WO2019065550A1 - System interconnection system - Google Patents

Abstract

The present disclosure addresses the problem of applying a ground voltage to an electrode of a distributed power supply. This system interconnection system (100) is provided with an inverter (3). The inverter (3) is connected between a distributed power supply (1) and a power system (6), and converts DC power from the distributed power supply (1) into AC power. The system interconnection system (100) is further provided with a backflow prevention diode (D1). The backflow prevention diode (D1) is provided on a current path including at least a portion of a circuit on a distributed power supply (1)-side from the perspective of the inverter (3), and prevents a leakage current that flows to a reference potential (Vb1) through the current path.

Description

Grid connection system

The present disclosure relates generally to grid-connected systems, and more particularly to grid-connected systems that connect distributed power sources to a power grid.

BACKGROUND Conventionally, a solar power generation system (grid connection system) for supplying power to an electric product using a direct current output of a solar power generation apparatus is known, and is disclosed, for example, in Patent Document 1. In the solar power generation system described in Patent Document 1, a solar battery array (distributed power supply) and a battery (storage battery) are connected in parallel to an inverter. The inverter converts direct current power from the solar cell array or battery into alternating current, and outputs the alternating current to the power system via the interconnection switch.

In the grid interconnection system described in Patent Document 1, when the DC power from the storage battery is converted to AC power by the inverter in a state where the distributed power source is not generating power, the ground voltage is applied to the electrodes of the distributed power source Problems could arise.

Japanese Patent Laid-Open No. 9-91049

This indication is made in view of the above-mentioned point, and it aims at providing a grid connection system to which ground voltage is hard to be impressed to an electrode of a distributed power supply.

A grid interconnection system according to an aspect of the present disclosure includes an inverter. The inverter is connected between a distributed power supply and a power system, and converts DC power from the distributed power supply into alternating current power. The grid connection system further includes a reverse current blocking diode. The reverse current blocking diode is provided in a current path including at least a part of the circuit on the distributed power supply side as viewed from the inverter, and prevents a leakage current flowing to a reference potential through the current path.

FIG. 1 is a schematic circuit diagram showing a grid interconnection system according to an embodiment of the present disclosure. FIG. 2 is an explanatory diagram of the operation of the grid interconnection system of the comparative example. FIG. 3 is an explanatory diagram of an operation of the grid interconnection system according to an embodiment of the present disclosure. FIG. 4A and FIG. 4B are schematic circuit diagrams showing a grid interconnection system according to a first modification of the embodiment of the present disclosure. FIG. 5 is a schematic circuit diagram showing a grid interconnection system according to a second modification of the embodiment of the present disclosure. FIG. 6 is a schematic circuit diagram showing a grid interconnection system according to a third modification of the embodiment of the present disclosure. FIGS. 7A and 7B are schematic circuit diagrams showing a grid interconnection system according to a fourth modification example of the embodiment of the present disclosure. FIG. 8 is a schematic circuit diagram showing a grid interconnection system according to a fifth modification of the embodiment of the present disclosure.

(1) Overview As shown in FIG. 1, the grid interconnection system 100 of the present embodiment is a system in which the distributed power source 1 is grid-connected to a single-phase three-wire power grid 6. The “power system” in the present disclosure means an entire system for a power company such as a power company to supply power to a power receiving facility of a customer. In this embodiment, as an example, it is assumed that such a grid connection system 100 is introduced to non-residential facilities such as office buildings, hospitals, commercial facilities, and schools.

The grid interconnection system 100 includes an inverter 3 as shown in FIG. The inverter 3 is connected between the distributed power supply 1 and the electric power system 6, and converts DC power from the distributed power supply 1 into AC power. In the present disclosure, "connecting" includes electrically connecting elements, in addition to mechanically connecting elements such as terminals, electronic components, or electric wires. The grid interconnection system 100 converts the DC power output from the distributed power source 1 into AC power by the inverter 3 and outputs the converted AC power to the power grid 6. In addition, the grid interconnection system 100 is configured to perform a self-sustaining operation that opens the disconnector and outputs AC power in a state of being disconnected from the power system 6 when an abnormality such as a power failure of the power system 6 occurs. There is.

The grid interconnection system 100 further includes a reverse current blocking diode D1. The reverse current blocking diode D1 is provided in a current path (a first path P1 and a second path P2 (see FIG. 2) described later) including at least a part of a circuit on the distributed power supply 1 side as viewed from the inverter 3. The reverse current blocking diode D1 is provided in a direction to block a leakage current flowing to the reference potential Vb1 (see FIG. 2) through the current path. The “reference potential Vb1” in the present disclosure refers to the potential of the ground when the neutral line of the power system 6 is connected to the ground.

As described above, in the present embodiment, the leakage current flowing to the reference potential Vb1 through the current path is blocked by the reverse current blocking diode D1. For this reason, in the present embodiment, a ground capacity (a first ground capacity Ce1 or a second ground capacity Ce2 described later, which will be described later) exists between the electrode (positive electrode 11 or negative electrode 12) of the dispersed power source 1 and the reference potential Vb1. )) Is difficult to charge due to leakage current. Therefore, in the present embodiment, there is an advantage that the charging voltage of the ground capacity (in other words, the ground voltage) is difficult to be applied to the electrodes of the distributed power supply 1.

(2) Details As shown in FIG. 1, the grid interconnection system 100 according to this embodiment includes an input capacitor C0 and an output capacitor C1, a DC / DC converter 2, an inverter 3, a filter circuit 4, and a control circuit. It has 10 and. The input capacitor C0, the output capacitor C1, the DC / DC converter 2, the inverter 3, the filter circuit 4, and the control circuit 10 are housed in one case (hereinafter also referred to as "first case") 7.

