Fault tolerance control of solid state transformer

A solid state transformer (SST) device comprising:

• an SST having three parallel phase branches, each phase branch comprising multiple cells, and each phase branch being connectable via at least one switch to a power grid;
• and
• a controller configured to:
• operate the SST in a first control mode, wherein each of the three phase branches is individually controlled;
• and
• based on an open-circuit fault or a short-circuit fault occurring in at least one cell of a particular phase branch, the controller is further configured to:
• open the at least one switch connecting the particular phase branch to the power grid;
• and
• operate the SST in a second control mode, wherein the two phase branches other than the particular phase branch are jointly controlled as a single phase branch.

A non-transitory computer readable program comprising instructions which, upon being executed by a computer or a controller, causes the computer or the controller to perform a method of operating a solid state transformer (SST), wherein the SST has three parallel phase branches, each phase branch comprises multiple cells, and each phase branch is connected via at least one switch to a power grid, and wherein the method comprises:

• operating the SST in a first control mode, wherein each of the three phase branches is individually controlled;
• and
• based on an open-circuit fault or a short-circuit fault occurring in at least one cell of a particular phase branch of the SST, the method further comprises:
• opening the at least one switch connecting the particular phase branch to the power grid;
• and
• operating the SST in a second control mode, wherein the two phase branches other than the particular phase branch are jointly controlled as a single phase branch.