Power generation system, monitoring device, and method for monitoring power generation system

Abstract

To achieve stable operation during self-sustained operation.SOLUTION: A display control unit configured to display, on a monitor, a graph including a first axis and a second axis in the interconnected operation state, the first axis representing a physical quantity related to a power generation output of any one of the two or more power generators, the second axis representing power consumption of an important load to which power is supplied from the two or more power generators in the isolated operation state, the display control unit displays, on the second axis of the graph, an operation allowable range indicating a range in which the operation of the two or more power generators after being switched to the self-sustained operation state is assumed not to be hindered.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to a power generation system, a monitoring device, and a method for monitoring a power generation system. [Background technology]

[0002] Patent Document 1 discloses a distributed power supply system in which a plurality of generators are interconnected to a grid or operate independently. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-81942 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a power generation system, a monitoring device, and a method for monitoring a power generation system that are capable of achieving stable operation during stand-alone operation. [Means for solving the problem]

[0005] [1] A power generation system comprising: two or more generators connected to an electric power grid and operating in parallel; a circuit breaker that switches between an interconnected operation state in which the electric power grid and the two or more generators are connected and an independent operation state in which the electric power grid and the two or more generators are disconnected; and a display control unit that displays a graph including a first axis and a second axis on a monitor in the interconnected operation state, wherein the first axis represents a physical quantity related to the power generation output of a target generator that is any one of the two or more generators, and the second axis represents the power consumption of a critical load to which power is supplied from the two or more generators in the independent operation state, and the display control unit displays an allowable operating range on the second axis of the graph, which represents a range within which it is expected that the operation of the two or more generators will not be hindered after switching to the independent operation state.

[0006] [2] The power generation system described in [1] above, wherein the display control unit displays the graph on the monitor so that the allowable operating range changes over time depending on the operating status of at least one of the two or more generators.

[0007] [3] The power generation system described in [2] above, further comprising an operating status acquisition unit that acquires the rotational speed or frequency of any one of the two or more generators as at least part of the operating status from a power generation control unit that controls the generator, and the display control unit displays the graph on the monitor so that the allowable operating range changes over time depending on the rotational speed or frequency acquired by the operating status acquisition unit.

[0008] [4] The power generation system described in any one of [1] to [3] above, wherein the display control unit displays, in the graph, an operating point including the current value of the power consumption of the important load and the current value of the physical quantity together with the allowable operating range.

[0009] [5] The power generation system according to [4] above, further comprising a warning notification unit that issues a warning to a user based on a comparison result between the operating point and the allowable operating range.

[0010] [6] A power generation system described in any one of [1] to [5] above, wherein a portion of the allowable operating range is defined by a first boundary line that represents the boundary between whether or not at least one of the two or more generators is overloaded.

[0011] [7] A power generation system described in any one of [1] to [5] above, wherein a portion of the allowable operating range is defined by a second boundary line that represents the boundary between whether or not at least one of the two or more generators is lightly loaded.

[0012] [8] The power generation system described in [6] or [7] above, wherein the first axis represents the power generation output of the generator, the allowable operating range represents the range on both the first axis and the second axis of the graph within which it is expected that the operation of the two or more generators will not be impaired after switching to the independent operation state, and the range of the allowable operating range related to the first axis is defined by at least one of a third boundary line representing the minimum output that the target generator can generate and a fourth boundary line representing the maximum output that the target generator can generate.

[0013] [9] The two or more generators include a first generator and a second generator, and the power generation system described in any one of [1] to [8] above further includes a first power generation control unit that controls the first generator according to an isochronous characteristic in the autonomous operation state, and a second power generation control unit that controls the second generator according to a droop characteristic in the autonomous operation state.

[0014]

[10] The two or more generators include a first generator and a second generator, and the power generation system described in any one of [1] to [8] above further includes a first power generation control unit that controls the first generator according to droop characteristics in the autonomous operation state, and a second power generation control unit that controls the second generator according to droop characteristics in the autonomous operation state.

[0015]

[11] A monitoring device provided in a power generation system including two or more generators connected to a power grid and operating in parallel, and a circuit breaker that switches between an interconnected operation state in which the power grid and the two or more generators are connected, and an independent operation state in which the power grid and the two or more generators are disconnected, the monitoring device having a display control unit that displays a graph including a first axis and a second axis on a monitor in the interconnected operation state, the first axis representing a physical quantity related to the power generation output of a target generator that is one of the two or more generators, and the second axis representing the power consumption of a critical load to which power is supplied from the two or more generators in the independent operation state, and the display control unit displays an acceptable operating range on the second axis of the graph, representing a range within which it is expected that the operation of the two or more generators will not be hindered after switching to the independent operation state.

[0016]

[12] A monitoring method for a power generation system comprising two or more generators connected to a power grid and operating in parallel, and a circuit breaker that switches between an interconnected operation state in which the power grid and the two or more generators are connected, and an independent operation state in which the power grid and the two or more generators are disconnected, the method including a display step of displaying on a monitor in the interconnected operation state a graph including a first axis and a second axis, wherein the first axis represents a physical quantity related to the power generation output of a target generator that is any one of the two or more generators, and the second axis represents the power consumption of a critical load to which power is supplied from the two or more generators in the independent operation state, and the display step displays on the second axis of the graph an allowable operating range that represents a range within which operation of the two or more generators is expected not to be impaired after switching to the independent operation state. [Effects of the Invention]

[0017] According to the present disclosure, a power generation system, a monitoring device, and a method for monitoring a power generation system are provided that enable stable operation during stand-alone operation. [Brief explanation of the drawings]

[0018] [Figure 1]FIG. 1 is a schematic diagram showing an example of a power generation system. [Figure 2] Fig. 2(a) is a schematic diagram showing an example of the flow of power during grid interconnection, and Fig. 2(b) is a schematic diagram showing an example of the flow of power during stand-alone operation. [Figure 3] Fig. 3(a) is a graph for explaining the droop characteristic, and Fig. 3(b) is a graph for explaining the isochronous characteristic. [Figure 4] FIG. 4 is a diagram for explaining the outputs from the two generators during stand-alone operation. [Figure 5] Fig. 5(a) is a diagram showing an example of the outputs from two generators when connected to the grid, and Fig. 5(b) is a diagram for explaining problems that may occur when transitioning to isolated operation. [Figure 6] FIG. 6 is a diagram for explaining an example of a method for avoiding the problem. [Figure 7] FIG. 7 is a schematic diagram illustrating an example of the functional configuration of the upper control device. [Figure 8] 8(a) and 8(b) are diagrams showing examples of graphs that the display control unit displays on the monitor. [Figure 9] FIG. 9 is a schematic diagram illustrating an example of a hardware configuration of the upper control device. [Figure 10] FIG. 10 is a flowchart showing an example of a series of processes executed by the upper control device during grid interconnection. [Figure 11] 11(a) and 11(b) are diagrams showing examples of graphs that the display control unit displays on the monitor. [Figure 12] 12(a) and 12(b) are diagrams showing examples of graphs that the display control unit displays on the monitor. [Figure 13] FIG. 13 is a diagram for explaining the outputs from the two generators during the stand-alone operation. [Figure 14] Fig. 14(a) is a diagram showing an example of outputs from two generators when connected to the grid, and Fig. 14(b) is a diagram for explaining problems that may occur when transitioning to isolated operation. [Figure 15]Fig. 15(a) is a diagram showing an example of a graph displayed on a monitor by a display control unit, and Fig. 15(b) is a diagram for explaining the calculation of the boundary portion of the permissible driving range. [Figure 16] FIG. 16 is a diagram showing an example of a graph displayed on the monitor by the display control unit. DETAILED DESCRIPTION OF THE INVENTION

[0019] An embodiment will be described below with reference to the drawings. In the description, the same elements or elements having the same functions are designated by the same reference numerals, and redundant description will be omitted.

[0020] [Power generation system] FIG. 1 schematically shows a power generation system according to one embodiment. The power generation system 1 shown in FIG. 1 is a system that generates power by connecting to a power grid. The power generation system 1 is installed, for example, in a customer facility such as a factory or in a power plant. The power generation system 1 includes two or more generators that operate in parallel. Below, the contents of the present disclosure will be described using an example in which the power generation system 1 includes two generators (two generators) that operate in parallel. In the following description, the term "generator" refers to equipment that includes a prime mover (generator in the broad sense).

[0021] The power generation system 1 includes two or more power generators, namely, a generator 10A and a generator 10B. The generators 10A and 10B are installed on a premises (for example, in a facility such as a factory). The generators 10A and 10B can be connected in parallel to each other to generate power. The generators 10A and 10B are interconnected to a power grid 200 to generate power and supply the power to a load 100. Each of the generators 10A and 10B is connected to, for example, one of a gas turbine and a steam turbine, or both a gas turbine and a steam turbine. The power generation method (i.e., the type of prime mover connected) may be different between the generators 10A and 10B. The output of at least one of the generators 10A and 10B may be adjustable by an operator.

[0022] The power system 200 is, for example, a commercial power system provided by an electric power company. In one example, the power system 200 can supply AC power (AC voltage) with a rated frequency of 50 Hz or 60 Hz to customer facilities.

[0023] The load 100 consumes power within the premises where the power generation system 1 is installed. The load 100 includes two or more load devices. Specific examples of the load devices include, but are not limited to, a motor, a heater, a cooler, and a light. The load 100 may be classified into an important load 110 and a general load 120. For example, the operator of the power generation system 1 may classify the load 100 into the important load 110 and the general load 120 by switching the connection destination of the load devices included in the load 100. Alternatively, the important load 110 and the general load 120 may be connected separately in advance at the time of construction. Each of the important load 110 and the general load 120 includes one or more load devices. The power (power consumption) required by the important load 110 and the general load 120 varies depending on the usage status of the devices included in these loads. Note that the load 100 may be composed only of the important load 110 without the general load 120.

