CN112736970A

CN112736970A - Photovoltaic system dynamic reconstruction method, device, system and electronic equipment

Info

Publication number: CN112736970A
Application number: CN202011576054.4A
Authority: CN
Inventors: 牛益国; 牛然; 孟菁; 王秀斌; 叶鞠
Original assignee: State Grid Corp of China SGCC; Qinhuangdao Power Supply Co of State Grid Jibei Electric Power Co Ltd
Current assignee: State Grid Corp of China SGCC; Qinhuangdao Power Supply Co of State Grid Jibei Electric Power Co Ltd
Priority date: 2020-12-28
Filing date: 2020-12-28
Publication date: 2021-04-30

Abstract

The present disclosure relates to a method, device, system and electronic device for dynamic reconstruction of a photovoltaic system, the method comprising: acquiring the power of an input end of an inverter component connected to the photovoltaic system; the optimal bridging mode between the photovoltaic system and the inverter assembly; predicting the power input to the inverter assembly when the photovoltaic system and the inverter assembly are connected according to the optimal bridging mode Whether the parameter satisfies the constraint condition; in response to satisfying the constraint condition, switch to the optimal bridging mode. Embodiments of the present disclosure can realize optimal dynamic switching of photovoltaic systems.

Description

Photovoltaic system dynamic reconstruction method, device, system and electronic equipment

Technical Field

The present disclosure relates to the field of photovoltaic power generation system planning technologies, and in particular, to a method, an apparatus, a system, and an electronic device for dynamically reconfiguring a photovoltaic system.

Background

In recent years, the installed capacity of distributed photovoltaic devices has increased year by year, and the annual installed capacity ratio has approached 50%. Distributed photovoltaic power generation gradually becomes a new mode of power production and photovoltaic energy consumption, and the power generation efficiency of the distributed photovoltaic power generation is more and more concerned. In general, in distributed photovoltaic power generation, a photovoltaic string is fixedly connected to an inverter. The inverter is operated under light load in the low light conditions such as morning and evening and rainy days. However, the inverter operates with low efficiency at light load. At present, a controllable switch can be added between the photovoltaic string and the inverter, and the high-power operation of part of the inverters can be realized by adjusting the starting number of the inverters, but the dynamic control for the connection of the photovoltaic string and the inverter is not mature.

Disclosure of Invention

The disclosure provides a photovoltaic system dynamic reconfiguration method, a device, a system and an electronic device, which can realize optimal dynamic switching of a photovoltaic system.

According to an aspect of the present disclosure, a method for dynamically reconstructing a photovoltaic system is provided, which includes:

acquiring power parameters of an inverter assembly connected with a photovoltaic system;

determining an optimal bridging manner between the photovoltaic system and the inverter assembly by using the power parameter;

predicting whether power parameters input to the inverter assembly satisfy constraint conditions when the photovoltaic system and the inverter assembly are connected in the optimal bridging manner;

and responding to the condition that the constraint condition is met, and switching to the optimal bridging mode.

In some possible embodiments, the determining the optimal bridging manner between the photovoltaic system and the inverter assembly by using the power parameter includes:

determining whether the power obtained within a preset time meets a power out-of-limit condition;

and under the condition that the power obtained within the preset time does not meet the power out-of-limit condition, determining an optimal bridging mode between the photovoltaic system and the inverter assembly.

In some possible embodiments, the method further comprises:

under the condition that the power obtained in preset time meets the power out-of-limit condition, determining the quantity value of the photovoltaic panel to be cut off according to the power;

cutting out photovoltaic tiles from the photovoltaic system based on the quantitative value.

In some possible embodiments, the determining whether the power obtained within a preset time meets a power out-of-limit condition includes:

responding to the fact that the number of times that the power obtained within the preset time exceeds the power threshold value is larger than or equal to the number of times threshold value, and determining that the power meets the power out-of-limit condition;

and determining that the power does not meet the power out-of-limit condition in response to the fact that the number of times that the power obtained within the preset time exceeds the power threshold is smaller than a number of times threshold.

In some possible embodiments, the determining the optimal bridging manner between the photovoltaic system and the inverter assembly includes:

determining the number of switching times required for switching from the current first connection state of the photovoltaic system and the inverter assembly to any second connection state;

determining a switching cost loss of any one of the second connection states using the number of switching times;

determining the operating benefit of the photovoltaic system for switching from the first connection state to any one of the second connection states by using the switching cost loss;

and determining the second connection state corresponding to the maximum photovoltaic system operation benefit as an optimal bridging mode.

In some possible embodiments, the switching to the optimal bridge mode in response to the constraint being satisfied includes:

determining switching time according to a preset time interval;

and responding to the condition that the constraint condition is met, and switching to the optimal bridging mode when the switching time is reached.

According to a second aspect of the present disclosure, there is provided a photovoltaic system dynamic reconfiguration device, including:

the acquisition module is used for acquiring the power of the input end of the inverter assembly connected with the photovoltaic system;

the determining module is used for determining an optimal bridging mode between the photovoltaic system and the inverter assembly by using the power within preset time;

the prediction module is used for predicting whether the power parameters input into the inverter assembly meet constraint conditions when the photovoltaic system and the inverter assembly are connected in the optimal bridging mode;

and the switching module is used for switching to the optimal bridging mode under the condition of meeting the constraint condition.

In some possible embodiments, the determining module is further configured to determine whether the power obtained within a preset time meets a power out-of-limit condition;

According to a third aspect of the present disclosure, there is provided a photovoltaic system dynamic reconfiguration system, comprising:

a photovoltaic system comprising at least one set of photovoltaic strings, the photovoltaic strings comprising at least one photovoltaic panel;

an inverter assembly including at least one inverter;

a switching assembly for connecting the photovoltaic system and the inverter assembly, the inverter being connected to at least one set of photovoltaic strings;

a control component for performing the method of dynamic reconfiguration of a photovoltaic system according to any one of the first aspect.

