Roof photovoltaic adaptive grid-connected control device and control method thereof

Abstract

The invention provides a roof photovoltaic adaptive grid-connected control device. The roof photovoltaic adaptive grid-connected control device provided by the invention comprises a voltage acquisition module, a current acquisition module, a resetting and monitoring module, a signal conditioning module, a single-chip microcomputer module, a 4G / 5G communication module, an isolation and driving module and a grid-connected execution module. The invention also provides a roof photovoltaic adaptive grid-connected control method. According to the roof photovoltaic adaptive grid-connected control device and the control method thereof provided by the invention, the amplitude of an overvoltage grid-connected constant value Ugb can be automatically changed online according to the real-time states of roof photovoltaic and power grid voltage, so that the magnitude of delta Ug is adjusted and optimized, the roof photovoltaic and power grid adaptive effective matching is realized, the roof photovoltaic is prevented from generating grid-connected / off-grid oscillation, and the system reliability is improved. And grid connection can be recovered in time during off-grid, the power generation effect achieves the effects of preferential line grabbing and complete power generation, roof photovoltaic safe and reliable operation is ensured, and the power generation income is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy grid-connected control and electrical fault protection, and in particular to a rooftop photovoltaic adaptive grid-connected control device and a control method thereof. Background Art

[0002] The construction of rooftop photovoltaic power stations is an important measure for rural revitalization. Properly controlling their connection to and disconnection from the grid is of great significance to protecting investors' property, power generation income, and farmers' housing property and personal safety.

[0003] At present, the well-known rooftop photovoltaic grid-connected control methods in the art are the self-resetting over / undervoltage protector method and the automatic reclosing circuit breaker method. This method is to disconnect the grid when the grid voltage exceeds the overvoltage disconnection setting value U gt (typical value 275VAC) or below the undervoltage tripping setting U qt (typical value 160VAC), cut off the connection between the rooftop photovoltaic and the grid, and when the grid voltage is lower than the overvoltage grid-connected setting value U gb (typical value 253VAC) or higher than the undervoltage grid-connected setting value U qb (typical value 195VAC), the rooftop photovoltaic is connected to the grid. However, the overvoltage disconnection setting U gt and overvoltage grid-connected setting value U gb The hysteresis difference ΔU g is a fixed value, which makes the source (rooftop photovoltaic) and the network (grid) unable to automatically and effectively match, that is: if ΔU g If ΔU is too small, the rooftop photovoltaic power generation is prone to repeated switching on and off the grid, threatening the safety of the power grid and farmers. g If it is too large, the photovoltaic power plant cannot be restored to the grid in time, resulting in loss of power generation, reducing investors' property and power generation income.

[0004] Therefore, it is necessary to provide an intelligent foundation pit detection system to solve the above technical problems. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a rooftop photovoltaic adaptive grid-connected control device. The rooftop photovoltaic adaptive grid-connected control device includes a voltage acquisition module, a current acquisition module, a reset and monitoring module, a signal conditioning module, a single-chip module, a 4G / 5G communication module, an isolation and drive module, and a grid-connected execution module; wherein the output ends of the voltage acquisition module and the current acquisition module are respectively connected to the input end of the signal conditioning module, and the output end of the signal conditioning module and the output end of the reset and monitoring module are respectively connected to the input end of the single-chip module; the output end of the single-chip module is electrically connected to the input end of the isolation and drive module and the 4G / 5G communication module; the output end of the isolation and drive module is electrically connected to the input end of the grid-connected execution module.

[0006] Preferably, the voltage acquisition module is a voltage transformer.

[0007] Preferably, the current acquisition module is a current transformer.

[0008] Preferably, the signal conditioning module is composed of an I / V conversion circuit, an RC filtering circuit, and a data preprocessing circuit which are electrically connected in sequence.

