Control Strategy for Improving Active Frequency Support Capability of Offshore Wind Farm

doi:10.16183/j.cnki.jsjtu.2023.581

Abstract

Abstract:

In low frequency alternating current (AC) transmission systems, offshore wind farm is unable to respond to changes in onshore grid frequency in a timely manner due to frequency decoupling and signal transmission delays between the offshore wind power system and the onshore AC system. To address this issue, a control strategy is proposed to improve the active frequency support capability of offshore wind farms by combining the system inertia. In terms of frequency signaling, an additional frequency sag controller is designed based on the V/f control strategy of the low-frequency-side structure network of modular multilevel matrix converter (M³C), combining with the system inertia. The frequency coupling link between the M³C net side and the low-frequency side is established to realize the real-time transmission of frequency information between the two sides. In terms of frequency support, when the system is disturbed to generate frequency deviation, the offshore wind turbine can adjust the power command value through additional droop control, thereby providing frequency support for the system. Finally, the effectiveness of the proposed coordinated control strategy is verified in MATLAB/Simulink by the simulation of load change and three-phase AC short circuit fault.

Key words: low frequency alternating current (LFAC) transmission system, frequency coupling, collaborative control strategy, frequency support

CLC Number:

TM732

LI Yibo, ZHOU Qian, ZHU Dandan, JIANG Yafeng, WU Qiuwei, CHEN Jian. Control Strategy for Improving Active Frequency Support Capability of Offshore Wind Farm[J]. Journal of Shanghai Jiao Tong University, 2025, 59(10): 1442-1450.

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装置	参数	数值
风电场	额定容量/MW	300
低频系统	额定线电压/kV	35
	额定频率/HZ	20
海缆	长度/km	28
M³C换流站	额定容量/MW	400
	子模块电容/mF	4
	额定电容电压/kV	3
	桥臂模块数/个	100
	桥臂电感/mH	40
	阀额定电压/kV	12
工频系统	额定线电压/kV	35
	额定频率/HZ	50

参数	数值
额定容量/MW	300
机端电压/kV	13.8
惯性时间常数/s	3.2
交轴电抗x_d,x'_d,x″_d	1.305, 0.296, 0.252
直轴电抗x_q,x'_q,x″_q	0.474, 0.243, 0.18
时间常数$\tau {\text{'}}_{d},\tau {″}_{d},\tau {\text{'}}_{q}$	1.01, 0.053, 0.1
励磁调节器增益	300
励磁时间常数/ms	1
原动机调差参数	0.35
伺服时间常数/s	0.5