Maximum Power Point Tracking Converter Based on the Open-Circuit Voltage Method for Thermoelectric Generators

Thermoelectric generators (TEGs) convert heat energy into electricity in a quantity dependent on the temperature difference across them and the electrical load applied. It is critical to track the optimum electrical operating point through the use of power electronic converters controlled by a maximum power point tracking (MPPT) algorithm. The MPPT method based on the open-circuit voltage is arguably the most suitable for the linear electrical characteristic of TEGs. This paper presents an innovative way to perform the open-circuit voltage measure during the pseudonormal operation of the interfacing power electronic converter. The proposed MPPT technique is supported by theoretical analysis and used to control a synchronous Buck-Boost converter. The prototype MPPT converter is controlled by an inexpensive microcontroller, and a lead-acid battery is used to accumulate the harvested energy. Experimental results using commercial TEG devices prove that the converter accurately tracks the maximum power point during thermal transients. Precise measurements in the steady state show that the converter finds the maximum power point with a tracking efficiency of 99.85%.