Unified Power Flow Controller

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Unified Power Flow Controller
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INTRODUCTION

• Two main objectives of FACTS
• Increase the TX capability of AC line
• Control of power flow over the TX routes
• UPFCs - most effective FACTS device
• UPFC a device which control TX line impedance,
  voltage and phase angle

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BASIC CONSTRUCTION OF A UPFC

• Consists of two switching GTO converters
• Shunt-connected
• Series-connected
• Both converters can operate in a rectifier mode
  or in an inverter mode
• A DC branch links these two converters by a
  storage capacitor.

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OPERATING PRINCIPLE
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Operating Principle

• Conceptually, a generalized SVS
• Converter2 injects a voltage Vpq with phase angle
  ? in series with TX line via an insertion
  transformer
• Main function of converter1 is to supply the real
  power demanded by converter2 at the DC link
• No reactive power flow through DC link

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TX control capabilities

• Vpq ?V (? 0). Vpq Vq
• Vpq V? Vpq ?V Vq V?

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Phasor representation of the UPFC
Basic asumption (Vpq 0) P0(d) V2/X sin d
sin d Q0(d) Q0r(d) -Q0r(d) V2/X1-cos d
I-cos d

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Phasor representation of the UPFC
For Vpq ? 0 ,
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Conclusion

• Most sophisticated power flow controller
  Expensive
• Gives better performance as compared to
  STATCOM,SSSC and TCSC
• Provide simultaneous, real-time control of all
  basic power system parameters (transmission
  voltage, impedance and phase angle) and dynamic
  compensation of ac system

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