Power supply system

Abstract

To provide a power supply system capable of obtaining stable autonomous operation output without causing high cost and complication.SOLUTION: A power supply system 10A includes: a first power conversion device 20 capable of performing autonomous operation; and a second power conversion device 40 and a third power conversion device 60, which include individual operation prevention functions. The second power conversion device 40 performs cancel operation for, when the third power conversion device 60 detects that reactive power is injected to a customer distribution line 11 by the individual operation prevention function when voltage of the customer distribution line 11 is maintained to voltage required by a consumer load L by power outputted by autonomous operation by the first power conversion device 20, cancelling this injection of the reactive power.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power supply system including a consumer distribution line that enables the supply of power from a commercial power system to a consumer load, and a power conversion device connected to the consumer distribution line. [Background technology]

[0002] Various power supply systems have been known in the past, each of which includes a consumer-premises distribution line that enables the supply of power from a commercial power system to a consumer load and a plurality of power conversion devices connected to the consumer-premises distribution line. For example, Patent Document 1 discloses a power supply system in which a power storage device including a storage battery, a V2H device that charges and discharges an electric vehicle such as an electric car, and a photovoltaic power generation device including a solar cell are connected to the consumer-premises distribution line. This system is configured so that under normal circumstances (when there is no power outage), the power storage device, the V2H device, and the photovoltaic power generation device are interconnected to the commercial power system. Furthermore, this system is configured so that during a power outage, the power storage device operates autonomously, and the V2H device and the photovoltaic power generation device are interconnected to the autonomous operation output of the power storage device (pseudo-grid interconnection). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-143688 Summary of the Invention [Problem to be solved by the invention]

[0004] A power conversion device that can be connected to a commercial power grid must have an "islanding prevention function" that prevents its own operation from becoming an islanding state. A known islanding prevention function, for example, injects a predetermined reactive power into a distribution line within a customer's premises, determines whether the injection causes a predetermined voltage fluctuation in the distribution line within the customer's premises, and if the predetermined voltage fluctuation occurs, recognizes that the device is in an islanding state and immediately stops operation.

[0005] The islanding prevention function is an essential and important function. However, when the target of interconnection is an islanding output rather than a commercial power grid, the reactive power injection by this function can destabilize the islanding output (i.e., cause large fluctuations in the voltage on the customer's distribution line), which could have a negative impact on the operation of the customer's load.

[0006] Destabilization of the isolated operation output can be suppressed by improving the hardware configuration or control system of the power conversion device that performs the isolated operation, but making such improvements increases the cost of the power conversion device.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a power supply system that can obtain a stable stand-alone operation output at low cost. [Means for solving the problem]

[0008] In order to solve the above problem, the power supply system of the present invention is a system comprising a consumer-premises distribution line that enables the supply of power from a commercial power system to a consumer load and a plurality of power conversion devices connected to the consumer-premises distribution line, wherein the plurality of power conversion devices include a first power conversion device capable of independent operation, and a second power conversion device and a third power conversion device that have an islanding prevention function, and the second power conversion device is configured such that when the voltage of the consumer-premises distribution line is maintained at the voltage required by the consumer load by the power output by the first power conversion device through independent operation, the second power conversion device performs a cancellation operation to cancel the injection when it detects that the third power conversion device has injected reactive power into the consumer-premises distribution line through the islanding prevention function.

[0009] In this configuration, when the third power conversion device injects reactive power into the customer's distribution line due to the islanding prevention function, the second power conversion device performs a canceling operation to cancel this reactive power injection. Therefore, with this configuration, it is possible to prevent the islanding prevention function of the third power conversion device from causing instability in the isolated operation output.

[0010] The power supply system may further include a current detector provided at the connection between the third power conversion device and the customer's distribution line, in which case the second power conversion device can detect the injection based on the detection result of this current detector.

[0011] The second power conversion device of the power supply system may perform a canceling operation by injecting reactive power having an opposite phase to the reactive power injected by the third power conversion device into the customer power distribution line.

[0012] The first power conversion device of the power supply system may notify the second power conversion device of the start of independent operation.

[0013] According to this configuration, it is possible to reliably notify the second power conversion device that the target of interconnection is not the commercial power grid but the isolated operation output of the first power conversion device.

