Power System Voltage Stability Research Articles

Hybrid model-data-driven dynamic VAR planning for wind-penetrated power system using spectral surrogate techniques

The increasing wind power penetration and proliferation of induction motor loads, of which dynamic impact cannot be revealed through steady-state analysis, bring challenges to the short-term voltage stability of modern power systems. This study proposes a hybrid model-data-driven approach for dynamic VAR source planning to enhance the short-term voltage stability of wind-penetrated power systems to reduce the computation burden of electro-mechanical transient models. Firstly, the theoretical background of Stochastic Spectral Embedding (SSE) is introduced. Then, a surrogate model for the electromechanical transient model is established using SSE following efficient expansion coefficient calculation and a designed partition strategy for the studied problem. Furthermore, a hybrid model-data-driven VAR deployment optimization model is established with 3 objectives, which is solved by a dual-population-based evolutionary algorithm (DPEA). The accuracy and effectiveness of the model are verified on a modified New England 39-bus system. Simulation results prove that the computational cost is reduced significantly in comparison with conventional model-based method without a compromise in accuracy and the proposed method is also more accurate than methods based on other surrogate models. The proposed SSE-based model can be applied to other power system analysis with electro-mechanical transient models to alleviate the computational cost.

The Impact of Hybrid Power Generations on a Power System's Voltage Stability

The Impact of Hybrid Power Generations on a Power System's Voltage Stability

Improving Power Quality Using D-STATCOM with Capacitor as Energy Storage System

Power electronics are used more frequently to raise awareness of power quality which must be considered when designing modern power systems for effective operation and continuous power supply to various load centers. Otherwise, it will be hazardous for residential and commercial customers, reducing the production of their work due to faults and equipment damage. Electronic technology known as Flexible AC Transmission System (FACTS) may improve power stability to make the electric power system efficient. Oscillation damping in the Power system is still a big concern for operating a safe and dependable power system. The static synchronous compressor (STATCOM) is connected to assist power networks with poor power quality and voltage regulation. Although there are several uses, voltage stability is the most frequently used. An average model of the D-STATCOM control approach is presented in this work to improve the transmission of power quality flow and voltage stability in electric power systems. An increase in system voltage stability, reactive power flow control for different loads, and dynamic response of STATCOM are the primary goals of this research work.

An Extended Continuation Power Flow Method for Static Voltage Stability Assessment of Renewable Power Generation-Penetrated Power Systems

The continuation power flow method (CPF) has been extensively used for obtaining the static voltage stability limit of power systems, which provides important guidance for the stable operation. However, the conventional CPF cannot account for the dynamic characteristics of renewable power generation, thus resulting in prominent errors for renewable power generation-penetrated power systems. In this paper, we investigate the static voltage stability assessment (SVSA) of power systems with high penetration of rgb0,0,0renewable power generation (RPG). An extended Jacobian matrix is firstly established by considering the dynamic characteristics of synchronous generators (SG) and renewable power generation in constant AC voltage control mode (CVRPG). Based on the extended Jacobian matrix, an extended CPF method is proposed for SVSA of the power system and a reactive power sensitivity index is proposed to indicate the voltage support capability of nodes. Simulation results show that the proposed extended CPF method has higher accuracy than conventional CPF in assessing the static voltage stability of power systems with high penetration of RPG. It is also revealed that that the voltage support capability of each node rises as the proportion coefficient is increases.

A Comprehensive Review on Voltage Stability in Wind-Integrated Power Systems

The fast growth of the world’s energy demand in the modernized world has stirred many countries around the globe to focus on power generation by abundantly available renewable energy resources. Among them, wind energy has attained significant attention owing to its environment-friendly nature along with other fabulous advantages. However, wind-integrated power systems experience numerous voltage instability complexities due to the sporadic nature of wind. This paper comprehensively reviews the problems of voltage instability in wind-integrated power systems, its causes, consequences, improvement techniques, and implication of grid codes to keep the operation of the network secure. Thorough understanding of the underlying issues related to voltage instability is necessary for the development of effective mitigation techniques in order to facilitate wind integration into power systems. Therefore, this review delves into the origin and consequences of voltage instability, emphasizing its adverse impacts on the performance and reliability of power systems. Moreover, it sheds light on the challenges of integrating wind energy with existing grids. This manuscript provides a comprehensive overview of the essential features required for critical analysis through a detailed examination of Voltage Stability Indices (VSIs). To address voltage stability issues in wind-integrated power systems, this review examines diverse techniques proposed by researchers, encompassing the tools utilized for assessment and mitigation. Therefore, in the field of power system operation and renewable energy integration, this manuscript serves as a valuable resource for researchers by comprehensively addressing the complexities and challenges associated with voltage instability in wind-integrated power systems.

