Three-phase rectifier control method and system considering abnormal operation mode

Abstract

The invention discloses a three-phase rectifier control method and system considering an abnormal operation mode, and belongs to the technical field of rectifier control. Comprising the following steps: acquiring a direct-current side current value and a direct-current side voltage value of a rectifier, and comparing the direct-current side current value and the direct-current side voltage value with a preset light-load load current critical value and a direct-current side voltage reference value; if the direct current side current value is smaller than the light load current critical value and the direct current side voltage value is larger than the direct current side voltage reference value, an abnormal operation control strategy is executed; otherwise, executing a normal mode control strategy; according to the abnormal operation strategy, a voltage reference value is adjusted through proportional control and direct current side voltage feedforward control, so that the three-phase duty ratio of the rectifier is adjusted, and the working mode of the rectifier is determined. The dynamic response speed of rectifier control can be improved, the direct current side voltage ripples are effectively suppressed, and the problems that light load and no load states are not considered in existing rectifier control, the control process is complex, and voltage overshoot exists in the switching process are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of rectifier control, and in particular to a three-phase rectifier control method and system considering an abnormal operating mode. Background Art

[0002] The statements in this section merely mention background art related to the present invention and do not necessarily constitute prior art.

[0003] In Vienna rectifiers, DC-side output voltage stability and AC-side current quality are two key performance indicators, with their priority depending on the specific application scenario and system requirements. Vienna rectifiers are typically backed by a DC / DC converter or directly connected to a DC load, so DC-side output voltage stability is crucial. This is especially true for electric vehicle chargers, which require CV charging, where voltage fluctuations can reduce system performance and reliability. High AC-side current quality can reduce grid harmonics and improve power system stability. Therefore, for high-power industrial applications, power quality should be prioritized to minimize harmonic impacts. For light-load applications and those requiring high reliability, DC-side voltage stability across the full load range is paramount.

[0004] However, it is worth noting that the Vienna rectifier is a unidirectional energy transmission converter. When it operates under no-load or light-load conditions, the energy on the DC side has nowhere to be transferred, which can easily lead to overvoltage or uncontrollable DC side, which will affect the stability and safety of the system. The main reasons for the difficulty in voltage control under light load are as follows:

[0005] (1) At light loads, the output power is low, and the low duty cycle results in reduced control accuracy, making it difficult to achieve stable voltage control. (2) The rectifier enters discontinuous conduction mode (DCM), causing the inductor current to lose control, making control more difficult. (3) The loss ratio increases, which can easily lead to voltage fluctuations. (4) The inductor value and switching frequency affect light load performance.

[0006] When the inductance value is small or the switching frequency is low, the inductor current is more likely to decay to zero. Therefore, appropriate measures should be taken to suppress output voltage fluctuations and avoid system overvoltage protection.

[0007] Current research on Vienna rectifiers has mostly focused on harmonic current suppression and control strategy improvements, with limited coverage of voltage control methods under light-load conditions. To improve the no-load performance of Vienna rectifiers, some researchers have proposed an intermittent control method based on output voltage hysteresis. This method uses hysteresis control to determine whether to trigger the driver, thereby limiting the output voltage to within the hysteresis range. However, whether hysteresis control is applied to the DC voltage or the voltage loop output, the DC voltage contains significant ripple. The introduction of a hysteresis comparator makes the voltage loop controller parameters sensitive, resulting in poor system robustness.

[0008] Another approach is to employ an accurate analytical feedforward control solution based on the DCM duty cycle under light load conditions. This approach does not require current measurement or a practical feedback control loop, as the duty cycle feedforward calculation is based on the actual current reference amplitude. However, the duty cycle calculation formula is complex, making it difficult to implement digital control. Furthermore, when switching to light load, the DC link voltage experiences significant overshoot. Summary of the Invention

[0009] In order to address the deficiencies of the prior art, the present invention provides a three-phase rectifier control method, system, electronic device, computer-readable storage medium, and computer program product that take into account abnormal operating modes. The rectifier is controlled under light load and no-load conditions based on the modulation index, which simplifies the control process and improves the dynamic response speed of the rectifier control.

