JP7378065B2 - Thermal power generation system and power supply method - Google Patents

Description

The present disclosure relates to a thermal power generation system and a power supply method.

Conventionally, distributed power sources such as solar power generation systems and thermal power generation systems have been interconnected with commercial power sources.

Patent Document 1 discloses that, in a power generation device that converts thermal energy into electric power, a DC voltage in a DC power line is maintained at a predetermined voltage by adjusting an output AC current from an inverter to a commercial grid.

Patent No. 4889956

When interconnecting a distributed power source to a commercial power source, it is important to avoid an excessive rise in voltage at the interconnection point and to supply as much power as possible to the commercial power source.

The present disclosure provides techniques for supplying as much power as possible to a commercial power source while avoiding excessive voltage rises at interconnection points.

The thermal power generation system in the present disclosure includes:
at least one heat exchanger that recovers heat from a single heat source;
at least one thermoelectric conversion device having a plurality of output lines and converting heat recovered by the at least one heat exchanger into electric power;
Equipped with
The plurality of output lines of the at least one thermoelectric conversion device are connected to a plurality of mutually different interconnection points in a commercial power source.

The power supply method in the present disclosure includes:
recovering heat from a single heat source;
Converting the recovered heat into electricity,
Supplying the generated power to a plurality of mutually different interconnection points of a commercial power source through a plurality of output lines;
including.

According to the present disclosure, as much power as possible can be supplied to the commercial power source while avoiding an excessive rise in voltage at the interconnection point.

Configuration diagram of thermoelectric power generation system in Embodiment 1 Configuration diagram showing the locations of interconnection points on low-voltage distribution lines Configuration diagram showing different locations of interconnection points on low-voltage distribution lines Configuration diagram showing further locations of interconnection points on low-voltage distribution lines Configuration diagram of a thermal power generation device in Embodiment 1 Control flowchart of controller in embodiment 1 Configuration diagram of thermal power generation system in Embodiment 2 Configuration diagram of thermal power generation system in Embodiment 3 Configuration diagram of thermoelectric conversion device in Embodiment 3 Control block diagram for the first inverter and second inverter in Embodiment 3 Configuration diagram of a thermoelectric conversion device in a modified example

(Findings, etc. that formed the basis of this disclosure)
At the time the inventors came up with the present disclosure, it was common to avoid excessive voltage rises at interconnection points by suppressing the output power of distributed power sources. In other words, the distributed power source has a function of suppressing the voltage increase at the interconnection point.

On the other hand, if a distributed power source with a large output power is connected to a specific low-voltage distribution line, grid congestion may occur frequently. When grid congestion occurs, the function to suppress voltage rises is frequently activated. In other words, the extraction of power from the distributed power sources must be frequently suppressed or stopped, and energy cannot be used effectively. It is also possible to install power storage equipment, but large-capacity power storage equipment is extremely expensive and hinders the spread of distributed power sources. Based on such findings, the present inventors have come to form the subject matter of the present disclosure.

Therefore, the present disclosure provides a technique for supplying as much power as possible to a commercial power source while avoiding an excessive rise in voltage at an interconnection point.

Hereinafter, embodiments will be described in detail with reference to the drawings. However, more detailed explanation than necessary may be omitted. For example, detailed explanations of well-known matters or redundant explanations of substantially the same configurations may be omitted. This is to avoid making the following description unnecessarily redundant and to facilitate understanding by those skilled in the art.

The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter recited in the claims.

(Embodiment 1)
Embodiment 1 will be described below using FIGS. 1 to 4.

[1-1. composition]
As shown in FIG. 1, the thermoelectric power generation system 100 includes a first heat exchanger 2a, a first thermoelectric conversion device 3a, a second heat exchanger 2b, and a second thermoelectric conversion device 3b.

The first heat exchanger 2a and the second heat exchanger 2b play the role of recovering heat from the single heat source 4.

The heat source 4 is, for example, equipment such as a factory or a geothermal well. A heat flow path 5 is connected to the heat source 4 . The heat flow path 5 is a flow path that guides a heating medium from the heat source 4 toward the heat exhaust port 6 . When the heat source 4 is equipment such as a factory, the heating medium is exhaust gas discharged from the equipment. When the heat source 4 is a geothermal well, the heating medium is steam or hot water. The heat flow path 5 is a duct or piping through which a gaseous heating medium or a liquid heating medium flows. The structure of the heat flow path 5 is determined depending on the state of the heating medium.

The first heat exchanger 2a and the second heat exchanger 2b are arranged in the heat flow path 5. The first heat exchanger 2a is arranged at an upstream position in the heat flow path 5. The second heat exchanger 2b is arranged at a downstream position in the heat flow path 5. The positional relationship between the first heat exchanger 2a and the second heat exchanger 2b is determined so that the heating medium flows through the first heat exchanger 2a and the second heat exchanger 2b in this order. The heating medium flows from the heat source 4 into the first heat exchanger 2a. The heating medium flowing out from the first heat exchanger 2a flows into the second heat exchanger 2b. The heating medium flowing out from the second heat exchanger 2b is guided to the heat exhaust port 6. According to such an arrangement, heat can be efficiently and sufficiently recovered from the heating medium.

