An island detection method and apparatus

Abstract

The embodiment of the application provides a kind of island detection method and device, it is related to circuit technical field, it can be applied to the direct current distributed power system including multiple distributed power supply units, multiple distributed power supply units are all accessed direct current bus;Each distributed power supply unit includes the converter for connecting power supply equipment, the input end of converter is connected power supply equipment, the output end of converter is accessed direct current bus, method includes: determining the current component at target port is less than or equal to first threshold;Wherein, target port is the port of converter access direct current bus;Target frequency disturbance current is injected to target port, and island detection is carried out according to disturbance current.This way, when injecting current disturbance of target frequency to power supply equipment, the current component at the target port of the power supply equipment access bus is less than or equal to first threshold, can avoid the offset of current component to the disturbance injected, to improve the accuracy of island detection result.

Description

Technical Field

[0001] This application relates to the field of circuit technology, and in particular to an islanding detection method and apparatus. Background Technology

[0002] In a DC distributed power system, each power supply device is connected via independent transmission and distribution lines to supply power to the DC bus and surrounding loads. However, during actual operation, due to various reasons, the power supply device may disconnect from the DC bus, forming an island with the surrounding loads. Islanding can lead to unstable power quality supplied to the loads, causing damage to electrical equipment. It can also result in electric shock accidents if grid maintenance personnel touch the island's power supply lines when they believe the power is off. Therefore, it is necessary to inspect islands to improve safety.

[0003] Currently, the commonly used islanding detection method is the output current disturbance method. For example, the control power supply device adds a disturbance to the output current. After detecting an increase in voltage fluctuation, the current disturbance component is added. When the voltage moves out of the normal range, it is determined that an islanding has occurred.

[0004] However, the island detection methods mentioned above are inaccurate and often result in false island detections. Summary of the Invention

[0005] This application provides an islanding detection method and apparatus. When a current disturbance of a target frequency is injected into a power supply device, the current component at the target port of the power supply device connected to the bus is less than or equal to a first threshold, which can avoid the current component canceling out the injected disturbance, thereby improving the accuracy of the islanding detection result. In a first aspect, this application provides an islanding detection method applied to a DC distributed power system. The DC distributed power system includes multiple distributed power supply units, all of which are connected to a DC bus. Each distributed power supply unit includes a converter for connecting a power supply device. The input terminal of the converter is connected to the power supply device, and the output terminal of the converter is connected to the DC bus. The method includes: determining that the current component at the target port is less than or equal to a first threshold; wherein the target port is the first threshold value of the port where any converter is connected to the DC bus; injecting a disturbance current of a target frequency into the target port, the target frequency being a preset frequency of the current component; and performing islanding detection based on the disturbance current. In this way, when a current disturbance of the target frequency is injected into a power supply device, the current component at the target port of the power supply device connected to the bus is less than or equal to the first threshold, which can avoid the current component canceling out the injected disturbance, thereby improving the accuracy of islanding detection results.

[0006] In one possible implementation, determining that the current component in the target port is less than or equal to a first threshold includes: sampling the voltage of the target port; determining whether there is a fluctuation in the voltage at a target frequency; and, if there is a fluctuation in the voltage at a target frequency, controlling the current component at the target frequency in the target port to be less than or equal to the first threshold. Thus, in this embodiment of the application, controlling the current component at the target frequency in the target port to be less than or equal to the first threshold when there is a fluctuation in the voltage at the target port can prevent the current component from canceling out the injected disturbance.

[0007] In one possible implementation, determining whether there is a fluctuation of the target frequency in the voltage includes: determining the amplitude of the voltage component corresponding to the target frequency in the voltage; if the amplitude is greater than a second threshold, determining that there is a fluctuation of the target frequency in the voltage; if the amplitude is less than or equal to the second threshold, determining that there is no fluctuation of the target frequency in the voltage.

[0008] In one possible implementation, controlling the current component at the target frequency in the target port to be less than or equal to a first threshold includes: sampling the current at the target port; generating a control signal based on the current, a current reference value, and an impedance current reference value; and using the control signal to control the current component at the target frequency in the target port to be less than or equal to the first threshold. Thus, by controlling the current component at the target frequency in the target port to be less than or equal to the first threshold, this embodiment of the application can prevent the current component from canceling out the injected disturbance when a current disturbance of the target frequency is injected into a power supply device.

[0009] In one possible implementation, a control signal is generated based on the current, a current reference value, and an impedance current reference value, including: adjusting the current difference between the current reference value and the current to obtain a DC control signal; adjusting the impedance difference between the current and the impedance current reference value to obtain an impedance control signal at the target frequency; and superimposing the DC control signal and the impedance control signal to obtain a control signal.

[0010] In one possible implementation, islanding detection is performed based on the disturbance current, including: calculating the equivalent impedance corresponding to the target frequency; and determining that the power supply device has islanded if the equivalent impedance is greater than a third threshold.

[0011] In one possible implementation, determining that the power supply device is islanding when the equivalent impedance is greater than a third threshold includes: determining that the power supply device is islanding when the equivalent impedance is greater than the third threshold for a period of time.

[0012] In one possible implementation, the method also includes: reporting islanding alarms, and / or controlling the power supply equipment to shut down.

[0013] In one possible implementation, the disturbance current includes a sinusoidal current signal or a square wave current signal.

[0014] Secondly, embodiments of this application provide a DC distributed power system, including multiple distributed power supply units and an islanding detection device, wherein the multiple distributed power supply units are all connected to a DC bus; wherein each distributed power supply unit includes a converter for connecting a power supply device, the input end of the converter is connected to the power supply device, and the output end of the converter is connected to the DC bus.

[0015] The islanding detection device is used to determine that the current component at a target port is less than or equal to a first threshold; wherein the target port is the port of any converter connected to the DC bus, and a disturbance current of the target frequency is injected into the target port, the target frequency being a preset frequency of the current component, so as to perform islanding detection based on the disturbance current.

[0016] In one possible implementation, the islanding detection device is further configured to sample the voltage of the target port to determine whether there is a fluctuation of the target frequency in the voltage, and if there is a fluctuation of the target frequency in the voltage, control the current component in the target port to be less than or equal to a first threshold.

[0017] In one possible implementation, the islanding detection device is further configured to: determine the amplitude of the voltage component corresponding to the target frequency in the voltage; if the amplitude is greater than a second threshold, determine that there is a fluctuation of the target frequency in the voltage; if the amplitude is less than or equal to the second threshold, determine that there is no fluctuation of the target frequency in the voltage.

[0018] In one possible implementation, the islanding detection device is further configured to sample the current at the target port and generate a control signal based on the current, a current reference value, and an impedance current reference value, so as to control the current component in the target port to be less than or equal to a first threshold.

[0019] In one possible implementation, the islanding detection device is further configured to sample the current at the target port and generate a control signal based on the current, a current reference value, and an impedance current reference value, and use the control signal to control the current component in the target port to be less than or equal to a first threshold.

[0020] In one possible implementation, the islanding detection device is further used to adjust the current difference between the current reference value and the current to obtain a DC control signal, and to adjust the impedance difference between the current and the impedance current reference value to obtain an impedance control signal at the target frequency. The DC control signal and the impedance control signal are superimposed to obtain a control signal.

[0021] In one possible implementation, the islanding detection device is also used to calculate the equivalent impedance corresponding to the target frequency; and to determine that the power supply equipment has experienced islanding if the equivalent impedance is greater than a third threshold.

