The Common Mode Voltage Control Using a Hybrid Compensation Structure and Derivative Method

Abstract

In this paper, the hybrid compensation loop is introduced to the front end of the load, which can increase the electromagnetic interference current shunt loop, and basically eliminate the common mode noise in the three-phase inverter from the perspective of the interference source. The expressions of the controlled voltage source and the parameter calculations of the shunt path are given in detail. The state of the controlled voltage source is determined by the instantaneous voltage of each phase bridge arm, which has already included the sequence of pulse width modulation, so the common mode noise can be eliminated under different modulation modes. An active method of suppressing common mode (CM) is proposed to regulate the high-frequency CM voltages on the AC buses with respect to the ground. The resultant CM compensation voltages are rendered symmetric to the AC common mode noise, so that load midpoint voltage relative to ground remains constant or zero. The experimental results demonstrated that the common mode voltage can be suppressed by the added compensation circuit effectively under the 2D-SVPWM non-zero vector modulation and 3D-SVPWM non-zero vector modulation. The amplitude, harmonics and frequency of the load voltage isn’t affected by the method of eliminating the common mode voltage.