混合级联直流输电系统整流/逆变不同控制回路动态交互作用与稳定性研究

Research on Dynamic Interaction and Stability of Rectifier/Inverter Control Loop in Hybrid Cascade HVDC System

为了研究混合级联直流输电系统整流侧和逆变侧各换流器控制系统间的交互作用,文中首先建立混合级联直流输电系统的状态空间模型,并推导得到系统的多输入多输出传递函数模型。然后针对不同的研究目标,根据单通道分析设计理论建立等效单输入单输出反馈控制模型;在此基础上,分离出不同控制回路的耦合控制通道,定量评估系统强度、逆变侧交流联络线与控制参数等对控制回路间交互作用的影响。理论分析表明,当整流侧或逆变侧交流系统强度降低时,两侧控制回路间交互作用增强;当交流联络线长度缩短时,逆变侧电网换相换流器(line commutated converter,LCC)和模块化多电平变换器(multilevel modular converter,MMC)控制回路间的动态交互增强,各控制环节参数之间存在相互制约关系。最后,在PSCAD/EMTDC上搭建混合级联直流输电系统的电磁暂态详细仿真模型,验证所建立单输入单输出反馈控制模型及上述理论分析结果的正确性。

In order to study the interaction between the converter control systems of rectifier and inverter of hybrid cascaded high voltage direct current(HVDC)system,the state space model of hybrid cascaded HVDC system is established.The multi-input-multi-output transfer function model of the system is obtained based on the state space model.Then,the equivalent single-input-single-output feedback control model is established according to the multivariable feedback control theory for different research objectives.On this basis,the interaction between different control loops is quantitatively analyzed and the effects of system strength,electrical distance and control parameters on the interaction between the control loops are revealed.It is concluded that the interaction between the control loops is enhanced when the SCR of rectifier or inverter decreases,and the dynamic interaction between the line commutated converter(LCC)and multilevel modular converter(MMC)control loops on the inverter side is enhanced when the length of the AC tie line is shortened,and the parameters of each control loop restrict each other.Finally,the detailed electromagnetic transient simulation model of hybrid cascaded HVDC system is built on PSCAD/EMTDC to verify the effectiveness of the established single-input-single-output feedback control model and the correctness of the theoretical analysis results.