JPH11220885A - Resonant power converter - Google Patents

Abstract

(57) [Problem] To realize a partial resonance type power conversion device with a simple configuration. SOLUTION: A resonance capacitor 6 and a resonance reactor are provided between a positive bus and a negative bus of a power conversion unit 2 in which main switching elements 3a to 3f and flywheel diodes 4a to 4f are bridge-connected between a positive bus and a negative bus. 7 are connected in series, and when one of the main switching elements 3a and 3b, 4a and 4b, 5a and 5b (for example, 3a and 3b) connected in series between the positive bus and the negative bus is switched, it is turned off until then. One main switching element (for example, 3
b) is turned on, the positive bus and the negative bus are short-circuited, and the resonance operation is started by the resonance capacitor 6 and the resonance reactor 7, and the resonance operation causes the voltage between the positive bus and the negative bus to become a negative voltage. , The other main switching element (for example, 3a) is turned off to perform zero voltage switching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resonance type power converter which is provided between a load such as an AC motor or an AC rotating machine and a DC power supply to perform power conversion.

[0002]

2. Description of the Related Art Conventionally, as a resonance type power conversion device, there is an all-resonance type power conversion device which always resonates by a resonance circuit. In this case, there is a problem that conduction loss in the resonance reactor increases because resonance is always performed. As a solution to this problem, a partial resonance type that resonates only at the time of switching has been proposed. As an example,
There is one shown in FIG. 21 (see US Pat. No. 5,047,913).

FIG. 21 shows one phase of a three-phase resonance type power converter. As shown in the drawing, a circuit composed of voltage dividing capacitors 42 and 43 connected in series, a circuit composed of flywheel diodes 49 and 50 connected in series, and main switching elements 51 and 52 connected in series. Are connected in parallel to the DC voltage source 41, respectively.

A circuit in which an auxiliary switching element 46 and a flywheel diode 44 are connected in anti-parallel, an auxiliary switching element 47 and a flywheel diode 4
5 and a circuit in which a resonance reactor 48 is connected in series. One terminal is connected to a connection point of the voltage dividing capacitors 42 and 43, and the other terminal is connected to a flywheel. The connection point between the wheel diodes 49 and 50, the connection point between the main switching elements 51 and 52, and the connection point between the resonance capacitors 53 and 54 are respectively connected.

In such a configuration, when the main switching element 51 is switched from on to off and the main switching element 52 is switched from off to on, the auxiliary switching element 46 is turned on, and the resonance inductor 48 and the resonance capacitor 53 are turned on. , Resonance occurs, and switching is performed when the voltage of the main switching element 51 becomes 0V. Also, the main switching element 51 is turned on from off,
When the main switching element 52 is switched from on to off, the auxiliary switching element 47 is turned on, resonance is generated by the resonance inductor 48 and the resonance capacitor 54, and the switching is performed when the voltage of the main switching element 52 becomes 0V. I do. With such an operation, the switching loss can be reduced to zero.

For the other two phases, the above components 44 are shared by using the voltage dividing capacitors 42 and 43 in common.
1 to 54 are provided.

[0007]

However, in the above-described three-phase resonance type power converter, three resonance reactors, six resonance capacitors, six auxiliary switching elements, and six flywheel diodes are required. . Further, as a component common to each phase, a voltage dividing capacitor 2
I need a piece. Therefore, there is a problem that the size and cost of the power conversion device are increased due to these additional components, and the control circuit is complicated due to the addition of the auxiliary switching element.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to realize a partial resonance type power converter with a simple configuration without using the above-described complicated configuration.

[0009]

In order to achieve the above object, according to the present invention, a single resonance circuit (8) having a resonance capacitor (6) and a resonance reactor (7) is used to perform main switching of a plurality of phases. The upper and lower arms of the power converter (2) having the elements (3a to 3f) are short-circuited to generate resonance, and at the time of the resonance, the main switching element of the power converter is switched to perform commutation.

According to the first aspect of the present invention, of the plurality of main switching elements connected in series between the positive bus and the negative bus in the phase to be switched, the main switching element which has been turned off is turned on. Then, resonance is started by the resonance capacitor and the resonance reactor, and the resonance current becomes larger than the load current due to the resonance. When the current flows through the flywheel diode means connected in anti-parallel to the main switching element that switches off. To
A control means (13) for turning off a main switching element to be turned off is provided.

In the state where the current starts to flow through the flywheel diode means due to the resonance, no switching loss occurs even if the main switching element connected in anti-parallel to the flywheel diode means is switched off. Therefore, zero voltage switching can be realized. In this case, the resonance capacitor and the resonance reactor connected in series
Since the main switching element of each phase performs zero voltage switching, a resonance type power converter can be realized without using an auxiliary switching element as in the related art.

Here, when the main switching element to be turned off is turned off, it is detected that the voltage between the positive bus and the negative bus is a negative voltage. You can do it. Further, as in the third aspect of the present invention, the detection can be performed by detecting that the voltage between both ends of the main switching element to be turned off is a negative voltage. Further, as in the invention described in claim 4, the detection can be performed even when a state in which current stops flowing to the main switching element that is turned off is detected. Further, as in the invention according to claim 5, it is also possible to detect and carry out a state in which a current is flowing through the flywheel diode means connected in anti-parallel to the main switching element to be turned off. Further, as in the sixth aspect of the present invention, it can be performed when a predetermined time has elapsed since the start of resonance.

According to the present invention, a plurality of main switching elements connected in series between a positive bus and a negative bus in a switching phase are turned on to start resonance by the resonance capacitor and the resonance reactor. This resonance causes the voltage between the positive bus and the negative bus to be substantially 0 V
When it becomes, the main switching element that is turned off is turned off. This invention has the same effect as the first aspect.

