Low-voltage intelligent miniature circuit breaker and active defense island detection method

Abstract

The application discloses a low-voltage intelligent miniature circuit breaker and an active defense island detection method, wherein two power supplies of the circuit breaker are independently operated, one is at the input terminal of the grid-connected circuit breaker, and the other is at the output terminal of the grid-connected circuit breaker; the working mode is to detect the grid and photovoltaic operation state in the line in real time; the two power supplies are simultaneously operated to avoid the safety hidden trouble caused by the failure of one of the circuits; and when the island is operated, the first MCU unit actively detects the island operation state at a fixed time. Through the method, the island operation can be quickly and efficiently monitored and detected by adding the anti-island detection function in the distributed photovoltaic grid-connected circuit breaker, the photovoltaic island effect is solved, and the safety hidden trouble caused by the inverter failure to the grid, equipment and line is solved.

Description

Technical Field

[0001] This invention relates to the field of islanding detection technology, and more specifically, to a low-voltage intelligent miniature circuit breaker and an active defense islanding detection method. Background Technology

[0002] The islanding effect has an adverse impact on the entire power distribution system equipment and user-end equipment, endangers the lives of power maintenance personnel, affects the operation of protection switches on the power distribution system, and the unstable nature of the power supply voltage and frequency in the islanded area can damage electrical equipment. When the power supply is restored, the voltage phase asynchrony will generate surge current, which may cause the circuit breaker to trip again or damage the photovoltaic system, load and power supply system. The photovoltaic grid-connected power generation system has a problem of insufficient phase power supply for the three-phase load due to single-phase power supply.

[0003] Currently, distributed photovoltaic grid-connected miniature circuit breakers only have over, under, and loss-of-voltage protection functions. When the photovoltaic power generation system is connected to the mains power, after the mains power is cut off, the inverter's islanding detection function fails, and it is impossible to complete the protection of the photovoltaic power generation system and line safety. Furthermore, photovoltaic circuit breakers do not currently have anti-islanding protection functions. Summary of the Invention

[0004] This invention proposes a low-voltage intelligent miniature circuit breaker and an active defense islanding detection method to solve the problem of how to perform islanding detection.

[0005] To address the aforementioned problems, according to one aspect of the present invention, a low-voltage intelligent miniature circuit breaker is provided, the circuit breaker comprising: an incoming line detection module, a grid photovoltaic link control unit, and an outgoing line detection module connected in sequence; wherein...

[0006] The incoming line detection module is located on the incoming line side of the photovoltaic grid-connected circuit breaker and is powered by the power grid.

[0007] The outgoing line detection module is located on the outgoing line side of the photovoltaic grid-connected circuit breaker and is powered by the photovoltaic power supply system.

[0008] The incoming line detection module and the outgoing line detection module are used to realize passive islanding detection and active islanding detection of the photovoltaic power supply system.

[0009] The grid photovoltaic link control unit is used to control the connection and disconnection of the grid side and the photovoltaic side inside the grid-connected circuit breaker when the handle is not open, and is a high-speed switching switch.

[0010] Preferably, the incoming line detection module includes: a first microcontroller unit (MCU) processing unit and a first voltage conversion unit, a first voltage detection unit, a first current detection unit, and a first island detection unit, all connected to the first processing unit;

[0011] The outgoing line detection module includes: a second microcontroller unit (MCU) processing unit, and a second voltage conversion unit, a second voltage detection unit, a second current detection unit, and a second island detection unit, all connected to the second processing unit.

[0012] The first voltage conversion unit supplies power to the first MCU unit, and the second voltage conversion unit supplies power to the second MCU unit.

[0013] Both the first voltage detection unit and the second voltage detection unit have the functions of detecting the voltage, frequency and phase of the power supply, which is a passive detection method;

[0014] Both the first current detection unit and the second current detection unit have current flow direction detection and current imbalance detection functions, which are passive detection methods;

[0015] The first islanding detection unit has an RLC simulated load function. When the first MCU processing unit sends a trip command to the grid photovoltaic link control unit, the first islanding detection unit starts working in advance for a first preset time. When the grid photovoltaic link control unit is disconnected, the first islanding detection unit generates current power consumption, which flows through the first current detection unit. If the first current detection unit detects a current value that meets the RLC threshold, the grid side supplies power normally. If no RLC current or generated power is detected, or if the swing amplitude of the RLC load current and power during operation is greater than the threshold, it is determined that the grid side is disconnected, and the photovoltaic power generation system operates in islanded mode.

[0016] The second islanding detection unit is used to start a first preset time in advance when the grid photovoltaic link control unit is disconnected, simulate the operation of the RLC simulated load, form a load current flowing through the second current detection unit, and the second MCU processing unit determines the operating status of the photovoltaic power supply system based on the current change.

