JPH04308474A - Inverter unit - Google Patents

Abstract

PURPOSE:To suppress overvoltage and the like by connecting reactors connected between a DC bus and an arm, and a series circuit of absorving capacitors, a snubber diode and a snubber capacitor, in parallel with the arm. CONSTITUTION:Upon turn OFF of a GTO 1A, load current I is interrupted and a current flows through an absorbing capacitor (AC) 21A, a snubber capacitor(SC) 6 and an output terminal P. At that time point, current produced by the energy of a reactor (LA) 2A flows through AC 21A, 21B, LA 2B. Furthermore, a free wheel diode(FD) 10B is conducted. When the energy of the LA 2A is absorbed by the AC 21A, 21B, the AC 21A, 21B are overcharged thus completing commutation of the load current I from the GTO 1A to the FD 10B. Subsequently, overcharged energy of the AC 21A, 21B is collected to the RC 23 through a path of the LA 2B, AC 21B, a collecting capacitor(RC) 23, AC 21A, LA 2A. An energy regenerative circuit 24 then takes out energy from the RC 23 and regenerates to a DC power supply 11.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a snubber circuit for suppressing overvoltage and current/voltage increase rate applied to a semiconductor element, an energy recovery circuit for absorbing the energy of this snubber circuit, and an energy recovery circuit for this energy recovery circuit. The present invention relates to an inverter device including an energy regeneration circuit that regenerates energy into a DC power source.

0002

2. Description of the Related Art In inverter devices using semiconductor elements, a snubber circuit is always provided to prevent damage caused by overvoltage, voltage rise, or current rise applied to the semiconductor elements.

The structure of a conventional example provided with a typical snubber circuit will be explained with reference to FIG. FIG. 9 is a circuit diagram showing one arm of a conventional inverter device.

In FIG. 9, the conventional inverter device is
Using GTO thyristors 1A and 1B as semiconductor elements,
Series snubber circuits 5A, 5B composed of reactors 2A, 2B, diodes 3A, 3B, and resistors 4A, 4B for suppressing the rate of increase in current; snubber capacitors 6A, 6B for suppressing the rate of voltage increase; It has parallel snubber circuits 9A and 9B configured from snubber diodes 7A and 7B and resistors 8A and 8B. In addition, 10A, 1
0B is a freewheel diode connected in antiparallel to GTO 1A and 1B, and 11 is a DC power supply.

Next, the operation of the above-mentioned conventional example will be explained with reference to FIG. When the GTOs 1A and 1B are switched, the energy storage elements in each snubber circuit, that is, the reactors 2A and 2B, the snubber capacitor 6A,
All the energy stored in 6B is transferred to resistors 4A, 4B, 8
Consumed by A and 8B. This energy loss is GTO
This increased significantly due to an increase in the switching frequency of 1A and 1B and an increase in inverter capacity, leading to a decrease in efficiency.

[0006] In order to reduce the above-mentioned energy loss,
There is another conventional inverter device that regenerates the energy stored in each snubber circuit to the DC power supply 11 by a regeneration circuit 12 using a transformer. FIG. 10 is a circuit diagram showing another conventional inverter device.

FIG. 10 shows the operation of another conventional inverter device.
, will be explained with reference to FIGS. 11 and 12. 11 and 12 are diagrams showing commutation operations of other conventional inverter devices.

It is assumed that the load current I flows in the direction of the arrow in FIG. 10, that the load has a large inductance component, and that the vector of the load current I does not change during the switching period. Then, as an inverter operation, G
The load current I is commutated between the TO1A and the freewheel diode 10B. The commutation operation of the inverter device when the GTO 1A is switched from on to off is shown in FIGS. 11(a)→(b)→(c)→(d)→(e). In addition, the commutation operation of the inverter device when GTO1A is switched from off to on is shown in Fig. 12(a) → (b).
)→(c)→(d)→(e).

In both FIGS. 11 and 12, the primary side of the transformer 13 is connected to the discharge paths of the snubber capacitors 6A and 6B and the discharge paths of the reactors 2A and 2B, and current is allowed to flow through the primary side. Therefore, the turns ratio n of the transformer 13 is
Accordingly, a current flows to the secondary side, and the energy of the snubber circuit is regenerated to the DC power supply 11.

However, in other conventional inverter devices, when the energy of the snubber circuit is regenerated through the transformer 13 every time the GTOs 1A and 1B switch, the exciting current flowing to the secondary side of the transformer 13 The iron core in the transformer is magnetized by this, but it is necessary to provide a reset time to prevent iron core saturation, which is a limiting factor in increasing the frequency of the inverter device.

