A multi-circuit variable voltage cogeneration system and control method

Abstract

The present application relates to the field of photovoltaic heating technology, and specifically to a multi-circuit variable voltage cogeneration system and control method, the method comprising: collecting system operating data of the cogeneration system; establishing a first relationship model between the system operating voltage and the temperature of the resistive heating terminal based on the system operating data, and establishing a second relationship model between the solar radiation intensity of the inclined surface and the temperature of the resistive heating terminal based on the first relationship model; determining the solar radiation intensity control point according to the second relationship model, and starting a multi-circuit control strategy when the real-time radiation intensity is lower than the solar radiation intensity control point. The method takes into account that the photovoltaic array in the cogeneration system will change its output voltage due to the influence of solar radiation intensity, thereby improving the thermal energy quality of the resistive heating terminal by formulating a reasonable heating terminal circuit control strategy.

Description

Technical Field

[0001] The present application relates to the technical field of photovoltaic heating, and in particular to a multi-circuit variable voltage cogeneration system and a control method. Background Art

[0002] The affordable price of photovoltaic panels makes them potentially suitable for widespread deployment and application. Combining off-grid solar photovoltaic systems with resistive heating terminals can reliably address the heating needs of distributed buildings in extremely cold regions. However, off-grid solar power systems are subject to local meteorological conditions, resulting in fluctuating and random power generation. When used with resistive heating terminals, the random voltage fluctuations, without utility power, can easily cause variations in the heating temperature of the resistive heating terminals. When solar power is abundant and power generation capacity is high, the resistive terminal operates at a high voltage and generates a high temperature. When solar power weakens and power generation capacity decreases, the voltage and temperature decrease. Due to the varying quality of thermal energy, when the temperature is below or close to the indoor ambient temperature, the thermal energy quality decreases significantly, rendering indoor heating ineffective (here, the heat generated when the resistive terminal temperature is below a certain indoor temperature setpoint is considered low-quality heat).

[0003] To address the issue of thermal energy quality variations caused by temperature fluctuations at the terminals in heating systems combining off-grid solar photovoltaic power generation systems with resistive terminals, this application proposes a multi-circuit, variable-voltage cogeneration system and control method. This system utilizes a multi-circuit solution to elevate the surface temperature of the resistive heating terminals when the off-grid solar photovoltaic power generation system is operating at low power generation capacity, maximizing the output of high-quality thermal energy. Summary of the Invention

[0004] The present application provides a multi-circuit variable voltage cogeneration system and control method. By considering that the photovoltaic array in the cogeneration system will change the output voltage due to the influence of solar radiation intensity, a reasonable heating terminal circuit control strategy is formulated to improve the thermal energy quality of the resistive heating terminal.

[0005] In a first aspect, embodiments of the present application provide a control method for a multi-circuit variable voltage cogeneration system, which can be applied to a control device in a multi-circuit variable voltage cogeneration system for controlling power supply to a resistive heating terminal. The method includes:

[0006] Collecting system operating data of the combined heat and power system;

[0007] Establishing a first relationship model between the system operating voltage and the resistive heating terminal temperature based on the system operating data, and establishing a second relationship model between the inclined surface solar radiation intensity and the resistive heating terminal temperature based on the first relationship model;

[0008] determining a solar radiation intensity control point according to the second relationship model, and starting a multi-loop control strategy when the real-time radiation intensity is lower than the solar radiation intensity control point;

[0009] The multi-loop control strategy includes:

[0010] The number of loop startups of the heating terminal is determined based on a control function with multi-objective constraints, and the number of loops of the heating terminal is dynamically adjusted to maintain the temperature of the heating terminal above a set temperature threshold.

[0011] In the above implementation, by establishing a two-layer relationship model between the photovoltaic system operating voltage and the heating terminal temperature, a precise response relationship between solar energy volatility and the heating terminal temperature is obtained, effectively solving the problem of low thermal energy quality at 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 sunlight is insufficient. By reducing the number of working loops, the supply voltage of the starting loop is increased, thereby ensuring that the heating terminal temperature 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 and taking into account the rational allocation of the heating area, achieving a dynamic balance between thermal energy quality and terminal heating range. In addition, this control method fully utilizes 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. It is particularly suitable for off-grid solar heating scenarios and provides a stable and reliable renewable energy heating solution for distributed buildings in cold regions.

[0012] In some embodiments, the first relationship model includes:

[0013]

[0014] 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 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, The area where the resistive heating terminal is laid is is the resistance of the photovoltaic array and other components in the cogeneration system, is the number of heating circuits running in the resistive heating terminal, It is the thermal efficiency of the resistive heating terminal.

[0015] In some embodiments, the second relationship model includes:

[0016]

[0017] in, is the solar radiation intensity on the inclined surface, is the photovoltaic panel installation area, is the power generation efficiency of the photovoltaic array in the cogeneration system, 额 is the rated output voltage of the PV array, It is the solar radiation intensity value when the photovoltaic array reaches the rated output voltage.

