Power conversion device, rotating electrical machine system, power conversion system, and hydroelectric power generation system

Abstract

Provided are a power converter, a rotating electrical machine system, a power conversion system, and a hydroelectric power generation system that can prevent an excessive electrical load from being applied to a current limiting circuit when the current limiting circuit is in a limiting state. [Solution] A power conversion device 30 includes a current limiting circuit 35, a power consumption circuit 36, and a control unit 37. The current limiting circuit 35 can switch between a limited state in which a capacitor 38 of a DC link unit 31 and a first switch 33 are connected via a resistor 35a, and a non-limited state in which the capacitor 38 and the first switch 33 are connected without the resistor 35a. The power consumption circuit 36 ​​can switch between a first state in which it consumes DC power from the DC link unit 31, and a second state in which it does not consume DC power from the DC link unit 31. The control unit 37 controls the power consumption circuit 36 ​​to enter the second state when the current limiting circuit 35 is in the limited state.

Description

[Technical Field]

[0001] The present disclosure relates to a power conversion device, a rotating electrical machine system, a power conversion system, and a hydroelectric power generation system. [Background technology]

[0002] Power conversion devices that convert AC to DC or DC to AC are known. The power conversion device has a capacitor that smooths the voltage of the DC link section. When AC power is applied to the power conversion device, an inrush current larger than the rated current of the device occurs to charge the capacitor. Power conversion devices are sometimes provided with a current limiting circuit to suppress the inrush current. Patent Document 1 discloses an inrush current limiting circuit as an example of a current limiting circuit. The inrush current limiting circuit in Patent Document 1 limits the current flowing into the smoothing capacitor of the power supply device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 4-54870 Summary of the Invention [Problem to be solved by the invention]

[0004] A power conversion device may be provided with a power consumption circuit for consuming surplus power. The power consumption circuit is connected to a DC link unit in the power conversion device so as to be arranged in parallel with a capacitor. The power consumption circuit consumes power in a current consumption connection state in which the power consumption circuit is connected so that current flows from the DC link unit to the power consumption circuit. If an AC power source is turned on to the power conversion device while the power consumption circuit is in the current consumption connection state, power will continue to be consumed in the power consumption circuit. This may result in an excessive electrical load being placed on the current limiting circuit. [Means for solving the problem]

[0005] A power conversion device according to a first aspect of the present invention for solving the above problem includes a DC link unit having a capacitor, a connection unit connectable to an AC power supply, a first switch provided between the capacitor and the connection unit, a first conversion circuit provided between the capacitor and the first switch, a current limiting circuit provided between the capacitor and the first switch, a power consumption circuit connected to the DC link unit, and a control unit, wherein the first switch is configured to electrically connect the connection unit and the first conversion circuit in a first on state and to electrically disconnect the connection unit and the first conversion circuit in a first off state, and the current limiting circuit is configured to The control unit can switch between a limited state in which the capacitor and the first switch are connected via a resistor and an unrestricted state in which the capacitor and the first switch are connected without the resistor, and the power consumption circuit can switch between a first state and a second state, the first state being a state in which DC power of the DC link unit is consumed, and the second state being a state in which power consumption is less than the amount of power consumption in the first state or a state in which DC power of the DC link unit is not consumed, and the control unit controls the power consumption circuit to be in the second state when the current limiting circuit is in the limited state.

[0006] This configuration prevents the power consumption circuit from entering the first state when the current limiting circuit is in the limiting state, thereby preventing an excessive electrical load from being applied to the current limiting circuit when the current limiting circuit is in the limiting state, such as when the AC power supply of the power conversion device is turned on.

[0007] A power conversion device of a second aspect is the power conversion device of the first aspect, wherein the control unit is configured to control the power consumption circuit to switch between the first state and the second state of the power consumption circuit, and controls the power consumption circuit so that the power consumption circuit is in the second state when the current limiting circuit is in the limiting state.

[0008] According to this configuration, when the current limiting circuit is in the limiting state, the control unit controls the power consumption circuit to be in the second state, thereby preventing the power consumption circuit from being in the first state when the current limiting circuit is in the limiting state.

[0009] A power conversion device of a third aspect is the power conversion device of the first aspect, further comprising a power supply capable of supplying power to the power consumption circuit, wherein the power consumption circuit operates in the first state or the second state when power is supplied from the power supply, and operates in the second state when power supply from the power supply is stopped, and the control unit stops the power supply from the power supply to the power consumption circuit by controlling the power supply or by controlling a power path between the power supply and the power consumption circuit when the current limiting circuit is in the limiting state.

[0010] According to this configuration, when the current limiting circuit is in the limiting state, the power supply from the power source to the power consumption circuit is stopped. Since the power supply is stopped and the power consumption circuit is in the second state, it is possible to prevent the power consumption circuit from being in the first state when the current limiting circuit is in the limiting state.

[0011] A power conversion device of a fourth aspect is the power conversion device of the first aspect, further comprising a second switch provided between the DC link unit and the power consumption circuit, wherein the control unit is configured to control the second switch to switch between a second on state and a second off state of the second switch, wherein the second switch is configured to electrically connect the DC link unit and the power consumption circuit in the second on state and to electrically disconnect the DC link unit and the power consumption circuit in the second off state, and the control unit controls the second switch to be in the second off state when the current limiting circuit is in the limiting state.

[0012] According to this configuration, when the current limiting circuit is in the limiting state, the control unit controls the second switch to the second off state. This electrically disconnects the DC link unit from the power consumption circuit, preventing the power consumption circuit from consuming DC power from the DC link unit. Therefore, the power consumption circuit can be prevented from being in the first state when the current limiting circuit is in the limiting state.

[0013] A fifth aspect of the power conversion device is the power conversion device of the fourth aspect, further comprising a first current detector that detects a current in a power path between the DC link unit and the power consumption circuit, and the control unit controls the second switch to the second on state based on the current detected by the first current detector being less than or equal to a first current when the current limiting circuit is in the non-limiting state.

[0014] According to this configuration, when the current limiting circuit is in the non-limiting state, the second switch can be switched to the second on state based on the current in the DC link section being equal to or less than the first current.

[0015] A sixth aspect of the power conversion device is the power conversion device of the fourth aspect, further comprising a voltage detector that detects the voltage of the capacitor, and the control unit controls the second switch to the second on state based on the voltage detected by the voltage detector being equal to or greater than a first voltage.

[0016] According to this configuration, the second switch can be switched to the on state when the voltage of the capacitor becomes equal to or higher than the first voltage.

[0017] The power conversion device of a seventh aspect is the power conversion device of the sixth aspect, further comprising an alarm unit that alarms an abnormality in the power conversion device, and the alarm unit alarms the abnormality based on the fact that the voltage detected by the voltage detector after the second switch switches from the second off state to the second on state is smaller than the voltage detected by the voltage detector before the second switch switches from the second off state to the second on state.

[0018] According to this configuration, when the second switch is switched from the second off state to the second on state, the voltage of the capacitor decreases, and based on this, an abnormality in the power conversion device can be detected.

[0019] The power conversion device of an eighth aspect is a power conversion device of any one of the first to seventh aspects, further comprising a first current detector that detects a current in a power path between the DC link unit and the power consumption circuit, and an alarm unit that notifies of an abnormality in the power conversion device, wherein the alarm unit notifies of the abnormality based on the fact that the current detected by the first current detector is greater than the second current when the power consumption circuit is controlled to the second state.

[0020] According to this configuration, when the power consumption circuit is controlled to the second state, an abnormality in the power conversion device can be detected.

[0021] A rotating electric machine system of a ninth aspect that solves this problem comprises a power conversion device of any one of the first to eighth aspects, a second conversion circuit connected to the DC link unit, and a rotating electric machine connected to the second conversion circuit, wherein the second conversion circuit can supply power from the DC link unit to the rotating electric machine, or can supply power from the rotating electric machine to the DC link unit.

[0022] According to this configuration, in a rotating electrical machine system, it is possible to prevent an excessive electrical load from being imposed on the current limiting circuit due to an inrush current.

[0023] A tenth aspect of the hydroelectric power generation system that solves this problem comprises a water turbine arranged in a flow path through which water flows, a generator driven by the water turbine, and the rotating electric machine system of the ninth aspect, wherein the rotating electric machine is the generator, and the second conversion circuit is capable of supplying power from the generator to the DC link section.

[0024] According to this configuration, the electric power generated by the water turbine can be supplied to the power conversion device.

