CN110266265B - Photovoltaic array circuit reconstruction system with partially shielded illumination and method thereof - Google Patents
Photovoltaic array circuit reconstruction system with partially shielded illumination and method thereof Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/34—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering
- H02J7/35—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering with light sensitive cells
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
- H02S40/00—Components or accessories in combination with PV modules, not provided for in groups H02S10/00 - H02S30/00
- H02S40/30—Electrical components
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
- H02S50/00—Monitoring or testing of PV systems, e.g. load balancing or fault identification
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The invention discloses a photovoltaic array circuit reconstruction system with partially shielded illumination and a method thereof. The system comprises a photovoltaic array circuit, a photovoltaic panel branch switching circuit, a bypass circuit, an electric quantity detection and analysis circuit and a PLC power optimization module; the photovoltaic array circuit comprises N rows and M columns of photovoltaic panels, each photovoltaic panel is connected with the branch switching circuit in series, and each column of photovoltaic panels is connected with the bypass circuit in parallel; each photovoltaic panel is connected with the electric quantity detection and analysis circuit in the corresponding row, and each row of electric quantity detection and analysis circuit is connected with the PLC power optimization module. The method comprises the following steps: step one, calculating the power of a reconstruction circuit; and step two, finding out the number of columns which need to be bypassed when the power reaches the maximum, and ensuring that the output power of the photovoltaic array reaches the optimum. And reconstructing a power generation circuit of the photovoltaic array based on the output voltage and power requirements, and improving the efficiency of photovoltaic power generation under non-uniform illumination.
Description
Technical Field
The invention relates to the technical field of photovoltaic power generation, in particular to a photovoltaic array circuit reconstruction system with partially shielded illumination and a method thereof.
Background
With the wide application of photovoltaic power generation systems, more and more distributed photovoltaic power stations and multi-terrain photovoltaic power stations face complex and variable illumination environments.
Under the conditions of partial shielding of trees or buildings, cloudy weather, surface dust or circuit damage and the like, a part of power generation panels in the photovoltaic array cannot generate power normally at some time, energy loss of photoelectric conversion is caused, the total output power is reduced, the circuit structure is changed, internal circulation is formed, the shaded photovoltaic panel becomes a load, and the load is locally overheated and permanently damaged.
In the prior art, a single photovoltaic panel is formed by connecting dozens of unequal photovoltaic cell units in series, and a method for solving local shadows mainly comprises the steps of connecting bypass diodes in parallel at two ends of each photovoltaic cell and connecting anti-reflux diodes in series at the head of a photovoltaic array connected in series.
Disclosure of Invention
In order to solve the above problems, the present invention provides a photovoltaic array circuit reconstruction system and method thereof, wherein the illumination part is blocked.
A photovoltaic array circuit reconstruction system with partially shielded illumination comprises a photovoltaic array circuit, a photovoltaic panel branch switching circuit, a bypass circuit driven by reconstruction logic, an electric quantity detection and analysis circuit and a PLC power optimization module; the photovoltaic array circuit comprises N rows of photovoltaic panels and M columns of photovoltaic panels, the photovoltaic panels are firstly connected in parallel to form M columns of photovoltaic panels, and then the M columns of photovoltaic panels are connected in series; each photovoltaic panel in each row is firstly connected with the branch switching circuit in series, and each row of photovoltaic panels is then connected with the bypass circuit in parallel; each photovoltaic panel is connected with the electric quantity detection and analysis circuit in the corresponding row, and each row of electric quantity detection and analysis circuit is connected with the PLC power optimization module.
The photovoltaic array dynamically changes the circuit topological structure through the circuit change-over switch, so that circuit reconstruction is realized in the power generation process, and the photovoltaic panel with low or no power generation caused by light shielding is isolated or bypassed, so that the integral power generation power of the photovoltaic system is improved.
Further, the photovoltaic panel branch switching circuit comprises a direct current undercurrent relay and a circuit switch; each photovoltaic panel is connected with a direct current undercurrent relay and a circuit change-over switch in series;
when the current of the direct current undercurrent relay is reduced to a given threshold value, the direct current undercurrent relay generates an isolation signal to drive a circuit change-over switch, isolates the photovoltaic panel, stops the power supply of the photovoltaic panel and switches to a voltage limiting circuit; after illumination is recovered, the voltage limiting circuit recognizes that the voltage of the photovoltaic panel is recovered, the driving circuit switches the switch to act, the main circuit, namely the photovoltaic array circuit, is switched back, power generation is recovered, and the photovoltaic array circuit is connected with the load in series.
