Power control device, power control method, and power production method

Abstract

To provide a power control device and a power control method capable of supplying maximum power by measuring the internal impedance or internal conductance of a power supply during power supply operation.SOLUTION: A power control device (10) includes a converter (1) equipped with a first switching element (Q1) capable of supplying and interrupting power supply from a power supply (TMG) and a second switching element (Q2) capable of shorting across the power supply, a first voltage detector (5) that outputs an input voltage value, a first current detector (7) that outputs an input current value, a second voltage detector (6) that outputs an output voltage value, a second current detector (8) that outputs an output current value, resistance value calculators (31, 32) that calculate a resistance value of the power supply using the input voltage value and the input current value, a resistance value updater (38) that updates the resistance value when the output power is output, and control units (33 to 36) for turning on and off the first switch element and the second switch element.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present application relates to a power control device. 、 Power Control Method and electricity production method This is regarding. [Background technology]

[0002] Conventional methods for controlling a thermoelectric conversion device include a method for searching for an optimal operating point by varying the output current of the thermoelectric conversion device at any control period using a hill-climbing method in order to maximize the output from the thermoelectric conversion device (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-055769 A Summary of the Invention [Problem to be solved by the invention]

[0004] In such a control method for a thermoelectric converter, if the control period is shorter than the thermal time constant of the thermoelectric converter, it is difficult to accurately obtain the maximum power point of the thermoelectric converter, resulting in a problem that the extracted power is lower than the maximum output power of the thermoelectric converter.

[0005] The present disclosure has been made in consideration of the above-described problems, and provides a technology for increasing the power extracted from a thermoelectric conversion device, and a power control device capable of supplying maximum power. 、 Power Control Method and electricity production method The purpose is to provide. [Means for solving the problem]

[0006] The power control device according to the present disclosure is a power control device including a power conversion circuit that converts power output from a thermoelectric conversion module and a control unit that controls the power conversion circuit, and the control unit calculates an internal resistance of the thermoelectric conversion module using an input current and an input voltage of the power conversion circuit. The composite value of and a reference point resistance value calculation unit that calculates a combined value of internal resistances of the thermoelectric conversion module using an input current and an input voltage of the power conversion circuit while power is supplied from the thermoelectric conversion module to the power conversion circuit, wherein the power conversion of the power output from the thermoelectric conversion module in the power conversion circuit is controlled so that the combined value of the internal resistances calculated by the operating point resistance value calculation unit approaches the reference point resistance value calculated by the reference point resistance value calculation unit, and the control unit further includes a resistance value update unit that identifies an operating point at which a value of the output power output from the power conversion circuit is maximized and updates the reference point resistance value, The combined value of the internal resistances calculated by the operating point resistance value calculation unit is The reference point resistance value updated by the resistance value update unit To value Get closer Before The power conversion of the power output from the thermoelectric conversion module is controlled.

[0007] The power control method according to the present disclosure includes: A power control method for controlling power output from a thermoelectric conversion module, comprising: supplying power from the thermoelectric conversion module to a power conversion circuit; and calculating an internal resistance of the thermoelectric conversion module using an input current and an input voltage of the power conversion circuit. The composite value of a first step of calculating an initial value of the internal resistance of the thermoelectric conversion module and setting it as a reference point; a second step of calculating a composite value of the internal resistance of the thermoelectric conversion module using an input current and an input voltage of the power conversion circuit while power is being supplied from the thermoelectric conversion module to the power conversion circuit, and controlling the power conversion of the power output from the thermoelectric conversion module so that the composite value of the internal resistance approaches the reference point; a third step of confirming that the temperature change of the thermoelectric conversion module has stabilized; The composite value of While increasing from the initial value, the internal resistance at which the output power of the power conversion circuit is maximized by the hill-climbing method is found. The composite value ofA fourth step of searching for an internal resistance at which the output power of the power conversion circuit is maximized. The composite value of and a fifth step of setting the reference point as the updated reference point. Effect of the Invention

[0008] According to at least the first aspect of the technique disclosed in the present specification, a power control device capable of increasing the power output (extracted power) from a thermoelectric conversion device and supplying maximum power is provided. 、 Power Control Method and electricity production method can be provided. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating a configuration example of a power control device according to a first embodiment of the present disclosure. [Diagram 2] 1A to 1C are diagrams illustrating an example of the voltage-current characteristics of a thermoelectric conversion module and changes in the voltage-current characteristics due to the Peltier effect. [Diagram 3] 1A to 1C are diagrams illustrating an example of the power-current characteristics of a thermoelectric conversion module and changes in the power-current characteristics due to the Peltier effect. [Figure 4] 1A to 1C are diagrams illustrating an example of the power-resistance characteristics of a thermoelectric conversion module and changes in the power-resistance characteristics due to the Peltier effect. [Diagram 5] 4 is a diagram illustrating an example of a method for updating a composite value in the power control device according to the first embodiment of the present disclosure. FIG. [Figure 6] 10A and 10B are diagrams illustrating a difference in current amount occurring between preceding and following maximum power points. [Figure 7] 13 is a flowchart illustrating an example of a reference point searching process. [Figure 8] 13 is a flowchart illustrating an example of a maximum power point search process. [Figure 9] 4 is a flowchart showing an overall flow of maximum power control according to the first embodiment. [Figure 10A] 13 is a flowchart showing another example of the reference point searching process. [Figure 10B] 13 is a flowchart showing another example of the reference point searching process. [Figure 11] 11 is another flowchart showing an example of a maximum power point search process. [Figure 12] 2 is a hardware configuration diagram of a control unit and a gate pulse generator according to the first embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, a power control device according to the present disclosure will be described. 、 Power Control Method and electricity production method An embodiment of the present invention will be described with reference to the drawings.

[0011] Embodiment 1 Fig. 1 is a diagram showing a configuration example of a power control device according to a first embodiment of the present disclosure. This power control device 10 converts power supplied from a power source in response to a power source whose amount of power supplied varies. In Fig. 1, a thermoelectric conversion module group TMG in which a total of n thermoelectric conversion modules TMG1 to TMGn are connected in series is connected to the power control device 10 as the power source. Any one of the thermoelectric conversion modules will be given the symbol "TMGz".

[0012] 1, the power control device 10 includes a converter 1, an inverter 2, a control unit 3, a gate pulse generator 4, two voltage sensors 5 and 6, and two current sensors 7 and 8. The control unit 3 is, for example, a microcomputer.

[0013] The converter 1 is a power conversion circuit capable of stepping up and down a voltage, and includes two smoothing capacitors Cin and Cout, two switch elements Q1 and Q2, two diodes D1 and D2, and an inductor L, as shown in Fig. 1. In the first embodiment, the switch element Q1 corresponds to a first switch element, and the switch element Q2 corresponds to a second switch element. Both of the two switch elements Q1 and Q2 are IGBTs (Insulated Gate Bipolar Transistors) with diodes connected in the opposite directions.

[0014] The smoothing capacitor Cin is connected between both ends of the thermoelectric conversion module group TMG, so that the voltage generated by the thermoelectric conversion module group TMG is applied to the smoothing capacitor Cin, which smoothes the voltage.

[0015] The collector of the switch element Q1 is connected to the positive terminal of the smoothing capacitor Cin. The emitter of the switch element Q1 is connected to the cathode of the diode D1 and the inductor L. Therefore, by turning on and off the switch element Q1, it is possible to supply and cut off the power generated by the thermoelectric conversion modules TMG. The switch element Q1 is mainly turned on and off for a step-down operation that converts the voltage of the supplied power to a voltage lower than that voltage.

[0016] The gates of the two switch elements Q1 and Q2 are connected to a gate pulse generator 4. Therefore, the two switch elements Q1 and Q2 are turned on and off by pulses generated by the gate pulse generator 4. "Q1_gate" and "Q2_gate" in FIG. 1 represent pulse signals for turning on and off supplied to the gates of the switch elements Q1 and Q2, respectively. In the first embodiment, the pulse signals are generated in the gate pulse generator 4 by PWM (Pulse Width Modulation) control. The two switch elements Q1 and Q2 may be other power devices such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors).