[0011] Furthermore, as the voltage of the DC power supply 11 increases due to the increase in the capacity of the inverter device, the transformer 13 becomes larger and an iron core with a higher maximum magnetic flux density is required, leading to an increase in cost. Furthermore, as the frequency of the inverter device becomes higher, increased loss or noise in the transformer 13 becomes a problem.

By the way, the conventional inverter device is provided with an overvoltage absorption circuit 17 as shown in FIG. 13 in order to suppress overcharging of the snubber capacitor due to the energy of the wiring inductance 16 of the positive and negative DC buses. The wiring inductance 1 is connected to the capacitor 18 of this overvoltage absorption circuit 17.
It performs its function by absorbing the energy of 6 and dissipating it by the resistor 19.

[0013]

[Problems to be Solved by the Invention] In the conventional inverter device as described above, the energy of the snubber circuit is consumed by the resistor, so there is a problem that the loss is large and it is difficult to increase the capacity and frequency. was there.

[0014] In other conventional inverter devices that take into account the energy regeneration of the snubber circuit by the transformer 13, it is necessary to provide a reset time for the transformer 13, which limits the increase in frequency and increases the capacity of the transformer when increasing the capacity. There are problems in that the size and cost increase, and as the frequency increases, both loss and noise increase.

Another problem is that a circuit is required to suppress overcharging of the snubber capacitor due to the wiring inductance 16 of the positive and negative DC buses.

The present invention was made in order to solve the above-mentioned problems, and an object of the present invention is to obtain an inverter device that can realize high efficiency and high frequency.

[0017]

[Means for Solving the Problems] An inverter device according to the invention of claim 1 is provided with the following means. [1] A reactor connected between the DC bus and the arm to suppress the rate of increase in current, an absorption capacitor to suppress overvoltage, a snubber diode, and a snubber capacitor to suppress the rate of voltage increase. , and a snubber circuit in which a circuit in which a snubber capacitor is connected in series is connected in parallel to the arm.

[0018] The inverter device according to the invention of claim 2 includes:
It is equipped with the following means. [1] An energy recovery circuit that includes a recovery capacitor that recovers excess energy from an absorption capacitor and a diode that determines the charging polarity of the recovery capacitor. [2] An energy regeneration circuit that extracts energy from the recovery capacitor and regenerates it into a DC power source.

[0019]

In the first aspect of the invention, the snubber circuit suppresses the rate of increase in current, overvoltage, and rate of voltage increase.

In the second aspect of the invention, the energy recovery circuit recovers excess energy from the absorption capacitor. Furthermore, the energy regeneration circuit extracts energy from the recovery capacitor and regenerates it into the DC power supply.

[0021]

[Example] Example 1. The configuration of Embodiment 1 of this invention will be described with reference to FIG. FIG. 1 is a circuit diagram showing one arm of Embodiment 1 of the present invention.

In FIG. 1, the first embodiment of the present invention uses GTO thyristors 1A and 1 as semiconductor elements as in the conventional case.
Reactor 2A for suppressing the current increase rate using B
, 2B, snubber capacitor 6 for suppressing the rate of voltage increase, snubber diodes 7A, 7B, absorption capacitors 21A, 21B for suppressing overvoltage, diodes 22A, 22B, and absorption capacitors 21A, 21B. It has a recovery capacitor 23 that recovers excess charge, and an energy regeneration circuit 24 that extracts energy from the recovery capacitor 23 and regenerates it to the DC power supply 11.

The absorption capacitors 21A and 21B are each always charged to a voltage that is half of the power supply voltage E, and their capacitance is sufficiently larger than that of the snubber capacitor 6 in order to reduce voltage fluctuations.

Furthermore, the relationship between the charging voltage polarity of the snubber capacitor 6 and the output voltage of the inverter device is shown in FIGS. 2(a) and 2(b). Note that the output terminal is indicated by P.

By the way, the snubber circuit of the present invention is composed of the reactors 2A, 2B, the snubber capacitor 6, the snubber diodes 7A, 7B, and the absorption capacitors 21A, 21B in the first embodiment of the present invention. In the first embodiment, the recovery circuit is a diode 22A.
, 22B and a recovery capacitor 23.

Next, the operation of the first embodiment described above will be explained. Note that the load has a large inductance component, and the load current I during the switching period of GTO1A and 1B
Assume that the vector of does not change.

