Method for automatically adjusting pressure and flow of electrolyte inlet of flow battery stack

Abstract

The invention belongs to the technical field of flow batteries, and particularly relates to a method for automatically adjusting pressure and flow of an electrolyte inlet of a flow battery stack. The method comprises the following steps: asynchronously adjusting the pump frequency of the positive and negative electrodes of the flow battery by adopting stepping logic, maintaining the pressure difference between the electrolyte inlets of the positive and negative electrodes of the electric pile of the flow battery in the adjusting process, and recording the adjusting duration in real time; and when the current pressure of the anode and cathode electrolyte inlets of the redox flow battery stack reaches a target pressure, or the adjustment duration reaches a preset time threshold, stopping adjusting the anode and cathode pump frequency of the redox flow battery. According to the method, under the condition that the response time / performance / service life of the pump, the slow variable response time, the galvanic pile safety, the system stability and the target adjusting speed are guaranteed, automatic adjustment of the pump frequency of the electrolyte circulating pump of the flow battery energy storage process system guided by the target pressure and the flow is achieved, and meanwhile the algorithm is suitable for liquid level unbalance of the storage tank.

Description

Technical Field

[0001] The present invention belongs to the technical field of liquid flow batteries, and in particular relates to a method for automatically adjusting the inlet pressure and flow rate of electrolyte of a liquid flow battery stack. Background Art

[0002] Liquid flow battery is a new type of electrochemical energy storage device. Its main features are high energy conversion efficiency, environmental friendliness, and good safety performance. It is widely used in power system peak regulation, renewable energy power generation grid connection, distributed power generation system and other fields. Among them, the electrolyte circulation pump is one of the key equipment of the liquid flow battery system, and its operating status directly affects the performance and life of the liquid flow battery stack and the entire energy storage system. Therefore, how to effectively control the operation of the electrolyte circulation pump, ensure the pressure or flow of the battery stack, and improve the charging and discharging efficiency and system stability of the energy storage system is an important research direction in the field of liquid flow battery technology.

[0003] The existing control method for the electrolyte circulation pump of a flow battery is mainly to set a fixed pump frequency and manually adjust it according to actual needs. Although this method is simple and easy to implement, it cannot achieve accurate matching with the charge and discharge current or power, which may reduce the efficiency of the battery and may even damage the battery. At the same time, the pump action can also be directly scheduled by the pump frequency, but it cannot be controlled with one button.

[0004] The existing control methods for electrolyte circulation pumps of flow batteries have the following major problems: First, it is impossible to achieve precise matching with the charging and discharging current or power, which may lead to reduced battery efficiency; second, it is impossible to respond to changes in pressure or flow in a timely manner. Considering the performance and life of the pump itself, it is impossible to perform one-click regulation, which may cause the battery's working state to be unstable and unable to meet the scheduling requirements of the power grid; third, there is no effective fault warning mechanism, which may lead to incorrect scheduling of the control method, causing the fault to expand and may even cause damage to the system. Summary of the invention

[0005] In view of the above problems, the present disclosure provides a method for automatically adjusting the electrolyte inlet pressure of a flow battery stack, the method comprising:

[0006] Adopting stepping logic to asynchronously adjust the positive and negative electrode pumping frequency of the flow battery, and maintaining the pressure difference between the positive and negative electrode electrolyte inlets of the flow battery stack during the adjustment process, and recording the adjustment time in real time;

[0007] When the current pressure of the electrolyte inlet of the positive and negative electrodes of the flow battery stack reaches the target pressure, or the adjustment time reaches a preset time threshold, the adjustment of the positive and negative electrode pump frequency of the flow battery is stopped.

[0008] Furthermore, the positive and negative electrode pumping frequencies of the flow battery are asynchronously adjusted using step-by-step logic, including:

[0009] The positive and negative electrode pumping frequencies of the liquid flow battery are adjusted so that the current pressures of the electrolyte inlets of the positive and negative electrodes of the liquid flow battery stack approach the target pressure.

[0010] Furthermore, maintaining the pressure difference between the positive and negative electrolyte inlets of the flow battery stack during the adjustment process includes:

[0011] Acquire the current pressure of the positive and negative electrode inlets of the flow battery stack in real time and calculate the pressure difference;

[0012] The pressure difference is compared with a preset pressure difference threshold, and if the pressure difference exceeds the pressure difference threshold, the positive electrode pumping frequency or the negative electrode pumping frequency of the flow battery is adjusted until the pressure difference is lower than the pressure difference threshold.

[0013] Furthermore, when the target pressure is lower than the pressure of the pump frequency lower limit, the positive and negative electrode pumps are synchronously adjusted to the pump frequency lower limit;

[0014] When the target pressure exceeds the upper limit of the pump frequency, the pump frequency is adjusted to the pump frequency value of the maximum pressure that can be achieved when the pressure difference between the positive and negative electrolyte inlets of the battery stack is balanced.

[0015] Furthermore, the method further comprises:

[0016] A predictive alarm mathematical model for the pumping frequency of the positive and negative electrolyte circulation pumps and the positive and negative electrolyte inlet pressures of the flow battery stack is constructed, and pressure anomalies are predicted through the mathematical model.

[0017] Furthermore, a mathematical model for predicting and alarming the pumping frequency of the positive and negative electrolyte circulation pumps and the inlet pressure of the positive and negative electrolytes of the flow battery stack is constructed, including:

[0018] Divide the pump frequency range into equal-difference segments to obtain a series of pump frequency values;

[0019] When the system is in a normal state, multiple sets of positive and negative electrode pump frequency value series corresponding to the positive and negative electrode electrolyte inlet pressure value series of the battery stack are obtained;

[0020] The multiple sets of data of the pump frequency value series and the corresponding pressure value series are curve fitted to obtain the mathematical model of the pump frequency of the positive and negative electrolyte circulation pumps and the positive and negative electrolyte inlet pressures of the flow battery stack;

[0021] Get the current positive and negative pump frequency values;

[0022] Substituting the current pump frequency value into the mathematical model to calculate and obtain the predicted pressure value;

[0023] The actual pressure value of the battery stack at the current pump frequency is subtracted from the predicted pressure value to obtain the prediction alarm mathematical model of the pump frequency of the positive and negative electrolyte circulation pumps and the positive and negative electrolyte inlet pressures of the flow battery stack.

