阅读说明：本技术 一种分布式光伏逆变器自主电压控制方法及运行模式控制方法 (Autonomous voltage control method and operation mode control method for distributed photovoltaic inverter ) 是由 石岩 于芃 王玥娇 孙树敏 李立生 程艳 王士柏 隽永龙 张兴友 王振华 于 2021-08-12 设计创作，主要内容包括：本发明属于光伏技术领域,公开一种分布式光伏逆变器自主电压控制方法,包括：当并网点电压落入自主电压控制区间时,随着并网点电压的升高,光伏逆变器自主下行调节输出功率。本发明实施例的方法确保用户电压合格为出发点和落脚点,按照源、网、荷共同参与电网治理的原则,在不增加用户额外投资的前提下,通过优化光伏逆变器运行控制策略,强制性实现光伏自主电压控制,当电压过高时,由光伏逆变器自主进行功率下行调节,最大限度把用户电压限制在合格范围内,同步解决电能大量上送引起的台区配变反向重过载问题。本发明实施例还提出了一种光伏逆变器运行模式控制方法。(The invention belongs to the technical field of photovoltaic, and discloses an autonomous voltage control method for a distributed photovoltaic inverter, which comprises the following steps: when the grid-connected point voltage falls into the autonomous voltage control interval, the photovoltaic inverter autonomously adjusts the output power downwards along with the rising of the grid-connected point voltage. The method of the embodiment of the invention ensures that the user voltage is qualified as a starting point and a foot-off point, forcibly realizes photovoltaic autonomous voltage control by optimizing the operation control strategy of the photovoltaic inverter according to the principle that the source, the network and the load participate in the power grid management together on the premise of not increasing the extra investment of the user, and autonomously regulates the power downwards by the photovoltaic inverter when the voltage is overhigh, so that the user voltage is limited in a qualified range to the maximum extent, and the problem of station area distribution transformation reverse overload caused by the large amount of electric energy transmission is synchronously solved. The embodiment of the invention also provides a control method for the operation mode of the photovoltaic inverter.)

1. A distributed photovoltaic inverter autonomous voltage control method, comprising:

when the grid-connected point voltage falls into the autonomous voltage control interval, the photovoltaic inverter adjusts the output power downwards along with the rising of the grid-connected point voltage.

2. The distributed photovoltaic inverter autonomous voltage control method of claim 1,

when the voltage of the grid-connected point U₃Falls into an autonomous voltage control interval U_a，U_b]During operation, the relation between the output power of the photovoltaic inverter and the voltage of the grid-connected point is shown as the following formula (1):

P_t＝P_real-(U₃-U_a)k (1)

P_ta power control target value at the current moment;

P_realactual output power of the current photovoltaic inverter;

k is a power adjustment coefficient.

3. The distributed photovoltaic inverter autonomous voltage control method of claim 2,

the power regulation coefficient is in direct proportion to the rated capacity of the photovoltaic inverter and the deviation degree of the grid-connected point voltage from the lower limit value of the autonomous voltage control interval.

4. The distributed photovoltaic inverter autonomous voltage control method of claim 2,

an adjustment dead zone is also provided for the power adjustment coefficient k.

5. The distributed photovoltaic inverter autonomous voltage control method of claim 4,

when (U)₃-U_a) If < i, k is 0 and i is a set value.

6. The distributed photovoltaic inverter autonomous voltage control method of claim 4,

when (U)₃-U_a) When the power regulation coefficient k is larger than i, the power regulation coefficient k meets the requirement of the formula (2):

wherein, P_nFor the rated power, i is a set value and j is a set value.

7. A distributed photovoltaic inverter autonomous voltage control method according to claim 5 or 6,

set i to 1V.

8. The distributed photovoltaic inverter autonomous voltage control method of claim 6,

set j to 7%.

9. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that the processor, when executing the computer program, implements the steps of the method of any of claims 1 to 8.

