Introduction 3/17/2015 3 Objective : To maintain the desired voltage at a high voltage bus. FC-TCR is a var generator arrangement using a Fixed capacitance with a TCR. The current in the reactor is varied by the method of firing delay angle control method. (Qc) of the fixed capacitor is opposed by the (QL) of the TCR.
3/17/2015 4 Capacitive var output : By increasing current in TCR lead to decrease in output. When TCR is off results in max var output. Zero var output : cancelling var by equalling both capacitive and inductive current. Inductive var output : further increase in current lead to increase in output.
Circuit diagram: 3/17/2015 5 Components : A TCR A fix capacitor across TCR High pass filter
Operating characteristics : 3/17/2015 6 Without stepdown transformer : I SVC =V J B SVC , where B SVC =B C +B TCR By dimensioning the ratings of the TCR and the capacitor, respectively, the production and absorption ranges can be selected according to the system requirements.
3/17/2015 7 With stepdown transformer : B SVC = B σ (B C +B TCR )/(B σ +B C +B TCR ) B SVC MAX = (1-B C /B σ )*B C (at α = 180˚) B SVC MIN = (1-(B C +B L )/B σ )*(B C +B L ) (at α = 90˚)
Losses in FC-TCR 3/17/2015 8 Circulation of large current for cancelling capacitive var resulting high steady state losses. Losses can be minimized by switching the fixed capacitors through mechanical breakers, ensuring that the capacitors are inserted in the compensator circuit only when leading vars are needed.
Conclusion 3/17/2015 9 FC-TCR is useful for getting controllable range of var output with a capacitor connected across TCR. And losses can be minimized by switching the fixed capacitor by mechanical breakers.
References 3/17/2015 10 ‘ Thyristor -based FACTS controllers for Electrical Transmission Systems,’ R. Mohan Mathur , R K Verma , Wiley IEEE Press ‘Reactive power control using FC-TCR’,Ms shilpa gupta , IJITR,volume-1,january-2013,india