[0022] In one possible implementation, the islanding detection device is also used to determine that the power supply device has experienced islanding if the equivalent impedance is greater than a third threshold for an extended period of time.

[0023] In one possible implementation, the islanding detection device is also used to report islanding alarms and / or control the shutdown of power supply equipment.

[0024] In one possible implementation, the disturbance current includes a sinusoidal current signal or a square wave current signal.

[0025] Thirdly, embodiments of this application provide an islanding detection device. This islanding detection device can be a terminal device, or a chip or chip system within the terminal device. The islanding detection device can include a processing unit. When the islanding detection device is a terminal device, the processing unit can be a processor. The islanding detection device can also include a storage unit, which can be a memory. The storage unit stores instructions, and the processing unit executes the instructions stored in the storage unit to cause the terminal device to implement an islanding detection method described in the first aspect or any possible implementation of the first aspect. When the islanding detection device is a chip or chip system within the terminal device, the processing unit can be a processor. The processing unit executes the instructions stored in the storage unit to cause the terminal device to implement an islanding detection method described in the first aspect or any possible implementation of the first aspect. The storage unit can be a storage unit within the chip (e.g., a register, cache, etc.), or a storage unit located outside the chip within the terminal device (e.g., a read-only memory, random access memory, etc.).

[0026] For example, the processing unit is used to determine that the current component at the target port is less than or equal to a first threshold; wherein the target port is the port of any converter connected to the DC bus; the processing unit is used to inject a disturbance current of the target frequency into the target port; the processing unit is used to perform islanding detection based on the disturbance current.

[0027] In one possible implementation, the processing unit is specifically used to sample the voltage of the target port; the processing unit is specifically used to determine whether there is a fluctuation of the target frequency in the voltage; if there is a fluctuation of the target frequency in the voltage, the processing unit is further used to control the current component of the target frequency in the target port to be less than or equal to a first threshold.

[0028] In one possible implementation, the processing unit is specifically used to determine the amplitude of the voltage component corresponding to the target frequency in the voltage; if the amplitude is greater than a second threshold, the processing unit is further used to determine that there is a fluctuation of the target frequency in the voltage; if the amplitude is less than or equal to the second threshold, the processing unit is further used to determine that there is no fluctuation of the target frequency in the voltage.

[0029] In one possible implementation, the processing unit is specifically configured to sample the current at the target port; the processing unit is further configured to generate a control signal based on the current, a current reference value, and an impedance current reference value; the processing unit is further configured to use the control signal to control the current component at the target frequency in the target port to be less than or equal to a first threshold.

[0030] In one possible implementation, the processing unit is specifically used to adjust the current difference between the current reference value and the current to obtain a DC control signal; the processing unit is also specifically used to adjust the impedance difference between the current and the impedance current reference value to obtain an impedance control signal with a target frequency; the processing unit is also specifically used to superimpose the DC control signal and the impedance control signal to obtain a control signal.

[0031] In one possible implementation, the processing unit is specifically used to calculate the equivalent impedance corresponding to the target frequency; the processing unit is also specifically used to determine that the power supply device has islanded when the equivalent impedance is greater than a third threshold.

[0032] In one possible implementation, the processing unit is specifically used to determine that the power supply device has experienced islanding if the equivalent impedance is greater than a third threshold for an extended period of time.

[0033] In one possible implementation, a communication unit is also included for reporting islanding alarms and / or controlling the shutdown of power supply equipment.

[0034] In one possible implementation, the disturbance current includes a sinusoidal current signal or a square wave current signal.

[0035] Fourthly, embodiments of this application provide an island detection device, comprising: a processor, configured to call a program in a memory to implement any island detection method in the first aspect or any possible implementation of the first aspect.

[0036] Fifthly, this application provides a chip or chip system including at least one processor and a communication interface, the communication interface and at least one processor being interconnected via a line, the at least one processor being used to run a computer program or instructions to perform the island detection method described in any of the implementations of the first aspect.

[0037] The communication interface in the chip can be an input / output interface, pins, or circuits.

[0038] In one possible implementation, the chip or chip system described above in this application further includes at least one memory storing instructions. The memory can be an internal storage unit of the chip, such as a register or cache, or it can be a storage unit of the chip itself (e.g., read-only memory, random access memory, etc.).

[0039] Sixthly, embodiments of this application provide a computer-readable storage medium storing a computer program or instructions that, when executed on a computer, cause the computer to perform the island detection method as described in any implementation of the first aspect.

[0040] It should be understood that the second to sixth aspects of the embodiments of this application correspond to the technical solutions of the first aspect of the embodiments of this application, and the beneficial effects achieved by each aspect and the corresponding feasible implementation are similar, and will not be described again. Attached Figure Description

[0041] Figure 1 A schematic diagram of the architecture of a DC distributed power system provided in this application embodiment;

[0042] Figure 2 This application provides a schematic diagram of the architecture of an isolated system.

[0043] Figure 3 This is a schematic diagram of an existing island detection method;

[0044] Figure 4 This is a schematic diagram of an existing island detection method;

[0045] Figure 5 This is a schematic diagram of an existing island detection method;

[0046] Figure 6 A schematic diagram illustrating the problems with existing island detection methods;

[0047] Figure 7 This application provides a schematic diagram of the architecture of a distributed power system.

[0048] Figure 8 A schematic diagram of another DC distributed power system provided in the embodiments of this application;

[0049] Figure 9 A schematic diagram of an island detection unit provided in an embodiment of this application;

[0050] Figure 10A flowchart illustrating an island detection method provided in an embodiment of this application;

[0051] Figure 11 A flowchart illustrating an island detection method provided in an embodiment of this application;

[0052] Figure 12 A flowchart illustrating an island detection method provided in an embodiment of this application;

[0053] Figure 13 A schematic diagram of a control signal provided in an embodiment of this application;

[0054] Figure 14 A flowchart illustrating an island detection method provided in an embodiment of this application;

[0055] Figure 15 A schematic diagram of another control signal provided in an embodiment of this application;

[0056] Figure 16 A schematic diagram of a DC distributed power system provided in an embodiment of this application;

[0057] Figure 17 A timing diagram provided for an embodiment of this application;

[0058] Figure 18 A schematic diagram of an islanded system provided in an embodiment of this application;

[0059] Figure 19 A system equivalent diagram of an islanded system corresponding to a target frequency is provided in an embodiment of this application;

[0060] Figure 20 This is a schematic diagram of the structure of an island detection device provided in an embodiment of this application;

[0061] Figure 21 This is a schematic diagram of the structure of a chip provided in an embodiment of this application. Detailed Implementation

[0062] To facilitate a clear description of the technical solutions in the embodiments of this application, the terms "first" and "second" are used in the embodiments of this application to distinguish identical or similar items with essentially the same function and effect. For example, the first threshold and the second threshold are merely used to distinguish different thresholds used in island detection, and do not limit their order. Those skilled in the art will understand that the terms "first" and "second" do not limit the number of items, and that the terms "first" and "second" are not necessarily different.

[0063] It should be noted that, in this application, the terms "exemplary" or "for example" are used to indicate that something is being described as an example, illustration, or illustration. Any embodiment or design described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or design solutions. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0064] In this application, "at least one" means one or more, and "more" means two or more. "And / or" describes the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, or B exists alone, where A and B can be singular or plural.

