Improved Control Strategy of MMC–HVDC to Improve Frequency Support of AC System

Zhang, Zicong; Lee, Jung-Hun; Jang, Gilsoo

doi:10.3390/app10207282

Cited by 7 publications

(6 citation statements)

References 26 publications

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“…For OWPs connected by a single VSC HVDC connection, FFR contributions, in particular, are studied in the literature [25][26][27][28][29][30][31][32][33][34]. The required energy is inherently taken from the DC link of the HVDC connection, thereby lowering the DC voltage.…”

Section: Related Work and Contributions Of This Articlementioning

confidence: 99%

Analysis of Onshore Synthetic Inertia and Primary Control Reserve Contributions of Alternating Current-Side Meshed Offshore Grids with Voltage-Source Converter and Diode Rectifier Unit High-Voltage Direct Current Connections

Herrmann,

Alkemper,

Hofmann

2023

Energies

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The increasing use of renewable energy sources in place of conventional generation units is leading to a reduction in onshore inertia and to the development of offshore wind park grids connected by multiple high-voltage direct current (HVDC) connections to the onshore alternating current (AC) grid. For AC-side meshed offshore grids with voltage-source converter (VSC) and diode rectifier unit (DRU) HVDC connections towards onshore grids, this study focuses on the energetic feasibility of synthetic inertia (SI) and primary control reserve (PCR) contributions triggered locally at the onshore converters of both connection types. To this end, the obstacles preventing contributions for VSC HVDC connections and the mechanisms allowing contributions for DRU HVDC connections are identified first. Based on these findings, the article proposes an enhancement of the offshore HVDC converter controls that is continuously active and allows locally triggered onshore contributions at all onshore HVDC converters of both connection types without using communication and requiring only minimal system knowledge. Additional simulations confirm that, although the enhancement is continuously active, the operational performance of the offshore HVDC converter controls for normal offshore grid operation and its robustness against offshore AC-side faults are not affected.

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Section: Related Work and Contributions Of This Articlementioning

confidence: 99%

Analysis of Onshore Synthetic Inertia and Primary Control Reserve Contributions of Alternating Current-Side Meshed Offshore Grids with Voltage-Source Converter and Diode Rectifier Unit High-Voltage Direct Current Connections

Herrmann,

Alkemper,

Hofmann

2023

Energies

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“…So, the extenuating variables i.e. circulating currents and Vcommon mode are used in the low-frequency spectrum to reduce voltage instability [22]. On the flip side, the machine is operated in a high-frequency spectrum when extenuating signals are no longer required.…”

Section: Introductionmentioning

confidence: 99%

An ingenious MMC topology appropriate for motor drives across their entire frequency spectrum

Patil¹,

Thakre

Sonawane

et al. 2023

Bulletin EEI

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Modular multilevel converter (MMC) modules have popped up as among the best choices for medium and high-powered uses. This paper proposes a control scheme for the entire frequency range of operation for the MMC, focusing on supplying a three-phase machine. The machine is required to be controlled in the outer as well as the inner loop. Standard field oriented control (FOC) manages the three-phase machine in the outer closed loop while the inner control has to come up against the problem of energy balancing. That is unevenly distributed and stored in the capacitance of the upper and lower arms of the converter. There are two operating methods used in the inner control loop: a low-frequency method is used for start-up and low-speed operation, and a high-frequency method is for higher speed. In low-frequency mode (LF-mode), a special control strategy has to be implemented to minimize the energy oscillation in the capacitances of the converter arms. It makes utilization of the 3-phase machine's common mode voltage (Vc) as well as internal circulatory currents to verify a symmetrical energy distribution inside this MMC arms and also to avert whatever AC currents inside the DC source.

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“…The implementation of an MMC in a wind power generator, however, has not been extensively reported. The majority of reports have investigated the stability of grid-connected wind farms using MMC-based High Voltage Direct Current (HVDC) transmission systems [6][7][8][9][10], but only a few papers have discussed the topology concept of the implementation of MMC-controlled wind turbine generators. The performance and topology of MMCs for 2 MW 0.69 kV and 10 MW 10 kV has been discussed in [11]; however, the study only discusses the grid side converter and concentrates mainly on loss distribution between submodules.…”

Section: Introductionmentioning

confidence: 99%

Detailed and Average Models of a Grid-Connected MMC-Controlled Permanent Magnet Wind Turbine Generator

et al. 2022

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In this paper, a detailed model and an average model of an MMC (Modular Multilevel Converter)-controlled Permanent Magnet Synchronous Generator (PMSG)-based direct drive wind turbine are proposed. The models are used to analyze the steady-state and transient characteristics of the grid connectivity study of the wind turbine generator. Configuration of the electrical topology and the control scheme of the wind turbine generator for both models are comprehensively presented. In the detailed model, the MMC circuit is represented by power electronic IGBTs, with switching phenomena considered. Meanwhile, in the average model, the MMC circuit is simplified by using voltage source representation, hence the complexity of the MMC circuit and the simulation duration of the analysis can be reduced. Comparative analysis between the detailed and the simplified models is also investigated through simulation performed using PSCAD/EMTDC. The simulation results show that both models have a good controllability and dynamic stability under steady-state and transient conditions. The simulation results also confirm that the average model has adequate accuracy, and simulation time can be reduced significantly.

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Improved Control Strategy of MMC–HVDC to Improve Frequency Support of AC System

Cited by 7 publications

References 26 publications

Analysis of Onshore Synthetic Inertia and Primary Control Reserve Contributions of Alternating Current-Side Meshed Offshore Grids with Voltage-Source Converter and Diode Rectifier Unit High-Voltage Direct Current Connections

Analysis of Onshore Synthetic Inertia and Primary Control Reserve Contributions of Alternating Current-Side Meshed Offshore Grids with Voltage-Source Converter and Diode Rectifier Unit High-Voltage Direct Current Connections

An ingenious MMC topology appropriate for motor drives across their entire frequency spectrum

Detailed and Average Models of a Grid-Connected MMC-Controlled Permanent Magnet Wind Turbine Generator

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