Power control device, thermoelectric power generation system, and power control method

Abstract

The object is to increase the output power of a thermoelectric conversion device. The power control device according to the present application includes a power measuring unit that measures the electric power output from the thermoelectric conversion device, and a control unit that controls the electric power output from the thermoelectric conversion device, wherein the power measuring unit measures the electric power output from the thermoelectric conversion device after a lapse of a time corresponding to the thermal time constant of the thermoelectric conversion device after a change in the load on the output of the thermoelectric conversion device.

Description

Technical Field

[0001] The technology disclosed in this application relates to thermoelectric power generation technology. Background Technology

[0002] As a conventional control method for thermoelectric converters, there is a method that uses a hill-climbing method to search for the optimal operating point by varying the output current of the thermoelectric converter with arbitrary control cycles in order to maximize the output from the thermoelectric converter (for example, see Patent Document 1, Japanese Patent Application Publication No. 2013-055769).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-055769 Summary of the Invention

[0006] In such control methods for thermoelectric converters, it is difficult to obtain the accurate maximum power point of the thermoelectric converter when the control cycle is shorter than the thermal time constant of the thermoelectric converter. As a result, the extracted power is lower than the maximum output power of the thermoelectric converter.

[0007] The technology disclosed in this application specification was made in view of the problems described above, and is a technology for increasing the output power of a thermoelectric conversion device.

[0008] The first aspect of the technology disclosed in this application discloses a power control device that controls the electrical power of a thermoelectric converter that outputs electrical power based on heat generation. The power control device includes: a power measuring unit that measures the electrical power output from the thermoelectric converter; and a control unit that controls the electrical power output from the thermoelectric converter. The power measuring unit measures the electrical power output from the thermoelectric converter after a change in the load on the output of the thermoelectric converter and after a time corresponding to the thermal time constant of the thermoelectric converter has elapsed.

[0009] According to at least a first aspect of the technology disclosed in this application, it is possible to increase the electrical power (extracted power) output from the thermoelectric conversion device.

[0010] Furthermore, the objectives, features, aspects, and advantages related to the technology disclosed in this application will become clearer through the following detailed description and accompanying drawings. Attached Figure Description

[0011] Figure 1 This is a diagram illustrating an example of the structure of a thermoelectric power generation system according to an embodiment.

[0012] Figure 2 This is a flowchart illustrating an example of the operation (maximum output control) of a power control device.

[0013] Figure 3 This is a diagram showing an example of the value of the electrical power (taken power) output from the thermoelectric converter when the control waiting time, i.e., the control cycle, changes using the power control device of the embodiment.

[0014] Figure 4 This is a schematic diagram illustrating the thermal circuit of a thermoelectric conversion device.

[0015] Figure 5 This is a diagram illustrating an example of the transient characteristics of the electrical power output from the thermoelectric converter when the current to the thermoelectric converter is increased by ΔI (when the current is disturbed by +ΔI using the hill-climbing method).

[0016] Figure 6 This is a diagram illustrating an example of the current-voltage characteristics of a thermoelectric conversion device at thermal equilibrium.

[0017] Figure 7 This is a diagram illustrating an example of the voltage characteristics of a thermoelectric converter when the current to the thermoelectric converter is increased by ΔI (when the current is disturbed by +ΔI using the hill-climbing method).

[0018] Figure 8 This is a diagram illustrating an example of the transient characteristics of the electrical power P output from the thermoelectric converter when the current to the thermoelectric converter is reduced by ΔI (when the current is disturbed by -ΔI using the hill-climbing method).

[0019] Figure 9 This is a diagram illustrating an example of the current-voltage characteristics of a thermoelectric conversion device at thermal equilibrium.

[0020] Figure 10 This is a diagram illustrating an example of the voltage characteristics of a thermoelectric converter when the current is reduced by ΔI (by perturbing the current by -ΔI using the hill-climbing method).

[0021] Figure 11 This is a diagram illustrating an example of the structure of a thermoelectric power generation system according to an embodiment.

[0022] Figure 12 This is a flowchart illustrating an example of how a power control device works to obtain a thermal time constant.

[0023] Figure 13 This is a diagram illustrating an example of the transient characteristics of the voltage of a thermoelectric converter when it changes from a short-circuit state to an open-circuit state.

[0024] Figure 14 This is a flowchart illustrating an example of the operation (maximum output control) of a power control device.

[0025] Figure 15 This is a general example. Figure 1 and Figure 11 The diagram shows the hardware structure of the illustrated thermoelectric power generation system in actual use.

[0026] Figure 16 This is a general example. Figure 1 and Figure 11 The diagram shows the hardware structure of the illustrated thermoelectric power generation system in actual use.

[0027] Figure Labels

[0028] 11: Thermoelectric conversion device; 11a: Thermoelectric conversion module; 11b: High-temperature side heat exchanger; 11c: Low-temperature side heat exchanger; 12, 22: Power control device; 12a, 22a: Thermal time constant acquisition unit; 12b, 22b: Power measurement unit; 12c, 22c: Power conversion control unit; 12d, 22d: Power conversion unit; 13: Load; 100, 101: Thermoelectric power generation system; 1102A, 1102B: Processing circuit; 1103: Storage device. Detailed Implementation

[0029] The embodiments will now be described with reference to the accompanying drawings. Although detailed features are shown in the following embodiments for the purpose of illustrating the technology, these are illustrative and are not necessarily essential features for making the embodiments implementable.

[0030] Furthermore, the accompanying drawings are schematic representations, and structural details may be omitted or simplified as appropriate for ease of explanation. Additionally, the relative sizes and positions of structures shown in different drawings are not necessarily accurately depicted and may be modified as needed. Furthermore, in non-sectional top views and other accompanying drawings, shaded lines are sometimes added to facilitate understanding of the embodiments.

[0031] Furthermore, in the following descriptions, the same symbols are used to illustrate the same constituent elements, and their names and functions are also assumed to be the same. Therefore, to avoid repetition, detailed descriptions of them are sometimes omitted.

[0032] Furthermore, in the following descriptions, when a constituent element is described as "possessing," "including," or "having," unless otherwise specified, it is not an exclusive statement that excludes the existence of other constituent elements.

[0033] Furthermore, in the following description, even when using ordinal numbers such as "first" or "second", these terms are merely for the convenience of making the content of the implementation method easier to understand, and are not limited to the order that can be generated by these ordinal numbers.

[0034] Furthermore, in the following descriptions, expressions indicating equal states, such as "same," "equal," "uniform," or "homogeneous," unless otherwise specified, include both cases indicating strictly equal states and cases where differences arise within tolerances or within the range where the same level of functionality can be obtained.

