JP7150683B2 - power converter - Google Patents

Description

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

There is a power converter that converts power between AC and DC. 2. Description of the Related Art In power converters installed in social infrastructures such as electric power systems and railroads, factory facilities, etc., there are cases where a plurality of power converters are multiplexed to increase the capacity of electric power to be handled.

A communication path is provided between the controller and the power converters to transmit control commands to and receive status from the multiplexed power converters. In multiplexed power converters, if a communication path is provided for each converter, communication paths must be provided according to the number of converters, and it is necessary to reduce these from the viewpoint of cost, space, and the like.

By configuring the communication path between the control device and each power converter by daisy chain connection, the communication path between the plurality of power converters can be integrated into one. In a power converter that uses a daisy-chained communication path, the data to be transmitted is transferred from the control device to each converter in sequence, so the operation of the power converter is restricted by the period of one cycle of the communication path loop. be done.

JP 2017-143626 A

Embodiments provide a power conversion device that has few operational restrictions even if it has a daisy-chained communication path.

A power converter according to an embodiment includes: a power converter including a plurality of converters; a first area in which the packet data stores a plurality of control data for controlling the plurality of converters; A second area storing identification data for identifying a transducer, and a third area storing transducer data for a transducer among the plurality of transducers having the identification data. The number of pieces of identification data stored in the second area is one or more and less than the number of the plurality of converters.

In this embodiment, a power conversion device with few operational restrictions is realized even if it has a daisy-chained communication path.

1 is a schematic block diagram illustrating a power converter according to an embodiment; FIG. FIG. 2 is a schematic block diagram illustrating part of the power converter of FIG. 1; 2 is a schematic diagram illustrating packet data transmitted within the power converter of FIG. 1; FIG. It is a schematic diagram for demonstrating operation|movement of the power converter device of embodiment. It is an example of the flowchart for demonstrating operation|movement of the power converter device of embodiment. FIG. 5 is a schematic diagram illustrating packet data transmitted within a power conversion device of a comparative example;

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

FIG. 1 is a schematic block diagram illustrating a power conversion device according to an embodiment.
As shown in FIG. 1 , the power converter 10 of this embodiment includes a power converter 20 and a control device 50 . The power converter 10 is connected to the AC system 1 via AC terminals 21a to 21c. As in this example, the power converter 10 may be connected to the AC grid 1 via the transformer 2 . For example, the AC system 1 may be configured to include a three-phase or single-phase 50 Hz or 60 Hz power source, loads, and AC transmission lines. The power converter 10 is connected to the DC system 3 . DC system 3 includes, for example, a DC transmission line.

The power converter 10 is connected between the AC system 1 and the DC system 3 and can perform bidirectional power conversion.

Power converter 20 includes unit arms 22 corresponding to respective phases of three-phase alternating current. The unit arms 22 are connected in series between the DC terminals 21d and 21e to form legs. The unit arms 22 are provided corresponding to UP phase, VP phase and WP phase on the high potential side and UN phase, VN phase and WN phase on the low potential side.

Transformers 24 are connected in series to the unit arms 22 connected in series between the DC terminals 21d and 21e. A buffer reactor may be connected instead of the transformer 24 .

Unit arm 22 includes unit converters (cells) 30 connected in cascade. Although one or more cells 30 may be provided per unit arm 22, C cells 30 are connected in series (C is an integer equal to or greater than 2).

Here, an example of a modular multilevel converter (MMC) in which a plurality of unit converters are cascaded among multiplexing control methods will be described, but the communication method described below is not limited to MMC, but other can be applied to the power converter of the multiplex control system. For example, the applicable power conversion device may include power converters connected in parallel.

