JP6796392B2 - 3-level power converter - Google Patents

Description

The present invention relates to a three-level power conversion device configured by using a plurality of power switching elements.

The power conversion device has an AC power generation function that converts DC power to a voltage equivalent to an AC voltage command of an arbitrary amplitude and frequency by operating multiple power switching elements, and DC power that converts in the opposite direction. Has a generation function. In this power conversion device, a device capable of outputting three positive / negative voltage and zero voltage to the AC terminal side is called a three-level power conversion device. The three-level power converter includes, for example, a circuit configuration having four types of switching operation categories. In this 3-level power conversion device, by giving a command signal of a switching pattern to each gate driver in response to an AC voltage command, each power switching element operates on and off, and is equivalent to an AC voltage command at the AC output end. Output voltage. The three-level power converter can also convert an AC voltage of any amplitude and frequency into a DC voltage.

Generally, in order to increase the output capacity in a three-level power conversion device using a power switching element, a power conversion cell (power switching element set) in which a plurality of power conversion main circuits are integrated in a box-shaped housing. There is a method of connecting a plurality of bodies) in parallel. This power conversion cell includes the above-mentioned four types of switching operation categories.

With the increase in capacity of AC induction motors in recent years, there is a demand for larger capacity and smaller size of 3-level power converters. As a solution to the abstract of Patent Document 1, "In a three-level power conversion device, power is supplied so that the longitudinal direction of the power conversion modules 1 to 4 including the switching element and the recirculation diode is parallel to the bottom surface of the device housing. Arranged in the conversion module assembly 20. Power conversion modules 1 to 4 are sequentially arranged side by side in a direction parallel to the device housing within a specified length range, and the power conversion module 1 exceeding the specified length is arranged. ~ 4 are arranged in different stages. "

Japanese Unexamined Patent Publication No. 2014-116995

In this power conversion device, the conventional power conversion cell is configured by arranging parts in a plane so as to include one phase of the three-level power conversion circuit. In such a configuration, if each power switching element is configured to have two or more series for the purpose of increasing the applied voltage, the circuit scale becomes large and the power conversion device may become large.
Similarly, if each power switching element is arranged in parallel for the purpose of increasing the power capacity of the device, the degree of freedom in design is reduced due to mounting restrictions, and as a result, the power conversion device may become large. there were.

Further, in order to restore the power conversion device when an accident such as conduction damage occurs in the power switching element, it is necessary to make the characteristics of the power switching element uniform between parallels. Therefore, not only the power conversion cell including the damaged power conversion switching element but also other power conversion cells having a parallel configuration with the power conversion cell are within the exchange range. Therefore, since the replacement range is wider than the failure range, the recovery time and recovery cost may increase.
In addition, if the power switching element in the power conversion cell causes a failure such as a short circuit during the operation of the power conversion device, the influence spreads to other power switching elements on the short circuit path in a chain reaction. There is a risk of conduction damage. Therefore, it is desired to prevent secondary damage in the event of an accident.
Therefore, it is an object of the present invention to reduce the size of the power conversion device and to reduce the secondary damage in the event of an accident.

In order to solve the above-mentioned problems, the three-level power converter of the present invention is used.
The DC voltage applied to the positive side DC terminal and the negative side DC terminal is connected in parallel between the positive side DC terminal and the negative side DC terminal and the U phase terminal, and the DC voltage of the U phase of arbitrary frequency and amplitude is applied. A plurality of power conversion main circuits that convert to AC voltage are connected in parallel between the positive side DC terminal and the negative side DC terminal and the V phase terminal, and become the positive side DC terminal and the negative side DC terminal. Multiple power conversion main circuits that convert the applied DC voltage into V-phase AC voltage of arbitrary frequency and amplitude are connected in parallel between the positive-side DC terminal and the negative-side DC terminal and the W-phase terminal. A plurality of power conversion main circuits that convert the DC voltage applied to the positive side DC terminal and the negative side DC terminal into a W-phase AC voltage having an arbitrary frequency and amplitude are provided. In this three-level power conversion device, the plurality of power conversion main circuits of the U phase, the V phase, and the W phase are arranged in a plurality of configurations in which two or more power switching elements are connected in series. The first to fourth switching element structures, the first diode element connected to the other end of one of the configurations of the first switching element structure from the neutral point of the DC voltage, and the first from the neutral point. The configuration includes a diode element structure in which a plurality of second diode elements connected to the other end of one of the configurations of the four switching element structures are arranged. One end of each configuration of the first switching element structure is connected to the positive side DC terminal, and each configuration of the second switching element structure is one of the configurations of the first switching element structure and the U. Each configuration of the fourth switching element structure is connected to any of the AC terminals of the phase, the V phase, and the W phase, and one end of each configuration is connected to the negative side DC terminal, and the third switching. Each configuration of the element structure is connected between one of the configurations of the fourth switching element structure and any of the AC terminals of the U phase, the V phase, and the W phase, and the first configuration is described. Each configuration of the fourth switching element structure stops the operation of the other power switching elements connected in series when an overvoltage is applied to any of the power switching elements connected in series.
Other means will be described in the form for carrying out the invention.

According to the present invention, it is possible to provide a power conversion device capable of reducing the size of the power conversion device and reducing secondary damage in the event of an accident.

