Current source type PWM (Pulse Width Modulation) rectification system with high power factor

Abstract

The invention relates to the technical field of electronic power, and provides a current source type PWM rectification system with a high power factor, which comprises a plurality of active rectification modules and at least one reactive power control module, the alternating current input sides of the active rectification modules and the reactive power control module are connected in parallel, the direct current output ends of the active rectification modules are connected in parallel, and the reactive power control module is connected with the reactive power control module. And the direct current output end of the reactive power control module is short-circuited. At least one reactive power control module is added in the current source type PWM rectification system, the direct current output end of the reactive power control module is short-circuited, reactive power modulation is carried out on the PWM rectification system by internally controlling the reactive power current of the reactive power control module, the reactive power current is allowed to be independently adjusted, and the current source type PWM rectification system has good application value.

Description

Technical Field

[0001] The invention relates to the technical field of power electronic control, and in particular to a current source type PWM rectification system with a high power factor. 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] For a traditional current source rectifier, if three-pulse control is used, that is, one pulse is used to control the A / B / C phases respectively, the three-phase current passing through the switch tube needs to be in phase with the voltage to ensure that the current is not distorted.

[0004] Traditional current source rectifiers are not easy to compensate for the reactive power of the capacitor on the AC side because the three-phase current passing through the switch tube is in phase with the three-phase voltage. At the same time, for scenarios where the power factor needs to be adjusted, additional controllers need to be added. Summary of the invention

[0005] In order to solve the deficiencies existing in the above-mentioned prior art, the present invention provides a current source PWM rectification system with a high power factor, comprising a plurality of active rectification modules and at least one reactive control module, wherein the AC input sides of the active rectification modules and the reactive control modules are connected in parallel, the DC output ends of the plurality of active rectification modules are connected in parallel, and the DC output end of the reactive control module is short-circuited.

[0006] Furthermore, the reactive power control module is connected in parallel with the active power rectification module through a first wire and a second wire, the first wire is connected to a first switch, the second wire is connected to a second switch, and a third switch is connected between the first wire and the second wire.

[0007] Furthermore, when the DC side output cannot meet the reactive current demand, the third switch is disconnected, and the first switch and the second switch are turned on; when the DC side output meets the reactive current demand, the first switch and the second switch are disconnected, and the third switch is turned on.

[0008] Furthermore, the active rectification module and the reactive control module are both three-phase current source PWM rectifiers.

[0009] Furthermore, the input AC voltage cycle is divided into 12 sectors, each sector contains 5 modulations. When the DC port voltage is , , , , The order of switching is as follows:

[0010] in, is the input AC voltage of the first phase, is the input AC voltage of the second phase, is the input AC voltage of the third phase, is the peak current of the AC input side, is the switching cycle, The duration of zero voltage difference at the DC port, For the small voltage difference of DC port, is the duration of large voltage difference at the DC port, is the power frequency angle, For time, is the DC output current.

[0011] Furthermore, the three-phase current source PWM rectifier of the active rectification module is controlled by three independent active pulses.

[0012] Furthermore, when the voltage starting phase and the current starting phase are 0, the first active pulse controls the first switch tube and the second switch tube of phase A, the second active pulse controls the third switch tube and the fourth switch tube of phase B, and the third active pulse controls the fifth switch tube and the sixth switch tube of phase C.

[0013] Furthermore, the three-phase current source PWM rectifier of the reactive power control module is controlled by 6 independent reactive pulses.

[0014] Furthermore, when the voltage starting phase and the current starting phase are not equal to 0, the first reactive pulse controls the first switch tube of phase A, the second reactive pulse controls the second switch tube of phase A, the third reactive pulse controls the third switch tube of phase B, the fourth reactive pulse controls the fourth switch tube of phase B, the fifth reactive pulse controls the fifth switch tube of phase C, and the sixth reactive pulse controls the sixth switch tube of phase C.

[0015] Based on the above, compared with the prior art, the high power factor current source PWM rectifier system provided by the present invention adds at least one reactive power control module to the current source PWM rectifier system, the DC output end of the reactive power control module is short-circuited, and the reactive current of the reactive power control module is internally controlled to perform reactive modulation on the PWM rectifier system, allowing the reactive current to be adjusted separately, thereby improving the controllability of the current source PWM rectifier system and having good application value.

