The Research Of DC-DC Converters Based On Switching Control

DC-DC power converters have received great attention both in power electronics and the automatic control community. This is due to its extensive applicability in the related fields that range from domestic equipments to advanced communication systems. A DC-DC converter forms an interesting case study because it is a variable-structure nonlinear system in the automatic control field. Although there are many advanced control methods for regulation of the DC-DC power converter circuit, they still have some inadequacies in urgent need of further optimization. This thesis studies an important kind of DC-DC power converter--Boost converter, from a switching control viewpoint. The study includes the following two aspects.Three main nonlinear controllers, namely, feedback linearizing controller, passivity-based controller and sliding mode controller based on well-known average PWM model, are introduced and their designs and performances are compared from the theoretical analysis and the simulation results of MATLAB. The non-minimum phase feature of boost converters makes it hard to achieve perfect tracking of output voltage reference signals. In the design, we resort to a feasible regulation alternative based on an indirect output capacitor voltage control, achievable through the regulation of the inductor current. Based on the analysis and comparison, this thesis constructs a switching between these nonlinear controllers under a hybrid switching rule, which fulfills the complementary advantages of each controller and improves the dynamic performance of this system studied. Also, the dwell time method is used to analyze the stability of the system.A switched system is defined by the pulse width modulation (PWM) and the pulse frequency modulation (PFM), and a switching law between PWM and PFM is designed. First of all, each subsystem is analyzed under the influence of the adaptive passivity-based controllers and adaptive laws, separately. Secondly, a common Lyapunov function of the switched system is constructed through the analysis of the subsystem, which means the switched system is always global uniform asymptotic stability under arbitrary switching. On this basis, in order to improve the dynamic performance of PSM, and increase the load range of the switched system and advance the whole conversion efficiency, we design duty ratio-dependent switching and load-dependent switching separately to achieve switching between PWM and PSM. On the one hand, this design makes the switched system have wider load range and a certain referential value in comparison with the sole modulation; on the other hand, the switched system has good robustness because of the application of adaptive law.A large number of simulation results showed that under the designed switching rule, the system has satisfactory tracking performance, goodish steady state and dynamic performance. This indicates that the control strategy we proposed can meet the requirements of DC-DC Power converters. Moreover, the forms of the controllers are simple, and it is easy to implement and the effect is obvious.