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Power quality improvement with a pulse width modulation control method in modular multilevel converters under varying nonlinear loads
- Source :
- Applied Sciences, Vol 10, Iss 3292, p 3292 (2020), Applied Sciences, Volume 10, Issue 9
- Publication Year :
- 2020
-
Abstract
- In order to reach better results for pulse width modulation (PWM)-based methods, the reference waveforms known as control laws have to be achieved with good accuracy. In this paper, three control laws are created by considering the harmonic components of modular multilevel converter (MMC) state variables to suppress the circulating currents under nonlinear load variation. The first control law consists of only the harmonic components of the MMC&rsquo<br />s output currents and voltages. Then, the second-order harmonic of circulating currents is also involved with both upper and lower arm currents in order to attain the second control law. Since circulating current suppression is the main aim of this work, the third control law is formed by measuring all harmonic components of circulating currents which impact on the arm currents as well. By making a comparison between the switching signals generated by the three proposed control laws, it is verified that the second-order harmonic of circulating currents can increase the switching losses. In addition, the existence of all circulating current harmonics causes distributed switching patterns, which is not suitable for the switches&rsquo<br />lifetime. Each upper and lower arm has changeable capacitors, named &ldquo<br />equivalent submodule (SM) capacitors&rdquo<br />in this paper. To further assess these capacitors, eliminating the harmonic components of circulating currents provides fluctuations with smaller magnitudes, as well as a smaller average value for the equivalent capacitors. Moreover, the second-order harmonic has a dominant role that leads to values higher than 3 F for equivalent capacitors. In comparison with the first and second control laws, the use of the third control-law-based method will result in very small circulating currents, since it is trying to control and eliminate all harmonic components of the circulating currents. This result leads to very small magnitudes for both the upper and lower arm currents, noticeably decreasing the total MMC losses. All simulation results are verified using MATLAB software in the SIMULINK environment.
- Subjects :
- 020209 energy
02 engineering and technology
lcsh:Technology
Circulating currents
law.invention
lcsh:Chemistry
Materials Science(all)
Computer Science::Systems and Control
Control theory
law
0202 electrical engineering, electronic engineering, information engineering
Waveform
General Materials Science
lcsh:QH301-705.5
Instrumentation
Engineering(all)
Physics
Fluid Flow and Transfer Processes
modular multilevel converter
lcsh:T
circulating currents
Process Chemistry and Technology
020208 electrical & electronic engineering
General Engineering
control laws
Converters
harmonic component
Modular multilevel converter
lcsh:QC1-999
Computer Science Applications
Harmonic component
Nonlinear system
Capacitor
Second-order harmonic
second-order harmonic
lcsh:Biology (General)
lcsh:QD1-999
lcsh:TA1-2040
Harmonics
Harmonic
Control laws
lcsh:Engineering (General). Civil engineering (General)
Pulse-width modulation
lcsh:Physics
Voltage
Subjects
Details
- Language :
- English
- Database :
- OpenAIRE
- Journal :
- Applied Sciences, Vol 10, Iss 3292, p 3292 (2020), Applied Sciences, Volume 10, Issue 9
- Accession number :
- edsair.doi.dedup.....20b88d9f1fa347cde301dd23defcadd0