CN113178902A - Power supply grouping system based on high-specific-energy lithium electronic capacitor - Google Patents

Power supply grouping system based on high-specific-energy lithium electronic capacitor Download PDF

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CN113178902A
CN113178902A CN202110378323.4A CN202110378323A CN113178902A CN 113178902 A CN113178902 A CN 113178902A CN 202110378323 A CN202110378323 A CN 202110378323A CN 113178902 A CN113178902 A CN 113178902A
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soc
lithium ion
ion capacitor
value
current
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CN113178902B (en
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郑俊生
孙晗斌
于冬铭
张璐瑶
宋与非
辛亚行
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Tongji University
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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
    • H02J7/0016—Circuits for equalisation of charge between batteries using shunting, discharge or bypass 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
    • H02J7/0047—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with monitoring or indicating devices or circuits
    • H02J7/0048—Detection of remaining charge capacity or state of charge [SOC]
    • 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
    • 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
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries

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  • Power Engineering (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)
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Abstract

The invention relates to a power grouping system based on a high-specific-energy lithium electronic capacitor, which comprises: the charge state estimation module of the series lithium ion capacitor system is used for estimating the corresponding charge state of the high-specific-energy lithium ion capacitor by a method of SOC partition and data fusion; the balancing control module after the high-specific-energy lithium ion capacitor group comprises a secondary balancing circuit structure based on a Buck-Boost converter and a fuzzy controller structure capable of realizing current adjustment of a balancing circuit, and is used for realizing that the lithium ion capacitor group operates according to requirements in working states under any states. Compared with the prior art, the method has the advantages of realizing high efficiency and rapid balance of the lithium ion capacitor group in any state, improving consistency, prolonging service life of the lithium ion capacitor group and the like.

Description

Power supply grouping system based on high-specific-energy lithium electronic capacitor
Technical Field
The invention relates to the technical field of energy storage components, in particular to a power supply grouping system based on a high-specific-energy lithium-ion capacitor.
Background
The lithium ion capacitor is a novel asymmetric capacitor, and compared with the traditional double-electric-layer capacitor, the lithium ion capacitor has been greatly improved in aspects of energy density, power density and the like, has a very wide development prospect, and can be applied to multiple fields of automobiles, standby power supplies, tracks, renewable energy power generation and storage, Automatic Guided Vehicles (AGV), uninterruptible power supplies and the like. The State of charge (SOC) of a battery describes the remaining battery capacity, and is an important parameter for representing the State information of the battery. The SOC of the vehicle-mounted power battery can be accurately estimated, scientific and effective information can be provided for BMS decision making, the battery performance can be fully exerted, and the SOC estimation method has important significance for ensuring efficient operation of a battery system and improving the performance of the whole vehicle. The definition of the explicit SOC is a precondition for accurately estimating the SOC, the definition of the SOC can be performed from various angles, and the current more uniform knowledge is that the definition of the SOC is performed from the viewpoint of the remaining capacity. In the electric vehicle battery experimental manual issued by the united states advanced battery association, the SOC is defined as: the ratio of the residual capacity of the battery to the rated capacity of the battery under the same condition is determined under a certain discharge rate. The high specific energy lithium ion capacitor SOC value has obvious non-linear and strong time-varying characteristics, and the errors of the traditional ampere-hour method and the open-circuit voltage method in the estimation of the capacitor are very large. The ampere-hour method is an open-loop method and can bring obvious errors when being used in the working condition of a lithium ion capacitor; the open circuit voltage method requires a certain standing time of the power supply to measure so as to ensure the accuracy.
In addition, in practical application, the voltage and the capacity of a single lithium ion capacitor cannot meet the working requirement of a system, and therefore the single lithium ion capacitor needs to be used in a certain series and parallel connection mode. Due to the limitation of practical process conditions, the inconsistency of the lithium ion capacitor is difficult to avoid, and even the capacitor monomers in the same batch have obvious differences in capacity, internal resistance and the like. In order to fully utilize the energy of the capacitor and prolong the service life of the capacitor, the capacitor bank needs to be subjected to balanced management in the using process, so that each single capacitor achieves the effect of finishing charging and discharging simultaneously, and the capacity utilization rate of the capacitor is improved.
