CN111555614A - Interleaved DC-DC converter of automobile dual power supply system and control method thereof - Google Patents
Interleaved DC-DC converter of automobile dual power supply system and control method thereof Download PDFInfo
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- CN111555614A CN111555614A CN202010288151.7A CN202010288151A CN111555614A CN 111555614 A CN111555614 A CN 111555614A CN 202010288151 A CN202010288151 A CN 202010288151A CN 111555614 A CN111555614 A CN 111555614A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
- H02M3/1584—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load with a plurality of power processing stages connected in parallel
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
- H02J7/0014—Circuits for equalisation of charge between batteries
- H02J7/0016—Circuits for equalisation of charge between batteries using shunting, discharge or bypass circuits
Abstract
The invention provides an interleaved DC-DC converter of an automobile dual-power system and a control method thereof, wherein the interleaved DC-DC converter consists of N non-isolated DC-DC converters, the N non-isolated DC-DC converters are mutually interleaved and connected in parallel, the complementary PWM driving signals between the N non-isolated DC-DC converters have a 360 DEG/N difference, each non-isolated converter adopts a Buck-Boost topology with reversed polarity, and the circuit structures of the Buck-Boost topology are the same. Compared with the prior art, the converter can reduce the cost of the existing battery pack, reduce the rated design power of a single DC-DC converter, reduce current ripples, reduce the stress of devices and facilitate the modularized installation and capacity expansion of the converter.
Description
Technical Field
The invention belongs to the field of electronic and power electronic converters of hybrid vehicles, and particularly relates to an interleaved DC-DC converter of a dual power supply system of a vehicle and a control method thereof.
Background
In recent years, the functions of automobiles are increasing, a 12V power supply system is difficult to bear increasing engine load, strict emission regulations in 2020 make the hybrid and pure electric vehicles become the best technical routes. With the release of the 48V power system specification LV148, automotive low voltage auxiliary power systems are transitioning from 12V to 48V systems, which requires extensive coordination by both the finished vehicle plant and the solution dealer. A dual power supply (48V/12V) system architecture is gradually attracting attention as a transition scheme of a 12V to 48V system, and a 12V power supply supplies power to equipment with small load current, such as a sound, an instrument, a wiper and the like. The 48V power supply supplies power to equipment with large load current, such as: air conditioners, lights, fans, and the like. Generally, a dual power supply (48V/12V) system is generally composed of the following parts: 48V battery, 48V load, DC-DC converter, 12V battery, 12V load.
However, in the existing dual power supply (48V/12V) system, a 48V battery and a 12V battery are generally used, are independent from each other, are connected through a DC-DC converter, and are commonly connected to a common ground. By adopting the structure, the structure is complex, the volume is large, and the cost of the system is increased by two groups of batteries. For example, chinese patent CN201910216695, a dual-voltage power supply system for an automobile and a control method thereof, discloses that an isolated DC-DC converter specially designed is used for voltage energy conversion, but the isolated DC-DC converter still has the problems of many devices, complex structure, large volume and complex control, and in addition, because the fluctuation of a 12V load existing in a vehicle is often large, the actual output power capacity of the isolated DC-DC converter is not large enough, so that a power device needs to be designed with a larger safety margin for practical application in a hybrid automobile power supply to obtain sufficient output power.
Therefore, it is highly desirable to design a converter of dual power supply system for automobile, which can realize automatic voltage-sharing function, reduce the hardware cost and system volume of the dual power supply system for hybrid automobile, increase the output power and reduce the control complexity of the switching device,
disclosure of Invention
Technical problem to be solved
Based on the defects mentioned in the background technology, the invention designs the staggered DC-DC converter of the automobile dual-power system and the control method thereof, which can realize the automatic voltage equalization of the battery pack, reduce the battery pack cost of the existing system, improve the actual output power capacity of the DC-DC converter and greatly reduce the cost and the volume of the hybrid automobile dual-power supply system. In addition, the improved staggered DC-DC converter is formed by connecting N non-isolated DC-DC converters in parallel, and the complementary PWM driving signals of the converters have a difference of 360 DEG/N, so that the converter not only can reduce current ripples, but also is convenient for modularized installation and capacity expansion, and is particularly suitable for a 48V/12V dual-power system of an automobile.
