Modularized three-phase single-stage AC-DC converter topological structure, control system and control method

Abstract

The invention discloses a modular three-phase single-stage AC-DC converter topological structure, a control system and a control method, the modular three-phase single-stage AC-DC converter topological structure comprises three single-phase single-stage modules, the input ends of the three single-phase single-stage modules are respectively connected with three-phase AC voltage, and the output ends of the three single-phase single-stage modules are connected in parallel and output DC voltage; the single-phase single-stage module comprises an interlaced totem-pole PFC converter and an LLC resonant converter, and a switching tube of the interlaced totem-pole PFC converter and a switching tube of the LLC resonant converter are multiplexed to realize single-stage power conversion. According to the technical scheme, through switching tube multiplexing, the use number of power devices is reduced, the cost of the converter is saved, the efficiency is improved, and meanwhile three-phase power factor correction and stable direct-current voltage output can be achieved only through conversion of a first-stage power circuit.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of power electronics, and particularly relates to a modular three-phase single-stage AC-DC converter topology structure and a control method. BACKGROUND

[0002] With the development of science and technology, power electronics technology has penetrated into various aspects of production and life, such as electric vehicle charging equipment, renewable energy power generation systems, data center power supplies and special power supplies. Among them, higher requirements are put forward for three-phase AC-DC converters in various application fields, such as high power density, high efficiency and low current harmonics.

[0003] However, at present, three-phase two-stage converters are mostly used in practical applications, but such converters have many problems. First, the three-phase two-stage converter converts power through two stages, which increases the loss and reduces the efficiency. Second, the three-phase two-stage converter has a large number of switching tubes and needs a large bus electrolytic capacitor to support between the front and rear stages, resulting in a large overall volume of the converter and a low power density. Third, the three-phase two-stage converter needs to coordinate two independent control loops, which is difficult to control.

[0004] Therefore, it is urgent to develop a three-phase single-stage AC-DC converter that effectively overcomes the above problems. SUMMARY

[0005] The application aims to provide a modular three-phase single-stage AC-DC converter to solve the technical problems of low efficiency, low power density and difficult control of the three-phase two-stage converter.

[0006] To solve the above technical problems, in a first aspect, the application provides a modular three-phase single-stage AC-DC converter topology structure, comprising: three single-phase single-stage modules, the input ends of which are connected to three-phase alternating voltage, and the output ends of which are connected in parallel to output direct current voltage; The single-phase single-stage module comprises an interleaved totem pole PFC converter and an LLC resonant converter, wherein the switching tubes of the interleaved totem pole PFC converter and the switching tubes of the LLC resonant converter are multiplexed to realize single-stage power conversion.

[0007] Optionally, the interleaved totem pole PFC converter operates in an interleaved parallel mode.

[0008] Optionally, the interleaved totem pole PFC converter comprises a first branch, a second branch, a third branch and a capacitor connected in parallel; The first branch comprises a first switching tube and a second switching tube connected in series, one end of a first inductor is connected to a first-phase alternating current source, and the other end is connected between the first switching tube and the second switching tube; The second branch comprises a third switch tube and a fourth switch tube connected in series, one end of the second inductor is connected to the first phase AC source, and the other end is connected between the third switch tube and the fourth switch tube. The third branch comprises a first diode and a second diode connected in series, and the neutral point of the three-phase AC voltage is connected between the first diode and the second diode.

[0009] Optionally, the high-frequency input pulse of the LLC resonant converter comes from the interleaved totem pole PFC converter.

[0010] Optionally, the LLC resonant converter comprises a resonant inductor, a resonant capacitor, a transformer, and a secondary side rectification circuit. The same name end of the primary winding of the transformer is connected between the first switch tube and the second switch tube through the resonant inductor. The different name end of the primary winding of the transformer is connected between the third switch tube and the fourth switch tube through the resonant capacitor.

