The invention discloses an additional phase angle compensation method based on voltage feedforward. The method comprises the steps of: based on a generalized impedance theory, establishing an invertergrid-connected model considering negative sequence control in an unbalanced grid, calculating the phase angle of a system open-loop transfer function at an angular frequency [Omega]1, according to anexpected phase margin [phi]', calculating a phase angle [phi]1 required to be compensated by the open-loop transfer function, calculating the amplitude and the phase angle of a compensated voltage feedforward link transfer function G'ff(s) according to the phase angle requirement, and combining the amplitude and the phase angle of a voltage feedforward link transfer function Gff(s) before compensation to calculate the amplitude and the phase angle of a compensation link transfer function Gc(s) at the angular frequency [Omega]1 to obtain parameters of an additional phase angle compensation link. The additional phase angle compensation method can effectively solve the instability phenomenon caused by introduction of a quasi-resonant controller for achieving the target of the negative sequence control in the grid-connected inverter and can ensure the stable operation of the photovoltaic inverter grid-connected system.