[0024] Furthermore, the predicted pressure value is obtained, including:

[0025] Get the current pump frequency value and random pressure error;

[0026] The current pump frequency value is weighted and summed with the random error to obtain the predicted pressure value.

[0027] The present disclosure also provides a method for automatically adjusting the flow rate of an electrolyte inlet of a flow battery stack, the method comprising:

[0028] Adopting stepping logic to asynchronously adjust the positive and negative electrode pumping frequency of the flow battery, and maintaining the pressure difference between the positive and negative electrode electrolyte inlets of the flow battery stack during the adjustment process, and recording the adjustment time in real time;

[0029] When the current flow rate of the electrolyte inlet of the positive and negative electrodes of the flow battery stack reaches the target flow rate, or the adjustment time reaches a preset time threshold, the adjustment of the positive and negative electrode pump frequency of the flow battery is stopped.

[0030] Furthermore, the positive and negative electrode pumping frequencies of the flow battery are asynchronously adjusted using step-by-step logic, including:

[0031] The positive and negative electrode pumping frequencies of the liquid flow battery are adjusted so that the current flow rates of the electrolyte inlets of the positive and negative electrodes of the liquid flow battery stack are close to the target flow rate.

[0032] Furthermore, maintaining the pressure difference between the positive and negative electrolyte inlets of the flow battery stack during the adjustment process includes:

[0033] Acquire the current pressure of the positive and negative electrode inlets of the flow battery stack in real time and calculate the pressure difference;

[0034] The pressure difference is compared with a preset pressure difference threshold, and if the pressure difference exceeds the pressure difference threshold, the positive electrode pumping frequency or the negative electrode pumping frequency of the flow battery is adjusted until the pressure difference is lower than the pressure difference threshold.

[0035] Furthermore, when the target flow rate is lower than the flow rate of the lower limit of the pump frequency, the positive and negative electrode pumps are synchronously adjusted to the lower limit of the pump frequency;

[0036] When the target flow rate exceeds the upper limit of the pump frequency, adjust the pump frequency to the pump frequency value of the maximum flow rate that can be achieved when the pressure difference between the positive and negative electrolyte inlets of the battery stack is balanced.

[0037] Furthermore, the method further comprises:

[0038] A mathematical model for predicting and alarming the pumping frequency of the positive and negative electrolyte circulation pumps and the inlet flow rate of the positive and negative electrolyte of the flow battery stack is constructed, and flow abnormalities are predicted through the mathematical model.

[0039] Furthermore, a mathematical model for predicting and alarming the pump frequency of the positive and negative electrolyte circulation pumps and the inlet flow rate of the positive and negative electrolytes of the flow battery stack is constructed, including:

[0040] Divide the pump frequency range into equal-difference segments to obtain a series of pump frequency values;

[0041] When the system is in a normal state, multiple sets of positive and negative electrode pump frequency value series corresponding to the positive and negative electrode electrolyte inlet flow value series of the battery stack are obtained;

[0042] The multiple sets of data of the pump frequency value series and the corresponding flow value series are curve fitted to obtain the mathematical model of the pump frequency of the positive and negative electrolyte circulation pumps and the inlet flow rate of the positive and negative electrolyte of the flow battery stack;

[0043] Get the current positive and negative pump frequency values;

[0044] Substituting the current pump frequency value into the mathematical model to calculate and obtain the predicted flow value;

[0045] The actual flow value of the battery stack at the current pump frequency is subtracted from the predicted flow value to obtain the prediction alarm mathematical model of the pump frequency of the positive and negative electrolyte circulation pumps and the positive and negative electrolyte inlet flow rates of the flow battery stack.

[0046] Furthermore, the predicted flow value is obtained, including:

[0047] Get the current pump frequency value and random flow error;

[0048] The current pump frequency value is weighted and summed with the random error to obtain the predicted flow value.

[0049] The present disclosure has the following beneficial effects:

[0050] (1) The present invention realizes automatic regulation of the pump frequency of the electrolyte circulation pump of the flow battery energy storage process system guided by target flow or pressure while ensuring the response time / performance / life of the pump itself, the response time of the slow variable (pressure or flow), the safety of the battery stack, the stability of the system, and the target regulation speed. At the same time, the algorithm is suitable for operating the system when the tank liquid level is unbalanced and the initial pressure difference of the battery stack inlet is large;

[0051] (2) The present disclosure realizes the matching of flow rate or pressure with the charging and discharging current and power of the energy storage system, and cooperates with the process system automation scheduling to realize the overall automated operation of the liquid flow battery energy storage system. At the same time, the BMS realizes the underlying logic of safety protection, constrains the current / power value of PCS charging and discharging, and ensures the safety of system charging and discharging from the bottom layer;

[0052] (3) The present disclosure can detect system fault information warnings through mathematical model prediction and correction, prevent incorrect scheduling of control methods, and avoid possible damage to the battery.

