Search

Maintaining stability in modern power systems is challenging due to complex structures, rising power demand, and load disturbances. The integration of renewable energy sources further threatens stability by causing imbalances between generation and demand. Conventional load frequency stabilization methods fall short in such scenarios. This paper proposes an optimal fractional‐order proportional‐integral‐derivative‐acceleration (FOPIDA) controller, enhanced by a robust adaptive neuro‐fuzzy inference system (ANFIS), to improve load frequency control and reliability in power systems with wind and solar generators. First, the dynamical model of a multi‐area interconnected power system, including a thermal power plant, wind turbine, and solar photovoltaic generators, is developed. A decentralized ANFIS‐FOPIDA controller is then designed for load frequency control objectives. The gains of this controller are optimized using the whale optimization algorithm (WOA), focusing on frequency deviation and tie‐line power exchange. Simulations on a New England IEEE 10‐generator 39‐bus power system demonstrate the approach's effectiveness under various disturbances, including random load‐generation disturbances and nonlinear generation behaviors. Comparisons with other strategies, such as fractional order (FO) beetle swarm optimization algorithm (FOBSOA)‐FOPIDA, WOA‐PIDA, and WOA‐ANFIS‐PIDA, and recent control approaches highlight the superior performance of the WOA‐ANFIS‐FOPIDA method in enhancing power system stability. [ABSTRACT FROM AUTHOR]

This document is a guest editorial from the journal IET Generation, Transmission & Distribution. It emphasizes the need to improve the reliability and resilience of modern power systems in the face of various threats. The editorial highlights the importance of modeling, assessing, and enhancing the reliability and resilience of power grids that are increasingly incorporating grid-edge resources. The document also provides a summary of the papers included in a special issue of the journal, which cover topics such as planning reliable energy systems, analyzing power grid operations, and enhancing service restoration and grid-support load response. Additionally, the text discusses the issue of equity in power distribution system restoration processes and proposes a model called the equity-aware power distribution system restoration model. The model aims to balance equity and resilience in restoring power after outages by focusing on fair distribution of energy resources while maintaining operational efficiency. The text also includes brief biographies of several authors who have contributed to the field of power electronics and power system reliability. [Extracted from the article]

This paper proposes an approach for segmentation of power systems to prevent uncontrolled islanding. With the development of microgrids (MGs) and increased penetration of renewable energy sources (RESs) in the power system, it is necessary to consider the effect of MGs and the stochastic behaviour of RESs in the controlled islanding process. First, the enormous search space for finding the boundary points is reduced by the clustering of the coherent generators and the buses which are placed in sections that cannot be separated from the coherent groups. Then, linear AC power flow is defined as a sub‐problem and solved by linear programming to satisfy the power system and MG constraints. In this step, an optimization model is defined, and a mixed‐integer linear programming (MILP)‐based model is suggested to find cut‐sets and islands arrangement with reduced load shedding. In view of the fact that the fluctuation of RESs may have the significant effects on the power imbalance, to cover the uncertainties a scenario based stochastic simulation is considered. Finally, the effect of uncertainties on cut‐sets and load curtailment is evaluated. The effectiveness of the proposed methodology is demonstrated by the simulation on the test system. [ABSTRACT FROM AUTHOR]

Interference amongst stability phenomena has been raising concerns due to the potential maladjustment of control parameters in large‐scale and interconnected power systems. In consequence of such interference, power system security is threatened. In order to preclude any inconsistency and ensure maximum security, a comprehensive study needs to be carried out in short‐term operational planning concentrating on the determination of an economic operating point with enhanced static and dynamic security. In this paper, an integrated approach with incorporation of voltage and rotor‐angle stabilities into the optimal operation of power system is proposed. This study is based on a many‐objective optimisation problem providing a cost‐effective security solution prior to real‐time operation whereby the operating point of power system is maximally secure and economic. The output of the proposed approach is a vector of adaptively adjusted control parameters consisting of terminal voltage and active power of generating units, reactive power of SVCs, and tap position of transformers. In addition, active power production and reactive power opportunity costs, static, and dynamic security criteria constitute the vector of objective functions with eight elements. The performance of the approach is assessed in several scenarios including various load patterns and different power limits of generators. [ABSTRACT FROM AUTHOR]

