Power systems
Niloofar Mohammadi; Masoud Rashidinejad; Amir Abdollahi; Peyman Afzali
Abstract
Smart homes could have a significant impact on supplying the demand of both household consumers and smart grid. The household consumers can trade energy via peer-to-peer (P2P) energy trading to reduce their cost. In other words, each of them can participate in the smart grid as a prosumer that can both ...
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Smart homes could have a significant impact on supplying the demand of both household consumers and smart grid. The household consumers can trade energy via peer-to-peer (P2P) energy trading to reduce their cost. In other words, each of them can participate in the smart grid as a prosumer that can both produce and consume energy. On the other hand, the more participation of smart homes in the demand-side management (DSM) program could help to electricity decentralization. Also, the energy storage systems (ESSs) and distributed energy resources (DERs) can lead to further decentralization of a smart microgrid. The production of renewable energy resources, such as photovoltaic (PV) systems, are associated with uncertainty. The ESSs could able to be used as a reserve of PV systems. This paper presents a new risk-based model for P2P energy management of smart homes consist of PV system and EES and participate in the DSM program. The risk associated with the uncertainties of PVs’ production and market price has been modeled by conditional value-at-risk (CVaR). The mixed integer non-linear programming (MINLP) model of the problem has been solved by COUENNE in GAMS software. Numerical results show the expected cost of all resources and the related risk is reduced by the proposed decision making model for smart homes.
Power systems
Mehrdad Manshor; Mahmood Joorabian; Afshin Lashkarara
Abstract
Power management in microgrids is a major challenge due to its low total inertia and capacity. The lower the microgrid generation capacity is, the higher the share of each generation unit in total power will be, and the higher the frequency deviation in less time will be when an outage occurs. So, preventive ...
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Power management in microgrids is a major challenge due to its low total inertia and capacity. The lower the microgrid generation capacity is, the higher the share of each generation unit in total power will be, and the higher the frequency deviation in less time will be when an outage occurs. So, preventive actions can be more reasonable and affordable than corrective actions for microgrid power and frequency control. In this regard, a new primary frequency response-constrained unit commitment model is presented here to prevent excessive frequency deviations by more commitment of higher inertia power plants and more contribution of renewable energy resources or energy storage systems’ fast inertia response. To have a mixed-integer linear programming model, the primary frequency response constraints are linearized. The model is solved by the combination of two commercial solvers named MOSEK and YALMIP in the MATLAB 2018 environment. The proposed model is examined on a real isolated microgrid (an island). The results show that by activating the primary frequency support of distributed energy resources, the power can be managed with lower costs because there will be less need to start up fast (and expensive) gas turbine generation units. In addition, although comparing the model with others shows the more expensive management procedure, better frequency stability is obtained in contingencies.
Power systems
Ali Masoudi; Mohsen Simab; Hamidreza Akbarj; Seyed Amin Saeed; Tahereh Daemi
Abstract
With an increasing penetration rate of electric vehicles in distribution networks, it is becoming vital to schedule their battery charging/discharging to maintain the network balance and increase the vehicle owners’ profit. Electric vehicles are now considered one of the most important and accessible ...
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With an increasing penetration rate of electric vehicles in distribution networks, it is becoming vital to schedule their battery charging/discharging to maintain the network balance and increase the vehicle owners’ profit. Electric vehicles are now considered one of the most important and accessible sources of revenue for their owners since they can be connected to the grid (V2G) as a power source during peak hours. As such, while flattening the power profile, they can improve the voltage drop across the grid buses. If charging/discharging of the vehicles is scheduled irregularly, the power drawn from the phases will become unbalanced, which can cause global outages and impair system stability in addition to increasing the harmonic volume and decreasing power quality. The present paper uses dynamic programming to reduce operating costs and enhance the profits of vehicle owners who participate in the V2G program. This optimization algorithm eliminates the undesirable paths leading to unconventional responses in the search space, which will greatly increase the speed and accuracy by which the optimal response is achieved. This model, along with multi-part tariffs on electricity prices, can lead to the more active participation of vehicle owners and help improve the power quality indices of the electrical parameters of the grid. The proposed method is simulated on a sample distribution network, and the case studies conducted prove the validity of the proposed algorithm.