[0025] A power conversion system according to an eleventh aspect for solving the problem is a power conversion system comprising: a DC link unit having a capacitor; a connection unit connectable to an AC power supply; a first switch provided between the capacitor and the connection unit; a first conversion circuit provided between the capacitor and the first switch; a current limiting circuit provided between the capacitor and the first switch; a power consumption circuit connected to the DC link unit; a DC power supply connected to the DC link unit; a control unit; a second current detector that detects a current of the DC power supply; and an alarm unit that notifies of an abnormality in the power conversion system, wherein the first switch is configured to electrically connect the connection unit and the first conversion circuit in a first on state and to electrically disconnect the connection unit and the first conversion circuit in a first off state, and the current limiting circuit is configured to connect the capacitor and the first switch via a resistor in a limiting state and to electrically disconnect the capacitor and the first switch in a second off state. and an unrestricted state in which the switch is connected to the DC link unit without the resistor, the power consumption circuit being capable of switching between a first state and a second state, the first state being a state in which DC power of the DC link unit is consumed, and the second state being a state in which power consumption is less than the amount of power consumption in the first state or a state in which DC power of the DC link unit is not consumed, the control unit controlling the first switch to switch between the first on state and the first off state of the first switch, and controlling the DC power supply to apply a second voltage from the DC power supply to the DC link unit when the first switch is controlled to the first off state, and the notification unit notifying the abnormality based on the fact that the current detected by the second current detector is greater than a third current when the control unit is controlling the DC power supply to apply the second voltage from the DC power supply to the DC link unit.

[0026] When the DC power supply applies a voltage to the DC link unit, if the power consumption circuit is in the first state, the current of the DC power supply becomes large. According to the above configuration, when the DC power supply applies a second voltage to the DC link unit, an abnormality in the power conversion system is notified based on the current of the DC power supply being larger than the third current. The abnormality notification by the notification unit indicates that the power consumption circuit may be in the first state. Since the abnormality notification by the notification unit is performed when the first switch is controlled to the first off state, it is possible to prevent an excessive electrical load from being placed on the current limiting circuit when the first switch is controlled to the on state due to an abnormality in the power conversion system.

[0027] A twelfth aspect of the hydroelectric power generation system that solves this problem comprises a water turbine placed in a flow path through which water flows, a generator driven by the water turbine, a third conversion circuit connected to the generator, a head adjustment device that adjusts the effective head of the water turbine, and the power conversion system of the eleventh aspect, wherein the third conversion circuit is connected to the DC link unit and is capable of supplying power from the generator to the DC link unit, the DC power source includes the generator and the third conversion circuit and is configured to apply the second voltage to the DC link unit when the generator is driven by the water turbine, and the control unit drives the water turbine by adjusting the effective head using the head adjustment device.

[0028] According to this configuration, a reference voltage can be applied to the DC link section by the back electromotive force from the generator. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a block diagram showing the configuration of a hydroelectric power generation system according to a first embodiment. [Figure 2] 2 is a flowchart showing the flow of processing performed by the control unit in FIG. 1. [Figure 3] FIG. 10 is a block diagram showing the configuration of a hydroelectric power generation system according to a second embodiment. [Figure 4] 4 is a flowchart showing the flow of processing performed by the control unit in FIG. 3. [Figure 5]FIG. 10 is a block diagram showing the configuration of a hydroelectric power generation system according to a third embodiment. [Figure 6] 6 is a flowchart showing the flow of processing performed by the control unit in FIG. 5. [Figure 7] FIG. 10 is a block diagram showing the configuration of a hydroelectric power generation system according to a fourth embodiment. [Figure 8] 8 is a flowchart showing the flow of processing performed by the control unit in FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0030] First Embodiment A hydroelectric power generation system 10, a rotating electrical machine system 20, and a power conversion device 30 according to a first embodiment will be described with reference to FIGS.

[0031] <Hydroelectric power generation system> As shown in FIG. 1 , a hydroelectric power generation system 10 is connected to an AC power source 1 of an AC system. The hydroelectric power generation system 10 can switch between grid-connected operation and stand-alone operation. A specific load 3 is connected to the hydroelectric power generation system 10. In grid-connected operation, the hydroelectric power generation system 10 supplies power to the specific load 3 by connecting to the AC system. That is, in grid-connected operation, the specific load 3 can be supplied with either power generated by the hydroelectric power generation system 10 or power supplied from the AC system. In stand-alone operation, the hydroelectric power generation system 10 independently supplies power to the specific load 3. For example, when the AC system cannot supply power to the hydroelectric power generation system 10 due to a power outage or the like, the hydroelectric power generation system 10 supplies power to the specific load 3 in stand-alone operation. Examples of the specific load 3 are factories, schools, hospitals, and homes.

[0032] The hydroelectric power generation system 10 normally performs grid-connected operation with an AC system. The present technology is a technology for suppressing problems that occur when an AC system is connected to the hydroelectric power generation system 10. The present technology will be described below.

[0033] The hydroelectric power generation system 10 includes a water turbine 11, a generator 12, and a rotating electric machine system 20. The water turbine 11 is disposed in a flow path 2 through which water flows. The generator 12 is driven by the water turbine 11. The generator 12 is, for example, a permanent magnet synchronous generator. The generator 12 rotates integrally with the rotating shaft of the water turbine 11. When the rotating shaft of the water turbine 11 rotates, the generator 12 generates electricity.

[0034] <Rotating Electrical Systems> The rotating electrical machine system 20 includes a second conversion circuit 21, a rotating electrical machine 22, and a power conversion device 30.

[0035] The second conversion circuit 21 is connected to a DC link unit 31, which will be described later. The second conversion circuit 21 can supply power from the DC link unit 31 to the rotating electric machine 22, or can supply power from the rotating electric machine 22 to the DC link unit 31. In this embodiment, the second conversion circuit 21 can supply power from at least the rotating electric machine 22, which is the generator 12, to the DC link unit 31. The second conversion circuit 21 is, for example, a converter. The second conversion circuit 21 converts AC power into DC power.

[0036] The rotating electric machine 22 is connected to the second conversion circuit 21. The rotating electric machine 22 in this embodiment is the generator 12. The rotating electric machine 22 receives a supply of electric power from the DC link unit 31 via the second conversion circuit 21. The rotating electric machine 22, which is the generator 12, operates by the supply of electric power from the DC link unit 31. The rotating electric machine 22 supplies electric power to the DC link unit 31 via the second conversion circuit 21. The rotating electric machine 22, which is the generator 12, supplies the generated electric power to the DC link unit 31.

[0037] <Power conversion device> The power conversion device 30 includes a DC link unit 31 , a connection unit 32 , a first switch 33 , a first conversion circuit 34 , a current limiting circuit 35 , a power consumption circuit 36 ​​, and a control unit 37 .

[0038] The DC link unit 31 receives DC power from the second conversion circuit 21. The DC link unit 31 includes a capacitor 38. The capacitor 38 is a smoothing capacitor that smoothes the DC voltage.

[0039] The connection unit 32 can be connected to the AC power source 1. The hydroelectric power generation system 10 is electrically connected to the AC power source 1 via the connection unit 32. When the hydroelectric power generation system 10 is operating independently, the connection unit 32 does not have to be connected to the AC power source 1. As long as the connection unit 32 includes a power line for exchanging power between the hydroelectric power generation system 10 and the AC grid, other components may be omitted.

[0040] The first switch 33 is provided between the capacitor 38 and the connection unit 32. The first switch 33 is configured to electrically connect the connection unit 32 and the first conversion circuit 34 in a first on state and to electrically disconnect the connection unit 32 and the first conversion circuit 34 in a first off state. The first switch 33 is, for example, an electromagnetic switch. The first switch 33 is configured to switch to a first off state when an abnormality in the AC system is detected during grid-connected operation. The abnormality in the AC system is, for example, a power outage.

[0041] The first conversion circuit 34 is provided between the capacitor 38 and the first switch 33. The first conversion circuit 34 can supply power bidirectionally between the capacitor 38 and the first switch 33. The first conversion circuit 34 converts AC power from the AC power source 1 into DC power, or converts DC power from the DC link unit 31 into AC power. The first conversion circuit 34 is, for example, a grid-connected inverter.

[0042] The current limiting circuit 35 is provided between the capacitor 38 and the first switch 33. In the example of FIG. 1, the current limiting circuit 35 is provided between the first conversion circuit 34 and the capacitor 38. The current limiting circuit 35 may also be provided between the first conversion circuit 34 and the first switch 33.

[0043] The current limiting circuit 35 has a first resistor 35a and a first switch 35b. The first resistor 35a is provided between the capacitor 38 and the first switch 33. The first switch 35b is provided in parallel with the first resistor 35a. When the first switch 35b is in an off state, the current flowing between the capacitor 38 and the first switch 33 passes through the first resistor 35a. When the first switch 35b is in an on state, both ends of the first resistor 35a are short-circuited, and therefore the current flowing between the capacitor 38 and the first switch 33 does not pass through the first resistor 35a.

