Download HVDC TRANSMISSION SYSTEM USING MULTILEVEL POWER

HVDC TRANSMISSION SYSTEM USING
MULTILEVEL POWER CONVERTERS BASED
ON DUAL THREE-PHASE TWO-LEVEL
INVERTERS
ABSTRACT
Multilevel converters are now an attractive solution for high-voltage direct-current (HVDC)
electrical energy transmission systems. Unlike the well-known two-level voltage source converters,
multilevel converters use 3 or more voltage levels or steps per leg to modulate the ac voltages,
decreasing voltage distortion and reducing electromagnetic interference. This work presents a HVDC
transmission system based on a new multilevel structure using a dual two-level converter topology.
This structure attains multilevel operation and advantages using two well known three-phase voltage
source two-level inverters connected to one three-phase open windings transformer.
CIRCUIT DIAGRAM
EXISTING SYSTEM
Initially thyristor based current source converters (CSC) were used in HVDC systems to transmit
power of production sites very far from consumers, or to make asynchronous interconnections. Long
distance transmission HVDC systems do not need reactive compensation as required by HVAC
transmission systems. HVDC allows also for a transmission capacity increase. In fact, for a given
conductor cross section, HVDC transmission can carry more current through a conductor
comparedwith conventional HVAC transmission. Recently backto- back HVDC links using voltage
source converters (VSC) are used for the interconnection of asynchronous networks, eliminating the
harmonics filters needed in CSC HVDC.
PROPOSED SYSTEM
The well known VSC HVDC transmission structure consists in a combination of a DC cable or line
with two power electronics converters, each one at a link terminal for AC/DC and DC/AC conversion.
The power electronic converters are usually two level VSC converters with series connected
semiconductor devices. To obtain AC voltage waveforms with several voltage levels, instead of the
classical VSC topology, multilevel topologies like the neutral-point clamped or the modular
multilevel converter have been proposed. Instead of the classical structure, a HVDC transmission
structure with two DC links, as presented , is proposed. In this HVDC system two three-phase two
level H-bridge converters (VSC) connected in each side of the link terminal are used. These two
VSCs are connected to the open-end secondary windings of a three phase transformer
TOOLS AND SOFTWARE USED:
 MP LAB
 ORCAD/PSPICE
 MATLAB/SIMULINK
OUTPUT:
 HARDWARE
 SIMULATION