Active front-end converter and resonance suppression method thereof

Abstract

The invention discloses an active front-end converter and a resonance suppression method thereof, and the active front-end converter comprises a rectifier circuit which is used for converting the AC electric energy of a power grid into DC electric energy and outputting the DC electric energy; the control module is connected with the rectifier circuit and is used for controlling the output current of the rectifier circuit; the filter circuit comprises an inductor unit and a capacitor unit, the capacitor unit comprises a filter capacitor and a split capacitor, the inductor unit is connected between the power grid and the input end of the rectifier circuit, one end of the filter capacitor is connected to the inductor unit, the other end of the filter capacitor is grounded, and the split capacitor is connected to the two ends of the filter capacitor in parallel. According to the active front-end converter, the loss can be reduced while resonance can be effectively suppressed, and the overall efficiency of the converter is higher.

Description

Technical Field

[0001] The present invention relates to the technical field of active front-end converters, and in particular to an active front-end converter and a resonance suppression method thereof. Background Art

[0002] The Active Front End (AFE) consists of an IGBT power module, an LCL filter circuit, and a PWM rectifier for a DC smoothing system. Figure 1 As shown in Figure 1, using current closed-loop control and PWM modulation technology in the active front end can achieve a higher power factor. However, the switching action of the power devices introduces switching-order harmonic current components and their integer multiples. To suppress these current harmonics, a filter must be added between the converter and the grid. Filters mainly come in two types: L-type and LCL-type. Because LCL filtering has obvious advantages over L filtering in terms of cost, THD reduction, and control system speed, LCL filters are also chosen on the AFE grid side. Because LCL filters have resonant peaks at the resonant frequency and phase jumps, they cause grid current instability and current distortion. Currently, passive damping is commonly used to eliminate the effects of resonance. A capacitor-in-series resistor topology is generally used to suppress resonance. However, this method not only reduces the filter's high-frequency filtering effect, but also, like capacitors, allows power frequency current to flow through resistors, resulting in significant power loss. Summary of the Invention

[0003] The embodiments of the present invention provide an active front-end converter and a resonance suppression method thereof, which solve the problem that the introduction of passive damping into the filter of a traditional AFE reduces the high-frequency filtering effect and increases power loss.

[0004] In a first aspect, an embodiment of the present invention provides an active front-end converter, comprising:

[0005] Rectifier circuit, used to convert AC power from the power grid into DC power output;

[0006] a control module, connected to the rectifier circuit, and configured to control an output current of the rectifier circuit;

[0007] The filter circuit includes an inductor unit and a capacitor unit, wherein the capacitor unit includes a filter capacitor and a split capacitor. The inductor unit is connected between the power grid and the input end of the rectifier circuit. One end of the filter capacitor is connected to the inductor unit and the other end is grounded. The split capacitor is connected in parallel to both ends of the filter capacitor.

[0008] In the active front-end converter provided in an embodiment of the present invention, the inductor unit includes a grid-side inductor and a rectifier-side inductor, the grid-side inductor and the rectifier-side inductor are connected in series between the grid and the input end of the rectifier circuit in sequence, one end of the filter capacitor is connected between the grid-side inductor and the rectifier-side inductor, and the other end is grounded.

[0009] In the active front-end converter provided in an embodiment of the present invention, the filter circuit further includes a resistance unit, the filter capacitor is grounded through the resistance unit, one end of the split capacitor is connected to an end of the filter capacitor connected to the inductance unit, and the other end of the split capacitor is connected to an end of the resistance unit connected to the ground.

[0010] In the active front end converter provided by the embodiment of the present invention, the resistance unit includes at least one damping resistor, one end of the damping resistor is connected to the filter capacitor, and the other end of the damping resistor is grounded.

[0011] In the active front-end converter provided by the embodiment of the present invention, the capacitance of the filter capacitor is equal to that of the split capacitor.

