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FRACTIONAL ORDER CALCULUS BASED CONTROLLERS FOR VOLTAGE SOURCE CONVERTERS OPERATING IN DG SYSTEMS OR HVDC STRUCTURES.

Grant number: 15/23029-0
Support type:Scholarships in Brazil - Doctorate
Effective date (Start): March 01, 2016
Effective date (End): February 29, 2020
Field of knowledge:Engineering - Electrical Engineering - Power Systems
Principal researcher:Ricardo Quadros Machado
Grantee:Klebber de Araujo Ottoboni
Home Institution: Escola de Engenharia de São Carlos (EESC). Universidade de São Paulo (USP). São Carlos , SP, Brazil

Abstract

The Brazilian government has encouraged, by means of the regulatory agencies and of the Ministry of Mines and Energy, the inclusion of alternative sources in the national energy matrix in order to meet the growing demand, avoiding a future energy crisis and also expand the application of the concept of Distributed Generation (DG) associated with the intelligent management of available sources. The diversification of the sources, i.e. the integration and subsequent optimization of available resources for energy generation, has been treated as an important tool for, following the principles of sustainability and the minimum environment protection actions, ensure stability and security of the power system. It is also valuable to note that if the power system is unable to provide the necessary conditions for industry and other production sectors prosecute their activities properly, the economy suffers directly serious consequences.Systems based on power electronics capable of generate variables voltage and current waveforms have been associated with control techniques and applied into energy systems with the objective, among others, to ensure the adequation of the variables to quality parameters, even the electrical system having inherently the characteristic of being subjected to multiple disturbance sources.The classic PID controllers and forward-backward controllers have limitations when applied to systems that have oscillatory reference signal or high-frequency components. One solution is the use of resonant controllers designed to operate at specific frequencies. However, for Voltage Source Converters applied, for example, to the connection of distributed generating systems into the power grid, when subjected to a RLC local load with resonant frequency equal to the fundamental frequency of the grid, the resonant controllers provide an unstable response.The replacement of the resonant controller by a fractional order controller PI», optimized so that for the fundamental frequency it has minimum attenuation, results in a stable and appropriate response for various types of local loads, including for the aforementioned RLC load with resonant frequency equal to the fundamental. Then, it has been observed the greater capacity for adjustment of the fractional order controller to the plant's requirements by having the design parameter ».As the PI» controller is the simplest fractional order controller, there is a clear need to deepen the analysis of other structures of this family of controllers applied in the control of power system's variables, trying to embrace in the optimization of the design parameters others limitations found in systems based on Voltage Source Converters.