Cascaded power balancing mechanism based on resonant switched capacitor topology for photovoltaic systems

In order to enhance the power output of PV panels and lower the power loss in the conversion stage, resonant switched capacitor circuits (ReSC) have been developed, which feature high power density and high efficiency. This paper introduces two operation modes of ReSC used for cascaded power balancing in PV system: equalization mode and MPPT mode. In the equalization mode the open loop control is adopted with four MOSFETs controlled by a pair of complementary signals. The ReSC works at two states and realizes voltage equalization of PV modules. In the MPPT mode, a third switching state and a controllable dead time are involved so that the differential current can be adjusted. The working principle of ReSC in the MPPT mode is investigated and the control algorithm is proposed. Simulations and experiments verify that the output power of the system in both modes have been enhanced by using the ReSC. By comparing these two modes it can be found that, the system control in the equalization mode is much simpler than that in the MPPT mode, however, the output power increase of the MPPT mode is over the one of the equalization mode, which would be more prominent as the power mismatch between PV modules increases.