[0024] Fig. 2(a) schematically shows the flow of power when the generators 10A and 10B operate in connection with the power grid 200. Fig. 2(b) schematically shows the flow of power when the generators 10A and 10B operate without being connected to the power grid 200. In the present disclosure, the state in which the generators 10A and 10B operate in connection with the power grid 200 is referred to as the "grid-connected operation state," and the state in which the generators 10A and 10B operate without being connected to the power grid 200 is referred to as the "isolated operation state."

[0025] The power generation system 1 includes a circuit breaker 20. The circuit breaker 20 is a device that connects or disconnects the power system 200 and two or more generators (generators 10A and 10B). That is, the circuit breaker 20 switches between a state in which the power system 200 and the generators 10A and 10B are connected (grid-connected operation state) and a state in which the power system 200 and the generators 10A and 10B are disconnected (independent operation state). For example, when the circuit breaker 20 is turned on, the generators 10A and 10B are connected to the power system 200, and when the circuit breaker 20 is turned off, the generators 10A and 10B are disconnected from the power system 200.

[0026] In the grid-connected operation state, the generators 10A and 10B operate in parallel with the power system 200. In this case, for example, as shown in FIG. 2( a), the generators 10A and 10B supply power to an important load 110 and a general load 120. If the power generation outputs of the generators 10A and 10B are less than the power required by the important loads 110 and the general loads 120, the power system 200 also supplies power to the important loads 110 and the general loads 120. That is, power is purchased from the power system 200. If the power generation outputs of the generators 10A and 10B exceed the power required by the important loads 110 and the general loads 120, the surplus power generation outputs of the generators 10A and 10B are supplied to the power system 200. That is, power is sold to the power system 200.

[0027] In the isolated operation state, for example, as shown in FIG. 2(b), power is not supplied from the generators 10A and 10B to the general load 120, and the generators 10A and 10B supply power to the important load 110. In the isolated operation state, the important load 110 can be said to be a load to which power is supplied from the generators 10A and 10B. The power consumption (load power) of the important load 110 may be adjustable by an operator by stopping some of the load devices included in the important load 110 or by changing the operating status of the load devices.

[0028] Returning to FIG. 1 , the power generation system 1 includes a protective relay 22. The protective relay 22 is a device that causes a circuit breaker 20 to disconnect the power system 200 from the generators 10A and 10B so that the power system 1 switches from the grid-connected operation state to the isolated operation state when an abnormality occurs in the power system 200. By providing the protective relay 22 and the circuit breaker 20, the power generation system 1 shifts (transitions) from the grid-connected operation state to the isolated operation state when an abnormality such as a power outage or momentary voltage drop occurs in the power system 200. In the isolated operation state, the power supply from the generators 10A and 10B to the important load 110 continues, so that the important load 110 can continue to operate even if an accident occurs in the power system 200.

[0029] The power generation system 1 includes a control device 12A and a rotational speed measurement unit 14A. The control device 12A (first power generation control unit) is connected to the generator 10A (first generator) and controls the generator 10A. The rotational speed measurement unit 14A is a device that measures the rotational speed (number of rotations per unit time) of the generator 10A and outputs the measured rotational speed to the control device 12A. The rotational speed of the generator 10A and the frequency of the power generated by the generator 10A are basically proportional to each other (unless an extreme system fault or generator abnormality occurs). Hereinafter, the frequency of the power generated by the generator 10A will be simply referred to as the "frequency of the generator 10A." The rotational speed measurement unit 14A may measure the frequency of the generator 10A as information indicating the rotational speed of the generator 10A. The control device 12A may also convert the rotational speed obtained from the rotational speed measurement unit 14A into the frequency of the generator 10A.

[0030] The power generation system 1 includes a control device 12B and a rotational speed measurement unit 14B. The control device 12B (second power generation control unit) is connected to the generator 10B (second generator) and controls the generator 10B. The rotational speed measurement unit 14B is a device that measures the rotational speed (number of rotations per unit time) of the generator 10B and outputs the measured rotational speed to the control device 12B. The rotational speed of the generator 10B and the frequency of the power generated by the generator 10B are basically proportional to each other (unless an extreme grid fault or generator abnormality occurs). Hereinafter, the frequency of the power generated by the generator 10B will be simply referred to as the "frequency of the generator 10B." The rotational speed measurement unit 14B may measure the frequency of the generator 10B as information indicating the rotational speed of the generator 10B. Furthermore, the control device 12B may convert the rotational speed obtained from the rotational speed measurement unit 14B into the frequency of the generator 10B.

[0031] Each of the above-mentioned control devices 12A and 12B is also referred to as a “governor” or a “speed governor.” The control devices 12A and 12B check the connection state of the circuit breaker 20, and when the circuit breaker 20 is in the on state, they control the generators 10A and 10B in the grid-connected operation control mode, and when the circuit breaker 20 is in the off state, they control the generators 10A and 10B in the isolated operation control mode.

[0032] In the grid-connected operation control mode, the control device 12A controls the generator 10A according to the droop characteristic, and the control device 12B controls the generator 10B according to the droop characteristic. The droop characteristic is a characteristic in which the frequency is determined according to the power generation output, as shown by "line Ld" in FIG. 3(a). The droop characteristic (line Ld) is set so that the frequency decreases as the power generation output increases. In the droop characteristic, the rotational speed may be used instead of the frequency. Furthermore, the control device 12A and the control device 12B may control the generators by internally converting the rotational speed and the frequency. In the grid-connected operation control mode, the frequency of the power supplied to the load 100 is determined by the power grid 200. Therefore, the power generation output of each of the generators 10A and 10B is determined according to the frequency determined by the power grid 200. The frequency of the power supplied from the power grid 200 fluctuates within a range near the rated frequency (e.g., 60 Hz). Each of the control devices 12A and 12B adjusts the input (e.g., the amount of fuel or steam input) to the prime mover of the generator to be controlled so that the power output from the generator to be controlled reaches a target value for power output determined by the frequency and droop characteristics of the power system 200. The droop rate (slope of line Ld) of the droop characteristics is predetermined, for example, by the manufacturer of the generator. The operator may be able to change the speed setting value L0 in the droop characteristics (the upper or lower position of line Ld on the graph representing the droop characteristics).

[0033] In the isolated operation control mode, the control method for one of the two or more generators may be switched from a method using droop characteristics (hereinafter referred to as "droop control") to a method using isochronous characteristics (hereinafter referred to as "isochronous control"). In one example, in the isolated operation control mode, the control device 12A may control the generator 10A according to the isochronous characteristics, and the control device 12B may control the generator 10B according to the droop characteristics. The isochronous characteristics are characteristics (constant frequency characteristics) that maintain a constant frequency regardless of the power generation output, as shown by the "line La" in FIG. 3(b). In the isochronous characteristics, the rotational speed may be used instead of the frequency. Furthermore, the control devices 12A and 12B may control the generators by internally converting the rotational speed and frequency. When control according to the isochronous characteristics is performed, the power generation output from the generator is determined by the load (power consumption of the load) connected to the generator. The frequency in the isochronous characteristics is set to, for example, the same value as the rated frequency of the power grid 200. The control device 12A adjusts the input (for example, the amount of fuel or steam input) to the generator 10A so that the frequency in the generator 10A becomes the set value of the frequency in the isochronous characteristic.

[0034] As shown in FIG. 1 , the power generation system 1 includes a power measurement unit 16A, a power measurement unit 16B, a power measurement unit 40, a frequency measurement unit 18, and a monitoring device 50. The power measurement unit 16A is a device that measures the power generation output from the generator 10A and outputs the measured power generation output to the control device 12A. The power measurement unit 16B is a device that measures the power generation output from the generator 10B and outputs the measured power generation output to the control device 12B. The power measurement units 16A and 16B may output the measured power generation output to the monitoring device 50. The control devices 12A and 12B may also output the received power generation output to the monitoring device 50. The power measurement unit 40 is a device that measures the power supplied to the important load 110. The power measured by the power measurement unit 40 corresponds to the power consumed by the important load 110. The power measurement unit 40 outputs the measured power to the monitoring device 50. The frequency measurement unit 18 is a device that measures the frequency of the power system 200 or the frequency of the power supplied from the generators 10A and 10B.

[0035] The monitoring device 50 is provided above the control devices 12A and 12B, and is a device that monitors the power generation system 1. The monitoring device 50 may be, for example, part of a plant control device that controls the entire power generation facility including the power generation system 1. The control device 12A may output the rotational speed measurement result obtained from the rotational speed measurement unit 14A, or a result of converting the measurement result into a frequency, to the monitoring device 50. The control device 12B may output the rotational speed measurement result obtained from the rotational speed measurement unit 14B, or a result of converting the measurement result into a frequency, to the monitoring device 50. The frequency measurement unit 18 outputs the frequency measurement result to the monitoring device 50. Details of the monitoring device 50 will be described later.

