CN109256946B - High-gain fuel cell automobile DC/DC converter - Google Patents

High-gain fuel cell automobile DC/DC converter Download PDF

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CN109256946B
CN109256946B CN201811128956.4A CN201811128956A CN109256946B CN 109256946 B CN109256946 B CN 109256946B CN 201811128956 A CN201811128956 A CN 201811128956A CN 109256946 B CN109256946 B CN 109256946B
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diode
inductor
switching tube
voltage
signal
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CN109256946A (en
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吴晓刚
于渤洋
石文文
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Harbin University of Science and Technology
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Harbin University of Science and Technology
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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
    • H02M3/157—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 with digital control
    • 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

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)
  • Fuel Cell (AREA)

Abstract

A high-gain fuel cell automobile DC/DC converter relates to a DC converter, and belongs to the field of design and application of new energy automobile power systems. The invention solves the problems that the boost topology boost ratio of the existing battery automobile DC/DC converter is low, and the output voltage is disturbed when the input voltage is in a wide range. The invention introduces the feedforward control of the input voltage, counteracts the disturbance of the input voltage to the output voltage when the input voltage changes in a wide range and does not have overhigh cost. Meanwhile, a mathematical model is established by using a state space averaging method, when two basic topological upper bridge circuits and two basic topological lower bridge circuits are used in parallel and 180-degree phase shift control is adopted, the current fluctuation of the fuel cell is small, the service life of the fuel cell is prolonged, the feed-forward control of the input voltage is introduced, and the disturbance of the input voltage to the output voltage in the wide range change can be counteracted. The invention is suitable for being used as a DC/DC converter.

Description

High-gain fuel cell automobile DC/DC converter
Technical Field
The invention relates to a direct current converter, and belongs to the field of design and application of a new energy automobile power system.
Background
With the popularization of new energy automobiles, the fuel cell automobile has the advantages of no hot air heater process, no limitation of Carnot cycle, incomparable advantages of internal combustion engine automobiles such as high energy conversion efficiency, environmental friendliness and the like, can still keep the performances of high speed, long-distance running, safety, comfort and the like of the traditional internal combustion engine automobiles, and is considered as a first-choice clean and efficient transportation tool in the 21 st century.
However, a DC/DC converter must be added between the output terminal of the fuel cell and the DC bus to overcome the disadvantages of wide output voltage range and slow dynamic response of the fuel cell, so as to meet the power requirement of the entire vehicle. The converter has the function of ensuring that the output voltage of the fuel cell is matched with the voltage of a direct-current bus when the output voltage of the fuel cell changes in a wide range, and simultaneously ensuring smaller ripples. Therefore, the DC/DC converter for a fuel cell vehicle should reduce the cost and improve the stability and power density as much as possible while satisfying the functions of high step-up ratio, high efficiency, and the like.
Current research on fuel cell automotive DC/DC converters has focused primarily on isolated and non-isolated topologies. The isolated topology has the advantages of large volume, high cost and relatively low efficiency due to the existence of the coupling transformer; although the conventional non-isolated boost topology (such as boost, buck-boost, etc.) has good dynamic response and high efficiency, the requirement of a high-voltage platform of a direct-current bus cannot be met due to low boost ratio.
Disclosure of Invention
The invention provides a high-gain fuel cell automobile DC/DC converter, aiming at solving the problems that the boost topology boost ratio of the existing battery automobile DC/DC converter is low, and the output voltage is disturbed when the input voltage is in a wide range.
