Energy-saving control method, system and medium for a capacitive deionization device

Abstract

The present invention discloses an energy-saving control method, system and medium for a capacitive deionization device. The method of the present invention includes establishing a dynamic equivalent circuit for a capacitive deionization device including a DC / DC converter and two CDI devices, setting the capacitance value of the equivalent double-layer capacitance of the CDI device, the resistance value of the equivalent parallel resistance, and the initial value of the equivalent series resistance, establishing a correction model for the equivalent series resistance when the conductivity of the electrolyte solution changes during the energy recovery process, and comprehensively considering the correction model of the equivalent series resistance and the charge and discharge rate and ohmic loss of the double-layer capacitance of the CDI device during the energy recovery process, and using the dynamic equivalent circuit to obtain the reference current required for the DC / DC converter to perform energy recovery control. The purpose of the present invention is to solve the problem of energy loss caused by the change of solution conductivity during the energy recovery process of traditional capacitive deionization equipment, improve the energy recovery efficiency by dynamically optimizing the energy transmission process, reduce the system operation energy consumption, and achieve efficient energy recovery.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and particularly to an energy-saving control method, system and medium for a capacitive deionization device. Background Art

[0002] Capacitive deionization technology (CDI), also known as electro-adsorption technology, can be used for the treatment of seawater, sewage and wastewater. The electro-adsorption technology drives the ions in the solution to migrate towards the electrodes with opposite charges by applying a stable external electric field, and temporarily stores the ions in the electrical double layer (EDL) formed on the surface of the electrodes and the micropores of the porous electrodes. During this process, the flowing solution purifies the water quality, and then fresh water with a low salt concentration is obtained. When the adsorption of the electrical double layer reaches saturation, after disconnecting the external power supply, reversing the power supply or short-circuiting the two ends of the electrodes can perform desorption, so that the adsorbed ions return to the main body of the solution again and flow out of the CDI device with the flowing solution, obtaining concentrated water with a high salt concentration.

[0003] It should be noted that a key feature of the electro-adsorption technology is its energy storage capacity similar to that of supercapacitors, which allows the use of the electric double layer to store energy during the desalination process and recover it during the desorption stage. During the adsorption process of a CDI device, most of the input energy of the externally applied electric field will be stored in the electric double layer formed at the interface between the electrode and the solution. As the adsorption progresses, the number of ions accumulated on the formed electric double layer increases, and the adsorption process can be equivalently considered as a process of charging the electric double layer capacitor. During the desorption process of a CDI device, ions return to the intermediate flow channel from the electric double layer at the interface and the micropores of the porous electrode, and the process of the gradual disappearance of the electric double layer formed at the interface between the electrode and the solution can be equivalently considered as the discharging of the formed electric double layer capacitor. Existing experimental studies have shown that under a reasonable energy recovery scheme for a Membrane Capacitive Deionization (MCDI) unit, the energy recovery rate for capacitor charging can reach 83%, and the energy recovery rate of the CDI unit can reach 62.1%. Recycling the energy released during the desorption process of a CDI device will directly improve the energy efficiency of the CDI device. Before the introduction of a DC / DC (direct current) converter, the energy recovery process of a CDI device was often difficult to control. When energy is transferred from one CDI series unit to another, the transferred current may be instantaneously too large, causing system instability and even permanent damage to the device and the electrode. In addition, when the voltages of two CDI devices reach the same value, the energy transfer will automatically stop, thus making the seawater desalination process unable to continue and resulting in energy waste. To overcome the above problems, the introduction of a DC / DC converter can accurately control the energy recovery and transfer process, not only avoiding the problem of excessive current but also maintaining the effective transfer of energy under different voltage conditions.

[0004] Existing research has not proposed a comprehensive regulation strategy for the reference current, making the adjustment of the reference current unable to fully reflect the actual requirements during the energy recovery process, resulting in unstable energy recovery efficiency and the possibility of significant energy losses. Existing research usually discusses the experimental results of energy recovery rate, loss distribution, and energy recovery rate under different working conditions using different reference currents for energy recovery. When it comes to the method of dynamically adjusting the reference current, it only focuses on the evaluation and calculation of a certain performance index and has not proposed a regulation strategy that takes into account both the energy recovery rate and the recovery efficiency. This makes the adjustment of the reference current often unable to fully reflect the actual requirements during the energy recovery process under different working conditions, resulting in unstable energy recovery efficiency and possible significant losses. Summary of the Invention

[0005] Technical problem to be solved by the present invention: In view of the above-mentioned problems in the prior art, an energy-saving control method, system and medium for capacitor deionization equipment are provided. The present invention aims to solve the problem of energy loss caused by changes in solution conductivity that are not taken into account in the energy recovery process of traditional capacitor deionization equipment, and to improve energy recovery efficiency by dynamically optimizing the energy transmission process, reduce system operating energy consumption, and achieve efficient energy recovery.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A method for energy saving control of capacitor deionization equipment comprises the following steps:

[0008] S1, establishing a dynamic equivalent circuit for a capacitor deionization equipment including a DC / DC converter and two CDI devices, wherein each CDI device is equivalent to an equivalent double-layer capacitor, an equivalent parallel resistor and an equivalent series resistor, the equivalent parallel resistor and the equivalent double-layer capacitor are connected in parallel and then connected in series with the equivalent series resistor, the DC / DC converter is equivalent to an inductor L, a sensor resistor Rsensor, two equivalent power electronic switches and a controller, one end of the two CDI devices is directly connected and the other end is connected through two equivalent power electronic switches, the series branch formed by the inductor L and the sensor resistor Rsensor is connected in parallel between the loops of the two CDI devices, and the control ends of the two equivalent power electronic switches are connected to the controller;

