Power system and its control method

Abstract

To provide technology which contributes to flexible system design in a power system for supplying power from a power supply device to a charger when abnormality occurs in a power system.SOLUTION: A power system S1 interconnected with a power system 1 via an interconnection line L0 includes: power supply devices 10 and 30; a switching circuit 35 for switching a connection destination of a load 70 to the power system 1 or the power supply devices 10 and 30; a vehicle charger 100; and a controller 50. The controller 50 changes, when power is supplied from the power supply device 50 to the charger 100 when abnormality occurs in the power system 1, maximum charge power of the charger 100 from a first setting value that is set when the power system 1 is normal to a second setting value different from the first setting value.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a power system connected to a power grid.

Background Art

[0002] From the viewpoints of reducing dependence on fossil fuels and environmental problems, the introduction of distributed power sources typified by photovoltaic (PV) power generation systems has been promoted. A PV system converts the power generated by a photovoltaic panel from DC to AC using an inverter circuit and outputs it. Patent Document 1 below discloses a photovoltaic power generation system connected to a power grid.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a power system connected to a power grid, when an abnormality occurs in the power grid, power may be supplied from the power supply device of the power system to a vehicle charger.

[0005] An object of the present invention is to provide a technology that contributes to a flexible system design in a power system that supplies power from a power supply device to a vehicle charger when an abnormality occurs in a power grid.

Means for Solving the Problems

[0006] A power system connected to a power grid via a tie line includes a power supply device, a switching circuit that switches a connection destination of a load to the power grid or the power supply device, a vehicle charger, and a control device.

[0007] When the power system malfunctions and the control device supplies power to the charger from the power supply unit, it changes the maximum charging power of the charger from a first setting value (used when the power system is normal) to a second setting value (different from the first setting value). [Effects of the Invention]

[0008] According to the present invention, in a power system that supplies power from a power supply to a charger when an abnormality occurs in the power grid, it is possible to provide a technology that contributes to flexible system design. [Brief explanation of the drawing]

[0009] [Figure 1] Block diagram of a power system [Figure 2] Perspective view of a charger and a car [Figure 3] Diagram showing the power supply path when the power system is functioning normally. [Figure 4] Diagram showing the power supply path during a power system malfunction. [Figure 5A] Diagram showing the power supply path during a power outage. [Figure 5B] Diagram showing the power supply path during a power outage. [Figure 6] Chart showing the relationship between the maximum charging output of the charger under normal conditions and during a power outage. [Figure 7A] Diagram showing the maximum charging output of the charger (during a power outage) [Figure 7B] Diagram showing the maximum charging output of the charger (under normal conditions) [Figure 8] Flowchart for charger output control [Figure 9] Block diagram of a power system [Figure 10] Block diagram of a power system [Figure 11] Block diagram of a power system [Figure 12] Block diagram of a power system [Figure 13] Block diagram of a power system [Figure 14] Block diagram of a power system [Figure 15]Block diagram of a power system

Embodiment for carrying out the invention

[0010] (Overview of this embodiment) (1) A power system according to an embodiment of the present invention is a power system connected to a power grid via an interconnection line, and includes a power supply device, a switching circuit that switches the connection destination of a load to the power grid or the power supply device, a vehicle charger, and a control device.

[0011] When an abnormality occurs in the power grid and the control device supplies power from the power supply device to the charger, the control device changes the maximum charging power of the charger from a first set value when the power grid is normal to a second set value different from the first set value. An abnormality in the power grid refers to a state unsuitable for the power source that operates the load, such as a power outage, frequency abnormality, voltage abnormality, etc. The charger only needs to be configured to be supplied with power from the power supply device at least when an abnormality occurs in the power grid. When the power grid is normal, it may be supplied with power from the power grid or from the power supply device.

[0012] According to the power system according to an embodiment of the present invention, it is possible to change the maximum charging capacity of the charger when an abnormality occurs in the power grid, enabling a flexible system design.

[0013] (2) In the power system described in (1) above, the second set value may be a value smaller than the first set value.

