计及频率适应和快速稳定特性的多端直流电网改进协调控制策略

doi:10.11930/j.issn.1004-9649.202406059

摘要/Abstract

摘要：

多端柔性直流输电（voltage source converter multi-terminal DC，VSC-MTDC）技术在大规模、大范围多种类型可再生能源并网与外送方面具有广泛应用前景。针对柔性直流电网不平衡功率大扰动下交直流耦合对直流电压及交流系统频率影响问题，首先，提出基于直流电压下垂控制的改进协调控制策略，消除扰动前后直流电网电压偏离额定运行点问题；然后，通过引入自适应下垂系数，提高直流电网电压稳态恢复速率以及一定的控制可靠性。其次，对改进协调控制频率适应能力提升进行分析研究，以实现换流站参与交流系统频率调控，弥补交流侧调频能力缺失。最后，基于PSCAD/EMTDC搭建新能源经四端直流电网外送仿真模型，验证了所提改进协调控制策略及其对交流电网频率调控的可行性和有效性。

关键词: 柔性直流电网, 下垂控制, 协调控制, 加速策略, 频率调控

Abstract:

Multi-terminal flexible DC transmission (VSC-MTDC) technology has a wide range of application prospects in large-scale and wide-range multiple types of renewable energy grid-connection and outward transmission. To address the influence of AC-DC coupling on DC voltage and AC system frequency under large unbalanced power disturbances of flexible DC network, an improved coordinated control strategy based on DC voltage sag control is firstly proposed to eliminate the DC network voltage deviation from the rated operation point before and after the disturbances. And then the adaptive sag coefficients are introduced to improve the DC network voltage steady state recovery rate and certain control reliability. Thirdly, the adaptive capacity enhancement of the improved coordination control frequency is analyzed in order to realize the participation of converter station in AC system frequency regulation and control, and to make up for the lack of AC-side FM capacity. Finally, a simulation model of new energy transmission via four-terminal DC grid is constructed based on the PSCAD/EMTDC, which verifies the feasibility and effectiveness of the proposed improved coordinated control strategy and its AC grid frequency regulation.

Key words: voltage source converter multi-terminal DC, sag control, coordinated control, acceleration strategy, frequency control

吴云锐, 张建坡, 田新成, 应恺锋, 陈忠. 计及频率适应和快速稳定特性的多端直流电网改进协调控制策略[J]. 中国电力, 2025, 58(3): 31-42.

Yunrui WU, Jianpo ZHANG, Xincheng TIAN, Kaifeng YING, Zhong CHEN. Improved Coordinated Control Strategy of Multi-terminal DC Grids Considering Frequency Adaptation and Fast Stabilization Characteristics[J]. Electric Power, 2025, 58(3): 31-42.

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链接本文: https://www.electricpower.com.cn/CN/10.11930/j.issn.1004-9649.202406059

https://www.electricpower.com.cn/CN/Y2025/V58/I3/31

图/表 15

图 1 四端口VSC-MTDC模型

Fig.1 Four-port VSC-MTDC model

图 2 新能源站极U/f控制模型

Fig.2 New energy station pole U/f control model

表 1 协调控制模式对比

Table 1 Comparison of coordinated control modes

控制策略	模式切换	站间通信	不平衡功率	稳态电压偏差	主要缺陷
主从控制	需要	需要	主站承担	无差	动态特性差，稳定速度慢
电压裕度控制	需要	不需要	主站承担	无差	电压裕度整定复杂
直流电压下垂控制	不需要	不需要	共同承担	有差	功率分配精度低

图 3 频率调节下垂控制框图

Fig.3 Frequency regulation sag control block diagram

图 4 频率调节下垂控制电压-频率-出力特性分析

Fig.4 Frequency regulation sag control voltage-frequency-output characteristic analysis

图 5 加速策略原理

Fig.5 Acceleration strategy principle

图 6 ICC控制框图

Fig.6 ICC control block diagram

图 7 频率适应性ICC控制原理

Fig.7 Frequency adaptive ICC control principle

表 2 仿真模型基本参数

Table 2 Basic parameters of the simulation model

参数名称		数值
额定直流电压/kV		500
VSC1侧额定交流电压/kV		500
VSC1额定输送容量/MW		800
VSC2侧额定交流电压/kV		500
VSC2额定输送容量/MW		800
VSC3侧额定交流电压/kV		500
VSC3额定输送容量/MW		1200
VSC4侧额定交流电压/kV		500
VSC4额定输送容量/MW		1200

表 3 各控制模式主要参数

Table 3 Main parameters of each control mode

参数	VSC2	VSC4
主从控制 P_refj/MW		–750
下垂控制 P_refj/MW	–500	–750
下垂系数 k_j/(kV·MW^–1)	0.2	0.1
改进协调控制 P_refj/MW	–500	–750
单位下垂功率 ∆P_refj/MW	50	50
功率分配系数 K_j	0.1	0.2
频率下垂系数 k_fj	200	200
频率调节效应系数 K_sj/(MW∙Hz^–1)	1000	1000

图 8 VSC1退出运行仿真分析

Fig.8 VSC1 decommissioning simulation analysis

图 9 加速恢复能力仿真分析

Fig.9 Simulation analysis of accelerated resilience

图 10 频率适应性ICC参与场景1调频仿真对比

Fig.10 Frequency modulation simulation comparison of frequency adaptative ICC participating in scenario 1

图 11 负荷增大及切机状态调频能力验证

Fig.11 Verification of frequency modulation capability for load increasing and generator triping

图 12 负荷减小及切机状态调频能力验证

Fig.12 Verification of frequency modulation capability for load reduction and generator triping

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