Frequency Stability Evaluation in Low Inertia Systems Utilizing Smart Hierarchical Controllers

Abstract

<jats:p>The high penetration of the Renewable Energy Sources and other emerging technologies likely to be installed in future power grids will pose new operational challenges to grid operators. One of the main issues expected to affect the operation of the power grid is the impact of inverter-based technologies to the power system inertia and, hence, to system stability. Consequently, the main challenge of the future grid is the evaluation of the frequency stability in the presence of inverter-based systems and how the aforementioned technology can support frequency stability without the help of the rotating masses of the traditional power grid systems. To assess the above problem, this paper proposes a methodology to evaluate the frequency stability in a projection of the real distribution grid in Cyprus with the time horizon to be the year 2030. The power grid under investigation is evaluated with and without the presence of smart hierarchical controllers for providing support to the power system under disturbance conditions. The advanced controllers were applied to manage the available power resource in a fast and effective manner to maintain frequency within nominal levels. The controllers have been implemented in two hierarchical levels revealing useful responses for managing low-inertia networks. The first is set to act locally within a preselected area and the second level effectively supporting the different areas for optimal operation. After undertaking a significant number of simulations for time-series of one year, it was concluded from the results that the local control approach manages to minimize the frequency excursion effectively and influence all related attributes including the rate of change of frequency (RoCoF), frequency nadir and frequency zenith.</jats:p>

A Study on Frequency Stability and Primary Frequency Response of the Korean Electric Power System Considering the High Penetration of Wind Power

“…In Stages I and III, while β sys_bef is the same as that in case study 1, β req was increased from 688 MW/0.1 Hz to 915 MW/0.1 Hz compared to case study 1. This is because WPPs do not provide PFR to compensate for the loss in (10). Thus, the difference between β req and β sys_bef was increased for this case study.…”

“…However, as WPPs were available to provide PFR of 371 MW, the size of P loss decreased to 1129 MW. As the result, β req was calculated as 688 MW/0.1 Hz by (10). Since β sys_bef , which is 621 MW/0.1 Hz, is lower than the β req , the f set cannot be stabilized within f SSband .…”

“…However, WPPs operating in this method do not provide any frequency responses when a large disturbance such as a generation trip occurs. Therefore, as WPPs replace conventional SGs, which provide an inertial response (IR) and primary frequency response (PFR), frequency stability is severely impacted [9,10]. To solve this problem, many studies have developed effective control methods to provide ancillary services and support power system stability [11][12][13][14].…”

Smart frequency control in low inertia energy systems based on frequency response techniques: A review

“…Similarly, a two-level hierarchical control applying on both transmission and distribution energy systems are proposed in [137,138], where a fast frequency control mechanism is presented. A combination of centralized plus distributed approach is adopted for the coordinated control strategy presented in [139].…”