JP2022126987A - Power conversion device - Google Patents

Abstract

To provide a power conversion device that can prevent a failure due to overvoltage with a simpler configuration.SOLUTION: There is provided a power conversion device comprising: a converter that is connected with an electric charge storage element and connected with a rotary machine through AC power lines, converts DC power supplied from the electric charge storage element into AC power, and supplies the AC power to the rotary machine; a control unit that controls the operation of the power conversion performed by the converter; and an overvoltage detection circuit that detects overvoltage of the converter and inputs a result of detection to the control unit. The converter has a plurality of switching elements and a plurality of rectifiers connected in reverse parallel to the plurality of switching elements. When overvoltage is detected by the overvoltage detection circuit, the control unit controls switching of the plurality of switching elements to short-circuit between the AC power lines.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD Embodiments of the present invention relate to power converters.

A rotating machine drive system is known that includes a rotating machine such as a generator or an electric motor, and a power conversion device that drives the rotating machine. The power conversion device includes a converter that drives the rotating machine by converting DC power into AC power and supplying the AC power to the rotating machine, and a control unit that controls the operation of the converter. In such a rotary machine drive system, if an accident occurs and the power conversion device is stopped for protection, the inflow of energy from the rotary machine may cause overvoltage, leading to failure of the rotary machine and the power conversion device.

For example, since the rotating body has inertia, energy flows into the power converter via diode rectification or the like. Also, if a ground fault or short-circuit occurs in the primary circuit of a wound-rotor induction machine, an excessive voltage is generated in the secondary circuit.

In this way, if an accident occurs and the power conversion device is stopped for protection, there is a possibility that failure due to overvoltage will occur in the rotating machine and the power conversion device due to the factors described above. Moreover, if the rotating machine and the power converter are designed to withstand this overvoltage, the rotating machine and the power converter become large.

As a countermeasure against such overvoltage, it has been proposed to connect an overvoltage protection circuit in parallel with the converter in a power converter. The overvoltage protection circuit is connected to the AC power line between the rotating machine and the converter, and short-circuits the lines of the AC power line in response to detection of overvoltage to suppress the overvoltage and prevent the rotating machine and the power converter from overvoltage. protect from As a result, it is possible to optimize the insulation design of the rotating machine and the power converter, and to suppress the enlargement of the rotating machine and the power converter.

However, since the overvoltage protection circuit must withstand the short-circuit current of the rotating machine, it requires a large current capacity. Therefore, in a configuration in which an overvoltage protection circuit is provided, there is a possibility that the overvoltage protection circuit will increase the overall size of the power converter and increase the manufacturing cost.

Furthermore, it is rare for the overvoltage protection circuit to operate within the life of the power conversion device, and the increase in the size and cost of the entire device due to the infrequently used circuit is cost-effective. inefficient in For this reason, it is desired that the power conversion device be able to suppress failures due to overvoltage with a simpler configuration.

JP-A-7-111730

An embodiment of the present invention provides a power converter that can suppress failures due to overvoltage with a simpler configuration.

According to an embodiment of the present invention, there is provided a power conversion device that supplies AC power to a rotating machine, is connected to a charge storage element, is connected to the rotating machine via an AC power line, and is connected to the rotating machine via an AC power line. a converter that converts the supplied DC power into AC power and supplies the AC power to the rotating machine; a control unit that controls the operation of power conversion by the converter; an overvoltage of the converter; and an overvoltage detection circuit for inputting a detection result to the control unit, wherein the converter includes a plurality of switching elements and a plurality of rectifying elements connected in anti-parallel to each of the plurality of switching elements. an ON state in which electric power is converted by switching the plurality of switching elements, the plurality of switching elements having a pair of main terminals and allowing current to flow between the pair of main terminals; and an off state that cuts off current flow between a pair of main terminals, and the control unit controls switching of the plurality of switching elements between the on state and the off state, thereby causing the converter to In addition to controlling the operation of power conversion, after turning off the plurality of switching elements, when an overvoltage is detected by the overvoltage detection circuit, the lines of the AC power line are short-circuited. A power conversion device is provided that controls switching between the ON state and the OFF state of a switching element.