10. A method for controlling the operation mode of a photovoltaic inverter to control the operation mode of the photovoltaic inverter in different voltage intervals is characterized by comprising the following steps:

when U is turned₃＜U_T1When the power grid is connected, the power grid is disconnected;

when U is turned_T1≤U₃<U_aThen, operating in a maximum power capture mode;

when the voltage of the grid-connected point falls into the autonomous voltage control interval [ U ]_a，U_b]When the photovoltaic inverter operates in an autonomous voltage control mode, the output power is regulated in a downlink mode along with the increase of the voltage of a grid-connected point;

when U is turned_b<U₃<U_T2When the power is not output, stopping power output;

when U is turned₃≥U_T2When the power grid is connected, the power grid is disconnected;

wherein, U₃To grid point voltage, U_T1Is a first threshold voltage, U_T2Is a second threshold voltage, U_aFor autonomous voltage control interval lower limit, U_bThe upper limit value of the autonomous voltage control interval.

11. The photovoltaic inverter operation mode control method according to claim 10,

the photovoltaic inverter operation modes corresponding to different voltage intervals are as follows:

U₃<85％U_ndisconnecting the connection with the power grid;

85％U_n≤U₃<105％U_noperating in a maximum power capture mode;

105％U_n≤U₃≤107％U_nthe photovoltaic inverter operates in an autonomous voltage control mode, and adjusts output power downwards along with the increase of the voltage of a grid-connected point;

107％U_n<U₃<110％U_nstopping power output;

U₃≥110％U_ndisconnecting the connection with the power grid;

wherein, U_nIs connected to the voltage for photovoltaic.

12. The photovoltaic inverter operation mode control method according to claim 10,

when the voltage of the grid-connected point U₃Falls into an autonomous voltage control interval U_a，U_b]During operation, the relation between the output power of the photovoltaic inverter and the voltage of the grid-connected point is shown as the following formula (1):

P_t＝P_real-(U₃-U_a)k (1)

P_ta power control target value at the current moment;

P_realactual output power of the current photovoltaic inverter;

k is a power adjustment coefficient.

13. The photovoltaic inverter operation mode control method according to claim 12,

the power regulation coefficient is in direct proportion to the rated capacity of the photovoltaic inverter and the deviation degree of the grid-connected point voltage from the lower limit value of the autonomous voltage control interval.

14. The photovoltaic inverter operation mode control method according to claim 12,

an adjustment dead zone is also set for the power adjustment coefficient k, when (U)₃-U_a) If < i, k is 0 and i is a set value.

15. The photovoltaic inverter operation mode control method according to claim 12,

when (U)₃-U_a) When the power regulation coefficient k is larger than i, the power regulation coefficient k meets the requirement of the formula (2):

wherein, P_nFor the rated power, i is a set value and j is a set value.

16. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that the processor realizes the steps of the method of any one of claims 10 to 15 when executing the computer program.

Technical Field

The invention relates to the technical field of photovoltaic, in particular to an autonomous voltage control method for a distributed photovoltaic inverter and an operation mode control method for the photovoltaic inverter.

Background

With continuous and rapid growth of low-voltage distributed photovoltaic, during a period of a large power generation of distributed photovoltaic, the system voltage of a local area rises and even exceeds the limit, and the dynamic reactive power supporting capability of a power grid is insufficient.

Distributed photovoltaic distribution grid topology, U, as shown in FIG. 1₁For the terminal voltage of the user (namely the voltage of the photovoltaic grid-connected point of the user), according to the empirical value, in order to guarantee the quality of the power supply voltage of the end user, a power supply company generally sets the running voltage of the low-voltage side of the distribution transformer to be 105% U_n(U_n380V); u shape₂Is the line side voltage in the distribution area; u shape₃For distributing and transforming voltage side voltage, according to the national standard GB/T12325 power quality supply voltage biasDifference, the 380 volt user qualified voltage interval is 107% U_n-93％U_nThe 220V user qualified voltage interval is 107% U_n-90％U_n。

