A photovoltaic heating adapter device

Abstract

The application provides a photovoltaic heating adapter device, which comprises a power module, a driving circuit, a signal acquisition circuit, a power tracking circuit, a temperature control circuit, an interface control circuit, a button control circuit, a liquid crystal display circuit, a control unit and a control power input circuit. The control unit analyzes the voltage, current and power of the photovoltaic and load, controls the output of the power device through the driving circuit according to the MPPT algorithm, directly drives the heating body, and changes the load to track the power change of the photovoltaic cell, so that the photovoltaic cell always works at the maximum power point. The interface control circuit can be connected to the upper controller, and the photovoltaic heating adapter device is complementary matched with the mains driving heating, directly heated and stored energy. The photovoltaic heating adapter device has high practicability, high safety, stable operation balance and the like, utilizes the photovoltaic to heat the heating body, saves a large amount of energy, and is applied to a heat circulation system to improve the heat energy efficiency.

Description

Technical Field

[0001] This application belongs to the field of energy-saving technology, and more specifically, relates to a photovoltaic heating adapter device. Background Technology

[0002] In the heating sector, modern electric boiler heating technology has made great progress in recent years and has been widely used in various industries. Currently, many domestic manufacturers are engaged in the research and development of this technology and have applied it in production, showing very good prospects for saving electricity, improving production efficiency, and improving the working environment.

[0003] In order to further reduce the energy consumption of the heating system, it is urgent to propose a new heating system solution. Summary of the Invention

[0004] The purpose of this application is to provide a photovoltaic heating adapter device to reduce the energy consumption of the heating system.

[0005] The photovoltaic heating adapter device of this application embodiment includes a power module, a power tracking circuit, a signal acquisition circuit, a drive circuit, and a control unit;

[0006] The input terminal of the power module is used to connect to the output terminal of the photovoltaic cell, and the output terminal of the power module is used to supply power to the heating element;

[0007] The power tracking circuit is configured to acquire the actual output voltage and actual output current of the photovoltaic cells.

[0008] The signal acquisition circuit is configured to acquire the actual output voltage and actual output current of the power module.

[0009] The control unit is configured to:

[0010] Based on the actual output voltage and actual output current of the photovoltaic cell, and the actual output voltage and actual output current of the power module, the MPPT algorithm is used to determine the maximum power point of the photovoltaic cell and its corresponding target output voltage.

[0011] The control signal of the power module is determined based on the maximum power point of the photovoltaic cell and the target output voltage of the corresponding photovoltaic cell.

[0012] The control signal is output to the drive circuit so that the drive circuit drives the power module to output power according to a first power; wherein, the first power is the power corresponding to the maximum power point of the photovoltaic cell.

[0013] In one embodiment of this application, the photovoltaic heating adapter device further includes an interface control circuit, and the control unit is further configured to:

[0014] The target power is determined based on the first difference between the actual heating temperature and the target heating temperature;

[0015] If the ratio of the first power to the target power is less than the first threshold, the first identification information is sent to the upper-level controller through the interface control circuit, so that the upper-level controller controls the electric auxiliary heating module to start working.

[0016] In one embodiment of this application, the control unit is further configured to:

[0017] If the ratio of the first power to the target power is greater than the second threshold, the second identification information is sent to the upper-level controller through the interface control circuit, so that the upper-level controller controls the electric auxiliary heating module to stop working; wherein, the second threshold is greater than the first threshold.

[0018] In one embodiment of this application, the control unit is further configured to:

[0019] The reference value for determining the target power is based on the actual heating temperature and ambient temperature;

[0020] The power increment is determined based on the first difference between the actual heating temperature and the target heating temperature; wherein, the first difference is positively correlated with the power increment.

[0021] The target power is obtained by adjusting the reference value of the target power based on the power increment.

[0022] In one embodiment of this application, the MPPT algorithm specifically employs a random voltage perturbation method, wherein the method for determining the voltage perturbation step size includes:

[0023] The slope change of the VI curve of the photovoltaic cell is determined based on the voltage and current data corresponding to multiple consecutive acquisition cycles; wherein, the voltage and current data corresponding to each acquisition cycle includes the actual output voltage and the corresponding actual output current of the photovoltaic cell in that acquisition cycle.

