Abstract
Existing large-signal control schemes for DC/DC converters formulate control strategies based primarily on nonlinear control theory, and the associated design and implementation are relatively complex. In this work, a decomposition modeling and inverse-system decoupling control method is proposed for DC/DC converters that operate under large-signal disturbances. First, a large-signal circuit-averaged model for DC/DC converters is established. The proposed control system has a double closed-loop control structure composed of a voltage loop and a current loop. Then, the voltage-loop and current-loop controlled subsystems are decoupled and compensated to first-order integral elements using the inverse system method. Several linear feedback controllers are designed for first-order integral systems under various optimization criteria using the optimal control theory. Simulation and experiment were performed on buck–boost converters with resistive and constant power loads. The results show that under the control of the proposed controller, all systems exhibited excellent dynamic and steady-state performance. The proposed method allows the disturbance control of the DC/DC converter, the dynamic behavior control of the voltage loop, and the current loop to become independent processes. The local controller design follows the classical linear control design method and is a simple and effective large-signal control strategy.
Highlights
Small-signal modeling of DC/DC converters with linear feedback control is a mature method [1]
(1) By taking full advantage of the parametric and structure information of the large-signal model for a DC/DC converter, the proposed modeling method does not ignore any nonlinear terms, for a DC/DC converter, the proposed modeling method does not ignore any nonlinear terms, which ensures the accuracy of the system model
Load impedance is not included in the model; the model is applicable for designing a controller for DC/DC converters not the model; the model is applicable for designing a controller for DC/DC converters only with linear load and with nonlinear load, and it is suited to different operating points
Summary
Small-signal modeling of DC/DC converters with linear feedback control is a mature method [1]. The model of a DC/DC converter using this method has three independent input variables, of which the duty cycle, d(s) is a control input variable and both the DC power supply voltage, vi (s), and the load current, îo (s), are disturbance input variables Because of the presence of multiple power sources or loads, the control system of a multiport integrated converter is often composed of multiple closed voltage and current loops. For decoupling the control of converters, the impact of load disturbances on the output voltage is eliminated by adding a nonlinear feedback element [25]. Thepulse current-loop and voltage-loop large-signal model is established using the three-terminal width modulation sub-modules are individually decoupled and compensated to first-order integral elements using the switch modeling method [12].
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