| Distributed power architectures comprised of power electronic converters are becoming increasing common in recent years. Tightly regulated closed-loop converters exhibit instantaneous constant-power-load (CPL) characteristics. Without appropriate controls, the negative impedance characteristics of CPL may lead to significant oscillations in the output voltage of feeder converters and impact power quality and system stability. And because of the nonlinearity of converters, classical linear control methods, which are often used to design controllers, have stability limitations. This paper introduced nonlinear control theory into modeling and control design of interconnecting converters to ensure large-signal stability.Take a Boost converter operating with an inverter as an example, the nonlinear characteristics, dynamics, and stability problems are analyzed firstly. Tightly-regulated inverters, which have negative impedance characteristics at the input terminals, might seriously impact the dynamics and stability of the Boost converter.Then, this paper presents an exact linearization technique for DC-DC converters feeding inverters. An affine nonlinear model of a Boost converter operating with an inverter has been set up by introducing control aims into system state equations. Exact state feedback linearization is proved to be easily performed on this model. A nonlinear feedback can be found to cancel the nonlinearity of the interconnecting system.Finally the classical control theory and the optimal control method are respectively used to deduce the control law of the transformed linear system and nonlinear controllers derived can approximately linearize the system. The controllers are exemplified and validated by a Matlab Simulation model. Simulation results illustrate that the output voltage of the boost converter feeding an inverter has a large-signal stability characteristic. It is conclude that state feedback exact linearization ensures cascaded systems operating steadily. |
PDF Full Text Request