Photovoltaic reverse power control device and control method thereof

Abstract

The invention discloses a photovoltaic reverse power control device and a control method thereof, the photovoltaic reverse power control device is installed at a grid-connected point of a photovoltaic inverter and electric equipment, and the control method comprises the following steps: detecting power generation parameters of all photovoltaic inverters connected with the grid-connected point; when the grid-connected point power at the grid-connected point is negative, distributing all the photovoltaic inverters to operate in a first distribution mode or a second distribution mode according to the power generation parameters; in the first distribution mode, all the photovoltaic inverters limit the current output power in proportion; and in the second distribution mode, the photovoltaic inverter limits the current output power according to a threshold interval in which the current output power is located. Compared with the prior art, by detecting the power of the grid-connected point and combining the power generation parameters of the photovoltaic inverters, reverse power control can be carried out on a plurality of different photovoltaic inverters, and photovoltaic residual power is prevented from surfing the internet.

Description

Technical Field

[0001] The invention relates to a photovoltaic system, in particular to a photovoltaic reverse power control device and a control method thereof. Background Art

[0002] At present, the application of distributed photovoltaic systems at home and abroad is increasing year by year. Its common grid-connected modes include surplus power grid-connected, pure grid-connected and self-use. The first two forms are more common in applications. For some special scenarios, it is necessary to require that the photovoltaic power be self-generated and self-used within a certain area, and the excess power is not allowed to be fed back to the upper power grid through the distribution transformer. In some areas, the power grid has tended to be saturated, and power supply companies generally require that the power generated by newly added photovoltaic power generation systems is not allowed to enter the power grid to avoid affecting the voltage, current and frequency of the power grid, generating harmonics and reactive power, causing instability in the power grid, and thus avoiding damage to the equipment in the power grid.

[0003] The existing products of anti-backflow control system on the market are mainly divided into two types: non-intelligent and intelligent. Once the non-intelligent anti-backflow control system detects reverse power at the grid, it immediately operates the contactor to disconnect all electrical connections on the photovoltaic side. It communicates with multiple photovoltaic inverters simultaneously through RS485 communication. When reverse power is detected at the grid and according to the size of the reverse power, the electrical connections of some inverters are selectively closed and disconnected. Among them, patent CN 102097817A adopts an intelligent control method. The main disadvantage of this control method is that the photovoltaic inverter needs to be switched back and forth at the electrical level to achieve reverse power control. Such a hard-cut operation is harmful to the life of such equipment as photovoltaic inverters, and the sudden output of the photovoltaic inverter means that the grid needs to instantly supplement the power gap, which is easy to affect the stability of the grid. Patent CN 103138282 A optimizes this problem. The photovoltaic inverter of this patent monitors the current of the load through an additional current transformer. When the current of the load is less than the output current of the photovoltaic inverter, the output power of the inverter is reduced to avoid power transmission to the grid. This reverse power control method does not require the photovoltaic inverter to be switched on and off, and the reverse power at the grid connection point can be suppressed online. However, this method can only ensure that a single photovoltaic inverter itself does not transmit power to the grid. When multiple types of inverters from different manufacturers in the system work at the same time, it is difficult to ensure that reverse power will not occur at the grid connection point.

[0004] Therefore, how to design a photovoltaic reverse power control device and a control method thereof, which can distribute the reverse power of multiple photovoltaic inverters, is a technical problem that needs to be solved urgently in the industry. Summary of the invention

[0005] In view of the prior art, the photovoltaic reverse power control method can only ensure that a single photovoltaic inverter itself does not transmit power to the power grid. When multiple photovoltaic inverters work at the same time, it is difficult to ensure that there is no reverse power problem at the grid connection point. The present invention proposes a photovoltaic reverse power control device and a control method thereof.

[0006] The technical solution of the present invention is to propose a control method for a photovoltaic reverse power control device, wherein the photovoltaic reverse power control device is installed at a grid connection point between a photovoltaic inverter and an electrical device, and is characterized in that the control method comprises:

[0007] Detecting power generation parameters of all photovoltaic inverters connected to the grid connection point;

[0008] When the grid connection point power at the grid connection point is negative, allocating all the photovoltaic inverters to operate in a first allocation mode or a second allocation mode according to the power generation parameters;

[0009] And in the first allocation mode, all the photovoltaic inverters limit the current output power proportionally;

[0010] In the second allocation mode, the photovoltaic inverter limits the current output power according to a threshold interval in which the current output power is located.