[0014] According to the power system described in (2), by changing the maximum charging power of the charger from the first set value when the power grid is normal to a second set value smaller than the first set value, it is possible to relax the constraint on the maximum value of the power that can be supplied from the power supply device to the load. Therefore, it is possible to expand the size and selection of available loads.

[0015] (3) In the power system described in (1) above, the second set value may be a value larger than the first set value.

[0016] According to the power system described in (3), the constraint on the maximum charging capacity of the charger can be eased by changing the maximum charging power of the charger from a first setting value, which is the value when the power system is functioning normally, to a second setting value, which is greater than the first setting value. In this case, it becomes possible to limit or stop the power supply to the load and operate the system in a way that is specialized for charging.

[0017] <Embodiment 1> 1. Description of Power System S1 Figure 1 is a block diagram of power system S1. Power system S1 includes a stationary power supply 10, a power conditioner 20, a grid connection switch 33, a switching circuit 35, and a charger 100.

[0018] The stationary power source 10 consists of a stationary generator 11 and a stationary battery 15. The term "generator" is a general term for any device that generates electricity, not limited to machines that convert machinery into electricity. The stationary generator 11 can be a generator that uses renewable energy, such as a solar power generation panel (PV). The stationary generator 11 may also be a generator that does not use renewable energy, such as a synchronous generator or cogeneration generator that uses gas or oil. The stationary battery 15 can be a rechargeable secondary battery, such as a lithium-ion secondary battery.

[0019] The power conditioner 20 includes a first converter circuit 21, a second converter circuit 25, an inverter circuit 30, a measurement unit 31, a control device 50, and a communication unit 57.

[0020] The stationary generator 11 is connected to the first converter circuit 21. The first converter circuit 21 is a DC / DC converter. The output of the stationary generator 11 can be controlled by the first converter circuit 21. The first converter circuit 21 may also be a chopper.

[0021] The stationary battery 15 is connected to the second converter circuit 25. The second converter circuit 25 is a bidirectional DC / DC converter that discharges and charges the stationary battery 15. The second converter circuit 25 may also be a bidirectional chopper. The second converter circuit 25 may include a measuring unit for measuring the charging current and discharging current of the stationary battery 15. The measuring unit for measuring the charging current and discharging current may also be located in the stationary battery 15.

[0022] The first converter circuit 21 and the second converter circuit 25 are connected to the inverter circuit 30.

[0023] The inverter circuit 30 is a bidirectional conversion circuit that selectively performs reverse conversion (inverter) to convert DC to AC and forward conversion (converter) to convert AC to DC. The inverter circuit 30 may also be a conversion circuit that performs only reverse conversion (inverter). The inverter circuit 30 is a power conversion device.

[0024] By operating the inverter circuit 30 in reverse conversion mode, the DC power input from the stationary power supply 10 can be converted to AC power and output.

[0025] By operating the inverter circuit 30 in a forward conversion mode, the AC power input from the power system 1 can be converted to DC power and output. The output DC power can be used to charge the stationary battery 15. The stationary battery 15 can also be charged with surplus power from the stationary generator 11. The stationary power supply 10, converters 21 and 25, and inverter circuit 30 constitute the "power supply device" of the present invention.

[0026] The measurement unit 31 measures the output voltage Vinv and output current Iinv of the inverter circuit 30 during reverse conversion operation. During forward conversion operation, it measures the input voltage Vinv and input current Iinv. The measurement results from the measurement unit 31 are input to the control device 50.

[0027] The control device 50 has a CPU 51 and a memory 53. The control device 50 can control the switching between forward conversion and reverse conversion operations by giving commands to the inverter circuit 30.

[0028] Memory 53 stores the control program for the inverter circuit 30 and the program for changing the maximum charging power of the charger 100. It also stores other data necessary for controlling the inverter circuit 30 and changing the maximum charging power of the charger 100.

[0029] The power conditioner 20 has a first output terminal O1 and a second output terminal O2. The first output terminal O1 of the power conditioner 20 is connected to the power system 1 via a grid connection switch 33 and a grid connection line L0. The grid connection switch 33 is controlled to close when there is no abnormality in the power conditioner 20 or the power system 1.

