An involute water electrode photovoltaic power generation and thermal storage system and its control method

Abstract

This invention provides an involute water electrode photovoltaic power generation and thermal storage system and control method. The system mainly includes a thermal storage tank, an involute water electrode, a fixed water electrode, a photovoltaic power supply system, and a monitoring system. The involute water electrode is made of a thin conductive metal plate material, formed by rolling the thin conductive metal plate into an involute shape to create a 360° involute water electrode. The control method includes initialization settings, photovoltaic maximum power point tracking (MPPT), rapid locking of the photovoltaic maximum power point segment, and refined photovoltaic MPPT control. Based on the principle of a water electrode hot water boiler, this invention utilizes a photovoltaic array to power the water electrode hot water boiler. Since the photovoltaic array outputs DC power, and to ensure maximum photovoltaic power output, this invention focuses on solving the problems of water electrode polarization and low-cost photovoltaic MPPT during photovoltaic array heating of the water electrode boiler, thus achieving efficient utilization of photovoltaic power generation.

Description

Technical Field

[0001] This invention belongs to the fields of heating, heat use and new energy, and specifically relates to an involute water electrode photovoltaic power generation and heat storage system and control method. Background Technology

[0002] The rapid development of solar photovoltaic (PV) power generation, coupled with its inherent instability and frequent curtailment, necessitates a high proportion of local renewable energy consumption. This addresses both grid stability and line losses, as well as local load demand. However, the key to successful local consumption lies in its grid-friendly nature and load controllability. For businesses and regions with heating and gas supply needs, hydroelectric boiler thermal storage offers a relatively ideal and controllable load option.

[0003] In high-altitude and high-latitude regions, where solar energy resources are abundant and the load characteristics are mainly for heating, water is sourced from glacial meltwater, which is at a low temperature. Therefore, photovoltaic power generation can be utilized locally through thermal storage, improving the local quality of life, reducing carbon emissions, and improving the stability of the power grid by flexibly controlling the load.

[0004] The current principle of electrode hot water boilers is based on the release of a large amount of heat energy through three-phase voltage and current passing through water with a set conductivity, directly converting electrical energy into heat energy and generating steam. The heating power can be steplessly adjusted. Because the water resistance heats the water directly, 100% of the electrical energy is converted into heat, resulting in high efficiency with almost no heat loss, making it a highly efficient heating method.

[0005] The water electrode hot water boiler is powered by AC. The photovoltaic power generation is output through the inverter to meet the power supply requirements of the water electrode hot water boiler. However, the efficiency of the inverter is greatly reduced under low light conditions, making it impossible to achieve high-efficiency utilization of photovoltaic power generation, and the cost is relatively high.

[0006] If photovoltaic power generation is directly applied to thermal storage in hydroelectric boilers, efficiency and cost can be improved. However, two major problems remain:

[0007] 1. When the DC output power of photovoltaic power generation is applied to the water electrode, a polarization reaction will occur. Since water is composed of hydrogen and oxygen ions, the influence of the electrode will cause ion separation and break the metallic bonds, resulting in the separation of the water electrode into anode and cathode. If other minerals are present in the water, impurities such as calcium carbonate will form on the cathode. This phenomenon does not occur with AC voltage. Therefore, it is necessary to solve the problem of high-efficiency, lossless photovoltaic power generation polarity conversion.

[0008] 2. Due to the characteristics of photovoltaic power generation, how can the load characteristics be matched with the characteristics of photovoltaic power generation, i.e., the maximum power point tracking problem of photovoltaic power generation. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides an involute water electrode photovoltaic power generation and thermal storage system and control method, which mainly solves the problems of water electrode polarization and photovoltaic maximum power tracking in the heating of water electrode boilers by photovoltaic arrays, thereby achieving efficient utilization of photovoltaic power generation.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] An involute water electrode photovoltaic power generation and heat storage system includes a heat storage tank, a water electrode assembly, a photovoltaic power supply system, and a monitoring system; the water electrode assembly is placed in the heat storage tank, and the photovoltaic power supply system is placed around the heat storage tank; a heat exchanger is installed inside the heat storage tank, and an inlet, an outlet, an exhaust pipe, and a pressure reducing valve are installed on the heat storage tank body;

[0012] The water electrode assembly includes an involute water electrode, an involute water electrode rotating link, a stepper motor, a fixed water electrode, a fixed water electrode fine-tuning rod, and a water electrode fixing bracket. The water electrode fixing bracket is equipped with the involute water electrode rotating link, a bearing hole, and a fixed water electrode slide rail. The fixed water electrode slides left and right on the fixed water electrode slide rail. The involute water electrode rotating link is installed at the center of the base circle of the involute water electrode. One end of the involute water electrode rotating link is connected to the stepper motor, and the other end is connected to the bearing through the water electrode fixing bracket. Driven by the stepper motor, the involute water electrode rotates via the involute water electrode rotating link, changing its relative position to the fixed water electrode. The fixed water electrode is mounted on the water electrode fixing bracket, and a fixed water electrode fine-tuning rod is installed at the lower middle position of the fixed water electrode. The position of the fixed water electrode is changed by rotating the fixed water electrode fine-tuning rod.

[0013] The photovoltaic power supply system includes a photovoltaic array and a power electronic square wave commutator. The positive and negative output terminals of the photovoltaic array are connected to the power electronic square wave commutator. The power electronic square wave commutator switches the power supply formed by the positive and negative output terminals of the photovoltaic array into a square wave output power supply through a power electronic switch. The square wave output of the power electronic square wave commutator is connected to the involute water electrode and the fixed water electrode through two power lines respectively, providing the water electrode group with a periodically changing positive and negative power supply.

[0014] The monitoring system includes a controller, a water electrode current sensor, a water electrode voltage sensor, and a temperature sensor for the thermal storage tank. It is connected to the water electrode current sensor, the water electrode voltage sensor, and the temperature sensor for the thermal storage tank via communication cables, and to all controlled units and stepper motors via control cables.

[0015] Furthermore, the involute water electrode rotating connecting rod, the fixed water electrode fine-tuning rod, and the water electrode fixing bracket are made of insulating material; the involute water electrode and the fixed water electrode are made of metal conductive thin plate material, and have several holes on them to facilitate water flow and reduce the disturbance of water electrodes by bubbles generated during the water heating process; by rolling the metal conductive thin plate into an involute shape, a 360° involute water electrode is formed.

[0016] Furthermore, the stepper motor is mounted on the outside of the heat storage tank.

[0017] Furthermore, the handle end of the fixed water electrode fine-tuning rod passes through the outside of the tank wall of the thermal storage tank.

[0018] Furthermore, the controller is placed around the thermal storage tank, reads sensor data in real time, and controls the controlled unit according to the algorithm, model, and control strategy.

[0019] This invention also provides a control method for an involute water electrode photovoltaic power generation and thermal storage system, specifically including the following steps:

[0020] Step 1: Initialize settings;

[0021] Step 2: Quickly locate the section with the maximum photovoltaic power generation;

[0022] Step 3: Perform refined photovoltaic power generation maximum power tracking control.

[0023] Furthermore, step 1 specifically includes:

[0024] Step 1.1: Input photovoltaic array parameters, including installed capacity, array tilt angle, array orientation, horizontal diffuse reflection coefficient, open circuit voltage, short circuit current, photovoltaic power generation, total solar irradiance, and a table of typical photovoltaic maximum power points;

[0025] Step 1.2: Determine the maximum and minimum displacement step sizes of the involute water electrode and the corresponding maximum power point of photovoltaic power generation, specifically including:

[0026] (1) Fine-tune the fixed water electrode to determine

[0027] First, the controller uses the maximum step size n. θ =m θ Drive the rotating involute water electrode to rotate to a straight distance L from the fixed water electrode. n The closest position, at this moment, the heating water resistance R w To minimize the distance, according to equation (9), the linear distance L between the fixed water electrode and the involute water electrode is finely adjusted by manually adjusting the stroke of the fine-tuning rod of the fixed water electrode. n To make the maximum point power P of the water electrode waterMaximum point power of photovoltaic power generation with the maximum local irradiance Equal, that is

[0028]

[0029] Where, δ d S is the electrical conductivity of water. g To fix the area of ​​the water electrode; U water P is the resistance voltage applied to the heated water in the water body. water L is the maximum point power of the water electrode. n To fine-tune the linear distance between the fixed water electrode and the involute water electrode; R w For heating water resistance; n θ This represents the number of step sizes for the stepper motor.

