JP2008191780A - Conversion unit for power generated by natural energy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power conversion unit capable of effectively utilizing natural energy by appropriately coping with varied wind power etc. with a simple configuration. <P>SOLUTION: A power conversion unit 101 includes a rectifier circuit 1 for converting an alternating voltage received from a power generator unit 102 into a first direct current voltage; a direct current voltage conversion circuit 2 for converting the first direct current voltage into a second direct current voltage; and a common input terminal T1 for receiving the second direct current voltage and the third direct current voltage. The power conversion unit 101 further includes an inverter circuit 4 for generating an alternating voltage to be applied to a load 103 based on the direct current voltage received in the input terminal T1; a control circuit 7 for controlling the direct current voltage conversion circuit 2 so that the output current of the rectifier circuit 1 becomes lower than a predetermined value and that the voltage at the input terminal T1 becomes lower than a first predetermined voltage value; and a battery 3 for outputting a third direct current voltage in case of the voltage at the input terminal T1 being lower than a second predetermined voltage value smaller than the first predetermined voltage value, and for charging based on the output current of the direct current voltage conversion circuit 2 in case of being not lower than the second predetermined voltage value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power conversion device, and more particularly, to a power conversion device generated by natural energy.

Power generation devices that generate power using natural energy such as wind power have been developed. For example, Patent Documents 1-3 disclose a power generation device that generates power using wind power. That is, the generated AC voltage is rectified by a rectifier circuit and converted into a DC voltage, and the converted DC voltage is converted into an AC voltage by an inverter and supplied to a load. With such a configuration, it is possible to prevent the supply power to the load from fluctuating due to fluctuations in natural energy.
Special table 2001-522218 gazette Japanese Patent Laid-Open No. 11-62814 JP 2005-538673 A

  By the way, in the power generation device that generates power using wind power, such as the power generation device described in Patent Documents 1-3, the generated power decreases when the wind becomes weak. For this reason, the conventional power generation device includes, for example, a storage battery, and when the generated power of the power generation device is insufficient, the storage battery is discharged to compensate for the shortage of power.

  However, in the power generation device described in Patent Document 1-2, if the generated power is insufficient and the output voltage of the power generation device is too low, no power is supplied from the power generation device to the load.

  Further, in the power generation device described in Patent Document 3, it is possible to continue to supply the generated power to the load even if the wind becomes weak, but since a configuration for switching between the synchronous operation and the asynchronous operation of the generator is required, The configuration of the power generation device becomes complicated.

  SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a power converter that can effectively use natural energy by appropriately responding to fluctuations in wind power and the like with a simple configuration.

  In order to solve the above problems, a power converter according to an aspect of the present invention includes a rotating machine that rotates by natural energy, and a power generator that generates electric power based on the rotation of the rotating machine is disposed outside. A converter for power generated by natural energy, which converts power from the power generator and supplies it to a load, a rectifier circuit for converting an AC voltage received from the power generator into a first DC voltage, and rectification A DC voltage conversion circuit that converts the first DC voltage received from the circuit into a second DC voltage; a battery that outputs and charges the third DC voltage; and the second DC voltage and the third DC voltage. An inverter circuit that has a common input terminal for receiving and generates an AC voltage to be supplied to the load based on a DC voltage received at the input terminal, and an output current of the rectifier circuit is less than a predetermined value And a control circuit for controlling the voltage value of the second DC voltage converted by the DC voltage conversion circuit so that the voltage of the input terminal is equal to or lower than the first predetermined voltage value, and the battery has a voltage of the input terminal. Is less than the second predetermined voltage value smaller than the first predetermined voltage value, the third DC voltage is output, and when the input terminal voltage is greater than or equal to the second predetermined voltage value, the DC voltage conversion circuit Charging is performed based on the output current.

  Preferably, the DC voltage conversion circuit includes a switch element, and converts the first DC voltage received from the rectifier circuit into a second DC voltage by switching with the switch element, and the control circuit outputs the output current of the rectifier circuit. The switching of the switch element is controlled so that the voltage at the input terminal is equal to or lower than the first predetermined voltage value.

  Preferably, when the first DC voltage received from the rectifier circuit is larger than the predetermined voltage value, the DC voltage conversion circuit steps down the first DC voltage received from the rectifier circuit and has a DC voltage equal to or lower than the predetermined voltage value. And a step-up circuit for stepping up a DC voltage received from the step-down circuit to generate a second DC voltage.

