Research paper
A. Benyaghoob sani; M. Sedighizadeh; D. Sedighizadeh; R. Abbasi
Abstract
An optimal day-ahead operation of a microgrid based on coastal energy hub is presented in this paper. The proposed CEH included wind turbine, photovoltaic unit, combined cooling, heat and power, and seawater desalination. The purpose of the optimization is minimization of the operational and environmental ...
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An optimal day-ahead operation of a microgrid based on coastal energy hub is presented in this paper. The proposed CEH included wind turbine, photovoltaic unit, combined cooling, heat and power, and seawater desalination. The purpose of the optimization is minimization of the operational and environmental costs considering several technical limitations. The CEH includes an ice storage conditioner together with an energy storage system, i.e. thermal energy storage system. Particularly, the impacts of an innovative rechargeable and emerging ESS that is solar-powered compressed air energy storage is scrutinized, on the efficiency and operational and pollution costs of the CEH. It is clear that there is an intrinsic deviation between predicted and actual uncertainty variables in MG. This paper presents a bi-level stochastic optimal operation model based on risk averse strategy of information gap decision theory to overcome this information gap and to help Microgrid operator. To reduce the complexity of the proposed model, Karush-Kuhn-Tucker method is used for converting the bi-level problem into a single level. The Augmented Epsilon Constraint method is used to deals with multi objective optimization problem to harvest the maximum horizon of the uncertainties of the parameters. The proposed model implemented the Time of Use program as a price-based demand response program. Finally, the efficacy of the SPCAES for minimizing the operational cost and pollutions in the day-ahead operation is depicted by implementation of the presented model on the typical CEH.
Research paper
M. Shahriyari; H. Khoshkhoo
Abstract
Unlike other rotor angle stability assessment methods which only deal with either transient or small-signal (SS) stability, in this paper, a new stability prediction approach has been proposed which considers both transient and SS stability status. Therefore, the proposed method, which utilizes Multi-Layer ...
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Unlike other rotor angle stability assessment methods which only deal with either transient or small-signal (SS) stability, in this paper, a new stability prediction approach has been proposed which considers both transient and SS stability status. Therefore, the proposed method, which utilizes Multi-Layer Perceptron-based deep learning model, can comprehensively predict the post-disturbance rotor angle stability. Since the proposed method uses the voltage of the generating units directly measured by WAMS in the early moments after the disturbance occurrence and does not need to calculate the generators' rotor angle (which requires a high computational burden), it can timely predict the stability stiffness using data provided by PMUs installed at generators' buses. In this respect, this method provides a proper chance for the system operators to take appropriate corrective measures. To evaluate the proposed method's efficiency, it has been implemented and tested on IEEE14-bus and IEEE 39-bus test systems. The dynamic simulation results show that although the proposed method requires fewer PMUs than previous methods that exist in the literature, it can timely evaluate the stability status. Also, to properly show the power system stability stiffness from the transient and SS stability point of view, the suggested method accurately classifies the post-disturbance operating point into Unstable, Alarm, or Normal categories.
Research paper
J. Salehi; F.S. Gazijahani; A. Safari
Abstract
Executing interruptible loads (ILs) can be significantly effective for optimal and secure operation of power systems. These ILs can aid the operators not only to increase the reliability of the power supply but also to reduce the procurement costs of the whole system. Therefore, determining the optimal ...
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Executing interruptible loads (ILs) can be significantly effective for optimal and secure operation of power systems. These ILs can aid the operators not only to increase the reliability of the power supply but also to reduce the procurement costs of the whole system. Therefore, determining the optimal location and capacity of ILs for a given incentive rate is of great interest to distribution companies. To do so, in this paper simultaneous allocation and sizing of ILs, wind turbines (WT), photovoltaic (PV) and capacitors have been done in the radial distribution network for different demand levels and subsequently the optimal value of compensation price for the ILs has been determined. Given the probabilistic nature of load, wind and solar generation as well as the price of energy at the pool, we have also proposed a stochastic model based on fuzzy decision making for modelling the technical constraints of the problem under uncertainty. The objective functions are technical constraint dissatisfaction, the total operating costs of the Distribution Company and CO2 emissions which are minimized by NSGA2. To model the uncertainties, a scenario-based method is used and then by using a scenario reduction method the number of scenarios is reduced to a certain number. The performance of the proposed method is assessed on the IEEE 33-node test feeder to verify the applicability and effectiveness of the method.
Research paper
P. Omidi; S. Abazari; S.M. Madani
Abstract
The relay coordination problem of directional overcurrent has been an active research issue in distribution networks and power transmission. In general, the problem of relay coordination is the nonlinearity of the optimization problem, which increases or decreases with different network structures. ...
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The relay coordination problem of directional overcurrent has been an active research issue in distribution networks and power transmission. In general, the problem of relay coordination is the nonlinearity of the optimization problem, which increases or decreases with different network structures. This paper presents a new method with directional overcurrent relay coordination approach to reduce the operating time of the relays between the primary and backup relays by using hybrid programming of ILP (interval linear programming) and DE (differential evolution). Due to the difference in short circuit current level from grid connected to the isolated mode, therefore, it is necessary to use a reliable protection solution to reduce this discrimination time and also to prevent the increase of coordination time interval (CTI). The ability of the objective function used in this paper is to reduce the discrimination time of primary and backup relays and simultaneously reduce the operating time of primary and backup relays by introducing a new method. The basic parameters of the directional overcurrent relay (DOCR) such as time multiplier setting (TMS) and plug setting (PS) have been adjusted such that the relays operation time should be optimized. Optimization is based on a new objective function, described as a highly constrained non-linear problem to simultaneously minimize operating time in backup and primary relays. A function of penalty is also used to check the problem constraints in case the backup relay time is fewer than that of the main relay. The method is implemented on modified IEEE 14- and 30-bus distribution networks. The results demonstrate the efficiency of the method, and the values are optimal compared to those of other algorithms. MATLAB program has also been used to simulate optimization.
