JP6105476B2 - Power generation system, control device, and power control method - Google Patents

Description

  The present invention relates to a power generation system, and more particularly, to a control device and a power control method for controlling output power of a power generation unit.

  2. Description of the Related Art In recent years, power generation units including fuel cells, for example, have been widely used as an auxiliary power source for commercial power systems in power consumers. A fuel cell is a power generation device that generates power by a chemical reaction between hydrogen extracted from gas and oxygen in the air (see, for example, Patent Document 1). A fuel cell unit is constituted by the fuel cell and the power converter (power conditioner).

  Since the output power of the fuel cell unit can be controlled, it is common to apply “load following operation” that increases or decreases the output power of the fuel cell unit in accordance with the increase or decrease of the power consumption of the load provided to the consumer. It is.

  In addition, fuel cell systems (so-called cogeneration systems) that collect exhaust heat generated during power generation in the fuel cell unit, store hot water in the hot water storage unit, and use the hot water stored in the hot water storage unit for hot water supply are also widespread. Since such a fuel cell system can use not only electric energy obtained from gas but also thermal energy, gas can be used efficiently.

JP 2005-278337 A

  For example, in summer when the demand for hot water supply is small, the fuel cell unit performs load following operation, and as a result, hot water storage in the hot water storage unit often remains. When the hot water storage amount reaches the maximum hot water amount, the exhaust heat of the fuel cell unit is discarded without being recovered, and there is a problem that the gas cannot be used efficiently.

  Accordingly, an object of the present invention is to provide a power generation system, a control device, and a power control method that can ensure exhaust heat utilization efficiency as much as possible while considering the power generation efficiency of the power generation unit.

  According to a feature of the present invention, there is provided a power generation system comprising: a power generation unit using fuel; and a control device that controls output power of the power generation unit so that the power generation unit performs a load following operation. When the output power of the power generation unit required for performing the load following operation exceeds a first threshold set to a value smaller than the maximum output possible power of the power generation unit, the load A power generation system that controls to perform a suppression operation that suppresses the output power of the power generation unit to a constant value is provided instead of the follow-up operation.

  According to another feature of the invention, the control device performs the suppression operation when exhaust heat recovery from the power generation unit is unnecessary.

  According to another feature of the invention, the control device receives exhaust heat recovery information for determining whether or not exhaust heat recovery is necessary from a device that uses exhaust heat from the power generation unit.

  According to another feature of the invention, the power generation unit is linked to a commercial power system.

  According to another feature of the invention, the control device calculates a temporary target output power of the power generation unit that is required to perform the load following operation, and the temporary target output power is the first threshold value. In the following cases, the temporary target output power is set as the target output power, and when the temporary target output power exceeds the first threshold, the constant value is set as the target output power.

  According to another feature of the invention, the first threshold value is the output power of the power generation unit at which the power generation efficiency of the power generation unit is equal to or lower than a third threshold value, or the power generation efficiency of the power generation unit is fourth. It is set according to the output power of the power generation unit that is greater than or equal to the threshold value.

  According to another feature of the invention, the third threshold or the fourth threshold is updated based on learning for one day or more.

  According to another aspect of the present invention, it further includes a hot water storage unit that stores hot water obtained by recovering exhaust heat of the power generation unit, and the control device has a second hot water storage amount or a second heat storage amount. If the temporary target output power exceeds the first threshold, the constant value is set as the target output power.

  According to another feature of the invention, the second threshold value depends on at least one of a predicted hot water supply demand pattern, a predicted power load pattern, a predicted outside air temperature, and a predicted water temperature. Is set.

  According to another feature of the invention, the second threshold is updated based on learning for one day or more.

  According to another feature of the present invention, the provisional target further includes another power generation unit linked to a commercial power system, and the provisional target output power is exceeded even when the provisional target output power exceeds the first threshold. If the output power is set as the target output power, it is possible to sell the output power of the other power generation unit to the commercial power system, and the unit price of the power sale is the power generation unit price of the power generation unit. If higher, the control device sets the temporary target output power as the target output power.

