Weak Buses Research Articles

Investigation of Power Networks and their Patterns by Mathematical methods in order to Voltage Stability Enhancement

Authors in the research paper has considered IEEE 14-bus and 34-bus test network for creation generation and load patterns. This paper aims at analysing the potential impacts that distributed generation (DG) might have on voltage stability of electrical power networks. It is expected that increasing amounts of new generation technologies will be connected to electrical power systems in the near future. Most of these technologies are considerably smaller scale than conventional synchronous generators. In this paper, the impact of DG pattern (size and location of DG) on the voltage stability of two test system is investigated. The simulation methodology is discussed as well. It is found that the effects of DG the voltage stability of a power system strongly depend on the size and location of the distributed generators. The results show that install of DG on the weak bus, improve loadability limit and voltage stability and decrease loss of system. By investigating and reviewing the results of similar patterns in these two systems, the different generation and load patterns impact mechanism of DG units over the behaviour of the systems in terms loadability limit and voltage stability is achieved.

Fractional-Order PID Controlled Unified Power Quality Conditioner System with Enhanced Response

Recently, ‘UPQC’ has been urbanized as a FACTS controller near weak buses and buses with non linear loads. ‘UPQC’ can improve receiving end voltage and provide time harmonics to the load. The UPFC and ‘UPQC’ systems are compared to find a better FACTS controller. The recommended closed loop ‘UPQC’ framework is to augment dynamic response of ‘UPQC’ system using FOPID controller. Simulink replicas are extended for PI &FOPID controlled ‘UPQC’ frameworks. The denouements of PI&FOPID based ‘UPQC’ frameworks designate that voltage retaliation of FOPID is predominant to the denouement of PI managed ‘UPQC’ system. The investigation denotes that FOPID ’UPQC’ framework has diminished settling time& steady state error.

ANN Based SVC FACTS Controller to Enhance Voltage Stability of Multi-Machine Power System

Voltage stability is the most vital phenomena in power systems which may be disturbed by the mismatch between the reactive power supply and demand. The occurrence of internal faults in the equipment and short circuit faults also there may be voltage collapse at the buses. Voltage stability can be improved using Static VAR Compensator (SVC) which is a shunt device. It can generate or absorb reactive power in a controlled manner such that it can enhance voltage stability of the system. L- Index method is used to determine voltage sensitivity at each bus and the bus having highest L- index value can be considered as a weak bus which is the optimal location of FACTS controller. The investigation is made to observe how susceptance in susceptance model and firing angle in firing angle model of the SVC is predicted to enhance the voltage at each bus by the artificial neural network under chaotic load. Standard IEEE 5 bus and 30 bus systems are considered as test systems and simulations are performed in MATLAB software.

Voltage Sag Compensation Using Dynamic Voltage Restorer

Power quality plays a very important vital role in the modern utility grid where sensitive loads are employed. Equipment damage, temporary shutdowns, product quality degradation and Voltage Sag are the major problem associated with power quality. Dynamic Voltage Restorer (DVR) is a powerful device which is used to improve voltage mitigation of weak buses associated in a multi-bus system. This paper incorporates the functional performance of DVR during voltage sag in the power system. Penetrating a voltage of required magnitude and frequency to restore the voltage across the load within the desired amplitude is the main objective of DVR. The proposed work based on modeling and simulation of DVR, in a closed-loop control of an eight bus system. Voltage compensation is done effectively using DVR in the Closed loop FLC controlled system and its analyzed with PID Controlled system. The simulation result shows Closed loop FLC system using DVR is observed to be faster than PID controlled systems.

