JP2005218151A - Power conversion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power conversion device that can effectively utilize generated power without converting surplus power into heat, and also without generating an adverse tidal current to a system. <P>SOLUTION: Part of power generate by a DC power supply 11 is charged into the power conversion device as power by the operation of a second converter 18 and a storage means 19, and the stored power can be taken out to the outside as needed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a power conversion device that converts DC power, such as a solar cell or a fuel cell, into AC power having a commercial frequency and injects power into the system.

  Conventionally, as this type of power conversion device, for example, a resonance capacitor and a switching element are arranged on the primary side of a high-frequency transformer, and a zero voltage switching operation is performed by resonating the voltage waveform of the switching element. By performing sinusoidal modulation with a double period, and further rectifying high-frequency components with a diode and a capacitor on the secondary side of the high-frequency transformer, and switching the polarity with a secondary inverter arranged on the secondary side of the high-frequency transformer, There has been a high-efficiency power converter that generates a sine wave current with a rate of 1 (see, for example, Patent Document 1).

FIG. 7 is a connection diagram illustrating a configuration of a power conversion device that is conventionally used. The output power of the DC power supply 1 is converted into high frequency power by the first inverter 2 and then transmitted to the secondary side via the high frequency transformer 3. The high-frequency power generated on the secondary side of the high-frequency transformer 3 is converted into a high-frequency pulsating flow by the rectifying means 4, and only the high-frequency current component is removed by the filter capacitor 9. It is converted into a wavy alternating current and injected into the system 6. Here, the first inverter 2 is constituted by a switching element 8 and a resonance capacitor 7, and the second inverter 5 is constituted by a full bridge with four switching elements Q1 to Q4.
JP 2000-32751 A

  However, in the conventional configuration, in a direct current power source such as a fuel cell in which reverse power flow is difficult in terms of economy and responsiveness is low, if the generated power is not consumed by household equipment connected to the system, the device It was necessary to convert the generated energy into heat internally.

  The present invention solves the above-described conventional problems, and provides a power conversion means that has means for accumulating electric power generated by a DC power source and that can effectively utilize generated power without generating a reverse power flow. For the purpose.

  In order to achieve the above object, a power converter according to the present invention is provided with a second converter and a power storage means connected thereto at the output of a DC power supply. Electric power is charged inside by the operation of the second converter and power storage means, and the stored power can be taken out as needed.

  The power conversion device of the present invention can charge the power storage means connected to the output of the DC power supply to prevent the reverse power flow to the system of the generated power, thereby enabling stable operation of the DC power supply. Become.

  A first invention includes a high-frequency transformer, a DC power source on a primary side insulated by the high-frequency transformer, a first converter that converts DC power into high-frequency power, and a second converter that converts DC power into a predetermined voltage. The power storage means, the rectifier means on the secondary side of the high-frequency transformer, and an inverter that is composed of four switching elements and injects alternating current into the system are arranged, and the first converter and the second converter are output to the output of the direct current power supply Are connected in parallel, and the power storage means is connected in series to the output of the second converter, so that it is possible to charge the power storage means with the surplus power whose power generation exceeds the consumption of household devices.

  In the second invention, in particular, the power storage means of the first invention is constituted by a secondary battery, so that an inexpensive configuration can be obtained.

  According to a third invention, in the first or second invention, the voltage detection means for detecting the DC voltage of the power storage means is arranged, and the output current of the second converter is determined based on the DC voltage, so that the power storage means It can be a versatile device that does not depend on serial and parallel configurations.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the life of the power storage means can be extended by controlling the output current of the second converter at a predetermined value or less.

  According to a fifth invention, in any one of the first to fourth inventions, the second converter is configured to be capable of bidirectional output, and power is supplied from the power storage means to the inverter. Even when power is not supplied from a DC power supply, power can be supplied to household devices.

  According to a sixth invention, in any one of the first to fifth inventions, the second converter is a step-up / step-down converter, thereby ensuring a charge / discharge operation regardless of the voltage of the DC power supply or the voltage of the storage means. it can.

  According to a seventh invention, in any one of the first to sixth inventions, when the detection voltage of the voltage detection means is equal to or lower than a threshold value, the control means stops the operation of the second converter, so that there is no power storage means. This can be a safe device that automatically determines this.

  According to an eighth invention, in any one of the first to seventh inventions, the bidirectional converter operates regardless of the operating state of the DC power supply and the system by supplying the control power of the second converter from the power storage means. Therefore, it is possible to stably supply power.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the present embodiment.

(Embodiment 1)
This embodiment relates to claims 1 and 2. FIG. 1 shows a connection diagram of the power conversion device according to the first embodiment of the present invention.