[0017] The other end of the inductor L is connected to the collector of the switch element Q2 and the anode of the diode D2. The emitter of the switch element Q2 is connected to the negative terminals of the two smoothing capacitors Cin and Cout, the anode of the diode D1, and the negative side of the thermoelectric conversion module group TMG. Therefore, by turning the switch element Q2 on and off, it is possible to short-circuit both ends of the thermoelectric conversion module group TMG and release the short-circuit during the on-drive period of the switch element Q1. The switch element Q2 is mainly turned on and off for a boost operation that converts the voltage of the supplied power to a voltage higher than that voltage.

[0018] One terminal of the smoothing capacitor Cout is connected to the cathode of the diode D2, and the other terminal is connected to the emitter of the switch element Q2, so that the smoothing capacitor Cout smoothes the voltage of the power supplied as an output from the converter 1.

[0019] A voltage sensor 5 is connected to both ends of the smoothing capacitor Cin, that is, both ends of the thermoelectric conversion module group TMG. Therefore, the voltage sensor 5 outputs a signal indicating the voltage value between both ends of the smoothing capacitor Cin as a voltage detection result. Here, the voltage value is expressed as an "input voltage value Vin". For convenience, the input voltage value Vin is also used to mean the information output by the voltage sensor 5. Similarly, the voltage value indicated by the signal output by the voltage sensor 6 is expressed as an "output voltage value Vout", the current value indicated by the signal output by the current sensor 7 is expressed as an "input current value IL", and the current value indicated by the signal output by the current sensor 8 is expressed as an "output current value Iout". The voltage sensor 5 corresponds to a first voltage detector in this embodiment.

[0020] A voltage sensor 6 is also connected across the smoothing capacitor Cout. Therefore, the voltage sensor 6 outputs a signal indicating the voltage value across the smoothing capacitor Cout. Here, the voltage value is expressed as "output voltage value Vout." The voltage sensor 6 corresponds to a second voltage detector in this embodiment.

[0021] Current sensor 7 detects the current flowing through inductor L and outputs a signal indicating the value of the detected current. Here, this current value is referred to as the "input current value IL". Current sensor 8 detects the current flowing through diode D2 and outputs a signal indicating the value of the detected current. Here, this current value is referred to as the "output current value Iout". Current sensors 7 and 8 correspond to the first and second current detectors in this embodiment, respectively.

[0022] The converter 1 configured as above is a power conversion circuit that performs DC-DC conversion. The inverter 2 is a power conversion circuit that performs DC-AC conversion. As shown in FIG. 1, the inverter 2 includes a smoothing capacitor CD and an inverter main body 21.

[0023] The smoothing capacitor CD smoothes the voltage applied from the converter 1. The inverter body 21 is connected to both ends of the smoothing capacitor CD. The inverter body 21 includes, for example, three half bridges or full bridges. The power converted into AC by the inverter body 21 is supplied to a load. The circuit configuration of the inverter body 21 is not particularly limited.

[0024] In this embodiment, as described above, the power control device 10 includes two power conversion circuits, the converter 1 and the inverter 2. However, the power conversion circuit only needs to include at least the converter 1, that is, a power conversion circuit capable of stepping up and down a voltage. The power conversion circuit includes at least one of two types of switch elements with different uses so that the voltage can be stepped up and down.

[0025] As shown in FIG. 1, the control unit 3 has the following functional components: a reference point resistance value calculation unit 31, an input power calculation unit 32, a control state determination unit 33, a converter state determination unit 34, an output voltage control unit 35, a target setting unit 36, an operating point resistance value calculation unit 37, and a maximum power control unit 38.

[0026] The reference point resistance value calculation unit 31 calculates the internal impedance of the thermoelectric conversion module group TMG, that is, the composite value of the internal resistance. The "composite value r" is used as a general term for the composite value of the internal resistance. The composite value ro, which is the initial value of the composite value r, is calculated by turning on both the switch elements Q1 and Q2 and using two or more input voltage values ​​Vin and input current values ​​IL obtained in that state. In this case, the composite value ro can be calculated by ro = (Vin1 - Vin2) / (IL2 - IL1) - (Rq1 + Rq2). Rq1 and Rq2 are the on-resistance values ​​of the switch elements Q1 and Q2. These on-resistance values ​​Rq1 and Rq2 are sufficiently small compared to the composite value ro, so they may be ignored. In this embodiment, the on-resistance values ​​Rq1 and Rq2 are ignored for convenience. Thereby, the composite value ro is calculated by ro = (Vin1 - Vin2) / (IL2 - IL1). The composite value ro may be a value indicated by data input from outside or data stored in advance in the control unit 3. This reference point resistance value calculation unit 31 corresponds to the resistance value calculation unit in the present embodiment 1. The calculation target may be the internal conductance, which is the reciprocal of the internal impedance, instead of the internal impedance. The composite value ro calculated as the initial value is measured in a state where the decrease in temperature difference due to the Peltier effect is slight, and will be distinguished from the initial value ro hereinafter by being referred to as the "initial value ro". The reference point resistance value calculation unit 31 outputs the calculated composite value ro to the maximum power control unit 38 as the reference point resistance value.

[0027] The input power calculation unit 32 calculates the input power value Pin using the input voltage value Vin and the input current value IL. The input power value Pin can be calculated, for example, by Pin=Vin×IL. The input power calculation unit 32 outputs the calculated input power value Pin to the maximum power control unit 38.

[0028] The control state determination unit 33 refers to the input power value Pin input from the input power calculation unit 32 and determines the control method of the converter 1. If the input power value Pin is excessively large, the control state determination unit 33 selects protection stop as the control method in order to protect the converter 1.

[0029] In this embodiment, in consideration of the rating of the converter 1, a plurality of setting values for controlling the converter 1 are provided. The target setting unit 36 is a component for realizing control that reflects the plurality of provided setting values. The target setting unit 36 outputs data indicating various setting values to the converter state determination unit 34 and the output voltage control unit 35.

[0030] In FIG. 1, "Vco", "Vch", and "VH" are shown as the setting values set by the target setting unit 36. These setting values are as follows respectively.

[0031] Vco and Vch are setting values used for controlling the voltage generated by the converter 1. Vch is a value larger than Vco and indicates the voltage value at which the suppression control of the generated voltage starts. Hereinafter, Vco will be referred to as "first set voltage value Vco" and Vch will be referred to as "second set voltage value Vch" respectively.

[0032] VH is also a voltage value set in consideration of, for example, the rating of the converter 1 and serves as a reference for starting the control to protect the converter 1. Thereby, the conversion of the power supplied from the thermoelectric conversion module group TMG is performed on the condition that the voltage value of the power is equal to or less than VH. When the voltage value exceeds VH, the converter 1 is not allowed to perform power conversion. That is, the converter 1 is stopped. From this, including the first set voltage value Vco and the second set voltage value Vch, the magnitude relationship between them is Vco < Vch < VH. Hereinafter, VH will be referred to as "set upper limit voltage value VH".

[0033] As described above, the converter 1 is a power conversion circuit that steps up and down the voltage of the power supplied from the thermoelectric conversion module group TMG. Therefore, each set voltage value Vco and Vch becomes the target value of the voltage generated by the converter 1 and also serves as a reference for determining whether to perform step-up or step-down of the voltage of the supplied power. The set upper limit voltage value VH is used for determining whether to cut off the supplied power because there is a risk that the power control device 10 will be damaged by the supplied power.

[0034] Although not shown in Fig. 1, the target setting unit 36 ​​sets various set values ​​for selecting a control method for the control state determination unit 33. The control state determination unit 33 refers to these set values ​​and selects a control method. These set values ​​are values ​​that are set in consideration of, for example, the ratings. Specifically, the set values ​​include Pco1, Pco2, PH, etc.