[0065] Figure 1 This is a schematic diagram of the architecture of a DC distributed power system, such as... Figure 1 As shown, the DC distributed power system includes multiple distributed power supply units (e.g., distributed power supply units 101 to 10N, where N is a natural number) connected by transmission and distribution lines (e.g., transmission and distribution line 1011 to 101N, where N is a natural number), jointly supplying power to the DC bus 100 and the local load 110. Each distributed power supply unit includes a converter for connecting power supply equipment. The input of the converter is connected to the power supply equipment, and the output of the converter is connected to the DC bus. The power supply equipment may include: photovoltaic power generation equipment, power storage equipment, fuel cell equipment, and / or micro-cogeneration equipment, etc. The DC bus has strong voltage support capability and can also be referred to as a large power grid.

[0066] Since the output current of power devices such as photovoltaics and batteries has the characteristics of DC power, DC distributed power systems adopt a DC architecture, which has advantages such as reducing system losses and lowering system costs compared to common AC distributed power systems.

[0067] However, in actual operation, DC distributed power systems can experience faults due to various reasons. For example... Figure 2 As shown, the converter in the distributed power supply unit 10N is disconnected from the DC bus port at point A, and the distributed power supply unit 10N and the local load 104 constitute an islanded system. When the DC distributed power system does not experience islanding, it can be understood as being in grid-connected mode; when the DC distributed power system experiences islanding, it can be understood as being in islanded mode.

[0068] Due to their different causes, islanding systems can be divided into planned islanding and unplanned islanding. Planned islanding is generated by planned scheduling and operation and falls within the scope of normal operation. Unplanned islanding, on the other hand, arises from unforeseen circumstances. When a DC distributed power system operates in an unplanned islanding state, it can have serious consequences, such as:

[0069] 1) This leads to unstable power quality in isolated areas.

[0070] 2) The operating procedure of the protective switches that affect the power distribution system.

[0071] One possible interpretation is that if the household's electricity comes from the DC bus, turning off the power switch will cut off the power when an appliance fails. However, if the household's electricity comes from small photovoltaic (PV) power generation devices, turning off the power switch only interrupts the connection to the external power grid. Other PV power generation devices or energy storage devices in the house will remain energized. In this case, the protective switch's operating procedure needs to be redesigned.

[0072] 3) When the power grid is restored, there may be inrush current.

[0073] 4) It may cause power grid maintenance personnel to come into contact with isolated power supply lines when they believe that the power has been cut off, resulting in a risk of electric shock.

[0074] Therefore, in order to ensure the normal operation of DC distributed power systems and the safety of personnel, it is necessary to detect unplanned islanding (hereinafter referred to as islanding).

[0075] For the aforementioned islanded system, possible islanding detection methods include: output voltage detection method, output current disturbance method, bus voltage positive feedback method, and impedance detection method.

[0076] For example, one possible implementation of islanding detection using output voltage detection is as follows: The presence of islanding in the DC distributed power system is determined by detecting the voltage deviation at the output port of the power supply unit. If islanding does not occur, the converter in the distributed power supply unit remains connected to the DC bus. Since the DC bus has strong voltage support capabilities, the port voltage of the power supply unit will remain within a small range near the system's rated operating voltage. If islanding occurs, the converter disconnects from the DC bus, losing the voltage support from the main grid. In this situation, when the power generated by the power supply unit exceeds the power consumed by the local load, the system voltage will gradually increase; when the power generated by the distributed generation unit is less than the power consumed by the local load, the system voltage will gradually decrease. Therefore, when the system voltage exceeds a preset upper or lower limit, it can be determined that the system has lost the support of the main grid and is operating in an islanded state.

[0077] However, when using the output voltage detection method for islanding detection, there must be a significant mismatch between the power generation within the islanded system and the power consumption of the local load to cause a large deviation in the system voltage within a short period of time, thus detecting islanding. If the power generation within the islanded system and the power consumption of the local load are well matched, for example, if the voltage deviation is very small, the preset upper or lower limit value cannot be reached, and islanding cannot be detected. Therefore, this method has a large detection blind zone.

[0078] For example, one possible implementation of islanding detection using the output current perturbation method is as follows: a periodic square wave perturbation is superimposed on the output current of the power supply device. When islanding does not occur, the converter is still connected to the DC bus. Because the DC bus has a strong voltage support capability, the system voltage fluctuation caused by the injected perturbation is small. However, after islanding occurs, the system voltage fluctuation caused by the injected perturbation is large due to the loss of the DC bus voltage support. Figure 3 As shown, before time t1, a positive feedback loop can be observed between the current disturbance component and the voltage fluctuation; for example, the system voltage decreases as the current disturbance component decreases. At time t2, the disturbance coefficient K of the current disturbance component is continuously reduced until the system voltage is moved out of the normal range, thus indicating that islanding has occurred.

[0079] However, while using the output current perturbation method for islanding detection compensates for the limitations of the output voltage detection method to some extent, adding a certain amount of perturbation to the output current will affect the output current, thereby impacting the power generation efficiency of the power supply equipment. Furthermore, determining the appropriate perturbation value is very difficult. A large perturbation value affects the power supply quality of the system, while a small perturbation value results in minimal voltage disturbance to the DC bus, easily leading to detection failure.

[0080] For example, one possible implementation of islanding detection using the bus voltage positive feedback method is as follows: Figure 4 As shown, a voltage positive feedback loop is introduced into the control loop. Through reasonable feedback parameter design, the DC bus voltage remains stable when no islanding occurs, and the DC bus voltage oscillates when islanding occurs. If the bus voltage is removed from the normal range, it can be determined that islanding has occurred.

[0081] However, when using the positive feedback method of bus voltage for islanding detection, it has the same drawbacks as the above-mentioned output current disturbance method, which will reduce the stability of the normal operation of the system and may also endanger the safe operation of the DC bus voltage.

[0082] For example, one possible implementation of islanding detection using impedance sensing is as follows: a small sinusoidal current disturbance is injected into the output current of the power supply device. The equivalent impedance of the system is calculated based on the fluctuation of the DC bus voltage and the disturbance current. The islanding phenomenon is detected by the difference in the equivalent impedance between grid-connected mode and islanded mode. Figure 5 As shown, when the system is in grid-connected mode, the converter remains connected to the DC bus, and the system equivalent impedance corresponding to the power supply port is... The system impedance includes the DC bus side impedance Z2, which is related to the local load impedance R. L Because the circuit is in parallel and the amplitude of Z2 is very small, the total equivalent impedance is relatively small. When the system is in islanded mode, the power supply is disconnected from the DC bus, and the system equivalent impedance corresponding to the power supply is... In islanded mode, the equivalent impedance is larger because there is no parallel effect of DC bus side impedance Z2.

[0083] However, while the impedance detection method can compensate for the limitations of the three islanding detection methods mentioned above to some extent and has a smaller impact on the power generation efficiency of the power supply equipment and the power supply quality of the system, for DC distributed power systems that include several power supply equipment, the current disturbances injected into different power supply equipment will cancel each other out due to asynchrony, resulting in inaccurate islanding detection results.

[0084] For example, in a DC distributed power system, there are two power supply devices, with output currents i1 and i2 respectively. Figure 6 As shown, if sinusoidal current disturbances of the same frequency but with a phase difference of half a cycle are injected into two power supply devices, the current disturbances injected into the two power supply devices will cancel each other out due to asynchrony, thus making it impossible to detect the disturbance to the DC bus voltage, resulting in inaccurate islanding detection results.

