Research paper
Ebrahim Babaei; S. Laali; M.B.B. Sharifian
Volume 2, Issue 2 , December 2014, Pages 81-90
Abstract
In this paper, a new cascaded multilevel inverter by capability of increasing the number of output voltage levels with reduced number of power switches is proposed. The proposed topology consists of series connection of a number of proposed basic multilevel units. In order to generate all voltage levels ...
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In this paper, a new cascaded multilevel inverter by capability of increasing the number of output voltage levels with reduced number of power switches is proposed. The proposed topology consists of series connection of a number of proposed basic multilevel units. In order to generate all voltage levels at the output, five different algorithms are proposed to determine the magnitude of DC voltage sources. Reduction of the used power switches and the variety of DC voltage sources magnitudes are two main advantages of the proposed topology. These results are obtained by comparison of the proposed inverter with the H-bridge cascaded multilevel inverter and one of recently presented topologies. The remarkable ability of the proposed topology with its algorithms in generating all voltage levels (even and odd) is verified through PSCAD/EMTDC simulation and experimental results of a 17-level inverter.
Research paper
H. Bagheri Tolabi; M. H. Ali; M. Rizwan
Volume 2, Issue 2 , December 2014, Pages 91-102
Abstract
This paper presents a new hybrid method for optimal multi-objective reconfiguration in a distribution feeder in addition to determining the optimal size and location of multiple-Distributed Generation (DG). The purposes of this research are mitigation of losses, improving the voltage profile and equalizing ...
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This paper presents a new hybrid method for optimal multi-objective reconfiguration in a distribution feeder in addition to determining the optimal size and location of multiple-Distributed Generation (DG). The purposes of this research are mitigation of losses, improving the voltage profile and equalizing the feeder load balancing in distribution systems. To reduce the search space, the improved analytical method has been employed to select the optimum candidate locations for multiple-DGs, and the intelligent water drops approach as a novel swarm intelligence based algorithm is used to simultaneously reconfigure and identify the optimal capacity for installation of DG units in the distribution network. In order to facilitate the algorithm for multi-objective search ability, the optimization problem is formulated for minimizing fuzzy performance indices. The proposed method is validated using the Tai-Power 11.4-kV distribution system as a real distribution network. The obtained results proved that this combined technique is more accurate and has the lowest fitness value as compared with other intelligent search algorithms. Also, the obtained results leadto the conclusion that multi-objective simultaneous placement of DGs along with reconfiguration can be more beneficial than separate single-objective optimization.
Research paper
R. Kazemzadeh; E. Najafi Aghdam; M. Fallah; Y. Hashemi
Volume 2, Issue 2 , December 2014, Pages 103-112
Abstract
This paper presents a comparative analysis between two current control strategies, constant source power and generalized Fryze current, used in Active Power Filter (APF) applications having three different modulation methods. The Hysteresis Band (HB) and first-order Delta-Sigma Modulation (DSM) as well ...
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This paper presents a comparative analysis between two current control strategies, constant source power and generalized Fryze current, used in Active Power Filter (APF) applications having three different modulation methods. The Hysteresis Band (HB) and first-order Delta-Sigma Modulation (DSM) as well as the second-order DSM is applied. The power section of the active power filter is viewed as an Analogue to Digital Converter (ADC), then as a result a three-phase shunt active filter modulator controller which, uses Delta-Sigma analogue to digital converter is presented to improve modulator performance. As a result, using second-order Delta-Sigma modulator makes low switching rate compared with first-order Delta-Sigma and hysteresis modulators under same sampling frequency. So, applying this modulator increases system efficiency and reduces cost of switches. In addition, simulation results on MATLAB software show that by using the Delta-Sigma modulator, Total Harmonic Distortion (THD) can be significantly decreased. Moreover, active filter based on the second-order DSM with constant source power has high efficiency and provides lower source current THD.
Research paper
M. Allahnoori; Sh. Kazemi; H. Abdi; R. Keyhani
Volume 2, Issue 2 , December 2014, Pages 113-120
Abstract
The microgrid concept provides attractive solutions for reliability enhancement of power distribution systems. Normally, microgrids contain renewable-energy-based Distributed Generation (DG) units, which their output power varies with different environmental conditions. In addition, load demand usually ...
