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LUND UNIVERSITY LIBRARIES

Simulation, Control and Analysis of a 3-phase 3-level NPC Converter in Grid-Connected Systems

Karlsson, Tom LU and Lekman, Joachim LU (2024) In CODEN:LUTEDX/TEIE EIEM01 20241
Industrial Electrical Engineering and Automation
Abstract
The integration of renewable energy sources into modern power grids necessitates
the use of power electronic converters capable of handling high voltages. Multilevel
converters offer advantages compared to traditional 2-level converters by provid-
ing multiple voltage levels, improved efficiency, and better power quality. However,
maintaining balanced DC link voltages presents additional complexity in control
algorithms. This thesis aims to implement a functional grid-connected 3-level NPC
(Neutral Point Clamped) converter.

Initially, simpler designs such as a buck converter, an H-bridge converter, and a
2-level converter were investigated and simulated. This ensured a structured ap-
proach as each design introduced relevant... (More)
The integration of renewable energy sources into modern power grids necessitates
the use of power electronic converters capable of handling high voltages. Multilevel
converters offer advantages compared to traditional 2-level converters by provid-
ing multiple voltage levels, improved efficiency, and better power quality. However,
maintaining balanced DC link voltages presents additional complexity in control
algorithms. This thesis aims to implement a functional grid-connected 3-level NPC
(Neutral Point Clamped) converter.

Initially, simpler designs such as a buck converter, an H-bridge converter, and a
2-level converter were investigated and simulated. This ensured a structured ap-
proach as each design introduced relevant challenges and concepts necessary for the
implementation of the 3-level converter. After simulation, the core focus was on code
implementation using a microcontroller where the 2-level converter was first imple-
mented, followed by the 3-level converter. Experimental setups involved connecting
the 2-level and 3-level converters to the grid and controlling the output currents.

The power quality of the converters was evaluated and compared to each other and
the corresponding simulations. In conclusion, the power quality of the 3-level con-
verter surpasses that of the 2-level converter. Discrepancies in power quality between
simulations and experimental results suggest potential factors such as transformer-
induced voltage distortions or electromagnetic interference in the setup. Further
research could focus on integrating DC-voltage control and running the converter as
an active dynamic filter. (Less)
Popular Abstract
A converter converts direct current (DC) to alternating current (AC) and vice versa.
This process is typically achieved with a 2-level converter, which can output two
distinct constant potentials, such as -500 V and 500 V. The converter can switch
between these levels at several kHz. When an inductor is connected to the output
and the converter switches appropriately, a sinusoidal current can be generated.

For improved efficiency and better power quality, a 3-level converter can be used.
This type of converter can output three distinct constant potentials, such as -500 V,
0 V, and 500 V. This thesis simulated both 2-level and 3-level converters and im-
plemented them in a lab prototype, confirming that the 3-level converter... (More)
A converter converts direct current (DC) to alternating current (AC) and vice versa.
This process is typically achieved with a 2-level converter, which can output two
distinct constant potentials, such as -500 V and 500 V. The converter can switch
between these levels at several kHz. When an inductor is connected to the output
and the converter switches appropriately, a sinusoidal current can be generated.

For improved efficiency and better power quality, a 3-level converter can be used.
This type of converter can output three distinct constant potentials, such as -500 V,
0 V, and 500 V. This thesis simulated both 2-level and 3-level converters and im-
plemented them in a lab prototype, confirming that the 3-level converter produced
a current with higher quality.

The 3-level converter can be used to convert DC from sources such as solar parks
or battery energy storage systems to AC, which can then be transmitted to the
electrical grid. Additionally, it can function as an active dynamic filter, enhancing
phase current by adding a filter current that cancels out unwanted components of
the phase current. (Less)
Please use this url to cite or link to this publication:
author
Karlsson, Tom LU and Lekman, Joachim LU
supervisor
organization
alternative title
Simulering, styrning och analys av en 3-fas 3-nivå NPC-omvandlare i nätanslutna system
course
EIEM01 20241
year
type
H3 - Professional qualifications (4 Years - )
subject
keywords
converter, 3-level, three-level, 2-level, two-level, NPC, power electronics, pi, p regulator, voltage balancing, simulations, microcontroller, STM32, IGBT, THD, PWM, clarke, park, PLL, current control, H-bridge, 3-phase, grid, C code, simulink, matlab, AC, DC-link, SPWM, carrier wave, phase-locked loop
publication/series
CODEN:LUTEDX/TEIE
report number
5519
language
English
id
9174361
date added to LUP
2024-10-02 15:30:51
date last changed
2024-10-02 15:30:51
@misc{9174361,
  abstract     = {{The integration of renewable energy sources into modern power grids necessitates
the use of power electronic converters capable of handling high voltages. Multilevel
converters offer advantages compared to traditional 2-level converters by provid-
ing multiple voltage levels, improved efficiency, and better power quality. However,
maintaining balanced DC link voltages presents additional complexity in control
algorithms. This thesis aims to implement a functional grid-connected 3-level NPC
(Neutral Point Clamped) converter.

Initially, simpler designs such as a buck converter, an H-bridge converter, and a
2-level converter were investigated and simulated. This ensured a structured ap-
proach as each design introduced relevant challenges and concepts necessary for the
implementation of the 3-level converter. After simulation, the core focus was on code
implementation using a microcontroller where the 2-level converter was first imple-
mented, followed by the 3-level converter. Experimental setups involved connecting
the 2-level and 3-level converters to the grid and controlling the output currents.

The power quality of the converters was evaluated and compared to each other and
the corresponding simulations. In conclusion, the power quality of the 3-level con-
verter surpasses that of the 2-level converter. Discrepancies in power quality between
simulations and experimental results suggest potential factors such as transformer-
induced voltage distortions or electromagnetic interference in the setup. Further
research could focus on integrating DC-voltage control and running the converter as
an active dynamic filter.}},
  author       = {{Karlsson, Tom and Lekman, Joachim}},
  language     = {{eng}},
  note         = {{Student Paper}},
  series       = {{CODEN:LUTEDX/TEIE}},
  title        = {{Simulation, Control and Analysis of a 3-phase 3-level NPC Converter in Grid-Connected Systems}},
  year         = {{2024}},
}