JP2009142052A - Power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the efficiency and reliability of a control power supply circuit for operating a control part and to enlarge the input voltage range of a power converter, in a power converter which outputs AC power at an inverter portion for controlling output voltage by the sum of voltages generated by a plurality of single-phase inverters after stepping-up or stepping-down the voltage of a solar battery. <P>SOLUTION: The power converter generates the voltage V1 of a first capacitor 3 having a maximum DC voltage, of the capacitors 3 to 5 of a plurality of single-phase inverters 6 to 8 constituting an inverter section B, within a predetermined highly efficient voltage range of a control power supply circuit 30, through a step-up/down circuit A from the solar battery 1. The solar battery 1 and the first capacitor 3 include a switching section 32, respectively, and the input side of the control power supply circuit 30 is connected to both solar batter 1 and the first capacitor 3. In starting, voltage is supplied from the solar battery 1, and then the switching section 32 is used to select either the voltage of the solar battery 1 or the voltage of the first capacitor 3 to be supplied. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a power conversion device that converts DC power into AC power, and more particularly to a power conversion device that is used in a power conditioner or the like that connects a distributed power source to a system.

In the conventional power conditioner, the AC side of the first single-phase inverter using the DC voltage V1 of the first capacitor as the DC source and the other second and third single-phase inverters are connected in series, The output voltage is obtained as the sum of the voltages generated by each single-phase inverter. The voltage of the first capacitor, which is the maximum voltage among the DC voltages of the plurality of single-phase inverters, is generated from the solar cell to a desired voltage via the step-down converter and the step-up chopper.
In the power conditioner configured as described above, a voltage higher than the DC voltage V1 of the first capacitor can be output, and each inverter can be configured with an element having a low withstand voltage. A good device configuration can be achieved (see, for example, Patent Document 1).

JP 2007-166783 A

  In the power conditioner that obtains the output voltage by the sum of the voltages generated by a plurality of single-phase inverters, the voltage of the first capacitor generated from the output voltage of the solar cell may be lower than the peak voltage of the AC output. Even if the voltage of the solar cell, which is a voltage, fluctuates, the device configuration can output with good efficiency and reliability. However, a control power supply circuit for operating a control unit that controls a plurality of single-phase inverters, a step-down converter, and a step-up chopper is required to output a large number of power supply voltages with high accuracy. In the conventional power conditioner, the input voltage of the control power circuit is supplied from the solar battery, and when the voltage of the solar battery fluctuates greatly, it is difficult to stably obtain the output from the control power circuit, particularly in a low voltage region. As a result, the input voltage range of the inverter is also narrowed. In addition, there is a problem that the efficiency of the control power supply circuit is poor in both the low voltage region and the high voltage region of the solar cell, and the efficiency of the entire power conditioner is reduced. In some cases, the input voltage of the control power supply circuit is supplied from the system power supply. However, the power consumption of the system power supply is consumed, which is equivalent to reducing the conversion efficiency.

  The present invention has been made to solve the above-described problems, and in a power converter that converts electric power from a DC power source such as a solar cell into AC and outputs it to a system or a load. The purpose is to improve the efficiency and reliability of the power supply circuit, to improve the conversion efficiency of the power converter and to expand the input voltage range.

  A power converter according to the present invention includes a first DC power source, a step-up / step-down circuit that boosts or steps down the voltage of the first DC power source, an inverter unit, and a control unit that controls the inverter unit and the step-up / down circuit. And a control power supply circuit for operating the control unit. The inverter unit includes a first single-phase inverter that converts the DC power of the second DC power source generated at the output of the step-up / step-down circuit into AC power, and a DC that is equal to or lower than the voltage of the second DC power source. The AC side of one or a plurality of second single-phase inverters that convert DC power of the power source into AC power is connected in series, and a voltage is output by the sum of the generated voltages of the first and second single-phase inverters. The control power supply circuit includes switching means and is connected to both the first DC power supply and the second DC power supply, and is supplied with voltage from the first DC power supply when the apparatus is started up, and then the first DC power supply. The voltage is supplied from either the direct current power source or the second direct current power source.

  Since the power converter according to the present invention outputs a voltage by the sum of the voltages generated by the first and second single-phase inverters, the voltage range of the second DC power source, which is the DC power source of the first single-phase inverter, is set. Can be reduced. Further, since the control power supply circuit is provided with switching means and is connected to both the first DC power supply and the second DC power supply, the input voltage of the control circuit power supply circuit is switched to improve the efficiency and reliability of the control power supply circuit. It becomes possible to improve the property. Thereby, the conversion efficiency improvement of a power converter device and expansion of an input voltage range can be aimed at.

Embodiment 1 FIG.
Hereinafter, a power conversion apparatus (hereinafter referred to as a power conditioner) according to Embodiment 1 of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram illustrating a power conditioner according to Embodiment 1 of the present invention. As shown in FIG. 1, the inverter unit B is configured by connecting the AC sides of a plurality (in this case, three) of single-phase inverters 6 to 8 in series. Each of the single-phase inverters 6 to 8 includes a plurality of self-extinguishing semiconductor switching elements 28 (hereinafter referred to as switch elements 28) such as IGBTs having diodes connected in antiparallel, and serve as a second DC power source. The second single-phase inverters 7 and 8 are connected to both terminals on the AC side of the first single-phase inverter 6 having the first capacitor 3 as an input. One of the two second single-phase inverters 7 and 8 is hereinafter referred to as a third single-phase inverter 8 for convenience. Also, two self-extinguishing semiconductor switching elements such as IGBTs connected in reverse parallel as a short-circuit switch 9 for short-circuiting both terminals on the AC side of the first single-phase inverter 6 are connected in series with opposite polarities. The shorting switch 9 is connected in parallel to the first single-phase inverter 6.

  In addition, a step-up / step-down circuit A is connected via an input capacitor 2 downstream of a solar panel 1 (hereinafter referred to as a solar cell 1) as a first DC power source. The step-up / down circuit A is configured by connecting a step-down converter 17 as a step-down unit and a step-up chopper 11 as a step-up unit in series, and the first capacitor 3 serving as an input of the first single-phase inverter 6 is a solar cell. 1 through the step-down converter 17 and the step-up chopper 11. The step-down converter 17 includes a step-down switching element 23, a reactor 27, and a step-down diode 24 having a cathode connected to a connection point between the elements 23 and 27. The step-up chopper 11 includes a reactor 27 that is also used as a step-down converter 17, a step-up diode 25 as a rectifying element, and a step-up switch element 26 connected to a connection point between the elements 27 and 25. .

