CN117639538A

CN117639538A - Power conversion device

Info

Publication number: CN117639538A
Application number: CN202310731252.0A
Authority: CN
Inventors: 马场俊之; 安冈育雄; 长谷川隆太
Original assignee: Toshiba Corp; Toshiba Infrastructure Systems and Solutions Corp
Current assignee: Toshiba Corp; Toshiba Infrastructure Systems and Solutions Corp
Priority date: 2022-09-01
Filing date: 2023-06-19
Publication date: 2024-03-01
Also published as: JP2024034874A

Abstract

The invention provides a power conversion device with suppressed energy loss. The power conversion device of the embodiment is provided with: first to fourth self-extinguishing elements (T1) - (T4) connected in series between a first DC terminal (P) and a second DC terminal (N); and diodes (D5) - (D6), a fifth self-extinguishing element (T5) and a sixth self-extinguishing element (T6), wherein the diodes are connected in anti-parallel between a connection point of the first self-extinguishing element (T1) and the second self-extinguishing element (T2) and a connection point of the fourth self-extinguishing element (T4) and the third self-extinguishing element (T3), the second self-extinguishing element (T2) and the third self-extinguishing element (T3) are bipolar elements, the third self-extinguishing element (T3) and the fourth self-extinguishing element (T4) are always disconnected during the switching of the first self-extinguishing element (T1) and the second self-extinguishing element (T2), and the first self-extinguishing element (T1) and the second self-extinguishing element (T2) are always disconnected during the switching of the third self-extinguishing element (T3) and the fourth self-extinguishing element (T4).

Description

Power conversion device

Technical Field

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

Background

In a neutral point clamped (NPC: neutral Point Clamped) type power conversion circuit, for example, an output voltage is clamped to a neutral point voltage by a clamp diode, and a plurality of voltage levels can be output. In the NPC power conversion circuit, an active NPC power conversion circuit (hereinafter referred to as an a-NPC power conversion circuit) has been proposed in which a self-extinguishing element type power semiconductor element (active element) is added to a clamp diode. According to the a-NPC power conversion circuit, current concentration can be reduced, and a commutation path can be shortened to reduce switching loss and surge voltage.

Disclosure of Invention

On the other hand, when a bipolar transistor such as a Si-IGBT (insulated gate bipolar transistor) is used as an active element of an a-NPC power conversion circuit, switching loss may occur due to residual carriers after the switching element is turned off in a switching element inside each branch.

The present invention has been made in view of the above circumstances, and an object thereof is to suppress energy loss in a power conversion device.

The power conversion device according to the embodiment includes: first to fourth self-extinguishing elements connected in series between a first direct current terminal and a second direct current terminal, the second direct current terminal being at a different potential from the first direct current terminal; a first diode and a second diode connected in anti-parallel between a connection point of the first self-extinguishing element and the second self-extinguishing element, one end of which is electrically connected to the first direct current terminal, and a connection point of the fourth self-extinguishing element and the third self-extinguishing element, the other end of which is electrically connected to the second direct current terminal; the fifth self-extinguishing component is connected with the first diode in anti-parallel; a sixth self-extinguishing component connected in anti-parallel with the second diode; and a control circuit that controls operations of the first to sixth self-extinguishing devices, wherein a connection point between the fifth self-extinguishing device and the sixth self-extinguishing device is electrically connected to a third dc terminal, the third dc terminal is a potential between the first dc terminal potential and the second dc terminal potential, a connection point between the second self-extinguishing device and the third self-extinguishing device is electrically connected to an ac terminal, the second self-extinguishing device and the third self-extinguishing device are bipolar devices, and the control circuit always turns off the third self-extinguishing device and the fourth self-extinguishing device during switching of the first self-extinguishing device and the second self-extinguishing device, and always turns off the first self-extinguishing device and the second self-extinguishing device during switching of the third self-extinguishing device and the fourth self-extinguishing device.

According to the embodiment of the present invention, energy loss in the power conversion device can be suppressed.

Drawings

Fig. 1 is a diagram schematically showing an example of the configuration of a power conversion device according to a first embodiment.

Fig. 2 is a diagram schematically showing one configuration example of the control circuit shown in fig. 1.

Fig. 3 is a diagram for explaining an example of the operation of the control circuit shown in fig. 2.

Fig. 4 is a timing chart for explaining an example of the operation of the power conversion device according to the first embodiment.

Fig. 5 is a timing chart for explaining an example of the operation of the power conversion device according to the first embodiment.

Fig. 6 is a diagram schematically showing an example of the configuration of a control circuit of the power conversion device according to the second embodiment.

Fig. 7 is a timing chart for explaining an example of the operation of the power conversion device according to the second embodiment.

Fig. 8 is a timing chart for explaining an example of the operation of the power conversion device according to the second embodiment.

Fig. 9 is a diagram for explaining an example of the operation of the power conversion device according to the first embodiment.

Fig. 10 is a diagram for explaining an example of the operation of the power conversion device according to the first embodiment.

Fig. 11 is a diagram for explaining an example of the operation of the power conversion device according to the second embodiment.

Fig. 12 is a diagram for explaining an example of the operation of the power conversion device according to the second embodiment.

Detailed Description

Hereinafter, a power conversion device according to an embodiment will be described in detail with reference to the accompanying drawings.

The power conversion device of the present embodiment includes a power conversion circuit 1 and a control circuit CTR.