The invention relates to a high-gain fuel cell automobile DC/DC converter, which comprises a DC/DC converter main circuit 1 and a DC/DC converter control circuit 2;
the DC/DC converter main circuit 1 comprises an upper bridge circuit, a lower bridge circuit and a fuel cell voltage source E; the upper bridge circuit includes: diode D1, diode D2, diode D3, diode D4, diode D5, diode D6, inductor L1, inductor L2, inductor L3, switching tube Q1, switching tube Q2, switching tube Q3 and capacitor C1;
the lower bridge circuit includes: diode D7, diode D8, diode D9, diode D10, diode D11, diode D12, inductor L4, inductor L5, inductor L6, switching tube Q4, switching tube Q5, switching tube Q6 and capacitor C2;
the anode of the diode D1 is simultaneously connected with the anode of the diode D4, the anode of the diode D6, one end of the capacitor C2, the drain of the switching tube Q4, the drain of the switching tube Q5, the drain of the switching tube Q6 and the anode of the fuel cell voltage source E;
the cathode of the diode D1 is simultaneously connected with one end of the inductor L1 and the cathode of the diode D3; the other end of the inductor L1 is simultaneously connected with the anode of the diode D2 and the drain of the switching tube Q3, and the cathode of the diode D2 is simultaneously connected with one end of the capacitor C1 and one end of the load resistor R;
the cathode of the diode D4 is simultaneously connected with one end of the inductor L2 and the cathode of the diode D5; the other end of the inductor L2 is simultaneously connected with the anode of the diode D3 and the drain of the switching tube Q2;
the negative electrode of the diode D6 is connected with one end of the inductor L3, and the other end of the inductor L3 is simultaneously connected with the positive electrode of the diode D5 and the drain electrode of the switching tube Q1;
the cathode of the diode D11 is simultaneously connected with the cathode of the diode D9, the cathode of the diode D7, the other end of the capacitor C1, the source of the switching tube Q1, the source of the switching tube Q2, the source of the switching tube Q3 and the cathode of the fuel cell voltage source E;
the anode of the diode D11 is simultaneously connected with one end of the inductor L6 and the anode of the diode D10; the other end of the inductor L6 is simultaneously connected with the cathode of the diode D12 and the source electrode of the switching tube Q6, and the anode of the diode D12 is simultaneously connected with the other end of the capacitor C2 and the other end of the load resistor R;
the anode of the diode D9 is simultaneously connected with one end of the inductor L5 and the anode of the diode D8; the other end of the inductor L5 is simultaneously connected with the cathode of the diode D10 and the source electrode of the switching tube Q5;
the anode of the diode D7 is connected with one end of the inductor L4, and the other end of the inductor L4 is simultaneously connected with the cathode of the diode D8 and the source of the switching tube Q4;
the switching tube driving signal output end of the DC/DC converter control circuit 2 is simultaneously connected with the grid electrode of the switching tube Q1, the grid electrode of the switching tube Q2, the grid electrode of the switching tube Q3, the grid electrode of the switching tube Q4, the grid electrode of the switching tube Q5 and the grid electrode of the switching tube Q6;
the voltage signal of the capacitor C1, the voltage signal of the capacitor C2, the output voltage signal of the DC/DC converter main circuit 1 and the output voltage signal of the fuel cell voltage source E are simultaneously input to the DC/DC converter control circuit 2;
the current signal of the inductor L1 and the current signal of the inductor L2 are simultaneously input to the DC/DC converter control circuit 2; a target voltage signal is input to a target voltage signal input terminal of the DC/DC converter control circuit 2.
Further, the DC/DC converter control circuit 2 includes a protection circuit 201, a DSP system 202, a voltage sensor 203, and a current sensor 204;
the voltage sensor 203 collects a voltage signal of a capacitor C1 of the DC/DC converter main circuit 1, a voltage signal of a capacitor C2, an output voltage signal of the DC/DC converter main circuit 1 and an output voltage signal of a fuel cell voltage source E; the collected voltage signal of the capacitor C1, the voltage signal of the capacitor C2, the output voltage signal of the DC/DC converter main circuit 1 and the output voltage signal of the fuel cell voltage source E are simultaneously output to the DSP system 202;
the current sensor 204 collects a current signal of the inductor L1 and a current signal of the inductor L2, and simultaneously outputs the collected current signal of the inductor L1 and the collected current signal of the inductor L2 to the DSP system 202;
a target voltage is input to a target voltage signal input end of the DSP system 202; the duty cycle control signal output end of the switching tube of the DSP system 202 is connected to the duty cycle control signal input end of the switching tube of the protection circuit 201, and the duty cycle control signal output end of the switching tube of the protection circuit 201 is the duty cycle control signal output end of the switching tube of the DC/DC converter control circuit 2.
