Power conversion devices, rotating electric machine systems, power conversion systems, and hydroelectric power generation systems

Abstract

The present invention provides a power conversion device, a rotating electric machine system, a power conversion system, and a hydroelectric power generation system that can suppress excessive electrical load on a current limiting circuit when the current limiting circuit is in a limiting state. [Solution] The power converter 30 comprises 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 the capacitor 38 of the DC link section 31 and the first switch 33 are connected via a resistor 35a, and an unlimited 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 the DC power of the DC link section 31 is consumed, and a second state in which the DC power of the DC link section 31 is not consumed. 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 Art

[0002] Power conversion devices that convert alternating current to direct current or direct current to alternating current are known. A power conversion device has a capacitor that smoothes the voltage of a DC link section. When an AC power supply is connected to the power conversion device, a large inrush current occurs compared to the rated current of the device to charge the capacitor. The power conversion device may be 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 of Patent Document 1 limits the current flowing into the smoothing capacitor of a power supply device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A power conversion device may be provided with a power consumption circuit for consuming excess power. The power consumption circuit is connected to the DC link section so as to be arranged in parallel with a capacitor in the power conversion device. The power consumption circuit consumes power in a current consumption connection state in which current flows from the DC link section to the power consumption circuit. If an AC power supply is connected to the power conversion device when the power consumption circuit is in the current consumption connection state, power continues to be consumed in the power consumption circuit. Then, there is a risk that an excessive electrical load is applied to the current limiting circuit.

Means for Solving the Problems

[0005] A power conversion device according to the first aspect of solving this problem comprises a DC link section equipped with a capacitor, a connection section connectable to an AC power source, a first switch provided between the capacitor and the connection section, 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 section, and a control unit, wherein the first switch is configured to electrically connect the connection section and the first conversion circuit in a first ON state and to electrically disconnect the connection section and the first conversion circuit in a first OFF state, and the current limiting circuit is configured to The current limiting circuit can switch between a restricted 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. The power consumption circuit can switch between a first state and a second state, the first state being a state in which the DC power of the DC link section is consumed, and the second state being a state in which the power consumption is less than the power consumption in the first state, or a state in which the DC power of the DC link section is not consumed. The control unit controls the power consumption circuit to be in the second state when the current limiting circuit is in the restricted state.

[0006] This configuration prevents the power consumption circuit from entering the first state when the current limiting circuit is in the limiting state. Therefore, it is possible to prevent excessive electrical load from being placed on the current limiting circuit when it is in the limiting state, such as when the AC power supply to the power converter is turned on.

[0007] The power converter according to the second perspective is configured such that, in the power converter according to the first perspective, the control unit controls 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 to enter the second state when the current limiting circuit is in the limiting state.

[0008] In this configuration, when the current limiting circuit is in the limiting state, the control unit controls the power consumption circuit to enter the second state. Therefore, 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.

[0009] The power converter according to the third aspect further comprises a power supply capable of supplying power to the power consumption circuit, wherein the power consumption circuit operates in the first or second state when power is supplied from the power supply, and operates in the second state when the 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 the power path between the power supply and the power consumption circuit when the current limiting circuit is in the limiting state.

[0010] In 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. Because the power supply is stopped, the power consumption circuit enters the second state, thus preventing the power consumption circuit from being in the first state when the current limiting circuit is in the limiting state.

[0011] The power converter of the fourth aspect further comprises a second switch provided between the DC link section and the power consumption circuit in the power converter of the first aspect, wherein the control unit is configured to control the second switch to switch between a second ON state and a second OFF state, wherein the second switch is configured to electrically connect the DC link section and the power consumption circuit in the second ON state and to electrically disconnect the DC link section 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] In 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 section and the power consumption circuit, preventing the power consumption circuit from consuming the DC power of the DC link section. Therefore, 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.

[0013] The power converter according to the fifth perspective further comprises a first current detector for detecting the current in the power path between the DC link section and the power consumption circuit, and the control unit controls the second switch to the second ON state based on the fact that the current detected by the first current detector is less than or equal to the first current when the current limiting circuit is in the unlimiting state.

[0014] With this configuration, when the current limiting circuit is in the unlimiting state, the second switch can be switched to the second ON state based on the fact that the current in the DC link section is less than or equal to the first current.

[0015] The power converter according to the sixth aspect further comprises a voltage detector for detecting the voltage of the capacitor, and the control unit controls the second switch to the second ON state based on the fact that the voltage detected by the voltage detector is equal to or greater than the first voltage.

[0016] With this configuration, the second switch can be switched to the ON state based on the capacitor voltage being equal to or greater than the first voltage.

[0017] The power converter according to the seventh aspect further comprises a notification unit for notifying an abnormality in the power converter according to the sixth aspect, wherein the notification unit notifies 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] With this configuration, when the second switch is switched from the second off state to the second on state, an abnormality in the power converter can be detected based on the decrease in the capacitor voltage.

[0019] The power converter of the eighth perspective further comprises, in any one of the power converters of the first to seventh perspectives, a first current detector for detecting the current in the power path between the DC link section and the power consumption circuit, and a notification unit for notifying an abnormality in the power converter, wherein the notification unit notifies 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] With this configuration, when the power consumption circuit is controlled to the second state, an abnormality in the power converter can be detected.

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

[0022] This configuration makes it possible to suppress excessive electrical load on the current limiting circuit due to inrush current in a rotating electric machine system.