[0053] Other features and advantages of the present disclosure will be described in the following description, and partly become apparent from the description, or be understood by implementing the present disclosure. The purpose and other advantages of the present disclosure can be realized and obtained by the structures indicated in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0055] Figure 1 A diagram showing a method for automatically adjusting the electrolyte inlet pressure of a flow battery stack in an embodiment of the present disclosure;

[0056] Figure 2 A partial diagram showing an algorithm flow chart of a method for automatically adjusting the electrolyte inlet pressure of a flow battery stack in an embodiment of the present disclosure;

[0057] Figure 3 A partial diagram showing an algorithm flow chart of a method for automatically adjusting the electrolyte inlet pressure of a flow battery stack in an embodiment of the present disclosure;

[0058] Figure 4 A partial diagram showing an algorithm flow chart of a method for automatically adjusting the electrolyte inlet pressure of a flow battery stack in an embodiment of the present disclosure;

[0059] Figure 5 A diagram showing an automatic adjustment method for the inlet flow rate of electrolyte of a flow battery stack using flow guidance as an example in an embodiment of the present disclosure;

[0060] Figure 6 A partial diagram showing an algorithm flow chart of a method for automatically adjusting an inlet flow rate of an electrolyte of a flow battery stack in an embodiment of the present disclosure;

[0061] Figure 7 A partial diagram showing an algorithm flow chart of a method for automatically adjusting an inlet flow rate of an electrolyte of a flow battery stack in an embodiment of the present disclosure;

[0062] Figure 8 A partial diagram showing an algorithm flow chart of a method for automatically adjusting an electrolyte inlet flow rate of a flow battery stack in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0063] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as being limited to the examples set forth herein; on the contrary, these embodiments are provided so that the present disclosure will be more comprehensive and complete, and the concepts of the example embodiments are fully conveyed to those skilled in the art. The described features, structures, or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced while omitting one or more of the specific details, or other methods, components, devices, steps, etc. may be adopted. In other cases, known technical solutions are not shown or described in detail to avoid obscuring various aspects of the present disclosure.

[0064] In addition, the accompanying drawings are only schematic illustrations of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software form, or implemented in one or more hardware units or integrated circuits, or implemented in different networks and / or processor devices and / or microcontroller devices.

[0065] The flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the steps. For example, some steps may be decomposed, while some steps may be combined or partially combined, so the actual execution order may change according to the actual situation.

[0066] The terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example.

[0067] In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or sub-modules is not necessarily limited to those steps or sub-modules explicitly listed, but may include other steps or sub-modules not explicitly listed or inherent to these processes, methods, products, or apparatuses.

[0068] Taking pressure guidance as an example, the detailed technical content of this disclosure is as follows:

[0069] The control method disclosed in the present invention adjusts the positive / negative electrode pump frequency through an algorithm, wherein the main body of the algorithm consists of four parts, namely the target pressure adjustment stage, the positive and negative electrode electrolyte inlet pressure difference balance stage of the battery stack (group), the over-limit voltage stabilization stage and the timeout exit stage. By independently adjusting the positive and negative electrode pump frequencies in the same set of flow battery energy storage process systems, and limiting the positive and negative electrode electrolyte inlet pressure difference balance of the battery stack (group), the overall scheduling and regulation is achieved. At the same time, considering the inverter response speed, pump performance and pressure or flow response speed, target pressure difference, positive and negative electrode pressure difference, the stepping (stepping back) frequency interval of the positive and negative electrode pump frequency is respectively given, thereby maintaining the safety and stability of the energy storage equipment, the battery stack and the overall energy storage system.

[0070] (1) The target pressure adjustment stage is the core part of the pump frequency adjustment algorithm. It uses step-by-step logic to asynchronously adjust the positive / negative electrode pump frequency so that the current pressure at the positive / negative electrode electrolyte inlet of the stack (group) gradually approaches the target pressure value, reducing the step iteration step and speeding up the step iteration completion time. Among them, the target pressure is the predetermined pressure value at the positive / negative electrode inlet of the stack (group) required by humans or the superior system. It is the only input of the algorithm disclosed in this disclosure and the final effect target of the algorithm operation adjustment.

[0071] (2) The pressure difference balance stage is a concomitant stage of the target pressure regulation. In the target pressure regulation stage, the pressure difference is calculated in real time. When the pressure difference threshold is exceeded, the target pressure regulation is stopped and the pressure difference balance stage is entered. According to the relationship between the target pressure and the current pressure, the positive or negative electrode pump frequency is adjusted until the pressure difference is less than the threshold, the pressure difference balance is stopped, and the target pressure regulation stage is entered. The pressure difference balance can also solve the initial pressure difference inconsistency caused by liquid level imbalance, triggering the pressure difference alarm and the pump cannot be started (the current maximum adjustable level is 40kPa, about 3m of liquid level difference). Among them, in the liquid flow battery process system, the pressure difference is the difference between the inlet pressure of the positive electrode electrolyte of the stack (group) and the inlet pressure of the negative electrode electrolyte of the negative electrode. This value needs to be guaranteed to be within the safe range. Excessive pressure difference imbalance will cause permanent physical damage to the stack.

[0072] (3) The over-limit voltage stabilization stage is the safety protection logic of the regulation algorithm. When the target pressure is lower than the lower limit of the pump frequency, the positive and negative pumps are synchronously adjusted to the lower limit of the pump frequency. When the target pressure exceeds the upper limit of the pump frequency, the critical voltage stabilization logic is enabled to adjust the pump frequency to the maximum pressure that can be achieved when the pressure difference between the positive and negative inlets of the stack (group) is balanced.

[0073] (4) The timeout exit phase is the safety protection logic of the regulation algorithm. If the given target pressure or flow rate is not reached after a certain time step, the algorithm may not converge or the system may fail. At this time, the algorithm will stop adjusting and stop the algorithm on the premise of ensuring that the pressure difference between the positive and negative electrodes of the stack (group) meets the protection threshold, so as to prevent endless pump frequency scheduling.

[0074] like Figure 1 As shown, the present disclosure proposes a method for automatically adjusting the electrolyte inlet pressure of a flow battery stack, the method comprising:

[0075] Adopting stepping logic to asynchronously adjust the positive and negative electrode pumping frequency of the flow battery, and maintaining the pressure difference between the positive and negative electrode electrolyte inlets of the flow battery stack during the adjustment process, and recording the adjustment time in real time;

[0076] When the current pressure of the electrolyte inlet of the positive and negative electrodes of the flow battery stack reaches the target pressure, or the adjustment time reaches a preset time threshold, the adjustment of the positive and negative electrode pump frequency of the flow battery is stopped.

