Grid interconnection device and power conditioner

Abstract

To simplify and downsize a configuration.SOLUTION: A grid connection device includes an insulated DC / DC conversion unit that converts DC power supplied from a DC power supply into DC power of a first voltage, an inverter unit that converts the DC power of the first voltage converted by the DC / DC conversion unit into AC power that can be connected to a grid, and supplies the AC power to an AC load, an AC / DC conversion unit that rectifies AC power supplied from a system power supply into DC power, and converts the rectified DC power into DC power of a second voltage which is a power supply for control, a power supply line for DC power of the first voltage converted by the DC / DC conversion unit, and a connection unit that performs connection of a power supply line for the rectified DC power rectified by the AC / DC conversion unit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a grid interconnection device and a power conditioner. [Background technology]

[0002] In recent years, a grid-connected device has become known that enables power to be supplied to an AC load from both AC power generated from a DC power source with a fluctuating output voltage, such as a solar cell, and AC power supplied by a grid power source (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-55508 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the conventional grid interconnection device described above requires a constant supply of DC control power for overall control. To ensure operation even if either the DC power supply or the grid power supply is lost, the conventional grid interconnection device includes both a DC / DC converter that generates control power from the DC power supply and an AC / DC converter that generates control power from the grid power supply. This poses a problem of the grid interconnection device becoming larger in configuration and size.

[0005] The present invention has been made to solve the above problems, and an object of the present invention is to provide a grid interconnection device and a power conditioner that can be simplified in configuration and made smaller in size. [Means for solving the problem]

[0006] In order to solve the above problem, one aspect of the present invention is a control system including an isolated DC / DC conversion unit that converts DC power supplied from a DC power source into DC power of a first voltage, an inverter unit that converts the DC power of the first voltage converted by the DC / DC conversion unit into AC power that can be connected to a grid and supplies the AC power to an AC load, an AC / DC conversion unit that rectifies the AC power supplied from the grid power source into DC power and converts the rectified DC power into DC power of a second voltage that is a control power supply, and an inverter unit that converts the DC power of the first voltage converted by the DC / DC conversion unit into AC power that can be connected to a grid and supplies the AC power to an AC load. and a connection unit that connects a power supply line of the DC power of the first voltage to a power supply line of the rectified DC power rectified by the AC / DC conversion unit, the AC / DC conversion unit including a synchronous rectification unit that rectifies the AC power supplied from the system power supply, the connection unit being a system interconnection connection in which an output line of the inverter unit and a power supply line of the system power supply are connected, and the synchronous rectification unit is operating, the connection unit being a system interconnection connection in which an output line of the inverter unit and a power supply line of the system power supply are connected, and the synchronous rectification unit is operating, the connection unit being a system interconnection connection in which an output line of the inverter unit and a power supply line of the system power supply are connected, and but The grid interconnection device is characterized by comprising a switch that is controlled to be in an on state between the grid interconnection device and the power supply line for the rectified DC power when the grid interconnection device is not in operation.

[0007] Furthermore, one aspect of the present invention is characterized in that, in the above-mentioned grid interconnection device, the AC / DC conversion unit includes a synchronous rectification unit that rectifies AC power supplied from the grid power supply, and the connection unit includes a switch that cuts off the connection between the power supply line for the DC power of the first voltage and the power supply line for the rectified DC power when the synchronous rectification unit operates in a state where the output line of the inverter unit and the power supply line of the grid power supply are connected.

[0008] Furthermore, one aspect of the present invention is characterized in that, in the above-mentioned grid interconnection device, the connection unit includes the switch having a body diode, and a connection diode arranged so as to be in a forward direction when DC power is supplied from the power supply line of the DC power of the first voltage to the power supply line of the rectified DC power.

[0009] Furthermore, one aspect of the present invention is characterized in that, in the above-mentioned grid interconnection device, the synchronous rectification unit includes an upper diode and a lower switching element connected in series, the connecting diodes include a first diode arranged on the low-potential side connecting line and a second diode arranged on the high-potential side connecting line, and the switch is arranged on the low-potential side connecting line.

[0010] Furthermore, one aspect of the present invention is characterized in that, in the above-mentioned grid interconnection device, the synchronous rectification unit includes an upper switching element and a lower switching element connected in series, and the switches include a first switch arranged on the low-potential side connecting line and a second switch arranged on the high-potential side connecting line.

[0011] Another aspect of the present invention is a power supply device including an isolated DC / DC conversion unit that converts DC power supplied from a DC power source into DC power of a first voltage; an inverter unit that converts the DC power of the first voltage converted by the DC / DC conversion unit into AC power that can be connected to a grid and supplies the AC power to an AC load; an AC / DC conversion unit that rectifies the AC power supplied from the grid power source into DC power and converts the rectified DC power into DC power of a second voltage that is a control power supply; and a power line for the DC power of the first voltage converted by the DC / DC conversion unit. and a connection unit that connects a power supply line of the rectified DC power rectified by the AC / DC conversion unit to a power supply line of the rectified DC power rectified by the AC / DC conversion unit, the AC / DC conversion unit including a synchronous rectification unit that rectifies the AC power supplied from the system power supply, the connection unit being a system interconnection connection in which an output line of the inverter unit and a power supply line of the system power supply are connected, and when the synchronous rectification unit is operating, the connection unit cuts off the connection between the power supply line of the DC power of the first voltage and the power supply line of the rectified DC power, and when the system interconnection connection is not established or the synchronous rectification unit but The power conditioner is characterized by including a switch that is controlled to be in an on state between the power supply line of the rectified DC power when the power conditioner is not in operation. [Effects of the Invention]

