KR101799369B1 - Multilevel inverter using bi-directional converter - Google Patents

Multilevel inverter using bi-directional converter Download PDF

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KR101799369B1
KR101799369B1 KR1020160019524A KR20160019524A KR101799369B1 KR 101799369 B1 KR101799369 B1 KR 101799369B1 KR 1020160019524 A KR1020160019524 A KR 1020160019524A KR 20160019524 A KR20160019524 A KR 20160019524A KR 101799369 B1 KR101799369 B1 KR 101799369B1
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voltage
bidirectional
link
inverter
converter
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KR1020160019524A
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Korean (ko)
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KR20170097885A (en
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강필순
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한밭대학교 산학협력단
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H02M7/49—Combination of the output voltage waveforms of a plurality of converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/505—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
    • H02M7/515—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
    • H02M7/521—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only in a bridge configuration

Abstract

A multilevel inverter using a bidirectional converter according to the present invention is configured to vary the voltage of a DC link functioning as an input power source of a bidirectional inverter to a bidirectional converter so that a bidirectional inverter outputs a voltage having a multilevel. According to the present invention, the voltage of the DC link can be varied by the bidirectional converter, thereby widening the variable range of the output voltage. Further, according to the present invention, there is no need to use a low-frequency transformer or an LC filter at the output stage of the multi-level inverter, so that there is no restriction on the frequency variation and a problem of weight and volume increase due to the use of the magnetic body.

Description

[0001] MULTILEVEL INVERTER USING BI-DIRECTIONAL CONVERTER [0002]

The present invention relates to a multi-level inverter using a bidirectional converter configured to vary the voltage of a DC link functioning as an input power source of a bidirectional inverter to a bidirectional converter so that a bidirectional inverter outputs voltages having multi levels.

Generally, multilevel inverters are used to connect a system of DC voltage, such as solar or electric vehicles, to the power system. For example, since the voltage developed from a solar cell is a direct current, a multilevel inverter can be used to convert it and supply it to an AC power system.

The multi-level inverter adopts a method of outputting a sinusoidal voltage by synthesizing a DC voltage through a plurality of switching elements. The effect of dv / dt is small due to the small DC voltage to be switched, and EMI / EMC (electromagnetic interference / Suitability) can also be reduced. As the number of levels of the voltage output from the multi-level inverter increases, the total harmonic distortion (THD) decreases and a good AC voltage can be obtained.

Generally, the magnitude of the output voltage of the multilevel inverter varies depending on the amplitude modulation ratio (M a ) when the input voltage is fixed. However, in order to widen the variable range of the output voltage, Is required.

On the other hand, Patent Document 1 (Korean Patent Laid-Open Publication No. 2013-0062970) discloses a multilevel inverter having a DC link switch capable of power factor control and a method of driving the inverter. However, the voltage of the DC link The voltage applied across both ends) can not be started.

Korean Patent Laid-Open Publication No. 2013-0062970 (June 23, 2013)

An object of the present invention is to provide a multi-level inverter capable of varying the voltage of a DC link in order to widen a variable range of an output voltage.

It is another object of the present invention to provide a multilevel inverter capable of generating an output voltage of 27 levels by easily varying a voltage provided to a DC link even when a power supply unit that supplies a DC voltage of the same size is used do.

In order to achieve the above object, a multi-level inverter using a bidirectional converter according to the present invention includes a first power source unit, a first bidirectional converter for converting a DC voltage of the first power source unit to a DC voltage of another level, A first bidirectional inverter coupled to the first DC link, the first DC link being provided with a DC voltage converted by the first bidirectional converter; A second bidirectional converter for converting a DC voltage of the second power supply unit to a DC voltage of a different level; a second DC link receiving a DC voltage converted by the second bidirectional converter; A second bidirectional inverter connected to the DC link; A third bidirectional converter for converting the DC voltage of the third power supply unit to a DC voltage of a different level, a third DC link receiving the DC voltage converted by the third bidirectional converter, Wherein the first bidirectional inverter, the second bidirectional inverter, and the third bidirectional inverter are cascade-connected, and the first bidirectional inverter, the second bidirectional inverter, and the third bidirectional inverter are connected in cascade manner, The inverter converts the DC voltage provided to each of the first DC link, the second DC link and the third DC link into a voltage having a multilevel by the operation of the plurality of switching elements included in each of the inverters, and outputs the converted voltage .