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

[0024] With this configuration, the electricity 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 this problem is a power conversion system, comprising a DC link section provided with a capacitor, a connection section connectable to an AC power source, a first switch provided between the capacitor and the connection section, 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 section, a DC power source connected to the DC link section, a control section, a second current detector for detecting the current of the DC power source, and a notification section for notifying an abnormality of the power conversion system. The first switch is configured to electrically connect the connection section and the first conversion circuit in a first on state and to electrically disconnect the connection section and the first conversion circuit in a first off state. The current limiting circuit can switch between a limiting state in which the capacitor and the first switch are connected via a resistor and a non-limiting state in which the capacitor and the first switch are connected without passing through the resistor. The power consumption circuit can switch between a first state and a second state. The first state is a state in which DC power of the DC link section is consumed, and the second state is a state in which the power consumption amount is smaller than the power consumption amount in the first state or a state in which the DC power of the DC link section is not consumed. The control section controls the first switch to switch between the first on state and the first off state of the first switch. When the first switch is controlled to be in the first off state, the control section controls the DC power source to apply a second voltage from the DC power source to the DC link section. The notification section notifies the abnormality based on that the current detected by the second current detector is larger than a third current when the control section controls the DC power source to apply the second voltage from the DC power source to the DC link section.

[0026] When a DC power supply applies a voltage to a DC link section, if a power consumption circuit is in a first state, the current of the DC power supply increases. According to the above configuration, when the DC power supply applies a second voltage to the DC link section, an abnormality of the power conversion system is notified based on the fact that the current of the DC power supply is greater than a third current. By the notification of the abnormality by the notification unit, it can be known that there is a possibility that the power consumption circuit is in the first state. Since the notification of the abnormality by the notification unit is performed when the first switch is controlled to the first off state, it is possible to suppress an excessive electrical load from being applied to the current limiting circuit when the first switch is controlled to the on state due to an abnormality of the power conversion system.

[0027] A hydroelectric power generation system according to a twelfth aspect for solving this problem includes a water turbine disposed 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 for adjusting the effective head of the water turbine, and the power conversion system according to the eleventh aspect. The third conversion circuit is connected to the DC link section and can supply power from the generator to the DC link section. The DC power supply includes the generator and the third conversion circuit, and is configured such that the generator drives the water turbine to apply the second voltage to the DC link section. The control unit drives the water turbine by adjusting the effective head by 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 Description of the Drawings

[0029] [Figure 1] It is a block diagram showing the configuration of a hydroelectric power generation system according to the first embodiment. [Figure 2] It is a flowchart showing the flow of processing performed by the control unit of FIG. 1. [Figure 3] It is a block diagram showing the configuration of a hydroelectric power generation system according to the second embodiment. [Figure 4] It is a flowchart showing the flow of processing performed by the control unit of FIG. 3. [Figure 5]This is a block diagram showing the configuration of a hydroelectric power generation system according to the third embodiment. [Figure 6] Figure 5 is a flowchart showing the processing flow performed by the control unit. [Figure 7] This is a block diagram showing the configuration of a hydroelectric power generation system according to the fourth embodiment. [Figure 8] Figure 7 is a flowchart showing the processing flow performed by the control unit. [Modes for carrying out the invention]

[0030] <First Embodiment> Referring to Figures 1 and 2, the hydroelectric power generation system 10, the rotating electric machine system 20, and the power conversion device 30 according to the first embodiment will be described.

[0031] <Hydroelectric power generation system> As shown in Figure 1, the hydroelectric power generation system 10 is connected to the AC power source 1 of the AC grid. The hydroelectric power generation system 10 can switch between grid-connected operation and independent 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 grid. In other words, in grid-connected operation, the specific load 3 can receive power from either the power generated by the hydroelectric power generation system 10 or the power supplied from the AC grid. In independent operation, the hydroelectric power generation system 10 supplies power to the specific load 3 independently. For example, if the AC grid 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 through independent operation. An example of a specific load 3 is a factory, school, hospital, or house.

[0032] The hydroelectric power generation system 10 normally operates in grid-connected mode with the AC grid. This technology is designed to suppress problems that may occur when the AC grid is connected to the hydroelectric power generation system 10. This technology will be described below.

[0033] The hydroelectric power generation system 10 comprises a water turbine 11, a generator 12, and a rotating electric machine system 20. The water turbine 11 is positioned in the water channel 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 rotation shaft of the water turbine 11. The rotation of the rotation shaft of the water turbine 11 causes the generator 12 to generate electricity.

[0034] <Rotating Electrical Machinery Systems> The rotating electric machine system 20 comprises a second conversion circuit 21, a rotating electric machine 22, and a power converter 30.

[0035] The second conversion circuit 21 is connected to the DC link section 31, which will be described later. The second conversion circuit 21 can supply power from the DC link section 31 to the rotating electric machine 22, or can supply power from the rotating electric machine 22 to the DC link section 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 section 31. The second conversion circuit 21 is, for example, a converter. The second conversion circuit 21 converts AC power to DC power.

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

[0037] <Power converter> The power conversion device 30 includes a DC link section 31, a connection section 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 section 31 receives DC power from the second conversion circuit 21. The DC link section 31 includes a capacitor 38. The capacitor 38 is a smoothing capacitor that smooths the DC voltage.

[0039] The connection section 32 can be connected to the AC power supply 1. The hydroelectric power generation system 10 is electrically connected to the AC power supply 1 via the connection section 32. When the hydroelectric power generation system 10 is operating independently, the connection section 32 does not need to be connected to the AC power supply 1. The connection section 32 can include power lines that exchange power between the hydroelectric power generation system 10 and the AC grid, but other components may be omitted.

