KR102453339B1 - Controlling circuit for multilevel inverter and controlling method thereof - Google Patents

Abstract

The present invention relates to a multi-level inverter, and a method for avoiding failure of a multi-level inverter according to an aspect of the present invention for achieving the above object is a three-phase multi-level inverter composed of a plurality of H-bridge inverter cells, the determining a failure of the H-bridge inverter; and bypassing the entire inverter cell when the entire H-bridge inverter cell is faulty as a result of the determination, and converting the H-bridge inverter to a 2-level inverter when the switch in the H-bridge inverter cell is faulty. characterized by including.

Description

Multilevel inverter having a fault avoidance circuit {Controlling circuit for multilevel inverter and controlling method thereof}

The present invention relates to a multilevel inverter, and more particularly to an apparatus and method for converting a multilevel inverter into a two-level inverter in case of failure.

In general, a pulse width modulator (PWM) inverter capable of simultaneously controlling a switching frequency and an output voltage is common in power devices. In general industrial PWM inverters, a 2-level inverter is used for a low voltage, and a multi-level inverter is used for a high voltage. Compared to the 2-level inverter, the multi-level inverter has the following advantages.

First, since the dv/dt voltage-time slope of the inverter output waveform is reduced, the influence on the insulation of the Insulated Gate Bipolar Transistor (IGBT) and the electric motor can be reduced.

Second, by reducing the dv/dt voltage-time slope, electromagnetic radiation can also be improved.

Third, since a lower voltage is used compared to a 2-level inverter, conduction loss and switching loss can be reduced, resulting in increased efficiency.

Fourth, the output voltage distortion does not occur because the dead time required for the prevention of short circuit in the 2-level inverter is not required in the multi-level inverter.

Fifth, THD (Total Harmonic Distortion) is reduced because a lower voltage is used compared to the 2-level inverter.

Currently, 2-level PWM inverters are applied to electric power converters for vehicles mounted on electric vehicles, hybrid vehicles, and fuel cell vehicles. Therefore, it is necessary to improve the performance by lowering the heat generation of the IGBT due to conduction and switching losses.

In addition, in order to efficiently transfer the limited capacity of the battery to the motor and convert it into driving force, it is necessary to improve the inverter efficiency and to improve the vehicle driving performance by lowering the distortion.

Therefore, applying a multi-level inverter can solve the problems of the above-described 2-level PWM inverter, but there are some problems to be solved.

The multi-level inverter includes a 3-level NPC (Neutral Point Clamped) method, a diode clamped method, a flying capacitor method, and an H-Bridge cascade method.

The NPC method uses a diode to clamp the voltage applied to the switching element to make the voltage distribution of the element constant.

Since the inverter uses a high voltage, a diode clamp method extending the NPC method can be used to increase the output voltage. The diode clamp method consists of multiple switches, clamping diodes, and multiple DC-Link capacitors per phase.

In the diode clamp method, the applied voltage of the clamping diode is not constant, and there is a difficulty in balancing the voltage of the DC-Link capacitor.

The flying capacitor is a circuit configuration that compensates the voltage balance of the clamping diode and the DC-Link capacitor through the capacitor.

The H-Bridge series connection method connects cells composed of H-Bridges in series. There is no clamping circuit and a constant voltage is applied to the switch. The downside is that each cell's DC-Link capacitor must be isolated. However, it is possible to control the voltage by controlling the number of H-Bridge cells, and since it is configured in units of cells, it has the advantage of being able to replace cells in case of cell failure.

The inverter includes an IGBT that converts power from the battery through switching and supplies it to the motor, and an inverter control board and a gate board for operating the IGBT. The inverter control board and the gate board are composed of a PCB on which semiconductor devices are mounted.

If the semiconductors of the inverter control board and the gate board are destroyed due to an electrical overload (EOS, Electrical OverStress) problem, the IGBT cannot operate properly and the motor cannot be operated or the motor cannot be driven properly. As a warning signal is generated, the phenomenon of stopping the vehicle may occur. If such a phenomenon occurs while driving on a highway or general road, a dangerous situation such as a collision may occur due to a vehicle following. Therefore, it is necessary to configure a fail-safety system that can guarantee user safety despite such failures.