[0036] Here, to facilitate understanding of the contents of the present disclosure, the contents of the control of the generators 10A and 10B will be further described with reference to Figures 4 to 6. As described above, in the isolated operation state (isolated operation control mode), the generators 10A and 10B operate in parallel while disconnected from the power grid 200, and power is supplied from the generators 10A and 10B to the important load 110. Also, as shown in Figure 4, the control device 12A controls the generator 10A according to the isochronous characteristic, and the control device 12B controls the generator 10B according to the droop characteristic. Hereinafter, the parallel operation performed by the generators 10A and 10B while disconnected from the power grid 200 may be referred to as "parallel isolated operation."

[0037] Because generators 10A and 10B are electrically connected in parallel, the frequencies of the power output by generators 10A and 10B are the same. Because isochronous control is performed on generator 10A, the frequency of the power output during parallel independent operation is determined by generator 10A. That is, the frequency of the power output during parallel independent operation is the set frequency fs of isochronous control for generator 10A. Because droop control is performed on generator 10B, the power output of generator 10B is determined by the set frequency fs (the frequency of generator 10A). The set frequency fs is set to, for example, 50 Hz or 60 Hz, but the actual frequency of generator 10A deviates from 50 Hz or 60 Hz due to an error (change in error over a long period of time).

[0038] In FIG. 4, the power generation output from generator 10A is indicated by "x1," and the power generation output from generator 10B is indicated by "x2." In generator 10B, the power generation output is determined by the frequency, which is the set frequency fs, so the power generation output x2 from generator 10B is substantially fixed (constant). On the other hand, the power generation output x1 from generator 10A is independent of the frequency and can therefore vary. In this case, the sum of the power generation output x1 and the power generation output x2 matches the load power of important load 110, so the power generation output x1 varies in accordance with fluctuations in the load power of important load 110, while the power generation output x2 is maintained constant.

[0039] A generator has a range of power output within which it can operate (hereinafter referred to as the "operable range"). For example, if the power required by the load (the output from the generator) becomes too large, the generator may become overloaded and trip, i.e., may malfunction and shut down. Even if the generator does not shut down, the output power may become unstable, and the equipment included in the load may shut down. Conversely, if the power required by the load (the output from the generator) is too small, the generator may become lightly loaded, causing abnormalities in the generator's control, and the device operating the generator may experience thermal and mechanical strain due to its structure, resulting in a trip. For example, in the case of a steam turbine generator, a light load can increase the exhaust temperature from the steam turbine, causing thermal strain. In this disclosure, "light load" means a load that is light enough to potentially interfere with the operation of the generator.

[0040] In FIG. 4, the region of power generation output where the generator is lightly loaded (hereinafter referred to as the "light load region") is indicated by "R1", and the region of power generation output where the generator is overloaded (hereinafter referred to as the "overload region") is indicated by "R2". The region between the light load region R1 and the overload region R2 is the operable range. In the grid-connected operation control mode, the power shortage can be supplied from the power grid 200, so the generators 10A and 10B are controlled by the control devices 12A and 12B or adjusted by the operator so as to operate within the operable range.

[0041] On the other hand, when switching from the grid-connected operation control mode to the isolated operation control mode, the factors that determine the frequency of the output power change, and therefore the frequency may change. When the frequency changes, the output from the generator changes accordingly. As a result, the output of the generator may fall outside the operable range. In other words, the generator may be underloaded or overloaded. The change in the output from the generator occurs instantaneously or within a short time after switching to the isolated operation control mode.

[0042] FIG. 5(a) illustrates the relationship between the frequency and power output of each generator in the grid-connected operation control mode. In FIG. 5(a), "fc" represents the frequency in the power grid 200. This frequency fc is adjusted by the power company, but it constantly fluctuates relative to a rated frequency such as 50 Hz or 60 Hz. The generator 10A outputs a power output w1 corresponding to the frequency fc according to the line Lda representing the droop characteristics. The generator 10B outputs a power output w2 corresponding to the frequency fc according to the line Ldb representing the droop characteristics.

[0043] FIG. 5(b) illustrates the relationship between the frequency and power generation output of each generator when transitioning from the operating state shown in FIG. 5(a) to the isolated operation control mode. When transitioning to the isolated operation control mode, the frequency of each generator changes to the set frequency fs on line Laa, which represents the isochronous characteristics used to control generator 10A. In the example shown in FIGS. 5(a) and 5(b), frequency fc (variable value) is smaller than set frequency fs (constant value). In this case, the frequency of each generator increases with transition to the isolated operation control mode. Accordingly, the power generation output from generator 10B decreases from power generation output w2 to power generation output x2.

[0044] Assuming that the sum of the power generation outputs w1 and w2 is approximately the same as the load power of the important load 110, a decrease in the power generation output of the generator 10B may cause the power generation output of the generator 10A to increase from the power generation output w1 to the power generation output x1. This may cause the power generation output of the generator 10A to deviate from the operable range, resulting in the generator 10A becoming overloaded. Unlike the example shown in FIG. 5(b), depending on the frequency fc and the load power of the important load 110, the generator 10A may become lightly loaded when transitioning to the isolated operation control mode.

[0045] If it is possible to determine whether the power generation output of generator 10A will deviate from the operable range if the system is switched to the isolated operation control mode in the current state while connected to the grid in the grid-connected operation control mode, it becomes possible to take measures while the system is connected to the grid. An example of such a measure will be described with reference to Fig. 6. In Fig. 6, "before change" means before the measure was taken, and "after change" means after the measure was taken.

[0046] In the grid-connected operation control mode (before the change), the generator 10B is controlled according to the droop characteristics represented by the line Ldb0, and generates power at a power output corresponding to the frequency fc in the power grid 200. If the mode were to transition to the isolated operation control mode in this state, the frequency would become the set frequency fs, and the power output from the generator 10B would drop to x20. Accordingly, depending on the current power consumption (load power) of the important load 110, the power output x10 from the generator 10A may fall into the overload region R2.

[0047] Therefore, one possible countermeasure is to shift the line representing the droop characteristics in the droop control of generator 10B upward while the generator is connected to the grid, and change the control so that generator 10B is controlled in accordance with line Ldb1. If this countermeasure is implemented, the power generation output of generator 10B when the mode is assumed to transition to the isolated operation control mode will increase from x20 before the change to x21. Therefore, the power generation output of generator 10A when the mode is assumed to transition to the isolated operation control mode will decrease from x10 before the change to x11, and will not deviate from the operable range.

[0048] As a countermeasure, the power consumption of the important load 110 may be adjusted instead of or in addition to the power generation output of the generator 10B. For example, in order to reduce the power consumption of the important load 110, measures may be taken to remove some of the devices included in the important load 110 from the targets to which power is supplied in the isolated operation control mode, or, if the power generation system 1 is installed in a production facility, measures may be taken to reduce the production volume. Note that the important load 110 in the present disclosure is a load to which power is supplied from the generators 10A and 10B in the isolated operation state when measures are not taken to remove the important load 110 from the targets to which power is supplied in the isolated operation mode.

[0049] The above countermeasures require constant changes (adjustments) during grid-connection, and it is necessary to know the extent of the change from the operating state before the change. In the example shown in FIG. 5(b), it is necessary to at least know the extent to which the power generation output of generator 10B will change when the system transitions to the isolated operation control mode. Furthermore, adjustments to the load equipment included in critical load 110 often require manual intervention, such as adjusting operation timing and contacting the relevant production equipment. Adjusting the power generation output may also require manual adjustments, such as reducing the amount of steam supplied to a production facility, in a back-pressure turbine that uses used steam in the production facility. For these reasons, a system is needed that visually displays the type and extent of adjustments required. In other words, if it is possible to visually determine or understand whether the power generation output of generator 10A will deviate from its operable range when the system transitions to the isolated operation control mode under the current conditions during grid-connection in the grid-connected operation control mode, countermeasures can be implemented during grid-connection. The monitoring device 50 described above is configured to provide a user such as an operator with visual information for determining or understanding whether the power generation output of the generator 10A deviates from the operable range.

[0050] Returning to FIG. 1 , the power generation system 1 includes a monitor 52. The monitor 52 is connected to the monitoring device 50. The monitor 52 is an output device for displaying information to a user of the monitoring device 50. The monitor 52 may be any device capable of displaying information, such as a liquid crystal display. The monitor 52 displays information to a user of the monitoring device 50, and may also be an input / output device equipped with a touch panel, buttons, or the like, for receiving input from the user.

[0051] The monitoring device 50 will be described in detail with reference to Figures 7 to 9. The monitoring device 50 is configured to display a graph on the monitor 52 as information for determining whether the power generation output of the generator 10A deviates from the operable range in the grid-connected operation state (grid-connected operation control mode).

[0052] 7 shows an example of the functional configuration of the monitoring device 50. The monitoring device 50 has, as functional components (hereinafter referred to as "functional blocks"), a driving status acquisition unit 62, a display control unit 66, and a warning notification unit 68. The processes executed by these functional blocks correspond to the processes executed by the monitoring device 50.

[0053] The operating status acquisition unit 62 acquires various operating statuses of the power generation system 1. The operating statuses of the power generation system 1 include the operating statuses of the generators 10A and 10B. The operating status acquisition unit 62 may repeatedly acquire various operating statuses at predetermined intervals (every predetermined period). In one example, the operating status acquisition unit 62 acquires power measurement results from each of the power measurement unit 16A, the power measurement unit 16B, and the power measurement unit 40.

[0054] The operating status acquisition unit 62 may acquire, from the control device 12A, the rotational speed or frequency of the generator 10A (for example, the rotational speed measured by the rotational speed measurement unit 14A) as the operating status of the generator 10A. The operating status acquisition unit 62 may acquire, from the control device 12B, the rotational speed or frequency of the generator 10B (for example, the rotational speed measured by the rotational speed measurement unit 14B) as the operating status of the generator 10B. The operating status acquisition unit 62 may acquire a frequency (for example, the frequency of the power system 200) from the frequency measurement unit 18.

