I have designed a robust controller for the control of grid tied PV system. The control involves controlling the active and reactive current reference currents in dq frame. Now i want to see if the controller is robust against any disturbances. I have decided to use part of reference signal as a disturbance. However i am not sure where to add this disturbance? I am using the universal bridge as inverter unit in simulink. Any help would be highly appreciated. Thank you.
Dear Ammar,
I suggest you to see links in subject.
-Voltage-Sensorless Control Scheme for a Grid Connected Inverter ...
www.mdpi.com/1996-1073/10/2/166/pdf
-A Study on Components Used In Grid Connected ... - IOSR Journals
www.iosrjournals.org/iosr-jeee/Papers/Conf.../10.%2069-80.pdf
-Improved Control Strategy for Grid Connected Scheme Based on PV ...
www.indjst.org/index.php/indjst/article/viewFile/64036/50025
-Control Strategy for Three-Phase Grid-Connected PV Inverters ... - VBN
vbn.aau.dk/files/263403675/ALL_16_TIE_3739.pdf
-modeling and analysis of a pv grid-tied smart inverter's
digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=2071...
-Power Quality and Efficiency Improvements for Transformerless Grid ...
https://eprints.usq.edu.au/19467/2/Bowtell_2010_whole.pdf
-Studying the effect of over-modulation on the output voltage of three ...
https://www.sciencedirect.com/science/article/.../S11100168130005...
Best regards
Hi Ammar,
I suggest to take a step back and to consider the application in the real world. What disturbances are likely to happen: Variation in power generation due to change in sunlight, change in load , capacitive or inductive reactive power, further more you could studdy failure modes, cut or disturbed connections to the load, to the grid, etc.
Ammar,
I agree with the answer from Fabian Wolz above, that the disturbance motivation should come from real world considerations.
However, in a classical control scenes you can use input disturbances and output disturbances for simplification. You would need to put a disturbance (e.g., step, ramp, impulse) on the input of the plant, i.e. between controller and your system. For the output disturbance you simply put these signals on the sensor.
As background: this might be a simplification, however, you often can rewrite real disturbances of and in the model as input or output disturbances. Thus it gives you a first validation of the disturbance rejection capabilities of your controller without a detailed modelling of the the plant disturbances.
Godd luck.
For starter you can see the comparison of your controller and previously known by grid isolation. you just need to put a timer switch called "fault" in SIMULINK library in series with the grid. But to be honest, i like the answer from Fabian Wolz.
Dear Ammar,
welcome,
I came late to this question. There is some satisfactory answer. However, i would like to add some clarifying points. The grid connected inverter are controlled such that one fix the current delivered to grid.
The testing of such inverter is accomplished by applying unit step reference current either in phase or in quadrature phase and observing how the the output current will change with time. Here the main function of the controller is to follow the the set reference current. So, is interested in the settling time and the accuracy of the steady sate value.
In such inverters there is the DC/DC converter with the maximum power point control witch conditions the input voltage to the inverter to keep it almost constant. The role of the output current control of the inverted is to keep the output voltage constant.
You can also change the reference in up steps and down steps and see how far it will be tracked.
For more information please see the paper in the link: Article Simulation and Implementation of Grid-connected Inverters,
If you find it useful please recommend for other colleagues.
Best wishes
This paper is helpful for you
A Systematic Controller Design for a Grid-Connected Inverter with LCL Filter Using a Discrete-Time Integral State Feedback Control and State Observer
You can check your control system by applying faults (single phase, 3 phase) to your system. The fault will cause dip in voltage while current will increase. See if your controller can tackle voltage disturbances or not.
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