The power conversion circuit 1 is an a-NPC three-level inverter circuit, and includes self-extinguishing element type power semiconductor elements (self-extinguishing elements) T1 to T6, diodes D1 to D6, and capacitors C1 and C2. The power conversion circuit 1 further includes a dc terminal P, O, N and an ac terminal a. The dc terminal (first dc terminal) P is a high-potential-side terminal, the dc terminal (second dc terminal) N is a low-potential-side terminal, and the dc terminal (third dc terminal) O is a terminal of a neutral point potential between the potential of the dc terminal P and the potential of the dc terminal N.

The capacitor C1 is connected between the dc terminal P and the dc terminal O. The capacitor C2 is connected between the dc terminal O and the dc terminal N.

The self-extinguishing elements T1 to T4 are connected in series between the dc terminals P and N. That is, one end of the self-extinguishing element (first self-extinguishing element) T1 is electrically connected to the dc terminal P, and the other end is electrically connected to one end of the self-extinguishing element (second self-extinguishing element) T2. The other end of the self-extinguishing element T2 is electrically connected to one end of a self-extinguishing element (third self-extinguishing element) T3, and the other end of the self-extinguishing element T3 is electrically connected to one end of a self-extinguishing element (fourth self-extinguishing element) T4. The other end of the self-extinguishing element T4 is electrically connected to the dc terminal N. The intermediate connection point between the self-extinguishing element T2 and the self-extinguishing element T3 is electrically connected to the ac terminal a.

In the present embodiment, the self-extinguishing elements T1 to T4 are bipolar transistors, for example, si-IGBTs. In the power conversion device of the present embodiment, at least the self-extinguishing devices T2 and T3 may be bipolar devices, and the self-extinguishing devices T1 and T2 are not limited to bipolar devices, and may be unipolar devices such as MOSFETs.

Diodes D1 to D4 are reflux diodes connected in anti-parallel to self-extinguishing elements T1 to T4, respectively.

The self-extinguishing element (fifth self-extinguishing element) T5 is connected between the dc terminal O and a connection point of the self-extinguishing element T1 and the self-extinguishing element T2. In the present embodiment, the self-extinguishing element T5 is a bipolar transistor, for example, a Si-IGBT. The self-extinguishing device T5 is not limited to a bipolar device, and may be a unipolar device such as a MOSFET.

The self-extinguishing element (sixth self-extinguishing element) T6 is connected between the dc terminal O and the connection points of the self-extinguishing element T3 and the self-extinguishing element T4. In the present embodiment, the self-extinguishing element T6 is a bipolar transistor, for example, a Si-IGBT. The self-extinguishing device T6 is not limited to a bipolar device, and may be a unipolar device such as a MOSFET.

The diodes D5 and D6 are clamp diodes, respectively, and are connected in antiparallel with the self-extinguishing elements T5 and T6, respectively. That is, the diode (first diode) D5 is connected between the connection point of the self-extinguishing element T1 and the self-extinguishing element T2 and the dc terminal O with the direction from the dc terminal O toward the connection point of the self-extinguishing element T1 and the self-extinguishing element T2 as the forward direction. The diode (second diode) D6 is connected between the connection point of the self-extinguishing element T3 and the self-extinguishing element T4 and the dc terminal O with the direction from the connection point of the self-extinguishing element T3 and the self-extinguishing element T4 toward the dc terminal O as the forward direction.

The control circuit CTR receives an output command from a higher-level control device, for example, and generates and outputs control signals from the arc extinguishing elements T1 to T6 based on the output command. The control circuit CTR may be configured to include a processor and a program executed by the processor, and to implement various functions by software or a combination of software and hardware.

The control circuit CTR includes a PWM circuit 2 and a gate signal generation circuit 3.

The PWM circuit 2 compares the output command (modulated wave) W1 with triangular waves (carrier waves (japanese: carrier waves)) W2 and W3, and generates the on control command PWM1U, PWM2U, PWM1X, PWM2X. The triangular waves W2 and W3 may be values preset in the PWM circuit 2 or may be externally supplied values.

In the example shown in fig. 3, the output command W1 is, for example, a sine wave having an amplitude V, the minimum value of the triangular wave (first carrier wave) W2 is 0 (or reference potential), the maximum value thereof is V (reference potential+v) or more, the minimum value of the triangular wave (second carrier wave) W3 is-V (reference potential-V) or less, and the maximum value thereof is 0 (reference potential). The period of the triangular waves W2, W3 is 1/10 of the period of the output command W1. Therefore, the waveform of the triangular wave W2 crosses the waveform of the output command W1 in a period (P-O output period) in which the value of the output command W1 is 0 (reference potential) or more, and the waveform of the triangular wave W3 crosses the waveform of the output command W1 in a period (N-O output period) in which the value of the output command W1 is 0 (reference potential) or less.

The PWM circuit 2 generates a conduction control command (first conduction control command) PWM1U and a conduction control command PWM1X by comparing the value of the output command W1 with the value of the triangular wave W2. The on control command PWM1X is a value based on the non-value (japanese: negative value) of the on control command PWM1U, and is switched between 2 values, i.e., 1 (high level) and 0 (low level), based on the result of comparing the value of the output command W1 and the value of the triangular wave W2.

The on control command PWM1U is "1" when the output command W1 is equal to or greater than the triangular wave W2, and is "0" when the output command W1 is smaller than the triangular wave W2. The on control command PWM1X is "1" when the output command W1 is smaller than the triangular wave W2, and is "0" when the output command W1 is equal to or greater than the triangular wave W2. In addition, the dead time DT is given to one (or both) of the on control command PWM1U and the on control command PWM1X, so that the on control command PWM1U and the on control command PWM1X can be prevented from being simultaneously "1".