[0014] It is preferable that the second power conversion device of the above-mentioned power supply system stops performing the cancellation operation for a predetermined time when it detects that there is a fluctuation in the voltage of the distribution line within the consumer's facility corresponding to a sign of isolated operation while the voltage of the distribution line within the consumer's facility is maintained at the voltage required by the consumer load by the power output by the first power conversion device through isolated operation.

[0015] With this configuration, the injection of reactive power from the third power conversion device is canceled only when there are no signs of islanding operation (effectively disabling the islanding operation prevention function of the third power conversion device), thereby stabilizing the islanding operation output.

[0016] It is preferable that the second power conversion device of the power supply system stops its own islanding prevention function upon receiving a notification from the first power conversion device.

[0017] According to this configuration, the islanding operation prevention function of the second power conversion device can prevent the isolated operation output from becoming unstable.

[0018] It is preferable that the second power conversion device of the above-mentioned power supply system, after receiving the notification, cancels the suspension of its own islanding prevention function when it detects that there has been a fluctuation in the voltage of the distribution line within the consumer that corresponds to a sign of islanding operation.

[0019] With this configuration, when there are no signs of islanding operation, the system can prioritize stabilizing the independent operation output by disabling its own islanding operation prevention function, and when there are signs of islanding operation, the system can prioritize preventing islanding operation by enabling its own islanding operation prevention function.

[0020] The second power conversion device of the power supply system is preferably connected to a power supply device including a storage battery.

[0021] This configuration can prevent the reactive power from being unable to be canceled out properly due to a power shortage. [Effects of the Invention]

[0022] According to the present invention, it is possible to provide a power supply system that can obtain a stable stand-alone operation output without incurring high costs. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a block diagram showing a schematic configuration of a power supply system according to a first embodiment of the present invention. [Figure 2] 1 is a schematic diagram roughly showing the activation timing of an islanding prevention function and a cancellation function of a power supply system according to a first embodiment of the present invention. FIG. [Figure 3] FIG. 10 is a block diagram showing a schematic configuration of a power supply system according to a second embodiment of the present invention. [Figure 4] FIG. 10 is a block diagram showing a schematic configuration of a power supply system according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, an embodiment of a power supply system according to the present invention will be described with reference to the accompanying drawings.

[0025] [First Example] 1 shows a power supply system 10A according to a first embodiment of the present invention. As shown in the figure, the power supply system 10A includes a consumer-side distribution line 11 that enables the supply of power from a commercial power system G to a consumer load L, and a first power conversion device 20, a second power conversion device 40, and a third power conversion device 60 that are connected to the consumer-side distribution line 11.

[0026] The first power conversion device 20 includes an AC / DC conversion unit 21 that operates bidirectionally and a control unit 22 that includes a microcomputer or the like that controls the AC / DC conversion unit 21, and is connected to a power supply device 30 that includes a storage battery. The first power conversion device 20 is also called a storage power conditioner.

[0027] Under normal circumstances, the first power conversion device 20 is connected to the commercial power system G and can convert AC power supplied from the consumer's distribution line 11 into DC power and supply it to the power supply device (storage battery) 30, or convert DC power (discharge power) supplied from the power supply device 30 into AC power and supply it to the consumer's distribution line 11.

[0028] Furthermore, during a power outage, the first power conversion device 20 can open the parallel-off relay 12, convert the DC power supplied from the power supply device 30 into AC power, and supply the AC power to the consumer's distribution line 11. In other words, the first power conversion device 20 can operate autonomously.

[0029] When the voltage of the consumer-side distribution line 11 detected by a voltage detector (not shown) reaches a value indicating a power outage in the commercial power system G, the control unit 22 immediately stops the AC / DC conversion unit 21 and switches the parallel-off relay 12 from a closed state to an open state, and then causes the AC / DC conversion unit 21 to start supplying AC power. Furthermore, when the control unit 22 causes the AC / DC conversion unit 21 to start supplying AC power, that is, when the first power conversion device 20 starts independent operation, the control unit 22 notifies the second power conversion device 40 of this.

[0030] The third power conversion device 60 includes an AC / DC conversion unit 61 and a control unit 62 that includes a microcomputer or the like for controlling the AC / DC conversion unit 61, and is connected to a power supply device 70 that includes a solar cell. The third power conversion device 60 is also called a solar power conditioner.

[0031] The third power conversion device 60 can convert DC power (generated power) supplied from the power supply device 70 into AC power and supply it to the distribution line 11 within the consumer facility while being connected to the commercial power system G during normal operation.

