Journal of Operation and Automation in Power Engineering
http://joape.uma.ac.ir/
Journal of Operation and Automation in Power Engineeringendaily1Mon, 01 Aug 2022 00:00:00 +0430Mon, 01 Aug 2022 00:00:00 +0430Risk Averse Optimal Operation of Coastal Energy Hub Considering Seawater Desalination and Energy Storage Systems
http://joape.uma.ac.ir/article_1189.html
An optimal day-ahead operation of a microgrid based on coastal energy hub is presented in this paper. The proposed CEH included wind turbine, photovoltaic unit, combined cooling, heat and power, and seawater desalination. The purpose of the optimization is minimization of the operational and environmental costs considering several technical limitations. The CEH includes an ice storage conditioner together with an energy storage system, i.e. thermal energy storage system. Particularly, the impacts of an innovative rechargeable and emerging ESS that is solar-powered compressed air energy storage is scrutinized, on the efficiency and operational and pollution costs of the CEH. It is clear that there is an intrinsic deviation between predicted and actual uncertainty variables in MG. This paper presents a bi-level stochastic optimal operation model based on risk averse strategy of information gap decision theory to overcome this information gap and to help Microgrid operator. To reduce the complexity of the proposed model, Karush-Kuhn-Tucker method is used for converting the bi-level problem into a single level. The Augmented Epsilon Constraint method is used to deals with multi objective optimization problem to harvest the maximum horizon of the uncertainties of the parameters. The proposed model implemented the Time of Use program as a price-based demand response program. Finally, the efficacy of the SPCAES for minimizing the operational cost and pollutions in the day-ahead operation is depicted by implementation of the presented model on the typical CEH.A Deep Learning-Based Approach for Comprehensive Rotor Angle Stability Assessment
http://joape.uma.ac.ir/article_1210.html
Unlike other rotor angle stability assessment methods which only deal with either transient or small-signal (SS) stability, in this paper, a new stability prediction approach has been proposed which considers both transient and SS stability status. Therefore, the proposed method, which utilizes Multi-Layer Perceptron-based deep learning model, can comprehensively predict the post-disturbance rotor angle stability. Since the proposed method uses the voltage of the generating units directly measured by WAMS in the early moments after the disturbance occurrence and does not need to calculate the generators' rotor angle (which requires a high computational burden), it can timely predict the stability stiffness using data provided by PMUs installed at generators' buses. In this respect, this method provides a proper chance for the system operators to take appropriate corrective measures. To evaluate the proposed method's efficiency, it has been implemented and tested on IEEE14-bus and IEEE 39-bus test systems. The dynamic simulation results show that although the proposed method requires fewer PMUs than previous methods that exist in the literature, it can timely evaluate the stability status. Also, to properly show the power system stability stiffness from the transient and SS stability point of view, the suggested method accurately classifies the post-disturbance operating point into Unstable, Alarm, or Normal categories.Stochastic Simultaneous Planning of Interruptible Loads, Renewable Generations and Capacitors in Distribution Network
http://joape.uma.ac.ir/article_1217.html
Executing interruptible loads (ILs) can be significantly effective for optimal and secure operation of power systems. These ILs can aid the operators not only to increase the reliability of the power supply but also to reduce the procurement costs of the whole system. Therefore, determining the optimal location and capacity of ILs for a given incentive rate is of great interest to distribution companies. To do so, in this paper simultaneous allocation and sizing of ILs, wind turbines (WT), photovoltaic (PV) and capacitors have been done in the radial distribution network for different demand levels and subsequently the optimal value of compensation price for the ILs has been determined. Given the probabilistic nature of load, wind and solar generation as well as the price of energy at the pool, we have also proposed a stochastic model based on fuzzy decision making for modelling the technical constraints of the problem under uncertainty. The objective functions are technical constraint dissatisfaction, the total operating costs of the Distribution Company and CO2 emissions which are minimized by NSGA2. To model the uncertainties, a scenario-based method is used and then by using a scenario reduction method the number of scenarios is reduced to a certain number. The performance of the proposed method is assessed on the IEEE 33-node test feeder to verify the applicability and effectiveness of the method.Optimal Coordination of Directional Overcurrent Relays for Microgrids Using Hybrid Interval Linear Programming - Differential Evolution
