Control method for equalizing positive and negative voltages of ViennaPFC (Power Factor Correction) topology

Abstract

The invention discloses a ViennaPFC (Power Factor Correction) topology positive and negative voltage equalizing control method, which comprises the following steps of: acquiring three-phase voltage, calculating a sector in which the three-phase voltage is positioned, acquiring output end positive voltage end voltage and output end negative voltage end voltage, and comparing the output end positive voltage end voltage and the output end negative voltage end voltage. A state flag bit is set according to the comparison value of the output end positive voltage end voltage and the output end negative voltage end voltage, and PWM drive of the three-phase circuit is controlled and adjusted according to the sector where the three-phase voltage is located and the state flag bit. According to the voltage-sharing adjusting method, the charging and discharging action time of the capacitors connected with the output end positive-voltage end voltage and the output end negative-voltage end voltage is changed from the energy flow level of the main topology, dynamic voltage-sharing adjustment of the output end positive-voltage end voltage and the output end negative-voltage end voltage is achieved, the problem that the Vienna topology is difficult to control that PFC output voltage is unbalanced is solved, and the power factor correction effect of the Vienna topology is improved. And the product reliability and stability are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of Vienna rectifiers, and more specifically, to a control method for equalizing positive and negative voltages in a Vienna PFC topology. Background Art

[0002] The Vienna PFC (power factor correction) topology, also known as the Vienna rectifier, is a three-phase bridgeless power factor correction circuit that is widely used in applications that require high efficiency, high power factor, and low harmonic distortion. The Vienna PFC topology is particularly suitable for applications with higher input voltages, such as industrial power supplies, uninterruptible power supplies (UPS), motor drives, and renewable energy systems. The Vienna PFC topology is designed for three-phase AC power and can effectively convert three-phase AC power into stable DC power. Unlike the traditional diode rectifier bridge, the Vienna PFC topology does not use a diode bridge, but is directly connected to the AC input through a switching element (such as a MOSFET or IGBT), which reduces the conduction loss of the diode and improves efficiency.

[0003] There is a difficulty in controlling the unbalanced output voltage of the Vienna PFC topology. The conventional positive and negative voltage equalization control methods of the Vienna PFC topology are the vector SVPWM control strategy and the single cycle / average current method. The vector SVPWM control strategy is to change the action time of the small sector, and the single cycle / average current method is to change the current reference value of the positive and negative cycles. The commonality of the two methods is to detect the difference between the positive voltage terminal voltage (VP) and the negative voltage terminal voltage (VN) at the output end of the topology, and use this difference as the reference for the PID current inner loop, thereby realizing PID control and adjusting the PWM waveform or current command. In general, the above-mentioned voltage equalization adjustment method is very effective when there is a heavy load at the output end and there is a charging and discharging circuit for the voltage equalization capacitor.

[0004] However, in actual product applications, when the output end is unloaded (no-load) and the voltage-equalizing capacitor is charged and discharged, or when the voltage feedback and current feedback sampling of the main circuit sampling elements are disturbed and abnormal, the above-mentioned vector SVPWM control strategy or single-cycle / average current method is used. This midpoint balance control method will have the risk of voltage-equalizing out of control, and may result in poor midpoint voltage balance control, damage to the power tube, breakdown of the output filter capacitor, etc.

[0005] When the output end is unloaded (no-load) and the voltage-equalizing capacitor is charged and discharged, the energy is discharged only by the filter capacitor's own ESR (equivalent series resistance), and the voltage-equalizing regulation ability is limited, resulting in voltage-equalizing regulation failure. In addition, when the main circuit sampling element is disturbed, resulting in abnormal voltage feedback and current feedback sampling, the PID controller calculates based on the wrong data, and the control logic of the current loop and the midpoint voltage loop deviates, resulting in errors in the conventional idealized midpoint voltage balance PID regulation calculation, and the PID controller output generates positive feedback, which incorrectly increases the charging or discharging of a capacitor, and ultimately makes the imbalance between the positive voltage terminal (VP) and the negative voltage terminal (VN) at the output terminal even worse. Summary of the invention

[0006] In order to realize positive and negative voltage balancing when the output end of the Vienna PFC topology charges and discharges the balancing capacitor without load or when the main circuit sampling element is disturbed, the present invention provides a control method for positive and negative voltage balancing of the Vienna PFC topology.