It is a block diagram of the 3 level power conversion apparatus in this embodiment. It is a circuit diagram which shows the 3 level power conversion circuit in this embodiment. It is a circuit diagram which shows the detail of the IGBT cell. It is a figure which shows that the failure occurred in the 3 level power conversion circuit in this embodiment. It is a figure which shows that it stopped after the failure in the 3 level power conversion circuit in this embodiment. It is a front view of a three-level power conversion circuit. It is a circuit diagram which shows 3 level power conversion circuit for one phase. It is a front view of the power conversion cell. It is a side view of the power conversion cell. It is a perspective view of the power conversion cell. It is a front view which shows the clamp diode cell. It is a side view which shows the clamp diode cell. It is a perspective view which shows the clamp diode cell. It is a block diagram of the 3 level power conversion apparatus of the comparative example. It is a circuit diagram which shows the 3 level power conversion circuit of the comparative example. It is a circuit diagram which shows the detail of the IGBT element and the gate driver. It is a figure which shows that the failure occurred in the 3 level power conversion circuit of the comparative example. It is a figure which shows that each element was conduction damaged by the failure in the 3 level power conversion circuit of the comparative example.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the respective drawings. The common components in each figure are designated by the same reference numerals, and duplicate description will be omitted.
The three-level power conversion device of the comparative example and the present embodiment is an inverter that converts a DC voltage into an AC voltage having an arbitrary frequency and amplitude. This three-level power converter is applied to drive control of an AC induction motor used in, for example, a steel rolling plant.

<< 3-level power converter in comparative example >>
FIG. 14 is a configuration diagram of the three-level power conversion device 9 of the comparative example.
The three-level power converter 9 is composed of three phases, a U-phase circuit 91u, a V-phase circuit 91v, and a W-phase circuit 91w. The configurations of the V-phase circuit 91v and the W-phase circuit 91w are the same as those of the U-phase circuit 91u.
The U-phase circuit 91u is configured by connecting power conversion main circuits 92a to 92c in parallel. These power conversion main circuits 92a to 92c are positive DC power supply bus (hereinafter referred to as "P bus"), neutral point bus (hereinafter referred to as "C bus"), and negative DC power bus (hereinafter, "C bus"), respectively. It is connected to the "N bus") to supply a DC voltage, and outputs a U-phase AC voltage to the node UACO. The circuit configuration of the power conversion main circuits 92b and 92c is the same as that of the power conversion main circuit 92a.

The V-phase circuit 91v is configured by connecting power conversion main circuits 92d to 92f in parallel. These power conversion main circuits 92d to 92f are connected to the P bus, C bus, and N bus, respectively, to supply a DC voltage, and output a V-phase AC voltage to the node VACO. The circuit configuration of the power conversion main circuits 92e and 92f is the same as that of the power conversion main circuit 92d.
The W-phase circuit 91w is configured by connecting power conversion main circuits 92g to 92i in parallel. These power conversion main circuits 92g to 92i are connected to the P bus, C bus, and N bus, respectively, to supply a DC voltage, and output a W phase AC voltage to the node WACO. The circuit configuration of the power conversion main circuits 92h and 92i is the same as that of the power conversion main circuit 92g.
Hereinafter, when the power conversion main circuits 92a to 92i are not particularly distinguished, they are simply referred to as the power conversion main circuit 92.

The load L is connected to the nodes UACO, VACO, and WACO, and an AC voltage is applied. This load L is, for example, an AC induction motor or the like.
The U-phase circuit 91u, the V-phase circuit 91v, and the W-phase circuit 91w have the same configuration in all three phases. In each phase of the U-phase circuit 91u, the V-phase circuit 91v, and the W-phase circuit 91w, the output capacitance of the three-level power conversion device 9 can be increased by connecting a plurality of similar power conversion main circuits 92 in parallel. it can.

FIG. 15 is a circuit diagram showing a power conversion main circuit 92 of a comparative example.
The power conversion main circuit 92 is an NPC (Neutral Point Clamped) type power conversion circuit that uses IGBT elements Q11 to Q14 as power switching elements and clamps them to a neutral point by diode elements D3 and D4. The IGBT elements Q11 to Q14 are elements including an insulated gate bipolar transistor (IGBT: hereinafter referred to as "IGBT") and a circulation diode connected between a collector and an emitter. A gate driver 18 is connected to each of the IGBT elements Q11 to Q14, and the gate driver 18 is controlled by the control unit 90. Details of these IGBT elements Q11 to Q14 will be described later with reference to FIG.

In the comparative example, the IGBT element Q11 on the positive side outputs the potential of the P bus to the node ACO via the IGBT element Q12. A DC voltage is applied to the P bus by the DC power supply Ep.
The IGBT element Q12 at the first neutral point and the IGBT element Q13 at the second neutral point output the potential of the C bus to the node ACO when the IGBT elements Q11 and Q12 are off.

The negative side IGBT element Q14 outputs the potential of the N bus to the node ACO via the IGBT element Q13. These IGBT elements Q11 to Q14 are connected in series between the P bus and the N bus. Each gate driver 18 is connected to the control unit 90, and supplies a drive signal to the gates of the respective IGBT elements Q11 to Q14.

Further, the power conversion main circuit 92 includes two diode elements D3 and D4 for clamping. The diode element D3 for the positive side clamp and the diode element D4 for the negative side clamp are 2in1 diode elements. A diode element D3 for a positive side clamp for outputting the potential of the C bus is connected between the connection points of the IGBT elements Q11 and Q12 and the C bus. Further, a diode element D4 for a negative clamp for outputting the potential of the C bus is connected between the connection points of the IGBT elements Q13 and Q14 and the C bus. In the power conversion main circuit 92, each IGBT element Q11 to Q14 performs a switching operation, so that AC power is output from the node ACO, which is an output point, to the load L.