[0030] (2) Determine

[0031] First, the controller uses the minimum step size n. θ =1 Drive the involute water electrode to rotate to a straight distance L from the fixed water electrode. n At the furthest position, the heating water resistance R is... w To find the maximum power, based on equations (9), (10), (11), and (12) and the typical photovoltaic maximum power point table, find the straight-line distance L between the involute water electrode and the fixed water electrode. n Power P at the farthest point water The maximum power point of photovoltaic power generation corresponding to the local lower irradiance. Right now

[0032]

[0033]

[0034]

[0035] Where r is the radius of the base circle of the involute water electrode; oA is the length of the line segment between the center of the base circle of the involute water electrode and the fixed water electrode; θ is the angle of rotation of the involute water electrode. This is the point at which photovoltaic power generation reaches its maximum power. This refers to the voltage at the maximum power point of photovoltaic power generation. This refers to the current at the maximum power point of photovoltaic power generation.

[0036] Step 1.3: Establish the step size points of the segmented stepper motor for quickly locking the maximum power point of photovoltaic power generation under different illumination conditions, specifically including:

[0037] Considering the response speed of mechanical photovoltaic maximum power point tracking (MPPT), segmented photovoltaic MPPT is adopted. First, based on the input photovoltaic array parameters and irradiance, a table for quickly locking the segmented photovoltaic power generation maximum power points under different illumination conditions is established. The stepper motor operates with an angle θ as a step size n. θ =1 Rotate the involute water electrode 360 ​​degrees to obtain the number of steps of the stepper motor. Where n θ =1,2,3,...,m θ Then, the number of steps is in units of 10. The maximum power point of photovoltaic power generation at the local maximum irradiance. and the maximum power point of photovoltaic power generation at lower local irradiance. Range, divided by The number of segments for quickly identifying the maximum power point of photovoltaic power generation under different illumination conditions is obtained, i.e.:

[0038]

[0039] And the maximum power points of photovoltaic power generation corresponding to the segment endpoints:

[0040]

[0041] Where, n m The point where the maximum photovoltaic power generation is known for a certain segment. The number of step sizes of the stepper motor, i.e., n m =1,2,3,...,mp, and thus the point of maximum photovoltaic power generation at each segment point is determined by looking up a table. The value is a constant α, where the difference in maximum power output between adjacent photovoltaic power generation segments is α.

[0042]

[0043] Where mp is the number of segments at the maximum power point of photovoltaic power generation; θ represents the maximum power point value of photovoltaic power generation under the local maximum irradiance; θ is the angle of rotation of the involute water electrode. n is the number of steps in the stepper motor θ The point of maximum photovoltaic power generation; n is the number of steps in the stepper motor θ The maximum power output of photovoltaic power generation at a given point and the voltage at that point; n is the number of steps in the stepper motor θ The maximum power of photovoltaic power generation at a given point is the point current; α is the difference in maximum power of photovoltaic power generation between adjacent segments, which is a constant. Let n be the point where the photovoltaic power generation reaches its maximum at a certain segmentation point. m =1,2,3,...,mp;n θn is the number of stepper motor steps required for the involute water electrode to rotate 360 ​​degrees. θ =1,2,3,...,m θ Maximum number of step sizes n θ =m θ up to the minimum step size number n θ =1, and according to equation (12), the maximum power points of photovoltaic power generation corresponding to the local maximum and minimum irradiance ranges can be obtained:

[0044]

[0045] Furthermore, step 2, quickly identifying the segment with the maximum photovoltaic power generation:

[0046] The controller reads the photovoltaic power generation current I in real time. pv and photovoltaic power generation voltage U pv The photovoltaic power output P was calculated. pv Based on the output power P pv Compared with the previous moment's maximum photovoltaic power generation point Perform the difference calculation, that is:

[0047]

[0048] 2.1 When ΔP pv ≥0, when the photovoltaic power generation power increases, the photovoltaic power generation output power P pv Divide by the constant α of the maximum power difference point of photovoltaic power generation in each adjacent segment, that is:

[0049]

[0050] The result of the divisor is rounded to one decimal place, and the modulo function is used to determine its value.

[0051] mod(P pv ,α)≥0.5 (19)

[0052] in, n represents the point at which photovoltaic power generation reaches its maximum power at the previous moment. θ-1 The point at which photovoltaic power generation reaches its maximum power at the previous moment. The number of step lengths of the stepper motor; I pv U represents the current photovoltaic power generation current. pv P represents the current photovoltaic power generation voltage. pv This represents the current output power of photovoltaic power generation;

[0053] (1) For example, the modulo function determines mod(P) pv When α)≥0.5, then according to the floor function:

[0054]

[0055] Using the principle of rounding up to the nearest whole number, determine the maximum power point of photovoltaic power generation in a certain segment. And determine the maximum power point of photovoltaic power generation. Falling and Between, thus obtaining n θ =n m ×10 stepper motor step lengths, based on the nth step θ =n m ×10 step size of stepper motors minus the maximum power point of photovoltaic power generation at the previous moment Number of steps of the stepper motor nθ-1 The increase or decrease of the stepper motor Δn is obtained. θ Each step size, i.e., Δn θ =10n m -n θ-1 Where mod is the modulo function; INT is the integer function; for nm The maximum power point of segmented photovoltaic power generation; for nm-1 The maximum power point of segmented photovoltaic power generation; Number of steps of the stepper motor nθ The point at which photovoltaic power generation reaches its maximum power; This represents the point at which photovoltaic power generation reached its maximum power at the previous moment. nθ-1 The point at which photovoltaic power generation reaches its maximum power at the previous moment. The number of stepper motor steps; Δn θ To increase or decrease the number of stepper motor steps;

[0056] Where, n m The point where the maximum photovoltaic power generation is known for a certain segment. The number of stepper motor steps is set during initialization. The controller then adjusts the step size based on the increment / decrement Δn. θ The stepper motor rotates to 10n using a step control. m At the point of maximum photovoltaic power generation Reduce the linear distance L between the involute water electrode and the fixed water electrode. n This reduces the resistance of the heating water, allowing for rapid locking of the maximum power point of segmented photovoltaic power generation. Simultaneously, the controller reads the photovoltaic power generation current I in real time. pv and voltage U pv The photovoltaic power output P was calculated. pv Step 3 involves refined photovoltaic power generation maximum power tracking control.

[0057] (2) For example, the modulo function determines mod(P) pvWhen α) < 0.5, the maximum power point of photovoltaic power generation in a certain segment is determined according to the rounding function INT in equation (20) and the principle of rounding to the nearest whole number. And determine the maximum power point of photovoltaic power generation. Falling and Between, thus obtaining n θ =n m ×10 stepper motor step lengths, based on the nth step θ =n m ×10 step size of stepper motors minus the maximum power point of photovoltaic power generation at the previous moment Number of steps of the stepper motor nθ-1 The increase or decrease of the stepper motor Δn is obtained. θ Each step size, i.e., Δn θ =10n m -n θ-1 , where n m The point where the maximum photovoltaic power generation is known for a certain segment. The number of stepper motor steps is set during initialization; at this time, the controller adjusts the step size based on the increment / decrement Δn. θ The stepper motor rotates to 10n using a step control. m At the point of maximum photovoltaic power generation Reduce the linear distance L between the involute water electrode and the fixed water electrode. n This reduces the resistance of the heating water, allowing for rapid locking of the maximum power point of segmented photovoltaic power generation. Simultaneously, the controller reads the photovoltaic power generation current I in real time. pv and photovoltaic power generation voltage U pv The photovoltaic power output P was calculated. pv Step 3 involves refined photovoltaic power generation maximum power tracking control.