The existing H-Bridge multi-level inverter basically implemented cell-level fault monitoring and diagnosis, but it was a method of manually disabling cells by installing an auxiliary switch that bypasses each cell. However, in the dynamic environment of the vehicle, the user cannot manually set these settings for breakdowns that occur while driving the vehicle, so a configuration that can be prepared by automatically adjusting the voltage level in an emergency situation is required.

The present invention has been devised in the technical background as described above, and an object of the present invention is to provide a circuit having a function of automatically bypassing a malfunctioning switch inside a cell when a cell failure of a multi-level inverter used in an eco-friendly vehicle or the like.

Objects of the present invention are not limited to the objects mentioned above, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

In accordance with an aspect of the present invention for achieving the above object, there is provided a method for avoiding failure of a multi-level inverter, comprising: determining a failure of the H-bridge inverter; and bypassing the entire inverter cell when the entire H-bridge inverter cell is faulty as a result of the determination, and converting the H-bridge inverter to a 2-level inverter when the switch in the H-bridge inverter cell is faulty. characterized by including.

According to the present invention, since it is possible to apply a multi-level inverter instead of a 2-level inverter, it is possible to solve the electromagnetic interference problem by reducing electromagnetic radiation, and there is an effect that the motor driving performance is improved by reducing the harmonics. Instead of composing, it is possible to implement functions with only a few switches, which has the effect of reducing the number of parts and saving costs.

1 is a view showing a multi-level inverter connected to the H-bridge.
2 to 5 are structural diagrams showing switching to a two-level inverter in case of a switch failure in the H-bridge according to an embodiment of the present invention.
6 to 7 are structural diagrams showing the output voltage when the H-bridge fails in the three-phase multi-level inverter according to an embodiment of the present invention.
8 is a flowchart illustrating a failure avoidance method according to an embodiment of the present invention.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the technical field to which the present invention belongs It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims. Meanwhile, the terminology used herein is for the purpose of describing the embodiments and is not intended to limit the present invention. In this specification, the singular also includes the plural, unless specifically stated otherwise in the phrase. As used herein, "comprises" and/or "comprising" refers to the presence of one or more other components, steps, operations and/or elements mentioned. or addition is not excluded.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 shows an H-bridge type multi-level inverter. A multi-level inverter is constructed by connecting H-bridges in this way.

The multi-level inverter can obtain various voltages by turning on/off each switch constituting the H-bridge.

For example, in the multilevel inverter of FIG. 1, by adjusting the switches S1 to S4 of the first H-bridge, three voltages +Vc/2, 0, -Vc/2 can be obtained. S1 and S4 are turned on (shorted) and S2 By turning off (open) and S3, a voltage of +Vc/2 can be obtained, and when all switches are opened, the voltage becomes 0, and when S2 and S3 are turned on and S1 and S4 are turned off, a voltage of -Vc/2 is obtained. it can be

In the same way, you can get three voltages +Vc/2, 0, -Vc/2 from the second H-bridge, so if you combine the two H-bridge voltages, +Vc, +Vc/2, 0, -Vc/2 It is possible to obtain five voltages of , -Vc .

2 to 5 show how the output voltage of the H-bridge changes when a failure occurs in some of the switches of the H-bridge.

2 shows a case where S1 causes a short circuit failure in the first H-bridge. Since the S1 switch is in a state in which a short circuit has occurred, the short circuit (short) state is always maintained.

Among the remaining switches, when S2 and S3 are turned off (open) and S4 is turned on (short-circuited), the output of the H-bridge becomes +Vc/2 as shown in Fig. 2 (a), and when S2 and S4 are turned off and S3 is turned on The output of the H-bridge is zero. Therefore, if one of the switches fails, the H-bridge operates as a 2-level inverter rather than a multi-level inverter.

In FIG. 2, if the remaining H-bridges are normal, +Vc/2, 0, -Vc/2 are possible. Therefore, the output of the multi-level inverter by the combination of the two H-bridges is +Vc, +Vc/2, unlike the normal case. , 0, -Vc/2 are possible, that is, the output of -Vc is impossible.