[0017] According to another aspect of the present invention, a method for active defense islanding detection of a low-voltage intelligent miniature circuit breaker is provided, characterized in that the method comprises:

[0018] When the power grid fails and the photovoltaic power supply system stops supplying power to the grid, causing the grid and photovoltaic sides to disconnect, the first voltage detection unit acquires the first voltage, first frequency and first phase of the grid and photovoltaic grid connection point.

[0019] The first MCU processing unit determines whether the photovoltaic power supply system is in islanded operation based on the first voltage, first frequency, and first phase according to preset criteria, so as to realize passive islanding detection of the photovoltaic power supply system.

[0020] Preferably, it is determined whether the voltage amplitude swing range of the first voltage within the first preset time period exceeds the preset voltage range, or whether the first frequency swing range of the first voltage exceeds the preset frequency range, or whether the difference between the first phase and the nominal phase of any phase meets the preset phase difference threshold. If the conditions are met, it is determined that the photovoltaic power supply system is in islanded operation. The criterion is based primarily on the frequency swing of the voltage and secondarily on the voltage amplitude swing. When the frequency swing criterion of the voltage is met, the grid connection point is disconnected within the preset disconnection time.

[0021] According to another aspect of the present invention, an active defense islanding detection method for low-voltage intelligent miniature circuit breakers is provided, the method comprising:

[0022] When the grid-PV link control unit between the grid side and the PV side is disconnected, causing the grid side and the PV side to disconnect, and the disconnection time reaches the preset disconnection time, the RLC simulated load current generated by the first current detection unit and the second current detection unit are measured respectively to obtain the first current and the second current.

[0023] The first voltage detection unit is used to obtain the current first voltage, first frequency and first phase, and the second voltage detection unit is used to obtain the second voltage, second frequency and second phase;

[0024] The first MCU processing unit determines whether the photovoltaic power supply system is operating in islanded mode based on the first current, the first voltage, the first frequency and / or the first phase.

[0025] The second MCU processing unit determines whether the photovoltaic power supply system is in islanded operation based on the second current, second voltage, second frequency and / or second phase, so as to realize active islanding detection of the photovoltaic power supply system.

[0026] Preferably, the method further includes:

[0027] The clock unit within the incoming line detection module provides accurate time to the first MCU processing unit;

[0028] The first MCU processing unit sends commands to the grid photovoltaic link control unit according to a preset time period, so that the grid side and the photovoltaic side are disconnected to perform active islanding detection.

[0029] Preferably, the first islanding detection unit starts working at a first preset time before disconnecting the grid photovoltaic link control unit, the first current detection unit collects the first current generated by the first islanding detection unit at this time, and detects the first operating current generated by the first islanding detection unit during a second preset time period after disconnecting the grid photovoltaic link control unit, and compares the first current and the first operating current. When the fluctuation of the first operating current exceeds the first current of a first preset percentage, it is determined that the photovoltaic power supply system is in islanding operation.

[0030] Preferably, the first islanding detection unit starts working a first preset time before the grid photovoltaic link control unit is disconnected, and the first voltage acquisition unit acquires the first voltage, the first frequency, and the first phase.

[0031] The first MCU processing unit determines whether the voltage amplitude swing range of the first voltage exceeds the preset voltage range within the first preset time period, or whether the first frequency swing range of the first voltage exceeds the preset frequency range, or whether the difference between the first phase and the nominal phase of any phase meets the preset phase difference threshold. If the conditions are met, the photovoltaic power supply system is determined to be in islanded operation. The criterion is based primarily on the frequency swing of the voltage, and secondarily on the voltage amplitude swing.

[0032] Preferably, the second islanding detection unit starts working at a first preset time before disconnecting the grid photovoltaic link control unit. The second current detection unit collects the second current generated by the second islanding detection unit at this time, and detects the second operating current generated by the second islanding detection unit during a second preset time period after disconnecting the grid photovoltaic link control unit. The second current and the second operating current are compared. When the fluctuation of the second operating current exceeds the second current of a second preset percentage, it is determined that the photovoltaic power supply system is in islanded operation.

[0033] Preferably, the second islanding detection unit starts working at a first preset time before the grid photovoltaic link control unit is disconnected, and the second voltage acquisition unit acquires the second voltage, the second frequency, and the second phase.

[0034] The second MCU processing unit determines whether the voltage amplitude swing range of the second voltage exceeds the preset voltage range within the first preset time period, or whether the second frequency swing range of the second voltage exceeds the preset frequency range, or whether the difference between the second phase and the nominal phase of any phase meets the preset phase difference threshold. If the conditions are met, the photovoltaic power supply system is determined to be in islanded operation.