[0024] If the change in the slope of the VI curve of the photovoltaic cell is less than or equal to the change threshold, the voltage perturbation step size is set to the first step size.

[0025] If the change in the slope of the VI curve of the photovoltaic cell is greater than the change threshold, the voltage perturbation step size is set to a second step size; the second step size is greater than the first step size.

[0026] In one embodiment of this application, the control unit is specifically used for:

[0027] The target output voltage of the power module is determined based on the maximum power point of the photovoltaic cell and the impedance of the heating element.

[0028] The duty cycle of each switch in the power module is determined based on the target output voltage of the power module.

[0029] The control signal of the power module is determined based on the duty cycle of each switching transistor in the power module.

[0030] In one embodiment of this application, the power module specifically employs a DC-DC circuit.

[0031] In one embodiment of this application, the photovoltaic heating adapter device further includes:

[0032] A temperature control circuit is used to detect the temperature of the heat sink in the power module in real time and control the start or stop of the fan based on the temperature of the heat sink.

[0033] In one embodiment of this application, the photovoltaic heating adapter device further includes:

[0034] The button control circuit is used for user input of adjustment parameters;

[0035] The liquid crystal display circuit is used for users to input adjustment parameters and to display the operating parameters of the photovoltaic heating adapter device.

[0036] The beneficial effects of the photovoltaic heating adapter device provided in this application embodiment are as follows:

[0037] In this embodiment, the controller uses the MPPT algorithm to calculate the maximum power point of the photovoltaic cell and its corresponding target output voltage in real time. Based on the maximum power point of the photovoltaic cell and its corresponding target output voltage, the controller adjusts the output voltage of the power module to adjust the heating power of the heating element. This ensures that the heating power tracks the power change of the photovoltaic cell, so that the photovoltaic cell always works at its maximum power point, achieving full utilization of solar energy and reducing the consumption of traditional energy sources. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a structural block diagram of a photovoltaic heating adapter device provided in one embodiment of this application;

[0040] Figure 2 This is a structural block diagram of a power module provided in an embodiment of this application;

[0041] Figure 3 This is a structural block diagram of a power module provided in another embodiment of this application. Detailed Implementation

[0042] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0043] To make the objectives, technical solutions, and advantages of this application clearer, the following description will be provided in conjunction with the accompanying drawings and specific embodiments.

[0044] Figure 1 This is a schematic diagram of the photovoltaic heating adapter device provided in an embodiment of this application. (Refer to...) Figure 1 The photovoltaic heating adapter device includes a power module, a power tracking circuit, a signal acquisition circuit, a drive circuit, and a control unit;

[0045] The input terminal of the power module is used to connect to the output terminal of the photovoltaic cell, and the output terminal of the power module is used to supply power to the heating element;

[0046] The power tracking circuit is configured to acquire the actual output voltage and actual output current of the photovoltaic cells;

[0047] The signal acquisition circuit is configured to acquire the actual output voltage and actual output current of the power module;

[0048] The control unit is configured as follows:

[0049] Based on the actual output voltage and actual output current of the photovoltaic cell, as well as the actual output voltage and actual output current of the power module, the MPPT algorithm is used to determine the maximum power point of the photovoltaic cell and its corresponding target output voltage.

[0050] The control signal of the power module is determined based on the maximum power point of the photovoltaic cell and its corresponding target output voltage.

[0051] A control signal is output to the drive circuit so that the drive circuit drives the power module to output power according to the first power; wherein, the first power is the power corresponding to the maximum power point of the photovoltaic cell.

[0052] In this embodiment, the photovoltaic cell can convert solar energy into electrical energy. The output terminal of the photovoltaic cell is connected to the input terminal of the power module, which converts the input voltage and outputs a voltage of a set level to power the heating element, thereby achieving heating.