  According to another feature of the invention, the power generation unit is a power generation unit using a fuel cell.

  According to a feature of the present invention, a control device for controlling the output power of the power generation unit so that the power generation unit performs load following operation, the power generation unit of the power generation unit required for performing the load following operation. Suppression to suppress the output power of the power generation unit to a constant value instead of the load following operation when the output power exceeds a first threshold value set to a value smaller than the maximum output possible power of the power generation unit A control device is provided for controlling the operation.

  According to the characteristics of the present invention, the step of controlling the output power of the power generation unit so that the power generation unit performs load following operation, and the output power of the power generation unit required for performing the load following operation When the first threshold set to a value smaller than the maximum output power of the power generation unit is exceeded, instead of the load following operation, a suppression operation is performed to suppress the output power of the power generation unit to a constant value. And a power control method is provided.

  According to the present invention, it is possible to provide a power generation system, a control device, and a power control method that can ensure exhaust heat utilization efficiency as much as possible while considering the power generation efficiency of the power generation unit.

FIG. 1 is a block diagram of a power generation system according to an embodiment of the present invention. FIG. 2 is a block diagram of the SOFC controller according to the embodiment of the present invention. FIG. 3 is a diagram illustrating an example of power generation efficiency and exhaust heat recovery efficiency with respect to SOFC output power. FIG. 4 is an operation flowchart of the setting operation of the SOFC target output power by the SOFC controller according to the embodiment of the present invention. FIG. 5 is a block diagram of a power generation system according to a modification of the embodiment of the present invention.

  An embodiment of the present invention will be described with reference to the drawings. In the drawings according to the following embodiments, the same or similar parts are denoted by the same or similar reference numerals.

  FIG. 1 is a block diagram of a power generation system according to the present embodiment. In FIG. 1, a thick line shows a power line, and a broken line shows a control line. The control line may be wireless.

  As shown in FIG. 1, the power generation system according to the present embodiment includes a solid oxide fuel cell (SOFC) unit 100, an SOFC controller 140, a hot water storage unit 150, a distribution board 300, one or more loads 400, and a house. It has an energy management system (HEMS) 500. The SOFC unit 100, the SOFC controller 140, the hot water storage unit 150, the distribution board 300, the load 400, and the HEMS 500 are provided in a consumer who receives supply of alternating current (AC) power from the commercial power system (hereinafter “system”) 10. . In the present embodiment, the SOFC unit 100 is a fuel cell unit linked to the system 10, and corresponds to an example of a power generation unit. The SOFC controller 140 corresponds to a control device that controls output power of the SOFC unit 100 (hereinafter referred to as “SOFC output power P”) so that the SOFC unit 100 performs load following operation. The SOFC unit 100, the SOFC controller 140, and the hot water storage unit 150 constitute a fuel cell system as an example of a power generation system.

  The SOFC unit 100 includes an SOFC 110, an SOFC power conditioner (PCS) 120, and a heat exchanger 130. The SOFC 110 is a type of fuel cell, and generates power by a chemical reaction between hydrogen extracted from natural gas and oxygen in the air, for example, and outputs generated direct current (DC) power. The power generation amount of the SOFC 110 changes according to the amounts of gas and air input to the SOFC 110. The amount of gas and air is controlled by the SOFC controller 140. The SOFC PCS 120 receives DC power output from the SOFC 110, converts the input DC power into AC power, and outputs the AC power to the distribution board 300 via the SOFC power line 12. Also, the SOFC PCS 120 periodically notifies the SOFC controller 140 of the SOFC output power P. The heat exchanger 130 is supplied with water from the hot water storage unit 150, converts the heat generated during power generation (chemical reaction) in the SOFC 110 into hot water by heat exchange, and outputs the hot water to the hot water storage unit 150.