[0055] In the grid-connected operation state, the display control unit 66 displays a graph including a first axis and a second axis (hereinafter referred to as "graph Gr") on the monitor 52. The graph Gr may be a two-dimensional graph consisting of the first axis and the second axis (see FIG. 8(a)). The first axis represents a physical quantity related to the power generation output of a target generator, which is one of two or more generators included in the power generation system 1. The second axis represents the power consumption of an important load 110 to which power is supplied from the two or more generators in the isolated operation state (hereinafter referred to as "important load power").

[0056] FIG. 8(a) shows an example of a graph Gr displayed on the monitor 52. Note that the monitor 52 is omitted from the diagram showing the graph Gr. The first axis of the graph Gr is, for example, the horizontal axis (x-axis), and represents the power generation output of the generator 10B as a physical quantity related to the power generation output of the target generator. Note that the physical quantity related to the power generation output includes the power generation output itself. The second axis of the graph Gr is, for example, the vertical axis (y-axis), and represents the important load power (power required by the important load 110).

[0057] The display control unit 66 displays the permissible operation range PA on the graph Gr. The permissible operation range PA illustrated in FIG. 8(a) means a range within which operation of the generator 10A is expected to be unimpeded even if the current state transitions to the independent operation state when the current value of the power generation output of the generator 10B and the current value of the important load power (power consumption of the important load 110) are within the permissible operation range PA. The display control unit 66 displays, at least on the second axis of the graph Gr, a range within which operation of the two or more generators is expected to be unimpeded after switching to the independent operation state as the permissible operation range PA. For example, on the vertical axis of the graph Gr, the display control unit 66 displays, as the permissible operation range PA, a range within which the generator 10A is expected to operate without hindrance after switching to the independent operation state (when switching to the independent operation control mode). In the example illustrated in FIG. 8(a), the area marked with many dots is the permissible operation range PA.

[0058] The display control unit 66 may display the graph Gr on the monitor 52 so that the allowable operating range PA changes over time in accordance with the operating status of at least one of the generators 10A and 10B (for example, the generator 10A). For example, when the operating status acquisition unit 62 acquires the rotation speed of the generator 10A from the control device 12A as the operating status, the display control unit 66 displays the graph Gr on the monitor 52 so that the allowable operating range PA changes over time in accordance with the rotation speed of the generator 10A. When the operating status acquisition unit 62 acquires the frequency of the generator 10A from the control device 12A as the operating status, the display control unit 66 displays the graph Gr on the monitor 52 so that the allowable operating range PA changes over time in accordance with the frequency of the generator 10A.

[0059] In the example shown in FIG. 8(a), a portion of the permissible operation range PA is defined by a boundary line y1 (first boundary line) that indicates the boundary of whether the generator 10A will be overloaded when transitioning to the independent operation control mode. That is, a portion of the permissible operation range PA is demarcated by the boundary line y1. The boundary line y1 is calculated, for example, by functions (functions with x as a variable) shown in the following equations (1) to (3). In equations (1) to (3), "x" is the power generation output [kW] of the generator 10B. In equation (3), "min[i,j]" means a function that outputs the smaller of i and j.

number

[0060] In the example shown in FIG. 8(a), another part of the permissible operation range PA is defined by a boundary line y2 (second boundary line) that indicates the boundary of whether the generator 10A will be lightly loaded when transitioning to the isolated operation control mode. In the graph Gr, the boundary line y1 is located above the boundary line y2. The boundary line y2 is calculated, for example, by the function shown in the following equation (4). Pbi(x) in equation (4) is expressed by equation (2).

number

[0061] In the formulas (1) to (4), the various variables are described as follows, divided into set values ​​and measured values. <Setting value> Ta: Rated output of generator 10A [kW] Tac: Minimum output of generator 10A [kW] Ka: The likelihood of output relative to the rated output to respond to load fluctuations during islanded operation Tb: Rated output of generator 10B [kW] Nas: Rated rotation speed of the main shaft when generator 10A is self-sustaining [% rpm], or frequency setting value when generator 10A is self-sustaining [% Hz] Db: Droop rate [%] in droop control of generator 10B <Measurement value> ·Na: Current rotation speed of the main shaft of generator 10A [% rpm], or current frequency of generator 10A [% Hz]

[0062] In the graph Gr shown in Fig. 8(a), if the point formed by the combination of the current value of the power generation output of the generator 10B and the current value of the important load power (operating point OP described below) is located above the boundary line y1, it means that the generator 10A will be overloaded when transitioning to the isolated operation control mode. Also, if the point formed by the combination of the current value of the power generation output of the generator 10B and the current value of the important load power (operating point OP described below) is located below the boundary line y2, it means that the generator 10A will be underloaded when transitioning to the isolated operation control mode.

[0063] When the allowable operation range PA (boundary of the allowable operation range PA) is calculated using equations (1) to (4), the function "Pbi(t)" includes the measured value "Na." Therefore, the allowable operation range PA changes over time according to the above Na (the current rotational speed or frequency of the generator 10A). If there is no change in Na over a certain period of time, the allowable operation range PA does not change either. Na may be information obtained from the control device 12A. For example, the allowable operation range PA may be calculated using a frequency recognized by the control device 12A when controlling the generator 10A. Na may be obtained from a source other than the control device 12A, for example, it may be a frequency obtained from the frequency measurement unit 18.

[0064] The display control unit 66 may display, within the graph Gr, an operating point OP including the current value of the important load power (power consumption of the important load 110) and the current value of the power generation output of the generator 10B, together with the allowable operating range PA. The operating point OP may be a point consisting of the current value of the important load power and the current value of the power generation output of the generator 10B. If the coordinates on the graph Gr are expressed as (x coordinate, y coordinate), the operating point OP can be expressed as OP = (Pb, Pi). "Pb" and "Pi" are both measured values ​​and have the following meanings. Pb: Current power output of generator 10B [kW] Pi: Current power consumption of the important load 110 [kW] "Pi" can be said to be the power consumption of the loads that the generators 10A and 10B will shoulder (supply power to) when the generators 10A and 10B transition to an independent operation state in the current state.

[0065] The warning notification unit 68 issues a warning to the user based on the comparison result between the operating point OP and the permissible operating range PA. For example, the warning notification unit 68 issues a warning to the user when the operating point OP is outside the permissible operating range PA, and does not issue a warning to the user when the operating point OP is within the permissible operating range PA. The warning notification unit 68 may issue a warning in any manner, but for example, the warning notification unit 68 displays information indicating a warning on the monitor 52. In one example, the warning notification unit 68 displays a message 58 indicating a warning on the monitor 52, as shown in FIG. 8(b).

[0066] Instead of or in addition to the message 58 indicating the warning, the warning notification unit 68 may change the color or blink a part of an area, such as the operating point OP, on the screen of the monitor 52 as information indicating the warning. Instead of or in addition to a display on the monitor 52, the warning notification unit 68 may notify the user of the warning by other notification means (for example, sound) than the monitor 52.

[0067] FIG. 9 shows an example of the hardware configuration of the monitoring device 50. The monitoring device 50 is configured by a computer such as a PLC (Programmable Logic Controller). The monitoring device 50 has, for example, a circuit 80. The circuit 80 has a processor 81, a memory 82, a storage 83, an input / output port 84, a communication port 85, and a timer 86. The storage 83 is configured by one or more non-volatile memory devices such as a flash memory or a hard disk. The storage 83 stores a program that causes the monitoring device 50 to display the graph Gr on the monitor 52. For example, the storage 83 stores a program that causes the monitoring device 50 to configure the above-mentioned functional blocks.

[0068] The memory 82 is composed of one or more volatile memory devices such as a random access memory. The memory 82 temporarily stores programs loaded from the storage 83. The processor 81 is composed of one or more arithmetic devices such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). The processor 81 executes the programs loaded in the memory 82, thereby configuring each functional block such as the driving condition acquisition unit 62 described above in the monitoring device 50. The calculation results by the processor 81 are temporarily stored in the memory 82.

[0069] The input / output port 84 inputs and outputs electrical signals between the power measuring units 16A, 16B, 40, the protective relay 22, the monitor 52, etc. in accordance with instructions from the processor 81. The communication port 85 communicates with the control device 12A and the control device 12B wirelessly, via wire, or via a network line in response to a request from the processor 81. The timer 86 measures elapsed time, for example, by counting reference pulses at a fixed interval. Note that the circuit 80 is not necessarily limited to one that configures each functional block, such as the operating status acquisition unit 62, described above, by a program. For example, at least some of the functional blocks of the circuit 80 may be configured by an integrated circuit in which logic circuits are integrated.

[0070] The monitoring device 50 may be configured by multiple computers. When the monitoring device 50 is configured by multiple computers, each functional block may be realized by an individual computer. Alternatively, each functional block may be realized by a combination of two or more computers. In these cases, the multiple computers may be connected to each other so as to be able to communicate with each other and may cooperate to perform monitoring of the power generation system 1. The monitoring device 50 and at least one of the control device 12A and the control device 12B may be configured by a single computer (a single circuit).

[0071] [Monitoring method for power generation systems] Next, a description will be given of a monitoring method for the power generation system 1. This monitoring method includes at least a display step. The display step is a step of displaying a graph Gr including a first axis and a second axis on the monitor 52 in a grid-connected operation state.