[0011] Further, the power generation parameters include the maximum power generation power of the photovoltaic inverter, the minimum power generation power of the photovoltaic inverter, and the rated output power of the photovoltaic inverter;

[0012] The step of allocating all the photovoltaic inverters to operate in the first allocation mode or the second allocation mode according to the power generation parameters includes:

[0013] Calculating the difference between the maximum power generation and the minimum power generation of each photovoltaic inverter;

[0014] Determining whether the difference is greater than a threshold output power;

[0015] When the determination is yes, setting the current photovoltaic inverter as the first photovoltaic inverter;

[0016] The number of first photovoltaic inverters is obtained, and when the number of the first photovoltaic inverters is greater than a preset threshold, all the photovoltaic inverters are controlled to operate in a first allocation mode.

[0017] Furthermore, the step of allocating all the photovoltaic inverters to operate in the first allocation mode or the second allocation mode according to the power generation parameters further includes:

[0018] When it is determined that the difference is less than the threshold output power, setting the current photovoltaic inverter as a second photovoltaic inverter;

[0019] The number of the second photovoltaic inverters is obtained, and when the number of the second photovoltaic inverters is greater than a preset threshold, all the photovoltaic inverters are controlled to operate in a second allocation mode.

[0020] Furthermore, the allocation method of the first allocation mode is:

[0021] Detecting the current output power of all the photovoltaic inverters, and obtaining the ratio between the current output powers of all the photovoltaic inverters;

[0022] The grid-connected point power is distributed to all the photovoltaic inverters so that the sum of the current output powers limited by all the photovoltaic inverters is the grid-connected point power, and the ratio between the current output powers limited by all the photovoltaic inverters is consistent with the ratio between the current output powers.

[0023] Furthermore, the allocation method of the second allocation mode is:

[0024] Detecting the current output power of all the photovoltaic inverters, and determining the threshold interval of the current output power of each photovoltaic inverter;

[0025] Each of the photovoltaic inverters limits the current output power according to the threshold range in which the current output power is located.

[0026] Further, the threshold interval includes a first threshold interval, a second threshold interval, and a third threshold interval;

[0027] In the first threshold interval, the current output power of the photovoltaic inverter is greater than 60% of the rated output power of the photovoltaic inverter;

[0028] In the second threshold interval, the current output power of the photovoltaic inverter is between 30% and 60% of the rated output power of the photovoltaic inverter;

[0029] In the third threshold interval, the current output power of the photovoltaic inverter is less than 30% of the rated output power of the photovoltaic inverter.

[0030] Furthermore, each of the photovoltaic inverters limits the current output power according to the threshold range in which the current output power thereof is located, including:

[0031] When the current output power is within the first threshold interval, the limit value of the current output power is 10% of the rated output power of the photovoltaic inverter;

[0032] When the current output power is within the second threshold interval, the limit value of the current output power is 5% of the rated output power of the photovoltaic inverter;

[0033] When the current output power is within the third threshold interval, the limit value of the current output power is 2.5% of the rated output power of the photovoltaic inverter.

[0034] Further, when the grid connection point power at the grid connection point is positive, the control method further includes:

[0035] Detecting the current output power of all the photovoltaic inverters, and determining the threshold interval of the current output power of each photovoltaic inverter;

[0036] Each of the photovoltaic inverters increases the current output power according to the threshold range in which the current output power is located.

[0037] Furthermore, each of the photovoltaic inverters increases the current output power according to the threshold range of the current output power thereof, including:

[0038] When the current output power is within a first threshold interval, controlling the photovoltaic inverter to operate in an MPPT mode;

[0039] When the current output power is within the second threshold interval, the increase value of the current output power is 5% of the rated output power of the photovoltaic inverter;

[0040] When the current output power is within the third threshold interval, the increase value of the current output power is 2.5% of the rated output power of the photovoltaic inverter.

[0041] The present invention also proposes a photovoltaic reverse power control device using the above control method, comprising:

[0042] A detection unit, which is used to detect the power generation parameters of all photovoltaic inverters;

[0043] A control unit is used to allocate the photovoltaic inverter to operate in a first allocation mode or a second allocation mode according to the power generation parameter.

