Control method and control system of power converter

Abstract

The invention relates to a control method and a control system of a power converter, and relates to the technical field of circuit control, the control system at least comprises a control unit and a transfer unit; the transfer unit is connected between the power converter and the power grid, when the transfer unit is in a closed state, the power converter is connected with the power grid, and when the transfer unit is in an open state, the power converter is isolated from the power grid; the control method comprises the steps that the control unit continuously obtains the current moment and judges whether the current moment is in a preset transfer unit disconnection time period in a current control period or not, and the transfer unit disconnection time period is determined by a sunrise recording moment and a sunset recording moment in a historical control period; and if the current moment is in the switching-off period of the transfer unit, the control unit controls the transfer unit to be in a switching-off state, otherwise, the control unit controls the transfer unit to be in a switching-on state. According to the invention, the connection between the power converter and the power grid can be timely disconnected at night, and the connection between the power converter and the power grid can be timely recovered at daytime.

Description

Technical Field

[0001] The present application relates to the field of circuit control technology, and in particular to a control method and control system for a power converter. Background Art

[0002] In the current household photovoltaic system and photovoltaic storage integrated grid-connected system, the power converter can obtain direct current from the solar photovoltaic panel, convert it into alternating current and then connect it to the grid. When there is sufficient sunlight during the day, the power converter can operate stably and continuously transmit photovoltaic power to the grid. However, at night or when there is insufficient sunlight, the photovoltaic panel no longer generates direct current, and the power converter loses the DC power supply and stops working.

[0003] While photovoltaic panels no longer generate electricity at night, the AC side of the power converter remains connected to the grid, causing the power converter to behave as a capacitive load, which will generate a large amount of reactive power, affecting the power quality of the household grid and reducing the grid's power supply efficiency. At the same time, the reactive power generated at night may also cause line voltage loss and waste of electricity, which will have an adverse impact on household users' electricity use.

[0004] At present, large-scale photovoltaic systems such as industrial and commercial and ground power stations are usually equipped with relatively complete reactive power control and compensation mechanisms, which can effectively deal with the reactive power problems caused by changes in load properties. However, for household photovoltaic systems, since the total photovoltaic power is not large, the negative impact of reactive power on the power grid at night is often ignored. Summary of the invention

[0005] Based on this, it is necessary to provide a control method and control system for a power converter in order to solve the above technical problems.

[0006] In a first aspect, the present application provides a control method for a power converter. The control method is applied to a control system of the power converter, and the control system at least includes a control unit and a transfer unit;

[0007] The transfer unit is connected between the power converter and the power grid. When the transfer unit is in a closed state, the power converter is connected to the power grid. When the transfer unit is in a disconnected state, the power converter is isolated from the power grid.

[0008] The control method comprises:

[0009] The control unit continuously obtains the current time, and determines whether the current time is in a preset transfer unit disconnection period in the current control cycle, wherein the transfer unit disconnection period is determined by the sunrise record time and the sunset record time in the historical control cycle;

[0010] If the current moment is in the disconnection period of the transfer unit, the control unit controls the transfer unit to be in a disconnected state; otherwise, the control unit controls the transfer unit to be in a closed state.

[0011] In one embodiment, the determining whether the current moment is before a preset transfer unit disconnection period in the current control cycle further includes:

[0012] The control unit acquires the real-time state of the power converter and determines the real-time illumination state according to the real-time state of the power converter;

[0013] The determining whether the current moment is in a preset transfer unit disconnection period in the current control cycle includes:

[0014] If the real-time illumination state is a no-illumination state, the control unit determines whether the current moment is in a preset transfer unit disconnection period in the current control cycle;

[0015] If the real-time illumination state is an illumination state, the transfer unit is controlled to be in a closed state.

[0016] In one embodiment, if the current moment is in the disconnection period of the transfer unit, the control unit controls the transfer unit to be in a disconnected state, including:

[0017] If the current moment is in the transfer unit disconnection period, the control unit continuously monitors the real-time illumination state, wherein the real-time illumination state is obtained from the real-time state of the power converter;

[0018] If the real-time illumination state continues to be a no-illumination state, and the duration is longer than a first preset duration, the control unit controls the transfer unit to be in a disconnected state.

[0019] In one embodiment, if the current moment is in the disconnection period of the transfer unit, the control unit controls the transfer unit to be in a disconnected state, including:

[0020] If the current moment is in the transfer unit disconnection period, and the difference between the current moment and the end moment of the transfer unit disconnection period is not less than a second preset duration, the control unit controls the transfer unit to be in a disconnected state.

[0021] In one embodiment, the control method further includes:

[0022] In one control cycle, the control unit continuously obtains the real-time state of the power converter, and determines the real-time illumination state according to the real-time state of the power converter, wherein the real-time illumination state includes an illumination state and a non-illumination state;

[0023] The control unit counts the state switching moments between the illuminated state and the unilluminated state, and selects the sunrise recording moment and the sunset recording moment of the control period from all the state switching moments.

[0024] In one embodiment, the control method further includes:

[0025] For any control cycle, the control unit determines a reference historical control cycle of the control cycle;

[0026] The control unit determines a relay unit disconnection period of the control cycle according to the sunrise record time and the sunset record time of the reference historical control cycle.

[0027] In one embodiment, the control unit determines the transfer unit disconnection period of the control cycle according to the sunrise record time and the sunset record time of the reference historical control cycle, including:

[0028] The control unit obtains the earliest sunrise record time and the latest sunset record time in all the reference historical control cycles;

[0029] The control unit determines a transfer unit disconnection period of the control cycle according to the earliest sunrise recording time and the latest sunset recording time.