[0035] This invention provides a low-voltage intelligent miniature circuit breaker and an active islanding detection method. The circuit breaker has two independent power supplies: one at the incoming end and the other at the outgoing end. The operating mode is to monitor the grid and photovoltaic (PV) operation status in real time. Simultaneous operation of both power supplies avoids safety hazards caused by the failure of one circuit. Furthermore, during islanding operation, the first MCU unit actively monitors the islanding status periodically. By adding anti-islanding detection functionality to the distributed PV grid-connected circuit breaker, this invention enables rapid and efficient monitoring of islanding operation, solving the safety hazards to the grid, equipment, and lines caused by PV islanding and inverter failure. Attached Figure Description

[0036] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0037] Figure 1 This is a schematic diagram of the structure of a low-voltage intelligent miniature circuit breaker 100 according to an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of grid and photovoltaic grid connection according to an embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram of a power grid photovoltaic link control unit according to an embodiment of the present invention;

[0040] Figure 4 This is a schematic diagram of the islanding detection principle of a photovoltaic grid-connected circuit breaker according to an embodiment of the present invention;

[0041] Figure 5 A flowchart of an active defense islanding detection method 500 for low-voltage intelligent miniature circuit breakers according to an embodiment of the present invention;

[0042] Figure 6 This is a flowchart of an active defense islanding detection method 600 for low-voltage intelligent miniature circuit breakers according to an embodiment of the present invention. Detailed Implementation

[0043] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0044] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0045] Figure 1 This is a schematic diagram of the structure of a low-voltage intelligent miniature circuit breaker 100 according to an embodiment of the present invention. Figure 1 As shown, this invention provides a low-voltage intelligent miniature circuit breaker. The circuit breaker has two independent power supplies: one at the incoming end and the other at the outgoing end. The operating mode is to monitor the grid and photovoltaic (PV) operation status in real time. Simultaneous operation of both power supplies avoids safety hazards caused by the failure of one circuit. Furthermore, during islanded operation, the first MCU unit periodically and actively monitors the islanded operation status. By adding anti-islanding detection functionality to the distributed PV grid-connected circuit breaker, this invention enables rapid and efficient monitoring of islanded operation, solving the problems of PV islanding effects and safety hazards to the grid, equipment, and lines caused by inverter failure. The low-voltage intelligent miniature circuit breaker 100 provided in this embodiment includes: an incoming-side detection module 101, a grid-PV link control unit 102, and an outgoing-side detection module 103 connected in sequence.

[0046] Preferably, the incoming line detection module 101 is located on the incoming line side of the photovoltaic grid-connected circuit breaker and is powered by the power grid;

[0047] Preferably, the outgoing line detection module 102 is located on the outgoing line side of the photovoltaic grid-connected circuit breaker and is powered by the photovoltaic power supply system;

[0048] Preferably, the incoming line detection module and the outgoing line detection module are used to realize passive islanding detection and active islanding detection of the photovoltaic power supply system;

[0049] The grid photovoltaic link control unit 103 is used to control the connection and disconnection of the grid side and the photovoltaic side inside the grid-connected circuit breaker when the handle is not open, and is a high-speed switching switch.

[0050] Preferably, the incoming line detection module includes: a first microcontroller unit (MCU) processing unit and a first voltage conversion unit, a first voltage detection unit, a first current detection unit, and a first island detection unit, all connected to the first processing unit;

[0051] The outgoing line detection module includes: a second microcontroller unit (MCU) processing unit, and a second voltage conversion unit, a second voltage detection unit, a second current detection unit, and a second island detection unit, all connected to the second processing unit.

[0052] The first voltage conversion unit supplies power to the first MCU unit, and the second voltage conversion unit supplies power to the second MCU unit.

[0053] Both the first voltage detection unit and the second voltage detection unit have the functions of detecting the voltage, frequency and phase of the power supply, which is a passive detection method;

[0054] Both the first current detection unit and the second current detection unit have current flow direction detection and current imbalance detection functions, which are passive detection methods;

[0055] The first islanding detection unit has an RLC simulated load function. When the first MCU processing unit sends a trip command to the grid photovoltaic link control unit, the first islanding detection unit starts working in advance for a first preset time. When the grid photovoltaic link control unit is disconnected, the first islanding detection unit generates current power consumption, which flows through the first current detection unit. If the first current detection unit detects a current value that meets the RLC threshold, the grid side supplies power normally. If no RLC current or generated power is detected, or if the swing amplitude of the RLC load current and power during operation is greater than the threshold, it is determined that the grid side is disconnected, and the photovoltaic power generation system operates in islanded mode.

[0056] The second islanding detection unit is used to start a first preset time in advance when the grid photovoltaic link control unit is disconnected, simulate the operation of the RLC simulated load, form a load current flowing through the second current detection unit, and the second MCU processing unit determines the operating status of the photovoltaic power supply system based on the current change.

[0057] In this invention, such as Figure 2 As shown, the power grid is mainly the municipal power public network, the grid connection point with the photovoltaic system is the photovoltaic grid-connected circuit breaker, the grid-connected inverter and the photovoltaic module unit is the photovoltaic DC to AC operation system.

