阅读说明：本技术 一种燃料电池用高增益低应力dc/dc变换器 (High-gain low-stress DC/DC converter for fuel cell ) 是由 周美兰 付俊 王嘉明 吴晓刚 张宇 于 2020-06-08 设计创作，主要内容包括：本发明公开了一种燃料电池用高增益低应力DC/DC变换器,包括燃料电池、储能电路、开关电容电路和负载,储能电路包括第一储能电感、第二储能电感、第三储能电感、第一储能电容、第二储能电容、第三储能电容、第一储能二极管、第二储能二极管、第三储能二极管和第一功率开关管,开关电容电路包括第二功率开关管、第一开关电容、第二开关电容、第三开关电容、第一开关二极管、第二开关二极管、第三开关二极管和第四开关二极管,本发明通过储能电路的作用,在占空比较小的情况下可获得电压高增益,有效避免出现极端占空比的问题,同时通过开关电容电路的作用,实现器件低电压应力。(The invention discloses a high-gain low-stress DC/DC converter for a fuel cell, which comprises a fuel cell, an energy storage circuit, a switch capacitor circuit and a load, wherein the energy storage circuit comprises a first energy storage inductor, a second energy storage inductor, a third energy storage inductor, a first energy storage capacitor, a second energy storage capacitor, a third energy storage capacitor, a first energy storage diode, a second energy storage diode, a third energy storage diode and a first power switch tube, the switch capacitor circuit comprises a second power switch tube, a first switch capacitor, a second switch capacitor, a third switch capacitor, a first switch diode, a second switch diode, a third switch diode and a fourth switch diode, the invention can obtain high voltage gain under the condition of small duty ratio through the action of the energy storage circuit, effectively avoid the problem of extreme duty ratio, and simultaneously through the action of the switch capacitor circuit, and low voltage stress of the device is realized.)

1. A high-gain low-stress DC/DC converter for a fuel cell, characterized in that: comprising a fuel cell U_inEnergy storage circuit, switched capacitor circuit and load R_LThe energy storage circuit comprises a first energy storage inductor L1, a second energy storage inductor L2, a third energy storage inductor L3, a first energy storage capacitor C1, a second energy storage capacitor C2, a third energy storage capacitor C3, a first energy storage diode D1, a second energy storage diode D2, a third energy storage diode D3 and a third energy storage diode D2A first power switch Q1; the switched capacitor circuit comprises a second power switch tube Q2; two ends of the first energy storage inductor L1 are respectively connected with the fuel cell U_inThe anode of the first energy storage diode D1 is connected with the anode of the second energy storage diode D2, and two ends of the first energy storage capacitor C1 are respectively connected with the cathode of the first energy storage diode D1 and the fuel cell U_inThe negative electrode of the second energy storage inductor L2 is connected with the negative electrode of the first energy storage diode D1 and the negative electrode of the second energy storage diode D2, the negative electrode of the second energy storage diode D2 is connected with the drain electrode of the first power switch tube Q1, and the source electrode of the first power switch tube Q1 is connected with the fuel cell U_inThe cathode of the third energy storage diode D3 is connected with the cathode of the second energy storage diode D2, and the cathode of the third energy storage diode D3 is connected with the fuel cell U through the second energy storage capacitor C2_inThe negative electrodes of the third energy storage inductor L3 are connected to the cathode of the third energy storage diode D3 and the drain of the second power switch Q2, respectively, and the two ends of the third energy storage capacitor C3 are connected to the anode of the third energy storage diode D3 and the source of the second power switch Q2, respectively.

