Multi-loop variable-voltage working combined heat and power system and control method

Abstract

The invention relates to the technical field of photovoltaic heating, in particular to a multi-loop variable-voltage working heat and power cogeneration system and a control method, and the method comprises the steps that system working data of the heat and power cogeneration system are collected; based on the system working data, a first relation model of the system working voltage and the temperature of the resistive heating tail end is established, and based on the first relation model, a second relation model of the inclined plane solar radiation intensity and the temperature of the resistive heating tail end is established; and determining a solar radiation intensity control point according to the second relation model, and starting a multi-loop control strategy under the condition that the real-time radiation intensity is lower than the solar radiation intensity control point. According to the method, it is considered that the output voltage of a photovoltaic array in the combined heat and power system can be changed due to the influence of the solar radiation intensity, and therefore the heat energy grade of the resistive heating tail end is improved by formulating a reasonable heating tail end loop control strategy.

Description

Technical Field

[0001] This application relates to the technical field of photovoltaic heating, and particularly relates to a cogeneration system with multi-loop variable voltage operation and a control method therefor. Background Art

[0002] The popularization of the price of photovoltaic panels makes it possible to widely promote and apply them. Combining an off-grid solar photovoltaic power generation system with a resistive heating terminal can reliably solve the heating problem of decentralized buildings in severely cold and cold regions. However, the off-grid solar power generation system is affected by local meteorological conditions, and its power generation capacity shows volatility and randomness. When the off-grid solar power generation system is used for a resistive heating terminal, due to the lack of mains power supplement, the random voltage fluctuation is likely to cause a change in the heat generation temperature of the resistive heating. When the solar energy is sufficient and the power generation capacity is strong, the working voltage of the resistive terminal is high and the heating temperature is also high. When the solar energy weakens and the power generation capacity decreases, the working voltage of the resistive terminal is low and the heating temperature is also low. Due to the difference in the quality of heat energy, when the temperature is lower than or close to the indoor ambient temperature, the quality of heat energy is significantly reduced, and indoor heating cannot play a heating role (here, it is considered that the heat generation when the temperature of the resistive terminal is lower than a certain indoor temperature setting value is low-grade heat energy).

[0003] Aiming at the problem of the change in the quality of heat energy caused by the fluctuating change in the terminal heating temperature in the heating system combining an off-grid solar photovoltaic power generation system with a resistive terminal, this application proposes a cogeneration system with multi-loop variable voltage operation and a control method therefor. This system uses a multi-loop technical solution to increase the surface temperature of the resistive heating terminal when the off-grid solar photovoltaic power generation system has a low power generation capacity and outputs high-grade heat energy as much as possible. Summary of the Invention

[0004] This application provides a cogeneration system with multi-loop variable voltage operation and a control method therefor. By considering that the output voltage of the photovoltaic array in the cogeneration system will change under the influence of solar radiation intensity, a reasonable control strategy for the heating terminal loop is formulated to improve the quality of heat energy of the resistive heating terminal.

[0005] In a first aspect, an embodiment of this application provides a control method for a cogeneration system with multi-loop variable voltage operation, which can be applied to a control device in a cogeneration system with multi-loop variable voltage operation. The cogeneration system is used to control the power supply of a resistive heating terminal. The method includes: Collecting the system operation data of the cogeneration system; Based on the system operation data, establishing a first relationship model between the system operation voltage and the temperature of the resistive heating terminal, and based on the first relationship model, establishing a second relationship model between the inclined-plane solar radiation intensity and the temperature of the resistive heating terminal; Determine a solar radiation intensity control point according to the second relationship model, and start a multi-loop control strategy when the real-time radiation intensity is lower than the solar radiation intensity control point; The multi-loop control strategy includes: The number of circuit startups of the heating terminal is determined based on a control function with multi-objective constraints, and the number of circuits of the heating terminal is dynamically adjusted to maintain the temperature of the heating terminal above a set temperature threshold.

[0006] In the above implementation, by establishing a double-layer relationship model between the working voltage of the photovoltaic system and the terminal temperature of the heating, the precise response relationship between the solar energy volatility and the terminal temperature of the heating is obtained, which effectively solves the problem of low thermal energy quality of the resistive heating terminal when the off-grid solar photovoltaic power generation system has low power generation capacity; secondly, based on the dynamic judgment mechanism of the solar radiation intensity control point, it can automatically trigger multi-loop optimization control when the light is insufficient, and increase the supply voltage of the start-up loop by reducing the number of working loops, thereby ensuring that the terminal temperature of the heating is always maintained in the effective heating range, avoiding ineffective heating of low-grade thermal energy; thirdly, a multi-objective constraint function is used to optimize the number of loops, while ensuring the heating temperature, taking into account the rational allocation of the heating area, and realizing a dynamic balance between the thermal energy quality and the terminal heating range; in addition, the control method makes full use of the fast response characteristics of the resistive heating terminal, forming a perfect match with the photovoltaic DC power supply system, which not only improves the heating effect, but also reduces the system complexity, and is particularly suitable for off-grid solar heating scenarios, providing a stable and reliable renewable energy heating solution for distributed buildings in cold areas.

[0007] In some embodiments, the first relationship model includes:

[0008] in, is the system operating voltage, is the end temperature of resistive heating, is the air temperature outside the resistance heating terminal, that is, the indoor temperature, is the thermal conductivity of the resistive heating terminal to the indoor wall, is the thickness from the end of the resistive heating to the indoor wall, is the surface heat transfer coefficient of the resistive heating terminal, is the resistance of a single heating module in a resistive heating terminal, and Respectively represent the total number of circuits in the resistive heating terminal and the number of heating modules in each circuit, It is the installation area of the resistive heating terminal. is the resistance of the photovoltaic array and other components in the cogeneration system, is the number of heating circuits in operation in the resistive heating terminal, is the thermal efficiency of the resistive heating terminal.