[0035] <First Implementation>

[0036] The following describes the power control device, thermoelectric power generation system, and power control method of this embodiment.

[0037] <On the structure of thermoelectric power generation systems>

[0038] Figure 1 This is a diagram illustrating an example of the structure of a thermoelectric power generation system according to this embodiment. (See diagram for example.) Figure 1 The illustrated thermoelectric power generation system 100 includes a thermoelectric conversion device 11, a power control device 12 for controlling the electrical power output from the thermoelectric conversion device 11, and a load 13. The load 13 includes a constant voltage source such as a battery.

[0039] The thermoelectric conversion device 11 includes a thermoelectric conversion module 11a and a high-temperature side heat exchanger 11b and a low-temperature side heat exchanger 11c disposed between the thermoelectric conversion module 11a and the thermoelectric conversion module 11a.

[0040] Thermoelectric conversion module 11a includes, for example, a thermoelectric conversion element. In the thermoelectric conversion module 11a, when a temperature difference is applied across the element, an electromotive force is generated due to the Seebeck effect. When the thermoelectric conversion module 11a includes a thermoelectric conversion element, the thermoelectric conversion element is connected in series or parallel within the thermoelectric conversion module 11a. Furthermore, the electromotive force generated in the thermoelectric conversion module 11a is extracted from the positive and negative terminals of the thermoelectric conversion module 11a.

[0041] The high-temperature side heat exchanger 11b has a heat sink structure made of, for example, aluminum or SUS. The high-temperature side heat exchanger 11b transfers heat from high-temperature fluids such as exhaust gas to the high-temperature side of the thermoelectric conversion module 11a.

[0042] On the other hand, the low-temperature heat exchanger 11c is constructed, for example, by cooling water flowing within a block of aluminum or copper. The low-temperature heat exchanger 11c absorbs heat transferred from the low-temperature side of the thermoelectric conversion module 11a.

[0043] Through these structures, heat is transferred (through) from the high-temperature side surface of the thermoelectric conversion module 11a to the low-temperature side surface.

[0044] The power control device 12 includes a thermal time constant acquisition unit 12a, a power measurement unit 12b, a power conversion control unit 12c, and a power conversion unit 12d.

[0045] The power control device 12 is connected to the positive and negative terminals of the thermoelectric conversion device 11. Furthermore, the electrical power generated by the thermoelectric conversion device 11 is input to the power control device 12.

[0046] In addition, a load 13 is connected to the power control device 12. Moreover, the electrical power converted by the power conversion unit 12d is output to the load 13.

[0047] Regarding the power conversion unit 12d, a positive and a negative terminal are provided on the input side, which are respectively connected to the positive and negative terminals of the thermoelectric converter 11. Furthermore, the electrical power generated by the thermoelectric converter 11 is input to the power conversion unit 12d.

[0048] Similarly, the power conversion unit 12d also has a positive and a negative terminal on the output side, which are connected to the positive and negative terminals of the load 13, respectively. Furthermore, the electrical power converted by the power conversion unit 12d is output to the load 13.

[0049] The power conversion unit 12d includes, for example, a boost, buck, or buck-boost DC-DC converter. The load of the power conversion unit 12d as observed from the input terminal of the power conversion unit 12d can be changed by controlling the on-off time ratio (duty cycle) of the switching elements of the power conversion unit 12d.

[0050] Control based on the switching element's on / off state is achieved by transmitting a periodic rectangular wave (e.g., PWM (Pulse Width Modulation) wave or PFM (Pulse Frequency Modulation) wave, i.e., a switching signal, from the power conversion control unit 12c to the switching element.

[0051] A thermal time constant acquisition unit 12a, a power measurement unit 12b, and a power conversion unit 12d are connected to the power conversion control unit 12c.

[0052] The thermal time constant acquisition unit 12a uses thermocouples or the like to detect and acquire the temperature of the high-temperature side surface and the low-temperature side surface of the thermoelectric conversion module 11a. Furthermore, the thermal time constant acquisition unit 12a calculates the thermal time constant based on the temperature of the high-temperature side surface and the low-temperature side surface of the thermoelectric conversion module 11a, and sends the thermal time constant to the power conversion control unit 12c.

[0053] The power measurement unit 12b measures the electrical power output from the thermoelectric converter 11 by measuring the current and voltage output from the thermoelectric converter 11. Furthermore, it obtains the internal resistance of the thermoelectric converter 11 based on the current and voltage values ​​output from the thermoelectric converter 11. The power measurement unit 12b then transmits the measured electrical power as power data to the power conversion control unit 12c.

[0054] The power conversion control unit 12c controls the maximum output of electrical power from the thermoelectric conversion device 11 based on the input thermal time constant and power data.

[0055] <Regarding the operation of power control devices in thermoelectric power generation systems>

[0056] Figure 2 This is a flowchart illustrating an example of the operation of the power control device 12 (mainly the maximum output control performed by the power conversion control unit 12c). Here, a maximum power point search algorithm based on hill climbing is used as an example of maximum power point search.

[0057] First, in step ST10, the thermal time constant acquisition unit 12a calculates and acquires the thermal time constant T of the thermoelectric conversion device 11. The thermal time constant T is acquired in the following manner.

[0058] When the value of the current output from the thermoelectric converter 11 changes from I to I+ΔI, the temperature T on the high-temperature side of the thermoelectric converter module 11a... h Change to T h +ΔT h0 The temperature T on the low-temperature side of thermoelectric conversion module 11a c Change to T c +ΔT c0 At this time, the temperature difference applied to the thermoelectric conversion module 11a changes as shown in the following equation (1).

[0059] T h -T c →T h -T c +(ΔT h0 -ΔT c0 (1)

[0060] After a certain time (t seconds), the temperature on the high-temperature side of the thermoelectric conversion module 11a becomes T. h +ΔT h1 The temperature on the low-temperature side of the thermoelectric conversion module 11a becomes T. c +ΔT c1 Therefore, the temperature difference change of the thermoelectric conversion module 11a in t seconds is as shown in equation (2).

[0061] ΔT h1 -ΔT h0 +ΔT c1 -ΔT c0 …(2)

[0062] The thermal time constant T is calculated based on the transient characteristics of the temperature difference with respect to time t obtained above.

[0063] Next, in step ST11, the duty cycle of the switching signal input from the power conversion control unit 12c to the power conversion unit 12d is changed. Furthermore, the value of the current output from the thermoelectric converter 11 to the power conversion unit 12d is changed from I to I+ΔI.