According to a fourth aspect of the present disclosure, there is provided an electronic device comprising:

a processor;

a memory for storing processor-executable instructions;

wherein the processor is configured to invoke the memory-stored instructions to perform the method of any of the first aspects.

In the embodiment of the disclosure, the automatic switching of the connection state between the photovoltaic system and the inverter assembly can be realized, and meanwhile, according to the set constraint condition, the connection mode can be optimized, the stability of the electric power between the photovoltaic system and the inverter system is ensured, and the reliability of the inverter is improved.

In addition, by using the reconstruction method disclosed by the invention, the number of the working inverters of the group control system can be switched in real time according to the change of the illumination intensity, the output utilization rate of the photovoltaic grid-connected inverter can be effectively improved, and the generated energy can be increased. Aiming at the condition of complicated and changeable weather, the condition that the power of the inverter is out of limit can be prevented, and the reliability of the photovoltaic system is enhanced. The control assembly can automatically switch the number of inverter circuits through the switch assembly at any time according to the output current of each battery panel (photovoltaic panel), and if the inverter suddenly fails, the photovoltaic group string can be connected to other inverters to normally work; and the number of strings of panels is not limited to the same number as the number of inverters. Namely, when the inverter is damaged in operation, the number of battery plate strings and the number of switches do not need to be changed;

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 disclosure.

Other features and aspects of the present disclosure will become apparent from the following detailed description of exemplary embodiments, which proceeds with reference to the accompanying drawings.

Drawings

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

Fig. 1 shows a topological schematic of a photovoltaic group control system according to an embodiment of the present disclosure;

FIG. 2 illustrates a flow diagram of a method of dynamic reconfiguration of a photovoltaic system according to an embodiment of the present disclosure;

fig. 3 shows a flowchart of step S20 in a photovoltaic system dynamic reconfiguration method according to an embodiment of the present disclosure;

FIG. 4 illustrates a flow chart for determining an optimal bridging manner in accordance with an embodiment of the present disclosure;

fig. 5 shows a flowchart of step S30 in the dynamic reconfiguration method of a photovoltaic system according to an embodiment of the present disclosure;

FIG. 6 shows a graph comparing conversion efficiency at different powers for a group control system of different capacity configurations according to a method of an embodiment of the disclosure;

FIG. 7 shows a schematic diagram of an operational scenario in which only the objective function is considered in view of normal operation;

FIG. 8 shows a schematic diagram in view of the anti-power-violation function;

fig. 9 shows a block diagram of a photovoltaic system dynamic reconfiguration device according to an embodiment of the present disclosure;

FIG. 10 shows a block diagram of an electronic device 800 in accordance with an embodiment of the disclosure;

FIG. 11 shows a block diagram of another electronic device 1900 in accordance with an embodiment of the disclosure;

fig. 12 shows another flow diagram of a method of dynamic reconfiguration of a photovoltaic system according to an embodiment of the present disclosure.

Detailed Description

Various exemplary embodiments, features and aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. In the drawings, like reference numbers can indicate functionally identical or similar elements. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

The term "and/or" herein is merely an association describing an associated object, meaning that three relationships may exist, e.g., a and/or B, may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the term "at least one" herein means any one of a plurality or any combination of at least two of a plurality, for example, including at least one of A, B, C, and may mean including any one or more elements selected from the group consisting of A, B and C.

Furthermore, in the following detailed description, numerous specific details are set forth in order to provide a better understanding of the present disclosure. It will be understood by those skilled in the art that the present disclosure may be practiced without some of these specific details. In some instances, methods, means, elements and circuits that are well known to those skilled in the art have not been described in detail so as not to obscure the present disclosure.

It is understood that the above-mentioned method embodiments of the present disclosure can be combined with each other to form a combined embodiment without departing from the logic of the principle, which is limited by the space, and the detailed description of the present disclosure is omitted.

The execution main body of the photovoltaic system dynamic reconfiguration method provided by the embodiment of the present disclosure may be an information processing apparatus, for example, the photovoltaic system dynamic reconfiguration method may be executed by a terminal device or a server or other processing devices, where the terminal device may be a User Equipment (UE), a mobile device, a User terminal, a cellular phone, a cordless phone, a Personal Digital Assistant (PDA), a handheld device, a computing device, a vehicle-mounted device, a wearable device, or the like. In some possible implementations, the photovoltaic system dynamic reconfiguration method may be implemented by a processor calling computer readable instructions stored in a memory.

Before explaining embodiments of the present disclosure, regarding connection relationships and specific frameworks between a photovoltaic system and an inverter assembly in the embodiments of the present disclosure, fig. 1 shows a schematic topology structure of a photovoltaic group control system according to an embodiment of the present disclosure. As shown in fig. 1, the photovoltaic group control system (photovoltaic system dynamic reconfiguration system) may include: photovoltaic system 10, inverter assembly 20, switching assembly 30 and control assembly 40. Wherein, the photovoltaic system 10 comprises at least one group of photovoltaic strings, and the photovoltaic strings comprise at least one photovoltaic panel; the inverter assembly 20 includes at least one inverter; the switch assembly 30 is used for connecting the photovoltaic system 10 and the inverter assembly 20, and an inverter in the inverter assembly 20 is connected with at least one group of photovoltaic string; and the control component is used for controlling the switch component 30 to execute connection switching between the photovoltaic system and the inverter component according to the acquired output power parameters of the photovoltaic system 10 and the acquired input power parameters of the inverter component 20, so as to realize dynamic reconfiguration of the photovoltaic system.

