WO2017094379A1

WO2017094379A1 - Power conversion device

Info

Publication number: WO2017094379A1
Application number: PCT/JP2016/080889
Authority: WO
Inventors: 充弘門田; 泰明乗松
Original assignee: 株式会社日立製作所
Priority date: 2015-11-30
Filing date: 2016-10-19
Publication date: 2017-06-08
Also published as: CN108370221A; JP6476318B2; CN108370221B; JPWO2017094379A1

Abstract

A power conversion device is provided with a plurality of power converter cells and a control unit for controlling the power converter cells, wherein the power converter cells are each provided with: a converter for converting an input voltage from the outside to generate a DC link voltage; an inverter for converting the DC link voltage to an AC voltage and outputting the AC voltage; and a bypass unit for short-circuiting the output terminals of the inverter. When detecting a failure in a part of the power converter cells, the control unit operates the bypass unit of a power converter cell in which the failure has been detected to short-circuit the output terminals and increases the DC link voltages of at least one or more power converter cells among the power converter cells in which no failure occurs.

Description

Power converter

The present invention relates to a power conversion device.

In high-voltage or large-capacity power conversion, a power conversion device in which a plurality of power converter cells (hereinafter abbreviated as “cells”) are connected in series or in parallel is used. For example, for driving a high voltage motor, the output terminals of a plurality of inverters (a type of power converter) are connected in series, and the output voltage of each inverter is synthesized to output a high voltage (such as a multiple inverter method) Is called). In this system, a high voltage can be output directly to the motor without using a large low-frequency step-up transformer.

Also, the introduction of natural energy power generation such as solar power generation and wind power generation is expanding worldwide. There is a PCS (Power Conditioning System) as a power conversion device for converting electric power obtained from natural energy and outputting it to an electric power system. In this PCS as well, a configuration using a plurality of cells as described above is considered effective when dealing with higher voltages and larger capacities.

In such a power conversion device having a plurality of cells, it is important to ensure reliability. As an example of a function related to reliability, it is desirable that operation can be continued using the remaining power converter cells even when some cells fail. If the output of each cell is connected in series, a bypass unit is provided so that the output terminals of each cell can be short-circuited, and if some cells fail, the output terminals of the same cell can be short-circuited. The operation using the remaining cells becomes possible. However, since the number of series stages of cells is reduced, the maximum voltage that can be output by the power converter is also reduced. As a result, the operating range (rotational speed and torque range) is narrow for a motor, and the operation may not be achieved for a PCS.

There is a direct high-voltage inverter device described in Patent Document 1 as a power converter that solves this problem. In this direct high-voltage inverter device, the outputs of a plurality of single-phase inverters are respectively connected in series to obtain a three-phase high-voltage output. Also, each phase is provided with a spare single-phase inverter. During normal operation, the output terminal of the spare single-phase inverter is operated in a short-circuit state. When one single-phase inverter fails in at least one phase, Operation of the equipment is resumed by the operation of the phase backup inverter.

JP 2009-033943 A

In Patent Document 1, since a spare power converter cell is provided, there is a problem that the apparatus becomes larger by that amount and the control becomes complicated.

Therefore, in the present invention, in the power conversion device composed of a plurality of power converter cells, even if some of the power converter cells fail, the operation can be continued using the remaining power converter cells. A highly reliable and small power converter capable of expanding the output voltage is realized.

In order to solve the above-described problem, for example, a power conversion device including a plurality of power converter cells and a control unit that controls them, each of the power converter cells converts an input voltage from the outside. A converter that generates a DC link voltage, an inverter that converts the DC link voltage into an AC voltage and outputs the output, and a bypass unit that short-circuits between output terminals of the inverter, and the control unit includes the power When some failure is detected among the converter cells, the bypass portion of the power converter cell in which the failure is detected is operated to short-circuit between the output terminals, and at least one of the power converter cells that have not failed The DC link voltage of the above power converter cell is increased.

In a power conversion device composed of a plurality of power converter cells, even if some of the power converter cells fail, operation can be continued using the remaining power converter cells, and the output voltage after the failure A highly reliable and compact power converter that can expand

It is the structure of the power converter device 100 in this invention. 2 is a configuration of a power converter cell 101 in the first embodiment. It is an output voltage waveform during normal operation. It is an output voltage waveform when one cell fails. 3 is a specific example of a control unit 200 according to the first embodiment. It is a flowchart of determination of DC link voltage Vdc based on the failure cell determination of a present Example. It is an output voltage waveform at the time of normal operation in Example 2. It is an output voltage waveform when one cell in Example 2 fails. 6 is an example of a PWM modulation operation during normal operation in the second embodiment. It is an example of the PWM modulation | alteration operation | movement when one cell in Example 2 fails. This is a configuration of the power converter 100 when a resonant converter is used as a specific example of the isolated DC-DC converter in the third embodiment. It is a specific example of the control part 200 in Example 3. FIG. It is a structure of the power converter device 1000 in Example 4. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a configuration of a power conversion apparatus 100 according to the present invention. A configuration common to all the embodiments will be described with reference to FIG.