[0085] To address the problems of the four islanding detection methods mentioned above, this application provides an islanding detection method that, before injecting a disturbance current into the target port of the power supply device connected to the DC bus, determines that the current component at the target port is less than or equal to a first threshold. Thus, when a current disturbance of the target frequency is injected into the power supply device, if the current component at the target port of the power supply device connected to the bus is less than or equal to the first threshold, the cancellation of the injected disturbance by the current component can be avoided, thereby improving the accuracy of the islanding detection results.

[0086] The island detection method provided in this application can be applied to, for example... Figure 1 The DC distributed power system shown is illustrated. (The text abruptly ends here, likely due to an incomplete sentence or a formatting error.) Figure 1 Unlike the DC distributed power system shown, the DC distributed power system provided in this application embodiment adds, for example... Figure 7 The island detection device shown. Figure 7 As shown, the islanding detection device may include: a current sampling unit, a voltage sampling unit, an islanding detection unit, and a modulation unit. The current sampling unit and the voltage sampling unit may also exist independently in the DC distributed power system.

[0087] Figure 8 This application illustrates a specific DC distributed power system according to an embodiment of the present application, such as... Figure 8 As shown, the system includes a distributed power supply unit and an islanding detection device. The distributed power supply unit is connected to a DC bus. The distributed power supply unit includes a converter 801 for connecting to a power supply device 806. The input terminal of the converter 801 is connected to the power supply device 806, and the output terminal of the converter 801 is connected to the DC bus. The islanding detection device may include an islanding detection unit 804 and a modulation unit 805. The relevant processing in the islanding detection unit 804 and the modulation unit 805 may be executed by a processor or chip.

[0088] like Figure 8 As shown, the input terminal of the DC / DC converter 801 is connected to the power supply device 806, and the output terminal of the DC / DC converter 801 is connected to the DC bus. The target port 808 is the port where the DC / DC converter 801 connects to the DC bus. Current sampling units 802 and 803 are used to sample the voltage and current of the target port 808. The sampled target port voltage and current are input to the islanding detection unit 804 for islanding detection, and a corresponding control signal is generated. In a possible interpretation, this control signal can be a high-frequency carrier wave, which, after being processed by the modulation unit, is converted into a corresponding drive signal to control the switching on or off of the semiconductors in the DC / DC converter.

[0089] Figure 8 The present application provides a DC distributed power system using a single distributed power supply unit as an example. It can be understood that the DC distributed power system may include multiple distributed power supply units, and each distributed power supply unit is equipped with an islanding detection device 800.

[0090] The DC / DC converter 801 includes capacitors, inductors, and semiconductor switching devices, and has functions such as power transmission, voltage boosting, and / or voltage bucking.

[0091] The current sampling unit 802 and the voltage sampling unit 803 are used to convert the current and voltage corresponding to the target port 808 into the corresponding current and voltage signals in the island detection unit 804, so as to realize electrical isolation between the hardware system and the software system.

[0092] In one possible interpretation, the DC distributed power system consists of a hardware system and a software system. The hardware system is characterized by high voltage, while the software system is characterized by low voltage. For example, the voltage of the DC power system is very high, possibly several hundred volts, but the voltage of the control chip in the islanding detection unit 802 is very low, possibly a few volts. If the chip in the islanding detection unit 802 is directly connected to the DC power system, interference in the DC power system will also cause strong interference to the chip. Therefore, methods such as coils or transformers can be used to isolate the DC power system and the islanding detection unit 804, transmitting only the digital signal of the high voltage in the DC power system to the islanding detection unit 804. For example, if the high voltage is 100V, only the digital signal 100 is transmitted to the islanding detection unit 804. This achieves electrical isolation between the hardware and software systems.

[0093] The islanding detection unit 804 executes the islanding detection method proposed in this invention based on the current sampled by the current sampling unit 802 and the voltage sampled by the voltage sampling unit 803, outputs the corresponding control signal, and determines whether the system is in an islanded state.

[0094] For example, such as Figure 9 As shown, the islanding detection unit 804 may include a measurement unit 901 and a mode selection unit 902. The mode selection unit 902 may determine, based on the corresponding measurement results of the measurement unit 901, whether the current component in the target port is less than or equal to a first threshold (also known as the power supply device entering a high-impedance mode), or whether to inject a disturbance current of the target frequency into the target port (also known as the power supply device entering a disturbance mode).

[0095] In this embodiment, the high-impedance mode can be defined as determining that the current component in the target port is less than or equal to a first threshold. A possible interpretation is that after determining that the current component in the target port is less than or equal to the first threshold, the equivalent impedance of the distributed DC power system at the target frequency approaches infinity; therefore, this can be referred to as the power supply device entering a high-impedance mode. The disturbance mode described in this embodiment can be defined as determining the disturbance current injected into the target port at the target frequency. The implementation methods related to the high-impedance mode and the disturbance mode will be specifically described in subsequent embodiments.

[0096] The modulation unit 905 is used to convert the control signal into a semiconductor switch drive signal that matches the DC / DC converter 801, and control the on or off state of the semiconductor in the DC / DC converter 801.

[0097] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be implemented independently or in combination with each other. The same or similar concepts or processes may not be described again in some embodiments.

[0098] Figure 10 This is a flowchart illustrating an island detection method provided in an embodiment of this application. This method is applicable to the above-mentioned... Figure 8 The corresponding DC distributed power system. The islanding detection method provided in this application embodiment can be executed by the islanding detection device provided in this application embodiment. This device can be implemented by software and / or hardware. For example, the islanding detection device can be part or all of a terminal device, such as the processor in the terminal device. The islanding detection method provided in this application embodiment is described below using the terminal device as the execution subject. Figure 10 As shown in the embodiments of this application, an island detection method may include the following steps:

[0099] S1001: Determine that the current component in the target port is less than or equal to the first threshold.

[0100] In this embodiment, the target port is any port where a converter is connected to the DC bus. For example, the location of the target port can correspond to... Figure 8 As shown in Figure 808.

[0101] In possible implementations, determining that the current component in the target port is less than or equal to the first threshold may include: determining that the current component in the target port is less than or equal to the first threshold through a sensor in the terminal device, or determining that the current component in the target port is less than or equal to the first threshold through the transmission interface of the processor, or sampling the current component of the target port using a voltage sampling unit or a current sampling unit to determine that the current component is less than or equal to the first threshold. This application embodiment does not limit the method of determining that the current component in the target port is less than or equal to the first threshold.

[0102] Understandably, if the current component of the target port is greater than the first threshold, it indicates that there is a disturbance in the target port. This disturbance may be injected by other power supply devices for islanding detection or it may be generated in the circuit. If a disturbance current used for islanding detection of that power supply device is injected into the target port, the disturbance current may be canceled out by the current component, affecting the accuracy of islanding detection.

[0103] In a possible implementation, if the current component of the target port is greater than the first threshold, subsequent steps S1002 and S1003 can be temporarily suspended until it is determined that the current component of the target port is less than or equal to the first threshold before proceeding with subsequent steps S1002 and S1003.

[0104] In this embodiment, the value of the first threshold can be set according to actual conditions, and this embodiment does not impose specific limitations on it. For example, the first threshold can be 0, or any value close to 0, etc.

[0105] S1002: Inject a disturbance current of the target frequency into the target port.

[0106] In this embodiment, the target frequency is a preset frequency of the current component. This can be understood as the frequency of the disturbance current injected into the target port being the same as the frequency of the current component.

