Photovoltaic inverter, its startup control method, and photovoltaic power generation system

Abstract

The present invention discloses a photovoltaic inverter, its startup control method, and a photovoltaic power generation system, which relate to the technical field of photovoltaic power generation. The photovoltaic inverter includes an auxiliary power supply module, a boost module, an input control switch, and a control module; the auxiliary power supply module is used to convert the output voltage of the photovoltaic module into a first DC voltage; the control module is used to control the duty cycle of the primary side switch tube of the boost module, so that the boost module boosts the first DC voltage to a second DC voltage to charge the DC bus; and predicts the peak output power of the photovoltaic module according to the detected output voltage of the photovoltaic module, and determines whether the peak output power of the photovoltaic module meets the startup condition of the photovoltaic inverter. If it meets the condition, it controls the input control switch to close, so that the photovoltaic inverter starts to operate. The present invention can shorten the judgment time of whether the photovoltaic inverter can be started, and improve the judgment efficiency and accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic power generation, and in particular, to a photovoltaic inverter, a startup control method thereof, and a photovoltaic power generation system. Background Art

[0002] A photovoltaic inverter is a core device of a photovoltaic power generation system, which is used to convert the direct current generated by photovoltaic modules into alternating current to meet the requirements of the power grid. In actual applications, the output voltage and power of the photovoltaic modules need to meet the minimum startup voltage and power values of the photovoltaic inverter, so that the photovoltaic inverter can operate in parallel with the grid normally. If the photovoltaic inverter starts up and runs when the output power of the photovoltaic modules is low, it may lead to a small power generation of the photovoltaic system and a high harmonic content in the grid-connected current, which in turn causes the bus voltage of the photovoltaic inverter not to be maintained stably, and the photovoltaic inverter to start and stop frequently. Therefore, before the photovoltaic inverter is connected to the grid, it is necessary to detect the output voltage and output power of the photovoltaic modules, and then judge whether the photovoltaic inverter starts up and runs.

[0003] In the prior art, the photovoltaic inverter judges whether the output voltage of the photovoltaic modules can be kept stable by turning on open-loop wave generation and according to the loss generated by the open-loop wave generation. If the output voltage of the photovoltaic modules drops less and stabilizes at a certain voltage value, the photovoltaic inverter can start up and run normally. If the output voltage continues to drop, it means that the energy of the photovoltaic modules is insufficient and the photovoltaic inverter cannot start up and run. However, since the open-loop wave generation is turned on after all self-checks of the photovoltaic inverter are completed, the waiting time is relatively long, the efficiency is low, and there is a certain error in the estimation of the inverter loss generated by the open-loop wave generation, and the judgment result is also inaccurate. Summary of the Invention

[0004] An embodiment of the present invention provides a photovoltaic inverter, which is used to shorten the judgment time of whether the photovoltaic inverter can start up, and improve the judgment efficiency and accuracy. The photovoltaic inverter includes: a DC conversion module and an AC inverter module. The input end of the DC conversion module is connected to the photovoltaic modules, the output end of the DC conversion module is connected to the input end of the AC inverter module through a DC bus, and the output end of the AC inverter module is connected to the power grid; the photovoltaic inverter further includes: an auxiliary power supply module, a boost module, an input control switch, and a control module;

[0005] The input control switch is arranged between the photovoltaic modules and the DC conversion module; the input end of the auxiliary power supply module is connected to the photovoltaic modules, and the output end of the auxiliary power supply module is connected to the input end of the boost module; the output end of the boost module is connected to the DC bus;

[0006] The auxiliary power supply module is used to convert the output voltage of the photovoltaic modules into a first DC voltage;

[0007] A control module is used to control the duty cycle of the primary switch tube of the boost module, so that the boost module boosts the first DC voltage to the second DC voltage to charge the DC bus; and predicts the peak output power of the photovoltaic module according to the detected output voltage of the photovoltaic module, and determines whether the peak output power of the photovoltaic module meets the startup condition of the photovoltaic inverter. If it meets the condition, it controls the input control switch to close so that the photovoltaic inverter starts to operate.

[0008] In one embodiment, the photovoltaic inverter further includes a charging control switch, and the charging control switch is arranged between the boost module and the DC bus;

[0009] The control module is further used for: controlling the charging control switch to close when it detects that the auxiliary power module outputs the first DC voltage.

[0010] In one embodiment, the control module specifically is used for: controlling the duty cycle of the primary switch tube of the boost module to be a fixed value, detecting the output voltage and output power of the photovoltaic module when the duty cycle of the primary switch tube is the fixed value, and predicting the peak output power of the photovoltaic module according to the output voltage and output power of the photovoltaic module; when the peak output power of the photovoltaic module is greater than the preset startup power threshold, controlling the input control switch to close so that the photovoltaic inverter starts to operate.

