Decentralized Control Method for Modular Multilevel Converters

Xia, Bing; Li, Yaohua; Li, Zixin; Konstantinou, Georgios; Xu, Fei; Gao, Fanqiang; Wang, Ping

doi:10.1109/tpel.2018.2866258

Cited by 25 publications

(5 citation statements)

References 30 publications

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“…In the centralized architecture, after receiving i s from a high-level controller, all the control subsystems related to the converter control and switching control layers are run in a single central controller, and the switching signals are transmitted directly to each submodule [1]. If the processing capabilities, the available number of input/outputs, or the communication bandwidth of the central controller are not sufficient, centralized control can be expanded to multiple control layers [27], [28], and called as decentralized control [28]. In these cases, the mentioned control tasks are hierarchically structured and shared between a central controller located at the top and several arm/valve/group controllers below that (the arm/valve/group controllers can be in hierarchical order).…”

Section: B MMC Internal Control Architecturesmentioning

confidence: 99%

Wireless Control of Modular Multilevel Converter Submodules

Ciftci

Schiessl²,

Gross

et al. 2021

IEEE Trans. Power Electron.

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Wireless control of modular multilevel converter (MMC) submodules offers several potential benefits to exploit, such as decreased converter costs and ease in converter installation. However, wireless control comes with several challenging engineering requirements. The control methods used with wired communication networks are not directly applicable to the wireless control due to the latency and reliability differences of wired and wireless networks. This article reviews the existing control architectures of MMCs and proposes a control and communication method for wireless submodule control. Also, a synchronization method for pulsewidth modulation carriers is proposed suitable for wireless control. The imperfections of wireless communication, such as higher latency and packet losses compared to wired communication, are analyzed for the operation of MMCs. The latency is fixed with a proper controller and wireless network design. The converter is rendered immune to the packet losses by decreasing the closed-loop control bandwidth. The functionality of the proposal is verified, for the first time, experimentally on a laboratory-scale MMC using a simple wireless network. It is shown that wireless control of MMC submodules with the proposed approach can perform comparably to the wired control.

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Section: B MMC Internal Control Architecturesmentioning

confidence: 99%

Wireless Control of Modular Multilevel Converter Submodules

Ciftci

Schiessl²,

Gross

et al. 2021

IEEE Trans. Power Electron.

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“…Different approaches for MMC control have also been proposed, which can mainly be divided into two approaches. The first approach is based on a unique main controller for the whole converter [12][13][14], while the other uses a master/slave control scheme [15][16][17]. The conventional centralized control is based on one main controller, typically a DSP, with, usually, an auxiliary FPGA in charge of the capacitor Voltage Balancing Algorithm (VBA), as initially proposed in [1].…”

Section: Introductionmentioning

confidence: 99%

“…These slave controllers are dedicated to the submodule capacitor voltages' control and protection. To reduce the number of external slave controllers, submodules are grouped in [16]. Each slave controller is in charge of a submodule group, which expands the modularity of the control structure.…”

Section: Introductionmentioning

confidence: 99%

Cascaded Smart Gate Drivers for Modular Multilevel Converters Control: A Decentralized Voltage Balancing Algorithm

