CN107834827B - Harmonic current compensation device for rectifier - Google Patents
Harmonic current compensation device for rectifier Download PDFInfo
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- CN107834827B CN107834827B CN201711096987.1A CN201711096987A CN107834827B CN 107834827 B CN107834827 B CN 107834827B CN 201711096987 A CN201711096987 A CN 201711096987A CN 107834827 B CN107834827 B CN 107834827B
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Abstract
The invention discloses a harmonic current compensation device for a rectifier, which comprises a harmonic injection circuit, wherein the harmonic injection circuit comprises a first filter capacitor, a second filter capacitor, a third filter capacitor, a compensation filter inductor, a first switch tube and a second switch tube; the first current detection module is used for detecting the current passing through the compensation filter inductor; the second current detection module is used for detecting the load current of the rectifier; the voltage detection module is used for detecting the voltage of the three-phase power grid; and the control module is respectively connected with the current detection module, the voltage detection module, the control end of the first switch tube and the control end of the second switch tube, and is used for generating a switch control signal according to the voltage and the load current of the three-phase power grid and the current passing through the compensation filter inductor, and controlling the first switch tube and the second switch tube according to the switch control signal so as to distribute the harmonic compensation current generated by the harmonic injection circuit to the three-phase power grid.
Description
Technical Field
The invention relates to the technical field of harmonic current compensation, in particular to a harmonic current compensation device for a rectifier.
Background
In general, a diode rectifier is used in a front stage of a three-phase ac power supply system in which a motor is used as a load, and a three-phase full-bridge inverter is used in a rear stage. The rectifier can rectify three-phase alternating current into direct current, and the direct current is filtered by an alternating current inductor and a direct current capacitor. However, the topology of the three-phase ac power supply system can provide stable dc power to the load when the dc capacitance is large, but generates large harmonic current on the ac side. Currently, the standards for harmonic currents applicable to three-phase rectifiers include: EN61000-3-2 (current less than 16A), IEEE519, and the like. These standards specify the allowable injection values for each harmonic at different voltage levels.
The harmonic current generated by the topology cannot meet the standard requirement of the network-access harmonic current. In order to make the network-accessing harmonic current meet the standard requirement, the front-stage diode rectification is often required to be changed into three-phase full-bridge rectification. Although the current harmonic content generated by using the three-phase full-bridge rectification is low, the achieved effect is good, the cost is high, an additional control driving circuit is required to be added, and the production cost is greatly increased.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the art described above. Therefore, an object of the present invention is to provide a harmonic current compensation device for a rectifier, which can reduce the harmonic content of the current injected into the power grid to meet the requirement of the harmonic current standard, and has a simple structure and a low production cost.
In order to achieve the above object, a first embodiment of the present invention provides a harmonic current compensation apparatus for a rectifier, an ac side of the rectifier is connected to a three-phase power grid, a dc side of the rectifier is used to connect a load, and the harmonic current compensation apparatus includes: a harmonic injection circuit, including a first filter inductor, a second filter inductor, a third filter inductor, a compensation filter inductor, a first switch tube and a second switch tube, where one end of the first filter inductor is connected to a first ac end of the ac side, one end of the second filter inductor is connected to a second ac end of the ac side, one end of the third filter inductor is connected to a third ac end of the ac side, the other ends of the first filter inductor, the second filter inductor and the third filter inductor are connected and have a first node, one end of the first switch tube is connected to a first dc end of the dc side, the other end of the first switch tube is connected to one end of the second switch tube and has a second node, and the other end of the second switch tube is connected to a second dc end of the dc side, the compensation filter inductor is connected between the first node and the second node; a first current detection module for detecting a current through the compensation filter inductance; a second current detection module for detecting a load current of the rectifier; the voltage detection module is used for detecting the voltage of the three-phase power grid; and the control module is respectively connected with the first current detection module, the second current detection module, the voltage detection module, the control end of the first switch tube and the control end of the second switch tube, and is used for generating a switch control signal according to the voltage of the three-phase power grid, the load current and the current passing through the compensation filter inductor, and controlling the first switch tube and the second switch tube according to the switch control signal so as to distribute the harmonic compensation current generated by the harmonic injection circuit to the three-phase power grid.