[0012] In the active front-end converter provided in an embodiment of the present invention, the rectifier circuit includes a power switch module and a bus capacitor, the input end of the power switch module is connected to the inductor unit, the bus capacitor is connected in parallel to the output end bus of the power switch module, and the control module is connected to the power switch module.

[0013] In the active front-end converter provided in an embodiment of the present invention, the control module includes a current loop, a voltage loop and an SVPWM generator, the input end of the voltage loop is connected to the output bus of the power switch module, the output end of the voltage loop is connected to the input end of the current loop, the output end of the current loop is connected to the input end of the SVPWM generator, and the output end of the SVPWM generator is connected to the power switch module.

[0014] In the active front-end converter provided in an embodiment of the present invention, the control module further includes a negative feedback unit, a first conversion unit, and a second conversion unit. The input end of the first conversion unit is connected to the branch where the filter capacitor is located, the output end of the first conversion unit is connected to the input end of the negative feedback unit, the output end of the negative feedback unit is connected to the output end of the current loop, the input end of the second conversion unit is connected to the output end of the current loop, and the output end of the second conversion unit is connected to the input end of the SVPWM generator.

[0015] In a second aspect, an embodiment of the present invention provides a resonance suppression method for an active front-end converter, which is applied to the active front-end converter described in the first aspect above, and the method includes: obtaining the current of the three-phase branch where the filter capacitor is located, and performing a 3s / 2r transformation based on the current of the three-phase branch where the filter capacitor is located to obtain a current superposition component; superimposing the current superposition component with the current component output by the current loop; performing a 2r / 2s transformation based on the current component after superimposing the current superposition component to obtain a modulation voltage component; performing SVPWM modulation based on the modulation voltage component to obtain a switch configuration signal; and driving the rectifier circuit to operate with the switch configuration signal.

[0016] An embodiment of the present invention provides an active front-end converter and a resonance suppression method thereof, wherein the active front-end converter includes: a rectifier circuit for converting the AC power of the power grid into DC power output; a control module connected to the rectifier circuit for controlling the output current of the rectifier circuit; a filter circuit including an inductor unit and a capacitor unit, wherein the capacitor unit includes a filter capacitor and a split capacitor, wherein the inductor unit is connected between the power grid and the input end of the rectifier circuit, one end of the filter capacitor is connected to the inductor unit and the other end is grounded, and the split capacitor is connected in parallel to both ends of the filter capacitor. The active front-end converter of the present application splits the capacitor in parallel with the branch of the filter capacitor in the filter circuit, and the split capacitor branch filters the harmonics input to the front end of the rectifier circuit, thereby effectively reducing losses while suppressing resonance, and the overall efficiency of the converter is higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. 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 any creative work.

[0018] Figure 1 A circuit diagram of an active front-end converter provided in an embodiment of the present invention;

[0019] Figure 2 A circuit diagram of a filter circuit provided by an embodiment of the present invention;

[0020] Figure 3 is a circuit diagram of a conventional active front-end converter;

[0021] Figure 4 This is the frequency characteristic diagram of the traditional LCL filter circuit;

[0022] Figure 5 Frequency characteristics diagram of the filter circuit provided by an embodiment of the present invention;

[0023] Figure 6 Grid-side input current harmonic spectrum analysis diagram of the active front-end converter provided by an embodiment of the present invention;

[0024] Figure 7 A schematic flow chart of the steps of the method provided in an embodiment of the present invention.

[0025] The reference numerals in the figures are:

[0026] 1. Rectifier circuit; 11. Power switch module; 12. Bus capacitor; 2. Control module; 21. Voltage loop; 22. Current loop; 23. SVPWM generator; 24. Negative feedback unit; 25. First conversion unit; 26. Second conversion unit; 3. Filter circuit; 31. Inductor unit; 311. Grid-side inductor; 312. Rectifier-side inductor; 32. Capacitor unit; 33. Resistor unit. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0028] Directional terms used herein, such as "upper," "lower," "front," "back," "left," "right," "inner," "outer," and "side," refer only to directions in the accompanying drawings. Therefore, these directional terms are intended to illustrate and facilitate understanding of the present invention and are not intended to limit the present invention. Furthermore, in the accompanying drawings, similar or identical structures are denoted by the same reference numerals.

