O100

0.01s

1 + 5s pi controller

Pitch actuator

Fig. 8. Pitch angle controller of wind turbine

Rate limiter (Max ±10/sec)

Pitch Angleß

IG

FESS

Stator resistance (pu)

0.01

0.02

Stator leakage reactance (pu)

0.07

0.08

Magnetizing reactance (pu)

4.1

3.5

Rotor resistance (pu)

0.007

0.02

Rotor leakage reactance (pu)

0.07

0.08

Table II. Parameters of induction machines. Synchronous generator model

A Synchronous Generator (SG) is considered as a main power supply unit in the network in this study, which is assumed to be a diesel engine driven power plant. The characteristics of the diesel engine and its governor system in [6] are considered. The governor controls fuel supply to maintain the engine speed at the synchronous speed. Its block diagram is shown in Fig. 9, and its parameters are shown in Table III.

If FESS regulates the network frequency by its power compensation, the output of SG may not change, because the network frequency is controlled to be constant. Consequently, there is a possibility that FESS performs all of the network frequency control instead of SG. In such case, when the stored energy in FESS becomes full or empty, the power balance of the network cannot be maintained and thus the network frequency can deviate significantly. To avoid such situation, the output of SG also needs to be regulated according to the stored energy of FESS. In this chapter, a cooperative control is proposed, in which the output of SG is increased (or decreased) when the rotor speed of FESS is below (or over) 1.044pu which corresponds to a half of the maximum storage energy of FESS. But if the additional command to the main source generator changes fast, its output will also vary widely, and then it suffers large mechanical stress. Therefore a control gain is set for the additional command to change slowly as shown in Fig. 10. The governor of SG in this study has been designed to control only engine speed, and thus the output of SG can be changed by modifying a monitored signal of the engine speed to the governor. These control systems are shown in Fig. 10. In addition, a simple AVR model shown in Fig. 11 is used in SG model. Parameters of the synchronous generator (SG) are shown in Table IV.

Controller

Fig. 9. Governor model of the diesel engine

0.02

1.044

+

+ .

1.2s

30s +1

To SG governo r

Fig. 10. Additional signal controller for output adjustment of the diesel engine w, ex

Vto (Reference) Efdo (Initial value) Efd

Fig. 11. AVR model of the synchronous generator

Proportional Gain of Kp 8.0

Integral Gain Ki 2.0

Pilot servo time constant TA 0.2 s

Dead time of engine T 0.25 s

Table III. Parameters of the diesel engine governor

Armature resistance (pu) 0.0025

Stator leakage reactance (pu) 0.14

Field resistance (pu) 0.0004 Field leakage reactance (pu) 0.2

D-axis Q-axis Magnetizing reactance (pu) 1.66 0.91

Damper resistance (pu) 0.005 0.0084

Damper leakage reactance (pu) 0.044 0.106

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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