[0011] In one embodiment, the peak output power of the photovoltaic module is estimated by the following formula:

[0012]

[0013] wherein, is the output voltage of the photovoltaic module when the duty cycle of the primary switch tube is 0; is the peak output voltage of the photovoltaic module, , k is a preset coefficient; is the peak output power of the photovoltaic module; is the output voltage of the photovoltaic module when the duty cycle of the primary switch tube is the fixed value; is the output power of the photovoltaic module when the duty cycle of the primary switch tube is the fixed value.

[0014] In one embodiment, the startup power threshold is set according to the startup loss power before the photovoltaic inverter is connected to the grid and the power required for grid connection.

[0015] An embodiment of the present invention further provides a starting control method for a photovoltaic inverter, which is used to shorten the judgment time of whether the photovoltaic inverter can be started, and improve the judgment efficiency and accuracy. This method is applied to a photovoltaic inverter, which includes a DC conversion module and an AC inversion module. The input end of the DC conversion module is connected to a photovoltaic module, the output end of the DC conversion module is connected to the input end of the AC inversion module through a DC bus, and the output end of the AC inversion module is connected to the power grid; the photovoltaic inverter further includes: an auxiliary power supply module, a boost module, an input control switch, and a control module; wherein, the input control switch is arranged between the photovoltaic module and the DC conversion module; the input end of the auxiliary power supply module is connected to the photovoltaic module, and the output end of the auxiliary power supply module is connected to the input end of the boost module; the output end of the boost module is connected to the DC bus; this method includes:

[0016] The auxiliary power supply module converts the output voltage of the photovoltaic module into a first DC voltage;

[0017] The control module controls the duty ratio of the primary switch tube of the boost module, so that the boost module boosts the first DC voltage to a second DC voltage to charge the DC bus; and predicts the peak output power of the photovoltaic module according to the detected output voltage and output power of the photovoltaic module, and judges whether the peak output power of the photovoltaic module meets the starting condition of the photovoltaic inverter. If it meets, control the input control switch to close so that the photovoltaic inverter starts to operate.

[0018] In one embodiment, the control module controls the duty ratio of the primary switch tube of the boost module to a fixed value, detects the output voltage and output power of the photovoltaic module when the duty ratio of the primary switch tube is a fixed value, and predicts the peak output power of the photovoltaic module according to the output voltage and output power of the photovoltaic module; when the peak output power of the photovoltaic module is greater than the preset starting power threshold, control the input control switch to close so that the photovoltaic inverter starts to operate.

[0019] In one embodiment, the peak output power of the photovoltaic module is estimated by the following formula:

[0020]

[0021] Wherein, is the output voltage of the photovoltaic module when the duty ratio of the primary switch tube is 0; is the peak output voltage of the photovoltaic module, , k is a preset coefficient; is the peak output power of the photovoltaic module; is the output voltage of the photovoltaic module when the duty ratio of the primary switch tube is a fixed value; is the output power of the photovoltaic module when the duty ratio of the primary switch tube is a fixed value.

[0022] In one embodiment, the startup power threshold is set according to the startup loss power before grid connection and the power required for grid connection of the photovoltaic inverter.

[0023] An embodiment of the present invention further provides a photovoltaic power generation system, which includes a photovoltaic module and the above-mentioned photovoltaic inverter; the input side of the photovoltaic inverter is connected to the photovoltaic module, and the output side of the photovoltaic inverter is connected to the power grid.

[0024] An embodiment of the present invention further provides a computer device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the startup control method of the above-mentioned photovoltaic inverter is implemented.

[0025] An embodiment of the present invention further provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the startup control method of the above-mentioned photovoltaic inverter is implemented.

[0026] An embodiment of the present invention further provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the startup control method of the above-mentioned photovoltaic inverter is implemented.