A power conversion device is provided that can suppress failures due to overvoltage with a simpler configuration.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which represents typically the rotary machine drive system which concerns on embodiment. It is a block diagram which represents typically an example of the converter which concerns on embodiment. It is a block diagram which represents typically the modification of the converter which concerns on embodiment. It is a block diagram which represents typically the modification of a power converter device. It is a block diagram which represents typically the modification of a power converter device. It is a block diagram which represents typically the modification of a power converter device.

Each embodiment will be described below with reference to the drawings.
Note that the drawings are schematic or conceptual, and the relationship between the thickness and width of each portion, the size ratio between portions, and the like are not necessarily the same as the actual ones. Also, even when the same parts are shown, the dimensions and ratios may be different depending on the drawing.
In addition, in the present specification and each figure, the same reference numerals are given to the same elements as those described above with respect to the already-appearing figures, and detailed description thereof will be omitted as appropriate.

FIG. 1 is a block diagram schematically showing a rotating machine drive system according to an embodiment.
As shown in FIG. 1 , the rotating machine drive system 2 includes a rotating machine 4 and a power conversion device 10 .

The rotating machine 4 rotates a rotor by being supplied with AC power from the power conversion device 10 . The rotating machine 4 is, for example, a synchronous motor or an induction machine. The rotating machine 4 is not limited to these, and may be any electric motor, generator, or the like that can rotate the rotor by supplying AC power.

The power conversion device 10 includes a converter 12 , a charge storage element 14 , a control section 16 and an overvoltage detection circuit 18 . The power conversion device 10 supplies AC power to the rotating machine 4 .

The converter 12 is connected with the rotating machine 4 and the charge storage element 14 . Charge storage element 14 supplies DC power to converter 12 . The charge storage element 14 is, for example, a capacitor. However, charge storage element 14 may be any element capable of supplying DC power to converter 12 .

Converter 12 is connected to rotating machine 4 via AC power lines 21-23. In FIG. 1, the inductance components of the AC power lines 21 to 23 are shown as inductance components 21L to 23L for convenience. Also, an AC reactor may be provided on the route of the AC power lines 21 to 23 in order to suppress current during an accident. The current flowing into the converter 12 at the time of an accident is given by the formula I=V/(ωL), where I is the phase current of the AC power lines 21 to 23, V is the phase voltage, and L is the inductance of the AC power lines 21 to 23. , can be derived. When an AC reactor is provided, the inductance L of the AC power lines 21 to 23 is the total inductance of the parasitic inductance of the power line and the inductance of the AC reactor. If the inductance L of the AC power lines 21 to 23 (the inductance of the AC reactor) is increased, the current at the time of an accident can be suppressed, but the voltage drop at the inductance L during steady operation also increases, and the converter capacity increases. put away. Therefore, when providing an AC reactor, it is necessary to appropriately set the inductance in consideration of the magnitude of the current at the time of an accident, the state during steady operation, and the like.

The converter 12 converts the DC power supplied from the charge storage element 14 into AC power, and supplies the converted AC power to the rotating machine 4 via the AC power lines 21 to 23, thereby rotating the rotating machine 4. rotate the child. The converter 12 , for example, converts the DC power supplied from the charge storage element 14 into three-phase AC power, and supplies the three-phase AC power to the rotating machine 4 . However, the AC power supplied from the converter 12 to the rotating machine 4 is not limited to three-phase AC power, and may be single-phase AC power or the like. In this case, the number of AC power lines may be two.

Further, the converter 12 converts, for example, AC power flowing from the rotating machine 4 side into DC power, and supplies the DC power to the charge storage element 14 to charge the charge storage element 14 . However, the converter 12 only needs to be configured to be able to supply AC power to at least the rotating machine 4 . The charge storage element 14 may be charged, for example, by supplying DC power from a charging circuit, another DC circuit, or the like.

