Showing 6 results for Voltage Stability
M. Gitizadeh, M. Kalantar,
Volume 4, Issue 4 (12-2008)
Abstract
This paper presents a novel optimization based methodology to allocate Flexible
AC Transmission Systems (FACTS) devices in an attempt to improve the previously
mentioned researches in this field. Static voltage stability enhancement, voltage profile
improvement, line congestion alleviation, and FACTS devices investment cost reduction,
have been considered, simultaneously, as objective functions. Therefore, multi-objective
optimization without simplification has been used in this paper to find a logical solution to
the allocation problem. The optimizations are carried out on the basis of location, size and
type of FACTS devices. Thyristor Controlled Series Compensator (TCSC) and Static Var
Compensator (SVC) are utilized to achieve the determined objectives. The problem is
formulated according to Sequential Quadratic Programming (SQP) problem in the first
stage. This formulation is used to accurately evaluate static security margin with congestion
alleviation constraint incorporating voltage dependence of loads in the presence of FACTS
devices and estimated annual load profile. The best trade-off between conflicting objectives
has been obtained through Genetic Algorithm (GA) based fuzzy multi-objective
optimization approach, in the next stage. The IEEE 14-bus test system is selected to
validate the allocated devices for all load-voltage characteristics determined by the
proposed approach.
M. Sharma, K. P. Vittal,
Volume 6, Issue 4 (12-2010)
Abstract
The recent trends in electrical power distribution system operation and management are aimed at improving system conditions in order to render good service to the customer. The reforms in distribution sector have given major scope for employment of distributed generation (DG) resources which will boost the system performance. This paper proposes a heuristic technique for allocation of distribution generation source in a distribution system. The allocation is determined based on overall improvement in network performance parameters like reduction in system losses, improvement in voltage stability, improvement in voltage profile. The proposed Network Performance Enhancement Index (NPEI) along with the heuristic rules facilitate determination of feasible location and corresponding capacity of DG source. The developed approach is tested with different test systems to ascertain its effectiveness.
M. Aghamohammadi, S. S. Hashemi, M. S. Ghazizadeh,
Volume 7, Issue 1 (3-2011)
Abstract
This paper presents a new approach for estimating and improving voltage stability margin from phase and magnitude profile of bus voltages using sensitivity analysis of Voltage Stability Assessment Neural Network (VSANN). Bus voltage profile contains useful information about system stability margin including the effect of load-generation, line outage and reactive power compensation so, it is adopted as input pattern for VSANN. In fact, VSANN establishes a functionality for VSM with respect to voltage profile. Sensitivity analysis of VSM with respect to voltage profile and reactive power compensation extracted from information stored in the weighting factor of VSANN, is the most dominant feature of the proposed approach. Sensitivity of VSM helps one to select most effective buses for reactive power compensation aimed enhancing VSM. The proposed approach has been applied on IEEE 39-bus test system which demonstrated applicability of the proposed approach.
M. Heydaripour, A. Akbari Foroud,
Volume 8, Issue 4 (12-2012)
Abstract
Congestion in the transmission lines is one of the technical problems that appear particularly in the deregulated environment. The voltage stability issue gets more important because of heavy loading in this environment. The main factor causing instability is the inability of the power system to meet the demand for reactive power. This paper presents a new approach for alleviation congestion relieving cost by feeding required reactive power of system in addition to re-dispatching active power of generators and load shedding. Furthermore with considering different static load models in congestion management problem with both thermal and voltage instability criteria, tries to the evaluated congestion management cost become more real, accurate and acceptable. The voltage stability is a dynamic phenomenon but often static tools are used for investigating the stability conditions, so this work offers new method that considers two snapshots after contingency to consider voltage stability phenomena more accurate. This algorithm uses different preventive and corrective actions to improve unsuitable voltage stability margin after contingency. The proposed method is tested on IEEE 24-bus Reliability test system, the simulation results shows the effectiveness of the method.
Z. Rafiee, M. Rafiee, M. R. Aghamohammadi,
Volume 16, Issue 3 (9-2020)
Abstract
Improving transient voltage stability is one of the most important issues that must be provided by doubly fed induction generator (DFIG)-based wind farms (WFs) according to the grid code requirement. This paper proposes adjusted DC-link chopper based passive voltage compensator and modified transient voltage controller (MTVC) based active voltage compensator for improving transient voltage stability. MTVC is a controller-based approach, in which by following a voltage dip (VD) condition, the voltage stability for the WF can be improved. In this approach, a voltage dip index (VDI) is proposed to activate/deactivate the control strategy, in which, two threshold values are used. In the active mode, the active and reactive power are changed to decrease the rotor current and boost the PCC voltage, respectively. Based on the control strategy, in a faulty grid, DFIG not only will be able to smooth DC-link voltage fluctuations and reduces rotor overcurrents but also it will increase the voltage of point of common coupling (PCC). Therefore, it improves transient voltage stability. The simulation results show the effectiveness of the proposed strategy for improving voltage stability in the DFIG.
A. H. Poursaeed, F. Namdari,
Volume 16, Issue 3 (9-2020)
Abstract
In this paper, a novel method is proposed to monitor the power system voltage stability using Support Vector Machine (SVM) by implementing real-time data received from the Wide Area Measurement System (WAMS). In this study, the effects of the protection schemes on the voltage magnitude of the buses are considered while they have not been investigated in previous researches. Considering overcurrent protection for transmission lines not only resolves some drawbacks of the previous studies but also brings the case study system closer to the realities of actual systems. Online monitoring of system stability is performed by prediction of the Voltage Stability Index (VSI) and carried out by using Support Vector Regression (SVR). Due to the direct effect of appropriate SVR parameters on the prediction quality, the optimum value is chosen for learning machine hyperparameters using Differential Evolution (DE) algorithm. The obtained simulation results demonstrate high accuracy, effectiveness, and optimal performance of the proposed technique in comparison with Back-Propagation Neural Network (BPNN) and Adaptive Neuro-Fuzzy Inference System (ANFIS) approaches. The presented method is carried out on the 39 bus New England system.