The distributed power supply 1 is connected to the grid interconnection system 100. In the present embodiment, the distributed power source 1 is a solar power generation device including a solar cell. Furthermore, the storage battery 5 is connected to the grid interconnection system 100 via the charge / discharge circuit 50. The storage battery 5 and the charge / discharge circuit 50 are connected in parallel to the distributed power supply 1 with respect to the grid interconnection system 100. In the following description, although it is described that distributed power supply 1, storage battery 5, and charge / discharge circuit 50 are not all included in the components of grid interconnection system 100, a part or all of these components are included in the configuration of grid interconnection system 100. It may be included in the element.

The input capacitor C 0 is connected between the distributed power supply 1 and the DC / DC converter 2. The first electrode 13 of the input capacitor C0 is connected to the positive electrode 11 of the distributed power supply 1 and the high potential input terminal of the DC / DC converter 2. The second electrode 14 of the input capacitor C0 is connected to the negative electrode 12 of the distributed power supply 1 and the low potential input terminal of the DC / DC converter 2. The input capacitor C0 has a function of stabilizing the DC voltage output from the distributed power supply 1.

The output capacitor C 1 is connected between the DC / DC converter 2 and the inverter 3. The first electrode 15 of the output capacitor C <b> 1 is connected to the high potential output end of the DC / DC converter 2 and the high potential input end of the inverter 3. The second electrode 16 of the output capacitor C 1 is connected to the low potential output end of the DC / DC converter 2 and the low potential input end of the inverter 3. The output capacitor C1 has a function of stabilizing the DC voltage output from the DC / DC converter 2.

The DC / DC converter 2 is a non-insulated step-up DC / DC converter, and includes an inductor L0, a diode D0, a switching element Q0, and a reverse current blocking diode D1. The first end of the inductor L0 is connected to the high potential input end of the DC / DC converter 2 and is connected to the first electrode 13 of the input capacitor C0. The second end of the inductor L0 is connected to the anode of the diode D0. The cathode of the diode D0 is connected to the high potential output end of the DC / DC converter 2 and is connected to the first electrode 15 of the output capacitor C1.

The switching element Q0 is formed of an enhancement type n-channel MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). The source of the switching element Q0 is connected to the low potential input end and the output end of the DC / DC converter 2 and is connected to the second electrode 14 of the input capacitor C0. The drain of switching element Q0 is connected to the connection point between the second end of inductor L0 and the anode of diode D0. The switching element Q0 is turned on / off by a control signal S0 supplied from a control circuit 10 (described later). The switching element Q0 is not limited to a MOSFET, and may be, for example, an IGBT (Insulated Gate Bipolar Transistor) or another semiconductor switching element such as a bipolar transistor.

The cathode of the reverse current blocking diode D1 is connected to the low potential input end of the DC / DC converter 2, and is connected to the second electrode 14 of the input capacitor C0 and the source of the switching element Q0. The anode of the reverse current blocking diode D1 is connected to the low potential output end of the DC / DC converter 2 and connected to the second electrode 16 of the output capacitor C1 via the intermediate bus MB. The “intermediate bus” in the present disclosure is a current path between the DC / DC converter 2 and the inverter 3.

In the DC / DC converter 2, the switching element Q <b> 0 is subjected to PWM (Pulse Width Modulation) control by the control circuit 10 to boost the voltage across the input capacitor C <b> 0. Then, the DC / DC converter 2 outputs the boosted DC voltage to the output capacitor C1 and the inverter 3 connected to the intermediate bus MB. In other words, the DC / DC converter 2 is connected between the distributed power supply 1 and the inverter 3 and converts the DC voltage output from the distributed power supply 1 into a DC voltage of a predetermined magnitude.

The inverter 3 has four switching elements Q1 to Q4 connected in full bridge. In the inverter 3, a series circuit of the switching element Q1 and the switching element Q3 and a series circuit of the switching element Q2 and the switching element Q4 are connected in parallel with each other across the output capacitor C1. The drains of the switching elements Q1 and Q2 are connected to the high potential output end of the DC / DC converter 2 and the first electrode 15 of the output capacitor C1. The sources of the switching elements Q3 and Q4 are both connected to the low potential output end of the DC / DC converter 2 and the second electrode 16 of the output capacitor C1.

The switching elements Q1 to Q4 are all formed of depletion type n-channel MOSFETs. The switching elements Q1 to Q4 are not limited to MOSFETs, and may be, for example, IGBTs or other semiconductor switching elements such as bipolar transistors.

The inverter 3 converts the DC voltage to the AC voltage or the AC voltage to the DC voltage between the output capacitor C1 and the filter circuit 4 by PWM control of the switching elements Q1 to Q4 by the control circuit 10. Bidirectional DC / AC converter. That is, inverter 3 has a function of converting DC power from output capacitor C1 (DC power from intermediate bus MB) into AC power and outputting it to power system 6, and converts AC power from power system 6 into DC power. And the function of outputting to the output capacitor C1 (intermediate bus MB).

Thus, in the present embodiment, inverter 3 is configured to perform bidirectional power conversion between output capacitor C 1 and power system 6 so as to be able to handle both charging and discharging of storage battery 5. It is done. Thus, the grid interconnection system 100 links the storage battery 5 to the power grid 6 and charges the storage battery 5 with the power supplied from the power grid 6 or connects the power output from the storage battery 5 to the power grid 6 It is possible to supply to the load being

The filter circuit 4 includes two inductors L1 and L2 and a capacitor C2. The first end of the inductor L1 is connected to the connection point of the source of the switching element Q1 and the drain of the switching element Q3. The second end of the inductor L1 is connected to the power system 6. The first end of the inductor L2 is connected to the connection point of the source of the switching element Q2 and the drain of the switching element Q4. The second end of the inductor L2 is connected to the power system 6. A capacitor C2 is connected between the second end of the inductor L1 and the second end of the inductor L2. The filter circuit 4 has a function of removing a high frequency component of the AC voltage output from the inverter 3 to generate a sinusoidal voltage.

