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    SUBMODULE HYBRID MMC WITH LOW FULL-BRIDGE RATIO AND DC FAULT PROCESSING METHOD THEREOF
    1.
    发明公开
    SUBMODULE HYBRID MMC WITH LOW FULL-BRIDGE RATIO AND DC FAULT PROCESSING METHOD THEREOF 审中-公开

    公开(公告)号：US20240030715A1

    公开(公告)日：2024-01-25

    申请号：US17312809

    申请日：2020-10-28

    Applicant: Zhejiang University

    Inventor： Zheng Xu ,  Yuzhe Xu ,  Zheren Zhang

    IPC: H02M1/32 ,  H02M7/04 ,  H02J3/36

    CPC classification number: H02M1/32 ,  H02M7/04 ,  H02J3/36

    Abstract: The present disclosure discloses a sub-module hybrid MMC with low full-bridge ratio and a DC fault processing method thereof. The hybrid MMC prevents the energy at the AC side from entering a DC system by artificially creating three-phase interphase short circuit at the AC side of a converter in the DC fault processing process, which greatly reduces the ratio of full-bridge sub-modules required for DC fault processing. Moreover, the hybrid MMC has the same DC fault processing speed as the sub-module hybrid MMC with high full-bridge. The duration of the artificially created three-phase interphase short circuit fault in the fault processing process does not exceed 30 ms, which will not have a great impact on the AC system. Compared with the existing sub-module hybrid MMC, the MMC of the present disclosure can also deal with DC faults under the condition of using fewer full-bridge sub-modules, which can reduce the number of required power electronic devices, greatly reduces the cost of building an overhead line high-voltage flexible DC transmission system, and has very strong reference significance and use value in engineering.

    High-frequency uncontrolled rectifier-based DC transmission system for offshore wind farm
    2.
    发明授权
    High-frequency uncontrolled rectifier-based DC transmission system for offshore wind farm 有权

    公开(公告)号：US11791632B2

    公开(公告)日：2023-10-17

    申请号：US17298341

    申请日：2020-08-07

    Applicant: ZHEJIANG UNIVERSITY

    Inventor： Zheng Xu ,  Yingjie Tang ,  Zheren Zhang

    IPC: H02J3/00 ,  H02J3/36 ,  H02J3/38

    CPC classification number: H02J3/36 ,  H02J3/381 ,  H02J2300/28

    Abstract: The present disclosure provides a high-frequency uncontrolled rectifier-based DC transmission system for an offshore wind farm, including a DC system and an offshore AC system. The offshore AC system mainly includes wind turbines based on permanent magnet synchronous generators with full-scale power converters, AC submarine cables, and offshore step-up stations. The DC system includes an offshore station and an onshore station that are connected by DC submarine cables, where a converter of the offshore is a three-phase six-pulse uncontrolled rectifier bridge, while a converter of the onshore station is MMC. Each of the offshore AC system and the offshore station has a rated frequency far above 50 Hz, which can usually be chosen to be in a range of about 100 Hz to 400 Hz. The disclosed transmission system allows for a great reduction in construction costs and demonstrating great application potentials in actual engineering.

    OFFSHORE WIND FARM LOW-FREQUENCY ALTERNATING-CURRENT UNCONTROLLED RECTIFICATION ELECTRIC POWER TRANSMISSION SYSTEM
    3.
    发明申请
    OFFSHORE WIND FARM LOW-FREQUENCY ALTERNATING-CURRENT UNCONTROLLED RECTIFICATION ELECTRIC POWER TRANSMISSION SYSTEM 有权

    公开(公告)号：US20220393473A1

    公开(公告)日：2022-12-08

    申请号：US17771358

    申请日：2020-08-05

    Applicant: Zhejiang University

    Inventor： Zheng Xu ,  Yingjie Tang ,  Zheren Zhang

    IPC: H02J3/36 ,  F03D9/25 ,  H02M7/483 ,  H02J3/46 ,  H02J3/38

    Abstract: The present disclosure discloses an offshore wind farm low-frequency alternating-current uncontrolled rectification electric power transmission system, comprising an onshore converter station and an offshore alternating-current system. The offshore alternating-current system comprises wind turbine generators, alternating-current submarine cables, a confluence bus, and offshore booster stations; the onshore converter station comprises a wind field side alternating-current bus, an alternating-current system side alternating-current bus, an alternating-current filter, an energy dissipation device, a rectifier, and a converter; the rectifier is composed of a three-phase six-pulse uncontrolled rectifier bridge, and the converter may be an MMC or an LCC; the rated frequency of the offshore alternating-current system is selected to be close to 10 Hz.

