Due to an exponential increase in load demand and lack of capital resources to improve the existing transmission line infrastructure, power utilities are focusing on methods to increase the efficiency and loadability of existing infrastructure. This study presents a new approach for simultaneous optimum distributed generation (DG) placement and optimum tie-switch allocation based on maximisation of system loadability using discrete artificial bee colony algorithm. The proposed algorithm is tested on 16-Bus, 33-Bus and 69-Bus radial distribution test system. The obtained results show that with simultaneous optimum DG placement and optimum tie-switch allocation, better results are achieved rather than solving two problems independently. Further it was also found that the proposed method has improved the efficiency of the system in terms of maximisation of system loadability, reduction in power system losses, improving the kVA margin to maximum loadability and voltage quality improvement.

This study proposes a novel dynamic reliability network-equivalent approach (RNEA) for distribution generations (DGs) enhanced distribution system. This method includes a bottom-up process and a top-down process, which are developed based on equivalent principle, and the synthesis of both processes yields the reliability performance of any node in the system. In addition, a novel switch zone concept is defined and introduced into the bottom-up equivalent process as to save the computation cost. Besides, a hybrid restoration model is proposed to account for the practical restoration process in power grids, and solved using particle swarm optimisation. The most significant of the proposed approach over other equivalent methods such as section technique, RNEA, and zone-branch method is that it provides a more generalised element-by-element equivalent approach that can greatly simplify the network for reliability assessment irrespective of the network topology. The proposed methodology has been successfully tested on a real 362-node urban distribution system in China, with and without DGs considered.

This study proposes a multi-function power system protective relay hardware design built with various functional hardware processing cores on the field programmable gate array (FPGA). This practical and systematic method lends itself to a paralleled and pipelined hardware emulation of individual signal processing and protection components. Detailed emulation designs are presented for the following protective relays: distance, directional overcurrent, voltage, and frequency protection. The necessary signal processing functions required to operate these relays are also emulated, allowing the protection system to be stand-alone and fed with instantaneous fault data. Real-time experimental results are presented to verify the functions of the target hardware relay on the Xilinx^® Virtex-7 FPGA. Case studies provide the efficacy of the multi-function relay design in terms of accuracy, latency, and resource consumption.

The adequate reactive power resources are expected to maintain system integrity under both normal and post contingency operations. Nowadays, the power systems are leading to high-risk operating points, hence, the number of probable contingencies, which should be considered in security constrained reactive power planning (SCRPP), has widely increased. However, considering a large number of contingencies in SCRPP is not practically possible. This study presents an index named expected violation index to consider numerous contingencies in SCRPP. At first, a multi-objective algorithm for the proposed expected SCRPP approach is presented. This novel algorithm uses the probability of each contingency to invest on them more efficiently. Next, it presents a method for selecting candidate buses to install reactive power resources. Then, the effectiveness of the proposed method is analysed using a multi-objective particle swarm optimisation algorithm on IEEE 30-bus test system. Finally, a reliability-based quantitative method is presented for selecting among final Pareto optimal solution. Using the proposed method, the system designers are capable to consider a large number of contingencies in their SCRPPs, to invest more purposefully in reactive power equipment, and to select their most appropriate option among different feasible choices in the optimal Pareto solution.

This study proposes a new particle swarm optimisation algorithm for combined problem of capacitor placement and network reconfiguration simultaneously in the presence of non-linear loads. Here, the minimising cost of real power losses and capacitor installation and also improving the power quality criteria have been pursued as the goals of an optimisation problem. In the proposed method, to achieve better control on the algorithm's exploration and exploitation capabilities, particles velocity will be dependent upon both particle's fitness and time. Perturbation module is adopted to perform perturbation on some particles and provide extra diversity to jump out from local optima and avoid premature convergence. The proposed model is implemented on two typical networks including 33-bus IEEE standard well-known test system and a 77-bus radial distribution network of Sirjan, Iran. Through showing numerical results, the performance of the presented method will be discussed in comparison to previously proposed ones. The numeric comparison also indicates that simultaneously capacitor placement and network reconfiguration lead to far better results than they are considered non-simultaneously. Furthermore, in regard to harmonic distortion, as a term of a multi-objective function, it also improves the power quality of the network during the reconfiguration and capacitor placement procedures.