The first bidirectional inverter, the second bidirectional inverter, and the third bidirectional inverter are each an H-bridge module including a plurality of switching elements.

Wherein the magnitude ratio of the DC voltage supplied to each of the first DC link, the second DC link and the third DC link is 1: 3: 9 And the first bidirectional inverter, the second bidirectional inverter, and the third bidirectional inverter convert the voltage into a voltage having 27 levels and output the voltage.

Wherein the first bidirectional converter is a buck converter type and the second bidirectional converter and the third bidirectional converter are boost converter types.

According to the present invention, the voltage of the DC link functioning as the input power source of the bidirectional inverter can be varied by the bidirectional converter, thereby widening the variable range of the output voltage. Further, according to the present invention, there is no need to use a low-frequency transformer or an LC filter at the output stage of the multi-level inverter, so that there is no restriction on frequency variation and no increase in weight and volume due to use of the magnetic body.

Further, in the present invention, the bidirectional converter boost ratio of the H-bridge module capable of normal operation can be increased even if any one of the three H-bridge modules coupled to the bidirectional converter is damaged (booster converter is utilized as a bidirectional converter) The magnitude of the output voltage can be kept the same as the normal condition (that is, the reliability improvement using the redundancy of the multilevel inverter). For example, when the present invention is applied to an inverter for driving a motor of an electric vehicle, even if an H-bridge module of one of the three H-bridge modules is damaged during operation of the electric vehicle, - Alternative operation via bridge module is possible. That is, in this case, since the number of output levels of the multi-level inverter is reduced and the linear integer ratio of the level is broken, even if the form of the output voltage is far from the sinusoidal wave, there is no problem in driving the motor.

According to the present invention, the voltage of the DC link required to generate the 27-level output voltage can be easily provided to the three bidirectional converters, wherein one of the three bidirectional converters is a buck converter Type and the other two bidirectional converters are of the boost converter type, the voltage provided to the DC link can be easily varied even when a power supply unit that supplies a DC voltage of the same size is used.

1 is a diagram illustrating a multi-level inverter using a bidirectional converter according to the present invention.
FIG. 2 is a view showing the output voltage of each H-bridge module and the output voltage of the multi-level inverter shown in FIG. 1 according to switching angles.
FIG. 3 is a result of simulating the output voltage of each H-bridge module and the output voltage of the multi-level inverter shown in FIG.

Hereinafter, a multi-level inverter using a bidirectional converter according to the present invention will be described in detail with reference to the accompanying drawings. It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to be illustrative of and in a mature and descriptive sense only and is not for the purpose of limiting the invention as defined by the appended claims and their equivalents. Lt; / RTI > The detailed description of known functions and configurations that may unnecessarily obscure the gist of the present invention will be omitted.

1 is a diagram illustrating a multi-level inverter using a bidirectional converter according to the present invention. FIG. 2 is a diagram showing the output voltage of each H-bridge module and the output voltage of the multilevel inverter shown in FIG. 1 according to switching angles (only half period is shown), and each H- (FIG. 2 (a), FIG. 2 (b), and FIG. 2 (c)) and the output voltage of the multilevel inverter according to the present invention (FIG. FIG. 3 shows simulation results of the output voltage of each H-bridge module and the output voltage of the multi-level inverter shown in FIG. 1. For example, the multilevel inverter according to the present invention is connected to a power system of AC 220V (rms) The maximum voltage (v o1 ) of 23.85 V is output in the upper H-bridge module (Fig. 3 (a)), and the maximum voltage (v o2 ) of 71.54 V in the H- 3 (b)), the maximum voltage (v o3 ) of 214.61 V is output from the lower H-bridge module (Fig. 3 (b)). Thus, in the multilevel inverter according to the present invention, (V out ) is outputted (Fig. 3 (d)).

