A power unit trigger control method suitable for a three-stage staggered totem pole power unit

Abstract

The present application relates to the field of industrial power over Ethernet, and particularly relates to a power unit trigger control method suitable for three-stage staggered totem pole power unit, comprising: setting a count threshold, starting an ADC register in the three-stage staggered totem pole power unit, and outputting a voltage value; inputting the voltage value into three power units in sequence, obtaining inductance values of the power units through corresponding inductance value calculation modules; sorting the inductance values through an inductance value sorting module, and sorting the power units according to the sorting result; counting up by one; comparing the current count in the count register with the set count threshold, if the current count is less than the set count threshold, then reacquiring the input voltage, otherwise setting a duty cycle threshold, calculating the duty cycle according to the current power unit sorting, comparing the duty cycle with the set duty cycle threshold, and controlling the power unit according to the comparison result; the present application has the advantages of stable control and high quality of input current and output voltage.

Description

Technical Field

[0001] This invention relates to power electronics technology and industrial Ethernet power supply, specifically to a power unit triggering control method applicable to a three-level interleaved totem pole power unit. Background Technology

[0002] For high-power applications, a multi-stage interleaved totem-pole power factor corrector (PFC) is required for ease of implementation and cost optimization, with each stage of the interleaved structure called a power unit. A three-stage interleaved totem-pole PFC comprises three power units, each containing one power inductor. For a three-stage interleaved totem-pole PFC, to effectively reduce the ripple of the combined current of the three inductors and the combined current of the three reverse fast recovery diodes, thereby improving the accuracy of the input current and output voltage, ideally, the values ​​of the three inductors should be as close as possible, and the power switch's initial trigger pulse in each power unit should be phase-shifted by 120°, or 1 / 3 of a switching cycle. However, currently, the power inductor deviation rate can reach 10%-15%. This leads to a situation where the triggering sequence of the three power units doesn't match the values ​​of the three power inductors. When the inductance values ​​deviate significantly, it causes fluctuations in the voltage outer loop and current inner loop control output of the three-stage interleaved totem pole PFC, resulting in system instability and severe input current and output voltage ripple. One solution is to use experimental screening to select three power inductors with similar inductance values ​​for use in the same three-stage interleaved totem pole PFC. This method requires additional tedious manual operation and makes it difficult to guarantee very similar inductor values. Another approach is to measure the inductance values ​​online and sort them from largest to smallest. Based on this sorting, the three power units are then reordered, and the triggering and phase shifting sequences are arranged accordingly. This enhances the stability of the control system and improves the accuracy of input current and output voltage. Furthermore, due to the use of continuous conduction mode (CCM) and average current control mode, the average current of the three power inductors is equal, but the ripple magnitude is different. Therefore, when the power inductors are different, the synthesized current ripple is larger, which is not conducive to the suppression of high-order harmonic current on the grid side and the suppression of output capacitor voltage ripple. For this reason, targeted control methods are also required. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention proposes a power unit triggering control method suitable for a three-level interleaved totem pole power unit, comprising: a three-level interleaved totem pole power unit including an ADC register, a counting register, three inductor value calculation modules, an inductance value sorting module, a power unit sorting module, and three power units, wherein the three inductor value calculation modules are respectively connected to the three power units; the process of controlling the power units in the three-level interleaved totem pole power unit includes:

[0004] S1: Set the counting threshold and clear the counting register;

[0005] S2: Input the input voltage into the three-stage interleaved totem pole power unit to start the ADC register and output the voltage value;

[0006] S3: Input the voltage values ​​sequentially into the three power units, and obtain the inductance values ​​of the power units through the corresponding inductance value calculation module;

[0007] S4: Use the inductance value sorting module to sort the obtained inductance values, and sort the power units according to the inductance value sorting results;

[0008] S5: Increment the count in the counter register by 1;

[0009] S6: Compare the current count in the counter register with the set count threshold. If the current count is less than the set count threshold, reacquire the input voltage and return to step S2; otherwise, execute step S7.

