Equivalent circuit of fusion model of all-vanadium redox flow battery and parameter determination method
阅读说明：本技术 全钒液流电池融合模型等效电路及参数确定方法 (Equivalent circuit of fusion model of all-vanadium redox flow battery and parameter determination method ) 是由 孟青 苏承启 张家乐 张文 于 2021-02-01 设计创作，主要内容包括：本发明提供的全钒液流电池融合模型等效电路及参数确定方法,包括用于模拟全钒液流电池堆电压的等效电压V-s,用于模拟全钒液流电池电堆内阻损耗的内阻损耗模拟电路,用于模拟循环泵损耗的泵损模拟电路,用于模拟全钒液流电池动态响应能力的等效电容C-e；所述内阻损耗模拟电路的一端与等效电压V-s的负极相连,内阻损耗模拟电路的另一端分别与泵损模拟电路的一端、全钒液流电池端电压U-d的负极相连；泵损模拟电路的另一端分别与全钒液流电池端电压U-d的正极、等效电容C-e的一端相连,等效电容C-e的另一端与内阻损耗模拟电路相连；本发明具有可以表现全钒液流电池的电堆外特性、并同时融合了全钒液流电池内部化学特性的有益效果,适用于电池领域。(The invention provides an equivalent circuit of an all-vanadium redox flow battery fusion model and a parameter determination method, wherein the equivalent circuit comprises an equivalent voltage V for simulating the voltage of an all-vanadium redox flow battery stack s The device comprises an internal resistance loss simulation circuit for simulating internal resistance loss of a pile of the all-vanadium redox flow battery, a pump loss simulation circuit for simulating loss of a circulating pump, and an equivalent capacitor C for simulating dynamic response capability of the all-vanadium redox flow battery e (ii) a One end of the internal resistance loss analog circuit and the equivalent voltage V s The other end of the internal resistance loss analog circuit is respectively connected with one end of the pump loss analog circuit and the terminal voltage U of the all-vanadium redox flow battery d The negative electrodes are connected; the other end of the pump loss analog circuit is respectively connected with the terminal voltage U of the all-vanadium redox flow battery d Positive electrode and equivalent capacitance C e Is connected to an equivalent capacitor C e The other end of the analog circuit is connected with an internal resistance loss analog circuit; the method has the beneficial effects of expressing the out-of-pile characteristics of the all-vanadium redox flow battery and simultaneously fusing the internal chemical characteristics of the all-vanadium redox flow battery, and is suitable for the field of batteries.)
1. The equivalent circuit of the fusion model of the all-vanadium redox flow battery is characterized in that: the method comprises the following steps:
equivalent voltage V for simulating all-vanadium redox flow battery stack voltagesThe device comprises an internal resistance loss simulation circuit (1) for simulating the internal resistance loss of the pile of the all-vanadium redox flow battery, a pump loss simulation circuit (2) for simulating the loss of a circulating pump, and an equivalent capacitor C for simulating the dynamic response capability of the all-vanadium redox flow batterye；
One end of the internal resistance loss analog circuit (1) and the equivalent voltage VsIs connected with the negative pole of the internal resistance loss analog circuit (1), and the other end of the internal resistance loss analog circuit (1) is respectively connected with one of the pump loss analog circuits (2)Terminal voltage U of all-vanadium redox flow batterydThe negative electrodes are connected;
the other end of the pump loss analog circuit (2) is respectively connected with the terminal voltage U of the all-vanadium redox flow batterydPositive electrode and equivalent capacitance CeIs connected to one end of the equivalent capacitor CeThe other end of the analog circuit is connected with the internal resistance loss analog circuit (1).
2. The equivalent circuit of the fusion model of the all-vanadium redox flow battery according to claim 1, characterized in that: the internal resistance loss simulation circuit (1) includes: polarization resistance RreaAnd ohmic internal resistance RresSaid polarization resistance RreaOne terminal and equivalent voltage VsIs connected to the negative pole of the said polarization resistor RreaThe other end of the resistor is connected in series with ohmic internal resistance RresThe rear end and the end voltage U of the all-vanadium redox flow battery are respectively connected with one end of the pump loss analog circuit (2) and one end of the all-vanadium redox flow battery terminal voltage UdThe negative electrodes are connected;
the equivalent capacitance CeIs connected in parallel with the polarization resistor R at the other endreaAnd ohmic internal resistance RresOn the connecting line between them.