According to another aspect of the present invention, a DC voltage source is provided when the main switching element is switched.
If an overcurrent preventing means (9) for preventing an overcurrent from flowing through the main switching element is provided, it is possible to prevent the main switching element from being damaged by the overcurrent. As the overcurrent prevention means, a reactor (9a) can be used as in the ninth aspect of the present invention. In this case, the reactor may be an inductance that does not cause resonance by the reactor, the resonance capacitor, and the resonance reactor when the resonance is performed by the resonance capacitor and the resonance reactor. It is desirable to have a value. That is, claim 1
As described in 1, it is necessary to make the relationship between the inductance components Ld and Lr of the reactor for preventing overcurrent and the resonance reactor satisfy Ld> Lr. Further, the relationship between the load and the inductance components Lm and Ld of the reactor may be set to satisfy Lm> Ld so that the power can be supplied from the power converter to the load without any problem.

Further, according to the invention of claim 12,
By providing a voltage clamping circuit (10) having a voltage clamping reactor (10a) coupled to the above-described reactor and clamping the voltage between the positive bus and the negative bus to a predetermined voltage, the positive bus and the negative bus can be provided. The voltage between the buses can be limited to a desired voltage. Further, according to the present invention as described in claim 13, if the power is regenerated to the DC voltage source by the current flowing through the voltage clamping reactor,
Power can be saved. In this case, claim 14
As described in the invention described in the above, if the state in which the current flowing through the voltage clamping reactor is zero or a minimum value is detected and resonance is started, resonance is not affected by current fluctuation at the time of clamping. Can be generated.

The above-mentioned overcurrent preventing means may be a DC voltage source and a power conversion unit at least during a period from before starting resonance to turning off a main switching element to be turned off. Switching means (9b) for turning off the connection between. In this case, as in the invention according to claim 16, if a switching means capable of flowing a current bidirectionally is used, and if a switch that performs regenerative braking is used as a load, the switching from the power conversion unit is performed. A current can be caused to flow through the DC voltage source.

Also, in the resonance type power converter according to the first to ninth aspects, as in the seventeenth aspect,
If a voltage clamp circuit (10) for clamping the voltage between the positive bus and the negative bus to a predetermined voltage is provided, the voltage between the positive bus and the negative bus can be limited to a desired voltage. In this case, as the voltage clamp circuit, one configured using a diode (10c) as in the invention of claim 18, or a second DC voltage source (as in the invention of claim 19) 10d) and a diode (10e) or a capacitor (10) connected in series to a DC voltage source as in the invention of claim 20.
f), a diode (10g), and switching means (10h) for discharging a capacitor at the time of clamping.

According to the present invention, the upper and lower arms of the power converter having a plurality of main switching elements are short-circuited by one resonance circuit having a resonance capacitor and a resonance reactor. Raise,
During this resonance, the main switching element of the power conversion unit is switched to perform commutation. According to the present invention, it is possible to realize a resonance type power converter in which switching loss is reduced without using an auxiliary switching element as in the related art.

In the invention according to claim 22, the upper and lower arms in the power converter are short-circuited to generate resonance by the resonance capacitor and the resonance reactor,
When current flows through the flywheel diode means connected in anti-parallel to the main switching element that performs switching by this resonance, the main switching element is switched. This invention has the same effect as the first aspect.

In this case, the control means includes a timing detection means (161) for detecting a timing for switching the main switching element, and a short circuit between the upper and lower arms upon detection of the timing. (162). Further, the upper and lower arms can be short-circuited by turning on all the main switching elements in the power converter, as in the invention according to claim 24.

Further, in the resonance type power converter according to the twenty-first to twenty-fourth aspects, a short circuit between the DC voltage source and the power converter is prevented when the main switching element is switched as in the twenty-fifth aspect. Short circuit prevention means (9)
Is provided, it is possible to prevent the destruction of the main switching element due to the overcurrent. Note that the reference numerals in parentheses described above indicate the correspondence with specific means described in the embodiment described later.

[0022]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 1 shows an overall configuration of a resonance type power converter according to one embodiment of the present invention. In this embodiment, the DC voltage of the DC voltage source 1 is converted into an AC voltage by the power converter 2 to drive a load 5 such as a three-phase AC motor.

The power conversion unit 2 has three main switching elements (for example, IGBTs) 3a to 3f as self-turn-off switching elements between a positive bus and a negative bus.
Phase, W phase). Further, anti-parallel diodes (flywheel diodes) 4a to 4f are connected to the main switching elements 3a to 3f, respectively. One arm is constituted by one main switching element and one flywheel diode connected in anti-parallel to the main switching element, and the one connected to the positive bus is connected to the upper arm and the negative bus. Is the lower arm. In the power converter 2, the main switching elements 3a and 3b, the main switching element 3
c, 3d and main switching elements 3e, 3f
The on / off control is performed by shifting the phase by 120 ° by each of the three, and a three-phase AC voltage is output to the load 5.

A resonance capacitor 6 and a resonance reactor 7 are connected in series between the positive bus and the negative bus. Resonant capacitor 6 and resonant reactor 7
Constitutes a resonance circuit 8, and as described later, resonance occurs when the main switching elements of the upper and lower arms between the positive bus and the negative bus are both turned on to form a path through which a resonance current flows. Do.

Further, short-circuit preventing means 9 is connected in series with the DC voltage source 1. As the short-circuit preventing means 9, for example, a reactor 9a can be used. This reactor 9a is larger than the inductance component of the resonance reactor 7, so that both main switching elements of the upper and lower arms between the positive bus and the negative bus are turned on, and the positive bus and the negative bus are short-circuited. This also prevents overcurrent from flowing through each main switching element. That is, when the upper and lower arms are short-circuited, short-circuiting between the DC voltage source 1 and the power converter 2 is prevented by the reactor 9a, so that overcurrent does not flow through the main switching element.

