JP7705695B2 - Power Conversion Equipment - Google Patents

Description

An embodiment of the present invention relates to a power conversion device.

A power conversion device is known that includes a main circuit section that performs at least one of the conversions from AC power to DC power and the conversion from DC power to AC power, and a control device that controls the operation of the main circuit section. In such power conversion devices, the main circuit section is configured as a multi-stage configuration in which multiple converters are connected in series. Power conversion devices that include a multi-stage main circuit section are used, for example, in DC power transmission systems that convert AC power to DC power and transmit it.

Each converter has multiple switching elements and a charge storage element connected in parallel to each switching element. Each converter controls the switching of each switching element based on a control signal input from the control device. This allows conversion from AC power to DC power or conversion from DC power to AC power.

The control device acquires information necessary for control from each converter. The control device also periodically acquires information necessary for control from each converter to update the information. The control device generates a control signal for each converter based on the acquired information, and controls the operation of each converter by transmitting the generated control signal to each converter. In other words, the control device performs feedback control of each converter based on the information acquired from each converter. This allows for more appropriate control according to the state of each converter. For example, it is possible to control the amount of power output from the main circuit unit to a more appropriate amount according to a command value, or to stop the operation of a converter in which an abnormality has occurred.

In such power conversion devices, a repeater is provided between the control device and each converter, and a star-type communication method is adopted with the repeater at the center. The repeater is connected to the control device via a signal line, and is connected to the multiple converters via multiple other signal lines. The repeater transmits control signals sent from the control device to the multiple converters, and transmits signals sent from the multiple converters to the control device. In this configuration, the total length of the signal lines can be shortened compared to a configuration in which the control device and the multiple converters are directly connected via multiple signal lines. This can reduce costs, for example.

However, when adopting the star-type communication method described above, when transmitting signals from each of the multiple converters to the control device, the signals of the multiple converters must be transmitted from the repeater to the control device with a time lag so that the signals of the multiple converters do not overlap on the signal line between the repeater and the control device. This results in a longer communication cycle compared to a configuration in which the control device and the multiple converters are directly connected via multiple signal lines. As a result, it takes time for the control device to update the information required for control, which can cause delays in control.

For this reason, it is desirable to be able to suppress control delays in power conversion devices even when a star-type communication method centered on a repeater is adopted.

JP 2019-140738 A

The embodiment provides a power conversion device that can suppress control delays even when a star-type communication method centered on a repeater is adopted.

According to an embodiment, a power conversion device is provided that includes a plurality of converters, a control device that transmits control signals for controlling the plurality of converters, and a repeater connected to the plurality of converters and the control device and relaying communication between the plurality of converters and the control device, wherein the control device periodically transmits a request signal to the plurality of converters requesting the transmission of information necessary for control, acquires the information necessary for control from response signals to the request signals received from the plurality of converters, and generates the control signal for controlling the plurality of converters based on the acquired plurality of pieces of information, and each of the plurality of converters transmits the response signal to the control device at a different timing than other converters in response to receiving the request signal , and the information necessary for control included in the response signal includes at least first information and second information that has a lower importance set with respect to converter control than the first information, and the frequency of transmission of the response signal including only the first information is higher than the frequency of transmission of the response signal including the first information and the second information .

In this embodiment, a power conversion device is provided that can suppress control delays even when a star-type communication method centered on a repeater is adopted.

1 is a block diagram illustrating a power conversion device according to a first embodiment. FIG. 2 is a block diagram illustrating a converter according to the first embodiment. FIG. 4 is an explanatory diagram illustrating an example of a signal transmitted from each converter to a control device. FIG. 2 is an explanatory diagram illustrating an example of an operation of the power conversion device according to the first embodiment. FIG. 10 is an explanatory diagram illustrating a reference example of an operation of the power conversion device; FIG. 11 is an explanatory diagram illustrating an example of a response signal according to the second embodiment. FIG. 11 is an explanatory diagram illustrating an example of an operation of the power conversion device according to the second embodiment. FIG. 13 is an explanatory diagram illustrating an example of a response signal according to the third embodiment. FIG. 13 is a block diagram illustrating a power conversion device according to a fourth embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not necessarily the same as in reality. Even when the same part is shown, the dimensions and ratios of each part may be different depending on the drawing.
In this specification and each drawing, elements similar to those described above with reference to the previous drawings are given the same reference numerals and detailed description thereof will be omitted as appropriate.

First Embodiment
FIG. 1 is a block diagram illustrating a power conversion device according to a first embodiment.
As shown in FIG. 1, the power conversion device 10 includes a main circuit unit 20, a relay 40, and a control device 50. The power conversion device 10 is connected to an AC power system 1 via AC terminals 21a to 21c. The power conversion device 10 is connected to the power system 1 via, for example, a transformer 2. The power system 1 can include, for example, a three-phase or single-phase 50 Hz or 60 Hz power source, a load, and an AC transmission line. The power conversion device 10 is connected to a DC circuit 3 via DC terminals 21d and 21e. The DC circuit 3 includes, for example, a DC transmission line. In the following, it is assumed that the power conversion device 10 is linked to the three-phase power system 1.

The power conversion device 10 is connected between the power system 1 and the DC circuit 3, and can perform bidirectional power conversion between AC and DC. However, the power conversion by the power conversion device 10 may be in only one direction, from AC to DC or from DC to AC.