[0007] The technical solution of the present invention is as follows:

[0008] A control method for equalizing positive and negative voltages in Vienna PFC topology.

[0009] Collect three-phase voltage and calculate the sector where the three-phase voltage is located.

[0010] Collect the positive voltage at the output end and the negative voltage at the output end, compare the positive voltage at the output end and the negative voltage at the output end, and set the status flag according to the comparison value between the positive voltage at the output end and the negative voltage at the output end.

[0011] The PWM drive of the three-phase circuit is controlled and adjusted according to the sector where the three-phase voltage is located and the status flag.

[0012] In the above-mentioned control method for equalizing positive and negative voltages of a Vienna PFC topology, the status flag is a variable preset by the main controller for control; the main controller presets an allowable bias value; the main controller collects and obtains the positive voltage terminal voltage of the output end and the negative voltage terminal voltage of the output end, when the positive voltage terminal voltage of the output end is greater than the sum of the negative voltage terminal voltage of the output end and the allowable bias value, the main controller assigns a status flag bit value of 1, and when the negative voltage terminal voltage of the output end is greater than the sum of the positive voltage terminal voltage of the output end and the allowable bias value, the main controller assigns a status flag bit value of 0.

[0013] In the above-mentioned control method for equalizing positive and negative voltages of a Vienna PFC topology, the main controller monitors the positive voltage at the output end and the negative voltage at the output end in real time. When the bias voltage between the positive voltage at the output end and the negative voltage at the output end exceeds the allowable bias value, the PWM drive signal of the corresponding sector is turned off, so that the charging circuit of the output capacitor connected to the positive voltage at the output end or the negative voltage at the output end of the corresponding power tube is disconnected.

[0014] The above-mentioned control method for balancing positive and negative voltages of Vienna PFC topology has a sector distribution as follows:

[0015] (1) The three-phase voltages are all on the positive half axis, and 60°-120° is sector A;

[0016] (2) The three-phase voltages are all in the positive half axis, 180°-240° is sector B;

[0017] (3) The three-phase voltages are all in the positive half axis, 300°-360° is the C sector;

[0018] (4) The three-phase voltages are all in the negative half axis, 240°-300° is the D sector;

[0019] (5) The three-phase voltages are all in the negative half axis, 120°-180° is the E sector;

[0020] (6) The three-phase voltages are all in the negative half axis, and 0°-60° is the F sector.

[0021] Furthermore, when the main controller determines that the voltage at the negative voltage terminal of the output end is greater than the sum of the voltage at the positive voltage terminal of the output end and the allowable bias value, the main controller executes a first voltage equalizing drive action; when the voltage at the positive voltage terminal of the output end is greater than the sum of the voltage at the negative voltage terminal of the output end and the allowable bias value, the main controller executes a second voltage equalizing drive action.

[0022] Furthermore, the first voltage-balanced driving action is:

[0023] When the three-phase voltages are all in sector A, the PWM drive signal of the power tube connected to the first phase voltage is turned off, the PWM drive signal of the power tube connected to the second phase voltage is turned on, and the PWM drive signal of the power tube connected to the third phase voltage is turned on;

[0024] When the three-phase voltages are all in sector B, the PWM drive signal of the power tube connected to the first phase voltage is turned on, the PWM drive signal of the power tube connected to the second phase voltage is turned off, and the PWM drive signal of the power tube connected to the third phase voltage is turned off;

[0025] When the three-phase voltages are all in sector C, the PWM drive signal for the power tube connected to the first phase voltage is turned on, the PWM drive signal for the power tube connected to the second phase voltage is turned on, and the PWM drive signal for the power tube connected to the third phase voltage is turned off.

