KR20100055281A - The control method for overmodulation operation of npc type 3-level inverter - Google Patents

Abstract

PURPOSE: According to over modulation control method of the NP C type 3- level inverter for the railway vehicle is the modulation index, the inverter output voltage is linear. The harmonic noise at over modulation domain is minimized. CONSTITUTION: According to the modulation index, over modulation domain I or more modulation domain II are instituted. By using the reference angle, the new voltage reference vector becomes on 4 branch area linear at π/2. The reference angle is induced through the Fourier series of the voltage reference vector to the size of the fundamental component.

Description

The control method for overmodulation operation of npc type 3-level inverter}

The present invention relates to an overmodulation control method of an NPC type 3-level inverter for a railroad car, and more particularly, to an overmodulation operation of an NPC type 3-level inverter for an induction motor of a railroad car according to a modulation index (MI). An overmodulation control method for an NPC type 3-level inverter for a railway vehicle for compensating a voltage reference vector in an overmodulation region I and a voltage reference vector in an overmodulation region II so that an output voltage is linearly controlled.

Railroad cars use high line voltages to extend the static torque range, and are typically provided with two-level inverters as inverters for (towing) induction motors. In these two-level inverters, expensive switching devices having higher rated voltages are used as the line voltage is increased. In a railroad vehicle using a general high voltage inverter, inverters are stacked in order to reduce device ratings.

However, stacking inverters require an independent DC power supply and have a large number of switching combinations. Thus, pulse width modulation (PWM) has a complex disadvantage.

On the other hand, NPC type three-level inverters, which are in the spotlight recently, do not need an independent DC power supply and are configured in series with switching elements, so that the inverter structure is simpler and more economical than the inverter stacking method. This will be explained in detail as follows.

NPC type three-level inverter outputs DC-link voltage in three stages, which can reduce the harmonic content of output voltage and current by more than half compared to two-level inverter at the same switching frequency, and switching is applied to the induction motor winding. Can reduce the voltage stress. In addition, unlike the serial connection structure of the device, even voltage distribution can be achieved during turn-off, so the hardware configuration is simple because there is no need to consider the synchronization of the turn-off operation.

In addition, since the cutoff voltage of each switching element is half of the DC-link voltage, EMI noise generated due to a sudden voltage change during switching can be reduced.

Next, the characteristics of the induction motor of the aforementioned railway vehicle will be described with reference to FIG. 1.

1 is a speed / torque curve of an induction motor of a railway vehicle.

As shown in FIG. 1, the constant torque region corresponds to the rated speed of the induction motor, and the maximum torque is constantly output from the induction motor so that the railway vehicle can have a constant acceleration capability.

To this end, the inverter of the variable voltage variable frequency (VVVF) method controls the ratio of the induction motor input voltage and frequency to obtain the required torque.

Induction motors in the constant torque region are operated with constant air gap flux, which increases the stator current torque sensitivity and makes the railway vehicle drive system respond quickly.

As a PWM technique of a conventional railway vehicle driving system, a sinusoidal PWM method is mostly used. The sinusoidal PWM method has a nonlinear overmodulation area because the limit of the modulation index (MI) that can be output linearly is about 78.5% of the square wave inverter.

In addition, since the number of pulses is determined in advance as the frequency of the inverter increases, there is a disadvantage in that the riding comfort of the railway vehicle is not good due to the pulsation of torque due to the nonlinear output caused by the variation in the number of pulses. On the other hand, the voltage of the inverter to which the space vector modulation method (SVM method) is applied is 0.907 times that of the square wave inverter, and the overmodulation area is smaller than that of the sinusoidal PWM method.

On the other hand, in the conventional railroad vehicle driving system, in order to make full use of the DC link voltage of the inverter device for driving an induction motor, the PWM operation is stopped and operated in one-pulse mode above the rated speed.

Therefore, in order to operate the induction motor in the constant torque region on the full speed region, an overmodulation technique should be used to enable continuous operation between the PWM linear operation region and the 1 pulse mode operation region.