(II) technical scheme
The invention discloses an interleaved DC-DC converter of an automobile dual-power system, which consists of N non-isolated DC-DC converters, wherein the N non-isolated DC-DC converters are mutually interleaved and connected in parallel, complementary PWM (pulse width modulation) driving signals between the N non-isolated DC-DC converters have a difference of 360 degrees/N, N is more than or equal to 2, each non-isolated converter adopts a Buck-Boost topology with reversed polarity and has the same circuit structure, a 36V battery pack is connected to the input end of each non-isolated DC-DC converter, the output end of each non-isolated converter is simultaneously connected to a 12V battery pack and a 12V load, and the 36V battery pack and the 12V battery pack are connected in series to form a 48V battery pack and then supply power to the 48V load;
each non-isolated DC-DC converter comprises a first switch tube, a second switch tube, an input filter capacitor, an output filter capacitor and an energy storage inductor, wherein one end of the input filter capacitor is connected with the drain electrode of the first switch tube; the source electrode of the first switch tube is connected with the drain electrode of the second switch tube and one end of the energy storage inductor; one end of the output filter capacitor is connected with the source electrode of the second switch tube; the other end of the input filter capacitor is connected with the other end of the output filter capacitor and the other end of the energy storage inductor, one end of the output filter capacitor is connected with the negative electrode of the 12V battery pack, the other end of the output filter capacitor is connected with the positive electrode of the 12V battery pack, the positive electrode of the 36V battery pack is connected with one end of the input filter capacitor, and the negative electrode of the 36V battery pack is connected with the other end of the input filter capacitor.
Furthermore, the source electrode of the second switch tube is the cathode of the non-isolated DC-DC converter, the other end of the output filter capacitor is the anode of the non-isolated DC-DC converter, and the outputs of the non-isolated DC-DC converters are connected in parallel in a staggered mode.
Furthermore, the controller collects input voltage, output voltage and output current of the converter through the signal conditioning circuit and forms a double closed-loop control system, the double closed-loop control system comprises a voltage outer loop and a current inner loop, peak current mode control is adopted, when overload occurs, driving blocking protection is carried out on a first switch tube and a second switch tube of each group of non-isolated DC-DC converters, and the voltage outer loop and the current inner loop are preferably controlled by a PI controller.
Further, the 48V load is jointly supplied with power by a 36V battery pack connected in series with a 12V battery pack; the 12V load was delivered by the 36V battery pack through the interleaved DC-DC converter with the required load power of 3/4, and additionally 1/4 load power was provided by the 12V battery pack.
In addition, the invention also discloses a control method of the interleaved DC-DC converter of the automobile dual power supply system, which comprises the following steps:
step 1: the controller collects the voltage of the 36V battery pack and the voltage of the 12V battery pack;
step 2: the controller selects to send an enable signal or a blocking signal to the driving circuit according to the voltage condition in the step 1; detecting a voltage ratio between the 36V battery pack and the 12V battery pack: when the voltage ratio is greater than 3, sending an enabling signal to a driving circuit, enabling a converter to work, supplying power to a 12V load by the converter, realizing automatic voltage equalization of the voltage of the battery pack, and entering the step 3; when the voltage ratio is less than 3, the converter is in a standby state and continuously detects the voltage ratio; when a fault occurs or other conditions needing shutdown occur, a blocking signal is sent to the driving circuit to carry out wave-blocking protection;
and step 3: the converter normally works, the controller controls the switching tubes of each group of non-isolated DC-DC converters in a peak current control mode, and if the current is overlarge, the controller gives out an adjusted PWM signal to limit the current so as to realize power amplitude limiting protection.