The PWM circuit 2 generates a conduction control instruction (second conduction control instruction) PWM2U and a conduction control instruction PWM2X by comparing the value of the output instruction W1 with the value of the triangular wave W3. The on control command PWM2X is a value based on the non-value of the on control command PWM2U, and is switched between 2 values of "1 (high level)" and "0 (low level)" based on the result of comparing the value of the output command W1 and the value of the triangular wave W3.

The on control command PWM2U is "1" when the output command W1 is smaller than the triangular wave W3, and is "0" when the output command W1 is equal to or greater than the triangular wave W3. The on control command PWM2X is "1" when the output command W1 is equal to or greater than the triangular wave W3, and is "0" when the output command W1 is smaller than the triangular wave W3. In addition, the dead time DT is given to one (or both) of the on control command PWM2U and the on control command PWM2X, so that the on control command PWM2U and the on control command PWM2X can be prevented from being simultaneously set to "1".

The gate signal generating circuit 3 generates and outputs a gate signal for the self-extinguishing elements T1 to T6 based on the on control command PWM1U, PWM1X, PWM2U, PWM X.

The control commands of the self-extinguishing elements T1, T2 are generated based on the on control command PWM1U, and the control commands of the self-extinguishing elements T3, T4 are generated based on the on control command PWM 2U. Control commands from the arc suppression elements T5, T6 are generated based on the on control command PWM1X, PWM X.

In the present embodiment, as shown in fig. 3, the self-extinguishing elements T3 and T4 are always turned off while the self-extinguishing elements T1 and T2 are being turned on and off. Conversely, the self-extinguishing elements T1, T2 are always turned off while the self-extinguishing elements T3, T4 are switched on and off.

The gate signal generating circuit 3 includes delay circuits 30 to 37 AND logical product circuits (AND) 38 AND 39.

The on control command PWM1U is input to the delay circuit 30. The delay circuit 30 is an on-delay circuit (first on-delay circuit) that delays the on timing of the on-control command PWM1U by the period TD1 and outputs the delayed on timing. The output signal of the delay circuit 30 is a gate signal of the self-extinguishing element T1.

The on control command PWM1U is input to the delay circuit 31. The delay circuit 31 is an off delay circuit (first off delay circuit) that delays the off timing of the on control command PWM1U by a period TD1 and outputs the delayed off timing. The output signal of the delay circuit 31 is a gate signal of the self-extinguishing element T2.

The on control command PWM2U is input to the delay circuit 32. The delay circuit 32 is an off delay circuit (second off delay circuit) that delays the off timing of the on control command PWM2U by a period TD1 and outputs the delayed off timing. The output signal of the delay circuit 32 is a gate signal of the self-extinguishing element T3.

The on control command PWM2U is input to the delay circuit 33. The delay circuit 33 is an on delay circuit (second on delay circuit) that delays the on timing of the on control command PWM2U by the period TD1 and outputs the delayed on timing. The output signal of the delay circuit 33 is a gate signal of the self-extinguishing element T4.

The on control command PWM1X is input to the delay circuit 34. The delay circuit 34 is an on-delay circuit (third on-delay circuit) that delays the on timing of the on-control command PWM1X by the period TD2 and outputs the delayed on timing.

The on control command PWM2X is input to the delay circuit 35. The delay circuit 35 is an off delay circuit (third off delay circuit) that delays the off timing of the on control command PWM2X by the period TD2 and outputs the delayed off timing.

The on control command PWM1X is input to the delay circuit 36. The delay circuit 36 is an off delay circuit (fourth off delay circuit) that delays the off timing of the on control command PWM1X by the period TD2 and outputs the delayed off timing.

The on control command PWM2X is input to the delay circuit 37. The delay circuit 37 is an on-delay circuit (fourth on-delay circuit) that delays the on timing of the on control command PWM2X by the period TD2 and outputs the delayed on timing.

In the present embodiment, the following relationship is described as being present among the dead time DT, the delay period TD2, and the delay period TD 1. The present invention is not limited to this, and the delay period of the on timing and the delay period of the off timing may be set to different periods, and it is not necessarily required to set the delay periods to be the same.

TD1＝TD2、DT＜TD1(＝TD2)

The output value of the delay circuit 34 and the output value of the delay circuit 35 are input to a logical product circuit (first logical product circuit) 38. The logical product circuit 38 calculates and outputs a logical product of the output value of the delay circuit 34 and the output value of the delay circuit 35. The output signal of the logical product circuit 38 is the gate signal of the self-extinguishing element T5.

The output value of the delay circuit 36 and the output value of the delay circuit 37 are input to a logical product circuit (second logical product circuit) 39. The logical product circuit 39 calculates and outputs a logical product of the output value of the delay circuit 36 and the output value of the delay circuit 37. The output signal of the logical product circuit 39 is the gate signal of the self-extinguishing element T6.

Next, an example of the operation of the power conversion device according to the present embodiment will be described.

Here, an example of the on control command PWM1U, PWM1X, PWM2U, PWM X and the gate signals of the self-extinguishing elements T1 to T6 when the input value of the dc terminal P or the dc terminal O is output from the output terminal of the power conversion circuit 1 (P-O output period) is shown.

First, at time T1, when the on control command PWM1X changes from 1 to 0, the gate signal of the self-extinguishing element T5 changes from 1 to 0, and the self-extinguishing element T5 is turned off.

