DC-AC Inverter Topology for the Control and Stable Operation of HVDC

Department of Electrical Engineering,
University of Engineering and Technology, Lahore
DC-AC Inverter Topology for the Control
and Stable Operation of HVDC
Group No: 12
Project Advisor: Dr. Tahir Izhar
Co Advisor:Nauman Ahmed Zaffar
(Associate Professor LUMS)
Undergraduate Final Year Project Presentation
Dated: 4th April, 2018

Team Introduction
Saifa Khalid (Team Leader)
2014-EE-101
Specialization: Power
Laraib Khan
2014-EE-107
Haroon Ahmed
2014-EE-138

Problem Statement
● The generation-demand gap has been a long standing
issue in Pakistan.
● Generation stations are at distant places from the load
centres and limitations of AC transmission system puts
a constraint on the system
● HVDC links provides an efficient and reliable solution
for far distance transmission with little losses and stable
voltage profile and improved efficiency

Problem Statement
AC system DC systemversus
50 to 80 km no limitationsmax cable length
huge amount of
line losses
negligible losseslosses profile

Proposed Solution
● HVDC links laid between Matiari and lahore to fulfill the
load demand
● Stability analysis of the HVDC lines in comparison to the
already present AC transmission system.
● Voltage source inverters to convert back DC to AC to
supply to the load centres

Proposed Solution
AC
GENERATION
AC/DC
conversion
DC/AC
inversion
AC GRIDDC transmission
stability studies of HVDC
network between matiari and
lahore

Objective
The major objective of our project is to analyze stability
of transmission system including the 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 Despatch
Company (NTDC) studies.We are also focused to develop
a prototype of 12 pulse VSC inverter for understanding
HVDC concept deeply.

Block Diagram

Flow Diagram

12 Level Voltage Source Inverter
Specifications:
● 315 volts DC input
● 220 volts AC Output
● 1 kw power
● 12 pulse output
Topology Used

● Twelve pulses are generated using 150 degree
mode of conduction.
● The proposed topology is cost effective
● Compact size
● Less losses

PWM Gating signals of 150 degrees mode of conduction

SPWM Gating signals of 150 degrees mode of conduction

Output using simple PWM VS SPWM
Simple PWM output with THD SPWM output with THD

Stability studies
● The HVDC link is laid between Matiari to Lahore having
total transmission length of 878 km ,power capability of
2000MW and 660KV DC voltage levels.
● This link will overall improve the stability of the existing
Power system
● Enhances the voltage profile and reduce the transmission
losses
● It provides greater power transfer capability
● Eco Friendly

Stability studies
Proposed HVDC route in Pakistan

Stability studies
Single Line Diagram under study

Stability studies
● Performed steady state analysis on the given data by NTDC
for HVDC lines using software tool PSS/E
● Results shows that the system reaches its required tolerance
within 5 iterations using NEWTON RAPHSON power flow
calculation technique
● N-1 contingency results shows that the system remains in
the stable condition

Stability studies
● None of the line overloads
● Voltage levels remains within the limits according to
NTDC standards
● Reactive Power Compensation requirement reduced
● The system does not face any major power outage.

Applications
● HVDC have low losses as compared to HVAC hence
long-distance transmission is possible.
● Smaller filter requirement makes it more cost effective.
● HVDC transmission is much more economical and
feasible as compared to HVAC system.
● Grid tie as well as standalone capability makes the
inverter more compatible in the industry.
● Used for connecting Asynchronous systems
● HVDC lines opens a vast research area for students as
well as for industries.

Audience
The concept of project targets mainly
● Generation and Transmission Companies
● Research Students
● Industries

What we have done so far?
● Hardware implementation of 12 pulse inverter
Output With filterOutput Without filter

Stability Analysis
Contingency Analysis

Hardware Developed
Our inverter has 315 volts DC input and gives 220 volts
AC having the power rating of 1KW.The gating signals to
the IGBTS are given through SPWM hence, the THD of
final deliverable is around 13% which is much less as
compare to other topologies.

Future Deliverables
• Results of dynamic stability performed on the Matiari
to Lahore HVDC network on software PSS/E
• Add Grid Tie feature in the inverter
• Increase the switching frequency to reduce Filter size
• Further collaboration with NTDC to improve the
stability results further

Gantt Chart

References
[1] P. Kundur, Power System Stability and Control,
McGraw-Hill, New York, 1994.
[2] Dimitris G., Soubhik A., Mats H., Mukherjee S., Tomas
J., Bopparaju G., Carl H., An arrangement for controlling
the electric power transmission in a HVDC power
transmission system, PCT WO 2013/091700A1, 2013
[3] Power System Simulator for Engineering (PSS/E),
‘’Program Application Guide’’,Vol I PTI, Inc., 1991.
[4] Daniel W. Hart, Introduction to Power Electronics, first
edition

DC-AC Inverter Topology for the Control and Stable Operation of HVDC

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