The control circuit 10 is configured by, for example, a microcomputer having one or more processors and a memory. In other words, the control circuit 10 is realized by a computer system having one or more processors and a memory, and the computer system functions as the control circuit 10 by executing a program stored in the memory. Function. Here, the program is pre-recorded in the memory of the control circuit 10, but may be provided through a telecommunication line such as the Internet or in a non-transitory recording medium such as a memory card. The control circuit 10 may be configured by, for example, a field-programmable gate array (FPGA) or an application specific integrated circuit (ASIC).

Control circuit 10 outputs control signals S0 to S4 for controlling five switching elements Q0 to Q4. The control signals S0 to S4 are applied to the gates of the switching elements Q0 to Q4 directly or via a drive circuit to individually turn on / off the switching elements Q0 to Q4. The control circuit 10 controls the switching elements Q0 to Q4 by the PWM method capable of adjusting the duty ratio.

The charge / discharge circuit 50 is a bi-directional DC / DC converter, and is connected to an intermediate bus MB between the storage battery 5 and the output capacitor C1. The charge / discharge circuit 50 has a function of converting DC power output from the storage battery 5 into DC power of a predetermined magnitude, and outputting the converted DC power to the output capacitor C1. The charge / discharge circuit 50 also has a function of converting DC power output from the output capacitor C1 into DC power of a predetermined magnitude, and outputting the converted DC power to the storage battery 5.

As described above, the reverse current blocking diode D1 is more dispersed than the connection point where the dispersed power source 1 side, more specifically, the storage battery 5 (and the charge / discharge circuit 50) is connected to the intermediate bus MB when viewed from the inverter 3. It is provided on the mold power source 1 side.

(3) Operation First, the basic operation of the grid interconnection system 100 according to the present embodiment will be described with reference to FIG. In the daytime, when the distributed power supply 1 receives enough sunlight to generate electric power, the distributed power supply 1 outputs DC power to the inverter 3 via the DC / DC converter 2. The inverter 3 converts the input DC power into AC power, and outputs the converted AC power to the power system 6. Thereby, the electric power generated by the distributed power supply 1 is supplied to the load connected to the electric power system 6. Further, when there is surplus power in the power generated by the dispersed power source 1, the dispersed power source 1 charges the storage battery 5 by outputting the surplus power to the storage battery 5 via the DC / DC converter 2 and the charge / discharge circuit 50. Do. In addition, the storage battery 5 may be charged by the power system 6 outputting DC power to the storage battery 5 via the inverter 3 and the charge / discharge circuit 50.

On the other hand, when the weather is cloudy or rainy, or at night, the dispersed power source 1 can not receive sufficient sunlight and does not generate power, the storage battery 5 transmits DC power to the inverter 3 via the charge / discharge circuit 50. Output The inverter 3 converts the input DC power into AC power, and outputs the converted AC power to the power system 6. Thereby, the electric power which the storage battery 5 discharges is supplied to the load connected to the electric power grid | system 6. As shown in FIG.

Here, the operation of the grid interconnection system 100 of the present embodiment will be described together with the operation of the grid interconnection system of the comparative example. In the grid connection system of the comparative example, as shown in FIG. 2, the reverse current blocking diode D1 is not connected between the source of the switching element Q0 of the DC / DC converter 2 and the second electrode 16 of the output capacitor C1. It differs from the grid interconnection system 100 of the present embodiment in terms of points.

As described above, even when the distributed power source 1 does not generate power, such as at night, the inverter 3 may operate when supplying power from the storage battery 5 to the power system 6. In this case, a ground voltage V1 that makes the first electrode 15 a high potential is generated between the first electrode 15 of the output capacitor C1 and the reference potential Vb1. Further, between the second electrode 16 of the output capacitor C1 and the reference potential Vb1, a ground voltage V2 with the reference potential Vb1 as a high potential is generated.

In addition, in this embodiment, since the grid connection system 100 using the solar cell as the distributed power supply 1 and the storage battery 5 is demonstrated, when the distributed power supply 1 is not generating electric power, the inverter 3 operate | moves. Although night is mentioned as an example to do, it is not the meaning limited to this. For example, depending on the distributed power supply 1 or another DC power supply instead of the storage battery 5, the inverter 3 may operate even when the distributed power supply 1 is not generating power even in a situation other than night.

Here, the positive electrode 11 and the negative electrode 12 of the dispersed power source 1 are both relatively large electrodes. Therefore, between the positive electrode 11 of the dispersed power supply 1 and the reference potential Vb1, and between the negative electrode 12 of the dispersed power supply 1 and the reference potential Vb1, the first capacitance to ground Ce1 and the ground capacitance Ce1 having a size that can not be ignored. A second ground capacity Ce2 is generated. Then, with the ground voltage V1 as a voltage generation source, a current path (hereinafter also referred to as "first path P1") through which leakage current flows in the order of high potential of the DC / DC converter 2, first ground capacitance Ce1, and reference potential Vb1 It can be formed. Similarly, a current path through which a leakage current flows in the order of reference potential Vb1, second ground capacitance Ce2 and low potential of DC / DC converter 2 with voltage to ground V2 as a voltage generation source (hereinafter also referred to as "second path P2") Can be formed. Each of these current paths includes at least a part of the circuit on the distributed power supply 1 side as viewed from the inverter 3. Also, these current paths include at least one of the high potential and the low potential of the DC / DC converter 2. In the present embodiment, among the current paths, the first path P1 includes the electric path on the high potential side of the DC / DC converter 2, and the second path P2 includes the electric path on the low potential side of the DC / DC converter 2. It is.

