Comparison of Loss of Induction Motor Systems for Driving a Constant Mechanical Power Load from Solar Power

Abstract

If the mechanical load such as a pump is dirctly driven by solar power, CO₂ gas can be reduced considerably. It is necessary to interconnect the solar power system to the utility line so that a mechanical load can be driven stably and economically even in varying solar power.
This paper compares the loss between two interconnection systems which can generate the constant mechanical power from variable solar power. The first is named DC electric interconnection system in which DC power of photovoltaic arrays is connected to the output of a converter at the DC power line in a general-purpose inverter. The second is named a mechanical interconnection system which is composed of two coupled induction motors. One induction motor is driven by electric power of the photovoltaic arrays through a general-purpose inverter and the other induction machine is connected to the utility line. The loss of each system is represented as a function of the solar power of the photovoltaic arrays. As insolation varies randomly, a probability distribution function of the solar power is taken into consideration. Each average power loss is calculated from the distribution. It is shown from the comparison of two losses that a mechanical interconnection system is more efficient than a DC electric interconnection system.