JP2022009985A - Power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion device of a multistage configuration which can simplify a configuration of a host control device even when bypass of a failed converter is allowed to improve operation continuity.

SOLUTION: There is provided a power conversion device, which comprises: a main circuit part which converts power by operations of a plurality of converters connected in series; and a host control device which controls the operations of the plurality of converters, in which each of the plurality of converters comprises: a plurality of switching elements; a plurality of rectifiers connected in parallel with the plurality of switching elements; a charge storage element connected in parallel with the plurality of switching elements; a control part which controls on/off of the plurality of switching elements; a feeder circuit which generates control power supply of the control part on the basis of electric charges stored in the charge storage element; and a storage part which stores failure information representing a failure of itself, and the control part makes a converter stored as a failure into a bypass state by referring to the failure information of the storage part.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2022,JPO&INPIT

Description

Embodiments of the present invention relate to a power conversion device.

There is a multi-stage power conversion device including a plurality of converters connected in series and a higher-level control device for controlling the operation of each converter. Each converter controls on / off of a plurality of switching elements, a rectifying element connected in parallel to each switching element, a charge storage element connected in parallel to each switching element, and each switching element. It has a control unit.

When the number of series of each converter is large, the potential of the upper controller is lower than the potential of each converter. In such a case, it is difficult to supply control power from the host control device to the control unit of each converter from the viewpoint of insulation. Therefore, each converter is provided with a power supply circuit that supplies control power to the control unit from the main circuit side such as a charge storage element.

Further, in the multi-stage power converter, the failure of each converter is monitored by the host control device, and when the failure is detected, the converter is put into a bypass state. As a result, even if any of the plurality of converters connected in series fails, the operation can be continued, and the operation continuity of the power converter can be improved.

However, if it is attempted to control the failure of a plurality of converters only by the upper control device, the configuration of the upper control device becomes complicated. For example, it causes an increase in size and cost of the host control device.

Therefore, in a multi-stage power converter, it is desired to simplify the configuration of the host controller even when the failed converter can be bypassed to improve the operation continuity.

Japanese Unexamined Patent Publication No. 2013-27260

An embodiment of the present invention provides a multi-stage power conversion device that can simplify the configuration of a higher-level control device even when the failed converter can be bypassed to improve operation continuity.

According to the embodiment of the present invention, there are a plurality of converters connected in series, and the conversion of AC power to DC power and the conversion of DC power to AC power by the operation of the plurality of converters. A main circuit unit that performs at least one of the above, and a higher-level control device that controls the operation of the plurality of converters, each of the plurality of converters being connected by a half bridge or a plurality of full bridges. On / off of a switching element, a plurality of rectifying elements connected in parallel to each of the plurality of switching elements, a charge storage element connected in parallel to the plurality of switching elements, and the plurality of switching elements. A power supply circuit that generates a control power supply for the control unit based on the charge stored in the charge storage element and supplies the generated control power supply to the control unit, and represents its own failure. It has a storage unit for storing failure information, and the control unit is activated in response to the supply of the control power supply from the power supply circuit, and then refers to the failure information in the storage unit and is stored as a failure. If so, a power converter is provided that puts the converter, which is stored as a failure, in a bypass state.

A multi-stage power converter that can simplify the configuration of the host controller is provided even when the failed converter can be bypassed to improve the operation continuity.

It is a block diagram schematically showing the power conversion apparatus which concerns on 1st Embodiment. It is a block diagram which shows typically the converter which concerns on 1st Embodiment. It is a block diagram schematically showing the module which concerns on 1st Embodiment. It is a flowchart which schematically shows an example of the operation of the power conversion apparatus which concerns on 1st Embodiment. It is a block diagram schematically showing the module which concerns on 2nd Embodiment. It is a flowchart which schematically shows an example of the operation of the power conversion apparatus which concerns on 2nd Embodiment. It is a block diagram schematically showing the modification of the module which concerns on 2nd Embodiment. It is a block diagram which shows the modification of the main circuit schematically.

Hereinafter, each embodiment will be described with reference to the drawings.
It should be noted that the drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the ratio of the sizes between the parts, and the like are not necessarily the same as the actual ones. Further, even when the same part is represented, the dimensions and ratios may be different from each other depending on the drawing.
In the specification of the present application and each figure, the same elements as those described above with respect to the above-mentioned figures are designated by the same reference numerals, and detailed description thereof will be omitted as appropriate.

(First Embodiment)
FIG. 1 is a block diagram schematically showing a power conversion device according to the first embodiment.
As shown in FIG. 1, the power conversion device 10 includes a main circuit unit 12 and an upper control device 14. The power converter 10 is used, for example, in a DC power transmission system. The power conversion device 10 is connected to the AC power system 2 and the pair of DC transmission lines 3 and 4 in the DC transmission system.

