A method and system for controlling a Vienna rectifier

Abstract

The application discloses a control method and system of a Vienna rectifier, which is used for controlling switch tubes of the Vienna rectifier when direct current is input into the Vienna rectifier. The control method comprises the following steps: establishing an equivalent circuit when direct current is input into the Vienna rectifier, collecting output voltage values, output voltage reference values, upper capacitor voltage values and lower capacitor voltage values of the equivalent circuit; obtaining first control results through closed-loop control of an output voltage loop according to the output voltage values and the output voltage reference values, obtaining second control results through closed-loop control of a midpoint potential balance loop according to the upper capacitor voltage values and the lower capacitor voltage values, and obtaining first modulation waves and second modulation waves according to the first control results and the second control results; and comparing the first modulation waves and the second modulation waves with first carriers and second carriers respectively, and controlling switch tubes of the equivalent circuit through first driving signals and second driving signals according to comparison results.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a control method and system for a Vienna rectifier. Background Technology

[0002] The Vienna rectifier is a novel PWM rectifier topology invented in the 1990s by Professor JW Kolar and others at the University of Vienna, Austria. Common types include three-phase and single-phase Vienna rectifier circuits. The Vienna rectifier is a power factor correction (PFC) circuit capable of AC-DC conversion. It is a three-level PWM rectifier topology. During normal operation, the maximum voltage that the switching transistors can withstand is half the DC bus voltage. There is no shoot-through phenomenon in the switching transistors. Compared to other topologies, at the same switching frequency, it has lower inductor ripple, smaller inductor size, relatively higher power density, and lower input current harmonics. Therefore, the Vienna rectifier has been widely used in applications requiring high power factor and low current harmonics, especially in the fields of new energy vehicle charging piles, on-board chargers, and aircraft generators in recent years.

[0003] Typically, three-phase Vienna rectifiers can only be used in applications with three-phase AC input, while single-phase Vienna rectifiers can only be used in applications with single-phase AC input. When AC power is unavailable, the Vienna rectifier will not operate, limiting its application flexibility. When a Vienna rectifier is connected to a DC input, there is usually no specific control method; the switching transistor is always off, and the DC power is directly input to the output side of the Vienna rectifier through diodes. This means the output voltage of the Vienna rectifier is equal to the input DC power. The Vienna rectifier cannot boost or regulate the input voltage; when the input voltage fluctuates, the output voltage also fluctuates, and it lacks midpoint potential balancing capability. When the downstream load changes dynamically, voltage imbalance problems easily occur in the DC bus capacitor voltage. Summary of the Invention

[0004] This invention addresses the technical problem that Vienna rectifiers cannot operate when AC power is unavailable by proposing a control method and system for Vienna rectifiers that enables them to be compatible with DC input.

[0005] In a first aspect, embodiments of this application provide a control method for a Vienna rectifier, used to control the switching transistors of the Vienna rectifier when DC power is input to it, the control method comprising:

[0006] Voltage acquisition steps: Establish an equivalent circuit when DC power is input to the Vienna rectifier, and acquire the output voltage value, output voltage reference value, upper capacitor voltage value, and lower capacitor voltage value of the equivalent circuit;

[0007] Modulation wave generation steps: Based on the output voltage value and the output voltage reference value, a first control result is obtained through closed-loop control of the output voltage loop; based on the upper capacitor voltage value and the lower capacitor voltage value, a second control result is obtained through closed-loop control of the midpoint potential balance loop; and a first modulation wave and a second modulation wave are obtained based on the first control result and the second control result.

[0008] Switching control steps: The first modulation wave and the second modulation wave are compared with the first carrier wave and the second carrier wave, respectively. Based on the comparison results, the switching transistors of the equivalent circuit are controlled by the first driving signal and the second driving signal.

[0009] The above control method, wherein the modulation wave generation step includes:

[0010] The first control result acquisition step is as follows: the difference between the output voltage reference value and the output voltage value is input into the PI controller in the output voltage loop, and the first control result is output through the PI controller.

[0011] The second control result acquisition step is as follows: The difference between the upper capacitor voltage value and the lower capacitor voltage value is input into the PI controller in the midpoint potential balance loop, and the second control result is output through the PI controller.

[0012] The above control method further includes the following step: using the sum of the first control result and the second control result as the first modulated wave, and using the difference between the first control result and the second control result as the second modulated wave.

