阅读说明：本技术 逆变器控制装置 (inverter control device ) 是由 李学俊 于 2019-03-12 设计创作，主要内容包括：本发明提供一种逆变器控制装置,本发明的一实施例的装置包括：逆变器部,将直流端电压变换为交流电压,由三相的上部开关元件和下部开关元件构成；变换部,利用所述直流端电压、脉宽调制指数、能够调节不连续调制区间的不连续调制角度以及相电压指令与所述逆变器部的输出电流的相位差来将三相的相电压指令变换为极电压指令；以及控制部,利用三角载波从所述极电压指令生成用于控制所述上部开关元件和所述下部开关元件的信号。(The present invention provides an inverter control device, the device of one embodiment of the present invention includes: an inverter unit configured to convert a dc voltage into an ac voltage, the inverter unit including three-phase upper and lower switching elements; a conversion unit that converts the three-phase voltage command into an electrode voltage command by using the dc terminal voltage, a pulse width modulation index, a discontinuous modulation angle that can adjust a discontinuous modulation section, and a phase difference between the phase voltage command and the output current of the inverter unit; and a control unit that generates a signal for controlling the upper switching element and the lower switching element from the voltage command by using a triangular carrier.)

1. An inverter control device having a minimum loss regardless of a power factor in a discontinuous modulation section, wherein,

The method comprises the following steps:

An inverter unit configured to convert a dc voltage into an ac voltage, the inverter unit including three-phase upper and lower switching elements;

a conversion unit that converts the three-phase voltage command into an electrode voltage command by using the dc terminal voltage, a pulse width modulation index, a discontinuous modulation angle that can adjust a discontinuous modulation section, and a phase difference between the phase voltage command and the output current of the inverter unit; and

and a control unit that generates a signal for controlling the upper switching element and the lower switching element from the voltage command by using a triangular carrier.

2. The inverter control device according to claim 1,

The conversion unit includes:

An offset voltage command calculation unit that calculates an offset voltage command from the phase voltage command, the dc voltage, the pulse width modulation index, the discontinuous modulation angle, and the phase difference; and

And an electrode voltage command calculation unit that calculates the electrode voltage command from the phase voltage command and the offset voltage command.

3. The inverter control device according to claim 2,

The offset voltage command calculation unit includes:

A first coordinate conversion unit that converts the phase voltage commands of the three phases into d-axis and q-axis voltage commands of a static coordinate system;

An angle conversion unit that converts the phase difference between the phase voltage command and the current into a virtual phase difference;

A rotation conversion unit that performs rotation conversion of the d-axis and q-axis voltage commands by the virtual phase difference;

A second coordinate conversion unit for converting the d-axis and q-axis voltage commands after the rotation conversion into virtual phase voltage commands; and

And an offset voltage command generation unit configured to generate the offset voltage command using the phase voltage command, the dc voltage, the pulse width modulation index, the discontinuous modulation angle, and the virtual phase voltage command.

4. the inverter control device according to claim 3,

The offset voltage command generation unit includes:

a first determination unit configured to determine a maximum value and a minimum value of the phase voltage command;

A second determination unit configured to determine a maximum value and a minimum value of the virtual phase voltage command; and

A third determination unit that determines the offset voltage command using the dc terminal voltage, the pulse width modulation index, the discontinuous modulation angle, the maximum value and the minimum value of the phase voltage command, and the maximum value and the minimum value of the virtual phase voltage command.

5. The inverter control device according to claim 4,

the third determination unit determines the offset voltage command using the following equation:

Wherein the content of the first and second substances,Is the offset voltage command, V_dcIs the DC terminal voltage, k is MIcos θ_DMI is the pulse width modulation index, θ_DIs the angle of the discontinuous modulation,AndAre the maximum value and the minimum value of the phase voltage command,andAre the maximum and minimum values of the virtual phase voltage command.

6. The inverter control device according to claim 3,

At said phase difference ofIn the case of (2), the angle conversion unit determines the virtual phase difference to be phi_V＝φ，

where φ is said phase difference, φ_VIs the virtual phase difference.

7. The inverter control device according to claim 3,

At said phase difference ofIn the case of (2), the angle conversion unit determines the virtual phase difference as

8. The inverter control device according to claim 3,

At said phase difference ofin the case of (2), the angle conversion unit determines the virtual phase difference as

9. The inverter control device according to claim 1,

The control section includes:

A comparison unit that compares the pole voltage command with the triangular carrier, and outputs 1 as a switching function of the upper switching element when a difference between the pole voltage command and the triangular carrier is a positive number or 0, and outputs 0 as a switching function of the upper switching element when a difference between the pole voltage command and the triangular carrier is a negative number; and

An inverting section for inverting an output of the comparing section to output as a switching function of the lower switching element.