The power conversion device 100 converts the power input from the external power supply 300 and outputs it to the external load 400. The power conversion device 100 includes a plurality of power converter cells 101 to 104 and a control unit 200. The output terminal of each cell is connected in series to form an output as the power conversion device 100. Although FIG. 1 shows an example in which four cells are used, the number of cells is arbitrary.

The power supply 300 may be either a DC power supply or an AC power supply. FIG. 1 shows a configuration in which each cell is connected in parallel to the power supply 300. However, similarly to the output side of the power conversion apparatus 100 (connection with the load 400), the input terminal of each cell may be connected to the power supply 300 in series.

Each of the power converter cells 101 to 104 converts converters 111 to 114 that convert external input voltages to generate DC link voltages (Vdc1 to Vdc4) and Vdc1 to Vdc4 to AC voltages (Vo1 to Vo4), respectively. Inverters 121 to 124 that convert and output, and bypass units 131 to 134 for short-circuiting the output terminals of the inverters 121 to 124 are provided. In addition to these, elements such as protective components (relays, fuses, etc.) and noise filters may be provided.

Vdc1 to Vdc4 may all have the same voltage value or different voltage values. Since the output terminals of the inverters are connected in series, the output voltage Vos of the power conversion device 100 is a sum of the output voltages of the inverters of the cells (Vo1 + Vo2 + Vo3 + Vo4). In the drawings and the following description, Vdc and Vo may be referred to as general names of the DC link voltage and the inverter output voltage (for each cell), respectively.

Supplementary explanation of the internal configuration of the power converter cell. If power supply 300 is a DC power supply, converters 111 to 114 are each a DC-DC converter. Examples of DC-DC converters include switching power supply type converters such as choppers, flyback converters, and resonant converters. Further, a linear (dropper) converter such as a series regulator may be used. When connecting each cell in parallel to the power supply 300 as shown in FIG. 1, among them, a converter that can insulate the input and output with a transformer, such as a flyback converter or a resonant converter, is used.

If the power source 300 is an AC power source, the converters 111 to 114 are each AC-DC converters. As an example of the AC-DC converter, there is a configuration in which the above-described DC-DC converter is connected to a subsequent stage of a rectifier circuit using a diode. As described above, the converters 111 to 114 may have a plurality of configurations, but any specific configuration may be used as long as Vdc1 to Vdc4 can be generated and varied.

A plurality of configurations can be considered for the inverters 121 to 124, but any specific configuration may be used as long as Vdc1 to Vdc4 can be converted into Vo1 to Vo4, respectively. One example is an H-bridge single-phase inverter. Examples of the bypass units 131 to 134 include a relay, a semiconductor switching element, and a mechanical switch. Further, semiconductor switching elements included in the inverters 121 to 124 may be used.

Next, the control unit 200 will be described. The control unit 200 detects the physical quantity and state of each cell and outputs a control signal to each cell. The control unit 200 performs the above detection and control signal output so that the operation can be continued using the remaining cells even when some of the cells fail.

FIG. 1 shows only signals between the control unit 200 and the cell 101 in order to prevent the drawing from becoming complicated. Actually, the control unit 200 exchanges signals with the cells 102 to 104 in the same manner. Moreover, each signal expressed as one arrow in FIG. 1 may include a plurality of pieces of information. As the internal configuration of the control unit 200, a failure detection unit 201, a DC link voltage (Vdc) control unit 202, an output voltage (Vos) control unit 203, and a bypass control unit 204 that are particularly important in the present invention are shown.

The physical quantity detection signal input to the control unit 200 specifically indicates detection signals such as the voltage, current, and temperature of converters and inverters in each cell. The failure detection unit 201 of the control unit 200 grasps phenomena such as “a voltage not being output as a target value”, “overcurrent has occurred”, “temperature is abnormally high” from these physical quantity detection signals. To do. That is, the failure detection unit 201 can compare a detected physical quantity with a physical quantity standard and specify a cell different from the standard. The failure detection unit 201 detects that a cell failure or abnormality has occurred from these phenomena, and outputs a failure detection signal that indicates the presence or absence of a failure or abnormality in each cell. In addition, the control part 200 can output the control signal which specifies the said cell, when maintaining, diagnosing, and checking arbitrary cells. Although not shown in FIG. 1, the control unit 200 can use the physical quantity detection signal (particularly voltage and current information) not only for failure detection but also for output feedback control. Hereinafter, the case where the failure detection unit 201 specifies a cell different from the reference will be referred to as a failure.