[0013] The above control method, wherein the switching transistor control step includes:

[0014] First driving signal control steps: When the first modulated wave is greater than or equal to the first carrier wave, the switching transistor is turned on by the first driving signal; when the first modulated wave is less than the first carrier wave, the switching transistor is turned off by the first driving signal.

[0015] The second driving signal control step is as follows: when the second modulated wave is greater than or equal to the second carrier wave, the switching transistor is turned on by the second driving signal; when the second modulated wave is less than the second carrier wave, the switching transistor is turned off by the second driving signal.

[0016] The above control method, wherein the switching transistor control step further includes:

[0017] If the positive terminal of the input DC power is connected to the first bridge arm of the equivalent circuit, the first drive signal controls the switching on and off of the first and second switches of the equivalent circuit, and the second drive signal controls the switching on and off of the third and fourth switches of the equivalent circuit.

[0018] If the positive terminal of the input DC power is connected to the second bridge arm of the equivalent circuit, the first drive signal controls the switching on and off of the third and fourth switches of the equivalent circuit, and the second drive signal controls the switching on and off of the first and second switches of the equivalent circuit.

[0019] In the control method described above, the first carrier and the second carrier are triangular waves with amplitudes ranging from 0 to 1 and the same phase.

[0020] Secondly, embodiments of this application provide a control system for a Vienna rectifier to implement the above-described control method, comprising:

[0021] The voltage acquisition unit establishes an equivalent circuit when DC power is input to the Vienna rectifier, and acquires the output voltage value, output voltage reference value, upper capacitor voltage value, and lower capacitor voltage value of the equivalent circuit.

[0022] The modulation wave generation unit obtains a first control result by performing closed-loop control through the output voltage loop based on the output voltage value and the output voltage reference value, and obtains a second control result by performing closed-loop control through the midpoint potential balance loop based on the upper capacitor voltage value and the lower capacitor voltage value, and obtains a first modulation wave and a second modulation wave based on the first control result and the second control result.

[0023] The switching control unit compares the first modulation wave and the second modulation wave with the first carrier wave and the second carrier wave, respectively, and controls the switching transistor of the equivalent circuit through the first driving signal and the second driving signal according to the comparison result.

[0024] In the aforementioned control system, the modulation wave generation unit includes:

[0025] The first control result acquisition module inputs the difference between the output voltage reference value and the output voltage value into the PI controller in the output voltage loop, and controls the output of the first control result through the PI controller;

[0026] The second control result acquisition module inputs the difference between the upper capacitor voltage value and the lower capacitor voltage value into the PI controller in the midpoint potential balance loop, and outputs the second control result through the PI controller.

[0027] The aforementioned control system, wherein the modulation wave generation unit further includes:

[0028] Modulation wave acquisition module: The sum of the first control result and the second control result is used as the first modulation wave, and the difference between the first control result and the second control result is used as the second modulation wave.

[0029] The aforementioned control system, wherein the switching transistor control unit includes:

[0030] First drive signal control module: When the first modulated wave is greater than or equal to the first carrier wave, the first drive signal controls the switch to turn on; when the first modulated wave is less than the first carrier wave, the first drive signal controls the switch to turn off.

[0031] Second drive signal control module: When the second modulated wave is greater than or equal to the second carrier wave, the second drive signal controls the switch to turn on; when the second modulated wave is less than the second carrier wave, the second drive signal controls the switch to turn off.

[0032] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0033] The control method for Vienna rectifiers proposed in this invention enables Vienna rectifiers to be compatible with DC input, realize DC-DC conversion function when Vienna rectifiers have DC input, output stable DC voltage, and achieve midpoint potential balance. This broadens the application range of Vienna rectifiers, improves the flexibility of use, and can meet the usage requirements of Vienna rectifiers in special situations such as emergency conditions. Attached Figure Description

[0034] Figure 1 A flowchart of the control method for the Vienna rectifier provided by the present invention;

[0035] Figure 2 The equivalent circuit diagram of the Vienna rectifier with DC input provided by the present invention;

[0036] Figure 3 The present invention provides a basis for Figure 1 Flowchart of step S2;

[0037] Figure 4 The present invention provides a basis for Figure 1 Flowchart of step S3;

[0038] Figure 5 The present invention provides a block diagram of a DC-DC control algorithm for a Vienna rectifier with DC input.

