JP2010276203A - Control device of power plant condensate system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the control device of a condensate system improving efficiency, in particular, in the condensate system to improve efficiency of thermal power and nuclear power plants. <P>SOLUTION: In this control device of the power plant condensate system having a condensate recirculating system for circulating a part of the condensate from between the condensate system and a water supply system to a condenser, in the power plant in which the condensate in the condenser is supplied to a boiler or a nuclear reactor from the condensate system through the water supply system, a pump disposed in the condensate system, a variable-frequency power source for driving the pump, and a speed control device for adjusting the output of the variable-frequency power source to control a rotational speed of the pump of the condensate system based on a load-equivalent signal of the power plant, are further disposed. As the condensate pump with the rotational speed controlled, supplies only the condensate of the adequate amount according to the load, the condensate of the optimum amount for the thermal power and nuclear power plants can be obtained without using unnecessary power, thus this control device can contribute to the improvement of efficiency as the thermal power and nuclear power plants. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a control device for a condensate system of a thermal / nuclear power plant, and more particularly to a control device for a condensate system of a thermal / nuclear power plant in which a pump in the condensate system can be operated at a variable speed.

  The condensate system of a thermal power / nuclear power plant is provided to supply the condensate of the condenser to the boiler or the reactor via the water supply system. The pump constituting this condensate system is composed of a condensate pump and a condensate booster pump arranged downstream thereof, and a plurality of systems are arranged in parallel with this as one system. In addition, a condensate recirculation system is provided between the condensate booster pump and the condenser on the downstream side, and a condensate recirculation valve is installed in this system.

  In the condensate system of the thermal power / nuclear power plant, the number of operating pumps of the condensate system is controlled, and the flow rate flowing through the condensate recirculation system is adjusted by the condensate recirculation valve. The condensate inside is supplied to the boiler / reactor side.

  For this reason, for example, in the case of supplying condensate using two parallel pumps, it is necessary to supply about 30% of the rated flow to the boiler and reactor side during the startup process of the thermal power / nuclear power plant. In some cases, one system of the pump is operated and the other system is stopped. However, since the 50% condensate flow rate will be supplied and the initial purpose cannot be achieved, the condensate recirculation valve of the condensate recirculation system installed between the pump outlet and the condenser will be turned off. By using this, about 30% of the pump flow rate is returned to the condenser to achieve a 30% flow rate supply.

  Patent Document 1 discloses a condensate system including the above-described parallel pump and its control device.

Japanese Patent Laid-Open No. 2001-4102

  The above prior art lacks a viewpoint to consider from the viewpoint of energy saving when operating a condensate pump and a condensate booster pump, which are large-capacity pumps of thermal power and nuclear power plants.

  In other words, where 30% flow rate should be supplied, power equivalent to 50% flow is spent on the pump, and 20% is returned to the condenser is that 20% of power is wasted. become.

  An object of this invention is to provide the control apparatus of the condensate system of the thermal / nuclear power plant considered from the viewpoint of energy saving.

  The above problem is a power plant that supplies condensate in a condenser from a condensate system to a boiler or a reactor via a water supply system, and a part of the condensate is formed between the condensate system and the water supply system. In a control device for a power plant condensate system having a condensate recirculation system for circulating the water to the condenser, a pump provided in the condensate system, a variable frequency power source for driving the pump, and a pump of the condensate system This is achieved by providing a speed control device that adjusts the output of the variable frequency power source so as to control the rotational speed of the power source by a load equivalent signal of the power plant.

  As described above, according to the present invention, the pump rotation speed in the condensate system is variably adjusted according to the load equivalent signal, so that the condensate recirculation amount can be reduced as much as possible. As a result, the power plant efficiency can be increased because less auxiliary power is required for the thermal power / nuclear power plant.

It is a control functional block diagram regarding the turbine control apparatus in one Embodiment of this invention. 1 is a configuration diagram of a condensate system, a power supply system, and a control device for a thermal power / nuclear power plant according to an embodiment of the present invention. It is a characteristic view which shows the function of the function generators 909 and 911 by the side of the recirculation flow rate control of FIG. It is a characteristic view which shows the function of the function generators 914 and 916 of the pump control side of FIG. The figure which shows the transition in the starting process of a thermal power / nuclear power plant.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 2 shows a configuration of a condensate system of a thermal power / nuclear power plant to which the present invention is applied and a drive power system thereof.

