Three-phase rectifier input voltage control method and system suitable for input imbalance

Abstract

The present invention provides a three-phase rectifier input voltage control method and system suitable for input imbalance, which relates to the field of three-phase rectification, wherein the method comprises: obtaining a proportional gain coefficient of a B-phase modulation function and a proportional gain coefficient of a C-phase modulation function; determining a three-phase modulation signal after eliminating a zero-sequence component according to the proportional gain coefficient of the B-phase modulation function, the proportional gain coefficient of the C-phase modulation function and a three-phase signal; using the three-phase modulation signal as a modulation signal of a three-phase Buck rectifier space vector modulation, sinusoiding the three-phase input current and eliminating the output ripple, which has the advantages of reducing the cost of eliminating the output voltage low-frequency ripple and input current low-order harmonics of the three-phase Buck rectifier under unbalanced input conditions, and improving the efficiency.

Description

Technical Field

[0001] The invention relates to the field of three-phase rectification, and in particular to an input voltage control method and system for a three-phase rectifier with unbalanced input. Background Art

[0002] The three-phase PWM rectifier has the advantages of unity power factor operation, stable and controllable DC bus voltage, and sinusoidal input current. It is widely used in the power supply system of data transmission center, power supply of multi-electric aircraft, etc. According to the characteristics of the DC side output voltage, the three-phase six-switch PWM rectifier can be divided into three-phase Buck rectifier and three-phase Boost rectifier. Compared with the three-phase Boost rectifier, the three-phase Buck rectifier has the advantages of output voltage adjustment from zero, small startup surge current, strong output short-circuit protection capability, and low input current THD. At the same time, since the upper and lower switches of the same bridge arm are turned on, it is a normal working state of the three-phase Buck rectifier, so there is no need to set the dead time for its switch drive signal.

[0003] In actual power supply systems, three-phase input imbalance is inevitable. If the traditional control strategy with balanced input voltage is still used, the rectifier input power will show double-frequency pulsation, and the output voltage will contain double-frequency ripple, which will introduce a large number of odd harmonics into the input current. In severe cases, it will cause serious failures in the power supply system.

[0004] Under the condition of unbalanced input voltage, the control technology of the three-wire Buck rectifier with partial indirect current control is as follows: 1. The three-phase modulation function is reconstructed using the phase voltage to eliminate the positive and negative sequence coupling components in the input power, thereby suppressing the input power pulsation, realizing the sinusoidalization of the input current, and eliminating the low-frequency ripple of the output voltage. However, this method requires real-time differential calculation of the input phase voltage when reconstructing the three-phase modulation signal, and is extremely sensitive to input voltage noise when digitally implemented. 2. The three-phase voltage is reconstructed into a more balanced three-phase phasor according to the amplitude relationship, and power tracking control is introduced in the DC side current loop and voltage loop, thereby obtaining a relatively balanced input current of the three phases. Compared with other technologies, although this technology obtains a more balanced three-phase input current, as the input voltage imbalance increases, the input current THD and output voltage ripple will also increase significantly. 3. By introducing virtual impedance in the two-phase stationary coordinate system, a new three-phase modulation function is constructed, thereby eliminating the output voltage ripple and input power pulsation, and obtaining a sinusoidal current, but this technology introduces additional peak detection and phase detection circuits, which increases the hardware cost.

[0005] Therefore, it is necessary to provide a three-phase rectifier input voltage control method and system suitable for unbalanced input, so as to reduce the cost of eliminating the output voltage low-frequency ripple and input current low-order harmonics of the three-phase Buck rectifier under unbalanced input conditions and improve efficiency. Summary of the invention

[0006] The present invention provides a three-phase rectifier input voltage control method suitable for input imbalance, comprising: obtaining a proportional gain coefficient of a B-phase modulation function and a proportional gain coefficient of a C-phase modulation function; determining a three-phase modulation signal after eliminating a zero-sequence component according to the proportional gain coefficient of the B-phase modulation function, the proportional gain coefficient of the C-phase modulation function and a three-phase signal; using the three-phase modulation signal as a modulation signal of a three-phase Buck rectifier space vector modulation, sinusoiding the three-phase input current and eliminating the output ripple.

