Capacitance Reduction of the Hybrid Modular Multilevel Converter by Decreasing Average Capacitor Voltage in Variable-Speed Drives

Zhou, Shaoze; Li, Binbin; Guan, Mingxu; Zhang, Xinyi; Xu, Dianguo

doi:10.1109/tpel.2018.2833503

Cited by 31 publications

(15 citation statements)

References 21 publications

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“…The ripple voltage will increase to its maximum value (about 20%) at standstill. For this reason, Zhou et al [67] proposed reducing the average value of the capacitor voltage at extremely low frequencies, so that the peak voltage, or the device voltage stress, will not exceed a certain limit.…”

Section: Variable DC Voltage Methodsmentioning

confidence: 99%

Review on low‐frequency ripple suppression methods for MMCs for medium‐voltage drive applications

Wang

Chen

Liao

et al. 2018

IET Power Electronics

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Advantages of the modular multilevel converter (MMC) such as modularity, scalability, fault-tolerant ability, low device switching frequency, transformerless grid connection etc. have made it the most promising converter topology for medium-tohigh-voltage, high-power applications. However, in MMC-based medium-voltage drives, the excessive fundamental-frequency submodule capacitor voltage ripple at low speeds or start-up poses a major technological challenge. A lot of low-frequency ripple suppression methods have been proposed to address this problem. This study summarises the state of the art in this area and classifies these methods into three categories. The pros and cons of them are discussed. An in-depth analysis of these methods from a practical viewpoint is given. Some future research trends are also discussed.

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Section: Variable DC Voltage Methodsmentioning

confidence: 99%

Review on low‐frequency ripple suppression methods for MMCs for medium‐voltage drive applications

Wang

Chen

Liao

et al. 2018

IET Power Electronics

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show abstract

“…The balancing of the active power between ac and dc terminals can be achieved by varying the duty cycle 𝐷: (𝑈 𝑑𝑐 𝐼 𝑑𝑐(𝑟𝑎𝑡𝑒𝑑) 𝐷 = must be occurred when the motor speed varies. Hence the duty cycle 𝐷 can be derived for constant torque drives with 𝐼 𝑂 = 𝐼 𝑂(𝑟𝑎𝑡𝑒𝑑) [25].…”

Section: Operation Principle Of Hybrid MMCmentioning

confidence: 99%

Design and Simulation of Modular Multilevel Converter Fed Induction Motor Drive

Hannan

Hassan

2021

IJEEI

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Traditional modular multilevel converter (MMC) applications in medium voltage induction motor drive are difficult, particularly at low speeds because of the higher amplitude of the voltage ripple of the sub-module capacitor. This paper uses a hybrid MMC to achieve a lower peak-to-peak voltage ripple of the sub-module capacitor particularly at low frequencies. The vector control strategy with the closed-loop speed control is used to indicate an accurate and wide-speed range. MATLAB / Simulink is used to simulate and obtain the simulation results of hybrid and traditional MMC with induction motor drive and compare from the standpoint of capacitor voltage ripple. The results are shown the reduction of peak-to-peak voltage ripple of the sub-module capacitor as the hybrid MMC is operated.

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“…Although this solution reduces the capacitor voltage oscillation at low speed, it doubles the number of switches and consequently the losses are significantly increased. In [18], [19], the dc-port voltage is modulated using series switches. In this case, the mean value of the dc-link is regulated.…”

Section: Introductionmentioning

confidence: 99%

Experimental Validation of a Nested Control System to Balance the Cell Capacitor Voltages in Hybrid MMCs

et al. 2021

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In a hybrid modular multilevel converter (MMC), capacitor voltage balance between the Full-Bridge Sub-Modules (FBSMs) and Half-Bridge Sub-Modules (HBSMs) is only possible when the arm currents are bipolar. For a grid-connected MMC, operating at unity power factor, this is typically achievable when the modulation index is less than 2. Previous control methodologies, based on open-loop feed-forward compensating currents, have been proposed to operate an MMC with a higher modulation index. However, these solutions do not minimize the compensating currents; they cannot compensate entirely for both the variations in the operating conditions and the parameters typically encountered in a real implementation; and they do not consider the actual capacitor voltage imbalance between the FBSM and HBSMs. In this paper, a new nested closed-loop control algorithm based on an outer voltage control loop with an inner current loop is proposed and experimentally validated. Feed-forward currents are still utilised in the inner loop, but they are calculated using a new optimising algorithm which minimises the required compensating currents. Moreover, to the best of our knowledge, this is the first work where explicit algebraic equations to calculate these compensating currents are provided. Experimental results to validate the approach, obtained with an 18-cell hybrid MMC, are presented and discussed in the paper.

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Capacitance Reduction of the Hybrid Modular Multilevel Converter by Decreasing Average Capacitor Voltage in Variable-Speed Drives

Cited by 31 publications

References 21 publications

Review on low‐frequency ripple suppression methods for MMCs for medium‐voltage drive applications

Review on low‐frequency ripple suppression methods for MMCs for medium‐voltage drive applications

Design and Simulation of Modular Multilevel Converter Fed Induction Motor Drive

Experimental Validation of a Nested Control System to Balance the Cell Capacitor Voltages in Hybrid MMCs

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