JP2013219966A - Power generation system, and control method for power generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power generation system and a control method for the power generation system having a higher possibility rate of load input by a simpler configuration or control.SOLUTION: A power generation system 1 comprises: a load unit 9; a gas engine 3 capable of automatically changing power generation output depending on load fluctuation of the load unit 9 when being separated from a power grid 101; a fuel cell 5; and a power transmission unit 11 electrically connected to each of the load unit 9, the gas engine 3, the fuel cell 5, and the power grid 101. The fuel cell 5 comprises a control unit 7 capable of controlling power generation output of the fuel cell 5. In an after-block load increase time in the case that a load of the load unit 9 increases in a situation where power supply from the power grid 101 is blocked, the control unit 7 first increases power generation output of the gas engine 3, and, after that, decreases the power generation output of the gas engine 3 by increasing the power generation output of the fuel cell 5.

Description

  The present invention relates to a power generation system capable of supplying power to a load that consumes power when the power supply from the power system is lost, and a method for controlling the power generation system.

Usually, a distributed power generation system performs control based on active power and power factor when connected to the power system, and control based on frequency and voltage when separated from the power system.
When interconnected with the power system, the system absorbs even if there is a load change, so the power generation system installed individually does not need to change the output at high speed.
On the other hand, when the load system fluctuates when it is separated from the power system and operates independently, the fluctuation must be borne by the power generation system. However, an allowable load input rate is determined for each gas engine (FIG. 2).

Patent Document 1 describes that a gas engine power generation system having a high commercial value can be obtained by improving the initial load input rate in summer, for example, and performing load input as quickly as possible. A technique for improving the initial load application rate of a gas engine by using dry air other than external air as combustion air in order to improve the initial load input rate of the engine is disclosed.
Patent Document 2 describes that frequency stability during self-sustained operation by a gas engine generator is improved while suppressing a decrease in utilization efficiency of the gas engine generator, and a gas engine and a power storage device are used. In other words, a technique for suppressing large output fluctuations of a gas engine by charging and discharging an electric power storage device with respect to large load fluctuations is disclosed.
Patent Document 3 provides an operation method that eliminates inconvenience caused by load fluctuations when operating a private power generation facility independently from a commercial system. There is disclosed a technique for improving the loadable possibility rate by monitoring the generated frequency fluctuation and assisting the output fluctuation of the gas engine when the load fluctuation occurs with a power storage device.
Patent Document 4 provides a private power generation system that can perform an efficient operation by making use of the rated capacity of the private power generation facility. When carrying out a self-sustained operation, power is supplied to a load without using an inverter. Techniques for implementing the supply are disclosed.

JP2011-190688A JP 2008-301545 A JP 2007-6595 JP 2002-152977

In general, in a distributed power generation system such as a gas engine, when a self-sustaining operation is performed separately from a power system, the loadable amount is determined by the load before being turned on as shown in FIG. For this reason, if the load before charging increases, the loadable amount decreases.
Patent Document 1 does not suggest that the loadable rate is increased by combining a gas engine with another power source and by reducing the operating load factor of the gas engine.
Moreover, in patent document 2, the load throw-in rate is only apportioned by two gas engines, and its control is not suggested.
Furthermore, Patent Document 3 does not suggest reducing the output of the gas engine by placing a load on the power source combined with the gas engine.
In addition, in patent document 4, there is no description regarding the combination of generators and the input load.

This invention is made | formed in view of the said subject, and an example of the subject is providing the electric power generation system with a higher loadable possibility rate by simpler structure or control.
A power generation system including a second power generation system capable of outputting, increasing the output of the second power generation system, and increasing the loadable amount by decreasing the output of the first power generation system, and a control method of the power generation system Is an offer.

  The power generation system of the present invention includes a load unit, a first power generation unit capable of automatically varying a power generation output according to a load variation of the load unit when disconnected from the power system, and a second power generation unit. , The load unit, the first power generation unit, the second power generation unit, and the power system, and a power transmission unit electrically connected to each other, and the second power generation unit includes the second power generation unit. A control unit capable of controlling the power generation output of the unit, the control unit, in the state where the supply of power from the power system is cut off, when the load of the load unit rises, The power generation output of the first power generation unit is increased, and then the power generation output of the first power generation unit is decreased by increasing the power generation output of the second power generation unit.

