CN111181397A - Three-mode control method of four-switch buck-boost converter - Google Patents

Abstract

The invention relates to a three-mode control method of a four-switch buck-boost converter, which adopts a three-mode control method, direct-current voltage outer-loop control and four-switch buck-boost converter output voltage V when the input voltage and the output voltage are close in amplitude and the voltage conversion ratio is discontinuous and enters a transition region_oWith output voltage given reference value V_refThe voltage difference is sent to a PI regulator, and the PI regulator calculates an output control signal d_ctr，d_ctrThe PWM waveform corresponding to the switching tube is adjusted for determining the three-mode selection, and the three-mode selection comprises the following steps: a transient buck mode, a transient boost mode, a boost mode. The problem of 'transition zone' of the four-switch converter is solved, and smooth transition between different modes is realized. The four-switch converter has improved stability, and ensures the whole-course stability of the converter in work.

Description

Three-mode control method of four-switch buck-boost converter

Technical Field

The invention relates to a converter control technology, in particular to a three-mode control method of a four-switch buck-boost converter.

Background

The four-switch buck-boost converter can realize the boosting and the reducing operations of the input voltage and output the same-phase voltage. When the input voltage is higher than the output voltage, the converter operates in a buck mode; when the input voltage is lower than the output voltage, the converter operates in a boost mode, which is a two-mode control strategy. However, the duty ratio is limited due to factors such as switching delay and dead time, and when the amplitude of the input voltage is close to that of the output voltage, the voltage conversion ratio is discontinuous. This region of discontinuous switching ratio near the output voltage is called the "transition region", and the presence of the transition region affects the stability of the converter, so a multi-mode control is needed to solve the problem of the "transition region".

Disclosure of Invention

The invention provides a three-mode control method of a four-switch buck-boost converter aiming at the problem of unstable conversion of a transition region of the four-switch buck-boost converter, which can solve the problem of the transition region of the four-switch converter and realize smooth transition among different modes.

The technical scheme of the invention is as follows: a three-mode control method of a four-switch buck-boost converter adopts a three-mode control method when the voltage conversion ratio is discontinuous and enters a transition region when the amplitude of an input voltage is close to that of an output voltage, and comprises the following specific steps:

direct-current voltage outer loop control, four-switch buck-boost converter output voltage V_oWith output voltage given reference value V_refThe voltage difference is sent to a PI regulator, and the PI regulator calculates an output control signal d_ctr，d_ctrThe PWM waveform corresponding to the switching tube is adjusted for determining the three-mode selection, and the three-mode selection comprises the following steps: in a transition depressurization mode, a working point P belongs to DF; in a transition boosting mode, a working point P belongs to CD; in the boosting mode, a working point P belongs to AB; point A position (d)_2min1), position of point B (d)_2max1), point C position (d)_1max*d_2max，d_1max) Point D position (D)_2max，d_1max) Point F position (d)_2max，d_1min) And d is_2max＝d_1max＝d_maxSwitching tube Q₁And Q₄Are respectively d₁、1-d₁As a pair of complementary duty cycle switching tubes, wherein d_1min、d_1maxAre respectively a switching tube Q₁Minimum and maximum duty cycles of; switch tube Q₂And Q₃Respectively duty ratio ofIs d₂、1-d₂As a pair of complementary duty cycle switching tubes, wherein d_2min、d_2maxAre respectively a switching tube Q₂Minimum and maximum duty cycles of; the three-mode control is performed according to the following formula,

d_ctra transition depressurization mode is not more than 0.5; 0.5<d_ctrl<0.5/d_2maxA transition boosting mode is adopted; formula d_ctrl≥0.5/d_2maxThe boost mode is used.

The invention has the beneficial effects that: according to the three-mode control method of the four-switch buck-boost converter, the stability of the four-switch converter is improved, and the stability of the converter in the whole working process is ensured.

Drawings

FIG. 1 is a block diagram of a four-switch buck-boost converter;

FIG. 2 is a logic diagram of the four-switch buck-boost converter control of the present invention;

FIG. 3 is a schematic diagram of the four-switch three-mode control of the present invention;

FIG. 4 is a graph showing the experimental effect of the present invention under the three-mode control.

Detailed Description

The four-switch buck-boost converter structure is shown in figure 1, V_inIs the converter input voltage, V_oIs the converter output voltage with a load of R, Q₁～Q₄Is a switch tube, a switch tube Q₁And Q₄Are respectively d₁、1-d₁As a pair of switching tubes with complementary duty cycles; switch tube Q₂And Q₃Are respectively d₂、1-d₂As a pair of switch tubes with complementary duty cycles.

