CN113629797A - Multi-path staggered battery pulse charging converter - Google Patents
Multi-path staggered battery pulse charging converter Download PDFInfo
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- CN113629797A CN113629797A CN202110721508.0A CN202110721508A CN113629797A CN 113629797 A CN113629797 A CN 113629797A CN 202110721508 A CN202110721508 A CN 202110721508A CN 113629797 A CN113629797 A CN 113629797A
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- 238000010278 pulse charging Methods 0.000 title claims abstract description 46
- 238000007600 charging Methods 0.000 claims abstract description 59
- 230000002441 reversible effect Effects 0.000 claims abstract description 6
- 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 18
- 238000013459 approach Methods 0.000 claims description 10
- 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
- 230000001939 inductive effect Effects 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 6
- 230000000295 complement effect Effects 0.000 description 2
- 238000010586 diagram 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
- 238000009792 diffusion process Methods 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000010438 heat treatment Methods 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
- 238000011160 research Methods 0.000 description 1
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- 230000001360 synchronised effect Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
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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
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
- H02J7/0014—Circuits for equalisation of charge between batteries
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
- H02J7/0014—Circuits for equalisation of charge between batteries
- H02J7/0019—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
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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
- 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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- 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-reverse diode which are connected in series; the controlled current source is used for generating continuous current with adjustable amplitude to complete the control of the pulse charging current amplitude; the pulse control switches are switched on in a staggered mode to complete control over pulse frequency and duty ratio of each path of pulse current, and the pulse control switches are used for generating multi-path staggered pulse charging current; the anti-reverse diode is connected with the battery load in series and used for avoiding direct parallel connection between the charged batteries or the battery packs when the voltage difference of the charged batteries or the battery packs is large, so that large reverse impact current is prevented. The invention can eliminate the extension of the pulse interval to the charging time and shorten the charging time; flexible control of pulse amplitude, frequency and duty ratio in pulse charging is realized; the balance among the charged batteries or battery packs can be well realized.
Description
Technical Field
The invention relates to the technical field of battery charging, in particular to a multipath interleaved battery pulse charging converter.
Background
Lithium ion batteries have become the main choice for electric vehicles, power grid systems and a large number of electronic products due to their numerous advantages, and in order to maximize the potential of batteries, charging technology is becoming one of the focuses of increasing attention.
Pulse charging is first applied to capacity recovery and polarization cancellation of lead acid batteries, and the method increases the interval between two consecutive pulses. Such short intervals may also provide many benefits to lithium ion batteries, including elimination of polarization, greater acceptable current, suppression of dendrite growth, slowing of capacity fade, and acceleration of ion diffusion, among others. Due to its excellent properties, pulse charging is considered to be a promising fast charging method, and is also used as a self-heating technique for batteries in a low-temperature environment. Since the controlled variables of the pulse current include pulse frequency, amplitude and duty cycle, optimization of the charging parameters is inevitable.
The advantages of the pulse charging strategy are undeniable, but there are two inherent disadvantages. First, the pulse spacing can eliminate polarization-accelerated charging processes, but the pulse spacing also increases the charging time, which is contradictory. The second is that under the condition that 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 promote the application thereof, research on the pulse charging method needs to be further deepened.
Disclosure of Invention
In view of the above, in order to solve the above problems in the prior art, the present invention provides a multi-channel interleaved battery pulse charging converter, which aims to eliminate the extension of the pulse interval to the charging time in the pulse charging and simultaneously realize the flexible control of the pulse amplitude, the frequency and the duty ratio. The charging loss in the pulse charging process can be reduced by optimizing the pulse amplitude and the frequency, the charging efficiency is improved, the use safety of the battery is enhanced, and the balance among the charged batteries or the battery packs can be realized by controlling the pulse duty ratio.
The invention solves the problems through the following technical means:
a multi-path interleaved 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-reverse diode which are connected in series;
the controlled current source is used for generating continuous current with adjustable amplitude to complete the control of the pulse charging current amplitude, 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 switches are switched on in a staggered mode to complete control over pulse frequency and duty ratio of each path of pulse current, and the pulse control switches are used for generating multi-path staggered pulse charging current;
the anti-reverse diode is connected with the battery load in series and used for avoiding direct parallel connection between the charged batteries or the battery packs when the voltage difference of the charged batteries or the battery packs is large, so that large reverse impact current is prevented.