Further, the capacitance values of the capacitor C1 and the capacitor C2 are the same.
Further, the inductance values of the inductor L1, the inductor L2, the inductor L3, the inductor L4, the inductor L5, and the inductor L6 are the same.
Further, the DSP system 202 includes a PI controller, two subtractors 2024, and an adder 2025; the PI controller includes a voltage loop controller 2021 and a current loop controller 2022;
target reference voltage UrefAnd the output voltage U collected by the voltage sensor 2030After subtraction by a first subtractor 2024, a voltage error signal e is obtained1；
Voltage error signal e1After input to the voltage loop controller 2021 for PI algorithm processing, the desired inductor current I 'is obtained'L1；
Desired inductor Current l'L1The inductive current signal I collected by the second subtractor 2024 and the current sensor 204L1After subtraction, a current error signal e is obtained2；
The feedforward controller 2023 receives the voltage U of the fuel cell voltage source E collected by the voltage sensor 203inThen, a feedforward output signal k/U is obtainedin；
Current error signal e2The output signal and the feedforward output signal k/U are input to the current loop controller 2022 and processed by the PI algorithminAfter summing by adder 2025 obtainAnd obtaining a control signal of the duty ratio d of the switching tube, namely a driving signal of the switching tube.
The invention provides a non-isolated DC/DC converter which can greatly improve the boost ratio, solve the defect of low boost ratio of the traditional boost topology, and simultaneously introduce the feedforward control of input voltage, can offset the disturbance of the input voltage to the output voltage in wide-range change without overhigh cost. Meanwhile, the invention analyzes the proposed topology, establishes a mathematical model by using a state space average method, and provides a corresponding control method, so that the dynamic response requirement of a fuel cell automobile power system can be met, and the stability of the direct current bus voltage in the wide-range output of the fuel cell can be ensured; according to the direct current bus converter, an isolating device is not arranged between the fuel cell and the direct current bus, so that the efficiency of the converter is improved; when two basic topologies are used in parallel and 180-degree phase shift control is adopted, the current fluctuation of the fuel cell is small, the service life of the fuel cell is prolonged, the feed-forward control of input voltage is introduced, the disturbance of the input voltage to output voltage in wide range change can be counteracted, the Boost ratio of the DC/DC converter circuit is 1+5d times of that of the traditional Boost circuit, and the purpose of large-amplitude Boost is realized.
Drawings
FIG. 1 is a schematic circuit diagram of a high gain fuel cell automotive DC/DC converter in accordance with the present invention;
FIG. 2 is an electrical block diagram of a DSP system according to a fifth embodiment;
FIG. 3 is a schematic block diagram of the voltage regulation of the high gain fuel cell automotive DC/DC converter;
FIG. 4 is an equivalent circuit diagram of a main circuit of a DC/DC converter with a switch tube in an on state, wherein a dotted line with an arrow direction indicates a current direction;
FIG. 5 is an equivalent circuit diagram of a main circuit of a DC/DC converter with a switch tube closed, wherein a dotted line with an arrow indicates a current direction; (ii) a
FIG. 6 is a waveform diagram of driving signals of a switch tube Q1 and a switch tube Q3 in a main circuit of a DC/DC converter;
FIG. 7 is a graph of the voltage waveforms of the switch Q1 and the switch Q3 in the main circuit of the DC/DC converter;
fig. 8 is a current waveform diagram of an inductor L1 in an upper bridge circuit of a main circuit of a DC/DC converter;
fig. 9 is a voltage waveform diagram of a capacitor C1 in an upper bridge circuit of a main circuit of a DC/DC converter;
FIG. 10(a) is a graph showing an output voltage waveform;
fig. 10(b) is a voltage waveform diagram of the capacitor C1;
fig. 10(C) is a voltage waveform diagram of the capacitor C2.