In the comparative example, in the first path P1, the diode D0 of the DC / DC converter 2 functions as the reverse current blocking diode D1, whereby the leakage current flowing to the reference potential Vb1 is suppressed. For this reason, it is difficult for the first ground capacity Ce1 to be charged with a leakage current, and the ground voltage (that is, the voltage between the positive electrode 11 and the reference potential Vb1) is hard to be applied to the positive electrode 11 of the dispersed power source 1. On the other hand, in the comparative example, since the backflow blocking diode D1 does not exist in the second path P2, a leakage current can flow to the reference potential Vb1 through the second path P2. Therefore, the second ground capacitance Ce2 is charged by the leakage current, and the ground voltage (that is, the voltage between the negative pole 12 and the reference potential Vb1) can be applied to the negative electrode 12 of the dispersed power source 1.

As described above, when the ground voltage is applied to at least one of the positive electrode 11 and the negative electrode 12 of the distributed power supply 1, the distributed power supply 1 may be adversely affected. For example, when the distributed power supply 1 is a photovoltaic power generation device, the occurrence of a PID (Potential Induced Degradation) phenomenon may deteriorate the photovoltaic power generation device and reduce the power generation amount of the distributed power supply 1 .

On the other hand, in the present embodiment, as shown in FIG. 3, since the backflow blocking diode D1 exists in the second path P2, it is possible to suppress the leakage current flowing to the reference potential Vb1 through the second path P2. It is possible. As described above, in the present embodiment, the charging path of the first ground capacitance Ce1 and the second ground capacitance Ce2 is blocked by the diode D0 of the DC / DC converter 2 and the backflow blocking diode D1. For this reason, in the present embodiment, the ground voltage is hard to be applied to any of the positive electrode 11 and the negative electrode 12 of the dispersed power source 1, and as a result, the possibility that the dispersed power source 1 is adversely affected can be reduced.

That is, in the present embodiment, the current path through which the leakage current flows includes the first path P1 including the positive electrode 11 of the dispersed power supply 1 and the second path P2 including the negative electrode 12 of the dispersed power supply 1. . The backflow blocking diode D1 is provided in each of the first path P1 and the second path P2 (the backflow blocking diode D1 in the first path P1 is the diode D0 of the DC / DC converter 2). For this reason, in the present embodiment, it is difficult for the leakage current to flow through any of the first path P1 and the second path P2, so that the ground voltage is less likely to be generated in any of the positive electrode 11 and the negative electrode 12 of the dispersed power source 1. There is an advantage of.

Here, as an aspect in which the charging path of the first ground capacity Ce1 and the second ground capacity Ce2 is shut off, it is conceivable to provide a mechanical relay between the distributed power supply 1 and the DC / DC converter 2, for example. Also in this embodiment, when the distributed power source 1 is not generating power, the mechanical relay disconnects between the distributed power source 1 and the DC / DC converter 2 to obtain the first ground capacitance Ce1 and the second ground capacitance Ce2. It is possible to shut off the charging path.

However, in this aspect, there is a problem that the cost of the mechanical relay is higher than that of the reverse current blocking diode D1, and it is necessary to secure a power supply for driving the mechanical relay. In addition, in this aspect, there is a problem that the number of times of opening and closing of the mechanical relay is limited (that is, the mechanical relay has a lifetime), and occurrence of chattering may make the operation unstable.

On the other hand, in the present embodiment, the current path is blocked by a simple configuration in which the backflow blocking diode D1 is provided in the current path where the leakage current flows to the reference potential Vb1 (here, the charging path of the second ground capacitance Ce2). It is possible. Therefore, the present embodiment has an advantage that the problem that may occur in the aspect of providing the mechanical relay described above does not occur.

Further, in the present embodiment, the reverse current blocking diode D1 in the first path P1 is also used as the diode D0 of the DC / DC converter 2. For this reason, in the present embodiment, it is not necessary to newly provide the backflow blocking diode D1 for the current path including the diode D0 of the DC / DC converter 2, and there is an advantage that the circuit design can be simplified. .

(4) Modifications The above-described embodiment is only one of various embodiments of the present disclosure. The above-mentioned embodiment can be variously changed according to design etc. if the object of the present disclosure can be achieved. Hereinafter, modifications of the above-described embodiment will be listed. The modifications described below can be applied in combination as appropriate.

(4.1) First Modification In the grid interconnection system 100A of the first modification, the above-mentioned grid interconnection system 100A is connected to a plurality of (here, two) distributed power sources 1 as described above. It differs from the grid interconnection system 100 of the embodiment. Specifically, in the present modification, as shown in FIGS. 4A and 4B, one input is applied to one dispersed power supply 1 (that is, the positive electrode 11 and the negative electrode 12 of one dispersed power supply 1). Capacitor C0 and one DC / DC converter 2 are connected. And two distributed power supplies 1 are connected to grid connection system 100A of this modification. Therefore, the grid interconnection system 100A of this modification is different from the grid interconnection system 100 of the above-described embodiment in that it includes two input capacitors C0 and two DC / DC converters 2.

In the example shown to FIG. 4A and 4B, illustration of the distributed power supply 1, the control circuit 10, the inverter 3, the filter circuit 4, the storage battery 5, the charging / discharging circuit 50, and the electric power grid | system 6 is abbreviate | omitted. The same applies to FIGS. 5 to 8 below.

In this modification, one input capacitor C0 and one DC / DC converter 2 are combined into one set of function units A1, and two sets of function units A1 are connected in parallel to the output capacitor C1. In this modification, in the example shown in FIG. 4A, the reverse current blocking diode D1 is connected between the connection point of low potential of the two functional units A1 and the second electrode 16 of the output capacitor C1. That is, in the example shown in FIG. 4A, the reverse current blocking diode D1 is shared by the two functional units A1.

On the other hand, in the present modification, in the example shown in FIG. 4B, the backflow blocking diode D1 is provided in each of the two functional parts A1. Specifically, in each of the two functional units A1, the reverse current blocking diode D1 is connected between the source of the switching element Q0 of the DC / DC converter 2 and the second electrode 16 of the output capacitor C1.

