Photovoltaic inverter system control method and device

Abstract

The present invention provides a photovoltaic inverter system control method and device, which relates to the photovoltaic inverter technology field. The photovoltaic inverter system control method includes: when the photovoltaic inverter system is in standby mode and it is detected that the photovoltaic open-circuit voltage is greater than a first preset threshold, controlling the boost converter in the photovoltaic inverter system to start working so that the bus voltage in the photovoltaic inverter system rises to a first target value; turning on the DC switching power supply in the photovoltaic inverter system; when the bus voltage in the photovoltaic inverter system drops to less than the start-up threshold, turning off the DC switching power supply. The present invention can improve the life and reliability of the photovoltaic inverter system.

Description

Technical Field

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

[0002] Photovoltaic Inverter System is a power conversion system used to convert direct current generated by photovoltaic modules (solar panels) into alternating current. In photovoltaic inverter systems, DC switching power supplies are usually used to provide stable DC power to loads such as controllers in photovoltaic inverter systems to ensure efficient operation of photovoltaic inverter systems.

[0003] The DC switching power supply works by drawing power from the bus. When the bus voltage is higher than the DC switching power supply's turn-on threshold, the DC switching power supply will work. When the bus voltage is lower than the turn-on threshold, the DC switching power supply will not work. When the light intensity is low, the bus voltage is the photovoltaic open-circuit voltage. If the photovoltaic open-circuit voltage reaches the DC switching power supply's turn-on threshold, the switching power supply chip starts working, and the DC switching power supply will have a certain power output. When the DC switching power supply outputs power, the bus voltage will drop, which will cause the bus voltage to be lower than the DC switching power supply's turn-on threshold, and the DC switching power supply will stop working. At this time, the photovoltaic module no longer outputs power, and the bus voltage returns to the DC switching power supply's turn-on threshold open-circuit voltage point.

[0004] In this scenario, the DC switching power supply is constantly started and stopped, entering a "hiccup" mode, which affects the life and reliability of the photovoltaic inverter system. Summary of the invention

[0005] The problem solved by the present invention is how to solve the problem that when the light intensity is low, the DC switching power supply is constantly started and stopped, thereby reducing the life and reliability of the photovoltaic inverter system.

[0006] In order to solve the above problems, the present invention provides a photovoltaic inverter system control method and device.

[0007] In a first aspect, the present invention provides a photovoltaic inverter system control method, comprising: when the photovoltaic inverter system is in a standby mode and it is detected that the photovoltaic open-circuit voltage is greater than a first preset threshold, controlling a boost converter in the photovoltaic inverter system to start working, so as to boost the photovoltaic open-circuit voltage through the boost converter so that the bus voltage in the photovoltaic inverter system rises to a first target value;

[0008] Turning on a DC switching power supply in the photovoltaic inverter system, wherein the first preset threshold is less than a turn-on threshold of the DC switching power supply, and the first target value is greater than the turn-on threshold;

[0009] When the bus voltage in the photovoltaic inverter system drops below the start-up threshold, the DC switching power supply is turned off and the boost converter is controlled to stop working, so that the photovoltaic inverter returns to the standby mode.

[0010] In a second aspect, the present invention provides a photovoltaic inverter system control device, comprising:

[0011] A control unit, configured to control a boost converter in the photovoltaic inverter system to start working when the photovoltaic inverter system is in a standby mode and detects that the photovoltaic open-circuit voltage is greater than a first preset threshold value, so as to boost the photovoltaic open-circuit voltage through the boost converter so that the bus voltage in the photovoltaic inverter system rises to a first target value;

[0012] A start-up unit, configured to start a DC switching power supply in the photovoltaic inverter system, wherein the first preset threshold is less than a start-up threshold of the DC switching power supply, and the first target value is greater than the start-up threshold;

[0013] The shutdown unit is used to shut down the DC switching power supply and control the boost converter to stop working when the bus voltage in the photovoltaic inverter system drops below the start-up threshold, so as to return the photovoltaic inverter to the standby mode.

[0014] In a third aspect, the present invention provides an electronic device, including a memory and a processor;

[0015] The memory is used to store computer programs;

[0016] The processor is used to implement the photovoltaic inverter system control method as described in the first aspect when executing the computer program.

[0017] In a fourth aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the photovoltaic inverter system control method as described in the first aspect is implemented.

[0018] The photovoltaic inverter system control method and device of the present invention have the following beneficial effects: in standby mode, the photovoltaic open-circuit voltage is continuously detected, and the boost converter in the photovoltaic inverter system does not work in the standby mode. At this time, the bus voltage is equal to the photovoltaic open-circuit voltage. If the photovoltaic open-circuit voltage is less than or equal to the first preset threshold, that is, the bus voltage is less than or equal to the first preset threshold, and the first preset threshold is less than the start-up threshold of the DC switching power supply, that is, the DC switching power supply is in an off state at this time; but if the photovoltaic open-circuit voltage is greater than the first preset threshold, the boost converter will be controlled to start working, so that the bus voltage rises to the first target value, and the first target value is greater than the start-up threshold. At this time, the bus voltage detected by the bus voltage detection unit is greater than the start-up threshold, and the DC switching power supply is turned on. When the photovoltaic open-circuit voltage is greater than the first preset threshold, the bus voltage is increased to the first target value through the boost converter, and the DC switching power supply will be in a startup state. At this time, since the bus voltage is the first target value and the first target value is greater than the startup threshold, it supports power output within a certain range, that is, after the DC switching power supply is started, even if there is a certain power output, the bus voltage is reduced, but when the output power is within a certain range, the bus voltage will not drop below the startup threshold, that is, the DC switching power supply can be kept in the startup state and will not enter the hiccup mode, and even if the output power exceeds the support range of photovoltaic energy, the bus voltage will gradually drop below the startup threshold. Since the first target value is greater than the startup threshold, a certain buffering effect is provided for the DC switching power supply from being turned on to being turned off, so that the DC switching power supply will not be turned off immediately after being turned on, thereby reducing the start-stop frequency of the DC switching power supply, thereby improving the life and reliability of the photovoltaic inverter system. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A topological diagram of a photovoltaic inverter system according to an embodiment of the present invention;

[0020] Figure 2 A schematic diagram of a "hiccup" mode of a DC switching power supply according to an embodiment of the present invention;

[0021] Figure 3 A schematic flow chart of a photovoltaic inverter system control method according to an embodiment of the present invention;

[0022] Figure 4 A topological diagram of another photovoltaic inverter system according to an embodiment of the present invention;

[0023] Figure 5 A schematic diagram of controlling a boost converter using a first control loop according to an embodiment of the present invention;

[0024] Figure 6 A schematic diagram of controlling a boost converter using a second control loop according to an embodiment of the present invention;

[0025] Figure 7is a control block diagram of the first control loop control of an embodiment of the present invention;

[0026] Figure 8 A schematic diagram of a process of switching from a standby mode to a low-light operation mode according to an embodiment of the present invention;