[0027] The photovoltaic inverter provided in the embodiment of the present invention includes a DC conversion module, an AC inversion module, an auxiliary power supply module, a boost module, an input control switch, and a control module; the input end of the DC conversion module is connected to a photovoltaic module, the output end of the DC conversion module is connected to the input end of the AC inversion module through a DC bus, and the output end of the AC inversion module is connected to the power grid; the input control switch is arranged between the photovoltaic module and the DC conversion module; the input end of the auxiliary power supply module is connected to the photovoltaic module, and the output end of the auxiliary power supply module is connected to the input end of the boost module; the output end of the boost module is connected to the DC bus; the auxiliary power supply module converts the output voltage of the photovoltaic module into a first DC voltage; the control module is used to control the duty cycle of the primary switch tube of the boost module, so that the boost module boosts the first DC voltage to a second DC voltage to charge the DC bus; and predicts the peak output power of the photovoltaic module according to the detected output voltage and output power of the photovoltaic module, and determines whether the peak output power of the photovoltaic module meets the startup condition of the photovoltaic inverter. If it meets, it controls the input control switch to close, so that the photovoltaic inverter starts to operate. Compared with the prior art, the photovoltaic inverter in the embodiment of the present invention does not need to wait for the self-check to be completed. As long as the photovoltaic module outputs electricity, the auxiliary power supply module of the photovoltaic inverter can work. By controlling the duty cycle of the primary switch tube of the boost module through the control module, the boost module charges the DC bus, and detects the output voltage and output power of the photovoltaic module, predicts the peak output power of the photovoltaic module, and then determines whether it meets the startup condition of the photovoltaic inverter according to the predicted peak output power of the photovoltaic module. In this way, it can quickly determine whether the photovoltaic inverter can start up and operate normally, improve the startup operation judgment efficiency of the photovoltaic inverter, and moreover, determine whether to start up according to the predicted peak output power of the photovoltaic module, improving the accuracy of the judgment. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to these drawings. In the drawings:

[0029] Figure 1 It is a structural diagram of a photovoltaic power generation system provided in the embodiment of the present invention;

[0030] Figure 2 It is an example diagram of an auxiliary power supply module provided in the embodiment of the present invention;

[0031] Figure 3 It is an example diagram of a boost module provided in the embodiment of the present invention;

[0032] Figure 4 Schematic diagram of the power-voltage curve of a photovoltaic module provided in an embodiment of the present invention;

[0033] Figure 5 Flowchart of a start-up control method for a photovoltaic inverter provided in an embodiment of the present invention;

[0034] Figure 6 Flowchart of another start-up control method for a photovoltaic inverter provided in an embodiment of the present invention. Detailed implementation manners

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer and more understandable, the following further describes the embodiments of the present invention in detail with reference to the accompanying drawings. Herein, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but not to limit the present invention.

[0036] In the description of this specification, the terms "including", "comprising", "having", "containing", etc. are all open-ended terms, that is, they are intended to include but not limited to. The descriptions with reference to terms such as "an embodiment", "a specific embodiment", "some embodiments", "for example", etc. mean that the specific features, structures, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. The step sequences involved in each embodiment are used to schematically illustrate the implementation of the present application, and the step sequences are not limited and can be adjusted appropriately as needed.

[0037] In the prior art, a photovoltaic inverter determines whether the output voltage of a photovoltaic module can be kept stable based on the losses generated by the open-loop wave generation of the photovoltaic inverter. If the output voltage of the photovoltaic module drops less and stabilizes at a certain voltage value, the photovoltaic inverter can be started and operated normally. If the output voltage continues to drop, it indicates that the energy of the photovoltaic module is insufficient and the photovoltaic inverter cannot be started and operated. However, since the open-loop wave generation is turned on after all self-checks of the photovoltaic inverter are completed, the waiting time is relatively long, the efficiency is low, and there are certain errors in the estimation of the inverter losses generated by the open-loop wave generation, and the judgment result is also inaccurate.

[0038] Therefore, an embodiment of the present invention provides a photovoltaic inverter. After the photovoltaic module outputs electricity, the photovoltaic inverter can determine whether it can be started and operated, without waiting until the self-check of the photovoltaic inverter is completed, which shortens the time for determining whether the photovoltaic inverter can be started and improves the judgment efficiency. At the same time, it is also not necessary to make a judgment based on the inverter losses, which improves the accuracy of the start-up judgment result.

[0039] Figure 1 The structural diagram of a photovoltaic power generation system provided by an embodiment of the present invention is as follows. Figure 1 As shown, the photovoltaic power generation system may include a photovoltaic module 10 and a photovoltaic inverter 20. Among them, the input side of the photovoltaic inverter 20 is connected to the photovoltaic module 10, and the output side of the photovoltaic inverter 20 is connected to the power grid.

[0040] It should be noted that the number of photovoltaic modules 10 may be multiple, and multiple photovoltaic modules are connected in series and / or in parallel and then connected to the input side of the photovoltaic inverter 20.

[0041] See Figure 1 , an embodiment of the present invention also provides a photovoltaic inverter. The photovoltaic inverter 20 may include: a DC conversion module 201, an AC inversion module 202, an auxiliary power supply module 203, a boost module 204, a control module 205, and an input control switch K1. The input end of the DC conversion module 201 is connected to the photovoltaic module 10, the output end of the DC conversion module 201 is connected to the input end of the AC inversion module 202 through a DC bus (BUS+, BUS-), and the output end of the AC inversion module 202 is connected to the power grid; the input control switch K1 is arranged between the photovoltaic module 10 and the DC conversion module 201; the input end of the auxiliary power supply module 203 is connected to the photovoltaic module 10, and the output end of the auxiliary power supply module 203 is connected to the input end of the boost module 204; the output end of the boost module 204 is connected to the DC bus (BUS+, BUS-).

