An Efficient Angle Search Algorithm for FPS-PLLs in Encoderless Control of PMVG-Based Wind Turbine System Applications

This study aims to present an efficient angle search (EAS) algorithm to improve the computational efficacy and accuracy of finite position set-phase-locked loops (FPS-PLLs), which are used in rotor position estimation of permanent magnet vernier generator (PMVG)-based wind turbine system encoder-less control applications. The angle search algorithm employed in conventional FPS-PLLs has many suboptimal search area redundancies, therefore yielding a low accuracy. To address this issue, we presented an EAS algorithm that retains the optimal values of both the cost function and angle from the previous iteration
$(i-1)$
and employs them in the current iteration
$(i)$
. Furthermore, we have modified the angle discretization principle to confine the search area in each subsequent iteration
$(i+1)$
to the region identified as optimal in the preceding iteration
$(i)$
. The effectiveness of the presented scheme is experimentally investigated by employing it in FPS-PLLs by using a 5-kW PMVG laboratory prototype.