Further, a voltage clamp circuit 10 for clamping a voltage between the positive bus and the negative bus to a predetermined voltage is provided. The voltage clamp circuit 10 includes a voltage clamp reactor 10a and a diode 10b that are differentially connected to the reactor 9a. The voltage clamping reactor 10a and the diode 10b are connected in parallel to the DC voltage source 1, and are configured to regenerate power in the DC voltage source 1 when a current flows through the voltage clamping reactor 10a during clamping. . The ratio between the number of turns of the voltage clamping reactor 10a and the number of turns of the reactor 9a is n (1 <n).

The operation of the above configuration will be described with reference to a signal waveform diagram shown in FIG. In FIG. 3, i _S1 is a current flowing through the upper arm, i _S2 is a current flowing through the lower arm, i _Lr is a current flowing through the resonance reactor 7,
_Ld is the current flowing through the reactor 9a, i _Lc denotes the current flowing through the voltage clamping reactor 10a, V _PN is the voltage across the resonant capacitor 6 and the resonance reactor 7, i.e. the voltage between the upper and lower arms.

The switching operation of the power conversion unit 2 is performed by setting the phase to be switched to the U-phase by using the main switching element 3.
The commutation from a to the flywheel diode 4b and the commutation from the flywheel diode 4b to the main switching element 3a will be described as examples. First, a case where commutation is performed from the main switching element 3a to the flywheel diode 4b will be described. In a state before this commutation is performed, the main switching element 3a is turned on and current is supplied to the load side. Then, when the main switching element 3b is turned on (at _a point of time ta in FIG. 3), a short circuit occurs between the positive bus and the negative bus, that is, the upper and lower arms of the power converter 2 short-circuit, and the resonance capacitor 6 and the resonance reactor 7 Then, a resonance path is formed by the main switching elements 3a and 3b, and a resonance current starts to flow. At this time, the resonance current and the load current i
_l flows in the same direction as the main switching element 3a.
, A current in which the load current and the resonance current are superimposed flows. A resonance current flows through the main switching element 3b. Note that even if the power conversion unit 2 is short-circuited with the arm, the reactor 9
Due to a, no overcurrent flows through each main switching element. When resonance is performed by the resonance capacitor 6 and the resonance reactor 7, the reactor 9a is connected to the resonance reactor 7a so that no resonance is caused by the reactor 9a, the resonance capacitor 6, and the resonance reactor 7 when the upper and lower arms are short-circuited. It has a sufficiently large inductance value (for example, a value that is about two digits larger).

[0029] After this, the resonance current is reversed polarity, the absolute value is greater than the load current of the resonant current and (t _b when ~t _c point in FIG. 3), the flywheel diodes 4a, 4
Current flows through b. Therefore, the collector-emitter voltage of each of the main switching elements 3a and 3b becomes negative.
In the period t _c from the t _b, given a clear signal to the gate terminal of the main switching element 3a, switching loss is not generated by the zero voltage switching.

[0030] Then, it reduces resonance current gradually, the flywheel diode 4a is turned off, (t _c point in FIG. 3) the load current to start flowing the flywheel diode 4b. At this time, of the current flowing through the reactor 9a,
Since a current equivalent to the current flowing through the flywheel diode 4b flows through the resonance capacitor 6 and the resonance reactor 7, the resonance capacitor 6 is charged, and the potential of the positive electrode of the resonance capacitor 6 rises. When the voltage V _PN between both ends of the resonance capacitor 6 and the resonance reactor 7 becomes (1 + 1 / n) times the DC voltage of the DC voltage source 1 (at time t _{d in} FIG. 3), the voltage V _PN becomes The voltage clamp circuit 10 is clamped to this value and includes a voltage clamp reactor 10a and a voltage clamp diode 10b.
, And the electric power is regenerated to the DC voltage source 1.
Note that n is (the number of turns of the voltage clamping reactor 10a).
/ (Number of turns of reactor 9a). In addition, the current flowing through reactor 9a and the current flowing through reactor 10a for voltage clamping hardly change in the switching cycle.

Next, a case where commutation is performed from the flywheel diode 4b to the main switching element 3a will be described. Turns on the main switching element 3a (in FIG. 3 t _e
), The upper and lower arms of the power converter 2 are short-circuited, and a resonance current flows through a resonance path formed by the resonance capacitor 6, the resonance reactor 7, and the main switching elements 3a and 3b. At this time, since the resonance current and the load current i _l flow in the same direction, a current in which the load current and the resonance current are superimposed flows through the main switching element 3a.

[0032] After this, the resonance current is reversed polarity, the absolute value is greater than the load current of the resonant current with (t _f time ~t _g point in FIG. 3), the flywheel diodes 4a, 4
Current flows through b. Therefore, the collector-emitter voltage of each of the main switching elements 3a and 3b becomes negative.
In period t _g from the t _f, given a clear signal to the gate terminal of the main switching element 3b, the switching loss is not generated by the zero voltage switching. When the resonance current gradually decreases, the flywheel diodes 4a and 4b are turned off in this order, and the resonance ends to return to the initial state.

In the V-phase and W-phase other than the U-phase, the same commutation operation as described above is performed to perform zero voltage switching. As described above, according to the present embodiment, a configuration is used in which batch commutation is performed by using one set of the resonance capacitor 6 and the resonance reactor 7 to perform zero-voltage switching of the three-phase main switching elements. A partial resonance type power converter can be realized without using such an auxiliary switching element.

Next, the main switching elements 3a to 3
A description will be given of the control unit 13 that performs switching control of 3f to output a desired AC voltage from the power conversion unit 2. The control unit 13 includes a gate signal generation circuit 14, a voltage detection circuit 15, a control circuit 16, and a drive circuit 17, as shown in FIG. FIG. 2 shows a specific circuit configuration thereof.

In FIG. 2, gate signal generation circuit 14
Are a U-phase upper arm gate signal generation circuit 14a, a U-phase lower arm gate signal generation circuit 14b, a V-phase upper arm gate signal generation circuit 14c, and a V-phase lower arm gate signal generation circuit 1.
4d, a W-phase upper arm gate signal generation circuit 14e, and a W-phase lower arm gate signal generation circuit 14f,
For example, a pulse width modulated signal (PWM signal) for driving the load 5 is output.

