A detection device and method for inverter island protection

Abstract

The present invention discloses a detection device and method for inverter islanding protection in the field of dust removal technology. The device comprises an AC sampling circuit, a relay circuit, and an inverter output line voltage detection circuit. The AC sampling circuit is responsible for real-time acquisition of current grid voltage, current, power, and other parameters. The relay circuit is responsible for disconnecting the grid at an appropriate time to simulate a grid fault. The inverter output line voltage detection circuit is responsible for detecting the inverter output voltage, thereby determining whether the inverter's islanding protection function is functioning properly. Since the AC acquisition circuit can only acquire voltage signals at the grid end, when the relay is disconnected, the grid end and the inverter output end are separated. At this time, a separate voltage detection circuit is required to detect the inverter voltage signal. Since only a single voltage signal needs to be acquired and it is sufficient to determine whether the voltage is 0, any abnormality can be reported to the system in real time, thus playing an early warning role. This effectively prevents the occurrence of islanding safety accidents.

Description

Technical Field

[0001] The present invention relates to the technical field of dust removal, and in particular to a detection device and method for inverter islanding protection. Background Art

[0002] With the continuous increase in the proportion of distributed energy such as photovoltaic and wind power, the island protection function of distributed energy plays an important role in the integrity of the power grid. Island protection is specifically for access to the mains. When the mains fails, the grid-connected inverter detects and determines the island and stops supplying electricity to the mains to ensure the personal safety of the mains maintenance personnel. Among the current protection measures, the main one is the active protection of the inverter itself, supplemented by some passive switches to achieve the island protection function. This method is heavily dependent on the product performance of the inverter itself. When the inverter has quality problems, it cannot be discovered in time, which can easily cause safety accidents. Based on this, the present invention designs a detection device and method for inverter island protection to solve the above problems. Summary of the Invention

[0003] The object of the present invention is to provide a detection device and method for inverter islanding protection to solve the problems raised in the above background technology.

[0004] To achieve the above object, the present invention provides the following technical solution: a detection device for inverter island protection, comprising an AC sampling circuit, a relay circuit, and an inverter output voltage detection circuit;

[0005] The AC sampling circuit is responsible for real-time collection of the current grid parameters such as voltage, current, and power. The relay circuit is responsible for disconnecting the grid at the appropriate time to simulate a grid fault. The inverter output voltage detection circuit is responsible for detecting the inverter's output voltage to determine whether the inverter's islanding protection function is functioning properly.

[0006] Preferably, since the AC acquisition circuit can only acquire the voltage signal of the grid end, when the relay is disconnected, the grid end and the inverter output end are separated. At this time, a separate voltage detection circuit is required to detect the voltage signal of the inverter. Since only a single voltage signal needs to be acquired and it is sufficient to determine whether the voltage is 0.

[0007] Preferably, the voltage detection circuit only needs two resistors, a diode, an optocoupler and a capacitor to complete the detection function.

[0008] Preferably, when there is an AC voltage input, the positive half-cycle flows through the optocoupler after being stepped down by a resistor, and the optocoupler is turned on. The optocoupler signal can be sampled at the back end. During the negative half-cycle, the optocoupler is protected from reverse breakdown by a reverse diode. The back end of the tube is filtered by a capacitor to filter the signal into a smooth DC signal, that is, the level can be sampled by the AD acquisition function of the MCU to determine whether the AC voltage is 0.

[0009] A detection method for inverter islanding protection, the judgment detection process is as follows:

[0010] Step 1: Determine whether the current voltage and load meet the load monitoring conditions;

[0011] Step 2: disconnect the relay circuit to simulate a power grid failure;

[0012] Step 3: Quickly detect the inverter output voltage and determine whether it can drop to 0V within 2 seconds;

[0013] Step 4: If the value is 0, it indicates that the island function is normal and the test ends;

[0014] Step 5: If it cannot be 0, it means that the island function is abnormal. Repeat the test 3 times. If it is abnormal all 3 times, it is determined that the island function is abnormal and report it to the system.

[0015] Compared with existing technologies, the present invention has the following advantages: by integrating an inverter islanding protection monitoring device into the data collection equipment at the inverter's grid-connected port, the present invention enables real-time monitoring of the inverter's islanding protection function. Any anomalies can be reported to the system in real time, providing an early warning and effectively preventing islanding safety accidents.