[0011] Optionally, the secondary side rectification circuit comprises a first rectification branch and a second rectification branch. The first rectification branch comprises a third diode and a fourth diode connected in series, and the same name end of the secondary winding of the transformer is connected between the third diode and the fourth diode. The second rectification branch comprises a fifth diode and a sixth diode connected in series, and the different name end of the secondary winding of the transformer is connected between the fifth diode and the sixth diode. The modular three-phase single-stage AC-DC converter topology further comprises a filter capacitor connected in parallel with the second rectification branch.

[0012] Optionally, the switch tube comprises a silicon carbide field effect tube.

[0013] Optionally, the three-phase single-stage AC-DC converter is configured to have a 220V, 50Hz AC input and a 200V DC output.

[0014] In a second aspect, the application further provides a control system of a modular three-phase single-stage AC-DC converter topology, comprising: A voltage comparator comprising a first input end receiving an output voltage and a second input end receiving a reference voltage, for outputting a first error signal; A first PI regulator connected to the output end of the voltage comparator, for converting the first error signal into a line current reference amplitude; A multiplier comprising a first input end receiving the line current reference amplitude and a second input end receiving a phase voltage phase, for outputting a phase line current AC reference value; The current comparator comprises a first input end receiving an actual current, a second input end receiving an AC reference value of the current, and an output end outputting a second error signal; The second PI regulator is connected to the output end of the current difference generator and is used for converting the second error signal into a duty cycle signal. The PWM modulator is used for converting the duty cycle signal into a switch tube driving waveform, which is amplified by a driving circuit and is used for controlling the switch tube.

[0015] In a third aspect, the application provides a control method of a modular three-phase single-stage AC-DC converter topology, which comprises the following steps: An output voltage and a three-phase actual current of the converter are obtained. The output voltage is subtracted from a reference voltage signal to obtain a first error signal. A first PI regulator is used to generate a line current reference amplitude based on the first error signal. The line current reference amplitude is multiplied by a corresponding voltage phase of each phase to generate an AC reference value of the line current of each phase. The AC reference value of the line current of each phase is subtracted from a corresponding three-phase actual current to obtain a second error signal. A second PI regulator is used to generate a duty cycle signal of each phase based on the second error signal. A PWM modulator is used for converting the duty cycle signal into a switch tube driving waveform, which is amplified by a driving circuit and is used for controlling the switch tube.

[0016] The three-phase single-stage AC-DC converter has the following advantages: 1. The modular three-phase single-stage AC-DC converter topology provided by the application multiplexes switch tubes of an interleaved totem pole PFC converter and an LLC resonant converter, reduces the number of switch tubes, reduces the number of power conversion stages, reduces power loss and hardware cost, and improves the overall efficiency of the converter.

[0017] 2. The three-phase single-stage AC-DC converter provided by the application adopts a modular design, each single-stage module operates independently without coupling, has strong scalability, and is easy to replace in case of failure, thereby increasing system reliability.

[0018] 3. The three-phase single-stage AC-DC converter provided by the application operates the interleaved totem pole PFC converter of each phase in an interleaved parallel mode, reduces the ripple of the input current, doubles the ripple frequency, reduces the high-frequency harmonic content of the input current, and reduces the total harmonic distortion (THD) of the input current.

[0019] 4. The three-phase single-stage AC-DC converter provided by the application has independent control of each phase module and the same control mode, adopts voltage-current double-loop PI control, and has simple control mode. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A schematic diagram of a modular three-phase single-stage AC-DC converter topology of an embodiment of the application is shown in the figure. Figure 2 A schematic diagram of a control system structure of a modular three-phase single-stage AC-DC converter topology of an embodiment of the application is shown in the figure. Figure 3 A schematic diagram of AC side voltage and current waveforms of a modular three-phase single-stage AC-DC converter topology of an embodiment of the application is shown in the figure. Figure 4 A schematic diagram of AC and DC side voltage waveforms of a modular three-phase single-stage AC-DC converter topology of an embodiment of the application is shown in the figure. DETAILED DESCRIPTION

[0021] In order to better understand the purpose, structure and function of the application, a three-phase single-stage AC-DC converter topology of the application is described in further detail below in combination with the drawings.

