Three-phase current source type rectifier, modulation method thereof and efficient rectification circuit

Abstract

The invention relates to the technical field of electronic power, in particular to a three-phase current source type rectifier which comprises an alternating current input circuit, a three-phase six-bridge-arm structure circuit and a direct current output circuit. The three-phase six-bridge-arm structure circuit comprises six bridge arm circuits, and each bridge arm circuit is formed by connecting at least two MOSFETs in series. According to the three-phase current source type rectifier, all diodes of an existing three-phase current source type rectifier are replaced with MOSFETs, the conduction loss is greatly reduced through the reverse conduction characteristic of the MOSFETs, and the three-phase current source type rectifier has good application value.

Description

Technical Field

[0001] The present invention relates to the field of electronic power technology, and in particular to a three-phase current source rectifier and a modulation method thereof, and a high-efficiency rectifier circuit. Background Art

[0002] At present, three-phase rectifiers are divided into three-phase voltage source rectifiers and three-phase current source rectifiers. Three-phase current source rectifiers have the advantages of short-circuit protection and high reliability, and are widely used.

[0003] Traditional current source rectifier circuits generally use Figure 1 The three-phase current source rectifier shown in the figure needs to pass through two diodes and two IGBT / MOSFET devices on the AC side before it can be transmitted to the DC side. Since the conduction tube voltage drop of the power diode is relatively fixed, especially in the application of DC low-voltage output, each bridge arm needs to be connected to a diode in series with a switch tube, resulting in large conduction losses, which greatly affects the conversion efficiency of the rectifier. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a three-phase current source rectifier, including an AC input circuit, a three-phase six-bridge arm structure circuit and a DC output circuit; the three-phase six-bridge arm structure circuit includes six bridge arm circuits, and each bridge arm circuit is composed of at least two MOSFETs connected in series.

[0005] Furthermore, there are two MOSFETs, namely a first MOSFET and a second MOSFET, the first MOSFET and the second MOSFET are connected in series, the drain of the first MOSFET is connected to the AC input circuit, the source of the first MOSFET is connected to the source of the second MOSFET, and the drain of the second MOSFET is connected to the DC output circuit.

[0006] Furthermore, the three-phase current source rectifier also includes a freewheeling circuit, which is connected to the DC output circuit.

[0007] Furthermore, the freewheeling circuit is composed of a freewheeling diode.

[0008] The present invention also provides a modulation method for a three-phase current source rectifier, comprising the following steps: S100, sampling the grid-side input AC voltage of the AC input circuit of the three-phase current source rectifier, the DC-side output voltage of the DC output circuit, and the DC-side output current; S200, confirming the current maximum value, minimum value and near-zero value of the AC voltage according to the input AC voltage; S300, determining a DC output voltage according to a maximum AC voltage, a minimum AC voltage, and a near-zero AC voltage; S400, controlling the on-off of the MOSFET of the three-phase six-bridge-arm structure circuit to control the DC output voltage, so as to modulate the total circuit.

[0009] Further, in step S400, the three-phase six-bridge-arm structure circuit is controlled. When the first bridge arm circuit in the three-phase six-bridge-arm structure circuit needs to be closed and the second bridge arm circuit needs to be opened, the steps are as follows: S410, first turn off the first MOSFET of the first bridge arm circuit; S420, turning on the second MOSFET of the second bridge arm circuit; S430, turn off the second MOSFET of the first bridge arm circuit; S440, turn on the second MOSFET of the second bridge arm circuit.

[0010] The present invention also provides a high-efficiency rectifier circuit, comprising the three-phase current source rectifier of any one of the above embodiments.

[0011] Compared with the prior art, the three-phase current source rectifier provided by the present invention replaces all the diodes of the existing three-phase current source rectifier with MOSFETs, and utilizes the reverse conduction characteristics of MOSFETs to greatly reduce conduction losses, thus having good application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0013] Figure 1 It is a schematic diagram of the structure of a traditional three-phase current source rectifier; Figure 2 A schematic diagram of the structure of a three-phase current source rectifier provided in Embodiment 1 of the present invention; Figure 3 A schematic diagram of the structure of a three-phase current source rectifier provided in Embodiment 2 of the present invention; Figure 4 A flow chart of a modulation method for a three-phase current source rectifier provided in Embodiment 3 of the present invention; Figure 5 This is a flow chart of a modulation method for a three-phase current source rectifier provided in Embodiment 3 of the present invention.