[0039] Figure 6 The present invention provides a Simulink simulation model of the Vienna rectifier under DC input.

[0040] Figure 7 The output voltage simulation results provided for this invention;

[0041] Figure 8 The simulation results of the voltage difference between the upper capacitor C1 and the lower capacitor C2 provided by this invention;

[0042] Figure 9 This is a schematic diagram of the control system of the Vienna rectifier provided by the present invention. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this application clearer, the application is described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0044] Obviously, the accompanying drawings described below are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios based on these drawings without any inventive effort. Furthermore, it is understood that although the efforts made in this development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0045] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0046] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms “a,” “an,” “an,” “the,” and similar words used in this application do not indicate quantity limitation and may indicate singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units not listed, or may include other steps or units inherent to these processes, methods, products, or devices. The terms “connected,” “linked,” “coupled,” and similar words used in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. “Multiple” used in this application refers to two or more. “And / or” describes the relationship between related objects, indicating that three relationships may exist; for example, “A and / or B” can represent: A alone, A and B simultaneously, and B alone. The character " / " generally indicates that the preceding and following objects are in an "or" relationship. The terms "first," "second," and "third" used in this application are merely to distinguish similar objects and do not represent a specific ordering of the objects.

[0047] The present invention will now be described in detail with reference to the embodiments shown in the accompanying drawings. However, it should be noted that these embodiments are not intended to limit the present invention. All equivalent changes or substitutions in function, method, or structure made by those skilled in the art based on these embodiments are within the scope of protection of the present invention.

[0048] Example 1:

[0049] Figure 1 A flowchart of the control method for the Vienna rectifier provided by the present invention; as follows: Figure 1 As shown, the control method of the present invention is used to control the switching transistors of the Vienna rectifier when DC power is input to it. The control method includes:

[0050] Step S1: Establish the equivalent circuit when DC power is input to the Vienna rectifier, and collect the output voltage value, output voltage reference value, upper capacitor voltage value and lower capacitor voltage value of the equivalent circuit;

[0051] Specifically, the circuits of a three-phase Vienna rectifier connected to DC power and a single-phase Vienna rectifier connected to DC power can be equivalently represented as follows: Figure 2 The circuit shown. Also, when the three-phase Vienna rectifier input is connected to DC power, the floating bridge arm switch should always be off, controlling only the two bridge arms connected to DC power.

[0052] exist Figure 2 In the circuit shown, the bridge arm consisting of diode D1, diode D2, switch Q1, and switch Q2 is defined as bridge arm A, and the bridge arm consisting of diode D3, diode D4, switch Q3, and switch Q4 is defined as bridge arm B.

[0053] The circuit needs to sample the voltage u of the upper capacitor C1. C1 and the voltage u of capacitor C2 C2 Used for midpoint potential balance control, i.e., controlling u C1 equal to u C2 The output voltage u also needs to be collected. dc Or use u C1 u C2 Constitutes the output voltage (u) dc =u C1 +u C2 ), used for controlling the output voltage.

[0054] by Figure 2 Taking the circuit as an example, let's analyze the circuit's operating modes:

[0055] (1) When switching transistors Q1, Q2, Q3, and Q4 are turned on, the voltage u between A and B is... AB =0, the DC power supply stores energy in the inductor L, and capacitors C1 and C2 supply power to the load RL;

[0056] (2) When switches Q1 and Q2 are turned on and switches Q3 and Q4 are turned off, the voltage u between A and B is... AB =u C2 =u dc / 2, DC power supply and inductor L charge capacitor C2, DC power supply, inductor L and capacitor C1 supply power to load RL;

[0057] (3) When switches Q1 and Q2 are off and switches Q3 and Q4 are on, the voltage u between A and B is... AB =u C1 =u dc / 2, DC power supply and inductor L charge capacitor C1, DC power supply, inductor L and capacitor C2 supply power to load RL;

[0058] (4) When switching transistors Q1, Q2, Q3, and Q4 are turned off, the voltage u between A and B is... AB =u dc The DC power supply and inductor L charge capacitors C1 and C2, while simultaneously supplying power to the load RL.

[0059] When the input of the Vienna rectifier is connected to DC power, the Vienna rectifier is equivalent to a three-level DC-DC Boost circuit.

