By Engr. Laraib Khan & Group
The shortage of power is the major crisis we are facing these days in Pakistan. It has developed an urge to shift our attention to the more reliable and efficient methods for the power generation and transmission. As the power flow control is very difficult in AC systems, so the transfer of power is done over long distances with less power losses using HVDC links. Common applications of HVDC transmission technology have continuously based on interconnecting asynchronous AC systems, essentially for economic transportation of electric energy from remote resources. Therefore, NTDC has joined hand with private energy generation companies to overcome the shortfall of energy and laid 878 km long 660kV HVDC line from Matiari to Lahore having the capacity to transmit the power of 4000MW.
Stability problems, such as inter-area oscillations, have become increasingly common in large interconnected power systems and the primary function of HVDC controls are fast and flexible power control between the terminals under steady state and transient operation, better stability of ac system, fast protection of ac and dc system faults. The main focus of the project is to analyze all these issues in HVDC lines being laid in Pakistan using the simulation software Power System Simulation for Engineers (PSS/E) and to compare the results with National Transmission and Dispatch Company (NTDC) studies. Moreover, we are also aimed to study different multilevel inverter topologies and to implement the conventional HVDC 12 pulse Voltage source inverter topology (VSI) to understand the concept of HVDC deeply. The gating signals for the switching devices are generated using SPWM technique as result 12 pulses are generated output. The proposed topology reduces the amount of harmonic currents drawn from the utility lines and gives excellent performance in case of unbalancing in the practical power systems with much less component as compared to other 12 pulse inverter topologies. Hence it is low cost and is more feasible.