3-Phase MPPT Charge Controller Design

We are developing a proprietary MPPT solar charge controller for manufacture in China. We are looking for an experienced independent engineer to design and validate the Stage 1 prototype. The design Three-phase interleaved synchronous buck, 120° phase offset 40 A charge current, 12/24/48 V battery, PV input up to 100 V Switching frequency 30–50 kHz per phase, to be determined during the project GigaDevice GD32 microcontroller, CR Micro MOSFETs Firmware in C: perturb-and-observe MPPT, two-stage charging, self-calibration, UART telemetry Stage 1 is an instrumented test bed, not a product. No display, no keypad, no communications. The focus is thermal validation, phase current sharing, efficiency and switching behaviour. Deliverables Schematic, PCB files, BOM, commented firmware source, design calculations, test report, and two working prototypes. Structure Five milestones over 8–12 weeks, with payment against deliverables. Full specification and milestone plan provided under NDA. You need Demonstrated experience with switching converters above 1 kW Multiphase or interleaved converter experience Firmware for real-time control: timer synchronisation, ADC triggering, control loops Lab access: programmable DC source of at least 1 kW, oscilloscope ≥100 MHz, high-voltage differential probe, multi-channel thermocouple logging To be considered, please answer in your proposal How would you synchronise three advanced timers with a 120° phase offset, and trigger ADC conversions so each phase is sampled at the correct point in the switching cycle? How would you implement a high-side floating gate supply that sustains 100% duty cycle indefinitely? We want a single current sense amplifier, not one per phase. How would you characterise phase current imbalance with that constraint? What switching frequency would you propose, and why? What lab equipment do you have, by make and model? Please include estimated hours per milestone, with firmware broken out separately, and how many board revisions you have assumed. Proposals without answers to the five questions will not be reviewed. NDA is required before detailed specifications are shared.