It is an object of the present invention to provide a multi-level inverter capable of varying the voltage of a DC link functioning as an input power source of a bidirectional inverter in order to widen a variable range of an output voltage.

To this end, the multilevel inverter according to the present invention may include a plurality of power sources, a bidirectional converter, a DC link, and a bidirectional inverter, and the present invention will be described in detail with reference to the accompanying drawings.

First, the upper end of the multilevel inverter according to the present invention may include a first power source unit 110, a first bidirectional converter 120, a first DC link 130, and a first bidirectional inverter 140.

The first power source unit 110 may be a direct current voltage source such as a solar cell, or may be configured to receive a commercial power source of AC, such as wind power, and convert it to a DC voltage and output the same. (Not shown) for rectifying the AC voltage and a smoothing circuit portion (not shown) for smoothing the voltage output from the rectifying portion when the first power supply portion 110 converts and outputs the AC voltage to the DC voltage, .

The first bidirectional converter 120 is connected to the first power supply unit 110 to convert the DC voltage of the first power supply unit 110 to a DC voltage of a different level.

1, when the first bidirectional converter 120 is referred to as a buck converter type (hereinafter referred to as " buck converter type ") when the discharge direction of the first power source unit 110 (i.e., the direction from the first power source unit 110 to the first DC link 130) The first bidirectional converter 120 may convert the input DC voltage to a DC voltage of a different level (for example, two switching elements and one inductor), as in the case of a boost converter type or a buck-boost converter type. It is enough if it can be converted to.

However, when the first bidirectional converter 120 is a buck converter type, the DC voltage of the first power supply unit 110 is lowered so that the multilevel inverter according to the present invention can supply the first DC voltage The voltage of the link 130 can be easily generated.

The first DC link 130 may be connected in parallel to the first bidirectional converter 120 and may include a capacitor to receive and store the DC voltage converted by the first bidirectional converter 120 have. The first DC link 130 also serves to remove and stabilize the AC component from the DC voltage output from the first bidirectional converter 120.

The first bidirectional inverter 140 may be connected to the first DC link 130 in parallel and may include an H-bridge circuit including a plurality of switching elements Q 11 , Q 12 , Q 13 , and Q 14 . Module. That is, one end of the first switch Q 11 constituting the first bidirectional inverter 140 is connected to one end of the first DC link 130, and the other end of the second switch Q 12 is connected to the first switch Q 12 Q 11 and the other end of the second switch Q 12 is connected to the other end of the first DC link 130. And the third one is the third switch (Q 13 of one end of the switch (Q 13) is connected to one end of the one end and the first switch (Q 11) of the first DC link 140, the fourth switch (Q 14) ) being connected to the other terminal of the fourth switch, the other end (Q 14) is preferably connected to the other terminal of the other terminal and the second switch (Q 12) of claim 1 DC link 130.

The output voltage of the first bi-directional inverter (140) (v o1) is the other end of the first switch and the other terminal 2 to the node once the forming of the switch (Q 12), the third switch (Q 13) of the (Q 11) 4 means that once the voltage of the node between the forming of the switch (Q 14).

Here, the output voltage v o1 of the first bidirectional inverter 140 is a voltage of the first switching element Q 11 , Q 12 , Q 13 , and Q 14 when the voltage of the first DC link 130 is an input voltage. Can be represented as shown in Fig. 2 (a) (or Fig. 3 (a)) by a complementary switching operation.

The interruption of the multilevel inverter according to the present invention may be constituted by the second power source unit 210, the second bidirectional converter 220, the second DC link 230 and the second bidirectional inverter 240, And the lower stage may include a third power source unit 310, a third bidirectional converter 320, a third DC link 330, and a third bidirectional inverter 340.

The second power source unit 210 and the third power source unit 310 may be a direct current voltage source like the first power source unit 110 or may be configured to receive an AC voltage and convert it to a DC voltage and output it.

The second bidirectional converter 220 is connected to the second power supply unit 210 to convert the DC voltage of the second power supply unit 210 to a DC voltage of a different level and the third bidirectional converter 320 is connected to the third power supply unit 310, And converts the DC voltage of the third power supply unit 310 to a DC voltage of a different level.