Realization of Small Scale Models of FCATS Devices and its Optimization in Power Systems using Stability Indices and Particle Swarm Optimization

This article focuses on the physical realization of SVC, TCSC, combined SVC and TCSC scale down models, which have been realized in the laboratory, developed and tested and presented the experimental results. These practical test results have been proven the effectiveness of these devices with closed loop control systems developed with microcontrollers. The voltage stability can be assessed accurately using stability indices. These indices can either reveal the critical bus or line of a power system. The said indices plays vital role in identifying the most critical n-1 and n-2 contingencies. This article further focuses on optimization of these devices in IEEE 9 bus, 14 bus and 30 bus test systems using stability indices and Particle Swarm Optimization (PSO). The simulation results for all these systems have been presented and which proves the tremendous improvement in voltage stability of power systems.

An Easy Method for Simultaneously Enhancing Power System Voltage and Angle Stability Using STATCOM

An Easy Method for Simultaneously Enhancing Power System Voltage and Angle Stability Using STATCOM

Detecting Power System Voltage Stability in Large Test System

The unpredictable changes in electricity demand, along with potential risks, require power system operators to act quickly to prevent voltage instability. To do this, real-time monitoring is crucial, especially in larger systems, but it is a challenging task for power system engineers. The existing methods for detecting voltage instability need to be tested and validated for complex systems. This study aims to validate a voltage instability detection index called SQLVIDI in a larger test system with 118 buses (IEEE 118 bus test system). The simulation results manifest that this index has the capability to detect potential voltage instability in the power system with larger number of buses.

A comparative study of voltage stability NVSI Index and load margin index

With the development of new energy generation technologies, photovoltaic (PV) power generation has gained widespread application as a clean and sustainable source of electricity. However, the intermittency and variability of PV generation pose new challenges to power system secure and stable operation. The WSCC 9-bus system is used in this paper to investigate the effect of PV integration on static voltage stability in power systems. An improved voltage stability index (NVSI) considering the new energy was used to measure the voltage stability of the access point of PV plant. Compared with the P-V curve and the classic load margin index (ILM), even if the index value is less than 0, the NVSI index has still a better measure effect on voltage stability.

Power system harmonic analysis with real geomagnetically induced current from the 2003 halloween storm

It is well understood that geomagnetically induced currents (GICs) flow through the grounded neutrals of wye-connected transformers, generating harmonic currents that flow along frequency-dependent transmission lines. Harmonic currents affect protection systems and cause harmonic voltage drops that disturb power system voltage stability. In the literature, GICs are modelled as dc-currents for harmonic analysis. However, GICs are multi-frequency currents having both positive and negative polarities. Therefore, a representative harmonic analysis of power systems is only possible when GICs are modelled as multi-frequency AC currents. In this paper, the authors subjected a multi-machine power system model to real GICs from the 2003 halloween storm. Representative time intervals within the storm were selected, and a harmonic analysis of transmission line and generator stator currents was carried out. The results showed that the harmonic spectrum of currents fluctuated with a real GIC instead of reaching a steady state with a DC model for GIC. Moreover, harmonics induced on generator windings increase the risk of dynamic voltage and power system instability. The results confirm the susceptibility of power system generators to GICs and validate the use of synthetic GIC for modelling the effect of power system stability.

Improvement of voltage stability and loadability of power system employing the placement of unified power flow controller using artificial neural network

<span lang="EN-US">This paper proposes a voltage stability and loadability improvement model of power systems by incorporating the optimal placement of flexible alternating current transmission systems (FACTS) using an artificial neural network (ANN) called OPFANN. The key aspect of this model is to identify the weakest lines which having the most probability of voltage collapse utilized for placing FACTS devices. As installing a new power system network with rapidly increasing power demand cannot be possible, the operator usually operates the power system close to the stability limit. In this regard, continuous monitoring and improvement of system voltage stability and loadability of the existing system are vital issues for energy management systems nowadays. However, the proposed OPFANN introduces a more straightforward and faster scheme for voltage stability monitoring systems using ANN. Intelligent and reliable data samples have been designed to train the ANN based on two-line voltage stability indices (LVSI) techniques. Compared with other works, OPFANN effectively improves voltage stability and loadability at the load point by installing the unified power flow controller (UPFC) FACTS devices to the weakest lines. OPFANN can provide information on voltage collapse points using ANN and reduce the further computational cost of LVSI. Finally, OPFANN ensures faster and more secure operation of the power system.</span>

A Comprehensive Review on the Modelling and Significance of Stability Indices in Power System Instability Problems