[0064] Next, in step ST12, a time corresponding to the thermal time constant T obtained in step ST10 is waited. Since the value of the current output from the thermoelectric converter 11 to the power conversion unit 12d is changed from I to I+ΔI in step ST11, a Peltier effect occurs in the thermoelectric converter module 11a, resulting in a decrease in thermal resistance. Then, the thermal equilibrium of the thermoelectric converter 11 is temporarily disrupted.

[0065] Therefore, in response to the system, the system is allowed to wait for any constant multiple of time T, such as T or 3T, to achieve thermal stability.

[0066] Next, in step ST13, the power measurement unit 12b measures the electrical power P (output power) output from the thermoelectric converter 11. The power measurement unit 12b measures the voltage V output from the thermoelectric converter 11 and the current I output from the thermoelectric converter 11, and calculates the electrical power according to the formula: electrical power P = voltage V × current I.

[0067] Next, in step ST14, the electrical power P measured in step ST13 is compared with the electrical power P' measured in the previous loop (i.e., the electrical power before the current value changed in step ST11). Furthermore, when step ST14 is the first loop, the electrical power P' is set to 0 for this comparison.

[0068] Then, when P>P', that is, corresponding to from Figure 2 When the illustrated step ST14 branch is "Yes", the process proceeds to step ST15. On the other hand, when P is not P>P', i.e., corresponding to... Figure 2 When the "No" condition is met in the illustrated step ST14 branch, proceed to step ST16.

[0069] In step ST15, it is determined that the value ΔI of the current change in step ST11 in the next cycle will be the same as the value ΔI in the previous step ST11. Then proceed to step ST17.

[0070] In step ST16, it is determined that the value ΔI, which changes the current in step ST11 in the next cycle, will be a value with the opposite sign (same absolute value) – ΔI. Then proceed to step ST17.

[0071] Next, in step ST17, the electrical power P measured in step ST13 is updated as the value used as the electrical power P' in step ST14 of the next cycle. Then, the process returns to step ST11.

[0072] Through these processes, the power control device 12 performs cyclical control that repeatedly cycles around the current value that maximizes the electrical power output from the thermoelectric converter 11. In this way, the power control device 12 searches for the maximum value of the electrical power output from the thermoelectric converter 11.

[0073] Furthermore, although this embodiment shows a maximum power point search based on the hill-climbing method, other power search methods can also be used as long as the current value is changed to search for the maximum power point.

[0074] Next, we will discuss the optimal value of the control cycle of the thermoelectric conversion device 11. Figure 3 This is a diagram illustrating an example of the value of the electrical power P (extracted power) output from the thermoelectric converter 11 when the control waiting time, i.e., the control period t, changes using the power control device 12 of this embodiment. Figure 3 In the diagram, the vertical axis represents the value of electrical power P, and the horizontal axis represents the control cycle of the thermoelectric conversion device 11.

[0075] like Figure 3 As illustrated, there exists a point X during the control period t where the electrical power P output from the thermoelectric converter 11 is at its maximum. Point X is near the thermal time constant T of the thermoelectric converter 11. The reason for this is explained below.

[0076] When the control period t is shorter than the thermal time constant T, and the electrical power P output from the thermoelectric converter 11 is measured after the current I output from the thermoelectric converter 11 is changed in step ST11, the temperature of the thermoelectric converter 11 has not yet reached equilibrium. Therefore, the output has not reached equilibrium, and the true maximum power point cannot be obtained.

[0077] Figure 4 This is a schematic diagram illustrating the thermal circuit of the thermoelectric conversion device 11. In the thermoelectric conversion device 11, on the high-temperature side of the thermoelectric conversion module 11a, surface T... hs Temperature fixed point T on the high-temperature side h Between them, the thermal resistance R is mainly formed by the high-temperature side heat exchanger 11b. h and heat capacity C h They exist in parallel. Similarly, on the low-temperature side of thermoelectric conversion module 11a, surface T... cs Temperature fixed point T on the low-temperature side c Between (the temperature of the cooling water) and (the temperature of the cooling water), the thermal resistance R is mainly formed by the low-temperature side heat exchanger 11c. c and heat capacity C c They exist in parallel.

[0078] In the thermoelectric conversion module 11a, by varying the current I flowing through it, the heat transferred from the high-temperature side to the low-temperature side of the thermoelectric conversion element increases from Q to Q+ΔQ according to the Peltier effect, and the thermal resistance R... TEG A change occurs. At this time, the thermal resistance of the thermoelectric conversion module 11a when the current is 0 is set to r. TEG0 When the Peltier coefficient is set to Π, the heat Q flowing through the thermoelectric conversion module 11a is as shown in the following formula (3).

[0079] Q=∏×I+ΔT / r TEG0 …(3)

[0080] Therefore, the thermal resistance R of the thermoelectric conversion module 11a TEG As shown in equation (4) below.

[0081] R TEG =ΔT / Q=ΔT / (∏I+ΔT / r) TEG0 (4)

[0082] That is, when the current is increased by ΔI, the thermal resistance R TEG It is reduced according to the above formula (4).

[0083] Like this, because of the thermal resistance R of the thermoelectric conversion module 11a TEG Due to variations in current and the individual heat capacities of the high-temperature heat exchanger 11b and the low-temperature heat exchanger 11c, there is a delay before the temperature difference involved in the thermoelectric conversion element reaches equilibrium. Consequently, the response of the thermoelectric electromotive force of the thermoelectric conversion module 11a is also delayed.

[0084] Figure 5 This is a diagram illustrating an example of the transient characteristics of the electrical power P output from the thermoelectric converter 11 when the current to the thermoelectric converter 11 is increased by ΔI (when the current is disturbed by +ΔI using the hill-climbing method). Figure 5 In the diagram, the vertical axis represents the power value, and the horizontal axis represents the current value.

[0085] in addition, Figure 6 This is a diagram illustrating an example of the current-voltage characteristics of the thermoelectric conversion device 11 at thermal equilibrium. Figure 6 In the diagram, the vertical axis represents the voltage value, and the horizontal axis represents the current value.

[0086] in addition, Figure 7 This is a diagram illustrating an example of the voltage characteristics of the thermoelectric converter 11 when the current of the thermoelectric converter 11 is increased by ΔI (when the current is perturbed by +ΔI using the hill-climbing method). Figure 7 In the diagram, the vertical axis represents the voltage value, and the horizontal axis represents the time.

[0087] Assuming Vpmax I pmax The maximum power at thermal equilibrium is represented by electrical power P. max (Refer to Figure 5 ), when the current I is made to flow from I pmax Increase ΔI to I pmax At +ΔI, the voltage V gradually approaches V from the instant the current increases, according to the current-voltage characteristics of the thermoelectric conversion device 11 at thermal equilibrium. pmax -ΔV (reference) Figure 6 and Figure 7 Here, the time constant during the gradual approach is the thermal time constant T.