[0018] In some embodiments, determining the solar radiation intensity control point according to the second relationship model includes:

[0019] Set the lowest effective value of the resistance heating terminal temperature to T set +p,

[0020] Determine the solar radiation intensity control point E that meets the minimum effective value of the temperature based on the minimum effective value of the terminal temperature and the second relationship model. set , 0 E set :

[0021]

[0022] Among them, p is the temperature difference threshold parameter, which represents the minimum effective temperature difference between the resistive heating terminal temperature and the indoor set temperature.

[0023] In some embodiments, determining the number of circuit activations of the heating terminal based on a control function with multi-objective constraints, and dynamically adjusting the number of circuits of the heating terminal to maintain the temperature of the heating terminal above a set temperature threshold, includes:

[0024] Maximize the weighted benefit of terminal temperature and heating area;

[0025] The control function is obtained based on the constraints of the upper limit of the number of circuits, the terminal temperature safety threshold and the minimum effective temperature difference; and the target number of circuits at the heating terminal is determined by dynamic programming or integer programming;

[0026] The control function is:

[0027]

[0028]

[0029]

[0030] in, is a multi-objective control function, is the end temperature of resistive heating, is the effective heating area, is the air temperature outside the resistance heating terminal, is the thermal conductivity of the resistive heating terminal to the indoor wall, is the thickness from the end of 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, The area where the resistive heating terminal is laid is is the resistance of the photovoltaic array and other components in the cogeneration system, is the number of heating circuits running 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 photovoltaic panel installation area, is the power generation efficiency of the photovoltaic array in the cogeneration system, 额 is the rated output voltage of the PV array, It is the maximum value of the resistive heating terminal temperature.

[0031] In the control method of a multi-circuit variable voltage cogeneration system, the multi-circuit control strategy specifically includes:

[0032] During the heating period, the electricity from the combined heat and power system is used for heating or electricity storage;

[0033] 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 step of controlling the start and stop of the combined heat and power system according to the indoor temperature includes:

[0034] If the indoor temperature is higher than the upper limit temperature of the room temperature, the combined heat and power system is controlled to stop running; if the indoor temperature is lower than the indoor set temperature value, the combined heat and power system is started; if there is excess electricity, the battery of the combined heat and power system is charged based on the excess electricity; when the real-time solar radiation intensity is not higher than the solar radiation intensity control point and is greater than zero, the multi-loop control strategy is started; when the real-time solar radiation intensity is equal to zero, the battery and the external power grid are replenished with electricity, and if the battery power is used up, the external power grid is started to replenish electricity; in the non-heating period, the power of the combined heat and power system is output to the end of domestic electricity consumption; the battery of the combined heat and power system is controlled to discharge when there is insufficient light, and is switched to the external power grid for charging when the power is lower than the power threshold.

[0035] In a second aspect, an embodiment of the present application provides a multi-circuit variable voltage cogeneration system, the cogeneration system including a control device, the control device including a processor and a computer program stored in the memory and executable on the processor, and the processor implements the method provided in the above description when executing the computer program.

[0036] In some embodiments, the cogeneration system includes an off-grid photovoltaic power generation system, a heating terminal and a household electricity terminal; the control device is a system control cabinet in the off-grid photovoltaic power generation system, and the off-grid photovoltaic power generation system includes: a photovoltaic array, an irradiator, a temperature recorder and a battery, and the system control cabinet is respectively connected to the photovoltaic array, the irradiator, the temperature recorder and the battery.

[0037] In some embodiments, the system control cabinet is also connected to the domestic electricity terminal and the external power grid through an inverter control box.

[0038] Compared with the existing technology, the beneficial effects of this application are: by establishing a double-layer relationship model between the working voltage of the photovoltaic system and the temperature of the heating terminal, the precise response relationship between the solar energy volatility and the heating terminal temperature can be 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 starting loop by reducing the number of working loops, thereby ensuring that the heating terminal temperature is always maintained in 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, while ensuring the heating temperature, taking into account the rational allocation of the heating area, and achieving a dynamic balance between thermal energy quality and terminal heating range. It can be considered that the photovoltaic array in the cogeneration system will change the output voltage due to the influence of solar radiation intensity, so as to improve the thermal energy quality of the resistive heating terminal by formulating a reasonable heating terminal loop control strategy. In addition, this control method fully utilizes the rapid 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. It is particularly suitable for off-grid solar heating scenarios and provides a stable and reliable renewable energy heating solution for distributed buildings in cold regions. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic diagram of the steps of a control method for a multi-circuit variable voltage cogeneration system provided in an embodiment of the present application.

[0040] Figure 2 Schematic diagram of a multi-circuit variable voltage cogeneration system provided in an embodiment of the present application.

[0041] Figure 3 This is the heating control logic diagram in this application example.

[0042] Figure 4 This is a logic diagram of battery charging control in the application example of this application. DETAILED DESCRIPTION

[0043] The present application is further described in detail below in conjunction with test examples and specific implementation methods. However, this should not be understood as limiting the scope of the above-mentioned subject matter of the present application to the following embodiments. All technologies implemented based on the content of the present application fall within the scope of protection of the present application.

