CN103208913B - Filter reactance stage and variable frequency drive system using the filter reactance stage - Google Patents

Abstract

The invention discloses a filtering reactance stage and a variable frequency driving system applying the same. The filter reactance stage is coupled between the rectification input stage and the inversion output stage and comprises a magnetic core module, a first winding group, a second winding group and a third winding group. The magnetic core module comprises a center pillar, a first side pillar and a second side pillar. The first winding group is wound on the first side column, the second winding group is wound on the second side column, and the first winding group and the second winding group are connected in series with a first direct current arm between the rectifying input stage and the inverting output stage. The third winding group is wound on the middle column, and two ends of the third winding group are connected in series on a second direct current arm between the rectification input stage and the inversion output stage. The three-winding group of the filter reactance stage can provide enough common-mode inductance to restrain common-mode current and form adjustable differential-mode inductance to reduce the energy loss of the filter reactance.

Description

Filter reactance stage and variable frequency drive system using the filter reactance stage

technical field

The present invention relates to a filter reactance stage, and in particular to a filter reactance stage applied in a variable frequency drive system.

Background technique

In the control of electric machines or induction motors, motor speed regulation is an important issue. The traditional DC speed control technology used in existing electric machines is limited in its application due to its large hardware size and high failure rate.

Inverter (Variable-frequency Drive, VFD) applies frequency conversion technology and electronic active component technology to control the output of the AC motor by changing the frequency and amplitude of the working power from the input terminal.

The function of the frequency converter is to change the frequency and amplitude of the AC power supplied to the induction motor, and further change the period of its moving magnetic field, so as to achieve the purpose of smoothly controlling the speed of the induction motor. The appearance of the frequency converter simplifies the complex speed control. The combination of the frequency converter and the AC induction motor replaces most of the work that can only be done by the DC motor, which makes the circuit system smaller and lowers the maintenance rate.

An existing frequency converter usually includes a rectifier and an inverter, and there may be current ripple noise during the signal transmission between them. A common practice is to install an inductor on the unilateral DC arm to filter out the current ripple noise . However, when the frequency converter is in operation, a common-mode current will be generated on the two DC arms to flow from the rectifier to the inverter, and the common-mode current will cause unnecessary electromagnetic interference (EMI) during actual operation. The traditional common-mode current solution is to install inductors on the two DC arms respectively to reduce the common-mode current, thereby suppressing electromagnetic interference. However, traditional inductors have limited suppression of common-mode currents.

Contents of the invention

In order to solve the above problems, the object of the present invention is to provide a filter reactance stage and a variable frequency drive system using the filter reactance stage, wherein the filter reactance stage can generate enough common-mode inductance to suppress the common-mode current and form an adjustable Differential-mode inductors to reduce energy loss in the filter reactance.

The filter reactance stage in a preferred embodiment of the present invention has three sets of winding groups, wherein two sets of winding groups are coupled to a DC arm of the variable frequency drive system and are respectively wound on the two side columns of the magnetic core module, Another set of windings is coupled to another DC arm of the variable frequency drive system and wound on the center column of the magnetic core module. In the common mode state, the magnetic fluxes of the three winding groups are mutually accumulated; in the differential mode state, the magnetic fluxes of the two winding groups on the side column and the winding group on the center column cancel each other out. Therefore, the three windings can provide sufficient common-mode inductance to suppress common-mode current, and form smaller differential-mode inductance to reduce energy loss of filter reactance.

In a preferred embodiment, the present invention provides a variable frequency drive system, which is coupled to a three-phase power grid. The variable frequency drive system includes a rectification input stage, an inverter output stage, and a filter reactance stage. A rectifier input stage is coupled to the three-phase grid. The filter reactance stage is coupled between the rectification input stage and the inverter output stage, and the filter reactance stage includes a magnetic core module, a first winding set, a second winding set and a third winding set. The magnetic core module includes a central column, a first side column and a second side column. The first winding group is wound on the first side column, the second winding group is wound on the second side column, and the first winding group and the second winding group are connected in series to the rectifier input stage and the first DC arm between the inverter output stage. The third winding group is wound on the central column, and the two ends of the third winding group are serially connected to a second DC arm between the rectification input stage and the inverter output stage.

