Open Access

ARTICLE

Analysis of DC-Side Harmonic Characteristics and Optimization of Filter Design for Hybrid DC Transmission Systems

Chunyan Li¹, Luo Li¹, Yushuang Li², Yong Jia¹, Wenyan Li^3,*

1 School of Electrical and Electronic Engineering, Chongqing University of Technology, Chongqing, 400054, China
2 Shi Bei Power Supply Branch, State Grid Chongqing Electric Power Company, Chongqing, 401120, China
3 Carbon Neutrality Research Institute, Chongqing Communication Design Institute Co., Ltd., Chongqing, 400041, China

* Corresponding Author: Wenyan Li. Email:

(This article belongs to the Special Issue: Operation and Control of Grid-connected New Energy and Emerging Loads)

Energy Engineering 2025, 122(10), 4313-4330. https://doi.org/10.32604/ee.2025.070187

Received 10 July 2025; Accepted 28 August 2025; Issue published 30 September 2025

Abstract

To accelerate the large-scale integration of renewable energy and support the strategic goals of “carbon peaking and carbon neutrality,” High Voltage Direct Current (HVDC) transmission technology has made significant breakthroughs. Among the various approaches, a hybrid DC transmission system that combines a line-commutated converter (LCC) and a voltage source converter (VSC) retains the inherent fault self-clearing capability of the LCC topology while mitigating the risk of commutation failure when connected to a weak grid. In this paper, based on the harmonic generation mechanisms of hybrid DC transmission systems, an improved 3-pulse harmonic source model of the LCC and a dynamic phase-sequence harmonic analysis model of the VSC are developed. The integrated harmonic model demonstrates strong adaptability in accurately calculating DC-side harmonics under the influence of power imbalances and background harmonics. Based on this model, the fundamental characteristics of DC-side harmonics in hybrid DC transmission systems are analyzed. To mitigate harmonic effects, this paper proposes an LCLC-trap2 high-order filter structure with parallel RC damping circuits and a co-optimized design of filter parameters. Finally, a ±500 kV hybrid DC transmission system is modeled using the MATLAB/Simulink platform, and the harmonic filtering performances of the conventional LC filter, the Butterworth filter, and the proposed filter are simulated and compared. The results verify that the proposed filter offers superior performance in suppressing low-order harmonics under non-ideal operating conditions.

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Keywords

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