针对高压交流输电系统输电距离不足和高压直流输电系统投入成本过高的问题,提出了一种基于模块化多电平矩阵变换器(M3C)的分频输电(FFTS)系统.在不升高电压等级的条件下,通过降低远距离输电线路中交流电的频率来减小输电的电气距离,从而提高输电功率,实现交流电远距离输电的目的.M3C是一种新型的电力电子变换器,具有可以在高压、大功率和低频条件下稳定运行的特点.提出了一种基于改进电压空间矢量法的M3C控制策略.采用H桥臂两端的电压代替输出端的有功功率,进行脉冲宽度调制PWM控制.根据直驱式风力发电机的最大功率跟踪原理和分频输电系统的频率特性,提出了一种分频输电系统的低频侧频率控制策略,即在追求最大功率的同时,保证输出频率控制在10~20 Hz.最后采用MATLAB/Simulink进行仿真,验证了这两种控制策略的有效性.%For the problems that the transmission distance of the HVAC transmission system is insufficient and the high input costs of the HVDC transmission system,the fractional frequency transmission system(FFTS) based onmodular multilevel matrix converter(M3C) is proposed. It refers to reducing the electrical distance of the transmission by reducing the frequency of current in long distance transmission line while without increasing the voltage level,thereby improving the transmission power and achieving the goal of long distance AC transmission.As a new type of power electronic converter,M3C features the ability to operate stably under high voltage, high power and low frequency conditions; it can be used as a cross-over frequency converter for fractional frequency wind power system. An improved voltage space vector method is put forward to be used as the control strategy of M3C. The active power at the output end is replaced by the voltage across the H bridge arm to control the PWM. According to the maximum powerpoint tracking principle of direct-driven wind turbine generator and the frequency characteristics of the fractional frequency transmission system,the frequency control strategy forthe low-frequency side is proposed,that is,in the pursuit of maximum power at the same time,to ensure that the output frequency controlled in 10~20 Hz.The effectiveness of these two control strategies are verified by simulation.
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