domingo, 10 de junho de 2012
Power Quality Improvement of Single-Phase Grid-Connected Photovoltaic Inverter
A Dissertation for the Degree of Doctor of Philosophy
Power Quality Improvement of Single-Phase
Grid-Connected Photovoltaic Inverter
Department of Information and Communications Engineering
Chungnam National University
The economical and environmental impacts of fossil fuels have forced society to investigate sustainable solutions. The interest has
focused on the renewable energy sources since the green and clean benefits. Consequently, investments in research and development in the field of power electronics have increased proportionally, especially in high voltage and high power grid-connected systems.
The distributed power generation (DG) systems are becoming more common as the need for electric power increases because of taking advantage of using different energy sources such as wind and solar. A few examples are hybrid cars, solar houses or hospitals in remote areas where providing clean, efficient and reliable electric power is critical to the loads. In such systems, the power is distributed from the source side to the load side via power electronic converters in the system. At low and medium power applications, the task is often left to single-phase inverters where they are the only interface between sources connected to dc bus and loads connected to an ac bus. This dissertation investigates the power quality improvements to properly regulate the power flow between renewable source and the utility network. The control method for single-phase inverters used in low and medium power DG systems is based on (and also takes the advantage of) the well-known d-q transformation (which is mostly employed for three-phase converters’ analysis and control design). The transformation requires at least two independent phases for each state variable in the system; thus a second phase must be created. This virtual-phase can be done by DSP implementation, hence there is no need for additional hardware in the system, making it more attractive and cost effective method.
The Proportional-Resonant (PR) controller based current control scheme, compared with conventional Proportional-Integral (PI)
controller, not only provides a superior transient response but also provides a zero steady-state error as well as a high disturbance rejection and a low output current THD under grid-tie mode operation. The entire controller can be implemented in a DSP digital control boardLINK THESIS