Assuming that the direction of the arrow in FIG. 1 is the positive polarity of the load current I, when the load current I is positive, GTO1
The switching operation of A causes the load current I to be commutated between the GTO 1A and the freewheel diode 10B. In the case of negative polarity, GTO1B of load current I and freewheeling diode 1 are connected by the switching operation of GTO1B.
Commutation with 0A is performed. Since this commutation operation has symmetry, only the former case will be explained below.

The off-operation and on-operation of the GTO 1A will be explained in order. The off operation of GTO1A is as follows: GTO1A and 1B are on and off, respectively, and the potential of the output terminal P is the power supply voltage E,
Load current I is transferred from DC power supply 11 to reactor 2A, GTO
When the current is flowing through 1A and the output terminal P, the initial state is a state in which the snubber capacitor 6 is charged to E/2 with the output terminal P side as the positive electrode.

When the GTO 1A is turned off, the load current I is cut off, and the current is passed through the recovery capacitor 21A,
The current flows through the snubber capacitor 6 and the output terminal P, and the snubber capacitor 6 is charged with the opposite polarity. When the snubber capacitor 6 is charged to E/2 with the output terminal P side set as a negative electrode, the potential of the output terminal P becomes 0 (zero).

[0030] The current due to the energy stored in reactor 2A at that point continues to flow through the path of reactor 2A, absorption capacitors 21A and 21B, and reactor 2B. Furthermore, the freewheel diode 10B becomes conductive. The energy of reactor 2A is absorbed by capacitor 21A,
21B, absorption capacitors 21A and 2
1B is in an overcharged state, and the GTO of load current I
The commutation from 1A to freewheeling diode 10B is completed.

Next, reactor 2B, absorption capacitor 2
1B, recovery capacitor 23, absorption capacitor 21A, and reactor 2A, the energy corresponding to the overcharge of absorption capacitors 21A and 21B is recovered to recovery capacitor 23. Furthermore, energy is extracted from the recovery capacitor 23 by the energy regeneration circuit 24 and regenerated to the DC power supply 11. Once the commutation from GTO1A to freewheeling diode 10B is completed, the state will not change even if GTO1B is subsequently switched. This series of operations is shown in the order of FIG. 3(a)→(b)→(c)→(d)→(e).

Next, the on operation of GTO1A is performed by turning on GTO1A.
Both A and 1B are off, the potential of output terminal P is 0, the load current I is reactor 2B, and freewheel diode 10B.
When the current is flowing through the output terminal P, the initial state is a state in which the snubber capacitor 6 is charged to E/2 with the output terminal P side as the negative electrode.

When the GTO 1A is turned on, a current starts to flow from the DC power supply 11 through the reactor 2A and the GTO 1A, and soon the current causes the freewheel diode 1 to
The current flowing in 0B becomes 0, and the current in GTO 1A reaches the load current I.

Furthermore, the current of the GTO 1A maintains the load current I, and the current of the reactor 2A increases, but the increased current is transferred to the snubber capacitor 6 and the recovery capacitor 21B.
, flows through the reactor 2B, and the snubber capacitor 6 is charged with the opposite polarity.

When the snubber capacitor 6 is charged to E/2 with the output terminal P side as the positive electrode, the potential of the output terminal P becomes the power supply voltage E. At that point, the energy stored in the reactors 2A, 2B causes a current equivalent to the load current I or more to flow through the reactor 2A, recovery capacitors 21A, 21B,
It continues to flow through the path of reactor 2B.

The energy of the reactors 2A and 2B is absorbed by the absorption capacitors 21A and 21B, and the current flowing through them decreases. When all the energy of the reactor 2B is absorbed, the absorption capacitors 21A and 21B become overcharged. Also, the current of the reactor 2A settles to the load current I, and the freewheeling diode 1 of the load current I
The commutation from 0B to GTO1A is completed.

Next, reactor 2B, absorption capacitor 2
1B, recovery capacitor 23, absorption capacitor 21A, reactor 2A path, absorption capacitors 21A, 21B
The energy corresponding to the overcharge is recovered by the recovery capacitor 23. Furthermore, the energy regeneration circuit 24 extracts energy from the recovery capacitor 23 and regenerates it to the DC power supply 11. This series of operations is shown in Figure 4(a)→(
They are shown in the order of b) → (c) → (d) → (e) → (f).

The energy regeneration circuit 24, which has the function of extracting energy from the recovery capacitor 23 and regenerating it to the DC power supply 11, has a book boost type as shown in FIG. 5, or a flyback type DC-type as shown in FIG. A DC converter can be applied. Furthermore, an energy regeneration circuit as shown in FIG. 7 can also be applied.