3 is a case in which S2 causes a short circuit failure in the first H-bridge. Since S2 is always short-circuited, only two outputs -Vc/2, 0 are possible by the combination of the remaining switches. For output -Vc/2, S1 and S4 should be off and S3 should be on. For output 0, S1 and S3 should be off and S4 should be on.

Therefore, as shown in FIG. 3 , when S2 is a short-circuit failure, only +Vc/2, 0, -Vc/2, and -Vc outputs of the entire 2-level inverter are possible, and the output of +Vc is impossible.

4 shows a case where S3 is a short circuit failure in the first H-bridge. Since S3 is always short-circuited, the first H-bridge shows -Vc/2 output when S1 and S4 are off and S2 is on, and 0 when S1 is on and the other switches S2 and S4 are off. indicates

In this case, the output of the multi-level inverter can only be +Vc/2, 0, -Vc/2, -Vc, and cannot be +Vc, as in the case of FIG. 3 .

5 is a case in which S4 is a short circuit failure in the first H-bridge. Since S4 is always a short circuit, the first bridge outputs a voltage of +Vc/2 when S1 is on and S2 and S3 are off, and 0 when S1 and S3 are off and S2 is on.

Therefore, the 2-level inverter of FIG. 5 can output voltages of +Vc, +Vc/2, 0, and -Vc/2, but cannot output the voltage of -Vc due to the failure of S4.

는 H-브리지가 배터리로 동작하는 경우의 연결 스위치를 말하고,

는 H-브리지 전체의 바이패스 스위치를 말하여, X는 스위치의 값이 온인지 오프인지 상관없는 Don't Care 상태를 말한다.Table 1 is a table expressing all the switch combinations of the multi-level inverter including N H-bridges in the case of the short-circuit failure described above. ON indicates that the switch is in the ON state including short circuit faults, and OFF indicates that the switch is OFF including open faults.

refers to the connection switch when the H-bridge is operated by battery,

is the bypass switch of the entire H-bridge, and X is the don't care state regardless of whether the value of the switch is on or off.

As described above, in the case of a failure in one switch in the unit H-bridge constituting the multi-level inverter, a situation occurs that the required voltage cannot be obtained. Therefore, the prior art uses a method of driving the motor by lowering the DC voltage level A method was used in which the entire failed H-bridge was not used by using a pass switch.

However, according to the present invention, even if a failure occurs in a multi-level inverter of one phase in a three-phase multi-level inverter, by using the failed H-bridge as a 2-level inverter without simply bypassing it, the output voltage of the other phase is controlled through the above-described method of controlling the output voltage. It is possible to drive the motor without voltage drop by using the output of the multi-level inverter together.

6 shows a multi-level inverter in which each phase consists of three H-bridges and uses three phases of U, V, and W phases.

의 전압을 출력할 수 있고 이들의 조합에 의해, 즉 U-V상, V-W상, W-U상 전압을 +Vc, -Vc, 0으로 만들어 내어 모터를 구동하는 구조이다.Three-phase multi-level inverters have U, V and W phases respectively.

It is a structure that drives the motor by outputting the voltage of , and creating +Vc, -Vc, and 0 voltages of UV phase, VW phase, and WU phase by a combination of these.

를 출력할 수 있는데 H-브리지의 스위치가 고장인 경우 종래 방식과 같이 바이패스 스위치를 사용하게 되면 고장 난 H-브리지는 항상 전압이 0이므로 고장이 있는 상의 최대 가능전압은

로 낮아지게 된다. 따라서 3상에서 U-V상, V-W상, W-U상 사이의 전압을 원하는 전압으로 만들 수 없는 문제가 발생한다.In normal case, the voltage of each phase is

In case the switch of the H-bridge is faulty, if the bypass switch is used as in the conventional method, the faulty H-bridge always has a voltage of 0, so the maximum possible voltage of the faulty phase is

will be lowered to Therefore, there is a problem that the voltage between the UV phase, VW phase, and WU phase cannot be made to a desired voltage in three phases.

Fig. 7 shows a three-phase multilevel inverter when the number of H-bridges is N.