[0030] Power system 1 is a system operated by an electric utility company and has a power source 3. A measuring instrument 5 is installed at the power receiving point F of power system S1.

[0031] The measuring instrument 5 measures the power Pgrid and voltage Vgrid at the power receiving point F of the power system S1. The measurement results Pgrid and Vgrid from the measuring instrument 5 are transmitted to the control device 50 via the communication line. The dashed line shown in Figure 1 indicates the boundary between power grid 1 and power system S1.

[0032] A car charger 100 is connected to the second output terminal O2 of the power conditioner 20 via a branch line L1.

[0033] The charger 100 comprises a power converter 110, a control unit 121, a storage unit 123, and a communication unit 127. The power converter 110 converts alternating current (AC) power to direct current (DC) power.

[0034] Figure 2 is a perspective view of the charger 100 and the vehicle 200. The vehicle 200 is an electric vehicle or a hybrid vehicle. The vehicle 200 is an example of a vehicle. The charger 100 can be connected to the vehicle 200 via an electrical cable 130 and can charge the vehicle's onboard battery 230.

[0035] Specifically, the power converter 110 charges the onboard battery 230 by its forward conversion operation (the operation of converting AC to DC). The charger 100 may also be equipped with a measuring unit for measuring the charging current.

[0036] The electrical cable 130 includes a power line 130A for charging, as well as a signal line 130B. The control unit 121 is connected to the automobile 200 via the signal line 130B for communication.

[0037] The control unit 121 receives information on the remaining capacity [Ah] of the mounted battery 230 from the vehicle ECU 210 of the automobile 200. Based on the charging current of the mounted battery 230, the control unit 121 can calculate the charge amount [Ah] of the mounted battery 230 and manage the remaining capacity [Ah] of the mounted battery 230.

[0038] The memory unit 123 stores data on the charging history of the automobile 200 and the remaining capacity of the onboard battery 230. The charger 100 is connected to the control device 50 of the power conditioner 20 via the communication unit 127.

[0039] The switching circuit 35 is a circuit that switches the connection point of the load line L2. The switching circuit 35 includes a first switch 36 and a second switch 37. The first switch 36 and the second switch 37 are connected in series.

[0040] The first switch 36 is connected to the power system side endpoint D of the interconnection switch 33, which has two endpoints C and D. The second switch 37 is connected to point B of the branch line L1.

[0041] A load 70 is connected to the connection point E of the two switches 36 and 37 via a load line L2.

[0042] Load 70 refers to specific loads such as elevators, refrigerators, and air conditioners, which are desirable to be powered and operated even during a power outage.

[0043] If there is no abnormality in power system 1, the first switch 36 is controlled to close and the second switch 37 is controlled to open. By closing the first switch 36 and opening the second switch 37, the load 70 is connected to the interconnection line L0 and power is supplied from power system 1, as shown in Figure 3.

[0044] If there is an abnormality in power system 1, the first switch 36 is controlled to open and the second switch 37 is controlled to close. By opening the first switch 36 and closing the second switch 37, the load 70 is connected to branch line L1 and power is supplied from inverter circuit 30, as shown in Figure 4.

[0045] 2. Maximum charging output of charger 100 The power system S1 allows the destination of the load 70 to be switched by the switching circuit 35. When power system 1 is functioning normally, the load 70 is connected to power system 1 via the interconnection line L0, and power is supplied from power system 1 (Figure 3). On the other hand, if there is an abnormality in power system 1, the load 70 is connected to branch line L1, and power is supplied to the load 70 from the inverter circuit 30 (Figure 4).

[0046] Since the charger 100 is connected to the branch line L1 of the inverter circuit 30, as shown in Figure 4, when an abnormality occurs in the power system 1, the inverter circuit 30 supplies power to both the load 70 and the charger 100.