Further, a first bypass circuit 12 that bypasses a circuit in which the step-down converter 17 and the step-up chopper 11 are connected in series is connected. The first bypass circuit 12 includes a bypass relay 21 and bypass switch elements 19 and 20 that are connected in parallel to the bypass relay 21 and constitute a cutoff circuit for blocking the bypass relay 21. The bypass switch elements 19 and 20 are connected in series with opposite polarities by two semiconductor switches having diodes connected in antiparallel.
Further, a second bypass circuit 18 that bypasses the step-down converter 17 is connected. The second bypass circuit 18 includes a bypass relay 22 connected so as to bypass the step-down switch element 23.

The voltage V1 of the first capacitor 3 that is input to the first single-phase inverter 6 is the second and third capacitors as DC power sources that are input to the other second and third single-phase inverters 7 and 8. The voltages V2 and V3 are larger than the voltages V2 and V3 of 4 and 5, and are controlled by the DC / DC converter 10 so as to be a predetermined voltage, for example. Here, it is assumed that the voltages of the second and third capacitors 4 and 5 are equal.
These single-phase inverters 6 to 8 can generate positive and negative voltages and zero as outputs, and the inverter unit B outputs a voltage as a sum total of these generated voltages. The output voltage is smoothed by a smoothing filter including reactors 13 and 14 and a capacitor 15, and an AC voltage _Vout is supplied to a system (load) 16. It is assumed that the system 16 is grounded at the midpoint with a columnar transformer.

The output of the second single-phase inverter 7 and the output of the third single-phase inverter 8 are equal, and each single-phase inverter 7, 8 has a difference between the target output voltage and the output voltage of the first single-phase inverter 6. Is output by PWM control so as to compensate.
Further, during the period in which the output voltage of the first single-phase inverter 6 is 0, the short-circuit switch 9 for short-circuiting both terminals on the alternating current side of the first single-phase inverter 6 is turned on to be in a conductive state. All semiconductor switches in one single-phase inverter 6 are turned off. Thereby, the midpoint potential of the first capacitor 3 generated from the solar cell 1 can be fixed to the ground potential, and the potential fluctuation of the solar cell 1 can be suppressed.

  Further, such a power conditioner generates the voltage V1 of the first capacitor 3 from the voltage of the solar cell 1 via the step-up / down circuit A, and obtains an AC output from the inverter unit B. A control unit 31 for controlling the inverter unit B and a control power circuit 30 for supplying power to the control unit 31 are provided. The control unit 31 includes a sensor circuit 31a as a detection circuit that detects the voltage and current of each unit necessary for controlling the power conditioner, and the step-up / down circuit A and each of the inverter units B based on information from the sensor circuit 31a. And a control circuit 31b for controlling the elements. The input side of the control power circuit 30 is connected to both the positive electrode of the solar cell 1 and the positive electrode of the first capacitor 3 with a switching unit 32. The control power supply circuit 30 is supplied with a voltage from the solar cell 1 when the power conditioner is started, and is then switched by the switching unit 32 and supplied with a voltage from the first capacitor 3. Generate and output power supply voltage. Reference numeral 33 denotes a ground potential input line.

By the way, the maximum output voltage required for the AC output of 200 V is about 282 V, and the output voltage of the inverter B can output up to V1 + V2 + V3. For this reason, if V1 + V2 + V3 is about 282V or more, the power conditioner can output an alternating current of 200V. In this case, the voltage V1 of the first capacitor 3 is controlled to, for example, DC200V to DC250V.
If the rated voltage of the solar cell 1 is DC250V, the voltage V1 of the first capacitor 3 can be generated without the need for step-up / down at the rated voltage. Since the voltages V2 and V3 of the second and third capacitors 4 and 5 are lower than V1, each of the single-phase inverters 6 to 8 can be composed of an element having a low withstand voltage, and an efficient inverter with reduced loss. It becomes part B.

The charging operation to the first capacitor 3 via the step-up / down circuit A will be described below.
During no-load operation such as when the system of the power conditioner is started, the voltage of the solar cell 1 may be higher than the rated voltage (DC250V), for example, about DC400V. In this way, when the voltage of the solar cell 1 exceeds the rated voltage during operation, the voltage is stepped down by the step-down converter 17 to generate the voltage V1 of the first capacitor 3. When the solar cell 1 falls below the rated voltage and becomes a predetermined voltage, for example, DC 200 V or less, the voltage is boosted by the boost chopper 11 to generate the voltage V1 of the first capacitor 3.

First, when the voltage generated by the solar cell 1 is within a predetermined range including the rated voltage (for example, DC 200 V to rated voltage DC 250 V), the bypass switch elements 19 and 20 of the first bypass circuit 12 are turned on, and the input capacitor 2 After flowing the inrush current to the first capacitor 3, the bypass relay 21 is turned on. Thereby, the current flows through the rated current path via the bypass relay 21 of the first bypass circuit 12 without impairing the reliability of the bypass relay 21.
Next, when the voltage of the solar cell 1 is out of the predetermined range and the step-down converter 17 or the step-up chopper 11 needs to be operated, the first bypass circuit 12 is shut off. At this time, first, the bypass switch elements 19 and 20 are turned on to generate a current path to the bypass switch elements 19 and 20, and then the bypass relay 21 is cut off, so that the current flowing through the bypass relay 21 is bypassed. The bypass relay 21 can be cut off without generating an arc through the switch elements 19 and 20. Then, by turning off the bypass switch elements 19 and 20, the first bypass circuit 12 can be interrupted without impairing the reliability of the bypass relay 21, and current flows to the step-down converter 17 and the step-up chopper 11.