[0058] Combination Figure 3 and Figure 4As shown, in this invention, the circuit breaker provides two power supply methods: one is power supply from the grid side to the grid-connected circuit breaker on the incoming side, and the other is power supply from the photovoltaic side to the grid-connected circuit breaker on the outgoing side. The two power supply methods are independent of each other and play a key role in passive and active anti-islanding detection. The incoming side islanding detection consists of a voltage conversion unit 1 (i.e., the first voltage conversion unit), a voltage detection unit 1 (i.e., the first voltage detection unit), a current detection unit 1 (i.e., the first current detection unit), an islanding detection unit 1 (i.e., the first islanding detection unit), a clock unit, and an MCU processing unit 1 (i.e., the first MCU processing unit). The outgoing side islanding detection consists of a voltage conversion unit 2 (i.e., the second voltage conversion unit), a voltage detection unit 2 (i.e., the second voltage detection unit), a current detection unit 2 (i.e., the second current detection unit), an islanding detection unit 2 (i.e., the second islanding detection unit), an MCU processing unit 2 (i.e., the second MCU processing unit), and a grid photovoltaic link control unit jointly controlled by MCU processing units 1 and 2.

[0059] The circuit breaker body has functions such as overcurrent protection, short circuit protection, and isolation. The grid-connected photovoltaic (PV) link control unit enables the connection and disconnection of the grid point and PV point within the circuit breaker when the PV grid-connected circuit breaker handle is not open; it functions as a high-speed switching switch. Voltage conversion units 1 and 2 provide power to MCU processing units 1 and 2. Voltage detection units 1 and 2 perform voltage, frequency, and phase detection of the power supply, using a passive detection method. Current detection units 1 and 2 perform current flow direction detection and current imbalance detection, also using a passive detection method.

[0060] The islanding detection unit 1 has an RLC simulated load function. When the MCU processing unit 1 issues a trip command to the "grid photovoltaic link control unit", the islanding detection unit 1 starts working 2 seconds in advance. When the grid photovoltaic link control unit is disconnected, the islanding detection unit generates current power consumption, which flows through the current detection unit 1. If the current detection unit 1 detects a current value that meets the RLC threshold, the grid side supplies power normally. If no RLC current or generated power is detected, or if the RLC load current and power swing value is greater than the threshold during operation, it is determined that the grid side is disconnected and the photovoltaic power generation system is in islanded operation.

[0061] The islanding detection unit 2 is activated 2 seconds in advance when the grid photovoltaic link control unit is disconnected. The internal RLC simulates the load and forms a load current flowing through the detection unit 2. The MCU processing unit 2 checks the operating status of the photovoltaic system based on the change in current.

[0062] The mains power input provides voltage to the incoming side of the grid-connected circuit breaker. The photovoltaic power input provides voltage to the outgoing side of the grid-connected circuit breaker. The miniature circuit breaker provides accurate time to the MCU processing unit 1 via a clock unit, performing anti-islanding detection at the hour and agreed-upon times. The miniature circuit breaker MCU processing unit 1 issues disconnect and connect commands to the "grid photovoltaic link control unit," with a disconnect time of 100ms (a disconnect time greater than 150ms is considered a grid power outage, affecting the normal operation of the photovoltaic side). The "grid photovoltaic link control unit" is a high-speed switching switch for controlling the grid and photovoltaic system, connected in series in the circuit loop, and is not the handle switch of the photovoltaic circuit breaker. The islanding detection unit is an RLC simulated load that starts working 2 seconds before the "grid photovoltaic link control unit" disconnects, and operates for 5 seconds. The resulting load current flows through the current detection unit, and based on the acquired current data, it filters and calculates to determine the operating status of the photovoltaic power generation system and whether islanding has occurred. The MCU processing units 1 and 2 operate independently, performing protection processing based on the anti-islanding detection feedback. The photovoltaic grid-connected circuit breaker disconnects the power grid from the photovoltaic system in two ways: one is by lever tripping, and the other is by high-speed switching action.

[0063] Figure 5 This is a flowchart of a low-voltage intelligent miniature circuit breaker active defense islanding detection method 500 according to an embodiment of the present invention. Figure 5 As shown, the low-voltage intelligent miniature circuit breaker active defense islanding detection method 500 provided by the embodiment of the present invention includes:

[0064] Step 501: When the power grid fails and the photovoltaic power supply system stops supplying power to the power grid, causing the power grid and photovoltaic sides to disconnect, the first voltage detection unit acquires the first voltage, first frequency and first phase of the grid and photovoltaic grid connection point.

[0065] Step 502: The first MCU processing unit determines whether the photovoltaic power supply system is in islanded operation according to the first voltage, the first frequency and the first phase and a preset criterion, so as to realize passive islanding detection of the photovoltaic power supply system.