et al. 2021

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Recent Modular Multilevel Converter (MMC) topology allows for drastic improvements in power electronic conversion such as higher energy quality, lower power semiconductors electrical stress, decreased Electro-Magnetic Interferences (EMI), and reduced switching losses. MMC is widely used in High Voltage Direct-Current (HVDC) transmissions as it offers, theoretically, no voltage limit. However, its control electronic structure is not modular itself. Especially, the insulation voltage between the submodule gate drivers’ primaries and secondaries depends on the number of submodules. The converter voltage levels cannot be increased without designing all gate driver isolations again. To solve that issue, the novel concept of distributed galvanic insulation is introduced for multilevel converters. The submodule’s gate drivers are daisy-chained, which naturally reduces the insulation voltage to the submodule capacitor voltage, regardless of the number of submodules. The MMC becomes truly modular as the number of submodules can be increased without impacting on the previous control electronic circuit. Such an innovative control structure weakens the link between the main control unit and the gate drivers. This inherent structural problem can be solved through the use of Smart-Gate Drivers (SGD), as they are often equipped with fast and bidirectional communication channels, while highly increasing the converter reliability. The innovation proposed in that work is the involvement of smart gate drivers in the distributed galvanic insulation-based MMC control and monitoring. First, the numerous benefits of smart gate drivers are discussed. Then, an innovative Voltage Balancing Algorithm directly integrated on the chained gate drivers is proposed and detailed. It features a tunable parameter, offering a trade-off between accurate voltage balancing and execution time. The proposed embedded algorithm features a low execution time due to simultaneous voltage comparisons. Such an algorithm is executed by the gate drivers themselves, relieving the main control unit in an original decentralized control scheme. A simulation model of a multi-megawatts three-phase grid-tied MMC inverter is realized, allowing validation of the proposed algorithm. Matlab/Simulink logic blocs allow us to simulate a typical CPLD/FPGA component, often embedded on smart gate drivers. The converter with the proposed embedded algorithm is simulated in steady-state and during load impact. The controlled delay and slew rate inferred by the algorithm do not disturb the converter behavior, allowing its conceptual validation.

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“…The switching-cells can be connected in parallel in a multiphase converter ( Figure 1a) to increase its current output and to reduce the output current ripple [1,2] or in series in a multilevel converter ( Figure 1b) to increase its voltage output and to obtain lower total harmonic distortion [3,4]. In case of large numbers of switching cells that need to be managed, the control system is the main issue of these converter topologies for applying the centralized control structure [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…According to the first research direction, the decentralized control is characterized by a hierarchical architecture that has two control levels, such as primary-secondary controller [9,11] and master-slave or central-local controller [12][13][14][15][16][17][18][19], and the information exchange between these levels is conducted by communication links. The system level controllers, namely secondary/master/central, are responsible for general information management and for performing tasks such as voltage balance, current balance, and power exchange.…”

Section: Introductionmentioning

confidence: 99%

A Fast, Decentralized, Self-Aligned Carrier Method for Multicellular Converters

et al. 2020

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This paper proposes a fast, decentralized method for self-aligning the carriers of a multiphase/multilevel converter operating on the basis of phase-shifted pulse width modulation or level-shifted pulse width modulation. In the proposed method, each cell of the converter synchronizes and updates simultaneously its own carrier angle or carrier level based on the information shared with its neighboring cell, such as its angle/level, its index number, and the total number of activated cells of the converter. Different from the conventional decentralized method (with basic and modified updating rules), which requires some conditions in terms of cell number and initial carrier angles to start up and operate properly, the proposed method can be applied to the system with any number of cells and does not require special conditions of initial carrier angles. Further, while the conventional method needs an iteration process to adjust the inter-carrier phase-shifts and can be applied only to a multiphase converter which uses phase-shifted pulse width modulation, the proposed method offers an accurate and fast alignment of phases (for phase-shifted pulse width modulation) or levels (for level-shifted pulse width modulation) and thus can be applied to both multiphase and multilevel converter types. The simulations and the experimental results are presented in detail to show the validity and the effectiveness of the proposed methods. Further, thorough simulations on multiphase converters with different number of cells also show that the proposed method is much faster than the conventional method in both configuration and reconfiguration processes, especially in case the system has a large number of cells.

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Decentralized Control Method for Modular Multilevel Converters

Cited by 25 publications

References 30 publications

Wireless Control of Modular Multilevel Converter Submodules

Wireless Control of Modular Multilevel Converter Submodules

Cascaded Smart Gate Drivers for Modular Multilevel Converters Control: A Decentralized Voltage Balancing Algorithm

A Fast, Decentralized, Self-Aligned Carrier Method for Multicellular Converters

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