In the conventional sinusoidal PWM method, the fundamental wave component can be increased by 15.5% by using a third harmonic addition technique of the reference voltage to increase the inverter voltage utilization rate.

On the other hand, in the conventional space vector modulation method, 'Holtz' technique 'is used in which the overmodulation area is divided into one pulse to naturally enter the one pulse mode. However, the 'Holtz' technique has a problem in that the output characteristics of the inverter are not linear and the harmonic content of the output voltage is large.

Accordingly, the present invention has been proposed to solve the above problems and to meet the above demands, and the technical problem to be achieved is to modulate for overmodulation operation of an NPC type 3-level inverter for induction motor of a railway vehicle. Overmodulation of NPC type 3-level inverters for railway vehicles to compensate for the voltage reference vector in the overmodulation region I and the voltage reference vector in the overmodulation region II according to the index MI so that the output voltage is linearly controlled. It is to provide a control method.

)과 실제 전압기준벡터의 페이스 앵글(

,

)을 사용하여 π/2마다 선형화된 4가지 영역 상에서 새로운 전압기준벡터를 생성하는 것을 특징으로 한다.In order to achieve the above object, the method according to an embodiment of the present invention, in the overmodulation control method of the NPC type three-level inverter for railway vehicles, according to the modulation reference (MI) over The modulation region I and the overmodulation region II are set, and in order to compensate the voltage reference vector in the overmodulation region I, a reference angle derived by the magnitude of the fundamental wave component through the Fourier series of the corresponding voltage reference vector ( A new voltage reference vector is generated on four regions linearized every π / 2 using), and to compensate for the voltage reference vector in the overmodulation region II, the Fourier series of the voltage reference vector Size-induced holding angle (

) And the face angle of the actual voltage reference vector (

,

) Is used to generate a new voltage reference vector on four regions linearized every π / 2.

As described above, the present invention can accurately compensate the voltage reference vector in the overmodulation region I and the voltage reference vector in the overmodulation region II in the overmodulation operation of the NPC type 3-level inverter for induction motor of a railway vehicle. It works.

In addition, the present invention can linearize the inverter output voltage (fundamental wave component of the phase voltage) according to the modulation index (MI), while naturally minimizing harmonic noise in the over-modulation region, while PWM linear operation region and one-pulse mode operation region. There is an effect to enable continuous operation in between.

In addition, the present invention can improve the voltage utilization of the NPC three-level inverter for induction motors of railway vehicles without increasing the line voltage, and by applying the present invention to the railway vehicle drive system, The electrical and audio noise can be significantly reduced, the size of the propulsion device can be reduced, the link voltage can be increased, and the size of the busbar copper plate can be reduced.

In addition, the present invention can reduce the rated capacity of the device compared to the existing two-level inverter at the same switching frequency, reduce the harmonic components of the output voltage and current by more than half and induce switching by applying the present invention to a railway vehicle drive system. Since the voltage stress applied to the winding of the motor can be reduced and the cutoff voltage of each switching element is half of the DC-link voltage, EMI noise due to the sudden voltage change during switching can be reduced.

Specific details of other embodiments are included in the detailed description and the drawings.

Advantages and features of the present invention, and methods for achieving them will be 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 may be implemented in various forms. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

Although the first, second, etc. are used to describe various elements, components or sections, these elements, components or sections are of course not limited by these terms. These terms are only used to distinguish one element, component or section from another element, component or section. Therefore, the first device, the first component, or the first section mentioned below may be a second device, a second component, or a second section within the technical spirit of the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, the term "comprises" or "comprising" does not exclude the presence or addition of one or more other components, steps, operations or elements. . And "A or B" means A, B, A and B. In addition, like reference numerals refer to like elements throughout the following specification.

Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification may be used in a meaning that can be commonly understood by those skilled in the art. In addition, terms defined in a commonly used dictionary are not ideally or excessively interpreted unless they are clearly defined in particular.