Existing equalization techniques are mainly classified into energy-dissipative and non-energy-dissipative types. The energy dissipation type is realized through the parallel resistors, the method is simple in structure and low in requirement on a control system, but energy waste is serious, the heating of the energy consumption resistors can cause adverse effect on the capacitor bank, and the magnitude of the balance current is limited. In the non-energy dissipation type method, the capacitive switch array is complex and has low balancing speed. The transformer type transformer has high cost, large volume, low efficiency and difficult system change. The traditional converter type energy can only be transmitted between adjacent batteries, and if the positions of the single cells to be balanced are not adjacent, the balancing time is prolonged, and the balancing efficiency is reduced.
Disclosure of Invention
It is an object of the present invention to overcome the above-mentioned drawbacks of the prior art and to provide a power grouping system based on a high specific energy lithium electronic capacitor.
The purpose of the invention can be realized by the following technical scheme:
a power banking system based on high specific energy lithium electronic capacitors, the system comprising:
the charge state estimation module of the series lithium ion capacitor system is used for estimating the corresponding charge state of the high-specific-energy lithium ion capacitor by a method of SOC partition and data fusion;
the balancing control module after the high-specific-energy lithium ion capacitor group comprises a secondary balancing circuit structure based on a Buck-Boost converter and a fuzzy controller structure capable of realizing current adjustment of a balancing circuit, and is used for realizing that the lithium ion capacitor group operates according to requirements in working states under any states.
Further, the process of estimating the corresponding state of charge for the high specific energy lithium ion capacitor by the SOC partition and data fusion method specifically includes: and constructing a corresponding battery model for the high-specific-energy lithium ion capacitor by using an algorithm, estimating dynamic quantity based on the model, and estimating the SOC in a partition mode according to the estimated value of the dynamic quantity to obtain a corresponding state of charge.
Go toStep one, the battery model is a first-order RC model, a method for estimating dynamic quantity aiming at the battery model is a recursive least square method with forgetting factors, and the dynamic quantity comprises four dynamic quantities brought by a polarization phenomenon estimated according to end current end voltage: internal resistance of battery polarization RdBattery polarization capacitor CdRC link voltage drop UdAnd battery open circuit voltage UOC。
Further, the SOC partition estimation process according to the dynamic quantity estimation value is estimated by using an extended Kalman filtering method in an interval with dominant capacitance characteristics according to the electrochemical characteristics of the lithium ion capacitor; in the interval where the battery characteristics are dominant, the ampere-hour method is used for estimation.
Further, the Buck-Boost converter-based secondary equalization circuit structure comprises a first MOS tube, a second MOS tube, a first single diode, a second single diode, an inductor and a resistor, wherein the first MOS tube and the second MOS tube respectively form a closed loop with a lithium ion capacitor respectively corresponding to the first MOS tube and the second MOS tube after passing through the inductor and the resistor which are connected in parallel, and the first MOS tube and the second MOS tube are respectively connected with the first single diode and the second single diode correspondingly in parallel through another branch.
Further, the corresponding mathematical description formula of the equalizing current of the equalizing circuit structure is as follows:
Figure BDA0003011716440000031
in the formula imaxFor current balancing, V1 is the first MOS transistor voltage, R0And L is the equivalent resistance and capacitance, tonIs the closing time of the first MOS tube.
The system further comprises a controller, a state of charge estimation module and a balance control module, wherein the state of charge estimation module is used for integrally controlling the series lithium ion capacitor system, the balance control module is used for grouping the high specific energy lithium ion capacitors, the controller comprises an MCU, a voltage and current sensor and a balance control circuit module, the MCU is used for transmitting SOC related data to a vehicle main controller through a CAN, and the voltage and current sensor is used for collecting voltage and current signals of single lithium ion capacitors to assist the state of charge estimation module of the series lithium ion capacitor system to realize SOC estimation.