[0030] In one of the embodiments, when the power generation power of the power converter is less than a preset power threshold and the power converter is in a communication loss state, the real-time illumination state is a no illumination state;

[0031] When the power generation power of the power converter is not less than a preset power threshold, or the power converter is in a normal communication state, the real-time illumination state is an illumination state.

[0032] In one embodiment, the power converter includes at least one micro-inverter, and the transfer unit is connected between the at least one micro-inverter and a power grid. When the transfer unit is in a closed state, the micro-inverter is connected to the power grid, and when the transfer unit is in a disconnected state, the micro-inverter is isolated from the power grid.

[0033] In one embodiment, the control method further includes:

[0034] When the duration of the transfer unit being in the disconnected state is greater than a third preset duration, the control unit controls the transfer unit to switch to the closed state.

[0035] In a second aspect, the present application also provides a control system for a power converter, the control system comprising at least a control unit and a transfer unit;

[0036] The transfer unit is connected between the power converter and the power grid. When the transfer unit is in a closed state, the power converter is connected to the power grid. When the transfer unit is in a disconnected state, the power converter is isolated from the power grid.

[0037] The control unit is used for:

[0038] Continuously acquiring the current time, and determining whether the current time is in a preset transfer unit disconnection period in the current control cycle, wherein the transfer unit disconnection period is determined by the sunrise record time and the sunset record time in the historical control cycle;

[0039] If the current moment is in the disconnection period of the transfer unit, the transfer unit is controlled to be in a disconnected state; otherwise, the transfer unit is controlled to be in a closed state.

[0040] In a third aspect, the present application further provides a chip, comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the method provided in the first aspect when executing the computer program.

[0041] By adopting the control method of the power converter disclosed in this embodiment, a transfer unit is set between the power converter and the power grid, and the disconnection period of the transfer unit is set according to the historical sunrise time and sunset time, and the control unit controls the on and off state of the transfer unit according to the disconnection period of the transfer unit to achieve the connection or isolation between the power converter and the power grid. In this way, by setting the disconnection period of the transfer unit, the on and off state of the transfer unit can be managed according to the recorded sunrise and sunset time, and the connection state of the power converter and the power grid can be adjusted in time, so that the connection between the power converter and the power grid can be disconnected in time at night, avoiding invalid power loss, reducing the user's electricity cost, and the connection between the power converter and the power grid can be restored in time during the day, ensuring the normal operation of photovoltaic power generation, and greatly optimizing the user's electricity experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related technologies, the drawings required for use in the embodiments or the related technical descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] FIG. 1 is a schematic diagram of a control system of a power converter in one embodiment.

[0044] FIG2 is a schematic flow chart of a control method for a power converter in one embodiment;

[0045] FIG3 is a schematic flow chart of a control method for a power converter in yet another embodiment;

[0046] FIG4 is a schematic flow chart of a method for determining sunrise / sunset recording time in one embodiment;

[0047] FIG5 is a schematic flow chart of a method for determining a transfer unit disconnection period in one embodiment;

[0048] FIG6 is a schematic flow chart of a method for determining a disconnection period of a transfer unit in another embodiment;

[0049] Figure 7 is a structural schematic diagram of a control system of a power converter in yet another embodiment;

[0050] Figure 8 FIG. 4 is a schematic diagram of the structure of a control system of a power converter in another embodiment. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0053] It is understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0054] It can be understood that the “connection” in the following embodiments should be understood as “electrical connection”, “communication connection”, etc. if the connected circuits, modules, units, etc. have electrical signals or data transmission between each other.

[0055] It is understood that the term "based on" used in this application is used to describe one or more factors that affect the determination, and does not exclude other factors that may affect the determination. For example, the phrase "determine A based on B" means that the determination of A can be based entirely or at least partially on factor B, that is, B is a factor that affects the determination of A, but does not exclude that the determination of A is also based on C.

[0056] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the relevant listed items.

[0057] In household photovoltaic systems, power converters become capacitive loads at night, resulting in reactive power. To address this problem, traditional industrial and commercial or large-scale photovoltaic systems are usually equipped with dedicated reactive power generation compensation equipment to maintain the voltage stability of the power grid and avoid the degradation of power quality of the power grid due to excessive reactive power. However, these reactive power generation compensation devices are expensive, bulky, and difficult to install and apply to household photovoltaic systems. Compensating for reactive power is essentially to reduce reactive power loss by adjusting the phase relationship of the grid voltage, which usually requires active power to be drawn from the grid. However, household photovoltaic systems are designed to make full use of solar energy for power generation and reduce the dependence of user families on the grid, but reactive power compensation at night increases the active power burden of the grid, which greatly reduces the energy efficiency of the entire system. The active power consumed by reactive power compensation will also be directly converted into the user's electricity bill expenditure, which is not conducive to saving the user's electricity cost.

[0058] In view of the above problems, an embodiment of the present application provides a control method for a power converter, which can be applied to a control system of a power converter.

[0059] Power converters are power conversion devices used to convert electrical energy from one form to another to achieve energy transmission and control under different power requirements. Power converters can be inverters, micro-inverters, and energy storage converters, etc. Exemplarily, a micro-inverter can convert DC direct current into AC alternating current. The DC end (input) of the micro-inverter is connected to a DC source (photovoltaic module), and the AC end (output) can be connected to an AC grid and an AC device to connect to the grid or supply power to a load. In the embodiments of the present application, the power converter is taken as an inverter in a household photovoltaic system for illustration, and other situations are similar and will be explained where necessary.