  First, the condensate system is shown in the figure from the condenser 1 through the condensate pump CP, the condensate pump outlet valve CPV, the ground steam condenser 4, the condensate boost pump CBP, and the condensate boost pump outlet valve CBPV. Supply water to a water supply system (not shown). Further, a condensate recirculation system is provided between the front of the water supply system and the condenser 1, and a part of the condensate can be appropriately returned to the condenser 1 by the condensate recirculation valve 8 provided here. It is configured as follows.

  Here, the equipment group composed of the condensate pump CP and the condensate pump outlet valve CPV, and the equipment group composed of the condensate booster pump CBP and the condensate booster pump outlet valve CBPV are each provided with a plurality of systems in parallel. The numerical values “1” and “2” attached to these symbols (CP, CPV, CBP, CBPV) mean the first condensate system and the second condensate system. In addition, although the example which made the condensate system 2 systems is shown in this figure, it can carry out easily to comprise similarly 3 systems or more.

  Next, the drive power system of each pump of the condensate system will be described. Although not shown in FIG. 2, each pump is provided with an electric motor for driving it. The drive power system means a power supply system to the motor. In FIG. 2, the drive power system includes a bus 11, a plurality of circuit breakers CB, and an inverter INV. Here, among the numerical values attached to the symbol CB, “1” of the high-order numerical value (“1” in the case of CB12) is the driving power system of the first condensate system, and 2 is the second condensing system. It means that the power device constitutes the drive power system.

  As is clear from this figure, the pumps of the first condensate system (CP condensate pump 1, CBP condensate booster pump 1) are fed from the first drive power system, and the second condensate system The pumps (CP2, CBP2) are supplied with power from the second drive power system.

  And each pump is comprised so that it may be electrically fed from each of a commercial frequency power supply and a variable frequency power supply. That is, in the example of the first drive power system, in the state where the circuit breakers CB12 and CB14 are closed and the circuit breakers CB13 and CB16 are opened, the drive motors of the pumps CP1 and CBP1 are supplied with power at commercial frequency. CP1 and CBP1 are driven. When the circuit breaker CB14 is opened and the circuit breakers CB12, CB13, and CB16 are closed, the inverter INV operates to supply variable frequency power to the drive motors of the pumps CP1 and CBP1, and the condensate pumps CP1 and CP1. The water booster pump CBP1 is driven at a variable speed.

  Thus, the drive power supply of the pumps (CP, CBP) is used so as to be switchable between the commercial frequency power supply and the variable frequency power supply from the inverter INV. For this reason, although not shown, power switching means between a commercial frequency power source and a variable frequency power source is provided. Although this switching logic can be adopted as appropriate, one effective use is to use a commercial frequency power supply as a backup. That is, normally, a high-efficiency operation is realized by pumping with a variable frequency power supply from the inverter INV, and when the variable frequency power supply becomes unusable due to a failure of the inverter INV or the inverter control device 10, the power supply line Is switched from the inverter side to the commercial frequency power supply side.

  Although FIG. 2 shows an example in which two condensate systems and two drive power systems are provided, it is easy to make three or four condensate systems.

  As described above, the configuration of the condensate system of the thermal power / nuclear power plant and the drive power system thereof has been described with reference to FIG. 2, but the control device that appropriately controls the condensate flow rate by starting, operating, and stopping these is a pump. And a turbine control device 9 that performs sequence control and process amount control related to starting and stopping of various valves, and an inverter control device 10 that performs output control of the inverter INV.

  The turbine controller 9 starts and stops the condensate pump CP, the condensate pump outlet valve CPV, the condensate booster pump CBP, the condensate booster pump outlet valve CBPV, etc., in accordance with a predetermined order built in the turbine controller 9. A command 19 to be controlled is output. The operation according to the command 19 can also be performed by manual control by an operator of the thermal power / nuclear power plant.

