基于PET控制特性的交直流配电网直流侧低频振荡分析

随着新能源、储能和柔性直流技术的发展，交直流混合配电网逐渐成为未来配电网的重要发展方向，大量电力电子设备接入给配电网带来了低频振荡等动态问题。为深入研究交直流混合配电网直流侧低频振荡问题，文中根据交直流配电网系统实际工程应用，对电力电子变压器主阀塔中的H桥串联和隔离型双向有源桥结构、三相逆变器以及三相Buck变换器等关键环节进行详细建模。通过时域仿真，复现了该交直流配电网实际工程中直流侧的4 Hz低频振荡现象，验证了所建数学模型的正确性。基于所建数学模型对功率和控制器参数等关键影响因素进行了定性分析，最终得出结论如下：功率水平、Buck环节电压环控制参数影响系统稳定性；Buck环节电流环积分系数影响振荡频率。

Analysis for low frequency oscillation on the DC side of AC/DC distribution network based on PET control characteristics

With the development of new energy,energy storage,and flexible DC technology,AC/DC hybrid distribution networks have gradually become an important development direction for future distribution networks. The access of a large number of power electronic devices has brought dynamic problems such as low frequency oscillations to the distribution network. In order to deeply study the low frequency oscillation problem on the DC side of AC/DC distribution networks,detailed modeling of key links is conducted such as H-bridge series and isolated bidirectional active bridge structures,three-phase inverters,and three-phase Buck converters in the main valve tower of power electronic transformer. Through time domain simulation,the 4 Hz low frequency oscillation phenomenon on the DC side of the AC/DC distribution network in the actual project is reproduced,and the correctness of the established mathematical model is verified. Based on the established mathematical model,qualitative analysis is conducted on key influencing factors such as power and controller parameters,and the final conclusions are as follows:power level and Buck link voltage loop control parameters affect system stability,the integral coefficient of the current loop in the Buck link affects the oscillation frequency.