[0029] In order to facilitate understanding of the present invention, the active front-end converter provided by the embodiment of the present invention is first described. Figures 1 to 6 , please refer to Figure 1 An embodiment of the present invention provides an active front-end converter, which includes: a rectifier circuit 1, used to convert the AC power of the power grid into DC power output; a control module 2, connected to the rectifier circuit 1, used to control the output current of the rectifier circuit 1; a filter circuit 3, including an inductor unit 31 and a capacitor unit 32, the capacitor unit 32 including a filter capacitor Cf and a split capacitor Cd, the inductor unit 31 is connected between the power grid and the input end of the rectifier circuit 1, one end of the filter capacitor Cf is connected to the inductor unit 31, and the other end is grounded, and the split capacitor Cd is connected in parallel to both ends of the filter capacitor Cf.

[0030] The circuit diagram of the traditional active front-end converter is as follows Figure 3As shown in the figure, the front-end filter circuit adopts the LCL topology of capacitor series resistor to suppress resonance. This method not only reduces the high-frequency filtering effect of the filter, but also the resistor and capacitor will flow the power frequency current, causing greater loss.

[0031] To this end, this embodiment provides an active front-end converter. The active front-end converter as a whole is mainly composed of a rectifier circuit 1, a control module 2, and a filter circuit 3. The rectifier circuit 1 is used to convert the AC power of the power grid into DC power suitable for load use. The rectifier circuit 1 is composed of power devices such as IGBTs. The control module 2 is connected to the rectifier circuit 1, and the output of the rectifier circuit 1 is controlled by the control module 2. The filter circuit 3 is mainly arranged between the power grid and the rectifier circuit 1, and is mainly used to filter the input of the rectifier circuit 1. The filter circuit 3 is mainly composed of two parts: an inductor unit 31 and a capacitor unit 32. Specifically, the inductor unit 31 is composed of multiple inductors. In each phase, the capacitor unit 32 is specifically composed of multiple capacitors, wherein the capacitor unit 32 mainly includes a filter capacitor Cf and a split capacitor Cd. The inductor unit 31 is connected between the power grid and the input end of the rectifier circuit 1, specifically, between the three-phase output end of the power grid and the three-phase input end of the rectifier circuit 1. One end of the filter capacitor Cf is connected to the inductor unit 31, and the other end of the filter capacitor Cf is grounded. The split capacitor Cd is connected in parallel across the filter capacitor Cf. Specifically, in the three-phase branch of the power grid, each phase branch has at least one filter capacitor Cf and at least one split capacitor Cd. Each phase branch is connected to at least one filter capacitor Cf and at least one split capacitor Cd connected in parallel with the filter capacitor Cf. Overall, the split capacitor Cd is connected in parallel with the filter capacitor Cf. Both the split capacitor Cd and the filter capacitor Cf act as passive damping. The split capacitor Cd branch filters harmonics input to the front end of the rectifier circuit 1, achieving a better filtering effect than a traditional LCL filter, improving the overall efficiency of the active front-end converter, reducing power loss, and improving the frequency response of the LCL filter.