[0044] Compared with the prior art, the present invention has at least the following beneficial effects:

[0045] The present invention detects the power of the grid connection point and switches the photovoltaic inverter to operate in the first distribution mode or the second distribution mode in combination with the power generation parameters of the photovoltaic inverter, thereby realizing reverse power control of multiple different photovoltaic inverters and preventing photovoltaic surplus power from being connected to the grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0047] Figure 1 This is an appearance diagram of the photovoltaic reverse power control device of the present invention;

[0048] Figure 2 is an internal diagram of the photovoltaic reverse power control device of the present invention;

[0049] Figure 3 This is a control flow chart under the first allocation mode of the present invention;

[0050] Figure 4 This is a control flow chart under the second allocation mode of the present invention;

[0051] Figure 5 It is an overall control flow chart of the control method of the photovoltaic reverse power control device in the present invention;

[0052] Among them, 1 is the main control unit, 2 is the communication interface, 3 is the three-phase power output interface, 4 is the three-phase power input interface, and 5 is the current transformer. DETAILED DESCRIPTION

[0053] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention 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 invention and are not intended to limit the present invention.

[0054] Thus, a feature indicated in this specification will be used to illustrate one of the features of an embodiment of the present invention, rather than implying that each embodiment of the present invention must have the described feature. In addition, it should be noted that this specification describes many features. Although some features can be combined together to illustrate possible system designs, these features can also be used in other combinations that are not explicitly described. Thus, unless otherwise stated, the described combinations are not intended to be limiting.

[0055] The principle and structure of the present invention are described in detail below with reference to the accompanying drawings and embodiments.

[0056] In the current scheme, the photovoltaic reverse power control method can only ensure that a single photovoltaic inverter itself does not transmit power to the grid. When there are multiple photovoltaic inverters working at the same time, it is difficult to ensure that there is no reverse power problem at the grid connection point.

[0057] In view of the above scheme, the present invention designs a control method that can realize the control of the reverse power of multiple photovoltaic inverters. The specific scheme is as follows:

[0058] Detect the power generation parameters of all photovoltaic inverters connected to the grid;

[0059] When the grid connection point power at the grid connection point is negative, all photovoltaic inverters are allocated to operate in the first allocation mode or the second allocation mode according to the power generation parameters;

[0060] And in the first allocation mode, all photovoltaic inverters limit the current output power proportionally;

[0061] In the second allocation mode, the photovoltaic inverter limits the current output power according to the threshold interval in which the current output power is located.

[0062] Here, the power at the grid-connected point is negative, that is, the load stops being used. At this time, the total current output power of the photovoltaic inverter at the grid-connected point is higher than the power required by the load, and a reverse power situation will occur. Therefore, it is necessary to limit the current output power of the photovoltaic inverter.

[0063] Here, the first allocation method and the second allocation method are allocation methods that limit the current output power of all photovoltaic inverters. For example, if a 10kW load stops being used, the power at the grid connection point is negative and the magnitude is 10kW. This part of the reverse power needs to be shared by all photovoltaic inverters connected to the grid connection point.

[0064] The first allocation mode is to allocate based on the ratio of the current output power of the photovoltaic inverter. For example, if there are four photovoltaic inverters and the ratio of the current output power of the four photovoltaic inverters is 1:2:3:4, then when limiting the current output power of the photovoltaic inverter, the 10kW reverse power is also allocated according to the ratio of 1:2:3:4.

[0065] The second allocation mode is to restrict based on the threshold range of the current output power of the photovoltaic inverter. Since the current output power of some photovoltaic inverters is high and the current output power of some photovoltaic inverters is low, more restrictions can be placed on photovoltaic inverters with higher current output power, while fewer restrictions can be placed on photovoltaic inverters with lower current output power, thereby adapting to the allocation suppression of each photovoltaic inverter;

[0066] In the above scheme, the first allocation mode and the second allocation mode are determined according to power generation parameters to achieve an allocation mode that is more suitable for the current working environment.

[0067] It can be seen from the above scheme that the present invention provides two allocation modes, and both can realize the allocation of reverse power of multiple photovoltaic inverters, solving the problem that only a single photovoltaic inverter can be controlled in the prior art.