[0022] As shown in the figure, a modular three-phase single-stage AC-DC converter topology of an embodiment of the application includes: Figure 1 three single-phase single-stage modules, such as module A, module B and module C shown in the figure, whose input ends are connected to three-phase AC voltages va, vb and vc respectively, and whose output ends are connected in parallel to output DC voltage. Figure 1

[0023] The single-phase single-stage module includes an interleaved totem pole PFC converter and an LLC resonant converter, wherein the switching tube of the interleaved totem pole PFC converter is multiplexed with the switching tube of the LLC resonant converter to realize single-stage power conversion.

[0024] The modular three-phase single-stage AC-DC converter of the embodiment has its single-phase single-stage module obtained by multiplexing the switching tubes of the interleaved totem pole PFC converter and the LLC resonant converter, and obtains the three-phase single-stage AC-DC converter by assigning three-phase voltage to the three single-phase single-stage modules. Through multiplexing of the switching tubes, the number of power devices is reduced, the cost of the converter is saved, the efficiency is improved, and three-phase power factor correction and stable DC output voltage can be realized by only one stage of power circuit conversion.

[0025] ​​In some embodiments, the interleaved totem-pole PFC converter operates in interleaved parallel mode, which can reduce input current ripple, double the ripple frequency, and reduce the high frequency harmonic content in the input current, which helps the design of the filter circuit. Figure 3 The input voltage and current waveforms are shown in the figure. The input current is substantially in phase with the input voltage. The three-phase current THD is 1.21%, 1.22%, and 1.20%, respectively.

[0026] Specifically, the interleaved totem-pole PFC converter includes a first branch, a second branch, a third branch, and a capacitor C1 in parallel.

[0027] The first branch includes a first switch S1 and a second switch S2 in series, one end of a first inductor L1 is connected to the first-phase alternating current source va, and the other end is connected between the first switch S1 and the second switch S2.

[0028] The second branch includes a third switch S3 and a fourth switch S4 in series, one end of a second inductor L2 is connected to the first-phase alternating current source va, and the other end is connected between the third switch S3 and the fourth switch S4.

[0029] The third branch includes a first diode D1 and a second diode D2 in series, and the neutral point N of the three-phase alternating current is connected between the first diode D1 and the second diode D2.

[0030] In some embodiments, the high-frequency input pulse of the LLC resonant converter comes from the interleaved totem-pole PFC converter.

[0031] Specifically, the LLC resonant converter includes a resonant inductor Lr1, a resonant capacitor Cr1, a transformer Tr, and a secondary rectifier circuit. The same name end of the primary winding of the transformer Tr is connected between the first switch S1 and the second switch S2 through the resonant inductor Lr1. The different name end of the primary winding of the transformer Tr is connected between the third switch S3 and the fourth switch S4 through the resonant capacitor Cr1.

[0032] Further, the secondary rectifier circuit includes a first rectifier branch and a second rectifier branch. The first rectifier branch includes a third diode D3 and a fourth diode D4 in series, and the same name end of the secondary winding of the transformer Tr is connected between the third diode D3 and the fourth diode D3. The second rectifier branch includes a fifth diode D5 and a sixth diode D6 in series, and the different name end of the secondary winding of the transformer Tr is connected between the fifth diode D5 and the sixth diode D6. The modular three-phase single-stage AC-DC converter topology further comprises a filter capacitor C4 connected in parallel with the second rectification branch.

[0033] In some embodiments, the switching tube comprises a silicon carbide field effect tube, and the interleaved totem pole PFC converter can work in a CCM mode.

[0034] Specifically, the three-phase single-stage AC-DC converter is configured to have a 220V, 50Hz AC input and a 200V DC output.

