Three-phase single-stage ac / dc converter control method and converter

Abstract

The application discloses a three-phase single-stage AC / DC converter control method and a converter. The method comprises the following steps: collecting three-phase input currents of a low-frequency rectification circuit and generating three-phase input current reference values of the low-frequency rectification circuit; generating injection current values according to the three-phase input currents; superimposing the three-phase input current reference values and the injection current values to generate three-phase input current updated values; generating switch tube control signals of a high-frequency conversion circuit according to the three-phase input current updated values, and controlling input currents of a three-phase rectification bridge to the three-phase input current updated values. Through optimization of the control algorithm, the peak current of the high-frequency conversion circuit is reduced without increasing the circuit cost and changing the external characteristics of the converter, thereby reducing the current specifications of related devices and improving the reliability of the converter.

Description

Technical Field

[0001] This invention relates to the field of power control technology, and in particular to a control method for a three-phase single-stage AC / DC converter and the converter itself. Background Technology

[0002] With the continuous development of new energy technologies and AI technologies, the demand for high-efficiency three-phase AC / DC converters is also constantly increasing.

[0003] In recent years, a quasi-single-stage architecture based on low-frequency rectification combined with high-frequency conversion has emerged in the power supply industry. Compared with the traditional two-stage AC / DC conversion module, it has significant advantages such as high efficiency, high power density, and low cost, and has received widespread attention and favor in scenarios such as new energy vehicle charging, server power supplies, and artificial intelligence data centers (AIDC).

[0004] When a quasi-single-stage architecture combining low-frequency rectification and high-frequency conversion is applied to high-power applications, the current in both the low-frequency rectification circuit and the high-frequency conversion circuit is relatively high. This necessitates larger current ratings for the switching devices and larger saturation currents for the magnetic components. In high-power scenarios, the high-frequency conversion circuit in a three-phase AC / DC converter generates large currents, requiring switching devices with higher current ratings and magnetic components with larger saturation currents. This leads to a surge in losses, cost, and size for both switching and magnetic components, and also reduces the reliability of the converter.

[0005] In the existing technology, the connection method of AC line voltage to low frequency rectifier circuit is used to replace phase voltage to low frequency rectifier circuit in order to reduce the current of high frequency conversion circuit. However, as the power demand continues to increase, the current specification problem of switching devices and magnetic devices will become apparent. Summary of the Invention

[0006] The purpose of this invention is to propose a control method and converter for a three-phase single-stage AC / DC converter, which aims to solve the technical problems of low loss and low reliability of switching devices and magnetic devices caused by the high peak current of the high-frequency conversion circuit in existing AC / DC converters.

[0007] In a first aspect, the present invention relates to a control method for a three-phase single-stage AC / DC converter, comprising: The three-phase input current of the low-frequency rectifier circuit is collected, and a reference value for the three-phase input current of the low-frequency rectifier circuit is generated. The injection current value is generated based on the three-phase input current; The three-phase input current reference value and the injected current value are superimposed to generate the updated three-phase input current value of the three-phase input current reference value. Based on the updated three-phase input current value, the switching control signal of the high-frequency converter circuit is generated, and the input current of the three-phase rectifier bridge is controlled to the updated three-phase input current value.

[0008] In this embodiment, the generated injected current value is a periodic function: Wherein, the preferred value of the period T is 1 / 3K times the period of the input current, and K is a positive integer. In a current injection embodiment, the step of generating the injection current value according to the operating conditions and control objectives further includes: Injected current value The calculation formula is: in, It is a periodic function, and the preferred value of the period is 1 / 3K times the period of the input current, where K is a positive integer. ~ , , All are constants, where, ~ The absolute value is less than or equal to the peak value of the three-phase input current reference value.

[0009] In one current injection embodiment, the step of generating the injection current value based on the operating conditions and control objectives further includes: Injected current value The calculation formula is: in, It is a periodic function, and the preferred value of the period is 1 / 3K times the period of the input current. It is an infinite positive integer. ~ , , All are constants, where, ~ The absolute value is less than or equal to the peak value of the three-phase input current reference value.