Further, the step 3 further includes: during normal operation, each group of switching tubes is controlled according to the following two modes in one switching period of the non-isolated DC-DC converter:
the first mode is as follows: at an initial time t0When the energy storage inductor is in a working state, the first switching tube is switched on, the second switching tube is switched off, and the current of the energy storage inductor linearly rises; rises to t1The time is converted into a second mode;
mode two: at t1At the moment, the first switch tube is turned off, the second switch tube is turned on, the second switch tube provides a follow current loop for the energy storage inductor, the current of the energy storage inductor is linearly reduced, and at t2At that time, modality two ends.
Further, the duty ratio calculation formula of the first switching tube is as follows:
the conduction time of the first switching tube is as follows: t ison＝t1-t0＝D/fs(ii) a The first off time of the switch tube is as follows: t isoff＝t2-t1＝(1-D)/fsWherein f issIs the switching frequency.
(III) advantageous effects
The invention can save a group of 12V battery packs, and under the condition of the same 12V load, the power requirement of the non-isolated staggered DC-DC converter for the hybrid electric vehicle dual-power system only has the power 3/4 of the DC-DC converter of the traditional dual-voltage power supply system, thereby reducing the actual output power capacity of the DC-DC converter. In addition, compared with the existing patent CN201910216695, the interleaved DC-DC converter of the dual power supply system of the automobile of the present invention is formed by connecting the non-isolated DC-DC converters in parallel, so that the hardware cost and the occupied volume of the dual power supply system of the hybrid automobile can be further reduced (the non-isolated converter is simpler and smaller than the isolated converter), and the control method is simpler. In addition, in a dual-power supply system of 48V/12V, because the 48V battery pack and the 12V battery pack need to be connected to the same reference ground, the invention selects and adopts the improved reverse polarity topological structure of Buck-Boost to ensure that the 12V battery pack and the 36V battery pack are just connected in series, and the 48V battery pack and the 12V battery pack which are connected in series can be connected to the same reference ground after the non-isolated DC-DC converter is used, and in addition, when the interleaved DC-DC converter discharges the battery packs, the automatic voltage equalization of the battery pack is completed by N groups of non-isolated staggered DC-DC converters with PWM driving signal difference of 360 DEG/N, so that the output power can be increased, the ripple waves can be reduced, the converters can be connected in parallel in a modularized way, the installation and the use are easy, and the system is stable and reliable, and can be widely applied to a hybrid electric vehicle dual-power (48V/12V) power supply system.
Drawings
In order to more clearly illustrate the technical scheme of the invention or the prior art, the following figures are given by taking an automobile dual-power system with three non-isolated DC-DC converters connected in parallel in an interleaving manner as an example, and the figures required by the embodiment are briefly described:
FIG. 1 is a schematic diagram of a dual power system of an automobile with interleaved DC-DC converters according to the present invention;
FIG. 2 is a control block diagram of an interleaved DC-DC converter of the dual power system of the vehicle of the present invention;
FIG. 3 is a waveform diagram illustrating the operation of the non-isolated DC-DC converter 1 according to the present invention;
FIG. 4 is a waveform diagram of the simulation of the interleaved DC-DC converter of the dual power system of the automobile.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
The invention provides an interleaved DC-DC converter of an automobile dual-power system and a control method thereof, wherein the automobile dual-power system comprises: a 36V battery pack, a 12V battery pack, an interleaved DC-DC converter, a 48V load and a 12V load; the 36V battery pack is obtained by connecting 3 12V battery packs in series, is used as an input end of the interleaved DC-DC converter, and is connected with the 12V battery packs in series to be used as a power supply of a 48V load; the 12V battery pack is connected with the 12V load in parallel, the input end of the staggered DC-DC converter is connected with the 36V battery pack, the output end of the staggered DC-DC converter is connected with the 12V load and the 12V battery pack, namely, the positive and negative poles of the output end of the staggered DC-DC converter are correspondingly connected with the positive and negative poles of the 12V battery pack and the 12V battery pack. It should be noted that, in order to reduce the hardware cost and the occupied volume of the dual power supply system of the hybrid electric vehicle, the interleaved DC-DC converter of the present invention is a non-isolated converter, and in addition, as shown in fig. 1, since the interleaved DC-DC converter including the Buck-Boost improved circuit is a non-isolated reverse polarity output, the switching tube S is a switching tube S1～S6The output of one side is negative polarity, and the negative polarity is connected to the negative pole of the 12V battery pack and the 12V load after being connected in parallel. In a dual-power supply system (48V/12V), because a 48V battery pack and a 12V battery pack need to be connected to the same reference ground, the 12V battery pack and a 36V battery pack can be just connected in series by adopting a Buck-Boost topological structure, and the 48V battery pack and the 12V battery pack which are connected in series can be connected to the same reference ground.