[0012] According to the present invention, the grid interconnection device includes a connection unit that connects a power supply line of DC power of a first voltage converted from a DC power supply by a DC / DC conversion unit to a power supply line of rectified DC power rectified from a grid power supply by an AC / DC conversion unit that converts DC power of a second voltage, which serves as a control power supply, so that the AC / DC conversion unit can generate control power from both the DC power supply and the grid power supply. Therefore, the grid interconnection device does not need to include both a DC / DC conversion unit that generates control power from a DC power supply and an AC / DC conversion unit that generates control power from the grid power supply, thereby enabling a simplified and compact configuration. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a block diagram illustrating an example of a power conditioner according to a first embodiment. [Figure 2] 4 is a flowchart showing an example of an operation of the power conditioner according to the first embodiment. [Figure 3] FIG. 2 is a diagram illustrating an example of the operation of the power conditioner according to the first embodiment when the power conditioner is interconnected to a grid. [Figure 4] FIG. 1 is a block diagram showing an example of a conventional power conditioner. [Figure 5] FIG. 10 is a block diagram illustrating an example of a power conditioner according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A grid interconnection device according to an embodiment of the present invention will be described below with reference to the drawings.

[0015] [First embodiment] FIG. 1 is a block diagram showing an example of a power conditioner 1 according to the first embodiment. 1, the power conditioner 1 includes a DC / DC conversion unit 10, an inverter unit 20, an AC / DC conversion unit 30, a connection unit 40, a control unit 50, and a capacitor C1. In this embodiment, the power conditioner 1 is an example of a grid-connected device that can be connected to a commercial power source 3.

[0016] The DC / DC conversion unit 10 is, for example, an insulating DC / DC converter, and converts DC power supplied from the DC power supply 2 into DC power of voltage V1 (first voltage). Here, the DC power supply 2 is a power source such as a solar cell or a fuel cell. The DC / DC conversion unit 10 includes an input filter 11, an inverter circuit 12, a transformer 13, a synchronous rectification unit 14, and a conversion control unit 15.

[0017] The input filter 11 is, for example, a low-pass filter circuit, and reduces noise in the DC power supplied from the DC power supply 2 and smoothes it.

[0018] The inverter circuit 12 generates three-phase AC signals (for example, a U-phase AC signal, a V-phase AC signal, and a W-phase AC signal) from DC power supplied from the DC power supply 2. The inverter circuit 12 includes three pairs of switching elements connected in series between two power supply lines of the DC power supply 2. The inverter circuit 12 generates the three-phase AC signals by switching each switching element under the control of a conversion control unit 15 (described later). Here, the switching elements are, for example, MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors). The inverter circuit 12 supplies the generated three-phase AC signals to a transformer 13.

[0019] The transformer 13 includes, for example, three transformers, and converts the three-phase AC signal generated by the inverter circuit 12 into a three-phase AC signal of a predetermined voltage. The transformer 13 supplies the AC signal with the converted voltage to the synchronous rectifier 14.

[0020] The synchronous rectifier 14 rectifies the three-phase AC signals supplied from the transformer 13 into DC power of voltage V1 (first voltage). The synchronous rectifier 14 includes three pairs of switching elements connected in series between a high-potential power line L1 and a low-potential power line L2. Here, the switching elements are, for example, MOSFETs. The synchronous rectifier 14 switches each of the switching elements under the control of a conversion control unit 15 (described later) to generate DC power of voltage V1 obtained by rectifying the three-phase AC signals.

[0021] Conversion control unit 15 is, for example, a processor including a CPU (Central Processing Unit), and performs overall control of DC / DC conversion unit 10. Conversion control unit 15 controls each unit of DC / DC conversion unit 10 based on control commands from a control unit 50, which will be described later. Conversion control unit 15 controls the switching of each MOSFET in inverter circuit 12 and each MOSFET in synchronous rectification unit 14, for example, so that the voltage output by synchronous rectification unit 14 becomes voltage V1.

[0022] The capacitor C1 is a smoothing capacitor that is disposed between the power supply line L1 and the power supply line L2 and smoothes the output voltage of the DC / DC conversion unit 10 (voltage V1).

[0023] The inverter unit 20 converts the DC power of the voltage V1 converted by the DC / DC conversion unit 10 into AC power that can be connected to a grid and supplies it to an AC load (not shown). The inverter unit 20 generates an AC signal whose phase is synchronized with that of the commercial power source 3 so that it can be connected to the grid. The inverter unit 20 includes an inverter circuit 21, a noise filter 22, an independent relay 23, a system relay 24, an inverter control unit 25, and a connection switch 42.

[0024] The inverter circuit 21 generates a two-phase AC signal from the DC power of the voltage V1 supplied from the DC / DC conversion unit 10. The inverter circuit 21 includes two sets of two switching elements connected in series between two power supply lines of the voltage V1 (between the power supply line L1 and the power supply line L2). The inverter circuit 21 generates an AC signal that can be connected to the commercial power supply 3 by switching each switching element under the control of an inverter control unit 25, which will be described later. Here, the switching elements are, for example, MOSFETs. The inverter circuit 21 supplies the generated AC signal to a noise filter 22.

