CN111884497B - Quick soft start control method and system for double-active-bridge direct current converter - Google Patents

Quick soft start control method and system for double-active-bridge direct current converter Download PDF

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CN111884497B
CN111884497B CN202010642409.9A CN202010642409A CN111884497B CN 111884497 B CN111884497 B CN 111884497B CN 202010642409 A CN202010642409 A CN 202010642409A CN 111884497 B CN111884497 B CN 111884497B
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bridge
converter
full bridge
switching
active
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CN111884497A (en
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张宇
陈杨帆
陈庆
刘瑞煌
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Huazhong University of Science and Technology
State Grid Jiangsu Electric Power Co Ltd
Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
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Huazhong University of Science and Technology
State Grid Jiangsu Electric Power Co Ltd
Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
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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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/36—Means for starting or stopping converters
    • 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
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
    • H02M3/33584—Bidirectional converters

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  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention discloses a quick soft start control method and a system for a double-active-bridge direct current converter, which are characterized in that all switching tubes are set to simultaneously shift the phase at the starting moment
Figure DDA0002571670110000011
The angle of the angle is set to be,
Figure DDA0002571670110000012
the amplitude of the starting current is reduced to half of the original amplitude, so that the stability of the double-active bridge in the first starting period is ensured; meanwhile, the invention adopts a control method of phase shift angle beat-time change, namely, the phase shift angle alpha (K +1) of the K +1 th switching half period is determined by averaging the phase shift angle instruction value alpha '(K) of the K +1 th switching half period and the phase shift angle instruction value alpha' (K +1) of the K +1 th switching half period, and the phase shift angle beta (K +1) is averaged in the same way, thereby avoiding the problem that direct current components are generated by transmission inductance current due to phase shift angle signal mutation on the premise of ensuring the rapidity of closed loop starting. Therefore, the overcurrent risk of the device is greatly reduced, and the efficiency of the converter is improved.

Description

Quick soft start control method and system for double-active-bridge direct current converter
Technical Field
The invention belongs to the field of direct current converters of power electronic technology, and particularly relates to a quick soft start control method and system for a double-active-bridge direct current converter.
Background
In recent years, with the rapid development of new energy power generation and energy internet, direct current power distribution networks have been intensively studied. The direct current power electronic transformer is the core equipment of the direct current distribution network, and compared with other circuit topologies, the double-active-bridge direct current converter has the following advantages: 1) energy flows in two directions; 2) high-frequency electrical isolation; 3) the efficiency and the power density are high; 4) the regulation and control are rapid. It is therefore one of the preferred circuits to build dc transformers.
For a dual active bridge dc converter, after the circuit is turned on, until a steady operation state is reached, this phase is called the start-up process of the dual active bridge. At the moment of starting, an equivalent circuit of the double active bridges is equivalent to that an input power supply is directly applied to a transmission inductor, and because the initial value of the current on the transmission inductor is 0, the current of the transmission inductor generates an impact current containing direct current bias in the first half switching period of starting according to a volt-second balance principle, the impact current can cause the damage of a switching device, the attenuation of the direct current bias needs a certain time, the efficiency of a system can be greatly reduced due to the existence of the direct current bias, and if the system is serious, the magnetic saturation of a transformer can be caused by the direct current bias.
The existing double-active-bridge soft start method still has the defects that: (1) the starting method of the pre-charging concept is introduced by using an auxiliary circuit, the method additionally increases the cost of the system and simultaneously increases the complexity of control; (2) the starting method of the input side series resistor can reduce the starting impact current in a limited way, but the method can greatly increase the loss of the system; (3) with soft start with a smaller control signal duty cycle, this approach can suppress the start current but does not guarantee the elimination of the dc bias. It can be known that the existing improvement methods suppress the current by reducing the starting transmission power, and simultaneously greatly prolong the starting process of the double active bridges, which is unfavorable for the rapidity of the starting process; in addition, in a commonly used method for regulating a voltage-stabilizing closed-loop PI of an output voltage, the output of the PI is used for controlling the phase shift of a switching tube, and when the output voltage reaches a reference value, a transient of the PI output can cause a transient of a control signal of the switching tube, so that a new direct current bias is brought to a transmission inductance current.
