CN113629797B - Multi-path staggered battery pulse charging converter - Google Patents
Multi-path staggered battery pulse charging converter Download PDFInfo
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- CN113629797B CN113629797B CN202110721508.0A CN202110721508A CN113629797B CN 113629797 B CN113629797 B CN 113629797B CN 202110721508 A CN202110721508 A CN 202110721508A CN 113629797 B CN113629797 B CN 113629797B
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- 238000010278 pulse charging Methods 0.000 title claims abstract description 43
- 238000007600 charging Methods 0.000 claims abstract description 48
- 230000002441 reversible effect Effects 0.000 claims abstract description 5
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 19
- 229910001416 lithium ion Inorganic materials 0.000 claims description 19
- 238000000034 method Methods 0.000 claims description 19
- 238000013459 approach Methods 0.000 claims description 8
- 230000010287 polarization Effects 0.000 claims description 7
- 230000005284 excitation Effects 0.000 claims description 6
- 230000003071 parasitic effect Effects 0.000 claims description 6
- 239000004065 semiconductor Substances 0.000 claims description 6
- 230000007423 decrease Effects 0.000 claims description 4
- 238000001453 impedance spectrum Methods 0.000 claims description 4
- 150000002500 ions Chemical class 0.000 claims description 4
- 238000011084 recovery Methods 0.000 claims description 4
- 239000003990 capacitor Substances 0.000 claims description 3
- 238000009795 derivation Methods 0.000 claims description 3
- 238000012546 transfer Methods 0.000 claims description 3
- 238000005457 optimization Methods 0.000 description 7
- 230000000295 complement effect Effects 0.000 description 2
- 230000008030 elimination Effects 0.000 description 2
- 238000003379 elimination reaction Methods 0.000 description 2
- 230000001133 acceleration Effects 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 210000004027 cell Anatomy 0.000 description 1
- 238000010280 constant potential charging Methods 0.000 description 1
- 238000010277 constant-current charging Methods 0.000 description 1
- 230000008094 contradictory effect Effects 0.000 description 1
- 210000001787 dendrite Anatomy 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
- H02J7/0014—Circuits for equalisation of charge between batteries
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
- H02J7/0014—Circuits for equalisation of charge between batteries
- H02J7/0019—Circuits for equalisation of charge between batteries using switched or multiplexed charge circuits
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
-
- 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
- H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
- H02J7/00304—Overcurrent protection
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/007—Regulation of charging or discharging current or voltage
- H02J7/00711—Regulation of charging or discharging current or voltage with introduction of pulses during the charging process
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Secondary Cells (AREA)
- Charge And Discharge Circuits For Batteries Or The Like (AREA)
Abstract
The invention discloses a multi-path staggered battery pulse charging converter, which comprises two stages, wherein the front stage is a controlled current source, the rear stage is a multi-path pulse control unit, and each path of pulse control unit comprises a pulse control switch and an anti-reflection diode which are connected in series; the controlled current source is used for generating continuous current with adjustable amplitude and controlling the amplitude of the pulse charging current; the pulse control switch is conducted in an interlaced manner, so that the control of the pulse frequency and the duty ratio of each path of pulse current is completed, and the pulse control switch is used for generating multipath interlaced pulse charging current; the anti-reverse diode is connected with the battery load in series, and is used for avoiding direct parallel connection between the charged batteries or the battery packs when the pressure difference between the charged batteries or the battery packs is large, so as to prevent large reverse impact current. The invention can eliminate the extension of the pulse interval to the charging time and shorten the charging time; the flexible control of pulse amplitude, frequency and duty ratio in pulse charging is realized; the balance between the charged batteries or the battery packs can be well realized.
Description
Technical Field
The invention relates to the technical field of battery charging, in particular to a multipath staggered battery pulse charging converter.
Background
Lithium ion batteries are a major choice for electric vehicles, power grid systems, and a large number of electronic products due to their numerous advantages, and charging technology is becoming one of the focus of attention in order to maximize the potential of the batteries.
