Technical Scheme Design of an MVAC Distribution Network Project for Demonstration with MVDC-Flexible Interconnection

doi:10.12204/j.issn.1000-7229.2022.03.001

Abstract

Abstract:

Combined with the actual problems of the medium-voltage (MV) AC distribution network in Songshan Lake area of Dongguan, the technical scheme of an MVAC distribution network project for demonstration with HVDC-flexible interconnection is studied. The main wiring mode, connection transformer configuration and grounding mode are demonstrated. The modular multi-level converter and power electronic DC transformer in the system are preliminarily designed, and the technical requirements for key equipment are determined. The system overcurrent and overvoltage characteristics are analyzed by simulation, thus overcurrent tolerance and insulation coordination requirements being put forward. The overall control architecture and protection configuration of the system are designed, and the control and protection strategy of the system is defined. The new main connection topology proposed in this article is used in a practical demonstration project. The scheme of high-ripple design for compact equipment is adopted and the AC fault coordination response strategy is proposed. All those new technologies are demonstrated and verified with simulation, which provide reference for follow-up related research and engineering practice.

Key words: MVDC-flexible interconnection, demonstration project, system analysis, modular multilevel converter (MMC), power electronic DC transformer

CLC Number:

TM72

WEI Zhiwen, LUO Yu, ZENG Yuanfang, ZHAO Biao, CUI Kangsheng, LI Haibo, SHI Jian. Technical Scheme Design of an MVAC Distribution Network Project for Demonstration with MVDC-Flexible Interconnection[J]. ELECTRIC POWER CONSTRUCTION, 2022, 43(3): 1-11.

Figures/Tables 15

Fig.1 MVAC distribution network project for demonstration with MVDC-flexible interconnection in Dongguan Songshan Lake area

Fig.2 Topology of the demonstration project

Fig.3 Single-phase fault simulation results of different transformer configurations

Fig.4 Grounding methods of main circuit under different operation modes

Fig.5 Single-phase short-circuit current under different DC grounding resistance

Fig.6 Structural sketch of MMC

Table 1 Technical requirements of MMC

Fig.7 Structural sketch of DCT

Table 2 Technical requirements of DCT

Table 3 System current withstand requirementskA

Table 4 Requirements for system insulation coordinationkV

Fig.8 Control system block diagram of thedemonstration project

Fig.9 Transition relationship of system operation modes

Fig.10 Relaying protection functions of MMC

Fig.11 Relaying protection functions of DCT

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