Cascaded sliding mode control for global stability of three phase AC/DC PWM rectifier with rapidly varying power electronic loads

It can be seen presently widespread electrification of high power vehicular systems such as more electric aircrafts and electric ships. To further improve the efficiency, flexibility and reliability of such systems, zonal DC electric distribution technology is proposed. In most cases, the zonal DC bus is fed by front-end AC/DC voltage source rectifiers and is responsible for supporting many onboard loads with complex dynamic characteristics. Due to the small-signal constant power nature of tightly regulated power electronic loads and the large-signal load variations, stability of the zonal DC bus becomes a major concern. It is clear that conventional PI controllers stabilize the system in a small-signal sense. However, they are ineffective under some large-signal disturbances and load changes. Passivity based control method is known to provides global stability under passive loads, such as resistive loads. Nonetheless, the global stability of voltage regulation with nonlinear loads has not been discussed. This paper proposes a cascaded sliding mode control method with global stability and online observation of load power. Moreover, system stability limit constrained by catastrophic bifurcation is also discussed. Simulation results are provided to verify the proposed method.