Practical Framework for Frequency Stability Studies in Power Systems With Renewable Energy Sources

Abstract

The transition from power systems dominated by synchronous machines to systems based on converter-based generation technologies (CGTs), is weakening currently robust power systems by reducing system inertia with the replacement of synchronous generators with low-inertia CGTs. From a frequency stability viewpoint, this is resulting in faster frequency dynamics and more frequent and larger frequency excursions after system contingencies, thus significantly affecting the stability of power systems dominated by CGTs, requiring detailed stability assessments to ensure the secure integration of CGTs. In this paper, a practical framework is presented for frequency stability studies based on time domain simulations of power systems with CGTs. A fundamental part of the proposed approach is the use of a filter to first identify worst-case scenarios among various possible system operating conditions. Once these worst-case scenarios are identified, a clustering technique is used to select representative worst-case operating conditions to evaluate the frequency stability of the system using time-domain simulations. The effectiveness of the proposed framework is demonstrated on the Chilean Northern Interconnected System (NIS), where it is shown that the proposed filter is able to quickly identify worst-case scenarios for further study. Moreover, we show that the selected representative operating conditions cover a wide-range of worst-case frequency responses, demonstrating the effectiveness of the proposed tool for frequency stability analyses.

Determination of Control Requirements to Impose on CIG for Ensuring Frequency Stability of Low Inertia Power Systems

“…As is common in stability assessments of large-scale power systems, we adopt a worst-case approach, meaning that only a limited set of critical operating points and contingencies are investigated [69]. Since frequency stability problems are more likely to arise during periods of low system inertia [2], [17], the study is undertaken for the minimum net load operating point (i.e., when SGs generate the least amount of power), in which case only few SGs are available to support the system frequency response.…”

“…Additionally, the red dots indicate the location of the critical contingencies studied. Note that, as usual in frequency stability assessments of realistic size power systems, critical contingencies considered for the simulations are sudden outages of large online generation units [69], [75].…”

A Frequency and Voltage Stability-Based Load Shedding Technique for Low Inertia Power Systems

“…These are variable speed machines, which are electrically detached from the corresponding host network via power electronics interfaces. As a result, these WTGs are incapable of offering inertial support and governor response without additional control strategy [3]. Therefore, frequency response of a power system is likely to deteriorate under high wind penetration [4].…”

Power Configuration Scheme for Battery Energy Storage Systems Considering the Renewable Energy Penetration Level

“…Meanwhile, the output of REG has high fluctuation and intermittency, which requires more active power reserves to maintain the system frequency stability. Also, the frequency stability issue becomes worse (Ortiz-Villalba et al, 2020;He et al, 2020), when REG is absorbed across control areas via the transmission lines in the interconnected power grid. Therefore, with the increase of the renewable energy penetration (REP) level, the frequency instability caused by the insufficient system inertia and the active power reserve becomes a distinct threat of the interconnected power grid.…”