Each of the first heat exchanger 2a and the second heat exchanger 2b is designed to be able to recover a predetermined amount of heat depending on the temperature of the heating medium and the flow rate of the heating medium. Examples of the first heat exchanger 2a and the second heat exchanger 2b include a fin and tube heat exchanger, a plate heat exchanger, and a shell and tube heat exchanger.

The first thermoelectric conversion device 3a and the second thermoelectric conversion device 3b play a role of converting the heat recovered by the first heat exchanger 2a and the second heat exchanger 2b into electric power. The first thermoelectric conversion device 3a and the second thermoelectric conversion device 3b each have a first output line 13a and a second output line 13b. The first output line 13a and the second output line 13b are connected to the first interconnection point P1 and the second interconnection point P2, respectively. The first interconnection point P1 and the second interconnection point P2 are a plurality of different interconnection points in the commercial power source 8.

According to such a configuration, it is possible to avoid the generated power from concentrating on a specific interconnection point, so compared to the case where a single high-output output line is connected to a specific interconnection point. , voltage increases at the first interconnection point P1 and the second interconnection point P2 can be suppressed. Therefore, the frequency of operation of the voltage rise suppressing function of the first thermoelectric conversion device 3a and the second thermoelectric conversion device 3b is reduced. By reducing the frequency of operation of the voltage rise suppression function, as much power as possible can be extracted and the recovered energy can be used effectively.

The first thermoelectric conversion device 3a and the second thermoelectric conversion device 3b each have a voltage rise suppressing function. The voltage rise suppression function is a function that monitors the voltage at the interconnection point and adjusts the output power so that the voltage at the interconnection point does not exceed a threshold voltage (for example, 107 V). In order to realize the voltage rise suppression function, the thermal power generation system 100 may include a voltage detector that detects the voltage at each of the plurality of interconnection points.

The thermoelectric power generation system 100 of the present embodiment includes a first output line 13a, which is the output line of the first thermoelectric conversion device 3a, and a second output line, which is the output line of the second thermoelectric conversion device 3b, as a plurality of output lines. Including line 13b. Since there is a one-to-one correspondence between the thermoelectric conversion device and the output line, it is easier to adjust the output power compared to the case where a plurality of output lines are taken out from a single high-output thermoelectric conversion device.

The commercial power supply 8 includes a high voltage distribution line 10, a first transformer 7a, a first low voltage distribution line 9a, a second transformer 7b, and a second low voltage distribution line 9b. The high voltage distribution line 10 is, for example, a three-phase, three-wire, 6600V AC power transmission line. Each of the first low-voltage distribution line 9a and the second low-voltage distribution line 9b is, for example, a single-phase three-wire 200V (and 100V) AC power transmission line. Each of the first transformer 7a and the second transformer 7b is a pole transformer or a ground transformer. A first low voltage distribution line 9a is connected to a high voltage distribution line 10 via a first transformer 7a. A second low voltage distribution line 9b is connected to a high voltage distribution line 10 via a second transformer 7b. The first low-voltage distribution line 9a and the second low-voltage distribution line 9b may be distribution lines within the same factory, or may be distribution lines in an urban area. The first low-voltage distribution line 9a and the second low-voltage distribution line 9b are independent of each other in the sense that voltage maintenance can be performed on each of the first low-voltage distribution line 9a and the second low-voltage distribution line 9b by tap switching or the like. There is.

The first interconnection point P1 is an interconnection point on the first low voltage distribution line 9a connected to the first transformer 7a. The second interconnection point P2 is an interconnection point on the second low voltage distribution line 9b connected to the second transformer 7b. According to such a configuration, the first thermoelectric conversion device 3a and the second thermoelectric conversion device 3b can respectively supply power to the first low voltage distribution line 9a and the second low voltage distribution line 9b.

In this embodiment, only the first interconnection point P1 exists on the first low voltage distribution line 9a. Only the second interconnection point P2 exists on the second low voltage distribution line 9b. In other words, there is a one-to-one correspondence between the low-voltage distribution line and the interconnection point. According to such a configuration, it is possible to easily control the supply of power to each low-voltage distribution line while avoiding an excessive rise in the voltage of each low-voltage distribution line.

FIGS. 2A to 2C are configuration diagrams showing the position of the first interconnection point P1 on the first low-voltage distribution line 9a. The following explanation regarding the position of the first interconnection point P1 on the first low-voltage distribution line 9a also applies to the explanation of the position of the second interconnection point P2 on the second low-voltage distribution line 9b.

As shown in FIG. 2A, the first interconnection point P1 may be located at the end of the first low voltage distribution line 9a. A plurality of loads 12 are connected to the first low voltage distribution line 9a. The distance of the wiring from the first transformer 7a to the first interconnection point P1 is longer than the distance of the wiring from the first transformer 7a to each of the plurality of loads 12. For example, if there is a large load 12 at a location far from the first transformer 7a, placing the first interconnection point P1 at the end of the first low-voltage distribution line 9a can prevent voltage overload at the first interconnection point P1. Easy to avoid rising.