[0009] The present invention also provides a rooftop photovoltaic adaptive grid-connected control method, the control method adopts the rooftop photovoltaic adaptive grid-connected control device, and the control method comprises the following steps:

[0010] S1: Provide a rooftop photovoltaic power station with a rooftop photovoltaic adaptive grid-connected control device installed, and collect the instantaneous phase voltage value u of the grid through the voltage acquisition module and current acquisition module of the rooftop photovoltaic adaptive grid-connected control device. j (t), photovoltaic power generation current value i j (t), where the subscript j = A, B, C, respectively represents the A phase, B phase, and C phase of the three-phase AC system, and t is a time variable. After being processed by the signal conditioning module, the single-chip microcomputer module calculates the effective value of the grid phase voltage U according to the effective value definition formula. j (t), Photovoltaic power generation current effective value I j (t);

[0011] S2: When U j (t) qt When the single-chip computer module of the roof photovoltaic adaptive grid-connected control device sends a disconnection command to the grid-connected execution module through the isolation and drive module, cutting off the connection between the roof photovoltaic and the grid, and clearing the preset status flag C1, making C1 = 0; U qt It is the setting value of undervoltage disconnection;

[0012] S3: When U qb j (t) gb When the single-chip microcomputer module sends a grid-connection instruction to the grid-connection execution module through the isolation and drive module, the rooftop photovoltaic is connected to the grid, and the preset status flag C1 is cleared to make C1 = 0; U qb is the undervoltage grid-connected fixed value, U gb Set the value for overvoltage grid connection;

[0013] S4: When U j (t)>U gt When the grid voltage U j (1) Set the flag C1 = 1, and send a disconnection command to the grid-connected execution module through the isolation and drive module to cut off the connection between the roof photovoltaic and the grid. The single-chip module records the grid voltage U after disconnection.​​​j (1)′, calculate ΔU according to formula (1) j (1), and update U according to formula (2) gb ; U gt Set the value for overvoltage disconnection;

[0014] ΔU j (1) = U j (1)-U j (1)′ (1)

[0015] U gb =U gt -ΔU j (1)-1v (2)

[0016] S5: When C1=1, after the delay time T, record the grid voltage U j (2)′, the single-chip microcomputer module sends a grid-connection instruction to the grid-connection execution module through the isolation and drive module, connects the rooftop photovoltaic power generation to the grid, and records the voltage U after the rooftop photovoltaic power generation is connected to the grid. j (2), calculate ΔU according to formula (3) j (2) Calculate the update timing time T according to formula (4);

[0017] ΔU j (2) = U j (2)-U j (twenty three)

[0018] T=T+sign(ΔU j (2)-ΔU j (1))×T / 2 (4).

[0019] Preferably, in S2, U qt =0.6U gt .

[0020] Preferably, in S3, U qb =0.7U gt , U gb The initial value is 0.94U gt .

[0021] Preferably, in S4, U gt It is pre-set in the microcontroller module to 275VAC.

[0022] Preferably, in S5, the initial value of the timing time T is set in advance in the single-chip microcomputer module and is set to 1000s.

[0023] Compared with the related art, the rooftop photovoltaic adaptive grid-connected control device and control method provided by the present invention have the following beneficial effects:

[0024] 1. It can automatically change the overvoltage grid-connected setting value U online according to the real-time status of rooftop photovoltaic and grid voltage gb Amplitude to adjust and optimize ΔU g The size of the rooftop photovoltaic power plant can be adaptively matched with the power grid to avoid grid-connected / off-grid oscillation of the rooftop photovoltaic power plant, and the grid connection can be restored in time when it is off-grid. The power generation effect can achieve "priority to grab the line and generate as much power as possible", ensuring the safe and reliable operation of the rooftop photovoltaic power plant and increasing the power generation income.

[0025] 2. It integrates the functions of follow-up switching, panoramic data acquisition, electrical fault protection and electrical fire prevention and control, power generation monitoring, remote control and measurement, etc. It can identify the fault area, realize the intelligence of photovoltaic grid-connected boxes, and transform the operation and maintenance of photovoltaic grid-connected boxes from periodic scheduled maintenance to precise status maintenance, thereby reducing the intensity of operation and maintenance, improving efficiency and reducing costs, and avoiding risks. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the structure of a rooftop photovoltaic adaptive grid-connected control device provided by the present invention;

[0027] Numbers in the figure: A-rooftop photovoltaic adaptive grid-connected control device, A1-voltage acquisition module, A2-current acquisition module, A3-signal conditioning module, A4-microcontroller module, A5-4G / 5G communication module, A6-isolation and drive module, A7-grid-connected execution module, A8-reset and monitoring module. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with the accompanying drawings and implementation modes.

