What is the purpose of Maximum Power Point Tracking (MPPT) in TENG applications?

The purpose of Maximum Power Point Tracking (MPPT) in TENG applications is to maximize the power transfer from the TENG to the load, typically an energy storage device like a capacitor or battery. TENGs, like solar cells, have a characteristic current-voltage (I-V) curve where the power output varies depending on the operating point (voltage and current). The maximum power point (MPP) is the point on the I-V curve where the product of voltage and current is highest, representing the maximum power that the TENG can deliver under given conditions. However, the MPP changes with factors such as the frequency and amplitude of the mechanical excitation, the load resistance, and the temperature. MPPT algorithms dynamically adjust the load impedance to match the TENG's internal impedance at the MPP, ensuring that the maximum possible power is extracted from the TENG and transferred to the load. This is crucial for optimizing the energy harvesting efficiency of the TENG system. MPPT techniques can involve adjusting a DC-DC converter's duty cycle or using more advanced control strategies. For example, if a TENG's MPP voltage is 3V and its MPP current is 1mA, the MPPT algorithm will adjust the load resistance to be 3kΩ to ensure that the TENG operates at its maximum power output of 3mW.