CN115566899A - Bidirectional direct current converter, lithium battery formation system and control method - Google Patents

Bidirectional direct current converter, lithium battery formation system and control method Download PDF

Info

Publication number
CN115566899A
CN115566899A CN202211124962.9A CN202211124962A CN115566899A CN 115566899 A CN115566899 A CN 115566899A CN 202211124962 A CN202211124962 A CN 202211124962A CN 115566899 A CN115566899 A CN 115566899A
Authority
CN
China
Prior art keywords
lithium battery
voltage
inductor
battery
formation system
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202211124962.9A
Other languages
Chinese (zh)
Inventor
秦岭
尹小娟
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nantong University
Original Assignee
Nantong University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nantong University filed Critical Nantong University
Priority to CN202211124962.9A priority Critical patent/CN115566899A/en
Publication of CN115566899A publication Critical patent/CN115566899A/en
Pending legal-status Critical Current

Links

Images

Classifications

    • 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
    • H02M3/1582—Buck-boost converters
    • 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
    • H02J7/34—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering
    • H02J7/345—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering using capacitors as storage or buffering devices
    • 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
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H02M1/0054—Transistor switching losses
    • H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
    • 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
    • H02J2207/00—Indexing scheme relating to details of circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J2207/20—Charging or discharging characterised by the power electronics converter
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)

Abstract

The application belongs to the technical field of direct current converters, and particularly relates to a bidirectional direct current converter, a lithium battery formation system and a control method. The bidirectional direct current converter comprises two switching tubes, two inductors and two capacitors. The bidirectional buck-boost conversion can be realized, and the voltage of the storage battery is allowed to change in a wide range; the power devices are few, and the cost is low; the input and output have the same polarity and are grounded, the electromagnetic interference is small, and the structure of the sampling circuit is simple; zero-voltage switching-on of the two switching tubes can be realized in the full working range, and the switching device has smaller switching loss and higher conversion efficiency; the high-efficiency recovery and reutilization of the energy stored by the lithium battery can be realized, and the energy loss and the production cost in the formation of the battery are reduced.