[0032] In one embodiment, referring to Figure 1 and Figure 2 The inductor unit 31 includes a grid-side inductor 311 and a rectifier-side inductor 312. The grid-side inductor 311 and the rectifier-side inductor 312 are sequentially connected in series between the grid and the input end of the rectifier circuit 1. One end of the filter capacitor Cf is connected between the grid-side inductor 311 and the rectifier-side inductor 312, and the other end is grounded. In a specific implementation, the inductor unit 31 is mainly composed of the grid-side inductor 311 and the rectifier-side inductor 312. Figure 1As shown, the grid-side inductor 311 includes inductors L1-L3, and the rectifier-side inductor 312 includes inductors L4-L6. The grid-side inductor 311 and the rectifier-side inductor 312 are sequentially connected in series between the grid and the input terminal of the rectifier circuit 1. Specifically, the grid-side inductor 311 and the rectifier-side inductor 312 are divided into three groups, and each group of grid-side inductors 311 and rectifier-side inductors 312 is connected in series with each phase branch between the grid and the input terminal of the rectifier circuit 1. One end of the filter capacitor Cf is connected between the grid-side inductor 311 and the rectifier-side inductor 312, that is, connected to the connection point of the grid-side inductor 311 and the rectifier-side inductor 312 in series, and the other end of the filter capacitor Cf is connected to ground. In specific applications, the grid-side inductor 311 is mainly used to filter out harmonic currents in the power grid and reduce voltage fluctuations and current distortion in the power grid, while the rectifier-side inductor 312 is used to filter out the pulsating components in the rectified DC voltage, making the output voltage smoother and more stable. Through the combination of the grid-side inductor 311, the rectifier-side inductor 312, the filter capacitor Cf and the split capacitor Cd, the entire filter circuit 3 forms an LCCL topology structure, effectively reducing input-side voltage fluctuations and providing a stable output for the rectifier circuit 1.

[0033] In one embodiment, referring to Figure 2 The filter circuit 3 further includes a resistor unit 33, wherein the filter capacitor Cf is grounded through the resistor unit 33, one end of the split capacitor Cd is connected to the end of the filter capacitor Cf connected to the inductor unit 31, and the other end of the split capacitor Cd is connected to the grounded end of the resistor unit 33. In a specific implementation, the filter circuit 3 further includes a resistor unit 33, which can be designed by one or more resistor devices. The filter capacitor Cf is connected to the ground through the resistor unit 33, that is, the resistor unit 33 is connected in series with the branch where the filter capacitor Cf is located, one end of the split capacitor Cd is connected to the end of the filter capacitor Cf connected to the inductor unit 31, and the other end of the split capacitor Cd is connected to the end of the active damping connected to the ground. Overall, the split capacitor Cd is connected in parallel with the two ends of the RC passive branch formed in series with the filter capacitor Cf and the resistor unit 33. By introducing the resistor unit 33, the charging and discharging process of the filter capacitor Cf and the split capacitor Cd becomes smoother, which can reduce voltage fluctuations and make the voltage at the input end of the rectifier circuit 1 more stable.

[0034] Further, refer to Figure 2, the resistance unit 33 includes at least one damping resistor R, one end of the damping resistor R is connected to the filter capacitor Cf, and the other end of the damping resistor R is grounded. In a specific implementation, the resistance unit 33 is composed of at least one damping resistor R. The resistance unit 33 can be designed with multiple damping resistors R. When multiple damping resistors R are used, the multiple damping resistors R are connected in series or in parallel. In this embodiment, the resistance unit 33 takes a damping resistor R as an example. One end of the damping resistor R is connected to the filter capacitor Cf, and the other end of the damping resistor R is connected to the ground, that is, the damping resistor R is connected in series with the branch of the filter capacitor Cf. By introducing the damping resistor R, the charging and discharging process of the filter capacitor Cf and the split capacitor Cd becomes smoother, the voltage fluctuation is reduced, and the stability of the voltage at the input end of the rectifier circuit 1 is improved.

[0035] In one embodiment, the capacitance of the filter capacitor Cf is equal to that of the split capacitor Cd. In a specific implementation, the capacitance of the filter capacitor Cf and the split capacitor Cd are set to be equal.

