Stability Analysis And Research Of Cascaded Converters For Distributed Power Systems

DC converter cascade technology has been widely applied in the field of consumer electronics; communication power supply; board power supply and power adapter products. The typical cascade structure has played an important role in energy conversion and efficiency transmission. In this paper, the stability problem of two cascade DC-DC converter is analyzed in the background of distributed power system.Firstly, advantages and disadvantages of the cascade structure are introduced in this paper. And the stability problems of the DC-DC converter cascade is analyzed and the stability criterion is introduced. The DC-DC converter usually uses closed loop control to achieve constant voltage output. the problem of instability, caused by a negative resistance effect, can be described through constant power equivalent. Cascaded DC-DC converters are classified and the equivalent control block diagram and closed-loop control block diagram are described. By the impedance the stability of the converter cascade can be judged and through the Nyquist criterion the stability of the cascade structure can be analyzed.Secondly, the open-loop small signal model of Buck and Boost converter is set up, along with gain function and impedance function. Because the current control has very common applications, and the current loop has decoupling effect.Then the current loop decoupling model is set up and its control block diagram is described; meanwhile the voltage, current closed-loop is given and the input and output impedance function is built. Then from the converter impedance angle,the loop gain compensation and the closed-loop control mode are analyzed, to achieve impedance optimization and improve the stability of the cascade.Finally, by means of control theory of Bode plot and the Nyquist impedance criterion and loop analysis theory, the cascade converter design basis is summed up. The feasibility of the design basis is verificatied by the Matlab simulation.After the circuit parameters design and component selection is given in detail, the prototype of a two-cascade Buck converter is designed and the experiments are made on this prototype. The simulation and experiments show that the design for converter stability cascade is reliable and correct.