As shown in fig. 1, a photovoltaic string in a photovoltaic system is connected to an inverter in an inverter assembly through a switch control box; the switch control box mainly comprises a switch component and a DSP controller (control component); the control assembly can acquire photovoltaic system parameters output by the photovoltaic string and power grid parameters input to the inverter from real-time collection; a switch assembly in the switch control box may establish an electrical connection between each adjacent photovoltaic string and the inverter. The direct-current side group control topological structure can enable each photovoltaic group string to be flexibly connected to an operating inverter in a matching mode so as to enable a target function to be optimal; the control assembly can automatically switch the number of the inverter circuits according to the output current of each photovoltaic panel, if the inverter fails suddenly, the photovoltaic string can be connected to other inverters to work normally, or the photovoltaic string can be switched to an optimal connection state in time when the power parameters change due to weather reasons. In addition, the number of photovoltaic strings in the embodiments of the present disclosure may be the same as or different from the number of inverters.

A photovoltaic system dynamic reconfiguration method applied in the above photovoltaic group control system is described below, and fig. 2 shows a flowchart of a photovoltaic system dynamic reconfiguration method according to an embodiment of the present disclosure, and as shown in fig. 2, the photovoltaic system dynamic reconfiguration method includes:

s10: acquiring power parameters of an inverter assembly connected with a photovoltaic system;

in some possible embodiments, the photovoltaic system parameters and the grid parameters in the photovoltaic group control system may be obtained in real time, the photovoltaic system parameters include a first direct current and a first direct voltage output by the real-time photovoltaic system, and the grid parameters include a second direct current and a second direct voltage input to the inverter, and a grid-connected point real-time voltage of the photovoltaic system. Specifically, a first direct current and a first direct voltage output by the whole photovoltaic system can be determined according to the direct voltage and the current output by each photovoltaic string, and a second direct current and a second direct voltage at the input end of the inverter assembly can be determined according to the direct voltage and the direct current at the input end of each inverter. Alternatively, the direct current and the direct voltage at the output end of the photovoltaic system may also be directly used as the first direct current and the first direct voltage, and the direct current and the direct voltage at the input end of the inverter assembly may also be directly determined as the second direct current and the second direct voltage, which is not specifically limited in this disclosure.

Further, the input power of the inverter may be determined from the direct current and the direct voltage at the input of the inverter, and the input power of the inverter assembly may also be determined from the second direct current and the second direct voltage at the input of the inverter assembly.

That is to say, the embodiments of the present disclosure may utilize the parameters, such as the input current, the input voltage, and the power, of each inverter obtained in real time, and may obtain the parameters, such as the output current, the output voltage, and the output power, of the photovoltaic string, which is not limited in this disclosure.

S20: determining an optimal bridging manner between the photovoltaic system and the inverter assembly by using the power parameter;

in some possible embodiments, the switching component may be controlled to execute the bridging mode between the photovoltaic system and the inverter according to a time interval, that is, the on-off combination mode of each switch in the switching component may be controlled, and specifically, the determination of the optimal bridging mode may be executed by using the collected photovoltaic system parameters and the collected grid parameters. Moreover, in the embodiment of the present disclosure, the time interval between the two switching operations is determined, and the preset time may be equal to or less than the time interval.

S30: predicting whether power parameters input to the inverter satisfy constraint conditions when the photovoltaic system and the inverter are connected in the optimal bridging manner;

in some possible embodiments, it may be determined whether a predetermined constraint condition is satisfied when the connection switching for performing the optimal bridging manner is predicted, where the predetermined constraint condition is related to parameters such as the inverter input power.

S40: and responding to the condition that the constraint condition is met, and switching to the optimal bridging mode.

And under the condition that the inverter is determined to meet the constraint condition, executing the switching of the optimal bridging mode, wherein whether the switching time is reached can be determined according to a preset interval, and if the switching time is reached, executing the connection switching of the optimal bridging mode.

Based on the configuration, the embodiment of the disclosure can realize automatic switching of the connection state between the photovoltaic system and the inverter assembly, and simultaneously, according to the set constraint condition, the connection mode can be optimized, and the stability of the electric power between the photovoltaic system and the inverter system can be ensured.

The embodiments of the present disclosure are described in detail below. The embodiment of the disclosure may obtain, in real time, a first direct current and a first direct voltage output by each photovoltaic string, where each photovoltaic string may be assigned a corresponding first identifier, for example, the photovoltaic strings are numbered and sorted according to the

sequence

1,2, …, X (total X photovoltaic strings PV)₁…PV_X) The X photovoltaic string groups are divided into m groups, each group including at least one photovoltaic string group, and the photovoltaic string groups of the same group are connected to the same inverter, and the photovoltaic ancestors of different groups are connected to different inverters. The unconnected inverters remain in a standby state. Based on the above configuration, the string output voltage and current of the z-th string photovoltaic string in the jth group can be expressed as

Wherein, U_d,m,jAnd I_d,m,jInput voltage and input current of the j-th group of inverters before switch reconfiguration are respectively represented by dFlow, k_jThe number of the photovoltaic string groups in the jth group is j belongs to m, and m is the number of the inverters and is the same as the group number of the photovoltaic string groups.

Based on the above, the power at the input of each inverter in the inverter assembly can be determined. As described in the foregoing embodiment, the switching may be performed at preset intervals to complete dynamic reconfiguration, where in the preset intervals after completing one switching, the power of the inverter in the preset intervals may be collected in real time, and the determination of the optimal bridging manner may be performed based on the power.

Fig. 3 shows a flowchart of step S20 in the photovoltaic system dynamic reconfiguration method according to the embodiment of the present disclosure. Wherein said determining an optimal manner of bridging between the photovoltaic system and the inverter assembly using the power parameter comprises:

s21: determining whether the power obtained within a preset time meets the power out-of-limit condition;

s22: and under the condition that the power obtained within the preset time does not meet the power out-of-limit condition, determining an optimal bridging mode between the photovoltaic system and the inverter assembly.

In some possible embodiments, in response to a number of times that the power acquired within a preset time exceeds a power threshold value being greater than or equal to a number of times threshold value, determining that the power satisfies the power out-of-limit condition; and determining that the power does not meet the power out-of-limit condition in response to the fact that the number of times that the power obtained within the preset time exceeds the power threshold is smaller than a number of times threshold.