  Preferably, the DC voltage conversion circuit includes a coil that receives the first DC voltage at the first end, a first capacitor that has the first end coupled to the first end of the coil, and a second end that is the second end of the coil. A switch element coupled to the end, a diode having an anode coupled to the first end of the switch element, a first end coupled to the cathode and input terminal of the diode, and a second end coupled to the second end of the switch element A second capacitor coupled, a first end coupled to the second end of the switch element and a second end of the second capacitor, and a second end coupled to the second end of the first capacitor. The control circuit detects the output current of the rectifier circuit based on the voltage at the second end of the current detection resistor, and the voltage of the input terminal is set so that the output current of the rectifier circuit is less than a predetermined value. So that it is less than or equal to the first predetermined voltage value. It controls the switching of the pitch elements.

  ADVANTAGE OF THE INVENTION According to this invention, natural energy can be effectively utilized by responding | corresponding appropriately to fluctuations, such as wind power, with a simple configuration.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

FIG. 1 is a circuit diagram showing a configuration of a power conversion system according to an embodiment of the present invention.
Referring to FIG. 1, a power conversion system 201 includes a power conversion device 101 and a wind power generation device 102. The power conversion device 101 includes a rectifier circuit 1, a DC voltage conversion circuit 2, a storage battery 3, an inverter circuit 4, a low-pass filter 5, a DC voltage control circuit 6, and an inverter control circuit 7. The DC voltage conversion circuit 2 includes a step-down circuit 11 and a step-up circuit 12.

  The wind power generator 102 includes a rotating machine that is rotated by wind power that is natural energy, generates AC power based on the rotation of the rotating machine, and outputs the generated AC voltage to the power converter 101.

  The power converter 101 converts the AC voltage received from the wind power generator 102 into a DC voltage, converts the converted DC voltage into an AC voltage having a predetermined frequency and a predetermined amplitude, and outputs the AC voltage to the load 103.

  More specifically, the rectifier circuit 1 converts the AC voltage received from the wind power generator 102 into a DC voltage (first DC voltage).

  The DC voltage conversion circuit 2 converts the DC voltage received from the rectifier circuit 1 into a new DC voltage (second DC voltage) based on the control signal received from the DC voltage control circuit 6. More specifically, when the DC voltage received from rectifier circuit 1 is greater than a predetermined voltage value, step-down circuit 11 steps down the DC voltage received from the rectifier circuit to generate a DC voltage that is equal to or lower than the predetermined voltage value. Note that the step-down circuit 11 may output the direct-current voltage received from the rectifier circuit as it is, or may output the step-down circuit to some extent when the direct-current voltage received from the rectifier circuit 1 is equal to or lower than a predetermined voltage value. Good. When the DC voltage received from the step-down circuit 11 is equal to or lower than a predetermined voltage value, the step-up circuit 12 boosts the DC voltage received from the step-down circuit 11 to generate a DC voltage that is equal to or higher than the predetermined voltage value.

  The storage battery 3 outputs a DC voltage (third DC voltage) to the inverter circuit 4. The storage battery 3 is charged based on the direct current received from the direct current voltage conversion circuit 2.

  The DC voltage control circuit 6 controls the voltage value of the DC voltage converted by the DC voltage conversion circuit 2 so that the output current of the rectifier circuit 1, that is, the output current of the wind power generator 102, is less than a predetermined value.

  Based on the control signal received from inverter control circuit 7, inverter circuit 4 converts the DC voltage received from DC voltage conversion circuit 2 and the DC voltage received from storage battery 3 into an AC voltage to be supplied to load 103.

  The low pass filter 5 removes high frequency noise included in the AC voltage received from the inverter circuit 4. The AC voltage that has passed through the low-pass filter 5 is output to the load 103.

  The inverter control circuit 7 generates a control signal so that the AC voltage that has passed through the low-pass filter 5 has a predetermined frequency and a predetermined amplitude, and outputs the control signal to the inverter circuit 4.

  Here, to give specific numerical examples of each voltage, the rectifier circuit 1 converts the three-phase AC voltage of 45V to 225V received from the wind power generator 102 and outputs the DC voltage of 70V to 330V.

  The step-down circuit 11 steps down the DC voltage received from the rectifier circuit 1 and outputs a DC voltage of 25V to 150V.

  Booster circuit 12 boosts the DC voltage received from step-down circuit 11 and outputs a DC voltage of 205 V to inverter circuit 4.

