一种基于多频段动态相量的LCC换流器电磁暂态建模方法研究

A Modeling Method for LCC Electromagnetic Transient Simulation Based on Multi Frequency Band Dynamic Phasor

为了提高仿真速度,在大规模交直流电网仿真中通常忽略换流器内部电力电子开关动作细节,重点关注换流器外部特性,动态相量法和频率偏移法常用来对换流器外特性进行建模。动态相量法通对信号进行时变傅里叶频率分解和移频变换,降低信号频率,能够增大仿真步长,但由于存在谐波截断误差,导致模型精度较低。频率偏移法一般适用于窄带信号,用于宽频域仿真时,无法采用大步长提高仿真速度。为了解决仿真精度和速度的矛盾。基于此该文建立换相换流器(line-commuted converter,LCC)的多频段动态相量模型,实现提高精度和增大仿真步长的目的。首先引入能够反映交流系统不对称的换流器改进开关函数模型,在此基础上,以六脉动为例推导LCC多频段动态相量耦合模型。然后,根据LCC的运行特性对上述模型进行频段解耦,得到多频段解耦模型,使其可应用于多核CPU的并行仿真。最后通过算例,验证该文多频段LCC动态相量模型的有效性。

In order to improve the simulation speed,in the large-scale AC/DC power grid simulation,the details of the action of the power electronic switch inside the converter are usually ignored,and the external characteristics of the converter are focused on.The dynamic phasor(DP)and the shifted frequency analysis(SFA)are often used to model the external characteristics of the converter.The DP performs time-variant Fourier frequency decomposition and frequency shift on the signal to reduce the signal frequency,which can increase the simulation step size.However,due to the harmonic truncation error,the model accuracy is low.The SFA is only applicable to narrow-band signals and not suitable for wide-frequency domain EMT simulation.In order to solve the contradiction between simulation accuracy and speed,the multi-frequency band dynamic phasor(MFBDB)model of line-commuted converter(LCC)converter was established to improve the accuracy and increase the simulation step.Firstly,an improved switching function model of LCC was introduced to include the asymmetry of AC system.Then a coupled and decoupled MFBDP model of LCC were derived respectively.The decoupled MFBDP model can be applied to parallel EMT simulation with multi-core CPU.Finally,an example was given to verify the validity of the MFBDP LCC dynamic phasor model.