Further, the process of implementing the adjustable current of the equalization circuit by the fuzzy controller structure specifically includes: converting the accurate input value into a fuzzy value, then sending the fuzzy value to an inference engine, processing according to a control rule table, finally inputting the result into a defuzzifier, converting the result into an accurate value, and controlling an actuator for adjusting the current of the equalizing circuit.
Further, the control rule table is as follows:
when the SOC difference value and the SOC average value of the two capacitors are larger than the corresponding threshold values, current in a set range is adopted for balancing;
when the SOC difference value and the SOC mean value are both smaller than the corresponding threshold values, adopting a balance current smaller than a set value to prevent excessive balance;
when the SOC difference value is smaller than the corresponding threshold value and the SOC mean value is larger than the corresponding threshold value, the balance current smaller than a set value is adopted to prevent over-balance on the premise of ensuring the balance speed;
and when the SOC difference value and the SOC average value are smaller than the smaller corresponding threshold values, the equalizing current larger than the set value is adopted to accelerate the equalizing process of the capacitor.
Further, the power pack system based on the high-specific-energy lithium-ion capacitor is applied to the design of a 48V automobile start-stop power pack.
Compared with the prior art, the invention has the following advantages:
1. the first-order RC circuit parameter identification method provided by the invention has the advantages of strong applicability, reliable precision, intuitive principle, flexible structure, convenience for quantitative analysis, capability of better reflecting dynamic characteristics such as polarization effect of a power battery and the like, uncomplicated structure and higher calculation speed, so that an accurate parameter identification result is provided, and a foundation is laid for accurate SOC estimation.
2. The SOC partition estimation method provided by the invention aims at the characteristics of nonlinearity and strong time variation of the lithium ion capacitor during high-power charging and discharging, adopts a calculation method suitable for the characteristics of the lithium ion capacitor according to different energy storage characteristics of different SOC intervals, and overcomes the problem that the estimation of the SOC of the capacitor by the traditional estimation method is not accurate enough.
3. The invention provides a two-stage balancing device based on the existing Buck-Boost topological structure balancing circuit, which modularizes a series capacitor bank, improves the balancing speed and the balancing efficiency.
4. The method adopts the principle of a fuzzy logic device, takes the SOC of the lithium ion capacitor as an equalization variable, controls the equalization current of the equalizer by controlling the closing time of the MOS tube, realizes larger degree of freedom, improves the anti-interference performance and the robustness, matches with the working condition of a 48V start-stop system, and prolongs the service life of the lithium ion capacitor set.
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In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is a first-order RC circuit diagram according to an embodiment of the present invention;
FIG. 2 is a diagram illustrating partitioning results of electrochemical characteristics of a lithium ion capacitor according to an embodiment of the present invention;
FIG. 3 is a schematic diagram illustrating an application of the extended Kalman filtering method in an embodiment of the present invention;
FIG. 4 is a circuit diagram of a single Buck-Boost converter-based equalization topology according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of the operation of a single equalization topology circuit in an embodiment of the present invention;
FIG. 6 is a flow chart of the fuzzy controller operation in an embodiment of the present invention;
FIG. 7 is a diagram of a controller according to an embodiment of the present invention;
FIG. 8 is a 2D effect diagram of a PCB board according to an embodiment of the present invention;
fig. 9 is a flowchart of a state of charge estimation algorithm for a series li-ion capacitor system according to an embodiment of the present invention;
FIG. 10 is a simplified model diagram of a high specific energy lithium ion capacitor after grouping in an embodiment of the present invention;
fig. 11 is a schematic diagram of the operation of the equalizing system in the embodiment of the present invention.
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 some, not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, shall fall within the scope of protection of the present invention.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. 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.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings or the orientations or positional relationships that the products of the present invention are conventionally placed in use, and are only used for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," "third," and the like are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance.