In a preferred embodiment, the rectification input stage is used to convert an AC input voltage with a fixed operating frequency from the three-phase grid into a DC voltage, and the inverter output stage is used to convert the DC voltage to An AC output voltage with variable frequency is used to drive an external load.

In a preferred embodiment, the central column, the first side column and the second side column in the magnetic core module are substantially parallel, and the first side column and the second side column are located on both sides of the central column .

In a preferred embodiment, in a differential mode state, the magnetic flux generated by the first winding set and the second winding set are in the same direction, and counteracted with the magnetic flux generated by the third winding set. In this embodiment, in the differential mode state, the direction of the differential mode currents on the first DC arm and the second DC arm are opposite.

In a preferred embodiment, the magnetic fluxes generated by the first winding set, the second winding set and the third winding set are in the same direction under a common mode state. In this embodiment, in the common mode state, the common mode currents on the first DC arm and the second DC arm have the same direction, and flow from the rectifier input stage to the inverter output stage.

In a preferred embodiment, the magnetic core module is any one of EI combined magnetic core and EE combined magnetic core.

In a preferred embodiment, the present invention also provides a filter reactance stage, coupled between a rectifier input stage and an inverter output stage, the filter reactance stage includes a magnetic core module, a first winding group, a second The winding group and the third winding group. The magnetic core module includes a central column, a first side column and a second side column. The first winding group is wound on the first side column, the second winding group is wound on the second side column, and the first winding group and the second winding group are connected in series between the rectifier input stage and the On a first DC arm between the inverter output stages. The third winding group is wound on the central column, and the third winding group is connected in series on a second DC arm between the rectification input stage and the inverter output stage.

In a preferred embodiment, the central column, the first side column and the second side column in the magnetic core module are substantially parallel, and the first side column and the second side column are located on both sides of the central column .

In a preferred embodiment, in a differential mode state, the magnetic flux generated by the first winding set and the second winding set are in the same direction, and counteracted with the magnetic flux generated by the third winding set. In the differential mode state, the directions of the differential mode currents on the first direct current arm and the second direct current arm are opposite.

In a preferred embodiment, the magnetic fluxes generated by the first winding set, the second winding set and the third winding set are in the same direction under a common mode state. In the common mode state, the direction of the common mode current on the first direct current arm and the second direct current arm is the same, and flows from the rectification input stage to the inverter output stage.

The filtering reactance stage of the present invention has three winding groups, and the three winding groups can provide sufficient common-mode inductance to suppress common-mode current, and form adjustable differential-mode inductance to reduce energy loss of the filter reactance.

Description of drawings

In order to make the above and other objects, features, advantages and embodiments of the present invention more clearly understood, the accompanying drawings are described as follows:

Fig. 1 shows a functional block diagram of a variable frequency drive system according to a preferred embodiment of the present invention;

Fig. 2 is a schematic circuit diagram of a variable frequency drive system according to a preferred embodiment of the present invention;

FIG. 3 is a schematic diagram of a filter reactance stage according to a preferred embodiment of the present invention;

Figure 4 is a schematic diagram of the filter reactance stage in Figure 3 in a differential mode state;

FIG. 5 is a schematic diagram of the filter reactance stage in FIG. 3 in a common mode state.

Wherein, the reference signs are explained as follows:

100: variable frequency drive system

120: rectified input stage

140: inverter output stage

160: filter reactance level

200: three-phase grid

220: Motor load

180: Energy storage module

D1: the first DC arm

D2: second DC arm

W1: the first winding group

W2: Second winding group

W3: The third winding group

162: Magnetic core module

162a, 162b: magnetic core assembly

164: First side post

166: Second side post

168: center column

Id: differential mode current

Ic1, Ic2: common mode current

FD1, FD2, FD3, FC1, FC2, FC3: Magnetic flux

Detailed ways

Please refer to FIG. 1 , which is a functional block diagram of a variable-frequency drive (Variable-frequency Drive, VFD) system 100 in a preferred embodiment of the present invention. As shown in FIG. 1 , the variable frequency drive system 100 includes a rectifier input stage 120 , an inverter output stage 140 and a filter reactance stage 160 .