[0053] The power module consists of power devices (such as IGBTs and MOSFETs). The control signal (PWM signal) output by the control unit can control the power devices in the power module to turn on or off (one power device corresponds to one PWM signal). By adjusting the duty cycle of the PWM signal, the voltage conversion factor of the power module can be adjusted, thereby adjusting the output voltage of the power module.

[0054] Considering that the relationship between the output power (P) of a photovoltaic cell and its voltage (V) and current (I) is a non-linear curve (PV curve) and is significantly affected by environmental factors such as light intensity and temperature, in order to ensure that the photovoltaic cell always operates near its maximum power point, this embodiment uses a power tracking circuit to collect the actual output voltage and actual output current of the photovoltaic cell. At the same time, a signal acquisition circuit is configured to collect the actual output voltage and actual output current of the power module. Based on this, the MPPT algorithm is used to track the maximum power point of the photovoltaic cell to obtain the maximum power point of the photovoltaic cell and its corresponding target output voltage.

[0055] Furthermore, the control unit can adjust the output voltage of the power module according to the maximum power point of the photovoltaic cell and its corresponding target output voltage, thereby adjusting the heating power of the heating element so that the heating power tracks the power change of the photovoltaic cell, ensuring that the photovoltaic cell always operates at its maximum power point.

[0056] Specifically, the control unit can determine the target output voltage of the power module based on the maximum power point of the photovoltaic cell and its corresponding target output voltage. Then, based on the target output voltage of the power module, it can determine the duty cycle of the PWM signal corresponding to each power device in the power module. After the PWM signal output by the control unit is amplified by the drive circuit, it can drive each power device to turn on or off, so that the output voltage of the power module is the target output voltage.

[0057] As can be seen from the above, in this embodiment, the control unit uses the MPPT algorithm to calculate the maximum power point of the photovoltaic cell and its corresponding target output voltage in real time, and adjusts the output voltage of the power module according to the maximum power point of the photovoltaic cell and its corresponding target output voltage, thereby adjusting the heating power of the heating element so that the heating power tracks the power change of the photovoltaic cell, so that the photovoltaic cell always works at the maximum power point, realizing the full utilization of solar energy and helping to reduce the consumption of traditional energy.

[0058] In one embodiment of this application, the photovoltaic heating adapter device further includes an interface control circuit, and the control unit is further configured to:

[0059] The target power is determined based on the first difference between the actual heating temperature and the target heating temperature;

[0060] If the ratio of the first power to the target power is less than the first threshold, the first identification information is sent to the upper-level controller through the interface control circuit, so that the upper-level controller controls the electric auxiliary heating module to start working.

[0061] In this embodiment, the actual heating temperature is the actual temperature of the heating area corresponding to the photovoltaic heating adapter device. A temperature sensor can be set in the heating area corresponding to the photovoltaic heating adapter device to realize the real-time acquisition of the actual heating temperature.

[0062] The target heating temperature is the target temperature for the heating area corresponding to the photovoltaic heating adapter device, which can be set by the user according to actual needs. The target power is the heating power required to raise the temperature of the heating area from the actual heating temperature to the target heating temperature. The larger the initial difference between the actual heating temperature and the target heating temperature, the larger the target power.

[0063] In this embodiment, the degree to which the first power of the power module deviates from the target power is evaluated based on the ratio of the first power to the target power. When the ratio of the first power to the target power is less than a preset first threshold, it indicates that the first power cannot meet the heating demand of the heating area. At this time, the control unit can send the first identification information to the upper-level controller through the interface control circuit. After receiving the first identification information, the upper-level controller starts the electric auxiliary heating module to start working. The electric auxiliary heating module and the photovoltaic cell work together to provide heating for the heating area to make up for the insufficient energy of the photovoltaic cell.

[0064] As can be seen from the above, this embodiment collects the actual heating temperature of the heating area in real time, determines the target power based on the first difference between the actual heating temperature and the target heating temperature, evaluates the degree of deviation of the first power of the power module from the target power based on the ratio of the first power to the target power, and promptly starts the electric auxiliary heating module when the deviation is too large. Through the complementary matching of photovoltaic cells and electric auxiliary heating module (mains heating module), the heating needs of the heating area can be ensured.

