Photovoltaic control system and method for coping with extremely cold and snowy weather

Abstract

This application discloses a photovoltaic control system and method for coping with extremely cold and snowy weather. The method includes the following steps: obtaining data from the inverter and photovoltaic panels; determining whether the cooling fan is frozen based on the data from the inverter and the cooling fan; if the cooling fan is frozen, adjusting the control loop corresponding to the inverter so that the inverter operates in SVG mode; determining the snow accumulation on the photovoltaic panel based on the environmental data and status data of the photovoltaic panel; and if the photovoltaic panel is snowed in, controlling the heating device installed on the photovoltaic panel to heat the photovoltaic panel. The system is used to implement the above method. The beneficial effects of this application include the ability to simultaneously defrost the cooling fan and remove snow from the photovoltaic panel, ensuring that the photovoltaic system can better cope with extremely cold weather. Furthermore, the defrosting of the cooling fan and the snow removal of the photovoltaic panel are both simple and safe, and do not require excessive hardware structure, ensuring that no excessive additional costs are incurred.

Description

Technical Field

[0001] The present application relates to the field of renewable energy power generation, and in particular to a photovoltaic control system for coping with extremely cold and snowy weather. Background Art

[0002] During winter operation, photovoltaic power generation systems can encounter extreme weather conditions such as heavy snowfall. Accumulated snow can cover photovoltaic modules, resulting in low power generation efficiency or even no power generation. This requires clearing the snow from the modules. Traditional snow removal methods often rely on manual removal or waiting for natural snowmelt, while others utilize mechanical mechanisms to tilt the modules. Currently, manual snow removal is difficult, dangerous, and prone to damage to the panels. Mechanical mechanisms that tilt and tilt the modules are also cumbersome, costly, and significantly impact power generation, making them difficult to meet user needs.

[0003] Furthermore, when temperatures fall below freezing, moisture inside the inverter (if present) may freeze, causing the fan blades or motor to freeze. Frozen fans prevent the fan from rotating properly, preventing the inverter from dissipating heat quickly. Overheating can affect inverter performance, reducing conversion efficiency and stability. Prolonged overheating can also accelerate the aging of the inverter's internal circuit components, increasing safety risks such as fire. If the inverter fan is frozen, it's often necessary to heat the inverter with a hair dryer or heater to melt the ice. Because overheating can damage the inverter's circuitry, heating should be performed quickly and is complex and manual. Summary of the Invention

[0004] One of the purposes of the present application is to provide a photovoltaic control system for coping with extremely cold and snowy weather that can solve at least one of the defects in the above-mentioned background technology.

[0005] Another object of the present application is to provide a photovoltaic control method for extremely cold and snowy weather that can solve at least one of the defects in the above-mentioned background technology.

[0006] In order to achieve at least one of the above-mentioned purposes, the technical solution adopted in the present application is: a photovoltaic control method for coping with extremely cold and snowy weather, comprising the following steps: obtaining environmental data of the inverter and photovoltaic panels, as well as status data of the photovoltaic panels and the cooling fan installed on the inverter; judging the freezing condition of the cooling fan in combination with the environmental data of the inverter and the status data of the cooling fan; if it is judged that the cooling fan is in a frozen state, adjusting the control loop corresponding to the inverter so that the inverter operates in SVG mode; judging the snow accumulation condition of the photovoltaic panel in combination with the environmental data and status data of the photovoltaic panel; if the photovoltaic panel is in a snow accumulation state, controlling the heating device installed on the photovoltaic panel to heat the photovoltaic panel.

[0007] Preferably, the environmental data of the inverter includes temperature data and humidity data, and the status data of the cooling fan includes forward speed and reverse speed; when the ambient humidity of the inverter is higher than the set humidity threshold, the ambient temperature of the inverter is lower than the set temperature threshold, and the forward speed and reverse speed of the cooling fan are both zero, it is judged that the cooling fan is in a frozen state.

[0008] Preferably, when the inverter is in SVG mode, the control loop uses the current loop as the outer loop and the voltage loop as the inner loop; the d-axis current reference value i on the input side of the current loop is d *The value is 0, the q-axis current reference value i q *The value range is (-k·I rate , + k·I rate ); where I rate It represents the rated current of the inverter, k represents the coefficient, and the value of k is less than the active power factor of the inverter.

[0009] Preferably, the q-axis current reference value i q The value of * is periodically changed by a square wave with an interval of Δt, and the peak value of the square wave is +k·I rate , the valley value of the square wave is -k·I rate .

[0010] Preferably, an air inlet and an air outlet are respectively provided on opposite sides of the inverter, the cooling fan is installed at the air inlet, and the air outlet is installed at the air outlet fin; when the inverter enters the SVG mode, the air outlet fin is suitable for closing the air outlet under the drive of the corresponding control device.

[0011] Preferably, the inverter needs to be dehumidified after the cooling fan is unfrozen in the SVG mode of the inverter. The specific dehumidification process is as follows: maintain the SVG mode of the inverter and open the air outlet fins; send a reverse control signal to the cooling fan to control the cooling fan to reverse; complete dehumidification when the ambient humidity of the inverter is lower than the humidity threshold and the ambient temperature is higher than the temperature threshold; after dehumidification is completed, send a forward control signal to the cooling fan and adjust the inverter to exit the SVG mode.

[0012] Preferably, the status data of the photovoltaic panel includes current data and surface pressure data, and the environmental data of the photovoltaic panel includes surface temperature data; when the output current of the photovoltaic panel drops to a set current threshold, the surface temperature of the photovoltaic panel is lower than a set temperature threshold, and the surface pressure of the photovoltaic panel is higher than a set pressure threshold, it is judged that there is snow on the surface of the photovoltaic panel.

