Maclaurin–Newton algorithms in 132 kV subtransmission security simulations

This paper examines how applicable approximate Jacobian inversions are when implemented in the security analysis simulations of 132 kV power subtransmission. The complete Scottish 400/275/132 kV power transmission network was simulated, including the 132 kV subtransmission network with its high r/x ratios. Both the coupled and decoupled Maclaurin–Newton load flow algorithms were tested. It was proved that high r/x ratios found in the 132 kV level, five times higher than in 400/275 kV, have an important influence on convergence and accuracy of the inversion Jacobian load flow algorithms. It was found that the decoupled inversion load flow was applicable for 132 kV, it converged regularly, but had worse convergence and accuracy characteristics, compared to 400/275 kV applications, while the coupled inversion load flow was not applicable at all for 132 kV, it always diverged.     

An online power system static security assessment module using multi-layer perceptron and radial basis function network

Efficient contingency screening and ranking method has gained importance in modern power systems for its secure operation. This paper proposes two artificial neural networks namely multi-layer feed forward neural network (MFNN) and radial basis function network (RBFN) to realize the online power system static security assessment (PSSSA) module. To assess the severity of the system, two indices have been used, namely active power performance index and voltage performance index, which are computed using Newton–Raphson load flow (NRLF) analysis for variable loading conditions under N − 1 line outage contingencies. The proposed MFNN and RBFN models based PSSSA module, are fed with power system operating states, load conditions and N − 1 line outage contingencies as input features to train the neural network models, to predict the performance indices for unseen network conditions and rank them in descending order based on performance indices for security assessment. The proposed approaches are tested on standard IEEE 30-bus test system, where the simulation results prove its performance and robustness for power system static security assessment. The comparison of severity obtained by the neural network models and the NRLF analysis in terms of time and accuracy, signifies that the proposed model is quick, accurate and robust for power system static security evaluation for unseen network conditions. Thus, the proposed PSSSA module implemented using MFNN and RBFN models are found to be feasible for online implementation.     

Model of distribution system total supply capability considering feeder and substation transformer contingencies

This paper proposes a model for calculating the total supply capability (TSC) for distribution system considering both feeder and substation transformer contingencies. Existing models and methods for TSC only consider substation transformer contingencies and ignore feeder contingencies. However, the feeder contingencies occur much more frequently than substation transformer contingencies in practice. Moreover, some operation state fail the feeder contingencies N − 1 verification even they pass the transformer contingencies N − 1 verification. In this paper, a TSC model is firstly proposed in which feeder and transformer N − 1 contingencies are fully considered. This model is designed in feeder level, which means the topology of interconnection among feeders is accurately modeled. Secondly, a supplementary model for load balancing is set up for a better load distribution solution on feeders and transformers at TSC loading. Finally, the method is tested in a test distribution system and a real partial distribution network and the results are verified by the traditional N − 1 simulation.     

Automatic generation control of a multi-area system using ant lion optimizer algorithm based PID plus second order derivative controller

This article presents the automatic generation control of an unequal three area thermal system. Single stage reheat turbines and generation rate constraints of 3%/min are considered in each control area. Controllers such as Integral (I), Proportional – Integral (PI), Proportional – Integral – Derivative (PID), and Proportional – Integral – Derivative Plus Second Order Derivative (PID + DD) are treated as secondary controllers separately. A nature inspired optimization technique called Ant Lion Optimizer (ALO) algorithm is used for simultaneous optimization of the controller gains. Comparison of dynamic responses of frequencies and tie line powers corresponding to ALO optimized I, PI, PID and PID + DD controller reveal the better performance of PID + DD controller in terms of lesser settling time, peak overshoots as well as reduced oscillations. Robustness of the optimum gains of best controller obtained at nominal conditions is evaluated using sensitivity analysis. Analysis exposed that the optimum PID + DD controller gains obtained at nominal are robust and not necessary to reset again for changes in loading, parameter like inertia constant (H), size and position of disturbance. Furthermore, the performance of PID + DD controller is found better as compared to PID controller against random loading pattern condition.     

