Power Electronics and Control to Enable A Clean-Powered Society
For the project on PV microinverter with DPP converters, we have developed a flyback converter operating at 300 kHz and using GaN Switches that is able to handle bidirectional power. Fig. 1 shows the measured efficiency in both the forward and backward directions. It has a higher power density than the previous design and equivalent efficiency. Further improvements to the coupled inductor are expected to further improve performance. Fig. 2 shows the simulation results of the conventional and proposed MPPT algorithm after a sudden light change. Both converter control algorithms directly perturbing the duty ratio and using peak current mode (PCM) control are compared with the conventional and proposed algorithm. Both cases of the proposed MPPT algorithm outperform the conventional algorithm with PCM control showing the best overall performance. Further improvements to the algorithm are being studied and compared.
For the project on PV-powered wearable applications, Fig. 3 shows the concept for the PV-powered health-monitoring sleeve application. Studies of the flexible PV panels found that bending around the forearm reduces output power, but the angle relative to the light source has a more pronounced effect on both output power and voltage characteristics. Among various panel arrangements on the forearm, multiple PV panels of smaller widths provided higher output power while being controlled by a boost converter power stage. Testing verified that the PV sleeve can provide over 100 mW outdoors, which can effectively reduce the battery in wearables. Another topic in this research is the control algorithm to quickly adjust the power converter operation when lighting conditions change. Fig. 4 shows the power captured using a conventional constant-voltage control compared to a control method that we developed that quickly adjusts to the changing conditions to yield more power to the load over the measured time period. Our control method also considers user safety in wearable devices by quickly reacting to overheating conditions.