Hydraulic power-generating system, power conversion device used for the same, and power generation output control method

Abstract

To provide a system suited to an application to micro hydraulic power generation capable of maximizing output efficiency by minimizing the loss, with a simpler circuit configuration.SOLUTION: A circuit configuration is simplified as a whole system by omitting an LC resonance circuit by directly connecting a primary wiring 321 of a transformer 32 to a half-bridge inverter 31 while constituting a full-wave rectifier circuit 20 and a rectifier circuit 33 from diodes as passive elements. Further, circuits other than the half-bridge inverter 31 constituted using the passive elements from which no switching loss is generated maximizes output efficiency by preventing the loss from being generated, by omitting the LC resonance circuit where loss thereof is generated in capacitor itself as well as inductor itself. Further, an input voltage and an output current of a power conversion device 30 are monitored to perform MPPT control, and thus an output power is maximized.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hydroelectric power generation system, a power conversion device used therein, and a power generation output control method, and is particularly suitable for application to small-scale micro-hydroelectric power generation in which the output power is below a certain value. [Background technology]

[0002] In recent years, global warming caused by an increase in greenhouse gases due to the mass consumption of fossil fuels has become a serious problem. As a measure to solve this problem, the introduction of renewable energy, which is a clean energy that does not emit carbon dioxide, has been promoted. As a means of obtaining electricity from renewable energy, power generation systems such as solar, wind, and hydroelectric power have been actively developed, and various configurations of related peripheral technologies have also been proposed (see, for example, Patent Documents 1 and 2).

[0003] The power conversion device described in Patent Document 1 includes a half-bridge inverter that converts DC power output from a high-voltage vehicle battery into AC power, a transformer with the half-bridge inverter connected to its primary side, a rectifier circuit connected to the secondary side of the transformer, a smoothing circuit that smooths the rectified voltage and outputs it to an output terminal, and a control circuit that controls the switching of the half-bridge inverter. The half-bridge inverter includes a capacitor connected in parallel to two series-connected semiconductor switching elements and an inductor connected to an AC output line, and the control circuit controls each semiconductor switching element to perform zero-voltage switching in accordance with the current input to the half-bridge inverter.

[0004] The power conversion device described in Patent Document 2 includes a half-bridge inverter that converts DC power generated by a wind power generator and stabilized by a power conditioner into AC power, a transformer that receives the AC output of the half-bridge inverter, an AC-DC converter consisting of a rectifier diode and an output capacitor that converts the AC output of the transformer into DC, and a filter circuit consisting of a reactor and a capacitor that removes ripples remaining in the DC voltage output from the AC-DC converter. The transformer is a multi-winding transformer, and an AC-DC converter is provided for each of its secondary windings.

[0005] One example of hydroelectric power generation is known as micro-hydropower generation. Micro-hydropower generation is a small-scale hydroelectric power generation system with an output of 100 kW or less, and can generate electricity anywhere there is a water flow or head, such as in agricultural irrigation channels, general rivers, and water and sewerage systems. Compared to solar and wind power generation, it is less susceptible to the effects of weather and has smaller fluctuations in the amount of power generated, making it economically advantageous.

[0006] However, since the power generated by micro-hydropower generation is smaller and fluctuates less than that of solar and wind power generation, there is a growing need for innovations to minimize losses and maximize output efficiency with a simpler circuit configuration. For this reason, the power conversion devices described in Patent Documents 1 and 2 cannot be applied directly to micro-hydropower generation systems.

[0007] For example, the power conversion device described in Patent Document 1 is applied to an in-vehicle system, and performs LC resonance using a capacitor and inductor provided in a half-bridge inverter, and aims to reduce losses through zero-voltage switching. However, in a micro-hydroelectric power generation system of 100 kW or less, LC resonance is unlikely to improve losses. Instead, output efficiency deteriorates due to losses occurring in the capacitor itself and the inductor itself. Furthermore, the inclusion of an LC resonant circuit increases the size of the circuit configuration.