[0060] As shown in Figure 1, the control system may at least include a control unit and a transfer unit, wherein the transfer unit is connected between the power converter and the power grid to realize the connection and disconnection of the power converter and the power grid. Specifically, the transfer unit may at least have two states of closing and disconnection, wherein when the transfer unit is in a closed state, the power converter is connected to the power grid, and when the transfer unit is in a disconnected state, the power converter is isolated from the power grid. The transfer unit may be a relay. The control unit may be built with an execution logic for controlling the state switching of the transfer unit, so as to control the transfer unit to perform closing or disconnection processing when the conditions are met. Of course, the control unit may also be used to execute other control logics in the control system, and provide an operation and maintenance channel for the power converter and / or the control system, such as monitoring and controlling the state of the power converter, detecting and warning the failure of related equipment, collecting and analyzing the operation data of the power converter and / or the control system, etc.

[0061] In one embodiment, as shown in FIG2 , a control method for a power converter is provided, comprising the following steps:

[0062] Step 201: The control unit continuously obtains the current time and determines whether the current time is in a preset transfer unit disconnection period in the current control cycle.

[0063] The disconnection period of the transfer unit is determined by the sunrise record time and sunset record time in the historical control cycle. The control cycle can be a specified time length according to the actual operation of the power converter. For the control cycle of the disconnection and closing state of the transfer unit, one control cycle can be one day or multiple consecutive days. In this embodiment, one control cycle is described as one day, and additional supplements will be made for the case of multiple consecutive days where necessary.

[0064] In implementation, the control unit may be pre-set with a transfer unit disconnection period corresponding to the current control cycle to specify the period in which the transfer unit needs to be in a disconnected state in the current control cycle. The transfer unit disconnection period may be determined by the recorded sunrise and sunset times in the historical control cycle. For example, the recorded sunrise and sunset times in the past day or days may be used to generate the transfer unit disconnection period for the day. After configuring the transfer unit disconnection period, the control unit may continuously obtain the current time and determine whether the current time is within the transfer unit disconnection period. It can be understood that the transfer unit disconnection period is generated based on the daily operating rules of the inverter, that is, the time switching between day and night, and mainly refers to the actual time of sunrise and sunset.

[0065] It is worth mentioning that this embodiment chooses to set the disconnection period of the transfer unit according to the sunrise recording time and the sunset recording time, instead of choosing to set the disconnection period of the transfer unit based on the cloud data obtained through the Internet (such as the local sunrise and sunset time, weather forecast, etc.), mainly considering the following two points:

[0066] First, because the installation location of photovoltaic panels may be blocked by buildings, trees or other objects, photovoltaic panels cannot receive sunlight and generate electricity immediately after sunrise, and may not receive sunlight before sunset. Therefore, the sunrise and sunset times in the cloud data cannot be synchronized with the actual power generation of photovoltaic panels. The sunrise and sunset times are only a theoretical time point, and whether the photovoltaic panels start to generate electricity depends on the lighting conditions on site. Therefore, if the opening and closing of the transfer unit is controlled solely by the sunrise and sunset times in the cloud, the power converter will start too early or shut down too late. The disconnection period of the transfer unit generated by the historical sunrise and sunset record times can more accurately reflect the actual lighting conditions.

[0067] Secondly, from the perspective of execution logic, the power converter starts working only when the photovoltaic panels start to generate electricity. Therefore, it is unreasonable to use cloud data to determine the disconnection and closing of the transfer unit. The working status of the household photovoltaic system should depend on the actual power generation of the photovoltaic panels, rather than the theoretical sunrise and sunset information or weather forecast information. Therefore, from a theoretical analysis point of view, the disconnection period of the transfer unit should also be determined based on the actual power generation situation.

[0068] Step 202: If the current moment is in the disconnection period of the transfer unit, the control unit controls the transfer unit to be in a disconnected state; otherwise, the control unit controls the transfer unit to be in a closed state.

[0069] In implementation, if the current moment is in the disconnection period of the transfer unit, the control unit can control the transfer unit to be in a disconnected state, that is, if the transfer unit is currently in a disconnected state, the control unit does not adjust the state of the transfer unit, and if it is in a closed state, the control unit can send a disconnection instruction to the transfer unit. Similarly, if the current moment is not in the disconnection period of the transfer unit, the control unit can control the transfer unit to be in a closed state, that is, if the transfer unit is currently in a closed state, the control unit does not adjust the state of the transfer unit, and if it is in a disconnected state, the control unit can send a closing instruction to the transfer unit.

[0070] By adopting the control method of the power converter disclosed in this embodiment, a transfer unit is set between the power converter and the power grid, and the disconnection period of the transfer unit is set according to the historical sunrise record time and sunset record time, and the control unit controls the on and off state of the transfer unit according to the disconnection period of the transfer unit to achieve the connection or isolation between the power converter and the power grid. In this way, by setting the disconnection period of the transfer unit, the on and off state of the transfer unit can be managed according to the recorded sunrise and sunset time, and the connection state of the power converter and the power grid can be adjusted in time, so that the connection between the power converter and the power grid can be disconnected in time at night, avoiding invalid power loss, reducing the user's electricity cost, and the connection between the power converter and the power grid can be restored in time during the day, ensuring the normal operation of photovoltaic power generation, and greatly optimizing the user's electricity experience. Furthermore, the historical sunrise record time and sunset record time are not a theoretical time point, but a reference data that can reflect the actual power generation situation of the photovoltaic panels, which takes into account the lighting conditions on site, such as the presence of obstructions, the angle of the sun and other factors. The disconnection period of the transfer unit determined based on the sunrise record time and the sunset record time can make the opening and closing of the transfer unit more matched with the actual lighting status of the photovoltaic panels, thereby reducing the situation where the power converter is connected to the grid too early or disconnected from the grid too late.