The DC power transmission system has, for example, a transformer 6. The main circuit unit 12 of the power conversion device 10 is connected to the AC power system 2 via the transformer 6. The AC power of the AC power system 2 is a three-phase AC power. More specifically, it is symmetrical three-phase AC power. The transformer 6 converts the three-phase AC power of the AC power system 2 into AC power corresponding to the main circuit unit 12. The transformer 6 changes the effective value of each phase of the three-phase AC power according to the main circuit unit 12. The transformer 6 is a three-phase transformer. The transformer 6 is provided as needed and can be omitted. The three-phase AC power of the AC power system 2 may be directly supplied to the main circuit unit 12.

The power conversion device 10 converts the three-phase AC power supplied from the AC power system 2 into DC power, and supplies the converted DC power to the DC transmission lines 3 and 4. Further, the power conversion device 10 converts the DC power supplied from the DC transmission lines 3 and 4 into three-phase AC power, and supplies the converted three-phase AC power to the AC power system 2. In this way, the power conversion device 10 performs AC / DC conversion from AC to DC and AC / DC conversion from DC to AC.

For example, the DC transmission line 3 is a transmission line on the high voltage side of DC power, and the DC transmission line 4 is a transmission line on the low voltage side of DC power. The power conversion device 10 outputs the converted DC power to the DC transmission lines 3 and 4 so that the DC transmission line 3 side has a high voltage and the DC transmission line 4 side has a low voltage.

The main circuit unit 12 is provided between the AC power system 2 and the DC transmission lines 3 and 4. The main circuit unit 12 performs conversion from three-phase AC power to DC power and conversion from DC power to three-phase AC power. The main circuit unit 12 is, for example, an MMC (Modular Multilevel Converter) type power converter. The MMC type main circuit unit 12 has a plurality of converters connected in series. Each converter has a plurality of switching elements connected in half bridge or full bridge, and a charge storage element connected in parallel to each switching element. The main circuit unit 12 performs AC / DC conversion by switching each switching element.

The upper control device 14 is connected to the main circuit unit 12. The host control device 14 controls the conversion of the three-phase AC power to the DC power and the conversion of the DC power to the three-phase AC power by the main circuit unit 12 by controlling the on / off of each switching element. ..

The main circuit unit 12 includes a pair of first and second DC terminals 20a and 20b, three first to third AC terminals 21a to 21c, and six first to sixth arm units 22a to 22f. , Have.

The first DC terminal 20a is connected to the DC transmission line 3 on the high voltage side. The second DC terminal 20b is connected to the DC transmission line 4 on the low voltage side. As a result, the DC power converted by the main circuit unit 12 is supplied to the DC transmission lines 3 and 4, and the DC power supplied from the DC transmission lines 3 and 4 is input to the main circuit unit 12.

The first arm portion 22a is connected to the first DC terminal 20a. The second arm portion 22b is connected between the first arm portion 22a and the second DC terminal 20b. The first arm portion 22a and the second arm portion 22b are connected in series between the DC terminals 20a and 20b.

The third arm portion 22c is connected to the first DC terminal 20a. The fourth arm portion 22d is connected between the third arm portion 22c and the second DC terminal 20b. The third arm portion 22c and the fourth arm portion 22d are connected in parallel to the first arm portion 22a and the second arm portion 22b.

The fifth arm portion 22e is connected to the first DC terminal 20a. The sixth arm portion 22f is connected between the fifth arm portion 22e and the second DC terminal 20b. That is, the fifth arm portion 22e and the sixth arm portion 22f are connected in parallel to the first arm portion 22a and the second arm portion 22b, and are connected to the third arm portion 22c and the fourth arm portion 22d. Connected in parallel.

In the main circuit unit 12, the first arm portion 22a and the second arm portion 22b form the first leg LG1, the third arm portion 22c and the fourth arm portion 22d form the second leg LG2, and the fifth arm portion 22d. The third leg LG3 is configured by the 22e and the sixth arm portion 22f. That is, in this example, the main circuit unit 12 is a three-leg, six-arm three-phase inverter. The first arm portion 22a, the third arm portion 22c, and the fifth arm portion 22e are upper arms. The second arm portion 22b, the fourth arm portion 22d, and the sixth arm portion 22f are lower arms.

The first arm portion 22a has a plurality of converters UP1, UP2 ... UPM ₁ connected in series. The second arm portion 22b has a plurality of converters UN1, UN2 ... UNM ₂ connected in series. The third arm portion 22c has a plurality of converters VP1, VP2 ... VPM ₃ connected in series. The fourth arm portion 22d has a plurality of converters VN1, VN2 ... VNM ₄ connected in series. The fifth arm portion 22e has a plurality of converters WP1, WP2 ... WPM ₅ connected in series. The sixth arm portion 22f has a plurality of converters WN1, WN2 ... WNM ₆ connected in series.

