Bidirectional Power Conversion of Isolated Switched-Capacitor Topology for Photovoltaic Differential Power Processors

Abstract

Differential power processing (DPP) systems are among the most effective architectures for photovoltaic (PV) power systems because they are highly efficient as a result of their distributed local maximum power point tracking ability, which allows the fractional processing of the total generated power. However, DPP systems require a high-efficiency, high step-up/down bidirectional converter with broad operating ranges and galvanic isolation. This study proposes a single, magnetic, highefficiency, high step-up/down bidirectional DC-DC converter. The proposed converter is composed of a bidirectional flyback and a bidirectional isolated switched-capacitor cell, which are competitively cheap. The output terminals of the flyback converter and switched-capacitor cell are connected in series to obtain the voltage step-up. In the reverse power flow, the converter reciprocally operates with high efficiency across a broad operating range because it uses hard switching instead of soft switching. The proposed topology achieves a genuine on-off interleaved energy transfer at the transformer core and windings, thus providing an excellent utilization ratio. The dynamic characteristics of the converter are analyzed for the controller design. Finally, a 240 W hardware prototype is constructed to demonstrate the operation of the bidirectional converter under a current feedback control loop. To improve the efficiency of a PV system, the maximum power point tracking method is applied to the proposed converter.

Novel differential power processing technique for uneven partial shading mitigation in PV systems

“…Since, in partially shaded PV module, the shaded submodule determines PV module current, drawn from the terminals of PV module, hence unshaded submodules and the whole PV string will be operating below their optimum power [11], [12]. DPP topologies using variety of DPP converters at submodule level are developing rapidly to overcome small level mismatch within the module to enhance power output capability [3], [10], [13]- [21]. These techniques improve the output from PV system using equal number of DPP converters as substrings in each module, raises to increased system cost and complexity.…”

Design and Control of a 13.2 kV/10 kVA Single-Phase Solid-State-Transformer with 1.7 kV SiC Devices

“…By doing so, the losses induced in Q 4 can be significantly reduced. This is based on exactly the same concept with a synchronous rectification mode of a DC-DC converter using MOSFETs [27][28][29]. The inductor current and the pole voltage are written as:…”