JP4177710B2 - Inverter device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inverter device, and more particularly to a technique for reducing drive power of an inverter device that converts DC power supplied from a plurality of DC power sources into AC power.
[0002]
[Prior art]
The electric power obtained by converting the direct current generated by the direct current power source into the alternating current of the commercial frequency by the inverter device is used to move the alternating current load of electric products and the like in the same way as the commercial power supplied from the electric power company. Can be used. As a form of use of such an inverter device, an AC power source in an undistributed area, an emergency power source when commercial power is interrupted, or a system that reversely flows generated power to the power system in conjunction with the commercial power system Examples include interconnected systems.
[0003]
In particular, solar cells that have been attracting attention in recent years as a DC power source that can be used at home have been widely spread for general homes as grid-connected solar power generation systems. In addition to DC power sources other than solar cells, not only DC power generators such as secondary batteries and fuel cells, but also those obtained by rectifying AC power generated by wind power generators or motor generators, etc. be able to. As an example of the above-described inverter device, a conventional grid-connected inverter device for a residential solar power generation system will be described with reference to FIG.
[0004]
The DC power of the solar battery 101 is converted into AC power having a commercial frequency by the grid interconnection inverter device 102 and connected to the single-phase 200V commercial power system 103. The grid-connected inverter device 102 is an inverter main circuit 104 that converts the DC power of the solar battery 101 into AC power of commercial frequency, and an opening / closing means that opens and closes the connection between the AC output terminal of the inverter main circuit 104 and the commercial power system 103. 105, a drive circuit 106 that performs gate drive of the switching elements in the inverter main circuit 104, a control circuit 107 that controls the switching means 105 and the drive circuit 106, and a drive circuit 106 that receives DC power from the solar cell 101. And a power supply circuit 108 for supplying constant voltage power to the control circuit 107.
[0005]
In addition to the gate drive control of the switching elements in the inverter main circuit 104, the control circuit 107 performs automatic start / stop of the grid interconnection inverter device 102 and various protection controls. When the power supply circuit 108 is activated by receiving power supply from the solar battery 101 and starts supplying power to the control circuit 107, the control circuit 107 is activated, and there is no abnormality in the voltage or frequency of the commercial power system 103, After confirming that the battery 101 can supply power necessary for inverter operation, the switching means 105 is closed and inverter output is started.
[0006]
In the configuration illustrated in FIG. 4, the input power of the power supply circuit 108 is supplied from the solar battery 101, but there is a system in which power is supplied from the commercial power system 103 or a system having both. The specifications of the grid-connected inverter device 101 for a residential system as described above are generally those in which the rated input DC voltage is about 200 V and the rated output AC power is in the range of 3 to 5 kW.
[0007]
By the way, since the said solar power generation system can generate electric power only in the daytime, for example, for a consumer who consumes a large amount of power even at night, such as a factory, the operating rate is low and the economic attractiveness is small. In the future, the demand for hybrid power generation systems that combine solar power with new energy power generation such as secondary batteries and fuel cells is expected to increase as a power generation system that can be operated at all times.
[0008]
In such a hybrid system grid-connected inverter device 110, for example, as shown in FIG. 5, a fuel cell 109 is connected in addition to the solar cell 101 as a DC power source input to the inverter main circuit 104. In the inverter main circuit 104, voltage adjusting means 104a for converting the voltage of the solar cell 101 into a predetermined voltage, voltage adjusting means 104b for converting the voltage of the fuel cell 109 into a predetermined voltage, and these voltage adjusting means 104a. , 104b are collectively converted into an alternating current circuit 104c. The input of the power circuit 108 is connected in parallel to the solar cell 101 and the fuel cell 109 so that the operating power of the drive circuit 106 and the control circuit 107 can be supplied from either the solar cell 101 or the fuel cell 109. Here, since the output voltages of the solar cell 101 and the fuel cell 109 are different, backflow prevention diodes 111 and 112 are connected to the path from the solar cell 101 or the fuel cell 109 to the power supply circuit 108. With such a configuration, as long as only one of the solar cell 101 and the fuel cell 109 is operating, power can be supplied from the power supply circuit 108 to the drive circuit 106 and the control circuit 107, so that the grid interconnection inverter device 110 is continuous. Can generate electricity.