[0044] The current limiting circuit 35 can be switched between a limited state and a non-limited state. In the limited state, the capacitor 38 and the first switch 33 are connected via the first resistor 35a. In the non-connected state, the capacitor 38 and the first switch 33 are connected without the first resistor 35a. In the limited state, the first switch 35b of the current limiting circuit 35 is in the off state, and in the non-limiting state, the first switch 35b of the current limiting circuit 35 is in the on state.

[0045] When the hydroelectric power generation system 10 is connected to the AC power source 1 of the AC system, an excessive current flows to charge the capacitor 38 of the DC link unit 31. This excessive current is also called an inrush current. When the hydroelectric power generation system 10 is connected to the AC power source 1, the current limiting circuit 35 enters a limited state, and the first resistor 35a is inserted between the capacitor 38 and the first switch 33, thereby suppressing the inrush current. For example, the current limiting circuit 35 switches from the limited state to the non-limited state when a predetermined period of time has elapsed since the hydroelectric power generation system 10 was connected to the AC power source 1.

[0046] The power consumption circuit 36 ​​is connected to the DC link unit 31. The power consumption circuit 36 ​​consumes power from the DC link unit 31. If power is supplied from the generator 12 to the DC link unit 31 when the first switch 33 is in the first off state, the voltage of the DC link unit 31 may increase. In such a case, the power consumption circuit 36 ​​consumes the power of the DC link unit 31, thereby suppressing the voltage increase of the DC link unit 31.

[0047] The power consumption circuit 36 ​​has a second resistor 36a and a second switch 36b. The second switch 36b is provided between the second resistor 36a and the DC link unit 31. When the second switch 36b is turned on, the DC link unit 31 and the second resistor 36a are connected, and the power consumption circuit 36 ​​consumes DC power from the DC link unit 31.

[0048] The power consumption circuit 36 ​​can be switched between a first state and a second state. In the first state, the power consumption circuit 36 ​​consumes DC power from the DC link unit 31. In the second state, the power consumption circuit 36 ​​does not consume DC power from the DC link unit 31. In the first state, the second switch 36b of the power consumption circuit 36 ​​is in an ON state, and in the second state, the second switch 36b of the power consumption circuit 36 ​​is in an OFF state.

[0049] For example, during grid-connected operation of the hydroelectric power generation system 10, the power of the generator 12 is supplied to the AC grid and the specific load 3, so the power consumption circuit 36 ​​is in the second state. During independent operation of the hydroelectric power generation system 10, if there is surplus power generated by the generator 12, the power of the generator 12 is consumed, so the power consumption circuit 36 ​​is in the first state.

[0050] The control unit 37 includes an arithmetic processing device such as a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit). The control unit 37 uses built-in memory such as a ROM (Read Only Memory) or RAM (Random Access Memory), a clock, a counter, etc. to execute various programs stored in a ROM or storage unit (not shown), and control the operation of each of the above-mentioned hardware components. The storage unit includes a hard disk, an EEPROM (Electrically Erasable Programmable ROM), a flash memory, or other non-volatile storage device. The storage unit stores various computer programs and data referenced by the control unit 37.

[0051] The power conversion device 30 further includes a first current detector 41 and a notification unit 42.

[0052] The first current detector 41 detects the current in the power path between the DC link unit 31 and the power consumption circuit 36. The first current detector 41 outputs information about the detected current to the control unit 37.

[0053] The alarm unit 42 outputs an alarm signal to output a signal related to an abnormality in the hydroelectric power generation system 10. Based on the output of the alarm unit 42, information related to the abnormality in the hydroelectric power generation system 10 may be output to a device such as a display or a speaker. The alarm unit 42's notification of an abnormality is controlled by the control unit 37. The alarm unit 42 may be configured by an arithmetic processing unit of the control unit 37.

[0054] The notification unit 42 notifies of an abnormality in the power conversion device 30. The abnormality in the power conversion device 30 may be, for example, a short-circuit failure of a switch included in the power conversion device 30. The notification unit 42 notifies of the abnormality based on the current detected by the first current detector 41 being greater than a first predetermined current when the power consumption circuit 36 ​​is controlled to the second state. The first predetermined current is set based on the current flowing through the power consumption circuit 36 ​​when the power consumption circuit 36 ​​is in the second state. The first predetermined current is set to a current that can determine that a current is occurring between the DC link unit 31 and the power consumption circuit 36 ​​even when the power consumption circuit 36 ​​is in the second state. If the current detected by the first current detector 41 is greater than the first predetermined current, there is a risk of an abnormality, such as a short-circuit failure of the second switch 36b of the power consumption circuit 36.

[0055] The power conversion device 30 further includes a power supply 51. The power supply 51 is capable of supplying power to the power consumption circuit 36. The power supply 51 is connected to the power consumption circuit 36 ​​via a power path 52. The power consumption circuit 36 ​​operates by receiving power from the power supply 51. For example, the second switch 36b of the power consumption circuit 36 ​​is a semiconductor switch.

[0056] The power consumption circuit 36 ​​operates in a first state or a second state when power is supplied from the power source 51, and operates in the second state when the power supply from the power source 51 is stopped. Whether the power consumption circuit 36 ​​operates in the first state or the second state when power is supplied from the power source 51 is determined based on a command signal from the control unit 37. When the power supply from the power source 51 is stopped, the power consumption circuit 36 ​​enters the second state. Note that operation in the second state caused by the stop of power supply from the power source 51 includes a state in which the power consumption circuit 36 ​​does not operate electrically.

[0057] <Control unit> The control unit 37 controls the first switch 33 to switch between a first on state and a first off state of the first switch 33. The control unit 37 controls the first switch 33 by outputting a command signal relating to the first on state or the first off state to the first switch 33.

[0058] The control unit 37 of this embodiment controls the current limiting circuit 35 to switch between the limited state and the non-limited state of the current limiting circuit 35. The control unit 37 controls the current limiting circuit 35 by outputting a command signal to the current limiting circuit 35 regarding the limited state or the non-limited state.

[0059] The control unit 37 is configured to control the power consumption circuit 36 ​​to switch between a first state and a second state of the power consumption circuit 36. The control unit 37 controls the power consumption circuit 36 ​​by outputting a command signal to the power consumption circuit 36 ​​regarding the first state or the second state.

[0060] The control unit 37 sets the current limiting circuit 35 to the limiting state before the first switch 33 is set to the first on state. The control unit 37 controls the power consumption circuit 36 ​​to be in the second state when the current limiting circuit 35 is in the limiting state. More specifically, the control unit 37 controls the power consumption circuit 36 ​​to be in the second state when the current limiting circuit 35 is in the limiting state and the first switch 33 is in the first on state. Preferably, the control unit 37 sets the power consumption circuit 36 ​​to the second state before the current limiting circuit 35 is set to the limiting state.

[0061] In this embodiment, the control unit 37 controls the power consumption circuit 36 ​​to enter the second state when the current limiting circuit 35 is in the limited state. For example, when the current limiting circuit 35 switches from the non-limited state to the limited state, the control unit 37 outputs a command signal to the power consumption circuit 36 ​​to enter the second state.

[0062] <Pre-setting process> The first switch 33 is switched from the first on state to the first off state when the hydroelectric power generation system 10 is disconnected from the AC power supply 1 of the AC system. As a specific example, the first switch 33 is switched from the first on state to the first off state when the AC system experiences a power outage. Alternatively, the first switch 33 is switched from the first on state to the first off state when the AC power supply 1 is repaired.

[0063] The control unit 37 switches the first switch 33 from a first off state to a first on state, for example, when starting grid-connected operation by connecting the hydroelectric power generation system 10 to the AC power source 1. The control unit 37 performs a pre-setting process when switching the first switch 33 from the first off state to the first on state. In the pre-setting process, the control unit 37 switches the current limiting circuit 35 to the limiting state and switches the power consumption circuit 36 ​​to the second state.

[0064] The process performed by the control unit 37 of this embodiment will be described with reference to Fig. 2. For example, the control unit 37 repeats the process of Fig. 2 at predetermined time intervals during independent operation.

[0065] In step S11, the control unit 37 determines whether or not an ON command for the first switch 33 has been input. The ON command for the first switch 33 is a command requesting the control unit 37 to set the first switch 33 to the first ON state. For example, when the hydroelectric power generation system 10 switches from independent operation to grid-connected operation, the ON command for the first switch 33 is input to the control unit 37. If an ON command for the first switch 33 has been input, the control unit 37 proceeds to step S12. If an ON command for the first switch 33 has not been input, the control unit 37 ends the processing of FIG. 2.