In the power conversion device 10, the control device 50 and the repeater 40 are connected via a signal line 60 and transmit data between them. The repeater 40 and the main circuit section 20 are connected via a signal line 42 and transmit data between them. In other words, the control device 50 can transmit data between itself and the main circuit section 20 via the signal line 60, the repeater 40, and the signal line 42.

The main circuit section 20 is installed on an insulating stand 26. The insulating stand 26, the repeater 40, and the control device 50 are placed, for example, on the same installation surface 4. The insulating stand 26 is made of an insulating material, and the main circuit section 20 is electrically insulated from the repeater 40 and the control device 50. The installation surface 4 on which the insulating stand 26, the repeater 40, and the control device 50 are placed means that they are at approximately the same potential, and may be physically different surfaces. For example, the insulating stand 26 and the repeater 40 may be placed on the floor of a control room on the second floor of a building, and the control device 50 may be placed on the floor of the first floor of the same building.

The main circuit section 20 includes a number of arms 22 corresponding to each phase of the three-phase AC. The arms 22 are connected in series between the DC terminals 21d and 21e.

A buffer reactor 24 is connected in series to each of the arms 22 connected in series between the DC terminals 21d and 21e. The buffer reactor 24 prevents momentary short-circuit current from flowing between the upper and lower arms 22. The taps of the buffer reactor 24 are connected to the AC terminals 21a to 21c, respectively.

Each arm 22 has multiple converters 30 connected in series. In the following description, it is assumed that M converters 30 are connected in series to one arm 22 (M is an integer equal to or greater than 2). The number of converters 30 connected in series in each arm 22 is, for example, 100 or more. However, the number of converters 30 connected in series is not limited to this and may be any number.

The number of converters 30 provided in each arm 22 is substantially the same. For example, when a large number of converters 30 are connected, the number of converters 30 provided in each arm 22 may differ as long as it does not affect the operation of the main circuit section 20. For example, when 100 converters 30 are connected in series to one arm 22, the number of converters 30 provided in another arm 22 may differ by one or two.

The repeater 40 is connected to the control device 50 via a signal line 60. The repeater 40 is connected to the converters 30 via a signal line 42. The repeater 40 distributes the control signal transmitted from the control device 50 to each of the multiple converters 30 via the signal line 42 corresponding to the converter 30. The repeater 40 also transmits the signal transmitted from each of the multiple converters 30 to the control device 50. The repeater 40, for example, merges the data of each signal transmitted from the multiple converters 30 into data of one signal, thereby making it substantially serial data, and transmits it to the control device 50. The power conversion device 10 employs a star-type communication method with the repeater 40 at the center.

For example, optical communication is used for communication between the control device 50 and each converter 30. The control signal transmitted from the control device 50 to each converter 30 and the signal transmitted from each converter 30 to the control device 50 are optical signals, for example. The signal lines 42 and 60 are optical fiber cables, for example. The repeater 40 is an optical distributor or star coupler, for example.

However, the communication between the control device 50 and each converter 30 does not necessarily have to be optical communication. The communication between the control device 50 and each converter 30 may be, for example, communication by electrical signals. The repeater 40 is not limited to an optical distributor or star coupler, but may be any component that can distribute and transmit a control signal from the control device 50 to each converter 30, and that can merge signals from each converter 30 and transmit them to the control device 50. In other words, the repeater 40 may be any component that allows the adoption of a star-type communication method centered on the repeater 40 in the communication between the control device 50 and each converter 30.

For example, only the communication between the repeater 40 and each converter 30 may be optical communication, and the communication between the repeater 40 and the control device 50 may be electrical signal communication. Conversely, only the communication between the repeater 40 and the control device 50 may be optical communication, and the communication between the repeater 40 and each converter 30 may be electrical signal communication. For example, when each converter 30 handles a large amount of power, it is preferable to use optical communication for at least a portion of the communication between the multiple converters 30 and the control device 50 as described above, and to electrically insulate the multiple converters 30 from the control device 50.

The repeater 40 can be installed near the main circuit section 20. Therefore, the signal line 42 can be long enough to be laid inside the main circuit section 20. The control device 50 can be installed in a location sufficiently far away from the main circuit section 20 and the repeater 40. For example, the control device 50 may be installed in a building or on a floor different from the location where the repeater 40 and the main circuit section 20 are installed. The length of the signal line 42 can be sufficiently shorter than the length of the signal line 60. This makes it possible to shorten the total length of the signal lines compared to, for example, a case in which multiple signal lines 42 corresponding to the number of converters 30 are directly connected to the control device 50. This makes it possible to reduce costs.

The power conversion device 10 includes, for example, multiple repeaters 40. For example, if the number of converters 30 provided in one arm 22 of the main circuit section 20 is 96, the power conversion device 10 includes six repeaters 40 for one arm 22. In this case, one repeater 40 is connected to 16 converters 30 via signal lines 42 and communicates with the 16 converters 30. In this case, the power conversion device 10 includes six repeaters 40 for each of the six arms 22, for a total of 36 repeaters 40.

The control device 50 has multiple communication ports (communication connection parts) and is connected to each of the multiple repeaters 40 via multiple signal lines 60. This allows communication between the control device 50 and each converter 30 even when multiple repeaters 40 are provided.

However, the number of repeaters 40 and the number of converters 30 connected to one repeater 40 are not limited to the above and may be any number. For example, all converters 30 provided in the main circuit unit 20 may be connected to one repeater 40. The number of repeaters 40 may be set appropriately depending on, for example, the number of signals that can be distributed by the repeater 40.

