A Capacitor Voltage Balancing Strategy With Minimized AC Circulating Current for the DC–DC Modular Multilevel Converter

Yang, Huazhong; Saeedifard, Maryam

doi:10.1109/tie.2016.2613059

Cited by 83 publications

(45 citation statements)

References 28 publications

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“…The functioning principles of the M2DC were first proposed in [9], then its design and steady state operation validating the technological viability of the M2DC topology shortly after in [10]. Following publications combined design and control studies as in [11]- [12]. Even if MMC and M2DC share similarities, a first major difference has to be highlighted: contrary the MMC, M2DC continuously requires internal AC currents to balance the stored energies in its upper and lower arms [11] [12], even in steady state.…”

Section: Introductionmentioning

confidence: 99%

“…Following publications combined design and control studies as in [11]- [12]. Even if MMC and M2DC share similarities, a first major difference has to be highlighted: contrary the MMC, M2DC continuously requires internal AC currents to balance the stored energies in its upper and lower arms [11] [12], even in steady state. As with the MMC, two different types of AC currents may be used: one AC current flows through the first DC terminal (top of legs in Fig.…”

Section: Introductionmentioning

confidence: 99%

“…The aim of this paper is to expand the idea developed in [12] in a more general control which ensures a full control of all the state variables of the M2DC in order to avoid the potential instabilities mentioned previously. For doing so, a methodology similar to MMC control methods (i.e.…”

Section: Introductionmentioning

confidence: 99%

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Full State Regulation of the Modular Multilevel DC Converter (M2DC) Achieving Minimization of Circulating Currents

Gruson

Moigne

et al. 2020

IEEE Trans. Power Delivery

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The M2DC exploits the interleaving between the three legs of an MMC to realize a promising uninsulated DC/DC converter to interconnect HVDC grids. This paper details a current and energies decoupled model of the M2DC. The major idea proposed in this paper is focused on the full energy control generating optimal current references to minimize the internal currents magnitude. The energy sum and difference models are fully detailed. Both current and energy control loops are based on the model inversion principle in order to control all the state variables. The proposed control is based a dynamic control developed with the model inversion principle associated with an optimization of the current magnitude deduced from a quasi-static analysis. All dynamics of the system are then explicitly controlled, which guarantee a good dynamic behavior during the transient. Therefore, current and energy controls are presented in detail. Simulation results show the dynamic behavior of the converter for various operating points.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Full State Regulation of the Modular Multilevel DC Converter (M2DC) Achieving Minimization of Circulating Currents

Gruson

Moigne

et al. 2020

IEEE Trans. Power Delivery

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“…In comparison with conventional multilevel converters, MMCs are characterized by low switching losses due to the low switching operating frequency required, flexibility [2], and low harmonic distortion which allows the use of smaller filters. MMCs have been proven to be suitable for different applications such as electrical vehicles, variable speed drives, high-voltage direct current systems (HVDC), battery storage systems (BSSs), DC-DC power conversion and flexible AC transmission systems (FACTSs) [3,4].…”

Section: Introductionmentioning

confidence: 99%

“…This also requires a great many voltage sensors in order to achieve the voltage-balancing of the system. This problem has been extensively investigated in recent research [3,7]; but many voltage sensors are always used in such studies. However, it would be preferable if this issue could be resolved with lower cost and complexity.…”

mentioning

confidence: 99%

Submodule Voltage Estimation Scheme in Modular Multilevel Converters with Reduced Voltage Sensors Based on Kalman Filter Approach

Abushafa¹,

Dahidah

Gadoue

et al. 2018

IEEE Trans. Ind. Electron.

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On the other hand, as with most conventional converters, the MMC has specific control requirements. For instance, the voltage-balancing of the submodule (SM) capacitors in the converter is critical. However, due to the series of cascaded SMs which are used to construct the converter, the reliability of the MMC is an important challenge [5]. In one example of a real application based on the MMC is presented in [6], where hundreds of SMs per leg were used. This also requires a great many voltage sensors in order to achieve the voltage-balancing of the system. This problem has been extensively investigated in recent research [3,7]; but many voltage sensors are always used in such studies. However, it would be preferable if this issue could be resolved with lower cost and complexity.Several proposals have been attempted to minimise the number of voltage and current sensors required. For instance, successful simulation and practical results have been achieved with fewer current sensors [8][9][10]. However, no reductions in voltage sensor number were discussed in those studies. Another attempt based on an open-loop scheme has been suggested, where fixed PWM signals were applied to the converter [11]. Although, this proposed scheme does not use any sensors since it does not require any form of feedback control, the wellknown disadvantages of open-loop control schemes may threaten the performance of the system. In some recent studies, online observers have been introduced to estimate individual SM voltages [12,13]. For example, fewer voltage sensors could be achieved based on a sliding mode where the proposed method merely monitors the total input voltage and arm current of the converter [12]. This technique has been proposed for fault detection scheme. However, variations in SM capacitance were not considered in this study. In an attempt to ameliorate this problem, the estimation of capacitance values for each individual SM was considered in [13]. This improvement provides an important solution against concerning capacitance; however, in all observer-based methods the effect of variations associated with arm inductor values was not included in the design. In very recent research [14,15], the voltage-balancing of a seven-level MMC has been achieved with important reductions in the number of voltage sensors required, where the lowest number of voltage sensors needed is two when sevenlevel MMC is used. Two sensors are contributed to measure total arm voltage of the converter. On the other hand, the main UK

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A hybrid two‐stage modular DC–DC converter with zero‐voltage switching

Nazih

Hossam-Eldin

Elserougi

2021

Circuit Theory & Apps

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Conventional modular multilevel converters (MMCs) are widely used in high power applications due to their various astonishing advantages; however, they fail to achieve balanced capacitor voltage in DC operation. In this paper, a hybrid two-stage modular DC-DC converter is proposed to solve the issue of unbalanced capacitor voltages. The proposed converter consists of a singlephase half-bridge MMC with half-bridge submodules followed by a medium voltage valves-based H-bridge rectifier. The proposed converter is used in medium-voltage applications such as feeding a DC-load or interconnection between two DC grids of different voltage levels. The proposed configuration achieves successful DC-DC conversion with a low number of switches, a high conversion ratio with bidirectional power flow, low current stresses, soft switching across the second stage, and low switching losses. The operational concept and the control algorithm have been illustrated in detail. Finally, the effectiveness of the proposed DC-DC converter is evaluated based on simulation studies of MATLAB SIMULINK and a scaled-down laboratory experimental test rig.

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A Capacitor Voltage Balancing Strategy With Minimized AC Circulating Current for the DC–DC Modular Multilevel Converter

Cited by 83 publications

References 28 publications

Full State Regulation of the Modular Multilevel DC Converter (M2DC) Achieving Minimization of Circulating Currents

Full State Regulation of the Modular Multilevel DC Converter (M2DC) Achieving Minimization of Circulating Currents

Submodule Voltage Estimation Scheme in Modular Multilevel Converters with Reduced Voltage Sensors Based on Kalman Filter Approach

A hybrid two‐stage modular DC–DC converter with zero‐voltage switching

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