[0088] At this time, Figure 2 In step ST12 of the flowchart shown, if the waiting time (control cycle t) is shorter than the thermal time constant T, then... Figure 2 The voltage V measured in step ST13 of the flowchart shown becomes Figure 6 and Figure 7 V1 shown is the value of the voltage V at specific heat equilibrium. pmax -ΔV_high value.

[0089] Regarding making the current I from I pmax Increase ΔI to I pmax The value of voltage V at +ΔI can be used to gradually approach V as the thermal time constant T approaches V. pmax -ΔV is expressed by the following formula (5).

[0090]

[0091] For example, when the control period t is 1 / 100 of the thermal time constant T, the voltage V is as follows when 1 / 100 is substituted into t / T in equation (5).

[0092] V = V pmax -0.01×ΔV

[0093] Therefore, the voltage V becomes approximately the same as V pmax The same value, specific to V at thermal equilibrium pmax The value of -ΔV is measured as voltage V. In this case, at Figure 2 The electrical power P calculated in step ST13 of the flowchart shown is as follows.

[0094]

[0095] As mentioned above, the calculated electrical power P is higher than the maximum power V at thermal equilibrium. pmax I pmax Therefore, in Figure 2 In step ST14 of the flowchart shown, P>P' is true (i.e., corresponding to the step from...). Figure 2 The illustrated step ST14 branch "Yes" enters... Figure 2 Step ST15 of the flowchart shown.

[0096] Then, in Figure 2 In step ST15 of the flowchart shown, the value ΔI of the current that was changed in step ST11 in the next cycle is made to be the same value ΔI as in the previous step ST11, so that the process returns to the previous step in the subsequent process. Figure 2 In step ST11 of the flowchart shown, the value of the current output from the thermoelectric converter 11 to the power conversion unit 12d changes from I... pmax +ΔI changes to I pmax +2ΔI, the current I is further greater than I pmax .

[0097] Furthermore, in repeated practice Figure 2 During the cyclical process of steps ST11 to ST17 in the flowchart shown, the temperature difference involved in the thermoelectric conversion module 11a (thermoelectric conversion element) decreases and the electromotive force decreases as time passes. Therefore, in Figure 2 In step ST14 of the flowchart shown, P>P' no longer true (i.e., corresponding to the step from...). Figure 2 The illustrated step ST14 branch "No" will proceed to... Figure 2 Step ST16 of the flowchart shown.

[0098] Then, in Figure 2 In step ST16 of the flowchart shown, the value ΔI of the current change in step ST11 in the next cycle is made to be the value with the opposite sign (same absolute value) -ΔI, so that the subsequent process returns to the previous step ST11. Figure 2 In step ST11 of the flowchart shown, the value of the current output from the thermoelectric converter 11 to the power conversion unit 12d changes from I... pmax +ΔI changes to I pmax .

[0099] As described above, the value of the current output from the thermoelectric conversion device 11 to the power conversion unit 12d is greater than I. pmax The cycle repeats repeatedly around the value of large ΔI, therefore... Figure 2 In step ST13 of the flowchart shown, the measured electrical power P is less than the maximum power at thermal equilibrium, i.e., the electrical power P max .

[0100] On the other hand, the following will also explain the case in which the current of the thermoelectric conversion device 11 is reduced by ΔI.

[0101] Figure 8This is a diagram illustrating an example of the transient characteristics of the electrical power P output from the thermoelectric converter 11 when the current to the thermoelectric converter 11 is reduced by ΔI (when the current is disturbed by -ΔI using the hill-climbing method). Figure 8 In the diagram, the vertical axis represents the power value, and the horizontal axis represents the current value.

[0102] in addition, Figure 9 This is a diagram illustrating an example of the current-voltage characteristics of the thermoelectric conversion device 11 at thermal equilibrium. Figure 9 In the diagram, the vertical axis represents the voltage value, and the horizontal axis represents the current value.

[0103] in addition, Figure 10 This is a diagram illustrating an example of the voltage characteristics of the thermoelectric converter 11 when the current is reduced by ΔI (when the current is perturbed by -ΔI using the hill-climbing method). Figure 10 In the diagram, the vertical axis represents the voltage value, and the horizontal axis represents the time.

[0104] Assuming V pmax I pmax The maximum power at thermal equilibrium is represented by electrical power P. max (Refer to Figure 8 ), when the current I is made to flow from I pmax +ΔI decreases ΔI to I pmax At that moment, the voltage V, starting from the instant the current decreases, follows the current-voltage characteristics of the thermoelectric conversion device 11 at thermal equilibrium (refer to...). Figure 9 And gradually approaching V pmax Here, the time constant during the gradual approach is the thermal time constant T.

[0105] In this case, Figure 2 In step ST12 of the flowchart shown, when the waiting time (control cycle t) is shorter than the thermal time constant T, Figure 2 The voltage V measured in step ST13 of the flowchart shown becomes Figure 9 and Figure 10 V1 shown is the value of the voltage V at specific heat equilibrium. pmax Low value.

[0106] For example, when the control period t is 1 / 100 of the thermal time constant T, the voltage V becomes approximately the same as V. pmax -ΔV is the same value, compared to V at thermal equilibrium. pmax The lower value is measured as voltage V. In this case, at Figure 2 The electrical power P calculated in step ST13 of the flowchart shown is as follows.

[0107]

[0108] As mentioned above, the calculated electrical power P is lower than the maximum power V at thermal equilibrium.pmax I pmax Therefore, in Figure 2 In step ST14 of the flowchart shown, P>P' no longer true (i.e., corresponding to the step from...). Figure 2 The illustrated step ST14 branch "No" will proceed to... Figure 2 Step ST16 of the flowchart shown.

[0109] Then, in Figure 2 In step ST16 of the flowchart shown, the value ΔI of the current change in step ST11 in the next cycle is made to be the value with the opposite sign (same absolute value) + ΔI, which is the same as the value in the previous step ST11. Therefore, in the subsequent process, it returns to... Figure 2 In step ST11 of the flowchart shown, the value of the current output from the thermoelectric converter 11 to the power conversion unit 12d changes from I... pmax Change to I pmax +ΔI.

[0110] Furthermore, in repeated practice Figure 2 During the cycle of steps ST11 to ST17 in the flowchart shown, the temperature difference involved in the thermoelectric conversion module 11a (thermoelectric conversion element) decreases and the electromotive force decreases as time passes.

[0111] Therefore, the value of the current output from the thermoelectric converter 11 to the power conversion unit 12d is greater than I. pmax The cycle repeats repeatedly around the value of large ΔI, so in Figure 2 The measured electrical power P in step ST13 of the flowchart shown is less than the maximum power at thermal equilibrium, i.e., the electrical power Pmax max .