The control device 50 is connected to the repeater 40, communicates with the multiple converters 30 via the repeater 40, and controls the operation of the main circuit unit 20 by inputting control signals to each of the multiple converters 30. The control device 50 also communicates with each converter 30 via the signal line 42, the repeater 40, and the signal line 60 to obtain information necessary for control from each converter 30. The control device 50 periodically updates the information by obtaining information necessary for control from each converter 30.

The control device 50 generates a control signal for each converter 30 based on the acquired information, and controls the operation of each converter 30 by transmitting the generated control signal to each converter 30. That is, the control device 50 performs feedback control of each converter 30 based on the information acquired from each converter 30. This allows more appropriate control according to the state of each converter 30. For example, it is possible to control the amount of power output from the main circuit unit 20 to a more appropriate amount according to the command value, or to stop the operation of a converter 30 in which an abnormality has occurred.

FIG. 2 is a block diagram illustrating a converter according to the first embodiment.
2, the converter 30 has a pair of terminals 31a, 31b. The converter 30 is connected in series with other converters 30, etc., via the terminals 31a, 31b. The converter 30 has a control circuit 32, a drive circuit 33, a conversion circuit 35, and a main circuit power supply unit 36.

The conversion circuit 35 has a plurality of switching elements 35S1 and 35S2, diodes 35D1 and 35D2, and a charge storage element 35C. The switching elements 35S1 and 35S2 are connected in series. The diodes 35D1 and 35D2 are connected in anti-parallel to the switching elements 35S1 and 35S2, respectively. The charge storage element 35C is connected in parallel to the series circuit of the switching elements 35S1 and 35S2.

By switching the multiple switching elements 35S1 and 35S2, the conversion circuit 35 switches between an output state in which the voltage of the charge storage element 35C is output between a pair of terminals 31a and 31b, a stop state in which the output of the voltage of the charge storage element 35C between the pair of terminals 31a and 31b is stopped, and a bypass state in which the pair of terminals 31a and 31b is conductive.

In this example, the conversion circuit 35 can be put into a bypass state by turning off the upper switching element 35S1 and turning on the lower switching element 35S2. The stopped state is a state in which both switching elements 35S1 and 35S2 are in the off state. The stopped state is sometimes called, for example, a gate block state.

The switching elements 35S1 and 35S2 are, for example, self-extinguishing semiconductor switches such as IGBTs (Insulated Gate Bipolar Transistors). The switching elements 35S1 and 35S2 are driven by a drive signal supplied from the drive circuit 33, and charge and discharge the charge storage element 35C.

The conversion circuit 35 is not limited to a half-bridge circuit as described above, but may be a full-bridge circuit using four switching elements. The number of switching elements in the conversion circuit 35 is not limited to two, but may be four or more.

The control circuit 32 receives the control signal transmitted from the control device 50 via the signal line 60, the repeater 40, and the signal line 42, and generates a switching control signal for controlling the switching of the multiple switching elements 35S1 and 35S2 based on the control signal, and inputs the generated switching control signal to the drive circuit 33.

The drive circuit 33 performs level conversion on the switching control signal supplied from the control circuit 32, and generates a drive signal for driving the switching elements 35S1 and 35S2 based on the switching control signal. The drive circuit 33 then inputs the generated drive signal to the switching elements 35S1 and 35S2 of the conversion circuit 35, thereby switching the switching elements 35S1 and 35S2 on and off.

The main circuit power supply unit 36 receives power from the charge storage element 35C, converts it to an appropriate voltage, and supplies it to each part of the converter 30, such as the control circuit 32 and the drive circuit 33. Each part of the converter 30 operates based on the power supply from the main circuit power supply unit 36.

FIG. 3 is an explanatory diagram illustrating an example of a signal transmitted from each converter to the control device.
When the control device 50 obtains information necessary for control from each converter 30, it transmits a request signal requesting the transmission of the necessary information to each converter 30 via the repeater 40. In response to receiving the request signal from the control device 50, each converter 30 transmits a response signal SA1 to SAn shown in FIG.

As shown in FIG. 3, the response signals SA1 to SAn transmitted from each converter 30 to the control device 50 include, for example, multiple pieces of information. Furthermore, the response signals SA1 to SAn are configured with a predetermined data structure (frame). The data structures of the response signals SA1 to SAn are substantially the same. FIG. 3 illustrates an example in which each of the response signals SA1 to SAn has a data structure including four pieces of information, information A to information D.

The information A items, information B items, information C items, and information D items are the same in each of the response signals SA1 to SAn. Each converter 30 acquires its own information A to D in response to receiving a request signal, and transmits the acquired information A to D to the control device 50 as response signals SA1 to SAn.

Each item of information may be, for example, the voltage of the charge storage element 35C, the current (arm current) flowing between the pair of terminals 31a, 31b, the presence or absence of a failure in the switching elements 35S1, 35S2, etc. However, the number of pieces of information contained in the response signals SA1 to SAn is not limited to four, and may be any number. In addition, the information (items of information) contained in the response signals SA1 to SAn is not limited to the above, and may be any information necessary for controlling each converter 30.

As shown in FIG. 3, the multiple pieces of information contained in the response signals SA1 to SAn are divided into first information, which is important for controlling each converter 30, and second information, which is less important than the first information. In other words, the first information is information that needs to be updated quickly. In other words, the second information is information that does not need to be updated quickly.