When the voltage of the solar cell 1 becomes equal to or lower than a predetermined voltage (for example, DC 200V) and boosting is required, the first bypass circuit 12 is shut off and the step-down converter 17 is bypassed as described above. At this time, the step-down switch element 23 is turned on and an inrush current flows from the input capacitor 2 to the first capacitor 3, and then the bypass relay 22 of the second bypass circuit 18 is turned on. As a result, current flows through a path that bypasses the step-down converter 17 without impairing the reliability of the bypass relay 22. Then, the boosting switch element 26 is turned on / off to boost the voltage to a predetermined voltage. In this way, loss generation in the step-down switch element 23 can be prevented, and a step-up operation by the step-up chopper 11 can be realized.
When the voltage of the first capacitor 3 is higher than the voltage of the input capacitor 2, no inrush current flows from the input capacitor 2 to the first capacitor 3.

When the voltage of the solar cell 1 exceeds the rated voltage and the voltage needs to be stepped down, the first bypass circuit 12 is cut off as described above, and the step-down converter 17 performs the step-down operation. At this time, the step-down switching element 23 is once turned on, and the bypass relay 22 of the second bypass circuit 18 is cut off. Thereafter, the step-down switch element 23 is turned on and off to step down to a predetermined voltage. By doing so, the bypass relay 22 can be cut off without generating an arc, and the current flows through the path via the step-down switch element 23, so that the step-down operation of the step-down converter 17 can be started.
Further, when the voltage of the solar cell 1 returns to a predetermined range (DC 200 V to rated voltage DC 250 V) during the operation of the step-down converter 17 or the step-up chopper 11, the step-down operation and the step-up operation are stopped and the first bypass circuit 12 is stopped. By turning on the bypass relay 21 in the order described above, it is possible to return to the operation in which the current flows through the rated current path.

Next, the configuration and operation of the control power supply circuit 30 will be described in detail.
FIG. 2 is a schematic circuit diagram according to an example of the control power supply circuit 30. As shown in the figure, the control power supply circuit 30 is a flyback multi-output power supply including a flyback transformer 38 and a primary side switching element 34. A power supply control IC 35, a feedback circuit 36, an activation circuit 37, and a bias winding 41 are provided. FIG. 3 is a sectional structural view of the multi-output flyback transformer 38. FIG. 4 is a diagram showing operation waveforms of each part of the control power supply circuit 30. FIG. 4A shows a case where the input voltage of the control power supply circuit 30 is low at 50V DC, and FIG. It was shown to.
When the input voltage is applied, the activation circuit 37 operates to supply power to the power supply control IC 35. As a result, the power supply control IC 35 starts and oscillates and supplies a primary side switching element gate signal (hereinafter simply referred to as a gate signal) to the primary side switching element 34, and the primary side switching element 34 starts switching.

At time t1, when the primary side switching element 34 is turned on by the gate signal from the power supply control IC 35, the current I1 that is the primary side switching element drain current is inclined to the primary side exciting inductance L1 of the flyback transformer 38. It flows with an integral waveform. The increase I1 of this current is I1 [A] = (input voltage / on time) / (primary excitation inductance L1). At this time, energy of energy W [J] = 1/2 · (L1 · I1 ² ) is stored in the primary side excitation inductance L1. At this time, since the secondary side rectifier diode 39 connected to the secondary side of the flyback transformer 38 is reverse-biased to the secondary side magnetically coupled secondary side exciting inductance L2, no current flows. .
Next, when the primary side switching element 34 is turned off (time t2 in FIG. 4A), the energy W stored in the primary side excitation inductance L1 tends to be released as the back electromotive force VL. Back electromotive force is also generated in the secondary side excitation inductance L2 magnetically coupled at the time, and the secondary side rectifier diode 39 becomes forward biased and becomes conductive. Therefore, the secondary current I2 flows, and the secondary rectifier capacitor 40 is charged via the secondary rectifier diode 39, that is, the energy discharge of the secondary excitation inductance L2 is completed.

As described above, the flyback transformer 38 operates as described above by repeating the on / off switching of the primary side switching element 34, and the single-phase inverters 6 to 8, the boost switch are arranged on the secondary side of the flyback transformer 38. Each voltage is output as a power source for the element 26, the step-down switch element 23, the relays of the bypass circuits 12 and 18, the sensors of the sensor circuit 31a, the control circuit 31b, and the like. In addition, the voltage of the bias winding 41 is also proportionally output and supplied to the power supply control IC 35 as a power supply, whereby the oscillation of the power supply control IC 35 continues.
Further, the output serving as the power supply for the control circuit of the secondary side output (+5 V in this case) is fed back to the power supply control IC 35 via the feedback circuit 36 having an insulating function. In the feedback circuit 36, the gate signal to the primary side switching element 34 is adjusted so that the voltage of the control circuit power supply, which is the secondary side output voltage, becomes the set target voltage (+ 5V). That is, if the voltage of the control circuit power supply is higher than the target voltage, the on-time of the gate signal is shortened, and if it is low, the on-time is lengthened to adjust the input energy to the flyback transformer 38, and the predetermined target voltage and To do. Thus, the control power supply circuit 30 operates with a function of stabilizing the voltage of each secondary output by performing so-called PWM control (pulse width modulation control).

Next, each output of the control power supply circuit 30 will be described.
The output of the control power supply circuit 30 varies depending on various factors described below. For example, individual variations due to mass production, output temperature characteristics when the ambient temperature rises or falls, for example, changes from 0 ° C. to 80 ° C., output load of the control power supply circuit 30 fluctuates, and load of each output Output load fluctuation characteristics when there is a bias, output fluctuation characteristics for a wide range of input voltages, and the like. Each output of the control power supply circuit 30 needs to satisfy the accuracy required for each power supply voltage of each output even when each of the above fluctuation conditions or a combination thereof is combined.
First, the power supply for the control circuit supplies power to the control circuit 31b that controls the step-up / down circuit A of the power conditioner, each switch element of the inverter unit B, and the like. When the specification of the power supply voltage of the IC used in the control circuit 31b is, for example, 5V, the recommended power supply voltage range of this IC is generally 4.75V to 5.25V, or 4.5V to 5.5V. If the voltage is outside this range, the IC malfunctions or is damaged at worst. Among a plurality of outputs, the power supply for the control circuit is required to be highly stabilized with the smallest voltage width in which the fluctuation of the power supply voltage is allowed. The control circuit power supply must guarantee the recommended power supply voltage range of the IC used in the control circuit 31b even for each of the above-described variation conditions and combinations thereof. For this reason, the voltage of the control circuit power supply among a plurality of outputs is input to the feedback circuit 36 to achieve high stabilization of the control circuit power supply.

