1. Project Overview & Architecture The goal of a smart solar inverter is to take DC power from solar panels, convert it into clean AC power for appliances, and optimize efficiency using MPPT (Maximum Power Point Tracking). Core Stages: 1. DC-DC Boost Stage: Steps up the varying low voltage from solar panels (e.g., 12V–48V) to a stable high-voltage DC bus (e.g., 380V). 2. DC-AC Inverter Stage: Converts the high-voltage DC into a 50/60Hz Sine Wave using a Full-Bridge (H-Bridge) topology. 3. Control Stage: The STM32 acts as the "brain," generating PWM signals and monitoring sensors. 2. Hardware Components Microcontroller: STM32F4 series (like STM32F405/407) or the STM32G4 (specifically designed for digital power). Switching Devices: MOSFETs or IGBTs (e.g., IRF540N for low voltage or high-voltage variants for the H-bridge). Gate Drivers: Necessary to interface the 3.3V STM32 logic with the high-voltage gates (e.g., IR2110). Sensors: * ACS712 or ACS711 for current sensing. Voltage dividers for voltage sensing. Filtering: LC Filter (Inductor and Capacitor) to smooth the PWM into a clean Sine Wave. Communication: ESP8266 or ESP32 for Wi-Fi connectivity (making it "Smart"). 3. Key Software Algorithms The STM32 runs several concurrent loops to ensure stability and efficiency: A. MPPT (Maximum Power Point Tracking) Solar panels have a non-linear output. The Perturb and Observe (P&O) algorithm is commonly used. The STM32 slightly adjusts the PWM duty cycle of the DC-DC converter, measures the power change, and continues moving in the direction that increases power. B. SPWM (Sinusoidal Pulse Width Modulation) To create a 50Hz sine wave, the STM32 generates a high-frequency (20kHz+) PWM signal where the duty cycle varies according to a sine look-up table. C. Feedback Control (PID) A PID loop monitors the output voltage and current. If the load increases and the voltage drops, the STM32 adjusts the PWM duty cycle in real-time to maintain a constant 230V/110V AC. 4. "Smart" Features By integrating a communication module, your project moves beyond a standard inverter: Remote Monitoring: Send real-time data (Battery level, Solar yield, Load) to a mobile app or dashboard (Blynk or MQTT). Data Logging: Save energy production stats to an SD card or cloud. Protections: Implement software-defined over-voltage, under-voltage, and short-circuit protection that sends an alert to your phone. 5. Technical Challenges to Consider Dead-Time Insertion: Crucial to prevent "shoot-through" (where both MOSFETs in a leg turn on at once, causing a short). STM32 advanced timers have built-in dead-time hardware support. Isolation: Use optocouplers to isolate the high-power AC side from the sensitive STM32 logic. Heat Dissipation: Efficient heat sinking for the MOSFETs is mandatory.