[0060] Step S2: Based on the output voltage value and the output voltage reference value, a first control result is obtained by performing closed-loop control through the output voltage loop; based on the upper capacitor voltage value and the lower capacitor voltage value, a second control result is obtained by performing closed-loop control through the midpoint potential balance loop; and a first modulation wave and a second modulation wave are obtained based on the first control result and the second control result.

[0061] like Figure 3 As shown, step S2 specifically includes the following:

[0062] Step S21: Input the difference between the output voltage reference value and the output voltage value into the PI controller in the output voltage loop, and control the output of the first control result through the PI controller;

[0063] Step S22: Input the difference between the upper capacitor voltage value and the lower capacitor voltage value into the PI controller in the midpoint potential balance loop, and output the second control result through the PI controller.

[0064] Step S23: The sum of the first control result and the second control result is used as the first modulation wave, and the difference between the first control result and the second control result is used as the second modulation wave.

[0065] Step S3: Compare the first modulated wave and the second modulated wave with the first carrier wave and the second carrier wave respectively, and control the switching transistor of the equivalent circuit according to the comparison result through the first driving signal and the second driving signal.

[0066] like Figure 4 As shown, step S3 specifically includes the following:

[0067] Step S31: When the first modulated wave is greater than or equal to the first carrier wave, the switch is turned on by the first driving signal; when the first modulated wave is less than the first carrier wave, the switch is turned off by the first driving signal.

[0068] Step S32: When the second modulated wave is greater than or equal to the second carrier wave, the switch is turned on by the second drive signal; when the second modulated wave is less than the second carrier wave, the switch is turned off by the second drive signal.

[0069] Both the first and second carriers mentioned above are triangular waves with amplitudes ranging from 0 to 1 and the same phase.

[0070] In the above embodiment, step S3 further includes:

[0071] If the positive terminal of the input DC power is connected to the first bridge arm of the equivalent circuit, the first drive signal controls the switching on and off of the first and second switches of the equivalent circuit, and the second drive signal controls the switching on and off of the third and fourth switches of the equivalent circuit.

[0072] If the positive terminal of the input DC power is connected to the second bridge arm of the equivalent circuit, the first drive signal controls the switching on and off of the third and fourth switches of the equivalent circuit, and the second drive signal controls the switching on and off of the first and second switches of the equivalent circuit.

[0073] This invention proposes a DC-DC control method for Vienna rectifiers when receiving DC input, enabling the Vienna rectifier to be compatible with DC input. When the Vienna rectifier is connected to DC input, it functions as a three-level DC-DC Boost circuit. By implementing this method, the Vienna rectifier can continue to operate normally and output DC voltage.

[0074] Please refer to Figure 5 , Figure 5 This invention provides a block diagram of a DC-DC control algorithm for a Vienna rectifier with DC input; the following is in conjunction with... Figure 5 This invention describes the specific implementation of the control method for the Vienna rectifier proposed in this paper.

[0075] The DC-DC control algorithm for the Vienna rectifier with DC input designed in this invention consists of two closed-loop control loops: an output voltage loop and a midpoint potential balance loop. Both loops use PI controllers.

[0076] Output voltage reference value u dc * With output voltage acquisition value u dc The difference is used as the input to the output voltage loop PI controller, whose output range is 0 to 1. The output voltage loop controls the output voltage to stabilize at the reference value u. dc * .

[0077] upper capacitor voltage u C1 With lower capacitor voltage u C2 The difference is used as the input to the midpoint potential balancing loop PI controller, whose output range is -1 to 1. The midpoint potential balancing loop controls the capacitor voltage u. C1 Equal to the lower capacitor voltage u C2 .

[0078] The sum of the output of the output voltage loop PI controller and the output of the midpoint potential balance loop PI controller constitutes modulation wave 1, and the difference between the output of the output voltage loop PI controller and the output of the midpoint potential balance loop PI controller constitutes modulation wave 2. Carrier 1 and carrier 2 are triangular waves with amplitudes ranging from 0 to 1 and the same phase.

[0079] When modulation wave 1 is greater than or equal to carrier wave 1, drive signal 1 controls the switch to turn on; when modulation wave 1 is less than carrier wave 1, drive signal 1 controls the switch to turn off. When modulation wave 2 is greater than or equal to carrier wave 2, drive signal 2 controls the switch to turn on; when modulation wave 2 is less than carrier wave 2, drive signal 2 controls the switch to turn off.