Wherein, in the time interval of two switching operations, the input power of the inverter can be obtained, for example, 20-50 times of power data P can be detected in the time interval, if the power data P exceeds the power threshold P_maxIf the number of the power data is larger than or equal to the time threshold, the power out-of-limit condition is met, otherwise, the power out-of-limit condition is not met, wherein the time threshold is larger than or equal to 2. In addition, the preset time may be a time value less than or equal to the time interval.

In addition, the disclosed embodimentsUnder the condition that the power obtained within the preset time meets the power out-of-limit condition, determining the quantity value of the photovoltaic panel to be cut off according to the power; cutting a preset number of photovoltaic panels from the string of photovoltaic groups connected to the inverter based on the magnitude value. The predetermined amount is determined by the power data P exceeding Pmax. In particular, a predetermined number

Wherein, P_PVRated power, P, for a single photovoltaic panel_maxFor the power threshold, P is the maximum power value that exceeds the power threshold.

The preset number of photovoltaic panels may be randomly deleted from a plurality of groups of photovoltaic strings connected to the inverter, or the preset number of photovoltaic panels may be sequentially deleted from the photovoltaic strings according to the sequence of the photovoltaic panels, which is not specifically limited in the present disclosure.

In addition, an optimal bridging manner between the photovoltaic system and the inverter assembly is determined when the power obtained within a preset time does not satisfy the power out-of-limit condition. That is, if the power of the inverters obtained within the time interval is less than the power threshold, the determination of the optimal bridge manner may be performed.

Fig. 4 shows a flowchart of determining an optimal bridging manner according to an embodiment of the present disclosure, where the determining the optimal bridging manner between the photovoltaic system and the inverter assembly includes:

s201: determining the number of switching times required for switching from the current first connection state of the photovoltaic system and the inverter assembly to any second connection state;

s202: determining a switching cost loss of any one of the second connection states using the number of switching times;

s203: determining the operating benefit of the photovoltaic system for switching from the first connection state to any one of the second connection states by using the switching cost loss;

s204: and determining the second connection state corresponding to the maximum photovoltaic system operation benefit as an optimal bridging mode.

In some possible embodiments, the connection modes between each inverter in the inverter assembly and each photovoltaic string in the photovoltaic system may constitute a connection set, and the connection set may include N connection modes. In the embodiment of the present disclosure, the current connection manner may be determined as the first connection state, and any one of the N connection manners in the connection set may be referred to as the second connection state, that is, the second connection state includes all connection states, including the first connection state itself, where N is an integer greater than or equal to 1. The switches in the switch assembly have different on-off states in different connection states.

In the embodiment of the disclosure, an exhaustive method can be adopted to obtain an optimal bridging mode, and the photovoltaic system operation benefit C under various connection modes can be obtained on the assumption that there are N types of bridging modes in total_ope(1)，C_ope(2)，…，C_opeAnd (N), the bridge connection mode corresponding to the maximum value of the operation benefit is the optimal bridge connection mode. The switch bridging manner of the embodiments of the present disclosure can be expressed as:

wherein X is 1,2, … X, y is 1,2, …, m. S_x,yTaking 0 indicates switch off or inverter shutdown, and 1 indicates switch on or inverter operation. The controller can control the bridge-crossing switch and the inverter to start and stop by using a 0-1 matrix algorithm. Symbol S for start/stop state of inverter y_y,yThe bridge-crossing switch connection state between the photovoltaic array x and the inverter y is represented by S_x,yWherein x < y. Taking a power generation unit consisting of 3 photovoltaic strings and 3 inverters as an example, S_y,yAnd S_x,yThe upper triangular matrix is represented by a 0-1 matrix as shown below.

Wherein 0/1 represents a connected or on-off state; 0 indicates switch off or inverter shutdown; 1 represents a switch connection or inverter operation; "×" indicates no such connection.

The number of times of switching actions can be conveniently solved by the XOR relation between 0 and 1 during two times of switching. In addition, as can be seen from the switching topology of fig. 1, 0 and 1 are not fully reconfigurable combinations. Generally, the number of photovoltaic strings and the number of inverters in the photovoltaic power generation unit are small, and the number of combination modes is small.

Taking 3 arrays and 3 inverters as an example to form a power generation unit, 10 combination modes are provided in total. One connection mode corresponds to one objective function, and the connection mode is limited. And solving by adopting an exhaustion method to quickly and accurately obtain the target function results of various connection schemes. Specifically, the objective function results of various connection modes are calculated, the objective functions are ranked from large to small, and the connection mode with the largest objective function is preferentially selected.

According to the current bridging mode (first connection state) of the switch, the switching times of the switch when the current bridging mode is switched to the nth bridging mode (any second connection state) are obtained

Wherein k is_SW(n) is the switching times when the current bridging mode is switched to the nth bridging mode, S' (n) is the switching bridging mode under the nth bridging mode, and S is the current bridging mode; n is 1,2, …, and N is the total number of switch bridging modes;

based on the above configuration, the number of switching times of the switch that performs switching between the first connection state and either of the second connection states can be obtained, and the cost loss of the switching action of the corresponding second connection state can be determined based on the number of switching times.

Specifically, the number k of switching times may be determined according to the switching frequency when the current bridging mode (first connection state) is switched to the nth bridging mode (second connection state)_SW(n) and market price of switch C_swAnd service life K of switching device_selObtaining the cost loss of the switch action when the current bridge connection mode is switched to the n-th bridge connection mode,

wherein, C_switching(n) is a loss of switching cost, k, when switching from the current bridge mode to the n-th bridge mode_swAnd (n) is the switching times when the current bridging mode is switched to the nth bridging mode, Csw is the market price of the switch, and Ksel is the electrical service life of the switch.