[0071] In one embodiment, the opening and closing state of the transfer unit can be controlled preferentially according to the real-time lighting state. As shown in FIG3 , the following processing may exist before step 201: In step 200 , the control unit obtains the real-time state of the power converter and determines the real-time lighting state according to the real-time state of the power converter.

[0072] In implementation, in a household photovoltaic system, the power converter converts the direct current generated by the photovoltaic panel into alternating current and transmits it to the power grid. When the light conditions change, the working state of the power converter will also be affected. Therefore, the control unit can monitor the operating state of the power converter in real time and determine the real-time light state through the real-time state of the power converter.

[0073] Based on the above processing, the processing of step 201 may include:

[0074] Step 201a: if the real-time illumination state is a no-illumination state, the control unit determines whether the current moment is in a preset transfer unit disconnection period in the current control cycle.

[0075] Step 201b: if the real-time illumination state is an illumination state, the control unit controls the transfer unit to be in a closed state.

[0076] Based on the above processing, it is possible to effectively avoid the situation where the electric energy generated by the household photovoltaic system cannot be transmitted to the power grid due to the disconnection of the transfer unit in the light state, thereby ensuring the energy utilization rate of the household photovoltaic system.

[0077] It should be noted that when determining the real-time illumination state, it can be mainly judged by the power generation power and communication state of the power converter. Specifically, when the illumination is insufficient, the power generation power of the power converter will be greatly reduced, even close to zero. At this time, the control unit can judge the real-time illumination state by detecting the power generation power of the power converter, that is, when the power generation power of the power converter is lower than the preset power threshold, the illumination is weak, and the photovoltaic panel cannot effectively generate electricity. The preset power threshold here can be a preset minimum effective power generation value.

[0078] In some scenarios, relying solely on the generated power may not be enough to accurately determine the lighting status, because the generated power may be affected by factors such as device performance and environmental conditions. Therefore, the communication status between the power converter and the control unit can be considered at the same time. For example, if the power converter is detected to be in a communication loss state, it may indicate that the device cannot work properly. When the above two situations occur at the same time, that is, when the power generated by the power converter is less than the preset power threshold and the communication is lost, the control unit can determine that the real-time lighting status is a no-light state.

[0079] In contrast, when the power generation of the power converter exceeds the preset power threshold, it means that the photovoltaic panel is receiving enough light and the household photovoltaic system is in normal working condition, so the control unit can determine that the real-time light state is in the light state. When the communication between the power converter and the control unit is normal, the control unit can obtain the operating status and power generation of the power converter in time, thereby ensuring the operating stability of the household photovoltaic system. Therefore, even if the power generation of the power converter is lower than the preset power threshold, as long as the communication status is normal, the control unit can also obtain accurate light information.

[0080] In this way, combining the dual judgment criteria of power generation threshold and communication status, the control unit can accurately judge the real-time lighting status of the household photovoltaic system when the lighting changes and the equipment status is different, which not only improves the operating efficiency of the household photovoltaic system, but also avoids unnecessary power loss.

[0081] In one embodiment, during the period when the relay unit is disconnected, the real-time lighting status may also be considered to control the opening and closing status of the relay unit. Accordingly, part of the processing of step 202 may be as follows: if the current moment is in the period when the relay unit is disconnected, the control unit continuously monitors the real-time lighting status; if the real-time lighting status continues to be a no-light state, and the duration is greater than the first preset duration, the control unit controls the relay unit to be in a disconnected state.

[0082] In implementation, as described above, the real-time state of the power converter can reflect the power generation capacity of the photovoltaic panel, and the power generation capacity is directly determined by the light intensity. Therefore, the control unit can determine the real-time light state by reading and analyzing the real-time state of the power converter, so it can be set that after entering the transfer unit disconnection period, the control unit continues to monitor the real-time light state. When the control unit determines that the current state is no light, it can continue to monitor the real-time light state to the first preset time. If it is in the no light state within the first preset time, the control unit can control the transfer unit from the closed state to the disconnected state. It can be understood that the setting of the first preset time is to avoid misjudgment of the light state due to short-term light fluctuations or equipment delays. For example, in some cases, cloud cover may cause a short-term no light state, and at this time it is not necessary to disconnect the power converter and the power grid. The first preset time can be set to 15min, 30min, etc., which can be obtained based on the empirical data of light changes in different regions at different times.

[0083] In one embodiment, if the disconnection period of the transit unit is about to end, the transit unit can be controlled to close in advance. Accordingly, part of the processing of step 202 can be as follows: if the current moment is in the disconnection period of the transit unit, and the difference between the current moment and the end moment of the disconnection period of the transit unit is not less than the second preset duration, the control unit controls the transit unit to be in a disconnected state.