[0027] Fig. 9 A schematic diagram of a process of switching from a low-light operation mode to a standby mode according to an embodiment of the present invention;

[0028] Fig.10 A schematic diagram of determining a speed limit value of a fan according to an embodiment of the present invention;

[0029] Fig.11 A schematic diagram of the operation process of a fan according to an embodiment of the present invention;

[0030] Fig.12 A schematic diagram of using a third control loop to control an inverter circuit according to an embodiment of the present invention;

[0031] Fig.13 is a control block diagram of a third control loop according to an embodiment of the present invention;

[0032] Fig.14 A schematic diagram of using a fourth control loop to control an inverter circuit according to an embodiment of the present invention;

[0033] Fig.15 is a control block diagram of a fourth control loop according to an embodiment of the present invention;

[0034] Fig.16 A schematic diagram of controlling a boost converter using a fifth control loop according to an embodiment of the present invention;

[0035] Fig.17 is a control block diagram of a fifth control loop according to an embodiment of the present invention;

[0036] Fig.18 A schematic diagram of a process of switching from a low-light operation mode to a grid-connected operation mode according to an embodiment of the present invention;

[0037] Fig.19 A schematic diagram of the switching logic of three operation modes of a photovoltaic inverter system according to an embodiment of the present invention;

[0038] Fig. 20 A schematic diagram of a switching process of switching from a grid-connected operation mode to a standby mode according to an embodiment of the present invention;

[0039] Fig.21 A schematic diagram of a photovoltaic inverter system control device according to an embodiment of the present invention;

[0040] Fig. 22 The figure is a schematic diagram of the structure of an electronic device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0041] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. Although certain embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be interpreted as being limited to the embodiments described herein. On the contrary, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are only for exemplary purposes and are not intended to limit the scope of protection of the present invention.

[0042] It should be understood that the various steps described in the method embodiments of the present invention may be performed in different orders and / or in parallel. In addition, the method embodiments may include additional steps and / or omit the steps shown. The scope of the present invention is not limited in this respect.

[0043] The term "including" and its variations used in this document are open inclusions, that is, "including but not limited to"; the term "based on" means "based at least in part on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment"; the term "some embodiments" means "at least some embodiments"; the term "optionally" means "optional embodiments". The relevant definitions of other terms will be given in the following description. It should be noted that the concepts of "first", "second", etc. mentioned in the present invention are only used to distinguish different devices, modules or units, and are not used to limit the order or interdependence of the functions performed by these devices, modules or units.

[0044] It should be noted that the modifications of "one" and "plurality" mentioned in the present invention are illustrative rather than restrictive, and those skilled in the art should understand that, unless otherwise clearly indicated in the context, it should be understood as "one or more".

[0045] The names of the messages or information exchanged between multiple devices in the embodiments of the present invention are only used for illustrative purposes, and are not used to limit the scope of these messages or information.

[0046] Topology diagram of photovoltaic inverter system in related technology, such as Figure 1 As shown, the photovoltaic inverter system includes photovoltaic components (corresponding to Figure 1 PV in), boost converter, inverter circuit (corresponding to Figure 1 The DC / DC circuit in the photovoltaic module is usually composed of a solar panel, which converts sunlight into direct current. The photovoltaic module is the input of the photovoltaic inverter system and provides direct current power to the system. The boost converter generates a DC voltage (corresponding to Figure 1 In ) boost, the boosted voltage is the target voltage (corresponding to Figure 1 In ); The inverter circuit converts DC power into AC power; The DC switching power supply includes a bus voltage detection unit (corresponding to Figure 1 The detection unit in the DC switching power supply), that is, the DC switching power supply takes power from the bus. When the bus voltage is higher than the start-up threshold of the DC switching power supply, the DC switching power supply starts to work. When the bus voltage is lower than the start-up threshold of the DC switching power supply, the DC switching power supply stops working. When the DC switching power supply is working, it will affect the key loads such as DSP, sampling, driving, and control loops (corresponding to Figure 1 The controller in the system provides a stable DC power supply to ensure the normal operation of the system.

[0047] like Figure 1 For the photovoltaic inverter system shown in the figure, when the light intensity is very low, the photovoltaic open-circuit voltage is very low. At this time, the inverter cannot be connected to the grid, and the boost converter does not work. At this time, the bus voltage is equal to the photovoltaic open-circuit voltage. Figure 2 As shown in the figure, when the photovoltaic open-circuit voltage reaches the start-up threshold, that is, the bus voltage reaches the start-up threshold, the DC switching power supply starts to work and has a certain power output. The photovoltaic components will reduce the output voltage to provide power, that is, the photovoltaic open-circuit voltage is reduced, so that the bus voltage is lower than the start-up threshold, and the DC switching power supply stops working. After the DC switching power supply stops working, the photovoltaic open-circuit voltage will return to the start-up threshold, that is, the bus voltage returns to the start-up threshold, and the aforementioned DC switching power supply start-stop process is repeated. That is, under low light, there may be a scene where the DC switching power supply is constantly started and stopped, that is, the DC switching power supply enters the "hiccup" mode, which will reduce the service life and reliability of the photovoltaic inverter system.

[0048] In view of the problems existing in the above-mentioned related technologies, this embodiment provides a photovoltaic inverter system control method and device.

[0049] like Figure 3 As shown, a photovoltaic inverter system control method provided by an embodiment of the present invention includes:

[0050] S100, when the photovoltaic inverter system is in standby mode and detects that the photovoltaic open-circuit voltage is greater than a first preset threshold, control the boost converter in the photovoltaic inverter system to start working, so as to boost the photovoltaic open-circuit voltage through the boost converter so that the bus voltage in the photovoltaic inverter system rises to a first target value.

[0051] Specifically, the photovoltaic inverter system control method is executed by a controller, such as Figure 4 As shown, the photovoltaic inverter system in this embodiment includes photovoltaic components (corresponding to Figure 4 PV in), boost converter (corresponding to Figure 4 DC / DC circuit in), inverter circuit (corresponding to Figure 4 DC / AC circuit in), DC switching power supply, AC switching power supply, AC inverter (corresponding to Figure 4 The AC / DC circuit in the embodiment of the present invention is a circuit in which the AC switching power supply and the DC switching power supply are connected to the controller to supply power through the DC switching power supply and the AC switching power supply. The power of the controller is usually small, generally around 5W. In addition, the DC switching power supply is also connected to a target load, and the operating power of the target load is relatively large, generally above 100W.

[0052] It should be noted that the controller includes key loads such as DSP (digital signal processing) chips, drivers, samplers, etc., which are used to perform photovoltaic inverter system control. The target load refers to the load that is only connected to the DC switching power supply. The target load can be flexibly adjusted or temporarily interrupted during the operation of the system without having a significant impact on the core functions of the system. The target load can be fans, lighting equipment, water pumps, etc. In low-light scenarios, PV energy is input to the DC switching power supply to power the target load, which can improve the energy utilization of the system in low-light scenarios. The AC inverter is connected to the power grid, takes the AC power of the power grid as input, adjusts the frequency, amplitude or phase, and outputs the adjusted AC power. The adjusted AC power is used as the input of the AC switching power supply to provide power for the controller. The DC switching power supply takes the bus voltage as input to provide power for the target load and the controller.