[0058] in, for nm The maximum power point of segmented photovoltaic power generation; for nm+1 The maximum power point of segmented photovoltaic power generation; Number of steps of the stepper motor nθ The point at which photovoltaic power generation reaches its maximum power; Δn θ To increase or decrease the number of stepper motor steps;

[0059] 2.2 When ΔP pv When the photovoltaic power generation power is less than 0, the current photovoltaic power generation output power P will be reduced. pv Divide by the constant α of the maximum power difference point of photovoltaic power generation in each adjacent segment, as shown in equation (18). The divisor result is rounded to one decimal place, and mod(P) is determined according to the mod remainder function. pv ,α)≥0.5:

[0060] (1) For example, the modulo function determines mod(P) pv When α)≥0.5, the maximum power point of photovoltaic power generation in a certain segment is determined according to the rounding function INT in equation (20) and the principle of rounding to the nearest whole number. And determine the maximum power point of photovoltaic power generation. Falling and Between, thus obtaining n θ =n m ×10 stepper motor step sizes, based on the previous moment's maximum photovoltaic power generation point. The number of steps n of the stepper motor θ-1 Subtract n θ =n m Multiply by 10 stepper motor step lengths to obtain the stepper motor reduction Δn. θ Each step size, i.e., Δn θ =n θ-1 -10n m , where n m The point where the maximum photovoltaic power generation is known for a certain segment. The number of stepper motor steps is set during initialization; at this time, the controller determines the step size based on the decrement Δn. θ Each step controls the rotation of the stepper motor, increasing the linear distance L between the involute water electrode and the fixed water electrode. n This increases the resistance of the heating water, quickly locking in the maximum power point of the segmented photovoltaic power generation. Simultaneously, the controller reads the photovoltaic power generation current I in real time. pv and voltage U pv The photovoltaic power output P was calculated. pv Step 3 involves refined photovoltaic power generation maximum power tracking control.

[0061] (2) For example, the modulo function determines mod(P) pv When α) < 0.5, the maximum power point of photovoltaic power generation in a certain segment is determined according to the rounding function INT in equation (20) and the principle of rounding to the nearest whole number. And determine the maximum power point of photovoltaic power generation. Falling and Between, thus obtaining n θ =n m ×10 stepper motor step sizes, based on the previous moment's maximum photovoltaic power generation point. Number of steps of the stepper motor nθ-1 Subtract n θ =n m Multiply by 10 stepper motor step lengths to obtain the stepper motor reduction Δn. θEach step size, i.e., Δn θ =n θ-1 -10n m , where n m The point where the maximum photovoltaic power generation is known for a certain segment. The number of stepper motor steps is set during initialization; at this time, the controller determines the step size based on the decrement Δn. θ Each step controls the rotation of the stepper motor, increasing the linear distance L between the involute water electrode and the fixed water electrode. n This increases the resistance of the heating water, quickly locking in the maximum power point of the segmented photovoltaic power generation. Simultaneously, the controller reads the photovoltaic power generation current I in real time. pv and voltage U pv The photovoltaic power output P was calculated. pv Step 3 involves refining the maximum power tracking control of photovoltaic power generation.

[0062] Furthermore, step 3 specifically includes:

[0063] After quickly identifying the maximum power point range of photovoltaic power generation in step 2, the controller reads the photovoltaic power generation current I in real time. pv and photovoltaic power generation voltage U pv The photovoltaic power output P was calculated. pv and the maximum power point of segmented photovoltaic power generation Compare and judge separately or

[0064] Step 3.1: Determine ΔP based on equation (17). pv ≥0, when photovoltaic power generation increases, and the known maximum power point of photovoltaic power generation in segments. Compare, judge hour:

[0065] (1) Determine mod(P) based on the mod modulo function. pv When α)≥0.5, then according to the rounding function INT in equation (20) and the principle of rounding to the nearest whole number, the following steps are controlled:

[0066] Step A: The controller adjusts the increment / decrement Δn based on the previous time step. θ-1 Subtracting one perturbation step from each step size yields the current increment / decrement Δn. θ The step size is Δn θ =Δn θ-1 -1 controls the stepper motor to rotate, changing the resistance value of the heating water resistor, while the controller continues to read the photovoltaic power generation current I. pv and voltage U pv The output power of photovoltaic power generation was calculated. And compared with the photovoltaic power generation at the previous moment Compare;

[0067] When judging The controller repeats step A.

[0068] When judging At that time, the heating water resistance generated by the distance between the current involute water electrode and the fixed water electrode is determined and adapted to the maximum power point of photovoltaic power generation.

[0069] in, This represents the current output power of photovoltaic power generation; Δn represents the photovoltaic power generation at the previous moment. θ-1 The increment or decrement is the step size of the increment or decrement from the previous time step; Δn θ This represents the current increment / decrement step size;

[0070] (2) Determine mod(P) based on the mod remainder function. pv When α) < 0.5, then according to the integer function INT in equation (20) and the principle of rounding to the nearest whole number, the following steps are performed:

[0071] Step B, the controller adjusts the increment / decrement Δn based on the previous time step. θ-1 Adding a perturbation step size to the current increase / decrease Δn gives the current increment / decrement. θ The step size is Δn θ =Δn θ-1 +1 controls the stepper motor to rotate, changing the resistance value of the heating water resistor, while the controller continues to read the photovoltaic power generation current I. pv and voltage U pv The output power of photovoltaic power generation was calculated. And compared with the photovoltaic power generation at the previous moment Compare;

[0072] When judging The controller repeats step B.

[0073] When judging At that time, the heating water resistance generated by the distance between the current involute water electrode and the fixed water electrode is determined and adapted to the maximum power point of photovoltaic power generation.

[0074] The present invention has the following advantages: lower cost compared to inverters; adaptable to 100% fluctuation of photovoltaic power generation with high efficiency; low switching loss, such as the loss of a second-level switching time switch is much less than the 50Hz switching loss; simple controller structure and high reliability; and high maximum power point tracking efficiency for photovoltaic power generation across the entire time domain. Attached Figure Description

[0075] Figure 1This is a structural diagram of an involute water electrode photovoltaic power generation and thermal storage system according to the present invention;

[0076] Figure 2 This is a schematic diagram showing the connection relationship between components of an involute water electrode photovoltaic power generation and thermal storage system according to the present invention;

[0077] Figure 3 This is a schematic diagram of the unfolded involute water electrode of an involute water electrode photovoltaic power generation and thermal storage system according to the present invention;

[0078] Figure 4 This is a control flowchart of an involute water electrode photovoltaic power generation and thermal storage system according to the present invention. Detailed Implementation

[0079] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0080] like Figure 1 and Figure 2 As shown, the involute water electrode photovoltaic power generation and thermal storage system of the present invention mainly includes a thermal storage tank 1, a water electrode assembly, a photovoltaic power supply system, and a monitoring system; wherein the water electrode assembly is placed in the thermal storage tank 1, and the photovoltaic power supply system is placed around the periphery of the thermal storage tank 1. The thermal storage tank 1 is equipped with an inlet 13, an outlet 14, an exhaust pipe 12, and a pressure reducing valve 11. The inlet 13 is located at the top of the thermal storage tank 1; the outlet 14 is located at the bottom of the thermal storage tank 1; the exhaust pipe 12 is located on the top side of the thermal storage tank 1 near the inlet 13; and the pressure reducing valve 11 is located at the top of the thermal storage tank 1 near the inlet 13.

[0081] The water electrode assembly includes an involute water electrode 2, an involute water electrode rotating link 5, a stepper motor 4, a fixed water electrode 3, a fixed water electrode fine-tuning rod 6, and a water electrode fixing bracket 7.

[0082] Among them, the involute water electrode rotating connecting rod 5, the fixed water electrode fine adjustment rod 6, and the water electrode fixing bracket 7 are made of insulating material; the involute water electrode 2 and the fixed water electrode 3 are made of metal conductive thin plate material, and have several holes on it to facilitate water flow and reduce the disturbance of water electrodes by bubbles generated during the water heating process. The 360° involute water electrode 2 is formed by rolling the metal conductive thin plate based on the involute shape.

[0083] The water electrode fixing bracket 7 is equipped with an involute water electrode rotating connecting rod 5, a bearing hole 8, and a water electrode fixing slide rail 9. The fixed water electrode 3 slides left and right on the fixed water electrode slide rail 9.