Provision of secured and uninterrupted supply of power is an essential pre-requisite for the electrical industry. Hence, FACTS devices need to be employed efficiently to ensure the security of the power system. This study proposes, a repetition of severity-based strategy of placement of interline power flow controller (IPFC) using composite severity index (CSI) for contingency management. The formulated CSI is a combination of real power performance index) and line stability index L_mn . Thus, the CSI is expected to provide an exact measure of stress on the lines in terms of MW overloading and voltage instability. The IPFC is further tuned for a multi-objective function using firefly algorithm. To verify the proposed methodology, it has been tested and implemented on IEEE 30 and Indian utility 62 bus system. The system has been further tested under highly stressful condition by increasing the load on the maximum loaded bus up to the critical value. The results have been presented and analysed to determine the effectiveness of IPFC for contingency management.

This study presents a new design of a wide area damping controller for the convertible static compensator (CSC) to limit some major blackouts due to asynchronous oscillations. The adaptive neuro-fuzzy inference system (ANFIS) approach is adopted in the dual heuristic programming method to have an optimal response at different disturbances. The proposed ANFIS parameters are optimised by using the multi-swarm particle swarm optimisation method. The CSC dynamic performance in both of unified power flow controller and interline power flow controller configurations is investigated to increase the damping of inter-area oscillations and to prevent the uncontrolled network islanding. The Iranian power grid and New England power system are selected to install CSC and to apply the designed damping controller. It is shown that the considerable number of wide area blackouts could be avoided by CSC application equipped with the proposed damping controller. In other scenarios, which the controlled islanding is an unavoidable task, the boundaries of islands are determined adaptively considering the changes of generators coherency and the loadings of lines. Simulation results verify that the load shedding amounts are decreased and the stability margins of islands are increased. The uncontrolled islanding condition is also delayed significantly.

Transmission expansion planning is receiving an increased attention, primarily due to the large-scale grid upgrades that will be necessary to accommodate renewable generation or to increase cross-border capacity. The intermittency of renewables, and the uncertainties inherent to long-term planning, makes it advisable to use solution methods that cope with uncertainty explicitly. Stochastic Optimisation and, in particular, Benders’ decomposition, is one of the most widely applied approaches in this context. However, large-scale planning can still present computational problems. Several techniques have been proposed to accelerate Benders’ decomposition. However, they appear disperse and usually without a clear application scope. Most of them have not been applied to TEP yet. This study presents a comprehensive view on TEP applied to Benders’ decomposition and the techniques available to accelerate its resolution, together with semi-relaxed cuts, a technique proposed in the previous work by Lumbreras and Ramos in 2013. Then, for three case studies based on IEEE test cases, the most promising of these techniques are implemented and their effectiveness is compared. All test cases could save about 50% of solution time using simple and easy-to-implement techniques, showing that there is an interest in using these approaches in academic and practical TEP applications.

With the technological improvement in energy storage field, energy storage systems (ESSs) are exerting increasingly profound influence on future electrical grid which is the combination of numerous renewable energy generation units. However, the problem remains debatable how to appropriately determine the ESS configuration. On the basis of three types of filters, this study proposes a practical and economical method for ESS configuration to stabilise the power fluctuation of distribution feeder lines. According to the historical power data in feeders for a typical day, different ESS configurations are calculated with respect to the rated power and capacity based on various filtering methods. It is found that moving average algorithm is more suitable in the process of solving ESS configuration, considering its compromise between fewer points in average and economical results for ESS configuration. Furthermore, the characteristics of three typical filters as well as explanation for each configuration result are theoretically discussed from the perspective of signal analysis, which helps to illustrate that the circular convolution is the main drawback for larger ESS configuration results solved by ideal low-pass filtering method.

This study proposes a model predictive control (MPC)-based home energy management system for residential microgrid (RM) in which all related information such as the time-varying information of the load demand, electricity price and renewable energy generations, are all taken into account. A novel finite-horizon mixed-integer linear programming problem is iteratively formulated to investigate the optimal control actions of the RM under an MPC framework. Three case studies are conducted to discuss the technical and economic impacts of the responsive electrical and thermal loads, plug-in hybrid electric vehicles, and electrical and thermal energy storage units. Moreover, a sensitivity analysis is performed to demonstrate the superiority of the proposed approach when forecasts of related information are imperfect.

