Analysis of stable area of two-cell cascaded H-Bridge rectifier

In this paper, analysis of the stability in two-cell cascaded H-bridge (CHB) rectifier is presented. The stability problem is caused by the couple controllers which are used to balance the DC-link voltages of each cell. The analysis is carried on by phasorial diagram method and general conclusions about the stable area are derived. Based on the conclusions, the stable area is continued to study for a practical control scheme. The index λ_p is introduced to denote the unbalance degree of the two-cell rectifier. Then the stable area is defined by a group of equations. The stable area expression shows that the grid voltage, DC-link reference voltages and the expected power factor are all contributed to the stable area. Experimental results are given to verify the feasibility and validity of the proposed method.