In order to achieve the above purpose, the present disclosure further provides a power conversion system, including: at least two power conversion cells, first terminals of the at least two power conversion cells being electrically coupled, and each of the power conversion cells including a controller, and each controller including a resonance control unit, wherein the controller in each of the power conversion cells is configured to: generate an AC harmonic according to a first electrical signal at the first terminal of the corresponding power conversion cell, wherein an amplitude of the AC harmonic represents first information of the power conversion cell generating the AC harmonic correspondingly, and all the AC harmonics are at the same frequency; and inject the AC harmonic generated by the corresponding power conversion cell into the first terminal of the corresponding power conversion cell, and apply, by the resonance control unit in the corresponding power conversion cell, a closed-loop suppression to the AC harmonic generated by the power conversion cell correspondingly, and control the resonance control unit to output a second electrical signal related to the first information, wherein the second electrical signal includes the common mode information of the power conversion cell, or is used to generate the common mode information of the power conversion cell with the injected AC harmonic.

The present disclosure may present the following technical advantages:

• • (1) The common mode information may be transmitted without relying on additional communication lines;