Anti-countercurrent grid-connected system and control method thereof
By directly obtaining and comparing the power grid current using inverters and anti-countercurrent detection modules in anti-countercurrent grid connection systems, the problem of slow response time caused by complicated detection and control in the prior art is solved, and fast response anti-countercurrent control is achieved.
Patent Information
- Application Number
- CN202411501387.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-25
- Publication Date
- 2025-01-14
AI Technical Summary
The existing anti-countercurrent device has complicated detection and control, requiring complex vector calculations, resulting in slow response time.
Design a anti-countercurrent grid connection system, directly obtain the current in the power grid through the inverter and anti-countercurrent detection module, and output control is performed based on the smaller current, avoiding complex vector calculations and achieving rapid response.
It effectively alleviates the problem of slow response time for countercurrent prevention, simplifies the detection and control process, and improves the system's response speed.
Smart Images
Figure CN119315623A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of grid-connected power generation, and in particular to a backflow prevention grid-connected system and a control method thereof. Background Art
[0002] At present, the detection and control of the split-phase backflow prevention device are very complicated, and various vector calculations are required. For example, the current backflow prevention device mostly uses a three-phase meter for detection, and then performs vector calculations on the detected structure, which is then output to the inverter after the calculation is completed. This increases the processing workload and slows down the response time of the backflow prevention device.
[0003] Therefore, the current technology still needs to be improved and enhanced. Summary of the invention
[0004] The present application provides a backflow prevention grid-connected system and a control method thereof, which can alleviate the current problem of slow response time of backflow prevention.
[0005] The present application provides a backflow prevention grid-connected system, comprising:
[0006] An inverter, the inverter is located at the user side of the power grid, and the inverter is connected to the first live wire and the second live wire of the power grid;
[0007] The anti-backflow detection module is located at the household entrance side of the power grid and is connected to the inverter, the first live wire, the second live wire and the neutral wire of the power grid; the anti-backflow detection module is used to obtain the first current of the first live wire and the second current of the second live wire, and output the first current or the second current to the inverter; the inverter is used to adjust its output current according to the first current or the second current, so that the output current is not greater than the first current or the second current.
[0008] In some embodiments of the anti-backflow grid-connected system, the anti-backflow detection module includes a detection unit and a comparison unit, the detection unit is connected to the first live wire, the second live wire and the neutral wire; the detection unit is used to obtain the first current and the second current; the comparison unit is used to compare the magnitudes of the first current and the second current, and output the smaller of the first current and the second current to the inverter.
[0009] In some embodiments of the anti-backflow grid-connected system, the detection unit includes a current transformer or a Hall sensor.
[0010] In some embodiments, the anti-reverse current grid-connected system, the inverter includes a phase-locked loop unit, a current comparison unit, a regulation unit and a power output unit connected in sequence, the phase-locked loop unit is also connected to the first live wire and the second live wire, and the power output unit is also connected to the first live wire;
[0011] The phase-locked loop unit is used to output a feedback signal to the current comparison unit according to the reference voltage and the grid voltage between the first live wire and the second live wire; the current comparison unit is used to obtain the output current, output the feedback signal to the adjustment unit, and output the comparison signal to the adjustment unit after comparing the output current with the first current or the second current; the adjustment unit is used to output a corresponding PWM signal to the power output unit according to the comparison signal, so that the output current is not greater than the first current or the second current, and control the phase of the output current according to the feedback signal.
[0012] In the anti-backflow grid-connected system in some embodiments, the regulating unit is specifically configured to reduce the pulse width of the PWM signal when the output current is greater than the first current or the second current.
[0013] In the anti-backflow grid-connected system of some embodiments, the regulating unit is also connected to a DC voltage, and the regulating unit is further used to adjust the magnitude of the output voltage according to the DC voltage;
[0014] The regulating unit is further used to control the phase of the output voltage according to the feedback signal.
