KR101524064B1 - Driving apparatus and mehtod of multi-level converter, and multi-level converter system thereof - Google Patents

Abstract

An apparatus and method for driving a multi-level converter and a multi-level converter system using the same are provided. A driving apparatus for a multi-level converter according to an embodiment of the present invention is a driving apparatus for a multi-level converter for driving a multi-level converter, comprising: a current sensing unit for sensing a current flowing in the multi-level converter; A control unit for generating a control signal for controlling a period or frequency of a carrier signal according to a current value sensed by the current sensing unit; A carrier signal generator for generating a variable carrier signal according to the control signal; And a PWM signal generator for generating a PWM signal of the multi-level converter based on the variable carrier signal.

Description

TECHNICAL FIELD [0001] The present invention relates to a driving apparatus and method for a multi-level converter, and a multi-level converter system using the same. BACKGROUND ART [0002]

The present invention relates to an apparatus and method for driving a multi-level converter, and a multi-level converter system using the same. More particularly, the present invention relates to a multi- Level converter, and a multi-level converter system using the same.

Conventional voltage-type converters require a large number of switching times of the converter, and a filter to make a sine wave. Therefore, a high-capacity converter which requires less distortion of the voltage waveform and does not require the installation of a filter is required, and a multi-level converter is introduced. Such a system using a multi-level converter or a multi-level inverter is an efficient system for applications requiring low harmonic components and high power.

When a multi-level converter (inverter) operates, a loss occurs in the switches constituting them. As the level increases, the number of switch elements increases proportionally. The loss in this switch element is a very important consideration in terms of minimizing volume and minimizing loss in system implementation.

The loss of the switching element is the loss of the off state, the conduction state loss, and the switching loss. In the case of the multi-level converter, it is important to reduce the switching loss because of the high switching frequency. For example, in the case of an insulated gate bipolar transistor (IGBT), which is often used as a switching element in a multi-level converter, a loss occurs when switching occurs.

1 is a graph showing a switching loss according to a current of an IGBT.

Referring to FIG. 1, it can be seen that the switching loss increases more steeply as the magnitude of the current increases. That is, when the switching occurs at the moment when a large current flows, the loss increases accordingly.

Therefore, switching loss occurs due to the switching of the IGBT or the like used in the converter, so it is necessary to reduce the switching loss of the multi-level converter having a large number of switching times.

Korean Patent Publication No. 2002-0071616

SUMMARY OF THE INVENTION The present invention has been accomplished in order to solve the above problems, and it is an object of the present invention to provide a method and an apparatus for adjusting a period or a frequency of a carrier signal according to a magnitude of a current, The present invention provides a driving apparatus and method of a multi-level converter capable of reducing a switching loss while maintaining the same as possible, and a multi-level converter system using the same.

Also, there is provided a driving apparatus and method for a multi-level converter for switching a PWM using a fixed frequency in a multi-level converter according to an amount of a current passing through the converter so that an IGBT is switched by avoiding a section having a large switching loss, And to provide a multi-level converter system using the same.

The problems to be solved by the present invention are not limited to the above-mentioned problems, and other matters not mentioned can be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided an apparatus for driving a multi-level converter for driving a multi-level converter, the apparatus comprising: ; A control unit for generating a control signal for controlling a period or frequency of a carrier signal according to a current value sensed by the current sensing unit; A carrier signal generator for generating a variable carrier signal according to the control signal; And a PWM signal generator for generating a PWM signal of the multi-level converter based on the variable carrier signal.

According to an aspect of the present invention, there is provided a method of driving a multi-level converter, the method comprising: sensing a current flowing through the multi-level converter; Generating a control signal for controlling a period or a frequency of the carrier signal according to the sensed current value; Generating a variable carrier signal according to the control signal; And generating a PWM signal applied to the multi-level converter based on the variable carrier signal.

According to an aspect of the present invention, there is provided a multi-level converter system including: a power supply for supplying AC power; A multi-level converter for converting the AC power into DC power; A current sensor for sensing a current of the multi-level converter; And a microcomputer for controlling the operation of the multi-level converter by varying the switching frequency of the multi-level converter based on the sensed current value.

Other specific details of the invention are included in the detailed description and drawings.