According to the harmonic current compensation device for the rectifier of the embodiment of the invention, the harmonic injection circuit comprises three filter capacitors correspondingly connected with the alternating current side of the rectifier, the three filter capacitors can be connected with one ends of the first switch tube and the second switch tube through compensation filter inductors, the other ends of the first switch tube and the second switch tube can be respectively connected with the direct current side of the rectifier, the current passing through the compensation filter inductor is detected through a first current detection module, the load current of the rectifier is detected through a second current detection module, the voltage of the three-phase power grid is detected through a voltage detection module, and generating a switch control signal by the control module according to the voltage of the three-phase power grid, the load current and the current passing through the compensation filter inductor, and the first switching tube and the second switching tube are controlled according to the switching control signal so as to distribute the harmonic compensation current generated by the harmonic injection circuit to the three-phase power grid. Therefore, the harmonic content of the current injected into the power grid can be reduced to meet the requirement of the harmonic current standard, and the device is simple in structure and low in production cost.
In addition, the harmonic current compensation device for a rectifier according to the above embodiment of the present invention may further have the following additional technical features:
in one embodiment of the invention, the control module comprises: the minimum voltage acquisition unit is used for acquiring the minimum voltage of the three-phase power grid; the maximum voltage acquisition unit is used for acquiring the maximum voltage of the three-phase power grid; the operation unit is used for operating the voltage minimum value, the voltage maximum value and the load current to obtain a harmonic current given value; a current controller for generating the switch control signal according to the harmonic current set value and the current passing through the compensation filter inductance.
In one embodiment of the present invention, the arithmetic unit includes: an adder for performing a superposition calculation on the voltage minimum value and the voltage maximum value to obtain a first voltage value; an inverter for inverting the first voltage value to obtain a phase voltage intermediate value; a corrector for multiplying a preset coefficient by the phase voltage intermediate value to obtain a second voltage value; a multiplier for multiplying the second voltage value with the load current to obtain the harmonic current given value.
Further, the arithmetic unit further includes: a phase delayer for phase delaying the second voltage value to keep a phase of a harmonic compensation current distributed to the three-phase power grid in synchronization with a phase of an incoming voltage of the rectifier.
In one embodiment of the invention, the rectifier includes first to sixth diodes, the first to sixth diodes constitute three-phase bridge arms, an intermediate node of a first phase bridge arm of the three-phase bridge arms is connected to a phase a of the three-phase power grid through a first filter inductor, an intermediate node of a second phase bridge arm of the three-phase bridge arms is connected to a phase B of the three-phase power grid through a second filter inductor, and an intermediate node of a third phase bridge arm of the three-phase bridge arms is connected to a phase C of the three-phase power grid through a third filter inductor.
In one embodiment of the present invention, the rectifier includes first to sixth diodes constituting a three-phase leg connected in parallel to have a third node connected to one end of the first switching tube through a fourth filter inductor and a fourth node connected to the other end of the second switching tube through a fifth filter inductor.
In one embodiment of the present invention, a dc voltage stabilizing capacitor is connected between the first dc terminal and the second dc terminal.
Drawings
FIG. 1 is a block schematic diagram of a harmonic current compensation arrangement for a rectifier according to an embodiment of the present invention;
FIG. 2 is a schematic of a topology of a three-phase diode rectifier according to one embodiment of the invention;
FIG. 3 is a block diagram of a control module according to one embodiment of the present invention;
FIG. 4 is a block diagram of an arithmetic unit according to an embodiment of the present invention;
FIG. 5 is a waveform diagram illustrating a maximum voltage value of a three-phase power grid, a minimum voltage value of the three-phase power grid, an intermediate phase voltage value, and a phase delay for a second voltage value, in accordance with an exemplary embodiment of the present invention;
fig. 6 is a waveform diagram of a harmonic compensation current distributed to a three-phase power grid and a grid voltage of a rectifier according to an embodiment of the present invention;
fig. 7 is a harmonic analysis diagram of harmonic compensation currents distributed to a three-phase power grid in accordance with an embodiment of the present invention.