[0009] S2, setting the capacitance value of the equivalent double-layer capacitor, the resistance value of the equivalent parallel resistor and the initial value of the equivalent series resistor of the CDI device, and establishing a correction model of the equivalent series resistor when the conductivity of the electrolyte solution changes during the energy recovery process;

[0010] S3, combining the correction model of equivalent series resistance and the charge and discharge rate and ohmic loss of the double-layer capacitor of the CDI device during the energy recovery process, and using the dynamic equivalent circuit to obtain the reference current required for the DC / DC converter to perform energy recovery control;

[0011] The functional expression of the correction model of the equivalent series resistance in step S2 is:

[0012] ,

[0013] in, For the The equivalent series resistance of CDI devices in this round The correction value of For the The initial value of the equivalent parallel resistance of each CDI device, is the distance between the electrodes of the CDI device, is the electrode surface area of ​​the CDI device, is the initial electrolyte solution conductivity of the th CDI device, is the electrolyte solution conductivity of the th CDI device in this round.

[0014] Optionally, step S3 includes:

[0015] S3.1, initialize the iteration variable to 1, detect and obtain the initial voltage of the desorption energy-releasing CDI device and the electrolyte solution conductivity , and the initial voltage of the adsorption energy-consuming CDI device and the electrolyte solution conductivity ;

[0016] S3.2, calculate the reference current in this round :

[0017] ,

[0018] wherein, is the initial voltage value of the desorption energy-releasing CDI device, is the double-layer capacitance value of the desorption energy-releasing CDI device, is the expected construction period for energy recovery;

[0019] S3.3, use the reference current in this round to control the DC / DC converter to perform energy recovery operation within the period of this round ; detect and obtain the parameters at the end of the period of this round , including: the voltage and the electrolyte solution conductivity of the desorption energy-releasing CDI device in this round , and the voltage and the electrolyte solution conductivity of the adsorption energy-consuming CDI device in this round ; if the voltage of the desorption energy-releasing CDI device in this round is less than the preset threshold, then end and exit; otherwise, jump to step S3.5;

[0020] S3.4, calculate the ohmic loss in this round and the ideal voltage of the desorption energy-releasing CDI device according to the parameters at the end of the period in this round ​ ;

[0021] S3.5, if the ohmic loss in this round is greater than or equal to the ohmic loss in the previous round , then reduce the reference current in this round to obtain the reference current in the next round ; if the ohmic loss in this round is less than the ohmic loss in the previous round , and the voltage of the desorption exothermic CDI device in this round is less than the ideal voltage of the desorption exothermic CDI device , then reduce the reference current in this round to obtain the reference current in the next round ; if the ohmic loss in this round is less than the ohmic loss in the previous round , and the voltage of the desorption exothermic CDI device in this round is greater than or equal to the ideal voltage of the desorption exothermic CDI device , then increase the reference current in this round to obtain the reference current in the next round

[0022] Optionally, the calculation function expression of the ohmic loss n in this round in step S3.4 is:

[0023] ,

[0024] where and are the loss values of the equivalent series resistance in this round and of the desorption exothermic CDI device and the adsorption endothermic CDI device respectively, and are the loss values of the equivalent parallel resistance They are the capacitance values ​​of the double-layer capacitors of the desorption energy-releasing CDI equipment and the adsorption energy-using CDI equipment, respectively. and They are desorption energy release CDI equipment and adsorption energy use CDI equipment. The voltage is:

[0025] ,

[0026] ,

[0027] in, For the The equivalent series resistance of CDI devices in this round The loss value, For this round The reference current, For the The equivalent series resistance of CDI devices in this round n The correction value of To adjust the interval time parameters, For the The equivalent parallel resistance of CDI devices in this round The loss value, For the CDI equipment in this round The voltage, The value is 1 or 2. When it is 1, it means desorption and energy release CDI equipment, When it is 2, it indicates adsorption energy CDI equipment.

[0028] Optionally, in step S3.4, this round n The ideal voltage for desorption and release of CDI equipment The calculation function expression is:

[0029] ,

[0030] in, For the previous round n- 1 Ideal voltage for desorption and energy release CDI equipment, For this round n The reference current, To adjust the interval time parameters, It is the capacitance value of the double-layer capacitor of the desorption energy-releasing CDI device.

[0031] Optionally, in step S3.5, the current round is reduced Reference current To get the next round Reference current The function expression is:

[0032] ,

[0033] wherein, is an adjustment ratio factor less than 1.

[0034] Optionally, in step S3.5, the reference current of this round is increased to obtain the reference current of the next round The function expression of is:

[0035] ,

[0036] wherein, is an adjustment ratio factor less than 1.

[0037] In addition, the present invention also provides an energy-saving control system for a capacitive deionization device, including a microprocessor and a memory connected to each other, and the microprocessor is programmed or configured to execute the energy-saving control method of the capacitive deionization device.

[0038] In addition, the present invention also provides a computer-readable storage medium, in which a computer program or instruction is stored, and the computer program or instruction is programmed or configured to execute the energy-saving control method of the capacitive deionization device through a processor.

[0039] In addition, the present invention also provides a computer program product, including a computer program or instruction, and the computer program or instruction is programmed or configured to execute the energy-saving control method of the capacitive deionization device through a processor.

[0040] Compared with the prior art, the present invention mainly has the following advantages: The method of the present invention includes establishing a correction model of the equivalent series resistance when the conductivity of the electrolyte solution changes during the energy recovery process, integrating the dynamic change characteristics of the electrolyte conductivity, comprehensively considering the charge and discharge rate and ohmic loss of the double-layer capacitor of the CDI device during the energy recovery process, and using a dynamic equivalent circuit to obtain the reference current required for the DC / DC converter to perform energy recovery control, which can solve the problem of energy loss caused by the change of solution conductivity not being considered during the energy recovery process of traditional capacitive deionization equipment, improve the energy recovery efficiency by dynamically optimizing the energy transmission process, reduce the system operation energy consumption, and achieve efficient energy recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a schematic diagram of the basic process of the method of the embodiment of the present invention.