1, when the second bidirectional converter 220 is referred to as a boost converter type (hereinafter, referred to as a " boost converter ") when the discharge direction of the second power supply unit 210 The third bidirectional converter 320 is connected to the third power supply line 310 in the discharge direction of the third power supply line 310, The second bidirectional converter 220 (or the third bidirectional converter 320) is shown as being of a boost converter type (consisting of one inductor and two switching elements) Such as a buck converter type or a buck-boost converter type, to convert an input DC voltage into a DC voltage of a different level.

However, when the first bidirectional converter 120 is of the buck converter type and the second bidirectional converter 220 and the third bidirectional converter 320 are of the boost converter type, It is possible to easily generate the voltage of the DC link 130, 230, and 330 required to output the voltage of the DC link 130. [

The second DC link 230 may be connected in parallel to the second bidirectional converter 220 and may include a capacitor to receive and store the DC voltage converted by the second bidirectional converter 220 have. The second DC link 230 also serves to remove and stabilize the AC component from the DC voltage output from the second bidirectional converter 220.

Similarly, the third DC link 330 may be connected in parallel to the third bidirectional converter 320, and may include a capacitor to receive and store the DC voltage converted by the third bidirectional converter 320 . The third DC link 330 also serves to remove and stabilize the AC component from the DC voltage output from the third bidirectional converter 320.

The second bidirectional inverter 240 may be connected in parallel to the second DC link 230 and may be an H-bridge module composed of a plurality of switching elements Q 21 , Q 22 , Q 23 , Q 24 . That is, one end of the one end of the fifth switch (Q 21) constituting the second bi-directional inverter 240 is interconnected to one end of the second DC link 230, the sixth switch (Q 22) is the fifth switch ( Q 21 and the other end of the sixth switch Q 22 is connected to the other end of the second DC link 230. One end of the seventh switch Q 23 is connected to one end of the second DC link 240 and one end of the fifth switch Q 21 and one end of the eighth switch Q 24 is connected to the seventh switch Q 23 And the other end of the eighth switch Q 24 is connected to the other end of the second DC link 230 and the other end of the sixth switch Q 22 .

The second output voltage of the bi-directional inverter (240) (v o2) is the other end of the fifth switch (Q 21) the other end of the sixth switch (Q 22) nodes, the seventh switch (Q 23) once the forming of the 8 refers to one of a voltage between nodes constituting a switch (Q 24).

Here, the second bi-directional inverter 240, the output voltage (V o2) is the second time the voltage of the DC link 230 hayeoteul the input voltage, the switching elements (Q 21, Q 22, Q 23, Q 24) of the It can be represented by FIG. 2 (b) (or FIG. 3 (b)) by a complementary switching operation.

The third bidirectional inverter 340 may be connected to the third DC link 330 in parallel and may be an H-bridge module composed of a plurality of switching elements Q 31 , Q 32 , Q 33 , Q 34 . have. That is, one end of the ninth switch Q 31 constituting the third bidirectional inverter 340 is connected to one end of the third DC link 330, and one end of the tenth switch Q 32 is connected to the ninth switch Q 31 Q 31 and the other end of the tenth switch Q 32 is connected to the other end of the third DC link 330. One end of the eleventh switch Q 33 is connected to one end of the third DC link 340 and one end of the ninth switch Q 31 and one end of the twelfth switch Q 34 is connected to one end of the eleventh switch Q 33 And the other end of the twelfth switch Q 34 is connected to the other end of the third DC link 330 and the other end of the tenth switch Q 32 .

The output voltage v o3 of the third bidirectional inverter 340 is connected to the node between the other end of the ninth switch Q 31 and one end of the tenth switch Q 32 and the node between the other end of the eleventh switch Q 33 12 refers to the end of the voltage between the nodes constituting a switch (Q 34).

Here, the third output voltage of the bi-directional inverter (340) (v o3) is a third DC when the voltage of the link 330 hayeoteul the input voltage, the switching elements (Q 31, Q 32, Q 33, Q 34) Can be represented by a complementary switching operation as shown in Fig. 2 (c) (or Fig. 3 (c)).

