Project 1
Aim: To design battery pack configuration for car, draw BMS topology for this battey pack and to design 3s2P battery pack model in Matlab/Simulink
Given:
Require Power =120 kW
Require Voltage= 120V
NMC Cell
Nominal capacity: 3500mAh
Nominal voltage:3.6 V
Solution:
a. Design the battery pack configuration:
1. Number of cells in series:
Number of cells in series = Require Voltage/ Cell Nominal Voltage
= 120/3.6 = 33.33
Case 1= 34 cells in series which whould be give battery pack voltage of 34 *3.6=122.4V
Case 2= 33 cells in series which whould be give battery pack voltage of 33 *3.6=118.8V
In case 2 battery pack voltage is less than require voltage hence we will select case 1.
Number of cells in series is 34.
2.Number of cells in parallel:
Number of cells in parallel = Require Current/ Cell Nominal Capacity
Power = Current * Voltage
Require Power= 150 kW and Require Voltage is 120 V
Hence, Require Current = Require Power/Require Voltage = 150000/120=1250 A
Cell Nominal Capcity is 3500mAh= 3.5Ah
Number of cells in parallel = 1250/3.5 = 157.1
To meet require current number of cells in parallel would be 158
Conclusion: As per given information, battery pack of configuration 34S 158 P is selected
b. Draw the BMS topology for this battery pack.
Solution:
BMS topologies fall in three categories:
Centralized:
a single controller is connected to the battery cells through a multitude of wires. This Topology is used for only pack of 18 cells or less than 18 cells in a series only
Distributed:
a BMS board is installed at each cell, with just a single communication cable between the battery and a controller. This Topology is used for pack of 18 cells or grater than 18 cells in a series .Very large Large Energy storage purpose
Modular:
a few controllers, each handling a certain number of cells, with communication between the controllers. This Topology is used for pack of 18 cells or grater than 18 cells in a series .Large Energy storage purpose
Master-Slave: Slaves are connected for certain number of cells and then this slave communicated to Master. This Topology is used for pack of 18 cells or grater than 18 cells in a series .High Energy storage purpose
Hence Master-Slave Topology has more advantage compare to other topologies for battery pack which has more than 18 cells are in series.
Lets consider single Slave can monitor 17 cells hence we will need 2 slaves 1 master topology for this configuration as shown in below image:
Conclusion:
Master - Slave topology selected for given battery pack car requirement of 120 kW with 120V with configuration of 34S 158P.
Que 2: Build a 3S2P battery pack configuration with generic battery block using Matlab/Simulink.
Solution:
Step 1:
Batteries in 3S2P configuration in Matlab/Simulink. That is 3 cells should be connected in series and 2 cells should be connected in parallel
Total cells in battery pack = 3*2= 6
Step 2: Take 6 cells from library in simulink as shown in below image
Step 3: Make 2P parallel connection of this cells as shown below:
Step 4: Make 3S series cofiguration by connecting this cells in series as shown below:
Step 5: Following cell parameters are set in each cell
Step 6 : Current source is added to discharge this battery pack, Voltage measurement added to check battery pack voltage and scope is added to check indivisual cell voltage, temp and soc drop as shown below:
Step 7: after discharging battery with 10 A for 100sec which drop soc from 100 to 97.5. results are shown below:
Conclusion : Design a 3S2P battery pack configuration with generic battery block using Matlab/Simulink.