[0042] Figure 2 is a schematic diagram of the structure of the capacitive deionization device in the embodiment of the present invention.

[0043] Figure 3 Schematic diagram of the circuit principle of the dynamic equivalent circuit in the embodiment of the present invention.

[0044] Figure 4 Schematic diagram of the energy recovery control process in the embodiment of the present invention.

[0045] Figure 5 Magnitude of the inductor current of the DC / DC converter in the embodiment of the present invention Schematic curve diagram.

[0046] Figure 6 Schematic diagram of the change in the outlet solution concentration of the CDI device for three schemes in the embodiment of the present invention.

[0047] Figure 7 Result comparison chart of four indicators including energy recovery time, ion removal amount, ion removal rate, and energy recovery rate for three schemes in the embodiment of the present invention. Detailed implementation manners

[0048] The present invention aims to consider the influence of the change in the electrolyte solution concentration on energy loss during the energy recovery process of a CDI (Capacitive Deionization) device, dynamically regulate and optimize the magnitude of the reference current in the DC / DC converter, and achieve more efficient energy recovery. Existing methods guide the adjustment of the reference current of the DC / DC converter by electrical modeling of the CDI device, but do not consider the influence of solution concentration changes on ion loss and resistance, and use fixed equivalent values for calculation. This approach results in inaccurate adjustment of the reference current, which may lead to distortion of the electric energy recovery efficiency and cause energy waste. To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings in the embodiments of the present invention.

[0049] As Figure 1 shown, the energy-saving control method for the capacitive deionization equipment in this embodiment includes the following steps:

[0050] S1. Establish a dynamic equivalent circuit for the capacitive deionization equipment including a DC / DC converter and two CDI devices.

[0051] S2. Set the capacitance value of the equivalent double-layer capacitor of the CDI device, the resistance value of the equivalent parallel resistor, and the initial value of the equivalent series resistor, and establish a correction model for the equivalent series resistor when the conductivity of the electrolyte solution changes during the energy recovery process;

[0052] S3. Using the corrected model of the equivalent series resistance and the charging and discharging rates and ohmic losses of the double-layer capacitance of the CDI device during the energy recovery process, obtain the reference current required for the DC / DC converter to perform energy recovery control using the dynamic equivalent circuit.

[0053] As Figure 2 shown, the capacitive deionization equipment in this embodiment includes a DC / DC converter and two CDI devices. Raw water is respectively sent into the two CDI devices through a water pump. One of the two CDI devices is used as a desorption energy-releasing CDI device, and the other is used as an adsorption energy-consuming CDI device. The raw water is treated by the desorption energy-releasing CDI device to obtain concentrated water with a higher ion concentration than the raw water and generate directed electrons that are sent into the DC / DC converter. Under the action of the DC / DC converter, a reference current is generated and applied to the electrodes of the adsorption energy-consuming CDI device to generate a potential difference to treat the raw water flowing into the adsorption energy-consuming CDI device to obtain fresh water with a lower ion concentration than the raw water. The double-layer formed at the interface between the electrode and the solution in the desorption energy-releasing CDI device gradually disappears, and ions return to the intermediate flow channel from the double-layer at the interface and the micropores of the porous electrode, driving the metal current collector plate to generate directed electrons to supply the DC / DC buck-boost converter device. Under the action of the DC / DC buck-boost converter device, a reference current is output and applied to the electrodes of the adsorption energy-consuming CDI device, thereby generating a certain potential difference between its electrodes. The adsorption energy-consuming CDI device starts to adsorb ions in the solution and stores most of the input energy in the double-layer formed at the interface between the electrode and the solution.

[0054] During the operation of the multi-capacitive deionization equipment, raw water to be treated is introduced into one end of both the desorption energy-releasing CDI device and the adsorption energy-consuming CDI device. The other end treated by the desorption energy-releasing CDI device will obtain concentrated water with a higher ion concentration than the raw water, and the other end treated by the adsorption energy-consuming CDI device will obtain fresh water with a lower ion concentration than the raw water. The capacitive deionization equipment may further include a raw water storage tank, an electric pump, a concentrated water storage tank, and a fresh water storage tank. The raw water stored in the raw water storage tank is sent into the two CDI devices through the electric pump. The water outlet of the desorption energy-releasing CDI device among the two CDI devices is communicated with the concentrated water storage tank, and the water outlet of the adsorption energy-consuming CDI device is communicated with the fresh water storage tank. The raw water, concentrated water, and fresh water are stored in different storage tanks, and an electric pump is used to pump the solution into the desorption energy-releasing CDI device and the adsorption energy-consuming CDI device. In this embodiment, the DC / DC converter is composed of two series-connected power electronic switches.

