Voltage Stability Improvement Research Articles

Continuation Power Flow Analysis of Power System Voltage Stability with Unified Power Flow Controller

The rising power demand has forced power systems all over the world to operate very close to their stability limits. When power systems are overloaded, faulty, or in lack of reactive power, voltage collapses would ensue. The capacity of a power system to keep the voltage of every bus constant under disturbances is called voltage stability. This dynamic phenomenon hinges on the load features. It is commonly known that flexible AC transmission systems (FACTS) can improve voltage stability. This paper puts forward a load flow model with the unified power flow controller (UPFC), and relies on the model to investigate the voltage stability of a power system through continuation power flow (CPF) method. The validity of the model was verified through a simulation, using the power system analysis toolbox (PSAT) in MATLAB/Simulink environment.

A Reactive Power Reserve Constrained Optimum Reactive Power Dispatch Using Coronavirus Herd Immunity Optimizer

The Optimal Reactive Power Dispatch (ORPD) is a very important study in planning the power system operation. The conventional ORPD formulations focus only on driving the objective functions toward optima and ignore the benefits to retain adequate Reactive Power Reserve (RPR) in the system. Studies show that inadequate RPR can jeopardize the power system voltage security under stressed conditions. In view of this, a Reserve Constrained ORPD (RC-ORPD) is proposed in this paper and solved using the recently developed, Coronavirus Herd Immunity Optimizer (CHIO). For this purpose, the minimum required Effective Reactive Reserve (ERR) is devised and introduced as a constraint in the ORPD problems. Here, the minimization of power loss and L-index are taken as objective functions, and the problem is formulated as a non-linear constrained optimization problem. The proposed problem is tested on standard IEEE 30 bus and IEEE 57 bus systems. To assess the impact of the proposed strategy, the same problems are also solved by relaxing the ERR constraint. Comparisons reveal that the added constraint improves voltage stability linked parameters and offers more RPR in the system without sacrificing much on the optimum solution. Further, the proficiency of CHIO is verified through various case studies and comparisons.

Voltage Stability Control Based on Angular Indexes from Stationary Analysis

This paper presents a novel methodology for the calculation of angular indexes of an electrical system from stationary analysis, using load flow and nose curves (P–V) in each of the buses of the system to perform control actions and preserve or improve voltage stability. The control actions are proposed considering a novel method based on the concepts of the cutset angle (CA) and center of angle (COA). The target is a fast estimation of voltage-stability margins through an appropriate angular characterization of the whole system and for each load bus with a complete network and N-1 contingency criteria. The most significant enhancement is that the angular characterization is based on the COA, which is related to the angular dynamics of the system, and indirectly reflects the inertia and the respective angles of the generator rotor, as well as the impact on the angular equivalent-system model. Simulations showed that the COA is an important index to determine the location of occurrence of the events. The COA can also help aim where control actions, like the amount of load shedding, should be carried out to remedy the voltage problems. The proposed method is assessed and tested in the benchmark IEEE 39-bus system.

Optimal Allocation of Distributed Generation, Capacitor Banks and D-STATCOM in Distribution Systems

This paper demonstrates the problem of simultaneous optimal allocation of distributed generations (DGs), shunt capacitor banks (CBs), and distribution FACTSs based D-STATCOMs in distribution network for the improvement of the entire system performance. Here, two objectives, total power loss minimization, and overall voltage stability index (VSI) maximization are considered. In general, minimization of power loss is the primary objective, and VSI is considered for improved voltage stability. VSI must be positive to obtain a stable operation and a higher VSI value represents better stability of the RDS. These objectives are solved subject to constraints related to power balance, DGs, CBs, D-STATCOM powers, bus voltages, and VSI. Here, single objective problem is solved using Particle swarm optimization (PSO), and the multi-objective problem is solved using multi-objective PSO (MO-PSO). Standard 33 bus RDS is considered for solving this problem. The results obtained show that proposed optimization has improved the voltage profile and overall VSI of the RDS and minimized the system power losses.