As shown in FIG. 2B, the first interconnection point P1 may be located at the starting end of the first low voltage distribution line 9a. The wiring distance from the first transformer 7a to the first interconnection point P1 is shorter than the wiring distance from the first transformer 7a to each of the plurality of loads 12. In addition, when a large load 12 exists near the first transformer 7a, by placing the first interconnection point P1 at the starting end of the first low-voltage distribution line 9a, the voltage at the first interconnection point P1 can be increased. Easy to avoid rising.

As shown in FIG. 2C, the first interconnection point P1 may be located in the middle of the first low voltage distribution line 9a. The wiring distance from the first transformer 7a to the first interconnection point P1 is longer than the wiring distance from the first transformer 7a to a specific load 12, and the wiring distance from the first transformer 7a to another load 12 is shorter than the wiring distance.

Next, the configuration of the first thermoelectric conversion device 3a will be described using FIG. 3. Since the second thermoelectric conversion device 3b has the same configuration as the first thermoelectric conversion device 3a, a detailed explanation of the configuration of the second thermoelectric conversion device 3b will be omitted.

As shown in FIG. 3, the first thermoelectric conversion device 3a includes an expander 22 and a generator 28. The first heat exchanger 2a constitutes a Rankine cycle device 26 together with the expander 22. The first heat exchanger 2a is an evaporator in the Rankine cycle device 26. The heat recovered by the first heat exchanger 2a is converted into electric power by the expander 22 and the generator 28. The first heat exchanger 2a heats and vaporizes the working fluid. The expander 22 expands the high-pressure working medium that has been heated and vaporized by the first heat exchanger 2a. In the expander 22, the thermal energy of the working fluid is converted into mechanical energy. In generator 28, mechanical energy is converted to electrical energy.

The first thermoelectric conversion device 3a further includes a pump 19 and a condenser 23. pump 1
9 and the condenser 23 constitute a Rankine cycle device 26 together with the first heat exchanger 2a and the expander 22. The pump 19, the first heat exchanger 2a, the expander 22, and the condenser 23 are connected in this order in an annular manner to form a working fluid circuit 20. The working fluid circuit 20 is filled with working fluid.

Pump 19 plays the role of transporting working fluid. In pump 19, the working fluid is pressurized. The pump 19 may be a variable rotation speed pump.

The type of working fluid is not particularly limited. The working fluid may be an inorganic working fluid or an organic working fluid. Inorganic working fluids include water. When the temperature of the heating medium is relatively low, organic working fluids are suitable as working fluids. Examples of the organic working fluid include hydrofluoroolefin (HFO)-based working fluids.

The temperature and flow rate of the heating medium from the heat source 4 tend not to vary significantly over time. That is, the temperature and flow rate of the heating medium to be supplied to the first heat exchanger 2a are generally stable. In such a stable state, the first heat exchanger 2a is designed such that heat exchange is performed to transfer a predetermined amount of heat from the heating medium to the working fluid. That is, when the pump 19 is operated at a rotation speed preset according to the outside air temperature, the temperature of the working fluid flowing out from the first heat exchanger 2a reaches a predetermined temperature, and the state of the working fluid flowing into the expander 22 is determined. The first heat exchanger 2a is designed taking into consideration the temperature and flow rate of the heating medium so that the temperature and flow rate of the heating medium are in a predetermined state. Specifically, in the first heat exchanger 2a, the number of stages of heat exchanger tubes, the number of rows of heat exchanger tubes, the length of heat exchanger tubes, the pitch of fins, the number of fins, etc. are determined.

The expander 22 may be a displacement type expander or a velocity type expander. Examples of the positive displacement expander include a rotary expander and a scroll expander. Examples of speed type expanders include radial flow turbines, mixed flow turbines, and axial flow turbines.

A generator 28 is mechanically connected to the expander 22 . Generator 28 is rotated by expander 22 and converts mechanical energy into electrical energy.

Condenser 23 condenses the working fluid. Specifically, the condenser 23 cools the working fluid with a cooling medium to condense the working fluid. Examples of the condenser 23 include a fin-and-tube heat exchanger, a plate heat exchanger, a double-tube heat exchanger, and the like. The cooling medium may be a liquid such as water or a gas such as air. Condenser 23 is typically a fin-and-tube heat exchanger.

The Rankine cycle device 26 has a temperature sensor 21 and a bypass flow path 24. The temperature sensor 21 is arranged at the inlet of the expander 22 and detects the temperature of the working fluid to be drawn into the expander 22. The bypass flow path 24 has a bypass valve 25. The bypass passage 24 connects the inlet portion of the expander 22 and the outlet portion of the expander 22 in the working fluid circuit 20 . When the bypass valve 25 is opened, the working fluid bypasses the expander 22 and flows into the bypass passage 24 . When bypass valve 25 is closed, working fluid flows to expander 22 . The bypass valve 25 may be a flow control valve whose opening degree is variable.