[0026] Furthermore, the second voltage-balanced driving action is:

[0027] When the three-phase voltages are all in the D sector, the PWM drive signal of the power tube connected to the first phase voltage is turned off, the PWM drive signal of the power tube connected to the second phase voltage is turned on, and the PWM drive signal of the power tube connected to the third phase voltage is turned on;

[0028] When the three-phase voltages are all in sector E, the PWM drive signal of the power tube connected to the first phase voltage is turned on, the PWM drive signal of the power tube connected to the second phase voltage is turned off, and the PWM drive signal of the power tube connected to the third phase voltage is turned on;

[0029] When the three-phase voltages are all in sector F, the PWM drive signal for the power tube connected to the first phase voltage is turned on, the PWM drive signal for the power tube connected to the second phase voltage is turned on, and the PWM drive signal for the power tube connected to the third phase voltage is turned off.

[0030] In the above-mentioned control method for equalizing positive and negative voltages of a Vienna PFC topology, the three-phase voltages are connected to the common mode voltage via different power tubes, and capacitors are provided between the power voltage and the negative voltage terminal voltage of the output end and the positive voltage terminal voltage of the output end.

[0031] Furthermore,

[0032] The Vienna PFC topology circuit structure is shown below.

[0033] The first phase voltage is connected to the anode of the first diode, the anode of the seventh diode, the cathode of the ninth diode, and the cathode of the fourth diode respectively through the first inductor and the first resistor.

[0034] The cathode of the seventh diode is connected to the cathode of the eighth diode and the drain of the first power tube respectively.

[0035] The anode of the ninth diode is connected to the source of the first power tube and the anode of the tenth diode respectively.

[0036] The second phase voltage is connected to the anode of the second diode, the anode of the eleventh diode, the cathode of the thirteenth diode, and the cathode of the fifth diode respectively through the second inductor and the second resistor.

[0037] The cathode of the eleventh diode is connected to the cathode of the twelfth diode and the drain of the second power tube respectively.

[0038] The anode of the thirteenth diode is connected to the anode of the fourteenth diode and the source of the second power tube respectively.

[0039] The third phase voltage is connected to the anode of the third diode, the anode of the fifteenth diode, the cathode of the seventeenth diode, and the cathode of the sixth diode respectively via the third inductor and the third resistor.

[0040] The cathode of the fifteenth diode is connected to the drain of the third power tube and the cathode of the sixteenth diode respectively.

[0041] The anode of the seventeenth diode is connected to the source of the third power tube and the anode of the eighteenth diode respectively.

[0042] The cathode of the first diode, the cathode of the second diode, and the cathode of the third diode are all connected to one end of the first capacitor and the positive power supply voltage.

[0043] The anode of the fourth diode, the anode of the fifth diode, and the anode of the sixth diode are connected to the other end of the second capacitor and the negative power supply voltage respectively.

[0044] The anode of the eighth diode, the cathode of the tenth diode, the anode of the twelfth diode, the cathode of the fourteenth diode, the anode of the sixteenth diode, and the cathode of the eighteenth diode are all connected to the common mode voltage, the other end of the first capacitor, and one end of the second capacitor.

[0045] Furthermore, the main controller is respectively connected to the first phase voltage, the second phase voltage, and the third phase voltage to obtain the three-phase voltage, connected to the topological circuit structure positive power supply voltage to obtain the output positive voltage, and connected to the topological circuit structure negative power supply voltage to obtain the output negative voltage.

[0046] The present invention according to the above scheme has the beneficial effect that:

[0047] The voltage equalization regulation method of the present invention changes the charging and discharging time of the capacitors respectively connected to the positive voltage terminal of the output end and the negative voltage terminal of the output end from the energy flow level of the main topology, thereby realizing dynamic voltage equalization regulation of the positive voltage terminal of the output end and the negative voltage terminal of the output end, solving the control difficulty of the unbalanced PFC output voltage in the Vienna topology and improving the product reliability and stability.

[0048] The method of the present invention determines the distribution interval of the three-phase power grid distribution sector and compares the difference between the positive voltage at the output end and the negative voltage at the output end. The method actively turns off the main power tube PWM drive signal of the corresponding phase voltage to achieve voltage equalization regulation. The calculation is simple and easy, which improves the code execution efficiency of the main control.

[0049] The present invention does not adopt the method of changing the output of the current inner loop and indirectly adjusting the midpoint voltage balance, removes the dependence on the accuracy of current feedback sampling, enhances the anti-interference ability of voltage balancing regulation, and makes the Vienna PFC rectifier have strong grid adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0051] Figure 1 It is a schematic diagram of the judgment process of the present invention.