《Switching operation》
When outputting a positive voltage pulse to the node ACO, the control unit 90 turns on the IGBT elements Q11 and Q12 and turns off the IGBT elements Q13 and Q14. As a result, the potential of the P bus is output to the node ACO.
Further, when the zero voltage is output to the node ACO, the control unit 90 turns on the IGBT elements Q12 and Q13 and turns off the IGBT elements Q11 and Q14. As a result, the potential of the C bus is output to the node ACO.

When outputting a negative voltage pulse to the node ACO, the control unit 90 turns on the IGBT elements Q13 and Q14 and turns off the IGBT elements Q11 and Q12. As a result, the potential of the N bus is output to the node ACO.
Since the control unit 90 of the power conversion main circuit 92 outputs a PWM (Pulse Width Modulation) pulse composed of a positive pulse and a negative pulse centered on the zero point as described above, it is more sine than the two-level power conversion circuit. An AC voltage close to a wave can be output to the node ACO.

FIG. 16 is a circuit diagram showing details of the IGBT element Q11, the gate driver 18, and the like.
A gate driver 18, an overvoltage detection circuit 19, and an overvoltage suppression circuit 20 are connected to the IGBT element Q11 of the comparative example.
The overvoltage suppression circuit 20 includes a Zener diode (not shown) connected in parallel between the collector and the gate of the IGBT element Q11. When an overvoltage is applied between the collector and the gate, the overvoltage suppression circuit 20 causes a current to flow through the Zener diode and supplies a charging current to the gate of the IGBT element Q11. As a result, the impedance of the IGBT element Q11 is lowered, and the IGBT element Q11 is protected from overvoltage.
The overvoltage detection circuit 19 and the gate driver 18 are connected between the gate and the emitter. The gate driver 18 sends a command signal to the gate of the IGBT element Q11. The overvoltage detection circuit 19 determines that an overvoltage has occurred by recognizing that the output signal of the overvoltage suppression circuit 20 and the command signal flowing from the gate driver 18 to the IGBT element Q11 do not match. As a result, the control unit 90 (see FIG. 15) can stop the operation and prevent the continuity of the element from being damaged.

<< Problems of comparative examples >>
In the power conversion main circuit 92 of the comparative example, when any one of the IGBT elements Q11 to Q14 is conduction-damaged, secondary element damage may occur. This will be described with reference to FIGS. 17 and 18.
FIG. 17 is a diagram showing that a failure has occurred in the power conversion main circuit 92 of the comparative example.
The current flowing through the power conversion main circuit 92 when the IGBT elements Q11 and Q12 are turned on and the IGBT elements Q13 and Q14 are turned off is shown as the route 73. The current flows from the P bus to the load L via the IGBT elements Q11 and Q12 and the node ACO. At this time, if the IGBT element Q13 is erroneously turned on or the conduction is damaged, the other elements are also conduction-damaged as shown in FIG.

FIG. 18 is a diagram showing that each element is conductively damaged due to a failure.
The current flowing through the power conversion main circuit 92 at this time is shown as a route 74. The current flows from the P bus to the C bus via the IGBT elements Q11, Q12, Q13 and the diode element D4. Due to such a DC short circuit, the IGBT elements Q11 and Q12 and the diode element D4 are damaged.
The voltage of four elements of the IGBT elements Q11 to Q14 is applied to the IGBT elements Q11 connected in series to raise the voltage, but the overvoltage detection circuit 19 (see FIG. 16) detects the failure of the nearby IGBT element and operates. Further damage can be stopped by stopping. However, considering that the IGBT element Q13 is damaged by the overvoltage, it is necessary to replace the IGBT elements Q11 to Q14 with the diode element D4 after the operation is stopped. That is, all the configurations for one phase must be replaced.

<< Example of power conversion circuit configuration of this embodiment >>
The three-level power conversion device 1 shown in FIG. 1 is a U-phase circuit 11u and a V-phase circuit using three power conversion main circuits 12 (see FIG. 2) that convert a DC voltage into an AC voltage having an arbitrary frequency and amplitude. It has three phases of 11v and W-phase circuit 11w. The configuration of the V-phase circuit 11v and the W-phase circuit 11w is the same as the configuration of the U-phase circuit 11u.

The U-phase circuit 11u is configured by connecting power conversion main circuits 12a to 12c in parallel. These power conversion main circuits 12a to 12c are connected to the P bus, C bus, and N bus, respectively, to supply a DC voltage, and output a U-phase AC voltage to the node UACO. The circuit configuration of the power conversion main circuits 12b and 12c is the same as that of the power conversion main circuit 12a. Further, the power conversion main circuits 12a to 12c share the IGBT cells 14 to 17 in which the IGBT elements of the same operation unit are arranged and the clamp diode cells 13 in which the diodes are arranged. In the power conversion main circuits 12a to 12c, these IGBT cells 14 to 17 and the clamp diode cells 13 are parallelized in a structure composed of mountings regardless of top, bottom, left, and right. The IGBT elements and diodes are the same, respectively. Since the cells are formed in operation units, they can be easily exchanged in the same operation unit.

The IGBT cell 14 of FIG. 1 has “QP” indicating an operation unit, and operates in the same manner as the IGBT element Q11 (see FIG. 15) of the comparative example. In the IGBT cell 15, "QPC" indicating an operation unit is described, and the IGBT cell 15 operates in the same manner as the IGBT element Q12 (see FIG. 15) of the comparative example. The IGBT cell 16 is described with "QNC" indicating an operation unit, and operates in the same manner as the IGBT element Q13 (see FIG. 15) of the comparative example. The IGBT cell 17 has a “QN” indicating an operation unit, and operates in the same manner as the IGBT element Q14 (see FIG. 15) of the comparative example. In the clamp diode cell 13, "D" indicating an operating unit is described.