[0009] In some embodiments, the second relational model includes:

[0010] where is the solar radiation intensity on the inclined plane, is the laying area of the photovoltaic panel, is the power generation efficiency of the photovoltaic array in the cogeneration system, 额 is the rated output voltage of the photovoltaic array, is the solar radiation intensity value when the photovoltaic array reaches the rated output voltage.

[0011] In some embodiments, determining the solar radiation intensity control point according to the second relational model includes: Set the minimum effective value of the resistive heating terminal temperature as T set +p, Based on the minimum effective value of the terminal temperature and the second relational model, determine the solar radiation intensity control point E set , 0 E set :

[0012] where p is the temperature difference threshold parameter, representing the minimum effective temperature difference between the resistive heating terminal temperature and the indoor set temperature.

[0013] In some embodiments, determining the number of loop starts of the heating terminal based on the multi-objective constraint control function, and dynamically adjusting the number of loops of the heating terminal to maintain the temperature of the heating terminal higher than the set temperature threshold, includes: Maximize the weighted benefit of the terminal temperature and the heating area; Based on the constraint conditions of the upper limit of the number of loops, the terminal temperature safety threshold, and the minimum effective temperature difference, obtain the control function; and determine the target number of loops of the heating terminal through dynamic programming or integer programming; The control function is:

[0014]

[0015]

[0016] where is the multi-objective control function, is the resistive heating terminal temperature, is the effective heating area, is the air temperature outside the resistive heating terminal, is the thermal conductivity of the resistive heating terminal to the indoor wall surface, is the thickness from the resistive heating terminal to the indoor wall surface, is the surface heat transfer coefficient of the resistive heating terminal, is the resistance of a single heating module in the resistive heating terminal, and respectively represent the total number of circuits in the resistive heating terminal and the number of heating modules in each circuit, is the laying area of the resistive heating terminal, is the resistance of the photovoltaic array and other components in the combined heat and power system, is the number of operating heating circuits in the resistive heating terminal, is the thermal efficiency of the resistive heating terminal, is the solar radiation intensity on the inclined surface, is the laying area of the photovoltaic panel, is the power generation efficiency of the photovoltaic array in the combined heat and power system, 额 is the rated output voltage of the photovoltaic array, is the maximum value of the temperature of the resistive heating terminal.

[0017] In the control method of the combined heat and power system with multi-circuit variable voltage operation, the multi-circuit control strategy specifically includes: In the heating period, the electric power of the combined heat and power system is used for heating or electricity storage; When the real-time solar radiation intensity is higher than the solar radiation intensity control point, all circuits of the heating system are started, and the start and stop of the combined heat and power system are controlled according to the indoor temperature. The steps of controlling the start and stop of the combined heat and power system according to the indoor temperature include: If the indoor temperature is greater than the upper limit temperature of the room to be heated, control the combined heat and power system to stop running; if the indoor temperature is less than the indoor set temperature value, start the combined heat and power system; if there is excess electricity, charge the battery of the combined heat and power system based on the excess electric energy; when the real-time solar radiation intensity is not higher than the solar radiation intensity control point and greater than zero, start the multi-circuit control strategy; when the real-time solar radiation intensity is equal to zero, the battery and the external power grid conduct power supplement, and if the battery runs out of power, start the external power grid for power supplement; in the non-heating period, output the electric power of the combined heat and power system to the domestic electricity end; control the battery of the combined heat and power system to discharge in case of insufficient light, and switch to connect with the external power grid for charging when the power is lower than the power threshold.

[0018] In a second aspect, an embodiment of the present application provides a combined heat and power supply system with multi-loop variable voltage operation. The combined heat and power supply system includes a control device. The control device includes a processor and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the methods provided in the above description are implemented.

[0019] In some embodiments, the combined heat and power supply system includes an off-grid photovoltaic power generation system, a heating terminal, and a domestic power consumption terminal; the control device is a system control cabinet in the off-grid photovoltaic power generation system. The off-grid photovoltaic power generation system includes: a photovoltaic array, an irradiance meter, a temperature recorder, and a storage battery. The system control cabinet is respectively connected to the photovoltaic array, the irradiance meter, the temperature recorder, and the storage battery.

[0020] In some embodiments, the system control cabinet is further connected to the domestic power consumption terminal and the external power grid through an inverter control box.

[0021] Compared with the prior art, the beneficial effects of the present application are as follows: By establishing a double-layer relationship model between the working voltage of the photovoltaic system and the temperature of the heating terminal, an accurate response relationship between the solar energy volatility and the temperature of the heating terminal is obtained, effectively solving the problem of low thermal energy grade of the resistive heating terminal when the off-grid solar photovoltaic power generation system has low power generation capacity; Secondly, based on the dynamic judgment mechanism of the solar radiation intensity control point, multi-loop optimization control can be automatically triggered when the light is insufficient, and the supply voltage of the starting loop can be increased by reducing the number of working loops, so as to ensure that the temperature of the heating terminal is always maintained within the effective heating range, avoiding ineffective heating of low-grade thermal energy; Furthermore, a multi-objective constraint function is used to optimize the number of loops, taking into account the reasonable distribution of the heating area while ensuring the heating temperature, realizing the dynamic balance between the thermal energy grade and the terminal heating range. It can be considered that the output voltage of the photovoltaic array in the combined heat and power supply system will change due to the influence of the solar radiation intensity, so by formulating a reasonable control strategy for the heating terminal loop, the thermal energy grade of the resistive heating terminal can be improved. In addition, this control method makes full use of the fast response characteristics of the resistive heating terminal and forms a perfect match with the photovoltaic DC power supply system, improving both the heating effect and reducing the system complexity, especially suitable for off-grid solar heating scenarios, providing a stable and reliable renewable energy heating solution for decentralized buildings in cold regions. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the steps of a control method for a combined heat and power supply system with multi-loop variable voltage operation provided by an embodiment of the present application.

