Modular Photovoltaic (PV) Step-up Converter With A Coupled Power Balancing Scheme for DC-Distributed System

The total global energy capacity for renewable energy systems has been increasing exponentially, with photovoltaic (PV) energy having 25% growth rates along with a continual decrease in cost. A high-power PV energy conversion system typically consists of a medium voltage (MV) grid that collects power from individual PV arrays. In a MV Direct Current (DC) distributed grid architecture, since the output voltage of the PV array is significantly lower than the voltage level of medium voltage grid (such as tens of kV), a power electronic interface with sufficiently high voltage gain is required. To safely and effectively connect multiple PV energy sources to the MVDC grid, modular structure of PV power converter is used to convert and maximize the capture of PV energy. The converter consists of external power balancing units to ensure equal power distribution and safe operation amongst all the converter modules. Developing highly power-efficient and cost-efficient power converter topologies and controllers with minimal number of components is the key to achieve a truly optimized PV energy power conversion system.

In this dissertation, a highly power-efficient modular PV power converter with high voltage gain and coupled power balancing stages is developed. The first part of this dissertation focuses on the development of a novel current-sensor-less maximum power point tracking (MPPT) technique utilizing a single voltage sensor for the devised high voltage gain PV converter module. In the second part of this dissertation, a new embedded power balancing scheme that utilizes high frequency (HF) interlinking active voltage quadruplers (AVQ) is proposed for the developed modular PV power architecture. The proposed design allows the devised MPPT stage in the PV converter to ensure optimal PV power extraction under all conditions while the interlinking AVQs distribute power equally across all modules to ensure safe operation. In the final part of this dissertation, a power efficiency optimization control scheme is proposed to allow the devised modular PV converter system to achieve high efficiency over a wide range of PV irradiation level. The feasibility of the devised modular PV converter and control concepts are validated through simulation and hardware experiments on proof-of-concept prototypes.