可变频变压器数学模型及仿真分析

可变频变压器(variable frequency transformer，VFT)是一种概念新颖、性能优越的异步电网互联装置。文章简要介绍了VFT的基本结构和工作原理，建立了VFT的数学模型，推导了VFT传输功率与驱动转矩之间的函数关系，在此基础上提出了VFT的控制策略和数字仿真思路。通过PSCAD/EMTDC中的三相绕线式异步电机来表征VFT中的旋转变压器模型进行仿真试验，结果验证了数学模型的正确性以及控制策略和仿真模型的可行性，同时说明了采用VFT进行异步电网互联与HVDC相比的突出优势：调节平滑，具有更好的电压质量并且能够抑制故障，有较好的稳定性。

Mathematical Model and Simulation Analysis of Variable Frequency Transformers

Variable frequency transformer(VFT) is an asynchronous network interconnection device with a new conception and superior performance. In this paper the basic structure and working principle of VFT are presented and a mathematical model of VFT is built,and the functional relation between the transmission power and driving torque of VFT are derived. On this basis,the control strategy and the thinking of its simulation are proposed. The model of rotating transformer in VFT is characterized by three-phase asynchronous machine with wound rotor in PSCAD/EMTDC software and the simulation experiment is conducted. Simulation results show that the proposed mathematical model is correct and both control strategy and simulation model are feasible,meanwhile,comparing with HVDC,the evident superiority of VFT such as smooth adjustment,better voltage quality and excellent performance in fault restraint and more stable operation are explained.