Patent ID: 8653823

Claim:
A line converter system for connecting a power source to a utility grid, comprising: an inverter having a DC bus and a plurality of inverter switches; a plurality of lines for connecting the inverter to the utility grid, each line having a first end connected to the inverter and a second end for connection to the utility grid; a plurality of line switches, a pair of the line switches being connected in series into each of the lines; a voltage detector connected to the lines, respectively, the voltage detector being connected to each of the lines at a point between the line switches; and a controller connected to the inverter switches and the line switches, the controller comprising a processor and computer readable medium having program instructions stored thereon, which when executed by the processor are operable to perform a method of detecting stuck contacts in the line switches when the line converter system is connected to the utility grid, the method comprising: (a.) opening the inverter switches so that no voltage from the DC bus is applied to the line switches located toward the first ends of the lines; (b.) transmitting open commands to the line switches; (c.) after transmitting the open commands, determining whether the voltage detector has detected a voltage; and (d.) if the voltage detector is determined to have detected a voltage in step (c.), determining that the line switches located toward the second ends of the lines have contacts that are stuck together.