Power
S. Abbasi; D. Nazarpour; S. Golshannavaz
Abstract
Background and Objectives: Distributed generations (DGs) based on renewable energy, such as PV units, are becoming more prevalent in distribution networks due to technical and environmental benefits. However, the intermittency and uncertainty of these sources lead to technical and operational challenges. ...
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Background and Objectives: Distributed generations (DGs) based on renewable energy, such as PV units, are becoming more prevalent in distribution networks due to technical and environmental benefits. However, the intermittency and uncertainty of these sources lead to technical and operational challenges. Energy storage application, uncertainty analysis, and network reconfiguration are apt therapies to resist these challenges. Methods: Energy management of modern, smart, and renewable-penetrated distribution networks is tailored here considering the uncertainties correlations. Network operation costs including switching operations, the expected energy not served (EENS) index as the reliability objective, and the node voltage deviation suppression as the technical objective are mathematically modeled. Multi-objective particle swarm optimization (MOPSO) is considered as the optimization engine. Scenario generation method and Nataf transformation are used in probabilistic evaluations of the problem. Moreover, the technique for Order Preference by Similarity to the Ideal Solution (TOPSIS) is deployed to make a final balance between different objectives to yield a unified solution.Results: To show the effectiveness of the proposed approach, the IEEE 33-node distribution network is put under extensive simulations. Different cases are simulated and interrogated to assess the performance of the proposed model.Conclusion: For different objectives dealing with different aspects of the network, remarkable achievements are attained. In brief, the final solution shows 4.50% decrease in operation cost, 13.07% improvement in reliability index, and 18.85% reduction in voltage deviation compared to the initial conditions.
Power
M. Tolou Askari
Abstract
Background and Objectives: Development of intermittent wind generation has necessitated the inclusion of several creative approaches in modeling the deregulated power market with presence of wind sources. The uncertain nature of wind resources will cause the private companies meet several risk in their ...
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Background and Objectives: Development of intermittent wind generation has necessitated the inclusion of several creative approaches in modeling the deregulated power market with presence of wind sources. The uncertain nature of wind resources will cause the private companies meet several risk in their medium and long term planning in a restructured power market. In addition to considering the uncertainties such as load, fuel costs, wind power generation and technical actions of rivals for modeling the restructured power market, the regulatory policies i.e incentive policy for wind resources and Carbon tax should be assumed in this approach. Methods: The first contribution of this article is to propose a developed mathematical model in order to evaluate the medium term deregulated power market by assuming the hybrid wind-thermal power plants. The second contribution is to evaluate the impact of different types of Feed in Tariff supports on Market Clearing Price, Expected Cost for Government, profits and contribution of each firm in electricity generation in the restructured power market. Also the scenario based method has been used to generate the scenarios for wind uncertainties and then their reliability validate based on the statistical methods.Results: The proposed mathematical model in the first contribution is calculated for each season and load levels based on the proposed wind scenarios. The functionality and feasibility of this model is demonstrated by simulation studies. Conclusion: The proposed model in this article can be so useful for evaluating the different types of incentive policies for renewable energies. Moreover, this study confirms the previous researches that selected the Feed in Tariff as an efficient approach for developing the wind resources.
Power
P. Naderi; B. Ehsan Maleki; H. Beiranvand
Abstract
Background and Objectives: In this paper, a novel objective function is proposed for designing the power system stabilizers (PSSs). Although the object of the previous designs was to enhance the critical modes' stability, the derived stability indices were, to some extent, low and in some cases not acceptable ...
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Background and Objectives: In this paper, a novel objective function is proposed for designing the power system stabilizers (PSSs). Although the object of the previous designs was to enhance the critical modes' stability, the derived stability indices were, to some extent, low and in some cases not acceptable at all. The prospect of attaining higher stability motivated authors to design a new objective function in this study. In all the previous objective functions, the same priority is accorded to all modes, and an objective function is generally defined. A novel function is presented, called Variable Slope Damping Scale (VSDS), based on the assumed variable slope for the straight line in the fan-shaped region, which is an area in the complex plane for determining the eigenvalue placement range, with a reference tip at the negative point. This can be an efficient solution to the low value of critical modes' stability. In general, more damping for critical modes and lower priority for searching non-critical modes are taken as key points. The result of applying VSDS leads to a high value of damping scales for critical modes. The nonlinear simulation results and eigenvalues analysis has demonstrated that the proposed approach in this study is highly effective in damping the most critical modes.Methods: The proposed method assumes a variable slope for the straight line of the convergence region (specified area for placement of poles) in a fan-shaped type. Indeed, the increase in critical mode's damping scale is taken into account as a key point to introduce a powerful objective function.Results: The value of the damping scale and also the overall dynamic stability of the test system has increased by using the proposed objective function.Conclusion: Also, it has been shown that a variable slope convergence region is better than that of a constant slope one to the optimal tuning of WAPSS. In other words, the value of the damping scale with the proposed method over the existing techniques clearly shows that the proposed objective function is more effective than the other ones.