10. The inverter control device according to claim 9,

The period of the triangular carrier wave is the same as the switching frequency, and the maximum value of the triangular carrier wave isThe minimum value of the triangular carrier is

Technical Field

the present invention relates to an inverter control device.

Background

With the development of power semiconductor technology, power supplies of Variable Voltage and Variable Frequency (VVVF) can be relatively easily realized by using power elements capable of switching at high speed. As a circuit for generating VVVF, a voltage-source inverter is mainly used, and a dc voltage source of the inverter is used as a variable voltage source that receives an input and generates an ac current.

Such voltage-type inverters are mainly used in Energy Storage Systems (ESS), Photovoltaic (PV) inverters, and motor drive (motor drive) technologies.

Various pulse width modulation methods have been developed for applying the voltage source inverter as described above. As the pulse width modulation method, Sinusoidal Pulse Width Modulation (SPWM), Space Vector PWM (SVPWM), and the like are mainly used in the industrial field. The above-mentioned SPWM and SVPWM belong to a continuous pulse width modulation method.

In addition, Discontinuous Pulse Width Modulation (DPWM) methods are also used to reduce the switching loss of the power semiconductor, and among them, the 60 ° Discontinuous Pulse Width Modulation (DPWM) method is the most representative discontinuous pwm method. Such a discontinuous pulse width modulation method can be realized by appropriately selecting an offset voltage in a pulse width modulation method using an offset voltage and a triangular carrier comparison pulse width modulation method.

In contrast, a method of performing discontinuous pulse width modulation by adjusting the discontinuous pulse width modulation interval is disclosed as a discontinuous pulse width modulation method. The technology can realize the optimal Total Harmonic Distortion (THD) and loss of current at each working point through the free adjustment of discontinuous pulse width modulation intervals. In this technique, there is always the minimum loss when the power factor is 1, and therefore, it is necessary to have the minimum loss regardless of the power factor.

Disclosure of Invention

The present invention is directed to an inverter control device, wherein a user controls a trade-off between a switching loss and a current THD by adjusting a discontinuous modulation interval, so that a minimum loss is always achieved in a given discontinuous modulation interval regardless of a power factor.

In order to solve the technical problem described above, an inverter control device according to an embodiment of the present invention may include: an inverter unit configured to convert a dc voltage into an ac voltage, the inverter unit including three-phase upper and lower switching elements; a conversion unit that converts the three-phase voltage command into an electrode voltage command by using the dc terminal voltage, a pulse width modulation index, a discontinuous modulation angle that can adjust a discontinuous modulation section, and a phase difference between the phase voltage command and the output current of the inverter unit; and a control unit that generates a signal for controlling the upper switching element and the lower switching element from the voltage command by using a triangular carrier.

In an embodiment of the present invention, the transformation unit may include: an offset voltage command calculation unit that calculates an offset voltage command from the phase voltage command, the dc voltage, the pulse width modulation index, the discontinuous modulation angle, and the phase difference; and an electrode voltage command calculation unit that calculates the electrode voltage command from the phase voltage command and the offset voltage command.

in an embodiment of the present invention, the offset voltage command calculation unit may include: a first coordinate conversion unit that converts the phase voltage commands of the three phases into d-axis and q-axis voltage commands of a static coordinate system; an angle conversion unit that converts the phase difference between the phase voltage command and the current into a virtual phase difference; a rotation conversion unit that performs rotation conversion of the d-axis and q-axis voltage commands by the virtual phase difference; a second coordinate conversion unit for converting the d-axis and q-axis voltage commands after the rotation conversion into virtual phase voltage commands; and an offset voltage command generation unit configured to generate the offset voltage command using the phase voltage command, the dc voltage, the pulse width modulation index, the discontinuous modulation angle, and the virtual phase voltage command.

In an embodiment of the present invention, the offset voltage command generating unit may include: a first determination unit configured to determine a maximum value and a minimum value of the phase voltage command; a second determination unit configured to determine a maximum value and a minimum value of the virtual phase voltage command; and a third determination unit configured to determine the offset voltage command using the dc terminal voltage, the pulse width modulation index, the discontinuous modulation angle, the maximum value and the minimum value of the phase voltage command, and the maximum value and the minimum value of the virtual phase voltage command.