Distributed multi‐area economic dispatch (MAED) can overcome the deficiencies of a large amount of information processing and regional privacy leakage faced by centralized scheduling. However, multiple iterations may increase communication and computing costs, as well as operational risk. Therefore, this paper proposes a double spatial scale search (DSSS) algorithm to accelerate the iterative process. First, each area performs the multi‐parametric quadratic programming (MPQP) with load and phase angles of boundary buses as parameters to pre‐process the MAED problem as a piecewise quadratic programming (PQP) problem. To reduce the complexity of MPQP, a parameter variables reduction method and a fitting‐based imprecise MPQP (i‐MPQP) algorithm are developed. Then, aided by the i‐MPQP results, we design a DSSS algorithm to optimize the PQP problem efficiently. Finally, two interconnected power systems of different sizes are used for numerical testing. The results show that the i‐MPQP can produce a 77.98% and 88.65% reduction in the number of precise MPQP (p‐MPQP) function segments. Compared with the existing algorithm, the iterations of DSSS algorithm are decreased by 75% and 76.35%, and it can converge with one iteration in most cases. Moreover, the performance of the proposed method is insensitive to the system settings and algorithm parameters. [ABSTRACT FROM AUTHOR]

Most cascading failure analysis methods successfully capture cascading developments within one control zone, or region comprised of multiple control zones, controlled by a single transmission system operator (TSO). They neglect, however, the operations of multi-zonal systems. To bridge this gap, the authors introduce the multi-zonal method for cascading failure analyses of large interconnected power systems. The method accounts for all control zones in amulti-zonal system, assesses their power flows, re-evaluates the system topology after disturbances and applies frequency balancing measures in each control zone independently, thus effectively simulating the actions of multiple TSOs. To demonstrate the capabilities of this method, a case study is investigated which compares the security benefits of the multi-zonal (national) versus the single-zone (regional) frequency balancing methods in a multi-zonal system. The application to the IEEE 118-bus test system shows that the regional approach increases the security of this system in small and medium cascades, whose expected demand not served is reduced by 28% and 26%, respectively, in comparison to the national approach. However, the expected load shedding for large-scale cascading events in the regional approach is 42 times as large as in the national approach. This is mainly caused by overloads occurring in transmission lines adjacent to the cross-zonal tie lines, which are 154% higher with the regional method compared to the national in large cascading events. The capability to identify congestions is presented by devising an upgrading strategy, which makes the regional frequency balancing approach viable from a security aspect. [ABSTRACT FROM AUTHOR]

The reserve sharing amongst the interconnected power systems will facilitate the improvements on their anti‐disturbance capability and operating economy. Based on the design of reserve sharing mechanism across different areas, a multi‐area generation‐reserve sharing model is constructed. The stochastic fluctuation of load and wind power will cause the power grid to be in an unpredictable random state when the reserve is needed, and the transmission capacity constraint of the power grid may restrict the effective deployment of the reserve. To address these issues, a max‐min bi‐level optimization model is proposed to check the reserve availability. The joint generation and reserve optimization sub‐model, together with the reserve check sub‐model, constitutes the two‐stage robust optimization model in this paper. The column‐and‐constraint generation (C&CG), algorithm is adopted to solve the proposed model. The modified IEEE 118‐node test case is used to verify the proposed model and algorithm. The test results indicate that the proposed method can realize the multi‐area generation‐reserve joint optimization under the condition of guaranteeing the reserve availability, and it possesses the advantage of high efficiency in dealing with stochastic scenarios. [ABSTRACT FROM AUTHOR]