[0010] In another current injection embodiment, the step of generating the injection current value according to the operating conditions and control objectives further includes: Injected current value The calculation formula is: in, It is a periodic function, and the preferred value of the period is 1 / 3K times the period of the input current, where K is a positive integer. ~ , ~ Both are constants, and X and Y are user-defined time intervals.

[0011] In some embodiments, the zero-sequence current based on the current input voltage phase sequence of the low-frequency rectifier circuit is injected into the injected current value, so that the three-phase input currents obtained after superimposing the injected current values ​​have the same shape and a phase difference of 120 degrees.

[0012] In another example of input current update value: Obtain the absolute value of the three-phase input current reference value; Obtain the absolute value of the injected current; The absolute values ​​of the three-phase input current reference values ​​and the absolute values ​​of the injected current values ​​are superimposed to generate the updated three-phase input current values. Based on the updated three-phase input current values, the switching control signals of the high-frequency conversion circuit are generated, and the input current of the three-phase rectifier bridge is controlled to the updated three-phase input current values.

[0013] In one embodiment, the step of acquiring and generating reference values ​​for the three-phase input current of the low-frequency rectifier circuit includes: The input current reference peak is generated based on the voltage outer loop or current loop. The input current reference value is obtained by multiplying the input current reference peak with a sine wave that is in phase with the input current of the low-frequency rectifier circuit; or The active power reference value of the three-phase input current is generated based on the voltage outer loop or current loop, and the input current reference value is obtained through coordinate transformation. The low-frequency rectifier circuit can be a diode bridge rectifier circuit or a low-frequency bridge rectifier circuit.

[0014] In a second aspect, the present invention relates to a three-phase single-stage AC / DC converter, applied to the three-phase single-stage AC / DC converter control method described in the first aspect, including a control module and a low-frequency rectifier circuit and a high-frequency conversion circuit electrically connected to the control module. The control module includes an input current reference value generation module, an injection current generation module, a current superposition module, and a current control module. The input current reference value generation module is used to collect the three-phase input current and generate the three-phase input current reference value for the low-frequency rectifier circuit; The injection current generation module is used to generate injection current values ​​based on the three-phase input current; The current superposition module is used to superimpose the three-phase input current reference value and the injected current value to update the three-phase input current update value that generates the three-phase input current reference value; The current control module is used to generate switching control signals for the high-frequency converter circuit based on the updated three-phase input current value, and to control the input current of the three-phase rectifier bridge of the high-frequency converter circuit to the updated three-phase input current value.

[0015] In some embodiments, the waveform of the three-phase input current updated according to the three-phase input current value is a non-sinusoidal wave; or The three-phase single-stage AC / DC converter also includes a voltage loop control unit; The voltage loop control unit generates an input current reference peak value based on the outer voltage loop or current loop. The input current reference value generation module is used to obtain the input current reference value by multiplying the input current reference peak value by a sine wave that is in phase with the input current of the low-frequency rectifier circuit; or The voltage loop control unit generates active power reference values ​​for the three-phase input current based on the voltage outer loop or the current loop. The input current reference value generation module is used for coordinate transformation to obtain the input current reference value.

[0016] The embodiments of the present invention have the following beneficial effects: This embodiment optimizes the current control algorithm to reduce the peak current of the high-frequency conversion circuit without increasing circuit cost, changing the existing connection method, or altering the external characteristics of the converter. This reduces the current specifications of switching devices, magnetic devices, protection devices, and other components, indirectly lowering the cost and size of the three-phase single-stage AC / DC converter and improving its reliability. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] in: Figure 1 This is a flowchart of a control method for a three-phase single-stage AC / DC converter in one embodiment.

[0019] Figure 2 This is a schematic diagram of a three-phase single-stage AC / DC converter in one embodiment.

[0020] Figure 3 This is a schematic diagram of the architecture of a three-phase single-stage AC / DC converter in one embodiment.