[0016] Other features and beneficial effects of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other beneficial effects of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] 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 creative work. The positional relationships described in the drawings in the following description are based on the directions in which the components are drawn in the diagrams, unless otherwise specified. Figure 1 A schematic diagram of the structure of a current source PWM rectification system with high power factor provided by an embodiment of the present invention; Figure 2 A schematic diagram of the structure of a three-phase current source rectifier provided in one embodiment of the present invention; Figure 3 Another structural schematic diagram of a three-phase current source rectifier provided by an embodiment of the present invention; Figure 4 Another structural schematic diagram of a three-phase current source rectifier provided by an embodiment of the present invention; Figure 5 Another structural schematic diagram of a three-phase current source rectifier provided by an embodiment of the present invention; Figure 6 Another structural schematic diagram of a high power factor current source PWM rectification system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions 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, rather than all the embodiments; the technical features designed in different implementation modes of the present invention described below can be combined with each other as long as they do not conflict with each other; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0019] In the description of the present invention, it should be noted that all terms (including technical terms and scientific terms) used in the present invention have the same meanings as those generally understood by ordinary technicians in the field to which the present invention belongs, and should not be understood as limitations on the present invention; it should be further understood that the terms used in the present invention should be understood to have the same meanings as these terms in the context of this specification and in the relevant fields, and should not be understood in an idealized or overly formal sense, unless explicitly defined in this invention.

[0020] The present invention provides a current source type PWM rectification system with high power factor, such as Figure 1 As shown, it includes several active rectifier modules and at least one reactive control module, the AC input sides of the active rectifier modules and the reactive control modules are connected in parallel, the DC output ends of the several active rectifier modules are connected in parallel, and the DC output end of the reactive control module is short-circuited.

[0021] During specific implementation, the DC output side of the reactive power control module is short-circuited. This module adjusts the upper limit of reactive current by controlling the short-circuit current of the DC output, thereby achieving the effect of arbitrary reactive power output and adjusting the reactive output of the system.

[0022] When there is voltage at the DC output end of the active rectifier module, there is a certain correlation between the reactive current of the system and the current size of the DC output end. Due to power limitation, the DC current of the DC output end itself may not be output at an excessively large value. For example, if the DC output end of the active rectifier module is to output a DC current of 50V 100A, the AC current peak value of the AC input side of the active rectifier module is 100A. When the DC output side does not need to output DC power, the reactive current is not controlled. Through the present invention, at least one reactive control module is added, the AC input side of which is connected in parallel with other active rectifier modules, and the DC output end is short-circuited. The reactive control capability of the entire system is enhanced by the reactive control module. The reactive control module with a short-circuited DC output end is not limited by the active rectifier module. Because the short-circuit voltage of the DC output end of the reactive control module is 0, the current can be controlled and output inside the reactive control module according to the output demand, so that the reactive current is controllable. The reactive control module and the active rectifier module are combined together, so that the entire system is controllable within a large range.

[0023] In one embodiment, both the active rectification module and the reactive control module are three-phase current source PWM rectifiers. The three-phase current source rectifier can be as follows: Figure 2 The conventional three-phase current source PWM rectifier shown in FIG. Figure 3 The three-phase current source rectifier shown in FIG. 1 is a conventional three-phase current source PWM rectifier, in which a freewheeling diode D13 is connected to the DC output side of the conventional three-phase current source PWM rectifier; Figure 4The three-phase current source rectifier shown in the figure replaces all diodes with MOS tubes on the basis of the traditional three-phase current source rectifier, and can be Figure 5 As shown, after the diode is replaced with a MOS tube, a freewheeling diode D13 is added on the DC output side.

[0024] In one embodiment, if Figure 6 As shown, the reactive control module is connected in parallel with the active rectification module through a first wire and a second wire, the first wire is connected to a first switch, the second wire is connected to a second switch, and a third switch is connected between the first wire and the second wire.

[0025] Specifically, when the DC side output cannot meet the reactive current demand, the third switch is disconnected, the first switch and the second switch are turned on, and the reactive control module rectifies and expands the active rectifier module. When the DC side output meets the reactive current demand, the first switch and the second switch are disconnected, the third switch is turned on, and the reactive control module is used to simply control the reactive power. The on and off of the first switch, the second switch, and the third switch are controlled according to the specific needs of the system, so that the reactive control module can simply provide the required reactive current for the system, and can also rectify and expand the active rectifier module.

