A cascaded interleaved totem pole bridgeless PFC device and its control strategy

Abstract

The present invention discloses a cascaded staggered totem pole bridgeless PFC device and its control strategy. The device belongs to the field of power electronics technology. The cascaded staggered totem pole bridgeless PFC device specifically includes 2 power frequency bridge arms, 4 high frequency bridge arms, 2 boost inductors and 2 filter capacitors. Among them, the midpoints of the two power frequency bridge arms are respectively connected to the two ends of the AC power supply, and the high frequency bridge arms between the upper and lower paths are connected through the boost inductor. A control strategy proposed based on this device includes two PWM modulation strategies: voltage equalization control, current equalization control, and carrier phase shift and level shift. The technical effects of reducing inductance volt-seconds, reducing input current ripple and suppressing common mode noise can be achieved; and when the capacitance values ​​of the two output filter capacitors are not equal or the load sizes are inconsistent, the circuit can still achieve the control goals of equal output voltage and equal current.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and relates to a PFC circuit based on a multi-level technology, and in particular to a cascaded interleaved totem pole bridgeless PFC device and a control strategy thereof. Background Art

[0002] With the continuous development of power electronics technology and semiconductor device technology, the research on PFC topology circuits has begun to deepen in the direction of high efficiency and high power density. Magnetic components are one of the important factors that determine the power density of PFC circuits. The inductor volt-second of traditional two-level PFC circuits is large, resulting in a large volume of the circuit occupied by the inductor. This has become the main reason for limiting the improvement of the power density of traditional two-level PFC circuits.

[0003] With the development of multi-level technology, the problem of large inductor volume in traditional two-level PFC has been effectively solved. Multi-level technology can not only reduce the level jump size of the inductor, but also increase the equivalent switching frequency of the system, thereby greatly reducing the volume of the inductor. At present, the cascaded totem pole bridgeless PFC circuit based on multi-level technology can increase the power density to 1000W / in 3 , while the peak efficiency is greater than 99%, but there are also serious common-mode problems and circulating current problems. These problems will not only interfere with the normal operation of other electronic devices, but also reduce the stability of the circuit itself. Therefore, it is very meaningful to study how to solve the common-mode problem of the cascaded totem pole bridgeless PFC and improve its power density. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention proposes a cascaded interleaved totem pole bridgeless PFC device and a control strategy thereof, which can improve the power density of the three-level cascaded interleaved totem pole bridgeless PFC while solving the common mode problem of the three-level cascaded interleaved totem pole bridgeless PFC.

[0005] A cascade interleaved totem pole bridgeless PFC device comprises six bridge arms forming two branches, two boost inductors connected in parallel between the two branches, two filter capacitors and two load resistors.

[0006] One of the branches includes a first power frequency bridge arm, a second high frequency bridge arm, and a third high frequency bridge arm, and the other branch includes a fourth power frequency bridge arm, a fifth high frequency bridge arm, and a sixth high frequency bridge arm.

[0007] Each bridge arm includes a first switch tube and a second switch tube, and the source of the first switch tube is connected to the drain of the second switch tube. In one branch, the drain of the first switch tube of the power frequency bridge arm is connected to the drain of the first switch tube of the high frequency bridge arm, and the source of the second switch tube is connected to the source of the second switch tube of the high frequency bridge arm.

[0008] The positive and negative polarity ends of the AC power supply are connected to the source electrodes of the first switch tubes of the first power frequency bridge arm and the fourth power frequency bridge arm respectively. The first boost inductor is connected in parallel between the source electrodes of the first switch tubes of the second high frequency bridge arm and the fifth high frequency bridge arm. The second boost inductor is connected in parallel between the source electrodes of the first switch tubes of the third high frequency bridge arm and the fourth high frequency bridge arm.

[0009] Two ends of the filter capacitor are respectively connected to the drain of the first switch tube and the source of the second switch tube in the branch, and the load resistor is connected in parallel to the two ends of the filter capacitor.