In an embodiment of the present invention, the third determination unit may determine the offset voltage command by using the following equation:

wherein the content of the first and second substances,is the offset voltage command, V_dcis the DC terminal voltage, k is MIcos θ_DMI is the pulse width modulation index, θ_Dis the angle of the discontinuous modulation,Andare the maximum value and the minimum value of the phase voltage command,AndAre the maximum and minimum values of the virtual phase voltage command.

In an embodiment of the present invention, the phase difference isIn the case of (3), the angle conversion unit may determine the virtual phase difference as phi_V＝φ，

Where φ is said phase difference, φ_Vis the virtual phase difference.

In an embodiment of the present invention, the phase difference isIn the case of (3), the angle conversion unit may determine the virtual phase difference as

In an embodiment of the present invention, the phase difference isIn the case of (3), the angle conversion unit may determine the virtual phase difference as

In an embodiment of the present invention, the control unit may include: a comparison unit that compares the pole voltage command with the triangular carrier, and outputs 1 as a switching function of the upper switching element when a difference between the pole voltage command and the triangular carrier is a positive number or 0, and outputs 0 as a switching function of the upper switching element when a difference between the pole voltage command and the triangular carrier is a negative number; and an inverting section for inverting an output of the comparing section to output as a switching function of the lower switching element.

In an embodiment of the present invention, the period of the triangular carrier may be the same as the switching frequency, and the maximum value of the triangular carrier isThe minimum value of the triangular carrier is

According to the present invention as described above, a virtual phase voltage command is generated by a rotation conversion of an actual phase voltage command, and a rotation angle used for the rotation conversion can be determined by a phase difference between the voltage command and a current and a discontinuous modulation angle. Further, pulse width modulation is performed using the virtual phase voltage command, the actual phase voltage command, and the discontinuous modulation angle, whereby the contradictory relationship between the switching loss and the current THD can be appropriately controlled by adjusting the discontinuous modulation section. Furthermore, in a given discontinuous modulation interval, minimal losses are always present, regardless of the power factor.

Drawings

Fig. 1 is a schematic circuit diagram of a two-level three-phase voltage-type inverter.

Fig. 2A and 2B are schematic diagrams for explaining a triangular carrier-based comparison pulse width modulation method controlled by the PWM control unit of fig. 1.

Fig. 3 is a schematic diagram showing spatially in vectors the output phase voltages based on the switching function.

FIG. 4 illustrates a phase voltage command as a voltage command vector V when the phase voltage command is expressed in a space vector^*the operation of the 60 ° discontinuous pulse width modulation method based on the a-phase.

fig. 5 is a schematic diagram for explaining another embodiment of the discontinuous pulse width modulation method.

Fig. 6 is a schematic diagram for explaining Adjustable Discontinuous Pulse Width Modulation (ADPWM) as a Discontinuous pulse width modulation method.

Fig. 7 is a block diagram of an implementation of ADPWM.

Fig. 8 is a schematic diagram for explaining a case where the phase voltage command is changed to the pole voltage command in the inverter control device according to the embodiment of the present invention.

Fig. 9 is a detailed configuration diagram of the offset voltage command calculation unit of fig. 8.

Fig. 10 is a detailed configuration diagram of an embodiment of the offset voltage command generating unit of fig. 9.

FIGS. 11A to 11C are diagrams for explaining a phase difference φ between a voltage command and a current and a virtual phase difference φ as angle information for generating a virtual phase voltage command in an embodiment of the present invention_VA schematic diagram of the relationship of (a).

Fig. 12 is a schematic diagram for explaining an operation of the angle conversion unit of fig. 9.

Fig. 13 is a schematic diagram for explaining a switching loss of the inverter control device according to the embodiment of the present invention.

description of reference numerals

10: an offset voltage command calculation unit; 20: an electrode voltage command calculation unit; 11. 14: a coordinate transformation unit; 12: a rotation conversion unit; 13: an angle changing unit; 15: an offset voltage command generation unit; 31. 32, 33: determining part

Detailed Description

In order that the structure and effects of the present invention can be fully understood, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described below, but may be implemented in various forms and may be variously changed. However, the description of the present embodiments is intended to provide a complete disclosure of the present invention and to fully disclose the scope of the present invention to those of ordinary skill in the art to which the present invention pertains. In the drawings, the size of structural elements is exaggerated and the scale of structural elements may be exaggerated or reduced for convenience of explanation.