Description

Bidirectional direct current converter, lithium battery formation system and control method
Technical Field
The invention belongs to the technical field of direct current converters, and particularly relates to a bidirectional direct current converter, a lithium battery formation system and a control method.
Background
Lithium batteries have become the most promising efficient secondary batteries and the fastest-developing chemical energy storage devices at present due to the advantages of small size, large capacity, high working voltage, long cycle life, no memory and the like. According to the chemical characteristics of the lithium battery, multiple constant-voltage and constant-current charging and discharging are needed before the lithium battery leaves a factory, so that the energy storage capacity of the battery is enhanced, and the process is called formation. Most of the existing formation equipment does not have a reliable and reasonable energy recovery system, and when a lithium battery discharges, the lithium battery directly generates heat through a power resistor for consumption, so that the heat generation is large, and the energy utilization rate is low; in addition, in order to reduce the room temperature of the formation plant, a high-power air conditioning facility has to be installed and activated, thereby further increasing the power consumption. Therefore, the conventional battery formation system seriously increases the production cost of the battery and has serious energy waste. If the super capacitor is adopted to recover the discharge energy of the lithium battery and then used for charging the lithium battery, the utilization rate of electric energy can be improved, energy waste is avoided, and the production cost of the battery is reduced, so that the super capacitor has important significance for promoting the utilization of renewable energy and the development of electric automobiles and achieving the goal of a double-carbon strategy as early as possible. The bidirectional direct current converter is a key technical device in a lithium battery formation system based on a super capacitor and is responsible for voltage matching and energy bidirectional flow control of a lithium battery pack and the super capacitor. Because the output voltage variation range of the lithium battery is wide, and the service life of the lithium battery is closely related to the size of the current ripple, the bidirectional direct current converter in the lithium battery formation system based on the super capacitor needs to have a wide voltage gain range and small current ripple. At present, bidirectional dc converters are mainly classified into two categories: isolated and non-isolated. Compared with the former, the non-isolated bidirectional direct current converter has the advantages of small volume and weight, simple structure, low cost, high efficiency and the like. The conventional Buck/Boost bidirectional direct-current converter is widely applied due to the advantages of continuous current at the low-voltage side, common ground at the high-voltage side and the low-voltage side, small number of devices and the like. However, the converter cannot realize bidirectional voltage increase and decrease. The four-switch buck-boost converter can realize bidirectional boost and buck and has the advantages of low voltage stress of a power device, few passive elements, same input and output polarities, common ground and the like. However, the input and output currents are intermittent, the number of power devices is large, and the cost is high.
Disclosure of Invention
In view of this, the invention provides a bidirectional dc converter, a lithium battery formation system and a control method, where the bidirectional dc converter only includes two Switching tubes, and when the bidirectional dc converter is applied to the lithium battery formation system, the bidirectional up/down conversion and Zero Voltage Switching-on (ZVS) of all the Switching tubes can be realized, the bidirectional dc converter can efficiently operate in a full working range, and the bidirectional dc converter has the characteristics of continuous current at the side of a lithium battery, small number of devices, small volume, low cost, and wide-range variation of Voltage of the lithium battery, and the like.
In order to achieve the above object, the following solutions are proposed:
a bidirectional dc converter comprising: lithium battery side capacitor C b A first capacitor C 1 A first inductor L 1 A second inductor L 2 A first switch tube S 1 A second switch tube S 2 ；
The side capacitor C of the lithium battery b Positive pole and first inductance L 1 Is connected with one end of the connecting rod;
the first inductor L 1 And the other end of the first capacitor C 1 Positive pole of (2), the first switching tube S 1 Is connected with the drain electrode of the transistor;
the second inductor L 2 And the first capacitor C 1 Negative pole of (1), the second switching tube S 2 Is connected to the source of (a);
the side capacitor C of the lithium battery b Negative pole of (2) and first switch tube S 1 Source electrode of, second inductance L 2 The other end of the connecting rod is connected;
the side capacitor C of the lithium battery b The positive electrode of (a) is a positive polarity end of the lithium battery side;
the second switch tube S 2 The drain of (a) is used as the positive polarity end of the super capacitor side;
the side capacitor C of the lithium battery b The negative electrodes of (a) are used as negative polarity ends of a lithium battery side and a super capacitor side;
further, the first inductor L 1 It must satisfy:
Figure BDA0003848178840000011
in the formula of U b 、U dc The terminal voltages of the lithium battery and the super capacitor are respectively; f. of s,min Is the lowest switching frequency; i is L1 Is a first inductance L 1 Average current of (d); delta% is the first inductor current ripple rate, which is generally 20% -30%.
The second inductor L 2 The requirements are satisfied:
Figure BDA0003848178840000012
wherein, delta I is current margin, namely the peak value I of the second inductive current in the lithium battery discharge mode L2,peak And the first inductor current valley value i L1,val The difference of (a) is usually 2A-4A o,max Is the maximum output power.
The invention also provides a control method of the bidirectional direct current converter for the lithium battery formation system, which specifically comprises the following steps:
s1, sampling value i of the first inductive current L1,f And a reference value i L1,fef Comparing to obtain an error signal i L1,e ；
S2, the error signal i is processed L1,e Sending the signal to a lithium battery current controller, and obtaining an adjusting signal u through a one-way amplitude limiting link r ；
S3, sampling value U of voltage of lithium battery side b First inductor current sampling value i L1,f Average value of (1) L1 And super capacitor side voltage sampling value U dc Sending the data to a switching frequency calculation link to obtain a switching frequency f s And further generating a frequency f s Of a unipolar triangular carrier u c (ii) a The calculation formula of the switching frequency calculation link is as follows:
Figure BDA0003848178840000021
s4, adjusting the signal u r With a unipolar triangular carrier u c Intercept to generate PWM signal u PWM ；
