Analysis of Sub/Super-Synchronous Oscillation of Direct-Drive Offshore Wind Power Grid-Connected System via VSC-HVDC

doi:10.16183/j.cnki.jsjtu.2021.434

Abstract

Abstract:

The system of offshore direct-drive wind farm connected to the power grid via voltage source converter based high voltage direct current (VSC-HVDC) transmission consists of several converters, which have different time scale control loops and complex dynamic characteristics. Based on an example case with two direct-drive wind farms and VSC-HVDC transmission system, the sub/super-synchronous oscillation modes of the system and its relationship with current control loops are studied by state space analysis. The research shows that there are three dominant modes related to the current control of the converter in the system, which are the oscillation mode between wind farms and the offshore converter station, the mode between the offshore wind farms, and the mode between the onshore converter station and the alternating current (AC) system. The modes at the wind farm side are decoupled from the mode between the onshore converter station and the AC system. The relevant control parameters of the converters and the operating conditions have an important impact on the stability of the three modes. The oscillation caused by the single dominant mode may spread to the other side of VSC-HVDC, which means it is necessary to identify the root cause of oscillation in order to design the suppression strategy. The research results is of guidance to the understanding of the dynamic characteristics of offshore wind power grid-connected systems via VSC-HVDC, parameter design, and oscillation suppression.

Key words: offshore wind power, voltage source converter based high voltage direct current (VSC-HVDC) transmission, state space analysis, sub/super-synchronous oscillation

CLC Number:

TM712

ZHANG Zhiqiang, LI Qiutong, YU Hao, CHEN Honglin, SUN Haishun. Analysis of Sub/Super-Synchronous Oscillation of Direct-Drive Offshore Wind Power Grid-Connected System via VSC-HVDC[J]. Journal of Shanghai Jiao Tong University, 2022, 56(12): 1572-1583.

Figures/Tables 21

Fig.1

Tab.1

Tab.2

Fig.2

Fig.3

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Fig.12

Fig.13

Fig.14

Fig.A1

Fig.A2

Tab.A1

Definition of variables

变量	含义	变量	含义
P_sr	风电有功指令值的标幺值	ω₀	电网额定角频率标幺值
P_s	风电有功实际值的标幺值	L_r	柔直送端滤波电感标幺值
z₁	风电机侧有功外环控制状态变量	u_w	风电直流电压指令值的标幺值
i_s_q_r	风电机侧q轴电流指令值的标幺值	u_wr	风电直流电压参考值
i_s_q	风电机侧q轴滤波后电流标幺值	z₄	风电网侧直流电压外环控制状态变量
z₂	风电机侧q轴电流内环控制状态变量	i_g_d_r	风电网侧d轴电流指令值的标幺值
ω_m	发电机转子角速度标幺值	i_gm_d	风电网侧d轴滤波后电流的标幺值
ψ_f	转子磁链标幺值	z₅	风电网侧d轴电流内环控制状态变量
u_s_q_r	风电机侧q轴变流器出口电压指令值的标幺值	u_gm_d	风电网侧d轴滤波后电压的标幺值
i_s_d_r	风电机侧d轴电流指令值的标幺值	u_gc_d_r	风电网侧d轴变流器出口电压指令值的标幺值
i_s_d	风电机侧d轴电流实际值的标幺值	i_g_q_r	风电网侧q轴电流指令值的标幺值
z₃	风电机侧d轴电流内环控制状态变量	i_gm_q	风电网侧q轴滤波后电流的标幺值
u_s_d_r	风电机侧d轴变流器出口电压指令值的标幺值	z₆	风电网侧q轴电流内环控制状态变量
L_s_d	同步电机定子直轴电感标幺值	u_gm_q	风电网侧q轴滤波后电压的标幺值
L_s_q	同步电机定子交轴电感标幺值	u_gc_q_r	风电网侧q轴变流器出口电压指令值的标幺值
u_rm_d	柔直送端d轴滤波后电压的标幺值	L_g	风电网侧滤波电感标幺值
u_r_d_r	柔直送端d轴变流器出口电压指令值的标幺值	u_hi	柔直受端直流电压实际值的标幺值
z₇	柔直送端d轴电压外环控制状态变量	u_hir	柔直受端直流电压指令值的标幺值
变量	含义	变量	含义
i_r_d_r	柔直送端d轴电流指令值的标幺值	u_rc_q_r	柔直送端q轴变流器出口电压指令值的标幺值
i_rm_d	柔直送端d轴滤波后电流的标幺值	z₁₁	柔直受端直流电压控制外环状态变量
z₈	柔直送端d轴电流内环控制状态变量	i_i_d_r	柔直受端d轴电流指令值的标幺值
u_rm_d	柔直送端d轴滤波后电压的标幺值	i_im_d	柔直受端d轴滤波后电流的标幺值
u_rc_d_r	柔直送端d轴变流器出口电压指令值的标幺值	u_ic_d_r	柔直受端d轴变流器出口电压指令值的标幺值
z₉	柔直送端q轴电压外环控制状态变量	i_im_q	柔直受端q轴滤波后电流的标幺值
i_r_q_r	柔直送端q轴电流指令值的标幺值	i_i_q_r	柔直受端q轴电流指令值的标幺值
i_rm_q	柔直送端q轴滤波后电流的标幺值	u_ic_q_r	柔直受端q轴变流器出口电压指令值的标幺值
z₁₀	柔直送端q轴电流内环控制状态变量	s	拉普拉斯算子
u_rm_q	柔直送端q轴滤波后电压的标幺值