[0112] As mentioned above, when the control period t is shorter than the thermal time constant T of the thermoelectric converter 11, the electrical power P (output power) output from the thermoelectric converter 11 is lower than the maximum output at thermal equilibrium (steady state).

[0113] Therefore, by setting the control period t to a value near the thermal time constant T, a power characteristic close to that of the thermoelectric converter 11 in thermal equilibrium (steady state) can be obtained, which can maximize the electrical power P (output power) output from the thermoelectric converter 11.

[0114] On the other hand, when the control period t is much larger than the thermal time constant T, if the heat source on the high-temperature side or the heat source on the low-temperature side changes with a period longer than the thermal time constant T and shorter than the control period t, sometimes the electrical power P output from the thermoelectric converter 11 cannot keep up with the temperature change and remains at the maximum power, i.e., the electrical power P max The deviation value. Therefore, the electrical power P output from the thermoelectric converter 11 is lower than the electrical power P0. max .

[0115] Therefore, in order to maximize the electrical power P output from the thermoelectric converter 11, the control period t is preferably a value near the thermal time constant T of the thermoelectric converter 11. By setting the control period t to a value near the thermal time constant T, the electrical power P output from the thermoelectric converter 11 can be maximized even for heat sources with varying temperature differences.

[0116] <Second Implementation Method>

[0117] The power control device, thermoelectric power generation system, and power control method of this embodiment will be described. Furthermore, in the following description, the same reference numerals are used to illustrate the same components as those described in the above-described embodiments, and detailed descriptions thereof will be omitted as appropriate.

[0118] <On the structure of thermoelectric power generation systems>

[0119] Figure 11 This is a diagram illustrating an example of the structure of a thermoelectric power generation system according to this embodiment. (See diagram for example.) Figure 11 As illustrated, the thermoelectric power generation system 101 includes a thermoelectric conversion device 11, a power control device 22 for controlling the electrical power output from the thermoelectric conversion device 11, and a load 13. The load 13 includes a constant voltage source such as a battery.

[0120] The power control device 22 includes a thermal time constant acquisition unit 22a, a power measurement unit 22b, a power conversion control unit 22c, and a power conversion unit 22d.

[0121] The power control device 22 is connected to the positive and negative terminals of the thermoelectric conversion device 11. Furthermore, the electrical power generated by the thermoelectric conversion device 11 is input to the power control device 22.

[0122] In addition, a load 13 is connected to the power control device 22. Furthermore, the electrical power converted by the power conversion unit 22d is output to the load 13.

[0123] Regarding the power conversion unit 22d, a positive and a negative terminal are provided on the input side, which are respectively connected to the positive and negative terminals of the thermoelectric converter 11. Furthermore, the electrical power generated by the thermoelectric converter 11 is input to the power conversion unit 22d.

[0124] Similarly, the power conversion unit 22d also has a positive and a negative terminal on the output side, which are connected to the positive and negative terminals of the load 13, respectively. Furthermore, the electrical power converted by the power conversion unit 22d is output to the load 13.

[0125] The load of the power converter 22d as observed from the input terminal of the power converter 22d can be changed by controlling the on-off time ratio (duty cycle) of the switching element of the power converter 22d.

[0126] A thermal time constant acquisition unit 22a, a power measurement unit 22b, and a power conversion unit 22d are connected to the power conversion control unit 22c.

[0127] Figure 1 The illustrated thermal time constant acquisition unit 12a uses thermocouples or the like to directly detect the temperature of the high-temperature side and the low-temperature side of the thermoelectric conversion module 11a. In contrast, the thermal time constant acquisition unit 22a of this embodiment is connected to the power measurement unit 22b and calculates the thermal time constant T solely based on the power measurement results (electrical data) sent from the power measurement unit 22b. Furthermore, the thermal time constant acquisition unit 22a sends the calculated thermal time constant T to the power conversion control unit 22c.

[0128] The power measurement unit 22b measures the electrical power output from the thermoelectric converter 11 by measuring the current and voltage output from the thermoelectric converter 11. Furthermore, the power measurement unit 22b sends the measured electrical power as power data to the thermal time constant acquisition unit 22a and the power conversion control unit 22c.

[0129] The power conversion control unit 22c performs maximum output control of the electrical power output from the thermoelectric conversion device 11 based on the input thermal time constant T and electrical data.

[0130] <Regarding the operation of power control devices in thermoelectric power generation systems>

[0131] The operation of the power control device 22 in this embodiment (mainly the maximum output control performed by the power conversion control unit 22c) and Figure 2 The example work is the same.

[0132] However, when obtaining the thermal time constant in step ST10, the power control device 22 obtains the thermal time constant according to the following procedure.

[0133] Figure 12 This is a flowchart illustrating an example of how the power control device 22 operates to obtain the thermal time constant.

[0134] First, in step ST120, the positive and negative electrodes of the thermoelectric conversion device 11 are short-circuited and a certain time is waited. This time is any value that is preset, but in order to obtain an accurate thermal time constant T, it is preferable to be a length longer than the thermal time constant T. When there is a previously measured thermal time constant T, the waiting time in step ST120 can be approximately three times that time.

[0135] Next, in step ST121, the thermoelectric conversion device 11 is made into an open circuit state momentarily, and the transient characteristics of the voltage V between the positive and negative terminals of the thermoelectric conversion device 11 are obtained over a certain period of time.

[0136] Next, in step ST122, the time constant is obtained based on the time change of the voltage V of the thermoelectric converter 11 after a certain period of time following the opening of the thermoelectric converter 11.

[0137] Figure 13 This is a diagram illustrating an example of the transient characteristics of the voltage of the thermoelectric converter 11 when it changes from a short-circuit state to an open-circuit state. Figure 13 In the diagram, the vertical axis represents the voltage value, and the horizontal axis represents the time.

[0138] like Figure 13 As illustrated, when the voltage V that has just become open-circuit is set to V... oc1 Let V be the voltage V at which the temperature of the thermoelectric converter 11 stabilizes after a sufficiently long period of time following the change to an open circuit state. oc2 When the voltage V is t, the theoretical curve of the voltage V with respect to time t can be represented by the following equation (6).

[0139]

[0140] Furthermore, by using the least squares method or similar methods to fit the time constant to the transient characteristics of the measured V using the above formula (6), the thermal time constant T of the thermoelectric conversion device 11 can be obtained.

[0141] Due to the Seebeck effect, the electromotive force of the thermoelectric converter 11 is proportional to the temperature difference ΔT between the high-temperature side and the low-temperature side of the thermoelectric converter 11. Therefore, the time response of the voltage value exhibits the same behavior as the time response of the temperature difference ΔT.