  In FIG. 1, DC power generated by a DC power supply 11 is converted into high-frequency power by a first converter 12, then boosted by a high-frequency transformer 13 and transmitted to the secondary side. A rectifier 14 is disposed on the secondary side of the high-frequency transformer 13, and an inverter 15 having a filter capacitor 16 and a system 17 are connected to the output of the rectifier 14 in this order. Further, a second converter 18 is disposed in parallel with the first converter 12 at the output of the DC power supply 11, and a power storage means 19 is connected to the output of the second converter.

  The operation | movement and effect | action are demonstrated below about the power converter device comprised as mentioned above.

  First, when the output of the DC power supply 11 is smaller than the power consumption of the home appliance, the first converter 12 performs sinusoidal modulation with a commercial double cycle, and the high frequency power generated on the secondary side of the high frequency transformer 13. Among them, the high frequency component is removed by the filter capacitor 16 and the polarity of the commercial frequency component is switched by the inverter 15 to generate a low distortion AC current synchronized with the system voltage. On the other hand, when the output of the DC power supply 11 is larger than the household power and a reverse power flow to the grid 17 occurs as it is, the second converter 18 charges the power storage means 19 with the surplus power.

  As described above, in the present embodiment, the second converter charges the power storage means with the power that is not consumed at home out of the power generated by the DC power supply, thereby realizing the continuation of power generation and the system. It is possible to prevent reverse current flow.

  In addition, it can be set as an inexpensive structure by making the electrical storage means 19 into a secondary battery.

(Embodiment 2)
This embodiment relates to claim 3. FIG. 2 is a connection diagram of the power conversion device according to the second embodiment of the present invention.

  2 is different from the circuit configuration of FIG. 1 in that a voltage detection means 20, a second converter control means 21, and a second converter power command means 22 of the power storage means 19 are arranged, and a current is supplied to the second converter. The command value is given. Components other than those described above are the same as those in the first embodiment, and a description thereof will be omitted.

  The operation | movement and effect | action are demonstrated below about the power converter device comprised as mentioned above.

  When the output of the DC power supply 11 is larger than the household power and a reverse power flow to the grid 17 occurs as it is, the surplus power of the second converter 18 is calculated as charging power, and the second converter power A power command value is generated from the command means 22. At the same time, the voltage detection means 20 detects the voltage of the power storage means 19 and divides the power command value to obtain a current command value. The current command value is given as a drive signal for the switching element of the second converter 18 through the second converter control means 21.

  As described above, the present embodiment has voltage detection means for detecting the DC voltage of the power storage means, and determines the output current command value of the second converter based on the DC voltage of the power storage means. It is possible to provide a versatile device that does not depend on the serial and parallel configurations.

(Embodiment 3)
This embodiment relates to claim 4. FIG. 3 is a connection diagram of the power conversion device according to the third embodiment of the present invention.

  3 is different from the circuit configuration of FIG. 2 in that an output current limiter 23 is arranged at the output of the second converter control means 21. Components other than those described above are the same as those in the second embodiment, and a description thereof will be omitted.

  About the power converter device comprised as mentioned above, the operation | movement and an effect | action are demonstrated below with reference to FIG.

  In FIG. 3, when the output of the DC power supply 11 is larger than the household power and a reverse power flow to the grid 17 occurs as it is, the surplus power of the second converter 18 is calculated as the charging power, A power command value is generated from second converter power command means 22. At the same time, the voltage detection means 20 detects the voltage of the power storage means 19 and divides the power command value, whereby the current command value is obtained by the second converter control means 21. Here, when the output current command value to the second converter 18 determined by the power command value and the voltage of the power storage means 19 is larger than the output current limiter 23, the current command value is changed to the output current limiter value. Then, it is given as a drive signal for the switching element of the second converter 18. The output current limiter value is determined by the capacity of the power storage means 19.

  As described above, in this embodiment, it is possible to extend the life of the power storage means by controlling the output current of the second converter at a certain value or less.

(Embodiment 4)
This embodiment relates to claims 5 and 6. FIG. 4 is a connection diagram of the power conversion device according to the fourth embodiment of the present invention.

  4 is different from the circuit configuration of FIG. 3 in that the second converter is a bidirectional converter 24 and a relay is arranged between the inverter 15 and the system 17 so that the device and the system 17 can be disconnected. is there. Components other than those described above are the same as those in the first embodiment, and a description thereof will be omitted.

  About the power converter device comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  In the configuration in which the inverter 15 and the system 17 can be disconnected, the output of the DC power supply 11 is larger than the domestic power, and if the reverse power flow to the system 17 is generated as it is, bidirectional The converter 24 charges the power storage means 19 with a part of the power generated by the DC power supply 11. Further, when the output of the inverter 15 is output independently of the system 17, the voltage of the power storage means 19 is converted into the same voltage as the DC voltage of the first converter 12 by the bidirectional converter 24. Further, the first converter performs commercial double-cycle sine wave modulation by high-frequency switching, and power is transmitted by the high-frequency transformer 13, and an AC voltage independent of the system 17 is generated by the rectifier 14 and the inverter 15.

