CN104868724A - Mixed-mode modulation method for multi-phase staggered bidirectional DC converter - Google Patents

Abstract

The invention discloses a mixed-mode modulation method for a multi-phase interleaved bidirectional DC converter. If the power flow direction is from VS1 to VS2, switching tubes Q12 and Q22 apply a driving square wave with a phase shift of 180°, and Q11 and Q21 are turned off; if The power flow direction is from VS2 to VS1, the switching tubes Q11 and Q21 apply a driving square wave with a phase shift of 180°, and Q12 and Q22 are turned off; if the input power ranges from half load to full load, the driving square wave duty ratio of switching tubes Q12 and Q22 The range is [0,0.5]; if the input power ranges from no-load to half-load, the range of the square wave duty cycle of the switching tubes Q12 and Q22 is [0,1]; the inductance value is optimally designed as a bidirectional DC converter At half load, it works at the critical point of continuous conduction and discontinuous conduction. The invention combines the advantages of the continuous conduction mode and the discontinuous conduction mode of the multi-phase interleaved DC converter, and can switch the mode according to the output power range to improve the efficiency of the full power range, while satisfying the input current ripple condition Reduce the inductance value and increase the power density.

Description

A Mixed Mode Modulation Method for Multiphase Interleaved Bidirectional DC Converter

technical field

The invention relates to a bidirectional DC converter, in particular to a mixed mode modulation method for a multi-phase interleaved bidirectional DC converter.

Background technique

As one of the key technologies for energy storage systems, distributed power generation and electric vehicles, power converters require small size, light weight, stable performance, reliable system, high power density and excellent dynamic control performance. Especially in the application of high-power electric vehicles, the high-power energy storage inductor of the bidirectional DC converter is its key component, which accounts for the main volume and weight of the system. Designing a high-current, high-power energy storage inductor is difficult and has a Challenging work.

The two-phase interleaved bidirectional DC converter shown in Figure 1 can reduce the volume and weight of the converter and improve the reliability of the system. It is the preferred topology for high-power applications. Its specific circuit structure includes two bidirectional DC converters: converter 1 composed of inductor L1, switch tubes Q11 and Q12, converter 2 composed of inductor L2, switch tubes Q21 and Q22; DC filter capacitor Co. In order to reduce the volume of the converter, especially the inductor, it is necessary to use a smaller inductance value; however, if the inductance is too small, it is easy to generate obvious input current ripple, which affects the working life of the energy storage battery. Therefore, the value of the converter inductance must be optimized. At the same time, considering the discharge depth of the energy storage battery, the converter will work in a wide range of voltage and power. In some working ranges, the converter will easily lose its soft switching characteristics, produce obvious reactive power and circulating current, and reduce the power conversion efficiency. . Considering that there are multiple working modes in the small and medium power range; and there are obvious differences in the output power range, soft switching and reactive current distribution of each working mode, resulting in the different working modes of the same modulation strategy affecting the efficiency of the converter. There is a huge difference in optimization performance, so how to determine the optimal working mode under the multi-phase-shift modulation strategy has become another difficult problem to be solved urgently.

Contents of the invention

In order to overcome the above-mentioned defects in the prior art, the present invention provides a mixed-mode modulation method for a multi-phase interleaved bidirectional DC converter.

Technical scheme of the present invention is:

A mixed-mode modulation method for a multi-phase interleaved bidirectional DC converter, the modulation method comprising the steps of:

(1) First, according to the power flow direction, set the drive square wave of four switching tubes Q11, Q12, Q21, Q22: If the power flow direction is from VS1 to VS2, the switching tubes Q12 and Q22 apply a PWM driving square wave, and the switching tube Q22 The driving square wave has a 180° phase shift relative to Q12, and the switching tubes Q11 and Q21 are turned off by their anti-parallel diodes; if the power flow direction is from VS2 to VS1, the switching tubes Q11 and Q21 apply PWM driving square waves, and the switching tubes The driving square wave of Q21 has a 180° phase shift relative to Q12, and the switch tubes Q12 and Q22 are turned off by their anti-parallel diodes; the following steps are for the case of power flow from VS1 to VS2;

(2) If the input power ranges from half load to full load, the bidirectional DC converter adopts the continuous conduction mode, and the duty cycle of the PWM driving square wave of the switching tubes Q12 and Q22 is in the range of [0, 0.5];

(3) If the input power ranges from no-load to half-load, the bidirectional DC converter adopts discontinuous conduction mode, and the duty cycle of the PWM driving square wave of the switches Q12 and Q22 is [0, 1];

(4) The optimal design of the inductance value is that when the bidirectional DC converter is half-loaded, it works at the critical point of continuous conduction and discontinuous conduction.