3. The all-vanadium redox flow battery fusion model equivalent circuit according to claim 1 or 2, characterized in that: the pump loss simulation circuit (2) includes: pump loss current IPAnd internal resistance Rf(ii) a Pump loss current IPAnd internal resistance RfAre connected in parallel.
4. The equivalent circuit of the fusion model of the all-vanadium redox flow battery according to claim 3, characterized in that: the equivalent voltage VsThe expression of (a) is:
wherein: n is the number of the single batteries connected in series; vcellIs the voltage of the cell; r is a gas constant; t is the temperature; f is a Faraday constant; the SOC is a charge state, and the value range is 0-1.
5. The equivalent circuit of the fusion model of the all-vanadium redox flow battery according to claim 4, characterized in that: polarization resistance RreaThe expression of (a) is:
the ohmic internal resistance RresThe expression of (a) is:
wherein: pstackOutputting power for the stack; w1％、W2% of the respective polarization resistances RreaOhmic internal resistance RresThe rate of loss caused by; i ismaxThe maximum current of the battery.
6. The equivalent circuit of the fusion model of the all-vanadium redox flow battery of claim 4, characterized in that: pump loss current IPThe expression of (a) is:
the internal resistance RfThe expression of (a) is:
wherein: l is the pump loss constant of the battery; i issA current that is the stack voltage; w3% of internal resistance RfThe rate of loss caused.
7. The equivalent circuit of the fusion model of the all-vanadium redox flow battery of claim 4, characterized in that: the equivalent capacitance CeBy a value ofThe capacitance of the battery and the connection mode of the single battery are jointly determined; in NcellUnder the condition that the single batteries are connected in series, the single electric capacity is 6F; thus:
the equivalent capacitance CeThe expression of (a) is:
8. the parameter determination method of the equivalent circuit of the all-vanadium redox flow battery fusion model is characterized by comprising the following steps of: the method comprises the following steps:
s10, constructing an equivalent circuit of the fusion model of the all-vanadium redox flow battery; the all-vanadium redox flow battery fusion model equivalent circuit is the all-vanadium redox flow battery fusion model equivalent circuit of any one of claims 1 to 7;
s20, simulating according to the constructed equivalent circuit of the all-vanadium redox flow battery fusion model, and specifically comprising the following steps:
s201, obtaining operation data of an all-vanadium redox flow battery system, and obtaining the loss rate W% of battery loss power in stack power when the vanadium battery is in different SOC values; polarization resistance RreaOhmic internal resistance RresInternal resistance RfIs caused by (2) loss rate W1％、W2％、W3％；
S202, according to the rated power P of the all-vanadium redox flow batteryrateStack power P to batterystackDetermining parameters;
s203, calculating the equivalent voltage V according to the formulas (1) to (5)sPolarization resistance RreaOhmic internal resistance RresInternal resistance RfPump loss current IPThe value of (c).
Technical Field
The invention relates to the technical field of batteries, in particular to an equivalent circuit of a fusion model of an all-vanadium redox flow battery and a parameter determination method.
Background
The all-vanadium redox flow battery is a liquid redox battery which takes vanadium as an active substance and is in circulating flow. The electric energy is stored in the electrolyte in a chemical energy mode, and the electrolyte circularly flows between the liquid storage tank and the electric pile through an external circulating pump.
From the generation of all-vanadium redox flow batteries to date, expert scholars at home and abroad have researched a plurality of widely known battery models. Starting from the constructed principle, the all-vanadium redox flow battery model is mainly divided into an electrochemical model and an equivalent circuit model.
The electrochemical model of the vanadium redox battery can comprehensively reflect the characteristics of the battery, but when parameter estimation is carried out, the involved mathematical equation operation is complex, and a diffusion phenomenon can occur during experiment, so that the electrochemical model is difficult to be applied to actual engineering.