The V-phase circuit 11v is configured by connecting power conversion main circuits 12d to 12f in parallel. These power conversion main circuits 12d to 12f are connected to the P bus, C bus, and N bus, respectively, to supply a DC voltage, and output a V-phase AC voltage to the node VACO. The configuration of the power conversion main circuits 12e and 12f is the same as the configuration of the power conversion main circuit 12d. Further, the power conversion main circuits 12d to 12f share the IGBT cells 14 to 17 in which the IGBT elements of the same operation unit are arranged and the clamp diode cells 13 in which the diodes of the same operation unit are arranged. As a result, the IGBT element and the diode can be replaced in the same operation unit.

The W-phase circuit 11w is configured by connecting power conversion main circuits 12g to 12i in parallel. These power conversion main circuits 12g to 12i are connected to the P bus, C bus, and N bus, respectively, to supply a DC voltage, and output a W phase AC voltage to the node WACO. The circuit configuration of the power conversion main circuits 12h and 12i is the same as that of the power conversion main circuit 12g. Further, the power conversion main circuits 12g to 12i share the IGBT cells 14 to 17 in which the IGBT elements of the same operation unit are arranged and the clamp diode cells 13 in which the diodes of the same operation unit are arranged. As a result, the IGBT element and the diode can be replaced in the same operation unit.
Hereinafter, when the power conversion main circuits 12a to 12i are not particularly distinguished, they are simply referred to as the power conversion main circuit 12.

In the U-phase circuit 11u, the V-phase circuit 11v, and the W-phase circuit 11w, three elements are arranged in parallel in each cell to form three power conversion main circuits 12. Therefore, the output of the AC power of the three-level power converter 1 is the combined output of the three circuits of the power conversion main circuit 12.

FIG. 2 is a circuit diagram showing the power conversion main circuit 12 in the present embodiment.
The power conversion main circuit 12 of the present embodiment differs from the power conversion main circuit 92 of the comparative example (see FIG. 15) in that two IGBT elements that perform the same switching operation are connected in series to form a power conversion cell. It is a composition. As a result, the rated voltage of the power conversion cell can be shared by the two IGBT elements, the input DC voltage can be increased about twice, and the output capacity can be increased.

The power conversion main circuit 12 is an NPC type power conversion circuit that uses IGBT cells 14 to 17 as power conversion cells and clamps them to a neutral point by a clamp diode cell 13. The IGBT cell 14 connects two IGBT elements Q1 and Q2 that perform the same switching operation in series. The IGBT cell 15 connects the IGBT elements Q3 and Q4 that perform the same switching operation in series. The IGBT cell 16 connects the IGBT elements Q5 and Q6 that perform the same switching operation in series. The IGBT cell 17 connects the IGBT elements Q7 and Q8 that perform the same switching operation in series. The IGBT cells 14 to 17 are switching element structures in which two IGBT elements connected in series are arranged in three rows. Further, the clamp diode cell 13 is a diode element structure in which diode elements D1 and D2 are arranged in three rows. As a result, as shown in FIG. 1, three power conversion main circuits 12 can be parallelized. The IGBT elements Q1 to Q8 are elements including an insulated gate bipolar transistor and a recirculation diode connected between a collector and an emitter.

FIG. 3 is a circuit diagram showing details of the IGBT cell.
The gate driver 18, the overvoltage detection circuit 19, and the overvoltage suppression circuit 20 are connected to the IGBT elements Q1 and Q2 as in the comparative example shown in FIG.
When an overvoltage is applied between the collector gates of the IGBT elements Q1 and Q2, the overvoltage suppression circuit 20 supplies a charging current to the gate of the IGBT element. As a result, the impedance of the IGBT elements Q1 and Q2 is lowered, and the IGBT elements Q1 and Q2 are protected from overvoltage.
The overvoltage detection circuit 19 and the gate driver 18 are connected between the gate and the emitter of the IGBT elements Q1 and Q2. The gate driver 18 sends a command signal to the gates of the IGBT elements Q1 and Q2. The overvoltage detection circuit 19 recognizes that the output signal of the overvoltage suppression circuit 20 and the command signal flowing from the gate driver 18 to the IGBT elements Q1 and Q2 do not match, and thus determines that an overvoltage is generated in each IGBT element. To do.

Thereby, the IGBT cell 14 can detect the application of the overvoltage of the IGBT elements Q1 and Q2. When an overvoltage is applied to one of the IGBT elements Q1 and Q2, the control unit 10 of the power conversion main circuit 12 stops the operation of the other IGBT element to reduce secondary damage in the event of an accident.
Similarly, the IGBT cell 15 can detect the application of an overvoltage to the IGBT elements Q3 and Q4. When an overvoltage is applied to one of the IGBT elements Q3 and Q4, the power conversion main circuit 12 stops the operation of the other IGBT element to reduce secondary damage in the event of an accident.

The IGBT cell 16 can detect the application of an overvoltage to the IGBT elements Q5 and Q6. When an overvoltage is applied to one of the IGBT elements Q5 and Q6, the power conversion main circuit 12 stops the operation of the other IGBT element to reduce secondary damage in the event of an accident.
The IGBT cell 17 can detect the application of an overvoltage to the IGBT elements Q7 and Q8. When an overvoltage is applied to one of the IGBT elements Q7 and Q8, the power conversion main circuit 12 stops the operation of the other IGBT element to reduce secondary damage in the event of an accident.