[0013] A photovoltaic control system for coping with extremely cold and snowy weather, used to implement the above-mentioned photovoltaic control method for coping with extremely cold and snowy weather; comprising a detection module and a controller; the detection module is suitable for monitoring environmental data of the inverter and the surface pressure and environmental data of the photovoltaic panel; the controller is suitable for receiving status data of the cooling fan and feedback data from the detection module, and the controller is suitable for judging the freezing condition of the cooling fan and the snow accumulation condition of the photovoltaic panel based on the received data, and adjusting the control loop according to the judgment result to operate the inverter in SVG mode, or controlling the heating device to heat the photovoltaic panel.

[0014] Preferably, the detection module includes a temperature sensor and a humidity sensor installed inside the inverter, and the controller includes a signal receiving module, a signal analysis module, a fault judgment module and a control module; the signal receiving module is used to receive feedback data from the temperature sensor, the humidity sensor and the cooling fan, the signal analysis module is suitable for comparing the data received by the signal receiving module with a set threshold, and the fault judgment module judges the freezing condition of the cooling fan based on the comparison result of the signal analysis module; the control module sends a control instruction to the cooling fan or the control loop based on the judgment result of the fault judgment module.

[0015] Preferably, the heating device draws power from the power grid, and the circuit for drawing power from the heating device is controlled to be on and off by a control switch; the detection module includes a current detection unit, a pressure detection unit and a temperature detection unit installed; the controller includes a current judgment circuit, a pressure judgment circuit, a temperature judgment circuit, a drive circuit and a control module; the current detection unit is used to monitor the output current of each photovoltaic panel, the pressure detection unit is used to monitor the surface pressure of each photovoltaic panel, and the temperature detection unit is used to monitor the surface temperature of each photovoltaic panel; the current judgment circuit is suitable for receiving all the collected data of the current detection unit and performing threshold judgment, the pressure judgment circuit is suitable for receiving all the collected data of the pressure detection unit and performing threshold judgment, and the temperature judgment circuit is suitable for receiving all the collected data of the temperature detection unit and performing threshold judgment; the control module is suitable for sending a control signal to the drive circuit according to the judgment results of the current judgment circuit, the pressure judgment circuit and the temperature judgment circuit, and then the drive circuit controls the opening or closing of the control switch according to the received control signal.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] Being able to simultaneously defrost the cooling fan and remove snow from the photovoltaic panels ensures that the photovoltaic system can better cope with extreme cold weather. Furthermore, both the defrosting of the cooling fan and the removal of snow from the photovoltaic panels are simple and safe to operate, without requiring excessive hardware, thus minimizing the additional cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the overall workflow of this application.

[0019] Figure 2 A schematic diagram of the workflow for detecting and recovering from a freezing condition of a cooling fan in this application.

[0020] Figure 3 This is a timing diagram of the application for judging the freezing condition of the cooling fan through the inverter environment data and the cooling fan speed data.

[0021] Figure 4 This is a timing diagram of the application for judging the freezing situation by controlling the speed of the cooling fan.

[0022] Figure 5 This is a timing diagram of the cooling fan in this application performing a re-freezing condition determination during the thawing process.

[0023] Figure 6 This is a simplified diagram of the internal structure of the inverter in this application.

[0024] Figure 7 This is a timing diagram of dehumidifying the interior of the inverter through the cooling fan in this application.

[0025] Figure 8 Schematic diagram of the control loop operation flow of the inverter in normal operation mode in this application.

[0026] Figure 9 Schematic diagram of the working process of the control loop of the inverter in SVG mode in this application.

[0027] Figure 10 Schematic diagram of the workflow for detecting and restoring snow accumulation on photovoltaic panels for this application.

[0028] Figure 11 This is a timing diagram of the application for judging the snow accumulation condition of photovoltaic panels through the environmental data and status data of photovoltaic panels.

[0029] Figure 12 This is a structural diagram of the controller and detection module in this application detecting and controlling the cooling fan.

[0030] Figure 13 This is a schematic diagram of the structure of the controller and detection module in this application for detecting and controlling the photovoltaic panel.

[0031] In the figure: inverter 10, power conversion unit 101, cooling fan 102, radiator 103, air outlet fins 104, controller 20, signal receiving module 201, signal analysis module 202, fault judgment module 203, control module 204, current judgment circuit 205, pressure judgment circuit 206, temperature judgment circuit 207, drive circuit 208, feedback signal line 2001, control signal line 2002, temperature sensor 301, humidity sensor 302, pressure sensor 303, current sensor 304, current detection circuit 305, pressure detection circuit 306, temperature detection circuit 307, heating device 400, photovoltaic panel 500. DETAILED DESCRIPTION

[0032] Below, the present application is further described in conjunction with specific implementation methods. It should be noted that, in the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" and the like are intended to mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0033] In the description of this application, it should be noted that for directional words, such as the terms "center", "horizontal", "longitudinal", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and so on, indicating the orientation and position relationship are based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and cannot be understood as limiting the specific scope of protection of this application.

[0034] It should be noted that the terms "first", "second", etc. in the description and claims of this application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0035] In this application, unless otherwise expressly specified or limited, terms such as "mounted," "connected," "connect," and "fixed" should be understood in a broad sense. For example, they may refer to connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0036] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0037] The terms "comprises" and "having" and any variations thereof in the specification and claims of this application are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus that includes a series of steps or units is not necessarily limited to those steps or units expressly listed, but may include other steps or units not expressly listed or inherent to such process, method, product or apparatus.

