Development of methodologies to analyze distributed generators in electric distribution systems

Author(s)

Hugo Murici Ayres

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Elétrica e de Computação
• Defense date: 2010-10-25

Examining board members

Walmir de Freitas Filho; Glauco Nery Taranto; Ricardo Bernardo Prada; André Luiz Morelato França; Madson Cortes de Almeida

• Advisor: Walmir de Freitas Filho

Abstract

The installation and operation of medium generators in electrical distribution systems demand the analysis of several technical aspects. The main methodologies are based on repetitive power flow and short-circuit calculations in order to obtain the locations and generation levels allowed for the connection of theses generators without violating any technical constraint of steady-state operation. Although these analyses are very precise, such quantitative studies do not bring further information to suitably manage the technical impacts due to multiple generators, that is, the determination of individual generator influence on the technical aspects so that they can be penalized or rewarded in a proper manner. Moreover, these methodologies require a high number of man-hours and processing time. This Ph.D. thesis presents new methodologies for analysis of the impact of distributed generation connected to electrical distribution systems taking into account technical aspects of steady-state operation. Based on sensitivities matrices obtained from only one power flow solution and from one impedance matrix calculation, the proposed methods allow the determination of the maximum power that these generators can export to the grid regarding the voltage regulation, feeder current limits and short-circuit current limits. With simple matrix operations, the impact of adding new generators at any bus of the grid, with any capacity, and any operating mode (leading, lagging or unitary power factor) can be estimated for different power demand. Moreover, such methods based on sensitivities permit a rapid calculation of responsibility factors, which quantify the individual impact of each generator in the technical aspects under analysis. Such indices can be used by electric utility managers and distribution engineers to penalize or reward the electricity producers who depreciate or not the power quality, by violating any limit or operational constraint of the distribution systems. Since these methodologies are based on linearized methods, the results are compared with those obtained by repetitive power flow and short-circuit current calculations. The comparison reveals that the results from the linearized methods are accurate (AU)