[0036] In one embodiment, referring to Figure 1 The rectifier circuit 1 includes a power switch module 11 and a bus capacitor 12. The input end of the power switch module 11 is connected to the inductor unit 31. The bus capacitor 12 is connected in parallel to the output bus of the power switch module 11. The control module 2 is connected to the power switch module 11. In a specific implementation, the rectifier circuit 1 is mainly composed of the power switch module 11 and the bus capacitor 12. The power switch module 11 is a power topology structure composed of a certain number of power switch tubes (such as IGBTs) connected through a specific connection method. The input end of the power switch module 11 is connected to the inductor unit 31, that is, the three-phase input end of the power switch module 11 is connected to the power grid via the inductor unit 31. The bus capacitor 12 is connected in parallel to the output bus of the power switch module 11, specifically in parallel between the positive and negative busbars of the output end. The bus capacitor 12 is mainly used to smooth the voltage and current fluctuations of the output busbar to ensure the stability of the output voltage and current. The control module 2 is connected to the power switch module 11 . The control module 2 mainly drives the power switch module 11 to operate through a switch configuration signal (such as a PWM signal), thereby controlling the output current and voltage of the rectifier circuit 1 .

[0037] Further, refer to Figure 1The control module 2 includes a current loop 22, a voltage loop 21, and an SVPWM generator 23. The input end of the voltage loop 21 is connected to the output bus of the power switch module 11, the output end of the voltage loop 21 is connected to the input end of the current loop 22, the output end of the current loop 22 is connected to the input end of the SVPWM generator 23, and the output end of the SVPWM generator 23 is connected to the power switch module 11. In a specific implementation, the control module 2 mainly includes the current loop 22, the voltage loop 21, and the SVPWM generator 23. The control module 2 adopts a dual closed-loop control structure, with the outer loop being the voltage loop 21 and the inner loop being the current loop 22. The input end of the voltage loop 21 is connected to the output bus of the power switch module 11, the output end of the voltage loop 21 is connected to the input end of the current loop 22, the output end of the current loop 22 is connected to the input end of the SVPWM generator 23, and the output end of the SVPWM generator 23 is connected to the power switch module 11. The voltage loop 21 is used to regulate the output bus voltage of the rectifier circuit 1 to maintain the bus voltage at the output end of the power switch module 11 at a constant set value. The output of the voltage loop 21 serves as the input of the current loop 22. The SVPWM generator 23 is used to modulate and generate a switch configuration signal that can control the power switch module 11.

[0038] Furthermore, refer to Figure 1The control module 2 further includes a negative feedback unit 24, a first conversion unit 25, and a second conversion unit 26. The input of the first conversion unit 25 is connected to the branch where the filter capacitor Cf is located, the output of the first conversion unit 25 is connected to the input of the negative feedback unit 24, the output of the negative feedback unit 24 is connected to the output of the current loop 22, the input of the second conversion unit 26 is connected to the output of the current loop 22, and the output of the second conversion unit 26 is connected to the input of the SVPWM generator 23. In a specific implementation, the control module 2 further includes a negative feedback unit 24, a first conversion unit 25, and a second conversion unit 26. The input of the first conversion unit 25 is connected to the three-phase branch where the filter capacitor Cf is located, the output of the first conversion unit 25 is connected to the input of the negative feedback unit 24, the output of the negative feedback unit 24 is connected to the output of the current loop 22, the input of the second conversion unit 26 is connected to the output of the current loop 22, and the output of the second conversion unit 26 is connected to the input of the SVPWM generator 23. The first conversion unit 25 is used to perform a 3s / 2r transformation on the current, transforming the current signal from a three-phase stationary coordinate system to a two-phase rotating coordinate system. The current signal output by the first conversion unit 25 after transformation is superimposed on the output of the current loop 22 via the negative feedback unit 24. The output of the current loop 22, through the superimposed current signal, serves as the input of the second conversion unit 26. The second conversion unit 26 performs a 2r / 2s transformation, transforming the input signal from a two-phase rotating coordinate system to a two-phase stationary coordinate system, i.e., an inverse Park transform. This results in a signal modulatable by the SVPWM generator 23, which then modulates the switching configuration signal for driving the power switch module 11.