[0010] Preferably, the switch tube in the power frequency bridge arm is a Si MOSFET tube, a SiC MOSFET tube or a GaN tube.

[0011] Preferably, the switch tube in the high-frequency bridge arm is a SiC MOSFET tube or a GaN tube.

[0012] A control strategy for a cascaded interleaved totem pole bridgeless PFC device specifically comprises the following steps:

[0013] Step 1: In the cascaded interleaved totem pole bridgeless PFC device, currents IL1 and IL2 flowing through the first and second boost inductors, voltage values ​​VC1 and VC2 across two filter capacitors, and an instantaneous voltage value VA and a phase PH of the AC power source are collected.

[0014] Step 2: Compare the instantaneous voltage value VA of the AC power supply with the zero value to generate the switch control signal V of the first and fourth power frequency bridge arms. control :

[0015]

[0016] Step 3: After adding the voltage values ​​VC1 and VC2, subtract the voltage from the first reference voltage V0, and then pass the calculation result through the PI regulator and multiply it by the instantaneous phase PH of the AC power supply to obtain a reference inductor current signal.

[0017] Step 4: subtract the reference inductor current signal obtained in step 3 from the current IL2, and then pass the calculation result through the PI regulator, and then compare it with the second carrier and the fourth carrier respectively to obtain the switch tube control signals of the third high-frequency bridge arm and the sixth high-frequency bridge arm.

[0018] Step 5: Subtract the voltage value VC1 from the second reference voltage V1, and then pass the calculation result through the PI regulator and multiply it by the instantaneous phase PH of the AC power supply to obtain a voltage correction signal.

[0019] Step 6: Subtract the reference inductor current signal obtained in step 3 from the current IL1, and then pass the calculation result through the PI regulator, and then subtract and add it from the voltage correction signal obtained in step 5, and then compare the calculation result with the first carrier and the third carrier respectively to obtain the switch tube control signals of the second high-frequency bridge arm and the fifth high-frequency bridge arm.

[0020] The first to fourth carrier waves are triangular waves, the peak values ​​are equal to the peak-to-peak values, and the phases of the first to fourth carrier waves differ by 90° respectively.

[0021] Preferably, the first to fourth carrier waves are rectangular waves.

[0022] Preferably, the peak values ​​of the first and second carriers are equal to the peak-to-peak values, the peak values ​​of the third and fourth carriers are equal to the peak-to-peak values, the peak value of the first carrier is twice the peak value of the third carrier, and the phases of the first and third carriers are equal, the phase difference between the first and second carriers is 180°, and the phases of the second and fourth carriers are equal.

[0023] The present invention has the following beneficial effects:

[0024] 1. The two ends of the AC power supply are connected to the midpoints of the two power frequency bridge arms respectively, and the high frequency bridge arms of the upper and lower branches are connected through a boost inductor. This structure effectively suppresses the common mode noise and circulating current of the cascaded totem pole bridgeless PFC, thereby reducing the volume of the common mode filter.

[0025] 2. The cascaded high-frequency bridge arm adopts the control method of carrier phase shift or level shift, which can reduce the ripple factor of the input current, reduce the THD of the input current and improve the PF value of the circuit; using carrier phase shift or level shift control can increase the equivalent switching frequency of the system, reduce the volt-second of the inductor, and thus reduce the volume of the inductor;

[0026] 3. The control strategy includes voltage equalization control and current equalization control. When there are differences in the capacitance of the two output filter capacitors or the load size, the circuit will automatically adjust to a steady state where the two output voltages are equal through the control loop. This control strategy enhances the stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of a cascaded interleaved totem pole bridgeless PFC device and its control strategy.

