Power systems
Mehdi Bekrani; Mojtaba Heydari; Seyedeh Tahereh Behrooz
Abstract
In this paper, a new adaptive control method is proposed for direct matrix converters. The proposed method uses interval type-2 fuzzy logic integrated with sliding mode control. Employing the sliding mode control in matrix converters leads to an efficient choice of switching combinations and a reliable ...
Read More
In this paper, a new adaptive control method is proposed for direct matrix converters. The proposed method uses interval type-2 fuzzy logic integrated with sliding mode control. Employing the sliding mode control in matrix converters leads to an efficient choice of switching combinations and a reliable reference tracking. The main problem of the sliding mode control is the chattering phenomenon that degrades the controller performance through injecting high-frequency variations in the controller variables. The proposed method incorporates the interval type-2 fuzzy with the sliding mode control to mitigate the chattering problem. The sliding mode switch surface can be adjusted adaptively according to the system state and the proposed fuzzy compensation based on the Lyapunov stability theorem, so that the control system has the characteristics of low chattering effect and appropriate operation quality. Comprehensive evaluations of the waveforms are conducted for the new matrix converter through various simulations. Simulation results verify the effectiveness of the proposed adaptive control method for matrix converter in various conditions, and its superiority in chattering suppression in comparison to the conventional sliding mode control and the boundary layer method.
Power systems
Reza Yazdanpanah
Abstract
Design methodology of the compact size charging system for emergency uses is investigated in this paper. The system consists of a gearing unit, generator, charger and battery cells. The system electrical model has been introduced and a 3-phase axial flux surface mounted PM generator with concentrated ...
Read More
Design methodology of the compact size charging system for emergency uses is investigated in this paper. The system consists of a gearing unit, generator, charger and battery cells. The system electrical model has been introduced and a 3-phase axial flux surface mounted PM generator with concentrated winding is picked as a generation unit. The basic equations needed for the generator design are presented as well as general considerations and constraints for the designs. After validating the design equations using Finite Element Analysis, sizing equations are used to design different machines. The resulted designs are compared based on main characteristics including output power, delivered power to the battery, and generator efficiency. Finally, the performances of valid designs in the system model are analyzed on the wide speed range. The proposed methodology could be used for portable power generation units design for applications such as rescuing, power system outage, camping, so on.
Power systems
Majid Akbarian; Najmeh Eghbal; Naser Pariz
Abstract
: In this paper, a novel optimal control design method by discontinuous quadratic Lyapunov function and continuous quadratic Lyapunov function for 2-dimensional piecewise affine systems via semi-definite programming and LMI constraints is proposed.In fact, for designing optimal control we use from two ...
Read More
: In this paper, a novel optimal control design method by discontinuous quadratic Lyapunov function and continuous quadratic Lyapunov function for 2-dimensional piecewise affine systems via semi-definite programming and LMI constraints is proposed.In fact, for designing optimal control we use from two different criteria. At the first, an upper bound for a quadratic cost function for a stable closed-system is obtained. Then after, considering a state-feedback control approach, not only sufficient conditions for the stability of the closed-loop system but also the upper bound of the cost function are obtained. The optimization problem is formulated as a semi-definite programming with bilinear constraints (BMI). Some variables in BMIs are searched by genetic algorithm, so the bilinear constraints are converted to linear constraints and the controller coefficients are calculated. The effectiveness of the proposed method is verified by numerical examples. The simulation results show that discontinuous quadratic lyapunov functions are more efficient that continuous quadratic lyapunov functions.
Power systems
Roholamin Zeinali; MohamadKazem Salehi
Abstract
In this paper different representations of a wind farm based on double-cage induction generators connected to a series-compensated line is studied and their effect on the Subsynchronous Resonance (SSR) is analyzed. For this purpose, three representation types of wind turbines in SSR studies of the wind ...
