AC-(LCC)DC系统的全电磁暂态数值计算方法一:数学模型

Numerical Algorithm of Full Electromagnetic Transient Simulation for AC-(LCC)DC Hybrid Power Grids Part 1——Mathematical Modelling

为实现大规模交直流混联电网快速、准确的全电磁暂态仿真计算,需要研究、开发新的仿真计算方法。为此,采用状态空间法及Park变换,该文第一部分首先建立了交流-电网换相换流器型高压直流输电(AC-line commutated converter high voltage direct current,AC-(LCC)DC)混联系统的全微分数学模型。在不计变压器非线性特性的情况下,推导了能够反映变压器变比、接线方式以及相移等特性的电磁暂态模型;考虑换流变压器的接线方式,将换流变-换流器-平波电抗器作为一个整体来考虑,建立了电网换相换流器型高压直流输电(line commutated converter high voltage direct current,LCC-HVDC)输电系统的全微分电磁暂态模型;通过在发电机与出口变压器之间接入一个三相对地电容,简捷地解决了机-网接口问题。通过引入附加状态变量,将上述模型以及锁相控制器中的非线性部分转化为二次型向量,由此,建立了基于二次向量场形式的AC-(LCC)DC系统全微分计算模型,为第二部分的电磁暂态仿真计算提供基础。

In order to accurately and quickly compute the full electromagnetic transient process of the large-scale AC/DC hybrid power grids,it is necessary to study or develop new numerical methods.To this end,by using the state-space method and the Park transformation,in the first part of this paper the full differential model for AC-(LCC)DC(AC-line commutated converter high voltage direct current)system is established.In the case of ignoring the nonlinear characteristics of the transformer,an electromagnetic transient model which reflects the characteristics of the transformer ratio,the winding connection modes,and the phase shift is derived;Considering the connection modes of the converter transformer,and taking the converter transformer,the converter and the smoothing inductor as a whole,a fully differential electromagnetic transient model of the LCC-HVDC(line commutated converter high voltage direct current)system is built;The machine-network interface problem is treated simply and conveniently by inserting a three-phase grounded capacitor between the generator and the outlet transformer.By introducing the additional state variables,the nonlinear part involved in the above model and the phase-locked controller has been transformed into a quadratic vector,thus a full differential model of the AC-(LCC)DC system in the form of the quadratic vector field is established.The derived mathematical model provides the basis for the electromagnetic transient simulation to be described in the second part.