Hi every body,
I want to simulate a power network with two generators and transmission line and a R-L load in matlab. the figure illustrate this system:
I write the one phase equations of this model as below
But result of simulation is unstable!
Is this model theoretically correct ?
There is not any theoretical problem with the network. Actually it is one of the simplest models one can think about.
Check for your code. Are you going to implement a dynamic model to study stability of the system? I'd rather apply state space equations, and then simulate it by ODE solvers. Anyhow, it can be unstable, depending on the parameters values.
Dear Prof. Shakouri,
I agree with you, I think the problem is accordance of parameters. do you have parameters and initial conditions of a network same this ? I look for it in many books and papers but can not find complete parameters of network.
Dear Davood,
You first need to solve a static model with a feasible solution. Then the higher is set the H and/or resistance parameters, the more stable will be the dynamics of the system.
can you explain further please?
1 - What do you mean from feasible solution ? How can i get it ?
*. I solve the static model (model obtained from the dynamic model equal to zero) for get the initial conditions.
2- How cam i set the H and resistance parameters ?
*. I set this parameters from examples of Prof. Kundur's book.
In a fictitious network you have always a solution, no matter weather it has a real example or not. So, one of the sources may be in generation mode while the other is working as a motor. Then the equations should be corrected to admit the case.
Ask prof. Bathaei for further details.
Dear Prof. Shakouri,
Can we expect the network to be stable without any control on the field voltage or mechanical torque? I mean, if the parameters and initial values be suitable for this network, with a constant mechanical torque and field voltage, can this network have a stable terminal voltage of generators ?
Dear Mina,
Generally speaking, yes. With resistances tight enough and inertia (H) high enough, which is rare to happen in the reality, yes, depending on the magnitude of perturbation from its initial condition.
Dear Prof. Shakouri,
Thanks for your answer and attention.
I have another question about the internal inductance of the stator windings, Is it reasonable that the value of internal inductance of generator becomes larger than the inductance value of load?
To answer Mina's question:
It depends on the power factor of the load which is usually leading in phase (inductive). With a high pf (as for a residential area), the answer is yes. As we know the maximum power transmission occurs when the load impedance is conjugate of the Thevenin equivalent of the network at the load nodes. So the load should be lagging phase (negative inductance: compensated with capacitors), which means higher (positive) inductance for the Thevenin equivalent.
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