[0066] Preferably, it is determined whether the voltage amplitude swing range of the first voltage within the first preset time period exceeds the preset voltage range, or whether the first frequency swing range of the first voltage exceeds the preset frequency range, or whether the difference between the first phase and the nominal phase of any phase meets the preset phase difference threshold. If the conditions are met, it is determined that the photovoltaic power supply system is in islanded operation. The criterion is based primarily on the frequency swing of the voltage and secondarily on the voltage amplitude swing. When the frequency swing criterion of the voltage is met, the grid connection point is disconnected within the preset disconnection time.

[0067] In this invention, the first preset time period is a continuous 150ms.

[0068] Combination Figure 4 As shown, in this invention, the mains power input unit provides voltage to the MCU processing unit 1 on the incoming side of the grid-connected circuit breaker. The voltage detection unit 1 operates based on the normal mains power supply voltage Vg being AC220V, frequency fg being 50Hz, and phases A (120°), B (240°), and C (360°). When the grid side experiences a power outage, and the photovoltaic power supply system stops supplying power to the grid side, causing a disconnection between the grid side and the photovoltaic side, the first voltage detection unit acquires the first voltage, first frequency, and first phase at the grid-connected point of the photovoltaic system; then, the first MCU processing unit compares the sampled parameters. Specifically, if the voltage amplitude fluctuation range exceeds 187V~242V within 150ms, it is determined to be an island; if the voltage frequency fluctuation range exceeds 49.5Hz~50.2Hz within 150ms, it is determined to be an island; if the phase of A, BC, and A differs from the nominal value by 10° within 150ms, it is determined to be an island. The collected voltage data is transmitted to MCU processing unit 1 for processing. The judgment is based primarily on voltage frequency fluctuation and secondarily on voltage amplitude fluctuation. When the voltage frequency fluctuation judgment is valid, the grid connection point is disconnected within 2s.

[0069] Figure 6 This is a flowchart of a low-voltage intelligent miniature circuit breaker active defense islanding detection method 600 according to an embodiment of the present invention. Figure 6 As shown, the low-voltage intelligent miniature circuit breaker active defense islanding detection method 600 provided by the embodiment of the present invention includes:

[0070] Step 601: When the grid photovoltaic link control unit between the grid side and the photovoltaic side is disconnected, causing the grid side and the photovoltaic side to be disconnected, and the disconnection time reaches the preset disconnection time, the RLC simulated load current generated by the first current detection unit and the second current detection unit are measured respectively to obtain the first current and the second current.

[0071] Step 602: Use the first voltage detection unit to obtain the current first voltage, first frequency and first phase, and use the second voltage detection unit to obtain the second voltage, second frequency and second phase;

[0072] Step 603: The first MCU processing unit determines whether the photovoltaic power supply system is in islanded operation based on the first current, the first voltage, the first frequency and / or the first phase.

[0073] Step 604: The second MCU processing unit determines whether the photovoltaic power supply system is in islanded operation based on the second current, the second voltage, the second frequency and / or the second phase, so as to realize active islanding detection of the photovoltaic power supply system.

[0074] Preferably, the method further includes:

[0075] The clock unit within the incoming line detection module provides accurate time to the first MCU processing unit;

[0076] The first MCU processing unit sends commands to the grid photovoltaic link control unit according to a preset time period, so that the grid side and the photovoltaic side are disconnected to perform active islanding detection.

[0077] Preferably, the first islanding detection unit starts working at a first preset time before disconnecting the grid photovoltaic link control unit, the first current detection unit collects the first current generated by the first islanding detection unit at this time, and detects the first operating current generated by the first islanding detection unit during a second preset time period after disconnecting the grid photovoltaic link control unit, and compares the first current and the first operating current. When the fluctuation of the first operating current exceeds the first current of a first preset percentage, it is determined that the photovoltaic power supply system is in islanding operation.

[0078] Preferably, the first islanding detection unit starts working a first preset time before the grid photovoltaic link control unit is disconnected, and the first voltage acquisition unit acquires the first voltage, the first frequency, and the first phase.

[0079] The first MCU processing unit determines whether the voltage amplitude swing range of the first voltage exceeds the preset voltage range within the first preset time period, or whether the first frequency swing range of the first voltage exceeds the preset frequency range, or whether the difference between the first phase and the nominal phase of any phase meets the preset phase difference threshold. If the conditions are met, the photovoltaic power supply system is determined to be in islanded operation. The criterion is based primarily on the frequency swing of the voltage, and secondarily on the voltage amplitude swing.

[0080] Preferably, the second islanding detection unit starts working at a first preset time before disconnecting the grid photovoltaic link control unit. The second current detection unit collects the second current generated by the second islanding detection unit at this time, and detects the second operating current generated by the second islanding detection unit during a second preset time period after disconnecting the grid photovoltaic link control unit. The second current and the second operating current are compared. When the fluctuation of the second operating current exceeds the second current of a second preset percentage, it is determined that the photovoltaic power supply system is in islanded operation.