[0021] Figure 4 This is a schematic diagram of the algorithm module of the control module in one embodiment.

[0022] Figure 5 This is a schematic diagram of the architecture of a three-phase single-stage AC / DC converter in another embodiment.

[0023] Figure 6 This is a schematic diagram of the algorithm module of the control module in another embodiment.

[0024] Figure 7 The waveform diagram shows the reference value of the three-phase input current of a low-frequency rectifier circuit in one embodiment.

[0025] Figure 8 The waveform diagram after injecting current to the input current reference value in one embodiment is shown.

[0026] Figure 9 Waveform diagram after injecting current to the input current reference value in another embodiment. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Please refer to Figure 1 The diagram shown is the main flowchart of the three-phase single-stage AC / DC converter control method in this embodiment. This three-phase single-stage AC / DC converter control method is based on... Figure 2 The converter structure shown is implemented. This three-phase single-stage AC / DC converter includes a control module 5, a low-frequency rectifier circuit 1, and a high-frequency conversion circuit 2 electrically connected to the control module 5.

[0029] Please refer to this as well. Figure 2 as well as Figure 3 The low-frequency rectifier circuit 1 includes a low-frequency rectifier circuit 11 for processing the first phase, a low-frequency rectifier circuit 12 for processing the second phase, and a low-frequency rectifier circuit 13 for processing the third phase. The high-frequency converter circuit 2 includes a high-frequency converter circuit 21 for processing the first phase, a high-frequency converter circuit 22 for processing the second phase, and a high-frequency converter circuit 23 for processing the third phase. v a , v b , v c Represents the phase voltage of a three-phase system; i a , i b , i c This indicates the input current for the three phases; v ab , v bc , v ca Represents the line voltage of the three phases; i ab ,i bc , i ca This represents the input current of the three-phase low-frequency rectifier.

[0030] In this embodiment, the low-frequency rectifier circuit 1 can be a diode bridge rectifier circuit or a low-frequency bridge rectifier circuit composed of active switching devices (MOSFET, IGBT, thyristor, etc.).

[0031] The high-frequency conversion circuit 2 includes a three-phase rectifier bridge. The high-frequency conversion circuit 2 can adopt: flyback circuit, Sepic circuit, Boost circuit, Cuk circuit, Zeta circuit, etc.

[0032] like Figure 1 As shown, the control method for this three-phase single-stage AC / DC converter includes: Step S1: Collect the three-phase input current of the low-frequency rectifier circuit and generate the reference value of the three-phase input current of the low-frequency rectifier circuit.

[0033] There are many methods for acquiring and generating reference values ​​for the three-phase input current of a low-frequency rectifier circuit. For example, in some embodiments, these include: The input current reference peak is generated based on the voltage outer loop. The input current reference value is obtained by multiplying the input current reference peak with a sine wave that is in phase with the input current of the low-frequency rectifier circuit; or The active reference value of the three-phase input current is generated based on the voltage outer loop, and the input current reference value is obtained through coordinate transformation.

[0034] In this embodiment, the low-frequency rectifier circuit can be a diode bridge rectifier circuit or a low-frequency bridge rectifier circuit.

[0035] Step S2: Generate the injection current value based on the operating conditions and control objectives. .

[0036] Depend on Figure 3 The connection relationship shows that: If the input current of the three-phase low-frequency rectifier circuit 11-13 is... i ab , i bc , i ca Instead of a three-phase sinusoidal current, a single injection current is injected into the three-phase sinusoidal current. i inj Injecting the same injection current iinj It will not affect the three-phase input current. i a , i b , i c This has an impact. That is, without changing the overall characteristics of the AC / DC converter, different injection currents can be selected. Shape change i a , i b , i c It indicates the shape of the three-phase input current to cope with different operating conditions or achieve different control objectives, such as reducing device current stress, reducing the effective value of device current, reducing the average value of device current, and improving efficiency.

[0037] In this embodiment, the generated injected current value is a periodic function: The preferred value of the period T is 1 / 3K times the period of the input current, where K is a positive integer.