[0052] Figure 2 This is a schematic diagram of the circuit structure used in the present invention. DETAILED DESCRIPTION

[0053] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0054] A control method for equalizing positive and negative voltages in Vienna PFC topology.

[0055] Collect three-phase voltage and calculate the sector where the three-phase voltage is located.

[0056] Collect the positive voltage at the output end and the negative voltage at the output end, compare the positive voltage at the output end and the negative voltage at the output end, and set the status flag (uiVpOverVnFlag) according to the comparison value of the positive voltage at the output end and the negative voltage at the output end.

[0057] The PWM drive of the three-phase circuit is controlled and adjusted according to the sector where the three-phase voltage is located and the status flag.

[0058] The status flag is a variable used for preset control of the main controller; the main controller presets the allowable bias value; the main controller collects and obtains the positive voltage at the output end and the negative voltage at the output end. When the positive voltage at the output end is greater than the sum of the negative voltage at the output end and the allowable bias value, the main controller assigns the status flag bit value to 1; when the negative voltage at the output end is greater than the sum of the positive voltage at the output end and the allowable bias value, the main controller assigns the status flag bit value to 0.

[0059] The main controller presets the allowable bias value to prevent frequent adjustments to the control strategy due to slight voltage differences. Only when the difference between the positive and negative voltages exceeds the allowable bias value will the system make corresponding adjustments, thereby improving the stability of the system, avoiding unnecessary control actions, and reducing system fluctuations and energy losses.

[0060] The existence of the status flag assists the main controller in determining the relationship between positive and negative voltages. When the positive voltage at the output end is larger than the negative voltage at the output end, the status flag is assigned a value of 1. When the negative voltage at the output end is larger than the positive voltage at the output end, the status flag is assigned a value of 0. This clear value helps the main controller to quickly understand the distribution of the output voltage so that it can take corresponding control measures.

[0061] The main controller monitors the positive voltage at the output end and the negative voltage at the output end in real time. When the bias voltage between the positive voltage at the output end and the negative voltage at the output end exceeds the allowable bias value, the PWM drive signal of the corresponding sector is turned off, so that the charging circuit of the output capacitor connected to the positive voltage at the output end or the negative voltage at the output end of the corresponding power tube is disconnected.

[0062] When the main controller detects that the bias voltage of the positive voltage terminal and the negative voltage terminal of the output terminal exceeds the limit, it indicates that the current capacitor charging and discharging situation is abnormal and needs to be adjusted. The key to the adjustment is to find the sector corresponding to the current three-phase voltage state, because each sector is associated with a specific capacitor charging and discharging energy flow. By turning off the PWM drive signal of the sector, the charging circuit of the corresponding power tube to the capacitor can be cut off, the charging and discharging time can be changed, and voltage equalization control can be achieved.

[0063] The sectors are distributed as follows:

[0064] (1) The three-phase voltages are all on the positive half axis, and 60°-120° is sector A;

[0065] (2) The three-phase voltages are all in the positive half axis, 180°-240° is sector B;

[0066] (3) The three-phase voltages are all in the positive half axis, 300°-360° is the C sector;

[0067] (4) The three-phase voltages are all in the negative half axis, 240°-300° is the D sector;

[0068] (5) The three-phase voltages are all in the negative half axis, 120°-180° is the E sector;

[0069] (6) The three-phase voltages are all in the negative half axis, and 0°-60° is the F sector.

[0070] like Figure 1As shown, the main controller determines that when the negative voltage at the output end is greater than the sum of the positive voltage at the output end and the allowable bias value, the main controller executes the first voltage-equalizing driving action; when the positive voltage at the output end is greater than the sum of the negative voltage at the output end and the allowable bias value, the main controller executes the second voltage-equalizing driving action.

[0071] The first voltage-balanced driving action is:

[0072] When the three-phase voltages are all in sector A, the PWM drive signal of the power tube connected to the first phase voltage is turned off, the PWM drive signal of the power tube connected to the second phase voltage is turned on, and the PWM drive signal of the power tube connected to the third phase voltage is turned on;

[0073] When the three-phase voltages are all in sector B, the PWM drive signal of the power tube connected to the first phase voltage is turned on, the PWM drive signal of the power tube connected to the second phase voltage is turned off, and the PWM drive signal of the power tube connected to the third phase voltage is turned off;

[0074] When the three-phase voltages are all in sector C, the PWM drive signal for the power tube connected to the first phase voltage is turned on, the PWM drive signal for the power tube connected to the second phase voltage is turned on, and the PWM drive signal for the power tube connected to the third phase voltage is turned off.

