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CN-122001218-A - Control method of multi-level Buck-Boost converter

CN122001218ACN 122001218 ACN122001218 ACN 122001218ACN-122001218-A

Abstract

The invention discloses a control method of a multi-level Buck-Boost converter, which belongs to the technical field of power converters, and aims to control an inductor current into a pentagon form by reasonably utilizing each control degree of freedom of the converter, so that soft switching of all switching tubes can be realized, meanwhile, minimization of inductor current pulsation and effective values can be realized, and an optimal working mode is adopted, and rising and falling slopes of the inductor current are adjusted in a pseudo-inductor current intermittent mode so as to reduce the circulation time of negative current, thereby improving the light load efficiency of the converter.

Inventors

  • CHEN LINGXUAN
  • RUAN XINBO

Assignees

  • 南京航空航天大学

Dates

Publication Date
20260508
Application Date
20260327

Claims (10)

  1. 1. A control method of a multi-level Buck-Boost converter is applied to the multi-level Buck-Boost converter, the multi-level Buck-Boost converter comprises a Buck conversion unit, a Boost conversion unit and a filtering unit, and the Buck conversion unit comprises Multiple switch tubes ~ Body diode of switch tube ~ Sum junction capacitance ~ A kind of electronic device Flying capacitor ~ The fly capacitor of the Buck conversion unit is formed during steady operation 、 、...、 Respectively maintain the voltage of (2) 、 、...、 Composition of The Boost conversion unit comprises Multiple switch tubes ~ Body diode of switch tube ~ Sum junction capacitance ~ A kind of electronic device Flying capacitor ~ The Boost conversion unit fly capacitor is formed during steady-state operation 、 、...、 Respectively maintain the voltage of (2) 、 、...、 Composition of A personal level; a first end of a filter inductor in the filter unit is connected with a bridge arm midpoint of the Buck conversion unit, and a second end of the filter inductor is connected with a bridge arm midpoint of the Boost conversion unit; Characterized in that the control method comprises the following steps, Step S1, the voltage of the midpoint of the bridge arm of the Buck conversion unit is kept to be zero by increasing the voltage of the midpoint of the bridge arm of the Boost conversion unit, and linearly-increased filter inductance current is output: Step S1, conducting j 1 upper tubes in the Buck conversion unit, and controlling the voltage of the middle point of the bridge arm of the Buck conversion unit And maintaining the voltage of the midpoint of the bridge arm of the Boost conversion unit The current of the filter inductor linearly rises; Step S2, the voltage of the midpoint of the bridge arm of the Boost conversion unit is increased by reducing the voltage of the midpoint of the Buck conversion unit, and the filter inductance current after rising and falling is output: step S2, the voltage of the middle point of the bridge arm of the Buck conversion unit is calculated from Gradually reducing to 0, and gradually increasing the voltage of the middle point of the bridge arm of the Boost conversion unit from 0 to , wherein, The upper tube conduction number of the OP section Buck conversion unit, The upper tube of the RS section Boost conversion unit is conducted, the inductance voltage is continuously reduced, and the current of the filtering inductance is firstly increased and then decreased; Step S3, by turning off all upper tubes of the Buck conversion unit and keeping the upper tubes of the Boost conversion unit partially on, outputting linearly-reduced inductance current, and when the inductance current is reduced to a negative current reference value for realizing soft switching of the switching tube When the Boost unit is in the soft switch state, all lower tubes of the Boost unit are turned off, and the inductive current is maintained at a negative current reference value for realizing the soft switch of the switch tube : Step S3, when the current of the filter inductor is reduced to the R point and the current of the R point When the voltage of the middle point of the bridge arm of the Buck conversion unit is zero, wherein I ZVS is the minimum current for realizing the soft switching of the switching tube, all upper tubes of the Buck conversion unit are turned off, the Boost conversion unit is provided with k 1 upper tubes which are turned on, and the voltage of the middle point of the bridge arm of the Boost conversion unit is equal to the voltage of the middle point of the bridge arm of the Buck conversion unit The current of the filter inductor linearly drops to a negative current reference value for realizing the soft switching of the switching tube ; Step S4, according to the relation between the input voltage V in and the output voltage V o of the real-time monitoring converter, the current working mode is adaptively switched, and the optimal current control waveform adapting to the current working condition is output: In the step S4, when V in ≤V o /n is adopted, the inductance current takes on a quadrilateral form with a monotonously-decreasing middle section, and when V in /m>V o is adopted, the inductance current takes on a quadrilateral form with a monotonously-increasing middle section.
  2. 2. The method of claim 1, wherein in order to realize that the inductance voltage difference between the PQ section and the QR section is minimum and the polarities are opposite, one side of the inductance voltage difference between the PQ section and the QR section is kept fixed, and the other side of the inductance voltage difference between the PQ section and the QR section is kept at the adjacent level, and the first scheme is that when V in /m≤V o /n is carried out, a Buck conversion unit upper tube is turned off at the corresponding moment of the Q point, so that the voltage of the middle point of a bridge arm of the Buck conversion unit is reduced by one level, and the voltage of the middle point of the bridge arm of the Boost conversion unit is kept unchanged.
  3. 3. The control method of a multi-level Buck-Boost converter according to claim 2, wherein the second scheme is that when V in /m>V o /n is set, a Boost conversion unit upper tube is turned on at a moment corresponding to a Q point, so that a voltage at a midpoint of a bridge arm of the Boost conversion unit is raised by one level, and the voltage at the midpoint of the bridge arm of the Buck conversion unit is kept unchanged.