[0107] One possible interpretation is that after determining that the current component in the target port is less than or equal to a first threshold, a disturbance current with the same preset frequency as the current component is injected into the target port. This can prevent the current component of the target frequency in the target port from canceling out the injected disturbance current, or it can be understood that the cancellation caused by the disturbance current of the target frequency injected into the target port can be ignored. When a disturbance current of the target frequency is injected into the target port, it can be understood that the power supply device enters a disturbance mode.

[0108] In possible implementations, the disturbance current can be injected into the target port intermittently and / or periodically, which is not limited in the embodiments of this application.

[0109] S1003: Islanding detection based on disturbance current.

[0110] In this embodiment, islanding detection can be performed by observing the effect of disturbance current on the target port voltage.

[0111] For example, when islanding does not occur, the power supply equipment is still connected to the DC bus. Because the DC bus has a strong voltage support capability, the voltage fluctuation caused by injected current disturbances is small. However, after islanding occurs, the voltage support of the DC bus is lost, resulting in larger voltage fluctuations caused by injected disturbances.

[0112] Therefore, it can be detected that the target port voltage fluctuates significantly with the injected disturbance current. That is, when the disturbance current and the target port voltage form positive feedback, the disturbance coefficient of the injected disturbance current is reduced until the target port voltage is moved out of the normal range. Then it can be determined that an islanding phenomenon has occurred.

[0113] One possible implementation involves injecting a periodic current disturbance into the target port and measuring the corresponding component of the voltage fluctuation at the target port. If the amplitude of the corresponding component exceeds a set threshold, it is determined that an islanding phenomenon has occurred.

[0114] One possible implementation involves sampling the target port using voltage and current sampling units to obtain the target port voltage and current. The voltage and current components corresponding to the target frequency in the target port voltage and current are then calculated. Finally, the system impedance is obtained by dividing the voltage component corresponding to the target frequency by the current component. If the system impedance value is higher than a preset threshold, islanding can be determined.

[0115] It is understood that the embodiments of this application may also use any possible form to determine whether an islanding phenomenon has occurred, and the specific method of islanding detection is not limited here.

[0116] In this embodiment, after determining that the current component in the target port is less than or equal to a first threshold, a disturbance current with the same preset frequency as the current component is injected into the target port, and islanding detection is performed based on the disturbance current. Thus, when a current disturbance of the target frequency is injected into any power supply device, the current component at the target port of that power supply device connected to the bus is less than or equal to the first threshold, which avoids the current component canceling out the injected disturbance, thereby improving the accuracy of the islanding detection results.

[0117] exist Figure 10 Based on the corresponding embodiments, one possible implementation is as follows: Figure 11 As shown, S1001 includes:

[0118] S1101: Sample the voltage at the target port.

[0119] Among the possible implementations, such as Figure 8 As shown, the voltage of the target port is obtained through the voltage sampling unit 803.

[0120] S1102: Determine whether there is a fluctuation in the target frequency in the voltage.

[0121] In this embodiment of the application, the amplitude v of the voltage component corresponding to the target frequency in the voltage can be determined. s When the amplitude is greater than the second threshold v th For example, satisfying |v S |>v th If the voltage amplitude is less than or equal to the second threshold, it is determined that there is a fluctuation in the target frequency in the voltage; if the amplitude is less than or equal to the second threshold, it is determined that there is no fluctuation in the target frequency in the voltage.

[0122] In this embodiment, the second threshold can be set by a machine or manually, and the specific value of the second threshold can be adjusted according to user needs. For example, the second threshold can be 0, or any value close to 0, etc.

[0123] In one possible implementation, when the second threshold is 0, the voltage v at the target port can be calculated using Fourier transform. dc The amplitude v corresponding to the target frequency s At amplitude v s If the value is greater than 0, the voltage v can be determined. dc There are fluctuations in the target frequency; in amplitude v s When the voltage v is less than or equal to 0, it can be determined that the voltage v is zero. dc There is no fluctuation in the target frequency.

[0124] In practical applications, signal or noise interference may occur during the sampling of the voltage at the target port and the determination of the amplitude of the voltage component corresponding to the target frequency. In this case, setting the second threshold to 0 may cause misjudgment. Therefore, the second threshold can be set to a relatively small value according to the actual system conditions. For example, the second threshold can be any value close to 0.

[0125] S1103: When there is a fluctuation in the target frequency in the voltage, control the current component in the target port to be less than or equal to the first threshold.

[0126] In possible implementations, if there is no fluctuation of the target frequency in the voltage, S1103 is an optional step, which can be understood as S1002 being executed directly after S1102.

[0127] One possible interpretation is that when there are fluctuations in the target frequency in the voltage, these fluctuations may be caused by current disturbances of the target frequency injected into other power supply devices. To avoid canceling out these current disturbances, the current component in the target port is controlled to be less than or equal to a first threshold. This can also be understood as the power supply device entering a high-impedance mode.

[0128] In possible implementations, to avoid canceling out current disturbances injected into other power supply devices at the target frequency, the disturbances injected into each power supply device can be synchronized through communication.

[0129] In the embodiments of this application, when there is a fluctuation in the target frequency in the voltage, the current component of the target frequency in the target port is controlled to be less than or equal to a first threshold. In this way, when a current disturbance of the target frequency is injected into a power supply device, the current component of the target frequency in the target port of other devices is less than or equal to the first threshold, which can prevent the disturbances injected by different devices from canceling each other out.

[0130] exist Figure 11 Based on the corresponding embodiments, one possible implementation is as follows: Figure 12 As shown, S1103 includes:

[0131] S1201: Samples the current at the target port.

[0132] One possible implementation is to obtain the voltage of the target port through a voltage sampling unit.

[0133] S1202: Generates control signals based on current, current reference value, and impedance current reference value.

[0134] In this embodiment, the current reference value can be the current value under normal conditions (or when no islanding occurs), and the current at the target port can be the real-time current at the target port obtained by the current sampling unit. The impedance current reference value can be the current component reference value corresponding to the target frequency; for example, the impedance current reference value can be 0.

[0135] In this embodiment, the difference between the current reference value and the current is used to adjust the current to obtain a DC control signal, and the difference between the current and the impedance current reference value is used to adjust the impedance to obtain an impedance control signal at the target frequency. The DC control signal and the impedance control signal are superimposed to obtain a control signal.

[0136] For example, such as Figure 13 As shown, one possible implementation of obtaining a DC control signal by adjusting the difference between the current reference value and the current is as follows: A current error signal is generated based on the difference between the current reference value and the current. This current error signal is then input into the current regulator to obtain the DC control signal. The current regulator can be a proportional-integral controller (PI controller), and the transfer function of the PI controller is: Among them, K p K is a proportional parameter. i Let be the integration parameter, and s be the Laplace operator.

[0137] For example, such as Figure 13 As shown, one possible implementation of impedance control signaling at the target frequency by adjusting the difference between the current and the impedance current reference value is as follows: An impedance error signal is generated based on the difference between the impedance current reference value and the current. This impedance error signal is then input to an impedance regulator to obtain the impedance control signal. The impedance regulator can be a proportional resonant controller (PR controller), and the transfer function of the PR controller is: Among them, K PR K is a proportional parameter. R Let be the resonance parameter, and s be the Laplace operator.

[0138] S1203: Use a control signal to control the current component of the target frequency in the target port to be less than or equal to the first threshold.

