Hybrid Back-to-Back MMC System for Variable Speed AC Machine Drives

Li, Binbin; Hu, Junlin; Zhou, Shaoze; Xu, Dianguo

doi:10.24295/cpsstpea.2020.00010

Cited by 31 publications

(19 citation statements)

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“…Lower FB/HB share for zero-to-rated DC voltage operating range is achieved compared to [25], at the price of higher power factor reduction towards the grid. Higher FB/HB share (62 % against 50 %) is required compared to [36]. Unlike [36], grid can be supported by reactive power under reduced DC link voltage without branch current overload, as grid current component is equally shared between the branches.…”

Section: Discussionmentioning

confidence: 99%

“…Higher FB/HB share (62 % against 50 %) is required compared to [36]. Unlike [36], grid can be supported by reactive power under reduced DC link voltage without branch current overload, as grid current component is equally shared between the branches.…”

Section: Discussionmentioning

confidence: 99%

“…As converter operation relies on the newly introduced switch, high reliability based on MMC redundancy is compromised. H-MMC AFE with all-FB upper branches and all-HB lower branches is presented in [36], demonstrating DC link voltage reduction down to practically zero. Non-equal insertion voltage references of FB-and HB-based branches call for non-equal AC current component share among the branches, where at certain operating frequencies, sum of AC current component in branches is a couple of times higher than the grid (output) current.…”

Section: Introductionmentioning

confidence: 99%

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Hybrid Modular Multilevel Converter Design and Control for Variable Speed Pumped Hydro Storage Plants

Basic¹,

Utvić

Dujić

2021

IEEE Access

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Hybrid modular multilevel converter control and design for pumped hydro storage plants is presented, addressing application-specific shortcoming of conventional back-to-back half-bridge modular multilevel converter: high common-mode-voltage machine stress. Common-mode-voltage-free operation in the entire or partial frequency range is enabled by variable DC link voltage control, through introduction of minimal full-bridge submodule share in hybrid active front-end converter stage. The developed generalized converter design approach for arbitrary DC link voltage range operation and additional internal energy balancing control layers enable down-to-zero DC voltage control. The results are verified through highfidelity switched-model simulations of 6 kV converter, with 10/6 ratio of full-bridge to half-bridge submodules in active front-end. The analyzed hybrid active front-end stage benefits from lower converter losses for equal machine operation flexibility compared to full-bridge design, while trade-off between gridside power factor range and full-bridge submodule share is offered within the design stage. Compared to the state-of-the-art, zero-to-rated DC link voltage operation is possible at lower full-bridge submodule share (62 % against 75 %), at the penalty of reduced grid-side power factor. Alternatively, operation at higher fullbridge submodule share (62 % against 50 % existing solution) enables grid-side reactive power support over wide speed range, without branch current overload.INDEX TERMS Hydroelectric power generation, modular multilevel converter, retrofit.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Hybrid Modular Multilevel Converter Design and Control for Variable Speed Pumped Hydro Storage Plants

Basic¹,

Utvić

Dujić

2021

IEEE Access

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“…This engrossed many researchers to focus on its technical challenges associated for reliable operation and extend it to various low power applications. In addition to this, its modular and voltage scalable features, have become a growing attention in industrial applications compared to traditional converter [1][2][3][4]. The MMC was first proposed in 2003 [5] for wide power range applications, which are further extended to medium power applications such as variable speed drives, static compensator [6][7] etc.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Voltage Sorting Algorithm for Balancing the Capacitor Voltage in Modular Multilevel Converter

Ismail

Kaliyaperumal²

2021

IEEE Access

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In this paper, an enhanced voltage sorting algorithm is proposed for balancing each sub module capacitor voltage in modular multilevel converter (MMC). However, the submodule (SM) voltage strategy becomes more complex when it increases to a number of levels, which eventually increases voltage ripples and circulating current. In order to overcome this problem, an enhanced voltage sorting algorithm is proposed, which implies an enhanced control logic function for capacitor voltage balancing of the converter. The switching pattern of each SM floating capacitor is determined based on the modulating signal methodology, which is then compared with the hybrid state condition using arm current direction in the MMC. Additionally, the generated hybrid signals are once again compared with the dynamic implicit number by conjoining the switching logic state variables. Due to this comparison of logic function, the capacitor voltage is balanced properly and reduces the capacitor ripple voltage to a permissible limit compared to the conventional method. Hence, compared to other balancing techniques, the circulating current is reduced by using conventional control techniques. The desired pulse signals for the power devices are obtained based on the multi carrier pulse width modulation techniques. The superior performance of the proposed algorithm is tested using MATLAB/Simulink software and real time laboratory hardware setup for different load conditions. Apart from this, the effective performance of the proposed method has been validated in the HVDC transmission system.

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“…4 The control targets in MMCs can be included control of output current, circulating current, and voltage of the capacitors. 1 In Reference 5, the PI controller is used to control the circulating current and decrement of the capacitor voltage fluctuations based on the second component of the grid main frequency; although the control structure can remove the second-order harmonics, the higher-order harmonics are still remaining. A resonance controller is used to eliminate even order harmonics to reduce the circulating current, which is illustrated in Reference 6; while this control method does not require direct modeling of the system and can also track sinusoidal references with arbitrary frequencies and zero steady-state error, but to eliminate even harmonics, multiple resonant controllers must be used.…”

Section: Introductionmentioning

confidence: 99%

Improved model predictive control for modular multilevel converter with reduced voltage sensors based on Kalman filter

Sheybanifar

Barakati

Torabi

et al. 2021

Int Trans Electr Energ Syst

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Modular multilevel converters (MMCs) are used in medium and high power applications due to various advantages, such as modularity, scalability, high efficiency, and low THD. In this paper, an improved model predictive control (IMPC) is used to control the converter output current and the circulating current. Using a discrete mathematical model of MMC and the neighboring index values with respect to their previously applied values, the calculation burden can be reduced rapidly even the number of sub-modules (SMs) increases. By applying this method, the control system complexity and the number of switching states are reduced. In addition, a Kalman filter (KF) is applied to estimate the capacitor voltage of the SMs, by using two arm voltage sensors in each leg of MMC. The combination of IMPC and KF reduces the computational burden and the number of voltage sensors. The efficiency and superiority of the proposed method are verified by simulation results of 5-and 11-level three-phase MMC and practical implementation of a laboratory single-phase converter with four SMs in each arm.

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Hybrid Back-to-Back MMC System for Variable Speed AC Machine Drives

Cited by 31 publications

References 0 publications

Hybrid Modular Multilevel Converter Design and Control for Variable Speed Pumped Hydro Storage Plants

Hybrid Modular Multilevel Converter Design and Control for Variable Speed Pumped Hydro Storage Plants

Enhanced Voltage Sorting Algorithm for Balancing the Capacitor Voltage in Modular Multilevel Converter

Improved model predictive control for modular multilevel converter with reduced voltage sensors based on Kalman filter

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