ASSESSMENT OF OPERATIONAL RELIABILITY OF POWER SYSTEMS UNDER INTEGRATION OF HIGH-CAPACITY RENEWABLE ENERGY SOURCES

ABSTRACT

The integration of high-capacity renewable energy sources (RES) into power systems has accelerated over the past decade, resulting in new challenges to system reliability. This study evaluates the impact of increasing RES penetration on key reliability indices such as Loss of Load Probability (LOLP), Expected Energy Not Supplied (EENS), and System Average Interruption Duration Index (SAIDI). The analysis reveals that higher RES penetration levels significantly increase reliability risks, particularly when the share exceeds 50%. The findings underscore the importance of adaptive reliability assessment methods and advanced grid-support technologies to ensure stable power system operation.

АННОТАЦИЯ

Интеграция крупномасштабных возобновляемых источников энергии (ВИЭ) в энергосистемы значительно ускорилась за последнее десятилетие, что привело к возникновению новых вызовов для надежности систем. В настоящем исследовании оценено влияние растущей доли ВИЭ на ключевые показатели надежности: вероятность потери нагрузки (LOLP), ожидаемую недопоставленную энергию (EENS) и среднюю продолжительность перерыва в электроснабжении (SAIDI). Анализ показал, что при уровне проникновения ВИЭ выше 50% риски нарушения надежности существенно возрастают. Полученные результаты подчеркивают необходимость разработки адаптивных методов оценки надежности и внедрения современных технологий поддержки сетей для обеспечения устойчивой работы энергосистем..

Keywords: Renewable energy integration, Power system reliability, High-capacity RES, Loss of Load Probability (LOLP), Expected Energy Not Supplied (EENS), System stability, SAIDI, Inverter-based generation, Grid resilience, Reliability assessment.

Ключевые слова: Интеграция возобновляемых источников энергии, Надёжность энергосистемы, Крупномасштабные ВИЭ, Вероятность потери нагрузки (LOLP), Ожидаемая недопоставленная энергия (EENS), Стабильность системы, SAIDI, Генерация на базе инверторов, Устойчивость сети, Оценка надёжности.

Introduction

The purpose of this study is to assess the operational reliability of power systems under the large-scale integration of high-capacity renewable energy sources, taking into account their variable generation profiles and the resulting impact on system stability and security of supply. To achieve this goal, the study sets the following objectives: to analyze existing approaches to reliability assessment in power systems with a high share of renewables; to identify key risk factors and uncertainties related to renewable generation; to develop suitable criteria and indicators for quantifying operational reliability; to model system behavior under different renewable penetration scenarios; and to propose measures and recommendations for enhancing system reliability through advanced control, forecasting, and reserve management strategies.

The rapid growth in renewable energy deployment is reshaping the operational landscape of power systems worldwide. As of 2024, the total installed renewable energy capacity has reached approximately 3200 GW, a significant rise from 1300 GW in 2015, representing a 146% increase over the past decade (Figure 1) [1,2]. According to the International Renewable Energy Agency (IRENA), this expansion has been driven predominantly by utility-scale solar photovoltaic (PV) and wind energy projects, particularly in China, the European Union, India, and the United States.

Figure 1. Global installed renewable energy capacity (2015–2024)

The large-scale integration of high-capacity renewable energy sources (RES) poses significant challenges to the operational reliability of power systems. Unlike traditional fossil fuel and hydro generators, solar and wind units are variable, weather-dependent, and inverter-based, offering limited inertia and controllability. This complicates frequency stability, voltage regulation, and fault response. As RES penetration exceeds 40–50% in many regions, traditional reliability assessment tools become inadequate [3,4]. Advanced models that account for stochastic variability, real-time dynamics, and new ancillary services are essential to ensure system-wide stability and reliability under uncertain conditions.

Methods

To assess the impact of high-capacity renewable energy integration on power system reliability, several reliability indices were evaluated under increasing levels of RES penetration. The results are summarized in Table 1.

Table 1.

 Reliability indices under varying levels of RES penetration.

Results And Discussion

As observed, higher levels of renewable penetration result in a significant increase in both the Loss of Load Probability (LOLP) and the Expected Energy Not Supplied (EENS). The SAIDI index also increases, indicating greater interruption durations for end-users. These trends underline the growing importance of deploying advanced control, storage, and forecasting technologies to mitigate the variability introduced by renewables [5-7].

Key reliability indicators used in the analysis are defined as follows:

The integration of high-capacity renewables significantly affects power system reliability, increasing risks such as energy shortfalls (EENS), load loss (LOLP), and service interruptions (SAIDI), especially beyond 50% penetration. Ensuring stability requires advanced forecasting, grid-forming inverters, flexible demand management, and energy storage. Future work should prioritize adaptive models and real-time control to manage renewable variability without compromising system reliability.

References:

1. International Renewable Energy Agency (IRENA). (2024). Renewable capacity statistics 2024. Abu Dhabi: IRENA. Retrieved from https://www.irena.org/Statistics/View-Data-by-Topic/Capacity-and-Generation/Technologies
2. Global Wind Energy Council (GWEC). (2024). Global Wind Report 2024. Retrieved from https://gwec.net/global-wind-report-2024/
3. Niyozov, N.N., Liu, C., & Usmonov, E.G. (2025, May 15-16). An overview of the current approaches to evaluating the stability and reliability of power systems with large-scale renewable energy integration. In Proceedings of the Republican Scientific-Technical Conference "Development of Modern Electric Machines and Drives for Green Economy" (pp. 126-128). Tashkent.
4. Niyozov, N.N., Liu, C., & Usmonov, E.G. (2025, May 15-16). Algorithmic approach to frequency and voltage control for static and dynamic stability analysis in electrical power networks. In Proceedings of the Republican Scientific-Technical Conference "Development of Modern Electric Machines and Drives for Green Economy" (pp. 418-421). Tashkent.
5. R. Billinton and R. N. Allan, Reliability Evaluation of Power Systems. New York: Springer, 1996.
6.  W. Li and K. Xie, Reliability Assessment of Electric Power Systems Using Monte Carlo Methods. Springer, 2017.
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