Power systems
Esmaeel Rokrok; Saman Dehghaninejad; Amir Hossein Poursaeed
Abstract
Recent technical advances in Wide-Area Measurement Systems (WAMS) have made it possible to use a combination of measured signals from remote locations to design centralized control. However, the transmission delay of remote signals and changes in the power system operating point are significant issues ...
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Recent technical advances in Wide-Area Measurement Systems (WAMS) have made it possible to use a combination of measured signals from remote locations to design centralized control. However, the transmission delay of remote signals and changes in the power system operating point are significant issues in the operation of the Wide-Area Damping Controller (WADC). Regarding issues and uncertainties in the power system, mixed H_2/H_∞ synthesis has been proposed for wide-area robust controller design. In this paper, an adaptive wide-area robust controller for Thyristor Controlled Series Capacitors (TCSC) is presented to improve the inter-area oscillation damping in multi-machine power systems in which the time-varying delays in feedback signal time are taken into account. So, an Adaptive Delay Compensator (ADC) is used to compensate for the delay of receiving remote signals. Despite the nonlinearity of the power system, the changes in the operating point, and the presence of time-varying delays, the proposed scheme shows robust performance in damping the low-frequency oscillations. The efficiency of the proposed control system in the presence of TCSC is shown through simulation results that show its superiority over the conventional control system. The simulation of the paper is carried out on the Four-Machine Two-Area test system and 10-machine, 39-bus New England power system.
Power systems
Hamed Sadeghi; Hamid Reza Mohammadi
Abstract
Electric spring (ES) is a new technology that can be used for fast demand-side management to balance the power between generation and consumption in smart grids. In this paper, the back-to-back structure of electric spring is controlled to operate simultaneously as electric spring and shunt active power ...
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Electric spring (ES) is a new technology that can be used for fast demand-side management to balance the power between generation and consumption in smart grids. In this paper, the back-to-back structure of electric spring is controlled to operate simultaneously as electric spring and shunt active power filter (shunt-APF). That means the series part of the back-to-back electric spring regulates the critical load voltage and applies the demand-side management and the parallel part operates as a shunt active power filter capable of power factor correction and current harmonic compensation. In the proposed structure, due to harmonic compensation and power factor improvement by the parallel inverter, the output power capacity of the electric spring is increased compared with the first and second generation of electric springs (ES-1 and ES-2), and the performance is improved in critical conditions. Additionally, to improve the robustness of the control system against uncertainties in the grid system, two fuzzy logic controllers are designed to control the voltage of the electric spring and the DC link voltage. The theoretical analysis is validated by simulation results using MATLAB/SIMULINK software.
Power systems
Iman Mousaviyan; Seyyed Ghodratollah Seifossadat; Mohsen Saniei
Abstract
This study introduces a single-ended method to detect the protection zone and distinguish faults occurring in the back of the relay in the transmission lines and then provides an algorithm to classify different types of faults, including a lightning strike on phases and shield wire. Accordingly, using ...
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This study introduces a single-ended method to detect the protection zone and distinguish faults occurring in the back of the relay in the transmission lines and then provides an algorithm to classify different types of faults, including a lightning strike on phases and shield wire. Accordingly, using the Wavelet Transform (WT), the first class of Traveling Wave (TW) current is separated at the beginning of all bus-connected lines. The faulty line and the protection zone are selected based on the relations governing the radiation and reflection. Then, given the features and relations extracted from these waves, the faults caused by lightning strikes on the transmission line and conventional faults are classified, with considering the mutual induction between TWs on the transmission line phases. This action is essential and helpful for transmission line with single phase tripping and auto-reclosing mechanisms. Over 1100 faults with varying conditions and locations are implemented on a 100-km line with a voltage level of 230 kV in the PSCAD software to evaluate and test the proposed method. The results of this heavy simulation confirmed the validity, speed, and accuracy of the proposed method.
Power systems
Seyed Arman Shirmardi; Mahmood Joorabian; Hassan Barati
Abstract
This paper presents microgrid (MG) operation constrained to the reliability, flexibility, and environment indices in the presence of distributed generations (DGs) and energy storage systems (ESSs). The proposed scheme minimizes the total expected operating cost of MGs and DGs. It is also subject to alternating ...