Fig. 8 is a schematic of a topology of a three-phase diode rectifier according to another embodiment of the invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
The harmonic current compensation device for a rectifier according to an embodiment of the present invention will be described with reference to the accompanying drawings.
Fig. 1 is a block diagram of a harmonic current compensation apparatus for a rectifier according to an embodiment of the present invention.
As shown in fig. 1, the harmonic current compensation apparatus for a rectifier according to an embodiment of the present invention includes a harmonic injection circuit 10, a first current detection module 20, a second current detection module 30, a voltage detection module 40, and a control module 50.
The ac side of the rectifier of the embodiments of the present invention is connected to a three-phase grid, and the dc side of the rectifier is used to connect to a load.
In one embodiment of the invention, as shown in fig. 2, the rectifier 1 includes first to sixth diodes constituting three-phase legs, an intermediate node of a first phase leg of the three-phase legs being connectable to a phase a of a three-phase power grid, an intermediate node of a second phase leg of the three-phase legs being connectable to a phase B of the three-phase power grid, and an intermediate node of a third phase leg of the three-phase legs being connectable to a phase C of the three-phase power grid.
In one embodiment of the present invention, as shown in fig. 2, the harmonic injection circuit 10 in the harmonic current compensation device for a rectifier includes a first filter capacitor Cf1, a second filter capacitor Cf2, a third filter capacitor Cf3, a compensation filter inductor Lf, a first switching tube S1, and a second switching tube S2, one end of the first filter capacitor Cf1 is connected to a first ac terminal a on the ac side, one end of the second filter capacitor Cf2 is connected to a second ac terminal b on the ac side, one end of the third filter capacitor Cf3 is connected to a third ac terminal c on the ac side, the other end of the first filter capacitor Cf1, the other end of the second filter capacitor Cf2, and the other end of the third filter capacitor Cf3 are connected and have a first node, one end of the first switching tube S1 is connected to a first dc terminal P on the dc side, the other end of the first switching tube S1 is connected to a second terminal S2 of the second switching tube S2 and has a second node, the other end of the second switching tube S2 is connected to a second dc terminal N on the dc side, and the compensation filter inductance Lf is connected between the first node and the second node.
The first current detection module 20 is configured to detect a current passing through the compensation filter inductor Lf; the second current detection module 30 is used for detecting the load current of the rectifier 60; the voltage detection module 40 is used for detecting the voltage of the three-phase power grid; the control module 50 is respectively connected to the first current detection module 20, the second current detection module 30, the voltage detection module 40, and the control terminal of the first switch tube S1 and the control terminal of the second switch tube S2, and the control module 50 is configured to generate a switch control signal according to the voltage of the three-phase power grid, the load current, and the current passing through the compensation filter inductor, and control the first switch tube S1 and the second switch tube S2 according to the switch control signal, so as to distribute the harmonic compensation current generated by the harmonic injection circuit 10 to the three-phase power grid.
In one embodiment of the present invention, the first filter capacitor Cf1, the second filter capacitor Cf2 and the third filter capacitor Cf3 in the harmonic injection circuit 10 may be star-connected, not only having a filtering function, but also providing a conducting path for harmonic current.
In one embodiment of the present invention, as shown in fig. 3, the control module 50 may include a minimum voltage obtaining unit 100, a maximum voltage obtaining unit 200, an operation unit 300, and a current controller 400.