Further, the voltage limiting circuit comprises an overvoltage relay connected with each column of photovoltaic panels in parallel.
Further, the bypass circuit driven by the reconfiguration logic comprises a bypass relay and a one-way diode connected with the bypass relay in series; the bypass relay is connected with each row of photovoltaic panels in parallel;
the PLC power optimization module comprises a PLC controller, and the PLC controller is connected with each row of photovoltaic panels in parallel; the PLC power optimization module is used for changing the connection and bypass of a single column or a plurality of columns in the photovoltaic array circuit, so that the reconstruction of the circuit structure of the system is realized.
Furthermore, the PLC power optimization module adopts a serial input mode, judges and isolates the photovoltaic panel according to power maximization logic with respect to the total current, voltage and power output by the photovoltaic array circuit, reconstructs a circuit topology structure, meets the requirement of outputting direct-current voltage, generates a switching signal, and drives a circuit reconstruction switch to realize circuit optimization operation.
Further, the PLC power optimization module adopts Siemens s7-200 series PLC.
Furthermore, the electric quantity detection and analysis circuit detects the connection or disconnection condition of each photovoltaic panel in each row by taking each row of photovoltaic panels as a unit, transmits data to the PLC power optimization module, measures the connection condition of each row of photovoltaic panels, marks the connected photovoltaic panel as a signal 1, and disconnects the connected photovoltaic panel as a signal 0; the method comprises the steps of transmitting signals to a PLC power optimization module in a multi-bit binary mode, establishing an adjacent matrix of branch switches in a photovoltaic array circuit through operation analysis, forming a circuit dynamic topology reflecting the on-off state of a photovoltaic panel and the change of generated electricity quantity according to the output total voltage and current of the photovoltaic array circuit, performing reconstruction operation by using the PLC power optimization module, and optimizing the overall power generation efficiency of the photovoltaic array circuit.
The electric quantity detection and analysis circuit is connected with the EM231 module as an extension.
When the illumination is recovered to enable the voltage of the photovoltaic panel to be increased to a certain degree, the overvoltage relay generates a signal for recovering power supply of the isolated photovoltaic panel, and the drive circuit switches the switch to act, so that a switching interlocking logic control circuit is formed; when one group of parallel photovoltaic panels is isolated, the bypass relay is closed, and the whole group of parallel photovoltaic panels is isolated. When the photovoltaic bypass relay is applied to engineering, the field working conditions, such as the geographic environment and the ecological environment of the installation position of a photovoltaic system, need to be considered, the working ranges of the undercurrent relay and the overvoltage relay are determined according to the actual illumination change conditions on the field, so that the current and voltage parameters of the photovoltaic panel are consistent with the actual working conditions when the photovoltaic panel is shielded and the illumination is normal, and the bypass relay can be ensured to work correctly.
The reconstruction logic of the invention estimates the total current value generated by each group of parallel photovoltaic panels according to the running condition of the parallel photovoltaic panels, calculates the total output power of the circuit reconstruction system after the parallel photovoltaic rows outputting the total current (the total current is an estimated value, and the size of the total current is in direct proportion to the number of the rows with the least photovoltaic panel connected by the photovoltaic array) are bypassed in sequence by sequencing the current values from small to large, and determines the parallel photovoltaic rows needing to be bypassed when the power is the maximum.
According to the photovoltaic power generation circuit, the switching interlocking logic control circuit is introduced, and through the design of a circuit structure, the photovoltaic power generation circuit is accurately and timely disconnected when the photovoltaic panel is shielded by light, and is switched to be connected with the voltage limiting circuit; the illumination shading may result in a reduction in the output current of one or more photovoltaic panels which need to be fully disconnected from the main circuit and simultaneously connected in parallel with the voltage limiting circuit. After the illumination is recovered, the voltage limiting circuit outputs signals to the circuit change-over switch, all the photovoltaic panels connected in parallel are recovered to be connected with the main circuit, the current output condition of each photovoltaic panel is determined by the direct current undercurrent relay, and the photovoltaic panels which are still shielded in the current output condition are disconnected with the main circuit.
