Photovoltaic control system and method for coping with extremely cold wind and snow weather

Abstract

The invention discloses a photovoltaic control system and method for coping with extremely cold wind and snow weather. The method comprises the following steps: acquiring data of an inverter and a photovoltaic panel; judging the freezing condition of the cooling fan in combination with the data of the inverter and the cooling fan; if it is judged that the cooling fan is in the frozen state, a control loop corresponding to the inverter is adjusted to enable the inverter to work in an SVG mode; judging the snow accumulation condition of the photovoltaic panel by combining the environment data and the state data of the photovoltaic panel; if the photovoltaic panel is in the snow accumulation state, a heating device installed on the photovoltaic panel is controlled to heat the photovoltaic panel. The system is used for implementing the method. The photovoltaic system has the advantages that the cooling fan can be unfrozen, accumulated snow of the photovoltaic panel can be removed, and it can be guaranteed that the photovoltaic system can better cope with extremely cold weather. And in addition, the unfreezing process of the cooling fan and the snow removing process of the photovoltaic panel are simple and safe, excessive hardware structures are not added, and it can be guaranteed that excessive extra cost is not increased.

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] When the photovoltaic power generation system encounters extreme weather such as heavy snow during winter operation, the accumulated snow will cover the photovoltaic modules, resulting in low power generation efficiency or even no power generation. At this time, it is necessary to clean up the snow covering the photovoltaic modules. Most traditional snow removal methods rely on manual snow removal or waiting for natural snowmelt, and some use mechanical structures to flip the battery modules. Regarding the problem of snow accumulation on photovoltaic modules, the current manual snow removal method is difficult to construct, has a high risk factor, and is prone to damage to the photovoltaic panels; the mechanical structure is used to make the battery modules tilt and flip for snow removal, which is a relatively cumbersome process, with high snow removal costs and a large impact on power generation, making it difficult to meet the needs of users.

[0003] At the same time, when the temperature is below freezing, the moisture inside the inverter (if any) may freeze, causing the fan blades or motor parts to freeze. After the fan is frozen, it cannot rotate normally, resulting in the heat inside the inverter not being able to dissipate in time. When the inverter works in an overheated state, its performance may be affected, reducing conversion efficiency and stability; long-term overheating may also accelerate the aging of the circuit components inside the inverter, increasing safety risks such as fire. In the scenario where the inverter fan is frozen, it is often necessary to use tools such as hair dryers and heaters to heat the inverter to melt the internal ice; because overheating of the inverter will cause circuit damage, the heating time cannot be too long, and the operation is more complicated and requires manual work. 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 to make the inverter work 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 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 * changes periodically with a square wave at intervals 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 position 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, and 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 for implementing 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 the environmental data of the inverter and the surface pressure and environmental data of the photovoltaic panel; the controller is suitable for receiving the status data of the cooling fan and the feedback data of the detection module, the controller is suitable for judging the freezing condition of the cooling fan and the snow accumulation condition of the photovoltaic panel according to the received data, and adjusting the control loop to operate the inverter in SVG mode according to the judgment result, 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 according to 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.

[0015] Preferably, the heating device draws power from the power grid, and the circuit of the heating device for drawing power 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 thereon; 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 beneficial effects of this application are: Being able to defrost the cooling fan and remove snow from the photovoltaic panel at the same time can ensure that the photovoltaic system can better cope with extreme cold weather. In addition, the operation of defrosting the cooling fan and removing snow from the photovoltaic panel is relatively simple and safe, and does not increase too much hardware structure, which can ensure that no excessive additional costs are added. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The figure is a schematic diagram of the overall workflow of this application.

[0018] Figure 2 A schematic diagram of the workflow for detecting and recovering from freezing of a cooling fan in this application.

[0019] Figure 3 This is a timing diagram of the present application for judging the freezing condition of the cooling fan through the inverter environment data and the cooling fan speed data.

[0020] Figure 4 This is a timing diagram of judging the freezing situation by controlling the speed of the cooling fan in this application.

[0021] Figure 5 This is a timing diagram of the cooling fan in this application performing a freezing condition judgment again during the thawing process.