[0038] One aspect of the present application provides a photovoltaic control method for dealing with extremely cold and snowy weather, such as Figure 1 As shown, one preferred embodiment includes the following steps: obtaining environmental data of the inverter 10 and the photovoltaic panel 500, as well as status data of the photovoltaic panel 500 and the cooling fan 102 mounted on the inverter 10. The freezing condition of the cooling fan 102 is determined based on the environmental data of the inverter 10 and the status data of the cooling fan 102. If the cooling fan 102 is determined to be frozen, the corresponding control loop of the inverter 10 is adjusted to enable the inverter 10 to operate in SVG mode. The snow accumulation condition of the photovoltaic panel 500 is determined based on the environmental data and status data of the photovoltaic panel 500. If the photovoltaic panel 500 is snowed in, the heating device 400 mounted on the photovoltaic panel 500 is controlled to heat the photovoltaic panel 500.

[0039] It should be noted that for the entire photovoltaic system, the following three situations may occur in extremely cold and snowy weather. The first is: only the cooling fan 102 is frozen; the second is: only the surface of the photovoltaic panel 500 is covered with snow; the third is: the surface of the photovoltaic panel 500 is covered with snow, and the cooling fan 102 is also frozen. Therefore, in this embodiment, the operating mode switching process of the inverter 10 and the startup process of the heating device 400 installed on the photovoltaic panel 500 are relatively independent. Depending on the situation, only the operating mode of the inverter 10 can be switched, only the heating device 400 can be started, or the operating mode of the inverter 10 can be switched and the heating device 400 can be started at the same time.

[0040] It is understood that the SVG mode of the inverter 10 is a reactive power compensation mode, and the specific operating principles and processes of this mode are well known to those skilled in the art. In SVG mode, the inverter 10 can absorb reactive power to significantly increase its internal temperature. This heat can then be transferred to the cooling fan 102 for defrosting. The specific structure and operating principles of the heating device 400 are well known to those skilled in the art. The heating device 400 often utilizes a resistance wire, which can be arranged in an S-shape on the photovoltaic panel 500 to ensure uniform heating across the entire surface of the photovoltaic panel 500 during operation, thereby accelerating the melting of accumulated snow. Compared to traditional methods, this embodiment can defrost the cooling fan 102 and remove snow from the photovoltaic panel 500, ensuring that the photovoltaic system is better able to cope with extreme cold weather. Furthermore, the defrosting of the cooling fan 102 and the snow removal of the photovoltaic panel 500 are both simple and safe, without requiring excessive hardware, thus minimizing additional costs. For ease of understanding, the thawing process of the cooling fan 102 and the snow removal process of the photovoltaic panel 500 will be described in detail below.

[0041] 1. Detection of the freezing state of the cooling fan 102 and the thawing process.

[0042] In this embodiment, Figure 2 and Figure 3 As shown, the environmental data of the inverter 10 primarily includes temperature and humidity data, and the status data of the cooling fan 102 includes forward and reverse rotational speeds. When the ambient humidity of the inverter 10 is higher than a set humidity threshold, it indicates that there is sufficient moisture inside the inverter 10 to freeze the cooling fan 102. When the ambient temperature of the inverter 10 is lower than a set temperature threshold, it indicates that the temperature inside the inverter 10 is sufficient to freeze the moisture. When the environmental conditions of the inverter 10 meet the freezing conditions for the cooling fan 102, the rotational speed of the cooling fan 102 can be determined. If both the forward and reverse rotational speeds of the cooling fan 102 are zero, it can be determined that the cooling fan 102 is in a frozen state.

[0043] It should be noted that the specific value of the humidity threshold corresponding to the internal environment of the inverter 10 can be set according to actual needs; the specific value of the temperature threshold corresponding to the internal environment of the inverter 10 can also be set according to actual needs. Generally speaking, the relative humidity corresponding to the ambient humidity that can freeze is usually greater than 70%, and the temperature that can freeze is usually below 0°C; that is, the humidity threshold can be set to 70% relative humidity, and the temperature threshold can be set to 0°C.

[0044] It is understood that after determining that the cooling fan 102 is frozen, the inverter 10 can be controlled to enter SVG mode, allowing the inverter 10 to absorb reactive power to generate heat and thaw the cooling fan 102. Since the SVG mode of the inverter 10 primarily performs reactive power compensation to generate heat, the inverter 10 cannot operate in this mode for too long. Therefore, after the inverter 10 enters SVG mode, the freezing state of the cooling fan 102 is checked at set intervals. If the cooling fan 102 is still frozen, the inverter 10 will continue to operate in SVG mode. If the cooling fan 102 is completely thawed, the inverter 10 will exit SVG mode and resume normal operation.

[0045] For ease of understanding, the entire freezing state determination and thawing process of the cooling fan 102 will be described in detail below in a time sequence manner.

[0046] Specifically, such as Figure 3 As shown, during the time from time 0 to time t1, the freezing state of the cooling fan 102 is detected, including environmental data detection and fan speed detection. Environmental data detection is to determine whether the current environmental data meets the freezing conditions; fan speed detection includes the following specific processes:

[0047] like Figure 4 As shown, the forward speed test of the cooling fan 102 is first performed, and at t s1_0 At this moment, a forward PWM control signal is sent to the cooling fan 102, and the forward speed information of the cooling fan 102 is detected at the same time. If the speed signal is always zero, that is, the cooling fan 102 does not rotate forward and continues for Δt time, it can be determined that the cooling fan 102 has a forward rotation fault, and the forward fault signal changes from low level to high level. Then, a reverse speed test of the cooling fan 102 is performed. At t s1_3 At this moment, a reverse PWM control signal is sent to the cooling fan 102, and the reverse speed information of the cooling fan 102 is detected at the same time. If the speed signal is always zero, that is, the cooling fan 102 does not reverse and lasts for Δt time, it can be determined that the cooling fan 102 has a reverse fault, and the reverse fault signal changes from low level to high level.