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

)을 사용하여 π/2마다 선형화된 4가지 영역 상에서 새로운 전압기준벡터를 생성하며, 과변조영역Ⅱ에서의 전압기준벡터를 보상하는데 있어 해당 전압기준벡터의 퓨리에 급수를 통해 기본파 성분의 크기로 유도된 홀딩 앵글(holding angle,

)과 실제 전압기준벡터의 페이스 앵글(phase angle,

,

)을 사용하여 π/2마다 선형화된 4가지 영역 상에서 새로운 전압기준벡터를 생성한다. The present invention proposes an output voltage linearization control technique of an NPC type 3-level inverter in an overmodulation region for driving a towing motor of a railroad vehicle driving system. To this end, the present invention divides the overmodulation region into overmodulation region I and overmodulation region II according to a modulation index (MI), and compensates the voltage reference vector in the overmodulation region I accordingly. The reference angle derived from the magnitude of the fundamental wave component through the Fourier series of

) To generate a new voltage reference vector over four regions linearized every π / 2, and to compensate for the voltage reference vector in the overmodulation region II, to obtain the magnitude of the fundamental wave component through the Fourier series of the voltage reference vector. Induced holding angle,

) And the phase angle of the actual voltage reference vector

,

We generate a new voltage reference vector on four regions linearized every π / 2 using

By doing so, the present invention enables continuous operation (linear acquisition of the PWM inverter output voltage up to 1 pulse mode) between the PWM linear operation region and the 1 pulse mode operation region.

On the other hand, in the present invention, as an overmodulation technique (linearly controlling the output voltage in the overmodulation region), the NPC uses the 'Lee's technique', which compensates the fundamental wave by developing the output phase voltage in a Fourier series in a two-level inverter. Applies to type 3-level inverters.

Then, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

2 is a diagram illustrating an embodiment of an NPC type three-level inverter to which the present invention is applied, FIG. 3 is a space voltage vector diagram of an NPC type three-level inverter, and FIG. 4 is an operation of the NPC type three-level inverter. It is an area diagram.

As shown in Fig. 2, the NPC type 3-level inverter to which the present invention is applied includes four switching elements, four antiparallel diodes, and two branch diodes in each phase. Here, each of the equivalent switching states, there are three states of + V _dc / 2, 0, -V _dc / 2 according to the conduction state of the switching element, so as to total 27 kinds of switching in the NPC type three-level inverter as shown in FIG. Combination is possible.

로 나타낼 수 있다.The NPC type three-level inverter uses a space vector modulation method, and the input reference values a, b, and c phase three phase voltages are converted into voltage reference vectors on a two-dimensional plane through dq conversion.

It can be represented as.

, 전압기준벡터

의 관계를 나타낸다.[Equation 1] to [Equation 3] below is the modulation index (MI), inverter input voltage

, Voltage reference vector

Indicates a relationship.

In the spatial voltage vector diagram of the NPC type three-level inverter shown in FIG. 3, 'A, B, C, D, E, F' is classified into six regions, and each region is again represented by '1, 2, 3, 4 'It can be divided into 4 areas and it can be divided into 24 areas.

On the other hand, when the induction motor of the railroad vehicle drive system reaches the rated speed, the NPC type three-level inverter operates in one-pulse mode to output the maximum voltage. Therefore, in order to linearly control the fundamental wave of the output voltage from the PWM linear operation region to the 1 pulse mode operation region, an overmodulation control technique for the intermediate region is required.

Therefore, in order to improve the voltage utilization of the spatial vector modulation, a new voltage reference vector should be generated using the overmodulation technique.

As shown in FIG. 4, the PWM linear driving region may be divided into a linear region and an overmodulation region according to the operation region of the voltage reference vector.

In the operating region diagram of the NPC type 3-level inverter shown in FIG. 4, the region where the voltage reference vector exists in the inscribed circle of the outer hexagon of the vector diagram is a linear region, and from the portion where the voltage reference vector escapes the inscribed circle of the outer hexagon. The area up to the circumscribed circle of the outer hexagon is an overmodulation area.

