A thermal power generation apparatus includes a control circuit that selects a single operation mode from among a plurality of modes including a normal mode and a specific mode on the basis of a voltage in a commercial system. The normal mode is an operation mode in which alternating-current power output from an inverter is adjusted so that a direct-current voltage in a direct-current power line follows a target voltage. The specific mode is an operation mode in which direct-current power absorbed by an electric power absorber and/or the amount of heat per unit time supplied to a heat engine are/is adjusted so that the direct-current voltage follows the target voltage.