[0139] Among the possible implementations, such as Figure 8 As shown, after executing S1202 above, it can be understood that the power supply device selects the disturbance mode in the islanding detection unit 804 to perform islanding detection and obtains the corresponding control signal. This control signal is output to the modulation unit 805, which converts it into a semiconductor switch drive signal that matches the hardware of the DC / DC converter 801, controlling the opening of the semiconductor switch in the DC / DC converter. This can be understood as putting the equivalent circuit corresponding to the target frequency in an open state.

[0140] In this embodiment, a control signal generated based on the current, current reference value, and impedance current reference value is used to control the current component of the target frequency in the target port to be less than or equal to a first threshold. In this way, when a current disturbance of the target frequency is injected into a power supply device, the current component of the target frequency in the target port of other devices is less than or equal to the first threshold, thus avoiding mutual cancellation of disturbances injected by different devices.

[0141] exist Figure 10 Based on the corresponding embodiments, one possible implementation is as follows: Figure 14 As shown, S1003 includes:

[0142] S1401: Calculate the equivalent impedance corresponding to the target frequency.

[0143] In this embodiment of the application, the disturbance current injected into the target port at the target frequency may include a sinusoidal current signal or a square wave current signal.

[0144] For example, when the disturbance current injected into the target port is a square wave current signal, it will change the operating current of the DC distributed power system, thereby affecting the power generation efficiency and power quality of the DC distributed power system. For example, as Figure 3 As shown, if the operating current I under normal conditions of a DC distributed power system... d The operating current can be 0.8A after a square wave current disturbance is injected. When the disturbance current injected into the target port is a sinusoidal current signal, since the sinusoidal current signal is a high-frequency small signal, it will not change the operating current of the system, thus having a small impact on the power generation efficiency and power quality of the DC distributed power system.

[0145] In a possible implementation, the target port voltage and target port current are obtained using a voltage sampling unit and a current sampling unit. The voltage component and current component corresponding to the target frequency in the target port voltage and target port current are calculated. The voltage component is divided by the current component to obtain the equivalent impedance corresponding to the target frequency.

[0146] S1402: If the equivalent impedance is greater than the third threshold, it is determined that the power supply equipment is islanding.

[0147] In this embodiment of the application, the third threshold can be set by a machine or manually, and the specific value of the third threshold can be adjusted according to user needs.

[0148] In possible implementations, to avoid misjudgment caused by factors such as noise or errors in the system during the detection process, if the equivalent impedance is greater than the third threshold and continues to exceed the time threshold, it is determined that the power supply device has experienced islanding.

[0149] This application does not limit the specific duration of the time threshold, which can be set according to user needs. In one possible implementation, the time threshold can be 2 seconds, etc. This application does not limit it.

[0150] exist Figure 14 Based on the corresponding embodiments, in possible implementations, the islanding detection method provided in this application embodiment further includes: reporting islanding alarms, and / or controlling the power supply equipment to shut down.

[0151] In one possible implementation, once it is determined that an islanding phenomenon has occurred in the power supply equipment, the islanding detection results can be reported to the monitoring center, which can then control other power supply equipment to shut down based on the islanding detection results.

[0152] Among the possible implementations, such as Figure 15 As shown, after injecting a disturbance current of the target frequency into the target port, the power supply device enters disturbance mode and can generate corresponding control signals based on the current, the current reference value, and the current disturbance value. Here, the current is the current acquired by the current sampling unit, the current reference value is the current value under normal conditions (or when no islanding occurs), the current is the current at the target port acquired by the current sampling unit, and the current disturbance value is the reference value of the current component corresponding to the target frequency. A corresponding error signal is generated based on the current, the current reference value, and the current disturbance value. This error signal is then input to the current regulator to obtain the corresponding control signal. The current regulator can be a PI regulator or a PR regulator; the corresponding transfer function can be found in S1202, and will not be elaborated here.

[0153] In one possible implementation, the control signal obtained when the power supply device is in disturbance mode is output to a modulation unit and converted into a semiconductor switch drive signal that matches the DC / DC converter hardware, thereby controlling the opening and closing of the semiconductor switch in the DC / DC converter. This can be understood as the power supply device being in a shutdown state when the semiconductor switch in the DC / DC converter is open.

[0154] When the island detection method provided in the embodiments of this application is applied to Figure 1 In the DC distributed power system shown, if Figure 1 This is a DC distributed power system consisting of two distributed generation units. The structure of this DC distributed power system can be as follows: Figure 16 As shown, the system includes a DC / DC converter 1601, a DC / DC converter 1602, a DC grid, a grid-connected switch, and a local load. For ease of understanding, only the connection to the DC bus port of the DC / DC converter is shown, and details of the power supply equipment side are omitted.

[0155] The following is combined with Figure 17 The specific implementation of the island detection method provided in the embodiments of this application will be described.

[0156] At time t1, the power supply equipment experiences islanding. Figure 16 When the grid-connected switch is disconnected, it can be understood as the power supply equipment being disconnected from the DC grid. In a DC distributed power system, there are only two power supply devices and local loads. In this case, the corresponding islanded system is as follows: Figure 18 As shown. Since the power generation and local load consumption in the islanded system are well matched at time t1, the target port voltage does not fluctuate, and neither DC / DC converter 1801, DC / DC converter 1802 nor the local load detect that they are in an islanded system.

[0157] At time t2, the DC / DC converter 1801 executes the islanding detection method provided in this embodiment. The voltage sampling unit samples the target port and determines that there is no fluctuation of the target frequency in the target port voltage. Then, it injects a disturbance current of the target frequency into the target port output current i1. This can be understood as the power supply device connected to the DC / DC converter 1801 entering a disturbance mode. The injected disturbance current is a sinusoidal current signal. Since the islanded system loses the voltage support capability of the bus, this disturbance current of the target frequency creates a voltage fluctuation of the target frequency on the target port voltage.

[0158] The DC / DC converter 1802 executes the islanding detection method provided in the embodiments of this application. The voltage sampling unit samples the target port and detects that there is a fluctuation of the target frequency on the voltage of the target port. Then it is determined that the current component of the target frequency in the target port is less than or equal to the first threshold. This can be understood as the power supply device connected to the DC / DC converter 1802 entering a high-impedance mode.

[0159] For example, if the current component at the target frequency in the target port is 0, then the effective circuit corresponding to the target frequency in the power supply device connected to the DC / DC converter 1802 is essentially disconnected. The output current at the target port of the DC / DC converter 1802 contains only the DC component. The equivalent system diagram of the islanded system corresponding to the target frequency is shown below. Figure 19 As shown. In a possible interpretation, after the power supply device connected to DC / DC converter 1802 enters high-impedance mode, it can prevent the current disturbance injected into DC / DC converter 1802 from canceling out the current disturbance injected into DC / DC converter 1801.

[0160] At time t3, the DC / DC converter 1801 obtains the equivalent impedance corresponding to the target frequency based on the injected disturbance current. The calculated equivalent impedance is greater than the third threshold, so it reports an islanding alarm to the monitoring system and / or controls the power supply equipment to shut down, and the output current of the DC / DC converter 1801 is 0.