[0028] Figure 2 is the current waveform flowing through the boost inductor in Example 1;

[0029] Figure 3 is the voltage waveform across the filter capacitor in Example 1;

[0030] Figure 4is the current waveform flowing through the boost inductor in Example 3;

[0031] Figure 5 : is the voltage waveform across the filter capacitor in Example 3. DETAILED DESCRIPTION

[0032] The present invention will be further explained below with reference to the accompanying drawings;

[0033] like Figure 1 As shown, a cascaded interleaved totem pole bridgeless PFC device includes six bridge arms forming two branches, two boost inductors, two filter capacitors and two load resistors.

[0034] Among them, the first power frequency bridge arm includes switch tubes S1 and S2, the second high frequency bridge arm includes switch tubes S3 and S4, the third high frequency bridge arm includes switch tubes S5 and S6, the fourth power frequency bridge arm includes switch tubes S7 and S8, the fifth high frequency bridge arm includes switch tubes S9 and S10, and the sixth high frequency bridge arm includes switch tubes S11 and S12. The drains of switch tubes S1, S3, and S5 are connected, and the sources are connected to the drains of switch tubes S2, S4, and S6 respectively; the sources of switch tubes S2, S4, and S6 are connected. The drains of switch tubes S7, S9, and S11 are connected, and the sources are connected to the drains of switch tubes S8, S10, and S12 respectively; the sources of switch tubes S8, S10, and S12 are connected.

[0035] The sources of the switch tubes S1 and S7 are connected to the positive and negative polarity ends of the AC power supply respectively. The sources of the switch tubes S3 and S9 are connected to the two ends of the first boost inductor L1 respectively. The sources of the switch tubes S5 and S11 are connected to the two ends of the second boost inductor L2 respectively.

[0036] One end of the first filter inductor C1 and the first resistor R1 is connected to the drain of the switch tubes S1, S3, and S5, and the other end is connected to the source of the switch tubes S2, S4, and S6. One end of the second filter inductor C2 and the second resistor R2 is connected to the drain of the switch tubes S7, S9, and S11, and the other end is connected to the source of the switch tubes S8, S10, and S12.

[0037] A control strategy for a cascaded interleaved totem pole bridgeless PFC device specifically comprises the following steps:

[0038] Step 1: In the cascaded interleaved totem pole bridgeless PFC device, currents IL1 and IL2 flowing through the first and second boost inductors, voltage values ​​VC1 and VC2 across two filter capacitors, and an instantaneous voltage value VA and a phase PH of the AC power source are collected.

[0039] Step 2: Compare the instantaneous voltage value VA of the AC power supply with the zero value to generate the switch control signal V of the first and fourth power frequency bridge arms. control :

[0040]

[0041] Step 3: After adding the voltage values ​​VC1 and VC2, subtract the voltage from the first reference voltage V0, and then pass the calculation result through the PI regulator and multiply it by the instantaneous phase PH of the AC power supply to obtain a reference inductor current signal.

[0042] Step 4: subtract the reference inductor current signal obtained in step 3 from the current IL2, and then pass the calculation result through the PI regulator, and then compare it with the second carrier and the fourth carrier respectively to obtain the switch tube control signals of the third high-frequency bridge arm and the sixth high-frequency bridge arm.

[0043] Step 5: Subtract the voltage value VC1 from the second reference voltage V1, and then pass the calculation result through the PI regulator and multiply it by the instantaneous phase PH of the AC power supply to obtain a voltage correction signal.

[0044] Step 6: Subtract the reference inductor current signal obtained in step 3 from the current IL1, and then pass the calculation result through the PI regulator, and then subtract and add it from the voltage correction signal obtained in step 5, and then compare the calculation result with the first carrier and the third carrier respectively to obtain the switch tube control signals of the second high-frequency bridge arm and the fifth high-frequency bridge arm.

[0045] Example 1

[0046] In this embodiment, carrier phase shift control is adopted, and the first to fourth carriers are all triangular waves with an amplitude of 1, and the phases differ by 90° respectively, that is, the phases of the first to fourth carriers are 0°, 90°, 180°, and 270° respectively.

[0047] In the positive half cycle of the AC power supply, the switch tube S1 and the switch tube S8 are always turned on, and the switch tube S2 and the switch tube S7 are always turned off.