Read More
In this paper different representations of a wind farm based on double-cage induction generators connected to a series-compensated line is studied and their effect on the Subsynchronous Resonance (SSR) is analyzed. For this purpose, three representation types of wind turbines in SSR studies of the wind farm are considered as 1) Single Turbine Representation (STR), 2) Multiple Turbine Representation (MTR), and 3) Full Turbine Representation (FTR). To select the acceptable representation of the wind farm in SSR analysis, the wind farm is modeled by three representation and the test system eigenvalues are obtained for different conditions of the power system and the results are compared together. For this purpose, three scenarios are considered. In the first and second scenarios, all of the Wind Turbine Generators (WTGs) have identical electrical and mechanical parameters but WTGs in the third scenario are different. In the first scenario, all wind turbines are subjected to the same wind speed, and in the second and third scenarios, each group of wind turbines is subjected to the same wind speed. In addition, the analytical results are validated by electromagnetic transient simulation using PSCAD/EMTDC software.
Power systems
Shervin Bikdeli; Mohammad Farshad
Abstract
Developments in power systems like the installation of new generation resources and interconnections may increase short-circuit current levels and consequently, impose additional costs of replacing circuit breakers and equipment. In these cases, one of the best methods to reduce short-circuit currents ...
Read More
Developments in power systems like the installation of new generation resources and interconnections may increase short-circuit current levels and consequently, impose additional costs of replacing circuit breakers and equipment. In these cases, one of the best methods to reduce short-circuit currents in power systems and avoid significant replacement costs is to use fault current limiters (FCLs). This paper suggests a new method for optimally locating and sizing FCLs using an imperialist competitive algorithm (ICA). The ICA finds the optimal locations and sizes of FCLs such that not only are short-circuit currents reduced, but the size of the installed FCLs is also minimized, and the system reliability is increased. Indeed, three indices including the short-circuit level, the economic cost of FCLs, and the lost power are integrated into an objective function with a new formulation. The results obtained from multiple executions of the suggested procedure for the 39-bus New England benchmark system confirm that the formulation of indices in the objective function is suitable and the indices can be prioritized easily. Also, the results indicate that the ICA can find the optimal locations and sizes of FCLs with good convergence and accuracy considering the specified objectives and priorities.
Power systems
Ali Sefidgar-dezfouli; Mahmood Joorabian; Elaheh Mashhour
Abstract
This paper deals with the optimal scheduling of a microgrid (MG) equipped with dispatchable distributed generators (DGs), renewable generators and electrical storages (batteries). A chance-constrained model is developed to handle normal operation and emergency conditions of MG including DG outage and ...
Read More
This paper deals with the optimal scheduling of a microgrid (MG) equipped with dispatchable distributed generators (DGs), renewable generators and electrical storages (batteries). A chance-constrained model is developed to handle normal operation and emergency conditions of MG including DG outage and unwanted islanding. Purchasing reserve from the upstream grid is also considered. Moreover, the uncertainties of loads and renewable resources are incorporated into the model. Furthermore, a novel probabilistic formulation is presented to determine the amount of required reserve in different conditions of MG by introducing separate probability distribution functions (PDFs) for each condition. Accordingly, an index named as the probability of reserve sufficiency (PRS) is introduced. The presented model keeps a given value of PRS in normal and emergency conditions of MG operation. In addition, some controllable variables are added to the chance constraints as an innovative technique to reduce the complexity of the model. Finally, a test microgrid is studied in different case studies and the results are evaluated.
Power systems
Sanaz Ghanbari; Hamdi Abdi
Abstract
The advent of DG and SEGs has led to fundamental changes in various fields of power system operation. The current paper is aimed to investigate the reliability of SEGs considering DGRs based on the self-healing concept. Due to the emergence of new uncertainties in the power system resulted from the presence ...
Read More
The advent of DG and SEGs has led to fundamental changes in various fields of power system operation. The current paper is aimed to investigate the reliability of SEGs considering DGRs based on the self-healing concept. Due to the emergence of new uncertainties in the power system resulted from the presence of DGRs, this paper is dedicated to comparing network reliability indices before and after the entry of DGRs and analyzing their effect on improving network reliability. To do so, improving the indices based on customer satisfaction, such as reducing the SAIFI, and SAIDI, is evaluated. More specifically, the improvement of the most important index based on load and energy, namely energy not supplied (ENS), is investigated. To do this, the MCS method is used given the pdf of the samples due to the presence of uncertainty created by the presence of DGRs, demanded load change and network restoration time after the presence of DG. Also, after providing an appropriate model for problem analysis, results of applying this model to the case study system are investigated using reliability indices. Subsequently, in order to improve performance of the system, impacts of the changes of various parameters on the given indices are reported. One of the most important points in this regard is to investigate the impacts of the changes in the system configuration on the results. It is observed that self-healing positively affects the reduction of the electrical energy restoration time as well as the system reliability.
