Patent Application
20160252015
The present invention relates to a combination of renewable energy with a power generation apparatus using a gas turbine. In particular, the present invention relates to a control apparatus and a control method for suppressing an output change, satisfying requirements of a system to be connected, and improving an output and an efficiency of the gas turbine according to operation conditions.
A thermal power generation plant mainly generates power by burning fossil fuel to take out combustion heat, and using the combustion heat to operate a power generator. Various apparatuses have been provided according to the combinations of fuel and power generators. Examples of such apparatuses include an apparatus that generates power by burning coal or heavy oil in a boiler to take out combustion heat, and generating steam by the combustion heat to operate a steam turbine, a gas turbine power generation apparatus that generates power by compressing atmospheric air with a compressor, and mixing and burning the compressed air with fuel in a combustor to operate a gas turbine, or a combined cycle power generation apparatus that operates a steam turbine with steam generated in an exhaust heat recovery boiler using an exhaust heat burned in a gas turbine.
Meanwhile, power generation using renewable energy, such as natural energy, has been attracting attentions from a viewpoint of reducing carbon dioxide. In particular, power generation using wind power generation or solar power generation has been rapidly spreading. However, it is not possible to control natural conditions, and a load of the obtained power generation output becomes a variable load instead of a constant load. If such a power supply is connected to a system, the load of the system becomes unstable and a constant frequency of the system cannot be maintained. Meanwhile, steam power generation, such as the power generation using a gas turbine, is generally designed to reach the maximum efficiency during rated operations, such that the efficiency decreases during partial load operations.
PTL 1 discloses a control apparatus that issues a power generation command according to the system load, and adjusts an exhaust heat recovery volume or heat storage volume of the thermoelectric load a power system in which a plurality of power supplies and thermoelectric loads having different volumes, such as a gas engine or a gas turbine power generator, are connected to correspond to an unstable power supply of wind power generation or solar power generation. PTL 2 discloses an apparatus and a control method when the electric power obtained by wind power generation is combined with a combined plant, such as a plant for reforming heavy oil.
PTL 1: Publication of JP 2005-151746 A
PTL 2: Publication of JP 2008-285571 A
In the power generation facility using renewable energy, a load change is a problem, because the output of such power generation facility is affected by the change of weather. In the future, the renewable energy will be further introduced by considering environment and diversification of energy sources, and the problem of the load change will be more apparent. In the methods disclosed in PTL 1 and PTL 2, the renewable energy is combined with an existing power generation apparatus represented by a gas turbine power generation apparatus, while a separate apparatus that recovers excessive power relative to necessary power supply volume are also provided. However, regulations and rules of the system to be connected are not considered. Since the output characteristics of each power generation apparatus are not considered, a desired load is not always attained when the actual output corresponding to a load command is combined with the power generation output obtained from the renewable energy. It is, therefore, difficult to correspond to generation and supply of power within the regulations of the system to be connected, relative to the load change of the renewable energy.
It is an object of the present invention to provide a power generation system having a high following property to follow a load change.
To solve the above problem, an embodiment of the present invention is a multi-shaft gas turbine power generation system including a compressor that compresses air to generate compressed air, a combustor that generates a combustion gas from the compressed air and fuel, a gas generator including a high pressure turbine driven by the combustion gas, a power turbine including a low pressure turbine driven by a gas exhausted from the gas generator and a main power generator that generates power by a rotational force of the low pressure turbine to supply power to a system, an electric motor and power generator connected to the gas generator and the power turbine via a frequency converter, and a control apparatus, the gas generator and the power turbine having different shafts, in which the control apparatus receives a load target of the system and a load change factor of the system and outputs a control signal of the frequency converter.
According to the embodiment of the present invention, a power generation system having a high following property to follow a load change is provided.
A best mode of a control apparatus and a control method of a gas turbine capable of corresponding to renewable energy will be described below by referring to the accompanying drawings.