[0055] Figure 3 is a schematic diagram of the circuit principle of the dynamic equivalent circuit in this embodiment. As Figure 3As shown, the dynamic equivalent circuit of the capacitive deionization system with a buck-boost converter established in this embodiment includes: an equivalent circuit of a CDI device that is desorbing and releasing energy, an equivalent circuit of a CDI device that is adsorbing and consuming energy, and an equivalent circuit of a DC / DC converter. Among them, the test methods for the equivalent circuit configuration and parameters of the capacitive deionization device during desorption and energy release or adsorption and energy consumption are the same. It is only the distinction in the working state of the capacitive deionization device. One belongs to equivalent discharge, and the other belongs to equivalent charge. The parameter values of the capacitive deionization equivalent circuit elements should be obtained according to the performance differences and operating conditions of the device itself. In Figure 3 the subscript number 1 is marked for the equivalent circuit element parameters of the desorbing and energy-releasing CDI module, and the subscript number 2 is marked for the equivalent circuit element parameters of the adsorbing and energy-consuming CDI module. In this embodiment, each CDI device in the dynamic equivalent circuit is equivalent to an equivalent double-layer capacitor, an equivalent parallel resistor, and an equivalent series resistor. The equivalent parallel resistor and the equivalent double-layer capacitor are connected in parallel and then connected in series with the equivalent series resistor. This equivalent circuit model is widely used in the performance evaluation of CDI devices, the analysis of energy recovery efficiency, and system optimization research due to its reasonable simplification of the parameters of the real complex circuit and its high generalization of the CDI system behavior. Among them, the equivalent series resistor in the capacitive deionization equivalent circuit is a key time-varying parameter in the energy recovery optimization process, which is used to equivalent various constant or stable resistances generated by the device circuit wires and their connection points, the collector and the electrode porous medium contact during the operation of the CDI device, and the ion resistance suffered by the directional migration of ions in the electrolyte solution under the action of the electric field. This value needs to be corrected in real time during the energy recovery process. The equivalent parallel resistor is used to equivalent the non-ideal behavior in the actual system, such as the leakage phenomenon on the double-layer capacitor. This value can be regarded as a constant during the energy recovery process. The equivalent double-layer capacitor is used for the charge distribution and storage ability between the electrode and the solution. Its value describes the charge storage characteristics at the electrode and electrolyte interface and is also a specific equivalent element for the specific adsorption effect of the CDI device on the ions in the solution. This value can be regarded as a constant during the energy recovery process. The current input or output on the double-layer capacitor is called the double-layer current. Without considering more complex ion effects and losses, the amount of charge transferred by the double-layer current can be approximately used to obtain the number of ions adsorbed by the CDI device through Faraday's law (Faraday's law is: , where: is the amount of charge transferred by the double-layer current, unit, Coulomb; is the number of ions adsorbed by the CDI device, unit, mole; is the Faraday constant, approximately 96485, unit, Coulomb per mole).

[0056] In this embodiment, the DC / DC converter is equivalent to a bidirectional buck-boost converter circuit. The bidirectional buck-boost converter circuit includes an inductor L, a sensing resistor Rsensor, two equivalent power electronic switches (MOSFET 1 and MOSFET 2), and a controller. One end of two CDI devices is directly connected, and the other end is connected through two equivalent power electronic switches. The series branch composed of the inductor L and the sensing resistor Rsensor is connected in parallel between the circuits of the two CDI devices. The control ends of the two equivalent power electronic switches are connected to the controller. When the capacitive deionization system recovers energy, one of the capacitive deionization devices desorbs and releases energy, and the other capacitive deionization device adsorbs and uses energy, and the energy is transferred through the buck-boost converter circuit. Among them, in addition to MOSFETs, IGBTs can also be used as power electronic switches. The test methods for the equivalent circuit parameters when the capacitive deionization device desorbs and releases energy or adsorbs and uses energy are the same. It is only the distinction in the working state of the capacitive deionization device. One belongs to equivalent discharge, and the other belongs to equivalent charge. The equivalent circuit element parameter values of the capacitive deionization are different according to the differences of the device itself and the operating conditions. During the energy transfer process, the DC / DC buck-boost converter uses a feedback control system (such as a PID controller) to adjust the switching frequency and duty cycle, so as to adjust the relationship between the input voltage and the output voltage in real time. In this embodiment, the controller regulates the switching states of MOSFET1 and MOSFET2 by outputting PWM signals generated by the PID controller, ensuring that the current passing through the inductor L approaches the set reference current value, and then controllably adjusting the magnitude of the transfer current during the energy recovery of the CDI device. The bidirectional buck-boost converter circuit constitutes a switching power supply. Because of its high efficiency, small size, and strong adaptability, it is widely used in modern electronic devices, covering almost all fields that require electric energy conversion. It can not only provide a stable output but also has good regulation ability. In this embodiment, the switching power supply can effectively manage energy during the charging and discharging processes of the device. One capacitive deionization device is used for energy desorption, and the other capacitive deionization device is used for energy adsorption, and the energy is transferred through the buck-boost converter.

[0057] The capacitance value of the equivalent double-layer capacitor of the CDI device is regarded as a constant value. Using the change information of the potential during the stable adsorption operation of the device, the corresponding equivalent capacitance value can be equivalently obtained. The acquisition method is as follows: During the adsorption stage of the capacitive deionization device, a constant DC current source I is applied to the capacitive deionization device for adsorption and desalination. Its voltage almost linearly rises with time, which is considered to be the linear voltage rise caused by the constant current charging of the equivalent double-layer capacitor. According to the formula:

[0058] ,

[0059] Among them, is the voltage value of the CDI device at time t, is the voltage value of the CDI device after t = 0 (i.e., the voltage value after an overvoltage jump), is a constant DC current value, is the capacitance value of the equivalent electric double layer capacitor, is time. By using an oscilloscope or a voltmeter to obtain the slope K of the diagonal line in the V - t (voltage - time) graph of the voltage change of the capacitive deionization device over time, the capacitance value of the equivalent electric double layer capacitor can be obtained. .

[0060] The resistance value of the equivalent parallel resistance of the CDI device is a constant value, which is used to equivalent the non - ideal behavior in the actual system, such as the leakage phenomenon on the electric double layer capacitor. The acquisition method is as follows: During the adsorption stage of the capacitive deionization device, it can be considered that the capacitance value of the equivalent electric double layer capacitor is charged. When the voltage change is sufficient to obtain the slope K of the diagonal line in the above - mentioned V - t graph of the voltage change of the capacitive deionization device over time and deduce the capacitance value of the equivalent electric double layer capacitor, the solution conductivity fluctuation in the channel of the capacitive deionization device is still relatively gentle. At this time, the external DC current source can be disconnected, and it is regarded as the charged electric double layer capacitor discharging to the equivalent parallel resistance. According to the voltage formula of capacitor discharging in the RC circuit:

[0061] ,

[0062] where, is the initial voltage value during discharging after disconnecting the external power supply, e is the base of the natural logarithm, t is time, Cdl is the measured value of the equivalent electric double layer capacitor, is the equivalent parallel resistance. By obtaining the voltage value of the capacitive deionization device at the corresponding time t, the numerical value of the equivalent parallel resistance can be calculated.

