Modular Multilevel Converter for Unified Power Flow Controller Application

Guying, Zhuo; Jiang, Daozhuo; Lian, Xiaorang

doi:10.1109/icdma.2012.129

Cited by 22 publications

(3 citation statements)

References 11 publications

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“…Therefore, arm-differential energy W Δ can be controlled by introducing a fundamental frequency component i cΔ into the arm-common current i c . On the other hand, (5) shows that the arm-sum energy W Σ depends on the difference between the average DC power (product v c i c ) and average AC power (product v s i s ). Thus arm-sum energy is controlled by controlling the power differences on a per-phase basis.…”

Section: B MMC Voltages and Currents As The Arm Energy Control Variamentioning

confidence: 99%

Direct Arm Energy Control in Modular Multilevel Converter Under Unbalanced Grid Conditions

Utvić

Dujić

2020

2020 International Symposium on Power Electronics, Electrical Drives, Automation and Motion (SPEEDAM)

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This paper studies the behaviour of the gridconnected modular multilevel converter under unbalanced grid conditions in terms of the energy imbalances within the converter, and proposes a novel approach for dealing with imbalances. Since the energy content within the arms of modular multilevel converter depends on the interaction between the terminal and internal voltages and currents, standard energy control methods, designed mainly for balanced grid conditions require improvement. This paper proposes a novel approach for the direct arm energy control, valid for both balanced and unbalanced grid conditions. The approach is characterized with its simple implementation, minimization of the current stress imposed on the converter, as well as with minimization of the risk of overmodulation. Theoretical foundation for mitigating the problem are supported with the simulation results, thus verifying the validity and performance of the proposed control concepts.

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Section: B MMC Voltages and Currents As The Arm Energy Control Variamentioning

confidence: 99%

Direct Arm Energy Control in Modular Multilevel Converter Under Unbalanced Grid Conditions

Utvić

Dujić

2020

2020 International Symposium on Power Electronics, Electrical Drives, Automation and Motion (SPEEDAM)

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“…This modulation mechanism can be used in MMC applications, however with limited bounds because it is not sensitive to the capacitor voltages drifts [61][62][63]. The reference [50,64,65] adapts the PSC-PWM to operate associated with an additional ranking and selection of cells approach.…”

Section: Phase-shift Carrier Pwmmentioning

confidence: 99%

Modulation techniques applied to medium voltage modular multilevel converters for renewable energy integration: A review

Antonio-Ferreira

Collados‐Rodríguez

Gomis‐Bellmunt

2018

Electric Power Systems Research

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Modular multilevel converters (MMC) inherent features are gaining more attention for dc voltage transmission systems. One of the main research paths regarding the converter performance deals with its voltage modulation. Specifically, for medium voltage applications with relatively small number of submodules, the voltage modulation techniques impact on the MMC performance needs to be studied. This work provides an extensive review of the carrier-based pulse with modulation (CB-PWM) techniques proposed to be applied on previous multilevel inverter versions. The CB-PWM methods were adapted to be compatible with an additional cell ranking and selection algorithm to ensure equal energy distribution on the arm cells. The state-of-the-art of zero sequence signals (ZSS) applied on three-phase inverters is also reviewed. The alliance between the ZSS with the CB-PWM, as well as the nearest level modulation (NLM), has an important impact on the MMC harmonic content, efficiency and voltage ripple of its cells capacitors. A 15 MW 28-cell-based MMC is used to investigate each particular combination between the modulation method and the common mode ZSS.Postprint (author's final draft

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“…This modulation mechanism can be used in MMC applications, however with limited bounds because it is not sensitive to the capacitor voltages drifts [95]. The reference [69,132,133] adapts the PSC-PWM to operate associated with an additional ranking and selection of cells approach.…”

Section: Phase-shift Carrier Pwmmentioning

confidence: 99%

Modular multilevel converters for power system applications

Ferreira¹

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This thesis discusses the operation of the grid-tied modular multilevel converters (MMC) applied on the dc power transmission, particularly on the medium and high-voltage applications. First, it is presented the evolution of the power converters used on the high-voltage dc transmission field (HVdc) with special focus on the modular multilevel-based power converters. Then, due to the intrinsic nature of the converter, besides the control requirements for its dc and ac buses interactions, its energy storage should be carefully managed in order to achieve a safe and knowledgeable operation of this power converter. Hence, its control requirements are presented and mathematically supported. Moreover, the progressive design and validation of its control loops is addressed in this thesis by means of the converter simulation over a broad range of operating conditions. One key-point factor of the MMC performance is the strategy followed to modulate the voltages generated on its arms. In this vision, different modulation techniques were combined with peculiar zero sequence signals in order to analyze their impact on the voltages across the converter arms and its intrinsic performance. This study was also complemented by different procedures followed to balance the energy storage of its capacitors. A transversal research question of this voltage source converter topology is its efficiency. Then, besides the analysis of the ac power flow impact on the power losses produced by its semiconductors, it is deduced and proposed a mathematical expression that that can describe the power losses produced semiconductors, over a broad range of operating conditions of the MMC. Finally, it is explored the possible degrees of freedom of an half-bridge-based MMC whenever it is operating in the static synchronous compensation (STATCOM) mode. Depending on the converter operation aspect that is required to be optimized, the voltage across its dc poles can be adjusted to achieve an improved performance of the MMC La presente tesis trata sobre el funcionamiento de los convertidores modulares de multinivel (MMC) utilizados en la transmisión de energía eléctrica en corriente continua, en particular para aplicaciones de media y alta tensión. En primer lugar, se presenta la evolución de los convertidores utilizados en el campo de la transmisión de energía eléctrica mediante enlaces en corriente continua de alta tensión(HVdc), haciendo especial énfasis en los convertidores de topología multinivel. Debido a la naturaleza intrínseca del convertidor MMC, se debe regular el intercambio de potencia entre las redes de corriente alterna y continua a las que se conecta, junto con la energía interna almacenada, para asegurar un buen funcionamiento del mismo. Por ello, se presenta una descripción del control del convertidor soportada por un riguroso análisis matemático. El diseño de los diferentes lazos de control se valida mediante simulaciones representando diferentes condiciones de funcionamiento posibles. Un factor clave del rendimiento del MMC es la estrategia de modulación utilizada para aplicar voltajes en cada una de sus ramas. Para evaluar sus diferencias a nivel de pérdidas, se presenta una comparativa entre diferentes técnicas de modulación incorporando secuencia homopolar. Este estudio se complementa con el estudio de diferentes procedimientos seguidos para equilibrar el almacenamiento de energía en los condensadores de una rama. Una cuestión de investigación transversal de esta topología de convertidor de tensión es su eficiencia. Posteriormente, se obtiene una expresión matemática que permite describir las pérdidas de los semiconductores del convertidor en funcionamiento, para diferentes niveles de transferencia de potencia. Finalmente, se analizan los posibles grados de libertad de un MMC operando en modo de compensación de potencia reactiva (STATCOM). En base a la operación de dicho convertidor y de la variable que se requiera optimizar, resulta posible variar la tensión entre sus polos DC para lograr un mejor funcionamiento del convertidor

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Modular Multilevel Converter for Unified Power Flow Controller Application

Cited by 22 publications

References 11 publications

Direct Arm Energy Control in Modular Multilevel Converter Under Unbalanced Grid Conditions

Direct Arm Energy Control in Modular Multilevel Converter Under Unbalanced Grid Conditions

Modulation techniques applied to medium voltage modular multilevel converters for renewable energy integration: A review

Modular multilevel converters for power system applications

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