[0048] like Figure 2 , Figure 3 As shown, when the switch tubes S3, S10, S6, and S12 are turned on and the switch tubes S5, S11, S4, and S9 are turned off, the AC power supply forms a loop through the switch tubes S1, S3, S10, S8, and the first boost inductor L1 and charges the first boost inductor L1, and the current IL1 flowing through the first boost inductor L1 increases with a certain slope; and the boost inductor L2 forms a loop and discharges through S12, S8, the AC power supply, the switch tube S1, the first filter capacitor C1, and the switch tube S6, and the current IL2 flowing through the second boost inductor L2 decreases with a certain slope.

[0049] When the switches S3, S5, S12, and S9 are turned on and the switches S10, S4, S6, and S11 are turned off, the first boost inductor L1 is discharged through the loop formed by the switch S9, the second filter capacitor C2, the switch S8, the AC power supply, the switch S1, and the switch S3, and the current IL1 flowing through the first boost inductor L1 decreases at a certain slope. The AC power supply charges the second boost inductor L2 through the loop formed by the switch S1, S5, the second boost inductor L2, the switch S12, and S8, and the current IL2 flowing through the second boost inductor L2 increases at a certain slope.

[0050] When the switches S3, S10, S5, and S11 are turned on and the switches S4, S9, S6, and S12 are turned off, the AC power supply charges the first boost inductor L1 through the loop formed by the switches S1, S3, S10, S8, and the first boost inductor L1, and the current IL1 flowing through the first boost inductor L1 increases with a certain slope; the second boost inductor L2 discharges through the loop formed by the switches S1, S5, the AC power supply, the switch S11, the second filter capacitor C2, and the switch S8, and the current IL2 flowing through the second boost inductor L2 decreases with a certain slope.

[0051] When the switch tubes S4, S10, S5, and S12 are turned on and the switch tubes S3, S9, S6, and S11 are turned off, the first boost inductor L1 is discharged through the loop formed by the switch tubes S10, S8, the AC power supply, S1, the first filter capacitor C1, and the switch tube S4, and the current IL1 flowing through the first boost inductor L1 decreases at a certain slope. The AC power supply charges the second boost inductor L2 through the loop formed by the switch tube S5, the second boost inductor L2, the switch tubes S12, and S8, and the current of the second boost inductor L2 increases at a certain slope.

[0052] Example 2

[0053] In this embodiment, carrier phase shift control is adopted, the first to fourth carriers are all rectangular waves with an amplitude of 1, and the phases of the first to fourth carriers are 0°, 90°, 180°, and 270°, respectively.

[0054] Example 3

[0055] In this embodiment, level shift control is adopted, the first and second carriers are triangular waves with an amplitude of 2, the third and fourth carriers are triangular waves with an amplitude of 1, the phases of the first and third carriers are 0°, and the phases of the second and fourth carriers are 180°.

[0056] The current waveform flowing through the boost inductor and the voltage waveform across the filter capacitor are as follows: Figure 4 , Figure 5 shown.

[0057] Example 4

[0058] In this embodiment, level shift control is adopted, the first and second carriers are rectangular waves with an amplitude of 2, the third and fourth carriers are rectangular waves with an amplitude of 1, the phases of the first and third carriers are 0°, and the phases of the second and fourth carriers are 180°.

[0059] The two control methods in the above embodiments can achieve the technical effects of reducing inductance volt-seconds, reducing input current ripple and suppressing common-mode noise; and when the capacitance values ​​of the two output filter capacitors are not equal or the load sizes are inconsistent, the circuit can still achieve the control goals of equal output voltage and equal current.

