The Predictive Closed-Loop Averaging Control of MMC Phase-Unit Losses Under Unbalanced Conditions

Xu, Jianzhong; Yongjie, Yu; Zhao, Chengyong

doi:10.1109/tpwrd.2018.2868772

Cited by 14 publications

(6 citation statements)

References 32 publications

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“…Equation (23) shows that the active power ripple could be suppressed (e.g., P ac = 0) by controlling AC component i d,ac under unbalanced grid conditions. Reference commands for the inner current control system shown in Figure 4 were derived from Equation (23) to eliminate power ripple P ac as follows:…”

Section: Feedforward Control Methods For the Active Power Ripplementioning

confidence: 99%

“…The authors in [22] proposed a predictive closed-loop averaging control algorithm to eliminate uneven loss distribution due to unbalanced DC, and double-frequency components to indirectly eliminate power ripples. The authors in [23] suggested a dual-vector current control algorithm to separately control positive and negative sequence components with several proportional integral (PI) controllers in the DQ reference frame. However, having multiple PI controllers can further complicate the system and increase computation time.…”

Section: Introductionmentioning

confidence: 99%

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Power Ripple Control Method for Modular Multilevel Converter under Grid Imbalances

et al. 2022

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Modular multilevel converters (MMCs) are primarily adopted for high-voltage applications, and are highly desired to be operated even under fault conditions. Researchers focused on improving current controllers to reduce the adverse effects of faults. Vector control in the DQ reference domain is generally adopted to control the MMC applications. Under unstable grid conditions, it is challenging to control double-line frequency oscillations in the DQ reference frame. Therefore, active power fluctuations are observed in the active power due to the uncontrolled AC component’s double line frequency component. This paper proposes removing the active power’s double-line frequency under unbalanced grid conditions during DQ transformation. Feedforward and feedback control methods are proposed to eliminate ripple in active power under fault conditions. An extraction method for AC components is also proposed for the power ripple control to eliminate the phase error occurring with the conventional high-pass filters. The system’s stability with the proposed controller is tested and compared with a traditional MMC controller using the Nyquist stability criterion. A real-time digital simulator (RTDS) and Xilinx Virtex 7-based FPGA were used to verify the proposed control methods under single-line-to-ground (SLG) faults.

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Section: Feedforward Control Methods For the Active Power Ripplementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Power Ripple Control Method for Modular Multilevel Converter under Grid Imbalances

et al. 2022

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“…The power losses minimization strategy is proposed for MMCs, as illustrated in Figure 6. Figure 6A illustrates the P control and Q control of MMCs, 26 where e d , e q , and i d , i q are the grid voltage and current in dq frame, respectively. L = L s /2 + L f .…”

Section: Proposed Power Losses Minimization Methods For Mmcsmentioning

confidence: 99%

Power losses minimization for modular multilevel converter s with second‐order and fourth‐order harmonic circulating current injection

Zhao

Deng

Liu

et al. 2021

Int Trans Electr Energ Syst

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Summary Modular multilevel converters (MMCs) are regarded as promising topologies in medium/high‐voltage and high‐power applications. The reduction of power losses is an important issue for MMCs. This paper proposes a power loss minimization control (PLMC) by injecting optimal second‐ and fourth‐order harmonic circulating current into the arm current of MMCs. The proposed control can further reduce the power loss in comparison with the conventional control by only injecting the second‐order harmonic circulating current. In addition, the proposed control not only reduces the peak value of the arm current, but also improves the reliability of MMCs. Simulation with the PSCAD/EMTDC and experiment with 1‐kW MMC prototype are also conducted and their results confirm the validity of the proposed PLMC for MMCs.

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“…In 53 the authors proposed a zero-sequence voltage injection (ZSVI) method to detect unbalancing of arm current, which causes the phase unit loss in MMC. A close-loop ZSVI method is implemented to overcome phase unit loss, which is more accurate and reliable verified by transient electromagnetic simulations.…”

Section: Fault Diagnosis and Control Techniques For MMCmentioning

confidence: 99%

A comprehensive review of fault diagnosis and fault-tolerant control techniques for modular multi-level converters

et al. 2022

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Background Many faults occur in the modular multi-level converters (MMCs), including unbalancing capacitor voltage, lower and upper arm unbalancing, the line to line voltage unbalancing, sensors and actuators fault, system fault, and sub-modules fault in high as well as medium voltage applications. Introduction Several fault-tolerant approaches are presented to overcome these problems, such as active fault-tolerant control system (AFTCS), passive fault-tolerant control system (PFTCS), hybrid fault-tolerant control system (HFTCS), redundant system technique, special power circuit with the controller, and zero sequence voltage methods, which we will explain extensively in this article. Methodology This review emphasizes the types of faults in the MMCs and discusses the protection methods under failure conditions. The MMC is more popular in high voltage applications because it not only improves the quality of the grid but also has good harmonic performance in high power transmission. There is no need for any isolated dc sources to operate it. When faults are removed, the efficiency and reliability of the system will be increased. Results This extensive explanation of the current literature on MMC fault diagnosis and control techniques will conclude which methods provide a more valuable solution. Finally, this paper discusses the best approach to reduce MMC faults and provides a future research direction to the readers.

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The Predictive Closed-Loop Averaging Control of MMC Phase-Unit Losses Under Unbalanced Conditions

Cited by 14 publications

References 32 publications

Power Ripple Control Method for Modular Multilevel Converter under Grid Imbalances

Power Ripple Control Method for Modular Multilevel Converter under Grid Imbalances

Power losses minimization for modular multilevel converter s with second‐order and fourth‐order harmonic circulating current injection

A comprehensive review of fault diagnosis and fault-tolerant control techniques for modular multi-level converters

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