[0084] An involute water electrode rotating link 5 is installed at the center 10 of the base circle of the involute water electrode. One end of the involute water electrode rotating link 5 is connected to a stepper motor 4, and the other end is connected to a bearing 8 via a water electrode fixing bracket 7. Driven by the stepper motor 4, the involute water electrode 2 rotates via the involute water electrode rotating link 5, changing its relative position to the fixed water electrode 3. The stepper motor 4 is mounted on the outside of the thermal storage tank 1.

[0085] The fixed water electrode 3 is mounted on the water electrode fixing bracket 7, and a fixed water electrode fine-tuning rod 6 is installed at the lower middle position of the fixed water electrode 3. The position of the fixed water electrode 3 is changed by rotating the fixed water electrode fine-tuning rod 6. The handle end of the fixed water electrode fine-tuning rod 6 passes through the outside of the tank wall of the thermal storage tank 1.

[0086] The photovoltaic power supply system includes a photovoltaic array 17 and a power electronic square wave commutator 20.

[0087] The positive and negative output terminals 18 and 19 of the photovoltaic array 17 are connected to a power electronic square wave commutator 20. The power electronic square wave commutator 20, through power electronic switching, converts the power supplied by the positive and negative output terminals 18 and 19 of the photovoltaic array 17 into a square wave output power. The square wave output terminal of the power electronic square wave commutator 20 is connected to the involute water electrode 2 via a first wire 21, and to the fixed water electrode 3 via a second wire 22, providing a periodically changing positive and negative power supply to the water electrode group. If the power electronic square wave commutator 20 switches the square wave output at a frequency on the order of seconds, the switching loss time of its power electronic devices is negligible on the order of nanoseconds. Compared to the inverter switching frequency of 5K to 20K, the loss is significantly reduced.

[0088] The monitoring system includes a controller 23, a water electrode current sensor, a water electrode voltage sensor, and a temperature sensor for the thermal storage tank 1. The controller 23 is positioned around the thermal storage tank 1 and is connected to the water electrode current sensor, water electrode voltage sensor, and temperature sensor for the thermal storage tank 1 via communication cables. It is also connected to all controlled units and the stepper motor 4 via control cables. The controller 23 reads sensor data in real time and controls the controlled units based on algorithms, models, and control strategies.

[0089] This invention is based on the heating principle of an electrode hot water boiler. Three-phase voltage and current release a large amount of heat energy through water with a set conductivity, directly converting electrical energy into heat energy and generating steam. The heating power can be steplessly adjusted. Due to the direct heating by water resistance, 100% of the electrical energy is converted into heat with high efficiency, while there is almost no heat loss.

[0090] Mathematical expression based on the principle of electrical work:

[0091]

[0092] It can be seen that under the same heating water resistance voltage U water Below, heating water resistance R w The smaller the value, the larger the current flowing through it. Based on the mathematical expression of Joule's law, we get:

[0093]

[0094] and

[0095] It can be seen that the resistance voltage U of the heated water is within the same time t. water Or heating water resistance current I water Changes in the resistance of heating water, and the heat generated Q water The voltage U of the heating water resistance changes exponentially with the square of the change. water Or heating water resistance current I water The larger the resistance of the heated water, the greater the heat generated, Q. water The larger.

[0096] The heating water resistance current I water The size of the heating water resistance R w Related to the resistance R of the heating water w The size of the resistance R of the heated water is related to the electrode area and the distance between the two electrodes. The larger the electrode area, the smaller the equivalent parallel resistance and the larger the current; the closer the distance between the two electrodes, the smaller the resistance R of the heated water. w The smaller the value, the lower the resistance current I of the heating water. water The larger the area, the greater the heating power of the water electrodes; thus, the heating power of the water electrodes can be changed by adjusting the area and spacing of the water electrodes.

[0097] The relative position of the area of ​​the involute water electrode 2 and the fixed water electrode 3 is analyzed as follows: (e.g.) Figure 3 As shown, based on the definition of the involute and the arc length formula, the product of the angle and the radius, θ·r, yields the sum of the arc lengths corresponding to n angles θ. This length is the point of tangency J on the base circle of the involute. n Point k on the involute line n Length of tangent segment Therefore, it can be seen that on the same circle, the length of a straight line increases with the cumulative increase of the number of angles; thus, when rotating about the center 10 of the base circle of the involute water electrode, the area of ​​the involute water electrode 2 and the distance between it and the fixed water electrode 3 change. For example, the involute shape is curled into 360° and divided into 12 involute points at an angle θ = 30°.

[0098] Among them, J n Let K be any point on the circumference of the involute base circle. n Let x be any point on the involute, where n = 1, 2, 3, ..., x.

[0099] When the length of the line segment between the fixed water electrode A and the center o of the base circle of the involute water electrode is oA, then the minimum distance between the involute water electrode 2 and the fixed water electrode 3 is:

[0100] L min =oA-12×θr (4)

[0101] The maximum spacing is:

[0102] L max =oA-θr (5)

[0103] The distance between any point on the involute and the fixed water electrode 3 is:

[0104] L n =oA-n θ ·θr (6)

[0105] Among them, U water I is the resistance voltage applied to the heated water in the water body. water Q is the resistance current passing through the heated water in the water body. water The heating element is the resistance heat generated by the water; A is the position of the fixed water electrode; o is the center of the base circle of the involute water electrode; r is the radius of the base circle of the involute water electrode; oA is the length of the line segment between the center of the base circle of the involute water electrode and the fixed water electrode; θ is the angle; n θ = any point on the involute in the sequence 1, 2, 3, ..., x.

[0106] If a stepper motor 4 is used to drive the rotating involute water electrode 2 with a step size angle θ = 3° each time, 120 points are determined on the outline of the involute water electrode 2. According to equation (6), the distance between these 120 involute points and the fixed water electrode 3 can be determined. At this time, n θ Let be any point from 1 to 120 on the involute.

[0107] Due to the resistance R of the heating water wConcentrated between the projected areas of the fixed water electrode 3 and the involute water electrode 2, and without considering the electric field distribution around the fixed water electrode 3 and the involute water electrode 2, and the reduction in the area of ​​the holes in the water electrodes, its cross-sectional area is equal to the area S of the fixed water electrode. g The area of ​​the involute water electrode 2 is equal to the surface area projected from the fixed water electrode 3. The heating water resistance R... w It should be: the distance L between the fixed water electrode and the involute water electrode n With water conductivity δ d The product of the fixed water electrode area S g The ratio, that is:

[0108]

[0109] Due to the curved surface structure of the involute water electrode 2, there is also a distributed water resistance between the projected area and the fixed water electrode 3, and the heating water resistance R. w Since the water resistance is relatively large when connected in parallel, it will not be included in the analysis here.

[0110] Due to the electrical conductivity δ of water d Dispersed water resistance and fixed water electrode area S g It is a constant, the position of the fixed water electrode 3 is relatively fixed, and the linear displacement distance L of the involute water electrode is rotated. n That is, the distance between the rotational change of the involute water electrode 2 and the linear displacement of the fixed water electrode 3. From equation (7), we can see that the heating water resistance R... w The distance L of the linear displacement of the involute water electrode during rotation n Proportional to the linear displacement distance L of the involute water electrode during rotation. n Increase the resistance R of the heating water w Increase, and conversely, decrease the linear displacement distance L of the involute water electrode rotation. n Reduce the resistance R of the heating water w Reduce, based on the principle of electrical work:

[0111]

[0112] Without considering the resistance of the dispersed water, substituting equation (6) into equation (8) yields the linear displacement distance L of the involute water electrode. n The relationship with power is:

[0113]

[0114] Equation (9) shows that the voltage U applied to the heating water resistor water Under constant conditions, for each step of rotation of the involute water electrode 2, there is a corresponding applied resistance power P to the heating water. water .

[0115] Similarly, when stepper motor 4 drives the involute water electrode 2 to rotate in a step of θ = 3°, the involute water electrode 2 is divided into 120 involute points. According to equation (7), there are 120 involute points and the heating water resistance R between them and the fixed water electrode 3. w It can be adapted to the maximum power tracking point of photovoltaic power generation under different lighting conditions, at which point n θ Let be any point on the involute line from 1 to 120.