[0066] In step S12, the control unit 37 switches the power consumption circuit 36 ​​to the second state, and then the process proceeds to step S 13. The control unit 37 outputs a command signal to the power consumption circuit 36 ​​to switch to the second state.

[0067] In step S13, the control unit 37 switches the current limiting circuit 35 to the limiting state, and then proceeds to step S14. In step S14, the control unit 37 switches the first switch 33 to the first on state, and then proceeds to step S15.

[0068] In step S15, the control unit 37 determines whether the current between the DC link unit 31 and the power consumption circuit 36 ​​is equal to or less than a first predetermined current. The control unit 37 acquires the current between the DC link unit 31 and the power consumption circuit 36 ​​from the first current detector 41. If the current between the DC link unit 31 and the power consumption circuit 36 ​​is equal to or less than the first predetermined current, the control unit 37 ends the processing in FIG. 2. If the current between the DC link unit 31 and the power consumption circuit 36 ​​is not equal to or less than the first predetermined current, that is, if the current in the DC link unit 31 is greater than the first predetermined current, the control unit 37 causes the notification unit 42 to notify of an abnormality in step S16, and then ends the processing in FIG. 2.

[0069] <Operation of the embodiment> The operation of this embodiment will be described. When the first switch 33 is switched to the first on state, the control unit 37 switches the current limiting circuit 35 to the limiting state to suppress inrush current. If the power consumption circuit 36 ​​is in the first state at this time, current continues to flow through the second resistor 36a of the power consumption circuit 36, which may cause a problem of excessive electrical load being placed on the current limiting circuit 35. In the power conversion device 30 of this embodiment, when the current limiting circuit 35 is in the limiting state, the power consumption circuit 36 ​​is controlled to be in the second state. Specifically, the control unit 37 of this embodiment switches the current limiting circuit 35 to the limiting state and the power consumption circuit 36 ​​to the second state, and then switches the first switch 33 to the first on state. Because the second resistor 36a of the power consumption circuit 36 ​​is not connected to the DC link unit 31, excessive electrical load is less likely to be placed on the current limiting circuit 35.

[0070] <Effects of the embodiment> The effects of this embodiment will be described. (1-1) The power conversion device 30 includes a DC link unit 31, a connection unit 32, a first switch 33, a first conversion circuit 34, a current limiting circuit 35, a power consumption circuit 36, and a control unit 37. The DC link unit 31 includes a capacitor 38. The connection unit 32 is connectable to an AC power source 1. The first switch 33 is provided between the capacitor 38 and the connection unit 32. The first conversion circuit 34 is provided between the capacitor 38 and the first switch 33. The current limiting circuit 35 is provided between the capacitor 38 and the first switch 33. The power consumption circuit 36 ​​is connected to the DC link unit 31. The first switch 33 is configured to electrically connect the connection unit 32 and the first conversion circuit 34 in a first on state and to electrically disconnect the connection unit 32 and the first conversion circuit 34 in a first off state. The current limiting circuit 35 can be switched between a limiting state and a non-limiting state. The limiting state is a state in which the capacitor 38 and the first switch 33 are connected via a resistor. The non-connecting state is a state in which the capacitor 38 and the first switch 33 are connected without a resistor. The power consumption circuit 36 ​​can switch between a first state and a second state. The first state is a state in which the DC power of the DC link unit 31 is consumed. The second state is a state in which the DC power of the DC link unit 31 is not consumed. The control unit 37 controls the power consumption circuit 36 ​​to be in the second state when the current limiting circuit 35 is in the limiting state.

[0071] This configuration prevents the power consumption circuit 36 ​​from entering the first state when the current limiting circuit 35 is in the limiting state. Therefore, when the current limiting circuit 35 is in the limiting state, such as when the AC power supply of the power conversion device 30 is turned on, it is possible to prevent an excessive electrical load from being applied to the current limiting circuit 35.

[0072] (1-2) The control unit 37 is configured to control the power consumption circuit 36 ​​to switch between a first state and a second state of the power consumption circuit 36. The control unit 37 controls the power consumption circuit 36 ​​so that the power consumption circuit 36 ​​is in the second state when the current limiting circuit 35 is in the limiting state.

[0073] According to this configuration, when the current limiting circuit 35 is in the limiting state, the control unit 37 controls the power consumption circuit 36 ​​to be in the second state. Therefore, when the current limiting circuit 35 is in the limiting state, the power consumption circuit 36 ​​can be prevented from being in the first state.

[0074] (1-3) The power conversion device 30 further includes a first current detector 41 and a notification unit 42. The first current detector 41 detects a current in a power path between the DC link unit 31 and the power consumption circuit 36. The notification unit 42 notifies of an abnormality in the power conversion device 30. When the power consumption circuit 36 ​​is controlled to the second state, the notification unit 42 notifies of the abnormality based on the fact that the current detected by the first current detector 41 is greater than a first predetermined current.

[0075] According to this configuration, when the power consumption circuit 36 ​​is controlled to the second state, an abnormality in the power conversion device 30 can be detected.

[0076] (1-4) The rotating electric machine system 20 includes a power conversion device 30, a second conversion circuit 21, and a rotating electric machine 22. The second conversion circuit 21 is connected to a DC link unit 31. The rotating electric machine 22 is connected to the second conversion circuit 21. The second conversion circuit 21 can supply power from the DC link unit 31 to the rotating electric machine 22, or can supply power from the rotating electric machine 22 to the DC link unit 31.

[0077] According to this configuration, in the rotating electrical machine system 20, it is possible to prevent an excessive electrical load from being imposed on the current limiting circuit 35 due to an inrush current.

[0078] (1-5) The hydroelectric power generation system 10 includes a water turbine 11, a generator 12, and a rotating electric machine system 20. The water turbine 11 is disposed in a flow path 2 through which water flows. The generator 12 is driven by the water turbine 11. The rotating electric machine 22 is the generator 12. The second conversion circuit 21 can supply power from the generator 12 to a DC link unit 31.

[0079] According to this configuration, the electric power generated by the water turbine 11 can be supplied to the power conversion device 30.

[0080] Second Embodiment 3 and 4, a hydroelectric power generation system 10, a rotating electrical machine system 20, and a power conversion device 30 according to the second embodiment will be described. Components in this embodiment that are common to the first embodiment will be assigned the same reference numerals as in the first embodiment, and duplicated descriptions will be omitted.

[0081] In the first embodiment, the control unit 37 directly controls the power consumption circuit 36 ​​so that the power consumption circuit 36 ​​is in the second state when the current limiting circuit 35 is in the limited state. The control unit 37 of the present embodiment controls the power path 52 to control the power consumption circuit 36 ​​so that the power consumption circuit 36 ​​is in the second state when the current limiting circuit 35 is in the limited state.

[0082] The control unit 37 of this embodiment is configured to control a power path 52 between the power supply 51 and the power consumption circuit 36. A power switch 52a is provided in the power path 52. When the power switch 52a is in the on state, power is supplied from the power consumption circuit 36 ​​to the power supply 51. When the power switch 52a is in the off state, power is not supplied from the power consumption circuit 36 ​​to the power supply 51. The control unit 37 controls the power path 52 by outputting a command signal regarding the on state or off state to the power switch 52a.

[0083] When the current limiting circuit 35 is in the limited state, the control unit 37 controls the power path 52 to stop the power supply from the power source 51 to the power consumption circuit 36. This switches the power consumption circuit 36 ​​to the second state. When the current limiting circuit 35 is in the limited state, the control unit 37 controls the power switch 52a of the power path 52 to the off state to stop the power supply from the power source 51 to the power consumption circuit 36. For example, the control unit 37 switches the power switch 52a to the off state before switching the first switch 33 to the on state. For example, the control unit 37 switches the power switch 52a to the on state when a first period has elapsed since the first switch 33 was switched to the on state. The first period is, for example, the period during which the flow of inrush current due to connection to the AC power source 1 ends.

[0084] The power consumption circuit 36 ​​is configured to be maintained in the second state because the second switch 36b is in the off state even when the power switch 52a is switched from the off state to the on state. Even if the control unit 37 switches the first switch 33 to the on state and then switches the power switch 52a to the on state, the power consumption circuit 36 ​​remains in the second state. The power consumption circuit 36 ​​is switched to the first state based on a command signal from the control unit 37.

