This block implements a variable RC.

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The model consists of a controlled voltage source in series with an RL snubber. The value of the generated voltage is determined by the current measured through it, the resistance, and the capacitance, the latter are send as input.

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Model Formulation

The current through a parallel variable RC is the sum of the current through the resistance (Ohm’s law) and the rate of change of the charge inside the capacitor, determined by the equation:

Since the capacitance is the ratio between charge and the voltage:

thus,

It is considered that the current due to the change of the capacitanceis negligible as compared with the change of the voltage.

The discretization of equation above results:

Finally,

The voltage across the capacitance is the state variable and its initial value is a parameter of the block, the Initial voltage (V₀).

Parameters