The switching interlocking logic control circuit realizes automatic switching of the photovoltaic panels under normal shielding and illumination conditions, transmits the on-off conditions of each row of photovoltaic panels to the PLC module in binary information, realizes logic operation by the PLC, and calculates the isolated photovoltaic rows required by outputting the maximum electric energy by taking each group of photovoltaic panels connected in parallel as a controlled unit; a bypass relay is adopted as an actuating mechanism to bypass the photovoltaic columns with low generating current, so that the output power of the photovoltaic array is improved.
In addition, each bypass relay is connected with a diode in series to realize the unidirectional conduction of the circuit, and the photovoltaic panel and the bypass circuit are prevented from forming a closed loop to be short-circuited. The photovoltaic panel branch switching circuit can ensure that the shielded photovoltaic panel is disconnected with the main circuit in time, so that internal circulation of the photovoltaic panel caused by insufficient illumination and excessively low photoproduction voltage is avoided.
A reconstruction method of a photovoltaic array circuit with partially shielded illumination comprises the following steps:
the method comprises the following steps that firstly, the output power of a photovoltaic array circuit is estimated by adopting a PLC power optimization module;
step two, finding out the power reaching the maximum through the logic operation of the PLC
The number of columns which need to be bypassed is increased, and the columns are bypassed, so that the output power of the photovoltaic array circuit is optimized.
Further, the estimation process of the first step is as follows:
the number of each row of parallel photovoltaic panels of the photovoltaic array circuit is M, N groups of parallel photovoltaic panels are sequentially connected in series, the N and M values are not less than 3, and all the photovoltaic panels have the following normal power generation times:
(1) the total voltage output is
ViFor the voltage of the node at two ends of the photovoltaic panels connected in parallel, i represents a row of the photovoltaic panels connected in parallel, i is 1,2, …, N, and V is required according to the output voltage of the photovoltaic power generationminr≤V≤VmaxrI.e. the output voltage is allowed at a nominal minimum VminrAnd a maximum voltage VmaxrChange in between;
(2) the total current output is
IiOutput current for a single parallel node, i ═ 1,2, …, N; a single parallel node current of
Let each branch in parallel current IijThe ratio of the total current of the node is kijAnd then:
Iij＝kijI
wherein M represents the number of photovoltaic panels in a single row of photovoltaic panels that are operating normally, and M represents the total number of photovoltaic panels in a single row, and
(3) the total power output by the photovoltaic array circuit is as follows:
when a single photovoltaic panel is shielded due to illumination, the branch current I is causedijWhen the total output current I is reduced, so that the total generated power P of the whole circuit is reduced, the PLC calculates the output current of each row and the whole output voltage according to the shielding number of the photovoltaic panel, and when the shielding condition occurs, I is reducedijAnd when the PLC becomes smaller, the PLC selects proper N to be 1,2, …, N and m through logic operation i1,2, …, M, to increase P, i.e.:
wherein n is*And
respectively representing the number of photovoltaic columns which are not bypassed when the output power reaches the maximum and the number of photovoltaic panels which normally work in the photovoltaic columns with the minimum generating current, wherein n represents the number of the photovoltaic columns which are not bypassed, and m represents the number of the photovoltaic columns which are not bypassediRepresenting the number of normal power generation of each group of parallel photovoltaic panels.
Further, the second step is to determine the optimal series-parallel photovoltaic array circuit structure by adopting an iterative search algorithm according to the characteristics of the photovoltaic array circuit, and the specific process is as follows:
1) starting a search process when the photovoltaic panel exits the power generation and the total current I or the total power P output by the photovoltaic array circuit decreases, according to which
Output current I of parallel photovoltaic paneliNumber m of photovoltaic panelsiIn direct proportion, namely:
Ii＝I0mi
I0representing the output current of a single photovoltaic panel, InormRepresenting the output current of the single photovoltaic panel in normal operation, calculating the total output power of the photovoltaic array circuit:
selecting a maximum output power
And satisfies the following conditions:
2) these are
Then the corresponding n is determined*，
Quantity, otherwise, continuing searching and comparing;
3) according to n*And
value of (a), reconstructing the photovoltaic array circuit
When the photovoltaic panel is shielded, the photovoltaic panel is withdrawn by a bypass, so that the power generation quantity of the whole parallel photovoltaic panel row group is lower than a certain value, the PLC power optimization module withdraws the whole row of parallel photovoltaic panel bypasses, and the output power of the photovoltaic array circuit is as follows:
as the number of the exiting photovoltaic panel rows increases, the total output voltage also decreases, the whole row of photovoltaic panels with the lowest output current is gradually bypassed, and the total output current increases; through the steps 1) and 2), finding out that the power reaches the maximum
And the number of the columns needing the bypass is increased, then the PLC power optimization module controls the bypass relay switch to perform bypass processing on the corresponding whole column of photovoltaic panels, and the output power of the photovoltaic array circuit is ensured to be optimal.