The equivalent circuit model of the vanadium cell is a model provided by combining the volt-ampere characteristic and the internal loss of the vanadium cell, has the characteristic of nonlinearity, and mainly comprises: the method comprises an alternating current impedance model and a three-order model, wherein the alternating current impedance model shown in figure 1 is a simpler model in a vanadium battery simulation model, but the simulation precision is lower, and the SOC estimation error is larger; meanwhile, the charging and discharging current of the vanadium battery energy storage system is direct current, and the direct current impedance is different from the alternating current impedance, so that the alternating current impedance model cannot meet the requirements of the micro-grid energy storage system; as shown in fig. 2, compared with the ac impedance model, the three-order model with branch current can dynamically and comprehensively reflect the working state of the vanadium redox battery, and has the advantages of simple parameter identification and convenient operation, but has higher requirement on the acquisition precision of the equipment, which will improve the simulation and test cost.
In conclusion, the electrochemical model of the all-vanadium redox flow battery can fully reflect the chemical characteristics of the battery, but the mathematical equation is complex, the analog calculation amount is large, the speed is slow, and the required microscopic parameters in the modeling process are difficult to obtain; the equivalent circuit model considers the nonlinear characteristic, the volt-ampere characteristic and the internal loss of the vanadium battery system, but ignores the mutual restriction relation among the chemical reaction in the battery, the loss and the ion movement of each component including a pump and a galvanic pile and the concentration.
Disclosure of Invention
Aiming at the defects in the related technology, the technical problem to be solved by the invention is as follows: the method for determining the equivalent circuit and the parameters of the fusion model of the all-vanadium redox flow battery can express the out-of-stack characteristics of the all-vanadium redox flow battery and simultaneously fuse the internal chemical characteristics of the all-vanadium redox flow battery.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
the equivalent circuit of the fusion model of the all-vanadium redox flow battery comprises: equivalent voltage V for simulating all-vanadium redox flow battery stack voltagesThe device comprises an internal resistance loss simulation circuit for simulating internal resistance loss of a pile of the all-vanadium redox flow battery, a pump loss simulation circuit for simulating loss of a circulating pump, and an equivalent capacitor C for simulating dynamic response capability of the all-vanadium redox flow batterye；
One end of the internal resistance loss analog circuit and the equivalent voltage VsThe other end of the internal resistance loss analog circuit is respectively connected with one end of the pump loss analog circuit and the terminal voltage U of the all-vanadium redox flow batterydThe negative electrodes are connected;
the other end of the pump loss analog circuit is respectively connected with the terminal voltage U of the all-vanadium redox flow batterydPositive electrode and equivalent capacitance CeIs connected to one end of the equivalent capacitor CeAnd the other end of the resistor is connected with the internal resistance loss analog circuit.
Preferably, the internal resistance loss simulation circuit includes: polarization resistance RreaAnd ohmic internal resistance RresSaid polarization resistance RreaOne terminal and equivalent voltage VsIs connected to the negative pole of the said polarization resistor RreaThe other end of the resistor is connected in series with ohmic internal resistance RresThe rear end and the end voltage U of the all-vanadium redox flow battery are respectively connected with one end of the pump loss analog circuitdThe negative electrodes are connected; the equivalent capacitance CeIs connected in parallel with the polarization resistor R at the other endreaAnd ohmic internal resistance RresOn the connecting line between them.
Preferably, the pump loss simulation circuit includes: pump loss current IPAnd internal resistance Rf(ii) a Pump loss current IPAnd internal resistance RfAre connected in parallel.
Preferably, the equivalent voltage VsThe expression of (a) is:
wherein: n is the number of the single batteries connected in series; vcellIs the voltage of the cell; r is a gas constant; t is the temperature; f is a Faraday constant; the SOC is a charge state, and the value range is 0-1.
Preferably, the polarization resistance RreaThe expression of (a) is:
the ohmic internal resistance RresThe expression of (a) is:
wherein: pstackOutputting power for the stack; w1％、W2% of the respective polarization resistances RreaOhmic internal resistance RresThe rate of loss caused by; i ismaxThe maximum current of the battery.
Preferably, the pump loss current IPThe expression of (a) is:
the internal resistance RfThe expression of (a) is:
wherein: l is the pump loss constant of the battery; i issA current that is the stack voltage; w3% of internal resistance RfThe rate of loss caused.
