For three-level neutral point clamped photovoltaic inverters, a suppression method based on discontinuous pulse width modulation (DPWM) and with the selection of a specific vector for control, has shortcomings such as long calculation time of vector decomposition, large injection common-mode voltage component and large leakage current. In this paper, a leakage current suppression method based on I-DPWM for a three-level neutral point clamped photovoltaic inverter is proposed. The injected low-frequency common-mode voltage component is analyzed by calculating various DPWM equivalent modulation waves. Aiming at DPWM1, which has the lowest low-frequency common-mode voltage component, a new zero-sequence component is injected at the low-frequency common-mode voltage discontinuity point, and the leakage current amplitude is suppressed by reducing the low-frequency common-mode voltage. At the same time, a carrier is adopted to realize the DPWM, without complex vector operation. Finally, a simulation model of a 20 kW three-level neutral point clamp photovoltaic inverter is established on the Matlab/Simulink platform, and the effectiveness of the proposed method is verified by combining with the designed 125 W experimental prototype.