this current is used to simulate the battery. The flow of current is from positive terminal to the negative terminal, hence the positive terminal of controlled current source is connected with the negative terminal of the battery.
The complete model connected with each other is shown below.
Bus Selector:
These are three outputs from the battery as follows:
1. SOC(State of Charge) which shows the amount of charge left inside the battery
2. The current profile
3. The voltage profile.
The bus selector is used to select particular signals from a group of signals as outputs. Here the above three signals are selected to display it on the graph (scope).
Results:
The UDDS cycle is of about 1370 seconds, but in this project a part of it, is simulated for about 320 seconds.
Hence the result after simulating the above model for 320 seconds is shown below:
Results Explained:
SOC Graph
The SOC remaining in the battery after running the vehicle for about 320 seconds is 98%. The decrease in the graph of SOC shows the discharging of the vehicle and the sudden increase shows the charging due to regeneration.
Current Graph:
The positive current shows that the battery is supplying the power(discharging) as per the requirement of the vehicle. The negative current shows that the vehicle is charging.
Voltage Graph:
When the current increases the voltage decrease and vice-versa. This is because due to the internal resistance of the battery.