The voltage detection circuit 15 includes a resonance capacitor 6
And a voltage between both ends of the resonance reactor 7, that is, a voltage V _PN between the upper and lower arms. The control circuit 16 includes a comparator 16a, OR gates 16b to 16g, and latch circuits 16h to 16m, and outputs an upper arm gate signal and a lower arm gate signal to the drive circuit 17.

In such a configuration, the operation of the control unit 13 will be described by taking the above-described commutation in the U phase as an example. In a state before the commutation is performed, as shown in FIG. 3, the upper arm PWM signal output from the U-phase upper arm gate signal generation circuit 14a is at a high level (indicated by ON in FIG. 3) and the U-phase lower signal. The lower arm PWM signal output from the arm gate signal generation circuit 14b is at a low level (indicated by OFF in FIG. 3), the upper arm gate signal output from the latch circuit 16h is at a high level, and the lower gate PWM signal is output from the latch circuit 16i. The output lower arm gate signal is at a low level. Since the voltage _VPN between the upper and lower arms is a positive voltage, the voltage is detected by the voltage detection circuit 15, and a high-level signal is output from the comparator 16a.

In this state, the upper arm PWM signal changes from a high level to a low level to perform commutation (O
N → OFF), and the lower arm PWM signal changes from low level to high level (OFF → ON). At this time, in the latch circuit 16i, CLK (clock)
Since the voltage input to the terminal changes to high level, the lower arm gate signal changes to high level. Therefore, the main switching element 3b is turned on (t _a point in FIG. 3), the resonance capacitor 6 as described above, resonant reactor 7, the main switching element 3a, the resonance is the path in which the resonance current flows formed by 3b Occur.

[0039] After this, the resonance current is reversed polarity, the absolute value of the resonant current becomes larger than the load current (t _b point in Fig. 3), a current flows through the flywheel diode 4a, a 4b. For this reason, the voltage _VPN between the upper and lower arms becomes a negative voltage, and the signal output from the comparator 16a becomes a low level. Then, the output of the OR circuit 16b goes low, and the upper arm gate signal output from the latch circuit 16h goes low, so that the main switching element 3a outputs an off signal, and zero voltage switching is performed.

When the upper arm PWM signal changes to high level (OFF → ON) and the lower arm PWM signal changes to low level (ON → OFF), first, the upper arm signal output from the latch circuit 16h is output. When the gate signal goes high, the main switching element 3a turns on (FIG. 3).
At t _e ). Thereafter, the resonance current has the opposite polarity, and the absolute value of the resonance current becomes larger than the load current (t _{f in} FIG. 3).
), Current flows through the flywheel diodes 4a and 4b, and the voltage _VPN between the upper and lower arms becomes a negative voltage. For this reason, the signal output from the comparator 16a becomes low level, and the lower arm gate signal output from the latch circuit 16i becomes low level, so that the main switching element 3b outputs an off signal and zero voltage switching is performed.

In the above-described embodiment, it is detected that the voltage V _PN between the upper and lower arms has become negative,
The main switching element that is turned off is turned off, but it is detected that the resonance between the resonance capacitor 6 and the resonance reactor 7 has started and the voltage V _PN between the upper and lower arms has dropped to a positive voltage near 0 V. Thus, the main switching element that is turned off may be turned off. The point is that it detects that the voltage between the positive bus and the negative bus has become substantially 0 V due to resonance by the resonance capacitor 6 and the resonance reactor 7, and turns off the main switching element that is turned off. do it.

Further, in the above-described embodiment, an AC motor is used as the load 5, but an AC rotating machine that performs regenerative braking may be used. In the above-described embodiment, the IGBT is used as the main switching elements 3a to 3f. However, a MOSFET, a power transistor, a thyristor, a GTO (gate turn-off thyristor), an MCT (moss control thyristor), or the like may be used. it can.

In the above-described embodiment, the flywheel diodes 4a to 4f are used as flywheel diode means. However, any other flywheel diodes having the same rectifying function may be used. Good. The resonance capacitor 6 and the resonance reactor 7 connected in series in the resonance circuit 8 are a combination of one or a plurality of resonance capacitors and one or a plurality of resonance reactors selected from a plurality of resonance reactors prepared in advance. It is good also as thing of. By doing so, a desired resonance frequency and / or a peak value of the output current can be set. The connection order of the resonance capacitor 6 and the resonance reactor 7 may be reversed as long as they are connected in series.

In the above embodiment, the control circuit 16 is constituted by hardware.
It can also be configured by software using computer means such as a microcomputer. FIG. 4 shows a control process in this case. FIG. 4 shows a U phase,
9 shows a control process when switching is performed for one of the V phase and the W phase.

First, it is determined whether or not the upper and lower arms are short-circuited by switching of another phase (step 10).
1). When the upper and lower arms are short-circuited, even if switching is performed as it is, zero voltage switching is performed, so that phase switching is performed (step 102).
If the upper and lower arms are not short-circuited, the upper and lower arms in that phase are short-circuited (step 103). After this,
Upper and lower arm voltage V _PN detected by voltage detection circuit 15
It is determined whether or not has become a negative voltage (step 10
4). Then, when the voltage _VPN between the upper and lower arms becomes a negative voltage, the main switching element that is turned off is turned off (step 105). In this way, switching in a certain phase is completed.

In the above-described embodiment, the main switching element is switched when the voltage _VPN between the upper and lower arms becomes a negative voltage. It is also possible to detect that the voltage is negative and turn off the main switching element. In this case, as shown in FIG. 5A, the voltage detection circuit 15
To 3f, the voltage between both ends of the main switching element which is turned off after the upper and lower arms are short-circuited is a negative voltage (a current flows through a flywheel diode connected in anti-parallel to the main switching element). Voltage of the main switching voltage when
When the voltage is 1.5 V), the main switching element is turned off. The voltage detection circuit 15 is composed of six voltage detection circuits for detecting the voltage between both ends of each of the main switching elements 3a to 3f. One of the voltage detection circuits is shown in FIG. Show. The voltage detection circuit 15a shown in FIG. 5B detects the voltage between both ends of the main switching element 3a.
It is configured to divide the voltage between both ends of the main switching element by two capacitors and output a detection voltage via a buffer. The voltage detection circuit 15 shown in FIG.
The configuration is the same as that of the voltage detection circuit 15a.