the terms "first", "second", etc. may be used to describe various structural elements, but the structural elements should not be limited to the above terms. The above terms may be used only to distinguish one structural element from another. For example, a "first structural element" may be named a "second structural element," and similarly, a "second structural element" may also be named a "first structural element," without departing from the scope of the present invention. Furthermore, unless the context clearly dictates otherwise, expressions in the singular include expressions in the plural. Terms used in the embodiments of the present invention may be construed as meanings well known to those skilled in the art, unless otherwise defined.

next, an inverter control apparatus and method according to an embodiment of the present invention will be described with reference to fig. 2A to 5.

Fig. 1 is a schematic circuit diagram of a two-level three-phase voltage-type inverter, which is an example of an inverter used for an energy storage system ESS, a photovoltaic inverter, and a motor drive.

The inverter is composed of a dc terminal 101 and an inverter unit 102. N of the dc terminal 101 represents a virtual dc terminal neutral position. The inverter unit 102 is constituted by three-phase power switches. S of the inverter section 102_a、S_b、S_cRespectively, the switching functions of the three-phase power switch. S_a1 denotes that the a-phase upper switch is on, S_aAnd 0 indicates that the lower switch is on. I.e. S_aAndare in a complementary relationship. The same applies to S_bAnd S_c. The ac voltage of inverter unit 102 is transmitted to load 200.

The three-phase voltage command is input to a Pulse Width Modulation (PWM) control unit 110. The PWM control unit 110 determines a switching function to be applied to the inverter unit 102 and supplies the determined switching function to the inverter unit 102.

the triangular carrier comparison modulation by the PWM control unit 110 will be described with reference to fig. 2A and 2B.

Fig. 2A and 2B are schematic diagrams for explaining a triangular carrier-based comparison pulse width modulation method controlled by the PWM control unit of fig. 1. Fig. 2A is a schematic diagram for explaining the structure of the pole voltage, and fig. 2B shows a triangular carrier comparison pulse width modulation method.

Offset voltage command calculation unit 111 calculates an offset voltage command using three-phase voltage command 2AThe pole voltage command calculation unit 112 calculates the pole voltage command 2B using the three-phase voltage command 2A and the offset voltage command. This is expressed by the following equation 1.

[ EQUATION 1 ]

The offset voltage is a component which is present in common in the three-phase pole voltages. Since the offset voltage represents a zero sequence voltage, it does not contribute to the synthesis of line-to-line voltages.

Referring to fig. 2B, a triangular carrier 2C (triangle) compared with the pole voltage command 2Bcarrier wave) has the same period as the switching frequency. The maximum and minimum values of carrier 2C are respectivelyAnd

The comparison unit 113 compares the pole voltage command 2B with the triangular carrier 2C. As a result of the comparison, when the difference between the pole voltage command 2B and the triangular carrier 2C is a positive number or 0, the switching function output may be 1. Further, as a result of the comparison, when the difference between the voltage command 2B and the triangular carrier 2C is negative, the switching function output may be 0. When a triangular carrier is defined as v_triThe respective switching functions may be organized using relational expressions such as the following equations 2, 3, and 4.

[ equation 2 ]

[ equation 3 ]

[ EQUATION 4 ]

the inverter 114 can determine the switching function of the lower switching element of the inverter 102. Since the lower switching element and the upper switching element operate complementarily, the output of the comparator 113 can be inverted.

Fig. 3 is a schematic diagram showing spatially in vectors the output phase voltages based on the switching function. The output phase voltage corresponding to the switching function is as follows equation 5.

[ EQUATION 5 ]

The output phase voltage is output from V according to the switching function_oTo V₇For a total of eight voltages. Voltage vector V_oAnd V₇As a vector of no output voltage, it is defined as a zero voltage vector. On the other hand, V₁to V₆With a difference in phase of 60 deg.. In addition, the size is defined asA fixed effective voltage vector. The phase voltage command 2A is modulated into an actual voltage by an appropriate synthesis of the effective voltage vector and the zero voltage vector and output.

There are various types of offset voltage commands calculated by the offset voltage command calculation section 111 in fig. 2A and 2B.

The offset voltage command in the sinusoidal pulse width modulation method (SPWM) is as follows equation 6.

[ equation 6 ]

The offset voltage command in the space vector pulse width modulation method (SVPWM) is as follows in equation 7.