Pulse charging is first applied to capacity recovery and polarization elimination of lead acid batteries, which increases the separation between two successive pulses. Such short term spacing may also provide many benefits to lithium ion batteries, including elimination of polarization, greater acceptable current flow, inhibition of dendrite growth, slowing of capacity fade, and acceleration of ion diffusion, among others. Because of its excellent performance, pulse charging is considered as a promising rapid charging method, and is also used as a self-heating technique for batteries in low-temperature environments. Optimization of the charging parameters is unavoidable because the controllable variables of the pulse current include pulse frequency, amplitude and duty cycle.
The advantages of the pulse charging strategy are undeniable, but there are two inherent disadvantages. First, pulse spacing can eliminate polarization to accelerate the charging process, but pulse spacing also increases charging time, which is contradictory. Second, in the case where the average charging current is the same, the root mean square of the pulse current is larger than the constant current, so the loss of pulse charging is larger. Therefore, in order to further improve the pulse charging performance and to popularize the application thereof, the research on the pulse charging method is necessary to be further deepened.
Disclosure of Invention
In view of the above, the present invention provides a multi-path interleaved battery pulse charging converter, which is capable of eliminating the extension of the charging time by the pulse interval during pulse charging and realizing flexible control of the pulse amplitude, frequency and duty ratio. The pulse amplitude and the pulse frequency are optimized, so that the charging loss in the pulse charging process can be reduced, the charging efficiency is improved, the use safety of the battery is enhanced, and the balance between the charged battery or the battery pack can be realized through pulse duty ratio control.
The invention solves the problems by the following technical means:
the multi-path staggered battery pulse charging converter comprises two stages, wherein the front stage is a controlled current source, the rear stage is a multi-path pulse control unit, and each path of pulse control unit comprises a pulse control switch and an anti-reflection diode which are connected in series;
the controlled current source is used for generating continuous current with adjustable amplitude, controlling the amplitude of the pulse charging current, and the output current of the front-stage controlled current source is used as the input of the rear-stage pulse control unit;
the pulse control switch is conducted in an interlaced manner, so that the control of the pulse frequency and the duty ratio of each path of pulse current is completed, and the pulse control switch is used for generating multipath interlaced pulse charging current;
the anti-reverse diode is connected with the battery load in series, and is used for avoiding direct parallel connection between the charged batteries or the battery packs when the pressure difference between the charged batteries or the battery packs is large, so as to prevent large reverse impact current.
Further, the controlled current source is a power electronic converter or other form of current source device.
Further, in the controlled current source, if the pulse frequency is fixed, ohmic loss in the charging process can be reduced by optimizing the pulse charging current amplitude.
Further, for a power electronic converter as a controlled current source, the battery pulse charge converter can achieve front-to-back stage power decoupling because the semiconductor switching frequency is much higher than the battery charge current pulse frequency.
Further, the battery pulse charging converter can realize front-stage and back-stage power decoupling specifically as follows:
the simplified derivation of the battery model is as follows:
z in AC The impedance of the lithium ion battery is alternating current, and omega is the angular frequency of an excitation signal; v (V) ocv For an ideal voltage source, the open-circuit voltage of the battery is represented by R 0 The resistor is an internal resistance ohmic resistor, and L is parasitic inductance; r is R CT For charge transfer impedance, C DL Double layer capacitor as electrode interface, Z W Warberg impedance for ion concentration polarization; j is the sign of the imaginary part, V B For battery terminal voltage, V 0 Is internal resistance and pressure drop, V L For parasitic inductance voltage drop, V p Is the double layer capacitance voltage drop;
according to the AC impedance model, the most effective method for eliminating the negative influence of the AC component in the pulse power is to obtain the minimum impedance frequency f z-min The method comprises the steps of carrying out a first treatment on the surface of the At this frequency, the battery impedance is internal resistance, the ac impedance is zero;measuring impedance spectrums of lithium ion batteries with different SOCs; the intersection point of the curves and the horizontal axis is the internal resistance of the battery, and the corresponding excitation frequency is the minimum impedance frequency; as SOC increases, internal resistance gradually decreases; therefore, according to the alternating current impedance analysis of the lithium ion battery, the optimal pulse charging current frequency, namely the switching frequency of the pulse control switch, is obtained, and the minimum impedance frequency f of the lithium ion battery is generally obtained z-min For KHz, well below the switching frequency of the power electronic converter, the proposed pulse charger enables power decoupling between the front-stage controlled current source and the following pulse controlled switch.