  The inverter circuit 4 generates an AC voltage having an amplitude of 100 V to be supplied to the load 103 from the DC voltage received from the DC voltage conversion circuit 2 and the DC voltage received from the storage battery 3.

FIG. 2 is a circuit diagram showing a configuration of the power conversion device according to the embodiment of the present invention.
Referring to FIG. 2, power converter 101 includes rectifier circuit 1, DC voltage converter circuit 2, storage battery 3, inverter circuit 4, low-pass filter 5, DC voltage control circuit 6, and inverter control circuit 7. And a resistor R2 and a diode D2. The DC voltage conversion circuit 2 includes a step-down circuit 11 and a step-up circuit 12. Inverter circuit 4 includes N-channel MOS transistors M11 to M14, a coil L2, a transformer TR1, a capacitor C3, and input terminals T1 and T2. The DC voltage control circuit 6 includes a generated current monitoring circuit 21, a boost voltage monitoring circuit 22, a charging current monitoring circuit 23, and a PWM control signal generation circuit 24. The booster circuit 12 includes a capacitor (first capacitor) C1, a capacitor (second capacitor) C2, a coil L1, a current detection resistor R1, an N-channel MOS transistor (switch element) M1, and a diode D1. Including.

  Coil L1 has a first end coupled to the output of step-down circuit 11. Capacitor C1 has a first end coupled to a first end of coil L1. N-channel MOS transistor M1 has a drain (first end) coupled to a second end of coil L1. Diode D1 has an anode coupled to the drain of N channel MOS transistor M1. Capacitor C2 has a first end coupled to the cathode of diode D1 and input terminal T1, and a second end coupled to the source of N-channel MOS transistor M1 and input terminal T2. Current detection resistor R1 has a first end coupled to the source of N-channel MOS transistor M1 and a second end of capacitor C2, and a second end coupled to a second end of capacitor C1.

  Inverter control circuit 7 generates control signals CONT1 to CONT4 such that the AC voltage that has passed through low-pass filter 5 has a predetermined frequency and a predetermined amplitude, and outputs the control signals to N-channel MOS transistors M11 to M14.

  N-channel MOS transistors M11 to M14 perform switching based on control signals CONT1 to CONT4, respectively, convert a DC voltage that is a voltage across capacitor C2 into an AC voltage, and output it to the primary winding of transformer TR1.

  The AC voltage induced in the secondary winding of the transformer TR1 passes through the low-pass filter 5 and is output to the load 103.

FIG. 3 is a graph showing the output characteristics of the wind turbine generator 102.
With reference to FIG. 3, in general, when a wind turbine generator outputs a current of a certain value or more, the output voltage rapidly decreases. That is, generally, in a wind power generator having a rotating machine, for example, when the wind weakens and the generated power decreases, the generated voltage also decreases. In addition, since a general power supply device, for example, a conversion device such as an inverter, always operates to supply necessary power to the load, when the input voltage of the power supply device, that is, the power generation voltage of the wind power generator decreases, the power supply device The input current, that is, the output current of the wind power generator will increase. For this reason, if the wind is weakened and the generated power and the generated voltage are reduced, as shown in FIG. 3, if an electric current of a certain value or more is caused to flow from the wind power generator, the output current of the wind power generator decreases more rapidly. As a result, power cannot be supplied.

  Therefore, in the power converter according to the embodiment of the present invention, the DC voltage control circuit 6 includes a DC voltage converter circuit so that the output current of the rectifier circuit 1, that is, the output current of the wind power generator 102 is less than the current value IA. 2 controls the voltage value of the DC voltage to be converted. That is, the DC voltage control circuit 6 prevents the output voltage of the rectifier circuit 1 from being lowered due to overcurrent by limiting the output current of the wind turbine generator 102.

  In normal times, that is, when the power generated by the wind power generator 102 is larger than the power consumed by the load 103, the current flowing through the current detection resistor R1 is smaller than the current value IA to be current-limited. Therefore, the DC voltage control circuit 6 does not limit the current, that is, does not decrease the voltage between the input terminals T1 and T2, that is, the voltage across the capacitor C2.

