Module Multilevel-Clamped Composited Multilevel Converter (M-MC²) with Dual T-Type Modules and One Diode Module

Haoze Luo,Yufei Dong,Wuhua Li,Xiangning He 전력전자학회 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.6

A modular multilevel-clamped composited multilevel converter (M-MC²) is proposed. M-MC² enables topology reconfiguration, power device reuse, and composited clamping. An advanced five-level converter (5L-M-MC²) is derived from the concept of M-MC². 5L-M-MC² integrates dual three-level T-type modules and one three-level neutral point clamped module. This converter can also integrate dual three-level T-type modules and one passive diode module by utilizing the device reuse scheme. The operation principle and SPWM modulation are discussed to highlight converter performance. The proposed M-MC² is comprehensively compared with state-of-the-art five-level converters. Finally, simulations and experimental results are presented to validate the effectiveness of the main contributions of this study.

Analysis of the Operating Principle and Parameter Design for the Modular Multilevel DC/DC Converter

Binbin Li,Shaolei Shi,Yibo Zhang,Rongfeng Yang,Gaolin Wang,Dianguo Xu 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

The modular multilevel converter (MMC) has become more and more attractive in the field of high-voltage high-power dc/ac power conversions. In the very recent years, the dc/dc modular multilevel converter is proposed intended for high-voltage dc/dc applications, such as the solid-state transformers and future dc-grid networks, which is extended from the traditional MMC. However, it remains unknown how to optimize the operation of this dc/dc modular multilevel converter and how to dimension the parameters of the elements in it. In this paper, a detailed analysis is performed to indentify the operating principle of the dc/dc modular multilevel converter. Using these analyses, the selection rules and parameter design method of the components are given to maximize the utilization ratio, improve the power density, and increase efficiency. Finally, the validity and effectiveness of this paper are verified by simulation results.

Modular multilevel converter predictive control strategy based on energy balance

Xia, Xiangyang,Xu, Lei,Zhao, Xinxin,Zeng, Xiaoyong,Zhang, Jing,He, Yedan,Yi, Haigan The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.5

In MMC-HVDC (modular multilevel converter-based high-voltage direct current) applications, conventional control methods have defects such as complicated control and difficulty in controlling the internal energy of the converter. To ensure the safe and stable operation of an MMC-HVDC system, the problem of uneven internal energy distribution and increased fluctuations in the modular multilevel converter under asymmetrical network voltage conditions must be addressed. This paper has designed, a novel model predictive control (MPC) for MMC-HVDC applications. Through the proposed strategy, the switching states of all the MMC units can be optimized, which eliminates the circulating currents and achieves a voltage balance of the capacitor by redundant switching states. Moreover, an energy control circuit is established to adjust the DC bus power distribution in the MMC three-phase bridge arm. Thus, the symmetrical ac-side current can be realized, and the MMC internal energy imbalance caused by the transient process of the system can be avoided. Finally, the proposed novel predictive control strategy is tested via a case study. The obtained simulation and experimental results verify the effectiveness of the proposed control strategy.

Lifetime and reliability improvements in modular multilevel converters using controlled circulating current

Kadandani, Nasiru B.,Dahidah, Mohamed,Ethni, Salaheddine,Muhammad, Musbahu The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.10

Circulating current has been an inherent feature of modular multilevel converters (MMC), which results in second-order harmonics on the arms currents. If not properly controlled, the circulating current can affect the lifetime and reliability of a converter by increasing the current loading, loss distribution, and junction temperature of its semiconductor devices. This paper proposes controlled circulating current injection as a means of improving the lifetime and reliability of an MMC. The proposed method involves modifying the reference modulating signals of the converter arms to include the controlled differential voltage as an offset. The junction temperature of the semiconductor devices obtained from an electro-thermal simulation is processed to deduce the lifetime and reliability of the converter. The obtained results are benchmarked against a case where the control method is not incorporated. The incorporation of the proposed control method results in a 68.25% increase in the expected lifetime of the converter and a 3.06% increase on its reliability index. Experimental results of a scaled down laboratory prototype validate the effectiveness of the proposed control approach.