In this modification, the charging path of the first ground capacitance Ce1 and the second ground capacitance Ce2 is blocked by the diode D0 and the reverse current blocking diode D1 of the DC / DC converter 2 for each of the plurality of distributed power supplies 1. For this reason, in the present modification, the ground voltage is hard to be applied to any of the positive electrode 11 and the negative electrode 12 for each of the plurality of dispersed power sources 1, and as a result, the possibility of adverse effects on the plurality of dispersed power sources 1 is reduced. can do.

(4.2) Second Modification In the grid connection system 100B of the second modification, as shown in FIG. 5, the backflow blocking diode D1 has a second housing different from the first housing 7 that houses the inverter 3. It differs from the grid interconnection system 100A of the first modification in that it is housed in the body 8. The second housing 8 has two reverse current blocking diodes D1. The second housing 8 is connected between the positive electrode 11 and the negative electrode 12 of the plurality (two in this case) of the dispersed power source 1 and the first housing 7. Then, by connecting the second housing 8 as described above, the backflow blocking diode D1 is connected between the negative electrode 12 and the second electrode 14 of the input capacitor C0 for each of the plurality of distributed power sources 1 Ru.

In this modification, as in the first modification, the ground voltage is hard to be applied to any of the positive electrode 11 and the negative electrode 12 for each of the plurality of dispersed power sources 1, and as a result, the plurality of dispersed power sources 1 are adversely affected. The possibility of reaching can be reduced. Further, in the present modification, the backflow blocking diode D1 is not built in the first housing 7, and it is possible to externally attach the backflow blocking diode D1. That is, in this modification, by externally attaching the second casing 8 to the first casing 7, there is an advantage that the backflow blocking diode D1 can be easily connected to the existing inverter 3.

(4.3) Third Modification In the grid connection system 100C of the third modification, as shown in FIG. 6, in addition to the reverse current blocking diode D1, the switching element SW1 is accommodated in the second housing 8 This differs from the grid interconnection system 100B of the second modification. Further, in the grid interconnection system 100C of this modification, the second detection circuit 9 is connected in parallel to the input capacitor C0 with respect to the DC / DC converter 2 in each of the two functional units A1. It differs from the grid interconnection system 100B of the modification example.

The second housing 8 has two switching elements SW1 in addition to the two reverse current blocking diodes D1. In the state where the second housing 8 is connected to the first housing 7, the two switching elements SW1 are connected between the positive electrode 11 of the distributed power supply 1 and the high potential input end of the functional unit A1, respectively. Ru. The switching element SW1 opens and closes a path between the positive electrode 11 of the dispersed power source 1 and the high potential input end of the functional unit A1 by, for example, being controlled by the control circuit 10 and switching on / off. The switching element SW1 may be a mechanical relay or a semiconductor switching element such as a MOSFET.

The detection circuit 9 is a circuit that detects the voltage across the input capacitor C0, that is, the output voltage of the distributed power supply 1. The detection circuit 9 has, for example, a series circuit of a plurality of resistors. In the present modification, the control circuit 10 monitors the detection voltage of the detection circuit 9 and operates the DC / DC converter 2 and the inverter 3 according to the detection voltage. Specifically, when the detected voltage exceeds a predetermined voltage value, the control circuit 10 operates the DC / DC converter 2 and the inverter 3 assuming that the amount of power generation of the distributed power source 1 is sufficient. On the other hand, when the detected voltage falls below the predetermined voltage value, the control circuit 10 stops the DC / DC converter 2 and the inverter 3 on the assumption that the amount of power generation of the distributed power supply 1 is insufficient. The control circuit 10 operates the inverter 3 when the storage battery 5 is discharged.

The control according to the detection voltage of the detection circuit 9 by the detection circuit 9 and the control circuit 10 is the fourth and fifth modifications described below, in addition to the embodiment, the first modification, and the second modification described above. The example can also be applied.

Here, in the aspect in which the second housing 8 does not have the opening / closing element SW1 as in the second modified example, the following problems may occur. That is, as described above, when the distributed power supply 1 is not generating power and the inverter 3 is operating to supply power from the storage battery 5 to the power system 6, ground voltages V1 and V2 are generated. At this time, using ground voltage V2 as a voltage generation source, a current path (hereinafter, also referred to as "third path P3") is formed through which a leakage current flows in the order of reference potential Vb1, first ground capacitance Ce1, and resistance component of detection circuit 9. It can be done. Therefore, when the leakage current flows through the third path P3, the first ground capacity Ce1 can be charged, and the ground voltage can be applied to the negative electrode 12 of the distributed power supply 1.

Therefore, in the present modification, the above problem is solved by providing the opening / closing element SW1 in the second housing 8. That is, when the detection voltage of the detection circuit 9 falls below a predetermined voltage value, that is, when the distributed power supply 1 is not generating power, the control circuit 10 turns off the switching element SW1. As a result, it is possible to cut off the charging path of the first ground capacity Ce1 via the third path P3 and make it difficult to apply the ground voltage to the negative electrode 12 of the dispersed power source 1.

Here, it is also conceivable to provide a reverse current blocking diode D1 instead of the switching element SW1 in the third path P3. However, in this aspect, the backflow blocking diode D1 will block the current in the direction from the distributed power supply 1 to the power system 6. That is, in this aspect, the backflow blocking diode D1 inhibits the distributed power source 1 from grid-linking with the power system 6. In other words, the third path P3 is a path that prevents the distributed power source 1 from grid connection with the power system 6 by inserting the backflow blocking diode D1 among the current paths through which the leakage current flows.

So, in this modification, the above-mentioned problem is solved by providing switching element SW1 in the 3rd course P3. That is, the control circuit 10 opens / closes when the detection voltage of the detection circuit 9 exceeds a predetermined voltage value, that is, when the distributed power supply 1 generates power and the distributed power supply 1 interconnects with the power system 6. The element SW1 is turned on. Thus, the switching element SW1 does not inhibit the distributed power supply 1 from being interconnected with the power system 6.