Controller 50 includes control circuitry 52 . Control circuit 52 is connected to power converter 20 via communication path 60 . In this example, the communication path 60 is provided for each unit arm 22 . In order to avoid complication, the figure shows mutual connection with the cell 30 for the communication path 61 corresponding to the unit arm 22 corresponding to the UN phase. For other unit arms 22, the UP phase indicates that "a" on the control device 50 side and "a" on the cell 30 side are connected to each other. Similarly, in the VP phase, "b" on the control device 50 side and "b" on the cell 30 side are connected to each other, and in the WP phase, "c" on the control device 50 side and "c" on the cell 30 side are connected to each other. interconnected. The same is true for each phase on the low potential side. In the VN phase, "d" on the control device 50 side and "d" on the cell 30 side are connected to each other, and in the WN phase, "e" on the control device 50 side is connected. and "e" on the cell 30 side are connected to each other.

In each of the communication paths 60 and 61 , the control circuit 52 on the control device 50 side and the control circuit on the cell 30 side are similarly connected in a loop by daisy chain connection for each unit arm 22 . The UN phase and communication path 61 will be described below, but the other phases and communication path 60 are the same.

In the UN-phase communication path 61, the control circuit 52 on the control device 50 side is connected to the control circuit 36 of the cell 30 on the highest potential side (denoted as cell 1 in FIG. 1). The control circuit 36 of the cell 30 on the highest potential side is connected to the control circuit 36 of the cell 30 (denoted as cell 2 in FIG. 1) cascade-connected to this cell 30 (cell 1). Similarly, the cells 30 are connected to each other by a communication path 61 toward the low potential side. The control circuit 36 of the cell 30 on the lowest potential side (denoted as cell C in FIG. 1) is connected to the control circuit 52 on the control device 50 side. That is, by forming a loop of the communication path 61 in the order of the control device 50 →cell 1 →cell 2 → .

Although the number of cells 30 included in one daisy chain connection is the number of unit arms 22 in the above description, an appropriate number can be arbitrarily set. For example, one loop may include UP-phase and UN-phase cells 30, or all cells 30 may be daisy-chained within one loop. Alternatively, one phase may be split into multiple loops.

Packet data corresponding to the communication paths 60 and 61 are transmitted to the communication paths 60 and 61, respectively. The packet data includes data for controlling the operation of the cell 30, data for identifying the cell 30, and data indicating the state of the cell 30, which will be described in detail later.

FIG. 2 is a schematic block diagram illustrating a part of the power converter of FIG. 1. FIG.
As shown in FIG. 2, cell 30 includes terminals 31a and 31b. The cell 30 is connected to other cells 30 and the like by terminals 31a and 31b. The cell 30 includes a main circuit 32 , a main circuit power supply 34 , a control circuit 36 and a gate drive circuit 35 . The main circuit power supply unit 34 is connected to the main circuit 32 and receives power from the main circuit 32 to generate power for the control circuit 36, the gate drive circuit 35, and the like. The control circuit 36 and the gate drive circuit 35 are operated by power supply from the main circuit power supply section 34 . The control circuit 36 acquires its own control data from packet data transmitted through the communication path 61, and generates a gate drive signal based on the acquired control data.

The main circuit 32 includes a switching element 32a, a diode 32b, and a capacitor 32c. The switching element 32a is a self arc-extinguishing semiconductor element. Two switching elements 32a are connected in series.

Diode 32b is a freewheeling diode. The two diodes 32b are connected in anti-parallel to the switching elements 32a connected in series.

The capacitor 32c is connected in parallel with the two switching elements 32a connected in series.

Although not shown, each cell 30 has a voltage detector for detecting the cell voltage across the capacitor 32c and the voltage between the terminals 31a and 31b, and a current detector for detecting input/output current. The voltage and current detected by the detector and current detector are supplied to the controller 50 .

In this example, the MMC uses cells 30 with a half-bridge configuration, but it is of course possible to replace all the cells with a full-bridge configuration by replacing the cells with a full-bridge configuration. Also, in this example, each cell 30 has a main circuit power supply unit 34, and a part of the energy of the capacitor 32c is used to supply power to its own control circuit or the like. Of course, a method of supplying electric power to each cell may be used.

The control circuit 52 of the control device 50 processes data acquired from a host control system (not shown) and other parts of the control device 50 and data acquired from each cell 30 to provide control for each cell 30. Generate data. Control data is data for controlling the operation of each cell 30 . The control data includes data relating to control commands such as gate drive pulses for driving the switching elements in each cell 30 .

