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A robust mechanical sensorless control strategy for active rectification of small wind turbines

Adrien Prévost, Vincent Léchappé, Romain Delpoux, Xavier Brun

TL;DR

The paper addresses robustly controlling small wind turbines with a surface-mounted PMSG in a sensorless setup. It develops a Lyapunov-based GAS proof for the closed-loop, and leverages a Sliding Mode Observer to estimate rotor position and speed despite uncertain $R$ and $L$, enabling field-oriented control without a mechanical sensor. A detailed current controller and an observer architecture yield analytic models for the BEMF observation error and current equilibrium, demonstrating resilience to parameter uncertainty. Experimental validation on a wind turbine emulator shows sensorless operation maintaining energy harvesting near encoder-based performance, with energy yields meeting or exceeding 98% of the encoder case in stationary and near-typical wind conditions.

Abstract

This article proposes a mechanical sensorless control strategy for the synchronous rectification of small wind turbines equipped with a surface-mounted Permanent Magnet Synchronous Generator (PMSG). By means of Lyapunov theory, the Global Asymptotic Stability (GAS) of the closed loop system is proven. It allows the use of a classical Sliding Mode Observer (SMO) to remove the mechanical sensor in the control loop despite uncertainties on the resistance and inductance parameters. The analysis of the equilibrium points have made it possible to propose an analytic model of the angular misalignment between the true and the observer rotating frames, responsible for current tracking errors. Experimental tests on a wind turbine emulator show that despite large errors on the the resistance and inductance parameters, the impact on the energy harvest is low, proving that the strategy's performance is robust to high uncertainties.

A robust mechanical sensorless control strategy for active rectification of small wind turbines

TL;DR

The paper addresses robustly controlling small wind turbines with a surface-mounted PMSG in a sensorless setup. It develops a Lyapunov-based GAS proof for the closed-loop, and leverages a Sliding Mode Observer to estimate rotor position and speed despite uncertain and , enabling field-oriented control without a mechanical sensor. A detailed current controller and an observer architecture yield analytic models for the BEMF observation error and current equilibrium, demonstrating resilience to parameter uncertainty. Experimental validation on a wind turbine emulator shows sensorless operation maintaining energy harvesting near encoder-based performance, with energy yields meeting or exceeding 98% of the encoder case in stationary and near-typical wind conditions.

Abstract

This article proposes a mechanical sensorless control strategy for the synchronous rectification of small wind turbines equipped with a surface-mounted Permanent Magnet Synchronous Generator (PMSG). By means of Lyapunov theory, the Global Asymptotic Stability (GAS) of the closed loop system is proven. It allows the use of a classical Sliding Mode Observer (SMO) to remove the mechanical sensor in the control loop despite uncertainties on the resistance and inductance parameters. The analysis of the equilibrium points have made it possible to propose an analytic model of the angular misalignment between the true and the observer rotating frames, responsible for current tracking errors. Experimental tests on a wind turbine emulator show that despite large errors on the the resistance and inductance parameters, the impact on the energy harvest is low, proving that the strategy's performance is robust to high uncertainties.

Paper Structure

This paper contains 24 sections, 1 theorem, 81 equations, 11 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Modelling of the WECS
  3. Aerodynamics
  4. Rotating system
  5. Generator
  6. WECS control scheme
  7. Problem statement
  8. Optimal Torque Control
  9. Field Oriented Control
  10. Current controller design
  11. Observer design
  12. Currents observer design
  13. BEMF and speed observer
  14. Robustness analysis
  15. Modelling of the BEMF observation error
  16. ...and 9 more sections

Key Result

Theorem 1

The closed-loop system given by eq. eq:cl_system is GAS if the following condition is met with $a=\dfrac{3}{4b}p\phi_f\sqrt{p^2(\phi_f+Li_d^\#)^2+(L{i_q^\#}p)^2}-\dfrac{3p^2\phi_f(\phi_f+Li_d^\#)}{4b}$.

Figures (11)

  • Figure 1: The WECS architecture.
  • Figure 2: WECS control scheme overview.
  • Figure 3: Wind turbine emulator test bench. (a) PMSM (b) Torque-meter (c) axial flux PMSG
  • Figure 4: The turbulent wind velocity time series
  • Figure 5: Tracking error of the current $i_d$ for different scenario of parameters uncertainty. Experimental data are plotted in continuous lines and results from the analytical model in dashed.
  • ...and 6 more figures

Theorems & Definitions (6)

  • Remark 1
  • Remark 2
  • Theorem 1
  • Remark 3
  • Remark 4
  • Remark 5