[0009]
Further, in a photovoltaic power generation apparatus that supplies an electric power to a load by connecting an inverter circuit that converts a direct current output generated from a solar battery into an alternating current output of a predetermined voltage and outputs the output to a commercial power system. The output from the power system is converted and output to a predetermined reference value, the output is supplied to the inverter circuit, and the output of the solar cell is detected, and commercial power is supplied to the control power circuit according to the detection result. Output supply means for selectively supplying the output from the system, the output supply means supplies the output from the commercial power system to the control power supply circuit when the output of the solar cell is below a set value, Patent Document 1 below discloses a grid-connected inverter device configured to supply an output from a solar battery to the control power supply circuit when the output of the solar battery is equal to or higher than a set value. According to this conventional technology, the operating power of the control power supply circuit is supplied from the commercial power system during the period when the solar battery cannot supply sufficient output to operate the control power supply circuit. In some cases, it is possible to prevent the control power supply circuit from repeatedly starting and stopping.
[0010]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-149659
[Problems to be solved by the invention]
However, since the grid-connected inverter device 110 shown in FIG. 5 has a plurality of different DC power sources as inputs, the power supply circuit 108 can drive the drive circuit 106 and any of the DC power sources. It is necessary to have an ability to continue supplying the operation power required by the control circuit 107. For this purpose, when the DC power source is a power source having very different output characteristics such as a solar cell and a fuel cell, the power supply circuit 108 can guarantee an operating range that covers the characteristics of both DC power sources. Must.
[0012]
For example, the operating voltage range of a solar cell in a general grid-connected inverter device for a residential solar power generation system is 80V to 320V, and the operating voltage range of the fuel cell in a grid-connected inverter device for fuel cell is 30V to 60V. It is. Therefore, the fact that the power supply circuit 108 covers the output characteristics of the solar cell and the fuel cell requires the ability to continue supplying power to the drive circuit 106 and the control circuit 107 in the entire input voltage range of 30V to 320V. Is done. Such a wide-range input power supply circuit is required to have a high breakdown voltage, and the input current also increases at the time of low voltage input. Therefore, it is necessary to use components having a large voltage rating and current rating, as shown in FIG. Compared with the power supply circuit of the grid-connected inverter device, the cost is increased. Moreover, since the high breakdown voltage element has a large resistance loss, an increase in the internal loss of the power supply circuit is inevitable. Furthermore, since the voltage required by the drive circuit 106 and the control circuit 107 is a constant voltage such as ± 15 V, +5 V, it is difficult to maintain the same conversion efficiency for all the above input voltage ranges. The conversion efficiency in the area tends to decrease.
[0013]
Further, as in the prior art described in Patent Document 1, when the output of a solar cell is lower than a set value in the morning or evening, a system for supplying power from a commercial power system to a power supply circuit is a grid-connected inverter device. Since the power circuit consumes the power of the commercial power system even at night when power cannot be generated, the loss in the power circuit cannot be reduced.
[0014]
The present invention has been made in view of the above problems, and an object thereof is to provide an inverter device capable of reducing power circuit loss in an inverter device having a plurality of DC power sources and performing power conversion with higher efficiency. It is to provide.
[0015]
[Means for Solving the Problems]
In order to achieve this object, an inverter device according to the present invention includes an inverter main circuit configured to convert DC power from a plurality of DC power sources into AC power, a drive circuit that drives the inverter main circuit, In an inverter device comprising: a control circuit that controls the drive circuit; and a plurality of power supply circuits that receive power from at least one of the plurality of DC power sources and supply power to the drive circuit and the control circuit. And at least two of the power supply circuits have input voltage ranges corresponding to output characteristics of the separate DC power sources, and the drive circuit and the control circuit when the input voltages are within the input voltage range. Selecting means for selecting a power supply circuit that supplies power to the drive circuit and the control circuit from among the plurality of power supply circuits. Characterized in that it comprises.