[0063] The equivalent series resistance of the CDI device is a key time-varying parameter in the energy recovery optimization process, and its initial value must be obtained first. Obtaining the initial value of the equivalent series resistance of the CDI device includes: when the capacitive deionization device starts to enter the adsorption stage, a constant DC current source is applied to it first. At the moment when the switch is closed and turned on, it is considered that the voltage value on the equivalent double-layer capacitor in the equivalent circuit does not change suddenly. Therefore, at t = 0, the instantaneous voltage change value of the capacitive deionization device is divided by the applied DC current value to approximately obtain the initial value of the series resistance of the equivalent circuit. Among them, the constant DC current can be provided by a constant current supply, and the voltage change can be measured by connecting a voltmeter in parallel. Similarly, a constant voltage source can also be applied when entering the adsorption stage. At the moment when the switch is closed and turned on, it is considered that the voltage value on the equivalent double-layer capacitor Cdl in the equivalent circuit does not change suddenly. Therefore, at t = 0, the instantaneous current change value of the capacitive deionization device is measured, and the constant voltage source value is divided by the instantaneous current change value to approximately obtain the initial value of the series resistance of the equivalent circuit. Among them, the constant voltage can be provided by a constant current voltage supply, and the current change value can be measured by connecting an ammeter in series.

[0064] In addition, the inductance L used in the bidirectional buck-boost converter circuit can be selected according to experience. Generally, a value of 10 μH - 100 μH is selected as needed. The circuit switches composed of power electronic components IGBT or MOSFET and components such as sensing resistors, amplifiers, and controllers that meet the usage requirements are all acceptable. The correction model of the equivalent series resistance in step S2 includes the correction value of the equivalent series resistance of the CDI device and the functional relationship between the electrolyte solution conductivities at different times during the energy recovery process. The functional expression of the correction model of the equivalent series resistance in step S2 of this embodiment is:

[0065] ,

[0066] Among them, is the correction value of the equivalent series resistance of the th CDI device in this round, is the initial value of the equivalent parallel resistance of the th CDI device, is the distance between the electrodes of the CDI device, is the electrode surface area of the CDI device, is the initial electrolyte solution conductivity of the th CDI device, is the electrolyte solution conductivity of the th CDI device in this round, is the The conductivity of the electrolyte solution. The various constant or stable resistances generated by the device circuit wires and their connection points during the operation of the CDI device, the collector and the contact of the electrode porous medium, as well as the ionic resistance encountered by the directional migration of ions in the electrolyte solution under the action of the electric field. As the CDI device releases electrical energy during desorption, the ions adsorbed on the electrode surface return to the spacer channels of the CDI device, and the concentration of the electrolyte solution increases; as the CDI device absorbs electrical energy during adsorption, the ions in the spacer channels of the CDI device are adsorbed on the electrode surface, and the concentration of the electrolyte solution decreases. Use a conductivity meter to measure the initial solution conductivity of the CDI device and the instantaneous conductivity value of the spacer channel , input the conductivity value into the correction relation of the equivalent series resistance, and then correct the equivalent series resistance parameter value.

[0067] In the energy recovery system based on the CDI device, in this embodiment, the reference current of the bidirectional buck-boost converter circuit is dynamically regulated Iref to achieve optimal control of energy transfer. During operation, the voltage at the energy input end (i.e., the CDI device that releases energy during desorption) gradually decreases, while the voltage at the energy output end (i.e., the CDI device that consumes energy during adsorption) gradually increases. This dynamic change in voltage directly affects the energy transfer efficiency. In addition, as the CDI device operates, the time-varying resistance characteristics of the electrolyte solution cause the ohmic loss of the system to show a non-linear change law. Therefore, reasonably adjusting the value of the reference current can not only effectively reduce the ohmic loss of the CDI device, but also compensate and eliminate the random errors during the operation of the CDI device, enabling the device to reach the set construction period on time. As Figure 4 shown, step S3 in this embodiment includes:

[0068] S3.1, initialize the iteration variable to 1, detect and obtain the initial voltage of the CDI device that releases energy during desorption and the conductivity of the electrolyte solution , as well as the initial voltage of the CDI device that consumes energy during adsorption and the conductivity of the electrolyte solution ;

[0069] S3.2, calculate the reference current for this round :

[0070] ,

[0071] wherein, is the initial voltage value of the CDI device that releases energy during desorption, is the double-layer capacitance value of the CDI device that releases energy during desorption, The expected duration for energy recovery;

[0072] S3.3, Use the reference current of this round to control the DC / DC converter to perform energy recovery operation within the period of this round ; Detect and obtain the parameters at the end of the period of this round , including: the voltage of the desorption and energy release CDI device in this round and the conductivity of the electrolyte solution , as well as the voltage of the adsorption energy consumption CDI device in this round and the conductivity of the electrolyte solution ; If the voltage of the desorption and energy release CDI device in this round is less than the preset threshold (e.g., 0.1V), then end and exit; otherwise, jump to step S3.5;

[0073] S3.4, Calculate the ohmic loss of this round and the ideal voltage of the desorption and energy release CDI device based on the parameters at the end of the period of this round ;