A Critical Analysis of Modeling Aspects of D-STATCOMs for Optimal Reactive Power Compensation in Power Distribution Networks

Distribution static compensators (D-STATCOMs) can enhance the technical performance of the power distribution network by providing rapid and continuous reactive power support to the connected bus. Accurate modeling and efficient utilization of D-STATCOMs can maximize their utility. In this regard, this article offers a novel current-injection-based D-STATCOM model under the power control mode of operation for the reactive power compensation of the power distribution network. The versatility of the proposed D-STATCOM model is demonstrated by combining it with two of the most established distribution load flow techniques, viz., the forward–backward sweep load flow and the BIBC–BCBV-matrix-based direct load flow. Further, the allocation of the proposed D-STATCOM model is carried out under a multiobjective mathematical formulation consisting of various technical and economic indices such as the active power loss reduction index, voltage variation minimization index, voltage stability improvement index and annual expenditure index. A novel parameter-free metaheuristic algorithm, namely a student-psychology-based optimization algorithm, is proposed to determine the optimal assignment of the different number of D-STATCOM units under the multiobjective framework. The proposed allocation scheme is implemented on a standard 33-bus test system and on a practical 51-bus rural distribution feeder. The obtained results demonstrate that the proposed D-STATCOM model can be efficiently integrated into the distribution load flow algorithms. The student-psychology-based optimization algorithm is found to be robust and efficient in solving the optimal allocation of D-STATCOMs as it yields minimum power loss compared to other established approaches for 33-bus PDNs. Further, the economic analysis carried out in this work can guide network operators in deciding on the number of D-STATCOMs to be augmented depending on the investment costs and the resulting savings.

Reactive Power Compensation for Preventing Voltage Instabilities in Distribution Lines Enriched with PV Power Plants

The efficient voltage regulation method by capacitive reactive power usage is represented in the article. The stochastic electricity generation of multiple PV stations placed in local distribution lines induces voltage instabilities. These voltage fluctuations may overcome the allowable limits and cause technical problems and economic losses. The method of applying reactive power generated by a capacitor bank at the load is proposed. Primarily, a strict analytical solution of nonlinear equations describing voltage deviations in the distribution line connected with photovoltaic systems was obtained. The control system can fast select optimal capacitors based on the analytical solution and then connect them smoothly to a load. The developed experimental setup verified and approved the correctness and accuracy of theoretical analysis. Experimental measurements confirmed the proposed method’s ability to improve voltage stability in distribution grids. The proposed method is supposed to be used together with the transformer tap-changers in electrical substations. The capacitive power is applied in a time of inappropriate voltage deviations only and is disconnected as the tapchanger corrected the transformation ratio.

Voltage Stability Assessments and Their Improvement Using Optimal Placed Static Synchronous Compensator (STATCOM)

In this paper, static voltage stability assessments and their improvement using analytical and optimization techniques with different loading scenarios are described. In this study, the 400 kV, 230 kV, and 132 kV Ethiopian electric power networks are modeled using Power System Analysis Toolbox (PSAT), and the load flow analysis is carried out using MATLAB source code. Then, different voltage stability indices, such as the user-defined advanced voltage stability index (AVSI), modified voltage stability index (MVSI), and fast voltage stability index (FVSI), are used to identify the voltage unstable buses. Besides this, particle swarm optimization (PSO) is also used to find the optimal size and placement of the Static Synchronous Compensator (STATCOM) for the most severe buses identified by voltage stability indices. The result presents three special arguments: whether the most severe buses that are ranked at the top based on the voltage stability indices are optimal buses for compensation placement or not, the voltage stability improvement, and power loss reduction with the introduction of STATCOM. Accordingly, it is observed that the weakest bus that is identified through the stability indices may not be the optimal placement of the compensation device. It is also indicated that, with the introduction of STATCOM to the optimal selected bus, the network power loss is reduced from 46.65 MW to 33.32 MW and its voltage magnitude in all buses is also improved. All bus voltages are within the IEEE standard acceptable limit.

Controller Coordination Strategy for DC Microgrid Using Distributed Predictive Control Improving Voltage Stability

The paper presents the design and control strategy of an isolated DC microgrid, which is based on classical control techniques, predictive control and iterative algorithms. The design control parameters are maximum overshoot, settling time and voltage ripple. The strategy is designed to operate in two different modes, end-users minimum and maximum demand scenarios, and this is achieved through the incorporation of network dynamic loads. The control methodology developed allows to obtain a fast response of the design set points, and an efficient control for disturbance rejection. The simulation results obtained satisfy the proposed design guidelines by obtaining a maximum overshoot of 4.8%, settling time of 0.012 seconds and a voltage ripple of 0.1 percentage. The implemented system simulation was developed in Matlab-Simulink software.