  The SOFC controller 140 basically performs control for performing load following operation. In the present embodiment, the SOFC controller 140 controls the target output power of the SOFC unit 100 so that the measured value indicating the purchased power from the grid 10 becomes a predetermined value (for example, zero) as control for performing the load following operation. (Hereinafter referred to as “SOFC target output power Pt”) is set, and the SOFC 110 is controlled so that the SOFC output power P becomes the SOFC target output power Pt. Alternatively, the SOFC controller 140 acquires a measured value indicating the total power consumption of the load 400, sets the SOFC target output power Pt equal to the measured value indicating the total power consumption, and the SOFC output power P is the SOFC target output power. The SOFC 110 may be controlled to be Pt. Details of the operation of the SOFC controller 140 will be described later. The SOFC controller 140 may be housed in a housing different from the SOFC unit 100, or may be housed in the same housing as the SOFC unit 100.

  The hot water storage unit 150 includes a hot water storage tank 151 connected to a heat exchanger 130 provided in the SOFC unit 100. The hot water storage tank 151 stores hot water output from the heat exchanger 130, and the hot water storage in the hot water storage tank 151 is used for hot water supply in the consumer 1. The hot water storage unit 150 periodically notifies the SOFC controller 140 of the hot water storage amount V of the hot water storage tank 151. Alternatively, the hot water storage unit 150 compares the hot water storage amount V of the hot water storage tank 151 with a second threshold value Vth (details will be described later) set from the SOFC controller 140, and periodically sends information related to the comparison result to the SOFC controller 140. Notice. The “hot water storage amount V” may be a temperature-converted value (that is, a heat storage amount).

  The distribution board 300 is connected to the system power line 11, the SOFC power line 12, and the load power line 14. Distribution board 300 distributes purchased power input from system 10 via system power line 11 and SOFC output power P input from SOFC unit 100 via SOFC power line 12 to load 400. . In the present embodiment, the distribution board 300 includes a measurement unit 310 that periodically measures the purchased power from the grid 10. The measurement unit 310 periodically notifies the SOFC controller 140 of a measured value indicating the purchased power via a control line with the SOFC controller 140. The measuring unit 310 only needs to be able to periodically measure the purchased power from the grid 10 and may be provided outside the distribution board 300.

  The load 400 receives AC power from the distribution board 300 via the load power line 14, and operates by consuming the input AC power. The load 400 is, for example, home appliances such as lighting, an air conditioner, a refrigerator, and a television.

  The HEMS 500 is for performing power management in the customer 1. The HEMS 500 manages and displays the power consumption of the load 400 and performs control for power saving on the load 400. The HEMS 500 stores and manages at least one of a hot water supply demand pattern, a power load pattern, an outside air temperature change pattern, and a water temperature change pattern in the customer 1 by learning for one day or more or information obtained from an external network. May be.

  Next, the configuration of the SOFC controller 140 will be described. FIG. 2 is a block diagram of the SOFC controller 140.

  As shown in FIG. 2, the SOFC controller 140 includes a communication unit 141, a storage unit 142, and a control unit 143. The communication unit 141 communicates with the SOFC unit 100, the hot water storage unit 150, and the measurement unit 310. In addition, the communication unit 141 performs communication with each device provided in the consumer 1.

  The storage unit 142 is configured by a memory, for example, and stores various types of information used for control in the control unit 143. The storage unit 142 stores the rated output power of the SOFC unit 100 (hereinafter referred to as “SOFC rated output power Pm”), the first threshold value Pth, and the second threshold value Vth. The SOFC rated output power Pm corresponds to the maximum power that can be generated by the SOFC unit 100. The storage unit 142 may store the power purchase unit price from the grid 10 and the power generation unit price of the SOFC unit 100. The power generation unit price of the SOFC unit 100 can be, for example, the unit price of gas input to the SOFC unit 100 in order for the SOFC 110 to generate power.

