A method for controlling the maximum output power of a rectifier under three-phase imbalance

Abstract

The present invention relates to a method for controlling the maximum power output of a rectifier under three-phase imbalance, comprising: determining the total active power of the three-phase input in a three-phase working mode; determining the maximum power of the two-phase input in a two-phase working mode; comparing the total active power of the three-phase input with the maximum power of the two-phase input; and switching the three-phase mode to the two-phase mode when the total active power of the three-phase input is less than the maximum power of the two-phase input. The present invention intelligently switches between the three-phase mode and the two-phase mode according to the current imbalance of the grid voltage, so that the rectifier operates at the maximum output power point. The final effect is: under the condition of grid imbalance, the rectifier circuit system always maintains a high DC power supply output through real-time switching, which greatly improves the utilization rate of the grid voltage and improves the reliability of the rectifier equipment and the power-consuming equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of rectifier circuit control, and in particular to a method for controlling the maximum power output of a rectifier under three-phase imbalance. Background Art

[0002] In weak grid conditions, the grid voltage is prone to abnormal conditions such as three-phase imbalance and phase deviation. This can lead to increased grid harmonics and reactive power, resulting in current distortion and increased output DC voltage ripple. Therefore, to ensure device reliability, rectifiers typically limit output power to mitigate the impact of three-phase imbalance.

[0003] In actual operation, if the three-phase imbalance of the power grid is too great, the allowable output power will be close to 0. In this case, if two of the phases are used for operation, not only can higher power be output, but input distortion caused by three-phase imbalance can also be avoided and the power factor can be improved.

[0004] Take the Vienna rectifier circuit as an example, Figure 1 and Figure 2 The three-phase three-level Vienna rectifier circuit has the advantages of high power factor, low harmonic content, high efficiency, etc., and can operate in three-phase mode and any two-phase mode at the same time.

[0005] Therefore, an efficient control strategy is needed to adjust the input mode of the rectifier in the case of three-phase imbalance, so that the rectifier circuit can output higher power and ensure the power demand of the DC load. Summary of the Invention

[0006] In view of this, it is necessary to provide a method for controlling the maximum power output of the rectifier under three-phase imbalance. In the case of three-phase imbalance, the input mode of the rectifier is adjusted so that the rectifier circuit can output higher power to ensure the power demand of the DC load.

[0007] In order to solve the above problems, the present invention provides a method for controlling the maximum output power of a rectifier under three-phase imbalance, comprising:

[0008] In three-phase operation mode, determine the total active power of the three-phase input ;

[0009] In two-phase operation mode, determine the maximum power of the two-phase input ;

[0010] Compare the total active power of the three-phase input Maximum power with two-phase input size;

[0011] when When the three-phase mode is switched to the two-phase mode.

[0012] In a possible implementation, after switching the three-phase mode to the two-phase mode, the method further includes:

[0013] Select the two phases corresponding to the maximum input line voltage for operation and disconnect the phase with lower voltage.

[0014] In one possible implementation, the total active power of the three-phase input is determined ,include:

[0015] Get grid phase voltage Phase current And the phase angle between each phase voltage and current Calculate the input power of each phase ;

[0016] According to the input power of each phase Calculate the total active power of the three-phase input .

[0017] In one possible implementation, the input power of each phase is calculated , specifically including:

[0018] .

[0019] In one possible implementation, the total active power of the three-phase input is calculated as , specifically including:

[0020] .

[0021] In one possible implementation, the phase angle between the voltage and current of each phase is obtained. Specifically include:

[0022] Detect the time interval between two positive zero crossings of the input voltage and obtain the cycle of the input voltage ;

[0023] According to the time interval of the voltage and current positive zero crossing Calculate the phase angle between each phase voltage and current:

[0024] .

[0025] In one possible implementation, the maximum power of the two-phase input is determined include:

[0026] Get the grid line voltage ;

[0027] Set the input current upper limit ;

[0028] Based on the grid line voltage and input current limit Calculate the maximum power in two-phase mode .

[0029] In one possible implementation, the maximum power in two-phase mode is calculated include:

[0030] .