  Preferably, when the power generation output of the first power generation unit is reduced when the power generation system is cut off from the power system, the power generation output amount by which the control unit increases the power generation output of the second power generation unit is The first power generation unit is the same as the power generation output amount automatically increased to cope with the load increase of the load unit.

  As an example, the control unit controls the power generation output by a signal from the control unit for both the first power generation unit and the second power generation unit immediately before the supply of power from the power system is cut off. .

  Preferably, the first power generation unit is a gas engine.

  Preferably, the second power generation unit is a fuel cell.

  According to the power generation system control method of the present invention, in the state where the power supply from the power system is cut off, when the load of the load unit rises, the power generation output of the first power generation unit is first raised when the load increases after the cut-off. 1 process and the 2nd process of reducing the electric power generation output of a 1st electric power generation part by raising the electric power generation output of a 2nd electric power generation part.

  According to the power generation system of the present invention, it is possible to provide a power generation system with a higher loadable rate and a method for controlling the power generation system with a simpler configuration or control.

It is explanatory drawing of a structure of 1st Embodiment in this invention. It is explanatory drawing of the relationship of the load increase amount which a gas engine can respond when load increases. It is a flowchart of control by which a control part makes the gas engine output of a gas engine the minimum output of a gas engine. In the electric power generation system comprised like this embodiment, when there is no electric power supply from an electric power grid | system, it is explanatory drawing of the behavior of an electric power generation system when load increases. It is explanatory drawing of the effect of this embodiment.

<First Embodiment>
FIG. 1 is an explanatory diagram of the configuration of the first embodiment of the present invention.
1A is an explanatory diagram in the case where the power generation system 1 is receiving power supply from the power system 101, and FIG. 1B is a description in the case where there is no power supply from the power system 101. FIG.

As shown in FIG. 1A and FIG. 1B, the power generation system 1 is electrically connected to the power system 101 via the power transmission unit 11 and the transformation equipment 103.
The power generation system 1 includes a gas engine 3 and a fuel cell 5 that can supply power, a load unit 9 that consumes power, a control unit 7 that controls them, and a power transmission unit 11.
Here, the electric power output from the gas engine 3 is represented by a gas engine output Pg, and the electric power output from the fuel cell 5 is represented by a fuel cell output Pf.

When connected to the power system 101, the gas engine output control unit 33 controls the gas engine output Pg output from the gas engine 3 based on the output command CPg from the control unit 7.
When disconnected from the power system, the gas engine output control unit 33 automatically controls the amount of gas supplied to the gas engine 3 in accordance with the rotational speed of the gas engine 3 (governor control). Specifically, when the rotational speed of the gas engine 3 is lower than a predetermined rotational speed, control for automatically increasing the amount of combustion gas (hereinafter simply referred to as “gas”) supplied to the gas engine 3 is performed. When the rotational speed of the gas engine 3 is higher than the predetermined rotational speed, control is performed to automatically reduce the amount of gas supplied to the gas engine 3.
The gas engine output control unit 33 performs control independently of the control unit 7 in accordance with the rotational speed and performs autonomous control.

  Further, the gas engine output measuring unit 31 outputs gas engine output information IPg corresponding to the measured gas engine output Pg to the control unit 7.

Further, the fuel cell 5 includes a fuel cell output measuring unit 51 that measures the fuel cell output Pf, and a fuel cell output control unit 53.
The fuel cell output control unit 53 controls the fuel cell output Pf output from the fuel cell 5 based on the output command CPf from the control unit 7. Specifically, the amount of fuel and oxygen supplied to the fuel cell 5 is adjusted. More specifically, when the output command CPf is larger than the current output value, the amounts of fuel and oxygen supplied to the fuel cell 5 are increased, and when the output command CPf is smaller than the current output value. Decreases the amount of fuel and oxygen supplied to the fuel cell 5.
The fuel cell outputs the fuel cell based on the output command from the control unit 7 both when it is connected to the power system and when it is shut off.

  Further, the fuel cell output measuring unit 51 outputs fuel cell output information IPf corresponding to the measured fuel cell output Pf to the control unit 7.

The control unit 7 calculates an output command CPf to be output to the fuel cell 5 based on the gas engine output information IPg and the fuel cell output information IPf, and uses the output command CPf calculated as a result of the calculation as a fuel cell of the fuel cell 5. Output to the output controller 53.
The method for calculating the output command CPf will be described with reference to FIG.