  Next, the sensor power supply will be described. In order for the control circuit 31b to precisely control the power conditioner, the sensor circuit 31a detects the voltage and current of each part of the power conditioner. The sensor circuit 31a includes a sensor for output of the control power supply circuit 30. Power is supplied from the power supply. If the accuracy of the voltage and current detection values of the sensor circuit 31a is poor, the control circuit 31b cannot perform optimal control of the power conditioner. Therefore, high accuracy is required for detection of the sensor circuit 31a, and the voltage of the sensor power supply is also high. Accuracy is required. For this reason, the sensor power supply is equipped with a voltage stabilization circuit in the output stage so that the voltage accuracy of the sensor power supply can be guaranteed even for each of the above-described fluctuation conditions and combinations thereof. Yes.

  Next, the relay power supply will be described. This is a power supply for driving the bypass relays 21 and 22 in the first and second bypass circuits 12 and 18 and the grid interconnection relay (not shown) provided in the output stage of the power conditioner. Here, the relay coil voltage is 24 VDC. The maximum allowable voltage of these relay coils is generally 110% of the rated voltage, and in the case of DC 24V, it is necessary to set it to DC 26.4V or less. Therefore, it is necessary to guarantee the relay power supply voltage to be 26.4 V or less even for each of the above-described variation conditions and combinations thereof. This voltage varies depending on the relay coil voltage used.

Next, the first single-phase inverter / step-up switch element power supply, the second and third single-phase inverter power supplies, and the step-down switch element power supply will be described. These are gate power supplies for the switch elements 28, the step-up switch elements 26, and the step-down switch elements 23 of the plurality of single-phase inverters 6 to 8 of the power conditioner, and supply power to the gate drive circuit in the control circuit 31b. ing.
In general switch elements, the maximum rated voltage of the gate withstand voltage of each switch element is 20V or 30V withstand voltage, and the voltage of the gate power supply is determined based on this. In addition, in order to obtain high reliability by reducing stress on the gate of the switch element, it is recommended by the manufacturer to use the switch element at 80% or less of the maximum rated voltage. Here, the voltage of the gate power supply is set to 15V by using a switch element having a gate withstand voltage of 20V. For this reason, the output for gate power supply of each switch element is not required to be as highly stable and accurate as the above-described control circuit power supply or sensor power supply, and the allowable voltage fluctuation range is, for example, 15 It is about ± 1V.

The inverter section B of the power conditioner according to this embodiment includes a plurality of single-phase inverters 6 to 8, and includes a switch element of the first single-phase inverter 6, a boost switch element 26, and a second single-phase inverter. The ground potential reference of the gate power supply of each of the switch elements of the inverter 7, the switch element of the third single-phase inverter 8, and the step-down switch element 23 is different. For this reason, more gate power supplies are needed than the power conditioner comprised with one general single phase inverter.
As shown in the cross-sectional structure diagram of FIG. 3, the flyback transformer 38 is wound around the bobbin 45 with both primary side windings and secondary side windings by multilayer winding. Reference numeral 46 denotes a winding, 47 denotes an insulating tape, and 48 denotes a transformer core. The control power supply circuit 30 of the power conditioner having the plurality of single-phase inverters 6 to 8 needs to output a large number of gate power supplies, and further has a multi-layer winding. For this reason, the secondary winding (for example, N8) farther to the outer periphery than the primary winding N1 has a poor coupling with the primary winding, or the winding state of the multi-layer winding Are not uniform, and the individual variations tend to be large. That is, the secondary output voltage variation of the flyback transformer 38 including each gate power supply tends to be large.

  It should be noted that the voltage level of the secondary output gate power supply can be lowered to make it 80% or less of the maximum rated voltage recommended by the manufacturer even if it fluctuates due to the above various factors. The speed decreases, the switching loss increases, and the efficiency of the power conditioner decreases. In addition, the gate power supply is provided with a voltage stabilizing circuit for all outputs as in the case of the sensor power supply. Although it is possible to configure a plurality of control power supply circuits in parallel with the same number of 37, etc., the cost is high and it is difficult to reduce the size, and the efficiency of the control power supply circuit 30 is reduced.

Next, the efficiency of the control power supply circuit 30 will be described.
FIG. 5 is a graph showing the efficiency of the control power supply circuit 30 with respect to the input voltage.
As described with reference to FIG. 4, when the primary side switching element 34 is turned on by the gate signal from the power source control IC 35 at time t1, the control power source circuit 30 sets the primary side excitation inductance L1 of the flyback transformer 38 to the primary side exciting inductance L1. A current I1 serving as a primary-side switching element drain current flows in an inclined integral waveform. The increase I1 of this current is I1 [A] = (input voltage / on time) / (primary excitation inductance L1). At this time, energy of energy W [J] = 1/2 · (L1 · I1 ² ) is stored in the primary side excitation inductance L1.

As can be seen from these equations, when the input voltage is low, the predetermined energy W required for the primary side of the flyback transformer 38 can be obtained by increasing the ON time of the primary side switching element 34. As shown in FIG. 4A, when the input voltage is low (for example, 50 V), the ON time of the primary side switching element 34 is long. Therefore, the loss time due to the on-resistance of the primary side switching element 34 becomes longer and the loss amount increases, and the efficiency of the control power supply circuit 30 decreases as shown by the arrow 51 in FIG. On the other hand, when the input voltage is high (for example, 400 V), as shown in FIG. 4B, the on-time of the primary side switching element 34 is shortened, and the loss time due to the on-resistance of the primary side switching element 34 is Loss is reduced by shortening. However, when the input voltage is high, the primary side switching element 34 switches the high voltage of the input, so the primary side switching loss increases, and the efficiency of the control power supply circuit 30 is as shown by the arrow 52 in FIG. To drop.
In this case, the control power supply circuit 30 operates most efficiently when the input voltage is DC 250 V, from the minimum voltage to the maximum voltage of the solar battery output voltage that is the input voltage of the power conditioner.