[0142] Therefore, the time constant of the voltage value can be regarded as the thermal time constant T as is, so the thermal time constant T can be obtained by voltage measurement alone.

[0143] Therefore, without the need for additional hardware such as thermocouples for thermal measurement, the thermal time constant T of the thermoelectric converter 11 can be obtained solely through power measurement by the power measurement unit 22b. Thus, the electrical power output from the thermoelectric converter 11 can be maximized inexpensively and easily.

[0144] Furthermore, in this embodiment, the thermal time constant T is obtained by changing the thermoelectric conversion device 11 from a short-circuit state to an open-circuit state, but the thermal time constant T can also be obtained by changing the current value ΔI based on the transient characteristics of the voltage value at that time.

[0145] <Third Implementation Method>

[0146] The power control device, thermoelectric power generation system, and power control method of this embodiment will be described. Furthermore, in the following description, the same reference numerals are used to illustrate the same components as those described in the above-described embodiments, and detailed descriptions thereof will be omitted as appropriate.

[0147] In the embodiments described above, the power control device 12 (or power control device 22) can also perform maximum output control by controlling the load 13 to vary.

[0148] Figure 14 This is a flowchart illustrating an example of the operation of a power control device (primarily maximum output control performed by the power conversion control unit 12c). Furthermore, in Figure 14 The control described is performed by power control device 12, but it can also be replaced by control performed by power control device 22.

[0149] First, in step ST310, the thermal time constant acquisition unit 12a calculates and acquires the thermal time constant T of the thermoelectric conversion device 11.

[0150] Next, in step ST311, the value of load 13 is changed from R to R+ΔR.

[0151] Next, in step ST312, a time corresponding to the thermal time constant T obtained in step ST310 is waited. Since the value of load 13 is changed from R to R+ΔR in step ST311, the thermal equilibrium of the thermoelectric converter 11 is temporarily disrupted.

[0152] Therefore, in response to the system, the system is allowed to wait for any constant multiple of time T, such as T or 3T, to achieve thermal stability.

[0153] Next, in step ST313, the power measuring unit 12b measures the electrical power P (output power) output from the thermoelectric converter 11. The power measuring unit 12b measures the voltage V output from the thermoelectric converter 11 and the current I output from the thermoelectric converter 11, and calculates the electrical power according to the formula: electrical power P = voltage V × current I.

[0154] Next, in step ST314, the electrical power P measured in step ST313 is compared with the electrical power P' measured in the previous cycle's step ST313. Furthermore, when step ST314 is the first cycle, the electrical power P' is set to 0 for this comparison.

[0155] Then, when P>P', that is, corresponding to from Figure 14When the illustrated step ST314 branch is "Yes", the process proceeds to step ST315. On the other hand, when P is not P>P', i.e., corresponding to... Figure 14 When the "No" condition is met in the illustrated step ST314 branch, the process proceeds to step ST316.

[0156] In step ST315, it is determined that the value ΔR of the load change in step ST311 in the next cycle will be the same as the value ΔR in the previous step ST311. Then proceed to step ST317.

[0157] In step ST316, it is determined that the value ΔR of the load change in step ST311 in the next cycle will be a value with the opposite sign (same absolute value) -ΔR. Then proceed to step ST317.

[0158] Next, in step ST317, the electrical power P measured in step ST313 is updated as the value used as the electrical power P' in step ST314 of the next cycle. Then, the process returns to step ST311.

[0159] Through these processes, the power control device 12 performs cyclical control that repeatedly cycles around the current value that maximizes the electrical power output from the thermoelectric conversion device 11.

[0160] When the load value 13 is kept constant, even if the temperature of the heat source or cooling source changes, compared to... Figure 2 In the subsequent cycles following step ST11, the current value is kept constant, which also keeps the electrical power output from the thermoelectric converter 11 near its maximum power.

[0161] If the current value is kept constant when the temperature of the heat source or cooling source changes, the electromotive force changes proportionally to the temperature difference, so the deviation from the maximum power point caused by temperature changes becomes larger.

[0162] In contrast, if the load 13 is kept constant, and the internal resistance of the thermoelectric converter 11 remains unchanged, there will be no shift from the maximum power point.

[0163] In reality, the internal resistance of the thermoelectric conversion element tends to increase as the temperature rises, but this effect is generally small. Therefore, compared to control that keeps the current value constant, control that keeps the load 13 constant results in greater electrical power output from the thermoelectric conversion device 11. Thus, compared to the case where the current value is kept constant during the control period t, the electrical power output from the thermoelectric conversion device 11 can be increased.

[0164] <Hardware Structure of Power Control Device in Thermoelectric Power Generation Systems>

[0165] Figure 15 and Figure 16 This is a general example. Figure 1 and Figure 11 The illustrated diagram shows the hardware structure of the thermoelectric power generation system (especially the power control device) in actual use.

[0166] In addition, regarding Figure 15 and Figure 16 The illustrated hardware structure and Figure 1 and Figure 11 The illustrated structures sometimes have mismatched quantities, etc., because... Figure 1 and Figure 11 The illustrated structures are derived from conceptual units.

[0167] Therefore, at least it can be assumed Figure 1 and Figure 11 The illustrated structure consists of Figure 15 and Figure 16 The examples illustrate the configuration of multiple hardware structures. Figure 1 and Figure 11 The example structure and Figure 15 and Figure 16 The illustrated part of the hardware structure corresponds to the following situation, and then Figure 1 and Figure 11 The illustrated structures are set in Figure 15 and Figure 16 The example illustrates one hardware architecture.

[0168] Figure 15 The diagram shows a processing circuit 1102A that performs calculations and a storage device 1103 that can store information, as a means of implementing... Figure 1 China and Figure 11 The hardware structure of the thermal time constant acquisition unit 12a, thermal time constant acquisition unit 22a, power measurement unit 12b, power conversion control unit 12c, power conversion control unit 22c, power conversion unit 12d, and power conversion unit 22d is described. These structures are the same in other embodiments.

[0169] Figure 16 The diagram shows a processing circuit 1102B that performs calculations, used for implementing... Figure 1 and Figure 11 The hardware structure of the thermal time constant acquisition unit 12a, thermal time constant acquisition unit 22a, power measurement unit 12b, power conversion control unit 12c, power conversion control unit 22c, power conversion unit 12d, and power conversion unit 22d is described. This structure is the same in other embodiments.

[0170] The storage of thermal time constant in thermal time constant acquisition unit 12a, thermal time constant in thermal time constant acquisition unit 22a, electrical power measured in power measurement unit 12b, or electrical power measured in power measurement unit 22b can be realized by using storage device 1103 or other storage device (not shown here).