Disclosure of Invention
Aiming at the defects and improvement requirements of the prior art, the invention provides a quick soft start control method and a quick soft start control system for a double-active-bridge direct current converter, aiming at overcoming the defects in the existing soft start technology of the double-active-bridge direct current converter, and providing a control method for ensuring the stability in the starting process of the double active bridges and simultaneously improving the starting rapidity, so that the output of the direct current converter is ensured to be stable in the shortest possible time, and the whole starting process is ensured to transmit inductive current without impact and oscillation.
To achieve the above object, according to one aspect of the present invention, there is provided a fast soft start control method for a dual active bridge dc converter, comprising the steps of:
s1: setting the switching tubes Q connected in series in the full bridge H11And Q2Are complementary to the control signal of (1), and are connected in series to Q3And Q4Are complementary to each other, Q1And Q4Has a phase difference of alpha; setting the switching tubes Q connected in series in the full bridge H25And Q6Are complementary to the control signal of (1), and are connected in series to Q7And Q8Are complementary to each other, Q5And Q8Has a phase difference of alpha; setting the phase shift angle between the full bridge H1 and the full bridge H2 to β; wherein, alpha is an internal shift phase angle, the adjusting range is 0-pi/2, beta is an external shift phase angle, and the adjusting range is 0-pi/2;
s2: setting all switch tubes at the starting time of the system and simultaneously shifting the phase
Figure BDA0002571670090000021
An angle of rotation of the rotor, wherein,
Figure BDA0002571670090000022
is pi/2 or-pi/2;
s3: k is equal to K, wherein K is the repetition frequency of the switching half cycle, and K is an integer greater than or equal to 1;
s4: sampling the output voltage value V of the double active bridges at the end moment of the Kth switching half period2(K)；
S5: taking the output voltage error signal delta V (K) as the input of the PI regulator, and obtaining an inward phase angle instruction value alpha '(K +1) of the next half period and an outward phase angle instruction value beta' (K +1) of the next half period through a steady state optimization algorithm; wherein Δ V (k) ═ Vref-V2(K)，VrefThe voltage is a given value of the final steady-state output voltage of the double-active-bridge direct-current converter;
s6: setting the phase shift angle within the K +1 th switching half cycle
Figure BDA0002571670090000031
Setting the phase shift angle within the K +1 th switching half cycle
Figure BDA0002571670090000032
S7: and repeating the steps S4-S6 when K is equal to K +1, so that the output voltage of the double-active-bridge direct current converter gradually rises to the output voltage set value Vref；
Wherein the dual active bridge DC converter comprises: DC power supply V1An input capacitor C1A primary full bridge H1, a transmission inductor LtA high-frequency isolation transformer T with the turn ratio of N:1, a secondary side full bridge H2, and an output capacitor C2And a load resistor RL。
Furthermore, in the double-active-bridge direct current converter, an input capacitor C1An output capacitor C connected in parallel to the primary full bridge H12Connected in parallel to the secondary side full bridge H2, and transmitting inductance LtConnected in series between the primary full bridge H1 and the transformer T, and outputting a voltage V at the initial start time2Is 0V.
Further, the primary side full bridge H1 is composed of a switch tube Q1～Q4Is composed of a switching tube Q1And Q2Series, switch tube Q3And Q4Two bridge arms which are connected in series and respectively form a primary full bridge H1, wherein the midpoint of the two bridge arms is led out to be used as an alternating current port H1, and the voltage of the alternating current port is VH1；
The secondary side full bridge H2 consists ofSwitch tube Q5～Q8Is composed of a switching tube Q5And Q6Series, switch tube Q7And Q8Two arms connected in series and respectively forming a secondary side full bridge H2, wherein the midpoint of the two arms leads out an alternating current port H2, and the voltage of the alternating current port is VH2；
In the first initial switching period, the high-frequency link voltage V of the double-active-bridge DC converterH1And VH2Decomposed by a fourier series, expressed as:
Figure BDA0002571670090000033
wherein, V1Is a DC power supply, alpha is an internal phase shift angle, omegasIn order to be the angular frequency of the system,
Figure BDA0002571670090000041
is pi/2 or-pi/2.
