Simulate a PSU that has CC/CV/CP and is in parallel with a battery and inverter

I am trying to simulate a PSU, that has limits for CC (contstant current), CV (constant voltage) and CP (constant power).

The PSU is connected to a battery (lithium) and a traction inverter.

I was hoping to model this in Simscape, but I have no experience of Simscape and cannot find anything in the library to create this model.

Is it possible to model this in Simscape and if so how ?

The aim is to find the currents and voltages in the system under different conditions.

i.e.

• DC link voltage
• Battery current
• Inverter current
• PSU current

I dont need to model the battery or inverter in any detail. For the battery I'm just using the OCV (open circuit voltage) and internal resistance, for the inverter I'm just using the inverter power.

I have identifited 4 scenarios:

1. PSU does not supply any power
2. PSU only charges battery (inverter not running)
3. PSU charges the battery and PSU powers the inverter
4. PSU and battery both power the inverter

I created a spreadsheet and tried to derive the equations, but the spreadsheet only works under certain scenarios.

I have not been able to derive the equations for some scenarios, such as scenarios 3 and 4 when the PSU is in CC

The spreadsheet uses VBA (to avoid circular references) - see attached PowerShare.zip for reference.

Below are examples of the different scenarios,

1. PSU does not supply any power

In this scenario:

• the inverter is not drawing any power
• the battery open circuit voltage is 600 V
• the battery internal resistance is 1 R
• the PSU power limit is set 2,000W
• the PSU voltage limit is set to 600 V
• the PSU current limit is set to 20 A

2. PSU charges battery (inverter not running)

In this scenario:

• the inverter is not drawing any power
• the battery internal resistance is 1 R
• the PSU power limit is set 2,000W
• the PSU voltage limit is set to 600 V
• the PSU current limit is set to 20 A

The votlage and currents when the battery open circuit voltage is at 597 V:

• the PSU is in CV
• battery current is 3A
• psu current is 3A
• DC link voltage is 600V

The votlage and currents when the battery open circuit voltage is at 590 V are:

• the PSU is in CP
• battery current is 3.37A
• psu current is 3.37A
• DC link voltage is 593.37V

The votlage and currents when the battery open circuit voltage is at 70 V are:

• the PSU is in CC
• battery current is 20A
• psu current is 20A
• DC link voltage is 90V

3. PSU charges the battery AND powers the inverter

In this scenario:

• the inverter is drawing 1,000W
• the battery internal resistance is 1 R
• the PSU power limit is set 2,000W
• the PSU voltage limit is set to 600 V
• the PSU current limit is set to 20 A

The votlage and currents when the battery open circuit voltage is at 500 V are:

• the PSU is in CP
• battery current is 1.99A
• inverter current is 1.99A
• psu current is 3.98A
• DC link voltage is 501.99V

I have not been able to derive the equations for following condition when the PSU is in CC, because I don't know how to calculate the inverter current, battery current or DC link voltage.

The votlage and currents when the battery open circuit voltage is at 70 V are:

• the PSU is in CP..... INCORRECT (should be CC)
• battery current is 12.17A..... INCORRECT
• inverter current is 12.17A..... INCORRECT
• psu current is 24.34A..... INCORRECT (current limit is 20A)
• DC link voltage is 82.17V..... INCORRECT

The VBA code is shown below for reference:

Answer 1

[venkateswara mallireddy]

pls contact me i will explain how to design in matlab 8919483814