General Information
The specification of a 1.5MW wind turbine with active pitch control states that the rated wind speed is 14 m/s and that the rotor dismeter is 77m. The generator is a double-fed induction machine. The turbine range of operation is 11.0 rpm to 20.4 rpm and the gearbox ratio is 90:1. The generator is a four-pole machine and the grid frequency is 50 Hz.
Part 1: The generator operates at a slop of -0.2 at rated output. Determine the rotational speed of the generator (in rpm) under these conditions. Calculate the speed of rotation of the turbine under these conditions. Confirm that this speed is within the turbine's range of operation
Part 2: Assuming that the active power is shared between the stator and rotor circuits in proportion to the slip(s):
Pr = -sPs
Determine the rotor and stator power under rated conditions
Part 3: The wind speed increases to 15m/s but the slip is maintained at a value of s=-0.2. The power output of the turbine remains at 1.5MW.
Calculate the tip-speed ratio under these conditions. Determine the power co-efficient (Cp) required. How is this combination (Tip Speed & Cp) achieved in this turbine.
So here are my attempts/methods, I mainly stuck on part 2 but I want to get part 1 and part 3 checked.
Part 1 Attempt
Generator Speed = \(\frac{Frequency*60}{Pairs of Poles}\)
Generator Speed = \(\frac{50*60}{2}\)
Generator Speed = 1500 rpm
Rotor Speed = Generator Speed-(Slip)(Generator Speed)
Rotor Speed = 1500-(-0.2)(1500)
Rotor Speed = 1800 rpm
Turbine Speed = \(\frac{Rotor Speed}{Gearbox Ratio}\)
Turbine Speed = \(\frac{1800}{90}\)
Turbine Speed = 20 rpm
As the turbine speed is 20 rpm is within the range of operation
Part 2 Attempt
I orginally tried to used the rotor power formula for a turbine which is Pr=0.5*p*A*Cp*U^3 but there is no Cp value provided and in the next part of the question you are asked to find it. It can't be 1.5=1.5*-0.2 ????
Part 3 Attempt
Blade Tip Speed = \(\frac{Turbine Speed*pi*Diameter}{60}\)
Blade Tip Speed = \(\frac{20*pi*77}{60}\)
Blade Tip Speed = 80.64
Tip Speed Ratio = \(\frac{Blade Tip Speed}{Wind Speed}\)
Tip Speed Ratio = \(\frac{80.64}{15}\)
Tip Speed Ratio = 5.376
Coefficient of Performance = \(\frac{Power}{0.5*rho*pi*R^2*U^3}\)
Coefficient of Performance = \(\frac{1500000}{0.5*1.225*pi*38.5^2*15^3}\)
Coefficient of Performance = 0.1559
Part 2 is my main issue but I want to make sure I did part 1 and 3 correctly.
The specification of a 1.5MW wind turbine with active pitch control states that the rated wind speed is 14 m/s and that the rotor dismeter is 77m. The generator is a double-fed induction machine. The turbine range of operation is 11.0 rpm to 20.4 rpm and the gearbox ratio is 90:1. The generator is a four-pole machine and the grid frequency is 50 Hz.
Part 1: The generator operates at a slop of -0.2 at rated output. Determine the rotational speed of the generator (in rpm) under these conditions. Calculate the speed of rotation of the turbine under these conditions. Confirm that this speed is within the turbine's range of operation
Part 2: Assuming that the active power is shared between the stator and rotor circuits in proportion to the slip(s):
Pr = -sPs
Determine the rotor and stator power under rated conditions
Part 3: The wind speed increases to 15m/s but the slip is maintained at a value of s=-0.2. The power output of the turbine remains at 1.5MW.
Calculate the tip-speed ratio under these conditions. Determine the power co-efficient (Cp) required. How is this combination (Tip Speed & Cp) achieved in this turbine.
So here are my attempts/methods, I mainly stuck on part 2 but I want to get part 1 and part 3 checked.
Part 1 Attempt
Generator Speed = \(\frac{Frequency*60}{Pairs of Poles}\)
Generator Speed = \(\frac{50*60}{2}\)
Generator Speed = 1500 rpm
Rotor Speed = Generator Speed-(Slip)(Generator Speed)
Rotor Speed = 1500-(-0.2)(1500)
Rotor Speed = 1800 rpm
Turbine Speed = \(\frac{Rotor Speed}{Gearbox Ratio}\)
Turbine Speed = \(\frac{1800}{90}\)
Turbine Speed = 20 rpm
As the turbine speed is 20 rpm is within the range of operation
Part 2 Attempt
I orginally tried to used the rotor power formula for a turbine which is Pr=0.5*p*A*Cp*U^3 but there is no Cp value provided and in the next part of the question you are asked to find it. It can't be 1.5=1.5*-0.2 ????
Part 3 Attempt
Blade Tip Speed = \(\frac{Turbine Speed*pi*Diameter}{60}\)
Blade Tip Speed = \(\frac{20*pi*77}{60}\)
Blade Tip Speed = 80.64
Tip Speed Ratio = \(\frac{Blade Tip Speed}{Wind Speed}\)
Tip Speed Ratio = \(\frac{80.64}{15}\)
Tip Speed Ratio = 5.376
Coefficient of Performance = \(\frac{Power}{0.5*rho*pi*R^2*U^3}\)
Coefficient of Performance = \(\frac{1500000}{0.5*1.225*pi*38.5^2*15^3}\)
Coefficient of Performance = 0.1559
Part 2 is my main issue but I want to make sure I did part 1 and 3 correctly.
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