[0010] In a first aspect, the present invention provides a three-phase rectifier control method taking into account an abnormal operating mode;

[0011] A three-phase rectifier control method considering an abnormal operating mode, comprising:

[0012] Obtaining the DC side current value and DC side voltage value of the rectifier, and comparing them with the preset light load current critical value and DC side voltage reference value;

[0013] If the DC side current value is less than the light load current critical value and the DC side voltage value is greater than the DC side voltage reference value, the abnormal operation control strategy is executed; otherwise, the normal mode control strategy is executed;

[0014] The abnormal operation strategy adopts proportional control and DC side voltage feedforward control to adjust the voltage reference value, so as to adjust the three-phase duty cycle of the rectifier and determine the working mode of the rectifier.

[0015] In some embodiments, the amplitude of the voltage reference value is adjusted by using proportional control and DC side voltage feedforward control as follows: the DC side voltage reference value and the DC side voltage value are processed by a proportional controller, and its output is added to the DC side voltage value to obtain a d-axis voltage reference value.

[0016] In some embodiments, adjusting the three-phase duty cycle of the rectifier according to the voltage reference value to determine the operating mode of the rectifier specifically includes:

[0017] The d-axis voltage reference value is used as the three-phase voltage reference value of the rectifier, and combined with the DC side voltage value, the modulation index of the rectifier is determined;

[0018] Determine the duty cycle of each phase switch according to the modulation index of the rectifier;

[0019] The operating mode of each phase switch is determined according to the modulation index and the duty cycle of each phase switch.

[0020] In some implementations, the duty cycle of each phase switch is expressed as:

[0021]

[0022] Where, d x Indicates the duty cycle of each phase switch, u x_ref Indicates the voltage reference value of each phase, u d_ref Indicates the d-axis voltage reference value, ω tx Indicates the phase of each phase switch.

[0023] In some embodiments, determining the operating mode of the three-phase switch according to the modulation index and the duty cycle of each phase switch specifically includes:

[0024] When the modulation index is less than 1 and the duty cycle of each phase switch is greater than 0, each phase switch operates in PWM mode;

[0025] When the modulation index is greater than 1 and the duty cycle is 0 at the peak of the three-phase voltage, the switches of each phase are in the off state;

[0026] When the duty cycle is greater than 0 at the zero-crossing point of each phase voltage, each phase switch operates in PWM mode.

[0027] In some embodiments, the abnormal operating state of the rectifier includes light load and no load.

[0028] In a second aspect, the present invention provides a three-phase rectifier control system taking into account an abnormal operating mode;

[0029] A three-phase rectifier control system considering an abnormal operating mode includes:

[0030] The state detection module is configured to: obtain a DC side current value and a DC side voltage value of the rectifier, and compare them with a preset light load current critical value and a DC side voltage reference value;

[0031] The control module is configured to: if the DC side current value is less than the light load current critical value and the DC side voltage value is greater than the DC side voltage reference value, execute the abnormal operation control strategy; otherwise, execute the normal mode control strategy;

[0032] The abnormal operation strategy adopts proportional control and DC side voltage feedforward control to adjust the voltage reference value, so as to adjust the three-phase duty cycle of the rectifier and determine the working mode of the rectifier.

[0033] In a third aspect, the present invention provides an electronic device;

[0034] An electronic device includes a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the above-mentioned three-phase rectifier control method considering abnormal operating modes.

[0035] In a fourth aspect, the present invention provides a computer-readable storage medium;

[0036] A computer-readable storage medium stores a computer program / instruction thereon, which, when executed by a processor, implements the steps of the above-mentioned three-phase rectifier control method considering an abnormal operating mode.