[0010] S7: Set the duty cycle threshold, calculate the duty cycle based on the current power unit sorting, compare the duty cycle with the set duty cycle threshold, if it is greater than the set duty cycle threshold, the second power unit will shift phase normally, and the third power unit will shift phase normally; otherwise, the second power unit will decrease the phase shift, and the third power unit will increase the phase shift.

[0011] Preferably, the configured ADC register includes the following functions: single or continuous conversion mode, conversion end flag or interrupt, automatic calibration, and 16-bit data register storage mode.

[0012] Preferably, the process by which the inductance value calculation module obtains the inductance value of the power unit includes: calculating the difference between the peak-to-peak values ​​of the power inductor current of the power unit within one switching cycle, and calculating the inductance value of the power unit based on the difference between the peak-to-peak values ​​of the power inductor current.

[0013] Furthermore, the expression for calculating the peak-to-peak difference of the power inductor current in the power unit is as follows:

[0014] ΔI pv =I Li,p -I Li,v =ton u i / L i =t off (U o -u i ) / L i

[0015] Furthermore, the formula for calculating the inductance value of the power unit is:

[0016] L i =[(t on -t off )u i +t off U o ] / 2ΔI pv =[(2t on -1)u i +(t on -1)U o ] / 2ΔI pv

[0017] Preferably, the sorting of the obtained inductance values ​​using the inductance value sorting module includes: sorting the power unit inductance values ​​obtained by the inductance value calculation module from largest to smallest.

[0018] Preferably, the normal phase shift of the second power unit and the normal phase shift of the third power unit include: the normal phase shift of the second power unit is 120°, and the normal phase shift of the carrier of the third power unit is 240°.

[0019] Preferably, the second power unit's phase shift reduction and the third power unit's phase shift increase include: the second power unit's carrier phase shift reduction is empirically calculated as the ratio of the second sensing value to the first sensing value divided by 20%, and then multiplied by 8%; the third power unit's carrier phase shift increase is empirically calculated as the ratio of the third sensing value to the first sensing value divided by 20%, and then multiplied by 8%.

[0020] The beneficial effects of this invention are:

[0021] This invention uses the power inductance values ​​of the three power units obtained before operation or online calculation to redetermine the order of the power units according to their magnitude. The power unit with the largest inductance value is the first power unit, the power unit with the second largest inductance value is the second power unit, and the power unit with the smallest inductance value is the third power unit. It still adopts a dual closed-loop control structure, namely one voltage outer loop and three current inner loops. When the current inner loop outputs, that is, the duty cycle is in [2 / 3, 1], the power switch drive pulses formed in the second and third power units are phase-shifted by 120° and 240° respectively according to the new order, that is, 1 / 3 and 2 / 3 of the switching cycle, regardless of the power inductance value relationship. This is the so-called normal phase shift. When the duty cycle is in the range of [0, 2 / 3], the power switch drive pulses formed in the second and third power units are triggered in a new order. The phase shift of the carrier in the second power unit is no longer 120°. The phase shift is reduced, and the empirical value of the reduction is "the ratio of the second inductance value to the first inductance value divided by 20%, and then multiplied by 8%". The phase shift of the carrier in the third power unit is increased, and the empirical value of the increase is "the ratio of the third inductance value to the first inductance value divided by 20%, and then multiplied by 8%". This can obtain an input current waveform with reduced ripple, reduce harmonic current pollution to the power grid, and has the advantages of not adding hardware circuits, pure software design, stable control, and high quality of input current and output voltage. Attached Figure Description

[0022] Figure 1 This is a flowchart of an embodiment of the present invention;

[0023] Figure 2 This is a power circuit diagram of a three-level interleaved totem pole PFC according to an embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram of a driving pulse for a first power unit according to an embodiment of the present invention;

[0025] Figure 4 The effect of current synthesis of three inductors and current synthesis of three diodes in one embodiment of the present invention;

[0026] Figure 5 This is an example of an inductor current waveform according to an embodiment of the present invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] A power unit triggering control method applicable to a three-level interleaved totem pole power unit, the method comprising: a three-level interleaved totem pole power unit including an ADC register, a counter register, three inductor value calculation modules, an inductance value sorting module, a power unit sorting module, and three power units, wherein the three inductor value calculation modules are respectively connected to the three power units; for example Figure 1 As shown, the process of controlling the power units in the three-level staggered totem pole power unit includes:

[0029] S1: Set the counting threshold and clear the counting register;

[0030] S2: Input the input voltage into the three-stage interleaved totem pole power unit to start the ADC register and output the voltage value;

[0031] S3: Input the voltage values ​​sequentially into the three power units, and obtain the inductance values ​​of the power units through the corresponding inductance value calculation module;

[0032] S4: Use the inductance value sorting module to sort the obtained inductance values, and sort the power units according to the inductance value sorting results;

[0033] S5: Increment the count in the counter register by 1;

[0034] S6: Compare the current count in the counter register with the set count threshold. If the current count is less than the set count threshold, reacquire the input voltage and return to step S2; otherwise, execute step S7.

[0035] S7: Set the duty cycle threshold, calculate the duty cycle based on the current power unit sorting, compare the duty cycle with the set duty cycle threshold, if it is greater than the set duty cycle threshold, the second power unit will shift phase normally, and the third power unit will shift phase normally; otherwise, the second power unit will decrease the phase shift, and the third power unit will increase the phase shift.

[0036] The ADC register settings include the following functions: single or continuous conversion mode, conversion end flag or interrupt, automatic calibration, and 16-bit data register storage mode.

[0037] The process of obtaining the inductance value of the power unit by the inductance value calculation module includes: calculating the difference between the peak and peak values ​​of the power inductor current of the power unit within one switching cycle, and calculating the inductance value of the power unit based on the difference between the peak and peak values ​​of the power inductor current.

[0038] The expression for calculating the peak-to-peak difference of the power inductor current in the power unit is:

[0039] ΔI pv =I Li,p -I Li,v =t on ui / L i =t off (U o -u i ) / L i

[0040] Among them, I Li,p I represents the peak value of the power inductor current. Li,v t represents the valley value of the power inductor current. on Indicates the on-time of the power switch, u i L represents the single-phase AC input sinusoidal voltage. i Indicates the value of the power inductance, t off U represents the off-time of the power switch. o This indicates the output DC voltage.

[0041] The formula for calculating the inductance value of a power unit is:

[0042] L i =t on u i / ΔI pv =t off (U o -u i ) / ΔI pv

[0043] For accuracy, the power inductor value is:

[0044] L i =[(t on -t off )u i +t off U o ] / 2ΔI pv =[(2t on -1)u i +(t on -1)U o ] / 2ΔI pv

[0045] Among them, t on The on-time of the power switch, t off Indicates the off-time of the power switch, ΔI pv This represents the difference between the peak-to-peak values ​​of the power inductor current in the power unit.

[0046] The power unit sorting program determines the new first, second, and third power units by sorting the three default power inductor values ​​from largest to smallest. This order of power units is the optimal sequence for phase-shift triggering. The three power inductors are labeled L1, L2, and L3. After testing the inductance values, L... TC1 >LTC2 >L TC3 ,L TC1 Defined as the first power inductor, L TC2 Defined as the second power inductor, L TC3 Defined as the third power inductor. The second power switch drive pulse adopts normal drive, and the phase offset of the second power switch drive pulse is (L TC2 -L TC1 ) / 3L TC1 The phase offset of the third power switch drive pulse is (L) TC3 -L TC1 ) / 3L TC1 .

[0047] Power Unit Sequencing Principle: The three-level staggered totem pole PFC adopts a phase-shift triggering principle. Switches S1 and S2, S3 and S4, and S5 and S6 are complementary triggers, with S1, S3, and S5 phase-shifted by 120°. The three-level staggered totem pole PFC uses the average value control of the power inductor current in a continuous conduction mode. The average current values ​​of the three inductors L1, L2, and L3 are equal. The inductor with the larger inductance value has a smaller ripple current, while the inductor with the smaller inductance value has a larger ripple current. The output of the three inner current loops is the same, and the duty cycle of the power switches in each power unit is the same. Under these circumstances, only by triggering the power switches in the power units with the largest and largest inductance values ​​first, and then triggering the power switches in the power units with the smallest and smallest inductance values, can the ripple current gradually change from small to large. This makes the dual closed-loop control system the easiest to stabilize. This conclusion has been verified by simulation analysis and experiments.