A New Modulation Method for the Modular Multilevel Converter Allowing Fundamental Switching Frequency

K. Ilves,A. Antonopoulos,S. Norrga,H-P. Nee 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

This paper presents a new modulation method for the modular multilevel converter. The proposed method is based on a fixed pulse pattern where harmonic elimination methods can be applied. Modulation methods with harmonic elimination based on calculated pulse patterns have been presented for other multilevel topologies. However, similar modulation schemes have not yet been presented for the modular multilevel topology. In the proposed modulation method, the pulse pattern is chosen in such a way that the stored energy in each submodule remains stable. It is shown that this can be done at the fundamental switching frequency without measuring the capacitor voltages or using any other form of feedback control. Such a modulation scheme has not been presented before. The theoretical results are verified by both simulations and experimental results. The simulation results show successful operation at the fundamental switching frequency with a larger number of submodules. When a smaller number of submodules are used, harmonic elimination methods may be applied. This is verified experimentally on a converter with eight submodules per phase leg. The experimental results verify that stable operation can be maintained at the fundamental switching frequency while successfully eliminating the fifth harmonic in the ac-side voltage.

Operation of a Modular Multilevel Converter with Selective Harmonic Elimination PWM

Georgios S. Konstantinou,Mihai Ciobotaru,Vassilios G. Agelidis 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

The modular multilevel converter (MMC) is based on the cascaded interconnection of half-bridge switching sub-modules and features modular characteristics that allow its expandability while providing high quality voltage and current output waveforms and removing the need for filtering. The switching frequency of each of the individual converter sub modules being maintained low and the balancing of the capacitor voltages are important requirements for the operation of the converter. Two different modulation approaches of the converter are discussed. Selected simulation and experimental results taken from a low-power laboratory prototype are presented.

Module Multilevel-Clamped Composited Multilevel Converter (M-MC²) with Dual T-Type Modules and One Diode Module

Luo, Haoze,Dong, Yufei,Li, Wuhua,He, Xiangning The Korean Institute of Power Electronics 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.6

A modular multilevel-clamped composited multilevel converter ($M-MC^2$) is proposed. $M-MC^2$ enables topology reconfiguration, power device reuse, and composited clamping. An advanced five-level converter ($5L-M-MC^2$) is derived from the concept of $M-MC^2$. $5L-M-MC^2$ integrates dual three-level T-type modules and one three-level neutral point clamped module. This converter can also integrate dual three-level T-type modules and one passive diode module by utilizing the device reuse scheme. The operation principle and SPWM modulation are discussed to highlight converter performance. The proposed $M-MC^2$ is comprehensively compared with state-of-the-art five-level converters. Finally, simulations and experimental results are presented to validate the effectiveness of the main contributions of this study.

Mathematical Analysis and Experiment Validation of Modular Multilevel Converters

Zhang, Yushu,Adam, Grain Philip,Lim, Tee-Chong,Finney, Stephen J.,Williams, Barry W. The Korean Institute of Power Electronics 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.1

This paper describes operating and capacitor voltage balancing of the modular multilevel converter. The paper focuses on sizing of the cell capacitor and establishes approximate expressions for the capacitor voltage. Simulations and experiments results obtained from three-level modular converter are used to demonstrate its viability in medium voltage applications. It is shown that the modular converter can operate over the full modulation index linear range independent of load power factor.

Mathematical Analysis and Experiment Validation of Modular Multilevel Converters

Yushu Zhang,Grain Philip Adam,Tee Chong Lim,Stephen J. Finney,Barry W. Williams 전력전자학회 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.1

This paper describes operating and capacitor voltage balancing of the modular multilevel converter. The paper focuses on sizing of the cell capacitor and establishes approximate expressions for the capacitor voltage. Simulations and experiments results obtained from three-level modular converter are used to demonstrate its viability in medium voltage applications. It is shown that the modular converter can operate over the full modulation index linear range independent of load power factor.

A modular multilevel converter with active power filter (APF‑MMC) under low‑frequency operation

Guanlong Jia,Mingshuo Li,Lin Chen,Binhao Shi,Feng Niu,Yu Tang 전력전자학회 2024 JOURNAL OF POWER ELECTRONICS Vol.24 No.5

In the realm of medium/high voltage applications, the modular multilevel converter with an active power filter (APF-MMC) emerges as a technology that eliminated the inherent voltage fluctuations of larger sub-module (SM) capacitors. However, the introduced APF circuit in each phase can only deal with power in even frequencies, and the APF-MMC cannot be directly applied in the field of motor drives with low-frequency operation. In this paper, based on the APF-MMC topology, by adding two high-frequency variables as control degrees of freedom, the base frequency power is transferred to highfrequency power, which can considerably minimize the capacitor voltage ripple in the low-frequency region of the topology. In addition, the influence of the injected high-frequency variables on the output characteristics of the topology is eliminated by controlling the APF circuit as hardware degree of freedom. Its equivalent circuit and operating principle are introduced in detail. Concurrently, a control method is proposed for the APF circuit, ensuring seamless operation of the converter. Finally, through a combination of simulation and experimental results, it is demonstrated that the APF-MMC topology surpasses the conventional MMC in its efficacy under low-frequency operation.