JPH07231673A - Bridge circuit and inverter device - Google Patents

Abstract

PURPOSE:To make the voltage of a switch a divided voltage when outputting the potential on multiple levels by providing at least two or more clamp circuits consisting of a plurality of diodes connected in series, and clamping the potentials of the junctions of switch elements in series to the potentials of the junctions of power sources in series. CONSTITUTION:A DC power source consists of three power sources E1-E3 connected in series, and a positive arm and a negative arm consist of three pieces each of switch elements connected in series, where diodes are connected reversely in parallel, and a first clamp circuit consists of diodes D2.1-D2.4, and a second clamp circuit consists of diodes D1.1-D1.2. For example, when the switches S3a, S2a, S1a are turned on, the output voltage becomes V1, and an output current flows, when positive, to the course of S3a, S2a, and S1a, and, when negative, to the course of D1a, D2a, and D3a. This way, the four levels of the potentials V1 and V2 of the positive pole or negative pole of the DC power source or the potentials V2, V3, and V4 of the series junctions the power sources can be gotten.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilevel output inverter device and a bridge circuit.

[0002]

2. Description of the Related Art When converting DC power into AC power by pulse width modulation (hereinafter referred to as PWM), a multilevel output inverter device is used as an inverter that suppresses harmonic components. FIG. 10 shows a conventional bridge circuit used as a main circuit of a conventional inverter device of this type.

FIG. 10 shows the structure for one phase.
Three levels of output voltage can be generated per phase. In the figure, E ₁ and E ₂ are DC voltage sources, and S _{11 to} S
₁₄ is a switch element, D _{11 to} D ₁₆ are diodes, and OUT is an output terminal.

[0004] The output voltage of the output terminal OUT of the bridge circuit, the switch element S ₁₁ and S ₁₂ are turned on, next to voltages V ₁ when the switch element S ₁₃ and S ₁₄ is in the off state, the switch element S ₁₂ and S ₁₃ is turned on, switching elements S ₁₁ and S ₁₄
When the switch is off, the voltage becomes V ₂ and the switch element S ₁₃
And S ₁₄ are turned on and the switch elements S ₁₁ and S ₁₂ are turned off, the voltage becomes V ₃ and three-level output is obtained. By performing PWM control of these switch elements, the output voltage shown in FIG. 11 can be obtained.

FIG. 12 shows a conventional bridge circuit having another main circuit configuration (4 levels) of a multi-level output inverter. In the figure, E ₁ , E ₂ , and E ₃ are DC voltage sources, and S _{21 to} S
₂₆ is a switch element, D _{21 to} D ₃₂ are diodes, and OUT is an output terminal.

The output voltage of this bridge circuit becomes a voltage V ₁ when the switch elements S _{21 to} S ₂₃ are turned on and the switch elements S _{24 to} S ₂₆ are turned off, and the switch elements S _{22 to} S ₂₄ are turned on and the switch elements are turned on. When the elements S ₂₁ , S _25, and S ₂₆ are off, the voltage becomes V ₂ , the switch elements S _{23 to} S ₂₅ are turned on, and when the switch elements S ₂₁ , S _22, and S ₂₆ are off, the voltage becomes V ₃ .
The switch elements S _{24 to} S ₂₆ are turned on, and the switch elements S ₂₁ to
When S ₂₃ is off, the voltage becomes V ₄ and a 4-level output is obtained.

As described above, in order to obtain a multi-level voltage output, the DC power source of the inverter is connected in series with a plurality of voltage sources, and each switch element is turned on / off so that the potential at the connection point is also output. Controlled.

[0008]

In order to increase the high voltage and high capacity of the inverter device by using the conventional bridge circuit, a plurality of elements are connected in series for voltage sharing or a high voltage and large capacity element is used. There is a need.

However, if a large number of elements are connected in series, the load balance between the elements becomes a problem. On the other hand, since a high-voltage, large-capacity element cannot increase the switching frequency, it is difficult to perform high-frequency PWM control for improving the output waveform.

