Abstract：Aiming at the problem that the circulating currents analysis of modular multilevel matrix converter

（M3C）is not deep enough and the frequency component of circulating currents is not clear，the coupling process of submodule capacitor voltage fluctuation，bridge voltage fluctuation and circulating currents in M3C was deeply

analyzed，and the primary coupling model of M3C circulating currents and its four main frequency components

were obtained. The analysis results provided a theoretical foundation for using PR controller to suppress the

circulating currents of corresponding frequency components. The theoretical analysis and suppression of circulating

currents were verified by experiments. The experimental results prove that the theoretical analysis of the frequency

components of circulating currents is correct，and it is also proved that the PR controller designed according to the

analysis results has better suppression effect on circulating currents than the P controller.

      Key words：variable speed pumped storage；modular multilevel matrix converter（M3C）；capacitor voltage

fluctuation；circulating currents