Quantitative Feedback Theory design of robust MPPT controller for Small Wind Energy Conversion Systems: Design, analysis and experimental study

Abstract

This paper addresses the design of a robust Maximum Power Point Tracking (MPPT) controller for a small wind energy conversion system fed by a Permanent Magnet Synchronous Generator (PMSG). The proposed MPPT controls the generator rectified voltage instead of the rotational speed avoiding the need for a mechanical sensor. Traditionally, this control problem is performed using a Proportional Integrator (PI) controller optimised at a specific operating point. However, the PI controller does not guarantee the promising transient performance under changing operating conditions. In this work, the Quantitative Feedback Theory (QFT) has been applied to synthesis a robust DC-voltage controller to ensure a robust stability and tracking specifications for all operating points. The performance of the designed controller has been compared with the classical PI controller experimentally on laboratory benchmark. The experimental results prove that the proposed controller outperforms the conventional PI controller reducing the overshoot between 26.67% and 82.53% and the response time between 36.36% and 71.33%, reducing by the way the mechanical stress on the PMSG under a turbulent wind speed profile. In addition, the extracted electrical energy using the proposed controller over 90 s of a typical wind speed profile is 1.7015% higher.