Fault-tolerant Control of a Wind Turbine with a Squirrel-cage Induction Generator and Rotor Bar Defects

Transcription

1 Fault-tolerant Control of a Wind Turbine with a Squirrel-cage Induction Generator and Rotor Bar Defects V. Lešić 1, M. Vašak 1, N. Perić 1, T. Wolbank 2 and G. Joksimović 3 vinko.lesic@fer.hr 1 University of Zagreb Faculty of Electrical Engineering and Computing 2 Vienna University of Technology Faculty of Electrical Engineering and Information Technology 3 University of Montenegro Faculty of Electrical Engineering Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

2 Presentation outline 1 Motivation Wind energy The problem we tackle 2 Fault-tolerant control Fault description Fault-tolerant control - fast loop Field-oriented control Wind turbine control system Fault-tolerant control - slow loop 3 Simulation results 4 Conclusions Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

3 Wind energy Motivation Wind energy The fastest-growing renewable energy source Major influence on political and economic trends Expensive energy Wind turbines are located on remote locations High-cost repairs and maintenance Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

4 The problem we tackle Motivation The problem we tackle Electric machines failure frequency in industry is around 0.04 per year, in wind turbines up to 0.35 Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

5 The problem we tackle Motivation The problem we tackle Electric machines failure frequency in industry is around 0.04 per year, in wind turbines up to 0.35 In case of generator fault wind turbine shut-down Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

6 The problem we tackle Motivation The problem we tackle Electric machines failure frequency in industry is around 0.04 per year, in wind turbines up to 0.35 In case of generator fault wind turbine shut-down Lots of expensive monitoring and control equipment is already installed Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

7 The problem we tackle Motivation The problem we tackle We show how to: Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

8 The problem we tackle Motivation The problem we tackle We show how to: stop or postpone the generator fault development once the fault is characterised - fault-tolerant control Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

9 The problem we tackle Motivation The problem we tackle We show how to: stop or postpone the generator fault development once the fault is characterised - fault-tolerant control achieve maximum energy production under emergency circumstances Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

10 Fault description Fault-tolerant control Fault description Rotor bar fault (squirrel-cage induction machine) Stator inter-turn isolation fault Both can be well characterized with machine flux path areas Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

11 Fault description Fault-tolerant control Fault description Rotor bar fault (squirrel-cage induction machine) Stator inter-turn isolation fault Both can be well characterized with machine flux path areas Faults tend to spread safety device wind turbine shut-down Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

12 i Fault description Fault-tolerant control Fault description Rotor bar fault (squirrel-cage induction machine) Stator inter-turn isolation fault Both can be well characterized with machine flux path areas Faults tend to spread safety device wind turbine shut-down a a a θ 1 c' i θ 1 b c' θ 1 b c' b θ 2 θ 2 θ 2 θ 2 θ 2 i θ 2 b' c b' c b' c θ 1 θ 1 a' a' θ 1 a' Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

13 Fault-tolerant control Fault-tolerant control - fast loop Fault-tolerant control - fast loop We propose: Fast loop: Current (torque) reduction below safety value on the faulty part of the flux path and restoration elsewhere using field-oriented control Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

14 i Fault-tolerant control Fault-tolerant control - fast loop Fault-tolerant control - fast loop We propose: Fast loop: Current (torque) reduction below safety value on the faulty part of the flux path and restoration elsewhere using field-oriented control a c' θ 1 b i θ 2 θ 2 b' c θ 1 a' Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

15 Field-oriented control Fault-tolerant control Field-oriented control i.e. voltage-controlled rotor-flux-based field-oriented control T g = k m i sd i sq i sd is kept constant, T g i sq Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

16 Field-oriented control Fault-tolerant control Field-oriented control i.e. voltage-controlled rotor-flux-based field-oriented control T g = k m i sd i sq i sd is kept constant, T g i sq angle Δu sd,δu sq U max i sd,i sq T g_ref estimation & ref. calc. i sd_ref i sq_ref + - PI K r 1+T I s T I s + - u sd u sq (d,q) (a,b,c) i a i b i c SCIG T g i abc ω g Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

17 Field-oriented control Fault-tolerant control Field-oriented control i.e. voltage-controlled rotor-flux-based field-oriented control T g = k m i sd i sq i sd is kept constant, T g i sq angle Δu sd,δu sq U max i sd,i sq T g_ref estimation & ref. calc. i sd_ref i sq_ref + - PI K r 1+T I s T I s + - u sd u sq (d,q) (a,b,c) i a i b i c SCIG T g i abc ω g T Closed loop transfer function g(s) T g REF (s) = isq(s) i sq REF (s) = 1 1+τ s Time lag τ determines the transient dynamic (time to achieve referent torque value) Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

18 Fault-tolerant control Fault-tolerant control - fast loop Field-oriented control a θ 2 c' T g_nonf T gf θ 1 b θ 2 Generator torque (Nm) T g_nonf T gf T g1 (t) Δθ T g2 (t) b' θ 1 a' c t off t 1 t 2 t on τ π (θ off )(θ 1 ) (θ 2 ) (θ on ) (π) Rotor flux linkage angle (rad) Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