[0047] Since the system must be configured so as not to exceed the maximum capacity of the inverter circuit 30, the maximum value P2 of the load 70 is the value obtained by subtracting the maximum charging output P1 of the charger 100 from the maximum capacity P0 of the inverter circuit 30, as shown in equation (1).

[0048] If the maximum capacity P0 of the inverter circuit 30 is 20 [kVA] and the maximum charging output P1 of the charger 100 is 10 [kVA], then the maximum value P2 of the load 70 is 10 [kVA].

[0049] P2 = P0 - P1 ... (1)

[0050] However, the battery charging of the vehicle 200 depends on the charging capacity of the vehicle 200 and is not necessarily charged at the maximum charging output of the charger 100. Also, as shown in Figure 4, if there is a problem with the power system 1, power may be supplied to both the load 70 and the vehicle 200, as shown in Figure 5A, or the vehicle 200 may be disconnected and power supplied only to the load 70, as shown in Figure 5B.

[0051] When the vehicle 200 is not connected and power is supplied only to the 10 [kVA] load 70, the output of the inverter circuit 30 has a margin above its maximum capacity of 20 [kVA], which presents a problem as the inverter circuit 30 is not being fully utilized.

[0052] In this embodiment, the maximum charging output P1 of the charger 100 is changed according to the state of the power system 1. Specifically, as shown in Figure 6, when the power system 1 is normal, the maximum charging output P1 of the charger 100 is set to 10 [kVA]. When an abnormality occurs in the power system 1, the maximum charging output P1 of the charger 100 is changed to a value smaller than the maximum charging power P1 under normal conditions. For example, it is changed from 10 [kVA] to 5 [kVA]. 10 [kVA] corresponds to the "first setting value" of the present invention, and 5 [kVA] corresponds to the "second setting value" of the present invention.

[0053] If power system 1 is abnormal, the maximum charging output P1 of charger 100 can be limited to 5 [kVA], thereby increasing the maximum value P2 of load 70 to 15 [kVA] without exceeding the maximum capacity of inverter circuit 30, which is 20 [kVA] (see Figure 7A).

[0054] When power system 1 is functioning normally, as shown in Figure 7B, power is supplied to load 70 from power system 1, and inverter circuit 30 supplies power only to charger 100, so the maximum capacity of inverter circuit 30 of 20 [kVA] will not be exceeded.

[0055] Figure 8 is a flowchart of the control for changing the maximum charging output P1 of the charger 100. The control for changing the maximum charging output consists of five steps, S10 to S50, in one cycle. In this embodiment, the control device 50 executes these steps at predetermined intervals after the power conditioner 20 is started up.

[0056] The initial settings of the switching circuit 35 are that switch 36 is closed and switch 37 is open, and the load 70 is supplied with power from power system 1 via interconnection line L0.

[0057] In S10, the control device 50 acquires data on the voltage value at the power receiving point F, and in S20, it determines the state of the power system 1 based on the voltage value at the power receiving point F.

[0058] If power system 1 is functioning normally (S20:YES), the control device 50 maintains the maximum charging output P1 of the charger 100 at the initial setting of 10 [kVA].

[0059] If power system 1 is abnormal (S20: NO), the control device 50 switches the interconnection switch 33 from closed to open, and switches switch 36 of the switching circuit 35 to open and switch 37 to closed (S40).

[0060] Switching the interconnection switch 33 disconnects the load 70 from power system 1, and switching switches 36 and 37 switches the connection destination of the load 70 from interconnection line L0 to branch line L1.

[0061] The control device 50 sends a command to the control unit 121 of the charger 100 to change the maximum charging output P1 of the charger 100 from the initial setting of 10 [kVA] to 5 [kVA].

[0062] As a result, after an abnormality is detected in power system 1, the load 70, which has been disconnected from power system 1, is supplied with power from the inverter circuit 30 at a maximum value of 15 [kVA].

[0063] 3. Explanation of Effects This configuration has the advantage of reducing the constraint on the maximum value of the load 70 when designing the power system S1, thus expanding the range of sizes and choices of load 70 that can be connected to the inverter circuit 30.