[0029] See also Figure 1 , which is a structural schematic diagram of a rooftop photovoltaic adaptive grid-connected control device provided by the present invention; the rooftop photovoltaic adaptive grid-connected control device A comprises a voltage acquisition module A1, a current acquisition module A2, a signal conditioning module A3, a single-chip computer module A4, a 4G / 5G communication module A5, an isolation and drive module A6, a grid-connected execution module A7 and a reset and monitoring module A8. The output ends of the voltage acquisition module A1 and the current acquisition module A2 are respectively connected to the input end of the signal conditioning module A3, and the output end of the signal conditioning module A3 and the output end of the reset and monitoring module A8 are respectively connected to the input end of the single-chip computer module A4; the output end of the single-chip computer module A4 is electrically connected to the input end of the isolation and drive module A6 and the input end of the 4G / 5G communication module A5; the output end of the isolation and drive module A6 is electrically connected to the input end of the grid-connected execution module A7.

[0030] The voltage acquisition module A1 is a voltage transformer.

[0031] The current acquisition module A2 is a current transformer.

[0032] The signal conditioning module A3 is composed of an I / V conversion circuit, an RC filtering circuit, and a data preprocessing circuit which are electrically connected in sequence.

[0033] In the structural design of the specific example, the voltage acquisition module A1 adopts a voltage transformer (such as TS31140CI), the current acquisition module A2 adopts a current transformer (such as ZHT102W-TM), the RC filtering circuit in the signal conditioning module A3 is realized by a general resistor and capacitor device, the I / V conversion circuit is realized by RVC420 and peripheral auxiliary components, and the data preprocessing circuit can be realized by ATT7022 series devices. The single-chip microcomputer module A4 can be implemented by the STM32 series (such as STM32F103C8T6), MCS series single-chip microcomputer or digital signal processor series (such as Dspic30F6014A, TSM320XX), the 4G / 5G communication module A5 can adopt a general 4G / 5G communication module (such as WH-LTE-7S1), the isolation and drive module A6 uses an optocoupler device with large output drive capability (such as TLP127), and the grid-connected execution module A7 uses a general relay or a solid-state relay SSR (such as S310ZK series).

[0034] The working process of the rooftop photovoltaic adaptive grid-connected control device of the present invention for performing rooftop photovoltaic adaptive grid-connected operation is as follows:

[0035] 1. System power-on, self-test, initialization, setting or modifying the overvoltage disconnection setting value U gt , the initial value of the timing time T.

[0036] 2. Check whether the system of the device of the present invention has any faults. If there is a fault, enter the corresponding processing program and give a fault diagnosis prompt message. If there is no fault, execute the next step.

[0037] 3. Collect the instantaneous phase voltage value u of the power grid j (t), photovoltaic power generation current value i j (t), calculate the effective value of the grid phase voltage U j (t), Photovoltaic power generation current effective value I j (t).

[0038] 4. When U j (t) qt When the rooftop photovoltaic adaptive grid-connected control device cuts off the connection between the rooftop photovoltaic and the grid, and clears the preset status flag C1, making C1=0.

[0039] 5. When U qb j (t) gb ​​​When the rooftop photovoltaic adaptive grid-connected control device connects the rooftop photovoltaic into the grid, and clears the preset status flag C1, making C1=0.

[0040] 6. When U j (t)>U gt By recording the grid voltage U i (1) Set the flag C1 = 1, disconnect the rooftop photovoltaic power plant from the grid, and record the grid voltage U after disconnection. j (1)′, calculate and update ΔU according to formulas (1) and (2) i (1) U gb .

[0041] ΔU j (1) = U j (1)-U j (1)′ (1)

[0042] U gb =U gt -ΔU j (1)-1v (2)

[0043] 7. When C1=1, after the delay time T, record the grid voltage U j (2)′, connect the rooftop photovoltaic power generation to the grid and record the voltage U after connection to the grid j (2), calculate ΔU according to formula (3) (4) i (2) T.

[0044] ΔU j (2) = U j (2)-U j (twenty three)

[0045] T=T+sign(ΔU j (2)-ΔU j (1))×T / 2 (4)

[0046] 8. Calculate other parameters, such as photovoltaic power generation current, power generation, etc.

[0047] 9. The working status and working parameters of the rooftop photovoltaic adaptive grid-connected device are uploaded to the cloud monitoring platform by the 4G / 5G communication module.

[0048] 10. Repeat step 2.

[0049] The above description and embodiments describe the basic principle, main features and advantages of the present invention, and in particular, show that the essence of the present invention is to automatically change the overvoltage grid-connected constant value U online according to the real-time status of the roof photovoltaic and grid voltage. gb Amplitude to adjust and optimize ΔU gSize makes the rooftop photovoltaic and the power grid adaptively matched effectively, so as to solve the problem of repeated switching oscillation of photovoltaic grid connection / off-grid connection and loss of power generation due to failure to connect to the grid in time.

