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Dear whom may answer of it.

The schematic diagram implemented in Matlab simulink-simscape is same as Fig. 1

Then, when the electrical voltage of Vb across the inductor (Li) exceeds the forward voltage accompanied by diode forward voltage (2*Vf) and storage capacitor voltage (Vc1), meaning that Vb > 2Vf + Vc1,

electrical current can be flowed in storage capacitor (Cs1) ans this is shown by the current Is as can be seen in Fig. 2. (See blue line)

However, as can be seen the zoomed view of Is in Fig. 2, there are unexpected high frequency electrical vibrations, which have approximately 0.5 Mhz.

I don`t know why this vibration in current occurred.

The time step was set to be fixed step with 1e-8 to cover the shortest vibration of the simulation model (I thought the shortest vibration may occur at inductor (Li:0.9H) and junction capacitance of diode (Cpc: 100pF).

Then, the ODE4 solver was used.

Thanks, Best Regard

Fig. 1 : Schematic diagram Fig. 2 : Simulation Results

권성철
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1 Answers1

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It's hard to comment as to why exactly these oscillations are occurring, they might actually be a physical phenomena or due to numerical issues. You're using a global fixed-step solver (ODE4), this is not recommended with Simscape. Because most equations used to describe physical systems are stiff, an implicit solver is more appropriate. You can either use a global implicit solver (ode14x) or enable the local implicit solver to your Simscape network (solver configuration). In my experience fixed-step solvers are almost never warranted for desktop simulation and are only useful in hardware-in-the-loop scenarios.

Best practice is to use a variable-step implicit/stiff solver such as ode15s or ode23t. For an electrical circuit set max time-step to 1e-4, and tolerances to 1e-4,1e-5 for relative/absolute respectively.

If the simulation still exhibits these oscillations it is likely they are physical in nature.

ngautier
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