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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$(i-1)$</tex-math></inline-formula> and employs them in the current iteration <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$(i)$</tex-math></inline-formula>. Furthermore, we have modified the angle discretization principle to confine the search area in each subsequent iteration <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$(i+1)$</tex-math></inline-formula> to the region identified as optimal in the preceding iteration <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$(i)$</tex-math></inline-formula>. The effectiveness of the presented scheme is experimentally investigated by employing it in FPS-PLLs by using a 5-kW PMVG laboratory prototype.