Autonomous water pumping system based on wind generation. Control by rotor frequency

There exists in Argentina a growing interest in alternative energy sources such as wind and solar energy for water pumping in remote areas. In this context, the main objective of the paper is to present and evaluate a configuration for an autonomous wind energy conversion system oriented to water pumping. It consists of a wind turbine with a wound rotor generator, electrically coupled with a squirrel cage induction machine moving a centrifugal-type water pump. The power flow control is performed through the rotor winding of the generator by changing the frequency and voltage of its excitation. The system is controlled by means of a torque control which follows the optimal turbine torque in order to maximize the volume of water pumped based on the optimization of the wind energy capture. The energy injection from a secondary energy source to DC-link is also foreseen, in such a way that the pump could absorb both power sources. An analysis of the system operation points and the power flow for different wind speed and solar radiation is accomplished, supported by simulation results.

I. Introduction

Water supply is one of the principal problems in the development of remote regions of northern and southern Argentina, especially for small towns in Patagonia. A recently proposed solution to this problem is the use of autonomous wind generators to electrically propel centrifugal water pumps [1] [2]. With an electric coupling between them, the water pump location can be selected independent of the wind turbine location; therefore, the turbine could be placed in a site of optimum wind energy while the pump could be located near the water well, improving the system efficiency [3] [4].