Desenvolvimento de ferramentas para análise de regime permanente de microrredes ilhadas

Abstract

This work aims to propose a Power Flow (PF) and an Optimal Power Flow (OPF) based tools for steady-state microgrids assessment. More specifically, voltage control schemes were developed to coordinate reactive power injection to improve voltage profile, while maintaining a reactive margin for emergency scenarios. Firstly, this work proposes a modified Governor OPF formulation for the particular aspects of microgrids. This modification focuses on an alternative behavior for the voltage variations in the generation bus profile during the solution process. As generators normally presented in microgrids are from alternative energy sources, which are usually connected via power electronics devices, they can emulate the voltage control normally presented in synchronous generators through gains, or voltage/reactive power droops. Therefore, this work proposes the addition of an equation that represents the aforementioned droops in the OPF problem. Also, this work proposes a change in the verification of reactive power generation limits during OPF solutions, through complementarity constraints, to accommodate the new behavior of the voltage profile of the generation buses. It will be seen such methodology can be seen as a generalization of the generators’ representation in the OPF problem. Next, this work proposes a methodology based on sigmoid functions for the representation of hierarchical control schemes, as well as control schemes whose equation is defined by parts. The sigmoid functions built according to the control variables form equations that represent the steady-state behavior of these devices, in a way that eliminates the need for any change in the control equations externally to the Jacobian matrix. Therefore, this methodology is resolved completely by the full Newton method and the sigmoid functions aim to deactivate or activate the equations to automatically move between the control’s operating ranges. Thus, control schemes aimed at maintaining reactive power margins for emergency scenarios, as static var compensator and reactive limits verification, which are control schemes whose equations are defined by parts, will be used to show the effectiveness of the method. For tests and validation purposes, the following test systems will be used: a 61-bus test microgrid, the IEEE 39-bus New-England test system and an 11-bus, an 2 areas test system and the Nordic system. The methodologies were implemented in Matlab ® . The results demonstrate the efficiency and robustness of the proposed methods.