[0014] Reference numerals: DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0017] Embodiment 1 like Figure 1 As shown, it is a three-phase current source rectifier commonly used in the prior art, each bridge arm circuit of which includes a MOSFET and a diode. Under high current conditions, the three-phase current source rectifier composed of MOSFET and diode has a large loss as a conduction voltage element.

[0018] In order to solve the above technical problems, the present invention provides a three-phase current source rectifier, including an AC input circuit, a three-phase six-bridge arm structure circuit and a DC output circuit; the three-phase six-bridge arm structure circuit includes six bridge arm circuits, and each bridge arm circuit is composed of at least two MOSFETs connected in series.

[0019] In a specific implementation, the six-way bridge arm circuit includes a first A-phase bridge arm circuit 10, a second A-phase bridge arm circuit 20, a first B-phase bridge arm circuit 30, a second B-phase bridge arm circuit 40, a first C-phase bridge arm circuit 50 and a second C-phase bridge arm circuit 60. The first A-phase bridge arm circuit 10 and the second A-phase bridge arm circuit 20 are connected to the A-phase voltage of the AC input circuit, the first B-phase bridge arm circuit 30 and the second B-phase bridge arm circuit 40 are connected to the B-phase voltage of the AC input circuit, and the first C-phase bridge arm circuit 50 and the second C-phase bridge arm circuit 60 are connected to the C-phase voltage of the AC input circuit.

[0020] Preferably, there are two MOSFETs, namely a first MOSFET and a second MOSFET, the first MOSFET and the second MOSFET are connected in series, the drain of the first MOSFET is connected to the AC input circuit, the source of the first MOSFET is connected to the source of the second MOSFET, and the drain of the second MOSFET is connected to the DC output circuit.

[0021] Specifically, Figure 2 As shown, the first A-phase bridge arm circuit 10 and the second A-phase bridge arm circuit 20 both include a first MOSFET and a second MOSFET connected in series, the drain of the first MOSFET of the first A-phase bridge arm circuit 10 and the second A-phase bridge arm circuit 20 is connected to the A-phase voltage, the drain of the second MOSFET is connected to the DC output circuit, and the source of the first MOSFET is connected to the source of the second MOSFET. The first B-phase bridge arm circuit 30 and the second B-phase bridge arm circuit 40 both include a first MOSFET and a second MOSFET connected in series, the drain of the first MOSFET of the first B-phase bridge arm circuit 30 and the second B-phase bridge arm circuit 40 is connected to the B-phase voltage, the drain of the second MOSFET is connected to the DC output circuit, and the source of the first MOSFET is connected to the source of the second MOSFET. The first C-phase bridge arm circuit 50 and the second C-phase bridge arm circuit 60 both include a first MOSFET and a second MOSFET connected in series, the drain of the first MOSFET of the first C-phase bridge arm circuit 50 and the second C-phase bridge arm circuit 60 is connected to the C-phase voltage, the drain of the second MOSFET is connected to the DC output circuit, and the source of the first MOSFET is connected to the source of the second MOSFET.

[0022] Preferably, MOSFET has reverse conduction characteristics and low internal resistance characteristics, which ensure that MOSFET has lower losses than diodes. The present invention replaces the diodes in the existing three-phase current source rectifier with MOSFETs, and utilizes the reverse conduction and low internal resistance characteristics of MOSFETs to greatly reduce the losses of the three-phase current source rectifier provided by the present invention.

[0023] In one embodiment, each bridge arm circuit is formed by at least two IGBTs connected in series.

[0024] In a specific implementation, the MOSFETs connected in series in the first A-phase bridge arm circuit 10, the second A-phase bridge arm circuit 20, the first B-phase bridge arm circuit 30, the second B-phase bridge arm circuit 40, the first C-phase bridge arm circuit 50, and the second C-phase bridge arm circuit 60 can be replaced with IGBTs. Preferably, each bridge arm circuit is composed of two IGBTs connected in series, namely, a first IGBT and a second IGBT, the first IGBT is connected to the AC input circuit, and the second IGBT is connected to the DC output circuit.

[0025] In one embodiment, the first A-phase bridge arm circuit 10, the second A-phase bridge arm circuit 20, the first B-phase bridge arm circuit 30, the second B-phase bridge arm circuit 40, the first C-phase bridge arm circuit 50, and the second C-phase bridge arm circuit 60 may also be formed by MOSFET and IGBT connected in series. Preferably, each bridge arm circuit is composed of a MOSFET and an IGBT, and the first MOSFET may be replaced by an IGBT, and the second MOSFET may also be replaced by an IGBT.