The controller 16 is connected with the converter 12 . The control unit 16 controls the operation of power conversion by the converter 12 . The control unit 16 is connected to a higher-level controller via a network, for example, and controls the operation of the converter 12 in normal operation based on control signals input from the higher-level controller. Thereby, the control unit 16 rotates the rotor of the rotating machine 4 at, for example, the number of revolutions according to the control signal. The configuration of the control unit 16 is not limited to this. The operation of the converter 12 and the rotation of the rotor of the rotating machine 4 may be controlled based on a command input from an operation unit or the like connected to the controller. The configuration of the control unit 16 may be any configuration that can control the operation of power conversion by the converter 12 .

Overvoltage detection circuit 18 detects overvoltage in converter 12 . The overvoltage detection circuit 18 is connected, for example, to the AC power lines 21-23 between the converter 12 and the rotating machine 4, and detects line voltages of the AC power lines 21-23. In other words, the overvoltage detection circuit 18 detects the line voltage of the AC power supplied from the converter 12 to the rotating machine 4 . The overvoltage detection circuit 18 detects overvoltage of the converter 12 when the detected line voltage is equal to or higher than a predetermined threshold. When the AC power supplied from the converter 12 to the rotating machine 4 is three-phase AC power, the overvoltage detection circuit 18 detects three line voltages corresponding to each phase, and detects three line voltages. An overvoltage of the converter 12 is detected when any one of the voltages exceeds the threshold. The overvoltage detection circuit 18 is connected to the control section 16 . The overvoltage detection circuit 18 inputs the overvoltage detection result to the control unit 16 .

FIG. 2 is a block diagram schematically showing an example of a converter according to the embodiment;
As shown in FIG. 2, the converter 12 has a plurality of switching elements SW1-SW6 and a plurality of rectifying elements D1-D6.

The converter 12 has, for example, six switching elements SW1 to SW6 connected in a three-phase bridge. Converter 12 is, for example, a two-level converter. The converter 12 performs power conversion by switching a plurality of switching elements SW1 to SW6.

Semiconductor switching elements (self-extinguishing elements) such as GTOs (Gate Turn Off thyristors) and IGBTs (Insulated Gate Bipolar Transistors) are used for the switching elements SW1 to SW6. The switching elements SW1 to SW6 have, for example, a pair of main terminals and a control terminal. The switching elements SW1 to SW6 switch between an ON state in which current flow between the pair of main terminals is allowed and an OFF state in which current flow between the pair of main terminals is cut off, depending on the voltage of the control terminal.

Control terminals of the switching elements SW1 to SW6 are connected to the control section 16. FIG. Thus, the switching of the switching elements SW1 to SW6 is controlled by the control of the control section 16. FIG. The control unit 16 controls the operation of power conversion by the converter 12 by controlling switching between the ON state and the OFF state of the switching elements SW1 to SW6.

Each of the plurality of rectifying elements D1-D6 is connected in anti-parallel to each of the plurality of switching elements SW1-SW6. More specifically, the rectifying elements D1-D6 are connected in anti-parallel to a pair of main terminals of the switching elements SW1-SW6. The forward direction of the rectifying elements D1-D6 is opposite to the direction of the current flowing between the pair of main terminals of the switching elements SW1-SW6. The rectifying elements D1 to D6 are so-called freewheeling diodes. The rectifying elements D1 to D6 are not limited to diodes, and may be any element that allows current to flow in only one direction.

Thus, when the rectifying elements D1 to D6 are connected in anti-parallel to the switching elements SW1 to SW6, when the converter 12 is stopped for protection and the switching elements SW1 to SW6 are turned off, , energy flows into the charge storage element 14 from the rotating machine 4 via the rectifying elements D1 to D6, and the voltage of the charge storage element 14 and the line voltage of the AC power lines 21 to 23 may become overvoltage. . Such overvoltage causes the rotating machine 4 and the converter 12 to malfunction.

Therefore, after turning off the switching elements SW1 to SW6, the control unit 16 turns off the switching element SW1 so as to short-circuit the AC power lines 21 to 23 when an overvoltage is detected by the overvoltage detection circuit 18. to control switching between ON and OFF states of SW6.