In this preferred embodiment, the variable frequency drive system 100 can receive an AC input voltage with a fixed operating frequency from the three-phase grid 200, adjust the frequency and amplitude of the AC input voltage, and then use the adjusted AC output voltage to drive an external motor load 220 (such as an induction motor), in this way, the rotational speed of the motor load 220 can be smoothly controlled.

As mentioned above, the rectifier input stage 120 is electrically connected to the three-phase grid 200 . The rectifying input stage 120 is used to convert the AC input voltage with a fixed operating frequency transmitted from the three-phase grid 200 into a DC input voltage, and the inverter output stage 140 is used to convert the DC input voltage into an AC output voltage with a variable frequency. The AC output voltage is used to drive the motor load 220 .

It should be noted that, in this preferred embodiment, a filter reactance stage 160 is coupled between the rectifier input stage 120 and the inverter output stage 140, and the filter reactance stage 160 can be used to filter DC current ripple noise and electromagnetic Interference (Electromagnetic interference, EMI), and ensure the electrical signal transmission quality between the rectifier input stage 120 and the inverter output stage 140, in this preferred embodiment, the filter reactance stage 160 forms adjustable differential mode inductance and common mode Inductors, differential mode inductors can be used to block DC current ripple noise, and common mode inductors can be used to reduce electromagnetic interference.

Please also refer to FIG. 2 , which is a schematic circuit diagram of a variable frequency drive system 100 according to a preferred embodiment of the present invention. As shown in FIG. 2 , the rectification input stage 120 and the inverter output stage 140 are electrically connected through the first DC arm D1 and the second DC arm D2 .

In the differential mode state, the differential mode current Id flows from the rectifier input stage 120 to the inverter output stage 140 along the first DC arm D1, and flows from the inverter output stage 140 to the rectifier input stage 120 along the second DC arm D2. The differential mode currents on the first DC arm D1 and the second DC arm D2 flow in opposite directions.

In the common-mode state, part of the common-mode current Ic1 flows from the rectifier input stage 120 to the inverter output stage 140 along the first DC arm D1, and another part of the common-mode current Ic2 flows from the second DC arm D2 to the inverter output stage 140. The rectified input stage 120 flows to an inverted output stage 140 . The common mode currents on the first direct current arm D1 and the second direct current arm D2 flow in the same direction.

Please also refer to FIG. 3 , which is a schematic diagram of the filtering reactance stage 160 according to a preferred embodiment of the present invention. The filtering reactance stage 160 includes a magnetic core module 162 , a first winding set W1 , a second winding set W2 and a third winding set W3 . Wherein, the magnetic core module 162 includes a central column 168 , a first side column 164 and a second side column 166 .

As shown in FIG. 3 , the central column 168 , the first side column 164 and the second side column 166 of the magnetic core module 162 are substantially parallel, and the first side column 166 and the second side column 168 are located on two sides of the central column 166 .

In this preferred embodiment, the magnetic core module 162 may include two magnetic core assemblies 162a and 162b, wherein the magnetic core assemblies 162a and 162b are E-shaped magnetic cores and I-shaped magnetic cores respectively. That is to say, in this preferred embodiment, the magnetic core module 162 adopts an EI combined magnetic core composed of E-shaped and I-shaped magnetic core components 162a and 162b. Wherein, the three arms of the E-shaped magnetic core assembly 162a and the I-shaped magnetic core assembly 162b can be separated by the same gap (gap), which is easier in gap setting and magnetic adjustment.

It should be noted that the magnetic core module 162 of the present invention is not limited to the EI combined magnetic core, and in other preferred embodiments, the magnetic core module 162 can also be an EE combined magnetic core or other equivalent of various magnetic cores.

The first winding group W1 is wound on the first leg 164 , and both ends of the first winding group W1 are coupled to the first DC arm D1 between the rectification input stage 120 and the inverter output stage 140 . The second winding group W2 is wound on the second side column 166, and both ends of the second winding group W2 are also coupled to the first DC arm D1. Further, the two ends of the second winding group W2 Terminals are respectively coupled to the first winding group W1 and the inverter output stage 140, that is, the first winding group W1 and the second winding group W2 are connected in series to the rectifier input stage 120 and the inverter output stage 140 Between the first DC arm D1. The third winding group W3 is wound on the center column 168 , and both ends of the third winding group W3 are connected in series to the second DC arm D2 between the rectifying input stage 120 and the inverter output stage 140 .