[0025] The noise filter 22 is a filter circuit that reduces high-frequency noise by passing, for example, an AC signal having the frequency of the commercial power supply 3 connected to the grid. The noise filter 22 reduces noise in the AC signal generated by the inverter circuit 21 and supplies the AC signal to the independent relay 23 and the grid relay 24.

[0026] The self-sustaining relay 23 is a relay switch for outputting an AC signal when the AC signal generated by the inverter circuit 21 is used for self-sustaining operation. The self-sustaining relay 23 supplies AC power to a connected load (not shown) during self-sustaining operation. The connection of the self-sustaining relay 23 is controlled by the inverter control unit 25, which will be described later.

[0027] The grid relay 24 is a relay switch for outputting an AC signal when the AC signal generated by the inverter circuit 21 is connected to the grid. When connected to the grid, the grid relay 24 supplies AC power to a load (not shown) connected to the commercial power supply 3, or sells power to the commercial power supply 3. The connection of the grid relay 24 is controlled by the inverter control unit 25, which will be described later.

[0028] The connection switch 42 is a switch that connects the power supply line (power supply line L2) of DC power of voltage V1 and the power supply line (power supply line L4) of rectified DC power of the AC / DC conversion unit 30, which will be described later. The connection switch 42 will be described in detail later.

[0029] The inverter control unit 25 is, for example, a processor including a CPU, and performs overall control of the inverter unit 20. The inverter control unit 25 controls each unit of the inverter unit 20 based on a control command from a control unit 50, which will be described later. The inverter control unit 25 controls, for example, the switching of each MOSFET of the inverter circuit 21, the independent relay 23, the system relay 24, and the connection switch 42 so that the AC signal output from the inverter circuit 21 can be connected to the commercial power supply 3 (can be interconnected to the grid).

[0030] The AC / DC converter 30 rectifies AC power supplied from the commercial power supply 3, which is a system power supply, into DC power, and converts the rectified DC power into DC power of voltage V2 (second voltage), which is a control power supply. The AC / DC converter 30 supplies the converted DC power of voltage V2 to the control unit 50.

[0031] The AC / DC conversion unit 30 includes a noise filter 31, a synchronous rectification unit 32, a capacitor C2, an inverter circuit 33, a transformer 34, a synchronous rectification unit 35, a conversion control unit 36, and connecting diodes 41 (41-1, 41-2).

[0032] The noise filter 31 is, for example, a filter circuit that passes an AC signal having the frequency of the commercial power supply 3 and reduces high-frequency noise, and reduces noise in the AC signal supplied from the commercial power supply 3 and supplies the signal to the synchronous rectification unit 32.

[0033] The synchronous rectifier 32 rectifies the AC signal supplied from the commercial power supply 3 via the noise filter 31 into DC power (rectified DC power) of voltage V1 (first voltage). The synchronous rectifier 32 includes two pairs of diodes 37 and switching elements 38 connected in series between a high-potential power line L3 and a low-potential power line L4. That is, the synchronous rectifier 32 includes upper diodes 37 (37-1, 37-2) and lower switching elements 38 (38-1, 38-2) connected in series. The synchronous rectifier 32 generates DC power of voltage V1 by rectifying the AC signal when the switching elements 38 are switched under the control of a conversion control unit 36 ​​(described later).

[0034] In this embodiment, the diode 37-1 and the diode 37-2 have the same configuration, and will be described as the diode 37 when referring to any diode included in the synchronous rectifier 32 or when no particular distinction is made.

[0035] In addition, in this embodiment, the switching element 38-1 and the switching element 38-2 have the same configuration, and when referring to any switching element included in the synchronous rectification unit 32 or when no particular distinction is made, they will be described as switching element 38.

[0036] The diode 37-1 has an anode terminal connected to a node N1 connected to one of the output lines of the noise filter 31, and a cathode terminal connected to the high-potential power line L3. The diode 37-2 has an anode terminal connected to a node N2 connected to the other output line of the noise filter 31, and a cathode terminal connected to the high-potential power supply line L3.

[0037] The switching element 38-1 is, for example, an N-type MOSFET. The source terminal of the switching element 38-1 is connected to the low-potential power supply line L4, and the drain terminal is connected to a node N1. The gate terminal (control terminal) of the switching element 38-1 is connected to a signal line for a control signal output from the conversion control unit 36, which will be described later.

[0038] The switching element 38-2 is, for example, an N-type MOSFET. The source terminal of the switching element 38-2 is connected to the low-potential power supply line L4, and the drain terminal is connected to a node N2. The gate terminal (control terminal) of the switching element 38-2 is connected to a signal line for a control signal output from the conversion control unit 36, which will be described later. The switching of the switching elements 38-1 and 38-2 is controlled by a conversion control unit 36, which will be described later.

[0039] The capacitor C2 is a smoothing capacitor that is disposed between the power supply line L3 and the power supply line L4 and smoothes the output voltage of the synchronous rectifier 32 (voltage V1).

[0040] The inverter circuit 33 generates an AC signal from the DC power supplied from the synchronous rectifier 32. The inverter circuit 33 includes two switching elements connected in series between two power supply lines of the voltage V2 (between the power supply line L3 and the power supply line L4) and a capacitor C3. The inverter circuit 33 generates an AC signal by switching each switching element under the control of a conversion control unit 36 ​​(described later). Here, the switching elements are, for example, MOSFETs. The inverter circuit 33 supplies the generated AC signal to a transformer 34. The capacitor C3 is disposed between the power supply line L4 and one input terminal of the transformer .