Development of A Newton Raphson Symmetrical Component Based Technique for Fault Analysis on Nigerian 330 KV Transmission Lines

Fault analysis is one of the basic problems of power system engineering. It plays a significant role in the power system security for supply of stable and economical operations of power systems. This study carried out fault analysis on Nigerian 330 kV, 28 bus system using Newton-Raphson analysis and symmetrical components method to determine the voltage magnitude and fault magnitude in the system. Newton-Raphson method was used to calculate the short circuit pre-fault voltages and currents on power system. This was used to check the weak buses that are out of acceptable voltage limit of ± 10%. After identifying the buses with problems, a three-phase fault on the power network was then calculated using symmetrical component analysis and was simulated using MATLAB to determine the post-fault voltage magnitudes, angles and fault magnitudes of the power network. The pre-fault result showed that buses 13 (New-Haven), 14 (Onitsha) 19 (Jos), 22 (Kano) and 25 (Markurdi) were the buses that fell out of tolerance range of ± 10% and were termed as weak buses. These buses with low voltage values were examined and post-fault calculations were carried out and the results of voltage magnitude and voltage angle were reduced to zeros.The results of pre-fault current magnitude showed that the selected weak buses namely; Makurdi, New-Haven, Kano, Onitsha and Jos have the current magnitude values of 10.4200 p.u, 9.4350 p.u, 8.4501 p.u, 7.5440 p.u and 5.3320 p.u respectively. The results also showed that Makurdi, had the highest fault magnitudes with a value of 25.1006 p.u followed by New-Haven with value of 23.9455, Kano with value of 22.4917, Jos with value of 21.4686 and Onitsha had the least fault magnitude value of 19.8765 p.u under post-fault condition. More so, it was observed that the voltage on the affected buses was reduced however current magnitudes of these buses when fault occurred were excessively high compared to the pre-fault currents.The result confirmed that symmetrical three phase fault is the most severe kind at the transmission lines. The result also revealed the abnormally high magnitude of current that flows through the Nigerian power network to the point of fault. Therefore, the Nigeria power regulator and policies are required to determine the flow of current regularly during faults occurrences in the power system so as to ensuring improvements in the country power sector. The study therefore recommendations that additional lines should be introduced into the network to assist in the strengthening and reduction of long lines to improve the voltage profile of the network, especially New-Haven, Kano, Onitsha and Markurdi lines. The study will assist the power regulators for selection of circuit breakers and rating of protective switchgears installed in power system to enhance the efficiency of the power supply in Nigeria. Keywords: Fault Analysis, Nigerian Power Network, Newton-Raphson, Symmetrical Components, Three-Phase Fault, Voltage Magnitude, Fault Magnitude. DOI : 10.7176/JNSR/9-16-02 Publication date : August 31 st 2019

Menangani Isu Turun Naik Voltan di dalam Sistem Pembahagian Tersambung Penjana Teragih menggunakan Kaedah Faktor Kuasa Tidak Berpusat

Power quality issues has evidently become one of the crucial issues in power system studies. With the integration of distributed generations (DGs) in the power system, the issue of voltage control has become very important as the power system has become dynamic due to the bidirectional power flow. Delivering power while maintaining acceptable voltage limits has become very challenging for the distribution network operators (DNOs). In order to maintain power delivery to the customers whilst maintaining good power quality, the DNOs has undertaken several measures including implementing several voltage control methods to guarantee that the voltage limits in the power system are within permissible limits. This includes the centralized and decentralized voltage control techniques in the system connected with DGs. The DGs are connected to buses 9 and 14 of the test system where these two buses have been identified as the weakest bus. The decentralized voltage control method has also become an acceptable option due to its ease in having limited communication and lower costs in the system. One of the decentralized voltage control method which has been widely used is the power factor control (PFC) method. The IEEE 14 bus distribution test system has been used and integrated with DGs to show the effectiveness of the PFC method in managing the voltage fluctuation issues in the distribution system.

An SVC based Power Quality Improvement Model for Consumers Connected to Weak Busses in Distribution Systems

Power quality is a major concern considering weak bus systems. In order to improve power quality, residential consumers go with voltage stabilizers as a cheap solution consequently overstressing weak busses. Industrial consumers use other alternatives like switched capacitor banks to cope with low power factor but the limitation is step-wise reactive power injection which does not meet the changing load requirements. Real time improvement requires constant monitoring and real-time injection of Volt-Ampere-Reactive (VAR) which is possible with the help of a Static VAR Compensator (SVC). An SVC based Power Quality Improvement (PQI) is proposed in this paper which addresses the real time varying reactive VAR requirement with reduced harmonic content.

