模块化多电平矩阵换流器准比例谐振控制研究

Research on Quasi-proportional Resonant Control of Modular Multilevel Matrix Converter

模块化多电平矩阵换流器(MMMC)作为一种新型的AC/AC变换装置,在分频输电等低频大容量场合很具优势,但其桥臂电流的控制较为复杂。首先对MMMC的拓扑结构进行分析并建立了数学模型,研究了桥臂电流的构成。针对桥臂电流传统的直接控制法控制精度较差的问题,引入了准比例谐振(QPR)控制策略,根据分频输电系统的特性设计了基于输入输出频率的准比例谐振控制器。根据系统有功和无功的控制要求,给出了定有功控制和定无功控制的外环控制策略。同时,推导了子模块电容电压和有功功率的关系,并对其应用双Clarke变换,提出了基于系统有功功率的子模块电压平衡策略。最后,在仿真平台上搭建了MMMC-FFTS系统仿真模型,对系统的稳态和暂态响应分别进行了仿真,并对直接控制和QPR两种控制方法的仿真结果进行了比较。仿真结果表明:改进的控制方法具有良好的稳态和暂态性能,且参考值跟踪精确度更高,验证了所提方法的可行性与优越性。

As a new AC/AC conversion device,modular multilevel matrix converter(MMMC)has advantages in low frequency and large capacity applications such as fractional frequency transmission system,whereas its bridge arm current control is complicated.In this paper,the topological structure of MMMC is analyzed and the mathematical model is established to study the structure of bridge arm current.In order to solve the problem of poor control precision of bridge arm current by traditional direct control method,quasi-proportional re-sonant(QPR)control strategy is introduced,and a quasi-proportional resonant controller based on input and output frequencies is designed according to the characteristics of fractional frequency transmission system.According to the control requirements of the system active and reactive power,the outer loop control strategy of constant active power control and constant reactive power control is given.At the same time,the relationship between the capacitive voltage of the sub-module and active power is deduced,and the voltage balance strategy of the submodule based on active power of the system is proposed by applying double Clarke transform.Finally,the MMMC-FFTS system simulation model is built on the simulation platform,the steady-state and transient response of the system are simulated respectively,and the simulation results of direct control and QPR control methods are compared.The simulation results show that the improved control method has good steady-state and transient performance,and the accuracy of reference tracking is higher,which verifies the feasibility and superiority of the proposed method.