  The first threshold value Pth is a threshold value used for determination of switching between the load following operation and the suppression operation. The second threshold value Vth is a threshold value used for determining whether the exhaust heat recovery of the SOFC unit 100 is necessary. When the hot water storage amount V exceeds the second threshold value Vth, the control unit 143 determines that the maximum exhaust heat recovery is unnecessary, that is, the exhaust heat recovery that is obtained to the maximum by the load following operation is unnecessary. In addition, the control unit 143 determines that the SOFC output power (hereinafter referred to as “SOFC temporary target output power Px”) required for performing the load following operation has the first threshold value Pth when the maximum exhaust heat recovery is unnecessary. When exceeding, it controls not to perform load following operation but to perform suppression operation. The suppression operation is an operation mode in which the SOFC output power P is suppressed to a constant value. In the present embodiment, the certain value is equal to the first threshold value Pth. The first threshold Pth is set to a value smaller than the SOFC rated output power Pm.

  Here, the first threshold value Pth will be described. FIG. 3 is a diagram illustrating an example of power generation efficiency and exhaust heat recovery efficiency with respect to SOFC output power P. In FIG. 3, the exhaust heat recovery efficiency is considered to be substantially constant with respect to the SOFC output power P.

  As shown in FIG. 3, when the SOFC output power P is small, the power generation efficiency is low because the proportion of the amount of gas consumed to operate the auxiliary machinery is large in the amount of gas consumed by the SOFC 110. Furthermore, when the SOFC output power P is small, the module temperature is low and the internal resistance is high, so that the power generation efficiency is low from this viewpoint.

  On the other hand, when the SOFC output power P reaches a certain value, the power generation efficiency does not change much. That is, since the power generation efficiency is nearly constant in the high output region, the decrease in SOFC output power P is substantially proportional to the amount of gas decrease.

For this reason, when it is desired to reduce the amount of unnecessary exhaust heat recovery, in the high output region, the output power P does not decrease too much even if the gas amount is reduced. However, since the power generation efficiency is low in the low output region, if the gas amount is reduced, the SOFC output power P is reduced more than the reduction amount. That is, when reducing the amount of gas to reduce the amount of unnecessary exhaust heat recovered in the low output region, the power is reduced compared to reducing the amount of gas to reduce the amount of unnecessary exhaust heat recovery in the high output region. Will tend to be insufficient, and power purchase will increase. Therefore, the SOFC output power P in which the slope of the power generation efficiency in FIG. 3 is equal to or lower than the third threshold, or the SOFC output power P in which the power generation efficiency in FIG. 3 is equal to or higher than the fourth threshold is set to the first threshold Pth. Set as. The first threshold value Pth is basically fixedly set, but may be set adaptively (dynamically). For example, the control unit 143 sets the third threshold value and / or the fourth threshold value according to learning for one day or more, and uses the third threshold value and / or the fourth threshold value to set the first threshold value. Pth may be set automatically. In this case, for example, the control unit 143 performs output suppression with the first threshold value Pth set according to a certain third threshold value, but when the exhaust heat is discarded due to, for example, the operation of the radiator, Further lowering the third threshold value.

  Next, the second threshold value Vth will be described. As described above, when the hot water storage amount V exceeds the second threshold value Vth, it is determined that exhaust heat recovery is unnecessary, and heat is radiated, for example, by operating a radiator. That is, the second threshold value Vth defines a criterion for determining whether or not the hot water storage amount V is sufficient. The second threshold value Vth is set to a value smaller than the maximum hot water storage amount Vm. The second threshold value Vth is basically fixedly set, but may be set adaptively (dynamically). For example, the control unit 143 communicates with the HEMS 500 by the communication unit 141, predicts a hot water supply demand pattern (information on how hot water supply demand is generated), and predicted power load pattern (how power consumption is generated). At least one of the predicted outside temperature (information about how the outside temperature changes) and the predicted water temperature (information about how the water temperature changes) from the HEMS 500 get. Then, the control unit 143 sets the second threshold value Vth according to at least one of the predicted hot water supply demand pattern, the predicted power load pattern, the predicted outside air temperature, and the predicted water temperature. For example, when the first threshold Pth is applied over a predetermined period after the present, the hot water storage amount required at the present time is set as the second threshold Vth. That is, the amount of stored hot water V (t) calculated from the amount of boiling water expected from the power load pattern and the amount of hot water expected from the hot water supply demand pattern at all times t within 24 hours from the present time. In order to guarantee 0 or more, the hot water storage amount required at the present time is set as the second threshold value Vth. Further, similarly to the first threshold value Pth, the second threshold value Vth may be set according to learning for one day or more.

