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This study discusses a droop-based proportional load sharing control of parallel connected dc-dc converters in photovoltaic (PV)-based low-voltage dc microgrid. Droop control is the popular scheme for power sharing in dc microgrid. In this study, proportional droop index (PDI) algorithm with droop (R droop) shifting is introduced to improve the load sharing performance of the dc microgrid, which is a function of normalised current sharing difference and voltage deviation in the output side of the converters. This proposed control method calculates adaptive virtual resistance, R droop , and allows the converter to share the load current based on PV power available. By incorporating a new R droop shifting method with PDI, the proposed scheme eliminates the trade-off between current sharing and voltage regulation of the conventional method. The detailed analysis and design procedures are explained, and the effectiveness of the proposed method is verified by detailed simulation and experimental studies.

Active clamp dcdc converters are recently intro'duced family of two switch pulse width modulated converters featuring zerovoltage switching. The topological structure of these converters in relation to their hard-switched PWM converters is highlighted. With proper designation of the circuit variables (throw voltage V and the pole current I), all these convertem are seen to be governed hy an identical set oiequations. In this framework, these circuits exhibit 6 sub-periods per cycle with identical current waveform in the resonant inductor. With idealized switches, the steady-state performance is obtainable in an analytical form. This set of equations may be solved through a simple spreadsheet programme. The steady-state performance provides a design constraint on the normalized current. The conversion ratio of the converter is also readily available. A generalized equivalent circuit emerges for all these converters from this steady-state conversion ratio. It is interesting to note that this equivalent circuit provides a dynamic model as well. The circuit model proposed in this paper enables one to use the familiar state space averaged results of the standard PWM de-to-de convertem (both steadystate and dynamic) for their ZVS active clamp counterparts

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