The self-inductance and mutual inductance of the three-winding group can be expressed as a matrix:

${\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; xy</span>}}<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}}& {\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}& {\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 13</span>}}\\ {\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}& {\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}& {\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; three</span>}}\\ {\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 31</span>}}& {\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 32</span>}}& {\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 33</span>}}\end{array}\right]<span\; class="notranslate">\; ;</span>$

Wherein L represents self-inductance, M represents mutual inductance, x and y are numbers of the first winding group W1 , the second winding group W2 and the third winding group W3 respectively.

Please also refer to FIG. 4 , which is a schematic diagram of the filter reactance stage 160 in FIG. 3 in a differential mode state. In the differential mode state, the magnetic flux FD1 generated by the first winding group W1 is in the same direction as the magnetic flux FD2 generated by the second winding group W2, and the magnetic flux FD1 and the magnetic flux FD2 are opposite to the magnetic flux FD3 generated by the third winding group W3 offset. In this way, an adjustable differential mode inductance can be generated by adding the magnetic flux FD1 to the magnetic flux FD2 minus the magnetic flux FD3 . The size of the differential mode inductor can be adjusted through the winding density, number of turns and ratio of the first winding group W1 , the second winding group W2 and the third winding group W3 .

The following details, in the differential mode state, the magnetic flux generated by the coils on both sides (ie, the first winding group W1 and the second winding group W2) and the magnetic flux generated by the middle coil (ie, the third winding group W3) are transmitted to the module 162 Inner phase cancellation, using this principle to control the differential mode magnetic flux, can design the differential mode inductance value and the saturation current of the filter reactance stage 160. If it is represented by the inductance matrix of the winding group, the inductance in the differential mode state is:

L _DM = (L ₁₁ +M ₁₂ +M ₁₃ )+(L ₂₂ +M ₂₁ +M ₂₃ )+(L ₃₃ +M ₃₁ +M ₃₂ );

And in the differential mode state, M ₁₂ M ₁₃ M ₂₁ M ₂₃ M ₃₁ M ₃₂ <0.

On the other hand, please also refer to FIG. 5 , which is a schematic diagram of the filter reactance stage 160 in FIG. 3 in a common mode state. In the common mode state, the magnetic flux FC1 generated by the first winding group W1, the magnetic flux FC2 generated by the second winding group W2, and the magnetic flux FC3 generated by the third winding group W3 are in the same direction. large common-mode inductance. The size of the common mode inductance can be adjusted through the winding density, number of turns and ratio of the first winding set W1 , the second winding set W2 and the third winding set W3 .

In the common-mode state, the magnetic flux generated by the three winding groups in the same direction is added in the magnetic core. If represented by the inductance matrix of the winding group, the formed common-mode inductance is:

L _CM = (L ₁₁ +M ₁₂ +M ₁₃ )+(L ₂₂ +M ₂₁ +M ₂₃ )//(L ₃₃ +M ₃₁ +M ₃₂ );

And in the common mode state, M ₁₂ M ₂₁ <0.

In practical applications, since the common-mode current is smaller than the differential-mode current, although the magnetic flux adds up, it will not cause the current saturation problem of the filter reactance stage 160 .

In addition, in the preferred embodiment shown in FIG. 2 , the variable frequency drive system 100 also includes an energy storage module 180. In practical applications, the energy storage module 180 includes a capacitive element (as shown in FIG. 2 ), and the two energy storage modules 180 The terminals are respectively coupled to the two DC arms (namely the first DC arm D1 and the second DC arm D2), and the energy storage module 180 is arranged between the filter reactance stage 160 and the inverter output stage 140, and the energy storage module 180 is used for Temporarily store the DC voltage rectified by the rectifier input stage 120 to drive the inverter output stage 140 .