  The control unit 143 is configured by a processor, for example, and controls various functions of the SOFC controller 140.

  First, the control unit 143 acquires notification of various measurement values received by the communication unit 141. In the present embodiment, the control unit 143 measures the measured value indicating the purchased power notified from the measuring unit 310, the measured value indicating the SOFC output power P notified from the SOFC PCS 120, and the hot water storage notified from the hot water storage unit 150. A measurement value indicating the amount V (or information on a comparison result between the measurement value and the second threshold value Vth) is acquired.

  Secondly, the control unit 143 measures the measured value indicating the purchased power notified from the measuring unit 310 and the measured value indicating the hot water storage amount V notified from the hot water storage unit 150 (or the measured value and the second threshold value). Information on the comparison result with Vth), the SOFC rated output power Pm stored in the storage unit 142, and the first threshold value Pth (and the second threshold value Vth) stored in the storage unit 142. Thus, it is determined which of the operation modes of load following operation and suppression operation is applied. Then, the control unit 143 sets the SOFC target output power Pt according to the operation mode to be applied. The setting operation of the SOFC target output power Pt will be described later.

  Third, the control unit 143 controls the SOFC unit 100 so that the SOFC output power P becomes the SOFC target output power Pt based on the set SOFC target output power Pt and the measured value indicating the SOFC output power P. To control. Specifically, the control unit 143 controls the communication unit 141 to transmit a control command for controlling the SOFC unit 100.

  Next, the setting operation of the SOFC target output power Pt by the SOFC controller 140 will be described. FIG. 4 is an operation flowchart of the setting operation of the SOFC target output power Pt. In this operation flow, a case where the information indicating the comparison result between the measured value indicating the hot water storage amount V and the second threshold value Vth is notified from the hot water storage unit 150 to the SOFC controller 140 as exhaust heat recovery request information (exhaust heat recovery information). explain. When the measured value indicating the hot water storage amount V exceeds the second threshold value Vth, the exhaust heat recovery request information indicates that exhaust heat recovery is not required, and when the measured value indicating the hot water storage amount V does not exceed the second threshold value Vth. The waste heat recovery request information indicates that waste heat recovery is required. The flow of FIG. 4 is periodically executed.

  As illustrated in FIG. 4, in step S <b> 101, the control unit 143 calculates the SOFC temporary target output power Px based on the measurement value indicating the purchased power notified from the measurement unit 310. Specifically, the control unit 143 calculates the SOFC temporary target output power Px so that the purchased power becomes a predetermined value Pr. The predetermined value Pr is, for example, zero. In this case, the power consumption of the load 400 is covered by the output power from the SOFC unit 100 without receiving power supply from the grid 10. When the SOFC temporary target output power Px is calculated, the process proceeds to step S102.

  In step S <b> 102, the control unit 143 determines whether or not exhaust heat recovery is necessary based on the exhaust heat recovery request information received from the hot water storage unit 150 by the communication unit 141. Specifically, the control unit 143 confirms whether the exhaust heat recovery request information indicates whether exhaust heat recovery is required or indicates that exhaust heat recovery is not required. For example, the exhaust heat recovery request information is configured as a 1-bit flag that is “1” when exhaust heat recovery is required and “0” when exhaust heat recovery is not required. If the exhaust heat recovery request information indicates that exhaust heat recovery is required (step S102; YES), the process proceeds to step S103. On the other hand, when the exhaust heat recovery request information indicates that exhaust heat recovery is not required (step S102; NO), the process proceeds to step S106.