[0007] Furthermore, obtaining the proportional gain coefficient of the B-phase modulation function and the proportional gain coefficient of the C-phase modulation function includes: obtaining the A-phase voltage amplitude, the B-phase voltage amplitude and the C-phase voltage amplitude; calculating the proportional gain coefficient of the B-phase modulation function and the proportional gain coefficient of the C-phase modulation function based on the A-phase voltage amplitude, the B-phase voltage amplitude, the C-phase voltage amplitude, the phase angle difference between the B-phase voltage and the A-phase voltage, and the phase angle difference between the C-phase voltage and the A-phase voltage.

[0008] Further, the proportional gain coefficient of the B-phase modulation function and the proportional gain coefficient of the C-phase modulation function are calculated based on the following formula: Among them, k b is the proportional gain coefficient of the B phase modulation function, k c is the proportional gain coefficient of the C-phase modulation function, V ao is the voltage amplitude of phase A, θ c is the phase angle difference between phase C voltage and phase A voltage, θ b is the phase angle difference between the B phase voltage and the A phase voltage, V bo is the voltage amplitude of phase B, V co is the voltage amplitude of phase C.

[0009] Furthermore, based on the proportional gain coefficient of the B-phase modulation function, the proportional gain coefficient of the C-phase modulation function and the three-phase signal, the three-phase modulation signal after eliminating the zero-sequence component is determined, including: calculating the three-phase signal with the proportional gain coefficient of the B-phase modulation function and the proportional gain coefficient of the C-phase modulation function introduced; calculating the zero-sequence component of the three-phase signal; based on the three-phase signal and the zero-sequence component, determining the three-phase modulation signal after eliminating the zero-sequence component.

[0010] Furthermore, the three-phase signal is calculated based on the following formula: v a =V ao cos(ωt),v b =V bo cos(ωt+θ b ), v c =Vco cos(ωt+θ c ),in, is the A phase signal, is the B phase signal, It is the C phase signal.

[0011] Furthermore, the zero-sequence component of the three-phase signal is calculated based on the following formula: in, is the zero-sequence component of the three-phase signal.

[0012] Furthermore, the three-phase modulated signal after eliminating the zero-sequence component is calculated based on the following formula: Among them, σ a To eliminate the zero-sequence component of the A-phase modulation signal, σ b To eliminate the B-phase modulation signal after the zero-sequence component, σ c It is the C-phase modulation signal after eliminating the zero-sequence component.

[0013] Furthermore, the three-phase modulation signal is used as a modulation signal for space vector modulation of a three-phase Buck rectifier to sinusoid the three-phase input current and eliminate the output ripple, including: dividing a switching cycle of the three-phase modulation signal into multiple sectors; in each of the switching cycles, determining the current sector, calculating the action time of each current vector to synthesize the three-phase current corresponding to the three-phase modulation signal, comparing the three-phase modulation signal with a triangular carrier signal, generating a drive signal for the switch tube on the bridge arm, and realizing space vector modulation.

[0014] Furthermore, dividing a switching cycle of the three-phase modulation signal into a plurality of sectors includes: dividing the sectors by 30 electrical degrees per sector, and dividing a switching cycle of the three-phase modulation signal into 12 sectors in a counterclockwise direction.

[0015] The present invention provides a three-phase rectifier input voltage control system suitable for input imbalance, comprising: a proportional gain coefficient acquisition module, used for acquiring the proportional gain coefficient of a B-phase modulation function and the proportional gain coefficient of a C-phase modulation function; a three-phase modulation function construction module, used for determining a three-phase modulation signal after eliminating a zero-sequence component according to the proportional gain coefficient of the B-phase modulation function, the proportional gain coefficient of the C-phase modulation function and a three-phase signal; and a three-phase modulation module, used for using the three-phase modulation signal as a modulation signal of a three-phase Buck rectifier space vector modulation to perform sinusoidalization of a three-phase input current and eliminate output ripple.

