Small photovoltaic power station fault diagnosis method

The invention discloses a small photovoltaic power station fault diagnosis method. The method includes judging a fault, eliminating the fixed shelter shadow and judging a specific typical fault; in other words, according to the current, voltage, irradiance and temperature of a maximum power point of a photovoltaic array, calculating the system fault judgment factor; if the system fault judgment factor is smaller than a set threshold, alarming and starting a fault diagnosis program; calculating the fault judgment factor of each string of photovoltaic components, if the fault judgment factor is smaller than the corresponded threshold, calculating the shelter shadow area, if the shadow area of one moment is capable of sheltering the components, reducing the current of the string of the sheltered components, and judging the shadow as the fixed shelter shadow instead of a system fault; judging the specific typical fault by analyzing the judgment conditions of various fault types. The purpose of fault diagnosis can be achieved through a small amount of sensors, and the method has the advantages of low operation cost, high diagnosis efficiency and high precision.