For example, in the case of the configuration of the two-level converter shown in FIG. 2, the control unit 16 turns on the switching elements SW1, SW3, and SW5 of the upper arm, and turns off the switching elements SW2, SW4, and SW6 of the lower arm. state. As a result, the lines of the AC power lines 21 to 23 can be short-circuited.

FIG. 2 shows, as an example, a state in which the current C1 flowing from the AC power line 21 to the converter 12 flows to the AC power line 23 via the rectifying element D1 and the ON-state switching element SW5. In other words, the AC power line 21 and the AC power line 23 are short-circuited by the rectifying element D1 and the ON-state switching element SW5.

In the case of the configuration of the two-level converter shown in FIG. 2, contrary to the above, the switching elements SW1, SW3, and SW5 in the upper arm are turned off, and the switching elements SW2, SW4, and SW6 in the lower arm are turned on. The AC power lines 21 to 23 can also be short-circuited by setting the state.

As described above, in the power converter 10 according to the present embodiment, after the control unit 16 turns off the switching elements SW1 to SW6, when the overvoltage detection circuit 18 detects an overvoltage, the AC power lines 21 to 23 The switching of the switching elements SW1 to SW6 between the ON state and the OFF state is controlled so as to short-circuit between the lines. As a result, the inflow of energy from the rotating machine 4 to the charge storage element 14 is suppressed, and failure of the rotating machine 4 or the converter 12 due to overvoltage of the voltage of the charge storage element 14 or the line voltage of the AC power lines 21 to 23 is prevented. can be suppressed.

In addition, in the configuration of the power converter 10 , there is no need to provide an overvoltage protection circuit or the like that withstands the short-circuit current of the rotating machine 4 separately from the converter 12 . In other words, in the power converter 10 , the converter 12 bears the short-circuit current of the rotating machine 4 while performing overvoltage protection. Accordingly, in the power conversion device 10, compared to a configuration in which an overvoltage protection circuit or the like is separately provided, it is possible to suppress an increase in the size of the device and an increase in the manufacturing cost. Therefore, in the power conversion device 10 according to the present embodiment, it is possible to suppress failure due to overvoltage with a simpler configuration.

FIG. 3 is a block diagram schematically showing a modification of the converter according to the embodiment;
As shown in FIG. 3, in this example, the converter 12 has multiple switching elements SW11 to SW22, multiple rectifying elements D11 to D22, and multiple rectifying elements D31 to D36. It should be noted that the same reference numerals are given to the parts that are substantially the same as those of the above-described embodiment in terms of function and configuration, and detailed description thereof will be omitted.

The converter 12 has three AC terminals A1 to A3, and is connected to the AC power lines 21 to 23 and the rotating machine 4 via the AC terminals A1 to A3. For example, when the AC power supplied from the converter 12 to the rotating machine 4 is single-phase AC power, the converter 12 has two AC terminals. Thus, converter 12 has a plurality of AC terminals corresponding to the AC power to be output.

A plurality of switching elements SW11 to SW22 are connected in a three-phase bridge. Each of the plurality of rectifying elements D11-D22 is connected in anti-parallel to each of the plurality of switching elements SW11-SW22.

In this example, both ends of each leg of a plurality of switching elements SW11 to SW22 connected in a three-phase bridge form DC connection points. In this power conversion device 10, two charge storage elements 14 are connected in series between the DC connection points of the converter 12, and the connection point of the two charge storage elements 14 is the neutral point NP.

The transducer 12 is of bridge type and has six arms. The configuration of each phase arm connected to each AC terminal A1 to A3 is substantially the same. Therefore, two arms, an upper arm and a lower arm, connected to the AC terminal A1 will be described here as an example.

The upper arm includes two switching elements SW11 and SW12 connected in series, rectifying elements D11 and D12 connected in antiparallel to the switching elements SW11 and SW12, respectively, and the switching elements SW11 and SW12 connected in series. and a rectifying element D31 connected between the point and the neutral point NP.

