JP3312396B2 - Gas pressure control method for combined cycle power plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for supplying LNG from an LNG storage base to a combined cycle power plant with one gas supply, and more particularly to a method for stably controlling the LNG inlet pressure at each of the power plants. The present invention relates to a method for controlling a gas supply pressure of a combined cycle power plant.

[0002]

2. Description of the Related Art In a gas transmission system of a combined cycle power plant, power plants separated from each other at a distance are connected through a single gas transmission conduit, and the total power generation amount is matched from the LNG storage base via the gas transmission conduit. The amount of LNG is supplied to drive the power generation turbine of each power plant. When driving the turbine of each power plant, the fluctuation range of the inlet pressure of the turbine needs to be suppressed to ³ to 5 kg / cm ² .

[0003] Usually, the gas sending pressure of the gas sending conduit is set higher than the inlet pressure of the turbine, and a pressure reducing valve is connected to each power plant, and the opening of the pressure reducing valve is adjusted according to the amount of power generated at each power plant. Adjustment is made to introduce LNG corresponding to the amount of power generation, and to ensure that the inlet pressure of the turbine falls within a predetermined range.

[0004]

The power plants are connected to each other through a single gas supply pipe. Since each power plant operates independently, the pressure control at each power plant is performed. There is a problem in selecting points.

[0005] For example, if the consumption of LNG is determined, the set pressure at the inlet of the pressure reducing valve is set in consideration of the pressure loss based on this, and LNG is supplied in accordance with the consumption, the LNG at each power plant Is at a set pressure, and the turbine inlet pressure can be kept within a predetermined fluctuation range. However, although the set pressure of each power plant is set in consideration of the distance of each power plant, if the LNG consumption changes, the set pressure also changes. On the other hand, it is difficult to properly select the pressure control points of each power plant.

Normally, even if the pressure fluctuates with respect to the set pressure, it is possible to temporarily fall within the fluctuation range by adjusting the pressure with the pressure reducing valve. However, the adjustment by the pressure reducing valve is limited. If LNG consumption is low on one side and LNG consumption is high on the other side, if LNG is to be supplied based on the total consumption of LNG at these power plants, pressure loss will occur at distant power plants. However, there is a problem that the pressure exceeds the fluctuation range of the turbine, and the pressure at the inlet of the turbine cannot be suppressed to a predetermined fluctuation range by the pressure reducing valve.

Therefore, an object of the present invention is to solve the above-mentioned problems and to suppress the turbine inlet pressure of each power plant to a predetermined fluctuation range when supplying LNG to each power plant via one gas feed pipe. It is an object of the present invention to provide a method of controlling a gas supply pressure of a combined cycle power plant.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is to supply LNG from an LNG storage base to a plurality of power plants through a single gas feed conduit via a regulating valve and to generate electricity at each of a plurality of power plants. In a gas supply pressure control method for a combined cycle power plant in which LNG from a gas supply conduit is regulated by a pressure reducing valve and supplied to a turbine, the inlet pressure of the pressure reducing valve of each power plant is determined in advance by a gas supply pipe. Set according to the pressure loss, determine the control output from the difference between the actual supply pressure at the pressure reducing valve inlet side and the set pressure at each power plant, and select the largest control output among the control outputs. The value is set as the flow rate control, and the total flow rate of the LNG storage base is controlled by the set value.

[0009]

According to the above construction, the LN introduced into each power plant
The control output is obtained from the difference between the actual pressure of G and the set pressure, the larger one of the control outputs is selected, and the total output is corrected by using the control output value as the set value, so that an appropriate value corresponding to the actual fluctuation is obtained. Pressure control can be performed, and the fluctuation range of the inlet pressure of the turbine of the power plant can be suppressed within a predetermined range.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

In FIG. 1, a gas supply conduit 7 is connected to an LNG storage base 6 via a flow control valve 1. An outlet side of the flow control valve 1 is connected to a gas inlet flow meter 5b and a gas inlet pressure gauge 5a. This gas supply conduit 7 is connected to LN
It is laid to a power station 8a at a distance a from the G storage base 6, and is laid to a power station 8b at a distance b from the power station 8a. L from the gas transmission pipe 7 to each power station 8a, 8b
NG is supplied to each power station 8 via the pressure reducing valves 2a and 2b.
a and 8b.
Gas inlet pressure gauges 3a, 3b and gas inlet flow meters 4a, 4b are connected to the inlet sides of the pressure reducing valves 2a, 2b.

In each of the power stations 8a and 8b, the necessary amount of consumption is measured to drive the number of turbines 9 corresponding to the required power generation and to supply LNG to the turbines 9 by the flow meters 4a and 4b.
The opening degree of the pressure reducing valves 2a and 2b is adjusted based on the flow rate value of (1).