[0072] In the monitoring method for the power generation system 1, the monitoring device 50 executes a series of processes related to the display step. Fig. 10 shows the series of processes executed by the monitoring device 50. The series of processes will be described using an example in which, when the system transitions to the independent operation control mode, the generator 10A is controlled according to the isochronous characteristic, and the control of the generator 10B is maintained according to the droop characteristic.

[0073] In the above series of processes, the monitoring device 50 executes step S11 in a state in which the circuit breaker 20 is maintained in the on state and the generators 10A and 10B are controlled in the grid-connected operation control mode. In step S11, for example, the operation status acquisition unit 62 of the monitoring device 50 determines whether the open / close state of the circuit breaker 20 is the on state. The operation status acquisition unit 62 may acquire a signal indicating the state of the circuit breaker 20 from the circuit breaker 20, or may acquire information indicating the current control mode from the control device 12A and the control device 12B.

[0074] If it is determined in step S11 that the circuit breaker 20 is in the on state (step S11: YES), the processing executed by the monitoring device 50 proceeds to step S12. In step S12, for example, the operating status acquisition unit 62 acquires information indicating the operating status of the generators 10A and 10B. In one example, the operating status acquisition unit 62 acquires the frequency of the generator 10A from the control device 12A as the information indicating the operating status. The operating status acquisition unit 62 may acquire the power generation output from the generator 10A from the power measurement unit 16A and the power generation output from the generator 10B from the power measurement unit 16B. The operating status acquisition unit 62 may acquire the power supplied to the important load 110 (important load power) from the power measurement unit 40.

[0075] Next, the monitoring device 50 executes step S13. In step S13, for example, the display control unit 66 of the monitoring device 50 calculates the permissible operation range PA. In one example, the display control unit 66 calculates the boundary line y1 shown in the above-mentioned equation (1) and the boundary line y2 shown in the above-mentioned equation (4). In this case, the display control unit 66 uses the frequency of the generator 10A acquired in step S12 in calculating the boundary line y1 and the boundary line y2.

[0076] Next, the monitoring device 50 executes step S14. In step S14, for example, the display control unit 66 uses the result of calculation in step S13 to display a graph Gr including the permissible operation range PA on the monitor 52. In one example, the display control unit 66 displays a two-dimensional (two-dimensional Cartesian coordinate system) graph Gr on the monitor 52, with the horizontal axis representing the power generation output of the generator 10B and the vertical axis representing the important load power, and displays the permissible operation range PA on the vertical axis. If the graph Gr including the permissible operation range PA is already displayed on the monitor 52, the display control unit 66 updates the drawing of the graph Gr on the monitor 52.

[0077] The display control unit 66 may use the information acquired in step S12 to display, in the graph Gr, an operating point OP representing the current value of the power generation output of the generator 10B and the current value of the important load power, together with the allowable operating range PA.

[0078] Next, the monitoring device 50 executes step S15. In step S15, for example, the warning notification unit 68 of the monitoring device 50 compares the permissible driving range PA calculated in step S13 with the operating point OP obtained from part of the information acquired in step S12. In one example, the warning notification unit 68 determines whether the operating point OP is located outside the permissible driving range PA defined by boundary line y1 and boundary line y2. The warning notification unit 68 may determine that the operating point OP is located outside the permissible driving range PA when the operating point OP is located above boundary line y1 or below boundary line y2 on the graph Gr.

[0079] If it is determined in step S15 that the operating point OP is outside the permissible operating range PA (step S15: YES), the processing executed by the monitoring device 50 proceeds to step S16. In step S16, for example, the warning notification unit 68 issues a warning to the user indicating that the operating point OP is outside the permissible operating range PA. In one example, the warning notification unit 68 displays text information (a message or guidance) on the monitor 52 indicating that the operating point OP deviates from the permissible operating range PA.

[0080] After step S16 is executed, or if it is determined in step S15 that the operating point OP is not outside the permissible operation range PA (step S15: NO), the process executed by the monitoring device 50 returns to step S11. The monitoring device 50 repeats the series of processes from step S11 to step S15 (or step S16) as long as it is determined in step S11 that the circuit breaker 20 is in the on state. In this case, the monitoring device 50 may repeat the series of processes from step S12 to step S15 at predetermined intervals (at every predetermined interval). As a result, the graph Gr changes over time depending on the operating status of at least one of the generators 10A and 10B (for example, the generator 10A).

[0081] On the other hand, if it is determined in step S11 that the circuit breaker 20 is not in the ON state (step S11: NO), the processing executed by the monitoring device 50 proceeds to step S17. In step S17, for example, the display control unit 66 displays information indicating that the power generation system 1 has switched to an independent operation state on the monitor 52. The processing of step S17 continues until it is determined in step S11 that the circuit breaker 20 is in the ON state. The series of processing operations described above by the monitoring device 50 may be continuously executed until the power generation system 1 stops operating.

[0082] [Variations] The series of processes shown in Fig. 10 is an example and can be modified as appropriate. In the series of processes described above, the monitoring device 50 may execute one step and the next step in parallel, or may execute the steps in an order different from that of the example described above. The monitoring device 50 may execute steps with different content from that of the example described above. Instead of executing steps, the entire series of processes described above by the monitoring device 50 may be deployed in a logic circuit or an analog circuit, or may be executed by interrupt.

[0083] As shown in Fig. 8(a), the display control unit 66 may display a boundary line y3 in addition to the boundary line y1 located at the upper side within the allowable operation range PA. The boundary line y3 indicates a line above which, if the operating point OP is located, a sudden load input exceeding the capacity of the generator 10A may cause the generator 10A to trip or the generator 10A may become overloaded when transitioning to independent operation. The boundary line y3 can also be considered a limit value (limit line) that takes into account the capacity to which the generator 10A can stably transition when the load on the generator 10A increases after transitioning to independent operation.

[0084] The boundary line y3 is calculated, for example, by the function (function with x as a variable) shown in the following equation (5).

number

number

[0085] The warning notification unit 68 may issue a warning to the user when the operating point OP is located above the boundary line y3 on the graph Gr. The warning notification unit 68 may issue a warning in a different manner depending on whether the operating point OP is above the boundary line y3 and below the boundary line y1 or above the boundary line y1.

[0086] Although not shown in the figure, the display control unit 66 may display the allowable driving range PA defined by the boundary line y3 shown in either equation (5) or equation (6) instead of the boundary line y1. In this case, the upper limit of the allowable driving range PA on the graph Gr is determined by the boundary line y3. The warning notification unit 68 may issue a warning when the operating point OP is located above the boundary line y3.

[0087] 11(a), the allowable driving range PA may be defined by a boundary line y1 and a first axis (e.g., the horizontal axis). In this case, in the graph Gr, the lower limit of the allowable driving range PA is defined by the first axis. The warning notification unit 68 may determine whether the operating point OP is located within the allowable driving range PA simply by determining whether the operating point OP exceeds the boundary line y1.

[0088] The permissible operation range PA may be a fixed range that does not change over time. Fig. 11(b) shows the permissible operation range PA calculated using a predicted value of the maximum frequency change range (worst value of the change range) when transitioning to the independent operation control mode. The display control unit 66 may calculate the boundary line y1 using the functions (functions with x as a variable) shown in the following equations (7) to (9).

number

[0089] In equation (9), "Fs" represents the rated frequency [Hz] of the power system 200. ΔF1 is the predicted minimum value of the value obtained by subtracting the frequency of the generator 10A during isolated operation from the system frequency, or the predicted worst-case value in the decreasing direction (negative side) of the fluctuation range of the system frequency. However, in calculating ΔF1, it is assumed that the system frequency is smaller than the frequency of the generator 10A during isolated operation.

[0090] The display control unit 66 may calculate the boundary line y3 using the function shown in the following equation (10).

number

number

[0091] The display control unit 66 may calculate the boundary line y2 using the functions shown in the following equations (12) to (14).

number

[0092] In equation (14), ΔF2 is a predicted maximum value of the value obtained by subtracting the frequency of the generator 10A during isolated operation from the system frequency, or a predicted worst-case value in the increasing direction (positive side) of the fluctuation range of the system frequency. However, in calculating ΔF2, it is assumed that the system frequency is higher than the frequency of the generator 10A during isolated operation. ΔF1 and ΔF2 may be determined based on the management range of the frequency (system frequency) in the power system 200.

[0093] As shown in Fig. 12(a), the allowable driving range PA may be defined by a boundary line y2 with respect to the second axis without using the boundary line y1. In the example shown in Fig. 12(a), the area above the boundary line y2 on the graph Gr is the allowable driving range PA. The warning notification unit 68 may determine whether the operating point OP is located within the allowable driving range PA only by determining whether the operating point OP is below the boundary line y2.

[0094] The permissible operating range PA in the various examples described above indicates a range on the second axis (e.g., the vertical axis). Alternatively, the permissible operating range PA may represent a range on both the first and second axes of the graph Gr within which operation of the generators 10A and 10B is expected not to be impaired after switching to the independent operation state. As shown in FIG. 12(b), in the graph Gr, the permissible operating range PA may also be defined (divided) by two vertical lines extending along the vertical axis in addition to the boundary lines y1 and y2.

[0095] In the example shown in FIG. 12(b), boundary line x5 (third boundary line) is a line that represents the minimum power output that the generator 10B can generate. For example, if a steam turbine is connected to the generator 10B, x5 represents the power output of the generator 10B when the flow rate of steam introduced into the steam turbine is minimum. Furthermore, if the generator 10B is controlled by droop control during independent operation, the change in output of the generator 10B due to the change in frequency when transitioning to independent operation, as expressed by equation (3) or equation (9), may be taken into account.