[0023] Figure 2 It is a schematic diagram of a combined heat and power supply system with multi-loop variable voltage operation provided by an embodiment of the present application.

[0024] Figure 3 This is a schematic diagram of the heating control logic in this application example.

[0025] Figure 4 This is a schematic diagram of the charging control logic of the storage battery in this application example of the present application. Detailed implementation manners

[0026] The present application will be further described in detail below in combination with test examples and detailed implementation manners. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present application to the following embodiments. Any technology implemented based on the content of the present application falls within the scope of protection of the present application.

[0027] In the description of the specific embodiments of the present application, without special explanation, the expression terms indicating the orientation or positional relationship such as "upper", "lower", "left", "right", "center", "inner", "outer", "side", etc. are all based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the product / device / device is usually used. These orientation or positional relationship terms are only for the convenience of describing the solution of the present application or simplifying the description in the specific embodiments, so as to facilitate technicians to quickly understand the solution, rather than indicating or implying that a specific device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship. Therefore, it should not be construed as a limitation to the present application.

[0028] In the description of the embodiments of the present application, the technical terms "first", "second", etc. only distinguish one entity or operation from another entity or operation, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise clearly and specifically defined.

[0029] Referring to "embodiment" herein means that the specific features, structures or characteristics described in combination with the embodiment may be included in at least one embodiment of the present application. The appearance of this phrase at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0030] Please refer to Figure 1 and Figure 2 , Figure 1 This is a schematic diagram of the steps of a control method for a cogeneration system with multi-loop variable voltage operation provided by an embodiment of the present application. Figure 2 This is a schematic diagram of a cogeneration system with multi-loop variable voltage operation provided by an embodiment of the present application.

[0031] Figure 2 Among them, the cogeneration system includes an off-grid photovoltaic power generation system, a heating terminal, and a domestic electricity consumption terminal; the control device is the system control cabinet in the off-grid photovoltaic power generation system, and the off-grid photovoltaic power generation system includes: a photovoltaic array 1, a system control cabinet 2, an irradiance meter 3, a temperature recorder 4, and a storage battery 5. The system control cabinet 2 is respectively connected to the photovoltaic array 1, the irradiance meter 3, the temperature recorder 4, and the storage battery 5. The heating terminal includes a terminal control switch 6 and a resistive heating terminal 7; the system control cabinet 2 is also connected to the domestic AC electricity consumption terminal 9 and the external power grid 10 through an inverter control box 8. In some cases, the external power grid 10 can be the mains power grid.

[0032] Specifically, the photovoltaic array 1 consists of m groups of photovoltaic panels with the same specifications and the same quantity, and the number of photovoltaic panels in each group is n. The photovoltaic panels within each group are connected in series with each other, and the m groups of photovoltaic panels are connected in parallel. The system control cabinet 2 includes functions such as power collection, maximum power point tracking, and data acquisition and analysis. The power collection device inside the system control cabinet 2 integrates the power input by the photovoltaic array 1 and outputs the system working voltage through the maximum power point tracking technology. The system control cabinet 2 transmits the power signal , the hourly inclined-plane solar radiation intensity collected by the irradiance meter 3 , the indoor temperature monitored by the temperature recorder 4 and the resistive heating terminal temperature signal, the power signal of the storage battery 5 are collected, so as to control the system according to the working strategy.

[0033] The heating terminal is composed of a terminal control switch 6 and a resistive heating terminal 7; the other electricity consumption terminals are composed of an inverter control box 8, a domestic AC electricity consumption terminal 9, and the mains power grid 10.

[0034] Specifically, the resistive heating terminal 7 internally consists of x heating circuits, and each circuit has y resistive heating modules. The terminal control switch 6 controls the on / off of the heating circuits in the resistive heating terminal 7 by receiving the signal from the system control cabinet 2, that is, during the heating period, the system control cabinet 2 commands the terminal control switch 6 to control the number of activated heating circuits according to the system signal. When heating with photovoltaic power generation during the day, there is no mains power to supplement the heating terminal 7, and it relies entirely on solar power generation for DC heating. At this time, its working voltage changes with the fluctuation of the power generation capacity. During the non-heating season or when heating is not required, the system control cabinet 2 switches the circuit according to the system signal and supplies power to the domestic AC electricity consumption terminal 9 through the inverter control box 8; when the photovoltaic power supply system is damaged or under maintenance, the mains power grid 10 can supply power to the domestic AC electricity consumption terminal 9 through the inverter control box 8. Specifically, the inverter control box 8 includes functions such as inverting the DC input into AC and merging it with the mains power, and power quantity statistics.

[0035] The control method of the cogeneration system with multi-circuit variable voltage operation can be applied to the system control cabinet 2, and the steps of this method can include: S1. Collect the system operating data of the cogeneration system.

[0036] Among them, the system operating data of the cogeneration system can include the output voltage of the photovoltaic array 1 , the indoor temperature , the temperature of the resistive heating terminal , the solar radiation intensity on the inclined surface of the photovoltaic panel and the power signal of the storage battery etc. The resistive heating terminal 7 is a heating device in the cogeneration system that directly converts electrical energy into heat energy, and its core principle is to generate Joule heat through the current flowing through the resistive material to achieve heating.

