Indirect Power Control (IDPC) of DFIG Using Classical & Adaptive Controllers Under MPPT Strategy

In this chapter, we present a comparative study of conventional Indirect Power Control (IDPC) algorithm of DFIG-Wind turbine in grid-connection mode, using PI and PID controllers via Maximum power point tracking (MPPT) strategy. Firstly, the conventional IDPC based on PI controllers will be described using simplified model of DFIG through stator flux orientation and wind-turbine model. The MPPT strategy is developed using Matlab/Simulink® with two wind speed profiles in order to ensure the robustness of wind-system by maintaining the Power coefficient (Cp) at maximum value and reactive power at zero level; regardless unexpectedF wind speed variation. Secondly, the rotor side converter (RSC) and Grid side converter (GSC) are illustrated and developed using Space vector modulation (SVM) in order to minimize the stress and the harmonics and to have a fixed switching frequency. In this context, the switching frequency generated by IDPC to control the six IGBTs of the inverter (RSC), and this control algorithm works under both Sub- and Supersynchronous operation modes and depending to the wind speed profiles. The quadrants operation modes of the DFIG are described in details using real DFIG to show the power flow under both modes (motor and generator in the four (04) quadrants. Finally, the conventional IDPC have several drawbacks as: response time, power error and overshoot. In this context, the PID and MRAC (adaptive regulator) controllers are proposed instead of the PI to improve the wind-system performances via MPPT strategy with/without robustness tests. The obtained simulation results under Matlab/Simulink® show high performances (in terms of power error, power tracking and response time) in steady and transient states despite sudden wind speed variation, whereas big power error and remarkable overshoot are noted using robustness tests, so the proposed IDPC can not offer big improvement under parameter variation.

Keywords: Indirect Power Control (IDPC) algorithm, Maximum power point tracking (MPPT) strategy, Model Reference Adaptive Control (MRAC), Space vector modulation (SVM).