Detailed Description
The first embodiment is as follows: the present embodiment will be described with reference to fig. 1, and the present embodiment describes a high gain fuel cell vehicle DC/DC converter including a DC/DC converter main circuit 1 and a DC/DC converter control circuit 2;
the DC/DC converter main circuit 1 comprises an upper bridge circuit, a lower bridge circuit and a fuel cell voltage source E; the upper bridge circuit includes: diode D1, diode D2, diode D3, diode D4, diode D5, diode D6, inductor L1, inductor L2, inductor L3, switching tube Q1, switching tube Q2, switching tube Q3 and capacitor C1;
the lower bridge circuit includes: diode D7, diode D8, diode D9, diode D10, diode D11, diode D12, inductor L4, inductor L5, inductor L6, switching tube Q4, switching tube Q5, switching tube Q6 and capacitor C2;
the anode of the diode D1 is simultaneously connected with the anode of the diode D4, the anode of the diode D6, one end of the capacitor C2, the drain of the switching tube Q4, the drain of the switching tube Q5, the drain of the switching tube Q6 and the anode of the fuel cell voltage source E;
the cathode of the diode D1 is simultaneously connected with one end of the inductor L1 and the cathode of the diode D3; the other end of the inductor L1 is simultaneously connected with the anode of the diode D2 and the drain of the switching tube Q3, and the cathode of the diode D2 is simultaneously connected with one end of the capacitor C1 and one end of the load resistor R;
the cathode of the diode D4 is simultaneously connected with one end of the inductor L2 and the cathode of the diode D5; the other end of the inductor L2 is simultaneously connected with the anode of the diode D3 and the drain of the switching tube Q2;
the negative electrode of the diode D6 is connected with one end of the inductor L3, and the other end of the inductor L3 is simultaneously connected with the positive electrode of the diode D5 and the drain electrode of the switching tube Q1;
the cathode of the diode D11 is simultaneously connected with the cathode of the diode D9, the cathode of the diode D7, the other end of the capacitor C1, the source of the switching tube Q1, the source of the switching tube Q2, the source of the switching tube Q3 and the cathode of the fuel cell voltage source E;
the anode of the diode D11 is simultaneously connected with one end of the inductor L6 and the anode of the diode D10; the other end of the inductor L6 is simultaneously connected with the cathode of the diode D12 and the source electrode of the switching tube Q6, and the anode of the diode D12 is simultaneously connected with the other end of the capacitor C2 and the other end of the load resistor R;
the anode of the diode D9 is simultaneously connected with one end of the inductor L5 and the anode of the diode D8; the other end of the inductor L5 is simultaneously connected with the cathode of the diode D10 and the source electrode of the switching tube Q5;
the anode of the diode D7 is connected with one end of the inductor L4, and the other end of the inductor L4 is simultaneously connected with the cathode of the diode D8 and the source of the switching tube Q4;
the switching tube driving signal output end of the DC/DC converter control circuit 2 is simultaneously connected with the grid electrode of the switching tube Q1, the grid electrode of the switching tube Q2, the grid electrode of the switching tube Q3, the grid electrode of the switching tube Q4, the grid electrode of the switching tube Q5 and the grid electrode of the switching tube Q6;
a voltage signal of the capacitor C1, a voltage signal of the capacitor C2, an output voltage signal of the DC/DC converter main circuit 1, and an output voltage signal of the fuel cell voltage source E are simultaneously input to the DC/DC converter control circuit 2;
the current signal of the inductor L1 and the current signal of the inductor L2 are simultaneously input to the DC/DC converter control circuit 2; a target voltage signal is input to a target voltage signal input terminal of the DC/DC converter control circuit 2.