2. A high-gain low-stress DC/DC converter for a fuel cell according to claim 1, characterized in that: the switched capacitor circuit comprises a first switched capacitor C4, a second switched capacitor C5, a third switched capacitor C6, a first switched diode D4, a second switched diode D5, a third switched diode D6 and a fourth switched diode D7, wherein the source electrode of the second switched tube Q2 passes through the first switched diode D4 and a load R_LIs connected to the load R, the drain of the second switching tube Q2 passes through the second switching diode D5, the third switching diode D6 and the fourth switching diode D7 which are connected in series with each other and the load R_LIs connected to the load R, a second switched capacitor C5 and a third switched capacitor C6 connected in series with the load R_LThe drains of the second switching tubes Q2 are connected in parallel, the drains of the second switching tubes Q2 are connected with the middle points of the third switching diodes D6 and the fourth switching diodes D7 which are connected in series through the first switching capacitors C4, and the middle points of the second switching diodes D5 and the third switching diodes D6 which are connected in series are connected with the second switching capacitors C connected in series5 to the midpoint of the third switched capacitor C6.

3. A high-gain low-stress DC/DC converter for a fuel cell according to claim 1, characterized in that: the first power switch tube Q1 and the second power switch tube Q2 are turned on and off simultaneously, and the same PWM driving signal Vg is adopted.

4. A high-gain low-stress DC/DC converter for a fuel cell according to claim 3, characterized in that: the first power switch tube Q1 and the second power switch tube Q2 comprise a first working mode and a second working mode, and in the first working mode, the first power switch tube Q1 and the second power switch tube Q2 are simultaneously conducted; in the second working mode, the first power switch Q1 and the second power switch Q2 are turned off simultaneously.

5. The high-gain low-stress DC/DC converter according to claim 4, wherein: in the first working mode, the fuel cell U_inA first energy storage inductor L1 is charged by connecting a second energy storage diode D2 and a first power switch tube Q1 in series, a first energy storage capacitor C1 is charged by connecting a first power switch tube Q1 in series to a second energy storage inductor L2, a third energy storage capacitor C3 is charged by connecting a second power switch tube Q2 in series to a third energy storage inductor L3, and a first switch capacitor C4 and a third switch capacitor C6 are charged by connecting a third switch diode D6 to the first switch capacitor C4; the second switched capacitor C5 and the third switched capacitor C6 pass through a load R_LAnd (4) discharging.

6. The high-gain low-stress DC/DC converter according to claim 4, wherein: in the second working mode, the fuel cell U_inThe first energy storage diode D1 is connected in series with the first energy storage inductor L1 to charge the first energy storage capacitor C1; fuel cell U_inThe first energy storage inductor L1, the second energy storage inductor L2, the third energy storage inductor L3 and the first switch capacitor C4 are connected in series with a first energy storage diode D1, a third energy storage diode D3 and a fourth switchDiode D7 is load R_LSupplying power; fuel cell U_inThe first energy storage inductor L1, the second energy storage inductor L2 and the third energy storage inductor L3 are connected in series with the first energy storage diode D1, the third energy storage diode D3 and the second switching diode D5 to charge the third switching capacitor C6; fuel cell U_inThe first energy storage inductor L1, the second energy storage inductor L2 are connected in series with the first energy storage diode D1 and the first switch diode D4 to charge the third energy storage capacitor C3; fuel cell U_inThe first energy storage inductor L1, the second energy storage inductor L2 are connected in series with the first energy storage diode D1, and the third energy storage diode D3 to charge the second energy storage capacitor C2.

7. The high-gain low-stress DC/DC converter according to claim 4, wherein: the voltage gain M of the converter is:

in the formula, d is the duty ratio of the first power switch Q1 and the second power switch Q2.

8. The high-gain low-stress DC/DC converter according to claim 4, wherein: the voltage stress of the first power switch tube Q1 isThe voltage stress of the second power switch tube Q2 isThe voltage stress of the first energy storage capacitor C1 isThe voltage stress of the second energy storage capacitor C2 and the third energy storage capacitor C3 isThe voltage stress of the first switch capacitor C4 and the second switch capacitor C5 isThe voltage stress of the third switch capacitor C6 isWherein U is_oIs the output voltage.

Technical Field

The invention relates to the field of converters, in particular to a high-gain low-stress DC/DC converter for a fuel cell.