The cost loss is caused by the switching action, and the photovoltaic system operation benefit C when the current bridging mode is switched to the nth bridging mode can be obtained according to the switching action cost loss when the current bridging mode is switched to the nth bridging mode_ope(n) photovoltaic System operational benefit C_ope(n) operational benefit C that can be of the photovoltaic system before switching_pAnd loss of switching cost C_switching(n) difference between (n).

C_ope(n)＝C_p-C_switching(n)

Wherein, C_opeAnd (n) is the operation benefit of the photovoltaic system when the current bridging mode is switched to the nth bridging mode, and Cp is the operation benefit of the photovoltaic system before switching.

Specifically, the operating benefit C of the photovoltaic system before the switching of the switch_pThe determination method of (2) may include: determining the input current and the input voltage of the ith inverter after the switch is reconstructed; solving the total output power of the group control system by using the input power and the conversion efficiency of the inverter; and determining the operation benefit of the photovoltaic system before switching by using the output total power and the switching time interval.

The input current and the input voltage of the ith inverter after the switch is reconstructed can be calculated according to the following mode, wherein i belongs to m;

wherein, U'_d,m,iAnd l'_d,m,iAfter the switch is reconstructed, the input voltage and current k of the i-th group of inverters are respectively_iRepresents the ith groupA total number of photovoltaic strings in the photovoltaic string.

Obtaining the total output power P of the group control system by using the input power and the conversion efficiency of the inverter_totalThe method comprises the following steps:

wherein, P_totalOutput the total power, eta, for the group control system_iThe conversion efficiency of the ith inverter is obtained. The output power gain of the group control system (the operation benefit of the photovoltaic system before the switch of the photovoltaic system),

C_p＝P_totalT_{sw_interval}C_G

wherein, C_GFor photovoltaic on-line electricity prices, T_{sw_interval}The time interval for two consecutive control commands for the control assembly, i.e. the time interval for sending the connection state of the changeover switch assembly to the switch assembly.

Based on the above, it may be determined that the operating benefit of the photovoltaic system for switching from the first connection state to any one of the second connection states, specifically, N connection modes exist, and the operating benefit of the photovoltaic system for each connection mode may be represented as C_ope(1)，C_ope(2)，…，C_ope(N), the maximum photovoltaic system operating benefit max [ C ] can then be calculated_ope(1)，C_ope(2)，…，C_ope(N)]And determining the second connection state corresponding to the maximum photovoltaic system operation benefit as an optimal bridging mode.

In the case where the optimal bridge connection method is obtained, it may be determined whether or not the power parameter input to the inverter module satisfies the constraint condition when performing connection switching of the optimal bridge connection method, and the switching of the optimal bridge connection method may be performed in the case where the constraint condition is satisfied.

Specifically, fig. 5 shows a flowchart of step S30 in the dynamic reconfiguration method of the photovoltaic system according to the embodiment of the present disclosure. Wherein the predicting whether a power parameter input to the inverter assembly satisfies a constraint condition when the photovoltaic system and the inverter assembly are connected in the optimal bridging manner includes:

s31: determining whether the input parameters of the inverter assembly meet a first constraint condition when the optimal bridge connection mode is switched;

s32: determining whether a fitted input power of the inverter assembly satisfies a second constraint condition within a first time range, the first time range including a switching time point at which a switching operation of the optimal bridge manner is performed;

s33: determining that the constraint condition is satisfied in a case where the first constraint condition and the second constraint condition are satisfied.

In some possible embodiments, the constraints may include a first constraint and a second constraint. The first constraint condition may constrain the out-of-limit condition of the inverter, that is, determine the out-of-limit condition of parameters such as current, voltage, and power input to the inverter. And constraining the power of the inverter under a second constraint condition, the embodiment of the disclosure can fit and generate the input power of the inverter at a plurality of moments before and after the switch reconfiguration, and determine the stability and reliability of the inverter by using the fitted input power.

Specifically, the power parameters of the input end of the inverter after the switching of the switching elements in the optimal bridging manner may be determined, that is, the power parameters of the input current, the voltage, the power, and the like of the inverter when the switching of the connection state between the inverter elements and the photovoltaic system is performed are predicted. And determining whether the power parameter of the input end of the inverter meets a first constraint condition based on the following first preset conditions, wherein the first constraint condition comprises the following steps: the input voltage range after the switch is switched is U_dmin,U_dmax]In the current is less than or equal to I_dmaxThe input power is greater than 0 and less than or equal to the power threshold P_maxBetween the time a before the optimal bridge connection mode is switched and the time b after the optimal bridge connection mode is switched, the voltage output by the inverter is less than or equal to the variable limit value of the voltage diagram, and the first constraint condition is expressed as:

wherein, U_dminAnd U_dmaxMinimum and maximum operating voltage allowed for the inverter, respectively, I_dmaxMaximum input current, P, specified for the inverter_maxIs the maximum allowable input power limit for the inverter, Δ U is the voltage transient limit, | U'_d,m,i,a-U’_d,m,i,bI represents the amount of output voltage variation of the inverter m between the times a and b, the time between a and b being less than the time interval, which may take 5 to 15 minutes (min).

In addition, the second constraint may be expressed as:

of formula (II) to (III)'_d,m,iT before the switching time point_{sw_interval}Linear fitting value, P', of input power of i-th group of inverters at time m when inverters work "_d,m,iFor T after the switching time point_{sw_interval}Fitting value of input power of inverter of ith group at moment, P_ymax,iFor switching time point T before_{sw_before}Maximum fitting value delta P of input power data of ith group of inverters at moment_i＝max(P_Yp,i-P_yp,i) Real-time measurement of power data P for photovoltaic strings in group i_Yp,iFitting function P to power_yp,iMaximum difference of e₀The power fluctuation coefficient of the fitting function can be 1 to 5 percent.

