Maximum power transfer from a nonlinear energy source to an arbitrary load

Abstract

A more general approach to the matching procedure of an arbitrary load to a nonlinear energy source is presented. The matching procedure is required to assure a maximum power transfer to the load. The matching system is modelled by a linear network, capable of transforming DC power as well as AC power, which is characterised by a transformer matrix. The load and energy-source time variations call for a transformer with a controlled time-variable transfer ratio (TVT). The matching procedure is analysed and discussed. As a practical case, the matching of a photovoltaic (PV) array to a DC motor is studied. The theoretical results are compared to experimental ones. These results allow the determination of the operation and the starting-torque gain (and its maximum value) of the drive system. The torque gain is defined as the ratio of the torque in a matched system to the one in the system without a matching device. By using the TVT it has been found that the torque gain depends on the characteristics of the energy source (say, a PV array) and the electric motor. This study shows in which cases the use of a matching device is recommended and what is the technical improvement of the system. The relatively low costs of the matching device (1–2%) compared with the cost of PV array also helps to determine the economic benefit.