I have a Matlab simulation which implements vector control with an LC filter
The simulation comprises a voltage source inverter feeding an LC filter model whose output is passed to an induction motor dynamic model
I am trying to implement active damping as detailed here
http://vbn.aau.dk/ws/files/73019790/EPSH1_730_appendix_report.pdf
http://vbn.aau.dk/ws/files/71774890/EPSH1_730_paper.pdf
Which shows the transfer function block
My problem is the report is very vague, it doesnt explain a lot and I am struggling to understand what I am supposed to do
The authors don't go into much detail such as transforms, given there is a PI controller then that tells me that Vref should be a Dc quantity hence I need to transform into the e-frame which is fine
My problems are multiple there is a top heavy transfer function which simulink cant handle and it looks like the Vout is calculated where as in the report they mention measuring the output voltage again I believe this needs to be transformed to the eframe
My simulink model measures output voltage and load currents and the angle is calculated with an encoder and slip equation
I am at a loss as to how I implement this system
Do I measure the filter output voltages and transform to e frame and subtract from the Vref? which is the output voltage from the VC?
How do I get simulink to work with a transfer function that has an higher order numerator than denominator?
Any help/guidance would be most appreciated
Best Answer
Active damping, for the T LCL filter in your example, can be simplified like this:
either get the voltage at the junction (between the inductors), differentiate it, multiply it by a damping constant (
sqrt(2)is an optimal [?, not sure] choice), then subtract it from your reference value, orget the current through the capacitor, multiply it by the inverse of the damping constant, then subtract it from your reference value.
The reference values are in whatever frame you're working on. If you did the Clarke, the Park, or whatever transform you concoct up. I made a simple example once, here's a screenshot:
It's for a single phase, only, but you can see this would have been a Clarke transform. The yellow blocks are, from left to right, the PID (PI) controller, the 3-level PWM controller, the bridge. The virtual damping is modelled with both voltage and current, but only one of them is active, set by one of the parameters, so only consider either the lower branch (voltage+diff), or the upper branch (current), not both. The whole ordeal could have been more tiier, particularly the PID values, but, as I said, this is an example, only. I hope it helps.