In particular, in the present invention, a new voltage reference vector is generated to compensate for the voltage reference vector deviating from the outer hexagon in the overmodulation area, and the overmodulation area I and the overmodulation area II according to the method of generating the voltage reference vector. Divide

That is, the overmodulation region I and the overmodulation region II are set according to the modulation index MI.

)을 사용하고, 과변조영역Ⅱ에서는 전압기준벡터의 퓨리에 급수를 통해 기본파 성분의 크기로 유도된 홀딩 앵글(

)과 실제 전압기준벡터의 페이스 앵글(

,

)을 사용한다.In the present invention, in the overmodulation region I, the reference angle induced by the magnitude of the fundamental wave component through the Fourier series of the voltage reference vector (

In the overmodulation region II, the holding angle (derived from the Fourier series of the voltage reference vector to the magnitude of the fundamental wave component)

) And the face angle of the actual voltage reference vector (

,

).

Next, a process of compensating the voltage reference vector in the linear region will be described with reference to FIG. 5, and a process of compensating the voltage reference vector in the overmodulated region I will be described with reference to FIG. 6. A process of compensating the voltage reference vector in II will be described with reference to FIG. 7.

5 is a voltage vector diagram in section A of FIG.

)과 하이브리드영역(

)과 선형영역II(

)로 구분된다.In the linear region, the voltage reference vector is used without modification. The output voltage of the sine wave is generated by the space vector modulation method. As mentioned above, the linear region depends on the magnitude of the voltage reference vector.

) And hybrid zones (

) And linear domain II (

Separated by).

In the linear region I, the voltage reference vector operates only between the inner hexagons and is the region in which the line voltage is output in three stages as in the conventional two-level inverter. In the hybrid region, the voltage reference vector operates in the inner hexagon or the outer hexagon, and when operating in the inner hexagon, the line voltage is output in three stages as in the two-level inverter. Is output. In the linear region II, the voltage reference vector operates only in the outer hexagon and the line voltage is output in five steps.

In the linear region as described above, 'T _a , T _b , T _{c for} each of the three voltage vectors adjacent to the region where the current voltage reference vector exists for each sampling of the output voltage vector following the voltage reference vector It is generated by applying the average application time of '.

As an example of generating a voltage reference vector in the linear region, when the voltage reference vector is located in '3 region' of 'A section' in FIG. 5, the voltage reference vectors are located at the vertex voltage vectors of '3 region' where the voltage reference vector is located. The voltage reference vector is generated by applying the average application time of T _a (POO / ONN), T _b (PON), and T _c (PPO / OON). The same applies to the remaining five regions.

Next, a process of compensating the voltage reference vector in the overmodulation region I will be described with reference to FIG. 6.

FIG. 6 is an exemplary diagram for explaining a process of compensating a voltage reference vector in an overmodulation region I according to the present invention. FIG. 6 shows a trajectory and a phase voltage waveform of a voltage reference vector in the overmodulation region I. It is.

이 되면 전압기준벡터가 과변조영역I에서 동작하게 된다.In the present invention, the modulation index

In this case, the voltage reference vector operates in the overmodulation region I.

를 보상 하기 위하여

보다 승압된 전압기준벡터

를 생성하며, 이 승압된 전압기준벡터

가 벡터도의 내접원일 때부터 육각형의 외접원 사이에 위치할 때까지 동작한다. 도 6에 있어, 세 개의 전압기준벡터의 궤도가 복소평면에서 회전하는 것과 실제 전압기준벡터

을 시변영역에서 표현하였다.In the over-modulation region I, the voltage reference vector is outside the hexagon

To compensate

More Voltage Reference Vector

And the stepped up voltage reference vector

It operates until is located between the inscribed circle of the vector diagram and the inscribed circle of the hexagon. In Fig. 6, the trajectories of the three voltage reference vectors rotate in a complex plane and the actual voltage reference vectors.