Power systems
Seyed Mohammad Hoseini; Nastaran Vasegh; Ali Zangeneh
Abstract
In this paper, a new robust hybrid controller (RHC) is proposed to regulate current, voltage and, as a result, power output of a three-phase grid connected PV system. The creative process of the proposed controller consists of two steps. First, an input-output linearization method is used to eliminate ...
Read More
In this paper, a new robust hybrid controller (RHC) is proposed to regulate current, voltage and, as a result, power output of a three-phase grid connected PV system. The creative process of the proposed controller consists of two steps. First, an input-output linearization method is used to eliminate system nonlinearities. Then, a robust PI controller is designed to reach the desired control objective. The robustness of PI is guaranteed by Lyapunov stability theory. Also, a maximum power point tracking (MPPT) algorithm is provided to adjust the PV output voltage for extracting MPP under various atmospheric conditions. To evaluate the performance of the proposed controller, different system conditions such as standard, considering uncertainties and three-phase short-circuit fault, are simulated and the results are compared with a feedback linearization controller (FLC). The results show superiority of the performance and robustness of the designed RHC versus various uncertainties such as solar irradiation and ambient temperature.
Power systems
Ali Karimabadi; Mohammad Ebrahim Hajiabadi; Ebadollah Kamyab; Ali Asghar Shojaei
Abstract
Over the recent years, a number of new maintenances methods for high voltage substations have been introduced to reduce the number of substation events. The primary purpose of the present study is to presents a Cost-benefit analysis for Circuit-Breakers (CBS) in a substation equipped with Condition Monitoring ...
Read More
Over the recent years, a number of new maintenances methods for high voltage substations have been introduced to reduce the number of substation events. The primary purpose of the present study is to presents a Cost-benefit analysis for Circuit-Breakers (CBS) in a substation equipped with Condition Monitoring (CM) devices. To this end, a mathematical formulation to categorize and model equipment failures based on their severity is developed. By CM, some of severity failures, named major failures, can be detected early, and corrected as the minor failure. This formulation quantifies the effect of CM devices on the outage rate and Predictive Maintenance (PDM) rate of the equipment. The PDM rate is used to modify the Markov maintenance model for the equipment. The proposed modified Markov model quantifies the effect of CM on the maintenance costs and lifetime of CB. The New Markov model is compared with the Preventive Maintenance (PM) model. Expected Energy Not Supply (EENS) and reliability Cost are calculated with and without CM on CBs. Finally, the proposed model is applied on the CBs of 400/132/20KV substation in the Khorasan Regional Electricity Company (KREC) in Iran. The obtained results show that CM on CBs of substations improves the EENS and reliability cost by 82.43 %. Moreover, the maintenance cost of the proposed model shows an improvement of 9.07 % compared to PM model. Finally, the total annual costs show an improvement of 80.67% due to CM on CBs.
Power systems
Akbar Karimipouya; Shahram Karimi; Hamdi Abdi
Abstract
the main challenge in associate islanded Micro grid (MG) is the frequency stability due to the inherent low-inertia feature of distributed energy resources. That is why, energy storage devices, are utilized in MGs as the promising sources for grid short-term frequency regulation. Though energy storage ...
Read More
the main challenge in associate islanded Micro grid (MG) is the frequency stability due to the inherent low-inertia feature of distributed energy resources. That is why, energy storage devices, are utilized in MGs as the promising sources for grid short-term frequency regulation. Though energy storage devices, improve the dynamic response of the load frequency control system, these devices increase system costs. Moreover, the modification or uncertainty of the system parameters will significantly degrade the performance of the conventional load-frequency control system. This article proposes the implementation of rotating-mass-based virtual inertia in Double-Fed Induction Generator (DFIG) to support the primary frequency control associated an adaptive Neuro-Fuzzy Inference System (ANFIS) controller, as the secondary frequency control. The simulation results illustrate that the suggested control scheme ameliorate the dynamic response and performance of the load frequency control system and also the studied islanded MG remains stable, despite severe load variation and parametric uncertainties.
