Control of Electromechanical systems
Ali Abdul Razzaq Altahir
Abstract
An electric drive controller for AC microgrids with renewable energy sources is a system that controls the flow of electricity in an alternating current (AC) microgrid. The role of distributed generation in the electricity industry has been expanding in recent years. Distributed (DGs) are small, scalable ...
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An electric drive controller for AC microgrids with renewable energy sources is a system that controls the flow of electricity in an alternating current (AC) microgrid. The role of distributed generation in the electricity industry has been expanding in recent years. Distributed (DGs) are small, scalable units, generally with a capacity of less than 10 MW which can be connected to the grid, distribution feeders or customer levels. Nowadays, the high penetration of distributed resources in power systems is increasing. Since these units can play an important role in electricity markets and provide ancillary services for system operators, integrating these resources within power systems has been considered. Therefore, this paper focuses on modelling, designing and simulating a suitable controller to ensure AC microgrids stability and stable performance (AC M.G) in both grid-connected and islanded modes. Meanwhile, all simulations have been fulfilled in MATLAB environment. After designing the controllers and ensuring the performance of their frequency response using the bode diagram and the system step response, these controllers were used to command the voltage and current in real scenarios. After applying the controllers, the performance has dramatically improved in the voltage and current controller presence. As a result, the controller can be programmed to respond into changes in the energy supply and demand, adjusting the output of the green resources and managing energy storage systems within the microgrid. This allows the system to operate in a stable and sustainable manner, even when there are fluctuations in the energy supply or demand.
Control of Electromechanical systems
Mohsen Dashtbani; Majid Hasanzadeh; Reza Roshanfekr
Abstract
The conventional direct torque control (DTC) method suffers a flux drop at low speeds, which is due to the long selection of zero (neutral) voltage vectors in these speed areas. Past studies with the continuous switch of direct and reverse active vectors to achieve proper flux adjustment, this procedure ...
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The conventional direct torque control (DTC) method suffers a flux drop at low speeds, which is due to the long selection of zero (neutral) voltage vectors in these speed areas. Past studies with the continuous switch of direct and reverse active vectors to achieve proper flux adjustment, this procedure causes high and consecutive overshoots in the hysteresis band that causes a sharp increase in the switching frequency and increase in the torque and current ripple, which means decrease in the drive efficiency. In this article, a modified method for setting the standard DTC current is introduced, which can be achieved by controlling only one band (low or high band) at low speeds. The introduced method by reducing the selection of zero voltage vectors and at the same time minimizing the number of reverse voltage vectors prevents the loss of flux in low speed areas. In addition, it is effective in reducing torque ripple and current in low speed mode and a significant reduction in switching frequency will also be achieved. The effectiveness of the proposed method in the simulation which is done in MATLAB software will be proved.
Control of Electromechanical systems
Adel Mohseni; Aref Doroudi; Mehdi Karrari
Abstract
The excitation system is one of the most crucial components of a power plant. Knowing the exact parameters of the excitation system and their changes over time is essential for efficient and accurate power system dynamic studies. In this paper, the parameters of a typical and well-known type of excitation ...
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The excitation system is one of the most crucial components of a power plant. Knowing the exact parameters of the excitation system and their changes over time is essential for efficient and accurate power system dynamic studies. In this paper, the parameters of a typical and well-known type of excitation system are estimated using different types of Kalman filters, including unscented Kalman filter (UKF), spherical-simplex Kalman filter (SS-UKF), and cubature Kalman filter (CKF). The efficacy of these Kalman filter methods in the excitation system parameters estimation problem is investigated under three different planned and unplanned events as the input of the methods. The planned disturbances will be internal type (a reference voltage step) and external type (unit transformer tap changing) whereas the unplanned disturbance is caused by power grid events (neighbor generator outage). Comparison is done between the simulation results and experimental ones and the best appropriate approach is selected.
Control of Electromechanical systems
mohammadmahdi kazemi; alireza rezazade
Abstract
In this paper, two different structures of a multiphase inverter for controlling a Brushless DC (BLDC) motor are presented and compared parameters These two structures are in fault mode. In the first structure, each phase of the BLDC motor is fed from an individual H-Bridge inverter, which is controlled ...
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In this paper, two different structures of a multiphase inverter for controlling a Brushless DC (BLDC) motor are presented and compared parameters These two structures are in fault mode. In the first structure, each phase of the BLDC motor is fed from an individual H-Bridge inverter, which is controlled by a Proportional-Resonance (PR) controller. The system dealt with in this paper is designed especially for reliability-critical applications. In other words, the motor structure has to be implemented not to compromise the drive performance even in fault conditions. For these purposes, modular designs to minimize the coupling between each phase. in the second structure, a typical six-legged inverter is used, which is divided into two groups of three phases with double Y-connected windings displaced by 30 degrees is presented and switching is done using Space Vector Pulse Width Modulation (SVPWM). According to the model, the use of SVPWM modulation for a six-phase motor reduces computations. MATLAB/Simulink software has been used to analyze these two structures and the results of its simulations are given.