The first thermoelectric conversion device 3a further includes a motor 27, a pump inverter 29, and a motor drive wiring 30. Motor 27 is mechanically connected to pump 19. The motor 27 plays a role in driving the pump 19. Pump inverter 29 is electrically connected to motor 27 by motor drive wiring 30. Pump inverter 29 plays a role in driving motor 27.

The first thermoelectric conversion device 3a further includes a generator wiring 31, a converter 32, a DC wiring 33, an inverter 34, and a controller 35. Converter 32 is connected to generator 28 by generator wiring 31 and converts the generated power from AC power to DC power. The DC power output from the converter 32 is input to the inverter 34 and the pump inverter 29 via the DC wiring 33. Inverter 34 converts DC power into AC power. The AC power is output to the commercial power source 8 through the first output line 13a. Controller 35 controls inverter 34 . The controller 35 may be a dedicated controller for the first thermoelectric converter 3a, or may be a controller that is also used for the second thermoelectric converter 3b. The controller 35 may be a controller for controlling various control targets included in the thermoelectric power generation system 100.

[1-2. motion]
The operation of the thermoelectric power generation system 100 configured as described above will be described below.

Pump 19 transports the working medium. The first heat exchanger 2a recovers the heat of the heating medium supplied from the heat source 4 and evaporates the working medium. The expander 22 expands the high temperature, gaseous working medium. This causes the generator 28 connected to the expander 22 to rotate and generate electricity. The condenser 23 condenses the working medium by removing heat from the working fluid. The bypass valve 25 adjusts the ratio of the flow rate of the working medium flowing through the expander 22 and the flow rate of the working medium flowing through the bypass passage 24 . The ratio of these flow rates is adjusted depending on the opening degree of the bypass valve 25.

The above description relates to the basic operation of the first thermoelectric conversion device 3a. However, the basic operation of the second thermoelectric conversion device 3b is also the same as that of the first thermoelectric conversion device 3a.

FIG. 4 is a control flowchart of the controller 35. FIG. 4 shows control in the first thermoelectric conversion device 3a. The control in the second thermoelectric conversion device 3b is generally the same as the control in the first thermoelectric conversion device 3a.

In step S1, the pump 19 is started. When the pump 19 starts, the working medium is transported to flow through the first heat exchanger 2a, the bypass channel 24, and the condenser 23 in this order.

In step S2, the temperature T of the working medium is detected by the temperature sensor 21. It is determined whether the temperature T of the working medium exceeds the threshold temperature T1. The threshold temperature T1 is determined based on the pressure required to start the rotation of the expander 22.

When the temperature T of the working fluid exceeds the threshold temperature T1, the rotation speed of the generator 28 is set to zero (rpm) in step S3. Specifically, control of converter 32 is started so that the rotation speed of generator 28 becomes zero (rpm).

In step S4, the bypass valve 25 is closed. Specifically, the bypass valve 25 is controlled from an open state to a closed state.

When the temperature T of the working medium further increases, in step S5, it is determined whether the temperature T of the working medium exceeds the threshold temperature T2. The threshold temperature T2 is a temperature indicating that the thermoelectric power generation system 100 has reached a state where it can generate power.

When the thermal power generation system 100 reaches a state where it can generate electricity, the rotation speed of the generator 28 is controlled to a predetermined rotation speed N1 in step S6. Specifically, the converter 32 is controlled by setting the rotation speed command of the generator 28 to a predetermined rotation speed N1. The predetermined rotation speed N1 is, for example, the rated rotation speed of the generator 28.

When the generator 28 starts generating electricity, the voltage of the DC wiring 33 gradually increases due to the regenerated power from the converter 32. In step S7, it is determined whether the voltage Vpn of the DC wiring 33 exceeds the target value Vpn_ref.

When the voltage Vpn of the DC wiring 33 exceeds the target value Vpn_ref, in step S8, control of the first inverter 34a is started so that the voltage of the DC wiring 33 converges to the target value Vpn_ref.

In step S9, it is determined whether the voltage Vac_t at the first interconnection point P1 on the secondary side of the first transformer 7a exceeds the upper limit value Vac_max.

When the voltage Vac_t at the first interconnection point P1 exceeds the upper limit value Vac_max, in step S10, the pump 19 is controlled so that the flow rate of the working medium in the working fluid circuit 20 is reduced. Specifically, the rotation speed of the pump 19 is lowered. As a result, the amount of heat recovered in the first heat exchanger 2a decreases. When the amount of heat recovered in the first heat exchanger 2a decreases, the output power of the first thermoelectric conversion device 3a decreases, and therefore the voltage Vac_t at the first interconnection point P1 also decreases.

On the other hand, when the amount of heat recovered in the first heat exchanger 2a decreases, the temperature of the heating medium at the inlet of the second heat exchanger 2b increases. At this time, the pump 19 of the second thermoelectric conversion device 3b is controlled so that the flow rate of the working medium in the working fluid circuit 20 of the second thermoelectric conversion device 3b increases. This increases the amount of heat recovered in the second heat exchanger 2b. When the amount of heat recovered in the second heat exchanger 2b increases, the output power of the second thermoelectric conversion device 3b increases.

