Recently, lots of distributed energy resources such as PV are connected to the distribution network, hence causing some technical problem. One of the problem is voltage violation. In order to resolve the voltage violation, existing inverter monitors its node voltage and manipulate reactive power to maintain the voltage while generating maximum active power. If the inverter capacity gets full, it has to reduce the active power generation if voltage is too high even if it can generate more active power, say when sun is shiny.
This is an interesting question. The answer would depend on what you mean by "optimal" - do you mean optimal in terms of maximising the real power output of each PV in the network? In Germany and other countries that are very advanced in integrating solar generation, PV generators need to operate within a certain power factor (pf) range, or accept any setpoint from the network operator. The exact control method used depends on the capacity of the PV plant.
The use of pf setpoints or droop charactersitcs has been effective in managing voltage in many existing distribution networks. However, this often results in PV generators that are further from the substation providing more reactive power support than PVs close to substation (since PVs furthest from the substation typically have the "worst" voltage profiles).
There is a nice explanation given here: http://www.clean-coalition.org/site/wp-content/uploads/2013/10/CC_PV_AI_Paper_Final_Draft_v2.5_05_13_2013_AK.pdf
I think this would vary from case to case.
That depends on the specific requirement of the system. For example if the main requirement is the maximum active power transfer, then the reactive power compensation may be the second consideration, vice versa.
This is an interesting question. The answer would depend on what you mean by "optimal" - do you mean optimal in terms of maximising the real power output of each PV in the network? In Germany and other countries that are very advanced in integrating solar generation, PV generators need to operate within a certain power factor (pf) range, or accept any setpoint from the network operator. The exact control method used depends on the capacity of the PV plant.
The use of pf setpoints or droop charactersitcs has been effective in managing voltage in many existing distribution networks. However, this often results in PV generators that are further from the substation providing more reactive power support than PVs close to substation (since PVs furthest from the substation typically have the "worst" voltage profiles).
There is a nice explanation given here: http://www.clean-coalition.org/site/wp-content/uploads/2013/10/CC_PV_AI_Paper_Final_Draft_v2.5_05_13_2013_AK.pdf
Hi Shahnewaz,
Barry has given you a good feel of the way such situations are handled in some of the EU nations, but the fact remains that the operational bottlenecks you have described (reverse power flow and overvoltage due to underloading) are operational issues that do not allow any scope of optimality in the power network.
This is not a regular healthy operational condition open to reactive power management and optimisation. Rather, such problems in a PV based system are more to be handled as operational situations to be avoided !!
The only scope of optimality that we can see is in the domain of system configuration and design - that is, don't allow too many PV generators so as to avoid situations of reverse power flow and overvoltages altogether.
-Sanjay
In our Country our PVs working with power factor=1 and inverters are set on that value, to maintened it. The reason is the feed in tariff, since reactive power support from PV is not recognized and paid from National regulator. Inspite we use almost all inverters technology from Germany (SMA, Fronius...) and other inverters, which can give some support to the network with some ammount of reactive power.
In new EU regulative I think that it will be like in Germany. The reason why it is not now is unfortunately small amount of PV in our national power system :( less then 1% of installed power.
Srete
You can handle your problem by inserting PV system capability diagram.
Refer article http://www.sciencedirect.com/science/article/pii/S014206151400101X
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