Wherein, T_{sw_before}The historical time and time interval at which the dynamic reconfiguration can be performed by the photovoltaic system is determined, in particular, when the historical time T is of different values_{sw_before}Different values may be taken.

Wherein t is the system running time,

time of data analysis after stable operation of the system, k_TThe maximum integer satisfying the above formula. System stability indicates the situation where each acquired current parameter remains stable.

In addition, the embodiment of the present disclosure may utilize a least square method to fit the input power of the inverter at different times, for example, a first-order curve fitting may be performed, or a second-order or third-order curve fitting may also be performed, which is not specifically limited by the present disclosure. Wherein, the power data can be subjected to curve fitting according to a least square method to obtain the power fitting value P'_d,m,i、P”_d,m,i、P_ymax,i. And then whether the fitted power parameter meets the second constraint condition can be judged.

In the case where the first constraint condition and the second constraint condition are simultaneously satisfied, it may be determined that the optimal bridging manner satisfies the constraint conditions. Under which the switching of the optimal bridging mode can be performed. Alternatively, in another embodiment of the present disclosure, when one of the first constraint condition and the second constraint condition is satisfied, it may be determined that the optimal bridging manner satisfies the constraint condition.

Specifically, the switching to the optimal bridging manner when the constraint condition is satisfied includes: determining switching time according to a preset time interval; in response to the constraint condition being satisfied, switching to the optimal bridge mode when the switching time is reached

As described above, the embodiment of the present disclosure may perform the switching of the connection manner according to the preset time interval, that is, when the input power of the inverter does not satisfy the power out-of-limit condition and the determined optimal bridge manner satisfies the constraint condition, the switching of the optimal bridge manner may be performed at the time interval from the last switching operation. That is, when the set switching time is reached, the connection switching from the current first connection state to the optimal bridge connection mode is performed again.

In order to more clearly embody the embodiments of the present disclosure, the following exemplarily illustrates a dynamic reconfiguration method of a photovoltaic system of the embodiments of the present disclosure.

Fig. 12 shows another flowchart of a method for dynamically reconfiguring a photovoltaic system according to an embodiment of the present disclosure, and taking fig. 12 as an example, in the embodiment of the present disclosure, obtaining parameters of an inverter assembly and a photovoltaic system, such as current and voltage input by each inverter, and current and voltage output by a photovoltaic string, etc., may be implemented. In the time interval between two adjacent times of performing the bridge mode switching operation, if it is determined whether the obtained input power of the inverter has a condition greater than the power threshold, and the number of times of the condition is greater than the number threshold (e.g., 2 times), for example, the current bridge mode is kept unchanged, a preset number of photovoltaic panels are cut out from the photovoltaic panels in the photovoltaic group string connected to the inverter, and the preset number determination process refers to the above embodiment. And under the condition that the input power of the inverter is larger than the power threshold value and exceeds the time threshold value does not exist, further determining an optimal bridging mode by using the benefit index parameter, determining whether the optimal bridging mode meets the constraint condition, keeping the current bridging mode unchanged if any one of the first constraint condition and the second constraint condition is not met, and switching to the optimal bridging mode if the constraint condition is met.

According to the technical scheme, the photovoltaic system dynamic reconfiguration method provided by the embodiment can improve grid-connected benefit and reliability, can enable the group control system to switch the number of the inverters in real time according to the change of illumination intensity, can effectively improve the output utilization rate of the photovoltaic grid-connected inverter, and can increase the generated energy. Aiming at variable weather, the system can prevent the power of the inverter from exceeding the limit, and the reliability of the system is enhanced.

In order to verify the effectiveness of the control method provided by the invention, a photovoltaic group control system built by a plurality of photovoltaic group strings and a plurality of inverters is analyzed. The multiple photovoltaic string simulators emit constant output power, wherein the direct-current voltage is set to 360V. The configuration capacity of each single photovoltaic group string and each single inverter is 5kW, and the number k of each group of photovoltaic group strings in the initial state_iIs 1. At different powers, the output power of the inverter was measured. Various parameters of the system are shown in table 1, and the inverter has different loadsThe horizontal down conversion efficiency is shown in table 2.

TABLE 1 System parameter Table

TABLE 2 conversion efficiency of inverter at different load levels

The conversion efficiency of the group control system with different capacity configurations at different powers is plotted in fig. 6, wherein the abscissa is the total input power level of the group control system. When the number x of the photovoltaic strings is 3, 4, and 5, respectively, a group control system conversion efficiency graph of the rated power of the photovoltaic simulator, which varies from 0.05 to 1, is shown in fig. 3, wherein the abscissa is the total input level of the group control system. As can be seen from fig. 6, with the increase of the group control system, under the condition that the number x of the photovoltaic strings is 3, 4, 5 and under the condition that the input power level is lower than 25% of the system, the european efficiency is respectively improved by 0.40%, 0.44% and 0.45% through calculation of weighting coefficients compared with the conventional connection mode. It can be seen that as the number of photovoltaic strings in the group control system increases, the conversion efficiency of the system gradually increases. However, in order to reduce the complexity of the system, a photovoltaic group control system consisting of 3 to 5 photovoltaic group strings is suitable.

In another example, a group control system platform with 3 photovoltaic arrays and 3 inverters is established to perform 1-hour experimental operation, and the power out-of-limit prevention function is analyzed. The results of 1 hour operation comparing three operation schemes of conventional operation, only objective function operation and power-off-limit prevention operation are shown in fig. 7 and 8. It can be seen from fig. 7 that the photovoltaic fluctuation is random and abrupt so that the power off-limit situation is easy to occur only when considering the objective function. During the period of 50min-60min, the system exceeds the maximum output of the inverter due to photovoltaic fluctuation, so that the inverter cannot work normally. It can be seen in fig. 8 that the method effectively avoids the power out-of-limit condition caused by the sudden increase in power.