Figure 3 illustrates an example in which only information D of the first converter 30 (converter 1) is the first information, and the other information is the second information. Below, the multiple converters 30 may be referred to as converter 1 to converter N. Converter 1 includes the first information in response signal SA1, and the other converters 2 to converter N do not include the first information in response signals SA2 to SAn. Converter 1 to converter N are, for example, multiple converters 30 connected to one repeater 40.

The first information is, for example, information about the current (arm current) flowing between a pair of terminals 31a, 31b. The second information is, for example, information about the voltage of the charge storage element 35C or information about the presence or absence of a failure in the switching elements 35S1, 35S2. However, the first information is not limited to the above and may be any information that is important and requires rapid updating in the control device 50. The second information is not limited to the above and may be any information that is less important than the first information and does not require rapid updating in the control device 50.

FIG. 4 is an explanatory diagram illustrating an example of the operation of the power conversion device according to the first embodiment.
Figure 4 shows an example of request signals SR1 to SRn transmitted from the control device 50 to the repeater 40, request signals SR1 to SRn distributed and transmitted from the repeater 40 to each converter 30, response signals SA1 to SAn transmitted from each converter 30 to the repeater 40, and a received signal SA received by the control device 50 from the repeater 40.

As shown in FIG. 4, when the control device 50 obtains information necessary for control from each converter 30, it first transmits a request signal SR1, including the first information, to the repeater 40, requesting the converter 1 to transmit the necessary information. When the repeater 40 receives the request signal SR1 from the control device 50, it distributes and transmits the received request signal SR1 to each converter 30.

When each converter 30 receives a request signal SR1, it determines whether the received request signal SR1 is for itself. Of the multiple converters 30, converter 1 determines that the request signal SR1 is for itself, and in response to receiving the request signal SR1, it transmits a response signal SA1 including information necessary for control to the repeater 40. The other converters 30 determine that the request signal SR1 is not for themselves, and do not transmit response signals SA2 to SAn. When the repeater 40 receives the response signal SA1 from converter 1, it transmits the received response signal SA1 to the control device 50.

When the control device 50 receives the response signal SA1 from the converter 1, it then transmits a request signal SR2 to the repeater 40 in response to receiving the response signal SA1, requesting the converter 2 to transmit the necessary information. In response to receiving the request signal SR2, the converter 2 transmits a response signal SA2 including the information necessary for control to the repeater 40.

The control device 50 then repeats the same process, acquiring information on each converter 30 in the order of converter 1 → converter 2 → converter 1 → converter 3 → converter 1 → converter 4 → ... converter 1 → converter N, as shown in FIG. 4.

In a star-type communication method centered on the repeater 40, when each of the multiple converters 30 transmits a response signal SA1-SAn to the control device 50, the response signals SA1-SAn of the multiple converters 30 must be transmitted from the repeater 40 to the control device 50 with a time lag so that the response signals SA1-SAn of the multiple converters 30 do not overlap on the signal line 60 between the repeater 40 and the control device 50.

In this example, the control device 50 generates multiple request signals SR1 to SRn corresponding to each converter 30, and transmits the multiple request signals SR1 to SRn to each converter 30 with a time lag, so that each converter 30 transmits response signals SA1 to SAn with a time lag based on the request signals SR1 to SRn. This makes it possible to prevent the response signals SA1 to SAn of the multiple converters 30 from overlapping on the signal line 60 between the repeater 40 and the control device 50.

In this way, in response to receiving the request signals SR1 to SRn, the multiple converters 30 transmit response signals SA1 to SAn, which include multiple pieces of information required for control, to the control device 50, and transmit the respective response signals SA1 to SAn of the multiple converters 30 to the control device 50 with a time lag based on the request signals SR1 to SRn.

By receiving the response signals SA1 to SAn, the control device 50 acquires multiple pieces of information necessary for control from the multiple converters 30, generates control signals for the multiple converters 30 based on the acquired multiple pieces of information, and periodically transmits request signals SR1 to SRn and periodically acquires the multiple pieces of information, thereby updating the multiple pieces of information.

The multiple converters 30 transmit response signals SA1 to SAn based on the request signals SR1 to SRn with a time lag, and transmit response signals from converters 30 that include the first information in their response signals to the control device 50 more frequently than transmit response signals from converters 30 that do not include the first information in their response signals to the control device 50. This allows the control device 50 to update the first information, which is of high importance, more frequently than it updates the second information, which is of low importance.

FIG. 5 is an explanatory diagram illustrating a reference example of the operation of the power conversion device.
5 shows an example of a request signal SR transmitted from the control device 50 to the repeater 40, a request signal SR distributed and transmitted from the repeater 40 to each converter 30, response signals SA1 to SAn transmitted from each converter 30 to the repeater 40, and a received signal SA received by the control device 50 from the repeater 40. Note that FIG. 3 shows an example of a reference operation of the control device 50 when a star-type communication method with the repeater 40 at the center is adopted, and does not show the operation of the control device 50 according to this embodiment.

As shown in FIG. 5, in the reference operation, when the control device 50 obtains information necessary for control from each converter 30, it transmits a request signal SR to the repeater 40 requesting each converter 30 to transmit the necessary information. When the repeater 40 receives the request signal SR from the control device 50, it distributes and transmits the received request signal SR to each converter 30.

