Robust average current-mode control of multimodule parallel DC-DC PWM converter systems with improved dynamic response

This paper presents a novel average current-mode control (ACC) strategy for the control of multimodule parallel pulsewidth modulation DC-DC converters, which represents a drastic improvement over conventional ACC. This new method consists of the addition of an auxiliary controller into the control loop, besides the current and voltage regulators. The reference-model-based auxiliary controller improves the robustness of the ACC dynamics in buck-derived distributed power systems, preserving loop gain crossover frequency and stability margins over significant changes of the number of connected modules, the load and the line voltage. Moreover, this control scheme shows much better disturbance rejection properties, i.e., closed-loop output impedance and audiosusceptibility, than conventional ACC. From a control theory point of view robust performance is achieved, preserving stability. A multimodule buck prototype has been experimentally tested with different numbers of modules on stream, line, and load conditions, including discontinuous conduction mode. Measurements of the small-signal frequency response of the converter have been carried out, showing the improvement achieved by the proposed control scheme. The empirical large-signal response of the converter under load steps is also shown in order to validate the concept.