[0042] Among them, the above-mentioned DC conversion module 201 is used for the energy exchange between the photovoltaic module 10 and the DC bus.

[0043] The above-mentioned AC inversion module 202 is used for the energy exchange between the power grid and the DC bus.

[0044] The above-mentioned auxiliary power supply module 203 is used to convert the output voltage of the photovoltaic module 10 into a first DC voltage VCC. Among them, the first DC voltage VCC is a low-voltage power supply required for the photovoltaic inverter, and the range is generally 3V to 24V.

[0045] The above-mentioned boost module 204 is used to boost the first DC voltage VCC into a second DC voltage to charge the DC bus. Figure 1 Among them, C1 is the DC bus capacitor.

[0046] The above control module 205 is used to control the duty cycle of the primary switch tube of the boost module 204, so that the boost module 204 boosts the first DC voltage to the second DC voltage according to the duty cycle of the primary switch tube to charge the DC bus; and predicts the peak output power of the photovoltaic module 10 according to the detected output voltage and output power of the photovoltaic module 10, and determines whether the peak output power of the photovoltaic module 10 meets the startup condition of the photovoltaic inverter 20. If it meets the condition, it controls the input control switch K1 to close, so that the photovoltaic inverter 20 starts to operate. At this time, the photovoltaic inverter 20 enters the preparation stage before grid connection. The photovoltaic inverter 20 of the embodiment of the present invention further includes an output control switch K2. After the grid connection preparation is completed, it controls the output control switch K2 to close, and the photovoltaic inverter 20 operates in grid connection.

[0047] In the photovoltaic inverter according to the embodiment of the present invention, there is no need to wait for the self-check to be completed. As long as the photovoltaic module outputs electricity, the auxiliary power supply module of the photovoltaic inverter can work. The duty cycle of the primary switch tube of the boost module is controlled by the control module, so that the boost module charges the DC bus, and the output voltage and output power of the photovoltaic module are detected, and the peak output power of the photovoltaic module is predicted. Furthermore, it is determined whether the startup condition of the photovoltaic inverter is met according to the predicted peak output power of the photovoltaic module. In this way, it can be quickly determined whether the photovoltaic inverter can start up and operate normally, improving the startup operation judgment efficiency of the photovoltaic inverter. Moreover, determining whether to start up according to the predicted peak output power of the photovoltaic module improves the accuracy of the judgment.

[0048] Specifically, the above DC conversion module 201 can be a DC (direct current) / DC converter, which is specifically used to convert the output voltage (direct current) of the photovoltaic module 10 into DC voltages of different voltages and supply them to the DC bus; the above AC inverter module 202 can be a DC / AC (alternating current) converter, which is specifically used to convert the DC bus voltage into alternating current and supply it to the power grid.

[0049] Specifically, Figure 2 is an example diagram of an auxiliary power supply module provided by an embodiment of the present invention. As Figure 2 shown, the auxiliary power supply module 203 can include an auxiliary power supply converter and an auxiliary power supply output capacitor C2. The input side of the auxiliary power supply converter is connected to the photovoltaic module 10, and the output side of the auxiliary power supply converter is connected in parallel with the auxiliary power supply output capacitor C2. Therefore, the input of the auxiliary power supply module 203 is the output voltage of the photovoltaic module 10. The positive output of the output side of the auxiliary power supply module 203 is the first DC voltage VCC, and the negative output of the output side of the auxiliary power supply module 203 is grounded. GND represents the ground terminal.

[0050] It should be noted that, Figure 2This is only a specific example of the auxiliary power supply module. The auxiliary power supply module can also be implemented by other methods, which is not limited herein.

[0051] During specific implementation, Figure 3 This is an example diagram of a boost module provided by an embodiment of the present invention. As Figure 3 shown, the boost module 204 includes a primary switching transistor Q2, an inductor L, and a boost module output capacitor C3. The first end of the primary switching transistor Q2 is connected to the negative pole of the output end of the auxiliary power supply module. The second end of the primary switching transistor Q2 is connected to the first end of the primary winding of the inductor L. The third end of the primary switching transistor Q2 is used for the control signal of the module. The second end of the primary winding of the inductor L is connected to the positive pole of the output end of the auxiliary power supply module. The two ends of the secondary winding of the inductor L are respectively connected to the two ends of the boost module output capacitor C3. Therefore, the input of the boost module 204 is the first DC voltage VCC, and the second DC voltage is output to the DC bus capacitor C1. Among them, the first DC voltage VCC is a low-voltage direct current, and the second DC voltage is a high-voltage direct current.

[0052] It should be noted that Figure 3 This is only a specific example of the boost module. The boost module can also be implemented by other methods, which is not limited herein.