According to the analysis of the flow direction of the power distribution station area shown in fig. 1, the following results are obtained: when the power flow in the platform area flows from the platform area side to the user side, the voltage gradually decreases along the platform area side-line side-user side (U)₁>U₂>U₃) (ii) a When the distributed photovoltaic output in the transformer area is equal to the user load, the photovoltaic power generation in the transformer area reaches self-using balance, the transformer area side and the user side are nearly equal in potential, and the voltage of the user side in the transformer area is close to the distribution transformer low-voltage side no-load voltage (U)₁≈U₃Distribution transformer low-voltage side no-load voltage of about station area, namely 105% U_n) (ii) a When the distributed photovoltaic output in the transformer area exceeds the load of a user, the reverse transmission of the power flow (from the user side to the transformer area side) occurs, and the voltage in the transformer area is gradually increased along the transformer area side, the line side and the user side (U)₁<U₂<U₃) Subscriber side voltage U₃Highest (greater than 105% rated voltage, larger return current, U₃The larger the output is), when the output of the distributed photovoltaic power generation exceeds a certain value, the voltage U of the grid connection point₃Will exceed 107% U_nCausing user overvoltage. As the backward power flow continues to increase, the overvoltage condition of the user is aggravated, and the overvoltage condition occurs on the line side and the distribution voltage side in succession.

Along with the generation of overvoltage of users, the distribution transformer feedback power is also increased. When the distributed photovoltaic output reaches a certain value (S)₂) In the process, the distribution transformer transmits heavy load in a reverse mode (80% of distribution transformer capacity according to national network enterprise standard Q/GDW565 'guide rules for estimating the operation level and the power supply capacity of the urban distribution network'); when it reaches a certain value (S)₃) When the load is full, the distribution transformer is reversely fed. That is to say, when the distributed photovoltaic distribution transformer is subjected to heavy feedback overload, user overvoltage is certainly generated, and as long as the user overvoltage is not generated, heavy feedback overload of the distribution transformer is not generated.

Disclosure of Invention

The embodiment of the invention provides an autonomous voltage control method and an operation mode control method for a distributed photovoltaic inverter, and aims to solve the problems of station overvoltage and reverse heavy overload caused by reverse of distributed photovoltaic power flow in the prior art. The following presents a simplified summary in order to provide a basic understanding of some aspects of the disclosed embodiments. This summary is not an extensive overview and is intended to neither identify key/critical elements nor delineate the scope of such embodiments. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.

According to a first aspect of embodiments of the present invention, a distributed photovoltaic inverter autonomous voltage control method is provided.

In one embodiment, a distributed photovoltaic inverter autonomous voltage control method includes:

when the grid-connected point voltage falls into the autonomous voltage control interval, the photovoltaic inverter adjusts the output power downwards along with the rising of the grid-connected point voltage.

Alternatively, when the grid-connected point voltage U₃Falls into an autonomous voltage control interval U_a，U_b]During operation, the relation between the output power of the photovoltaic inverter and the voltage of the grid-connected point is shown as the following formula (1):

P_t＝P_real-(U₃-U_a)k (1)

P_ta power control target value at the current moment;

P_realactual output power of the current photovoltaic inverter;

k is a power adjustment coefficient.

Optionally, the magnitude of the power regulation coefficient is directly proportional to the rated capacity of the photovoltaic inverter and the degree of deviation of the grid-connected point voltage from the lower limit value of the autonomous voltage control interval.

Optionally, an adjustment dead zone is further provided for the power adjustment coefficient k.

Alternatively, when (U)₃-U_a) If < i, k is 0 and i is a set value.

Alternatively, when (U)₃-U_a) When the power regulation coefficient k is larger than i, the power regulation coefficient k meets the requirement of the formula (2):

wherein, P_nFor the rated power, i is a set value and j is a set value.

Alternatively, i is set to 1V.

Optionally, j is set to 7%.

According to a second aspect of embodiments of the present invention, there is provided a computer apparatus.

In some embodiments, the computer device comprises a memory storing a computer program and a processor implementing the steps of the distributed photovoltaic inverter autonomous voltage control method described above when the processor executes the computer program.

According to a third aspect of embodiments of the present invention, a photovoltaic inverter operation mode control method is provided.