As shown in fig. 4, the minimum voltage obtaining unit 100 is configured to obtain a minimum voltage value Vmin of the three-phase power grid; the maximum voltage obtaining unit 200 is configured to obtain a maximum voltage Vmax of the three-phase power grid; the operation unit 300 is configured to operate the voltage minimum value Vmin, the voltage maximum value Vmax, and the load current I1 to obtain a harmonic current given value Ih _ ref; the current controller 400 is used to generate a switching control signal according to the harmonic current set value Ih _ ref and the current Ih _ fb through the compensation filter inductor.
Specifically, the minimum voltage obtaining unit 100 may perform comparative analysis on the voltage of the three-phase power grid detected by the voltage detecting module 40 to obtain a minimum value, that is, a minimum voltage value Vmin of the three-phase power grid, and the maximum voltage obtaining unit 200 may perform comparative analysis on the voltage of the three-phase power grid detected by the voltage detecting module 40 to obtain a maximum value, that is, a maximum voltage value Vmax of the three-phase power grid.
Further, the minimum voltage value Vmin of the three-phase power grid, the maximum voltage value Vmax of the three-phase power grid, and the load current detected by the second current detection module 30 may be respectively input to the operation unit 300, so that the operation unit 300 performs operation processing on the minimum voltage value Vmin, the maximum voltage value Vmax of the three-phase power grid, and the load current.
Specifically, as shown in fig. 4, the operation unit 300 may include an adder 310, an inverter 320, a modifier 330, and a multiplier 340.
The adder 310 is configured to perform a superposition calculation on the voltage minimum value Vmin and the voltage maximum value Vmax to obtain a first voltage value V1; the inverter 320 is configured to perform an inverting calculation on the first voltage value V1 to obtain a phase voltage intermediate value Vmid; the corrector 330 is configured to multiply the preset coefficient K by the phase voltage intermediate value Vmid to obtain a second voltage value V2; the multiplier 340 is configured to multiply the second voltage value V2 with the load current I1 to obtain a harmonic current given value Ih _ ref.
That is, after the voltage minimum value Vmin and the voltage maximum value Vmax are input to the adder 310, the adder 310 may perform a superposition calculation on the voltage minimum value Vmin and the voltage maximum value Vmax to obtain the first voltage value V1, i.e., V1 ═ Vmin + Vmax, and may input the first voltage value V1 to the inverter 320. The inverter 320 performs an inversion calculation on the first voltage value V1, and obtains a phase voltage intermediate value Vmid, that is, Vmid — V1, and inputs the phase voltage intermediate value Vmid to the corrector 330. The corrector 330 corrects the phase voltage intermediate value Vmid by a predetermined coefficient K to obtain a second voltage value V2, i.e., V2 ═ K × Vmid, and inputs the second voltage value V2 to the multiplier 340. The multiplier 340 multiplies the second voltage value V2 by the load current I1 detected by the second current detecting module 30 to obtain a harmonic current given value Ih _ ref, i.e., Ih _ ref is V2I 1.
Thus, the minimum voltage value Vmin, the maximum voltage value Vmax, and the load current I1 detected by the second current detection module 30 are input to the operation unit 300, and are subjected to the operation processing by the adder 310, the inverter 320, the corrector 330, and the multiplier 340 in the operation unit 300, so that the harmonic current given value Ih _ ref can be obtained.
In an embodiment of the present invention, as shown in fig. 5, after the voltage minimum value Vmin of the three-phase power network and the voltage maximum value Vmax of the three-phase power network are processed by the above method, waveforms of the voltage minimum value Vmin, the voltage maximum value Vmax and the phase voltage intermediate value Vmid can be obtained, wherein the waveform w1 is the waveform of the voltage maximum value Vmax, the waveform w2 is the waveform of the voltage minimum value Vmin, and the waveform w3 is the waveform of the phase voltage intermediate value Vmid.
