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Bad behaviour with simple power electronics
Bad behaviour with simple power electronics
The simple circuit I've tried works well on Dymola and is faulty in OpenModelica.
The problem is that the current in inductor Lf drops suddenly to zero (at 0.6, 0,16, 0,26, etc. ms) and this is incorrect, and not even physically possible!
Exactly the same code works well within Dymola.
Since the circuit is very simple it may indicate a very basic issue of OpenModelica when used with power electronics.
If my outcomes are not wrong, they may indicate that OpenModelica 1.7 cannot be used for Power Electronics circuits.
Massimo
Code:
model Chopper
Modelica.Electrical.Analog.Sources.ConstantVoltage V1(V=100)
annotation (
Placement(transformation(
extent={{-10,-10},{10,10}},
rotation=270,
origin={-72,12})));
Modelica.Electrical.Analog.Ideal.IdealGTOThyristor idealGTOThyristor
annotation (Placement(transformation(
extent={{-10,-10},{10,10}},
rotation=270,
origin={-32,50})));
Modelica.Electrical.Analog.Ideal.IdealDiode idealDiode
annotation (Placement(
transformation(
extent={{-10,-10},{10,10}},
rotation=90,
origin={-32,-14})));
Modelica.Electrical.Analog.Basic.Resistor Rf(R=0.1)
annotation (Placement(transformation(extent={{-18,6},{2,26}})));
Modelica.Electrical.Analog.Basic.Inductor Lf(L=10e-3, i(start=1))
annotation (Placement(transformation(extent={{14,6},{34,26}})));
Modelica.Electrical.Analog.Basic.Capacitor Cf(C=100e-6, v(start=70))
annotation (Placement(
transformation(
extent={{-10,-10},{10,10}},
rotation=270,
origin={44,-12})));
Modelica.Electrical.Analog.Basic.Resistor Load(R=30)
annotation (Placement(
transformation(
extent={{-10,-10},{10,10}},
rotation=270,
origin={72,-8})));
Modelica.Blocks.Sources.SawTooth sawTooth(period=0.001,offset=0,startTime=0)
annotation (Placement(
transformation(
extent={{-9,-9},{9,9}},
rotation=180,
origin={31,47})));
Modelica.Blocks.Logical.LessThreshold lessThreshold(threshold=0.8)
annotation (Placement(transformation(
extent={{-8,-8},{8,8}},
rotation=180,
origin={-2,46})));
Modelica.Electrical.Analog.Basic.Ground ground
annotation (Placement(transformation(extent={{-82,-66},{-62,-46}})));
equation
connect(idealDiode.n, idealGTOThyristor.n) annotation (Line(
points={{-32,-4},{-32,40}},
color={0,0,255},
smooth=Smooth.None));
connect(idealGTOThyristor.p, V1.p) annotation (Line(
points={{-32,60},{-32,68},{-72,68},{-72,22}},
color={0,0,255},
smooth=Smooth.None));
connect(V1.n, idealDiode.p) annotation (Line(
points={{-72,2},{-72,-34},{-32,-34},{-32,-24}},
color={0,0,255},
smooth=Smooth.None));
connect(Rf.p, idealDiode.n) annotation (Line(
points={{-18,16},{-32,16},{-32,-4}},
color={0,0,255},
smooth=Smooth.None));
connect(Lf.p, Rf.n) annotation (Line(
points={{14,16},{2,16}},
color={0,0,255},
smooth=Smooth.None));
connect(Cf.p, Lf.n) annotation (Line(
points={{44,-2},{44,16},{34,16}},
color={0,0,255},
smooth=Smooth.None));
connect(Cf.n, idealDiode.p) annotation (Line(
points={{44,-22},{44,-34},{-32,-34},{-32,-24}},
color={0,0,255},
smooth=Smooth.None));
connect(Load.p, Lf.n) annotation (Line(
points={{72,2},{72,16},{34,16}},
color={0,0,255},
smooth=Smooth.None));
connect(Load.n, Cf.n) annotation (Line(
points={{72,-18},{72,-34},{44,-34},{44,-22}},
color={0,0,255},
smooth=Smooth.None));
connect(lessThreshold.y, idealGTOThyristor.fire) annotation (Line(
points={{-10.8,46},{-12,46},{-12,43},{-21,43}},
color={255,0,255},
smooth=Smooth.None));
connect(sawTooth.y, lessThreshold.u) annotation (Line(
points={{21.1,47},{16,47},{16,46},{7.6,46}},
color={0,0,127},
smooth=Smooth.None));
connect(ground.p, V1.n) annotation (Line(
points={{-72,-46},{-72,2}},
color={0,0,255},
smooth=Smooth.None));
annotation (uses(Modelica(version="3.2")), Diagram(graphics),
experiment(StopTime=0.005, NumberOfIntervals=2000),
experimentSetupOutput);
end Chopper;
- ceraolo
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- 147 Posts
Thank you
Re: Bad behaviour with simple power electronics
As far as I know, the Ideal Diode is not really working in OpenModelica (gives wrong results)...
- sjoelund.se
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-
- 1700 Posts
Re: Bad behaviour with simple power electronics
I've studied the issue.
First comment: the Modelica Ideal diode code is very brillant. But it is difficult to understand for a human, let alone for parsing algorithms! OpenModelica parser get confused by this code, while Dymola's does not.
Second: the problem with diodes was indeed already known since it was reported as a bug (N. 1214). However we should not expect it to get solved soon, as it has already been on the site since a year ago and has not been assigned to anyone.
Third My example not only had an ideal diode, but also an ideal thyristor, that caused itself troubles.
Workarounds for my circuit:
1) use the diode model from the Modelica "Semiconductor" library.
2) use an IdealClosingSwitch in series with a diode in stead of the Ideal Thyristor
Using similar workarounds I deem that neaqrly any power electronics cicuit can be simulated with OpenModelica.
- ceraolo
-
-
- 147 Posts
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