[0084] In implementation, if the control unit detects that the preset transfer unit disconnection period has been entered, it can determine the difference between the current time and the end time of the transfer unit disconnection period. For example, if the transfer unit disconnection period is "18:00 to 6:00 the next day", then the end time is 6:00. If the current time is 3:00, the difference is 3h. If the current time is 8:00, it is not in the transfer unit disconnection period, so no difference judgment is performed. Afterwards, the control unit can compare the difference with the second preset duration. If the difference is not less than the second preset duration, the transfer unit can be controlled to be in a disconnected state. Otherwise, the transfer unit can be controlled to enter a closed state. Here, the second preset duration can be understood as the redundant buffer time of the transfer unit disconnection period, which can be set to 0.5h, 1h, etc. It can be imagined that if there are errors in the statistics of historical sunrise and sunset, or if the current sunrise is ahead of schedule, the disconnection period of the transfer unit will not match the actual sunrise and sunset. If the sun rises before the end of the disconnection period of the transfer unit, the transfer unit fails to close, and the electricity generated by the photovoltaic panels cannot be output to the power grid in time, resulting in low energy utilization. However, by setting the redundant buffer time (i.e., the second preset duration mentioned above), the closure of the transfer unit can be controlled in advance, which can effectively deal with the above situation and make full use of the light resources to realize photovoltaic power generation.

[0085] In one embodiment, the sunrise recording time and the sunset recording time may be determined by the real-time state of the power converter. Accordingly, there may be a process as shown in FIG. 4 , including the following steps:

[0086] Step 401: within a control cycle, the control unit continuously obtains the real-time state of the power converter, and determines the real-time illumination state according to the real-time state of the power converter.

[0087] Among them, the real-time illumination state includes an illumination state and a non-illumination state;

[0088] In implementation, within a control cycle, the control unit can continuously obtain the real-time state of the power converter, which may include parameters such as input voltage, output power, and current to reflect the power generation of the photovoltaic panel. The power generation of the photovoltaic panel is related to the real-time illumination state, so according to the real-time state of the power converter, the control unit can determine the current real-time illumination state, that is, the illumination state or the non-illumination state.

[0089] Step 402 , the control unit counts the state switching moments between the illuminated state and the non-illuminated state, and selects the sunrise recording moment and the sunset recording moment of the control period from all the state switching moments.

[0090] In implementation, during the entire control cycle, the change in the lighting state is not only related to sunrise and sunset, but also to weather changes (such as cloud cover, cloudy or rainy weather), the presence of obstructions (such as buildings, trees, etc.), the presence of fallen leaves and snow, etc., which will cause the real-time lighting state to change. Therefore, the control unit can count the state switching moments of the real-time lighting state from "no lighting state" to "light state" and from "light state" to "no lighting state", forming a series of state switching moments within a control cycle. Afterwards, among all the state switching moments counted, the control unit can select the sunrise recording moment (corresponding to a certain moment when the "no lighting state" switches to the "light state") and the sunset recording moment (corresponding to the moment when the "light state" switches to the "no lighting state") within the control cycle according to the time sequence and actual conditions. Specifically, the control unit may first determine the estimated sunrise time and the estimated sunset time of the current control cycle. The estimated sunrise time and the estimated sunset time may be the time when sunrise and sunset may occur in the current control cycle, and may be determined by the recorded sunrise time and sunset time of the historical control cycle, or may be determined based on the cloud data obtained through the Internet. Afterwards, the control unit may select the earliest state switching time from "no light state" to "light state" as the sunrise recording time, and the latest state switching time from "light state" to "no light state" as the sunset recording time within the adjacent time period of the estimated sunrise time (such as 1 hour before and after). In this way, the control unit can accurately identify and record the sunrise and sunset times within the control cycle based on the real-time state changes of the power converter, thereby achieving precise control of the photovoltaic system.

[0091] In one embodiment, the disconnection period of the transfer unit in one control cycle may be determined by the sunrise and sunset times of multiple control cycles. Accordingly, there may be a process as shown in FIG. 5 , including the following steps:

[0092] Step 501: For any control cycle, the control unit determines a reference historical control cycle of the control cycle.

[0093] In implementation, for any control cycle, the control unit can first determine the reference historical control cycle of the control cycle. The reference historical control cycle can be one or more control cycles that have ended before, and its environmental conditions (such as season, weather, etc.) should be similar to the environmental conditions of the control cycle. For example, a reference historical control cycle with the same season and the same weather (such as all sunny days, or all thunderstorms, etc.) can be selected, or it can be multiple control cycles with close time to the control cycle. For example, if a control cycle is 1 day, the reference historical control cycle can be multiple days in the past (a week, 15 days or a month, etc.). Of course, the reference historical control cycle can also be multiple control cycles that meet the requirements of close time and similar environmental conditions. This embodiment does not limit the method for judging the similarity of environmental conditions, and can adopt existing evaluation methods for multiple environmental conditions.

[0094] Step 502: The control unit determines the transfer unit disconnection period of the control cycle according to the sunrise record time and sunset record time of the reference historical control cycle.

[0095] In implementation, the control unit can obtain the sunrise record time and sunset record time of the reference historical control cycle, and then determine the transfer unit disconnection time of the control cycle based on all the sunrise record times and all the sunset record times obtained. In this way, for any control cycle, the transfer unit disconnection period is determined according to the sunrise and sunset times recorded in the reference historical control cycle, so that the transfer unit disconnection period can be more closely matched to the actual sunrise and sunset conditions of the control cycle, thereby effectively improving the control effect of the power converter and optimizing the overall performance of the household photovoltaic system.