[0048] like Figure 2 The diagram shows the power circuit of a three-stage staggered totem pole PFC according to an embodiment of the present invention. In the diagram, the input is a single-phase AC voltage ACL-ACN, and the output is a DC voltage ACL-ACN. The power inductor L1, power switches GaN S1 and S2, SiC MOSFET S7 and S8, and electrolytic capacitor C1 constitute a first-stage power unit. The power inductor power switches GaN S3 and S4, SiC MOSFET S7 and S8, and electrolytic capacitor C1 constitute a first-stage power unit. The power inductor L3, power switches GaN S5 and S6, SiC MOSFET S7 and S8, and electrolytic capacitor C1 constitute a first-stage power unit. The SiC MOSFET S7 and S8 and electrolytic capacitor C1 are shared components. The power inductors L1, L2, and L3 need to be reordered from largest to smallest, and the first, second, and third power units are redefined accordingly.

[0049] like Figure 3 The figure shows a schematic diagram of a driving pulse for a first power unit according to an embodiment of the present invention. The figure illustrates the driving pulse for a first-stage power unit. Figure 3 (a) is u i Represents a single-phase AC input sinusoidal voltage. Figure 3 (b) and (c) are the complementary driving signals for GaN S1 and GaN S2, respectively. Figure 3 (d) and (e) are the drive signals of SiC MOSFET S7 and S8, respectively, which are used as power diodes.

[0050] like Figure 4 The image shows the combined current of three inductors and three diodes according to an embodiment of the present invention. Figure 4 (a) shows the current segments of the three inductors and the combined current segment when the duty cycle is less than 1 / 3 and the three power inductors are equal in three switching cycles. Figure 4 (b) shows the current segments of the three power inductors from largest to smallest and the combined current segment during three switching cycles when the duty cycle is less than 1 / 3. Figure 4 (c) shows the current segments of the three diodes and the combined current segment of the three power inductors in three switching cycles, from largest to smallest, when the duty cycle is less than 1 / 3. From Figure 4 As can be seen from (b) and (c), determining the power unit sequence and driving pulse phase-shift triggering according to the inductance value from large to small can achieve a stable control effect of totem pole PFC.

[0051] The three-level interleaved totem pole PFC power unit digital sorting and optimal phase shifting method and device in this embodiment of the invention, through online measurement of power inductance values, sorting power units according to inductance value, and pulse driving to shift the phase by 120° according to the power unit size order, still adopts a dual closed-loop control structure, sharing a voltage outer loop and using their own current inner loops. However, the inner loop sawtooth carrier shifts the phase by 120° in sequence. Any other power unit sorting and phase shifting sequence cannot achieve good control effect, or even loses stability. It has the advantage of not requiring additional hardware and only requiring one software programming.

[0052] Specifically, for a three-stage interleaved totem-pole power factor corrector (TP-PFC), in one switching cycle, if the three inductor values ​​are the same, the drive signals of the three power switches are sequentially phase-shifted by 120°, which is called normal phase-shift drive. If the three inductor values ​​are different and the duty cycle is greater than 2 / 3, the three power switches adopt normal phase-shift drive to reduce the magnitude of the combined current ripple of the three inductor currents. If the three inductor values ​​are different and the duty cycle is less than 2 / 3, in order to reduce the magnitude of the combined current ripple of the three inductor currents, the second power switch adopts reduced phase-shift drive, and the third power switch adopts increased phase-shift drive. The actual values ​​of the three power inductors are determined by the inductance operator, which can sample and calculate the current in real time. In one power cycle (not a switching cycle), the duty cycle of the power switches changes regularly from a small "0" to a large "1"; the waveform of one inductor current is as follows: Figure 5 As shown.

[0053] In this embodiment, the duty cycle is the ratio of the on-time of the power switch to the switching cycle in one switching cycle, and the duty cycle ranges from [0,1].