Further, for the current to transmit inductance LtHigh frequency chain current iL(t) during a first switching cycle:
Figure BDA0002571670090000042
starting i in the first periodLThe Fourier series of (t) is represented as:
Figure BDA0002571670090000043
further, in the first starting period, the current flows through the transmission inductor LtThe amplitude expression of the high-frequency chain current is as follows:
Figure BDA0002571670090000044
in another aspect, the present invention provides a fast soft start control system for a dual active bridge dc converter, including:
a first setting unit for setting the middle string of the full bridge H1Connected switch tube Q1And Q2Are complementary to the control signal of (1), and are connected in series to Q3And Q4Are complementary to each other, Q1And Q4Has a phase difference of alpha; setting the switching tubes Q connected in series in the full bridge H25And Q6Are complementary to the control signal of (1), and are connected in series to Q7And Q8Are complementary to each other, Q5And Q8Has a phase difference of alpha; setting the phase shift angle between the full bridge H1 and the full bridge H2 to β; wherein, alpha is an internal shift phase angle, the adjusting range is 0-pi/2, beta is an external shift phase angle, and the adjusting range is 0-pi/2;
a second setting unit for setting the phase shift of all the switch tubes at the system start time
Figure BDA0002571670090000045
An angle of rotation of the rotor, wherein,
Figure BDA0002571670090000046
is pi/2 or-pi/2;
the sampling unit is used for enabling K to be K, wherein K is the repetition frequency of the switching half cycle, and K is an integer larger than or equal to 1; sampling the output voltage value V of the double active bridges at the end moment of the Kth switching half period2(K)；
A third setting unit, configured to use the output voltage error signal Δ v (K) as an input of the PI regulator, and obtain an instruction value α '(K +1) of an inward shift phase angle of the next half cycle and an instruction value β' (K +1) of an outward shift phase angle of the next half cycle through a steady-state optimization algorithm; wherein Δ V (k) ═ Vref-V2(K)，VrefThe voltage is a given value of the final steady-state output voltage of the double-active-bridge direct-current converter; setting the phase shift angle within the K +1 th switching half cycle
Figure BDA0002571670090000051
Setting the phase shift angle within the K +1 th switching half cycle
Figure BDA0002571670090000052
A circulation unit for circulatingK +1, and then the output voltage of the dual-active bridge DC converter gradually rises to the given value V of the output voltage through the sampling unit and the third setting unitref；
Wherein the dual active bridge DC converter comprises: DC power supply V1An input capacitor C1A primary full bridge H1, a transmission inductor LtA high-frequency isolation transformer T with the turn ratio of N:1, a secondary side full bridge H2, and an output capacitor C2And a load resistor RL。
Furthermore, in the double-active-bridge direct current converter, an input capacitor C1An output capacitor C connected in parallel to the primary full bridge H12Connected in parallel to the secondary side full bridge H2, and transmitting inductance LtConnected in series between the primary full bridge H1 and the transformer T, and outputting a voltage V at the initial start time2Is 0V.
Generally, by the above technical solution conceived by the present invention, the following beneficial effects can be obtained:
(1) the invention introduces phase shift angle to all switch tube signals at the initial starting time
Figure BDA0002571670090000053
Figure BDA0002571670090000054
Is pi/2 or-pi/2, thereby ensuring that the inductive current i is transmitted in the first period of startingLAnd (t) the transformer does not contain direct current, so that the magnetic saturation of the transformer is avoided, and meanwhile, the amplitude of the starting current is reduced to half of the original amplitude, so that the stability of the double-active-bridge starting in the first period is ensured.
(2) The invention adopts a control method of phase shift angle beat-time change, namely, the phase shift angle alpha (K +1) of the K +1 th switching half period is determined by averaging the phase shift angle instruction value alpha '(K) of the Kth switching half period output by a PI controller and the phase shift angle instruction value alpha' (K +1) of the K +1 th switching half period output by the PI controller, and the phase shift angle beta (K +1) is also averaged, thereby avoiding the problem that the direct current component is generated by the transmission inductance current due to the sudden change of phase shift angle signals on the premise of ensuring the rapidity of closed loop starting.
