Page 246 - Renewable Energy Devices and System with Simulations in MATLAB and ANSYS

Electric Generators and their Control for Large Wind Turbines 233

×10 4 Component weight
3
Iron used
Stator iron
2.5
Copper
PM
2 Rotor iron
Machine
Weight (kg) 1.5

1

0.5

0
0 200 400 600 800 1000 1200
(a) Steps

×10 5 Cost
2
1.8

1.6
1.4 Copper
Material cost (USD) 0.8 1 Lamination
1.2
PM
Rotor iron

0.6 Weight

0.4
0.2
0
0 200 400 600 800 1000 1200
(b) Steps

FIGURE 9.20 Evolution of (a) weight and (b) material cost for different components during optimization
design for an 8 MW, 480 rpm PMSG.

This leads automatically to an “underexcited” operation mode (generated voltage is higher than
the terminal voltage), which is favorable for the voltage-boosting operation of the machine-side
PWM voltage source converter, with V being the DC-link voltage (the DC-link voltage is decided
DC
by the grid voltage) in steady state:
π
2
2
Li q ; V q = ω ψ PM + i R s ; V s = V d + V q ; V s < (9.30)
V d =−ω 1 q r q V DC
33