[0037] When the cogeneration system is built, the following parameters are default input to the system and are known parameters: the rated output voltage of the photovoltaic array 1 额 (V); the total number of circuits x in the resistive heating terminal 7, the number of resistive heating modules y (pieces) in each circuit; the resistance R (Ω) of a single heating module; the resistance of the photovoltaic panels and other components in the cogeneration system (Ω); the thermal efficiency of the resistive heating terminal 7 ; the laying area of the resistive heating terminal 7 (m 2 ); the thickness δ (m) from the resistive heating terminal 7 to the indoor wall surface; the thermal conductivity λ (W / (m·K)) from the resistive heating terminal 7 to the indoor wall surface; the indoor set temperature or indoor heating temperature T set (°C); the laying area of the photovoltaic panel (m 2 ); the photovoltaic power generation efficiency ; the upper limit temperature T set (°C).

[0038] S2. Establish a first relationship model between the system operating voltage and the temperature of the resistive heating terminal based on the system operating data, and establish a second relationship model between the solar radiation intensity on the inclined surface and the temperature of the resistive heating terminal based on the first relationship model.

[0039] Exemplarily, the first relationship model includes:

[0040] Among them, is the system operating voltage, is the temperature of the resistive heating terminal, is the air temperature outside the resistive heating terminal 7, i.e., the indoor temperature, is the thermal conductivity of the resistive heating terminal 7 to the indoor wall surface, is the thickness from the resistive heating terminal 7 to the indoor wall surface, is the surface heat transfer coefficient of the resistive heating terminal 7, is the resistance of a single heating module in the resistive heating terminal, and respectively represent the total number of circuits in the resistive heating terminal 7 and the number of heating modules in each circuit, is the laying area of the resistive heating terminal 7, is the resistance of the photovoltaic array 1 and other components in the combined heat and power system, is the number of operating heating circuits in the resistive heating terminal 7, is the thermal efficiency of the resistive heating terminal 7.

[0041] Exemplarily, the method for establishing the first relationship model between the system operating voltage and the temperature of the resistive heating terminal based on the system operating data includes: obtaining the current terminal heating power according to the collected data and the known component information of the system, and deriving the relationship between the system operating voltage and the temperature of the resistive heating terminal in combination with the terminal heat transfer mechanism.

[0042] 1. Determine the heating power per unit area of the resistive heating terminal ( ): The resistive heating terminal generally refers to a heating device that generates heat by passing current through a resistor, such as a resistance wire heater, an electric heating film, an electric blanket, etc. In the circuit, ignoring the influence of temperature on the resistance, the resistive terminal conforms to Ohm's law and Joule's law. Therefore, the electric power and heat generation can be calculated according to the voltage and current conditions on both sides of the heating terminal.

[0043] The number of operating heating circuits in the resistive heating terminal 7 is z ( ). When z heating circuits are operating, the voltage of the resistive heating terminal is: ; the current is ; the heating power is: ; when z heating circuits are operating, the heating power per unit area of the resistive heating terminal is: , where is the laying area of the resistive heating terminal, with the unit of m 2 ; is the heat conversion efficiency of the resistive heating terminal.

[0044] 2. Determine the relationship between the heat transfer amount ( ) and the temperature ( ) of the resistive heating terminal: When resistive heating terminals are installed in a room for heating, the heat transfer situation of the heating terminals is closely related to building envelope parameters, ventilation conditions, indoor and outdoor temperatures, etc. The heat transfer of the heating terminals to the indoor environment includes heat conduction, heat convection, and heat radiation (ignored). The heat transfer process is expressed as: In the formula, is the heat transfer per square meter of the heating terminal, W / m 2 ; and are the temperature of the resistive heating terminal and the air temperature outside the resistive heating terminal 7 (regarded as the indoor air temperature), °C; is the surface heat transfer coefficient, W / (m 2 ·K). When the indoor air flow changes little, the surface heat transfer coefficient h can be regarded as a constant. And in the established system, δ, parameters such as λ are fixed values. Then is proportional to ( ).

[0045] 3. Determine the relationship between the system operating voltage ( ) and the temperature of the resistive heating terminal ( ): The heat transfer per unit area of the heating terminal is equal to the heating power of the heating terminal . Then the first relationship model can be obtained: . By simplifying the first relationship model, the functional relationship between the system operating voltage and the temperature of the resistive heating terminal can be obtained: . In the formula, k represents the proportionality coefficient and is a positive value. k The value of is related to the system configuration and the value of z. It can be obtained from the formula that is positively correlated with (

[0046] When the system operating voltage is relatively low, the temperature of the resistive heating terminal 7 will also decrease accordingly, that is, the energy grade of the heat energy will decrease. Once the temperature of the resistive heating terminal is close to the room temperature or lower than the indoor set value , the resistive heating terminal 7 will not be able to play a heating role.

[0047] Furthermore, the second relationship model is:

[0048] Among them, is the solar radiation intensity on the inclined surface, is the laying area of the photovoltaic panel, is the power generation efficiency of the photovoltaic array 1 in the combined heat and power system, 额 is the rated output voltage of the photovoltaic array 1, is the solar radiation intensity value when the photovoltaic array 1 reaches the rated output voltage.