To sum up, the filter reactance stage in the present invention has three winding groups, wherein two winding groups are coupled to a DC arm of the variable frequency drive system and wound on both sides of the magnetic core module, and the other winding The set is coupled to the other DC arm of the variable frequency drive system and wound on the center post of the magnetic core module. In the common mode state, the magnetic fluxes of the three winding groups are mutually accumulated; in the differential mode state, the magnetic fluxes of the two winding groups on the side column and the winding group on the center column cancel each other out. Therefore, the three windings can provide sufficient common-mode inductance to suppress the common-mode current, and form adjustable differential-mode inductance to reduce energy loss of the filter reactance.

Although the content of the present invention has been disclosed above in terms of implementation, it is not intended to limit the content of the present invention. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the content of the present invention. Therefore, The scope of protection of the content of the present invention should be defined by the scope of the appended patent application.

Claims (12)

1. A variable frequency drive system, which is coupled with a three-phase grid, the variable frequency drive system comprising: a rectification input stage coupled to the three-phase grid; an inverter output stage; and A filter reactance stage, coupled between the rectification input stage and the inverter output stage, the filter reactance stage includes: A magnetic core module, which includes a central column, a first side column and a second side column; A first winding group and a second winding group, the first winding group is wound on the first side post, the second winding group is wound on the second side post, and the first winding A first DC arm connected in series with the second winding group between the rectification input stage and the inverter output stage; and A third winding group wound around the center column, and the two ends of the third winding group are connected in series to a second DC arm between the rectification input stage and the inverter output stage; Wherein in a differential mode state, the magnetic flux generated by the first winding group and the second winding group is in the same direction, and counteracts the magnetic flux generated by the third winding group in opposite directions. 2. The variable frequency drive system according to claim 1, wherein the rectifier input stage is used to convert an AC input voltage with a fixed operating frequency from the three-phase grid into a DC voltage, and the inverter output stage is used to The DC voltage is converted into an AC output voltage with variable frequency, and the AC output voltage is used to drive an external load. 3. The variable frequency drive system as claimed in claim 1, wherein the central column, the first side column and the second side column in the magnetic core module are substantially parallel, and the first side column and the second side column are located at both sides of the center column. 4. The variable frequency drive system as claimed in claim 1, wherein in the differential mode state, the direction of differential mode currents on the first DC arm and the second DC arm are opposite. 5. The variable frequency drive system as claimed in claim 1, wherein the magnetic fluxes generated by the first winding set, the second winding set and the third winding set are in the same direction under a common mode state. 6. The variable frequency drive system according to claim 5, wherein in the common mode state, the common mode currents on the first DC arm and the second DC arm are in the same direction and flow from the rectifier input stage to the inverter output class. 7. The variable frequency drive system according to claim 1, wherein the magnetic core module is any one of an EI combined magnetic core and an EE combined magnetic core. 8. A filter reactance stage, coupled between a rectifier input stage and an inverter output stage, the filter reactance stage comprising: A magnetic core module, which includes a central column, a first side column and a second side column; A first winding group and a second winding group, the first winding group is wound on the first side column, the second winding group is wound on the second side column, and the first winding group and The second winding group is connected in series on a first DC arm between the rectification input stage and the inverter output stage; and A third winding group wound around the center column, and the third winding group is connected in series to a second DC arm between the rectification input stage and the inverter output stage; Wherein in a differential mode state, the magnetic flux generated by the first winding group and the second winding group is in the same direction, and counteracts the magnetic flux generated by the third winding group in opposite directions. 9. The filter reactance stage as claimed in claim 8, wherein the central column, the first side column and the second side column in the magnetic core module are substantially parallel, and the first side column and the second side column are located at both sides of the center column. 10. The filter reactance stage as claimed in claim 8, wherein in the differential mode state, the direction of the differential mode current on the first DC arm and the second DC arm is opposite. 11. The filter reactance stage as claimed in claim 8, wherein the magnetic fluxes generated by the first winding set, the second winding set and the third winding set are in the same direction under a common mode state. 12. The filter reactance stage according to claim 11, wherein in the common mode state, the common mode currents on the first DC arm and the second DC arm are in the same direction, and flow from the rectifier input stage to the inverter output stage.