[0008] Furthermore, the power conversion device described in Patent Document 2 is applied to a wind power generation system, and includes a power conditioner in the front stage of the power conversion device, as well as multiple sets of unit modules each including a half-bridge inverter, a transformer, and an AC-DC converter, resulting in a large circuit configuration. The power conditioner is an AC-DC converter that uses active elements to control power stabilization, which makes the circuit complex and increases switching loss. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 5558631 [Patent Document 2] Patent No. 6470645 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made to solve these problems, and aims to provide a system that is suitable for application to micro-hydropower generation, which has a simpler circuit configuration and is capable of minimizing losses and maximizing output efficiency. [Means for solving the problem]

[0011] In order to solve the above-mentioned problems, the hydroelectric power generation system of the present invention includes a micro-hydroelectric generator, a diode full-wave rectifier circuit that converts power generated by the micro-hydroelectric generator into DC power, and a power conversion device that converts and outputs the DC power output from the diode full-wave rectifier circuit. The power conversion device includes a half-bridge inverter that converts the DC power output from the diode full-wave rectifier circuit into AC power, a transformer having a primary winding connected to the half-bridge inverter, a rectifier circuit using diodes connected to a secondary winding of the transformer, a smoothing circuit that smoothes the DC voltage rectified by the rectifier circuit, and a control unit that monitors the input voltage and output current of the power conversion device and controls the switching of switching elements of the half-bridge inverter so as to maximize the output power of the power conversion device. [Effects of the Invention]

[0012] As described above, the present invention includes a full-wave rectifier circuit composed of passive diodes as a circuit for converting the power generated by the micro-hydroelectric generator into DC power, and the rectifier circuit of the power conversion device connected downstream of the diode full-wave rectifier circuit is also composed of passive diodes. Furthermore, the primary winding of the transformer is directly connected to the half-bridge inverter, and no LC resonant circuit is present. This simplifies the circuit configuration of the entire system after the generator.

[0013] In addition, no switching loss occurs in full-wave rectifier circuits or rectifier circuits that use passive elements. Although some switching loss occurs in half-bridge inverters, the output efficiency is not degraded by losses occurring in the capacitors of the LC resonant circuit or in the inductors themselves. This minimizes losses.

[0014] In addition, since the full-wave rectifier circuit using passive elements does not actively stabilize the voltage, the input voltage of the half-bridge inverter fluctuates depending on the power generated by the micro-hydroelectric generator, but the input voltage and output current of the power conversion device are monitored and control is performed to maximize the output power of the power conversion device.

[0015] As described above, according to the present invention, it is possible to provide a system suitable for application to micro-hydroelectric power generation, which has a simpler circuit configuration and is capable of minimizing losses and maximizing output efficiency. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a diagram showing an example of the configuration of a hydroelectric power generation system according to an embodiment of the present invention; [Figure 2] 1 is an example of a PV characteristic graph showing the relationship between the input voltage and the output power of a power conversion device. [Figure 3] FIG. 1 is a diagram illustrating an example of the configuration of a hydroelectric power generation system according to an application example of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] An embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a diagram showing an example of the configuration of a hydroelectric power generation system according to this embodiment. As shown in Fig. 1, the hydroelectric power generation system of this embodiment is configured to include a micro hydroelectric generator 10, a diode full-wave rectifier circuit 20, and a power conversion device 30.

[0018] The micro hydroelectric generator 10 comprises a micro hydro turbine installed in a location where there is a water flow, and a generator that converts the rotational energy of the micro hydro turbine into AC power. Figure 1 shows a configuration using a three-phase generator as an example. That is, the micro hydroelectric generator 10 generates three-phase AC power using the rotational energy of the micro hydro turbine. Note that the three-phase generator is just an example, and the present invention is not limited to this configuration.

[0019] The diode full-wave rectifier circuit 20 is a three-phase rectifier circuit composed of diodes that converts the three-phase power generated by the micro-hydroelectric generator 10 into DC power by full-wave rectification and outputs the rectified DC power to the power converter 30. The diode full-wave rectifier circuit 20 does not include any active elements such as switching elements, and is a simple circuit composed only of diodes, which are passive elements. A voltage sensor 36 that detects the input voltage of the power converter 30 is provided on the output side of the diode full-wave rectifier circuit 20, and the voltage value detected by the voltage sensor 36 is transmitted to the control unit 35.

[0020] The power conversion device 30 is a DC-DC converter that converts the DC power output from the diode full-wave rectifier circuit 20 into DC power of a different value and outputs it. In this embodiment, a battery (hereinafter also referred to as battery 100) is used as an example of a load 100 connected to the output side of the power conversion device 30. The battery 100 can be regarded as a voltage source because the change in voltage with respect to the charge / discharge current is small. The power conversion device 30 functions as a control current source that controls the charge / discharge of the battery 100 as a voltage source.

