In order to improve the static and dynamic performance of cascaded power electronic transformers（PETs） in parallel operation

an improved droop control strategy is proposed on the basis of the traditional droop control. Firstly

the equivalent circuit of the traditional droop control for parallel system is established

and the reasons for the problems such as large voltage control deviation

low current sharing control accuracy and poor dynamic characteristics are studied. Then

the closed-loop control realizes the compensation of the output voltage control deviation

and the Taylor-expansion of the function of the load current and the phase shift angle is derived and linearized to use as the current feedforward coefficient

thus the accuracy of voltage control and the balance of current control in static performance

as well as the rapid adjustment ability in dynamic performance

can be improved. Finally

the common DC bus voltage is used to replace the output voltage of each PET as the control feedback

which reduces the influence of the line impedance on the current sharing. The experimental results of a set of 3 PETs in a parallel system show that the improved droop control strategy can reduce the power dispersion of the parallel system to 0.18% and the DC voltage control deviation to 0.2 V

which verifies the effectiveness

feasibility and practicability of the engineering application.