[0037] In a fifth aspect, the present invention provides a computer program product;

[0038] A computer program product includes a computer program / instruction, which, when executed by a processor, implements the steps of the above-mentioned three-phase rectifier control method considering an abnormal operating mode.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1. The technical solution provided by the present invention judges the normal operating mode and the light load and no-load operating modes (abnormal operating modes), and then adopts different control strategies to control the three-phase rectifier, thereby being applicable to different working states of the three-phase rectifier and improving the adaptability of the control method.

[0041] 2. The technical solution provided by the present invention addresses the problem of uncontrollable voltage of the Vienna rectifier under light load, and proposes a direct modulation index control method that is simple to implement and highly stable. It is applicable to both light load and no-load conditions; it can effectively suppress DC side voltage ripple and provide excellent dynamic response speed.

[0042] 3. The technical solution provided by the present invention can reduce the energy transfer path and simplify the operating principle and control strategy of the rectifier under light load; and when the strategy switches between no-load and normal states, the system can always remain stable and has good robustness and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0044] Figure 1 A schematic diagram of a typical circuit topology of a Vienna rectifier provided in an embodiment of the present invention;

[0045] Figure 2 A control block diagram of a Vienna rectifier in a synchronously rotating coordinate system provided by an embodiment of the present invention;

[0046] Figure 3 Example diagrams of the duty cycle and drive signal of a Vienna rectifier provided in an embodiment of the present invention, wherein (a) is an example diagram of the duty cycle and drive signal of a Vienna rectifier when the modulation index is less than 1, and (b) is an example diagram of the duty cycle and drive signal of a Vienna rectifier when the modulation index is greater than 1;

[0047] Figure 4 An example diagram of three-phase duty cycle and switch state when the modulation index is greater than 2 provided by an embodiment of the present invention;

[0048] Figure 5 A control block diagram of the Vienna rectifier under light load and no load provided by an embodiment of the present invention;

[0049] Figure 6 A schematic flow chart of a three-phase rectifier control method considering an abnormal operating mode provided by an embodiment of the present invention;

[0050] Figure 7 Schematic diagrams of the operating ranges and switch state distributions of the Vienna rectifier provided by an embodiment of the present invention. (a) shows the six operating ranges and switch state distributions of the Vienna rectifier under normal conditions, and (b) shows the six operating ranges and switch state distributions of the Vienna rectifier using the proposed strategy under light load conditions.

[0051] Figure 8 Different switch states provided by the embodiment of the present invention taking interval 2 as an example [S a S b S c ] working mode and current loop example diagram; where (a) is the light load state [S a S b S c ]=

[000] working mode and current loop example diagram, (b) is the light load state [S a Sb S c ]=

[001] working mode and current loop example diagram, (c) is the light load state [S a S b S c ]=

[010] working mode and current loop example diagram, (d) is [S a S b S c ]=

[011] working mode and current loop example diagram, (e) is [S a S b S c ]=

[100] working mode and current loop example diagram, (f) is [S a S b S c ]=

[101] working mode and current loop example diagram, (g) is [S a S b S c ]=

[110] working mode and current loop example diagram, (h) is [S a S b S c ]=

[111] working mode and current loop example diagram;

[0052] Figure 9 This is an example diagram of the simulation waveform of the Vienna rectifier under full load provided by an embodiment of the present invention;

[0053] Figure 10 This is an example diagram of the simulation waveform of the Vienna rectifier in the no-load state provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0054] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0055] In the absence of conflict, the embodiments of the present invention and the features thereof may be combined with each other.

[0056] Example 1

[0057] Existing improvements to Vienna rectifier control methods focus on harmonic current suppression and control strategy improvements. These complex processes result in poor real-time control and robustness, and fail to account for the diverse operating states of the Vienna rectifier. This leads to significant DC-side voltage overshoot during state switching. Therefore, the present invention provides a three-phase rectifier control method that considers abnormal operating modes. This method utilizes proportional control and voltage feedforward control, and controls the rectifier under light and no-load conditions based on the modulation index.