[0041] The transformer 34 converts, for example, the AC signal generated by the inverter circuit 33 into an AC signal of a predetermined voltage. The transformer 34 supplies the AC signal whose voltage has been converted to the synchronous rectifier 35.

[0042] The synchronous rectifier 35 rectifies the AC signal supplied from the transformer 34 into DC power of voltage V2 (second voltage). The synchronous rectifier 35 includes two switching elements. The synchronous rectifier 35 generates DC power of voltage V2 by rectifying the AC signal as each switching element is switched under the control of the conversion control unit 36 ​​(described later). The synchronous rectifier 35 supplies the rectified DC power of voltage V2 to the control unit 50.

[0043] The conversion control unit 36 ​​is, for example, a processor including a CPU, and performs overall control of the AC / DC conversion unit 30. The conversion control unit 36 ​​controls each unit of the AC / DC conversion unit 30 based on a control command from a control unit 50, which will be described later. The conversion control unit 36 ​​controls, for example, the switching of the switching element 38 of the synchronous rectification unit 32 so that the voltage output by the synchronous rectification unit 32 becomes voltage V1. The conversion control unit 36 ​​also controls, for example, the switching of each MOSFET of the inverter circuit 33 and each MOSFET of the synchronous rectification unit 35 so that the voltage output by the synchronous rectification unit 35 becomes voltage V2. The conversion control unit 36 ​​controls the switching of each MOSFET of the inverter circuit 33 and each MOSFET of the synchronous rectification unit 35 by, for example, an LLC system, to generate voltage V2.

[0044] The inverter circuit 33, the transformer 34, and the synchronous rectifier 35 function as an insulating DC / DC converter that converts DC power of the voltage V1 into DC power of the voltage V2.

[0045] The connecting diode 41 is arranged so that it is in the forward direction when DC power is supplied from the power supply lines (power supply lines L1 and L2) of DC power of voltage V1 to the power supply lines (power supply lines L3 and L4) of rectified DC power.

[0046] In this embodiment, the connecting diode 41-1 and the connecting diode 41-2 will be described as the connecting diode 41 when they indicate any connecting diode included in the power conditioner 1 or when no particular distinction is made between them. In this embodiment, the connection diodes 41-1 and 41-2 and the connection switch 42 correspond to the connection unit 40. That is, the connection unit 40 includes the connection diodes 41-1 and 41-2 and the connection switch 42.

[0047] The connecting diode 41-1 (first diode) is arranged so as to be in the forward direction when DC power is supplied from the power supply lines (power supply lines L1 and L2) of DC power at voltage V1 to the power supply lines (power supply lines L3 and L4) of rectified DC power. For example, the anode terminal of the connecting diode 41-1 is connected to the power supply line L4, and the cathode terminal is connected to the power supply line L2 via the connecting switch 42. The cathode terminal of the connecting diode 41-1 is connected to the drain terminal of the connecting switch 42. The connecting diode 41-1 is arranged on the low-potential side connecting line.

[0048] The connecting diode 41-2 (second diode) is arranged so as to be in the forward direction when DC power is supplied from the power supply lines (power supply lines L1 and L2) of DC power at voltage V1 to the power supply lines (power supply lines L3 and L4) of rectified DC power. For example, the anode terminal of the connecting diode 41-2 is connected to the power supply line L3, and the cathode terminal is connected to the power supply line L1. The connecting diode 41-2 is arranged on the high-potential side connecting line.

[0049] The connection switch 42 is, for example, an N-type MOSFET, and has a source terminal connected to the power supply line L2 and a drain terminal connected to the cathode terminal of the connection diode 41-1. In other words, the connection switch 42 is arranged on the low-potential side connection line.

[0050] Furthermore, a gate terminal (control terminal) of the connection switch 42 is connected to, for example, a signal line for a control signal output from the inverter control unit 25. When the output line of the inverter unit 20 and the power line of the commercial power source 3 (system power supply) are connected and the synchronous rectification unit 32 operates, the connection switch 42 cuts off the connection between the power supply line L2 for DC power of voltage V1 and the power supply line L4 for rectified DC power.

[0051] The connection unit 40 connects the power supply lines (power supply lines L1 and L2) of the DC power of voltage V1 converted by the DC / DC conversion unit 10 to the power supply lines (power supply lines L3 and L4) of the rectified DC power rectified by the AC / DC conversion unit 30.

[0052] The control unit 50 is, for example, a processor including a CPU, and performs overall control of the power conditioner 1. The control unit 50 receives supply of DC power of voltage V2 output by the AC / DC conversion unit 30 and executes various control processes. The control unit 50 controls, for example, the DC / DC conversion unit 10, the inverter unit 20, the AC / DC conversion unit 30, and the connection unit 40.

[0053] Next, the operation of the power conditioner 1 according to this embodiment will be described with reference to the drawings. First, the overall operation of the power conditioner 1 will be described with reference to FIG. The DC / DC conversion unit 10 first converts DC power output from a DC power source 2, which is a solar cell or a fuel cell, into DC power of voltage V1 and supplies it to the inverter unit 20.

[0054] In the DC / DC converter 10, the DC power output from the DC power supply 2, with noise reduced by the input filter 11, is converted into a three-phase AC signal by the inverter circuit 12. The inverter circuit 12 supplies the three-phase AC signal to the transformer 13, which then converts it into a three-phase AC signal of a predetermined voltage. The transformer 13 supplies the AC signal with the converted voltage to the synchronous rectifier 14.