[0040] The first switch 33 is provided between the capacitor 38 and the connection part 32. The first switch 33 is configured to electrically connect the connection part 32 and the first conversion circuit 34 in the first ON state and to electrically disconnect the connection part 32 and the first conversion circuit 34 in the first OFF state. The first switch 33 is, for example, an electromagnetic switch. The first switch 33 is configured to switch to the first OFF state when an abnormality in the AC system is detected during grid-connected operation. An 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 the AC power of the AC power source 1 to DC power, or converts the DC power of the DC link section 31 to 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 shown in Figure 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 includes 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 the 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 turned on, the ends of the first resistor 35a are short-circuited, so 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 switch between a limiting state and an unlimiting state. The limiting state is when the capacitor 38 and the first switch 33 are connected via the first resistor 35a. The unlimiting state is when the capacitor 38 and the first switch 33 are connected without the first resistor 35a. In the limiting state, the first switch 35b of the current limiting circuit 35 is in the off state, and in the unlimiting 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 grid, an excessive current flows to charge the capacitor 38 of the DC link section 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 limiting state, and the first resistor 35a is inserted between the capacitor 38 and the first switch 33, thereby suppressing the inrush current. The current limiting circuit 35 switches from a limiting state to an unlimiting state, for example, after 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 section 31. The power consumption circuit 36 ​​consumes power from the DC link section 31. When the first switch 33 is in the first off state, if power is supplied from the generator 12 to the DC link section 31, the voltage of the DC link section 31 may rise. In such cases, the power consumption circuit 36 ​​consumes power from the DC link section 31 to suppress the voltage rise of the DC link section 31.

[0047] The power consumption circuit 36 ​​includes a second resistor 36a and a second switch 36b. The second switch 36b is provided between the second resistor 36a and the DC link section 31. When the second switch 36b is turned ON, the DC link section 31 and the second resistor 36a are connected, and the power consumption circuit 36 ​​consumes the DC power of the DC link section 31.

[0048] 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 section 31 is consumed. The second state is a state in which the DC power of the DC link section 31 is not consumed. In the first state, the second switch 36b of the power consumption circuit 36 ​​is in the ON state, and in the second state, the second switch 36b of the power consumption circuit 36 ​​is in the OFF state.

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

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

[0051] The power converter 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 section 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 notification unit 42 outputs a signal regarding an abnormality in the hydroelectric power generation system 10 by outputting a notification signal. Based on the output of the notification unit 42, information regarding the abnormality in the hydroelectric power generation system 10 may be output to devices such as a display or speaker. The notification of abnormalities by the notification unit 42 is controlled by the control unit 37. The notification unit 42 may be configured as the arithmetic processing unit of the control unit 37.

[0054] The notification unit 42 notifies of an abnormality in the power converter 30. An abnormality in the power converter 30 is, for example, a short-circuit failure of a switch included in the power converter 30. The notification unit 42 notifies of the abnormality when the power consumption circuit 36 ​​is controlled to the second state and the current detected by the first current detector 41 is greater than the first predetermined current. 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 allows the system to determine that current is being generated between the DC link unit 31 and the power consumption circuit 36, even though 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 possibility that an abnormality such as a short-circuit failure of the second switch 36b of the power consumption circuit 36 ​​has occurred.

[0055] The power converter 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 ​​by 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 either a first or second state when power is supplied from the power supply 51, and operates in the second state when the power supply from the power supply 51 is stopped. Whether it operates in the first or second state when power is supplied from the power supply 51 is based on a command signal from the control unit 37. When the power supply from the power supply 51 is stopped, the power consumption circuit 36 ​​enters the second state. Note that operation in the second state due to the cessation of power supply from the power supply 51 includes a state in which the power consumption circuit 36 ​​is not electrically operating.

[0057] <Department Head> The control unit 37 controls the first switch 33 to switch between a first ON state and a first OFF state. The control unit 37 controls the first switch 33 by outputting a command signal to the first switch 33 regarding the first ON state or the first OFF state.

[0058] In this embodiment, the control unit 37 controls the current limiting circuit 35 to switch between a limited state and an unlimited state. 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 unlimited state.

[0059] The control unit 37 is configured to control the power consumption circuit 36 ​​so as to switch between a first state and a second state. 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 a limiting state before the first switch 33 enters a first ON state. The control unit 37 controls the power consumption circuit 36 ​​to enter a second state when the current limiting circuit 35 is in a limiting state. More specifically, the control unit 37 controls the power consumption circuit 36 ​​to enter a second state when the current limiting circuit 35 is in a limiting state AND the first switch 33 is in a first ON state. Preferably, the control unit 37 sets the power consumption circuit 36 ​​to a second state before the current limiting circuit 35 enters a limiting state.

[0061] In this embodiment, the control unit 37 controls the power consumption circuit 36 ​​so that it enters a second state when the current limiting circuit 35 is in a limiting state. For example, when the current limiting circuit 35 switches from an unlimited state to a limiting state, the control unit 37 outputs a command signal to the power consumption circuit 36 ​​so that it enters a second state.

[0062] <Pre-configuration process> The first switch 33 is switched from a first ON state to a first OFF state when the hydroelectric power generation system 10 is disconnected from the AC power source 1 of the AC grid. Specifically, when the AC grid experiences a power outage, the first switch 33 is switched from a first ON state to a first OFF state. Alternatively, when the AC power source 1 is being repaired, the first switch 33 is switched from a first ON state to a first OFF state.

