Virtual inertia control is an efficient way for wind generators to participate in system frequency regulation.Based on the principle of PD virtual inertia control and the simplified model of frequency response of wind generators integrated system

the response characteristics and the mechanism of PD virtual inertia control were analyzed

and the quantitative relation between PD virtual inertia control and system frequency was deduced.It is indicated that PD virtual inertia control is a temporary frequency modulation process

and the proportional control has a direct effect on the minimum frequency

while the differential control mainly affects the frequency descent rate and the time to reach the minimum value.Experiments were performed in the laboratory

and the results indicated that the maximum frequency deviation reduced from 0.84 Hz to 0.59 Hz and the rotor speed of the wind turbine reduced from 15.7 rad/s to 13.4 rad/s respectively with the increase of the proportional control coefficient under the same load disturbance

while the frequency descent rate reduced with the increase of the differential control coefficient.The experimental results are in accordance with the theoretical analysis

and validity of the response characteristic and mechanism analysis are proved

which provide some references for the PD virtual inertia control on parameters setting and control method modification.