Airborne wind energy system test bench electrical emulator

Abstract

Airborne wind energy systems (AWESs) offer a promising route to high-altitude wind harvesting, but their commercialization remains limited by the challenge of converting highly dynamic tethered flight power into stable electrical energy. While most research has focused on flight trajectories and control, the mechanical-to-electrical conversion stage requires further experimental validation. This paper introduces a validated electrical test bench emulator and a torque-ripple-optimized model predictive control (MPC) strategy, evaluated using two real AWES flight datasets. The emulator reproduces variable tether forces and reeling dynamics under optimal figure-eight crosswind flight. Two DC-bus topologies are compared: a separated bus that accurately mimics AWES storage dynamics (≈ 98 % fidelity) but demands 45 %–55 % more battery capacity and a common bus that recirculates energy, reducing storage needs by two-thirds. When realistic storage dynamic emulation is required, the separated-bus configuration is the only suitable option. The proposed MPC ensures precise generator speed and torque regulation, achieving torque-tracking root mean squared errors (RMSEs) below 0.11 % (Dataset 1) and 0.14 % (Dataset 2) and speed-tracking RMSEs of 0.44 % and 0.82 %, respectively. Overall energy efficiencies reach 82 % with Dataset 1 and 60 % with Dataset 2, with peak instantaneous efficiencies of 93 % and 88 %. Permanent magnet synchronous generators (PMSGs) outperform induction machines (IMs) by 4 % in Dataset 1 and up to 20 % in Dataset 2, with instantaneous gains of 2 %–10 % at high power. Off-nominal operation degrades cycle efficiency and drives higher battery cycling even in a common-bus setup, highlighting the importance of correct machine dimensioning. However, when storage dynamics are not under study, the common-bus configuration is the most cost-effective option, requiring less hardware and imposing lower peak discharge stresses. These results establish electrical test bench emulators as essential platforms for systematic evaluation and optimization of AWES power conversion, informing both machine design and control strategies for scalable, efficient AWES deployment.