Similarly, the lower arm includes two switching elements SW13 and SW14 connected in series, rectifying elements D13 and D14 connected in anti-parallel to these switching elements SW13 and SW14, and switching elements SW13 and SW14. and a rectifying element D32 connected between the series connection point of and the neutral point NP.

The upper arm and lower arm are connected in series between a pair of DC connection points, and the series connection point (AC terminal A1) of the upper arm and lower arm is connected to AC power line 21 . The potential at the series connection point of the two switching elements SW11 and SW12 of the upper arm is clamped to the potential at the neutral point NP via the rectifying element D31. Similarly, the potential of the series connection point of the two switching elements SW13 and SW14 of the lower arm is clamped to the potential of the neutral point NP via the rectifying element D32. Each of the rectifying elements D11-D14 is a so-called freewheeling diode. Each rectifying element D31, D32 is a so-called clamp diode.

In this converter 12, according to the switching of the switching elements SW11 to SW22, the potentials of the AC terminals A1 to A3 are clamped to one of three levels of positive potential, negative potential, and neutral potential. . This converter 12 is a so-called Neutral-Point-Clamped (NPC) type converter.

In the case of the configuration of the 3-level NPC converter shown in FIG. The elements SW12, SW13, SW16, SW17, SW20 and SW21 are turned on, and the outer switching elements SW11, SW14, SW15, SW18, SW19 and SW22 are turned off. As a result, the lines of the AC power lines 21 to 23 can be short-circuited.

As an example, FIG. 3 shows a state in which the current C2 flowing from the AC power line 21 to the converter 12 flows to the AC power line 22 via the switching element SW13, the rectifying elements D32 and D33, and the switching element SW16. In other words, the AC power line 21 and the AC power line 22 are short-circuited by the switching element SW13, the rectifying elements D32 and D33, and the switching element SW16.

Thus, the configuration of the converter 12 may be a 2-level converter configuration, a 3-level NPC converter configuration, or the like. The configuration of the converter 12 includes at least a plurality of switching elements and a plurality of rectifying elements connected in anti-parallel. Any configuration capable of short-circuiting the lines of the AC power lines 21 to 23 by switching may be used.

FIG. 4 is a block diagram schematically showing a modification of the power converter.
As shown in FIG. 4, the power conversion device 10a further includes an overvoltage protection circuit 30. As shown in FIG. The overvoltage protection circuit 30 is connected to the AC power lines 21-23 via wirings 31-33. The wiring 31 is connected to the AC power line 21 . The wiring 32 is connected to the AC power line 22 . The wiring 33 is connected to the AC power line 23 . The overvoltage protection circuit 30 is in other words connected in parallel with the converter 12 .

The overvoltage protection circuit 30 switches between a protection state in which the lines of the AC power lines 21 to 23 are short-circuited and a normal state in which the short-circuit between the lines of the AC power lines 21 to 23 is eliminated. The overvoltage protection circuit 30 has, for example, a switching element inside, and switches between a protected state and a normal state by switching the switching element.

The overvoltage protection circuit 30 is connected with the control section 16 . The overvoltage protection circuit 30 switches between a protection state and a normal state under the control of the control section 16 .

In normal operation, the control unit 16 puts the overvoltage protection circuit 30 in the normal state, and puts the overvoltage protection circuit 30 in the protection state when the overvoltage detection circuit 18 detects an overvoltage. After turning off the plurality of switching elements of the converter 12, the control unit 16 switches the converter 12 so as to short-circuit the AC power lines 21 to 23 when an overvoltage is detected by the overvoltage detection circuit 18. While controlling the switching between the ON state and the OFF state of the plurality of switching elements, the overvoltage protection circuit 30 is switched from the normal state to the protection state.

