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The commutation torque ripple adversely affects the performance of the six-phase inverter of the BLDC motor with trapezoidal back EMF and creates vibration and noise for industrial applications. In this paper, the motor model is obtained in non-commutation times and during the commutation period, and according to that, a suitable method to reduce the torque ripple, by equalizing the slope of the current disconnected from the motor and the slope of the current connected to the motor during commutation, is presented. At low speeds, torque ripple is reduced using predictive pulse width modulation technique. With this method, the duty cycle of the switch involved in the commutation is predicted and applied to the switch during the commutation intervals. At high speeds, this reduction is done using quasi z-source converter and selector circuit. The quasi z-source converter and the selector circuit increase the input voltage of the inverter during commutation intervals and increase its value to four times the back EMF voltage of the motor, thus reducing the torque ripple at high speeds. The theoretical and analytical results are verified using the simulations performed in the PLECS software. [ABSTRACT FROM AUTHOR]

Single-phase rectifiers are one of the most practical instruments with various applications. Among them, active front-end (AFE) rectifiers are introduced with bidirectional power transfer capability for power factor correction and the elimination of current harmonics. This paper proposes an adaptive model predictive control (MPC) for a single-phase AFE rectifier. The AFE topology used in this paper is a half-bridge boost converter. This topology has higher efficiency than other single-phase AFEs due to the fewer number of active semiconductor devices. Considering the presence of one leg of capacitors in this topology, balancing the voltages of these capacitors is a challenge, along with other control objectives. Also, this paper benefits from an MPC approach by which the switching signal for every switching state is chosen such that the defined cost function is minimized in the operation state to achieve all control goals based on the predefined model of the rectifier. Furthermore, an adaptive algorithm for the inductor current estimation is presented to robustify the control system against any unwanted disturbance in the control system. As a demonstration of the superior performance of the proposed method, a 1kW rectifier setup with 700Vdc output voltage fed from a 230Vrms/50Hz grid is built in the laboratory. The applicability of the MPC controller is verified and all operation waveforms of the test setup are presented. The proposed method offers a high-quality input current with total harmonic distortion (THD) below 5% and a high-power factor (PF) close to one. Also, the efficiency is comparable with the available commercialized rectifiers. [ABSTRACT FROM AUTHOR]

In this paper, the Hunger Games Search (HGS) optimization algorithm is used to estimate the electrical parameters of the induction machine steady state model. Induction machine nameplate data is used as input to the proposed algorithm. The performance of the proposed method is confil'med by comparing the output characteristics obtained by estimating the motor parameters including torque, current and power factor in the steady state model of the induction machine with the values provided by the manufacturer. In addition, by evaluating and comparing the results of the proposed method with the results of previous research, it is shown that the proposed algorithm is a very effective and accurate method for the acceptable estimation of induction machine parameters. [ABSTRACT FROM AUTHOR]

In this paper, to estimate the parameters of a three-phase induction motor, the current measured in one phase and Harris Hawk's optimization algorithm (HHO) as well as the recently introduced improved technique of this algorithm (IHHO) are used. This method includes estimating the electrical equivalent circuit parameters of a three-phase induction motor, including rotor and stator resistance, leakage inductance, magnetizing inductance, as well as mechanical parameters including the moment of inertia and friction coefficient. As three-phase induction motors are widely used in various industries, it is necessary to identify their parameters to implement adjustable speed control systems for such motors. Therefore, it is necessary to develop appropriate algorithms to accurately estimate the induction motor parameters. The main inspiration of the proposed method is the behavior of the Harris hawk group in nature. The objective function is defined as the calculation of the least mean squares of the error resulting from the numerical simulation of the dynamic equations of the motor and the measured value of the current of one motor's phase. The proposed method is applied to the dynamic model of a specific motor and the results of the proposed method are compared with other previously published methods. The obtained results demonstrate the remarkable capability of the proposed method and its rapid convergence. [ABSTRACT FROM AUTHOR]

In this study, a new DC--DC single-input--dual-output (SIDO) converter is proposed which is able to step up and share the input voltage between the output terminals with constant duty cycle for whole ranges of duty cycles. Due to the fact that the voltage stresses on the semiconductors of the proposed converter are considerably low, the proposed converter can be applied in both low- and high-power applications. This topology can be used instead of two boost converters, which have very improved conversion ratios in comparison with the recently presented step-up converters. The proposed configuration can be used in many applications such as renewable energy sources and diode-clamped inverter in the grid-tied systems. In this paper, steady-state and small-signal analyses of the SIDO converter are presented and the simulation and experimental results are extracted and compared. In practical applications that SIDO is needed, using single-input--single-output can be a solution, resulting high cost. To reduce the costs, this study proposes a novel topology, which has reduced components and can step up the input voltage into two separate ports. Finally, a prototype circuit with 42 V input and 510 V/372 W and 730 V/381 W outputs are built to validate the theoretical analysis. [ABSTRACT FROM AUTHOR]

