Direct Power Control Based on Fractional Order Proportional Integral of DFIG: Real-Time Implementation on STM32F4

This paper presents the design, implementation, and real-time testing of a fractional-order PI (FOPI) controller for the Rotor Side Converter (RSC) of a Doubly-Fed Induction Generator (DFIG) used in wind energy systems. Compared to traditional PI controllers, the FOPI controller provides an extra tuning parameter, allowing better trade-off between speed and stability. The fractional integral operator is approximated using Oustaloup’s recursive method and discretized via the Tustin transformation for implementation on the STM32F4DISCOVERY board. The study highlights how increasing the approximation order slightly improves accuracy but also adds to the computational load, which must be considered in embedded systems. A Direct Power Control (DPC) scheme is used, where the estimated active and reactive powers are compared with references to generate control signals via the FOPI controller. The setup is tested through a Processor-In-the-Loop (PIL) simulation where we verified the feasibility of the real-time implementation.