6 Effect of power imbalance on system frequency

# 6 Effect of power imbalance on system frequency - Lecture 8...

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Lecture 8 Effect of power imbalance on system frequency Consider the analogy of a mechanical system, where a car is traveling with a velocity v , there is mechanical power, and friction, as depicted in Figure 1 . Figure 1 - Mechanical analogy The kinetic energy of the car with mass m is 2 1 2 e km v = If P mech < P friction then the car slows down. Alternatively if we push the pedal then the car speeds up, i.e. v decreases, as well as the kinetic energy. A similar situation occurs in rotating machines. A generator is a rotating device connected to a turbine with a moment of inertia I . Figure 2 - Power Conversion If P mech = P elec then the speed of rotation ( ω m ) is constant and the electric frequency ( ω ) as well. This is called the steady state mode of operation. Hence if P elec increases, analog to P friction , then ω m decreases and the input of steam or water should be increased, but this response is slow (couple of minutes).

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Therefore if P mech cannot keep up with the change on P elec
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6 Effect of power imbalance on system frequency - Lecture 8...

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