ESPInverterCore

Three-phase inverter ( Simulink simulation + Hardware test with ESP32 )

3-Phase Inverter Project

This project focuses on the design and implementation of a 3-phase inverter. It includes a Simulink model for simulation to validate the inverter's performance, alongside a hardware implementation and circuit testing. The inverter is controlled using an ESP32 to generate 3-phase switching signals.

Modulation Technique

The project employs the Sinusoidal Pulse Width Modulation (SPWM) technique. In SPWM, the width of the pulses is modulated according to a sinusoidal reference waveform for each phase. This method generates a stepped approximation of a sine wave, reducing harmonic distortion in the output voltage.

Code Explanation

The ESP32 code leverages the MCPWM (Motor Control PWM) module to generate precise 3-phase switching signals. Below are the key components of the implementation:

• Lookup Tables Calculation:
  Sine values for each phase, offset by 120 degrees, are precomputed in the calc_sine_val function (from SineVal.h). These values are calculated for half a grid cycle (e.g., 10 ms at 50 Hz), exploiting sine wave symmetry.

  

• Variable Width PWM Implementation:
  The MCPWM timer operates in up-down counting mode at 25 kHz (derived from a 160 MHz clock and 3200-tick period), producing symmetric PWM signals. Comparators set the duty cycles, and generators output the PWM signals to GPIO pins driving the inverter switches. An Interrupt Service Routine (ISR), marked with IRAM_ATTR for fast execution, triggers on the timer’s TEZ (Timer Event Zero) event, setting a flag to update duty cycles. A FreeRTOS task, pinned to core 1, checks this flag and updates the comparators with the next duty cycle values from the lookup table.

• Dynamic Control:
  An analog input from GPIO34, read via analogRead, adjusts a multiplier (0 to 1), scaling the duty cycles to control the modulation index and thus the output voltage dynamically.

Key Features

• Efficient Lookup Tables: Precomputing sine values optimizes performance.
• MCPWM Utilization: Precise PWM generation with dead-time and up-down mode configuration.
• ISR Handling: Time-critical updates via a high-priority interrupt routine.
• FreeRTOS Multitasking: Concurrent task execution on ESP32’s dual-core architecture.
• Dynamic Modulation: Real-time voltage control using analog input.
• Logging: Use of ESP_LOGI for effective debugging.

line-voltages captured by osciloscope:

Contributing

Contributions are welcome! Feel free to fork the repository and submit pull requests with enhancements or fixes.