Further, the pulse control switch adopts a semiconductor power switch device;
the number of the pulse control switches is at least two, and the pulse control switches can be adjusted according to the number of the charged batteries or the battery packs;
the pulse control switches provide the alternating characteristics of the pulse currents of all the charged batteries or battery packs, and all the pulse control switches are not allowed to be turned off at the same time.
Further, the pulse control switch can quickly balance each charged battery or battery pack by adjusting the pulse duty ratio of the charging current of each charged battery or battery pack.
Further, in the process of carrying out rapid equalization on each charged battery or battery pack through pulse duty cycle modulation, in order to avoid errors of charge state estimation, the charged battery or battery pack with the same specification takes the SOC as an equalization object before the battery terminal voltage approaches the charge cut-off voltage, and takes the battery terminal voltage as an equalization object after the battery terminal voltage approaches or reaches the charge cut-off voltage.
Further, when the terminal voltage between the charged batteries or the battery packs is close, the anti-reverse diode can be removed, and all pulse control switches have zero-voltage switching characteristics;
the turn-on and turn-off frequency of the anti-reverse diode is the pulse charging current frequency, and a fast recovery Schottky diode can be adopted.
Further, for the charged batteries or the battery packs, to meet the requirement that the terminal voltages are consistent or close during charging, the charged batteries or the battery packs can be in a parallel operation state before charging, and the parallel connection relationship is relieved through a pulse control switch during charging.
Compared with the prior art, the invention has the beneficial effects that at least:
1) The invention can eliminate the extension of the pulse interval to the charging time and shorten the charging time;
2) The invention realizes the flexible control of pulse amplitude, frequency and duty ratio in pulse charging;
3) The invention can well realize the balance between the charged batteries or the battery packs.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a multi-path interleaved battery pulse charge converter according to the present invention;
FIG. 2 is a topology of a pulse charge inverter employed in the illustrated example of the invention;
FIG. 3 is a model of the alternating current impedance of a lithium ion battery;
FIG. 4 is an AC impedance spectrum of a lithium ion battery;
FIG. 5 is a battery equalization strategy employed in the illustrated example of the invention;
FIG. 6 is a pulse charge current voltage waveform in an illustrative example of the invention;
fig. 7 shows a charge waveform after the battery terminal voltage reaches the cutoff voltage in the example of the present invention.
Detailed Description
In order to make the above objects, features and advantages of the present invention more comprehensible, the following detailed description of the technical solution of the present invention refers to the accompanying drawings and specific embodiments. It should be noted that the described embodiments are only some embodiments of the present invention, and not all embodiments, and that all other embodiments obtained by persons skilled in the art without making creative efforts based on the embodiments in the present invention are within the protection scope of the present invention.
As shown in FIG. 1, the invention provides a multi-path staggered battery pulse charging converter, which comprises two stages, wherein the front stage is a controlled current source, the rear stage is a multi-path pulse control unit, and each path pulse control unit is formed by connecting a pulse control switch and an anti-reflection diode in series. The method comprises the following steps:
controlled current source: the controlled current source can be a power electronic converter or other forms of current source devices and is used for generating continuous current with adjustable amplitude, so that flexible control of the amplitude of the pulse charging current is completed, and the output current of the front-stage controlled current source is used as the input of the rear-stage pulse control unit; the characteristics are as follows:
1) The pulse amplitude is used as an important measurement index of the pulse current, so that on one hand, the instantaneous charging current can be reflected, and on the other hand, the average charging current can be reflected by combining the pulse duty ratio;
2) If the pulse frequency is fixed, the optimization of the pulse amplitude can be used as an effective means for reducing ohmic loss in the charging process.