Transmission congestion management in bilateral markets: An interruptible load auction solution

This paper demonstrates that appropriate invocation of interruptible loads by the independent system operator (ISO) can aid in relieving transmission congestion in power systems. An auction model is proposed, for an ISO operating in a bilateral contract dominated market, for real-time selection of interruptible load offers while satisfying the congestion management objective. The proposed congestion management scheme using interruptible loads can specifically identify load buses where corrective measures are needed for relieving congestion on a particular transmission corridor. The N − 1 contingency criterion has been taken into account to simulate various cases, and hence, examine the effectiveness of the proposed method. It has been shown that the method can assist the ISO to remove the overload from lines in both normal and contingency conditions in an optimal manner.     

Effect of varying concentration and temperature on steady and dynamic parameters of low concentration photovoltaic energy system

Low-concentration photovoltaic (LCPV) system has huge potential for further cost reduction of solar photovoltaic (PV) power as compared to flat panel PV. The dependence of steady state and dynamic parameters on concentration and temperature is crucial to extract maximum power from solar photovoltaic system. This article aims to present the effect of varying concentration and temperature on steady state and dynamic parameters of LCPV system under actual test conditions (ATC). The rate of change in I_SC with solar irradiation i.e., dI_SC/dG is found as 0.25 A/W assuming ≈±1 °C change in module temperature. The effect of temperature on inherent material properties responsible for photo-conversion efficiency is studied using impedance spectroscopy technique. A linear response of series resistance of LCPV module is observed with respect to change in module temperature, i.e. dR_S/dT from 297 to 333 K is in the range of 1.15–1.20 Ω with a rate of 1 mΩ/K. From real-time analysis of LCPV system open-circuit voltage found decreasing from 21 to 20.6 V with temperature coefficient of voltage ≈−0.061 V/K. The dynamic resistance has a positive coefficient of module temperature i.e., dr_d/dT given by 0.49 Ω/K.     

Evaluation and measurement of magnetic field exposure over human body near EHV transmission lines

Power frequency (50/60 Hz) magnetic field exposure still draws the attention of many researchers worldwide to investigate its harmful effects on living bodies. In light of this attention, as the population increases, the overlap between the power transmission lines and the settlement areas causes a problem (as in the case of exposure in random, residential, commercial and other areas, which lie very near or under the power transmission lines). In this paper, the power frequency magnetic fields, over a human body, at different positions, near extra high voltage (EHV) transmission lines are demonstrated, both analytically and practically. For the analytical part, the human body is approximately simulated as a parallelepiped. Two different positions for a human are selected near 500 and 220 kV power transmission lines. The magnetic field intensity along the vertical center line of the human is calculated. The effects of two different line configurations (for 220 and 500 kV power systems) and human positions, with respect to the transmission line, are considered. The paper also presents the actual practical magnetic field values measured near actual power transmission lines (220 and 500 kV) using a magnetic field measuring instrument. These transmission lines represent parts of the transmission network of the Egyptian united power system, near Cairo and El-Asher of Ramadan, under the actual loads. The results obtained, from the analytical studies and practical measurements, are compared with the international standards of the magnetic field exposures.     

Particle swarm optimization algorithm for capacitor allocation problem in distribution systems with wind turbine generators

This paper aims at adopting the Particle Swarm Optimization (PSO) technique to find the near-optimal solutions for the capacitor allocation problem in distribution systems for the modified IEEE 16-bus distribution system connected to wind energy generation based on a cost function. The proper allocation and the optimized number of capacitors have led to adequate power losses reduction and voltage profile enhancement. Because of the wind power generation variations due to the nature of wind speed intermittency and the lack of reactive power compensation, the problem under study have been presented involving a nonlinear fitness function. In order to solve it, the corresponding mathematical tools have to be used. The formulated fitness cost function has consisted of four terms: cost of real power loss, capacitor installation cost, voltage constraint penalty, and capacitor constraint penalty. PSO technique has been used to obtain the near-optimum solution to the proposed problem. Simulation results demonstrate the efficiency of the proposed fitness cost function when applied to the system under study. Furthermore, the application of PSO to the modified IEEE 16-bus system has shown better results in terms of power losses cost and voltage profile enhancement compared to Genetic Algorithm (GA). In order to verify the successful adaptation of PSO toward attaining adequate near-optimal capacitor allocations in distribution systems, this metaheuristic technique has been employed to the large-scale IEEE 30-bus system. The proposed PSO technique has provided adequate results while modifying the objective function and constraints to include the power factor and transmission line capacities for normal and contingency (N-1) operating conditions.     