Further, even if the number of divisions of the DC voltage source is increased,
There is a problem that the load between the elements cannot be sufficiently balanced. The present invention has been made in order to solve the above problem. Even if the number of divisions of the DC voltage source is increased, one element is applied with the voltage of only one of the divided DC voltage sources. Even if you do not use PWM control by reducing the load on the element and increasing the number of output levels,
Another object of the present invention is to provide a bridge circuit and an inverter device that can easily improve the waveform even if the switching frequency of PWM control is lowered and can easily increase the capacity.

[0011]

[Means for Solving the Problems]

(1) As an invention corresponding to claim 1, a positive side arm and a negative side arm formed by connecting at least three or more switch elements in which diodes are connected in antiparallel are connected in series between a positive electrode and a negative electrode of a DC voltage source. Then, in the bridge circuit that outputs AC power from the intermediate point at the connection point of the positive side arm and the negative side arm, the same number of voltage sources as the number of series of the switching elements are connected in series to form the DC voltage source. , At least two or more clamp circuits each composed of a plurality of diodes connected in series are provided between the series connection points of the switch elements of the positive side arm and the negative side arm, which are located at the intermediate point as a starting point, The clamp circuit clamps the potential at the series connection point of the switch element to the potential at the series connection point of the voltage source.

(2) As an invention corresponding to claim 2, a first connection between the series connection points of the switch elements at the symmetrical positions closest to the positive electrode and the negative electrode of the DC voltage source is further provided.
Connecting the series connection points of a plurality of series-connected diodes of the clamp circuit to the series connection point of the voltage source,
The switch of the first clamp circuit connected to both ends of the voltage source located in the middle is a series circuit of two diodes and is located at the symmetrical position next to the positive electrode and the negative electrode of the DC voltage source. The series contacts of the plurality of series-connected diodes of the second clamp circuit connected between the series connection points of the elements are connected to the series connection point of the two diodes of the first clamp circuit.

(3) As an invention corresponding to claim 3, a first connection is provided between the series connection points of the switch elements at the symmetrical positions closest to the positive electrode and the negative electrode of the DC voltage source.
Connecting the series connection points of a plurality of series-connected diodes of the clamp circuit to the series connection point of the voltage source,
The switch of the first clamp circuit, which is connected to both ends of the voltage source located in the middle, is a series circuit of two diodes, and is located at the symmetrical position close to the positive electrode and the negative electrode of the DC voltage source. A series connection point of a plurality of diodes connected in series of a plurality of clamp circuits connected between the series connection points of the elements is sequentially connected to a series connection point of two diodes of the first clamp circuit and the plurality of clamp circuits. The diodes of the plurality of clamp circuits, which are connected to each other and are connected between the series connection points of the two diodes, are each configured by a series circuit of two diodes.

(4) As an invention corresponding to claim 4, further, a part of the switching elements of the positive side arm and the negative side arm, which are connected in series, are connected in parallel to increase the current carrying capacity.

(5) As an invention corresponding to claim 5, further, some of the diodes connected in series in the clamp circuit are connected in parallel to increase the current carrying capacity. (6) As an invention corresponding to claim 6, in the above-mentioned item (1), all the positive side or all the negative side or the positive side of the switch elements connected in series of the positive side arm and the negative side arm. A part of the switch elements connected in series to the arm and the negative side arm are made conductive, and the potential of the positive electrode or the negative electrode of the DC voltage source or the potential of the series connection point of the plurality of voltage sources of the DC voltage source is changed. Output to the intermediate point.

(7) As an invention corresponding to claim 7, the bridge circuit according to claim (1) is provided, and the DC voltage source used in the bridge circuit is a series circuit of a plurality of voltage-controlled voltage sources. Use an inverter device.

(8) As an invention corresponding to claim 8, there is provided an inverter device which comprises at least two or more bridge circuits according to item (1) and outputs single-phase or multi-phase AC power.