In the present embodiment, the positive side IGBT cell 14 outputs the potential of the P bus to the node ACO. A DC voltage is applied to the P bus by the DC power supply Ep.
The first neutral point IGBT cell 15 and the second neutral point IGBT cell 16 output the potential of the C bus to the node ACO.

The negative side IGBT cell 17 outputs the potential of the N bus to the node ACO. These IGBT cells 14 to 17 are connected in series between the P bus and the N bus. Each gate driver 18 is connected to the control unit 10 and supplies a drive signal to the gates of the IGBT elements Q1 to Q8 included in the IGBT cells 14 to 17.

Further, the power conversion main circuit 12 includes two diode elements D1 and D2 for clamping. The diode element D1 for the positive side clamp and the diode element D2 for the negative side clamp are 2in1 diode elements. A diode element D1 for a positive side clamp for outputting the potential of the C bus is connected between the connection points of the IGBT cells 14 and 15 and the C bus. Further, a diode element D2 for a negative side clamp for outputting the potential of the C bus is connected between the connection points of the IGBT cells 16 and 17 and the C bus. In the power conversion main circuit 12, the IGBT elements Q1 to Q8 included in the IGBT cells 14 to 17 perform a switching operation, so that AC power is output from the node ACO, which is an output point, to the load L.

《Switching operation》
When outputting a positive voltage pulse to the node ACO, the control unit 10 turns on the IGBT elements Q1 to Q4 included in the IGBT cells 14 and 15, and turns off the IGBT elements Q5 to Q8 included in the IGBT cells 16 and 17. As a result, the potential of the P bus is output to the node ACO.
Further, when outputting a zero voltage to the node ACO, the control unit 10 turns on the IGBT elements Q3 to Q6 included in the IGBT cells 15 and 16, and the IGBT elements Q1 and Q2 included in the IGBT cell 14 and the IGBT element included in the IGBT cell 17. Turn off Q7 and Q8. As a result, the potential of the C bus is output to the node ACO.

When outputting a negative voltage pulse to the node ACO, the control unit 10 turns on the IGBT elements Q5 to Q8 included in the IGBT cells 16 and 17, and turns off the IGBT elements Q1 to Q4 included in the IGBT cells 14 and 15. As a result, the potential of the N bus is output to the node ACO.
The control unit 10 of the power conversion main circuit 12 is closer to a sine wave than a two-level power conversion circuit by a PWM (Pulse Width Modulation) pulse composed of a positive pulse and a negative pulse centered on the zero point as described above. The AC voltage can be output to the node ACO.

<< Effect of connecting IGBT elements in series >>
In the power conversion main circuit 12 of the present embodiment, two IGBT elements each performing the same switching operation are connected in series to the IGBT cells 14 to 17. This makes it possible to double the input DC voltage by sharing the rated voltage of the IGBT cells 14 to 17 among the two IGBT elements. Further, there is also an effect of reducing secondary element damage when any of the IGBT elements is conduction-damaged. This will be described with reference to FIGS. 4 and 5.

FIG. 4 is a diagram showing that a failure has occurred in the power conversion main circuit 12 in the present embodiment.
The current flowing through the power conversion main circuit 12 when the IGBT elements Q1 to Q4 are turned on and the IGBT elements Q5 to Q8 are turned off is shown as a route 71. The current flows from the P bus to the load L via the IGBT elements Q1 to Q4 and the node ACO. At this time, consider the case where the IGBT element Q5 is erroneously turned on or the conduction is damaged.

FIG. 5 is a diagram showing that the product has stopped after a failure.
As shown by route 72, the voltage applied to the P bus is also applied to the collector terminal of the IGBT element Q6. The voltage corresponding to the five elements of the IGBT elements Q1 to Q5 is applied to the IGBT element Q6, and the voltage rises. However, the control unit 10 detects the failure of the nearby IGBT element by the overvoltage suppression circuit 20 and the overvoltage detection circuit 19, and stops the operation of the power conversion main circuit 12. As a result, the power conversion main circuit 12 can prevent further damage.

In the present embodiment, since the IGBT element Q6 is off, no DC short-circuit current is generated. The replacement points due to this failure are only the IGBT element Q5 and the IGBT element Q6 damaged by the overvoltage. Further, since the three-level power conversion device 1 of the present embodiment is cellized for each switching operation unit, only the IGBT cell 16 is replaced, and the number of parts to be replaced is smaller than that of the comparative example. Therefore, as compared with the power conversion main circuit 92 of the comparative example, the power conversion main circuit 12 of the present embodiment can reduce the secondary damage due to the damage of the IGBT element, and can suppress the recovery time and the recovery cost.
Note that each IGBT cell 14 to 17 may be connected in series with three or more IGBT elements that perform the same switching operation, and is not limited.

<< Structural layout example of the 3-level power conversion device of this embodiment >>
FIG. 6 is an arrangement example of the unit structure of the IGBT cells 14 to 17 and the clamp diode cells 13 constituting the power conversion main circuit 12 in the present embodiment.
In the unit structure of FIG. 6, the IGBT cells 14 to 17 and the clamp diode cells 13 are arranged in three rows in the depth direction of the figure in a structure composed of mountings of the IGBT cells 14 to 17 and the clamp diode cells 13 in any direction. The parallelized power conversion main circuits 12a to 12c in the U-phase circuit 11u can be easily realized.
In the unit structure example of FIG. 6, the IGBT cells 14 to 17 all have the same structure. As a result, the number of types of replacement parts prepared in case of failure of the IGBT cell can be one type, and the types of replacement parts and the number of stocks can be reduced.