Drawings
FIG. 1 is a schematic diagram of a topology of a dual active bridge DC converter;
FIG. 2 is a start-up waveform diagram of a dual active bridge DC converter during direct start-up;
FIG. 3 is a waveform diagram illustrating the start-up of a dual active bridge DC converter using both a smaller signal duty cycle and a ramp-up of the output voltage set-point;
FIG. 4 is a start-up waveform diagram of the fast soft start control method according to the present invention;
FIG. 5 is a waveform diagram of a PWM pulse signal without using the method provided by the present invention;
fig. 6 is a block diagram of a control system provided by the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
As shown in fig. 1, it is a topological diagram of a dual active bridge dc converter. The present invention relates to a dual active bridge DC converter, comprising: DC power supply V1An input capacitor C1A primary full bridge H1, a transmission inductor LtA high-frequency isolation transformer T with the turn ratio of N:1, a secondary side full bridge H2, and an output capacitor C2And a load resistor RL. The switching frequency of the system being fsAngular frequency of the system is omegasDefining the half switching period of the system as Ts。
The primary side full bridge H1 is composed of a switch tube Q1～Q4Is composed of a switching tube Q1And Q2Series, switch tube Q3And Q4Two arms connected in series and respectively forming a primary full bridge H1, the midpoint of the two arms is led out as H1An AC port having a voltage VH1(ii) a The secondary side full bridge H2 is composed of a switch tube Q5～Q8Is composed of a switching tube Q5And Q6Series, switch tube Q7And Q8Two arms connected in series and respectively forming a secondary side full bridge H2, wherein the midpoint of the two arms leads out an alternating current port H2, and the voltage of the alternating current port is VH2。
Setting the switch tube Q in the full bridge H11And Q2Are complementary to each other, Q3And Q4Are complementary to each other, Q1And Q4Has a phase difference of alpha; setting the switch tube Q in the full bridge H25And Q6Are complementary to each other, Q7And Q8Are complementary to each other, Q5And Q8Has a phase difference of alpha; setting the phase shift angle between the full bridge H1 and the full bridge H2 (i.e., switching tube Q)1And a switching tube Q5The phase shift angle therebetween) is β; wherein alpha is an internal shift phase angle, the adjusting range is 0-pi/2, beta is an external shift phase angle, and the adjusting range is 0-pi/2.
Transfer inductance LtVoltage drop across and VH1、VH2Current-carrying inductance L related to transformer turn ratio NtHas a current of iL(t) of (d). For high frequency chain current iL(t) during a first switching cycle:
Figure BDA0002571670090000071
in the first initial switching period, the output capacitor C2High frequency link voltage V of double active bridge DC converter with almost no voltageH1And VH2Decomposed by a fourier series, expressed as:
Figure BDA0002571670090000072
during the first switching cycle of the start-up, iL(t) can be calculated approximately as:
Figure BDA0002571670090000073
integrating the expression to obtain a transmission inductance current direct current bias expression in the period:
Figure BDA0002571670090000074
the direct current offset can not be eliminated by changing the phase shift angle, the existence of the direct current offset can influence the magnetic bias, and i can be broughtLRush current of (t):
Figure BDA0002571670090000075
in order to solve the problems of impact current and direct current bias of the double-active-bridge transmission inductor in the first starting period, the specific control method provided by the invention comprises the following steps: at the system starting time, introducing VH1、VH2Common phase shift angle of
Figure BDA0002571670090000076
Then in the first initial switching period, the high frequency link voltage V of the dual active bridge DC converterH1And VH2Decomposed by a fourier series, expressed as:
Figure BDA0002571670090000081
during the first switching cycle of the start-up, iL(t) can be calculated approximately as:
Figure BDA0002571670090000082
integrating the first time to obtain i in the first starting periodL(t) DC offset tableThe expression is as follows:
Figure BDA0002571670090000083
in order to make the transfer inductor current have no DC bias in the first starting period, let idcIs equal to 0, is calculated to obtain
Figure BDA0002571670090000084
At this time, the amplitude expression of the starting current is:
Figure BDA0002571670090000085
therefore, at the starting time of the system, all switch tube signals are introduced with phase shift angles
Figure BDA0002571670090000086
That is, the inductor current i is transmitted in the first period of startingLAnd (t) the transformer does not contain direct current, so that the magnetic saturation of the transformer is avoided, and meanwhile, the amplitude of the starting current is reduced to half of the original amplitude, so that the stability of the double-active-bridge starting in the first period is ensured.