Backbone of a real time monitoring and controlling operations in power systems is state estimation. The main goal of the paper is to use all useful data (collected by measurements) in the process of the robust state estimation. Data acquisition by Phasor Measurement Units (PMUs) has an important role in providing an accurate robust forecasted estimator. Conventional measurements have much lower data transfer rate than the PMUs. On other hands, the number of received data from PMUs is fewer than the conventional measurements and due to this fact, the state of the system are not observable by only PMUs. This fact leads to use the benefits of all kind of measured data. Robustness of the proposed method is guaranteed by rejecting outlier (large amplitude error) by forecasting conventional measurements data and using robustness property of the Kalman filter against noise in data (small amplitude error). Moreover, the proposed estimator tracks dynamic behavior of system much faster than traditional methods. The proposed estimator has been implemented on the IEEE 9-bus and the IEEE 118-bus systems. Comparison results of the proposed algorithm with those of a traditional dynamic estimator proves the efficiency, accuracy and robustness of the proposed method against falsified data.

This study integrates earth fault location computation with fault management-control schemes for distribution networks. To realise this target, a panel substation is located at the lateral outlet. The faulted section is identified precisely via a fault-location algorithm. Then, isolating the faulted section is accomplished through control signals between the lateral-panel substation and the faulted section isolators. The service restoration is achieved by a direct communication between the lateral-panel substation and the feeder primary substation. The proposed fault-location algorithm is based on the pure fault circuit with the initial condition of the earth fault using the measurements at each lateral panel. For phase-to-ground fault, the initial condition is the series connection for the sequence networks from the fault point. For phase-to-phase-to-ground fault, the initial condition is that the summation of the sequence currents at the fault point is equal to zero. The proposed fault-location algorithm is, therefore, suitable for equipping distribution systems with distributed generation. Moreover, it is applicable for earthed or unearthed networks with all possibilities of transformer connection and load taps. For investigation purposes, simulation tests are performed using the IEEE 33-bus automated feeder example. The simulation test results corroborated the efficacy of the proposed fault management system.

This study discusses a security-constrained unit commitment (SCUC) based optimal power tracing approach, which adopts the proportional power tracing method to trace power flows of the network for simultaneously satisfying physical contract paths and financial contract quantities of bilateral transactions. Thus, optimal solutions of the proposed model, including unit commitment and generation dispatch of generators and angle statuses of phase shifters, would simultaneously meet physical and financial requirements of bilateral transactions, and in turn reduce the impacts of loop flows induced by bilateral transactions to third parties of the networked system. The proposed model is a mixed integer non-linear programming problem because of the non-linear proportional power tracing constraints, and the revised outer approximation algorithm is discussed to effectively solve the problem. The effectiveness of the proposed model is further evaluated via an integrated power-money flow analysis, based on the locational marginal price based energy payments and the min–max fairness policy based transmission usage charges. Numerical case studies show that the proposed model, as compared with traditional financial bilateral transaction models, presents potential advantages to avoid loop flows and reduce the impacts to third parties in terms of energy and transmission usage payments.

Predictive control is an emerging alternative in the control of power converters because of its potential for achieving fast transient response and increased control accuracy. Research on this topic has increased in recent years owing to the availability of high speed digital controllers that can be used for the control of power electronic systems. This study proposes a predictive current control scheme for an improved topology of distribution static compensator (DSTATCOM) intended for load compensation. The proposed strategy derives the converter switching pulses using a cost function that defines the desired system behaviour. An improved DSTATCOM topology employing predictive current control algorithm tracks reference current effectively and makes source current sinusoidal and also in-phase with voltage at the point of common coupling in both steady state and transient conditions. In addition, this scheme does not require any modulation technique. The control scheme has been implemented using field programmable gate array. Simulation and experimentation have been carried out to verify and validate the performance of the proposed scheme and the results are reported in this study.