  Further, as will be described later with reference to FIG. 1, the turbine control device 9 receives the output of the condensate flow rate detector 7 as an input and outputs a pump rotation speed command 17 and a flow rate control signal 20 of the condensate recirculation valve 8.

  The inverter control device 10 outputs an inverter output command 18 to each of the inverters INV1 and INV2 based on the pump rotational speed command 17 from the turbine control device 9, and the rotational speeds of the condensate pump CP and the condensate booster pump CBP are turbines. Control is performed to be the same as the pump rotation speed command 17 from the control device 9.

  Next, detailed functions of the turbine control device 9 will be described with reference to FIG. The turbine control device 9 inputs the output of the condensate flow rate detector 7 and outputs the flow rate control signal 20 of the condensate recirculation valve 8 and the pump rotation speed command 17 for the inverter control device 10. The circuit part for deriving the flow rate control signal 20 of the condensate recirculation valve 8 constitutes a so-called condensate recirculation valve adjusting means. Moreover, the part which outputs the pump rotation speed instruction | command 17 with respect to the inverter control apparatus 10 comprises some speed control apparatuses, such as a condensate pump. The flow rate control signal 20 of the condensate recirculation valve 8 is selected and provided by the switching circuits 905, 908, 910, and 912. These switching circuits are appropriately selected according to the operation mode of the pump and output an optimal control signal as the flow rate control signal 20 of the condensate recirculation valve 8. A changing means for changing characteristics is configured. The operation mode of the pump is determined according to the combination of drive power sources.

  The operation of FIG. 1 will be described in detail below, but before that, the operation mode of the pump for determining the switching logic of the switching circuit will be described by taking the case of three condensing systems in FIG. 2 as an example.

As operation modes of the three systems of pumps, there are the following 10 cases of combinations in the case of using a variable frequency power source and a commercial frequency power source.
(1) 0 system operation (all stops)
(2) 1 system operation (1 system variable frequency power supply)
(3) 1 system operation (1 system commercial frequency power supply)
(4) 2 system operation (1 system variable frequency power supply, 1 system commercial frequency power supply)
(5) 2-system operation (2-system variable frequency power supply)
(6) Two-line operation (two-line commercial frequency power supply)
(7) 3 system operation (1 system variable frequency power supply, 2 systems commercial frequency power supply)
(8) 3 system operation (2 system variable frequency power supply, 1 system commercial frequency power supply)
(9) 3 system operation (3 system variable frequency power supply)
(10) 3-system operation (3-system commercial frequency power supply)
When this relationship is arranged more simply, the following four types are obtained.

1. Full stop state (Case (1))
2. All active systems are variable frequency power supplies (Case (2) (5) (9))
3. All active systems are commercial frequency power supplies (cases (3) (6) (10))
4). Operation with variable frequency power supply and commercial frequency power supply ((4) (7) (8))

  The operation mode of the pump is roughly divided into the above 1, 2, 3, and 4. The switching circuits 905, 908, 910, and 912 are switched between the a side and the b side according to the operation mode. Hereinafter, the operation of the circuit of FIG. 1 in each operation mode will be described.

1. Full stop state (Case 1)
1) Control on the pump side In the all-stop state, power is not supplied from the power supply system of FIG. 2, and the pump is in the stop state. Therefore, the control signal for the inverter control device 10 in the circuit of FIG. 1 is not effective for driving the inverter.

2) Control on the recirculation flow rate control valve side The switching circuit 905 is switched to the b side, the switching circuit 908 is switched to the a side, and the output of the signal generation circuit 915 passes through the switching circuits 908 and 905 and the change rate limiter 906. The flow rate control signal 20 is given to the condensate recirculation valve 8. The signal of the signal generation circuit 915 is a signal having a magnitude that means that the condensate recirculation valve 8 is fully closed. Therefore, the signal is switched to 0% signal, and the condensate recirculation valve 8 is closed to prevent the water from falling in the pipe.

2. All active systems are operating at variable frequency (Case (2) (5) (9))
Since this is the most efficient operation for operating all units with variable frequency power supplies, this operation mode is considered to have the most adoption opportunities among various operations of thermal power and nuclear power plants.

