Photovoltaic grid-connected control device and method with phase selection grid-connected and power regulation functions

Abstract

The present invention belongs to the field of distributed photovoltaic grid-connected control, and relates to a photovoltaic grid-connected control device with phase selection grid-connected and power regulation functions, including a housing and an operating parameter acquisition module installed in the housing, a data processing and control module, a phase selection grid-connected execution module, a communication module, a display screen module, and a power management module. The present invention obtains operating parameters with high accuracy and is not affected by human factors, thereby greatly improving the accuracy of grid connection; it also ensures the accuracy of the test, meets the test requirements of multi-phase automatic switching, and has good applicability.

Description

Technical Field

[0001] The present invention belongs to the field of distributed photovoltaic grid-connected control, and relates to a photovoltaic grid-connected control device and method with phase selection grid-connected and power regulation functions. Background Art

[0002] With the continuous development of "dual carbon" and the continuous advancement of energy transformation, the traditional power system is evolving towards a new power system that is clean, low-carbon, safe, controllable, intelligent and friendly. The wide access of a high proportion of new energy in the new power system, especially the high proportion of new energy represented by distributed photovoltaics, has accelerated the replacement of fossil energy with new energy. However, with the batch access of a large number of distributed photovoltaic power sources, new challenges such as instability and uncontrollable factors brought to the operation of the power grid will also limit its development. Therefore, the participation of distributed photovoltaic power sources in the regulation of the new power system is a new direction for the development of distributed power sources.

[0003] At present, the traditional grid-connected mode of distributed photovoltaic power generation adopts the traditional grid-connected mode with fixed grid-connected phase. For the fixed-phase grid-connected mode of distributed photovoltaic power generation with single-phase full grid-connected or self-generated and surplus power grid-connected, it will increase the three-phase voltage imbalance and distribution line network loss. Summary of the invention

[0004] The purpose of the present invention is to overcome the technical deficiencies of existing single-phase grid-connected photovoltaic power sources in grid-connected control. Aiming at the problem that the distributed photovoltaic grid-connected phase of a single-phase fixed-phase grid-connected power source cannot be switched and the grid-connected parameters cannot be adjusted, a photovoltaic grid-connected control device and method with phase selection grid-connected and power control functions are provided. The phase selection grid-connected and power adjustment functions of a single-phase grid-connected distributed photovoltaic power source can be realized, and at the same time, the district autonomy can be realized according to the adjustment to zero of the district fusion terminal, or overall planning can be realized according to the adjustment instructions issued by the master station.

[0005] The technical solution adopted by the present invention to solve the technical problem is:

[0006] The first aspect of the present invention is to provide a photovoltaic grid-connected control device with phase selection and grid-connected and power regulation functions, including a shell and an operating parameter acquisition module installed in the shell, a data processing and control module, a phase selection and grid-connected execution module, a communication module, a display screen module and a power management module; the operating parameter acquisition module collects the photovoltaic grid-connected point voltage, the three-phase current on the distributed photovoltaic power supply side, the three-phase current of the distribution line and harmonics; the data processing and control module performs data processing and logical judgment according to the operating parameters collected at the grid-connected point and the distributed photovoltaic power supply side, selects the one with a larger active and reactive power shortage of the distribution line, and issues instructions to the phase selection and grid-connected execution module to realize grid-connected phase conversion; the phase selection and grid-connected execution module includes a soft switch module and a high-power switch control module, and realizes the high-power grid-connected switch phase change operation with a small power control loop; the communication module is used for the photovoltaic grid-connected control device to interact with the distributed photovoltaic power inverter and the intelligent fusion terminal of the substation, completes the distributed photovoltaic power inverter parameter adjustment according to the control strategy issued by the master station, and changes the distributed photovoltaic power inverter grid-connected active and reactive output; the display screen module is used for data display, equipment control and data transmission; the power management module supplies power to the device.

[0007] Furthermore, the operating parameter acquisition module includes multiple current transformers, which are installed on the three-phase distribution lines of the photovoltaic grid-connected point and the distributed photovoltaic power inverter lead-out lines, and collect voltage and current operating parameters through current transformers and built-in voltage transmitter elements.