[0022] Figure 6 This is a simplified diagram of the internal structure of the inverter in this application.

[0023] Figure 7This is a timing diagram of dehumidifying the inside of the inverter through the cooling fan in this application.

[0024] Figure 8 Schematic diagram of the working process of the control loop of the inverter in the normal operation mode in this application.

[0025] Fig. 9 Schematic diagram of the working process of the control loop of the inverter in SVG mode in this application.

[0026] Fig.10 Schematic diagram of the workflow for detecting and restoring snow accumulation on photovoltaic panels for this application.

[0027] Fig.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.

[0028] Fig.12 This is a schematic diagram of the structure of the controller and detection module in this application for detecting and controlling the cooling fan.

[0029] Fig.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.

[0030] In the figure: inverter 10, power conversion unit 101, cooling fan 102, radiator 103, air outlet fin 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

[0031] 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 description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means 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 being directed 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.

[0032] In the description of the present application, it should be noted that directional words, such as the terms "center", "lateral", "longitudinal", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc., indicating directions and positional relationships are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of narrating the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and cannot be understood as limiting the specific scope of protection of the present application.

[0033] It should be noted that the terms "first", "second", etc. in the description and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0034] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be connected, detachably connected, or integrated; it can be mechanically connected or electrically connected; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] In the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0036] The terms "including" and "having" and any variations thereof in the specification and claims of the present application are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or apparatuses.

[0037] 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, and status data of the photovoltaic panel 500 and the cooling fan 102 installed on the inverter 10. The freezing condition of the cooling fan 102 is judged in combination with the environmental data of the inverter 10 and the status data of the cooling fan 102; if the cooling fan 102 is judged to be in a freezing state, the control loop corresponding to the inverter 10 is adjusted to make the inverter 10 work in the SVG mode. The snow accumulation condition of the photovoltaic panel 500 is judged in combination with the environmental data and status data of the photovoltaic panel 500; if the photovoltaic panel 500 is in a snow accumulation state, the heating device 400 installed on the photovoltaic panel 500 is controlled to heat the photovoltaic panel 500.

[0038] It should be known that, for the entire photovoltaic system, there are three possible situations in extremely cold and snowy weather. The first one: only the cooling fan 102 is frozen; the second one: only the surface of the photovoltaic panel 500 is covered with snow; the third one: the surface of the photovoltaic panel 500 is covered with snow, and the cooling fan 102 is frozen. Therefore, in this embodiment, the working mode switching process of the inverter 10 and the start-up process of the heating device 400 installed on the photovoltaic panel 500 are relatively independent. According to different situations, only the working mode of the inverter 10 can be switched, or only the heating device 400 can be started, or the working mode of the inverter 10 can be switched and the heating device 400 can be started at the same time.

[0039] It can be understood that the SVG mode of the inverter 10 is a reactive compensation mode, and the specific working principle and working process of this mode are well-known technologies to those skilled in the art. In the SVG mode, the inverter 10 can absorb reactive power to significantly increase the internal temperature, and then the heat inside the inverter 10 can be transferred to the cooling fan 102 for thawing. The specific structure and working principle of the heating device 400 are well-known to those skilled in the art. The heating device 400 often uses a resistance wire, and the resistance wire can be arranged in an S shape on the photovoltaic panel 500 to ensure that the resistance wire can evenly heat the surface of the entire photovoltaic panel 500 when working, thereby accelerating the melting speed of the accumulated snow. Compared with the traditional method, this embodiment can realize the thawing of the cooling fan 102 and the snow removal of the photovoltaic panel 500, which can ensure that the photovoltaic system can better cope with extreme cold weather. In addition, the operation of the thawing of the cooling fan 102 and the snow removal process of the photovoltaic panel 500 is relatively simple and safe, and does not increase too much hardware structure, which can ensure that no excessive additional costs are added. 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.

[0040] 1. Detection of the freezing state of the cooling fan 102 and the thawing process.

