Control method and device in photovoltaic power generation grid-connected system

Abstract

The invention relates to a low-voltage ride-through control method and device in a photovoltaic power generation grid-connected system. The photovoltaic power generation grid-connected system comprises photovoltaic power generation equipment; a DC-DC converter, which is connected to the photovoltaic power generation equipment; an inverter, which is connected to the DC-DC converter through a DC link capacitor; and transformation isolation equipment, which is connected to the inverter through a common grid-connected point and is connected to a main power grid. The method comprises the followingsteps: when detecting that the voltage drop of the common grid-connected point exceeds a preset threshold value, calculating an active component and a reactive component of the output current of the inverter according to the voltage drop degree and low-voltage ride-through requirements specified by a corresponding power grid, and feeding the calculated active component and the reactive component of the current to the inverter, wherein the low-voltage ride-through requirements comprise at least one of the longest time when the inverter needs to be kept networked and reactive current proportionneeding to be provided when the voltage drop of the common grid-connected point exceeds the preset threshold value. The device and method can keep higher active energy output in a low-voltage fault ofthe power grid. 本发明涉及一种光伏发电并网系统中的低电压穿越控制方法和装置，光伏发电并网系统包括：光伏发电设备；直流‑直流变换器，连接到光伏发电设备；逆变器，经由直流链路电容连接到直流‑直流变换器；及变压隔离设备，经由公共并网点连接到逆变器并接入主电网，方法包括：当检测到公共并网点的电压下降超过一预定阈值时，根据电压下降程度和相应电网规定的低电压穿越要求计算逆变器输出电流的有功分量和无功分量，并将计算出的电流的有功分量和无功分量反馈给逆变器，低电压穿越要求包括在公共并网点的电压下降超过该预定阈值时逆变器需保持连网的最长时间及所需提供的无功电流比例其中至少之一。本发明可在电网低电压故障中保持更高有功能量输出。