Instead of detecting the voltage between both ends of each of the main switching elements 3a to 3f, a current flowing through the main switching element to be turned off is detected by, for example, a current mirror circuit having the main switching element as a component. The main switching element to be turned off may be turned off when the current stops flowing to the main switching element to be turned off. FIG. 6 shows a specific circuit thereof. In this embodiment, a current detection circuit 18 is applied instead of the voltage detection circuit 15 shown in FIG. The current detection circuit 18 is connected to each main switching element 3a.
It comprises six current detection circuits for detecting the current flowing through .about.3f. These current detection circuits have a configuration other than the above-described current mirror circuit.
Means integrated with the main switching element as disclosed in Japanese Patent No. 34221 and Japanese Patent No. 2715399 can also be applied. In addition, a current flowing in a flywheel diode connected in anti-parallel to the main switching element to be turned off is detected by, for example, a current detecting diode connected in parallel to the flywheel diode, and a current flows through the flywheel diode. The main switching element that is switched off may be turned off when the switch is on.

The timing for turning off the main switching element to be turned off is not limited to the above-described detection of the voltage or current, and may be performed based on the elapsed time from the start of resonance. it can. That is, assuming that the capacitance of the resonance capacitor 6 is C and the inductance of the resonance reactor 7 is L, the period of the resonance is 2π (LC) ^1/2 , so that after starting the resonance, π (LC) ^{1 /} A time t until the absolute value of the resonance current becomes larger than the load current is set in a time between ² and 2π (LC) ^1/2 , and as shown in FIG. The main switching element, which is turned off when the time has elapsed, is turned off. FIG. 8 shows a control process of the control circuit 16 in this embodiment. Step 10
It is determined that the set time t has elapsed after the upper and lower arms are short-circuited to cause resonance in step 3 (step 1).
06), the main switching element to be turned off is turned off (step 105).

Since the switching loss can be reduced during the period in which the resonance current is a negative current, from the viewpoint of reducing the switching loss,
The above set time t is π (LC) ^1/2 <t <2π (L
C) It is only necessary to satisfy the relationship of ^1/2 . In the case of a circuit for determining the set time t and short-circuiting the upper and lower arms, FIG.
As shown in (1), there is no need to provide a voltage detection circuit or a current detection circuit in the resonance circuit 8 or the main switching elements 3a to 3f, and the power converter 2 can be simplified accordingly.

As shown in FIG. 1, a reactor 9a is connected in series with the DC voltage source 1, and a voltage clamp circuit 10 is connected.
When the voltage between the positive bus and the negative bus is clamped to a predetermined voltage, the current i _Lr flowing through the resonance reactor 7 and the current i flowing through the reactor 9a at the time of the clamping.
_Ld varies as shown in FIG. It is not preferable to start resonance when the current fluctuates.

Therefore, when such a current fluctuation is detected by the current i _Lc flowing through the voltage clamping reactor 10a, and resonance is started when the current i _Lc is zero or a minimum value, Resonance can be generated when the current is not fluctuating. in this case,
The current i _Lc flowing through the voltage clamping reactor 10a is detected by detecting the voltage between both ends of the voltage clamping reactor 10a by a voltage detection circuit, or directly detecting the current i _Lc flowing through the voltage clamping reactor 10a by a Hall element or the like. You can do it. FIG. 10 shows a specific circuit in this case. This circuit differs from the circuit shown in FIG. 9, for example, in that a current detection circuit 19 for detecting a current i _LC flowing through the voltage clamping reactor 10a is provided.
The current detection circuit 19 detects the current i _LC and controls the control circuit 1
At 6, it is determined whether the current i _LC is minimum or zero, and the upper and lower arms are short-circuited.

The timing of upper and lower arm short circuits during voltage clamping will be specifically described with reference to FIG. Note that the current i _LC shown in FIG. 11 is shown as the magnitude of the current value. In this figure, the current i _LC is a current that oscillates due to the action of the resonance circuit 8, but is a current that attenuates due to the resistance. The state where the current i _LC is zero or a minimum value is defined as times t ₁ , t ₂ , t _{3 to} t _{4 in the} graph.
It is. For example, a switching command by a PWM signal,
That is, when the upper / lower arm short-circuit command is generated between times t ₁ and t ₂ , the main switching element for the upper / lower arm short circuit is switched at time t ₂ when the current i _LC has the minimum value following the command. . When the upper and lower arm short-circuit command is generated between times t ₂ and t ₃ , the current i
_LC performs switching of the main switching element for the upper and lower arm short circuit in a period of time t ₃ ~t ₄ becomes zero. This can reduce the switching loss of the main switching element when the upper and lower arms are short-circuited. That is, when the current i _LC is large, when the main switching element is switched, a current based on the current i _LC flows instantaneously through the main switching element, causing a loss. However, when the current i _LC has a minimum value or zero. In such a case, switching can be performed to minimize the loss. FIG. 12 shows a control process of the control circuit 16 in this embodiment. In this control process, it is determined whether or not the current i _Lc has become zero or a minimum value based on the current i _Lc flowing through the voltage clamping reactor 10a detected by the above-described voltage or current detection means (step 107). ), The upper and lower arms are short-circuited when the current i _Lc becomes zero or a minimum value (step 103). In step 108, it is determined whether or not the timing to switch off has been reached by any of the methods shown in FIGS. 4, 5, and 8.