S5, enabling the lithium battery side voltage sampling value U b And the upper limit threshold value U of the voltage of the lithium battery side b,upp Sending the voltage to a voltage comparator 1 to obtain a lithium battery side voltage overvoltage protection signal U pro,up ；
S6, enabling the lithium battery side voltage sampling value U b Lower limit threshold U of voltage on lithium battery side b,low Sent into a voltage comparator 2 to obtain a lithium battery side voltage under-voltage protection signal U pro,low ；
S7, overvoltage is conducted on the side voltage of the lithium batteryProtection signal U pro,up And lithium battery side voltage under-voltage protection signal U pro,low PWM signal u PWM And then, obtaining a first switch tube S 1 Drive signal u of gs,S1 Will u gs,S1 After being inverted, the second switching tube S is used as the second switching tube 2 Drive signal u of gs,S2 ；
The invention also provides a lithium battery formation system which comprises the bidirectional direct current converter for the lithium battery formation system, a lithium battery and a super capacitor, wherein the lithium battery is connected with the lithium battery side of the bidirectional direct current converter for the lithium battery formation system, and the super capacitor is connected with the super capacitor side of the bidirectional direct current converter for the lithium battery formation system.
The invention also provides a control method of the lithium battery formation system, which comprises the following steps:
by varying said first inductor current reference value i L1,fef To set the operating mode of the lithium battery. When i is L1,fef >When the voltage is 0, the formation system works in a lithium battery discharge mode, and the energy of the lithium battery is transferred to the super capacitor; when i is L1,fef <When 0, the formation system works in a lithium battery charging mode, and the energy stored by the super capacitor is transferred to a lithium battery;
by varying said first inductor current reference value i L1,fef The current value of the constant current charging and discharging of the lithium battery is set;
by changing the upper threshold U of the voltage on the lithium battery side b,upp To set a charge cutoff voltage;
by changing the lower threshold U of the voltage on the lithium battery side b,low The discharge cutoff voltage is set.
Compared with the prior art, the invention has the following technical effects:
1) The converter can realize bidirectional buck-boost conversion, allows wide-range change of the voltage of the lithium battery, and has the advantages of few power devices, low cost, homopolarity of input and output, common ground and the like;
2) Can realize the first switch tube S in the full working range 1 And a second switching tube S 2 Zero voltage onTurn-on (ZVS), with less Switching losses and higher conversion efficiency.
3) The high-efficiency recovery and reutilization of the energy stored by the lithium battery can be realized, and the energy loss and the production cost in the formation of the battery are reduced.
Drawings
Fig. 1 is a schematic circuit structure diagram of a lithium battery formation system based on a super capacitor according to an embodiment of the present invention;
FIG. 2 is a block diagram of a system control strategy for a bi-directional DC converter in the lithium battery formation system shown in FIG. 1;
FIG. 3 is a diagram of a modal analysis of the bi-directional DC converter in a lithium battery discharge mode;
FIG. 4 is a schematic diagram of the principal waveforms of the bi-directional DC converter in the lithium battery discharge mode;
FIG. 5 is a modal analysis diagram of the bi-directional DC converter in the lithium battery charging mode;
FIG. 6 is a schematic diagram of the principal waveforms of the bi-directional DC converter in the lithium battery charging mode;
FIG. 7 is a steady state simulation waveform diagram of the bi-directional DC converter in the lithium battery discharge mode;
FIG. 8 is a steady state simulation waveform diagram of the bi-directional DC converter in the lithium battery charging mode;
FIG. 9 is a transient simulation waveform of the bi-directional DC converter in the lithium battery discharge mode;
FIG. 10 shows a first inductor current reference value from i L1,ref Transient simulation waveforms of the bidirectional direct current converter when the frequency of the converter is changed from 2.5A to-2.5A.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
FIG. 1 shows an embodiment of the present inventionIn fig. 1, a dashed-line frame shows a bidirectional dc converter, which includes: lithium battery side capacitor C b A first capacitor C 1 A first inductor L 1 A second inductor L 2 A first switch tube S 1 A second switch tube S 2 (ii) a The side capacitor C of the lithium battery b Positive pole and first inductance L 1 Is connected with one end of the connecting rod; the first inductor L 1 And the other end of the first capacitor C 1 The positive electrode of the first switch tube S 1 Is connected with the drain electrode of the transistor; the second inductor L 2 And the first capacitor C 1 Negative pole of (1), the second switching tube S 2 Is connected to the source of (a); the side capacitor C of the lithium battery b Negative pole of (2) and first switch tube S 1 Source electrode of (1), second inductance L 2 The other end of the first and second connecting rods is connected; the side capacitor C of the lithium battery b The positive electrode of (a) is a positive terminal on the side of the lithium battery; the second switch tube S 2 The drain of (a) is used as the positive polarity end of the super capacitor side; the side capacitor C of the lithium battery b As negative polarity terminals on the lithium battery side and the supercapacitor side. The lithium battery side of the bidirectional direct current converter is connected with the lithium battery, and the super capacitor side of the bidirectional direct current converter is connected with the super capacitor.
As shown in fig. 2, the method for controlling the bidirectional dc converter in the lithium battery formation system specifically includes the following steps:
s1, sampling value i of the first inductive current L1,f And a reference value i L1,fef Comparing to obtain an error signal i L1,e ；
S2, the error signal i is processed L1,e Sending the signal to a lithium battery current controller, and obtaining an adjusting signal u through a one-way amplitude limiting link r ；
S3, sampling value U of voltage of lithium battery side b First inductor current sampling value i L1,f Average value of (1) L1 And super capacitor side voltage sampling value U C Sending the data to a switching frequency calculation link to obtain a switching frequency f s And further generating a frequency f s Unipolar triangular carrier u c ；
S4. Will instituteThe regulating signal u r With a unipolar triangular carrier u c Intercept to generate PWM signal u PWM ；
S5, enabling the lithium battery side voltage sampling value U b And the upper limit threshold value U of the voltage of the lithium battery side b,upp Sending the voltage to a voltage comparator 1 to obtain a lithium battery side voltage overvoltage protection signal U pro,up ；
S6, enabling the lithium battery side voltage sampling value U b Lower limit threshold U of voltage on lithium battery side b,low Sent into a voltage comparator 2 to obtain a lithium battery side voltage under-voltage protection signal U pro,low ；