However, in the following, the converters UP1, UP2 ... UPM ₁ , UN1, UN2 ... UNM ₂ , VP1, VP2 ... VPM ₃ , VN1, VN2 ... VNM ₄ , WP1, WP2 ... WPM ₅ , WN1, WN2 ... WNM ₆ are used. When collectively referred to, it is referred to as "converter CELL".

In each of the arm portions 22a to 22f, M ₁ , M ₂ , M ₃ , M ₄ , M ₅ , and M ₆ represent the number of converters CELL connected in series. The number of converter CELLs connected in series in each of the arm portions 22a to 22f is, for example, about 100 to 120. However, the number of converters CELL connected in series is not limited to this, and may be any number.

The number of converters CELL provided in the arm portions 22a to 22f is substantially the same. For example, when a large number of converter CELLs are connected, the number of converters CELLs provided in the arm portions 22a to 22f may be different within a range that does not affect the operation of the main circuit unit 12. For example, when 100 converters CELLs are connected in series to one arm portion, the number of converters CELLs provided in another arm portion may be different by 1 or 2.

Each of the arm portions 22a to 22f further has a buffer reactor 23a to 23f and a plurality of current detectors 24a to 24f. Further, the power conversion device 10 further includes a voltage detection unit 25.

The buffer reactors 23a to 23f are connected in series to each converter CELL in each of the arm portions 22a to 22f. The buffer reactor 23a of the first arm portion 22a is provided between the connection point between the AC terminal 21a and the first arm portion 22a and the second arm portion 22b and the converter UP1. The buffer reactor 23b of the second arm portion 22b is provided between the connection point between the AC terminal 21a and the first arm portion 22a and the second arm portion 22b and the converter UN1. The buffer reactor 23c of the third arm portion 22c is provided between the connection point between the AC terminal 21b, the third arm portion 22c and the fourth arm portion 22d, and the converter VP1. The buffer reactor 23d of the fourth arm portion 22d is provided between the connection point between the AC terminal 21b, the third arm portion 22c and the fourth arm portion 22d, and the converter VN1. The buffer reactor 23e of the fifth arm portion 22e is provided between the AC terminal 21c, the connection point between the fifth arm portion 22e and the sixth arm portion 22f, and the converter WP1. The buffer reactor 23f of the sixth arm portion 22f is provided between the AC terminal 21c, the connection point between the fifth arm portion 22e and the sixth arm portion 22f, and the converter WN1.

The current detector 24a is provided in the first arm portion 22a and detects the current flowing through the first arm portion 22a. That is, the current detector 24a detects the arm current of the first arm portion 22a. The current detector 24a is connected to the host control device 14 via wiring or the like (not shown). The current detector 24a inputs the detected current value of the first arm unit 22a to the host control device 14. As a result, the current value of the first arm portion 22a is input to the upper control device 14.

Similarly, the current detector 24b detects the current flowing through the second arm portion 22b, and inputs the detected current value to the host control device 14. The current detector 24c detects the current flowing through the third arm unit 22c, and inputs the detected current value to the host control device 14. The current detector 24d detects the current flowing through the fourth arm unit 22d, and inputs the detected current value to the host control device 14. The current detector 24e detects the current flowing through the fifth arm unit 22e, and inputs the detected current value to the host control device 14. The current detector 24f detects the current flowing through the sixth arm portion 22f, and inputs the detected current value to the host control device 14.

The voltage detection unit 25 detects the AC voltage (phase voltage) of each phase of the AC power system 2 and inputs the detected value to the host control device 14. The voltage detection unit 25 may be connected to the primary side of the transformer 6 or may be connected to the secondary side.

In the main circuit portion 12, the connection point between the first arm portion 22a and the second arm portion 22b, the connection point between the third arm portion 22c and the fourth arm portion 22d, and the fifth arm portion 22e and the sixth arm portion Each of the connection points with 22f becomes an AC output point.

The first AC terminal 21a is connected to a connection point between the first arm portion 22a and the second arm portion 22b. The second AC terminal 21b is connected to the connection point between the third arm portion 22c and the fourth arm portion 22d. The third AC terminal 21c is connected to the connection point between the fifth arm portion 22e and the sixth arm portion 22f. Each AC terminal 21a to 21c is connected to, for example, a transformer 6.

Each converter CELL is connected to the host control device 14 via the signal line 26. The host control device 14 controls the operation of the converter CELL by inputting a control signal to the converter CELL via the signal line 26. Further, the converter CELL inputs, for example, a control signal or a protection signal related to control and operation protection of the converter CELL to the host control device 14 via another signal line (not shown).