  Then, the DC voltage control circuit 6 controls the DC voltage conversion circuit 2 so that the voltage between the input terminals T1 and T2, that is, the voltage across the capacitor C2, becomes the voltage at which the storage battery 3 charges. For example, when the nominal voltage of the storage battery 3 is 180V, the DC voltage control circuit 6 controls the DC voltage conversion circuit 2 so that the voltage across the capacitor C2 is 205V. More specifically, the boost voltage monitoring circuit 22 monitors the voltage Vc across the capacitor C2 and notifies the PWM control signal generation circuit 24 whether or not the voltage Vc is 205V or less. The PWM control signal generation circuit 24 reduces the duty ratio of the control signal CONT5 output to the gate of the N-channel MOS transistor M1 when the voltage Vc across the capacitor C2 is greater than 205V. Then, the ON period of N channel MOS transistor M1 in a predetermined period is shortened, and voltage Vc across capacitor C2 is decreased. On the other hand, when the voltage Vc across the capacitor C2 is lower than 205V, the PWM control signal generation circuit 24 increases the duty ratio of the control signal CONT5 and increases the voltage Vc across the capacitor C2.

  At this time, the DC voltage conversion circuit 2 supplies power to the inverter circuit 4 while charging the storage battery 3. That is, the output current of the DC voltage conversion circuit 2 flows to the storage battery 3 and the inverter circuit 4.

  Here, when the storage battery 3 is charged, the direct current from the direct-current voltage conversion circuit 2 flows through the resistor R2 without flowing through the diode D2. The charging current monitoring circuit 23 monitors the voltage across the resistor R2. When the voltage across the resistor R2 is greater than the predetermined voltage, the charging current monitoring circuit 23 determines that the battery is overcharged and notifies the PWM control signal generation circuit 24. When the PWM control signal generation circuit 24 receives a notification from the charging current monitoring circuit 23 that it is overcharged, the PWM control signal generation circuit 24 decreases the duty ratio of the control signal CONT5 regardless of the monitoring result of the boost voltage monitoring circuit 22. As a result, the ON period of the N-channel MOS transistor M1 in a predetermined period is shortened, the voltage Vc across the capacitor C2 is reduced, the DC current from the DC voltage conversion circuit 2 to the storage battery 3 is reduced, and the overcurrent is eliminated.

  On the other hand, when power generation is insufficient, that is, when the power generation voltage of the wind power generator 102 decreases due to a decrease in the power generation power of the wind power generation apparatus 102 and becomes smaller than the power consumption of the load 103, or the power consumption of the load 103 increases. Therefore, when the power supplied to the inverter circuit 4 increases, the current flowing through the current detection resistor R1 increases and becomes larger than the current value IA to be current-limited.

  When the current flowing through the current detection resistor R1 becomes larger than the current value IA, the DC voltage control circuit 6 performs current limitation. That is, the DC voltage control circuit 6 controls the DC voltage conversion circuit 2 so that the voltage across the capacitor C2 becomes small.

  When the voltage at both ends of the capacitor C <b> 2 decreases to, for example, less than 180 V, the storage battery 3 is discharged and supplies the inverter circuit 4 with a shortage of generated power relative to the power to be supplied to the load 103.

  Here, the voltage across the capacitor C2 is Vc, the input current of the inverter circuit 4 is Iinv, the DC voltage that the booster circuit 12 receives from the step-down circuit 11 is Vi, and the DC current that the booster circuit 12 receives from the step-down circuit 11 is Ii. Assuming that the discharge current of the storage battery 3 is Ib, the following equation is established.

Vc × Iinv = Vi × Ii + Vc × Ib (1)
That is, when the DC voltage Vi decreases due to a decrease in generated power or when the power supplied to the inverter circuit 4 increases due to an increase in power consumption of the load 103, the current flowing through the current detection resistor R1, that is, the output current of the wind power generator 102 is growing. Here, the terminal on the inverter circuit 4 side of the current detection resistor R1 is at zero potential. For this reason, the terminal voltage on the step-down circuit 11 side of the current detection resistor R1 is a negative voltage. When the terminal voltage on the step-down circuit 11 side of the current detection resistor R1 becomes small and becomes equal to or lower than the voltage value corresponding to the current value IA, the generated current monitoring circuit 21 converts the output current of the step-down circuit 11, that is, the output current of the rectifier circuit 1 Recognizing that the value is equal to or greater than IA, the PWM control signal generation circuit 24 is notified.

  The PWM control signal generation circuit 24 receives the notification from the generated current monitoring circuit 21 and reduces the duty ratio of the control signal CONT5. Then, the ON period of N channel MOS transistor M1 in a predetermined period is shortened, and voltage Vc across capacitor C2 is decreased.

  Further, the storage battery 3 increases the discharge current Ib so as to satisfy the expression (1) because the voltage Vc across the capacitor C2 decreases. Then, the current flowing through the current detection resistor R1 becomes less than the current value IA. That is, the storage battery 3 compensates for the shortage of generated power.