[0081] Preferably, the second islanding detection unit starts working at a first preset time before the grid photovoltaic link control unit is disconnected, and the second voltage acquisition unit acquires the second voltage, the second frequency, and the second phase.

[0082] The second MCU processing unit determines whether the voltage amplitude swing range of the second voltage exceeds the preset voltage range within the first preset time period, or whether the second frequency swing range of the second voltage exceeds the preset frequency range, or whether the difference between the second phase and the nominal phase of any phase meets the preset phase difference threshold. If the conditions are met, the photovoltaic power supply system is determined to be in islanded operation.

[0083] In this invention, the second preset time period is a continuous 100ms; the first preset percentage is 10%, the second preset percentage is 30%, and the first preset time is 2s.

[0084] In this invention, the current detection unit 1 detects the current operating status of the grid-connected circuit breaker and the operating status of the islanding detection unit 1. The clock unit provides accurate time to the MCU processing unit 1, and active detection is performed at the hour and at an agreed time. The MCU processing unit 1 sends a command to the "grid photovoltaic link control unit" to disconnect the mains power and photovoltaic power supply system 100ms. Two seconds before disconnecting the mains power and photovoltaic power supply system, the islanding detection unit 1 (RLC simulated load) starts to work. The current detection unit 1 collects the current generated by the islanding detection unit 1 (RLC simulated load) at this time, and detects the current of the islanding detection unit 1 when disconnecting the grid photovoltaic link control unit 1 100ms. The current data of the two time periods are compared. The current amplitude fluctuation when disconnecting the grid photovoltaic link control unit 1 100ms should be consistent with the load current generated by the RLC simulated load when the islanding detection unit 1 is running. The criterion is that the fluctuation is greater than 10% of the nominal value of the RLC simulated load current, which is judged as islanding operation.

[0085] When islanding occurs, the mains power and photovoltaic power supply system are disconnected for 100ms. Simultaneously, the current disturbance of islanding detection unit 1 (RLC simulated load) remains active, causing voltage, frequency, and phase fluctuations. At this point, the operating status of the mains input unit can be determined. MCU processing unit 1 performs anti-islanding processing, using frequency and voltage as the basis for judgment, and checks the voltage V at the common coupling point of the grid-connected circuit breaker. PCC and frequency f PCC The changes are calculated to determine if they meet the anti-islanding protection testing requirements. From the most basic photovoltaic topology, the following relationship can be derived: The quality factor Q of the RLC load... f for:

[0086]

[0087] In the formula, R is the resistance of the load circuit; L is the inductance of the load circuit; C is the capacitance of the load circuit; ω is the voltage angular frequency at PCC; Q L Q represents the reactive power generated by the inductor. C P represents the reactive power generated by the capacitor.R This represents the active power generated by the resistor.

[0088] When the RLC load is connected to a voltage of Vg and a frequency of f g When connected to the power grid, the active power P consumed by the local load load and reactive power Q load They are respectively

[0089]

[0090]

[0091] Wherein, the initial frequency f0 is:

[0092]

[0093] Islanding detection methods, which use frequency and voltage as criteria, detect V... PCC and f PCC This was done by changing the setting of V. PCC and f PCC The thresholds are as follows:

[0094] V min ≤V PCC ≤V max (5)

[0095] f min ≤f PCC ≤f max (6)

[0096] According to NBT 32004-2018 Photovoltaic Grid-Connected Inverter Technical Specification V max =110%Vg,V min =85% Vg, f max =50.2Hz, f min =49.5Hz, when the oscillation amplitude is greater than the threshold range, it is determined to be islanded operation.

[0097] The photovoltaic power input unit, located on the outgoing (load) side of the grid-connected circuit breaker, provides voltage to the MCU processing unit 2. The voltage detection unit 2 detects the photovoltaic side voltage of the grid-connected circuit breaker and determines the photovoltaic operating status based on parameters such as voltage, frequency, and phase. If the voltage amplitude fluctuates between 187V and 242V within 150ms, islanding is determined; if the voltage frequency fluctuates between 49.5Hz and 50.2Hz within 150ms, islanding is determined; if the A / BC phase differs from the nominal value by 10° within 150ms, islanding is determined. The collected voltage, frequency, and phase data are transmitted to the MCU processing unit 2 for processing. The current detection unit 2 detects the photovoltaic power supply... The system tracks the direction of current output during operation and the operating status of the current when the islanded detection unit 2 (RLC simulated load) is working. Three seconds before the MCU processing unit 1 issues a trip command to the "grid photovoltaic link control unit", the MCU processing units 1 and 2 interact to record current, voltage, frequency, phase and other parameters and operating status. Before and after the grid photovoltaic link control unit is disconnected (disconnection time 100ms), the system judges the status of the photovoltaic power generation system based on the RLC simulated load current generated by the islanded detection units 1 and 2, the current flowing through the current detection units 1 and 2, and the voltage, frequency and phase collected by the voltage detection units 1 and 2 when the grid photovoltaic link control unit is disconnected.

