In order to realize the low cost and lightweight of the co-phase power supply system

a non-isolated cascaded AC-DC converter without the isolation stage of the active power compensator is proposed in this paper. However

the traditional modulation strategy cannot avoid the short-circuit paths in the proposed topology

which causes the DC voltage instability and the internal current surge. Therefore

this paper analyzes the short-circuit characteristics of the proposed topology

defines the causes of DC capacitors short-circuit and the law of available switching state

and proposes an iterative two-phase space vector pulse width modulation (SVPWM) modulation strategy. In the proposed modulation strategy

the input and output converters are uniformly modulated to ensure that the output voltage does not jump

and then the optimal voltage balancing vector of each module is selected according to the principle of optimal voltage balancing. Finally

the vector of each module is reconstructed according to the short-circuit path law

and the available switching state of the zero vector is reassigned to avoid the short-circuit path. Simulation and experimental results show that the proposed modulation strategy can avoid the the DC capacitor short-circuiting paths. Moreover

the proposed topology can reduce the volume

weight

and cost of isolated active power compensators by more than 50%.