The second embodiment is as follows: the present embodiment will be described with reference to fig. 1, and the present embodiment further describes a high-gain fuel cell vehicle DC/DC converter described in the first embodiment, in which the DC/DC converter control circuit 2 includes a protection circuit 201, a DSP system 202, a voltage sensor 203, and a current sensor 204;
the voltage sensor 203 collects a voltage signal of a capacitor C1 of the DC/DC converter main circuit 1, a voltage signal of a capacitor C2, an output voltage signal of the DC/DC converter main circuit 1 and an output voltage signal of a fuel cell voltage source E; the collected voltage signal of the capacitor C1, the voltage signal of the capacitor C2, the output voltage signal of the DC/DC converter main circuit 1 and the output voltage signal of the fuel cell voltage source E are simultaneously output to the DSP system 202;
the current sensor 204 collects a current signal of the inductor L1 and a current signal of the inductor L2, and simultaneously outputs the collected current signal of the inductor L1 and the collected current signal of the inductor L2 to the DSP system 202;
a target voltage is input to a target voltage signal input end of the DSP system 202; the switch tube driving signal output end of the DSP system 202 is connected to the switch tube driving signal input end of the protection circuit 201, and the switch tube driving signal output end of the protection circuit 201 is the switch tube driving signal output end of the DC/DC converter control circuit 2.
The third concrete implementation mode: the present embodiment will be described with reference to fig. 1, and the present embodiment further describes a high-gain fuel cell vehicle DC/DC converter described in the first embodiment, in which the capacitance values of the capacitor C1 and the capacitor C2 are the same.
The fourth concrete implementation mode: the present embodiment will be described with reference to fig. 1, and the inductance values of the inductor L1, the inductor L2, the inductor L3, the inductor L4, the inductor L5, and the inductor L6 are the same in this embodiment, which further describes the high-gain fuel cell vehicle DC/DC converter described in the first embodiment.
The fifth concrete implementation mode: referring to fig. 2, to describe the present embodiment, the DSP system 202 includes a PI controller, two subtractors 2024 and an adder 2025; the PI controller includes a voltage loop controller 2021 and a current loop controller 2022;
target reference voltage UrefAnd the output voltage U collected by the voltage sensor 2030After subtraction by a first subtractor 2024, a voltage error signal e is obtained1；
Voltage error signal e1Input to the voltage loop controller 2021 for PI calculationAfter processing, the desired inductor current I 'is obtained'L1；
Desired inductor Current l'L1The inductive current signal I collected by the second subtractor 2024 and the current sensor 204L1After subtraction, a current error signal e is obtained2；
The feedforward controller 2023 receives the voltage U of the fuel cell voltage source E collected by the voltage sensor 203inVoltage U is coupled by the feedforward coefficient of feedforward controller 2023inAdjusting to obtain feedforward output signal k/Uin；
Current error signal e2The output signal and the feedforward output signal k/U are input to the current loop controller 2022 and processed by the PI algorithminThe control signal of the duty ratio d of the switching tube, i.e. the driving signal of the switching tube, is obtained after the summation by the adder 2025.
FIG. 3 is a control schematic block diagram of the present embodiment, in which UrefIs the set reference voltage; cPI(s) and CP2(s) a PI controller for the designed voltage and current loops; k/UinThe controller is a feedforward controller, wherein k is a constant, the controller has the functions of acting the change of the input voltage on a duty ratio d in advance to counteract the disturbance to the output when the input voltage changes, and acting the functions of protecting the topology when the duty ratio d is not zero when the converter is just started and has the function of soft start;
a) collecting input voltage U of the fuel cellinAnd the output voltage U of the DC/DC converter circuit0The current sensor collects the inductive current I of the conversion unitL1And performing digital-to-analog conversion;
b) voltage value U to be output0And a reference voltage UrefComparing to obtain a voltage error signal e1And apply the voltage error signal e1Sending the current to a voltage ring PI controller for processing to obtain expected inductor current I'L1；
c) Subjecting the desired inductor current I 'obtained in step b)'L1With the inductor current IL1The error signals obtained by comparison are sent to a current loop PI controller to obtain the duty ratio d, and one PWM wave is adjusted according to different duty ratiosPeriod tonAnd toffThe time of (a), specifically;
at tonIn the time period, the first switching tube, the second switching tube and the third switching tube are opened, and the fourth switching tube, the fifth switching tube and the sixth switching tube are closed; the fuel cell charges a first inductor L1, a second inductor L2 and a third inductor L3 through a first switching tube Q1, a second switching tube Q2 and a third switching tube Q3, a fourth inductor L4, a fifth inductor L5, a sixth inductor L6 and the fuel cell are connected in series to charge a second capacitor C2, and a first capacitor C1 and a second capacitor C2 supply power to a load R, as shown in fig. 4, the corresponding state equation is:
Figure GDA0002284327340000071
wherein, UinIs the input voltage of the converter, t is time, R represents the load, L is the inductance, C is the capacitance, UC1Is the output voltage of the capacitor C1, the inductive current signal IL1The inductor L1 and the inductor L2 have equal currents.