Next, at time T2 after dead time DT has elapsed from time T1, when on control command PWM1U changes from 0 to 1, the gate signal of self-extinguishing element T2 changes from 0 to 1, and self-extinguishing element T2 is turned on.

Next, at a time T3 delayed by the delay period TD2 from the time T1, the gate signal of the self-extinguishing element T6 is changed from 1 to 0 by the delay circuit 36, and the self-extinguishing element T6 is turned off.

Next, at time T4 delayed by delay period TD1 from time T2, the gate signal of self-extinguishing element T1 is changed from 0 to 1 by delay circuit 30, and self-extinguishing element T1 is turned on.

Since the dead time DT, the delay period TD2, and the delay period TD1 have a relationship of DT < TD2 < dt+td1, the on time T2 of the self-extinguishing element T2 precedes the off time T3 of the self-extinguishing element T6, and the time T3 precedes the on time T4 of the self-extinguishing element T1.

Next, at time T5, when the on control command PWM1U changes from 1 to 0, the gate signal of the self-extinguishing element T1 changes from 1 to 0, and the self-extinguishing element T1 is turned off.

Next, at time T6 after dead time DT has elapsed from time T5, when on control command PWM1X is changed from 0 to 1, the gate signal of self-extinguishing element T6 is changed from 0 to 1, and self-extinguishing element T6 is turned on.

Next, at time T7 delayed by delay period TD1 from time T5, the gate signal of self-extinguishing element T2 is changed from 1 to 0 by delay circuit 31, and self-extinguishing element T2 is turned off.

Next, at time T8 delayed by delay period TD2 from time T6, the gate signal of self-extinguishing element T5 is changed from 0 to 1 by delay circuit 34, and self-extinguishing element T5 is turned on.

Since the dead time DT, the delay period TD2, and the delay period TD1 have a relationship of DT < TD2 < dt+td1, the on time T6 of the self-extinguishing element T6 precedes the off time T7 of the self-extinguishing element T2, and the time T7 precedes the on time T8 of the self-extinguishing element T5.

Here, for example, when the self-extinguishing elements T3 and T5 are turned on, a path through which a current flows from the ac terminal a to the dc terminal O via the diode D2 and the self-extinguishing element T5, and a path through which a current flows from the ac terminal a to the dc terminal O via the self-extinguishing element T3 and the diode D6 can be formed. When the self-extinguishing element T3 is turned off in this state, a path through which current flows from the ac terminal a to the dc terminal O via the self-extinguishing element T3 and the diode D6 is cut off, and only a path through which surplus current flows from the ac terminal a to the dc terminal O via the diode D2 and the self-extinguishing element T5. Then, the self-extinguishing element T5 is turned off, and the current is commutated to a path through which the current flows from the ac terminal a to the dc terminal P via the diodes D1 and D2. At this time, a pulse current also flows through a path in which a current flows from the ac terminal a to the dc terminal O via the self-extinguishing element T3 and the diode D6 due to the influence of the residual carrier of the self-extinguishing element T3, and a voltage is applied to the self-extinguishing element T3, so that a switching loss occurs in the self-extinguishing element T3.

In contrast, in the present embodiment, the self-extinguishing element T3 is always turned off and not turned on during the p—o output period, and therefore, no residual carriers are generated in T3, and no switching loss is generated in the self-extinguishing element T3.

For example, when the self-extinguishing elements T1 and T2 are turned on and a current flows from the dc terminal P to the ac terminal a, a fault occurs in which the self-extinguishing element T1 cannot be turned off, and when the self-extinguishing element T5 is turned on after the dead time DT has elapsed, a path through which a current flows from the dc terminal P to the dc terminal O via the self-extinguishing elements T1 and T5 is short-circuited. Then, when the self-extinguishing element T3 is turned on, the current is further shorted through the path from the dc terminal P to the dc terminal O through the self-extinguishing elements T1 to T3 and the diode D6, and the fault range due to the short circuit is increased.

In contrast, in the power conversion device of the present embodiment, for example, when a fault occurs in which the self-extinguishing element T1 cannot be turned off, the self-extinguishing element T3 is always turned off and not turned on during the P-O output period, and therefore, the short-circuit path ranges from the self-extinguishing element T1 to the self-extinguishing element T5, and the range of the fault caused by the short-circuit can be reduced.

Here, an example of the on control command PWM1U, PWM1X, PWM2U, PWM X and the gate signals of the self-extinguishing elements T1 to T6 when the input value of the dc terminal N or the dc terminal O is output from the output terminal of the power conversion circuit 1 (N-O output period) is shown.

First, at time T9, when the on control command PWM2X changes from 1 to 0, the gate signal of the self-extinguishing element T6 changes from 1 to 0, and the self-extinguishing element T6 is turned off.

Next, at time T10 after the dead time DT has elapsed from time T9, when the on control command PWM2U changes from 0 to 1, the gate signal of the self-extinguishing element T3 changes from 0 to 1, and the self-extinguishing element T3 is turned on.

Next, at time T11 delayed by delay period TD2 from time T9, the gate signal of self-extinguishing element T5 is changed from 1 to 0 by delay circuit 35, and self-extinguishing element T5 is turned off.

Next, at time T12 delayed by delay period TD1 from time T10, the gate signal of self-extinguishing element T4 is changed from 0 to 1 by delay circuit 33, and self-extinguishing element T4 is turned on.

Since the dead time DT, the delay period TD2, and the delay period TD1 have a relationship of DT < TD2 < dt+td1, the on time T10 of the self-extinguishing element T3 precedes the off time T11 of the self-extinguishing element T5, and the time T11 precedes the on time T12 of the self-extinguishing element T4.