The bypass control unit 204 outputs a bypass control signal for turning on / off the bypass units 131 to 134 of each cell based on the failure detection signal and the control signal. During normal operation (when all cells operate without failure), control is performed so that the bypass parts of all cells are off. When a cell failure is detected, or when maintenance, diagnosis, or inspection is performed, the bypass unit included in the cell is operated. For example, when a failure of the cell 101 is detected, control is performed so that the bypass unit 131 included in the cell 101 is turned on. As a result, the power conversion apparatus 100 can continue operation with the remaining cells 102 to 104.

The DC link voltage (Vdc) control unit 202 determines the Vdc target value of each cell based on the failure detection signal. Further, a converter control signal is output so that the converter outputs Vdc as the target value. For example, when the cell 101 fails, control is performed so that Vdc is increased in at least one of the cells 102 to 104 that are not failed. Thereby, the output voltage range after the failure can be expanded.

The output voltage (Vos) control unit 203 generates an inverter control signal for each cell so that Vos according to the target value can be obtained. Details will be described in the following examples.

Note that not all elements of the control unit 200 need be mounted on a single board. The elements of the control unit 200 may be mounted on a substrate on which the converter and inverter of each cell are mounted.

As Example 1, the method in which the power conversion device 100 converts the voltage of the power supply 300 into an AC voltage and outputs the voltage to the load 400, and the operation is continued even when some of the cells fail, and the output voltage is expanded. The method will be specifically described.

FIG. 2 shows a configuration of the power converter cell 101 in the first embodiment, and shows a configuration using an H-bridge type single-phase inverter as a specific example of the inverter. In FIG. 2, only the power converter cell 101 is shown, and other cells are omitted. The cells 102 to 104 are also provided with the same single-phase inverter. The specific configuration of the converter 111 is arbitrary, and a plurality of configurations can be considered as already described.

As shown in FIG. 2, the single-phase inverter 121 is an H-bridge circuit including four semiconductor switching elements (11 to 14). As an example of the semiconductor switching element, a MOSFET is shown, but other kinds of elements such as a bipolar transistor and an IGBT may be used.

The control unit 200 outputs a gate signal for driving the four MOSFETs (11 to 14) as an inverter control signal output to the inverter 121. The inverter 121 outputs an output voltage (Vo1) detected by the voltage detector 15 and an output current detected by the current detector 16 as a physical quantity detection signal output to the control unit 200. The physical quantity detection signal may include other physical quantities such as the inverter temperature. The converter 111 also outputs a physical quantity detection signal to the control unit 200.

Here, the value of the DC link voltage (Vdc ₁ ) is V0. The inverter 121 can output three values of + V0 (positive voltage), 0 (zero), and −V0 (negative voltage) as instantaneous values by ON / OFF control of the MOSFETs (11 to 14). For example, if MOSFETs 11 and 14 (12 and 13) are turned on and MOSFETs 12 and 13 (11 and 14) are turned off, Vo1 becomes + V0 (−V0). If the MOSFETs 11 and 13 (12 and 14) are turned on and the MOSFETs 12 and 14 (11 and 13) are turned off, Vo1 becomes almost zero.

In normal operation, when the DC link voltages (Vdc1 to Vdc4) of all the cells are V0, the power conversion device 100 is -4V0, -3V0, ..., 0, ..., + 3V0, + 4V0. Nine different voltages can be output at every V0. For example, if the cells 101 and 102 output + V0 and the cells 103 and 104 output 0, Vos is + 2V0. If only the cell 104 outputs 0 and the remaining cells output -V0, Vos becomes -3V0. That is, the output voltage range of the power conversion device 100 is −4V0 ≦ Vos ≦ + 4V0.

When one cell fails, the bypass section is turned on in the failed cell, so the output voltage is forced to zero. At this time, if the Vdc of each cell is kept at V0, the output voltage range of the power conversion device 100 becomes −3V0 ≦ Vos ≦ + 3V0, which is (3/4) times narrower than that during normal operation.