The study of integrated electricity systems that consist of several interconnected areas in the long term often results in large‐scale complex models, that are difficult to solve. The already large spatial size of these systems, combined with a fine‐grained time representation, necessary to capture the short‐term variability arising from the high penetration of renewable generation, increases the complexity of the problem, and thus, its computational cost. To overcome this issue, temporal reduction techniques are generally applied. However, the application of time aggregation in interconnected systems represents a challenge. The goal is to select the best possible time aggregation that considers at the same time the particularities of each of the areas that make up the whole system. To do so, the authors propose a new methodology for temporal aggregation in multi‐area energy system models. By implementing a multi‐dimensional clustering algorithm, the original hourly data is transformed into system states, or group of hours that share similar characteristics, reducing significantly the computational burden required to solve it. Together, an accurate representation of the variability of the system is achieved. The main conclusions are derived from a real‐size case study based on the electricity markets of three European countries. The sensitivity analysis performed shows the degree of accuracy of the results obtained, as well as the computing cost incurred for different temporal configurations. Ultimately, the results show the benefits of using this methodology over a more conventional approach. [ABSTRACT FROM AUTHOR]

Optimal coordination of directional overcurrent relays (DOCRs) in interconnected power systems is a highly constrained, non‐convex and non‐linear optimisation problem. In this study, use of a series of linear programming (LP) problems in a variable neighbourhood search (VNS) framework is proposed, in which pickup current settings can be considered either as continuous or discrete variables. Therefore, the proposed hybrid algorithm (VNS–LP) is suitable for coordination problem‐solving in a network with different types of DOCRs. Furthermore, two versions of the VNS algorithm are proposed, the first of which is very easy to implement, while, the other is somewhat more sophisticated, and at the same time much faster and possibly suitable for online coordination in smart grids applications. One advantage of the second algorithm is that it relies only on elementary arithmetic and requires low RAM, which makes it implementable in any low‐level programming environment. This, in turn, can increase the interoperability, which is of crucial importance when automating tasks. The efficiency of the proposed algorithm was investigated in several test systems. Numerical results indicate that the two proposed approaches outperform the previous methods. Moreover, the coordination problem is solved in a reasonably short time using a faster approach. [ABSTRACT FROM AUTHOR]

The low and variable inertia due to the integration of large-scale wind generation poses severe challenges to the frequency control of the power grid. In this study, a novel model predictive control (MPC)-based load frequency controller (LFC), which can adapt to the changes in system inertia, is proposed to improve the frequency control effect. First, the inertia estimation scheme based on measurements is designed. Then, the state-space model, which is the key that determines the control effect of MPC, is corrected in time based on the estimated inertia. The proposed method in this study can avoid the problem of MPC-based LFC failure caused by inaccurate model parameters. The performance of the proposed strategy is demonstrated in two scenarios, i.e. wind power fluctuation and load multi-step, using a two-area interconnected power system with time-variant inertia. [ABSTRACT FROM AUTHOR]

Ambient‐based oscillation modes extraction is an effective means of monitoring the small signal stability of a power system on‐line. In this study, a data‐driven approach based on output‐only observer/Kalman filter identification (O3KID) combined with the eigensystem realisation algorithm (ERA) was proposed to extract electromechanical modes (frequency, damping ratio and mode shape) from synchronised ambient data. As a key for extracting a reduced‐order state matrix using the ERA, the Markov parameters (impulse responses) are first estimated by employing O3KID on multi‐channel ambient data. O3KID makes it possible to identify the modes with the ERA using only output ambient data, while ensuring the reliability of the extractions of frequencies, damping ratios and mode shapes. The performance of the proposed method was evaluated by employing the IEEE 16‐generator 5‐area system and measured data from a real power system. The estimation results in all cases as well as comparison results with the RDT‐ERA method and NExT‐ERA method indicate that the O3KID‐ERA method is a promising method for ambient data‐driven electromechanical oscillation modes extraction. [ABSTRACT FROM AUTHOR]