[0008] Furthermore, the data processing and control module processes data by filtering first and then smoothing.

[0009] Furthermore, the power management module includes AC-DC, DC-DC and voltage stabilization modules.

[0010] Furthermore, the communication module is IoT communication, wireless communication or 4G communication, and a RS485 communication interface is reserved.

[0011] The second aspect of the present invention is to provide a photovoltaic grid-connected control method for the above device, comprising the following steps:

[0012] S1: Collect the voltage of the photovoltaic grid-connected point, the three-phase current of the distributed photovoltaic power supply side, the three-phase current of the distribution line and harmonics; S2: Perform data processing and logical judgment based on the operating parameters collected at the grid-connected point and the distributed photovoltaic power supply side, select the one with the larger active and reactive power shortage of the distribution line, and send instructions to the phase selection and grid-connected execution module to realize the grid-connected phase conversion.

[0013] The advantages and positive effects of the present invention are:

[0014] 1. This photovoltaic grid-connected control device detects and transmits the current data timely and accurately to the data processing and control module through the operating parameter acquisition module for data processing and control, and realizes the real-time display function through the display. The display sets the parameters and transmits other collected data to the intelligent fusion terminal of the substation through the communication module. This photovoltaic grid-connected control device obtains operating parameters with high accuracy and is not affected by human factors, thereby greatly improving the accuracy of grid connection.

[0015] 2. This photovoltaic grid-connected control device selects and connects the channel to the grid through the data processing and control module, so that it automatically switches to the unbalanced phase, ensuring the accuracy of the test, meeting the test requirements of multi-phase automatic switching, and has good applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of a photovoltaic grid-connected control device according to an embodiment of the present invention;

[0017] Figure 2 A structural diagram of a photovoltaic grid-connected control device according to an embodiment of the present invention;

[0018] Figure 3 1 is a photovoltaic grid-connected control flow chart according to an embodiment of the present invention.

[0019] The above drawings include the following reference numerals:

[0020] 1. Photovoltaic grid connection point, 2. Phase sequence switching soft switch, 3. Soft switch control device, 4. Current transformer. DETAILED DESCRIPTION

[0021] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0022] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs.

[0023] Figure 1 The control principle diagram of the photovoltaic grid-connected control with phase selection and power regulation functions provided by the present invention is shown in the figure. The operation parameter acquisition module is connected to the data processing and control module, the data processing and control module is respectively connected to the display screen module, the communication module and the phase selection and grid-connected execution module, and the phase selection and grid-connected execution module is connected to the distributed photovoltaic power supply. The power management module supplies power to the data processing and control module, the phase selection and grid-connected execution module, the display screen module and the communication module.

[0024] The operating parameter acquisition module is used to collect the voltage of the photovoltaic grid-connected point, the three-phase current of the distributed photovoltaic power supply side, the three-phase current of the distribution line, and harmonics. It includes multiple current transformers, which are installed on the three-phase distribution line of the photovoltaic grid-connected point and the lead-out line of the distributed photovoltaic power inverter. The voltage and current operating parameters are collected through the current transformers and the built-in voltage transmitter elements.

[0025] The data processing and control module processes data by filtering first and then smoothing. According to the operating parameters collected from the grid connection point and the distributed photovoltaic power supply side, data processing and logical judgment are performed, and the one with the larger active and reactive power shortage of the distribution line is selected, and instructions are issued to the phase selection and grid connection execution module to realize the grid connection phase conversion.

[0026] The phase selection and grid-connected execution module includes a soft switch module and a high-power switch control module, which realizes the phase-changing operation of the high-power grid-connected switch with a small-power control loop.

