Design and evaluation of a modular resonant switched capacitors equalizer for PV panels

Abstract

Abstract-A switched-capacitor based equalization scheme is proposed for overcoming the adverse effect of shaded panels in a serially connected PV array. The proposed solution is based on a modular approach, in which each two panels are connected to a resonant switched-capacitor converter. The distribution of currents and power extraction improvement have been derived and verified experimentally and design guidelines to meet desired power loss level requirements have been developed. The experimental equalizing module was designed for 185W PV panels and was found to boost the maximum available power by about 50% when interfaced with two serially connected PV panels under insolation ratios between 20% and 100%. The analytical, simulation and experimental results suggest that the proposed approach is effective in extracting all available power with relatively high efficiency.

Two-Switch Voltage Equalizer Using an LLC Resonant Inverter and Voltage Multiplier for Partially Shaded Series-Connected Photovoltaic Modules

“…Equation (18) suggests that the impact of the parameter mismatch would be negligible, if the voltage equalizer is designed so that V D and I Ci R eq-i are negligibly small compared to V PVi . In other words, it is advised that the voltage equalizer is designed to satisfy V PVi >> V D and V PVi >> I Ci R eq-i in order to minimize the impact of parameter mismatch.…”

“…Thus, the virtual operating point of PV 1 with equalization was determined as B, at which the operating voltage and current were equivalent to those of PV 1 and PV 2 -PV 4 , respectively. These operating points can be determined based on (18), and hence readily estimated based on simulation analysis using the derived dc equivalent circuit illustrated in Fig. 12, as will be shown in the next subsection.…”

“…The voltage equalizer supported currents corresponding to A − D and A − C for PV 1 and PV 2 , respectively, so that all the modules would be subject to the same current of 2.85 A, and the virtual operating point of PV 1 and PV 2 was determined as B. According to (18), the larger the current supported by the equalizer, the lower the operating voltage of the shaded modules will be due to the voltage drop in R eq-i . Although the current supported for PV 1 from the equalizer was almost double that for PV 2 , the measured virtual characteristics of PV 1 and PV 2 were nearly the same, thanks to the low resistance value of R eq-i = 0.11 Ω, as determined in the previous subsection.…”

“…2. Most conventional topologies are based on individual multiple bidirectional dc-dc converters such as buck-boost converters [3]- [10] (and some extended topologies [11]- [14]), multi-stage buck-boost converters [15], [16], and switched capacitor converters [17], [18], shown in Figs. 2(a)-(c), respectively.…”

Single-Switch Voltage Equalizer Using Multistacked Buck–Boost Converters for Partially Shaded Photovoltaic Modules

“…In most conventional topologies, which are based on bidirectional converters shown in Figs. 2(a)-(c), such as buck-boost converters [5]- [12], multi-stage choppers [16], [17], switched capacitor converters [18], [19], and other topologies [13]- [15], [20]- [23], more than one switch per substring is required as a minimum, meaning the switch count tends to soar with increasing the number of substrings/modules. With the multi-winding flyback converter [25] shown in Fig.…”