[0080] Define the input DC power connection flag (flagAB). If the positive terminal of the input DC power is connected... Figure 2 If bridge arm A is connected, then flagAB = 1; if the positive terminal of the input DC power is connected... Figure 2 If the bridge arm is B, then flagAB = -1.

[0081] If flagAB equals 1, drive signal 1 controls switches Q1 and Q2, and drive signal 2 controls switches Q3 and Q4; if flagAB equals -1, drive signal 1 controls switches Q3 and Q4, and drive signal 2 controls switches Q1 and Q2.

[0082] By controlling the switching transistors Q1, Q2, Q3, and Q4 to turn on and off, the output voltage u can be controlled. dc The control simultaneously achieves midpoint potential balance, i.e., controls the capacitor voltage equalization u. C1 =u C2 .

[0083] To verify the DC-DC control method designed in this invention, a Simulink simulation model of the Vienna rectifier with DC input was built, as follows: Figure 6 As shown. The output voltage reference value is DC700V, and the output load is 5kW. The simulation results are as follows. Figure 7 , Figure 8 The output voltage is stabilized at DC 700V, and the voltage of the upper capacitor C1 is equal to the voltage of the lower capacitor C2. The invented DC-DC control method enables the Vienna rectifier to perform DC-DC conversion when a DC input is received, outputting a stable DC voltage while achieving midpoint potential balance. It allows both three-phase and single-phase Vienna rectifiers to be compatible with DC input, broadening the application range of Vienna rectifiers, improving their flexibility, and meeting the requirements of Vienna rectifiers in special situations such as emergency operations.

[0084] Example 2:

[0085] In conjunction with the control method for a Vienna rectifier disclosed in Embodiment 1, this embodiment discloses a specific implementation example of a control system (hereinafter referred to as "the system") for implementing the above control method for a Vienna rectifier.

[0086] like Figure 9 As shown, the control system of the aforementioned Vienna rectifier includes:

[0087] Voltage acquisition unit 11 establishes an equivalent circuit when DC power is input to the Vienna rectifier, and acquires the output voltage value, output voltage reference value, upper capacitor voltage value and lower capacitor voltage value of the equivalent circuit;

[0088] The modulation wave generation unit 12 obtains a first control result by performing closed-loop control through the output voltage loop based on the output voltage value and the output voltage reference value, and obtains a second control result by performing closed-loop control through the midpoint potential balance loop based on the upper capacitor voltage value and the lower capacitor voltage value, and obtains a first modulation wave and a second modulation wave based on the first control result and the second control result.

[0089] Specifically, the modulation wave generation unit 12 includes:

[0090] The first control result acquisition module 121 inputs the difference between the output voltage reference value and the output voltage value into the PI controller in the output voltage loop, and controls the output of the first control result through the PI controller;

[0091] The second control result acquisition module 122 inputs the difference between the upper capacitor voltage value and the lower capacitor voltage value into the PI controller in the midpoint potential balance loop, and outputs the second control result through the PI controller.

[0092] Modulation wave acquisition module 123: The sum of the first control result and the second control result is used as the first modulation wave, and the difference between the first control result and the second control result is used as the second modulation wave.

[0093] The switching control unit 13 compares the first modulation wave and the second modulation wave with the first carrier wave and the second carrier wave, respectively, and controls the switching transistor of the equivalent circuit through the first driving signal and the second driving signal according to the comparison result.

[0094] Specifically, the switching control unit 13 includes:

[0095] First drive signal control module 131: When the first modulated wave is greater than or equal to the first carrier wave, the first drive signal controls the switch to turn on; when the first modulated wave is less than the first carrier wave, the first drive signal controls the switch to turn off.

[0096] Second drive signal control module 132: When the second modulated wave is greater than or equal to the second carrier wave, the second drive signal controls the switch to turn on; when the second modulated wave is less than the second carrier wave, the second drive signal controls the switch to turn off.