The output power of the first thermoelectric conversion device 3a is the output power on the first output line 13a. The output power of the second thermoelectric conversion device 3b is the output power on the second output line 13b. Both output powers may be adjusted, or only one.

That is, in step S9 and step S10, the controller 35 performs control to adjust at least one of the output powers of the plurality of output lines. Specifically, control is performed to increase or decrease at least one of the output powers. In this embodiment, as the control, the ratio of the output power on the second output line 13b to the output power on the first output line 13a is changed. According to such a configuration, voltage increases at each interconnection point can be suppressed more reliably. Even if the voltage fluctuates due to disturbances such as transmission/distribution line conditions or load conditions, it is possible to extract as much power as possible compared to using a single high-output thermoelectric conversion device. can.

The controller 35 performs control to adjust at least one of the output powers of the plurality of output lines in accordance with at least one of the voltages at the first interconnection point P1 and the second interconnection point P2. Thereby, fluctuations in voltage at the first interconnection point P1 and the second interconnection point P2 can be further suppressed.

As shown in FIG. 1, the second heat exchanger 2b recovers heat from the heating medium that has passed through the first heat exchanger 2a and is lowered in temperature. By performing control to reduce the heat recovery amount of the first heat exchanger 2a and control to increase the heat recovery amount of the second heat exchanger 2b in parallel, it is possible to recover as much electricity as possible. .

The controller 35 may perform control to change at least one upper limit value Pac_max of output power in a plurality of output lines. By changing the upper limit Pac_max, it is possible to indirectly change the output power ratio. Thereby, fluctuations in voltage at the first interconnection point P1 and the second interconnection point P2 can be further suppressed.

[1-3. Effects, etc.]
As described above, in this embodiment, heat is recovered from a single heat source 4 by the first heat exchanger 2a and the second heat exchanger 2b, and the heat is recovered from the single heat source 4 by the first thermoelectric conversion device 3a and the second thermoelectric conversion device 3b. Convert heat into electricity. The first thermoelectric conversion device 3a and the second thermoelectric conversion device 3b are connected to a plurality of points of the commercial power source 8.

According to such a configuration, it is possible to avoid the generated power from concentrating on a specific interconnection point, so compared to the case where a single high-output output line is connected to a specific interconnection point. , voltage rise at each interconnection point can be suppressed. Therefore, the frequency of operation of the voltage rise suppressing function of the first thermoelectric conversion device 3a and the second thermoelectric conversion device 3b is reduced. By reducing the frequency of operation of the voltage rise suppression function, as much power as possible can be extracted and the recovered energy can be used effectively.

In this embodiment, the plurality of mutually different interconnection points may be the plurality of interconnection points on the plurality of low voltage distribution lines connected to the plurality of transformers. Examples of the plurality of interconnection points are a first interconnection point P1 and a second interconnection point P2. An example of the plurality of transformers is a first transformer 7a and a second transformer 7b. Examples of the plurality of low voltage distribution lines are the first low voltage distribution line 9a and the second low voltage distribution line 9b. According to such a configuration, the first thermoelectric conversion device 3a and the second thermoelectric conversion device 3b can respectively supply power to the first low voltage distribution line 9a and the second low voltage distribution line 9b. There may be a one-to-one correspondence between the low-voltage distribution line and the interconnection point.

In this embodiment, at least one of the plurality of interconnection points that are different from each other may be present at the starting end or the terminal end of the low voltage distribution line connected to the transformer. For example, if a large load exists at a location far from a transformer, placing the interconnection point at the end of the low-voltage distribution line makes it easier to avoid an excessive rise in voltage at the interconnection point. If a large load exists near the transformer, placing the interconnection point at the starting end of the low-voltage distribution line makes it easier to avoid an excessive rise in voltage at the interconnection point. It is desirable to change the location of interconnection points on low-voltage distribution lines depending on the size of the load.

In this embodiment, the thermoelectric power generation system 100 further includes a controller 35 that performs control to adjust at least one of the output powers of the plurality of output lines. According to such a configuration, voltage increases at each interconnection point can be suppressed more reliably.

In this embodiment, the controller may perform control to adjust at least one of the output powers of the plurality of output lines in accordance with at least one of the voltages at the plurality of mutually different interconnection points. Thereby, fluctuations in voltage at each interconnection point can be further suppressed.

In this embodiment, the plurality of output lines include a first output line 13a and a second output line 13b. The controller 35 changes the ratio of the output power in the second output line 13b to the output power in the first output line 13a as a control for adjusting at least one of the output powers in the plurality of output lines. According to such a configuration, voltage increases at each interconnection point can be suppressed more reliably. Even if the voltage fluctuates due to disturbances such as transmission/distribution line conditions or load conditions, it is possible to extract as much power as possible compared to using a single high-output thermoelectric conversion device. can.

