Dear STM32 and digital-power fans :) ,
I’d like to share here all the material (HW + SW) solving the challenges of a Digital MPPT solar converter running at high frequency. This system is a DC-DC converter featuring a PhotoVoltaic (PV) system at lower size and cost than classically found.
This PhotoVoltaic DC-DC conversion uses the high-efficiency LLC topology. It operates at 1 MHz to be as compact as possible. For this purpose, the design uses the High-resolution timer (HRTIM1) embedded in the STM32F334 microcontroller, together with analog features such as the embedded operational amplifiers and high-speed analog-to-digital converters.
This demonstrator operates from 30 V dc to 50 V dc (input range), to supply 50 W (max) @400 V dc. Additionally, multiple converters can be connected in parallel to a large common-grid inverter.
The input section includes an EMI filter to prevent noise injection into the PV panel, followed by the high-frequency LLC resonant converter, operating an optimized asymmetrical structure for soft start-up and low-load operation. Then, a secondary voltage rectification is performed to double the voltage and an output voltage surge control/feedback is implemented.
The selected architecture, operating at 1 MHz, enables the use of smaller and more reliable components. Thus allowing the smallest PCB size together with an excellent efficiency levels, above 90% over a wide power range.
More detailed explanations can be found in application note AN5324.
The source code, as well as the manufacturing files supplied here, can be used for reference and by anybody who would like to replicate the board or modify its software. The project was created with the STM32CubeMX tool, for which the configuration file (*.ioc) is provided. Then, it is easy to re-generate the project on multiple toolchains (so far, the system was tested using IAR™ and Keil®).
I’d like to share this design with the community, and I’m sure the community can improve this thread and get inspiration from it for new developments, thus supporting the green power.