By controlling Q₁～Q₄The charging and discharging of the inductor L are realized, and energy is transferred to the load R. In particular, the switching tube Q₁And Q₃Turning on, and storing energy by the inductor L; switch tube Q₂And Q₄Turn on, inductance L is negativeEnergy is supplied by the carrier R; switch tube Q₁And Q₂On, the inductive state being dependent on the input voltage V_inAn output voltage V₀Size.

The control logic of the present invention is shown in FIG. 2, and the DC voltage outer loop controls the converter output voltage V_oWith output voltage given reference value V_refThe voltage difference is sent to a PI regulator, and the PI regulator calculates an output control signal d_ctr，d_ctrFor determining the operating mode of a four-switch converter, the mode selection module is dependent on d_ctrRespectively output the switch tube Q₁、Q₄Duty ratio d of₁、d₂And adjusting the corresponding PWM waveform of the switching tube.

The three-mode control strategy of the invention is respectively a transition voltage reduction mode (working point P belongs to DF), a transition voltage increase mode (working point P belongs to CD) and a voltage increase mode (working point P belongs to AB) as shown in figure 3.

Under three modes, the formula of the mode selection module in FIG. 2 is guided: as can be seen from FIG. 3, the position of point A (d)_2min1), position of point B (d)_2max1), point C position (d)_1max*d_2max，d_1max) Point D position (D)_2max，d_1max) Point F position (d)_2max，d_1min) And d is_2max＝d_1max＝d_maxIs obtained by

Transient depressurization mode according to formula (1) d_ctrlLess than or equal to 0.5, switch tube Q₂Constant duty ratio of d_2maxRegulating Q₁Duty ratio d of₁。

Transition boost mode according to equation (1)0.5<d_ctrl<0.5/d_2maxSwitching tube Q₁Constant duty cycle of d_1maxRegulating the switching tube Q₂Duty ratio of d₂。

A boosting mode: according to the formula (1) d_ctrl≥0.5/d_2maxSwitching tube Q₁Constant conduction (duty cycle d₁1), openClosing tube Q₂Duty ratio of d₂。

Applying a three-mode control strategy, the voltage conversion ratio at points B and C is equal, i.e. M_C＝M_BThis causes the four-switch converter to switch in mode, with the same input voltage V_inLower, output voltage V_oInvariable (V)_o-B＝V_o-C) Therefore, the four-switch converter stability is improved.

As shown in fig. 4, at an input voltage V_inUnder the condition of a certain 32V, the output voltage is changed to set a reference value V_refThe output voltage V can be realized when the voltage is respectively 33V, 30V and 26V₀The voltage was varied in the order of 33V, 30V and 26V. The converter can still realize the output voltage V₀The method is continuous and stable, and the converter stably runs in the whole process.

Claims (1)

1. A three-mode control method of a four-switch buck-boost converter is characterized in that when an input voltage and an output voltage are close in amplitude, a three-mode control method is adopted when a voltage conversion ratio is discontinuous and enters a transition region, and the method specifically comprises the following steps:

direct-current voltage outer loop control, four-switch buck-boost converter output voltage V_oWith output voltage given reference value V_refThe voltage difference is sent to a PI regulator, and the PI regulator calculates an output control signal d_ctr，d_ctrThe PWM waveform corresponding to the switching tube is adjusted for determining the three-mode selection, and the three-mode selection comprises the following steps: in a transition depressurization mode, a working point P belongs to DF; in a transition boosting mode, a working point P belongs to CD; in the boosting mode, a working point P belongs to AB; point A position (d)_2min1), position of point B (d)_2max1), point C position (d)_1max*d_2max，d_1max) Point D position (D)_2max，d_1max) Point F position (d)_2max，d_1min) And d is_2max＝d_1max＝d_max，

Switch tube Q₁And Q₄Are respectively d₁、1-d₁As a pair of complementary duty cycle switching tubes, wherein d_1min、d_1maxAre respectively a switching tube Q₁Minimum and maximum duty cycles of; switch tube Q₂And Q₃Are respectively d₂、1-d₂As a pair of complementary duty cycle switching tubes, wherein d_2min、d_2maxAre respectively a switching tube Q₂Minimum and maximum duty cycles of; the three-mode control is performed according to the following formula,

d_ctra transition depressurization mode is not more than 0.5; 0.5<d_ctrl<0.5/d_2maxA transition boosting mode is adopted; formula d_ctrl≥0.5/d_2maxThe boost mode is used.

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