S7, enabling the lithium battery side voltage overvoltage protection signal U pro,up And lithium battery side voltage under-voltage protection signal U pro,low PWM signal u PWM And then, obtaining a first switch tube S 1 Drive signal u of gs,S1 U is to be gs,S1 After being inverted, the second switching tube S is used as the second switching tube 2 Drive signal u of gs,S2 。
The control method of the lithium battery formation system comprises the following steps:
by varying said first inductor current reference value i L1,fef To set the operating mode of the lithium battery. When i is L1,fef >When the voltage is 0, the formation system works in a lithium battery discharge mode, and the energy of the lithium battery is transferred to the super capacitor; when i is L1,fef <When the energy is 0, the formation system works in a lithium battery charging mode, and the energy stored by the super capacitor is transferred to the lithium battery;
by varying said first inductor current reference value i L1,fef The current value of the constant current charging and discharging of the lithium battery is set.
By changing the upper limit threshold U of the side voltage of the lithium battery b,upp To set a charge cutoff voltage;
by changing the lower threshold U of the voltage on the lithium battery side b,low The discharge cutoff voltage is set.
The operation principle of the bidirectional dc converter in the lithium battery formation system shown in fig. 1 will be described below.
To simplify the analysis, the following assumptions were made:first switch tube S 1 A second switch tube S 2 Lithium battery side capacitor C b A first capacitor C 1 A first inductor L 1 A second inductor L 2 Are all ideal devices; lithium battery side capacitor C b A first capacitor C 1 Large enough that voltage ripple is negligible; lithium battery side capacitor C b The negative electrode of (2) is a zero potential reference point; first switch tube S 1 A second switch tube S 2 Respectively is D S1 、D S2 (ii) a Super capacitor C dc Has a very large capacity, so C dc Can be regarded as a constant voltage source U dc 。
Based on the above assumptions, the steady-state working processes of the bidirectional dc converter for the super-capacitor-based lithium battery formation system in the lithium battery discharge mode and the lithium battery charge mode can be divided into 4 modes, which are described below.
(1) Lithium battery discharge mode
When the first inductor current reference value i L1,fef >And when 0, the formation system works in a lithium battery discharge mode, and the energy of the lithium battery is transferred to the super capacitor.
In this mode, equivalent circuits of the modes are shown in fig. 3 (a) - (d), and main waveforms in one switching period are shown in fig. 4.
t 0 Before the moment, the first switch tube S 1 Body diode D of S1 The freewheeling has been turned on.
Modal 1,t 0 ～t 1 Stage (2): (the equivalent circuit is shown in FIG. 3 (a))
t 0 At the moment, the first switch tube S 1 Turned on by ZVS and its body diode D S1 Is naturally turned off and mode 1 begins. First, the second inductor L 2 Through a first switch tube S 1 For the first capacitor C 1 Charging, lithium battery and second inductor L 2 Simultaneously to the first inductance L 1 Charging is carried out; then, the lithium battery passes through a first switch tube S 1 For the first inductance L 1 Charging is carried out, the first capacitor C 1 Firstly from the lithium battery and the second inductance L 2 Absorbing energy and then passing through a first switch tube S 1 For the second inductance L 2 Charging; first inductor current i L1 Linearly increasing in the forward direction, second inductor current i L2 The forward linearity decreases to zero and then the reverse linearity increases. At this time, there are:
Figure BDA0003848178840000041
in the formula, L 1 Is the inductance of the first inductor, L 2 Is the inductance of the second inductor, U C1 Is a first capacitor C 1 Terminal voltage of U b Is the lithium battery terminal voltage.
Modal 2,t 1 ～t 2 Stage (2): (the equivalent circuit is shown in FIG. 3 (b))
t 1 At the moment, the first switch tube S 1 Is turned off, the second switch tube S 2 Body diode D of S2 Conduction and mode 2 begins. Via the body diode D S2 Lithium battery and first inductor L 1 Simultaneously to the first capacitor C 1 And a super capacitor C dc Charging, second inductance L 2 For super capacitor C dc Releasing energy; first inductor current i L1 Linearly decreasing in the forward direction, second inductor current i L2 The inverse linearity decreases, at this point:
Figure BDA0003848178840000042
modal 3,t 2 ～t 3 Stage (2): (the equivalent circuit is shown in FIG. 3 (c))
t 2 At the moment, the second switch tube S 2 Turned on by ZVS with body diode D S2 Is naturally switched off and modality 3 starts. First, pass through the second switch tube S 2 Lithium battery and first inductor L 1 Simultaneously to the first capacitor C 1 And a super capacitor C dc Charging, second inductance L 2 For super capacitor C dc Releasing energy; then, the lithium battery and the first inductor L 1 Simultaneously to the first capacitor C 1 A second inductor L 2 Charging, super capacitor C dc Firstly from the lithium battery and the first inductance L 1 After releasing energy, the second inductor L is connected 2 Releasing energy; first inductor current i L1 Linearly decreasing in the forward direction, second inductor current i L2 The current expression is the same as that of equation (2) by first linearly decreasing the reverse direction to zero and then linearly increasing the forward direction.
Modal 4,t 3 ～t 4 Stage (2): (the equivalent circuit is shown in FIG. 3 (d))
t 3 At the moment, the second switch tube S is turned off 2 A first switch tube S 1 Body diode D of S1 Conduction and mode 4 begins. Through a first switch tube S 1 Second inductance L 2 For the first capacitor C 1 Charging, lithium battery and second inductor L 2 Simultaneously to the first inductance L 1 And charging is carried out. First inductor current i L1 Linearly increasing in the forward direction, second inductor current i L2 The forward linearity decreases and the current expression is the same as that of equation (1).
Neglecting dead time according to the first inductance L 1 A second inductor L 2 The volt-second equilibrium of (a) can be obtained from the formulae (1) and (2):
Figure BDA0003848178840000043
in the formula, T s For a switching period, D is a first switching tube S 1 The duty cycle of the drive signal.
Further, from fig. 3 (a), it can be obtained:
U C1 ＝U b (4)
according to the equations (3) and (4), the voltage gain of the bidirectional dc converter in the lithium battery discharging mode is obtained as follows:
Figure BDA0003848178840000044
(2) Lithium battery charging mode
When the first inductor current reference value i L1,fef <When 0 hour, the formation system works in the lithium battery chargingIn the electric mode, the energy stored by the super capacitor is transferred to the lithium battery;
in this mode, equivalent circuits of the modes are shown in fig. 5 (a) - (d), and main waveforms in one switching period are shown in fig. 6.
Modal 1,t 0 ～t 1 Stage (2): (the equivalent circuit is shown in FIG. 5 (a))
t 0 Before the moment, the second switch tube S 2 Body diode D of S2 Freewheeling has been turned on.