Further, as shown in fig. 4, the harmonic current given value Ih _ ref and the current Ih _ fb through the compensation inductor detected by the first current detecting module 20 may be input to the current controller 400 in the control module 50, so that the current controller 400 generates a switching control signal (which may be a PWM control signal) according to the harmonic current given value Ih _ ref and the current Ih _ fb through the compensation filter inductor. The control module 50 may control the first switch tube S1 and the second switch tube S2 according to the switch control signal to distribute the harmonic compensation current generated by the harmonic injection circuit 10 to the three-phase power grid. Therefore, the harmonic content of the current injected into the power grid can be reduced, so that the requirement of the power grid harmonic current standard is met.
In an embodiment of the present invention, as shown in fig. 4, the arithmetic unit 300 may further include a phase delay 350, wherein the phase delay 350 is configured to perform a phase delay on the second voltage value V2, so as to synchronize the phase of the harmonic compensation current distributed to the three-phase power grid with the phase of the grid-connected voltage of the rectifier. The waveform w4 shown in fig. 5 is obtained after the phase delay is performed on the second voltage value V2.
Specifically, the harmonic injection circuit comprises three filter capacitors connected in star, after current is injected into the filter capacitors, the phase of the network access current can be advanced, and the phase delayer can carry out phase delay on the second voltage value, so that the phase of the harmonic compensation current distributed to the three-phase power grid and the phase of the network access voltage of the rectifier are kept synchronous, the power factor of the system is improved, and the output total power factor is close to 1.
In an embodiment of the present invention, the power of the load is about 8KW, and after the voltage of the three-phase grid, the load current I1 and the current Ih _ fb passing through the compensation filter inductor are processed by the above method and the first switching tube S1 and the second switching tube S2 are controlled, the waveform of the grid-connected voltage of the rectifier (the waveform w5 in fig. 6) and the waveform of the harmonic compensation current distributed to the three-phase grid (the waveform w6 in fig. 6) can be obtained, so that the phase of the harmonic compensation current distributed to the three-phase grid and the phase of the grid-connected voltage of the rectifier can be synchronized, and the power factor is close to 1.
Further, after performing harmonic analysis on the harmonic compensation current distributed to the three-phase power grid in fig. 6, a current harmonic analysis graph (the abscissa of which represents the number of harmonics and the ordinate of which represents the harmonic amplitude) as shown in fig. 7 can be obtained, as can be seen from fig. 7, the total harmonic content of the harmonic compensation current distributed to the three-phase power grid is 4.11%, and the fundamental amplitude is 16.35, and each harmonic satisfies the requirement of the network-connected harmonic current standard.
In an embodiment of the present invention, as shown in fig. 2, the ac side of the rectifier may be connected to the a, B and C phases of the three-phase power grid through a first filter inductor L1, a second filter inductor L2 and a third filter inductor L3, and connected to the first filter capacitor Cf1, the second filter capacitor Cf2 and the third filter capacitor Cf3 of the harmonic injection circuit 10, and the dc side of the rectifier may be connected to the first switch tube S1 and the second switch tube S2 of the harmonic injection circuit 10.
Specifically, as shown in fig. 2, the first diode D1 and the fourth diode D4 may form a first phase leg, and an intersection point of the first diode D1 and the fourth diode D4 is an intermediate node of the first phase leg, and the intermediate node may be connected to the a phase of the three-phase grid through the first filter inductor L1, and may also be connected to one end of the first filter capacitor Cf 1. The second diode D2 and the fifth diode D5 may form a second phase leg, and an intersection point of the second diode D2 and the fifth diode D5 is a middle node of the second phase leg, and the middle node may be connected to a phase B of the three-phase power grid through a second filter inductor L2, or may be connected to one end of a second filter capacitor Cf 2. The third diode D3 and the sixth diode D6 may form a third phase leg, and an intersection point of the third diode D3 and the sixth diode D6 is an intermediate node of the third phase leg, and the intermediate node may be connected to a C phase of a three-phase power grid through a third filter inductor L3, or may be connected to a third filter capacitor Cf 3.
Therefore, alternating current output from the three-phase power grid can output stable direct current after being filtered by the first filter inductor L1, the second filter inductor L2 and the third filter inductor L3, rectified by the rectifier 1 and stabilized by the direct current voltage stabilizing capacitor Cdc.
