Power generation plant and method for operating power generation plant

Abstract

A power generation plant includes a plant device, an AC motor for starting the plant device, at least one DC power source, and an inverter disposed between the at least one DC power source and the AC motor and between the at least one DC power source and an electrical power grid. The inverter is configured to convert DC power from the at least one DC power source to AC power and is capable of selectively supplying the AC power to the AC motor or the electrical power grid.

1 - 19 . (canceled) 
     
     
         20 . A power generation plant comprising:
 a plant device having a rotational shaft;   an AC motor for starting the plant device by rotationally driving the rotational shaft, the AC motor being coupled to the rotational shaft;   an AC generator configured to be driven by the plant device serving as a prime mover and configured to supply generated electric power to an electrical power grid; and   at least one DC power source; and a first inverter disposed between the at least one DC power source and the AC motor and between the at least one DC power source and the electrical power grid,   wherein the first inverter is configured to convert DC power from the at least one DC power source to AC power and is capable of selectively supplying the AC power to the AC motor or the electrical power grid.   
     
     
         21 . The power generation plant according to  claim 20 , further comprising:
 a first switch for switching a connection state between the first inverter and the electrical power grid;   a rectifier, disposed between the at least one DC power source and the electrical power grid in parallel with the first inverter and the first switch, for converting AC power from the electrical power grid to DC power; and   a second switch, disposed between the at least one DC power source and the electrical power grid in parallel with the first inverter and the first switch, for switching a connection state between the rectifier and the electrical power grid,   wherein the at least one DC power source includes a secondary battery or an electrochemical fuel production power generation device configured to receive DC current from the rectifier.   
     
     
         22 . The power generation plant according to  claim 20 , further comprising:
 a rectifier, disposed between the at least one DC power source and the AC generator, for converting AC power from the AC generator to DC power,   wherein the at least one DC power source includes a secondary battery or an electrochemical fuel production power generation device configured to receive DC power from the rectifier.   
     
     
         23 . The power generation plant according to  claim 20 , further comprising:
 a second inverter disposed between the at least one DC power source and the electrical power grid in parallel with the first inverter,   wherein the second inverter is configured to convert DC power from the at least one DC power source to AC power and supply the AC power to a power demand part different from the AC motor while the first inverter supplies AC current to the AC motor.   
     
     
         24 . The power generation plant according to  claim 20 , wherein the AC generator is configured to function as the AC motor for starting the prime mover. 
     
     
         25 . The power generation plant according to  claim 20 , wherein the AC generator is configured to be supplied with DC power from the at least one DC power source as excitation power of the AC generator. 
     
     
         26 . The power generation plant according to  claim 24 , wherein the AC generator is used as the AC motor. 
     
     
         27 . The power generation plant according to  claim 20 , wherein:
 the plant device includes a gas turbine; and   the AC motor is configured to drive the gas turbine.   
     
     
         28 . The power generation plant according to  claim 27 , wherein:
 the at least one DC power source includes a fuel cell including an anode, a cathode configured to be supplied with a gas containing carbon dioxide, and an electrolyte configured to transport a carbonate ion derived from the carbon dioxide from the cathode to the anode; and   the cathode is configured to be supplied with an exhaust gas from the gas turbine as the gas containing the carbon dioxide.   
     
     
         29 . The power generation plant according to  claim 20 , further comprising an electrochemical fuel production device disposed in parallel with the at least one DC power source. 
     
     
         30 . The power generation plant according to  claim 20 , wherein the first inverter is configured to supply the AC power to the AC motor while increasing a frequency of the AC power at start-up of the plant device, and the first inverter is configured to supply the AC power with a normal frequency to the electrical power grid during a period other than start-up of the plant device. 
     