Arc characteristics and a single-pole auto-reclosure scheme for Alexandria HV transmission system

Arcing faults are the most common faults that occur in the 220 kV transmission line national grid of Egypt, in the vicinity of ‘Alexandria’ city. This part of the network also feeds a large industrial load in the form of steel works, which injects a large amount of harmonics into the network. In this paper, the performance of this 220 kV TL network during arcing faults is studied with the aid of the PSCAD/EMTDC program together with a specially designed arcing fault custom model incorporated in the program. Several arcing faults are simulated, and the effect of harmonics on the fault current and secondary arc duration time is demonstrated. Based upon the simulation results, recommendations regarding single-pole autoreclosing and arc suppression methods are suggested.     

System wide MV distribution network technical losses estimation based on reference feeder and energy flow model

This paper presents an integrated analytical approach to estimate technical losses (TL) of medium voltage (MV) distribution network. The concept of energy flow in a radial MV distribution network is modelled using representative feeders (RF) characterized by feeder peak power demand, feeder length, load distribution, and load factor to develop the generic analytical TL equations. The TL estimation approach is applied to typical utility MV distribution network equipped with energy meters at transmission/distribution interface substation (TDIS) which register monthly inflow energy and peak power demand to the distribution networks. Additional input parameters for the TL estimation are from the feeder ammeters of the outgoing primary and secondary MV feeders. The developed models have been demonstrated through case study performed on a utility MV distribution network supplied from grid source through a TDIS with a registered total maximum demand of 44.9 MW, connected to four (4) 33 kV feeders, four (4) 33/11 kV 30 MVA transformers, and twelve (12) 11 kV feeders. The result shows close agreement with TL provided by the local power utility company. With RF, the approach could be extended and applied to estimate TL of any radial MV distribution network of different sizes and demography.     

Methods used for evaluation of actual power generating thermal cycles and comparing them

In this study, thermodynamic optimization criteria used for assessing thermal engines are investigated and compared. The Purpose of this is to determine the most advantageous criteria. An irreversible Carnot cycle is analyzed by using five different methods and results are compared. According to calculations, the ecological function criterion (ECF) is defined as the most convenient optimization method. Although, its work output is less than the maximum work criteria and maximum available work (MAW), it has advantageous in terms of entropy generation and first law efficiency. In addition, ecological coefficient of performance (ECOP) and exergetic performance criteria (EPC) values provide minimum entropy generation and maximum efficiency at their maximum, however, their work output is very small. ECF obtains its maximum values at x = 0.488 (377.175 kW) for endoreversible cycle and at x = 0.477 (329.812 kW) for irreversible cycle. For these reasons, ECF is suggested as the best optimization criteria.     

Optimal design of a robust discrete parallel FP + FI + FD controller for the Automatic Voltage Regulator system