Research paper
P. Sarvghadi; M. Monfared
Abstract
Parallel connection of two or even more single-phase inverter modules is a successful solution to increase the reliability and the efficiency of an inverter at moderate power levels. Stable operation and proper current sharing among parallel inverter modules is a key issue, especially when they are connected ...
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Parallel connection of two or even more single-phase inverter modules is a successful solution to increase the reliability and the efficiency of an inverter at moderate power levels. Stable operation and proper current sharing among parallel inverter modules is a key issue, especially when they are connected to a common load through unequal output filter impedances. In this paper, a new formulation and consequently a proper current sharing control algorithm for parallel connected inverter modules with the possibility of unequal filter impedances is proposed. Also a dual-loop voltage control with the filter current as the inner loop feedback signal, considering the effect of digital control delay, is adopted. The controller parameters are designed according to a frequency domain analysis. Finally, theoretical achievements are confirmed by experimental test results on a test rig with two 250 W parallel connected single phase inverters.
Research paper
R. Younesi; J. Rastegar; M. Rastgarpour
Abstract
High Efficiency Video Coding (HEVC) is one of the latest coding standards targeting high-resolution video contents. Due to the high complexity of the existing hardware implementation, this paper presents the low-cost and efficient DCT architectures for HEVC, which are able to perform DCT operation of ...
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High Efficiency Video Coding (HEVC) is one of the latest coding standards targeting high-resolution video contents. Due to the high complexity of the existing hardware implementation, this paper presents the low-cost and efficient DCT architectures for HEVC, which are able to perform DCT operation of multiple transform sizes in a single unified architecture. Our objective is to reuse the hardware resources in a DCT architectures using configurable constant multipliers as well as reducing the hardware cost and trading off between hardware complexity and efficiency. We propose three different shift-and-add units with different hardware cost and throughput. The main advantage of the proposed architectures over the existing architectures is a lower hardware and it can also perform DCT transform of different transform units which is available in HEVC standard. The experimental results over 90-nm technology show that the proposed 2D-DCT architecture #1 archives the lowest hardware cost amongst the rest of the architectures with around 57% reduction in gate count, on average. The unfolded 2D-DCT architectures #2 and #3 offer the moderate reduction in gate count around 47%, on average, with a moderate throughput. Apart from architectures #1, #2, and #3, we also develop a reusable architecture by adding an extra ( )-point DCT alongside the main DCT.
Research paper
M. Nikpayam; M. Ghanbari; A. Esmaeli; M. Jannati
Abstract
Reliability for electric motor drive systems is very vital in some industries. Selecting an appropriate control strategy for driving an electric motor during fault conditions is one of the most important issues mainly for safety-critical applications. Recently, vector control (VC) strategies have been ...
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Reliability for electric motor drive systems is very vital in some industries. Selecting an appropriate control strategy for driving an electric motor during fault conditions is one of the most important issues mainly for safety-critical applications. Recently, vector control (VC) strategies have been extensively developed for star-connected three-phase induction motor drives during single-phase cut-off fault (COF) based on two different transformation matrices (TMs). Despite the effectiveness of these methods during the fault, these control systems are very complex due to their extensive on-line computation. This paper presents two simple methods based on indirect VC (IVC) and direct VC (DVC) methods for controlling a star-connected three-phase induction motor during the fault condition. The fault in this paper is limited to single-phase COF which can occur in motor stator coils. In this paper, it is shown that using a suitable TM and some changes in the control parameters, it is possible to control the faulted drive system. Performance of the proposed control methods is verified using MATLAB software and DSP/TMS320F28335 controller board for a 0.75kW star-connected three-phase induction motor drive system. The achieved results show the good performance of the introduced control systems in different operating conditions. In addition, the results demonstrate the performance of the proposed VC strategies and that of the previous works are almost the same. However, the proposed VC methods in this paper need less modification in the structure of the standard VC strategy than the previous works.
Research paper
F. Babaei; A. Safari; J. Salehi
Abstract
In the integrated electrical systems, frequency control service considering the electric vehicle (EV) aggregators could lead to time-varying delay in load frequency control (LFC) schemes. These delays influence the LFC system efficiency, and in some situations, the lack of a clear choice of a control ...
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In the integrated electrical systems, frequency control service considering the electric vehicle (EV) aggregators could lead to time-varying delay in load frequency control (LFC) schemes. These delays influence the LFC system efficiency, and in some situations, the lack of a clear choice of a control strategy considering the time-varying delays causes power system instability. Thus, this paper illustrates different time-varying delays based on the stability of an LFC system in the EV aggregators presence. The LFC's delay-dependent stability study is executed for finding the stability region and, stability criteria is suggested using the linear matrix inequality (LMI) method and Lyapunov-Krasovskii theory. Also, Wirtinger-based improved inequality and bounding lemma are applied to compute the greatest allowable delay in the LFC system, including the EV aggregators.