[0116] Substituting equation (6) into equation (7), we get:

[0117]

[0118] From equation (10), it can be seen that as the stepper motor 4 drives the involute water electrode to rotate 360 ​​degrees with an angle θ as one step, the angular displacement of the stepper motor increases from 1 step to n. θ Each step size corresponds to a heating water resistor R. w .

[0119] Because the photovoltaic power generation is applied to the heating water resistance R between the water electrode assembly. w Above, when the stepper motor's angular displacement increases from 1 step to n... θ In a step-size change process, photovoltaic power is applied to the heating water resistance R. w The power outputs on each grid correspond one-to-one to the maximum power output of photovoltaic power generation. That is, the voltage at the maximum power point of photovoltaic power generation. With the maximum power point current of photovoltaic power generation The product of:

[0120]

[0121] The maximum power point of this photovoltaic power generation Maximum power point voltage of photovoltaic power generation With the maximum power point current of photovoltaic power generation The ratio is equal to the resistance of the heating water:

[0122]

[0123] Among them, S g To fix the area of ​​the water electrode, which is also the surface area of ​​the projection of the water electrode onto the involute water electrode; R w For heating water resistance; L n To fix the linear distance between the water electrode and the involute water electrode; δ d n is the electrical conductivity of water. θ This represents the number of step sizes for the stepper motor. n is the step size of the stepper motor θ The number of photovoltaic power generation maximum power points; n is the step size of the stepper motorθ The maximum power point voltage of the number of photovoltaic power generation units; n is the step size of the stepper motor θ The maximum power point current of the number of photovoltaic power generation.

[0124] like Figure 4 As shown, the control method of an involute water electrode photovoltaic power generation and thermal storage system of the present invention includes the following steps:

[0125] Step 1, Initialization settings, specifically including:

[0126] 1.1 Input photovoltaic array parameters, including installed capacity, array tilt angle, array orientation, horizontal diffuse reflection coefficient, open circuit voltage, short circuit current, photovoltaic power generation, total solar irradiance, and a table of typical photovoltaic maximum power points;

[0127] 1.2 Determine the maximum and minimum displacement step sizes of the involute water electrode and the corresponding maximum power point of photovoltaic power generation, specifically including:

[0128] (1) Fine-tune the fixed water electrode to determine

[0129] First, the controller uses the maximum step size n. θ =m θ The linear distance L between the displacement of the driving rotating involute water electrode and the fixed water electrode n At the closest point, the heating water resistance R is... w To minimize the distance, according to equation (9), the linear distance L between the fixed water electrode and the involute water electrode is finely adjusted by manually adjusting the stroke of the fine-tuning rod of the fixed water electrode. n To make the maximum point power P of the water electrode water Maximum point power of photovoltaic power generation with the maximum local irradiance Equal, that is

[0130] (2) Determine

[0131] First, the controller uses the minimum step size n. θ =1. Displacement of the rotating involute water electrode relative to the linear distance L between the fixed water electrode and the displacement of the rotating involute water electrode. n At the farthest point, the heating water resistance R is... w To find the maximum power, based on equations (9), (10), (11), and (12) and the typical photovoltaic maximum power point table, find the straight-line distance L between the involute water electrode and the fixed water electrode. n Power P at the farthest point water The maximum power point of photovoltaic power generation corresponding to the local lower irradiance. Right now

[0132] 1.3 Establish a segmented stepper motor step size point for quickly locking the maximum power point of photovoltaic power generation under different illumination conditions, specifically including:

[0133] Considering the response speed of mechanical photovoltaic maximum power point tracking (MPPT), segmented photovoltaic MPPT is adopted. First, based on the input photovoltaic array parameters and irradiance, a table is established to quickly lock the segmented photovoltaic power generation maximum power points under different irradiance conditions. The stepper motor operates with a step size n, where angle θ is one step. θ =1 Rotate the involute water electrode 360 ​​degrees to obtain the number of steps of the stepper motor. Where n θ =1,2,3,...,m θ Then, the number of steps is in units of 10. The maximum power point of photovoltaic power generation at the local maximum irradiance. and the maximum power point of photovoltaic power generation at lower local irradiance. Range, divided by The number of segments for quickly identifying the maximum power point of photovoltaic power generation under different illumination conditions is obtained, i.e.:

[0134]

[0135] And the maximum power points of photovoltaic power generation corresponding to the segment endpoints:

[0136]

[0137] Where, n m The point where the maximum photovoltaic power generation is known for a certain segment. The number of step sizes of the stepper motor, n m =1,2,3,...,mp, and thus the point of maximum photovoltaic power generation at each segment point is determined by looking up a table. The value is a constant α, where the difference in maximum power output between adjacent photovoltaic power generation segments is α.

[0138]

[0139] Where mp is the number of segments at the maximum power point of photovoltaic power generation; θ represents the maximum power point value of photovoltaic power generation under the local maximum irradiance; θ is the angle of rotation of the involute water electrode. n is the number of steps in the stepper motor θ The point of maximum photovoltaic power generation; n is the number of steps in the stepper motor θ The maximum power output of photovoltaic power generation at a given point and the voltage at that point; n is the number of steps in the stepper motor θ The maximum power of photovoltaic power generation at a given point is the point current; α is the difference in maximum power of photovoltaic power generation between adjacent segments, which is a constant. For each segment point, n represents the point where the photovoltaic power generation reaches its maximum. m =1,2,3,...,mp;n θ The number of stepper motor steps (n) is the maximum number of steps (n) required for the involute water electrode to rotate 360 ​​degrees. θ =m θ up to the minimum step size number n θ =1, and according to equation (12), the maximum power points of photovoltaic power generation corresponding to the local maximum and minimum irradiance ranges can be obtained:

[0140]

[0141] Step 2: Quickly locate the section with the maximum photovoltaic power generation:

[0142] The controller reads the photovoltaic power generation current I in real time. pv and photovoltaic power generation voltage U pv The photovoltaic power output P was calculated. pv Based on the output power P pv Compared with the previous moment's maximum photovoltaic power generation point Perform the difference calculation, that is:

[0143]

[0144] 2.1 When ΔP pv ≥0, when the photovoltaic power generation power increases, the photovoltaic power generation output power P pv Divide by the constant α of the maximum power difference point of photovoltaic power generation in each adjacent segment, that is:

[0145]

[0146] The result of the divisor is rounded to one decimal place, and the modulo function is used to determine its value.

[0147] mod(P pv ,α)≥0.5 (19)

[0148] in, n represents the point at which photovoltaic power generation reaches its maximum power at the previous moment. θ-1 The point at which photovoltaic power generation reaches its maximum power at the previous moment. The number of step lengths of the stepper motor; I pv U represents the current photovoltaic power generation current. pv P represents the current photovoltaic power generation voltage. pv This represents the current output power of photovoltaic power generation;

[0149] (1) For example, the modulo function determines mod(P) pv When α)≥0.5, then according to the floor function:

[0150]

[0151] Using the principle of rounding up to the nearest whole number, determine the maximum power point of photovoltaic power generation in a certain segment. And determine the maximum power point of photovoltaic power generation. Falling and Between, thus obtaining n θ =n m ×10 stepper motor step lengths, based on the nth step θ =n m ×10 step size of stepper motors minus the maximum power point of photovoltaic power generation at the previous moment The number of steps n of the stepper motor θ-1 The increase or decrease of the stepper motor Δn is obtained. θ Each step size, i.e., Δn θ =10n m -n θ-1 .

[0152] Where mod is the modulo function; INT is the integer function; for nm The maximum power point of segmented photovoltaic power generation; For n m The maximum power point of photovoltaic power generation in the -1 segment; Number of steps of the stepper motor nθ The point at which photovoltaic power generation reaches its maximum power; n represents the point at which photovoltaic power generation reaches its maximum power at the previous moment. θ-1 The point at which photovoltaic power generation reaches its maximum power at the previous moment. The number of stepper motor steps; Δn θ To increase or decrease the number of stepper motor steps; where n m The point where the maximum photovoltaic power generation is known for a certain segment. The number of stepper motor steps is set during initialization. The controller then adjusts the step size based on the increment / decrement Δn. θ The stepper motor rotates to 10n using a step control. m At the point of maximum photovoltaic power generation Reduce the linear distance L between the involute water electrode and the fixed water electrode. n This reduces the resistance of the heating water and quickly locks in the maximum power point of segmented photovoltaic power generation. Simultaneously, the controller reads the photovoltaic power generation current I in real time. pv and voltage U pv The photovoltaic power output P was calculated. pv Step 3 involves refined photovoltaic power generation maximum power tracking control.