A Comprehensive Evaluation Approach for Static Voltage Stability Analysis in Electric Power Grids

Large-scale voltage collapse incidences, which result in power outages over large regions and extensive economic losses, are presently common occurrences worldwide. Therefore, the voltage stability analysis of power systems has become a topic of increasing interest. This article presents a comprehensive method for conducting static voltage stability analysis in electric power systems. To overcome the limitations associated with single-index systems in the evaluation of static voltage stability, the analysis approach employs a multi-index system with three primary criteria based on separate analysis methods with six sub-criteria based on individual indices. In addition, we propose a comprehensive method for establishing index weights, which combines the subjective analytic hierarchy process weighting method and the objective entropy weighting method. An innovative index-weight optimization method based on the Lagrange Conditioned Extreme Value (LCEV) is also presented and sensitive analysis is applied to test the robust of the proposed method. Finally, Fuzzy Order Preference by Similarity to Ideal Solution (Fuzzy-TOPSIS) method is employed to rank the voltage buses of a power system as the final results, considering system functionality and proportionality. The results obtained for the wind farms of an actual power grid in Hami City, China demonstrate that the proposed method represents an innovative approach for determining the weakest bus in static voltage stability analysis of power systems.

ON-LINE VOLTAGE STABILITY EVALUATION USING NEURO-FUZZY INFERENCE SYSTEM AND MOTH-FLAME OPTIMIZATION ALGORITHM

Purpose. In recent years, the problem of voltage instability has received special attention from many utilities and researchers. The present paper deals with the on-line evaluation of voltage stability in power system using Adaptive Neuro-Fuzzy Inference System (ANFIS). The developed ANFIS model takes the voltage magnitudes and their phases obtained from the weak buses in the system as input variables. The weak buses identification is formulated as an optimization problem considering the operating cost, the real power losses and the voltage stability index. The recently developed Moth-Flame Optimization (MFO) algorithm was adapted to solve this optimization problem. The validation of the proposed on-line voltage stability assessment approach was carried out on IEEE 30-bus and IEEE 118-bus test systems. The obtained results show that the proposed approach can achieve a higher accuracy compared to the Multi-Layer Perceptron (MLP) and Radial Basis Function (RBF) neural networks.

Identification of the Weakest Buses to Facilitate the Search for Optimal Placement of Var Sources Using “Kessel and Glavitch” Index

In this paper, the main objective is to identify the weakest buses in the power system in order to facilitate the search process of optimal placement of reactive power sources using “Kessel and Glavitch” voltage stability index ( $$L_{KG}$$ ). To reach our goal, particle swarm optimization algorithm (PSO) is used and has been applied to the standard IEEE 30-bus for different objectives. The obtained results have been compared to the existing papers reported in the literature. The originality of this work is the use of “Kessel and Glavitch” voltage stability index to provide to the electric power systems research field more accurate and high quality results in the optimal location search of Var supports (such as FACTS devices…etc.) in the power systems.

Voltage instability analysis based on modal analysis technique and artificial neural network

<span>One of the paramount importance in the operation of electrical power system operation order to sustain the equilibrium of the system is the stability of the load buses’ voltages. If the load buses voltages are not stable, this can cause serious problem especially power system blackout. This paper presents the analysis of voltage instability in electric power system by using modal analysis technique. However, one of the challenges of modal analysis is the intencive and complex calculation procedures. In order to overcome that, this paper implements Artificial Neural Network (ANN) to improve the implementation of modal analysis technique. ANN is used to determine the participation factors obtained from the modal analysis technique. The results show that modal analysis technique is able to show which bus is close towards experiencing voltage instability. In addition, the results also show that ANN is able to predict the values of participation factors. A load bus is considered a weak bus if the bus has high tendency towards experiencing voltage instability. IEEE-14 bus test power system has been chosen as the test power system.</span>