[0032] In addition, during a power outage, the third power conversion device 60 can convert the DC power supplied from the power supply device 70 to AC and supply it to the consumer's distribution line 11 while connecting to the isolated operation output of the first power conversion device 20 (i.e., pseudo-grid connection).

[0033] The control unit 62 immediately stops the AC / DC conversion unit 61 when the voltage of the consumer power distribution line 11 detected by a voltage detector (not shown) reaches a value indicating a power outage in the commercial power system G, and then releases the aforementioned stop when the voltage of the consumer power distribution line 11 returns to its original value (normal value) from the value indicating the power outage. The voltage of the consumer power distribution line 11 returns to its original value when the commercial power system G recovers from the power outage or the first power conversion device 20 starts independent operation.

[0034] The third power conversion device 60 has an islanding prevention function. That is, the control unit 62 is configured to control the AC / DC conversion unit 61 under predetermined conditions to inject reactive power into the consumer's distribution line 11. The control unit 62 injects reactive power under predetermined conditions regardless of whether the target of interconnection is the commercial power system G or an isolated operation output. The control unit 62 then determines whether a predetermined voltage fluctuation has occurred in the consumer's distribution line 11 due to this injection, and if so, recognizes that the operation state of the third power conversion device 60 is an islanding state and promptly stops the AC / DC conversion unit 61.

[0035] The second power conversion device 40 includes an AC / DC conversion unit 41 that operates bidirectionally and a control unit 42 that includes a microcomputer or the like that controls the AC / DC conversion unit 41, and is connectable to a power supply device 50 that is an electric vehicle equipped with a storage battery. The second power conversion device 40 is also called a V2H (Vehicle to Home) device.

[0036] Under normal circumstances, the second power conversion device 40 is connected to the commercial power system G and can convert AC power supplied from the consumer's distribution line 11 into DC power and supply it to the power supply device (storage battery of an electric vehicle) 50, or convert DC power (discharge power) supplied from the power supply device 50 into AC power and supply it to the consumer's distribution line 11.

[0037] In addition, during a power outage, the second power conversion device 40 can convert AC power supplied from the consumer's distribution line 11 into DC power and supply it to the power supply device 50 while being connected to the isolated operation output of the first power conversion device 20 (i.e., pseudo-grid connection), or convert DC power supplied from the power supply device 50 into AC power and supply it to the consumer's distribution line 11.

[0038] The control unit 42 immediately stops the AC / DC conversion unit 41 when the voltage of the consumer power distribution line 11 detected by a voltage detector (not shown) reaches a value indicating a power outage in the commercial power system G. Thereafter, the control unit 42 cancels the above-mentioned stop when the voltage of the consumer power distribution line 11 returns to its original value (normal value) from the value indicating a power outage. The voltage of the consumer power distribution line 11 returns to its original value when the commercial power system G recovers from the power outage or the first power conversion device 20 starts independent operation.

[0039] The second power conversion device 40, like the third power conversion device 60, has an islanding prevention function. That is, the control unit 42 is configured to control the AC / DC conversion unit 41 under predetermined conditions to inject reactive power toward the consumer-side distribution line 11. The control unit 42 injects reactive power under predetermined conditions regardless of whether the interconnection target is the commercial power grid G ​​or an isolated operation output. The control unit 42 then determines whether a predetermined voltage fluctuation has occurred in the consumer-side distribution line 11 due to this injection. If a predetermined voltage fluctuation has occurred, the control unit 42 recognizes that the second power conversion device 40 is in an islanding operation state and promptly stops the AC / DC conversion unit 41. However, upon receiving a notification of the start of isolated operation from the first power conversion device 20, the control unit 42 disables its own islanding prevention function. That is, the control unit 42 injects reactive power only when the interconnection target is essentially the commercial power grid G.

[0040] The second power conversion device 40 further has a cancellation function. When the detection result of the current detector 13 provided at the connection between the third power conversion device 60 and the customer-premises distribution line 11 indicates that the third power conversion device 60 has injected reactive power into the customer-premises distribution line 11, the cancellation function executes a cancellation operation to cancel this injection. The cancellation function can also be said to be a function that essentially disables the islanding prevention function of the third power conversion device 60. An example of the cancellation operation is to inject reactive power that is opposite in phase to the injected reactive power. The cancellation operation is executed by the control unit 42 controlling the AC / DC conversion unit 41.