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 through optimizing the amplitude of the pulse charging current.
Further, for the power electronic converter as a controlled current source, the battery pulse charging converter can realize the power decoupling of the front stage and the rear stage because the semiconductor switching frequency is far higher than the battery charging current pulse frequency.
Further, the battery pulse charging converter can realize front and rear stage power decoupling specifically as follows:
the simplified derivation of the cell model is as follows:
in the formula ZACThe AC impedance of the lithium ion battery is adopted, and omega is the angular frequency of the excitation signal; vocvIs an ideal voltage source and represents the open circuit voltage, R, of the battery0The resistance is internal resistance ohmic resistance, and L is parasitic inductance; rCTIs charge transfer impedance, CDLDouble layer capacitors being electrode interfaces, ZW(ii) Warberg impedance due to ion concentration polarization; j is the imaginary symbol, VBIs the terminal voltage of the battery, V0For internal resistance drop, VLFor parasitic inductive voltage drop, VpVoltage drop is the electric double layer capacitance;
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 find the minimum impedance frequency fz-min(ii) a At this frequency, the battery impedance is internal resistance and 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; the internal resistance gradually decreases as the SOC increases; 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, can be obtained, and the minimum impedance frequency f of the common lithium ion batteryz-minThe frequency is several KHz and is far lower than the switching frequency of a power electronic converter, so the proposed pulse charger can realize the power decoupling between a preceding stage controlled current source and a following pulse control 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 cause the pulse current of all the charged batteries or battery packs to have an interleaved characteristic, and all the pulse control switches are not allowed to be turned off at the same time.
Further, the pulse control switch can quickly equalize 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 rapidly equalizing the charged batteries or battery packs through pulse duty ratio modulation, in order to avoid errors of state of charge estimation, the charged batteries or battery packs with the same specification take SOC as an equalization object before the battery terminal voltage approaches the charge cut-off voltage, and take the battery terminal voltage as the 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 approaches, the anti-reverse diode can be removed, and all the 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.
Furthermore, for the charged batteries or battery packs, the charged batteries or battery packs can be in a parallel operation state before charging in order to meet the requirement that the terminal voltages are consistent or close during charging, and the parallel connection relation is released 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 the pulse amplitude, frequency and duty ratio in the pulse charging;
3) the invention can well realize the balance among the charged batteries or the battery packs.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of a multi-path interleaved battery pulse charging converter according to the present invention;
FIG. 2 is a topology of a pulsed charge converter employed in an illustrative example of the invention;
FIG. 3 is a lithium ion battery AC impedance model;
FIG. 4 is a lithium ion battery AC impedance spectrum;
FIG. 5 is a diagram of a battery equalization strategy employed in an exemplary embodiment of the present invention;
FIG. 6 is a pulsed charging current voltage waveform in an exemplary embodiment of the invention;
fig. 7 is a charging waveform after the battery terminal voltage reaches the cutoff voltage in the illustrated example of the invention.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. It should be noted that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and all other embodiments obtained by those skilled in the art without any inventive work based on the embodiments of the present invention belong to the protection scope of the present invention.
As shown in fig. 1, the present invention provides a multi-path interleaved 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 is formed by connecting a pulse control switch and an anti-reverse diode in series. The method comprises the following specific steps:
a controlled current source: the controlled current source can be a power electronic converter or other current source devices and is used for generating continuous current with adjustable amplitude and finishing flexible control on 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 characteristics are as follows:
1) the pulse amplitude is used as an important measurement index of the pulse current, so that the instantaneous charging current can be reflected on one hand, the pulse duty ratio is combined, and the average charging current can be reflected on the other hand;
2) if the pulse frequency is fixed, the pulse amplitude can be optimized to be an effective means for reducing ohmic loss in the charging process.
