Small-Disturbance Voltage Stability of Power Systems: Dependence on Network Structure

The high penetration of inverter-fed renewable energy sources (RESs) in modern energy systems has led to a reduction in the system’s inertial response. This reduction in the rotational inertial response is associated with synchronous generation and might result in a deteriorated frequency response following a power disturbance. This paper investigates the frequency stability of the Kingdom of Saudi Arabia’s (KSA) grid. It includes a description of the changing energy landscape of the KSA’s electricity grid and an investigation of the impact of high penetration levels of inverter-fed RESs on the dynamic behavior of the KSA grid. The impact of RESs has been studied through a simulation of case studies of the future KSA power system using the MATLAB/Simulink simulation software. The frequency stability of the KSA’s power system has been evaluated with various RES levels under peak and base load conditions. The simulation results show that the high penetration levels of RESs dramatically affect the system’s frequency response, especially under off-peak conditions. In addition, the significance of battery energy storage systems (BESSs) for compensating the reduction in the system inertial response has been addressed. The results show the effectiveness of aggregated BESSs for enhancing the system frequency control of the KSA grid.

Increasing penetration of Renewable Energy Sources (RESs) such as wind, solar plants equipped with fast-acting control systems to the weak points of a power system could be concerned about the problem from classical voltage instability to control instability and control interactions. System strength is one of the important concerns in the integration of RES. Short circuit ratio (SCR) is often used as an index of the system strength. However, when RES are installed in an adjacent location, system strength can be lower than evaluation by SCR. Weighted Short Circuit Ratio (WSCR) is an index that reflects RESs interaction by assuming a 100% influence. This paper propose Inverter Interaction Level Short Circuit Ratio (IILSCR) method using inverter-based resource's output tracing. IILSCR can accurately estimate system strength which RESs are connected in adjacent spot by reflecting the interaction between RESs.

Evaluating the inertia of the Jordanian power grid

An innovative technique to evaluate network equivalent for voltage stability assessment in a widespread sub-grid system

Purpose of the Study. The study aims to investigate various approaches to mitigating the impact of renewable energy sources on the stability of the power system and to determine the optimal combination of conventional and renewable energy sources to ensure stable and reliable energy supply. The effectiveness of different approaches to minimizing the impact of renewable energy on grid stability is evaluated. Materials and Methods. Methods of eigenvalue analysis and transient process modeling were used. Correlation and regression analysis methods were used to assess the impact of renewable energy sources (RES) on the stability of the energy system. Data from the system operator «Ukrenergo» were used, including power system load schedules (hourly, daily, seasonal). Data from the Ukrainian Hydrometeorological Center for the years 2023–2024 were used to model RES generation: data on solar radiation (hourly, daily) and wind speed (hourly, daily). Technical specifications of solar panels and wind turbines installed in Ukraine were also used. The QGIS software was utilized for geoinformation analysis. The study employed artificial neural network theory, optimization methods based on linear programming and logical production rules, as well as methods for assessing and regulating steady-state operating conditions of the system, taking into account energy storage devices. Results. The scientific novelty lies in the development of an innovative method for assessing the reduction of the impact of renewable energy sources on power system stability. The feasibility of using artificial neural networks to forecast wind and solar power generation was demonstrated, as well as the optimization of the model structure and parameters to improve forecasting accuracy. The optimal combination of conventional and renewable energy sources was determined to ensure stable and reliable operation of the power system. Practical Significance. Based on experimental and theoretical research, specific recommendations and solutions are provided aimed at ensuring the stability of the power system during the integration of renewable energy sources, including optimization of management, use of new technologies, and infrastructure development

This paper investigates on-load tap changer OLTC effect on voltage stability. Chaos theory used in this analysis is via the calculation of the maximum power transmission. Resulted chaotic behavior is exhibited by singular induced bifurcation which clearly shows the voltage stability of the power system with OLTC from a singular induced bifurcation point of view. The paper is organized as follows: 1) increasing in the maximum reactive power via increasing the ratio of OLTC and the possibility of voltage collapse decrease under the same load command. 2) Noting that the voltage instability is directly affected by the load characteristics, shown via the effect of OLTC on the voltage instability under different static load models. 3) Studying voltage stability in state space and the effects of the generator excitation current limit, the OLTC and load dynamics on voltage collapse. In addition, a small-disturbance voltage stability region of a power system is constructed. The voltage stability of the system is determined by the dynamic characteristics of both the OLTC and the load.