Pulse control switch: the pulse control switches adopt semiconductor power switch devices, the number of the pulse control switches is at least two, and the pulse control switches can be adjusted according to the number of the charged batteries or the battery packs. The pulse control switch is conducted in an interlaced manner, so that flexible control of pulse frequency and duty ratio of each path of pulse current is completed, and the pulse control switch is used for generating multipath interlaced pulse charging current; the characteristics are as follows:
1) The complementary turn-on between the pulse control switches, the staggered nature of the charged battery or battery pack charging currents allows the pulse intervals to be utilized, which eliminates the extension of the charging time by the pulse intervals. Because the input is a current source, the pulse control switch is not allowed to be turned off all at the same time;
2) The pulse frequency can be controlled by controlling the switch of the pulse control switch tube, and the pulse frequency can be optimized according to the alternating current impedance characteristic of the battery to reduce reactive power loss in the charging process;
3) The duty ratio of the pulse charging current of the corresponding battery or battery pack is controlled by controlling the on time of each pulse control switch, and the pulse duty ratio is also an important factor influencing the average charging current. The pulse control switch can quickly realize the balance of each battery or battery pack by adjusting the pulse duty ratio of each battery or battery pack;
4) When each battery or battery pack is rapidly balanced through pulse duty cycle modulation, in order to avoid errors of state of charge (SOC) estimation, the battery or battery pack with the same specification can take the SOC as an equalization object before the battery terminal voltage approaches a charge cut-off voltage, and can take the battery terminal voltage as an equalization object after the battery or battery pack terminal voltage approaches or reaches the charge cut-off voltage;
5) All pulse control switches have Zero Voltage Switching (ZVS) characteristics when the terminal voltages between the charged cells or battery packs are close.
Anti-reverse diode: the anti-reverse diode is connected with the pulse control switch and the battery load in series, and is used for avoiding direct parallel connection between the batteries or the battery packs when the pressure difference of the charged batteries or the battery packs is large, so as to prevent large reverse impact current; the characteristics are as follows:
1) When the voltage of the front end of the charged battery or the battery pack to be charged is close, the anti-reflection diode can be removed, so that the charging efficiency of the system is improved;
2) The turn-on and turn-off frequency of the anti-reverse diode is the pulse charging current frequency, and a fast recovery Schottky diode can be adopted.
For the proposed battery pulse charging converter, the terminal voltage of the charged battery or battery pack is consistent or close to that of the charged battery or battery pack when the charged battery or battery pack is charged, each battery or battery pack can be in a parallel operation state before charging, and the parallel connection relation is relieved by controlling a switch when the charged battery or battery pack is charged.
As shown in fig. 1, the controlled current source outputs a current through a pulse control switch S 3 -S n Split, battery or battery pack Bat 1 -Bat n Charging, pulse control switch S 3 -S n Staggered guideOn, and not allow all off. Diode D 1 -D n The reverse direction of the battery current can be prevented, and the direct parallel connection of batteries with large voltage difference is avoided. For different batteries or battery packs with the same specification, the battery pack can be discharged through the controlled switch K 1 -K n-1 And (3) running in parallel. Can be disconnected during charging 1 -K n-1 Charging is performed using the proposed pulse charging topology. Due to the consistency of terminal voltages among the batteries of each group, the anti-reverse diode D 1 -D n Can be removed. Pulse control switch S when the voltage between the charged batteries or battery packs is balanced 3 -S n With Zero Voltage Switching (ZVS) characteristics. For the power electronic converter as a controlled current source, the semiconductor switching frequency is far higher than the pulse frequency of the battery charging current, and the proposed pulse charger can realize front-stage and back-stage power decoupling.