In this embodiment, as described above, the input side of the control power supply circuit 30 is connected to both the solar cell 1 and the first capacitor 3 with the switching unit 32, and voltage is supplied from the solar cell 1 at the time of startup. Thereafter, the voltage is supplied from the first capacitor 3 to operate. When the power conditioner is activated and the step-up / down circuit A operates, the voltage V1 of the first capacitor 3 is a predetermined voltage range (DC200V to DC250V) including the input voltage (DC250V) at which the control power supply circuit 30 operates most efficiently. ) Is controlled.
When the inverter is activated, for example, if the output voltage of the solar cell 1 is 50V, the input voltage of the control power supply circuit 30 is also low and the efficiency is low, but the input voltage of the control power supply circuit 30 is DC200V ~ Since it becomes DC250V, the efficiency is improved as shown by the arrow 50 in FIG. When the rated voltage of the solar cell 1 and the input voltage at which the control power supply circuit 30 operates most efficiently are set to the same DC 250 V, the efficiency of the control power supply circuit 30 becomes the best during rated operation.

  Thus, the input voltage range of the control power supply circuit 30 after the start of the power conditioner is a predetermined voltage range (DC200V to DC250V) including the input voltage (DC250V) at which the control power supply circuit 30 operates most efficiently. The control power supply circuit 30 has good efficiency. Further, in a power conditioner including a plurality of single-phase inverters 6 to 8, as described above, there is a tendency that a large number of power supply voltages, which are secondary outputs of the control power supply circuit 30, vary greatly. After the start-up, the input voltage of the control power supply circuit 30 is controlled within a predetermined voltage range and does not fluctuate greatly. Therefore, a large number of power supply voltages can be output with high accuracy. The control power supply circuit 30 outputs a large number of power supply voltages with high accuracy and stability by controlling the input voltage within a predetermined voltage range, even if the specification is compatible with a wide range of input voltages. Reduces stress due to overvoltage and improves reliability.

  Also, in recent years, the input voltage range of the power conditioner has been lowered in order to improve the power generation amount per day by operating the power conditioner until the day when the amount of solar radiation is low, or at the time of sunrise or sunset when the amount of solar radiation is low. It is required to expand to an area and make it about DC50V to DC400V. In the conventional power conditioner, since the control power supply circuit is supplied with voltage from the solar cell 1, the input voltage range of the control power supply circuit and the input voltage range of the power conditioner are equal, and the efficiency and accuracy of the control power supply circuit However, the inverter could not be operated in a bad voltage range. In this embodiment, the input voltage range of the control power supply circuit is separated from the input voltage range of the power conditioner, and the control power supply circuit obtains an input voltage that operates in a state with good efficiency and accuracy. For this reason, the input voltage range of the power conditioner can be expanded, the amount of power generation can be increased by increasing the power generation time per day, and the efficiency and reliability of the entire power conditioner are also improved.

  In the above embodiment, the voltage V1 of the first capacitor 3 is controlled within a predetermined voltage range (DC200V to DC250V), but the input voltage (DC250V) at which the control power supply circuit 30 operates most efficiently. If the voltage V1 is controlled so as to be maintained at (), the efficiency and output accuracy of the control power supply circuit 30 are further improved.

  The voltage V1 of the first capacitor 3 is controlled to a predetermined voltage range (DC200V to DC250V) including the input voltage (DC250V) at which the control power supply circuit 30 operates most efficiently. The voltage V1 may be controlled within a range of an input voltage (for example, DC200V to DC300V) in which the efficiency is equal to or higher than a predetermined value, for example, 87.5% or higher. In a power conditioner using a combination of a plurality of single-phase inverters 6-8, the voltage V1, which is the DC voltage of the first single-phase converter 6, can be lowered, so that the input voltage (DC200V- It is not necessary to use a high voltage region within the range of DC300V.

Embodiment 2. FIG.
In the power conditioner according to the first embodiment, an example in which the configuration of the switching unit 32 that switches the input of the control power supply circuit 30 is specifically shown below based on FIG.
As shown in FIG. 6, the switching unit 32 is connected in series to a logical sum (OR) circuit including a first diode 55 and a second diode 56 and to the first diode 55 and the second diode 56. The first switch 57 and the second switch 58 are included. The OR circuit is configured by connecting the cathodes of the first diode 55 and the second diode 56, the anode of the first diode 55 is connected to the positive electrode of the solar cell 1, and the anode of the second diode 56. Is connected to the positive electrode of the first capacitor 3.
The connection order of the first and second switches 57 and 58 and the first and second diodes 55 and 56 may be reversed.

Next, the operation of the switching unit 32 and the operation of the entire power conditioner related to the operation will be described.
When the inverter is activated, the first switch 57 of the switching unit 32 is turned on, and the input voltage is supplied from the DC voltage (for example, DC 50V) of the solar cell 1 to the control power supply circuit 30 via the first diode 55 and activated. To do. Thereby, the control part 31 becomes operable and the step-up / step-down circuit A and the inverter part B are controlled. And after producing | generating the DC voltage of the 1st capacitor | condenser 3 which is the input of the 1st single phase inverter 6 via the step-up / down circuit A from the output voltage of the solar cell 1, several single phase inverters 6-8 are operated. And generate AC power. At this time, the second switch 58 of the switching unit 32 is turned on, and the first switch 57 is turned off.
Note that, when the power conditioner is activated, the voltage of the solar cell 1 may be as high as about 400 V DC, for example. However, the operation of the switching unit 32 is the same, and the first of the switching unit 32 is activated when the power conditioner is activated. The switch 57 is turned on, and then the second switch 58 is turned on and the first switch 57 is turned off.

As a result, the control power supply circuit 30 is switched from the DC voltage of the solar cell 1 that has been supplied via the first diode 55 at the time of start-up, from the DC voltage of the first capacitor 3 (for example, DC 250 V). The input voltage is supplied by a current path passing through the second diode 56.
Since the voltage V1 of the first capacitor 3 is controlled within a predetermined voltage range (DC200V to DC250V) including the input voltage (DC250V) at which the control power supply circuit 30 operates most efficiently, the control after the start of the power conditioner is performed. The input voltage range of the power supply circuit 30 is also in the predetermined voltage range (DC200V to DC250V), and the control power supply circuit 30 can output a large number of power supply voltages with high efficiency and high accuracy.
When the inverter is stopped, the first switch 57 of the switching unit 32 is turned on and the second switch 58 is turned off, so that the voltage from the DC voltage of the solar cell 1 to the control power circuit 30 is the same as at the time of startup. Supply.

