A power conversion system, comprising: a power conversion device configured to be connected to a power system; a connector, whose attached state, in which the connector is connected to a connecting port provided in an apparatus having a battery mounted therein, and unattached state, in which the connector is detached from the connecting port, can be selected; a processing module; a switching device which intervenes in an electric path (511, 512) between the power conversion device and the battery, the switching device is configured so that a closed state in which the electric path (511, 512) is made conductive and an open state in which the electric path (511, 512) is made non-conductive are selectable; and a switching mechanism, which is configured to allow the switching device to enter the closed state when the connector is in the attached state and to place the switching device in the open state when the connector is in the unattached state, and wherein the processing module comprises: a first detector configured to detect whether the switching device is in the open state or the closed state; a second detector configured to detect whether the connector is in the attached state or the unattached state; and a determining module configured to determine that a malfunction has occurred when the first detector detects the closed state and the second detector detects the unattached state; characterized in that the switching device is provided in the connector; in that the switching mechanism is provided in the connector; in that the switching device includes two main contacts (311, 312) that are configured to open and close the electric path (511, 512) and the switching device further includes an auxiliary contact that is configured to be opened or closed in synchronization with the main contacts (311, 312), wherein the auxiliary contact includes a common contact, a first contact, and a second contact, and the common contact is configured to be selectively connected to one of the first and second contacts, and wherein, when both the main contacts (311, 312) are in the open state, the common contact is electrically connected to the first contact, and when any one of the main contacts (311, 312) is in the closed state, the common contact is electrically connected to the second contact; and in that the first detector is connected with the auxiliary contact and is configured to detect whether the switching device is in the open state or the closed state by monitoring a contact state of the auxiliary contact. a power conversion device configured to be connected to a power system; a connector, whose attached state, in which the connector is connected to a connecting port provided in an apparatus having a battery mounted therein, and unattached state, in which the connector is detached from the connecting port, can be selected; a processing module; a switching device which intervenes in an electric path (511, 512) between the power conversion device and the battery, the switching device is configured so that a closed state in which the electric path (511, 512) is made conductive and an open state in which the electric path (511, 512) is made non-conductive are selectable; and a switching mechanism, which is configured to allow the switching device to enter the closed state when the connector is in the attached state and to place the switching device in the open state when the connector is in the unattached state, and wherein the processing module comprises: a first detector configured to detect whether the switching device is in the open state or the closed state; a second detector configured to detect whether the connector is in the attached state or the unattached state; and a determining module configured to determine that a malfunction has occurred when the first detector detects the closed state and the second detector detects the unattached state; a first detector configured to detect whether the switching device is in the open state or the closed state; a second detector configured to detect whether the connector is in the attached state or the unattached state; and a determining module configured to determine that a malfunction has occurred when the first detector detects the closed state and the second detector detects the unattached state; characterized in that the switching device is provided in the connector; in that the switching mechanism is provided in the connector; in that the switching device includes two main contacts (311, 312) that are configured to open and close the electric path (511, 512) and the switching device further includes an auxiliary contact that is configured to be opened or closed in synchronization with the main contacts (311, 312), wherein the auxiliary contact includes a common contact, a first contact, and a second contact, and the common contact is configured to be selectively connected to one of the first and second contacts, and wherein, when both the main contacts (311, 312) are in the open state, the common contact is electrically connected to the first contact, and when any one of the main contacts (311, 312) is in the closed state, the common contact is electrically connected to the second contact; and in that the first detector is connected with the auxiliary contact and is configured to detect whether the switching device is in the open state or the closed state by monitoring a contact state of the auxiliary contact.