Preferably, the equivalent capacitance CeThe value of the voltage is determined by the capacitance of the single battery and the connection mode of the single battery; in NcellUnder the condition that the single batteries are connected in series, the single electric capacity is 6F; thus:
the equivalent capacitance CeThe expression of (a) is:
correspondingly, the parameter determination method for the equivalent circuit of the fusion model of the all-vanadium redox flow battery comprises the following steps:
s10, constructing an equivalent circuit of the fusion model of the all-vanadium redox flow battery; the all-vanadium redox flow battery fusion model equivalent circuit is the all-vanadium redox flow battery fusion model equivalent circuit;
s20, simulating according to the constructed equivalent circuit of the all-vanadium redox flow battery fusion model, and specifically comprising the following steps:
s201, obtaining operation data of an all-vanadium redox flow battery system, and obtaining the loss rate W% of battery loss power in stack power when the vanadium battery is in different SOC values; polarization resistance RreaOhmic internal resistance RresInternal resistance RfIs caused by (2) loss rate W1％、W2％、W3％；
S202, according to the rated power P of the all-vanadium redox flow batteryrateStack power P to batterystackDetermining parameters;
s203, calculating the equivalent voltage V according to the formulas (1) to (5)sPolarization resistance RreaOhmic internal resistance RresInternal resistance RfPump loss current IPThe value of (c).
The invention has the beneficial technical effects that:
the equivalent circuit of the all-vanadium redox flow battery fusion model simulates the battery characteristics by combining the engineering practice and equivalent circuit models on the basis of a chemical model Nernst equation, fully considers the internal resistance caused by the chemical reaction of the all-vanadium redox flow battery, utilizes the Nernst equation to estimate the SOC, comprehensively considers the pump loss and some mechanical characteristics, and improves the accuracy and the feasibility of the battery model; the physical significance of each element of the model is clear, the model is suitable for simulating a single galvanic pile or simulating a plurality of galvanic piles in series and parallel, the expansion is easy, and the practicability is extremely strong.
Drawings
FIG. 1 is a graph of an AC impedance model of an all-vanadium redox flow battery in the prior art;
FIG. 2 is a three-order model diagram of a branch-containing current of an all-vanadium redox flow battery in the prior art;
FIG. 3 is a schematic circuit structure diagram of an equivalent circuit of the all-vanadium redox flow battery fusion model of the invention;
FIG. 4 is a schematic diagram of a simulation structure of an equivalent circuit of an all-vanadium redox flow battery fusion model in the embodiment of the invention;
FIG. 5 is a SOC simulation graph of a 5kW cell stack fusion model in the embodiment of the invention;
FIG. 6 is a graph of the voltage change of the cell stack according to the embodiment of the present invention;
FIG. 7 is a graph of SOC versus OCV for an embodiment of the present invention;
FIG. 8 is a graph of current change of a stack according to an embodiment of the present invention;
in the figure: 1 is an internal resistance loss analog circuit, and 2 is a pump loss analog circuit.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, 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 embodiments, but not all embodiments, of the present 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.
An embodiment of the equivalent circuit of the all-vanadium redox flow battery fusion model and a parameter determination method is described in detail below with reference to the accompanying drawings.
Example one
Fig. 3 is a block diagram of a circuit structure of an all-vanadium redox flow battery microgrid control system according to an embodiment of the present invention; as shown in fig. 3, the equivalent circuit of the fusion model of the all-vanadium redox flow battery includes:
equivalent voltage V for simulating all-vanadium redox flow battery stack voltagesAn internal resistance loss simulation circuit 1 for simulating internal resistance loss of the pile of the all-vanadium redox flow battery, a pump loss simulation circuit 2 for simulating loss of a circulating pump, and an equivalent capacitor C for simulating dynamic response capability of the all-vanadium redox flow batterye；
One end of the internal resistance loss analog circuit 1 and the equivalent voltage VsThe other end of the internal resistance loss analog circuit 1 is respectively connected with one end of the pump loss analog circuit 2 and the terminal voltage U of the all-vanadium redox flow batterydThe negative electrodes are connected;
the other end of the pump loss analog circuit 2 is respectively connected with the terminal voltage U of the all-vanadium redox flow batterydPositive electrode and equivalent capacitance CeIs connected to one end of the equivalent capacitor CeAnd the other end thereof is connected with the internal resistance loss analog circuit 1.