Voltage Stability Analysis of Photovoltaic Plant with STATCOM Connected to Weak Buses of Distribution Network

Voltage Stability Analysis of Photovoltaic Plant with STATCOM Connected to Weak Buses of Distribution Network

A modified harmony search algorithm applied to capacitor placement of radial distribution networks considering voltage stability index

In power system, capacitor placement of distribution networks is a complex combinatorial optimisation problem. In this paper, in order to effectively solve optimal capacitor placement (OCP), an aggregate harmony search (AHS) optimiser, a stochastic population-based metaheuristic algorithm, is proposed which introduces a new pitch adjustment mechanism for harmony search (HS). The objective function contains three goals: 1) minimisation of the power losses; 2) minimisation of the capacitor installation cost; 3) improvement of the voltage stability index at the weakest bus. On two case studies, 23 kV nine-section feeder and 33-bus radial system, simulation results show that the proposed AHS not only finds more accurate results than the other investigated HS variants and particle swarm optimisation (PSO) techniques but also has the best robustness. Promising performance of AHS makes this technique as an efficient alternative to solve capacitor placement problem.

A modified harmony search algorithm applied to capacitor placement of radial distribution networks considering voltage stability index

In power system, capacitor placement of distribution networks is a complex combinatorial optimisation problem. In this paper, in order to effectively solve optimal capacitor placement (OCP), an aggregate harmony search (AHS) optimiser, a stochastic population-based metaheuristic algorithm, is proposed which introduces a new pitch adjustment mechanism for harmony search (HS). The objective function contains three goals: 1) minimisation of the power losses; 2) minimisation of the capacitor installation cost; 3) improvement of the voltage stability index at the weakest bus. On two case studies, 23 kV nine-section feeder and 33-bus radial system, simulation results show that the proposed AHS not only finds more accurate results than the other investigated HS variants and particle swarm optimisation (PSO) techniques but also has the best robustness. Promising performance of AHS makes this technique as an efficient alternative to solve capacitor placement problem.

Optimal placement of DSTATCOM, DG and their performance analysis in deregulated power system

Recently, incorporation of distributed generation (DG) and distributed static compensator (DSTATCOM) is increased in radial distribution system (RDS) due to the enormous electrical energy demand, power system deregulation, and different restriction over existing network expansion. However, the proper allocation of these devices is essential to ensure maximum potential benefit from the device. In this article, the optimal placement of DG and DSTATCOM is determined on IEEE 33-bus and 69-bus RDS with an aim to enhance voltage profile, reduce line losses, and maximise financial benefit. To reduce the search space and computational burden, the performance assessments of these devices are carried out only at weak bus locations that are identified using voltage stability index (VSI). To quantify the financial benefit after a certain period of time, authors developed a logical formula namely economic benefit (EB). In addition, an innovative formula namely relative pollution index (RPI) is developed to assess the environmental impact of these devices. First time, on the basis of the technical, economical, and environmental aspects, performance comparison between DG and DSTATCOM is thoroughly analysed in this study, which will facilitate the planning engineers to identify the most beneficial device for the RDS.

Optimal placement of DSTATCOM, DG and their performance analysis in deregulated power system

Recently, incorporation of distributed generation (DG) and distributed static compensator (DSTATCOM) is increased in radial distribution system (RDS) due to the enormous electrical energy demand, power system deregulation, and different restriction over existing network expansion. However, the proper allocation of these devices is essential to ensure maximum potential benefit from the device. In this article, the optimal placement of DG and DSTATCOM is determined on IEEE 33-bus and 69-bus RDS with an aim to enhance voltage profile, reduce line losses, and maximise financial benefit. To reduce the search space and computational burden, the performance assessments of these devices are carried out only at weak bus locations that are identified using voltage stability index (VSI). To quantify the financial benefit after a certain period of time, authors developed a logical formula namely economic benefit (EB). In addition, an innovative formula namely relative pollution index (RPI) is developed to assess the environmental impact of these devices. First time, on the basis of the technical, economical, and environmental aspects, performance comparison between DG and DSTATCOM is thoroughly analysed in this study, which will facilitate the planning engineers to identify the most beneficial device for the RDS.