Voltage Stability Improvement by Optimized STATCOM Controller for Grid Connected Hybrid Network System

n a renewable energy system, the major task to maintain the voltage regulation of the system and other hands improvement of system stability. A proposed new STATCOM with advanced control technique are introduced in this paper. It is to mitigate the bus voltage variations caused by the large disturbances. A proposed STATCOM consists of voltage regulator and current regulator. Here, the current regulator is to produce the phase angle of voltage source converter, while the voltage regulator outputs the current reference on the quadrature axis of the devices. The voltage and current regulator parameters are treated as a membership function. This membership functions involving by dual fuzzy algorithm (Type-2 Fuzzy controller) which reduces the voltage regulation caused by large disturbances. The proposed controller obtains the faster and more stable responses so that the reactive power required by the proposed method is to stabilize the voltage. Keywords: STATCOM, Type II Fuzzy Set, Particle Swarm Optimization (PSO)

Hierarchical control scheme for proportional power sharing and robust operation in multiple virtual synchronization‐based DC/DC converters

Virtual synchronization control can be applied to DC/DC converter for enhanced inertia support by imitating the rotor dynamics of the synchronous generator (SG). However, efficient power sharing and robust operation ability cannot be guaranteed in a multiple parallel-operated DC/DC converters system. This paper proposes the hierarchical control scheme to achieve higher efficiency and superior anti-disturbance ability for multiple DC/DC converters with virtual synchronization-based control. The primary control layer enables proportional power sharing by using improved virtual synchronization control for each DC/DC converter, which aims at eliminating the influence of line parameter mismatch among converters. The secondary control layer deals with DC voltage stability improvement through the extended disturbance-observer-based backstepping control with the consideration of external power fluctuation on the whole system. Two control levels are integrated as the hierarchical control architecture to realize different control objectives in different time scales, while only neighbouring communications and DC voltage information are needed among the system. Simulations on PSCAD/EMTDC are conducted and show that the load power is accurately and proportionally shared, while system oscillations are eliminated with the extended disturbance-observer-based backstepping control, which validates the advantages of the proposed hierarchical control scheme.

Voltage Stability Improvement In Multi-bus System Using Static Synchronous Series Compensator

Abstract: Network stability has become a major worry as the power system has become increasingly complicated as a result of open access electricity market activities and increased demand. Voltage unbalance and collapse have become a global issue for a variety of reasons. FACTS devices are used to manage system stability issues. Use of a static synchronous series compensator (SSSC) to enhance the voltage stability of a power system is investigated in this paper. IEEE 9 bus networks are modelled using MATLAB Simulink software to investigate voltage management and reactive power compensation. For a multibus system, the effectiveness of SSSC on voltage stability is examined. Using a static synchronous series compensator enhances voltage stability. Keywords: SSSC, Faults, voltage improvement

ENHANCEMENT OF VOLTAGE STABILITY IN THE POWER SYSTEM USING GENETIC ALGORITHM

The power system should ensure safe and consistent power to the customer. For secure operation, the voltage should be within the desired limits, or else it will result in voltage collapse and power losses. The power system will be more competent, economic, reliable, and reduce power losses if the voltage stability is enhanced. Since the voltage stability is determined by the reactive power of the network, a reactive power source should be provided to safeguard the stability of the power system. This paper presents the enhancement of voltage stability in the power system using a Genetic Algorithm (GA). The GA approach is used to find the optimal value of control variables such as generator bus voltage, shunt capacitance, and transformer tap setting which are the source of reactive power. The GA was executed via MATLAB programming with MATPOWER. The propounded method was tested on the western grid of Bhutan to minimize the real power losses. The results demonstrate improved voltage stability in the power system and a significant reduction in power losses. The results will help Power System Operators to make a better decision while encountering voltage issues in their power lines. Moreover, this research will guide future research in dealing with similar research especially in calculating the optimal location of FACT devices for reactive power compensation.