[0018]

[Action]

(1) In the invention corresponding to claim 1, at least four or more kinds of potentials are output at the intermediate point by a combination of ON / OFF of each switch element of the positive side arm and the negative side arm connected in series. can get. In this case, in the output state of each potential, the series connection point potential of the switch element in the off state is clamped to the series connection point potential of the voltage source through the series-connected diode circuit of the clamp circuit. The voltage of one of the voltage sources is applied to the switch element in the off state.

(2) In the invention according to claim 2, when the series connection point potential of the switch element in the off state is clamped to the series connection point potential of the voltage source, the second clamp circuit of the first clamp circuit is used. A series circuit of diodes and the second
It is clamped via the diode of the clamp circuit.

(3) According to a third aspect of the invention, when the series connection point potential of the switch element in the OFF state is clamped to the series connection point potential of the voltage source, the second clamp circuit of the first clamp circuit is used. Clamping is performed via a series circuit of the diodes and a series circuit of the two diodes of the plurality of clamp circuits.

(4) The invention according to claim 4 averages the power loss of the switch elements by connecting some of the switch elements in parallel. (5) The invention corresponding to claim 5 averages the power loss of the diodes by connecting some of the diodes in parallel.

(6) The invention according to claim 6 is characterized in that a part (the number equal to the total number of series elements of the positive side arm or the negative side arm) of the switching elements connected in series is made conductive. An arbitrary series connection point potential of the plurality of voltage sources is output to the intermediate point.

(7) The invention according to claim 7 maintains the voltage of each voltage source at a predetermined value by suppressing the voltage, and suppresses the voltage fluctuation due to the current flowing through the clamp circuit. (8) The invention according to claim 8 outputs multi-level potentials to the neutral point of each bridge circuit by PWM control, and outputs single-phase or multi-phase AC power between the neutral points.

[0024]

FIG. 1 shows a first embodiment of the bridge circuit of the present invention. In FIG. 1, E _{1 to} E ₃ are DC voltage sources, and S _1a to
S _3a , S _{1b to} S _3b are switching elements, and D _{1a to} D _3a , D _1b to
D _3b , D _{1,1 to} D _2,4 are diodes, OUT is an output terminal, and V _{1 to} V ₄ are potentials of the terminals of the DC voltage source. Further, the direction (arrow direction) in which the output current I _o flows from the output terminal toward the load is positive.

In the first embodiment, the DC voltage source is composed of three voltage sources E _{1 to} E ₃ connected in series, and the positive side arm and the negative side arm each have a switch element in which diodes are connected in anti-parallel.
Made into individual series, the first clamp circuit comprises a diode D _2,1 to D _{2, 4,} the second clamp circuit comprises a diode D _{1, 1,} D _1, claim 2 , 6 is an example of the invention.

In the above structure, the switch elements S _3a and S _{3
When 2a} and S _1a are turned on, the output voltage becomes V ₁ , and when the output current is positive, it is in the path of S _3a / S _2a / S _1a , and when it is negative, it is D
It flows in the route of _1a / D _2a / D _3a .

When the switch elements S _2a , S _1a and S _1b are turned on, the output voltage becomes V ₂ and the output current is D when the output current is positive.
_2,1・ S _2a・ S _1a , when negative, S _1b・ D _1,2・ D
It flows in the route of _2,2 .

When the switch elements S _1a , S _1b and S _2b are turned on, the output voltage becomes V ₃ and the output current is D when the output current is positive.
_2,3・ D _1,1・ S _1a , when negative, S _1b・ S _2b・ D
It flows to the route of _2,4 .

When the switch elements S _1b , S _2b and S _3b are turned on, the output voltage becomes V ₄ and the output current is D _3b when the output current is positive.
The current flows through the path of D _2b and D _1b , and when negative, flows through the path of S _1b , S _2b and S _3b .

In this way, four-level outputs of the positive or negative potentials V ₁ and V _{4 of} the DC voltage source or the potentials V ₂ and V ₃ of the series connection points of the voltage source are obtained, and shown in FIG. Such an output voltage can be obtained.

Further, with the above structure, the output capacitance can be increased without increasing the voltage applied to one element, and the output waveform can be improved without increasing the PWM modulation frequency. it can.