The proposed pulse charging converter has the following advantages: 1) The pulse charging current side staggering characteristic is utilized, so that the extension of the charging time by the pulse interval is thoroughly eliminated; 2) The pulse amplitude can be flexibly adjusted through a controlled current source; 3) The pulse frequency and the duty ratio can be flexibly adjusted by the pulse control switch. 4) Equalization can be quickly realized between the charged batteries or battery packs through pulse duty ratio modulation.
The lithium ion battery pulse charging converter in the example adopts two paths of pulse control switches, and can be adjusted according to the number of the charged batteries or the battery packs in practical application. The controlled power supply adopts a Buck converter, and the charger topology is shown in figure 2.
The control of the pulse amplitude, frequency and duty cycle by the pulse charger is described in detail below.
First, as a current source, a Buck converter is used to control the inductor current i L I.e. the amplitude of the pulsed charging current. The process takes the inductance current as a control target and takes the Buck converter switching tube S as a control target 1 As a control variable, a switching tube S 2 For synchronous rectifiers, PI controllers may be used. The optimization of the charging current amplitude can reduce ohmic loss in the charging process, and the optimization problem is described as follows:
the optimization problem has a charging time constraint, and the whole charging process can be uniformly divided into N sections according to the SOC of the battery. i.e i 、R i 、t i The current, the internal resistance and the charging time of the battery in the ith SOC stage are respectively. Q is battery capacity, I is charging current adopted in traditional constant current charging. SOC (State of Charge) CC (I) The SOC of the battery when the battery voltage reaches the off-voltage when the constant current I is charged. All of the above parameters can be obtained by battery testing.
After the optimal current amplitude is obtained through the optimization problem, the pulse charging current duty ratio is 0.5 after the charged battery is rapidly balanced, and at the moment, the amplitude of the pulse current can be controlled to be twice the optimal solution of the optimization problem, and the optimal current amplitude is dynamically adjusted along with the change of the SOC.
The pulse frequency is then adjusted by the pulse control switch. The alternating current impedance model of the lithium ion battery is shown in fig. 3. V (V) ocv For an ideal voltage source, the Open Circuit Voltage (OCV) of the battery is represented, R 0 Is an internal resistance ohmic resistance, and L is a parasitic inductance. By R CT 、C DL And Z W The polarization of lithium ion batteries was characterized. Wherein R is CT For charge transfer impedance, C DL Double layer capacitor as electrode interface, Z W Is the Warberg impedance caused by ion concentration polarization. Based on fig. 3, a simplified derivation of the battery model is as follows:
z in AC The impedance is the alternating current impedance of the lithium ion battery, and omega is the angular frequency of the excitation signal. j is the sign of the imaginary part, V B For battery terminal voltage, V 0 Is internal resistance and pressure drop, V L For parasitic inductance voltage drop, V p Is the double layer capacitance voltage drop.
According to AC impedance modeThe most effective way to eliminate the negative effects of the ac component in the pulse power is to find the minimum impedance frequency f z-min . At this frequency, the battery impedance is internal resistance and the ac impedance is zero. The measured impedance spectra of the lithium ion battery for different SOCs are shown in FIG. 4. The intersection point of the curves and the horizontal axis is the internal resistance of the battery, and the corresponding excitation frequency is the minimum impedance frequency. As the SOC increases, the internal resistance gradually decreases. Therefore, according to the alternating current impedance analysis of the lithium ion battery, the optimal pulse charging current frequency, namely the switching frequency of the pulse control switch, is obtained, and the minimum impedance frequency f of the lithium ion battery is generally obtained z-min For KHz, well below the switching frequency of the power electronic converter, the proposed pulse charger enables power decoupling between the front-stage controlled current source and the following pulse controlled switch.