[0021] The power conversion device 30 is configured to include a half-bridge inverter 31, a transformer 32, a rectifier circuit 33, a smoothing circuit 34, and a control unit 35. The half-bridge inverter 31 has a half-bridge circuit configured by connecting in parallel two sets of switching elements 311 connected in series and two input capacitors 313 for voltage division connected in series, thereby converting the DC power output from the diode full-wave rectifier circuit 20 into AC power. Load commutation diodes 312 are connected in anti-parallel to each of the two switching elements 311.

[0022] The switching elements 311 are configured by, for example, MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) or IGBTs (Insulated Gate Bipolar Transistors). The effective value of the AC voltage output from the half-bridge inverter 31 is controlled by controlling signals input to the gate terminals of the two switching elements 311 in the control unit 35. The signals input by the control unit 35 to the gate terminals of the switching elements 311 can be rectangular waves or pulse-width modulated waves (PWM waves) with any duty ratio.

[0023] The transformer 32 transforms the output voltage of the half-bridge inverter 31 at a transformation ratio corresponding to the turns ratio between the primary winding 321 and the secondary winding 322 of the transformer 32. In this embodiment, the primary winding 321 of the transformer 32 is directly connected to the half-bridge inverter 31, and no LC resonant circuit exists between the half-bridge inverter 31 and the transformer 32. In this embodiment, the transformer 32 has two secondary windings 322.

[0024] The rectifier circuit 33 is configured by a diode 331 connected to the secondary winding 322 of the transformer 32. That is, in this embodiment, the rectifier circuit 33 connected to the secondary side of the transformer 32 is configured by connecting two diodes 331 to the two secondary windings 322, respectively, and forms a full-wave rectifier circuit with two windings that can halve the loss due to the voltage drop of the diode 331.

[0025] The smoothing circuit 34 smoothes the DC voltage rectified by the rectifier circuit 33. In this embodiment, the smoothing circuit 34 is composed of one reactor 341 connected in series to the rectifier circuit 33. A charging current is supplied to the battery 100 by the DC voltage smoothed by the smoothing circuit 34. A current sensor 37 that detects a circuit current flowing through the power conversion device 30 is provided on the output side of the smoothing circuit 34, and the current value detected by the current sensor 37 is transmitted to the control unit 35.

[0026] The control unit 35 is configured by a microcomputer equipped with a CPU, RAM, ROM, etc., and executes the control described below by running a program stored in a storage medium such as the RAM, ROM, hard disk, or semiconductor memory. Note that the control unit 35 may also be equipped with a DSP (Digital Signal Processor) in addition to the microcomputer.

[0027] The control unit 35 monitors the input voltage of the power conversion device 30 (power generated by the micro hydroelectric generator 10) detected by the voltage sensor 36 and the output current of the power conversion device 30 detected by the current sensor 37, and controls the switching of the switching elements 311 of the half-bridge inverter 31 so as to maximize the output power of the power conversion device 30. Here, the control unit 35 controls the switching of the switching elements 311 by MPPT (Maximum Power Point Tracking) control using a so-called hill-climbing method so as to maximize the output power of the power conversion device 30. By MPPT control, the maximum power operating point is tracked and controlled in response to output fluctuations of the micro hydroelectric generator 10.

[0028] In this embodiment, a diode full-wave rectifier circuit 20 is provided upstream of the power converter 30, and voltage stabilization control, such as that performed by a power conditioner, is not performed. Therefore, the input voltage of the power converter 30 detected by the voltage sensor 36 fluctuates depending on the power generated by the micro-hydroelectric generator 10. Furthermore, unlike solar and wind power generation, micro-hydroelectric power generation tends to have a gentler, less sharp peak-shaped PV characteristic, which indicates the relationship between fluctuations in input voltage and fluctuations in output power. Therefore, conventional MPPT control has difficulty detecting the peak at which output power changes from an increase to a decrease. Therefore, in this embodiment, MPPT control specific to micro-hydroelectric power generation is performed. Details of the MPPT control specific to this embodiment are described below with reference to FIG. 2.

