Control of Permanent-Magnet Generators Applied to Variable-Speed Wind-Energy Systems Connected to the Grid

TLDR

Wind energy relies on variable‑speed generators that must operate at the grid frequency. The study presents the operation and control strategy for a direct‑driven permanent‑magnet synchronous generator in wind energy. The system employs a fully controlled PWM converter (rectifier, DC link, inverter) with vector‑controlled grid‑side inverter to maximize wind power extraction, maintain high efficiency across loads, and regulate power factor, as validated on a 3‑kW prototype. Dynamic tests on the prototype confirm the system’s performance and benefits.

Abstract

Wind energy is a prominent area of application of variable-speed generators operating on the constant grid frequency. This paper describes the operation and control of one of these variable-speed wind generators: the direct driven permanent magnet synchronous generator (PMSG). This generator is connected to the power network by means of a fully controlled frequency converter, which consists of a pulsewidth-modulation (PWM) rectifier, an intermediate dc circuit, and a PWM inverter. The generator is controlled to obtain maximum power from the incident wind with maximum efficiency under different load conditions. Vector control of the grid-side inverter allows power factor regulation of the windmill. This paper shows the dynamic performance of the complete system. Different experimental tests in a 3-kW prototype have been carried out to verify the benefits of the proposed system.