[0049] Exemplarily, since the power generation capacity in the photovoltaic power generation system shows randomness and volatility with the change of solar radiation intensity, the system operating voltage output when the solar radiation intensity is weak decreases, and the surface temperature of the resistive heating terminal 7 decreases accordingly. Therefore, the method of establishing the second relationship model between the inclined-plane solar radiation intensity and the temperature of the resistive heating terminal based on the first relationship model may include: 1. The relationship between the inclined-plane solar radiation intensity ( E i ) and the system operating voltage ( ): First, the calculation formula for the power generation efficiency of the photovoltaic array 1 is , where is the area of the photovoltaic panel, m 2 ; is the solar radiation intensity on the inclined plane of the photovoltaic panel, W / m 2 ; is the photovoltaic power generation efficiency, which is related to factors such as the power generation characteristics of the photovoltaic panel itself, the temperature of the photovoltaic panel, and the environmental temperature and humidity. Generally, the value range of

[0050] is between 10% and 25%. 额 It should be noted that under strong solar irradiation conditions, when the photovoltaic module reaches the rated output voltage , the output voltage no longer increases with the increase of light intensity. Set the solar radiation intensity value at this time as ,

[0051] 2. Determine the relationship between the system operating voltage ( ) and the temperature of the resistive heating terminal ( ): The relationship between the solar radiation intensity E i and the system operating voltage U 1,i is substituted into the system operating voltage U 1,i and the temperature of the resistive heating terminal In the relationship, obtain the solar radiation intensity of the inclined surface E i And the temperature of the resistive heating terminal The relationship of:

[0052] In the formula λ , δ , h、 , , R, r0, η 0, And other parameters are positive. Simplifying the above formula can obtain:

[0053] In the formula, ε , k Are constants.

[0054] S3. Determine the solar radiation intensity control point according to the second relationship model. When the real-time radiation intensity is lower than the solar radiation intensity control point, start the multi-loop control strategy.

[0055] Among them, the process of determining the solar radiation intensity control point according to the second relationship model includes: Set the minimum effective value of the temperature of the resistive heating terminal to be . According to the second relationship model, when the light intensity is , the predicted working temperature of the resistive heating terminal Is related to ε , , . Since ε, k Are all positive values, when It satisfies , but the smaller the solar radiation intensity, And Are closer, and the heating effect is less ideal.

[0056] Set the indoor heating temperature to T set . To ensure the heat exchange effect between the heating terminal and the indoor, Should be greater than the indoor heating temperature by a certain value, that is: T set

[0057] Among them, p is the temperature difference threshold parameter, indicating the minimum effective temperature difference between the temperature of the resistive heating terminal and the indoor set temperature. Generally, it can be taken as 5-10°C to ensure effective terminal heating.

[0058] When T set At this time, the corresponding solar radiation intensity is defined as the solar radiation intensity control point E set (0 E set ), and the multi-loop control strategy is started at At this time

[0059] Based on the lowest effective value of the terminal temperature and the second relationship model, determine the solar radiation intensity control point E that meets the lowest effective value of the temperature set :

[0060] Furthermore, the multi-loop control strategy may include: Based on the control function with multi-objective constraints, determine the number of loops started at the heating terminal, and dynamically adjust the number of loops at the heating terminal to maintain the temperature at the heating terminal higher than the set temperature threshold

[0061] Specifically, the control logic of the multi-loop variable voltage control strategy is: at E set At this time, all loops at the heating terminal are started to heat the indoor space E set At this time, start the multi-loop variable voltage control strategy, and increase the terminal temperature by changing the number of loops. Essentially E set At this time, the reason for the improvement of the thermal energy grade of the resistive heating terminal 7 is that: with a certain solar radiation intensity, reducing the number of operating loops of the resistive heating terminal 7 will cause an increase in the voltage of the resistive heating terminal 7, thereby increasing the terminal temperature. And at this time, the voltage of the resistive heating terminal always satisfies: 额 , E set At this time, the voltage of the resistive heating terminal is always less than the system voltage under the rated working condition At this time, it can be known that , expand and simplify to get: , the physical meaning of this inequality means that at E set At this time, the maximum power generation of the photovoltaic power generation is always less than the electric power of the resistive heating terminal 7 under the rated conditions

[0062] The goal of the multi-loop variable voltage control strategy is to increase the temperature of the resistive heating terminal 7, that is, to improve the thermal energy grade of the terminal under low irradiation intensity ( ). On this basis, the larger the number of loops of the resistive heating terminal 7, the better its heat transfer effect. Considering the safety and comfort of the heating temperature, a maximum value constraint ( ) is imposed on the temperature of the resistive heating terminal. Generally speaking is around °C. The multi-objective function can be expressed as:

[0063] During a certain period h 、 、 values such as etc. can be regarded as fixed values. Users can select the weights of the resistive heating terminal temperature and the operating area of the resistive heating terminal according to their needs, and optimize and calculate the optimal number of loops z ( , ).

[0064] Furthermore, in the method provided by this application, when the real-time radiation intensity is higher than the solar radiation intensity control point, all loops of the heating system are started, and the start and stop of the combined heat and power system are controlled according to the indoor temperature. The steps of controlling the start and stop of the combined heat and power system according to the indoor temperature may include: If the indoor temperature is greater than the upper limit temperature T of the heated room temperature set , then control the combined heat and power system to stop running; If the indoor temperature is less than the indoor set temperature value T set , then start the combined heat and power system; if there is excess power, charge the battery of the combined heat and power system based on the excess electrical energy. In the case of non-heating period, output the power of the combined heat and power system to the domestic electricity end; Control the battery of the combined heat and power system to discharge in case of insufficient light, and switch to connect to the external power grid 10 for charging when the power is lower than the power threshold.

[0065] Exemplarily, the solution provided by this application mainly involves two aspects of heating and power supply. The overall control logic is: during the heating period, photovoltaic power generation is used for heating, and the excess electrical energy during the day is stored through the battery 5, and the battery 5 is used for heating at night; while during the non-heating period, the system only supplies power to the AC load.