The multi-level inverter according to the present invention is configured such that the first bidirectional inverter 140, the second bidirectional inverter 240 and the third bidirectional inverter 340 are connected in a cascade manner (that is, connected in series) The output voltage v out of the multilevel inverter is a node between the other end of the first switch Q 11 and one end of the second switch Q 12 and a node between the other end of the eleventh switch Q 33 and the node Lt; RTI ID = 0.0 > 34 < / RTI > FIG. 2 (d) illustrates an example in which the multilevel inverter shown in FIG. 1 outputs a voltage of 27 levels (only 14 levels corresponding to the half period are shown), and thus the first bidirectional inverter The second bidirectional inverter 240 and the third bidirectional inverter 340 are controlled by the operation of the plurality of switching elements included in each of the first DC link 130, the second DC link 230, Converts the DC voltage supplied to the DC link 330 into a voltage having a multilevel and outputs it.

As described above, the multilevel inverter according to the present invention includes a bidirectional converter (120, 220, 320) that converts a voltage provided to a DC link (130, 230, 330) serving as an input power source of a bidirectional inverter ). ≪ / RTI > If the multi-level inverter according to the present invention is applied to an electric vehicle (i.e., the power source unit of the present invention corresponds to a battery of an electric vehicle), the operation of the bidirectional converters 120, 220, 230 and 330 can be increased to generate a higher output voltage and the operation of the bidirectional converters 120, 220 and 320 allows the DC link 130, 230, 330 can be reduced to reduce the size of the output voltage, and the output voltage frequency can be easily varied, which can be advantageously used to improve the running performance of an electric vehicle.

On the other hand, since the total harmonic distortion THD decreases as the number of levels of the voltages output by the multilevel inverter increases, a high-quality alternating-current voltage can be obtained. Therefore, the multilevel inverter according to the present invention outputs a voltage of seven levels It is preferable to output the 27-level voltage instead. At this time, in order for the bidirectional inverters 140, 240, and 340 to output the 27-level voltage by the operation of the plurality of switching elements, the magnitude ratio of the DC voltage to be supplied to the DC links 130, 230, The bidirectional converters 120, 220, and 320 must convert the DC voltages of the voltage sources 110, 210, and 310 so that the voltages of the first and second capacitors are 9 (aVdc: 3aVdc: 9aVdc).

For example, in a photovoltaic system, a plurality of solar cells are used as voltage sources 110, 210, and 310 that provide the same DC voltage (for example, 48 V) rms), the total voltage of the DC link 130, 230, and 330 connected in series with each other is required to be 310V. Since 23.85 V is required for the first DC link 130, 71.54 V for the second DC link 230, and 214.61 V for the third DC link 330 in order to output the 27 level voltage at this time, Preferably, the bidirectional converter 120 is of the buck converter type and the second bidirectional converter 220 and the third bidirectional converter 320 are of the boost converter type.

That is, in order to output the 27-level voltage to the multilevel inverter according to the present invention, the DC voltage magnitude ratio provided to the first DC link 130, the second DC link 230, and the third DC link 330 is 1 3, and the DC voltage magnitude of the voltage sources 110, 210, 310 is the same and the DC voltage magnitude ratio provided to the DC links 130, 230, 330 is taken into consideration, three bidirectional converters 120, 220 , 320 are operated in the step-down mode and the other two bidirectional converters 220 are operated in the step-up mode.

Hereinafter, a description will be made in detail of a method of outputting a 27-level voltage by the multilevel inverter according to the present invention. In this case, the bidirectional inverters 140, 240 and 340 may be H-bridge modules (upper H-bridge module, suspended H-bridge module, lower H-bridge module) composed of a plurality of switching elements have.

When the multilevel inverter shown in FIG. 1 outputs a voltage of 27 levels, the output voltage v out of the multilevel inverter is expressed by the sum of the output voltages of the respective H-bridge modules as shown in the following equation.

Figure 112016016542324-pat00001

At this time, when the voltages of the DC links 130, 230 and 330 are provided in a 3n ratio (for example, 1: 3: 9), and when three H- ) Becomes 27 (= 3 3 ) levels.