[0035] Pco1 is a threshold value set to switch the control method based on the amount of power supplied to the converter 1. Pco2 is a threshold value set as an upper limit of the amount of power output from the converter 1, for example a rated value. PH is a threshold value set to protect the converter 1 from the supply of excessive power. The magnitude relationship between them is Pco2 <Pco1<PH、である。

[0036] The value of the power supplied from the converter 1 can be calculated, for example, by multiplying the output voltage value Vout by the output current value Iout. Hereinafter, this value is referred to as the "output power value Pout."

[0037] The converter state determination unit 34 receives the input voltage value Vin, the output voltage value Vout, and the output current value Iout in addition to the determination result of the control state determination unit 33. As a result, the converter state determination unit 34 selects a mode for on / off driving of the switch elements Q1 and Q2 from among the control methods determined by the control state determination unit 33. The result of this selection is notified to the output voltage control unit 35. The output voltage control unit 35 also receives the input voltage value Vin, the input current value IL, and the output voltage value Vout.

[0038] The output voltage control unit 35 drives the switch elements Q1 and Q2 in a mode selected by the converter state determination unit 34. When the control state determination unit 33 or the converter state determination unit 34 selects the protection stop control, the output voltage control unit 35 turns off both the switch elements Q1 and Q2. When the protection stop control is not selected, the output voltage control unit 35 generates a command to turn on or turn off at least one of the switch elements Q1 and Q2. When turning on and off at least one of the switch elements Q1 and Q2, the output voltage control unit 35 determines the on-period by referring to the input voltage value Vin, the input current value IL, the output voltage value Vout, the first set voltage value Vco, the second set voltage value Vch, the set upper limit voltage value VH, the set upper limit current value IH, and the set output power value Pco2. The off-period is automatically determined by the on-period. The gate pulse generator 4 is driven by the output voltage control unit 35 according to this determination, and generates a signal to be output to the gate of each of the switch elements Q1 and Q2.

[0039] The drive contents of the switch elements Q1 and Q2 change depending on the mode. The switch element Q1 is turned on or driven on / off when the protection stop control is not selected. The switch element Q2 is driven on, off, or on / off when the protection stop control is not selected. Thus, both the switch elements Q1 and Q2 are driven on / off when the protection stop control is not selected. The on-period of the switch element that is driven on / off among the switch elements Q1 and Q2, that is, each duty ratio, is determined by the output voltage control unit 35. Thus, the output voltage control unit 35, the converter state determination unit 34, and the control state determination unit 33 correspond to the control unit in this embodiment.

[0040] The operating point resistance value calculation unit 37 calculates the impedance of the operating point during the power supply operation, that is, the composite value R of the operating point resistance. The "composite value R" is used as a general term for the composite value of the operating point. The composite value R can be calculated by R=Vin / IL using the input voltage value Vin and the input current value IL obtained during the power supply when the switch elements Q1 and Q2 are turned on and off. The on-resistance values ​​Rq1 and Rq2 of the switch elements Q1 and Q2 are sufficiently small compared to the composite value R, so they may be ignored. In this embodiment, the on-resistance values ​​Rq1 and Rq2 are ignored for convenience. This operating point resistance value calculation unit 37 corresponds to the resistance value calculation unit in the first embodiment. The operating point resistance value calculation unit 37 outputs the calculated composite value R of the operating point resistance to the maximum power control unit 38. In the reference point control described later, the maximum power control unit 38 takes into account ΔV so as to bring the combined value R of the operating point resistances closer to the combined value r of the reference point resistance values, and adjusts the on-periods of the switch elements Q1 and Q2 to maximize the output power from the thermoelectric conversion module group TMG.

[0041] Maximum power control unit 38 sets an operating point for output voltage control unit 35 so that output power value Pout is maximized. The operating point here refers to the value of Vin or IL that maximizes output power value Pout, which is a target of maximum power control unit 38. To maximize output power value Pout, it is necessary to maximize input power value Pin, and operation amounts ΔV and ΔI are provided to output voltage control unit 35 to drive switch elements Q1 and Q2 on and off, thereby bringing the value of Vin or IL closer to the target value.

[0042] Before starting the supply of power from the thermoelectric conversion module group TMG, the reference point resistance calculation unit 31 drives the switch elements Q1 and Q2 on and off and measures the voltage and current values ​​at two or more points, thereby causing the reference point resistance calculation unit 31 to calculate an initial value ro, which is a resistance value including the internal impedance of the thermoelectric conversion module group TMG. The initial value ro calculated by the reference point resistance calculation unit 31 at this time may be calculated by measuring the input voltage value Vin obtained with the switch element Q1 turned off as an open voltage value, setting 1 / 2 of the open voltage value as a temporary operating point, and calculating the resistance value from the voltage and current values ​​measured at the time of setting. The initial value ro of the reference point resistance value calculated by the reference point resistance calculation unit 31 is output to the maximum power control unit 38. The maximum power control unit 38 outputs to the output voltage control unit 35 to control ΔV and ΔI so that the operating point becomes the initial value ro of the reference resistance value. By controlling in this manner, the internal impedance of the converter 1 can be matched with the internal impedance of the thermoelectric conversion module group TMG, and the converter 1 is efficiently supplied with power from the thermoelectric conversion module group TMG.

[0043] Here, a problem with the conventional power control technology for reducing the temperature difference due to the Peltier effect of the thermoelectric conversion module group TMG will be described. First, a conventional technology using internal impedance or internal conductance for control will be described. Conventionally, a thermoelectric conversion module has been assumed as a power source for calculating internal impedance or internal conductance. This is because a thermoelectric conversion module has a characteristic that the internal impedance during power generation is larger when the temperature is higher than room temperature, but the internal impedance hardly changes even if the power generation environment (operating environment) changes thereafter, that is, even if the temperature difference between the high-temperature side and the low-temperature side changes. The open-circuit voltage increases as the temperature difference increases. Based on this characteristic, the calculated internal impedance or internal conductance can be used for control to track the operating point so as to maximize the power output from the converter.

[0044] However, even if the power generation environment is constant, the temperature difference of the thermoelectric conversion module decreases due to the Peltier effect at the time of power supply. This is because the Peltier effect works by cooling the high-temperature side and overheating the low-temperature side by passing a current in the direction in which the thermoelectric conversion module supplies power. In other words, the higher the current, the stronger the Peltier effect becomes and the lower the temperature difference of the module. The internal impedance calculated from the voltage and current that can be measured in a short time before power supply does not reflect the temperature change due to this Peltier effect. Therefore, the output power output by the converter cannot necessarily be maximized appropriately by control that tracks the operating point using the calculated internal impedance or internal conductance of the thermoelectric conversion module. This is because there is a difference between the internal impedance calculated before power supply and the impedance of the operating point where maximum power is obtained after the influence of the Peltier effect has subsided. For this reason, it is actually very difficult to maintain the operating point of the converter at the maximum power point with control that uses the internal impedance calculated before power supply.

[0045] The Peltier effect increases the amount of temperature difference drop depending on the thermal resistance of the high-temperature and low-temperature parts that the thermoelectric conversion module contacts, and the impedance of the operating point where maximum power is obtained increases, and the difference from the internal impedance calculated before power supply becomes large. In addition, it takes time depending on the heat capacity of the high-temperature and low-temperature parts of the thermoelectric conversion module until the temperature change due to the Peltier effect stabilizes. This time is relatively long. Taking this time into consideration, it is possible to recalculate the internal impedance or internal conductance of the thermoelectric conversion module by re-measuring the open circuit voltage, resetting the operating point from the re-measurement result, and re-measuring the voltage value and short-circuit current value. However, in order to do this, it is necessary to temporarily stop the power supply from the converter. Stopping the power supply, even if only temporarily, is highly undesirable.

[0046] Therefore, in this embodiment, a mode will be described in which the internal impedance or internal conductance of the power source is measured during power supply operation, thereby making it possible to more reliably supply maximum power.