The communication method between the upper control device 14 and each converter CELL is not limited to the above, and for example, the upper control device 14 and each converter CELL may be daisy-chained. The communication method between the upper control device 14 and each converter CELL may be any communication method capable of transmitting and receiving signals between the upper control device 14 and each converter CELL.

FIG. 2 is a block diagram schematically showing the converter according to the first embodiment.
As shown in FIG. 2, the converter CELL includes a main circuit 40, a charge storage element 45, a control unit 46, a feeding circuit 48, and a voltage detector 50.

The main circuit 40 includes a first connection terminal 40a, a second connection terminal 40b, a first switching element 41, and a second switching element 42. Each of the switching elements 41 and 42 includes a pair of main terminals and a control terminal. The control terminal controls the current flowing between the pair of main terminals. For each of the switching elements 41 and 42, for example, a self-extinguishing element such as an IGBT is used. The pair of main terminals are, for example, emitters and collectors, and the control terminals are, for example, gates. Further, for each of the switching elements 41 and 42, for example, a normally-off type semiconductor element is used.

The pair of main terminals of the second switching element 42 are connected in series to the pair of main terminals of the first switching element 41. The first connection terminal 40a is connected between the first switching element 41 and the second switching element 42. The second connection terminal 40b is connected to a main terminal on the opposite side of the main terminal connected to the second switching element 42 of the first switching element 41.

The charge storage element 45 is connected in parallel to the first switching element 41 and the second switching element 42. The charge storage element 45 is, for example, a capacitor. Power is supplied to the converter CELL via the connection terminals 40a and 40b, respectively. In other words, the charge storage element 45 is charged by the electric power supplied via the connection terminals 40a and 40b.

Further, a rectifying element 41d is connected to the first switching element 41 in antiparallel to a pair of main terminals. The forward direction of the rectifying element 41d is opposite to the direction of the current flowing between the pair of main terminals of the first switching element 41. Similarly, the rectifying element 42d is connected to the second switching element 42 in antiparallel to the pair of main terminals. The rectifying elements 41d and 42d are so-called freewheeling diodes.

In this example, in the main circuit 40, the switching elements 41 and 42 are half-bridge connected. The main circuit 40 is, in other words, a chopper circuit. The first switching element 41 is a so-called low-side switch, and the second switching element 42 is a so-called high-side switch.

The control unit 46 controls the on / off of each of the switching elements 41 and 42. The control unit 46 is connected to the control terminal of the first switching element 41 via the gate circuit 51. The control unit 46 is connected to the control terminal of the second switching element 42 via the gate circuit 52. Further, the control unit 46 is connected to the host control device 14 via, for example, a signal line 26.

The host control device 14 transmits a control signal for controlling the on / off of each of the switching elements 41 and 42 to the control unit 46 via the signal line 26. The control unit 46 inputs a drive signal for switching on / off of each of the switching elements 41 and 42 to the gate circuits 51 and 52 based on the input control signal.

The gate circuit 51 is connected to the control terminal of the first switching element 41. The gate circuit 52 is connected to the control terminal of the second switching element 42. The gate circuits 51 and 52 switch on / off of the switching elements 41 and 42 based on the drive signal input from the control unit 46. As a result, the on / off of each of the switching elements 41 and 42 is controlled according to the control signal from the host control device 14. The host control device 14 generates a control signal for each converter CELL and controls on / off of each switching element 41, 42 of each converter CELL. As a result, the host control device 14 controls the power conversion by the main circuit unit 12.

The configuration of the converter CELL is not limited to the above, and may be any configuration capable of controlling the on / off of the switching elements 41 and 42. For example, the gate circuits 51 and 52 are provided as needed and can be omitted.

The power feeding circuit 48 is connected in parallel to the charge storage element 45. The power feeding circuit 48 generates a control power supply for the control unit 46 based on the charge stored in the charge storage element 45, and supplies the generated control power supply to the control unit 46. Further, in this example, the power feeding circuit 48 also supplies control power to the gate circuits 51 and 52. The power supply circuit 48 generates, for example, a control power supply corresponding to each of the control unit 46 and the gate circuits 51 and 52, and supplies the corresponding control power supply to each of the control unit 46 and the gate circuits 51 and 52. The control unit 46 operates in response to the supply of control power from the power supply circuit 48.

The voltage detector 50 is electrically connected to the charge storage element 45. Further, the voltage detector 50 is connected to the control unit 46 and is also connected to the host control device 14 via, for example, the control unit 46 and the signal line 26. The voltage detector 50 detects the voltage of the charge storage element 45 and outputs the detection result to the control unit 46 and the host control device 14. The configuration of the voltage detector 50 may be any configuration capable of outputting the detection result to the control unit 46 and the host control device 14.