[0085] The process performed by the control unit 37 of this embodiment will be described with reference to FIG. In step S21, the control unit 37 determines whether or not an ON command has been input for the first switch 33. If an ON command for the first switch 33 has been input, the control unit 37 proceeds to step S22. If an ON command for the first switch 33 has not been input, the control unit 37 ends the processing of FIG.

[0086] In step S22, the control unit 37 switches the power switch 52a to the OFF state, and then proceeds to step S23. The control unit 37 outputs a command signal to the power switch 52a to switch it to the OFF state. When the power switch 52a of the power path 52 switches to the OFF state, the power consumption circuit 36 ​​switches to the second state.

[0087] In step S23, the control unit 37 switches the current limiting circuit 35 to the limiting state, and then proceeds to step S24. In step S24, the control unit 37 switches the first switch 33 to the first on state, and then proceeds to step S25. In step S25, the control unit 37 determines whether a first period has elapsed since the first switch 33 was switched to the first on state. The control unit 37 has, for example, a timer function that measures the period since the first switch 33 was switched to the first on state. The control unit 37 repeats the processing of step S25 until the first period has elapsed. If the first period has elapsed in step S25, the control unit 37 proceeds to step S26. In step S26, the control unit 37 switches the power switch 52a to the on state, and then proceeds to step S27. The control unit 37 outputs a command signal to the power switch 52a to switch it to the on state. It should be noted that even if the power switch 52a is switched to the on state in step S26, the power consumption circuit 36 ​​remains in the second state.

[0088] In step S27, the control unit 37 determines whether the current between the DC link unit 31 and the power consumption circuit 36 ​​is equal to or less than a first predetermined current. If the current between the DC link unit 31 and the power consumption circuit 36 ​​is equal to or less than the first predetermined current, the control unit 37 ends the processing in Fig. 4. If the current between the DC link unit 31 and the power consumption circuit 36 ​​is not equal to or less than the first predetermined current, the control unit 37 causes the notification unit 42 to notify of an abnormality in step S28, and then ends the processing in Fig. 4.

[0089] <Effects of the embodiment> The effects of this embodiment will be described. (2) The power conversion device 30 includes a power supply 51. The power supply 51 is capable of supplying power to a power consumption circuit 36. The power consumption circuit 36 ​​operates in a first state or a second state when power is supplied from the power supply 51, and operates in the second state when the power supply 51 stops supplying power. When the current limiting circuit 35 is in the limiting state, the control unit 37 stops the power supply from the power supply 51 to the power consumption circuit 36 ​​by controlling the power supply 51 or the power path 52 between the power supply 51 and the power consumption circuit 36.

[0090] According to this configuration, when the current limiting circuit 35 is in the limited state, the power supply from the power supply 51 to the power consumption circuit 36 ​​is stopped. Since the power supply is stopped, the power consumption circuit 36 ​​enters the second state, and therefore, when the current limiting circuit 35 is in the limited state, the power consumption circuit 36 ​​can be prevented from being in the first state.

[0091] <Third embodiment> 5 and 6, a hydroelectric power generation system 10, a rotating electrical machine system 20, and a power conversion device 30 according to a third embodiment will be described. Components in this embodiment that are common to the first embodiment will be assigned the same reference numerals as in the first embodiment, and duplicated descriptions will be omitted.

[0092] The power conversion device 30 of this embodiment includes a second switch 61 and a voltage detector 62. The second switch 61 is provided between the DC link unit 31 and the power consumption circuit 36. The second switch 61 is configured to electrically connect the DC link unit 31 and the power consumption circuit 36 ​​in a second on state and to electrically disconnect the DC link unit 31 and the power consumption circuit 36 ​​in a second off state. The second switch 61 is, for example, an electromagnetic switch.

[0093] The voltage detector 62 detects the voltage of the capacitor 38. The voltage of the capacitor 38 may be the voltage across both ends of the capacitor 38, or the voltage of the power path of the DC link unit 31 may be detected as the voltage of the capacitor 38. The voltage detector 62 outputs information related to the detected voltage to the control unit 37.

[0094] The control unit 37 is configured to control the second switch 61 to switch between a second on state and a second off state of the second switch 61. The control unit 37 controls the second switch 61 by outputting a command signal relating to the second on state or the second off state to the second switch 61.

[0095] The control unit 37 controls the second switch 61 to be in the second off state when the current limiting circuit 35 is in the limiting state. When the second switch 61 is in the second off state, the DC link unit 31 and the power consumption circuit 36 ​​are electrically disconnected, and the power consumption circuit 36 ​​is in the second state. For example, when a second period has elapsed since the control unit 37 switched the second switch 61 to the second off state, the control unit 37 switches the second switch 61 to the on state. The second period is, for example, a period during which the flow of inrush current due to connection with the AC power source 1 ends.

[0096] The power consumption circuit 36 ​​is configured to be maintained in the second state because the second switch 36b is in the off state even when the second switch 61 is switched from the off state to the on state. The power consumption circuit 36 ​​is switched to the first state based on a command signal from the control unit 37.

[0097] The control unit 37 controls the second switch 61 to enter the second on state based on the voltage of the capacitor 38 when the second switch 61 is in the second off state. The control unit 37 controls the second switch 61 to enter the second on state based on the voltage detected by the voltage detector 62 being equal to or higher than a first predetermined voltage. The first predetermined voltage is a voltage at which it can be determined that the capacitor 38 is charged. Preferably, the control unit 37 controls the second switch 61 to enter the second on state based on the voltage detected by the voltage detector 62 being equal to or higher than the first predetermined voltage when the current limiting circuit 35 is in the non-limiting state.

[0098] The post-switching voltage is defined as the voltage of the capacitor 38 after the second switch 61 switches from the second off state to the second on state. The pre-switching voltage is defined as the voltage of the capacitor 38 before the second switch 61 switches from the second off state to the second on state. The control unit 37 determines that an abnormality has occurred in the power consumption circuit 36 ​​when the post-switching voltage is lower than the pre-switching voltage. The notification unit 42 notifies of the abnormality based on the fact that the post-switching voltage is lower than the pre-switching voltage. The notification unit 42 notifies of the abnormality based on a command signal from the control unit 37.

[0099] The second switch 36b of the power consumption circuit 36 ​​is configured to be in the off state when the second switch 61 is in the second off state. Furthermore, even if the second switch 61 switches from the second off state to the first on state, the second switch 36b of the power consumption circuit 36 ​​is configured to maintain the off state unless a command signal is received from the control unit 37. Therefore, even if the second switch 61 switches from the second off state to the second on state, the power consumption circuit 36 ​​does not consume power, so the post-switching voltage becomes equal to the pre-switching voltage or becomes greater than the pre-switching voltage. An example of an abnormality caused by the post-switching voltage being lower than the pre-switching voltage is a short-circuit abnormality of the second switch 36b of the power consumption circuit 36.

[0100] The presetting process performed by the control unit 37 of this embodiment will be described with reference to FIG. In step S31, the control unit 37 determines whether or not an ON command has been input for the first switch 33. If an ON command for the first switch 33 has been input, the control unit 37 proceeds to step S32. If an ON command for the first switch 33 has not been input, the control unit 37 ends the processing of FIG.

[0101] In step S32, the control unit 37 switches the second switch 61 to the second off state, and then proceeds to step S33. The control unit 37 outputs a command signal to the second switch 61 to switch to the second off state. When the second switch 61 of the power path 52 switches to the second off state, the power consumption circuit 36 ​​switches to the second state.

[0102] In step S33, the control unit 37 switches the current limiting circuit 35 to the limiting state, and then proceeds to step S34. In step S34, the control unit 37 switches the first switch 33 to the first on state, and then proceeds to step S35. In step S35, the control unit 37 determines whether a second period has elapsed since the first switch 33 was switched to the first on state. The control unit 37 repeats the processing of step S35 until the second period has elapsed. If the second period has elapsed in step S35, the control unit 37 proceeds to step S36. In step S36, the control unit 37 switches the second switch 61 to the second on state, and then proceeds to step S37.

[0103] In step S37, the control unit 37 determines whether the post-switching voltage is equal to or greater than the pre-switching voltage. For example, the control unit 37 acquires the pre-switching voltage from the voltage detector 62 before the processing of step S36, and acquires the post-switching voltage from the voltage detector 62 after the processing of step S36. If the post-switching voltage is equal to or greater than the pre-switching voltage, the control unit 37 ends the processing of Fig. 6. If the post-switching voltage is not equal to or greater than the pre-switching voltage, that is, if the post-switching voltage is smaller than the pre-switching voltage, the control unit 37 causes the notification unit 42 to notify of an abnormality in step S38, and then ends the processing of Fig. 6.