Here, if all the Vdc of the cells that have not failed are changed to V1, the output voltage range of the power converter 100 becomes −3V1 ≦ Vos ≦ + 3V1. At this time, if the relational expression of V1 = (4/3) × V0 is established, the output voltage range is maintained at −4V0 ≦ Vos ≦ + 4V0. However, if V1> V0 holds, that is, if Vdc is increased, the effect of expanding the output voltage range after the failure can be obtained. Further, even if Vdc is increased in at least one cell among non-failed cells, the same effect can be obtained.

Here, assuming that the total number of cells is N, the above relational expression V1 = (4/3) × V0 is generalized. When the number of cells to be operated (cells that are not faulty or abnormal) is N ′ and Vdc at this time is V ′, the relational expression is V ′ = (N / N ′) × V0. That is, Vdc is controlled to be inversely proportional to the number of cells to be operated.

If the number of failures increases and Vdc increases accordingly, the voltage applied to each cell component (such as a MOSFET) may exceed the rated value. As a method for solving this problem, a method of increasing Vdc as described above is conceivable only when the number of failed cells is less than a predetermined threshold. That is, when the number of failed cells is greater than the above threshold, Vdc may be controlled to be constant regardless of the number of failed cells.

3 (A) and 3 (B) are output voltage (Vos) waveforms of the power conversion apparatus 100 according to the first embodiment. FIG. 3 (A) shows a waveform during normal operation, and FIG. 3 (B) shows a waveform when one cell fails. A sine wave indicated by a broken line is a fundamental wave component included in Vos. FIG. 3A shows a case where Vdc during normal operation is V0, and FIG. 3B shows a case where Vdc when failure occurs is V1 = (4/3) × V0.

The power conversion device 100 cannot output the sine wave voltage itself due to the above principle, and outputs a staircase-like pseudo sine wave voltage as shown in FIGS. 3 (A) and 3 (B). The Vos waveforms in FIGS. 3A and 3B show + V0 (or + V1) in the positive half cycle and −V0 (or −V1) in the negative half cycle depending on the phase of the AC voltage to be output. It is obtained by changing the number of cells to be output. In the normal operation of FIG. 3A, Vos has a stepped waveform of 8 steps when the positive and negative regions are combined, and the voltage value per step is V0. When a failure occurs in FIG. 3B, Vos has a 6-step staircase waveform that is (3/4) times that of normal operation. However, since the voltage value per step is increased to V1 which is (4/3) times, the amplitude of Vos is maintained as compared with the normal operation of FIG.

FIG. 4 is a specific example of the control unit 200 in the first embodiment, and shows a configuration for realizing the control described above. Each control signal is represented as an arrow, but these signals include a plurality of pieces of information. For example, in FIG. 2, four arrows are shown for each MOSFET as the inverter control signal, but in FIG. 4, they are summarized as one arrow. More precisely, the inverter control signal is information for 4 cells, that is, 16 MOSFETs. In FIG. 4, specific contents of some signals are shown on the assumption that the cell 104 has failed.

The failure detection unit 401 of the control unit 200 detects a failure of the cell 104 from the physical quantity detection signal and outputs the detected failure signal to the bypass control unit 402, the Vdc control unit 403, and the output voltage (Vos) control unit 404. As already described, the bypass control unit 402 outputs a bypass control signal to turn on the bypass unit 134 of the failed cell 104.

The Vdc control unit 403 of the control unit 200 includes a Vdc setting unit 405 and a converter control unit 406. As shown in FIG. 4, the Vdc setting unit 405 includes a table that associates the number of failures with Vdc, and generates a Vdc target value for each cell from the failure detection signal. The Vdc of the non-failed cells 101 to 103 is changed from V0 to V1, and the operation of the failed cell 104 is stopped. Converter control unit 406 outputs a converter control signal so that the converter of each cell outputs Vdc as the target value.

The Vos control unit 404 of the control unit 200 outputs an inverter control signal so that Vos has the waveform shown in FIG. The Vos target value in FIG. 4 represents an instantaneous value or phase of an AC voltage to be output, and may be considered as a fundamental wave component indicated by a broken line in FIG. 3, for example. The Vos target value is generated inside the control unit 200, and the generation method differs depending on application applications such as motor drive and PCS, and is thus arbitrary in the present invention.

The Vos control unit 403 changes the number of cells that output a positive voltage (+ V0 or + V1) or a negative voltage (−V0 or −V1) based on the Vos target value. As can be seen from FIG. 3, even if the Vos target value is the same, parameters such as the number of cells that output a positive voltage or a negative voltage and the timing for changing the number of the parameters are the values of Vdc (that is, the number of cells to be operated). It depends on the number of units. Therefore, the failure detection signal and the Vdc target value are input to the Vos control unit 403, and the above parameters are adjusted according to the situation. Further, as shown in the following embodiments, a detected value of Vdc may be used instead of the Vdc target value.