In one embodiment, a method for controlling an operation mode of a photovoltaic inverter to control an operation mode of the photovoltaic inverter in different voltage intervals includes:

when U is turned₃＜U_T1When the power grid is connected, the power grid is disconnected;

when U is turned_T1≤U₃<U_aThen, operating in a maximum power capture mode;

when the voltage of the grid-connected point falls into the autonomous voltage control interval [ U ]_a，U_b]When the photovoltaic inverter operates in an autonomous voltage control mode, the output power is regulated in a downlink mode along with the increase of the voltage of a grid-connected point;

when U is turned_b<U₃<U_T2When the power is not output, stopping power output;

when U is turned₃≥U_T2When the power grid is connected, the power grid is disconnected;

wherein, U₃To grid point voltage, U_T1Is a first threshold voltage, U_T2Is a second threshold voltage, U_aFor autonomous voltage control interval lower limit, U_bThe upper limit value of the autonomous voltage control interval.

Optionally, the photovoltaic inverter operation modes corresponding to different voltage intervals are as follows:

U₃<85％U_ndisconnecting the connection with the power grid;

85％U_n≤U₃<105％U_noperating in a maximum power capture mode;

105％U_n≤U₃≤107％U_nthe photovoltaic inverter operates in an autonomous voltage control mode, and autonomously adjusts the output power in a downlink mode along with the increase of the voltage of a grid-connected point;

107％U_n<U₃<110％U_nstopping power output;

U₃≥110％U_ndisconnecting the connection with the power grid;

wherein, U_nIs connected to the voltage for photovoltaic.

Alternatively, when the grid-connected point voltage U₃Falls into an autonomous voltage control interval U_a，U_b]During operation, the relation between the output power of the photovoltaic inverter and the voltage of the grid-connected point is shown as the following formula (1):

P_t＝P_real-(U₃-U_a)k (1)

P_ta power control target value at the current moment;

P_realactual output power of the current photovoltaic inverter;

k is a power adjustment coefficient.

Optionally, the magnitude of the power regulation coefficient is directly proportional to the rated capacity of the photovoltaic inverter and the degree of deviation of the grid-connected point voltage from the lower limit value of the autonomous voltage control interval.

Optionally, an adjustment dead zone is further provided for the power adjustment coefficient k, when (U)₃-U_a) If < i, k is 0 and i is a set value.

Alternatively, when (U)₃-U_a) When the power regulation coefficient k is larger than i, the power regulation coefficient k meets the requirement of the formula (2):

wherein，P_nFor the rated power, i is a set value and j is a set value.

According to a fourth aspect of embodiments of the present invention, there is provided a computer apparatus.

In some embodiments, the computer device comprises a memory storing a computer program and a processor implementing the steps of the above-described photovoltaic inverter operation mode control method when the processor executes the computer program.

The technical scheme provided by the embodiment of the invention has the following beneficial effects:

ensuring that the user voltage is qualified as a starting point and a foot-off point, forcibly realizing photovoltaic autonomous voltage control by optimizing a photovoltaic inverter operation control strategy according to the principle that a source, a network and a load jointly participate in power grid management on the premise of not increasing extra investment of a user, and autonomously carrying out power downlink regulation by the photovoltaic inverter when the voltage is overhigh to limit the user voltage within a qualified range to the maximum extent (107 percent U of 380V accessed photovoltaic)_n-93％U_n220V Access photovoltaic is 107% U_n-90％U_n) And the problem of distribution transformer reverse heavy overload caused by large-scale power supply is synchronously solved.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.

Fig. 1 is a schematic diagram of a distributed photovoltaic distribution bay topology;

FIG. 2 is a graph illustrating operation of a photovoltaic inverter during autonomous voltage control according to an exemplary embodiment;

FIG. 3 is a flowchart illustrating a photovoltaic inverter operating mode control method according to an exemplary embodiment;

FIG. 4 is a schematic diagram illustrating the structure of a computer device according to an example embodiment.

