Modeling and Damping Control of Modular Multilevel Converter Based DC Grid

Li, Yunfeng; Tang, Guangfu; Ge, Jun; He, Zhiyuan; Pang, Hui; Yang, Jie; Wu, Yanan

doi:10.1109/tpwrs.2017.2691737

Cited by 105 publications

(59 citation statements)

References 22 publications

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“…With the increased need for renewable energy utilization and resource optimization, the modular multilevel converter (MMC) based DC grid has been a competitive candidate to integrate bulk renewable energy over long distance [1]- [3]. Different to the two-terminal HVDC systems, in a DC grid, multiple converters will feed fault currents to the faulted lines during DC faults, leading to high over-currents [4].…”

Section: Introductionmentioning

confidence: 99%

A Transient Voltage-Based DC Fault Line Protection Scheme for MMC-Based DC Grid Embedding DC Breakers

Xiang

Yang

et al. 2019

IEEE Trans. Power Delivery

203

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Abstract-Fast and reliable DC fault detection is one of the main challenges for modular multilevel converter (MMC) based DC grid with DC circuit breakers (DCCBs). This paper extracts the high frequency components of transient voltages by wavelet transform and proposes a fault identification method based on the difference of transient voltages to identify the faulted lines for DC grids using overhead lines. Meanwhile, a faulted pole discrimination method based on the difference between the change of positive and negative pole voltages is presented. A line protection scheme including detection activation, fault identification, faulted pole discrimination and post-fault re-closing is designed. Using only the local measurements, the scheme can realize the protection of the whole line without communication and has the capability of fault resistance endurance and anti-disturbance. The proposed method is tested with a four-terminal MMC based DC grid in PSCAD/EMTDC. The selection methods of threshold values are presented and the impact of DCCB operation on the reliability of DC fault protection is analysed. Simulation results verify the fast detection and reliability of the designed DC line protection scheme. Index Terms-DC fault protection, fault identification, transient voltage, hybrid DC breaker, modular multilevel converter (MMC), post-fault re-closing.This paper is a post-print of a paper submitted to and accepted for publication in IEEE Transaction on Power Delivery and is subject to Institution of Electrical and Electronic Engineering

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Section: Introductionmentioning

confidence: 99%

A Transient Voltage-Based DC Fault Line Protection Scheme for MMC-Based DC Grid Embedding DC Breakers

Xiang

Yang

et al. 2019

IEEE Trans. Power Delivery

203

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“…To increase the maximum transmission power, the DC side oscillation must be suppressed. The suppression methods of DC side oscillation can be classified into passive methods [20,21] and active methods [22][23][24][25][26][27][28][29]. Passive methods suppress resonance by introducing a passive damper branch into the circuit to remodel the impedance of the source converter or load converter in a cascaded system.…”

Section: Introductionmentioning

confidence: 99%

“…Active methods suppress resonance by introducing voltage and current feedback control in a controller to improve the impedance of the source converter or load converter. Virtual impedance is widely used in control systems as an active damping control method [24][25][26][27][28][29]. It can be introduced to suppress DC-side oscillation [24,25], to limit output current for voltage controlled inverters during overloads or faults [26,27], to improve the stability of a grid-connected inverter by change its input admittance [28], and to enhance the small-signal stability of a modular multilevel converter (MMC) based DC grid [29].…”

Section: Introductionmentioning

confidence: 99%

A Virtual Impedance Control Strategy for Improving the Stability and Dynamic Performance of VSC–HVDC Operation in Bidirectional Power Flow Mode

Liu

Liao

et al. 2019

Applied Sciences

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It is a common practice that one converter controls DC voltage and the other controls power in two-terminal voltage source converter (VSC)-based high voltage DC (HVDC) systems for AC gird interconnection. The maximum transmission power from a DC-voltage-controlled converter to a power-controlled converter is less than that of the opposite transmission direction. In order to increase the transmission power from a DC-voltage-controlled converter to a power-controlled converter, an improved virtual impedance control strategy is proposed in this paper. Based on the proposed control strategy, the DC impedance model of the VSC-HVDC system is built, including the output impedance of two converters and DC cable impedance. The stability of the system with an improved virtual impedance control is analyzed in Nyquist stability criterion. The proposed control strategy can improve the transmission capacity of the system by changing the DC output impedance of the DC voltage-controlled converter. The effectiveness of the proposed control strategy is verified by simulation. The simulation results show that the proposed control strategy has better dynamic performance than traditional control strategies.

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“…The virtual impedance can improve the impedance characteristic of the converter and increase the degree of freedom of the converter control system [11][12][13], and is mainly used for active damping oscillations [14], power flow control [15], harmonic compensation [16], and enhancement of fault ride-through capability [17]. In this paper, the virtual impedance is used to suppress the DC oscillation in a VSC-HVDC system and the parameters of the virtual impedance are obtained from the impedance characteristics analysis of the converter station.…”

Section: Introductionmentioning

confidence: 99%

Analysis and suppression of DC oscillation caused by DC capacitors in VSC‐based offshore island power supply system

Zhu

Liu

Qin

et al. 2018

IEEJ Transactions Elec Engng

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Voltage source converter-high-voltage direct current (VSC-HVDC) is an effective way to ensure the reliable supply of offshore island power. However, it is easily liable to direct current (DC) oscillation or even instability due to the interaction between the rectifier and inverter stations. In order to solve this problem, this paper analyzes the stability of the VSC-HVDC system caused by DC capacitors based on VSC impedance modeling and impedance stability criterion. Besides, an adaptive virtual impedance control strategy to suppress the DC oscillation is proposed. The impedance models of the VSC in the rectifier and inverter stations are constructed and verified. Then, the influence of the DC capacitors on the system stability is analyzed based on impedance stability criteria. The analysis shows that the decrease of DC capacitors will cause DC oscillation, and the DC virtual impedance is used to damping the oscillation. Finally, this paper presents a simple but effective adaptive fuzzy segmented virtual impedance control strategy to suppress the oscillation. Electromagnetic transient simulation and hardware-in-the-loop (HIL) test results show that the proposed adaptive virtual impedance is more effective and has better robustness than the conventional virtual impedance.

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Modeling and Damping Control of Modular Multilevel Converter Based DC Grid

Cited by 105 publications

References 22 publications

A Transient Voltage-Based DC Fault Line Protection Scheme for MMC-Based DC Grid Embedding DC Breakers

A Transient Voltage-Based DC Fault Line Protection Scheme for MMC-Based DC Grid Embedding DC Breakers

A Virtual Impedance Control Strategy for Improving the Stability and Dynamic Performance of VSC–HVDC Operation in Bidirectional Power Flow Mode

Analysis and suppression of DC oscillation caused by DC capacitors in VSC‐based offshore island power supply system

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