A New Bidirectional Three-phase Neutral Point Clamped (NPC) Grid-Connected Converter: Analysis and Simulation
This paper deals with the theoretical development, analysis, and simulation of the new topology of three-phase NPC (Neural Point Clamped) converter. The proposed 6-kW three-phase converter is connected to a three-phase electrical network and due to its bidirectional characteristics can either send energy to the grid or receive it from the grid. The classic strategy of vectorial control at the DQ synchronous reference frame, along with a simple algorithm for Unit Vector Generation (UVG), have been employed to control the line currents in the grid and the DC-bus voltage, thus substituting the PLL (Phase Locked Loop). A PWM (Pulse Width Modulation) strategy is presented in the form of an analog circuit and used for switching the semiconductors in the converter. The obtained results were verified using Matlab/Simulink software. The proposed converter has five voltage levels at the output for each phase and proven more advantageous than the conventional NPC. In addition, it was obtained a better harmonic content in the grid currents because there is very low Total Harmonic Distortion (THD) both when acting as a rectifier and as an inverter.