[0016] Compared with the prior art, the input voltage control method and system for a three-phase rectifier with unbalanced input provided by the present invention have at least the following beneficial effects:

[0017] The existing input voltage feedforward control method under unbalanced input conditions requires the calculation of the real-time differential value of the input voltage in each control cycle. At the same time, the differential operation is sensitive to input voltage noise and has high requirements for sampling accuracy, or requires additional peak detection and phase detection circuits. The input voltage control method for a three-phase rectifier with unbalanced input proposed in this specification only requires one proportional coefficient calculation in one input voltage cycle, has no high requirements for sampling accuracy, does not require additional peak detection and phase detection circuits, does not require real-time differential operation of the input voltage, is insensitive to input voltage noise, can eliminate the output voltage low-frequency ripple and input current low-order harmonics of the three-phase Buck rectifier under unbalanced input conditions, and the control method is simple and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] This specification will be further described in the form of exemplary embodiments, which will be described in detail by the accompanying drawings. These embodiments are not restrictive, and in these embodiments, the same number represents the same structure, wherein:

[0019] Figure 1 It is a flowchart of a method for controlling input voltage of a three-phase rectifier with unbalanced input according to some embodiments of this specification;

[0020] Figure 2 It is a flowchart of a method for controlling input voltage of a three-phase rectifier with unbalanced input according to some embodiments of this specification;

[0021] Figure 3a is a schematic diagram of an input current waveform and an output voltage ripple corresponding to an existing control method shown in some embodiments of this specification;

[0022] Figure 3b It is a schematic diagram of an input current waveform and an output voltage ripple corresponding to an input voltage control method for a three-phase rectifier with unbalanced input as shown in some embodiments of this specification;

[0023] Figure 4 It is a module schematic diagram of a three-phase rectifier input voltage control system suitable for input imbalance according to some embodiments of this specification. DETAILED DESCRIPTION

[0024] In order to more clearly illustrate the technical solutions of the embodiments of this specification, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some examples or embodiments of this specification. For ordinary technicians in this field, this specification can also be applied to other similar scenarios based on these drawings without creative work. Unless it is obvious from the language environment or otherwise explained, the same reference numerals in the figures represent the same structure or operation.

[0025] Figure 1 is a flow chart of a method for controlling input voltage of a three-phase rectifier with unbalanced input according to some embodiments of this specification, such as Figure 1 As shown, the input voltage control method of a three-phase rectifier suitable for input imbalance may include the following steps.

[0026] Step 110, obtaining a proportional gain coefficient of a B-phase modulation function and a proportional gain coefficient of a C-phase modulation function.

[0027] Specifically include:

[0028] Obtain the voltage amplitude of phase A, phase B and phase C;

[0029] Based on the A-phase voltage amplitude, the B-phase voltage amplitude, the C-phase voltage amplitude, the phase angle difference between the B-phase voltage and the A-phase voltage, and the phase angle difference between the C-phase voltage and the A-phase voltage, the proportional gain coefficient of the B-phase modulation function and the proportional gain coefficient of the C-phase modulation function are calculated.

[0030] Specifically, any unbalanced three-phase input voltage can be expressed as:

[0031] v a =V ao cos(ωt)

[0032] v b =V bo cos(ωt+θ b )

[0033] v c =V co cos(ωt+θ c )

[0034] Among them, V ao is the voltage amplitude of phase A, θ c is the phase angle difference between phase C voltage and phase A voltage, θ b is the phase angle difference between the B phase voltage and the A phase voltage, V bo is the voltage amplitude of phase B, V co is the voltage amplitude of phase C.

[0035] When the A phase voltage reaches its peak value, that is, when the A phase voltage phase ωt is 0, the two-phase phase angle corresponds to the trigonometric function cosθ b 、cosθ c It can be expressed as:

[0036] cosθ b =V bo cos(θ b ) / V bo =v b / V bo

[0037] cosθ c =V co cos(θ c ) / V co =v c / V co

[0038] In the process of three-phase peak detection, the peak value of phase A is detected and the voltage of phases B and C is detected at the same time, so that the phase angle of phases B and C corresponds to the trigonometric function cosθ. b ,cosθ c Detection.

[0039] In some embodiments, the proportional gain coefficient of the B-phase modulation function and the proportional gain coefficient of the C-phase modulation function may be calculated based on the following formula:

[0040]

[0041] Among them, k b is the proportional gain coefficient of the B phase modulation function, k c is the proportional gain coefficient of the C-phase modulation function.