Power
Z. Dehghani Arani; S. A. Taher; M. H. Karimi; M. Rahimi
Abstract
Background and Objectives: The wind turbines (WTs) with doubly fed induction generator (DFIG) have active and reactive power as well as electromagnetic torque oscillations, rotor over-current and DC-link over-voltage problems under grid faults. Solutions for these problems presented in articles can be ...
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Background and Objectives: The wind turbines (WTs) with doubly fed induction generator (DFIG) have active and reactive power as well as electromagnetic torque oscillations, rotor over-current and DC-link over-voltage problems under grid faults. Solutions for these problems presented in articles can be classified into three categories: hardware protection devices, software methods, and combination of hardware and software techniques.Methods: Conventional protection devices used for fault ride through (FRT) capability improvement of grid-connected DFIG-based WTs impose difficulty in rotor side converter (RSC) controlling, causing failure to comply with grid code requirements. Hence, the main idea in this paper is to develop a novel coordinated model predictive control (MPC) for the power converters without need to use any auxiliary hardware. Control objectives are defined to maintain DC-link voltage, rotor current as well as electromagnetic torque within permissible limits under grid fault conditions by choosing the best switching state so as to meet and exceed FRT requirements. Model predictive current and electromagnetic torque control schemes are implemented in the RSC. Also, model predictive current and DC-link voltage control schemes are applied to grid side converter (GSC).Results: To validate the proposed control method, simulation studies are compared to conventional proportional-plus-integral (PI) controllers and sliding mode control (SMC) with pulse-width modulation (PWM) switching algorithm. In different case studies comprising variable wind speeds, single-phase fault, DFIG parameters variations, and severe voltage dip, the rotor current and DC-link voltage are respectively restricted to 2 pu and 1.2 times of DC-link rated voltage by the proposed MPC-based approach. The maximum peak values of DC-link voltage are 1783, 1463 and 1190 V by using PI control, SMC and the proposed methods, respectively. The maximum peak values of rotor current obtained by PI control, SMC and the proposed strategies are 3.23, 3.3 and 1.95 pu, respectively. Also, PI control, SMC and the proposed MPC methods present 0.8, 0.4 and 0.14 pu, respectively as the maximum peak values of electromagnetic torque.Conclusion: The proposed control schemes are able to effectively improve the FRT capability of grid-connected DFIG-based WTs and keep the values of DC-link voltage, rotor current and electromagnetic torque within the acceptable limits. Moreover, these schemes present fast dynamic behavior during grid fault conditions due to modulator-free capability of the MPC method.
Power
F. Amiri; M. Moradi
Abstract
Background and Objectives: Virtual inertia control, as a component of a virtual synchronous generator, is used for the implementation of synchronous generator behaviour in microgrids. In microgrids that include high-capacity distributed generation resources, in addition to virtual inertia, virtual damping ...
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Background and Objectives: Virtual inertia control, as a component of a virtual synchronous generator, is used for the implementation of synchronous generator behaviour in microgrids. In microgrids that include high-capacity distributed generation resources, in addition to virtual inertia, virtual damping can also lead to improvement of frequency stability of the microgrid. The purpose of the control method for the islanded microgrid is to be: 1) robust to the uncertainty of the microgrid parameters. 2) Weaken the disturbances on the islanded microgrid (wind turbine, solar cell, Loads). 3) Improved response speed related to microgrid frequency deviation (reduced settling time).Methods In this paper, designing a new robust control method for controlling virtual inertia in microgrids, with regard to virtual damping, has been attempted. The proposed method has a higher degree of freedom compared to the conventional robust controllers, which provides better control of the system.Results: Results of the proposed method for virtual inertia control with regard to virtual damping has been compared in several scenarios –with virtual inertia control based on optimized PI controllers with regard to virtual damping, virtual inertia control based on model predictive control (controller) with regard to virtual damping,Self-adaptive virtual inertia control using fuzzy logic, virtual inertia control with regard to virtual damping, and virtual inertia control without virtual damping (conventional methods). Compared to other control methods, the proposed controller has improved the settling time due to the frequency deviations of the islanded microgrid by 27%. According to the results of the scenarios, the proposed controller has been able to reduce the frequency error due to load and distributed generation resource disturbances and compared to other controllers, and this frequency deviation has been reduced by 68%.Conclusion: According to the simulation results, the proposed controller has a better performance than other controllers in improving the frequency stability of the islanded microgrid.
