Design and Development of Three-Level Inverter

A bidirectional three-level inverter device was designed to reduce single IGBT voltage and grid harmonics in response to the integration of high proportion distributed renewable energy and energy storages. The DC side voltage stabilizing circuit and control protection circuit of the three-level inverter were designed separately. The main circuit explores a LCL filtering, and the control circuit uses TMS320F28379D digital signal processor, which can achieve parallel grid connection and independent operation of multiple inverters. The design of DC voltage stabilizing circuit is composed of voltage-stabilizing electrolytic capacitor and film capacitor of filter in series and parallel. The design of control and protection circuits mainly includes sampling circuits, voltage conversion circuits, driving and protection circuits, etc. The operating principle is as follows: firstly, the voltage and current signals required by the controller are collected using Hall sensors, processed by signal voltage conversion circuits, and sent to the DSP core board. The core board undergoes A/D conversion, control algorithm operation, and SVPWM modulation for waveform generation. The PWM pulse signal is output, and the three-level inverter is driven to operate through the FPGA protection circuit and driving circuit. The experiment designed a virtual synchronous machine (VSG) controller and SVPWM modulation algorithm in a Matlab/Simulink code generation environment, and compared real-time simulation results with physical experimental results in a visual environment. The experimental results verified the feasibility and effectiveness of developing a three-level inverter device.