[0104] <Effects of the embodiment> The effects of this embodiment will be described. (3-1) The power conversion device 30 further includes a second switch 61. The second switch 61 is provided between the DC link unit 31 and the power consumption circuit 36. The control unit 37 is configured to control the second switch 61 to switch between a second on state and a second off state of the second switch 61. The second switch 61 is configured to electrically connect the DC link unit 31 and the power consumption circuit 36 ​​in the second on state and to electrically disconnect the DC link unit 31 and the power consumption circuit 36 ​​in the second off state. The control unit 37 controls the second switch 61 so that the second switch 61 is in the second off state when the current limiting circuit 35 is in the limiting state.

[0105] According to this configuration, when the current limiting circuit 35 is in the limiting state, the control unit 37 controls the second switch 61 to be in the second off state. This electrically disconnects the DC link unit 31 and the power consumption circuit 36, preventing the power consumption circuit 36 ​​from consuming DC power from the DC link unit 31. Therefore, it is possible to prevent the power consumption circuit 36 ​​from being in the first state when the current limiting circuit 35 is in the limiting state.

[0106] (3-2) The power conversion device 30 further includes a voltage detector 62. The voltage detector 62 detects the voltage of the capacitor 38. The control unit 37 controls the second switch 61 to be in the second on state based on the voltage detected by the voltage detector 62 being equal to or higher than the first predetermined voltage.

[0107] According to this configuration, the second switch 61 can be switched to the on state when the voltage of the capacitor 38 becomes equal to or higher than the first predetermined voltage.

[0108] (3-3) The power conversion device 30 includes a notification unit 42. The notification unit 42 notifies of an abnormality in the power conversion device 30. The notification unit 42 notifies of the abnormality based on the fact that the voltage detected by the voltage detector 62 after the second switch 61 switches from the second off state to the second on state is lower than the voltage detected by the voltage detector 62 before the second switch 61 switches from the second off state to the second on state.

[0109] According to this configuration, when the second switch 61 is switched from the second off state to the second on state, the voltage of the capacitor 38 decreases, and therefore an abnormality in the power conversion device 30 can be detected.

[0110] <Fourth embodiment> 7 and 8, a hydroelectric power generation system 10, a rotating electrical machine system 20, and a power conversion device 30 according to a fourth embodiment will be described. Components in this embodiment that are common to the first embodiment will be assigned the same reference numerals as in the first embodiment, and duplicated descriptions will be omitted.

[0111] In this embodiment, before the first switch 33 is switched to the first on state, an abnormality is notified based on the back electromotive force from the generator 12. The hydroelectric power generation system 10 of this embodiment includes a water turbine 11, a generator 12, a third conversion circuit 71, a head adjustment device 72, and a power conversion system 73.

[0112] The third conversion circuit 71 of this embodiment is connected to the generator 12. The third conversion circuit 71 is connected to the DC link unit 31. The third conversion circuit 71 can supply power from the generator 12 to the DC link unit 31. The third conversion circuit 71 does not necessarily have to supply power from the DC link unit 31 to the generator 12. The third conversion circuit 71 of this embodiment is configured similarly to the second conversion circuit 21 of the first embodiment.

[0113] The head adjustment device 72 adjusts the effective head of the water turbine 11. The head adjustment device 72 is, for example, an electric valve. The head adjustment device 72 is composed of an inlet valve 72a arranged in the flow path 2 and an electric motor 72b that drives the inlet valve 72a. Opening the inlet valve 72a increases the flow rate of the flow path 2, and closing the inlet valve 72a decreases the flow rate of the flow path 2.

[0114] <Power conversion system> The power conversion system 73 is a system that combines the power conversion device 30 and a DC power supply 75. The power conversion system 73 converts the power of the DC power supply 75 using the power conversion device 30 and outputs the converted power. The DC power supply 75 includes a generator 12 and a third conversion circuit 71. The DC power supply 75 is connected to the DC link unit 31. The DC power supply 75 supplies power generated by the generator 12 to the DC link unit 31 via the third conversion circuit 71. The DC power supply 75 is configured to apply a second predetermined voltage to the DC link unit 31 when the generator 12 is driven by the water turbine 11.

[0115] Specifically, the power conversion system 73 includes a DC link unit 31, a connection unit 32, a first switch 33, a first conversion circuit 34, a current limiting circuit 35, a power consumption circuit 36, a DC power supply 75, a control unit 37, a second current detector 76, and an alarm unit 42.

[0116] The second current detector 76 detects the current of the DC power supply 75. The current detected by the second current detector 76 is a current on the DC power supply 75 side of the part to which the power consumption circuit 36 ​​is connected in the power path connecting the DC power supply 75 and the DC link unit 31. The second current detector 76 outputs information related to the detected current to the control unit 37.

[0117] The control unit 37 of this embodiment controls the DC power supply 75. When the first switch 33 is controlled to be in the first off state, the control unit 37 controls the DC power supply 75 to apply a second predetermined voltage to the DC link unit 31 from the DC power supply 75. When the first switch 33 is in the first off state, the control unit 37 applies the second predetermined voltage to the DC power supply 75. The control unit 37 controls the head adjusting device 72 to control the DC power supply 75 to apply the second predetermined voltage to the DC link unit 31.

[0118] The control of the DC power supply 75 by the control unit 37 is performed by the control unit 37 controlling the head adjusting device 72. The control unit 37 drives the water turbine 11 by adjusting the effective head using the head adjusting device 72. The control unit 37 drives the water turbine 11 by controlling the valve opening of the inlet valve 72a of the head adjusting device 72. When the water turbine 11 is driven, a back electromotive force is generated in the generator 12. The control unit 37 controls the head adjusting device 72 so that the back electromotive force of the generator 12 becomes a second predetermined voltage. The control unit 37 obtains the back electromotive force of the generator 12 based on, for example, the rotation speed of the generator 12.

[0119] The second predetermined voltage is applied before the first switch 33 is switched from the first off state to the first on state. The control unit 37 causes the notification unit 42 to notify the occurrence of an abnormality based on the fact that the current detected by the second current detector 76 while the second predetermined voltage is being applied to the DC link unit 31 is greater than the second predetermined current.

[0120] The notification unit 42 of this embodiment notifies of an abnormality in the power conversion system 73. In this embodiment, the abnormality in the power conversion system 73 is, for example, the power consumption circuit 36 ​​being in the first state. The abnormality in the power conversion system 73 may include an abnormality such as a short-circuit failure of the second switch 36b of the power consumption circuit 36.

[0121] The notification unit 42 notifies of an abnormality based on the fact that the current detected by the second current detector 76 is greater than the second predetermined current when the control unit 37 controls the DC power supply 75 to apply the second predetermined voltage from the DC power supply 75 to the DC link unit 31. The second predetermined current is smaller than the current generated in the DC power supply 75 when the second predetermined voltage is applied to the DC link unit 31 when the power consumption circuit 36 ​​is in the first state. The second predetermined current is larger than the current generated in the DC power supply 75 when the second predetermined voltage is applied to the DC link unit 31 when the power consumption circuit 36 ​​is in the second state. When the power consumption circuit 36 ​​is in the second state, the current of the DC power supply 75 becomes larger than the second predetermined current, and therefore the notification unit 42 notifies of an abnormality.

[0122] The process performed by the control unit 37 of this embodiment will be described with reference to FIG. In step S41, the control unit 37 determines whether or not an ON command for the first switch 33 has been input. If an ON command for the first switch 33 has been input, the control unit 37 proceeds to step S42. If an ON command for the first switch 33 has not been input, the control unit 37 ends the processing of FIG. 8. In step S42, the control unit 37 switches the power consumption circuit 36 ​​to the second state, and then proceeds to step S43.

[0123] In step S43, the head adjusting device 72 is opened, and then the process proceeds to step S44. The opening operation of the head adjusting device 72 is an operation to open the inlet valve 72a of the head adjusting device 72. The control unit 37 continues to increase the valve opening degree until the opening operation of the head adjusting device 72 is stopped in step S45, which will be described later.

[0124] In step S44, it is determined whether the rotation speed of the generator 12 is equal to or greater than a predetermined rotation speed. The predetermined rotation speed is the rotation speed at which the generator 12 generates a second predetermined voltage. If the rotation speed of the generator 12 is not equal to or greater than the predetermined rotation speed, that is, if the rotation speed of the generator 12 is lower than the predetermined rotation speed, the control unit 37 repeats the process of step S44. If the rotation speed of the generator 12 is equal to or greater than the predetermined rotation speed, the control unit 37 proceeds to step S45. In step S45, the control unit 37 stops the opening operation of the head adjusting device 72, and then proceeds to step S46. At the stage of step S45, the second predetermined voltage is applied to the DC link unit 31.