Is expressed in the time-varying region.

)은 정점에서 보상된 전압기준벡터 궤도의 교점까지 측정된 기준각을 의미한다.Particularly, in the present invention, in order to generate a boosted voltage reference vector in the overmodulation region I, the voltage reference vectors are represented by the following Equations 4 to 10 on four regions linearized every π / 2. The function of each section in overmodulation area I is used. Where the reference angle (

) Is the reference angle measured from the vertex to the intersection of the compensated voltage reference vector trajectory.

는 인버터 입력전압을,

를,

는 전압기준벡터의 각속도를 각각 나타낸다.In [Equation 4] to [Equation 10],

The inverter input voltage,

To,

Denotes the angular velocity of the voltage reference vector, respectively.

Next, a process of compensating the voltage reference vector in the overmodulation area II will be described with reference to FIG. 7.

FIG. 7 is an exemplary explanatory diagram illustrating a process of compensating a voltage reference vector in an overmodulation area II according to the present invention. FIG. 7 shows a trajectory and a phase voltage waveform of a voltage reference vector in the overmodulation area II. It is.

이 되면 전압기준벡터가 과변조영역Ⅱ에서 동작하게 된다. 예컨대,

가 되면 승압된 전압기준벡터가 벡터도 육각형에 외접하게 되어 전압 손실분을 더 이상 보상해 주지 못하기 때문에 이 영역에 서는 과변조영역I에서 사용한 방식을 사용하지 못한다. 이를 본 발명에서는 과변조영역II라 정의한 것이다.In the present invention, the modulation index

In this case, the voltage reference vector operates in the overmodulation region II. for example,

Since the boosted voltage reference vector circumscribes the vector in a hexagon and cannot compensate for the voltage loss anymore, the method used in the overmodulation region I cannot be used in this region. This is defined as overmodulation region II in the present invention.

가 시간에 따라 가변할 때 홀딩 앵글(

) 구간 동안 실제 전압기준벡터

가 각 구간 최고의 전압값을 낼 수 있는 정점에 있게 되고, 나머지 시간을 육각형 면을 따라서 움직인다.In the overmodulation region II, the voltage reference vector

Holding angle (when is variable over time)

Actual voltage reference vector

Is at the peak that can produce the highest voltage for each interval, and moves the rest of the time along the hexagonal plane.

,

)은 실제 전압기준벡터

의 위상각을 나타낸다.In the present invention, in order to generate a voltage reference vector in the overmodulation region II, the overmodulation region II represented by the following Equations 11 to 19 on four regions linearized by π / 2. Use the function for each section in. Where the face angle (

,

) Is the actual voltage reference vector

Indicates the phase angle of.

는 인버터 입력전압을,

를,

는 전압기준벡터의 각속도를,

,

는 실제 전압기준벡터

의 위상각을 각각 나타낸다.In [Equation 11] to [Equation 19],

The inverter input voltage,

To,

Is the angular velocity of the voltage reference vector,

,

Is the actual voltage reference vector

Each phase angle of is shown.

Next, the simulation and the performance evaluation results of the algorithm proposed in the present invention as described above will be described with reference to FIGS. 8 to 17.

8 and 9 are space vector overmodulation operation simulation block diagrams of the NPC type 3-level inverter to which the present invention is applied.

In the simulation of the linear region and overmodulation region operation of the NPC type 3-level inverter to which the algorithm of the present invention is applied, the input voltage is 311 [V] and the DC smoothing capacitor is 6,400 [uF], respectively. Three phase RL loads of 20 [mH] and 33 [uhm] were configured and controlled at a sampling frequency of 4 [kHz] using a TMS320C33 DSP board for inverter control.