The invention has the beneficial effects that: the photovoltaic panel branch switching circuit is adopted in the invention, so that the shielded photovoltaic panel can be ensured to be disconnected with the main circuit in time, and internal circulation of the photovoltaic panel caused by over-low photovoltage due to insufficient illumination is avoided.
Drawings
FIG. 1 is a topological diagram of a circuit reconfigurable photovoltaic array structure of an embodiment;
FIG. 2 is a PLC logic circuit control block diagram of an embodiment;
fig. 3 is a photovoltaic array topology diagram of the 10 × 9 photovoltaic power generation system of the embodiment under a certain shading condition.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited thereto.
A photovoltaic array circuit reconfiguration system with partially occluded illumination, as shown in fig. 1-2, comprising: the device comprises a photovoltaic array circuit, a photovoltaic panel branch switching circuit, a bypass circuit driven by a reconfiguration logic, an electric energy detection and analysis circuit and a PLC power optimization module.
The photovoltaic array circuit adopts a connection mode of firstly connecting in parallel and then connecting in series to form an m multiplied by n photovoltaic array, and m photovoltaic panels are connected in parallel to be regarded as a unit group. The photovoltaic panel of each unit group is connected with a direct current undercurrent relay and a circuit change-over switch in series, and each unit group is connected with a voltage limiting circuit with an overvoltage relay in parallel; when the illumination of the photovoltaic panel is blocked, the output current is reduced, so that the direct current undercurrent relay generates an isolation signal to drive a circuit switch, and the photovoltaic panel is stopped to supply power; when the illumination is recovered to enable the voltage of the photovoltaic panel to rise to a certain degree, the voltage limiting circuit generates a signal for recovering power supply of the isolated photovoltaic panel, and the drive circuit switches the switch to act, so that a switching interlocking logic control circuit is formed; when a group of parallel photovoltaic panels are isolated, the bypass relay connected in parallel with the group of parallel photovoltaic panels can be automatically closed, and the whole group of parallel photovoltaic panels is isolated. When the photovoltaic bypass relay is applied in engineering, the field working conditions, such as the geographical environment and the ecological environment of the installation position of a photovoltaic power generation system, need to be considered, the working ranges of the undercurrent relay and the overvoltage relay are determined according to the actual illumination change conditions on site, so that the current and voltage parameters of the photovoltaic panel are consistent with the actual working conditions when the photovoltaic panel is shielded and the illumination is normal, and the bypass relay can be ensured to work correctly.
When the photovoltaic array circuit meets the condition that partial illumination is sheltered from, the output current of the photovoltaic panel can be reduced, when the current value is reduced to a certain degree, the sheltering condition is shown to be serious, the series undercurrent relay in the sheltered photovoltaic panel can disconnect the photovoltaic panel from the main circuit, the circuit structure is changed, and the sheltered panel is connected with the voltage limiting circuit in parallel through circuit switching. After illumination is recovered, the output voltage of the photovoltaic panel can be recovered, and the voltage limiting circuit detects the recovered voltage and generates a switching signal to drive the relay to enable the panel to be connected with the main circuit in a recovery mode. The process realizes the automatic switching of the parallel branch when the illumination of the photovoltaic array circuit is partially shielded, and the topological structure of power generation is automatically changed.
In the circuit structure, as shown in fig. 1, each group of parallel photovoltaic panels adopts an overvoltage protection relay and an undercurrent relay to form a switching interlocking logic control circuit, the overvoltage protection relay controls the on-state of the whole column of parallel photovoltaic panels, and the undercurrent relay connected with each photovoltaic panel in series controls whether the single photovoltaic panel needs to be disconnected. Therefore, illumination is weakened, the output current of the photovoltaic panel is reduced, and the photovoltaic panel is automatically disconnected; and (4) the illumination is recovered, the output voltage of the photovoltaic panel is increased, and the photovoltaic panel is automatically switched on.