[0055] Next, the synchronous rectifier 14 synchronously rectifies the AC signal whose voltage has been converted by the transformer 13, and supplies DC power of voltage V1 to the inverter 20. Next, the inverter circuit 21 of the inverter unit 20 converts the DC power of the voltage V1 into AC power that can be grid-connected to the commercial power source 3, and supplies the AC power to the commercial power source 3 via the grid relay 24. Furthermore, when the inverter unit 20 performs stand-alone operation, it supplies the AC power generated by the inverter circuit 21 to a load unit (not shown) that performs stand-alone operation via the stand-alone relay 23.

[0056] Furthermore, AC / DC conversion unit 30 converts AC power from commercial power supply 3 into DC power of voltage V1, and further converts the DC power of voltage V1 into DC power of voltage V2 and supplies it to control unit 50. In AC / DC conversion unit 30, synchronous rectification unit 32 converts the AC power supplied from commercial power supply 3 into DC power of voltage V1, and further, inverter circuit 33, transformer 34, and synchronous rectification unit 35, which are insulating DC / DC converters, convert the DC power of voltage V1 into DC power of voltage V2.

[0057] Furthermore, the connection unit 40 supplies the DC power of the voltage V1 converted by the DC / DC conversion unit 10 to power supply lines (power supply lines L3 and L4) for the rectified DC power rectified by the synchronous rectification unit 32 of the AC / DC conversion unit 30. The AC / DC conversion unit 30 generates DC power of the voltage V2 from the DC power of the voltage V1 converted by the DC / DC conversion unit 10 supplied by the connection unit 40 or the rectified DC power of the voltage V1 rectified by the synchronous rectification unit 32.

[0058] That is, for example, when the synchronous rectifier 32 is stopped, the AC / DC converter 30 can generate DC power of voltage V2 to be supplied to the control unit 50 from DC power of voltage V1 converted by the DC / DC converter 10. Furthermore, for example, when the DC / DC converter 10 is stopped, the AC / DC converter 30 can generate DC power of voltage V2 to be supplied to the control unit 50 from DC power of voltage V1 rectified by the synchronous rectifier 32.

[0059] Next, the control process of the connection switch 42 in this embodiment will be described with reference to FIG. 2 is a flowchart showing an example of the operation of the power conditioner 1 according to this embodiment. Here, a control process of the connection switch 42 of the connection unit 40 will be described.

[0060] 2, the inverter control unit 25 of the inverter unit 20 determines whether the power conditioner 1 is connected to the grid and whether the synchronous rectification unit 32 is operating (step S101). If the power conditioner 1 is connected to the grid and the synchronous rectification unit 32 is operating (step S101: YES), the inverter control unit 25 proceeds to step S102. If the power conditioner 1 is not connected to the grid or the synchronous rectification unit 32 is not operating (step S101: NO), the inverter control unit 25 proceeds to step S103.

[0061] In step S102, the inverter control unit 25 turns off the connection switch 42 of the connection unit 40. That is, the connection switch 42 cuts off the connection by the connection unit 40, as shown in FIG.

[0062] FIG. 3 is a diagram illustrating an example of the operation of the power conditioner 1 according to this embodiment when it is connected to a grid. In FIG. 3, when the connection switch 42 is in the on state, the grid relay 24 is in the on state, the power conditioner 1 is connected to the grid, and the synchronous rectification unit 32 is in operation, a loop RP is formed in which the power supplied from the commercial power source 3 returns to the commercial power source 3, and there is a possibility that a grid short circuit will occur.

[0063] Here, the loop RP runs from the commercial power supply 3 through the noise filter 31, the lower switching element 38 of the synchronous rectifier 32, the connection diode 41-1, the connection switch 42, the lower switching element of the inverter circuit 21, the noise filter 22, and the system relay 24, and returns to the commercial power supply 3.

[0064] In this case, the inverter control unit 25 controls the connection switch 42 to the OFF state, disconnecting the inverter unit 20 from the AC / DC conversion unit 30 and breaking the loop RP described above. Returning to FIG. 2, after the process of step S102, the inverter control unit 25 returns the process to step S101.

[0065] In step S103, the inverter control unit 25 turns on the connection switch 42 of the connection unit 40. That is, the connection switch 42 turns on the connection by the connection unit 40. After the process of step S103, the inverter control unit 25 returns the process to step S101.

[0066] As described above, the power conditioner 1 (grid-connected device) according to this embodiment includes a DC / DC conversion unit 10, an inverter unit 20, an AC / DC conversion unit 30, and a connection unit 40. The DC / DC conversion unit 10 is an insulated DC / DC converter that converts DC power supplied from a DC power supply 2 into DC power of voltage V1 (first voltage). The inverter unit 20 converts the DC power of voltage V1 converted by the DC / DC conversion unit 10 into AC power that can be connected to a grid and supplies it to an AC load (not shown). The AC / DC conversion unit 30 rectifies AC power supplied from a commercial power supply 3 (grid power supply) into DC power (DC power of voltage V1) and converts the rectified DC power into DC power of voltage V2 (second voltage), which is a control power supply. The connection unit 40 connects the power supply lines (power supply lines L1 and L2) of the DC power of voltage V1 converted by the DC / DC conversion unit 10 to the power supply lines (power supply lines L3 and L4) of the rectified DC power rectified by the AC / DC conversion unit 30.

[0067] As a result, the power conditioner 1 (grid-connected device) according to this embodiment is equipped with the connection unit 40, and therefore the AC / DC conversion unit 30 can generate a control power supply (DC power of voltage V2) from both the DC power supply 2 and the commercial power supply 3 (grid power supply).

