CONTROL OF REAL & REACTIVE POWER BY MULTILEVEL UPFC

ELECTRICAL ENGGINERING

High-voltage and power capability of multilevel converters better used for unified power-flow controller (UPFC application). The three-level neutral-point- clamped (NPC) converter allows back-to- back connection as the UPFC shunt and series converters than other multilevel topologies. In place of the pulse width-modulated (PWM) multilevel control schemes, constant dc-link voltage and balanced voltages in the NPC multilevel dc capacitors is necessary for UPFCs. The proposed work provides three main contributions to increase the performance of the system of multilevel UPFCs as this can be operated in STATCOM, SSSC and exactly in the UPFC mode with the double balancing of dc capacitor voltages under line faults, overall enhancing the UPFC ride-through capability.NPC series and shunt converters keep the dc-link voltage steady, results the effectiveness of the real-time PWM generation and dc-link capacitor voltages balancing. Transients are the causes of fault in power system, Power System Stabilizer (PSS) and Automatic Voltage Regulator (AVR) are used to stabilize the response. Mostly to analyze the transients introduced in the system due to the occurrence of faults load flow analysis is used. The UPFC are becoming important and effective in suppressing power system oscillations, improving system damping and control the active and reactive power. This proposed work investigating the performance of UPFC with respect to the ideal and actual response of the system to achieve stability and it is seen and verified by the results. The effectiveness of the proposed dc link switch based UPFC in suppressing power system oscillation is investigated by analyzing line injection voltage, real and reactive power, dc link voltage and current. A proportional integral (PI) controller has been use in the UPFC to control the voltage source converters (VSC) current, voltage and phase of the transmission lines.

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