The plurality of converters CELL are modularized for each of at least two converters CELL. In this example, one module MDL is formed by two transducers CELL. Therefore, the main circuit unit 12 has a plurality of modules MDL. In the two converters CELL of the module MDL, the power supply is multiplexed. The power supply circuit 48 supplies control power to the control unit 46 and the gate circuits 51 and 52 of each converter CELL included in the module MDL. As a result, even if any of the power supply circuits 48 of each converter CELL in the module MDL fails, control power is supplied from the power supply circuit 48 of the other converter CELLs to the control unit 46 and the gate circuits 51 and 52. be able to. Therefore, even if one power supply circuit 48 fails, the operation of the power conversion device 10 can be continued, and the operation continuity of the power conversion device 10 can be improved.

In the following, one converter CELL included in the module MDL will be referred to as "first converter CELL1", and the other converter CELL will be referred to as "second converter CELL2". The power supply circuit 48 of the first converter CELL1 supplies control power to the control unit 46 and the gate circuits 51 and 52 of the first converter CELL1, and also supplies the control power to the control unit 46 and the gate circuits 51 and 52 of the second converter CELL2. Also supplies control power. Similarly, the power supply circuit 48 of the second converter CELL2 supplies control power to the control unit 46 and the gate circuits 51 and 52 of the second converter CELL2, and also supplies the control power to the control unit 46 and the gate circuit 51 of the first converter CELL1. , 52 is also supplied with control power.

The number of converters CELL included in the module MDL is not limited to two, and may be three or more. Further, each converter CELL does not necessarily have to be modularized.

FIG. 3 is a block diagram schematically showing the module MDL according to the first embodiment.
As shown in FIG. 3, the control unit 46 of each converter CELL outputs the voltage of the charge storage element 45 (hereinafter referred to as cell voltage) detected by the voltage detector 50 to the host control device 14. The cell voltage of each converter CELL is input to the host controller 14. The cell voltage may be input to the upper control device 14 directly from the voltage detector 50 without going through the control unit 46.

The host control device 14 calculates the average value of the cell voltage of each converter CELL based on the cell voltage of each of the input converters CELL. Then, the upper control device 14 outputs the calculated average value to each control unit 46 of each converter CELL.

The control unit 46 of each converter CELL has a determination circuit 54. The determination circuit 54 determines an abnormality in the cell voltage of the charge storage element 45 based on the detection result of the voltage detector 50 and the input average value. For example, when the difference between the detection result of the voltage detector 50 and the average value is less than a predetermined value, the determination circuit 54 determines that the cell voltage is normal, and the difference between the detection result of the voltage detector 50 and the average value is. When it is equal to or more than a predetermined value, the cell voltage is determined to be abnormal.

When the determination circuit 54 determines that the determination circuit 54 is normal, the control unit 46 controls the on / off of the switching elements 41 and 42 according to the control signal from the host control device 14. On the other hand, when the determination circuit 54 determines an abnormality, the control unit 46 sets a bypass state between the connection terminals 40a and 40b of the converter CELL determined to be abnormal.

Here, the "bypass state" is a state in which the first connection terminal 40a and the second connection terminal 40b are conducted (short-circuited). In this example, for example, the bypass state can be set by turning the first switching element 41 into an on state and the second switching element 42 into an off state. As a result, in each converter CELL connected in series, even if one of the converters CELL fails, the failed converter CELL is placed in the bypass state to continue the operation of the power converter 10. be able to. The bypass state may be, for example, a state in which the first connection terminal 40a and the second connection terminal 40b are made conductive by using a switch other than the switching elements 41 and 42.

When the determination circuit 54 determines the abnormality and puts the bypass state between the connection terminals 40a and 40b of the converter CELL determined to be abnormal, the control unit 46 outputs information indicating the failure of the converter CELL to the upper control device 14. Output to. For example, the host control device 14 integrates the number of failed converters CELL for each arm unit 22a to 22f based on the information from the control unit 46, and the number of failed converters CELL reaches a predetermined number. In this case, the power conversion by the main circuit unit 12 is stopped.

Each converter CELL included in the module MDL is connected to each other. The first converter CELL1 is connected to the second converter CELL2. For example, when each converter CELL and the upper control device 14 are individually connected by a signal line 26 or the like, the first converter CELL 1 and the second converter CELL 2 are connected to each other via a dedicated signal line or the like. Connected to each other. For example, when each converter CELL and the upper control device 14 are daisy-chained, the first converter CELL1 and the second converter CELL2 are connected to each other via a signal line of the daisy chain.