[0063] The control unit 37 switches the first switch 33 from the first off state to the first on state when starting grid-connected operation by connecting the hydroelectric power generation system 10 to the AC power source 1. When the control unit 37 switches the first switch 33 from the first off state to the first on state, it performs a pre-setting process. 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] Referring to Figure 2, the processing performed by the control unit 37 in this embodiment will be explained. For example, during autonomous operation, the control unit 37 repeats the processing shown in Figure 2 at predetermined intervals.

[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 that requests the control unit 37 to turn the first switch 33 to the first ON state. For example, when the hydroelectric power generation system 10 switches from standalone operation to grid-connected operation, an ON command for the first switch 33 is input to the control unit 37. If an ON command for the first switch 33 is input, the control unit 37 proceeds to step S12. If an ON command for the first switch 33 is not input, the control unit 37 terminates the process shown in Figure 2.

[0066] In step S12, the control unit 37 switches the power consumption circuit 36 ​​to the second state and then proceeds to step S13. The control unit 37 outputs a command signal to the power consumption circuit 36 ​​to enter 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 less than or equal to a first predetermined current. The control unit 37 obtains 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 less than or equal to the first predetermined current, the control unit 37 terminates the process shown in Figure 2. If the current between the DC link unit 31 and the power consumption circuit 36 ​​is not less than or equal to 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 terminates the process shown in Figure 2 in step S16 after notifying the notification unit 42 of the abnormality.

[0069] <Operation of the Embodiment> The operation of this embodiment will now be explained. When the first switch 33 is switched to the first ON state, the control unit 37 sets the current limiting circuit 35 to a limited state in order to suppress inrush current. At this time, if the power consumption circuit 36 ​​is in the first state, current will continue to flow through the second resistor 36a of the power consumption circuit 36, which may cause an excessive electrical load on the current limiting circuit 35. In the power converter 30 of this embodiment, when the current limiting circuit 35 is in the limited 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 limited state and switches the power consumption circuit 36 ​​to the second state, and then switches the first switch 33 to the first ON state. Since the second resistor 36a of the power consumption circuit 36 ​​is not connected to the DC link section 31, it is less likely that an excessive electrical load will be placed on the current limiting circuit 35.

[0070] <Effects of the Embodiment> The effects of this embodiment will now be explained. (1-1) The power conversion device 30 comprises a DC link section 31, a connection section 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 section 31 includes a capacitor 38. The connection section 32 is connectable to the AC power supply 1. The first switch 33 is provided between the capacitor 38 and the connection section 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 section 31. The first switch 33 is configured to electrically connect the connection section 32 and the first conversion circuit 34 in the first ON state, and to electrically disconnect the connection section 32 and the first conversion circuit 34 in the first OFF state. The current limiting circuit 35 can switch between a limited state and an unlimited state. The restricted state is when the capacitor 38 and the first switch 33 are connected via a resistor. The disconnected state is when 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 when the DC power of the DC link section 31 is consumed. The second state is when the DC power of the DC link section 31 is not consumed. The control unit 37 controls the power consumption circuit 36 ​​to enter the second state when the current limiting circuit 35 is in the restricted state.

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

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

[0073] With this configuration, when the current limiting circuit 35 is in a limiting state, the control unit 37 controls the power consumption circuit 36 ​​to enter a second state. Therefore, it is possible to prevent the power consumption circuit 36 ​​from being in a first state when the current limiting circuit 35 is in a limiting state.

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

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

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

[0077] This configuration makes it possible to suppress excessive electrical load on the current limiting circuit 35 due to inrush current in the rotating electric machine system 20.

[0078] (1-5) The hydroelectric power generation system 10 comprises a water turbine 11, a generator 12, and a rotating electric machine system 20. The water turbine 11 is positioned in the water channel 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 the DC link section 31.

[0079] With this configuration, the electricity generated by the water turbine 11 can be supplied to the power converter 30.

[0080] <Second Embodiment> Referring to Figures 3 and 4, the hydroelectric power generation system 10, the rotating electric machine system 20, and the power conversion device 30 according to the second embodiment will be described. Components in this embodiment that are common to the first embodiment are denoted by the same reference numerals as in the first embodiment, and redundant descriptions are omitted.

[0081] In the first embodiment, the control unit 37 directly controls the power consumption circuit 36 ​​so that it enters a second state when the current limiting circuit 35 is in a limiting state. In this embodiment, the control unit 37 controls the power path 52 so that the power consumption circuit 36 ​​enters a second state when the current limiting circuit 35 is in a limiting state.

[0082] The control unit 37 in this embodiment is configured to control the 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, no power is 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 to the power switch 52a regarding the ON or OFF state.

[0083] The control unit 37 stops supplying power from the power supply 51 to the power consumption circuit 36 ​​by controlling the power path 52 when the current limiting circuit 35 is in a limiting state. This switches the power consumption circuit 36 ​​to a second state. The control unit 37 stops supplying power from the power supply 51 to the power consumption circuit 36 ​​by controlling the power switch 52a of the power path 52 to an off state when the current limiting circuit 35 is in a limiting state. For example, the control unit 37 switches the power switch 52a to an off state before switching the first switch 33 to an on state. For example, the control unit 37 switches the power switch 52a to an on state when a first period has elapsed after switching the first switch 33 to an on state. The first period is, for example, the period during which the inrush current due to the connection with the AC power supply 1 has finished flowing.