  In step S103, the control unit 143 compares the SOFC temporary target output power Px calculated in step S101 with the SOFC rated output power Pm stored in the storage unit 142. When the SOFC temporary target output power Px exceeds the SOFC rated output power Pm (step S103; YES), the process proceeds to step S104. On the other hand, when the SOFC temporary target output power Px does not exceed the SOFC rated output power Pm (step S103; NO), the process proceeds to step S105.

  In step S104, the control unit 143 sets the SOFC rated output power Pm as the SOFC target output power Pt. When the SOFC rated output power Pm is set as the SOFC target output power Pt, the control unit 143 transmits a control command to the SOFC unit 100 so that the SOFC output power P becomes the SOFC target output power Pt.

  In step S105, the control unit 143 sets the SOFC temporary target output power Px calculated in step S101 as the SOFC target output power Pt. When the SOFC temporary target output power Px is set as the SOFC target output power Pt, the control unit 143 transmits a control command to the SOFC unit 100 so that the SOFC output power P becomes the SOFC target output power Pt.

  As described above, when the exhaust heat recovery request information indicates that exhaust heat recovery is required (step S102; YES), the control unit 143 performs control for normal load following operation in steps S103 to S105.

  On the other hand, when the exhaust heat recovery request information indicates that exhaust heat recovery is not required (step S102; NO), in step S106, the control unit 143 stores the SOFC temporary target output power Px calculated in step S101 in the storage unit 142. The first threshold value Pth is compared. When the SOFC temporary target output power Px exceeds the first threshold value Pth (step S106; YES), the process proceeds to step S107. On the other hand, when the SOFC temporary target output power Px does not exceed the first threshold value Pth (step S106; NO), the process proceeds to step S108.

  In step S107, the control unit 143 sets a value equal to the first threshold value Pth as the SOFC target output power Pt. When the value equal to the first threshold value Pth is set as the SOFC target output power Pt, the control unit 143 transmits a control command to the SOFC unit 100 so that the SOFC output power P becomes the SOFC target output power Pt.

  In step S108, the control unit 143 sets the SOFC temporary target output power Px calculated in step S101 as the SOFC target output power Pt. When the SOFC temporary target output power Px is set as the SOFC target output power Pt, the control unit 143 transmits a control command to the SOFC unit 100 so that the SOFC output power P becomes the SOFC target output power Pt.

  As described above, the control unit 143 indicates that the exhaust heat recovery request information indicates that exhaust heat recovery is not required (step S102; NO), and the SOFC temporary target output power Px does not exceed the first threshold value Pth (step S106; NO), in step S108, control for normal load following operation is performed. On the other hand, when the SOFC temporary target output power Px exceeds the first threshold value Pth (step S106; YES), in step S107, a value equal to the first threshold value Pth is set as the SOFC target output power Pt. Then, control is performed so as to perform the suppression operation instead of the load following operation.

  When the SOFC unit 100 performs the suppression operation, an excess of the power consumption of the load 400 from the output power of the SOFC unit 100 (that is, Px−Pt) is covered by the purchased power from the system 10. Here, even if the exhaust heat recovery request information indicates that the exhaust heat recovery is not required and the SOFC temporary target output power Px exceeds the first threshold value Pth, the power purchase unit price from the grid 10 is When it is higher than the power generation unit price, the control for the load following operation as usual may be performed.

  In the present embodiment, the control unit 143 corresponds to a load following output calculation unit that calculates the SOFC output power P (that is, the SOFC temporary target output power Px) required for performing the load following operation. The control unit 143 corresponds to target output setting means for setting the SOFC target output power Pt.

  As described above, in the fuel cell system having the SOFC unit 100 linked to the grid 10 and the SOFC controller 140 that controls the SOFC output power P so that the SOFC unit 100 performs load following operation, the SOFC When the exhaust heat recovery is not necessary, the controller 140, when the SOFC output power P required for performing the load following operation (that is, the SOFC temporary target output power Px) exceeds the first threshold Pth, Instead of the load following operation, control is performed so as to perform a suppression operation that suppresses the SOFC output power P to a constant value.

