In an electric power system characterized by a low value of inertia it would be recommended the adoption of a rapid primary regulating logic. In fact an increase of Rate of Change of Inertia (RoCoF) allows machine controllers a shorter reaction time before the frequency reaches the load shedding trip threshold. What are the solutions that can be adopted to reduce the intervention time of primary frequency regulation without using storage systems ?
There are some suggested methods to reduce the impacts of the low inertia of wind, and solar energy power plants. In wind power plant, a power boost can be achieved by operating the wind farm below its maximum power point (MPP). Consequently, contribution of the wind farm in the primary frequency control is possible, and limited by the margin between the selected operating point and the MPP. The same approach may be applied to solar-PV plants. Another method is to add synthetic inertia control loops within the power control loops of DFIG-based WTG, and the solar-PV active power control. The mentioned methods do not require energy storage; however, there is resulting lost opportunity of renewable energy capture. I guess you can find relevant literature. Any possible collaboration will be appreciated.
Thank you for your kind and detailed answer. Actually I know the possible solutions mentioned by you but I would like to analyze in deep solutions that involve the traditional generating plants. Specifically the use of a quicker primary regulation (reducing drastically the activation time from 15 s 30 s to less than 1 second) is solution that is worth being investigated. I would like to have comments and remarks about the possibility to utilize pratically such solution.
A perfect point of research; however, reduction of the activation time of the primary frequency control is, unfortunately, is constrained by inherent characteristics such as the governor dead band (GDB), and generation rate constraints (GRC). Therefore, significant reduction of the activation time to reach the order of 1 s may be physically impossible.
You are right as1 s is the lowest limit that has been reached in UK by using a storage system connected to the conventional generator [1]. However I would like to discuss with you and other researchers what is the lowest credible (means that are solutions that are already technologically available value) for the intervention time
[1] National Grid (UK), Enhanced Frequency Response. http://www2.nationalgrid.com/Enhanced-Frequency-Response.aspx
To me, the estimation of the lowest credible value of the intervention time is a stiff problem as it is highly dependent on the considered units, and their technologies as well as the operating conditions. Please consider to inspect the mention URL as it is referring to an unavailable content. If you have the report, please sent it to me.
Dear Mohamed, I am sorry for the web link, please try the following one:
https://www.nationalgrid.com/uk/electricity/balancing-services/frequency-response-services/enhanced-frequency-response-efr.
Dear Tina, thank you very much for posting a valid link. Do you have information about the adpoted approach for securing the required 200MW enhanced response to 1 sec?
yes, this enhanced primary frequency regulation system is based on the use of storage system. But what I would like to check and discuss is the possibility to improve excitation and governor systems in such a way to cope with the presence of inertia free generators. This problem in the past has been neglected due to presence of traditional generators, but today it is worth investigating on it. what is your opinion ?
Dear Tina,
Unfortunately, I did not attempt that approach of directly handling the inertial problems of low inertia (wind), and nearly zero inertia (solar-PV) through modifications of the controls of the conventional generators. In a previous research (below), I evaluated the impacts of WTGs on the inertia of power systems. In addition, I constructed a very fast corrective action approach based on the extended equal area criterion for load shedding minimization under emergency state conditions.
Article Stability-based minimization of load shedding in weakly inte...
(with details presented in chapters 4 to 7 of
Book Dynamic Security of Interconnected Electric Power Systems - ...
The research point you mentioned is of critical importance, and I will provide any possible collaboration with you for achieving the technical possible minimum intervention time of primary frequency control actions during the normal and abnormal states.
IMHO, the future application of low, and zero inertial generators should be limited to grid-connected distributed generation, or off-grid systems. The large scale power plants of that kind may be used for supplying Power-to-fuel systems where the fuel may be used directly, on in the reverse process i.e. fuel-to-power. Based on recent advances, there are serious and continuous efforts for providing feasible infrastructure for the power-to-fuel-to-power technologies. You may read the following publications:
Conference Paper Overview of Power-to-Hydrogen-to-Power (P2H2P) Systems Based...
Chapter Operational Characteristics of Renewable Sources, Challenges...
Powering the power-to-fuel-to-power systems via nuclear energy may also be the most feasible alternative to bulk power generation from fossils, and for large grid support. You may read the following discussions which also include valuable references.
https://www.researchgate.net/post/What_is_your_opinion_about_the_following_system_for_retrofitting_future_mixed_energy_production?_ec=topicPostOverviewAuthoredQuestions
Best regards,
M. EL-Shimy
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