In response to receiving the request signal SR, each converter 30 transmits a response signal SA1-SAn, including information necessary for control, to the repeater 40. In this case, as described above, in a star-type communication method with the repeater 40 at the center, the response signals SA1-SAn of the multiple converters 30 must be transmitted from the repeater 40 to the control device 50 with a time lag. Figure 5 shows an example in which the response signals SA1-SAn are transmitted from the repeater 40 to the control device 50 with a fixed interval T lag.

For example, the multiple converters 30 have a transmission delay adjustment function for transmitting the response signals SA1 to SAn at different times. For example, the first converter 30 transmits the response signal SA1 to the repeater 40 immediately in response to receiving the request signal SR, the second converter 30 transmits the response signal SA2 to the repeater 40 T seconds after receiving the request signal SR, the third converter 30 transmits the response signal SA3 to the repeater 40 2T seconds after receiving the request signal SR, and the same process is repeated thereafter, with the Nth converter 30 transmitting the response signal SAn to the repeater 40 (N-1)T seconds after receiving the request signal SR. This makes it possible to suppress overlapping of the response signals SA1 to SAn on the signal line 60 between the repeater 40 and the control device 50, and to allow the control device 50 to properly receive the information of the response signals SA1 to SAn as the received signal SA.

The transmission delay adjustment function may be provided, for example, in the repeater 40. For example, each converter 30 transmits response signals SA1-SAn to the repeater 40 immediately in response to receiving the request signal SR. The repeater 40 receives the response signals SA1-SAn from each converter 30 substantially simultaneously, and then transmits the received response signals SA1-SAn to the control device 50 with a time shift. In this case, as in the above, it is possible to suppress overlapping of the response signals SA1-SAn on the signal line 60.

The transmission delay adjustment function may also be provided in, for example, the control device 50. For example, as shown in FIG. 4, multiple request signals SR1 to SRn corresponding to each converter 30 are generated, and the multiple request signals SR1 to SRn are sequentially transmitted to each converter 30 with a time lag. Each converter 30 transmits a response signal SA1 to SAn to the repeater 40 in response to receiving the request signal SR1 to SRn corresponding to itself. In this case, too, it is possible to suppress overlapping of the response signals SA1 to SAn on the signal line 60, as described above.

In this way, the transmission delay adjustment function may be provided in each converter 30, in the repeater 40, or in the control device 50. The configuration in which the response signals SA1 to SAn of multiple converters 30 are transmitted from the repeater 40 to the control device 50 with a time shift can be any configuration that can appropriately suppress overlap of the response signals SA1 to SAn on the signal line 60.

However, in the example shown in FIG. 5, in a configuration in which the response signals SA1 to SAn of the multiple converters 30 are transmitted from the repeater 40 to the control device 50 with a time lag, the communication cycle becomes longer than in a configuration in which the control device 50 and the multiple converters 30 are directly connected via multiple signal lines.

For example, if the response signal SA1 of the converter 1 contains first information of high importance, and the response signals SA1 to SAn are transmitted from the repeater 40 to the control device 50 at fixed intervals of T seconds as shown in FIG. 5, the first information of high importance of the converter 1 will be updated every n×T seconds, which may cause delays in control.

In contrast, in the power conversion device 10 according to the present embodiment, as shown in FIG. 4, multiple converters 30 transmit response signals SA1-SAn based on request signals SR1-SRn with a time lag, and the frequency of transmission of response signals from converters 30 that include the first information in their response signals to the control device 50 is set higher than the frequency of transmission of response signals from converters 30 that do not include the first information in their response signals to the control device 50, thereby making the frequency of updates of the first information, which is of high importance, higher than the frequency of updates of the second information, which is of low importance, in the control device 50. This makes it possible to suppress control delays even when a star-type communication method centered on the repeater 40 is adopted.

For example, when the main circuit unit 20 is protected based on the first information, the power conversion device 10 can be stopped quickly in response to updates to the first information, improving the safety of the power conversion device 10. In addition, control commands, feedback signals, and the like can be transmitted quickly as the first information, improving the operability of the power conversion device 10.

In the example shown in FIG. 4, a response signal that does not include the first information is transmitted from converter 30 to control device 50 once every two times, such as converter 1 → converter 2 → converter 1 → converter 3 → converter 1 → converter 4 → ... converter 1 → converter N.

Without being limited thereto, for example, a response signal not including the first information in the response signal may be transmitted from the converter 30 to the control device 50 once every three times, such as converter 1 → converter 1 → converter 2 → converter 1 → converter 1 → converter 3 → converter 1 → converter 1 → converter 4 → ... converter 1 → converter 1 → converter N. This allows the first information, which is of high importance, to be updated more frequently.

Conversely, a response signal including the first information in the response signal may be transmitted from converter 30 to control device 50 once every three times, for example, converter 1 → converter 2 → converter 3 → converter 1 → converter 4 → converter 5 → ... converter 1 → converter (N-1) → converter N. In this case, it is possible to increase the frequency of updates of the first information of high importance while preventing the frequency of updates of the second information from becoming too low. The frequency of updates of the first information of high importance is not limited to the above and may be any frequency.

The frequency of transmission of a response signal from the converter 30 containing the first information in the response signal to the control device 50 may be determined, for example, according to the number of converters 30 connected to the repeater 40. For example, after sending each response signal of the converters 30 connected to the repeater 40, a response signal containing the first information in the response signal is transmitted from the converter 30 to the control device 50. In this case, it is possible to increase the frequency of updating the first information, which is of high importance, while further preventing the frequency of updating the second information from becoming too low.

