An Operating Condition-Based Scheme to Alternate Between Control Strategies for Improved Steady-State and Transient Behavior

The control strategies that use modulation techniques have great acceptance in the current control of static power converters. Indeed, they offer a wide variety of alternatives to address the steady-state characteristics required by the system. Nevertheless, its computation and modulation delay negatively affects its dynamic performance. In order to improve the time response of the system, the modulator is avoided and the strategies of direct choice of the switching state have been presented. They can provide a very fast dynamic response; however, the absence of switching state sequences makes more complex the task of establishing specific switching features for improved steady-state performance. In this work, a control scheme that selects a specific control strategy according to the operating condition of the system is proposed. This allows using modulators to satisfy the switching characteristics required in steady-state and avoids its use when a rapid dynamic response is required. In addition, a soft transition method between the control strategies is presented to prevent unwanted behaviors when these are alternated. The proposed control scheme allows simplifying the design and keeps the main advantages of each selected strategy. To validate the scheme, experimental results are obtained for a control structure that alternates between a finite set model predictive control (direct type for rapid dynamic response) and a proportional integral (PI) control with sinusoidal pulse width modulation (SPWM) (modulated type for high steady-state performance).