[0044] Unless otherwise specified, in the description of the specific embodiments of this application, the terms indicating the orientation or position relationship such as "up", "down", "left", "right", "center", "inside", "outside", and "side" are based on the expression of the orientation or position relationship shown in the accompanying drawings, or the orientation or position relationship in which the product / device / apparatus is placed when it is usually used. These terms of orientation or position relationship are only for the convenience of describing the scheme of this application or simplifying the description in the specific embodiments to facilitate the technicians to quickly understand the scheme, and do not indicate or imply that a specific device / component / element must have a specific orientation, or be constructed and operated in a specific position relationship, and therefore should not be understood as limiting this application.

[0045] In the description of the embodiments of this application, the technical terms "first," "second," etc., merely distinguish one entity or operation from another and are not to be understood as indicating or implying relative importance or implicitly specifying the quantity, specific order, or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, "plurality" means two or more, unless otherwise specifically defined.

[0046] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0047] Please refer to Figure 1 and Figure 2 , Figure 1 A schematic diagram of the steps of a control method for a multi-circuit variable voltage cogeneration system provided in an embodiment of the present application. Figure 2 Schematic diagram of a multi-circuit variable voltage cogeneration system provided in an embodiment of the present application.

[0048] Figure 2 In the example, the combined heat and power system includes an off-grid photovoltaic power generation system, a heating terminal, and a household power terminal. The control device is the system control cabinet in the off-grid photovoltaic power generation system. The off-grid photovoltaic power generation system includes: a photovoltaic array 1, a system control cabinet 2, an irradiator 3, a temperature recorder 4, and a battery 5. The system control cabinet 2 is connected to the photovoltaic array 1, the irradiator 3, the temperature recorder 4, and the battery 5 respectively. 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 household AC power terminal 9 and the external power grid 10 via an inverter control box 8. In some cases, the external power grid 10 can be a mains power grid.

[0049] Specifically, the photovoltaic array 1 consists of m groups of photovoltaic panels of the same specifications and number, with each group containing n photovoltaic panels. The photovoltaic panels within each group are connected in series, and the m groups of photovoltaic panels are connected in parallel. The system control cabinet 2 includes functions such as current confluence, maximum power point tracking, and data acquisition and analysis. The confluence device within the system control cabinet 2 integrates the power input from the photovoltaic array 1 and outputs the system operating voltage through maximum power point tracking technology. System control cabinet 2 converts the power signal , the solar radiation intensity of the inclined surface collected hourly by irradiator 3 , Indoor temperature monitored by temperature recorder 4 and resistive heating terminal temperature Signal, battery 5 power signal Collect data and control the system according to the working strategy.

[0050] The heating terminal is composed of a terminal control switch 6 and a resistive heating terminal 7; other power terminals are composed of an inverter control box 8, a domestic AC power terminal 9, and a mains power grid 10.

[0051] Specifically, the resistive heating terminal 7 is internally composed of x heating circuits, and each circuit has y resistive heating modules. The terminal control switch 6 controls the on and off of the heating circuits in the resistive heating terminal 7 by receiving signals 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 heating circuits started according to the system signal. During the daytime, when photovoltaic power generation is used for heating, the heating terminal 7 has no mains power to supplement it, and relies 100% on solar power generation for DC heating. At this time, its working voltage changes with the fluctuation of power generation capacity. In 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 power 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 power 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 counting power.

[0052] The control method of the heat and power combined supply system with multiple circuits and variable voltage operation can be applied to the system control cabinet 2. The steps of the method may include:

[0053] S1. Collect system operating data of the combined heat and power system.

[0054] The system operation data of the combined heat and power system may include the output voltage of the photovoltaic array 1 , indoor temperature , Resistive heating terminal temperature , solar radiation intensity on the inclined surface of photovoltaic panels and battery charge signal The resistive heating terminal 7 is a heating device in a combined heat and power system that converts electrical energy directly into thermal energy. Its core principle is to generate Joule heat by passing current through a resistive material to achieve heating.

[0055] When the combined heat and power system is built, the following parameters are entered into the system by default and are known parameters: Rated output voltage of PV array 1 额 (V); the total number of circuits x in the resistive heating terminal 7, the number of resistive heating modules y in each circuit; the resistance R (Ω) of a single heating module; the resistance of photovoltaic panels and other components in the combined heat and power system (Ω); Thermal efficiency of resistive heating terminal 7 ; Resistive heating terminal 7 laying area (m 2 ); thickness δ (m) from the resistive heating terminal 7 to the indoor wall; thermal conductivity λ (W / (m·K)) from the resistive heating terminal 7 to the indoor wall; indoor set temperature or indoor heating temperature T set (℃); photovoltaic panel installation area (m 2 ); Photovoltaic power generation efficiency ; The upper limit temperature of room temperature is T set (℃).