[0026] In one embodiment, the input AC voltage cycle is sectorized into 12 sectors, each sector having 5 modulation segments. When the DC port voltage is , , , , The order of switching is as follows:

[0027] in, is the input AC voltage of the first phase, is the input AC voltage of the second phase, is the input AC voltage of the third phase, is the peak current of the AC input side, is the switching cycle, The duration of zero voltage difference at the DC port, For the small voltage difference of DC port, is the duration of large voltage difference at the DC port, is the power frequency angle, For time, is the DC output current.

[0028] In specific implementation, it is divided into 12 sectors, each sector is 30°. The five-segment modulation is , , , , order of switching.

[0029] in, , , They are , , One of the three, and they are different. is the input AC voltage of phase A, is the input AC voltage of phase B, is the input AC voltage of phase C. For example, ignoring the voltage drop of the switching device, the DC port voltage will be , , , , The principles of other sectors are similar and will not be described here.

[0030] Preferably, the three-phase current source PWM rectifier of the active rectification module is controlled by three independent active pulses.

[0031] When the voltage starting phase and the current starting phase are 0, the first active pulse controls the first switch tube and the second switch tube of phase A, the second active pulse controls the third switch tube and the fourth switch tube of phase B, and the third active pulse controls the fifth switch tube and the sixth switch tube of phase C.

[0032] Preferably, the three-phase current source PWM rectifier of the reactive power control module is controlled by 6 independent reactive power pulses.

[0033] When the voltage starting phase and the current starting phase are not equal to 0, the first reactive pulse controls the first switch tube of phase A, the second reactive pulse controls the second switch tube of phase A, the third reactive pulse controls the third switch tube of phase B, the fourth reactive pulse controls the fourth switch tube of phase B, the fifth reactive pulse controls the fifth switch tube of phase C, and the sixth reactive pulse controls the sixth switch tube of phase C.

[0034] The specific principle is as follows: Considering the fundamental wave of 50HZ, the starting phase of the AC current is 0 and the peak value is ; The starting phase of the AC voltage is θ, and the peak value is , then the AC current is considered to be: (1) (2) According to the first sector of 0°~30° (i.e. ) to analyze and consider It is the duty cycle of the upper bridge arm; This is the duty cycle of the lower bridge arm. At this time, the duty cycle of each phase is: (3) And satisfy: (4) (5) If the 5-segment modulation is used, the DC port voltage will be , , , , The order of switching; (6) For pure active modulation, it can be seen from the above formulas (1) and (2) that Taking the first sector as an example, consider the T2 state: for phase A, when A is expected to be positive, VA is also positive, such as Figure 2 and Figure 3 As shown, when the first switch tube S2 and the second switch tube S4 of the active rectifier module are turned on at the same time, the current only passes through the first switch tube S2 and the first diode D1, and cannot pass through the second diode D3 in the reverse direction, and the current flows from A+ to the DC output side; for the B phase, when the B phase is expected to be negative, VB is also negative, and the third switch tube S6 and the fourth switch tube S8 are given a conduction signal at the same time, the current only passes through the fourth switch tube S8 and the fourth diode D7, and cannot pass through the third diode D5 in the reverse direction, and the current flows from the DC output side to B-.

[0035] Therefore, for pure active power debugging, the first switch tube S2 and the second switch tube S4 of phase A can be controlled by one pulse, the third switch tube S6 and the fourth switch tube S8 of phase B can be controlled by one pulse, and the fifth switch tube S10 and the sixth switch tube S12 of phase C can be controlled by one pulse, for a total of three pulses. When the active rectifier module is modulated, the five-segment modulation instructions and states of the first sector are shown in Table 1 below: Table 1

[0036] Among them, "O" is the on state, "\" is the uncontrollable state, and "X" is the off state.