Next, at time T13, when the on control command PWM2U changes from 1 to 0, the gate signal of the self-extinguishing element T4 changes from 1 to 0, and the self-extinguishing element T4 is turned off.

Next, at time T14 after the dead time DT has elapsed from time T13, when the on control command PWM2X is changed from 0 to 1, the gate signal of the self-extinguishing element T5 is changed from 0 to 1, and the self-extinguishing element T5 is turned on.

Next, at a time T15 delayed by the delay period TD1 from the time T13, the gate signal of the self-extinguishing element T3 is changed from 1 to 0 by the delay circuit 32, and the self-extinguishing element T3 is turned off.

Next, at a time T16 delayed by the delay period TD2 from the time T14, the gate signal of the self-extinguishing element T6 is changed from 0 to 1 by the delay circuit 37, and the self-extinguishing element T6 is turned on.

Since the dead time DT, the delay period TD2, and the delay period TD1 have a relationship of DT < TD2 < dt+td1, the on time T14 of the self-extinguishing element T5 precedes the off time T15 of the self-extinguishing element T3, and the time T15 precedes the on time T16 of the self-extinguishing element T6.

Here, for example, when the self-extinguishing elements T2 and T6 are turned on, a path through which a current flows from the dc terminal O to the ac terminal a via the diode D5 and the self-extinguishing element T2, and a path through which a current flows from the dc terminal O to the ac terminal a via the self-extinguishing element T6 and the diode D3 can be formed. When the self-extinguishing element T2 is turned off in this state, a path of current flowing from the dc terminal O to the ac terminal a via the diode D5 and the self-extinguishing element T2 is cut off, and only a path of residual current flowing from the dc terminal O to the ac terminal a via the self-extinguishing element T6 and the diode D3 is cut off. Then, the self-extinguishing element T6 is turned off, and the current is commutated to a path from the dc terminal N to the ac terminal a via the diodes D3 and D4. At this time, a pulse current also flows through a path in which a current flows from the dc terminal O to the ac terminal a via the diode D5 and the self-extinguishing element T2 due to the influence of the residual carrier of the self-extinguishing element T2, and a voltage is applied to the self-extinguishing element T2, so that a switching loss occurs in the self-extinguishing element T2.

In contrast, according to the present embodiment, the self-extinguishing element T2 is always turned off and not turned on during the n—o output period, and therefore, switching loss occurs in the self-extinguishing element T2.

For example, when the self-extinguishing elements T3 and T4 are turned on and a current flows from the ac terminal a to the dc terminal N, a fault occurs in which the self-extinguishing element T4 cannot be turned off, and when the self-extinguishing element T6 is turned on after the dead time DT has elapsed, a path through which a current flows from the dc terminal 0 to the dc terminal N via the self-extinguishing elements T4 and T6 is short-circuited. Then, when the self-extinguishing element T2 is turned on, the current is further shorted through the path from the dc terminal O to the dc terminal N through the self-extinguishing elements T2 to T4 and the diode D5, and the fault range due to the short circuit is increased.

In contrast, in the power conversion device of the present embodiment, for example, when a fault occurs in which the self-extinguishing element T4 cannot be turned off, the self-extinguishing element T2 is always turned off and not turned on during the N-O output period, and therefore, the short-circuit path ranges from the self-extinguishing element T6 to the self-extinguishing element T4, and the range of the fault caused by the short-circuit can be reduced.

That is, according to the present embodiment, energy loss in the power conversion device can be suppressed.

Next, a power conversion device according to a second embodiment will be described in detail with reference to the accompanying drawings. In the following description, the same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

The configuration of the control circuit of the power conversion device of the present embodiment is different from that of the power conversion device of the first embodiment described above.

Fig. 6 is a diagram schematically showing an example of the configuration of a control circuit of the power conversion device according to the second embodiment. In the power conversion device according to the present embodiment, the control circuit CTR includes the PWM circuit 2 and the gate signal generation circuit 3.

The PWM circuit 2 has the same configuration as the control circuit CTR in the first embodiment described above. That is, the PWM circuit 2 compares the output command (modulated wave) W1 with the triangular waves (carrier waves) W2 and W3, generates the on control command PWM1U, PWM2U, PWM1X, PWM X, and outputs the on control command PWM1U, PWM2U, PWM X, PWM X to the gate signal generating circuit 3.

The on control command PWM1U is a control command for the self-extinguishing devices T1 and T2, and the on control command PWM2U is a control command for the self-extinguishing devices T3 and T4. The on control command and PWM1U, PWM2U, PWM1X, PWM2X are control commands for the self-extinguishing elements T5 and T6. As in the first embodiment described above, the self-extinguishing elements T3 and T4 are always turned off while the self-extinguishing elements T1 and T2 are being turned on and off. Conversely, the self-extinguishing elements T1, T2 are always turned off while the self-extinguishing elements T3, T4 are switched on and off.

The gate signal generating circuit 3 includes delay circuits 30 to 34, 35b, 35c, 36b, 36c, 37, non-circuits (japanese: negative circuits) (NOT) 35a, 36a, AND logical product circuits (AND) 38, 39. The on control command PWM1U is input to the delay circuit 30. The delay circuit 30 is an on-delay circuit (first on-delay circuit) that delays the on timing of the on-control command PWM1U by the period TD1 and outputs the delayed on timing. The output signal of the delay circuit 30 is a gate signal of the self-extinguishing element T1.

