Well-being in our modern society depends on the availability of electrical power. However, the observed climate change and increasing prices of fossil fuels make the annually growing need for energy challenging to be satisfied. Photovoltaic (PV) power generation seems to be one of the most promising alternatives for fossil fuels, because it has been estimated that utilizing 1 % of global sunlight with a conversion efficiency of 1 % would be enough to cover our energy needs. The PV power systems are interfaced to the utility grid by single or three-phase inverters. Robust and safe operation of these inverters can be guaranteed by proper power-stage and control system design. In control engineering, the control system is usually tuned by using the small-signal model of the system. This book presents a small-signal model that can be used to design a robust and stable control system for a three-phase PV inverter. This book can be used as a self-study material or as an additional source of information by researchers and design engineers dealing with power electronics and control issues in PV applications.