Zero current and zero voltage static error control of a multi-cell dc/dc converter

In this paper we deal with the control of a two-cell DC/DC buck converter. The design is based on a discrete state space model obtained by expressing current and voltage at the beginning of the (n+1)th period in terms of values of the preceding period. It is shown that the describing model is nonlinear, therefore it is expected that a standard linear controller (e.g. PID) would not be efficient. In this work, we suggest four controllers which are simple to construct. The investigation of their performance is based on linear analysis. The controllers are designed step-by-step where each next controller improves the action of the previous one. The first controller (CI) is found to be the simplest that can lead to a linear closed loop system, hence it can be considered as a simple input-to-state linearizing controller. With the application of CI we can only obtain a correct reference current but the voltage remains uncontrollable. The second controller (C2) is the classic proportional controller. Although, it has remedied the problem of voltage controlling, it resulted in a constant static error of the current. After analyzing the first two controllers, a third controller (C3) is designed to achieve the correct reference values. The only drawback of C3 was the slow convergence of the current to the desired value. The fourth controller (C4) has been finally suggested to circumvent all the crossed drawbacks of the preceding controllers. The efficiency of C4 is shown using numerical simulations. The application onto a real circuit is being carried and results will be published in a future work.