Detailed Description

The following description and the drawings sufficiently illustrate specific embodiments herein to enable those skilled in the art to practice them. Portions and features of some embodiments may be included in or substituted for those of others. The scope of the embodiments herein includes the full ambit of the claims, as well as all available equivalents of the claims. The terms "first," "second," and the like, herein are used solely to distinguish one element from another without requiring or implying any actual such relationship or order between such elements. In practice, a first element can also be referred to as a second element, and vice versa. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a structure, apparatus, or device that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such structure, apparatus, or device. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a structure, device or apparatus that comprises the element. The embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.

The terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like herein, as used herein, are defined as orientations or positional relationships based on the orientation or positional relationship shown in the drawings, and are used for convenience in describing and simplifying the description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present invention. In the description herein, unless otherwise specified and limited, the terms "mounted," "connected," and "connected" are to be construed broadly, and may include, for example, mechanical or electrical connections, communications between two elements, direct connections, and indirect connections via intermediary media, where the specific meaning of the terms is understood by those skilled in the art as appropriate.

Herein, the term "plurality" means two or more, unless otherwise specified.

Herein, the character "/" indicates that the preceding and following objects are in an "or" relationship. For example, A/B represents: a or B.

Herein, the term "and/or" is an associative relationship describing objects, meaning that three relationships may exist. For example, a and/or B, represents: a or B, or A and B.

In one embodiment, the present invention provides a distributed photovoltaic inverter autonomous voltage control method, including: when the voltage of the grid-connected point U₃When falling into the autonomous voltage control interval, i.e. U_a≤U₃≤U_bThe photovoltaic inverter operates according to an active-voltage droop characteristic mode, and the relation between the output power and the grid-connected point voltage is shown as the formula (1):

P_t＝P_real-(U₃-U_a)k (1)

P_tthe power control target value at the current moment is the real-time output power control target;

P_realactual output power of the current photovoltaic inverter;

k is a power regulation coefficient, the size of the power regulation coefficient, the rated capacity of the photovoltaic inverter and U₃Deviation from autonomous voltage control interval lower limit U_aIs proportional to the degree of the pressure difference.

U_aThe voltage of the grid-connected point is the lower limit value of the autonomous voltage control interval, namely the starting point of autonomous voltage control of the photovoltaic inverter when the grid-connected point voltage U₃Falling into an autonomous voltage control interval, and autonomously and downwards regulating output power of the photovoltaic inverter along with the increase of the voltage of the grid-connected point, namely, autonomously controlling the photovoltaic inverter to reduce output power, and aiming at controlling the voltage U of the grid-connected point₃No more than U_b，U_bThe upper limit value of the autonomous voltage control interval.

Lower limit value U of autonomous voltage control interval_aAnd an upper limit value U of an autonomous voltage control interval_bThe value of (a) is set according to the relevant criteria.

In one embodiment, a regulation dead zone is further arranged for the power regulation coefficient k, so that frequent reciprocating regulation of the photovoltaic inverter caused by small-range fluctuation of voltage is avoided.

Alternatively, when (U)₃-U_a) If < i, k is 0, i is a set value and is set according to a required dead zone range, and the larger i is, the larger the dead zone range is. Optionally, i ═ 1V.

Alternatively, when (U)₃-U_a) When the power regulation coefficient k is larger than i, the power regulation coefficient k meets the requirement of the formula (2):

wherein, P_nJ is a set value for the rated power of the photovoltaic inverter. Optionally, i ═ 1V. Optionally, j is 7%.

According to the formula (2), as the voltage of the photovoltaic grid-connected point is increased continuously, the higher the photovoltaic inverter downlink power regulation coefficient k is, namely the higher the photovoltaic inverter downlink power regulation rate is, the higher the power down regulation degree is, the maximum power regulation coefficient (namely the maximum power regulation rate) reaches 2jP_n。

In one embodiment, the control period T should be 10-15 s during autonomous voltage control. In each control period, the control signal is passed through delta U (delta U ═ U)₃-U_a) And power P_realThe feedback control ensures that the photovoltaic output is continuously adjusted downwards along with the increase of the voltage of the grid-connected point. Optionally, the photovoltaic inverter control response time per regulation should be less than 60 ms.

A specific embodiment of a distributed photovoltaic inverter autonomous voltage control method is given below.