1) Pump-side control The output of the condensate flow rate detector 7 is square-root calculated by the square-root calculating circuit 901, and this signal is given to the function generators 914 and 916 to obtain the pump rotation speed program signals 958 and 959. Each signal controls the pump rotation speed of each pump in the condensate system via the change rate limiters 913, 915 and the inverter control device 10.

  FIG. 4 shows the functions of the function generators 914 and 916. Among these, the function of the function generator 914 is shown in FIG. This function creates a control signal that is fed to the first condensate pump in operation. This function gives an output of 0% to 100% (pump speed setting signal) when the flow signal on the horizontal axis ranges from 0% to 50%.

  The function of the function generator 916 is shown in FIG. This function is a function given to the pump in the second condensing system in operation. This function gives 0% to 100% output (pump speed setting signal) in the range of 50% to 100% of the flow signal on the horizontal axis. Note that the function generator 916 is used in combination with the function generator 914 when operating.

  As can be understood from the above description, the operation from 0% to 50% is performed as one method for operating the two pumps at a variable speed in the entire range of the feed water flow rate from 0% to 100%. The first pump of the single condensate system covers the flow, and in the range of 50% to 100%, the flow rate is supplied together with the second pump of the second condensate system that is additionally activated.

  In an aspect where all the condensate systems are operated at a variable speed, the optimum flow rate without waste should be supplied to the water supply system side by the pump rotation speed control of the condensate system itself. It is desirable to operate as follows.

2) Control on the recirculation flow rate control valve side In this operation mode, the switching circuits 905 and 908 select the b side, and the switching circuit 910 selects the a side, so that the condensate is generated by the signal 956 of the function generator 909. The recirculation valve 8 is operated. As shown in FIG. 3A, the function of the function generator 909 is to reduce the recirculation amount by reducing the recirculation amount by reducing the opening degree of the condensate recirculation valve 8 as the condensate flow rate increases. It can be seen that the recirculation amount is secured from the viewpoint of pump protection in the area.

  Here, what is meant to mean that the rotational speed control is performed according to the condensate flow rate on the pump control side will be described. First, for load control in a thermal power / nuclear power plant, in the case of a boiler, the boiler control device appropriately controls the fuel amount, feed water flow rate, generated steam flow rate, etc. in order to obtain a desired power amount based on the load request signal. Yes. In addition, in the case of a nuclear power plant, in addition to these, the reactor recirculation flow rate and the like are also subject to operation.

  Among these, regarding the feed water flow rate, the feed water flow rate to be sent to the boiler is determined by controlling the rotation speed and the number of operating pumps of the feed water pump according to the load request signal for the power plant. Therefore, the role of control in the condensate system on the upstream side of the water supply system is to provide a flow rate (condensate flow rate) without excess or deficiency following the control on the water supply system side. That is, the flow rate is not necessarily determined.

  In the present invention, as a result of examining how the condensate system should be operated in order to improve the efficiency of a thermal power / nuclear power plant by driving the condensate pump with a variable frequency power source, In consideration of the role, the overall balance is achieved by determining the rotation speed of the condensate pump following the signal corresponding to the load of the power plant.

  Therefore, in the embodiment of FIG. 1, the rotational speed control is performed following the condensate flow rate, but it goes without saying that various signals can be adopted as signals corresponding to the load. For example, as a signal from a load command system of a thermal power / nuclear power plant, each controlled process quantity other than a load request signal, a water supply request signal, a generator output quantity signal, etc. is used as a load equivalent signal. It can be applied instead of the example condensate flow rate.

  Needless to say, when using these signals, appropriate correction (control gain, delay, advance, etc.) should be made according to the relationship between the load equivalent signal and the condensate flow rate.

  As a result, in the present invention, as a result of controlling the pump side as described above, the pump power is controlled to an appropriate amount according to the load equivalent signal, and the amount of water that is recirculated is minimized from the viewpoint of pump characteristics. Since it can suppress, the efficiency as the whole system can be made high.

3. All active systems are commercial frequency power supplies (cases (3) (6) (10))
1) Control on the pump side This operating state is no different from the conventional operation. Since the operation state is based on the commercial frequency power supply, the inverter control device 10 on the pump rotation speed control side in FIG. 1 does not perform any control on the inverter INV.