[0096] It should be noted that if multiple control cycles with close time are selected as reference historical control cycles, each time a new control cycle arrives, a new reference historical control cycle data will be added, and the earliest reference historical control cycle data will be automatically overwritten. In this way, the transfer unit disconnection period can have a certain dynamic adjustment capability, that is, as the lighting conditions of each control cycle are recorded and integrated into the entire reference historical control cycle, the control unit can continuously update and optimize the judgment of the sunrise and sunset times. It is not difficult to understand that with the alternation of seasons, the time of sunrise and sunset will change, and the dynamic setting of multiple reference historical control cycles can smoothly cope with these changes. The latest data of each control cycle will participate in the calculation of the transfer unit disconnection period of the next control cycle, so that an accurate period model can be gradually formed, which can enable the control unit to gradually adjust the transfer unit disconnection period when facing multiple influencing factors such as seasonal changes and weather fluctuations, so that it is more in line with the current actual lighting conditions, ensuring that the setting of the transfer unit disconnection period remains flexible enough.

[0097] In addition, this dynamic adjustment capability does not require complex algorithm support and does not rely on external data sources. The control unit can adjust itself only through local lighting history records, which can simplify the design of the control unit and reduce maintenance costs, while improving the accuracy and flexibility of setting the disconnection period of the transit unit.

[0098] In one embodiment, the disconnection period of the transfer unit may be determined by referring to the maximum value of the sunrise and sunset times in the historical control cycle. Accordingly, as shown in FIG6 , step 502 may include the following processing:

[0099] Step 5021: The control unit obtains the earliest sunrise record time and the latest sunset record time in all reference historical control cycles.

[0100] In implementation, by comparing the reactive power generated by the power converter at night and the photovoltaic power generation during the day, it can be considered that the utilization rate of the light resources should be maximized, that is, the transfer unit should be in a closed state when there is light as much as possible, and the transfer unit should be in a disconnected state when there is no light. Therefore, after obtaining the sunrise record time and sunset record time of the reference historical control period, the earliest sunrise record time and the latest sunset record time can be determined from them to maximize the use of daytime light resources. For example, there are three reference historical control periods A, B, and C, and the sunrise record time of the reference historical control period A is 6:00, the sunrise record time of B is 6:05, and the sunrise record time of C is 5:58, then the earliest sunrise record time can be determined to be 5:58. If a control cycle contains multiple days, there may be multiple sunrise record times in a reference historical control cycle. Then, for multiple reference historical control periods, the earliest sunrise record time can be the earliest sunrise record time in all reference historical control periods; similarly, the latest sunset record time can be the latest sunset record time in all reference historical control periods.

[0101] Step 5022: The control unit determines the transfer unit disconnection period of the control cycle according to the earliest sunrise record time and the latest sunset record time.

[0102] In implementation, the control unit can determine the transit unit disconnection period of the control cycle based on the earliest sunrise record time and the latest sunset record time. Specifically, the start time of the transit unit disconnection period can be the latest sunset record time, or other adjacent times selected based on the latest sunset record time (such as 10 minutes in advance or 20 minutes later relative to the latest sunset record time, etc.); similarly, the end time of the transit unit disconnection period can be the earliest sunrise record time, or other adjacent times selected based on the earliest sunrise record time (such as 10 minutes in advance or 20 minutes later relative to the earliest sunrise record time, etc.). Of course, if there are multiple transit unit disconnection periods in a control cycle, the start or end time of each transit unit disconnection period can be obtained from the earliest sunrise record time or the latest sunset record time. For example, a control cycle starts at 00:00 in the morning of one day and ends at 12:00 in the morning of the next day. The earliest sunrise record time is 6:00 and the latest sunset record time is 18:00. Then there can be two transfer unit disconnection periods in a control cycle, "00:00-6:00" and "18:00-24:00". It can be seen that the end time of the first transfer unit disconnection period is obtained by the earliest sunrise record time, and the start time of the second transfer unit disconnection period can be obtained by the latest sunset record time.

[0103] Further, such as Figure 7 As shown, the power converter may include at least one micro-inverter, the power input end of each micro-inverter may be connected to a photovoltaic panel, the power output ends of all micro-inverters may be connected to the power grid through a transfer unit, and the control unit may control the connection and isolation of the micro-inverter and the power grid by controlling the closed or open state of the transfer unit. In another embodiment, as Figure 8 As shown, a control unit can be connected to multiple transfer units, each transfer unit can be connected between at least one micro inverter and the grid, and the control unit can achieve connection and isolation of different groups of micro inverters and the grid through the closed and open states of different transfer units.

[0104] In one embodiment, under some abnormal working conditions, the transfer unit may enter an abnormal disconnected state, thereby affecting the normal operation of the household photovoltaic system and its effective connection with the power grid. To prevent the transfer unit from entering an abnormal disconnected state due to system abnormalities or unexpected situations, the following abnormal protection strategy can be used to ensure the stability and reliability of the household photovoltaic system:

[0105] 1. Abnormal protection strategy when the system time jump exceeds the threshold:

[0106] During the operation of a household photovoltaic system, if the system time jumps due to some reason, and the amplitude of the time jump exceeds the preset threshold, it may affect the normal control operation of the transfer unit. In this regard, it can be set that when the system time jump is detected to exceed the preset threshold, the control unit controls the transfer unit to enter a closed state to ensure that the power converter remains connected to the grid during the time jump, avoiding the problem of the system being unable to generate electricity or power transmission being interrupted due to the disconnection of the transfer unit. Afterwards, the control unit can re-collect relevant data on the current environment and equipment status (such as power generation, light status, etc.), and re-execute the control strategy based on the collected data, so that after the time jump, it can quickly restore to normal control logic.

