Method and apparatus for controlling low voltage ride through of photovoltaic grid-connected inverter

摘要

A method and an apparatus for controlling a Low Voltage Ride Through of a photovoltaic grid-connected inverter. The method for controlling comprises: judging whether a voltage value of a grid is smaller than an upper limit of a low voltage value and is not greater than a lower limit of the low voltage value; when it is judged that a root mean square value of the voltage in the grid is smaller than the upper limit of the low voltage value and greater than the lower limit of the low voltage value, controlling an active current value outputted from the inverter to be equal to a target active current value and controlling a reactive current value outputted to be equal to a target reactive current value, so that a comparison difference between a total current outputted by the inverter in a Low Voltage Ride Through state and a current outputted by the inverter in a normal state is smaller than a preset value. The method and apparatus settle problem that the poor stability is caused since control on the waveform and amplitude of the current is ignored in the Low Voltage Ride Through control on the inverter, such that the total current changes slightly before and after a voltage dip, which can support and stabilize the grid.

主权项

1. A method for controlling a Low Voltage Ride Through of a photovoltaic grid-connected inverter, comprising steps of:
judging whether a root mean square value of a voltage in a grid is lower than an upper limit of a low voltage value; controlling the inverter to operate in a normal state when it is judged that the root mean square value of the voltage in the grid is not lower than the upper limit of the low voltage value, wherein an active current value outputted from the inverter in the normal state is controlled to be a target active current value outputted from the inverter in the normal state and a reactive current value outputted from the inverter in the normal state is controlled to be zero; and judging whether the root mean square value of the voltage in the grid is lower than a lower limit of the low voltage value when it is judged that the root mean square value of the voltage in the grid is lower than the upper limit of the low voltage, controlling the inverter to stop operating when it is judged that the root mean square value of the voltage in the grid is lower than the lower limit of the low voltage value, and controlling an active current value outputted from the inverter to be equal to the target active current value in the normal state and a reactive current value outputted from the inverter to be equal to a target reactive current value when it is judged that the root mean square value of the voltage in the grid is not lower than the lower limit of the low voltage value, wherein the target reactive current value is determined by a preset fluctuation range of the amplitude of a total current outputted by the inverter and the target active current value in the normal state, such that the fluctuation of the amplitude of the total current outputted by the inverter in a Low Voltage Ride Through state relative to the current outputted in the normal state is within the preset fluctuation range.