2) Control on the recirculation flow rate control valve side At this time, the recirculation system control side calculates the difference from the flow rate desired on the water supply system side because the condensate system pump is operated with power equivalent to 100% flow rate. Control to recirculate to the condenser 1 is performed. A conventional method may be applied to this method, but as an example, it is performed as follows.

  The condensate flow rate input from the condensate flow rate detector 7 is square root calculated by the square root calculation circuit 901, and the condensate recirculation flow rate process value 951 is derived through the temporary delay circuit 902. On the other hand, the condensate recirculation flow rate setting signal generator 907 gives a recirculation amount setting signal 954, the subtractor 903 calculates the condensate recirculation flow rate deviation signal 952, and the condensate recirculation flow rate deviation signal 952 is obtained. A proportional integral calculation is performed by the proportional integral calculator 904 to create a condensate recirculation flow rate control signal 953. In this operation mode, the switching circuit 905 selects the a side. As a result, the condensate recirculation flow rate control signal 953 passes through the switching circuit 905, the change rate limiter 906, and then becomes the flow rate control signal 20, which is the condensate. Open and close the recirculation valve 8. According to this circuit system, the recirculation amount is determined by the signal from the condensate recirculation flow rate setting signal generator 907, and as a result, a desired water supply amount is realized.

4). Operation with variable frequency power supply and commercial frequency power supply ((4) (7) (8))
1) Control on the pump side This operation mode is realized by using one of the two function generators 914 and 916 shown in FIG.

  There are two possible methods in this case. The first method uses the function shown in FIG. 4 (a) to start the pump of the first condensate system from 0% load to a variable speed to 50% load. At that time, the circuit breaker is operated to drive the pump of the second condensate system with the commercial frequency power supply. In the second method, first, the circuit breaker is turned on to drive the pump of the first condensate system with the commercial frequency power supply at the time of 0% load, and then the output of the function generator 916 is used to make 50% to 100%. In this range, the pump of the second condensate system is controlled to a variable speed.

2) Control on the side of the recirculation flow rate control valve Next, regarding the control on the side of the recirculation flow rate control valve at this time, the switching circuit 905, 908, 910 has selected the b side, and the signal 957 of the function generator 911 is selected. The recirculation amount is determined by Here, the signal 957 has the characteristics shown in FIG. 3B, and an appropriate amount of recirculation flow rate in a region where the flow rate exceeds 50% is secured.

  In the embodiment shown in FIG. 1, when the monitor relay 917 is installed and the necessary minimum amount is secured, the switching circuit 905, 908, 910, 912 is switched to select the signal of the signal generation circuit 915 and recirculation is performed. Switch to the operation where the target flow rate is 0%.

  Although the control method by the circuit of FIG. 1 in each operation mode has been described in detail above, the time-series transition of the control amount performed as a result will be described.

  FIG. 5 shows changes in various process amounts (the number of revolutions of the condensate pump A, the number of revolutions of the condensate pump B, and the recirculation control valve opening degree) during the startup process of the thermal power / nuclear power plant.

  First, FIG. 5 (a) is a case of “all the systems that are running are variable frequency operation (cases (2), (5), (9))” described earlier, and the first condensing pump A is condensate. The second condensate pump B rises to a variable speed in accordance with the condensate flow rate. During this time, the opening degree of the recirculation valve is operated to be fully closed at 100% load according to the function of the function generation circuit 909 (FIG. 3A).

  FIG. 5B is a case of the first method of “operation with variable frequency power source and commercial frequency power source ((4) (7) (8))”, and the first condensing pump A is condensate. It rises to a variable speed according to the flow rate, and then, in a state where the load is 50% or more, the second condensate pump B is turned on and activated by the commercial frequency power supply. During this time, the opening degree of the recirculation valve is operated so as to be fully closed when the necessary minimum amount of the condensate pump B is secured according to the function of the function generation circuit 911 (FIG. 3B).