According to the present invention, in the PWM application based on the carrier signal of the multi-level converter, the switching loss can be reduced while maintaining the performance of the converter as much as possible by adjusting the period or frequency of the carrier signal according to the magnitude of the current.

Also, in the multi-level converter, the PWM using the fixed frequency can be switched according to the amount of the current passing through the converter, thereby avoiding a period where the switching loss is large, thereby reducing the switching loss.

FIG. 1 is a graph showing a switching loss due to an insulated gate bipolar transistor (IGBT) current.
2 is a block diagram of a driving apparatus for a multi-level converter according to an embodiment of the present invention.
3 is a diagram illustrating a process of generating a PWM signal according to a carrier signal for driving a multi-level converter.
FIG. 4 is a diagram showing a cycle control of a carrier signal and a carrier signal as a basis of the PWM signal of FIG. 3. FIG.
5 is a flowchart of a method of driving a multi-level converter according to an embodiment of the present invention.
6 is a block diagram of a multi-level converter system according to an embodiment of the present invention.
FIG. 7 is a diagram illustrating an embodiment of a multi-level converter constituting the multi-level system of FIG.
8 is a graph showing an example of a variable relationship of the switching frequency according to the current in the multi-level converter system of FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Also, commonly used predefined terms are not ideally or excessively interpreted unless explicitly defined otherwise.

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

FIG. 2 is a block diagram of a driving apparatus for a multi-level converter according to an embodiment of the present invention, FIG. 3 is a diagram illustrating a process of generating a PWM signal according to a carrier signal for driving a multi-level converter, FIG. 4 is a diagram showing a cycle control of a carrier signal and a carrier signal as a basis of the PWM signal of FIG. 3. FIG.

2, a driving apparatus 100 of a multi-level converter according to an embodiment of the present invention is a driving apparatus 100 of a multi-level converter for driving a multi-level converter 200, A control unit 120 for generating a control signal for controlling a period or a frequency of a carrier signal according to a current value sensed by the current sensing unit 110, a current sensing unit 110 for sensing current flowing through the level converter 200, A carrier signal generation unit 130 for generating a variable carrier signal in accordance with a control signal of the control unit 120 and a PWM signal generating unit 130 for generating a PWM signal of the multi- And a PWM signal generator 140 for generating a PWM signal.

The current sensing unit 110 senses a current flowing through the multi-level converter 200. That is, the current sensing unit 110 serves as a current sensor. A current transformer method in which a primary current is detected by measuring a secondary current by winding a primary coil and a secondary coil around a core and a Hall element in a magnetic field generated by the current, A Hall element type which detects the intensity of the magnetic field, that is, the intensity of the current, can be used by measuring the voltage. Of course, it will be apparent to those skilled in the art that many other ways of sensing current can be used.

The control unit 120 generates a control signal for controlling the period or the frequency of the carrier signal according to the current value sensed by the current sensing unit 110. At this time, the control unit 120 generates a control signal to reduce the switching loss of the multi-level converter 200. Therefore, in order to reduce the switching loss as the current value sensed by the current sensing unit 110 increases, the controller 120 generates a control signal to increase the period of the carrier signal or decrease the frequency of the carrier signal, (130). Here, the control unit 120 may generate a control signal for adjusting the period or the frequency of the carrier signal only when the current value is equal to or greater than a preset current value.

The carrier signal generation unit 130 generates a variable carrier signal according to the control signal of the control unit 120. The variable carrier signal means that the period of the carrier signal or the frequency of the carrier signal is changed by the control signal. The reference of the period of the carrier signal or the frequency of the carrier signal is the current. It goes without saying that the carrier signal can use various waveforms such as a triangular wave or a saw tooth wave. At this time, the carrier signal generation unit 130 may generate a plurality of variable carrier signals. For example, a plurality of variable carrier signals can be generated by dividing a level to generate a multicarrier and adjusting the period or frequency of each of the multicarrier. Such a multicarrier (a plurality of carriers) can be used as a basis of PWM (Pulse Width Modulation). This will be described in detail later with reference to FIG. 3 and FIG. And, the plurality of variable carrier signals can maintain the same period or the same frequency with each other. That is, when there are a plurality of carrier signals, a plurality of carrier signals can be simultaneously periodically adjusted or frequency-adjusted by a control signal transmitted from the control unit 120.

