多电压等级直流配电网平均动态相量建模及稳定性分析

为了精确实现多电压等级直流配电网的稳定性评估和时域模拟,提高系统分析效率,提出基于双有源全桥(DAB)直流变压器电流重构的多电压等级直流配电网平均动态相量建模方法.以系统中各变量的动态相量作为状态和输入变量,并通过忽略其高次分量,降低模型的复杂性.引入误差修正,将等效移相占空比作为修正后的代数变量,降低忽略高次动态相量所引起的偏差,实现对平均动态相量模型中直流变量的准确表征;采用傅里叶级数对模型无法精确描述的变压器电流进行重构,实现对平均动态相量模型中交流变量的准确表征.在单个DAB变压器平均相量模型基础上,引入直流线路方程,形成可拓展的系统全局模型.分析对比基于MATLAB/Simulink的多电压等级直流配电网平均动态相量模型和电磁暂态模型,在负荷突增和断线故障2种场景下证明所提出的平均动态相量模型和电流重构方法的正确性和准确性,并在变压器频率和漏感变化时,验证了系统全局模型的稳定性.

Average Dynamic Phasor Modeling and Stability Analysis of Multi-voltage-level DC Distribution Network

For the purpose of accurately realizing the stability evaluation and time domain simulation of multi-voltage-level DC distribution networks and improving the efficiency of system analysis, an average dynamic phasor modeling method of the multi-voltage-level DC distribution system based on current reconstruction of the dual-active-bridge (DAB) DC transformer is proposed. The dynamic phasor of each variable in the system is taken as state or input variables, and the complexity of the model is reduced by neglecting its high-order component. The equivalent phase shift duty cycle is regarded as the modified algebraic variable by introducing the error correction, and the deviation caused by neglecting the high-order dynamic phasors is reduced, so that the accurate characterization of the DC component in the average dynamic phasor model is realized. Fourier series (FS) is used to reconstruct the transformer current which cannot be precisely described. Thus, the AC variables in the average dynamic phasor model are accurately characterized. Based on the average phasor model of a single DAB transformer, the DC line equation is introduced to form an extensible global model of the system. By analyzing and comparing the average dynamic phasor model and the electromagnetic transient model of a multi-voltage-level DC distribution network based on MATLAB/Simulink, the correctness and accuracy of the proposed average dynamic phasor model and current reconstruction method are proven in the two scenarios of sudden load increase and line breakdown. Also, the stability of the system global model with changing the transformer frequency and leakage inductance is verified.