[0016] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 This is a flowchart of the detection process of the present invention;

[0019] Figure 2 This is the inverter island protection circuit diagram of the present invention. DETAILED DESCRIPTION

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0021] See also Figures 1 to 2The present invention provides a device and method for detecting inverter islanding protection. The device consists of three components: an AC sampling circuit, a relay circuit, and an inverter output voltage detection circuit. The AC sampling circuit collects real-time grid parameters such as voltage, current, and power. The relay circuit disconnects the grid at the appropriate time to simulate a grid fault. The inverter output voltage detection circuit monitors the inverter's output voltage to determine whether the inverter's islanding protection is functioning properly.

[0022] See the flowchart Figure 1 , the judgment process is as follows:

[0023] Step 1: Determine whether the current voltage and load meet the load monitoring conditions.

[0024] Step 2: Disconnect the relay circuit to simulate a power grid failure.

[0025] Step 3: Quickly check the inverter output voltage to determine whether it can drop to 0V within 2 seconds.

[0026] Step 4: If the value can be 0, it indicates that the island function is normal and the test ends.

[0027] Step 5: If it cannot be 0, it means that the island function is abnormal. Repeat the test three times. If it is abnormal all three times, it is determined that the island function is abnormal and report it to the system.

[0028] Since the AC acquisition circuit can only collect the voltage signal of the grid end, when the relay is disconnected, the grid end and the inverter output end are separated. At this time, a separate detection circuit is required to detect the voltage signal of the inverter. Since only a single voltage signal needs to be collected and whether the voltage is 0 is determined, the present invention designs a simple detection circuit that only requires two resistors, a diode, an optocoupler and a capacitor to complete the detection function. The schematic diagram is shown in FIG. Figure 2 , the implementation principle is as follows:

[0029] When an AC voltage is input, the positive half-cycle is stepped down by a resistor and flows through the optocoupler, turning it on. The optocoupler signal can be sampled at the backend. During the negative half-cycle, a reverse diode protects the optocoupler from reverse breakdown. The backend filters the signal through capacitors, converting it into a smooth DC signal. This allows the MCU's AD acquisition function to sample the level and determine whether the AC voltage is zero.

[0030] A specific application of this embodiment is:

[0031] The product model provided by the present invention is only for the use of this technical solution based on the structural characteristics of the product. The product will be adjusted and modified after purchase to make it more compatible with and consistent with the technical solution of the present invention. It is a technical solution for the best application of this technical solution. The model of its product can be replaced and modified according to the required technical parameters, which is well known to technical personnel in this field. Therefore, technical personnel in this field can clearly obtain the corresponding use effect through the technical solution provided by the present invention.

[0032] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0033] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the content of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A detection device for inverter island protection, characterized in that: The detection device consists of three parts: AC sampling circuit, relay circuit, and inverter output voltage detection circuit; The AC sampling circuit is responsible for collecting the voltage, current, and power parameters of the current power grid in real time. The relay circuit is responsible for disconnecting the power grid at the appropriate time to simulate a power grid failure. The inverter output voltage detection circuit is responsible for detecting the inverter's output voltage to determine whether the inverter's islanding protection function is functioning properly. Since the AC acquisition circuit can only collect the voltage signal of the grid end, when the relay is disconnected, the grid end and the inverter output end are separated. At this time, a separate voltage detection circuit is required to detect the voltage signal of the inverter. Since only a single voltage signal needs to be collected and whether the voltage is 0 is sufficient; The voltage detection circuit only needs two resistors, a diode, an optocoupler and a capacitor to complete the detection function; When there is an AC voltage input, the positive half-cycle is stepped down by a resistor and flows through the optocoupler. When the optocoupler is turned on, the optocoupler signal can be sampled at the back end. During the negative half-cycle, the optocoupler is protected from reverse breakdown by a reverse diode. The optocoupler back end filters the signal into a smooth DC signal through capacitor filtering, which means that the level can be sampled by the AD acquisition function of the MCU to determine whether the AC voltage is 0.

2. The detection device for inverter islanding protection according to claim 1, characterized in that: The detection method includes the following steps: Step 1: Determine whether the current voltage and load meet the monitoring conditions; Step 2: Disconnect the relay circuit to simulate a power grid failure; Step 3: Quickly check the inverter output voltage to determine whether it can drop to 0V within 2 seconds; Step 4: If the value is 0, it indicates that the island function is normal and the test ends; Step 5: If it cannot be 0, it means that the island function is abnormal. Repeat the test three times. If it is abnormal all three times, it is determined that the island function is abnormal and report it to the system.

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