[0027] The communication module is IoT communication, wireless communication or 4G communication, and RS485 communication interface is reserved. It realizes the information interaction between the photovoltaic grid-connected control device and the distributed photovoltaic power inverter and the intelligent fusion terminal of the substation area, and realizes the real-time tracking of the operation status of the grid-connected equipment by the master station. At the same time, it can also complete the parameter adjustment of the distributed photovoltaic power inverter according to the control strategy issued by the master station, change the grid-connected active and reactive output of the distributed photovoltaic power inverter, and achieve the purpose of reducing the voltage imbalance of the distribution network while increasing the grid connection point voltage, reducing the reactive power flow in the system, and reducing network losses.

[0028] The display screen module includes a display screen and a fixed bracket, which realizes functions such as data display, equipment control and data transmission operation, and realizes interface human-computer interaction.

[0029] The power management module is used to power the entire system to achieve a stable power supply voltage. This module includes but is not limited to AC-DC, DC-DC and voltage stabilization modules.

[0030] The structure diagram of the photovoltaic grid-connected control device according to the embodiment of the present invention is as follows: Figure 2 As shown. Multiple current transformers 4 are installed on the three-phase distribution line of the photovoltaic grid-connected point 1 and the lead-out line of the distributed photovoltaic power inverter. The power management module includes a power module AC-DC and a power module DC-DC, which are powered by 24V. The operating parameter acquisition module collects the three-phase current of the distribution line. And photovoltaic grid connection point voltage And the three-phase current of the distributed photovoltaic power supply side The distributed photovoltaic power inverter is connected to the RS485 interface of the main control board of the data processing and control module, the operation parameter acquisition module is connected to the RS485 interface of the main control board of the data processing and control module, and the phase sequence switching soft switch 2 is installed on the lead-out line of the distributed photovoltaic power inverter, located between the photovoltaic grid-connected point 1 and the distributed photovoltaic power inverter. The soft switch control device 3 is connected to the main control board of the data processing and control module.

[0031] The present invention provides a photovoltaic grid-connected control method with phase selection grid-connected and power regulation functions, comprising the following steps:

[0032] S1: Collect the voltage at the photovoltaic grid-connected point, the three-phase current on the distributed photovoltaic power supply side, the three-phase current of the distribution line, and harmonics;

[0033] S2: Data processing and logical judgment are performed based on the operating parameters collected from the grid-connected point and the distributed photovoltaic power supply side. The data is processed by filtering and then smoothing. After the three-phase voltage imbalance is checked, the phase with the largest active and reactive power shortages is determined. At the same time, the data processing and control module will determine whether the current grid-connected phase of the distributed photovoltaic is consistent with the selected phase. If it is inconsistent, a grid-connected phase sequence adjustment instruction will be issued and an adjustment instruction will be issued to the phase selection and grid-connected execution module to change the grid-connected phase sequence, so as to achieve controllable grid-connected phase.

[0034] The data processing and control module re-evaluates the operating status of the low-voltage distribution network after the structural change, and at the same time explores the adjustment potential of the distributed photovoltaic power inverter based on the operating data of the distributed photovoltaic power inverter, and issues adjustment instructions to the distributed photovoltaic power inverter.

[0035] The communication module exchanges information with the intelligent fusion terminal of the substation, and executes the regulation instructions issued by the fusion terminal according to the comprehensive evaluation results of the power quality of the substation, completes the substation autonomy, or completes the overall planning of the whole network according to the regulation instructions issued by the main network.

[0036] The specific process is as follows Figure 3 As shown, first, it is determined whether the distributed photovoltaic power supply of the photovoltaic grid-connected control device operates normally. If the distributed photovoltaic power supply cannot operate normally, an alarm is issued; if the distributed photovoltaic power supply can operate normally, the distributed photovoltaic power supply inverter and the grid-connected line operating parameters are collected; next, it is determined whether there is a three-phase voltage imbalance:

[0037] If there is no three-phase voltage imbalance, directly determine whether there is low voltage at the grid connection point; if there is no low voltage at the grid connection point, directly end; if there is low voltage at the grid connection point, adjust the active and reactive outputs of the distributed photovoltaic power inverter to further determine whether there is three-phase voltage imbalance or low terminal voltage. If there is no three-phase voltage imbalance or low terminal voltage, directly end; if there is three-phase voltage imbalance or low terminal voltage, a time delay is generated, and then return to continue to determine whether the distributed photovoltaic power supply is operating normally;