A pulse control switch: the pulse control switches are semiconductor power switch devices, and the number of the pulse control switches is at least two and can be adjusted according to the number of the charged batteries or the battery packs. The pulse control switches are switched on in a staggered mode to complete flexible control over pulse frequency and duty ratios of all paths of pulse current, and the pulse control switches are used for generating multi-path staggered pulse charging current; the characteristics are as follows:
1) the complementary turn-on between the pulse control switches, the interleaved nature of the charging currents of the charged battery or battery pack allows the pulse intervals to be exploited, which eliminates the lengthening 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 the reactive loss in the charging process;
3) and respectively controlling the duty ratio of the pulse charging current of the corresponding battery or the battery pack by controlling the conducting time of each pulse control switch, wherein 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 the batteries or the battery packs are rapidly equalized 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 can use SOC as an equalization object before the terminal voltage of the batteries approaches the charging cut-off voltage, and can use the terminal voltage of the batteries as the equalization object after the terminal voltage of the batteries approaches or reaches the charging cut-off voltage;
5) and when the terminal voltage between the charged batteries or the battery packs is close, all the pulse control switches have Zero Voltage Switching (ZVS) characteristics.
Anti-reverse diode: the anti-reverse diode is connected in series with the pulse control switch and the battery load, and is used for avoiding direct parallel connection between the batteries or the battery packs and preventing large reverse impact current when the voltage difference of the charged batteries or the battery packs is large; the characteristics are as follows:
1) when the voltage of the charged battery or the battery pack approaches to the voltage of the battery before charging, the anti-reverse diode can be removed, and the charging efficiency of the system is improved;
2) and 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 charged batteries or battery packs have the same or similar terminal voltage during charging, and the batteries or battery packs can be in parallel operation before charging, and the parallel connection is released by controlling the switch during charging.
As shown in FIG. 1, the controlled current source outputs current through a pulse controlled switch S3-SnShunting, respectively batteries or battery packs Bat1-BatnCharging, pulse control switch S3-SnStaggered on and not allowed to all off. Diode D1-DnThe reverse current of the batteries can be prevented, and the batteries with large voltage difference are prevented from being directly connected in parallel. For different batteries or battery packs with the same specification, the discharge can be realized through the controlled switch K1-Kn-1And are operated in parallel. Disconnectable K during charging1-Kn-1The proposed pulsed charging topology is used for charging. At this time, the reverse diode D is prevented due to the consistency of the terminal voltage among the batteries1-DnCan be removed. When the voltage of the charged battery or the battery pack is balanced, the switch S is controlled by the pulse3-SnHas Zero Voltage Switching (ZVS) characteristics. For a power electronic converter as a controlled current source, the proposed pulse charger can achieve front and rear stage power decoupling because the semiconductor switching frequency is much higher than the battery charging current pulse frequency.
The proposed pulse charge converter has the following advantages: 1) the extension of the pulse interval to the charging time is thoroughly eliminated by using the staggered characteristic of the pulse charging current side; 2) the pulse amplitude can be flexibly adjusted by a controlled current source; 3) the pulse frequency and the duty ratio can be flexibly adjusted by the pulse control switch. 4) And the charged batteries or the battery packs can be quickly equalized through pulse duty ratio modulation.
The lithium ion battery pulse charging converter in the embodiment adopts two paths of pulse control switches, and can be adjusted according to the number of the charged batteries or battery packs in practical application. The controlled power supply adopts a Buck converter, and the topology of the charger 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 an inductor current iLI.e. the amplitude of the pulsed charging current. The process takes the inductive current as a control target and uses a Buck converter switching tube S1As a control variable, wherein the switching tube S2For 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. ii、Ri、tiThe current, the internal resistance of the battery and the charging time of the ith SOC stage are respectively. Q is the battery capacity, and I is the charging current adopted in the traditional constant current charging. SOCCC(I) When charging is performed at a constant current I, the SOC of the battery is determined when the battery voltage reaches a cut-off voltage. The above parameters can all be obtained by battery testing.