[0053] When the photovoltaic inverter system is in standby mode, that is, the photovoltaic inverter system is in a state of waiting to work, in standby mode, the boost converter, inverter circuit, and DC switching power supply are not working, and only the AC switching power supply and AC inverter are in working state to ensure the power supply of the controller. In terms of hardware, the key loads in the controller are powered by dual power supplies of DC switching power supply and AC switching power supply to ensure the continuity of power supply to the controller.

[0054] In standby mode, the controller continuously detects the photovoltaic open circuit voltage (corresponding to Figure 4 In When it is detected that the photovoltaic open-circuit voltage is greater than the first preset threshold, the standby mode is exited, that is, the boost converter is controlled to start working. The input of the boost converter is the photovoltaic open-circuit voltage, and the photovoltaic open-circuit voltage is boosted to obtain the bus voltage. In the boost converter, when the input voltage, that is, the photovoltaic open-circuit voltage, is applied to the circuit, the switch tube (corresponding to Figure 4 The energy is transferred and stored between the inductor and the capacitor by turning on and off the S1 in the circuit. When the switch is on, the energy is stored in the inductor; when the switch is off, the inductor releases the energy, and the output voltage increases. The output voltage corresponds to the bus voltage (corresponding to Figure 4 In ).

[0055] After the boost operation is performed by the boost converter, the bus voltage rises to the first target value.

[0056] S200, turning on a DC switching power supply in the photovoltaic inverter system, wherein the first preset threshold is less than a turn-on threshold of the DC switching power supply, and the first target value is greater than the turn-on threshold.

[0057] Specifically, the DC switching power supply includes a bus voltage detection unit, that is, the DC switching power supply draws power from the bus. When the bus voltage is higher than the start-up threshold of the DC switching power supply, the DC switching power supply starts working, and when the bus voltage is lower than the start-up threshold of the DC switching power supply, the DC switching power supply stops working.

[0058] In standby mode, the boost converter does not work, and the bus voltage detected by the bus voltage detection unit is equal to the photovoltaic open-circuit voltage. If the photovoltaic open-circuit voltage is less than or equal to the first preset threshold, that is, the bus voltage is less than or equal to the first preset threshold, and the first preset threshold is less than the start-up threshold of the DC switching power supply, that is, the DC switching power supply is in the off state at this time; if the photovoltaic open-circuit voltage is greater than the first preset threshold, the boost converter will be controlled to start working, so that the bus voltage rises to the first target value, and the first target value is greater than the start-up threshold. At this time, the bus voltage detected by the bus voltage detection unit is greater than the start-up threshold, and the DC switching power supply is turned on.

[0059] S300, when the bus voltage in the photovoltaic inverter system drops to less than the start-up threshold, turning off the DC switching power supply and controlling the boost converter to stop working, so that the photovoltaic inverter returns to the standby mode.

[0060] Specifically, after the DC switching power supply is turned on, if the photovoltaic energy is too low, even if the boost operation is performed through the boost converter, the bus voltage will be difficult to reach the first target value. When the photovoltaic energy is insufficient, the bus voltage will gradually decrease. When the bus voltage drops below the switching threshold, the DC switching power supply will be turned off, and the boost converter will also stop working, that is, the photovoltaic inverter system will return to standby mode.

[0061] In this embodiment, in standby mode, the photovoltaic open-circuit voltage is continuously detected. In standby mode, the boost converter in the photovoltaic inverter system does not work. At this time, the bus voltage is equal to the photovoltaic open-circuit voltage. If the photovoltaic open-circuit voltage is less than or equal to the first preset threshold, that is, the bus voltage is less than or equal to the first preset threshold, and the first preset threshold is less than the start-up threshold of the DC switching power supply, that is, the DC switching power supply is in an off state at this time; but if the photovoltaic open-circuit voltage is greater than the first preset threshold, the boost converter will be controlled to start working, so that the bus voltage rises to the first target value, and the first target value is greater than the start-up threshold. At this time, the bus voltage detected by the bus voltage detection unit is greater than the start-up threshold, and the DC switching power supply is turned on. When the photovoltaic open-circuit voltage is greater than the first preset threshold, the bus voltage is increased to the first target value through the boost converter, and the DC switching power supply will be in a startup state. At this time, since the bus voltage is the first target value and the first target value is greater than the startup threshold, it supports power output within a certain range, that is, after the DC switching power supply is started, even if there is a certain power output, the bus voltage is reduced, but when the output power is within a certain range, the bus voltage will not drop below the startup threshold, that is, the DC switching power supply can be kept in the startup state and will not enter the hiccup mode, and even if the output power exceeds the support range of photovoltaic energy, the bus voltage will gradually drop below the startup threshold. Since the first target value is greater than the startup threshold, a certain buffering effect is provided for the DC switching power supply from being turned on to being turned off, so that the DC switching power supply will not be turned off immediately after being turned on, thereby reducing the start-stop frequency of the DC switching power supply, thereby improving the life and reliability of the photovoltaic inverter system.

[0062] Optionally, controlling the boost converter in the photovoltaic inverter system to start working includes: sending a first control signal to the boost converter through a first control loop, wherein the first control signal is used to control the operation of the boost converter so that the bus voltage reaches the first target value, and the first control loop is open-loop control.

[0063] Specifically, Figure 5 As shown, a first control signal is sent to a boost converter through a first control loop. The first control signal controls the operation of the boost converter by controlling the switching frequency and duty cycle of the switch tube in the boost converter. After the operation of the boost converter is controlled by the first control signal for a preset time, the control target of the first control signal is to make the voltage value of the bus voltage reach a first target value.

[0064] For example, the boost converter is subjected to open-loop pulsation through the first control loop to increase the bus voltage to the first target value. At this time, since the first target value is greater than the start-up voltage of the DC switching power supply, the DC switching power supply starts to work. The open-loop pulsation method can adopt a fixed duty cycle form or a variable duty cycle form, and the pulsation time (corresponding to the above-mentioned preset time) should ensure that the bus voltage can rise to near the first target value.

[0065] In this embodiment, the boost converter is operated in an open loop through the first control loop, so that the boost converter can respond quickly to the first control signal, thereby quickly increasing the bus voltage to the first target value.

[0066] Optionally, after sending the first control signal to the boost converter through the first control loop, the photovoltaic inverter system control method further includes: when it is detected that the boost current in the boost converter is less than a preset current threshold, switching the control loop of the boost converter from the first control loop to the second control loop; sending a second control signal to the boost converter through the second control loop, wherein the second control signal is used to control the operation of the boost converter so that the bus voltage is stabilized at the first target value, and the second control loop is a closed-loop control.

