Transient performance of voltage source converter connected to grid through LCL-filter under unbalanced voltage conditions

Grid-connected voltage source converters (VSC's) are used in many applications with power quality concerns due to good controllability and output power quality. However, the major drawback is their sensitivity to grid disturbances, e.g. voltage dips. Moreover, when VSCs are used in distributed generation (DG) applications, voltage imbalance may be intolerant. The VSC may trip due to current imbalance or due to overcurrent. In this paper, dual vector current controller is adopted for the VSC connected to the grid through LCL-filter to achieve sinusoidal grid currents with no harmonics and smooth DC-link voltage during voltage dips. The LCL-filter resonance is damped by adjusting the controller gain. Proper current references are generated using a signal command from the DC- link voltage controller and compensates for oscillating powers produced in fault cases. The controller is examined for all types of unbalanced dips.