Multilevel Converter Topologies for STATCOMs

Shukla, Anshuman; Nami, Alireza

doi:10.1007/978-981-287-281-4_2

Cited by 2 publications

(2 citation statements)

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“…Hence, it globally reduces the losses produced in comparison to the first VSC generation [12]. The 3L-NPC structure has a major drawback which is the uneven loss distribution among the semiconductor devices [39,40]. During the state that the point o is connected to the point j, this is inevitably done through the upper or lower clamping diodes in case of positive or negative current flow respectively.…”

Section: Three Level Convertersmentioning

confidence: 99%

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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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Section: Three Level Convertersmentioning

confidence: 99%

“…Several methods to estimate the semiconductor' power losses have been proposed [36][37][38][39][40]. The methodology followed was proposed by the MMC's manufacturer Siemens AG [36], and it is being widely used since then [12,25,26,41].…”

Section: Quantification Of the Semiconductors Power Lossesmentioning

confidence: 99%