The frequency of transmission of a response signal from the converter 30 including the first information in the response signal to the control device 50 may be set according to, for example, the sampling period of the first information. For example, each time new first information is acquired by a measuring device or the like, a response signal including the first information is transmitted from the converter 30 to the control device 50. In other words, the frequency of transmission of a response signal from the converter 30 including the first information in the response signal to the control device 50 is set to be equal to or greater than the sampling period of the first information. This makes it possible to prevent the same first information from being repeatedly transmitted to the control device 50, unnecessarily increasing the frequency of updates.

In the example shown in FIG. 4, the control device 50 transmits individually set request signals SR1 to SRn to each converter 30, so that the frequency of transmission of a response signal from a converter 30 that includes the first information in its response signal to the control device 50 is higher than the frequency of transmission of a response signal from a converter 30 that does not include the first information in its response signal to the control device 50.

Without being limited thereto, for example, the timing of transmitting a response signal may be preset for each converter 30, a common request signal SR (see FIG. 5) may be transmitted from the control device 50 to each converter 30, and each converter 30 may transmit a response signal at the preset transmission timing in response to receiving the request signal SR, so that the frequency of transmission of a response signal from a converter 30 that includes the first information in its response signal to the control device 50 may be higher than the frequency of transmission of a response signal from a converter 30 that does not include the first information in its response signal to the control device 50.

In the above embodiment, the plurality of pieces of information are divided into two pieces of information with different importance, the first information and the second information. In other words, two levels of importance are set for the plurality of pieces of information. Without being limited to this, the importance may be set to three or more levels, and the plurality of pieces of information may be divided into three or more pieces of information. The plurality of pieces of information included in the response signal may be divided according to multiple levels of importance set for the control of the plurality of converters 30. The control device 50 may update the plurality of pieces of information with a higher importance more frequently than the information with a lower importance.

For example, multiple converters 30 may transmit response signals at different times based on a request signal, and converters 30 whose response signals contain information of higher importance may transmit response signals to the control device 50 more frequently, thereby allowing the control device 50 to update information of higher importance more frequently than information of lower importance.

For example, when the multiple pieces of information are divided into three pieces of information, first information to third information, the frequency of transmission of a response signal from a converter 30 including the first information, which is the most important, is set to be the highest, the frequency of transmission of a response signal from a converter 30 including the second information, which is more important than the third information, is set to be higher than the frequency of transmission of a response signal from a converter 30 including the third information, and the frequency of transmission of a response signal from a converter 30 including only the third information is set to be the lowest. In this way, even when the multiple pieces of information are divided into three pieces, the control device 50 can update the information of higher importance more frequently than the information of lower importance.

In addition, for example, the frequency of transmitting a response signal from the converter 30, whose response signal includes information of high importance, to the control device 50 may be set according to the sampling period of the information of high importance.

Second Embodiment
FIG. 6 is an explanatory diagram illustrating an example of a response signal according to the second embodiment.
6, in this example, the data configuration of the response signals SA1 to SAn is changed for each of the multiple converters 30. Note that the same reference numerals are used for components that are substantially the same in function and configuration as those in the above embodiment, and detailed description thereof will be omitted.

Each converter 30, for example, reduces the number of pieces of information in a response signal that does not include the first information to be less than the number of pieces of information in a response signal that includes the first information. In other words, each converter 30, for example, reduces the frame length of a response signal that does not include the first information to be shorter than the frame length of a response signal that includes the first information.

For example, in multiple converters 30 connected in series to the same arm 22, the information about the current (arm current) flowing between a pair of terminals 31a, 31b is substantially the same. For this reason, only the response signal including the first information includes information about the arm current, and the response signal not including the first information does not include information about the arm current. For example, in the example shown in FIG. 6, only the response signal SA1 includes information about the arm current, and the response signals SA2 to SAn do not include information about the arm current. This makes it possible to make the frame length of the response signal not including the first information shorter than the frame length of the response signal including the first information.

In this case, the items of information A, B, and C do not necessarily have to be the same in each of the response signals SA1 to SAn. The multiple pieces of information included in the response signal may be arbitrarily set to correspond to each of the converters 30.

FIG. 7 is an explanatory diagram illustrating an example of the operation of the power conversion device according to the second embodiment.
Figure 7 shows a schematic diagram of an example of a request signal SR transmitted from the control device 50 to the repeater 40, a request signal SR distributed and transmitted from the repeater 40 to each converter 30, response signals SA1 to SAn transmitted from each converter 30 to the repeater 40, and a received signal SA received by the control device 50 from the repeater 40.

As shown in FIG. 7, when the control device 50 obtains information necessary for control from each converter 30, it transmits a request signal SR to the repeater 40, requesting each converter 30 to transmit the necessary information. When the repeater 40 receives the request signal SR from the control device 50, it distributes and transmits the received request signal SR to each converter 30.

In response to receiving the request signal SR, each converter 30 transmits a response signal SA1-SAn, which includes information required for control, to the repeater 40. At this time, each converter 30 transmits the response signals SA1-SAn to the control device 50 at time intervals according to the data structure (frame length) of the response signals SA1-SAn, rather than at fixed intervals, so that the response signals SA1-SAn are transmitted from the repeater 40 to the control device 50 with a time lag.