  FIG. 4 is a diagram showing the results of measuring the generated voltage and generated current of the wind power generator 102 and the output voltage and output current of the power converter 101. FIG. 4 shows a case where the load resistance (power consumption) of the load 103 is 400 W. Here, the output voltage (generated voltage) of the wind power generator 102 is a three-phase AC voltage, and the frequency is about 400 Hz. However, the frequency of the output voltage of the wind power generator 102 varies according to the power generation voltage value of the wind power generator 102. The output voltage of the power converter 101 is a single-phase AC voltage having a frequency of 60 Hz.

  Referring to FIG. 4, for example, when the generated voltage of wind power generator 102 is 90 V and the generated current is 2.86 A, the generated power is 90 × 2.86 × √3≈445 [W]. In this case, the DC voltage conversion circuit 2 supplies power to the inverter circuit 4 while charging the storage battery 3. When the power generation voltage of the wind power generator 102 is 105 V to 225 V, the generated power exceeds 400 W, and thus the same as in the case of 90 V.

  When the generated voltage of the wind power generator 102 is 75 V and the generated current is 2.62 A, the generated power is 75 × 2.62 × √3≈340 [W]. In this case, although the generated power of the wind power generator 102 is insufficient with respect to the power consumed by the load 103, the shortage of the generated power of the wind power generator 102 is compensated by discharging the storage battery 3. When the power generation voltage of the wind power generator 102 is 0 V to 60 V, the generated power is less than 400 W, and thus the same as in the case of 75 V.

  Therefore, the power conversion device 101 can stably generate an AC voltage having an amplitude of about 100 V in a wide range of generated voltages from 0 V to 225 V.

  Here, the operable range of a general power converter is a range of ± 10% of the rated input voltage. For example, when the rated input voltage of a general power conversion device is 150V, an AC voltage with a desired output of 100V can be generated only when the generated voltage is in the range of 135V to 165V. On the other hand, in the power conversion device according to the embodiment of the present invention, a power generation current of 1.52 A or more is supplied from the wind power generation device 102 to the power conversion device 101 when the power generation voltage of the wind power generation device 102 is in the range of 45V to 225V. Yes. That is, in the power conversion device according to the embodiment of the present invention, natural energy can be effectively used in a wide range of generated voltages.

  By the way, in the power generation device described in Patent Document 1-2, if the generated power is insufficient and the output voltage of the power generation device is too low, no power is supplied from the power generation device to the load. Further, in the power generation device described in Patent Document 3, it is possible to continue to supply the generated power to the load even if the wind becomes weak, but since a configuration for switching between the synchronous operation and the asynchronous operation of the generator is required, The configuration of the power generation device becomes complicated.

  However, in the power conversion device according to the embodiment of the present invention, the DC voltage control circuit 6 is configured so that the output current of the wind power generator 102 is less than a predetermined value and the input voltage of the inverter circuit 4, that is, the input terminal T1 and The voltage value of the DC voltage converted by the DC voltage conversion circuit 2 is controlled so that the voltage between T2 becomes the first predetermined voltage value. The storage battery 3 outputs a DC voltage when the input voltage of the inverter circuit 4 is less than a second predetermined voltage value smaller than the first predetermined voltage value, and the input voltage of the inverter circuit 4 is equal to or higher than the second predetermined voltage value. In this case, charging is performed based on the output current of the DC voltage conversion circuit 2.

  With such a configuration, even if the generated power of the wind turbine generator is reduced and the generated power of the wind turbine generator is insufficient, or even if the power consumption of the load is increased and the generated power of the wind turbine generator is insufficient, the inverter While being able to continue supplying generated electric power to a load via a circuit, it can be set as the simple structure which does not have the structure which switches the synchronous operation | movement and asynchronous operation | movement of a generator. Therefore, in the power conversion device according to the embodiment of the present invention, natural energy can be effectively used by appropriately responding to fluctuations in wind power or the like with a simple configuration.

  In the power conversion device according to the embodiment of the present invention, when the DC voltage received from the rectifier circuit 1 is greater than a predetermined voltage value, the step-down circuit 11 steps down the DC voltage received from the rectifier circuit. A DC voltage that is equal to or lower than the voltage value is generated. When the DC voltage received from the step-down circuit 11 is equal to or lower than a predetermined voltage value, the step-up circuit 12 boosts the DC voltage received from the step-down circuit 11 to generate a DC voltage that is equal to or higher than the predetermined voltage value. With such a configuration, as described above, a predetermined AC voltage can be stably generated in a wider range of generated voltage than in a general power converter. The present invention is particularly effective when converting electric power generated by natural energy, such as wind power, in which the generated electric power varies greatly depending on weather conditions.