[0065] In one embodiment of this application, the control unit is further configured to:

[0066] If the ratio of the first power to the target power is greater than the second threshold, the second identification information is sent to the upper-level controller through the interface control circuit, so that the upper-level controller controls the electric auxiliary heating module to stop working; wherein, the second threshold is greater than the first threshold.

[0067] In this embodiment, when the ratio of the first power to the target power is greater than a preset second threshold, it indicates that the first power can meet the heating needs of the heating area. At this time, the control unit can send second identification information to the upper-level controller through the interface control circuit. After receiving the second identification information, the upper-level controller stops the operation of the electric auxiliary heating module, which can save energy consumption. The first and second thresholds are both preset constants, and they define a hysteresis interval to avoid frequent starting or stopping of the electric auxiliary heating module.

[0068] In one embodiment of this application, the control unit is further configured to:

[0069] The reference value for determining the target power is based on the actual target heating temperature and ambient temperature;

[0070] The power increment is determined based on the first difference between the actual heating temperature and the target heating temperature; wherein, the first difference is positively correlated with the power increment.

[0071] The target power is obtained by adjusting the reference value of the target power based on the power increment.

[0072] In this embodiment, a specific implementation method is given for determining the target power based on the first difference between the actual heating temperature and the target heating temperature.

[0073] Here, ambient temperature refers to the air temperature surrounding the heating area. When calculating the target power, a reference value for the target power can first be determined based on the actual heating temperature and ambient temperature. This reference value characterizes the heating power required to maintain the temperature of the heating area at the actual heating temperature. Based on historical data of the heating area, the heating power required to raise the temperature of the heating area by 1°C within a set time period can be calculated and denoted as the unit heating power. Then, by calculating the second difference between the actual heating temperature and the ambient temperature, and multiplying this second difference by the unit heating power, the reference value for the target power can be obtained.

[0074] Furthermore, a first difference between the actual heating temperature and the target heating temperature can be calculated. Multiplying the first difference by the unit heating power yields the power increment, which is used to characterize the heating power required to raise the temperature of the area from the actual heating temperature to the target heating temperature.

[0075] Based on the reference value and power increment of the target power, the target power can be obtained by adding the reference value and power increment.

[0076] Specifically, the target power can be calculated using the following first formula:

[0077] ;

[0078] in, ;

[0079] In the first formula above, Indicates the target power. A reference value representing the target power. Indicates the power increment. Indicates unit heating power, Indicates ambient temperature. This indicates the actual heating temperature. Indicates the target heating temperature. The threshold representing the temperature difference, This indicates the preset scaling factor.

[0080] In the first formula above, and All are preset constants, when When the first difference between the actual heating temperature and the target heating temperature is small, a proportionality coefficient between 0 and 1 can be used. Adjust the power increment to reduce the target power, and use photovoltaic cells to heat the heating area as much as possible without triggering the electric auxiliary heating module, thereby saving energy consumption.

[0081] In one embodiment of this application, the MPPT algorithm specifically employs a random voltage perturbation method, wherein the method for determining the voltage perturbation step size includes:

[0082] The slope change of the VI curve of the photovoltaic cell is determined based on the voltage and current data corresponding to multiple consecutive acquisition cycles; wherein, the voltage and current data corresponding to each acquisition cycle includes the actual output voltage and the corresponding actual output current of the photovoltaic cell in that acquisition cycle.

[0083] If the change in the slope of the VI curve of the photovoltaic cell is less than or equal to the change threshold, the voltage perturbation step size is set to the first step size.

[0084] If the change in the slope of the VI curve of the photovoltaic cell is greater than the change threshold, the voltage perturbation step size is set to the second step size; the second step size is greater than the first step size.

[0085] In this embodiment, the random voltage perturbation method is specifically used for MPPT calculation. This method involves superimposing random small perturbations on the operating voltage of the photovoltaic cell and observing the direction of power change. If the power increases, the perturbation direction is maintained, and vice versa, gradually approaching the maximum power point.

