Modular High-Voltage Gain PV Converter With Embedded Output Power Balancer and a Controllable ZVS-Assisted Auxiliary Circuit for Extended Soft-Switching Range for MVDC Grid Application

This paper proposes a new modular interconnected step up DC-DC converter system that utilizes individual maximum power point tracking (MPPT), integrated modular output voltage distribution, and extended soft-switching range for input-independent output-series (IIOS) connected PV energy systems. The proposed DC-DC modules are capable of individual MPPT through phase-shift control on the input full-bridge inverter switches. An LLC resonant circuit allows for zero-voltage switching (ZVS) operation on the full-bridge inverter switches. By the use of an ZVS assisted auxiliary circuit controller, ZVS operation can be extended on all module switches over a wide range of MPPT conditions. By utilizing an active voltage doubler, the proposed system achieves balanced output voltage for each module which is typically a challenge for modular IIOS configurations. The system’s performance is verified with a five-module 100kHz, 20kW/15kV-output simulation and a 95kHz, 1.5kW/1.7kV-output two-module proof-of-concept hardware prototype with an efficiency range between 95.6% and 97.4%.