For example, an interval T1 is set for the response signal SA1 of converter 1 that includes the first information, and an interval T2 that is shorter than the interval T1 is set for the response signals SA2 to SAn of converters 2 to N that do not include the first information.

As shown in FIG. 7, converter 1 transmits a response signal SA1 to repeater 40 immediately in response to receiving the request signal SR. Converter 2 transmits a response signal SA2 to repeater 40 T1 seconds after receiving the request signal SR. Converter 3 transmits a response signal SA3 to repeater 40 T1+T2 seconds after receiving the request signal SR. Converter 4 transmits a response signal SA4 to repeater 40 T1+2×T2 seconds after receiving the request signal SR. The same process is repeated thereafter, and converter N transmits a response signal SAn to repeater 40 T1+(N-2)T2 seconds after receiving the request signal SR.

As a result, even when the time intervals correspond to the data configuration of the response signals SA1 to SAn, it is possible to prevent overlapping of the response signals SA1 to SAn on the signal line 60 between the repeater 40 and the control device 50, and to allow the information of the response signals SA1 to SAn to be properly received by the control device 50 as the received signal SA.

In this way, the data configuration of the response signals SA1 to SAn is changed for each of the multiple converters 30, and the number of pieces of information in the response signals that do not include the first information is made smaller than the number of pieces of information in the response signals that include the first information. In this case, the communication cycle can be shortened compared to when the data configuration of the response signals SA1 to SAn is the same. This makes it possible to increase the frequency of updates to the first information, which is of high importance, compared to when the data configuration of the response signals SA1 to SAn is the same. Therefore, in this embodiment as well, as in the above embodiment, control delays can be suppressed even when a star-type communication method centered on the repeater 40 is adopted.

In addition, since the communication cycle can be shortened, for example, the number of converters 30 connected to the repeater 40 can be increased. This makes it possible to reduce, for example, the number of repeaters 40, the number of signal lines 60 between the repeater 40 and the control device 50, and the number of communication ports of the control device 50.

For example, when the number of converters 30 provided in one arm 22 of the main circuit section 20 is 96, if the number of converters 30 that can be connected to one repeater 40 increases from 16 to 32, the number of repeaters 40 for one arm 22 can be reduced from 6 to 3. Accordingly, the number of signal lines 60 and the number of communication ports of the control device 50 can also be reduced. Furthermore, the installation location of the repeaters 40 can be reduced. Therefore, for example, the power conversion device 10 can be made smaller and the manufacturing costs reduced.

In the example shown in FIG. 7, the control device 50 transmits a common request signal SR to each converter 30, and each converter 30 transmits a response signal at a preset transmission timing in response to receiving the request signal SR, so that response signals SA1 to SAn are transmitted to the control device 50 at time intervals according to the data configuration. Without being limited to this, for example, the control device 50 may transmit request signals SR1 to SRn that are individually set to each converter 30, and transmit response signals SA1 to SAn in response to receiving the corresponding request signals SR1 to SRn, so that response signals SA1 to SAn are transmitted to the control device 50 at time intervals according to the data configuration.

Also in this example, the importance may be set to three or more levels, and the multiple pieces of information may be divided into three or more pieces of information. The multiple converters 30 may make the number of pieces of information in the response signal that do not contain information of high importance less than the number of pieces of information in the response signal that contain information of high importance.

For example, when the multiple pieces of information are divided into three pieces of information, first information, second information, and third information, the number of pieces of information contained in the response signal of the converter 30 including the first information, which is the most important, may be made the largest, the number of pieces of information contained in the response signal of the converter 30 including the second information, which is more important than the third information, may be made greater than the number of pieces of information contained in the response signal of the converter 30 including the third information, and the number of pieces of information contained in the response signal of the converter 30 including only the third information may be made the smallest.

Third Embodiment
FIG. 8 is an explanatory diagram illustrating an example of a response signal according to the third embodiment.
As shown in Figure 8, in this example, a converter 1 including the first information in a response signal transmits a response signal SA1a including multiple pieces of information A to D, and transmits a response signal SA1b including only the first information, information D, to a control device 50.

The control device 50 transmits a request signal SR1a that requests the converter 1 to transmit all of the multiple pieces of information A to D, and transmits a request signal SR1b that requests the converter 1 to transmit only the first piece of information, information D. The converter 1 transmits a response signal SA1a in response to receiving the request signal SR1a, and transmits a response signal SA1b in response to receiving the request signal SR1b.

For example, as shown in FIG. 4, when a response signal including the first information is transmitted from the converter 1 to the control device 50 once every two times, the control device 50 transmits a request signal SR1a when the first request signal is transmitted, and transmits a request signal SR1b when the second or subsequent request signal is transmitted.

In this example, each converter 30 transmits response signals SA1a, SA1b, SA2 to SAn in the following order: converter 1 (information A to D) → converter 2 → converter 1 (information D only) → converter 3 → converter 1 (information D only) → converter 4 → ... converter 1 (information D only) → converter N.

Thus, in this example, the converter 1, whose response signal includes the first information, transmits to the control device 50 a response signal SA1a including a plurality of pieces of information A to D, and a response signal SA1b including only the first information, information D, and transmits the response signal SA1b including only the first information more frequently than the response signal SA1a including the plurality of pieces of information A to D. As a result, in this example, the control device 50 can update the first information, which is of high importance, more frequently than the second information, which is of low importance. This makes it possible to further suppress control delays even when a star-type communication method centered on the repeater 40 is adopted.