FIG. 13 is a detailed circuit diagram of the current detection circuit 19 described above. A current flowing through the voltage clamp circuit 10 is detected by, for example, a current sensor 191 composed of a Hall element, and is converted into a voltage by a voltage converter 192. The voltage is a signal proportional to the current. The signal is input to a differential operation circuit 193 using an operational amplifier. The output signal of this circuit becomes a differential signal of the current, and becomes a positive value or a negative value depending on the gradient of the current. In this case, when the minimum value is exceeded, the output signal from the differential operation circuit 193 changes from negative to positive, and the output of the comparison operation unit 194 switches from low to high. The rising edge detection circuit 195 detects the signal switched from low to high from the comparison operation unit 194, and detects the minimum value.

The control circuit 16 can also be configured as follows. FIG. 14 shows a specific circuit, and FIG. 15 shows signal waveforms at various parts in the circuit.
The control circuit 16 receives the input signal from the gate signal generation circuit 14, that is, the gate signal generation circuit 14a shown in FIG.
14f, the upper and lower arm gate signals of the U, V, and W phases (U ⁺ , U ⁻ , V ⁺ , V ⁻ ,
(Shown as W ⁺ , W ⁻ )), and a pulse signal for outputting a short-circuit signal for short-circuiting the upper and lower arms by a signal from the gate signal switching timing detector 161 for detecting a gate signal switching timing based on the signal. Generation circuit section 162
When the output signal at the OR logic of the input signal from the signal and the gate signal generating circuit 14 from the pulse signal generating circuit ^{162 U +, U -, V} +, V -, W +, W - a drive circuit 17 , And an OR circuit section 163 for output to

Gate signal switching timing detector
161 is the input signal U⁺, U^-, V ⁺, V^-, W⁺, W
^-One that generates a pulse signal at the rising timing of
Equipped with shot multivibrators 161a to 161f
And one-shot multivibrators 161a-1
61f, a pulse signal is output,
The circuit 161g receives a pulse signal indicating the switching timing.
Output a signal. The pulse signal generation circuit 162 includes a latch
Circuit 162a, and outputs from the OR circuit 161g.
A high-level short-circuit signal is detected when the rise of the force signal is detected.
Is output. The short-circuit signal from the latch circuit 162a
Are OR circuits 163a to 163a in the OR circuit section 163
The signal is output to the drive circuit 17 via 3f. The result
As a result, all the main switching elements 3 in the power converter 2
a to 3f are turned on, and the upper and lower arms are short-circuited.

The pulse signal generating circuit section 162 includes one-shot multivibrators 162b and 162c. The one-shot multivibrator 162b has a low level for a certain period at the rising timing of the output signal from the OR circuit 161g. The one-shot multivibrator 162c outputs a pulse signal that has a low level for a certain period at the rising timing of the output signal from the one-shot multivibrator 162a. Then, when a low-level signal is input to the CLR terminal that is low active, the latch circuit 162a changes its output signal to low level. Therefore, as shown in FIG. 15, when any of the input signals U ⁺ , U ⁻ , V ⁺ , V ⁻ , W ⁺ , and W ⁻ changes to a high level, the pulse signal generation circuit 162 outputs a signal for a certain period of time. A short-circuit signal of a high level is output by t, and all the main switching elements 3a to 3f in the power converter 2 are turned on to short-circuit the upper and lower arms.

The short-circuit time t is set in the same manner as the set time t shown in FIG. 8, and the short-circuit of the upper and lower arms is released depending on the time. However, also in this embodiment, as in the case shown in FIGS. 1, 4, and 5, the short circuit can be released when the voltage _VPN between the upper and lower arms becomes negative. In the above-described embodiment, the three phases are collectively short-circuited at the time of switching. However, any one phase or any two phases may be short-circuited.

In the all-phase short-circuit in which the three phases are collectively short-circuited as in the above-described embodiment, since the resonance current flows through each phase by １ ／, the heat generation due to the resistance component of the element of each phase is reduced. (Heat generation = resistance component × resonance current × resonance current). In addition, the resonance current peak value of the switching element of each phase is 1 /
3, the current stress can be reduced. In addition, the control of the short circuit is simpler than the short circuit control of each phase, so that the control is simple.

In the various embodiments described above, the reactor 9a is used as the overcurrent prevention means or the short-circuit prevention means, but the switching means 9b may be used as shown in FIG. in this case,
The switching means 9b is controlled by the control circuit 16 to be turned off at least during a period from before the resonance is started until the main switching element to be turned off is turned off. Specifically, in the case of the control processing shown in FIGS.
Is provided, and after step 105, a step of turning on the switching means 9b is provided. Note that a unidirectional or bidirectional semiconductor element can be used as the switching means 9b. In this embodiment, as the voltage clamp circuit 10, the anode is connected to the power conversion unit 2 side, and the cathode is the DC voltage source 1
Is connected to the diode 10c.

When a semiconductor element having a high withstand voltage is used as the main switching elements 3a to 3f, the configuration can be made without the voltage clamp circuit 10. However, when an AC rotating machine that performs regenerative braking is used as the load 5, it is necessary to supply a current from the power conversion unit 2 to the DC power supply 1 during regenerative braking. A bidirectional semiconductor element such as a transistor is used. Similarly, in the configuration shown in FIG. 1, when a semiconductor device having a high withstand voltage is used as the main switching elements 3a to 3f, the configuration can be made without the voltage clamp circuit 10.

The voltage clamp circuit 10 can be configured as shown in FIG. In this case, the voltage clamp circuit 10 includes a second DC voltage source 10 d connected in series to the DC voltage source 1, and an anode connected to the power converter 2.
It has a diode 10e connected to the side and a cathode connected to a second DC voltage source 10d. In such a configuration, the voltage to be clamped is increased by the voltage of the second DC voltage source 10d, and the period during which the power is regenerated by clamping is shortened. Therefore, driving when the load 5 is driven becomes easier. Further, the configuration may be such that the second DC voltage source 10d is omitted depending on the use situation.