t 0 At the moment, the second switch tube S 2 Turned on by ZVS and its body diode D S2 Is naturally switched off and mode 1 starts. First, the second inductor L 2 And a first capacitor C 1 Together pair the first inductance L 1 Charging with lithium battery, super capacitor C dc Through a second switch tube S 2 First from the second inductor L 2 After absorbing energy, the first inductor L is connected 1 And the lithium battery releases energy; then, the first capacitor C 1 And a super capacitor C dc Together pair the first inductance L 1 And the lithium battery releases energy, and a second inductor L 2 From the super capacitor C dc Absorbing energy; first inductor current i L1 Linearly increasing in the opposite direction, second inductor current i L2 First the reverse linearity decreases to zero and then the forward linearity increases. At this time, the inductance L 1 、L 2 The current expression of (2) is shown in the following formula.
Modal 2,t 1 ～t 2 Stage (2): (the equivalent circuit is shown in FIG. 5 (b))
t 1 At the moment, the second switch tube S 2 Is turned off, the first switch tube S 1 Body diode D of S1 Conduction and mode 2 begins. Via the body diode D S1 First inductance L 1 For charging lithium battery, a second inductor L 2 For the first capacitor C 1 Releasing energy; first inductor current i L1 Inverse linear decrease, second inductor current i L2 The forward linearity decreases. At this time, the inductance L 1 、L 2 The current expression of (2) is shown in formula (1).
Modal 3,t 2 ～t 3 Stage (2): (equivalent CircuitAs shown in FIG. 5 (c)
t 2 At any moment, the first switch tube S 1 Turned on by ZVS with body diode D S1 Is naturally switched off and modality 3 starts. First, pass through the first switch tube S 1 First inductance L 1 Continuously releasing energy to the lithium battery, and a second inductor L 2 First, the first capacitor C is aligned 1 Release energy from the first inductor L 1 And a first capacitor C 1 Absorbing energy; then, the first inductance L 1 And a first capacitor C 1 For charging lithium battery, a second inductor L 2 From the first capacitance C 1 Energy is absorbed. First inductor current i L1 Inverse linear decrease, second inductor current i L2 The current expression is the same as that of the formula (1) by linearly decreasing the forward direction to zero and then linearly increasing the reverse direction.
Modal 4,t 3 ～t 4 Stage (2): (the equivalent circuit is shown in FIG. 5 (d))
t 3 At the moment, the first switch tube S 1 Is turned off, the second switch tube S 2 Body diode D of S2 Conduction and mode 4 begins. Via the body diode D S2 Second inductance L 2 And a first capacitor C 1 Combined pair first inductor L 1 And charging a lithium battery; at the same time, the second inductance L 2 And also for super capacitor C dc Charging; first inductor current i L1 Linearly increasing in the opposite direction, second inductor current i L2 The inverse linearity decreases and the current expression is the same as that of equation (2).
Neglecting dead time according to the first inductance L 1 A second inductor L 2 The voltage gain of the bidirectional direct current converter in the lithium battery charging mode can be obtained by the voltage-second balance of the invention as follows:
Figure BDA0003848178840000051
furthermore, from modal analysis it is known that:
U S1 ＝U S2 ＝U b +U dc (7)
in the formula of U S1 、U S2 Are respectively a first switch tube S 1 And a second switching tube S 2 The voltage stress experienced.
Lithium battery side capacitor C b And a first capacitor C 1 The voltage stress of (a) is:
U Cb ＝U C1 ＝U b (8)
the average current stress of each inductor is:
Figure BDA0003848178840000052
in the formula I L1 、I L2 Are respectively a first inductance L 1 A second inductor L 2 Average current of (d); i is b 、I dc Respectively a lithium battery and a super capacitor C dc Average current of (2).
According to the formulas (1), (2) and (5), the following can be obtained:
Figure BDA0003848178840000053
first inductor current i L1 The peak-to-peak value of (a):
Figure BDA0003848178840000054
second inductor current i L2 The peak-to-peak value of (a):
Figure BDA0003848178840000055
to realize the first switching tube S in the lithium battery discharge mode 1 A second switch tube S 2 The ZVS of the first inductor current is required to make the peak value I of the second inductor current in the mode L2,peak A valley value I greater than the first inductance current L1,val . At this time, there are:
Figure BDA0003848178840000061
to realize the first switch tube S in the lithium battery charging mode 1 A second switch tube S 2 ZVS of (d) is turned on, requiring the absolute value | I of the valley of the second inductor current in this mode L2,val I is greater than the peak absolute value I of the first inductor current L1,peak L. At this time, there are:
Figure BDA0003848178840000062
in the formula, Δ I is called a current margin, and its value range is: 2A to 4A.
It can be seen that equation (13) is the same as equation (14), which indicates that the soft switching conditions are the same for the lithium battery charge mode and the discharge mode.
By substituting equations (11) and (12) into equation (13):
Figure BDA0003848178840000063
in order to ensure that ZVS (zero voltage switching) of all switching tubes is realized in the full working range, the lowest lithium battery voltage U needs to be ensured b,min And a maximum load P o,max Under conditions satisfying formula (14), thereby having:
Figure BDA0003848178840000064
in the formula (f) s,min Is the lowest switching frequency;
first inductance L 1 The design is carried out according to the current ripple rate not exceeding delta%. At this time, there are:
Figure BDA0003848178840000065
in addition, if the switching frequency of the converter is not changed, the voltage of the lithium battery rises or the lithium battery is under loadDecreasing the valley value I of the first inductor current L1,val Will drop and the peak value I of the second inductor current will decrease L2,peak The variation is small, resulting in an excessive current margin Δ I. The larger current margin is helpful for realizing ZVS (zero voltage switching) switching-on of the switching tube, but larger on-state loss is brought, so that the conversion efficiency is reduced on the contrary. Therefore, in order to ensure that the switching tube reliably realizes ZVS turn-on and avoid excessive on-state loss, the switching frequency needs to be calculated and changed in real time according to the working conditions of the converter, so that the current margin Δ I remains approximately unchanged. From equation (18), the calculation formula for the switching frequency is obtained:
Figure BDA0003848178840000066
after the variable switching frequency control method is adopted, the switching frequency of the bidirectional converter is at the lowest lithium battery voltage U b,low And a maximum load P o,max And the condition reaches the lowest.
Specific examples of the present invention are given below. The design criteria are shown in table 1.
TABLE 1 design index
Figure BDA0003848178840000067
The present invention designs the related inductance based on the design index shown in table 1.
By substituting the parameters shown in Table 1 into equation (16), it is possible to obtain:
Figure BDA0003848178840000071
actually taking a first inductance: l is 1 ＝750μH。
The parameters shown in Table 1 and L 1 If equation (15) is substituted with 750 μ H, the following can be obtained:
Figure BDA0003848178840000072
actually taking a second inductance: l is 2 ＝22μH。