Background

With the increasing number of vehicles, the use of a large amount of fossil fuels causes serious energy shortage and environmental pollution problems, and the rapid development of new energy automobiles is an urgent requirement at present. Fuel cell vehicles are favored by the automotive industry due to their characteristics of cleanliness and high efficiency, however, there are many problems in developing fuel cell vehicles, such as the output characteristics of fuel cells are soft, and as the output current increases, the output voltage rapidly decreases, and thus the fuel cell vehicles cannot be directly used for supplying power to vehicles. Therefore, it is important to develop a DC/DC converter having a high gain to develop a fuel cell vehicle. The traditional Boost circuit is difficult to obtain high voltage gain, the requirement of a fuel cell automobile cannot be met, and in the high gain process, the problem of extreme duty ratio can occur to a switching tube, so that the switching tube is too long in conduction time and damaged.

In some existing non-isolated high-gain DC/DC converters, the problems that voltage stress of devices such as a switch tube and a capacitor is overlarge and an input end and an output end are not in common are solved, on one hand, difficulty is brought to type selection of the converter devices, and on the other hand, high-frequency pulsating voltage can be generated between the input end and the output end due to the structure that the input end and the output end are not in common, so that the working reliability of the converter is reduced. The existing isolated DC/DC converter can obtain high voltage gain through the coupling inductor, but the isolated structure increases the volume of the converter, is not suitable for being used in fuel cell automobiles, and cannot meet the daily requirements of people.

Disclosure of Invention

In order to solve the above problems, the present invention provides a high-gain low-stress DC/DC converter for a fuel cell, which has the advantages of high gain, low stress, simple control, common ground for an input terminal and an output terminal, and the like.

A high-gain low-stress DC/DC converter for fuel cell comprises a fuel cell U_inEnergy storage circuit, switched capacitor circuit and load R_LThe energy storage circuit comprises a first energy storage inductor L1, a second energy storage inductor L2, a third energy storage inductor L3, a first energy storage capacitor C1, a second energy storage capacitor C2, a third energy storage capacitor C3, a first energy storage diode D1, a second energy storage diode D2, a third energy storage diode D3 and a first power switch tube Q1; the switched capacitor circuit comprises a second power switch tube Q2; two ends of the first energy storage inductor L1 are respectively connected with the fuel cell U_inThe anode of the first energy storage diode D1 is connected with the anode of the second energy storage diode D2, and two ends of the first energy storage capacitor C1 are respectively connected with the cathode of the first energy storage diode D1 and the fuel cell U_inThe negative electrode of the second energy storage inductor L2 is connected with the negative electrode of the first energy storage diode D1 and the negative electrode of the second energy storage diode D2, the negative electrode of the second energy storage diode D2 is connected with the drain electrode of the first power switch tube Q1, and the source electrode of the first power switch tube Q1 is connected with the fuel cell U_inThe cathode of the third energy storage diode D3 is connected with the cathode of the second energy storage diode D2, and the cathode of the third energy storage diode D3 is connected with the fuel cell U through the second energy storage capacitor C2_inThe negative electrodes of the third energy storage inductor L3 are connected to the cathode of the third energy storage diode D3 and the drain of the second power switch Q2, respectively, and the two ends of the third energy storage capacitor C3 are connected to the anode of the third energy storage diode D3 and the source of the second power switch Q2, respectively.

Further, the switched capacitor circuit includes a first switched capacitor C4, a second switched capacitor C5, a third switched capacitor C6, a first switched diode D4, a second switched diode D5, a third switched diode D6 and a fourth switched diode D7, and a source of the second switched diode Q2 passes through the first switched diode D4 and a load R_LIs connected to the load R, the drain of the second switching tube Q2 passes through the second switching diode D5, the third switching diode D6 and the fourth switching diode D7 which are connected in series with each other and the load R_LIs connected to the load R, a second switched capacitor C5 and a third switched capacitor C6 connected in series with the load R_LIn parallelThe drain of the second switch tube Q2 is connected to the midpoint of the third switch diode D6 and the fourth switch diode D7 connected in series through the first switch capacitor C4, and the midpoint of the second switch diode D5 and the third switch diode D6 connected in series is connected to the midpoint of the second switch capacitor C5 and the third switch capacitor C6 connected in series.