The IGBT cell 14 arranged in the upper left of FIG. 6 has an IGBT element Q1 having a collector terminal connected to the bus 21 and an emitter terminal connected to the bus 22, and a collector terminal connected to the bus 22 and an emitter terminal to the bus 23. Is included in the IGBT element Q2 to which the is connected.
In the IGBT cell 14, the collector terminal of the IGBT element Q1 is connected to the P bus via the bus 21, and the emitter terminal of the IGBT element Q2 is connected to the IGBT cell 15 via the bus 23 and 24.

The IGBT cell 15 arranged in the upper right of FIG. 6 has an IGBT element Q3 having a collector terminal connected to the bus 25 and an emitter terminal connected to the bus 26, and a collector terminal connected to the bus 26 and an emitter terminal to the bus 27. Is included in the IGBT element Q4 to which the is connected.
In the IGBT cell 15, the collector terminal of the IGBT element Q3 is connected to the emitter terminal of the IGBT element Q2 via the bus 25, 24, 23, and is connected to the cathode terminal of the diode element D1 via the bus 25, 32. Further, the emitter terminal of the IGBT element Q4 is connected to the bus 28 via the bus 27. The bus 28 is a node ACO that outputs the power output from the power conversion main circuit 12.

The clamp diode cell 13 arranged at the center on the right side of FIG. 6 includes a diode element D1 in which an anode terminal is connected to the bus 31 and a cathode terminal is connected to the bus 32. The clamp diode cell 13 further includes a diode element D2 in which the cathode terminal is connected to the bus 33 and the anode terminal is connected to the bus 34.
The anode terminal of the diode element D1 is connected to the bus 30 which has the same potential as the C bus via the bus 31. The cathode terminal of the diode element D1 is connected to the connection point between the IGBT cell 14 and the IGBT cell 15 via the bus 32.

The cathode terminal of the diode element D2 is connected to the bus 30 which has the same potential as the C bus via the bus 33. The anode terminal of the diode element D1 is connected to the connection point between the IGBT cell 16 and the IGBT cell 17 via the bus 44.
These diode elements D1 and D2, and the bus 31, 32 and bus 33, 34 connected to them are arranged symmetrically in plane.

The IGBT cell 17 arranged at the lower left of FIG. 6 has an IGBT element Q8 in which an emitter terminal is connected to the bus 41 and a collector terminal is connected to the bus 42, and an emitter terminal is connected to the bus 42 and a collector terminal is connected to the bus 43. Is included in the IGBT element Q7 to which the is connected.
In the IGBT cell 17, the emitter terminal of the IGBT element Q8 is connected to the N bus via the bus 41, and the collector terminal of the IGBT element Q7 is connected to the IGBT cell 16 via the bus 43 and 44.

The IGBT cell 16 arranged at the lower right of FIG. 6 has an IGBT element Q6 having an emitter terminal connected to the bus 45 and a collector terminal connected to the bus 46, and an emitter terminal connected to the bus 46 and a collector to the bus 47. It is configured to include an IGBT element Q5 to which terminals are connected.
In the IGBT cell 16, the emitter terminal of the IGBT element Q6 is connected to the collector terminal of the IGBT element Q7 via the bus 45, 44, 43, and is connected to the anode terminal of the diode element D2 via the bus 45, 34. Further, the collector terminal of the IGBT element Q5 is connected to the bus 28 which is the node ACO via the bus 47.

As shown in FIG. 6, the IGBT cell 14 and the IGBT cell 17 are arranged symmetrically with the bus 30 interposed therebetween. The IGBT cell 14 is arranged upside down with respect to the IGBT cell 17.
Further, the IGBT cell 15 and the IGBT cell 16 are arranged symmetrically with the clamp diode cell 13 interposed therebetween. The IGBT cell 14 is arranged upside down with respect to the IGBT cell 17.
Further, the diode element D1 and the diode element D1 of the clamp diode cell 13 are arranged plane-symmetrically. As a result, the width of the 3-level power converter 1 can be suppressed.

Further, in the IGBT cells 14 to 17 and the clamp diode cell 13, the IGBT elements and the diode elements can be arranged in the depth direction of the three-level power conversion device 1 to parallelize a plurality of power conversion main circuits 12. .. Therefore, by increasing the number of cell wiring buses to the same number as the number of parallel wires, it is possible to increase the output capacity of the three-level power conversion device 1 without increasing the dimensions in the width direction and the vertical direction of FIG.

Further, in the three-level power conversion device 1, the bus 32,34 is arranged so as to sandwich the bus 31, 30, 33, and the bus 25, 26, 45, 46 is arranged so as to sandwich the bus 32, 34. There is. Further, in the three-level power conversion device 1, the bus 21, 22, 23, 24 and the bus 41, 42, 43, 44 are arranged so as to sandwich the bus 30. The three-level power converter 1 arranges the IGBT cells 14 to 17 in this way and brings the bus close to each other to reduce the distance between the bus and reduce the mutual inductance, so that the IGBT element bounces during the switching operation. The influence of the uplink voltage can be reduced. Here, it is desirable that each bus is arranged at a distance where a short-circuit accident due to contact does not occur even when the tolerance of component dimensions is taken into consideration, and the mutual inductance between the bus is reduced. The distance between the two bushes is, for example, 0.1 to 10.0 mm, more preferably 1.0 to 5.0 mm.

The width dimension of the three-level power conversion device 1 of the present embodiment can be suppressed to about 1,400 mm. The conventional product having the same capacity was about 3,000 mm when compared with the three parallel configuration which is the maximum number of parallels in this embodiment.

Since the structure of the present embodiment is complicated, a circuit diagram in which the IGBT cells 14 to 17 and the clamp diode cells 13 are arranged in the same manner as in FIG. 6 is shown in FIG. 7 in order to promote understanding.