[ EQUATION 7 ]

At this time, v_maxIndicating the maximum voltage, v, of the three-phase voltage commands_minIndicating the minimum voltage.

In addition, the offset voltage commands of equations 6 and 7 are a continuous pulse width modulation method that changes the switching functions of all phases during one period of the carrier wave.

In order to reduce the switching losses, the pulse width modulation method in which the switching function of one phase is constant is referred to as discontinuous pulse width modulation method. A representative discontinuous pulse width modulation method is as follows.

first, it is assumed that the phase voltage command is defined as the following equation 8 and the phase current is defined as the following equation 9.

[ EQUATION 8 ]

[ equation 9 ]

i_xs＝I_mcos(θ-φ)

At this time, the subscript "xs" indicates a specific phase. For example, phase a is as, phase b is bs, and phase c is cs. Theta represents the angle of the alternating current,Indicating the phase difference of the voltage and the current. And, V_mAnd I_mRespectively, represent peak values of the phase voltage command and the current.

A 60 ° discontinuous pulse width modulation method (DPWM), which is a representative discontinuous pulse width modulation method, is a method having a switching discontinuous section of 60 ° with reference to the maximum value of the phase voltage command when the period of the ac frequency is 360 °, and an offset voltage command of this type is given by the following equation 10. The DPWM is the phase difference between the phase voltage command and the phase currentA pulse width modulation method that minimizes switching loss at 0 °.

[ EQUATION 10 ]

FIG. 4 illustrates that the phase voltage commands are represented as voltage commands in space vectorsVector V^*The operation of the 60 ° discontinuous pulse width modulation method based on the a-phase.

As can be seen from the shaded area of fig. 4, when the a-phase voltage command is a positive value and the absolute value thereof is the maximum value of the three phases, the a-phase switching function S_aIs 1 and is always in an on state in a corresponding interval. In addition, when the a-phase voltage command is a negative value and the absolute value thereof is the maximum value among the three phases, the a-phase switching function S_aIs 0 and is always in an off state during the corresponding interval.

This discontinuous pulse width modulation method can reduce switching loss, but has a disadvantage of increasing Total Harmonic Distortion (THD) of current. The continuous pulse width modulation method has a lower current THD than the discontinuous pulse width modulation method. But has a disadvantage that its switching loss increases.

When the discontinuous pulse width modulation method using the conventional offset voltage command is used, the discontinuous pulse width modulation interval is always set to 120 ° of 1/3 ° which is one cycle of the fundamental wave. Thus, when discontinuous pulse width modulation is typically employed with a low pulse width modulation index, the current THD will be very large.

In addition, a degree of freedom for appropriately selecting between the switching loss and the current THD is provided by adjusting the discontinuous modulation interval. This reduces switching loss in a region where the pulse width modulation index is low, as compared with the continuous pulse width modulation method. Further, a method capable of reducing the current THD compared to the discontinuous pulse width modulation method is disclosed.

fig. 5 is a schematic diagram for explaining another embodiment of the discontinuous pulse width modulation method. In fig. 5, 5A, 5B, and 5C represent phase voltage commands for phases a, B, and C, respectively5D denotes a peak value of each phase voltage, which is equal to MI when the pulse width modulation index is defined as MI

The pulse width modulation index is defined as the following equation 11.

[ equation 11 ]

Fig. 5E shows the voltage level at which discontinuous pulse width modulation starts. The voltage value is equal to

Therefore, when 5A, which is the a-phase voltage command, is larger than 5E, the a-phase switching function is always 1. Further, when 5A is less than the negative value of 5E, the a-phase switching function is always 0. The same applies to 5B as the B-phase voltage command and 5C as the C-phase voltage command.

Therefore, the implementation of the 60 ° discontinuous pulse width modulation method can also be redefined as the following equation 12.

[ EQUATION 12 ]

Wherein k is

In addition, fig. 6 is a schematic diagram for explaining adpwm (adjustable Discontinuous pwm) as another Discontinuous pulse width modulation method.

In fig. 6, reference numerals 6A, 6B, and 6C denote a phase voltage command for a, B, and C phases, respectively Further, 6D denotes a peak value of each phase voltage command, which is equal to MI when the pulse width modulation index is defined as MI6E represents the voltage level at which the discontinuous pulse width modulation method is started, said voltage level being equal toat this time, θ_Dwhich refers to a discontinuous pulse width modulation angle indicating the size of the discontinuous pulse width modulation interval. When theta is_Dthe value of 0 is the same as the space vector pulse width modulation which is a continuous pulse width modulation method. When theta is_DAt 30 deg., the same as the 60 deg. discontinuous pulse width modulation method described above.

