分析了导致SPWM 逆变器输出变压器偏磁的几种主要因素：控制系统引起的偏磁，驱动电路元件参数的分散性引起的偏磁和主电路引起的偏磁以及偏磁对逆变器的影响，其中控制系统所引起的偏磁是主要因素。在此基础上提出基于DSP的单相逆变器直流偏磁抑制技术，通过检测变压器原边的直流电流并进行闭环数字PI控制，可使原边的直流电流值稳态下近似为0。仿真和实验结果表明, 所提出的方案可以有效地抑制逆变器变压器的直流偏磁。关键词： SPWM 逆变器； 偏磁；PI控制；DSPAbstract：The key factors which result in output transformer bias magnetic in SPWM inverter are analyzed.These factors include control system, the difference between the device parameters of drive circuit and the main circuit. And the first factor is main. An anti-bias-magnetic method used in single phase inverter based on DSP digital control is presented. The direct current of transformer primary windings is sensed. Under the PI closed-loop control, the stable state direct current of transformer primary windings will be approximately 0.Simulation and experimental results show the proposed method is simple and effective, and the magnetic bias in the transformer of inverter can be restricted.Key words: SPWM inverter; magnetic bias;PI control ; DSP