The PWM signal generating unit 140

And generates the PWM signal of the multi-level converter 200 based on the variable carrier signal of the carrier signal generation unit 130. Here, the PWM signal is a signal generated by PWM (Pulse Width Modulation) of a variable carrier signal. This will be described in detail later with reference to FIG. 3 and FIG. The PWM signal generated based on the variable carrier signal is applied to the multi-level converter 200 to divide the current section of the multi-level converter 200, thereby lowering the switching frequency in the high current portion. That is, by adjusting the period or frequency of the carrier signal according to the magnitude of the current, the PWM signal based on the variable carrier is input to the multi-level converter 200 to reduce the switching loss of the multi-level converter 200.

In Fig. 3, the number of levels of the carrier signal is shown as four, and a sine wave is shown as a reference signal. When using four carrier signals in this way, a 5-level converter can be implemented in carrier-based PWM applications. The carrier signal is level 1, level 2, level 3, level 4 according to the number of levels from top to bottom. Here, it will be apparent to those skilled in the art that each carrier signal is shown as a triangle wave, but may be another waveform as described above. The carrier signal of each level has the same frequency and period, but the average value of the signal, that is, the position on the vertical axis is different. The carrier signals of Level 1 and Level 2 are opposite in phase to each other, and the carrier signal of Level 3 and the carrier signal of Level 4 are opposite in phase to each other. The PWM signal of the 5-level converter shown in the lower stage can be generated by comparing the carrier signal of each level with the sinusoidal wave. As described above, a conventional multi-level converter uses a PWM using a fixed frequency. That is, the period and the frequency of the carrier signal are fixed and used.

In Fig. 4, one carrier signal is shown. The PWM signal can be generated by comparing the carrier signal with the sinusoidal signal as the reference signal. In order to adjust such a carrier signal, the period of the carrier signal can be controlled. Although not shown in FIG. 4, the frequency of the carrier signal may be controlled to adjust the carrier signal. Thus, it is possible to improve the switching loss of the multi-level converter 200 by controlling the period or frequency of the carrier signal according to the magnitude of the current to apply the PWM signal based on the variable carrier to the multi-level converter 200 .

5 is a flowchart of a method of driving a multi-level converter according to an embodiment of the present invention.

Referring to FIG. 5, a method of driving a multi-level converter according to an embodiment of the present invention includes sensing a current flowing in a multi-level converter (S10) (S20), generates a variable carrier signal according to the control signal (S30), and generates a PWM signal to be applied to the multi-level converter based on the variable carrier signal (S40 ).

Here, as described above, a control signal is generated so as to reduce the switching loss. Therefore, in order to reduce the switching loss as the sensed current value increases, a control signal is generated so as to increase the cycle of the carrier signal or decrease the frequency of the carrier signal, thereby generating a variable carrier signal whose cycle is increased or whose frequency is shortened .

FIG. 6 is a block diagram of a multi-level converter system according to an embodiment of the present invention, FIG. 7 is a diagram illustrating an embodiment of a multi-level converter constituting the multi-level system of FIG. 6, 8 is a graph showing an example of a variable relationship of the switching frequency according to the current in the multi-level converter system of FIG.

Referring to FIG. 6, the multi-level converter system includes a power supply 10 for supplying AC power, a multi-level converter 20 for converting AC power into DC power, The microcomputer 40 controls the operation of the multi-level converter 20 by varying the switching frequency of the multi-level converter 20 based on the current value sensed by the current sensor 30 and the current sensor 30, .

Therefore, the multi-level converter system can change the switching frequency of the multi-level converter 20 according to the value of the current flowing in the multi-level converter 20, thereby reducing the switching loss of the multi-level converter 20.

Here, the multi-level converter 20 includes a plurality of submodules, and each submodule can include a pair of IGBTs. For example, referring to FIG. 7, the multi-level converter 20 may be composed of three legs, six arms, and each arm may include n submodules SM . Each sub-module may include a pair of IGBTs. Switching of the submodules is performed by the on / off operation of the IGBT. As an example of charging and discharging, the sub module corresponding to On can be charged and discharged according to the current direction of the dark current. For example, if the dark current has a positive value, the submodule having the lowest voltage is selected. If the dark current has a negative value, the submodule having the highest voltage is selected to discharge. Therefore, the number of switching times per submodule is small, but the number of switching times of the multi-level converter 20 including a plurality of submodules is increased. Therefore, the switching loss of the multi-level converter 20 can be varied based on the sensed current value, so that the IGBT can be switched over in a section where the switching loss is large, that is, .