[0050] The present invention also provides a rooftop photovoltaic adaptive grid-connected control method, the control method adopts the rooftop photovoltaic adaptive grid-connected control device, and the control method comprises the following steps:

[0051] S1: Provide a rooftop photovoltaic power station with a rooftop photovoltaic adaptive grid-connected control device installed, and collect the instantaneous phase voltage value u of the grid through the voltage acquisition module and current acquisition module of the rooftop photovoltaic adaptive grid-connected control device. j (t), photovoltaic power generation current value i j (t), where the subscript j = A, B, C, respectively represents the A phase, B phase, and C phase of the three-phase AC system, and t is a time variable. After being processed by the signal conditioning module, the single-chip microcomputer module calculates the effective value of the grid phase voltage U according to the effective value definition formula. j (t), Photovoltaic power generation current effective value I j (t).

[0052] S2: When U j (t) qt When the single-chip computer module of the roof photovoltaic adaptive grid-connected control device sends a disconnection command to the grid-connected execution module through the isolation and drive module, cutting off the connection between the roof photovoltaic and the grid, and clearing the preset status flag C1, making C1 = 0; U qt U is the undervoltage disconnection setting value; qt =0.6U gt .

[0053] S3: When U qb j (t) gb When the single-chip microcomputer module sends a grid-connection instruction to the grid-connection execution module through the isolation and drive module, the rooftop photovoltaic is connected to the grid, and the preset status flag C1 is cleared to make C1 = 0; U qb is the undervoltage grid-connected fixed value, U gb It is the overvoltage grid-connected setting value; U qb =0.7U gt , U gb The initial value is 0.94U gt .

[0054] S4: When U j (t)>U gt When the grid voltage U j ​​​(1) Set the flag C1 = 1, and send a disconnection command to the grid-connected execution module through the isolation and drive module to cut off the connection between the roof photovoltaic and the grid. The single-chip module records the grid voltage U after disconnection. j (1)′, calculate ΔU according to formula (1) j (1), and update U according to formula (2) gb ; U gt Overvoltage tripping setting value; U gt It is pre-set in the microcontroller module to 275VAC.

[0055] ΔU j (1) = U j (1)-U j (1)′ (1)

[0056] U gb =U gt -ΔU j (1)-1v (2)

[0057] S5: When C1=1, after the delay time T, record the grid voltage U j (2)′, the single-chip microcomputer module sends a grid-connection instruction to the grid-connection execution module through the isolation and drive module, connects the rooftop photovoltaic power generation to the grid, and records the voltage U after the rooftop photovoltaic power generation is connected to the grid. j (2), calculate ΔU according to formula (3) j (2) Calculate the updated timing time T according to formula (4); the initial value of the timing time T is set in advance in the single-chip microcomputer module and is set to 1000s.

[0058] ΔU j (2) = U j (2)-U j (twenty three)

[0059] T=T+sign(ΔU j (2)-ΔU j (1))×T / 2 (4)

[0060] Compared with the related art, the rooftop photovoltaic adaptive grid-connected control device and control method provided by the present invention have the following beneficial effects:

[0061] 1. It can automatically change the overvoltage grid-connected setting value U online according to the real-time status of rooftop photovoltaic and grid voltage gb Amplitude to adjust and optimize ΔU g The size of the rooftop photovoltaic power plant can be adaptively matched with the power grid to avoid grid-connected / off-grid oscillation of the rooftop photovoltaic power plant, and the grid connection can be restored in time when it is off-grid. The power generation effect can achieve "priority to grab the line and generate as much power as possible", ensuring the safe and reliable operation of the rooftop photovoltaic power plant and increasing the power generation income.

[0062] 2. It integrates the functions of follow-up switching, panoramic data acquisition, electrical fault protection and electrical fire prevention and control, power generation monitoring, remote control and measurement, etc. It can identify the fault area, realize the intelligence of photovoltaic grid-connected boxes, and transform the operation and maintenance of photovoltaic grid-connected boxes from periodic scheduled maintenance to precise status maintenance, thereby reducing the intensity of operation and maintenance, improving efficiency and reducing costs, and avoiding risks.