[0029] Figure 2 is an example of a PV characteristic graph showing the relationship between the input voltage and output power of the power conversion device 30. Figures 2(a) to 2(c) show the PV characteristics observed when a constant flow rate of water is flowed through three waterways with different heads. Figure 2(a) shows the PV characteristics obtained when a micro hydro turbine is installed in a waterway with a water flow that results in an output power of approximately 40 W or less. Figure 2(b) shows the PV characteristics obtained when a micro hydro turbine is installed in a waterway with a water flow that results in an output power of approximately 25 W or less. Figure 2(c) shows the PV characteristics obtained when a micro hydro turbine is installed in a waterway with a water flow that results in an output power of approximately 15 W or less. Each plot point on the graph represents the measurement results of input voltage and output power.

[0030] Although there is variation in the plot points in all of the PV characteristics shown in Figures 2(a) to (c), when an approximate curve is calculated by regression, the approximate curve takes on a mountain-like shape. Although the approximate curve has a gentle mountain-like shape, it has a peak where the output power changes from increasing to decreasing. Here, from the PV characteristics shown in Figures 2(a) and (b), it can be inferred that there is a possibility that the output power peak exists when the input voltage is in the range of 120 [V] to 160 [V]. Furthermore, from the PV characteristics shown in Figure 2(c), it can be inferred that there is a possibility that the output power peak exists when the input voltage is in the range of 80 [V] to 120 [V].

[0031] Therefore, the control unit 35 generates and stores in advance a characteristic model of the approximate curve shown in Figure 2 as an assumed model of PV characteristics that shows how the output power of the power conversion device 30 varies with fluctuations in the input voltage of the power conversion device 30, in accordance with the waterway in which the micro hydro turbine is installed.The control unit 35 then calculates an expected value of the output power of the power conversion device 30 based on the assumed characteristic model of the approximate curve that has been stored in advance and the input voltage and output current of the power conversion device 30 monitored by the voltage sensor 36 and the current sensor 37, and performs MPPT control using the hill-climbing method based on the expected value.

[0032] For example, the control unit 35 determines the output power corresponding to the input voltage of the power conversion device 30 detected by the voltage sensor 36 from a pre-stored PV characteristic model. Hereinafter, the output power determined in this manner is referred to as the "model output power." Meanwhile, the control unit 35 determines the output power of the power conversion device 30 from the output current of the power conversion device 30 detected by the current sensor 37 and the operating voltage of the load 100 (for example, the operating voltage of the battery 100 is 12 V). Hereinafter, the output power determined in this manner is referred to as the "measured output power." Furthermore, the control unit 35 calculates an expected value of the output power from the error between the model output power and the measured output power, and performs MPPT control using a hill-climbing method based on the calculated expected value. In this case, for example, the average value of the model output power and the measured output power can be used as the expected value.

[0033] As described above, since it is assumed in advance that the input voltage of the power conversion device 30 at which the output power of the power conversion device 30 is likely to be maximized falls within a predetermined range, the transformer 32 sets the turns ratio of the primary winding 321 and the secondary winding 322 so as to achieve a transformation ratio determined from the value of the range assumed in advance as the input voltage and the value of the operating voltage of the load 100 (the operating voltage of 12 [V] of the battery 100). Then, the control unit 35 performs MPPT control within the assumed input voltage range.

[0034] For example, when the control unit 35 performs MPPT control based on a characteristic model assumed from the PV characteristics of Figure 2(a) or (b), the winding ratio of the transformer 32 is set to a transformation ratio that converts an input voltage of 120 [V] to 160 [V] to approximately the battery operating voltage of 12 [V]. Then, the control unit 35 performs MPPT control within the range of the input voltage of the power conversion device 30 being 120 [V] to 160 [V].

[0035] The control unit 35 also monitors the output current of the power conversion device 30 detected by the current sensor 37, and controls the switching of the switching element 311 of the half-bridge inverter 31 so as to stabilize the output current of the power conversion device 30. That is, since the input voltage of the power conversion device 30 (the output voltage of the micro hydroelectric generator 10) has a drooping characteristic with respect to an increase in the load current (as the output current of the power conversion device 30 increases, the input voltage decreases), feedback control of the output current detected by the current sensor 37 is used to maintain a region in which stable power generation operation is possible.

[0036] Through the MPPT control described above, by controlling (changing) the duty cycle of the signal supplied to the gate terminal of the switching element 311 in accordance with the input voltage of the power conversion device 30 (the power generated by the micro-hydroelectric generator 10), it is possible to maintain the maximum output operating point and supply a continuous and stable charging current to the battery 100.