[0038] In one current injection embodiment, the step of generating the injection current value based on the operating conditions and control objectives further includes: As expression one, the injected current value The calculation formula is: in, It is a periodic function, and the preferred value of the period is 1 / 3K times the period of the input current, where K is a positive integer. ~ , , All are constants and can be specifically designed according to the current working conditions and application objectives.

[0039] The value is 3N* , Fundamental angular frequency. =2π Where N is an integer, The fundamental frequency of the grid voltage.

[0040] ~ of .

[0041] For example in one ~ of The example is as follows: .

[0042] The value is 3N* , Fundamental angular frequency. =2π Where N is an integer, The fundamental frequency of the grid voltage.

[0043] Alternatively, as expression two, the injected current value The calculation formula is: in It is a periodic function, and the preferred value of the period is 1 / 3K times the period of the input current. , It is an infinite positive integer. ~ , , All are constants and have values ​​similar to those in Expression 1, allowing for specific design based on current operating conditions and application objectives. Among them, ~ The absolute value is less than or equal to the peak value of the three-phase input current reference value.

[0044] In another current injection embodiment, the step of generating the injection current value according to the operating conditions and control objectives further includes: Injected current value The calculation formula is: in, It is a periodic function, and the preferred value of the period is 1 / 3K times the period of the input current, where K is a positive integer. ~ , ~ Both are constants, and X and Y are user-defined time intervals. Specific designs can be implemented based on current operating conditions and application objectives.

[0045] In some embodiments, the zero-sequence current based on the current input voltage phase sequence of the low-frequency rectifier circuit is injected into the injected current value, so that the three-phase input currents obtained after superimposing the injected current values ​​have the same shape and a phase difference of 120 degrees.

[0046] The preferred method is to inject a zero-sequence current based on the current input voltage phase sequence, which can improve the reference current obtained after current reference superposition processing. i ab_ref_new , i bc_ref_new , i ca_ref_newThey have the same shape but are 120° out of phase. Understandably, the injected current may not be zero-sequence current.

[0047] Step S3: Superimpose the three-phase input current reference value and the injected current value to generate the three-phase input current update value; The current superposition module 53 is used to superimpose the initial input current reference value of the three-phase low-frequency rectifier circuit. i ab_ref , i bc_ref , i ca_ref and injection current value i inj The values ​​are superimposed to generate new updated three-phase input current values ​​for the three-phase low-frequency rectifier circuit. i ab_ref_new , i bc_ref_new , i ca_ref_new The formula is: Step S4: The control module 5 generates the switching control signal of the high-frequency conversion circuit based on the updated value of the three-phase input current, and controls the input current of the three-phase rectifier bridge of the high-frequency conversion circuit 2 to the updated value of the three-phase input current. In this embodiment, the instantaneous sum of the updated three-phase input current values ​​is three times the injected current value, in order to reduce the peak current of the high-frequency conversion circuit. .

[0048] At this time, the updated three-phase input current value and the input current reference value of the three-phase low-frequency rectifier circuit have the following characteristics: Please refer to Figure 5 as well as Figure 6 In another embodiment of the input current update value, Obtain the absolute value of the three-phase input current reference value; Obtain the absolute value of the injected current; The absolute values ​​of the three-phase input current reference values ​​and the absolute values ​​of the injected current values ​​are superimposed to generate the updated three-phase input current values. Based on the updated three-phase input current values, the switching control signals of the high-frequency conversion circuit are generated, and the input current of the three-phase rectifier bridge of the high-frequency conversion circuit 201-203 is controlled to the updated three-phase input current values.

[0049] It can be seen that the output current of the three-phase low-frequency rectifier circuit 101-103 is |i ab |、| i bc |、| i ca | is the three-phase input current of the low-frequency rectifier circuit. i ab , i bc , i ca Take the absolute value. In the three-phase input current | i ab |、| i bc |、| i ca Based on |, inject the injection current value i inj absolute value | i inj The same effect can also be achieved, including reducing the peak current of the high-frequency conversion circuit, thereby reducing the current specifications of switching devices, magnetic devices, protection devices, etc., and improving the reliability of the three-phase single-stage AC / DC converter.