[0161] If the method of this application embodiment is applied to a high-frequency communication system, after reporting an islanding alarm to the monitoring system, the monitoring system can send islanding alarms to other power supply devices and control them to shut down, without needing to perform islanding detection again. When the method of this application embodiment does not rely on a high-frequency communication system, because the communication frequency of the monitoring system is low, the DC / DC converter 1802 does not receive an islanding alarm from the monitoring system, therefore the DC / DC converter 1802 continues to execute the islanding detection algorithm provided in this application embodiment.

[0162] At time t4, since DC / DC converter 1801 has been shut down, the target port voltage of DC / DC converter 1802 contains only a DC component. Executing the islanding detection method provided in this embodiment of the application, it can be determined that there is no fluctuation of the target frequency in the target port voltage. Therefore, injecting a disturbance current of the target frequency into the target port output current i2 can be understood as the power supply device connected to DC / DC converter 1802 entering a disturbance mode. Because the islanded system loses the voltage support capability of the bus, this disturbance current of the target frequency forms a voltage fluctuation of the target frequency on the target port voltage.

[0163] At time t5, the DC / DC converter 1802 obtains the equivalent impedance corresponding to the target frequency based on the injected disturbance current. The calculated equivalent impedance is greater than the third threshold, so it reports an islanding alarm to the monitoring system and / or controls the power supply equipment to shut down, and the output current of the DC / DC converter 1802 is 0.

[0164] The above example uses an islanded system consisting of two power supply devices and a local load. In other possible implementations, the islanded system can also consist of multiple power supply devices and local loads. In this case, the islanding detection method provided in this application embodiment is still applicable.

[0165] Combination Figures 10-19 The method of the embodiments of this application has been described. The DC distributed power system applicable to the above method provided by the embodiments of this application is described below. The DC distributed power system includes multiple distributed power supply units and an islanding detection device. The multiple distributed power supply units are all connected to the DC bus. Each distributed power supply unit includes a converter for connecting power supply equipment. The input terminal of the converter is connected to the power supply equipment, and the output terminal of the converter is connected to the DC bus.

[0166] The islanding detection device is used to determine that the current component at a target port is less than or equal to a first threshold; wherein the target port is the port of any converter connected to the DC bus, and a disturbance current of the target frequency is injected into the target port, the target frequency being a preset frequency of the current component, so as to perform islanding detection based on the disturbance current.

[0167] In one possible implementation, the islanding detection device is further configured to sample the voltage of the target port to determine whether there is a fluctuation of the target frequency in the voltage, and if there is a fluctuation of the target frequency in the voltage, control the current component in the target port to be less than or equal to a first threshold.

[0168] In one possible implementation, the islanding detection device is further configured to: determine the amplitude of the voltage component corresponding to the target frequency in the voltage; if the amplitude is greater than a second threshold, determine that there is a fluctuation of the target frequency in the voltage; if the amplitude is less than or equal to the second threshold, determine that there is no fluctuation of the target frequency in the voltage.

[0169] In one possible implementation, the islanding detection device is further configured to sample the current at the target port and generate a control signal based on the current, a current reference value, and an impedance current reference value, so as to control the current component in the target port to be less than or equal to a first threshold.

[0170] In one possible implementation, the islanding detection device is further configured to sample the current at the target port and generate a control signal based on the current, a current reference value, and an impedance current reference value, and use the control signal to control the current component in the target port to be less than or equal to a first threshold.

[0171] In one possible implementation, the islanding detection device is further used to adjust the current difference between the current reference value and the current to obtain a DC control signal, and to adjust the impedance difference between the current and the impedance current reference value to obtain an impedance control signal at the target frequency. The DC control signal and the impedance control signal are superimposed to obtain a control signal.

[0172] In one possible implementation, the islanding detection device is also used to calculate the equivalent impedance corresponding to the target frequency; and to determine that the power supply equipment has experienced islanding if the equivalent impedance is greater than a third threshold.

[0173] In one possible implementation, the islanding detection device is also used to determine that the power supply device has experienced islanding if the equivalent impedance is greater than a third threshold for an extended period of time.

[0174] In one possible implementation, the islanding detection device is also used to report islanding alarms and / or control the shutdown of power supply equipment.

[0175] In one possible implementation, the disturbance current includes a sinusoidal current signal or a square wave current signal.

[0176] The above combination Figures 10-19 The methods described in the embodiments of this application have been explained. The islanding detection apparatus for performing the above methods, provided in the embodiments of this application, is described below. Those skilled in the art will understand that the methods and apparatus can be combined with and referenced by each other, and the islanding apparatus provided in the embodiments of this application can perform the steps of the above-described islanding method.

[0177] The following example illustrates how functional modules are divided according to their respective functions:

[0178] like Figure 20 As shown, Figure 20 A schematic diagram of the island detection device provided in an embodiment of this application is shown. The island detection device includes a processing unit 2001. The processing unit 2001 is used to perform the island detection steps.

[0179] In one example, taking the islanding detection device as a terminal device or a chip or chip system applied in a terminal device, the processing unit 2001 is used to support the islanding detection device in executing S1001 to S1003, or S1101 to S1103, or S1201 to S1203, or S1401 and S1402, etc. in the above embodiments.

[0180] In one possible embodiment, the islanding detection device may further include a communication unit 2002 and a storage unit 2003. The processing unit 2001, the communication unit 2002, and the storage unit 2003 are connected via a communication bus.

[0181] Storage unit 2003 may include one or more memories, which may be devices in one or more devices or circuits used to store programs or data.

[0182] The storage unit 2003 can exist independently and be connected to the processing unit 101 of the island detection device via a communication bus. Alternatively, the storage unit 2003 can be integrated with the processing unit.

[0183] Islanding detection devices can be used in communication equipment, circuits, hardware components, or chips.

[0184] Taking the islanding detection device as an example, which can be the terminal device in this embodiment, the communication unit 2002 can be an input or output interface, pin, or circuit, etc. For example, the storage unit 2003 can store computer-executable instructions for the methods of the terminal device, so that the processing unit 2001 executes the methods of the terminal device in the above embodiments. The storage unit 2003 can be a register, cache, or RAM, etc., and can be integrated with the processing unit 2001. The storage unit 2003 can be ROM or other types of static storage devices capable of storing static information and instructions, and can be independent of the processing unit 2001.

[0185] This application provides an islanding detection device, which includes one or more modules for implementing the above-described features. Figures 10-19 The methods included in the steps described above, wherein one or more modules can be used in conjunction with the above. Figures 10-19 The steps included in the method correspond to the steps in the method. Specifically, in each step of the method executed by the terminal device in the embodiments of this application, the terminal device has a unit or module that executes each step of the method. For example, a module that performs island detection can be called a processing module. A module that performs message or data processing on the island detection device side can be called a communication module.

[0186] Figure 21 This is a schematic diagram of the structure of chip 210 provided in an embodiment of the present invention. Chip 210 includes one or more (including two) processors 2110 and communication interfaces 2130.

[0187] In one possible embodiment, such as Figure 21 The illustrated chip 210 also includes a memory 2140, which may include read-only memory and random access memory, and provides operation instructions and data to the processor 2110. A portion of the memory 2140 may also include non-volatile random access memory (NVRAM).

[0188] In some implementations, memory 2140 stores executable modules or data structures, or subsets thereof, or extended sets thereof:

[0189] In this embodiment of the invention, the corresponding operation is executed by calling the operation instructions stored in the memory 2140 (which may be stored in the operating system).