[0068] FIG. 4 is a block diagram showing an example of a conventional power conditioner 100. As shown in FIG. 4, a conventional power conditioner 100 includes an isolated DC / DC conversion unit 110, an inverter unit 120, an AC / DC conversion unit 130, a DC / DC conversion unit 140, and a control unit 150. The conventional power conditioner 100 needs to include both the DC / DC conversion unit 140 that generates a control power supply from a DC power supply 2, and the AC / DC conversion unit that generates a control power supply from a commercial power supply 3 (system power supply). Here, the control power supply is a power supply of DC power supplied to the control unit 150.

[0069] In contrast, the power conditioner 1 according to this embodiment includes the connection unit 40, and therefore does not need to include both the DC / DC conversion unit 140 that generates control power from the DC power supply 2 and the AC / DC conversion unit 130 that generates control power from the commercial power supply 3 (system power supply), as in the above-described conventional power conditioner 100. Therefore, the power conditioner 1 according to this embodiment can have a simpler configuration and be more compact than the conventional power conditioner 100.

[0070] In this embodiment, the AC / DC conversion unit 30 includes a synchronous rectification unit 32 that rectifies AC power supplied from the commercial power supply 3 (system power supply). The connection unit 40 includes a connection switch 42 (switch). When the output line of the inverter unit 20 and the power line of the commercial power supply 3 are connected (system relay 24 is on) and the synchronous rectification unit 32 operates, the connection switch 42 cuts off the connection between the power line of the DC power of voltage V1 (power line L1 and power line L2) and the power line of the rectified DC power (power line L3 and power line L4).

[0071] As a result, the power conditioner 1 according to this embodiment can disconnect the loop RP shown in Fig. 3 described above using the connection switch 42, thereby preventing a grid short circuit that is prohibited when interconnected to the grid. The power conditioner 1 according to this embodiment can safely supply power to the control unit 50 even when, for example, the grid relay 24 is welded, and can operate the power conditioner 1 safely.

[0072] In addition, in this embodiment, the connection unit 40 includes a connection switch 42 (switch) having a body diode, and a connection diode 41 arranged so as to be in the forward direction when DC power is supplied from the power supply line for DC power of voltage V1 to the power supply line for rectified DC power.

[0073] As a result, the power conditioner 1 according to this embodiment can prevent reverse flow of power from the DC power of voltage V1 of the AC / DC conversion unit 30 to the DC power of voltage V1 of the DC / DC conversion unit 10 by using the connection diode 41.

[0074] In this embodiment, the synchronous rectifier 32 includes an upper diode 37 and a lower switching element 38 connected in series. The connection diode 41 includes a connection diode 41-1 (first diode) and a connection diode 41-2 (second diode). The connection diode 41-1 (first diode) is arranged on the low-potential side connection line (the connection line between the power supply line L2 and the power supply line L4). The connection diode 41-2 (second diode) is arranged on the high-potential side connection line (the connection line between the power supply line L1 and the power supply line L2). The connection switch 42 is arranged on the low-potential side connection line (the connection line between the power supply line L2 and the power supply line L4).

[0075] As a result, in the power conditioner 1 according to this embodiment, the connection switch 42 is arranged in the low-potential side connection line (the connection line between the power line L2 and the power line L4), and there is no need to arrange it in the high-potential side connection line (the connection line between the power line L1 and the power line L3). Therefore, the power conditioner 1 according to this embodiment can further simplify the configuration and reduce its size.

[0076] [Second embodiment] Next, a power conditioner 1a according to a second embodiment will be described with reference to the drawings. 5 is a block diagram showing an example of a power conditioner 1a according to the second embodiment. In this embodiment, a modified example in which the upper diode 37 of the synchronous rectifier 32 described above is replaced with a switching element 37a will be described.

[0077] 5, the power conditioner 1a includes a DC / DC conversion unit 10, an inverter unit 20, an AC / DC conversion unit 30a, a connection unit 40a, a control unit 50, and a capacitor C1. In this embodiment, the power conditioner 1a is an example of a grid-connected device that can be connected to a commercial power source 3. In addition, in FIG. 5, the same components as those in FIG. 1 are given the same reference numerals, and the description thereof will be omitted.

[0078] The AC / DC converter 30a rectifies AC power supplied from the commercial power supply 3, which is a system power supply, into DC power, and converts the rectified DC power into DC power of voltage V2 (second voltage), which is a control power supply. The AC / DC converter 30a supplies the converted DC power of voltage V2 to the control unit 50.

[0079] The AC / DC conversion unit 30a includes a noise filter 31, a synchronous rectification unit 32a, a capacitor C2, an inverter circuit 33, a transformer 34, a synchronous rectification unit 35, a conversion control unit 36, and connecting diodes 41 (41-1, 41-2).

[0080] The synchronous rectifier 32a rectifies an AC signal supplied from the commercial power supply 3 via the noise filter 31 into DC power (rectified DC power) of a voltage V1 (first voltage). The synchronous rectifier 32a includes two pairs of an upper switching element 37a and a lower switching element 38 connected in series between a high-potential power line L3 and a low-potential power line L4. That is, the synchronous rectifier 32a includes upper switching elements 37a (37a-1, 37a-2) and lower switching elements 38 (38-1, 38-2) connected in series. The synchronous rectifier 32a rectifies the AC signal by switching the switching elements (37a, 38) under the control of the conversion control unit 36, thereby generating DC power of a voltage V1.