Power systems
Ehsan Talebian Kouchaksaraei; Mehrdad Ahmadi Kamarposhti
Abstract
Limitation of fossil fuel reserves and environmental pollution resulting from their use, especially in cities, as well as low efficiency of current energy converters lead to the tendency towards the use of more efficient energy converters and renewable energy sources. The use of distributed generation ...
Read More
Limitation of fossil fuel reserves and environmental pollution resulting from their use, especially in cities, as well as low efficiency of current energy converters lead to the tendency towards the use of more efficient energy converters and renewable energy sources. The use of distributed generation (DG) is one of the appropriate solutions in this regard. There are various techniques provided to control these converters. In this study a new technique of Direct Power Control (DPC) is proposed to connect distributed generation sources to the nationwide grid. This technique not only adds power of distributed generation sources to the grid, but also is capable to compensate the reactive and harmonic power of non-linear loads as well. In this study, Converters’ voltage references for generating compensation current are directly calculated in synchronous rotating coordinate system in each period of sampling; then, a proper pulse width modulation (PWM) generates the used voltages. The proposed DPC technique has some advantages including simple algorithm of fast dynamic as well as fixed switching frequency and small sampling frequency. The performance of the proposed direct control technique is confirmed by simulation results.
Power systems
Reza Sedaghati; Mahmoud Reza Shakarami
Abstract
A single-phase distributed generation (DG) sources embedded in three-phase microgrids develop with a fast-paced trend, it is important to make use of suitable power sharing strategies among multiple DGs and utilizing the power generation of these units to the full capacity. This paper presents an innovative ...
Read More
A single-phase distributed generation (DG) sources embedded in three-phase microgrids develop with a fast-paced trend, it is important to make use of suitable power sharing strategies among multiple DGs and utilizing the power generation of these units to the full capacity. This paper presents an innovative sliding mode-based power control strategy for microgrids. The multi-bus microgrid consists of three-phase DG units that are two photovoltaic (PV) array, and three single-phase DG units including PV, battery and fuel cell (FC). The dynamic modeling of all DGs is based on voltage source inverter (VSI). One of the three-phase DGs is responsible for frequency and voltage control, and the other one for current control. The single-phase DGs are controlled based on the three-phase DGs. Finally, the voltage and power control operations are implemented in a per-unit system. The proposed control strategy has a fast response and the ability to trace a reference signal with a low steady-state error compared with the PI controller; moreover, it provides the accurate active and reactive power sharing among energy units under various loading and fault conditions along with robustness against the microgrid parameters. Additionally, the ability to maintain the dc-link voltage and frequency constant is another feature of this controller.
Power systems
mohammadreza sheibani; abbas ketabi; mostafa nosratabadi
Abstract
Harmonic state estimation (HSE) is the process of assigning a value to an unknown system state harmonic variable based on measurements from that system according to some criteria. Determining the best harmonic meters places in the system helps to increase the accuracy of the HSE. In this paper, a methodology ...
Read More
Harmonic state estimation (HSE) is the process of assigning a value to an unknown system state harmonic variable based on measurements from that system according to some criteria. Determining the best harmonic meters places in the system helps to increase the accuracy of the HSE. In this paper, a methodology is presented for optimal placement of power quality (PQ) meters in a power system. The PQ meters results are used to estimate the unknown harmonic variables. Mean square errors of estimated total harmonic distortions in normal condition is selected as the cost function, while single line and meter loss contingencies are also considered by formulating a multi-objective optimization exercise. To achieve this, seeker optimization algorithm (SOA) based on Pareto optimum method has been proposed here. Simulation are performed on an IEEE 14-bus test system. The simulation results demonstrate the effectiveness of the proposed methodology for harmonic state estimation and optimal meter placement.
Power systems
Zahra Nasiri-Gheidari; Mehrage Ghods; Hashem Oraee
Abstract
In this paper no-load and full-load performance of Permanent Magnet Vernier Generators (PMVGs) is investigated in fully-aligned condition and under different types of mechanical faults. The studied mechanical faults are Static Eccentricity (SE), Dynamic Eccentricity (DE), Inclined Rotor (IR), and Run-out ...