  In addition, although the power converter device which concerns on embodiment of this invention was set as the structure provided with the storage battery 3, it is not limited to this. Any device that can be used not only as a storage battery but also as a chargeable / dischargeable battery may be used. For example, the power converter may be configured to include an element such as a large-capacity capacitor instead of the storage battery.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a circuit diagram showing a configuration of a power conversion system according to an embodiment of the present invention. It is a circuit diagram which shows the structure of the power converter device which concerns on embodiment of this invention. It is a graph which shows the output characteristic of a wind power generator. It is a figure which shows the result of having measured the power generation voltage and power generation current of the wind power generator 102, and the output voltage and output current of the power converter device 101. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Rectification circuit, 2 DC voltage conversion circuit, 3 Storage battery, 4 Inverter circuit, 5 Low pass filter, 6 DC voltage control circuit, 7 Inverter control circuit, 11 Buck circuit, 12 Boost circuit, 21 Power generation current monitoring circuit, 22 Boost voltage monitoring Circuit, 23 charging current monitoring circuit, 24 PWM control signal generation circuit, 101 power converter, 102 wind power generator, 103, 201 power conversion system, C1 capacitor (first capacitor), C2 capacitor (second capacitor), C3 capacitor, L1, L2 coil, R1, R2 resistor, D1, D2 diode, T1, T2 input terminal, M1 N channel MOS transistor (switch element), M11 to M14 N channel MOS transistor, TR1 transformer.

Claims (4)

A generator that has a rotating machine that rotates by natural energy and that generates electric power based on the rotation of the rotating machine is arranged outside, and converts the electric power from the generator and supplies it to a load. A converted power converter,
A rectifier circuit that converts an AC voltage received from the power generation device into a first DC voltage;
A DC voltage conversion circuit for converting the first DC voltage received from the rectifier circuit into a second DC voltage;
A battery for outputting and charging a third DC voltage;
An inverter circuit having a common input terminal for receiving the second DC voltage and the third DC voltage, and generating an AC voltage to be supplied to the load based on the DC voltage received at the input terminal; ,
As the output current of the rectifier circuit is less than the predetermined value, and such that the voltage of the input terminal is equal to or less than the first predetermined voltage value, the voltage of the second DC voltage to be converted of the DC voltage converter A control circuit for controlling the value,
The battery outputs the third DC voltage when the voltage at the input terminal is less than a second predetermined voltage value that is smaller than the first predetermined voltage value, and the voltage at the input terminal is the second voltage. A converter for electric power generated by natural energy, which is charged based on an output current of the DC voltage conversion circuit when the voltage is equal to or higher than a predetermined voltage value. The DC voltage conversion circuit includes a switch element, and converts the first DC voltage received from the rectifier circuit into the second DC voltage by switching the switch element.
The control circuit controls switching of the switch element so that an output current of the rectifier circuit is less than a predetermined value and a voltage of the input terminal is equal to or lower than a first predetermined voltage value. Conversion device for power generated by natural energy. The DC voltage conversion circuit is:
When the first DC voltage received from the rectifier circuit is greater than a predetermined voltage value, the first DC voltage received from the rectifier circuit is stepped down to generate a DC voltage equal to or lower than the predetermined voltage value. Circuit,
The converter for the electric power generated by natural energy according to claim 1, further comprising: a booster circuit that boosts a DC voltage received from the step-down circuit to generate the second DC voltage. The DC voltage conversion circuit is:
A coil that receives the first DC voltage at a first end;
A first capacitor having a first end coupled to the first end of the coil;
A switching element having a first end coupled to a second end of the coil;
A diode having an anode coupled to the first end of the switch element;
A second capacitor having a first end coupled to the cathode of the diode and the input terminal and a second end coupled to a second end of the switch element;
A first end coupled to a second end of the switch element and a second end of the second capacitor, and a second end coupled to a second end of the first capacitor;
The control circuit detects the output current of the rectifier circuit based on the voltage at the second end of the current detection resistor, and the voltage of the input terminal is set so that the output current of the rectifier circuit is less than a predetermined value. The converter of the electric power generated with the natural energy of Claim 1 which controls switching of the said switch element so that it may become below 1st predetermined voltage value.

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