[0064] <Embodiment 2> In the power system S1 of Embodiment 1, when the power system 1 is functioning normally (Figure 3), power is supplied from the power system 1 to the charger 100 via the power conditioner 20, and power is supplied to the load 70 via the switching circuit 35. When an abnormality occurs in the power system 1 (Figure 4), the connection destination of the load 70 is switched to the power conditioner 20, and power is supplied from the inverter circuit 35 of the power conditioner 20 to the charger 100 and the load 70.

[0065] In the power system S2 of Embodiment 2, when the power system 1 is functioning normally, the interconnection switch 33 is open, the first switch 36 is open, and the second switch 37 is closed, supplying power from the inverter circuit 30 to the charger 100 and the load 70, as shown in Figure 10. When an abnormality occurs in the power system 1, the second switch 37 is opened to disconnect the load 70, and power is supplied from the inverter circuit 30 only to the charger 100, as shown in Figure 11.

[0066] In Embodiment 2, the control device 50 sets the maximum charging power P1 of the charger 100 to 5 [kVA] when the power system 1 is functioning normally. On the other hand, when an abnormality occurs in the power system 1, the control device 50 changes the maximum charging power P1 of the charger 100 to a value greater than the maximum charging power P1 under normal conditions. For example, it changes from 5 [kVA] to 10 [kVA].

[0067] The power system S2 of Embodiment 2 is intended for use as an EV station for disaster relief. When the grid is functioning normally, in order to save on electricity costs, the load 70 is also used via the power conditioner 20 in addition to the charger 100. In this case, by setting the maximum charging power P1 of the charger 100 to 5 [kVA], the upper limit of EV charging can be reduced, and the maximum value of the load 70 can be increased.

[0068] In the event of a disaster, load 70 is disconnected, and the maximum charging power P1 of charger 100 is changed from 5 [kVA] to 10 [kVA]. By relaxing the limitation on the maximum charging power P1, high-output charging becomes possible, enabling system operation specifically for EV charging.

[0069] <Embodiment 3> Figures 12 and 13 are block diagrams of the power system S3 of Embodiment 3. The power system S3 of Embodiment 3 differs from the power system S1 of Embodiment 1 in that a charger 77 is connected in parallel with the load 76. Hereinafter, the load 76 and the charger 77 will be referred to as the load group 75.

[0070] In the power system S3 of Embodiment 3, when the power system 1 is functioning normally, power is supplied from the power system 1 to the charger 100 via the power conditioner 20, and power is supplied to the load group 75 via the switching circuit 35, as shown in Figure 12.

[0071] When an abnormality occurs in power system 1, the connection destination of load group 75 is switched to power conditioner 20, and power is supplied from inverter circuit 30 to charger 100 and load group 75.

[0072] In the power system S3 of Embodiment 3, similar to the power system S1 of Embodiment 1, the control device 50 maintains the maximum charging output P1 of the charger 100 at the initial setting of 10 [kVA] when the power system 1 is functioning normally. When an abnormality occurs in the power system 1, the maximum charging output P1 of the charger 100 is changed from the initial setting of 10 [kVA] to 5 [kVA].

[0073] By changing the maximum charging output P1 of the charger 100 from the initial setting of 10 [kVA] to 5 [kVA], the constraint on the maximum value of the load group 75 is reduced, which has the advantage of expanding the size and selection of load groups 75 that can be connected to the inverter circuit 30.

[0074] <Other Embodiments> The present invention is not limited to the embodiments described above and in the drawings, and the following embodiments, for example, are also included in the technical scope of the present invention.

[0075] (1) In this embodiment, the battery 230 mounted on the automobile 200 was charged using the charger 100. The battery may be charged not only on the automobile 200, but also on the batteries of hybrid vehicles or electric motorcycles. It can be broadly applied to any mobile body equipped with a rechargeable power source, such as a vehicle towing a container equipped with a battery (storage battery).