[0048] It should be noted that if Figure 4 As shown, t s1_0 The moment indicates the start of forward detection, t s1_1 The moment indicates that the forward detection is successful, t s1_2 The moment indicates the end of forward detection, t s1_3 The moment indicates the start of reverse detection, t s1_4 The moment indicates that the reverse detection is successful, t s1_5 The moment indicates the end of reverse detection.

[0049] If the forward speed and the reverse speed of the cooling fan 102 are both zero, then the cooling fan 102 can be determined to be in a frozen state in combination with the environmental conditions of the inverter 10; Figure 3 As shown, at time t1 , it is determined that the cooling fan 102 is in a frozen state. Then, during the time period from t1 to t2 , the inverter 10 will operate in the SVG mode.

[0050] In this embodiment, in the SVG mode, after the inverter 10 de-icing operation has been running for a period of time, a fault detection will be performed again to confirm whether the freezing fault of the cooling fan 102 has been eliminated; the re-detection process corresponds to Figure 3 The re-detection process of the cooling fan 102 is basically the same as the detection process of the time period 0 to t1. Figure 5 As shown, first perform forward detection, at t s3_1 Send the forward PWM control signal to the cooling fan 102 at all times, and detect the forward speed information at the same time. The speed signal will be Δt' after time t s3_2 At this moment, the speed signal of the cooling fan 102 changes, and it is judged that the cooling fan 102 is driving normally in the forward direction, and the forward fault signal changes from high level to low level. Then reverse detection is performed, and at t s3_4 The reverse PWM control signal is sent to the cooling fan 102 at all times, and the reverse speed information is detected at the same time. The speed signal is t s3_5 At this moment, the speed signal of cooling fan 102 changes, indicating that cooling fan 102 is operating normally in reverse, and the reverse fault signal changes from a high level to a low level. At this point, it can be determined that cooling fan 102 has successfully completed defrosting and de-icing. If cooling fan 102 still fails to operate after receiving the forward and reverse PWM control signals, continue heating cooling fan 102 in SVG mode for a period of time, and then try again to issue forward and reverse PWM control signals to drive cooling fan 102 to ensure the successful completion of the de-icing process.

[0051] In this embodiment, Figure 2 and Figure 6As shown, the structure of inverter 10 mainly includes a housing, a heat sink 103, and power devices. The power devices are installed inside the housing and connected to the base plate of heat sink 103. An air inlet and an air outlet are provided on opposite sides of the housing, and the communication path between the air inlet and the air outlet passes through heat sink 103. A cooling fan 102 is installed at the air inlet. When inverter 10 is operating, heat sink 103 absorbs heat generated by the power devices through its fins. Cooling fan 102 draws cool air from the air inlet and blows it toward heat sink 103. The airflow from cooling fan 102 carries the heat from heat sink 103 and is discharged through the air outlet. Considering the operating environment of inverter 100, air outlet fins 104 are generally installed at the air outlet. When inverter 10 is not operating, air outlet fins 104 seal the air outlet, thereby preventing dust, rain, etc. from entering the interior of inverter 10. When the cooling fan 102 is defrosting and deicing in this embodiment, to minimize the duration of the inverter 10's SVG mode, the air outlet fins 104 can be controlled by a corresponding control device to close the air outlet. At this point, the interior of the inverter 10 is in a relatively sealed environment, and the heat generated by the inverter 10 in SVG mode can quickly heat the interior, thereby achieving rapid deicing of the cooling fan 102.

[0052] It should be noted that the specific structure and working principle of the control device for controlling the operation of the air outlet fins 104 are well known to those skilled in the art. A common control device adopts a combination structure of a relay and a rope, that is, the rope connects all the air outlet fins 104, and the relay is set on one side of the air outlet fins 104. The relay can be connected to one end of the rope, and then the rope is pulled by the closure of the relay to drive the air outlet fins 104 to rotate to close the air outlet. In order to ensure the stable operation of the air outlet fins 104, multiple relays and ropes can be set, for example Figure 6 As shown, there are two relays, namely relay KV1 and relay KV2, which are arranged at both ends of one side of the air outlet and are connected to all the air outlet fins 104 through corresponding ropes.

[0053] In this embodiment, as can be seen from the above, when the cooling fan 102 is defrosting and de-icing, the interior of the inverter 10 is relatively sealed. Figure 3 It can be seen from the time period t1 to t3 that the ice that freezes the cooling fan 102 will cause the internal humidity of the inverter 10 to increase significantly after melting. After the cooling fan 102 is de-iced and the air outlet fins 104 are opened, the cooling fan 102 may be frozen again in a high humidity environment within a short period of time due to the decrease in internal temperature. Therefore, the interior of the inverter 10 needs to be dehumidified after the cooling fan 102 is thawed and de-iced.

[0054] Specifically, such as Figure 2 and Figure 3 and Figure 7 As shown, the specific dehumidification process within inverter 10 is as follows: During the time period t3 to t4, inverter 10 maintains SVG mode and opens air outlet fins 104. At time t3, a reverse PWM control signal is sent to cooling fan 102 to control its reverse rotation. While cooling fan 102 is rotating, the ambient humidity and temperature within inverter 10 are monitored. Dehumidification is completed when the ambient humidity within inverter 10 falls below a humidity threshold and the ambient temperature exceeds a temperature threshold. After dehumidification is complete at time t4, a forward PWM control signal is sent to cooling fan 102, and inverter 10 exits SVG mode.

