In the photovoltaic grid system

in case of voltage sag form the grid side

such phenomenon asover voltage and overcurrent are often accompanied and grid operation of the photovoltaic system is de-stroyed. For assuring the photovoltaic system safe operation in case of grid fault

a kind of photovoltaic lowvoltage ride through control strategy is proposed. The strategy

on the basis of improving traditional photo-voltaic low voltage ride through control strategy

uses proportional resonant（PR）controller to generate refer-ence output signal

so to calculate both active and reactive power needing to be injected into the grid incase of fault in the grid and control them without phase-locked loop

and

on the basis of assuring to achievelow voltage ride through of the photovoltaic system

recues the construction cost of the system as well as thecalculation amount of the controller. Both symmetrical and asymmetrical fault of the grid voltage is taken asan example to set up simulation model and experimental platform

and it is proved by the result of themthat the control strategy described can achieve PV low voltage ride through and ensure the safe and stable operation of PV system.