A second embodiment of the bridge circuit of the present invention is shown in FIG.
Shown in. In FIG. 3, E _{1 to} E ₄ are DC voltage sources, S _1a
~S _4a, S _1b ~S _4b switch element, D _1a ~D _4a, D _1b
˜D _4b , D _1,1 ˜D _3,6 are diodes, OUT is an output terminal, and V ₁ ˜V ₅ are the potentials of the terminals of the DC voltage source.

In the second embodiment, the DC voltage source is formed by connecting _four voltage sources E _{1 to} E ₄ in series, and the positive side arm and the negative side arm are four switch elements each having a diode connected in antiparallel.
The first clamp circuit is composed of diodes D _{3,1 to} D _3,6 , and the second and third plurality of clamp circuits are composed of diodes D _{2,1 to} D _2,4 , D _{1. , 1 to} D _2,2 , which is an example of the invention corresponding to claims 1, 3, and 6.

In the above structure, the switch elements S _4a and S _{4a
When 3a} , S _2a and S _1a are turned on, the output voltage becomes V ₁ ,
The output current flows through the paths S _4a , S _3a , S _2a, and S _1a when positive, and flows through the paths D _1a , D _2a , D _3a, and D _4a when negative.

When the switch elements S _3a , S _2a , S _1a , and S _1b are turned on, the output voltage becomes V ₂ , and when the output current is positive, the path of D _3,1 · S _3a · S _2a · S _1a When negative, S _1b
- flows through a path of _{D 1,2 · D 2,2 · D 3,2} .

When the switch elements S _2a , S _1a , S _1b and S _2b are turned on, the output voltage becomes V ₃ , and when the output current is positive, D _3,3 · D _2,1 · S _2a · S _1a. On the path of, when negative, S
It flows to the route of _1b・ S _2b・ D _2,4・ D _3,4 .

When the switch elements S _1a , S _1b , S _2b and S _3b are turned on, the output voltage becomes V ₄ , and the output current is positive when D _3,5 , D _{2,3.D 1,1.} On the path of S _1a , when negative,
It flows in the route of S _1b , S _2b , S _3b , D _3,6 .

The switching element _{S 1b, S 2b, S 3b} , the S _4b is turned on, the output voltage V ₅ and the output current, when positive, D _4b, the path of _{D 3b · D 2b · D 1b} , When negative, S _1b
It flows through the route of S _2b , S _3b, and D _4b .

In this way, five-level outputs of the positive or negative potentials V ₁ and V _{5 of} the DC voltage source or the potentials V ₂ , V ₃ and V ₄ of the series connection points of the voltage sources are obtained. An output voltage as shown in 4 is obtained. Therefore, the output waveform can be further improved.

A third embodiment of the bridge circuit of the present invention is shown in FIG.
Shown in. In the third embodiment, a part of the switching elements of the positive side arm and the negative side arm connected in series is formed by connecting some switching elements S _1a , S _2a , S _1b and S _2b in parallel. Is an example of the invention corresponding to claims 1, 2, 4, 5, and 6, which are formed by connecting some of the diodes D _2,1 and D _2,4 in parallel.

6 and 7 show examples of waveforms when the AC load current I _o is supplied from the center point of the bridge circuit. Figure 6
Is an example of a case where the power factor of the load is poor. In the switch element, the closer the element is to the output terminal, the larger the amount of electricity passed, and the diode is almost the same.

FIG. 7 shows an example in which the load power factor is good,
It can be seen that S _2a , S _1a , S _1b , and S _2b in the switch element and D _2,1 and D _2,4 in the diode have a larger amount of energization than other elements. In this embodiment, in consideration of this state, by connecting in parallel the elements having a large load due to the energizing capacity of each element, the power loss generated in each element is averaged, and the operating rate of each element is improved, The output capacity of AC power can be increased.