Thus, by further providing the overvoltage protection circuit 30, the overvoltage protection operation is performed by the converter 12 and the overvoltage protection circuit 30, and the short-circuit current of the rotating machine 4 is shared between the converter 12 and the overvoltage protection circuit 30. may

In this case, the current capacity of the overvoltage protection circuit 30 can be reduced compared to the case where the overvoltage protection operation is performed only by the overvoltage protection circuit 30, thereby suppressing an increase in the size of the overvoltage protection circuit 30 and an increase in manufacturing cost. be able to. Therefore, even in the configuration of the power conversion device 10a, failure due to overvoltage can be suppressed with a simpler configuration.

For example, when the current capacity of the converter 12 is set to the current capacity required for normal operation, and the overvoltage protection operation is performed only by the overvoltage protection circuit 30, the current capacity of the overvoltage protection circuit 30 is set to the maximum current at the time of an accident. should be set to withstand On the other hand, as described above, the current capacity of the converter 12 is set to the current capacity necessary for normal operation, and the overvoltage protection circuit 30 is made to bear only the shortfall of the fault current in the converter 12. , the current capacity of the overvoltage protection circuit 30 can be reduced by the current capacity of the converter 12 . That is, the current capacity of the overvoltage protection circuit 30 can be made smaller than the current capacity that can withstand the maximum current during an accident. As a result, even when the overvoltage protection circuit 30 is provided, it is possible to suppress an increase in the size of the entire device and an increase in the manufacturing cost.

In FIG. 4, the inductance components of the wirings 31 to 33 are illustrated as inductance components 31L to 33L for convenience. Overvoltage is detected by the overvoltage detection circuit 18, and when the AC power lines 21 to 23 are short-circuited to the converter 12 and the overvoltage protection circuit 30, the current flowing into the converter 12 and the current flowing into the overvoltage protection circuit 30. can be obtained from the ratio of the inductance components 21L to 23L of the AC power lines 21 to 23 and the inductance components 31L to 33L of the wirings 31 to 33.

For example, the AC power line 21 ~ 23 and the inductance components 31L to 33L of the wirings 31 to 33 are set. Thereby, the current capacity of the overvoltage protection circuit 30 can be made smaller than the current capacity of the converter 12 as described above. The ratio between the inductance components 21L to 23L of the AC power lines 21 to 23 and the inductance components 31L to 33L of the wirings 31 to 33 may be set using, for example, AC reactors.

FIG. 5 is a block diagram schematically showing a modification of the power converter.
As shown in FIG. 5, the power converter 10b comprises two converters 12a, 12b and two charge storage elements 14a, 14b. In the power converter 10b, each of the two converters 12a and 12b is connected to the rotating machine 4. As shown in FIG. In the power converter 10b, two converters 12a and 12b are connected in parallel to the rotating machine 4. As shown in FIG. Charge storage element 14a supplies DC power to converter 12a. Charge storage element 14b supplies DC power to converter 12b. The configuration of transducers 12a, 12b may be any of the configurations described with respect to FIGS. 2, 3, and the like.

Converter 12a is connected to rotating machine 4 via AC power line 21a. Converter 12b is connected to rotating machine 4 via AC power line 21b. The AC power line 21b is connected to, for example, the AC power line 21a. In other words, the AC power line 21b branches from the AC power line 21a and connects the rotating machine 4 and the converter 12b.

The control unit 16 supplies AC power to the rotating machine 4 from each of the two converters 12a and 12b by controlling the operation of each of the two converters 12a and 12b. Then, after turning off the switching elements of the converters 12a and 12b, the control unit 16 short-circuits the AC power lines 21a and 21b when an overvoltage is detected by the overvoltage detection circuit 18. It controls switching between the ON state and the OFF state of the switching element of each converter 12a, 12b.

Thus, power converter 10b may comprise two converters 12a, 12b. As a result, the current duty of each converter 12a, 12b can be reduced. In other words, the current capacity of each converter 12a, 12b can be reduced.

When connecting the converters 12 a and 12 b in parallel, the AC power line 21 a has an AC reactor 41 and the AC power line 21 b has an AC reactor 42 . AC reactors 41 and 42 adjust the current sharing of converters 12a and 12b.