The switching function of the H-bridge module is as follows.

(Q k1 , Q k4 ) = on, S FBk = 1

(Q k1 , Q k3 ) = on, S FBk = 0

(Q k2 , Q k4 ) = on, S FBk = 0

(Q k2 , Q k3 ) = on, S FBk = -1

The switching function of the upper H-bridge module is as follows.

If S FB1 = 1, then v o1 = aV dc

If S FB1 = 0, v o1 = 0

If S FB1 = -1, then v o1 = -aV dc

The switching function of the suspended H-bridge module is as follows.

If S FB2 = 1, then v o1 = 3aV dc

If S FB2 = 0, v o1 = 0

If S FB2 = -1, then v o1 = -3aV dc

The switching function of the lower H-bridge module is as follows.

If S FB3 = 1, then v o1 = 9 aV dc

If S FB3 = 0, v o1 = 0

If S FB3 = -1, then v o1 = -9aV dc

Therefore, the output voltage v out of the multi-level inverter can be expressed by the following equation.

Figure 112016016542324-pat00002

The following [Table 1] shows a switching function for generating 0 and positive (+) output voltage levels.

Output voltage level (m) S FB3 S FB2 S FB1 0 0 0 0 One 0 0 One 2 0 One -One 3 0 One 0 4 0 One One 5 One -One -One 6 One -One 0 7 One -One One 8 One 0 -One 9 One 0 0 10 One 0 One 11 One One -One 12 One One 0 13 One One One

On the other hand, the switching function for generating the negative output voltage level is obtained by multiplying the switching function for generating the positive output voltage level by -1 as shown in the following Table 2 .

Output voltage level (m) S FB3 S FB2 S FB1 -One 0 0 -One -2 0 -One One -3 0 -One 0 -4 0 -One -One -5 -One One One -6 -One One 0 -7 -One One -One -8 -One 0 One -9 -One 0 0 -10 -One 0 -One -11 -One -One One -12 -One -One 0 -13 -One -One -One

The nth harmonic size of the output voltage through the Fourier analysis is as follows.

Figure 112016016542324-pat00003

Where n represents odd harmonics and even harmonics are zero. Also, s represents the output voltage level (s = 13), and θ k represents the switching angle.

When V 1 is the fundamental wave component of the output voltage of the multi-level inverter and V max is the maximum output voltage of the multilevel inverter, the magnitude modulation ratio (M a ) is as follows.

Figure 112016016542324-pat00004

At this time, since the multi-level inverter outputs a voltage level of 27, s = 13, and is a V max = 13aVdc. Therefore, the magnitude modulation ratio (M a ) is as follows.

Figure 112016016542324-pat00005

In the present invention, when the three bidirectional inverters 140, 240, and 340 are H-bridge modules, even if any one of the H-bridge modules is damaged, the H- The same can be maintained.

For example, if the interrupted H-bridge module is damaged and does not operate, the third bidirectional converter 320 (utilizing the boost converter) can boost the voltage across the third DC link 330 to 12aVdc. In this case, the output voltage of the multilevel inverter is reduced from the previous 27 levels to 9 levels (13aVdc, 12aVdc, 11aVdc, aVdc, 0, -aVdc, -11aVdc, -12aVdc, -13aVdc) Output.

In addition, even if any one of the three bidirectional converters 120, 220 and 320 is damaged in the present invention, the magnitude of the output voltage can be kept the same through the other bidirectional converter.

For example, when the first bidirectional converter 120 is damaged and does not operate, the second bidirectional converter 220 and the third bidirectional converter 320 are controlled to have the same step-up ratio of 1: 1, (If the AC voltage of 220V is to be output by the multilevel inverter according to the present invention, each converter requires about 3.2 times as much boosting voltage) .

Alternatively, when the first bidirectional converter 120 is damaged and does not operate, the second bidirectional converter 220 and the third bidirectional converter 320 can be controlled to have a boost ratio of 1: 3, A voltage of 4Vdc, 3aVdc, 2aVdc, aVdc, 0, -aVdc, -2aVdc, -3aVdc and -4aVdc can be output to the multilevel inverter according to the present invention. One of the bidirectional converters 220 and 320 is required to be boosted about 1.6 times in order to generate a DC voltage of 77.5 V and the other is required to be boosted to about 4.8 times in order to generate a DC voltage of 232.5 V. [ .