[0074] S3.5, If the ohmic loss of this round is greater than or equal to the ohmic loss of the previous round , then reduce the reference current of this round to obtain the reference current of the next round ; If the ohmic loss of this round is less than the ohmic loss of the previous round and the voltage of the desorption and energy release CDI device in this round is less than the ideal voltage of the desorption and energy release CDI device ​​​​​​​​​​​​​​​, and the desorption energy release CDI device in this cycle voltage is greater than or equal to the ideal voltage of the desorption energy release CDI device , then increase the reference current in this cycle to obtain the reference current in the next cycle ; increment the iteration variable by 1, and jump to step S3.3. ;

[0075] In step S3.1 of this embodiment, = 0.51 V (volt), = 0 V (volt), = 0.32 S / m (siemens per meter), = 0.28 S / m (siemens per meter); the expected construction period duration for energy recovery in step S3.2 can be taken according to actual needs. For example, in this embodiment, ; the initial reference current is 0.04 A (ampere). The initial ohmic loss in step S3.5 is 0.2.

[0076] In addition, to address the problem of lacking a multi-factor comprehensive regulation strategy for the reference current, this embodiment proposes a dynamic adjustment strategy based on real-time calculation of two key indicators: ohmic efficiency and energy recovery rate. In this strategy, the ohmic efficiency reflects the resistance loss situation in the current adjustment cycle, while the energy recovery rate measures whether the energy recovery meets the expectations. By considering these two indicators comprehensively, the reference current can be adjusted more precisely to maximize the energy recovery efficiency while ensuring the stability and continuity of the energy recovery process. This comprehensive regulation method takes into account both the energy conversion efficiency of the system and the energy recovery speed, and is a more reasonable and scientific method for adjusting the reference current, thereby optimizing the energy recovery performance of the CDI system.

[0077] In step S3.4 of this embodiment, the calculation function expression for the ohmic loss n in this cycle is:

[0078] ,

[0079] where and are the loss values of the equivalent series resistances of the desorption energy release CDI device and the adsorption energy consumption CDI device in this cycle , and are the equivalent parallel resistances of the desorption energy release CDI device and the adsorption energy consumption CDI device in this cycle The loss value, and They are the capacitance values ​​of the double-layer capacitors of the desorption energy-releasing CDI equipment and the adsorption energy-using CDI equipment, respectively. and They are desorption energy release CDI equipment and adsorption energy use CDI equipment. The voltage is:

[0080] ,

[0081] ,

[0082] in, For the The equivalent series resistance of CDI devices in this round The loss value, For this round The reference current, For the The equivalent series resistance of CDI devices in this round n The correction value of To adjust the interval time parameters, For the The equivalent parallel resistance of CDI devices in this round The loss value, For the CDI equipment in this round The voltage, The value is 1 or 2. When it is 1, it means desorption and energy release CDI equipment, When it is 2, it indicates adsorption energy CDI equipment.

[0083] In step S3.4 of this embodiment, this round n The ideal voltage for desorption and release of CDI equipment The calculation function expression is:

[0084] ,

[0085] in, For the previous round n- 1 Ideal voltage for desorption and energy release CDI equipment, For this round n The reference current, To adjust the interval time parameters, It is the capacitance value of the double-layer capacitor of the desorption energy-releasing CDI device.

[0086] It should be noted that in step S3.5, the current round is reduced Reference current To get the next round Reference current The desired implementation method can be adopted as needed, such as multiplying by a coefficient less than 1 or subtracting an increment, etc., where the increment can be a constant or a dynamically changing value. As an optional implementation method, in step S3.5 of this embodiment, the current round is reduced. Reference current To get the next round Reference current The function expression is:

[0087] ,

[0088] in, It is an adjustment proportional factor less than 1, and can be set according to actual needs. For example, in this embodiment, the value is 0.05.

[0089] It should be noted that the increase in this round in step S3.5 Reference current To get the next round Reference current The desired implementation method can be adopted as needed, such as multiplying by a coefficient greater than 1 or adding an increment, where the increment can be a constant or a dynamically changing value. As an optional implementation method, in step S3.5 of this embodiment, the current round is increased Reference current To get the next round Reference current The function expression is:

[0090] ,

[0091] in, An adjustment scale factor less than 1.

[0092] In the bidirectional buck-boost step-up and step-down circuit, the reference current value needs to be adjusted in real time to control the transfer current size of the energy input and output ends. During operation, the voltage of the energy input end, i.e., the desorption and release CDI device, will become lower and lower, and the voltage of the energy output end, i.e., the adsorption and use CDI device, will become higher and higher. The energy transmission loss varies at each stage, depending on the operation of the CDI device, especially the change in the resistance of the electrolyte solution. The adjustment interval time parameters are determined according to the accuracy of sampling instruments such as voltmeters and conductivity meters. (Unit: seconds, s), the reference current value is After a certain period of time, an evaluation adjustment is performed, so The value of the reference current is adjusted to adjust the frequency. In this embodiment s. The energy recovery adjustment period is named , ,…, , where n is the number of cycles. By analogy, when the voltage value of the desorption and energy release CDI device is less than 0.1 V (volt), it is regarded as the end of the energy recovery stage, and the power adjustment ends. At the beginning of the energy recovery stage, after determining the initial parameters, the adjustment period starts. The initial parameters include: the initial reference current value estimated from the expected total recovery duration: , the initial voltage value of the desorption and energy release CDI device: , the initial voltage value of the adsorption energy consumption CDI device: (usually 0 V, and the voltage value is measured by a voltmeter), the initial electrolyte solution conductivity of the desorption and energy release CDI device: , the initial electrolyte solution conductivity of the adsorption energy consumption CDI device: (the conductivity value is measured by a conductivity meter), and the initial reference ohmic loss (this value can be selected according to empirical values). During the energy recovery process of the system, the system will obtain real-time solution conductivity, current, and potential data to calculate and regulate the reference current in the DC / DC converter in real time until the output voltage of the desorption and energy release CDI device is less than 0.1 V, it is considered that the electric double layer capacitor can no longer drive the system for energy recovery and the energy recovery is terminated.