[0016]
According to the inverter device of the present invention, the power supply circuit having the lowest power consumption among the plurality of power supply circuits can be selected as the input as the power supply for the drive circuit and the control circuit. Can be achieved. Further, when at least one output of the DC power source cannot be sufficiently secured and the output state is such that the start and stop are repeated, the power supply circuit connected to the DC power source is not used as a power source, and the stable output Since it is possible to switch to the power supply circuit connected to the DC power source in the state, it is possible to avoid unnecessary starting and stopping of the power supply circuit. Further, this increases the operating time of the inverter device, and more power can be generated.
[0017]
Here, the selection unit is provided on the output side of the plurality of power supply circuits, and is configured to switch the power output from the plurality of power supply circuits and supply the power to the drive circuit and the control circuit, Or it is preferable that it is provided on the input side of the plurality of power supply circuits, and is configured to switch the DC power source to be input to the plurality of power supply circuits.
[0018]
When the selection means is provided on the output side of the power supply circuit, a fixed loss also occurs in the power supply circuit that is not used as a power supply. However, in the latter case, the selection means is provided on the input side of the power supply circuit. After the switching operation of the means, the DC voltage is not input to the power supply circuit that has been used as the power supply until then, and the power supply circuit is completely stopped, so that the loss generated in the power supply circuit that is not used as the power supply can be made zero. it can. Accordingly, the inverter device can be made more efficient.
[0019]
Further, it is preferable that the selection means select a power supply circuit that inputs a DC power source having a smaller number of start / stops per day among the plurality of DC power sources. As a result, even when at least one output of the DC power source cannot be sufficiently secured, the chattering operation in which the power supply frequently starts and stops can be eliminated, and stable operation can be performed.
[0020]
Moreover, it is preferable that the selection means select a power supply circuit that inputs a DC power source having a lower output voltage among the plurality of DC power sources. Thereby, since a power supply circuit with smaller power consumption can be selected as a power supply, the efficiency of the inverter device can be improved.
[0021]
Furthermore, it is preferable that the selection unit is configured to switch the selection to another power supply circuit when the input voltage of the selected power supply circuit is lower than a predetermined value. As a result, when the input voltage of the power supply circuit currently used as a power supply has decreased, the operation can be switched to another power supply circuit. Therefore, the inverter device must be operated as long as the voltage of all DC power sources does not decrease. Can continue.
[0022]
Further, the inverter according to the present invention may be a grid-connected inverter device in which an output of the inverter main circuit is connected to a commercial power system via an opening / closing means. According to this, since the output power of the inverter can flow to the commercial power system, the inverter can always be operated as long as at least one of the DC power sources is in an operating state regardless of the presence or absence of a power load. .
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an inverter device according to the present invention (hereinafter referred to as “the present device” as appropriate) will be described with reference to the drawings.
[0024]
<First Embodiment>
FIG. 1 is a block diagram showing a first embodiment of the apparatus of the present invention. In the device 2 of the present invention shown in FIG. 1, a plurality of DC power sources are connected to the input side, for example, a solar cell 1 and a fuel cell 9 are connected. In addition, as the direct current power source, a secondary battery, direct current power obtained by rectifying the alternating current output of the motor generator, and the like can be used as the direct current power source.
[0025]
The inverter main circuit 4 in the device 2 of the present invention includes voltage adjusting means 4a and 4b corresponding to the respective DC inputs, and the output voltages of the voltage adjusting means 4a and 4b are connected in parallel and then collectively connected to the inverter circuit 4c. Is converted into alternating current of commercial frequency. The voltage adjusting means 4a and 4b are DC-DC converters provided with a switch element, and on / off of the switch element is controlled based on a drive signal from the drive circuit 6 together with the inverter circuit 4c.