[0066] The control method can collect data hourly based on the system control cabinet 2, including the output voltage of the photovoltaic array 1 , the inclined-plane solar radiation intensity , the indoor air temperature , the actual heating terminal temperature . The room heating temperature is , and the solar radiation intensity control point is E set . After the system is put into trial operation, through the comparison of the calculated value and the measured value of the resistive heating terminal temperature , the corrected value is obtained. ε, k value.

[0067] During the heating period: When [time], all circuits of the heating system are started and controlled to start and stop according to the room temperature control system: Set the indoor air temperature greater than T set +M, the heating system stops running; when less than T set the heating system starts, and so on in a cycle. In addition, at this time, the light is sufficient, and the excess electric energy charges the battery 5, and it stops charging when it is full.

[0068] When [time], start the multi-circuit variable voltage control mode: According to the current , value, optimize and calculate the optimal z ([time], [time]) value of the number of heating circuits according to the scheme provided in the above description, and the resistive heating end 7 starts z circuits for heating until the end of this time step. ,

[0069] When it is night, the battery 5 and the mains power can be used for power supply. If the battery 5 power is less than 10%, the mains power heating is enabled; if the battery 5 power is not less than 10%, the remaining power of the battery 5 is used for heating until the battery 5 power is less than 10% and the heating switch of the battery 5 is disconnected, and the mains power is enabled.

[0070] During the non-heating period: The photovoltaic power generation system supplies power to the domestic AC power end 9: The system control cabinet 2 controls the photovoltaic power generation system to supply power to the domestic AC power end 9 during the day according to the solar radiation intensity E i of the irradiance meter 3 and the real-time data of the battery 5 power. The battery 5 stores the electricity for use at night. When the power of the photovoltaic power generation system cannot meet the demand of the domestic AC power end 9, the battery 5 and the mains power grid 10 supplement to ensure the demand of the domestic AC power end 9.

[0071] In the solution provided by the embodiment of the present application, the heating effect can be improved by sacrificing part of the heating end area to improve the thermal quality of the end heat generation. At E set When [time], start the multi-circuit variable voltage control mode, and use the multi-objective function to optimize to find the optimal solution to select the appropriate number of heating circuits. It can be seen that z changes There is an extreme value, and the specific improvement effect can refer to the following application examples.

[0072] To more clearly introduce the purpose, advantages and application scenarios of the present invention, the following further explains in combination with embodiments and drawings. The illustrative embodiments of the present invention and their descriptions are only used to explain the present application and are not used to limit the present application.​​

[0073] It should be noted that this application is applicable to a solar energy system for resistive heating terminals 7 used in photovoltaic power generation for heating, and is not limited to the specific system in the schematic diagram of the present invention. Please continue to refer to Figure 2 To highlight the control method of multi-loop variable voltage, Figure 1 the system control cabinet 2 and the inverter control box 8 are simplified in . The actual system control cabinet 2 includes functions such as bus collection, data acquisition and analysis, and system control. It mainly integrates the power input by the photovoltaic array 1, and controls the system power supply mode and the multi-loop mode according to the power signal of the photovoltaic array 1, the light intensity signal of the irradiance meter 3, and the indoor air temperature monitored by the temperature recorder 4 and the temperature of the heating terminal. Both the terminal control switch 6 and the inverter control box 8 can receive the switch signal transmitted by the system control cabinet 2 to control the resistive heating terminal 7 and the power consumption terminal 9.

[0074] To more clearly express the application of the method, the embodiment provides an application case of the control method. In the embodiment, the photovoltaic array 1 of the photovoltaic power generation system uses 10 solar panels with a rated output voltage of 45V, which are divided into 2 groups, with 5 panels in each group and the photovoltaic panels inside each group being connected in series and in parallel between groups. The total area of the photovoltaic array 1 is 22.09m 2 ; in this way, the photovoltaic power generation system can provide a photovoltaic power supply voltage of about 220V ( =5×44). The area of the heating room is about 9m 2 . The resistive heating terminal module has a total of 120 pieces, and the electric power of each piece at the rated voltage of 220V is 25W, and the laying area is 12m 2 . Here, the inside of the resistive heating terminal 7 is divided into 12 ( x ) heating circuits, and each circuit has 10 ( y ).

[0075] The system control cabinet 2 collects the output voltage of the photovoltaic array 1 , the indoor air temperature , the temperature of the heating terminal , the solar radiation intensity on the inclined surface of the photovoltaic panel , the battery 5 power signal and other hourly data.

[0076] The system configuration information in the embodiment heating system is shown in Table 1, which is stored in the system control cabinet 2.

[0077] Table 1 System configuration information

[0078] Establish the system operating voltage ( U 1,i)The first relationship model with the temperature of the resistive heating terminal ( T R,i ): 1. Determine the heating power per unit area of the resistive heating terminal ( ): In the resistive heating terminal 7, the number of operating heating circuits is z ( , ); the voltage is ; the current is ; the heating power is . In the embodiment ( ); ; ; when the photovoltaic system reaches the rated voltage and all heating circuits are turned on, the voltage at the heating terminal is 207.16V, the current is 12.84A, and the heating power is 2633.43W.

[0079] z When heating circuits are operating, the heating power per unit area of the resistive heating terminal is, , in the embodiment . Under the rated voltage of the embodiment, the heating power per unit area of the resistive heating terminal is 219.45W.

[0080] 2. Determine the relationship between the system operating voltage ( ) and the temperature of the resistive heating terminal ( ): The relationship between and

[0081] In the formula, , representing the proportionality coefficient; , are the temperatures of the resistive heating terminal and the indoor air respectively, in °C. Under the rated voltage, when all circuits are open in the embodiment k= 4.5347×10 -4 ; The relationship between and .