[0077] Specifically, the adjustment flow chart of the automatic adjustment method for the electrolyte inlet pressure of the flow battery stack is as follows: Figure 2-Figure 4 As shown, the adjustment of this technical solution involves algorithm adjustment, and the specific contents are as follows:

[0078] like Figure 2 As shown, step 1, determine whether there is a pump stop fault at present;

[0079] If there is a pump stop failure, the current process ends;

[0080] If there is no pump stop failure, the target pressure instruction is obtained, and the current operation mode is initially set to the target pressure adjustment stage, the cycle step count is initially set to 0, and step 2 is performed;

[0081] Step 2: Determine whether the current cycle step count is less than 100; in this embodiment, 100 is only a reference value and can be set according to actual conditions;

[0082] If the current loop step count is ≥100, the current process ends;

[0083] If the current cycle step count is less than 100, obtain the current positive and negative electrode pumping frequency, the current stack positive and negative electrode pressure and their pressure difference, set the required parameters and calculate multiple sets of data, obtain the next step positive and negative electrode pumping frequency value = the current positive and negative electrode pumping frequency value, and then execute step 3; wherein, the required parameters to be set include: upper and lower limits of positive and negative electrode pumping frequency, pressure difference balance cutoff threshold, algorithm single-step maximum adjustable balance pressure difference, pressure difference balance pumping frequency step upper and lower limits, target pressure difference adjustment cutoff threshold, algorithm single-step adjustable maximum target difference and target pressure difference adjustment pumping frequency step upper and lower limits, and the multiple sets of data calculated include: pressure difference normalization coefficient, pressure difference balance execution step pumping frequency, positive and negative electrode target pressure difference coefficient and target pressure adjustment execution step positive and negative electrode pumping frequency.

[0084] like Figure 3As shown, step 3, judging whether the current operation mode is the non-overlimit pressure stabilization stage, and the current pressure difference exceeds the pressure difference balance cut-off threshold or the current operation mode is the pressure difference balance stage;

[0085] If the above conditions are met at the same time, the operation mode is set to the pressure difference balance stage and step 4 is executed;

[0086] If the above conditions are not met at the same time, go to step 7;

[0087] Step 4: determine whether the current pressure difference meets the pressure difference balance cutoff threshold, or whether the positive and negative target pressure differences both meet the target pressure difference adjustment cutoff threshold;

[0088] If it meets the requirements, the operation mode is set to the target pressure adjustment stage, and then step 7 is executed;

[0089] If not, proceed to step 5;

[0090] Step 5, determine whether the current positive or negative electrode pressure needs to be increased;

[0091] If it needs to be increased, when the positive electrode pump frequency is lower than the negative electrode, the next positive electrode pump frequency = current positive electrode pump frequency + pump frequency pressure difference balance step; when the negative electrode pump frequency is lower than the positive electrode, the next negative electrode pump frequency = current negative electrode pump frequency + pump frequency pressure difference balance step;

[0092] If no promotion is required, proceed to step 6;

[0093] Step 6, determining whether the current positive electrode or negative electrode pressure needs to be reduced;

[0094] If it needs to be reduced, when the positive electrode pump frequency is greater than the negative electrode, the next positive electrode pump frequency = current positive electrode pump frequency - pump frequency pressure difference balance step; when the negative electrode pump frequency is greater than the positive electrode, the next negative electrode pump frequency = current negative electrode pump frequency - pump frequency pressure difference balance step;

[0095] If no promotion is required, proceed to step 7;

[0096] Step 7, determining whether the operation mode is the target pressure adjustment stage;

[0097] If yes, go to step 8;

[0098] If not, go to step 9;

[0099] Step 8: Determine whether both the positive and negative electrode pressures meet the target pressure adjustment threshold;

[0100] If all are met, go to step 9;

[0101] If not all of them are met, then when the positive electrode pressure is greater than the target pressure, the next step of positive electrode pump frequency = current positive electrode pump frequency - positive electrode pump frequency target pressure adjustment step; when the positive electrode pressure is less than the target pressure, the next step of positive electrode pump frequency = current positive electrode pump frequency + positive electrode pump frequency target pressure adjustment step; when the negative electrode pressure is greater than the target pressure, the next step of negative electrode pump frequency = current negative electrode pump frequency - negative electrode pump frequency target pressure adjustment step; when the negative electrode pressure is less than the target pressure, the next step of negative electrode pump frequency = current negative electrode pump frequency + negative electrode pump frequency target pressure adjustment step, and then execute step 9.

[0102] like Figure 4 As shown, in step 9, the positive or negative electrode pump frequency has reached the lower limit, but still does not meet the target pressure regulation threshold. Does the pressure need to be reduced or is it currently in the over-limit pressure stabilization stage (lower limit);

[0103] If any of the above conditions is met, the operation mode is set to the over-limit voltage stabilization stage (lower limit), the next step is that the positive and negative electrode pump frequency = the positive and negative electrode pump frequency lower limit, and then execute step 10;

[0104] If not satisfied, go directly to step 10;

[0105] Step 10: The positive or negative electrode pump frequency has reached the upper limit, but still does not meet the target pressure regulation threshold. Does the pressure need to be increased or is it currently in the over-limit pressure stabilization stage (high limit)?

[0106] If any of the above conditions is met, execute step 11;

[0107] If not satisfied, go directly to step 12;

[0108] Step 11, determining whether the current pressure difference exceeds the pressure difference balance cutoff threshold;

[0109] If it exceeds, set the operation mode to the over-limit voltage stabilization stage (high limit). If the negative electrode pump frequency is large, the next positive electrode pump frequency = the current positive electrode pump frequency, and the next negative electrode pump frequency = the current negative electrode pump frequency - pump frequency pressure difference balance step. If the positive electrode pump frequency is large, the next negative electrode pump frequency = the current negative electrode pump frequency, and the next positive electrode pump frequency = the current positive electrode pump frequency - pump frequency pressure difference balance step, and then execute step 12;

[0110] If it does not exceed, the next step is that the positive and negative electrode pump frequency = the current positive and negative electrode pump frequency, and step 12 is executed;

[0111] Step 12, constrain the positive and negative electrode pump frequencies to be within their respective upper and lower limits, and execute step 13;

[0112] Step 13, determine whether the positive and negative pump frequencies in the current positive and negative pump frequency domains are equal in the next step;

[0113] If they are equal, end the current process;

[0114] If they are not equal, the next step of positive and negative electrode pumping frequency is executed, delaying for 5s, waiting for the pressure change, the cycle step count +1, and executing step 2. In this embodiment, 5s is only a reference value and can be set according to actual conditions.

