基于单周控制的三电平三相四线制有源电力滤波器

针对电力工业三相四线制系统的零线电流、谐波、无功功率和三相不平衡问题,以及高电压、大容量有源电力滤波器APF(Active Power Filter)控制方案复杂的问题,提出一种单周控制的三电平三相四线制APF,其产生的补偿电流与负载的有害电流分量大小相等、方向相反,从而使得经该APF补偿后,电源电流只含有负载电流的基波有功分量。主电路采用三相三桥臂结构的三电平二极管箝位变换器,既无需升、降压变压器,也无需动态均压电路;控制策略采用单周控制,其兼有调制和控制的双重性,控制器结构简单,具有控制精度高、补偿效果好,滤波器工作于恒定开关频率的特点,适合推广到工业应用。在建立数学模型的基础上进行了仿真研究,仿真结果证明其能有效地补偿系统谐波、零序和无功电流,从而提高输电线功率因数和传输效率。

Three-level three-phase four-wire active power filter based on one-cycle control

Aiming at the neutral line current,power harmonic suppression,reactive power elimination,3-phase load balance in 3-phase 4-wire power system and the control complexity of high voltage and high power APF(Active Power Filter),3-level 3-phase 4-wire APF based on one-cycle control is presented.The compensating current generated by APF is equal to the harmful component of load current in amplitude and converse in polarity.After compensation,the power source current contains only fundamental active power component of load current.3-level diode-clamped converter with 3-phase 3-arm structure is employed as main circuit in the APF,so that neither coupling transformers nor dynamic voltage sharing circuits are needed.One-cycle control method is applied with simplified circuit,high precision and effectual compensation,which has both modulation and control characteristics.It employs constant switching frequency modulation that is desirable for industrial applications.On the basis of mathematic model development,simulation is carried out.The simulation results verify that the APF can effectively compensate power harmonics,reactive power and zero-sequence currents.Power factor and transmission efficiency of power lines are thus improved.