[0075] The second voltage-balanced driving action is:

[0076] When the three-phase voltages are all in the D sector, the PWM drive signal of the power tube connected to the first phase voltage is turned off, the PWM drive signal of the power tube connected to the second phase voltage is turned on, and the PWM drive signal of the power tube connected to the third phase voltage is turned on;

[0077] When the three-phase voltages are all in sector E, the PWM drive signal of the power tube connected to the first phase voltage is turned on, the PWM drive signal of the power tube connected to the second phase voltage is turned off, and the PWM drive signal of the power tube connected to the third phase voltage is turned on;

[0078] When the three-phase voltages are all in sector F, the PWM drive signal for the power tube connected to the first phase voltage is turned on, the PWM drive signal for the power tube connected to the second phase voltage is turned on, and the PWM drive signal for the power tube connected to the third phase voltage is turned off.

[0079] When the voltage at the negative voltage end of the output end is greater than the sum of the voltage at the positive voltage end of the output end and the allowable bias value, the voltage of the capacitor connected to the output end is unbalanced at this time, and the charging process needs to be adjusted to balance the voltage. Targeted changes in PWM drive signals in different sectors are actually regulating the power tube of the corresponding phase, thereby changing the charging time and charging current of the capacitor. For example, in sector A, turn off the PWM drive of the first phase and turn on the PWM drive of the other two phases. This adjusts the charging energy distribution of the capacitor connected to the output end in this sector, prevents the negative voltage end of the output end from overcharging, and guides more energy to flow to the positive voltage end capacitor of the output end, slowly reducing the voltage difference between the two. The different combinations of three-phase PWM drive signals in each sector are all for the purpose of accurately regulating the corresponding three-phase circuit in this sector, giving different charging and discharging energy distribution to the two capacitors connected to the positive voltage end and the negative voltage end of the output end, so as to promote the voltage at the positive voltage end of the output end to rise and tend to be equal to the voltage at the negative voltage end of the output end.

[0080] When the voltage at the positive voltage end of the output end is greater than the sum of the voltage at the negative voltage end of the output end and the allowable bias value, contrary to the above situation, the voltage of the capacitor at the positive voltage end of the output end is now too high. Similarly, the power tube must be regulated by using different switch combinations of the three-phase PWM drive signals of each sector to change the rhythm of capacitor charging. For example, in sector D, turn off the PWM drive of the first phase and turn on the other two phases to allow more charging energy to flow to the capacitor connected to the negative voltage end of the output end and reduce the charging amount of the capacitor connected to the positive voltage end of the output end. After such fine energy flow control, the voltage difference between the negative voltage end of the output end and the positive voltage end of the output end is finally returned to the allowable range, achieving the effect of dynamic voltage balancing.

[0081] The three-phase voltages are connected to the common mode voltage via different power tubes respectively, and capacitors are arranged between the power voltage and the negative voltage terminal voltage of the output end and the positive voltage terminal voltage of the output end.

[0082] like Figure 2 As shown, the ViennaPFC topology circuit structure is shown below.

[0083] The first phase voltage is connected to the anode of the first diode, the anode of the seventh diode, the cathode of the ninth diode, and the cathode of the fourth diode respectively through the first inductor and the first resistor.

[0084] The cathode of the seventh diode is connected to the cathode of the eighth diode and the drain of the first power tube respectively.

[0085] The anode of the ninth diode is connected to the source of the first power tube and the anode of the tenth diode respectively.

[0086] The second phase voltage is connected to the anode of the second diode, the anode of the eleventh diode, the cathode of the thirteenth diode, and the cathode of the fifth diode respectively through the second inductor and the second resistor.

[0087] The cathode of the eleventh diode is connected to the cathode of the twelfth diode and the drain of the second power tube respectively.

[0088] The anode of the thirteenth diode is connected to the anode of the fourteenth diode and the source of the second power tube respectively.