The photovoltaic panel which is shielded automatically switches on or off the circuit, and the total output current, voltage and power of the photovoltaic array circuit can be changed. If some part of the parallel photovoltaic panels are all automatically disconnected due to shielding, the system is completely in an open circuit state, or the output current of the system is too low, the overall output current of the system is also influenced, and the output power is reduced.
In order to avoid the complaint and improve the overall power generation power of the system, as shown in fig. 2, the switching interlocking logic control circuit serially inputs the on state (the number of normally connected photovoltaic panels in a single row) of each group of parallel photovoltaic panel circuits into the PLC power optimization module in a binary manner, obtains an optimal bypass strategy after PLC operation, and controls the relay switch to bypass a certain row or several rows of photovoltaic panel strings with lower corresponding output current values.
Whether each group of parallel photovoltaic panels in the photovoltaic array circuit is connected to the main circuit when the illumination is shielded is determined by the output voltage and the current of the parallel nodes and is not controlled by the PLC power optimization module, so that when a certain row of photovoltaic panels is bypassed, the photovoltaic panels can be automatically switched on to form a closed loop with the bypass circuit when the illumination is recovered, and a reverse current is formed to cause short circuit. Therefore, a diode needs to be connected in series in the circuit of the bypass relay to prevent the current from conducting reversely, and the circuit structure is as shown in fig. 1.
The calculation and PLC logical operation of circuit reconfiguration are as follows:
the method comprises the following steps that firstly, the output power of a photovoltaic array circuit is estimated by adopting a PLC power optimization module; (ii) a
If the number of each group of parallel photovoltaic panels of the photovoltaic array circuit is M, N groups of parallel photovoltaic panels are sequentially connected in series to form N rows and M columns of photovoltaic array circuits, and all the photovoltaic panels have the following time in normal power generation:
(1) the total voltage output is
ViFor the voltage of the node at two ends of the photovoltaic panels connected in parallel, i represents a row of the photovoltaic panels connected in parallel, i is 1,2, …, N, and V is required according to the output voltage of the photovoltaic power generationminr≤V≤VmaxrI.e. the output voltage is allowed at a nominal minimum VminrAnd a maximum voltage VmaxrChange in between;
(2) the total current output is
IiOutput current for a single parallel node, i ═ 1,2, …, N; a single parallel node current of
Let each branch in parallel current IijThe ratio of the total current of the node is kijAnd then:
Iij＝kijI
wherein M represents the number of photovoltaic panels in a single row of photovoltaic panels that are operating normally, and M represents the total number of photovoltaic panels in a single row, and
(3) the total power output by the photovoltaic array circuit is as follows:
when a single photovoltaic panel is shielded due to illumination, the branch current I is causedijWhen the total output current I is reduced, so that the total generated power P of the whole circuit is reduced, the PLC calculates the output current of each row and the whole output voltage according to the shielding number of the photovoltaic panel, and when the shielding condition occurs, I is reducedijAnd when the PLC becomes smaller, the PLC selects proper N to be 1,2, …, N and m through logic operation i1,2, …, M, to increase P, i.e.:
wherein n is*And
respectively representing the number of photovoltaic columns which are not bypassed when the output power reaches the maximum and the number of photovoltaic panels which normally work in the photovoltaic columns with the minimum generating current, wherein n represents the number of the photovoltaic columns which are not bypassed, and m represents the number of the photovoltaic columns which are not bypassediRepresenting the number of normal power generation of each group of parallel photovoltaic panels.
Step two, finding out the power reaching the maximum through the logic operation of the PLC
The number of columns which need to be bypassed is increased, and the columns are bypassed, so that the output power of the photovoltaic array circuit is optimized.