http://joape.uma.ac.ir/article_1286.html
The relay coordination problem of directional overcurrent has&nbsp; been an&nbsp; active research issue in distribution networks and power transmission. In general, the problem of relay coordination is the nonlinearity of the optimization problem, which increases or decreases with different network structures. This paper presents a new method with directional overcurrent relay coordination approach to reduce the operating time of the relays between the primary and backup relays by using hybrid&nbsp; programming&nbsp; of&nbsp; ILP&nbsp; (interval&nbsp; linear&nbsp; programming)&nbsp; and&nbsp; DE (differential&nbsp; evolution). &nbsp;Due to the difference in short circuit current level from grid connected to the isolated mode, therefore, it is necessary to use a reliable protection solution to reduce this discrimination time and also to prevent the increase of coordination time interval (CTI). The ability of the objective function used in this paper is to reduce the discrimination time of primary and backup relays and simultaneously reduce the operating time of primary and backup relays by introducing a new method. The basic parameters of the directional&nbsp; overcurrent&nbsp; relay&nbsp; (DOCR)&nbsp; such&nbsp; as&nbsp; time&nbsp; multiplier&nbsp; setting&nbsp; (TMS)&nbsp; and&nbsp; plug&nbsp; setting&nbsp; (PS)&nbsp; have been adjusted&nbsp; such&nbsp; that&nbsp; the relays&nbsp; operation&nbsp; time&nbsp; should&nbsp; be&nbsp; optimized.&nbsp; Optimization&nbsp; is&nbsp; based&nbsp; on&nbsp; a&nbsp; new objective function,&nbsp; described&nbsp; as&nbsp; a&nbsp; highly&nbsp; constrained&nbsp; non-linear&nbsp; problem&nbsp; to&nbsp; simultaneously&nbsp; minimize&nbsp; operating&nbsp; time&nbsp; in backup&nbsp; and&nbsp; primary&nbsp; relays.&nbsp; A&nbsp; function&nbsp; of&nbsp; penalty&nbsp; is&nbsp; also&nbsp; used&nbsp; to&nbsp; check&nbsp; the&nbsp; problem&nbsp; constraints&nbsp; in&nbsp; case&nbsp; the backup relay time is&nbsp; fewer&nbsp; than&nbsp; that of&nbsp; the main relay. The method is implemented on modified IEEE 14- and 30-bus distribution networks. The results demonstrate the efficiency of the method, and the values are optimal compared to those of other algorithms. MATLAB program has also been used to simulate optimization.Stable Operation and Current Sharing Control among Parallel Single-Phase Inverter Modules with Unequal Filter Impedances
http://joape.uma.ac.ir/article_1315.html
Parallel connection of two or even more single-phase inverter modules is a successful solution to increase the reliability and the efficiency of an inverter at moderate power levels. Stable operation and proper current sharing among parallel inverter modules is a key issue, especially when they are connected to a common load through unequal output filter impedances. In this paper, a new formulation and consequently a proper current sharing control algorithm for parallel connected inverter modules with the possibility of unequal filter impedances is proposed. Also a dual-loop voltage control with the filter current as the inner loop feedback signal, considering the effect of digital control delay, is adopted. The controller parameters are designed according to a frequency domain analysis. Finally, theoretical achievements are confirmed by experimental test results on a test rig with two 250 W parallel connected single phase inverters.A Low-Cost Multi-Sized HEVC Core Transform Using Time-Multiplexed DCT Architectures
http://joape.uma.ac.ir/article_1316.html
High Efficiency Video Coding (HEVC) is one of the latest coding standards targeting high-resolution video contents. Due to the high complexity of the existing hardware implementation, this paper presents the low-cost and efficient DCT architectures for HEVC, which are able to perform DCT operation of multiple transform sizes in a single unified architecture. Our objective is to reuse the hardware resources in a DCT architectures using configurable constant multipliers as well as reducing the hardware cost and trading off between hardware complexity and efficiency. We propose three different shift-and-add units with different hardware cost and throughput. The main advantage of the proposed architectures over the existing architectures is a lower hardware and it can also perform DCT transform of different transform units which is available in HEVC standard. The experimental results over 90-nm technology show that the proposed 2D-DCT architecture #1 archives the lowest hardware cost amongst the rest of the architectures with around 57% reduction in gate count, on average. The unfolded 2D-DCT architectures #2 and #3 offer the moderate reduction in gate count around 47%, on average, with a moderate throughput. Apart from architectures #1, #2, and #3, we also develop a reusable architecture by adding an extra ( )-point DCT alongside the main DCT.Vector Control Methods for Star-Connected Three-Phase Induction Motor Drives Under the Open-Phase Failure