[0015] The embodiment of the present application also provides a control method for a backflow prevention grid-connected system, and the control method for the backflow prevention grid-connected system includes:
[0016] The anti-backflow detection module obtains a first current of a first live wire in the power grid and a second current of a second live wire in the power grid, and outputs the first current or the second current to the inverter;
[0017] The inverter adjusts its output current according to the first current or the second current so that the output current is not greater than the first current or the second current.
[0018] In some embodiments, the control method of the anti-backflow grid-connected system, wherein the anti-backflow detection module obtains a first current of a first live wire in the grid and a second current of a second live wire in the grid, and outputs the first current or the second current to the inverter, specifically includes:
[0019] Acquiring a first current and a second current by a detection unit;
[0020] The comparison unit compares the magnitudes of the first current and the second current, and outputs the smaller one of the first current and the second current to the inverter.
[0021] In some embodiments, a control method for a reverse current prevention grid-connected system, wherein the inverter adjusts its output current according to a first current or a second current so that the output current is not greater than the first current or the second current, comprises:
[0022] The phase-locked loop unit outputs a feedback signal to the current comparison unit according to the reference voltage and the grid voltage between the first live wire and the second live wire;
[0023] The current comparison unit obtains the output current, outputs a feedback signal to the adjustment unit, and compares the output current with the first current or the second current and outputs a comparison signal to the adjustment unit;
[0024] The regulating unit outputs a corresponding PWM signal to the power output unit according to the comparison signal, so that the output current is not greater than the first current or the second current, and controls the phase of the output current according to the feedback signal.
[0025] In some embodiments, the control method of the anti-backflow grid-connected system further includes:
[0026] The regulating unit regulates the magnitude of the output voltage according to the input DC voltage, and controls the phase of the output voltage according to the feedback signal.
[0027] The present application provides an anti-backflow grid-connected system and a control method thereof, wherein an anti-backflow detection module is used to obtain a first current of a first live wire and a second current of a second live wire, and output the first current or the second current to an inverter; the inverter is used to adjust its output current according to the first current or the second current, so that the output current is not greater than the first current or the second current, so that there is no reverse flow to the external power grid on the inverter side, and the current direction of the first live wire and the current direction of the second live wire are not reversed. In the present application, only an anti-backflow detection module is set to detect the current in the power grid and then output it directly to the inverter, and the inverter itself adjusts the output current according to the current. In this process, no complex vector calculation is required, which can effectively alleviate the current problem of slow response time of anti-backflow. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The technical solution and other beneficial effects of the present application will be made apparent by describing in detail the specific implementation methods of the present application in conjunction with the accompanying drawings.
[0029] Figure 1 This is a structural block diagram of the anti-backflow grid-connected system provided in an embodiment of the present application.
[0030] Figure 2 This is a structural block diagram of the anti-backflow detection module in the anti-backflow grid-connected system provided in an embodiment of the present application.
[0031] Figure 3 This is a structural block diagram of the inverter in the anti-backflow grid-connected system provided in an embodiment of the present application.
[0032] Figure 4 This is a structural block diagram of a phase-locked loop unit, a current comparison unit and a regulation unit in the anti-backflow grid-connected system provided in an embodiment of the present application.
[0033] Figure 5 A flow chart of a control method for an anti-backflow grid-connected system provided in an embodiment of the present application.
[0034] Figure 6 A schematic flow chart of step 100 in the control method of the anti-backflow grid-connected system provided in an embodiment of the present application.
[0035] Figure 7 A schematic flow chart of step 200 in the control method of the anti-backflow grid-connected system provided in an embodiment of the present application. DETAILED DESCRIPTION
[0036] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.
[0037] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or suggesting relative importance or implicitly indicating the number of technical features indicated. The features specified as "first" and "second" may explicitly or implicitly include one or more features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.