Here, the difference in characteristics between the gas engine 3 and the fuel cell 5 will be described.
The gas engine 3 can increase its output in a relatively short time as a characteristic (high load followability).
Further, when the gas engine 3 is cut off from the power system of the present embodiment, the output of the gas engine 3 is controlled autonomously and automatically, so that the load followability is high from this point.
On the other hand, since the fuel cell 5 takes time to increase the load, the load followability is lower than that of the gas engine.

As shown in FIG. 1A, when power is supplied from the power system 101, the control unit 7 controls the power supply. For example, control is performed so that the power received from the power system 101 is 0 kW. Yes.
On the other hand, as shown in FIG. 1B, when there is no power supply from the power system 101, the load amount PI of the load unit 9 must be handled by the gas engine output Pg and the fuel cell output Pf.
That is, the relationship PI = Pg + Pf must always hold.
Furthermore, even when the load PI increases, it is necessary to cope with the increase by the gas engine 3 and / or the fuel cell 5.
The case where power supply from the power system 101 is lost means that power from the power system 101 can no longer be obtained due to a power failure or the like, and the case where the power generation system 1 is disconnected from the power system 101 by the substation facility 103. Is applicable.

As described above, the gas engine 3 has a relatively high load following capability.
FIG. 2 shows the load input rate of the gas engine 3.
The operating load on the horizontal axis represents what percentage of the maximum output of the gas engine 3 was operating before the load increased.
The load application possibility on the vertical axis corresponding to that represents how much of the maximum output of the gas engine 3 can withstand the increase in load at each operating load.
As a specific example, the gas engine 3 operating at 50% of the maximum output (50% of the collective load on the horizontal axis) can withstand a sudden increase in output of 20% of the maximum output. That is, the explanatory diagram of FIG. 2 shows that the output can be increased instantaneously up to a maximum of 70%.
2 is merely an example, and has different characteristics depending on the type of the gas engine 3, etc., but in this embodiment, the load during operation has a minimum output relative to the rated output. A description will be given below assuming a 50% gas engine 3.
In FIG. 2, 50% or less is not described, but there is a gas engine 3 that can be loaded at 50% or less. However, gas engines generally have a concern about efficiency reduction or NOx generation when operating at low loads, so even if the output is momentarily below the minimum output, it is rare to operate below the minimum output. The description is omitted.

As can be seen from FIG. 2, it is necessary to make the gas engine output Pg of the gas engine 3 close to the minimum output or the minimum output of the gas engine 3 in order to make the gas engine 3 have the highest possible load input rate. is there.
In addition, having such a high load input possibility rate means that the gas engine 3 has high resistance to fluctuations in the load amount PI. And that the gas engine 3 has high resistance to the load PI means that the power generation system 1 has high resistance to load fluctuations.

  Therefore, in this embodiment, the control unit 7 sets the gas engine output Pg of the gas engine 3 to 50% of the maximum output of the gas engine 3 by the following control.

  FIG. 3 is a flowchart of control in which the control unit 7 sets the gas engine output Pg of the gas engine 3 to the lowest output of the gas engine 3 (50% of the maximum output in this embodiment).

  In step ST01, the control unit 7 inputs the gas engine output Pg of the gas engine 3 measured by the gas engine output measurement unit 31 and the fuel cell output Pf of the fuel cell 5 measured by the fuel cell output measurement unit 51. receive.

In step ST03, it is determined whether the gas engine output Pg is greater than the minimum output of the gas engine 3.
When the gas engine output Pg is less than the minimum output of the gas engine 3, the process returns to step ST01.
If the gas engine output Pg is greater than or equal to the minimum output of the gas engine 3, the process proceeds to step ST05.
The reason why this determination is necessary is that when the gas engine output Pg is smaller than the minimum output of the gas engine 3, it is not possible to perform control for reducing the output of the gas engine 3.

In step ST05, it is determined whether the fuel cell output Pf is smaller than the maximum output of the fuel cell 5.
If the fuel cell output Pf is greater than or equal to the maximum output of the fuel cell 5, the process returns to step ST01.
When the fuel cell output Pf is less than the maximum output of the fuel cell 5, the process proceeds to step ST07.
The reason for this determination is that when the fuel cell output Pf is greater than or equal to the maximum output of the fuel cell 5, control for increasing the output of the fuel cell 5 cannot be performed.