[0026] Embodiment 2 In the first embodiment, although the circuit loss is reduced by replacing the diode with a MOSFET, since the MOSFET exhibits resistance characteristics when turned on and allows forward current and reverse current to pass, common conduction may be caused during the switching of the bridge arm circuit.

[0027] In order to solve the above technical problems, the three-phase current source rectifier provided by the present invention also includes a freewheeling circuit, and the freewheeling circuit is connected to the DC output circuit.

[0028] Preferably, if Figure 3 As shown, the freewheeling circuit is composed of a freewheeling diode. Specifically, after all the bridge arm circuits in the three-phase current source rectifier circuit are turned off, the DC inductor IDC will still generate a current. At this time, there is no circuit to clear the current generated by the DC inductor, which will cause circuit hazards. For this, a freewheeling diode is added. The diode allows the current generated by the DC inductor to flow in the circuit, ensuring the circuit safety. At the same time, the freewheeling diode also facilitates the conversion of different bridge arm circuits.

[0029] Embodiment 3 To solve the problem of the three-phase current source rectifier in the first embodiment, the present invention also provides a modulation method for the three-phase current source rectifier. The three-phase current source rectifier is the three-phase current source rectifier described in the first embodiment. Figure 4 As shown, the following steps are included: S100, sampling the grid-side input AC voltage of the AC input circuit of the three-phase current source rectifier, the DC-side output voltage of the DC output circuit, and the DC-side output current; Specifically, the grid-side input AC voltage, the DC-side output voltage, and the DC-side output current of the three-phase full-MOSFET current source rectifier are sampled.

[0030] S200, confirming the current maximum value, minimum value and near-zero value of the AC voltage according to the input AC voltage; Specifically, based on the AC input voltage, confirm the current maximum voltage Upos, minimum voltage Uneg, and near-zero voltage Unear0; considering the characteristics of the three-phase voltage, it is required that |Upos|>|Uneg|, and Uneg and Unear0 have the same sign; at the same time, obtain the sign of the maximum voltage Udir, when Upos≥0, Udir=1, otherwise Udir=-1; at the same time, obtain the phase sequence OdPos / OdNeg / OdNear0 corresponding to Upos\Uneg\Unear0.

[0031] S300, determining a DC output voltage according to a maximum AC voltage, a minimum AC voltage, and a near-zero AC voltage; Specifically, for the AC input voltage, VA+VB+VC=0; for the DC output voltage, it needs to be composed of three voltages: (VA-VC), (VA-VB), and 0.

[0032] S400, controlling the DC output voltage by controlling the on-off of MOSFETs in the three-phase six-bridge arm structure circuit.

[0033] In a specific implementation, for one switching cycle, the switching change is performed in the manner that (VA-VC) changes to 0 and then changes to (VA-VB), wherein 0 can be represented by (VA-VA).

[0034] Preferably, according to the above-mentioned (VA-VC) becoming (VA-VA) and then becoming (VA-VB), the first A-phase bridge arm circuit 10 is fully turned on; the second C-phase bridge arm circuit 60 is first turned on and then turned off; the second A-phase bridge arm circuit 20 is first turned off, then turned on and then turned off; the second B-phase bridge arm circuit 40 is first turned off and then turned on.

[0035] In step S400, the three-phase six-bridge-arm structure circuit is controlled. When the first bridge arm circuit in the three-phase six-bridge-arm structure circuit needs to be closed and the second bridge arm circuit needs to be opened, Figure 5 As shown, the steps are as follows: S410, first turn off the first MOSFET of the first bridge arm circuit; S420, turning on the second MOSFET of the second bridge arm circuit; S430, turn off the second MOSFET of the first bridge arm circuit; S440, turn on the second MOSFET of the second bridge arm circuit.

[0036] It should be noted that the first bridge arm circuit and the second bridge arm circuit can be composed of any one of the first A-phase bridge arm circuit 10, the second A-phase bridge arm circuit 20, the first B-phase bridge arm circuit 30, the second B-phase bridge arm circuit 40, the first C-phase bridge arm circuit 50 and the second C-phase bridge arm circuit 60. This is just a synonym for uniformly explaining the conversion between bridge arm circuits of different orders.

[0037] Specifically, according to the above (VA-VC) becoming (VA-VA) and then becoming (VA-VB), the first A-phase bridge arm circuit 10 is fully turned on; the second C-phase bridge arm circuit 60 is first turned on and then turned off; the second A-phase bridge arm circuit 20 is first turned off, then turned on, and then turned off; the second B-phase bridge arm circuit 40 is first turned off and then turned on.