[0035] Specifically, the operation principle of the modular three-phase single-stage AC-DC converter topology comprises the following stages (as the operation principles of the three modules are consistent, module A is taken as an example, and one power frequency cycle is analyzed): The first stage (va in the positive half cycle): the first switching tube S1, the fourth switching tube S4 and the second switching tube D2 are turned on, the first inductor L1 discharges to the capacitor C1, the inductor current iL1 linearly decreases, the input voltage charges the second inductor L2, the inductor current iL2 linearly increases, the third diode D3 and the sixth diode D6 in the secondary side are turned on, and the energy is transmitted to the secondary side through the transformer Tr to charge the filter capacitor C4.

[0036] The second stage (va in the positive half cycle): the second switching tube S2 and the fourth switching tube S4 are defined as the duty cycle D, according to the size of D, the circuit operation is divided into two types. (1) When D<0.5, the first switching tube S1, the third switching tube S3 and the second diode D2 are turned on, the first inductor L1 discharges to the capacitor C1, the inductor current iL1 linearly decreases, and the second inductor L2 discharges to the capacitor C1, the inductor current iL2 linearly decreases. (2) When D>0.5, the second switching tube S2, the fourth switching tube S4 and the second switching tube D2 are turned on, the input voltage charges the first inductor L1, the inductor current iL1 linearly increases, and the input voltage charges the second inductor L2, the inductor current iL2 linearly increases. At this time, no diode in the secondary side is turned on, and the energy is provided by the filter capacitor C4.

[0037] The third stage (va in the positive half cycle): the second switching tube S2, the third switching tube S3 and the second diode D2 are turned on, the input voltage charges the first inductor L1, the inductor current iL1 linearly increases, and the second inductor L2 discharges to the capacitor C1, the inductor current iL2 linearly decreases; the fourth diode D4 and the fifth diode D5 in the secondary side are turned on, and the energy is transmitted to the secondary side through the transformer Tr to charge the filter capacitor C4.

[0038] The fourth stage (va in the negative half cycle): the first switch S1, the fourth switch S4 and the first diode D1 are turned on, the input voltage charges the first inductor L1, and the inductor current iL1 linearly rises; the second inductor L2 discharges the capacitor C1, and the inductor current iL2 linearly falls; the third diode D3 and the sixth diode D6 on the secondary side are turned on, and energy is transmitted to the secondary side through the transformer Tr to charge the capacitor C4.

[0039] The fifth stage (va in the negative half cycle): the duty cycles of the second switch S2 and the fourth switch S4 are defined as D, and according to the size of D, the circuit operation is divided into two types. (1) When D < 0.5, the second switch S2 and the fourth switch S4 on the primary side and the first diode D1 are turned on, the first inductor L1 discharges the capacitor C1, and the inductor current iL1 linearly falls; the second inductor L2 discharges the capacitor C1, and the inductor current iL2 linearly falls. (2) When D > 0.5, the first switch S1 and the third switch S3 on the primary side and the first diode D1 are turned on, the input voltage charges the first inductor L1, and the inductor current iL1 linearly rises; the input voltage charges the second inductor L2, and the inductor current iL2 linearly rises. At this time, no diode on the secondary side is turned on, and energy is provided by the filter capacitor C4.

[0040] The sixth stage (va in the negative half cycle): the first inductor L1 on the primary side discharges the filter capacitor C4, and the inductor current iL1 linearly falls; the second switch S2 and the third switch S3 and the first diode D1 are turned on, the input voltage charges the second inductor L2, and the inductor current iL2 linearly rises; the fourth diode D4 and the fifth diode D5 on the secondary side are turned on, and energy is transmitted to the secondary side through the transformer Tr to charge the filter capacitor C4.

[0041] Based on the same inventive concept, the embodiment also proposes a control system of a modular three-phase single-stage AC-DC converter topology, please refer to Figure 2 , the control system comprises: A voltage comparator comprises a first input end receiving an output voltage and a second input end receiving a reference voltage, and is used for outputting a first error signal.