The feasibility of the bidirectional converter provided by the invention is verified through Saber simulation, the specific technical indexes are shown in table 1, and the circuit parameters are as follows: a first capacitor C 1 =10 μ F, lithium battery side capacitance C b =47 μ F; first inductance L 1 =750 μ H, second inductance L 2 =22 μ H. In the simulation, the first inductor current reference value i is changed L1,fef To set the operating mode of the lithium battery. If i L1,ref And =2.5A, the formation system is set to be in a lithium battery constant current discharge mode, and the constant current value is 2.5A. If i L1,ref And = -2.5A, the formation system is set to be in a lithium battery constant current charging mode, and the constant current value is 2.5A. Further, the discharge cut-off voltage is set to U b,low =80V, charge cutoff voltage is set to U b,up =120V. When the voltage of the lithium battery exceeds 120V, stopping charging; when the voltage of the lithium battery is lower than 80V, the discharge is immediately stopped. Therefore, the working voltage range of the lithium battery in the formation process is 80V-120V.
FIG. 7 shows the lithium battery discharge mode (first inductor current reference value set to i) L1,ref = 2.5A) is provided.
FIG. 7 (a) shows the first inductor current i in this mode L1 A second inductor current i L2 Lithium battery side voltage U b And super capacitor side voltage U dc The simulated waveform of (2). It can be seen that the voltage U of the lithium battery b =80V, super capacitor voltage U dc =100V, actual voltage gain U dc /U b =100/80=1.25, the measured duty cycle being approximately 0.534, which substantially corresponds to the theoretical duty cycle D = 0.56. First inductor current i L1 Average value of (1) L1 About 2.5A, second inductor current i L2 Average value of (1) L2 And = 1.93A. Peak value of second inductor current I L2,peak =5.31A, greater than the valley I of the first inductor current L1,val =2.22A, Δ I ≈ 3A, and satisfies the requirement of the first switch tube S 1 A second switch tube S 2 The zero voltage on condition.
FIG. 7 (b) shows the first switch tube S 1 Drive signal u of gs,S1 Terminal voltage u S1 And current i S1 The simulated waveform of (2). FIG. 7 (c) shows a second switch tube S 2 Drive signal u of gs,S2 Terminal voltage u S2 And current i S2 The simulated waveform of (2). As can be seen from FIGS. 7 (b) and 7 (c), the switching frequency f s Approximately equal to 114kHz; first switch tube S 1 And a second switching tube S 2 The voltage stress of the transformer is about 180V and is consistent with a theoretical value; first switching tube drive signal u gs,S1 And a second switching tube drive signal u gs,S2 Before going high, its terminal voltage u S1 And u S2 All have fallen to zero, indicating that the first switching tube S 1 And a second switching tube S 2 ZVS turn-on is achieved.
FIG. 8 shows a lithium battery charging mode (first inductor current reference value set to i) L1,ref = 2.5A) is provided.
FIG. 8 (a) shows the first inductor current i in this mode L1 A second inductor current i L2 Lithium battery side voltage U b And super capacitor side voltage U dc The simulated waveform of (2). It can be seen that the voltage U of the lithium battery b =80V, super capacitor voltage U dc =100V, actual voltage gain U b /U dc =80/100 ≈ 0.4, and the measured duty ratio is about 0.531, which substantially coincides with the theoretical duty ratio D = 0.56. First inductor current i L1 Average value of (1) L1 about-2.5A, second inductor current i L2 Average value of (1) L2 =2.00A. Second inductor current valley absolute value | I L2,val I | =5.14A, greater than the peak absolute value | I of the first inductor current L1,peak I | =2.17A, and delta I ≈ 3A, and meets the requirement of a first switch tube S 1 A second switch tube S 2 The zero voltage on condition.
FIG. 8 (b) shows the first switch tube S 1 Drive signal u of gs,S1 Terminal voltage u S1 And current i S1 The simulated waveform of (2). FIG. 8 (c) shows a second switch tube S 2 Drive signal u of gs,S2 Terminal voltage u S2 And current i S2 The simulated waveform of (2). As can be seen from FIGS. 8 (b) and 8 (c), the switching frequency f s About 115kHz; first switch tube S 1 And a second switching tube S 2 The voltage stress of the transformer is about 180V and is consistent with a theoretical value; first switching tube drive signal u gs,S1 And a second switching tube drive signal u gs,S2 Before going high, its terminal voltage u S1 And u S2 All have fallen to zero, indicating that the first switching tube S 1 And a second switching tube S 2 ZVS turn-on is achieved.
FIG. 9 shows the voltage U of the lithium battery in the discharging mode of the lithium battery b The transient state of the converter when changed simulates a waveform. It can be seen that the lithium battery voltage U is 200ms ago b =120V, first inductor current i L1 Average value of (1) L1 And the value is approximately equal to 2.5A, which indicates that the converter is in a lithium battery constant current discharge mode. 200ms, lithium battery voltage U b The voltage drops from 120V to 80V. It can be seen that after a regulation process of 10ms, the first inductor current i L1 Average value of (1) L1 Approximately equal to 2.5A, switching frequency f s The voltage of the lithium battery is changed from 124.3kHz to 115.4kHz, which shows that the converter can still realize constant-current discharge of the lithium battery when the voltage of the lithium battery is changed, and the switching frequency can be automatically adjusted.
FIG. 10 shows a first inductor current reference value from i L1,ref Transient simulation waveforms of the proposed bidirectional converter when =2.5A to-2.5A. It can be seen that the first inductor current i is 200ms ago L1 Average value of (1) L1 The output voltage is approximately equal to 2.5A, which indicates that the converter is in a lithium battery constant current discharge mode; at 200ms, the current reference value i is set L1,ref The temperature was changed from 2.5A to-2.5A. It can be seen that after a regulation process of 5ms, the first inductor current i L1 Average value of (1) L1 And =2.5A, the converter is indicated to enter a lithium battery constant current charging mode, so that the feasibility of the invention is verified.
From the simulation results, the bidirectional direct current converter, the lithium battery formation system and the control method provided by the invention have the following technical effects: 1) The converter can realize bidirectional buck-boost conversion, allows wide voltage change of the lithium battery, and has the advantages of few power devices and low costThe advantages of low cost, homopolarity of input and output, common ground and the like; 2) Can realize the first switch tube S in the full working range 1 And a second switching tube S 2 Zero Voltage Switching (ZVS) with less Switching losses and higher conversion efficiency. 3) The high-efficiency recovery and reutilization of the energy stored by the lithium battery can be realized, and the energy loss and the production cost in the formation of the battery are reduced.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising a … …" does not exclude the presence of another identical element in a process, method, article, or apparatus that comprises the element.
The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea, and not to limit it. It should be noted that, for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall into the protection scope of the present invention.