[0047] Next, the characteristics of the thermoelectric conversion module TMGz and the influence of the Peltier effect will be specifically described with reference to Figs. 2 to 4. Fig. 2 is a diagram illustrating an example of the voltage-current characteristics of the thermoelectric conversion module and the change in the voltage-current characteristics due to the Peltier effect. Fig. 3 is a diagram illustrating an example of the power-current characteristics of the thermoelectric conversion module and the change in the power-current characteristics due to the Peltier effect. Fig. 4 is a diagram illustrating an example of the power-resistance characteristics of the thermoelectric conversion module and the change in the power-resistance characteristics due to the Peltier effect.

[0048] 2 to 4 show a number of characteristics of different temperature differences of the thermoelectric conversion module TMGz. When the temperature difference is expressed as a temperature difference ratio (= target temperature difference × 100 / maximum temperature difference) with the maximum temperature difference being 100, there are a total of five types: 100%, 95%, 93%, 90%, and 85%. The last two digits of the code indicate the corresponding relationship. The last two digits 01 to 05 are characteristics with a temperature difference ratio of 100%, 95%, 93%, 90%, and 85%, respectively. For example, 101 in FIG. 2 is a voltage-current characteristic with a temperature difference ratio of 100%, and 201 in FIG. 3 is a power-current characteristic with a temperature difference ratio of 100%. 110, 210, and 310 are characteristics in which the Peltier effect is affected during power supply operation when the temperature difference ratio is 100%. This is similar to FIG. 5 and FIG. 6. Hereafter, the temperature difference will be expressed as "ΔTm" and the temperature difference ratio will be expressed as "ΔTm ratio."

[0049] As shown in Figures 2 and 3, the higher ΔTm is, the higher the voltage and power obtained from the thermoelectric conversion module TMGz become. The voltage-current characteristics, that is, the relationship between the voltage value V and the current value I, can be approximated by V = -a × I + b, as shown in Figure 2. Here, a is a coefficient indicating the slope of the voltage-current characteristics, and b is a constant indicating the voltage value V when the current value I is 0.

[0050] In the characteristics 101 to 105 shown in FIG. 2, the value of the slope a is constant, but the value of the constant b gradually decreases with the decrease in the ΔTm ratio due to the Peltier effect. The value of the slope a of the characteristic 110 influenced by the Peltier effect obtained during the power supply operation is larger than the value of the slope a of the characteristics 101 to 105. In other words, the temperature change due to the Peltier effect acts so that the value of the slope a becomes larger in the equation approximating the voltage-current characteristic. The slope a of the characteristics 101 to 105 corresponds to the initial value ro calculated by the reference point resistance value calculation unit 31. The slope a of the characteristic 110 needs to wait for the temperature change due to the Peltier effect, and cannot be calculated by the reference point resistance value calculation unit 31. Therefore, as shown in FIG. 3, the power-current characteristic has a lower maximum power value in the characteristic 210 influenced by the Peltier effect than in the characteristic 201 not influenced by the Peltier effect, and the amount of power reduction due to the influence of the Peltier effect increases as the current increases. In the power-resistance characteristics, as shown in FIG. 4, due to the influence of the Peltier effect, the resistance value at which the maximum power value is obtained is greater in characteristic 310 influenced by the Peltier effect than in characteristic 301 not influenced by the Peltier effect.

[0051] As shown in FIG. 2 to FIG. 4, the internal resistance value of the thermoelectric conversion module TMGz measured and calculated in a state where the temperature difference is reduced by the Peltier effect is larger than the internal resistance value measured and calculated in a state where the Peltier effect is not applied. Therefore, the influence of the Peltier effect causes a change in the maximum power point, that is, the operating point where the power supplied from the power source is the maximum power. For this reason, in this embodiment, a composite value rp, which is an internal resistance value corresponding to the maximum power point after the temperature change due to the Peltier effect is stable, that is, the temperature change is within a negligible range, is searched during the power supply operation, and the composite value r used for the reference point control is updated from the initial value ro to the composite value rp, thereby enabling maximum power operation. In this embodiment, the reference point control, as described below, is a control in which the composite value r is set as a reference point, and the on-periods of the switching elements Q1 and Q2 are adjusted in consideration of the operation amount ΔV so that the composite value R approaches the composite value r, thereby enabling the output of maximum power.

[0052] Returning to the explanation of FIG. 1, the maximum power control unit 38 can set an operating point by providing a control amount ΔV or ΔI to the output power control unit 35 in order to confirm the change in the composite value r due to the Peltier effect. The control amount ΔV is a control amount for the input voltage value Vin, and the control amount ΔI is a control amount for the input current value IL. The power supplied from the thermoelectric conversion module group TMG changes when either the voltage value or the current value of the power changes. In a situation where the control amount ΔV should be a positive value, the control amount ΔI becomes a negative value. When the control amount ΔV is a positive value, the input voltage value Vin is operated in the direction of increasing it.

[0053] The output voltage control unit 35 receives the set voltage value Vco from the target setting unit 36, and either steps up or steps down the input voltage value Vin so that the output voltage value Vout becomes constant. When the maximum power control unit 38 sets one of the manipulated variables ΔV and ΔI to a non-zero value, it manipulates the input voltage value Vin or the input current value IL, and uses the manipulated value to determine the on-period of each of the switch elements Q1 and Q2. In this way, the maximum power control unit 38 responds to the change in the composite value r due to the Peltier effect and maximizes the output power value Pout. The following describes the case where the manipulated variable ΔV, whose positive and negative values ​​match the increase and decrease in the composite value r, is used.

[0054] The calculation of the composite value r can be performed in a state where the power supply from the converter 1 is stopped as described above. However, the calculation of the composite value rp, which is the internal resistance value corresponding to the maximum power point after the temperature change due to the Peltier effect is stable, that is, after the temperature change falls within a negligible range, is highly undesirable because it stops the power supply from the converter 1 until the temperature change due to the Peltier effect is stable. This is because the converter 1 cannot be used as a stable power conversion device, and the power generated by the thermoelectric conversion module group TMG is wasted. Therefore, in the first embodiment, the composite value rp in a state where the temperature change due to the Peltier effect is stable is searched for without stopping the power supply from the converter 1. That is, during the power output, which is the power supply operation from the converter 1, the composite value rp in a state where the temperature change due to the Peltier effect is stable is searched for, and the value of the composite value r is updated. For this reason, in the present embodiment, the composite value rp in a state where the temperature change due to the Peltier effect is stable is searched for during the power supply operation, and the composite value r used for the reference point control is updated from the initial value ro to the composite value rp, thereby enabling maximum power operation.

[0055] FIG. 5 is a diagram for explaining an example of a method for updating the composite value r in the power conversion device according to the first embodiment of the present disclosure. FIG. 5 shows an enlarged view of the area X shown in FIG. 4. In FIG. 5, two lines 510 and 520 show resistance values ​​calculated from the input voltage value Vin and the input current value IL at different timings. More specifically, the line 510 shows the resistance value of the maximum power point obtained initially or immediately before, for example, the resistance value calculated from the input voltage value Vin and the input current value IL measured before the temperature change due to the Peltier effect becomes stable, and the line 520 shows the resistance value of the maximum power point reached by setting the operating point so that the resistance value is larger than that of the line 510 after the temperature change due to the Peltier effect becomes stable. Since both 510 and 520 are resistance values ​​at the maximum power point, they are also denoted as "maximum power point 510" and "maximum power point 520" for convenience of explanation. The line 510 corresponds to the initial value ro, and the line 520 corresponds to the resistance value of the operating point at which the searched maximum power is obtained, and corresponds to the composite value rp. In other words, the Peltier effect weakens and ΔTm increases when the input current value IL is reduced.

[0056] In the first embodiment, a hill climbing method is used to search for the maximum power point. The hill climbing method is a method of identifying an operating point at which the maximum power can be obtained while moving the operating point. As the hill climbing method, for example, maximum power point tracking (MPPT) is known. Immediately after starting the power supply from the thermoelectric conversion module group TMG, the influence of the Peltier effect is not present, or even if it is present, it is very slight. However, until the temperature change due to the Peltier effect becomes stable, the characteristics change due to the Peltier effect, and the supplied power continues to decrease. In the first embodiment, focusing on this, the search for the maximum power point is put on hold until the temperature change due to the Peltier effect becomes stable. The arrow A represents the transition until the temperature change becomes stable. During the standby state, a reference point control is performed to perform power conversion by eliminating the difference between the resistance value regarded as the reference point, that is, the composite value r and the composite value R.

