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ODE: dI1/dt and dI2/dt appear in the only same equation

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In the picture, I1, I2 and U are variables. I1 is the excitation of mf.VCoil_1 while I2 is the excitation of mf.VCoil_2. Coil1 and Coil2 are solved in the same solution domain.

The question is that, the equations can be solved from the perspective of the circuit. However, since dI1/dt and dI2/dt appear in the only same equation, I don't know how to write the equations in ODE, or if there is anther way to describe this set of circuit equations (without using the circuit physical field, there is no thyristor model in the physical field). Hoping someone can answer for me, grateful!


3 Replies Last Post Oct 23, 2017, 9:16 p.m. EDT

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Posted: 6 years ago Oct 23, 2017, 7:54 a.m. EDT
Updated: 6 years ago Oct 23, 2017, 7:55 a.m. EDT

Here is the picture.

Here is the picture.

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Posted: 6 years ago Oct 23, 2017, 7:56 a.m. EDT
Updated: 6 years ago Oct 23, 2017, 8:02 a.m. EDT

Sorry, I can't upload the picture. there are 3 equations, the first one contains mf.VCoil_1, mf.VCoil_2, I1 and I2. the second one contains U, mf.VCoil_1, I1, I2, dI1/dt and dI2/dt. the third one contains dU/dt, I1 and I2.

Sorry, I can't upload the picture. there are 3 equations, the first one contains mf.VCoil_1, mf.VCoil_2, I1 and I2. the second one contains U, mf.VCoil_1, I1, I2, dI1/dt and dI2/dt. the third one contains dU/dt, I1 and I2.

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Posted: 6 years ago Oct 23, 2017, 9:16 p.m. EDT

Oh, I suddenly find a way to avoid this problem. It is to use a new variable A to make dA/dt equal to (a1dI1/dt+a2dI2/dt), the second equation will be able to be describe in the ODE in this way. The original variable I2 is replaced by (I-a1*I1)/a2 to be the current excitation of Coil_2.

However, my model still does not work properly. It should be the problem with the solver settings.So this problem is solved.

Oh, I suddenly find a way to avoid this problem. It is to use a new variable A to make dA/dt equal to (a1*dI1/dt+a2*dI2/dt), the second equation will be able to be describe in the ODE in this way. The original variable I2 is replaced by (I-a1*I1)/a2 to be the current excitation of Coil_2. However, my model still does not work properly. It should be the problem with the solver settings.So this problem is solved.

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