  4. 4. The method for controlling a multi-level Buck-Boost converter according to claim 1, wherein in the step S2, the expression of the average power P PQ corresponding to the PQ segment is: , Wherein, the For the total time of one switching cycle, At the moment of the point P, At the moment of the Q-point, Is the voltage of the midpoint B of the bridge arm of the Boost conversion unit, In order to filter the current of the inductor, For the upper pipe turn-on number of the Boost conversion unit of the PQ section, In order to output the voltage, the voltage is, For all the upper pipe numbers in the Boost conversion unit, The current at the point P is the current at the point P, The current at the point Q is the current at the point Q, As the value of the inductance is to be given, For the upper pipe conduction number of the PQ section Buck conversion unit, For the input voltage to be applied to the circuit, For all upper pipe numbers in the Buck conversion unit.
  5. 5. The method for controlling a multi-level Buck-Boost converter according to claim 1, wherein in the step S2, the expression of the average power P QR corresponding to the QR segment is: , Wherein, the For the total time of one switching cycle, The moment of time at the point R, At the moment of the Q-point, Is the voltage of the midpoint B of the bridge arm of the Boost conversion unit, In order to filter the current of the inductor, The upper tube conduction number of the Boost conversion unit of the QR section, In order to output the voltage, the voltage is, For all the upper pipe numbers in the Boost conversion unit, The current at the point R is the current at the point R, The current at the point Q is the current at the point Q, As the value of the inductance is to be given, For the upper tube conduction number of the QR section Buck conversion unit, For the input voltage to be applied to the circuit, For all upper pipe numbers in the Buck conversion unit.
  6. 6. The method for controlling a multi-level Buck-Boost converter according to claim 1, wherein in the step S1, the voltage at the midpoint of the bridge arm of the Buck conversion unit is zero and the voltage at the midpoint of the bridge arm of the Boost conversion unit is zero when the voltage is satisfied at the initial time of each switching cycle.
  7. 7. The method for controlling a multi-level Buck-Boost converter of claim 1, wherein the control strategy for the optimal operating mode comprises: When the load is heavy, the multi-level Buck-Boost converter works in an inductance current pseudo-current continuous mode, the current at the P point, the current at the Q point and the current at the R point are all larger than the minimum current I ZVS for realizing the soft switching of the switching tube in the pseudo-current continuous mode, and when the current I P at the P point and the current I R at the R point are both reduced to the minimum current I ZVS for realizing the soft switching of the switching tube, the multi-level Buck-Boost converter reaches the critical working point of the pseudo-current continuous mode; When the load is further reduced, the converter will operate in an inductor current pseudo-current interrupt mode in which the current at point P and the current at point R will be fixed at a minimum current I ZVS for realizing soft switching of the switching tube, and when the current of the filter inductor drops to a negative current reference value for realizing soft switching of the switching tube When the Buck conversion unit and the Boost conversion unit are in synchronous conduction, the current of the filter inductor is maintained at a negative current reference value for realizing the soft switching of the switching tube ; Maintaining current of filter inductor at negative current reference value for realizing soft switching of switching tube Reducing the voltage applied to the inductor by the OP and RS sections, thereby shortening the negative current reference value in realizing the soft switching of the switching tube at a constant frequency Is a circulation time of the air conditioner.
  8. 8. The method for controlling a multi-level Buck-Boost converter as claimed in claim 7, wherein the current of the filter inductor is adjusted from a negative current reference value for soft switching of the switching tube The expression of the time variation Δt Lj that rises to the minimum current I ZVS that realizes the switching tube soft switching is: , Wherein, the As the value of the inductance is to be given, For all the upper pipe numbers in the Buck conversion unit, The upper tube conduction number of the OP section Buck conversion unit, Is the input voltage.
  9. 9. The method of claim 8, wherein the current of the filter inductor decreases from a minimum current I ZVS for soft switching of the switching tube to a negative current reference value for soft switching of the switching tube The expression of the time variation Δt Rk of (a) is: , Wherein, the As the value of the inductance is to be given, For all the upper pipe numbers in the Boost conversion unit, The upper tube conduction number of the Boost conversion unit of the RS section, Is the output voltage.
  10. 10. The method of claim 9, wherein to maintain the voltage in the voltage range The time T neg of the (a) is always kept at the minimum value, and the level values j 1 and k 1 of the OP section and the RS section are required to be gradually reduced along with the load reduction; as the load decreases, it is maintained at Will gradually increase in time T neg ; When maintained at Time T neg to reach the filter inductance The time variation delta T Lj rising to I ZVS and the current of the filter inductor drop from I ZVS to Immediately reducing the level number of the corresponding segment when the minimum value in the time variation delta T Rk ; Current slave having a minimum value of filter inductance Delta T Lj decreases j 1 when the time variation of I ZVS is increased, and the current of the minimum value filter inductor is reduced from I ZVS to Delta T Rk , decreasing k 1 , to maintain at Falling back to 0 at a time T neg of (a) as the load continues to decrease, ensuring maintenance at Is maintained at a minimum value until the converter enters an idle state.