[0042] A first PI regulator is connected to the output end of the voltage subtractor, and is used for converting the first error signal into a line current reference amplitude.

[0043] A multiplier comprises a first input end receiving the line current reference amplitude and a second input end receiving a voltage phase of the phase, and is used for outputting an AC reference value of the line current of the phase; specifically, in the embodiment, three multipliers are arranged, and each receives a voltage phase of the phase to output an AC reference value of the line current of the phase.

[0044] The current comparator comprises a first input end receiving the actual current of the phase, a second input end receiving the AC reference value of the current of the phase, and is configured to output a second error signal. Specifically, in the embodiment, two current comparators are arranged for each phase circuit, and the current i L1 of the branch in which the first inductor L1 is located and the current i L2 of the branch in which the second inductor L2 is located are collected respectively to output a plurality of second error signals.

[0045] The second PI regulator is connected to the output end of the current difference device, and is configured to convert the second error signal into a duty cycle signal. Specifically, in the embodiment, two second PI regulators are arranged for each phase.

[0046] The PWM modulator is configured to convert the duty cycle signal into a switch tube driving waveform, and the switch tube driving waveform is amplified by a driving circuit to control the switch tube. For example, for the phase line in which the module A is located, the PWM modulator generates a switch tube driving waveform based on the duty cycle signal output by one of the second PI modulators, and the switch tube driving waveform is used to drive the switching action of the first switch tube S1 and the second switch tube S2. The PWM modulator generates a driving waveform based on the duty cycle signal output by another second PI modulator, and the driving waveform is used to drive the switching action of the third switch tube S3 and the fourth switch tube S4.

[0047] Referring to Figure 2 In some embodiments, the control system further comprises an attenuator arranged between the multiplier and the current comparator, and configured to attenuate the amplitude of the AC reference value of the current of each phase.

[0048] Based on the same inventive concept, the embodiment further provides a control method of a modular three-phase single-stage AC-DC converter topology, comprising: obtaining the output voltage of the converter and the three-phase actual current; obtaining the output voltage of the converter and the three-phase actual current; generating a line current reference amplitude based on the first error signal by using a first PI regulator; multiplying the line current reference amplitude by the corresponding voltage phase of each phase to generate an AC reference value of the current of each phase; obtaining the output voltage of the converter and the three-phase actual current; generating a duty cycle signal of each phase based on the second error signal by using a second PI regulator; converting the duty cycle signal into a switch tube driving waveform by using a PWM modulator, and amplifying the switch tube driving waveform by a driving circuit to control the switch tube.

[0049] Referring to Figure 3 , Figure 4 , Figure 3 ,Figure 4 The AC side voltage and current waveforms and the DC side voltage waveform are shown. The input current phase basically follows the input voltage, and the power factor is above 0.99. The output voltage reaches a stable value after 0.1 s, and the ripple rate is less than 0.5%.

[0050] It can be understood that the present application is described by some embodiments, and those skilled in the art know that various changes or equivalent replacements can be made to these features and embodiments without departing from the spirit and scope of the present application. In addition, under the guidance of the present application, these features and embodiments can be modified to adapt to specific conditions and materials without departing from the spirit and scope of the present application. Therefore, the present application is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of the present application are within the scope of the present application.

Claims

1. A modular three-phase single-stage AC-DC converter topology, characterized in that, include: Three single-phase, single-stage modules are connected to three-phase AC voltage at their input terminals and output DC voltage in parallel at their output terminals. The single-phase single-stage module includes an interleaved totem pole PFC converter and an LLC resonant converter, wherein the switching transistors of the interleaved totem pole PFC converter and the LLC resonant converter are multiplexed to achieve single-stage power conversion.

2. The modular three-phase single-stage AC-DC converter topology as described in claim 1, characterized in that, The interleaved totem pole PFC converter operates in an interleaved parallel configuration.