[0055] It's understandable that if cooling fan 102 rotates forward for dehumidification, it's farther from the air outlet, resulting in poor dehumidification. Furthermore, the relatively high humidity area within inverter 10 is near cooling fan 102. By rotating cooling fan 102 in the reverse direction, the humid air near that area can be quickly expelled through the air inlet. Maintaining inverter 10 in SVG mode during the dehumidification process prevents the humid air inside inverter 10 from refreezing. Furthermore, the high temperature inside inverter 10 due to SVG mode can also dry out moisture that adheres to component surfaces during the thawing process of cooling fan 102.

[0056] In this embodiment, Figure 8 As shown, the specific structure of the control loop corresponding to the inverter 10 mainly includes a current loop and a voltage loop; the specific working process of the control loop is different when the inverter 10 is in normal operation mode and SVG mode. For ease of understanding, the working process of the control loop in the normal operation mode and SVG mode of the inverter 10 will be described in detail below.

[0057] like Figure 8 As shown, when the inverter 10 is in normal operation, the voltage loop serves as the outer loop of the control loop, and the current loop serves as the inner loop of the control loop. First, the grid side voltage u is sampled. a 、u b and u c And the grid side current i a 、i b and i c .

[0058] For the voltage outer loop, the DC bus voltage v of the inverter 10 can be dc As input and set bus voltage reference value v dc * By making a difference comparison, the d-axis current reference value i of the current inner loop can be obtained after PI control. d* .

[0059] For the current inner loop, the frequency and phase information of the grid voltage are obtained through the PLL (phase-locked loop) link. After obtaining the frequency and phase of the grid voltage, the three-phase current is decoupled into d-axis and q-axis components through dq0 transformation. The current i a 、i b and i c After the coordinate transformation from abc to dq0, the d-axis current i is obtained. gd and the q-axis current i gq . The q-axis current i gq and the given q-axis current reference value i q * After the difference is made, it is input into the PI controller and then converted into the reference value in the abc coordinate system through the coordinate transformation from dq0 to abc. At the same time, the d-axis current i gd And the current reference value i output by the voltage outer loop d * After the difference is made, it is input into the PI controller and then converted into a reference value in the abc coordinate system through the coordinate transformation from dq0 to abc. Finally, the driving signal of the inverter 10 is obtained through PWM modulation. The inverter 10 is generally represented by DC / AC.

[0060] like Figure 9 As shown, when the inverter 10 operates in SVG mode, the current loop serves as the outer loop of the control loop, and the voltage loop serves as the inner loop of the control loop. First, the grid side voltage u is sampled. a 、u b and u c And the grid side current i a 、i b and i c .

[0061] For the current outer loop, the d-axis current reference value i on the input side is d * The value of is set to 0, and the q-axis current reference value i q * The value range is set to (-k·I rate , + k·I rate The frequency and phase information of the grid voltage are obtained through the PLL (phase-locked loop) link. After obtaining the frequency and phase of the grid voltage, the three-phase current is decoupled into d-axis and q-axis components through dq0 transformation. The current i a 、i b and i c After the coordinate transformation from abc to dq0, the d-axis current i is obtained. gd and the q-axis current i gq . The q-axis current i gqand the given q-axis current reference value i q * After the difference is made, it is input into the PI controller to obtain the q-axis voltage reference value v of the voltage outer loop q * ; At the same time, the d-axis current i gd and the given d-axis current reference value i d * After the difference is made, it is input into the PI controller to obtain the d-axis voltage reference value v of the voltage outer loop d * .

[0062] For the voltage inner loop, the frequency and phase information of the grid voltage are obtained through the PLL (phase-locked loop) link. After obtaining the frequency and phase of the grid voltage, the three-phase voltage is decoupled into d-axis and q-axis components through dq0 transformation. The voltage u a 、u b and u c After the coordinate transformation from abc to dq0, the voltage v of the d axis is obtained. gd and the q-axis voltage v gq . Set the voltage v on the q axis gq And the obtained q-axis voltage reference value v q * After comparison, it is input into the PI controller and then converted into the reference value in the abc coordinate system through the coordinate transformation from dq0 to abc. At the same time, the voltage v of the d axis is converted into gd And the obtained d-axis voltage reference value v d * After comparison, the data is input into the PI controller and then converted into a reference value in the abc coordinate system through the coordinate transformation from dq0 to abc. Finally, the driving signal of the inverter 10 is obtained through PWM modulation.

[0063] What you need to know is that I rate Indicates the rated current of the inverter 10, k indicates the coefficient, and the value of k is less than the active power factor of the inverter 10. When the inverter 10 is in SVG mode, the inverter 10 only generates reactive power, and the active power is zero. In SVG mode, by adjusting the q-axis current reference value i q * The value of k can be used to adjust the reactive power of inverter 10. To ensure safe operation of inverter 10, the reactive power of inverter 10 must be less than the active power during normal operation. Therefore, the value of coefficient k must be less than the active power factor of inverter 10 during normal operation. The specific value of coefficient k can be selected based on the actual needs of those skilled in the art. For example, when inverter 10 is operating normally, the active power factor of inverter 10 is typically between 0.8 and 1, so the value of k can be 0.6.

[0064] In this embodiment, Figure 9 As shown, the q-axis current reference value i q * The value of can be changed periodically according to the square wave with an interval of Δt; the peak value of the square wave is + k·I rate , the valley value of the square wave is - k·I rate .

