Abstract: As the proportion of new energy gradually increases, the unified power quality conditioner(UPQC) is becoming increasingly important for improving the power quality of new power systems. To further enhance the voltage compensation capability and dynamic response performance of UPQC series side, an improved linear self disturbance rejection control strategy is proposed. A proportional differential link is introduced into the traditional linear extended state observer and its performance is analyzed. On the premise that the observer is not affected by noise interference, the dynamic characteristics and anti-interference ability of the controller are improved, the estimation error of the observer on total disturbance is reduced, and the voltage compensation ability of UPQC series measurement is improved. A UPQC simulation model was built to verify the correctness of theoretical analysis and the effectiveness of the proposed control strategy.