[0026]
The number of DC power sources is not limited to two systems as in the first embodiment, and by providing the same number of voltage adjusting means as the number of DC power sources, the output of a large number of DC power sources is one. It can be converted into alternating current with the inverter device. The drive signal of the drive circuit 6 is created based on the control signal from the control circuit 7. The drive power of the drive circuit 6 and the control circuit 7 is supplied from one of the power supply circuit 10 using the solar cell 1 as an input source and the power supply circuit 11 using the fuel cell 9 as an input source. The selection means 5 switches whether to use. In general, the output of the inverter main circuit 4 is connected to an AC load 3, but in the case of a grid-connected inverter device, instead of the AC load 3, switching means such as a relay (not shown) and a leakage breaker are used. Connected to the commercial power system. When the grid-connected inverter device is for residential use, generally, a grid-connected system with a commercial power system with a single-phase 200 V is used, and the output power is 3 to 5 kW. Hereinafter, this invention apparatus 2 is demonstrated as a grid connection inverter apparatus.
[0027]
The solar cell 1 has an output voltage of about 200 V during rated operation, but since the output voltage during actual operation varies depending on the amount of solar radiation and temperature, an operation range of 80 V to 320 V is guaranteed. On the other hand, the output voltage range of the fuel cell 9 is about 30 V to 60 V when the output power is 0.5 kW to 1 kW, but the output voltage also increases almost proportionally to the capacity when the output power is larger. . The output voltages of the solar cell 1 and the fuel cell 9 are boosted to a constant DC voltage of 320 to 350 V by the voltage adjusting means 4a and 4b. At this time, if the boosted voltage falls below the above voltage range, the harmonic distortion factor of the current output from the inverter circuit to the commercial power system rises and the power quality of the commercial power system deteriorates, so at least 320 V is secured. There is a need to.
[0028]
The outputs of the power supply circuits 10 and 11 include, for example, three systems of + 15V, −15V, and + 5V, respectively. The only difference between the power supply circuits 10 and 11 is that the input voltage range differs depending on the output voltage characteristics of the DC power sources 1 and 9. Accordingly, the power supply circuit 10 supplies the three systems of voltages to the selection means 5 when the input voltage is in the output voltage range 80V to 320V of the solar cell 1. Similarly, the power supply circuit 11 supplies the three systems of voltages to the selection means 5 when the input voltage is in the output voltage range 30 V to 60 V of the fuel cell 9.
[0029]
The drive circuit 6 is supplied with drive power for the switch elements in the inverter main circuit 4 from the power supply circuits 10 and 11 via the selection means 5. As the switch element, an IGBT, a MOSFET, or the like is used, and + 15V is often applied as the drive power supply voltage. The control circuit 7 starts its operation when supplied with + 15V, −15V and + 5V control power from the power supply circuits 10 and 11 via the selection means 5. The selection means 5 is a means for selecting which of the power supply circuit 10 or 11 supplies power to the drive circuit 6 and the control circuit 7, and is configured using a relay, a transistor switch, or the like.
[0030]
Next, the operating conditions of the selection means 5 will be described in detail below. In the first embodiment, the device 2 of the present invention is connected to DC power sources having different characteristics, that is, the solar cell 1 and the fuel cell 9, and the operating conditions are completely different. Specifically, the fuel cell 9 can be continuously operated for rated operation unless the fuel supply is cut off, but the solar cell 1 can be operated only during the daytime. In addition, since the solar cell 1 has a small amount of generated power in the morning, evening, or a time zone with a small amount of solar radiation such as a cloudy day, the operating voltage tends to become unstable.