[0076] (2) In the above embodiment, the stationary power supply 10 consisted of a stationary generator 11 and a stationary battery 15. The stationary generator 11 may be omitted, and the stationary power supply 10 may consist only of the stationary battery 15. The stationary battery 15 is not limited to a secondary battery, but may also be a capacitor. There may be multiple stationary batteries 15. The stationary battery 15 may be a group of batteries connected in parallel and controlled collectively.

[0077] (3) In the above embodiment, there is one charger 100 in the power system S1, but as shown in Figure 9, there may be multiple chargers 100. In the case of a system configuration having multiple chargers 100, it is preferable to change the sum of the maximum charging power of the multiple chargers 100 from a first setting value when the power system is normal to a second setting value which is smaller than the first setting value.

[0078] (4) In Embodiment 1, the control device 50 was installed inside the power conditioner 20. The control device 50 may be located inside the power conditioner 20, or inside the charger 100. It may also be located outside the power conditioner 20 or charger 100 if it can be controlled remotely.

[0079] (5) The charger 100 only needs to be capable of charging, and may be substituted with a charger / discharger that has both charging and discharging functions.

[0080] (6) In the above embodiment, the power supply unit 5 of the power system S is composed of a stationary power supply 10, converters 21 and 25, and an inverter circuit 30. The power supply unit 5 does not necessarily have to use converters 21 and 25 or an inverter circuit 30, and can be substituted with, for example, an AC generator 510. The power system S4 shown in Figure 14 is composed of an AC generator 510, a switching circuit 35, a charger 100, a control device 50, and a communication unit 57. The switching circuit 35 is located on the interconnection line L0 to the power system 1, and by closing the first switch 36 and opening the second switch 37, the load 70 and the charger 100 can be connected to the power system 1 (see Figure 14), and by opening the first switch 36 and closing the second switch 37, the load 70 and the charger 100 can be connected to the AC generator 510 (see Figure 15).

[0081] When the power system 1 is functioning normally, the control device 50 connects the load 70 and the charger 100 to the power system 1, as shown in Figure 14, and supplies power from the power system 1 to the load 70 and the charger 100. When an abnormality occurs in the power system 1, the control device 50 connects the load 70 and the charger 100 to the AC generator 510, as shown in Figure 15, and supplies power from the AC generator 510 to the load 70 and the charger 100.

[0082] In the power system S4, the control device 50 sets the maximum charging output P1 of the charger 100 to 10 [kVA] when the power system 1 is functioning normally. When an abnormality occurs in the power system 1, the maximum charging output P1 of the charger 100 is changed from 10 [kVA] to 5 [kVA]. Changing the maximum charging output P1 of the charger 100 from 10 [kVA] to 5 [kVA] reduces the constraint on the maximum value of the load 70, which has the advantage of expanding the size and selection of the load 70 that can be connected to the AC generator 510. [Explanation of symbols]

[0083] 1 Power system 3 grid power supply 10 Stationary power supply (power supply unit) 20 Power Conditioner 30. Inverter circuit (power supply unit) 50 Control device 100 charger 200 Automobile (An example of the "vehicle" of the present invention) 230 Battery

Claims

1. A power system that connects to the power grid via interconnection lines, Power supply unit, A switching circuit that switches the destination of the load to the power system or the power supply device, A vehicle charger, Includes a control device, When the control device supplies power from the power supply unit to the charger in the event of an abnormality in the power system, A power system that changes the maximum charging power of the charger from a first setting value, which is the value when the power system is functioning normally, to a second setting value that is different from the first setting value.

2. The power system according to claim 1, A power system in which the second setting value is smaller than the first setting value.

3. The power system according to claim 1, A power system in which the second setting value is greater than the first setting value.

4. A method for controlling a power system that is connected to a power grid via an interconnection line, The aforementioned power system, Power supply unit, A switching circuit that switches the destination of the load to the power system or the power supply device, Includes a vehicle charger, When power is supplied from the power supply device to the charger in the event of an abnormality in the power system, A power system control method for changing the maximum charging power of the charger from a first set value, which is the value when the power system is functioning normally, to a second set value, which is different from the first set value.

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