Claims (6)

1. A bidirectional direct current converter for a lithium battery formation system based on a super capacitor is characterized by comprising a storage battery side capacitor C b A first capacitor C 1 A first inductor L 1 A second inductor L 2 A first switch tube S 1 A second switch tube S 2 ；
The battery side capacitance C b Positive pole and first inductance L 1 Is connected with one end of the connecting rod;
the first inductor L 1 And the other end of the first capacitor C 1 Positive pole of (2), the first switching tube S 1 Is connected with the drain electrode of the transistor;
the second inductor L 2 And the first capacitor C 1 Negative pole of (2), the second switch tube S 2 Is connected to the source of (a);
the battery side capacitance C b And the first switch tube S 1 Source electrode of, second inductance L 2 The other end of the first and second connecting rods is connected;
the battery side capacitance C b The positive electrode of (a) is a positive polarity end of the storage battery side;
the second switch tube S 2 The drain of (b) is used as the positive polarity end of the super capacitor side;
the battery side capacitance C b As negative polarity terminals on the storage battery side and the supercapacitor side.
2. The bi-directional dc converter as recited in claim 1, wherein said first inductor L 1 Satisfies the following conditions:
Figure FDA0003848178830000011
in the formula of U b Is the battery side end voltage, U dc Is the side end voltage of the super capacitor, f s,min At the lowest switching frequency, I L1 Is a first inductance L 1 δ% is the first inductor current ripple rate;
the second inductor L 2 Satisfies the following conditions:
Figure FDA0003848178830000012
where Δ I is the current margin, i.e. the peak value I of the second inductor current in the battery discharge mode L2,peak And the first inductor current valley value i L1,val A difference of (2)A-4A，P o,max Is the maximum output power.
3. A control method of the bidirectional dc converter for the lithium battery formation system according to claim 2, wherein the control method comprises:
s1, sampling value i of the first inductive current L1,f And a reference value i L1,fef Comparing to obtain an error signal i L1,e ；
S2, the error signal i is processed L1,e Sending the signal to a current controller of a storage battery, and obtaining an adjusting signal u through a one-way amplitude limiting link r ；
S3, sampling value U of voltage at side end of storage battery b First inductor current sampling value i L1,f Average value of (1) L1 And sampling value U of side end voltage of super capacitor dc Sending the data to a switching frequency calculation link to obtain a switching frequency f s And further generating a frequency f s Unipolar triangular carrier u c (ii) a The calculation formula of the switching frequency calculation link is as follows:
Figure RE-FDA0003918433620000013
s4, adjusting the signal u r With a unipolar triangular carrier u c Intercept to generate PWM signal u PWM ；
S5, sampling value U of voltage at side end of storage battery b Upper limit threshold value U of side end voltage of storage battery b,upp Sending the voltage to a voltage comparator 1 to obtain a storage battery side end voltage overvoltage protection signal U pro,up ；
S6, sampling value U of voltage at side end of storage battery b Lower threshold value U of side end voltage of storage battery b,low Sent to a voltage comparator 2 to obtain a storage battery side end voltage undervoltage protection signal U pro,low ；
S7, enabling the voltage at the side end of the storage battery to be in overvoltage protection signal U pro,up And a storage battery side voltage undervoltage protection signal U pro,low PWM signal u PWM And then, obtaining a first switch tube S 1 Drive signal u of gs,S1 Will driveDynamic signal u gs,S1 After being inverted, the second switching tube S is used as the second switching tube 2 Drive signal u of gs,S2 。
4. A lithium battery formation system comprising the bidirectional dc converter for lithium battery formation system according to any one of claims 1 to 3, a lithium battery connected to a battery side of the bidirectional dc converter for lithium battery formation system, and a supercapacitor connected to a supercapacitor side of the bidirectional dc converter for lithium battery formation system.
5. The control method of the lithium battery formation system according to claim 4, wherein the control method comprises:
by varying said first inductor current reference value i L1,fef The polarity of the battery pack, and setting the working mode of the lithium battery, wherein the working mode of the lithium battery comprises a discharging mode and a charging mode;
by varying said first inductor current reference value i L1,fef Setting the charging rate and the discharging rate of the lithium battery;
by varying the upper threshold U of the battery side terminal voltage b,upp To set a charge cutoff voltage;
by varying the lower threshold U of the battery side terminal voltage b,low The discharge cutoff voltage is set.
6. The control method of claim 5, wherein the first inductor current reference value i is varied by changing the first inductor current reference value L1,fef The polarity of the lithium battery is used for setting the working mode of the lithium battery, and the working mode is specifically as follows:
when i is L1,fef >When the voltage of the super capacitor is 0, the lithium battery formation system works in a lithium battery discharge mode, and the energy of the lithium battery is transferred to the super capacitor;
when i is L1,fef <And 0, the lithium battery formation system works in a lithium battery charging mode, and the energy stored by the super capacitor is transferred to the lithium battery.
CN202211124962.9A 2022-09-15 2022-09-15 Bidirectional direct current converter, lithium battery formation system and control method Pending CN115566899A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202211124962.9A CN115566899A (en) 2022-09-15 2022-09-15 Bidirectional direct current converter, lithium battery formation system and control method