[0057] After the temperature change due to the influence of the Peltier effect has stabilized, the maximum power point 520 is searched for along the characteristic 310 influenced by the Peltier effect using the hill climbing method. The maximum power point 520 is identified by the search. The arrow B indicates the direction of the search. Since it has been confirmed that the Peltier effect increases the impedance of the operating point that is the maximum power point, the search for the maximum power point 520 is performed by identifying the operating point at which the maximum power is obtained while moving the operating point so that the resistance value increases. Thus, in the first embodiment, the search for the maximum power point 520 is performed by gradually increasing the composite value rp and increasing the operation amount ΔV in accordance with the increase. Therefore, the search for the maximum power point 520 is completed, and the composite value rp of the maximum power point 520 is determined. This composite value rp corresponds to the resistance value to be updated in the first embodiment.

[0058] In this way, in the first embodiment, the composite value rp in a state where the temperature change due to the Peltier effect is stable is searched for and the composite value r is updated without stopping the power supply from the converter 1. Therefore, no inconvenience occurs due to stopping the power supply. In addition, it is not necessary to wait until the change in ΔTm due to the influence of the Peltier effect settles before supplying power from the converter 1. It can be said that the influence of the Peltier effect is relatively small during a certain period of time after the start of power supply. Therefore, the converter 1 can supply maximum power or power close to the maximum power even during the period until the update of the composite value r is completed. From this, it is effective to match the composite value R that can be calculated during the power supply operation from the converter 1 with the initial value ro to continue operation at the maximum power point, perform reference point control to determine that the temperature change due to the Peltier effect has stabilized due to the change in power, and then reflect the result of searching for the composite value rp in the composite value r and gradually update the composite value r, which is the reference point, to a larger value. The portion of the power generated by the thermoelectric conversion module group TMG that is wasted can be further minimized.

[0059] FIG. 6 is a diagram for explaining the difference in the amount of current occurring between the maximum power points before and after the influence of the Peltier effect. Line 610 is the maximum power point reached before the Peltier effect becomes stable, and is a value equivalent to the initial value ro. Line 620 is the operating point searched for after the Peltier effect becomes stable, and is the composite value rp. ΔIL1 is the difference between the current value of line 610 and the current value of line 620. FIG. 6 shows the difference in the amount of current occurring between the maximum power points before and after the influence of the Peltier effect occurs at the maximum power point 610, and the current value after the influence of the Peltier effect settles at the maximum power point 620.

[0060] The current value also changes by controlling the resistance to a predetermined value according to the current-resistance characteristics. The power value also changes with the change in the current value. Here, the current value is reduced from the operating point of line 610, and the influence of the Peltier effect is weakened, the ΔTm ratio increases, and the operating point shifts to the operating point of line 620. From this, the difference ΔIL1 shown in FIG. 6 corresponds to an error in maximizing the output power value Pout. The output power value Pout can be maximized by minimizing this difference ΔIL1. The combined value r is updated in order to minimize this difference ΔIL1 and make it 0 or a value close to 0.

[0061] Fig. 7 is a flowchart showing an example of a reference point search process, and Fig. 8 is a flowchart showing an example of a maximum power point search process in Fig. 7. Also, Fig. 9 is a flowchart showing an overall flow of control for outputting maximum power according to the first embodiment. First, an overall flow of control for outputting maximum power according to the first embodiment of the present invention will be described with reference to Fig. 9. When power supply from the thermoelectric conversion module TMG starts, the control unit 3 first calculates an initial value ro (step S1), and then uses this to Reference Point ControlThe control unit 3 drives the gate pulse generator 4 to perform the above (step S2). When a current starts to flow through the thermoelectric conversion module TMG, a temperature change occurs due to the Peltier effect, and the control unit 3 confirms that the Peltier effect has stabilized by checking the fluctuation in the output power (step S3). The control unit 3 searches for the composite value rp that provides the maximum output power by a hill-climbing method (step S4). The control unit 3 updates the reference point based on the composite value rp, Reference Point Control (Step S5). After that, the composite value rp is searched for so as to obtain the maximum output power, and the reference point is updated. Reference Point Control This will be carried out.

[0062] The flowchart shown in FIG. 7 is a concrete example of the procedure in FIG. 9, and is an example mainly describing the process of searching for the reference point of the reference point control for outputting the maximum power. This reference point search process is a type of reference point control that searches for a composite value r, which is the internal resistance value of the power source that serves as the reference point, and keeps the composite value R of the operating point at a constant value. The process includes a process (corresponding to step S1) of determining an initial value ro that serves as the reference point when the control unit 3 is started, in other words, when the power supply from the thermoelectric conversion module group TMG starts, a process (corresponding to step S2) of controlling the reference point so that the composite value R matches the initial value ro, and a process (corresponding to step S5) of updating the reference point using the composite value rp obtained in the maximum power point search process (corresponding to step S4) after the temperature change due to the Peltier effect has stabilized (corresponding to step S3). The reference point control utilizes the relationship that maximum power is obtained when the internal resistance value of the power source and the resistance value of the operating point match, that is, when the composite value r=composite value R. Next, the reference point search process will be described in detail with reference to FIG. 7. Here, the description will be given assuming that the main body that executes the processing is the control unit 3.

[0063] The update of the initial value ro in the reference point search process is intended to deal with the Peltier effect that occurs when a current flows through the thermoelectric conversion module group TMG. However, the power generation environment may experience changes that are equal to or greater than the effects of the Peltier effect. The reference point search process is also intended to deal with such changes in the power generation environment.

[0064] First, in step S11, the control unit 3 assigns 0 to the variable M. In the next step S12, the control unit 3 calculates a composite value ro and assigns the calculation result to the variable ro as an initial value. The variable ro is a variable used to hold the initial value ro.

[0065] Immediately after the start of the control unit 3, the initial value ro does not exist. Therefore, when step S12 is executed immediately after the start, the initial value ro=(Vin1-Vin2) / (IL2-IL1) is calculated from two or more measured values ​​as described above to determine the operating point. It is also possible to measure the open circuit voltage value, set the operating point according to the measurement result, and calculate the initial value ro using the input voltage value Vin and input current value IL obtained at the operating point. The variable ro is substituted for the variable r used as the reference point in the reference point search process.

[0066] In step S13 following step S12, the control unit 3 sets an operating point corresponding to the value of the variable r, for example, 1 / 2 of the open circuit voltage value, to supply power and drives the gate pulse generator 4. In the next step S14, the control unit 3 calculates a composite value R using the input voltage value Vin and the input current value IL and assigns it to the variable R, and also assigns the result of subtracting the value of the variable r from the value of the variable R to the variable ΔR. After this assignment, the process proceeds to step S15.

[0067] In step S15, the control unit 3 judges whether the absolute value of the variable ΔR is less than a set value α. This set value α is a set value for judging whether the variable ΔR becomes sufficiently small and the variable R matches the variable r. Therefore, if the absolute value of the variable ΔR is less than the set value α, it is judged that the variable R matches the variable r, and the judgment in step S15 becomes YES, and the process moves to step S16. If the absolute value of the variable ΔR is equal to or greater than the set value α, it is judged that the variable R does not match the variable r, and the judgment in step S15 becomes NO, and the process returns to step S14, where the composite value R and the like are calculated. In this step S15, it is judged whether the variable ΔR, which is the difference between the variable R into which the calculated value of the composite value R is substituted and the variable r which is the reference point, becomes sufficiently small, and the composite value R of the operating point matches the value of the composite value r which is the reference point. If the determination in step S15 is YES, the combined value R of the operating point is on the line 510, and a transition state indicated by the arrow A in FIG. 5 occurs during the period from step S16 until step S20 becomes YES.

[0068] In step S16, the control unit 3 calculates the output power value Pout using the obtained output voltage value Vout and output current value Iout, and substitutes the calculated output power value Pout for the variable Pout 1. After the substitution, the process proceeds to step S17.