[0065] It can be understood that the q-axis current reference value i q * The value of can be a fixed value or a variable value. In this embodiment, the variable value of square wave can ensure that the average reactive power of the inverter 10 is substantially zero. Specifically, when the q-axis current reference value i q * When the value of is positive, the inverter 10 needs to output reactive power to the grid; when the q-axis current reference value i q * When the value of is negative, the inverter 10 needs to absorb reactive power from the grid; by adjusting the q-axis current reference value i q * The square wave value can ensure that the average reactive power absorbed by the inverter 10 on the grid side is substantially zero within one cycle. q * The value can also be taken according to the sine or cosine waveform, but compared with the square wave, the q-axis current reference value i corresponding to the sine and cosine waveforms is q * The value of is constantly changing, which may affect the working performance of the inverter 10.

[0066] 2. Snow cover status detection and snow removal process of photovoltaic panel 500.

[0067] In this embodiment, Figure 10 As shown, the status data of the photovoltaic panel 500 includes current data and surface pressure data, and the environmental data of the photovoltaic panel 500 includes surface temperature data. When the output current of the photovoltaic panel 500 drops to a set current threshold, the surface temperature of the photovoltaic panel 500 is lower than a set temperature threshold, and the surface pressure of the photovoltaic panel 500 is higher than a set pressure threshold, it is determined that snow is present on the surface of the photovoltaic panel 500. At this time, the heating device 400 installed on the photovoltaic panel 500 can be powered by the grid to start heating the photovoltaic panel 500 and continuously monitor the current, temperature, and pressure data of the photovoltaic panel 500. When the current of the photovoltaic panel 500 returns to the current threshold, the pressure is substantially zero, and the temperature exceeds the set temperature threshold, it is determined that the snow on the photovoltaic panel 500 has been removed, and the heating device 400 can be turned off.

[0068] It should be noted that when the photovoltaic panel 500 is covered with snow, it is difficult or impossible for light to directly reach the photovoltaic panel 500, causing the output current of the photovoltaic panel 500 to drop from above the set current threshold to near zero. When there is no snow on the photovoltaic panel 500, the surface pressure of the photovoltaic panel 500 can be considered zero. When snow accumulates on the photovoltaic panel 500, the surface pressure of the photovoltaic panel 500 can be essentially equal to the weight of the snow. If the surface temperature of the photovoltaic panel 500 is below the set temperature threshold, the snow accumulated on the surface of the photovoltaic panel 500 may not melt naturally. Therefore, when the output current of the photovoltaic panel 500 is below the set current threshold, the surface pressure is greater than the set pressure threshold, and the surface temperature is below the set temperature threshold, the photovoltaic panel 500 needs to be desnowed. The specific values of the above-mentioned current threshold, temperature threshold, and pressure threshold can be selected according to the actual needs of those skilled in the art; for example, the temperature threshold can be 0°C, the pressure threshold can be 1N, and the current threshold can be 10% of the rated current.

[0069] Specifically, such as Figure 11 As shown, before time t5, the photovoltaic panel 500 is in a normal state; starting from time t5, the surface pressure of the photovoltaic panel 500 gradually increases to exceed the set pressure threshold, the surface temperature gradually decreases to below the set temperature threshold, and the output current also gradually decreases to below the set current threshold. At time t6, it can be determined that there is snow on the surface of the photovoltaic panel 500 that needs to be removed. At this time, the heating device 400 can be controlled to start heating the photovoltaic panel 500, and the snow on the surface of the photovoltaic panel 500 begins to melt, and then the surface pressure of the photovoltaic panel 500 gradually decreases to below the set pressure threshold, the surface temperature gradually rises to exceed the set temperature threshold, and the output current returns to the rated value again; that is, the snow removal process of the photovoltaic panel 500 is completed at time t7, and the heating device 400 can be turned off at this time.

[0070] Another aspect of the present application provides a photovoltaic control system for coping with extremely cold and snowy weather, which is used to implement the above-mentioned photovoltaic control method for coping with extremely cold and snowy weather; Figure 12 and Figure 13 As shown, one preferred embodiment includes a detection module and a controller 20. The detection module can monitor the environmental data of the inverter 10 and the surface pressure and environmental data of the photovoltaic panel 500; the controller 20 can receive the status data of the cooling fan 102 and the feedback data from the detection module. Based on the received data, the controller 20 can determine the freezing status of the cooling fan 102 and the snow accumulation status of the photovoltaic panel 500. Based on the judgment results, the controller 20 can adjust the control loop to operate the inverter 10 in SVG mode or control the heating device 400 to heat the photovoltaic panel 500. For ease of understanding, the following will provide a detailed structural description of the thawing and deicing process of the cooling fan 102 and the snow removal process of the photovoltaic panel 500.

[0071] In this embodiment, Figure 12 As shown, the detection module includes a temperature sensor 301 and a humidity sensor 302 installed inside the inverter 10. The controller 20 includes a signal receiving module 201, a signal analysis module 202, a fault diagnosis module 203, and a control module 204. The inverter 10 can be provided with multiple cooling fans 102, each used to dissipate heat generated by the power conversion unit 101 within the inverter 10. The temperature sensor 301 and the humidity sensor 302 can respectively detect the ambient temperature and humidity within the inverter 10 and transmit the detection results to the signal receiving module 201.

[0072] At the same time, all the cooling fans 102 are also connected to the controller 20 through the feedback signal line 2001 and the control signal line 2002 respectively. The control module 204 can send forward and reverse PWM control signals to the cooling fans 102 through the control signal line 2002, and the speed information of the cooling fans 102 can be fed back to the signal receiving module 201 through the feedback signal line 2001.