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This paper presents microgrid (MG) operation constrained to the reliability, flexibility, and environment indices in the presence of distributed generations (DGs) and energy storage systems (ESSs). The proposed scheme minimizes the total expected operating cost of MGs and DGs. It is also subject to alternating current (AC) power flow equations of MGs, constraints of operation, reliability, and flexibility in MG, and operation model of power sources and storage devices. Stochastic programming is incorporated to model uncertainties of load, energy price, the active power of renewable energy generation, availability of MG equipment, sources, and storage devices. Following on, a hybrid solver formed by combining artificial bee colony (ABC) and sine-cosine algorithm (SCA) is adopted to achieve the optimal solution with approximate conditions of unique ultimate response. Eventually, the suggested scheme is implemented on a 69-bus radial MG, where the numerical results confirm the capability of the scheme in improving the operation, reliability, flexibility, and environment status of the MG.
Power systems
Fariba Forouzesh; Mahdiyeh Eslami; Mehdi Jafari Shahbazzadeh
Abstract
Power systems are categorized as nonlinear dynamical systems, and the importance and complexity associated with their stability have dramatically increased. Accordingly, the behavior of power systems can be characterized by interactions between continuous and discrete-event dynamics. This paper proposes ...
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Power systems are categorized as nonlinear dynamical systems, and the importance and complexity associated with their stability have dramatically increased. Accordingly, the behavior of power systems can be characterized by interactions between continuous and discrete-event dynamics. This paper proposes a systematic approach to the design and analysis of a supervisory control scheme for power systems using the hybrid automata (HA) model. The proposed model for optimal controller application is derived, and the power system's overall behavior is modeled using HA to enhance its stability. Hybrid systems' formulation incorporates continuous dynamics as well as discrete switching behavior into a modeling and control framework, thus allowing a complete system description while crystallizing the concepts of safety into system design criteria. This study uses a power system HA model as a discrete event system (DES) plant and controller. In the proposed method, to present the hybrid model, the discrete events used include the presence and absence of disturbances and voltage control elements, fault, sudden load increase, capacitor bank, and under-load tap changer (ULTC) transformer. Voltage stability and control are investigated by the generators’ rotor angle, bus voltage, eigenvalues, and the stability theory of the switched linear systems. Applications in voltage control, stability, and dynamic service restoration are presented on two benchmark power systems with 12 discrete states. The simulation results reveal the effective performance of the proposed supervisory controller model to enhance voltage stability in power systems.
Power systems
Alireza Malekijavan; Mehdi Aslinezhad; Hamidreza Zaferani
Abstract
The paper presents reliability-based operation (RBO) of an energy hub consisting of electric vehicles (EVs) and a combined cooling, heating, power (CCHP) system in the electricity, natural gas, and district heating networks. The proposed strategy aims to minimize the total expected operating and reliability ...
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The paper presents reliability-based operation (RBO) of an energy hub consisting of electric vehicles (EVs) and a combined cooling, heating, power (CCHP) system in the electricity, natural gas, and district heating networks. The proposed strategy aims to minimize the total expected operating and reliability costs of the mentioned energy networks as objective functions. Furthermore, the problem is subject to optimal power flow (OPF) equations, reliability constraints, and the hub energy model including constraints of EVs parking lot and CCHP. This strategy has a mixed-integer nonlinear programming (MINLP) model; hence, mixed-integer linear programming (MILP) will be utilized to achieve a unique optimal solution in less computational time for the proposed scheme. Moreover, the scheme includes uncertainties of the load, energy price, the demand of EVs, and equipment availability of the given systems, which are modeled using scenario-based stochastic programming (SBSP). Finally, the approach is implemented on a standard test system in the GAMS software environment. Then, according to the numerical results, it is observed that the mentioned outline can achieve optimal operation conditions and high reliability in energy systems if the EVs and CCHPs are optimally managed in the energy hub form.
Power systems
Zahra Moravej; Seyed Mahmood Mortazavi; Mojtaba Mohseni
Abstract
IIn this paper, an efficient method to detect and discriminate mechanical defects of transformer winding based on extracting the winding frequency responses using outlier data detection and ensemble algorithms ,which in total constitutes an efficient hybrid method has been proposed. First, the frequency ...