Double-active-bridge direct-current converter output capacitor C sampled every other switching half period2The voltage across the terminals is recorded as the output voltage V at the end of the Kth switching half cycle2(K) Setting VrefThe voltage is a given value of the final steady-state output voltage of the double-active-bridge direct-current converter. V obtained by sampling2(K) And a reference voltage value VrefSubtracting to obtain an output voltage error signal Δ V (K) ═ Vref-V2(K) The output voltage error signal Δ v (K) is used as an input of the PI regulator, and the output of the PI regulator is subjected to a steady-state optimization algorithm (it should be noted that the steady-state optimization algorithm is intended to indicate that the starting process is just performed according to an algorithm of a steady-state process, and control mode switching is not required to be introduced when the output voltage reaches a given value) to obtain an inward-shifting phase angle command value α '(K +1) of the next half cycle and an outward-shifting phase angle command value β' (K +1) of the next half cycle.
In the conventional PI closed-loop control, when the output voltage reaches the given value of the output voltage, the change of the error signal may cause a sudden change of the PI output, thereby causing a sudden change of the instruction value α '(K +1) of the phase shift angle in the next half cycle and a sudden change of the instruction value β' (K +1) of the phase shift angle in the next half cycle, and if the sudden change of the instruction value α '(K +1) of the phase shift angle and the sudden change of the instruction value β' (K +1) of the phase shift angle are directly applied to the switching tube signal, the transmission inductance current may generate a dc component, which may also cause magnetic saturation of the transformer, and the attenuation of the dc component also needs a certain time, and is not good for the rapidity and stability of the starting process.
In order to prevent the direct current component generated by sudden change of the phase shift angle signal when the output voltage reaches the given value of the output voltage and the transmission inductance current at any time after starting in closed-loop regulation, the mode of changing the phase shift angle by beats can be adopted: the phase shift angle alpha (K +1) of the K +1 th switching half period is determined by averaging the phase shift angle command value alpha '(K) of the Kth switching half period output by the PI controller and the phase shift angle command value alpha' (K +1) of the K +1 th switching half period output by the PI controller; the out-shift phase angle beta (K +1) of the K +1 th switching half period is determined by averaging the out-shift phase angle instruction value beta (K) of the Kth switching half period output by the PI controller and the out-shift phase angle instruction value beta' (K +1) of the K +1 th switching half period output by the PI controller. The formula is expressed as follows:
Figure BDA0002571670090000091
Figure BDA0002571670090000092
by adopting the control method for changing the phase shift angle in different beats, the sudden change of the phase shift angle signal can be avoided on the premise of ensuring the rapidity of the closed loop starting, thereby inhibiting the generation of the direct current component of the transmission inductive current.
To verify the utility of the present invention, the parameters of the dual active bridge circuit were set as follows:
parameter(s) Numerical value
Steady value of input voltage V1 200V
Steady value of output voltage V2 100V
Input side capacitance C1 1360uf
Output side capacitance C2 680uf
Switching frequency fs 10kHz
Transformer turns ratio N 2:1
Transfer inductance Lt 250uH
Load resistance RL 10Ω
The simulation parameters for the dual active bridge isolated dc converter in MATLAB/Simulink are as above. Using an outputThe closed-loop control method of the voltage is characterized in that all switching tubes (Q)1～Q8) The control signals of (2) are all phase-shifted at the starting time of the system
Figure BDA0002571670090000101
The output of the closed-loop PI regulator is subjected to an optimization algorithm to obtain a phase angle instruction value alpha '(K +1) of the next half cycle, the instruction value and the phase angle instruction value alpha' (K) of the first half cycle are averaged to obtain a phase angle alpha (K +1) of the (K +1) th switching half cycle acting on the switching tube control, the output of the closed-loop PI regulator is subjected to the optimization algorithm to obtain a phase angle instruction value beta '(K +1) of the next half cycle, and the instruction value and the phase angle instruction value beta' (K) of the first half cycle are averaged to obtain a phase angle beta (K +1) of the (K +1) th switching half cycle acting on the switching tube control. The control block diagram is shown in fig. 6.