[0031]
Specifically, when the selection unit 5 selects the power supply circuit 10 so that the drive power of the drive circuit 6 and the control circuit 7 is supplied from the power supply circuit 10, the solar cell 1 has at least the above-described drive power. It is necessary to supply. However, when the amount of solar radiation decreases below a certain threshold value, the solar cell output voltage cannot be maintained at 80 V or more due to the voltage drop of the solar cell due to the driving power supply. If it does so, since it becomes below the minimum input voltage which the power supply circuit 10 requires, the power supply circuit 10 stops operation | movement, and this invention apparatus 2 also stops a driving | operation. After that, even if the amount of solar radiation is constant, since the power supply circuit 10 is stopped, the solar cell 1 is not reduced in voltage due to the driving power supply, so the solar cell output voltage rises again to 80 V or more, and the power supply circuit 10 starts up. In this way, in the region where the amount of solar radiation is very low, chattering that the power supply circuit frequently starts and stops occurs, so that the life of the parts of the power supply circuit is reduced, the operation time of the device 2 of the present invention is reduced, and further the operation is continued. This leads to a decrease in reliability.
[0032]
Therefore, when the amount of solar radiation decreases and the voltage of the solar cell 1 falls below 80 V, the selection means 5 is based on a command from the control circuit 7 and from the power circuit 10 on the solar cell 1 side to the power circuit 11 on the fuel cell 9 side. Switch the selection to. Thereby, the unnecessary starting and stopping of the power supply circuit 10 as described above can be prevented, and the device 2 of the present invention can continuously operate.
[0033]
In addition, the reverse case described above is also possible. That is, when the selection unit 5 selects the power supply circuit 11 so that the drive power of the drive circuit 6 and the control circuit 7 is supplied from the power supply circuit 11 on the fuel cell 9 side, the output voltage of the fuel cell 9 is 30 V or less. The selection means 5 switches the selection to the power supply circuit 10 on the solar cell 1 side. Thereby, the unnecessary starting stop of the power supply circuit 11 as mentioned above can be prevented, and the device 2 of the present invention can continuously operate.
[0034]
Basically, when both the solar cell 1 and the fuel cell 9 are operating in the configuration of the first embodiment, the operating conditions are not affected by solar radiation, and the fuel cell can be operated at all times if fuel is supplied. If the selection of the selection means 5 is switched to the power supply circuit 11 on the 9th side, there is no possibility of unnecessary operation of the power supply as described above.
[0035]
Further, as the characteristics of the power supply circuit, the higher the input voltage, the lower the conversion efficiency of the power supply circuit. It is better to leave. Specifically, when the input voltage increases, it is necessary to use a high breakdown voltage element, and the resistance loss increases as the high breakdown voltage element tends to increase the internal loss of the power supply circuit. Further, since the output voltages of the power supply circuits 10 and 11 are constant values such as +15 V, −15 V, +5 V, etc., when the input voltage is high, the voltage drop in the power supply circuit increases. Loss and switch loss increase. For the above reasons, when comparing the power supply circuit 10 with 80V to 320V as input and the power supply circuit 11 with 30 to 60V as input, the latter has lower power consumption and improves the conversion efficiency of the device 2 of the present invention. .
[0036]
Second Embodiment
FIG. 2 is a block diagram showing a second embodiment of the apparatus of the present invention. The difference from the first embodiment is that the selection means 5 is provided on the input side instead of the output side of the power supply circuits 10 and 11. In the second embodiment shown in FIG. 2, the selection means 5 is provided only on the positive electrode side of the DC power sources 1 and 9, and the negative electrode side is connected in parallel and then input to both power supply circuits 10 and 11 at all times. Thus, the power supply to the power supply circuit can be switched only by the positive-side selection means.
[0037]
However, the power supply circuits 10 and 11 that are not used may be completely separated from the DC power sources 1 and 9 as a configuration in which both the positive and negative sides of the DC power sources 1 and 9 are switched by the selection means 5.