As described above, in the present modification, it is possible to realize control such that the switching element SW1 is closed when the distributed power supply 1 is grid-connected to the power system 6, and the switching element SW1 is opened otherwise. This control has the advantage that it is easy to prevent the ground voltage from being applied to the electrodes of the distributed power supply 1 without blocking the current flowing between the distributed power supply 1 and the power system 6.

(4.4) Fourth Modified Example The grid interconnection system 100D of the fourth modified example further includes the switches SW2 and SW3 connected in parallel to the reverse current blocking diode D1 as shown in FIG. 7A. It differs from the grid interconnection system 100 of the embodiment. The switch SW2 is connected in parallel to the diode D0 of the DC / DC converter 2 (in other words, the reverse current blocking diode D1). In the example shown in FIG. 7A, the switch SW2 is connected in parallel only to the diode D0 of the upper DC / DC converter 2, but the switch SW2 is also connected in parallel to the diode D0 of the lower DC / DC converter 2. It may be connected. The switch SW3 is connected in parallel to the reverse current blocking diode D1. The switches SW2 and SW3 may be either mechanical relays or semiconductor switch elements such as MOSFETs.

In the example shown in FIG. 7A, the detection circuit 9 is omitted. Hereinafter, the same applies to FIG. 7B.

The switches SW2 and SW3 are both controlled by the control circuit 10 to switch on / off. Specifically, the switches SW2 and SW3 are controlled by the control circuit 10 so that the switches SW2 and SW3 are turned on when the distributed power supply 1 is grid-connected to the power system 6, and turned off otherwise. Hereinafter, an example of control of the switches SW2 and SW3 by the control circuit 10 will be described.

The control circuit 10 uses the detection circuit 9 (see FIG. 6) to switch the switch SW2 when the detected voltage exceeds a predetermined voltage value, that is, when the distributed power supply 1 is interconnected with the power system 6 It turns on / off according to the on / off of Q0. Specifically, the control circuit 10 controls the switch SW2 to turn off the switch SW2 when the switching element Q0 is on, and to turn on the switch SW2 when the switching element Q0 is off. As described above, by controlling the DC / DC converter 2 in a synchronous rectification manner, it is possible to suppress the loss due to the conduction of the diode D0. The control circuit 10 also turns off the switch SW2 when the detected voltage falls below a predetermined voltage value. Thus, the diode D0 of the DC / DC converter 2 can function as the reverse current blocking diode D1 in the first path P1.

The control circuit 10 uses the detection circuit 9 to turn on the switch SW3 when the detected voltage exceeds a predetermined voltage value, that is, when the distributed power supply 1 is grid-connected to the power system 6. Thus, it is possible to suppress the loss due to the conduction of the reverse current blocking diode D1 during grid connection. The control circuit 10 also turns off the switch SW3 when the detected voltage falls below a predetermined voltage value. Thereby, it is possible to cause the reverse current blocking diode D1 to function in the second path P2.

As described above, in the present modification, when the distributed power supply 1 is linked to the power system 6, a loss occurs in the backflow blocking diode D 1 due to the current flowing between the distributed power supply 1 and the power system 6. There is an advantage that generation can be suppressed.

By the way, in the present modification, as shown in FIG. 7B, a switch SW4 which is a semiconductor switch element may be connected instead of the backflow blocking diode D1. In the example shown in FIG. 7B, the switches SW2 may be connected in parallel to the diodes D0 of the two DC / DC converters 2, respectively. The switch SW4 is a depletion type n-channel MOSFET. The source of the switch SW4 is connected to the second electrode 16 of the output capacitor C1. The drain of the switch SW4 is connected to the connection point between the second electrode of the input capacitor C0 and the source of the switching element Q0. The parasitic diode (body diode) D2 of the switch SW4 functions as a reverse current blocking diode D1.

In the example shown in FIG. 7B, the control circuit 10 uses the detection circuit 9 to switch the switch SW4 when the detected voltage exceeds a predetermined voltage value, that is, when the distributed power supply 1 is grid-connected to the power system 6. turn on. Thus, it is possible to suppress the loss due to the conduction of the reverse current blocking diode D1 during grid connection. Further, the control circuit 10 turns off the switch SW4 when the detected voltage falls below a predetermined voltage value. Thus, the parasitic diode D2 of the switch SW4 can function as the reverse current blocking diode D1 in the second path P2.

As described above, even in the aspect shown in FIG. 7B, the same effect as described above can be obtained. The switch SW4 is not limited to the MOSFET, and may be, for example, another semiconductor switch element such as an IGBT. When the switch SW4 is an IGBT, a commutation diode built in the IGBT functions as a reverse current blocking diode D1.

(4.5) Fifth Modification The grid interconnection system 100E of the fifth modification is, as shown in FIG. 8, one for each of a plurality of (here, two) distributed power sources 1. It differs from the grid interconnection system 100A of the first modification in that the 1 resistance R1 and the two second resistances R2 are connected.

The first resistor R1 is connected to the DC / DC converter 2 in parallel with the input capacitor C0. When the detection circuit 9 (see FIG. 6) is used, the resistance component of the detection circuit 9 corresponds to the first resistance R1. The first resistor R1 may be configured by combining a plurality of resistors.

One of the two second resistors R2 is a connection point between the high potential output end of the DC / DC converter 2 and the first electrode 15 of the output capacitor C1, and the first end of the first resistor R1. Connected between 17 and. The other second resistor R2 is connected between the connection point between the low potential output end of the DC / DC converter 2 and the second electrode 16 of the output capacitor C1 and the second end 18 of the first resistor R1. There is. The two second resistors R2 may be configured by combining a plurality of resistors, respectively.

The resistance value of the second resistor R2 is larger than the resistance value of the first resistor R1. The resistance value of the second resistor R2 is larger than the resistance value of the first resistor R1 to such an extent that the value obtained by dividing the resistance value of the first resistor R1 by the resistance value of the second resistor R2 becomes approximately zero. preferable.