[0041] In this embodiment, Figure 2 and Figure 3 As shown, the environmental data of the inverter 10 mainly includes temperature data and humidity data, and the status data of the cooling fan 102 includes forward speed and reverse speed. When the environmental humidity of the inverter 10 is higher than the set humidity threshold, it means that there is enough moisture inside the inverter 10 to freeze the cooling fan 102; when the environmental temperature of the inverter 10 is lower than the set temperature threshold, it means that the temperature inside the inverter 10 can freeze the moisture. When the environmental conditions of the inverter 10 can meet the freezing conditions of the cooling fan 102, the speed of the cooling fan 102 can be judged. If the forward speed and reverse speed of the cooling fan 102 are both zero, it can be determined that the cooling fan 102 is in a frozen state.

[0042] It should be known that the specific value of the humidity threshold corresponding to the internal environment of the inverter 10 can be set according to actual needs; at the same time, 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 70% of the relative humidity, and the temperature threshold can be 0°C.

[0043] It is understandable that after determining that the cooling fan 102 is in a frozen state, the inverter 10 can be controlled to enter the SVG mode, so that the inverter 10 absorbs reactive power to generate heat to defrost the cooling fan 102. Since the SVG mode of the inverter 10 is mainly for reactive power compensation to generate heat, the SVG mode of the inverter 10 cannot work for too long; therefore, after the inverter 10 enters the SVG mode, the freezing state of the cooling fan 102 is detected once every set period of time. If the cooling fan 102 is still in a frozen state, the inverter 10 will continue to work in the SVG mode; if the cooling fan 102 is completely defrosted, the inverter 10 will exit the SVG mode to return to the normal operating mode.

[0044] For ease of understanding, the entire freezing state determination and thawing process of the cooling fan 102 will be described in detail in a time sequence manner.

[0045] Specifically, Figure 3 As shown, during the time from 0 to 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: like Figure 4 As shown, the forward speed test of the cooling fan 102 is first performed, and at t s1_0 At the moment, a forward rotation PWM control signal is sent to the cooling fan 102, and the forward rotation speed information of the cooling fan 102 is detected at the same time. If the rotation 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 a low level to a high level. Then, a reverse rotation 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 has not reversed 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 a low level to a high level.

[0046] It should be noted that if Figure 4 As shown, t s1_0 The moment indicates the start of positive detection, t s1_1 The moment indicates that the forward detection is successful, t s1_2 The moment indicates the end of the 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.

[0047] If the forward speed and the reverse speed of the cooling fan 102 are both zero, it can be determined that the cooling fan 102 is 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.

[0048] 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, firstly, forward detection is performed, and then s3_1 The forward PWM control signal is sent to the cooling fan 102 at all times, and the forward speed information is detected at the same time. The speed signal is Δt' after time, that is, t s3_2 At this time, the speed signal of the cooling fan 102 changes, and it is judged that the cooling fan 102 is driven 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 Δt' after time, that is, t s3_5 At this time, the speed signal of the cooling fan 102 changes, and it is determined that the cooling fan 102 is normally driven in the reverse direction, and the reverse fault signal changes from a high level to a low level; at this time, it can be determined that the cooling fan 102 has successfully completed the defrosting and deicing. If the cooling fan 102 still cannot be driven after receiving the forward and reverse PWM control signal, continue to heat the cooling fan 102 in the SVG mode for a period of time, and then try to send the forward and reverse PWM control signal again to drive the cooling fan 102 to ensure that the deicing process is successfully completed.

[0049] In this embodiment, Figure 2 and Figure 6As shown, the structure of the 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 substrate of the heat sink 103, and the opposite sides of the housing are respectively provided with an air inlet and an air outlet, and the communication path between the air inlet and the air outlet passes through the heat sink 103. The cooling fan 102 is installed at the air inlet position, so that when the inverter 10 is working, the heat sink 103 can absorb the heat generated by the power devices through the heat sink fins, the cooling fan 102 can absorb the external cold air from the air inlet and blow it to the heat sink 103, and the air flow blown by the cooling fan 102 can carry the heat on the heat sink 103 and be discharged from the air outlet. Considering the working environment of the inverter 10, the air outlet fin 104 is generally installed at the air outlet position; when the inverter 10 is not working, the air outlet fin 104 will close the air outlet, thereby preventing dust or rain from entering the inside of the inverter 10. When the cooling fan 102 is thawed and de-iced in this embodiment, in order to shorten the duration of the SVG mode of the inverter 10 as much as possible, the air outlet fins 104 can be controlled to close the air outlet under the drive of the corresponding control device. At this time, the interior of the inverter 10 is in a relatively sealed environment, and the heat generated by the inverter 10 in the SVG mode can quickly heat up the interior to achieve rapid de-icing of the cooling fan 102.

