High Voltage Direct Current (HVDC) Transmission System use Direct Current for transmission of bulk power over long distances. Figure 1 show the general construction of a HVDC transmission system. HE First Power grid/ network HOW HVDC transformer Converter 1 Converter station Overheadline DO Converter 2 HVDC transformer Converter station Figure 1 HVDC Substation Layout Lo Second Power grid/ network a) Elaborate the operation of HVDC in transmitting DC power from one point to another point. (4 marks) b) Say that the converter station is operating on a three-phase bridge system, propose a suitable improved/upgraded circuit for both converter station and discuss how the magnitude of the power being transmitted is being controlled. Sketch the circuit and draw appropriate input/output waveforms with respect to the controlling parameter. (6 marks) c) Converter 2 can be replaced with a multilevel inverter so that the performance can be improved. Proposed a suitable circuit arrangement for the converter 2 if it is to be replaced by multilevel inverter. Discuss on how the multilevel structure can improved the output waveform of converter 2. (4 marks)