An Investigation of Frequency Control by Grid Side Converter of PMSG-Based Wind Turbine Generator

The development of offshore wind farms are being advanced in Japan and Permanent Magnet Synchronous Generators (PMSGs) are widely used there. Penetration of inverter-based power resources (IBRs) into power system reduces inertia of the system. As IBRs increase, concerns on deviations in system frequency are emerging. In wind turbine generation, PMSG is connected to the external system through a back-to-back (BTB) converter. BTB converter consist of Machine Side Converter (MSC), Grid Side Converter (GSC) and DC capacitor. Active power output of PMSG is controlled by GSC. The voltage of the DC capacitor has to be kept constant and it is generally controlled by GSC. In this study, we focus on the issue on system frequency and aims to improve the frequency deviation by controlling the active power output of PMSG by the GSC and controlling the capacitor voltage by MSC. The usefulness of the proposed control scheme is investigated through numerical simulations using XTAP, an electromagnetic transient analysis program. The results showed that the proposed control scheme is capable of suppressing frequency deviation successfully.