[0067] Specifically, since the first control loop is an open-loop control, it is easily affected by external interference or changes in system parameters and cannot correct system errors in time, which may cause system oscillation or instability, resulting in large fluctuations in bus voltage and difficulty in stabilizing near the first target value. In order to maintain the bus voltage stable near the first target value, after the first control loop is used to quickly increase the bus voltage to near the first target value, that is, after the control of the first control loop ends, Figure 6 As shown, the control loop of the boost converter is switched from the first control loop to the second control loop.

[0068] Furthermore, in order to avoid current shock when switching the control loop, after the control of the first control loop ends, the boost converter is not controlled, the current in the boost converter will continue to decrease, and the boost current in the boost converter (corresponding to Figure 5 In ), when it is detected that the boost current in the boost converter is less than a preset current threshold, the control loop of the boost converter is switched from the first control loop to the second control loop.

[0069] It should be noted that the inductor element in the boost converter will release the stored energy when the boost current decreases and continue to provide electrical energy, so that the bus voltage remains at a certain level for a period of time, that is, while waiting for the boost current to decrease, the bus voltage will still be maintained near the first target value, and the first target value is greater than the turn-on threshold, which provides a drop range for the bus voltage. Within this range, the drop in the bus voltage will not cause the DC switching power supply to shut down.

[0070] In this embodiment, when it is detected that the boost current is less than the preset current threshold, the control loop is switched to avoid current shock. It should be noted that the preset current threshold can be 0 or a very small current value set in advance, and no current shock will be caused below this current value. In addition, the control loop is switched from the first control loop to the closed-loop second control loop to maintain the bus voltage stable near the first target value, thereby ensuring the stable operation of the system.

[0071] Alternatively, if Figure 7 As shown, the control process of the second control loop includes: cyclically performing the following operations: obtaining the instantaneous value of the bus voltage and the instantaneous value of the boost current; determining the target value of the boost current according to the error value between the instantaneous value of the bus voltage and the first target value, and obtaining the second target value; determining the first duty cycle according to the error value between the second target value and the instantaneous value of the boost current; generating a second control signal according to the first duty cycle, and sending the second control signal to the boost converter.

[0072] Specifically, the control process of the second control loop is a cyclic control process, that is, outputting the second control signal to achieve control of the bus voltage, and continuously adjusting the second control signal based on the sampled control target (bus voltage), that is, cyclically performing the following operations: sampling the instantaneous value of the bus voltage (corresponding to Figure 7 In ), compared with the first target value (corresponding to Figure 7 In ), get the error value, pass the error value through PI controller 1 to get the target value of boost current, that is, the second target value (corresponding to Figure 7 In ), and then compared with the instantaneous value of the boost current obtained by sampling Compare, and then get the duty cycle (corresponding to Figure 7 In d DC / DC ) d DC / DC , after passing through the PWM generation module, a second control signal is obtained, and the second control signal is sent to the boost converter to control the switch tube in the boost circuit S 1, thereby controlling the operation of the boost converter to stabilize the bus voltage at the first target value.

[0073] Optionally, after turning on the DC switching power supply in the photovoltaic inverter system, the photovoltaic inverter system control also includes: when the bus voltage of the photovoltaic inverter is stabilized at the first target value, turning on a target load connected to the DC switching power supply, and controlling the workload of the target load.

[0074] Specifically, in the related art, when the light intensity is low, the photovoltaic inverter system cannot be connected to the grid, that is, it cannot be connected to the power grid and realize the transmission and supply of electricity, and when the DC switching power supply is turned on, it only provides stable power for the load in the controller, but the rated power of the controller is small, and the photovoltaic energy cannot be fully utilized. In order to avoid energy waste, the DC switching power supply is connected to the target load, and when the bus voltage is stable at the first target value, the target load is turned on and the workload of the target load is controlled.

[0075] In this embodiment, during low-light operation, after the bus voltage is stabilized, the target load should be turned on to improve the utilization rate of photovoltaic energy. The target load may be a fan for dust removal or a heating device for heating.

[0076] Optionally, the boost converter, the DC switching power supply, and the target load connected to the DC switching power supply in the photovoltaic inverter system are in the working state and are determined to be in the low light operation mode, that is, when it is detected that the photovoltaic open circuit voltage is greater than the first preset threshold, the photovoltaic inverter system is controlled to exit the standby mode and switch from the standby mode to the low light operation mode. The switching process from the standby mode to the low light operation mode is as follows Figure 8 As shown, it includes: when the photovoltaic inverter is in the standby mode, continuously detecting the photovoltaic open circuit voltage, and when it is detected that the photovoltaic open circuit voltage is greater than the first preset threshold value (corresponding to Figure 8 middle ), the boost converter in the photovoltaic inverter system is controlled to start working (i.e., the boost converter is open-loop pulsed), so that the bus voltage in the photovoltaic inverter system rises to the first target value. At this time, the DC switching power supply is turned on. After the control of the first control loop ends, the current in the boost converter will continue to decrease. When the boost current drops to 0 (corresponding to the preset current threshold), the boost converter is controlled by the second control loop to work. When the bus voltage stabilizes at the first target value, the target load is turned on. At this point, the photovoltaic inverter is switched from standby mode to low-light operation mode. In low-light operation mode, the operation of the target load improves the utilization rate of photovoltaic energy.

[0077] like Fig. 9 As shown in FIG. 1 , when the photovoltaic inverter system is in low-light operation mode, when the photovoltaic energy is insufficient to support the target load operation, the second control loop cannot support the bus voltage to be stable near the first target value, and the bus voltage will continue to decrease. If the bus voltage is detected to be less than the start-up threshold of the DC switching power supply (corresponding to Fig. 9 middle ), the DC switching power supply stops working, and the boost converter is controlled to be turned off and no longer works (boosting the photovoltaic open-circuit voltage), and then the target load stops working, and then exits the low-light operation mode and switches to the standby mode.

[0078] Optionally, when the target load is a fan, the workload of controlling the target load includes: obtaining the minimum speed and initial speed limit of the fan; controlling the fan to operate at variable speeds between the minimum speed and the initial speed limit; when a drop in the bus voltage is detected, obtaining the current speed of the fan; and updating the speed limit of the fan from the initial speed limit to the current speed.

[0079] Specifically, in order to ensure that the power provided by the photovoltaic module is in a balanced state with the operating power of the target load, it is necessary to control the operating speed of the target load. Taking fan reverse dust removal as an example, it is necessary to control the fan speed, that is, it is necessary to determine the fan speed limit. Fig.10 As shown, first determine the minimum speed and initial speed limit of the fan (corresponding to Fig.10 In ), where the minimum speed (corresponding to Fig.10 In ) The initial speed limit is determined by the fan's own parameters and dust removal requirements. The initial speed limit is the smaller value between the maximum speed supported by the fan itself and the maximum speed supported by the PV panel.

[0080] When the fan starts working, the fan first works at the lowest speed, and then gradually increases the speed to the initial speed limit of the fan, that is, it operates at a variable speed between the minimum speed and the initial speed limit. Specifically, the fan can be controlled to operate at a variable speed according to a preset logic, for example, working at the lowest speed for a preset time, increasing a certain operating speed (preset change value) based on the lowest speed, and then working at the increased speed for a preset time, and so on until the operating speed of the fan reaches the initial speed limit.