Meanwhile, the multilevel inverter according to the present invention not only converts the DC voltage of the power supply units 110, 210 and 310 into an AC voltage and supplies the AC voltage to the power system, but also converts an AC voltage input from the outside into a DC voltage, 110, 210, 310). Specifically, the power regenerated from the output terminals of the bidirectional inverters 140, 240, and 340 to the DC links 130, 230, and 330 increases the voltage of the DC links 130, 230, and 330. In the present invention, the bidirectional converters 120, 220, and 320 operate in combination with the DC links 130, 230, and 330, respectively, because the surplus power is preferably regenerated toward the power source units 110, It is possible to charge the power source units 110, 210, and 310 by regenerating surplus power to an input terminal.

In addition, since the power source units 110, 210 and 310 having relatively low energy can be selectively charged by selective bidirectional operation of the bidirectional converters 120, 220 and 320, The charge / discharge state can be efficiently managed. That is, if the voltage of each of the DC links 130, 230, and 330 is increased by the power supplied from the load (not shown), and the third power source unit 310 is in an overdischarge state State, the third bidirectional converter 320 can be driven in the step-down mode to charge the third power source unit 310.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Of course, this is possible. Accordingly, it is intended that the technical scope of the present invention be defined only by the appended claims, and that all equivalent or equivalent variations thereof fall within the technical scope of the present invention.

110: first power supply unit 120: first bidirectional converter
130: first DC link 140: first bidirectional inverter
210: second power supply unit 220: second bidirectional converter
230: second DC link 240: second bidirectional inverter
310: third power supply unit 320: third bidirectional converter
330: third DC link 340: third bidirectional inverter

Claims (4)

A first bidirectional converter for converting a DC voltage of the first power supply unit to a DC voltage of a different level; a first DC link for receiving a DC voltage converted by the first bidirectional converter; A first bidirectional inverter coupled to the DC link;
A second bidirectional converter for converting a DC voltage of the second power supply unit to a DC voltage of a different level; a second DC link receiving a DC voltage converted by the second bidirectional converter; A second bidirectional inverter connected to the DC link; And
A third bidirectional converter for converting the DC voltage of the third power supply unit to a DC voltage of a different level, a third DC link for receiving the DC voltage converted by the third bidirectional converter, And a third bidirectional inverter connected to the DC link,
The first bidirectional inverter, the second bidirectional inverter and the third bidirectional inverter are connected in a cascade manner,
The first power source unit, the second power source unit, and the third power source unit are solar cells providing the same DC voltage of 48V,
The first bidirectional converter is a buck converter type in order to convert a DC voltage of 48V provided from each of the first power source unit, the second power source unit and the third power source unit to AC 220V (rms) having 27 levels, The second bidirectional converter and the third bidirectional converter are of a boost converter type and are converted by the first bidirectional converter, the second bidirectional converter, and the third bidirectional converter to convert the first DC link, the second DC link, The ratio of the magnitude of the DC voltage provided to each DC link is 1: 3: 9,
The first bidirectional inverter, the second bidirectional inverter, and the third bidirectional inverter are connected to the first DC link, the second DC link, and the third DC link, respectively, by the operation of the plurality of switching elements included in each of the first bidirectional inverter, (Rms) having 27 levels, and outputs the converted AC 220V (rms). The multi-level inverter using the bidirectional converter. The method according to claim 1,
Wherein the first bidirectional inverter, the second bidirectional inverter, and the third bidirectional inverter are H-bridge modules each having a plurality of switching elements. delete delete
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KR101094002B1 (en) * 2009-12-16 2011-12-15 삼성에스디아이 주식회사 Power converting device

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Publication number Priority date Publication date Assignee Title
KR101094002B1 (en) * 2009-12-16 2011-12-15 삼성에스디아이 주식회사 Power converting device

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