A power turbine 16 includes a low pressure turbine 2b, a low pressure turbine shaft 12b and a power generator 5. For power generation, the power turbine 16 rotates at an approximately constant number of rotations and drives the power generator 5 at an approximately constant number of rotations. The power generated by the power generator 5 is sent to a power consumer via an electric power cable.
The gas generator 15 includes a compressor 1, a combustor 20, a high pressure turbine 2a, a sub-electric motor/power generator 6 that functions as an electric motor and a power generator, and a gas generator shaft 12a.
The gas generator 15 is mechanically separated from the power turbine 16, and can be rotated at the number of rotations different from that of the power turbine.
The compressor 1 sucks and compresses atmospheric air to generate compressed air 21. An inlet guide vane (IGV) 9 is provided at the inlet port of the compressor 1. The IGV 9 rotates by itself to change an opening area of the compressor 1. By changing the opening, the amount of air flowing into the compressor 1 can be changed.
The amount of air flowing into the compressor 1 can also be adjusted according to the number of rotations of the gas generator 15.
The combustor 20 mixes the compressed air 21 generated by the compressor 1 with fuel and burns the mixture by a burner 18 to generate a combustion gas 22. The combustion gas 22 passes through a combustor liner 19 to firstly flow into the high pressure turbine 2a. The fuel burned in the burner 18 is adjusted by a fuel flow rate control valve 8 provided in a fuel pipe.
The high pressure turbine 2a receives rotational force from the energy of the high temperature and high pressure combustion gas 22. The rotational force is transmitted to the compressor 1 through the gas generator shaft 12a to rotate the compressor 1. The combustion gas 22 flows into the low pressure turbine 2b of the power turbine 16 after a part of the energy is extracted in the high pressure turbine 2a. The low pressure turbine 2b obtains rotational force from the energy of the combustion gas 22, and transmits the rotational force to the generator 5 through the low pressure turbine shaft 12b to rotate the generator 5. The combustion gas 22 having passed through the low pressure turbine is discharged as an exhaust gas 14.
Part of the air compressed by the compressor 1 is bled as a cooling air 23 for turbines and supplied to the high pressure turbine 2a or the low pressure turbine 2b without passing through the combustor 20. Part of the cooling air 23 is used for cooling a stator vane 24 and a rotor vane 25 that constitute the turbine 2.
The sub-electric motor/power generator 6 connected to the high pressure turbine shaft 12a is connected to the power system via the frequency converter 10. By supplying and receiving the electric power to and from the power system, the operation of the high pressure turbine shaft can be adjusted. Specifically, the sub-electric motor/power generator 6 operates as a motor when the electric power is supplied from the frequency converter 10, and supplies energy to the high pressure turbine shaft 12a. In contrast, when the electric power is extracted by the frequency converter 10, the sub-electric motor/power generator operates as a generator and reduces energy of the high pressure turbine shaft 12a.
The controller 7a receives the input that includes the number of rotations of the high pressure turbine detected by a rotational speed detector 26a for the high pressure turbine, the number of rotations of the low pressure turbine detected by a rotational speed detector 26b for the low pressure turbine, and an output command (MWD). Subsequently, signals including an FFD signal that controls the flow rate control valve 8, a CIGV signal that controls the opening of the IGV 9, and an IMWD signal that controls the output power of the frequency converter 10 are transmitted. The control apparatus 7a may be configured to have various protecting functions.
In the present embodiment, if it is desired to increase the output, for example, in addition to the output control, by controlling the fuel flow rate, the number of rotations of the high pressure turbine shaft 12a is decreased to discharge the rotational energy of the shaft as the electric power. If it is desired to decrease the output, the number of rotations of the high pressure turbine shaft 12a is increased to allow the electric power to be stored as rotational energy. By using the output changing means that does not depend on the fuel flow rate, a high output changing speed can be attained, while preventing the reduction of service life due to thermal fatigue or the like.