[0171] Storage device 1103 may be, for example, a storage medium (storage medium) including volatile or non-volatile semiconductor memories such as hard disk drive (HDD), random access memory (RAM), read only memory (ROM), flash memory, erasable programmable read only memory (EPROM) and electrically erasable programmable read-only memory (EEPROM), disks, floppy disks, optical disks, compact disks, mini disks or DVDs, or any storage medium to be used in the future.

[0172] The processing circuit 1102A can execute programs stored in the storage device 1103, an external CD-ROM, an external DVD-ROM, or an external flash memory, etc. That is, it can be, for example, a central processing unit (CPU), a microprocessor, a microcomputer, or a digital signal processor (DSP).

[0173] When the processing circuit 1102A executes a program stored in the storage device 1103, an external CD-ROM, an external DVD-ROM, or an external flash memory, the thermal time constant acquisition unit 12a, thermal time constant acquisition unit 22a, power measurement unit 12b, power measurement unit 22b, power conversion control unit 12c, power conversion control unit 22c, power conversion unit 12d, and power conversion unit 22d can be implemented by the cooperation of multiple processing circuits.

[0174] The software and firmware can be described as programs and stored in the storage device 1103. In this case, the processing circuit 1102A implements the above-mentioned functions by reading and executing the programs stored in the storage device 1103. That is, the storage device 1103 can store programs that, when executed by the processing circuit 1102A, result in the implementation of the above-mentioned functions.

[0175] Additionally, the processing circuit 1102B can be dedicated hardware. That is, it can be, for example, a single circuit, a composite circuit, a programmable processor, a parallel programmable processor, an integrated circuit (application-specific integrated circuit, i.e., ASIC), a field-programmable gate array (FPGA), or a circuit composed of these.

[0176] When the processing circuit 1102B is dedicated hardware, the operation of the processing circuit 1102B enables the thermal time constant acquisition unit 12a, thermal time constant acquisition unit 22a, power measurement unit 12b, power measurement unit 22b, power conversion control unit 12c, power conversion control unit 22c, power conversion unit 12d, and power conversion unit 22d to perform the functions of the thermal time constant acquisition unit 12a, thermal time constant acquisition unit 22a, power measurement unit 12b, power measurement unit 22b, power conversion control unit 12c, power conversion control unit 22c, power conversion unit 12d, and power conversion unit 22d to perform the functions of different circuits or a single circuit.

[0177] Furthermore, the functions of the thermal time constant acquisition unit 12a, thermal time constant acquisition unit 22a, power measurement unit 12b, power measurement unit 22b, power conversion control unit 12c, power conversion control unit 22c, power conversion unit 12d, and power conversion unit 22d can be partially implemented in the processing circuit 1102A that executes the program stored in the storage device 1103, and partially implemented in the processing circuit 1102B that is dedicated hardware.

[0178] <Regarding the effects produced by the above-described implementation methods>

[0179] The following examples illustrate the effects produced by the embodiments described above. Furthermore, although the effects are described in the following description based on the specific structures illustrated in the embodiments described above, other specific structures illustrated in this specification may be substituted to produce the same effects. That is, for convenience, sometimes only one of the corresponding specific structures is described, but the described specific structure may be replaced with other corresponding specific structures.

[0180] Furthermore, this substitution can be performed across multiple implementations. That is, it can be a case where combining various structures exemplified in different implementations produces the same effect.

[0181] According to the embodiments described above, the power control device includes: a power measuring unit 12b (or power measuring unit 22b) for measuring the electrical power output from the thermoelectric converter 11; and a control unit for controlling the electrical power output from the thermoelectric converter 11. Here, the control unit corresponds to at least one of, for example, a power conversion control unit 12c or a power conversion control unit 22c. The thermoelectric converter 11 generates electricity based on heat. Furthermore, the thermoelectric converter 11 outputs electrical power. Here, after a change in the load on the output of the thermoelectric converter 11 and after a time corresponding to the thermal time constant of the thermoelectric converter 11 has elapsed, the power measuring unit 12b measures the electrical power output from the thermoelectric converter 11.

[0182] Furthermore, according to the embodiments described above, the power control device includes: a processing circuit 1102A for executing a program; and a storage device 1103 for storing the executed program. Moreover, the following operations are achieved by executing the program through the processing circuit 1102A.

[0183] That is, after the load on the output of the thermoelectric converter 11 changes and a time corresponding to the thermal time constant of the thermoelectric converter 11 has elapsed, the electrical power output from the thermoelectric converter 11 is measured.

[0184] Furthermore, according to the embodiments described above, the power control device includes a processing circuit 1102B as dedicated hardware. Moreover, the processing circuit 1102B, as dedicated hardware, performs the following operations.

[0185] That is, after the load on the output of the thermoelectric converter 11 changes and a time corresponding to the thermal time constant of the thermoelectric converter 11 has elapsed, the processing circuit 1102B, which is dedicated hardware, measures the electrical power output from the thermoelectric converter 11.

[0186] Based on this structure, after a time corresponding to the thermal time constant T has elapsed, the electrical power output from the thermoelectric converter 11 is measured, which can increase the electrical power P (extracted power) output from the thermoelectric converter 11.

[0187] Furthermore, the same effect can be achieved even when other structures illustrated in this application specification are added to the above structure as appropriate, that is, when other structures in this application specification not mentioned as the above structure are added as appropriate.

[0188] Furthermore, according to the embodiment described above, the power conversion control unit 12c searches for the maximum value of the electrical power output from the thermoelectric converter 11 based on the measured electrical power of the thermoelectric converter 11. With this structure, by repeatedly performing searches that vary the load on the output of the thermoelectric converter 11 using methods such as hill climbing, the maximum power output from the thermoelectric converter 11 can be found.

[0189] Furthermore, according to the embodiment described above, the power conversion control unit 12c changes the current value output from the thermoelectric converter 11 by varying the load on the output of the thermoelectric converter 11, and maintains the current value output from the thermoelectric converter 11 at a constant value during the time corresponding to the thermal time constant T. With this structure, by measuring the electrical power output from the thermoelectric converter 11 after the time corresponding to the thermal time constant T has elapsed, the electrical power P (extracted power) output from the thermoelectric converter 11 can be maximized.

[0190] Furthermore, according to the embodiment described above, the power conversion control unit 12c causes the load on the output of the thermoelectric converter 11 to vary, and maintains the load constant for a period of time corresponding to the thermal time constant of the thermoelectric converter 11. With this structure, even if the temperature of the heat source or cooling source varies, the electrical power output from the thermoelectric converter 11 can be maintained near its maximum power. Moreover, by measuring the electrical power output from the thermoelectric converter 11 after a period corresponding to the thermal time constant T, the electrical power P (extracted power) output from the thermoelectric converter 11 can be maximized.