[0081] During variable speed operation, the bus voltage is continuously detected. If the bus voltage drops before the fan reaches the initial speed (i.e. the bus voltage drops to the allowable drop value), the speed before the bus voltage drops (corresponding to the above current speed) is used as the speed limit. Otherwise, the initial speed limit is used as the speed limit (corresponding to the current speed). Fig.10 In ).

[0082] Combination Fig.10 To explain, the fan is controlled to run at variable speed, starting from the lowest speed at time t1, and gradually increasing the fan speed (operating speed). It should be noted that the fan starts at the moment ( Fig.10Around time t1 in the middle), due to the need to overcome inertia, generally a larger power is required. During this period (within the first preset time period), no bus voltage drop logic judgment is performed. That is, during this period, if the bus voltage drops, it is not determined that the current speed is the speed limit. Instead, the fan is still controlled to continuously increase the speed according to the preset logic. After exceeding the first preset time period, if the bus voltage drops ( Fig.10 If the bus voltage drops at time t2, the speed before the drop, that is, the current speed, is determined as the speed limit, and the speed corresponding to time t2 is determined as the speed limit, that is, the speed limit of the fan is updated from the initial speed limit to the current speed.

[0083] like Fig.11 As shown, the fan workflow includes: fan start, determining the speed limit: the speed limit at the beginning is the initial speed limit After the speed limit is determined, the fan runs at a variable speed between the minimum speed and the speed limit. During the operation, the bus voltage is detected to see if it drops. When the bus voltage drops, if the current speed limit is not equal to the minimum speed, the fan speed limit is updated to the speed before the drop. If the current speed limit is equal to the minimum speed, the fan is controlled to run at the minimum speed until the bus voltage is lower than the start-up threshold of the DC switching power supply to exit the low-light operation mode, that is, the fan stops running. In addition, when the determined speed limit is not equal to the initial speed limit, the fan needs to be kept running for the second preset time before the fan speed limit is re-determined to improve robustness.

[0084] Optionally, after turning on the DC switching power supply in the photovoltaic inverter system, the photovoltaic inverter system control method further includes: when it is detected that the photovoltaic open-circuit voltage is greater than a second preset threshold, controlling the inverter circuit in the photovoltaic inverter system to start working through a third control loop, wherein the three control loops are used to generate a third control signal, and the third control signal is used to control the operation of the inverter circuit so that the AC voltage output by the inverter circuit reaches the grid voltage, and the third control loop is an open-loop control.

[0085] Specifically, the second preset threshold is a pre-set threshold for connecting the photovoltaic inverter system to the power grid. When it is detected that the photovoltaic open-circuit voltage is greater than the second preset threshold, grid connection can be performed, that is, the photovoltaic inverter system is switched from the low-light operation mode to the grid-connected mode. In the grid-connected mode, the boost converter, inverter circuit, DC switching power supply, AC switching power supply, and AC inverter are all in working condition.

[0086] like Fig.12As shown, when it is detected that the photovoltaic open-circuit voltage is greater than the second preset threshold, the third control loop is used to control the inverter circuit in the photovoltaic inverter system to start working, that is, the inverter circuit is open-loop controlled so that the output voltage of the inverter circuit is consistent with the grid voltage. At this time, the control loop of the boost converter keeps the second control loop unchanged.

[0087] Furthermore, the control block diagram of the third control loop is as follows: Fig.13 Shown: Sampling grid voltage , , , after passing through the phase-locked loop (PLL), the grid voltage frequency is obtained With phase , then , , After dq conversion and duty cycle calculation, the d-axis duty cycle, q-axis duty cycle and 0-axis duty cycle are obtained. , , ,Will , , Then it is transformed to the abc axis and passes through the PWM generation module to obtain the third control signal, thereby realizing the output voltage control of the inverter circuit.

[0088] Alternatively, if Fig.14 As shown, after the inverter circuit in the photovoltaic inverter system starts working by controlling the third control loop, the photovoltaic inverter system control method also includes: controlling the inverter circuit to be connected to the power grid; switching the control circuit of the inverter circuit from the third control loop to the fourth control loop; controlling the operation of the inverter circuit by the fourth control loop, wherein the fourth control loop is a closed-loop control, the fourth control loop is used to generate a fourth control signal, and the fourth control signal is used to control the operation of the inverter circuit so that the AC voltage output by the inverter circuit is stabilized at the power grid voltage.

[0089] Specifically, after the inverter circuit in the photovoltaic inverter system is controlled by the third control loop to start working, so that the AC voltage output by the inverter circuit reaches the grid voltage, the inverter circuit and the grid can be connected to the grid, and the switch tube (corresponding to Fig.14 After the inverter circuit is connected to the grid, in order to maintain the output voltage of the inverter circuit stable at the grid voltage, the control circuit of the inverter circuit is switched from the third control circuit to the fourth control circuit, and at the same time, the control circuit of the boost converter remains the second control circuit unchanged.

[0090] Furthermore, the control block diagram of the fourth control loop is as follows: Fig.15 As shown, the sampling grid voltage , , , after passing through the phase-locked loop (PLL), the grid voltage frequency is obtained With phase , the three-phase current output by the inverter circuit , , Combined with grid voltage and frequency With phase , dq transformation gives , , ,Will , The two errors obtained after being compared with the corresponding reference values ​​enter the PI controller 4 and the PI controller 5 respectively, wherein the difference between the bus voltage and the target value (first target value) of the bus voltage is input into the PI controller 3 to obtain The corresponding reference value, while the grid voltage , , Combined with grid voltage and frequency With phase , do dq transformation to get , , As the feedforward of the control loop, the outputs of the PI controller 4 and the PI controller 5 are combined to perform dq conversion, and the output is passed through the PWM generation module to obtain the fourth control signal, thereby realizing closed-loop control of the output voltage of the inverter circuit.

[0091] In addition, when the third control loop switches to the fourth control loop, in order to prevent current shock caused by loop switching, the target load should remain in operation during the loop switching process to maintain power balance. When the loop is switched, the modulation signal when the third control loop is used needs to be recorded, and the fourth control loop is assigned in the first switching cycle when the fourth control loop is used for control.

[0092] Optionally, after switching the control circuit of the inverter circuit from the third control loop to the fourth control loop, the photovoltaic inverter system control method further includes: switching the control loop of the boost converter to the fifth control loop; wherein the control process of the fifth control loop includes: cyclically performing the following operations: obtaining the instantaneous value of the photovoltaic open-circuit voltage and the instantaneous value of the boost current; determining the target value of the photovoltaic open-circuit voltage according to the instantaneous value of the photovoltaic open-circuit voltage and the instantaneous value of the boost current to obtain a third target value; determining the target value of the boost current according to the third target value and the instantaneous value of the photovoltaic open-circuit voltage to obtain a fourth target value; determining a second duty cycle according to an error value between the fourth target value and the instantaneous value of the current of the boost converter; generating a fifth control signal according to the second duty cycle, and sending the fifth control signal to the boost converter.