[0038] For the above logic, if the switch tube of the corresponding phase is directly turned on to form a voltage drop, when (VA-VC) is switched to (VA-VA): ① If the first MOSFET S11 and the second MOSFET S12 of the second C phase bridge arm circuit 60 are turned off first, and then the first MOSFET S3 and the second MOSFET S4 of the second A phase bridge arm circuit 20 are turned on, the current will be interrupted and the DC inductor current idc will not be able to continue to flow; ② If the first MOSFET S3 and the second MOSFET S4 of the second A phase bridge arm circuit 20 are turned on first, and then the first MOSFET S11 and the second MOSFET S12 of the second C phase bridge arm circuit 60 are turned off, the current will flow directly from the second C phase bridge arm circuit 60 to the second A phase bridge arm circuit 20, causing a short circuit.

[0039] To avoid the above situation, the first MOSFET S11 of the second C-phase bridge arm circuit 60 should be disconnected first, and then the second MOSFET S4 of the second A-phase bridge arm circuit 20 should be turned on, and then the second MOSFET S12 of the second C-phase bridge arm circuit 60 should be disconnected, and then the second MOSFET S3 of the second A-phase bridge arm circuit 20 should be turned on; at this time, it can be ensured that the current cannot flow directly from the second C-phase bridge arm circuit 60 to the second A-phase bridge arm circuit 20, and the switching of the current direction is completed at the same time.

[0040] The switching strategies of other periods are the same as the above-mentioned strategy of changing (VA-VC) to (VA-VA) and then to (VA-VB), and will not be described in detail here.

[0041] Embodiment 4 The present invention also provides a high-efficiency rectifier circuit, comprising the three-phase current source rectifier of any one of the above embodiments.

[0042] Although the terms such as AC input circuit, three-phase six-bridge arm structure circuit, DC output circuit, bridge arm circuit, first A-phase bridge arm circuit, second A-phase bridge arm circuit, first B-phase bridge arm circuit, second B-phase bridge arm circuit, first C-phase bridge arm circuit and second C-phase bridge arm circuit 60 are used more frequently in this article, the possibility of using other terms is not excluded. The use of these terms is only for more convenient description and explanation of the essence of the present invention; interpreting them as any additional limitation is contrary to the spirit of the present invention.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A three-phase current source rectifier, characterized in that: It includes an AC input circuit, a three-phase six-bridge arm structure circuit and a DC output circuit; the three-phase six-bridge arm structure circuit includes six bridge arm circuits, and each bridge arm circuit is formed by at least two MOSFETs connected in series.

2. The three-phase current source rectifier according to claim 1, characterized in that: There are two MOSFETs, namely a first MOSFET and a second MOSFET. The first MOSFET and the second MOSFET are connected in series. The drain of the first MOSFET is connected to the AC input circuit, the source of the first MOSFET is connected to the source of the second MOSFET, and the drain of the second MOSFET is connected to the DC output circuit.

3. The three-phase current source rectifier according to claim 1, characterized in that: The three-phase current source rectifier further includes a freewheeling circuit, and the freewheeling circuit is connected to the DC output circuit.

4. The three-phase current source rectifier according to claim 3, characterized in that: The freewheeling circuit is composed of a freewheeling diode.

5. A modulation method for a three-phase current source rectifier, wherein the three-phase current source rectifier is the three-phase current source rectifier according to any one of claims 1 to 2, characterized in that: The steps include: S100, sampling the grid-side input AC voltage of the AC input circuit of the three-phase current source rectifier, the DC-side output voltage and the DC-side output current of the DC output circuit; S200, confirming the current maximum value, minimum value and near-zero value of the AC voltage according to the input AC voltage; S300, determining the DC output voltage according to the maximum AC voltage, the minimum AC voltage and the AC voltage near-zero value; S400, controlling the DC output voltage by controlling the on-off of the MOSFET of the three-phase six-bridge-arm structure circuit to modulate the total circuit.

6. The modulation method of the three-phase current source rectifier according to claim 5, characterized in that: In step S400, the three-phase six-bridge-arm structure circuit is controlled. When the first bridge arm circuit in the three-phase six-bridge-arm structure circuit needs to be closed and the second bridge arm circuit needs to be opened, the steps are as follows: S410, first close the first MOSFET of the first bridge arm circuit; S420, turning on the second MOSFET of the second bridge arm circuit; S430, turn off the second MOSFET of the first bridge arm circuit; S440, turn on the second MOSFET of the second bridge arm circuit.

7. A high efficiency rectifier circuit, characterized in that: A three-phase current source rectifier comprising any one of claims 1 to 4.

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