In order to verify the ability of transformer to withstand short-circuit impact under special working conditions, dynamic thermal stability test on transformer must be conducted. Bcause of dynamic thermal stability test generating a huge impact on the power grid, so independent power system is needed for the this test. A new type of power system based on cascaded H bridge used for dynamic thermal stability test is put up,which can be worked independent of the grid. This power system can effectively reduce the stress of the switching devices on each of the H bridge by adopting many cascade connection ways and reduce the harmonic content (THD) of AC. In this paper, the equivalent simulation model of the main circuit of the power system was built based on MATLAB simulation software, and the harmonic content generated by the system was analyzed and calculated. The simulation results verified the feasibility and effectiveness of the system.
 

Multilevel, Inverter, Cascaded H bridge