[0190] Processor 2110 controls the operation of the terminal device; processor 2110 can also be referred to as a central processing unit (CPU). Memory 2140 may include read-only memory and random access memory, and provides instructions and data to processor 2110. A portion of memory 2140 may also include non-volatile random access memory (NVRAM). For example, in an application, memory 2140, communication interface 2130, and memory 2140 are coupled together through bus system 2120, which, in addition to a data bus, may also include a power bus, control bus, and status signal bus, etc. However, for clarity, in... Figure 21 The general labeled all buses as Bus System 2120.

[0191] The communication unit described above can be an interface circuit or communication interface of the device, used to receive signals from other devices. For example, when the device is implemented as a chip, the communication unit is an interface circuit or communication interface used by the chip to receive or send signals from other chips or devices.

[0192] The methods disclosed in the above embodiments of the present invention can be applied to or implemented by processor 2110. Processor 2110 may be an integrated circuit chip with signal processing capabilities. During implementation, each step of the above methods can be completed by integrated logic circuits in the hardware of processor 2110 or by instructions in software form. Processor 2110 may be a general-purpose processor, digital signal processor (DSP), application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. It can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of the present invention. A general-purpose processor may be a microprocessor or any conventional processor. The steps of the methods disclosed in the embodiments of the present invention can be directly embodied in the execution of a hardware decoding processor, or executed by a combination of hardware and software modules in the decoding processor. Software modules may reside in random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, or other mature storage media in the art. The storage medium is located in memory 2140. Processor 2110 reads the information in memory 2140 and, in conjunction with its hardware, completes the steps of the above method.

[0193] In the above embodiments, the instructions stored in the memory for execution by the processor can be implemented in the form of a computer program product. The computer program product can be pre-written into the memory, or it can be downloaded and installed into the memory as software.

[0194] A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this application is generated. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions may be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium may be any available medium that a computer can store or a data storage device such as a server or data center that integrates one or more available media. The available media may be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., DVDs), or semiconductor media (e.g., solid-state drives, SSDs), etc.

[0195] This application also provides a computer-readable storage medium. The methods described in the above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any combination thereof. If implemented in software, the functionality can be stored as one or more instructions or code on or transmitted on a computer-readable medium. A computer-readable medium can include computer storage media and communication media, and can also include any medium that can transfer a computer program from one place to another. The storage medium can be any target medium accessible by a computer.

[0196] As one possible design, a computer-readable medium may include RAM, ROM, EEPROM, CD-ROM or other optical disc storage, disk storage or other magnetic storage device, or any other medium targeted to carry or to store the required program code in the form of instructions or data structures, and accessible by a computer. Furthermore, any connection is appropriately referred to as a computer-readable medium. For example, if software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave, then coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. As used herein, disks and optical discs include optical discs (CDs), laser discs, optical discs, digital versatile optical discs (DVDs), floppy disks, and Blu-ray discs, where disks typically reproduce data magnetically, while optical discs optically reproduce data using lasers. Combinations of the above should also be included within the scope of computer-readable media. The above descriptions are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be covered within the scope of protection of the present invention. Therefore, the scope of protection of this invention should be determined by the scope of the claims.

[0197] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An island detection method, characterized in that, This invention is applied to a DC distributed power system, which includes multiple distributed power supply units, all of which are connected to a DC bus. Each distributed power supply unit includes a converter for connecting a power supply device, with the input terminal of the converter connected to the power supply device and the output terminal of the converter connected to the DC bus. The method includes: The voltage of the first target port is sampled; it is determined whether there is a fluctuation of the target frequency in the voltage; if there is a fluctuation of the target frequency in the voltage, the current component in the first target port is controlled to be less than or equal to a first threshold; wherein, the first target port is the port where the first converter is connected to the DC bus; A perturbation current of a target frequency is injected into the second target port, the target frequency being the same as the frequency of the current component; the second target port is the port where the second converter is connected to the DC bus, and the first target port and the second target port are different; Islanding detection is performed based on the disturbance current.

2. The method according to claim 1, characterized in that, The step of determining whether there is a fluctuation of the target frequency in the voltage includes: Determine the amplitude of the voltage component corresponding to the target frequency in the voltage; If the amplitude is greater than the second threshold, it is determined that there is a fluctuation of the target frequency in the voltage; If the amplitude is less than or equal to the second threshold, it is determined that there is no fluctuation of the target frequency in the voltage.

3. The method according to claim 1, characterized in that, Controlling the current component in the first target port to be less than or equal to the first threshold includes: Sample the current at the first target port; A control signal is generated based on the current, current reference value, and impedance current reference value; The control signal is used to control the current component in the first target port to be less than or equal to the first threshold.

4. The method according to claim 3, characterized in that, The step of generating the control signal based on the current, the current reference value, and the impedance current reference value includes: The difference between the current reference value and the current is used to adjust the current to obtain a DC control signal; The impedance difference between the current and the impedance current reference value is adjusted to obtain the impedance control signal for the target frequency. The control signal is obtained by superimposing the DC control signal and the impedance control signal.

5. The method according to claim 1, characterized in that, The islanding detection based on the disturbance current includes: Calculate the equivalent impedance corresponding to the target frequency; If the equivalent impedance is greater than the third threshold, it is determined that the power supply device has experienced islanding.

6. The method according to claim 5, characterized in that, The step of determining that the power supply device has experienced islanding when the equivalent impedance is greater than the third threshold includes: If the equivalent impedance is greater than the third threshold for an extended period of time, it is determined that the power supply device has experienced the islanding phenomenon.

7. The method according to claim 5, characterized in that, Also includes: Report an islanding alarm and / or control the power supply equipment to shut down.

8. The method according to any one of claims 1-7, characterized in that, The disturbance current includes a sinusoidal current signal or a square wave current signal.

9. A DC distributed power system, comprising multiple distributed power supply units and an islanding detection device, wherein the multiple distributed power supply units are all connected to a DC bus; wherein, Each of the distributed power supply units includes a converter for connecting to a power supply device, wherein the input of the converter is connected to the power supply device and the output of the converter is connected to the DC bus; The islanding detection device is used to determine that the current component at a first target port is less than or equal to a first threshold; wherein, the first target port is the port where the first converter is connected to the DC bus, and a disturbance current of a target frequency is injected into the second target port, the target frequency being the same as the frequency of the current component, so as to perform islanding detection based on the disturbance current; the second target port is the port where the second converter is connected to the DC bus, and the first target port and the second target port are different; The island detection device is specifically used to sample the voltage of the first target port to determine whether there is a fluctuation of the target frequency in the voltage, and if there is a fluctuation of the target frequency in the voltage, control the current component in the first target port to be less than or equal to the first threshold.

10. The system according to claim 9, characterized in that, The island detection device is further configured to: determine the amplitude of the voltage component corresponding to the target frequency in the voltage; if the amplitude is greater than a second threshold, determine that there is a fluctuation of the target frequency in the voltage; if the amplitude is less than or equal to the second threshold, determine that there is no fluctuation of the target frequency in the voltage.

11. The system according to claim 9 or 10, characterized in that, The island detection device is specifically used to sample the current of the first target port and generate a control signal based on the current, current reference value and impedance current reference value, so as to use the control signal to control the current component in the first target port to be less than or equal to the first threshold.

12. The system according to claim 11, characterized in that, The island detection device is further configured to: adjust the current difference between the current reference value and the current to obtain a DC control signal; adjust the impedance difference between the current and the impedance current reference value to obtain an impedance control signal for the target frequency; and superimpose the DC control signal and the impedance control signal to obtain the control signal.

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