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IIn this paper, an efficient method to detect and discriminate mechanical defects of transformer winding based on extracting the winding frequency responses using outlier data detection and ensemble algorithms ,which in total constitutes an efficient hybrid method has been proposed. First, the frequency response of the high voltage winding of a real model of transformer (1.6 MVA) was extracted in different condition and arranged as primary data. Then, due to the high standard deviation of the characteristics and the weight of the outlier samples above the threshold of 1.1, the Local Outlier Factor (LOF) method was used to clean the samples. Finally, data mining algorithms have been used to detect and distinguish mechanical defects. Based on the results, the decision tree bagging ensemble method reported the best accuracy compared to other techniques and improved the accuracy of the decision tree with total accuracy of 92.68% by LOF. These results also showed that all methods improved accuracy by LOF. Therefore, it can be claimed that the proposed method has the ability to discriminate the mechanical defects of the transformer winding with appropriate accuracy.
Power systems
Mohammadreza Noori; Seyed Ghodratollah Seifossadat; Alireza Safarian
Abstract
In this paper, a novel selective DC fault detector approach based on the adaptive cumulative sum method (ACUSUM) is suggested for the protection of high voltage direct current (HVDC) transmission lines. Using a communication channel, the proposed method detects DC fault occurrence as well as determining ...
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In this paper, a novel selective DC fault detector approach based on the adaptive cumulative sum method (ACUSUM) is suggested for the protection of high voltage direct current (HVDC) transmission lines. Using a communication channel, the proposed method detects DC fault occurrence as well as determining faulty line at a multi-terminal HVDC (MT-HVDC) transmission system; the whole in less than 2ms. The suggested approach works in the time domain and employs the ACUSUM method as a mathematical tool for detecting abrupt variation at the magnitude of lines current for fault detection. Simulation results confirm the selectivity of the proposed algorithm at different DC fault situations which enhances the reliability of the power system. Besides the low sampling rate, the ACUSUM calculation burden is very low and its implementation needs no special or complicated hardware. Rather than appropriate speed, adaptivity, independence from system parameters, robustness against fault resistance, fault distance and noise are significant advantages of the proposed algorithm in comparison with other methods. adaptivity, independency from system parameters, robustness against fault resistance, fault distance and noise are significant advantages of the proposed algorithm in comparison with other methods.
Power systems
Masoud Maleki Rizi; Saeed Abazari; Nima Mahdian
Abstract
This paper presents enhancement of power system dynamic stability while equipped with both unified power flow controller and doubly fed induction generator by using LMI technique. We have used all UPFC (Unified Power Flow Controller) main basic PI controllers and its POD (Power Oscillation Damping) supplementary ...
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This paper presents enhancement of power system dynamic stability while equipped with both unified power flow controller and doubly fed induction generator by using LMI technique. We have used all UPFC (Unified Power Flow Controller) main basic PI controllers and its POD (Power Oscillation Damping) supplementary controller. More complete model of DFIG (Doubly Fed Induction Generator) and both RSC (Rotor Side Converter) and GSC (Grid Side Converter) dynamics with their controllers have considered too. These two devices controllers have simultaneously co-ordinate and optimized with compromising between their control variables parameters. PSO (Particle Swarm Optimization) algorithm has used to optimize an objective function based on Eigen values and damping ratio to reach to best parameters and variables of controllers of both of UPFC and DFIG. LMI (Linear Matrix Inequality) have applied to whole system linearized model to reach to optimally modified eigenvalues. Within steady state and dynamic study we considered practical line thermal capacity and UPFC power rating too. Simulation results in 39-bus 10-machine Ne-England power systems ilustrate the capability of applied method. The results demonstrated that coordinated control of these two devices beside using LMI tend to more damping of system modes oscillation and more stability in power system.
Power systems
Hojatolah Makvandi; Mahmood Joorabian; Hassan Barati
Abstract
The present study introduces a new extensive-area ANFIS (Adaptive Neuro-Fuzzy Interface System)-based method to detect wide area instability and control the time of controlled islanding execution within power systems. The ANFIS parameters are optimized by the PSO method to increase the method’s ...