[0042] Step 120, determining the three-phase modulation signal after eliminating the zero-sequence component according to the proportional gain coefficient of the B-phase modulation function, the proportional gain coefficient of the C-phase modulation function and the three-phase signal.

[0043] Specifically include:

[0044] Calculate the three-phase signal into which the proportional gain coefficient of the B-phase modulation function and the proportional gain coefficient of the C-phase modulation function are brought;

[0045] Calculate the zero-sequence component of the three-phase signal;

[0046] Based on the three-phase signal and the zero-sequence component, a three-phase modulated signal after eliminating the zero-sequence component is determined.

[0047] In some embodiments, the three-phase signal may be calculated based on the following formula:

[0048]

[0049] in, is the A phase signal, is the B phase signal, It is the C phase signal.

[0050] In some embodiments, the zero-sequence component of the three-phase signal may be calculated based on the following formula:

[0051]

[0052] in, is the zero-sequence component of the three-phase signal.

[0053] In some embodiments, the three-phase modulated signal after eliminating the zero-sequence component can be calculated based on the following formula:

[0054]

[0055]

[0056] Among them, σ a To eliminate the zero-sequence component of the A-phase modulation signal, σ b To eliminate the B-phase modulation signal after the zero-sequence component, σ c It is the C-phase modulation signal after eliminating the zero-sequence component.

[0057] Step 130: Use the three-phase modulation signal as a modulation signal of space vector modulation of a three-phase Buck rectifier to sinusoid the three-phase input current and eliminate the output ripple.

[0058] Specifically include:

[0059] Dividing a switching cycle of the three-phase modulation signal into a plurality of sectors, for example, dividing a switching cycle of the three-phase modulation signal into a plurality of sectors, including: dividing the sectors by 30 electrical degrees per sector, dividing a switching cycle of the three-phase modulation signal into 12 sectors in a counterclockwise direction;

[0060] In each switching cycle, the current sector is determined, and the action time of each current vector is calculated to synthesize the three-phase current corresponding to the three-phase modulation signal. The three-phase modulation signal is compared with the triangular carrier signal to generate the driving signal of the switch tube on the bridge arm to realize space vector modulation.

[0061] Specifically, Figure 2 is a flow chart of a method for controlling input voltage of a three-phase rectifier with unbalanced input according to some embodiments of this specification, such as Figure 2 As shown, the three-phase modulation signal σ a ,σ b ,σ cCompared with the triangular carrier, when the value of the three-phase modulation wave is greater than the triangular carrier signal Ut, the driving signal of the switch tube on the corresponding bridge arm is 1; when the value of the three-phase modulation wave is less than or equal to the triangular carrier signal Ut, the driving signal of the switch tube on the corresponding bridge arm is 0, and the driving signal v of each switch tube is generated. gs1 , v gs2 , v gs3 , v gs4 , v gs5 , v gs6 , realize space vector modulation, and then realize the sinusoidalization of input current and elimination of output ripple, Figure 2 In, v gsx Represents the driving signal of each switch tube, v dc represents the DC side voltage, v0 represents the output voltage, v0* represents the voltage external loop reference, i L Represents the output inductor current, i L * represents the current inner loop reference, i PI Represents the current inner loop output. For example, when the value of the modulation wave signal of a phase is greater than the value of the triangular carrier signal, it means that at this moment, the phase needs to output a higher voltage or current. In order to achieve this goal, it is necessary to control the switch tube on the bridge arm of this phase to be in the on state. Therefore, when the comparison result meets the above conditions, a drive signal is generated, and the value of the signal is 1 (or called a high-level signal), which is used to drive the switch tube on the bridge arm of this phase to turn on. The switch tube that receives the drive signal of 1 will turn on, so that the three-phase rectifier can output the corresponding voltage or current.

[0062] Figure 3a is a schematic diagram of an input current waveform and an output voltage ripple corresponding to an existing control method shown in some embodiments of this specification, Figure 3b is a schematic diagram of an input current waveform and an output voltage ripple corresponding to an input voltage control method for a three-phase rectifier with unbalanced input as shown in some embodiments of this specification, such as Figure 3a , Figure 3b As shown, by comparison, the input voltage control method for a three-phase rectifier with unbalanced input proposed in this specification is better in sinusoiding the three-phase input current and eliminating the output ripple.