The on control command PWM2U is input to the non-circuit (first non-circuit) 35 a. The non-circuit 35a outputs a non-value of the on control instruction PWM2U to the delay circuit 35b.

The delay circuits 35b and 35c are on-off delay circuits (first on-off delay circuits) that delay on-timing and off-timing of the output value of the non-circuit 35a, respectively.

The output value of the non-circuit 35a (non-value of the on control command PWM 2U) is input to the delay circuit 35b. The delay circuit 35b is an off delay circuit (fifth off delay circuit) that delays the off timing of the non-value of the input on control command PWM2U by the period TD3 and outputs the delayed off timing.

The output value of the delay circuit 35b is input to the delay circuit 35 c. The delay circuit 35c is an on delay circuit (fifth on delay circuit) that delays the non-value on timing of the input on control command PWM2U by the period TD4 and outputs the delayed result.

The on control command PWM1U is input to the non-circuit (second non-circuit) 36 a. The non-circuit 36a outputs a non-value of the on control instruction PWM1U to the delay circuit 36b.

The delay circuits 36b and 36c are on-off delay circuits (second on-off delay circuits) that delay on-timing and off-timing of the output value of the non-circuit 36a, respectively.

The output value of the non-circuit 36a (non-value of the on control command PWM 1U) is input to the delay circuit 36 b. The delay circuit 36b is an off delay circuit (sixth off delay circuit) that delays the off timing of the non-value of the input on control command PWM1U by the period TD3 and outputs the delayed off timing.

The output value of the delay circuit 36b is input to the delay circuit 36 c. The delay circuit 36c is an on delay circuit (sixth on delay circuit) that delays the non-value on timing of the input on control command PWM1U by the period TD4 and outputs the delayed result.

In the present embodiment, the following relationship exists between the dead time DT and the delay periods TD1 to TD 4. The present invention is not limited to this, and the delay period of the on timing and the delay period of the off timing may be set to different periods, and it is not necessarily required to set the delay periods to be the same.

TD1＝TD2、TD3＝TD4＝DT、DT＜TD1(＝TD2)

The output value of the delay circuit 34 and the output value of the delay circuit 35c are input to a logical product circuit (third logical product circuit) 38. The logical product circuit 38 calculates and outputs a logical product of the output value of the delay circuit 34 and the output value of the delay circuit 35 c. The output signal of the logical product circuit 38 is the gate signal of the self-extinguishing element T5.

The output value of the delay circuit 36c and the output value of the delay circuit 37 are input to a logical product circuit (fourth logical product circuit) 39. The logical product circuit 39 calculates and outputs a logical product of the output value of the delay circuit 36c and the output value of the delay circuit 37. The output signal of the logical product circuit 39 is the gate signal of the self-extinguishing element T6.

First, at time T17, when the on control command PWM1X changes from 1 to 0, the gate signal of the self-extinguishing element T5 changes from 1 to 0, and the self-extinguishing element T5 is turned off.

Next, at time T18 after the dead time DT has elapsed from time T17, when the on control command PWM1U changes from 0 to 1, the gate signal of the self-extinguishing element T2 changes from 0 to 1, and the self-extinguishing element T2 is turned on.

Next, at a time T19 delayed by the delay period TD3 from the time T18, the gate signal of the self-extinguishing element T6 is changed from 1 to 0 by the delay circuit 36b, and the self-extinguishing element T6 is turned off.

Next, at a time T20 delayed by the delay period TD1 from the time T18, the gate signal of the self-extinguishing element T1 is changed from 0 to 1 by the delay circuit 30, and the self-extinguishing element T1 is turned on. Here, since the relationship TD3 < TD1 exists between the delay period TD3 and the delay period TD1, the on time T18 of the self-extinguishing element T2 precedes the off time T19 of the self-extinguishing element T6, and the time T19 precedes the on time T20 of the self-extinguishing element T1.

Next, at time T21, when the on control command PWM1U changes from 1 to 0, the gate signal of the self-extinguishing element T1 changes from 1 to 0, and the self-extinguishing element T1 is turned off.

Next, at a time T22 delayed from the time T21 by the delay period TD4, the gate signal of the self-extinguishing element T6 is changed from 0 to 1 by the delay circuit 36c, and the self-extinguishing element T6 is turned on.

Next, at a time T23 delayed by the delay period TD1 from the time T21, the gate signal of the self-extinguishing element T2 is changed from 1 to 0 by the delay circuit 31, and the self-extinguishing element T2 is turned off.

Next, at a time T24 delayed by the delay period TD2 from the time T22, the gate signal of the self-extinguishing element T5 is changed from 0 to 1 by the delay circuit 34, and the self-extinguishing element T5 is turned on. Here, since the dead time DT, the delay period TD1, the delay period TD2, and the delay period TD4 have a relationship of TD4 < TD1, and TD1 < dt+td2, the on time T22 of the self-extinguishing element T6 precedes the off time T23 of the self-extinguishing element T2, and the time T23 precedes the on time T24 of the self-extinguishing element T5.

As described above, in the present embodiment as well, since the self-extinguishing element T3 is always turned off and not turned on during the P-O output period, no residual carriers are generated in T3, and no switching loss is generated in the self-extinguishing element T3.

In the power conversion device according to the present embodiment, for example, when a fault occurs in which the self-extinguishing element T1 cannot be turned off, the self-extinguishing element T3 is always turned off and not turned on during the P-O output period, and therefore, the short-circuit path ranges from the self-extinguishing element T1 to the self-extinguishing element T5, and the range of the fault caused by the short-circuit can be reduced.