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

[0085] Referring to Figure 4, the processing performed by the control unit 37 in this embodiment will be explained. In step S21, 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 S22. If an ON command for the first switch 33 has not been input, the control unit 37 terminates the process shown in Figure 4.

[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 turn it off. As the power switch 52a of the power path 52 turns off, the power consumption circuit 36 ​​enters 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 or not 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 process in 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 turn it ON. Furthermore, 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 less than or equal to a first predetermined current. If the current between the DC link unit 31 and the power consumption circuit 36 ​​is less than or equal to the first predetermined current, the control unit 37 terminates the process shown in Figure 4. If the current between the DC link unit 31 and the power consumption circuit 36 ​​is not less than or equal to the first predetermined current, the control unit 37 terminates the process shown in Figure 4 in step S28 after notifying the notification unit 42 of the abnormality.

[0089] <Effects of the Embodiment> The effects of this embodiment will now be explained. (2) The power converter 30 includes a power supply 51. The power supply 51 is capable of supplying power to the power consumption circuit 36. The power consumption circuit 36 ​​operates in a first or second state when power is supplied from the power supply 51, and operates in the second state when the power supply from the power supply 51 is stopped. 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 by controlling the power path 52 between the power supply 51 and the power consumption circuit 36 ​​when the current limiting circuit 35 is in a limiting state.

[0090] In this configuration, when the current limiting circuit 35 is in a limiting state, the power supply from the power source 51 to the power consumption circuit 36 ​​is stopped. Because the power supply is stopped, the power consumption circuit 36 ​​enters a second state, thus preventing the power consumption circuit 36 ​​from being in a first state when the current limiting circuit 35 is in a limiting state.

[0091] <Third Embodiment> Referring to Figures 5 and 6, the hydroelectric power generation system 10, the rotating electric machine system 20, and the power conversion device 30 according to the third embodiment will be described. Components in this embodiment that are common to the first embodiment are denoted by the same reference numerals as in the first embodiment, and redundant descriptions are 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 section 31 and the power consumption circuit 36. The second switch 61 is configured to electrically connect the DC link section 31 and the power consumption circuit 36 ​​in the second ON state and to electrically disconnect the DC link section 31 and the power consumption circuit 36 ​​in the second OFF state. The second switch 61 is, for example, an electromagnetic switch.

[0093] The voltage detector 62 detects the voltage across the capacitor 38. The voltage across the capacitor 38 may be the voltage across the capacitor 38, or the voltage in the power path of the DC link section 31 may be detected as the voltage across the capacitor 38. The voltage detector 62 outputs information about 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. The control unit 37 controls the second switch 61 by outputting a command signal to the second switch 61 regarding the second ON state or the second OFF state.

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

[0096] The power consumption circuit 36 ​​is configured to remain in the second state even when the second switch 61 switches from the off state to the on state, because the second switch 36b remains in the off state. The power consumption circuit 36 ​​switches 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 a second ON state based on the voltage of the capacitor 38 when the second switch 61 is in a second OFF state. The control unit 37 controls the second switch 61 to a second ON state based on the voltage detected by the voltage detector 62 being equal to or greater than a first predetermined voltage. The first predetermined voltage is a voltage at which it can be determined that the capacitor 38 has been charged. Preferably, the control unit 37 controls the second switch 61 to a second ON state based on the voltage detected by the voltage detector 62 being equal to or greater than a first predetermined voltage when the current limiting circuit 35 is in an unlimiting state.

[0098] The voltage after switching is defined as the voltage across capacitor 38 after the second switch 61 switches from the second off state to the second on state. The voltage before switching is defined as the voltage across 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 ​​if the voltage after switching is smaller than the voltage before switching. The notification unit 42 notifies of the abnormality based on the fact that the voltage after switching is smaller than the voltage before switching. The notification unit 42 notifies of the abnormality based on the 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 when 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 remain in the off state unless there is a command signal from the control unit 37. For this reason, even when 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 voltage after switching becomes equal to the voltage before switching, or the voltage after switching becomes greater than the voltage before switching. An example of an abnormality based on the voltage after switching being less than the voltage before switching is a short circuit abnormality of the second switch 36b of the power consumption circuit 36.

[0100] Referring to Figure 6, the pre-configuration process performed by the control unit 37 in this embodiment will be explained. In step S31, 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 S32. If an ON command for the first switch 33 has not been input, the control unit 37 terminates the process shown in Figure 6.

[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 enter the second off state. As the second switch 61 of the power path 52 enters the second off state, the power consumption circuit 36 ​​enters 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 the second period has elapsed since the first switch 33 was switched to the first ON state. The control unit 37 repeats the process in 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 voltage after switching is equal to or greater than the voltage before switching. For example, the control unit 37 obtains the voltage before switching from the voltage detector 62 before processing in step S36, and obtains the voltage after switching from the voltage detector 62 after processing in step S36. If the voltage after switching is equal to or greater than the voltage before switching, the control unit 37 terminates the process shown in Figure 6. If the voltage after switching is not equal to or greater than the voltage before switching, that is, if the voltage after switching is less than the voltage before switching, in step S38, the control unit 37 notifies the notification unit 42 of the abnormality and then terminates the process shown in Figure 6.

[0104] <Effects of the Embodiment> The effects of this embodiment will now be explained. (3-1) The power converter 30 further includes a second switch 61. The second switch 61 is provided between the DC link section 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. The second switch 61 is configured to electrically connect the DC link section 31 and the power consumption circuit 36 ​​in the second ON state and to electrically disconnect the DC link section 31 and the power consumption circuit 36 ​​in the second OFF state. The control unit 37 controls the second switch 61 to enter the second OFF state when the current limiting circuit 35 is in a limiting state.