[0115] The algorithm parameters in this disclosure are described as follows:

[0116] mode: 0 indicates the target pressure adjustment stage, 1 indicates the pressure difference balance stage, 3 / 4 indicates the over-limit pressure stabilization stage

[0117] set_point: The target pressure to be achieved by the regulation instruction

[0118] p_cur_freq: Current frequency of the positive pump

[0119] p_cur_press: Current pressure of the positive electrode pump

[0120] n_cur_freq: Current frequency of the cathode pump

[0121] n_cur_press: Current pressure of the cathode pump

[0122] p_max_freq=y1# Maximum range of positive electrode pump frequency

[0123] p_min_freq=y2#minimum range of positive electrode pump frequency

[0124] n_max_freq=y3# Maximum range of negative electrode pump frequency

[0125] n_min_freq=y4#minimum range of negative electrode pump frequency

[0126] press_diff_end=y5#pressure difference balance cutoff line, for example, y5=5, there is no need to balance the pressure difference within -5~5kpa

[0127] press_diff_max=y6# Maximum pressure difference set

[0128] balance_step_max=y7#The maximum balance pump frequency step set

[0129] balance_step_min=y8#minimum balance pump frequency step

[0130] press_diff = p_cur_press - n_cur_press # Assume this is the calculated pressure difference

[0131] press_diff_scale = press_diff / press_diff_max # Normalize decimals

[0132] balance_step=press_diff_scale*balance_step_max#Calculated pressure difference balance pump frequency step, constrained to the maximum and minimum set balance steps

[0133] According to the calculated balance_step, it is integrated on the current positive or negative pump frequency (p_output, n_output) to obtain the pump frequency for the next adjustment in the "pressure difference balance stage".

[0134] press_err_end=y9#Target pressure adjustment cut-off pressure line, the adjustment is completed when the difference with the target pressure is -2~2kpa

[0135] press_err_max=y10#Set the maximum target difference boundary

[0136] normal_step_max=y11#Set the maximum pump frequency step

[0137] normal_step_min=y12#Set the minimum pump frequency step

[0138] p_err = set_point - p_cur_press # The difference between the target value and the current pressure value of the positive electrode

[0139] n_err = set_point - n_cur_press # The difference between the target value and the current pressure value of the negative electrode

[0140] p_err_scale = p_err / press_err_max # decimal normalization

[0141] n_err_scale = n_err / press_err_max # decimal normalization

[0142] p_normal_step=p_err_scale*normal_step_max#The target difference adjusts the positive electrode pump frequency step and constrains it to the set maximum and minimum pump frequency step

[0143] n_normal_step=n_err_scale*normal_step_max#The target difference adjusts the negative electrode pump frequency step and constrains it to the set maximum and minimum pump frequency step

[0144] According to the calculated p_normal_step and n_normal_step, they are integrated on the current positive and negative electrode pump frequencies (p_output, n_output) to obtain the pump frequency for the next adjustment in the "target pressure adjustment stage".

[0145] p_output=max(min(p_output,p_max_freq),p_min_freq)

[0146] n_output=max(min(n_output,n_max_freq),n_min_freq)

[0147] All calculated pump frequency values ​​for the next step are constrained to the set maximum and minimum pump frequency values.

[0148] Flow regulation involves the following four operating modes:

[0149] (1) The target flow rate regulation stage is the core part of the pump frequency regulation algorithm. The positive and negative electrode pump frequencies are asynchronously adjusted using step-by-step logic so that the current flow rate at the positive / negative electrode electrolyte inlet of the stack (group) gradually approaches the target flow rate value, reducing the step iteration step and speeding up the step iteration completion time.

[0150] (2) The pressure differential balance stage is a concomitant stage of target flow regulation. In the target flow regulation stage, the pressure differential is calculated in real time. When the pressure differential exceeds the set pressure differential threshold, the target flow regulation is stopped and the stage of pressure differential balance is entered. According to the relationship between the target flow and the current flow, the positive or negative pump frequency is adjusted until the pressure differential is less than the threshold. The pressure differential balance is stopped and the stage of target flow regulation is entered. The pressure differential balance can also solve the initial pressure differential inconsistency caused by liquid level imbalance, triggering a pressure differential alarm and failing to start the pump (the current maximum adjustable test is 40kPa, about 3m of liquid level difference).

[0151] (3) The over-limit voltage stabilization stage is the safety protection logic of the regulation algorithm. When the target flow rate is lower than the lower limit of the pump frequency, the positive and negative electrode pumps are synchronously adjusted to the lower limit of the pump frequency. When the target flow rate exceeds the upper limit of the pump frequency, the critical voltage stabilization logic is enabled to adjust the pump frequency to the maximum pressure that can be achieved when the pressure difference between the positive and negative electrode inlets of the stack (group) is balanced.

[0152] (4) The timeout exit phase is the safety protection logic of the regulation algorithm. If the given target flow rate is still not reached after a certain time step, the algorithm may not converge or the system may fail. At this time, the algorithm will stop adjusting and stop the algorithm on the premise of ensuring that the pressure difference between the positive and negative electrodes of the stack (group) meets the protection threshold, so as to prevent endless pump frequency scheduling.

[0153] like Figure 5 As shown, the present disclosure also proposes a method for automatically adjusting the inlet flow rate of the electrolyte of a flow battery stack, the method comprising:

[0154] Adopting stepping logic to asynchronously adjust the positive and negative electrode pumping frequency of the flow battery, and maintaining the pressure difference between the positive and negative electrode electrolyte inlets of the flow battery stack during the adjustment process, and recording the adjustment time in real time;

[0155] When the current flow rate of the electrolyte inlet of the positive and negative electrodes of the flow battery stack reaches the target flow rate, or the adjustment time reaches a preset time threshold, the adjustment of the positive and negative electrode pump frequency of the flow battery is stopped.

