Incorrect initialization of synchronous machine when simulating with saturation in "continuous" simulation mode
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I am trying to simulate saturation in a synchronous machine in SimPowerSystems. I check the "simulate saturation" box and initialize the machine using "load flow" or "machine initialization". However, when I start the simulation at steady state in "continuous" mode , the machine speed does not stay at 1 p.u. and attains a new steady state speed which is different than 1.
This problem does not arise when I do not simulate saturation. I haven't been able to find a reason for this apparent error but have a hunch that initialization may not be taking the effect of saturation into account. I will really appreciate if anybody could shed some light on this issue.
Thanks Himanshu
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Bruno de Almeida
2019-3-10
Hello, I am facing the same issue. Did you get any way to solve this?
Thanks, Bruno.
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Joel Van Sickel
2021-8-18
I believe this was a bug that has been addressed, if anyone experiences is again (when using an up to date version of matlab) please comment here and contact me.
Regards,
Joel
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Joel Van Sickel
2024-2-20
Hello Adrian, are you able to share models demonstrating what you listed out here?
Adrián Solís Bajo
2024-2-21
I will demonstrate it with the following simple system:
Here we have a Synchronous Machine pu Standard model (Simscape -> Electrical -> Specialized Power Systems -> Electrical Machines) connected to a Three-Phase Series RLC Load (Simscape -> Electrical -> Specialized Power Systems -> Passives). The synchronous machine parameters are as follows:
The three-phase load has been parameterized so that is a purely resistive load with a very high impedance value, so the synchronous machine is practically open circuited:
The initial conditions of the synchronous machine model have been computed using the "machine initialization" tool, so that the machine is initialized open circuited (no active and reactive power) to a terminal voltage of 1.1 pu (440 V):
It can be seen that the initial value of all the magnitudes are correctly computed. The excitation voltage (Vf), however, is not correctly initialized. Looking at the previously shown open-circuit saturation curve, for a terminal voltage of 1.1 pu the required excitation current (and in steady-state also the required excitation voltage) should be 1.19 pu. Thus, it seems that the excitation voltage is initialized to the terminal voltage value, neglecting saturation. Actually, in a more general sense, what seems to be happening is that the "machine initialization" tool always initializes the excitation voltage to the magnetizing flux value which, in per unit and with no active and reactive power, is equal to the terminal voltage in per unit.
Even if the correct value of the excitation voltage (Vf=1.19 pu) is introduced in the input and in the initial conditions of the synchronous machine model, when simulating a significant initial transient is observed:
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