CN-121984351-A - Four-pipe bidirectional lifting pressure control method and device

CN121984351ACN 121984351 ACN121984351 ACN 121984351ACN-121984351-A

Abstract

A four-tube bidirectional Buck-Boost control method and device mainly comprises the steps of switching between a two-tube Buck/Boost mode, a four-tube BuckBoost mode and a four-tube diagonal mode by adjusting phase shifting angles according to different input and output voltage differences, adopting fixed phase shifting angles to increase control quantity frequency f, calculating switching frequency f of a converter according to input or output voltage, current and duty ratio D, implementing variable frequency control, and controlling the disconnection of a switching tube in the four-tube bidirectional Buck-Boost converter to realize soft switching circulation. The method and the device realize the switching of three control modes, adapt to different scenes, set the switching time of a four-tube Buck/Boost mode and a two-tube Buck/Boost mode through a phase angle phi, calculate the relation between frequency and duty ratio D1 through input and output current and soft switching current, adjust the switching frequency, enable the soft switching current of the inductor to be minimum, and achieve the optimal efficiency.

Inventors

SONG KELING
JIANG RENJUN
KONG DESHAN
DANG XUNYI
FAN LEI
LU CONGHUI

Assignees

中国北方车辆研究所

Dates

Publication Date: 20260505
Application Date: 20251222

Claims (5)

1. The four-pipe bidirectional lifting pressure control method is characterized by comprising the following steps of: s1, aiming at different input and output voltage differential pressures, switching among a two-tube Buck/Boost mode, a four-tube BuckBoost mode and a four-tube diagonal mode by adjusting a phase shift angle; s2, adopting a fixed phase shift angle, increasing the control quantity frequency f, calculating the switching frequency f of the converter according to the input or output voltage, current and duty ratio D, and implementing variable frequency control; S3, the switching-off of a switching tube in the four-tube bidirectional buck-boost converter is controlled, and soft switching circulation is realized.
2. The method according to claim 1, wherein in the step S1, the switching control method includes: The four-tube bidirectional buck-boost converter comprises a left bridge arm and a right bridge arm, wherein four switching tubes are S1-S4, corresponding on duty ratios are D1-D4, the left bridge arm is connected with an input end and is formed by connecting an upper tube S1 and a lower tube S1 in series, the right bridge arm is connected with an output end and is formed by connecting an upper tube S3 and a lower tube S4 in series, and control logic is as follows: (1) When the input-output pressure difference is large, adopting a two-pipe Buck mode and a two-pipe Boost mode; Setting dv=input voltage Vin/output voltage Vout, when 0.2 < Dv < 0.4, operating in Boost mode, S1 tube is normally on, S2 tube and S3 tube are off, when 0.8 > Dv > 0.6, operating in Buck mode, S2 tube and S4 tube are off, S3 tube is normally on; (2) When the differential pressure is similar, namely when the Dv is less than 0.4 and less than 0.6, the four-pipe Buck-Boost or diagonal mode is entered, the high-frequency soft switch is realized, and the conversion efficiency is improved; (3) The four-pipe diagonal control, the four-pipe Buck/Boost mode, the two-pipe Buck mode and the two-pipe Boost mode are switched through the value of the phase shift duty ratio phi converted from the phase shift angle; Wherein: when phi=0, d4=d1, in this case, for the four-pipe diagonal mode, PI is used to calculate D1; when 0< phi <1, adopting PI to calculate D1, D4=D1-phi, D1D4 phase difference fixed phase, and determining the automatic switching time of the two-pipe/four-pipe mode according to the magnitude relation of D1 and phi, wherein the automatic switching time is specifically as follows: wherein U out represents the output voltage value after switching; When Φ=1, this is a two-pipe Buck/Boost mode, where two cases d1=1 or d3=1 occur, corresponding to: S1 and S2 pipes realize Buck/Boost, a Buck mode of forward power and a Boost mode of reverse power, and S3 and S4 pipes realize Buck/Boost, a Boost mode of forward power and a Buck mode of reverse power.
3. The method according to claim 2, wherein the specific method of step S2 comprises: Collecting input or output voltage and current; According to the input/output voltage and current and the duty ratio D, the switching frequency f is calculated to track the set soft switching current I ZVS , and the frequency calculation equation set is as follows: the approximate frequency is: In the formula, vbat is input voltage, ibat is input current, D1 is the on duty ratio of an S1 tube, I ZVS is soft switching current, phi is the phase shift duty ratio converted by a phase shift angle, L is inductance value, T is switching period, I L1 is inductance current at T1, I L2 is inductance current at T2, vsc is actual output voltage value, f is the frequency of a wave, namely the switching frequency of the converter, and N is the number of staggered parallel phases.
4. A method according to claim 2 or 3, wherein the specific method of step S3 comprises: s2, S3 tube turn off at the same time, realize triangle-shaped soft switch electric current, in order to dispel the useless circulation, promote the system efficiency.
5. A four-pipe bi-directional buck-boost control apparatus employing the method of any one of claims 1-4, comprising: the mode switching control module is used for switching among three modes of a two-pipe Buck/Boost mode, a four-pipe BuckBoost mode and a four-pipe diagonal mode by adjusting a phase shifting angle according to different input and output voltage differences; The frequency conversion control module is used for calculating the switching frequency f of the converter according to the input or output voltage, current and duty ratio D based on the fixed phase shift angle and implementing frequency conversion control; and the soft switch circulation module is used for controlling the disconnection of the switching tube and realizing soft switch circulation.