[0038] See also Figure 1 This embodiment provides an anti-backflow grid-connected system, which includes a power grid 11, a transformer 12, an inverter 13 and an anti-backflow detection module 14, wherein the transformer 12 is connected to the power grid 11, the inverter 13 is located on the user side of the power grid 11, and is connected to the first live wire L1 and the second live wire L2 of the power grid 11, the anti-backflow detection module 14 is located on the household side of the power grid 11, that is, close to the transformer 12 relative to the inverter 13, and the anti-backflow detection module 14 is connected to the inverter 13, the first live wire L1, the second live wire L2 and the neutral wire N of the power grid 11; the anti-backflow grid-connected system also has a local load 15 on the user side.
[0039] In this embodiment, the anti-backflow detection module 14 is used to obtain the first current IL1 of the first live wire L1 and the second current IL2 of the second live wire L2, and output the first current IL1 or the second current IL2 to the inverter 13; the inverter 13 is used to adjust its output current according to the first current IL1 or the second current IL2, so that the output current is not greater than the first current IL1 or the second current IL2, so that there is no reverse flow from the inverter 13 side to the external power grid 11, and the current direction of the first live wire L1 and the current direction of the second live wire L2 are not reversed. In this application, only the anti-backflow detection module 14 is set to detect the current in the power grid 11 and then output it directly to the inverter 13, and the inverter 13 itself adjusts the output current according to the current. In this process, no complex vector calculation is required, which can effectively alleviate the current problem of slow response time of anti-backflow.
[0040] Please also read Figure 2 In some embodiments, the anti-backflow detection module 14 includes a detection unit 141 and a comparison unit 142. The detection unit 141 is connected to the first live wire L1, the second live wire L2 and the neutral wire N. The detection unit 141 is used to obtain the first current IL1 and the second current IL2; the comparison unit 142 is used to compare the magnitudes of the first current IL1 and the second current IL2, and output the smaller of the first current IL1 and the second current IL2 to the inverter 13. In this embodiment, the detection unit 141 directly detects the first current IL1 of the first live wire L1 and the second current IL2 of the second live wire L2, and then compares the magnitudes of the first current IL1 and the second current IL2, and outputs the smaller of the first current IL1 and the second current IL2 to the inverter 13, and the inverter 13 controls its output current not to be greater than the first current IL1 or the second current IL2, which is equivalent to allowing the power output by the inverter 13 to be consumed entirely by the local load 15, and will not be output to the external power grid 11 by reverse flow, so as to achieve the purpose of anti-backflow.
[0041] In some embodiments, the first current IL1 and the second current IL2 can be directly obtained by the detection unit 141, and the first current IL1 and the second current IL2 can be directly output to the inverter 13. The inverter 13 compares the magnitudes of the first current IL1 and the second current IL2, and then controls the output current to be no greater than the smaller one of the first current IL1 and the second current IL2.
[0042] As an embodiment, the detection unit 141 includes a current transformer or a Hall sensor. In this embodiment, the current transformer or the Hall sensor is directly used to detect the first current IL1 and the second current IL2, and then the comparison unit 142 compares the first current IL1 and the second current IL2 to compare the sizes of the first current IL1 and IL2, so as to output a smaller current to the inverter 13 to achieve anti-reverse current control.
[0043] See also Figure 3 In some embodiments, the inverter 13 includes a phase-locked loop unit 131, a current comparison unit 132, a regulation unit 133 and a power output unit 134 connected in sequence, the phase-locked loop unit 131 is also connected to the first live wire L1 and the second live wire L2, and the power output unit 134 is also connected to the first live wire L1.
[0044] Among them, the phase-locked loop unit 131 is used to output a feedback signal to the current comparison unit 132 according to the reference voltage and the grid voltage between the first live wire L1 and the second live wire L2; the current comparison unit 132 is used to obtain the output current, and output the feedback signal to the adjustment unit 133, and output the comparison signal to the adjustment unit 133 after comparing the output current with the first current IL1 or the second current IL2; the adjustment unit 133 is used to output a corresponding PWM signal to the power output unit 134 according to the comparison signal, so that the output current is not greater than the first current IL1 or the second current IL2, and control the phase of the output current according to the feedback signal.