[0056] S2. Establish a first relationship model between the system operating voltage and the resistive heating terminal temperature based on the system operating data, and establish a second relationship model between the inclined surface solar radiation intensity and the resistive heating terminal temperature based on the first relationship model.

[0057] For example, the first relationship model includes:

[0058]

[0059] in, is the system operating voltage, is the end temperature of resistive heating, is the air temperature outside the resistive heating terminal 7, that is, the indoor temperature, is the thermal conductivity of the resistive heating terminal 7 to the indoor wall, The thickness from the resistive heating terminal 7 to the indoor wall, is the surface heat transfer coefficient of the resistive heating terminal 7, 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 7 and the number of heating modules in each circuit, The area of ​​the resistive heating terminal is 7, is the resistance of the photovoltaic array 1 and other components in the combined heat and power system, is the number of heating circuits running in the 7 resistance heating terminals, It is the thermal efficiency of the resistive heating terminal 7.

[0060] For example, the method of establishing a first relationship model between the system operating voltage and the resistive heating terminal temperature 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 combining the terminal heat transfer mechanism to derive the relationship between the system operating voltage and the resistive heating terminal temperature.

[0061] 1. Determine the heating power per unit area of ​​resistive heating terminal ( ):

[0062] Resistive heating terminals typically refer to heating devices that generate heat by passing current through a resistor, such as resistance wire heaters, electric heating films, and electric blankets. Ignoring the effect of temperature on resistance in the circuit, resistive terminals obey Ohm's and Joule's laws. Therefore, the electrical power and heating value can be calculated based on the voltage and current across the terminal.

[0063] The number of heating circuits in operation in the resistive heating terminal 7 is z ( ). When z heating circuits are running, the voltage at the end of the resistive heating circuit is: ; The current is ; Heating power is: When z heating circuits are running, the heating power per unit area of ​​the resistive heating terminal is: , where The installation area of ​​the resistive heating terminal is in m 2 ; It is the heat conversion efficiency of the resistive heating terminal.

[0064] 2. Determine the heat transfer capacity of the resistive heating terminal ( ) and temperature ( ) is:

[0065] When a resistive heating terminal is installed in a room for heating, the heat transfer of the heating terminal is closely related to the building envelope parameters, ventilation conditions, indoor and outdoor temperatures, etc. The heat transfer from the heating terminal to the room includes heat conduction, heat convection, and heat radiation (negligible). The heat transfer process is expressed as: Where, The heat exchange rate per square meter of the heating terminal, W / m 2 ; and are the resistance heating terminal temperature and the air temperature outside the resistance heating terminal 7 (considered as the indoor air temperature), °C; is the surface heat transfer coefficient W / (m 2K), surface heat transfer coefficient when indoor air flow changes slightly h Can be considered a constant and in the built system δ、 Parameters such as λ are fixed, then and( ) is proportional to.

[0066] 3. Determine the system operating voltage ( ) and the terminal temperature of resistive heating ( ) is:

[0067] Heating terminal heat exchange per unit area Heating power at the heating terminal If they are equal, we can get the first relational model: By simplifying the first relationship model, the system operating voltage can be obtained and the terminal temperature of resistive heating Functional relationship: , where k Represents the proportional coefficient and is a positive value. k The value is related to the system configuration and the size of the z value. From the formula, we can get: and( ) are positively correlated.

[0068] When the system operating voltage When the temperature of the resistive heating terminal 7 is low, The heat energy quality will also decrease accordingly. Once the end temperature of the resistive heating Close to room temperature Or lower than the indoor setting value , the resistive heating terminal 7 will not have the effect of heating.

[0069] Furthermore, the second relational model is:

[0070]

[0071] in, is the solar radiation intensity on the inclined surface, is the photovoltaic panel installation area, is the power generation efficiency of PV array 1 in the combined heat and power system, 额 is the rated output voltage of PV array 1, It is the solar radiation intensity value when the photovoltaic array 1 reaches the rated output voltage.

[0072] For example, since the power generation capacity of the photovoltaic power generation system will show randomness and fluctuation with the change of solar radiation intensity, the system working voltage output when the solar radiation intensity is weak Reduce the surface temperature of the resistive heating terminal 7 Therefore, the method of establishing the second relationship model between the solar radiation intensity of the inclined surface and the terminal temperature of the resistive heating based on the first relationship model may include:

[0073] 1. Solar radiation intensity on inclined surface ( E i ) and system operating voltage ( ) relationship:

[0074] First, the calculation formula for the power generation efficiency of photovoltaic array 1 is: , where is the area of ​​photovoltaic panels, m 2 ; is the solar radiation intensity on the inclined surface of the photovoltaic panel, W / m 2 ; The photovoltaic power generation efficiency is related to the power generation characteristics of the photovoltaic panel itself, the temperature of the photovoltaic panel, the ambient temperature and humidity, and other factors. The value range is between 10% and 25%.