[0105] In this configuration, when the current limiting circuit 35 is in a limiting state, the control unit 37 controls the second switch 61 to a second off state. As a result, the DC link section 31 and the power consumption circuit 36 ​​are electrically disconnected, and the power consumption circuit 36 ​​cannot consume the DC power of the DC link section 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 a limiting state.

[0106] (3-2) The power converter 30 further includes a voltage detector 62. The voltage detector 62 detects the voltage of the capacitor 38. Based on the fact that the voltage detected by the voltage detector 62 is equal to or greater than a first predetermined voltage, the control unit 37 controls the second switch 61 so that the second switch 61 enters a second ON state.

[0107] With this configuration, the second switch 61 can be switched to the ON state based on the voltage across the capacitor 38 being equal to or greater than the first predetermined voltage.

[0108] (3-3) The power converter 30 is equipped with a notification unit 42. The notification unit 42 notifies of an abnormality in the power converter 30. The notification unit 42 notifies of an 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 smaller 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] With this configuration, when the second switch 61 is switched from the second off state to the second on state, an abnormality in the power converter 30 can be detected based on the decrease in the voltage across the capacitor 38.

[0110] <Fourth Embodiment> Referring to Figures 7 and 8, the hydroelectric power generation system 10, the rotating electric machine system 20, and the power conversion device 30 according to the fourth embodiment will be described. Components in this embodiment that are common with the first embodiment are denoted by the same reference numerals as in the first embodiment, and redundant descriptions are omitted.

[0111] In this embodiment, an abnormality is reported based on the back electromotive force from the generator 12 before the first switch 33 switches to the first ON state. 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 section 31. The third conversion circuit 71 can supply power from the generator 12 to the DC link section 31. The third conversion circuit 71 does not necessarily have to be able to supply power from the DC link section 31 to the generator 12. The third conversion circuit 71 of this embodiment is configured in accordance with 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 consists of an inlet valve 72a located 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 in the flow path 2, and closing the inlet valve 72a decreases the flow rate in the flow path 2.

[0114] <Power Conversion System> The power conversion system 73 is a system combining a power conversion device 30 and a DC power supply 75. The power conversion system 73 converts the power from 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 section 31. The DC power supply 75 supplies the power generated by the generator 12 to the DC link section 31 via the third conversion circuit 71. The DC power supply 75 is configured to apply a second predetermined voltage to the DC link section 31 when the generator 12 is driven by the water turbine 11.

[0115] Specifically, the power conversion system 73 includes a DC link section 31, a connection section 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 section 37, a second current detector 76, and an alert section 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 the current on the DC power supply 75 side of the power path connecting the DC power supply 75 and the DC link section 31, beyond the point where the power consumption circuit 36 ​​is connected. The second current detector 76 outputs information about the detected current to the control unit 37.

[0117] In this embodiment, the control unit 37 controls the DC power supply 75. The control unit 37 controls the DC power supply 75 so that a second predetermined voltage is applied from the DC power supply 75 to the DC link section 31 when the first switch 33 is controlled to a first off state. The control unit 37 causes the DC power supply 75 to apply a second predetermined voltage when the first switch 33 is in a first off state. The control unit 37 controls the DC power supply 75 so that a second predetermined voltage is applied to the DC link section 31 by controlling the drop adjustment device 72.

[0118] The control unit 37 controls the DC power supply 75 by controlling the head adjustment device 72. The control unit 37 drives the turbine 11 by adjusting the effective head using the head adjustment device 72. The control unit 37 drives the turbine 11 by controlling the valve opening of the inlet valve 72a of the head adjustment device 72. The driving of the turbine 11 generates a back electromotive force in the generator 12. The control unit 37 controls the head adjustment 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 rotational 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 notifies the notification unit 42 of the occurrence 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 second predetermined voltage is applied to the DC link unit 31.

[0120] In this embodiment, the notification unit 42 notifies of an abnormality in the power conversion system 73. In this embodiment, an abnormality in the power conversion system 73 is, for example, when the power consumption circuit 36 ​​is in a first state. An 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 when 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 section 31, and the current detected by the second current detector 76 is greater than the second predetermined current. 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 section 31 while 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 section 31 while the power consumption circuit 36 ​​is in the second state. When the power consumption circuit 36 ​​is in the second state, the current in the DC power supply 75 becomes larger than the second predetermined current, and therefore the notification unit 42 notifies of an abnormality.

[0122] Referring to Figure 8, the processing performed by the control unit 37 in this embodiment will be explained. 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 terminates the process shown in Figure 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 drop adjustment device 72 is opened, and then the process proceeds to step S44. Opening the drop adjustment device 72 is the operation to open the inlet valve 72a of the drop adjustment device 72. The control unit 37 continues to increase the valve opening until the opening operation of the drop adjustment device 72 is stopped in step S45, which will be described later.

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

[0125] In step S46, the control unit 37 determines whether the current of the DC power supply 75 is less than or equal to the second predetermined current. The control unit 37 obtains the current of the DC power supply 75 from the second current detector 76. If the current of the DC power supply 75 is less than or equal to the second predetermined current, the control unit 37 proceeds to step S47. If the current of the DC power supply 75 is not less than or equal to 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 terminates the process shown in Figure 8 in step S49 after notifying the notification unit 42 of the abnormality. This abnormality is, for example, that the power consumption circuit 36 ​​is in the first state when attempting to turn the first switch 33 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 terminates the process shown in Figure 8.