     
         31 . A method for operating a power generation plant including a plant device having a rotational shaft, an AC motor coupled to the rotational shaft, at least one DC power source, an AC generator configured to be connectable to an electrical power grid, and a first inverter disposed between the at least one DC power source and the AC motor and between the at least one DC power source and the electrical power grid, the method comprising:
 a step of generating DC power by the at least one DC power source;   a step of converting the DC power to AC power by the first inverter;   a step of supplying AC power from the first inverter to the AC motor and starting the plant device by rotationally driving the rotational shaft by the AC motor;   a step of, after the plant device is started, driving the AC generator by the plant device serving as a prime mover and supplying AC power generated by the AC motor to the electric power grid; and   a step of supplying AC power from the first inverter to the electrical power grid during operation of the plant device after the plant device is started.   
     
     
         32 . The method for operating the power generation plant according to  claim 31 ,
 wherein the power generation plant further includes a rectifier disposed between the at least one DC power source and the electrical power grid in parallel with the first inverter,   wherein the at least one DC power source includes a secondary battery or an electrochemical fuel production power generation device, and   wherein the method includes:
 a step of converting DC power from the at least one DC power source to AC power by the first inverter and supplying the AC power to the electrical power grid during operation of the plant device; and 
 a step of converting AC power from the electrical power grid to DC power by the rectifier and supplying the DC power to the secondary battery or the electrochemical fuel production power generation device when a power demand is below a specified value in the electrical power grid. 
   
     
     
         33 . The method for operating the power generation plant according to  claim 31 ,
 wherein the power generation plant includes a rectifier disposed between the at least one DC power source and the AC generator,   wherein the at least one DC power source includes a secondary battery or an electrochemical fuel production power generation device, and   wherein the method includes:
 a step of disconnecting the AC generator from the electrical power grid; and 
 a step of supplying regenerative power from the AC generator to the secondary battery or the electrochemical fuel production power generation device via the rectifier until the prime mover is stopped after the AC generator is disconnected. 
   
     
     
         34 . The method for operating the power generation plant according to  claim 33 ,
 wherein the at least one DC power source includes the secondary battery, and   wherein the method further includes a step of maintaining a free capacity for the regenerative power in the secondary battery during operation of the plant device.   
     
     
         35 . The method for operating the power generation plant according to  claim 31 ,
 wherein the power generation plant includes a second inverter disposed between the at least one DC power source and the electrical power grid in parallel with the first inverter, and   wherein the method further includes a step of converting DC power from the at least one DC power source to AC power by the second inverter and supplying the AC power to a power demand part different from the AC motor while the first inverter supplies AC current to the AC motor for starting the plant device.   
     
     
         36 . The method for operating the power generation plant according to  claim 31 ,
 wherein the at least one DC power source includes a secondary battery, and   wherein the method further includes a step of keeping the secondary battery storing a necessary amount of electric power for starting the plant device during operation of the plant device.   
     
     
         37 . The method for operating the power generation plant according to  claim 36 ,
 wherein the at least one DC power source further includes one or more power sources other than the secondary battery, and   wherein the keeping step includes supplying electric power from the one or more power sources to the secondary battery so that the secondary battery stores the necessary amount of electric power for starting the plant device.   
     
     
         38 . The method for operating the power generation plant according to  claim 37 ,
 wherein the one or more power sources include a solar cell, and   wherein the method further includes:
 a step of predicting electric power generated by the solar cell; and 
 a step of determining a power supply amount from the solar cell to the secondary battery in the keeping step, based on a prediction result in the predicting step. 
   
     
     
         39 . The method for operating the power generation plant according to  claim 31 ,
 wherein the at least one DC power source includes a secondary battery and one or more power sources other than the secondary battery, and   wherein the step of starting the plant device includes supplying DC power from the one or more power sources to the AC motor via the first inverter in preference to DC power stored in the secondary battery.   
     
     
         40 . The method for operating the power generation plant according to  claim 31 ,
 wherein the step of starting the plant device includes supplying the AC power to the AC motor while increasing a frequency of the AC power via the first inverter, and   wherein the step of supplying to the electrical power grid includes supplying the AC power with a normal frequency to the electrical power grid via the first inverter.