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The present study introduces a new extensive-area ANFIS (Adaptive Neuro-Fuzzy Interface System)-based method to detect wide area instability and control the time of controlled islanding execution within power systems. The ANFIS parameters are optimized by the PSO method to increase the method’s accuracy at various disturbances and loading circumstances. In addition, to take various stability margins within the areas into account, a novel parallel ANFIS network (P-ANFIS) is implemented in which a distinct ANFIS is allocated for every nearby area. Extended off-line studies are performed to train ANFIS to respond in real-time accurately based on the selected wide area input signals. These parameters are monitored continuously through a wide area measurement system (WAMS) and the proposed P-ANFIS starts to assess the stability between related areas in real-time in the case of potentially unstable oscillations. Once an unstable oscillation is detected, the islanding command is transmitted to perform the controlled islanding scheme. The suggested technique is used in an IEEE 39 bus power system and its performance is demonstrated at different disturbances in terms of both speed and accuracy. It is found that the suggested ANFIS-based technique can determine islanding requirement and its time of execution properly at different disturbances.
Power systems
Mahdi Vosoogh; Masoud Rashidinejad; Amir Abdollahi; Morteza Ghaseminezhad
Abstract
This article addresses the optimal energy management and operation of networked microgrids considering different types of dispatchable units like fuelcell and microturbine and nondispatchable units such as wind turbine and solar units. To change the just-consuming role of vehicles into an active role ...
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This article addresses the optimal energy management and operation of networked microgrids considering different types of dispatchable units like fuelcell and microturbine and nondispatchable units such as wind turbine and solar units. To change the just-consuming role of vehicles into an active role with the ability of making profit, the vehicle-to-grid technology (V2G) is deployed here. Due to the complex and nonlinear structure of the problem, an effective optimization energy management framework based on the bat algorithm (with a modification) and unscented transform is devised to find the most optimal operation point of the devices from the economic point of view. Due to the high uncertainties injected by electric vehicles pattern behavior in addition to the renewable sources output power variations, the unscented transform is proposed to make the analysis more realistic. The simulation results on an IEEE networked microgrid test system advocate the high capability and proper performance of the proposed method. The results show that the total system operation cost is 53897.004$ and 53711.704$ in the 1st and 2nd scenarios, respectively. Moreover, it is seen that considering uncertainty in the problem has added 0.586% and 0.762% to the cost function value in the first and second scenarios, compared to the deterministic framework.
Power systems
Navid Ghaffarzadeh
Abstract
In this paper a novel and simple approach for detection and classification of wide variety range of power quality(PQ) events based on discrete wavelet transform (DWT) and correlation coefficient is presented. For this purpose, two new indices is proposed and by comparing the values of the correlation ...
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In this paper a novel and simple approach for detection and classification of wide variety range of power quality(PQ) events based on discrete wavelet transform (DWT) and correlation coefficient is presented. For this purpose, two new indices is proposed and by comparing the values of the correlation coefficient between the value of these indices for pre-stored PQ events and for a recorded indistinct signal, type of PQ events will be detected. This algorithm has advantages of DWT and correlation coefficient which, it does not have disadvantage of neural network or neural network-fuzzy based algorithms such as; training, and high dimension input matrices nor it does not have disadvantage of Fourier transform based approach such as unsuitability for non-stationary signal as it does not track signal dynamics properly due to limitation of fixed window width. The effectiveness of this method has been tested using numerous PQ disturbance and simulation results confirm the competency and the ability of the proposed method in PQ disturbances detection and automatic diagnosis. Compared with the other methods, the simulation under different noises conditions, verify the effectiveness of noise immunity, and relatively better accuracy of the proposed method.
Power systems
Milad Niaz Azari; Reza Fathi shoob
Abstract
Synchronous generators are one of the most important components of power systems. Problems a generator may face are internal faults, system disturbances, or operational hazards. The operation of a generator may easily be affected by faults within the machine itself as opposed to external disturbances ...