  FIG. 5C shows a case of the second method of “operation with variable frequency power source and commercial frequency power source ((4) (7) (8))”, and the first condensing pump A is at the commercial frequency. When the power is turned on and activated, the second condensate pump B rises to a variable speed according to the condensate flow rate when the load is 50% or more. During this time, the opening degree of the recirculation valve is operated to be fully closed at 100% load according to the function of the function generation circuit 911 (FIG. 3B).

  FIG. 5D shows a case where “all the systems that are activated are commercial frequency power supplies (cases (3), (6), and (10))”. The first condensate pump A is turned on to the commercial frequency power supply. Then, the second condensate pump B is turned on and started up with the commercial frequency power supply in a state where the load is 50% or more. During this time, the opening degree of the recirculation valve is automatically controlled by the signal 954 of the condensate recirculation flow rate setting signal generator 907 to adjust the recirculation flow rate. Thus, recirculation occurs at any load condition. FIG. 5D shows the control result in the conventional method, and the difference from the case of the present invention is clear.

  As described above, in the present invention, when a plurality of condensate systems are operated in parallel, the pumps in the system can be controlled to a variable speed, and the rotation speed is controlled by a load equivalent signal.

1 Condenser 7 Condensate Flow Detector 8 Condensate Recirculation Valve 9 Turbine Controller 10 Inverter Controller 11 Bus 17 Pump Speed Command 18 Inverter Output Command 20 Flow Control Signals 905, 908, 910, 912 Switching Circuit 909, 911, 914, 916 Function generator CP Condensate pump CBP Condensate booster pump INV Inverter CB Breaker

Claims (5)

  A power generation plant that supplies condensate in a condenser to a boiler or a reactor from a condensate system via a water supply system, and a part of the condensate between the condensate system and the water supply system In a control device for a power plant condensate system having a condensate recirculation system for circulation to a pump, a pump provided in the condensate system, a variable frequency power source for driving the pump, and a rotation speed of the pump of the condensate system A control device for a power plant condensate system comprising a speed control device for adjusting the output of the variable frequency power source to be controlled by a load equivalent signal of the power plant.   2. The control apparatus for a power plant condensate system according to claim 1, further comprising: a commercial frequency power source that drives a pump of the condensate system; and a power source switching unit that switches to the commercial frequency power source when the variable frequency power source is abnormal.   The condensate recirculation valve adjusting means for adjusting the opening degree of the condensate recirculation valve according to the condensate recirculation valve provided in the condensate recirculation system and the condensate flow rate from the condensate system. A control device for a power plant condensate system, comprising: A power generation plant that supplies condensate in a condenser to a boiler or a reactor from a condensate system via a water supply system, and a part of the condensate between the condensate system and the water supply system A condensate recirculation system for circulation to the power plant condensate system control device configured by arranging a plurality of condensate pumps in parallel,
Select either the variable frequency power source that drives the condensate system condensate pump, the commercial frequency power source that drives the condensate system condensate pump, or the variable frequency power source or the commercial frequency power source as the condensate system pump drive power source A control device for a power plant condensate system comprising a power source selection means and a speed control device for adjusting the output of the variable frequency power source so as to control the rotation speed of the pump of the condensate system with a load equivalent signal of the power plant. A power generation plant that supplies condensate in a condenser to a boiler or a reactor from a condensate system via a water supply system, and a part of the condensate between the condensate system and the water supply system A condensate recirculation system for circulation to the power plant, wherein the condensate system has a plurality of condensate pumps arranged in parallel, and the condensate recirculation system is provided with a condensate recirculation valve. In the condensate system control device,
Select either the variable frequency power source that drives the condensate system condensate pump, the commercial frequency power source that drives the condensate system condensate pump, or the variable frequency power source or the commercial frequency power source as the condensate system pump drive power source A power source selection means, a speed control device for adjusting the output of the variable frequency power source to control the rotation speed of the pump of the condensate system by a load equivalent signal of the power plant, and the condensing system according to the condensate flow rate from the condensate system. Condensate recirculation valve adjusting means for adjusting the opening degree of the water recirculation valve, and changing means for changing the characteristics of the condensate recirculation valve adjusting means in accordance with the combination of drive power sources of a plurality of condensate pumps Control device for power plant condensate system.

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