FIG. 7 shows the circuit diagram of the power conversion main circuit 12 shown in FIG. 2 in the same arrangement as in FIG.
On the left side of FIG. 7, P bus, C bus, and N bus are arranged. The IGBT cells 14 and 15 are connected in series between the P bus and the node ACO. The IGBT cells 16 and 17 are connected in series between the node ACO and the N bus. The clamp diode cell 13 includes diode elements D1 and D2. The diode element D1 is connected from the C bus toward the connection nodes of the IGBT cells 14 and 15. The diode element D2 is connected from the connection nodes of the IGBT cells 16 and 17 toward the C bus.
The IGBT cell 14 is a first switching element structure in which one end is connected to a DC terminal on the positive electrode side of the P bus. The IGBT cell 15 is a second switching element structure connected between the IGBT cell 14 and the node ACO (AC terminal).
Further, the IGBT cell 17 is a fourth switching element structure in which one end is connected to the negative electrode side DC terminal of the N bus. The IGBT cell 16 is a third switching element structure connected between the IGBT cell 17 and the node ACO (AC terminal).
The diode element D1 is a first diode element connected from the C bus (neutral point) to the other end of the IGBT cell 14. The diode element D2 is connected from the C bus (neutral point) to the other end of the IGBT cell 17.

<< Structural example of power conversion cell >>
8 to 10 show structural examples of the IGBT cells 14 to 17 constituting the power conversion main circuit 12 of the present embodiment. Since all the IGBT cells 14 to 17 have the same configuration, the IGBT cells 14 will be described here, and the description of the IGBT cells 15 to 17 will be omitted.
FIG. 8 is a front view of the IGBT cell 14. In FIG. 8, the IGBT cell 14 turned upside down is viewed from the same direction as in FIG.

The IGBT cell 14 is an assembly of electrical components composed of three sets of IGBT elements Q1, Q2 and bushes 21, 22, and 23 arranged on heat sinks 50a and 50b. It should be noted that here, only one set out of the three sets of sequences is shown, and the other two sets are hidden behind. The IGBT cell 14 is further composed of a metal plate 53 for fixing the heat sinks 50a and 50b, a support 51 for supporting the metal plate 53 and the heat sinks 50a and 50b, and a flat metal plate 52.
The metal plate 53 fixes the heat sinks 50a and 50b and also fixes the support 51. The support 51 is formed so as to have a U-shaped cross section, and the upper side thereof is fixed to the metal plate 53. The metal plate 52 has a flat plate shape, and is fixed in the support 51 in the direction opposite to the metal plate 53 and the heat sinks 50a and 50b.

FIG. 9 is a side view of the IGBT cell 14. In FIG. 9, the IGBT cell 14 is viewed from the left side surface in FIG. 8.
In FIG. 9, in the IGBT cell 14, three arrangements of the IGBT element Q2 and the bus 23, a metal plate 53, a support 51, and a metal plate 52 are shown. The IGBT element Q1 and the bus 22, 21 are hidden behind the IGBT element Q2 and the bus 23. The heat sinks 50a and 50b are hidden behind the metal plate 53.

FIG. 10 is a perspective view of the power conversion cell. In FIG. 10, the IGBT cell 14 is viewed from diagonally above the right in FIG. 8.
In FIG. 10, it is shown that the IGBT cell 14 is configured by three sets of IGBT elements Q1 and Q2 and bus 21, 22, 23 arranged on heat sinks 50a and 50b. These three sets of bushes 21, 22, and 23 are arranged so as to form the same plane on the upper side of the drawing. These three rows of bus 21, 22, 23 are arranged in close proximity to the three rows of planar bus 30 (see FIG. 6).
The bus 21 connects the P bus and the collector terminal of the IGBT element Q1 at the same potential. The bus 22 connects the emitter terminal of the IGBT element Q1 and the collector terminal of the IGBT element Q2. The bus 23 connects the emitter terminal of the IGBT element Q2 and the collector terminal of the IGBT element Q3 of the adjacent IGBT cell 15.

The three rows of IGBT elements Q1 are fixed to the heat sink 50b, and the three rows of IGBT elements Q2 are fixed to the heat sink 50a. These heat sinks 50a and 50b are fixed on the metal plate 53 and supported by the support 51. The support 51 is fixed on the flat metal plate 52.

<< Structural example of clamp diode cell >>
11 to 13 show structural examples of the clamp diode cell 13 constituting the power conversion main circuit 12 of the present embodiment.
FIG. 11 is a front view showing the clamp diode cell 13. In FIG. 11, the clamp diode cell 13 is viewed upside down from the same direction as in FIG.

The clamp diode cell 13 is an electrical component composed of three sets of diode elements D1 and bushes 31 and 32 arranged on a heat sink 60p, and three sets of diode elements D2 and bushes 33 and 34 arranged on a heat sink 60n. It is an aggregate. It should be noted that here, only one set out of the three sets of sequences is shown, and the other two sets are hidden behind. The heat sink 60p is fixed to one surface of the support plate 61, and the heat sink 60n is fixed to the other surface of the support plate 61.
These diode elements D1 are P-side (2in1) clamp diodes. The diode element D2 is an N side (2in1) clamp diode.

As shown in FIG. 6, the bus 32 connects the emitter terminal of the IGBT element Q2, the collector terminal of the IGBT element Q3, and the cathode terminal of the diode element D1. The bus 31 connects the anode terminal of the diode element D1 and the bus 30 which is a neutral point.
As shown in FIG. 6, the bus 34 connects the collector terminal of the IGBT element Q7, the emitter terminal of the IGBT element Q6, and the anode terminal of the diode element D2. The bus 33 connects the cathode terminal of the diode element D2 and the bus 30 which is a neutral point.

