# Experimental Investigation of Controlled and Uncontrolled Rectifiers for Low-Power Wind Turbines
###### Abstract  
The holistic objective of producing 100% renewable generated electricity motivates the development of low-power and efficient domestic wind turbines. The wind turbine's efficiency can be maximized by operating it in a variable speed configuration, thus harvesting all the wind power. However, the harvesting process requires a two-stage conversion from AC to DC and from DC-DC or DC-AC. The paper aims to analyze the performance of the first stage of AC-DC rectification in terms of output voltage ripple and voltage regulation when the loading conditions vary abruptly. In addition, this work investigates the basic uncontrolled and controlled rectification methods for low-power wind turbines. The role of the output capacitance and its effect on output voltage ripples is illustrated. Finally, the paper highlights the design of a three-phase controlled rectifier using a simple yet effective firing angle control of a silicon-controlled rectifier (SCR) device. The delay caused due to the firing angle variations is reported in the simulations and experimental results to support the conclusion drawn from this study.  
wind technologies; low-power wind turbines; rectifiers; single-phase rectifiers; three-phase rectifiers; uncontrolled rectifiers; controlled rectifiers; firing angle control +
Footnote †: journal: Applied  
energy rotates the alternator blades to convert the mechanical power into electrical power. The process only utilizes clean, abundantly available, and inexhaustible wind resources, free from emissions [2,4]. As a result, the current-installed capacity of wind energy systems reduces more than 300 million metric tons of greenhouse gases, thus significantly resisting climate change. Moreover, wind turbines can be installed in multi-use sites, for example, agriculture fields, farms, solar parks, islands, or hydel power plants [6].  
However, despite all the advantages, many challenges hinder WE systems' growth to their full potential. First, WE systems need strategic locations having abundant winds. These are usually remote inhabited locations without a power grid, so the transmission of wind-generated electricity is a significant problem [6,7]. Improving and expanding the national electricity transmission and dispatch network is a way forward with this problem [6,8]. Wind turbines do not pollute the environment; however, turbine noise is often a concern to some people. Turbine noise can be improved by developing better mechanical and aerodynamic systems, so more research and experiments are needed to overcome this problem [9]. Finally, although WE systems are the cheapest electricity generators among renewable energy systems, technologies such as solar, geothermal, and hydrogen-generated electricity rapidly reduce costs. Thus, the WE systems must continue developing and reducing costs to remain in the competition [6,8,9].  
This study highlights the suitable topologies for the rectifier units for small wind energy systems. Both uncontrolled and controlled rectifiers are analyzed in terms of loading effects and voltage ripples. The paper includes analysis, simulation, and experimental results of the half-wave uncontrolled rectifier, full-wave rectifier, and fully controlled SCR device. The effect of increasing or decreasing output capacitance on the output voltage is also discussed concerning small, low-power wind energy systems.