[0096] The boundary line x6 (fourth boundary line) represents the maximum power output that the generator 10B can generate. For example, if a steam turbine is connected to the generator 10B, x6 represents the power output of the generator 10B when the flow rate of steam introduced into the steam turbine is at its maximum (maximum introducible flow rate). Alternatively, if the power generation system including the generator 10B is a combined cycle system, x6 may represent the maximum power output of the generator 10B, which is determined by limiting the flow rate of steam introduced from the gas turbine during autonomous operation. In this case, fluctuations in the amount of steam generated due to load fluctuations on the gas turbine accompanying a transition to the autonomous operation control mode may be taken into account. Furthermore, if the generator 10B is controlled by droop control during autonomous operation, the change in output of the generator 10B due to frequency changes during the transition to autonomous operation, as expressed by equation (3) or equation (14), may be taken into account.

[0097] 12(b), the allowable driving range PA is defined by the boundary line y1, the boundary line y2, the boundary line x5, and the boundary line x6. That is, the allowable driving range PA may be a range surrounded (closed) by the boundary line y1, the boundary line y2, the boundary line x5, and the boundary line x6. The warning notification unit 68 may also issue a warning when the operating point OP is to the left of the boundary line x5 or to the right of the boundary line x6.

[0098] 12(b), the permissible operating range PA may be defined by the boundary line x5 and at least one of the boundary lines y1 and y2. Alternatively, the permissible operating range PA may be defined by the boundary line x6 and at least one of the boundary lines y1 and y2. As described above, the range of the permissible operating range PA related to the first axis (horizontal axis) may be defined by both the boundary line x5 and the boundary line x6, by only the boundary line x5, or by only the boundary line x6 (i.e., at least one of the boundary line x5 and the boundary line x6).

[0099] The display control unit 66 may use, on the horizontal axis of the graph Gr, the power generation output of the generator 10A controlled by isochronous control during stand-alone operation, instead of the power generation output of the generator 10B controlled by droop control during stand-alone operation.

[0100] In the isolated operation state (isolated operation control mode), the control device 12A may control the generator 10A according to the droop characteristics, and the control device 12B may control the generator 10B according to the droop characteristics, as shown in Fig. 13. That is, in both the grid-connected operation control mode and the isolated operation control mode, droop control may be performed on each of the generators 10A and 10B.

[0101] Even if the control methods of both the generators 10A and 10B are maintained at droop control when the system transitions to an independent operation state, the generators 10A and 10B are electrically connected in parallel, and therefore the frequencies of the power output from the generators 10A and 10B match. In this case, the outputs from the generators 10A and 10B are balanced so that the power output from the generators 10A and 10B satisfies the power required by the important load 110. The frequencies of the generators 10A and 10B are then determined so that the sum (x1 + x2) of the outputs from the generators 10A and 10B matches the power required by the important load 110. In the example shown in FIG. 13 , the outputs from the generators 10A and 10B are balanced when the frequency of the generators 10A and 10B is “fx.”

[0102] Similarly, even when droop control is performed on each of the generators 10A and 10B in the isolated operation control mode, the output of at least one of the generators 10A and 10B may fall outside the operable range due to changes in factors that determine the frequency of the output power. In other words, when switching from the grid-connected operation control mode to the isolated operation control mode, at least one of the generators 10A and 10B may become lightly loaded or overloaded.

[0103] FIG. 14(a) illustrates the relationship between the frequency and power generation output of each generator in the grid-connected operation control mode. The operating state shown in FIG. 14(a) is the same as the operating state shown in FIG. 5(a). FIG. 14(b) illustrates the relationship between the frequency and power generation output of each generator when transitioning from the operating state shown in FIG. 14(a) to the isolated operation control mode. When transitioning to the isolated operation control mode, the frequency of each generator changes to a frequency fx that balances the output according to the power required by the important load 110.

[0104] In the examples shown in FIGS. 14(a) and 14(b), the frequency fc (fluctuation value) defined by the power system 200 is greater than the frequency fx (fluctuation value). That is, with the transition to the isolated operation control mode, the frequency of each generator decreases. Accordingly, depending on the power required by the important load 110, the power output from generator 10A increases from power output w1 to power output x1, and the power output from generator 10B increases from power output w2 to power output x2. In this case, as shown in FIG. 14(b), the power output from generator 10B may deviate from the operable range, and generator 10B may become overloaded.

[0105] Depending on the frequency fc and the power required by the important load 110, the generator 10A may be overloaded instead of or in addition to the generator 10B. Alternatively, depending on the frequency fc and the power required by the important load 110, one of the generators 10A and 10B, or both of the generators 10A and 10B, may be underloaded. As described above, if droop control continues for both the generators 10A and 10B during independent operation, the question arises as to whether the output of each of the generators 10A and 10B falls within the operable range.

[0106] If it is possible to determine whether the power generation output of each of the generators 10A and 10B will deviate from its operable range when the system transitions to the isolated operation control mode under the current conditions during grid connection in the grid-connected operation control mode, it becomes possible to take measures during grid connection. Examples of such measures include moving the line representing the droop characteristic up or down (increasing or decreasing the speed setting value L0) and / or adjusting the power consumption of the important load 110. The monitoring device 50 displays a graph Gr on the monitor 52 as information that enables taking measures during grid connection. In the above measures, the operator may be able to adjust the power generation output of the generator 10B but may not be able to adjust the power generation output of the generator 10A.

[0107] The display control unit 66 may calculate boundary lines y1 and y2 as shown in Figure 15(a) and display a graph Gr including the acceptable operating range PA on the monitor 52. The boundary line y1 may be calculated using the functions shown in the following equations (21) to (27).

number

[0108] Pbamax(x) in equation (21) represents the maximum output of generator 10A and generator 10B in the islanded operation control mode. Fbamin(x) in equation (25) represents the frequency at which either generator 10A or generator 10B achieves maximum output in the islanded operation control mode. Fbmin(x) in equation (26) represents the frequency when generator 10B alone achieves maximum output without considering parallel islanded operation, and Famin in equation (27) represents the frequency when generator 10A alone achieves maximum output without considering parallel islanded operation. Fp is a measured value and is the current frequency (a frequency determined by the power from the power grid 200). However, calculations may be performed using the rated frequency Fs (a constant value) instead of Fp. Da represents the droop rate [%] in the droop control for generator 10A. In equations (25) and elsewhere, max[i,j] represents a function that outputs the larger value of i and j.

[0109] The boundary line y2 may be calculated by the functions shown in the following equations (31) to (37).

number

[0110] Pbamin(x) shown in equation (31) represents the minimum output (minimum output) of generators 10A and 10B in the islanded operation control mode. Fbamax(x) shown in equation (35) represents the frequency at the minimum output of generators 10A and 10B in the islanded operation control mode. Fbmax(x) shown in equation (36) represents the frequency when generator 10B alone is set to the minimum output without considering parallel islanded operation, and Famax shown in equation (37) represents the frequency when generator 10A alone is set to the minimum output without considering parallel islanded operation. In equation (36), Tbmin represents the allowable minimum output [kW] of generator 10B, and in equation (37), Tamin represents the allowable minimum output [kW] of generator 10A.

[0111] The boundary line y1 shown in FIG. 15(a) can be broken down into lines y11 and y12 shown in FIG. 15(b). Conversely, when FIG. 15(a) is explained based on FIG. 15(b), the boundary line y1 can also be considered as a line defined by lines y11 and y12. Specifically, the boundary line y1 is defined by the lower portions of lines y11 and y12 (those with smaller values ​​on the vertical axis) when observing the graph Gr while changing the value on the horizontal axis. Similarly to the boundary line y1, the boundary line y2 shown in FIG. 15(a) can also be considered as a line defined by lines y21 and y22 shown in FIG. 15(b). Specifically, the boundary line y2 is defined by the upper portions of lines y21 and y22 (those with larger values ​​on the vertical axis) when observing the graph Gr while changing the value on the horizontal axis.

[0112] The line y11 is calculated by the following equations (41) to (43).

number

number

[0113] The line y21 is calculated by the following equations (47) to (49).

number

number

[0114] Line y11 represents the boundary of whether the generator 10A will be overloaded when transitioning to the isolated operation control mode. That is, if the operating point OP on the graph Gr is located above line y11, the generator 10A will be overloaded when transitioning to the isolated operation control mode in that state. Line y12 represents the boundary of whether the generator 10B will be overloaded when transitioning to the isolated operation control mode in that state. That is, if the operating point OP on the graph Gr is located above line y12, the generator 10B will be overloaded when transitioning to the isolated operation control mode in that state. If the operating point OP on the graph Gr is located above both line y11 and line y12, both the generators 10A and 10B will be overloaded when transitioning to the isolated operation control mode in that state. From the above, the boundary line y1 defined by lines y11 and y12 represents the boundary of whether at least one of the generators 10A and 10B will be overloaded.

[0115] Line y21 represents the boundary of whether the generator 10A will be lightly loaded when transitioning to the isolated operation control mode. That is, if the operating point OP on the graph Gr is located below line y21, the generator 10A will be lightly loaded when transitioning to the isolated operation control mode in that state. Line y22 represents the boundary of whether the generator 10B will be lightly loaded when transitioning to the isolated operation control mode in that state. That is, if the operating point OP on the graph Gr is located below line y22, the generator 10B will be lightly loaded when transitioning to the isolated operation control mode in that state. If the operating point OP on the graph Gr is located below both line y21 and line y22, both the generators 10A and 10B will be lightly loaded when transitioning to the isolated operation control mode in that state. From the above, the boundary line y2 defined by line y21 and line y22 represents the boundary of whether at least one of the generators 10A and 10B will be lightly loaded.