Power
E. Limuchi; A. Taher; B. Ganji
Abstract
Background and Objectives: The microgrid voltage and frequency are strongly affected by active and reactive load fluctuations. Load change in microgrid may result in the lack of balance among generation and consumption and as a result change in output voltage and frequency. If load change is great enough, ...
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Background and Objectives: The microgrid voltage and frequency are strongly affected by active and reactive load fluctuations. Load change in microgrid may result in the lack of balance among generation and consumption and as a result change in output voltage and frequency. If load change is great enough, distribution generation cannot stabilize the microgrid. The main objective of this article is to control the distribution of active and reactive power related to an inverter-based distributed generation (DG) in the microgrid using intelligent methods. Methods: In this study, frequency and voltage of an active generator connected to the microgrid is also controlled with applying adaptive the fuzzy sliding mode control (AFSMC) and the droop control Methods To solve the problems related to design of the sliding mode controller, a compensator control system is suggested. A rule based on the Lyapunov stability theory is also introduced to ensure the stability of closed loop system.Results: Using MATLAB/SIMULINIK software, simulation results are provided for the proposed controller and its performance under different conditions for a typical power system is evaluated. Simulation of the considered power system is done to track different values of active and reactive power.Conclusion: The provided simulation results show the effectiveness of suggested method to regulate active and reactive power and to control voltage and frequency of the microgrid.
Power
H. Amiri; G. Arab Markadeh; N. Mahdian
Abstract
Background and Objectives: Increasing DC loads along with DC nature of distributed energy resources (DERs) raises interest to DC microgrids. Conventional droop/non-droop power-sharing in microgrids suffers from load dependent voltage deviation, slow transient response, and requires the parameters of ...
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Background and Objectives: Increasing DC loads along with DC nature of distributed energy resources (DERs) raises interest to DC microgrids. Conventional droop/non-droop power-sharing in microgrids suffers from load dependent voltage deviation, slow transient response, and requires the parameters of the loads, system and DERs connection status.Methods: In this paper, a new nonlinear decentralized back-stepping control strategy for voltage control and load sharing of DC islanded microgrids is proposed. The proposed method is robust against the load variations and uncertainty in microgrid parameters and has excellent dynamic and steady-state performance under different operating conditions. The major purpose of the proposed controller is to improve the transient performance of MG with load variations and constant power loads (CPLs). The local controller regulates the terminal voltage of DC-DC converter regarding the local quantities without needs to additional data of other system components.Results: For simplicity, the proposed method is simulated with PSIM software on a DC microgrid with two DGs. Different scenarios are studied to present the performance of the proposed method under different operating conditions.Conclusion: The results indicate the capability of the proposed method for voltage control and load sharing in DC microgrids.
Power
H. Lasjerdi; Z. Nasiri-Gheidari; F. Tootoonchian
Abstract
Background and Objectives: Wound-Rotor resolvers are the most widely used position sensors in applications with harsh environmental conditions.Methods the resolver performance is exposed to failure due to the high risk of short circuit (SC) fault. Although the output current of the resolver is negligible, ...
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Background and Objectives: Wound-Rotor resolvers are the most widely used position sensors in applications with harsh environmental conditions.Methods the resolver performance is exposed to failure due to the high risk of short circuit (SC) fault. Although the output current of the resolver is negligible, its thin copper wires increase the probability of the short circuit fault. To avoid the propagation of the turn-to-turn SC fault to the whole coil and undesirable performance of the motion control drive, it is necessary to diagnose it at the very beginning of its development. Meanwhile, the first step of diagnosing faults is their modeling. Time stepping finite element analysis is the most accurate, but computationally expensive method for modeling electromagnetic devices. Therefore, it is required to establish an accurate,Results: In this paper, an analytical model based on d-q axes theory is proposed to consider multiple faults, simultaneously. Then, the success of the proposed model is validated by experimental tests on the studied sensor.Conclusion: the proposed model is fast and accurate, so it can be used for the design process.
Power
H. Berahmandpour; S. M. Kouhsari; H. Rastegar
Abstract
Background and Objectives: Uncertainty and variability are two main specifications of wind generation and the ability of the power system to overcome these challenges is called flexibility. The flexibility index is a measure to evaluate the flexibility level of the power system mainly to achieve the ...