[0082] Establish the second relationship model between the inclined-plane solar radiation intensity ( ) and the temperature of the resistive heating terminal ( ): The relationship between the inclined-plane solar radiation intensity and the system operating voltage is:

[0083] In the formula, is the minimum solar radiation intensity corresponding to the output voltage of the photovoltaic array 1 reaching the rated value, with the unit of W / m 2 ; in this embodiment, it is calculated that = 547 W / m 2 .

[0084] Solar radiation intensity on the inclined plane E i and the temperature of the resistive heating terminal The second relationship model is: ; In the embodiment, the calculation can obtain: ; It can be clearly found that when the light intensity is sufficient, the temperature difference between the resistive heating terminal and the indoor air temperature remains constant under ideal conditions; when the light intensity is insufficient, the greater the value of z, the smaller the degree of increase in the resistive heating terminal.

[0085] Determination of the solar radiation intensity control point (E set ) and control of the number of heating circuits (z) based on the solar radiation intensity control point: According to the relationship between E i and in the above steps, when , is always greater than . The value of the solar radiation intensity control point is taken as 0 E set , and in the embodiment, E set is taken, and the indoor heating temperature is taken as 18°C. p for ensuring the heating terminal effect is taken as 10°C, When it is not less than 28°C, the heat transfer effect of the operating heating terminal is better.

[0086] When , conventional mode photovoltaic power generation heating is adopted to control the indoor temperature to be greater than 18°C.

[0087] When , a multi-loop heating mode is adopted to improve the thermal energy grade of the resistive heating terminal while ensuring a certain terminal heating area. The optimization function in the embodiment is expressed as:

[0088] The embodiment performs optimization calculations for the following three cases: ① = 200, = 10°C; ② = 200, = 10°C; ③ = 00, = 10 °C, and the calculation results are shown in Table 2 below.

[0089] Table 2 Target values of each solution

[0090] In the concept of the embodiment of the present application, it is considered more important to improve the thermal energy grade of the resistive heating terminal 7. Therefore, the weights of the resistive heating terminal temperature and the operating area of the resistive heating terminal are taken as 0.7 and 0.3 respectively, and the calculated weighted comprehensive scores are shown in Table 3. The results show that the optimal number of loops for operating conditions 1, 2, and 3 are 4, 4, and 5 respectively.

[0091] Table 3 Weighted comprehensive scores

[0092] The optimal solutions for the three operating conditions are shown in Table 4: Table 4 Optimal solutions

[0093] Heating and power supply control method for a cogeneration system operating with multi-loop variable voltage: Please refer to Figure 3 , Figure 3 which is the schematic diagram of the heating control logic in this application example.

[0094] When is greater than 22 °C, the heating system stops running; when is less than 18 °C, the heating system starts, and so on in a cycle. At this time, when the light is sufficient, the battery 5 is charged, and the charging control method is: if the battery pack power is not equal to 100%, the battery 5 is charged until it is full, and then it stops. Please refer to Figure 4 , Figure 4 which is the schematic diagram of the charging control logic of the battery 5 in this application example of the present application.

[0095] When E i , values, referring to the process of the optimization calculation, the optimal z ( ) value of the number of heating loops is obtained, and z loops of the heating terminal are started for heating until the end of this time step.

[0096] When it is night, the battery 5 and the external power grid 10 are used for power replenishment. If the battery 5 power is less than 10%, the external power grid 10 is enabled for heating; if the battery 5 power is not less than 10%, the remaining power of the battery 5 is used for heating until the heating switch of the battery 5 is disconnected when the battery 5 power is less than 10%, and the mains power is enabled.

[0097] Non-heating period control method of this application example: The photovoltaic power generation system supplies power to the domestic AC power consumption terminal 9: The system control cabinet 2 controls the photovoltaic power generation system to supply power to the domestic AC power consumption terminal 9 during the day according to the solar radiation intensity of the irradiator 3 E i and the real-time data of the battery 5 power to store the power at night. When the power of the photovoltaic power generation system cannot meet the demand of the domestic AC power consumption terminal 9, the system control cabinet 2 controls the inverter control box 8 to connect the mains power to the domestic AC power consumption terminal 9.

[0098] Analysis of the improvement effect of the heat energy grade at the heating end: This application sacrifices part of the heating end area to improve the heat energy grade of the end heating. The degree of improvement of the heat energy grade is related to the weight of the optimization algorithm in S3. In this embodiment, the end temperature improvement effect is shown in Table 5. It can be found that under the method proposed by the present invention, the improvement effect of the heat energy grade at the heating end is obvious.

[0099] Table 5 Improvement effect of heat energy grade at the heating end

[0100] It should be understood that when each module of the cogeneration system provided in the above embodiments is working, only the division of each functional module in the above description content is used for illustration. In actual applications, the above functions can be allocated to different functional modules according to needs, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above.

[0101] Each functional module in the above embodiments can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above integrated unit can be implemented in the form of hardware or in the form of a software functional unit. In addition, the specific names of each functional unit and module are only for the convenience of mutual distinction and do not limit the protection scope of the embodiments of the present application.

[0102] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A control method for a cogeneration system with multi-loop variable voltage operation, characterized in that A control device applied to a cogeneration system with multi-loop variable voltage operation, where the cogeneration system is used to control the power supply to resistive heating terminals; The method includes: Collecting the system operating data of the cogeneration system; Based on the system operating data, establishing a first relationship model between the system operating voltage and the temperature of the resistive heating terminal, and based on the first relationship model, establishing a second relationship model between the inclined plane solar radiation intensity and the temperature of the resistive heating terminal; Determining the solar radiation intensity control point according to the second relationship model, and starting the multi-loop control strategy when the real-time radiation intensity is lower than the solar radiation intensity control point; The multi-loop control strategy includes: Determining the number of loops to be started at the heating terminal based on a control function with multi-objective constraints, and dynamically adjusting the number of loops at the heating terminal to maintain the temperature at the heating terminal higher than the set temperature threshold.