Many technological advancements in the modern era have made actual use of electrical power and the constrained operating of power systems within stability limits. Some expeditious load variations and rising power demands initiate complications in voltage stability and can put stress on performance, leading to voltage instability. Voltage Stability Indices can be used to perform voltage stability assessment. This review evaluates various VSIs based on mathematical derivations, assumptions, critical values, and methodology. VSIs determine the maximum loadability, voltage collapse proximity, stability margin, weak areas, and contingency ranking. Stability indices can also specify the optimal placing and sizing of Distributed Generators. Thus, VSIs play a vital role in power system voltage stability. This review is a comprehensive survey of various indices and analyses their accuracy in determining the instability of power systems. Voltage stability is a crucial concern in operating a reliable power system, and the systematic evaluation of voltage stability is essential in a power system. This review considered and analyzed 34 indices from 138 articles from the literature for their significant performance in various power system stability problems. Of 33 indices, were 22 derived from transmission line parameters, referred to as line indices, and 12 from bus and line parameters, referred to as bus indices.

Clustering Combined Multi-Objective Optimal Operation of Transmission Systems Considering Voltage Stability

In recent years, power systems have undergone major changes called energy transitions during which synchronous generators have been replaced with power electronics-based generation. Therefore, the voltage stability of power systems has become a major concern owing to the absence of synchronous generators. This study proposes multi-objective optimization using the non-dominated sorting genetic algorithm III to achieve optimal reactive power reserve procurement and improve the voltage stability of the overall system. These systematic approaches require high computational power and are unsuitable for the operational frameworks currently used for large-scale power systems. Previous works have rarely considered the local characteristics of reactive power or generation de-commitment with sufficient re-dispatch owing to greater renewable energy integration. We propose a framework for achieving systematic optimization by considering various objective functions while utilizing the regional aspect of reactive power via spectral clustering-based voltage control area (VCA) identification. The proposed method comprises systematic and regional approaches to optimizing systems for voltage stability improvement based on VCAs. The results demonstrate that the proposed method shows satisfactory performance. These results will be helpful for decision making for power system operations in harsher environments with more renewable energy.

A short-term voltage stability online assessment based on multi-layer perceptron learning

In this paper, a deep learning-based approach is used to analyze short-term voltage stability of power systems in order to completely learn the hidden timely dependencies from post fault behavior of the system. The direct measurements from the PMU, which did not require any significant amount of computation, have been used, and the results will be accurate. The proposed approach makes considerable use of a Multi-Layer Perceptron-based deep learning model in order to make the most accurate prediction feasible regarding the short-term voltage stability status. Rapid prediction of voltage stability allowed system operators sufficient time to take effective corrective action against large disturbances. In-depth offline simulations will be executed against various fault types, with the results being fed into the classifier as inputs. After the classifier has been trained using the results of the offline simulations, the online application will be applied to the test samples. The effectiveness of the suggested method will be evaluated based on the results of tests conducted on both small and large-scale test systems.

Analysis of overvoltage reactive power margin for future power systems with renewable energy generation

As modern power systems continue to adopt wide usage of Renewable Energy (RE) sources, the reliance on conventional generators is slowly reducing. Countries are adopting new energy policies to speed up the transition of future power systems to a fully renewable and clean system, and this is centered around the increase of RE penetration to reduce carbon emissions. However, it is expected that this transition will be met with stability issues due to the intermittent nature of REs and reduction of conventional generators. In recognition of these expected complications for the future systems, an analysis method is proposed in this paper to identify critical buses in terms of voltage stability for power systems with high RE penetration level. A new method that utilizes both modified continuation power flow and Q-V analysis to determine acceptable reactive power margins for each bus considering the intermittency of RE sources is presented in this study. This work is focused on the future Korea Power Systems with 16.05 GW of renewable energy. Considering different RE levels and loading conditions, several scenarios are studied to identify the voltage stability in the different Korea regions with a high penetration of RE. The resulting reactive power margins can be used to prevent overvoltage through the identification of weak and vulnerable buses for the future power systems.

Multi-task transient stability assessment of power system based on graph neural network with interpretable attribution analysis

Transient power angle stability analysis and voltage stability analysis are the key basis of power system security and stability control. The diversified operation modes of power system put forward higher requirements for real-time and topology generalization of transient stability assessment. Based on Convolution Neural Network (CNN) and Graph Attention Networks (GAT), this paper uses the wide-area transient response features to evaluate the transient angle stability and voltage stability of power system. Firstly, CNN is used to encode the temporal variation characteristics of transient features of electrical components in hidden layer space. Secondly, the encoded hidden layer features are mapped into graph data samples according to the spatial topological correlation of electrical components, so as to train and build a multi-task transient stability assessment model based on GAT. The model can adaptively capture the interaction relationship between encoded hidden layer features of topologically correlated components, and realizes real-time evaluation of transient angle stability and transient voltage stability by perceiving the temporal–spatial correlation of transient features. Finally, Shapley additive explanation (SHAP) method is used to explain the decision-making mechanism of the model and extract the key features that affect the transient stability, so as to enhance the ability of power grid operators to perceive the transient stability situation. The results of IEEE-39 system show that the transient stability assessment model has good accuracy and topology generalization, and the results of interpretable analysis are in line with the conclusions of traditional mechanism cognition, which helps to improve the credibility of the model results.