[0053] In one embodiment, as Figure 3 shown, the above photovoltaic inverter 20 may further include a charging control switch K3, and the charging control switch K3 is arranged between the boost module 204 and the DC bus. The control module 205 may further be configured to: control the charging control switch K3 to close when detecting that the auxiliary power supply module 203 outputs the first DC voltage.

[0054] During specific implementation, when the photovoltaic module 10 outputs electricity, the auxiliary power supply module 203 works, converts the output voltage of the photovoltaic module 10 into the first DC voltage. When the control module 205 detects that the auxiliary power supply module 203 outputs the first DC voltage, it can control the charging control switch K3 to close so that the boost module 204 charges the DC bus.

[0055] During specific implementation, the above input control switch K1 can be arranged between the negative pole of the photovoltaic module 10 and the negative pole of the input end of the DC conversion module 201; it can also be arranged between the positive pole of the photovoltaic module 10 and the positive pole of the input end of the DC conversion module 201, and is used to control the on / off between the photovoltaic module 10 and the DC conversion module 201. The above output control switch K2 can be arranged between the power grid and the AC inverter module 202, and is used to control the on / off between the AC inverter module 202 and the power grid.

[0056] The above input control switch K1, output control switch K2, and charging control switch K3 can all be relays or other control switches, and no specific limitation is made here.

[0057] In one embodiment, referring to Figure 1 and Figure 3 , the above control module 205 can specifically be used to: control the duty cycle of the primary switch tube Q2 of the boost module to a fixed value, detect the output voltage and output power of the photovoltaic module when the duty cycle of the primary switch tube is a fixed value, and predict the peak output power of the photovoltaic module according to the output voltage and output power of the photovoltaic module; in the case where the peak output power of the photovoltaic module is greater than the preset startup power threshold, control the input control switch to close to enable the photovoltaic inverter to start running.

[0058] During specific implementation, after the auxiliary voltage module outputs electricity, the output power of the boost module can be made constant by controlling the duty cycle of the primary switch tube Q2 of the boost module 204 to be unchanged to charge the DC bus, and then the peak output power of the photovoltaic module can be predicted according to the detected output voltage and output power of the photovoltaic module. The implementation principle is as follows:

[0059] First, it is necessary to set the inductor L of the boost module 204 and the frequency of the primary switch tube Q2 to ensure that the current operates in the discontinuous mode. For example, select a smaller inductor L and increase the frequency of the primary switch tube Q2, etc. In this way, because the second DC voltage output by the boost module 204 is much greater than the first DC voltage VCC, and the current of the boost module 204 operates in the discontinuous mode, the output power of the boost module 204 is linearly related to the duty cycle of the primary switch tube Q2. Therefore, when the duty cycle of the primary switch tube Q2 is a fixed value, the output power of the boost module 204 is constant. In the embodiment of the present invention, the fixed value of the duty cycle of the primary switch tube Q2 can be set within the range of 0.05 to 0.5.

[0060] The output voltage and output power of the photovoltaic module are a curve with a peak, as Figure 4 shown, which is a schematic diagram of the power-voltage curve of the photovoltaic module in the embodiment of the present invention. Figure 4 In , at point A, when the duty cycle of the primary switch tube Q2 is 0, the output voltage Voc (i.e., the open-circuit voltage) of the photovoltaic module and the output power are 0, which can be measured by controlling the duty cycle of the primary switch tube Q2 to 0 before the boost module runs; at point B, when the duty cycle of the primary switch tube Q2 is a fixed value d, the detected output voltage of the photovoltaic module is V1 and the output power is P1. From points A and B, linear programming can obtain the linear curve:

[0061] (1)

[0062] Assume that the peak output voltage of the photovoltaic module is k times the open-circuit voltage, where k is a preset coefficient and can usually be set to 0.8. Then the peak output voltage V2 of the photovoltaic module is obtained as follows:

[0063]

[0064] Therefore, the peak output power P2 of the photovoltaic module can be estimated by the following formula:

[0065] (2)

[0066] As Figure 4 shown, the difference between the estimated peak output power P2 (point D) and the actual peak output power P3 (point C) of the photovoltaic module is not significant. Therefore, the estimated peak output power P2 of the photovoltaic module can be used as the peak output power of the photovoltaic module.

[0067] Therefore, by controlling the duty cycle of the primary switch tube of the boost module to a fixed value, the output voltage and output power of the photovoltaic module are obtained, and the peak output power of the photovoltaic module is predicted with high accuracy. Furthermore, the accuracy of subsequent judgment on whether the start-up condition of the photovoltaic inverter is met is also improved.