Furthermore, the terms "horizontal", "vertical" and the like do not imply that the components are required to be absolutely horizontal or pendant, but rather may be slightly inclined. For example, "horizontal" merely means that the direction is more horizontal than "vertical" and does not mean that the structure must be perfectly horizontal, but may be slightly inclined.
In the description of the present invention, it should also be noted that, unless otherwise explicitly specified or limited, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly and may, for example, be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
The invention provides a 48V automobile start-stop power supply group design method based on a high-specific energy lithium ion capacitor, and a real object is correspondingly made, wherein the power supply group system is divided into two important modules:
1. and (3) a state of charge estimation algorithm of the series lithium ion capacitor system. The algorithm is based on the characteristics of strong time variation and nonlinearity of the high specific energy lithium ion capacitor, and is estimated by using an SOC partition estimation method and a data fusion method. Firstly, establishing a lithium ion capacitor as a first-order RC model, identifying dynamic variation parameters by using a recursive least square method with forgetting factors according to the measured terminal voltage terminal current, and then combining the identification result with the terminal current terminal voltage for SOC estimation. The ampere-hour method is used in the interval of 20-80% of SOC, and the extended Kalman filter method is used in the interval of 3-20% and 80-100% of SOC. The method overcomes the defects of the traditional SOC estimation method for the common battery, can provide higher precision when being applied to the charge and discharge of the high-specific energy lithium ion capacitor with instantaneous high power, and simultaneously ensures certain calculation speed, as shown in FIG. 9.
2. And (4) an equalization control system after grouping the high-specific-energy lithium ion capacitors. Due to the limitations of practical process conditions, there is inconsistency in the performance of supercapacitors. In the actual grouping process, the internal temperature difference further increases the inconsistency of the capacitor bank, and the simplified model in fig. 10 shows the "barrel effect" of (a) the post-charge state and (b) the post-discharge state, which indicates that the actual capacity utilization rate of the capacitor bank is greatly reduced. In the complex working condition of using 48 start-stop systems, great waste is generated, the cycle life is shortened, and the invention adopts balance control to solve the problem.
The equalizing system comprises a second-stage equalizing circuit structure based on a Buck-Boost converter and a fuzzy controller structure for realizing adjustable current of the equalizing circuit. The first-stage equalization circuit and the second-stage equalization circuit work independently; the fuzzy controller can realize larger degree of freedom, improve anti-interference performance and robustness and match with the working condition of a 48V start-stop system. The fuzzy device converts the precise input value into a fuzzy value, then sends the fuzzy value to the inference engine, processes the fuzzy value according to the rule table, finally inputs the result into the defuzzifier, converts the result into an accurate value, and controls the actuator to adjust the current of the equalizing circuit. The lithium ion capacitor pack can be efficiently and quickly balanced in any state, the consistency is improved, and the service life of the lithium ion capacitor pack is prolonged, as shown in fig. 11.