[0075] It should be noted that under strong solar radiation conditions, the photovoltaic modules reach the rated output voltage 额 When the output voltage no longer increases with the increase of light intensity, the solar radiation intensity value is set to , , so the relationship between the solar radiation intensity on the inclined surface and the photovoltaic output voltage can be obtained as follows:

[0076]

[0077] 2. Determine the system operating voltage ( ) and the terminal temperature of resistive heating ( ) relationship:

[0078] Solar radiation intensity E i With system operating voltage U 1,i Substitute the relationship into the system operating voltage U 1,i and the terminal temperature of resistive heating The solar radiation intensity on the inclined surface is obtained from the relationship E i and the terminal temperature of resistive heating Relationship:

[0079]

[0080] In the formula λ 、 δ 、h、 、 ,R,r0, η 0. The parameters are positive. Simplifying the above formula we can get:

[0081]

[0082] Where, ε 、 k is a constant.

[0083] S3. 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.

[0084] The process of determining the solar radiation intensity control point according to the second relationship model includes:

[0085] The lowest effective value for setting the terminal temperature of resistance heating is According to the second relational model, the light intensity is When the resistive heating terminal predicts the working temperature and ε 、 、 Because ε, k are all positive values, Satisfaction at the moment , but the smaller the solar radiation intensity, and The closer they are, the less ideal the heating effect will be.

[0086] Set the indoor heating temperature to T set In order to ensure the heat exchange effect between the heating terminal and the room, It should be greater than a certain value of indoor heating temperature, that is:

[0087] T set

[0088] Among them, p is the temperature difference threshold parameter, which represents the minimum effective temperature difference between the terminal temperature of the resistive heating and the indoor set temperature. It can generally be set to 5~10°C to ensure effective terminal heating.

[0089] when T set The corresponding solar radiation intensity at this time is Defined as the solar radiation intensity control point E set (0 E set ),exist The multi-loop control strategy is started at this time.

[0090] Determine the solar radiation intensity control point E that meets the minimum effective value of the temperature based on the minimum effective value of the terminal temperature and the second relationship model set :

[0091]

[0092] Furthermore, the multi-loop control strategy may include:

[0093] The control function based on multi-objective constraints determines the number of circuit startups at the heating terminal, and dynamically adjusts the number of circuits at the heating terminal to maintain the temperature of the heating terminal above the set temperature threshold.

[0094] Specifically, the control logic of the multi-circuit voltage control strategy is: E set When , all the circuits at the heating terminal start to heat the room; E set When the multi-circuit voltage control strategy is activated, the terminal temperature is increased by changing the circuit. E set The reason why the heat energy quality of the resistive heating terminal 7 is improved is that when the solar radiation intensity is constant, reducing the number of operating circuits of the resistive heating terminal 7 will cause the voltage of the resistive heating terminal 7 to increase, thereby increasing the terminal temperature. At this time, the voltage of the resistive heating terminal always satisfies: 额 , E set The voltage at the end of the resistive heating is always lower than the system voltage under rated conditions. When, you know , expand and simplify to get: , the physical meaning of this inequality is expressed in E set At this time, the maximum power of photovoltaic power generation is always less than the electric power of the resistive heating terminal 7 under rated conditions.

[0095] The goal of the multi-circuit variable voltage control strategy is to increase the temperature of the resistive heating terminal 7, that is, to increase the ) The thermal energy quality of the terminal. On this basis, the larger the number of 7 circuits of the resistive heating terminal, the better the heat transfer effect. Considering the safety and comfort of the heating temperature, the maximum temperature constraint of the resistive heating terminal is ( ). Generally speaking, for °C. The multi-objective function can be expressed as:

[0096]

[0097] within a certain period of timeh 、 、 The equal value can be regarded as a fixed value. The user selects the weight of the resistance heating terminal temperature and the resistance heating terminal operation area according to the demand, and optimizes the calculation of the optimal number of circuits z ( , ).

[0098] Furthermore, in the method provided in the present application, when the real-time 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 cogeneration system are controlled according to the indoor temperature. The step of controlling the start and stop of the cogeneration system according to the indoor temperature may include:

[0099] If the indoor temperature The upper limit temperature T of the heated object is greater than room temperature. set , then the combined heat and power system is controlled to stop running;

[0100] If the indoor temperature Less than the indoor set temperature T set , the combined heat and power system is started; if there is excess electricity, the battery of the combined heat and power system is charged based on the excess electricity. In the non-heating period, the electricity of the combined heat and power system is output to the end of life;

[0101] The storage battery of the cogeneration system is controlled to discharge when there is insufficient sunlight, and to switch to connection with the external power grid 10 for charging when the power level is lower than a power threshold.

[0102] For example, the solution provided in this application mainly involves two aspects: heating and power supply. The overall control logic is: photovoltaic power generation for heating during the heating period, excess electricity during the day is stored in battery 5, and battery 5 is used for heating at night; and during the non-heating period, the system only provides power for AC loads.

[0103] The control method can collect data hourly based on the system control cabinet 2, including the output voltage of the photovoltaic array 1 , solar radiation intensity on inclined surface , indoor air temperature , actual heating terminal temperature The room heating temperature is , the solar radiation intensity control point is E set After the system is put into trial operation, the terminal temperature of the resistive heating Calculated and measured values Compare and get the corrected ε, k value.