[0068] like Figure 1 As shown, it is an overall control flow chart of the control method of the photovoltaic reverse power control device in the present invention, and its basic process is as follows:

[0069] After the PV inverter is registered and online, the PV inverter power control device assigns an ID to the PV inverter. This step is mainly used to distinguish and identify all PV inverters connected to the grid point;

[0070] Then monitor the grid-connected point power and the output power of each photovoltaic inverter. The grid-connected point power here refers to the sum of the power required by the load at the grid-connected point and the output power of the photovoltaic inverter (the output power of the photovoltaic inverter is negative and the power required by the load is positive). Monitoring the output power of the photovoltaic inverter is used to obtain the current output power for subsequent adjustment actions.

[0071] Then determine whether the grid-connected point power is less than zero. Since the output power of the photovoltaic inverter is negative, when the grid-connected point power is less than zero, it means that the output power of the photovoltaic inverter is higher than the power required by the load. At this time, negative power will occur, and the current output power of the photovoltaic inverter needs to be suppressed.

[0072] In the suppression process, the allocation mode judgment is first performed to achieve the best suppression effect. As mentioned above, it is confirmed according to the power generation parameters. In the following text, the active power allocation mode is also the first allocation mode, and the passive power allocation mode is also the second allocation mode.

[0073] After entering the first allocation mode, the current output power is limited proportionally, which is the working logic in the first allocation mode mentioned above;

[0074] After entering the second allocation mode, the current output power is limited according to the threshold range, which is the working logic in the second allocation mode mentioned above.

[0075] The following is a description of how to allocate the first allocation mode or the second allocation mode in the present invention:

[0076] The power generation parameters in the above scheme include the maximum power generation power of the photovoltaic inverter, the minimum power generation power of the photovoltaic inverter, and the rated output power of the photovoltaic inverter;

[0077] In the above scheme, “allocating all photovoltaic inverters to operate in the first allocation mode or the second allocation mode according to power generation parameters” includes:

[0078] Calculate the difference between the maximum power generation and the minimum power generation of each photovoltaic inverter;

[0079] determining whether the difference is greater than a threshold output power;

[0080] When the determination is yes, the current photovoltaic inverter is set as the first photovoltaic inverter;

[0081] The number of first photovoltaic inverters is obtained, and when the number of first photovoltaic inverters is greater than a preset threshold, all photovoltaic inverters are controlled to operate in a first allocation mode.

[0082] When it is determined that the difference is less than the threshold output power, the current photovoltaic inverter is set as the second photovoltaic inverter;

[0083] The number of the second photovoltaic inverters is obtained, and when the number of the second photovoltaic inverters is greater than a preset threshold, all the photovoltaic inverters are controlled to operate in a second allocation mode.

[0084] Here, the threshold output power is set according to the rated output power of the photovoltaic inverter. In the present invention, the threshold output power is set to 20% of the rated output power;

[0085] By using the above method to determine whether to enter the first allocation mode or the second allocation mode, it is possible to better adapt to the current output power conditions of all photovoltaic inverters to achieve a better allocation effect.

[0086] Since all photovoltaic inverters are switched when switching to the first allocation mode or the second allocation mode, the above preset threshold needs to be set larger to represent the majority of photovoltaic inverters. In the present invention, the above preset threshold is set to 80% of the number of photovoltaic inverters connected to the grid connection point (for example, if the number of photovoltaic inverters connected to the grid connection point is 10, the preset threshold is set to 8).

[0087] When the first photovoltaic inverter or the second photovoltaic inverter reaches the preset threshold, it can indicate that most of the photovoltaic inverters meet the above allocation conditions, then the first allocation mode can be entered according to the fact that most of the photovoltaic inverters are the first photovoltaic inverters, or the second allocation mode can be entered according to the fact that most of the photovoltaic inverters are the second photovoltaic inverters.

[0088] The specific allocation methods of the first allocation mode and the second allocation mode are described below respectively;

[0089] See also Figure 3 , for the first allocation mode, the specific allocation method is:

[0090] Detect the current output power of all photovoltaic inverters and obtain the ratio between the current output powers of all photovoltaic inverters;

[0091] The grid-connected point power is distributed to all photovoltaic inverters so that the sum of the current output powers limited by all photovoltaic inverters is the grid-connected point power, and the ratio between the current output powers limited by all photovoltaic inverters is consistent with the ratio between the current output powers;

[0092] Among them, when executing the above-mentioned first allocation mode, it is also necessary to determine the average current output power that needs to be limited for all photovoltaic inverters based on the grid-connected point power and the number of photovoltaic inverters connected to the grid-connected point. If the current output power of a photovoltaic inverter is exactly equal to the average current output power, there is no need to limit the current output power of the photovoltaic inverter.