[0073] Signal receiving module 201 can summarize all received data and send it to signal analysis module 202. Signal analysis module 202 can receive the data sent by signal receiving module 201 and compare it with an internally set threshold. Signal analysis module 202 can then send the comparison result to fault diagnosis module 203. Fault diagnosis module 203 determines whether cooling fan 102 is frozen based on the comparison result of signal analysis module 202 and sends the result to control module 204. Control module 204 sends control instructions to cooling fan 102 or the control loop based on the determination result of fault diagnosis module 203. Specifically, if cooling fan 102 is not frozen, control module 204 sends a forward rotation control instruction to cooling fan 102 to ensure normal cooling operation. If cooling fan 102 is frozen, control module 204 can send a control instruction to the control loop to cause inverter 10 to operate in SVG mode to defrost and de-ice cooling fan 102.

[0074] It should be noted that the specific structures and operating principles of the temperature sensor 301, humidity sensor 302, signal receiving module 201, signal analysis module 202, fault diagnosis module 203, and control module 204 are well known to those skilled in the art and will not be elaborated upon in detail herein. For example, the signal receiving module 201 includes multiple signal receiving pins for connecting to the temperature sensor 301, humidity sensor 302, and feedback signal line 2001, respectively. The signal analysis module 202 may utilize a comparator circuit, with the data received by the signal receiving module 201 serving as the input to the gate circuit, and a built-in threshold value may also serve as the input to the gate circuit, and the two are compared to output a corresponding level signal. The fault diagnosis module 203 may utilize a gate circuit, such as an AND gate circuit, which outputs a high level to the control module 204 only when all freezing conditions for the cooling fan 102 are met. The control module 204 may utilize a control chip, such as a DSP chip.

[0075] In this embodiment, Figure 13 As shown, the heating device 400 draws power from the grid, and the circuit for drawing power from the heating device 400 controls the switch S heat The detection module includes a current detection unit, a pressure detection unit, and a temperature detection unit. The current detection unit is used to monitor the output current of each photovoltaic panel 500, the pressure detection unit is used to monitor the surface pressure of each photovoltaic panel 500, and the temperature detection unit is used to monitor the surface temperature of each photovoltaic panel 500.

[0076] The controller 20 includes a current judgment circuit 205, a pressure judgment circuit 206, a temperature judgment circuit 207, a drive circuit 208, and a control module 204. The current judgment circuit 205 can receive all the collected data of the current detection unit and perform threshold judgment; the pressure judgment circuit 206 can receive all the collected data of the pressure detection unit and perform threshold judgment; the temperature judgment circuit 207 can receive all the collected data of the temperature detection unit and perform threshold judgment; the control module 204 can send a control signal to the drive circuit 208 based on the judgment results of the current judgment circuit 205, the pressure judgment circuit 206, and the temperature judgment circuit 207, and the drive circuit 208 controls the control switch S according to the received control signal. heat is turned on or off.

[0077] It should be noted that multiple photovoltaic panels 500 are installed in a photovoltaic system by connecting them in series and / or in parallel to form photovoltaic strings. A photovoltaic system generally includes multiple photovoltaic strings. Because the layout of each photovoltaic string in a photovoltaic system is generally consistent, a recording and detection device can be selected for one or a few photovoltaic strings to determine snow accumulation on each photovoltaic panel 500. Of course, to improve the accuracy of the determination results, snow accumulation can be determined for all photovoltaic panels 500. For ease of understanding, the following detailed description will use the example of determining snow accumulation on each photovoltaic panel 500.

[0078] Specifically, such as Figure 13 As shown, each photovoltaic string corresponds to a current detection unit, a pressure detection unit, and a temperature detection unit. The current detection unit includes a current sensor 304 and a current detection circuit 305. The specific number of current sensors 304 may be related to the form of photovoltaic panels 500 forming a photovoltaic string. If multiple photovoltaic panels 500 are connected in series to form a photovoltaic string, each photovoltaic string corresponds to a current sensor 304. If multiple groups of photovoltaic panels 500 connected in series are connected in parallel to form a photovoltaic string, the number of current sensors 304 is equal to the number of photovoltaic panels 500. The current detection circuit 305 is used to receive the monitoring data of all current sensors 304 in each string and summarize it before sending it to the current judgment circuit 205. The pressure detection unit includes a pressure sensor 303 and a pressure detection circuit 306. The number of pressure sensors 303 is the same as the number of photovoltaic panels 500, so that each photovoltaic panel 500 corresponds to a pressure sensor 303. The pressure detection circuit 306 is used to receive the monitoring data of all pressure sensors 303 corresponding to each photovoltaic string and summarize it before sending it to the pressure judgment circuit 206. The temperature detection unit includes a temperature sensor 301 and a temperature detection circuit 307. The number of temperature sensors 301 is consistent with the number of photovoltaic panels 500, so that each photovoltaic panel 500 corresponds to a temperature sensor 301; the temperature detection circuit 307 is used to receive the monitoring data of all temperature sensors 301 corresponding to each photovoltaic string and summarize and send it to the temperature judgment circuit 207.

[0079] It should be noted that the specific structures and operating principles of the current sensor 304, pressure sensor 303, current detection circuit 305, pressure detection circuit 306, and temperature detection circuit 307 are well known to those skilled in the art and are not described in detail here. The specific structures and operating principles of the current determination circuit 205, pressure determination circuit 206, temperature determination circuit 207, and drive circuit 208 are also well known to those skilled in the art and are not described in detail here. The current determination circuit 205, pressure determination circuit 206, temperature determination circuit 207, and drive circuit 208 can all utilize commonly used gate circuits.

[0080] The above describes the basic principles, main features, and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-described embodiments. The above-described embodiments and the specification merely illustrate the principles of the present application. Various changes and improvements may be made to the present application without departing from the spirit and scope of the present application. These changes and improvements fall within the scope of the present application for which protection is sought. The scope of protection claimed by the present application is defined by the appended claims and their equivalents.