Specifically, according to the characteristics of the photovoltaic array circuit, an iterative search algorithm is adopted to determine an optimal series-parallel photovoltaic array circuit structure, and the specific process is as follows:
1) starting a search process when the photovoltaic panel exits the power generation and the total current I or the total power P output by the photovoltaic array circuit decreases, according to which
Output current I of parallel photovoltaic paneliNumber m of photovoltaic panelsiIn direct proportion, namely:
Ii＝I0mi
I0representing the output current of a single photovoltaic panel, InormRepresenting the output current of the single photovoltaic panel in normal operation, calculating the total output power of the photovoltaic array circuit:
selecting a maximum output power
And satisfies the following conditions:
2) when in use
Then determine the correspondingn*,
Quantity, otherwise, continuing searching and comparing;
3) according to n*And
value of (a), reconstructing the photovoltaic array circuit
When the photovoltaic panel is shielded, the photovoltaic panel is withdrawn by a bypass, so that the power generation quantity of the whole parallel photovoltaic panel row group is lower than a certain value, the PLC power optimization module withdraws the whole row of parallel photovoltaic panel bypasses, and the output power of the photovoltaic array circuit is as follows:
as the number of groups of parallel photovoltaic panels exiting increases, the total output voltage also decreases. Through PLC logical operation, the power reaches the maximum value
N of (a)*Value and
value and number of connected photovoltaic panels in each column is lower than
Column bypass processing.
In order to avoid the surge phenomenon possibly caused by current change, the delay time of a bypass relay can be set through a PLC power optimization module, and the parts with smaller current are sequentially bypassed at intervals, so that the current change of the system tends to be smooth.
Table 1 lists a circuit reconstruction power calculation table of a 9 × 10(9 columns and 10 rows) photovoltaic array when 2, 4, 5 and 6 groups of parallel photovoltaic panels generate illumination shielding, and the voltage can be approximate to V when the parallel photovoltaic panels generate power normallym. The occlusion situation is shown in FIG. 3, in which the table1 in m1、m2...m9The number of the photovoltaic panels in the ninth column is specifically the number of the photovoltaic panels in the first and second columns, the shaded part in fig. 3 represents the photovoltaic panel disconnected due to shielding, X in the figure represents 10, for example, 1X represents the tenth row in the first column, and the output power is 20V before the final system is reconstructedmI054V after reconstitutionmI0The ratio is improved by 2.7 times compared with the ratio before the structure.
TABLE 1 Circuit Reconfiguration Power calculation
The above description is only an illustrative embodiment of the present invention, and should not be taken as limiting the scope of the invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (4)
1. A photovoltaic array circuit reconfiguration system in which illumination is partially blocked, said circuit reconfiguration system comprising: the system comprises a photovoltaic array circuit, a photovoltaic panel branch switching circuit, a bypass circuit driven by reconfiguration logic, an electric quantity detection and analysis circuit and a PLC power optimization module; the photovoltaic array circuit comprises N rows of photovoltaic panels in M columns, N, M are positive integers, N photovoltaic panels in each column are connected in parallel, and the columns are connected in series; each photovoltaic panel is independently connected with one branch switching circuit in series, and each row of photovoltaic panels is connected with the bypass circuit in parallel; each row of photovoltaic panels is correspondingly provided with an electric quantity detection and analysis circuit, each photovoltaic panel in each row of photovoltaic panels is connected with the electric quantity detection and analysis circuit in the row, and each row of electric quantity detection and analysis circuit is connected with the PLC power optimization module;
the electric quantity detection and analysis circuit is used for detecting the connection or disconnection condition of each photovoltaic panel in each row by taking each row of photovoltaic panels as a unit and transmitting data to the PLC power optimization module; the electric quantity detection and analysis circuit is connected with the EM231 module;
the PLC power optimization module comprises a PLC controller, and the PLC controller is connected with each row of photovoltaic panels in parallel;
the PLC power optimization module adopts a serial input mode, judges and isolates a photovoltaic panel according to power maximization logic from the total current, voltage and power output by the photovoltaic array circuit, reconstructs a circuit topological structure, meets the requirement of outputting direct-current voltage, generates a switch signal, and drives a circuit to reconstruct a switch to realize circuit optimization operation;
the photovoltaic array circuit reconstruction system also comprises a voltage limiting circuit, wherein the voltage limiting circuit comprises an overvoltage relay connected with each row of photovoltaic panels in parallel; the photovoltaic panel branch switching circuit comprises a direct current undercurrent relay and a circuit switching switch; each photovoltaic panel is connected with a direct current undercurrent relay and a circuit change-over switch in series;
when the current of the direct current undercurrent relay is reduced to a given threshold value, the direct current undercurrent relay generates an isolation signal to drive a circuit change-over switch, isolates the photovoltaic panel, stops the power supply of the photovoltaic panel and switches to a voltage limiting circuit; after illumination is recovered, the voltage limiting circuit recognizes that the voltage of the photovoltaic panel is recovered, the driving circuit switches the switch to act, the main circuit, namely the photovoltaic array circuit is switched back, and power generation is recovered.