The frequency converter 10 according to the present embodiment can be configured to have a smaller volume compared to the one that adjusts the entire output of the gas turbine. In the two-shaft gas turbine according to the present embodiment, the low pressure turbine responsible for the majority of the output rotates at a constant speed. Since the frequency converter 10 adjusts the number of rotations on the side of the high pressure turbine that operates at a variable speed, the volume of the frequency converter 10 can be decreased. For example, if it is desired to change the output equivalent to 10% of the rated output of the gas turbine, in addition to the output change by the fuel flow rate, the frequency converter 10 having a volume equivalent to 10% of the rated output may be used. Thus, the cost of the frequency converter 10 can be decreased.
An operation of the two-shaft gas turbine 27 is described to implement the above-described technique.
In the two-shaft gas turbine, balance adjustment control in which the energy recovered by the high pressure turbine 2a is made to be equal to the energy consumed in the compressor 1 is performed. In general, this control method includes changing the number of rotations of the gas generator, or changing the flow rate of air sucked by the compressor by adjustment of the opening of the IGV 9. For example, when the number of rotations is higher than the setting value, the consumption power of the compressor 1 increases and the number of rotations decreases by increasing the opening of the IGV 9 to increase the flow rate of the air sucked by the compressor. In contrast, by decreasing the opening of the IGV 9, the number of rotations of the gas generator 15 can be increased.
When the output changes due to the fuel flow rate, the two-shaft gas turbine 27 operates as follows. The GT control apparatus 7a sends a fuel flow rate command (FFD) to the fuel flow rate control valve 8 according to a GT output command (MWD), and supplies necessary fuel to the combustor 20 to balance the recovery energy between the output of the generator 5 and the low pressure turbine 2b. Thus, the number of rotations of the power turbine 16 is controlled to be approximately constant. At this time the GT control apparatus 7a controls the opening of the IGV 9 such that the energy recovered by the high pressure turbine 2a is balanced with the energy needed for driving the compressor 1 to attain a preferable number of rotations of the gas generator 15. Thus, the number of rotations of the gas generator 15 is not uniquely determined, but is subject to change.
The operation of the gas turbine in the case of increasing the demand according to the present embodiment is described by referring to
In the case where the demand change is small in the gas turbine according to the related art technique, the demand change can be absorbed by the output control by the fuel flow rate. However, when the demand change becomes larger, the output change cannot follow the change and the output becomes insufficient. Accordingly, the number of rotations of the low pressure turbine shaft 12b decreases and the system frequency also decreases correspondingly.
In the gas turbine according to the present embodiment, the frequency converter 10 is used to extract, from the sub-electric motor/power generator, an insufficient portion of the output caused by the output change of the fuel flow rate. The electric power is insufficient when only the fuel flow rate is controlled. However, in the configuration of the present embodiment, the number of rotations of the high pressure turbine shaft 12a decreases and the rotational energy is converted to the electric power to compensate for the insufficiency. At this time, the opening of the IGV 9 is determined such that the power of the compressor 1 is balanced with the recovery power of the high pressure turbine 2a at the decreased number of rotations. The output frequency of the high pressure turbine shaft 12a is converted to a reference frequency by the frequency converter 10. By doing this, the frequency of the system can be stabilized even when the demand changes abruptly. The frequency converter 10 may be implemented by, for example, a known inverter/converter.
When the power of the compressor 1 is configured to be balanced with the recovery power of the high pressure turbine 2a, that is, the IGV 9 is opened when the number of rotations decreases, and the IGV 9 is closed when the number of rotations increases, the flow rate of the air sucked by the compressor 1 is approximately constant. Thus, the control apparatus controls the IGV 9 in such a manner that the flow rate change of the air flowing through the compressor 1 is suppressed when the number of rotations of the gas generator 15 changes due to the operation of the frequency converter 10. Therefore, a highly reliable operation can be achieved.