The purpose of this paper is to design a good tracking controller for the generator Automatic Voltage Regulator (AVR) system. A fuzzy logic-based controller that is called Fuzzy P + Fuzzy I + Fuzzy D (FP + FI + FD) controller has been designed optimally and applied to AVR system. In the proposed method, optimal tuning of controller parameters is very important to achieve the desired level of robust performance. Thus, a hybrid of Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) (HGAPSO) technique has been used to find a better fuzzy system control. The motivation for using this hybrid method is to increase disturbance rejection effort, reduce fuzzy system efforts and take large parametric uncertainties into account. The developed FP + FI + FD control strategy leads to a flexible controller with simple structure that is easy to implement. The simulation results have been compared with the conventional Proportional–Integral–Derivative (PID) and fuzzy PID controllers. Three cases of simulation have been performed, case 1: comparing the tracking capability of the controllers, case 2: comparing the disturbance rejection capability of the controller and case 3: evaluating the performance of the controllers assuming that amplifier and exciter system parameters have 50% uncertainty. The simulation results shows that the proposed parallel FP + FI + FD controller has good performance from the perspective of overshoot/undershoot, settling time, and rise time in comparison with both conventional and fuzzy PID controllers.     

Multi-objective optimization operation with corrective control actions for meshed AC/DC grids including multi-terminal VSC-HVDC

This paper presents a multi-objective optimal operation of meshed AC/DC power grids including multi-terminal voltage-source-converter-based high-voltage direct current (VSC-MTDC) systems. The proposed approach is modeled as a corrective security-constrained optimal power flow (CSC-OPF) problem, with the minimization of both the operation cost and power loss as the objectives. Moreover, it provides a cost-effective solution to assist in decision-making, and improves the system security during operation. The N − 1 contingency security criterion is enforced for both AC and DC transmission networks, and corrective control is used to eliminate or alleviate post-contingency security violations. The corrective control actions used in this paper include not only secure operation control actions, but also economical post-contingency corrective control of the multi-terminal VSC-HVDC. To increase the computation speed, a contingency screening technique is applied to CSC-OPF by efficiently selecting the most severe case of the N − 1 contingency, as obtained using a voltage security index (VSI). The proposed approach uses the non-dominated sorting genetic algorithm (NSGA-II) to find multi-objective OPF solutions by checking the post-contingency state feasibility while taking into account post-contingency corrective actions. Simulation results confirm the validity and effectiveness of this approach.     

Distributed generation planning using differential evolution accounting voltage stability consideration

This paper describes a technique for selection of buses in a sub transmission system for location of distributed generation (DG) and determination of their optimum capacities by minimizing transmission losses. The buses have been selected based on incremental voltage (dV/dP) sensitivities. Line flow constraints have been accounted. Type-3 DG i.e. wind turbine along with induction generator has been considered for the study. Differential evolution (DE) has been used to evaluate the optimum DG capacity and results have been compared with those obtained using bare bones particle swarm optimization (BBPSO) and multi-membered non-recombinative (μ + λ) evolution strategy (MMNRES). The developed algorithms have been implemented on standard 6-bus and 30-bus test systems.     

Energy management strategy for fuel cell/battery/ultracapacitor hybrid vehicle based on fuzzy logic

In order to enhance the fuel economy of hybrid vehicle and increase the mileage of continuation of journey, a fuzzy logic control is utilized to design energy management strategies for fuel cell/battery (FC + B) hybrid vehicle and fuel cell/battery/ultra-capacitor (FC + B + UC) hybrid vehicle. The models of hybrid vehicle for FC + B and FC + B + UC structure are developed by electric vehicle simulation software ADVISOR which uses a hybrid backward/forward approach. The results demonstrate that the proposed control strategy can satisfy the power requirement for four standard driving cycles and achieve the power distribution among various power sources. The comprehensive comparisons with the power tracking control strategy which is wide adopted in ADVISOR verify that the proposed control strategy has better rationality and validity in terms of fuel economy and dynamic property in four standard driving cycles. Therefore, the proposed strategy will provide a novel approach for the advanced energy management system of hybrid vehicle.     

