Combined generating plant and its start-up control device and start-up control method

A method for effecting start-up of a combined generating plant, using a high-pressure steam turbine, when the combined generating plant is in a warm start condition, said plant having a gas turbine, a steam turbine and a generator coupled to a single shaft, said steam turbine having said high pressure steam turbine and a low-pressure steam turbine driven by introducing high-pressure steam from a high-pressure drum and low-pressure steam from a low-pressure drum thereto, respectively, an auxiliary steam system for supplying auxiliary low-pressure steam to said low-pressure steam turbine, and high- and low-pressure steam regulating valves for regulating flow rates of the high- and low-pressure steam, respectively, comprising the following steps:

• determining whether said combined generating plant is in a warm start condition;
• disabling speed of rotation control of the low-pressure steam turbine by said low-pressure steam regulating valve when the warm start condition is recognized;
• controlling a speed of rotation of said low-pressure steam turbine to coincide with a set value of start-up speed of said high-pressure steam turbine whose speed of rotation is set beforehand, by regulating said high-pressure steam regulating valve;
• compensating for the change of rotational speed of said high-pressure steam turbine corresponding to an amount of the rotational torque applied to said high-pressure steam turbine by said gas turbine when fuel is introduced into said gas turbine by further regulating said high-pressure steam regulating valve;
• supplying to said high-pressure steam turbine a predetermined minimum flow rate of steam when the rotational speed of said high-pressure steam turbine reaches a predetermined value;
• and
• shifting to pressure control of said high-pressure drum by fully opening said high-pressure steam regulating valve when start-up of said combined generating plant is completed.

A combined generating plant, comprising:

• a gas turbine driven by combustion of fuel;
• a steam turbine;
• a generator coupled to said gas turbine and said steam turbine on a single shaft;
• steam generation means provided with a high-pressure drum for generating high-pressure steam and a low-pressure drum for generating low-pressure steam, by heat exchange with waste gas burnt in said gas turbine;
• first and second means for introducing said high- and low-pressure steam to said steam turbine, respectively, said steam turbine being provided with a high-pressure turbine driven by introducing the high-pressure steam from said high-pressure drum via said first means and a low-pressure turbine driven by introducing the low-pressure steam from said low-pressure drum via said second means;
• an auxiliary steam system connected to said second means for supplying auxiliary low-pressure steam to said low-pressure turbine during start-up;
• a high-pressure steam regulating valve disposed in said first means for regulating a flow rate of high-pressure steam into said high-pressure turbine from said high-pressure drum;
• a low-pressure steam regulating valve disposed in said second means for regulating a flow rate of low-pressure steam into said low-pressure turbine from said low-pressure drum and a flow rate of auxiliary low-pressure steam into said low-pressure turbine from said auxiliary steam system;
• and
• a start-up control device for effecting start-up in a cold start condition, using said low-pressure turbine, comprising:
• start-up preparation means, on being actuated by a start-up command, for determining whether said combined generating plant is in a cold start condition, and for actuating said auxiliary steam system when the cold start condition is recognized,
• rotational speed control means for controlling a speed of rotation of said low-pressure turbine to a set value of start-up speed of said low-pressure turbine by setting a degree of opening of said low-pressure steam regulating valve,
• speed of rotation control and correction means for compensating for a change of rotational speed of said low-pressure turbine corresponding to an amount of rotational torque applied to said low-pressure turbine by said gas turbine when said fuel is introduced into said gas turbine by regulating said degree of opening of said low-pressure steam regulating valve,
• low-pressure turbine overheating prevention means, actuated when the speed of rotation of said low-pressure turbine reaches a predetermined value, for preventing said degree of opening of said low-pressure steam regulating valve from falling below a predetermined value which supplies to said low-pressure turbine a predetermined minimum flow rate of said low-pressure steam, and
• start-up completion means for fully opening said low-pressure steam regulating valve when start-up of said combined generating plant is completed.

A combined generating plant, comprising:

• a gas turbine driven by combustion of fuel;
• a steam turbine;
• a generator coupled to said gas turbine and said steam turbine on a single shaft;
• steam generation means provided with a high-pressure drum for generating high-pressure steam and a low-pressure drum for generating low-pressure steam, by heat exchange with waste gas burnt in said gas turbine;
• first and second means for introducing said high- and low-pressure steam to said steam turbine, respectively, said steam turbine being provided with a high-pressure turbine driven by introducing the high-pressure steam from said high-pressure drum via said first means and a low-pressure turbine driven by introducing the low-pressure steam from said low-pressure drum via said second means;
• an auxiliary steam system connected to said second means for supplying auxiliary low-pressure steam to said low-pressure turbine during start-up;
• a high-pressure steam regulating valve disposed in said first means for regulating a flow rate of high-pressure steam into said high-pressure turbine from said high-pressure drum;
• a low-pressure steam regulating valve disposed in said second means for regulating a flow rate of low-pressure steam into said low-pressure turbine from said low-pressure drum and a flow rate of auxiliary low-pressure steam into said low-pressure turbine from said auxiliary steam system;
• and
• a start-up control device for effecting start-up in a warm start condition, using said high-pressure turbine, comprising:
• start-up preparation means, on being actuated by a start-up command, for determining whether said combined generating plant is in a warm start condition, and for disabling speed of rotation control of the low-pressure turbine by said low-pressure steam regulating valve when the warm start condition is recognized,
• rotational speed control means for controlling a speed of rotation of said high-pressure turbine to a set value of start-up speed by setting a degree of opening of said high-pressure steam regulating valve,
• speed of rotation control and correction means for compensating for a change of rotational speed of said high-pressure turbine corresponding to an amount of rotational torque applied by said gas turbine to said high-pressure turbine when said fuel is introduced into said gas turbine by regulating said degree of opening of said high-pressure steam regulating valve,
• high-pressure turbine overheating prevention means, actuated when the rotational speed of said high-pressure turbine reaches a predetermined value, for preventing said degree of opening of said high-pressure steam regulating valve from falling below a predetermined value which supplies to said high-pressure turbine a predetermined minimum flow rate of said high-pressure steam, and
• load control means for fully opening said high-pressure steam regulating valve when start-up of said combined generating plant is completed, and for shifting to pressure control of said high-pressure drum.