[0093] In this embodiment, an experimentally verified electrochemistry-fluid dynamics coupled multi-physics field simulation model is used to verify the energy-saving control method. Three comparative experimental schemes are set. The system parameters, initial voltages, inlet flow rates (0.42 ml / min in this embodiment, milliliters per minute), etc. of the desorption and energy release CDI device and the adsorption energy consumption CDI device used in the three groups of schemes are all the same. Scheme one is the direct energy transfer mode without a DC / DC converter. The output voltage of the desorption and energy release CDI device is directly connected to the input voltage of the adsorption energy consumption CDI device. The energy recovery termination condition is: = ±0.01 V (voltage balance threshold). Scheme two is the constant current control mode with a bidirectional buck-boost converter. A DC / DC buck-boost converter is used for energy recovery and utilization between CDI devices. The set constant reference current value is 0.04±2% A (ampere). The energy recovery termination condition is ≤0.1 V±5 mV measurement error. Scheme three is the dynamic current regulation mode with a bidirectional buck-boost converter. A DC / DC buck-boost converter is used for energy recovery and utilization between CDI devices. The initial reference current = 0.04 A (ampere). According to the charging and discharging rate of the electric double-layer capacitor and the ohmic loss index of the energy recovery system, the reference current is dynamically regulated. The value of Figure 5 is shown as a schematic diagram of the reference current of the DC / DC converter after dynamic current regulation operation. Figure 6 Shown is the variation of the concentration C at the outlet of the CDI device for adsorption energy consumption with the adsorption time t under the above three different schemes. For Scheme 1, after about 300 s, the energy transfer process can be regarded as stopped, and the concentration at the outlet finally stabilizes at about 16 mM. Moreover, the concentration decreases relatively fast, and the time efficiency of this scheme is relatively high. However, there are fluctuations and inflection points in the outlet concentration curve, indicating that the energy transfer process is not stable and controllable enough. For Scheme 2, after about 500 s, the energy transfer process can be regarded as stopped, which deviates from the expected construction period of 600 s to a certain extent. The concentration at the outlet continuously decreases to about 14 mM, and the concentration decreases at a uniform rate. After 200 s of adsorption, the concentration at the outlet can be considered to show a linear decrease, reflecting the high adsorption stability of this scheme. For Scheme 3, after about 610 s, the energy transfer process can be regarded as stopped, which is very close to the expected construction period of 600 s. The concentration at the outlet continuously decreases to about 12 mM, and the concentration decreases even more uniformly. After 200 s of adsorption, the concentration at the outlet can be considered to show a linear decrease, reflecting the high adsorption stability of this scheme. The dynamic regulation of the reference current has an effect on improving the system efficiency and controlling the electric double-layer discharge rate. Figure 7 Shown is a comparison chart of the results of the energy recovery time, ion removal amount, ion removal rate, and energy recovery rate under the above three different schemes. Among them, for Schemes 2 and 3 equipped with a DC / DC converter, both the ion removal amount and the energy recovery rate are increased compared with Scheme 1. And Scheme 3 with a dynamic current regulation mode is superior to the other two groups of schemes in terms of ion removal amount, ion removal rate, and energy recovery rate. In this embodiment, the scheme of configuring a DC / DC converter with a dynamic current regulation mode improves the energy recovery rate by 7.8%, the ion removal rate by 1.9%, and the ion removal amount by 1.36 times compared with the scheme without a DC / DC converter. Compared with the scheme of configuring a DC / DC converter with a constant current mode, it improves the energy recovery rate by 6.1%, the ion removal rate by 4.5%, and the ion removal amount by 0.7 times. And the error from the expected working duration is only 2%, which verifies that the method of this embodiment can effectively improve the energy utilization rate of the capacitive deionization equipment and achieve efficient energy recovery and reuse.

[0094] In addition, this embodiment also provides an energy-saving control system for a capacitive deionization equipment, including a microprocessor and a memory connected to each other. The microprocessor is programmed or configured to execute the energy-saving control method of the capacitive deionization equipment.

[0095] In addition, this embodiment also provides a computer-readable storage medium, in which a computer program or instruction is stored, and the computer program or instruction is programmed or configured to execute the energy-saving control method of the capacitive deionization equipment through a processor.

[0096] In addition, this embodiment also provides a computer program product, including a computer program or instruction, and the computer program or instruction is programmed or configured to execute the energy-saving control method of the capacitive deionization equipment through a processor.

[0097] Those skilled in the art should understand that the technical solutions provided by the embodiments of the present invention can be in the form of a method, a system, or a computer program product. Therefore, the present invention can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can adopt the form of a computer program product implemented on one or more computer-readable storage media (including but not limited to disk memories, CD-ROMs, optical memories, etc.) containing computer-usable program codes. The present invention is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram can be realized by computer program instructions, and the combination of the processes and / or blocks in the flowchart and / or block diagram can also be realized by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for realizing the functions specified in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks. These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured product including an instruction device, and the instruction device realizes the functions specified in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks. These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for realizing the functions specified in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0098] The above are only the preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the concept of the present invention belong to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art, several improvements and refinements made without departing from the principle of the present invention should also be regarded as within the protection scope of the present invention.