[0086] Meanwhile, considering that when light intensity changes rapidly (e.g., due to cloud cover), using a small voltage perturbation step size would lead to efficiency loss due to frequent adjustments and slow down the tracking speed, this embodiment addresses this issue. It considers that changes in light intensity alter the slope of the photovoltaic panel's V-I curve. Therefore, by continuously sampling multiple V-I points and calculating the slope k = ΔV / ΔI between adjacent points, if the slope change exceeds a threshold, it indicates a rapid change in light intensity. A larger step size (second step size) is then used for voltage perturbation to accelerate power tracking. Conversely, if the slope change is less than or equal to the threshold, it indicates stable light intensity. A smaller step size (first step size) is then used for voltage perturbation to improve power tracking accuracy.

[0087] Specifically, the methods for determining the threshold of change include:

[0088] Obtain a reference value for the threshold of change;

[0089] The adjustment coefficient is determined based on the current temperature of the photovoltaic cell;

[0090] The reference value of the change threshold is adjusted based on the adjustment coefficient to obtain the change threshold.

[0091] In this embodiment, the average value of the change in the slope of the VI curve within a set time period (e.g., 10 minutes) prior to the current moment can be calculated based on a set sliding window, and used as a reference value for the change threshold corresponding to the current moment.

[0092] Based on this, considering that the voltage and current of photovoltaic cells are affected by temperature—for example, the internal resistance of photovoltaic cells increases and the slope of the VI curve decreases at high temperatures, while the opposite is true at low temperatures—this embodiment can dynamically adjust the reference value of the rate of change threshold according to temperature to accurately determine the change threshold.

[0093] Specifically, the threshold for change can be calculated using the following second formula:

[0094]

[0095] in, Indicates the threshold of change. A reference value representing the threshold of change. This represents the preset first temperature coefficient. This indicates the preset second temperature coefficient. This indicates the temperature of the photovoltaic cell.

[0096] As can be seen from the above, this embodiment calculates the reference value of the change threshold based on the data within a set time period before the current moment, and dynamically adjusts the reference value of the change threshold based on the temperature of the photovoltaic cell, so that the obtained change threshold is more in line with the actual situation.

[0097] In one embodiment of this application, the control unit is specifically used for:

[0098] The target output voltage of the power module is determined based on the maximum power point of the photovoltaic cell and the impedance of the heating element.

[0099] The duty cycle of each switch in the power module is determined based on the target output voltage of the power module.

[0100] The control signal of the power module is determined based on the duty cycle of each switching transistor in the power module.

[0101] In this embodiment, a specific implementation method is given for the controller to determine the control signal of the power module based on the maximum power point of the photovoltaic cell and the corresponding target output voltage of the photovoltaic cell.

[0102] First, based on the power balance principle, the power corresponding to the maximum power point of the photovoltaic cell is taken as the output power of the power module. Then, based on the relationship between power and voltage... The target output voltage of the power module is obtained (where R is the impedance of the heating element). Then, closed-loop control is performed on the target output voltage of the power module to determine the duty cycle of each switch in the power module; finally, the corresponding PWM control signal is output according to the duty cycle of each switch in the power module.

[0103] The closed-loop control of the power module can be performed using an existing PI controller. Specifically, the actual output voltage of the power module can be acquired in real time, and then the actual output voltage and the target output voltage of the power module are input to the PI controller. The PI controller adjusts the duty cycle of the PWM control signal according to the deviation between the actual output voltage and the target output voltage of the power module, and outputs the PWM control signal to the control terminal of the corresponding switching transistor.

[0104] In one embodiment of this application, the power module specifically adopts a DC-DC circuit.

[0105] Reference Figure 2 In this embodiment, the heating element can be powered by DC. Therefore, the power module can be implemented using only a DC-DC circuit, with the output of the DC-DC circuit directly powering the heating element. In this case, the output voltage of the photovoltaic cell only undergoes one stage of conversion, which can improve the energy utilization rate of the photovoltaic cell.

[0106] In one embodiment of this application, the power module includes a DC-DC circuit and a DC-AC circuit connected in sequence, and each switch in the power module includes a first switch in the DC-DC circuit and a second switch in the DC-AC circuit.