[0191] Furthermore, according to the embodiment described above, the power control device 22 includes a thermal time constant acquisition unit 22a. This thermal time constant acquisition unit 22a changes the current value output from the thermoelectric converter 11 and acquires the thermal time constant of the thermoelectric converter 11 based on the time change of the voltage value output from the thermoelectric converter 11. With this structure, by short-circuiting the positive and negative terminals of the thermoelectric converter 11 and waiting for a certain time before opening the thermoelectric converter 11 again, and measuring the time change of the voltage value output from the thermoelectric converter 11, the time response of the temperature difference ΔT and the time response of the voltage value exhibit the same behavior. Therefore, even without acquiring the thermal time constant T through thermal measurement of the thermoelectric converter 11, it is possible to acquire the thermal time constant T.

[0192] Furthermore, according to the embodiment described above, the power measurement unit 12b obtains the internal resistance of the thermoelectric converter 11 based on the current and voltage values ​​output from the thermoelectric converter 11. With this structure, an accurate internal resistance of the thermoelectric converter 11 (including the thermal resistance between the surface of the thermoelectric converter module 11a on the high-temperature side (or low-temperature side) and the fixed temperature point on the high-temperature side (or low-temperature side)) can be measured, thus enabling effective control of the maximum power of the thermoelectric converter 11.

[0193] <Variations on the implementation methods described above>

[0194] In the embodiments described above, the material, size, shape, relative configuration, or implementation conditions of each component are sometimes described, but these are only examples in all respects and are not limiting.

[0195] Therefore, within the scope of the technology disclosed in this application, numerous variations and equivalents not illustrated are contemplated. For example, these include variations of at least one constituent element, addition of at least one constituent element, omission of at least one constituent element, and extraction of at least one constituent element from at least one embodiment combined with constituent elements from other embodiments.

[0196] Furthermore, in the embodiments described above, if the material name is described without special specification, it includes the presence of other additives, such as alloys, in the material, as long as there is no contradiction.

[0197] Furthermore, as long as there is no contradiction, the constituent element described as having "1" in the above-described implementation method can also have "more than 1".

[0198] Furthermore, each constituent element in the above-described embodiments is a conceptual unit. Within the scope of the technology disclosed in this application, it includes cases where one constituent element is composed of multiple structures, cases where one constituent element corresponds to a part of a certain structure, and cases where multiple constituent elements are disposed in one structure.

[0199] Furthermore, among the constituent elements in the embodiments described above, those that perform the same function include structures with other structures or shapes.

[0200] Furthermore, any descriptions in this application specification are referenced for all purposes related to this technology and should not be considered prior art.

[0201] Furthermore, the various constituent elements described in the above-described embodiments are conceived as both software or firmware and corresponding hardware. Under both concepts, each constituent element is referred to as a "section" or "processing circuit" or the like.

[0202] Furthermore, regarding the storage of the thermal time constant in the thermal time constant acquisition unit 12a, the storage of the thermal time constant in the thermal time constant acquisition unit 22a, the storage of the electrical power measured in the power measurement unit 12b, or the storage of the electrical power measured in the power measurement unit 22b, etc., in Figure 1 and Figure 11 The components are referred to as being installed within a thermoelectric power generation system, but at least one of them can be an external functional unit. In this case, the function of the thermoelectric power generation system can be achieved as a whole through the interaction of other functional units within the thermoelectric power generation system and external functional units.

Claims

1. A power control device that controls electric power output from a thermoelectric conversion device that generates electric power based on heat, the power control device comprising: a power measurement section that measures electric power output from the thermoelectric conversion device; and a control section that controls electric power output from the thermoelectric conversion device, wherein the power measurement section measures electric power output from the thermoelectric conversion device after a lapse of a time corresponding to a thermal time constant of the thermoelectric conversion device after a load on output from the thermoelectric conversion device is changed, and the power control device further comprises a thermal time constant acquisition section that changes a current value output from the thermoelectric conversion device and acquires the thermal time constant of the thermoelectric conversion device from a temporal change in a voltage value output from the thermoelectric conversion device.

2. The power control device according to claim 1, wherein the control section searches for a maximum value of electric power output from the thermoelectric conversion device based on the measured electric power of the thermoelectric conversion device.

3. The power control device according to claim 1 or 2, wherein the control section changes the current value output from the thermoelectric conversion device by changing the load on output from the thermoelectric conversion device and holds the current value output from the thermoelectric conversion device constant for a time corresponding to the thermal time constant of the thermoelectric conversion device.

4. The power control device according to claim 1 or 2, wherein the control section changes the load on output from the thermoelectric conversion device and holds the load constant for a time corresponding to the thermal time constant of the thermoelectric conversion device.

5. The power control device according to claim 1 or 2, wherein the power measurement section acquires an internal resistance of the thermoelectric conversion device based on the current value and the voltage value output from the thermoelectric conversion device.

6. The power control device according to claim 3, wherein the power measurement section acquires an internal resistance of the thermoelectric conversion device based on the current value and the voltage value output from the thermoelectric conversion device.

7. The power control device according to claim 4, wherein the power measurement section acquires an internal resistance of the thermoelectric conversion device based on the current value and the voltage value output from the thermoelectric conversion device.

8. A thermoelectric power generation system comprising: a thermoelectric conversion device that generates electric power based on heat and outputs electric power; and a power control device that measures electric power output from the thermoelectric conversion device and controls electric power output from the thermoelectric conversion device, wherein the power control device measures electric power output from the thermoelectric conversion device after a lapse of a time corresponding to a thermal time constant of the thermoelectric conversion device after a load on output from the thermoelectric conversion device is changed. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The power control device includes a thermal time constant acquisition unit that causes a variation in a current value output from the thermoelectric conversion device and acquires the thermal time constant of the thermoelectric conversion device based on a temporal change in a voltage value output from the thermoelectric conversion device.

9. A power control method of controlling electric power output from a thermoelectric conversion device that generates electric power based on heat, wherein measuring electric power output from the thermoelectric conversion device, controlling electric power output from the thermoelectric conversion device, measuring electric power output from the thermoelectric conversion device after a lapse of a time corresponding to a thermal time constant of the thermoelectric conversion device after a variation in a load on output from the thermoelectric conversion device, causing a variation in a current value output from the thermoelectric conversion device and acquiring the thermal time constant of the thermoelectric conversion device based on a temporal change in a voltage value output from the thermoelectric conversion device.

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