Claims

1. A method for energy saving control of capacitor deionization equipment, characterized in that: The steps include: S1, establishing a dynamic equivalent circuit for a capacitor deionization equipment including a DC / DC converter and two CDI devices, wherein each CDI device is equivalent to an equivalent double-layer capacitor, an equivalent parallel resistor and an equivalent series resistor, the equivalent parallel resistor and the equivalent double-layer capacitor are connected in parallel and then connected in series with the equivalent series resistor, the DC / DC converter is equivalent to an inductor L, a sensor resistor Rsensor, two equivalent power electronic switches and a controller, one end of the two CDI devices is directly connected and the other end is connected through two equivalent power electronic switches, the series branch formed by the inductor L and the sensor resistor Rsensor is connected in parallel between the loops of the two CDI devices, and the control ends of the two equivalent power electronic switches are connected to the controller; S2, setting the capacitance value of the equivalent double-layer capacitor, the resistance value of the equivalent parallel resistor and the initial value of the equivalent series resistor of the CDI device, and establishing a correction model of the equivalent series resistor when the conductivity of the electrolyte solution changes during the energy recovery process; S3, combining the correction model of equivalent series resistance and the charge and discharge rate and ohmic loss of the double-layer capacitor of the CDI device during the energy recovery process, and using the dynamic equivalent circuit to obtain the reference current required for the DC / DC converter to perform energy recovery control; The functional expression of the correction model of the equivalent series resistance in step S2 is: ， in, For the The equivalent series resistance of CDI devices in this round The correction value of For the The initial value of the equivalent parallel resistance of each CDI device, is the distance between the electrodes of the CDI device, is the electrode surface area of ​​the CDI device, For the The initial electrolyte solution conductivity of each CDI device, For the CDI equipment in this round The conductivity of the electrolyte solution.

2. The energy-saving control method for capacitive deionization equipment according to claim 1, characterized in that: Step S3 includes: S3.1, Initialize iteration variables =1, detect and obtain the initial voltage of the desorption and energy release CDI device and electrolyte solution conductivity , and the initial voltage of the adsorption energy CDI device and electrolyte solution conductivity ; S3.2, calculation of this round Reference current : ， in, is the initial voltage value of the desorption and energy release CDI device, is the double-layer capacitance value of the desorption and energy release CDI device, The expected duration of the energy recovery project; S3.3, use this round Reference current Control DC / DC converter in this round Cycle Perform energy recovery operation within; detect and obtain this round Cycle The parameters at the end include: desorption and energy release of CDI equipment in this round Voltage and electrolyte solution conductivity , and adsorption energy CDI equipment in this round Voltage and electrolyte solution conductivity ; If the desorption energy release CDI equipment is Voltage If the value is less than the preset threshold, the process ends and exits; otherwise, the process jumps to step S3.5; S3.4, according to this round Cycle The parameters at the end of this round are calculated Ohmic loss Ideal voltage for desorption and energy release CDI equipment ; S3.5, if this round Ohmic loss Greater than or equal to the previous round Ohmic loss , then reduce the current round Reference current To get the next round Reference current ; If this round Ohmic loss Less than the previous round Ohmic loss , and desorption and energy release CDI equipment in this round Voltage Less than the ideal voltage for desorption and energy release CDI equipment , then reduce the current round Reference current To get the next round Reference current ; If this round Ohmic loss Less than the previous round Ohmic loss , and desorption and energy release CDI equipment in this round Voltage Greater than or equal to the ideal voltage of the desorption and energy release CDI equipment , then increase this round Reference current To get the next round Reference current ; Iterate over the variable Add 1 and jump to step S3.

3.

3. The energy-saving control method for capacitive deionization equipment according to claim 2, characterized in that: In step S3.4, this round Ohmic loss The calculation function expression is: ， in, and The equivalent series resistance of the desorption energy release CDI equipment and the adsorption energy use CDI equipment is The loss value, and The equivalent parallel resistance of the desorption energy release CDI equipment and the adsorption energy use CDI equipment in this round The loss value, and They are the capacitance values ​​of the double-layer capacitors of the desorption energy-releasing CDI equipment and the adsorption energy-using CDI equipment, respectively. and They are desorption energy release CDI equipment and adsorption energy use CDI equipment. The voltage is: ， ， in, For the The equivalent series resistance of CDI devices in this round The loss value, For this round The reference current, For the The equivalent series resistance of CDI devices in this round n The correction value of To adjust the interval time parameters, For the The equivalent parallel resistance of CDI devices in this round The loss value, For the CDI equipment in this round The voltage, The value is 1 or 2. When it is 1, it means desorption and energy release CDI equipment, When it is 2, it indicates adsorption energy CDI equipment.

4. The energy-saving control method for capacitive deionization equipment according to claim 2, characterized in that: In step S3.4, this round n The ideal voltage for desorption and release of CDI equipment The calculation function expression is: ， in, For the previous round n- 1 Ideal voltage for desorption and energy release CDI equipment, For this round n The reference current, To adjust the interval time parameters, It is the capacitance value of the double-layer capacitor of the desorption energy-releasing CDI device.

5. The energy-saving control method for capacitive deionization equipment according to claim 2, characterized in that: In step S3.5, reduce the current round Reference current To get the next round Reference current The function expression is: ， in, An adjustment factor less than 1.

6. The energy-saving control method for capacitive deionization equipment according to claim 2, characterized in that: Add this round in step S3.5 Reference current To get the next round Reference current The function expression is: ， in, An adjustment factor less than 1.

7. An energy-saving control system for capacitive deionization equipment, comprising a microprocessor and a memory connected to each other, characterized in that: The microprocessor is programmed or configured to execute the energy-saving control method for capacitive deionization equipment according to any one of claims 1 to 6.

8. A computer-readable storage medium having a computer program or instruction stored therein, characterized in that: The computer program or instruction is programmed or configured to execute the energy-saving control method for capacitive deionization equipment according to any one of claims 1 to 6 through a processor.

9. A computer program product comprising a computer program or instructions, characterized in that The computer program or instruction is programmed or configured to execute the energy-saving control method for capacitive deionization equipment according to any one of claims 1 to 6 through a processor.

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