[0068] In specific implementation, after obtaining the peak output power of the photovoltaic module, the peak output power of the photovoltaic module can be compared with a preset start-up power threshold. If the peak output power of the photovoltaic module is greater than the preset start-up power threshold, the input control switch K1 can be controlled to close, and the photovoltaic inverter starts to operate; if the peak output power of the photovoltaic module is less than the preset start-up power threshold, it means that the output power of the photovoltaic module is insufficient, and the photovoltaic inverter cannot start to operate.

[0069] In one embodiment, the above start-up power threshold can be set according to the start-up loss power and grid-connection required power of the photovoltaic inverter before grid connection.

[0070] In specific implementation, after the photovoltaic inverter starts up, it enters the grid-connection preparation stage. Since the start-up operation of the photovoltaic inverter before grid connection also generates certain losses, in the embodiments of the present invention, the start-up power threshold is set according to the start-up loss power and grid-connection required power of the photovoltaic inverter. That is to say, the start-up power threshold can be set as the sum of the start-up loss power and grid-connection required power of the photovoltaic inverter. In this way, it can be avoided that the photovoltaic inverter cannot operate normally due to insufficient output power of the photovoltaic module during grid connection, and thus the judgment accuracy is improved.

[0071] In summary, the photovoltaic inverter provided by the embodiments of the present invention has the following beneficial effects:

[0072] 1. Without waiting for the self-check to complete, as long as the photovoltaic module outputs electricity, it is possible to determine whether the photovoltaic inverter can be started up based on the output voltage and output power of the photovoltaic module, which shortens the judgment time and improves the judgment efficiency.

[0073] 2. By controlling the duty cycle of the primary switching tube of the boost module to a fixed value, predicting the peak output power of the photovoltaic module according to the output voltage and output power of the photovoltaic module detected when the duty cycle of the primary switching tube is a fixed value, and then determining whether the photovoltaic inverter can be started up based on the peak output power of the photovoltaic module, the accuracy of the judgment is improved.

[0074] In an embodiment of the present invention, a method for controlling the startup of a photovoltaic inverter is also provided, as described in the following embodiments. The execution subject of this method is the above-mentioned photovoltaic inverter. Since the principle of solving problems by this method is similar to the principle of the above-mentioned photovoltaic inverter, the implementation of this method can refer to the implementation of the above-mentioned photovoltaic inverter, and the repeated parts will not be described again.

[0075] As Figure 5 shown, it is a flowchart of a method for controlling the startup of a photovoltaic inverter provided by an embodiment of the present invention. This method is applied to the above-mentioned photovoltaic inverter. The photovoltaic inverter includes a DC conversion module and an AC inverter module. The input end of the DC conversion module is connected to the photovoltaic module, the output end of the DC conversion module is connected to the input end of the AC inverter module through a DC bus, and the output end of the AC inverter module is connected to the power grid; the photovoltaic inverter further includes: an auxiliary power supply module, a boost module, an input control switch, and a control module; wherein, the input control switch is arranged between the photovoltaic module and the DC conversion module; the input end of the auxiliary power supply module is connected to the photovoltaic module, and the output end of the auxiliary power supply module is connected to the input end of the boost module; the output end of the boost module is connected to the DC bus.

[0076] This method may include:

[0077] Step 501, the auxiliary power supply module converts the output voltage of the photovoltaic module into a first DC voltage;

[0078] Step 502, the control module controls the duty cycle of the primary switching tube of the boost module, so that the boost module boosts the first DC voltage to a second DC voltage to charge the DC bus; and predicts the peak output power of the photovoltaic module according to the detected output voltage and output power of the photovoltaic module, and determines whether the peak output power of the photovoltaic module meets the startup condition of the photovoltaic inverter. If it meets, control the input control switch to close to start up the photovoltaic inverter.

[0079] In one embodiment, step 502 may specifically include: the control module controls the duty cycle of the primary side switch tube of the boost module to a fixed value, detects the output voltage and output power of the photovoltaic module when the duty cycle of the primary side switch tube is at the fixed value, and predicts the peak output power of the photovoltaic module according to the output voltage and output power of the photovoltaic module; in the case where the peak output power of the photovoltaic module is greater than the preset startup power threshold, control the input control switch to close so that the photovoltaic inverter starts to operate.

[0080] In one embodiment, the peak output power of the photovoltaic module is estimated by the following formula:

[0081]

[0082] where is the output voltage of the photovoltaic module when the duty cycle of the primary side switch tube is 0; is the peak output voltage of the photovoltaic module, , k is a preset coefficient; is the peak output power of the photovoltaic module; is the output voltage of the photovoltaic module when the duty cycle of the primary side switch tube is at the fixed value; is the output power of the photovoltaic module when the duty cycle of the primary side switch tube is at the fixed value.

[0083] In one embodiment, the above startup power threshold is set according to the startup loss power and grid connection required power before the photovoltaic inverter is connected to the grid.