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Synchronous generators are one of the most important components of power systems. Problems a generator may face are internal faults, system disturbances, or operational hazards. The operation of a generator may easily be affected by faults within the machine itself as opposed to external disturbances occurring on the network to which it is connected. Generator protection must therefore be designed to react efficiently in both conditions. Loss of excitation (LOE) is a common fault in synchronous generators. The most common causes of LOE include the loss of field to the main exciter, accidental tripping of the field breaker, short circuits in the field circuit, and poor brush contact in the exciter. The most widely applied method to detect a generator loss of field condition on major generators is the use of distance relays to sense the variations of impedance as viewed from the generator terminals. This approach may not be able to distinguish between LOE and stable power swing (SPS). This paper further explores a new method proposed for LOE detection and corrects its shortcomings. It also presents a new approach for LOE detection that exploits a combined scheme based on the derivative of the terminal voltage and the derivative power angle of the generator. Comprehensive simulation studies are conducted on various generator conditions and system disturbances to determine the relay setting and to evaluate its performance. These studies demonstrate that the proposed strategy enhances the security and operation time of the LOE relay compared with some existing methods.
Power systems
Navid Ghaffarzadeh; Hossein Faramarzi
Abstract
In this paper, a fault location approach is presented by using Whale Optimization Algorithm (WOA) strategy in two terminal transmission feeder. Also, Grey wolf Optimization (GWO) method is discussed. From both ends, affording the preparatory data for proposed strategies voltages and currents from both ...
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In this paper, a fault location approach is presented by using Whale Optimization Algorithm (WOA) strategy in two terminal transmission feeder. Also, Grey wolf Optimization (GWO) method is discussed. From both ends, affording the preparatory data for proposed strategies voltages and currents from both ends are measured. Several types of faults and simulations are considered in this paper and the objective function identifies the fault location with a high accuracy, correctness in a short time. Meanwhile, based on distributed model the line, the fault location is defined and since the optimization algorithm do not utilize compressed model of the line, the accuracy of the calculation is high. WOA based optimization method results in a notable reduction in the computational time. Accurate and timely location of the source of the fault greatly facilitates the job of the repair crew. This is the benefit of the proposed technique. Almost in all the cases, the accuracy of proposed procedure is very high and the error is kept below 1%.
Power systems
Mahyar Abasi; Mahmood Joorabian; Alireza Saffarian; Seyyed Ghodratollah Seifossadat
Abstract
Generalized Unified Power Flow Controller (GUPFC) is a member of the flexible alternating current transmission system (FACTS) devices family that operates based on voltage source converter (VSC) and is known as the most efficient FACTs device. GUPFC can control the voltage of one bus and the active and ...
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Generalized Unified Power Flow Controller (GUPFC) is a member of the flexible alternating current transmission system (FACTS) devices family that operates based on voltage source converter (VSC) and is known as the most efficient FACTs device. GUPFC can control the voltage of one bus and the active and reactive power flows on at least two transmission lines with equal voltage levels. This paper presents the mathematical modeling of power injection by GUPFC for the first time. Besides, the accurate design and details of the control system for series and shunt converters of a GUPFC, along with a new mathematical function for pulse generation based on a 48-pulse VSC when the GUPFC is placed in the middle point of a parallel transmission line, are presented in this study. The power injection modeling introduced in this paper is very useful and efficient in Newton-Raphson power flow studies and in modeling different parts of the control system and power electronics converter in dynamic and transient studies. The modeling is implemented in MATLAB/Simulink for a 400 km, 230 kV, and 60 Hz nominal frequency double-circuit transmission line. The satisfactory results provided in the simulations section of the paper verify the validity and accurate performance of the proposed model.
Power systems
Jamshid Barati; Seidghodratollah Seifossadat; Mahmood Joorabian
Abstract
Distance relays calculate the path impedance between the fault point and the relay location by sampling the voltage and current at the relay location. By using the ratio of the impedance estimated by the relay to the impedance of the line where the relay is installed, the location of the fault can be ...
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Distance relays calculate the path impedance between the fault point and the relay location by sampling the voltage and current at the relay location. By using the ratio of the impedance estimated by the relay to the impedance of the line where the relay is installed, the location of the fault can be estimated by a distance relay. However, several factors influence the estimated impedance and proper operation of distance relays. The most important of these factors is the resistive fault occurrence, which results in an increase in the impedance and deviation of the impedance estimated by the relay as well as causes relay under-reach. Therefore, in the present study, an adaptive method is proposed to modify the protection zones of distance relays settings under different operating conditions and resistive fault occurrence. Furthermore, the adaptive distance protection of transmission lines, wind farm collector lines and the protection coordination of the relays in these lines are investigated. In this method, an adaptive coefficient is added to the conventional characteristics of distance relays to improve the accuracy and coordination. The proposed adaptive method can also maintain the coordination of different protection zones of primary and backup relay pairs. In addition to analytical verification, the numerical results obtained from simulation show the efficiency of the proposed method. The proposed method is implemented on a power system with transmission lines and wind farms and simulated in MATLAB/Simulink environment.