  In this embodiment, the switching unit 32 shown in the first embodiment includes a logical sum (OR) circuit composed of a first diode 55 and a second diode 56, and first and second switches 57 and 58. Therefore, the switching unit 32 can be obtained with an easy circuit configuration, and the effects of the first embodiment can be obtained easily and reliably.

  The first and second switches 57 and 58 in the switching unit 32 may be mechanical switches or switches using semiconductor switch elements such as MOSFETs and IGBTs. However, when a mechanical switch is used, no separate gate power supply is required. In addition, there is no conduction loss and high efficiency.

Embodiment 3 FIG.
Next, a power conditioner according to Embodiment 3 of the present invention will be described with reference to FIG. As shown in FIG. 7, the configuration of a switching unit 32a for switching the input of the control power supply circuit 30 is different from the power conditioners according to the first and second embodiments.
As shown in FIG. 7, the switching unit 32 a includes a logical sum (OR) circuit in which the cathodes of the first diode 55 and the second diode 56 are connected to each other, and the anode of the first diode 55 is the solar cell 1. The anode of the second diode 56 is connected to the positive electrode of the first capacitor 3. The configuration other than the switching unit 32a is the same as in the first and second embodiments.

Next, the operation of the switching unit 32a and the entire operation of the power conditioner related to the operation will be described.
When the power conditioner is activated, it is activated by supplying an input voltage from the direct current voltage (for example, DC 50V) of the solar cell 1 to the control power supply circuit 30 via the first diode 55 of the switching unit 32a. Thereby, the control part 31 becomes operable and the step-up / step-down circuit A and the inverter part B are controlled.
And after producing | generating the DC voltage of the 1st capacitor | condenser 3 which is the input of the 1st single phase inverter 6 via the step-up / down circuit A from the output voltage of the solar cell 1, several single phase inverters 6-8 are operated. And generate AC power. At this time, the voltage V1 of the first capacitor 3 is controlled to a predetermined voltage range (DC200V to DC250V) including the input voltage (DC250V) at which the control power supply circuit 30 operates most efficiently. As described in the first embodiment, when the voltage of the solar cell 1 is lower than the predetermined voltage range, that is, 200 V or lower, the step-up / down circuit A performs a boosting operation, and the voltage of the solar cell 1 is higher than the predetermined voltage. When exceeding the range, that is, exceeding 250V, the step-up / down circuit A performs a step-down operation to generate the voltage V1.

After the power conditioner is activated, the switching unit 32a switches the voltage supply path to the control power supply circuit 30 according to the voltage of the solar cell 1 and the voltage V1 of the first capacitor 3, as described below.
When the voltage of the solar cell 1 is lower than the voltage V1 of the first capacitor 3, that is, when the step-up / step-down circuit A performs a boosting operation, the second voltage of the switching unit 32a is determined from the DC voltage (for example, DC 250V) of the first capacitor 3. The input voltage of the control power supply circuit 30 is supplied through a current path passing through the diode 56. When the voltage of the solar cell 1 is higher than the voltage V1 of the first capacitor 3, that is, when the step-up / step-down circuit A performs a step-down operation, the voltage of the solar cell 1 (for example, DC 400V) is used to change the first diode 55 of the switching unit 32a. The input voltage of the control power supply circuit 30 is supplied by a current path passing through. When the voltage of the solar cell 1 is DC200V to DC250V and equal to the voltage V1 of the first capacitor 3, that is, when the step-up / step-down circuit A does not perform step-up / step-down operation and uses the first bypass circuit 12 as a current path, the switching unit 32a The input voltage of the control power supply circuit 30 is supplied through a current path that passes through either one or both of the first and second diodes 55 and 56.

  As a result, the control power supply circuit 30 is supplied with a voltage from the DC voltage of the solar cell 1 via the first diode 55 at the start-up, and thereafter, either the voltage of the solar cell 1 or the voltage V1 of the first capacitor 3 is supplied. The higher voltage is supplied to the input voltage. The voltage V1 of the first capacitor 3 is controlled to a predetermined voltage range (DC200V to DC250V) including the input voltage (DC250V) at which the control power supply circuit 30 operates most efficiently. The input voltage range is DC 200 V to the maximum voltage of solar cell 1 (for example, 400 V).

  In a power conditioner including a plurality of single-phase inverters 6 to 8, as described above, there is a tendency that variations in a large number of power supply voltages that are secondary outputs of the control power supply circuit 30 tend to increase, and in particular, a voltage region where the input voltage is low. (For example, DC50V to DC100V), it is difficult to accurately output a large number of power supply voltages. In this embodiment, after the power conditioner is activated, the input voltage of the control power supply circuit 30 is controlled to a predetermined voltage (DC 200 V to the maximum voltage of the solar battery 1), and a low voltage is not input. A large number of power supply voltages can be output with high accuracy. Even if the control power supply circuit 30 is compatible with a wide range of input voltages, by controlling the input voltage, a large number of power supply voltages can be output accurately and stably, and stress due to gate overvoltages or the like on each semiconductor switch element can be obtained. Reduce and improve reliability.

  As described above, the control power supply circuit 30 operates most efficiently when the input voltage is in the vicinity of the center voltage of the maximum voltage from the minimum voltage of the solar battery voltage, and the voltage V1 of the first capacitor 3 is controlled. The power supply circuit 30 is controlled to a predetermined voltage range (DC200V to DC250V) including the input voltage (DC250V) at which the power supply circuit 30 operates most efficiently. For this reason, the input voltage range of the control power supply circuit 30 after startup is that in which the low voltage region, which is a low efficiency region, is reduced in the voltage range of the solar cell 1, and the control power supply circuit 30 is efficient. The operating time is increased and the efficiency is improved.