In step ST07, an output command CPf is calculated.
Specifically, it is calculated by the following formula.
CPf = (Pg + Pf) − (minimum output of gas engine 3)
Since (Pg + Pf) = load amount PI, this equation outputs the output command CPf so that the fuel cell 5 is burdened except for the minimum output of the gas engine 3, and the fuel cell 5 (fuel) is output according to the output command CPf. This is because the battery output control unit 53) controls the output.
Note that the division of the minimum output of the gas engine 3 (= the operating load with the highest load input possibility rate = 50% of the maximum output in the present embodiment) is made to burden the fuel cell 5 to that extent. This is because, conversely, the output falls below the minimum output of the gas engine 3.

In step ST09, the output command CPf is actually instructed to the fuel cell 5 (fuel cell output control unit 53).
And it returns to step ST01 and continues control.

  As described above, since the control unit 7 controls the fuel cell output Pf of the fuel cell 5, it is possible to keep the gas engine output Pg of the gas engine 3 in a state where the loadable possibility rate is the highest. This will be specifically described below.

  FIG. 4 is an explanatory diagram of the behavior of the power generation system 1 when the load increases in the power generation system 1 configured as in the present embodiment when there is no power supply from the power system 101.

When there is no power supply from the power system 101, the load PI is supplied by the gas engine output Pg and the fuel cell output Pf.
In this state, when the load PI increases in a relatively short time (time t1), the gas engine 3 performing the governor control automatically follows. This follow-up is performed in a relatively short time.
This is because when the load amount PI increases, the rotational speed of the gas engine 3 decreases, and the gas engine output control unit 33 increases the gas supply amount to cope with the decrease in the rotational speed. is there.
When the gas supply amount increases, the gas engine output Pg of the gas engine 3 increases, which corresponds to an increase in the load amount PI.
Thereafter, the control unit 7 performs the control shown in the flowchart of FIG. 3 to increase the fuel cell output Pf of the fuel cell 5. At this time, the control unit 7 has already output the output command CPf so that the gas engine output Pg of the gas engine 3 becomes the minimum output.
Therefore, as shown in FIG. 4, the fuel cell output Pf increases only at a gentle angle.
As the fuel cell output Pf of the fuel cell 5 increases, the gas engine output Pg automatically decreases as the gas engine output Pg instead.
This is because if the load amount PI is constant, when the fuel cell output Pf increases, the load that the gas engine 3 should bear decreases accordingly. And in connection with it, since the rotation speed of the gas engine 3 increases, in order to respond | correspond to this, it is for the gas engine output control part 33 to reduce the supply amount of gas automatically.

Then, at the time t2, the increase in the fuel cell output Pf of the fuel cell 5 ends when the gas engine 3 reaches the minimum output (see also the explanation of step ST07).
As a result, the gas engine output Pg is the lowest output value of the gas engine 3 (50 in the present embodiment, the maximum output of the gas engine 3) that the gas engine 3 before the load amount PI can most respond to. %).
In the present embodiment, the minimum output value of the gas engine 3 means a value that allows the gas engine 3 to most cope with load fluctuations.

  FIG. 5 is an explanatory diagram of the effect of this embodiment.

For example, assuming that the gas engine output Pg is 50 kW (50% of the maximum output of the gas engine 3) and the fuel cell output Pf is 50 kW (50% of the maximum output of the fuel cell 5) before the load is increased. explain.
When there is an increase in the load amount PI of 40 kW, the output that the gas engine 3 and the fuel cell 5 share when performing the control in the present embodiment is the first pattern on the right side.
Further, when the load amount PI is increased by 40 kW, when the control to apportion the load amount PI is performed, the output that the gas engine 3 and the fuel cell 5 share is the second pattern on the left side.

Then, in the first pattern (in the case of the present embodiment), the loadable possibility rate of the gas engine 3 is 20%, which is the same as before the load amount is increased (see also FIG. 2).
On the other hand, in the second pattern, the loadable possibility rate is 15%, and it can be seen that the resistance against the increase in the load amount PI is 5% lower than before the increase in the load amount (see also FIG. 2). )

  As described above, according to the present embodiment, it is possible to provide the power generation system 1 that can maintain a high loadable rate.

<Other embodiments>
In this embodiment, power is supplied only from the gas engine 3 and the fuel cell 5, but in addition to this, there are other gas engines and fuel cells, gas turbines, gasoline engines, diesel engines, capacitors, etc. You may do it.
As a result, it is possible to improve the possibility of instantly responding to an increase in power supply capability and instantaneous load amount PI.

  Further, the present invention is not limited to the above embodiment, and various changed structures, configurations, and controls may be performed.

