Analysis of the representation of wind generators in tool for voltage stability assessment

• Grant number: 21/06126-2
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: October 01, 2021
• End date: September 30, 2022
• Field of knowledge: Engineering - Electrical Engineering - Power Systems
• Principal Investigator: Rodrigo Andrade Ramos
• Grantee: Lucas Carnevalli de Almeida
• Host Institution: Escola de Engenharia de São Carlos (EESC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Associated research grant: 18/20104-9 - Wide-area monitoring, dynamic security analysis and control of modern power system networks, AP.TEM

Abstract

The increase in the incorporation of wind power in the power systems generates concerns about system performance, mainly due to the variability of the wind resource. The evaluation of the voltage stability margin of a system to prevent operation at an unsafe point requires an accurate model of the generation units and the ability of these units to provide reactive power to the system. In wind power operating requirements of many countries, it can be expected that the wind generators must also provide reactive power to the system in steady-state operation, so this capability can be used to increase the voltage security margin in the system operation. Most wind generators installed today consist of doubly-fed induction generators. These generators have the capacity to supply reactive power to the system according to the remaining capacity of the converter, which must primarily control the active output power of the wind generator. Thus, the capacity of the generator or wind farm to contribute with reactive power to the grid depends on the point of operation, which in turn depends on the wind speed. Therefore, it is necessary to represent the wind turbines in terms of their capacity to provide reactive power to the network. A model that has been widely accepted for the representation of doubly-fed induction generators for static studies is the representation of the capacity curve. In this model, the reactive power limits of the generator are represented by the converter limits, which, in turn, depend on the wind speed. For the use of this model in a method that employs the capacity of wind generators to contribute with reactive power to the system, wind variability must be considered. The most used probability function to represent the wind speed distribution is the Rayleigh function. Thus, the objective of this work is, given a determined point of operation of the wind generator with a respective margin of the contribution of reactive power, to associate the probability of the generator not having this margin due to changes in this operating point using the Weibull or Rayleigh distribution curve, which is available for wind farms. In this project, initially, the capacity curve of the doubly-fed induction generator will be modeled. This model will be included in a continuation power flow tool available in the PSAT toolbox, which runs in Matlab, to calculate the voltage stability margin. Then considering typical wind speed distribution curves, the probability that the wind generator under study is not able to provide the originally planned reactive power due to the wind speed variation, considering the wind speed distribution curve, will be taken into account in voltage stability studies.(AU)