가 된다. 하지만 전술한 바와 같이 H-브리지 내의 스위치의 조합을 이용한다면 고장난 스위치의 위치에 따라 +Vc 또는 -Vc 출력은 얻을 수 있으므로, 이와 함께 다른 상들의 전압을 조절하여 전압강하 없이 모터를 구동할 수 있다.If one of the N H-bridges fails and the H-bridge is not used by using the bypass switch as in the prior art, the maximum output voltage of one phase is

becomes However, if a combination of switches in the H-bridge is used as described above, +Vc or -Vc output can be obtained depending on the position of the faulty switch. .

8 is a flowchart illustrating a failure avoidance method according to the present invention when there is a failure of an H-bridge in a three-phase multi-level inverter.

First, the failure of the H-bridge cell is determined by measuring the output voltage or output current of the H-bridge (S810), and it is determined whether this is a failure of the entire H-bridge cell or a failure of a switch within the cell (S820).

As a result of the determination, if the entire H-bridge cell is faulty as in the case where both switches connected in series are short-circuited, the H-bridge is not used by bypassing the entire cell as in the conventional case (S830).

On the other hand, if only one switch inside the cell fails, the H-bridge is converted to a 2-level inverter as shown in FIGS. 2 to 5 without bypassing the entire cell and a limited operation is performed (S840).

In the case of a three-phase multi-level inverter, it is possible to generate the necessary voltage between each phase by obtaining voltage from cells other than the faulty phase. can be obtained

Table 2 is a table showing the relationship between the voltages required for each phase in order to obtain the necessary voltage between each phase in the case of a switch failure in the H-bridge.

Each voltage of U, V, and W phases to adjust Vu - Vv, the voltage between U-V phases, Vv-Vw, the voltage between V-W phases, and Vw-Vu, the voltage between W-U phases to +Vc, -Vc, and 0, respectively. It indicates how much Vu, Vv, and Vw should be.

의 전압을 출력할 수 있으므로 Vu =+Vc, Vv=0, Vw=+Vc의 출력을 각각 가진다면 필요로 하는 각 상 사이의 전압을 문제없이 맞출 수 있다. 하지만 각 상에 고장난 스위치가 포함된 H-브리지가 존재한다면 최대전압이

에 못 미치므로 표에 나타난 각 상의 전압값을 참조하여 각 상 사이의 전압을 만족시킬 수 있는 조합을 찾아내야 한다.In a normal case with no faults, each phase is

Since it is possible to output the voltage of However, if there is an H-bridge with a faulty switch on each phase, the maximum voltage is

Therefore, it is necessary to find a combination that satisfies the voltage between each phase by referring to the voltage values of each phase shown in the table.

또는 0의 전압이 가능하므로 결과적으로 U상의 출력은 -Vc의 전압은 출력이 가능하지만 +Vc 전압은 출력할 수 없고, 최대 전압은

까지만 출력이 가능하다. 그렇다면 표 1에서 첫 번째 행과 같이 +Vc를 가지는 것은 불가능하니, 두 번째 행처럼 Vu = Vw =

로 설정하고, Vv =

로 세팅 함으로써 상 사이의 필요전압인 Vu - Vv, Vv - Vw, Vw - Vu를 각각 +Vc, -Vc, 0으로 설정하는 것이 가능해진다.For example, when a short-circuit failure occurs in the S2 switch in the H-bridge of the U phase, the H-bridge in which the short-circuit failure occurs as shown in FIG. 3 is -

Alternatively, a voltage of 0 is possible. As a result, the output of phase U can output a voltage of -Vc but cannot output a voltage of +Vc, and the maximum voltage is

It is possible to print only up to Then in Table 1, it is impossible to have +Vc as in the first row, so as in the second row, Vu = Vw =

set to , and Vv =

It becomes possible to set the necessary voltages Vu - Vv, Vv - Vw, and Vw - Vu between phases to +Vc, -Vc, and 0, respectively.

이 된다면 Vv는

이 되어야 하는데 이는 Vv가 가질 수 있는 최대전압을 넘어서는 값이므로 이렇게 설정하는 것은 불가능하다. 따라서 표 2에서는 이러한 값들을 (Not Available)로 표시하였다.As the maximum possible voltage of Vc gradually decreases, the absolute value of Vv gradually increases. When Vc becomes 0, Vv becomes -Vc, and the absolute value becomes maximum. If Vc

If this happens, Vv is

However, it is impossible to set this as it is a value that exceeds the maximum voltage that Vv can have. Therefore, in Table 2, these values are indicated as (Not Available).