The specific implementation of the invention is realized by the following modes:
first, a first order RC model is constructed for the capacitor as shown in fig. 1, and the following circuit equations are as follows:
Figure BDA0003011716440000061
listing an equation set formed by two independent equations, carrying out Laplace transformation on a circuit equation, converting the circuit equation into a discrete time domain in a z domain, and according to the actual working condition situation: the model can be simplified by assuming that the variation of the SOC value in a unit sampling interval is 0, the temperature is constant and the aging state is constant. The model parameter matrix is identified by a recursive least square method with forgetting factors, and after the model parameter matrix of the result of parameter identification is obtained by the algorithm, the following parameter values of the Thevenin model can be obtained:
Figure BDA0003011716440000071
according to the electrochemical characteristics of the lithium ion capacitor, the partitioning result is shown in fig. 2, when the terminal voltage is 2.2V-2.90V, the corresponding SOC interval is 3-20%, the slope of the discharging OCV-SOC curve is large, the OCV value of the capacitor is changed drastically with the difference of the SOC value, and the total impedance curve is kept stable basically. The above characteristics show that: in the interval, the capacitive energy storage characteristic of the lithium ion capacitor is dominant. The capacitance energy storage characteristic is strong in nonlinearity, and the EKF method is suitable for a nonlinear system, is insensitive to initial parameters, and can reduce the accumulation of experimental errors, so that the SOC value of the battery interval at the section is estimated by using the EKF method. When the terminal voltage is 2.90V-3.35V, the corresponding SOC interval is 20% -80%, the slope of the discharging OCV-SOC curve is obviously reduced, the change amplitude of the OCV value is small along with the great increase of the SOC value, and the total impedance curve is sharply reduced in the interval. The above characteristics show that: in the interval, the energy storage characteristics of the lithium battery in the lithium ion capacitor are dominant, and the SOC value can be accurately estimated by using an Ah method. When the end voltage is 3.35V-3.8V, the corresponding SOC interval is 80% -100%, the slope of the discharging OCV-SOC curve is increased again, and the total impedance of the capacitor is reduced and is stable. The above characteristics show that: in the interval, the capacitance energy storage characteristic of the lithium ion capacitor is dominant, and the EKF method is still considered to be adopted for SOC estimation in the interval in consideration of the algorithm complexity and the system real-time requirement.
When the EKF algorithm is applied, the SOC and the U are compareddAs the state vector to be estimated, the system output quantity ItIs recorded as a data measurement matrix Yk(ii) a Control input UtIs recorded as a control matrix Uk。Wk，VkThe white noise of the system and the observation white noise are in Gaussian distribution, and the P matrix is a covariance matrix of the state vectors and is used for representing the state vectorsIs subsequently used to calculate the kalman gain. A first order Taylor expansion is used to linearize the system and then initialize variables, first determining an initial state vector X0And initial error covariance matrix P0Initial covariance matrix Q of two noises0And R0Then, predicting X and P at the next moment and calculating Kalman gain, multiplying the predicted value and the measured value according to the weight distributed by the Kalman gain, adding the multiplied values, calculating updated X and P, and continuously iterating, as shown in FIG. 3.
When the ampere-hour integration method is applied, the charging and discharging current of the battery within a specific time is integrated with the time, the integration result is taken as the change value of the battery capacity within the time period, and then the change value is added or subtracted with the initial value to obtain the current SOC value.
The invention provides a lithium ion capacitor equalization method and a fuzzy control method based on a Buck-Boost converter, wherein the equalization device is based on a Buck-Boost circuit and adds a secondary circuit to the original structural improvement, and the method is characterized in that the equalization circuit can be divided into a plurality of large modules, the equalization circuits in the modules are mutually independent, after the internal SOC equalization distribution is realized, the equalization circuits are also formed among the modules, and the secondary equalization among the modules is realized so as to solve the problems of overlong equalization time and reduced equalization efficiency when equalization monomer positions are not adjacent; a fuzzy controller is added to the balance control to realize the adjustability of the balance current and realize higher balance efficiency.
In order to achieve the purpose, the technical scheme of the invention is as follows:
the Buck-Boost circuit-based two-stage active equalization device comprises a two-stage Buck-Boost equalization circuit structure and a fuzzy controller connected with the two-stage Buck-Boost equalization circuit structure, wherein the Buck-Boost equalization circuit is composed of an MOS (metal oxide semiconductor) tube Q1, an MOS tube Q2, a single diode D1, a single diode D2, an inductor L1 and a resistor R1; MOS pipe Q1, inductance L1, resistance R1, diode D1 and capacitor Cell1 constitute a loop, MOS pipe Q2, inductance L1, resistance R1, diode D2 and capacitor Cell2 constitute a loop, and the two loops share inductance L1. The circuit structure is shown in figure 4 in the specification.
