Unified Grid-Forming Control of PMSG Wind Turbines for Fast Frequency Response and MPPT

TL;DR

This paper introduces a unified dual-port grid-forming control strategy for PMSG wind turbines that seamlessly integrates MPPT, inertia, and fast frequency response without mode switching, enhancing stability and performance.

Contribution

The work presents a novel control approach that unifies multiple functions in wind turbines, providing analytical stability conditions and detailed simulation validation.

Findings

Control strategy enables seamless transition between MPPT and grid support functions.

Analytical stability conditions relate control gains to steady-state response.

Simulation validates improved performance over existing MPPT controls.

Abstract

In this work we present a novel dual-port grid-forming control strategy, for permanent magnet synchronous generator wind turbines with back-to-back voltage source converters, that unifies the entire range of functions from maximum power point tracking (MPPT) to providing inertia and fast frequency response without explicit mode switching between grid-following and grid-forming control. The controls impose a well-defined AC voltage at the grid-side converter (GSC) and the machine-side converter (MSC) AC terminals and explicitly stabilize the DC-link capacitor voltage through both GSC and MSC. The wind turbine's kinetic energy storage and curtailment are adjusted through a combination of implicit rotor speed control and pitch angle control and directly determine the operating mode and level of grid support. Moreover, we provide analytical small-signal stability conditions for a simplified system and explicitly characterize the relationship between control gains, curtailment, and the wind turbines steady-state response. Finally, a detailed simulation study is used to validate the results and compared the proposed control with state-of-the-art MPPT control.