FIG. 5 is a flowchart for determining the DC link voltage Vdc based on the failure cell determination of this embodiment.

First, the failure detection unit 401 compares the detected physical quantity of each power converter cell with a physical quantity reference to determine whether there is a cell different from the reference (step 501).

If there is a power converter cell different from the reference (YES in step 501), the bypass control unit 204 outputs a bypass control signal so that the bypass unit of the corresponding cell is turned on (step 502).

On the other hand, if there is no cell different from the reference (No in step 501), the bypass unit of each cell is kept off and the determination in step 501 is performed again.

Following step 502, the DC link voltage (Vdc) control unit 202 determines the Vdc target value of each cell based on the failure detection signal obtained in the failure detection unit 401, and sets the converter so that the obtained Vdc is obtained. Control (step 503).

The output voltage (Vos) control unit 203 generates an inverter control signal for each cell so that Vos according to the target value is obtained (step 504).

As described above, even when a part of the cells fails, the operation can be continued using the remaining cells, and the highly reliable and small-sized power conversion device 100 that can expand the output voltage after the failure is realized. Further, Vdc during normal operation can be set to the minimum necessary value, that is, it is not necessary to provide a margin for Vdc in preparation for failure. As Vdc is lower, the loss generated in each cell, that is, heat generation, is reduced, and there is an effect of preventing cell failure itself. Further, since it is not necessary to provide a spare cell, it is possible to reduce the size and cost of the apparatus.

As Example 2, a case where PWM modulation (pulse width modulation) is applied to control of an inverter will be described. The configuration of the power conversion device 100 is the same as that of the first embodiment.

6 (A) and 6 (B) are output voltage (Vos) waveforms of the power conversion apparatus 100 according to the second embodiment. FIG. 6 (A) shows a waveform during normal operation, and FIG. 6 (B) shows a waveform when one cell fails. 6A, Vdc is set to V0 during normal operation, and FIG. 6B increases Vdc to V1 = (4/3) × V0 when a failure occurs.

The PWM modulation will be described taking the case of normal operation in FIG. 6A, that is, a case where Vdc = V0 as an example. As described in the first embodiment, the inverter of each cell can output three kinds of voltages, + V0, 0, and −V0. When using PWM modulation, the inverter of each cell outputs + V0 and 0 alternately, or −V0 and 0 alternately. Therefore, as shown in FIG. 6A, a period in which Vos alternately repeats + 3V0 and + 2V0 and a period in which -3V0 and -4V0 are alternately repeated occur.

The case where the inverter outputs + V0 and 0 alternately will be described. In a sufficiently short (switching) period Ts compared to the period of Vos, a time ratio (duty) at which the inverter outputs + V0 is set to d (0 ≦ d ≦ 1). The ratio when the inverter outputs 0 is 1-d. At this time, the average value of the output voltage (Vo) in the period Ts is d × V0. By controlling the time ratio d within the range of 0 ≦ d ≦ 1, the inverter can output any voltage satisfying 0 ≦ Vo ≦ + V0 as an average value in the period Ts. Considering the case where the inverter alternately outputs -V0 and 0, an arbitrary voltage satisfying -V0 ≦ Vo ≦ + V0 can be output as an average value in the period Ts.

Extending the above description to 4 cells, the power conversion apparatus 100 can output an arbitrary voltage satisfying −4V0 ≦ Vos ≦ + 4V0 as an average value in the period Ts. In FIG. 6A, the waveform in which the time axis is expanded is also shown for the period in which the power conversion apparatus 100 alternately outputs + 3V0 and + 4V0. As an example of the operation of each cell in this period, three cells always output + V0 (d = 1) during the period Ts, and one cell alternately outputs + V0 and 0 by PWM modulation. Conceivable. As shown in this enlarged view, Vos can be gradually increased according to the target value by increasing the time ratio of outputting + 4V0 in accordance with the increase of the Vos target value (broken line).

At the time of failure occurrence in FIG. 6B, V1 = (4/3) × V0. Therefore, the power conversion apparatus 100 has a range of −3V1 ≦ Vos ≦ + 3V1, that is, −4V0 ≦ Vos ≦ + 4V0. For example, an arbitrary voltage can be output as an average value in the cycle Ts. That is, (A) The operation can be continued in the same output voltage range as that in the normal operation. However, if V1> V0 holds, that is, if Vdc is increased, the effect of expanding the output voltage range after the failure can be obtained. Further, even if Vdc is increased in at least one cell among non-failed cells, the same effect can be obtained.