In fig. 6, 6F indicates a section in which the specific phase does not perform the switching operation. And 6G indicates a section in which the specific phase normally performs the switching operation. When 6A, which is the a-phase voltage command, is larger than 6E, the a-phase switching function is always 1, and the operation is performed in the section 6F in which the switching operation is not performed. When 6A is smaller than the negative value of 6E, the a-phase switching function is always 0, and similarly operates in the section 6F in which the switching operation is not performed. This is also the case with 6B as the B-phase voltage command and 6C as the C-phase voltage command.

therefore, the implementation of the ADPWM can be redefined as the following equation 13.

[ equation 13 ]

Wherein k is MIcos θ_D。

Fig. 7 is a block diagram of an implementation of ADPWM.

To implement the adpcm, offset voltage command calculation section 711 receives three-phase voltage command 7A, the dc terminal voltage, and k defined in equation 13, thereby calculating an offset voltage command. The pole voltage command calculation unit 712 adds an offset voltage command to the phase voltage command 7A to calculate a pole voltage command 7B for three phases.

The discontinuous pulse width modulation method described above has a disadvantage of increasing the current THD, although it can reduce the switching loss. To address this drawback, the user can appropriately control the trade-off relationship (trade-off) between switching loss and current THD by adjusting the discontinuous modulation interval.

Especially, when the pulse width modulation index is small, in order to reduce switching loss, a discontinuous pulse width modulation method may be used. At this time, in the case of using the discontinuous pulse width modulation method, deterioration of the current THD will have to be accepted. However, the switching loss can be reduced by this method in a region where the voltage modulation index is low, as compared with the continuous voltage modulation method. Also, the current THD can be reduced compared to the discontinuous voltage modulation method.

The conventional technique described above has a problem of having the least loss only in a state where the phase difference between the voltage and the current is 0 ° and the power factor is 1.

The present invention can provide an inverter control device in which a user can appropriately control a trade-off relationship (trade-off) between a switching loss and a current THD by adjusting a discontinuous modulation section. And, at a given discontinuous modulation interval, there is always minimal loss, regardless of power factor.

The inverter control device of the present invention is applied to a two-level three-phase voltage type inverter for ESS, photovoltaic inverter, motor drive as shown in fig. 1. The inverter control device of the present invention is based on a triangular carrier comparison pulse width modulation method using an offset voltage. Thus, the embodiment of fig. 2 comparing the pole voltage command and the triangular carrier is equally applicable to the present invention.

In the conventional ADPWM, the phase voltage command has a maximum value of θ on both sides_DThe method for switching discontinuous intervals. The method is that when the phase difference between phase voltage command and phase currentAnd 0, a pulse width modulation method that minimizes switching loss. That is, θ is generated to both sides based on the maximum absolute value of the phase current_Dthe handover discontinuity interval of (2). Therefore, there is minimal loss compared to other discontinuous pulse width modulation methods.

Based on this, the virtual model can be utilized in one embodiment of the inventionTo produce the least loss in the phase difference between the voltage command and the current. That is, at a given discontinuous modulation angle θ, regardless of power factor_Dresulting in minimal losses. An embodiment of the present invention may be implemented by matching the virtual voltage command with the phase of the current as much as possible, and using the ADPWM with reference to the virtual voltage command.

Fig. 8 is a schematic diagram for explaining a case where the phase voltage command is changed to the pole voltage command in the inverter control device according to the embodiment of the present invention.

As shown in the drawing, the inverter control device according to an embodiment of the present invention may include an offset voltage command calculation section 10 and a voltage command calculation section 20.

The present invention calculates an offset voltage command for ADPWM with minimal losses. Therefore, the offset voltage command calculation unit 10 according to an embodiment of the present invention may input the three-phase voltage command 8A and the dc terminal voltage V_dcK and as a phase difference between the voltage command and the inverter output currentFrom this, an offset voltage command can be calculated. Wherein k is MIcos θ_DMI represents a pulse width modulation index, θ_DIndicating a discontinuous modulation angle that can adjust the discontinuous modulation interval.

The voltage command calculation portion 20 may generate the voltage command 8B by adding the offset voltage command and the phase voltage command 8A.