Tables 3 to 7 are tables showing the voltage required for each phase according to the voltage required between each phase. Like Table 2 above, it is a table showing a method that can respond to a case where a broken H-bridge is included in each phase.

A multi-level inverter (not shown) including a fault avoidance circuit according to another embodiment of the present invention includes a plurality of H-bridges and a control unit.

In case of failure of the H-bridge, if the entire cell fails, the melt-level inverter is operated by manually bypassing it as in the conventional method.

On the other hand, if only one switch of the H-bridge is faulty, the control unit may control other switches other than the faulty switch to operate the faulty H-bridge as a 2-level inverter. A specific method is the same as described above with reference to FIGS. 2 to 5 .

In the case of operating the failed H-bridge as a 2-level inverter, the maximum voltage of the phase including the corresponding H-bridge is limited. As described above with reference to Tables 2 to 7, other phases not including the failed H-bridge By adjusting the voltage, it is possible to maintain the voltage between the phases of the entire 3-phase multi-level inverter as the voltage between the phases in a steady state without failure.

As described above, if the H-bridge is converted to a 2-level inverter, including the fixed switch, short-circuited or opened due to a fault without bypassing the entire H-bridge, the voltages of the surrounding phases are used together to the motor. Since it is possible to maintain the supplied voltage at the required voltage, there is an effect of reducing the number of parts and increasing the motor driving efficiency compared to using a bypass switch.

In the above, the configuration of the present invention has been described in detail with reference to the accompanying drawings, but this is merely an example, and those skilled in the art to which the present invention pertains may make various modifications and changes within the scope of the technical spirit of the present invention. Of course, this is possible. Therefore, the protection scope of the present invention should not be limited to the above-described embodiments and should be defined by the description of the following claims.

Claims (6)

In a three-phase multi-level inverter consisting of an H-bridge inverter cell including a plurality of switches,
1) determining a failure of the H-bridge inverter; and
2) As a result of the determination of 1), if one of the plurality of switches in the H-bridge inverter cell fails, the H-bridge inverter is converted to a 2-level inverter, and the phase including the H-bridge which is the switch failure maintaining the voltage between the phases of the three-phase multi-level inverter as a steady state voltage by adjusting the maximum voltage of the other phases; and
3) As a result of the determination of 1), when two or more of the plurality of switches in the H-bridge inverter cell fail, bypassing the entire inverter cell.
delete According to claim 1, wherein the conversion step of 2),
When one of the plurality of switches is a short-circuit failure, a switch connected in parallel with the failed switch and having no contact point with the failed switch is short-circuited and the remaining switches are opened to output the maximum voltage, and the failed switch and A method for avoiding failure of a multi-level inverter comprising outputting a zero voltage by short-circuiting a switch connected in parallel and having one end of the failed switch and one end connected to each other and opening the remaining switches.
H-bridge inverter cell including a plurality of switches; and
Including a control unit for operating the switch in the H-bridge inverter cell,
the control unit
determine a failure of the H-bridge inverter; As a result of the determination, if one of the plurality of switches in the H-bridge inverter cell is faulty, the H-bridge inverter is converted to a 2-level inverter, and the phases other than the phase including the H-bridge faulty maintaining the voltage between the phases of the three-phase multi-level inverter as a steady state voltage by adjusting the maximum voltage; A multi-level inverter including a fault avoidance circuit configured to bypass the entire inverter cell when at least two of the plurality of switches in the H-bridge inverter cell fail as a result of the determination.
delete 5. The method of claim 4, wherein the failure avoidance circuit of the control unit
When one of the plurality of switches is a short circuit failure, a switch connected in parallel with the failed switch and having no contact with the failed switch is short-circuited and the remaining switches are opened to output the maximum voltage, and the failed switch and A multi-level inverter connected in parallel and further configured to output a zero voltage by short-circuiting the switch having one end connected to the failed switch and opening the remaining switches.

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