[0069] In step S17, the control unit 3 judges whether a set time has elapsed since the output power value Pout was calculated. This set time is a time determined assuming a temperature change, that is, a characteristic change, occurring in the thermoelectric conversion module group TMG due to the Peltier effect. In order to confirm this characteristic change, the operating point set in step S13, in other words, the initial value ro substituted for the variable r, is maintained until a maximum power point search process is executed in step S23 described later, and a process is executed to update the reference point by substituting the composite value rp for the variable r. If the set time has elapsed since the output power value was calculated, the judgment in step S17 becomes YES, and the process proceeds to step S18. If the set time has not elapsed since the output power value was calculated, the judgment in step S17 becomes NO, and the judgment process is performed again in step S17. The above step S14 is also executed at set time intervals.

[0070] In step S18, the control unit 3 calculates an output power value Pout using the obtained output voltage value Vout and output current value Iout, and substitutes the calculated output power value Pout for a variable Pout2. After this substitution, the process proceeds to step S19, where the control unit 3 substitutes a value obtained by subtracting the value of the variable Pout2 from the value of the variable Pout1 for a variable ΔP. After this substitution, the process proceeds to step S20.

[0071] In step S20, the control unit 3 determines whether the absolute value of the variable ΔP is less than a set value β. This set value β is a threshold value determined to check whether the temperature change due to the influence of the Peltier effect has stabilized, that is, whether the temperature change has become within a negligible range. This is a value determined as a threshold value for determining whether the temperature change due to the Peltier effect has stabilized. This set value β is determined in combination with the above-mentioned set time. Therefore, if the temperature change of the thermoelectric conversion module group TMG due to the Peltier effect is stable, the determination in step S20 becomes YES and the process proceeds to step S21. If the temperature change is not stable, the determination in step S20 becomes NO and the process proceeds to step S26.

[0072] In step S21, the control unit 3 increments the value of the variable M. In the following step S22, the control unit 3 judges whether the value of the variable M is equal to or greater than a set value M1. This set value M1 is a set value of time provided to check whether a change occurs in the temperature difference of the thermoelectric conversion module group TMG after the temperature change due to the Peltier effect has stabilized, that is, whether the temperature change has become within a negligible range. This set value M1 is also determined in combination with the set value β and the set time. In the present embodiment 1, the condition for considering that the temperature change due to the influence of the Peltier effect has stabilized is that the time obtained by multiplying the set value M1 by the set time, that is, the absolute value of the variable ΔP, is less than the set value β. Therefore, when the value of the variable M is equal to or greater than the set value M1, it is determined that the condition is satisfied, and the judgment in step S22 becomes YES, and the process proceeds to step S23. If the value of the variable M is less than the set value M1, the condition is not satisfied, the determination in step S22 is NO, and the value of the variable Pout2 is substituted for the variable Pout1 in step S26, and the process returns to the above step S17. Note that the condition being satisfied means that the transition indicated by the arrow A in FIG. 5 has ended.

[0073] In step S23, the control unit 3 executes a maximum power point search process to search for an operating point that provides maximum power. The combined value rp obtained by executing the maximum power point search process is substituted for the variable r, thereby updating the value of the variable r, that is, the reference point. After this process is executed, the process proceeds to step S24.

[0074] In step S24, the control unit 3 judges whether or not the value of the variable r is greater than the result of multiplying the value of the variable ro by the set value γ. As shown in FIG. 5, the change in the variable r due to the Peltier effect is relatively small. For this reason, the set value γ is set in order to judge whether or not the value of the variable R has been updated to a value that can be regarded as abnormal by executing the maximum power point search process. A specific value of this is, for example, about 1.5. As a result, if the value of the variable r has been updated to a value that can be regarded as abnormal, the judgment in step S24 becomes YES and the process proceeds to step S25.

[0075] If the update of the variable r is within a range that can be considered appropriate, the determination in step S24 becomes NO, and the process returns to step S13. In this step S13, the gate pulse generator 4 is driven according to the contents set in the maximum power point search process. In this case, power supply is performed with reference point control at the searched maximum power point.

[0076] In step S25, the control unit 3 assigns the result of multiplying the value of the variable ro by the set value Kpel to the variable r. Then, the process returns to step S13. In this case, the maximum power point is used as the operating point and power is not supplied. However, the set value Kpel is a coefficient determined by assuming the characteristic change that occurs in the thermoelectric conversion module group TMG due to the Peltier effect. The assumed characteristic change is the characteristic change from the start of power supply from the thermoelectric conversion module group TMG to the time when the influence of the Peltier effect becomes stable. The characteristic change is the change in impedance of the operating point associated with the decrease in the temperature difference depending on the thermal resistance of the high-temperature side and the low-temperature side in contact with the thermoelectric conversion module. The set value Kpel is a value whose optimum value differs for each target facility. Kpel is a value of 1 or more, and when the target facility is different each time or when it is difficult to specify the optimum value, Kpel may be 1. The multiplication result is a value closer to the maximum power point 520 than the maximum power point 510 in FIG. 5. Therefore, a larger power than before is supplied by the reference point control.

[0077] Note that multiple set values ​​Kpel may be prepared according to the open circuit voltage value or the temperature of the high temperature side of the thermoelectric conversion module group TMG. When multiple set values ​​Kpel are prepared, a more appropriate set value Kpel can be used, which is effective in shortening the time required to search for the maximum power point. Instead of the set value Kpel being a coefficient, a fixed set value Kpel may be determined.

[0078] In step S26, to which the process proceeds when the determination in step S20 above becomes NO, the control unit 3 assigns 0 to the variable M. After this assignment, the process proceeds to step S27 above. By assigning 0 to the variable M in step S26, even if the determination in step S20 temporarily becomes YES, the YES determination is ignored. If the YES determinations in step S20 do not continue for the set value M1, the determination in step S22 will not be YES.

[0079] Fig. 8 is a flow chart showing an example of the maximum power point search process executed as step S23. This maximum power point search process is a kind of hill climbing method that searches for an operating point at which the set value is gradually changed to obtain the maximum power, that is, the maximum power point. The control unit 3 performs a process of searching for the maximum power point by gradually increasing the value of the composite value rp, and a process of updating the reference point using the composite value rp obtained in the maximum power point search process. Next, the maximum power point search process will be described in detail with reference to Fig. 8. By executing this maximum power point search process, a search for the maximum power point 520 indicated by the arrow B in Fig. 5 is realized.

[0080] First, in step S31, the control unit 3 judges whether the value of the variable r is equal to or greater than the value obtained by multiplying the initial value ro by the set value Kpel. The maximum power point search process is continuously executed multiple times while the reference point control is being executed. For this reason, the process of multiplying the set value Kpel is required for the first process, but the process of multiplying the set value Kpel is not required for the second or subsequent processes. If the value of the variable r is equal to or greater than the value obtained by multiplying the initial value ro by the set value Kpel, the update process is judged to be the second or subsequent process, the judgment in step S31 becomes YES, and the process proceeds to step S32. If the value of the variable r is less than the value obtained by multiplying the initial value ro by the set value Kpel, the update process is judged to be the first process, the judgment in step S32 becomes NO, and the process proceeds to step S33.

[0081] In step S32, to which the process proceeds when the determination in step S31 above is YES, the control unit 3 assigns the value of the variable r to a variable rp1. The variable rp1 is used to update the composite value r used for the reference point control.

[0082] In step S33, to which the process proceeds when the determination in step S31 above is NO, the control unit 3 assigns a value obtained by multiplying the initial value ro by the set value Kpel to the variable rp1.

