Design of Modular Multilevel Converter Based on STM32

Abstract

Aiming at the problems of high hardware cost and high programming difficulty in the design of modular multilevel converter (MMC) experimental prototype, a single-phase H-bridge MMC experimental prototype with a rated capacity of 600V/3KW based on STM32 is designed. STM32 with timer, Analog-to-Digital Converter (ADC), and Digital-to-Analog Converter (DAC) functions is used as the controller chip, which reduces the hardware cost and the difficulty of circuit design. STM32 is programmed with easy-to-understand C language, which reduces the difficulty of programming language. The optical fiber communication module is used to connect the serial ports of two single-chip microcomputers to realize the electrical isolation between two independent modules and ensure the reliability of the experimental prototype. The isolation drive chip and isolation sampling operational amplifier are used to realize the electrical isolation of strong current and weak current and improve the stability of the system. The carrier phase-shifting modulation strategy is adopted to control the MMC sub-module. The experimental results show that under the control of carrier phase-shifting modulation strategy of STM32 single-chip microcomputer, the alternating current (AC) voltage and current output by the prototype MMC prototype are smooth and sinusoidal, and the system can operate stably at 220V/3KW for a long time. Compared with the scheme using FPGA + DSP as the controller, STM32 has more advantages in hardware cost, circuit design and software programming. It is suitable for the application of prototype MMC experiment with a small number of sub modules.