[0104] During the heating period:

[0105] When the heating system is fully operational, all circuits are activated and the room temperature control system starts and stops according to the room temperature setting. Greater than T set +M, the heating system stops running; when Less than T set The heating system starts when the power is on, and so circulates. In addition, at this moment, the illumination is sufficient, and the unnecessary electric energy is charged to the storage battery 5, and is fully stopped.

[0106] When the multi-circuit voltage control mode is started: according to the current 、 The optimal number of heating circuits z ( , ) value, the resistive heating terminal 7 starts z circuits for heating until the end of the time step.

[0107] At night, the battery 5 and the mains electricity can be used to supplement the power. If the battery 5 power is less than 10%, the mains electricity is used 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 battery 5 power is less than 10%, and the battery 5 heating switch is disconnected and the mains electricity is used.

[0108] During the non-heating period:

[0109] The photovoltaic power generation system supplies power to the AC power terminal 9: the system control cabinet 2 is based on the solar radiation intensity of the irradiator 3. E i 、Battery 5 power Real-time data controls the photovoltaic power generation system to power the AC power terminals 9 during the day, while the battery 5 stores power for nighttime use. If the photovoltaic power generation system's power is insufficient to meet the needs of the AC power terminals 9, the battery 5 and the mains power grid 10 provide additional power to meet the needs of the AC power terminals 9.

[0110] In the solution provided in the embodiment of the present application, the heat energy quality of the terminal heat can be improved by sacrificing part of the heating terminal area, thereby improving the heating effect. E set When the multi-circuit variable voltage control mode is started, the optimal solution is obtained by multi-objective function optimization to select the appropriate number of heating circuits. It can be seen that z changes There are extreme values. For the specific improvement effect, please refer to the following application examples.

[0111] In order to more clearly introduce the purpose, advantages and application scenarios of the present invention, the following is further explained in conjunction with embodiments and drawings. The schematic implementation methods of the present invention and their description are only used to explain the present application and are not intended to limit the present application.

[0112] It should be noted that this application is applicable to a solar energy system in which photovoltaic power generation and a resistive heating terminal 7 are used for heating, and is not limited to the specific system in the schematic diagram of the present invention. Figure 2 , in order to highlight the control method of multi-circuit voltage transformation, Figure 1 The simplified system control cabinet 2 and inverter control box 8 are shown in the figure. The actual system control cabinet 2 includes functions such as convergence, data acquisition and analysis, and system control. It mainly integrates the power input from the photovoltaic array 1 and monitors the indoor air temperature based on the power signal of the photovoltaic array 1, the light intensity signal of the irradiator 3, and the temperature recorder 4. and heating terminal temperature The terminal control switch 6 and the inverter control box 8 can both receive the switch signal transmitted by the system control cabinet 2 to control the resistive heating terminal 7 and the power terminal 9.

[0113] In order 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, each with 5 panels. The photovoltaic panels in each group are connected in series and the groups are connected in parallel. The total area of ​​the photovoltaic array 1 is 22.09m 2 ; In this way, the photovoltaic power generation system can provide about 220V ( =5×44) photovoltaic power supply voltage. The heating room area is about 9m 2 There are 120 resistive heating terminal modules in total. The power of a single module is 25W at a rated voltage of 220V. The installation area is 12m 2 Here, the resistive heating terminal 7 is divided into 12 parts ( x ) heating circuits, 10 per circuit ( y ).

[0114] System control cabinet 2 collects the output voltage of photovoltaic array 1 , indoor air temperature , heating terminal temperature , solar radiation intensity on the inclined surface of photovoltaic panels , Battery 5 power signal Hourly data of other data.

[0115] The system configuration information of the heating system in the embodiment is shown in Table 1, which is stored in the system control cabinet 2.

[0116] Table 1 System configuration information

[0117]

[0118] Establish system operating voltage ( U 1,i) and the terminal temperature of resistive heating ( T R,i )'s first relational model:

[0119] 1. Determine the heating power per unit area of ​​resistive heating terminal ( ):

[0120] In the resistive heating terminal 7, the number of heating circuits in operation is z ( , ); voltage is ; The current is ; Heating power is In the embodiment ( ); ; When the photovoltaic system reaches the rated voltage and all heating circuits are turned on, the heating terminal voltage is 207.16V, the current is 12.84A, and the heating power is 2633.43W.

[0121] z When a heating circuit is running, the heating power per unit area of ​​the resistive heating terminal is, In the embodiment In the embodiment, at the rated voltage, the heating power per unit area of ​​the resistive heating terminal is 219.45W.

[0122] 2. Determine the system operating voltage ( ) and the terminal temperature of resistive heating ( ) is:

[0123] and The relationship:

[0124] Where, , represents the proportional coefficient; 、 are the resistance heating terminal and indoor air temperature respectively, in °C. k= 4.5347×10 -4 ; and The relationship is: .