[0050] The following examples illustrate the feasibility and advantages of reducing the peak current of high-frequency conversion circuits.

[0051] Example 1: The three-phase input current reference value is set as follows: In Example 1, the waveform diagram of the three-phase input current reference value is referenced. Figure 7 .

[0052] Example 1: Injection Current Case 1 Let the injected current value i inj The expression is: Figure 8 Reference value for the three-phase input current of the new three-phase low-frequency rectifier circuit i ab_ref_new , i bc_ref_new , i ca_ref_new The waveform diagram.

[0053] As can be seen, the peak current has decreased by more than 13% compared to before the injection, which can effectively reduce the current stress on the switching devices and magnetic devices of the converter.

[0054] Example 1 Injection Current Case 2: Let the injected current value i inj The expression is: Where M is an integer. Figure 9 For the new input current reference value of the three-phase low-frequency rectifier i ab_ref_new , i bc_ref_new , i ca_ref_new The waveform.

[0055] It can be seen that the peak current has decreased by more than 5% compared to before the injection, which can effectively reduce the current stress of the converter switching devices and the current stress of the magnetic devices.

[0056] Please refer to Figures 2 to 6 The three-phase single-stage AC / DC converter in this embodiment includes a control module 5, a low-frequency rectifier circuit 1, and a high-frequency conversion circuit 2 electrically connected to the control module.

[0057] As shown in the figure, the control module 5 includes algorithm software processing modules 51-53.

[0058] Specifically, the control module 5 includes an input current reference value generation module 51, an injection current generation module 52, a current superposition module 53, and a current control module 50.

[0059] The input current reference value generation module 51 is used to collect the three-phase input current of the low-frequency rectifier circuit and generate the three-phase input current reference value of the low-frequency rectifier circuit. The injection current generation module 52 is used to generate injection current values ​​based on the collected three-phase input currents; The current superposition module 53 is used to superimpose the three-phase input current reference value and the injected current value to update and generate the three-phase input current update value; The current control module 50 is used to generate switching control signals for the high-frequency conversion circuit based on the updated value of the three-phase input current, and to control the input current of the three-phase rectifier bridge of the high-frequency conversion circuit 2 to the updated value of the three-phase input current. The instantaneous sum of the three-phase input current update values ​​is three times the injected current value to reduce the peak current of the high-frequency conversion circuit.

[0060] In some embodiments, the waveform of the three-phase input current updated according to the three-phase input current is a non-sinusoidal wave.

[0061] In some embodiments, the three-phase single-stage AC / DC converter further includes a voltage loop control unit; The voltage loop control unit generates an input current reference peak value based on the outer voltage loop. The input current reference value generation module 51 is used to obtain the input current reference value by multiplying the input current reference peak value by a sine wave that is in phase with the input current of the low-frequency rectifier circuit; or The voltage loop control unit generates active reference values ​​for the three-phase input current based on the outer voltage loop or the current loop. The input current reference value generation module 51 is used for coordinate transformation to obtain the input current reference values.

[0062] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A control method for a three-phase single-stage AC / DC converter, characterized in that, include: The three-phase input current of the low-frequency rectifier circuit is collected, and a reference value for the three-phase input current of the low-frequency rectifier circuit is generated. Based on the three-phase input current, the injection current value is generated; The three-phase input current reference value and the injected current value are superimposed to generate the three-phase input current update value of the three-phase input current reference value; Based on the updated three-phase input current values, control signals for the switching transistors of the high-frequency converter circuit are generated, and the input current of the three-phase rectifier bridge is controlled to the updated three-phase input current values.

2. The control method for a three-phase single-stage AC / DC converter according to claim 1, characterized in that, The generated injected current value is a periodic function: The preferred value of the period T is 1 / 3K times the period of the input current, where K is a positive integer.

