This chapter presents an improved Indirect power control (compared to the
conventional one illustrated in chapter: 03) based on robust and suitable controllers
(Robust and Intelligent controllers) to control the d-q axes currents (Ird and Irq)
respectively. In order to overcome the speed/efficiency trade-off and divergence from
peak power under fast variation of wind speed; three intelligent controllers (based on,
T1-FLC, T2-FLC and NFC) are proposed to control the rotor direct and quadrature
currents (Ird and Irq) instead of PID controllers, for grid-connected doubly fed
induction generator (DFIG). The same wind-turbine (DFIG (4kW) and turbine (4.5
kW)) used in last chapter will be developed again in order to make a comparative study
between the wind-system performance algorithms. The SVM strategy (to ensure the
fixed switching frequency and to minimize the harmonics) is used in RSC for switching
signals generation to control the inverter. In this chapter, mathematical model of each
proposed controller is described in detail. The MPPT strategy is also developed in the
three proposed algorithms in order to extract the maximum wind power by keeping the
reactive power equal to zero value. The main aim of the proposed control is to improve
the wind system performance despite the sudden wind speed variation and the DFIG’s
parameter variation in transient and steady states. The simulation results using the
Matlab/Simulink environment (under three proposed modes and using robustness tests)
show that the intelligent controller offered high power quality in spite of wind-speed
variation have superior dynamic performance and are more robust during parameter
variation.
Keywords: Neuro-Fuzzy Logic (NFC), Type-1 Fuzzy Logic Control (T1-FLC),
Type-2 Fuzzy Logic Control (T2-FLC).