In this embodiment, the controller 35 may change at least one upper limit value of output power in a plurality of output lines. By changing the upper limit value, the output power ratio can be changed indirectly. Thereby, fluctuations in voltage at each interconnection point can be further suppressed.

In this embodiment, at least one thermoelectric conversion device may include a first thermoelectric conversion device 3a and a second thermoelectric conversion device 3b. The plurality of output lines may include a first output line 13a that is the output line of the first thermoelectric conversion device 3a and a second output line 13b that is the output line of the second thermoelectric conversion device 3b. Since there is a one-to-one correspondence between the thermoelectric conversion device and the output line, it is easier to adjust the output power compared to the case where a plurality of output lines are taken out from a single high-output thermoelectric conversion device.

In this embodiment, at least one heat exchanger may include a first heat exchanger 2a and a second heat exchanger 2b. The first heat exchanger 2 a may be arranged at an upstream position in the heat flow path 5 connected to the single heat source 4 . The second heat exchanger 2b may be placed at a downstream position in the heat flow path 5. According to such an arrangement, heat can be efficiently and sufficiently recovered from the heating medium.

(Embodiment 2)
Embodiment 2 will be described below using FIG. 5. Components that are the same as those in Embodiment 1 are given the same numbers and detailed explanations will be omitted.

[2-1. composition]
As shown in FIG. 5, the thermoelectric power generation system 200 includes a heat exchanger 2c, a first thermoelectric conversion device 3a, and a second thermoelectric conversion device 3b. The thermal power generation system 200 apparently includes a single heat exchanger 2c. However, the heat exchanger 2c has a first piping section 14a and a second piping section 14b. Heat is supplied to the first thermoelectric conversion device 3a through the first piping section 14a. Heat is supplied to the second thermoelectric conversion device 3b through the second piping section 14b. In this respect, this embodiment is the same as the first embodiment.

[2-2. motion]
The heating medium is supplied from the heat source 4 to the heat flow path 5, and exchanges heat with the working fluid flowing through the first piping section 14a. Thereafter, the heating medium is supplied to the second piping section 14b, and further exchanges heat with the working fluid flowing through the second piping section 14b.

[2-3. Effects, etc.]
In this embodiment as well, the same effects as in the first embodiment can be obtained.

The thermal power generation system 200 of this embodiment has only one heat exchanger 2c that recovers heat from a single heat source 4. Therefore, the cost spent on the heat exchanger can be reduced.

(Embodiment 3)
Embodiment 3 will be described below using FIGS. 6 to 8.

[3-1. composition]
As shown in FIG. 6, the thermoelectric power generation system 300 includes a heat exchanger 2 and a thermoelectric conversion device 3. The thermoelectric power generation system 300 includes a single heat exchanger 2 and a single thermoelectric conversion device 3. The thermoelectric conversion device 3 has a plurality of output lines. The plurality of output lines include a first output line 13a and a second output line 13b. The first output line 13a and the second output line 13b are connected to the first interconnection point P1 and the second interconnection point P2, respectively. The first interconnection point P1 and the second interconnection point P2 are a plurality of different interconnection points in the commercial power source 8.

As shown in FIG. 7, the thermoelectric conversion device 3 includes a first inverter 34a and a second inverter 34b. The first inverter 34a and the second inverter 34b are connected in parallel to a DC wiring 33 that is an output line of the converter 32. The output line of the first inverter 34a is the first output line 13a. The output line of the second inverter 34b is the second output line 13b. The first inverter 34a and the second inverter 34b are controlled by a controller 35. Except for these points, the configuration of the thermoelectric conversion device 3 is the same as the configuration of the first thermoelectric conversion device 3a (FIG. 3) of the first embodiment.

[3-2. motion]
FIG. 8 is a control block diagram for the first inverter 34a and the second inverter 34b by the controller 35.

As shown in FIG. 8, the controller 35 sets the target value Wa_ref of the output power of the first inverter 34a as a command value. The target value Wa_ref of the output power is a power corresponding to 50% of the initial value of the difference power between the power Wg input from the converter 32 to the DC wiring 33 and the power Wp input from the DC wiring 33 to the pump inverter 29. sell.

Next, the voltage Vac_A_t to which the first inverter 34a is connected and the voltage Vac_B_t to which the second inverter 34b is connected are compared. Target value Wa_ref is added or subtracted according to the magnitude relationship and difference between voltage Vac_A_t and voltage Vac_B_t. Specifically, when the voltage Vac_A_t is 1V lower than the voltage Vac_B_t, the target value Wa_ref is added by 10%. When voltage Vac_A_t is 1V higher than voltage Vac_B_t, target value Wa_ref is subtracted by 10%. The voltage Vac_A_t is, for example, the voltage of the first output line 13a. The voltage Vac_B_t is, for example, the voltage of the second output line 13b.

When adding or subtracting the target value Wa_ref of the output power, the addition or subtraction may be performed at a ratio other than 10% with respect to the 1V difference between the voltage Vac_A_t and the voltage Vac_B_t.

