Steady state reliability of maximum power point tracking algorithms used with a thermoelectric generator

A thermoelectric generator (TEG) with its near linear V-I characteristic makes its operation distinct from a photovoltaic (PV) cell. However, when maximum power point tracking (MPPT) is implemented in TEG power electronic systems, the established knowledge and wisdom surrounding PV oriented MPPT systems is often applied directly without consideration of the TEG's characteristics. Unsuitable MPPT algorithms generate large operating point variations thus deteriorating the steady state performance of the TEG. Therefore an algorithm that can reliably deliver power with low steady state error over a range of operating conditions is desired. This paper compares three common MPPT methods (perturb and observe, power gradient tracking and fractional open-circuit voltage / short-circuit current), in terms of their steady state performance and reliability, when used with a 4.2 V, 3.4 A (for matched load at ΔT = 270°C) TEG module. Experimental results are reported that confirm better and more reliable steady state performance of the fractional open-circuit voltage / short-circuit current method compared to the perturb and observe and power gradient tracking algorithms.