2. The method according to claim 1, characterized in that, The first relationship model includes: Wherein, is the system operating voltage, is the temperature of the resistive heating terminal, is the air temperature outside the resistive heating terminal, i.e., the indoor temperature, is the thermal conductivity of the resistive heating terminal to the indoor wall surface, is the thickness from the resistive heating terminal to the indoor wall surface, is the surface heat transfer coefficient of the resistive heating terminal, is the resistance of a single heating module in the resistive heating terminal, and respectively represent the total number of circuits in the resistive heating terminal and the number of heating modules in each circuit, is the laying area of the resistive heating terminal, is the resistance of the photovoltaic array and other components in the cogeneration system, is the number of operating heating circuits in the resistive heating terminal, is the thermal efficiency of the resistive heating terminal.

3. The method according to claim 2, wherein The second relationship model includes: Among them, is the solar radiation intensity on the inclined surface, is the laying area of the photovoltaic panel, is the power generation efficiency of the photovoltaic array in the cogeneration system, 额 is the rated output voltage of the photovoltaic array, is the solar radiation intensity value when the photovoltaic array reaches the rated output voltage.

4. The method according to claim 3, wherein Determining the solar radiation intensity control point according to the second relationship model includes: Set the minimum valid value of the resistive heating terminal temperature as T set +p, Determine the solar radiation intensity control point E that satisfies the lowest effective value of temperature based on the lowest effective value of the end temperature and the second relationship model set , 0 E set : Where p is a temperature difference threshold parameter, representing the minimum effective temperature difference between the temperature of the resistive heating terminal and the indoor set temperature.

5. The method according to claim 1, wherein Determining the number of loops to be started at the heating terminal based on the control function with multi-objective constraints, and dynamically adjusting the number of loops at the heating terminal to maintain the temperature at the heating terminal higher than the set temperature threshold includes: Maximizing the weighted benefit of the terminal temperature and the heating area; Obtaining the control function based on the constraint conditions of the upper limit of the number of loops, the safety threshold of the terminal temperature, and the minimum effective temperature difference; and determining the target number of loops at the heating terminal through dynamic programming or integer programming; The control function is: Among them, is the multi-objective control function, is the temperature of the resistive heating terminal, is the effective heating area, is the air temperature outside the resistive heating terminal, is the thermal conductivity of the resistive heating terminal to the indoor wall surface, is the thickness from the resistive heating terminal to the indoor wall surface, is the surface heat transfer coefficient of the resistive heating terminal, is the resistance of a single heating module in the resistive heating terminal, and respectively represent the total number of circuits in the resistive heating terminal and the number of heating modules in each circuit, is the laying area of the resistive heating terminal, is the resistance of the photovoltaic array and other components in the cogeneration system, is the number of operating heating circuits in the resistive heating terminal, is the thermal efficiency of the resistive heating terminal, is the inclined plane solar radiation intensity, is the laying area of the photovoltaic panel, is the power generation efficiency of the photovoltaic array in the cogeneration system, 额 is the rated output voltage of the photovoltaic array, is the maximum value of the resistive heating terminal temperature.

6. The method according to claim 1, characterized in that The method further includes: In the heating period, the power of the cogeneration system is used for heating or electricity storage; When the real-time radiation intensity is higher than the solar radiation intensity control point, starting all the loops of the heating system, and controlling the start and stop of the cogeneration system according to the indoor temperature. The steps of controlling the start and stop of the cogeneration system according to the indoor temperature include: If the indoor temperature is greater than the upper limit temperature of the heated indoor temperature, controlling the cogeneration system to stop operating; If the indoor temperature is less than the indoor set temperature value, starting the cogeneration system; If there is excess power, charging the battery of the cogeneration system based on the excess electrical energy; When the real-time solar radiation intensity is not higher than the solar radiation intensity control point and greater than zero, starting the multi-loop control strategy; When the real-time solar radiation intensity is equal to zero, the battery and the external power grid are used for power supplement. If the battery enables municipal power heating; if the battery runs out of power, starting the external power grid for power supplement.

7. The method according to claim 1, characterized in that The method further includes: In the non-heating period, outputting the power of the cogeneration system to the domestic power consumption terminal; Controlling the battery of the cogeneration system to discharge in case of insufficient light, and switching to connect with the external power grid for charging when the power is lower than the power threshold.

8. A cogeneration system with multi-loop variable voltage operation, characterized in that, The cogeneration system includes a control device, the control device includes a processor and a computer program stored in a memory and executable on the processor, and when the processor executes the computer program, the method described in any one of claims 1 to 7 is implemented.

9. The cogeneration system with multi-loop variable voltage operation according to claim 8, characterized in that, The cogeneration system includes an off-grid photovoltaic power generation system, a heating terminal, and a domestic power consumption terminal; the control device is the system control cabinet in the off-grid photovoltaic power generation system, and the off-grid photovoltaic power generation system includes: a photovoltaic array, an irradiance meter, a temperature recorder, and a storage battery, and the system control cabinet is respectively connected to the photovoltaic array, the irradiance meter, the temperature recorder, and the storage battery.

10. The cogeneration system with multi-loop variable voltage operation according to claim 8, characterized in that, The system control cabinet is also connected to the domestic power consumption terminal and the external power grid through an inverter control box.

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