The data acquired from the host control system is, for example, a DC power command value. The data acquired from other parts of the control device 50 includes, for example, data on the voltage and current of the system to which the power conversion device 10 is interconnected, and may include data on abnormalities such as ground faults. .

The control circuit 52 generates counter set values. The counter set value is data for identifying the cell 30, and is used to determine whether the cell 30 writes its own data to the packet data circulating in the daisy-chained loop. Each cell 30 checks the counter set value and determines whether or not to write its own data into the packet data.

The control circuit 36 of each cell 30 acquires its own control data from the packet data received from the control device 50 . Each control circuit 36 sets, for example, the operation of the main circuit 32 based on the acquired control data.

The control circuit 36 of each cell 30 checks the counter setting value and determines whether or not to write its own data to the packet data based on that value.

The control circuit 36 of each cell 30 writes its own data into the packet data and then transmits the updated packet data to the next cell 30 when the counter set value is a value to write its own data into the packet data. do. The control circuit 36 transmits the packet data to the next cell 30 as it is without doing anything when the counter set value is a value that does not need to write its own data.

Each cell 30 and controller 50 are insulated from each other. Therefore, the communication paths 60, 61 of each phase are preferably configured by optical fiber cables. When the communication paths 60 and 61 are configured by optical fibers, the control circuits 52 and 36 each include a photoelectric conversion circuit, and transmit and receive data via the photoelectric conversion circuit.

FIG. 3 is a schematic diagram illustrating packet data transmitted within the power converter of FIG. 1 .
As shown in FIG. 3, packet data 100 includes an area (first area) 102 containing control data, an area (second area) 104 containing counter setting values, and an area (third area) 106 containing converter data. contains each area. The control data, as described above, is a control command containing data of gate drive pulses for each cell 30 . Control data 1 for the cell 30 on the highest potential side (cell 1 in FIGS. 1 and 3) is stored in the corresponding area. Control data 2 for the cell on the low potential side of the cell 30 (cell 2 in FIGS. 1 and 3) is stored in the corresponding area. The same applies to other cells 30, and the control data C for the cell 30 on the lowest potential side (cell C in FIGS. 1 and 3) is also stored in the corresponding area.

In this example, an integer from 1 to C is stored in the counter set value area 104 . In FIG. 3, a variable i containing an integer from 1 to C is set. Variable i is set to an initial value by control circuit 52 and is incremented (for example, by adding 1) each time control circuit 52 transmits packet data 100 . Depending on the initial value, it may be decremented (for example, by subtracting 1).

The counter setting value area 104 is not limited to storing one variable (setting value) as in this example, and may store a plurality of setting values. In this example, as will be described later, the control circuit 52 increments the setting value by one each time the packet data 100 is transmitted, but the two setting values are incremented by one each time the packet data is transmitted. may be equal.

The converter data area 106 can store the converter data for the cell 30 identified by the value set by the counter setting.

The operation of the power converter 10 of the embodiment will be described.
FIG. 4 is a schematic diagram for explaining the operation of the power converter according to the embodiment.
As shown in FIG. 4, control circuit 52 stores control data for all cells 30 in packet data 100 and sets counter settings representing from which cell 30 transducer data is to be obtained. store. Control circuit 52 stores all control data and counter set values in packet data 100 and transmits the packet data 100 to first cell 30 (cell 1 in FIG. 4) via communication path 61 . Each cell 30 obtains control data for itself from the packet data 100 and forwards the packet data 100 to the next cell 30 .

A counter setting value is set in the packet data 100 in order to acquire the converter data of any cell 30 . The target cell 30 makes its own determination and writes its own converter data into the packet data 100 . The updated packet data 100a is transferred to the control circuit 52 when the transfer between the cells 30 is completed.

The control circuit 52 acquires the written converter data. The control circuit 52 transmits the transferred packet data 100a to the cell 30 again in order to obtain the converter data of another cell 30. FIG.