[0098] If the grid photovoltaic link control unit is disconnected, the mains power input unit—voltage detection unit 1—does not detect the mains voltage or the voltage amplitude swing range exceeds 187V to 242V, the frequency swing range exceeds 49.5Hz to 50.2Hz, and the current detection unit 1 does not detect the current of the islanding detection unit 1 (RLC simulated load) or the nominal value of the RLC simulated load current swings by more than 10%, it is determined that the mains power is cut off, and there is no voltage supplied on the incoming side of the photovoltaic grid-connected circuit breaker.

[0099] Meanwhile, the photovoltaic power supply input unit—voltage detection unit 2—detects the photovoltaic power supply voltage. The voltage range is 190V to 270V, which is normal for operation. The current generated by the island detection unit 2 (RLC simulated load) flows through the current detection unit 2. The current detection unit 2 determines the grid-connected operation status of the photovoltaic power generation system based on the current change before and after disconnection for 100ms. The current of the RLC simulated load during operation does not fluctuate by more than 30% from the nominal value.

[0100] like Figure 3As shown, the grid-connected circuit breaker has two operating control states: a handle switch and a grid-photovoltaic link control unit. The handle switch function is to automatically disconnect the handle switch when there is overvoltage, undervoltage, loss of voltage, voltage imbalance, current imbalance, frequency, phase and actual grid parameters fluctuating within a range greater than the threshold, or when the photovoltaic system forms an island. The grid-photovoltaic link control unit is responsible for actively detecting the operating status of the grid and photovoltaic system to prevent the photovoltaic system from forming an island.

[0101] The low-voltage intelligent miniature circuit breaker active defense islanding detection method 500 and the low-voltage intelligent miniature circuit breaker active defense islanding detection method 600 of the present invention are implemented based on the low-voltage intelligent miniature circuit breaker 100.

[0102] The invention has been described with reference to a few embodiments. However, as will be known to those skilled in the art, and as defined in the appended claims, other embodiments besides those disclosed above fall equivalently within the scope of the invention.

[0103] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the art, unless otherwise expressly defined herein. All references to “a / the / the [device, component, etc.]” ​​are openly interpreted as at least one instance of said device, component, etc., unless otherwise expressly stated. The steps of any method disclosed herein need not be performed in the exact order disclosed unless explicitly stated otherwise.

[0104] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0105] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0106] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0107] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A low-voltage intelligent miniature circuit breaker, characterized in that, The circuit breaker includes: an incoming-side detection module, a grid photovoltaic link control unit, and an outgoing-side detection module connected in sequence; wherein... The incoming line detection module is located on the incoming line side of the photovoltaic grid-connected circuit breaker and is powered by the power grid. The outgoing line detection module is located on the outgoing line side of the photovoltaic grid-connected circuit breaker and is powered by the photovoltaic power supply system. The incoming line detection module and the outgoing line detection module are used to realize passive islanding detection and active islanding detection of the photovoltaic power supply system. The grid photovoltaic link control unit is used to realize the connection and disconnection between the grid side and the photovoltaic side inside the grid-connected circuit breaker when the handle is not open, and is a high-speed switching switch; The incoming line detection module includes: a first microcontroller unit (MCU) processing unit, and a first voltage conversion unit, a first voltage detection unit, a first current detection unit, and a first island detection unit, all connected to the first processing unit. The outgoing line detection module includes: a second microcontroller unit (MCU) processing unit, and a second voltage conversion unit, a second voltage detection unit, a second current detection unit, and a second island detection unit, all connected to the second processing unit. The first voltage conversion unit supplies power to the first MCU unit, and the second voltage conversion unit supplies power to the second MCU unit. Both the first voltage detection unit and the second voltage detection unit have the functions of detecting the voltage, frequency and phase of the power supply, which is a passive detection method; Both the first current detection unit and the second current detection unit have current flow direction detection and current imbalance detection functions, which are passive detection methods; The first islanding detection unit has an RLC simulated load function. When the first MCU processing unit sends a trip command to the grid photovoltaic link control unit, the first islanding detection unit starts working in advance for a first preset time. When the grid photovoltaic link control unit is disconnected, the first islanding detection unit generates current power consumption, which flows through the first current detection unit. If the first current detection unit detects a current value that meets the RLC threshold, the grid side supplies power normally. If no RLC current or generated power is detected, or if the swing amplitude of the RLC load current and power during operation is greater than the threshold, it is determined that the grid side is disconnected, and the photovoltaic power generation system operates in islanded mode. The second islanding detection unit is used to start a first preset time in advance when the grid photovoltaic link control unit is disconnected, simulate the operation of the RLC simulated load, form a load current flowing through the second current detection unit, and the second MCU processing unit determines the operating status of the photovoltaic power supply system based on the current change.