It is to be noted that if the non-isolated converter of the present invention is usedIf Buck-Boost is not selected to realize reverse polarity output, the 48V power supply cannot be synthesized because C is used2When the upper end is positive and the lower end is negative (namely, when the output is positive and negative), the positive electrode of the 12V battery pack and the capacitor C are simultaneously connected1、C2And an energy storage inductor L1Connection, in which the lower end is C of negative polarity2The positive electrode and the negative electrode of the 12V battery pack must be connected to one end of the non-isolated converter belonging to the non-switching tube because of the requirement of energy conversion, and thus, the positive electrode and the negative electrode of the 12V battery pack are connected to one end of the non-isolated converter, and at this time, a short circuit of the 12V battery pack is formed, so that the synthesis of a 48V direct-current power supply cannot be stably realized.
Referring to fig. 1, taking three non-isolated DC-DC converters as an example, the interleaved DC-DC converter of the present invention is composed of three non-isolated DC-DC converters 1 to 3, the three non-isolated DC-DC converters 1 to 3 are connected in parallel in a staggered manner at 120 °, each non-isolated converter adopts a Buck-Boost topology with opposite polarity and has the same circuit structure, wherein a 36V battery pack is connected to an input end of each non-isolated DC-DC converter, an output end of the non-isolated converter is simultaneously connected to a 12V battery pack and a 12V load, the 36V battery pack and the 12V battery pack are connected in series to form a 48V battery pack, and the 48V battery pack is supplied to the 48V load, so that a group of 12V battery packs is reduced.
It should be noted that the interleaved DC-DC converter of the present invention may be composed of 2 or more than 4 non-isolated DC-DC converters (i.e., N is a natural number greater than or equal to 2), and during small-scale expansion, the number of the non-isolated DC-DC converters may be changed, and only the complementary PWM driving signal angle difference between the non-isolated DC-DC converters needs to be adjusted to 360 °/N. In addition, in order to realize larger output power, when large-scale capacity expansion is needed, the interleaved DC-DC converter with the N non-isolated DC-DC converters can also be connected in parallel with other interleaved DC-DC converters with the M non-isolated DC-DC converters, and in this case, the PWM driving signal of the non-isolated DC-DC converters in each interleaved DC-DC converter does not need to be changed.
The non-isolated DC-DC converter adopts a classic Buck-Boost reverse polarity topological structure, and needs to reduce the loss of a freewheeling diodeSwitching tube S with extremely low on-state resistance2So as to realize synchronous rectification modulation and improve the overall efficiency of the converter. Since the three non-isolated DC-DC converters have the same structure, taking one of the non-isolated DC-DC converters 1 as an example, the non-isolated DC-DC converter comprises a switch tube S1And a switch tube II S2An input filter capacitor C1An output filter capacitor C2Energy storage inductor L1. Input filter capacitor C1One end of (1) and a switch tube (S)1The drain electrodes of the two electrodes are connected; switch tube I S1Source electrode and switch tube II S2Drain electrode and energy storage inductor L1Are connected together at one end; output capacitor C2One end of the switch tube II S2The source electrodes of the two-way transistor are connected; input filter capacitor C1Another terminal of (1) and an output filter capacitor C2And the other end of (1) and L1And the other end of the two are connected. Wherein the switch tube is two S2Source and C of2One end of (1) is the negative pole of the non-isolated DC-DC converter 1, C2The other end of the non-isolated DC-DC converter is the anode of the non-isolated DC-DC converter 1, and the outputs of the non-isolated DC-DC converters are mutually staggered and connected in parallel.