[0050] It should be known that the specific structure and working principle of the control device for controlling the air outlet fins 104 to move 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, 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.

[0051] In this embodiment, it can be seen from the above contents that when the cooling fan 102 is defrosting and deicing, 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 environmental 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.

[0052] Specifically, Figure 2 and Figure 3 and Figure 7 As shown, the specific dehumidification process inside the inverter 10 is as follows: the SVG mode of the inverter 10 is maintained during the time period from t3 to t4 and the air outlet fins 104 are opened. And at time t3, a reverse PWM control signal is sent to the cooling fan 102 to control the cooling fan 102 to reverse. During the reversal of the cooling fan 102, the ambient humidity and ambient temperature inside the inverter 10 are detected. When the ambient humidity of the inverter 10 is lower than the humidity threshold and the ambient temperature is higher than the temperature threshold, dehumidification is completed. After dehumidification is completed at time t4, a forward PWM control signal is sent to the cooling fan 102 and the inverter 10 is adjusted to exit the SVG mode.

[0053] It is understandable that if the cooling fan 102 is rotated forward for dehumidification, the cooling fan 102 is far away from the air outlet, and the dehumidification effect is poor; and the relatively high humidity position inside the inverter 10 is located near the cooling fan 102. By reversing the cooling fan 102, the humid air near itself can be quickly discharged from the air inlet. Keeping the inverter 10 in the SVG mode during the dehumidification process can ensure that the humid air inside the inverter 10 will not freeze again; at the same time, the high temperature inside the inverter 10 based on the SVG mode can also dry the moisture attached to the surface of the device during the thawing process of the cooling fan 102.

[0054] 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 the normal operating mode and the SVG mode. For the sake of easy understanding, the working process of the control loop in the normal operating mode and the SVG mode of the inverter 10 will be described in detail below.

[0055] like Figure 8 As shown, when the inverter 10 is operating normally, 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 a 、u b and u c And the grid-side current i a 、i b and i c .

[0056] 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 * After the PI control, the d-axis current reference value i of the current inner loop can be obtained. d* .

[0057] For the current inner loop, the frequency and phase information of the grid voltage is 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 current i of the d axis 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 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.

[0058] like Fig. 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 a 、u b and u c And the grid-side current i a 、i b and i c .

[0059] 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 is 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 current i of the d axis 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 * .

[0060] For the voltage inner loop, the frequency and phase information of the grid voltage is 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 gd And the obtained d-axis voltage reference value v d * After comparison, the PI controller is input, and then the reference value in the abc coordinate system is converted through the coordinate transformation from dq0 to abc. Finally, the driving signal of the inverter 10 is obtained through PWM modulation.

[0061] What you need to know is that I rate represents the rated current of the inverter 10, k represents 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 can be used to adjust the reactive power of the inverter 10. In order to ensure the working safety of the inverter 10, the reactive power of the inverter 10 needs to be less than the active power during normal operation, so when the value of the coefficient k is taken, it needs to be less than the active power factor of the inverter 10 during normal operation. The specific value of the coefficient k can be selected according to the actual needs of those skilled in the art; for example, when the inverter 10 is operating normally, the active power factor of the inverter 10 is usually between 0.8 and 1, and the value of k can be taken as 0.6.

[0062] In this embodiment, Fig. 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 .

[0063] 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, a variable value in the form of a 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 of 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.

[0064] 2. Snow cover status detection of photovoltaic panel 500 and snow removal process.

[0065] In this embodiment, Fig.10 As shown, the state 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 decreases to the set current threshold, the surface temperature of the photovoltaic panel 500 is lower than the set temperature threshold, and the surface pressure of the photovoltaic panel 500 is higher than the set pressure threshold, it is determined that there is snow on the surface of the photovoltaic panel 500. At this time, the heating device 400 installed on the photovoltaic panel 500 can be powered from the power grid to start heating the photovoltaic panel 500 and continuously monitor the current, temperature and pressure data of the photovoltaic panel 500 until the current of the photovoltaic panel 500 is restored 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 at this time.

