Abstract
The paper considers a control system for a DC/DC converter with frequency-pulse modulation, which takes into account the possibility of undesired oscillations at the output associated with dynamic nonlinearities of the system. The device considered in the work is an automatic feedback control system based on a proportional controller, that is, it is the simplest system with droop. The structure of the control system is proposed, it includes an additional control system for nonlinear dynamic processes, built on the basis of the target-oriented control. This makes it possible to provide the desired dynamic mode when changing the system parameters or the parameters of external influences within a wide range. Calculation expressions are obtained for choosing the optimal parameters of the proportional controller and the reference signal to ensure the specified accuracy of maintaining the output voltage under changing load conditions. It is shown that high values of the P-controller gain in a system without control of nonlinear dynamic processes lead to the appearance of undesired dynamic modes, which can be eliminated only by reducing the specified coefficient, which leads to a drop in the static accuracy of a closed-loop automatic control system. The paper presents a nonlinear dynamic model of the system in the form of the Poincaré map and a small-signal structural model of the system based on the target-oriented control, which takes into account the discreteness of the control system due to the presence of sample-and-hold devices in it. Studies of systems without control of nonlinear dynamic processes and with their control based on the target-oriented control were carried out. It is shown that the small-signal structural model of the system makes it impossible to accurately determine the parametric boundaries of the system transition to undesired modes, which requires the use of nonlinear dynamic models to refine these boundaries. It is shown that the application of the target-orientedcontrol makes it possible to exclude undesired oscillations and ensure the stability of the system without changing the coefficient of the proportional controller, which makes it possible to maintain static accuracy. The proposed approach to the construction of control systems for converters with frequency-pulse modulation can also be applied to other types of controllers in the main control loop in order to improve the system dynamics.
Keywords
buck converter, pulse-frequency modulation, proportional controller, small-signal structural model, nonlinear dynamics, nonlinear oscillations, desired dynamic mode, stability margin
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Andriyanov A.I., Pugachev A.A. Control System for DC/DC Converter Based on Pulse-Frequency Modulation. Elektrotekhnicheskie sistemy i kompleksy [Electrotechnical Systems and Complexes], 2023, no. 2(59), pp. 55-64. (In Russian). https://doi.org/10.18503/2311-8318-2023-2(59)-55-64