Deadbeat Control for Circulating Harmonic Currents Suppression of a Level-Increased NLM Based Modular Multilevel Converter

Chen, Xingxing; Liu, Jinjun; Song, Shuguang; Ouyang, Shaodi; Wang, Di; Deng, Zhifeng

doi:10.1109/ecce.2019.8913003

Cited by 8 publications

(10 citation statements)

References 9 publications

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“…The single-phase MMC in the simulation contains seven SMs per arm (N = 7), along with the parameter configuration given in Table 1. For a full assessment, comparisons between the proposed control scheme as well as the conventional NLC and PNLC methods, the level-increased NLC with circulating harmonic current suppression based on deadbeat control approach in [39], and the reduced computational burden MPC approach in [45] were obtained via simulations. The sampling frequency exerts a significant impact on the control performance of predictive control.…”

Section: A Simulation Resultsmentioning

confidence: 99%

“…Figs. 7(a)-(e) illustrate the simulated results of the output current and voltage under steady-state operation using the conventional NLC, conventional PNLC, the level-increased NLC with circulating harmonic current suppression based on deadbeat control [39], the reduced computational burden MPC [45], and proposed I-PNLC methods, respectively. With reference to Fig.…”

Section: A Simulation Resultsmentioning

confidence: 99%

“…However, this adjustment to the number of SMs might degrade the output voltage performance. Another NLC approach [39] used deadbeat control to reduce the circulating current peak-to-peak value. A recent NLC method proposed in [40] defined the number of inserted SMs according to the output voltage level selection condition and circulating current regulation, thereby significantly improving the output performance and circulating current controllability.…”

Section: Introductionmentioning

confidence: 99%

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Predictive Nearest-Level Control Algorithm for Modular Multilevel Converters With Reduced Harmonic Distortion

Nguyen

Kwak

2021

IEEE Access

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Owing to the low number of submodules (SMs) in modular multilevel converters (MMCs), especially in medium-voltage applications, the output current and voltage generated by conventional nearestlevel control (NLC) methods contain evident distortions. Previously, various hybrid and level-increased NLC methods have been proposed to improve the output voltage quality, but such measures wither increased the complexity or did not regulate all the control objectives simultaneously. To further enhance the output performances of MMCs containing low numbers of SMs, an improved predictive NLC (I-PNLC) method combining NLC and model predictive control (MPC) is proposed, where the output and circulating currents are regulated with the corresponding predicted references, and the output voltage is controlled by the added voltage correction. The proposed I-PNLC not only reduces the output current and voltage total harmonic distortion (THD) considerably but also avoids additional complexity in the control system design. The results of simulations and an experiment are presented to verify the proposed approach, in addition to a comparison of the evaluations of conventional NLC methods.INDEX TERMS Modular multilevel converter, nearest-level control (NLC), nearest-level modulation, levelincreased NLC, output voltage, predictive control.

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Section: A Simulation Resultsmentioning

confidence: 99%

Section: A Simulation Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Predictive Nearest-Level Control Algorithm for Modular Multilevel Converters With Reduced Harmonic Distortion

Nguyen

Kwak

2021

IEEE Access

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“…Several methods have been proposed in the literature for CCC in MMCs for a variety of purposes [10][11][12][13][14][15]. However, none of these methods were focused on utilization for lifetime improvement.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2021

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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.

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“…This might result in deterioration of the output voltage quality. Recently, an NLC method with circulating harmonic current suppression with deadbeat control was proposed in [21], where the numbers of inserted SMs in the upper and lower arms from the levelincreased NLC II were adjusted based on the deadbeat controller to regulate the circulating current. This control scheme inherited the merits of both the level-increased NLC II and deadbeat controller to improve the output quality and control the circulating current.…”

Section: Introductionmentioning

confidence: 99%

Nearest-Level Control Method With Improved Output Quality for Modular Multilevel Converters

Nguyen

Kwak

2020

IEEE Access

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Nearest-level control (NLC) is a popular technique used in modular multilevel converters (MMCs) with a large number of submodules (SMs) owing to the NLC's flexibility and ease of implementation. However, in medium-voltage applications, MMCs contain a relatively low number of SMs, and the drawbacks of the NLC methods emerge, wherein the poor quality of output voltages and currents result in high total harmonic distortion, large ripples in SM capacitor voltages, and unsuppressed circulating currents. Several NLC methods have been proposed to handle these problems, but they do not satisfy all the control objectives simultaneously. This paper proposed a modified NLC capable of enhancing the output quality of MMCs with low number of SMs without deteriorating the control objectives. Unlike previously reported NLC methods, instead of directly calculating the numbers of SMs from the upper and lower arm voltage references, the difference and total number of SMs are obtained from the output voltage reference and circulating current control, respectively. Hence, the numbers of SMs in the upper and lower arms are acquired by simply solving a system of first-order two-variable equations. The simulated and experimental results for a single-phase MMC system were used to verify the appropriateness and effectiveness of the proposed modified NLC method.

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Deadbeat Control for Circulating Harmonic Currents Suppression of a Level-Increased NLM Based Modular Multilevel Converter

Cited by 8 publications

References 9 publications

Predictive Nearest-Level Control Algorithm for Modular Multilevel Converters With Reduced Harmonic Distortion

Predictive Nearest-Level Control Algorithm for Modular Multilevel Converters With Reduced Harmonic Distortion

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

Nearest-Level Control Method With Improved Output Quality for Modular Multilevel Converters

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