Specifically, the internal resistance loss simulation circuit 1 includes: polarization resistance RreaAnd ohmic internal resistance RresSaid polarization resistance RreaOne terminal and equivalent voltage VsIs connected to the negative pole of the said polarization resistor RreaThe other end of the resistor is connected in series with ohmic internal resistance RresThe rear end and the end voltage U of the all-vanadium redox flow battery are respectively connected with one end of the pump loss analog circuit 2 and one end of the all-vanadium redox flow battery terminaldThe negative electrodes are connected; the equivalent capacitance CeIs connected in parallel with the polarization resistor R at the other endreaAnd ohmic internal resistance RresOn the connecting line between them.
Further, the pump loss simulation circuit 2 includes: pump loss current IPAnd internal resistance Rf(ii) a Pump loss current IPAnd internal resistance RfAre connected in parallel.
As shown in FIG. 2, UdThe terminal voltage of the all-vanadium redox flow battery can be collected and measured by an instrument; pump loss is equivalent to pump loss current IPParallel internal resistance RfThe value of which is related to the selected power and operating voltage of the circulation pump, the battery stack current IstackAnd SOC; vsIs the stack voltage of the cell, also referred to as the core voltage or open circuit voltage of the cell, depending on the magnitude of the SOC of the cell and UdRelated, controlled voltage sources are used instead; the relationship of each parameter in the fusion model of the invention is as follows:
wherein, UeIs an equivalent capacitance CeThe voltage across; i is the ohmic internal resistance RresThe current of (a); u shapesIs VsThe voltage across; i issIs a polarization resistance RreaThe current of (a); i isdIs terminal voltage UdThe current of (a); i isfIs internal resistance RfThe current of (a); i iseIs an equivalent capacitance CeThe current of (2). According to the nernst equation, the cell open-circuit voltage of the all-vanadium flow battery can be expressed as:
wherein: e0The balance potential of the vanadium battery in a standard state is obtained; r is a gas constant, and R is 8.31J/K/mol; t is temperature in K; f is a Faraday constant, and F is 96500C/mol;
from the above, it can be seen that: the equivalent voltage V (the terminal voltage of the all-vanadium redox flow battery, also called the open-circuit voltage)sThe expression of (a) is:
wherein: n is the number of the single batteries connected in series;Vcellis the voltage of the cell; r is a gas constant; t is the temperature; f is a Faraday constant; the SOC is a charge state, and the value range is 0-1.
SOCt+1＝SOCt+ Δ SOC formula (1-4);
where Δ SOC represents the simulation step time TstepAn internal SOC variation; Δ Δ E is the energy change; ecapacityIs the total capacity of the system; pstackFor simulating step length TstepThe product of the stack output power and the stack output power is delta E; total system loss of PstackW% of (2), wherein the polarization resistance RreaOhmic internal resistance RresInternal resistance RfAnd pump loss current IPThe losses caused are respectively W1％、W2％、W3% and W4％；PratedFor output power of vanadium battery, TratingThe time for outputting power by the vanadium redox battery; this gives:
stack output power:
polarization resistor R in internal resistance loss analog circuitreaThe expression of (a) is:
ohmic internal resistance R in internal resistance loss analog circuitresThe expression of (a) is:
pump loss current I in pump loss analog circuitPThe expression of (a) is:
internal resistance R in pump loss analog circuitfThe expression of (a) is:
wherein: i ismaxIs the maximum current of the battery; l is the pump loss constant of the battery; i issA current that is the stack voltage; w3% of internal resistance RfThe rate of loss caused.
Further, the equivalent capacitance CeThe value of the voltage is determined by the capacitance of the single battery and the connection mode of the single battery; in NcellUnder the condition that the single batteries are connected in series, the single electric capacity is 6F; thus: in this embodiment, the equivalent capacitor CeThe expression of (a) is:
the electrochemical model of the traditional all-vanadium redox flow battery can fully reflect the chemical characteristics of the battery, but the mathematical equation is complex, the analog calculation amount is large, the speed is slow, and the required microscopic parameters in the modeling process are difficult to obtain; the equivalent circuit model considers the nonlinear characteristic, the volt-ampere characteristic and the internal loss of the vanadium battery system, but ignores the mutual restriction relation among the chemical reaction in the battery, the loss and the ion movement of each component including a pump and a galvanic pile and the concentration.