[0084] To facilitate understanding of the above startup control method of the photovoltaic inverter, the following uses a specific example to detail the above startup control method of the photovoltaic inverter.

[0085] As Figure 6 shown, it is the implementation flowchart of the startup control method of the photovoltaic inverter in the embodiment of the present invention. First, when there is light on the photovoltaic module, that is, the photovoltaic module outputs electricity and the auxiliary power supply module works; then, close the charging control switch K3, and the control module controls the duty cycle of the primary side switch tube of the boost module to a fixed value, so that the boost module charges the DC bus at a constant power; then, according to the detected output voltage and output power of the photovoltaic module when the duty cycle of the primary side switch tube is at the fixed value, predict the peak output power of the photovoltaic module according to the above formula (2); if the peak output power of the photovoltaic module > the preset startup power threshold, then control the input control switch K1 to close, and the photovoltaic inverter starts up and enters the grid connection preparation stage. If the peak output power of the photovoltaic module is not greater than the preset startup power threshold, it means that the output power of the photovoltaic module is insufficient and the photovoltaic inverter does not start to operate.

[0086] An embodiment of the present invention also provides a computer device, which includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the above-mentioned startup control method of the photovoltaic inverter is implemented.

[0087] An embodiment of the present invention also provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the above-mentioned startup control method of the photovoltaic inverter is implemented.

[0088] An embodiment of the present invention also provides a computer program product, which includes a computer program. When the computer conversion program is executed by a processor, the above-mentioned startup control method of the photovoltaic inverter is implemented.

[0089] The photovoltaic inverter provided in the embodiment of the present invention includes a DC conversion module, an AC inversion module, an auxiliary power supply module, a boost module, an input control switch, and a control module; the input end of the DC conversion module is connected to a photovoltaic module, the output end of the DC conversion module is connected to the input end of the AC inversion module through a DC bus, and the output end of the AC inversion module is connected to the power grid; the input control switch is arranged between the photovoltaic module and the DC conversion module; the input end of the auxiliary power supply module is connected to the photovoltaic module, and the output end of the auxiliary power supply module is connected to the input end of the boost module; the output end of the boost module is connected to the DC bus; the auxiliary power supply module converts the output voltage of the photovoltaic module into a first DC voltage; the control module is used to control the duty ratio of the primary switching tube of the boost module, so that the boost module boosts the first DC voltage to a second DC voltage to charge the DC bus; and predicts the peak output power of the photovoltaic module according to the detected output voltage and output power of the photovoltaic module, and determines whether the peak output power of the photovoltaic module meets the startup condition of the photovoltaic inverter. If it meets the condition, the input control switch is controlled to close, so that the photovoltaic inverter starts to operate. Compared with the prior art, the photovoltaic inverter of the embodiment of the present invention does not need to wait for the self-check to be completed. As long as the photovoltaic module outputs electricity, the auxiliary power supply module of the photovoltaic inverter can work. The duty ratio of the primary switching tube of the boost module is controlled by the control module, so that the boost module charges the DC bus, and the output voltage and output power of the photovoltaic module are detected, and the peak output power of the photovoltaic module is predicted. Then, according to the predicted peak output power of the photovoltaic module, it is determined whether the startup condition of the photovoltaic inverter is met. In this way, it can be quickly determined whether the photovoltaic inverter can start up and operate normally, improving the startup operation judgment efficiency of the photovoltaic inverter. Moreover, judging whether to start up according to the predicted peak output power of the photovoltaic module improves the accuracy of the judgment.

[0090] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memory, CD-ROM, optical memory, etc.) that contain computer-usable program code.

[0091] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be realized by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in Figure 1 one or more of the flows Figure 1 or blocks or the combination of blocks.

[0092] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing devices to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including instruction means, and the instruction means implements the functions specified in Figure 1 one or more of the flows Figure 1 or blocks or the combination of blocks.

[0093] These computer program instructions can also be loaded onto a computer or other programmable data processing devices, so that a series of operation steps are executed on the computer or other programmable devices to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable devices provide steps for implementing the functions specified in Figure 1 one or more of the flows Figure 1 or blocks or the combination of blocks.