Multi-objective reactive power optimization strategy of power system considering large-scale renewable integration

To fully tap the abilities of renewables in reactive power optimization, this paper develops a detailed model for the power regulation capabilities of wind turbines and photovoltaic units and studies their impact on the power system’s operation. First, the power system model with renewables integration is established using AC power flow. The wind turbines and photovoltaic units are modeled in detail according to their topologies and operating characteristics, and then further simplified according to the feasible region. An improved DC power flow model is adopted to handle the non-linear characteristics of the power system. On this basis, a multi-objective reactive power optimization model is constructed to minimize the power generation cost, wind and solar power curtailment, and voltage offset. Finally, comparisons between two types of models in different scenarios are designed. Numerical simulations demonstrate that the participation of renewables in reactive power regulation can improve the operational economy and voltage stability of power systems.

A virtual synchronous generator control method for remote island power system considering dynamic voltage stability

Remote island power systems are difficult to install renewable energy sources (RES) because of the small system capacity and the large impact of intermittency of RES. Virtual synchronous generators (VSG) can equip inverters with the inertia of synchronous generators and can suppress frequency and voltage fluctuations. This paper proposes a VSG control method for dynamic voltage stability in remote island power systems. In conventional VSG control methods, the command of active and reactive power is determined by the Droop characteristics of frequency and transmission line voltage. However, the command are not based on dynamic voltage stability indices. Therefore, the compensation amount of active and reactive power is inappropriate. The proposed method determines the command of active and reactive power based on dynamic voltage stability indices. The dynamic voltage stability index considers the critical boundary index (CBI). The CBI is defined as the distance between the operating point of active and reactive power flowing through a transmission line and the stability limit curve calculated from the power flow between two bus lines. The proposed method improves dynamic voltage stability by determining power command so that the operating points of active and reactive power are closer to the origin direction. Simulation verification is performed for load increase and three-phase ground fault. In the three-phase ground-fault simulation, FRT requirements are considered to verify continued operation and the case of gate blocking. The conventional Droop control and the proposed method are compared for the case of continued operation with FRT requirements during load increase and ground fault. Simulation verification results show that the proposed method improves the dynamic voltage stability compared to the conventional method. Furthermore, it is shown that the proposed method is capable of stable continuous operation of the system even after a transmission line failure considering the FRT requirement.

Voltage stability assessment for solar photovoltaic penetration using Reactive Power–Voltage and Active Power–Voltage modal analysis

The assessment of voltage stability in a power system is crucial to ensure all buses in the network can maintain the desired voltage or avoid maximum loadability when subjected to load disturbance. Current research has tended to concentrate on developing new voltage stability assessment tools rather than identifying the best location for the penetration of solar photovoltaic (SP) generation in the network. This paper examines and evaluate the power systems voltage stability with increasing SP penetration levels by employing both the Active Power–Voltage (PV) and Reactive Power–Voltage (QV) modal analysis. The effect of load flow study by penetrating SP at the weakest and the strongest load bus has been investigated in this work. Furthermore, the analysis in this work was carried out in the modified Brunei Darussalam Department of Electrical Services (DES) power system. The main contribution of this paper is to assess and identify the best and worst locations for SP penetration in the simplified DES power system network in Brunei Darussalam using both the QV and PV modal analysis. The load flow results show that the penetration of SP generation is much better at the strongest bus due to it does not influence other load buses as compared to the least reliable bus in the network.

A Power System Reserve Configuration Solution That Satisfies the Frequency Stability Constraint Under the Given New Energy Index

Aiming at the problem of frequency stability and voltage stability of a new power system, this paper provides a new energy index method based on frequency stability constraints in the standby category of the new power system. Several concepts, such as maximum disturbance constraint and minimum reserve capacity, are proposed. Two constraints, power balance, and frequency constraint are set, and the factors to be considered, such as load frequency effect, security and control measure, demand-side response, and primary frequency change amplitude of each type of unit, are specified. Through analysis and study of regional data, the peak load of power grid new energy is a given index in a given scenario, according to the research of regional power grid in each category of a frequency modulation amplitude, the installed capacity is set to build a solution, to the problem of frequency stability caused by clean energy consumption, thus determine the ratio of each category of power output and heat capacity. Finally, according to the actual data of one regional power grid, the PSD-BPA power system simulation software is used to verify the effectiveness of the method.