Energy balancing in the modular multilevel converter under unbalanced grid conditions

Schroeder, Markus; Mahr, Florian; Jaeger, Johann

doi:10.23919/epe17ecceeurope.2017.8099247

Cited by 8 publications

(5 citation statements)

References 7 publications

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“…To address the modulation stage, the carrier-arrangement PWM strategy is highlighted [6,[11][12][13]. Other strategies perform modifications of this strategy for different target functions, which is the case with existing modulation techniques that perform energy Table 1 shows the design specifications.…”

Section: Modulation Stagementioning

confidence: 99%

“…Three main strategies to perform energy balancing stand out [6,11,[15][16][17], which are: PSC PWM (phase shift carrier PWM) and LS PWM (level shifted PWM), with a carrier level shift, in two variants: a per modulator signal cycle (LS modulator) and a per carrier signal cycle (LS carrier) [13,[18][19][20][21].…”

Section: Existing Modulation Strategies For Energy Balancing Purposesmentioning

confidence: 99%

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Modification of SPWM Modulating Signals for Energy Balancing Purposes

et al. 2022

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There is currently a growing interest in efficient power generation and transformation without increasing the cost and complexity of a system. One type of transformation is the conversion of energy from a direct current to an alternating current, which is used in various applications, for example, in photovoltaic systems. One of the elementary components of these systems is the inverter. However, there are several drawbacks in the design of these systems, such as the energy balance between their semiconductor devices. Therefore, it is important to study alternatives to balance the energy and thus achieve a positive impact on both the economic and reliability aspects of the system. This article deals with the study, design, and implementation of the modification of a modulation technique with reconstructed modulating signals, which aims to ensure the energy balance in each cell of a multilevel inverter and, at the same time, present better results concerning the different parameters of comparison established, such as harmonic distortion, percentage of unbalance, percentage of use of digital resources, and power transferred to the load.

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Section: Modulation Stagementioning

confidence: 99%

Section: Existing Modulation Strategies For Energy Balancing Purposesmentioning

confidence: 99%

Modification of SPWM Modulating Signals for Energy Balancing Purposes

et al. 2022

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“…Management of critical parameters such as state of charge (SoC) and state of health (SoH) of each ESE can also be potentially integrated within the converter control [18]. The benefits of modularity have been validated in [19], [20] where batteries were integrated as ESE in the upper arms and UC in the lower arms in the former and uneven distribution of batteries is demonstrated in the later. Analysis carried out by some of the authors of this work in [21], shows that for an MMC at HVDC scale, replacing 4% of the standard Half-Bridge (HB) SMs by Full-Bridge (FB) ESE-SMs, can result in an additional 0.1 pu (10%) power delivery capability, with the drawback that the ESE-SMs require approximately twice the capacitive energy storage of the STD-SM.…”

Section: Converter Topologiesmentioning

confidence: 99%

A Delta-Connected Modular Multilevel STATCOM With Partially-Rated Energy Storage for Provision of Ancillary Services

Mian

Judge

Junyent-Ferr

et al. 2021

IEEE Trans. Power Delivery

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This paper proposes a delta-connected Modular Multilevel STATCOM with partially rated storage (PRS-STATCOM), capable of providing both reactive and active power support. The purpose is to provide short-term energy storage enabled grid support services such as inertial and frequency response, either alongside or temporarily instead of standard STATCOM voltage support. The topology proposed here contains two types of sub-modules (SM) in each phase-leg: standard submodules (STD-SMs) and energy storage element sub-modules (ESE-SMs) with a dc-dc interface converter between the SM capacitor and the ESE. A control structure has been developed that allows energy transfer between the SM capacitor and the ESE resulting in active power exchange between the converter and the grid. Injecting 3 rd harmonic current into the converter waveforms can be used to increase the amount of power that can be extracted from the ESE-SMs and so reduce the required ESE-SMs fraction in each phase-leg. Simulation results demonstrate that for three selected active power ratings, 1 pu, 2 3 pu, & 1 3 pu, the fraction of SMs that need be converted to ESE-SMs are only 69%, 59% & 38%. Thus, the proposed topology is effective in adding real power capability to a STATCOM without a large increase in equipment cost.

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“…Energy balancing mechanisms in [15]- [17] rely on the decomposition of unbalanced grid voltages into the positive/negative/zero sequence 3PH systems, and generation of a corresponding current components for the balancing purpose. The approach used in this paper is derived on a per phaselevel, omitting the need for the P/N/0 decomposition, which results in simpler implementation, minimization of the current stress imposed on the converter, as well as minimization of the risk of overmodulation.…”

Section: Novel Energy Control Scheme For Unbalanced Grid Conditionsmentioning

confidence: 99%

“…However, these concepts are applicable to the symmetrical grid conditions. Regarding the arm energy control under asymmetrical grid conditions, several references are also available, proposing different control methods aiming to ensure inter-arm energy balancing [15]- [17]. While the energy balancing methods proposed in these papers mostly employ decomposition of the control variables into the positive/negative/zero sequence components and manipulation with the matrices of state-variables in order to obtain energy balancing references, method proposed within this paper is developed on a per-phase basis, generating energy control references in a simple manner, and ensuring a minimal current stress to the converter as well as a minimal risk of overmodulation.…”

Section: Introductionmentioning

confidence: 99%

Direct Arm Energy Control in Modular Multilevel Converter Under Unbalanced Grid Conditions

Utvić

Dujić

2020

2020 International Symposium on Power Electronics, Electrical Drives, Automation and Motion (SPEEDAM)

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This paper studies the behaviour of the gridconnected modular multilevel converter under unbalanced grid conditions in terms of the energy imbalances within the converter, and proposes a novel approach for dealing with imbalances. Since the energy content within the arms of modular multilevel converter depends on the interaction between the terminal and internal voltages and currents, standard energy control methods, designed mainly for balanced grid conditions require improvement. This paper proposes a novel approach for the direct arm energy control, valid for both balanced and unbalanced grid conditions. The approach is characterized with its simple implementation, minimization of the current stress imposed on the converter, as well as with minimization of the risk of overmodulation. Theoretical foundation for mitigating the problem are supported with the simulation results, thus verifying the validity and performance of the proposed control concepts.

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Energy balancing in the modular multilevel converter under unbalanced grid conditions

Cited by 8 publications

References 7 publications

Modification of SPWM Modulating Signals for Energy Balancing Purposes

Modification of SPWM Modulating Signals for Energy Balancing Purposes

A Delta-Connected Modular Multilevel STATCOM With Partially-Rated Energy Storage for Provision of Ancillary Services

Direct Arm Energy Control in Modular Multilevel Converter Under Unbalanced Grid Conditions

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