After the optimal current amplitude is obtained through the optimization problem, after the charged battery is rapidly balanced, the duty ratio of the pulse charging current is 0.5, at the moment, the amplitude of the pulse current can be controlled to be twice of the optimal solution of the optimization problem, and the optimal current amplitude is dynamically adjusted along with the change of the SOC.
Then, the pulse frequency is adjusted by the pulse control switch. The lithium ion battery ac impedance model is shown in fig. 3. VocvIs an ideal voltage source and represents the Open Circuit Voltage (OCV), R of the battery0Is an internal resistance ohmic resistance, and L is a parasitic inductance. By the use of RCT、CDLAnd ZWThe polarization of a lithium ion battery was characterized. Wherein R isCTIs charge transfer impedance, CDLDouble layer capacitors being electrode interfaces, ZWIs the Warberg impedance caused by the polarization of the ion concentration. Based on fig. 3, the simplified derivation of the battery model is as follows:
in the formula ZACFor lithium ion battery ac impedance, ω is the angular frequency of the excitation signal. j is the imaginary symbol, VBIs the terminal voltage of the battery, V0For internal resistance drop, VLFor parasitic inductive voltage drop, VpIs the electric double layer capacitance 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 find the minimum impedance frequency fz-min. At this frequency, the battery impedance is internal resistance and the ac impedance is zero. The measured impedance spectra of lithium ion batteries at 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, can be obtained, and the minimum impedance frequency f of the common lithium ion batteryz-minThe frequency is several KHz and is far lower than the switching frequency of a power electronic converter, so the proposed pulse charger can realize the power decoupling between a preceding stage controlled current source and a following pulse control switch.
Finally, the pulse duty ratio is adjusted through a pulse control switch to realize the balance among the charged batteries or the battery packs. The principle of duty cycle modulation is shown in fig. 5. For the charged batteries or battery packs Bat with the same specification1And Bat2The difference in SOC between them exceeds the set limit SlimTime, pulse control switch S3And S4At a fixed duty dminAnd dmaxAnd is more than complementary conducting. Wherein Slim、dminAnd dmaxCan be used forAccording to the setting and adjustment of practical application occasions, the battery with low SOC corresponds to a large pulse duty ratio dmaxBattery with high SOC corresponds to small pulse duty dmin. Such as mixing SlimSet to 0.01, dminAnd dmaxAre 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 SlimTime, pulse control switch S3And S4The duty ratio of (a) is adjusted to be fine, the fine adjustment amplitude is Δ d, and Δ d can also be set and adjusted according to the practical application, for example, can be set to be 0.02. After SOC equalization, the final pulse controls switch S3And S4The duty cycles are all 0.5.
When each battery or battery pack is rapidly equalized by pulse duty ratio modulation, in order to avoid errors in state of charge (SOC) estimation, batteries or battery packs having the same specification may use SOC as an equalization target before the battery terminal voltage approaches the charge cut-off voltage, and may use the battery terminal voltage as an equalization target after the battery terminal voltage approaches or reaches the charge cut-off voltage. And converting the state of charge balance into end voltage balance, wherein the battery end voltage balance strategy based on duty ratio adjustment is consistent with the SOC balance strategy. Before the SOC of the battery is equalized, the pulse charging current voltage waveform is shown in fig. 6(a), and after the SOC is equalized, the pulse charging current voltage waveform is shown in fig. 6 (b).
When the voltage of the charged battery or battery pack reaches the charge cut-off voltage, the voltage of the battery is quickly equalized, and finally the pulse control switch S3And S4The duty cycles are all 0.5. At this time, the rechargeable battery or battery pack enters a constant voltage charging mode, the output current of the preceding current source gradually decreases, and the charging waveform is as shown in fig. 7. And ending the whole charging process until the pulse current amplitude value is reduced to the set charging cut-off current.
