Ride-through strategy of quasi-Z-source wind power generation system under the asymmetrical grid voltage fault

摘要

Asymmetrical grid voltage will introduce negative-sequence current components on the grid side and cause large voltage ripple of quasi-Z-source capacitors. It will lead to the torque ripple of generator. This study proposes a novel control method based on super-capacitor (SC) to improve the capability of asymmetric fault ride through in quasi-Z-source wind power generation system (WPGS). The stream of system power, in the condition of unbalanced grid voltage, is discussed in detail in this study. To limit the voltage rise and suppress the 2-order voltage ripple of quasi-Z-source capacitors, the throughput power of SC is controlled by proportional-resonant controller to track the output power subtraction between generator and quasi-Z-source inverter. Meanwhile, the negative-sequence component of the grid-connected current is decreased significantly. Finally, simulation and experimental results are given to verify the theoretical analysis.