Electronics
Electrical System modeling
We here consider the following electrical system, with an input voltage Ue and an output voltage Ua
Mathematical modeling
In order to model the system in a mathematical way, we need to use Kirchhoff’s laws:
(1) 
(2) 
In addition, we need to express the mathematical function of each component:
Resistance: 
Capacity: 
Inductor: 
Using the 2 mathematical expressions, we come to the following second order differential
equation:
Causal modeling
State-space system modeling
The equations for an RLC circuit are the following. They result from Kirchhoff’s voltage law and Newton’s law.
The R, L and C are the system’s resistance, inductance and capacitor.
We define the capacitor voltage Vc and the inductance current iL as the state variables X1 and X2.
thus
Rearranging these equations we get:
These equations can be put into matrix form as follows,
The required output equation is
The following diagram shows these equations modeled in Xcos.
To obtain the output Vc(t) we use CLSS block from Continuous time systems Palette.
Acausal with Modelica
