VOLTAGE CONTROL OF A DC-DC BUCK CONVERTER FOR ELECTROLYSIS USING FRACTIONAL ORDER SLIDING MODE CONTROL

Abstract

Switching DC-DC converters are non-linear and the most widely used circuits in power electronics. Generally, they are used in all conditions where there is need of stabilizing a given DC voltage to a desired value. DC-DC buck converters are used in voltage step down applications. A DC solar energy is converted to the desired voltage level using the a buck converter, for hydrogen generation with electrolysis process have been investigated. The electrolysis load for hydrogen production especially needs low voltage and high currents. To have these conditions the converter must be designed and controlled sensitively. For this aim, the fractional order sliding mode (FOSM) controller is used as a solution in this paper. Simulation results showed that, FOSM controller improved the rise time and settling time by 2% and 15.3% respectively compared the values using PID controller. Similarly, FOSM controller shows comparatively best performance improvement over SOSM in terms of high reduction of unwanted oscillation in addition to the rise time, settling time improvements. The overshoot is reduced from 46.3% to 5.208% using PID controller while it is totally removed when SOSM and FOSM controllers are applied. Both SOSM and FOSM controllers overcome the effect of electrolysis load variations. The actual output voltage is not deviated from desired value even for large input voltage variation using FOSM controller. Furthermore, the performance of controller was tested by increasing and decreasing 58.52% electrolysis load from operating point while desired output voltage is decreased by 50% and increased up to 20% from operating point. Generally, from the above analysis results it is evident enough that FOSM is better and preferable controller than the SOSM and PID controller