The operation of this modification will be described below. As described above, when the distributed power supply 1 is not generating power and the inverter 3 is operating to supply power from the storage battery 5 to the power system 6, ground voltages V1 and V2 are generated. The ground voltages V1 and V2 are divided by a series circuit of a first resistor R1 and a second resistor R2, respectively. Then, as described above, since the resistance value of the second resistor R2 is larger than the resistance value of the first resistor R1, the voltage across the first resistor R1 is smaller than the ground voltages V1 and V2 . Specifically, when the ground voltages V1 and V2 are one hundred and several tens [V], the voltage across the first resistor R1 becomes about several [V] to ten and several [V].

As described above, in the present modification, it is possible to bring the voltage across the first resistor R1, that is, the voltage applied between the positive electrode 11 and the negative electrode 12 of the dispersed power source 1 close to zero voltage. For this reason, in the present modification, the ground voltage is applied to both the positive electrode 11 and the negative electrode 12 by bringing the voltage applied to the first ground capacitance Ce1 and the voltage applied to the second ground capacitance Ce2 close to zero voltage. It is possible to make it hard to apply.

By the way, in the present modification, as described above, it is difficult to apply the ground voltage to any of the positive electrode 11 and the negative electrode 12 of the dispersed power source 1 by one first resistor R1 and two second resistors R2. The backflow blocking diode D1 may not be provided. That is, the grid connection system 100E of this modification should just be the following structures. That is, the grid interconnection system 100E includes the inverter 3, one first resistor R1, and two second resistors R2. The inverter 3 is connected between the distributed power supply 1 and the electric power system 6, and converts DC power from the distributed power supply 1 into AC power. The first resistor R 1 is connected between the positive electrode 11 and the negative electrode 12 of the dispersed power source 1. One second resistor R2 of the two second resistors R2 is connected to the high potential input terminal of the inverter 3 and is connected in series with the first resistor R1. The other second resistor R2 of the two second resistors R2 is connected to the low potential input terminal of the inverter 3 and is connected in series with the first resistor R1. The resistance value of each of the two second resistors R2 is larger than the resistance value of the first resistor R1.

(5) Other Modifications Hereinafter, other modifications will be listed. The modifications described below, including the modifications listed in “(4) Modifications”, can be appropriately combined and applied.

In the above embodiment, the backflow blocking diode D1 may not be provided at the position shown in FIG. 1 and may be provided on the second path P2.

In the above embodiment, the input capacitor C0 and the output capacitor C1, the DC / DC converter 2, the inverter 3, the filter circuit 4, and the control circuit 10 are housed in one case (first case) 7. , And may be stored separately in a plurality of cases.

In the above-described embodiment, the DC / DC converter 2 is a step-up DC / DC converter, but the present invention is not limited thereto. For example, the DC / DC converter 2 may be a step-down DC / DC converter, or may be both a step-up and step-down DC / DC converter.

In the above-mentioned embodiment, although inverter 3 is the composition which converts electric power bidirectionally, it is not the meaning limited to this. For example, the inverter 3 may be configured to convert power only in one direction (one direction) from the DC / DC converter 2 to the filter circuit 4. In this case, the storage battery 5 is not charged by the power supplied from the power system 6, but is charged by the surplus power of the generated power of the distributed power supply 1.

In the embodiment described above, the storage battery 5 is connected in parallel to the distributed power supply 1, but the present invention is not limited thereto. For example, another distributed power supply may be connected to the distributed power supply 1 instead of the storage battery 5. Also in this embodiment, the ground voltage is applied to both the positive electrode 11 and the negative electrode 12 of the dispersed power supply 1 when the dispersed power supply 1 does not generate power and the other dispersed power supplies output power. It is possible to make it difficult.

In the above-mentioned embodiment, although grid interconnection system 100 is provided with input capacitor C0, DC / DC converter 2, output capacitor C1, and filter circuit 4, it is not necessary to have a part or all of these. . For example, in the grid interconnection system 100, the DC / DC converter 2 may not be connected between the distributed power supply 1 and the inverter 3. In this aspect, since the diode D0 of the DC / DC converter 2 can not function as the backflow blocking diode D1, it is preferable to provide the backflow blocking diode D1 in each of the first path P1 and the second path P2.

In the above-mentioned embodiment, although distributed power supply 1 is a solar power generation device, it is not the meaning limited to this. For example, the distributed power source 1 may be a power generation device such as a storage battery (including a storage battery for an electric vehicle) or a fuel cell.

In the above-described embodiment, the grid interconnection system 100 is configured to open the disconnector to perform a self-sustaining operation when the power system 6 is abnormal, but the present invention is not limited thereto. For example, the grid interconnection system 100 may be configured not to perform a self-sustaining operation when the power grid 6 is abnormal.

In the above-mentioned embodiment, although grid connection system 100 is introduced in a non-residential institution, it is not the meaning limited to this. For example, the grid connection system 100 may be introduced into a house, or may be applied to facilities other than an electric vehicle or the like.

In the third to fifth modifications, although the plurality of distributed power sources 1 are connected to the grid interconnection systems 100C to 100E, only one distributed power source 1 may be connected.

(Summary)
As described above, the grid interconnection system (100, 100A to 100E) according to the first aspect includes the inverter (3). The inverter (3) is connected between the distributed power supply (1) and the power system (6), and converts DC power from the distributed power supply (1) into AC power. The grid interconnection system (100, 100A to 100E) further includes a reverse current blocking diode (D1). The reverse current blocking diode (D1) is provided in the current path (P1, P2) including at least a part of the circuit on the distributed power supply (1) side as viewed from the inverter (3), and the reference through the current path (P1, P2) Prevent the leakage current flowing to the potential (Vb1).

According to this aspect, there is an advantage that the ground voltage is difficult to be applied to the electrodes of the distributed power supply (1).