In general, when the IGV 9 is opened, the efficiency of the compressor 1 improves. At this time, if, for example, the flow rate of the fuel is increased and the number of rotations is decreased during the increase of the output, the efficiency of the compressor improves, the temperature of the air discharged from the compressor 1 decreases, and the operating power of the compressor 1 also decreases. In addition to the increase of the output caused by the increase of the fuel, the output also increases for the decrease of the operating power of the compressor 1. Further, due to the decrease of the temperature of the discharged air, the temperature of the combustion gas 22 also decreases. Accordingly, the temperature change of the gas corresponding to the output change can be decreased, and the reliability can be improved. In contrast, when the flow rate of the fuel is decreased and the number of rotations is increased, the compression efficiency decreases, the temperature of the air discharged from the compressor 1 increases, and the operating power of the compressor 1 also increases. Thus, in addition to the decrease of the output caused by the decrease of combustion, the output also decreases for the increase of the operating power of the compressor 1. Further, by the increase of the temperature of the discharged air, the temperature of the combustion gas 22 also increases. Accordingly, the temperature change of the gas corresponding to the output change can be decreased, and the reliability can be improved. A useful synergetic effect like this can be obtained.
In the design of the compressor, an operating point at which the compression efficiency increases during the decrease of the number of rotations and the compression efficiency decreases during the increase of the number of rotations may be set based on a reference state where the frequency converter 10 does not convert the frequency. Accordingly, a useful synergetic effect similar to that mentioned above can be obtained.
A two-shaft gas turbine power generation apparatus 100 receives a control signal 150 from the control apparatus 200 and is controlled to a desired state. A state quantity of each part of the two-shaft gas turbine power generation apparatus 100 is input to the control apparatus 200 as a measurement signal 140.
The control apparatus 200 executes control by manipulating operation terminals according to the measurement signal 140 from the gas turbine power generation apparatus to attain an operation state appropriate for a power generation request.
A related information database 300 stores information for predicting and understanding the current state of the wind power generation. An operation information database 600 stores the measurement signals 120, 140 obtained from the wind power generation facility 10 and the gas turbine power generation apparatus 100, respectively. Format of the data will be described in detail later.
A model calculator 400 calculates an output value to be obtained when a signal that offsets a prediction value and a change in the wind power generation from the information obtained from the measurement signals is input to the two-shaft gas turbine. To calculate the prediction value of the output of the wind power generation, information of the atmospheric air, such as a temperature of the outside air or humidity, a wind speed, an output of the wind power generator, or the like are needed as necessary data. Format of the data will be described in detail later.
A controller 500 receives the result of the model calculator and outputs an appropriate control signal 130. According to the control signal, the air volume and the fuel flow rate of the two-shaft gas turbine are manipulated and the output is controlled. This also applies to the control signal of the frequency converter. Signals and information generated in the control apparatus are also output to a maintenance tool 910. Algorithm to determine the control signals will be described in detail later.
A user who is related to the two-shaft gas turbine power generation apparatus 100 can see various information regarding the gas turbine power generation apparatus 100 with the input apparatus 900, which includes a keyboard 901 and a mouse 902, and the support tool 910 connected to an image display apparatus 950, and can also access to the information in the control apparatus 200.
The support tool 910 includes an external input interface 920, a data transmission/reception processing unit 930, and an external output interface 940.
An input signal 800 generated by the input apparatus 900 is input to the support tool 910 via the external input interface 920. Information from the inside of the control apparatus 200 is also input similarly via the external input interface 920. In the data transmission/reception processing unit 930, an input signal 801 is processed according to the information of the input signal 800 from the user, and transmitted to the external output interface 940 as an output signal 802. An output signal 803 is displayed on the image display apparatus 950.
The measurement signals stored in the related information database 300 and the operation information database 600 are described.
First,
As illustrated in
Other information, such as design information of the wind power generation facility, design information of the two-shaft gas turbine power generation apparatus, and information of regulations and rules of the system to be connected, are also stored.