Reactive Power Tracing Index LQP_LT for Voltage Unstable Load Bus Identification in Power Systems

Existing power systems are significantly susceptible to voltage instability problem since such systems are stressed with the huge power transfers across the grids. To guarantee power system stability during stressed conditions, it is important to first identify the voltage unstable load buses to determine appropriate locations for under voltage load shedding. In this study, a new method is proposed for determining weak load bus locations by using reactive power tracing to develop a novel reactive power tracing capable index, named as LQP_LT. The reactive power tracing algorithm is integrated with the LQP_LT index formulation to generate priority ranking list of weak load buses. The LQP_LT index was tested on the 57 bus system and the resulting priority ranking list is found to have successfully determined the weak load buses for load shedding in the test system. Comparison with other stability indices revealed that the LQP_LT has better sensitivity and response towards determining the location of the weakest load bus for under voltage load shedding implementation.

Fast Load Voltage Stability Index constrained PMU Placement for Complete Observability

This paper proposes a Fast Load Voltage Stability Index (FLVSI) constrained Binary Integer Programming (BIP) method for Phasor Measurement Unit placement at optimal locations in network to obtain complete observability. Every load bus of network is considered to sort out weak load bus from proposed FLVSI approach. PMUs are constrained to place at weak load buses using BIP approach for observability of network. Zero Injection (ZI) modeling is suggested to reduce PMU placement locations in network. Single line outage or PMU loss constraints are formulated for placement of PMUs. Bus Redundancy Index (BRI) is formulated and considered for every bus of network. With and without ZI modeling under normal and line outage cases is compared to present effectiveness of approach. IEEE –14- 30-and 57- bus networks are tested with MATLAB Programming and compared with other methods to show its effectiveness.

Comparison of Weak Load Bus Detection using LQP_LT Index with PV and QV Analysis of PSS/E

Identification of weak load buses which contributes to voltage instability problem is crucial in order for an appropriate mitigation action to be executed. The current power system transmission is not only stressed to deliver high load demand at the receiving end but also facing new challenges brought by the penetratrion of renewable energy sources. This new scenario requires power system operation and analysis to be robust and fast in detecting the accurate weak load bus for correction action. Due to this, many online indices to detect weak load bus during power system contingency have been developed. Nevertheless, LQP_LT is of the latest index developed which ultimately has the reactive power tracing capability for weak load bus detection and generate priority ranking list of the weak load buses. This index was tested on IEEE 14 bus test system for different contingency scenarios. The results obtained from the LQP_LT index is compared and validated with the PV and QV analyses obtained using industrial graded PSS/E software. It was concluded that the LQP_LT index is found to be robust, efficient and need less computation time as compared to the execution of voltage stability analysis using the PSS/E Tool.

Load Flow Based Voltage Stability Indices for Voltage Stability and Contingency Analysis for Optimal Location of STATCOM in Distribution Network with Integrated Distributed Generation Unit

Electrical power system is growing rapidly with the current increasing demand. One of many important issues being faced in power system is the voltage instability. With that being said, this work investigates the voltage stability indices with contingency analysis used in order to determine the voltage stability of the network system. These approaches are used to detect and avoid voltage instability in the distribution network. The behavior of the distribution network is determined based on the contingency analysis. STATCOM is injected into selected buses in the distribution network of the system to determine the system’s stability during the contingency condition. Distributed generation (DG) is utilized to enhance the network stability. Different scenarios have been assumed in order to test the proposed technique under different conditions. The work has been implemented in Digsilent power factory environment. The proposed technique has been tested on IEEE 30 bus system. Promising results have been obtained with respect to previous published literature, in term of identifying the weak buses and enhancing the overall stability of the network.