로 나타낸다. 전압기준벡터

의 위치에 따라 전압기준벡터

가 선형영역에 있는지 과변조영역에 있는지를 판별한 후, 전압기준벡터

가 위치한 인접한 3개의 벡터신호에 대한 시간값을 계산하여 스위칭 테이블에 맞추어 스위칭 신호를 인가한다.As shown in Fig. 9, given a three-phase input to the output voltage, the voltage reference vector represented by the d-axis and q-axis components of the two-dimensional plane through the three-phase input through dq conversion.

Represented by Voltage reference vector

Voltage reference vector depending on the position of

The voltage reference vector after determining whether is in the linear or overmodulation region

Calculate the time value of three adjacent vector signals where is located and apply the switching signal according to the switching table.

10 is a simulation waveform of line voltage (top) and phase current (bottom) in linear region I, FIG. 11 is a simulation waveform of line voltage (top) and phase current (bottom) in linear region II, and FIG. 12 is an overmodulation region. Line voltage (top) and phase current (bottom) simulation waveforms in I, FIG. 13 are line voltage (top) and phase current (bottom) simulation waveforms in the overmodulation region II, and FIG. 14: Line voltage in one pulse region. (Top) and phase current (bottom) simulation waveforms.

인 조건에서의 동작을 보이며, 전압기준벡터의 발생을 내부 육각형 벡터들만으로 구성하고 있어서 선간전압 파형이 2-레벨 인버터와 동일한 형태의 파형을 나타냄을 확인할 수 있다.The line voltage waveform and the phase current waveform shown in FIG. 10 are linear regions I.

In this case, the voltage reference vector generates only the internal hexagonal vectors, so the line voltage waveform shows the same waveform as the two-level inverter.

인 조건에서의 동작을 보이며, 기준전압이 내부 육각형 내접원과 외부 육각형 내접원 사이에서 존재하므로 3-레벨로 동작하여 선간전압 파형이 5단계로 출력되는 특징을 보임을 확인할 수 있다.The line voltage waveform and the phase current waveform shown in FIG. 11 are linear regions II.

It shows the operation under the condition that the reference voltage exists between the inner hexagonal inscribed circle and the outer hexagonal inscribed circle, so it can be seen that the line voltage waveform is output in five levels by operating in three-level.

인 조건에서의 동작을 보이며, 전압기준벡터가 외부 육각형의 외곽선을 따라서 도는 구간에서는 선간전압의 스위칭이 발생하지 않는 것을 확인할 수 있다.The line voltage waveform and the phase current waveform shown in FIG. 12 are overmodulation region I.

It shows the operation under the condition of, and it can be seen that the switching of the line voltage does not occur in the section in which the voltage reference vector follows the outline of the outer hexagon.

인 조건에서의 동작을 보이는데, 홀딩 앵글(

)이 확장됨에 따라 스위칭이 발생하지 않는 구간이 늘어나다가

인 1펄스 모드에서 전압기준벡터가 외부 육각형 꼭지점만 따라 돌기 때문에 도 14와 같이 선간전압 파형이 1펄스 모드인 구형파 인버터의 경우와 같게 나타남을 확인할 수 있다.The line voltage waveform and the phase current waveform shown in FIG. 13 are overmodulation region II.

In the in condition, the holding angle (

) Expands and the interval where no switching occurs

In the 1-pulse mode, since the voltage reference vector rotates along only the outer hexagonal vertex, it can be seen that the line voltage waveform is the same as in the case of the square-wave inverter having the 1-pulse mode as shown in FIG. 14.

15 and 16 are output waveforms according to overmodulation operation of the NPC type three-level inverter (FIG. 16 is an enlarged view of FIG. 15), and FIG. 17 is a harmonic spectrum when the fundamental wave is normalized to 100. FIG.

15 and 16, when the modulation index MI changes from '0' to '1', the value of the fundamental wave component of the output phase voltage changes linearly in proportion to the modulation index MI. You can see that.

FIG. 17 shows the result of analyzing the influence on the harmonic components of the output voltage as the modulation index MI is changed to operate in the linear region and the overmodulation region. The linear index MI is increased by increasing the modulation index MI. = 0.9), over-modulation region I (MI = 0.94), over-modulation region II (MI = 0.97), and 1-pulse mode region (MI = 1.0).