Tab.A1

Tab.B1

Tab.B2

References 20

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参数	取值
参数	工况一	工况二	工况三	工况四
风电机组出力P_s.pu	0.4	0.4	0.4	0.4
短路比	4	4	4	4
风电GSC电流环比例增益K_p5, K_p6	1	0.65	0.4	1
风电GSC电流环积分增益K_i5, K_i6	25	25	25	25
柔直SEC电流环比例增益K_p8, K_p10	0.8	0.8	0.8	0.8
柔直SEC电流环积分增益K_i8, K_i10	50	50	50	50
柔直REC电流环比例增益K_p12, K_p13	0.8	0.8	0.8	0.48
柔直REC电流环积分增益K_i12, K_i13	50	50	50	50
风电GSC电流环带宽/Hz	201	143	92	201
柔直SEC电流环带宽/Hz	224	224	224	224
柔直REC电流环带宽/Hz	267	267	267	197

SSO模态	特征值									振荡模式
SSO模态	工况一		工况二		工况三		工况四			振荡模式
λ_1,2	-6.36±	j61.10×2π	3.65±	j48.39×2π	23.77±	j38.32×2π	-6.36±	j61.10×2π	风场-柔直模式
λ_7,8	-115.08±	j112.66×2π	-144.46±	j98.76×2π	-174.26±	j86.60×2π	-115.08±	j112.66×2π
λ_9,10	-83.10±	j10.54×2π	-77.77±	j12.51×2π	-67.93±	j15.29×2π	-83.10±	j10.54×2π
λ_3,4	-66.26±	j70.21×2π	-37.05±	j51.96×2π	7.24±	j39.77×2π	-66.26±	j70.21×2π	风场间模式
λ_11,12	-198.21±	j124.81×2π	-242.92±	j104.25×2π	-296.25±	j84.21×2π	-198.21±	j124.81×2π
λ_13,14	-93.50+ -56.79+	j0×2π j0×2π	-99.78±	j4.39×2π	-122.16±	j13.71×2π	-93.50+ -56.79+	j0×2π j0×2π
λ_5,6	-74.96±	j26.94π	-74.96±	j26.94π	-74.96±	j26.94π	2.61±	j25.81×2π	柔直-交流系统模式
λ_15,16	-184.74±	j106.82×2π	-184.74±	j106.82×2π	-184.74±	j106.82×2π	-186.02±	j80.56×2π
λ_17,18	-366.61±	j31.54×2π	-366.61±	j31.54×2π	-366.61±	j31.54×2π	-540.99±	j1.95×2π

参数	数值	参数	数值
永磁同步电机额定频率f_sn/Hz	11.5	风电机组箱变阻抗电压/%	6.5
风电机组变流器直流电容电压额定值u_wn/kV	1.2	柔直连接变压器阻抗电压/%	10
风电机组变流器直流电容有名值C_w/μF	25 000	柔直送端换流电感L_r,L_i/H	0.069
风电机组GSC出口滤波电感有名值L_g/mH	0.11	柔直直流海缆集中等值电容及支撑电容之和C_h/mF	42.28
风电机组箱变变比/kV	36.75/0.69

参数	数值	参数	数值
GSC外环有功外环比例增益K_p1	1	柔直SEC dq轴直流电压外环比例增益K_p7, K_p9	0.8
GSC外环有功外环积分增益K_i1	20	柔直SEC dq轴直流电压外环积分增益K_i7, K_i9	12.5
GSC qd轴电流内环比例增益K_p2, K_p3	4	柔直SEC dq轴电流内环比例增益K_p8, K_p10	0.8
GSC qd轴电流内环积分增益K_i2, K_i3	66.67	柔直SEC dq轴电流内环积分增益K_i8, K_i10	50
GSC直流电压外环比例增益K_p4	0.6	柔直REC直流电压外环比例增益K_p1	0.8
GSC直流电压外环积分增益K_i4	10	柔直REC直流电压外环积分增益K_i11	10
GSC dq轴电流内环比例增益K_p5, K_p6	1	柔直REC dq轴电流内环比例增益K_p12, K_p13	0.8
GSC dq轴电流内环积分增益K_i5, K_i6	25	柔直 REC dq轴电流内环积分增益K_i12, K_i13	50
风电锁相环比例增益K_pPLLw	50	柔直锁相环比例增益K_pPLLh	50
风电锁相环积分增益K_iPLLw	1 000	柔直锁相环积分增益K_iPLLh	1 000