Each converter CELL included in the module MDL shares the detection result of the voltage detector 50 with each other. The detection result of the voltage detector 50 of the first converter CELL1 is input to the control unit 46 of the first converter CELL1 and also input to the control unit 46 of the second converter CELL2. Similarly, the detection result of the voltage detector 50 of the second converter CELL2 is input to the control unit 46 of the second converter CELL2 and also input to the control unit 46 of the first converter CELL1.

The control unit 46 determines an abnormality in the voltage of each charge storage element 45 of each modularized converter CELL. Then, the control unit 46 can put the converter CELL in which the abnormality is determined into the bypass state.

For example, when the control unit 46 of the second converter CELL2 determines that the cell voltage of the first converter CELL1 is abnormal, the control unit 46 outputs a bypass signal to the gate circuits 51 and 52 of the first converter CELL1. The gate circuits 51 and 52 of the first converter CELL1 set a bypass state between the connection terminals 40a and 40b in response to the input of the bypass signal.

Thereby, for example, even if the control unit 46 of any of the converters CELL included in the module MDL fails, the operation can be continued by bypassing between the connection terminals 40a and 40b. Therefore, the operation continuity of the power conversion device 10 can be further improved.

For example, when only the determination circuit 54 of the control unit 46 of the first converter CELL1 fails and the abnormality cannot be determined properly, the input is input from the control unit 46 of the second converter CELL2. Depending on the bypass signal, the control unit 46 of the first converter CELL1 may drive the gate circuits 51 and 52 to put the connection terminals 40a and 40b in a bypass state.

As described above, in the configuration in which the control unit 46 of the second converter CELL2 can bypass the first converter CELL1, the control unit 46 of the second converter CELL2 has each of the first converters CELL1. The connection terminals 40a and 40b may be directly controlled to be in a bypass state, or the control unit 46 of the first converter CELL1 connects to each connection in response to an instruction from the control unit 46 of the second converter CELL2. The configuration may be such that the terminals 40a and 40b are in a bypass state.

For example, when the control unit 46 is instructed to bypass by the control unit 46 of another converter CELL included in the module MDL while the determination circuit 54 has not determined that the abnormality is present, the control unit 46 gives priority to the bypass. This makes it possible to further improve the continuity of operation and safety.

FIG. 4 is a flowchart schematically showing an example of the operation of the power conversion device according to the first embodiment.
FIG. 4 schematically shows an example of the operation related to the bypass control of the control unit 46. Hereinafter, the control unit 46 of the first converter CELL1 will be described as an example. Since the operation of the control unit 46 of the second converter CELL2 is substantially the same as the operation of the control unit 46 of the first converter CELL1, detailed description thereof will be omitted.

At the start of operation of the power conversion device 10, the charge storage element 45 of each converter CELL is charged by, for example, an initial charging circuit (not shown). When the charge storage element 45 is charged, the power feeding circuit 48 starts operating. The power supply circuit 48 that has started operation supplies control power supplies corresponding to the control unit 46 and the gate circuits 51 and 52, respectively. As a result, the control unit 46 is activated in response to the supply of the control power supply from the power supply circuit 48 (step S11 in FIG. 4).

The detection result of the voltage detector 50 of the first converter CELL1 and the detection result of the voltage detector 50 of the second converter CELL2 are input to the control unit 46 of the first converter CELL1. The control unit 46 of the first converter CELL1 outputs the input cell voltages of the first converter CELL1 and the second converter CELL to the host control device 14 (step S12 in FIG. 4). The cell voltage may be output from the control unit 46 to the host control device 14 periodically or continuously at predetermined intervals.

When the cell voltage information is input from each converter CELL, the host controller 14 calculates the average value of the cell voltage of each input converter CELL (step S13 in FIG. 4). The average value of the cell voltage may be used for all the converters CELL, or may be averaged for each of an arbitrary number of converters CELL and calculated individually. For example, the average value of the cell voltage of each converter CELL may be calculated for each of the arm portions 22a to 22f. After that, the host control device 14 outputs the calculated average value to the control unit 46 of each converter CELL (step S14 in FIG. 4).

When the average value is input from the host control device 14, the control unit 46 causes the determination circuit 54 to determine the abnormality of the cell voltage (step S15 in FIG. 4).

When the cell voltage is determined to be normal, the control unit 46 returns to the process of step S12 and repeats the same process. On the other hand, when the cell voltage is determined to be abnormal, the control unit 46 sets a bypass state between the connection terminals 40a and 40b of the converter CELL determined to be abnormal (step S16 in FIG. 4).

As described above, in the power converter 10 according to the present embodiment, each converter CELL determines the abnormality of the cell voltage. As a result, the configuration of the upper control device 14 can be simplified as compared with the case where the upper control device 14 determines all the abnormalities of the cell voltage of each converter CELL. In the power conversion device 10 according to the present embodiment, the configuration of the host control device 14 can be simplified even when the failed converter CELL can be bypassed to improve the operation continuity. For example, it is possible to suppress an increase in size and cost of the upper control device 14.