2. The photovoltaic array circuit reconfiguration system according to claim 1, wherein said reconfiguration logic driven bypass circuit comprises a bypass relay and a unidirectional diode in series with the bypass relay; the bypass relay is connected with each column of photovoltaic panels in parallel.
3. The system for reconstructing a photovoltaic array circuit with partially blocked illumination according to claim 1, wherein said PLC power optimization module employs siemens s7-200 series PLC.
4. The method for implementing the photovoltaic array circuit reconstruction system with partially shielded illumination according to claim 1, comprising the following steps:
the method comprises the following steps that firstly, the output power of the photovoltaic array circuit is estimated by adopting a PLC power optimization module, and the estimation process is as follows:
the number of each row of parallel photovoltaic panels of the photovoltaic array circuit is M, N groups of parallel photovoltaic panels are sequentially connected in series, the N and M values are not less than 3, and all the photovoltaic panels have the following normal power generation times:
(1) the total voltage output is
ViFor the voltage of the node at two ends of the photovoltaic panels connected in parallel, i represents a row of the photovoltaic panels connected in parallel, i is 1,2, …, N, and V is required according to the output voltage of the photovoltaic power generationminr≤V≤VmaxrI.e. the output voltage is allowed at a nominal minimum VminrAnd a maximum voltage VmaxrChange in between;
(2) the total current output is
IiOutput current for a single parallel node, i ═ 1,2, …, N; a single parallel node current of
Let each branch in parallel current IijThe ratio of the total current of the node is kijAnd then:
Iij＝kijI
wherein M represents the number of photovoltaic panels in a single row of photovoltaic panels that are operating normally, and M represents the total number of photovoltaic panels in a single row, and
(3) the total power output by the photovoltaic array circuit is as follows:
when a single photovoltaic panel is shielded due to illumination, the branch current I is causedijWhen the total output current I is reduced, so that the total generated power P of the whole circuit is reduced, the PLC calculates the output current of each row and the whole output voltage according to the shielding number of the photovoltaic panel, and when the shielding condition occurs, I is reducedijWhen the PLC becomes smaller, the PLC controller selects N to be 1,2, …, N and m through logic operationi1,2, …, M to increase P, i.e.:
wherein n is*And
respectively representing the number of photovoltaic columns which are not bypassed when the output power reaches the maximum and the number of photovoltaic panels which normally work in the photovoltaic columns with the minimum generating current, wherein n represents the number of the photovoltaic columns which are not bypassed, and m represents the number of the photovoltaic columns which are not bypassediRepresenting the number of normal power generation of each group of parallel photovoltaic panels;
step two, finding out the maximum power through the reconfiguration operation of the PLC power optimization module
The number of columns that need to be bypassed and bypassing these columns to make the photovoltaic array circuitThe output power of the power amplifier is optimal; according to the characteristics of the photovoltaic array circuit, an iterative search algorithm is adopted to determine an optimal series-parallel photovoltaic array circuit structure, and the specific process is as follows:
1) starting a search process when the photovoltaic panel exits the power generation and the total current I or the total power P output by the photovoltaic array circuit decreases, according to which
Output current I of parallel photovoltaic paneliNumber m of photovoltaic panelsiIn direct proportion, namely:
Ii＝I0mi
I0representing the output current of a single photovoltaic panel, InormRepresenting the output current of the single photovoltaic panel in normal operation, calculating the total output power of the photovoltaic array circuit:
selecting a maximum output power
And satisfies the following conditions:
2) when in use
When the temperature of the water is higher than the set temperature,
then the corresponding n is determined*,
Quantity, otherwise, continuing searching and comparing;
3) according to n*And
value of (a), reconstructing the photovoltaic array circuit
When the photovoltaic panel is shielded, the photovoltaic panel is withdrawn by a bypass, so that the power generation quantity of the whole parallel photovoltaic panel row group is lower than a certain value, the PLC power optimization module withdraws the whole row of parallel photovoltaic panel bypasses, and the output power of the photovoltaic array circuit is as follows:
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