Robustification of the H∞ controller combined with fuzzy logic and PI&PID-Fd for hybrid control of Wind Energy Conversion System Connected to the Power Grid Based on DFIG

This paper proposes a strategy for hybrid control of variable speed wind turbines connected to the electrical grid, using a Double Fed Induction Generator (DFIG). An efficient validation approach is presented in three steps. The first step concerns the comparison of performances between Fuzzy Logic (FL), H infinity (H-infinity) and Integral Proportional action (PI) controllers. In a system context based on the DFIG direct vector control structure, the strengths of H-infinity are reinforced in the second step by implementing two new advanced mixed controllers, namely the FL-H-infinity and the combination of the PI, the Proportional Integral Derivative (PID) action, the Filter Derivative (Fd) action and the Hoo (PI&PID-Fd)-H-infinity. The second step, based on a simplified system of indirect vector control structure of the DFIG, allows the performance of the (PI&PID-Fd)-H-infinity to be compared with that of the FLHoo. In contrast to the latter, it emerges that, in addition to its simplicity of implementation and the reduction in calculation and simulation time, the (PI&PID-Fd)-H-infinity is very reassuring in terms of robustness against mixed uncertainties, stability, precision, tracking and decoupling between active (P-S) and reactive (Q(S))power. This makes (PI&PID-Fd)-H-infinity a very advantageous choice for the design of the proposed hybrid control system. The final step gives a more real-life picture of hybrid control of the wind system as follows, a random wind model is considered, an FL regulates the Maximum Power Point Tracking (MPPT) of the turbine model, the PI-H-infinity and (PID-Fd)-H-infinity control the Ps and Qs on the nominal DFIG model via a Rotor Side Converter (RSC), an FL regulates the DC-BUS voltage and the H-infinity control the currents via a Grid Side Converter (GSC) and filter. According to the results, and in contrast to a conventional PI control system, the hybrid control system offered has very good performance, particularly with regard to, for example, optimal extraction of energy from the wind, the currents fed into the grid are well balanced, the Total Harmonic Distortion (THD) is reduced and the cos phi is almost equal to unity. In addition, a good compromise between stability and expected performance is ensured. Consequently, the proposed strategy has reasonable and very favourable advantages for the optimisation of energy conversion in grid-connected wind energy systems. The results are developed in the MATLAB/Simulink environment. (C) 2021 The Authors. Published by Elsevier Ltd.

Automated summary

This paper proposes a strategy for hybrid control of variable speed wind turbines connected to the grid using a Double Fed Induction Generator (DFIG). By comparing different controllers and implementing new mixed controllers, a simple, robust, (PI&PID-Fd)-H∞ hybrid control system is presented. This system shows good performance in a practical wind power model, improving energy conversion efficiency and reducing system harmonic distortion.