FIG. 8 shows a first embodiment of the inverter device of the present invention. In FIG. 8, an AC power supply divided by a transformer 1 is converted into a DC power by each converter 2 configured by a thyristor bridge, and a DC power supply controlled to a predetermined voltage via each smoothing capacitor 3 is used. A DC voltage source connected in series to form a DC voltage source.
It is an example of the invention corresponding to. With the inverter device configured as described above, as shown in FIG. 7, the diodes D _{2,1 to} D
_The converter 2 controls so that the voltage of the smoothing capacitor does not change even if the currents flowing in ₂ and ₄ are different, so the voltage fluctuation of the DC power supply is suppressed and the output waveform is distorted or an overvoltage is applied to the diode. Can be prevented.

A second embodiment of the inverter device of the present invention is shown in FIG. In FIG. 9, 11 to 13 are bridge circuits according to the present invention, only 11 shows the internal structure, but 12 and 13 have the same structure. Although the internal configuration of 11 is the same as the configuration of FIG. 1, it may be the configuration of FIGS. 3 and 5 and is not limited to this.

In this embodiment, three bridge circuits of the present invention are used to output three-phase AC power, which is an example of the invention corresponding to claim 8. In this way, it is possible to easily construct a single-phase or multi-phase multi-level output inverter device.

[0046]

【The invention's effect】

(1) According to the invention corresponding to claim 1, one switching element and one diode are divided DC voltage sources.
Since only the voltage for each element is applied, the load on each element can be reduced. Furthermore, since the number of output levels increases, the waveform can be easily improved without using the PWM control or even with the PWM control with a low modulation frequency. Therefore, it is possible to use a large-capacity semiconductor element that cannot increase the switching frequency,
A bridge circuit that can easily increase the capacity of an inverter device can be obtained.

(2) According to the invention corresponding to claim 2,
When the DC voltage source is divided into three and three switch elements are connected in series, a bridge circuit that can easily distribute the divided voltage to the three switch elements in the OFF state can be obtained.

(3) According to the invention corresponding to claim 3,
Divide the DC voltage source into N (N> = 3) and switch elements to N
When they are connected in series, N switch elements are
A bridge circuit that can easily distribute the divided voltages is obtained.

(4) According to the invention corresponding to claim 4,
It is possible to obtain a bridge circuit capable of improving the operating rate of the switching elements connected in series as a whole and increasing the output capacity of AC power.

(5) According to the invention corresponding to claim 5,
It is possible to obtain a bridge circuit capable of improving the operating rate of the diodes connected in series as a whole and increasing the output capacity of AC power.

(6) According to the invention corresponding to claim 6,
Divide the DC voltage source into N (N> = 3) and switch elements to N
When connected in series, a bridge circuit capable of easily outputting an arbitrary potential of the N-divided DC voltage source can be obtained.

(7) According to the invention corresponding to claim 7,
Even if the current flowing through each of the divided DC voltage sources is different, the voltage is maintained at a predetermined value, so that a multi-level output inverter device that outputs AC power with less waveform distortion can be obtained.

(8) According to the invention corresponding to claim 8,
By using the bridge circuit of the present invention, a multi-level output inverter device that outputs single-phase or multi-phase AC power can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of a bridge circuit according to the present invention.

FIG. 2 is a waveform diagram for explaining the operation of the first embodiment.

FIG. 3 is a configuration diagram of a second embodiment of a bridge circuit according to the present invention.

FIG. 4 is a waveform diagram for explaining the operation of the second embodiment.

FIG. 5 is a configuration diagram of a third embodiment of a bridge circuit according to the present invention.

FIG. 6 is a waveform diagram for explaining the operation of the third embodiment, showing the current waveform of each part when the load power factor is poor.

FIG. 7 is a waveform diagram for explaining the operation of the third embodiment, showing the current waveforms at various points when the load power factor is good.

FIG. 8 is a configuration diagram of a first embodiment of an inverter device according to the present invention.

FIG. 9 is a configuration diagram of a second embodiment of an inverter device according to the present invention.

FIG. 10 is a configuration diagram of a conventional bridge circuit used in a multi-level output inverter device.

FIG. 11 is a waveform diagram for explaining the operation of the conventional bridge circuit.

FIG. 12 is another configuration diagram of a conventional bridge circuit.

