Dear Researchers,
To my knowledge, output voltage and reactive power in droop control dependent on each other. If I am using multiple grid connected Distributed Generators (DG's) and through any method I regulate Reactive power of the DG's then will the output voltage of all DG's be close to the voltage of the grid ? Or do I need to regulate voltage as well as reactive power ? I am confused about the deep scenario of this application. Proper deep thoughts are required.
Thank you.
In my opinion, two subjects must be considered in your work :
1- reactive power-voltage droop can be applied only in in inductive dominant lines. So if the line resistance is considerable in comparison to the line inductance, using the precise reactive and active power equations or virtual impedance control loop will be necessary.
2- The droop control loop can be considered in two different modes :
First, grid-support grid-feeding mode and second, the grid-support grid-forming mode. In the first mode, active and reactive generating efforts of DGs will be determined by the frequency and amplitude of the measured voltage and in the second mode, the situatuion will be opposite.
Shah Fahad It depends on the voltage sensitivity at the connection point of the DG (i.e. the PCC) and the line impedance connecting the DG.
Basically you control active and reactive power generation of DG, and observe the voltage. However, you cannot directly "control" voltage. The voltage level is a result of the active and reactive power generation at the connection point. So there is no strict rule that reactive power can always compensate for any active power generated.
In my opinion, two subjects must be considered in your work :
1- reactive power-voltage droop can be applied only in in inductive dominant lines. So if the line resistance is considerable in comparison to the line inductance, using the precise reactive and active power equations or virtual impedance control loop will be necessary.
2- The droop control loop can be considered in two different modes :
First, grid-support grid-feeding mode and second, the grid-support grid-forming mode. In the first mode, active and reactive generating efforts of DGs will be determined by the frequency and amplitude of the measured voltage and in the second mode, the situatuion will be opposite.
In theory, DG can regulate the PCC voltage to any desired value if it can produce or absorb infinite amount of reactive power. However, in real world every DG has an operating chart which will define how much reactive power can be produced or absorbed for a certain value of active power. Thus, depending upon the value of this reactive power, DG may or may not be able to regulate the voltage.
Severin Nowak Thank you for taking part in this discussion.
I have attached my graph for Reactive power and output voltage of DG on the same axis. Reactive Droop control is activated at 8 seconds because of which reactive power injection is reduced (as the reference for reactive power is considered zero).
What I want to understand is that Can i make reactive power zero and at the same time make DG output voltage closed to grid voltage. I mean theoretically it is possible but simulation is not showing it that way.
Samundra Gurung Farhad Yazdi Thank you for taking part. I appreciate that.
@Nowak I am facing the same challenge on my work, is it possible to use voltage mode control to control voltage on dc bus which is connected to wind turbine, solar power and storage system (battery and super capacitor).
Dear Severin Nowak thank you for the discussion. I think my issue is solved. I was ignoring a very important aspect of Power system and that is line impedance. My line impedance was highly inductive (Considering a very strong grid having X/R ratio very high). The moment I reduced the inductance of line the results changed. That reminded me basic concepts about which i was ignorant and too focused on reactive power output only. Anyways thank you for your time. I appreciate that.
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