The LNG consumption of each power station 8a, 8b (total flow value of the gas flow meters 4a, 4b), the gas inlet pressure gauge 3
The detected values of a and 3b are transmitted to the pressure control device A (FIG. 2) on the base 6 side. At the LNG storage base 6, LN
When the G consumption is input, the gas inlet pressure gauge 5a adjusts the opening of the flow control valve 1 so that the gas inlet flow meter 5b matches the LNG consumption at the set supply pressure. The flow rate of the flow control valve 1 is corrected and supplied in accordance with the above-described detected value, and the LNG is controlled so as to have a gas supply amount corresponding to the actual pressure loss.

FIG. 2 shows the pressure control device A.

First, in each of the power plants 8a and 8b, when LNG is supplied to the gas supply conduit 7 by setting a supply pressure and a flow rate in accordance with, for example, a standard LNG consumption, a pressure loss according to a distance is taken into consideration. The inlet set pressures SVa and SVb of the pressure reducing valves 2a and 2b of the power plants 8a and 8b are set. This set pressure S
Va and SVb are PID controllers 10a and 10b, respectively.
And the actual detection values PVa and PVb of the gas inlet pressure gauges 3a and 3b are input. PID controller 10
a and 10b perform a proportional / integral / differential operation on the set pressure SV and the actual pressure PV to output a control output value of 0 to 100, for example. The control output values of the PID controllers 10a and 10b are input to the high selector 11. The high selector 11 selects the larger one of the control output values, and inputs this to the flow controller 12 as a control value. The total flow rate of LNG at each of the power plants 8 a and 8 b is input to the flow rate controller 12, and the total flow rate is corrected by the control output value from the high selector 11, and the flow rate is adjusted via the high selector 13. To adjust the LNG supply amount.

As described above, the PID controllers 10a, 10b
To select the larger control output value of
By controlling the supply amount in accordance with the power plant having the largest pressure loss and the lowest pressure, it is possible to keep the pressure fluctuation width on the inlet side of the turbine within a predetermined range.

The high selector 13 has an LNG
When the supply amount of LNG at the storage base 6 is input and the transmission of the pressure and flow from each power plant cannot be received due to a disconnection accident or the like, the flow control valve 1 can be controlled at the base 6 side. I have. That is, L at each power station 8a, 8b
When the NG consumption is determined, the opening of the regulating valve 1 is set so that the supply amount matches the consumption. in this case,
First, the pressure detected by the inlet pressure gauge 5a is input to the pressure controller 14, and the control output is input to the flow controller 15 so that the pressure becomes the set supply pressure. The control flow rate value is output to the high selector 13 so that the flow rate value by the inlet flow meter 5b becomes appropriate. In this case, since the output value of the flow controller 12 considering the pressure loss is normally higher, the high selector 11
When the transmission of pressure and flow from each power plant cannot be received due to a disconnection accident or the like, the flow control valve 1 is controlled by the control flow value set on the base 6 side. It becomes possible.

In the above-described embodiment, two power stations have been described, but it goes without saying that there may be three or more power stations.

[0019]

In summary, according to the present invention, the control output is obtained from the difference between the actual pressure of the LNG introduced into each power plant and the set pressure, and the larger one of the control outputs is selected. By correcting the total flow rate based on the value, appropriate pressure control can be performed in accordance with the actual fluctuation, and the fluctuation width of the inlet pressure of the turbine of the power plant can be suppressed within a predetermined range.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the present invention.

FIG. 2 is a block diagram of a circuit showing details of a pressure control device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flow control valve 2a, 2b Pressure reducing valve 3a, 3b Gas inlet pressure gauge 4a, 4b Gas inlet flow meter 5a Gas outlet pressure gauge 5b Gas outlet flow meter 6 LNG storage base 7 Gas sending pipe 8a, 8b Power plant 9 Turbine

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-207831 (JP, A) JP-A-4-179835 (JP, A) JP-A-61-141018 (JP, A) 103711 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02C 1/00-9/58 G05D 16/00

Claims (1)

(57) [Claims] 1. An LNG from an LNG storage base is supplied to a plurality of power plants through one gas supply conduit via a regulating valve, and at each power plant, LNG from the gas supply conduit is pressure-reduced by a pressure reducing valve. In a method of controlling a gas supply pressure of a combined cycle power plant that adjusts and supplies the combined gas to a turbine,
The pressure at the inlet of the pressure reducing valve at each power plant is set in advance according to the pressure loss of the gas supply pipe, and at each power plant, the control output is obtained from the difference between the actual supply pressure at the pressure reducing valve inlet side and the set pressure, and The largest one of the control outputs is selected, and this control output value is set as a set value of the flow control.
A gas supply pressure control method for a combined cycle power plant, wherein a total flow rate of a G storage base is adjusted and controlled.