  Since the SOFC unit 100 has a property that the power generation efficiency is low when the output power is low, the power generation efficiency is increased as much as possible by performing the load following operation in a state where the power consumption of the load is small. In addition, since the SOFC unit 100 has a property that the power generation efficiency does not change so much when reaching a certain level of output power, in a situation where the power consumption of the load is large, a state where the power generation efficiency is high can be achieved by performing the suppression operation. While maintaining, the increase in the amount of stored hot water V can be suppressed. Therefore, according to the present embodiment, it is possible to suppress an increase in the amount of stored hot water V while suppressing a decrease in power generation efficiency of the SOFC unit 100.

[Example of change]
FIG. 5 is a block diagram of a power generation system according to a modified example of the above-described embodiment.

  As shown in FIG. 5, the power generation system according to this modification further includes a solar cell (PV) unit 200 that is linked to the grid 10 as a power generation unit other than the SOFC unit 100. In this modification, the SOFC unit 100, the SOFC controller 140, the PV unit 200, and the hot water storage unit 150 constitute a fuel cell system as an example of a power generation system.

  The PV unit 200 includes a PV 210 and a PV PCS 220. The PV 210 receives sunlight and generates power, and outputs the generated DC power. The amount of power generated by the PV 210 changes according to the amount of solar radiation irradiated on the PV 210. The PV PCS 220 receives DC power output from the PV 210, converts the input DC power into AC power, and outputs the AC power to the distribution board 300 via the PV power line 13.

  When the output power of the PV unit 200 (hereinafter referred to as “PV output power”) can be sold to the grid 10 and the unit price of the power sale is higher than the unit price of power generation of the SOFC unit 100, the PV output power is the load. It is preferable to sell power to the grid 10 as much as possible instead of supplying it to 400.

  Therefore, in the present modification example, the storage unit 142 further stores the unit price of PV output power sold and the unit price of power generation of the SOFC unit 100. In addition to the control according to the embodiment described above, the control unit 143 performs control based on the measurement value indicating the power sale power measured by the measurement unit 310 and the unit price information stored in the storage unit 142. Do.

  Specifically, the control unit 143 uses the SOFC temporary target output power Px as the SOFC target even when exhaust heat recovery is unnecessary and the SOFC temporary target output power Px exceeds the first threshold Pth. If the PV output power can be sold to the grid 10 if it is set as the output power Pt (that is, if the PV output power is Pp and the power consumption of the load 400 is Pl, then Pp + Px−Pl> 0) When the unit price of power sale is higher than the unit price of power generation of the SOFC unit 100, the SOFC temporary target output power Px is set as the SOFC target output power Pt. As a result, the power selling fee can be increased, and the utility cost can be reduced accordingly.

[Other Embodiments]
As mentioned above, although this invention was described by embodiment, it should not be understood that the description and drawing which form a part of this indication limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the above-described embodiment and its modification, the SOFC controller 140 implements the power control method according to the present invention, that is, the SOFC controller 140 as an example of the control device according to the present invention has been described. The HEMS 500 may implement the control method. In this case, the HEMS 500 corresponds to a control device according to the present invention. Alternatively, the power control method according to the present invention may be shared by the SOFC controller 140 and the HEMS 500. In this case, the SOFC controller 140 and the HEMS 500 correspond to a control device according to the present invention. In these cases, it is preferable to store the power purchase unit price from the grid 10 and the power generation unit price of the SOFC unit 100 on the HEMS 500 side rather than the SOFC controller 140 (storage unit 142) side.

  Further, the SOFC unit has been described as an example. However, any cogeneration system may be used. For example, another type of fuel cell such as PEFC, or a gas generator using a gas turbine engine may be used. That is, the present invention can be applied to any power generation apparatus that can intentionally control the power generation amount by adjusting the amount of fuel and that has an exhaust heat recovery function, without being limited to the SOFC unit.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein.

  Note that the entire contents of Japanese Patent Application No. 2011-213579 (filed on Sep. 28, 2011) are incorporated herein by reference.