[0153] (2) For example, the modulo function determines mod(P) pv When α) < 0.5, the maximum power point of photovoltaic power generation in a certain segment is determined according to the rounding function INT in equation (20) and the principle of rounding to the nearest whole number. And determine the maximum power point of photovoltaic power generation. Falling and Between, thus obtaining n θ =n m ×10 stepper motor step lengths, based on the nth step θ =n m ×10 step size of stepper motors minus the maximum power point of photovoltaic power generation at the previous moment Number of steps of the stepper motor nθ-1 The increase or decrease of the stepper motor Δn is obtained. θ Each step size, i.e., Δn θ =10n m -n θ-1 , where n m The point where the maximum photovoltaic power generation is known for a certain segment. The number of stepper motor steps is set during initialization. The controller then adjusts the step size based on the increment / decrement Δn. θ The stepper motor rotates to 10n using a step control. m At the point of maximum photovoltaic power generation Reduce the linear distance L between the involute water electrode and the fixed water electrode. n This reduces the resistance of the heating water and quickly locks in the maximum power point of segmented photovoltaic power generation. Simultaneously, the controller reads the photovoltaic power generation current I in real time. pv and photovoltaic power generation voltage U pv The photovoltaic power output P was calculated. pv Step 3 involves refined photovoltaic power generation maximum power tracking control.

[0154] in, For n m The maximum power point of segmented photovoltaic power generation; For n m The maximum power point of photovoltaic power generation in the +1 segment; Number of steps of the stepper motor nθ The point at which photovoltaic power generation reaches its maximum power; Δn θ To increase or decrease the number of stepper motor steps;

[0155] 2.2 When ΔP pv When the photovoltaic power generation power is less than 0, the current photovoltaic power generation output power P will be reduced. pvDivide by the constant α of the maximum power difference point of photovoltaic power generation in each adjacent segment, as shown in equation (18). The divisor result is rounded to one decimal place, and mod(P) is determined according to the mod remainder function. pv ,α)≥0.5.

[0156] (1) For example, the modulo function determines mod(P) pv When α)≥0.5, the maximum power point of photovoltaic power generation in a certain segment is determined according to the rounding function INT in equation (20) and the principle of rounding to the nearest whole number. And determine the maximum power point of photovoltaic power generation. Falling and Between, thus obtaining n θ =n m ×10 stepper motor step sizes, based on the previous moment's maximum photovoltaic power generation point. The number of steps n of the stepper motor θ-1 Subtract n θ =n m Multiply by 10 stepper motor step lengths to obtain the stepper motor reduction Δn. θ Each step size, i.e., Δn θ =n θ-1 -10n m , where n m The point where the maximum photovoltaic power generation is known for a certain segment. The number of stepper motor steps is set during initialization. At this time, the controller determines the step size based on the decrement Δn. θ The stepper motor rotates to 10n using a step control. m At the point of maximum photovoltaic power generation Increase the linear distance L between the involute water electrode and the fixed water electrode. n This increases the resistance of the heating water, allowing for rapid locking of the maximum power point of segmented photovoltaic power generation. Simultaneously, the controller reads the photovoltaic power generation current I in real time. pv and voltage U pv The photovoltaic power output P was calculated. pv Step 3 involves refining the maximum power tracking control of photovoltaic power generation.

[0157] (2) For example, the modulo function determines mod(P) pv When α) < 0.5, the maximum power point of photovoltaic power generation in a certain segment is determined according to the rounding function INT in equation (20) and the principle of rounding to the nearest whole number. And determine the maximum power point of photovoltaic power generation. Falling and Between, thus obtaining n θ =n m×10 stepper motor step sizes, based on the previous moment's maximum photovoltaic power generation point. The number of steps n of the stepper motor θ-1 Subtract n θ =n m Multiply by 10 stepper motor step lengths to obtain the stepper motor reduction Δn. θ Each step size, i.e., Δn θ =n θ-1 -10n m , where n m The point where the maximum photovoltaic power generation is known for a certain segment. The number of stepper motor steps is set during initialization. At this time, the controller determines the step size based on the decrement Δn. θ The stepper motor rotates to 10n using a step control. m At the point of maximum photovoltaic power generation Increase the linear distance L between the involute water electrode and the fixed water electrode. n This increases the resistance of the heating water, allowing for rapid locking of the maximum power point of segmented photovoltaic power generation. Simultaneously, the controller reads the photovoltaic power generation current I in real time. pv and voltage U pv The photovoltaic power output P was calculated. pv Step 3 involves refining the maximum power tracking control of photovoltaic power generation.

[0158] Step 3: Perform refined maximum power point tracking (MPPT) control for photovoltaic power generation, specifically including:

[0159] After quickly identifying the maximum power point range of photovoltaic power generation in step 2, the controller reads the photovoltaic power generation current I in real time. pv and photovoltaic power generation voltage U pv The photovoltaic power output P was calculated. pv and the maximum power point of segmented photovoltaic power generation Compare and judge separately or

[0160] 3.1 Determine ΔP based on equation (17) pv When the photovoltaic power generation increases by ≥0, and the known maximum photovoltaic power generation point in segments. Compare, judge hour.

[0161] (1) Determine mod(P) based on the mod modulo function. pv When α)≥0.5, then according to the rounding function INT in equation (20) and the principle of rounding to the nearest whole number, the following steps are controlled:

[0162] Step A: The controller adjusts the increment / decrement Δn based on the previous time step. θ-1Subtracting one perturbation step from each step size yields the current increment / decrement Δn. θ The step size is Δn θ =Δn θ-1 -1 controls the stepper motor to rotate, changing the resistance value of the heating water resistor, while the controller continues to read the photovoltaic power generation current I. pv and voltage U pv The output power of photovoltaic power generation was calculated. And compared with the photovoltaic power generation at the previous moment Compare.

[0163] When judging The controller repeats step A.

[0164] When judging At that time, the heating water resistance generated by the distance between the current involute water electrode and the fixed water electrode is determined and adapted to the maximum power point of photovoltaic power generation.

[0165] in, This represents the current output power of photovoltaic power generation; Δn represents the photovoltaic power generation at the previous moment. θ-1 The increment or decrement is the step size of the increment or decrement from the previous time step; Δn θ This represents the current increment / decrement step size;

[0166] (2) Determine mod(P) based on the mod remainder function. pv When α) < 0.5, then according to the rounding function INT in equation (20) and the principle of rounding to the nearest whole number, the following steps are controlled:

[0167] Step B, the controller adjusts the increment / decrement Δn based on the previous time step. θ-1 Adding a perturbation step size to the current increase / decrease Δn gives the current increment / decrement. θ The step size is Δn θ =Δn θ-1 +1 controls the stepper motor to rotate, changing the resistance value of the heating water resistor, while the controller continues to read the photovoltaic power generation current I. pv and voltage U pv The output power of photovoltaic power generation was calculated. And compared with the photovoltaic power generation at the previous moment Compare.

[0168] When judging The controller repeats step B.

[0169] When judging At that time, the heating water resistance generated by the distance between the current involute water electrode and the fixed water electrode is determined and adapted to the maximum power point of photovoltaic power generation.

