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Advanced incremental conductance MPPT for small wind turbines

University of British Columbia

Small wind turbines (WTs) are robust and commercially viable distributed generation alternatives to photovoltaic (PV) generation in locations deemed unsatisfactory due to low irradiance levels. However, small WTs are susceptible to variable environmental conditions and require sophisticated maximum power point tracking (MPPT) algorithms to ensure the system operates at the maximum power point (MPP) when subjected to fluctuating wind speeds. Optimal relationship based (ORB) and hill-climbing (HC) algorithms are the traditional MPPT methods for small WTs due to their simplicity, yet these strategies suffer from several challenges: ORB algorithms rely on parameterized coefficients that change over time, whereas HC variants are susceptible to algorithm confusion and lack standardized frameworks for choosing the optimal MPPT controller update frequency and perturbation magnitude. This work introduces a novel control-oriented small WT model that facilitates an intuitive approach for analyzing the electromechanical system. This modelling technique enables the development of two incremental conductance (InCond) based MPPT strategies that address the aforementioned challenges. The first presented MPPT strategy tracks the optimal system operating point using an adapted mechanical InCond algorithm and suppresses power oscillations around the MPP. This results in: 1) elimination of algorithm confusion, 2) accurate tracking and detection of the MPP and 3) improved steady state efficiency. The algorithm design requires only electrical sensing, thereby making this method sensorless from a mechanical perspective. The second presented MPPT framework uses the control-oriented model and an online impedance measurement technique to perform a system impedance frequency response analysis. Through this analysis, a small WT equivalent circuit is derived and MPPT controller is developed using a novel system identification (SysID) algorithm to perform InCond control. This methodology offers three advantages over conventional methods: 1) accurate tracking when subjected to erratic wind speeds, 2) optimal MPPT over the system lifetime and 3) a systematic approach for choosing the MPPT update frequency, facilitated by the system impedance frequency response analysis. The presented MPPT methods are supported with detailed mathematical procedures and validated with simulation and experimental results. This thesis significantly contributes to the advancement of small WT modelling and MPPT.

Text

2021-02-18

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/77337

Electrical and Computer Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/