The grid connection system (100, 100A to 100E) according to the second aspect further includes a non-insulated DC / DC converter (2) in the first aspect. The DC / DC converter (2) is connected between the distributed power supply (1) and the inverter (3), and converts the DC voltage output from the distributed power supply (1) into a DC voltage of a predetermined magnitude. The current paths (P1, P2) include at least one of the high potential and the low potential of the DC / DC converter (2).

According to this aspect, the ground voltage is applied to the electrodes of the dispersed power supply (1) while having a function of converting the DC voltage output from the dispersed power supply (1) into a DC voltage of a predetermined magnitude. It has the advantage of being easy to prevent.

In the grid connection system (100, 100A to 100E) according to the third aspect, in the second aspect, the reverse current blocking diode (D1) is shared with the diode (D0) of the DC / DC converter (2) .

According to this aspect, it is not necessary to newly provide the backflow blocking diode (D1) for the current path including the diode (D0) of the DC / DC converter (2), and the circuit design can be simplified. There is an advantage of.

In the grid connection system (100, 100A to 100E) according to the fourth aspect, in any of the first to third aspects, the current path (P1, P2) is a positive electrode (11) of the dispersed power source (1). And the second path (P2) including the negative electrode (12) of the dispersed power source (1). The reverse current blocking diode (D1) is provided in each of the first path (P1) and the second path (P2).

According to this aspect, it is difficult for leakage current to flow in any of the first path (P1) and the second path (P2), so in any of the positive electrode (11) and the negative electrode (12) of the dispersed power source (1). Also, there is an advantage that the generation of the ground voltage is difficult.

The grid connection system (100D) according to the fifth aspect further includes a switch (SW2, SW3, SW4) connected in parallel to the reverse current blocking diode (D1) in any of the first to fourth aspects. . The switches (SW2, SW3, SW4) are controlled to be on when the distributed power supply (1) is grid-connected to the power system (6) and to be off at other times.

According to this aspect, when the distributed power supply (1) is grid-connected to the electric power system (6), the backflow blocking diode (the current flowing between the distributed power supply (1) and the electric power system (6) There is an advantage that generation of loss can be suppressed in D1).

In the grid connection system (100B, 100C) according to the sixth aspect, in any of the first to fifth aspects, the backflow blocking diode (D1) is a first case (7) housing the inverter (3). Is housed in a second housing (8) different from.

According to this aspect, by externally attaching the second casing (8) to the first casing (7), it is possible to easily connect the reverse current blocking diode (D1) to the existing inverter (3). It has the advantage of being

In the grid connection system (100C) according to the seventh aspect, in the sixth aspect, in the predetermined path (third path) (P3), a switching element (SW1) is used instead of the reverse current blocking diode (D1). Connected The predetermined path (P3) is a path that prevents the distributed power source (1) from linking to the power system (6) by inserting the backflow blocking diode (D1) among the current paths.

According to this aspect, it is possible to realize control of closing the switching element (SW1) when the distributed power supply (1) is grid-connected to the power system (6) and opening the switching element (SW1) otherwise. . And by this control, it is easy to prevent application of the ground voltage to the electrodes of the distributed power supply (1) without blocking the current flowing between the distributed power supply (1) and the power system (6). It has the advantage of

In the grid connection system (100, 100A to 100E) according to the eighth aspect, in any of the first to seventh aspects, the inverter (3) is a storage battery connected in parallel to the distributed power supply (1). The DC power from (5) is configured to be converted to AC power. The distributed power source (1) is a solar power generator.

According to this aspect, there is an advantage that power can be supplied to the power system (6) even when either the distributed power source (1) or the storage battery (5) can not be used.

The configurations according to the second to eighth aspects are not essential for the grid interconnection system (100), and can be omitted as appropriate.

100, 100A to 100E grid interconnection system 1 distributed power supply 11 positive electrode 12 negative electrode 2 DC / DC converter 3 inverter 5 storage battery 6 power system 7 first case 8 second case D0 diode for DC / DC converter D1 reverse current blocking diode P1 first path (current path)
P2 second path (current path)
SW1 switching element SW2, SW3 switch Vb1 reference potential

Claims (8)

1. And an inverter connected between the distributed power source and the power system, for converting DC power from the distributed power source into AC power,
   A grid connection system, further comprising: a reverse current blocking diode provided in a current path including at least a part of the circuit on the distributed power supply side as viewed from the inverter and blocking a leak current flowing to a reference potential through the current path.
2. It further comprises a non-insulated DC / DC converter connected between the distributed power supply and the inverter and converting the DC voltage output from the distributed power supply into a DC voltage of a predetermined magnitude.
   The grid connection system according to claim 1, wherein the current path includes at least one of a high potential and a low potential of the DC / DC converter.
3. The grid connection system according to claim 2, wherein the reverse current blocking diode is also used as a diode of the DC / DC converter.
4. The current path has a first path including a positive electrode of the distributed power supply and a second path including a negative electrode of the distributed power supply,
   The grid connection system according to any one of claims 1 to 3, wherein the reverse current blocking diode is provided in each of the first path and the second path.
5. The switch further includes a switch connected in parallel to the reverse current blocking diode,
   The grid connection according to any one of claims 1 to 4, wherein the switch is controlled to be turned on when the distributed power supply is grid-connected to the power system and turned off at other times. System.
6. The grid connection system according to any one of claims 1 to 5, wherein the reverse current blocking diode is housed in a second housing different from the first housing for housing the inverter.
7. A switching element is connected in place of the backflow blocking diode in a path that prevents the distributed power supply from linking to the power system by inserting the backflow blocking diode among the current paths. The grid interconnection system according to Item 6.
8. The inverter is configured to convert direct current power from a storage battery connected in parallel to the distributed power source into alternating current power;
   The grid interconnection system according to any one of claims 1 to 7, wherein the distributed power source is a solar power generation device.

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