[0116] The display control unit 66 may display the boundary line y1 and the boundary line y2, and then display the allowable driving range PA, as shown in Fig. 15(a). The display control unit 66 may display the line y11, the line y12, the line y21, and the line y22, without displaying the boundary line y1 and the boundary line y2, and then display the allowable driving range PA, as shown in Fig. 15(b).

[0117] 16 shows another example of the graph Gr that is displayed when droop control is performed on both the generator 10A and the generator 10B during independent operation. The display control unit 66 may display the permissible operation range PA defined by the boundary line y1, the boundary line y2, the boundary line x5, and the boundary line x6, similar to the example shown in FIG.

[0118] The display control unit 66 may display the allowable operating range PA using the power generation output of generator 10A instead of the power generation output of generator 10B on the horizontal axis of the graph Gr shown in Figure 15(a), Figure 15(b), or Figure 16.

[0119] The display control unit 66 does not have to display the operating point OP on the graph Gr. In this case, the operator may determine whether or not the above-described measures are necessary by grasping the current value of the power generation output of the generator 10B and the current value of the important load power, and comparing them with information obtained from the permissible operation range PA on the graph Gr. The display control unit 66 may calculate the boundary line that defines the permissible operation range PA by a calculation method different from the various examples described above.

[0120] The display control unit 66 may calculate a three-dimensional graph including a third axis representing a physical quantity related to the power generation output from the generator 10A (for example, the power generation output of the generator 10A itself) in addition to the first and second axes. In this case, the display control unit 66 may be able to switch the display on the monitor 52 between a two-dimensional graph consisting of the power generation output and important load power of the generator 10B and a two-dimensional graph consisting of the power generation output and important load power of the generator 10A. For example, a user instruction indicating an instruction to switch the display may be input to the monitoring device 50 by the user. A corresponding allowable operating range PA may be displayed in each of the two-dimensional graphs.

[0121] Instead of switching the axes, the display control unit 66 may be capable of displaying a two-dimensional graph consisting of the first axis and the second axis for each of the multiple levels of values ​​on the third axis (for example, values ​​such as 1000, 2000, and 3000) on the monitor 52. The display control unit 66 may also display two-dimensional graphs for each of the multiple levels of values ​​on the third axis together on the monitor 52, or may be capable of switching the two-dimensional graphs to be displayed in response to a user input.

[0122] As a physical quantity related to the power generation output representing the first axis, etc., a physical quantity having a certain corresponding relationship, such as a proportional relationship, with the power generation output may be used instead of the power generation output of the generator itself. As a physical quantity correlated with the power generation output, the opening of a valve provided in a flow path of fuel or working fluid (e.g., steam) introduced into a prime mover connected to the generator may be used, or the amount of introduced fuel or the flow rate of the working fluid may be used. In a back-pressure turbine, the amount of exhaust steam may be used. In the droop characteristics used in droop control, the physical quantities exemplified above may also be used instead of the power generation output.

[0123] When the frequency of the generator 10B (or / and the generator 10A) is used to calculate the permissible operation range PA, the frequency may be output to the monitoring device 50 from a measuring means other than the control device 12B.

[0124] The warning notification unit 68 may issue a warning not only when the operating point OP deviates from the allowable operating range PA, but also when the operating point OP is located within the allowable operating range PA and approaches a predetermined amount to various boundary lines that define (divide) the allowable operating range PA.

[0125] Instead of the protective relay 22, the monitoring device 50 may be capable of outputting a signal to the circuit breaker 20 to instruct it to switch between an on state and an off state. Any component may switch the state of the circuit breaker 20 as long as the circuit breaker 20 can cut off the connection between the power grid 200 and two or more generators (for example, the generators 10A and 10B) so that the power generation system 1 switches from a grid-connected operation state to an independent operation state.

[0126] In one example of the various examples described above, at least some of the matters described in other examples may be combined.

[0127] Summary of this disclosure The power generation system (1) described above includes two or more generators (10A, 10B) connected to an electric power system (200) and operating in parallel, a circuit breaker (20) that switches between a grid-connected operation state in which the electric power system (200) and the two or more generators (10A, 10B) are connected and an isolated operation state in which the electric power system (200) and the two or more generators (10A, 10B) are disconnected, and a display control unit (66) that displays a graph (Gr) including a first axis and a second axis on a monitor (52) in the grid-connected operation state. The first axis represents a physical quantity related to the power output of a target generator (10B), which is one of the two or more generators (10A, 10B), and the second axis represents the power consumption of a significant load (110) to which power is supplied from the two or more generators (10A, 10B) in the isolated operation state. The display control unit (66) displays, on the second axis of the graph (Gr), an allowable operation range (PA) that indicates a range within which the operation of the two or more generators (10A, 10B) is not expected to be affected after switching to the independent operation state.

[0128] As described above, when a system transitions from grid-connected operation to an isolated operation state, the factors that determine the frequency of the output power change, which can cause the frequency to change. A change in frequency also changes the output power of at least one generator. As a result, the output power of at least one generator may fall outside the operable range. To reduce this possibility, it is possible to adjust the power generation output based on empirical rules, adjust the load power, or create an operating state with a high likelihood. However, this may require an uneconomical large power generation capacity or result in an uneconomical operating situation. Another method is to instantaneously shed less important loads after transitioning to an isolated operation state. However, this can result in damage due to an unexpected equipment outage. Furthermore, if the transition to isolated operation is due to a simple voltage sag, the load equipment that is instantaneously shed will experience a power outage rather than a voltage sag, further exacerbating the damage. Furthermore, since power continues to be supplied to important loads after transitioning to an isolated operation state, countermeasures may not be effective in time.

[0129] In contrast, in the power generation system (1), before switching to the grid-connected operation state, i.e., the isolated operation state, an allowable operation range (PA) is displayed on the monitor (52), which indicates a range within which the operation of the two or more generators (10A, 10B) is expected not to be affected after switching to the isolated operation state. Therefore, an operator or the like can determine or understand, from the allowable operation range (PA) displayed on the monitor (52), whether or not a problem will occur in the operation of the generators if the system is switched to the isolated operation state in the current state. If a problem is likely to occur in the operation of the generators, the operator or the like can take measures (e.g., adjusting the droop characteristics and / or adjusting the important load power) before switching to the isolated operation state. Therefore, the power generation system (1) can ensure stable operation during the isolated operation state.

[0130] The usefulness obtained by the power generation system (1) can be explained in more detail using specific examples as follows. The graph (Gr) above shows the relationship between the current operating state and the allowable operating range PA, allowing the operator to choose between changing the generator output or adjusting the critical load power. By clarifying the allowable operating range (PA), while human judgment (adjustments according to the load equipment status) is still involved in equipment operation, it is possible to maximize the use of power generation equipment capacity without relying on experience or likelihood. - After transitioning to an isolated operation state, the possibility of generators (power generation equipment including generators) becoming overloaded can be reduced. When constructing a new power generation facility, by incorporating the adoption of the power generation system (1) described above, it is possible to reduce the likelihood of facility capacity and construct a facility with an economical capacity. With the introduction of renewable energy, grid frequency has become unstable in recent years, and there is a possibility that the difference between the grid frequency and the frequency during stand-alone operation may become large. In this case, the power output of the generator (10B), which is subjected to droop control during stand-alone operation, will fluctuate greatly. However, by predicting the output using the power generation system (1), stable stand-alone operation can be performed even when such fluctuations occur.

[0131] The display control unit (66) may display a graph (Gr) on the monitor (52) so that the allowable operation range (PA) changes over time in accordance with the operating status of at least one of the two or more generators (10A, 10B). In this case, the operator can understand the allowable operation range PA in accordance with the actual status of the system including the two or more generators.

[0132] The power generation system (1) may further include an operating condition acquisition unit (62) that acquires, as at least a part of the operating conditions, a rotational speed or a frequency of one of the two or more power generators (10A, 10B) from a power generation control unit (12A) that controls the power generator (10A). The display control unit (66) may display a graph (Gr) on the monitor (52) so that the allowable operation range (PA) changes over time in accordance with the rotational speed or the frequency acquired by the operating condition acquisition unit (62). In this case, the rotational speed or the frequency recognized by the power generation control unit (12A) is reflected in the allowable operation range PA (for example, the difference from the rated frequency recognized by the control device 12A is reflected in the allowable operation range PA), and therefore the allowable operation range PA can be calculated with high accuracy.

[0133] The display control unit (66) may display, in the graph (Gr), an operating point (OP) including the current value of the power consumption of the important load (110) and the current value of the physical quantity, together with an allowable operating range (PA). In this case, by displaying both the allowable operating range PA and the operating point OP, an operator or the like can easily determine from the displayed contents whether or not measures are necessary.

[0134] The power generation system (1) may further include a warning notification unit (68) that issues a warning to a user based on a comparison result between the operating point (OP) and the allowable operation range (PA). In this case, the warning is issued to an operator or the like as a user, so that the operator can more reliably recognize that countermeasures are required.

[0135] A portion of the allowable operation range (PA) may be defined by a first boundary line (y1) that indicates the boundary between whether at least one of the two or more generators (10A, 10B) will be overloaded. In this case, by understanding the relationship between the allowable operation range PA and the current values ​​of the first and second axes and taking measures in advance, it is possible to reduce the possibility of the generators being overloaded when transitioning to the isolated operation mode.

