This paper presents a single-phase three-wire (1phi3W) grid-connection photovoltaic (PV) power inverter with a feature of partial active power filter (PAPF), which can not only deal with PV power but can filter current harmonics and improve power. factor. Once the processed power exceeds the switch ratings, the inverter can reduce its output reactive power and harmonic power, while still can supply the maximum real power generated by the PV arrays. In derivation of control laws, a limit circle is defined to confine the output power of the inverter. To determine the power that the inverter can process, a criterion is proposed to find reactive power, which can avoid complex detections of phase angle and magnitude of the fundamental component of a nonlinear load current. Simulation results and experimental measurements have verified the proposed algorithm and the feasibility of the inverter.