Next, the current output power Wa_t is calculated by the voltage detector and current detector provided in the first inverter 34a. The difference between the current output power Wa_t and the target output power Wa_ref is calculated, and the calculated difference is input to a proportional integrator (PI controller). The proportional integrator outputs the target value Ia_ref of the output current as a result of the calculation. The difference between the output current target value Ia_ref and the current output current Ia_t is calculated, and the calculated difference is input to the proportional integrator. The proportional integrator outputs the voltage command value Va_ref as a result of the calculation. A synchronized modulation signal is generated in the modulation signal generation section using the voltage command value Va_ref, the voltage phase on the secondary side of the first transformer 7a, and the current DC voltage Vpn_t of the DC wiring 33. In the carrier wave comparing section, the modulated signal and the carrier wave are compared and switching of the first inverter 34a is performed.

On the other hand, the control of the second inverter 34b is different from the control of the first inverter 34a. The difference between the target value Vpn_ref of the DC voltage of the DC wiring 33 and the current DC voltage Vpn_t of the DC wiring 33 is calculated, and the calculated difference is input to the proportional integrator (PI controller). The proportional integrator outputs the target value Ib_ref of the output current as a result of the calculation. The difference between the output current target value Ib_ref and the current output current Ib_t is calculated, and the calculated difference is input to the proportional integrator. The proportional integrator outputs a voltage command value Vb_ref as a result of the calculation. A synchronized modulation signal is generated in the modulation signal generation section using the voltage command value Vb_ref, the voltage phase on the secondary side of the second transformer 7b, and the current DC voltage Vpn_t of the DC wiring 33. In the carrier wave comparison section, the modulated signal and the carrier wave are compared and switching of the second inverter 34b is performed.

[3-3. Effects, etc.]
In this embodiment as well, the same effects as in the first embodiment can be obtained.

The thermoelectric power generation system 300 of this embodiment has only one heat exchanger 2 that recovers heat from a single heat source 4. Therefore, the cost spent on the heat exchanger 2 can be reduced.

The thermoelectric power generation system 300 of this embodiment has only one thermoelectric conversion device 3. In other words, only one Rankine cycle working fluid circuit 20 exists in the thermoelectric power generation system 300. The thermoelectric conversion device 3 includes a single DC wiring 33 , a first inverter 34 a connected to the single DC wiring 33 , and a second inverter 34 b connected to the single DC wiring 33 . The plurality of output lines include a first output line 13a that is the output line of the first inverter 34a and a second output line 13b that is the output line of the second inverter 34b. According to such a configuration, the cost spent on the thermal power generation system 300 can be reduced.

In the thermal power generation system 300 of the present embodiment, hunting of voltage in the DC wiring 33 is suppressed by balancing the total power supplied to the commercial power source 8 and the generated power. The first inverter 34a is controlled so that the output power on the output line of the first inverter 34a converges to a target value. The second inverter 34b is controlled so that the DC current in the single DC wiring 33 converges to a target value. That is, the first inverter 34a is controlled to output desired power by feeding back the output power. By feeding back the voltage of the DC wiring 33, the second inverter 34b is controlled so that the voltage of the DC wiring 33 converges to a desired voltage. According to such control, it is possible to balance the total power supplied to the commercial power source 8 and the generated power, and it is also possible to suppress voltage hunting in the DC wiring 33.

(Other embodiments)
As described above, Embodiments 1 to 3 have been described as examples of the technology disclosed in this application. However, the technology in the present disclosure is not limited to this, and can also be applied to embodiments in which changes, replacements, additions, omissions, etc. are made. Furthermore, it is also possible to create a new embodiment by combining the components described in the first to third embodiments.

Heat source 4 and heat flow path 5 may be part of thermoelectric power generation system 100, 200 or 300.

The number of thermoelectric conversion devices is not limited to 1 or 2, and may be 3 or more.

A plurality of heat exchangers may be arranged in parallel in the heat flow path 5 so that each heat exchanger is supplied with a heating medium having approximately the same temperature.

Instead of changing the ratio of the output power in the second output line 13b to the output power in the first output line 13a, the ratio of the output power in the second output line 13b to the output power in the first output line 13a is fixed. Good too. For example, when the output power on the first output line 13a is set to 100%, the output power on the second output line 13b is set to 80%.

FIG. 9 shows the configuration of a thermoelectric conversion device 3 in a modified example. As shown in FIG. 9, the thermoelectric conversion device 3 may include a plurality of expanders arranged in the working fluid circuit 20. The plurality of expanders include a first expander 22a and a second expander 22b. The first expander 22a and the second expander 22b are arranged in series so that the working fluid expanded in the first expander 22a is further expanded in the second expander 22b. In other words, the expander may be a multistage expander.

The thermoelectric conversion device 3 further includes a first generator 28a, a first generator wiring 31a, a first converter 32a, and a first DC wiring 33a. The heat recovered by the heat exchanger 2 is converted into electric power by the first expander 22a and the first generator 28a. The first converter 32a is connected to the first generator 28a by a first generator wiring 31a, and converts the generated power from AC power to DC power. The DC power output from the first converter 32a is input to the first inverter 34a and the pump inverter 29 via the first DC wiring 33a. The first inverter 34a converts DC power into AC power.