Claims

1. A photovoltaic control method for dealing with extremely cold and snowy weather, characterized in that: The steps include: Obtain environmental data of the inverter and photovoltaic panels, as well as status data of the photovoltaic panels and cooling fans installed on the inverter; The freezing status of the cooling fan is determined by combining the inverter's environmental data and the cooling fan's status data. If the cooling fan is determined to be frozen, the corresponding control loop of the inverter is adjusted to make the inverter operate in SVG mode. The snow accumulation condition of the photovoltaic panels is judged by combining the environmental data and status data of the photovoltaic panels; if the photovoltaic panels are in a snow accumulation condition, the heating device installed on the photovoltaic panels is controlled to heat the photovoltaic panels; When the inverter is in SVG mode, the control loop uses the current loop as the outer loop and the voltage loop as the inner loop; the d-axis current reference value i on the input side of the current loop is d *The value is 0, the q-axis current reference value i q *The value range is (-k·I rate , + k·I rate ); Among them, I rate Indicates the rated current of the inverter, k indicates the coefficient, and the value of k is less than the active power factor of the inverter; q-axis current reference value i q *The value of interval The square wave of time changes periodically, and the peak value of the square wave is +k·I rate , the valley value of the square wave is -k·I rate ; The inverter is provided with an air inlet and an air outlet on opposite sides. The cooling fan is installed at the air inlet, and the air outlet fins are installed at the air outlet. When the inverter enters the SVG mode, the air outlet fins are adapted to close the air outlet under the control of the corresponding control device.

2. The photovoltaic control method for dealing with extreme cold and snowy weather according to claim 1, characterized in that: The inverter's environmental data includes temperature and humidity data, and the cooling fan's status data includes forward and reverse speeds. When the ambient humidity of the inverter is higher than a set humidity threshold, the ambient temperature of the inverter is lower than a set temperature threshold, and the forward speed and reverse speed of the cooling fan are both zero, it is determined that the cooling fan is in a frozen state.

3. The photovoltaic control method for extreme cold and snowy weather according to claim 1, characterized in that: After the cooling fan is unfrozen in the inverter's SVG mode, the inverter needs to be dehumidified. The specific dehumidification process is as follows: Keep the inverter in SVG mode and open the air outlet fins; Sending a reverse control signal to the cooling fan to control the cooling fan to reverse; Dehumidification is completed when the ambient humidity of the inverter is lower than the humidity threshold and the ambient temperature is higher than the temperature threshold; After dehumidification is completed, a forward control signal is sent to the cooling fan and the inverter is adjusted to exit SVG mode.

4. The photovoltaic control method for dealing with extreme cold and snowy weather according to claim 1, characterized in that: The status data of the photovoltaic panel includes current data and surface pressure data, and the environmental data of the photovoltaic panel includes surface temperature data; When the output current of the photovoltaic panel drops to a set current threshold, the surface temperature of the photovoltaic panel is lower than a set temperature threshold, and the surface pressure of the photovoltaic panel is higher than a set pressure threshold, it is determined that snow is present on the surface of the photovoltaic panel.

5. A photovoltaic control system for coping with extreme cold and snowy weather, used to implement the photovoltaic control method for coping with extreme cold and snowy weather according to any one of claims 1 to 4, characterized in that: It includes a detection module and a controller; the detection module is suitable for monitoring the environmental data of the inverter and the surface pressure and environmental data of the photovoltaic panel, and the controller is suitable for receiving the status data of the cooling fan and the feedback data of the detection module; The controller is adapted to judge the freezing condition of the cooling fan and the snow accumulation condition of the photovoltaic panel based on the received data, and adjust the control loop to operate the inverter in SVG mode or control the heating device to heat the photovoltaic panel based on the judgment result.

6. The photovoltaic control system for coping with extreme cold and snowy weather according to claim 5, characterized in that: The detection module includes a temperature sensor and a humidity sensor installed inside the inverter, and the controller includes a signal receiving module, a signal analysis module, a fault judgment module and a control module; The signal receiving module is used to receive feedback data from the temperature sensor, the humidity sensor, and the cooling fan; the signal analysis module is adapted to compare the data received by the signal receiving module with a set threshold; the fault judgment module judges the freezing condition of the cooling fan based on the comparison result of the signal analysis module; The control module sends a control instruction to the cooling fan or the control loop according to the judgment result of the fault judgment module.

7. The photovoltaic control system for coping with extreme cold and snowy weather according to claim 5, characterized in that: The heating device draws power from the power grid, and the circuit for drawing power from the heating device is controlled by a control switch. The detection module includes a current detection unit, a pressure detection unit and a temperature detection unit; the current detection unit is used to monitor the output current of each photovoltaic panel, the pressure detection unit is used to monitor the surface pressure of each photovoltaic panel, and the temperature detection unit is used to monitor the surface temperature of each photovoltaic panel; The controller includes a current judgment circuit, a pressure judgment circuit, a temperature judgment circuit, a driving circuit, and a control module; the current judgment circuit is adapted to receive all collected data of the current detection unit and perform threshold judgment, the pressure judgment circuit is adapted to receive all collected data of the pressure detection unit and perform threshold judgment, and the temperature judgment circuit is adapted to receive all collected data of the temperature detection unit and perform threshold judgment; The control module is adapted to send a control signal to the drive circuit according to the judgment results of the current judgment circuit, the pressure judgment circuit and the temperature judgment circuit, and the drive circuit controls the opening or closing of the control switch according to the received control signal.

Images