Utilities are continuously investigating methods to economically reinforce their overhead line (OHL) networks by reconductoring with larger conductors or with novel high-temperature low-sag (HTLS) conductor technologies. To further optimise the OHL design, conductor creep ageing is calculated and mitigated at installation, which economically improves an OHLs’ performance. An already established methodology is used to investigate common and HTLS conductors ageing effect on sag and tension in order to highlight the benefits and risks that could result from existing creep mitigation methods particularly on HTLS conductors. The study aims to identify the impact of important design factors such as ice loading and emergency operation events and their frequency of occurrence on creep mitigation as well as to highlight the creep variation of the same materials used particularly on different HTLS conductors. The analysis presented here indicates that pre-tensioning could be more beneficial on soft aluminium HTLS conductors while over-tensioning can result in extensive durations of conductor over-stressing on steel supported and Gap-type conductors. Furthermore, the conductor technology majorly affects the creep of steel core which cannot be considered always as zero. The accuracy of the methodology is also re-validated using recent experimental data from Gap conductor.

Transmission congestion is one of the most challenging issues in operation of deregulated electricity markets of today. This study investigates into benefit of unified power flow controller (UPFC) as a viable solution to the problem of congestion management. A comprehensive load flow model for the UPFC is presented which has the capability to control active and reactive powers and voltage magnitude simultaneously. This study discusses about two different approaches for determination of suitable location of UPFC. One of them is sensitivity-based approach and the other is pricing-based method. Reduction in total system losses has been taken as objective in sensitivity-based approach. Furthermore, sensitivity of total system losses with respect to control parameters of UPFC have been evaluated using two different methods. A pricing-based approach which makes use of locational marginal price difference and congestion rent for determination of suitable location of UPFC. Minimisation of cost of rescheduling subjected to system operating constraints is the objective to be met for congestion management. Interior point method, a mathematical tool for non-linear optimisation, is used to obtain the solution of above-mentioned problem.

The increasing integration of renewables into the grid based on power electronics converters interfaces is affecting the power systems dynamics, requiring effective monitoring and visualisation to provide appropriate assessment during extreme events. The coherent group identification in power systems is of importance for dynamic studies and transmission capability improvement. This study analyses the coherency based on the mode shapes, the application of the Koopman mode analysis (KMA) and a Prony analysis (PA) on-line variation for the identification of coherent groups in power systems. KMA and PA use the voltage angle measurements obtained from simulation. The clustering of the coherent groups are evaluated in two test systems. The coherency methods are also evaluated taking into account the impact of a large gradual scale inclusion of non-synchronous generation under different penetration level cases. From the comparison and visualisation of the different methods it is possible to observe the impact of the large inclusion of non-synchronous generation on the coherency.

By researching models of hybrid cable-overhead multiple branch distribution lines with distributed generators, a novel fault location method is proposed which combines binary particle swarm optimisation (BPSO) and a genetic algorithm. These two methods are mixed using a double population evolution strategy and information sharing technology. The proposed fault location method consists of section line location and distance detection. On the basis of the mutation direction differences of the transient zero sequence current and voltage of each section line when a fault occurs, the authors propose a new coding criterion and method capable of section line location. Distance detection equations are built through double-end steady-state positive sequence voltage distribution regulations along the transmission lines and are then solved by the proposed hybrid BPSO genetic algorithm. Through simulation and experiment, the proposed hybrid algorithm is shown to have good performance. The effectiveness of the proposed fault location method is proven to be accurate and reliable and it is insensitive to impact factors such as fault distance, fault angle, and ground resistance.

The independent system operators (ISOs) usually offer financial transmission right (FTR) as a financial instrument for electricity market participants to hedge against the transmission congestion cost. Meanwhile, the development of demand response (DR) provides load serving entities (LSEs) opportunities to perform coupon based demand response (CBDR) programs, and thus LSEs can behave as strategic bidders in the whole-sale market by adjusting its demand level. In the existing approaches for modelling CBDR, the potential impact of FTR which leads LSEs to obtain the congestion compensation under a high load level is overlooked. Therefore, this study proposes a comprehensive strategic CBDR model in which the LSE's profit is maximised by providing CBDR to customers and the congestion compensation from the LSE bidder's FTR holding is also considered. The proposed model is formulated as a bi-level optimisation problem with the LSE's net revenue maximisation as the upper level and the ISO's economic dispatch considering wind power uncertainty as the lower level problem. The bi-level model is addressed with mathematic program with equilibrium constraints technique and mixed-integer linear programming, which can be solved using available optimisation software tools. In addition, the case studies of an illustrative two bus system, the PJM 5-bus system, and IEEE 39-bus system verify the proposed method.