[0031] In one possible implementation, the method further includes:

[0032] Set the maximum unbalance allowed in the power grid ;

[0033] Calculate the grid imbalance based on the input grid phase voltage ;

[0034] When the grid is unbalanced Less than the maximum unbalance allowed by the power grid , restore the two-phase mode to three-phase mode.

[0035] In one possible implementation, the grid imbalance The calculation formula is:

[0036] ;

[0037] in, Indicates the maximum phase voltage, Indicates the minimum phase voltage.

[0038] The beneficial effect of this invention is that it intelligently switches between three-phase and two-phase modes based on the current grid voltage imbalance, allowing the rectifier to operate at its maximum output power point. The ultimate effect is that the rectifier circuit system maintains a high DC power output through real-time switching even in grid imbalance conditions, significantly improving grid voltage utilization and enhancing the reliability of both the rectifier and the power-consuming equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0040] Figure 1The figure is a circuit diagram of a three-phase mode of a Vienna rectifier circuit in the prior art;

[0041] Figure 2 The figure is a circuit diagram of a two-phase mode of a Vienna rectifier circuit in the prior art;

[0042] Figure 3 A schematic flow chart of a method for controlling the maximum power output of a rectifier under three-phase imbalance provided by the present invention;

[0043] Figure 4 This is a structural diagram of the input voltage and input current provided by the present invention at the positive zero crossing point. DETAILED DESCRIPTION

[0044] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0045] The terms "first," "second," and so on, used in the embodiments of the present invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a technical feature designated as "first" or "second" may explicitly or implicitly include at least one such feature.

[0046] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0047] In order to solve the above technical problems, the present invention provides a method for controlling the maximum output power of a rectifier under three-phase imbalance, comprising:

[0048] In three-phase operation mode, determine the total active power of the three-phase input ;

[0049] In two-phase operation mode, determine the maximum power of the two-phase input ;

[0050] Compare the total active power of the three-phase input Maximum power with two-phase input size;

[0051] when When the three-phase mode is switched to the two-phase mode.

[0052] In a possible implementation, after switching the three-phase mode to the two-phase mode, the method further includes:

[0053] Select the two phases corresponding to the maximum input line voltage for operation and disconnect the phase with lower voltage.

[0054] In one possible implementation, the total active power of the three-phase input is determined include:

[0055] Get grid phase voltage Phase current And the phase angle between each phase voltage and current Calculate the input power of each phase ;

[0056] According to the input power of each phase Calculate the total active power of the three-phase input ;

[0057] In one possible implementation, the input power of each phase is calculated , specifically including:

[0058] .

[0059] In one possible implementation, the total active power of the three-phase input is calculated as Specifically include:

[0060] .

[0061] In one possible implementation, the phase angle between the voltage and current of each phase is obtained. See also Figure 4 , specifically including:

[0062] Detect the time interval between two positive zero crossings of the input voltage and obtain the cycle of the input voltage ;

[0063] According to the time interval of the voltage and current positive zero crossing Calculate the phase angle between each phase voltage and current:

[0064] .

[0065] In one possible implementation, the maximum power of the two-phase input is determined include:

[0066] Get the grid line voltage ;

[0067] Set the input current upper limit ;

[0068] Based on the grid line voltage and input current limit Calculate the maximum power in two-phase mode .

[0069] In one possible implementation, the maximum power in two-phase mode is calculated ,include:

[0070] .

[0071] In one possible implementation, the method further includes:

[0072] Set the maximum unbalance allowed in the power grid ;

[0073] Calculate the grid imbalance based on the input grid phase voltage ;

[0074] When the grid is unbalanced Less than the maximum unbalance allowed by the power grid , restore the two-phase mode to the three-phase mode;

[0075] In one possible implementation, the grid imbalance k The calculation formula is:

[0076] ;

[0077] in, Indicates the maximum phase voltage, Indicates the minimum phase voltage.

[0078] For a more complete description of the technical solution of the present invention, please refer to Figure 3 .