Further, as the voltage clamp circuit 10,
It can be configured as shown in FIG. in this case,
The voltage clamp circuit 10 includes a large-capacity capacitor 10f connected in series to the DC voltage source 1, a diode 10g having an anode connected to the power converter 2 side and a cathode connected to the capacitor 10f, and a capacitor 10f at the time of clamping.
It has a switching means 10h for charging and discharging f. In such a configuration, at the time of clamping, power is regenerated to the capacitor 10f via the diode 10g and the capacitor 10f is charged. This charging increases the potential of the capacitor 10f. Is turned on to discharge the capacitor 10f. That is, the capacitor 10f is charged and discharged at the time of clamping. The charging period and the discharging period need to be equal, and as described above, charging is performed in the first half of the clamping time and discharging is performed in the latter half of the clamping time, and charging and discharging are repeated every predetermined time during the clamping. It may be. In this case, ON / OFF of the switching means 10h is controlled by the control circuit 16. Note that a semiconductor element can be used as the switching means 10h.

FIG. 19 shows a circuit in which a smoothing capacitor 11 is provided between the DC voltage source 1, the resonance circuit 8, and the power converter 2. This is because when the DC voltage source 1 is arranged at a distance from the power conversion unit 2, the power conversion unit 2 can supply the power required by the power conversion unit 2 without delay.
It is placed near. In this figure, the control circuit and the like are not shown.

The power conversion unit 2 is not limited to the one having the above-described configuration, but is similarly applicable to multi-level power conversion such as three-level power conversion in which each of the upper arm and the lower arm is composed of two main switching elements. Can be applied.
Further, the present invention is not limited to the multi-phase type, and can be similarly applied to a single-phase type as shown in FIG. Although various embodiments have been described above, the feature of the present invention is that the resonance circuit 2
In addition, it can be said that zero current switching by resonance using the short-circuit state of the upper and lower arms of the main switching elements 3a to 3f of the power conversion unit. In contrast to this basic configuration, short-circuit prevention means (or current prevention means) for preventing an excessive current from flowing through the upper and lower arms when the upper and lower arms are short-circuited.
The voltage clamp circuit 10 includes a coupling reactor for voltage clamping, a diode, a power supply + diode, a capacitor + switch +
There are diodes and these various combinations are possible. However, when the short-circuit prevention means is a switch, a coupling reactor cannot be used as a voltage clamp circuit.
Means for determining the switching timing of the main switching element has been described in various examples such as detection of the voltage across the resonance circuit, detection of the voltage or current of each main switching element, detection of each FWD (diode) current, and time control. It is possible to combine the prevention means and the voltage clamp circuit as appropriate.

A short-circuit preventing means, a voltage clamp circuit,
The switching timing determining means is not limited to the above-described one, and any other configuration may be used as long as it performs its function.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a resonance type power converter according to one embodiment of the present invention.

FIG. 2 is a diagram showing a specific circuit configuration of a control unit 13 in FIG.

FIG. 3 is a diagram showing signal waveforms of respective parts for one phase shown in FIGS. 1 and 2;

FIG. 4 is a flowchart illustrating a control process of a control circuit 16 according to another embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a resonance type power converter according to another embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of a resonance-type power conversion device according to another embodiment of the present invention.

FIG. 7 is a waveform chart for explaining another embodiment of the present invention.

FIG. 8 is a flowchart illustrating a control process of a control circuit 16 according to another embodiment of the present invention.

FIG. 9 is a diagram showing a configuration of a resonance type power converter according to another embodiment of the present invention.

FIG. 10 is a diagram showing a configuration of a resonance type power converter according to another embodiment of the present invention.

FIG. 11 is a waveform chart for explaining another embodiment of the present invention.

FIG. 12 is a flowchart showing a control process of a control circuit 16 according to another embodiment of the present invention.

13 is a diagram showing a specific circuit configuration of a current detection circuit 19 in FIG.

FIG. 14 is a diagram showing a configuration of a control circuit 16 according to another embodiment of the present invention.

15 is a diagram showing signal waveforms at various parts in the control circuit 16 shown in FIG.

FIG. 16 is a diagram showing a configuration of a resonance type power converter according to another embodiment of the present invention.

FIG. 17 is a diagram showing a configuration of a resonance type power converter according to another embodiment of the present invention.

FIG. 18 is a diagram showing a configuration of a resonance type power converter according to another embodiment of the present invention.

FIG. 19 is a diagram showing a configuration of a resonance type power converter according to another embodiment of the present invention.

FIG. 20 is a diagram showing a configuration of a resonance type power converter according to another embodiment of the present invention.

FIG. 21 is a diagram showing a configuration of a conventional resonance type power converter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... DC voltage source, 2 ... Power conversion part, 3a-3f ... Main switching element, 4a-4f ... Flywheel diode, 5 ... Load, 6 ... Resonant capacitor, 7 ... Resonant reactor, 8 ... Resonant circuit, 9 ... reactor, 10 ... voltage clamp circuit, 10a ... reactor for voltage clamp, 10
b: diode, 13: control unit, 14: gate signal generation circuit, 15: voltage detection circuit, 16: control circuit, 17: drive circuit.

