Power Generation System and Power Generation Method

A power generation method that uses:

• a multi-shaft gas turbine, which includes a high pressure turbine shaft, a compressor which generates compressed air according to rotation of the high pressure turbine shaft, a combustor which generates a combustion gas by mixing and burning the compressed air and fuel, a high pressure turbine which rotates by receiving the combustion gas and drives the high pressure turbine shaft, a low pressure turbine shaft, and a low pressure turbine which rotates by receiving a gas discharged from the high pressure turbine and drives the low pressure turbine shaft;
• a first power generator that is connected to a power system, generates power using the rotation of the low pressure turbine shaft, and outputs the generated power to the power system;
• a second power generator that accelerates or decelerates the high pressure turbine shaft according to input or output of power;
• a frequency converter that is connected to a terminal of the second power generator;
• and a transformer that is connected between the frequency converter and a terminal of the first power generator, the method comprising:
• storing an output target value as a time-series target value of output of the power generation system;
• calculating an output prediction value of the first power generator in a case where a combustor is controlled so as to match the output of the first power generator to the output target value using a dynamic characteristic model simulating a dynamic characteristic of the multi-shaft gas turbine;
• calculating a first power generator output instruction value as an instruction value for the output from the first power generator to the power system and a second power generator output instruction value as an instruction value for the output from the second power generator to the power system based on the output target value and the output prediction value of the first power generator;
• controlling the combustor based on the first power generator output instruction value;
• controlling the frequency converter based on the second power generator output instruction value;
• performing frequency-conversion of the output of the second power generator by the frequency converter and outputting the converted output to the power system based on an instruction from the control unit when the first power generator output instruction value is smaller than the output target value, accordingly, outputting power to be obtained by decelerating the high pressure turbine shaft to the frequency converter by the second power generator, and boosting the output of the frequency converter by the transformer and outputting the boosted output to the power system;
• and
• performing frequency-conversion of a part of the output of the first power generator by the frequency converter and outputting the converted output to the second power generator based on an instruction from the control unit when the first power generator output instruction value is larger than the output target value, accordingly, stepping down the part of the output of the first power generator by the transformer and outputting the stepped-down output to the frequency converter, and accelerating the high pressure turbine shaft by the second power generator using the output of the frequency converter.