  Also, in recent years, the input voltage range of the power conditioner has been lowered in order to improve the power generation amount per day by operating the power conditioner until the day when the amount of solar radiation is low, or at the time of sunrise or sunset when the amount of solar radiation is low. It is required to expand to an area and make it about DC50V to DC400V. In the conventional power conditioner, since the control power supply circuit is supplied with voltage from the solar cell 1, the input voltage range of the control power supply circuit and the input voltage range of the power conditioner are equal, and the efficiency and accuracy of the control power supply circuit However, the power conditioner could not be operated in a bad voltage range, particularly in a low voltage range (for example, DC50V to DC100V). In this embodiment, the input voltage range of the control power supply circuit is separated from the input voltage range of the power conditioner, and the control power supply circuit obtains an input voltage that operates with improved efficiency and accuracy. For this reason, the input voltage range of the power conditioner can be expanded, the amount of power generation can be increased by increasing the power generation time per day, and the efficiency and reliability of the entire power conditioner are also improved.

  In the above embodiment, the voltage V1 of the first capacitor 3 is controlled within a predetermined voltage range (DC200V to DC250V), but the input voltage (DC250V) at which the control power supply circuit 30 operates most efficiently. When the voltage V1 is controlled to be the same voltage as in (1), the control power supply circuit 30 takes a long time to operate the control power supply circuit 30 most efficiently, thereby further improving the efficiency.

  The voltage V1 of the first capacitor 3 is controlled to a predetermined voltage range (DC200V to DC250V) including the input voltage (DC250V) at which the control power supply circuit 30 operates most efficiently. The voltage V1 may be controlled within a range of an input voltage (for example, DC200V to DC300V) in which the efficiency is equal to or higher than a predetermined value, for example, 87.5% or higher. In a power conditioner using a combination of a plurality of single-phase inverters 6-8, the voltage V1, which is the DC voltage of the first single-phase converter 6, can be lowered, so that the input voltage (DC200V- It is not necessary to use a high voltage region within the range of DC300V.

  Further, in this embodiment, since the switching unit 32a is configured by a logical sum (OR) circuit composed of the first diode 55 and the second diode 56, the switching unit 32a can be obtained with an easy circuit configuration and for switching. This control is also unnecessary, and the above effect can be obtained easily and reliably.

Embodiment 4 FIG.
Next, a power conditioner according to Embodiment 4 of the present invention will be described with reference to FIG. In this embodiment, as shown in FIG. 8, the configuration of the inverter unit B is different from that of the power conditioner according to the second embodiment. The inverter unit B is configured by one single-phase inverter circuit 60, and the inverter Part B outputs AC 100V AC power to the grid (load) 16. That is, the step-up / down circuit A is connected to the subsequent stage of the solar cell 1 through the input capacitor 2, and the first capacitor 3 charged from the solar cell 1 through the step-up / down circuit A is connected to the single-phase inverter circuit 60. DC input. The configuration other than the inverter unit B is the same as that of the second embodiment.
In the first to third embodiments, the description has been made assuming that the grid (load) 16 is 200 VAC. However, as in the fourth embodiment, when the grid (load) 16 is 100 VAC, there is one. The single-phase inverter circuit 60 does not need to switch a high voltage, and high efficiency can be obtained.

Next, the operation of the switching unit 32 and the operation of the entire power conditioner related to the operation will be described.
When the power conditioner is activated, the first switch 57 of the switching unit 32 is turned on, and the input voltage is supplied from the DC voltage of the solar cell 1 to the control power supply circuit 30 via the first diode 55 and activated. Thereby, the control part 31 becomes operable and the step-up / step-down circuit A and the inverter part B are controlled. And after producing | generating the DC voltage of the 1st capacitor | condenser 3 which is the input of the single phase inverter circuit 60 from the output voltage of the solar cell 1 via the buck-boost circuit A, the single phase inverter circuit 60 is operated by PWM control, Generate AC power.
At this time, the voltage V1 of the first capacitor 3 is controlled to a predetermined voltage higher than the peak voltage of the system voltage, for example, 180V. That is, when the voltage of the solar cell 1 is equal to or lower than the predetermined voltage (180V), the step-up / down circuit A performs a boosting operation. When the voltage of the solar cell 1 exceeds the predetermined voltage (180V), the step-up / down circuit A Performs a step-down operation to generate the voltage V1.

The switching unit 32 selects the input voltage on the side where the efficiency of the control power supply circuit 30 is improved based on the efficiency characteristic that changes according to the input voltage of the control power supply circuit 30 after the power conditioner is activated. Switching conditions are set in advance. Then, the voltage supply path to the control power supply circuit 30 is switched according to the voltage of the solar cell 1 and the voltage V1 of the first capacitor 3.
When the voltage of the solar cell 1 is lower than the voltage V1 of the first capacitor 3, that is, when the step-up / step-down circuit A performs a boosting operation, the second switch 58 of the switching unit 32 is turned on, and the first switch 57 is turned on. Turn off. Thereby, the input voltage of the control power supply circuit 30 is supplied from the direct current voltage (for example, DC 180 V) of the first capacitor 3 through the current path passing through the second diode 56 of the switching unit 32.
When the voltage of the solar cell 1 is higher than the voltage V1 of the first capacitor 3, that is, when the step-up / down circuit A performs a step-down operation, when the voltage of the solar cell 1 is, for example, DC 300V or less, the first of the switching unit 32 By turning on the switch 57 and turning off the second switch 58, the input voltage of the control power circuit 30 is supplied from the voltage of the solar cell 1. When the voltage of the solar cell 1 exceeds, for example, DC 300 V, the second switch 58 of the switching unit 32 is turned on and the first switch 57 is turned off, whereby the input voltage of the control power circuit 30 is changed to the first voltage. Supply from the DC voltage of the capacitor 3.

  In this way, the control power supply circuit 30 is supplied with voltage from the DC voltage of the solar cell 1 at the time of startup, and thereafter is selected by the switching unit 32 according to the voltage of the solar cell 1 and the voltage V1 of the first capacitor 3. Either voltage is supplied to the input voltage. Thus, after the power conditioner is started, the input voltage of the control power supply circuit 30 is controlled to a predetermined voltage (for example, DC180V to DC300V), the control power supply circuit 30 operates in an efficient state, and a low voltage is applied. Since it is not input, a large number of power supply voltages can be output with high accuracy. Even if the control power supply circuit 30 is compatible with a wide range of input voltages, by controlling the input voltage, a large number of power supply voltages can be output accurately and stably, and stress due to gate overvoltages or the like on each semiconductor switch element can be obtained. Reduce and improve reliability.