By the reconstruction method, the number of the working inverters of the group control system can be switched in real time according to the change of the illumination intensity, the output utilization rate of the photovoltaic grid-connected inverter can be effectively improved, and the generated energy can be increased. Aiming at the condition of complicated and changeable weather, the function of preventing the power of the inverter from exceeding the limit can be realized, and the reliability of the system is enhanced.

In particular, those skilled in the art will appreciate that in the above methods of the embodiments, the order of writing the steps does not imply a strict order of execution and any limitations on the implementation, and the specific order of execution of the steps should be determined by their function and possible inherent logic.

In addition, the present disclosure also provides a photovoltaic system dynamic reconfiguration device, a system, an electronic device, a computer-readable storage medium, and a program, which can be used to implement any one of the photovoltaic system dynamic reconfiguration methods provided by the present disclosure, and the corresponding technical solutions and descriptions and corresponding descriptions in the methods section are omitted for brevity.

Fig. 9 shows a block diagram of a photovoltaic system dynamic reconfiguration device according to an embodiment of the present disclosure, and as shown in fig. 9, the photovoltaic system dynamic reconfiguration device includes:

the acquisition module 10 is used for acquiring power parameters of an inverter assembly connected with a photovoltaic system;

a determination module 20 for determining an optimal bridging manner between the photovoltaic system and the inverter assembly according to the power parameter;

a prediction module 30, configured to predict whether a power parameter input to the inverter assembly satisfies a constraint condition when the photovoltaic system and the inverter assembly are connected in the optimal bridging manner;

and the switching module 40 is configured to switch to the optimal bridging manner when the constraint condition is satisfied.

In some embodiments, functions of or modules included in the apparatus provided in the embodiments of the present disclosure may be used to execute the method described in the above method embodiments, and specific implementation thereof may refer to the description of the above method embodiments, and for brevity, will not be described again here.

Embodiments of the present disclosure also provide a computer-readable storage medium having stored thereon computer program instructions, which when executed by a processor, implement the above-mentioned method. The computer readable storage medium may be a non-volatile computer readable storage medium.

An embodiment of the present disclosure further provides an electronic device, including: a processor; a memory for storing processor-executable instructions; wherein the processor is configured as the above method.

The electronic device may be provided as a terminal, server, or other form of device.

Fig. 10 illustrates a block diagram of an electronic device 800 in accordance with an embodiment of the disclosure. For example, the electronic device 800 may be a mobile phone, a computer, a digital broadcast terminal, a messaging device, a game console, a tablet device, a medical device, a fitness device, a personal digital assistant, or the like terminal.

Referring to fig. 10, electronic device 800 may include one or more of the following components: processing component 802, memory 804, power component 806, multimedia component 808, audio component 810, input/output (I/O) interface 812, sensor component 814, and communication component 816.

The processing component 802 generally controls overall operation of the electronic device 800, such as operations associated with display, telephone calls, data communications, camera operations, and recording operations. The processing components 802 may include one or more processors 820 to execute instructions to perform all or a portion of the steps of the methods described above. Further, the processing component 802 can include one or more modules that facilitate interaction between the processing component 802 and other components. For example, the processing component 802 can include a multimedia module to facilitate interaction between the multimedia component 808 and the processing component 802.

The memory 804 is configured to store various types of data to support operations at the electronic device 800. Examples of such data include instructions for any application or method operating on the electronic device 800, contact data, phonebook data, messages, pictures, videos, and so forth. The memory 804 may be implemented by any type or combination of volatile or non-volatile memory devices such as Static Random Access Memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, magnetic or optical disks.

The power supply component 806 provides power to the various components of the electronic device 800. The power components 806 may include a power management system, one or more power supplies, and other components associated with generating, managing, and distributing power for the electronic device 800.

The multimedia component 808 includes a screen that provides an output interface between the electronic device 800 and a user. In some embodiments, the screen may include a Liquid Crystal Display (LCD) and a Touch Panel (TP). If the screen includes a touch panel, the screen may be implemented as a touch screen to receive an input signal from a user. The touch panel includes one or more touch sensors to sense touch, slide, and gestures on the touch panel. The touch sensor may not only sense the boundary of a touch or slide action, but also detect the duration and pressure associated with the touch or slide operation. In some embodiments, the multimedia component 808 includes a front facing camera and/or a rear facing camera. The front camera and/or the rear camera may receive external multimedia data when the electronic device 800 is in an operation mode, such as a shooting mode or a video mode. Each front camera and rear camera may be a fixed optical lens system or have a focal length and optical zoom capability.

The audio component 810 is configured to output and/or input audio signals. For example, the audio component 810 includes a Microphone (MIC) configured to receive external audio signals when the electronic device 800 is in an operational mode, such as a call mode, a recording mode, and a voice recognition mode. The received audio signals may further be stored in the memory 804 or transmitted via the communication component 816. In some embodiments, audio component 810 also includes a speaker for outputting audio signals.

The I/O interface 812 provides an interface between the processing component 802 and peripheral interface modules, which may be keyboards, click wheels, buttons, etc. These buttons may include, but are not limited to: a home button, a volume button, a start button, and a lock button.

The sensor assembly 814 includes one or more sensors for providing various aspects of state assessment for the electronic device 800. For example, the sensor assembly 814 may detect an open/closed state of the electronic device 800, the relative positioning of components, such as a display and keypad of the electronic device 800, the sensor assembly 814 may also detect a change in the position of the electronic device 800 or a component of the electronic device 800, the presence or absence of user contact with the electronic device 800, orientation or acceleration/deceleration of the electronic device 800, and a change in the temperature of the electronic device 800. Sensor assembly 814 may include a proximity sensor configured to detect the presence of a nearby object without any physical contact. The sensor assembly 814 may also include a light sensor, such as a CMOS or CCD image sensor, for use in imaging applications. In some embodiments, the sensor assembly 814 may also include an acceleration sensor, a gyroscope sensor, a magnetic sensor, a pressure sensor, or a temperature sensor.