[0127] <Operation of the Embodiment> The operation of this embodiment will now be explained. 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 section 31. The notification unit 42 notifies of an abnormality based on the fact that 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 now be explained. (4-1) The power conversion system 73 comprises a DC link section 31, a connection section 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 alert unit 42. The DC link section 31 includes a capacitor 38. The connection section 32 is connectable to the AC power supply 1. The first switch 33 is provided between the capacitor 38 and the connection section 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 section 31. The DC power supply 75 is connected to the DC link section 31. The second current detector 76 detects the current of the DC power supply 75. The alert unit 42 alerts of any abnormality in the power conversion system 73. The first switch 33 is configured to electrically connect the connection part 32 and the first conversion circuit 34 in the first ON state, and to electrically disconnect the connection part 32 and the first conversion circuit 34 in the first OFF state. The current limiting circuit 35 can switch between a limiting state and an unlimiting state. The limiting state is when the capacitor 38 and the first switch 33 are connected via a resistor. The unlimiting state is when 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 when the DC power of the DC link part 31 is consumed. The second state is when the DC power of the DC link part 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. 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 section 31 when the first switch 33 is controlled to the first off state. The notification unit 42 notifies of an abnormality when the control unit 37 is controlling the DC power supply 75 to apply a second predetermined voltage from the DC power supply 75 to the DC link section 31, and the current detected by the second current detector 76 is greater than the second predetermined current.

[0129] When the DC power supply 75 applies voltage to the DC link section 31, if the power consumption circuit 36 ​​is in the first state, the current of the DC power supply 75 increases. According to the above configuration, when the DC power supply 75 applies a second predetermined voltage to the DC link section 31, an abnormality in the power conversion system 73 is reported based on the fact that the current of the DC power supply 75 is greater than the second predetermined current. The abnormality report by the notification unit 42 indicates that there is a possibility that the power consumption circuit 36 ​​is in the first state. Since the abnormality report by the notification unit 42 is made when the first switch 33 is controlled to the first off state, it is possible to suppress excessive electrical load on 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 comprises a turbine 11, a generator 12, a third conversion circuit 71, a head adjustment device 72, and a power conversion system 73. The turbine 11 is positioned in the water flow channel 2. The generator 12 is driven by the turbine 11. The third conversion circuit 71 is connected to the generator 12. The head adjustment device 72 adjusts the effective head of the turbine 11. The third conversion circuit 71 is connected to the DC link section 31 and can supply power from the generator 12 to the DC link section 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 section 31 when the generator 12 is driven by the turbine 11. The control unit 37 drives the turbine 11 by adjusting the effective head with the head adjustment device 72.

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

[0132] <Variation> The hydroelectric power generation system 10, the rotating electric machine system 20, and the power conversion device 30 of this disclosure may also be modified in ways other than those described above, such as those shown below, or in combination of at least two mutually non-inconsistent modifications.

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

[0134] The switching between the restricted state and the unrestricted state of the current limiting circuit 35 may be controlled by a control unit other than the control unit 37. The control unit other than the control unit 37 includes a processing unit such as a CPU or GPU. The control unit other than the control unit 37 switches the current limiting circuit 35 to the restricted 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 unrestricted state after a predetermined period has elapsed since the first switch 33 was switched to the first ON state. In this modified example, for example, step S14 may be omitted from the process in Figure 2.

[0135] In each embodiment, the rotating electric machine 22 has been described as a generator 12, but the rotating electric machine 22 may also be a regenerative motor. In this modified example, the rotating electric machine 22 supplies regenerative power to the DC link section 31. The regenerative power is consumed, for example, in the power consumption circuit 36.

[0136] • In each embodiment, the second state was a state in which the DC power of the DC link section 31 was not consumed, but 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 modified example, the power consumption circuit 36 ​​may consume the DC power of the DC link section 31 to such an extent that in the second state, there is no load on the current limiting circuit 35 due to inrush current, or the effect of the electrical load on the current limiting circuit 35 is negligible.

[0137] In each embodiment, the abnormality notified by the notification unit 42 was described as a short-circuit failure of the second switch 36b of the power consumption circuit 36. However, the notification unit 42 may also notify of abnormalities other than those in the power consumption circuit 36. Examples of abnormalities other than those in the power consumption circuit 36 ​​include abnormalities in the second conversion circuit 21, abnormalities in the power paths connecting each component, and abnormalities in the second switch 61.

[0138] In the second embodiment, the control unit 37 may be configured to control the start and stop of power supply from the power supply 51. In this modified example, instead of controlling the power path 52, the control unit 37 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 a limiting state.

[0139] In the second embodiment, the control unit 37 controls the power switch 52a to the ON state when a first period has elapsed since the first switch 33 was turned 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 greater than a first predetermined voltage after the first switch 33 has been turned to the first ON state. The control unit 37 acquires the voltage of the capacitor 38 by a voltage detector, for example, similar to the voltage detector 62 of the third embodiment.

[0140] In the third embodiment, the control unit 37 controlled the second switch 61 to a second ON state based on the fact that the voltage detected by the voltage detector 62 was equal to or greater than a first predetermined voltage. The control unit 37 may also control the second switch 61 to a second ON state based on the fact that the current detected by the first current detector 41 was less than or equal to a third predetermined current when the current limiting circuit 35 was in an unlimiting state. The third predetermined current is set based on the current generated in the DC link section 31 after the inrush current caused by the first switch 33 entering a first ON state has finished flowing. With this configuration, when the current limiting circuit 35 is in an unlimiting state, the second switch 61 can be switched to a second ON state based on the fact that the current in the DC link section 31 is less than or equal to a third predetermined current.

