A simplified control method for a water heating load coupled to a hybrid energy system to improve inverter longevity

Abstract

In this paper, the temperature characteristics of an inverter is determined through experimental validation. The experiment involves testing under two load scenarios. The first of which considers a low inverter load, which represents a baseload at approximately 18% of the maximum rated power of the inverter. The second includes an energy intensive water heater load, which increases the loading on the inverter to above 85%. The aim of this paper is to ensure that the operating limits with respect to the inverter temperature is maintained to at least 10% below the upper limit of the device. The experimental results indicated that the rate of change of the inverter temperature was 2.988 °C/min when loaded above 85% and −1.277 °C/min after returning to the 18% rated output power level. This indicated that if the inverter is subjected to a high load of above 85% for a certain amount of time and the operating temperature has reached its acceptable maximum limit, roughly twice the amount of time is necessary to cool the components down enough for another high loading event. A basic fuzzy logic control method is proposed to maintain the inverter temperature within acceptable limits to improve overall inverter longevity.