This study presents a robust method for detecting the location of fault in the wide-area power networks considering the limited number of synchronised phasor measurement units. In this manner, by employing the positive-sequence components in the governing equations at pre- and post-fault occurrence, the fault location (FL) problem is formulated as an optimisation problem. The constructed objective function consists of two terms that are dependent on the voltage and current changes so that each of them can be employed in the optimisation procedure, alone. Various factors, such as cyber attacks and measurement device failures, may lead to induce the bad data to the measurement set, and thus the results will not be valid. Automatic detection and elimination of erroneous measurements, contaminated with gross errors, from the measurement set, will be carried out utilising the least absolute value (LAV) estimator. This is the most important property of the LAV estimator, in which the bad measurements will be screened and suppressed during the iterative optimisation. An algorithm based on LAV estimation is presented to identify the FL. The efficiency of the proposed method is not affected by fault type and resistance. The method is tested on IEEE 14-bus, 57-bus and 118-bus case studies and simulation results indicate the accuracy of the developed technique.

This study discusses the implementation of a fully decentralised optimisation for the multi-area dynamic economic dispatch of large-scale power systems based on the cutting plane consensus (CPC) algorithm. Each area constructs a local master problem to approximate the original problem by generating its own cutting planes and receiving cutting planes from other areas, hence an upper-level coordinator is not required. Two modifications of the standard CPC algorithm have been developed. First, only the newest cutting planes are transmitted among different areas to reduce the amount of information transferred. Second, to reduce the required number of iterations, a cutting plane is deleted only if it is inactive over consecutive iterations. Theoretically, the convergence and correctness of this algorithm can be guaranteed for power systems with a wide range of scales without tuning the optimisation parameters, and a high-quality suboptimal solution can still be obtained if the algorithm is prematurely terminated. The proposed method is applied to simulations of a three-area IEEE Reliability Test System and an actual four-area 2298-bus provincial power system to demonstrate its effectiveness.

The accuracy of switching overvoltage measuring system is significantly affected by the input impedance of oscilloscope. First, the principle of switching overvoltage is presented, followed by a brief introduction to the structure of measuring system. Using the laplace transform, the transfer function of the measuring system is then derived. Its frequency response, ranging from DC to 1 GHz, is investigated in detail. The influences of the input impedance on the amplitude and phase angle responses are clearly revealed. Two typical cases, i.e. unit step response and sinusoidal step response, are also considered in the study. To validate the above analysis, a series of experiments has been performed at a substation. Both the theoretical analysis and the experimental results indicate that the input impedance affects the accuracy of switching overvoltage measuring system significantly. In the case that the impedance is rather small, the voltage waveform displayed on oscilloscope would be considerably distorted from the one stressed on the line. The impedance should be greater than 10⁷ Ω to satisfy the accuracy requirement. On the other hand, it can be also used as a direct indicator to assess the performance of oscilloscope.

The electrical characteristics of ice-covered insulators in coexisting conditions of high altitude, icing and pollution are a basis for external insulation selection of transmission lines in icing regions. Ice accretion on insulators has been studied for decades, while few studies focus on the flashover performance of ice-covered insulators polluted by two types of contamination, that is the solid layer method and icing water conductivity method, simultaneously. On the basis of the investigations on DC flashover performance of ice-covered insulators in the artificial climate chamber, the influence of different parameters, such as insulator string length, icing water conductivity, salt deposit density as well as atmospheric pressure on DC icing flashover voltage of insulator strings is studied. According to the experimental results, the relationships between the flashover voltage and each of such factors are determined and analysed. Moreover, the correction formula for DC flashover voltage of ice-covered insulators in complex ambient conditions is proposed.

Energy loss represents a traditional key objective in the optimal operation and planning of electrical networks, and various estimation methods have been studied. In this study, two formulas are proposed for calculation of the loss factor (LSF) to improve the classical LSF method based on the minimum load factor (MLF) and the LF. The former is an approximate formula, whose accuracy is good enough for engineering calculations. While the latter is an empirical quadratic equation determined by the statistical analysis, which is more accurate to estimate losses. To conduct a complete feasibility study for project practices, a large amount of measurement data is used to calculate energy losses in a district of Guangdong using the classical LSF method and the improved LSF (ILSF) method. Results of statistical analyses indicate that the real data fall in the proposed three-dimensional region and the use of MLF can help improve accuracy in the energy losses estimation. The classical and ILSF methods are used to estimate the effect in loss reduction by inserting a distributed generation in a 43-bus distribution network, and the candidate bus can be identified effectively.

