单相桥式逆变电路变压器直流偏磁研究与抑制

Investigation and Restraining of Magnetic Bias for the Output Transformer of Full Bridge Single-phase Inverter Circuit

分析了SPWM桥式逆变电路中工频变压器产生直流偏磁的原因,主要包括控制系统产生的直流分量、零点漂移、开关管特性不一致及系统动态响应对它的影响,并在此基础上提出了一种解决方案。通过检测变压器初级输入电压中所包含的直流分量,经隔离滤波后将其反馈给参考正弦电压以调节SPWM脉宽。该方案已成功应用于一台80kVA电力UPS中。经实验验证,该方案适用于UPS带阻性、整流性及半波负载等多种情况。阻性负载时,其输入电流中的直流分量由未加调节的15.4A减少到7.1A;半波负载时,其输入电流中的直流分量由未加调节的15.8A减少到5.5A。实验证明,该方案可以有效地抑制单相桥式逆变电路输出变压器的直流偏磁问题,且易于实现。

The main factors resulting in magnetic bias of the output transformer of full bridge SPWM inverter are analyzed, including the direct-current component of control system, zero floating, inconsistent characteristic of transistor, dynamic response of system,and so on.Then,one solution is proposed to overcome the problem.The solution is that,firstly, we can detect the input current＇s DC component value of the transformer,and put it through isolate and filter modules. Secondly,we can feedback the value to the reference voltage in order to adjust the width of SPWM pulse.The experimental results on an 80kVA Plant UPS show that the method is applicable to many occasions such as the UPS is feeding with resistance load,rectifier load and half-wave load.When the UPS is feed with resistance load,the DC component input of current values will change from 15.4A （ without magnetic bias method） to 7.1A;when the UPS is feed with rectifier load, the input current＇s DC component values will change from 15.8A （without magnetic bias method） to 5.5A.From the experiments,we can get the conclusion that this project can be effective for restraining magnetic bias for the output transformer of full bridge single-phase inverter circuit and it is easy to realize.