In the simulation, the start-up of the dual active bridge isolated dc converter starts from 0 s. Fig. 2 is a waveform of a dual active bridge closed loop direct start, and it can be seen that although the time of the establishment process of the output voltage is short, a dc bias of an inductive current is generated in the first period of the start, and the amplitude of the start impact current is large; and when the output voltage reaches a given value, the inductive current is subjected to direct current bias again. Fig. 3 is a waveform of starting by applying a small phase shift angle to the dual active bridge and a method for increasing the slope of a given voltage, which shows that the method can effectively avoid current impact at the moment of starting, but greatly prolong the starting time, and simultaneously, when the output voltage reaches the given value, the inductive current also has direct current bias. The starting waveform of the method provided by the invention is shown in fig. 4, the method ensures the rapidity of output voltage establishment, and the direct current bias can not occur to the inductive current in the whole starting process, thereby ensuring the stability of the system.
According to the simulation results, the starting method of the double-active-bridge direct-current converter applied to the direct-current power distribution network can effectively guarantee the rapidity of the starting process of the direct-current converter, simultaneously effectively inhibits the impact current and the direct-current bias, and does not have the direct-current magnetic bias phenomenon. The method can ensure the rapidity and the stability of the starting process of the double active bridges.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (7)

1. A fast soft start control method for a dual active bridge dc converter, the dual active bridge dc converter comprising: DC power supply V1An input capacitor C1A primary full bridge H1, a transmission inductor LtA high-frequency isolation transformer T with the turn ratio of N:1, a secondary side full bridge H2, and an output capacitor C2And a load resistor RLThe method is characterized by comprising the following steps:
s1: setting the switching tubes Q connected in series in the full bridge H11And Q2Are complementary to the control signal of (1), and are connected in series to Q3And Q4Are complementary to each other, Q1And Q4Has a phase difference of alpha; setting the switching tubes Q connected in series in the full bridge H25And Q6Are complementary to the control signal of (1), and are connected in series to Q7And Q8Are complementary to each other, Q5And Q8Has a phase difference of alpha; setting the phase shift angle between the full bridge H1 and the full bridge H2 to β; wherein, alpha is an internal shift phase angle, the adjusting range is 0-pi/2, beta is an external shift phase angle, and the adjusting range is 0-pi/2;
s2: setting the system start time, all the switch tubes simultaneously shift the phase
Figure FDA0003236375250000013
An angle of rotation of the rotor, wherein,
Figure FDA0003236375250000014
is pi/2 or-pi/2, so that the transmission inductive current in the first starting period does not contain direct current, and the amplitude of the starting current is reduced to half of the original amplitude;
s3: k is equal to K, wherein K is the repetition frequency of the switching half cycle, and K is an integer greater than or equal to 1;
s4: sampling the output voltage value V of the double active bridges at the end moment of the Kth switching half period2(K)；
S5: taking the output voltage error signal delta V (K) as the input of the PI regulator, and obtaining an inward phase angle instruction value alpha '(K +1) of the next half period and an outward phase angle instruction value beta' (K +1) of the next half period through a steady state optimization algorithm; wherein Δ V (k) ═ Vref-V2(K)，VrefThe voltage is a given value of the final steady-state output voltage of the double-active-bridge direct-current converter;
s6: setting the phase shift angle within the K +1 th switching half cycle
Figure FDA0003236375250000011
Setting the phase shift angle within the K +1 th switching half cycle
Figure FDA0003236375250000012
S7: and repeating the steps S4-S6 when K is equal to K +1, so that the output voltage of the double-active-bridge direct current converter gradually rises to the output voltage set value Vref。
2. The fast soft-start control method for a dual active bridge dc converter as claimed in claim 1, wherein in the dual active bridge dc converter, the input capacitance C1An output capacitor C connected in parallel to the primary full bridge H12Connected in parallel to the secondary side full bridge H2, and transmitting inductance LtConnected in series between the primary full bridge H1 and the transformer T, and outputting a voltage V at the initial start time2Is 0V.