A magnetohydrodynamic (MHD) thruster is a type of electric motors which does not have mechanical moving parts and directly converts electrical energy into mechanical energy. In this study, the effect of magnetic field intensity and seawater electrical conductivity on the performance of a marine MHD thruster model is investigated using fully three-dimensional numerical simulations. For the first time, all electric, magnetic and fluid flow fields are considered in three dimensions. The effects of seawater electrolysis and end loss are taken into account in all simulations and a simple analytical model is developed to verify the numerical results. It is shown that increasing the magnetic field intensity or the electrical conductivity of the working fluid decreases the electrochemical and ohmic losses of the thruster at a specific velocity. Therefore, a higher efficiency can be achieved at higher magnetic field strengths and higher seawater electrical conductivities. Also, it is revealed the end loss of the channel increases with an increase in the electrical conductivity of the working fluid and decreases with an increase in the magnetic field intensity. [ABSTRACT FROM AUTHOR]

An EM launcher can be used as an experimental tool to accelerate small-mass specimens up to 300 m/s to study impact phenomena. A plasma armature is employed to avoid the friction produced by a sliding metal armature and, in particular, to prevent high-Z impurities from entering the tokamak. High currents are used to achieve high accelerations, resulting in high plasma temperatures. For this purpose, two-dimensional (2-D) and axisymmetric plasma models are widely used as these are less complicated and fairly available. The presented model solves the complete set of Magneto Hydro Dynamic (MHD): transport equations of mass, momentum, and energy along, with the vector potential form of Maxwell's equations to account for the electromagnetic effects. Radiation of the energy balance is calculated using the P-1radiation method by dividing the electromagnetic spectrum into several gray bands. The model has the features of predicting properties of the whole domain. [ABSTRACT FROM AUTHOR]

This paper provides a mathematical model for voltage natural balancing process in multi-phase capacitor-clamped multicell converters. The analysis leads to state-space model of the multi-phase flying capacitor multicell converters. This analytic model can be utilized to investigate the start-up and steady states of clamping capacitor voltages. To provide verification, numeric solution results for multi-phase capacitor-clamped multicell converter's analytic model in different cases are presented. [ABSTRACT FROM AUTHOR]

Excitation system of synchronous generator can help to an effective voltage control and power system stability support. In fact, for the stability improvement, this excitation system should be able to apply proper input voltage to the generator field winding. In this paper limiters and protective circuits of generator excitation system are explained. Two important types of these limiters are over and under excitation ones. The over-excitation limiter protects the generator against over-temperature caused by high field current for long time. Under-excitation limiter prevents the decrease of generator field current to the values lower than the stability margin or the thermal limit of end side of the stator core. Various models of the over and under excitation limiters have been presented in the literature. Tuning these limiters can be performed in different ways by considering the generator,s capability curves. The limiter models and their parameters tuning affect voltage stability straightly. In this research, after implementation the proper model for our case study, the tuning of limiters is obtained by analyzing well known voltage stability methods. Some simulations have been done in Matlab/Simulink to analyze the effect of the selected model and tuned limiters on voltage stability both in single and multi-machines system. Also the dynamic parameters of a real system (Bistun power plant) are used as the case study. The results issued from this study are also discussed and validate the simulations. [ABSTRACT FROM AUTHOR]

A toroidal field coil (TFC) is composed of several individual toroidal coils (ITCs), which are connected in series and distributed in the toroidal and symmetrical forms. This paper presents the analytical equations of mutual inductance and electromagnetic torque of the TFC that are applicable to Tokamak reactors. The analytical equations of translational forces, which are imposed on the ITCs of the TFC, are also discussed in this paper. These equations are based on those formulated by Neumann. The numerical analysis of the integrations resulting from these equations is solved using the extended three-point Gaussian algorithm. The results obtained from the numerical simulation agree with the empirical results and the virtual work theorem, which indicates the reliability of the presented equations. The behavior of the mutual inductance of the coil shows that the maximum stored energy is obtained when the electromagnetic torque is zero and vice versa. [ABSTRACT FROM AUTHOR]

In this paper, equations for the calculation of the selfand mutual inductances of the modular toroidal coil (MTC) applicable to Tokamak reactors are presented. The MTC is composed of several solenoidal coils (SCs) connected in series and distributed in the toroidal and symmetrical forms. These equations are based on Biot-Savart's and Neumann's equations, respectively. The numerical analysis of the integrations resulting from these equations is solved using the extended three-point Gaussian algorithm. Comparing the results obtained from the numerical simulation with the experimental and the empirical results confirms the presented equations. Furthermore, the comparison of the behavior of these inductances, when the geometrical parameters of the MTC are changed, with the experimental results shows an error of less than 0.5%. The behavior of the inductance of the coil indicates that the optimum structure of this coil, with the stored magnetic energy as the optimization function, is obtained when the SCs are located on the toroidal planes. [ABSTRACT FROM AUTHOR]