An improved drive signal exchange strategy for cascaded H-bridge topology

In order to solve the inherent problem of ‘even power distribution’ or ‘dc-link capacitor voltage balance’ in the cascaded H-Bridge topology, the so called drive signal exchange scheme is always employed. However, the conventional exchange scheme ignores the problem of extra switching during the execution process which increases switching losses. The cause of switching cost increase during exchange process is deeply analyzed in this paper. In order to solve this problem, taking all kinds of potential exchange cases into consideration, this paper proposes an improved strategy which can eliminate extra switching totally. This algorithm makes a full use of the natural PWM action and optimize the exchange procedure to realize the switching states exchange. Finally, the validity and effectiveness of the proposed strategy is confirmed by several experimental tests on a seven-level cascaded H-bridge system.