[0125] Establish the solar radiation intensity of the inclined surface ( ) and the terminal temperature of resistive heating ( )'s second relational model:

[0126] Solar radiation intensity on inclined surface With system operating voltage The relationship is:

[0127]

[0128] Where, The minimum solar radiation intensity when the output voltage of PV array 1 reaches the rated value, in W / m 2 In this embodiment, the calculation is =547W / m 2 .

[0129] Solar radiation intensity on inclined surfaces E i and the terminal temperature of resistive heating The second relational model is:

[0130] ;

[0131] The calculation in the embodiment can be obtained: ;

[0132] It can be clearly found that when the light intensity is sufficient, under ideal conditions, the temperature difference between the resistive heating terminal and the indoor air temperature remains constant; when the light intensity is insufficient, the greater the z, the smaller the degree of improvement of the resistive heating terminal.

[0133] Solar radiation intensity control point (E set ) and control the number of heating circuits (z) based on the solar radiation intensity control point:

[0134] According to the above steps E i and relationship, in hour Always greater than Solar radiation intensity control point The value is 0 E set In the embodiment, E set , the indoor heating temperature is 18℃. The temperature to ensure the heating terminal effect is 10℃, When the temperature is not less than 28℃, the heat transfer effect of the operating heating terminal is better.

[0135] when When heating is required, conventional photovoltaic power generation is used to control the indoor temperature to be greater than 18°C.

[0136] when When the multi-circuit heating mode is used, the heat energy quality of the resistive heating terminal is improved while ensuring a certain terminal heating area. The optimization function of the embodiment is expressed as:

[0137]

[0138] The embodiment performs optimization calculations for the following three situations: ① =200, =10℃;② =200, =10℃;③ = 00, =10℃, the calculation results are shown in Table 2 below.

[0139] Table 2 Target values ​​of each solution

[0140]

[0141] In the embodiment of this application, it is considered more important to improve the thermal energy quality of the resistive heating terminal 7. Therefore, the weights of the resistive heating terminal temperature and the resistive heating terminal operating area are set to 0.7 and 0.3, respectively. The weighted comprehensive score is calculated and shown in Table 3. The results show that the optimal number of circuits for working conditions 1, 2, and 3 is 4, 4, and 5.

[0142] Table 3 Weighted comprehensive scores

[0143]

[0144] The optimal solutions for the three working conditions are shown in Table 4:

[0145] Table 4 Optimal solution

[0146]

[0147] Heating and power supply control method based on multi-circuit variable voltage combined heat and power system:

[0148] Please see Figure 3 , Figure 3 This is the heating control logic diagram in this application example.

[0149] When the heating system is fully operational, all circuits are activated and the room temperature control system starts and stops according to the room temperature setting. When the temperature is higher than 22℃, the heating system stops running; when When the temperature is lower than 18℃, the heating system starts, and the cycle repeats. At this time, there is sufficient sunlight to charge the battery 5. The charging control method is: if the battery pack power is If it is not equal to 100%, charge the battery 5 and stop when it is full. Figure 4 , Figure 4 This is a schematic diagram of the charging control logic of the battery 5 in the application example of this application.

[0150] When the multi-circuit voltage control mode is started: according to the current E i 、 Value, refer to the optimization calculation process, and get the optimal number of heating circuits z ( ) value, the heating terminal starts z circuits for heating until the end of the time step.

[0151] At night, the battery 5 and the external power grid 10 are used to supplement power. If the power of the battery 5 is less than 10%, the external power grid 10 is enabled for heating; if the power of the battery 5 is not less than 10%, the remaining power of the battery 5 is used for heating, until the power of the battery 5 is less than 10%, the heating switch of the battery 5 is disconnected and the mains power is enabled.

[0152] The control method for the non-heating period of this application example:

[0153] The photovoltaic power generation system supplies power to the AC power terminal 9: the system control cabinet 2 is based on the solar radiation intensity of the irradiator 3. E i 、Battery 5 power Real-time data controls the photovoltaic power generation system to supply power to the household AC power terminals 9 during the day, while the battery 5 stores power for nighttime use. When the photovoltaic power generation system's power cannot meet the needs of the household AC power terminals 9, the system control cabinet 2 controls the inverter control box 8 to connect the mains power to the household AC power terminals 9.

[0154] Analysis of the effect of improving the quality of heat energy at the end of heating:

[0155] This application improves the thermal energy quality of the heating terminal by sacrificing part of the heating terminal area. The degree of thermal energy quality improvement is related to the weight of the optimization algorithm in S3. The effect of the terminal temperature improvement in this embodiment is shown in Table 5. It can be found that under the method proposed by the present invention, the thermal energy quality of the heating terminal is significantly improved.

[0156] Table 5 Effect of improving the quality of heat energy at the end of heating

[0157]

[0158] It should be understood that, when the various modules of the cogeneration system provided in the above embodiment are working, the division of the various functional modules in the above description is only used as an example. In actual application, the above functions can be assigned to different functional modules as needed, 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.