[0045] In this embodiment, the grid voltage between the first live wire L1 and the second live wire L2 is obtained by the phase-locked loop unit 131, and the corresponding phase is obtained according to the grid voltage, and then a feedback signal is output to the current comparison unit 132, so as to control the phase of the output current later. At the same time, the current comparison unit 132 obtains the output current of the inverter 13 and the first current IL1 or the second current IL2, and outputs a comparison signal to the adjustment unit 133 after comparing the two, so that the adjustment unit 133 can adjust the magnitude of the output current so that the output current is not greater than the first current IL1 or the second current IL2.
[0046] Please also read Figure 4 As an embodiment, the phase-locked loop unit 131 in this embodiment includes a phase-locked loop 1311, a first comparator 1312 and a voltage compensator 1313. The phase-locked loop 1311 obtains the grid voltage between the first live wire L1 and the second live wire L2, and obtains the corresponding voltage phase according to the grid voltage, and outputs it to the first comparator 1312; the first comparator 1312 outputs a comparison result to the voltage compensator 1313 according to the voltage output by the phase-locked loop 1311 and the reference voltage, and the voltage compensator 1313 performs voltage compensation and outputs a feedback signal to the current comparison unit 132, so as to provide the current comparison unit 132 with corresponding phase information.
[0047] As an embodiment, the current comparison unit 132 includes a second comparator 1321 and a current compensator 1322. The second comparator 1321 obtains the first current IL1 or the second current IL2, compares the first current IL1 or the second current IL2 with the output current, and then outputs a comparison signal to the current compensator 1322. The current compensator 1322 performs current compensation and then outputs it to the adjustment unit 133 to facilitate subsequent adjustment of the output current.
[0048] As an embodiment, the regulating unit 133 in this embodiment is a PWM controller in the inverter 13. The regulating unit 133 is used to reduce the pulse width of the PWM signal when the output current is greater than the first current IL1 or the second current IL2, so that the output current of the power output unit 134 is not greater than the current or the second current IL2.
[0049] As an embodiment, the power output unit 134 includes a MOS tube and an energy storage inductor, and the PWM signal output by the PWM controller adjusts the duty cycle of the MOS tube to adjust the output current of the energy storage inductor. Among them, the output current obtained by the second comparator can actually be the inductor current, and the inductor current is compared with the first current or the second current to facilitate the adjustment of the output current of the energy storage inductor. The power output unit 134 in this application is a known structure in the inverter 13 and will not be described here.
[0050] As an embodiment, the regulating unit 133 is also connected to a DC power supply, and the regulating unit 133 is also used to adjust the output voltage according to the DC voltage Vbus provided by the DC power supply, so that the output voltage of the power output unit 134 is greater than the grid voltage, ensuring that the inverter 13 can provide an output voltage to power the load and meet the power demand of the load. At the same time, according to the phase of the grid voltage obtained by the phase-locked loop unit 131, the regulating unit 133 controls the phase of the output voltage to be consistent with the phase of the grid voltage. It should be noted that the inverter 13 in the present application is a known circuit structure, so the specific circuit structure of the inverter 13 is not repeated here.
[0051] The anti-backflow grid-connected system in the present application only obtains two currents, compares the two currents and outputs them to the inverter, and adds them to the output control process of the inverter, so that the inverter controls its output current according to the input current to be no greater than the smaller of the two currents, thereby realizing the anti-backflow control process. In this process, there is no need to perform a complex vector calculation process, and the detection current is directly output to the control loop of the inverter, which can achieve a rapid response to anti-backflow.