Fig. 9 is a detailed configuration diagram of the offset voltage command calculation unit 10 of fig. 8.

As shown in the figure, the offset voltage command calculation unit 10 according to an embodiment of the present invention may include: a first coordinate conversion unit 11, a rotation conversion unit 12, an angle conversion unit 13, a second coordinate conversion unit 14, and an offset voltage command generation unit 15.

The first coordinate transformation unit 11 can change the phase transformation amounts of a, b, and c to d and q-axis variables of the static coordinate system, and can be expressed as the following equation 14.

[ equation 14 ]

Therefore, the three-phase voltage command can be changed to the d-and q-axis voltage commands of the following equation 15 by the first coordinate conversion unit 11.

[ equation 15 ]

The rotation conversion unit 12 can convert the d and q axis variables into phi_VThe rotation transformation is performed and can be expressed as the following equation 16.

[ equation 16 ]

Therefore, the d-and q-axis voltage commands by the first coordinate conversion unit 11AndThe d-axis and q-axis voltage commands can be converted by the rotation conversion unit 12 into the rotation conversion according to the following equation 17.

[ equation 17 ]

The second coordinate transformation unit 14 can transform the d and q axis variable coordinates into a, b, and c phase transformation amounts, and can be expressed as the following equation 18.

[ equation 18 ]

Therefore, the d-and q-axis voltage commands are converted by the rotation converter 12The phase voltage command can be changed to a virtual phase voltage command by the second coordinate conversion unit 14

[ equation 19 ]

To sum up, the three-phase voltage command is expressed by the following equation 20The three-phase voltage command can be changed to a virtual three-phase voltage command by the first coordinate conversion unit 11, the rotation conversion unit 12, and the second coordinate conversion unit 13

[ equation 20 ]

At this time, the angle conversion unit 13 may receive a phase difference between the voltage and the currentThereby generating angle information for use in the rotation transformation. This will be explained in detail later.

offset voltage command generation unit 15 may generate an offset voltage command using three-phase voltage command 8A, dc terminal voltage, k, and a virtual three-phase voltage command

Fig. 10 is a detailed configuration diagram of an embodiment of the offset voltage command generating unit 15 in fig. 9.

As shown in the figure, the offset voltage command generating unit 15 according to an embodiment of the present invention may include: a first determination unit 31, a second determination unit 32, and a third determination unit 33.

The first determination unit 31 may determine the maximum value and the minimum value of the three-phase voltage command as follows.

[ equation 21 ]

The second determination unit 32 may determine the maximum value and the minimum value of the virtual three-phase voltage command as follows.

[ equation 22 ]

The third determination unit 33 can use the dc terminal voltage V_dcK, the maximum value and the minimum value of the three-phase voltage command, and the maximum value and the minimum value of the virtual three-phase voltage command, and the offset voltage command is determined by the following equation 23

[ equation 23 ]

As described above, the offset voltage command of an embodiment of the present invention can be generated using three-phase voltage commands.

FIGS. 11A-11C are diagrams illustrating the phase difference φ between a voltage command and a current and the phase difference φ used to generate a virtual phase voltage in an embodiment of the inventionVirtual phase difference phi of angle information of pressure command_VA schematic diagram of the relationship of (a). FIG. 11A is a graph showing a phase difference φ between a voltage command and a currentIn the case of (1), the voltage command vector V is shown on a space vector^*And a virtual voltage command vector V^vCase of current vector i.

As shown in the figure, θ exists from the position of the current vector i to both sides_DDiscontinuous modulation intervals of size. Therefore, the phase difference between the current vector and the virtual voltage vector is set to 0. For this purpose, the actual phase difference phi and the virtual phase difference phi used in the rotation conversion are set_VIdentical to each other and for pulse width modulation. That is, whentime, relation phi_VPhi may be true.

In addition, FIG. 11B shows a phase difference φ between a voltage command and a currentIn the case of (1), the voltage command vector V is shown on a space vector^*Virtual voltage command vector V^VAnd the case of current vector i.

Only sector 1(sector), sector 6, sector 3, and sector 4 are sections in which discontinuous pulse width modulation is possible, with phase a as a reference. Therefore, the phases of the virtual voltage vector and the current vector cannot be further matched. To minimize the loss in the discontinuous modulation interval, it is desirable to minimize the error in the phase of the virtual voltage vector and the current vector. To this end, can be selected fromStart to express virtual voltage command vector V^VPhi of phase (a)_Vis fixed to

That is, when the phase difference between the voltage command and the current is phiTime, relational expressionMay be true.