[0093] The first allocation mode of the present invention is described below with reference to a specific example:

[0094] Assume that there are currently 5 photovoltaic inverters a, b, c, d, and e online, and their current output powers are 4kW, 6kW, 10kW, 2kW, and 10kW respectively, with a total power generation of 30kW;

[0095] At this time, the 10kW load stops being used, resulting in a grid-connected power of -10kW, and reverse power occurs. At this time, the total power that needs to be limited for the five photovoltaic inverters is 10kW. According to calculations, the average current output power that needs to be limited is 2kW, so there is no need to limit photovoltaic inverter d.

[0096] At the same time, the ratio between photovoltaic inverters a, b, c, and e is 2:3:5:4, so photovoltaic inverters a, b, c, and e need to allocate and suppress the grid-connected point power according to this ratio. At this time, photovoltaic inverter a needs to suppress 1.4kW of the current output power in proportion, photovoltaic inverter b needs to suppress 2.1kW of the current output power in proportion, photovoltaic inverter c needs to suppress 3.6kW of the current output power in proportion, and photovoltaic inverter e needs to suppress 2.9kW of the current output power in proportion;

[0097] After the above distribution method, the current output power of photovoltaic inverters a, b, c, d, and e becomes: 2.6kW, 3.9kW, 6.4kW, 2kW, and 5.1kW. At this time, the total current output power of the five photovoltaic inverters is 20kW, the grid-connected power is reduced to 0, and the reverse power is eliminated.

[0098] See also Figure 4 , for the second allocation method, the specific allocation method is:

[0099] Detecting the current output power of all photovoltaic inverters and determining the threshold range of the current output power of each photovoltaic inverter;

[0100] Each photovoltaic inverter limits its current output power according to the threshold range in which its current output power is located;

[0101] The above threshold intervals include three, namely, a first threshold interval, a second threshold interval, and a third threshold interval;

[0102] In the first threshold interval, the current output power of the photovoltaic inverter is greater than 60% of the rated output power of the photovoltaic inverter;

[0103] In the second threshold interval, the current output power of the photovoltaic inverter is between 30% and 60% of the rated output power of the photovoltaic inverter;

[0104] In the third threshold interval, the current output power of the photovoltaic inverter is less than 30% of the rated output power of the photovoltaic inverter.

[0105] In the above scheme, each photovoltaic inverter limits the current output power according to the threshold range of its current output power, including:

[0106] When the current output power is within the first threshold interval, the current output power is limited to 10% of the rated output power of the photovoltaic inverter;

[0107] When the current output power is within the second threshold interval, the current output power is limited to 5% of the rated output power of the photovoltaic inverter;

[0108] When the current output power is within the third threshold interval, the limit value of the current output power is 2.5% of the rated output power of the photovoltaic inverter.

[0109] The second allocation mode of the present invention is described below with reference to a specific example:

[0110] Assuming that the rated output power of the photovoltaic inverter is 20kW, according to the allocation logic of the threshold interval, the first threshold interval is that the output power of the photovoltaic inverter is higher than 12kW;

[0111] The second threshold interval is when the output power of the photovoltaic inverter is between 6kW and 12kW;

[0112] The third threshold interval is when the output power of the photovoltaic inverter is less than 6kW;

[0113] Assume that there are three photovoltaic inverters a, b, and c, and their current output powers are 14kW, 10kW, and 5kW respectively, and their rated output powers are all 20kW;

[0114] The current output power of photovoltaic inverter a is in the first threshold range, and the current output power that needs to be limited is 2kW;

[0115] The current output power of photovoltaic inverter b is in the second threshold interval, and the current output power that needs to be limited is 1kW;

[0116] The current output power of the photovoltaic inverter c is in the third threshold interval, and the current output power that needs to be limited is 0.5 kW;

[0117] It can be seen from the above allocation method that under the second allocation method, more restrictions can be imposed on photovoltaic inverters with higher current output power and fewer restrictions can be imposed on photovoltaic inverters with lower current output power, which can better adapt to the current working environment of the photovoltaic inverter.