[0052] See also Figure 5 The embodiment of the present application also provides a control method for a backflow prevention grid-connected system, and the control method for a backflow prevention grid-connected system includes:
[0053] 100. The backflow prevention detection module obtains a first current of a first live wire in the power grid and a second current of a second live wire in the power grid, and outputs the first current or the second current to the inverter;
[0054] 200. The inverter adjusts its output current according to the first current or the second current so that the output current is not greater than the first current or the second current.
[0055] In this embodiment, the anti-backflow detection module obtains the first current of the first live wire and the second current of the second live wire, and outputs the first current or the second current to the inverter; the inverter adjusts its output current according to the first current or the second current, so that the output current is not greater than the first current or the second current, so that there is no reverse flow from the inverter side to the external power grid, and the current direction of the first live wire and the current direction of the second live wire are not reversed. In this application, the current in the power grid is directly output to the inverter after being detected by the anti-backflow detection module, and the inverter itself adjusts the output current according to the current. In this process, no complex vector calculation is required, which can effectively alleviate the problem of slow response time of the current anti-backflow.
[0056] See also Figure 6 In some embodiments, step 100 includes:
[0057] 110. Obtaining a first current and a second current by a detection unit;
[0058] 120. The comparison unit compares the first current and the second current, and outputs the smaller one of the first current and the second current to the inverter.
[0059] In this embodiment, the detection unit directly detects the first current of the first live wire and the second current of the second live wire, and then compares the first current and the second current, and outputs the smaller one of the first current and the second current to the inverter, and the inverter controls its output current to be no greater than the first current or the second current, which is equivalent to allowing all the power output by the inverter to be consumed by the local load, and will not be output to the external power grid by reverse flow, so as to achieve the purpose of preventing reverse flow.
[0060] See also Figure 7 In some embodiments, step 200 includes:
[0061] 210. The phase-locked loop unit outputs a feedback signal to the current comparison unit according to the reference voltage and the grid voltage between the first live wire and the second live wire;
[0062] 220. Obtaining the output current by the current comparison unit, and outputting a feedback signal to the adjustment unit, and outputting a comparison signal to the adjustment unit after comparing the output current with the first current or the second current;
[0063] 230. The regulating unit outputs a corresponding PWM signal to the power output unit according to the comparison signal, so that the output current is not greater than the first current or the second current, and controls the phase of the output current according to the feedback signal.
[0064] In this embodiment, the grid voltage between the first live wire and the second live wire is obtained by the phase-locked loop unit, and a feedback signal is output to the current comparison unit after the corresponding phase is obtained according to the grid voltage, so as to control the phase of the output current later. At the same time, the current comparison unit obtains the output current of the inverter and the first current or the second current, compares the two, and then outputs a comparison signal to the adjustment unit, so that the adjustment unit adjusts the magnitude of the output current so that the output current is not greater than the first current or the second current.
[0065] In some embodiments, the control method of the anti-backflow grid-connected system also includes: the adjustment unit adjusts the magnitude of its output voltage according to the connected DC voltage, and the adjustment unit controls the phase of the output voltage according to the feedback signal. In this embodiment, the adjustment unit adjusts the magnitude of the output voltage according to the DC voltage provided by the DC power supply, so that the output voltage of the power output unit is greater than the grid voltage, ensuring that the inverter can provide output voltage to power the load and meet the power demand of the load. At the same time, according to the phase of the grid voltage obtained by the phase-locked loop unit, the adjustment unit controls the phase of the output voltage to be consistent with the phase of the grid voltage.
[0066] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.
[0067] The anti-backflow grid-connected system provided in the embodiments of the present application is introduced in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solution and its core idea of the present application. Ordinary technical personnel in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some of the technical features therein with equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.