[0037] As explained in detail above, the hydroelectric power generation system of this embodiment includes a diode full-wave rectifier circuit 20 configured with passive diodes as a circuit for converting the power generated by the micro-hydroelectric generator 10 into DC power, and the rectifier circuit 33 connected downstream of the transformer 32 is also configured with passive diodes. Furthermore, in the configuration of the power conversion device 30, the primary winding 321 of the transformer 32 is directly connected to the half-bridge inverter 31, eliminating the need for an LC resonant circuit. Furthermore, the smoothing circuit 34 connected downstream of the rectifier circuit 33 is configured with a single reactor. This simplifies the circuit configuration of the entire system from the micro-hydroelectric generator 10 onwards.

[0038] Furthermore, in the hydroelectric power generation system according to this embodiment, all circuit components except for the half-bridge inverter 31 are composed of passive elements, and no switching loss occurs in these circuit components. Although some switching loss occurs in the switching element 311 of the half-bridge inverter 31, since the LC resonant circuit is omitted, there is no deterioration in output efficiency due to loss occurring in the capacitor itself or loss occurring in the inductor itself. This makes it possible to minimize loss and maximize output efficiency.

[0039] Furthermore, in the hydroelectric power generation system according to this embodiment, the diode full-wave rectifier circuit 20 using passive elements does not actively stabilize the voltage, so the input voltage of the half-bridge inverter 31 fluctuates depending on the power generated by the micro hydroelectric generator 10. In response to this, the control unit 35 monitors the input voltage and output current of the power conversion device 30, and performs MPPT control so that the output power of the power conversion device 30 is maximized and the output current of the power conversion device 30 is stabilized. This maximizes the output efficiency of the power conversion device 30, making it possible to obtain a continuous, stable output current.

[0040] As described above, according to this embodiment, a hydroelectric power generation system can be provided that is suitable for application to micro-hydroelectric power generation, with a simpler circuit configuration that can minimize losses and maximize output efficiency.

[0041] As an application example of the above embodiment, a hydroelectric power generation system may be configured as shown in Fig. 3. In Fig. 3, components having the same functions as those shown in Fig. 1 are assigned the same reference numerals. The hydroelectric power generation system shown in Fig. 3 further includes a flyback converter 40 having a configuration similar to that of the power conversion device 30, and the power conversion device 30 and the flyback converter 40 are connected in parallel via a switch 50. The switch 50 makes it possible to switch whether or not the flyback converter 40 is connected to the micro hydroelectric generator 10 for operation.

[0042] The flyback converter 40 shown in Fig. 3 has multiple USB terminals 41, and each USB terminal 41 can be connected to a load 200. For example, a USB memory can be connected as the load 200 to charge it, or a USB device can be connected and operated. When using the micro-hydroelectric generator 10 to charge the USB memory or to obtain power for the USB device, the switch 50 is manually switched from off to on, for example. Furthermore, by operating the flyback converter 40, it is possible to effectively utilize surplus power generated by the power conversion device 30 and prevent the micro-hydroelectric generator 10 from stalling.

[0043] Alternatively, the flyback converter 40 can also function as a safety circuit. For example, if an abnormality occurs in the power conversion device 30 that is operating with the switch 50 off, making it impossible to charge the battery 100, or if the battery 100 becomes fully charged and cannot be charged, the switch 50 can be turned on to operate the flyback converter 40, thereby avoiding a light load or no load condition and preventing excessive power generation in the micro-hydroelectric generator 10. In this case, the control unit 35 may monitor the input voltage of the power conversion device 30 detected by the voltage sensor 36 and automatically switch the switch 50 from off to on.

[0044] Although the configuration in which the flyback converter 40 is provided in addition to the power conversion device 30 has been described here, a configuration in which two power conversion devices 30 are connected in parallel via the switch 50 may also be used. Furthermore, although the example in which the flyback converter 40 functions as a safety circuit has been described here, a simple safety circuit such as a discharge circuit may be provided instead of or in addition to the flyback converter 40.