[0066] It should be known that when the photovoltaic panel 500 is covered with snow, it will be difficult or impossible for light to directly shine on the photovoltaic panel 500, thereby causing the output current of the photovoltaic panel 500 to drop from above the set current threshold to near zero. The surface pressure of the photovoltaic panel 500 when there is no snow can be regarded as zero. When snow is accumulated on the photovoltaic panel 500, the pressure on the surface of the photovoltaic panel 500 can be basically equal to the gravity of the snow. If the surface temperature of the photovoltaic panel 500 is lower than 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 lower than the set current threshold, the surface pressure is greater than the set pressure threshold, and the surface temperature is lower than 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 technicians in this field; 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.

[0067] Specifically, Fig.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, then 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.

[0068] Another aspect of the present application provides a photovoltaic control system for dealing with extremely cold and snowy weather, which is used to implement the above-mentioned photovoltaic control method for dealing with extremely cold and snowy weather; Fig.12 and Fig.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 of the detection module. The controller 20 can judge the freezing condition of the cooling fan 102 and the snow accumulation condition of the photovoltaic panel 500 according to the received data, and adjust the control loop to operate the inverter 10 in the SVG mode according to the judgment result, or control the heating device 400 to heat the photovoltaic panel 500. For easy understanding, the following will be 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.

[0069] In this embodiment, Fig.12 As shown, the detection module includes a temperature sensor 301 and a humidity sensor 302 installed inside the inverter 10, and the controller 20 includes a signal receiving module 201, a signal analysis module 202, a fault judgment module 203 and a control module 204. The number of cooling fans 102 inside the inverter 10 can be set to multiple, and the multiple cooling fans 102 are used to dissipate the heat generated by the power conversion unit 101 inside the inverter 10. The temperature sensor 301 and the humidity sensor 302 can detect the ambient temperature and ambient humidity inside the inverter 10 respectively, and send the detection results to the signal receiving module 201.

[0070] 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.

[0071] The signal receiving module 201 can summarize all the received data and send them to the signal analysis module 202. The signal analysis module 202 can receive the data sent by the signal receiving module 201 and compare it with the internally set threshold value, and the signal analysis module 202 can send the comparison result to the fault judgment module 203. The fault judgment module 203 judges the freezing condition of the cooling fan 102 according to the comparison result of the signal analysis module 202, and sends the judgment result to the control module 204. The control module 204 sends a control instruction to the cooling fan 102 or the control loop according to the judgment result of the fault judgment module 203; that is, when the cooling fan 102 is not frozen, the control module 204 sends a forward control instruction to the cooling fan 102 to ensure that the cooling fan 102 performs normal cooling work; if the cooling fan 102 is frozen, the control module 204 can send a control instruction to the control loop to make the inverter 10 work in the SVG mode to achieve thawing and deicing of the cooling fan 102.

[0072] It should be known that the specific structures and working principles of the temperature sensor 301, humidity sensor 302, signal receiving module 201, signal analysis module 202, fault judgment module 203 and control module 204 are well known to those skilled in the art, so they will not be elaborated in detail here. For example, the signal receiving module 201 includes a plurality of signal receiving pins to respectively connect the temperature sensor 301, humidity sensor 302 and feedback signal line 2001. The signal analysis module 202 can use a comparison circuit, the data received by the signal receiving module 201 is used as the input of the gate circuit, and the built-in threshold value can also be used as the input of the gate circuit, and the two are compared to output a corresponding level signal; the fault judgment module 203 can use a gate circuit, such as an AND gate circuit, and only when all the freezing conditions of the cooling fan 102 are met, the AND gate circuit outputs a high level to the control module 204; the control module 204 can use a control chip, such as a DSP chip.

[0073] In this embodiment, Fig.13 As shown, the heating device 400 obtains power from the power grid, and the circuit for obtaining 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.