This study presents a novel differential protection algorithm (DPA) for power transformer using chirplet transform (ChT). The proposed method combines the features of biased restraint characteristic (BRC) of the conventional differential relay and out-turn of ChT in a two-stage algorithm. In the first stage, the BRC plane is divided into three zones: namely, high-set (HS), non-trip and vulnerable zones. The tripping decisions are carried out in the first two zones based on differential and biased current. However, if the operating condition of the power transformer falls in the vulnerable zone, then there is an ambiguity in discriminating internal fault, inrush current and current transformer saturation cases. Therefore, in the second stage, ChT is applied to differential current signal to obtain an energy distribution on the time-frequency plane with respect to time, frequency and chirp rate. Then, using the mean and standard deviation of the normalised energy, power transformer operating conditions are classified. Also, most of the DPAs available in the literature are system dependent. However, the proposed novel DPA can be effectively used for any system. The proposed scheme is validated for two power transformer systems using PSCAD to simulate various operating conditions and MATLAB to implement the algorithm.

The increasing requirements for improved reliability of electrical power devices and optimisation of dielectric insulation design means that the analysis of impact due to overvoltages is of high importance. This analysis should also consider propagation of overvoltages transferred through power transformer windings to other parts of the electrical network. Hazard levels of overvoltages affected the insulation systems of electrical devices are determined by wave propagation conditions of overvoltages as well as the protection level of applied overvoltages protection. The analysis of overvoltages transferred to low voltage networks is very important due to the increasing number of electrical devices and electronic apparatus with low resistance to overvoltages. This study presents a detailed analysis of the propagation of overvoltages transferred through distribution transformer windings, in typical medium and low-voltage electrical networks. The analysis is based on simulation results carried out by the use of electromagnetic transients program–alternative transients program (EMTP–ATP). A high-frequency model for transformers done on the basis of frequency characteristics of admittance measurements was used in simulations. Detailed analysis of influence of length of medium- and low-voltage lines connected to the distribution transformers and metal oxide surge arresters on switching overvoltages transferred to low-voltage networks are presented in the study.

Investigating optimal value of the power factor for the optimally allocated and sized solar parking lots of the plug-in electric vehicles (PEVs) based on minimum total cost of the problem over the given planning period is the aim of this study. Covering a parking lot with photovoltaic (PV) panels can keep the PEVs cool, charge their batteries for free, and generate extra energy and deliver it to the grid. Moreover, the inverter installed in the charging station of a parking lot is capable of generating or absorbing reactive power by changing the operating mode of the inverter without any degradation of the PEV’s battery. Therefore, the PEVs and the solar parking lots can be applied as the auxiliary sources of active and reactive powers by the local distribution company (DISCO). In this study, in order to achieve realistic results, the economic aspects and technical factors of the system, and also the behavioural model of the PEVs fleet are taken into consideration in the planning problem. Moreover, the stochastic nature of the PEVs behaviour and power of the installed PV panels are modelled in the problem. Herein, the planning problem is solved applying quantum annealing (QA).

Considering system uncertainties prevailing in the restructured power system, congestion management (CM) is a vital issue in power system operation and control. The objective of CM is to remove congestion in the lines while satisfying all the constraints with minimum congestion cost. This study proposes a generation rescheduling-based approach for CM in electricity market using a novel ant lion optimiser (ALO) algorithm. ALO is a recently developed the nature-inspired algorithm based on the hunting mechanism of antlions. The effectiveness of the proposed approach is tested on modified IEEE 30-bus, modified IEEE 57-bus and IEEE 118-bus test systems. The security constraints like load bus voltage and line loading impact are incorporated in this study. To prove the validity of the proposed technique, the obtained results are compared to the results offered by various recent optimisation algorithms. The results show that the proposed ALO algorithm outperforms the other comparative algorithms. The proposed approach uses less number of fitness function evaluations, not traps into local minima and offers promising convergence characteristic. The proposed approach will ease the system operator to remove the contingency rapidly for secured and reliable operation of the power system under deregulated environment.