Hybrid Control of a Tri-state Boost Converter

A tri-state converter has three controllable switches and hence has more operating flexibility. This also brings additional control design flexibility when viewing the converter as a hybrid dynamical system. The operational and control design flexibility of a tri-state boost converter is explored in this paper to control its output voltage. The analysis and control design for the converter is based on an exact hybrid automaton model. The hybrid control design is carried out to ensure the required voltage regulation and switching stability. Using a system theoretical approach, a geometrical region in the state plane around the set point is determined as a stable 'safe-set' by ensuring that a vector field of the system pointing towards the set point always exists to ensure the stability of switching in the converter. Within this stable region, the guards for the hybrid automaton model are determined as the switching control law to satisfy the regulation requirements. The control algorithm is tested using a model of the tri-state boost converter constructed in MATLAB/SIMULINK environment. Modeling, analysis, control design and simulation results are presented. Using the proposed control scheme, it is found that the tri-state converter can work with a wide range of loads and input voltages without compromising on regulation requirements.