Transmission Capacity Analysis of Low-Frequency AC Transmission System with Onshore Renewable Energy Integration

doi:10.16183/j.cnki.jsjtu.2024.401

Abstract

Abstract:

Flexible low-frequency alternating current (AC) transmission technology features superior transmission capacity and flexible control capability compared with power-frequency AC transmission technology, thereby enabling its application to wide-area collection and delivery of large-scale onshore renewable energy. This paper investigates the transmission capacity of overhead lines to determine the applicable voltage levels and operating ranges of low-frequency systems. First, a function taking the reactance-to-resistance ratio (X/R) as the independent variable is established to analyze the line voltage-current characteristics as well as static voltage stability under different voltages and operating frequencies, and the dominant influencing factors limiting the power transfer capability of low-frequency systems are summarized. Then, the transmission capacity of overhead lines ranging from 10 kV to 1 000 kV is quantified. Calculation results reveal that for 220 kV and above voltage grades, low-frequency overhead lines achieve more than twice the transmission capacity and over three times the transmission radius of standard power-frequency counterparts. Finally, a 220 kV/1 000 MW low-frequency transmission model is built on the PSCAD/EMTDC platform to verify the effectiveness of the proposed low-frequency scheme for long-distance high-capacity power delivery.

Key words: transmission capacity, flexible low-frequency alternating current (FLFAC) transmission, overhead lines, renewable energy

CLC Number:

TM711

XIE Lijun, LU Zhengang, HAO Ruixiang, ZHAO Guoliang, HOU Gaoshan, CUI Jingxin. Transmission Capacity Analysis of Low-Frequency AC Transmission System with Onshore Renewable Energy Integration[J]. Journal of Shanghai Jiao Tong University, 2026, 60(7): 1110-1119.

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电压等级/kV	典型线路型号	I/A	R/(Ω·km^-1)	X/(Ω·km^-1)	工频X/R	低频X/R
1 000	8×JL/1A 500/35	8200	0.009038	0.28718	31.77	12.71
500	4×LGJ-500	4064	0.017	0.273	16.06	6.42
220	2×LGJ-630	1758	0.023	0.279	12.13	4.8
110	LGJ-400	879	0.08	0.373	4.66	1.86
35	LGJ-300	735	0.107	0.382	3.57	1.43
10	LGJ-70	265	0.609	0.414	0.68	0.27

设备	参数	取值
风电场	容量/MW	1000
	并网点电压/kV	220
架空线	长度/km	2×265
	电压/kV	220
	单位长度电容/(μF·km^-1)	0.012
	单位长度电感/(mH·km^-1)	0.89
	单位长度电阻/(Ω·km^-1)	0.023
M³C	容量/(MV·A)	1100
	电压/kV	220
	工低频变压器变比	220/165
	功率因数	0.909