Electrical Aspects of Wind Energy PDF

Electrical Aspects of Wind Energy Prof. Dr.-Ing. Siegfried Heier University of Kassel Fraunhofer IWES  4 Control concepts and operational results 4.3 Interconnection operation Prof. Dr.-Ing. Heier, wes.online, University of Kassel 21.01.2...

Electrical Aspects of Wind Energy Prof. Dr.-Ing. Siegfried Heier University of Kassel Fraunhofer IWES  4 Control concepts and operational results 4.3 Interconnection operation Prof. Dr.-Ing. Heier, wes.online, University of Kassel 21.01.2016 317 Interconnection operation Principle structure of a generating unit with options for power control Feed water tank 318 Interconnection operation Grid frequency during failures 1 Outage of a 150 MW block in an isolated grid 2 Outage of a 100 MW block in an isolated grid 3 Outage of a 1200 MW block in an interconnected grid 319 Interconnection operation WEC requirements during failures – Active power/frequency 320 Interconnection operation WEC requirements during failures – Active power/frequency 321 Interconnection operation WEC requirements during failures – Active power/frequency Active power as a function of time Reference: Conventional power plant 322 Interconnection operation WEC requirements during failures – Reactive power/voltage 323 Interconnection operation WEC requirements during failures – Reactive power/voltage Voltage support Normal operation 324  5 Control system Prof. Dr.-Ing. Heier, wes.online, University of Kassel 21.01.2016 325  5 Control system 5.1 Plant component characteristics Prof. Dr.-Ing. Heier, wes.online, University of Kassel 21.01.2016 326 Control structure of a wind energy converter Grid or consumer (island operation) Madj Blade pitch External Drive Mechanical Generator adjustment input moment drive train (electr.) device Blade pitch adjustment Management and control Blade Blade pitch Drive Turbine, Gearbox, Generator pitch Generato Grid or adjustment adjust- moment hub coupling rotor device r (electr.) consumer ment (mech.) 327 Plant component characteristics Dynamic effects and angular relationships at the turbine 328 Plant component characteristics Dynamic effects and angular relationships at the turbine Blade pitch system enables: − influencing the torque − controlling the output and rotational speed − limiting the rotor blade and tower bending Superposition of the processes enables: − reducing or damping the tower vibrations 329  Plant component characteristics Moments on a rotor blade Differential equation of the motioon of the blade turning about ist longitudinal axis:  dβ  d  ( J LB + J Bl )  dt  d ((kDB + kRB )β ) M St − M Bl =  + dt dt Differentiating and separating: d 2 β  dJBl dJLB  dβ M St = (J LB + J Bl ) 2 +  + + kLD + kRL  dt  dt dt  dt  dkLD dkRL  + + β + M Pr + Mlift + MT + Mbend + Mteeter  dt dt  330 Plant component characteristics Moments on a rotor blade Essential dependencies: − Moment of inertia of air mass: ( J LB = f β&&, v1,ψ Bl , n, b&&, t ) − Moment of inertia of mass: J Bl = f (β , v1,ψ Bl , n, b, t ) − Damping coefficient: ( kDB = kLD + kSD ≈ f β& , v1,ψ Bl , n, t ) − Coefficient of friction: ( kRB = kRL + kRV ≈ kRL = f β , β& , v1,ψ Bl , n, t ) − Propeller moment: M Pr = f (β , n, t ) − Moment due to lift on blade: Mlift = f (β , v1,ψ Bl , n, t ) − Moment due to blade bending: Mbend = f (β , v1,ψ Bl , n, b, t ) − Moment due to teetering: Mteeter = f (β , v1,ψ Bl , n, t ) − Torsional effect due to aerodynamic restorting torques in the direction of flow: MT = f (β , v1,ψ Bl , n, t ) 331  Plant component characteristics Moments on a rotor blade Standardizing and linearizing the variables: 332  Plant component characteristics Moments on a rotor blade Standardizing and linearizing the variables: − Lifting forces: − Resetting effects: − Propeller moments: − Resetting moments by springs: 333 Plant component characteristics Moments on a rotor blade Standardizing and linearizing the motion equation: − Acceleration-dependent component: − Damping value: − Angle-dependent: − Constant component: − Wind-speed equivalent: − Value proportional to rotation speed: 334  Plant component characteristics Moments on a rotor blade Torque matrix of the control system for rotor blade pitch adjustment: 335 Plant component characteristics Moments on a rotor blade Characteristic values of the torque matrix depending on the rotor configuration: Blade rotational axis position of TB/4: Moments by springs independent of wind and rotational speed: Systems without return springs: Blade axis of rotation in the centre of mass: 336  5 Control system 5.2 Control circuits and simplified dimensioning Prof. Dr.