[0156] The algorithm flow chart of the automatic adjustment method of the electrolyte inlet flow rate of the flow battery stack is as follows: Figure 6-Figure 8 The specific contents are as follows:

[0157] like Figure 6 As shown, step 1, determine whether there is a pump stop fault at present;

[0158] If there is a pump stop failure, the current process ends;

[0159] If there is no pump stop failure, the target flow command is obtained, and the current operation mode is initially set to the target flow adjustment stage, the cycle step count is initially set to 0, and step 2 is performed;

[0160] Step 2: Determine whether the current cycle step count is less than 100; in this embodiment, 100 is only a reference value and can be set according to actual conditions;

[0161] If the current loop step count is ≥100, the current process ends;

[0162] If the current cycle step count is less than 100, obtain the current positive and negative electrode pump frequency, the current stack positive and negative electrode pressure and their pressure difference, set the required parameters and calculate multiple sets of data, obtain the next step positive and negative electrode pump frequency value = the current positive and negative electrode pump frequency value, and then execute step 3; wherein, the required parameters to be set include: upper and lower limits of positive and negative electrode pump frequency, pressure difference balance cutoff threshold, algorithm single-step maximum adjustable balanced pressure difference, pressure difference balance pump frequency step upper and lower limits, target pressure difference adjustment cutoff threshold, algorithm single-step adjustable maximum target difference and target pressure difference adjustment pump frequency step upper and lower limits, and the multiple sets of data calculated include: pressure difference planning coefficient, pressure difference balance execution step pump frequency, positive and negative electrode target flow difference coefficient and target flow adjustment execution step positive and negative electrode pump frequency.

[0163] like Figure 7 As shown, step 3, judging whether the current operation mode is the non-overlimit pressure stabilization stage, and the current pressure difference exceeds the pressure difference balance cut-off threshold or the current operation mode is the pressure difference balance stage;

[0164] If the above conditions are met at the same time, the operation mode is set to the pressure difference balance stage and step 4 is executed;

[0165] If the above conditions are not met at the same time, go to step 7;

[0166] Step 4: determine whether the current pressure difference meets the pressure difference balance cutoff threshold, or whether the positive and negative target pressure differences both meet the target pressure difference adjustment cutoff threshold;

[0167] If it meets the requirements, the operation mode is set to the target flow adjustment stage, and then step 7 is executed;

[0168] If not, proceed to step 5;

[0169] Step 5, determine whether the current positive or negative electrode pressure needs to be increased;

[0170] If it needs to be increased, when the positive electrode pump frequency is lower than the negative electrode, the next positive electrode pump frequency = current positive electrode pump frequency + pump frequency pressure difference balance step; when the negative electrode pump frequency is lower than the positive electrode, the next negative electrode pump frequency = current negative electrode pump frequency + pump frequency pressure difference balance step;

[0171] If no promotion is required, proceed to step 6;

[0172] Step 6, determining whether the current positive electrode or negative electrode pressure needs to be reduced;

[0173] If it needs to be reduced, when the positive electrode pump frequency is greater than the negative electrode, the next positive electrode pump frequency = current positive electrode pump frequency - pump frequency pressure difference balance step; when the negative electrode pump frequency is greater than the positive electrode, the next negative electrode pump frequency = current negative electrode pump frequency - pump frequency pressure difference balance step;

[0174] If no promotion is required, proceed to step 7;

[0175] Step 7, determining whether the operation mode is the target flow adjustment stage;

[0176] If yes, go to step 8;

[0177] If not, go to step 9;

[0178] Step 8: Determine whether both the positive and negative electrode pressures meet the target flow rate adjustment threshold;

[0179] If all are met, go to step 9;

[0180] If not all of them are met, then when the positive flow rate is greater than the target flow rate, the next step of positive pump frequency = current positive pump frequency - positive pump frequency target pressure adjustment step; when the positive flow rate is less than the target flow rate, the next step of positive pump frequency = current positive pump frequency + positive pump frequency target pressure adjustment step; when the negative flow rate is greater than the target flow rate, the next step of negative pump frequency = current negative pump frequency - negative pump frequency target pressure adjustment step; when the negative flow rate is less than the target flow rate, the next step of negative pump frequency = current negative pump frequency + negative pump frequency target pressure adjustment step, and then execute step 9.

[0181] like Figure 8As shown, in step 9, the positive or negative electrode pump frequency has reached the lower limit, but still does not meet the target flow rate regulation threshold. Does the flow rate need to be reduced or is it currently in the over-limit voltage stabilization stage (lower limit);

[0182] If any of the above conditions is met, the operation mode is set to the over-limit voltage stabilization stage (lower limit), the next step is that the positive and negative electrode pump frequency = the positive and negative electrode pump frequency lower limit, and then execute step 10;

[0183] If not satisfied, go directly to step 10;

[0184] Step 10: The positive or negative electrode pump frequency has reached the upper limit, but still does not meet the target flow rate regulation threshold. Does the flow rate need to be increased or is it currently in the over-limit voltage stabilization stage (high limit)?

[0185] If any of the above conditions is met, execute step 11;

[0186] If not satisfied, go directly to step 12;

[0187] Step 11, determining whether the current pressure difference exceeds the pressure difference balance cutoff threshold;

[0188] If it exceeds, set the operation mode to the over-limit voltage stabilization stage (high limit). If the negative electrode pump frequency is large, the next positive electrode pump frequency = the current positive electrode pump frequency, and the next negative electrode pump frequency = the current negative electrode pump frequency - pump frequency pressure difference balance step. If the positive electrode pump frequency is large, the next negative electrode pump frequency = the current negative electrode pump frequency, and the next positive electrode pump frequency = the current positive electrode pump frequency - pump frequency pressure difference balance step, and then execute step 12;

[0189] If it does not exceed, the next step is that the positive and negative electrode pump frequency = the current positive and negative electrode pump frequency, and step 12 is executed;

[0190] Step 12, constrain the positive and negative electrode pump frequencies to be within their respective upper and lower limits, and execute step 13;

[0191] Step 13, determine whether the positive and negative pump frequencies in the current positive and negative pump frequency domains are equal in the next step;

[0192] If they are equal, end the current process;

[0193] If they are not equal, the next step of positive and negative electrode pump frequency is executed, delaying for 5 seconds, waiting for pressure and flow to change, the cycle step count is +1, and step 2 is executed; in this embodiment, 5 seconds is only a reference value and can be set according to actual conditions.