[0058] Next, combine Figures 1-10 , a three-phase rectifier control method considering an abnormal operating mode disclosed in this embodiment is described in detail. The three-phase rectifier control method considering an abnormal operating mode includes the following steps:

[0059] S1. Obtain the DC side current and DC side voltage of the Vienna rectifier and compare them with the preset light load current threshold and DC side voltage reference. If the DC side current is less than the light load current threshold and the DC side voltage is greater than the DC side voltage reference, execute S2. Otherwise, execute S3.

[0060] Under light load conditions, the DC side current value of the Vienna rectifier is i dc The energy stored in the DC side cannot be consumed in time, resulting in the DC side voltage value u dc Increase, if using Figure 2 The normal operating mode control strategy shown in the figure is as follows: d_ref The voltage will continue to increase slowly to further reduce the on-time of the switch tube, which will eventually lead to overvoltage on the DC side. Therefore, in this embodiment, two control strategies are designed. In practical applications, the Vienna rectifier is controlled in combination with its operating state.

[0061] Specifically, the criteria for judging the light load state are: i dc light Andu dc >u dc_ref , where i light It is the critical value of load current at light load.

[0062] S2. Use proportional control and DC side voltage feedforward control to adjust the voltage reference value. According to the voltage reference value, adjust the three-phase duty cycle of the Vienna rectifier and determine the operating mode of the three-phase switch in the Vienna rectifier.

[0063] Combine Figure 5 ​Under light-load and no-load conditions, the Vienna rectifier is controlled using proportional control (P control) and DC-side voltage feedforward control. Under light-load and no-load conditions, the DC-side voltage of the Vienna rectifier changes relatively slowly, allowing for a small steady-state error that does not significantly impact system performance. Therefore, a P controller monitors the DC-side voltage in real time, amplifies the error between it and the reference value, and then applies it to the control signal, achieving a fast response.

[0064] While proportional-integral control (PI control) applied during normal operating mode can eliminate steady-state errors, it can introduce unwanted delays and overshoot during light-load and no-load control. The integral term accumulates errors, potentially causing system overreaction and resulting in voltage fluctuations and oscillations. Furthermore, P controllers are simpler and easier to implement than PI controllers.

[0065] Because when u d_ref >u dc To ensure that at any time only one phase switch is turned on, the DC side voltage feedforward control is introduced in this embodiment and added to the output of the P controller as the updated u d_ref This can further speed up the response and make corrections immediately if a load drop occurs.

[0066] As an implementation method, S2 specifically includes:

[0067] S201 , processing the DC side voltage reference value and the DC side voltage value through a proportional controller, and adding the output thereof to the DC side voltage value to obtain a d-axis voltage reference value.

[0068] For example, the output of the proportional controller is expressed as:

[0069] u p =kp*(u dc_ref -u dc );

[0070] Where kp represents the parameter of the proportional controller.

[0071] The d-axis voltage reference value is expressed as:

[0072] u d_ref =u p +u dc .

[0073] S202. Use the d-axis voltage reference value as the three-phase voltage reference value of the rectifier and combine it with the DC side voltage value to determine the modulation index of the rectifier; and determine the duty cycle of each phase switch based on the modulation index of the rectifier. The modulation index and the duty cycle of each phase switch are expressed as follows:

[0074]

[0075] Where M represents the modulation parameter, d x Indicates the duty cycle of each phase switch, u x_ref Indicates the voltage reference value of each phase, u d_ref Indicates the d-axis voltage reference value, ω tx Indicates the phase of each phase switch.

[0076] S203 : Determine the operating mode of each phase switch according to the modulation index and the duty cycle of each phase switch.

[0077] Specifically, when the modulation index is less than 1 and the duty cycle of each phase switch is greater than 0, each phase switch operates in PWM mode; when the modulation index is greater than 1 and the duty cycle is 0 at the peak of the three-phase voltage, each phase switch is in the off state; when the duty cycle is greater than 0 at the zero crossing point of each phase voltage, each phase switch operates in PWM mode.