At toffIn the time period, the fourth switching tube, the fifth switching tube and the sixth switching tube are opened, and the first switching tube, the second switching tube and the third switching tube are closed; the fuel cell charges a fourth inductor L4, a fifth inductor L5 and a sixth inductor L6 through a fourth switching tube Q4, a fifth switching tube Q5 and a sixth switching tube Q6, the first inductor L1, the second inductor L2, the third inductor L3 and the fuel cell are connected in series to charge a first capacitor C1, the first capacitor C1 and the second capacitor C2 supply power to the load R, the current of the inductor first inductor L1 is equal to the current of the second inductor L2, and therefore the fuel cell only needs to use the current I of the inductor L1 when in useL1(ii) a As shown in fig. 5, the corresponding state equation is:
Figure GDA0002284327340000072
d) the feedforward controller receives the voltage U of the fuel cell voltage source E acquired by the voltage sensorinObtaining a feedforward output signal k/UinSummed with the duty cycle d of the current loop PI controller outputLate-in first transfer function
Figure GDA0002284327340000073
To obtain adjusted IL1(ii) a The first transfer function is a first characteristic function of a main circuit of the DC/DC converter;
e) subjecting the I obtained in step d)L1The output voltage U of the capacitor C1 adjusted as the input quantity of the second transfer functionC1After passing through U0＝2UC1-UinObtain the regulated output voltage U0. The second transfer function is a second characteristic function of the main circuit of the DC/DC converter;
the state space average equation of the converter in a complete PWM period is established by the formula (1) and the formula (2):
during a complete PWM cycle, the state space average equation of the converter is:
Figure GDA0002284327340000081
wherein the content of the first and second substances,
Figure GDA0002284327340000082
is the current I of the inductor L1 in one PWM periodL1Is determined by the average value of (a) of (b),
Figure GDA0002284327340000083
is the voltage U of the capacitor C1 in one PWM periodC1Is determined by the average value of (a) of (b),
Figure GDA0002284327340000084
for a fuel cell input voltage U within one PWM cycleinIs determined by the average value of (a) of (b),
Figure GDA0002284327340000085
is the average value of the duty ratio d of the PWM wave in one PWM period.
On the basis of establishing a system state average value model, introducing a small signal model and establishing an open loop transfer function of the proposed topology, specifically, firstly, stabilizing a DC/DC converter circuitIntroduction of small disturbing signals at the working point, i.e. to be about to
Figure GDA0002284327340000086
Figure GDA0002284327340000087
And
Figure GDA0002284327340000088
into equation (3), where,
Figure GDA0002284327340000089
for inductor current signal IL1The small-signal model of (a) is,
Figure GDA00022843273400000810
is the output voltage U of the capacitor C1C1The small-signal model of (a) is,
Figure GDA00022843273400000811
for inputting voltage U to fuel cellinThe small-signal model of (a) is,
Figure GDA00022843273400000812
a small signal model of the duty ratio d of the switching tube;
the direct-current steady-state model of the topology obtained after the degeneracy is changed to discard the high order infinitesimal magnitude is as follows:
Figure GDA00022843273400000813
from which the proposed topology U can be derivedinTo
Figure GDA00022843273400000814
Has a voltage-boosting ratio of 1+2d/1-d, and
Figure GDA00022843273400000815
the final step-up ratio of 1+5d/1-d for this topology can be obtained. The resulting small signal model is:
Figure GDA00022843273400000816
laplace transform and reduction are performed on equation (5):
control signal d to current IL1The transfer function of (a) is:
Figure GDA0002284327340000091
IL1to the output voltage UC1The transfer function of (a) is:
Figure GDA0002284327340000092
wherein s represents a complex variable, R is a load resistance, L is an inductance, C is a capacitance of a capacitor C1, and U isC1Is the output voltage, U, of the capacitor C1C1Is converted into an output voltage U0The concrete formula of (1) is as follows: u shape0＝2UC1-UinWherein, 2UC1＝UC1+UC2，UC2Is the voltage of the capacitor C2. A voltage closed-loop control system is designed according to the transfer functions shown in the formula (6) and the formula (7), and because the input voltage range is wide, feedforward control is introduced to counteract the influence caused by the change of the input voltage.