Security-constrained transmission expansion planning: A stochastic multi-objective approach

This article presents a stochastic multi-objective optimization framework for transmission expansion planning (TEP) with steady state voltage security management, using AC optimal power flow (AC-OPF). The objectives are to minimize the sum of transmission investment costs (ICs), minimize the Expected Operation Cost (EOC), minimize the Expected Load Shedding Cost (ELSC) and maximize the Expected Loading Factor (ELF). The system load uncertainty has been considered and the corresponding scenarios are generated employing the Monte Carlo (MC) simulations. A scenario reduction technique is applied to reduce the number of scenarios. A multi-objective mathematical programming (MMP) is formulated and the ε-constraint method is used to solve the formulated problem. The N − 1 contingency analysis is also considered for the proposed TEP problem.The proposed TEP model has been applied to the well-known IEEE 24-bus Reliability Test System. The detailed results of the case study are presented and thoroughly analyzed. The obtained TEP results show the efficiency of the proposed algorithm.     

Optimization models based on GM (1, 1) and seasonal fluctuation for electricity demand forecasting

In this paper, a novel combined approach which combines the first-order one-variable gray differential equation (GM (1, 1)) model derived from gray system theory and seasonal fluctuation from time series method (SFGM (1, 1)) is proposed. This combined model not only takes advantage of the high predictable power of GM (1, 1) model but also the prediction power of time series method. To improve the forecasting accuracy, an adaptive parameter learning mechanism is applied to SFGM (1, 1) model to develop a new model named APL-SFGM (1, 1). As an example, the statistical electricity demand data from 2002 to 2011 sampled from South Australia of Australia are used to validate the effectiveness of the two proposed models. Simulation and graphic results indicated that both of two proposed models achieve better performance than the original GM (1, 1) model. In addition, the APL-SFGM (1, 1) model, which is actually an adaptive adjustment model, obtains a higher forecasting accuracy as compared to the SFGM (1, 1) model.     

Backflashover simulation of HV transmission lines with concentrated tower grounding

For high voltage (HV) transmission lines (TLs) the backflashover phenomenon can occur when lightning strikes a tower or a shield wire (SW). In this paper, the backflashover phenomenon of typical HV-TLs has been studied. The simulation code, based on ATP/EMTP program, accounts for both the discharge process between the arcing horns of insulator strings, by means of a leader progression model and the non-linear transient behaviour of tower grounding systems consisting of vertical rod(s). The lightning current ranges, causing back flash in a 161 kV-50 Hz single circuit line with two grounded SWs, have been investigated in detail. Numerical results of the investigations are in good agreement with actual behavior of the studied TL.     

Application of wavelet multiresolution analysis for identification and classification of faults on transmission lines

This paper presents a new method for identification and classification of faults based on wavelet multiresolution analysis (MRA). Daubechies eight (D-8) wavelet transforms of the three phase currents on a transmission line fed from both ends are used. The peak absolute value, the mean of the peak absolute values and summation of the 3rd level output of MRA detail signals of current in each phase extracted from the original signals are used as the criterion for the analysis. The effects of fault distance, fault inception angle and fault impedance are also examined. Extensive simulations are carried out to generate time domain input signal using EMTP (Microtran) on a 230 kV, 200 km long line fed from both ends and simulation results show that the proposed method is a simple, effective and robust method suitable for high impedance faults also.     

Experimental analysis and optimization of key parameters of ZVS mode and its application in the proposed LLC converter designed for distributed power system application

This paper deals with experimental analysis of zero-voltage switching mode targeting high-frequency operation of chosen MOSFET type. After selection of specific type of transistor (IPW60R165CP) the experimental investigation has been made by changing parameters (e.g. dead-time, auxiliary capacitance of MOSFET, transistor current), that are influencing the ZVS commutation process. For these purposes we constructed the universal testing device, which is capable to secure realistic conditions of various types of commutation modes (hard switching, zero-voltage switching, zero-current switching). Afterwards the best settings of commutation mode have been utilized in proposed LLC converter suited for distributed power system application. Prototype is operating in ZVS region with optimized parameters. Switching frequency is from 130 kHz (input voltage 325 Vdc) to 210 kHz (input voltage 415 Vdc) with the output power of 1500 W. It is clear from the results that experimental analysis of the ZVS commutation mode brings expectation of transistor behavior which was totally confirmed also in the case of experimental analysis of LLC resonant converter.