Analytical Model of Doubly-fed Induction Generator-motors for Full-region Operation Analysis

The accurate modeling of large-scale doubly-fed induction generator-motors (DFIGMs) is crucial to support the development of variable-speed DFIGMs in pumped-storage plants. In this paper, a novel analytical model of DFIGMs is proposed, which takes into account both spatial- and time-harmonics using the spiral vector method and an improved permeance model. Additionally, the model considers the influences of full-region operation and pulse-width modulation (PWM) in the rotor converter. The distributions of magnetic field, electromotive force (EMF), and torque performance under various operating conditions are further analyzed by the model. To validate the proposed model, comparisons are made with finite-element simulations and experimental results obtained from a 3MW DFIGM prototype, confirming its accuracy and reliability. This analytical model serves as a crucial foundation for advancing variable-speed DFIGMs technology in pumped-storage plants.

I. Introduction

Large-scale doubly-fed induction generator-motors (DFIGMs), with wide control range and fast power responsibility, play a crucial role in enhancing the frequency and voltage stability of power systems with high renewable energy generation penetration [1]. The establishment of an analytical model for the analysis of DFIGMs serves as an efficacious methodology for elucidating the operational mechanisms and scrutinizing the interrelations between output characteristics and its parameters. The modeling research of DFIGMs involves the T-shaped equivalent circuit method and the two-axis model [2–3]. And the T-type equivalent circuit is improved and an asynchronous-synchronous (DFM-hust-yu) circuit model is proposed, which illustrates the operational principles and characteristics of the asynchronous and synchronous superposition of DFIGMs [4]. However, further improvements can be made to consider aspects such as rotor current harmonics and dynamic performance.