At this time, the microcomputer 40 may vary the switching frequency so as to be in inverse proportion to the current value. For example, referring to FIG. 8, as the magnitude of the current increases, the switching frequency can be reduced and the number of switching operations can be reduced. That is, when the carrier-based PWM is applied, the switching frequency is reduced to reduce the number of switching operations, thereby reducing the switching loss of the multi-level converter 20. [

The microcomputer 40 generates a variable carrier signal by adjusting the period or frequency of the carrier signal according to the current value, generates a PWM signal based on the variable carrier signal, and applies the PWM signal to the multi-level converter 20 have. In this case, as described above, the PWM using the fixed frequency is changed by changing the frequency according to the amount of the current passing through the converter, so that the switching loss can be avoided (i.e., the period in which the current greatly flows) .

This multi-level converter system can reduce the switching loss of the converter and can be used in conjunction with future offshore wind power generation. It can be used for high capacity converter such as medium and large HVDC (High Voltage Direct Current) and multi terminal HVDC As demand grows, it is expected to become more important. Also, it can be applied to medium and large-sized motor drives based on carrier modulation such as PWM.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

10: power supply 20: multi-level converter
30: current detector 40: microcomputer
100: Multi-level converter driving device
110: current sensing unit 120:
130: carrier signal generation unit 140: PWM signal generation unit
200: Multi-level converter

Claims (10)

A driving apparatus for a multi-level converter for driving a multi-level converter,
A current sensing unit sensing a current flowing in the multi-level converter;
Level converter to reduce the period or frequency of the carrier signal to be provided to the multi-level converter in response to the increase in the current value sensed by the current sensing unit to reduce the switching loss of the multi-level converter, To generate a control signal for increasing the number of switching times of the multi-level converter by decreasing the number of switching times or increasing the frequency or frequency of the carrier signal for providing to the multi-level converter in correspondence to the decrease in the current value A control unit;
A carrier signal generator for generating a plurality of variable carrier signals according to the control signal; And
And a PWM signal generator for generating a PWM signal of the multi-level converter based on the plurality of variable carrier signals. delete delete The method according to claim 1,
Wherein the plurality of variable carrier signals maintain the same period or the same frequency with each other. A method of driving a multi-level converter,
Sensing a current flowing in the multi-level converter;
The converter reduces the number of switching times of the multi-level converter by decreasing the period or frequency of the carrier signal to be provided to the multi-level converter in correspondence with the increase in the sensed current value so as to reduce the switching loss of the multi-level converter. Generating a control signal that increases the number of switching times of the multi-level converter by increasing the frequency or frequency of the carrier signal for providing to the multi-level converter corresponding to the decrease of the current value;
Generating a plurality of variable carrier signals according to the control signal; And
Generating a PWM signal to be applied to the multi-level converter based on the plurality of variable carrier signals. A power source for supplying AC power;
A multi-level converter for converting the AC power into DC power;
A current sensor for sensing a current of the multi-level converter; And
And a microcomputer for controlling the operation of the multi-level converter by varying the switching frequency of the multi-level converter based on the sensed current value,
Wherein the microcomputer reduces a period or a frequency of a carrier signal for providing to the multi-level converter in correspondence with the increase in the current value so as to reduce the switching loss of the multi-level converter, Level converter by increasing the frequency or frequency of the carrier signal for providing to the multi-level converter in response to the current value becoming smaller, thereby generating a plurality of variable carrier signals that increase the number of switching times of the multi-level converter And generates a PWM signal based on the plurality of variable carrier signals and applies the PWM signal to the multi-level converter. The method according to claim 6,
Wherein the multi-level converter comprises a plurality of sub-modules. 8. The method of claim 7,
Wherein each sub-module comprises a pair of IGBTs. The method according to claim 6,
Wherein the microcomputer varies the switching frequency in inverse proportion to the current value. delete

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