[0107] 2. Automatic closing strategy after the transfer unit is disconnected for a long time:

[0108] In some abnormal situations, the transfer unit may be in a disconnected state for a long time due to an abnormal accident, resulting in a long-term interruption of the connection between the household photovoltaic system and the power grid, which in turn affects the normal power generation and power transmission of the household photovoltaic system. Therefore, the control unit can continuously monitor the duration of the transfer unit being in a disconnected state and set a threshold (which can be called a third preset duration). If the duration exceeds the third preset duration, the control unit can actively control the transfer unit to switch to a closed state so that the power converter can reconnect to the power grid and resume normal operation.

[0109] 3. Transfer unit closing protection strategy under abnormal power failure or reset conditions:

[0110] During the operation of the household photovoltaic system, abnormal conditions such as system power failure and reset may occur. If the transfer unit is in a disconnected state, the household photovoltaic system will not be able to immediately restore the connection with the grid, resulting in the impact on normal power generation and power transmission. In this way, when the control unit detects the above abnormal conditions, the control unit can control the transfer unit to remain in a closed state during the current control cycle to ensure that after the household photovoltaic system is restarted, the power converter can still maintain connection with the grid, ensuring the continuity of power generation and power transmission.

[0111] 4. Closing protection strategy for transfer units after long-term non-use of the system:

[0112] In some cases, the household photovoltaic system may not be used for a long time, such as maintenance or shutdown. In this case, the control unit can control the transfer unit to close when the household photovoltaic system restarts. This ensures that the household photovoltaic system is quickly reconnected to the grid and restarts power generation. After that, the control unit can re-collect the current environmental data and equipment status, and execute the aforementioned control strategy based on the re-collected data.

[0113] It should be understood that, although the steps in the flowcharts involved in the above embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps is not strictly limited in order, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above embodiments may include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0114] Based on the same inventive concept, an embodiment of the present application further provides a control system for a power converter, the control system at least comprising a control unit and a transfer unit;

[0115] The transfer unit is connected between the power converter and the power grid. When the transfer unit is in a closed state, the power converter is connected to the power grid. When the transfer unit is in a disconnected state, the power converter is isolated from the power grid.

[0116] The control unit is used for:

[0117] Continuously acquiring the current time, and determining whether the current time is in a preset transfer unit disconnection period in the current control cycle, wherein the transfer unit disconnection period is determined by the sunrise record time and the sunset record time in the historical control cycle;

[0118] If the current moment is in the disconnection period of the transfer unit, the transfer unit is controlled to be in a disconnected state; otherwise, the transfer unit is controlled to be in a closed state.

[0119] In one embodiment, the control unit is further configured to:

[0120] Acquiring a real-time state of a power converter, and determining a real-time illumination state according to the real-time state of the power converter;

[0121] If the real-time illumination state is a no-illumination state, it is determined whether the current moment is in a preset transfer unit disconnection period in the current control cycle, otherwise the transfer unit is controlled to be in a closed state.

[0122] In one embodiment, the control unit is specifically used for:

[0123] If the current moment is in the transfer unit disconnection period, continuously monitoring the real-time illumination state, wherein the real-time illumination state is obtained from the real-time state of the power converter;

[0124] If the real-time illumination state continues to be a no-illumination state, and the duration is longer than a first preset duration, the transfer unit is controlled to be in a disconnected state.

[0125] In one embodiment, the control unit is specifically used for:

[0126] If the current moment is in the transfer unit disconnection period, and the difference between the current moment and the end moment of the transfer unit disconnection period is not less than a second preset duration, the transfer unit is controlled to be in a disconnected state.

[0127] In one embodiment, the control unit is further configured to:

[0128] In a control cycle, continuously acquiring a real-time state of the power converter, and determining a real-time illumination state according to the real-time state of the power converter, wherein the real-time illumination state includes an illumination state and a non-illumination state;

[0129] The state switching moments between the illuminated state and the non-illuminated state are counted, and the sunrise recording moment and the sunset recording moment of the control period are selected from all the state switching moments.

[0130] In one embodiment, the control unit is further configured to:

[0131] For any control cycle, determining a reference historical control cycle of the control cycle;

[0132] The transfer unit disconnection period of the control cycle is determined according to the sunrise record time and the sunset record time of the reference historical control cycle.

[0133] In one embodiment, the control unit is specifically used for:

[0134] Obtaining the earliest recorded sunrise time and the latest recorded sunset time in all the reference historical control periods;

[0135] The transfer unit disconnection period of the control cycle is determined according to the earliest sunrise recording time and the latest sunset recording time.

[0136] In one of the embodiments, when the power generation power of the power converter is less than a preset power threshold and the power converter is in a communication loss state, the real-time illumination state is a no illumination state;

[0137] When the power generation power of the power converter is not less than a preset power threshold, or the power converter is in a normal communication state, the real-time illumination state is an illumination state.

[0138] In one embodiment, the power converter includes at least one micro-inverter, and the transfer unit is connected between the at least one micro-inverter and a power grid. When the transfer unit is in a closed state, the micro-inverter is connected to the power grid, and when the transfer unit is in a disconnected state, the micro-inverter is isolated from the power grid.