[0063] The existing input voltage feedforward control method under unbalanced input conditions requires the calculation of the real-time differential value of the input voltage in each control cycle. At the same time, the differential operation is sensitive to input voltage noise and has high requirements for sampling accuracy, or requires additional peak detection and phase detection circuits. The input voltage control method for a three-phase rectifier with unbalanced input proposed in this specification only requires one proportional coefficient calculation in one input voltage cycle, has no high requirements for sampling accuracy, does not require additional peak detection and phase detection circuits, does not require real-time differential operation of the input voltage, is insensitive to input voltage noise, can eliminate the output voltage low-frequency ripple and input current low-order harmonics of the three-phase Buck rectifier under unbalanced input conditions, and the control method is simple and easy to implement.

[0064] Figure 4 is a module schematic diagram of a three-phase rectifier input voltage control system suitable for input imbalance according to some embodiments of this specification, such as Figure 4 As shown, the three-phase rectifier input voltage control system suitable for input imbalance may include a proportional gain coefficient acquisition module, a three-phase modulation function construction module and a three-phase modulation module.

[0065] The proportional gain coefficient acquisition module can be used to obtain the proportional gain coefficient of the B-phase modulation function and the proportional gain coefficient of the C-phase modulation function;

[0066] The three-phase modulation function construction module can be used to determine the three-phase modulation signal after eliminating the zero-sequence component according to the proportional gain coefficient of the B-phase modulation function, the proportional gain coefficient of the C-phase modulation function and the three-phase signal;

[0067] The three-phase modulation module can be used to use the three-phase modulation signal as the modulation signal of the three-phase Buck rectifier space vector modulation to sinusoid the three-phase input current and eliminate the output ripple.

[0068] The three-phase rectifier input voltage control system suitable for input imbalance can be used to execute the three-phase rectifier input voltage control method suitable for input imbalance. For more descriptions of the three-phase rectifier input voltage control system suitable for input imbalance, please refer to the relevant descriptions of the three-phase rectifier input voltage control method suitable for input imbalance, which will not be repeated here.

[0069] Finally, it should be understood that the embodiments described in this specification are only used to illustrate the principles of the embodiments of this specification. Other variations may also fall within the scope of this specification. Therefore, as an example and not a limitation, alternative configurations of the embodiments of this specification may be considered consistent with the teachings of this specification. Accordingly, the embodiments of this specification are not limited to the embodiments explicitly introduced and described in this specification.

Claims

1. A method for controlling input voltage of a three-phase rectifier with unbalanced input, characterized in that: include: Obtaining a proportional gain coefficient of a B-phase modulation function and a proportional gain coefficient of a C-phase modulation function; Determine a three-phase modulation signal after eliminating the zero-sequence component according to the proportional gain coefficient of the B-phase modulation function, the proportional gain coefficient of the C-phase modulation function and the three-phase signal; The three-phase modulation signal is used as the modulation signal of the three-phase Buck rectifier space vector modulation to sinusoid the three-phase input current and eliminate the output ripple; The obtaining of the proportional gain coefficient of the B-phase modulation function and the proportional gain coefficient of the C-phase modulation function includes: Obtain the voltage amplitude of phase A, phase B and phase C; Calculate the proportional gain coefficient of the B-phase modulation function and the proportional gain coefficient of the C-phase modulation function based on the A-phase voltage amplitude, the B-phase voltage amplitude, the C-phase voltage amplitude, the phase angle difference between the B-phase voltage and the A-phase voltage, and the phase angle difference between the C-phase voltage and the A-phase voltage; The proportional gain coefficient of the B-phase modulation function and the proportional gain coefficient of the C-phase modulation function are calculated based on the following formula: ， in, is the proportional gain coefficient of the B-phase modulation function, is the proportional gain coefficient of the C-phase modulation function, is the voltage amplitude of phase A, is the phase angle difference between the C phase voltage and the A phase voltage, is the phase angle difference between the B phase voltage and the A phase voltage, is the voltage amplitude of phase B, is the voltage amplitude of phase C.