This study describes a maiden application of salp swarm algorithm (SSA) optimised cascade tilt–integral–derivative controller (CC‐TID) for frequency and tie‐line power control of interconnected power systems (IPSs). The proposed controller includes both the merit of the cascade control algorithm and fractional‐order calculus. In the proposed CC‐TID controller, TID controller is used as a slave controller and a proportional–integral (PI) controller served the role of master controller. To elucidate the effectiveness, the designed controller has employed to, initially, two‐area IPS followed by four‐area IPS. SSA is used to pursue the optimum settings of the CC‐TID controller via the minimisation of area control error. Performances of CC‐TID controller is obtained and compared with I‐, PI‐, PI–derivative‐, cascade PI–PD, and TID controllers. Simulation results, apparently, show that SSA: CC‐TID controller exhibits superior performance compared with other controllers described above. Moreover, the performance of SSA is evaluated and compared with differential evolution and flower pollination algorithm in terms of convergence profile, power density, and statistical results. Finally, time‐varying step load perturbation and random load perturbation are applied to confirm the robust behaviour of SSA: CC‐TID controller. [ABSTRACT FROM AUTHOR]

This paper focuses on the impact of control system on small-signal stability of the Hybrid Multi-Infeed HVDC(H-MIDC) system, in which the Line-Commutated-Converter based HVDC (LCC-HVDC) and Voltage-Sourced-Converter based HVDC (VSC-HVDC) links feed into an AC system in close mutual proximity. A comprehensive linearized small-signal model is developed for an H-MIDC system. Based on the eigenvalue analysis and participation factor analysis, the inherent oscillatory modes of the H-MIDC system are revealed. Then, the impact of the most sensitive control system parameters on the leastdamped modes are investigated. The studies show that (i) the proportional gains of PLL functions of LCC and VSC stations, and AC voltage outer loop controller of VSC station are highly coupled, and presents the most sensitivity to the least damped modes; (ii) parameters of PLL in LCC station, and outer loop of AC voltage control and PLL in VSC station can highly impact the damping of the oscillatory modes and even cause instability, and (iii) smaller PLL gains in LCC and VSC stations, and smaller proportional gain of AC voltage control of VSC station are preferable and can enhance damping of dominant modes. [ABSTRACT FROM AUTHOR]

Identification of coherent generators (CGs) in power systems is one of the key steps in determining controlled islanding strategies. In this study, a wide-area measurement system (WAMS) and agglomerative hierarchical clustering (AHC) algorithm based coherency identification method is presented for interconnected power systems with aggregated renewable sources. First, the trajectories measured by WAMS are transformed to the centre of inertia based ones for better representing the dynamic behaviour of a given power system, and ten trajectory dissimilarity indexes are presented for determining the similarity of the trajectories of any two generators. Second, a CRITIC (CRiteria Importance Through Intercriteria Correlation) based method, in which entropy and the Spearman's rank correlation coefficient are integrated for reflecting the differences and correlations among multiple indexes, respectively, is presented to integrate the trajectory dissimilarity indexes. Next, the AHC algorithm is utilised to identify CGs. Finally, a modified New England--New York interconnected power system with a large number of renewables, a simplified actual Western Interconnection power system in North America and the eastern part of Guangdong power system in China with a recorded oscillation event happened are utilised to demonstrate the proposed widearea coherency identification methodology. [ABSTRACT FROM AUTHOR]

Identification of coherent generators (CGs) in power systems is one of the key steps in determining controlled islanding strategies. In this study, a wide‐area measurement system (WAMS) and agglomerative hierarchical clustering (AHC) algorithm based coherency identification method is presented for interconnected power systems with aggregated renewable sources. First, the trajectories measured by WAMS are transformed to the centre of inertia based ones for better representing the dynamic behaviour of a given power system, and ten trajectory dissimilarity indexes are presented for determining the similarity of the trajectories of any two generators. Second, a CRITIC (CRiteria Importance Through Intercriteria Correlation) based method, in which entropy and the Spearman's rank correlation coefficient are integrated for reflecting the differences and correlations among multiple indexes, respectively, is presented to integrate the trajectory dissimilarity indexes. Next, the AHC algorithm is utilised to identify CGs. Finally, a modified New England–New York interconnected power system with a large number of renewables, a simplified actual Western Interconnection power system in North America and the eastern part of Guangdong power system in China with a recorded oscillation event happened are utilised to demonstrate the proposed wide‐area coherency identification methodology. [ABSTRACT FROM AUTHOR]