[0041] As shown in FIG. 2, when the commercial power system G is normal, that is, when the voltage of the consumer distribution line 11 is maintained at the voltage required by the consumer load L by the power supplied from the commercial power system G, the second power conversion device 40 and the third power conversion device 60 always activate the islanding prevention function and inject reactive power when the conditions are met.

[0042] The islanding prevention function of the second power conversion device 40 stops when it receives a notification from the first power conversion device 20. In other words, the islanding prevention function of the second power conversion device 40 does not operate when the voltage of the consumer's distribution line 11 is maintained by the isolated operation output of the first power conversion device 20. On the other hand, the islanding prevention function of the third power conversion device 60 continues to operate even after the voltage of the consumer's distribution line 11 is maintained by the isolated operation output of the first power conversion device 20.

[0043] The canceling function of the second power conversion device 40 is activated when a notification is received from the first power conversion device 20. In other words, the canceling function of the second power conversion device 40 is activated when the voltage of the consumer distribution line 11 is maintained by the isolated operation output of the first power conversion device 20. In other words, when the second power conversion device 40 is notified of the start of isolated operation from the first power conversion device 20, it begins to inject reactive power using the canceling function instead of injecting reactive power using the islanding prevention function.

[0044] As described above, in the power supply system 10A according to the present embodiment, when the voltage of the consumer-side distribution line 11 is maintained by the isolated operation output of the first power conversion device 20, the islanding operation prevention function of the second power conversion device 40 is stopped. Also, in the power supply system 10A, when the voltage of the consumer-side distribution line 11 is maintained by the isolated operation output of the first power conversion device 20, the injection of reactive power due to the islanding operation prevention function of the third power conversion device 60 is canceled by the canceling function of the second power conversion device 40. Therefore, according to the power supply system 10A, a stable islanding operation output can be supplied to the consumer load L during a power outage.

[0045] [Second Example] A power supply system 10B according to a second embodiment of the present invention is shown in Fig. 3. As shown in the figure, the power supply system 10B differs from the power supply system 10A in that it includes a second power conversion device 40A instead of the second power conversion device 40 and two third power conversion devices 60A and 60B instead of the third power conversion device 60, but is otherwise common to the power supply system 10A.

[0046] The third power conversion devices 60A, 60B have the same configuration and functions (including an islanding prevention function) as the third power conversion device 60, and are connected to power supply devices 70A, 70B consisting of solar cells.

[0047] The second power conversion device 40A has the same configuration and functions (including an islanding prevention function and a cancellation function) as the second power conversion device 40, and is connected to a power supply device 50A consisting of an electric vehicle equipped with a storage battery. However, the cancellation function of the second power conversion device 40A differs from the cancellation function of the second power conversion device 40 in that the cancellation function of the second power conversion device 40A executes a cancellation operation when the detection result of a current detector 13A provided at the connection between the third power conversion device 60A and the customer-premises distribution line 11 indicates the injection of reactive power, and when the detection result of a current detector 13B provided at the connection between the third power conversion device 60B and the customer-premises distribution line 11 indicates the injection of reactive power.

[0048] According to the power supply system 10B of this embodiment, the cancellation function of the second power conversion device 40A can prevent the islanding prevention function of the third power conversion devices 60A, 60B from destabilizing the isolated operation output.

[0049] [Third Example] A power supply system 10C according to a third embodiment of the present invention is shown in Fig. 4. As shown in the figure, the power supply system 10C differs from the power supply system 10B in that it further includes a second power converter 40B and a third power converter 60C, but is otherwise common to the power supply system 10B.

[0050] The third power conversion device 60C has the same configuration and functions (including an islanding prevention function) as the third power conversion device 60, and is connected to a power supply device 70C made up of a solar cell.

[0051] The second power conversion device 40B has the same configuration and functions (including an islanding prevention function and a cancellation function) as the second power conversion device 40, and is connected to a power supply device 50B consisting of an electric vehicle equipped with a storage battery. The cancellation function of the second power conversion device 40B is to perform a cancellation operation when the detection result of a current detector 13C provided at the connection between the third power conversion device 60C and the customer-premises distribution line 11 indicates the injection of reactive power.