2. The input voltage control method for a three-phase rectifier with unbalanced input according to claim 1, characterized in that: Determining the three-phase modulation signal after eliminating the zero-sequence component according to the proportional gain coefficient of the B-phase modulation function, the proportional gain coefficient of the C-phase modulation function and the three-phase signal, comprising: Calculate a three-phase signal that incorporates a proportional gain coefficient of the B-phase modulation function and a proportional gain coefficient of the C-phase modulation function; Calculating the zero-sequence component of the three-phase signal; Based on the three-phase signal and the zero-sequence component, the three-phase modulated signal after the zero-sequence component is eliminated is determined.

3. The input voltage control method for a three-phase rectifier with unbalanced input according to claim 2, characterized in that: The three-phase signal is calculated based on the following formula: ， in, is the A phase signal, is the B phase signal, It is the C phase signal.

4. The input voltage control method for a three-phase rectifier with unbalanced input according to claim 3, characterized in that: The zero-sequence component of the three-phase signal is calculated based on the following formula: ， in, is the zero-sequence component of the three-phase signal.

5. The input voltage control method for a three-phase rectifier with unbalanced input according to claim 4, characterized in that: The three-phase modulated signal after eliminating the zero-sequence component is calculated based on the following formula: ， in, To eliminate the A-phase modulation signal after the zero-sequence component, To eliminate the B-phase modulation signal after the zero-sequence component, It is the C-phase modulation signal after eliminating the zero-sequence component.

6. The input voltage control method for a three-phase rectifier with unbalanced input according to any one of claims 1 to 5, characterized in that: The method of using the three-phase modulation signal as the modulation signal of the three-phase Buck rectifier space vector modulation to sinusoid the three-phase input current and eliminate the output ripple includes: Dividing a switching cycle of a three-phase modulation signal into a plurality of sectors; In each switching cycle, the current sector is determined, the action time of each current vector is calculated to synthesize the three-phase current corresponding to the three-phase modulation signal, the three-phase modulation signal is compared with the triangular carrier signal, and the driving signal of the switch tube on the bridge arm is generated to realize space vector modulation.

7. The input voltage control method for a three-phase rectifier with unbalanced input according to claim 6, characterized in that: The step of dividing a switching cycle of the three-phase modulation signal into a plurality of sectors comprises: The sectors are divided into sectors of 30 electrical degrees each, and one switching cycle of the three-phase modulation signal is divided into 12 sectors in a counterclockwise direction.

8. Applicable to the input voltage control system of a three-phase rectifier with unbalanced input, characterized in that: include: A proportional gain coefficient acquisition module is used to obtain the proportional gain coefficient of the B-phase modulation function and the proportional gain coefficient of the C-phase modulation function; A three-phase modulation function construction module is used to determine the three-phase modulation signal after eliminating the zero-sequence component according to the proportional gain coefficient of the B-phase modulation function, the proportional gain coefficient of the C-phase modulation function and the three-phase signal; The three-phase modulation module is used to use the three-phase modulation signal as the modulation signal of the three-phase Buck rectifier space vector modulation to sinusoid the three-phase input current and eliminate the output ripple; The obtaining of the proportional gain coefficient of the B-phase modulation function and the proportional gain coefficient of the C-phase modulation function includes: Obtain the voltage amplitude of phase A, phase B and phase C; Calculate the proportional gain coefficient of the B-phase modulation function and the proportional gain coefficient of the C-phase modulation function based on the A-phase voltage amplitude, the B-phase voltage amplitude, the C-phase voltage amplitude, the phase angle difference between the B-phase voltage and the A-phase voltage, and the phase angle difference between the C-phase voltage and the A-phase voltage; The proportional gain coefficient of the B-phase modulation function and the proportional gain coefficient of the C-phase modulation function are calculated based on the following formula: ， in, is the proportional gain coefficient of the B-phase modulation function, is the proportional gain coefficient of the C-phase modulation function, is the voltage amplitude of phase A, is the phase angle difference between the C phase voltage and the A phase voltage, is the phase angle difference between the B phase voltage and the A phase voltage, is the voltage amplitude of phase B, is the voltage amplitude of phase C.

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