A new method of virtual direct torque control of doubly fed induction generator for grid connection

Over the past few years, due to the shortage of fossil fuels and their unwanted environmental impacts, the use of renewable energy has vastly increased. Among them is wind power, which has been at the center of attention as one of the most important renewable energies. Many studies have been conducted regarding wind farms with variable speeds. Among these, the doubly fed induction generator (DFIG) has been of utmost importance due to its capability of separately controlling the active and reactive power, reducing the nominal converter capacity, maintaining constant variable speed frequency, and improving quality. The goal of this study is to control the synchronizing and network connection to the DFIG such that when connected to the network, no pulse is seen in the torque, rotor current, or stator. The method used in this study is known as virtual torque, which is derived from direct torque control, but instead of an electromagnetic torque, we use a virtual one. To implement this method, it is only required to measure the network voltage, current, and rotor position, and changing the control algorithm from synchronizing to grid connection only includes some changes in the flux references and torque, and calculating the electromagnetic torque instead of the virtual one

Design of Multivariate PID Controller for Power Networks Using GEA and PSO

The issue of proper modeling and control for industrial systems is one of the challenging issues in the industry. In addition, in recent years, PID controller design for linear systems has been widely considered. The topic discussed in some of the articles is mostly speed control in the field of electric machines, where various algorithms have been used to optimize the considered controller, and always one of the most important challenges in this field is designing a controller with a high degree of freedom. In these researches, the focus is more on searching for an algorithm with more optimal results than others in order to estimate the parameters in a more appropriate way. There are many techniques for designing a PID controller. Among these methods, meta-innovative methods have been widely studied. In addition, the effectiveness of these methods in controlling systems has been proven. In this paper, a new method for grid control is discussed. In this method, the PID controller is used to control the power systems, which can be controlled more effectively, so that this controller has four parameters, and to determine these parameters, the optimization method and evolutionary algorithms of genetics (EGA) and PSO are used.  One of the most important advantages of these algorithms is their high speed and accuracy. In this article, these algorithms have been tested on a single-machine system, so that the single-machine system model is presented first, then the PID controller components will be examined. In the following, according to the transformation function matrix and the relative gain matrix, suitable inputs for each of the outputs are determined. At the end, an algorithm for designing PID controller for multivariable MIMO systems is presented. To show the effectiveness of the proposed controller, a simulation was performed in the MATLAB environment and the results of the simulations show the effectiveness of the proposed controller

Comparative detection and fault location in underground cables using Fourier and modal transforms

In this research, we create a single-phase to ground synthetic fault by the simulation of a three-phase cable system and identify the location using mathematical techniques of Fourier and modal transforms. Current and voltage signals are measured and analyzed for fault location by the reflection of the waves between the measured point and the fault location. By simulating the network and line modeling using alternative transient programs (ATP) and MATLAB software, two single-phase to ground faults are generated at different points of the line at times of 0.3 and 0.305 s. First, the fault waveforms are displayed in the ATP software, and then this waveform is transmitted to MATLAB and presented along with its phasor view over time. In addition to the waveforms, the detection and fault location indicators are presented in different states of fault. Fault resistances of 1, 100, and 1,000 ohms are considered for fault creation and modeling with low arch strength. The results show that the proposed method has an average fault of less than 0.25% to determine the fault location, which is perfectly correct. It is varied due to changing the conditions of time, resistance, location, and type of error but does not exceed the above value

New Technology and Method for Monitoring the Status of Power Systems to Improve Power Quality—A Case Study

The identification and analysis of harmonics, frequency, and transient events are essential today. It is necessary to have available data relating to harmonics, frequency, and transient events to understand power systems and their proper control and analysis. Power quality monitoring is the first step in identifying power quality disturbances and reducing them and, as a result, improving the performance of the power system. In this paper, while presenting different methods for measuring these quantities, we have made some corrections to them. These reforms have been obtained through the analysis of power network signals. Finally, we introduce a new monitoring system capable of measuring harmonics, frequency, and transient events in the network. In addition, these values are provided for online and offline calculations of harmonics, frequency, and transient events. In this paper, two new and practical methods of the “algebraic method” are used to calculate network harmonics and wavelet transform to calculate transient modes in the network. Furthermore, the proposed monitoring system is able to reduce the amount of data-storage memory. The results of the simulations performed in this article show the superiority of using the new method presented for online and offline monitoring of power quality in electric power systems

The effects of steam valve on load economic distribution in steam powerhouse using bats algorithm

Abstract — Because of the advancement of technology and industry, continued access to electrical energy has become one of the essential requirements of the world. So, continue a large part of manufacturing activity, economic, social and agricultural is not possible without improvement of electrical energy. In this paper, a mutation operator based on three separate corrections is suggested to add to the original Bats Algorithm (BA) with an effective way to improve the algorithm performance. Also, the Bats modified algorithm (MBA) is implemented for solving complex non-convex and uneven RCED by three testing system. Finally, the results of modified algorithm are simulated and the convergence of the MBA is compared with BA to evaluate the accuracy of the proposed algorithm