Next, information of the measurement signal obtained from the wind power generation facility and the two-shaft gas turbine power generation apparatus is described.
Next, the operation of a prediction arithmetic function of the model calculator 400 in the control apparatus 200 is described by referring
To constitute the model, parameters within the model are learned based on the data accumulated in the past or the design data. After the operation has started, prediction is performed based on the learned parameters. When a difference between the prediction value and the actual measurement value becomes larger than the setting value, the model 15 learned again based on the data having been accumulated heretofore.
In addition, it is determined, according to the mode to be applied, as to whether different models may be generated for individual wind power generators, or one model may be generated for the entire wind firm.
A length of time for prediction is determined according to the characteristic of the power generation output of the two-shaft gas turbine. That is, it is necessary to predict in advance a delay from the supply of the load command to actual power generation. This is also related to the flowchart of
With the configuration including the prediction means for predicting the change of power supply and demand, and changing the number of rotations according to the prediction value of the change of power supply and demand, the control can be executed in a more appropriate manner.
Next, calculations of the output command to the two-shaft gas turbine power generation apparatus, that is, model calculations of the MWD, which is supplied, to the two-shaft gas turbine, and the IMWD, which is supplied to the frequency converter, are described. A model that expresses a dynamic characteristic of the two-shaft gas turbine 27 is previously determined. Usually, a dynamic characteristic model based on the mass balance of the pressure or the flow rate is used, but the modelling based on the neural network used in the prediction calculation of the wind power generation output can also be used. The maximum load change rate of the gas turbine is set in the dynamic characteristic of the two-shaft gas turbine. The amount of power to be supplied from the two-shaft gas turbine power generation apparatus is equivalent to the output that offsets the wind power generation output, that is, the output obtained by subtracting the wind power generation output from a certain target load. Since the two-shaft gas turbine includes a delay due to mechanical elements, the output may be delayed relative to the changing pattern of the input load. As a result of this, the output value from the wind power generation apparatus and the output value from the two-shaft gas turbine 27 do not exactly match, and an offset leakage is generated. This is calculated using the above-described dynamic characteristic model. In this case, the load is followed within the maximum load change rate at which the dynamic characteristic model is set, and the obtained output becomes the MWD to the two-shaft gas turbine without any change. The offset leakage becomes the IMWD to be supplied to the frequency converter.
Next, the operation regarding the generation of the MWD and the IMWD in the controller 500 is described by referring to the flowchart of FIG. By providing the means for calculating the requested load of the gas turbine and the drive load of the compressor so as to satisfy the load target and the system frequency, the control having an excellent system stability and a following property to follow a load target can be achieved.
First, in step 501, an error between the prediction value, which is output from the model generated by the prediction of the wind power generation of the model calculator 400, and the current measurement value calculated. It is confirmed whether the error is equal to or smaller than a predetermined value. If yes, the process proceeds to step 502. Otherwise, the process proceeds to step 504 and the model illustrated in
In step 503, the prediction value of the wind power generation is subtracted from the load target.
In step 505, the output value of the wind power generation is subtracted from the load target. That is, the prediction value is not used.
In step 506, the value calculated in step 503 or 505 is input to the gas turbine model to calculate the output value of the model. In step 507, the output value of the model calculated in step 506 is subtracted from the load target. In step 508, the model output value is regarded as the MWD and the remaining output value is regarded as the IMWD.
In step 509, the input load to the M/G is calculated according to the atmospheric temperature and the model output value. As a basic characteristic of the gas turbine, the mass flow rate of the compressed air input from the compressor decreases according to the increase of the atmospheric temperature. As a result of this, the power generation output decreases. This is indicated in
The two-shaft gas turbine power generation apparatus according to the present embodiment functions as a motor or a power generator by supplying electricity to or applying a load on the M/G connected on the side of the compressor. By supplying electricity to assist the compressor, the output can be improved even when the atmospheric temperature is high. This is illustrated in
This also applies to the efficiency of the power generation. As illustrated in
In step 510, the assist amount calculated in the previous step is set as the command for the M/G.
