Sensorless induction motor drive for photovoltaic pumping applications

Photovoltaic pumping systems without battery can provide a cost-effective use of solar energy. Initially, use of a dc motor was a standard. Nowadays, thanks to development of ac induction motor drive systems it is possible to use a more robust and less expensive motor for photovoltaic pumping application. Use of maximum power point tracker allows to improve system efficiency. On another hand, it must be ideally in accordance with the load profile. This paper proposes to use a high performance sensorless induction motor drive system that is tuned with the photovoltaic maximum power point operation. The control is based on a modified indirect field oriented control strategy that employs a direct estimation of the frequency of the rotor flux vector. Besides that, it is convenient for applications where there is no need for speed control or simply to insure the independency of rotor resistance. Detailed analysis including simulation and experimental results demonstrate the feasibility of the method.