[0083] In step S34 following steps S32 and S33, the variable rp1 is substituted for the variable rp. The variable rp is used to search for the composite value rp of the maximum power point after the temperature change due to the Peltier effect has stabilized. The variable rp1 records the result of searching for the composite value rp of the maximum power point, and updates the composite value r used for reference point control. By the processing of steps S31-33 described above, the variable rp1 becomes an initial value equal to or greater than the value obtained by multiplying the value of the initial value ro by the set value Kpel. In the second and subsequent processing, a value equal to or greater than the variable r becomes the initial value. In FIG. 5, this initial value is closer to the maximum power point 520 than the maximum power point 510. Therefore, the maximum power point 520 can be determined in a shorter time than when the value of the variable r, particularly the initial value ro, is used as the initial value in the first processing. Determining the maximum power point 520 in a shorter time means that the output power value Pout can be maximized more quickly.

[0084] In step S35 following step S34, the control unit 3 sets an operating point according to the value of the variable rp and drives the gate pulse generator 4. The operating point is set by the maximum power control unit 38 setting an operation amount ΔV such that the input voltage value Vin is increased in response to the increase from the variable r to the variable rp. Due to the characteristics of the power supply described above, the input current value IL becomes smaller and the value of the combined value R=Vin / IL after the operation becomes larger, which reflects the increase in the variable rp.

[0085] In the next step S36, the control unit 3 calculates an output power value Pout using the output voltage value Vout and the output current value Iout obtained by driving the gate pulse generator 4, and assigns the calculated output power value Pout to a variable Pout3. After the assignment, the process proceeds to step S37.

[0086] In step S37, the control unit 3 assigns a value obtained by adding a set value δ to the value of the variable r1 to the variable rp. This set value δ is a value determined as an update unit of the composite value r used for reference point control in searching for the maximum power point. In the following step S39, the control unit 3 sets an operating point corresponding to the value of the variable rp and drives the gate pulse generator 4. In setting the operating point here, an operation is performed to increase the operation amount ΔV by a voltage value equivalent to the set value δ. This operation increases the input voltage value Vin and decreases the input current value IL.

[0087] In step S38 following step S37, the control unit 3 sets an operating point according to the value of the variable rp and drives the gate pulse generator 4. The setting of the operating point here corresponds to the setting of the manipulated variable ΔV by the maximum power control unit 38. As described above, this manipulated variable ΔV is targeted at the input voltage value Vin. The value of this manipulated variable ΔV is a value according to the difference between the value of the variable rp and the value of the variable r and the set value δ.

[0088] In step S39 following step S38, the control unit 3 calculates an output power value Pout using the output voltage value Vout and the output current value Iout obtained by driving the gate pulse generator 4, and assigns the calculated output power value Pout to a variable Pout4. After the assignment, the process proceeds to step S40.

[0089] In step S40, the control unit 3 determines whether the value of the variable Pout4 is greater than the value of the variable Pout3. If the magnitude relationship is established, that is, if the operation of decreasing the input current value IL and increasing the input voltage value Vin in order to increase the variable rp results in an increase in the output power value Pout, the determination in step S40 becomes YES and the process proceeds to step S41. If the magnitude relationship is not established, the determination in step S40 becomes NO and the process proceeds to step S42.

[0090] In step S41, the control unit 3 assigns the value of the variable rp to the variable rp1, and assigns the value of the variable Pout4 to the variable Pout3. Then, the process returns to step S37. This allows the search for the maximum power point 520 to continue according to the process indicated by the arrow B in FIG.

[0091] The transition to step S42 means that the output power value Pout has changed from increasing to decreasing. Therefore, in step S42, the control unit 3 substitutes the value of the variable rp1 into the variable r as the search result of the maximum power point, and updates the composite value r used in the reference point control. After that, the maximum power point search process ends, and the process returns to the reference point search process.

[0092] The reference point is updated by substituting the value of variable rp1, which corresponds to the resistance value of the operating point found in the search for the maximum power point, into variable r used for the reference point control. That is, steps S36-S40 correspond to the search for the composite value rp1 of the maximum power point, and step S42 corresponds to the update of variable r, which is the reference point. In this manner, the search for the maximum power point and the update of composite value r used for the reference point control are performed by maximum power control unit 38. Therefore, the resistance value update unit in the present embodiment 1 corresponds to maximum power control unit 38. The control unit in the power conversion control device according to the present embodiment 1 corresponds to all of components 31 to 38.

[0093] In the first embodiment, the transition indicated by the arrow A in Fig. 5 is handled using the set time in step S17, the variable M in steps S21 and S22, and the set value M1, but the handling method is not particularly limited. For example, when the power supply from the power source starts, the maximum power point may be searched for, and after the search, the system may wait until the temperature change caused by the Peltier effect subsides, and then search for the maximum power point again. Various modifications including this are possible.

[0094] In the first embodiment, the stability of the temperature change due to the Peltier effect can be confirmed both by confirming that the set time has elapsed (step S17) and by using the variable M and the set value M1 (steps S21 to S22). Using the variable M and the set value M1 is synonymous with providing a second set time. The first set time (step S17) is mainly intended to reduce the temperature change due to the Peltier effect by waiting for the time when the temperature change determined by the heat capacity of the equipment and device that has the exhaust heat to which the thermoelectric conversion module is attached becomes saturated, and the second set time thereafter is also intended to determine whether the temperature change due to the Peltier effect and the power generation environment is small. In other words, the second set time can be made shorter than the first set time, and when the temperature change is small, the system can shift to the maximum power point search control earlier to increase the amount of power generation.

[0095] 7, when the maximum power point search process is completed and the process returns to the reference point search process, the process returns to step S13. However, since the stability of the temperature change due to the Peltier effect has already been confirmed, the process of confirming the stability of the Peltier effect in step S17 is not necessary. 10A and 10B are examples of a flowchart of a reference point search process different from that in FIG. 7. Step S125 and subsequent steps in FIG. 10A are different from those in FIG. 7. That is, as shown in FIG. 10B, in step S212, the composite value r obtained in the maximum power point search process is updated as a new reference point r, and the reference point control is performed in steps S213 to S215. If the composite value R of the operating point coincides with the composite value r as the reference point in step S215 (YES), the maximum power point search process is performed in steps S223 to S225, the reference point r to be updated is searched for, and the process returns to step S212. That is, this means that in FIG. 9, the process returns to step S4 after step S5.

[0096] Also, in the reference point search process, the process of determining that the temperature change is small in step S22 may be omitted, and a step of determining that the temperature change is small in the maximum power point search process may be provided. FIG. 11 is a flowchart showing an example of a maximum power point search process different from that in FIG. 8. In this example, step S40A is added after step S40 when step S22 is omitted in the reference point search process. As described above, in step S40, the control unit 3 judges whether the value of the variable Pout4 is larger than the value of the variable Pout3. In step S40A, if the magnitude relationship is established, it is judged that the increase in the variable Pout4 does not include the influence of the change in the power generation environment. If the difference between the variable Pout4 and the variable Pout3 is smaller than a preset threshold ε, it is judged that the temperature change is stable (YES), and the maximum power point search process is continued. If it becomes larger than the threshold ε, it is judged that the temperature change due to the power generation environment is large (NO), and the search for the maximum power point is terminated.

[0097] By providing this step S40A, it is possible to prevent a sudden increase in the resistance value rp during the maximum power point search procedure when a sudden temperature change occurs due to a change in the power generation environment. In addition, since the time required to transition from reference point control to maximum power point search control (corresponding to step S22) can be omitted, the transition to search control can be made earlier, and the amount of power generation can be increased. The threshold value ε in step S40A is set to a value larger than the increase in the amount of power generation due to the additional amount δ of the resistance value r. The smaller the threshold value ε, the more effective it is at maintaining the resistance value rp at an appropriate value, even when there is a large change in temperature due to a change in the power generation environment. Note that step S40A may be provided even when the process of determining whether the temperature change is small in step S22 in the reference point search process is not omitted.

[0098] As described above, the update of the initial value ro in the reference point search process is intended to deal with the Peltier effect that occurs when a current flows through the thermoelectric conversion module group TMG. However, the power generation environment may experience changes that are equal to or greater than the effects of the Peltier effect. For example, the start and stop of the equipment in which the thermoelectric conversion modules are installed may RepeatedIn some cases, large temperature changes may occur. For changes beyond the influence of the Peltier effect, it is better to perform the reference point search process that returns to step S13 as shown in Fig. 7. Alternatively, in order to respond to changes in the power generation environment, a combination of the processes shown in Fig. 7 and Figs. 10A and 10B may be executed.