[0045] Furthermore, the above-described embodiments are merely examples of specific embodiments for carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereby. In other words, the present invention can be carried out in various forms without departing from the gist or main characteristics thereof. [Explanation of symbols]

[0046] 10 Micro Hydroelectric Generator 20 Diode full-wave rectifier circuit 30 Power conversion device 31 Half-bridge inverter 311 Switching element 32 Trans 321 Primary Winding 322 Secondary Winding 33 Rectifier circuit 331 Diode 34 Smoothing circuit 341 Reactor 35 Control Unit 36 Voltage sensor 37 Current Sensor 40 Flyback Converter 100 Load (battery)

Claims

1. A micro hydroelectric generator, a diode full-wave rectifier circuit that converts the power generated by the micro hydroelectric generator into DC power; a power conversion device that converts and outputs the DC power output from the diode full-wave rectifier circuit, The power conversion device is a half-bridge inverter that converts the DC power output from the diode full-wave rectifier circuit into AC power; a transformer having a primary winding connected to the half-bridge inverter; a rectifier circuit using a diode connected to the secondary winding of the transformer; a smoothing circuit that smoothes the DC voltage rectified by the rectifier circuit; a control unit that monitors the input voltage of the power conversion device and the output current of the power conversion device, and controls switching of the switching elements of the half-bridge inverter so as to maximize the output power of the power conversion device. A hydroelectric power generation system.

2. the transformer has a plurality of secondary windings; the rectifier circuit is configured as a full-wave rectifier circuit in which a plurality of diodes are connected to each of the plurality of secondary windings, The smoothing circuit is composed of one reactor connected in series to the rectifier circuit.

2. The hydroelectric power generation system according to claim 1.

3. The hydroelectric power generation system described in claim 1 or 2, characterized in that the control unit calculates an expected value of the output power of the power conversion device based on a characteristic model that is pre-stored as an assumed model showing the relationship between how the output power of the power conversion device fluctuates in response to fluctuations in the input voltage of the power conversion device and the input voltage and output current of the power conversion device that are monitored, and performs MPPT control using a hill-climbing method based on the expected value.

4. a turn ratio between the primary winding and the secondary winding of the transformer is set so as to achieve a transformation ratio determined from a value of an input voltage of the power conversion device, which is assumed in advance as a range in which the output power of the power conversion device may be maximized, and a value of an operating voltage of a load connected to the output side of the power conversion device; The control unit performs the MPPT control within the range of the input voltage assumed in advance.

4. The hydroelectric power generation system according to claim 3.

5. The hydroelectric power generation system according to claim 1, further comprising a flyback converter having a configuration similar to that of the power conversion device, and the power conversion device and the flyback converter are connected in parallel via a switch.

6. a half-bridge inverter that converts input DC power into AC power; a transformer having a primary winding connected to the half-bridge inverter; a rectifier circuit using a diode connected to the secondary winding of the transformer; a smoothing circuit that smoothes the DC voltage rectified by the rectifier circuit; a control unit that monitors an input voltage to the half-bridge inverter and an output current from the smoothing circuit, and controls switching of switching elements of the half-bridge inverter so as to maximize the output power from the smoothing circuit. A power conversion device characterized by:

7. the transformer has a plurality of secondary windings; the rectifier circuit is configured as a full-wave rectifier circuit in which a plurality of diodes are connected to each of the plurality of secondary windings, The smoothing circuit is composed of one reactor connected in series to the rectifier circuit.

7. The power conversion device according to claim 6.

8. The power conversion device according to claim 6 or 7, characterized in that the control unit calculates an expected value of the output power of the power conversion device based on a characteristic model that is stored in advance as an assumed model that indicates the relationship of how the output power of the power conversion device fluctuates in response to fluctuations in the input voltage of the power conversion device and on the input voltage and output current of the power conversion device that are monitored, and performs MPPT control using a hill-climbing method based on the expected value.

9. a turn ratio between the primary winding and the secondary winding of the transformer is set so as to achieve a transformation ratio determined from a value of an input voltage of the power conversion device, which is assumed in advance as a range in which the output power of the power conversion device may be maximized, and a value of an operating voltage of a load connected to the output side of the power conversion device; The control unit performs the MPPT control within the range of the input voltage assumed in advance.

9. The power conversion device according to claim 8.

10. A power generation output control method for performing MPPT control to maximize output power of a power conversion device that converts and outputs DC power generated based on power generated by a micro hydroelectric generator through switching control of switching elements of a half-bridge inverter included in the power conversion device, the method comprising: a control unit of the power conversion device calculates an expected value of the output power of the power conversion device based on a characteristic model stored in advance as an assumed model showing the relationship of how the output power of the power conversion device fluctuates in response to fluctuations in the input voltage of the power conversion device, and on the input voltage and output current of the power conversion device being monitored, and performs MPPT control using a hill-climbing method based on the expected value.

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