Read More
In this paper no-load and full-load performance of Permanent Magnet Vernier Generators (PMVGs) is investigated in fully-aligned condition and under different types of mechanical faults. The studied mechanical faults are Static Eccentricity (SE), Dynamic Eccentricity (DE), Inclined Rotor (IR), and Run-out (RO). Furthermore, an analytical model is developed to calculate the permeance of the air-gap and the induced voltages in the health machine and under studied mechanical faults. Then, 2-D and 3-D time stepping finite element method is utilized for performance evaluation of the generator. Some discussions are made on the quality of induced voltages, torque ripples, variations of axial and radial forces and the output power of the generator under the mechanical faults considering resistive, inductive and capacitive loads connected to the terminals of the generator. Finally, the performance of an outer rotor conventional permanent magnet generator (CPMG), considering constant dimensions, constant PM, copper and iron usage is compared with the studied PMVG. The performance of two generators is studied in fully-aligned condition as well as under SE and DE.
Power systems
Javid Khorasani; Ehsan Monabbati; Habib Rajabi Mashhadi
Abstract
In this paper, the bidding problem in electricity markets is formulated from the viewpoint of a generation company. With focus on Iran's electricity market structure, the objective is to design an optimal linear bid function considering pay-as-bid pricing mechanism. The market clearing price is considered ...
Read More
In this paper, the bidding problem in electricity markets is formulated from the viewpoint of a generation company. With focus on Iran's electricity market structure, the objective is to design an optimal linear bid function considering pay-as-bid pricing mechanism. The market clearing price is considered as a stochastic variable. The bidding problem is formulated as a nonlinear optimization problem from the viewpoint of a price-taker generation company. Then a numerical study is performed to show the effect of stochastic characteristics of market price on the optimal values of bidding parameters. In order to have more expected profit, a mathematical problem is designed and solved to partition the generation capacity. The main aim of this paper is presentation of a classic method to find the optimal bid function while from the viewpoint of a price-taker generation company in a pay-as-bid electricity market. An example is designed to calculate a linear bid function using the proposed technique. Also a comparison between step-wise and linear bidding is presented.
Power systems
Mohammad Ghiasi
Abstract
Load flow (LF) is one of the most important parts to study and analyze power system operation. In this research paper, a detailed study for load flow analysis in distributed power system (DPS) is presented. A case study of modeling and simulation of the actual power distribution network is implemented ...
Read More
Load flow (LF) is one of the most important parts to study and analyze power system operation. In this research paper, a detailed study for load flow analysis in distributed power system (DPS) is presented. A case study of modeling and simulation of the actual power distribution network is implemented with the electrical transient analyzer program (ETAP) software (version: 12.6). Furthermore, a comparison of common load flow techniques of power distribution is presented. In this assessment, numerical and practical methods including Newton-Raphson (NR), Fast Decoupled (FD), and Accelerated Gauss-Seidel (AGS) are provided and compared. The results (total generation, loading, demand, system losses, and critical report of load flow) are obtained and analyzed. This paper focuses on the detailed assessment and monitoring by using the most modern ETAP software, from high voltage substation (HVS) to the loads. The capability and effectiveness of load flow assessment are demonstrated according to the simulation results obtained with ETAP by applying it to the actual distributed power system of Tehran metro (subway). Once the modeling is performed in ETAP for complete power system, it might be highly beneficial for converting conventional grid into smart grid.
Power systems
Hooman Khaloie; Amir Abdollahi; Masoud Rashidinejad
Abstract
This paper develops a new possibilistic-scenario model for a wind power plant to determine its optimal self-scheduling (SS) in the presence of high-impact low-probability events uncertainty. Nowadays, in the context of the power system, examining the effects of extreme weather events in the category ...
Read More
This paper develops a new possibilistic-scenario model for a wind power plant to determine its optimal self-scheduling (SS) in the presence of high-impact low-probability events uncertainty. Nowadays, in the context of the power system, examining the effects of extreme weather events in the category of high-impact low-probability (HILP) events has become one of the most important issues for researchers all around the world. There are so many reports of HILP events which acknowledge that these incidents can directly affect the power plants and cause them to fail. Generally, the self-scheduling of generating units in the pre-extreme weather conditions would be different from normal conditions. In such manners, this paper tries to address the self-scheduling problem of a wind power plant in pre-extreme weather conditions. For this purpose, there are numerous uncertainty sources in the SS problem that could affect the final results which include electricity prices, wind power production and contingency-based lack of production in the face of HILP events. In this regard, this paper proposes an efficient hybrid probabilistic-possibilistic assessment tool for dealing with these uncertainties. Additionally, CVaR evaluation was used as the intrinsic risk management tool of both probabilistic and possibilistic parameters in the SS problem.