[0052] According to the power supply system 10C of this embodiment, the islanding operation prevention function of the third power conversion devices 60A, 60B can be prevented from destabilizing the isolated operation output by the cancellation function of the second power conversion device 40A. Also, according to the power supply system 10C, the islanding operation prevention function of the third power conversion device 60C can be prevented from destabilizing the isolated operation output by the cancellation function of the second power conversion device 40B.

[0053] [Variations] Although the first, second and third embodiments of the power supply system according to the present invention have been described above, the configurations of the present invention are not limited to these.

[0054] For example, the second power conversion devices 40, 40A, 40B may be configured to cancel the suspension of their own islanding operation prevention function and suspend the execution of the cancellation operation for a predetermined time when they detect a sign of islanding operation after receiving a notification from the first power conversion device 20. The sign of islanding operation can be detected based on a predetermined fluctuation in the voltage of the consumer distribution line 11. Furthermore, the time for suspending the execution of the cancellation operation is preferably longer than the maximum time for which an islanding state is allowed as defined in the grid interconnection regulations, for example.

[0055] Furthermore, the first power conversion device 20 is not limited to a storage power conditioner, and may be any power conversion device connected to any power supply device capable of stably outputting DC power.

[0056] Furthermore, the second power conversion devices 40, 40A, and 40B are not limited to V2H devices. The second power conversion devices 40, 40A, and 40B may be any power conversion devices connected to any power supply device capable of stably outputting DC power. Note that if the output of the power supply device is unstable, the second power conversion devices 40, 40A, and 40B may not be able to properly cancel out the injected reactive power.

[0057] Furthermore, the third power conversion devices 60, 60A, 60B, and 60C are not limited to solar power conditioners. Furthermore, the power supply devices 70, 70A, 70B, and 70C connected to the third power conversion devices 60, 60A, 60B, and 60C are not limited to any power supply device capable of stably outputting DC power, and may be power supply devices that are not necessarily capable of stably outputting DC power. Examples of such power supply devices include power supply devices that utilize renewable energy sources such as solar power and wind power. [Explanation of symbols]

[0058] 10A, 10B, 10C Power Supply System 11 In-consumer distribution line 12 Parallel-off relay 13, 13A, 13B, 13C Current detector 20 First power conversion device 30 Power supply 40, 40A, 40B Second power conversion device 50,50A,50B power supply 60, 60A, 60B, 60C Third power conversion device 70,70A,70B,70C power supply G Commercial power system L Consumer load

Claims

1. A power supply system including a consumer distribution line that enables power to be supplied from a commercial power system to a consumer load, and a plurality of power conversion devices connected to the consumer distribution line, The plurality of power conversion devices a first power conversion device capable of independent operation; a second power conversion device and a third power conversion device each having an islanding prevention function; Including, When the voltage of the consumer distribution line is maintained at a voltage required by the consumer load by the power output by the first power conversion device through the isolated operation, the second power conversion device performs a canceling operation to cancel the injection when it detects that the third power conversion device has injected reactive power into the consumer distribution line through the isolated operation prevention function. A power supply system characterized by:

2. a current detector provided at a connection between the third power conversion device and the consumer distribution line; The second power conversion device detects the injection based on the detection result of the current detector.

2. The power supply system according to claim 1.

3. The second power conversion device injects reactive power having an opposite phase to the reactive power injected by the third power conversion device into the customer distribution line as the canceling operation.

2. The power supply system according to claim 1.

4. When the second power conversion device detects a fluctuation in the voltage of the consumer power distribution line corresponding to a sign of islanding operation while the voltage of the consumer power distribution line is maintained at a voltage required by the consumer load by the power output by the first power conversion device through the islanding operation, the second power conversion device stops execution of the cancellation operation for a predetermined time.

4. The power supply system according to claim 1, wherein the power supply system is a power supply system for supplying power to a power source.

5. The first power conversion device notifies the second power conversion device of the start of the independent operation.

4. The power supply system according to claim 1, wherein the power supply system is a power supply system for supplying power to a power source.

6. When the second power conversion device receives the notification, the second power conversion device stops the islanding operation prevention function of the second power conversion device.

6. The power supply system according to claim 5.

7. When the second power conversion device detects a fluctuation in the voltage of the distribution line within the customer after receiving the notification, the second power conversion device cancels the suspension of the islanding operation prevention function of the second power conversion device.

7. The power supply system according to claim 6.

8. The second power conversion device is connected to a power supply device including a storage battery.

4. The power supply system according to claim 1, wherein the power supply system is a power supply system for supplying power to a power source.

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