[0159] The functional modules in the above embodiments may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit. The above integrated units may be implemented in the form of hardware or software functional units. In addition, the specific names of the functional units and modules are only for the purpose of distinguishing them from each other and are not intended to limit the scope of protection of the embodiments of this application.

[0160] 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A control method for a multi-circuit variable voltage cogeneration system, characterized in that: A control device for use in a multi-circuit variable voltage combined heat and power system, wherein the combined heat and power system is used to control the power supply to a resistive heating terminal; The method comprises: Collecting system operating data of the combined heat and power system; Establishing a first relationship model between the system operating voltage and the resistive heating terminal temperature based on the system operating data, and establishing a second relationship model between the inclined surface solar radiation intensity and the resistive heating terminal temperature based on the first relationship model; determining a solar radiation intensity control point according to the second relationship model, and starting 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: Determining the number of circuits activated at the heating terminal based on a multi-objective constraint control function, and dynamically adjusting the number of circuits at the heating terminal to maintain the temperature of the heating terminal above a set temperature threshold; The control function based on multi-objective constraints determines the number of circuits activated at the heating terminal, and dynamically adjusts the number of circuits at the heating terminal to maintain the temperature of the heating terminal above a set temperature threshold, including: Maximize the weighted benefit of terminal temperature and heating area; The control function is obtained based on the constraints of the upper limit of the number of circuits, the terminal temperature safety threshold and the minimum effective temperature difference; and the target number of circuits at the heating terminal is determined by dynamic programming or integer programming; The control function is: in, is a multi-objective control function, is the end temperature of resistive heating, is the effective heating area, is the air temperature outside the resistance heating terminal, is the thermal conductivity of the resistive heating terminal to the indoor wall, is the thickness from the end of 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, The area where the resistive heating terminal is laid is is the resistance of the photovoltaic array and other components in the cogeneration system, is the number of heating circuits running 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 photovoltaic panel installation area, is the power generation efficiency of the photovoltaic array in the cogeneration system, 额 is the rated output voltage of the PV array, The maximum value of the resistance heating terminal temperature is T. set +p.

2. The method according to claim 1, characterized in that The first relationship model includes: 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 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, The area where the resistive heating terminal is laid is is the resistance of the photovoltaic array and other components in the cogeneration system, is the number of heating circuits running in the resistive heating terminal, It is the thermal efficiency of the resistive heating terminal.

3. The method according to claim 2, characterized in that The second relational model includes: in, is the solar radiation intensity on the inclined surface, is the photovoltaic panel installation area, is the power generation efficiency of the photovoltaic array in the cogeneration system, 额 is the rated output voltage of the PV array, It is the solar radiation intensity value when the photovoltaic array reaches the rated output voltage.

4. The method according to claim 3, characterized in that Determining the solar radiation intensity control point according to the second relationship model includes: Determine the solar radiation intensity control point E that meets the minimum effective value of the temperature based on the minimum effective value of the terminal temperature and the second relationship model. set , 0 E set : Among them, p is the temperature difference threshold parameter, which represents the minimum effective temperature difference between the resistive heating terminal temperature and the indoor set temperature.

5. The method according to claim 1, characterized in that The method further comprises: During the heating period, the electricity from the combined heat and power system is used for heating or electricity storage; When the real-time 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 step of controlling the start and stop of the combined heat and power system according to the indoor temperature includes: If the indoor temperature is greater than the upper limit temperature of the room temperature, the combined heat and power system is controlled to stop operating; If the indoor temperature is lower than the indoor set temperature, the combined heat and power system is started; If there is excess electricity, charging the battery of the combined heat and power system based on the excess electricity; When the real-time solar radiation intensity is not higher than the solar radiation intensity control point and is 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 charged. If the battery is used up, the mains power is used for heating. If the battery is used up, the external power grid is started for power replenishment.

6. The method according to claim 1, characterized in that The method further comprises: In the non-heating period, the power of the cogeneration system is output to the end-users of the household electricity supply; The storage battery of the cogeneration system is controlled to discharge when there is insufficient sunlight, and is switched to be connected to the external power grid for charging when the power level is lower than a power threshold.

7. A multi-circuit variable voltage cogeneration system, characterized in that: The combined heat and power system includes a control device, which includes a processor and a computer program stored in a memory and executable on the processor. When the processor executes the computer program, the method according to any one of claims 1 to 6 is implemented.

8. The multi-circuit voltage-variable cogeneration system according to claim 7, characterized in that: The cogeneration system includes an off-grid photovoltaic power generation system, a heating terminal and a household electricity terminal; the control device is a system control cabinet in the off-grid photovoltaic power generation system, and the off-grid photovoltaic power generation system includes: a photovoltaic array, an irradiator, a temperature recorder and a battery, and the system control cabinet is respectively connected to the photovoltaic array, the irradiator, the temperature recorder and the battery.

9. The multi-circuit voltage-variable cogeneration system according to claim 8, characterized in that: The system control cabinet is also connected to the domestic electricity terminal and the external power grid through the inverter control box.

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