In the double-power (48V/12V) power supply system structure of the hybrid electric vehicle, the non-isolated DC-DC converter is controlled to ensure that the 36V battery pack and the 12V battery pack keep charge balance, namely the output power ratio of the two battery packs is 3: 1. Therefore, when the 12V load power is P without considering the converter lossoThen the 12V battery output power is P under the structureoThe output power of the/4, 36V battery pack is 3/4Po. The effect of the three non-isolated DC-DC converters is to deliver the 36V battery pack output power to the 12V load, i.e. the non-isolated DC-DC converter delivers 3/4 with 12V load power, i.e. the output power of the converter and the 12V battery pack is distributed according to 3:1 when the converter is in operation. In addition, because the interleaved DC-DC converter of the automobile dual-power system adopts the non-isolated DC-DC converter to be formed in parallel, compared with the existing isolated converter, the interleaved DC-DC converter of the automobile dual-power system can further reduce the hardware cost and the occupied volume of the hybrid automobile dual-power system, and in addition, when the battery pack discharges, the interleaved DC-DC converter of the invention adopts the non-isolated converter to be formed in parallelThe interleaved DC-DC converter completes automatic voltage equalization of the battery pack, can increase output power, can modularly connect the converters in parallel, is easy to install and use, is stable and reliable, and is particularly suitable for being applied to a hybrid electric vehicle dual-power (48V/12V) power supply system.
The interleaved DC-DC converter is formed by connecting three Buck-Boost converters (namely, non-isolated DC-DC converters 1-3) in parallel in a 120-degree interleaved manner, a control part of each non-isolated DC-DC converter comprises a controller and a driving circuit, the controller adopts a digital control chip and is used for generating three groups of complementary PWM driving signals for driving a switching tube, and the PWM driving signals corresponding to each group of non-isolated DC-DC converters have a 120-degree difference (for example, S)1、S3、S5The difference between every two drive signals is 120 degrees); the driving circuit receives a PWM driving signal of the controller, provides driving voltage for a switching tube of the main circuit after isolation and boosting, and controls the switching tube to be switched on and off. In order to reduce the on-state loss of the freewheeling diode and improve the efficiency, a synchronous rectification technology is adopted; the controller collects input voltage, output voltage and output current of the converter through the signal conditioning circuit and forms a double closed-loop control system, the control block diagram is shown in figure 2, the double closed-loop control system comprises a voltage outer loop and a current inner loop, peak current mode control is adopted in the current inner loop, and when overload occurs, driving blocking protection is carried out on a first switch tube and a second switch tube of each group of non-isolated DC-DC converters. Under the control method, the voltage balance of the battery pack can be automatically realized.
The controller is used for controlling the non-isolated DC-DC converter, the controller is connected to the driving circuit, and the driving circuit drives the switching tube of the non-isolated DC-DC converter to normally work after processing the PWM driving signal, so that the closed-loop control of the converter is realized; the controller also receives some protection signals (overvoltage, overcurrent, etc.) to block the drive signal or to limit the current protection. Taking the non-isolated DC-DC converter 1 as an example, the control block diagram is shown in FIG. 2, and the output voltage VoutIs an outer loop, and is connected to a reference voltage VrefAfter error comparison, PI regulation is carried out to obtain a reference value i of the output currentrefTo output a current ioutIs an inner ring, and current flowsReference irefAfter error comparison, the control rate is obtained through PI regulation, and a group of complementary PWM signals are obtained through processing of a driving circuit to drive a switching tube S1And S2。
In another embodiment, in order to control the interleaved DC-DC converter to operate normally, the present invention further provides a control method of the interleaved DC-DC converter corresponding to the dual power supply system of the vehicle, where the control method includes the following steps:
step 1: the controller collects the voltage of the 36V battery pack and the voltage of the 12V battery pack;
step 2: the controller selects to send an enable signal or a blocking signal to the driving circuit according to the voltage condition in the step 1;
detecting a voltage ratio between the 36V battery pack and the 12V battery pack: when the voltage ratio is greater than 3, the converter works, supplies power to a 12V load, sends an enabling signal to the driving circuit, realizes automatic voltage equalization of the battery pack voltage, and enters step 3;
when the voltage ratio is less than 3, the converter is in a standby state and continuously detects the voltage ratio;
when a fault occurs or other conditions needing shutdown occur, a blocking signal is sent to the driving circuit to carry out wave-blocking protection;
and step 3: the converter normally works, the controller controls the switching tubes of each group of non-isolated DC-DC converters in a peak current control mode, and if the current is overlarge (namely, overload), the controller gives out an adjusted PWM signal to limit the current so as to realize power amplitude limiting protection.