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Background and Objectives: Uncertainty and variability are two main specifications of wind generation and the ability of the power system to overcome these challenges is called flexibility. The flexibility index is a measure to evaluate the flexibility level of the power system mainly to achieve the best level system flexibility.Methods: Flexibility index should show a good view of the ability of the power system and also be easily converted to an equivalent cost to be combined with the operation cost function. So, in this paper by using economic dispatch simulation for the economic trade-off between the generation cost and the cost of flexibility, the best level of system flexibility in the presence of wind farms considering unit constraints and system loss is achieved. Where the difference between flexibility index in the no wind base case and the flexibility index in each time zone with wind incorporation is defined as the flexibility penalty by the suitable penalty factor. The combination of generation cost and flexibility cost makes the main part of objective function.Results: The results on the test system verify the proposed method where by increasing penalty factor, improvement in flexibility index is achieved but the generation cost will be increased. So, it shows a good economic trade-off between generation cost and flexibility value. Also the desired flexibility level can be obtained by changing the penalty factor in each wind power penetration. So, the result of the sensitivity analysis shows the best level of flexibility regarding operation cost.Conclusion: In this paper a new flexibility index is introduced especially for wind power incorporation and for real time operation purpose. This index can be combined by economic dispatch objective function as the penalty (cost) for economic trade-off analysis and to show the best flexibility level of generation system in each operation point.
Power
R. Sedaghati; M. Mahmoudian
Abstract
Background and Objectives: Coriolis vibratory gyroscope is one of the most modern types of gyroscopes that has been substituted for the common gyroscopes with some differences in the test mass design and elastic suspension. According to the important features observed in the capacitive excitation of ...
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Background and Objectives: Coriolis vibratory gyroscope is one of the most modern types of gyroscopes that has been substituted for the common gyroscopes with some differences in the test mass design and elastic suspension. According to the important features observed in the capacitive excitation of the actuators regarding the piezoelectric actuators, the operation principles and their formulations are completely changed, which require both two dimensional and finite element analysis to evaluate their optimal performance. Because the sensors are usually vibrating continuously while operation.Methods: In this paper a general framework is presented that fully describes the influence of the parameters related to different frequency operating modes. The main idea of the vibration gyroscope is to replace the rotational rotor with a vibrational structure to utilize the effects of Coriolis force, which causes the secondary motion of a sensitive mass to match an angular velocity.Results: In this paper, the sensitivity analysis and performance evaluation of a hemispherical vibrational gyroscope are discussed. The frequency split phenomenon, the sensed voltage around the resonance frequency and Young's modulus variation are also investigated.Conclusion: Finally, the results of the simulated resonance frequencies are compared and validated with the mathematical and theoretical principles.
Power
M. Nikzad; A. Samimi
Abstract
Background and Objectives: Suitable scheming as well as appropriate pricing of demand response (DR) programs are two important issues being encountered by system operators. Assigning proper values could have effects on creating more incentives and raising customers’ participation level as well ...
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Background and Objectives: Suitable scheming as well as appropriate pricing of demand response (DR) programs are two important issues being encountered by system operators. Assigning proper values could have effects on creating more incentives and raising customers’ participation level as well as improving technical and economical characteristics of the power system. Here, time of use (TOU) as an important scheme of DR is linearly introduced based on the concepts of self and cross price elasticity indices of load demand. Methods: In order to construct an effective TOU program, a combined optimization model over the operation cost and customers’ benefit is proposed based on the security-constrained unit commitment (SCUC) problem. Supplementary constraints are provided at each load point with 24-hour energy consumption requirement along with DR limitations. Results: IEEE 24-bus test system has been employed to investigate the different features of the presented method. By varying DR potential in the system, TOU rates are determined and then their impacts on the customers' electricity bill, operation cost, and reserve cost as well as load profile of the system are analyzed. In addition, the effect of network congestion as a technical limitation is studied. The obtained results demonstrate the effectiveness and applicability of the proposed method. Conclusion: The simulation results demonstrate that the TOU rates leads to financial profit for all customers, reduction of peak load as well as the operation cost while 24-hour energy consumptions of customers at load buses have been fulfilled. Furthermore, the operation cost decreases gradually by attaining more flat load profile. In addition, the effect of lines congestion on the proposed method has been investigated and it has been shown that lines congestion leads to profit reduction of customers at load points connected to the congested lines.======================================================================================================Copyrights©2018 The author(s). This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, as long as the original authors and source are cited. No permission is required from the authors or the publishers.======================================================================================================
Power
P. Vahedi; B. Ganji
Abstract
Background and Objectives: One of the main drawbacks of switched reluctance motors (SRM) is high acoustic noise and significant research has been done to reduce it. In addition, reduction of temperature rise within the machine is usually considered as one of the most important goals of design. Therefore, ...