[0125] In step S46, the control unit 37 determines whether the current of the DC power supply 75 is equal to or less than a second predetermined current. The control unit 37 acquires the current of the DC power supply 75 from the second current detector 76. If the current of the DC power supply 75 is equal to or less than the second predetermined current, the control unit 37 proceeds to step S47. If the current of the DC power supply 75 is not equal to or less than the second predetermined current, that is, if the current of the DC power supply 75 is greater than the second predetermined current, the control unit 37 causes the notification unit 42 to notify of an abnormality in step S49, and then ends the processing of FIG. 8. This abnormality may be, for example, that the power consumption circuit 36 ​​is in the first state when the first switch 33 is to be set to the first on state.

[0126] In step S47, the control unit 37 switches the current limiting circuit 35 to the limiting state, and then proceeds to step S48. In step S48, the control unit 37 switches the first switch 33 to the first on state, and then ends the processing in FIG.

[0127] <Operation of the embodiment> The operation of this embodiment will be described. In this embodiment, when the first switch 33 is in the first off state, a second predetermined voltage is applied from the DC power supply 75 to the DC link unit 31. The notification unit 42 notifies of an abnormality when the current of the DC power supply 75 due to the second predetermined voltage is greater than the second predetermined current. For example, when the power consumption circuit 36 ​​is in the first state, the current of the DC power supply 75 becomes greater than the second predetermined current. Therefore, when the power consumption circuit 36 ​​is in the first state, the first switch 33 is prevented from entering the first on state.

[0128] <Effects of the embodiment> The effects of this embodiment will be described. (4-1) The power conversion system 73 includes a DC link unit 31, a connection unit 32, a first switch 33, a first conversion circuit 34, a current limiting circuit 35, a power consumption circuit 36, a DC power supply 75, a control unit 37, a second current detector 76, and an alarm unit 42. The DC link unit 31 includes a capacitor 38. The connection unit 32 is connectable to an AC power supply 1. The first switch 33 is provided between the capacitor 38 and the connection unit 32. The first conversion circuit 34 is provided between the capacitor 38 and the first switch 33. The current limiting circuit 35 is provided between the capacitor 38 and the first switch 33. The power consumption circuit 36 ​​is connected to the DC link unit 31. The DC power supply 75 is connected to the DC link unit 31. The second current detector 76 detects the current of the DC power supply 75. The alarm unit 42 alerts of an abnormality in the power conversion system 73. The first switch 33 is configured to electrically connect the connection unit 32 and the first conversion circuit 34 in a first on state and to electrically disconnect the connection unit 32 and the first conversion circuit 34 in a first off state. The current limiting circuit 35 can switch between a limited state and an unlimited state. The limited state is a state in which the capacitor 38 and the first switch 33 are connected via a resistor. The unlimited state is a state in which the capacitor 38 and the first switch 33 are connected without a resistor. The power consuming circuit 36 ​​can switch between a first state and a second state. The first state is a state in which the DC power of the DC link unit 31 is consumed. The second state is a state in which the DC power of the DC link unit 31 is not consumed. The control unit 37 controls the first switch 33 to switch between the first on state and the first off state of the first switch 33. When the first switch 33 is controlled to the first off state, the control unit 37 controls the DC power supply 75 to apply a second predetermined voltage from the DC power supply 75 to the DC link unit 31. When the control unit 37 controls the DC power supply 75 to apply the second predetermined voltage from the DC power supply 75 to the DC link unit 31, the notification unit 42 notifies of an abnormality based on the fact that the current detected by the second current detector 76 is larger than the second predetermined current.

[0129] If the power consumption circuit 36 ​​is in the first state when the DC power supply 75 applies a voltage to the DC link unit 31, the current of the DC power supply 75 increases. According to the above configuration, when the DC power supply 75 applies the second predetermined voltage to the DC link unit 31, an abnormality in the power conversion system 73 is notified based on the current of the DC power supply 75 being greater than the second predetermined current. The abnormality notification by the notification unit 42 indicates that the power consumption circuit 36 ​​may be in the first state. Because the abnormality notification by the notification unit 42 is performed when the first switch 33 is controlled to the first off state, it is possible to prevent an excessive electrical load from being applied to the current limiting circuit 35 when the first switch 33 is controlled to the on state due to an abnormality in the power conversion system 73.

[0130] (4-2) The hydroelectric power generation system 10 includes a water turbine 11, a generator 12, a third conversion circuit 71, a head adjustment device 72, and a power conversion system 73. The water turbine 11 is disposed in a flow path 2 through which water flows. The generator 12 is driven by the water turbine 11. The third conversion circuit 71 is connected to the generator 12. The head adjustment device 72 adjusts the effective head of the water turbine 11. The third conversion circuit 71 is connected to the DC link unit 31 and can supply power from the generator 12 to the DC link unit 31. The DC power supply 75 includes the generator 12 and the third conversion circuit 71 and is configured to apply a second predetermined voltage to the DC link unit 31 when the generator 12 is driven by the water turbine 11. The control unit 37 drives the water turbine 11 by adjusting the effective head using the head adjustment device 72.

[0131] According to this configuration, a reference voltage can be applied to the DC link unit 31 by the counter electromotive force from the generator 12 .

[0132] <Modification> In addition to the above-described embodiments, the hydroelectric power generation system 10, rotating electric machine system 20, and power conversion device 30 disclosed herein may also be configured in a form that combines, for example, the modified examples shown below, or at least two modified examples that are not mutually contradictory.

[0133] In each embodiment, the specific load 3 is connected to the hydroelectric power generation system 10, but the specific load 3 may be connected to the AC system. In this modification, the power generated by the hydroelectric power generation system 10 is supplied to the specific load 3 via the AC system.

[0134] The switching of the current limiting circuit 35 between the limited state and the non-limited state may be controlled by a control unit other than the control unit 37. The control unit other than the control unit 37 includes an arithmetic processing unit such as a CPU or a GPU. The control unit other than the control unit 37 switches the current limiting circuit 35 to the limited state based on the control unit 37 switching the first switch 33 to the first on state. The control unit other than the control unit 37 switches the current limiting circuit 35 to the non-limited state after a predetermined period has elapsed since the first switch 33 switched to the first on state. In this modification, for example, step S14 may be omitted from the processing in FIG. 2.

[0135] In each embodiment, the rotating electric machine 22 is described as the generator 12, but the rotating electric machine 22 may be a motor that performs regeneration. The rotating electric machine 22 of this modification supplies regenerated power to the DC link unit 31. The regenerated power is consumed, for example, in the power consumption circuit 36.

[0136] Although the second state in each embodiment is a state in which no DC power is consumed by the DC link unit 31, the second state may be a state in which the amount of power consumed is less than the amount of power consumed in the first state. In this modification, the power consumption circuit 36 ​​may consume the DC power of the DC link unit 31 to such an extent that no load due to an inrush current is applied to the current limiting circuit 35 in the second state, or the effect of the electrical load on the current limiting circuit 35 is negligible.

[0137] In each embodiment, the abnormality reported by the notification unit 42 has been described as a short-circuit fault of the second switch 36b of the power consumption circuit 36, but the notification unit 42 may also report an abnormality other than that of the power consumption circuit 36. Examples of abnormalities other than that of the power consumption circuit 36 ​​include an abnormality in the second conversion circuit 21, an abnormality in the power path connecting the various components, an abnormality in the second switch 61, etc.

[0138] In the second embodiment, the control unit 37 may be configured to be able to control the start and stop of power supply from the power supply 51. Instead of controlling the power path 52, the control unit 37 of this modification may stop the power supply from the power supply 51 to the power consumption circuit 36 ​​by directly controlling the power supply 51 when the current limiting circuit 35 is in the limited state.

[0139] In the second embodiment, the control unit 37 controls the power switch 52a to the ON state when the first period has elapsed since the first switch 33 was placed in the first ON state. The control unit 37 may also control the power switch 52a to the ON state when the voltage of the capacitor 38 becomes equal to or higher than a first predetermined voltage after the first switch 33 was placed in the first ON state. The control unit 37 obtains the voltage of the capacitor 38 using, for example, a voltage detector similar to the voltage detector 62 of the third embodiment.

[0140] In the third embodiment, the control unit 37 controls the second switch 61 to enter the second on state based on the voltage detected by the voltage detector 62 being equal to or greater than the first predetermined voltage. The control unit 37 may also control the second switch 61 to enter the second on state based on the current detected by the first current detector 41 being equal to or less than the third predetermined current when the current limiting circuit 35 is in the non-limiting state. The third predetermined current is set based on the current generated in the DC link unit 31 after the inrush current caused by the first switch 33 entering the first on state has ceased to flow. With this configuration, the second switch 61 can be switched to the second on state based on the current in the DC link unit 31 being equal to or less than the third predetermined current when the current limiting circuit 35 is in the non-limiting state.