The advantages of the present invention are:

The hybrid mode modulation method of the multi-phase interleaved bidirectional DC converter provided by the present invention combines the advantages of the continuous conduction mode and the discontinuous conduction mode of the multi-phase interleaved DC converter, and can switch the mode according to the output power range In order to improve the efficiency of the whole power range, and at the same time reduce the inductance value and improve the power density under the condition of satisfying the input current ripple.

Description of drawings

The present invention will be further described below in conjunction with accompanying drawing and embodiment:

Fig. 1 is the topology schematic diagram of the multi-phase interleaved bidirectional DC converter controlled by the method of the present invention;

Fig. 2 is a switch driving timing diagram and typical working waveforms of the continuous conduction working mode when the two-phase interleaved bidirectional DC converter according to the present invention is under heavy load;

Fig. 3 is a switch driving timing diagram and typical working waveforms of the light-load discontinuous conduction working mode of the two-phase interleaved bidirectional DC converter according to the present invention.

Detailed ways

Fig. 1 is the schematic diagram of the topological structure of the multi-phase interleaved bidirectional DC converter controlled by the method of the present invention, and its specific circuit structure includes two bidirectional DC converters: a converter 1 composed of an inductance L1, switching tubes Q11 and Q12, an inductance L2, Converter 2 composed of switching tubes Q21 and Q22; inductors L1 and L2 are connected to power supply VS1, and four switching tubes are connected to DC filter capacitor Co and power supply VS2.

The hybrid mode modulation method of the multi-phase interleaved bidirectional DC converter disclosed in the present invention, the modulation method includes the steps of:

(1) First, according to the power flow direction, set the drive square wave of four switching tubes Q11, Q12, Q21, Q22: If the power flow direction is from VS1 to VS2, the switching tubes Q12 and Q22 apply a PWM driving square wave, and the switching tube Q22 The driving square wave has a 180° phase shift relative to Q12, and the switching tubes Q11 and Q21 are turned off by their anti-parallel diodes; if the power flow direction is from VS2 to VS1, the switching tubes Q11 and Q21 apply PWM driving square waves, and the switching tubes The driving square wave of Q21 has a phase shift of 180° relative to Q12, and the switch tubes Q12 and Q22 are turned off by their anti-parallel diodes; the following steps are for the case of power flow from VS1 to VS2, and the case of power flow from VS1 to VS2 is the same as similar;

(2) If the input power ranges from half-load to full-load, the bidirectional DC converter adopts the continuous conduction mode, and the duty cycle of the PWM driving square wave of the switching tubes Q12 and Q22 is [0, 0.5]; as shown in Figure 2 , is the switch driving timing diagram and typical working waveform of the continuous conduction working mode of the two-phase interleaved bidirectional DC converter described in the present invention under heavy load;

(3) If the input power ranges from no-load to half-load, the bidirectional DC converter adopts discontinuous conduction mode, and the duty cycle of the PWM driving square wave of the switches Q12 and Q22 is [0, 1]; as shown in the figure 3 shows the switching drive timing diagram and typical operating waveforms of the light-load discontinuous conduction operating mode of the two-phase interleaved bidirectional DC converter according to the present invention.

(4) The optimal design of the inductance value is that when the bidirectional DC converter is half-loaded, it works at the critical point of continuous conduction and discontinuous conduction.

The above descriptions are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Within the technical scope disclosed in the present invention, any changes and substitutions shall fall within the protection scope of the present invention. Parts not described in detail in the present invention belong to the common knowledge of those skilled in the art.

Claims (1)

1. a mixed-mode modulation method for heterogeneous staggered bi-directional DC converter, is characterized in that, described modulator approach comprises step:

(1) first according to poower flow direction, the driving square wave of four switching tubes Q11, Q12, Q21, Q22 of two-way DC converter is set: if poower flow direction is from VS1 to VS2, switching tube Q12 and Q22 applies PWM and drives square wave, and the driving square wave of switching tube Q22 has 180 ° of phase shifts relative to Q12, switching tube Q11 and Q21 closes by its anti-paralleled diode afterflow; If poower flow direction is from VS2 to VS1, switching tube Q11 and Q21 applies PWM and drives square wave, and the driving square wave of switching tube Q21 has 180 ° of phase shifts relative to Q12, and switching tube Q12 and Q22 closes by its anti-paralleled diode afterflow; Following steps are the situation of poower flow from VS1 to VS2;

(2) if input power range is partly downloaded to fully loaded, two-way DC converter adopts continuous ON operation pattern, and the PWM of switching tube Q12 and Q22 drives the scope of duty cycle square wave to be [0,0.5];

(3) if input power range is from zero load to semi-load, two-way DC converter adopts Discontinuous Conduction mode of operation, and the PWM of switching tube Q12 and Q22 drives the scope of duty cycle square wave to be [0,1];

(4), when inductance value optimal design is two-way DC converter semi-load, the critical point of continuous conducting and Discontinuous Conduction is worked in.