As shown in fig. 6-9, the fluctuation of the fuel cell output current becomes half of the single partial current fluctuation per cycle, which is advantageous for prolonging the battery life, while the voltage fluctuation is also half of the fluctuation of the first capacitor C1 and the second capacitor C2. As can be seen from fig. 10(a), 10(b) and 10(C), the output voltage fluctuation is half of that of the capacitors C1 and C2.

Claims (5)

1. A high gain fuel cell vehicle DC/DC converter is characterized in that the converter comprises a DC/DC converter main circuit (1) and a DC/DC converter control circuit (2);
the DC/DC converter main circuit (1) comprises an upper bridge circuit, a lower bridge circuit and a fuel cell voltage source E; the upper bridge circuit includes: diode D1, diode D2, diode D3, diode D4, diode D5, diode D6, inductor L1, inductor L2, inductor L3, switching tube Q1, switching tube Q2, switching tube Q3 and capacitor C1;
the lower bridge circuit includes: diode D7, diode D8, diode D9, diode D10, diode D11, diode D12, inductor L4, inductor L5, inductor L6, switching tube Q4, switching tube Q5, switching tube Q6 and capacitor C2;
the anode of the diode D1 is simultaneously connected with the anode of the diode D4, the anode of the diode D6, one end of the capacitor C2, the drain of the switching tube Q4, the drain of the switching tube Q5, the drain of the switching tube Q6 and the anode of the fuel cell voltage source E;
the cathode of the diode D1 is simultaneously connected with one end of the inductor L1 and the cathode of the diode D3; the other end of the inductor L1 is simultaneously connected with the anode of the diode D2 and the drain of the switching tube Q3, and the cathode of the diode D2 is simultaneously connected with one end of the capacitor C1 and one end of the load resistor R;
the cathode of the diode D4 is simultaneously connected with one end of the inductor L2 and the cathode of the diode D5; the other end of the inductor L2 is simultaneously connected with the anode of the diode D3 and the drain of the switching tube Q2;
the negative electrode of the diode D6 is connected with one end of the inductor L3, and the other end of the inductor L3 is simultaneously connected with the positive electrode of the diode D5 and the drain electrode of the switching tube Q1;
the cathode of the diode D11 is simultaneously connected with the cathode of the diode D9, the cathode of the diode D7, the other end of the capacitor C1, the source of the switching tube Q1, the source of the switching tube Q2, the source of the switching tube Q3 and the cathode of the fuel cell voltage source E;
the anode of the diode D11 is simultaneously connected with one end of the inductor L6 and the anode of the diode D10; the other end of the inductor L6 is simultaneously connected with the cathode of the diode D12 and the source electrode of the switching tube Q6, and the anode of the diode D12 is simultaneously connected with the other end of the capacitor C2 and the other end of the load resistor R;
the anode of the diode D9 is simultaneously connected with one end of the inductor L5 and the anode of the diode D8; the other end of the inductor L5 is simultaneously connected with the cathode of the diode D10 and the source electrode of the switching tube Q5;
the anode of the diode D7 is connected with one end of the inductor L4, and the other end of the inductor L4 is simultaneously connected with the cathode of the diode D8 and the source of the switching tube Q4;
the switching tube driving signal output end of the DC/DC converter control circuit (2) is simultaneously connected with the grid electrode of the switching tube Q1, the grid electrode of the switching tube Q2, the grid electrode of the switching tube Q3, the grid electrode of the switching tube Q4, the grid electrode of the switching tube Q5 and the grid electrode of the switching tube Q6;
a voltage signal of a capacitor C1, a voltage signal of a capacitor C2, an output voltage signal of a DC/DC converter main circuit (1) and an output voltage signal of a fuel cell voltage source E are simultaneously input to a DC/DC converter control circuit (2);
the current signal of the inductor L1 and the current signal of the inductor L2 are simultaneously input into the DC/DC converter control circuit (2); the target voltage signal is input at the target voltage signal input end of the DC/DC converter control circuit (2), the upper bridge circuit and the lower bridge circuit are connected in parallel and use 180-degree phase shift control, the current fluctuation of the fuel cell is reduced, and the service life of the fuel cell is prolonged.