Further, the control unit 46 of the first converter CELL1 also determines an abnormality in the cell voltage of the second converter CELL2. Then, when the control unit 46 of the first converter CELL1 determines that the cell voltage of the second converter CELL2 is abnormal, the control unit 46 puts the second converter CELL2 in the bypass state. This makes it possible to further improve the continuity of operation.

(Second embodiment)
FIG. 5 is a block diagram schematically showing the module MDL according to the second embodiment.
The same reference numerals are given to those having substantially the same functions and configurations as those of the first embodiment, and detailed description thereof will be omitted.
As shown in FIG. 5, each converter CELL further has a storage unit 60. The storage unit 60 stores failure information 62 indicating the state of failure of the converter CELL itself.

The failure information 62 includes, for example, a determination result of an abnormality in the cell voltage determined by the determination circuit 54. As a result, the control unit 46 can recognize whether the cell voltage is in a normal state or an abnormal state by referring to the failure information 62.

The information included in the failure information 62 is not limited to the information of the determination result of the abnormality of the cell voltage. For example, information on abnormalities of the switching elements 41 and 42 may be included in the failure information 62. The information included in the failure information 62 may be any information related to the failure of the converter CELL.

Further, each converter CELL included in the module MDL shares the failure information 62 with each other. The failure information 62 includes, for example, information indicating the state of failure of each converter CELL included in the module MDL. For example, the failure information 62 of the first converter CELL1 includes the determination result of the cell voltage of the first converter CELL1 and the determination result of the cell voltage of the second converter CELL2. The failure information 62 of the second converter CELL2 includes the determination result of the cell voltage of the second converter CELL2 and the determination result of the cell voltage of the first converter CELL1. Thereby, by referring to the failure information 62, it is possible to recognize the failure state of each converter CELL included in the module MDL. The storage unit 60 may store, for example, a plurality of failure information 62 for each converter CELL included in the module MDL.

FIG. 6 is a flowchart schematically showing an example of the operation of the power conversion device according to the second embodiment.
FIG. 6 schematically shows an example of the operation of the control unit 46 at the time of activation.
As described above, the control unit 46 is activated in response to the supply of control power from the power supply circuit 48 (step S21 in FIG. 6). After starting, the control unit 46 refers to the failure information 62 of the storage unit 60 (step S22 in FIG. 6).

The control unit 46 refers to the failure information 62 and confirms whether or not the converter CELL in its own module MDL is stored as a failure in the failure information 62 (step S23 in FIG. 6).

When the control unit 46 is stored as having a failure, the converter CELL in the module MDL puts the converter CELL stored as a failure in a bypass state (step S24 in FIG. 6).

On the other hand, when it is stored that the control unit 46 has not failed, the control unit 46 controls on / off of the switching elements 41 and 42 according to the control signal from the host control device 14, and converts the power. Start control.

As described above, in the present embodiment, each of the converters CELL stores the failure information 62. Thereby, for example, the configuration of the upper control device 14 can be simplified as compared with the case where the upper control device 14 stores the failure information 62 of each converter CELL.

Further, the control unit 46 confirms the failure of each converter CELL included in the module MDL by referring to the failure information 62, and puts the converter CELL stored as the failure in the bypass state. The control unit 46 of the first converter CELL1 also confirms the failure of the second converter CELL2. The control unit 46 of the first converter CELL1 puts the second converter CELL2 in the bypass state when it is stored that the second converter CELL2 is out of order.

As a result, for example, even if the control unit 46 or the storage unit 60 of any of the converters CELL included in the module MDL is out of order, the operation can be continued, and the operation continuity is further improved. be able to.

For example, when the control unit 46 is instructed to bypass by the control unit 46 of another converter CELL included in the module MDL in a state where its own converter CELL has not determined to be abnormal, the control unit 46 gives priority to bypass. This makes it possible to further improve the continuity of operation and safety.

FIG. 7 is a block diagram schematically showing a modified example of the module MDL according to the second embodiment.
As shown in FIG. 7, in this example, the determination circuit 54 is omitted. In this example, for example, the host controller 14 determines all the abnormalities in the cell voltage of each converter CELL. As described above, the failure information 62 may be stored in each of the converter CELLs while the determination of the abnormality of the cell voltage of each converter CELL is performed by the host control device 14 or the like. Even in this case, the configuration of the upper control device 14 can be simplified as compared with the case where the upper control device 14 stores the failure information 62 of each converter CELL.

However, as shown in FIG. 5, each converter CELL is provided with a determination circuit 54 and a storage unit 60, and each converter CELL is made to determine the abnormality of the cell voltage and store the failure information 62. Thereby, the configuration of the upper control device 14 can be further simplified.

