Aiming at the problems of serious distortion and excessive peak value of grid-side current waveform in power conversion systems（PCS）under unbalanced voltage， this paper proposes an energy optimal control strategy for PCS under unbalanced grid voltage. The control strategy deeply analyzes the influence of parameter k and grid voltage imbalance on the energy operation of the system through the relationship between the control target parameter k， the grid voltage imbalance and the instantaneous power fluctuation， the grid-side current imbalance， and the grid-side current peak. On this basis， to focus on the two control objectives of suppressing the current amplitude and power fluctuations， the optimization algorithm is added， and the energy optimization control strategy of the current limiting PCS with the parameter k selected only within ［-1，0］ is proposed. The simulation results show that the control strategy can more quickly and effectively limit the current peak value to the maximum allowable peak value through the k parameter and current limiting control strategy， and further reduce the power fluctuation and improve the active power output capacity of PCS， which reflects the energy optimization of PCS operation.