Power systems
Reza Safipour; Mahmoud Oukati Sadegh
Abstract
Energy storage systems, along with many capabilities in the grid, are costly technologies. Therefore, their economic issues should be also considered while they are used in the grid. In this paper, a method has been proposed that can be used to determine the location, power, and capacity of the energy ...
Read More
Energy storage systems, along with many capabilities in the grid, are costly technologies. Therefore, their economic issues should be also considered while they are used in the grid. In this paper, a method has been proposed that can be used to determine the location, power, and capacity of the energy storage systems with consideration of the technical and economic aspects, simultaneously. Technical goals of this method are improvement of voltage profile and loss reduction, while economic objectives are including reduction of investment cost, operation and maintenance cost of the energy storage system. The problem of optimization is solved with the symbiotic organisms search algorithm. The main advantage of this algorithm is the absence of specific regulatory parameters compared to other meta-heuristic algorithms. The proposed plan has been implemented safely. Safe performance is achieved by enforcing security constraints such as voltage and power balancing and constraints for the energy storage system, such as capacity of energy and power constraints, and amount of energy stored. The distributed generation used in this plan is wind power plant. The output of each turbine is determined by a linear model reliant on wind speed. The proposed method has been implemented on the IEEE 33 bus grid. The results demonstrate the efficiency and capability of the proposed method.
Power systems
Parnian Fakhrooeian; mehrdad Abedi; peyman karimyan
Abstract
Nowadays short-term voltage instability is a major threat for power system reliability and stability owing to the increasing proportion of renewable energy sources such as solar and wind power, induction motor loads, HVDC links and etc. The aim of this paper is to determine the optimal location and size ...
Read More
Nowadays short-term voltage instability is a major threat for power system reliability and stability owing to the increasing proportion of renewable energy sources such as solar and wind power, induction motor loads, HVDC links and etc. The aim of this paper is to determine the optimal location and size of static VAR compensator (SVC) to counteract the short-term voltage instability. A multi-objective optimization problem (MOP) is defined to satisfy the two objective functions: 1) minimizing the whole investment cost 2) minimizing the undesirable behavior of transient voltage under multiple probable contingencies. Composite load model consisting of induction motor loads and other components is modeled accurately. Moreover, the system is considered with a high penetration of wind power. Severity and risk indices are proposed to measure the degree of transient voltage performances. Candidate buses for SVC deployment are determined based on trajectory sensitivity analysis. Genetic algorithm is employed to find optimal allocation of SVC. The effectiveness of proposed approach is verified on New England 39-bus system.
Power systems
Mehrdad Ahmadi Kamarposhti
Abstract
Microgrid is defined as a controllable unit which consists of Distributed Generations (DG), loads, energy storages and control devices. Microgrid has two operation modes including grid connected mode and islanding mode. In grid connected mode, voltage and frequency of microgrid is controlled by main ...
Read More
Microgrid is defined as a controllable unit which consists of Distributed Generations (DG), loads, energy storages and control devices. Microgrid has two operation modes including grid connected mode and islanding mode. In grid connected mode, voltage and frequency of microgrid is controlled by main grid and DG’s supply total or part of the loads. In the islanding mode, the microgrid is disconnected from main grid because of a fault or a preplanned switching in connecting line. In this mode, DG’s should satisfy the power demand of sensitive loads in microgrid. Since the only generation units in an islanded microgrid are existing DG units which usually are from several types. Consequently besides feeding total loads, voltage and frequency of microgrid should be controlled by these DG units. Hence, the microgrid could supply high power quality and reliability to customers. This paper presents an optimization method to optimize the parameters of the Microgrid controller in islanding mode. The controller optimal parameters have been obtained by using the particle swarm optimization (PSO). This is done based on minimization of the error in the current and voltage controllers. Finally, simulation has been carried out to verify the effectiveness of the optimized controller. Stability analysis of the controller is verified using classical approach.