[0093] like Fig.16 As shown, after the third control loop is switched to the fourth control loop, in order to meet the working requirements of the boost converter in the grid-connected mode, the control loop of the boost converter is switched to the fifth control loop. In the switching process of the control loop of the inverter circuit, the control loop of the boost converter is the second control loop (such as Figure 7 Therefore, when switching the control loop of the boost converter, it is switched from the second control loop to the fifth control loop.

[0094] Among them, Fig.17 As shown, the control process of the fifth control loop is a cyclic control process, that is, the fifth control signal is output to realize the control of the bus voltage, and the fifth control signal is continuously adjusted according to the photovoltaic open-circuit voltage and the boost current of the boost converter, that is, the following operations are performed cyclically: sampling the instantaneous value of the photovoltaic open-circuit voltage (corresponding to Fig.17 In ) and the instantaneous value of the boost current ( ), the target value of the photovoltaic open-circuit voltage is calculated by MPPT (corresponding to Fig.17 In ), that is, determining the target value of the photovoltaic open-circuit voltage according to the instantaneous value of the photovoltaic open-circuit voltage and the instantaneous value of the boost current, and obtaining a third target value ; Compared with the instantaneous value of the photovoltaic open circuit voltage, the error value obtained is Fig.17 The PI controller 6 in the boost current obtains the target value, i.e., the fourth target value (corresponding to Fig.17 In ); the fourth target value is compared with the instantaneous value of the boost current, and then the error value is passed through the PI controller 7 to obtain the duty cycle, and the fifth control signal is obtained after passing through the PWM generation module, and the fifth control signal is sent to the boost converter to control the switch tube in the boost circuit S1Work.

[0095] It should be noted that in order to prevent current shock caused by loop switching, when the second control loop is switched to the fifth control loop, the modulation signal when the second control loop is used needs to be recorded and the modulation signal when the second control loop is used needs to be recorded. Figure 7 The integrator values ​​of PI controller 1 and PI controller 2 in the fourth control loop are recorded, and the first switching cycle of the fourth control loop is assigned to the fourth control loop, that is, the recorded integrator values ​​of PI controller 1 and PI controller 2 are assigned to Fig.17 The integrator values ​​of PI controller 6 and PI controller 7 are shown.

[0096] Alternatively, if Fig.18 As shown, the process of switching the photovoltaic inverter system from the low light operation mode to the grid-connected operation mode includes: when operating in the low light operation mode, if the photovoltaic open circuit voltage is detected Greater than the second preset threshold When the inverter circuit is switched on, the third control loop is used to perform open-loop control on the inverter circuit so that the output voltage of the inverter circuit reaches the grid voltage, that is, the AC voltage follows the grid voltage. When the AC voltage follows the grid voltage, the modulation signal of the current third control loop is recorded, the switch tube between the inverter and the grid is closed, and the third control loop is switched to the fourth control loop of closed-loop control. During the switching process, the modulation signal of the current third control loop recorded in the first switching cycle of using the fourth control loop is assigned to the fourth control loop. After the switching is completed, the modulation signal in the current second control loop is recorded, the target load is controlled to stop working, and the second control loop is switched to the fifth control loop of closed-loop control. During the switching, the modulation signal of the current second control loop recorded in the first switching cycle of using the fourth control loop is assigned to the fifth control loop.

[0097] Optionally, the photovoltaic inverter system includes three operating modes, namely standby mode, low light operation mode, and grid-connected operation mode. The standby mode is a state in which the system is waiting to work. In this mode, the boost converter, inverter circuit, and DC switching power supply are not working, and only the AC switching power supply and AC inverter are in working state to ensure the power supply of the controller. The low light operation mode is a mode in which the system is not connected to the grid when the external light intensity is very low, and the PV energy is used to operate the target load to achieve functions such as dust removal. In this mode, the inverter circuit does not work, and the boost converter circuit, DC switching power supply, AC switching power supply and AC inverter are all in working state. The grid-connected operation mode is a mode in which the light intensity is high enough and the system is normally connected to the grid. In this mode, the entire system is in working state.

[0098] The switching logic of the three operating modes is as follows: Fig.19 As shown, in standby mode, if the photovoltaic open circuit voltage is detected Greater than or equal to the first preset threshold , the photovoltaic inverter system switches from standby mode to low light operation mode.

[0099] If the bus voltage is detected to be lower than the DC switching power supply start threshold in low light operation mode, , the photovoltaic inverter system switches from low-light operation mode to standby mode;

[0100] If the PV open circuit voltage is detected in low light operation mode v pv_oc Greater than or equal to the second preset threshold , the photovoltaic inverter system switches from low-light operation mode to grid-connected operation mode.

[0101] In the grid-connected operation mode, the photovoltaic inverter will work in the MPPT state. At this time, if it is detected that the maximum power of the photovoltaic module is less than the third preset threshold, the photovoltaic inverter system will switch from the grid-connected operation mode to the standby mode.

[0102] When the photovoltaic open-circuit voltage is greater than the first preset threshold, the maximum power of the photovoltaic component is greater than the maximum power of the target load, and when the photovoltaic open-circuit voltage is greater than the second preset threshold, the maximum power of the photovoltaic component is greater than the third preset threshold.

[0103] The switching processes of switching from the standby mode to the low-light operation mode, switching from the low-light operation mode to the standby mode, and switching from the low-light operation mode to the grid-connected operation mode have been explained in the aforementioned embodiments and will not be repeated here.

[0104] Optionally, the switching process from the grid-connected operation mode to the standby mode is as follows: Fig. 20 As shown, in the grid-connected operation mode, the maximum power of the photovoltaic module is detected When it is less than the third preset threshold , the 100-volt inverter system switches to standby mode, first controlling the boost converter to stop working, and at the same time adjusting the bus voltage target value to the lowest grid-connectable bus voltage value During this process, the target load of the DC switching power supply maintains normal operation, and the operation control logic of the target load here is different from the operation control logic of the target load in the low light operation mode.

[0105] When the bus voltage Reduce to After that, the inverter circuit stops working, and the three-phase current output by the inverter circuit , , It will continue to decrease. When it decreases to 0, the switch tube between the inverter circuit and the grid is disconnected; the DC switching power supply continues to work, and the bus voltage will continue to decrease. When the bus voltage Reduced to less than the DC switching power supply turn-on threshold When the DC switching power supply stops working, the target load also stops working, and the system enters "standby mode".