In another embodiment of the present invention, as shown in fig. 8, the ac side of the rectifier is connected to the a phase, the B phase and the C phase of the three-phase power grid, and is connected to the first filter capacitor Cf1, the second filter capacitor Cf2 and the third filter capacitor Cf3 in the harmonic injection circuit 10, and the dc side of the rectifier is connected to the first switch tube S1 and the second switch tube S2 through the fourth filter inductor L4 and the fifth filter inductor L5, respectively.
In particular, the first diode D1 and the fourth diode D4 may constitute a first phase leg, and the intersection of the first diode D1 and the fourth diode D4 is an intermediate node of the first phase leg, which may be directly connected to the a-phase of the three-phase power grid. The second diode D2 and the fifth diode D5 may constitute a second phase leg, and the intersection of the second diode D2 and the fifth diode D5 is an intermediate node of the second phase leg, which may be directly connected to the B-phase of the three-phase grid. The third diode D3 and the sixth diode D6 may constitute a third phase leg, and the intersection of the third diode D3 and the sixth diode D6 is an intermediate node of the third phase leg, which may be directly connected to the C-phase of the three-phase power grid.
The three-phase bridge arm is connected in parallel to have a third node and a fourth node, the third node is connectable to one end of the first switching tube S1 through a fourth filter inductor L4 and also connectable to the first direct current terminal P on the direct current side, and the fourth node is connectable to the other end of the second switching tube S2 through a fifth filter inductor L5 and also connectable to the second direct current terminal N on the direct current side.
Therefore, alternating current output from the three-phase power grid can output stable direct current to a load after being rectified by the rectifier 1, filtered by the fourth filter inductor L4 and the fifth filter inductor L5, and stabilized by the direct current stabilizing capacitor Cdc.
It should be noted that the harmonic current compensation device for the rectifier according to the embodiment of the present invention may be integrated in an independent module, and in a required application, the independent module may be directly connected in parallel to the diode rectification system to distribute the harmonic compensation current to the three-phase power grid, so as to reduce the harmonic content of the current injected into the power grid, so as to meet the requirement of the power grid harmonic current standard.
According to the harmonic current compensation device for the rectifier of the embodiment of the invention, the harmonic injection circuit comprises three filter capacitors correspondingly connected with the alternating current side of the rectifier, the three filter capacitors can be connected with one ends of the first switch tube and the second switch tube through compensation filter inductors, the other ends of the first switch tube and the second switch tube can be respectively connected with the direct current side of the rectifier, the current passing through the compensation filter inductor is detected through a first current detection module, the load current of the rectifier is detected through a second current detection module, the voltage of the three-phase power grid is detected through a voltage detection module, and generating a switch control signal by the control module according to the voltage of the three-phase power grid, the load current and the current passing through the compensation filter inductor, and the first switching tube and the second switching tube are controlled according to the switching control signal so as to distribute the harmonic compensation current generated by the harmonic injection circuit to the three-phase power grid. Therefore, the harmonic content of the current injected into the power grid can be reduced to meet the requirement of the harmonic current standard, and the device is simple in structure and low in production cost.