Finally, the pulse duty ratio is adjusted through the pulse control switch to realize the balance among the charged batteries or the battery packs. The principle of the duty cycle modulation is shown in fig. 5. For the same specification of the rechargeable battery or battery pack Bat 1 And Bat 2 The SOC difference between them exceeds the set limit S lim At the time, the switch S is controlled by the pulse 3 And S is 4 At a fixed duty d min And d max And is conducted in a complementary manner. Wherein S is lim 、d min And d max Can be set and adjusted according to practical application occasions, and the battery with low SOC corresponds to a large pulse duty ratio d max The battery with high SOC corresponds to a small pulse duty cycle d min . For example, S lim Set to 0.01, d min And d max Are set to 0.05 and 0.95, respectively, to ensure rapid SOC equalization. When the difference in SOC between the charged batteries or battery packs is less than the limit S lim At the time, the switch S is controlled by the pulse 3 And S is 4 The duty cycle of (a) starts fine tuning, and the fine tuning amplitude is Δd, and Δd can be set and adjusted according to practical application, for example, can be set to 0.02. After SOC equalization, the final pulse controls switch S 3 And S is 4 The duty cycles were all 0.5.
When the batteries or the battery packs are rapidly balanced through pulse duty ratio modulation, in order to avoid errors of state of charge (SOC) estimation, the batteries or the battery packs with the same specification take the SOC as an equalization object before the battery terminal voltage approaches the charge cut-off voltage, and can take the battery terminal voltage as an equalization object after the battery terminal voltage approaches or reaches the charge cut-off voltage. And converting the charge state balance into terminal voltage balance, wherein the battery terminal voltage balance strategy based on duty ratio adjustment is consistent with the SOC balance strategy. The pulse charge current voltage waveform before the battery SOC equalization is shown in fig. 6 (a), and the pulse charge current voltage waveform after the SOC equalization is shown in fig. 6 (b).
When the end voltage of the charged battery or the battery pack reaches the charge cut-off voltage, the battery voltage is quickly balanced, and finally the switch S is controlled by the pulse 3 And S is 4 The duty cycles were all 0.5. At this time, the rechargeable battery or the battery pack enters a constant voltage charging mode, the output current of the front stage current source gradually decreases, and the charging waveform is shown in fig. 7. And (3) until the pulse current amplitude is reduced to the set charging cut-off current, ending the whole charging process.
The multipath staggered battery pulse charging converter controls the amplitude of charging current through the power electronic converter or other devices, and realizes flexible control of pulse frequency and duty ratio through two or more pulse control switches. The proposed interleaved pulse strategy completely eliminates the prolonged charging time caused by the pulse interval. For an electric vehicle in which a plurality of battery packs are operated in parallel, the proposed pulse charging converter may be applied when allowing the parallel battery packs to be charged simultaneously in a plurality of groups.
The foregoing examples illustrate only a few embodiments of the invention and are described in detail herein without thereby limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (10)
1. The multi-path staggered battery pulse charging converter is characterized by comprising two stages, wherein the front stage is a controlled current source, the rear stage is a multi-path pulse control unit, and each path of pulse control unit comprises a pulse control switch and an anti-reflection diode which are connected in series;
the controlled current source is used for generating continuous current with adjustable amplitude, controlling the amplitude of the pulse charging current, and the output current of the front-stage controlled current source is used as the input of the rear-stage pulse control unit;
the pulse control switch is conducted in an interlaced manner, so that the control of the pulse frequency and the duty ratio of each path of pulse current is completed, and the pulse control switch is used for generating multipath interlaced pulse charging current;
the anti-reverse diode is connected with the battery load in series, and is used for avoiding direct parallel connection between the charged batteries or the battery packs when the pressure difference between the charged batteries or the battery packs is large, so as to prevent large reverse impact current.
2. The multi-path interleaved battery pulse charge converter according to claim 1 wherein the controlled current source is a power electronic converter or other form of current source device.