Optimization of Voltage Security with Placement of FACTS Device Using Modified Newton–Raphson Approach: A Case Study of Nigerian Transmission Network

Power flow reliability, voltage security and transmission congestion management are paramount operational issues in a power system. Flexible AC transmission system (FACTS) controllers are suitable technologies that can provide compensation and dynamic control of power system transmission parameters to enhance effective performance and reliability. The interline power flow controller (IPFC), if optimally placed, can regulate the impedance of multiple lines to improve active power transfer capacity and voltage profile. This study examines the performance of IPFCs for voltage enhancement by suppressing fluctuation. A modified Newton–Raphson load flow problem with an incorporated IPFC variable has been formulated with the objective to improve voltage stability and maintain active power flow. The effectiveness of the proposed method was tested on the Nigerian 41 bus transmission network. The obtained result of the system with an IPFC placed at the weakest bus of the network was compared with Newton–Raphson load flow analysis of the same network without an IPFC. The results of load flow analysis for Case 1 (the system without an IPFC) showed that the transmission network without an IPFC had a real power loss of 4.699488 p.u., and reactive power loss of 4.467413 p.u., whereas the integration of an IPFC to the power flow formation in Case 2 resulted in the reduction in the transmission network’s overall losses to 0.55297 p.u. and −38.3329 p.u. The modified method proves effective as the power system network with an IPFC returns a more stable voltage profile and improves active power flow. In addition, this method, similar to all other mathematical optimization approaches, returns a strong accurate result but may be a drawback in terms of longer computational time compared with metaheuristic methods which are preferred for a larger network system.

Optimal sizing and placement of shunt capacitors on the distribution system using Whale Optimization Algorithm

This paper aims at power loss minimization and reduction of cost due to losses in the distribution network as well as improvement of the network voltage stability and profile via optimal shunt capacitor allocation. The optimal shunt capacitor allocation was obtained using Whale Optimization Algorithm considering technical (real power loss and VSI) and economic objective functions as sub-optimal allocation may result in undesired effects on the network. The obtained optimal sizes of the shunt capacitors were placed on the obtained location of the distribution networks to ascertain the behavior of the networks before and after their placements taking power loss, cost due to losses, and voltage stability index as the performance metrics. A comparison of these performance metrics under four cases, namely base case (case one), installation of one SC (case two), installation of two SCs (case three), and installation of three SCs (case four) were demonstrated using standard IEEE 33-bus and Dada 46-bus distribution networks. The results gave a percentage loss reduction of 33.74% with 27.60% annual net saving for the IEEE 33-bus network and 22.24% loss reduction with 25.60% annual net saving for the Dada 46-bus network. Hence, reduction in the total power losses and costs. Also, the voltage profile and voltage stability index were significantly improved.

Latest Advances in the Implementation and Characterization of High-K Gate Dielectrics in SiC Power MOSFETs

Recently high-k gate dielectrics for SiC power MOSFETs attracted increasing research interest thanks to promising results related to improved specific channel resistances and threshold voltage stability. We investigated high-k gate stacks for 1.2kV and 3.3kV SiC power MOSFETs regarding on-state performance and stability during high temperature gate bias tests. Furthermore, we studied the high-k/SiC interface quality and the effect of burn-in pulses using SiC MOSCAPs. High-k SiC power MOSFETs show significant improvement in on-state performance and threshold voltage stability. We found that the burn-in pulses can be shorter for high-k gate dielectrics compared to SiO2-based devices.

Performance enrichment in optimal location and sizing of wind and solar PV centered distributed generation by communal spider optimization algorithm

PurposeThe distributed generation (DG) proper placement is an extremely rebellious concern for attaining their extreme potential profits. This paper aims to propose the application of the communal spider optimization algorithm (CSOA) to the performance model of the wind turbine unit (WTU) and photovoltaic (PV) array locating method. It also involves the power loss reduction and voltage stability improvement of the ring main distribution system (DS).Design/methodology/approachThis paper replicates the efficiency of WTU and PV array enactment models in the placement of DG. The effectiveness of the voltage stability factor considered in computing the voltage stability levels of buses in the DS is studied.FindingsThe voltage stability levels are augmented, and total losses are diminished for the taken bus system. The accomplished outcomes exposed the number of PV arrays accompanied by the optimal bus location for various penetration situations.Practical implicationsThe optimal placement and sizing of wind- and solar-based DGs are tested on the 15- and 69-test bus system.Originality/valueMoreover, the projected CSOA algorithm outperforms the PSOA, IAPSOA, BBO, ACO and BSO optimization techniques.

Optimal Location and Sizing of Reactive Power Compensation Devices for Voltage Stability Improvement of Radial Power Systems

With the advancement in technology, the electricity demand is increasing day by day. Power supply utilities are facing the problem to expand their network owing to the problems like availability of land in urban areas and Right of Way (ROW). Due to these problems, many of the existing lines are operating nearer to their thermal stability limit. Maintaining the voltage within the limits will be a challenging task for the utilities. Increased loading of the lines is making the power system to the verge of voltage stability. Many indices are proposed in the literature for predicting the voltage stability of the system. In this paper, L-Index is used for voltage stability analysis of the radial distribution system. L-Index sensitivity method is used to the locate and size the reactive power compensation devices. The effectiveness of L-Index sensitivity method on the larger power system like IEEE-33 bus system is presented in this paper and simulation studies are performed using MATLAB/SIMULINK.