The embodiment combines the requirements of national standard GB/T29319 technical provisions for connecting photovoltaic power generation system to distribution network for distributed photovoltaic operation intervals, formulates an autonomous voltage control interval, and uses 380V powerHousehold, i.e. switched-in, photovoltaic voltage U_n380V when grid connection point voltage U₃Falls within the autonomous voltage control interval of 105% U_n≤U₃≤107％U_nDuring operation, the photovoltaic inverter operates according to an active-voltage droop characteristic mode, and the relation between the output power and the grid-connected point voltage is shown as the formula (3):

P_t＝P_real-(U₃-105％U_n)k (3)

P_tthe power control target value at the current moment is the real-time output power control target;

P_realactual output power of the current photovoltaic inverter;

k is a power regulation coefficient, the size of the power regulation coefficient, the rated capacity of the photovoltaic inverter and U₃Deviation of 105% U_nIs proportional to the degree of the pressure difference.

105％U_nPerforming autonomous voltage control starting point for the photovoltaic inverter, and obtaining the voltage U of the grid-connected point₃Falling into an autonomous voltage control interval, and autonomously and downwards regulating output power of the photovoltaic inverter along with the increase of the voltage of the grid-connected point, namely, autonomously controlling the photovoltaic inverter to reduce output power, and aiming at controlling the voltage U of the grid-connected point₃Not more than 107% U_n。

When (U)₃-105％U_n) And when the voltage is less than 1V, k is 0, and the dead zone is adjusted. When (U)₃-105％U_n) When the voltage is more than 1V, the power regulation coefficient k meets the requirement of formula (4):

wherein, P_nThe rated power of the photovoltaic inverter. As can be seen from the equation (4), as the voltage of the photovoltaic grid-connected point increases, the higher the downlink power adjustment coefficient k of the photovoltaic inverter is, the power down-regulation degree is increased, and the maximum power adjustment coefficient (i.e., the maximum power adjustment rate) reaches 14% of rated power.

According to the formula (3) and the formula (4), the operation curve of the photovoltaic inverter in the autonomous voltage control process is obtained and is shown in fig. 2(AB section curve).

During the overvoltage suppression process, the line voltage difference from the station side to the user side is limited to 2% U_nWithin the range (considering the distribution transformer and the upper level 10kV system as an infinite system temporarily, the outlet voltage of the low-voltage side of the distribution transformer is 105 percent U_n(ii) a Due to the return of the power flow, the voltage of the user side rises and cannot exceed 107 percent U at most_n) When the reverse power flow is aboutAnd R is the equivalent resistance of the circuit in the transformer area, namely the maximum value of the allowable feedback power flow.

When the distribution transformer of the transformer area supplies power to the load with full capacity, the outlet voltage of the low-voltage side of the distribution transformer is 105 percent U under the condition that the distribution transformer and the upper 10kV system are temporarily considered as infinite systems_nUser side voltage reduction to 100% U_nThe line pressure difference from the low-voltage side of the distribution transformer to the user side is 5 percent U_nDistribution of normal full load capacity S₀Is composed of

Thus, the full capacity S relative to the distribution transformer₀The maximum value of the photovoltaic power flow allowed to be sent back is 16% S through a distributed photovoltaic autonomous voltage control method₀The suppressed photovoltaic reverse current isI.e. 84% S₀And further, the problem of reverse heavy overload of distribution transformer of the transformer area is avoided.

In other embodiments, for 220V users, i.e. access to photovoltaic voltage U_nWhen the distributed photovoltaic inverter autonomous voltage control method is implemented, the autonomous voltage control interval can be correspondingly adjusted according to the relevant standard, namely 220V.

In other embodiments, when the relevant standard is changed or adjusted, when the above-described method for controlling the autonomous voltage of the distributed photovoltaic inverter is implemented, the autonomous voltage control interval may be adjusted accordingly according to the relevant standard.