[0107] The control unit is also specifically used for:

[0108] Obtain a reference value for the modulation ratio of the DC-AC circuit; the modulation ratio of the DC-AC circuit is the ratio between the peak value of the AC side output voltage and the DC side voltage of the DC-AC circuit.

[0109] The target output voltage of the DC-DC circuit is determined based on the target output voltage of the power module and the reference value of the modulation ratio of the DC-AC circuit.

[0110] The duty cycle of the first switching transistor is determined based on the target output voltage of the DC-DC circuit, and the duty cycle of the second switching transistor is determined based on the target output voltage of the power module.

[0111] Reference Figure 3 In this embodiment, the heating element can also be powered by AC. In this case, the power module can include a DC-DC circuit and a DC-AC circuit connected in sequence. When the output voltage of the photovoltaic cell is low, the DC-DC circuit is used to boost the output voltage of the photovoltaic cell. On this basis, the DC-AC circuit is used to convert the DC voltage output by the DC-DC circuit into AC voltage to meet the power supply requirements of the heating element.

[0112] Based on the circuit composition of the power module described above, this embodiment provides a specific implementation method for determining the duty cycle of each switch in the power module. Specifically, in this embodiment, the control of the second switch in the DC-AC circuit can adopt sinusoidal pulse width modulation (SPWM) or space vector modulation (SVPWM). The ratio between the peak value of the AC side output voltage and the DC side voltage of the DC-AC circuit is called the modulation ratio. For SPWM or SVPWM modulation, when the modulation ratio is close to 0.8 (which may vary depending on the actual circuit design), the harmonic components of the DC-AC circuit output can be reduced, thus lowering the output filter loss.

[0113] Therefore, in this embodiment, when determining the duty cycle of each switch in the power module, a reference value for the modulation ratio can first be determined based on the specific circuit structure of the DC-AC circuit. Based on this, the peak value of the AC side output voltage of the DC-AC circuit can be obtained from the target output voltage (RMS) of the power module. Dividing the peak value of the AC side output voltage of the DC-AC circuit by the reference value of the modulation ratio yields the target output voltage of the DC-DC circuit. Then, closed-loop control of the DC-DC circuit based on the target output voltage of the DC-DC circuit determines the duty cycle of the first switch in the DC-DC circuit. Simultaneously, closed-loop control of the DC-AC circuit based on the target output voltage of the power module determines the duty cycle of the second switch in the DC-AC circuit.

[0114] In this case, both the DC-AC circuit and the closed-loop control of the DC-AC circuit can be performed using existing PI controllers. Taking the DC-AC circuit as an example, the actual output voltage of the DC-DC circuit can be acquired in real time. Then, the actual output voltage of the DC-DC circuit and the target output voltage of the DC-DC circuit are input to the PI controller. The PI controller adjusts the duty cycle of the PWM control signal of the first switching transistor according to the deviation between the actual output voltage of the DC-DC circuit and the target output voltage of the DC-DC circuit, and outputs the PWM control signal to the control terminal of the first switching transistor.

[0115] As can be seen from the above, this embodiment determines the target output voltage of the DC-DC circuit based on the target output voltage of the power module and the reference value of the modulation ratio of the DC-AC circuit. Then, it determines the duty cycle of the first switch in the DC-DC circuit based on the target output voltage of the DC-DC circuit, and determines the duty cycle of the second switch in the DC-AC circuit based on the target output voltage of the power module. While ensuring the tracking of the maximum power point of the photovoltaic cell, it can further reduce the harmonic content in the output voltage of the power module, thereby further reducing energy consumption.

[0116] In one embodiment of this application, the control unit is further configured to:

[0117] If the duty cycle of the first switch is greater than the duty cycle threshold, the duty cycle of the first switch is adjusted to the duty cycle threshold.

[0118] The target output voltage of the DC-DC circuit is re-determined based on the adjusted duty cycle of the first switching transistor and the target output voltage of the photovoltaic cell, thus obtaining the adjusted target output voltage of the DC-DC circuit.