Claims

1. A cascaded interleaved totem pole bridgeless PFC device, characterized in that: It includes 6 bridge arms forming two branches, 2 boost inductors connected in parallel between the two branches, 2 filter capacitors, and 2 load resistors; One of the branches includes a first power frequency bridge arm, a second high frequency bridge arm, and a third high frequency bridge arm, and the other branch includes a fourth power frequency bridge arm, a fifth high frequency bridge arm, and a sixth high frequency bridge arm; Each bridge arm includes a first switch tube and a second switch tube, and the source of the first switch tube is connected to the drain of the second switch tube; in one branch, the drain of the first switch tube of the power frequency bridge arm is connected to the drain of the first switch tube of the high frequency bridge arm, and the source of the second switch tube is connected to the source of the second switch tube of the high frequency bridge arm; The positive and negative polarity ends of the AC power supply are respectively connected to the source electrodes of the first switch tubes of the first power frequency bridge arm and the fourth power frequency bridge arm; the first boost inductor is connected in parallel between the source electrodes of the first switch tubes of the second high frequency bridge arm and the fifth high frequency bridge arm; the second boost inductor is connected in parallel between the source electrodes of the first switch tubes of the third high frequency bridge arm and the fourth high frequency bridge arm; Two ends of the filter capacitor are respectively connected to the drain of the first switch tube and the source of the second switch tube in the branch, and the load resistor is connected in parallel to the two ends of the filter capacitor.

2. The cascaded interleaved totem pole bridgeless PFC device according to claim 1, characterized in that: The switch tube in the industrial frequency bridge arm is selected from SiMOSFEET tube, SiC MOSFET tube or GaN tube.

3. The cascaded interleaved totem pole bridgeless PFC device according to claim 1, characterized in that: The switch tube in the high-frequency bridge arm is made of SiC MOSFET tube or GaN tube.

4. A control strategy for a cascaded interleaved totem pole bridgeless PFC device, characterized in that: The method is used to control the cascaded interleaved totem pole bridgeless PFC device as claimed in any one of claims 1 to 3, specifically comprising the following steps: Step 1, collecting the currents IL1 and IL2 flowing through the first and second boost inductors, the voltage values ​​VC1 and VC2 across the two filter capacitors, and the instantaneous voltage value VA and phase PH of the AC power supply; Step 2: Compare the instantaneous voltage value VA of the AC power supply with the zero value to generate the switch control signal V of the first and fourth power frequency bridge arms. control : Step 3, after adding the voltage values ​​VC1 and VC2, subtract the voltage from the first reference voltage V0, and then pass the calculation result through the PI regulator and multiply it by the instantaneous phase PH of the AC power supply to obtain a reference inductor current signal; Step 4, subtract the reference inductor current signal obtained in step 3 from the current IL2, and then pass the calculation result through the PI regulator, and then compare it with the second carrier and the fourth carrier respectively to obtain the switch tube control signals of the third high-frequency bridge arm and the sixth high-frequency bridge arm; Step 5: Subtract the voltage value VC1 from the second reference voltage V1, and then pass the calculation result through the PI regulator and multiply it by the instantaneous phase PH of the AC power supply to obtain a voltage correction signal; Step 6: Subtract the reference inductor current signal obtained in step 3 from the current IL1, and then pass the calculation result through the PI regulator, and then subtract and add the voltage correction signal obtained in step 5 respectively, and then compare the calculation result with the first carrier and the third carrier respectively to obtain the switch tube control signals of the second high-frequency bridge arm and the fifth high-frequency bridge arm; The first to fourth carrier waves are triangular waves, the peak values ​​are equal to the peak-to-peak values, and the phases of the first to fourth carrier waves differ by 90° respectively.

5. A control strategy for a cascaded interleaved totem pole bridgeless PFC device as claimed in claim 4, characterized in that: The first to fourth carrier waves are rectangular waves.

6. A control strategy for a cascaded interleaved totem pole bridgeless PFC device as claimed in claim 4 or 5, characterized in that: The peak values ​​of the third and fourth carriers are equal to the peak-to-peak values, and the peak value of the first carrier is twice the peak value of the third carrier; and the phases of the first and third carriers are equal, the phase difference between the first and second carriers is 180°, and the phases of the second and fourth carriers are equal.

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