Power systems
seyed hossein tabatabaei; Hussein Eliasi; Hamidreza Najafi; alireza jalilian
Abstract
A hybrid AC-DC microgrid consists of an AC and a DC subgrid that are connected to each other through an interlinking converter (IC). The main function of an IC under islanded conditions is to transfer power between the two subgrids. In this paper, a scheme is presented to reduce the voltage unbalance ...
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A hybrid AC-DC microgrid consists of an AC and a DC subgrid that are connected to each other through an interlinking converter (IC). The main function of an IC under islanded conditions is to transfer power between the two subgrids. In this paper, a scheme is presented to reduce the voltage unbalance factor in a hybrid AC-DC microgrid by using the free capacity of the IC. The free capacity of this converter is determined based on the current passing through each leg, and the amount of voltage unbalance compensation on the AC side of the microgrid is then obtained. The reference current of voltage unbalance compensation is calculated by using the positive, negative, and zero sequence components of the voltage of IC terminals. The total reference current is obtained by adding the reference current of voltage unbalance compensation and the current calculated for power transfer. Furthermore, a proportional-resonant (PR) controller is used in the control system of the four-leg inverter. Therefore, the reference current is properly tracked by the power stage of the inverter. Simulation results verify the accuracy of the proposed scheme under different conditions.
Power systems
Reza Ashrafi; Soodabeh soleymani; Mehdi Ehsan
Abstract
In this paper, a comprehensive centralized structure is proposed for Microgrids (MGs) operation incorporating active and reactive power resources. In this approach, the Distributed Generation (DGs), Energy Storage Systems (ESSs), Demand Response (DR) program, load shifting scheme, switchable capacitor ...
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In this paper, a comprehensive centralized structure is proposed for Microgrids (MGs) operation incorporating active and reactive power resources. In this approach, the Distributed Generation (DGs), Energy Storage Systems (ESSs), Demand Response (DR) program, load shifting scheme, switchable capacitor banks and Plug-in Hybrid Electric Vehicles (PHEV) are considered simultaneously. The operation modes of PHEVs is modeled to schedule their charging/discharging and calculate the pollution produced in fossil fuel mode. Fifteen types of costs are integrated into the objective function, and several operational constraints are considered. They include power generation costs from the main grid and DG units, the cost of pollution emitted by DG units and PHEVs, and the degradation of plug-in hybrid electric vehicles batteries. The proposed method is programmed using GAMS software as a Mixed-Integer Second-Order Cone Programming (MISOCP) problem, and it is implemented on a test MG. simultaneous management of active and reactive power sources can result in less cost compared to the separated scheduling.
Power systems
Mahdi Samadi; Karim Karami Nezhad; Elahe Zakikhani
Abstract
The interruptible load program (ILP) is one of the most common demand response programs, which is often used by industrial customers. The purpose of implementing this program is to reduce the customer's peak demand in response to the incentives set by a contract. If no attention is paid to characteristics ...
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The interruptible load program (ILP) is one of the most common demand response programs, which is often used by industrial customers. The purpose of implementing this program is to reduce the customer's peak demand in response to the incentives set by a contract. If no attention is paid to characteristics of the industrial customer's production process, the participation in ILP will not be possible. Therefore, complying with customer's technical constraints and optimal design of the program is of great importance. This study aims to present a new model for the optimal design of ILP from the perspective of a cement manufacturing company as an industrial customer. In this regard, the manufacturing process and the constraints of operation of a cement plant are fully modeled and all relevant constraints and requirements are considered. The objective function is the maximum profit, so the ILP is designed such that the cement plant's profit can be maximized without disrupting the normal performance of the production process. The proposed optimization problem is a mixed-integer non-linear one for which a suitable genetic algorithm is designed and used. In the proposed approach, the optimal incentive level is determined by assuming a specific budget level (related to the power company). The implementation of the proposed optimal design will satisfy the power system operator for reducing peak demand and the customer for earning more profit.