3. The modular three-phase single-stage AC-DC converter topology as described in claim 2, characterized in that, The interleaved totem pole PFC converter includes: a first branch, a second branch, a third branch, and a capacitor connected in parallel; The first branch includes a first switch and a second switch connected in series, one end of the first inductor is connected to the first phase AC source, and the other end is connected between the first switch and the second switch; The second branch includes a third switch and a fourth switch connected in series. One end of the second inductor is connected to the first phase AC source, and the other end is connected between the third switch and the fourth switch. The third branch includes a first diode and a second diode connected in series, with the neutral point of the three-phase AC voltage connected between the first diode and the second diode.

4. The modular three-phase single-stage AC-DC converter topology as described in claim 3, characterized in that, The high-frequency input pulses of the LLC resonant converter come from the interleaved totem pole PFC converter.

5. The modular three-phase single-stage AC-DC converter topology as described in claim 4, characterized in that, The LLC resonant converter includes a resonant inductor, a resonant capacitor, a transformer, and a secondary-side rectifier circuit. The primary winding of the transformer is connected between the first switch and the second switch via the resonant inductor. The opposite-named terminals of the primary winding of the transformer are connected between the third and fourth switching transistors via the resonant capacitor.

6. The modular three-phase single-stage AC-DC converter topology as described in claim 5, characterized in that, The secondary rectifier circuit includes a first rectifier branch and a second rectifier branch; The first rectifier branch includes a third diode and a fourth diode connected in series, and the secondary winding of the transformer is connected between the third diode and the fourth diode; The second rectifier branch includes a fifth diode and a sixth diode connected in series, and the opposite-named terminal of the secondary winding of the transformer is connected between the fifth diode and the sixth diode; The modular three-phase single-stage AC-DC converter topology also includes a filter capacitor, which is connected in parallel with the second rectifier branch.

7. The modular three-phase single-stage AC-DC converter topology as described in claim 1, characterized in that, The switching transistor includes a silicon carbide field-effect transistor.

8. The modular three-phase single-stage AC-DC converter topology as described in claim 1, characterized in that, The three-phase single-stage AC-DC converter is configured with 220V, 50Hz AC input and 200V DC output.

9. A control system for a modular three-phase single-stage AC-DC converter topology, characterized in that, include: A voltage comparator includes a first input terminal for receiving the output voltage and a second input terminal for receiving the reference voltage, used to output a first error signal; The first PI regulator, with its input terminal connected to the output terminal of the voltage differential, is used to convert the first error signal into a line current reference amplitude. The multiplier includes a first input terminal for receiving the reference amplitude of the line current and a second input terminal for receiving the phase of the local voltage, and is used to output the AC reference value of the local line current. The current comparator includes a first input terminal for receiving the actual current of the current phase and a second input terminal for receiving the AC reference value of the current phase line current, and is used to output a second error signal. The second PI regulator, with its input terminal connected to the output terminal of the current differential, is used to convert the second error signal into a duty cycle signal. A PWM modulator is used to convert a duty cycle signal into a switching transistor drive waveform, which is then amplified by the drive circuit to control the switching transistor's operation.

10. A control method for a modular three-phase single-stage AC-DC converter topology, characterized in that, include: Obtain the converter's output voltage and actual three-phase AC current; The first error signal is obtained by subtracting the output voltage from the reference voltage signal; A line current reference amplitude is generated based on the first error signal using a first PI regulator; The line current reference amplitude is multiplied by the corresponding voltage phase to generate AC reference values ​​for each phase line current. The second error signal is obtained by subtracting the AC reference value of each phase line current from the corresponding actual three-phase AC current. The second PI controller is used to generate the duty cycle signal of each phase based on the second error signal; The duty cycle signal is converted into a switching transistor drive waveform by a PWM modulator, and then amplified by the drive circuit to control the switching transistor's operation.

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