2. A method for active defense islanding detection of a low-voltage intelligent miniature circuit breaker based on the low-voltage intelligent miniature circuit breaker of claim 1, characterized in that, The method includes: When the power grid fails and the photovoltaic power supply system stops supplying power to the grid, causing the grid and photovoltaic sides to disconnect, the first voltage detection unit acquires the first voltage, first frequency and first phase of the grid and photovoltaic grid connection point. The first MCU processing unit determines whether the photovoltaic power supply system is in islanded operation based on the first voltage, first frequency, and first phase according to preset criteria, so as to realize passive islanding detection of the photovoltaic power supply system.

3. The method according to claim 2, characterized in that, The system determines whether the voltage amplitude swing range of the first voltage exceeds the preset voltage range, or whether the first frequency swing range of the first voltage exceeds the preset frequency range, or whether the difference between the first phase and the nominal phase of any phase meets the preset phase difference threshold. If these conditions are met, the photovoltaic power supply system is determined to be in islanded operation. The criteria are based primarily on the frequency swing of the voltage and secondarily on the voltage amplitude swing. When the frequency swing criterion is met, the grid connection point is disconnected within the preset disconnection time.

4. A method for active defense islanding detection of a low-voltage intelligent miniature circuit breaker based on the low-voltage intelligent miniature circuit breaker of claim 1, characterized in that, The method includes: When the grid-PV link control unit between the grid side and the PV side is disconnected, causing the grid side and the PV side to disconnect, and the disconnection time reaches the preset disconnection time, the RLC simulated load current generated by the first current detection unit and the second current detection unit are measured respectively to obtain the first current and the second current. The first voltage detection unit is used to obtain the current first voltage, first frequency and first phase, and the second voltage detection unit is used to obtain the second voltage, second frequency and second phase; The first MCU processing unit determines whether the photovoltaic power supply system is operating in islanded mode based on the first current, the first voltage, the first frequency and / or the first phase. The second MCU processing unit determines whether the photovoltaic power supply system is in islanded operation based on the second current, second voltage, second frequency and / or second phase, so as to realize active islanding detection of the photovoltaic power supply system.

5. The method according to claim 4, characterized in that, The method further includes: The clock unit within the incoming line detection module provides accurate time to the first MCU processing unit; The first MCU processing unit sends commands to the grid photovoltaic link control unit according to a preset time period, so that the grid side and the photovoltaic side are disconnected to perform active islanding detection.

6. The method according to claim 4, characterized in that, Before disconnecting the grid photovoltaic link control unit, the first islanding detection unit starts working at a first preset time. The first current detection unit collects the first current generated by the first islanding detection unit at this time, and detects the first operating current generated by the first islanding detection unit during a second preset time period after disconnecting the grid photovoltaic link control unit. The first current and the first operating current are compared. When the fluctuation of the first operating current exceeds the first preset percentage of the first current, it is determined that the photovoltaic power supply system is in islanding operation.

7. The method according to claim 4, characterized in that, Before disconnecting the grid photovoltaic link control unit, the first islanding detection unit starts working at a first preset time, and the first voltage acquisition unit acquires the first voltage, the first frequency and the first phase. The first MCU processing unit determines whether the voltage amplitude swing range of the first voltage exceeds the preset voltage range within the first preset time period, or whether the first frequency swing range of the first voltage exceeds the preset frequency range, or whether the difference between the first phase and the nominal phase of any phase meets the preset phase difference threshold. If the conditions are met, the photovoltaic power supply system is determined to be in islanded operation. The criterion is based primarily on the frequency swing of the voltage, and secondarily on the voltage amplitude swing.

8. The method according to claim 4, characterized in that, Before disconnecting the grid photovoltaic link control unit, the second islanding detection unit starts working at a first preset time. The second current detection unit collects the second current generated by the second islanding detection unit at this time, and detects the second operating current generated by the second islanding detection unit during a second preset time period after disconnecting the grid photovoltaic link control unit. The second current and the second operating current are compared. When the fluctuation of the second operating current exceeds the second preset percentage of the second current, it is determined that the photovoltaic power supply system is in islanding operation.

9. The method according to claim 4, characterized in that, Before disconnecting the grid photovoltaic link control unit, the second islanding detection unit starts working after a first preset time, and the second voltage acquisition unit acquires the second voltage, the second frequency, and the second phase. The second MCU processing unit determines whether the voltage amplitude swing range of the second voltage exceeds the preset voltage range within the first preset time period, or whether the second frequency swing range of the second voltage exceeds the preset frequency range, or whether the difference between the second phase and the nominal phase of any phase meets the preset phase difference threshold. If the conditions are met, the photovoltaic power supply system is determined to be in islanded operation.

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