[0097] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0098] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A control method of a Vienna rectifier, characterized by, A control method for controlling switch tubes of a Vienna rectifier when direct current is input into the Vienna rectifier, the control method comprising: a voltage acquisition step of establishing an equivalent circuit when direct current is input into the Vienna rectifier, and acquiring an output voltage value, an output voltage reference value, an upper capacitor voltage value and a lower capacitor voltage value of the equivalent circuit; a modulation wave generation step of obtaining a first control result through closed-loop control of an output voltage loop according to the output voltage value and the output voltage reference value, obtaining a second control result through closed-loop control of a midpoint potential balance loop according to the upper capacitor voltage value and the lower capacitor voltage value, and obtaining a first modulation wave and a second modulation wave according to the first control result and the second control result; a switch tube control step of comparing the first modulation wave and the second modulation wave with a first carrier wave and a second carrier wave respectively, and controlling the switch tubes of the equivalent circuit through a first drive signal and a second drive signal according to a comparison result; wherein the modulation wave generation step comprises: a first control result obtaining step of inputting a difference between the output voltage reference value and the output voltage value into a PI controller in the output voltage loop, and controlling the PI controller to output the first control result; a second control result obtaining step of inputting a difference between the upper capacitor voltage value and the lower capacitor voltage value into a PI controller in the midpoint potential balance loop, and controlling the PI controller to output the second control result; summing the first control result and the second control result as the first modulation wave, and subtracting the first control result from the second control result as the second modulation wave.

2. The control method according to claim 1, characterized by, The switch tube control step comprises: a first drive signal control step of controlling the switch tubes to turn on through the first drive signal when the first modulation wave is greater than or equal to the first carrier wave, and controlling the switch tubes to turn off through the first drive signal when the first modulation wave is less than the first carrier wave; a second drive signal control step of controlling the switch tubes to turn on through the second drive signal when the second modulation wave is greater than or equal to the second carrier wave, and controlling the switch tubes to turn off through the second drive signal when the second modulation wave is less than the second carrier wave.

3. The control method according to claim 1, characterized by, The switch tube control step further comprises: if a positive pole of the input direct current is connected to a first bridge arm of the equivalent circuit, the first drive signal controls turn-on and turn-off of first and second switch tubes of the equivalent circuit, and the second drive signal controls turn-on and turn-off of third and fourth switch tubes of the equivalent circuit; if a positive pole of the input direct current is connected to a second bridge arm of the equivalent circuit, the first drive signal controls turn-on and turn-off of the third and fourth switch tubes of the equivalent circuit, and the second drive signal controls turn-on and turn-off of the first and second switch tubes of the equivalent circuit.

4. The control method according to claim 1, characterized by, The first carrier wave and the second carrier wave are triangular waves with the same phase and an amplitude of 0 to 1.

5. A control system for a Vienna rectifier for implementing the control method according to any one of claims 1 to 4, characterized in that comprises: a voltage acquisition unit of establishing an equivalent circuit when direct current is input into the Vienna rectifier, and acquiring an output voltage value, an output voltage reference value, an upper capacitor voltage value and a lower capacitor voltage value of the equivalent circuit; The modulation wave generating unit obtains a first control result by closed-loop control of an output voltage loop according to the output voltage value and an output voltage reference value, obtains a second control result by closed-loop control of a midpoint potential balance loop according to the upper capacitor voltage value and the lower capacitor voltage value, and obtains a first modulation wave and a second modulation wave according to the first control result and the second control result; The switch control unit compares the first modulation wave and the second modulation wave with a first carrier wave and a second carrier wave respectively, and controls the switch of the equivalent circuit through a first drive signal and a second drive signal according to a comparison result; The modulation wave generating unit comprises: A first control result obtaining module inputs a difference between the output voltage reference value and the output voltage value into a PI controller in the output voltage loop, and controls the PI controller to output a first control result; A second control result obtaining module inputs a difference between the upper capacitor voltage value and the lower capacitor voltage value into a PI controller in the midpoint potential balance loop, and controls the PI controller to output a second control result; A modulation wave obtaining module takes a sum of the first control result and the second control result as the first modulation wave, and takes a difference between the first control result and the second control result as the second modulation wave.

6. The control system of claim 5, wherein, The switch control unit comprises: A first drive signal control module controls the switch to be turned on through the first drive signal when the first modulation wave is greater than or equal to the first carrier wave, and controls the switch to be turned off through the first drive signal when the first modulation wave is less than the first carrier wave; A second drive signal control module controls the switch to be turned on through the second drive signal when the second modulation wave is greater than or equal to the second carrier wave, and controls the switch to be turned off through the second drive signal when the second modulation wave is less than the second carrier wave.

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