-Ing. Heier, wes.online, University of Kassel 21.01.2016 337  Control circuits and simplified dimensioning Rotor blade pitch adjustment Linear transmission element for rotor blade pitch adjustment: Laplace transformation: Substitutions: 338 Control circuits and simplified dimensioning Rotor blade pitch adjustment Disturbance variable Command variable Regulator and Blade actuator Regulating variable/actual value Control system with the control circuit for blade pitch adjustment 339  Control circuits and simplified dimensioning Rotor blade pitch adjustment Transfer function: Regulation variable: − with: and Purpose: − Regulated variable in line with command variable − Suppress influence of the disturbance variable and 340 Control circuits and simplified dimensioning Rotor blade pitch adjustment Control system with the control circuit for blade pitch adjustment 341  Control circuits and simplified dimensioning Rotor blade pitch adjustment VS Proportional second-order control sections: FS ( p) = (T1 p +1)(T2 p + 1) Ti p +1 VS Open-loop transfer function with PI controller: Fk ( p) = VR Ti p (T1 p +1)(T2 p +1) Ti T1 1 With Ti = T1 T and ik = = : Fk ( p) = VRVs VRVs Tik p(T2 p + 1) T1 1 T1 With Tik = = 2T2 , i.e. VR = ⋅ VRVs Vs 2T2 1 and damping factor Dg = : 2 1 Resonance frequency: ωg = 2T2 342  5 Control system 5.2 Control circuits and simplified dimensioning Blade pitch speed (β) control circuit Prof. Dr.-Ing. Heier, wes.online, University of Kassel 21.01.2016 343 Control circuits and simplified dimensioning Blade pitch speed control circuit ˙ β-regulator Actuator 344  Control circuits and simplified dimensioning Blade pitch speed control circuit Open-loop transfer function: VMot 1 Fkβ& ( p) = Fβ&R ⋅ FS ,St ⋅ FS ,Bl = Vβ&R (TMot p + 1) TBl p with: − Vβ&R Gain of blade pitch angle controller − VMot Gain of actuator − TMot Delay time of actuator Jβ&N − TBl = Integration time constant of blade M rN 345  Control circuits and simplified dimensioning Blade pitch speed control circuit Closed-loop transfer function: 1 1 Fcβ& ( p) = = 1 TBl T T 1+ 1+ p + Bl Mot p2 Fkβ& Vβ&RVMot Vβ&RVMot 2Dβ TBl 1 TBlTMot = = With ω0 Vβ&RVMot and ω02 Vβ&RVMot : TBl 1 TBl Vβ&R = Dβ&R = Gain: 4Dβ2TMotVMot Damping: 2 TMotVMotVβ&R 346 Control circuits and simplified dimensioning Blade pitch speed control circuit 1 2,25 10 0,474 1/ 2 4,5 15 0,387 0,5 9 18 0,355 0,4 14,06 20 0,355 0,3 25 30 0,274 0,2 56,25 40 0,237 50 0,212 347  5 Control system 5.2 Control circuits and simplified dimensioning Blade pitch (β) control circuit Prof. Dr.-Ing. Heier, wes.online, University of Kassel 21.01.2016 348 Control circuits and simplified dimensioning Blade pitch control circuit β-regulator 349  Control circuits and simplified dimensioning Blade pitch control circuit Open-loop transfer function (PI-controller): VβR (TβR p +1) 1 1 Fkβ ( p) = FRβ ⋅ Fgβ ⋅ FSβ = ⋅ ⋅ TβR p TBl T T 1+ p + Bl Mot p2 Tβ p Vβ&RVMot Vβ&RVMot with: − VβR Gain of blade pitch angle controller − TβR Time constant of blade pitch angle controller β − Tβ = &N Time constant of blade pitch angle speed integrator βN 350  Control circuits and simplified dimensioning Blade pitch control circuit Approximation of the second-order blade pitch speed circuit by a first-order substitution function:  − t   f sub (t ) = Vsub 1 − e t sub      Substitution function measured 351  Control circuits and simplified dimensioning Blade pitch control circuit Assuming that TMot