Description

Four-pipe bidirectional lifting pressure control method and device Technical Field The invention relates to the technical field of power electronics, in particular to a four-pipe bidirectional lifting pressure control method and device. Background The four-pipe bidirectional synchronous DC/DC Buck-Boost (English name is Buck-Boost, boost and Buck) is widely applied to an energy storage system, an active capacitance system is formed by cascading with a super capacitor, the discharge depth is improved while stable control is realized, a composite energy storage system is further formed by cascading with a power battery, decoupling with the power generation system is realized, and effective management is implemented on the power battery. A typical four-tube bi-directional buck-boost converter topology is shown in fig. 1, wherein the four-tube bi-directional buck-boost converter has four controllable switching tubes (usually MOSFETs or IGBTs, labeled S1-S4) and D1-D4 respectively correspond to the on duty cycles of the four switching tubes, that is, the ratio of the on time of each switching tube to the total period in one switching period. PI is an abbreviation of Proportional-Integral (PI) controller, which is a core component of a closed-loop control system in four-pipe bidirectional buck-boost conversion control, and is often applied to regulation of a voltage outer loop or a current inner loop. The traditional four-tube bidirectional Buck-Boost conversion adopts fixed frequency control, the inductance current and the soft switching current are trapezoidal, and the control is implemented through three variables D 1、D2 and phi, wherein D 1 is the duty ratio of a Buck part, D2 is the duty ratio of a Boost part, phi is the phase shift angle, and the phase difference value between two groups of bridge arm driving signals in a four-tube topology. The control mode has the defects of complex working mode, large soft start impact current, large soft switch circulation, large operation amount and the like. Disclosure of Invention Aiming at the typical topological structure shown in fig. 1, the four-pipe bidirectional buck-boost control method is provided, a fixed phase shift angle phi is adopted, the control quantity frequency f is increased, soft switching circulation, variable frequency control and multimode control switching are realized through PI operation and variable frequency control, the control difficulty is reduced, and the conversion efficiency is improved. Aiming at different input and output voltage differences, the switching is performed among three modes of a two-pipe Buck/Boost mode, a four-pipe BuckBoost mode and a four-pipe diagonal mode by adjusting a phase shift angle phi so as to adapt to the use requirements of different scenes. In the present disclosure, four-pipe bidirectional Buck-Boost control modes are divided into two-pipe Buck/Boost mode, four-pipe Buck/Boost mode, and four-pipe diagonal control, wherein: The two-pipe Buck/Boost mode comprises a Buck mode and a Boost mode, and if the forward power flow is the Buck mode, the reverse power flow is the Boost mode; The four-pipe Buck/Boost mode supports bidirectional power flow, has the capability of boosting and reducing pressure, and has a wider adjusting range; the method can also comprise a two-pipe Buck mode, a two-pipe Boost mode and a four-pipe Buck/Boost mode, and D1 value calculated by PI (proportional integral controller) can be automatically switched; When four-tube diagonal control is performed, the inductor current is in a triangular wave form as shown in fig. 10, and in the mode, the peak value of the inductor current is large, so that the inductor generates serious heat, and the output power is influenced. The four-pipe bidirectional lifting pressure control method mainly comprises the following steps: s1, aiming at different input and output voltage differential pressures, switching among a two-tube Buck/Boost mode, a four-tube BuckBoost mode and a four-tube diagonal mode by adjusting a phase shift angle; s2, adopting a fixed phase shift angle, increasing the control quantity frequency f, calculating the switching frequency f of the converter according to the input or output voltage, current and duty ratio D, and implementing variable frequency control; S3, the switching-off of a switching tube in the four-tube bidirectional buck-boost converter is controlled, and soft switching circulation is realized. Further, in the step S1, the switching control method includes: The four-tube bidirectional buck-boost converter comprises a left bridge arm and a right bridge arm, wherein four switching tubes are S1-S4, corresponding on duty ratios are D1-D4, the left bridge arm is connected with an input end and is formed by connecting an upper tube S1 and a lower tube S1 in series, the right bridge arm is connected with an output end and is formed by connecting an upper tube S3 and a lower tube S4 in series, and control logic is as follow