Positive Feedforward Control for Multimodule Output-Series Power-Conversion Systems With Individual Nonideal Sources

This paper presents a positive feedforward control (PFFC) for a multimodule output-series (MMOS) system with individual nonideal sources. By adding PFFC-loop regulation into the conventional negative feedback control loop, the power module can easily harvest the maximum power from the source, and the output voltage of the converter can be slowly decreased when the input voltage is kept constant. In MMOS applications, an automatic master-loop regulation (AMLR) control is proposed to achieve voltage allocation among the individual power modules; however, this scheme has some drawbacks because its output voltage and power decrease immediately when the power of any one source is insufficient for the converter´s needs. By utilizing the characteristics of the PFFC loop, the output voltage of the individual modules can be effectively allocated for managing the output power of the MMOS system. In this paper, the characteristics of the PFFC-loop regulation are derived through dc analysis. An experimental prototype is implemented for three forward modules with individual nonideal sources, and the characteristics of the PFFC loop are verified. By adding the proposed PFFC loop to AMLR, the measured power rating of the experimental MMOS system can be increased by about 20%.