By repeating the above operation, the control circuit 52 acquires the converter data of all the cells 30 and based on these, generates new control data.

The series of operations described above will be described using a flowchart.
FIG. 5 is an example of a flowchart for explaining the operation of the power converter of the embodiment.
FIG. 5 shows the processing in the control device 50, the processing in the first cell 30 (cell 1), and the processing in the second cell 30 (cell 2). ing. The processing in the Cth cell (cell C) is also shown. Cell 1, Cell 2, . . . , Cell C correspond, for example, to Cell 1, Cell 2, . That is, the packet data is transferred in the order of control device 50→cell 1→cell 2→ . . . →cell C→control device.

Here, the cells N (N=1, 2, . . . , C) are called cell numbers (denoted as cell numbers in FIG. 5), and are assigned to each cell 30 in advance.

As shown in FIG. 5, the control device 50 starts processing from step S1. In step S 1 , the control circuit 52 of the control device 50 sets control data for each cell 30 .

In step S2, the control circuit 52 sets the counter set value i to 1, which is the initial value.

In step S3, the control circuit 52 transmits the packet data 100 in which the control data and the counter set value i are stored to the first cell 1. FIG.

In cell 1, processing starts from step S11. At step S11, the control circuit 36 of the cell 1 receives the packet data 100 transferred.

At step S12, the control circuit 36 of the cell 1 obtains and sets its own control data from the received packet data.

In step S13, the control circuit 36 of cell 1 determines whether or not the counter set value i matches its own cell number. In this example, the counter set value i is set to "1", so the process proceeds to the next step S14.

At step S 14 , the control circuit 36 of cell 1 writes its own converter data to the packet data 100 .

In step S13, when the counter set value i is different from the own cell number, the process proceeds to the next step S15 without performing the process of step S14.

At step S15, the control circuit 36 of cell 1 transmits the packet data to the next cell 2. FIG. In this example, since the converter data of cell 1 has been updated, the updated packet data 100a is transmitted.

In cell 2, in step S21, the control circuit 36 of cell 2 receives the transferred packet data. In this example, what is received is packet data 100a in which cell 1's transducer data has been updated.

At step S22, the control circuit 36 of the cell 2 obtains and sets its own control data from the received packet data.

In step S23, the control circuit 36 of cell 2 determines whether or not the counter set value i matches its own cell number. In this example, the counter set value i is set to "1", so the process proceeds to step S25 without performing the process of step S24.

If the counter set value i matches the own cell number in step S23, the process proceeds to step S24. At step S24, the control circuit 36 of cell 2 writes its own converter data into the packet data.

At step S25, the control circuit 36 of cell 2 transmits the packet data to the next cell 3 (not shown).

Thereafter, although not shown, in each of the cells 3 to (C-1), the control circuit 36 of each cell performs the same processing as in the cells 1 and 2 described above. In this example, since the counter set value i is set to "1", the second and subsequent cells do not write their own converter data to the transferred packet data 100a, but directly to the next cell. Transfer the packet data 100a.

In cell C, in step SC1, the control circuit 36 of cell 2 receives the transferred packet data. In this example, what is received is packet data 100a in which cell 1's transducer data has been updated.

At step SC2, the control circuit 36 of the cell C obtains and sets its own control data from the received packet data.

At step SC3, the control circuit 36 of the cell C determines whether or not the counter set value i matches its own cell number. In this example, the counter set value i is set to "1", so the process proceeds to step SC5 without performing the process of step SC4.

If the counter set value i matches its own cell number at step SC3, the process proceeds to step SC4. At step SC4, the control circuit 36 of cell 2 writes its own converter data into the packet data.

At step SC5, the control circuit 36 of the cell C transmits the packet data to the control circuit 52 of the control device 50. FIG.

The process moves to the control circuit 52 of the control device 50 again, and the control circuit 52 of the control device 50 receives the packet data transferred from the cell C in step S4. In this example, control circuit 52 receives packet data 100a updated with transducer data for cell 1 .