[0038]
In the first embodiment, even when one of the power supply circuits 10 or 11 is not used, that is, when the drive power is not supplied from the power supply circuit to the drive circuit 6 or the control circuit 7, the use is performed. Since a DC power source is connected to the input side of the power supply circuit that is not, a fixed loss of the power supply circuit continues to occur. On the other hand, in the second embodiment, the selection means 5 is provided on the input side of the power supply circuits 10 and 11, and no output from the DC power source is supplied to the unused power supply circuits. Wasteful loss can be reduced to zero.
[0039]
In the second embodiment shown in FIG. 2, the selection means 5 has a configuration in which the inputs of the power supply circuits 10 and 11 are shared and either one of the DC power sources 1 and 9 is switched and connected. For example, as shown in FIG. 3, the connection of the DC power sources 1 and 9 to the corresponding positive electrode side may be individually switched while the inputs of the power supply circuits 10 and 11 are made independent. In this case, the inputs of the power supply circuits 10 and 11 not connected to the DC power sources 1 and 9 may be fixed to a constant voltage (for example, ground potential) lower than a predetermined input voltage range. When the voltage ranges of the plurality of DC power sources 1 and 9 partially overlap, it is possible to avoid a situation in which an unselected power supply circuit operates unnecessarily.
[0040]
【The invention's effect】
As described above in detail, according to the device of the present invention, in the inverter device including a plurality of power supply circuits connected to a plurality of different DC power sources, the power supply circuit that supplies power to the drive circuit and the control circuit by the selection means Therefore, unnecessary start / stop operation of the power supply circuit can be eliminated. In addition, since a power supply circuit with a smaller power loss can be selected, the power generation efficiency of the entire inverter device can be improved.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an inverter device according to an embodiment of the present invention. FIG. 2 is a block diagram showing another embodiment of the inverter device according to the invention. FIG. 3 is an inverter device according to the invention. FIG. 4 is a circuit diagram showing a configuration example of a conventional grid-connected inverter device for a photovoltaic power generation system. FIG. 5 is a configuration diagram of a conventional grid-connected inverter device for a hybrid system. Circuit diagram showing an example [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,101: Solar cell 2: Inverter apparatus 102,110: Grid connection inverter apparatus 3,103: Commercial power system (or alternating current load)
4, 104: Inverter main circuit 5: Selection means 105: Opening / closing means 6, 106: Drive circuit 7, 107: Control circuit 10, 11, 108: Power supply circuit 210: MOSFET
211: Differential switching circuit

Claims (7)

An inverter main circuit configured to convert DC power from a plurality of DC power sources into AC power, a drive circuit that drives the inverter main circuit, a control circuit that controls the drive circuit, and the plurality of DC power In an inverter device comprising a plurality of power supply circuits that receive power supply from at least one of the sources and supply power to the drive circuit and the control circuit,
At least two of the power supply circuits each have an input voltage range corresponding to the output characteristics of the separate DC power sources, and when the input voltage is within the input voltage range, the drive circuit and the control circuit Configured to be able to supply power,
An inverter device comprising selection means for selecting a power supply circuit that supplies power to the drive circuit and the control circuit from the plurality of power supply circuits. The selection unit is provided on an output side of the plurality of power supply circuits, and is configured to switch power supplied from the plurality of power supply circuits and supply the power to the drive circuit and the control circuit. The inverter device according to claim 1. 2. The inverter device according to claim 1, wherein the selection unit is provided on an input side of the plurality of power supply circuits, and is configured to switch the DC power source input to the plurality of power supply circuits. . The said selection means selects the power supply circuit which uses as input the DC power source with the smaller number of times of starting and stopping per day among the plurality of DC power sources. The inverter device according to the item. 3. The inverter device according to claim 1, wherein the selection unit selects a power supply circuit that inputs a DC power source having a lower output voltage among the plurality of DC power sources. The said selection means switches a selection to the said other power supply circuit, when the input voltage of the selected said power supply circuit falls below predetermined value, The any one of Claims 1-5 characterized by the above-mentioned. Inverter device. The inverter device according to any one of claims 1 to 6, wherein an output of the inverter main circuit is connected to a commercial power system through an opening / closing means.

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