فهرست مطالب

Electrical and Computer Engineering Innovations - Volume:7 Issue:1, 2019
  • Volume:7 Issue:1, 2019
  • تاریخ انتشار: 1397/10/11
  • تعداد عناوین: 8
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  • Habib Amiri, Gholamreza Arab Markadeh *, Nima Mahdian Pages 1-10

    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. 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. 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. The results indicate the capability of the proposed method for voltage control and load sharing in DC microgrids.

    Keywords: DC Microgrids, Decentralized control, Disturbance observer, Load sharing, CPL
  • Hamed Lasjerdi, Zahra Nasiri Gheidari *, Farid Tootoonchian Pages 11-18

    Wound-Rotor (WR) resolvers are the most widely used position sensors in applications with harsh environmental conditions. However, their 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 the electromagnetic devices. Therefore, it is required to establish an accurate, yet computationally fast model. In this regard, 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.

    Keywords: Wound Rotor (WR) Resolver, Mathematical Model, Short-circuit (SC) fault, d-q axes
  • Fatemeh Abdi, Parviz Amiri *, Mohammad Hossein Refan Pages 19-26
    Adaptive algorithm adjusts the system coefficients based on the measured data. This paper presents a dichotomous coordinate descent method to reduce the computational complexity and to improve the tracking ability based on the variable forgetting factor. Vedic mathematics is used to implement the multiplier and the divider operations in the VFF equations. The proposed method decreases the area and increases the computation speed. The linear exponentially weighted recursive least squares as the main algorithm is implemented in many applications such as the adaptive controller, the system identification, active noise cancellation techniques, and etc. The DCD method calculates the inverse matrix in the ERLS algorithm and decreases the resources used in the field-programmable gate array, also the designer can use the cheaper FPGA board to implement the adaptive algorithm because the method doesn't need lots of resources. The proposed method leads to implementing complex algorithms with simple structures and high technology. The proposed method is implemented with ISE software on the Spartan 6 Xilinx board. The proposed algorithm calculates the multiplication result with less than 15ns time and reduces the used FPGA resources to lower than 20% as compared with the classic RLS.
    Keywords: Exponentially Weighted Recursive least squares (ERLS), Dichotomous Coordinate Descent (DCD), Variable Forgetting Factor (VFF), field-programmable gate array (FPGA)
  • Mohammad Karbalaei, Daryoosh Dideban *, Negin Moezi Pages 27-34
    In this work, a dual workfunction gate-source pocket-retrograde doping-tunnel field effect transistor (DWG SP RD-TFET) is proposed and investigated. DWG SP RD-TFET is a Silicon-channel TFET with two isolated metal gates (main gate and auxiliary gate) and a source pocket in the channel close to the source-channel junction to increase the carrier tunneling rate. For further enhancement in the tunneling rate, source doping near the source-channel junction, i.e., underneath the auxiliary gate is heavily doped to create more band bending in energy band diagram. Retrograde doping in the channel along with auxiliary gate over the source region also improve device subthreshold swing and leakage current. Based on our simulation results, excellent electrical characteristics with ION/IOFF ratio > 109, point subthreshold swing (SS) of 6 mV/dec and high gm/ID ratio at room temperature shows that this tunneling FET can be a promising device for low power applications.
    Keywords: Tunnel Field Effect Transistor (TFET), subthreshold swing (SS), source pocket, isolated gates, retrograde doping
  • Homayoun Berahmandpour *, Shahram Kouhsari, Hassan Rastegar Pages 35-44
    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. This 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. Through this approach, a good tradeoff between generation cost and needed flexibility can be carried out. In this paper, a conceptual flexibility index is introduced suitably for real-time operation in the presence of wind farms. Two main components of this index are up and down generation constraints and ramp rate limitations of each unit. Thus, by a combination of the flexibility indices of all units, the system flexibility index is introduced which can be used as the main part of flexibility cost in the objective function. Economic dispatch simulation is used for the economic tradeoff between the generation cost and the cost of flexibility to get the best level of system flexibility in the presence of wind farms considering unit constraints and system loss.
    Keywords: flexibility index, wind farm, real time operation, cost of flexibility, trade off
  • Reza Sedaghati *, Mehrdad Mahmoudian Pages 45-56
    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, 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. 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. Finally, the results of the simulated resonance frequencies are compared and validated with the mathematical and theoretical principles.
    Keywords: Gyroscopes, HRG, Capacitive Excitation, Coriolis Force, Sensor
  • M. Isaac Hosseini, Mohammadreza Jafari Harandi, S. Ahmad Khalilpour Seyedi, Hamid Taghirad * Pages 57-66
    Fast-tracking of reference trajectory and performance improvement in the presence of dynamic and kinematic uncertainties is of paramount importance in all robotic applications. This matter is even more important in the case of cable-driven parallel robots due to the flexibility of the cables. Furthermore, cables are limited in the sense that they can only apply tensile forces, for this reason, feedback control of such robots becomes more challenging than conventional parallel robots. To address these requirements for a suspended cable-driven parallel robot, in this paper a novel adaptive fast terminal sliding mode controller is proposed and then the stability of the closed-loop system is proven. In the proposed controller, a nonlinear term as a fractional power term is used to guarantee the convergent response at a finite time. At last, to show the effectiveness of the proposed controller in tracking the reference trajectory, simulations and the required experimental implementation is performed on a suspended cable-driven robot. This robot, named ARASCAM, has three degrees of transmission freedom. The obtained results confirm the suitable performance of this method for cable robots.
    Keywords: Suspended cable-driven, parallel manipulator, fast terminal sliding mode, finite-time convergence, cost of flexibility, robust control, adaptive control
  • Fatemeh Jamshidi, Mahsa Vaghefi * Pages 67-80
    The robot arm is a multi-input, multi-output and non-linear system that has many industrial applications. The parameter uncertainties and external disturbances attenuate the performance of this system and controller design is necessary to overcome them. In this paper, the interval Type II fuzzy fractional-order proportional integral differential (IT2FO-FPID) controller is designed to control the robot arm with 2 degrees of freedom (two-link robot arm). Whale Optimization Algorithm (WOA) is used to determine the optimal value of controller parameters. The performance of IT2FO-FPID is compared with PID, fractional-order PID (FOPID) and Fuzzy FOPID whose parameters are determined by WOA. The performance of IT2FO-FPID whose parameters are determined by WOA, genetic algorithm, and particle swarm optimization are compared. Quantitative and qualitative results of simulations indicate performance improvement with the IT2FO-FPID controller. The ability of WOA in optimizing the parameters of the IT2FO-FPID controller is demonstrated. Sensitivity analysis and the study of the effect of parameter variations and disturbances confirm the robust performance of WOA-based IT2FO-FPID.
    Keywords: Fractional order proportional integral differential, Interval type 2 fuzzy, Whale optimization algorithm, Genetic Algorithm, Particle swarm optimization