This paper deals with the modeling of discrete automatic gain control (AGC) controllers for an interconnected power system. The AGC supplementary controllers continuously try to reduce the ACE signal to zero by sending control commands/signals to the speed governor set points. Typically, control signals are sentin the form of discrete control pulses to adjust the generating unit outputs in discrete steps. However, in the preceding AGC studies, ZOH circuit has been misplaced in discrete supplementary controller models. Therefore, control signals feed to the speed governor set points no longer remains in discrete mode or in other words, controller action no longer remains in discrete steps. Therefore, the results and inferences drawn in these studies are erroneous and unrealistic. This paper presents the realistic model of discrete AGC controllers and removes the anomaly in existing works. Furthermore, it is also discovered that inappropriate selection of sampling period of ACE signal degrades the system dynamic performance or even cause system instability. Surprisingly, no proper guidelines/method has been provided yet to select the appropriate sampling period of ACE signals for discrete AGC operation. Here, a maiden attempt has been made to obtain the suitable values of ACE signal&s sampling periods using Shannon&s sampling theorem. [ABSTRACT FROM AUTHOR]

Automatic generation control (AGC) plays an important role in power systems, where it maintains the system frequency and tie-line power flow at their desired values. This study presents a novel symbiotic organisms search (SOS) algorithm in order to optimally design the proportional--integral--derivative (PID) controllers in the AGC of interconnected multiple-area power systems including wind farms uncertainty and system non-linearity. The PID controllers' parameters define the design variables of the optimisation problem. The SOS algorithm is applied to different objective functions such as integral square error and integral absolute of error. The efficacy of the proposed controller is compared with other competing evolutionary algorithms-based proportional--integral or PID controller. The system performance is evaluated under different operating conditions such as different loading, variation of system parameters, and an addition of wind energy uncertainty. For obtaining realistic responses, real wind speed data that extracted from Zafarana location in Egypt is used in this study. The validity of the proposed controller is extensively confirmed using the simulation results. With the SOS-based PID controllers, the dynamic responses for the AGC of interconnected power systems, including wind farms uncertainty can be further enhanced. [ABSTRACT FROM AUTHOR]

This study addresses proportional-integral-derivative (PID) optimal fine tuning of load frequency controllers for multiarea interconnected power systems. For realistic study, generation rate constraints are considered to increase system nonlinearity. The proposed method is applied to equal and unequal multi-area interconnected power systems. A methodology based on water cycle algorithm (WCA) is proposed. WCA is applied to generate optimal fine settings for the four parameters of the PID. A constrained optimisation problem with relevant integral of time multiplied by summation of absolute errors as an objective function is established. The time-domain dynamic performances using the generated optimal PID parameters are demonstrated under disturbed load conditions. At this moment, to show the robustness of the cropped optimised PID parameters, sensitivity analysis under uncertainty conditions is made by varying the system parameters from their nominal values. Specifications of time-domain dynamic performances are compared with other competing and Ziegler-Nichols PID tuning techniques which attest the significance of the proposed WCA-based LFC. Finally, the proposed WCA-based PID controllers are verified against random step load perturbations with different sampling times. [ABSTRACT FROM AUTHOR]

Integration of distributed energy resources in power networks make them interconnected and active. Depending upon the type, short circuit capability and location of distributed energy resource in transmission and distribution systems, design of protection coordination schemes becomes very challenging. Complexity further increases in the design of protection coordination schemes, when penetration effect of these resources reaches to upstream transmission lines and coordination among the distance and over current relays requires a review. The protection coordination scheme discussed in this article monitors the state of power network continuously. Depending upon the operational topology of the network, time dial settings as well as plug settings of over current relays and zone-2 setting of distance relays are selected from pre-optimsed relay group settings. Whenever there is any change in the network fault level either due to change in line parameters or incoming of new distributed energy resource, new relay group settings are communicated to corresponding relays. The proposed protection coordination scheme is implemented in RSCAD software for modified eight bus test bus and modified IEEE14 bus system. It is observed that the proposed protection approach is highly flexible to maintain the coordination among the over current and distance relays. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive analytical study of a fuzzy proportional-integral-derivative (fuzzy-PID) controller with derivative filter (fuzzy-PIDF) for automatic generation control (AGC) in multi-area power system tuned by a novel hybrid local unimodal sampling-teaching learning based optimisation (LUS-TLBO) algorithm. The relevant advantage of this recommended controller is its high sensitivity to load perturbation. Initially a two area non-reheat type thermal system is considered and the gains of PIDF controller are tuned employing hybrid LUS-TLBO algorithm. The supremacy of PIDF controller is shown by comparing the results with some recently published articles. The study is further extended to design fuzzy logic based PID controller with derivative filter (fuzzy-PIDF) for AGC of the same power system employing hybrid LUS-TLBO algorithm. Supremacy of the proposed approach is shown by comparing the results with another recently published article. In addition, the work is also extended to deal with AGC issues in two area multi source hydro thermal power system using the proposed controller. Finally, it is seen that fuzzy-PIDF controller retains its supremacy over PID/PIDF/fuzzy-PID controllers. In addition to it, robustness analysis is carried out for the non-reheat two area thermal power systems by varying different parameters within the range of ±50%. [ABSTRACT FROM AUTHOR]