Description

Control method of multi-level Buck-Boost converter Technical Field The invention relates to the technical field of power converters, in particular to a control method of a multi-level Buck-Boost converter. Background The four-tube Buck-Boost (Four-Switch Buck-Boost, FSBB) converter has the advantages of step-up and step-down, positive output voltage polarity, small number of passive devices, bidirectional energy flow and the like, and is widely applied to the fields of photovoltaic power generation systems, electric automobile charging systems, energy storage systems and the like. Limited by the voltage withstand levels of existing switching devices, multi-level techniques are often employed to reduce switching tube voltage stress when the input or output voltage is high, thereby forming a multi-level Buck-Boost converter. In order to reduce the inductor current ripple of the multi-level Buck-Boost converter, the prior art proposes a two-mode control method, although the inductor current ripple can be minimized, the converter works in an inductor current continuous mode (Continuous Current Mode, CCM) under the control method, and the switching tube is in a hard switching working state, so that the further improvement of the switching frequency is restricted. In recent years, wide bandgap semiconductor devices typified by gallium nitride (GaN) and silicon carbide (SiC) have been rapidly developed, and it has been possible to increase the switching frequency. Although the turn-off loss of the GaN and SiC devices is low, the turn-on loss is still remarkable, so that the realization of zero-voltage turn-on (Zero Voltage Switching, ZVS) of the wide-bandgap semiconductor devices is crucial to the improvement of the converter efficiency. Disclosure of Invention The invention aims to provide a control method of a multi-level Buck-Boost converter. In order to achieve the above purpose, the technical scheme of the invention is as follows: a control method of a multi-level Buck-Boost converter is applied to the multi-level Buck-Boost converter, the multi-level Buck-Boost converter comprises a Buck conversion unit, a Boost conversion unit and a filtering unit, and the Buck conversion unit comprises Multiple switch tubes~Body diode of switch tube~Sum junction capacitance~A kind of electronic deviceFlying capacitor~The fly capacitor of the Buck conversion unit is formed during steady operation、、...、Respectively maintain the voltage of (2)、、...、Composition ofThe Boost conversion unit comprisesMultiple switch tubes~Body diode of switch tube~Sum junction capacitance~A kind of electronic deviceFlying capacitor~The Boost conversion unit fly capacitor is formed during steady-state operation、、...、Respectively maintain the voltage of (2)、、...、Composition ofA personal level; a first end of a filter inductor in the filter unit is connected with a bridge arm midpoint of the Buck conversion unit, and a second end of the filter inductor is connected with a bridge arm midpoint of the Boost conversion unit; the manufacturing method comprises the steps of, Step S1, the voltage of the midpoint of the bridge arm of the Buck conversion unit is kept to be zero by increasing the voltage of the midpoint of the bridge arm of the Boost conversion unit, and linearly-increased filter inductance current is output: Step S1, conducting j 1 upper tubes in the Buck conversion unit, and controlling the voltage of the middle point of the bridge arm of the Buck conversion unit And maintaining the voltage of the midpoint of the bridge arm of the Boost conversion unitThe current of the filter inductor linearly rises; Step S2, the voltage of the midpoint of the bridge arm of the Boost conversion unit is increased by reducing the voltage of the midpoint of the Buck conversion unit, and the filter inductance current after rising and falling is output: step S2, the voltage of the middle point of the bridge arm of the Buck conversion unit is calculated from Gradually reducing to 0, and gradually increasing the voltage of the middle point of the bridge arm of the Boost conversion unit from 0 to, wherein,The upper tube conduction number of the OP section Buck conversion unit,The upper tube of the RS section Boost conversion unit is conducted, the inductance voltage is continuously reduced, and the current of the filtering inductance is firstly increased and then decreased; Step S3, by turning off all upper tubes of the Buck conversion unit and keeping the upper tubes of the Boost conversion unit partially on, outputting linearly-reduced inductance current, and when the inductance current is reduced to a negative current reference value for realizing soft switching of the switching tube When the Boost unit is in the soft switch state, all lower tubes of the Boost unit are turned off, and the inductive current is maintained at a negative current reference value for realizing the soft switch of the switch tube: Step S3, when the current of the filter inductor is red