Power systems
Mohsen Ramzanzadeh; Meysam Jafari Nokandi; Taghi Barforoushi; Javad Saebi
Abstract
In recent years, concerns about environmental pollutions have risen and in this respect, the power system and transportation section have been introduced as the main sources of their emission. Therefore, renewable energy sources (RESs), predominantly wind generation, can be effective for reducing emissions ...
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In recent years, concerns about environmental pollutions have risen and in this respect, the power system and transportation section have been introduced as the main sources of their emission. Therefore, renewable energy sources (RESs), predominantly wind generation, can be effective for reducing emissions caused by the power system, and electric vehicles (EVs) can be very useful for decreasing emissions in the transportation section. However, RESs are intermittent and uncertain, and on the other hand, high penetration of EVs into the system can be challenging for power system operation. Consequently, the stochastic behavior of RESs and charging demand of EVs should be considered in the daily operation scheduling of generating units that is known as the unit commitment (UC) problem. In this regard, this paper presents a two-stage stochastic programming model for the security-constrained unit commitment (SCUC) taking into account the effect of EVs penetration and wind power integration into the power system. The effect of EV travels on the demand of busses is modeled in the proposed framework. Moreover, the impact of demand response (DR) programs on the operation cost of the system is considered. The results of simulations in a six-bus test system illustrate that high EVs penetration reduces power system security and increases the system operation cost, but DR programs can compensate for these negative effects. Moreover, the increase in cost in a controlled charging mode can be insignificant.
Power systems
amir ghaedi; Khodakhast Nasiriani; mehdi nafar
Abstract
Ocean thermal energy conversion (OTEC) systems utilize from the difference between the temperatures of surface and deep water and drive a thermodynamic Rankine cycle for electric power generation. The generated power depend on the temperature of the surface water as warm source and due to the variation ...
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Ocean thermal energy conversion (OTEC) systems utilize from the difference between the temperatures of surface and deep water and drive a thermodynamic Rankine cycle for electric power generation. The generated power depend on the temperature of the surface water as warm source and due to the variation in the temperature of surface, the output power of the OTEC system frequently changes. This uncertainty nature results in the variation in the generated power and so, integration of large-scale OTEC generation units to the power system is a challenging problem and new techniques must be developed for studying the effects of resources on the power system. Therefore, the balance between generation and consumption is important and from reliability point of view, spinning reserve must be scheduled to prevent load curtailment in the events such as forced outages of generation units, transmission lines and so on. In a power system containing large-scale OTEC power plants, the uncertainty nature of these plants must be considered in the reserve scheduling and for this purpose, a reliability model considering both failure of composed components and variation in the output power, is developed and for determining a suitable multi-state model, fuzzy c-means clustering technique and XB index is utilized. Then, the proposed multi-state model is used for spinning reserve determination of a power system containing OTEC plants using of the modified PJM method. Numerical results associated to RBTS and IEEE-RTS present the effectiveness of the proposed technique for operation studies of power systems containing OTEC systems.
Power systems
Sirus Salehimehr; Behrooz Taheri; Seyed Amir Hosseini; Hossein Askarian Abyaneh; Farzad Razavi
Abstract
In this paper, a new method based on Hilbert transform is proposed to detect the power swing and faults occurring during the power swing. The proposed method operates independently from the system parameters. As well as, this method has the ability to detect different types of power swings, including ...
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In this paper, a new method based on Hilbert transform is proposed to detect the power swing and faults occurring during the power swing. The proposed method operates independently from the system parameters. As well as, this method has the ability to detect different types of power swings, including stable, unstable, and multi-mode power swings, and also can differentiate the power swing from the faults for blocking or unblocking the distance relay. In order to evaluate the proposed method, various types of power swing and simultaneous faults are simulated in DIgSILENT software and then using the obtained matrix data from the current signals, the proposed algorithm has been implemented in Matlab software using the Hilbert transform. The results of this study show that the proposed method can detect different types of power swing successfully. In addition, it has been shown that the proposed method operates very fast; besides when a fault occurs simultaneously with the power swing unblocks the relay as soon as possible. This method has been also implemented practically on a distance relay and is tested by a relay tester device made by Vebko Amirkabir knowledge-based company. The results obviously show that the proposed method has a better operation than industrial conventional methods.