Further, the first power switch Q1 and the second power switch Q2 are turned on and off simultaneously, and the same PWM driving signal Vg is used.

Further, the first power switch Q1 and the second power switch Q2 include a first working mode and a second working mode, and in the first working mode, the first power switch Q1 and the second power switch Q2 are turned on simultaneously; in the second working mode, the first power switch Q1 and the second power switch Q2 are turned off simultaneously.

Further, in the first operating mode, the fuel cell U_inA first energy storage inductor L1 is charged by connecting a second energy storage diode D2 and a first power switch tube Q1 in series, a first energy storage capacitor C1 is charged by connecting a first power switch tube Q1 in series to a second energy storage inductor L2, a third energy storage capacitor C3 is charged by connecting a second power switch tube Q2 in series to a third energy storage inductor L3, and a first switch capacitor C4 and a third switch capacitor C6 are charged by connecting a third switch diode D6 to the first switch capacitor C4; the second switched capacitor C5 and the third switched capacitor C6 pass through a load R_LAnd (4) discharging.

Further, in the second operation mode, the fuel cell U_inThe first energy storage diode D1 is connected in series with the first energy storage inductor L1 to charge the first energy storage capacitor C1; fuel cell U_inThe first energy storage inductor L1, the second energy storage inductor L2, the third energy storage inductor L3 and the first switch capacitor C4 are connected in series with a first energy storage diode D1, a third energy storage diode D3 and a fourth switch diode D7 to serve as a load R_LSupplying power; fuel cell U_inThe first energy storage inductor L1, the second energy storage inductor L2 and the third energy storage inductor L3 are connected in series with the first energy storage diode D1, the third energy storage diode D3 and the second switching diode D5 to charge the third switching capacitor C6; fuel cell U_inA first energy storage inductorThe L1, the second energy storage inductor L2 are connected in series with the first energy storage diode D1 and the first switch diode D4 to charge the third energy storage capacitor C3; fuel cell U_inThe first energy storage inductor L1, the second energy storage inductor L2 are connected in series with the first energy storage diode D1, and the third energy storage diode D3 to charge the second energy storage capacitor C2.

Further, the voltage gain M of the converter is:

in the formula, d is the duty ratio of the first power switch Q1 and the second power switch Q2.

Further, the voltage stress of the first power switch tube Q1 isThe voltage stress of the second power switch tube Q2 isThe voltage stress of the first energy storage capacitor C1 isThe voltage stress of the second energy storage capacitor C2 and the third energy storage capacitor C3 isThe voltage stress of the first switch capacitor C4 and the second switch capacitor C5 isThe voltage stress of the third switch capacitor C6 isWherein U is_oIs the output voltage.

Compared with the prior art, the application has the following beneficial effects:

1. the method and the device meet the requirement of high gain of the fuel cell automobile, and the problem of extreme duty ratio of the switching tube can be avoided while the high gain is realized;

2. in the converter circuit, the voltage stress of the power semiconductor device and the capacitor is low, so that the device type selection of the converter is facilitated, and the working safety of the converter is improved;

3. the converter belongs to a structure that the input end and the output end are grounded, the problem of high-frequency pulsating voltage between the input end and the output end is avoided, and the working reliability of the converter is improved;

4. the converter belongs to a non-isolated converter, and the size of the converter is effectively reduced;

5. two power switch tubes used by the converter are simultaneously turned on and turned off, and the complexity of circuit control is effectively reduced.