FIG. 12 is a side view showing the clamp diode cell 13. In FIG. 12, the clamp diode cell 13 is viewed from the left side surface in FIG.
In FIG. 12, in the clamp diode cell 13, three sets of diode elements D1 and bushes 31 and 32 are arranged on the heat sink 60p, and three sets of diode elements D2 and bushes 33 and 34 are arranged on the heat sink 60n. It is shown.

FIG. 13 is a perspective view showing the clamp diode cell 13. In FIG. 13, the clamp diode cell 13 is viewed from diagonally above to the right in FIG.
In FIG. 13, the clamp diode cell 13 shows that three sets of diode elements D1 and bushes 31 and 32 are arranged on the heat sink 60p. The heat sink 60p is fixed to one surface of the support plate 61. Further, three sets of bus 33 and one set of bus 34 on the front side are shown on the lower side of the support plate 61, but three sets of diode elements D2, two sets of bus 34 on the back side, and a heat sink 60n are shown. Is hidden by the support plate 61.

As described above, the present invention is not limited to each of the above-described embodiments, and it goes without saying that other types of modifications and applications can be taken as long as they do not deviate from the gist described in the claims. ..

For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to the one including all the described configurations. It is also possible to add a part of the configuration of one embodiment to the configuration of another embodiment. Further, it is possible to add / delete / replace a part of the configuration of each embodiment with another configuration. In addition, the control lines and information lines indicate what is considered necessary for explanation, and not all control lines and information lines are shown in the product. In practice, it can be considered that almost all configurations are interconnected.

Examples of modifications of the present invention include the following (a) to (e).
(A) The power conversion main circuit of the present invention is not limited to the NPC system, and may be configured by the A-NPC (Advanced-NPC) system.
(B) The conversion operation of the power conversion main circuit is not limited to the inverter operation, and may be a converter operation.
(C) The power conversion cell is not limited to the series connection of two power switching elements.
(D) The number of parallel power conversion cells is not limited to three columns.
(E) The power switching element used in the power conversion cell is not limited to the IGBT, and may be, for example, a gate turn-off thyristor.

1 3-level power converter 10 Control unit 11u U-phase circuit 11v V-phase circuit 11w W-phase circuit 12, 12a to 12i Power conversion main circuit 13 Clamp diode cell (diode element structure)
14 IGBT cell (first switching element structure)
15 IGBT cell (second switching element structure)
16 IGBT cell (third switching element structure)
17 IGBT cell (4th switching element structure)
18 Gate driver 19 Overvoltage detection circuit 20 Overvoltage suppression circuit 21-28, 30-34 Bus 41-48 Bus 50a, 50b Heat sink 51 Support 52 Metal plate 53 Metal plate 60p, 60n Heat shield 61 Support plate 9 3-level power converter 90 Control unit 91u U-phase circuit 91v V-phase circuit 91w W-phase circuit 92, 92a to 92i Power conversion main circuit

Claims (3)

The DC voltage applied to the positive side DC terminal and the negative side DC terminal is connected in parallel between the positive side DC terminal and the negative side DC terminal and the U phase terminal, and the DC voltage of the U phase of arbitrary frequency and amplitude is applied. Multiple power conversion main circuits that convert to AC voltage,
The DC voltage applied to the positive side DC terminal and the negative side DC terminal connected in parallel between the positive side DC terminal and the negative side DC terminal and the V phase terminal is V of an arbitrary frequency and amplitude. Multiple power conversion main circuits that convert to phase AC voltage,
The DC voltage applied to the positive electrode side DC terminal and the negative electrode side DC terminal connected in parallel between the positive electrode side DC terminal and the negative electrode side DC terminal and the W phase terminal is W of an arbitrary frequency and amplitude. Multiple power conversion main circuits that convert to phase AC voltage,
In a three-level power converter equipped with
The plurality of power conversion main circuits of the U phase, the V phase, and the W phase are
A first to fourth switching element structure in which a plurality of configurations in which two or more power switching elements are connected in series are arranged, and
One of the configuration of the first diode element connected to the other end of one of the configurations of the first switching element structure from the neutral point of the DC voltage and the configuration of the fourth switching element structure from the neutral point. A diode element structure in which a plurality of second diode elements connected to the other end are arranged, and
Consists of including
Each configuration of the first switching element structure has one end connected to the positive electrode side DC terminal.
Each configuration of the second switching element structure is connected between one of the configurations of the first switching element structure and an AC terminal of any one of the U phase, the V phase, and the W phase.
Each configuration of the fourth switching element structure has one end connected to the negative electrode side DC terminal.
Each configuration of the third switching element structure is connected between one of the configurations of the fourth switching element structure and one of the AC terminals of the U phase, the V phase, and the W phase. ,
Each configuration of the first to fourth switching element structures stops the operation of the other power switching elements connected in series when an overvoltage is applied to any of the power switching elements connected in series.
A 3-level power converter characterized by this. The U-phase first switching element structure, the second switching element structure, the third switching element structure, the fourth switching element structure, the V-phase first switching element structure, and the above. The second switching element structure, the third switching element structure, the fourth switching element structure, the W-phase first switching element structure, the second switching element structure, and the third switching element structure. The body and the fourth switching element structure all have the same structure.
The three-level power conversion device according to claim 1. The first to fourth switching element structures are cellized and can be replaced.
The three-level power conversion device according to claim 1.

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