The AC reactors 41 and 42, for example, suppress the current imbalance of the converters 12a and 12b, and substantially equalize the current supplied from the converter 12a to the rotating machine 4 and the current supplied from the converter 12b to the rotating machine 4. essentially the same. In addition, by providing the AC reactors 41 and 42 in this way, when an overvoltage is detected and the AC power lines 21a and 21b are short-circuited, the balance of the currents flowing through the converters 12a and 12b can be ensured. can be done. For example, when an overvoltage is detected and causes a short circuit between the AC power lines 21a, 21b, substantially the same amount of current can flow through the converters 12a, 12b.

However, the current sharing of the converters 12a and 12b may not necessarily be the same. For example, if the current capacities of the converters 12a and 12b are different, when an overvoltage is detected and the AC power lines 21a and 21b are short-circuited, the current capacities of the converters 12a and 12b are not exceeded. Additionally, the inductance ratio of the AC reactors 41 and 42 may be adjusted.

Note that the number of converters provided in the power converter 10b is not limited to two, and may be three or more. That is, the power electronics device 10b may include a plurality of converters. When the overvoltage detection circuit 18 detects an overvoltage, the control unit 16 controls switching between the ON state and the OFF state of the switching elements of the plurality of converters so as to short-circuit the lines of the AC power lines. good.

The power conversion device 10b is provided with two charge storage elements 14a and 14b respectively corresponding to the two converters 12a and 12b. Without being limited to this, for example, one charge storage element may be used in common for a plurality of converters. The charge storage element may provide DC power to multiple converters.

Further, when connecting a plurality of converters in parallel, as shown in FIG. Preferably, the line voltage of the AC power line is sensed at an intermediate location. As a result, even when a plurality of converters are connected in parallel, the overvoltage of the plurality of converters can be appropriately detected without complicating the configuration of the overvoltage detection circuit 18, and the overvoltage of the plurality of converters and the rotating machine 4 can be detected. Failure due to overvoltage can be appropriately suppressed.

Moreover, in the power conversion device 10b, a plurality of converters may be provided, and an overvoltage protection circuit 30 may be further provided. When an overvoltage is detected by the overvoltage detection circuit 18, the control unit 16 controls switching between ON and OFF states of the switching elements of the plurality of converters so as to short-circuit the lines of the AC power lines. The overvoltage protection circuit 30 may be switched from the normal state to the protection state.

FIG. 6 is a block diagram schematically showing a modification of the power converter.
As shown in FIG. 6, in the power converter 10c, the overvoltage detection circuit 18a is connected to the charge storage element 14 and detects the DC voltage of the charge storage element 14. FIG. In other words, the overvoltage detection circuit 18 a detects the DC voltage of the DC power supplied to the converter 12 . The overvoltage detection circuit 18a detects overvoltage of the converter 12 when the detected DC voltage is equal to or higher than a predetermined threshold. The overvoltage detection circuit 18 a is connected to the control unit 16 and inputs the overvoltage detection result to the control unit 16 .

Thus, the overvoltage detection circuit may detect the DC voltage on the DC side of the converter 12 without being limited to the line voltage of the AC power line. Also in this case, as in the above-described embodiments, it is possible to suppress failures due to overvoltage in the rotating machine 4 and the converter 12 with a simpler configuration.

However, for example, when an AC reactor is provided on the AC power line, the rise of the voltage on the DC side of the converter 12 is delayed, and the line voltage is overvoltage before the overvoltage is detected in the DC voltage. There is a possibility that it has become. Therefore, when an AC reactor is provided on the AC power line (when the inductance component of the AC power line is large), the overvoltage detection circuit detects the line voltage of the AC power line as described in FIG. is more preferable. As a result, for example, failure due to overvoltage of the rotating machine 4 can be suppressed more reliably.

Further, the overvoltage detection circuit, for example, detects both the line voltage of the AC power line and the DC voltage on the DC side of the converter 12, and when either the line voltage or the DC voltage exceeds a predetermined threshold, Alternatively, it may be configured to detect overvoltage. More specifically, the overvoltage detection circuit may be configured to detect overvoltage when the line voltage exceeds the first threshold or when the DC voltage exceeds the second threshold.