[0078] Taking phase a as an example, under normal conditions, the duty cycle and drive signal of the Vienna rectifier are as follows: Figure 3 (a). At this time, M<1, d a >0,S a In one line cycle, it always works in PWM mode. If u is increased d_ref , the duty cycle increases accordingly. When M>1, at u a Near the peak of d a =0, S a In the off state. At this time, the duty cycle and drive signal are as follows Figure 3 (b) is shown. Only when u a Near the zero crossing point of Figure 3 (b) The shaded area, d a >0,S a Works in PWM mode.

[0079] As long as a switch device is turned on, the rectifier will transfer energy to the DC side. Under light load, in this embodiment, the duty cycle is changed by directly controlling the modulation index. According to the trigonometric function relationship and the modulation index calculation formula, when u d_ref ≥u dc When M≥2, the conduction time of the three-phase switches does not overlap, such as Figure 4 As shown in Figure 2. In this case, at any given moment, only one phase's switches are in PWM mode, while the other two phases are off. Consequently, energy is transferred to the DC side via only one phase at any given time, significantly reducing the amount of energy drawn from the AC side. In the no-load condition, all switches are off most of the time. When any phase's switches are on, the three-phase system does not form a current loop and transfers no energy to the DC side.

[0080] S3. Use proportional-integral control to process the DC side current value and the current reference value of the Vienna rectifier to obtain a three-phase voltage reference value, and determine the operating mode of the Vienna rectifier according to the three-phase voltage reference value.

[0081] Combine Figure 2 Specifically, the normal mode control strategy includes a voltage outer loop and a current inner loop. The voltage outer loop is used to control u dc Stable, will u dc Input the first PI controller and use its output as the reference value i of the current loop d axis d_ref and with i d After subtraction, input into the second PI controller to get u d_ref .

[0082] The current inner loop controls the amplitude and phase of the input current, and the q-axis current reference value i q_ref The PI controller of this branch is set to 0, and the output u q_ref Thus, power factor correction is achieved. The output of the current loop u d_ref and u q_ref , after dq / abc conversion, it is used as the three-phase voltage reference value ux_ref (x=a, b, c) to generate the modulation signal.

[0083] For example, the PI controller is expressed as:

[0084]

[0085] Where u(t) represents the control quantity generated by the control system, K P represents the control gain, e(t) represents the control error, T I represents the integration time constant, and t represents the integration interval.

[0086] Example 2

[0087] This embodiment discloses a three-phase rectifier control system taking into account an abnormal operating mode, including:

[0088] The state detection module is configured to: obtain a DC side current value and a DC side voltage value of the rectifier, and compare them with a preset light load current critical value and a DC side voltage reference value;

[0089] The control module is configured to: if the DC side current value is less than the light load current critical value and the DC side voltage value is greater than the DC side voltage reference value, execute the abnormal operation control strategy; otherwise, execute the normal mode control strategy;

[0090] The abnormal operation strategy adopts proportional control and DC side voltage feedforward control to adjust the voltage reference value, so as to adjust the three-phase duty cycle of the rectifier and determine the working mode of the rectifier.

[0091] It should be noted that the aforementioned status detection module and control module correspond to the steps in Example 1. The examples and application scenarios implemented by the aforementioned modules and the corresponding steps are the same, but are not limited to the contents disclosed in Example 1. It should be noted that the aforementioned modules, as part of a system, can be executed in a computer system, such as a set of computer-executable instructions.

[0092] Example 3

[0093] Embodiment 3 of the present invention provides an electronic device, including a memory and a processor, and computer instructions stored in the memory and running on the processor. When the computer instructions are run by the processor, the steps of the above-mentioned three-phase rectifier control method considering the abnormal normal operating mode are completed.

[0094] Example 4

[0095] A fourth embodiment of the present invention provides a computer-readable storage medium for storing computer instructions. When the computer instructions are executed by a processor, the steps of the above-mentioned three-phase rectifier control method considering an abnormal operating mode are completed.