Since the PWM driving signals of the N groups of non-isolated DC-DC converters of the interleaved DC-DC converter are different by 360 °/N, their total current ripple is reduced and the total power is N times the power of the single isolated DC-DC converter.
Therefore, the interleaved DC-DC converter not only can increase the output power, but also can reduce the ripple, so that the converters are modularized and connected in parallel, and are easy to use, install and use.
The operating waveform of the non-isolated DC-DC converter 1 is as shown in fig. 3, and in one switching cycle when the converter is in normal operation, each group of switching tubes is controlled as follows:
mode one (t)0-t1) A switch tube-S1Switching-on and switching-off tube II S2Turn-off, energy storage inductor L1Current i ofLLinearly increasing; rises to t1The time is converted into a second mode;
modal two (t)1-t2) A switch tube-S1Turn-off and switch tube II S2Switching-on and switching-off tube II S2For an energy-storing inductor L1Providing a follow current loop, an energy storage inductor L1Current i ofLLinear decrease at t2At that time, modality two ends.
The duty ratio calculation formula of the first switching tube is as follows:
the conduction time of the first switching tube is as follows: t ison＝t1-t0＝D/fs(ii) a The first off time of the switch tube is as follows: t isoff＝t2-t1＝(1-D)/fsWherein f issIs the switching frequency.
Therefore, compared with the prior art, the operation states of each switching period of the interleaved DC-DC converter are two, and the control mode is simpler.
Fig. 4 is a simulation waveform of a three-phase interleaved DC-DC converter, and it can be seen that the inductor currents of the three converters are 120 ° interleaved, the input-to-output voltage ratio is 3:1, and the total power is 1200W. Specific simulation design parameters are shown in table 1.
TABLE 1 simulation design parameters
| |
36V |
| |
12V |
| Rated power P | 1200W |
| Switching frequency fs | 150kHz |
| Output capacitor C2＝C4＝C6 | 1200μf |
| Energy storage inductor L1＝L2＝L3 | 4.7μH |
In summary, the improvement point of the present invention is:
1. the interleaved DC-DC converter of the high-power automobile dual-power system and the control method thereof are combined with the dual-power system, and a non-isolated Buck-Boost reversed polarity topological structure in interleaved parallel connection is adopted, so that a group of 12V batteries can be omitted, the output power is increased, the size and the component cost of the converter are reduced, and the current ripple is also reduced.
2. The output power is limited by adopting peak current mode control, and the voltage balance of the battery pack can be automatically realized by the circuit in a simpler way under the control method.
3. Corresponding to a high-power interleaved DC-DC converter, a simpler control method is provided for energy conversion.
Finally, the description is as follows: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (7)
1. An interleaved DC-DC converter of an automobile dual power supply system is characterized in that:
the staggered DC-DC converter consists of N non-isolated DC-DC converters, the N non-isolated DC-DC converters are staggered and connected in parallel, the complementary PWM driving signals between the N non-isolated DC-DC converters have a difference of 360 DEG/N, N is more than or equal to 2, each non-isolated converter adopts a Buck-Boost topology with reversed polarity and has the same circuit structure, a 36V battery pack is connected to the input end of each non-isolated DC-DC converter, the output end of each non-isolated converter is simultaneously connected to a 12V battery pack and a 12V load, and the 36V battery pack and the 12V battery pack are connected in series to form a 48V battery pack and then supply power to the 48V load;
each non-isolated DC-DC converter comprises a first switch tube, a second switch tube, an input filter capacitor, an output filter capacitor and an energy storage inductor, wherein one end of the input filter capacitor is connected with the drain electrode of the first switch tube; the source electrode of the first switch tube is connected with the drain electrode of the second switch tube and one end of the energy storage inductor; one end of the output filter capacitor is connected with the source electrode of the second switch tube; the other end of the input filter capacitor is connected with the other end of the output filter capacitor and the other end of the energy storage inductor, one end of the output filter capacitor is connected with the negative electrode of the 12V battery pack, the other end of the output filter capacitor is connected with the positive electrode of the 12V battery pack, the positive electrode of the 36V battery pack is connected with one end of the input filter capacitor, and the negative electrode of the 36V battery pack is connected with the other end of the input filter capacitor.