3. The multi-path interleaved battery pulse charge converter according to claim 1 wherein ohmic losses during charging are reduced by optimizing the pulse charge current amplitude if the pulse frequency is fixed in the controlled current source.
4. The multiple interleaved battery pulse charge converter according to claim 1 wherein for a power electronic converter as a controlled current source, the battery pulse charge converter enables front-to-back stage power decoupling due to the semiconductor switching frequency being much higher than the battery charging current pulse frequency.
5. The multi-path interleaved battery pulse charge converter according to claim 4 wherein the battery pulse charge converter is capable of front-to-back stage power decoupling specifically:
the simplified derivation of the battery model is as follows:
z in AC The impedance of the lithium ion battery is alternating current, and omega is the angular frequency of an excitation signal; v (V) ocv For an ideal voltage source, the open-circuit voltage of the battery is represented by R 0 The resistor is an internal resistance ohmic resistor, and L is parasitic inductance; r is R CT For charge transfer impedance, C DL Double layer capacitor as electrode interface, Z W Warberg impedance for ion concentration polarization; j is the sign of the imaginary part, V B For battery terminal voltage, V 0 Is internal resistance and pressure drop, V L For parasitic inductance voltage drop, V p Is the double layer capacitance voltage drop;
according to the AC impedance model, the most effective method for eliminating the negative influence of the AC component in the pulse power is to obtain the minimum impedance frequency f z-min The method comprises the steps of carrying out a first treatment on the surface of the At this frequency, the battery impedance is internal resistance, the ac impedance is zero; measuring impedance spectrums of lithium ion batteries with different SOCs; the intersection point of the curves and the horizontal axis is the internal resistance of the battery, and the corresponding excitation frequency is the minimum impedance frequency; as SOC increases, internal resistance gradually decreases; therefore, according to the alternating current impedance analysis of the lithium ion battery, the optimal pulse charging current frequency, namely the switching frequency of the pulse control switch, is obtained, and the minimum impedance frequency f of the lithium ion battery is generally obtained z-min For KHz, well below the switching frequency of the power electronic converter, the proposed pulse charger enables power decoupling between the front-stage controlled current source and the following pulse controlled switch.
6. The multi-path interleaved battery pulse charge converter according to claim 1 wherein the pulse control switch employs a semiconductor power switching device;
the number of the pulse control switches is at least two, and the pulse control switches can be adjusted according to the number of the charged batteries or the battery packs;
the pulse control switches provide the alternating characteristics of the pulse currents of all the charged batteries or battery packs, and all the pulse control switches are not allowed to be turned off at the same time.
7. The multi-path interleaved battery pulse charge converter according to claim 1 wherein the pulse control switch rapidly equalizes each charged battery or battery pack by adjusting the pulse duty cycle of each charged battery or battery pack charge current.
8. The multi-path interleaved battery pulse charge converter according to claim 7 wherein in the process of rapidly equalizing each of the charged batteries or battery packs by pulse duty modulation, in order to avoid errors in state of charge estimation, the charged batteries or battery packs having the same specification are subjected to equalization by SOC before the battery terminal voltage approaches the charge cutoff voltage, and the battery terminal voltage is subjected to equalization after the battery terminal voltage approaches or reaches the charge cutoff voltage.
9. The multi-path interleaved battery pulse charge converter according to claim 1 wherein the anti-reflection diode is removable when terminal voltages between charged batteries or battery packs are close and all pulse control switches have zero voltage switching characteristics;
the turn-on and turn-off frequency of the anti-reverse diode is the pulse charging current frequency, and a fast recovery Schottky diode can be adopted.
10. The multi-path interleaved battery pulse charge converter according to claim 1 wherein for a charged battery or battery pack, the terminal voltages are consistent or close to each other when charged, each charged battery or battery pack may be in a parallel state prior to charging, and the parallel relationship is released by the pulse control switch when charged.
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