Frequency-Distinct Control of Wind Energy Conversion System Featuring Smooth and Productive Power Output

Abstract

Improving maximum power point tracking ability (MPPTA) and smoothing electric power fluctuation (EPF) are two important goals for optimizing wind power generation. Sufficient works have been done on both goals separately, but the multi-objective optimization of wind energy conversion system (WECS) is lack of theoretical analysis. In this paper, the small signal analysis method is applied to get a frequency-domain declaration for both MPPTA and EPF. The analysis results show when applying traditional optimal torque control (OTC), a larger moment of inertia of WECS is preferred for smoothing EPF, while a smaller moment of inertia is preferred for improving MPPTA, i.e., the two optimization goals contradict with each other. Furthermore, the existing control strategies for improving MPPTA are summarized as virtual-inertia embedded OTC, which turns out to have adverse impacts on EPF. To simultaneously optimize these two contradictory goals, a novel frequency-distinct optimal torque control approach is proposed, and a novel criterion for evaluating MPPTA is presented to facilitate controller parameter design. The analysis results and the proposed control strategy are fully verified by refined co-simulation platform based on GH Bladed and real time digital simulator.