In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are not to be considered limiting of the invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (6)
1. A harmonic current compensation device for a rectifier, wherein an ac side of the rectifier is connected to a three-phase power grid and a dc side of the rectifier is used to connect to a load, wherein the rectifier is a diode rectifier, the harmonic current compensation device comprising:
the harmonic injection circuit comprises a first filter capacitor, a second filter capacitor, a third filter capacitor, a compensation filter inductor, a first switch tube and a second switch tube, wherein one end of the first filter capacitor is connected to a first alternating current end of the alternating current side, one end of the second filter capacitor is connected to a second alternating current end of the alternating current side, one end of the third filter capacitor is connected to a third alternating current end of the alternating current side, the other end of the first filter capacitor, the other end of the second filter capacitor and the other end of the third filter capacitor are connected and provided with a first node, one end of the first switch tube is connected to a first direct current end of the direct current side, the other end of the first switch tube is connected with one end of the second switch tube and provided with a second node, and the other end of the second switch tube is connected to a second direct current end of the direct current side, the compensation filter inductor is connected between the first node and the second node;
a first current detection module for detecting a current through the compensation filter inductance;
a second current detection module for detecting a load current of the rectifier;
the voltage detection module is used for detecting the voltage of the three-phase power grid;
a control module, connected to the first current detection module, the second current detection module, the voltage detection module, and the control end of the first switch tube and the control end of the second switch tube, respectively, the control module is configured to generate a switch control signal according to the voltage of the three-phase power grid, the load current, and the current passing through the compensation filter inductor, and control the first switch tube and the second switch tube according to the switch control signal, so as to distribute the harmonic compensation current generated by the harmonic injection circuit to the three-phase power grid, where the control module includes:
the minimum voltage acquisition unit is used for acquiring the minimum voltage of the three-phase power grid;
the maximum voltage acquisition unit is used for acquiring the maximum voltage of the three-phase power grid;
the operation unit is used for operating the voltage minimum value, the voltage maximum value and the load current to obtain a harmonic current given value;
a current controller for generating the switch control signal according to the harmonic current set value and the current passing through the compensation filter inductance.
2. The harmonic current compensation apparatus for a rectifier of claim 1, wherein the operation unit comprises:
an adder for performing a superposition calculation on the voltage minimum value and the voltage maximum value to obtain a first voltage value;
an inverter for inverting the first voltage value to obtain a phase voltage intermediate value;
a corrector for multiplying a preset coefficient by the phase voltage intermediate value to obtain a second voltage value;
a multiplier for multiplying the second voltage value with the load current to obtain the harmonic current given value.
3. The harmonic current compensation apparatus for a rectifier of claim 2, wherein the operation unit further comprises:
a phase delayer for phase delaying the second voltage value to keep a phase of a harmonic compensation current distributed to the three-phase power grid in synchronization with a phase of an incoming voltage of the rectifier.
4. The harmonic current compensation device for a rectifier according to any one of claims 1 to 3, wherein the rectifier includes first to sixth diodes, the first to sixth diodes constituting three-phase legs, an intermediate node of a first one of the three-phase legs being connected to the A-phase of the three-phase power grid through a first filter inductance, an intermediate node of a second one of the three-phase legs being connected to the B-phase of the three-phase power grid through a second filter inductance, and an intermediate node of a third one of the three-phase legs being connected to the C-phase of the three-phase power grid through a third filter inductance.
5. The harmonic current compensation device for a rectifier as claimed in any one of claims 1 to 3, wherein the rectifier includes first to sixth diodes constituting a three-phase leg, the three-phase leg being connected in parallel to have a third node and a fourth node, the third node being connected to one end of the first switching tube through a fourth filter inductor, and the fourth node being connected to the other end of the second switching tube through a fifth filter inductor.
6. The harmonic current compensation device for a rectifier of claim 1, wherein a dc voltage stabilization capacitor is connected between said first dc terminal and said second dc terminal.
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| CN101378227A (en) * | 2008-09-28 | 2009-03-04 | 东南大学 | Power unit for cascade apparatus |
| CN106208735A (en) * | 2016-08-24 | 2016-12-07 | 中南大学 | The matrix converter of a kind of third-harmonic zero-sequence voltage and control method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101378227A (en) * | 2008-09-28 | 2009-03-04 | 东南大学 | Power unit for cascade apparatus |
| CN106208735A (en) * | 2016-08-24 | 2016-12-07 | 中南大学 | The matrix converter of a kind of third-harmonic zero-sequence voltage and control method |
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| 基于3次谐波无源注入法的谐波抑制技术;李小青等;《电力系统自动化》;20070725;第31卷(第14期);61-65 * |
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