Claims (25)

[Claims] 1. A main switching element (3a to 3f) and a plurality of flywheel diode means (4a to 4f) connected in anti-parallel to the main switching element for each phase between a positive bus and a negative bus. It is configured to be connected in series,
A power converter (2) provided between the DC voltage source (1) and the load (5) for performing power conversion; and a resonance capacitor (6) connected in series between the positive bus and the negative bus. And a resonance circuit (8) having a resonance reactor (7), and control means (1) for performing the power conversion by switching the plurality of main switching elements in a predetermined pattern.
3) wherein the control means turns on the main switching element, which has been turned off, of the plurality of main switching elements connected in series between the positive bus and the negative bus in the phase to be switched. When the resonance is started by the resonance capacitor and the resonance reactor, and the resonance current becomes larger than the load current due to the resonance, and the current flows through the flywheel diode means connected in anti-parallel to the main switching element that switches off. And turning off the main switching element which is turned off. 2. The control means detects that a voltage between the positive bus and the negative bus is a negative voltage,
2. The resonance type power converter according to claim 1, wherein the main switching element for switching off is turned off. 3. The control means detects that the voltage across the main switching element for switching off is a negative voltage and turns off the main switching element for switching off. Claim 1
3. The resonance type power converter according to claim 1. 4. The apparatus according to claim 1, wherein said control means detects a state in which no current flows through said main switching element to be turned off, and turns off said main switching element to be turned off. 3. The resonance type power converter according to claim 1. 5. The control means detects a state in which a current is flowing through flywheel diode means connected in anti-parallel to the main switching element to be turned off, and turns off the main switching element to be turned off. The resonance type power converter according to claim 1, wherein 6. The resonance according to claim 1, wherein the control unit turns off the main switching element to be turned off when a predetermined time has elapsed since the start of the resonance. Type power converter. 7. A main switching element (3a to 3f) and a plurality of flywheel diode means (4a to 4f) connected in anti-parallel to the main switching element for each phase between a positive bus and a negative bus. It is configured to be connected in series,
A power converter (2) provided between the DC voltage source (1) and the load (5) for performing power conversion; and a resonance capacitor (6) connected in series between the positive bus and the negative bus. And a resonance circuit (8) having a resonance reactor (7); and turning on a plurality of main switching elements connected in series between the positive bus and the negative bus in a phase to be switched, thereby forming the resonance capacitor and the resonance. Control means (13) for starting resonance by the reactor for use and turning off a main switching element to be turned off when a voltage between the positive bus and the negative bus becomes substantially 0 V due to the resonance. A resonance type power converter. 8. When a plurality of main switching elements connected in series to the DC voltage source and connected in series between the positive bus and the negative bus are turned on, an overcurrent flows through the main switching elements. The resonance type power converter according to any one of claims 1 to 7, further comprising an overcurrent prevention means (9) for preventing the occurrence of the electric current. 9. The reactor (9)
9. The resonance type power converter according to claim 8, wherein a) is satisfied. 10. The reactor has an inductance value such that when the resonance is performed by the resonance capacitor and the resonance reactor, resonance is not generated by the reactor, the resonance capacitor, and the resonance reactor. The resonance type power converter according to claim 9, wherein: 11. The inductance components Lm and L of the reactor, the resonance reactor, and the load, respectively.
The resonance type power converter according to claim 10, wherein d and Lr satisfy a relationship of Lm>Ld> Lr. 12. A voltage clamp circuit (10) having a voltage clamping reactor (10a) coupled to the reactor and clamping a voltage between the positive bus and the negative bus to a predetermined voltage. The resonance type power converter according to any one of claims 9 to 11, wherein: 13. The resonance type power converter according to claim 12, wherein the voltage clamp circuit is configured to regenerate power to the DC voltage source by a current flowing through the voltage clamping reactor. apparatus. 14. The resonance according to claim 13, wherein the control unit detects the state in which the current flowing through the voltage clamping reactor is zero or a minimum value, and starts the resonance. Type power converter. 15. The overcurrent prevention unit turns off a connection between the DC voltage source and the power conversion unit at least during a period from before starting the resonance to turning off the main switching element that is turned off. 9. Resonant power converter according to claim 8, characterized in that it is a switching means (9b). 16. The resonance type power converter according to claim 15, wherein said switching means is capable of flowing a current bidirectionally. 17. The resonance according to claim 1, further comprising a voltage clamp circuit for clamping a voltage between the positive bus and the negative bus to a predetermined voltage. Type power converter. 18. The voltage clamp circuit includes a diode (10c) having an anode connected to the power converter and a cathode connected to the DC voltage source. 18. The resonance type power converter according to item 17. 19. The voltage clamp circuit includes a second DC voltage source connected in series to the DC voltage source.
And a diode (10) having an anode connected to the power converter and a cathode connected to the second DC voltage source.
2. The method according to claim 1, wherein the method comprises:
8. The resonance type power converter according to 7. 20. The voltage clamp circuit, comprising: a capacitor (10f) connected in series to the DC voltage source; and a diode (10g) having an anode connected to the power converter and a cathode connected to the capacitor. 18. The resonance type power converter according to claim 17, further comprising switching means (10h) for charging and discharging the capacitor at the time of clamping. 21. A single resonance circuit (8) having a resonance capacitor (6) and a resonance reactor (7), and a power converter (2) having a plurality of main switching elements (3a to 3f). Short-circuit the arm to generate resonance,
A resonance type power converter in which commutation is performed by switching a main switching element of the power converter at the time of the resonance. 22. A main switching element (3a to 3f) and a flywheel diode means (4) connected in anti-parallel to the main switching element in each of the upper and lower arms.
a to 4f), a power conversion unit (2) configured with: a resonance circuit (8) having a resonance capacitor (6) and a resonance reactor (7) connected in series; and the upper and lower arms Is short-circuited to generate resonance by the resonance capacitor and the resonance reactor, and the resonance causes a current to flow through the flywheel diode means connected in anti-parallel to the main switching element that performs switching in the power conversion unit (2). Control means (1) for switching the main switching element when flowing.
3) A resonance type power conversion device characterized by comprising: 23. A control system comprising: a timing detecting means for detecting a timing for switching the main switching element; and a means for short-circuiting the upper and lower arms at the time of detecting the timing. The resonance type power converter according to claim 22. 24. The resonance type power supply according to claim 22, wherein said control means turns on all main switching elements in said power conversion section to short-circuit said upper and lower arms. Conversion device. 25. The power supply according to claim 21, further comprising a short-circuit preventing means for preventing a short circuit between the DC voltage source and the power converter when the main switching element is switched. The resonance-type power converter according to any one of the above.