大规模光伏发电经串补输电线路并网系统强迫次同步振荡机制

doi:10.16183/j.cnki.jsjtu.2021.415

摘要/Abstract

摘要：

大规模光伏经串补并网系统存在次同步振荡失稳风险,传统研究一般基于负阻尼振荡理论对此进行解释.本文将因最大功率跟踪控制(MPPT)导致的光伏间谐波作为扰动源,大规模光伏经串补并网系统作为受迫系统,采用强迫振荡理论揭示光伏发电基于扰动式MPPT与串补并网系统相互作用的次同步振荡机制,并在PSCAD/EMTDC仿真平台进行验证.结果表明:基于扰动式MPPT的光伏逆变器因交直流侧的调制耦合作用向系统输出间谐波电流,当该间谐波频率与系统固有弱阻尼模式频率接近时,可能导致严重的强迫次同步振荡问题,对系统稳定性造成冲击;算例仿真验证了所提理论的正确性.

关键词: 光伏, 间谐波, 次同步振荡, 强迫振荡

Abstract:

There exists the subsynchronous oscillation (SSO) instability risk in large-scale photovoltaic(PV) grid-connected systems with series compensation, which is generally explained by the negative damped oscillation theory. In this paper, the inter-photovoltaic harmonics due to maximum power point tracking (MPPT) control are used as the disturbance source and the large-scale PV grid-connected system with series compensation as the forced system. The forced oscillation theory is used to reveal the SSO mechanism of PV power generation based on the interaction between the perturbed MPPT and the series compensation grid-connected system, and verified in the PSCAD/EMTDC simulation platform. The results show that the perturbed MPPT-based PV inverter outputs interharmonic currents to the system due to the modulation coupling on the AC-DC side, which may lead to serious forced SSO problems when the interharmonic frequency is close to the frequency of inherent weakly damped mode of the system, causing a shock to the system stability. The simulation results verify the correctness of the proposed theory.

Key words: photovoltaic(PV), interharmonic, subsynchronous oscillation(SSO), forced oscillation

中图分类号:

TM721

林勇, 康佳乐, 余浩, 陈鸿琳, 杨彦霁, 陈武晖. 大规模光伏发电经串补输电线路并网系统强迫次同步振荡机制[J]. 上海交通大学学报, 2022, 56(9): 1118-1127.

LIN Yong, KANG Jiale, YU Hao, CHEN Honglin, YANG Yanji, CHEN Wuhui. Mechanism of Forced Subsynchronous Oscillation of Large-Scale Photovoltaic Power Generation Grid-Connected System with Series Compensation Tranmmission Lines[J]. Journal of Shanghai Jiao Tong University, 2022, 56(9): 1118-1127.

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设备数量	电压等级	变压器			输电线路
设备数量	电压等级	漏电抗(p.u.)	励磁电流/%	额定容量/(MV·A)	电压等级/kV	线路阻抗(p.u.)
i=4	0.48 kV/35 kV	0.065	0.65	1	330	Z₁=0.039+j0.297
m=3	35 kV/330 kV	0.140	0.44	240	750	Z₂=0.015+j0.196
n’=200	330 kV/750 kV	0.150	0.10	500

电流控制参数	直流电压控制参数	锁相环参数	交流侧滤波器
k_p1= k_p2=0.5	k_p3=3.5	k_p4=50	L_f=0.6 mH
k_i1= k_i2=12.5	k_i3=285	k_i4=10000	R_f=0.5 Ω C_f=35 μF

模式	特征值		f/Hz	ζ /%
λ_1,2	-389.420±	j6906.484	1099.200	5.630
λ_3,4	-391.137±	j6293.558	1001.651	6.203
λ_5,6	-0.898±	j313.284	49.861	0.287
λ_7,8	-6.670±	j61.992	9.866	10.698
λ_9,10	-0.079±	j3.272	0.521	2.438
λ₁₁	-807.660		-	-
λ₁₂	-792.464		-	-
λ₁₃	-25.803		-	-
λ₁₄	-25.758		-	-