2. The interleaved DC-DC converter according to claim 1, wherein the source of the second switching transistor is the negative electrode of the non-isolated DC-DC converter, the other end of the output filter capacitor is the positive electrode of the non-isolated DC-DC converter, and the outputs of the non-isolated DC-DC converters are interleaved and connected in parallel.
3. The interleaved DC-DC converter according to claim 1 wherein the controller of the switching tube collects the input voltage, output voltage, and output current of the converter through the signal conditioning circuit, and forms a dual closed-loop control system, the dual closed-loop control system includes a voltage outer loop and a current inner loop, and adopts peak current mode control, and in case of overload, drives and locks the first switching tube and the second switching tube of each group of the non-isolated DC-DC converter, and the voltage outer loop and the current inner loop are preferably controlled by a PI controller.
4. The interleaved DC-DC converter as claimed in claim 1 wherein said 48V load is commonly powered by a 36V battery in series with a 12V battery; the 12V load was delivered by the 36V battery pack through the interleaved DC-DC converter with the required load power of 3/4, and additionally 1/4 load power was provided by the 12V battery pack.
5. A control method of an interleaved DC-DC converter of a dual power supply system of an automobile according to any one of claims 1 to 4, characterized in that the control method comprises the steps of:
step 1: the controller collects the voltage of the 36V battery pack and the voltage of the 12V battery pack;
step 2: the controller of the switching tube selectively sends an enable signal or a blocking signal to the driving circuit according to the voltage condition in the step 1; detecting a voltage ratio between the 36V battery pack and the 12V battery pack: when the voltage ratio is greater than 3, sending an enabling signal to a driving circuit, enabling a converter to work, supplying power to a 12V load by the converter, realizing automatic voltage equalization of the voltage of the battery pack, and entering the step 3; when the voltage ratio is less than 3, the converter is in a standby state and continuously detects the voltage ratio; when a fault or other conditions needing shutdown occur, a blocking signal is sent to the driving circuit to carry out wave-blocking protection.
And step 3: the converter normally works, the controller of the switch tube controls the switch tube of each group of non-isolated DC-DC converters in a peak current control mode, and if the current is overlarge, the controller gives out an adjusted PWM signal to limit the current so as to realize power amplitude limiting protection.
6. The control method according to claim 5, wherein the step 3 further comprises: during normal work, each group of switching tubes is controlled according to the following two modes in one switching period of the non-isolated DC-DC converter, and the difference between the driving signals of each group of switching tubes is 360 degrees/N:
the first mode is as follows: at an initial time t0When the energy storage inductor is in a working state, the first switching tube is switched on, the second switching tube is switched off, and the current of the energy storage inductor linearly rises; rises to t1The time is converted into a second mode;
mode two: at t1At the moment, the first switch tube is turned off, the second switch tube is turned on, the second switch tube provides a follow current loop for the energy storage inductor, the current of the energy storage inductor is linearly reduced, and at t2At that time, modality two ends.
7. The control method according to claim 6, wherein the duty ratio of the first switching tube is calculated by the formula:
the conduction time of the first switching tube is as follows: t ison＝t1-t0＝D/fs(ii) a The first off time of the switch tube is as follows: t isoff＝t2-t1＝(1-D)/fsWherein f issIs the switching frequency.
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