[0039] In one embodiment, in order to further understand the present invention, the following Figures 2 to 5 The filter circuit 3 of the active front end converter of the present invention is described.

[0040] Figure 2 The circuit diagram of the LCCL filter circuit 3 is shown as follows: after adding the split capacitor Cd, the passive capacitor damping method is adopted. The filter capacitor Cf is designed to have the same capacitance as the split capacitor Cd, and the total capacitance of the branch is kept unchanged. The capacitance of the filter capacitor Cf and the split capacitor Cd is designed to be Figure 3 The damping resistor R is designed to be half the capacitance of the traditional LCL filter circuit. Figure 3 The transfer function of the LCCL filter circuit 3 formed by the parallel split capacitor Cd is obtained as follows:

[0041]

[0042] In the above formula, s represents the complex frequency variable. From the perspective of the transfer function, adding the split capacitor Cd adds two poles, which can better suppress high-frequency noise. The original zero point moves to the left, which is beneficial for suppressing the switching frequency and its integer multiple harmonics, ensuring that the filter circuit 3 has better filtering characteristics in the low and medium frequency bands. The resonant frequency of the LCL filter can also be adjusted by splitting the capacitor Cd, as shown in Figure 4 As shown in the frequency characteristics of the conventional LCL filter circuit, the maximum amplitude at the resonant frequency is 70. Figure 5 As shown, the LCCL filter circuit 3 formed by splitting capacitors Cd in parallel has a maximum amplitude of 60°. Its amplitude-frequency characteristic exhibits greater attenuation at high frequencies and a smoother phase-frequency characteristic at the resonant frequency, demonstrating a robust attenuation characteristic. This effectively suppresses the resonant peak inherent in traditional LCL filters at the resonant frequency and mitigates the two -180-degree phase jumps in the phase-frequency characteristic. The LCCL filter circuit 3 formed by splitting capacitors Cd in parallel matches the switching frequency of the AFE system, effectively suppressing switching ripple and improving the stability of the AFE system.

[0043] To sum up, the active front-end converter of the present application forms an LCCL type filter circuit structure by connecting the split capacitor in parallel to the branch of the filter capacitor in the filter circuit. The split capacitor branch filters the harmonics input to the front end of the rectifier circuit, suppresses resonance and reduces losses, thereby improving the efficiency of the converter.

[0044] like Figure 7 As shown, the present invention further provides a resonance suppression method for an active front-end converter, which is applied to the active front-end converter described in the above embodiment, and includes steps: S110-S150.

[0045] S110 , obtaining the current of the three-phase branch where the filter capacitor is located, and performing a 3s / 2r transformation on the current of the three-phase branch where the filter capacitor is located to obtain a current superposition component.

[0046] In the specific implementation, please refer to Figure 1The active front-end converter control logic adopts a dual closed-loop control structure, with the outer loop being the bus voltage loop and the inner loop being the current loop. The voltage loop regulates the output bus voltage of the rectifier circuit, maintaining the bus voltage at a constant set value. The output of the voltage loop serves as the input of the current loop. The control module controls the output of the current loop based on the current in the three-phase branch where the filter capacitor is located. The output of the current loop is converted into a drive signal that can drive the rectifier circuit through space voltage vector modulation, thereby controlling the output of the rectifier circuit. In specific applications, the control module uses a dedicated detection circuit or device (such as a Hall sensor) to detect the current in the three-phase branch where the filter capacitor is located in real time, thereby obtaining the currents iad, ibd, and icd of the three-phase branch where the filter capacitor is located. After obtaining the current in the three-phase branch where the filter capacitor is located, the control module performs a 3s / 2r transformation on the current in the three-phase branch where the filter capacitor is located, usually implemented using the Clark transform algorithm. The 3s / 2r transformation transforms the current in the three-phase branch where the filter capacitor is located from three-phase stationary coordinates to two-phase rotating coordinates, resulting in the current superposition component.