[0170] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An involute water electrode photovoltaic power generation and heat storage system, characterized in that: It comprises a heat storage tank, a water electrode group, a photovoltaic power supply system and a monitoring system; the water electrode group is arranged in the heat storage tank, and the photovoltaic power supply system is arranged around the heat storage tank; the heat storage tank is provided with a water inlet, a water outlet, an exhaust pipeline and a pressure reducing valve; The water electrode group comprises an involute water electrode, an involute water electrode rotating connecting rod, a stepping motor, a fixed water electrode, a fixed water electrode fine adjustment rod and a water electrode fixing support; the water electrode fixing support is respectively provided with the involute water electrode rotating connecting rod, a bearing hole and a fixed water electrode sliding rail; the fixed water electrode slides left and right on the fixed water electrode sliding rail, and the water electrode fixing support is made of an insulator; the involute water electrode rotating connecting rod is arranged at the center of the base circle of the involute water electrode; one end of the involute water electrode rotating connecting rod is connected with the stepping motor, and the other end of the involute water electrode rotating connecting rod is connected with a bearing through the water electrode fixing support; the involute water electrode rotates under the drive of the stepping motor, changes the relative position of the fixed water electrode through the involute water electrode rotating connecting rod, and the fixed water electrode is arranged on the water electrode fixing support and provided with the fixed water electrode fine adjustment rod at the middle position of the lower part; the position of the fixed water electrode is changed through the rotation of the fixed water electrode fine adjustment rod. The photovoltaic power supply system comprises a photovoltaic array and a power electronic square wave commutator; the output positive electrode and the output negative electrode of the photovoltaic array are connected with the power electronic square wave commutator; the power electronic square wave commutator is switched through a power electronic switch, so that the power supply formed by the output positive electrode and the output negative electrode of the photovoltaic array is converted into a square wave output power supply; the square wave output of the power electronic square wave commutator is connected with the involute water electrode and the fixed water electrode through two wires respectively, so as to provide a positive and negative alternating period change power supply for the water electrode group. The monitoring system comprises a controller, a water electrode current sensor, a water electrode voltage sensor and a temperature sensor of the heat storage tank; the controller is connected with the water electrode current sensor, the water electrode voltage sensor and the temperature sensor of the heat storage tank through a communication cable and connected with all controlled units and the stepping motor through a control cable.

2. The involute water electrode photovoltaic power generation and heat storage system according to claim 1, characterized in that: The involute water electrode rotating connecting rod, the fixed water electrode fine adjustment rod and the water electrode fixing support are made of an insulator; the involute water electrode and the fixed water electrode are made of a metal conductive sheet material and provided with a plurality of holes, which are beneficial to the flow of water and reduce the disturbance of bubbles generated in the water body heating process to the water electrode; the metal conductive sheet material is curled and formed into a 360° involute water electrode based on the involute shape.

3. The involute water electrode photovoltaic power generation and heat storage system according to claim 1, characterized in that: The stepping motor is arranged outside the heat storage tank.

4. The involute water electrode photovoltaic power generation and heat storage system according to claim 1, characterized in that: The handle end of the fixed water electrode fine adjustment rod penetrates the tank wall outside the heat storage tank.

5. The involute water electrode photovoltaic power generation and heat storage system according to claim 1, characterized in that: The controller is arranged around the heat storage tank, reads sensor data in real time, and controls the controlled units according to algorithms, models and control strategies.

6. The control method of the involute water electrode photovoltaic power generation and heat storage system according to any one of claims 1-5, characterized in that, Specifically, the method comprises the following steps: Step 1, initialization setting; Step 2, rapid locking of a photovoltaic power generation maximum power point section; Step 3, fine photovoltaic power generation maximum power tracking control.

7. The control method according to claim 6, characterized by The step 1 specifically comprises: Step 1.1, input photovoltaic array parameters, including installed capacity, array tilt angle, array orientation, horizontal diffuse reflection coefficient, open circuit voltage, short circuit current, photovoltaic power generation, solar total irradiance and typical photovoltaic maximum power point table; Step 1.2, determine the involute water electrode maximum minimum displacement step number and the corresponding photovoltaic power generation maximum power point, specifically including: (1) fine adjustment of the fixed water electrode to determine First, the controller uses the maximum step size n. θ =m θ Drive the rotating involute water electrode to rotate to a linear distance L between it and the fixed water electrode. n The closest position, at this moment, the heating water resistance R w To minimize the impact, according to equation (9), the involute water electrode is rotated to a linear distance L between itself and the fixed water electrode by manually adjusting the stroke of the fine-tuning rod of the fixed water electrode. n To make the maximum point power P of the water electrode water Maximum point power of photovoltaic power generation with the maximum local irradiance Equal, that is wherein, δ d is the water conductivity; S g is the fixed water electrode area; U water is the heating water resistance voltage applied in the water body; P water is the maximum point power of the water electrode; L n is the linear distance between the fine-tuning fixed water electrode and the involute water electrode; R w is the heating water resistance; n θ is the number of stepper motor steps; (2) determining Firstly, the controller drives the selected involute water electrode to rotate to the linear distance L from the fixed water electrode by the minimum step number n θ =1 n The farthest position, the heating water resistance R w The maximum, according to the formula (9), (10), (11) and (12) and the typical photovoltaic maximum power point table, find the involute water electrode and the linear distance L from the fixed water electrode n The power P water Corresponding to the local smaller irradiance photovoltaic power generation maximum power point That is Wherein, r is the base circle radius of the involute water electrode; oA is the length of the line segment between the center of the involute water electrode base circle and the fixed water electrode; θ is the angle of rotation of the involute water electrode; Vmp is the maximum power point voltage of photovoltaic power generation; Vmp is the maximum power point voltage of photovoltaic power generation; Vmp is the maximum power point voltage of photovoltaic power generation; Step 1.3, establish a fast locking photovoltaic power generation maximum power point section stepping motor step point, specifically including: Considering the response speed of mechanical photovoltaic maximum power tracking, the segmented photovoltaic maximum power tracking is adopted; first, based on the initialized photovoltaic array parameters and the total solar irradiance and the typical photovoltaic maximum power point table, the fast locking segmented photovoltaic maximum power point table under different illumination is established; the stepper motor rotates the angle θ with a step n θ =1, rotates the rotating involute water electrode by 360 degrees, and obtains the step number of the stepper motor Wherein n θ =1, 2, 3, …, m θ , the step number in units of 10 Through the photovoltaic maximum power point under the local maximum irradiance And the photovoltaic maximum power point under the local smaller irradiance Range, divided by Get the segmented number of photovoltaic maximum power point under different illumination, that is: And the photovoltaic power generation maximum power point corresponding to the segment endpoint: Wherein, n m The maximum power point of photovoltaic power generation known for a certain segment The number of stepping motor steps, n m =1,2,3,…,mp, thus determining the maximum power point of photovoltaic power generation at each segment point by table lookup method The value of each adjacent segment photovoltaic power generation maximum power point difference is a constant α, that is: Wherein, mp is the number of segments of the photovoltaic power generation maximum power point; is the photovoltaic power generation maximum power point value of the local maximum irradiance; θ is the angle of rotation of the involute water electrode; is the number of steps n of the stepper motor θ is the photovoltaic power generation maximum power point of the segment point; is the number of steps n of the stepper motor θ is the photovoltaic power generation maximum power point voltage of the segment point; is the number of steps n of the stepper motor θ is the photovoltaic power generation maximum power point current of the segment point; α is the difference value of each adjacent segment photovoltaic power generation maximum power point, which is a constant; is the photovoltaic power generation maximum power point corresponding to a certain segment point, n m = 1, 2, 3, …, mp; n θ is the number of steps n of the stepper motor when the involute water electrode rotates 360 degrees, the minimum number of steps n θ = 1 to the maximum number of steps n θ = m θ According to formula (12), the one-to-one corresponding photovoltaic power generation maximum power point in the local irradiance range is obtained That is:

8. The control method according to claim 7, characterized by The step 2, fast locking photovoltaic power generation maximum power point section specifically includes: The controller reads the photovoltaic power generation current I pv and the photovoltaic power generation voltage U pv in real time, calculates the photovoltaic power generation output power P pv , and calculates the difference between the output power P pv and the maximum power point T of the photovoltaic power generation at the previous moment. 2.1 When ΔP pv ≥ 0, the photovoltaic power generation output power P pv is divided by the maximum power point difference constant α of each adjacent section, that is: The divisor result keeps one digit after the decimal point, and is judged according to the mod remainder function: mod(P pv ,α)≥0.5 (19) Wherein, Pmax(n-1) is the maximum power point of photovoltaic power generation at the previous moment; n θ-1 Pmax(n-1) is the maximum power point of photovoltaic power generation at the previous moment N is the step motor step number of the previous moment; I pv I is the current photovoltaic power generation current; U pv U is the current photovoltaic power generation voltage; P pv P is the current photovoltaic power generation output power; (1) If mod(P pv ,α)≥0.5, then according to the rounding function: and the principle of rounding off to the nearest integer, the maximum power point of the photovoltaic power generation of a certain section is determined and the maximum power point of the photovoltaic power generation is determined falls between and , thereby obtaining n θ = n m × 10 stepper motor steps, according to the nth θ = n m × 10 stepper motor steps minus the stepper motor step number n θ-1 of the maximum power point of the photovoltaic power generation at the previous time , the increase / decrease amount Δn θ of the stepper motor in steps, i.e. Δn θ = 10n m -n θ-1 ; Wherein, mod is the remainder function; INT is the integer function; n m Segmented photovoltaic power generation maximum power point; n m -1Segmented photovoltaic power generation maximum power point; n θ Segmented photovoltaic power generation maximum power point at the time; n θ-1 Segmented photovoltaic power generation maximum power point at the time n θ Segmented photovoltaic power generation maximum power point at the time Wherein, n m The maximum power point of photovoltaic power generation known for a segment The number of step motor steps, set in the initialization. At this time, the controller controls the step motor to rotate to 10n θ The maximum power point of photovoltaic power generation m by n The linear distance L of the involute water electrode relative to the fixed water electrode is reduced n , thereby reducing the resistance of the heating water resistance and quickly locking the maximum power point of the segmented photovoltaic power generation At the same time, the controller reads the photovoltaic power generation current I pv and voltage U pv , calculates the photovoltaic power generation output power P pv , and performs fine photovoltaic power generation maximum power tracking control in step 3; (2) For example, the modulo modulo function determines mod(P) pv When α) < 0.5, the maximum power point of photovoltaic power generation in a certain segment is determined according to the rounding function INT in equation (20) and the principle of rounding to the nearest whole number. And determine the maximum power point of photovoltaic power generation. Falling and Between, thus obtaining n θ =n m ×10 stepper motor step lengths, based on the nth step θ =n m ×10 step size of stepper motors minus the maximum power point of photovoltaic power generation at the previous moment The number of steps n of the stepper motor θ-1 The increase or decrease of the stepper motor Δn is obtained. θ Each step size, i.e., Δn θ =10n m -n θ-1 , where n m The point where the maximum photovoltaic power generation is known for a certain segment. The number of stepper motor steps is set during initialization; at this time, the controller adjusts the step size based on the increment / decrement Δn. θ The stepper motor rotates to 10n using a step control. m At the point of maximum photovoltaic power generation Reduce the linear distance L between the involute water electrode and the fixed water electrode. n This reduces the resistance of the heating water and quickly locks in the maximum power point of segmented photovoltaic power generation. Simultaneously, the controller reads the photovoltaic power generation current I in real time. pv and photovoltaic power generation voltage U pv The photovoltaic power output P was calculated. pv Step 3 involves refined photovoltaic power generation maximum power tracking control. Wherein, n is the number of steps of the stepper motor m Segmented photovoltaic power generation maximum power point; n is the number of steps of the stepper motor m +1 segmented photovoltaic power generation maximum power point; n is the number of steps of the stepper motor θ Segmented photovoltaic power generation maximum power point at Δn θ n is the number of steps of the stepper motor 2.2 When ΔP pv < 0, the photovoltaic power generation output power P pv is divided by the maximum power point difference constant α of each adjacent section, as shown in formula (18), the result of the divisor is kept to one decimal place, and mod(P pv , α) ≥ 0.5: (1) For example, the modulo function determines mod(P) pv When α)≥0.5, the maximum power point of photovoltaic power generation in a certain segment is determined according to the rounding function INT in equation (20) and the principle of rounding to the nearest whole number. And determine the maximum power point of photovoltaic power generation. Falling and Between, thus obtaining n θ =n m ×10 stepper motor step sizes, based on the previous moment's maximum photovoltaic power generation point. The number of steps n of the stepper motor θ-1 Subtract n θ =n m Multiply by 10 stepper motor step lengths to obtain the stepper motor reduction Δn. θ Each step size, i.e., Δn θ =n θ-1 -10n m , where n m The point where the maximum photovoltaic power generation is known for a certain segment. The number of stepper motor steps is set during initialization; at this time, the controller determines the step size based on the decrement Δn. θ The stepper motor rotates to 10n using a step control. m At the point of maximum photovoltaic power generation Increase the linear distance L between the involute water electrode and the fixed water electrode. n This increases the resistance of the heating water, allowing for rapid locking of the maximum power point of segmented photovoltaic power generation. Simultaneously, the controller reads the photovoltaic power generation current I in real time. pv and voltage U pv The photovoltaic power output P was calculated. pv Step 3 involves refining the maximum power point tracking control of photovoltaic power generation. (2) For example, the modulo modulo function determines mod(P) pv When α) < 0.5, the maximum power point of photovoltaic power generation in a certain segment is determined according to the rounding function INT in equation (20) and the principle of rounding to the nearest whole number. And determine the maximum power point of photovoltaic power generation. Falling and Between, thus obtaining n θ =n m ×10 stepper motor step sizes, based on the previous moment's maximum photovoltaic power generation point. The number of steps n of the stepper motor θ-1 Subtract n θ =n m Multiply by 10 stepper motor step lengths to obtain the stepper motor reduction Δn. θ Each step size, i.e., Δn θ =n θ-1 -10n m , where n m The point where the maximum photovoltaic power generation is known for a certain segment. The number of stepper motor steps is set during initialization; at this time, the controller determines the step size based on the decrement Δn. θ The stepper motor rotates to 10n using a step control. m At the point of maximum photovoltaic power generation Increase the linear distance L between the involute water electrode and the fixed water electrode. n This increases the resistance of the heating water, allowing for rapid locking of the maximum power point of segmented photovoltaic power generation. Simultaneously, the controller reads the photovoltaic power generation current I in real time. pv and voltage U pv The photovoltaic power output P was calculated. pv Step 3 involves refining the maximum power tracking control of photovoltaic power generation.

9. The control method according to claim 8, characterized by, The step 3 specifically includes: Through the fast locking photovoltaic power generation maximum power point section of step 2, the controller reads the photovoltaic power generation current I in real time pv And photovoltaic power generation voltage U pv , the output power P of photovoltaic power generation is calculated pv And compared with the segmented photovoltaic power generation maximum power point Respectively judge Or Step 3.1, judging ΔP according to formula (17) pv ≥ 0, photovoltaic power generation increases, and the maximum power point of the segmented known photovoltaic power generation Comparison, judgment When: (1) If mod(P pv ,α)≥0.5, then control the following steps according to the rounding function INT and the principle of rounding 5 up in formula (20): Step A, the controller according to the previous time increment Δn θ-1 one disturbance step, the current increment Δn θ one step, namely Δn θ = Δn θ-1 -1, the controller continues to read the photovoltaic current I pv and voltage U pv , the photovoltaic power output is calculated and compared with the photovoltaic power output at the previous time ; When the judgment is repeated by the controller; When judging that the current heating water resistance generated by the distance between the involute water electrode and the fixed water electrode is adapted to the maximum power point of the photovoltaic power generation wherein, is the current photovoltaic power output; is the photovoltaic power output at the previous time; Δn θ-1 is the previous increment / decrement step; Δn θ is the current increment / decrement step; (2) If mod(P pv ,α) < 0.5, then according to the principle of rounding function INT and 4 rounding 5 in formula (20), the following steps are taken: Step B, the controller according to the previous time increment Δn θ-1 plus a perturbation step, the current increment Δn θ is obtained θ = Δn θ-1 + 1, the stepper motor is rotated to change the resistance value of the heating water resistance, and the controller continues to read the photovoltaic power generation current I pv and voltage U pv , the photovoltaic power generation output power P is calculated and compared with the photovoltaic power generation power P of the previous time The controller repeats step B when it judges that the battery is not fully charged. When judging that the current heating water resistance generated by the distance between the involute water electrode and the fixed water electrode is adapted to the maximum power point of the photovoltaic power generation

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