Distributed Piecewise Droop Control of DC Microgrid with Improved Load Sharing and Voltage Compensation

Liu, Sucheng; Zheng, Jiazhu; Li, Zhongpeng; Fang, Wei; Liu, Xiaodong

doi:10.1109/icdcm45535.2019.9232724

Cited by 11 publications

(7 citation statements)

References 18 publications

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“…Improved method with multiple droop characteristics [17][18][19][20] Outer loops with different droop slopes are integrated to create multiple droop characteristics.…”

Section: Reference Controller Structure Distinctive Featuresmentioning

confidence: 99%

“…As shown in Table 1, droop control schemes are generally classified into two types: conventional methods with a single droop characteristic [15,21,22] and improved methods with multiple droop characteristics [17][18][19][20]23]. Droop controllers have been modified to improve the transient performance [21] and enable frequency regulation in the AC system [22].…”

Section: This Papermentioning

confidence: 99%

“…Droop controllers have been modified to improve the transient performance [21] and enable frequency regulation in the AC system [22]. To achieve a better power control accuracy, multiple droop characteristics have been adopted [17][18][19][20]23], where control interactions may occur in the narrow droop range (high droop slope) of the piecewise droop curves [23].…”

Section: This Papermentioning

confidence: 99%

“…A generic voltage droop controller for DC grids was developed in [15]. References [16][17][18][19][20] presented DC voltage with multiple droop control characteristics to improve the accuracy of DC power flow control. In [21], a hybrid control strategy which combines DC voltage with power control was proposed.…”

Section: Introductionmentioning

confidence: 99%

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Demonstration of Converter Control Interactions in MMC-HVDC Systems

et al. 2022

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Although the control of modular multi-level converters (MMCs) in high-voltage direct-current (HVDC) networks has become a mature subject these days, the potential for adverse interactions between different converter controls remains an under-researched challenge attracting the attention from both academia and industry. Even for point-to-point HVDC links (i.e., simple HVDC systems), converter control interactions may result in the shifting of system operating voltages, increased power losses, and unintended power imbalances at converter stations. To bridge this research gap, the risk of multiple cross-over of control characteristics of MMCs is assessed in this paper through mathematical analysis, computational simulation, and experimental validation. Specifically, the following point-to-point HVDC link configurations are examined: (1) one MMC station equipped with a current versus voltage droop control and the other station equipped with a constant power control; and (2) one MMC station equipped with a power versus voltage droop control and the other station equipped with a constant current control. Design guidelines for droop coefficients are provided to prevent adverse control interactions. A 60-kW MMC test-rig is used to experimentally verify the impact of multiple crossing of control characteristics of the DC system configurations, with results verified through software simulation in MATLAB/Simulink using an open access toolbox. Results show that in operating conditions of 650 V and 50 A (DC voltage and DC current), drifts of 7.7% in the DC voltage and of 10% in the DC current occur due to adverse control interactions under the current versus voltage droop and power control scheme. Similarly, drifts of 7.7% both in the DC voltage and power occur under the power versus voltage droop and current control scheme.

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“…Improved method with multiple droop characteristics [17][18][19][20] Outer loops with different droop slopes are integrated to create multiple droop characteristics.…”

Section: Reference Controller Structure Distinctive Featuresmentioning

confidence: 99%

Section: This Papermentioning

confidence: 99%

Section: This Papermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Demonstration of Converter Control Interactions in MMC-HVDC Systems

et al. 2022

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“…This is achieved by using smaller droop slopes 𝑘 𝑑𝑟𝑜𝑜𝑝1 and 𝑘 𝑑𝑟𝑜𝑜𝑝3 to make the voltage less sensitive to such disturbance. The multiple-slope based decentralized control have been reported in [6]- [11]. In [6]- [9], different types of droop control and margin control which are commonly used in dc distribution networks are introduced.…”

Section: Introductionmentioning

confidence: 99%

Decentralized Control for Multi-Terminal Cascaded Medium-Voltage Converters Considering Multiple Crossovers

Chen

Wang

Liang

et al. 2024

IEEE Trans. Power Delivery

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Decentralized control with multiple droop characteristics can significantly improve the accuracy of power flow in medium-voltage direct-current (MVdc) networks. However, multiple crossovers caused by different control characteristics can lead to the drifts of power and voltage and instability issues. When this type of control is implemented in the cascaded three-level neutral-point-clamped (C3L-NPC) converters, on one hand, the mechanism of such the power and voltage drifts was not investigated. On the other hand, power control accuracy, dc voltage balancing across submodules (SMs) and multiple crossovers should all be considered, which requires suitable control methods. To address the challenges, firstly, the mechanism behind the power and dc voltage drifts is analyzed. Secondly, a control scheme is presented to improve the power control accuracy and dc voltage balancing and concurrently, to avoid the multiple crossovers. This is achieved by suitable droop gain design and adding a secondary power compensator. The presented control scheme is verified in MATLAB/Simulink simulation and experimentally validated in a three-terminal MVdc testbed. Results show that the accuracy of steady-state power flow is improved by 15% due to the elimination of multiple crossovers, while the power accuracy at dynamics improved by 13% with the secondary power compensator. Index Terms--Medium-voltage direct-current (MVdc), cascaded three-level neutral-point-clamped (C3L-NPC) converter, decentralized control, multiple crossovers. NOMENCLATURE C3L-NPC Cascaded three-level neutral-point-clamped. MVdc Medium-voltage direct-current. MMC Modular-multilevel converter. DSOs Distribution system operators. ESS Energy storage system. PLL Phased-locked loop LPF Low-pass filter V, I, P Magnitudes of voltage, current and power. v, i, p Instantaneous voltage, current and power.A. Subscripts i and j the i th and j th converters.d and q the d-axis and q-axis components on the synchronous coordinate frame.dc Direct-current components.

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A Critical Review on DC Microgrids Voltage Control and Power Management

Al-Ismail

2024

IEEE Access

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Direct current (DC) microgrids are becoming increasingly important due to a number of causes, including the widespread use of DC loads, the integration of solar photovoltaic (PV) and energy storage devices (ESDs), and the absence of frequency and reactive power control issues. The control of DC bus voltage, power management, effective power split among the ESDs, and state of charge (SoC) restorations are important in a DC microgrid. However, DC bus voltage control and power management are difficult since the microgrids connect several distributed generators (DGs), loads, utility grids, and ESDs to the DC bus using power electronic converters. It is imperative to properly control the DC bus voltage and manage power among the sources and loads in order to maintain the stability and reliability of DC microgrids. DC microgrids can be controlled by employing centralized, decentralized, distributed, multi-level, and hierarchical control systems to ensure safe and secure operation. Besides, advanced control techniques, such as nonlinear, robust, model predictive, artificial intelligence, and many others, are employed. This article critically reviews two main aspects of DC microgrids: voltage control and power management. The challenges and opportunities for voltage control and power management in DC

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Distributed Piecewise Droop Control of DC Microgrid with Improved Load Sharing and Voltage Compensation

Cited by 11 publications

References 18 publications

Demonstration of Converter Control Interactions in MMC-HVDC Systems

Demonstration of Converter Control Interactions in MMC-HVDC Systems

Decentralized Control for Multi-Terminal Cascaded Medium-Voltage Converters Considering Multiple Crossovers

A Critical Review on DC Microgrids Voltage Control and Power Management

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