Sensorless Maximum Power Control of a Stand-Alone Squirrel-Cage Induction Generator Driven by a Variable-Speed Wind Turb
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ORIGINAL ARTICLE
Sensorless Maximum Power Control of a Stand‑Alone Squirrel‑Cage Induction Generator Driven by a Variable‑Speed Wind Turbine Mateo Bašić1 · Matija Bubalo1 · Dinko Vukadinović1 · Ivan Grgić1 Received: 4 May 2020 / Revised: 17 September 2020 / Accepted: 12 October 2020 © The Korean Institute of Electrical Engineers 2020
Abstract For the cost-effectiveness of variable-speed wind energy conversion systems (WECSs), it is extremely important to extract the maximum available power at different wind speeds within the normal operating range. Furthermore, reduction of the electric generator losses additionally contributes to the efficiency of the WECS, whereas reduction of the number of sensors is beneficial in terms of reliability and cost. This paper presents sensorless control of a stand-alone WECS comprising a squirrel-cage induction generator (IG) and a battery system. An indirect rotor-field-oriented control (IRFOC) algorithm including stray load and iron losses and online tuning of IG’s equivalent resistances and magnetising inductance is adopted for IG control to achieve high level of agreement with the actual machine. Fuzzy-logic-based optimisations of the wind turbine (WT) and IG are implemented to maximise the IG output power. The IG speed, which is required by the IRFOC algorithm, is estimated by using a model-reference-adaptive-system. The estimated IG speed is also utilised for online WT optimisation in combination with the IG torque obtained from the IRFOC equations. The performance of the proposed control strategy has been experimentally evaluated and compared with two competing sensorless control strategies for two 1.5 kW IGs of different efficiency class. Keywords Induction machine · Iron losses · MRAS estimator · Parameter tuning · Sensorless vector control · Stray load losses
1 Introduction In small wind energy conversion systems (WECSs) installed in remote, isolated locations, squirrel-cage induction generators (IGs) represent a cost-effective alternative to permanentmagnet synchronous generators (PMSGs) due to their simple and rugged construction, low maintenance, small size, and low cost. However, their efficiency is lower compared to PMSGs of the same rating and they additionally require excitation capacitors and a gearbox system. This adversely * Mateo Bašić [email protected] Matija Bubalo [email protected] Dinko Vukadinović [email protected] Ivan Grgić [email protected] 1
Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, University of Split, Split, Croatia
affects the WECS cost and reliability. Moreover, amplitude and frequency variations in the IG terminal voltage due to the wind turbine (WT) speed and torque fluctuations need to be compensated. Given the stochastic nature of wind power, an energy storage/backup system is additionally required in stand-alone WECSs to ensure uninterrupted power supply [1]. Variable-speed WTs offer the possibility of extraction of the maximum power at different wind speeds through adjustment of the WT speed. This con
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