Abstract: The integration of large-scale renewable energy source causes the reduction of rotational inertia in

power systems. A motor-generator pair（MGP）can provide a real inertial response（IR）capability without delay for

renewable energy generations. The electrical-mechanical model of the MGP was established based on the grid

connection structure of the MGP system，and the inertial response principle between MGP system and virtual inertia

control was compared. Referring to the similarities and differences on frequency response between traditional

synchronous generators and MGP，a modified active power control strategy based on the combination of photovoltaic （PV）de-loading operation and droop control was proposed. The inertial response capability of the MGP and the improved control strategy were verified in the three machines and nine nodes simulation system. Furthermore，the promotion effect of the improved control strategy on frequency regulation ability was verified by comparing the virtual inertia with the droop control strategy. The experimental results show that the improved control strategy can enhance the frequency support capability of the PV integration via anMGP.

      Key words: photovoltaic generation；motor-generator pair（MGP）；inertia；droop control；primary frequency regulation