Harmonics, reactive power and three-phase unbalanced current have become common power quality problems in power systems. This paper researches on a modular smart power quality correction device based on the three-phase four wire diode clamped three-level topology, which can achieve harmonic suppression, reactive power compensation and three-phase unbalanced management. This paper presents the instruction current extraction algo-rithm based on instantaneous reactive power theory, and combined with the harmonic extraction algorithm based on discrete Fourier transform, fundamental negative sequence current and zero sequence current, reactive current and harmonic are tracked, and by the use of PI controller paralleled with repetitive controller, the direct control of the instruction current in static three phase ABC coordinate system is carried out. It is verified by experiments that the three-phase four wire modular three-level smart power quality correction device designed in this paper can not only dynamically compensate the reactive power, unbalanced and harmonic currents of the system, but also achieve dy-namic setting of different kinds of compensation capacity.%谐波、无功以及三相不平衡是电力系统中常见的电能质量问题.本文研究了基于三相四线制二极管钳位型三电平拓扑的模块化智能电能质量补偿装置,它可以实现指定次谐波补偿、无功功率和三相不平衡补偿.本文基于瞬时无功功率理论提取三相不平衡及无功补偿指令电流,并结合基于离散傅里叶变换的谐波提取算法,将负载电流中的基波负序电流、零序电流、无功电流和特定次谐波电流分离提取,通过PI控制器和重复控制器的并联,实现在静止三相ABC坐标系下指令电流的直接控制.经实验验证,本文所提的三相四线制模块化三电平智能电能质量补偿装置不仅可以动态补偿系统的无功、不平衡以及谐波电流,而且可以实现不同种类补偿容量的动态设置.
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