The thermoelectric conversion device 3 further includes a second generator 28b, a second generator wiring 31b, a second converter 32b, and a second DC wiring 33b. The heat recovered by the heat exchanger 2 is further converted into electric power by the second expander 22b and the second generator 28b. The second converter 32b is connected to the second generator 28b by a second generator wiring 31b, and converts the generated power from AC power to DC power. The DC power output from the second converter 32b is input to the second inverter 34b via the second DC wiring 33b.

According to the configuration shown in FIG. 9, not only the effects described in the previous embodiment can be obtained, but also higher thermoelectric conversion efficiency may be achieved.

Note that the above-described embodiments are for illustrating the technology of the present disclosure, and therefore various changes, substitutions, additions, omissions, etc. can be made within the scope of the claims or equivalents thereof.

The present disclosure is useful for thermal power generation systems having multiple output lines. The present disclosure is particularly useful for small-scale distributed power systems. Small-scale distributed power systems are suitable for factories, commercial facilities, hospitals, schools, public facilities, etc.

2a First heat exchanger 2b Second heat exchangers 2, 2c Heat exchanger 3 Thermoelectric conversion device 3a First thermoelectric conversion device 3b Second thermoelectric conversion device 4 Heat source 5 Heat flow path 6 Heat exhaust port 7a First transformer 7b 2 Transformer 8 Commercial power supply 9a First low voltage distribution line 9b Second low voltage distribution line 10 High voltage distribution line 12 Load 13a First output line 13b Second output line 14a First piping section 14b Second piping section 19 Pump 20 Working fluid circuit 21 Temperature sensor 22 Expander 22a First expander 22b Second expander 23 Condenser 24 Bypass passage 25 Bypass valve 26 Rankine cycle device 27 Motor 28 Generator 28a First generator 28b Second generator 29 Pump inverter 30 Motor Drive wiring 31 Generator wiring 31a First generator wiring 31b Second generator wiring 32 Converter 32a First converter 32b Second converter 33 DC wiring 33a First DC wiring 33b Second DC wiring 34 Inverter 34a First inverter 34b Second Inverter 35 Controller 100, 200, 300 Thermal power generation system P1 First interconnection point P2 Second interconnection point

Claims (12)

at least one heat exchanger that recovers heat from a single heat source;
at least one thermoelectric conversion device having a plurality of output lines and converting heat recovered by the at least one heat exchanger into electric power;
Equipped with
The plurality of output lines of the at least one thermoelectric conversion device are connected to a plurality of mutually different interconnection points in a commercial power supply,
Thermal power generation system. The plurality of mutually different interconnection points are a plurality of interconnection points in a plurality of low voltage distribution lines connected to a plurality of transformers,
The thermal power generation system according to claim 1. At least one of the plurality of interconnection points different from each other is present at a starting end or a terminal end of a low voltage distribution line connected to a transformer,
The thermal power generation system according to claim 1 or 2. further comprising a controller that performs control to adjust at least one of the output powers in the plurality of output lines;
The thermal power generation system according to any one of claims 1 to 3. The controller performs the control according to at least one of the voltages at the plurality of interconnection points that are different from each other.
The thermal power generation system according to claim 4. the plurality of output lines include a first output line and a second output line,
As the control, the controller changes a ratio of output power in the second output line to output power in the first output line.
The thermal power generation system according to claim 4 or 5. the controller changes at least one upper limit value of output power in the plurality of output lines;
The thermal power generation system according to any one of claims 4 to 6. The at least one thermoelectric conversion device includes a first thermoelectric conversion device and a second thermoelectric conversion device,
The plurality of output lines include a first output line that is an output line of the first thermoelectric conversion device and a second output line that is an output line of the second thermoelectric conversion device.
The thermal power generation system according to any one of claims 1 to 7. the at least one heat exchanger includes a first heat exchanger and a second heat exchanger;
The first heat exchanger is located at an upstream position in a heat flow path connected to the single heat source,
the second heat exchanger is located at a downstream position in the heat flow path;
The thermal power generation system according to any one of claims 1 to 8. The at least one thermoelectric conversion device includes a single DC wiring, a first inverter connected to the single DC wiring, and a second inverter connected to the single DC wiring,
The plurality of output lines include an output line of the first inverter and an output line of the second inverter,
The thermal power generation system according to any one of claims 1 to 7. The first inverter is controlled so that the output power in the output line of the first inverter converges to a target value,
The second inverter is controlled so that the DC current in the single DC wiring converges to a target value.
The thermal power generation system according to claim 10. recovering heat from a single heat source by a heat exchanger ;
Converting the recovered heat into electricity using a thermoelectric conversion device ,
Supplying the generated power from the thermoelectric conversion device to a plurality of mutually different interconnection points of a commercial power source through a plurality of output lines of the thermoelectric conversion device ;
including power supply methods.

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