    Parameter tuning approach for bypass damping filter to suppress subsynchronous resonance in power systems
    4.
    发明授权
    Parameter tuning approach for bypass damping filter to suppress subsynchronous resonance in power systems 有权

    公开(公告)号：US10374427B2

    公开(公告)日：2019-08-06

    申请号：US15523135

    申请日：2016-04-11

    Applicant: ZHEJIANG UNIVERSITY

    Inventor： Zheng Xu ,  Shijia Wang

    IPC: H02J3/24 ,  H02H9/08 ,  H02J3/01 ,  H03J3/22 ,  H04B15/02 ,  H02H9/00 ,  H04B15/00

    Abstract: The present invention discloses a parameter tuning approach for bypass damping filter to suppress subsynchronous resonance in power systems, namely determining the parameters of capacitor, inductor and damping resistor in BDF. Using this approach, the parameters of capacitor and inductor in BDF can be adjusted, so that the frequency where the negative electrical damping of generator reaches minimum can be away from the frequency range of low frequency oscillation mode and typical frequencies of each torsional mode; the parameter of damping resistor in BDF can be further adjusted so that the minimum value of negative electrical damping is in reasonable range. The application of BDF with parameters tuned by the present invention contributes to the suppression of both the torsional interaction effect and the transient torque amplification effect.

    LCC and MMC series-connected HVDC system with DC fault ride-through capability
    5.
    发明授权
    LCC and MMC series-connected HVDC system with DC fault ride-through capability 有权

    公开(公告)号：US10084387B2

    公开(公告)日：2018-09-25

    申请号：US15522954

    申请日：2016-04-11

    Applicant: ZHEJIANG UNIVERSITY

    Inventor： Zheng Xu ,  Shijia Wang ,  Huangqing Xiao

    IPC: H02J3/36 ,  H02M5/458

    CPC classification number: H02M5/4585 ,  H02J3/36 ,  H02J2003/365 ,  H02M7/7575 ,  H02M2001/325 ,  H02M2007/4835 ,  Y02E60/60

    Abstract: The present invention discloses an LCC and MMC series-connected HVDC system with DC fault ride-through capacity, comprising rectifier and inverter linked by DC transmission line; Both the positive pole and the negative pole of the rectifier and the inverter consist of line-commutated converter and modular converter in series-connection; the modular converter adopts one MMC or several parallel-connected MMCs. The present invention has the advantage of low cost, low power loss and high reliability of the LCC, as well as flexible control, low harmonics and AC voltage support of the MMC. Further, the present invention is able to deal with DC fault by itself, hence additional DC fault clearing equipment is not needed. As a result, the present invention is suitable for the field of long-distance large-capacity power transmission and has broad development potential.

    Submodule hybrid MMC with low full-bridge ratio and DC fault processing method thereof
    6.
    发明授权
    Submodule hybrid MMC with low full-bridge ratio and DC fault processing method thereof 有权

    公开(公告)号：US12062915B2

    公开(公告)日：2024-08-13

    申请号：US17312809

    申请日：2020-10-28

    Applicant: Zhejiang University

    Inventor： Zheng Xu ,  Yuzhe Xu ,  Zheren Zhang

    IPC: H02M7/483 ,  H02J3/36 ,  H02M1/32

    CPC classification number: H02J3/36 ,  H02M7/4835 ,  H02M1/32

    Abstract: The present disclosure discloses a sub-module hybrid MMC with low full-bridge ratio and a DC fault processing method thereof. The hybrid MMC prevents the energy at the AC side from entering a DC system by artificially creating three-phase interphase short circuit at the AC side of a converter in the DC fault processing process, which greatly reduces the ratio of full-bridge sub-modules required for DC fault processing. Moreover, the hybrid MMC has the same DC fault processing speed as the sub-module hybrid MMC with high full-bridge. The duration of the artificially created three-phase interphase short circuit fault in the fault processing process does not exceed 30 ms, which will not have a great impact on the AC system. Compared with the existing sub-module hybrid MMC, the MMC of the present disclosure can also deal with DC faults under the condition of using fewer full-bridge sub-modules, which can reduce the number of required power electronic devices, greatly reduces the cost of building an overhead line high-voltage flexible DC transmission system, and has very strong reference significance and use value in engineering.

    Resistive sub-module hybrid MMC and direct current fault processing strategy thereof
    9.
    发明授权
    Resistive sub-module hybrid MMC and direct current fault processing strategy thereof 有权

    公开(公告)号：US12040606B2

    公开(公告)日：2024-07-16

    申请号：US17399740

    申请日：2021-08-11

    Applicant: ZHEJIANG UNIVERSITY

    Inventor： Zheren Zhang ,  Zheng Xu ,  Yuzhe Xu

    IPC: H02H7/00 ,  H02H1/00 ,  H02H7/12 ,  H02J3/36

    CPC classification number: H02H7/1216 ,  H02H1/0007 ,  H02J3/36

    Abstract: The present disclosure discloses a resistive sub-module hybrid MMC and a direct current fault processing strategy thereof. The hybrid MMC prevents fault current from entering a direct current system from the alternating current side by artificially creating three-phase earthing short circuit on the alternating current side of a converter during the direct current fault processing process, and can reduce the number of required power electronic devices compared with the module hybrid MMC. At the same time, the direct current fault processing speed of the hybrid MMC is fast, and the duration of the artificially creating three-phase short circuit fault in the fault processing process is less than 60 ms, which will not have a great impact on the alternating current system. The present disclosure greatly reduces the cost of building an overhead line high-voltage flexible direct current transmission system, and has very strong reference significance and use value in engineering.

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