[0089] The third phase voltage is connected to the anode of the third diode, the anode of the fifteenth diode, the cathode of the seventeenth diode, and the cathode of the sixth diode respectively via the third inductor and the third resistor.

[0090] The cathode of the fifteenth diode is connected to the drain of the third power tube and the cathode of the sixteenth diode respectively.

[0091] The anode of the seventeenth diode is connected to the source of the third power tube and the anode of the eighteenth diode respectively.

[0092] The cathode of the first diode, the cathode of the second diode, and the cathode of the third diode are all connected to one end of the first capacitor and the positive power supply voltage.

[0093] The anode of the fourth diode, the anode of the fifth diode, and the anode of the sixth diode are connected to the other end of the second capacitor and the negative power supply voltage respectively.

[0094] The anode of the eighth diode, the cathode of the tenth diode, the anode of the twelfth diode, the cathode of the fourteenth diode, the anode of the sixteenth diode, and the cathode of the eighteenth diode are all connected to the common mode voltage, the other end of the first capacitor, and one end of the second capacitor.

[0095] The main controller is respectively connected to the first phase voltage, the second phase voltage, and the third phase voltage to obtain the three-phase voltage, connected to the positive power supply voltage of the topological circuit structure to obtain the positive voltage of the output end, and connected to the negative power supply voltage of the topological circuit structure to obtain the negative voltage of the output end.

[0096] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A control method for equalizing positive and negative voltages in Vienna PFC topology, characterized in that: Collect three-phase voltage and calculate the sector where the three-phase voltage is located. Collect the positive voltage at the output end and the negative voltage at the output end, compare the positive voltage at the output end and the negative voltage at the output end, and set the status flag bit according to the comparison value between the positive voltage at the output end and the negative voltage at the output end. The PWM drive of the three-phase circuit is controlled and adjusted according to the sector where the three-phase voltage is located and the status flag.

2. According to the control method of the Vienna PFC topology positive and negative voltage equalization described in claim 1, it is characterized in that: The status flag is a variable used by the main controller to preset the control; the main controller presets the allowable bias value; The main controller collects and obtains the positive voltage at the output end and the negative voltage at the output end. When the positive voltage at the output end is greater than the sum of the negative voltage at the output end and the allowable bias value, the main controller assigns a status flag bit value of 1. When the negative voltage at the output end is greater than the sum of the positive voltage at the output end and the allowable bias value, the main controller assigns a status flag bit value of 0.

3. According to the control method of the Vienna PFC topology positive and negative voltage equalization described in claim 1, it is characterized in that: The main controller monitors the positive voltage at the output end and the negative voltage at the output end in real time. When the bias voltage between the positive voltage at the output end and the negative voltage at the output end exceeds the allowable bias value, the PWM drive signal of the corresponding sector is turned off, so that the charging circuit of the output capacitor connected to the positive voltage at the output end or the negative voltage at the output end of the corresponding power tube is disconnected.

4. According to the control method of the Vienna PFC topology positive and negative voltage equalization described in claim 1, it is characterized in that: The sectors are distributed as follows: (1) The three-phase voltages are all in the positive half axis, 60°-120° is sector A; (2) The three-phase voltages are all in the positive half axis, 180°-240° is sector B; (3) The three-phase voltages are all in the positive half axis, 300°-360° is the C sector; (4) The three-phase voltages are all in the negative half axis, 240°-300° is the D sector; (5) The three-phase voltage is in the negative half axis, 120°-180° is the E sector; (6) The three-phase voltages are all in the negative half axis, and 0°-60° is the F sector.

5. A control method for balancing positive and negative voltages in Vienna PFC topology according to claim 4, characterized in that: The main controller determines that when the negative voltage at the output end is greater than the sum of the positive voltage at the output end and the allowable bias value, the main controller executes the first voltage-equalizing driving action; when the positive voltage at the output end is greater than the sum of the negative voltage at the output end and the allowable bias value, the main controller executes the second voltage-equalizing driving action.

