EHS SOLVER

This block implements a serial variable RL.

The model consists of a controlled current source in parallel with an RC snubber. The value of the generated current is determined by the voltage measured across it, the resistance, and the inductance, the latter are sent as an input.

 

Model Formulation

The voltage across a serial variable RL is the sum of the voltage drop across the resistance (Ohm’s law) and the induced voltage due to magnetic flux variation (Faraday's law), determined by the equation:

Since the self-inductance

is the ratio between magnetic flux and the current:

thus,

It is considered that the voltage drop related to the change of inductance

is negligible as compared with the drop from the change of current.

The discretization of equation above results in:

Finally,

The current through the inductance

is the state variable and its initial value

is a parameter of the block, the Initial current (I₀).

Limitations

For the model to be stable, the following condition must be satisfied on the resistance and inductance values:

Three phase systems that use the Variable RL feature require grounded neutral point connections in order to obtain correct results:

Parameters