Implement ideal switch device
Simscape / Electrical / Specialized Power Systems / Fundamental Blocks / Power Electronics
The Ideal Switch block does not correspond to a particular physical device. When used with appropriate switching logic, it can be used to model simplified semiconductor devices such as a GTO or a MOSFET, or even a power circuit breaker with current chopping. The switch is simulated as a resistor Ron in series with a switch controlled by a logical gate signal g.
The Ideal Switch block is fully controlled by the gate signal (g > 0 or g = 0). It has the following characteristics:
Blocks any forward or reverse applied voltage with 0 current flow when g = 0
Conducts any bidirectional current with quasi-zero voltage drop when g > 0
Switches instantaneously between on and off states when triggered
The Ideal Switch block turns on when a positive signal is present at the gate input (g > 0). It turns off when the gate signal equals 0 (g = 0).
The Ideal Switch block also contains a series Rs-Cs snubber circuit that can be connected in parallel with the ideal switch (between nodes 1 and 2).
The internal resistance of the switch device, in ohms (Ω). Default is
0.001
. The Internal resistance Ron
parameter cannot be set to 0
.
The initial state of the Ideal Switch block. Default is 0
. The
initial status of the Ideal Switch block is taken into account in the steady-state
calculation.
The snubber resistance, in ohms (Ω). Default is 1e5
. Set the
Snubber resistance Rs parameter to inf
to eliminate the snubber from the model.
The snubber capacitance in farads (F). Default is inf
. Set the
Snubber capacitance Cs parameter to 0
to
eliminate the snubber, or to inf
to get a resistive snubber.
If selected, add a Simulink® output to the block returning the ideal switch current and voltage. Default is selected.
g
Simulink signal to control the opening and closing of the switch.
m
The Simulink output of the block is a vector containing two signals. You can demultiplex these signals by using the Bus Selector block provided in the Simulink library.
Signal | Definition | Units |
---|---|---|
1 | Ideal switch current | A |
2 | Ideal switch voltage | V |
The Ideal Switch block is modeled as a current source. It cannot be connected in series with an inductor, a current source, or an open circuit, unless its snubber circuit is in use.
The power_switch
example
uses the Ideal Switch block to switch an RLC circuit on an AC source (60 Hz). The switch, which
is initially closed, is first opened at t = 50 ms (3 cycles) and then reclosed at
t = 138 ms (8.25 cycles). The Ideal Switch block has 0.01 ohms resistance and no snubber is
used.
[1] Mohan, N., T.M. Undeland, and W.P. Robbins, Power Electronics: Converters, Applications, and Design, John Wiley & Sons, Inc., New York, 1995.