[0139] In one embodiment, the control unit is further configured to:

[0140] When the duration of the transfer unit being in the disconnected state is greater than a third preset duration, the control unit controls the transfer unit to switch to the closed state.

[0141] An embodiment of the present application further provides a chip, which includes a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps in the above-mentioned method embodiments when executing the computer program.

[0142] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps in the above-mentioned method embodiments are implemented.

[0143] In one embodiment, a computer program product is provided, including a computer program, which implements the steps in the above method embodiments when executed by a processor.

[0144] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant regulations.

[0145] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The processor involved in each embodiment provided in this application can be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic unit, a data processing logic unit based on quantum computing, etc., but is not limited thereto.

[0146] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0147] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A control method for a power converter, characterized in that: A control system applied to the power converter, the control system comprising at least a control unit and a transfer unit; The transfer unit is connected between the power converter and the power grid. When the transfer unit is in a closed state, the power converter is connected to the power grid. When the transfer unit is in a disconnected state, the power converter is isolated from the power grid. The control method comprises: The control unit continuously obtains the current time, and determines whether the current time is in a preset transfer unit disconnection period in the current control cycle, wherein the transfer unit disconnection period is determined by the sunrise record time and the sunset record time in the historical control cycle; If the current moment is in the disconnection period of the transfer unit, the control unit controls the transfer unit to be in a disconnected state; otherwise, the control unit controls the transfer unit to be in a closed state.

2. The control method of the power converter according to claim 1, characterized in that: The determining whether the current moment is before a preset transfer unit disconnection period in the current control cycle also includes: The control unit acquires the real-time state of the power converter and determines the real-time illumination state according to the real-time state of the power converter; The determining whether the current moment is in a preset transfer unit disconnection period in the current control cycle includes: If the real-time illumination state is a no-illumination state, the control unit determines whether the current moment is in a preset transfer unit disconnection period in the current control cycle; If the real-time illumination state is an illumination state, the transfer unit is controlled to be in a closed state.

3. The control method of the power converter according to claim 1, characterized in that: If the current moment is in the disconnection period of the transfer unit, the control unit controls the transfer unit to be in a disconnected state, including: If the current moment is in the transfer unit disconnection period, the control unit continuously monitors the real-time illumination state, wherein the real-time illumination state is obtained from the real-time state of the power converter; If the real-time illumination state continues to be a no-illumination state, and the duration is longer than a first preset duration, the control unit controls the transfer unit to be in a disconnected state.

4. The control method of the power converter according to claim 1, characterized in that: If the current moment is in the disconnection period of the transfer unit, the control unit controls the transfer unit to be in a disconnected state, including: If the current moment is in the transfer unit disconnection period, and the difference between the current moment and the end moment of the transfer unit disconnection period is not less than a second preset duration, the control unit controls the transfer unit to be in a disconnected state.

5. The control method of the power converter according to claim 1, characterized in that: The control method further comprises: In one control cycle, the control unit continuously obtains the real-time state of the power converter, and determines the real-time illumination state according to the real-time state of the power converter, wherein the real-time illumination state includes an illumination state and a non-illumination state; The control unit counts the state switching moments between the illuminated state and the unilluminated state, and selects the sunrise recording moment and the sunset recording moment of the control period from all the state switching moments.

6. The control method of the power converter according to claim 5, characterized in that: The control method further comprises: For any control cycle, the control unit determines a reference historical control cycle of the control cycle; The control unit determines a relay unit disconnection period of the control cycle according to the sunrise record time and the sunset record time of the reference historical control cycle.

7. The control method of the power converter according to claim 6, characterized in that: The control unit determines the transfer unit disconnection period of the control cycle according to the sunrise record time and the sunset record time of the reference historical control cycle, including: The control unit obtains the earliest sunrise record time and the latest sunset record time in all the reference historical control cycles; The control unit determines a transfer unit disconnection period of the control cycle according to the earliest sunrise recording time and the latest sunset recording time.

8. The control method of a power converter according to any one of claims 2-3 and 5-7, characterized in that: When the power generated by the power converter is less than a preset power threshold and the power converter is in a communication loss state, the real-time illumination state is a no-illumination state; When the power generation power of the power converter is not less than a preset power threshold, or the power converter is in a normal communication state, the real-time illumination state is an illumination state.

9. The control method of a power converter according to any one of claims 1 to 7, characterized in that: The power converter includes at least one micro-inverter, and the transfer unit is connected between the at least one micro-inverter and the power grid. When the transfer unit is in a closed state, the micro-inverter is connected to the power grid, and when the transfer unit is in a disconnected state, the micro-inverter is isolated from the power grid.

10. The control method of a power converter according to claim 1, characterized in that: The control method further comprises: When the duration of the transfer unit being in the disconnected state is greater than a third preset duration, the control unit controls the transfer unit to switch to the closed state.

11. A control system for a power converter, characterized in that: The control system at least includes a control unit and a transfer unit; The transfer unit is connected between the power converter and the power grid. When the transfer unit is in a closed state, the power converter is connected to the power grid. When the transfer unit is in a disconnected state, the power converter is isolated from the power grid. The control unit is used for: Continuously acquiring the current time, and determining whether the current time is in a preset transfer unit disconnection period in the current control cycle, wherein the transfer unit disconnection period is determined by the sunrise record time and the sunset record time in the historical control cycle; If the current moment is in the disconnection period of the transfer unit, the transfer unit is controlled to be in a disconnected state; otherwise, the transfer unit is controlled to be in a closed state.

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