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

[0142] In the third embodiment, the notification unit 42 notified of an abnormality based on the fact that the voltage after switching is smaller than the voltage before switching, but it may also notify of an abnormality based on the fact that the current detected by the first current detector 41 is larger than the first predetermined current. For example, in the process in Figure 6, a process similar to step S15 in Figure 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 unit, 38...Capacitor, 41...First current detector, 42...Notification unit, 51...Power supply, 52...Power path, 61...Second switch, 62...Voltage detector, 71...Third conversion circuit, 72...Head adjustment device, 73...Power conversion system, 75...DC power supply, 76...Second current detector.

Claims

1. A DC link section (31) equipped with a capacitor (38), A connection part (32) that can be connected to an AC power supply (1), A first switch (33) is provided between the capacitor (38) and the connection part (32), A first conversion circuit (34) is provided between the capacitor (38) and the first switch (33), A current limiting circuit (35) is provided between the capacitor (38) and the first switch (33), A power consumption circuit (36) connected to the DC link section (31), It comprises a control unit (37) and The first switch (33) is configured to electrically connect the connection part (32) and the first conversion circuit (34) in the first ON state, and to electrically disconnect the connection part (32) and the first conversion circuit (34) in the 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 (35a), and an unlimiting 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 and a second state. The first state is a state in which the DC power of the DC link section (31) is consumed, The second state is a state in which the amount of power consumed is less than the amount of power consumed in the first state, or a state in which the DC power of the DC link section (31) is not consumed. The control unit (37) controls the power consumption circuit (36) to enter the second state when the current limiting circuit (35) is in the limiting state. Power converter.

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

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

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

5. The system further includes a first current detector (41) for detecting the current in the power path between the DC link section (31) and the power consumption circuit (36), The control unit (37) controls the second switch (61) to the second ON state based on the fact that the current detected by the first current detector (41) is less than or equal to the first current when the current limiting circuit (35) is in the unlimiting state. The power conversion device according to claim 4.

6. The system further includes a voltage detector (62) for detecting the voltage of the capacitor (38), The control unit (37) controls the second switch (61) so that it enters the second ON state, based on the fact that the voltage detected by the voltage detector (62) is equal to or greater than the first voltage. The power conversion device according to claim 4.

7. The power converter (30) is further equipped with a notification unit (42) that notifies of any abnormality, 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 smaller 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. The power conversion device according to claim 6.

8. A first current detector (41) detects the current in the power path between the DC link section (31) and the power consumption circuit (36), The power converter (30) is further equipped with a notification unit (42) that notifies of any abnormality in the power converter (30), The notification unit (42) notifies 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 conversion device (30) according to any one of claims 1 to 8, A second conversion circuit (21) connected to the DC link section (31), The system comprises a rotating electric machine (22) connected to the second conversion circuit (21), The second conversion circuit (21) can supply power from the DC link section (31) to the rotating electric machine (22), or can supply power from the rotating electric machine (22) to the DC link section (31). Rotating electrical machinery systems.

10. A water turbine (11) is positioned in the water channel (2) through which water flows, A generator (12) driven by the aforementioned water turbine (11), The rotating electric machine system (20) according to claim 9 comprises, The aforementioned rotating electric machine (22) is the generator (12), The second conversion circuit (21) can supply power from the generator (12) to the DC link section (31). Hydroelectric power generation system.

11. A power conversion system (73), A DC link section (31) equipped with a capacitor (38), A connection part (32) that can be connected to an AC power supply (1), A first switch (33) is provided between the capacitor (38) and the connection part (32), A first conversion circuit (34) is provided between the capacitor (38) and the first switch (33), A current limiting circuit (35) is provided between the capacitor (38) and the first switch (33), A power consumption circuit (36) connected to the DC link section (31), A DC power supply (75) connected to the DC link section (31), Control unit (37) and A second current detector (76) for detecting the current of the DC power supply (75), The system includes 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 part (32) and the first conversion circuit (34) in the first ON state, and to electrically disconnect the connection part (32) and the first conversion circuit (34) in the 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 (35a), and an unlimiting 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 and a second state. The first state is a state in which the DC power of the DC link section (31) is consumed, The second state is a state in which the amount of power consumed is less than the amount of power consumed in the first state, or a state in which the DC power of the DC link section (31) is not consumed. The control unit (37) The first switch (33) is controlled to switch between the first ON state and the first OFF state, When the first switch (33) is controlled to the first off state, the DC power supply (75) is controlled to apply a second voltage from the DC power supply (75) to the DC link section (31). The notification unit (42) notifies the abnormality based on the fact that the current detected by the second current detector (76) is greater than the third current when the control unit (37) is controlling the DC power supply (75) to apply the second voltage from the DC power supply (75) to the DC link unit (31). Power conversion system.

12. A water turbine (11) is positioned in the water channel (2) through which water flows, A generator (12) driven by the aforementioned water turbine (11), A third conversion circuit (71) connected to the generator (12), A head adjustment device (72) for adjusting the effective head of the water turbine (11), The power conversion system (73) according to claim 11 comprises, The third conversion circuit (71) is connected to the DC link section (31) and can supply power from the generator (12) to the DC link section (31). The DC power supply (75) includes the generator (12) and the third conversion circuit (71), and is configured such that the generator (12) is driven by the water turbine (11) to apply the second voltage to the DC link section (31). 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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