2. The high-gain fuel cell vehicle DC/DC converter according to claim 1, wherein the DC/DC converter control circuit (2) includes a protection circuit (201), a DSP system (202), a voltage sensor (203), and a current sensor (204);
the voltage sensor (203) collects a voltage signal of a capacitor C1 of the DC/DC converter main circuit (1), a voltage signal of a capacitor C2, an output voltage signal of the DC/DC converter main circuit (1) and an output voltage signal of a fuel cell voltage source E; the collected voltage signal of the capacitor C1, the voltage signal of the capacitor C2, the output voltage signal of the DC/DC converter main circuit (1) and the output voltage signal of the fuel cell voltage source E are simultaneously output to the DSP system (202);
the current sensor (204) collects a current signal of an inductor L1 and a current signal of an inductor L2, and simultaneously outputs the collected current signal of the inductor L1 and the collected current signal of the inductor L2 to the DSP system (202);
a target voltage signal input end of the DSP system (202) inputs a target voltage; the switch tube driving signal output end of the DSP system (202) is connected with the switch tube driving signal input end of the protection circuit (201), and the switch tube driving signal output end of the protection circuit (201) is the switch tube driving signal output end of the DC/DC converter control circuit (2).
3. The high-gain fuel cell vehicle DC/DC converter according to claim 1, wherein the capacitance values of the capacitor C1 and the capacitor C2 are the same.
4. The high-gain fuel cell vehicle DC/DC converter according to claim 1, wherein the inductance values of the inductor L1, the inductor L2, the inductor L3, the inductor L4, the inductor L5 and the inductor L6 are the same.
5. A high gain fuel cell vehicle DC/DC converter according to claim 2, wherein the DSP system (202) comprises a PI controller, two subtractors (2024) and an adder (2025); the PI controller comprises a voltage loop controller (2021) and a current loop controller (2022);
target reference voltage UrefThe output voltage U0 collected by the voltage sensor (203) is subtracted by a first subtracter (2024) to obtain a voltage error signal e1；
Voltage error signal e1After the current is input to a voltage loop controller (2021) for PI algorithm processing, the expected inductive current I is obtainedL′1；
Desired inductor current IL′1The inductive current signal I collected by the second subtracter (2024) and the current sensor (204)L1After subtraction, a current error signal e is obtained2；
The feedforward controller (2023) receives the voltage U of the fuel cell voltage source E collected by the voltage sensor (203)inThen, a feedforward output signal k/U is obtainedinWherein k is a constant;
current error signal e2The output signal and the feedforward output signal k/U are input to a current loop controller (2022) and processed by a PI algorithminAnd after summing by an adder (2025), a control signal of the duty ratio d of the switching tube, namely a driving signal of the switching tube is obtained.
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CN110445378A (en) * 2019-07-04 2019-11-12 常熟理工学院 A kind of three port DC/DC converters and its control method based on three inductance
CN110335579B (en) * 2019-08-16 2022-01-07 深圳南云微电子有限公司 Driving circuit of buzzer
CN110620502B (en) * 2019-09-29 2021-10-01 哈尔滨理工大学 DC/DC converter for high-power charging device of electric automobile
CN113135109B (en) * 2020-07-31 2022-10-25 清华大学 Topological structure of high-power charging device of electric automobile
CN114285272B (en) * 2021-12-13 2023-10-03 同济大学 Variable structure DCDC conversion topology suitable for fuel cell automobile

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