[0081] In this embodiment, the diode 37-1 and the diode 37-2 have the same configuration, and will be described as the diode 37 when referring to any diode included in the synchronous rectifier 32 or when no particular distinction is made.

[0082] In addition, in this embodiment, the upper switching element 37a-1 and the switching element 37a-2 have the same configuration, and when referring to any upper switching element provided in the synchronous rectification unit 32a, or when no particular distinction is made, they will be described as switching element 37a.

[0083] The switching element 37a-1 is, for example, an N-type MOSFET. The source terminal of the switching element 37a-1 is connected to the node N1, and the drain terminal is connected to the high-potential power line L3. The gate terminal (control terminal) of the switching element 37a-1 is connected to a signal line for a control signal output from the conversion control unit 36.

[0084] The switching element 37a-2 is, for example, an N-type MOSFET. The source terminal of the switching element 37a-2 is connected to the node N2, and the drain terminal is connected to the high-potential power line L3. The gate terminal (control terminal) of the switching element 37a-2 is connected to a signal line for a control signal output from the conversion control unit 36. The switching of the switching element 37a and the switching element is controlled by the conversion control unit .

[0085] In this embodiment, the connection diodes 41-1 and 41-2, the connection switches 42-1 and 42-2 correspond to the connection unit 40a. That is, the connection unit 40a includes the connection diodes 41-1 and 41-2, and the connection switches 42-1 and 42-2. In this embodiment, the connection switches 42 include a connection switch 42-1 (first switch) arranged on the low-potential side connection line and a connection switch 42-2 (second switch) arranged on the high-potential side connection line.

[0086] The connection switch 42-1 is a switch that connects the power supply line (power supply line L2) of DC power of voltage V1 and the power supply line (power supply line L4) of the rectified DC power of the AC / DC conversion unit 30a. The connection switch 42-1 is, for example, an N-type MOSFET, and has a source terminal connected to the power supply line L2 and a drain terminal connected to the cathode terminal of the connection diode 41-1. In other words, the connection switch 42-1 is arranged on the low-potential side connection line.

[0087] Furthermore, a gate terminal (control terminal) of the connection switch 42-1 is connected to, for example, a signal line for a control signal output from the inverter control unit 25. When the synchronous rectification unit 32a operates with the output line of the inverter unit 20 and the power line of the commercial power source 3 (system power supply) connected, the connection switch 42-1 cuts off the connection between the power line L2 for DC power of voltage V1 and the power line L4 for rectified DC power.

[0088] The connection switch 42-2 is a switch that connects the power supply line (power supply line L1) of DC power of voltage V1 and the power supply line (power supply line L3) of rectified DC power of the AC / DC conversion unit 30a. The connection switch 42-2 is, for example, an N-type MOSFET, and has a source terminal connected to the power supply line L1 and a drain terminal connected to the cathode terminal of the connection diode 41-2. In other words, the connection switch 42-2 is arranged on the high-potential side connection line.

[0089] Furthermore, a gate terminal (control terminal) of the connection switch 42-2 is connected to, for example, a signal line for a control signal output from the inverter control unit 25. When the output line of the inverter unit 20 and the power line of the commercial power source 3 (system power supply) are connected and the synchronous rectification unit 32a operates, the connection switch 42-2 cuts off the connection between the power line L1 for DC power of voltage V1 and the power line L3 for rectified DC power.

[0090] In addition, in this embodiment, other configurations are the same as those in the first embodiment described above, and therefore description thereof will be omitted here.

[0091] As described above, the power conditioner 1a according to this embodiment includes the DC / DC conversion unit 10, the inverter unit 20, the AC / DC conversion unit 30a, the connection unit 40a, and the control unit 50. As a result, the power conditioner 1a according to this embodiment has the same effects as the first embodiment described above, and can have a simplified configuration and be made smaller.

[0092] In this embodiment, the synchronous rectifier 32a includes an upper switching element 37a and a lower switching element 38 connected in series. The connection switch 42 includes a connection switch 42-1 (first switch) arranged on the low-potential side connection line and a connection switch 42-2 (second switch) arranged on the high-potential side connection line.

[0093] As a result, the power conditioner 1a according to this embodiment has the same effects as the first embodiment, due to the connection switches 42-1 and 42-2, and can prevent a grid short circuit, which is prohibited when grid-connected. Furthermore, the power conditioner 1a according to this embodiment can safely supply power to the control unit 50, for example, when the grid relay 24 is welded, and can operate the power conditioner 1a safely.

[0094] The present invention is not limited to the above-described embodiments, and can be modified within the scope of the present invention. For example, in each of the above embodiments, the power conditioner 1 (1a) has been described as an example of the grid interconnection device, but the present invention is not limited to this and may be any other grid interconnection device.

[0095] Furthermore, in each of the above embodiments, the DC / DC converter 10 has been described as an example of an isolated DC / DC converter, but the present invention is not limited to this, and the DC / DC converter 10 may be an isolated DC / DC converter with a different configuration.

[0096] Furthermore, in each of the above embodiments, the inverter section is not limited to the inverter section 20, and may be an inverter section with a different configuration. Furthermore, in each of the above embodiments, the AC / DC conversion unit is not limited to the AC / DC conversion unit 30 (30a) and may be an AC / DC conversion unit with another configuration. Although an example has been described in which the conversion control unit 36 ​​of the AC / DC conversion unit 30 (30a) controls the switching of each MOSFET in the inverter circuit 33 and each MOSFET in the synchronous rectification unit 35 by the LLC method to generate the voltage V2, the present invention is not limited to this and may control the switching by another method.