19 Fault-tolerant control Fault-tolerant control - fast loop Field-oriented control a θ 2 c' T g_nonf T gf θ 1 b θ 2 Generator torque (Nm) T g_nonf T gf T g1 (t) Δθ T g2 (t) b' θ 1 a' c t off t 1 t 2 t on τ π (θ off )(θ 1 ) (θ 2 ) (θ on ) (π) Rotor flux linkage angle (rad) By knowing the PI controller parameters, back EMF and voltage supplied to the inverter torque transient functions T g1 (t), T g2 (t) can be obtained as well as time instants t off, t 1, t 2 and t on Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

20 Fault-tolerant control Wind turbine control system Wind turbine control system 250 T gn Generator torque (knm) T gopt ω TORQUE controller T gref GENERATOR & INVERTER T g WIND ω Speed (rpm) ω gn 30 ω ref + - ω SPEED controller β ref PITCH servo & controller β Torque control loop (variable-speed) T g REF = K λ ω 2 g Speed control loop (variable-pitch) Proportional-integral(-derivative) gain scheduling Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

21 Fault-tolerant control Fault-tolerant control - slow loop Fault-tolerant control - slow loop We propose: Slow loop: Keeping the power production optimal under fault by selecting the optimal average torque Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

22 Fault-tolerant control Fault-tolerant control - slow loop Fault-tolerant control - slow loop We propose: Slow loop: Keeping the power production optimal under fault by selecting the optimal average torque a θ 2 c' b' T g_nonf T gf θ 1 b θ 2 c Generator torque (Nm) T g_nonf T gf T g1 (t) Δθ T g2 (t) θ 1 a' t off t 1 t 2 t on τ π (θ off )(θ 1 ) (θ 2 ) (θ on ) (π) Rotor flux linkage angle (rad) Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

23 Fault-tolerant control Fault-tolerant control - slow loop Fault-tolerant control - slow loop We propose: Slow loop: Keeping the power production optimal under fault by selecting the optimal average torque a θ 2 c' b' T g_nonf T gf θ 1 b θ 2 c Generator torque (Nm) T g_nonf T gf T g1 (t) Δθ T g2 (t) θ 1 a' t off t 1 t 2 t on τ π (θ off )(θ 1 ) (θ 2 ) (θ on ) (π) Rotor flux linkage angle (rad) Average torque = optimum torque Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

24 Fault-tolerant control Fault-tolerant control - slow loop Fault-tolerant control - slow loop Maximizing the power production under emergency circumstances 250 T gn Generator torque (knm) T av T gf Faulty machine T gopt Healthy machine ω g1 30 Speed (rpm) Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

25 Fault-tolerant control Fault-tolerant control - slow loop Fault-tolerant control - slow loop Interventions in conventional control system ω TORQUE controller T gref ' ω g T gref FAULT-TOLERANT control θ GENERATOR & INVERTER T g WIND ω ω ref + - SPEED controller β ref PITCH servo & controller β ω Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

26 Fault-tolerant control Fault-tolerant control - slow loop Fault-tolerant control - slow loop Interventions in conventional control system ω TORQUE controller T gref ' ω g T gref FAULT-TOLERANT control θ GENERATOR & INVERTER T g WIND ω ω ref + - SPEED controller β ref PITCH servo & controller β ω T, 1 T 2 θ T gref ' ω g SLOW loop T g_nonf θ start θ end FAST loop T gref T gf θ 1,θ 2 T gf Fault detection and characterization ω ref Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

27 Simulation results Simulation results Healthy and faulty wind turbine through entire operating area 20 Wind speed (m/s) healthy faulty Time (s) Power (kw) healthy faulty Time (s) Pitch angle (degrees) Time (s) Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

28 Simulation results Simulation results Torque modulation 250 Generator torque (knm) Generator torque (knm) Time (s) Time (s) Wind turbine rotor speed (rpm) Time (s) Wind turbine rotor speed (rpm) Time (s) Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

29 Conclusions Conclusions Proper reaction to diagnosed generator faults can save lots of money Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

30 Conclusions Conclusions Proper reaction to diagnosed generator faults can save lots of money We propose a fault-tolerant control for wind turbine generator electromechanical faults diagnosed fault is fully respected in operation power delivery under fault is deteriorated as less as possible compared to healthy machine conditions Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

31 Conclusions Conclusions Proper reaction to diagnosed generator faults can save lots of money We propose a fault-tolerant control for wind turbine generator electromechanical faults diagnosed fault is fully respected in operation power delivery under fault is deteriorated as less as possible compared to healthy machine conditions Simple extension of conventional wind turbine control system Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

32 Conclusions Conclusions Proper reaction to diagnosed generator faults can save lots of money We propose a fault-tolerant control for wind turbine generator electromechanical faults diagnosed fault is fully respected in operation power delivery under fault is deteriorated as less as possible compared to healthy machine conditions Simple extension of conventional wind turbine control system Can be applied to different types of machines (stator isolation fault) Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

33 Acknowledgement Conclusions The work has been supported by FP7 SEE-ERA.NET PLUS under contract No. ERA 80/1 (MONGS - Monitoring of Wind Turbine Generator Systems) Vinko Lešić (FER) EDPE 2011 September 28-30, / 18

34 Conclusions Thank you! Vinko Lešić (FER) EDPE 2011 September 28-30, / 18