[0038] If there is a three-phase voltage imbalance, determine whether the fusion terminal adjustment instruction is received. If the fusion terminal adjustment instruction cannot be received, determine and select a phase with a larger active and reactive power shortage to complete the grid connection, and then determine whether there is a low voltage at the grid connection point. If there is no low voltage at the grid connection point, end directly. If there is a low voltage at the grid connection point, adjust the active and reactive output of the distributed photovoltaic power inverter, and further determine whether there is a three-phase voltage imbalance or a low terminal voltage. If there is no three-phase voltage imbalance or a low terminal voltage, end directly. If there is a three-phase voltage imbalance or a low terminal voltage, a time delay is generated, and then return to continue to determine whether the distributed photovoltaic power supply is operating normally;

[0039] If there is a three-phase voltage imbalance, determine whether the fusion terminal adjustment instruction is received. If the fusion terminal adjustment instruction can be received, complete the phase selection and grid connection and output adjustment according to the fusion terminal adjustment instruction, and further determine whether there is a three-phase voltage imbalance or low terminal voltage. If there is no three-phase voltage imbalance or low terminal voltage, end directly. If there is a three-phase voltage imbalance or low terminal voltage, a time delay is generated, and then return to continue to determine whether the distributed photovoltaic power supply is operating normally.

Claims

1. A photovoltaic grid-connected control device with phase selection grid-connected and power regulation functions, characterized in that: It includes a housing and installed in the housing: Operation parameter collection module, collecting the voltage of photovoltaic grid connection point, three-phase current of distributed photovoltaic power supply side, three-phase current of distribution line and harmonics; The data processing and control module performs data processing and logical judgment based on the operating parameters collected from the grid connection point and the distributed photovoltaic power supply side, selects the phase with the largest active and reactive power shortage of the distribution line, and issues instructions to the phase selection and grid connection execution module to realize the grid connection phase conversion; it can also re-evaluate the operating status of the low-voltage distribution network after the structure is changed, and at the same time, explore the adjustment potential of the distributed photovoltaic power inverter based on the operating data of the distributed photovoltaic power inverter, and issue adjustment instructions to the distributed photovoltaic power inverter; The phase selection and grid-connected execution module includes a soft switch module and a high-power switch control module, which realizes the phase-changing operation of the high-power grid-connected switch with a low-power control loop; The communication module is used for information exchange between the photovoltaic grid-connected control device and the distributed photovoltaic power inverter and the intelligent fusion terminal of the substation area, and completes the parameter adjustment of the distributed photovoltaic power inverter according to the control strategy issued by the master station, and changes the active and reactive output of the distributed photovoltaic power inverter when connected to the grid; Display screen module for data display, equipment control and data transmission; The power management module provides power to the device.

2. The device according to claim 1, characterized in that The operating parameter acquisition module includes multiple current transformers, which are installed on the three-phase distribution lines of the photovoltaic grid-connected point and the distributed photovoltaic power inverter lead-out lines. Voltage and current operating parameters are collected through current transformers and built-in voltage transmitter elements.

3. The device according to claim 1, characterized in that The data processing and control module processes data by filtering first and then smoothing.

4. The device according to claim 1, characterized in that The power management module includes AC-DC, DC-DC and voltage stabilization modules.

5. The device according to claim 1, characterized in that The communication module is for Internet of Things communication, wireless communication or 4G communication, and a RS485 communication interface is reserved.

6. The photovoltaic grid-connected control method of the device according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: Collect the voltage at the photovoltaic grid-connected point, the three-phase current on the distributed photovoltaic power supply side, the three-phase current of the distribution line, and harmonics; S2: Perform data processing and logic judgment based on the operating parameters collected from the grid-connected point and the distributed photovoltaic power source side, select the phase with the largest active and reactive power shortages in the distribution line, and send instructions to the phase selection and grid-connected execution module to realize the grid-connected phase conversion.

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