[0141] In the third embodiment, the control unit 37 controls the second switch 61 to the second on state when the second period has elapsed since the first switch 33 was set to the first on state. The control unit 37 may also control the power switch 52a to the on state when the voltage of the capacitor 38 becomes equal to or higher than a first predetermined voltage after the first switch 33 was set to the first on state. The control unit 37 obtains the voltage of the capacitor 38 using, for example, the voltage detector 62.

[0142] In the third embodiment, the notification unit 42 notifies of an abnormality when the post-switching voltage is lower than the pre-switching voltage, but the notification unit 42 may also notify of an abnormality when the current detected by the first current detector 41 is higher than the first predetermined current. For example, in the process of FIG. 6, a process equivalent to step S15 of FIG. 2 may be performed instead of step S37. [Explanation of symbols]

[0143] 10...hydroelectric power generation system, 11...water turbine, 12...generator, 20...rotating electric machine system, 21...second conversion circuit, 22...rotating electric machine, 30...power conversion device, 31...DC link section, 32...connection section, 33...first switch, 34...first conversion circuit, 35...current limiting circuit, 36...power consumption circuit, 37...control section, 38...capacitor, 41...first current detector, 42...alarm section, 51...power source, 52...power path, 61...second switch, 62...voltage detector, 71...third conversion circuit, 72...head adjustment device, 73...power conversion system, 75...DC power source, 76...second current detector.

Claims

1. a DC link unit (31) having a capacitor (38); a connection part (32) connectable to an AC power source (1); a first switch (33) provided between the capacitor (38) and the connection portion (32); a first conversion circuit (34) provided between the capacitor (38) and the first switch (33); a current limiting circuit (35) provided between the capacitor (38) and the first switch (33); a power consumption circuit (36) connected to the DC link unit (31); a control unit (37), the first switch (33) is configured to electrically connect the connection portion (32) and the first conversion circuit (34) in a first on state, and to electrically disconnect the connection portion (32) and the first conversion circuit (34) in a first off state; The current limiting circuit (35) can switch between a limiting state in which the capacitor (38) and the first switch (33) are connected via a resistor (35 a) and a non-limiting state in which the capacitor (38) and the first switch (33) are connected without the resistor (35 a), The power consumption circuit (36) is switchable between a first state and a second state; The first state is a state in which DC power of the DC link unit (31) is consumed, The second state is a state in which the amount of power consumption is smaller than the amount of power consumption in the first state, or a state in which the DC link unit (31) does not consume DC power, The control unit (37) controls the power consumption circuit (36) to be in the second state when the current limiting circuit (35) is in the limiting state. Power conversion device.

2. The control unit (37) configured to control the power consumption circuit (36) to switch the power consumption circuit (36) between the first state and the second state; When the current limiting circuit (35) is in the limiting state, the power consuming circuit (36) is controlled so that the power consuming circuit (36) is in the second state. The power conversion device according to claim 1 .

3. The power supply (51) is further provided to supply power to the power consumption circuit (36), the power consumption circuit (36) operates in the first state or the second state when power is supplied from the power source (51), and operates in the second state when power supply from the power source (51) is stopped; When the current limiting circuit (35) is in the limited state, the control unit (37) stops the power supply from the power source (51) to the power consumption circuit (36) by controlling the power source (51) or by controlling the power path (52) between the power source (51) and the power consumption circuit (36). The power conversion device according to claim 1 .

4. The power supply further includes a second switch (61) provided between the DC link unit (31) and the power consumption circuit (36), the control unit (37) is configured to control the second switch (61) so as to switch the second switch (61) between a second on state and a second off state, the second switch (61) is configured to electrically connect the DC link unit (31) and the power consumption circuit (36) in the second on state, and to electrically disconnect the DC link unit (31) and the power consumption circuit (36) in the second off state; The control unit (37) controls the second switch (61) to be in the second off state when the current limiting circuit (35) is in the limiting state. The power conversion device according to claim 1 .

5. a first current detector (41) for detecting a current in a power path between the DC link unit (31) and the power consumption circuit (36); When the current limiting circuit (35) is in the non-limiting state, the control unit (37) controls the second switch (61) to be in the second on state based on the current detected by the first current detector (41) being equal to or less than a first current. The power conversion device according to claim 4.

6. A voltage detector (62) is further provided to detect the voltage of the capacitor (38), The control unit (37) controls the second switch (61) to be in the second on state based on the voltage detected by the voltage detector (62) being equal to or higher than a first voltage. The power conversion device according to claim 4.

7. The power converter further includes a notification unit (42) that notifies of an abnormality in the power converter (30), The notification unit (42) notifies of the abnormality based on the fact that the voltage detected by the voltage detector (62) after the second switch (61) is switched from the second off state to the second on state is smaller than the voltage detected by the voltage detector (62) before the second switch (61) is switched from the second off state to the second on state. The power conversion device according to claim 6.

8. a first current detector (41) for detecting a current in a power path between the DC link unit (31) and the power consumption circuit (36); and a notification unit (42) that notifies of an abnormality in the power conversion device (30), The notification unit (42) notifies of the abnormality based on the fact that the current detected by the first current detector (41) is greater than the second current when the power consumption circuit (36) is controlled to the second state. The power conversion device according to claim 1 .

9. A power converter (30) according to any one of claims 1 to 8; a second conversion circuit (21) connected to the DC link unit (31); a rotating electric machine (22) connected to the second conversion circuit (21), The second conversion circuit (21) can supply power from the DC link unit (31) to the rotating electric machine (22), or can supply power from the rotating electric machine (22) to the DC link unit (31). Rotating electric system.

10. a water wheel (11) disposed in a flow path (2) through which water flows; a generator (12) driven by the water turbine (11); The rotating electrical machine system (20) according to claim 9, the rotating electric machine (22) is the generator (12), The second conversion circuit (21) can supply power from the generator (12) to the DC link unit (31). Hydroelectric power generation system.

11. A power conversion system (73), a DC link unit (31) having a capacitor (38); a connection part (32) connectable to an AC power source (1); a first switch (33) provided between the capacitor (38) and the connection portion (32); a first conversion circuit (34) provided between the capacitor (38) and the first switch (33); a current limiting circuit (35) provided between the capacitor (38) and the first switch (33); a power consumption circuit (36) connected to the DC link unit (31); a DC power source (75) connected to the DC link portion (31); A control unit (37); a second current detector (76) for detecting the current of the DC power supply (75); a notification unit (42) that notifies of an abnormality in the power conversion system (73), the first switch (33) is configured to electrically connect the connection portion (32) and the first conversion circuit (34) in a first on state, and to electrically disconnect the connection portion (32) and the first conversion circuit (34) in a first off state; The current limiting circuit (35) can switch between a limiting state in which the capacitor (38) and the first switch (33) are connected via a resistor (35 a) and a non-limiting state in which the capacitor (38) and the first switch (33) are connected without the resistor (35 a), The power consumption circuit (36) is switchable between a first state and a second state; The first state is a state in which DC power of the DC link unit (31) is consumed, The second state is a state in which the amount of power consumption is smaller than the amount of power consumption in the first state, or a state in which the DC link unit (31) does not consume DC power, The control unit (37) controlling the first switch (33) to switch between the first on state and the first off state of the first switch (33); When the first switch (33) is controlled to the first off state, the DC power source (75) is controlled so as to apply a second voltage to the DC link portion (31) from the DC power source (75); The notification unit (42) notifies of the abnormality based on the current detected by the second current detector (76) being larger than the third current when the control unit (37) controls the DC power source (75) to apply the second voltage to the DC link unit (31) from the DC power source (75). Power conversion systems.

12. a water wheel (11) disposed in a flow path (2) through which water flows; a generator (12) driven by the water turbine (11); a third conversion circuit (71) connected to the generator (12); a head adjusting device (72) for adjusting the effective head of the water turbine (11); a power conversion system (73) according to claim 11; the third conversion circuit (71) is connected to the DC link unit (31) and is capable of supplying power from the generator (12) to the DC link unit (31); the DC power supply (75) includes the generator (12) and the third conversion circuit (71), and is configured to apply the second voltage to the DC link unit (31) when the generator (12) is driven by the water turbine (11); The control unit (37) drives the water turbine (11) by adjusting the effective head using the head adjustment device (72). Hydroelectric power generation system.

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