A. A. Khodadoost Arani, J. S. Moghani, A. Khoshsaadat, G. B. Gharehpetian,
Volume 12, Issue 2 (June 2016)
Abstract
Multilevel voltage source inverters have several advantages compare to traditional voltage source inverter. These inverters reduce cost, get better voltage waveform and decrease Total Harmonic Distortion (THD) by increasing the levels of output voltage. In this paper Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) methods are used to find the switching angles for achieving to the minimum THD for output voltage waveform of the Cascaded H-bridge Multi-Level Inverters (MLI). These methods are used for a 27-level inverter for different modulation indices. Result of two methods is identical and in comparison to other methods have the smallest THD. To verify results of two mentioned methods, a simulation using MATLAB/Simulink software is presented.
A. A. Khodadoost Arani, B. Zaker, G. B. Gharehpetian,
Volume 13, Issue 1 (March 2017)
Abstract
The Micro-Grid (MG) stability is a significant issue that must be maintained in all operational modes. Usually, two control strategies can be applied to MG; V/f control and PQ control strategies. MGs with V/f control strategy should have some Distributed Generators (DGs) which have fast responses versus load changes. The Flywheel Energy Storage System (FESS) has this characteristic. The FESS, which converts the mechanical energy to electrical form, can generate electrical power or absorb the additional power in power systems or MGs. In this paper, the FESS structure modeled in detail and two control strategies (V/f and PQ control) are applied for this application. In addition, in order to improve the MG frequency and voltage stability, two complementary controllers are proposed for the V/f control strategy; conventional PI and Fuzzy Controllers. A typical low voltage network, including FESS is simulated for four distinct scenarios in the MATLAB/ Simulink environment. It is shown that fuzzy controller has better performance than conventional PI controller in islanded microgrid.
A. S. Hoshyarzadeh, B. Zaker, A. A. Khodadoost Arani, G. B. Gharehpetian,
Volume 14, Issue 3 (September 2018)
Abstract
Recently, smart grids have been considered as one of the vital elements in upgrading current power systems to a system with more reliability and efficiency. Distributed generation is necessary for most of these new networks. Indeed, in all cases that DGs are used in distribution systems, protection coordination failures may occur in multiple configurations of smart grids using DGs. In different configurations, there are various fault currents that can lead to protection failure. In this study, an optimal DG locating and Thyristor-Controlled Impedance (TCI) sizing of resistive, inductive, and capacitive type is proposed for distribution systems to prevent considerable changes in fault currents due to different modes of the smart grid. This problem is nonlinear constrained programming (NLP) and the genetic algorithm is utilized for the optimization. This optimization is applied to the IEEE 33-bus and IEEE 69-bus standard distribution systems. Optimum DG location and TCI sizing has carried out in steady fault currents in the grid-connected mode of these practical networks. Simulation results verify that the proposed method is effective for minimizing the protection coordination failure in such distribution networks.