The frequency of transmission of the response signal SA1b including only the first information is not limited to the above, and may be any frequency, as described in the first embodiment above. Furthermore, the transmission of the response signal SA1b including only the first information is not limited to a configuration in which it is transmitted in response to receiving a request signal SR1b from the control device 50, and may be a configuration in which it is transmitted at a predetermined transmission timing.

In this example, the importance may be set to three or more levels, and the multiple pieces of information may be divided into three or more pieces of information. The converter 30, whose response signal includes information of high importance, may transmit a response signal including multiple pieces of information and a response signal including only information of high importance to the control device 50, and may transmit the response signal including only information of high importance more frequently than the response signal including multiple pieces of information.

For example, if the multiple pieces of information are divided into three pieces of information, first information, second information, and third information, the frequency of transmitting a response signal containing only the first information, which is the most important, may be set to be the highest, and the frequency of transmitting a response signal containing only the second information may be set to be higher than the frequency of transmitting a response signal containing multiple pieces of information.

(Fourth embodiment)
FIG. 9 is a block diagram illustrating a power conversion device according to the fourth embodiment.
As shown in FIG. 9, the power conversion device 10a further includes a dedicated signal line 62 that enables direct communication between the converter 30, whose response signal includes the first information, and the control device 50, in addition to the communication paths of the signal line 42, the repeater 40, and the signal line 60.

The control device 50, for example, by the operation shown in FIG. 5, obtains information necessary for control from each converter 30 using a star-shaped communication method centered on the repeater 40, and by communicating with converters 30 that include the first information in their response signals via a dedicated signal line 62, obtains the first information from converters 30 that include the first information in their response signals more frequently than through communication via the repeater 40.

As a result, even in the power conversion device 10a according to this embodiment, the frequency of updating the first information, which is of high importance, is higher than the frequency of updating the second information, which is of low importance, and control delays can be suppressed even when a star-type communication method centered on the repeater 40 is adopted. Note that the frequency of obtaining the first information from the converter 30, which includes the first information in its response signal, via the dedicated signal line 62 may be any frequency higher than the communication via the repeater 40.

In this example, the repeater 40 may be provided with a transmission delay adjustment function. The configuration in which the multiple converters 30 transmit their respective response signals to the control device 50 based on a request signal with a time lag may be a configuration in which the response signals of the multiple converters 30 are shifted in time in the repeater 40.

Also, in this example, the importance may be set to three or more levels, and the multiple pieces of information may be divided into three or more pieces of information. The control device 50 may periodically acquire multiple pieces of information by communicating with the multiple converters 30 via the repeater 40, and may communicate with the converters 30 whose response signals include information of high importance via a dedicated signal line 62, and acquire information of high importance from the converters 30 whose response signals include information of high importance more frequently than through communication via the repeater 40, thereby making it possible to update information of high importance more frequently than information of low importance.

For example, if the multiple pieces of information are divided into three pieces of information, first information, second information, third information, and the first information, which is the most important, may be updated most frequently through communication via the dedicated signal line 62, and the second information may be updated more frequently than the third information.

In each of the above embodiments, a main circuit section 20 having multiple converters 30 connected in series is shown. The above embodiments are not limited to this, and may also be applied to a main circuit section having multiple converters 30 connected in parallel, in which each converter 30 and the control device 50 communicate in a star configuration centered on a repeater 40.

Although several embodiments of the present invention have been described above, 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 forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their variations are included within the scope and gist of the invention, as well as within the scope of the invention and its equivalents described in the claims. In addition, the above-mentioned embodiments can be implemented in combination with each other.

REFERENCE SIGNS LIST 1 power system, 2 transformer, 3 DC circuit, 4 installation surface, 10, 10a power conversion device, 20 main circuit section, 22 arm, 24 buffer reactor, 26 insulating stand, 30 converter, 32 control circuit, 33 drive circuit, 35 conversion circuit, 35C charge storage element, 35D diode, 35S1, 35S2 switching element, 36 main circuit power supply section, 40 repeater, 42 signal line, 50 control device, 60 signal line, 62 dedicated signal line

Claims (4)

A plurality of converters ;
a control device that transmits control signals to control the plurality of converters;
a repeater connected to the plurality of converters and the control device , and configured to relay communication between the plurality of converters and the control device ;
Equipped with
the control device periodically transmits a request signal to the plurality of converters requesting transmission of information necessary for control , acquires the information necessary for control from response signals to the request signal received from the plurality of converters, and generates the control signal for controlling the plurality of converters based on the acquired information;
Each of the plurality of converters transmits the response signal to the control device at a timing different from that of the other converters in response to receiving the request signal;
A power conversion device in which the information necessary for control contained in the response signal includes at least first information and second information that has a lower importance set for converter control than the first information, and the frequency of transmission of a response signal including only the first information is higher than the frequency of transmission of a response signal including the first information and the second information . The power conversion device according to claim 1, wherein when the converter has the first information and the second information, the converter generates a response signal including only the first information and a response signal including the first information and the second information. The first information is information about a current flowing between two terminals of the converter for connecting the converter to another converter;
2. The power conversion device according to claim 1, wherein the second information is at least one of information regarding the presence or absence of a failure in a switching element constituting the converter and information regarding a voltage of a charge storage element constituting the converter. 4. The power conversion device according to claim 1, wherein at least a part of communication between the plurality of converters and the control device is optical communication.

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