Open Access

ARTICLE

Construction of MMC-CLCC Hybrid DC Transmission System and Its Power Flow Reversal Control Strategy

Yechun Xin¹, Xinyuan Zhao¹, Dong Ding², Shuyu Chen², Chuanjie Wang², Tuo Wang^1,*
1 Key Laboratory of Modern Power System Simulation and Control & Renewable Energy Technology, Northeast Electric Power University, Jilin, 132012, China
2 State Grid Henan Economic and Technical Research Institute, Zhengzhou, 450000, China
* Corresponding Author: Tuo Wang. Email:

Energy Engineering https://doi.org/10.32604/ee.2025.069748

Received 30 June 2025; Accepted 26 August 2025; Published online 15 September 2025

Abstract

To enhance power flow regulation in scenarios involving large-scale renewable energy transmission via high-voltage direct current (HVDC) links and multi-infeed DC systems in load-center regions, this paper proposes a hybrid modular multilevel converter–capacitor-commutated line-commutated converter (MMC-CLCC) HVDC transmission system and its corresponding control strategy. First, the system topology is constructed, and a submodule configuration method for the MMC—combining full-bridge submodules (FBSMs) and half-bridge submodules (HBSMs)—is proposed to enable direct power flow reversal. Second, a hierarchical control strategy is introduced, including MMC voltage control, CLCC current control, and a coordination mechanism, along with the derivation of the hybrid system’s power flow reversal characteristics. Third, leveraging the CLCC’s fast current regulation and the MMC’s negative voltage control capability, a coordinated power flow reversal control strategy is developed. Finally, an 800 kV MMC-CLCC hybrid HVDC system is modeled in PSCAD/EMTDC to validate the power flow reversal performance under a high proportion of full-bridge submodule configuration. Results demonstrate that the proposed control strategy enables rapid (1-s transition) and smooth switching of bidirectional power flow without modifying the structure of primary equipment: the transient fluctuation of DC voltage from the rated value (U_dcN) to the maximum reverse voltage (-kU_dcN) is less than 5%; the DC current strictly follows the preset characteristic curve with a deviation of ≤3%; the active power reverses continuously, and the system maintains stable operation throughout the reversal process.

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Keywords

Hybrid HVDC transmission; modular multilevel converter (MMC); controllable line commutated converter (CLCC); online power flow reversal; full-bridge and half-bridge submodules; new energy through dc transmission system

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