Therefore, the invention provides an all-vanadium redox flow battery fusion model equivalent circuit for an all-vanadium redox flow battery, the equivalent circuit of the fusion model is used for simulating the battery characteristics by combining engineering practice and an equivalent circuit model on the basis of a chemical model Nernst equation, the model fully considers internal resistance brought by chemical reaction of the all-vanadium redox flow battery, SOC estimation is carried out by using an Nernst equation, pump loss and some mechanical characteristics are comprehensively considered, and the accuracy and the feasibility of the battery model are improved; the physical significance of each element of the model is clear, the model is suitable for simulating a single galvanic pile or simulating a plurality of galvanic piles in series and parallel, the expansion is easy, and the practicability is extremely strong.
Example two
The invention provides a parameter determination method for an equivalent circuit of an all-vanadium redox flow battery fusion model, which comprises the following steps of:
s10, constructing an equivalent circuit of the fusion model of the all-vanadium redox flow battery; the all-vanadium redox flow battery fusion model equivalent circuit is the all-vanadium redox flow battery fusion model equivalent circuit;
s20, simulating according to the constructed equivalent circuit of the all-vanadium redox flow battery fusion model, and specifically comprising the following steps:
s201, obtaining operation data of an all-vanadium redox flow battery system, and obtaining the loss rate W% of battery loss power in stack power when the vanadium battery is in different SOC values; polarization resistance RreaOhmic internal resistance RresInternal resistance RfIs caused by (2) loss rate W1％、W2％、W3％；
S202, according to the rated power P of the all-vanadium redox flow batteryrateStack power P to batterystackDetermining parameters;
s203, calculating the equivalent voltage V according to the formulas (1) to (5)sPolarization resistance RreaOhmic internal resistance RresInternal resistance RfPump loss current IPThe value of (c).
Specifically, in the implementation of the invention, according to the operation data of the all-vanadium redox flow battery system, when the SOC of the vanadium redox flow battery is 0.2, the battery power loss is 21% of the stack power. Wherein the internal loss ratio is 15% and the external loss ratio is 6%; of the 15% internal losses, 9% is RreaLoss, 6% being RresAnd (4) loss. According to all-vanadium flow batteriesAnd (3) fusing the models, and establishing the following simulation parameters:
the rated power of the vanadium redox battery is 5kW, the battery capacity is 30kWh, the number of single batteries is 39, the single battery capacitance is 0.15F, and the maximum battery current is 105A; as can be seen from the above, when the SOC is 0.2, the following equations (1) to (6) can be obtained:
battery stack power:
equivalent resistance:
pump current loss
Wherein: stack current IstackAnd IsThe values are the same; after calculation, the simulation parameter table is obtained as follows:
TABLE 1 simulation parameter Table of all-vanadium redox flow battery
FIG. 4 is a schematic diagram of a simulation structure of an equivalent circuit of the all-vanadium redox flow battery fusion model of the invention; as shown in fig. 4, according to the equivalent circuit of the all-vanadium redox flow battery fusion model and the above calculation formula, in the invention, a simulation model of the all-vanadium redox flow battery fusion model is built in a Matlab/Simulink platform, the charging and discharging current is set to be 105A, and the charging and discharging time period is 5200 s.