Specifically, the soc equalization method is implemented as shown in fig. 5:
first, (a) Cell1 discharge process in the figure: and acquiring the voltage and current parameters of the single capacitor through the current and voltage sensors, and estimating the initial residual capacity SOC of the single capacitor through the SOC partition estimation algorithm. And calculating the SOC difference value delta SOC of the two adjacent capacitor units according to the difference value delta SOC. A control system sends out a control signal to control the Q1 to be conducted to form a charging loop, and electric energy is converted into magnetic energy to be stored in the inductor L1. During the transient of the inductor charging, the magnitude of the equalizing current depends on the closing time of Q1.
Second, (b) Cell2 charging process in the figure: cell2 charging process for low soc: q1 is disconnected, inductor L1 releases energy, the diode is conducted, a charging loop is formed, and in the discharging process of L1, the current is continuously reduced. The duration of this process is determined by the conduction time of diode D2, and when the voltage across D2 is less than the conduction voltage, the process terminates and the charging process ends.
Thirdly, the degaussing process in the figure (c): after Cell2 is charged, D2 is cut off, and at the time, a part of energy still exists in inductor L1, and L1 forms a discharge loop through R1, so that residual energy is dissipated and accumulation is avoided. The magnitude of the equalizing current is related to the closing time of the MOS tube, and the formula is as follows:
Figure BDA0003011716440000081
in the formula imaxFor current balancing, V1 is the first MOS transistor voltage, R0And L is the equivalent resistance and capacitance, tonIs the closing time of the first MOS tube.
A fuzzy controller is used for controlling the equalizing current (the closing time of an MOS tube, namely a PWM signal) so as to realize larger degree of freedom, improve the anti-interference performance and robustness and match the working condition of a 48V start-stop system.
The fuzzy device working process is as shown in figure 6 of the specification, the accurate input value is converted into the fuzzy value, then the fuzzy value is sent to the inference machine and processed according to the rule table, finally the result is input into the fuzzy resolving device and converted into the accurate value, the PWM signal is output, and the actuator is controlled to adjust the current of the equalizing circuit. The specific control rule table is
(1) When the SOC difference value and the SOC average value of the two capacitors are relatively large, balancing by adopting a medium current;
(2) when the SOC difference value and the SOC mean value are relatively small, relatively small balance current is adopted for preventing over-balance;
(3) when the SOC difference value is small and the SOC average value is relatively large, relatively small balance current is adopted, and over balance is prevented on the premise of ensuring the balance speed;
(4) when the SOC difference value and the SOC average value are small, large equalizing current is adopted to accelerate the equalizing process of the capacitor.
The soc estimation and balance control management after capacitor grouping are mainly completed by a controller, the block diagram of the controller is shown in the attached figure 7 of the specification, and the controller mainly comprises an MCU and a voltage current and balance control circuit. The voltage and current sensor is used for collecting voltage and current signals of the capacitor monomer, SOC estimation is achieved, and a Hall type current sensor is selected to measure current according to the characteristic that the grouped discharge current of the starting and stopping capacitor is large. And sending the SOC difference value and the SOC average value of two adjacent monomers in each module (primary equalization), the difference value of the SOC sum of two adjacent modules (secondary equalization) and the SOC average value MCU of the three modules to the equalization control module, and outputting a PWM signal through fuzzy processing in the modules to control the closing time of the MOSFET in the equalization circuit so as to control the equalization current. The controller will also send the data relating to the SOC to the vehicle master controller via the CAN.
The controller is integrated in the PCB which is designed and manufactured by the controller, the size is reduced, and the aim of light weight is fulfilled, as shown in a 2D effect diagram shown in the attached figure 8 of the specification.
While the invention has been described with reference to specific embodiments, the invention is not limited thereto, and various equivalent modifications and substitutions can be easily made by those skilled in the art within the technical scope of the invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (10)

1. A power banking system based on high specific energy lithium electronic capacitors, the system comprising:
the charge state estimation module of the series lithium ion capacitor system is used for estimating the corresponding charge state of the high-specific-energy lithium ion capacitor by a method of SOC partition and data fusion;
the balancing control module after the high-specific-energy lithium ion capacitor group comprises a secondary balancing circuit structure based on a Buck-Boost converter and a fuzzy controller structure capable of realizing current adjustment of a balancing circuit, and is used for realizing that the lithium ion capacitor group operates according to requirements in working states under any states.