<Configuration and Effect of Embodiment>
The power generation system 1 of the present embodiment includes a load unit 9, a gas engine 3 that can automatically vary a power generation output according to a load variation of the load unit 9 when separated from the power system, a fuel cell 5, The load unit 9, the gas engine 3, the fuel cell 5, and the power system 101, and a power transmission unit 11 electrically connected to each other, and the fuel cell 5 is a control unit that can control the power generation output of the fuel cell 5. 7, the control unit 7 first increases the power generation output of the gas engine 3 when the load of the load unit 9 rises when the load of the load unit 9 rises when the supply of power from the power system 101 is cut off. Thereafter, the power generation output of the gas engine 3 is decreased by increasing the power generation output of the fuel cell 5.
Since it has such a configuration, it is possible to provide the power generation system 1 that can maintain a high loadable rate.

When the power generation output of the first power generation unit is decreased, the power generation output amount that the control unit 7 increases the power generation output of the fuel cell 5 is automatically set in order for the gas engine 3 to cope with the load increase of the load unit 9. This is the same as the power generation output increased.
Since it has such a configuration, it is possible to return to a state where the load application possibility rate before the load amount increases is high.

The control unit 7 controls the power generation output by signals from the control unit in both the gas engine 3 and the fuel cell 5. For example, the power generation output is controlled so that the power from the power system is 0 kW.
From such a configuration, the power generation system 1 can be operated even when power cannot be obtained from the power system or when it is not desired to obtain power from the power system.

The power generation system 1 includes a gas engine 3.
Since it has such a configuration, it is possible to instantly respond to fluctuations in the load amount PI.

The power generation system 1 is constituted by a fuel cell.
Since it has such a structure, it becomes possible to increase a power generation output amount reliably.

The control method of the power generation system 1 according to the present embodiment first increases the power generation output of the gas engine 3 when the load of the load unit 9 increases and the load increases after the interruption in a state where the supply of electric power from the electric power system is interrupted. A first step and a second step of lowering the power generation output of the gas engine 3 by increasing the power generation output of the fuel cell 5.
Since it has such a structure, the control method of the electric power generation system 1 which can hold | maintain a load throwable rate high can be provided.

<Definition etc.>
An example of the first power generation unit of the present invention is a gas engine 3. An example of the second power generation unit of the present invention is the fuel cell 5. Therefore, the first power generation unit and the second power generation unit may be any of a gas engine, a fuel cell, a gas turbine, a gasoline engine, a diesel engine, a capacitor, and the like.

1 Power Generation System 3 Gas Engine (First Power Generation Unit)
5 Fuel cell (second power generation unit)
DESCRIPTION OF SYMBOLS 7 Control part 9 Load part 11 Power transmission part 31 Gas engine output measurement part 33 Gas engine output control part 51 Fuel cell output measurement part 53 Fuel cell output control part 101 Electric power system 103 Substation equipment CPf Output command IPf Fuel cell output information IPg Gas engine Output information PI load Pf Fuel cell output Pg Gas engine output

Claims (6)

A load section;
A first power generation unit capable of automatically varying a power generation output in accordance with a load variation of the load unit when disconnected from the power system;
A second power generation unit;
The load unit, the first power generation unit, the second power generation unit and the power system, and a power transmission unit electrically connected to each other,
The second power generation unit has a control unit capable of controlling the power generation output of the second power generation unit,
The controller is
In a state in which the supply of power from the power system is cut off, when the load of the load unit rises,
First, the power generation output of the first power generation unit increases,
Thereafter, the power generation output of the first power generation unit is decreased by increasing the power generation output of the second power generation unit. When the power generation output of the first power generation unit is decreased, the power generation output amount that the control unit increases the power generation output of the second power generation unit is the load increase of the load unit by the first power generation unit. The power generation system according to claim 1, wherein the power generation output amount is automatically increased to correspond to The controller is
The power generation system according to claim 2, wherein the power generation output is controlled by a signal from the control unit in both the first power generation unit and the second power generation unit immediately before the supply of power from the power system is cut off. The power generation system according to claim 3, wherein the first power generation unit is a gas engine. The power generation system according to claim 4, wherein the second power generation unit is a fuel cell. In the state where the supply of power from the power system is cut off, when the load rises after the interruption in which the load of the load unit rises, first, the first step of raising the power generation output of the first power generation unit;
And a second step of decreasing the power generation output of the first power generation unit by increasing the power generation output of the second power generation unit.

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