In FIG. 11C, the phase difference φ between the voltage command and the current isIn the case of (1), the voltage command vector V is shown on a space vector^*virtual voltage command vector V^VAnd the case of current vector i.

Only sector 1, sector 6, sector 3, and sector 4 are sections in which discontinuous pulse width modulation is possible, with phase a as a reference. Therefore, the phases of the virtual voltage vector and the current vector cannot be further matched. To minimize the loss in the discontinuous modulation interval, it is desirable to minimize the error in the phase of the virtual voltage vector and the current vector. For this purpose, a virtual voltage command vector V is set^VAlways out of phase with the current vectorThus, the discontinuous pulse width modulation intervals can be appropriately positioned in the sector 1, the sector 6, the sector 3, and the sector 4 with the current vector as a reference, thereby minimizing the switching loss.

That is, when the phase difference between the voltage command and the current is phitime, relational expressionMay be true.

fig. 12 is a schematic diagram for explaining the operation of the angle conversion unit 13 in fig. 9. That is, FIG. 12 shows the phase difference φ between the voltage command and the current and the method for generating the imaginaryVirtual phase difference phi of simulated voltage command_VThe relationship (2) of (c).

As can be seen from the figure, whenTime phi_Vphi is given. When in useWhen the temperature of the water is higher than the set temperature,In addition, whenWhen the temperature of the water is higher than the set temperature,And will have the morphology of an odd function.

Fig. 13 is a schematic diagram for explaining a switching loss of the inverter control device according to the embodiment of the present invention. The horizontal axis represents the phase difference phi between the voltage command and the current. The vertical axis represents the switching loss ratio of the discontinuous pulse width modulation system as compared with the continuous pulse width modulation system. That is, when the switching loss ratio is 1, the same switching loss as that of the continuous pulse width modulation system is exhibited. When the switching loss ratio is 0.5, the switching loss is reduced by 50% as compared with the continuous pulse width modulation method.

In FIG. 13, 13A and 13B are shown at discrete modulation angles θ, respectively_DWith the setting of 6 °, the switching loss ratio of the adpcm according to the related art and the switching loss ratio according to the embodiment of the present invention. 14A and 14B are shown at discrete modulation angles θ, respectively_DWith 12 °, the switching loss ratio of the adpcm according to the related art and the switching loss ratio according to the embodiment of the present invention are set. 15A and 15B are shown at discrete modulation angles theta_DWith the setting of 18 °, the switching loss ratio of the adpcm according to the related art and the switching loss ratio according to the embodiment of the present invention. 16A and 16B are shown at discrete modulation angles theta_DSet to 24 °The switching loss ratio of the adpcm based on the prior art and the switching loss ratio of the adpcm based on an embodiment of the present invention. And, 17A and 17B are shown at discrete modulation angles θ, respectively_DWith the setting of 30 °, the switching loss ratio of the adpcm according to the related art and the switching loss ratio according to the embodiment of the present invention.

As shown, the prior art adpcm exhibits minimal loss at a phase difference of phi between the voltage command and the current of 0 for a given discrete pulse width modulation angle. However, according to the control of the present invention, it can be confirmed that the least loss possible is exhibited in a given discontinuous pulse width modulation angle regardless of the phase difference.

As described above, the present invention utilizes the phase difference between the voltage command and the current and the discontinuous modulation angle for adjusting the discontinuous pulse width modulation section. Furthermore, by utilizing the generated virtual voltage command, the least possible loss is always exhibited in a given discontinuous pulse width modulation interval regardless of the power factor.

According to an embodiment of the present invention, a virtual phase voltage command is generated by a rotational transformation of an actual phase voltage command. The rotation angle used for the rotation conversion can be determined by using the phase difference between the voltage command and the current and the discontinuous modulation angle. As described above, the pulse width modulation is performed using the virtual phase voltage command, the actual phase voltage command, and the discontinuous modulation angle. Furthermore, the contradictory relationship between switching loss and current THD can be appropriately controlled by adjusting the discontinuous modulation interval. Furthermore, in a given discontinuous modulation interval, minimal losses can always be exhibited regardless of the power factor.

It should be noted that the above-mentioned embodiments of the present invention are merely exemplary, and those skilled in the art can implement various modifications and equivalent embodiments. Therefore, the true technical scope of the present invention should be determined by the appended claims.