[0094] The specific embodiments described above further elaborate on the objectives, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A photovoltaic inverter, comprising a DC conversion module and an AC inversion module, wherein the input end of the DC conversion module is connected to a photovoltaic module, the output end of the DC conversion module is connected to the input end of the AC inversion module through a DC bus, and the output end of the AC inversion module is connected to a power grid; characterized in that, The photovoltaic inverter further includes: an auxiliary power supply module, a boost module, an input control switch, and a control module; The input control switch is disposed between the photovoltaic module and the DC conversion module; the input end of the auxiliary power supply module is connected to the photovoltaic module, and the output end of the auxiliary power supply module is connected to the input end of the boost module; the output end of the boost module is connected to the DC bus; The auxiliary power supply module is configured to convert the output voltage of the photovoltaic module into a first DC voltage; The control module is configured to control the duty cycle of the primary side switch tube of the boost module, so that the boost module boosts the first DC voltage to a second DC voltage to charge the DC bus; and predict the peak output power of the photovoltaic module according to the detected output voltage and output power of the photovoltaic module, determine whether the peak output power of the photovoltaic module meets the startup condition of the photovoltaic inverter, and if so, control the input control switch to close to make the photovoltaic inverter start and run; Specifically, the control module is configured to: control the duty cycle of the primary side switch tube of the boost module to a fixed value, detect the output voltage and output power of the photovoltaic module when the duty cycle of the primary side switch tube is a fixed value, and predict the peak output power of the photovoltaic module according to the output voltage and output power of the photovoltaic module; when the peak output power of the photovoltaic module is greater than a preset startup power threshold, control the input control switch to close to make the photovoltaic inverter start and run; Estimate the peak output power of the photovoltaic module through the following formula: Among them, is the output voltage of the photovoltaic module when the duty cycle of the primary side switch tube is 0; is the peak output voltage of the photovoltaic module, , k is a preset coefficient; is the peak output power of the photovoltaic module; is the output voltage of the photovoltaic module when the duty cycle of the primary side switch tube is a fixed value; is the output power of the photovoltaic module when the duty cycle of the primary side switch tube is a fixed value.

2. The photovoltaic inverter according to claim 1, wherein The photovoltaic inverter further includes a charging control switch, and the charging control switch is disposed between the boost module and the DC bus; The control module is further configured to: control the charging control switch to close when it is detected that the auxiliary power supply module outputs the first DC voltage.

3. The PV inverter according to claim 1, characterized in that, The startup power threshold is set according to the startup loss power and grid connection required power before the photovoltaic inverter is connected to the grid.

4. A startup control method for a photovoltaic inverter, which is applied to the photovoltaic inverter. The photovoltaic inverter includes a DC conversion module and an AC inversion module. The input end of the DC conversion module is connected to a photovoltaic module, the output end of the DC conversion module is connected to the input end of the AC inversion module through a DC bus, and the output end of the AC inversion module is connected to a power grid; characterized in that, The photovoltaic inverter further includes: an auxiliary power supply module, a boost module, an input control switch, and a control module; wherein, the input control switch is disposed between the photovoltaic module and the DC conversion module; the input end of the auxiliary power supply module is connected to the photovoltaic module, and the output end of the auxiliary power supply module is connected to the input end of the boost module; the output end of the boost module is connected to the DC bus; The method includes: The auxiliary power supply module converts the output voltage of the photovoltaic module into a first DC voltage; The control module controls the duty cycle of the primary side switch tube of the boost module, so that the boost module boosts the first DC voltage to a second DC voltage to charge the DC bus; and predict the peak output power of the photovoltaic module according to the detected output voltage and output power of the photovoltaic module, determine whether the peak output power of the photovoltaic module meets the startup condition of the photovoltaic inverter, and if so, control the input control switch to close to make the photovoltaic inverter start and run; The control module controls the duty cycle of the primary switch tube of the boost module to be a fixed value, detects the output voltage and output power of the photovoltaic module when the duty cycle of the primary switch tube is the fixed value, and predicts the peak output power of the photovoltaic module according to the output voltage and output power of the photovoltaic module; when the peak output power of the photovoltaic module is greater than a preset starting power threshold, it controls the input control switch to close so that the photovoltaic inverter starts to operate; The peak output power of the photovoltaic module is estimated by the following formula: Among them, is the output voltage of the photovoltaic module when the duty cycle of the primary side switching transistor is 0; is the peak output voltage of the photovoltaic module, , k is a preset coefficient; is the peak output power of the photovoltaic module; is the output voltage of the photovoltaic module when the duty cycle of the primary side switching transistor is a fixed value; is the output power of the photovoltaic module when the duty cycle of the primary side switching transistor is a fixed value.

5. The startup control method of the photovoltaic inverter according to claim 4, characterized in that, The starting power threshold is set according to the starting loss power and the grid connection required power before the photovoltaic inverter is connected to the grid.

6. A photovoltaic power generation system, characterized in that, The photovoltaic power generation system includes a photovoltaic module and a photovoltaic inverter according to any one of claims 1-3; the input side of the photovoltaic inverter is connected to the photovoltaic module, and the output side of the photovoltaic inverter is connected to the grid.

7. A computer device, comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the starting control method of the photovoltaic inverter according to any one of claims 4 to 5.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, it implements the starting control method of the photovoltaic inverter according to any one of claims 4 to 5.

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