A Study On Hybrid Control Of DC/DC Converter Based On Hybrid Automata Model

With the rapid development of modern production technology, the power conversion techniques has been applied to every aspect of social life and industrial production and also has a broad application and development prospect. During actual work process, the switching operation interacts with continuous-time dynamic characteristics, which causes the DC/DC converter to possess nonlinear characteristic.Actually, the traditional modeling and control methods have fatal limitations and the application of the classical theory of circuit has been unable to analyze these topologies perfectly. Therefore, reasonable modeling process and control method have important theoretical and engineering value for the analysis,design and application of the power converter.Power converter circuit can be viewed as a kind of hybrid systems. This dissertation analysis the working process and the state space equation which describe the subsystems under different status of the DC/DC converter. Meanwhile, the hybrid automata model was established based on the hybrid control theory. And then the design of the controller was introduced in detail, the stability of the system was also analyzed particularly when the load changed. The main contributions of this dissertation are described as following:(1)Firstly, in response to the hybrid features of the switch, the hybrid characteristics of the DC/DC converter were analyzed with hybrid theories. In this paper, the Boost DC/DC power converter was listed as an example, its working characteristics in a cycle was introduced and the hybrid automata was establish with the theory of hybrid system. And also the switching boundary conditions were deduced when the system working in CCM and DCM mode by using the energy conservation law. Based on these, a new algorithm was proposed that the output current was estimated according to the principle of capacitor charge conservation after the load changed, thus lead in the hybrid control of DC/DC converter. By this way, it reduced the amount of detection and simplified the controller designing.(2)Secondly, according to the requirements of the converter, hardware circuit designs of the inverter based on hybrid automata are conducted. The design criterion and selection method of parameters in the main circuit are given, including the driving circuit design, current sampling circuits and their conditioning circuit for ADC.(3)Finally, the variables of the algorithm were digitized by using the digital control and the control block diagram was designed. Meanwhile, the program flow chart of digital control based on TMS320F28335 DSP numerical controller is given,and the configuration of the peripherals including sampling methods is also provided in detail. And then, the software design of entire system is carried out under Code Composer Studio.In order to verify the theoretical analysis, a simulation study on the platform of MATLAB/Simulink and hardware experiments were carried out. The results show that this control algorithm is not only simple but also has a good dynamic performance.