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202211124962.9A CN115566899A (en) 2022-09-15 2022-09-15 Bidirectional direct current converter, lithium battery formation system and control method

Publications (1)

Publication Number Publication Date
CN115566899A true CN115566899A (en) 2023-01-03

Family

ID=84741605

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202211124962.9A Pending CN115566899A (en) 2022-09-15 2022-09-15 Bidirectional direct current converter, lithium battery formation system and control method

Country Status (1)

Country Link
CN (1) CN115566899A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115360915A (en) * 2022-09-15 2022-11-18 南通大学 ZVS high-gain energy storage converter capable of realizing zero ripple of current of storage battery

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115360915A (en) * 2022-09-15 2022-11-18 南通大学 ZVS high-gain energy storage converter capable of realizing zero ripple of current of storage battery
CN115360915B (en) * 2022-09-15 2024-06-04 南通大学 ZVS high-gain energy storage converter capable of realizing zero ripple of storage battery current

Similar Documents

Publication Publication Date Title
Chuang et al. High-efficiency and low-stress ZVT–PWM DC-to-DC converter for battery charger
CN102832809A (en) Inductance regulating switch capacitor-type passive clamping soft switching high-gain boost-type converter
CN112583252B (en) High-power-density high-gain converter and control method thereof
CN111725993B (en) High-efficiency Sepic soft switch converter and control method thereof
CN108512423B (en) High-efficient high-power vehicle-mounted DCDC power supply
CN105939108A (en) Switch inductor type quasi-switch voltage-boosting DC-DC converter
CN105939112A (en) High-gain quasi-switch boost DC-DC converter
CN105939107A (en) Hybrid type quasi-switch voltage-boosting DC-DC converter
CN110829837B (en) Low-voltage stress ZVS high-gain Boost converter
Tseng et al. An integrated derived boost-flyback converter for fuel cell hybrid electric vehicles
CN115566899A (en) Bidirectional direct current converter, lithium battery formation system and control method
Zhou et al. High Step-Up Soft-Switching DC–DC Converter Integrated With Y-Source Network
CN103490635B (en) A kind of modified model H bridge buck-boost DC converter and control method thereof
CN219287377U (en) Bidirectional DC conversion circuit and corresponding device
CN205847090U (en) A kind of mixed type quasi-boost switching DC DC changer
CN114744876B (en) Zero-current ripple Buck-Boost converter for photovoltaic power generation
CN108429452B (en) Quadratic multi-bootstrap DC-DC converter for photovoltaic system
Kozhushko et al. Hybrid Energy Storage System of Power Supply for Micro Resistance Welding
CN112886817B (en) High-efficiency high-gain converter and control method thereof
Kajiwara et al. Performance Mechanism of Active Clamp Resonant SEPIC Converter in Renewable Energy Systems
CN113630009A (en) High-performance non-isolated bidirectional direct current converter and control method thereof
CN203522541U (en) Improved H bridge buck-boost DC converter
Abdolmaleki et al. A novel high-gain dc-dc topology based on coupled inductors and decreased voltage stresses on output elements
CN113054853A (en) Active clamping push-pull buck-boost direct current converter
Chen et al. A isolated bidirectional interleaved flyback converter for battery backup system application

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination