scholarly journals Power Quality Improvement with a Pulse Width Modulation Control Method in Modular Multilevel Converters under Varying Nonlinear Loads

2020 ◽  
Vol 10 (9) ◽  
pp. 3292 ◽  
Author(s):  
Majid Mehrasa ◽  
Radu Godina ◽  
Edris Pouresmaeil ◽  
Eduardo M. G. Rodrigues ◽  
João P. S. Catalão
Keyword(s):  
Pulse Width ◽  
Pulse Width Modulation ◽  
Second Order ◽  
Control Law ◽  
Nonlinear Load ◽  
Control Laws ◽  
The Third ◽  
Circulating Current ◽  
Harmonic Components ◽  
Circulating Currents

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’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’ lifetime. Each upper and lower arm has changeable capacitors, named “equivalent submodule (SM) capacitors” 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.

scholarly journals Study of a Synchronization System for Distributed Inverters Conceived for FPGA Devices

2021 ◽  
Vol 4 (1) ◽  
pp. 5
Author(s):  
Leonardo Saccenti ◽  
Valentina Bianchi ◽  
Ilaria De Munari
Keyword(s):  
Field Programmable Gate Array ◽  
Pulse Width ◽  
Pulse Width Modulation ◽  
Control Method ◽  
Synchronization System ◽  
Circulating Current ◽  
Field Programmable ◽  
Efficiency And Reliability ◽  
Circulating Currents

In a multiple parallel-connected inverters system, limiting the circulating current phenomenon is mandatory since it may influence efficiency and reliability. In this paper, a new control method aimed at this purpose and conceived to be implemented on a Field Programmable Gate Array (FPGA) device is presented. Each of the inverters, connected in parallel, is conceived to be equipped with an FPGA that controls the Pulse-Width Modulation (PWM) waveform without intercommunication with the others. The hardware implemented is the same for every inverter; therefore, the addition of a new module does not require redesign, enhancing system modularity. The system has been simulated in a Simulink environment. To study its behavior and to improve the control method, simulations with two parallel-connected inverters have been firstly conducted, then additional simulations have been performed with increasing complexity to demonstrate the quality of the algorithm. The results prove the ability of the method proposed to limit the circulating currents to negligible values.

scholarly journals Local Carrier PWM for Modular Multilevel Converters with Distributed PV Cells and Circulating Current Reduction

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5585
Author(s):  
Zaid A. Aljawary ◽  
Santiago de Pablo ◽  
Luis Carlos Herrero-de Lucas ◽  
Fernando Martinez-Rodrigo
Keyword(s):  
Pulse Width Modulation ◽  
Sampling Period ◽  
External Source ◽  
Multilevel Converters ◽  
Pv Systems ◽  
Circulating Current ◽  
Modular Multilevel Converters ◽  
Power Point ◽  
Current Reduction ◽  
Circulating Currents

A new topology has been recently proposed for grid-connected photovoltaic (PV) systems, using modular multilevel converters (MMCs) and distributing PV panels throughout the MMC cells. This topology has two main advantages: it reduces the power losses related to moving the energy into the MMC capacitors from an external source, and it removes the losses and costs related to the DC to DC converters used to track the maximum power point on string converters or central converters, because that task is delegated to MMC cells. However, traditional pulse width modulation (PWM) techniques have many problems when dealing with this application: the distortion at the output increases to unacceptable values when MMC cells target different voltages. This paper proposes a new modulation technique for MMCs with different cell voltages, taking into account the measured cell voltages to generate switching sequences with more accurate timing. It also adapts the modulator sampling period to improve the transitions from level to level, an important issue to reduce the internal circulating currents. The proposed modulation has been validated using simulations that show a consistent behavior in the output distortion throughout a wide operation range, and it also reduces the circulating currents and cuts the conduction losses by half. The behavior of this new topology and this new modulation has been compared to the mainstream topology with external PV panels and also to a fixed carrier modulation.

Analysis and design of a PWM chopper-on/off control via a second order filter

2014 ◽  
Vol 11 (2) ◽  
pp. 181-186 ◽  
Author(s):  
Abdelouahab Zaatri ◽  
Souad Belhour
Keyword(s):  
Pulse Width ◽  
Closed Loop ◽  
Pulse Width Modulation ◽  
Theoretical Study ◽  
Second Order ◽  
Power Supplies ◽  
Analysis And Design ◽  
System Parameters ◽  
Order Filter ◽  
The Relationship

This paper presents the analysis of a nonlinear on/off control system including a filter of a second order in the closed loop. The proposed system is capable of generating a pulse width modulation which is used to design and built up a PWM (Pulse Width Modulation) chopper dedicated to regulate fluctuating power supplies such as photovoltaic, wind turbine systems; etc. The use of the second order filter aims to compensate the output against the fluctuations of irradiation as well as the variation of the load. The study essentially focuses on determining the relationship between the pulse durations with respect to system parameters and technological requirements. The theoretical study is followed by a simulation of a DC-DC chopper.

scholarly journals A Review of Modular Multilevel Converters for Stationary Applications

2020 ◽  
Vol 10 (21) ◽  
pp. 7719
Author(s):  
Yang Wang ◽  
Ahmet Aksoz ◽  
Thomas Geury ◽  
Salih Baris Ozturk ◽  
Omer Cihan Kivanc ◽  
...  
Keyword(s):  
Pulse Width ◽  
Pulse Width Modulation ◽  
Low Voltage ◽  
Current Control ◽  
Switching Frequency ◽  
Power Losses ◽  
Circulating Current ◽  
High Switching Frequency ◽  
Wide Range ◽  
Balancing Control

A modular multilevel converter (MMC) is an advanced voltage source converter applicable to a wide range of medium and high-voltage applications. It has competitive advantages such as quality output performance, high modularity, simple scalability, and low voltage and current rating demand for the power switches. Remarkable studies have been carried out regarding its topology, control, and operation. The main purpose of this review is to present the current state of the art of the MMC technology and to offer a better understanding of its operation and control for stationary applications. In this study, the MMC configuration is presented regarding its conventional and advanced submodule (SM) and overall topologies. The mathematical modeling, output voltage, and current control under different grid conditions, submodule balancing control, circulating current control, and modulation methods are discussed to provide the state of the MMC technology. The challenges linked to the MMC are associated with submodule balancing control, circulating current control, control complexity, and transient performance. Advanced nonlinear and predictable control strategies are expected to improve the MMC control and performance in comparison with conventional control methods. Finally, the power losses associated with the advanced wide bandgap (WBG) power devices (such as SiC, GaN) are explored by using different modulation schemes and switching frequencies. The results indicate that although the phase-shifted carrier-based pulse width modulation (PSC-PWM) has higher power losses, it outputs a better quality voltage with lower total harmonic distortion (THD) in comparison with phase-disposition pulse width modulation (PD-PWM) and sampled average modulation pulse width modulation (SAM-PWM). In addition, WBG switches such as silicon carbide (SiC) and gallium nitride (GaN) devices have lower power losses and higher efficiency, especially at high switching frequency in the MMC applications.

Control of Circulating Current for Direct-Parallel Connected PWM Inverters

2013 ◽  
Vol 756-759 ◽  
pp. 612-617
Author(s):  
Chun Xue Wen ◽  
Kun Kun Fang
Keyword(s):  
Pulse Width ◽  
Pulse Width Modulation ◽  
Operation Time ◽  
Maximum Power ◽  
Parallel Structure ◽  
Space Vector ◽  
Circulating Current ◽  
Simulation Results ◽  
A Current

It can not only make the system more flexibly, but also can make the maximum power higher by using the direct-parallel connected inverters. However, when grid-connected inverters operate in direct-parallel structure, it may lead to potential circulating current. So its important to inhibit circulating current. Its found that the circulating current can be suppressed by controlling the operation time of zero vectors during every PWM cycle of space vector pulse width modulation (SVPWM). Meanwhile, we can add a current-average loop to the system so as to make the circulating current smaller. Simulation results in MATLAB are presented to prove the effectiveness of this method in this paper.

scholarly journals The impact of communications channel bandwidth on the accuracy of pulse-width signal transmission

2021 ◽  
Vol 2094 (3) ◽  
pp. 032021
Author(s):  
V Prokofiev ◽  
O A Golyshevsky ◽  
A E Savochkin
Keyword(s):  
Pulse Width ◽  
Additive Noise ◽  
Pulse Width Modulation ◽  
Signal Transmission ◽  
Pulse Signal ◽  
Frequency Range ◽  
Channel Bandwidth ◽  
Fluctuation Noise ◽  
Harmonic Components ◽  
The Impact

Abstract Pulse-width modulation (PWM) signals used in various areas are sent to the receiver through a communications channel that distorts their waveform due to the limitations of the frequency range. It is not always possible to reduce additive (fluctuation) noises that are also present within the PWM signal to negligible levels. Limiting the range of frequencies transmitted over a communications channel results in both the deterioration of PWM signal front slopes and the changes in the spectral specifications of the fluctuation noise. The simulation of pulse signal formation helped identify a correlation between the pulse front slope and the number of harmonic components transmitted over the communications channel. Through the analysis, we established a correlation between pulse time and the additive noise parameters along with the bandwidth of the real communications channel. These calculations might be useful for problems where it is necessary to formulate the requirements for the communications channel transmitting the PWM signal.

scholarly journals Research of modular multilevel converter with phase-shifted pulse-width modulation

2021 ◽  
Vol 280 ◽  
pp. 05009
Author(s):  
Ihor Kozakevych ◽  
Roman Siyanko
Keyword(s):  
Mathematical Model ◽  
Pulse Width ◽  
Output Voltage ◽  
Pulse Width Modulation ◽  
Electric Energy ◽  
Point Of View ◽  
Modular Multilevel Converter ◽  
Multilevel Converter ◽  
Energy Converter ◽  
Circulating Current

The work is devoted to the study of performance of a multilevel electric energy converter using phase-shifted pulse-width modulation. Equations describing the state of a dynamic system multilevel converter - load are investigated and a mathematical model of the system in Matlab / Simulink environment has been constructed. Variants of implementation of phase-shifted pulse-width modulation systems from the point of view of influence on harmonics of output voltage and magnitude of circulating current in the converter are investigated.

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