Asymmetry Three-Level Gird-Connected Current Hysteresis Control With Varying Bus Voltage and Virtual Oversample Method

Grid-connected current control plays an important role in the renewable grid-connected system. This paper investigates the grid-connected current hysteresis control of the asymmetry three-level inverter. In order to effectively utilize asymmetry three-level inverter and conquer the disadvantages of traditional hysteresis control, the multistage hysteresis control and current predict hysteresis control are developed. In the multistage hysteresis control method, the switching times of main switches can be declined by regularly adjusting the bus voltage without altering the inductor and bandwidth. In addition, the current predict hysteresis control is developed, which adapts to proper bus voltage without dividing bus switching time. In order to overcome the invalidation issue of the bandwidth in hysteresis control, virtual sample technology is used without increasing real sample frequency. Both simulation and experimental tests have been conducted to verify the efficacy of the proposed methods.