Claims
1. A backflow prevention grid-connected system, characterized in that: include: An inverter, wherein the inverter is located at a user side of a power grid, and the inverter is connected to a first live wire and a second live wire of the power grid; an anti-backflow detection module, the anti-backflow detection module is located at the household entrance side of the power grid and is connected to the inverter, the first live wire, the second live wire and the neutral wire of the power grid; the anti-backflow detection module is used to obtain a first current of the first live wire and a second current of the second live wire, and output the first current or the second current to the inverter; The inverter is used to adjust its output current according to the first current or the second current, so that the output current is not greater than the first current or the second current.
2. The anti-backflow grid-connected system according to claim 1, characterized in that: The anti-backflow detection module includes a detection unit and a comparison unit, the detection unit is connected to the first live wire, the second live wire and the neutral wire; the detection unit is used to obtain the first current and the second current; the comparison unit is used to compare the magnitudes of the first current and the second current, and output the smaller of the first current and the second current to the inverter.
3. The anti-backflow grid-connected system according to claim 2, characterized in that: The detection unit includes a current transformer or a Hall sensor.
4. The anti-backflow grid-connected system according to claim 1, characterized in that: The inverter comprises a phase-locked loop unit, a current comparison unit, a regulation unit and a power output unit connected in sequence, the phase-locked loop unit is also connected to the first live wire and the second live wire, and the power output unit is also connected to the first live wire; The phase-locked loop unit is used for outputting a feedback signal to the current comparison unit according to a reference voltage and a grid voltage between the first live wire and the second live wire; The current comparison unit is used to obtain the output current, output the feedback signal to the adjustment unit, and output the comparison signal to the adjustment unit after comparing the output current with the first current or the second current; the adjustment unit is used to output a corresponding PWM signal to the power output unit according to the comparison signal, so that the output current is not greater than the first current or the second current, and control the phase of the output current according to the feedback signal.
5. The anti-backflow grid-connected system according to claim 4, characterized in that: The regulating unit is specifically configured to reduce the pulse width of the PWM signal when the output current is greater than the first current or the second current.
6. The anti-backflow grid-connected system according to claim 4, characterized in that: The regulating unit is also connected to a DC voltage, and the regulating unit is further used to adjust the magnitude of the output voltage according to the DC voltage; The regulating unit is further configured to control the phase of the output voltage according to the feedback signal.
7. A control method for a backflow prevention grid-connected system, characterized in that: The control method of the anti-backflow grid-connected system includes: The anti-backflow detection module acquires a first current of a first live wire in the power grid and a second current of a second live wire in the power grid, and outputs the first current or the second current to the inverter; The inverter adjusts its output current according to the first current or the second current, so that the output current is not greater than the first current or the second current.
8. The control method of the anti-backflow grid-connected system according to claim 7, characterized in that: The step of obtaining, by the anti-backflow detection module, a first current of a first live wire in a power grid and a second current of a second live wire in a power grid, and outputting the first current or the second current to an inverter specifically includes: Acquiring the first current and the second current by a detection unit; The comparison unit compares the magnitudes of the first current and the second current, and outputs the smaller one of the first current and the second current to the inverter.
9. The control method of the anti-backflow grid-connected system according to claim 7, characterized in that: The inverter adjusting its output current according to the first current or the second current so that the output current is not greater than the first current or the second current comprises: The phase-locked loop unit outputs a feedback signal to the current comparison unit according to a reference voltage and a grid voltage between the first live wire and the second live wire; The output current is acquired by a current comparison unit, and the feedback signal is output to the adjustment unit, and the output current is compared with the first current or the second current and then a comparison signal is output to the adjustment unit; The regulating unit outputs a corresponding PWM signal to the power output unit according to the comparison signal, so that the output current is not greater than the first current or the second current, and controls the phase of the output current according to the feedback signal.
10. The control method of the anti-backflow grid-connected system according to claim 9, characterized in that: The control method of the anti-backflow grid-connected system also includes: The regulating unit regulates the magnitude of the output voltage according to the input DC voltage, and controls the phase of the output voltage according to the feedback signal.