[0119] The duty cycle of the second switch is redefined based on the target output voltage of the adjusted DC-DC circuit and the target output voltage of the power module.

[0120] In this embodiment, the DC-DC circuit can be a BOOST circuit, and its voltage conversion factor can be expressed by the following third formula:

[0121] ;

[0122] in, This indicates the output voltage of the BOOST circuit. This indicates the input voltage of the BOOST circuit. This indicates the first duty cycle.

[0123] As shown in the third formula above, a larger first duty cycle results in a higher output voltage for the DC-DC circuit. However, if the first duty cycle is too large (e.g., greater than 0.8), it will lead to decreased circuit efficiency and poor stability. To avoid these problems, a duty cycle threshold (e.g., 0.8) can be preset. When the duty cycle of the first switch exceeds the threshold, the duty cycle of the first switch is adjusted to the threshold. Then, the target output voltage of the DC-DC circuit is redefined based on the duty cycle threshold. Based on the adjusted target output voltage of the power module, the output voltage of the DC-AC circuit is re-controlled in a closed loop to redetermine the duty cycle of the second switch in the DC-AC circuit.

[0124] As can be seen from the above, in this embodiment, when the duty cycle of the first switch is too large, the duty cycle of the first switch and the duty cycle of the second switch are readjusted based on the duty cycle threshold of the first switch, which can ensure the stability of the circuit operation.

[0125] In one embodiment of this application, the photovoltaic heating adapter device further includes:

[0126] The temperature control circuit is used to detect the temperature of the heat sink in the power module in real time and control the start or stop of the fan based on the temperature of the heat sink.

[0127] In this embodiment, a temperature control circuit is installed inside the photovoltaic heating adapter device to monitor the temperature of the power device's heat sink in real time. When the heat sink temperature exceeds a first set temperature, an external fan is activated to cool the power device. When the heat sink temperature falls below a second set temperature, the external fan stops to reduce energy consumption. Both the first and second set temperatures are preset constants, with the first set temperature being greater than the second set temperature. Those skilled in the art can determine the specific values ​​of the first and second set temperatures according to actual needs.

[0128] In one embodiment of this application, the photovoltaic heating adapter device further includes:

[0129] Button control circuit for user input of adjustment parameters;

[0130] The LCD display circuit is used for users to input adjustment parameters and to display the operating parameters of the photovoltaic heating adapter device.

[0131] In this embodiment, considering that the environment of photovoltaic cells, such as location, sunlight, and temperature, varies throughout the year, a button-controlled circuit is provided. By inputting adjustment parameters through the button-controlled circuit, the photovoltaic heating adapter device can be fine-tuned to optimize its performance.

[0132] In addition, adjustment parameters can also be input through the LCD display circuit, which can also display voltage, current, power and total power in real time.

[0133] In one embodiment of this application, the photovoltaic heating adapter device also has overload protection, short circuit protection, and reverse connection protection functions to ensure the safe operation of the system.

[0134] In summary, the heating system combining the photovoltaic heating adapter device and mains auxiliary heating in this application is rationally designed, highly practical, safe, and operates in a balanced and stable manner. Through the interface circuit of the photovoltaic adapter (dedicated for heating), it can automatically match and switch the control of photovoltaic direct drive and mains auxiliary heating to the heating element for complementary heating and energy storage, making operation more convenient. Utilizing photovoltaics to heat the heating element saves a significant amount of energy and improves thermal efficiency when applied to the heat circulation system. In special circumstances, an electric auxiliary heating system can also be used for heating.

