Double-Integral Type of Indirect Sliding Mode Controller for Power Buck Converters fed with Constant Power Loads

Abstract

This article signifies the robust nonlinear technique to solve instability issues of dc-dc buck power converter connected with constant power load. When power electronic converter operates under tightly regulated condition will have constant power behavior at its input terminals.  This CPL will exhibit NII (negative incremental impedance) behavior, it is the main root cause of instability problems in the system. These instabilities can be eliminated by using the nonlinear controller of SMC. The Performance of a sliding mode controller (SMC) is mainly inclined by the choice of the sliding surface. SMC provides robust control actions in aspect of system uncertainties and eliminations steady-state error. For this, it uses integral SMC for tracking voltage error terms in its sliding surface. But it is ineffective to mitigate the steady state voltage errors, this can be overcome by the double integral SMC, i.e., an additional double integral term of controlled variable to be adopted for designing the sliding surface of the indirect sliding mode controller. To check the effectiveness of DISMC, in view of instability issues of CPL in buck converter system, a 24-12V, 100 W prototype buck converter was considered, and verified in MATLab/Simulink environment.