The communication component 816 is configured to facilitate wired or wireless communication between the electronic device 800 and other devices. The electronic device 800 may access a wireless network based on a communication standard, such as WiFi, 2G or 3G, or a combination thereof. In an exemplary embodiment, the communication component 816 receives a broadcast signal or broadcast related information from an external broadcast management system via a broadcast channel. In an exemplary embodiment, the communication component 816 further includes a Near Field Communication (NFC) module to facilitate short-range communications. For example, the NFC module may be implemented based on Radio Frequency Identification (RFID) technology, infrared data association (IrDA) technology, Ultra Wideband (UWB) technology, Bluetooth (BT) technology, and other technologies.

In an exemplary embodiment, the electronic device 800 may be implemented by one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), controllers, micro-controllers, microprocessors or other electronic components for performing the above-described methods.

In an exemplary embodiment, a non-transitory computer-readable storage medium, such as the memory 804, is also provided that includes computer program instructions executable by the processor 820 of the electronic device 800 to perform the above-described methods.

Fig. 11 shows a block diagram of another electronic device 1900 according to an embodiment of the disclosure. For example, the electronic device 1900 may be provided as a server. Referring to fig. 11, electronic device 1900 includes a processing component 1922 further including one or more processors and memory resources, represented by memory 1932, for storing instructions, e.g., applications, executable by processing component 1922. The application programs stored in memory 1932 may include one or more modules that each correspond to a set of instructions. Further, the processing component 1922 is configured to execute instructions to perform the above-described method.

The electronic device 1900 may also include a power component 1926 configured to perform power management of the electronic device 1900, a wired or wireless network interface 1950 configured to connect the electronic device 1900 to a network, and an input/output (I/O) interface 1958. The electronic device 1900 may operate based on an operating system stored in memory 1932, such as Windows Server, Mac OS XTM, UnixTM, LinuxTM, FreeBSDTM, or the like.

In an exemplary embodiment, a non-transitory computer readable storage medium, such as the memory 1932, is also provided that includes computer program instructions executable by the processing component 1922 of the electronic device 1900 to perform the above-described methods.

The present disclosure may be systems, methods, and/or computer program products. The computer program product may include a computer-readable storage medium having computer-readable program instructions embodied thereon for causing a processor to implement various aspects of the present disclosure.

The computer readable storage medium may be a tangible device that can hold and store the instructions for use by the instruction execution device. The computer readable storage medium may be, for example, but not limited to, an electronic memory device, a magnetic memory device, an optical memory device, an electromagnetic memory device, a semiconductor memory device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a Static Random Access Memory (SRAM), a portable compact disc read-only memory (CD-ROM), a Digital Versatile Disc (DVD), a memory stick, a floppy disk, a mechanical coding device, such as punch cards or in-groove projection structures having instructions stored thereon, and any suitable combination of the foregoing. Computer-readable storage media as used herein is not to be construed as transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission medium (e.g., optical pulses through a fiber optic cable), or electrical signals transmitted through electrical wires.

The computer-readable program instructions described herein may be downloaded from a computer-readable storage medium to a respective computing/processing device, or to an external computer or external storage device via a network, such as the internet, a local area network, a wide area network, and/or a wireless network. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers. The network adapter card or network interface in each computing/processing device receives computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in a computer-readable storage medium in the respective computing/processing device.

The computer program instructions for carrying out operations of the present disclosure may be assembler instructions, Instruction Set Architecture (ISA) instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C + + or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a Local Area Network (LAN) or a Wide Area Network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet service provider). In some embodiments, the electronic circuitry that can execute the computer-readable program instructions implements aspects of the present disclosure by utilizing the state information of the computer-readable program instructions to personalize the electronic circuitry, such as a programmable logic circuit, a Field Programmable Gate Array (FPGA), or a Programmable Logic Array (PLA).

Various aspects of the present disclosure are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the disclosure. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer-readable program instructions.

These computer-readable program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer-readable program instructions may also be stored in a computer-readable storage medium that can direct a computer, programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer-readable medium storing the instructions comprises an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks.

The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer, other programmable apparatus or other devices implement the functions/acts specified in the flowchart and/or block diagram block or blocks.

The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

Having described embodiments of the present disclosure, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terms used herein were chosen in order to best explain the principles of the embodiments, the practical application, or technical improvements to the techniques in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A photovoltaic system dynamic reconfiguration method is characterized by comprising the following steps:

2. The method of claim 1, wherein said determining an optimal bridge between the photovoltaic system and the inverter assembly using the power parameter comprises:

determining whether the power obtained in the preset time meets a power out-of-limit condition;

3. The method of claim 2, further comprising:

4. The method according to claim 2 or 3, wherein the determining whether the power obtained within a preset time meets a power out-of-limit condition comprises:

5. The method of claim 1, wherein the determining an optimal manner of bridging between the photovoltaic system and the inverter assembly comprises:

6. The method of claim 1, wherein switching to the optimal bridging mode in response to the constraint being satisfied comprises:

determining switching time according to a preset time interval;

7. A photovoltaic system dynamic reconfiguration device, comprising:

the acquisition module is used for acquiring power parameters of an inverter assembly connected with the photovoltaic system;

a determination module for determining an optimal bridging manner between the photovoltaic system and the inverter assembly using the power parameter;

8. The apparatus of claim 7, wherein the determining module is further configured to determine whether the power obtained within a preset time meets a power out-of-limit condition;

9. A photovoltaic system dynamic reconfiguration system, comprising:

an inverter assembly including at least one inverter;

control assembly for performing a method of dynamic reconfiguration of a photovoltaic system according to any one of claims 1 to 6.

10. An electronic device, comprising:

a processor;

a memory for storing processor-executable instructions;

wherein the processor is configured to invoke the memory-stored instructions to perform the method of any of claims 1-6.