[0118] The present invention also proposes a recovery logic for a photovoltaic inverter, and the specific method is as follows:

[0119] Detecting the current output power of all photovoltaic inverters and determining the threshold range of the current output power of each photovoltaic inverter;

[0120] Each photovoltaic inverter increases its current output power according to the threshold range of its current output power.

[0121] Each photovoltaic inverter increases its current output power according to the threshold range of its current output power, including:

[0122] When the current output power is within the first threshold interval, controlling the photovoltaic inverter to operate in the MPPT mode;

[0123] When the current output power is within the second threshold interval, the current output power is increased by 5% of the rated output power of the photovoltaic inverter;

[0124] When the current output power is within the third threshold interval, the increase value of the current output power is 2.5% of the rated output power of the photovoltaic inverter.

[0125] From the above recovery logic of the photovoltaic inverter, it belongs to the opposite control logic to the second allocation mode, and it also has the same beneficial effects as the second allocation mode, and can better adapt to the current working environment of each photovoltaic inverter.

[0126] It should be noted that the first allocation mode and the second allocation mode are both single controls for all photovoltaic inverters. In some environments where higher control accuracy is required, the third allocation mode can also be set in combination with the first allocation mode and the second allocation mode.

[0127] In the third allocation mode, when the difference between the maximum power generation and the minimum power generation is greater than 20% of the rated output power, the first allocation mode is entered; when the difference between the maximum power generation and the minimum power generation is less than 20% of the rated output power, the second allocation mode is entered. In this way, a more reasonable allocation mode can be achieved for each photovoltaic inverter.

[0128] Furthermore, based on the above control method, the present invention also proposes a photovoltaic reverse power control device, which has:

[0129] A detection unit, which is used to detect the power generation parameters of all photovoltaic inverters;

[0130] A control unit, which is used to allocate the photovoltaic inverter to operate in a first allocation mode or a second allocation mode according to the power generation parameter;

[0131] The appearance and interior of the photovoltaic reverse power control device are as follows: Figure 1 and Figure 2 As shown, the main control unit 1 has a display screen for observing power information and system setting operations;

[0132] Communication interface 2 is used for the photovoltaic reverse power control device to communicate with each photovoltaic inverter;

[0133] Aout, Bout, Cout and Nout in the three-phase power output interface 3 are connected to the power side A, B, C three phases and the neutral line respectively;

[0134] Ain, Bin, Cin and Nin in the three-phase power input interface 4 are respectively connected to the three phases A, B, C and the neutral line of the power grid side, and the voltage values ​​of the three phases are collected at the same time and the information is transmitted to the main control unit 1. G is the grounding point, which is used to ensure the reliable grounding of the equipment and the safety of electricity use;

[0135] The current transformer 5 is used to measure and collect the current values ​​of the three phases respectively and transmit the information to the main control unit 1.

[0136] The external structure of the photovoltaic reverse power control device is similar to that of a general electric meter, and the installation and wiring methods of conventional electric meters are continued. The present invention adopts a standard guide rail installation method, and the wiring socket adopts a left-in and right-out wiring method, so users can easily install the device in an existing distribution cabinet.

[0137] In summary, compared with the prior art, the present invention has at least the following beneficial effects:

[0138] The present invention detects the power of the grid connection point and switches the photovoltaic inverter to operate in the first distribution mode or the second distribution mode in combination with the power generation parameters of the photovoltaic inverter, thereby realizing reverse power control of multiple different photovoltaic inverters and preventing photovoltaic surplus power from being connected to the grid.

[0139] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A control method for a photovoltaic reverse power control device, wherein the photovoltaic reverse power control device is installed at a grid connection point between a photovoltaic inverter and an electric device, characterized in that: The control method comprises: Detecting power generation parameters of all photovoltaic inverters connected to the grid connection point; When the grid connection point power at the grid connection point is negative, allocating all the photovoltaic inverters to operate in a first allocation mode or a second allocation mode according to the power generation parameters; And in the first allocation mode, all the photovoltaic inverters limit the current output power proportionally; In the second allocation mode, the photovoltaic inverter limits the current output power according to a threshold interval in which the current output power is located.

