FACTS (Flexible AC Transmission System) By SVC (Static Variable Compensator) System: The FACTS by SVC is a system, which is very important in AC transmission lines for improving the power factor and voltage stabilization. The power factor is basically the cosine angel between current and voltage and its value is varied between zero and one. Its value near to one is consider a good power factor or leading power factor and near to zero is consider a bad power factor or lagging power factor. Both have different advantages and disadvantages but a leading power factor is necessary for smoothly transfer the power in AC transmission lines. As we know very well, the demand of power is increasing day by day but we have limited sources of energy and limited transmission lines. Besides of these we have mostly the inductive load at output side.
Due to these reasons the voltage de-stabilization and lagging power factors likes problems are created. In past, for resolving these problems a large rotating machine such synchronous generator or capacitor banks are used but these were in-efficient and costly because the large machine and capacitors banks are damaged quickly. Here we have proposed a FACTS (Flexible AC transmission system) by SVC (static variable compensator) with help pic microcontroller 18F452 for resolving the above issues. This FACTS by SVC system consists of capacitors connected in parallel and this parallel combination is operated by power electronics semi nonconductor switches such as SCRs etc. This system is connected in parallel with that system whose power factor we want to improve.
Block Diagram of the FACTS by SVC system
Figure 1 The Block Diagram ofFACTS (Flexible AC Transmission System) By SVC (Static Variable Compensator)
Components List with Detail of the FACTS by SVC System
Transformer:In this FACTS by SVC system, the transformer is used for step down the ac voltage. When this system is directly connected to the wapda then it steps down the 220V ac in to 12V ac. Its consists of two winding and work on the principle of mutual induction.
Bridge Rectifier:In this FACTS by SVC system, the bridge rectifier is used for converting the ac voltages into dc voltages which consists of four diodes and is connected at the output of transformer.
Blocking Diode:In this FACTS by SVC system, the blocking diode is connected at the output of bridge rectifier for blocking the reverse current.
Voltage Regulator: In this FACTS by SVC system, the voltage regulator is used for regulating the dc voltages and is connected at the output of bridge rectifier. In this system LM 7805 voltage regulator has been used.
LCD Display:In this FACTS by SVC system, the LCD display is used for displaying leading or lagging power factor of the connected system. The LCD display is powered up with 5V dc and interfaced with microcontroller.
Microcontroller PIC 18F452:In this FACTS by SVC system, the pic 18F452 microcontroller has been used for the intelligent control of this system. It is 40 pinsmicrocontroller and programmed in c language with the help of mikro/c software It is powered up with 5V dc and is interfaced with LCD display, Optocoupler and zero crossing detector amplifier.
Optocoupler: In this FACTS by SVC system, the optocoupler is used for the isolation purposes between the microcontroller and output side load. It is 6 pins integrated circuit IC and interfaced with microcontroller and back to back connected thyristor.
Back to Back Thyristor:In this FACTS by SVC system, the two semiconductor switches such as SCRs are connected back to back for switch on or off the capacitor bank.
Capacitor Bank:In this system, the capacitor bank is used for improving the power factor. The capacitor bank is made by connecting the four capacitors in parallel.
Zero Crossing Detector: In this system, the zero-crossing detector is basically the operation amplifier that is used for comparing the two inputs, when any one is greater than other it gives the logic high at output side.
Inductive Load:In this system, the inductive load is used for checking the how much power factor is improved by the capacitor bank.
Working of the FACTS by SVC System
This FACT by SVC system works on the principle of power factor lagging when the inductive load is connected at output side then the supply voltage is 90-degree lag than the supply current due to this the supply reactive power is decreased in other words the power factor is lag 90 degree. In this system two zero crossing detector are used one at input side and one at output side. The input side detector detects the input side voltage and gives the signal to the microcontroller, similarly the output side detector detects the output side current and gives the signal to the microcontroller. Suppose the power factor is lag by connecting the inductive load at output side this power factor is sensed by the microcontroller through the zero-crossing detectors then the microcontroller compared the output side power factor with the reference or input side power factor. After comparing the both sides power factor then the microcontroller gives the logic high signal to the optocoupler, then optocoupler turn on or off the semiconductor switches. The capacitor bank is directly attached with the semiconductor switches SCRs then these switches connect the capacitor bank parallel to the output load. So, this capacitor bank improves the power factor by increasing the reactive the power. The power factor improvement or leading power factor we can easily see on LCD display.
Advantages and Applications of the FACTS by SVC System
- This system could be used in transmission lines for improving the power factor and for voltage stabilization.
- This system could be used in industrial application for improving the power factor of industrial loads.
- This system could be used in domestic applications for improving the power factor of domestic loads.
- This system is more compact and reliable as compared to the other traditional power factor impartments systems.
- This system is less costly as compared the other systems.