Research On Buck Converter Loaded By Constant Power Load

All kinds of power electronic building block modules are widely used with the development of power electronics, especially the development of distributed power applications in a wide range, as well as the more electric technology. DC/DC converters are used in the field of aerospace, aircraft, ships, electric cars and communication power supply. Power electronic converters act as an important class of secondary power in the independent power systems.One power electronic converter can be viewed as a basic unit of a system. And the interaction between the converters constitutes the core issue of the interconnected system. Converter can be stable when working independently, but in the cascaded working state, dynamic characteristics could be bad and even system instability may appear. In most cases, the closed-loop control of DC/DC converter loaded by constant power load has the characteristic of negative impedance, and the negative impedance characteristic of the constant power load is one of the main reasons leading to system instability.This paper selected a flyback converter of closed-loop control as the load converter, and the first stage used a step-down circuit as the source converter. These two stages formed a two-stage cascaded system. Secondly, this paper respectively described the principles of two control modes of the switching power supply control circuit, the Middlebrook criterion based on the cascaded system, respectively derived the transfer function of the Buck converter and flyback converter, designed the regulator, calculated the component parameters and developed two closed-loop hardware circuits of converters. Simulation based on MATLAB software verified the correctness of the design.Finally, using passive damping method, the stability control of the two cascaded system was implemented. The simulated waveforms and experimental waveforms were given and verified the correctness of the control strategy.