A limit preserving equivalent method of interconnected power systems is proposed. Based on the equivalent network keeping the consistency of power flows and sensitivities, the equivalent active power constraints are derived under the condition of retaining the consistency of transfer capabilities before and after equivalence. The transfer capabilities are obtained by an optimisation model in which various limits of original external network are included. Based on the limit preserving equivalent network, an equivalent optimal power flow (EOPF) model for interconnected power systems is presented, which can effectively maintain both sensitivity and limit information of the external network. The accuracy and effectiveness of the proposed equivalent method and EOPF model are demonstrated using the IEEE 39‐bus system and an actual 661‐bus system. [ABSTRACT FROM AUTHOR]

Load frequency control (LFC) scheme communicates from remote terminal units to control centre, followed by control centre action on the corresponding plant units. The conventional dedicated communication channels have constant time delay, while open communication channel, i.e. shared one has time-varying delay. These delays degrade the dynamic performance or even lead to system instability. In an interconnected system, communications delays cannot be ignored and therefore the time delay is introduced in the area control error signal. In this study, a time delay-dependent H∞-based non-linear sliding mode controller for LFC scheme has been proposed for N area power system. The approach uses Lyapunov-Krasovskii functional based on time delay-dependent stability criteria and linear matrix inequalities optimisation. Simulation studies are presented for two-area LFC scheme against step and random step load disturbance and generation rate constraints. Comparison is also made with recently reported; two-term controller design. The simulation results establish the superiority and applicability of the proposed design for LFC application. The results illustrate that the proposed scheme can effectively enhance the frequency stability via improving the damping of the system. [ABSTRACT FROM AUTHOR]

The Central China Power Grid (CCPG) and North China Power Grid (NCPG) are connected together by a single AC ultra-high-voltage (UHV) transmission link. When suffering power disturbances, power oscillation with high magnitude and long period would happen on the UHV tie-line, which may affect the synchronous and stable operation of the interconnected two power grids. This study proposes a novel emergency control scheme for high-voltage direct current (HVDC) in CCPG to suppress the high peak value of the power oscillation. Based on a two-machine equivalent model, the maximum rising slope of power oscillat`ion is used to predict the peak value of power oscillation and power disturbance which is used as the reference of emergency power modulation. Simulation verification is carried out based on the full model of the CCPG and NCPG, using Power System Analysis Software Package. Moreover, field test has also been carried out in CCPG. Both simulation results and recorded wave curve show that the proposed HVDC emergency control scheme can effectively suppress the peak value under different power disturbances. This significantly improves the transient performance of the interconnected power system and the power transfer capacity of the UHV tie-line. [ABSTRACT FROM AUTHOR]