http://joape.uma.ac.ir/article_1223.html
Reliability for electric motor drive systems is very vital in some industries. Selecting an appropriate control strategy for driving an electric motor during fault conditions is one of the most important issues mainly for safety-critical applications. Recently, vector control (VC) strategies have been extensively developed for star-connected three-phase induction motor drives during single-phase cut-off fault (COF) based on two different transformation matrices (TMs). Despite the effectiveness of these methods during the fault, these control systems are very complex due to their extensive on-line computation. This paper presents two simple methods based on indirect VC (IVC) and direct VC (DVC) methods for controlling a star-connected three-phase induction motor during the fault condition. The fault in this paper is limited to single-phase COF which can occur in motor stator coils. In this paper, it is shown that using a suitable TM and some changes in the control parameters, it is possible to control the faulted drive system. Performance of the proposed control methods is verified using MATLAB software and DSP/TMS320F28335 controller board for a 0.75kW star-connected three-phase induction motor drive system. The achieved results show the good performance of the introduced control systems in different operating conditions. In addition, the results demonstrate the performance of the proposed VC strategies and that of the previous works are almost the same. However, the proposed VC methods in this paper need less modification in the structure of the standard VC strategy than the previous works.Evaluation of Delays-based Stability of LFC Systems in the Presence of Electric Vehicles Aggregator
http://joape.uma.ac.ir/article_1224.html
In the integrated electrical systems, frequency control service considering the electric vehicle (EV) aggregators could lead to time-varying delay in load frequency control (LFC) schemes. These delays influence the LFC system efficiency, and in some situations, the lack of a clear choice of a control strategy considering the time-varying delays causes power system instability. Thus, this paper illustrates different time-varying delays based on the stability of an LFC system in the EV aggregators presence. The LFC's delay-dependent stability study is executed for finding the stability region and, stability criteria is suggested using the linear matrix inequality (LMI) method and Lyapunov-Krasovskii theory. Also, Wirtinger-based improved inequality and bounding lemma are applied to compute the greatest allowable delay in the LFC system, including the EV aggregators.Improving the Thermal and Electrical Properties of Transformer Oil Using Hybrid Nanofluid
http://joape.uma.ac.ir/article_1251.html
Improving the insulating and thermal properties of transformer oil is one of the factors in the use of nanoparticles (NPs) in oil. However, the use of NPs may only have a positive effect on some properties of the oil or even have a negative effect on the other properties of the oil. For this reason, hybrids nanofluid(HNF) were used to improve the properties of the transformer oil. By performing the Breakdown Voltage (BDV) test on different weight percentages (wt%) of TiO2 and CNT, it was proved that the best wt% for TiO2 is 0.0075 and for CNT is 0.001 to maximize the BDV. In this case, the HNF was able to improve the BDV and heat transfer by 9% and 8%, respectively. Another surprise that the HNF has been able to reduce the amount of C2H4 and C2H6 dissolved in oil by more than 70%. This reduction in the number of gases has another very desirable result and has reduced the PD by 63%. HNF proved that by using the right combination of different nanomaterials in transformer oil, more properties of the transformer oil can be improved.A New Fuzzy Direct Power Control of Doubly-Fed Induction Generator in a Wind Power System
http://joape.uma.ac.ir/article_1284.html
This paper presents a new fuzzy direct power control of double-fed induction generators (DFIG) in the wind power system. The most important issue in the application of DFIG generators is proper control of the active and reactive powers of these generators, which are generally carried out by vector control or direct torque/power control methods. Direct power control (DPC) directly controls the active and reactive powers of the stator, and stems from results from direct torque control. To use the vector control method, it is necessary to use conventional PI controllers the main disadvantage being the controller robustness due to the nonlinear behavior of the wind turbine and blade oscillations, and it is unavoidable that after a while, the controller's coefficients need to be updated. Therefore, the main purpose of this paper is to present a direct power control method based on fuzzy construction to overcome the mentioned problem. Simulation results of the proposed strategy are extracted under different performance conditions, and these results are compared with the conventional vector-oriented control method. These comprehensive results exhibit the effectiveness of the proposed fuzzy DPC method for the DFIGs based wind power systems.Design and Implementation of Multi-Source and Multi-Consumer Energy Sharing System in Collaborative Smart Microgrid Installation