6. A control method for balancing positive and negative voltages in Vienna PFC topology according to claim 5, characterized in that: The first voltage-balanced driving action is: When the three-phase voltages are all in sector A, the PWM drive signal of the power tube connected to the first phase voltage is turned off, the PWM drive signal of the power tube connected to the second phase voltage is turned on, and the PWM drive signal of the power tube connected to the third phase voltage is turned on; When the three-phase voltages are all in sector B, the PWM drive signal of the power tube connected to the first phase voltage is turned on, the PWM drive signal of the power tube connected to the second phase voltage is turned off, and the PWM drive signal of the power tube connected to the third phase voltage is turned off; When the three-phase voltages are all in sector C, the PWM drive signal for the power tube connected to the first phase voltage is turned on, the PWM drive signal for the power tube connected to the second phase voltage is turned on, and the PWM drive signal for the power tube connected to the third phase voltage is turned off.

7. A control method for balancing positive and negative voltages in Vienna PFC topology according to claim 5, characterized in that: The second voltage-balanced driving action is: When the three-phase voltages are all in the D sector, the PWM drive signal of the power tube connected to the first phase voltage is turned off, the PWM drive signal of the power tube connected to the second phase voltage is turned on, and the PWM drive signal of the power tube connected to the third phase voltage is turned on; When the three-phase voltages are all in sector E, the PWM drive signal of the power tube connected to the first phase voltage is turned on, the PWM drive signal of the power tube connected to the second phase voltage is turned off, and the PWM drive signal of the power tube connected to the third phase voltage is turned on; When the three-phase voltages are all in sector F, the PWM drive signal for the power tube connected to the first phase voltage is turned on, the PWM drive signal for the power tube connected to the second phase voltage is turned on, and the PWM drive signal for the power tube connected to the third phase voltage is turned off.

8. A control method for balancing positive and negative voltages in Vienna PFC topology according to claim 1, characterized in that: The three-phase voltages are connected to the common mode voltage via different power tubes respectively, and capacitors are arranged between the power voltage and the negative voltage terminal voltage of the output end and the positive voltage terminal voltage of the output end.

9. A control method for balancing positive and negative voltages in Vienna PFC topology according to claim 8, characterized in that: The Vienna PFC topology circuit structure is: The first phase voltage is connected to the anode of the first diode, the anode of the seventh diode, the cathode of the ninth diode, and the cathode of the fourth diode respectively through the first inductor and the first resistor. The cathode of the seventh diode is connected to the cathode of the eighth diode and the drain of the first power tube respectively. The anode of the ninth diode is connected to the source of the first power tube and the anode of the tenth diode respectively. The second phase voltage is connected to the anode of the second diode, the anode of the eleventh diode, the cathode of the thirteenth diode, and the cathode of the fifth diode respectively through the second inductor and the second resistor. The cathode of the eleventh diode is connected to the cathode of the twelfth diode and the drain of the second power tube respectively. The anode of the thirteenth diode is connected to the anode of the fourteenth diode and the source of the second power tube respectively. The third phase voltage is connected to the anode of the third diode, the anode of the fifteenth diode, the cathode of the seventeenth diode, and the cathode of the sixth diode respectively via the third inductor and the third resistor. The cathode of the fifteenth diode is connected to the drain of the third power tube and the cathode of the sixteenth diode respectively. The anode of the seventeenth diode is connected to the source of the third power tube and the anode of the eighteenth diode respectively. The cathode of the first diode, the cathode of the second diode, and the cathode of the third diode are all connected to one end of the first capacitor and the positive power supply voltage. The anode of the fourth diode, the anode of the fifth diode, and the anode of the sixth diode are connected to the other end of the second capacitor and the negative power supply voltage respectively. The anode of the eighth diode, the cathode of the tenth diode, the anode of the twelfth diode, the cathode of the fourteenth diode, the anode of the sixteenth diode, and the cathode of the eighteenth diode are all connected to the common mode voltage, the other end of the first capacitor, and one end of the second capacitor.

10. A control method for equalizing positive and negative voltages in Vienna PFC topology according to claim 9, characterized in that: The main controller is respectively connected to the first phase voltage, the second phase voltage, and the third phase voltage to obtain the three-phase voltage, connected to the positive power supply voltage of the topological circuit structure to obtain the positive voltage of the output end, and connected to the negative power supply voltage of the topological circuit structure to obtain the negative voltage of the output end.

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