  According to the present invention, it is possible to provide a power generation system, a control device, and a power control method that can ensure exhaust heat utilization efficiency as much as possible while considering the power generation efficiency of the power generation unit.

Claims (10)

A power generation unit using fuel,
A control device for controlling the output power of the power generation unit;
Have
The controller is
When the target power of the power generation unit required for performing the load following operation exceeds a first threshold value, instead of the load following operation, a suppression operation that suppresses the output power of the power generation unit to a constant value. Controlling the power generation unit to perform
If the target power does not exceed the first threshold, the power generation unit is controlled to perform the load following operation,
The first threshold is a value smaller than the maximum value of the output power of the power generation unit, Ri value der set based on the power generation efficiency of the power generation unit,
The first threshold is the output power of the power generation unit at which the slope of the power generation efficiency of the power generation unit is equal to or less than a third threshold, or the power generation unit of the power generation unit where the power generation efficiency of the power generation unit is equal to or greater than a fourth threshold. A power generation system that is set according to output power . A hot water storage unit for storing hot water obtained by recovering the exhaust heat of the power generation unit;
The control device is configured to perform the suppression operation when the hot water storage amount or the heat storage amount of the hot water storage unit exceeds a second threshold value and the target power exceeds the first threshold value. The power generation system according to claim 1, wherein the unit is controlled.   The control device performs the load following operation when the hot water storage amount or the heat storage amount of the hot water storage unit exceeds the second threshold value and the target power does not exceed the first threshold value. The power generation system according to claim 2, wherein the power generation unit is controlled.   4. The power generation system according to claim 2, wherein the control device receives information indicating whether a hot water storage amount or a heat storage amount of the hot water storage unit exceeds the second threshold value. 5.   The power generation system according to claim 2, wherein the first threshold value or the second threshold value is updated based on learning for one day or more.   The second threshold value is set according to at least one parameter of a predicted hot water supply demand pattern, a predicted power load pattern, a predicted outside air temperature, and a predicted water temperature. The power generation system according to claim 2. It further has another power generation unit linked to the commercial power system,
The control device is capable of selling the output power of the other power generation unit to the commercial power system even when the target power exceeds the first threshold, and the unit price of the power sale The power generation system according to any one of claims 1 to 6 , wherein the load following operation is performed when the power generation unit price is higher than a power generation unit price of the power generation unit. The power generation system according to any one of claims 1 to 7 , wherein the power generation unit is a power generation unit using a fuel cell. A control device for controlling output power of a power generation unit using fuel,
When the target power of the power generation unit required for performing the load following operation exceeds a first threshold value, instead of the load following operation, a suppression operation that suppresses the output power of the power generation unit to a constant value. Controlling the power generation unit to perform
If the target power does not exceed the first threshold, the power generation unit is controlled to perform the load following operation,
The first threshold is a value smaller than the maximum value of the output power of the power generation unit, Ri value der set based on the power generation efficiency of the power generation unit,
The first threshold is the output power of the power generation unit at which the slope of the power generation efficiency of the power generation unit is equal to or less than a third threshold, or the power generation unit of the power generation unit where the power generation efficiency of the power generation unit is equal to or greater than a fourth threshold. A control device that is set according to output power . A power control method for controlling the output power of a power generation unit using fuel,
When the target power of the power generation unit required for performing the load following operation exceeds a first threshold value, instead of the load following operation, a suppression operation that suppresses the output power of the power generation unit to a constant value. Controlling the power generation unit to perform:
If the target power does not exceed the first threshold, the power generation unit is controlled to perform the load following operation,
The first threshold is a value smaller than the maximum value of the output power of the power generation unit, Ri value der set based on the power generation efficiency of the power generation unit,
The first threshold is the output power of the power generation unit at which the slope of the power generation efficiency of the power generation unit is equal to or less than a third threshold, or the power generation unit of the power generation unit where the power generation efficiency of the power generation unit is equal to or greater than a fourth threshold. A power control method that is set according to output power .

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