Power converters for residential PV and hybrid systems

This Ph.D. thesis focuses on multi-input single-phase grid-connected photovoltaic (PV) and hybrid systems in residential applications. Topological configurations of multi-input converter systems are discussed and analyzed. Methodologies of PV converter design and system modeling are presented. As an essential component of a PV system, the maximum power point tracking (MPPT) method is a major part of this thesis work. This thesis proposes a novel multi-stage MPPT that uses the golden section search (GSS) method. Also, it develops an improved current control algorithm for grid-connected inverters.;As part of this research, a multi-string inverter topology is applied to the system; boost choppers are selected for the modular input dc/dc converters. A single-phase structure is designed for the grid-connected inverter. The modular input converters are linked to a common dc link bus with capacitors. Then, the input converters and the inverter are connected in series with the dc link capacitors. A constant dc link voltage control scheme is proposed as a system-level power flow control strategy to maintain the power flow balance and to decouple the separate converter units and the inverter. Under this strategy, the different parts of the multiple-input system are decoupled and modularly extendible.;The MPPT is a crucial issue of the research. There are many MPPT algorithms found in the literature. However, they all have their benefits and weakness. An advanced multi- stage MPPT algorithm is proposed here with the new idea of integrating the GSS method into the MPPT. This MPPT algorithm provides fast response and high tracking accuracy, which is proved by the results of the simulations and experiments.;This thesis research also proposes a current control (CC) design with improved performance for single-phase grid-connected CC inverters. This proposed CC is optimized by taking into account the control delay when modeling the plant. Also, the influence of the grid voltage and dc link voltage disturbances is eliminated by using the disturbance decoupling technique. Comparative simulation and experimental results are provided to confirm the effectiveness and improvement of the proposed CC.