2. The control method of the photovoltaic reverse power control device according to claim 1, characterized in that: The power generation parameters include the maximum power generation power of the photovoltaic inverter, the minimum power generation power of the photovoltaic inverter, and the rated output power of the photovoltaic inverter; The step of allocating all the photovoltaic inverters to operate in the first allocation mode or the second allocation mode according to the power generation parameters includes: Calculating the difference between the maximum power generation and the minimum power generation of each photovoltaic inverter; Determining whether the difference is greater than a threshold output power; When the determination is yes, setting the current photovoltaic inverter as the first photovoltaic inverter; The number of first photovoltaic inverters is obtained, and when the number of the first photovoltaic inverters is greater than a preset threshold, all the photovoltaic inverters are controlled to operate in a first allocation mode.

3. The control method of the photovoltaic reverse power control device according to claim 2, characterized in that: The method of allocating all the photovoltaic inverters to operate in the first allocation mode or the second allocation mode according to the power generation parameters further includes: When it is determined that the difference is less than the threshold output power, setting the current photovoltaic inverter to a second photovoltaic inverter; The number of the second photovoltaic inverters is obtained, and when the number of the second photovoltaic inverters is greater than a preset threshold, all the photovoltaic inverters are controlled to operate in a second allocation mode.

4. The control method of the photovoltaic reverse power control device according to claim 1, characterized in that: The allocation method of the first allocation mode is: Detecting the current output power of all the photovoltaic inverters, and obtaining the ratio between the current output powers of all the photovoltaic inverters; The grid-connected point power is distributed to all the photovoltaic inverters so that the sum of the current output powers limited by all the photovoltaic inverters is the grid-connected point power, and the ratio between the current output powers limited by all the photovoltaic inverters is consistent with the ratio between the current output powers.

5. The control method of the photovoltaic reverse power control device according to claim 1, characterized in that: The allocation method of the second allocation mode is: Detecting the current output power of all the photovoltaic inverters, and determining the threshold interval of the current output power of each photovoltaic inverter; Each of the photovoltaic inverters limits the current output power according to the threshold range in which the current output power is located.

6. The control method of the photovoltaic reverse power control device according to claim 5, characterized in that: The threshold interval includes a first threshold interval, a second threshold interval, and a third threshold interval; In the first threshold interval, the current output power of the photovoltaic inverter is greater than 60% of the rated output power of the photovoltaic inverter; In the second threshold interval, the current output power of the photovoltaic inverter is between 30% and 60% of the rated output power of the photovoltaic inverter; In the third threshold interval, the current output power of the photovoltaic inverter is less than 30% of the rated output power of the photovoltaic inverter.

7. The control method of the photovoltaic reverse power control device according to claim 6, characterized in that: Each of the photovoltaic inverters limits the current output power according to the threshold range in which the current output power thereof is located, including: When the current output power is within the first threshold interval, the limit value of the current output power is 10% of the rated output power of the photovoltaic inverter; When the current output power is within the second threshold interval, the limit value of the current output power is 5% of the rated output power of the photovoltaic inverter; When the current output power is within the third threshold interval, the limit value of the current output power is 2.5% of the rated output power of the photovoltaic inverter.

8. The control method of the photovoltaic reverse power control device according to claim 7, characterized in that: When the grid connection point power at the grid connection point is positive, the control method further includes: Detecting the current output power of all the photovoltaic inverters, and determining the threshold interval of the current output power of each photovoltaic inverter; Each of the photovoltaic inverters increases the current output power according to the threshold range in which the current output power is located.

9. The control method of the photovoltaic reverse power control device according to claim 8, characterized in that: Each of the photovoltaic inverters increases the current output power according to the threshold range of the current output power thereof, including: When the current output power is within a first threshold interval, controlling the photovoltaic inverter to operate in an MPPT mode; When the current output power is within the second threshold interval, the increase value of the current output power is 5% of the rated output power of the photovoltaic inverter; When the current output power is within the third threshold interval, the increase value of the current output power is 2.5% of the rated output power of the photovoltaic inverter.

10. A photovoltaic reverse power control device using the control method according to any one of claims 1 to 9, characterized in that: include: A detection unit, which is used to detect the power generation parameters of all photovoltaic inverters; A control unit is used to allocate the photovoltaic inverter to operate in a first allocation mode or a second allocation mode according to the power generation parameter.

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