[0106] like Fig.21 As shown, a photovoltaic inverter system control device 2100 provided in an embodiment of the present invention includes:

[0107] The control unit 2110 is used to control the boost converter in the photovoltaic inverter system to start working when the photovoltaic inverter system is in a standby mode and detects that the photovoltaic open-circuit voltage is greater than a first preset threshold value, so as to boost the photovoltaic open-circuit voltage through the boost converter so that the bus voltage in the photovoltaic inverter system rises to a first target value;

[0108] A start-up unit 2120, configured to start a DC switching power supply in the photovoltaic inverter system, wherein the first preset threshold is less than a start-up threshold of the DC switching power supply, and the first target value is greater than the start-up threshold;

[0109] The shut-down unit 2130 is used to shut down the DC switching power supply and control the boost converter to stop working when the bus voltage in the photovoltaic inverter system drops below the start-up threshold, so as to return the photovoltaic inverter to the standby mode.

[0110] The photovoltaic inverter system control device of this embodiment is used to implement the photovoltaic inverter system control method as described above. Its advantages over the prior art are the same as the advantages of the photovoltaic inverter system control method as described above over the prior art, and will not be repeated here.

[0111] Optionally, the control unit is used to control the boost converter in the photovoltaic inverter system to start working in the following manner: sending a first control signal to the boost converter through a first control loop, wherein the first control signal is used to control the operation of the boost converter so that the bus voltage reaches the first target value, and the first control loop is open-loop control.

[0112] Optionally, the photovoltaic inverter system control device is also used to, after sending a first control signal to the boost converter through a first control loop: when it is detected that the boost current in the boost converter is less than a preset current threshold, switch the control loop of the boost converter from the first control loop to a second control loop; and send a second control signal to the boost converter through the second control loop, wherein the second control signal is used to control the operation of the boost converter so that the bus voltage is stabilized at the first target value, and the second control loop is a closed-loop control.

[0113] Optionally, the control process of the second control loop includes: cyclically performing the following operations: obtaining the instantaneous value of the bus voltage and the instantaneous value of the boost current; determining the target value of the boost current according to the error value between the instantaneous value of the bus voltage and the first target value, and obtaining the second target value; determining the first duty cycle according to the error value between the second target value and the instantaneous value of the boost current; generating the second control signal according to the first duty cycle, and sending the second control signal to the boost converter.

[0114] Optionally, the photovoltaic inverter system control device is also used to, after turning on the DC switching power supply in the photovoltaic inverter system, turn on a target load connected to the DC switching power supply and control the workload of the target load when the bus voltage of the photovoltaic inverter is stabilized at the first target value.

[0115] Optionally, the photovoltaic inverter system control device is also used to control the workload of the target load in the following manner when the target load is a fan: obtain the minimum speed and initial speed limit of the fan; control the fan to run at a variable speed between the minimum speed and the initial speed limit; when a drop in the bus voltage is detected, obtain the current speed of the fan; and update the speed limit of the fan from the initial speed limit to the current speed.

[0116] Optionally, the above-mentioned photovoltaic inverter system control device is also used to, after turning on the DC switching power supply in the photovoltaic inverter system: when it is detected that the photovoltaic open-circuit voltage is greater than a second preset threshold, control the inverter circuit in the photovoltaic inverter system to start working through a third control loop, wherein the three control loops are used to generate a third control signal, and the third control signal is used to control the operation of the inverter circuit so that the AC voltage output by the inverter circuit reaches the grid voltage, and the third control loop is an open-loop control.

[0117] Optionally, the photovoltaic inverter system control device is also used to, after the inverter circuit in the photovoltaic inverter system starts working through the third control loop: control the inverter circuit to be connected to the power grid; switch the control circuit of the inverter circuit from the third control loop to the fourth control loop; control the operation of the inverter circuit through the fourth control loop, wherein the fourth control loop is a closed-loop control, the fourth control loop is used to generate a fourth control signal, and the fourth control signal is used to control the operation of the inverter circuit so that the AC voltage output by the inverter circuit is stabilized at the power grid voltage.

[0118] Optionally, the photovoltaic inverter system control device is also used to switch the control loop of the boost converter to a fifth control loop after switching the control circuit of the inverter circuit from the third control loop to the fourth control loop; wherein the control process of the fifth control loop includes: cyclically performing the following operations: obtaining the instantaneous value of the photovoltaic open-circuit voltage and the instantaneous value of the boost current; determining the target value of the photovoltaic open-circuit voltage according to the instantaneous value of the photovoltaic open-circuit voltage and the instantaneous value of the boost current to obtain a third target value; determining the target value of the boost current according to the third target value and the instantaneous value of the photovoltaic open-circuit voltage to obtain a fourth target value; determining a second duty cycle according to an error value between the fourth target value and the instantaneous value of the current of the boost converter; generating a fifth control signal according to the second duty cycle, and sending the fifth control signal to the boost converter.

[0119] like Fig. 22 As shown, an electronic device 2200 provided in an embodiment of the present invention includes a memory 2210 and a processor 2220; the memory 2210 is used to store a computer program; the processor 2220 is used to implement the photovoltaic inverter system control method as described above when executing the computer program.

[0120] In other words, an electronic device 2200 includes a memory 2210 and a processor 2220 coupled to the memory 2210; the memory 2210 is configured to store a computer program; and the processor 2220 is configured to perform the following operations when executing the computer program:

[0121] When the photovoltaic inverter system is in a standby mode and it is detected that the photovoltaic open-circuit voltage is greater than a first preset threshold, control the boost converter in the photovoltaic inverter system to start working, so as to boost the photovoltaic open-circuit voltage through the boost converter so that the bus voltage in the photovoltaic inverter system rises to a first target value;

[0122] Turning on a DC switching power supply in the photovoltaic inverter system, wherein the first preset threshold is less than a turn-on threshold of the DC switching power supply, and the first target value is greater than the turn-on threshold;

[0123] When the bus voltage in the photovoltaic inverter system drops below the start-up threshold, the DC switching power supply is turned off and the boost converter is controlled to stop working, so that the photovoltaic inverter returns to the standby mode.

[0124] An embodiment of the present invention provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the photovoltaic inverter system control method as described above is implemented.

[0125] In other words, a non-volatile computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the processor performs the following operations:

[0126] When the photovoltaic inverter system is in a standby mode and it is detected that the photovoltaic open-circuit voltage is greater than a first preset threshold, control the boost converter in the photovoltaic inverter system to start working, so as to boost the photovoltaic open-circuit voltage through the boost converter so that the bus voltage in the photovoltaic inverter system rises to a first target value;

[0127] Turning on a DC switching power supply in the photovoltaic inverter system, wherein the first preset threshold is less than a turn-on threshold of the DC switching power supply, and the first target value is greater than the turn-on threshold;

[0128] When the bus voltage in the photovoltaic inverter system drops below the start-up threshold, the DC switching power supply is turned off and the boost converter is controlled to stop working, so that the photovoltaic inverter returns to the standby mode.

[0129] An electronic device 2200 that can be used as a server or client of the present invention will now be described, which is an example of a hardware device that can be applied to various aspects of the present invention. Electronic device 2200 is intended to represent various forms of digital electronic computer equipment, such as laptop computers, desktop computers, workbenches, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. Electronic device 2200 can also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples, and are not intended to limit the implementation of the present invention described herein and / or required.