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention belongs may be embodied in other specific forms without changing the technical spirit or essential features of the present invention. You will understand that. Therefore, the embodiments described above are to be understood in all respects as illustrative and not restrictive.

1 is a speed / torque curve of the induction motor of the railway vehicle.

Figure 2 is an embodiment configuration for an NPC type three-level inverter to which the present invention is applied.

3 is a space voltage vector diagram of an NPC type three-level inverter.

4 is an operation region diagram of an NPC type three-level inverter.

5 is a voltage vector diagram in section A of FIG.

FIG. 6 is an exemplary diagram for explaining a process of compensating a voltage reference vector in the overmodulation region I according to the present invention (trajectory and phase voltage waveform of the voltage reference vector in the overmodulation region I).

FIG. 7 is an exemplary explanatory diagram for explaining a process of compensating a voltage reference vector in the overmodulation area II according to the present invention (trajectory and phase voltage waveform of the voltage reference vector in the overmodulation area II). FIG.

8 and 9 are spatial vector overmodulation operation simulation block diagram of the NPC type three-level inverter to which the present invention is applied.

10 is a simulation waveform of line voltage (top) and phase current (bottom) in the linear region I;

11 is a simulation waveform of line voltage (top) and phase current (bottom) in the linear region II.

12 is a simulation waveform of line voltage (top) and phase current (bottom) in the overmodulation region I;

Fig. 13 is a simulation waveform of line voltage (top) and phase current (bottom) in overmodulation area II.

Fig. 14 is a simulation waveform of line voltage (top) and phase current (bottom) in one pulse region.

15 and 16 are output waveforms according to overmodulation operation of an NPC type three-level inverter.

17 is a harmonic spectrum when the normal wave is normalized to 100. FIG.

Claims (5)

In the overmodulation control method of the NPC three-level inverter for railway vehicles, The overmodulation area I and the overmodulation area II for the voltage reference vector overmodulation operation are set according to the modulation index MI. In order to compensate the voltage reference vector in the overmodulation region I, a reference angle derived by the magnitude of the fundamental wave component through the Fourier series of the voltage reference vector (

To generate a new voltage reference vector over four regions linearized every π / 2, In order to compensate the voltage reference vector in the overmodulation region II, the holding angle derived by the magnitude of the fundamental wave component through the Fourier series of the voltage reference vector (

) And the face angle of the actual voltage reference vector (

,

A method for overmodulation of an NPC type 3-level inverter for a railway vehicle, characterized by generating a new voltage reference vector on four regions linearized every .pi. The method of claim 1, The overmodulation area I is, The modulation index MI

An overmodulation control method for an NPC type 3-level inverter for a railway vehicle, characterized in that. The method of claim 2, The new voltage reference vector in the overmodulation region I is generated using the following Equations 4 to 10, wherein the overmodulation control method for an NPC type 3-level inverter for a railway vehicle. [Equation 4]

[Equation 5]

&Quot; (6) "

[Equation 7]

[Equation 8]

[Equation 9]

[Equation 10]

In [Equation 4] to [Equation 10],

The inverter input voltage,

To,

Denotes the angular velocity of the voltage reference vector, respectively. The method of claim 1, The overmodulation area II, The modulation index MI

An overmodulation control method for an NPC type 3-level inverter for a railway vehicle, characterized in that. The method of claim 4, wherein The new voltage reference vector in the overmodulation area II is generated using the following Equations 11 to 19: An overmodulation control method for an NPC type 3-level inverter for a railway vehicle. [Equation 11]

[Equation 12]

[Equation 13]

[Equation 14]

[Equation 15]

[Equation 16]

[Equation 17]

Equation 18

[Equation 19]

In [Equation 11] to [Equation 19],

The inverter input voltage,

To,

Is the angular velocity of the voltage reference vector,

,

Is the actual voltage reference vector

Each phase angle of.

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