First, at time T25, when the on control command PWM2X changes from 1 to 0, the gate signal of the self-extinguishing element T6 changes from 1 to 0, and the self-extinguishing element T6 is turned off.

Next, at time T26 when dead time DT has elapsed from time T25, when on control command PWM2U changes from 0 to 1, the gate signal of self-extinguishing element T3 changes from 0 to 1, and self-extinguishing element T3 is turned on.

Next, at a time T27 delayed by the delay period TD3 from the time T26, the gate signal of the self-extinguishing element T5 is changed from 1 to 0 by the delay circuit 35b, and the self-extinguishing element T5 is turned off.

Next, at time T28 delayed by delay period TD1 from time T26, the gate signal of self-extinguishing element T4 is changed from 0 to 1 by delay circuit 33, and self-extinguishing element T4 is turned on. Here, since the dead time DT, the delay period TD3, and the delay period TD1 have a relationship of TD3 < TD1, the on time T26 of the self-extinguishing element T3 precedes the off time T27 of the self-extinguishing element T5, and the time T27 precedes the on time T28 of the self-extinguishing element T4.

Next, at time T29, when the on control command PWM2U changes from 1 to 0, the gate signal of the self-extinguishing element T4 changes from 1 to 0, and the self-extinguishing element T4 is turned off.

Next, at a time T30 delayed by the delay period TD4 from the time T29, the gate signal of the self-extinguishing element T5 is changed from 0 to 1 by the delay circuit 35c, and the self-extinguishing element T5 is turned on.

Next, at a time T31 delayed by the delay period TD1 from the time T29, the gate signal of the self-extinguishing element T3 is changed from 1 to 0 by the delay circuit 32, and the self-extinguishing element T3 is turned off.

Next, at a time T32 delayed by the delay period TD2 from the time T30, the gate signal of the self-extinguishing element T6 is changed from 0 to 1 by the delay circuit 37, and the self-extinguishing element T6 is turned on. Here, since the dead time DT, the delay period TD1, the delay period TD2, and the delay period TD4 have a relationship of TD4 < TD1, and TD1 < dt+td2, the on time T30 of the self-extinguishing element T5 precedes the off time T31 of the self-extinguishing element T3, and the time T31 precedes the on time T32 of the self-extinguishing element T6.

According to the above, in the present embodiment, as in the first embodiment described above, the self-extinguishing element T2 is always turned off and not turned on during the n—o output period, and therefore, switching loss occurs in the self-extinguishing element T2.

In the power conversion device according to the present embodiment, for example, when a fault occurs in which the self-extinguishing element T4 cannot be turned off, the self-extinguishing element T2 is always turned off and not turned on during the N-O output period, and therefore, the short-circuit path is in the range from the self-extinguishing element T6 to the self-extinguishing element T4, and the range of the fault caused by the short-circuit can be reduced.

In the power conversion devices according to the first and second embodiments, for example, when the self-extinguishing element T1 is turned on, an operation when the operation of the power conversion circuit 1 is stopped (gate blocking) will be described below.

Fig. 9 and 10 are diagrams for explaining an example of the operation of the power conversion device according to the first embodiment.

Fig. 9 shows an example of a timing chart of gate signals of the self-extinguishing elements T1, T2, T5, T6 included in the timing at which the self-extinguishing element T1 is turned on in the power conversion device of the first embodiment, and fig. 10 shows a path of current flowing through the power conversion circuit 1 when the self-extinguishing elements T1, T2, T5, T6 are operated by the gate signals shown in fig. 9.

At the timing when the self-extinguishing element T1 is turned on, the self-extinguishing element T2 is turned on, and the self-extinguishing elements T5, T6 are turned off. In addition, during this period, the self-extinguishing elements T3, T4 are always turned off. In this state, a current flows through a path 1A from the dc terminal P to the ac terminal A1 via the self-extinguishing elements T1 and T2.

At this time, when Gate Block (GB) is performed, the self-extinguishing element T1 is turned off, whereby the current flowing through the power conversion circuit 1 is commutated to a path 1B flowing from the dc terminal O to the ac terminal A1 via the diode D5 and the self-extinguishing element T2. When the self-extinguishing element T2 is turned off, the current flowing through the power conversion circuit 1 is converted to a path 1C from the dc terminal N to the ac terminal A1 via the diodes D3 and D4, and the operation of the power conversion circuit 1 is stopped.

Fig. 11 and 12 are diagrams for explaining an example of the operation of the power conversion device according to the second embodiment.

Fig. 11 shows an example of a timing chart of gate signals of the self-extinguishing elements T1, T2, T5, T6 included in the timing at which the self-extinguishing element T1 is turned on in the power conversion device according to the second embodiment, and fig. 12 shows a path of current flowing through the power conversion circuit 1 when the self-extinguishing elements T1, T2, T5, T6 are operated by the gate signals shown in fig. 11.

At the timing when the self-extinguishing element T1 is turned on, the self-extinguishing element T2 is turned on, and the self-extinguishing elements T5, T6 are turned off. The self-extinguishing elements T3 and T4 are always turned off during this period. In this state, a current flows through a path 2A from the dc terminal P to the ac terminal A1 via the self-extinguishing elements T1, T2.

