Notes - Chapter 8 Summary

The following notes are taken from Wind Turbine Technology by Ahmad Hemami.

• P = IV
• Loads
• Resistive load is a load due to resistors and not dependent on frequency
• Capacitors and Inductors exhibit frequency dependent resistance called reactance
• Capacitive and Inductive loads act in opposite directions in phasor diagram can cancel each other's effect
• cause phase difference between voltage and current
• preferred value for the phase angle should be as close to zero as possible
• power factor is the value of the cosine of phase angle
• electric motors put both inductive and resistive loads into circuit
• Capacitors in parallel with motors reduce inductive load
• Current Leading Voltage, means current waveform reaches max or min value before voltage waveform
• Power types
• DC power corresponds to resistive load
• AC 
• reactive power
• corresponds to inductive and capacitive loads
• power stored in each half cycle and sent back to circuit
• active power
• resistive loads in AC
• real power that converts heat or work
• apparent power
• provided to maintain a current I in a circuit of voltage V, generator provides apparent power
• To connect turbine to a grid
• equal voltages
• same frequency
• synchronized waveforms
• have similar phase sequences
• Turbine must not lower the power factor of grid
• The output from all turbines in a wind farm goes to collector substation
• raises voltage from turbines to grid
• Power quality
• perfect sinusoid in AC circuit
• no fluctuations in voltage and frequency
• variations, flickers and spikes all indicate lack of quality
• Harmonics are low-voltage signals that are multiples of the frequency
• Islanding when a wind farm becomes isolated from the rest of the network which can lead to a drift and voltage and frequency
• Control actions
• control voltage
• control frequency
• control available current due to power from wind

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