This study presents the load frequency control of an interconnected two-area power system under deregulated environment with area1 as a thermal system having two generating companies and area2 as hydro-thermal system. Appropriate generation rate constraint, and governor dead band are provided in the areas. Three-degree-of-freedom integral-derivative (3DOF-ID) controllers are used as secondary controllers in the areas whose performance is compared with that of two-degree-of-freedom integral-derivative (2DOF-ID) and single-degree-of-freedom controllers such as integral (I), integral-derivative (ID). Biogeography-based optimisation (BBO) technique is used for simultaneous optimisation of controller gains and electric governor parameters. Analysis of the dynamic responses reveal the superiority of 3DOF-ID controller over I, ID, and 2DOF-ID controllers, in terms of settling time, peak deviation and magnitude of oscillation. Sensitivity analysis proved that, BBO optimised parameters obtained at nominal conditions are robust. 3DOF-ID controller parameters obtained at nominal distribution companies participation matrix (DPM) are healthy enough and not necessary to optimise for change in DPMs. Variation in frequency bias coefficient (B) concludes that the best selection for B is equal to area frequency response characteristics. Similarly, selection of governor speed regulation parameter (R) infers higher value for thermal-system, while hydro-system should be kept comparatively low. [ABSTRACT FROM AUTHOR]

The coordination of directional overcurrent relays is most commonly studied based on a fixed network topology within an interconnected power system. Due to its complexity and non-linearity, the relay coordination is formulated as an optimisation problem. Distribution systems often suffer consequences due to the dynamic changes of network topology and operation of elements. Such changes are for example the inputs and outputs of generators, lines and loads. The consequences are reduction of sensitivity and selectivity of relays. The principal objective of this study is to coordinate the directional overcurrent relays based on adaptive protection scheme. The secondary objective is to present the formulation of ant colony algorithm and a comparison of it with the genetic algorithm. [ABSTRACT FROM AUTHOR]

Commutation failure (CF) may be caused by AC fault in AC/DC interconnected system, and it will affect the performance of distance protection. The transient characteristic of equivalent current of power-frequency of the dc-ac inverter is first analysed by introducing the concept of quadrant. Then, the effect of CF on distance protection is studied in detail with consideration of the connection mode of distance relay. The analysis results show that both the fault position and fault resistance contribute to the effect of CF on the performance of distance protection significantly. Furthermore, a novel countermeasure based on the amplitude of second harmonic is put forward, and a concept of 'successive trip' by using the change of measured reactance is also presented. Simulation results based on PSCAD/ EMTDC prove the correctness of these conclusions. [ABSTRACT FROM AUTHOR]

Existing system restoration strategies are primarily based on operators' experience with no specific decision support tools. Restoration of interconnected grids in Europe is decentralised; restoration planning is limited to within the area of control for each national transmission system operator (TSO). Although coordination of restorative actions between TSOs is encouraged, few agreements exist. This study proposes a decision support methodology for system operators and restoration planners for restoration of interconnected grids. Solutions to optimal and coordinated utilisation of tie lines (TLs) are proposed. The proposed tool facilitates collaboration between TSOs affected by wide area blackouts. The decision support tool allows to adaptively develop restoration strategies based on system conditions, available resources and operating constraints. Optimisation algorithms are proposed to determine the optimal utilisation of TLs and/or black‐start (BS) units to crank non‐BS units. Optimal power flow problems are formulated for utilisation of TLs. They offer solutions for neighbouring TSOs to determine the extent to which TLs can be used without violating constraints. The proposed decision support tool is tested with IEEE 39‐bus system. [ABSTRACT FROM AUTHOR]

Wind is one of the fast growing renewable resources that can significantly contribute in achieving emission‐free electricity generation system. Since wind resources are distributed across geographical locations, wind resource sharing among different geographical locations is essential to facilitate wind energy penetration and its full utilisation. A wind resource sharing strategy, for interconnected electricity networks, to achieve the national and regional renewable energy target is presented in this study. A multi‐objective decision making problem has been formulated to optimally share the installed wind generation capacity in a multi‐area power systems. Computational models have been developed for wind generation adequacy, emission reduction from wind energy and capacity upgrade requirements for tie‐line interconnections. Trade‐off analysis has been used to select the best wind resource sharing options. The proposed wind resource sharing strategy has been applied to the interconnected power systems operated within the National Electricity Market (NEM) framework of Southeast Australia to share the available wind resources within the geographical areas of the participating states in the NEM. [ABSTRACT FROM AUTHOR]