Power plant and method of controlling same

A power plant comprising:

• a pump configured to compress a working fluid;
• a heat exchanger apparatus configured to cause heat exchange between the working fluid transferred from the pump and an external heat source;
• a power turbine generator configured to generate a rotational force by using the working fluid heated through the heat exchange performed in the heat exchanger apparatus, to generate electricity using the rotational force, and to supply the electricity to an electrical grid, the power turbine generator operating during a first operation session in which synchronization with the electrical grid is performed, during a second operation session in which the power turbine generator operates in synchronization with the electrical grid after the synchronization with the electrical grid is successfully performed through the first operation session, and during a third operation session in which a shut-down operation is performed during the second operation session, the power turbine generator exhibiting an inlet pressure and operating during the second operation session between upper and lower limits of a normal range of the inlet pressure;
• a condenser configured to cool the working fluid discharged from the power turbine generator;
• a working fluid supply line connected to the heat exchanger apparatus and the power turbine generator at respective ends thereof to provide a flow path from the heat exchanger apparatus to the power turbine generator for the working fluid discharged from the heat exchanger apparatus;
• a pressure sensor installed on the working fluid supply line and configured to measure a pressure of the working fluid supplied to the power turbine generator and to output a measurement value indicative of the inlet pressure of the power turbine generator;
• a working fluid recovery line connected to the power turbine generator and the condenser at respective ends thereof to provide a flow path from the power turbine generator to the condenser for the working fluid;
• a bypass line connected to the working fluid supply line and the working fluid recovery line at respective ends thereof to cause a portion of the working fluid flowing through the working fluid supply line to bypass the power turbine generator and to directly flow to the working fluid recovery line;
• a controller comprising a first controller and a second controller;
• a first control valve installed on the working fluid supply line and controlled by the first controller to control a flow rate of the working fluid flowing through the working fluid supply line according to a rotational speed of a turbine in the power turbine generator during the first operation session and to control the flow rate of the working fluid flowing through the working fluid supply line according to the measurement value of the pressure sensor during the second operation session;
• and
• a second control valve installed on the bypass line and controlled by the second controller to have an open state to control a flow rate of the working fluid flowing through the bypass line according to the measurement value of the pressure sensor during the first operation session, the flow rate through the second control valve rising during the first operation session,
• wherein the first controller is configured to automatically switch from a first mode corresponding to the first operation session in which the first controller controls the first control valve based on the rotational speed of the turbine to a second mode corresponding to the second operation session in which the first controller controls the first control valve based on the inlet pressure of the power turbine generator and is further configured
• to perform the second mode by increasing an opening of the first control valve when the measurement value of the pressure sensor reaches the lower limit of the normal range of the inlet pressure, and
• to completely close the opening of the first control valve in response to a shut-down command initiating the third operation session, and
• wherein the second controller is configured to control the second control valve to have the open state to control the flow rate of the working fluid flowing through the bypass line according to the measurement value of the pressure sensor during the first operation session, the flow rate through the second control valve rising during the first operation session, and is further configured
• to change the open state of the second control valve by increasing an opening of the second control valve when the measurement value of the pressure sensor reaches the upper limit of the normal range during the second operation session, and
• to gradually increase the open state of the second control valve in response to the shut-down command, the gradual increasing performed according to the measurement value of the pressure sensor.