Next, a method for displaying information, which includes the measurement signal 120, the control signal 130, the related information database 300, the setting values, and the operation information database 600, on the image display apparatus 950 by the user using the support tool 910 is described.
By clicking a back button 968 in
In a measurement signal display space 961, the user inputs, in an input space 981, the measurement signal or the operation signal desired to be displayed on the image display apparatus 950 together with a range (upper limit/lower limit) of the signal. In addition, the desired time to be displayed is input to a time input space 982.
By clicking a display button 963, trend graphs are displayed on the image display apparatus 950 as illustrated in
In a related information display space 984, any one of the weather, the temperature, the wind direction, the wind speed, humidity, and the amount of solar radiation is selected. A display button 985 is then clicked to search the related information database 300 and display information including the selected information. As described above, to express the weather, 15 kinds of weather conditions announced to the public by Japan Meteorological Agency are used. Numbers are allocated according to the type to display trends. That is, the numbers up to 14 are allocated in such a manner that 0 indicates very fine, 1 indicates fine, 2 indicates a bit cloudy, and so on. By inputting the desired time to be displayed in the time input space 985 and clicking the display button 986, the trend graphs are displayed on the image display apparatus 950 as illustrated in
By clicking a back button 989 in
By providing the output function to allow the control apparatus to output various signals to the display apparatus to display the screens described above, it is possible to help the operator to execute control in a better way. In particular, it would be preferable if at least the tolerance range of the load change or the tolerance range of the frequency change can be displayed, because the operator can then easily recognize how the current operation affects the load or the system.
In the embodiments described above, the multi-shaft gas turbine power generation system includes the compressor 1 that compresses air to generate compressed air, the combustor 20 that generates a combustion gas from the compressed air and fuel, the gas generator 15 including the high pressure turbine 2a driven by the combustion gas, the power turbine 16 including the low pressure turbine 2b driven by the gas exhausted from the gas generator 15 and the main power generator 5 that generates power by the rotational force of the low pressure turbine 2b to supply power to the system, the sub-electric motor/power generator 6 configured to be an electric motor and power generator and connected to the gas generator 15 and the power turbine 16 via the frequency converter 10, and the control apparatus 200. The gas generator 15 and the power turbine 16 have different shafts. The control apparatus 200 receives the load target of the system and the load change factor of the system, and outputs the control signal of the frequency converter.
By controlling the frequency converter according to the load target of the system and the output change of the system, the power generation system having an high following property to follow the load change can be provided. This is because the mechanical delay of the gas turbine is compensated for by inertia of the compressor shaft or absorption/discharging of the electric energy, such that power generation and power supply can be executed within the regulations of the system to be connected. This can be realized with the smallest system, because no facility corresponding to surplus power is needed. In addition, a high versatility is achieved, due to the ability of corresponding to any type of system.
Such effects becomes particularly apparent by changing the number of rotations of the gas generator 15 by the frequency converter 10, when the output change exceeding the change amount of the load change due to the flow rate control of the fuel of the gas turbine is requested.
As an example of the load change factor of the system herein, the information from the power generation system using the natural energy has been described. The wind power generation has been described in the first embodiment and the solar power generation has been described in the second embodiment. Similar effects can be obtained so long as the power generation system includes a variable power supply quantity to the systems.
In the embodiments, the databases have been described in the format included in the control apparatus 200, but the databases can be provided as separate devices. As to the control apparatus 200 itself, only an example has been described in
In the first and second embodiments, the power generation apparatus only includes the two-shaft gas turbine, but multi-shaft gas turbines having more than two shafts may be used. Alternatively, a combined cycle power generation apparatus that generates power using the exhaust heat of the gas turbine to generate steam and operate a steam turbine may also be applicable in a similar manner.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2013/081831 | 11/27/2013 | WO | 00 |