[0135] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A photovoltaic heating adapter device, characterized in that, It includes a power module, a power tracking circuit, a signal acquisition circuit, a drive circuit, and a control unit; The input terminal of the power module is used to connect to the output terminal of the photovoltaic cell, and the output terminal of the power module is used to supply power to the heating element; The power tracking circuit is configured to acquire the actual output voltage and actual output current of the photovoltaic cells. The signal acquisition circuit is configured to acquire the actual output voltage and actual output current of the power module. The control unit is configured to: Based on the actual output voltage and actual output current of the photovoltaic cell, and the actual output voltage and actual output current of the power module, the MPPT algorithm is used to determine the maximum power point of the photovoltaic cell and its corresponding target output voltage. The control signal of the power module is determined based on the maximum power point of the photovoltaic cell and the target output voltage of the corresponding photovoltaic cell. The control signal is output to the drive circuit so that the drive circuit drives the power module to output power according to a first power; wherein, the first power is the power corresponding to the maximum power point of the photovoltaic cell; The power module includes a DC-DC circuit and a DC-AC circuit connected in sequence. Each switching transistor in the power module includes a first switching transistor in the DC-DC circuit and a second switching transistor in the DC-AC circuit. The control unit is also specifically used for: Obtain a reference value for the modulation ratio of the DC-AC circuit; the modulation ratio of the DC-AC circuit is the ratio between the peak value of the AC side output voltage and the DC side voltage of the DC-AC circuit. The target output voltage of the DC-DC circuit is determined based on the target output voltage of the power module and a reference value of the modulation ratio of the DC-AC circuit. The duty cycle of the first switching transistor is determined based on the target output voltage of the DC-DC circuit, and the duty cycle of the second switching transistor is determined based on the target output voltage of the power module. The MPPT algorithm specifically employs a random voltage perturbation method, wherein the voltage perturbation step size is determined by: The slope change of the VI curve of the photovoltaic cell is determined based on the voltage and current data corresponding to multiple consecutive acquisition cycles; wherein, the voltage and current data corresponding to each acquisition cycle includes the actual output voltage and the corresponding actual output current of the photovoltaic cell in that acquisition cycle. If the change in the slope of the VI curve of the photovoltaic cell is less than or equal to the change threshold, the voltage perturbation step size is set to the first step size. If the change in the slope of the VI curve of the photovoltaic cell is greater than the change threshold, the voltage perturbation step size is set to a second step size; the second step size is greater than the first step size. The threshold for change is calculated using the following second formula: in, Indicates the threshold of change. A reference value representing the threshold of change. This represents the preset first temperature coefficient. This indicates the preset second temperature coefficient. This indicates the temperature of the photovoltaic cell.

2. The photovoltaic heating adapter device as described in claim 1, characterized in that, It also includes an interface control circuit, and the control unit is further used for: The target power is determined based on the first difference between the actual heating temperature and the target heating temperature; If the ratio of the first power to the target power is less than the first threshold, the first identification information is sent to the upper-level controller through the interface control circuit, so that the upper-level controller controls the electric auxiliary heating module to start working.

3. A photovoltaic heating adapter device as described in claim 2, characterized in that, The control unit is also used for: If the ratio of the first power to the target power is greater than the second threshold, the second identification information is sent to the upper-level controller through the interface control circuit, so that the upper-level controller controls the electric auxiliary heating module to stop working; wherein, the second threshold is greater than the first threshold.

4. A photovoltaic heating adapter device as described in claim 2 or 3, characterized in that, The control unit is also used for: The reference value for determining the target power is based on the actual heating temperature and ambient temperature; The power increment is determined based on the first difference between the actual heating temperature and the target heating temperature; wherein, the first difference is positively correlated with the power increment. The target power is obtained by adjusting the reference value of the target power based on the power increment.

5. A photovoltaic heating adapter device as described in claim 1, characterized in that, The control unit is specifically used for: The target output voltage of the power module is determined based on the maximum power point of the photovoltaic cell and the impedance of the heating element. The duty cycle of each switch in the power module is determined based on the target output voltage of the power module. The control signal of the power module is determined based on the duty cycle of each switching transistor in the power module.

6. A photovoltaic heating adapter device as described in claim 1, characterized in that, Also includes: A temperature control circuit is used to detect the temperature of the heat sink in the power module in real time and control the start or stop of the fan based on the temperature of the heat sink.

7. A photovoltaic heating adapter device as described in claim 1, characterized in that, Also includes: Button control circuit for user input of adjustment parameters; The liquid crystal display circuit is used for users to input adjustment parameters and to display the operating parameters of the photovoltaic heating adapter device.

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