[0037] For reactive modulation, according to the above formulas (1) and (2), it can be known that it is applied to , then take the first sector as an example, consider the T2 state: for phase A, when IA is expected to be positive, VA may be positive or negative. If the first switch tube S2 and the second switch tube S4 are given a conduction signal at the same time, the current may flow from A+ to the DC output terminal through the first switch tube S2 and the first diode D1, or from the DC output terminal to A- through the second switch tube S4 and the second diode D3, resulting in uncontrollable current; for phase B, when IB is expected to be negative, VB may be positive or negative. If the third switch tube S6 and the fourth switch tube S8 are given a conduction signal at the same time, the current may flow from the DC output terminal to B- through the fourth switch tube S8 and the fourth diode D7, or from B+ to the DC output terminal through the third switch tube S6 and the third diode D5. Therefore, when debugging using the reactive power control module, the first switch tube S2, the second switch tube S4, the third switch tube S6, the fourth switch tube S8, the fifth switch tube S10 and the sixth switch tube S12 need to be controlled separately, for a total of 6 pulses. When the reactive power control module is modulating, the five-segment modulation instructions and status of the first sector are shown in Table 2 below: Table 2

[0038] Among them, "O" is the on state, "\" is the uncontrollable state, and "X" is the off state.

[0039] It should be noted that the above is only the control logic of the first sector, and the control logic of other sectors is the same as that of the first sector, which will not be repeated here.

[0040] In addition, those skilled in the art should understand that, although there are many problems in the prior art, each embodiment or technical solution of the present invention can be improved in only one or several aspects, without having to solve all the technical problems listed in the prior art or background technology at the same time. Those skilled in the art should understand that the content not mentioned in a claim should not be used as a limitation on the claim.

[0041] Although the terms such as active rectifier module, reactive power control module, AC input side, DC output terminal, etc. are used more frequently in this article, the possibility of using other terms is not excluded. These terms are used only to more conveniently describe and explain the essence of the present invention; interpreting them as any additional restrictions is contrary to the spirit of the present invention; the terms "first", "second", etc. (if any) in the description and claims of the embodiments of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0042] 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 high power factor current source PWM rectification system, characterized in that: It comprises several active rectifier modules and at least one reactive control module, wherein the AC input sides of the active rectifier modules and the reactive control module are connected in parallel, the DC output ends of the several active rectifier modules are connected in parallel, and the DC output end of the reactive control module is short-circuited.

2. The high power factor current source PWM rectification system according to claim 1, characterized in that: The reactive power control module is connected in parallel with the active power rectification module through a first wire and a second wire, the first wire is connected to a first switch, the second wire is connected to a second switch, and a third switch is connected between the first wire and the second wire.

3. The high power factor current source PWM rectification system according to claim 2, characterized in that: When the DC side output cannot meet the reactive current demand, the third switch is disconnected, and the first switch and the second switch are turned on; when the DC side output meets the reactive current demand, the first switch and the second switch are disconnected, and the third switch is turned on.

4. The high power factor current source PWM rectification system according to claim 1, characterized in that: The active rectification module and the reactive control module are both three-phase current source PWM rectifiers.

5. The high power factor current source PWM rectifier system according to claim 4, characterized in that: The input AC voltage cycle is divided into 12 sectors, each sector contains 5 modulation segments. When the DC port voltage is , , , , The order of switching is as follows: in, is the input AC voltage of the first phase, is the input AC voltage of the second phase, is the input AC voltage of the third phase, is the peak current of the AC input side, is the switching cycle, The duration of zero voltage difference at the DC port, The DC port has a small voltage difference. is the duration of large voltage difference at the DC port, is the power frequency angle, For time, is the DC output current.

6. The high power factor current source PWM rectification system according to claim 5, characterized in that: The three-phase current source PWM rectifier of the active rectification module is controlled by three independent active pulses.

7. The high power factor current source PWM rectification system according to claim 6, characterized in that: When the voltage starting phase and the current starting phase are 0, the first active pulse controls the first switch tube and the second switch tube of phase A, the second active pulse controls the third switch tube and the fourth switch tube of phase B, and the third active pulse controls the fifth switch tube and the sixth switch tube of phase C.

8. The high power factor current source PWM rectification system according to claim 5, characterized in that: The three-phase current source PWM rectifier of the reactive power control module is controlled by 6 independent reactive pulses.

9. The high power factor current source PWM rectification system according to claim 8, characterized in that: When the voltage starting phase and the current starting phase are not equal to 0, the first reactive pulse controls the first switch tube of phase A, the second reactive pulse controls the second switch tube of phase A, the third reactive pulse controls the third switch tube of phase B, the fourth reactive pulse controls the fourth switch tube of phase B, the fifth reactive pulse controls the fifth switch tube of phase C, and the sixth reactive pulse controls the sixth switch tube of phase C.

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