In this study, a new decision tree-based method is proposed to assess the small disturbance (limited to load disturbance) voltage stability of power systems by only using synchronised phasors (synchrophasors) measured by phasor measurement units in a wide-area measurement system. To properly predict the voltage instability considering various load increase directions as well as load increase step sizes, a mathematical morphology algorithm is used to extract appropriate features from synchronised measured voltage phasors during the few seconds just after the disturbance. These features along with the pre-disturbance ones are then applied to a trained decision tree to predict the voltage instability of the power system. The proposed method is applied and tested on the Nordic32 test system. To examine the efficiency and accuracy of the proposed method, the dynamic behaviours of on-load tap changing transformers as well as the stator current limiters of synchronous generators are considered. The simulation results demonstrate that this method effectively predicts the voltage instability of the power system during the first two seconds just after the disturbance, for the test system.

Chapter 9 - Integrated Planning of Energy and Water Supply in Islands

This paper focuses on impact of renewable energy sources such as solar and wind on power flow control. The performance analysis of Flexible AC Transmission Systems (FACTS) devices namely SVC and TCSC in steady state power flow control without and with renewable energy sources are studied. Impact of renewable energy sources on thermal generating units and reduction in losses are discussed. Application of FACTS devices in a power system network is an efficient way for the control and transfer of bulk power for long distances. The performance of SVC and TCSC for reactive power injection, real power flow, power loss and voltage improvement are analyzed. Effective utilization of existing transmission line for the transfer of bulk power is demonstrated. The performance of FACTS devices during single line contingency is also analysed. The ability of SVC and TCSC to control power flow under various loading conditions and the modes of operation are discussed. Modelling of solar and wind farms is done using beta and weibull distribution functions respectively. SVC and TCSC are modelled using Variable Reactance modelling and are then incorporated into the existing Newton Raphson load flow algorithm. Numerical results on a benchmark 5 bus test system are presented.

Coordinated voltage control of wind-penetrated power systems via state feedback control

This paper analyzes the impact of inter-connection of large-scale wind power on the voltage stability of power system. First it presents three different voltage indexes obtained with the power flow equation. Then, it discusses the impacts with different penetration rates and interconnection locations. Simulation with typical power system shows that different indexes vary a lot with the interconnection of wind power and the impacts are different with respect to different locations.

This paper introduces battery energy storage systems (BESS) as one of the alternatives in dispatching power systems including renewable energy sources (RES) as well as thermal units. A stochastic based power dispatch model is proposed to optimize the operation of thermal units, RES and BESS involves the degradation cost of BESS. The RES operating cost considers the uncertainties of solar irradiance and wind speed by considering overestimation and underestimation penalty terms. The degradation cost of the BESS includes the starting and ending levels of the batteries’ state of charge as well as the discharge rate. Hybrid mean variance mapping optimization (MVMO-SH) algorithm is utilized to solve the dispatch problem. The model is tested using different case studies and the impact of RES as well as BESS penetration in power systems are investigated. The results show that there is a significant drop in the total operating cost caused by RES and BESS integration in the cases under study. This is attained by lessening the power drawn from thermal units.

The importance of probabilistic assessment in distribution systems is very high due to the increasing penetration of renewable energy sources (RESs) with their fluctuating behavior. Also, there are some other uncertain variables in distribution systems such as loads fluctuations. More awareness of the system state by considering many uncertainties provides more certainty in decision making and causes better risk management. Moreover, the distribution static compensator (DSTATCOM) has been recently implemented due to its efficient abilities in the distribution systems operation especially when RESs are integrated into them. This article investigates the probabilistic assessment of DSTATCOM operation in a distribution system using the k-means-based data clustering method (DCM). The uncertainty of load demands, wind speed, and solar radiation are considered in this study. The performance of DCM is compared to the Monte Carlo simulation (MCS) and Latin Hypercube sampling (LHS) methods in terms of accuracy and computational burden. The efficiency of k-means-based DCM is investigated in the IEEE 69-node test system.

Introduction: To date, a variety of studies have been published on the topic of long term energy system transition. Most studies on future energy systems, however, have a shorter time frame or adopt a supranational focus (e.g. the Energy Roadmap, 2011 or the World Energy Outlook, 2015). It then constitutes a sincere challenge to perform a national energy system transition study with as time horizon 2050 and covering a far-reaching transformation of the energy system. VITO, together with the FPB (Federal Planning Bureau) and ICEDD, performed a study to scrutinise the transition of the Belgian national energy system towards a future mix entirely based on renewable energy sources. The focus on renewable energy sources and on building a national energy system completely running on renewable energy can be traced back to three main concerns: – Climate change: Renewable energy sources (RES) are a major instrument in the fight against climate change as RES do not release (net) greenhouse gas emissions. – Security...

Analysis for Effects of Load Characteristics on Power System Voltage Stability