Photovoltaic DC system series arc detection method based on voltage harmonic characteristics

The invention discloses a photovoltaic DC system series arc detection method based on voltage harmonic characteristics. A harmonic expression of a DC transformer switching current is obtained based on the working characteristics of a one-way isolation type DC transformer in a photovoltaic DC system under the effect of inverter circuit cascade and an outlet filter capacitor; a large-current arc model numerical equation is utilized, switching current harmonics serve as current excitation of an arc, arc voltage response is obtained, and an arc fault detection criterion is constructed according to the arc voltage response; in order to solve the problem of misjudgment during load switching, opening and closing and current converter locking of the photovoltaic direct current system, disturbance detection auxiliary criteria are added; and the arc fault type of the photovoltaic direct current system is detected according to the obtained arc fault detection criterion, and corresponding protection measures are taken. T