Improvement of voltage stability for grid connected solar photovoltaic systems using static synchronous compensator with recurrent neural network

Purpose. This article proposes a new control strategy for static synchronous compensator in utility grid system. The proposed photovoltaic fed static synchronous compensator is utilized along with recurrent neural network based reference voltage generation is presented in grid system network. The novelty of the proposed work consists in presenting a Landsman converter enhanced photovoltaic fed static synchronous compensator with recurrent neural network algorithm, to generate voltage and maintain the voltage-gain ratio. Methods. The proposed algorithm which provides sophisticated and cost-effective solution for utilization of adaptive neuro-fuzzy inference system as maximum power point tracking assures controlled output and supports the extraction of complete power from the photovoltaic panel. Grid is interconnected with solar power, voltage phase angle mismatch, harmonic and voltage instability may occur in the distribution grid. The proposed control technique strategy is validated using MATLAB/Simulink software and hardware model to analysis the working performances. Results. The results obtained show that the power quality issue, the proposed system to overcome through elimination of harmonics, reference current generation is necessary, which is accomplished by recurrent neural network. By recurrent neural network, the reference signal is generated more accurately and accordingly the pulses are generated for controlling the inverter. Originality. Compensation of power quality issues, grid stability and harmonic reduction in distribution network by using photovoltaic fed static synchronous compensator is utilized along with recurrent neural network controller. Practical value. The work concerns the comparative study and the application of static synchronous compensator with recurrent neural network controller to achieve a good performance control system of the distribution network system. This article presents a comparative study between the conventional static synchronous compensator, static synchronous compensator with recurrent neural network and hardware implementation with different load. The strategy based on the use of a static synchronous compensator with recurrent neural network algorithm for the control of the continuous voltage stability and harmonic for the distribution network-linear as well as non-linear loads in efficient manner. The study is validated by the simulation results based on MATLAB/Simulink software and hardware model.

SMA-based optimal energy management study in a connected PV/MT/ DG/V2G/BESS/WT on IEEE-33 bus considering network losses and voltage deviations

The unpredictable nature of renewable energy resources (RERs) makes obtaining optimum operation and grid integration in today’s smart power distribution networks challenging. Thus, to mitigate the fluctuations in RERs, the penetration of diesel generators, batteries, and electric vehicles (EV) must be considered for an effective energy management study (EMS) in the IEEE-33 bus system. This paper addresses the energy management of a microgrid linked to the main power system under deterministic and probabilistic circumstances. Apart from economic considerations, modern distribution networks must maintain an acceptable range of system reliability indexes. Failure of reliability in the distribution network may result in irreversible harm to the distribution network. For multi-objective functions such as cost reduction, voltage profile improvement, and voltage stability improvement are the main objectives of this article. An efficient method known as a novel slime mould algorithm (SMA) is used to solve these issues and validate the performance with the existing evolutionary algorithms. However, the SMA can optimally address the grid-connected various types of RERs installed, which can significantly compensate network losses, voltage deviations and improve the system performance. Finally, the algorithm’s effectiveness on the EMS approach is verified under different algorithms through 2021a MATLAB/Simulink and the proposed methods prove the best results with the convergence of other algorithms also.

Single and Multiple Placements of Different DG Types On the Power Distribution System

Integration of distributed generation on power distribution system impacts the network for improved voltage stability and power quality. However, inaccurate sizing and placement of the energy sources can worsen the network performance. This paper proposes a hybrid particle swarm optimization/whale optimization algorithm for the optimal placement of different distribution generation types on a power network. Standalone metaheuristics are efficient and robust optimization tools but are mostly challenged with convergence and sub-optimal solutions. The exploration potential of particle swarm optimization with the selection of higher inertial weight is annexed with the exploitation phase of the whale optimization algorithm. The proposed technique is verified on IEEE 33 – bus distribution system. Results show 86.12% and 89.84% improvement in voltage deviation for Type I and Type III DG injection respectively. Besides, the convergence is achieved in less than 50 iterations compared to standalone methods.