[0099] In the first embodiment, the maximum power point search process shown in FIG. 8 searches using a hill climbing method. At this time, as described in FIG. 5, the hill climbing method is a one-way method in which the initial value ro is gradually increased. This is because, when the Peltier effect is applied, the internal resistance operates with a voltage-current characteristic larger than the actual value, and the maximum power point moves to the side of the larger composite value r. Therefore, the maximum power point can be reached more quickly than when the maximum power point is searched for while increasing and decreasing the resistance value on the characteristic 310. Then, even if the process returns to the reference point control and then transitions to the maximum power point search process again, the maximum point is searched for using a one-way hill climbing method in which the composite value r is increased, thereby enabling fine control that quickly reflects the reference point of the reference point control.

[0100] The control unit 3 and the gate pulse generator 4 are configured with a processor 1000 and a storage device 2000, as shown in FIG. 12, which is an example of hardware. Although the storage device is not shown, it includes a volatile storage device such as a random access memory and a non-volatile auxiliary storage device such as a flash memory. Also, instead of the flash memory, an auxiliary storage device such as a hard disk may be included. The processor 1000 executes a program input from the storage device 2000. In this case, the program is input from the auxiliary storage device to the processor 1000 via the volatile storage device. Also, the processor 1000 may output data such as a calculation result to the volatile storage device of the storage device 2000, or may store data in the auxiliary storage device via the volatile storage device. Furthermore, as a hardware configuration, the processor 1000 and the storage device 2000 of the control unit 3 and the gate pulse generator 4 may be shared and integrated.

[0101] Although the present application describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to application to a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless modifications not exemplified are assumed within the scope of the technology disclosed in the present specification, including, for example, modifying, adding, or omitting at least one component, and further, extracting at least one component and combining it with a component of another embodiment. [Explanation of symbols]

[0102] REFERENCE SIGNS LIST 1 Converter, 2 Inverter, 3 Control unit (power conversion control device), 4 Gate pulse generator, 5 Voltage sensor (first voltage detector), 6 Voltage sensor (second voltage detector), 7 Current sensor (first current detector), 8 Current sensor (second current detector), 10 Power control device, 21 Inverter main body, 31 Reference point resistance value calculation unit (resistance value calculation unit), 32 Input power calculation unit (control unit), 33 Control state determination unit (control unit), 34 Converter state determination unit (control unit), 35 Output voltage control unit (control unit), 36 Target setting unit (control unit), 37 Operating point resistance value calculation unit (resistance value calculation unit), 38 Maximum power control unit (resistance value update unit, control unit), Cin, Cout, CD Smoothing capacitor, D1, D2 Diode, L Inductor, Q1 Switch element (first switch element), Q2 Switch element (second switch element), TMG1, TMGn Thermoelectric conversion module, TMG thermoelectric conversion module group (power supply).

Claims

1. A power control device including a power conversion circuit that converts power output from a thermoelectric conversion module and a control unit that controls the power conversion circuit, The control unit is a reference point resistance value calculation unit that calculates a composite value of the internal resistances of the thermoelectric conversion module using an input current and an input voltage of the power conversion circuit, and sets the composite value as a reference point resistance value; an operating point resistance value calculation unit that calculates a combined value of internal resistances of the thermoelectric conversion module using an input current and an input voltage of the power conversion circuit while power is supplied from the thermoelectric conversion module to the power conversion circuit, controlling power conversion of the power output from the thermoelectric conversion module in the power conversion circuit so that the combined value of the internal resistances calculated by the operating point resistance value calculation unit approaches the reference point resistance value calculated by the reference point resistance value calculation unit; Furthermore, the control unit a resistance value update unit that identifies an operating point at which a value of an output power output from the power conversion circuit is maximized and updates the reference point resistance value; A power control device that controls the power conversion of the power output from the thermoelectric conversion module so that the combined value of the internal resistances calculated by the operating point resistance value calculation unit approaches the reference point resistance value updated by the resistance value update unit.

2. 2. The power control device according to claim 1, wherein the control unit identifies an operating point at which the value of the output power output from the power conversion circuit is maximized in the resistance value update unit after a difference between the combined value of the internal resistances calculated by the operating point resistance value calculation unit and the reference point resistance value becomes smaller than a predetermined threshold value and a preset time has elapsed.

3. 3. The power control device according to claim 2, wherein the control unit has a predetermined first set time and a second set time shorter than the first set time, a difference between the composite value of the internal resistances calculated by the operating point resistance value calculation unit and the reference point resistance value becomes smaller than the predetermined threshold value, and after the first set time has elapsed, a difference in output power output from the power conversion circuit before and after the first set time has elapsed becomes smaller than a predetermined value, and after the second set time has elapsed, the resistance value update unit identifies an operating point at which the value of the output power output from the power conversion circuit is maximized.

4. 4. The power control device according to claim 1, wherein the reference point resistance value calculation unit sets a composite value of the internal resistances of the thermoelectric conversion module at the time when power supply from the thermoelectric conversion module starts as an initial reference point resistance value, and the initial reference point resistance value is updated by the resistance value update unit.

5. the power conversion circuit includes a first switch element capable of supplying and cutting off power from the thermoelectric conversion module, and a second switch element capable of short-circuiting both ends of the thermoelectric conversion module when the first switch element is driven on, and a converter capable of increasing and decreasing a voltage of the power by driving the first switch element and the second switch element on and off; The power control device according to claim 1 , wherein the control unit controls on / off driving of the first switch element and the second switch element.

6. A power control method for controlling power output from a thermoelectric conversion module, comprising: a first step of supplying power from the thermoelectric conversion module to a power conversion circuit, and calculating an initial value of a composite value of internal resistances of the thermoelectric conversion module using an input current and an input voltage of the power conversion circuit, and setting the initial value as a reference point; a second step of calculating a composite value of internal resistances of the thermoelectric conversion module using an input current and an input voltage of the power conversion circuit while power is supplied from the thermoelectric conversion module to the power conversion circuit, and controlling power conversion of the power output from the thermoelectric conversion module so that the composite value of the internal resistances approaches the reference point; a third step of confirming that the temperature change of the thermoelectric conversion module has stabilized; a fourth step of searching for a composite value of the internal resistances that maximizes the output power of the power conversion circuit by a hill-climbing method while increasing the composite value of the internal resistances from the initial value; a fifth step of setting the combined value of the internal resistances at which the output power of the power conversion circuit is maximized, found in the fourth step, as an updated reference point.

7. The power control method according to claim 6 , further comprising the steps of: executing each step in sequence from the second step based on the reference point updated in the fifth step.

8. 7. The power control method according to claim 6, further comprising the steps of: executing the second step based on the reference point updated in the fifth step; and then executing the fourth step.

9. 9. The power control method according to claim 6, wherein in the third step, after a predetermined first time has elapsed, it is confirmed that the fluctuation in output power from the power conversion circuit is within a predetermined threshold value, and a predetermined second time has elapsed, whereby it is confirmed that the temperature change of the thermoelectric conversion module has stabilized.

10. A power production method for outputting power output from a thermoelectric conversion module through a power conversion circuit, comprising: an initial value of a combined value of the internal resistances of the thermoelectric conversion module at the start of power supply to the power conversion circuit is set as a reference point resistance value; While power is supplied from the thermoelectric conversion module to the power conversion circuit, Controlling the power conversion of the power output from the thermoelectric conversion module in the power conversion circuit so that a combined value of the internal resistances of the thermoelectric conversion modules approaches the reference point resistance value; A power production method comprising: updating the reference point resistance value to a combined value of internal resistances of the thermoelectric conversion module at an operating point where the value of the output power output from the power conversion circuit is maximum; and converting and outputting the power output from the thermoelectric conversion module so that the combined value of the internal resistances of the thermoelectric conversion module approaches the updated reference point resistance value.

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