[0047] S120: Superimpose the current superposition component with the current component output by the current loop.

[0048] Further, please refer to Figure 1 After the control module completes the 3s / 2r transformation, it obtains the current superposition component, and superimposes the current superposition component with the current component output by the current loop through the negative feedback link Kc, so that the current component output by the current loop includes the current superposition component related to the three-phase branch current iad, ibd, and icd where the filter capacitor is located.

[0049] Furthermore, the current superposition component includes a first current component and a second current component, and the superposition of the current superposition component with the current component output by the current loop includes: superimposing the first current component and the second current component to the active current component and the reactive current component of the current loop output end respectively through negative feedback.

[0050] Specifically, please refer to Figure 1 After the control module completes the 3s / 2r transformation, the current superposition component obtained includes a first current component id and a second current component iq. The current loop output end has two output components, namely, an active current component ud* and a reactive current component uq*. The control module superimposes the first current component id and the second current component iq on the active current component ud* and the reactive current component uq* output by the current loop through a negative feedback link Kc. That is, the first current component id is superimposed on the active current component ud* output by the current loop, and the second current component iq is superimposed on the reactive current component uq* output by the current loop, thereby obtaining two different current components respectively superimposed with the first current component id and the second current component iq.

[0051] S130 , performing a 2r / 2s transformation on the current component after the current superposition component is superimposed to obtain a modulated voltage component.

[0052] Further, please refer to Figure 1 The control module performs a 2r / 2s transformation on the current component after the superposition of the current superposition component, which is usually implemented by the inverse Park transformation algorithm. The 2r / 2s transformation transforms the current component after the superposition of the current superposition component from the two-phase rotating coordinate system to the two-phase stationary coordinate system to obtain the modulation voltage component u α and u β , modulation voltage component u α and u β Used to modulate the switch configuration signal that can drive the rectifier circuit.

[0053] S140 , performing SVPWM modulation according to the modulation voltage component to obtain a switch configuration signal.

[0054] Further, please refer to Figure 1 The control module obtains two different modulation voltage components u by performing 2r / 2s transformation on the current component after superimposing the current superposition component. α and u β After that, the modulation voltage component u α and u β The SVPWM generator in the module performs SVPWM modulation (Space Vector Pulse Width Modulation) to obtain a switch configuration signal that can drive the rectifier circuit. The switch configuration signal can specifically be a PWM signal.

[0055] S150: Drive the rectifier circuit to operate using the switch configuration signal.

[0056] Furthermore, after the control module modulates the switch configuration signal through SVPWM, it drives the rectifier circuit to operate with the switch configuration signal. The switch configuration signal controls the output DC voltage of the rectifier circuit, and the DC voltage can be output to the DC load or inverter module. At the same time, the bus voltage at the output end of the rectifier circuit is fed back to the voltage loop to complete the control closed loop.

[0057] In practical applications, such as Figure 6 As shown, Figure 6This is a harmonic spectrum analysis of the grid-side input current of the active front-end converter. The figure shows that the total harmonic content (THD) is controlled at approximately 6%, reducing power-frequency current losses in the capacitor branch and improving the filter circuit's attenuation of the switching frequency. The LCCL filter circuit formed by the parallel split capacitors matches the switching frequency of the active front-end converter system, effectively suppressing switching ripple. The switching operation of the power switching devices in the rectifier circuit introduces low harmonic current components of switching orders and their integer multiples. The high-order harmonic content of the input current Ia is low, approaching zero, effectively suppressing the resonant current.