[0079] Specifically, the control strategy is as follows:

[0080] (0), (1) System startup and initial configuration;

[0081] (2) Set the upper limit of input phase current Maximum imbalance with the grid ;

[0082] (3), (4), (5), (6), (7) Calculate the input power in three-phase mode based on the current input voltage and current Maximum power in two-phase mode Determine whether the system switches to two-phase mode;

[0083] (8), (9), and (10) calculate the current grid voltage imbalance in the two-phase mode and determine whether the system should switch to the three-phase mode.

[0084] It should be noted that the active power in three-phase mode and the maximum power in two-phase mode are calculated by detecting the amplitude and phase angle of the input voltage and current. In the event of a significant three-phase imbalance, the rectifier circuit switches to two-phase operation; in the event of a less severe imbalance, the rectifier circuit returns to three-phase operation. This control method ensures that the rectifier consistently outputs greater power, improving grid voltage utilization and better meeting the needs of electrical equipment.

[0085] In summary, the beneficial effect of the present invention is that it intelligently switches between three-phase and two-phase modes based on the current grid voltage imbalance, enabling the rectifier to operate at its maximum output power point. The ultimate effect is that the rectifier circuit system maintains a high DC power output through real-time switching in the event of grid imbalance, significantly improving grid voltage utilization and enhancing the reliability of both the rectifier and the power-consuming equipment.

[0086] The above are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for controlling the maximum output power of a rectifier under three-phase imbalance, characterized in that: include: In three-phase working mode, determine the total active power P of the three-phase input in_3phase ; In two-phase operation mode, determine the maximum power P of the two-phase input in_2phase ; Compare the total active power P of the three-phase input in_3phase The maximum power P of the two-phase input in_2phase size; When P in_3phase <P in_2phase When , the three-phase mode is switched to the two-phase mode; Determine the maximum power P of the two-phase input in_2phase ,include: Get the grid line voltage V AB 、V BC 、V CA ; Set the input current upper limit I in_max ; Based on the grid line voltage V AB 、V BC 、V CA and input current upper limit I in_max Calculate the maximum power P in two-phase mode in_2phase ; Calculate the maximum power P in two-phase mode in_2phase ,include: P in_2phase =max(V AB ,V BC ,V CA )*I in_max 。 2. The method for controlling the maximum output power of a rectifier under three-phase imbalance according to claim 1, characterized in that: After switching from three-phase mode to two-phase mode, it also includes: Select the two phases corresponding to the maximum input line voltage for operation and disconnect the phase with lower voltage.

3. The method for controlling the maximum output power of a rectifier under three-phase imbalance according to claim 1, characterized in that: Determine the total active power P of the three-phase input in_3phase ,include: Get the grid phase voltage V A 、V B 、V C , phase current I A , I B , I C , and the phase angles between the voltages and currents of each phase Calculate the input power P of each phase A 、P B 、P C ; According to the input power P of each phase A 、P B 、P C Calculate the total active power P of the three-phase input in_3phase .

4. The method for controlling the maximum output power of a rectifier under three-phase imbalance according to claim 3, characterized in that: Calculate the input power P of each phase A 、P B 、P C , specifically including:

5. The method for controlling the maximum output power of a rectifier under three-phase imbalance according to claim 3, characterized in that: Calculate the total active power P of the three-phase input in_3phase , specifically including: P in_3phase =P A +P B +P C 。 6. The method for controlling the maximum output power of a rectifier under three-phase imbalance according to claim 3, characterized in that: Get the phase angle between each phase voltage and current Specifically include: Detect the time interval between two positive zero crossings of the input voltage and obtain the input voltage period T i ; According to the time interval ΔT of the voltage and current positive zero crossing i , calculate the phase angle between each phase voltage and current:

7. The method for controlling the maximum output power of a rectifier under three-phase imbalance according to any one of claims 1 to 6, characterized in that: The method also includes: Set the maximum unbalance k allowed by the power grid ref ; Calculate the grid imbalance k based on the input grid phase voltage; When the grid imbalance k is less than the maximum imbalance k allowed by the grid ref , restore the two-phase mode to three-phase mode.

8. The method for controlling the maximum output power of a rectifier under three-phase imbalance according to claim 7, characterized in that: The calculation formula of the grid imbalance k is: Among them, V P_max Indicates the maximum phase voltage, V P_min Indicates the minimum phase voltage.

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