Analysis of the influence of induction motors under the dynamic behavior of a DFIG connected to a distribution system

Author(s)

Rafael Cruz Borges

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD)
• Defense date: 2017-03-24

Examining board members

Rodrigo Andrade Ramos; Igor Kopcak; Ricardo Vasques de Oliveira; Ahda Pionkoski Grilo Pavani; José Carlos de Melo Vieira Júnior

• Advisor: Rodrigo Andrade Ramos

Abstract

With the advent of distributed generation, the operation of the distribution system has been modified. Dynamic characteristics that were previously observed only in the transmission system can now also be present in distribution systems, such as problems related to electromechanical oscillations. Due to growth prospects of wind generator connections, it is evident the possibility of increasing the production of electricity through asynchronous distributed generators. In the distribution system several types of loads are present, being one of the most representative the loads of type induction motor. This type of load, the occurrence of short-circuits in the system can cause delay in the recovery of the system voltage, known as Fault Induced Delayed Voltage Recovery (FIDVR) problem. After the fault is eliminated, the voltage can remain at significantly reduced levels for several seconds. This time delay is usually caused by the high concentration of induction motors. So, it is necessary to perform studies to analyze the impacts that this type of energy source can bring to the electrical system as well as the impact of the loads on the wind generator. Thus, this thesis makes an analysis of the influence of induction motor loads on the dynamic behavior of a DFIG connected to a distribution system. A conventional synchronous generator was also used to make a comparison with the DFIG. As the two generators are working with voltage regulation, it would be intuitive to think that the responses of the two in the presence of induction motor loads would be similar. However, this thesis shows that in the same scenario, the machines have different behaviors and the reaction is different according to the type of load connected to the system. It was verified that when there is the FIDVR problem due to the presence of the induction motor, the oscillations in the speed of the DFIG are amplified. For the synchronous generator, the induction motor has little influence on the electromechanical oscillations. (AU)

• FAPESP's process: 13/24570-0 - Study of Distributed Generation Systems with the Connection with Asynchronous Generators
• Grantee: Rafael Cruz Borges
• Support Opportunities: Scholarships in Brazil - Doctorate