The output voltage (Vos) control unit of the control unit 200 shown in FIG. 4 uses the Ts as a control cycle, and outputs a Vos as the target value in each cycle, the PWM modulation cell, its time ratio, and the remaining Parameters such as the output state of each cell are determined, and an inverter control signal is output to each cell. Further, as described in the first embodiment, the failure detection signal and the Vdc set value are input to the Vos control unit. The control unit 200 can change the above parameters according to the value of Vdc (that is, the failure occurrence state).

7A and 7B are examples of the PWM modulation operation in the second embodiment. Specifically, in the case where the target value of Vos is + 2.4 × V0, the waveforms of the output voltages (Vo1 to Vo4) of each cell and the output voltage (Vos) of the power converter 100 in the cycle Ts are shown. FIG. 7A and FIG. 7B are waveforms during normal operation and when the cell 104 fails, respectively. How the Vos control unit determines the above parameters will be described with reference to FIG.

In the normal operation of FIG. 7A, the cells 101 and 102 always output + V0 (when d = 1), the cell 104 always outputs 0, and the cell 103 outputs + V0 and 0 when d = 0.4. By alternately outputting, the average value of Vos is set to + 2.4 × V0. When only the cell 104 fails as shown in FIG. 7B, since V1 = (4/3) × V0, the target value of Vos is revised to + 1.8 × V1. In the same manner as described above, the cell 101 always outputs + V1, the cell 103 always outputs 0, and the cell 102 alternately outputs + V1 and 0 at d = 0.8, whereby the average value of Vos is +2. 4 × V0 (+ 1.8 × V1).

Here, a state where + V0 (or + V1) is always output during the period Ts is considered as a time ratio 1, and a state where 0 is always output during the period Ts is considered as a time ratio 0. At this time, the total value of the duty ratio of PWM modulation in each cell is 2.4 in FIG. 7 (A) during normal operation, and 1.8 in FIG. 7 (B) when one cell failure occurs. Further, as described above, 2.4 × V0 = 1.8 × V1. That is, the product of the total value of the duty ratio and Vdc is a constant value.

A specific method of PWM modulation, that is, a specific calculation performed by the Vos control unit may be a method using a triangular wave carrier signal, and the details are omitted. In the above example, only the cell 104 performs PWM modulation, but the number of cells that perform PWM modulation is not limited to one, and a method of performing PWM modulation with a plurality of cells may be used. For example, (A) during normal operation, there is a method in which all four cells are PWM-modulated at a duty ratio of 0.6.
As described above, the power conversion apparatus 100 can output the output voltage as the target value. Further, low-order harmonic components such as the third order and the fifth order included in the Vos waveforms in FIGS. 6A and 6B are smaller than those in FIG. Similarly, the harmonic component of the current output from the power converter 100 is reduced. As a result, it is possible to reduce the loss generated in the load 400 (especially the winding of the motor or the reactor), and to prevent the harmonic component from becoming a noise and adversely affecting other devices.

In the third embodiment, a specific configuration of the converter is shown on the assumption that the power source 300 is a DC power source and the power source 300 and the load 400 are electrically insulated. At this time, an isolated DC-DC converter is required as the converter.

FIG. 8 shows the configuration of the power converter 100 when a resonant converter is used as a specific example of the isolated DC-DC converter. As for the inverter, an H-bridge type single-phase inverter was used as in FIG. In FIG. 8, only the cell 101 is shown as a power converter cell, and other cells are omitted. The cells 102 to 104 are also provided with similar resonant converters.

As shown in FIG. 8, the converter 111 is a resonant converter, and an H-bridge type single-phase inverter provided with four MOSFETs (21 to 24), a resonant circuit provided with a coil 25, a capacitor 26, and a transformer 27, A rectifier circuit including four diodes (28 to 31) and a capacitor 32 are provided.

The gate signals for driving the MOSFETs 21 to 24 are shown as inverter control signals output from the control unit 200 to the converter 111. As the physical quantity detection signal output from the converter 111 to the control unit 200, the Vdc detected by the voltage detector 33 and the converter output current detected by the current detector 34 are shown, but include other physical quantities such as the converter temperature. You may go out.