In step S5, the control circuit 52 of the control device 50 acquires converter data from the packet data. In this example, the transducer data for cell 1 is obtained.

In step S6, the control circuit 52 of the control device 50 checks whether or not the counter set value i of the received packet data is smaller than the number C of cells. If the counter set value i is smaller than the number of cells C, the process proceeds to the next step S7. If the counter set value i is greater than or equal to the number of cells C, the process is terminated. After completing the process, the control circuit 52 of the control device 50 returns the process to the first step S1 and repeats the above-described operations.

In step S7, the control circuit 52 of the control device 50 increments the counter set value i and shifts the process to step S3. The control circuit 52 of the control device 50 and the control circuit 36 of each cell 30 repeat the processes after step S3 in the same manner as described above.

In this example, the control circuit 52 of the control device 50 receives the packet data 100a in which the counter set value i is set to "1" and updated with the converter data of the cell 1, so the new counter set value i is , is set to "2". The above operation is repeated until the counter set value i is set to "C". By repeating the above operation "C" times, the control circuit 52 of the controller 50 can obtain the transducer data of all the cells 30. FIG.

In the above description, one counter set value is set and packet data transmission is repeated for the number of C cells 30 to acquire the converter data of all the cells 30. However, any counter set value Of course you can set it.

For example, by setting the counter setting values as [i, i+2, i+4, . can be obtained. The value to be added after the circulation is not limited to 1, and may be set arbitrarily. For example, if the counter set value is set to [i, i+1], the converter data of the adjacent cells can be obtained sequentially by adding 2 each time it cycles.

Effects of the power conversion device of the embodiment will be described.
FIG. 6 is a schematic diagram illustrating packet data transmitted within the power conversion device of the comparative example.
As shown in FIG. 6 , in the power converter of the comparative example, packet data 200 transferred through a daisy chain connection loop includes a control data area 202 and a converter data area 206 . The control data, as in the embodiment, is a control command containing data of gate drive pulses for each cell 30 .

In packet data 100 and 200, the required number of words is assigned to each data area. For example, the number of words of each control data is A [words] in both the comparative example and the embodiment, and the number of words can be the same.

In the case of the comparative example, packet data 200 includes an area for transducer data for each cell, and the number of words of transducer data is B [words]. Therefore, in the case of the comparative example, the length of the packet data 200 is A [words]×C [units]+B [words]×C [units].

In the power conversion device of the comparative example, each cell 30 measures the converter data each time it receives the packet data 200 and writes the measured converter data into the packet data 200 . Therefore, the time required to transfer the packet data 200 to the next cell 30 or control device 50 after receiving the packet data 200 is the time to acquire the converter data and the time to write the converter data to the packet data 200. becomes the sum of The time it takes for the packet data 200 to loop around the daisy-chained cells 30 and back to the controller 50 includes the total time for processing the transducer data in each such cell 30. will be

In the case of the embodiment, as in the examples of FIGS. 3 to 5, the converter data of one cell 30 is included, and the packet data 100 contains A [words]×C [units]+B [words]. ]×1 [units]+K [words] are set. K [word] is the area for the counter set value i, for example K=1.

Thus, in the power conversion device 10 of the embodiment, it is possible to suppress the length of the packet data 100 that circulates in the loop of the daisy chain connection.

Embodiments may reduce the time for processing transducer data. In the examples of FIGS. 3 to 5, one converter data is processed each time the packet data 100 goes through the loop. can be done. In the embodiment, by reducing the processing time of the converter data, it is possible to reduce the time required for the packet data to circulate through the communication channel compared to the comparative example.

In general, currents, voltages, and the like acquired by each cell 30 are used for feedback, and their fluctuations are sufficiently slow compared to the setting cycle of control data including gate drive pulses. Therefore, the transmission speed of packet data is determined according to the set period of the gate drive pulse for each cell 30 .

Analog data such as current and voltage acquired by each cell 30 is converted into digital data by an analog-digital converter (A/D converter) and processed by each control circuit 52, 36, and the like. The data conversion speed of the A/D converter is determined by a predetermined sampling period. This sampling period is usually sufficiently longer than the control data set period. May contain redundant data.