[0194] The present invention establishes a mathematical model based on the pump frequency and pressure or flow rate of real-time data, and the specific contents are as follows:

[0195] Through the real-time collection of pressure, flow and pump frequency data, the least squares method is used to establish a mathematical model of pump frequency and pressure or flow for prediction and correction, and real-time monitoring of the system's operating status. Once an abnormality is found, an early warning is immediately issued so that timely measures can be taken to prevent incorrect scheduling of the control method, protect the safety of the battery, and improve the stability and reliability of the system.

[0196] (1) The changes in the electrolyte flow and pressure in the pipeline caused by the change in pump frequency are related to the design of the inlet and outlet pipes of the fuel cell stack, the pump performance, the flow resistance inside the fuel cell stack, and the liquid level of the electrolyte storage tank of the flow battery. Therefore, after using the binary method to establish the pump frequency and flow or pressure mathematical model in the early stage, when the pressure or flow predicted by the pump frequency into the model shows a large deviation, it means that the system has failed.

[0197] (2) Fitting of the mathematical relationship model between pump frequency and pressure in the present disclosure:

[0198]

[0199] Where x represents the pump frequency value; random(-d,d) represents the addition of a random error of ±d to the model to simulate the non-fully steady-state environment of the actual operation of the energy storage system; pressure ture Indicates the actual stack inlet pressure value generated at the current pump frequency; pressure diff Indicates the difference between the predicted pressure value and the actual pressure value; pressure predict It indicates the predicted pressure value calculated by the mathematical model; a, b, and c indicate the constant parameters of the mathematical model, and the specific parameter values ​​are calibrated during the simulation. When the predicted and actual values ​​exceed a certain threshold, the algorithm disclosed in this disclosure will issue an alarm to prompt the inspection of relevant pumps, inverters, valve openings, pipelines, and tank level information.

[0200] (3) The mathematical relationship model fitting between pump frequency and flow rate in the present disclosure:

[0201]

[0202] Where x represents the pump frequency value; random(-e,e) represents the random error of ±e added to the model to simulate the non-fully steady-state environment of the actual operation of the energy storage system; flow ture Indicates the actual stack inlet flow value generated at the current pump frequency; flow diff Indicates the difference between the predicted flow value and the actual flow value; flow predict It indicates the predicted flow value calculated by the mathematical model; k, m, n, and p indicate the constant parameters of the mathematical model, and the specific parameter values ​​are calibrated during the simulation. When the predicted and actual values ​​exceed a certain threshold, the algorithm of this technical solution will issue an alarm to prompt the inspection of related pumps, inverters, valve openings, pipelines, and tank liquid level information.

[0203] Due to the advanced nature of the present disclosure, it can be widely used in application fields such as power system peak shaving, renewable energy power generation grid connection, and distributed power generation systems. First, the pressure or flow-oriented liquid flow battery electrolyte circulation pump control method disclosed in the present disclosure can achieve accurate matching with the charging and discharging current or power, thereby improving the efficiency and stability of the battery, and meeting the needs of the fields such as power system peak shaving and renewable energy power generation grid connection for efficient and stable energy storage systems. Secondly, the control method disclosed in the present disclosure can respond to changes in pressure or flow in a timely manner, ensure the stability of the battery's working state, and extend the service life of the energy storage system equipment and the overall system. It has important application value for fields such as distributed power generation systems that have high requirements for power supply stability. Finally, the control method disclosed in the present disclosure has an effective fault warning mechanism, which can prevent the wrong scheduling of the control method and avoid damage to the battery, which is of great significance for the safe operation of the battery. Therefore, the present disclosure has broad market demand and good application prospects.

[0204] Those skilled in the art should understand that although the present disclosure is described in detail with reference to the aforementioned embodiments, it is still possible to modify the technical solutions recorded in the aforementioned embodiments, or to make equivalent replacements for some of the technical features therein; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. A method for automatically adjusting the electrolyte inlet pressure of a flow battery stack, characterized in that: The method comprises: Adopting stepping logic to asynchronously adjust the positive and negative electrode pumping frequency of the flow battery, and maintaining the pressure difference between the positive and negative electrode electrolyte inlets of the flow battery stack during the adjustment process, and recording the adjustment time in real time; When the current pressure of the electrolyte inlet of the positive and negative electrodes of the flow battery stack reaches the target pressure, or the adjustment time reaches a preset time threshold, the adjustment of the positive and negative electrode pump frequency of the flow battery is stopped.

2. The method for automatically adjusting the electrolyte inlet pressure of a flow battery stack according to claim 1, characterized in that: Adopt stepping logic to asynchronously adjust the positive and negative pumping frequency of the flow battery, including: The positive and negative electrode pumping frequencies of the liquid flow battery are adjusted so that the current pressures of the electrolyte inlets of the positive and negative electrodes of the liquid flow battery stack approach the target pressure.

3. The method for automatically adjusting the electrolyte inlet pressure of a flow battery stack according to claim 1, characterized in that: Maintaining the pressure difference between the positive and negative electrolyte inlets of the flow battery stack during the adjustment process includes: Acquire the current pressure of the positive and negative electrode inlets of the flow battery stack in real time and calculate the pressure difference; The pressure difference is compared with a preset pressure difference threshold, and if the pressure difference exceeds the pressure difference threshold, the positive electrode pumping frequency or the negative electrode pumping frequency of the flow battery is adjusted until the pressure difference is lower than the pressure difference threshold.