The multi-path interleaved battery pulse charging converter controls the amplitude of the charging current through a power electronic converter or other devices, and realizes flexible control of the pulse frequency and the duty ratio through two or more pulse control switches. The proposed staggered pulse strategy completely eliminates the extended charging time caused by the pulse spacing. For an electric vehicle in which a plurality of battery packs are operated in parallel, the proposed pulse charging converter can be applied when it is allowed to charge these parallel battery packs into a plurality of groups simultaneously.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A multi-path interleaved 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-reverse diode which are connected in series;
the controlled current source is used for generating continuous current with adjustable amplitude to complete the control of the pulse charging current amplitude, 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 switches are switched on in a staggered mode to complete control over pulse frequency and duty ratio of each path of pulse current, and the pulse control switches are used for generating multi-path staggered pulse charging current;
the anti-reverse diode is connected with the battery load in series and used for avoiding direct parallel connection between the charged batteries or the battery packs when the voltage difference of the charged batteries or the battery packs is large, so that large reverse impact current is prevented.
2. The de-multiplexed interleaved battery pulse charge converter according to claim 1 wherein said controlled current source is a power electronic converter or other form of current source device.
3. The pulse charge converter for a multi-interleaved battery as claimed in claim 1 wherein said controlled current source optimizes the magnitude of the pulse charge current to reduce ohmic losses during charging if the pulse frequency is fixed.
4. The multiple interleaved battery pulse charge converter as claimed in claim 1 wherein said battery pulse charge converter is capable of achieving front and back stage power decoupling as the semiconductor switching frequency is much higher than the battery charging current pulse frequency for said power electronic converter as a controlled current source.
5. The multi-interleaved battery pulse charge converter as claimed in claim 4, wherein the battery pulse charge converter is capable of implementing front and back stage power decoupling by:
the simplified derivation of the cell model is as follows:
in the formula ZACThe AC impedance of the lithium ion battery is adopted, and omega is the angular frequency of the excitation signal; vocvIs an ideal voltage source and represents the open circuit voltage, R, of the battery0The resistance is internal resistance ohmic resistance, and L is parasitic inductance; rCTIs charge transfer impedance, CDLDouble layer capacitors being electrode interfaces, ZW(ii) Warberg impedance due to ion concentration polarization; j is the imaginary symbol, VBIs the terminal voltage of the battery, V0For internal resistance drop, VLFor parasitic inductive voltage drop, VpVoltage drop is the electric double layer capacitance;
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 find the minimum impedance frequency fz-min(ii) a At this frequency, the battery impedance is internal resistance and 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; the internal resistance gradually decreases as the SOC increases; therefore, according to the alternating current impedance analysis of the lithium ion battery, the optimal pulse charging current frequency can be obtainedRate, i.e. the switching frequency of the pulse control switch, the minimum impedance frequency f of the general lithium ion batteryz-minThe frequency is several KHz and is far lower than the switching frequency of a power electronic converter, so the proposed pulse charger can realize the power decoupling between a preceding stage controlled current source and a following pulse control switch.
6. The pulse charge converter according to claim 1, wherein said pulse control switch is 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 cause the pulse current of all the charged batteries or battery packs to have an interleaved characteristic, and all the pulse control switches are not allowed to be turned off at the same time.
7. The pulse charge converter according to claim 1, wherein said pulse control switch is capable of rapidly equalizing each charged battery or battery pack by adjusting a pulse duty cycle of a charging current of each charged battery or battery pack.
8. The pulse charging converter for multi-path interleaved batteries as claimed in claim 7, wherein during the rapid equalization of each charged battery or battery pack by pulse duty cycle modulation, to avoid the error of state of charge estimation, the charged batteries or battery packs with the same specification take SOC as the equalization object before the terminal voltage of the battery approaches the charge cut-off voltage, and take the terminal voltage of the battery as the equalization object after the terminal voltage of the charged battery or battery pack approaches or reaches the charge cut-off voltage.
9. The de-multiplexed interleaved battery pulse charge converter according to claim 1 wherein the anti-reverse diode is removable and all pulse control switches have zero voltage switching characteristics when the terminal voltage between the charged batteries or battery packs is close;
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 pulse charge converter according to claim 1, wherein the charged batteries or battery packs are charged in parallel before being charged by the pulse control switch to satisfy the terminal voltages at the time of charging.
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| CN202110721508.0A CN113629797B (en) | 2021-06-28 | 2021-06-28 | Multi-path staggered battery pulse charging converter |
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