[0096] Example 5

[0097] A fifth embodiment of the present invention provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the steps of the above-mentioned three-phase rectifier control method considering an abnormal operating mode.

[0098] The descriptions of the various embodiments in the above embodiments have different focuses. For parts not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0099] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A three-phase rectifier control method considering an abnormal operating mode, characterized in that: include: Obtaining a DC side current value and a DC side voltage value of the rectifier, and comparing them with a preset light load current critical value and a DC side voltage reference value; If the DC side current value is less than the light load current critical value and the DC side voltage value is greater than the DC side voltage reference value, executing an abnormal operation control strategy; Otherwise, the normal mode control strategy is executed; The abnormal operation strategy adopts proportional control and DC side voltage feedforward control to adjust the voltage reference value, so as to adjust the three-phase duty cycle of the rectifier and determine the working mode of the rectifier.

2. The three-phase rectifier control method considering abnormal operating mode according to claim 1, characterized in that: The method of adjusting the amplitude of the voltage reference value by using proportional control and DC side voltage feedforward control is as follows: the DC side voltage reference value and the DC side voltage value are processed by a proportional controller, and its output is added to the DC side voltage value to obtain a d-axis voltage reference value.

3. The three-phase rectifier control method considering abnormal operating mode according to claim 1, characterized in that: According to the voltage reference value, the three-phase duty cycle of the rectifier is adjusted to determine the working mode of the rectifier, which specifically includes: The d-axis voltage reference value is used as the three-phase voltage reference value of the rectifier, and combined with the DC side voltage value, the modulation index of the rectifier is determined; According to the modulation index of the rectifier, the duty cycle of each phase switch is determined; The working mode of each phase switch is determined according to the modulation index and the duty cycle of each phase switch.

4. The three-phase rectifier control method considering abnormal operation mode as claimed in claim 3, characterized in that: The duty cycle of each phase switch is expressed as: Where, d x Indicates the duty cycle of each phase switch, u x_ref Indicates the voltage reference value of each phase, u d_ref represents the d-axis voltage reference value, ω tx Indicates the phase of each phase switch.

5. The three-phase rectifier control method considering abnormal operation mode as claimed in claim 3, characterized in that: Determining the working mode of the three-phase switch according to the modulation index and the duty cycle of each phase switch specifically includes: When the modulation index is less than 1 and the duty cycle of each phase switch is greater than 0, each phase switch operates in PWM mode; When the modulation index is greater than 1 and the duty cycle is 0 at the peak of the three-phase voltage, the switches of each phase are in the off state; When the duty cycle is greater than 0 at the zero-crossing point of each phase voltage, each phase switch operates in PWM mode.

6. The three-phase rectifier control method considering abnormal operation mode as claimed in claim 1, characterized in that: Abnormal operating conditions of the rectifier include light load and no load.

7. A three-phase rectifier control system considering an abnormal operating mode, characterized in that: include: The state detection module is configured to: obtain a DC side current value and a DC side voltage value of the rectifier, and compare them with a preset light load current critical value and a DC side voltage reference value; A control module is configured to: if the DC side current value is less than the light load current critical value and the DC side voltage value is greater than the DC side voltage reference value, execute an abnormal operation control strategy; Otherwise, the normal mode control strategy is executed; The abnormal operation strategy adopts proportional control and DC side voltage feedforward control to adjust the voltage reference value, so as to adjust the three-phase duty cycle of the rectifier and determine the working mode of the rectifier.

8. An electronic device comprising a memory, a processor and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the steps of the three-phase rectifier control method considering the abnormal operating mode according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program / instruction stored thereon, characterized in that: When the computer program / instruction is executed by a processor, the steps of the three-phase rectifier control method considering an abnormal normal operation mode as described in any one of claims 1-6 are implemented.

10. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instruction is executed by a processor, the steps of the three-phase rectifier control method considering an abnormal normal operation mode as described in any one of claims 1-6 are implemented.

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