http://joape.uma.ac.ir/article_1285.html
Many published studies debated electrical energy management. They mainly investigate the multi-source installation to develop energy efficiency during its different phases: production, distribution, and consumption. Although it is rarely discussed, energy sharing is a critical part of the energy management system. In this contribution, a demand-side management algorithm is developed, that incorporates energy consumption scheduler capacity. It provides optimal energy sharing, counting on suitable energy cost parameters and adequate multi-source installation. Using this proposal, the electrical bill decreases thanks to the optimal daily attribution of schedules to households formed by a multi-consumer microgrid. This application guarantees a maximal reduction of electrical cost for the set of energy partners as one prosumer used to consume and produce power. In addition, it maintains energy efficiency as it aids in avoiding breakdowns, and depressing the peak-to-average ratio. It admits that the utility company is, as usual, always reachable non-renewable source. At the same time, renewable energy was engendered by photovoltaic panels concomitant with wind turbines stations. The application is based on the JNET protocol stack. The proposed energy sharing algorithm is implemented by using Arduino board and JN5148 nodes as a star Wireless Sensors Network topology. It is installed as a prototype in the Digital Research Center of Sfax in Tunisia.&nbsp; This proposed incentive-based algorithm managed to reduce the smart microgrid annual cost by almost 55% without harming the public utility. It can even ensure a more significant diminution by selling the surplus of renewable power at the end of each day.Investigating the Practical Applications of the Frequency Response of the Transformers Extracted Using the Lightning Impulse Test Results
http://joape.uma.ac.ir/article_1287.html
The Lightning Impulse (LI) test is performed on newly manufactured power transformers as a routine Factory Acceptance Test (FAT). A well-known Marx Impulse Generator (MIG) is utilized in this test. The setting of the MIG can be changed to obtain standard LI wave shape. Since various power transformers may have windings with dissimilar designs, different MIG settings may be required for each transformer. The accurate computer simulation of the LI test circuit can give help in finding the optimum setting of the MIG. The Frequency Response (FR) of the power transformer impedance is required in such simulations. Similarly, the transformer FR is required in calculating the Transient Recovery Voltage (TRV) across the contacts of the Circuit Breakers (CB) in the case of the Transformer Limited Fault (TLF). The accurate calculation of such TRVs has a great importance in selecting the proper rating for CBs. The FR of the transformer can be measured directly with network analyzers or some other conventional test instruments. However, performing an additional test to obtain the transformer FR imposes extra cost and efforts. Alternatively, it can be achieved by using the routine LI test results which is readily available. Fortunately in both mentioned applications similar connections are required for transformer terminals. In this paper, the procedure to extract the transformer FR using the LI test results is presented. Then, the validity of such extracted FRs is investigated by comparing them with the ones measured by conventional test instruments. As an innovation, the extracted transformer FRs are used in the LI test circuit simulation and the accuracy of the method is examined by experimental works. Moreover, the application of the extracted FR in TLF TRV calculation is investigated as well. The validity of the all presented theoretical concepts are evaluated using the experimental test results on a real large power transformer.Sensorless FOC Strategy for Current Sensor Faults in Three-Phase Induction Motor Drives
http://joape.uma.ac.ir/article_1306.html
Current sensors are required in Field-Oriented Control (FOC) strategies of Three-Phase Induction Motor (TPIM) drives. Nevertheless, the current sensors are subject to different electrical/mechanical faults which reduce the safety and dependability of the drive system. Single phase current sensor Fault-Tolerant Control (FTC) for sensorless TPIM drives using flux observer and Extended Kalman Filter (EKF) is proposed in this research. In the suggested FTC scheme, current sensor fault detection is based on axes transformation, a logic circuit is served as the fault isolation and reconstruction of faulted currents are achieved through flux observer and EKF. The presented FTC system is capable of detecting and localizing the current sensor fault and switching the drive system to tolerant FOC mode without the rotor speed measurement. The effectiveness of the suggested FTC system is confirmed by experiments on a 0.75kW TPIM drive platform.Reactive Power Scheduling Using Quadratic Convex Relaxation