  As described above, in the present embodiment, the second converter is configured to be capable of bidirectional output, and by supplying power from the power storage means to the inverter, a power failure occurs and power is not supplied from the DC power supply. Even in this case, it is possible to supply power to household devices.

(Embodiment 5)
This embodiment relates to claim 7. In the fifth embodiment, circuit components are the same as those in the second embodiment, and a description thereof will be omitted.

  About the power converter device comprised as mentioned above, the operation | movement and an effect | action are demonstrated below with reference to the waveform diagram of FIG.

  When the voltage detection means signal obtained by the voltage detection means 20 for detecting the voltage of the storage means 19 is equal to or greater than the threshold value, the second converter control means 21 sends an activation signal to the second converter 24, and this When it is below the threshold value, a stop signal is transmitted. Here, if the power storage means 19 is not connected due to reasons such as replacement, the voltage detection signal is not output, so that it is automatically determined that the power storage means 19 is not connected or has deteriorated, and the operation of the second converter 24 is performed. To stop.

  As described above, in the present embodiment, when the detection voltage of the voltage detection means is equal to or lower than the threshold value, the control means automatically determines that there is no power storage means by stopping the operation of the second converter. Device.

(Embodiment 6)
This embodiment relates to claim 8. FIG. 6 is a connection diagram of the power conversion device according to the sixth embodiment of the present invention. 6 is different from the circuit configuration of FIG. 2 in that the control power generation means 25 is arranged to supply power from the power storage means. Components other than those described above are the same as those in the second embodiment, and a description thereof will be omitted.

  About the power converter device comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  The control power generation means 25 generates power for driving the bidirectional converter 24 and the second converter control means 21 using the power storage means 19 as a power supply source. Therefore, the bidirectional converter 24 is always operated regardless of the operating conditions of the DC power supply 11 and the system 17.

  As described above, in the present embodiment, by supplying the control power of the bidirectional converter from the power storage means, the power for operating the bidirectional converter can be stably supplied regardless of the operating state of the DC power supply and the system. be able to.

  As described above, the power conversion device according to the present invention has power storage means and can realize efficient surplus power processing, and thus can be applied to uses such as solar cells, fuel cells, and wind power generation.

Connection diagram of power conversion device according to Embodiment 1 of the present invention Connection diagram of power conversion device in embodiment 2 of the present invention Connection diagram of power conversion device according to Embodiment 3 of the present invention Connection diagram of power conversion device according to embodiment 4 of the present invention Waveform diagram showing the operation of each part of the power converter in Embodiment 5 of the present invention Connection diagram of power conversion device according to Embodiment 6 of the present invention Connection diagram of conventional power converter

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 DC power supply 12 1st converter 13 High frequency transformer 14 Rectification means 15 Inverter 16 Filter capacitor 17 System | strain 18 2nd converter 19 Power storage means 20 Voltage detection means 21 2nd converter control means 22 2nd converter power command means 23 Output current limiter 24 Both Converter 25 Control power generation means

Claims (8)

A high-frequency transformer, a DC power source on the primary side insulated by the high-frequency transformer, a first converter that converts DC power into high-frequency power, a second converter that converts DC power into a predetermined voltage, and storage means; On the secondary side of the high-frequency transformer, a rectifying means and an inverter configured by four switching elements and injecting an alternating current into the system are arranged, and the first converter and the second converter are connected to the output of the direct-current power source. A power converter connected in parallel and connected to the power storage means in series with the output of the second converter. The power conversion device according to claim 1, wherein the power storage means is constituted by a secondary battery. The power conversion device according to any one of claims 1 and 2, wherein a voltage detection means for detecting a DC voltage of the storage means is arranged, and an output current of the second converter is determined based on the DC voltage. 4. The power conversion device according to claim 1, wherein the current command value output from the second converter control unit is compared with an output current limiter, and the output current of the second converter is controlled to be a predetermined value or less. 5. The power converter according to any one of claims 1 to 4, wherein the second converter is configured to be capable of bidirectional output and supplies power from the power storage means to the inverter. The power converter of any one of Claims 1-5 which comprised the 2nd converter with the buck-boost converter. The power converter according to any one of claims 1 to 6, wherein the operation of the second converter is stopped when a detection voltage of the voltage detection means is equal to or lower than a threshold value. The power converter according to any one of claims 1 to 7, wherein the control power of the second converter is supplied from the power storage means.

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