3. The control method for a three-phase single-stage AC / DC converter according to claim 2, characterized in that, Depending on the operating conditions and control objectives, the step of generating the injected current value further includes: The injected current value The calculation formula is: in, K is a positive integer. ~ , , All are constants. ~ The absolute value is less than or equal to the peak value of the three-phase input current reference value.

4. The control method for a three-phase single-stage AC / DC converter according to claim 2, characterized in that, Depending on the operating conditions and control objectives, the step of generating the injected current value further includes: The injected current value The calculation formula is: in, It is a periodic function, and the preferred value of the period is 1 / 3K times the period of the input current. It is an infinite positive integer. ~ , , All are constants. ~ The absolute value is less than or equal to the peak value of the three-phase input current reference value.

5. The control method for a three-phase single-stage AC / DC converter according to claim 1, characterized in that, The step of generating the injection current value based on the operating conditions and control objectives further includes: The injected current value The calculation formula is: in, It is a periodic function, and the preferred value of the period is 1 / 3K times the period of the input current, where K is a positive integer. ~ , ~ Both are constants, and X and Y are user-defined time intervals.

6. The control method for a three-phase single-stage AC / DC converter according to claim 1, characterized in that, The zero-sequence current is injected based on the current input voltage phase sequence of the low-frequency rectifier circuit, so that the three-phase input currents obtained after superimposing the injected current values ​​have the same shape and a phase difference of 120 degrees.

7. The control method for a three-phase single-stage AC / DC converter according to claim 1, characterized in that, Obtain the absolute value of the three-phase input current reference value; Obtain the absolute value of the injected current; The absolute values ​​of the three-phase input current reference values ​​are superimposed with the absolute values ​​of the injected current values ​​to generate the updated three-phase input current values. Based on the updated three-phase input current values, the switching control signals of the high-frequency conversion circuit are generated.

8. The control method for a three-phase single-stage AC / DC converter according to claim 1, characterized in that, The steps for acquiring and generating the three-phase input current reference values ​​for the low-frequency rectifier circuit include: The input current reference peak is generated based on the voltage outer loop or current loop. The input current reference value is obtained by multiplying the input current reference peak with a sine wave in phase with the input current of the low-frequency rectifier circuit; or The active power reference value of the three-phase input current is generated based on the voltage outer loop or current loop, and the input current reference value is obtained through coordinate transformation. The low-frequency rectifier circuit can be a diode bridge rectifier circuit or a low-frequency bridge rectifier circuit.

9. A three-phase single-stage AC / DC converter, characterized in that, The control method for a three-phase single-stage AC / DC converter according to any one of claims 1-8 includes a control module and a low-frequency rectifier circuit and a high-frequency conversion circuit electrically connected to the control module. The control module includes an input current reference value generation module, an injection current generation module, a current superposition module, and a current control module. The input current reference value generation module is used to collect the three-phase input current and generate the three-phase input current reference value of the low-frequency rectifier circuit. The injection current generation module is used to generate injection current values ​​based on the three-phase input current; The current superposition module is used to superimpose the three-phase input current reference value and the injected current value to update and generate the three-phase input current update value. The current control module is used to generate switching control signals for the high-frequency conversion circuit based on the updated three-phase input current value, and to control the input current of the three-phase rectifier bridge to the updated three-phase input current value.

10. The three-phase single-stage AC / DC converter according to claim 9, characterized in that, The three-phase input current waveform based on the updated three-phase input current value is a non-sinusoidal wave; or The three-phase single-stage AC / DC converter also includes a voltage loop control unit; The voltage loop control unit generates an input current reference peak value based on the voltage outer loop, and the input current reference value generation module is used to obtain the input current reference value by multiplying the input current reference peak value with a sine wave that is in phase with the input current of the low-frequency rectifier circuit. or The voltage loop control unit generates active reference values ​​for the three-phase input current based on the outer voltage loop, and the input current reference value generation module is used for coordinate transformation to obtain the input current reference values.

Images