In other words, the period for acquiring converter data can be determined based on the sampling rate of the A/D converter, and should be shorter than the sampling period of the A/D converter. For example, the cycle for acquiring converter data is preferably set to be slightly shorter than the minimum value (shortest cycle) of the sampling cycle, taking into consideration variations in the sampling cycle of the A/D converter. .

In the power conversion device 10 of the embodiment, the number of words of the packet data 100 can be reduced compared to the power conversion device of the comparative example. can be faster. Therefore, since the setting cycle of the control command including the gate driving pulse can be shortened, the power conversion device 10 can be safely operated such as stopping at high speed when an abnormality such as an accident occurs, thereby improving safety. becomes possible. In addition, the operability of the power converter 10 can be improved by shortening the setting cycle of the control command.

By setting the transmission speed of packet data 100 faster, the number of cells 30 per loop can be increased. By increasing the number of cells 30 per loop, it is possible to reduce the number of optical fiber cables that are the entire communication paths 60 and 61 of the power conversion device 10, thereby reducing the cost and the installation space of the power conversion device 10. can be reduced.

Also, the control circuit 52 of the control device 50 has a circuit scale corresponding to the number of the communication paths 60 and 61 . Therefore, by reducing the total number of communication paths 60 and 61, the circuit scale of the control circuit 52 can be reduced, which contributes to cost reduction and installation space restraint.

By setting the period for acquiring the converter data to an appropriate value based on the sampling period of the A/D converter of each cell 30, the control device 50 does not acquire redundant converter data. Therefore, the amount of calculation of the control circuit 52 of the control device 50 can be suppressed.

According to the embodiments described above, it is possible to realize a power converter with few operational restrictions even if it has a daisy-chained communication path.

Although several embodiments of the invention have been described above, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included within the scope and spirit of the invention, and are included within the scope of the invention described in the claims and equivalents thereof. Moreover, each of the above-described embodiments can be implemented in combination with each other.

1 AC system, 2 transformer, 3 DC system, 10 power converter, 20 power converter, 22 unit arm, 24 transformer, 30 unit converter (cell), 36 control circuit, 50 control device, 52 control circuit, 60, 61 communication path, 100, 100a packet data

Claims (7)

a power converter including a plurality of converters;
a control device daisy-chained to the plurality of converters in a loop to mutually transmit packet data for controlling the plurality of converters;
with
The packet data is
a first area storing a plurality of control data for controlling the plurality of transducers;
a second area storing identification data identifying the plurality of transducers;
a third area storing transducer data of a transducer having the identification data among the plurality of transducers;
including
The number of pieces of identification data stored in the second area is one or more, and the power conversion device is smaller than the number of the plurality of converters. The control device is
storing the plurality of control data in the first area;
storing the identification data in the second area;
transmitting a first packet of data having the plurality of control data and the identification data to a first transducer of the plurality of transducers;
The first converter is
if the identification data is self-identifying data, the self converter data is written in the third area of the first packet data;
2. The power of claim 1, wherein if the identification data is not self-identifying data, the first packet data is transmitted to one of the remaining converters of the plurality of converters without writing data. conversion device. a second converter, another one of the remaining converters, sending the packet data to the controller;
The control device is
receiving the first packet data to obtain the converter data;
3. The power converter according to claim 2, wherein a plurality of new control data are generated based on all the converter data of the plurality of converters. Each of the plurality of converters includes an analog-digital converter that measures its own state and converts it into digital data;
A period from when the controller transmits the first packet data to the first converter to when it receives the packet data from the second converter is set based on the sampling period of the analog-to-digital converter,
4. The power converter according to claim 3, wherein said period is set shorter than said sampling period. The power converter according to any one of claims 1 to 4, wherein the number of pieces of identification data stored in the second area is one. The power converter according to any one of claims 1 to 4, wherein the number of said identification data stored in said second area is 1/2 of said number. The power converter according to any one of claims 1 to 6, wherein said power converter includes a modular multi-level converter.

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