4. The method for automatically adjusting the electrolyte inlet pressure of a flow battery stack according to claim 1, characterized in that: When the target pressure is lower than the pressure of the pump frequency lower limit, the positive and negative pumps are synchronously adjusted to the pump frequency lower limit; When the target pressure exceeds the upper limit of the pump frequency, the pump frequency is adjusted to the pump frequency value of the maximum pressure that can be achieved when the pressure difference between the positive and negative electrolyte inlets of the battery stack is balanced.

5. The method for automatically adjusting the electrolyte inlet pressure of a flow battery stack according to claim 1, characterized in that: The method further comprises: A predictive alarm mathematical model for the pumping frequency of the positive and negative electrolyte circulation pumps and the positive and negative electrolyte inlet pressures of the flow battery stack is constructed, and pressure anomalies are predicted through the mathematical model.

6. The method for automatically adjusting the electrolyte inlet pressure of a flow battery stack according to claim 5, characterized in that: Construct a mathematical model for predicting and alarming the pump frequency of the positive and negative electrolyte circulation pumps and the positive and negative electrolyte inlet pressures of the flow battery stack, including: Divide the pump frequency range into equal-difference segments to obtain a series of pump frequency values; When the system is in a normal state, multiple sets of positive and negative electrode pump frequency value series corresponding to the positive and negative electrode electrolyte inlet pressure value series of the battery stack are obtained; The multiple sets of data of the pump frequency value series and the corresponding pressure value series are curve fitted to obtain the mathematical model of the pump frequency of the positive and negative electrolyte circulation pumps and the positive and negative electrolyte inlet pressures of the flow battery stack; Get the current positive and negative pump frequency values; Substituting the current pump frequency value into the mathematical model to calculate and obtain the predicted pressure value; The actual pressure value of the battery stack at the current pump frequency is subtracted from the predicted pressure value to obtain the prediction alarm mathematical model of the pump frequency of the positive and negative electrolyte circulation pumps and the positive and negative electrolyte inlet pressures of the flow battery stack.

7. The method for automatically adjusting the electrolyte inlet pressure of a flow battery stack according to claim 6, characterized in that: Get predicted pressure values, including: Get the current pump frequency value and random pressure error; The current pump frequency value is weighted and summed with the random error to obtain the predicted pressure value.

8. A method for automatically adjusting the inlet flow rate of electrolyte in a flow battery stack, characterized in that: The method comprises: Adopting stepping logic to asynchronously adjust the positive and negative electrode pumping frequency of the flow battery, and maintaining the pressure difference between the positive and negative electrode electrolyte inlets of the flow battery stack during the adjustment process, and recording the adjustment time in real time; When the current flow rate of the electrolyte inlet of the positive and negative electrodes of the flow battery stack reaches the target flow rate, or the adjustment time reaches a preset time threshold, the adjustment of the positive and negative electrode pump frequency of the flow battery is stopped.

9. The method for automatically adjusting the inlet flow rate of electrolyte of a flow battery stack according to claim 8, characterized in that: Adopt stepping logic to asynchronously adjust the positive and negative pumping frequency of the flow battery, including: The positive and negative electrode pumping frequencies of the liquid flow battery are adjusted so that the current flow rates of the electrolyte inlets of the positive and negative electrodes of the liquid flow battery stack are close to the target flow rate.

10. The method for automatically adjusting the inlet flow rate of electrolyte of a flow battery stack according to claim 8, characterized in that: Maintaining the pressure difference between the positive and negative electrolyte inlets of the flow battery stack during the adjustment process includes: Acquire the current pressure of the positive and negative electrode inlets of the flow battery stack in real time and calculate the pressure difference; The pressure difference is compared with a preset pressure difference threshold, and if the pressure difference exceeds the pressure difference threshold, the positive electrode pumping frequency or the negative electrode pumping frequency of the flow battery is adjusted until the pressure difference is lower than the pressure difference threshold.

11. The method for automatically adjusting the inlet flow rate of electrolyte of a flow battery stack according to claim 8, characterized in that: When the target flow rate is lower than the flow rate of the pump frequency lower limit, the positive and negative pumps are synchronously adjusted to the pump frequency lower limit; When the target flow rate exceeds the upper limit of the pump frequency, adjust the pump frequency to the pump frequency value of the maximum flow rate that can be achieved when the pressure difference between the positive and negative electrolyte inlets of the battery stack is balanced.

12. The method for automatically adjusting the inlet flow rate of electrolyte of a flow battery stack according to claim 8, characterized in that: The method further comprises: A mathematical model for predicting and alarming the pumping frequency of the positive and negative electrolyte circulation pumps and the inlet flow rate of the positive and negative electrolyte of the flow battery stack is constructed, and flow abnormalities are predicted through the mathematical model.

13. The method for automatically adjusting the inlet flow rate of electrolyte of a flow battery stack according to claim 12, characterized in that: Construct a mathematical model for predicting and alarming the pump frequency of the positive and negative electrolyte circulation pumps and the inlet flow rate of the positive and negative electrolytes of the flow battery stack, including: Divide the pump frequency range into equal-difference segments to obtain a series of pump frequency values; When the system is in a normal state, multiple sets of positive and negative electrode pump frequency value series corresponding to the positive and negative electrode electrolyte inlet flow value series of the battery stack are obtained; The multiple sets of data of the pump frequency value series and the corresponding flow value series are curve fitted to obtain the mathematical model of the pump frequency of the positive and negative electrolyte circulation pumps and the inlet flow rate of the positive and negative electrolyte of the flow battery stack; Get the current positive and negative pump frequency values; Substituting the current pump frequency value into the mathematical model to calculate and obtain the predicted flow value; The actual flow value of the battery stack at the current pump frequency is subtracted from the predicted flow value to obtain the prediction alarm mathematical model of the pump frequency of the positive and negative electrolyte circulation pumps and the positive and negative electrolyte inlet flow rates of the flow battery stack.

14. The method for automatically adjusting the inlet flow rate of electrolyte of a flow battery stack according to claim 13, characterized in that: Get predicted traffic values, including: Get the current pump frequency value and random flow error; The current pump frequency value is weighted and summed with the random error to obtain the predicted flow value.

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