Drawings

FIG. 1 is a schematic diagram of a high gain low stress DC/DC converter circuit for a fuel cell in accordance with the present invention;

FIG. 2 is a schematic diagram of a modulation scheme for a power switch in a converter according to the present invention;

fig. 3 is a schematic diagram of an equivalent circuit of the converter according to the present invention in a first operating mode;

FIG. 4 is a schematic diagram of an equivalent circuit of the converter according to the present invention in the second operating mode;

FIG. 5 is a graph comparing the theoretical voltage gain of the converter proposed by the present invention with the theoretical voltage gain of a conventional Boost circuit;

FIG. 6 is a graph of the inductor current waveform of the converter proposed by the present invention;

FIG. 7 is a graph of the voltage stress waveform of the converter diode proposed by the present invention;

fig. 8 is a voltage stress diagram of a converter switching tube according to the present invention.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict.

It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention, and the drawings only show the components related to the present invention rather than the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.

As shown in FIG. 1, a high-gain low-stress DC/DC converter for fuel cell comprises a fuel cell U_inEnergy storage circuit, switched capacitor circuit and load R_LThe energy storage circuit comprises a first energy storage inductor L1, a second energy storage inductor L2, a third energy storage inductor L3, a first energy storage capacitor C1, a second energy storage capacitor C2, a third energy storage capacitor C3, a first energy storage diode D1, a second energy storage diode D2, a third energy storage diode D3 and a first power switch tube Q1; the switched capacitor circuit comprises a second power switch tube Q2; two ends of the first energy storage inductor L1 are respectively connected with the fuel cell U_inThe anode of the first energy storage diode D1 is connected with the anode of the second energy storage diode D2, and two ends of the first energy storage capacitor C1 are respectively connected with the cathode of the first energy storage diode D1 and the fuel cell U_inThe negative electrode of the second energy storage inductor L2 is connected with the negative electrode of the first energy storage diode D1 and the negative electrode of the second energy storage diode D2, the negative electrode of the second energy storage diode D2 is connected with the drain electrode of the first power switch tube Q1, and the source electrode of the first power switch tube Q1 is connected with the fuel cell U_inThe cathode of the third energy storage diode D3 is connected with the cathode of the second energy storage diode D2, and the cathode of the third energy storage diode D3 is connected with the fuel cell U through the second energy storage capacitor C2_inThe negative electrode of the third energy storage inductor L3 is connected with the negative electrode of the third energy storage diode D3 and the drain electrode of the second power switch tube Q2, and the third energy storage capacitor C3Are respectively connected with the anode of the third energy storage diode D3 and the source of the second power switch Q2.

The switched capacitor circuit comprises a first switched capacitor C4, a second switched capacitor C5, a third switched capacitor C6, a first switched diode D4, a second switched diode D5, a third switched diode D6 and a fourth switched diode D7, wherein the source electrode of the second switched tube Q2 passes through the first switched diode D4 and a load R_LIs connected to the load R, the drain of the second switching tube Q2 passes through the second switching diode D5, the third switching diode D6 and the fourth switching diode D7 which are connected in series with each other and the load R_LIs connected to the load R, a second switched capacitor C5 and a third switched capacitor C6 connected in series with the load R_LThe drains of the second switching tubes Q2 are connected in parallel, the drains of the second switching tubes Q2 are connected to the middle points of the third switching diodes D6 and the fourth switching diodes D7 connected in series through the first switching capacitors C4, and the middle points of the second switching diodes D5 and the third switching diodes D6 connected in series are connected to the middle points of the second switching capacitors C5 and the third switching capacitors C6 connected in series.

As shown in fig. 2, the first power switch Q1 and the second power switch Q2 are turned on and off simultaneously, and a triangular carrier V is adopted_CAnd a modulation wave V_rAnd modulating to obtain the same PWM driving signal Vg.

As shown in fig. 3, the first power switch Q1 and the second power switch Q2 include a first operation mode and a second operation mode, and in the first operation mode, the first power switch Q1 and the second power switch Q2 are turned on simultaneously; in the second working mode, the first power switch Q1 and the second power switch Q2 are turned off simultaneously.