[0063] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A rooftop photovoltaic adaptive grid-connected control device, characterized in that: It includes a voltage acquisition module, a current acquisition module, a reset and monitoring module, a signal conditioning module, a single-chip computer module, a 4G / 5G communication module, an isolation and drive module, and a grid-connected execution module; wherein the output ends of the voltage acquisition module and the current acquisition module are respectively connected to the input end of the signal conditioning module, and the output end of the signal conditioning module and the output end of the reset and monitoring module are respectively connected to the input end of the single-chip computer module; the output end of the single-chip computer module is electrically connected to the input end of the isolation and drive module and the 4G / 5G communication module; the output end of the isolation and drive module is electrically connected to the input end of the grid-connected execution module.

2. A rooftop photovoltaic adaptive grid-connected control device according to claim 1, characterized in that: The voltage acquisition module is a voltage transformer.

3. A rooftop photovoltaic adaptive grid-connected control device according to claim 1, characterized in that: The current acquisition module is a current transformer.

4. A rooftop photovoltaic adaptive grid-connected control device according to claim 1, characterized in that: The signal conditioning module is composed of an I / V conversion circuit, an RC filtering circuit, and a data preprocessing circuit which are electrically connected in sequence.

5. A rooftop photovoltaic adaptive grid-connected control method, characterized in that: The control method adopts a rooftop photovoltaic adaptive grid-connected control device as described in any one of claims 1 to 4, and the control method comprises the following steps: S1: Provide a rooftop photovoltaic power station with a rooftop photovoltaic adaptive grid-connected control device installed, and collect the instantaneous phase voltage value u of the grid through the voltage acquisition module and current acquisition module of the rooftop photovoltaic adaptive grid-connected control device. j (t), photovoltaic power generation current value i j (t), where the subscript j = A, B, C, respectively represents the A phase, B phase, and C phase of the three-phase AC system, and t is a time variable. After being processed by the signal conditioning module, the single-chip microcomputer module calculates the effective value of the grid phase voltage U according to the effective value definition formula. j (t), Photovoltaic power generation current effective value I j (t); S2: When U j (t) qt When the single-chip computer module of the roof photovoltaic adaptive grid-connected control device sends a disconnection command to the grid-connected execution module through the isolation and drive module, cutting off the connection between the roof photovoltaic and the grid, and clearing the preset status flag C1, making C1 = 0; U qt It is the setting value of undervoltage disconnection;​ S3: When U qb j (t) gb When the single-chip microcomputer module sends a grid-connection instruction to the grid-connection execution module through the isolation and drive module, the rooftop photovoltaic is connected to the grid, and the preset status flag C1 is cleared to make C1 = 0; U qb is the undervoltage grid-connected fixed value, U gb Set the value for overvoltage grid connection;​​ S4: When U j (t)>U gt When the grid voltage U j (1) Set the flag C1 = 1, and send a disconnection command to the grid-connected execution module through the isolation and drive module to cut off the connection between the roof photovoltaic and the grid. The single-chip module records the grid voltage U after disconnection. j (1)′, calculate ΔU according to formula (1) j (1), and update U according to formula (2) gb ; U gt Set the value for overvoltage disconnection; ΔU j (1)=U j (1)-U j (1)′ (1) U gb =U gt -ΔU j (1)-1v (2) S5: When C1=1, after the delay time T, record the grid voltage U j (2)′, the single-chip microcomputer module sends a grid-connection instruction to the grid-connection execution module through the isolation and drive module, connects the rooftop photovoltaic power generation to the grid, and records the voltage U after the rooftop photovoltaic power generation is connected to the grid. j (2), calculate ΔU according to formula (3) j (2) Calculate the update timing time T according to formula (4); ΔU j (2)=U j (2)-U j (2)′ (3) T=T+sign(ΔU j (2)-ΔU j (1))×T / 2 (4)。 6. A rooftop photovoltaic adaptive grid-connected control method according to claim 5, characterized in that: In S2, U qt =0.6U gt .

7. A rooftop photovoltaic adaptive grid-connected control method according to claim 5, characterized in that: In S3, U qb =0.7U gt , U gb The initial value is 0.94U gt .

8. A rooftop photovoltaic adaptive grid-connected control method according to claim 5, characterized in that: In S4, U gt It is pre-set in the microcontroller module to 275VAC.

9. A rooftop photovoltaic adaptive grid-connected control method according to claim 5, characterized in that: In S5, the initial value of the timing time T is set in advance in the single-chip microcomputer module and is set to 1000s.

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