In fig. 4, the Current Source5 is a Current Source simulating the energy output part of the battery; rfix5 and Iump 4 are used for simulating pump loss current I in pump loss simulation circuitPAnd internal resistance Rf(ii) a C4 is used for simulating equivalent capacitance Ce(ii) a Controlled Voltage Source4 for simulating equivalent Voltage Vs(ii) a The Rinteraction 4 and the Rresidual 4 are respectively used for simulating the polarization resistance R in the internal resistance loss simulation circuitreaAnd ohmic internal resistance Rres。
Specifically, V in the formula (1) is expressed by the expression of the equivalent voltagecellThe voltage of the single battery is used, n is the serial number of the single batteries, and the value range of the SOC is 0-1. In the formulaThe data in the simulation was 0.0517, VcellThe data in the simulation is 1.37, the data in the simulation is 39, and the formula (1) is arranged as follows according to the parameters:
further, according to the expression of Δ SOC, in the expressions (1-5), a simulation parameter T is setstepIs 0.001, EcapacitySet to 30000 in the simulation, where: Δ SOC represents the simulation step sizeTime TstepThe internal SOC variation amount. Δ E is the energy change, EcapacityIs the total capacity of the system.
According to the above parameters, the formula (1-5) is arranged as follows:
further, according to the pump loss current IPIn equation (4), according to the above parameters:
FIG. 5 is a SOC simulation graph of a 5kW cell stack fusion model in the embodiment of the invention; as shown in fig. 5, under the specified simulation setting conditions, the SOC was increased to 88% after the SOC was charged for 2600s, and the SOC of the battery was decreased to less than 20% by performing the discharge simulation for 2600 s. As is clear from this figure, when the charge and discharge currents are uniform, the SOC curve is not completely symmetrical. This is because the pump loss and the equivalent internal resistance loss exist no matter charging or discharging, and therefore, the system itself consumes a part of energy regardless of the charging or discharging process; therefore, the battery discharge power is larger than the output power of the port during discharging, and the actual absorption power of the battery is smaller than the input power of the port during charging.
The traditional equivalent circuit model simulation result shows that the SOC curve is completely symmetrical in the charging and discharging process, because only external characteristics are considered, chemical characteristics are not really considered, and the actual operation result of the battery cannot be comprehensively reflected.
FIG. 6 is a graph showing the voltage variation of the cell stack according to the embodiment of the present invention, and as shown in FIG. 6, the terminal voltage and the SOC variation are substantially synchronous and have a one-to-one correspondence relationship; in actual operation, the data obtained from the quality inspection department, the single open-circuit voltage and the fitting curve of the SOC actual measurement data are basically consistent.
FIG. 7 is a SOC-OCV relationship graph in the embodiment of the present invention, as shown in FIG. 7, it can be seen from the measured curve that when the SOC of the vanadium redox battery is lower than 10%, the terminal voltage is linearly decreased, and the performance of the pile is greatly affected; vanadium cells therefore do not allow overdischarge, which would otherwise cause irreparable damage to the stack.
FIG. 8 is a graph of current change of a stack according to an embodiment of the present invention; as shown in fig. 8, fig. 8 reflects the change in the charging current in the stack during charging; due to pump losses and battery internal losses, the charge current of the stack is not equal to the charge current provided by the signal source. The input current is constant in the constant current charging process due to the existence of IPIs thus IsThe current is less than 105A;
during charging, the SOC increases along with the increase of chemical active substances in the electrolyte, and because the input current is fixed, namely the number of ions entering the stack is fixed, in the process that the SOC gradually increases, the flow of the electrolyte is reduced, and the pump loss current I is reducedPWill also be reduced, flowing through IsIs increased, so that the entire charging process I is carried outsIs a slightly rising curve. On the contrary, when discharging, the core voltage VsAs a power supply, the output current is 105A, again due to the presence of IPIs divided into streams, hence IsGreater than 105A. During constant current discharge, the electrolyte active material decreases as the SOC decreases, which increases the flow rate of the electrolyte and pumps the current IPWill also increase with it, IsWill also increase. When the discharge SOC is almost close to 0, IsAnd also tends to be negative infinity.
In conclusion, the all-vanadium redox flow battery fusion model provided by the invention fully considers the internal resistance brought by the chemical reaction of the all-vanadium redox flow battery, utilizes the nernst equation to carry out SOC estimation, and simultaneously comprehensively considers the pump loss and some mechanical characteristics, thereby improving the accuracy and the feasibility of the battery model; the physical significance of each element of the model is clear, the model is suitable for simulating a single electric pile or simulating a plurality of electric piles in series and parallel connection, and the model is easy to expand.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the foregoing embodiments, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.
It can be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working processes of the system and the module described above may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.