In another embodiment, the present invention further provides a method for controlling an operation mode of a photovoltaic inverter, which controls operation modes of the photovoltaic inverter in different voltage intervals, including:

when U is turned₃＜U_T1When the power grid is connected, the power grid is disconnected;

when U is turned_T1≤U₃<U_aThen, operating in a maximum power capture mode;

when the voltage of the grid-connected point falls into the autonomous voltage control interval [ U ]_a，U_b]When the photovoltaic inverter operates in an autonomous voltage control mode, the output power is autonomously regulated downwards along with the increase of the voltage of a grid-connected point;

when U is turned_b<U₃<U_T2When the power is not output, stopping power output;

when U is turned₃≥U_T2When the power grid is connected, the power grid is disconnected;

wherein, U₃To grid point voltage, U_T1Is a first threshold voltage, U_T2Is a second threshold voltage, U_aFor autonomous voltage control interval lower limit, U_bThe upper limit value of the autonomous voltage control interval.

When the photovoltaic inverter operates in the autonomous voltage control mode, the distributed photovoltaic inverter autonomous voltage control method is adopted to control the photovoltaic inverter.

A specific embodiment of the photovoltaic inverter operation mode control method is given below.

In this embodiment, the photovoltaic voltage U is switched on_n380V, combining the requirements of the national standard GB/T29319 technical regulation for connecting a photovoltaic power generation system to a power distribution network for distributed photovoltaic operation intervals, formulating operation modes of the photovoltaic inverter in different voltage intervals, as shown in FIG. 3, specifically as follows:

U₃<85％U_ndisconnecting the connection with the power grid;

85％U_n≤U₃<105％U_noperating in a maximum power capture mode;

105％U_n≤U₃≤107％U_nphotovoltaic inverters operating at autonomous voltage controlThe system mode is used for automatically regulating the output power in a downlink way along with the increase of the voltage of a grid-connected point;

107％U_n<U₃<110％U_nstopping power output;

U₃≥110％U_nand disconnecting the power grid.

When the photovoltaic inverter operates in the autonomous voltage control mode, the distributed photovoltaic inverter autonomous voltage control method is adopted to control the photovoltaic inverter.

In other embodiments, for a 220V user, when the photovoltaic inverter operation mode control method is implemented, the autonomous voltage control interval and the first threshold U are controlled according to the related standard_T1A second threshold value U_T2And (4) carrying out corresponding adjustment.

In other embodiments, when the relevant standard is changed or adjusted, the first threshold U and the autonomous voltage control interval are controlled according to the relevant standard when the above-mentioned method for controlling the operation mode of the photovoltaic inverter is implemented_T1A second threshold value U_T2And (4) carrying out corresponding adjustment.

In one embodiment, a computer device is provided, which may be a server, the internal structure of which may be as shown in fig. 4. The computer device includes a processor, a memory, and a network interface connected by a system bus. Wherein the processor of the computer device is configured to provide computing and control capabilities. The memory of the computer device comprises a nonvolatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of an operating system and computer programs in the non-volatile storage medium. The database of the computer device is used for storing static information and dynamic information data. The network interface of the computer device is used for communicating with an external terminal through a network connection. Which computer program is executed by a processor to carry out the steps in the above-described method embodiments.

Those skilled in the art will appreciate that the configuration shown in fig. 4 is a block diagram of only a portion of the configuration associated with aspects of the present invention and is not intended to limit the computing devices to which aspects of the present invention may be applied, and that a particular computing device may include more or less components than those shown, or may combine certain components, or have a different arrangement of components.

In an embodiment, there is also provided a computer device comprising a memory and a processor, the memory having stored therein a computer program, the processor implementing the steps of the above method embodiments when executing the computer program.

In an embodiment, a computer-readable storage medium is provided, on which a computer program is stored which, when being executed by a processor, carries out the steps of the above-mentioned method embodiments.

It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by hardware instructions of a computer program, which can be stored in a non-volatile computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. Any reference to memory, storage, database or other medium used in embodiments provided herein may include at least one of non-volatile and volatile memory. Non-volatile Memory may include Read-Only Memory (ROM), magnetic tape, floppy disk, flash Memory, optical storage, or the like. Volatile Memory can include Random Access Memory (RAM) or external cache Memory. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM), among others.

The present invention is not limited to the structures that have been described above and shown in the drawings, and various modifications and changes can be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.