FIG. 8 is a block diagram schematically showing a modified example of the main circuit.
As shown in FIG. 8, in this example, the main circuit 40 has a first switching element 41 and a second switching element 42, and further has a third switching element 43 and a fourth switching element 44. For the third switching element 43 and the fourth switching element 44, substantially the same elements as those of the first switching element 41 and the second switching element 42 are used.

The pair of main terminals of the fourth switching element 44 are connected in series to the pair of main terminals of the third switching element 43. Further, the third switching element 43 and the fourth switching element 44 are connected in parallel to the first switching element 41 and the second switching element 42. The charge storage element 45 is connected in parallel to the first switching element 41 and the second switching element 42, and is also connected in parallel to the third switching element 43 and the fourth switching element 44.

A rectifying element 43d is connected to the third switching element 43 in antiparallel to a pair of main terminals. A rectifying element 44d is connected to the fourth switching element 44 in antiparallel to a pair of main terminals.

The first connection terminal 40a of the converter CELL is connected between the first switching element 41 and the second switching element 42. The second connection terminal 40b is connected between the third switching element 43 and the fourth switching element 44. In this example, the second connection terminal 40b is connected to the main terminal on the opposite side of the main terminal connected to the second switching element 42 of the first switching element 41 via the third switching element 43. In this example, the switching elements 41 to 44 are fully bridge-connected.

That is, the main circuit 40 in this example is a so-called full bridge circuit. As described above, the main circuit 40 used in each converter CELL of the MMC type power converter 10 may be a chopper circuit or a full bridge circuit.

Although not shown in FIG. 8 for convenience, the third switching element 43 and the fourth switching element 44 are turned on and off by the control unit 46 in the same manner as the first switching element 41 and the second switching element 42. Is controlled. The converter CELL has, for example, four gate circuits corresponding to each of the switching elements 41 to 44. The control unit 46 controls the operation of each gate circuit based on the control signal input from the host control device 14. As a result, the on / off of each switching element 41 to 44 is controlled.

In each of the above embodiments, an MMC type power converter is used for the main circuit unit 12. The main circuit unit 12 is not limited to the MMC type, and may be another type of power converter in which a plurality of converters CELL are connected in series.

The power conversion device 10 is not limited to the DC power transmission system, and may be applied to any other system that requires conversion from alternating current to direct current and conversion from direct current to alternating current. The AC / DC conversion by the power conversion device 10 is not limited to both AC to DC and DC to AC, and may be only one of AC to DC or DC to AC. Further, the AC power converted by the power conversion device 10 is not limited to the three-phase AC power, but may be a single-phase AC power, a two-phase AC power, or the like.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

2 ... AC power system, 3, 4 ... DC transmission line, 6 ... Transformer, 10 ... Power converter, 12 ... Main circuit unit, 14 ... Upper control device, 20a, 20b ... DC terminal, 21a-21c ... 1st ~ 3rd AC terminal, 22a ~ 22f ... 1st ~ 6th arm part, 23a ~ 23f ... Buffalo reactor, 24a ~ 24f ... Current detector, 25 ... Voltage detector, 26 ... Signal line, 40 ... Main circuit, 41 ~ 44 ... Switching element, 45 ... Charge storage element, 46 ... Control unit, 48 ... Power supply circuit, 50 ... Voltage detector, 51, 52 ... Gate circuit, 54 ... Judgment circuit, 60 ... Storage unit, 62 ... Failure information

Claims (2)

With a main circuit unit that has multiple converters connected in series and performs at least one of conversion from AC power to DC power and conversion from DC power to AC power by the operation of the multiple converters. ,
An upper control device that controls the operation of the plurality of converters, and
Equipped with
Each of the plurality of converters
With multiple switching elements connected in half-bridge or full-bridge connection,
A plurality of rectifying elements connected in parallel to each of the plurality of switching elements,
A charge storage element connected in parallel to the plurality of switching elements and
A control unit that controls the on / off of the plurality of switching elements,
A power supply circuit that generates a control power supply for the control unit based on the charge stored in the charge storage element and supplies the generated control power supply to the control unit.
A storage unit that stores failure information indicating its own failure,
Have,
After the control unit is activated in response to the supply of the control power supply from the power supply circuit, the control unit refers to the failure information in the storage unit, and when it is stored as a failure, the conversion stored as a failure. A power converter that puts the device in a bypass state. The plurality of converters are modularized for each of at least two transducers.
The modularized at least two transducers share the fault information with each other.
After starting, the control unit confirms the failure of each of the at least two modularized converters by referring to the failure information, and bypasses the converter stored as a failure. The power converter according to claim 1, which can be in a state.

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