When a modular multilevel matrix converter (MMMC) is operated at a low or even zero frequency

the operation security of switching devices and sub-module capacitors will be threatened as the peak value of the main component of sub-module capacitors ripple voltage is inversely proportional to the output frequency. To solve this problem

this paper presents a low-frequency control scheme of MMMC. The balance of the sub-module capacitor voltage is achieved by hierarchical control in the outer loop. As useful components based on the rules of energy exchange

the doubling output frequency ripple voltage participates in the balancing control together with the DC components of capacitor voltage. Finally

the dual control of interphases balancing and ripple suppression is achieved by the unified hybrid controller. Moreover

the inner loop of the scheme adopts the arm current independent control

avoiding the occurrence of complicated vector transform and inner circulating currents. The scheme is suitable for special operation with zero output frequency. Eventually

the hardware-in-the-loop experiment system has successfully verified the feasibility and validity of the scheme. This work is supported by National Natural Science Foundation of China (No. 51177095

No. 51277115).