A voltage-centric approach for current-sensorless MPPT in thermoelectric generators with state observer-based linear extrapolation

Abstract

This article proposes a voltage-centric duty ratio (VC-DR) Maximum Power Point Tracking (MPPT) method for thermoelectric generators (TEGs) that operate without requiring current sensors or power estimation processes. Conventional current sensorless MPPT methods typically rely on additional circuitry for control and power estimation using time-based techniques, which restricts their use to converters operating in discontinuous conduction mode. The proposed VC-DR MPPT scheme efficiently computes the optimal duty ratio using only voltage parameters, supported by simplified mathematical expressions. Additionally, the proposed method estimates the open-circuit voltage using the Luenberger observer and the linear extrapolation principle. The open-circuit voltage is estimated using a two-step extrapolation process, utilizing two initial operating points defined by measured voltage and estimated current values. This approach, along with direct duty ratio computation, allows for a faster response and eliminates power oscillations around the MPP when compared to the conventional current sensor-based perturb and observe technique. Moreover, it simplifies the control process and operates effectively in continuous conduction mode with high tracking efficiency. Furthermore, a current state observer is designed by formulating the state-space equations for the boost converter. The proposed method is validated through MATLAB simulation, followed by experimental testing on a TMS320F28379D DSP controller-based setup.