A control method for preventing overvoltage of DC power grid

Abstract

The invention discloses a control method for preventing overvoltage of a DC power grid, comprising the following steps: constructing a voltage-power droop control curve of an AC / DC converter, the voltage-power droop control curve is composed of two sections of droop control curves with different slopes , the drooping control curves with different slopes at both ends are connected by the inflection point; if the voltage of the DC grid is lower than the inflection point voltage, the DC / DC converter operates in the maximum power tracking control mode, otherwise the DC / DC converter operates in the fixed-point voltage Control mode operation, the fixed point voltage is set to the knee point voltage. In the present invention, by adding an inflection point to the existing drooping control slope of the AC / DC converter, one drooping control slope is changed into two slopes with different slopes. When the operating voltage reaches the inflection point, the DC / DC converter The inverter stops the maximum power tracking control, and the DC grid will not have overvoltage. At this time, the remaining capacity of the AC / DC converter is very small, and the photovoltaic power generation has also been fully utilized.

Description

technical field [0001] The invention relates to the technical field of DC grid overvoltage control, in particular to a control method for preventing DC grid overvoltage. Background technique [0002] Gathering photovoltaic power generation through the low-voltage direct current grid and then sending the power to different points of the AC grid through multiple AC / DC converters can better collect photovoltaic energy, and at the same time have less impact on the power quality of the AC grid, and even help to improve the power grid. power supply reliability. In the DC power grid, if there are multiple AC / DC converters running in parallel, a master-slave control method can be adopted, one AC / DC converter controls the DC voltage, and the other controls the power; distributed control can also be used , that is, each AC / DC converter adopts a voltage-power droop control method. Distributed control is adopted, no host computer is required, and no communication between converters is...

AI Technical Summary

Problems solved by technology

[0004] The present invention mainly solves the technical problem that the original DC power grid overvoltage control method cannot improve the utilization rate of photovoltaic power generation capacity while ensuring that the DC power grid does not exceed the voltage; it provides a control method for preventing the DC power grid from overvoltage, through AC / Add an inflection point to the existing droop control slope of the DC converter, and change one droop control slope into two slopes with different slopes. When the DC operating voltage is close to the maximum allowable voltage, the slope becomes larger, and vice versa. , at the same time, set the knee voltage to the highest operating voltage of the DC grid

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