The generation and control of Vdc by the converter 11 will be described. When the DC voltage of the power supply 300 is Vin, the single-phase inverter composed of the MOSFETs 21 to 24 outputs + Vin when the MOSFETs 21 and 24 are turned on and the MOSFETs 22 and 23 are turned off. When the MOSFETs 22 and 23 are turned on and the MOSFETs 21 and 24 are turned off, −Vin is output. By alternately repeating these two states, the single-phase inverter generates a rectangular-wave AC voltage. This AC voltage is transmitted from the primary side to the secondary side of the transformer 27 via the resonance circuit. The amplitude of the AC voltage generated on the secondary side of the transformer 27 depends on the circuit constant of the resonance circuit and is different from the amplitude of the AC voltage output from the single-phase inverter. The AC voltage generated on the secondary side of the transformer 27 is rectified by the rectifier circuit and smoothed by the capacitor 26 to generate Vdc.

Here, the impedance of the resonance circuit varies depending on the frequency of the input AC voltage, that is, the switching frequency of the MOSFETs 21 to 24. Even if Vin is constant, if the switching frequency of the MOSFETs 21 to 24 is changed, it is possible to variably control the amplitude of the alternating voltage generated in the transformer 127, and thus Vdc. In general, the circuit constant of the resonance circuit and the condition of the switching frequency are set so that the lower the switching frequency, that is, the longer the switching period, the higher Vdc.

With the configuration in FIG. 8, it is possible to obtain the power conversion device 100 that outputs a high voltage to the load while insulating the power source and the load. As an example of the power conversion apparatus 100 that requires such specifications, there is the PCS described above. In the conventional PCS, the voltage output from one inverter is boosted by a transformer, but this transformer is large because it operates at the frequency of the power system. With the configuration of FIG. 8, the transformer 27 can be miniaturized by increasing the switching frequency of the MOSFETs 21 to 24. In addition, if it is assumed that a converter is provided for the purpose of insulation and boosting, the effect of the present invention can be achieved with a small-sized and low-cost power conversion device 100 as compared with the conventional method of providing a spare cell. can get.

FIG. 9 is a specific example of the control unit 200 in the third embodiment, and shows a configuration for realizing the control described above. In FIG. 9, the physical quantity detection signal input to the control unit 200 is divided into a Vdc detection signal and other detection signals. In FIG. 7, four arrows are shown for each MOSFET as the converter control signal, but in FIG. 9, they are combined into one arrow. The description of the configuration common to FIG. 4 is omitted.

The converter control unit 901 of the control unit 200 performs Vdc feedback control using the Vdc target value and the Vdc detection signal, and outputs a converter control signal so that the converter of each cell outputs Vdc as the target value. The control calculation unit 902 executes control calculation such as PI control (proportional integration control) and sets the switching cycle so that Vdc matches the target value. The control signal generation unit 903 generates a converter control signal according to the switching period set by the control calculation unit 902. Thereby, even if Vin changes, Vdc can be controlled to the target value. Note that Vdc detection and feedback control are performed independently for each cell.

9 shows a configuration in which a Vdc detection signal is input to the output voltage control unit instead of the Vdc target value. When the Vdc target value is increased when a cell failure occurs, Vdc gradually increases with a certain time constant. That is, a transient period occurs until Vdc actually increases and converges to the target value. The output voltage control unit grasps the change in Vdc during the transient period based on the input Vdc detection signal and reflects it in the PWM modulation time ratio. That is, under the same Vos target value, the PWM modulation duty ratio is changed according to the value of Vdc. For example, as described in the second embodiment, if the product of the total PWM modulation ratio in each cell and the Vdc is controlled to be a constant value, the output voltage of the power conversion device 100 can be changed even during the transition period. Operation can be continued without causing

In the fourth embodiment, the power converter 1000 that outputs three-phase alternating current is configured by using three sets of the power converter 1000 described above.

FIG. 10 shows a configuration of the power conversion apparatus 1000 according to the fourth embodiment. The power conversion apparatus 1000 includes a plurality of power converter cells including the cells 105 to 110 and the control unit 200. Only signals between the control unit 200 and the cell 110 are shown to prevent the drawing from becoming complicated. In practice, the control unit 200 exchanges signals with all cells.

10 is provided with output terminals for three phases of U phase, V phase, and W phase, and each output terminal is connected to a three-phase load 401. As an example of the load 401, a three-phase motor can be considered. Further, if it is connected to a three-phase power system through a filter, it can be used as a three-phase output PCS.

The cells are divided into three sets for U phase, V phase, and W phase, and the output terminals of the cells constituting each phase are connected in series. In FIG. 9,

cells

105 and 106 are for the U phase,

cells

107 and 108 are for the V phase, and cells 109 and 110 are for the W phase. As shown in FIG. 9, one end of the output terminals of the

cells

106, 108, and 110 is connected to form a neutral point in the Y connection of the three-phase circuit.