[0058] The method of the present application obtains the current of the three-phase branch where the filter capacitor is located, performs a 3s / 2r transformation on the current of the three-phase branch where the filter capacitor is located to obtain a current superposition component, superimposes the current superposition component with the current component output by the current loop, performs a 2r / 2s transformation on the current component after superimposing the current superposition component to obtain a modulation voltage component, performs SVPWM modulation on the modulation voltage component to obtain a switch configuration signal, and drives the rectifier circuit to operate with the switch configuration signal, thereby achieving effective suppression of resonance, reducing power loss and improving the efficiency of the converter, and improving the frequency response of the filter circuit.

[0059] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. An active front-end converter, characterized in that: include: Rectifier circuit, used to convert AC power from the power grid into DC power output; a control module, connected to the rectifier circuit, and configured to control an output current of the rectifier circuit; The filter circuit includes an inductor unit and a capacitor unit, wherein the capacitor unit includes a filter capacitor and a split capacitor. The inductor unit is connected between the power grid and the input end of the rectifier circuit. One end of the filter capacitor is connected to the inductor unit and the other end is grounded. The split capacitor is connected in parallel to both ends of the filter capacitor.

2. The active front end converter according to claim 1, wherein: The inductor unit includes a grid-side inductor and a rectifier-side inductor, the grid-side inductor and the rectifier-side inductor are connected in series between the grid and the input end of the rectifier circuit in sequence, one end of the filter capacitor is connected between the grid-side inductor and the rectifier-side inductor, and the other end is grounded.

3. The active front end converter according to claim 1, wherein: The filter circuit further includes a resistance unit, the filter capacitor is grounded through the resistance unit, one end of the split capacitor is connected to the end of the filter capacitor connected to the inductor unit, and the other end of the split capacitor is connected to the grounded end of the resistance unit.

4. The active front end converter according to claim 3, wherein: The resistance unit includes at least one damping resistor, one end of the damping resistor is connected to the filter capacitor, and the other end of the damping resistor is grounded.

5. The active front end converter according to claim 1, wherein: The capacitance of the filter capacitor is equal to that of the split capacitor.

6. The active front end converter according to any one of claims 1 to 5, characterized in that: The rectifier circuit includes a power switch module and a bus capacitor. The input end of the power switch module is connected to the inductor unit. The bus capacitor is connected in parallel to the output end bus of the power switch module. The control module is connected to the power switch module.

7. The active front end converter according to claim 6, characterized in that: The control module includes a current loop, a voltage loop and an SVPWM generator. The input end of the voltage loop is connected to the output bus of the power switch module, the output end of the voltage loop is connected to the input end of the current loop, the output end of the current loop is connected to the input end of the SVPWM generator, and the output end of the SVPWM generator is connected to the power switch module.

8. The active front end converter according to claim 7, characterized in that: The control module also includes a negative feedback unit, a first conversion unit and a second conversion unit, the input end of the first conversion unit is connected to the branch where the filter capacitor is located, the output end of the first conversion unit is connected to the input end of the negative feedback unit, the output end of the negative feedback unit is connected to the output end of the current loop, the input end of the second conversion unit is connected to the output end of the current loop, and the output end of the second conversion unit is connected to the input end of the SVPWM generator.

9. A resonance suppression method for an active front-end converter, characterized in that: Applied to the active front-end converter according to any one of claims 1 to 8, the method comprising: Obtaining the current of the three-phase branch where the filter capacitor is located, and performing a 3s / 2r transformation on the current of the three-phase branch where the filter capacitor is located to obtain a current superposition component; Superimposing the current superposition component with the current component output by the current loop; Performing a 2r / 2s transformation on the current component after the current superposition component is superimposed to obtain a modulation voltage component; performing SVPWM modulation according to the modulation voltage component to obtain a switch configuration signal; The rectifier circuit is driven to operate using the switch configuration signal.

10. The method according to claim 9, characterized in that The current superposition component includes a first current component and a second current component, and superimposing the current superposition component with the current component output by the current loop includes: The first current component and the second current component are respectively superimposed on the active current component and the reactive current component at the output end of the current loop through negative feedback.

Images