How to simulate DC Circuit breaker in Simulink
Working as an AC Breaker in a DC Circuit
Why Use a DC Circuit Breaker?
AC circuit breakers are readily available in Simulink. However, they are not suitable for DC circuits due to continuous current flow in DC loads, which prevents the AC breaker from functioning correctly.
Simulating an AC Circuit Breaker with DC Supply
Add Components:
Use the Single-Phase Circuit Breaker from the Simulink library.
Add a DC Voltage Source, Current Measurement, Voltage Measurement, and Series RLC Branch for the load.
Connect the Components:
Connect the DC voltage source to the breaker.
Connect current and voltage measurement blocks to measure the input current and voltage.
Connect the series RLC branch as the load.
Measure the load voltage and current.
Control the Breaker:
Use a Step block to control the breaker.
Set the step time to 5 seconds, initial value to 1, and final value to 0. This will close the breaker for the first 5 seconds and open it afterward.
Simulate the Model:
Run the simulation and observe that the breaker does not open even when the control signal changes to 0. This is because the AC breaker cannot interrupt the continuous DC current.
Creating a DC Circuit Breaker Model in Simulink
Using MOSFETs for DC Circuit Breaker
To create a DC circuit breaker, we can use MOSFETs arranged in opposite directions to interrupt the current flow.
Add MOSFETs:
Add two MOSFET blocks from the Simulink library.
Arrange them in opposite directions.
Configure the MOSFETs:
Connect the source of one MOSFET to the drain of the other and vice versa.
Connect the gates of both MOSFETs to the same control signal.
Create Subsystem:
Create a subsystem for the MOSFET arrangement to act as a DC circuit breaker.
Connect the subsystem's input and output terminals.
Replace AC Breaker with DC Breaker:
Replace the single-phase AC breaker in the original model with the MOSFET-based DC breaker.
Simulating the DC Circuit Breaker
Connect Components:
Connect the same DC voltage source, current measurement, voltage measurement, and series RLC branch as the load to the new DC breaker.
Control the DC Breaker:
Use the same Step block to control the MOSFET gates.
Run the Simulation:
Simulate the model and observe that the DC breaker successfully interrupts the current flow at the specified step time.
Simulation Results
Input Voltage and Current:Â The input voltage remains constant, and the input current drops to zero when the breaker opens.
Load Voltage and Current:Â The load voltage equals the source voltage when the breaker is closed. When the breaker opens, both the load voltage and current drop to zero.
Conclusion
In this tutorial, we demonstrated how to simulate a DC circuit breaker in Simulink. We discussed the limitations of using AC circuit breakers for DC circuits and created a DC breaker model using MOSFETs. This approach ensures that the breaker can interrupt the continuous current flow in DC circuits effectively.
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