While several embodiments of the invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

2 Rotating Machine Drive System 4 Rotating Machine 10, 10a to 10c Power Converter 12, 12a, 12b Converter 14, 14a, 14b Charge Storage Element 16 Control Section 18, 18a Overvoltage detection circuit 21 to 23 AC power line 21a, 21b AC power line 30 Overvoltage protection circuit 31 to 33 Wiring 41, 42 AC reactor D1 to D6, D11 to D22, D31 to D36 Rectification Elements, SW1 to SW6, SW11 to SW22...switching elements

Claims (7)

A power conversion device that supplies AC power to a rotating machine,
A converter connected to a charge storage element and connected to the rotating machine via an AC power line, converts DC power supplied from the charge storage element into AC power, and supplies the AC power to the rotating machine. When,
a control unit that controls the operation of power conversion by the converter;
an overvoltage detection circuit that detects overvoltage of the converter and inputs a detection result to the control unit;
with
The converter has a plurality of switching elements and a plurality of rectifying elements connected in inverse parallel to each of the plurality of switching elements, and performs power conversion by switching the plurality of switching elements,
Each of the plurality of switching elements has a pair of main terminals, and has an ON state that allows current flow between the pair of main terminals and an OFF state that blocks current flow between the pair of main terminals. switching,
The control unit controls the switching of the plurality of switching elements between the on state and the off state to control the operation of power conversion by the converter, and switches the plurality of switching elements between the off state and the off state. After that, when an overvoltage is detected by the overvoltage detection circuit, the power conversion device controls switching between the on state and the off state of the plurality of switching elements so as to short-circuit the lines of the AC power line. . An overvoltage protection circuit connected to the AC power line and switching between a protection state in which the lines of the AC power line are short-circuited and a normal state in which the line-to-line short circuit of the AC power line is eliminated,
The control unit controls switching of the overvoltage protection circuit between the protection state and the normal state, and in normal operation, the overvoltage protection circuit is in the normal state, and the plurality of switching elements are in the off state. After that, when an overvoltage is detected by the overvoltage detection circuit, switching between the ON state and the OFF state of the plurality of switching elements is controlled so as to short-circuit the lines of the AC power line, and the overvoltage is detected. 2. The power converter according to claim 1, wherein the protection circuit is switched from the normal state to the protection state. 3. The power converter according to claim 2, wherein the current capacity of the overvoltage protection circuit is smaller than the current capacity that can withstand the maximum current at the time of an accident. comprising a plurality of said converters connected in parallel;
After turning off the plurality of switching elements, the control unit causes the plurality of converters to short-circuit the AC power lines when an overvoltage is detected by the overvoltage detection circuit. 2. The power converter according to claim 1, wherein switching between said ON state and said OFF state of a plurality of switching elements is controlled. An overvoltage protection circuit connected to the AC power line and switching between a protection state in which the lines of the AC power line are short-circuited and a normal state in which the line-to-line short circuit of the AC power line is eliminated,
The control unit controls switching of the overvoltage protection circuit between the protection state and the normal state, and in normal operation, the overvoltage protection circuit is in the normal state, and the plurality of switching elements are in the off state. After that, when the overvoltage detection circuit detects an overvoltage, the plurality of switching elements of the plurality of converters are switched between the on state and the off state so as to short-circuit the lines of the AC power lines. 5. The power converter according to claim 4, which controls and switches the overvoltage protection circuit from the normal state to the protection state. 6. The overvoltage detection circuit according to any one of claims 1 to 5, wherein the overvoltage detection circuit detects the line voltage of the AC power line, and detects the overvoltage of the converter when the detected line voltage is equal to or higher than a predetermined threshold. 1. The power converter according to 1. 7. The overvoltage detection circuit according to any one of claims 1 to 6, wherein the overvoltage detection circuit detects the DC voltage of the charge storage element, and detects the overvoltage of the converter when the detected DC voltage is equal to or higher than a predetermined threshold. The power conversion device according to .

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