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Background and Objectives: One of the main drawbacks of switched reluctance motors (SRM) is high acoustic noise and significant research has been done to reduce it. In addition, reduction of temperature rise within the machine is usually considered as one of the most important goals of design. Therefore, a shape design method is introduced in the present paper for the SRM by which both heat transfer and acoustic noise are improved. Methods: For evaluation of the proposed shape design method, a simulation model based on finite element method (FEM) is also developed to predict both the temperature rise within the machine and the produced noise. The simulation model is created using ANSYS finite element (FE) package and it is build up totally as a parametric model in ANSYS parametric design language. Since the convection heat transfer coefficients depend on the temperature rise, they are determined in the developed thermal model based on an iterative algorithm. Results: The proposed shape design method is applied to a typical 8/6 SRM and simulation results including temperature distribution in various sections of the machine, displacement of stator and sound pressure level (SPL) are presented. Conclusion: Based on the obtained simulation results, it is illustrated that the temperature rise and the noise of the SRM could be improved significantly using the introduced shape design method.======================================================================================================Copyrights©2018 The author(s). This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, as long as the original authors and source are cited. No permission is required from the authors or the publishers.======================================================================================================
Power
S.E. Abdollahi; M. Mirzaei
Abstract
Background and Objectives: Linear induction motors (LIMs) are widely employed in rail transportation systems due to their robust, simple and low cost structure. Methods: Several methods have evaluated various topologies' performances in the literature. These methods are more and less effective ...
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Background and Objectives: Linear induction motors (LIMs) are widely employed in rail transportation systems due to their robust, simple and low cost structure. Methods: Several methods have evaluated various topologies' performances in the literature. These methods are more and less effective in the intended structures. In this paper, a new two-dimensional analytical method is presented in order to predict developed thrust force of a single-sided linear induction motor with a solid iron secondary. Results: The skin and saturation effects of the induced eddy currents in the solid iron of the secondary are considered in the proposed method. The analytical results are then compared with the 2D finite element simulation and the experimental ones of the research work of Gieras et al. . Conclusion: Results confirm the accuracy of the proposed analytical and finite element methods for the analysis and design of linear induction motors with solid iron secondary. ======================================================================================================Copyrights©2018 The author(s). This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, as long as the original authors and source are cited. No permission is required from the authors or the publishers.======================================================================================================
Power
B. Ehsan maleki; H. Beiranvand
Abstract
Background and Objectives: In this paper, a non-typical design method of flexible AC transmission systems power oscillation damping (FACTS-POD) controller is proposed to increase the efficiency of these devices. In all of the introduced FACTS-POD devices (taking IPFC-POD as an example), the supplementary ...
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Background and Objectives: In this paper, a non-typical design method of flexible AC transmission systems power oscillation damping (FACTS-POD) controller is proposed to increase the efficiency of these devices. In all of the introduced FACTS-POD devices (taking IPFC-POD as an example), the supplementary controller is designed based upon a conventional approach (i.e., based on optimization algorithms) and using a different method can be useful. Methods: In this paper, the graduated modal decomposition control (GMDC) is utilized as a specific strategy for POD controller design. Moreover, the dynamic model of the multi-machine power system with the presence of IPFC devices has been developed. Results: The obtained model is nonlinear; however, it is linearized around the operating point to design the controllers. The overall paper's structure is based upon the two scenarios, in the first of which conventional method for IPFC-POD design has been analyzed there upon the result compared with the introduced method in the second scenario. Finally, to ascertain responsive of the designed controller to load changes and stability of the system, the probabilistic sensitivity indices (PSIs) are investigated over a large set of operating conditions. As a verification, the time-domain simulations on a 10-machine power system emphasize the analysis of dynamic results and their information under the considered conditions. Conclusion: In general, the specific purpose of this paper is to enhance of the dynamic stability of concerned inter-area modes. The proposed method, especially using GRSA, offers better stability characteristics than the results of previous methods. ======================================================================================================Copyrights©2018 The author(s). This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, as long as the original authors and source are cited. No permission is required from the authors or the publishers.======================================================================================================