2. The system according to claim 1, wherein the process of estimating the corresponding state of charge for the high specific energy lithium ion capacitor by the method of SOC binning and data fusion specifically comprises: and constructing a corresponding battery model for the high-specific-energy lithium ion capacitor by using an algorithm, estimating dynamic quantity based on the model, and estimating the SOC in a partition mode according to the estimated value of the dynamic quantity to obtain a corresponding state of charge.
3. The system according to claim 2, wherein the battery model is a first-order RC model, and the method for estimating dynamic quantities of the battery model is a recursive least square method with a forgetting factor, and the dynamic quantities include four dynamic quantities resulting from estimating polarization phenomena according to terminal current terminal voltage: internal resistance of battery polarization RdBattery polarization capacitor CdRC link voltage drop UdAnd battery open circuit voltage UOC。
4. The system according to claim 2, wherein the SOC partition estimation process based on the dynamic quantity estimation values is based on electrochemical characteristics of the lithium ion capacitor, and estimation is performed by using an extended Kalman filter method in an interval with dominant capacitance characteristics; in the interval where the battery characteristics are dominant, the ampere-hour method is used for estimation.
5. The power grouping system based on the high-specific-energy lithium-ion capacitor as claimed in claim 1, wherein the Buck-Boost converter based two-stage equalizing circuit structure comprises a first MOS transistor, a second MOS transistor, a first single diode, a second single diode, an inductor and a resistor, the first MOS transistor and the second MOS transistor respectively form a closed loop with the corresponding lithium-ion capacitor after passing through the inductor and the resistor connected in parallel, and the first MOS transistor and the second MOS transistor are also respectively connected in parallel with the first single diode and the second single diode through another branch.
6. The system of claim 5, wherein the equalization circuit structure has an equalization current according to the mathematical description formula:
Figure FDA0003011716430000021
in the formula imaxFor current balancing, V1 is the first MOS transistor voltage, R0And L is the equivalent resistance and capacitance, tonIs the closing time of the first MOS tube.
7. The system according to claim 1, further comprising a controller for integrally controlling the state-of-charge estimation module of the series lithium ion capacitor system and the equalization control module after the high specific energy lithium ion capacitor system is grouped, wherein the controller comprises an MCU, a voltage current sensor and an equalization control circuit module, wherein the MCU is configured to transmit data related to SOC to a vehicle main controller through the CAN, and the voltage current sensor is configured to collect voltage current signals of the lithium ion capacitor cells to assist the state-of-charge estimation module of the series lithium ion capacitor system in SOC estimation.
8. The system according to claim 1, wherein the process of implementing the adjustable current of the equalization circuit by the fuzzy controller structure specifically comprises: converting the accurate input value into a fuzzy value, then sending the fuzzy value to an inference engine, processing according to a control rule table, finally inputting the result into a defuzzifier, converting the result into an accurate value, and controlling an actuator for adjusting the current of the equalizing circuit.
9. The system of claim 8, wherein the control rule table comprises:
when the SOC difference value and the SOC average value of the two capacitors are larger than the corresponding threshold values, current in a set range is adopted for balancing;
when the SOC difference value and the SOC mean value are both smaller than the corresponding threshold values, adopting a balance current smaller than a set value to prevent excessive balance;
when the SOC difference value is smaller than the corresponding threshold value and the SOC mean value is larger than the corresponding threshold value, the balance current smaller than a set value is adopted to prevent over-balance on the premise of ensuring the balance speed;
and when the SOC difference value and the SOC average value are smaller than the smaller corresponding threshold values, the equalizing current larger than the set value is adopted to accelerate the equalizing process of the capacitor.
10. The high specific energy lithium electronic capacitor based power pack system of claim 1, wherein the high specific energy lithium electronic capacitor based power pack system is applied to a 48V automotive start-stop power pack design.
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