[0130] The electronic device 2200 includes a computing unit that can perform various appropriate actions and processes according to a computer program stored in a read-only memory (ROM) or a computer program loaded from a storage unit into a random access memory (RAM). In the RAM, various programs and data required for the operation of the device can also be stored. The computing unit, ROM, and RAM are connected to each other via a bus. An input / output (I / O) interface is also connected to the bus.

[0131] A person of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment method can be implemented by instructing the relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, the storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc. In the present application, the unit described as a separate component may or may not be physically separated, and the component displayed as a unit may or may not be a physical unit, that is, it may be located in one place, or it may be distributed on multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the embodiment of the present invention. In addition, each functional unit in each embodiment of the present invention can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of a software functional unit.

[0132] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A photovoltaic inverter system control method, characterized in that: include: When the photovoltaic inverter system is in standby mode and it is detected that the photovoltaic open-circuit voltage is greater than a first preset threshold, a boost converter in the photovoltaic inverter system is controlled by a first control loop to start working, so as to boost the photovoltaic open-circuit voltage by the boost converter so that the bus voltage in the photovoltaic inverter system rises to a first target value; Turning on a DC switching power supply in the photovoltaic inverter system, wherein the first preset threshold is less than a turn-on threshold of the DC switching power supply, and the first target value is greater than the turn-on threshold; When the bus voltage in the photovoltaic inverter system drops below the start-up threshold, turning off the DC switching power supply and controlling the boost converter to stop working, so that the photovoltaic inverter returns to the standby mode; When it is detected that the boost current in the boost converter is less than a preset current threshold, the control loop of the boost converter is switched from the first control loop to the second control loop; a second control signal is sent to the boost converter through the second control loop, wherein the second control signal is used to control the operation of the boost converter so that the bus voltage is stabilized at the first target value, and the second control loop is a closed-loop control; Among them, the control process of the second control loop includes: cyclically performing the following operations: obtaining the instantaneous value of the bus voltage and the instantaneous value of the boost current; determining the target value of the boost current according to the error value between the instantaneous value of the bus voltage and the first target value, and obtaining the second target value; determining the first duty cycle according to the error value between the second target value and the instantaneous value of the boost current; generating the second control signal according to the first duty cycle, and sending the second control signal to the boost converter.

2. The photovoltaic inverter system control method according to claim 1, characterized in that: The step of controlling the boost converter in the photovoltaic inverter system to start working by using the first control loop includes: A first control signal is sent to the boost converter through the first control loop, wherein the first control signal is used to control the operation of the boost converter so that the bus voltage reaches the first target value, and the first control loop is an open-loop control.

3. The photovoltaic inverter system control method according to claim 1, characterized in that: After the DC switching power supply in the photovoltaic inverter system is turned on, the photovoltaic inverter system control further includes: When the bus voltage of the photovoltaic inverter is stabilized at the first target value, a target load connected to the DC switching power supply is turned on, and the workload of the target load is controlled.

4. The photovoltaic inverter system control method according to claim 3, characterized in that: In the case where the target load is a fan, the workload of controlling the target load includes: Obtaining the minimum speed and initial speed limit of the fan; Controlling the fan to run at a variable speed between the minimum speed and the initial speed limit; When a drop in the bus voltage is detected, obtaining a current rotation speed of the fan; The rotation speed limit of the fan is updated from the initial rotation speed limit to the current rotation speed.

5. The photovoltaic inverter system control method according to claim 1, characterized in that: After the DC switching power supply in the photovoltaic inverter system is turned on, the photovoltaic inverter system control method further includes: When it is detected that the photovoltaic open-circuit voltage is greater than a second preset threshold, the inverter circuit in the photovoltaic inverter system is controlled by a third control loop to start working, wherein the third control loop is used to generate a third control signal, and the third control signal is used to control the operation of the inverter circuit so that the AC voltage output by the inverter circuit reaches the grid voltage, and the third control loop is an open-loop control.

6. The photovoltaic inverter system control method according to claim 5, characterized in that: After the inverter circuit in the photovoltaic inverter system is controlled to start working by the third control loop, the photovoltaic inverter system control method further includes: Controlling the inverter circuit to be connected to a power grid; Switching the control circuit of the inverter circuit from the third control loop to a fourth control loop; The operation of the inverter circuit is controlled by the fourth control loop, wherein the fourth control loop is a closed-loop control, the fourth control loop is used to generate a fourth control signal, and the fourth control signal is used to control the operation of the inverter circuit so that the AC voltage output by the inverter circuit is stabilized at the grid voltage.

7. The photovoltaic inverter system control method according to claim 6, characterized in that: After switching the control circuit of the inverter circuit from the third control loop to the fourth control loop, the photovoltaic inverter system control method further includes: Switching the control loop of the boost converter to a fifth control loop; The control process of the fifth control loop includes: The following operations are performed in a loop: obtaining the instantaneous value of the photovoltaic open-circuit voltage and the instantaneous value of the boost current; Determining a target value of the photovoltaic open-circuit voltage according to the instantaneous value of the photovoltaic open-circuit voltage and the instantaneous value of the boost current to obtain a third target value; Determining a target value of the boost current according to the third target value and the instantaneous value of the photovoltaic open-circuit voltage to obtain a fourth target value; determining a second duty cycle according to an error value between the fourth target value and the instantaneous value of the current of the boost converter; A fifth control signal is generated according to the second duty cycle, and the fifth control signal is sent to the boost converter.

8. A photovoltaic inverter system control device, characterized in that: include: A control unit, configured to control a boost converter in the photovoltaic inverter system to start working through a first control loop when the photovoltaic inverter system is in a standby mode and detects that the photovoltaic open-circuit voltage is greater than a first preset threshold value, so as to boost the photovoltaic open-circuit voltage through the boost converter so that the bus voltage in the photovoltaic inverter system rises to a first target value; A start-up unit, configured to start a DC switching power supply in the photovoltaic inverter system, wherein the first preset threshold is less than a start-up threshold of the DC switching power supply, and the first target value is greater than the start-up threshold; A shut-down unit, configured to shut down the DC switching power supply and control the boost converter to stop working when the bus voltage in the photovoltaic inverter system drops below the start-up threshold, so as to return the photovoltaic inverter to the standby mode; The device is also used for switching the control loop of the boost converter from the first control loop to the second control loop when detecting that the boost current in the boost converter is less than a preset current threshold; sending a second control signal to the boost converter through the second control loop, wherein the second control signal is used to control the operation of the boost converter so that the bus voltage is stabilized at the first target value, and the second control loop is a closed-loop control; Among them, the control process of the second control loop includes: cyclically performing the following operations: obtaining the instantaneous value of the bus voltage and the instantaneous value of the boost current; determining the target value of the boost current according to the error value between the instantaneous value of the bus voltage and the first target value, and obtaining the second target value; determining the first duty cycle according to the error value between the second target value and the instantaneous value of the boost current; generating the second control signal according to the first duty cycle, and sending the second control signal to the boost converter.

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