[0136] A portion of the allowable operation range (PA) may be defined by a second boundary line (y2) that indicates the boundary between whether at least one of the two or more generators (10A, 10B) is lightly loaded. In this case, by understanding the relationship between the allowable operation range PA and the current values ​​of the first axis and the second axis and taking measures in advance, it is possible to reduce the possibility that the generators will be lightly loaded when transitioning to the isolated operation mode.

[0137] The first axis may represent the power generation output of the generator (10B). The permissible operation range (PA) may represent a range on both the first axis and the second axis of the graph (Gr) within which operation of the two or more generators (10A, 10B) is expected not to be impaired after switching to the independent operation state. The range of the permissible operation range (PA) related to the first axis may be defined by at least one of a third boundary line (x5) representing the minimum output that the target generator (10B) can generate and a fourth boundary line (x6) representing the maximum output that the target generator (10B) can generate. In this case, an operator or the like can easily grasp the relationship between the current value of the power generation output of the target generator (10B) and at least one of the minimum output and maximum output that can be generated, from the permissible operation range PA and the current value of the power generation output of the target generator (10B).

[0138] The two or more generators (10A, 10B) may include a first generator (10A) and a second generator (10B). The power generation system (1) may further include a first power generation control unit (12A) that controls the first generator (10A) according to an isochronous characteristic in the isolated operation state, and a second power generation control unit (12B) that controls the second generator (10B) according to a droop characteristic in the isolated operation state. In this case, as described above, there is a possibility that the generator (10A) may be overloaded or underloaded when transitioning to the isolated operation state. However, by displaying the allowable operation range (PA), it is possible to urge an operator or the like to avoid such a possibility.

[0139] The two or more generators (10A, 10B) may include a first generator (10A) and a second generator (10B). The power generation system (1) may further include a first power generation control unit (12A) that controls the first generator (10A) in accordance with the droop characteristic in the isolated operation state, and a second power generation control unit (12B) that controls the second generator (10B) in accordance with the droop characteristic in the isolated operation state. In this case, as described above, when the system transitions to the isolated operation state, at least one of the two or more generators may be overloaded or underloaded. However, by displaying the allowable operation range (PA), it is possible to urge an operator or the like to avoid such a possibility.

[0140] The monitoring device (50) described above is a device provided in a power generation system (1) including two or more generators (10A, 10B) connected to a power grid (200) and operating in parallel, and a circuit breaker (20) that switches between a grid-connected operation state in which the power grid (200) and the two or more generators (10A, 10B) are connected and an isolated operation state in which the power grid (200) and the two or more generators (10A, 10B) are disconnected. The monitoring device (50) includes a display control unit (66) that, in the grid-connected operation state, displays a graph (Gr) including a first axis and a second axis on a monitor (52). The first axis represents a physical quantity related to the power output of a target generator (10B), which is one of the two or more generators (10A, 10B), and the second axis represents the power consumption of a critical load (110) to which power is supplied from the two or more generators (10A, 10B) in the isolated operation state. The display control unit (66) displays, on the second axis of the graph (Gr), an allowable operation range (PA) representing a range within which the operation of the two or more generators (10A, 10B) is not expected to be affected after switching to the independent operation state. Since the allowable operation range (PA) is displayed for this power generation device (50) in the same way as for the power generation system (1), stable operation during independent operation can be achieved.

[0141] The monitoring method described above is a method for monitoring a power generation system (1) including two or more generators (10A, 10B) connected to a power grid (200) and operating in parallel, and a circuit breaker (20) that switches between a grid-connected operation state in which the power grid (200) and the two or more generators (10A, 10B) are connected and an isolated operation state in which the power grid (200) and the two or more generators (10A, 10B) are disconnected. This monitoring method includes a display step of displaying, on a monitor (52), a graph (Gr) including a first axis and a second axis in the grid-connected operation state. The first axis represents a physical quantity related to the power generation output of a target generator (10B), which is one of the two or more generators (10A, 10B), and the second axis represents the power consumption of a critical load (110) to which power is supplied from the two or more generators (10A, 10B) in the isolated operation state. In the display step, an allowable operation range (PA) is displayed on the second axis of the graph (Gr), representing a range within which the operation of the two or more generators (10A, 10B) is expected to be unimpeded after switching to the stand-alone operation state. This monitoring method displays the allowable operation range (PA) in the same way as the power generation system (1), making it possible to ensure stable operation during stand-alone operation. [Explanation of symbols]

[0142] 1...power generation system, 10A, 10B...generator, 12A, 12B...control device, 20...circuit breaker, 22...protective relay, 50...monitoring device, 52...monitor, 62...operating status acquisition unit, 66...display control unit, 68...warning notification unit, Gr...graph, PA...operating tolerance range, OP...operating point, y1, y2, y3, x5, x6...boundary line, 110...important load, 200...power system.

Claims

1. two or more generators connected to a power grid and operating in parallel; a circuit breaker that switches between a grid-connected operation state in which the power grid and the two or more generators are connected and an isolated operation state in which the power grid and the two or more generators are disconnected; a display control unit that displays a graph including a first axis and a second axis on a monitor in the grid-connected operation state, the first axis represents a physical quantity related to the power generation output of a target generator that is any one of the two or more generators; The second axis represents the power consumption of a significant load to which power is supplied from the two or more generators in the isolated operation state; The display control unit displays an acceptable operating range on the second axis of the graph, representing the range within which operation of the two or more generators is expected not to be impaired after switching to the independent operation state.

2. The power generation system according to claim 1 , wherein the display control unit displays the graph on the monitor so that the allowable operating range changes over time according to an operating condition of at least one of the two or more power generators.

3. an operating condition acquisition unit that acquires, from a power generation control unit that controls one of the two or more power generators, a rotation speed or a frequency of the power generator as at least a part of the operating condition; The power generation system according to claim 2 , wherein the display control unit displays the graph on the monitor so that the allowable operating range changes over time according to the rotation speed or frequency acquired by the operating condition acquisition unit.

4. The power generation system according to claim 1 , wherein the display control unit displays, in the graph, an operating point including a current value of the power consumption of the important load and a current value of the physical quantity, together with the permissible operating range.

5. The power generation system according to claim 4 , further comprising a warning notification unit that issues a warning to a user based on a result of comparison between the operating point and the allowable operating range.

6. The power generation system according to any one of claims 1 to 5, wherein a portion of the allowable operating range is defined by a first boundary line that represents a boundary as to whether or not at least one of the two or more generators is overloaded.

7. The power generation system according to any one of claims 1 to 5, wherein a portion of the allowable operating range is defined by a second boundary line that represents a boundary as to whether or not at least one of the two or more generators is in a light load state.

8. the first axis represents the power output of the generator; the allowable operation range represents a range on both the first axis and the second axis of the graph in which operation of the two or more generators after switching to the independent operation state is not expected to be impaired; 7. The power generation system of claim 6, wherein the range of the allowable operating range relating to the first axis is defined by at least one of a third boundary line representing the minimum output that the target generator can generate and a fourth boundary line representing the maximum output that the target generator can generate.

9. the first axis represents the power output of the generator; the allowable operation range represents a range on both the first axis and the second axis of the graph in which operation of the two or more generators after switching to the independent operation state is not expected to be impaired; 8. The power generation system of claim 7, wherein the range of the allowable operating range relating to the first axis is defined by at least one of a third boundary line representing the minimum output that the target generator can generate and a fourth boundary line representing the maximum output that the target generator can generate.

10. the two or more generators include a first generator and a second generator, The power generation system includes: a first power generation control unit that controls the first power generator in accordance with an isochronous characteristic in the stand-alone operation state; 6. The power generation system according to claim 1, further comprising: a second power generation control unit that controls the second power generator in accordance with a droop characteristic in the independent operation state.

11. the two or more generators include a first generator and a second generator, The power generation system includes: a first power generation control unit that controls the first generator in accordance with a droop characteristic in the stand-alone operation state; 6. The power generation system according to claim 1, further comprising: a second power generation control unit that controls the second power generator in accordance with a droop characteristic in the independent operation state.

12. two or more generators connected to a power grid and operating in parallel; a circuit breaker that switches between a grid-connected operation state in which the power grid and the two or more generators are connected and an isolated operation state in which the power grid and the two or more generators are disconnected; A monitoring device provided in a power generation system comprising: a display control unit that displays a graph including a first axis and a second axis on a monitor in the grid-connected operation state; the first axis represents a physical quantity related to the power generation output of a target generator that is any one of the two or more generators; The second axis represents the power consumption of a significant load to which power is supplied from the two or more generators in the isolated operation state; The display control unit of the monitoring device displays an acceptable operating range on the second axis of the graph, representing the range within which it is expected that operation of the two or more generators will not be impaired after switching to the independent operation state.

13. two or more generators connected to a power grid and operating in parallel; a circuit breaker that switches between a grid-connected operation state in which the power grid and the two or more generators are connected and an isolated operation state in which the power grid and the two or more generators are disconnected; A monitoring method for a power generation system comprising: a display step of displaying a graph including a first axis and a second axis on a monitor in the grid-connected operation state; the first axis represents a physical quantity related to the power generation output of a target generator that is any one of the two or more generators; The second axis represents the power consumption of a significant load to which power is supplied from the two or more generators in the isolated operation state; A monitoring method for a power generation system, in which the display process displays an acceptable operating range on the second axis of the graph, representing the range within which it is expected that the operation of the two or more generators will not be impaired after switching to the independent operation state.

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