http://joape.uma.ac.ir/article_1378.html
In this paper, quadratic convex relaxation (QCR) is used to relax AC optimal power flow (AC-OPF) used for reactive power scheduling (RPS) of the power system. The objective function is system active power loss minimization to optimally determine the tap position of tap-changers, the reactive power output of generating units, synchronous condensers, shunt capacitor banks, and reactors. The nonlinear and non-convex terms due to trigonometric functions cause the problem to be non-convex which results in trapping in local minimum or even not converging in large size power systems. Therefore, in this paper, the nonlinear terms and trigonometric function are relaxed by linear and quadratic functions. Furthermore, the product of two variables and multi-variables are relaxed by McCormick bilinear and multi-linear expressions, converting the AC-OPF of RPS to quadratic constraint programming (QCP) optimization problem. The proposed RPS method is studied based on IEEE RTS 24-bus test system. The results show the accuracy of the proposed (QCR) method to relax the AC-OPF optimization problem of RPS.&nbsp;&nbsp;&nbsp;Analysis of Structural Reliability of Complex Coefficients Fractional-Order System Using Plane Transformation
http://joape.uma.ac.ir/article_1384.html
The main goal of the paper is to achieve the structural reliability of the failure components in the system that can be modelled as a Transfer Function (TF). The classical reliability of the power system has been a major field for research in the past decades, which has resulted in the reliability of the power grid by integrating the failure rates of the system components. As a result, a gap analysis is carried out by modelling the failure components into TF, and a comparison of structural and classical reliability is explained in the paper. The paper expands on methodology of the mapping technique for transforming a system from one domain to another. By doing so, the transformation of the Complex Coefficients Integer Order (CCIO) and the Complex Coefficients Fractional Order (CCFO) system transfer function becomes the Non-complex Coefficients Integer Order (NCCIO) in nature. Therefore, the root locus plot for the transformed system is observed as the symmetrical structure about the real axis. Therefore, the plane transformation becomes advantageous in the field of structural reliability analysis. The root locus plot for the transformed system into a w-plane becomes reliable as per the symmetrical structure. The reliability index Loss of Load Probability (LOLE) has been evaluated with different forced outage rates of the system components to analysis the classical reliability of the system.Investigation of Increasing Accuracy Distributed Voltage on the Power Transformer Disks Considering Mutual Induction and Different Grounding System Models
http://joape.uma.ac.ir/article_1385.html
Power equipment are subjected to multiple shock voltages during their operations that are generally caused by a lightning strike, switching of electronic power devices, or transient voltages which across available in the power system. These impulses have a frequency range from several kHz to several MHz, which take pulses at very short intervals in several microseconds. Also, the equipment experiences the peak voltage and subsequently peak currents than their nominal values. These variations in voltage and current values, in very short intervals, have destructive effects on these equipment insulated systems as well as on the accuracy of measuring ground impedance. The primary purpose of this study is to investigate the effect of standard and non-standard voltage impulse on power transformers windings by considering the mutual induction of transformer windings. Furthermore In this paper, by applying lightning pulse on power transformer windings for different models of ground voltage distribution system on different disks of transformer windings terminal (20/0.4KV, 100KVA, 9 disks continuous winding) and the disks voltage are calculated as outputs in MATLAB/Simulink. In previous studies, the calculations were in the time domain, while in this study, the ground impedance was measured in the frequency domain. The simulation results show that considering the model RC and considering the mutual induction, the voltage distribution on the disks is higher than other models. This study provides functional information for improving the design of insulations that are installed between windings and core the results of the present research may lead to the minimization of the dielectric failures. Furthermore, the results of this study can be used in future studies about non-standard impulse voltages. This investigation can certainly lead to modifying available standards or creating new standards in power transformers.