At this time, when gate blocking GB is performed, the self-extinguishing element T1 is turned off, and thereby the current flowing through the power conversion circuit 1 is commutated to the path 2B flowing from the dc terminal O to the ac terminal A1 via the diode D5 and the self-extinguishing element T2. Further, in the present embodiment, the self-extinguishing element T6 is turned on after the self-extinguishing element T1 is turned off and before the self-extinguishing element T2 is turned off. In this state, a path 2C is generated in which a current flows from the dc terminal O to the ac terminal A1 through the self-extinguishing element T6 and the diode D3, in addition to a path in which a current flows from the dc terminal O to the ac terminal A1 through the diode D5 and the self-extinguishing element T2 in the power conversion circuit 1.

When the self-extinguishing element T2 is turned off, the path 2B is cut off, and the current flowing through the power conversion circuit 1 flows only through the path 2C. Finally, when the self-extinguishing element T6 is turned off, the current flowing through the power conversion circuit 1 is commutated to the path 2E flowing from the dc terminal N to the ac terminal A1 via the diodes D3, D4, and the operation of the power conversion circuit 1 is stopped.

As described above, according to the power conversion device of the second embodiment, since the self-extinguishing element T1 and the self-extinguishing element T2 are turned off and then the self-extinguishing element T6 is turned on, when the output current Iout is positive, the current flowing from the diode D5 to the self-extinguishing element T2 can be commutated from the path from the self-extinguishing element T6 through the diode D3 to the path from the diode D4 through the diode D3, and therefore the power conversion circuit 1 can be stopped in a commutating loop with low inductance.

Several embodiments of the present invention have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other modes, and various omissions, substitutions, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and their equivalents.

Claims

1. A power conversion device is provided with:

first to fourth self-extinguishing elements connected in series between a first direct current terminal and a second direct current terminal, the second direct current terminal being at a different potential from the first direct current terminal;

A first diode and a second diode connected in anti-parallel between a connection point of the first self-extinguishing element and the second self-extinguishing element, one end of which is electrically connected to the first direct current terminal, and a connection point of the fourth self-extinguishing element and the third self-extinguishing element, the other end of which is electrically connected to the second direct current terminal;

the fifth self-extinguishing component is connected with the first diode in anti-parallel;

a sixth self-extinguishing component connected in anti-parallel with the second diode; and

a control circuit for controlling the operations of the first to sixth self-extinguishing elements,

the connection point of the fifth self-extinguishing element and the sixth self-extinguishing element is electrically connected with a third direct current terminal, the third direct current terminal is a potential between the potential of the first direct current terminal and the potential of the second direct current terminal,

the connection point of the second self-extinguishing component and the third self-extinguishing component is electrically connected with an alternating current terminal,

the second self-extinguishing element and the third self-extinguishing element are bipolar elements,

the control circuit always turns off the third self-extinguishing element and the fourth self-extinguishing element during switching of the first self-extinguishing element and the second self-extinguishing element, and always turns off the first self-extinguishing element and the second self-extinguishing element during switching of the third self-extinguishing element and the fourth self-extinguishing element.

2. The power conversion device according to claim 1, wherein,

the control circuit includes:

a PWM circuit that generates a first on control command based on a value obtained by comparing an output command value with a first carrier wave, and a second on control command based on a value obtained by comparing the output command value with a second carrier wave; and

a signal generation circuit configured to generate control signals of the first and second self-extinguishing elements based on the first conduction control command, generate control signals of the third and fourth self-extinguishing elements based on the second conduction control command, generate control signals of the fifth and sixth self-extinguishing elements based on a non-value of the first conduction control command and a non-value of the second conduction control command,

the first carrier crosses the output command when the output command value is 0 or more, and the second carrier crosses the output command when the output command value is 0 or less.

3. The power conversion device according to claim 2, wherein,

the signal generation circuit includes:

A first turn-on delay circuit that outputs a control signal of the first self-extinguishing element that delays a turn-on timing of the first turn-on control instruction;

a first turn-off delay circuit that outputs a control signal of the second self-extinguishing element that delays a turn-off timing of the first turn-on control instruction;

a second turn-off delay circuit that outputs a control signal of the third self-extinguishing element that delays a turn-off timing of the second turn-on control instruction; and

and a second turn-on delay circuit configured to output a control signal of the fourth self-extinguishing element for delaying a turn-on timing of the second turn-on control command.

4. The power conversion device according to claim 3, wherein,

the signal generation circuit includes:

a third turn-on delay circuit configured to delay a non-value turn-on timing of the first turn-on control instruction;

a third off delay circuit configured to delay off timing of the non-value of the second on control command;

a first logical product circuit for calculating a logical product of the output value of the third on delay circuit and the output value of the third off delay circuit, and outputting a control signal of the fifth self-extinguishing element;

a fourth off delay circuit configured to delay off timing of the non-value of the first on control command;

A fourth turn-on delay circuit configured to delay a non-value turn-on timing of the second turn-on control instruction; and

and a second logical product circuit for calculating a logical product of the output value of the fourth off delay circuit and the output value of the fourth on delay circuit, and outputting the control signal of the sixth self-extinguishing element.

5. The power conversion device according to claim 3, wherein the signal generation circuit includes:

a first non-circuit outputting a non-value of the second on control instruction;

a first on-off delay circuit that delays on-timing and off-timing of an output value of the first non-circuit;

a third logical product circuit for calculating a logical product of an output value of the third on-delay circuit and an output value of the first on-off delay circuit, and outputting a control signal of the fifth self-extinguishing element;

a second non-circuit outputting a non-value of the first on control instruction;

a second on-off delay circuit that delays on-timing and off-timing of an output value of the second non-circuit; and

And a fourth logical product circuit for calculating a logical product of the output value of the second on/off delay circuit and the output value of the fourth on delay circuit, and outputting the control signal of the sixth self-extinguishing element.