[Explanation of symbols]

1 ... transformer 2 ... converter 3 ... smoothing capacitor 11 to 13 ... a bridge circuit (According to the _{Invention) D 1a ~D 4a, D 1b} ~D 4b, D 1,1 ~D 3,6 ... diode D ₁₁ to D ₁₆ , D ₂₁ ~D ₃₂ ... diodes E ₁ to E ₄ ... DC power supply OUT ... output terminal OUT1 to OUT3 ... output terminal _{S 1a ~S 4a, S 1b ~S} 4b ... switching element S ₁₁ ~S _14, S ₂₁ ~S ₂₆ … Switch element

Claims (8)

[Claims] 1. A positive side arm and a negative side arm formed by connecting at least three or more switching elements in which diodes are connected in antiparallel are connected in series between a positive electrode and a negative electrode of a DC voltage source, and a positive side arm and a negative side arm. In a bridge circuit that outputs AC power from the connection point of the side arm as an intermediate point, the same number of voltage sources as the switching elements in series are connected in series to form the DC voltage source, and the intermediate point is the starting point. , At least two or more clamp circuits composed of a plurality of diodes connected in series are provided between the series connection points of the switch elements of the positive side arm and the negative side arm at the symmetrical position, and the clamp circuit is provided with at least two clamp circuits. A bridge circuit, wherein a potential at a series connection point is clamped to a potential at a series connection point of the voltage source. 2. The bridge circuit according to claim 1, wherein a first connection is provided between the series connection points of the switch elements at the symmetrical positions closest to the positive electrode and the negative electrode of the DC voltage source.
Connecting the series connection points of a plurality of series-connected diodes of the clamp circuit to the series connection point of the voltage source,
The switch of the first clamp circuit connected to both ends of the voltage source located in the middle is a series circuit of two diodes and is located at the symmetrical position next to the positive electrode and the negative electrode of the DC voltage source. The series contact of the plurality of series-connected diodes of the second clamp circuit connected between the series connection points of the elements is connected to the series connection point of the two diodes of the first clamp circuit. A characteristic bridge circuit. 3. The bridge circuit according to claim 1, wherein a first connection is provided between the series connection points of the switching elements located at the symmetrical positions closest to the positive electrode and the negative electrode of the DC voltage source.
Connecting the series connection points of a plurality of series-connected diodes of the clamp circuit to the series connection point of the voltage source,
The switch of the first clamp circuit, which is connected to both ends of the voltage source located in the middle, is a series circuit of two diodes and is located at the symmetrical position near the positive electrode and the negative electrode of the DC voltage source. A series connection point of a plurality of diodes connected in series of a plurality of clamp circuits connected between the series connection points of the elements is sequentially connected to a series connection point of two diodes of the first clamp circuit and the plurality of clamp circuits. A bridge circuit, characterized in that the diodes of the plurality of clamp circuits connected to each other and connected between the series connection points of the two diodes are each formed of a series circuit of two diodes. 4. The bridge circuit according to claim 1, wherein a part of the switching elements of the positive side arm and the negative side arm, which are connected in series, are connected in parallel to increase the current-carrying capacity. Bridge circuit to do. 5. The bridge circuit according to claim 1, wherein a part of the series-connected diodes of the clamp circuit are connected in parallel to increase the conduction capacity. 6. The bridge circuit according to claim 1, wherein the positive side arm and the negative side arm are connected in series to all of the positive side or the negative side, or the positive side arm and the negative side arm. Conducting a part of the switching elements connected in series continuously, outputs the potential of the positive electrode or the negative electrode of the DC voltage source or the potential of the series connection point of the plurality of voltage sources of the DC voltage source to the intermediate point. A bridge circuit characterized by that. 7. The bridge circuit according to claim 1, comprising:
An inverter device characterized in that the direct-current voltage source used in the bridge circuit is a series circuit of a plurality of voltage-controlled voltage sources. 8. An inverter device comprising at least two bridge circuits according to claim 1 and outputting single-phase or multi-phase AC power.