  Also in the above embodiment, the input voltage range of the control power supply circuit and the input voltage range of the power conditioner are separated, and the control power supply circuit obtains an input voltage that operates with improved efficiency and accuracy. . For this reason, the input voltage range of the power conditioner can be expanded, the amount of power generation can be increased by increasing the power generation time per day, and the efficiency and reliability of the entire power conditioner are also improved.

  Note that the switching unit 32a shown in the third embodiment may be used as the switching unit that switches the input of the control power supply circuit 30. In that case, after the power conditioner is started, the input voltage of the control power supply circuit 30 is not limited. Is controlled to a predetermined voltage (for example, DC 180V to the maximum voltage of the solar cell 1). That is, as in the third embodiment, a low voltage is not input and a large number of power supply voltages can be output with high accuracy, and the control power supply circuit 30 can operate efficiently for a long time, improving the efficiency. And the input voltage range of the inverter can be expanded.

  Moreover, in the said Embodiment 1-4, although the 1st DC power supply was made into the solar cell 1, it is applicable also to the other distributed power supply with a large voltage fluctuation.

It is a schematic block diagram which shows the power conditioner by Embodiment 1 of this invention. 1 is a schematic circuit diagram showing a control power supply circuit according to a first embodiment of the present invention. 1 is a cross-sectional structure diagram of a flyback transformer according to a first embodiment of the present invention. It is a figure which shows the operation | movement waveform of each part of the control power supply circuit by Embodiment 1 of this invention. It is a figure which shows the efficiency of the control power supply circuit by Embodiment 1 of this invention. It is a schematic block diagram which shows the power conditioner by Embodiment 2 of this invention. It is a schematic block diagram which shows the power conditioner by Embodiment 3 of this invention. It is a schematic block diagram which shows the power conditioner by Embodiment 4 of this invention.

Explanation of symbols

1 solar cell as a first DC power source,
3 A first capacitor as a second DC power source,
4 Second capacitor as DC power supply, 5 Third capacitor as DC power supply,
6 first single-phase inverter, 7 second single-phase inverter,
8 third single-phase inverter (second single-phase inverter), 11 step-up chopper,
12 first bypass circuit, 17 step-down converter, 18 second bypass circuit,
23 Step-down switch element, 24 Step-down diode, 25 Step-up diode,
26 boosting switch element, 27 reactor, 30 control power supply circuit, 31 control unit,
31a Sensor circuit as detection circuit, 31b control circuit, 32, 32a switching unit,
34 primary side switching element, 38 flyback transformer,
55 first diode, 56 second diode, 57 first switch,
58 2nd switch, 60 single phase inverter part, A step-up / down circuit, B inverter part.

Claims (13)

A first DC power supply;
A step-up / step-down circuit for stepping up or stepping down the voltage of the first DC power supply;
The first single-phase inverter that converts the DC power of the second DC power source generated at the output of the step-up / step-down circuit into AC power, and the DC power of the DC power source that is equal to or lower than the voltage of the second DC power source. An inverter unit for connecting the AC side of one or a plurality of second single-phase inverters to be converted into AC power in series, and outputting a voltage by the sum of the generated voltages of the first and second single-phase inverters;
A control unit for controlling the inverter unit and the step-up / down circuit;
A control power supply circuit for operating the control unit,
The control power supply circuit includes switching means and is connected to both the first DC power supply and the second DC power supply, and is supplied with voltage from the first DC power supply when the apparatus is started up, and then the first DC power supply. A power conversion apparatus, wherein a voltage is supplied from either one of the DC power supply or the second DC power supply. 2. The voltage of the second DC power supply is controlled within a predetermined voltage range including an input voltage value of the control power supply circuit when the efficiency of the control power supply circuit is maximum. Power conversion device. 2. The power conversion device according to claim 1, wherein the voltage of the second DC power supply is controlled within a range of an input voltage of the control power supply circuit in which the efficiency of the control power supply circuit is equal to or higher than a predetermined value. . A first DC power supply;
A step-up / step-down circuit for stepping up or stepping down the voltage of the first DC power supply;
An inverter unit that converts the DC power of the second DC power source generated by the output of the step-up / down circuit to AC power and outputs the AC power;
A control unit for controlling the inverter unit and the step-up / down circuit;
A control power supply circuit for operating the control unit, and the control power supply circuit includes a switching unit and is connected to both the first DC power supply and the second DC power supply. A power conversion apparatus, wherein a voltage is supplied from a first DC power supply, and then a voltage is supplied from either the first DC power supply or the second DC power supply. 5. The switch according to claim 1, wherein the switching means of the control power supply circuit switches so that a voltage is supplied from the second DC power supply to the control power supply circuit after the apparatus is started. Power converter. The switching means of the control power supply circuit switches the voltage supply to the control power supply circuit in accordance with the voltage of the first DC power supply and the voltage of the second DC power supply after the apparatus is started. The power converter according to any one of claims 1 to 4. The power conversion device according to claim 5 or 6, wherein the switching means includes an OR circuit formed by connecting a diode to each output of the first DC power source and the second DC power source. . 8. The power conversion device according to claim 7, wherein a switch is connected in series to each of the diodes of the OR circuit, and the voltage supply path to the control power supply circuit is switched by the switch. . The power converter according to claim 8, wherein the switch of the switching means is a mechanical switch. 10. The electric power according to claim 1, wherein the step-up / step-down circuit includes a step-up unit, a step-down unit, and a bypass circuit that bypasses one or both of the step-up unit and the step-down unit. Conversion device. The control unit includes a detection circuit that detects a voltage and a current required for control, and a control circuit that controls the inverter unit and the step-up / down circuit according to an output of the detection circuit. The power converter of any one of Claims 1-10. The said control power supply circuit is comprised by the flyback transformer provided with the semiconductor switching element in the primary side, The power converter device of any one of Claims 1-11 characterized by the above-mentioned. The power converter according to any one of claims 1 to 12, wherein the first DC power supply is a solar battery.

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