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The microgrid concept provides attractive solutions for reliability enhancement of power distribution systems. Normally, microgrids contain renewable-energy-based Distributed Generation (DG) units, which their output power varies with different environmental conditions. In addition, load demand usually changes with factors such as hourly and seasonal customer activities. Hence, these issues have to be considered in evaluating the reliability of such a power distribution system. This paper evaluates the reliability performance of distribution systems with considering uncertainties in both generation and load demands. The results of applying the proposed approach on a case study system verify its advantages compared to the previous studies.
Research paper
V. Behjat; A. R. Dehghanzadeh
Volume 2, Issue 2 , December 2014, Pages 121-128
Abstract
In this research paper, the performance of an air-cored axial flux permanent magnet synchronous generator is evaluated for low speed, direct drive applications using 3D finite element modeling and experimental tests. The structure of the considered machine consists of double rotor and coreless stator, ...
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In this research paper, the performance of an air-cored axial flux permanent magnet synchronous generator is evaluated for low speed, direct drive applications using 3D finite element modeling and experimental tests. The structure of the considered machine consists of double rotor and coreless stator, which results in the absence of core losses, reduction of stator weight and elimination of cogging torque. In addition, the generator output voltage is sinusoidal in low speed operation and has a linear relationship with rotor speed, which makes it a suitable option for wind turbine applications. The simulation results of the proposed generator coincide very well with the experimental results on a system realized in the laboratory.
Research paper
F. Namdari; L. Hatamvand; N. Shojaei; H. Beiranvand
Volume 2, Issue 2 , December 2014, Pages 129-140
Abstract
Voltage stability issues are growing challenges in many modern power systems. This paper proposes optimizing the size and location of Static VAR Compensator (SVC) devices using a Fuzzy Weighted Seeker Optimization Algorithm (FWSOA), as an effective solution to overcome such issues. Although the primary ...
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Voltage stability issues are growing challenges in many modern power systems. This paper proposes optimizing the size and location of Static VAR Compensator (SVC) devices using a Fuzzy Weighted Seeker Optimization Algorithm (FWSOA), as an effective solution to overcome such issues. Although the primary purpose of SVC is bus voltage regulation, it can also be useful for voltage stability enhancement and even real power losses reduction in the network. To this aim, a multi-objective function is presented which includes voltage profile improvement, Voltage Stability Margin (VSM) enhancement and minimization of active power losses. Voltage stability is very close to Reactive Power Dispatch (RPD) in the network. Therefore, in addition to voltage regulation with locating SVCs, considering all of the other control variables including excitation settings of generators, tap positions of tap changing transformers and reactive power output of fixed capacitors in the network, simultaneous RPD and SVC placement will be achieved. Simulation results on IEEE 14 and 57-bus test systems, applying Genetic Algorithm (GA), Particle Swarm Optimization (PSO), Seeker Optimization Algorithm (SOA) and FWSOA verify the efficiency of FWSOA for the above claims.
Research paper
M. Moazen; M. Sabahi
Volume 2, Issue 2 , December 2014, Pages 141-150
Abstract
Using an Electric Differential (ED) in electric vehicle has many advantages such as flexibility and direct torque control of the wheels during cornering and risky maneuvers. Despite its reported successes and advantages, the ED has several problems limits its applicability, for instance, an increment ...
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Using an Electric Differential (ED) in electric vehicle has many advantages such as flexibility and direct torque control of the wheels during cornering and risky maneuvers. Despite its reported successes and advantages, the ED has several problems limits its applicability, for instance, an increment of control loops and an increase of computational effort. In this paper, an electric differential for an electric vehicle with four independent driven motors is proposed. The proposed ED is easy-to-implement and hasn’t the problems of previous EDs. This ED has been developed for four wheels steering vehicles. The synchronization action is achieved by using an improved fictitious master technique, and the Ackerman principle is used to compute an adaptive desired wheel speed. The proposed ED is simulated and the operation of the system is studied. The simulation results show that ED ensures both reliability and good path tracking.
