Battery system including battery modules connected between system terminals and control method thereof

In a method of controlling a battery system having a battery module comprising a plurality of battery sub modules connected in parallel between system terminals, the method includes: measuring voltage values of the plurality of battery sub modules and/or cells in the plurality of battery sub modules and current values that flow on the battery module; detecting an occurrence of an internal short in the battery module by monitoring the voltage values or the current values; and electrically separating at least one battery sub module in which the internal short occurs from among the plurality of battery sub modules from the system terminals in response to the internal short occurring in the battery module.