[0074] The controller 20 includes a current judgment circuit 205, a pressure judgment circuit 206, a temperature judgment circuit 207, a driving 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 driving circuit 208 according to the judgment results of the current judgment circuit 205, the pressure judgment circuit 206 and the temperature judgment circuit 207, and then the driving circuit 208 controls the control switch S according to the received control signal heat on or off.

[0075] It should be known that multiple photovoltaic panels 500 are installed in the photovoltaic system in the form of photovoltaic strings formed by series connection and / or parallel connection, and the photovoltaic system generally includes multiple photovoltaic strings. Since the layout environment of each photovoltaic string of the photovoltaic system is basically the same, one or a few recording and arrangement detection devices can be selected to perform snow accumulation judgment on the photovoltaic panel 500; of course, in order to improve the accuracy of the judgment result, snow accumulation judgment can be performed on all photovoltaic panels 500. For ease of understanding, the following will be described in detail by taking the snow accumulation judgment of each photovoltaic panel 500 as an example.

[0076] Specifically, Fig.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 photovoltaic strings; 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 path and send it to the current judgment circuit 205 after summarizing. The pressure detection unit includes a pressure sensor 303 and a pressure detection circuit 306. The number of pressure sensors 303 is consistent with 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 send it to the pressure judgment circuit 206 after summarizing. 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 send the data to the temperature judgment circuit 207 after summarizing them.

[0077] It should be known that the specific structures and working principles of the current sensor 304, the pressure sensor 303, the current detection circuit 305, the pressure detection circuit 306 and the temperature detection circuit 307 are all well-known technologies to those skilled in the art, so they will not be elaborated in detail here. The specific structures and working principles of the current judgment circuit 205, the pressure judgment circuit 206, the temperature judgment circuit 207 and the drive circuit 208 are also well-known technologies to those skilled in the art, so they will not be elaborated in detail here. The current judgment circuit 205, the pressure judgment circuit 206, the temperature judgment circuit 207 and the drive circuit 208 can all use commonly used gate circuits.

[0078] 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 by the above embodiments, and the above embodiments and the specification only describe the principles of the present application. The present application may have various changes and improvements without departing from the spirit and scope of the present application, and 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 attached 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 judged by combining the environmental data of the inverter and the status data of the cooling fan; if the cooling fan is judged to be in the freezing status, the control loop corresponding to the inverter is adjusted to make the inverter work in the SVG mode; The snow accumulation condition of the photovoltaic panel is judged in combination with the environmental data and status data of the photovoltaic panel; if the photovoltaic panel is in a snow accumulation condition, the heating device installed on the photovoltaic panel is controlled to heat the photovoltaic panel.

2. The photovoltaic control method for dealing with extremely cold and snowy weather according to claim 1, characterized in that: 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 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 dealing with extremely cold and snowy weather according to claim 1, characterized in that: 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 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 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.

4. The photovoltaic control method for dealing with extremely cold and snowy weather as claimed in claim 3, characterized in that: q-axis current reference value i q The value of * changes periodically with a square wave at intervals 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 .

5. The photovoltaic control method for dealing with extremely cold and snowy weather according to claim 1, characterized in that: The inverter is provided with an air inlet and an air outlet on opposite sides, a cooling fan is installed at the air inlet, and an air outlet fin is 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.

6. The photovoltaic control method for dealing with extremely cold and snowy weather as claimed in claim 5, 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 the SVG mode.

7. The photovoltaic control method for dealing with extremely 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 decreases 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.

8. A photovoltaic control system for dealing with extremely cold and snowy weather, used to implement the photovoltaic control method for dealing with extremely cold and snowy weather as claimed in any one of claims 1 to 7, 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 according to 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 according to the judgment result.

9. The photovoltaic control system for dealing with extremely cold and snowy weather as claimed in claim 8, 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 suitable for comparing the data received by the signal receiving module with a set threshold; the fault judgment module judges the freezing condition of the cooling fan according to 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.

10. The photovoltaic control system for dealing with extremely cold and snowy weather as claimed in claim 8, characterized in that: The heating device draws power from the power grid, and the circuit for drawing power from the heating device is controlled to open and close by a control switch; The detection module includes a current detection unit, a pressure detection unit and a temperature detection unit installed therein; 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 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.

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