Further, in the first operating mode, the fuel cell U_inThe first energy storage inductor L1 is charged by connecting the second energy storage diode D2 and the first power switch tube Q1 in series, the second energy storage inductor L2 is charged by connecting the first energy storage capacitor C1 and the first power switch tube Q1 in series, the third energy storage capacitor L3 is charged by connecting the third energy storage capacitor C3 and the second power switch tube Q2 in series, and the first switch capacitor C4 and the third switch capacitor C6 are charged by connecting the third switch diode D6 and the first switch capacitor C6 in seriesC4 charging; the second switched capacitor C5 and the third switched capacitor C6 pass through a load R_LAnd (4) discharging.

From kirchhoff's voltage law, equation (1) is derived according to the equivalent circuit of fig. 3.

In the formula of U_c1、U_c2、U_c3、U_c4、U_c5、U_c6The voltages of the first energy storage capacitor C1, the second energy storage capacitor C2, the third energy storage capacitor C3, the first switch capacitor C4, the second switch capacitor C5 and the third switch capacitor C6 are U_L1on、U_L2onAnd U_L3onWhen the first power switch Q1 and the second power switch Q2 are turned on, the voltage across the first energy storage inductor L1, the second energy storage inductor L2 and the third energy storage inductor L3, U_inFor the converter input voltage, U_oIs the output voltage.

In the second mode of operation, as shown in fig. 4, the fuel cell U_inThe first energy storage diode D1 is connected in series with the first energy storage inductor L1 to charge the first energy storage capacitor C1; fuel cell U_inThe first energy storage inductor L1, the second energy storage inductor L2, the third energy storage inductor L3 and the first switch capacitor C4 are connected in series with a first energy storage diode D1, a third energy storage diode D3 and a fourth switch diode D7 to serve as a load R_LSupplying power; fuel cell U_inThe first energy storage inductor L1, the second energy storage inductor L2 and the third energy storage inductor L3 are connected in series with the first energy storage diode D1, the third energy storage diode D3 and the second switching diode D5 to charge the third switching capacitor C6; fuel cell U_inThe first energy storage inductor L1, the second energy storage inductor L2 are connected in series with the first energy storage diode D1 and the first switch diode D4 to charge the third energy storage capacitor C3; fuel cell U_inThe first energy storage inductor L1, the second energy storage inductor L2 are connected in series with the first energy storage diode D1, and the third energy storage diode D3 to charge the second energy storage capacitor C2.

From kirchhoff's voltage law, equation (2) is derived according to the equivalent circuit of fig. 4.

In the formula of U_L1off、U_L2offAnd U_L3offWhen the first power switch Q1 and the second power switch Q2 are turned off, the voltage across the first energy storage inductor L1, the second energy storage inductor L2 and the third energy storage inductor L3.

According to the volt-second balance principle, a volt-second balance equation is listed for the first energy storage inductor L1 and the second energy storage inductor L2, and a formula (3) is obtained.

Obtaining the theoretical voltage gain M of the converter by combining the formula (1), the formula (2) and the formula (3) is shown in the formula (4), wherein the voltage gain M of the converter is:

in the formula, d is the duty ratio of the PWM driving signal Vg of the first power switch Q1 and the second power switch Q2, and 0< d < 1.

Fig. 5 is a comparison graph of the theoretical voltage gain of the converter proposed by the present invention and the theoretical voltage gain of the conventional Boost circuit, and it can be seen from the graph that the proposed converter voltage gain is higher than that of the conventional Boost circuit in the set duty ratio range.

By combining three formulas of formula (1), formula (2) and formula (3), the voltage stress of the relevant devices in the converter can be obtained as shown in formula (5).

In the formula of U_Q1And U_Q2For the voltage across the first power switch Q1 and the second power switch Q2, it can be seen from equation (5) that the power switch and the capacitor have lower voltage stress; the voltage stress of the first power switch tube Q1 isThe voltage stress of the second power switch tube Q2 isThe voltage stress of the first energy storage capacitor C1 isThe voltage stress of the second energy storage capacitor C2 and the third energy storage capacitor C3 isThe voltage stress of the first switch capacitor C4 and the second switch capacitor C5 isThe voltage stress of the third switch capacitor C6 isWherein U is_oIs the output voltage.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.