[0097] In addition, in each of the above embodiments, an example has been described in which N-type MOSFETs are used as the switching elements of each part, but this is not limited to this, and other switching elements may be used as some or all of the switching elements of each part.

[0098] In addition, in each of the above embodiments, an example has been described in which the inverter control unit 25 controls the connection switches 42 (42-1, 42-2), but this is not limitative, and other control units such as the control unit 50 may control the connection switches 42. Also, a dedicated control unit for controlling the connection switches 42 (42-1, 42-2) may be newly provided.

[0099] Furthermore, in each of the above embodiments, the conversion control unit 15, the inverter control unit 25, the conversion control unit 36, and the control unit 50 may be realized by circuit means, or may be realized by software processing that causes a CPU (Central Processing Unit) to execute a program.

[0100] Furthermore, some or all of the functions of the conversion control unit 15, inverter control unit 25, conversion control unit 36, and control unit 50 described above may be realized as an integrated circuit such as an LSI (Large Scale Integration). Each of the above functions may be implemented individually as a processor, or some or all of the functions may be integrated into a processor. Furthermore, the integrated circuit implementation method is not limited to LSI, and may be implemented using a dedicated circuit or a general-purpose processor. Furthermore, if an integrated circuit implementation technology that can replace LSI emerges due to advances in semiconductor technology, an integrated circuit based on that technology may be used. [Explanation of symbols]

[0101] 1, 1a, 100 power conditioner 2 DC power supply 3 Commercial power supply 10, 110 DC / DC conversion unit 11 Input Filter 12, 21, 33 Inverter circuit 13, 34 Transformer 14, 32, 35 Synchronous rectification section 15, 36 Conversion control unit 20, 120 Inverter section 22, 31 Noise filter 23 Self-sustaining relay 24-system relay 25 Inverter control unit 30, 130 AC / DC conversion unit 37, 37-1, 37-2 Diodes 37a, 37a-1, 37a-2, 38, 38-1, 38-2 Switching elements 40, 40a connection 41, 41-1, 41-2 connection diodes 42, 42-1, 42-2 Connection switch 50, 150 control section

Claims

1. an isolated DC / DC conversion unit that converts DC power supplied from a DC power supply into DC power of a first voltage; an inverter unit that converts the DC power of the first voltage converted by the DC / DC converter unit into AC power that can be connected to a grid and supplies the AC power to an AC load; an AC / DC conversion unit that rectifies AC power supplied from a system power supply into DC power and converts the rectified DC power into DC power of a second voltage that is a control power supply; a connection unit that connects a power supply line of the DC power of the first voltage converted by the DC / DC conversion unit and a power supply line of the rectified DC power rectified by the AC / DC conversion unit; Equipped with the AC / DC conversion unit includes a synchronous rectification unit that rectifies AC power supplied from the system power supply, The connection unit includes a switch that is controlled to cut off the connection between the power supply line of the DC power of the first voltage and the power supply line of the rectified DC power when the connection is not in the grid interconnection state in which the output line of the inverter unit and the power supply line of the system power supply are connected and the synchronous rectification unit is in operation, and is controlled to be in an on state between the power supply line of the DC power of the first voltage and the power supply line of the rectified DC power when the connection is not in the grid interconnection state or the synchronous rectification unit is not in operation. A grid interconnection device characterized by:

2. The connection portion is the switch having a body diode; a connection diode arranged so as to be in a forward direction when DC power is supplied from the power supply line of the DC power of the first voltage to the power supply line of the rectified DC power.

2. The grid interconnection device according to claim 1.

3. the synchronous rectification unit includes an upper diode and a lower switching element connected in series, the connecting diodes include a first diode disposed on a low potential side connecting line and a second diode disposed on a high potential side connecting line; The switch is disposed on the low potential side connection line.

3. The grid interconnection device according to claim 2.

4. the synchronous rectification unit includes an upper switching element and a lower switching element connected in series, The switches include a first switch disposed on a low-potential side connection line and a second switch disposed on a high-potential side connection line.

3. The grid interconnection device according to claim 1 or 2.

5. an isolated DC / DC conversion unit that converts DC power supplied from a DC power supply into DC power of a first voltage; an inverter unit that converts the DC power of the first voltage converted by the DC / DC converter unit into AC power that can be connected to a grid and supplies the AC power to an AC load; an AC / DC conversion unit that rectifies AC power supplied from a system power supply into DC power and converts the rectified DC power into DC power of a second voltage that is a control power supply; a connection unit that connects a power supply line of the DC power of the first voltage converted by the DC / DC conversion unit and a power supply line of the rectified DC power rectified by the AC / DC conversion unit; Equipped with the AC / DC conversion unit includes a synchronous rectification unit that rectifies AC power supplied from the system power supply, The connection unit includes a switch that is controlled to cut off the connection between the power supply line of the DC power of the first voltage and the power supply line of the rectified DC power when the connection is not in the grid interconnection state in which the output line of the inverter unit and the power supply line of the system power supply are connected and the synchronous rectification unit is in operation, and is controlled to be in an on state between the power supply line of the DC power of the first voltage and the power supply line of the rectified DC power when the connection is not in the grid interconnection state or the synchronous rectification unit is not in operation. A power conditioner characterized by the above.

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