Adaptive VSG Control Strategy of Sending End for Large-Scale Renewable Energy Connected to Weakly-Synchronized Support VSC-HVDC System

doi:10.11930/j.issn.1004-9649.202304066

Abstract

Abstract:

Renewable energy collection and output through voltage source converter based high voltage direct current (VSC-HVDC) technology is an effective way to promote renewable energy consumption. However, the continuous increase in the penetration rate of renewable energy has led to a continuous decline in the strength of the power grid, and the traditional grid-following (GFL) converter technology can no longer meet the needs of stable system operation. In order to improve the adaptability of the weak grid of the system and meet the application scenarios of large-scale renewable energy connected to weakly-synchronized support VSC-HVDC system, this paper proposes to adopt VSG control strategy in the converter station of the sending end of the VSC-HVDC system. Firstly, a small signal mathematical model of rectifier-side control is established, and the influence of virtual impedance on system stability is studied by the root locus method. Secondly, an improved virtual synchronous generator (VSG) control algorithm for constructing virtual reactance adaptive adjustment items using electrical quantities such as alternating voltage (AC) change rate and voltage difference is proposed, which can improve the equivalent short-circuit ratio of the AC system at the sending end while ensuring that the equivalent impedance of the system is inductive, so as to improve the overall performance of the system. Finally, the effectiveness of the proposed control strategy is verified by PSCAD/EMTDC electromagnetic transient simulation.

Key words: renewable energy power generation, weak AC power grid, VSC-HVDC system, virtual synchronous generator, adaptive algorithm

Zimin ZHU, Jinfang ZHANG, Qing CHANG, Zhuan ZHOU, Xiaolin ZHANG. Adaptive VSG Control Strategy of Sending End for Large-Scale Renewable Energy Connected to Weakly-Synchronized Support VSC-HVDC System[J]. Electric Power, 2024, 57(5): 211-221.

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URL: https://www.electricpower.com.cn/EN/10.11930/j.issn.1004-9649.202304066

https://www.electricpower.com.cn/EN/Y2024/V57/I5/211

Figures/Tables 12

Fig.1 Topology of large-scale renewable energy connected to weakly-synchronized support VSC-HVDC system

Fig.2 VSG control of rectifier station

Fig.3 Circuit model of rectifier side

Fig.4 Small signal model of system

Fig.5 Root locus

Fig.6 Principle of adaptive virtual impedance algorithm

Fig.7 Adaptive VSG control process

Table 1 Main parameters of system

主要参数		数值
交流侧额定电压/kV		500
直流侧额定电压/kV		±800
额定容量/MW		8 000
短路比		＜1.4

Fig.8 Unstable waveform under GFL control

Fig.9 VSG control of rectifier station

Fig.10 Improved VSG control and general VSG control

Fig.11 Rectifier-side waveform when 100% renewable energy is connected

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