For example, when a U-phase cell fails, the control unit 200 increases Vdc for the remaining U-phase cells. Thus, the effect of the present invention can be obtained also in the power conversion apparatus 1000 that outputs three-phase alternating current, and can be applied to a three-phase motor drive inverter and a three-phase power system PCS.

101-110 Power converter cell 111-114 Converter 121-124 Inverter 131-134 Bypass unit 200 Control unit 300

Power supply

400, 401 Load 11-14, 21-24 MOSFET
15, 33 Voltage detector 16, 34 Current detector 25

Coil

26, 32 Capacitor 27 Transformer 28-31 Diode

Claims

A power conversion device comprising a plurality of power converter cells and a controller for controlling them,
Each of the power converter cells includes a converter that converts an external input voltage to generate a DC link voltage, an inverter that converts the DC link voltage into an AC voltage, and an output, and an output terminal of the inverter. With a bypass to short circuit,
When the control unit detects a failure of a part of the power converter cell, the control unit operates the bypass unit of the power converter cell that detects the failure to short-circuit between the output terminals, and the power conversion is not failed. A power converter for increasing the DC link voltage of at least one power converter cell among the converter cells.
The power conversion device according to claim 1,
As the number of power converter cells in which a failure is detected among the power converter cells increases, the control unit increases the DC link voltage of at least one power converter cell among the power converter cells that have not failed. The power converter characterized by controlling the high.
The power conversion device according to claim 1,
The said control part controls the said DC link voltage so that it may be inversely proportional to the number of the power converter cells operated among the said power converter cells, The power converter device characterized by the above-mentioned.
The power conversion device according to claim 1,
The control unit is configured so that, as long as the number of power converter cells that have failed is less than a predetermined threshold, the power converter cell that has not failed is increased. A power conversion device that controls the DC link voltage of at least one power converter cell among the converter cells to be high.
The power conversion device according to claim 1,
When the number of power converter cells in which a failure has been detected is greater than the predetermined threshold value, the DC converter voltage is controlled to be constant regardless of the number of power converter cells in which the failure has occurred.
In the power converter device in any one of Claims 1-5,
The said control part controls the said inverter based on PWM modulation, and changes the time ratio of the said PWM modulation according to the said DC link voltage, The power converter device characterized by the above-mentioned.
The power conversion device according to claim 6, wherein
If the target value of the output voltage is the same, the control unit sets the inverter so that the product of the total value of the PWM modulation time ratios in each of the power converter cells and the DC link voltage is constant. The power converter characterized by controlling.
The power conversion device according to any one of claims 1 to 7,
The output terminals of the inverters included in the plurality of power converter cells are respectively connected in series, and the input terminals of the plurality of power converter cells are all connected in parallel to the power source. Power converter.
The power conversion device according to any one of claims 1 to 8,
The converter is a resonant converter including an inverter circuit including one or more semiconductor switching elements, a resonant circuit including a coil, a capacitor, and a transformer, and a rectifier circuit including one or more diodes. apparatus.
The power converter according to any one of claims 1 to 9,
The inverter is an H-bridge type single-phase inverter circuit including four semiconductor switching elements.
In the power converter device in any one of Claims 1 thru | or 10,
The control unit has a data table associating the number of the failed power converter cells and the DC link voltage of at least one power converter cell among the non-failed power converter cells. Power converter.
A power conversion device comprising a plurality of power converter cells and a controller for controlling them,
Each of the power converter cells includes a converter that converts an external input voltage to generate a DC link voltage, an inverter that converts the DC link voltage into an AC voltage, and an output, and an output terminal of the inverter. With a bypass to short circuit,
The control unit compares a physical quantity detected from the power converter cell with a reference of the physical quantity, operates a bypass unit of a power converter cell that takes a physical quantity different from the physical quantity reference, and short-circuits between output terminals. And increasing the DC link voltage of at least one power converter cell among the power converter cells that are not faulty.
A power conversion device comprising a plurality of power converter cells and a controller for controlling them,
Each of the power converter cells includes a converter that converts an external input voltage to generate a DC link voltage, an inverter that converts the DC link voltage into an AC voltage, and an output, and an output terminal of the inverter. With a bypass to short circuit,
The control unit operates a bypass unit of any power converter cell among the power converter cells to short-circuit between output terminals, and at least one power converter cell other than the arbitrary power converter cell. A power conversion device for increasing the DC link voltage of the above power converter cell.