[0054] The above-described embodiments further illustrate the purpose, technical solution, and advantages of the present invention. It should be understood that the above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A power unit triggering control method applicable to a three-level interleaved totem pole power unit, characterized in that, include: The three-level interleaved totem pole power unit includes an ADC register, a counter register, three inductor value calculation modules, an inductance value sorting module, a power unit sorting module, and three power units. The three inductor value calculation modules are connected to the three power units respectively. The process of controlling the power units in the three-level interleaved totem pole power unit includes: S1: Set the counting threshold and clear the counting register; S2: Input the input voltage into the three-stage interleaved totem pole power unit to start the ADC register and output the voltage value; S3: Input the voltage values ​​sequentially into the three power units, and obtain the inductance values ​​of the power units through the corresponding inductance value calculation module; S4: Use the inductance value sorting module to sort the obtained inductance values, and sort the power units according to the inductance value sorting results; S5: Increment the count in the counter register by 1; S6: Compare the current count in the counter register with the set count threshold. If the current count is less than the set count threshold, reacquire the input voltage and return to step S2; otherwise, execute step S7. S7: Set the duty cycle threshold, calculate the duty cycle based on the current power unit sorting, compare the duty cycle with the set duty cycle threshold, if it is greater than the set duty cycle threshold, the second power unit will shift phase normally, and the third power unit will shift phase normally; otherwise, the second power unit will decrease the phase shift, and the third power unit will increase the phase shift.

2. The power unit triggering control method for a three-level interleaved totem pole power unit according to claim 1, characterized in that, The ADC register settings include the following functions: single or continuous conversion mode, conversion end flag or interrupt, automatic calibration, and 16-bit data register storage mode.

3. The power unit triggering control method for a three-level interleaved totem pole power unit according to claim 1, characterized in that, The process of obtaining the inductance value of the power unit by the inductance value calculation module includes: calculating the difference between the peak and peak values ​​of the power inductor current of the power unit within one switching cycle, and calculating the inductance value of the power unit based on the difference between the peak and peak values ​​of the power inductor current.

4. The power unit triggering control method for a three-level interleaved totem pole power unit according to claim 3, characterized in that, The expression for calculating the peak-to-peak difference of the power inductor current in the power unit is: ΔI pv =I Li,p -I Li,v =t on the i / L i =t off (The o -u i ) / L i Among them, I Li,p I represents the peak value of the power inductor current. Li,v t represents the valley value of the power inductor current. on Indicates the on-time of the power switch, u i L represents the single-phase AC input sinusoidal voltage. i Indicates the value of the power inductance, t off U represents the off-time of the power switch. o This indicates the output DC voltage.

5. The power unit triggering control method for a three-level interleaved totem pole power unit according to claim 3, characterized in that, The formula for calculating the inductance value of a power unit is: L i =[(t on -t off )u i +t off U o ] / 2ΔI pv =[(2t on -1)u i +(t on -1)U o ] / 2ΔI pv Among them, t on The on-time of the power switch, t off Indicates the off-time of the power switch, u i This represents the single-phase AC input sinusoidal voltage, ΔI. pv This represents the difference between the peak-to-peak values ​​of the power inductor current in the power unit.

6. The power unit triggering control method for a three-level interleaved totem pole power unit according to claim 1, characterized in that, The sorting of the obtained inductance values ​​using the inductance value sorting module includes: sorting the power unit inductance values ​​obtained by the inductance value measurement module from largest to smallest.

7. The power unit triggering control method for a three-level interleaved totem pole power unit according to claim 1, characterized in that, The normal phase shift of the second power unit and the normal phase shift of the third power unit include: the normal phase shift of the second power unit is 120°, and the normal phase shift of the carrier of the third power unit is 240°.

8. The power unit triggering control method for a three-level interleaved totem pole power unit according to claim 1, characterized in that, The second power unit's phase shift reduction and the third power unit's phase shift increase include: the second power unit's carrier phase shift reduction is empirically calculated as the ratio of the second sensitivity value to the first sensitivity value divided by 20%, then multiplied by 8%; the third power unit's carrier phase shift increase is empirically calculated as the ratio of the third sensitivity value to the first sensitivity value divided by 20%, then multiplied by 8%.

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