| Solar energy is an efficient and clean new energy,PV research and application have received much attentions.PV grid-tied low voltage ride-through is the key technology of PV and plays an important role whether the grid-tied system operate safely and steadily.The low voltage ride-through control strategy is studied deeply based on the control of the PV grid-tied inverter to achieve the safe and stable operation of grid-tied system when the voltage falls.The model current predictive average current control strategy is designed on a basis of grid-connected inverter to make output current to follow accurately the parameters of active current and reactive current,aiming at achieving grid-tied operation of unity power factor of system.The effect of grid voltage sags on power characteristic of grid-connected inverter is analyzed and the low voltage ride-through strategy of PV grid-connected inverter is designed.When the grid voltage drops,the reassignment of output active power and reactive power during period of voltage sag is achieved through decoupling control of active component and reactive component of current.Meanwhile,the current output from inverter is controlled with limiting amplitude to make inverter support grid with wattless power under the premise of undercurrent for current.The inverter characteristics are analyzed when the grid voltage drops unequally,respectively regarding double frequency wave of negative-sequence current output and DC side voltage from hold-up AC side as the control target to design unbalance control strategy of the grid-connected inverter,reset referenced current value of each process in control target and achieve the purpose of improving output current on AC side and control wave of the direct voltage.The PV grid-connected control model is set up in the Matlab/Simulink simulation platform and the simulation verification of the control strategy proposed is conducted to verify effectiveness of the control. |
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