Combined power generation system and unit, method, and program for controlling the same

A control method of a combined power generation system that combines a fuel cell and an internal combustion engine and that is equipped with an exhaust fuel gas line that feeds exhaust fuel gas from the fuel cell by means of a blower, an exhaust-fuel-gas supplying line that splits off from a branching point of the exhaust fuel gas line and that supplies the exhaust fuel gas to the internal combustion engine, a recirculating line that splits off from the branching point and that circulates the exhaust fuel gas to the fuel cell, a shut-off valve that is provided in a vent line that splits off on an upstream side of the branching point, a pressure loss means that is provided on a downstream side of the shut-off valve in the vent line, a water supplying means for supplying liquid-phase water to the recirculating line, and a system-pressure-difference measuring means for measuring a pressure difference between an air system and a fuel system of the fuel cell,

• wherein, when stopping power generation by the fuel cell or when the power generation by the fuel cell comes to an abnormal stop, the control method opens the shut-off valve, while causing a predetermined amount of pressure loss in the vent line by using the pressure loss means, and thus controls a water flow volume of the water supplying means so that the pressure difference measured by the system-pressure-difference measuring means reaches a predetermined value.

A control program of a combined power generation system that combines a fuel cell and an internal combustion engine and that is equipped with an exhaust fuel gas line that feeds exhaust fuel gas from the fuel cell by means of a blower, an exhaust-fuel-gas supplying line that splits off from a branching point of the exhaust fuel gas line and that supplies the exhaust fuel gas to the internal combustion engine, a recirculating line that splits off from the branching point and that circulates the exhaust fuel gas to the fuel cell, a shut-off valve that is provided in a vent line that splits off on an upstream side of the branching point, a pressure loss means that is provided on a downstream side of the shut-off valve in the vent line, a water supplying means for supplying liquid-phase water to the recirculating line, and a system-pressure-difference measuring means for measuring a pressure difference between an air system and a fuel system of the fuel cell,

• wherein, when stopping power generation by the fuel cell or when the power generation by the fuel cell comes to an abnormal stop, the control program causes a computer to execute control in which the shut-off valve is opened, while causing a predetermined amount of pressure loss in the vent line by using the pressure loss means, and thus, a water flow volume of the water supplying means is controlled so that the pressure difference measured by the system-pressure-difference measuring means reaches a predetermined value.