3. The fast soft-start control method for a dual active bridge DC converter according to claim 1,
the primary side full bridge H1 is composed of a switch tube Q1～Q4Is composed of a switching tube Q1And Q2Series, switch tube Q3And Q4Are connected in series with each other,and respectively form two bridge arms of a primary full bridge H1, the midpoint of the two bridge arms is led out to be used as an alternating current port H1, and the voltage of the alternating current port is VH1；
The secondary side full bridge H2 is composed of a switch tube Q5～Q8Is composed of a switching tube Q5And Q6Series, switch tube Q7And Q8Two arms connected in series and respectively forming a secondary side full bridge H2, wherein the midpoint of the two arms leads out an alternating current port H2, and the voltage of the alternating current port is VH2；
Transfer inductance LtA voltage drop of V acrossL＝VH1-NVH2；
In the first initial switching period, the high-frequency link voltage V of the double-active-bridge DC converterH1And VH2Decomposed by a fourier series, expressed as:
Figure FDA0003236375250000021
wherein, V1Is a DC power supply, alpha is an internal phase shift angle, omegasIn order to be the angular frequency of the system,
Figure FDA0003236375250000022
is pi/2 or-pi/2.
4. The fast soft-start control method for a dual active bridge dc converter as claimed in claim 3, wherein L is a transfer inductance for the current flowingtHigh frequency chain current iL(t) during a first switching cycle:
Figure FDA0003236375250000023
starting i in the first periodLThe Fourier series of (t) is represented as:
Figure FDA0003236375250000031
5. the fast soft-start control method for a dual-active-bridge DC converter as claimed in claim 4, wherein during the first start-up period, the current flows through the transfer inductor LtThe amplitude expression of the high-frequency chain current is as follows:
Figure FDA0003236375250000032
6. a fast soft start control system for a dual active bridge dc converter, the dual active bridge dc converter comprising: DC power supply V1An input capacitor C1A primary full bridge H1, a transmission inductor LtA high-frequency isolation transformer T with the turn ratio of N:1, a secondary side full bridge H2, and an output capacitor C2And a load resistor RLThe method is characterized by comprising the following steps:
a first setting unit for setting the switching tubes Q connected in series in the full bridge H11And Q2Are complementary to the control signal of (1), and are connected in series to Q3And Q4Are complementary to each other, Q1And Q4Has a phase difference of alpha; setting the switching tubes Q connected in series in the full bridge H25And Q6Are complementary to the control signal of (1), and are connected in series to Q7And Q8Are complementary to each other, Q5And Q8Has a phase difference of alpha; setting the phase shift angle between the full bridge H1 and the full bridge H2 to β; wherein, alpha is an internal shift phase angle, the adjusting range is 0-pi/2, beta is an external shift phase angle, and the adjusting range is 0-pi/2;
a second setting unit for setting the phase shift of all the switch tubes at the system start time
Figure FDA0003236375250000034
An angle of rotation of the rotor, wherein,
Figure FDA0003236375250000033
is pi/2 or-pi/2, so that the transmission is started in the first periodThe transmission inductive current does not contain direct current, and the amplitude of the starting current is reduced to half of the original amplitude;
the sampling unit is used for enabling K to be K, wherein K is the repetition frequency of the switching half cycle, and K is an integer larger than or equal to 1; sampling the output voltage value V of the double active bridges at the end moment of the Kth switching half period2(K)；
A third setting unit, configured to use the output voltage error signal Δ v (K) as an input of the PI regulator, and obtain an instruction value α '(K +1) of an inward shift phase angle of the next half cycle and an instruction value β' (K +1) of an outward shift phase angle of the next half cycle through a steady-state optimization algorithm; wherein Δ V (k) ═ Vref-V2(K)，VrefThe voltage is a given value of the final steady-state output voltage of the double-active-bridge direct-current converter; setting the phase shift angle within the K +1 th switching half cycle
Figure FDA0003236375250000041
Setting the phase shift angle within the K +1 th switching half cycle
Figure FDA0003236375250000042
A circulating unit for making K equal to K +1, and making the output voltage of the dual-active-bridge DC converter gradually rise to the given value V of the output voltage through the sampling unit and the third setting unitref。
7. The fast soft-start control system for a dual active bridge dc converter of claim 6, wherein the input capacitance C of the dual active bridge dc converter1An output capacitor C connected in parallel to the primary full bridge H12Connected in parallel to the secondary side full bridge H2, and transmitting inductance LtConnected in series between the primary full bridge H1 and the transformer T, and outputting a voltage V at the initial start time2Is 0V.
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