Next, the energy stored in the wiring inductance 16 existing in the DC bus will be described. Equivalently, a filter circuit can be constituted by the absorption capacitors 21A and 21B arranged in series between the wiring inductance 16 and the DC bus. Therefore, this filter circuit reduces the placement inductance 16
The energy stored in the absorbing capacitors 21A and 21B
can be absorbed into. Naturally, the energy is similarly recovered by the recovery capacitor 23 and is transferred to the energy regeneration circuit 24.
It will be regenerated by

Embodiment 1 of the present invention, as described above,
High efficiency can be achieved because there is no resistance element in the inverter device, and a snubber circuit that integrates a series snubber, a parallel snubber, and an overvoltage absorption function is provided, so the snubber capacitor 6 can be shared by the positive and negative arms. This has the effect of reducing the number of parts and making it possible to use semiconductor elements with lower voltage ratings than before. In addition, a recovery capacitor 23 is provided to recover the energy stored in the snubber circuit, and the energy stored in the recovery capacitor 23 is regenerated to the DC power supply 11 by an energy regeneration circuit 24 such as a DC-DC converter. This has the effect of increasing the frequency.

Example 2. FIG. 8 is a circuit diagram showing a case where the first embodiment of the present invention is applied to three phases. in this case,
The configuration is such that a recovery capacitor 23 and an energy regeneration circuit 24 for each phase are provided in common. This has the effect of reducing the number of component parts.

[0042]

As explained above, the invention according to claim 1 includes a reactor connected between the DC bus and the arm to suppress the rate of increase in current, an absorption capacitor to suppress overvoltage, a snubber diode, and a voltage The invention according to claim 2, further comprising a snubber circuit having a snubber capacitor for suppressing the rate of increase, wherein a circuit in which the absorption capacitor, the snubber diode, and the snubber capacitor are connected in series is connected in parallel to the arm. As explained above, the energy recovery circuit includes a recovery capacitor that recovers excess energy from the absorption capacitor, a diode that determines the charging polarity of the recovery capacitor, and extracts energy from the recovery capacitor and regenerates it into a DC power source. Since it is equipped with an energy regeneration circuit, it is possible to realize high efficiency and high frequency.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one arm of a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing the relationship between charging voltage polarity and output voltage of the snubber capacitor according to the first embodiment of the present invention.

FIG. 3 is a circuit diagram showing a commutation operation in Example 1 of the present invention.

FIG. 4 is a circuit diagram showing a commutation operation in Example 1 of the present invention.

FIG. 5 is a circuit diagram showing an example of an energy regeneration circuit according to the first embodiment of the present invention.

FIG. 6 is a circuit diagram showing an example of an energy regeneration circuit according to the first embodiment of the present invention.

FIG. 7 is a circuit diagram showing an example of an energy regeneration circuit according to the first embodiment of the present invention.

FIG. 8 is a circuit diagram showing a case where the first embodiment of the present invention is applied to three phases.

FIG. 9 is a circuit diagram showing one arm of a conventional inverter device.

FIG. 10 is a circuit diagram showing one arm of another conventional inverter device.

FIG. 11 is a diagram showing a commutation operation of another conventional inverter device.

FIG. 12 is a diagram showing a commutation operation of another conventional inverter device.

FIG. 13 is a circuit diagram showing an overvoltage absorption circuit of a conventional inverter device.

[Explanation of symbols]

1A, 1B GTO thyristor 2A, 2B Reactor 6 Snubber capacitor 7A, 7
B Snubber diode 10A, 10B Freewheel diode 11
DC power supply 21A, 21B Absorption capacitor 22A, 22B Diode

Claims (2)

[Claims] 1. An inverter device comprising a pair of semiconductor elements forming positive and negative arms between positive and negative DC busbars, and a freewheeling diode connected in antiparallel to the semiconductor elements, wherein the semiconductor element is connected between the DC busbar and the arm. The circuit includes a reactor for suppressing the current increase rate, an absorption capacitor for suppressing overvoltage, a snubber diode, and a snubber capacitor for suppressing the voltage increase rate, and the absorption capacitor, the snubber diode, and the snubber capacitor are connected in series. An inverter device comprising a snubber circuit connected in parallel to the arm. 2. An energy recovery circuit having a recovery capacitor that recovers excess energy from the absorption capacitor, a diode that determines charging polarity of the recovery capacitor, and energy regeneration that extracts energy from the recovery capacitor and regenerates it to a DC power source. The inverter device according to claim 1, further comprising a circuit.