WO2022165701A1 - 一种控制方法和分布式电力系统 - Google Patents

一种控制方法和分布式电力系统 Download PDF

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Publication number
WO2022165701A1
WO2022165701A1 PCT/CN2021/075241 CN2021075241W WO2022165701A1 WO 2022165701 A1 WO2022165701 A1 WO 2022165701A1 CN 2021075241 W CN2021075241 W CN 2021075241W WO 2022165701 A1 WO2022165701 A1 WO 2022165701A1
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WIPO (PCT)
Prior art keywords
inverter
voltage
source mode
target port
islanding
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PCT/CN2021/075241
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English (en)
French (fr)
Inventor
徐志武
李琳
郭国伟
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华为数字能源技术有限公司
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Application filed by 华为数字能源技术有限公司 filed Critical 华为数字能源技术有限公司
Priority to EP21923726.0A priority Critical patent/EP4277073A4/en
Priority to PCT/CN2021/075241 priority patent/WO2022165701A1/zh
Priority to CN202180052305.5A priority patent/CN115917912A/zh
Publication of WO2022165701A1 publication Critical patent/WO2022165701A1/zh
Priority to US18/229,289 priority patent/US20230378764A1/en

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/388—Islanding, i.e. disconnection of local power supply from the network
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/36—Means for starting or stopping converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators

Definitions

  • the present application relates to the field of control technology, and in particular, to a control method and a distributed power system.
  • a distributed power system usually consists of a new energy power generation device, an inverter, a local load and a power grid.
  • the inverter and the power grid jointly supply power to the local load.
  • the inverter acts as a current source to control the current power input to the grid.
  • the grid disconnects the inverter from the grid due to faults or line disconnection, the inverter is connected to the local load.
  • the output voltage of the inverter may be much higher than the rated voltage, causing problems such as damage to the local load. Therefore, when the voltage of the output port of the inverter rises too high, it is necessary to control the voltage of the output port of the inverter to improve the safety of the system.
  • the commonly used control method is the active control method. For example, by detecting the amplitude of the voltage at the output port of the inverter, when the voltage amplitude exceeds a preset threshold, the inverter triggers protection and shuts down.
  • the embodiment of the present application provides a control method and a distributed power system.
  • the working mode of the inverter is adjusted, and the output voltage of the inverter can be controlled within a safe range, so that there is no detection
  • the local load can be protected and a relatively continuous power supply can be provided for the local load.
  • an embodiment of the present application provides a control method, which is applied to a distributed power system, where the distributed power system includes a plurality of distributed power supply units, and the plurality of distributed power supply units are all connected to an AC power grid;
  • Each distributed power supply unit includes an inverter for connecting the power supply device, the input end of the inverter is connected to the power supply device, and the output end of the inverter is connected to the AC power grid;
  • the method includes: controlling the inverter to work in a current source mode, In the current source mode, the inverter acts as a current source to convert the DC power generated by the power supply equipment into AC power and output it to the AC power grid; when it is detected that the voltage of the first target port jumps, the inverter is controlled to switch from the current source mode to the voltage source mode.
  • the first target port is the port of any inverter connected to the AC power grid; the voltage of the voltage jumping to the first target port within the first time period changes more than the preset value, and the voltage source mode is the inverter
  • the device acts as a voltage source for voltage output.
  • the output voltage of the inverter is detected. If it is detected that the output voltage of the inverter is greater than the threshold value and the voltage is boosted quickly, the inverter is switched to a voltage The source still supplies power to the load, and the voltage of the voltage source is constant, which can protect the load and provide a more continuous power supply for the load. Further, after the inverter is switched to a voltage source, perform islanding detection on the inverter, and when it is confirmed that the inverter is islanded, shut down the inverter. If the inverter does not have islanding, the inverter can be installed. The inverter switches to the current source to supply power to the AC bus to achieve continuous power supply.
  • the voltage jump is specifically that the voltage of the first target port is greater than the first threshold, and the variation of the voltage of the first target port within the first time period is greater than a preset value.
  • the voltage of the first target port is less than the first threshold, it means that the voltage of the first target port usually does not cause damage to the load, and it can be considered that the voltage of the first target port has not jumped.
  • the inverter still works in the current source mode, which can realize the continuous power supply of the inverter.
  • the method further includes: performing islanding detection on the inverter; and turning off the inverter when an islanding phenomenon is detected in the inverter.
  • islanding detection is performed on the inverter, so as to determine whether the cause of the voltage jump of the first target port is the power failure of the power grid or the high voltage ride-through of the power grid. When the voltage jumps, the inverter is better controlled.
  • performing islanding detection on the inverter includes: cyclically performing islanding detection on the inverter during a period when the inverter is in the voltage source mode for less than a second threshold; wherein, cyclically performing islanding detection on the inverter
  • the islanding detection of the inverter is as follows: if the islanding phenomenon of the inverter is not detected in the last islanding detection, the islanding detection of the inverter is performed again until the islanding phenomenon of the inverter is detected. In this way, the islanding detection of the inverter can be performed cyclically within the second threshold to prevent misjudgment.
  • performing islanding detection on the inverter includes: using a phase-locked loop in the inverter to track the phase change of the voltage of the first target port, and injecting positive feedback disturbance into the first target port ; When the voltage frequency of the phase-locked loop output based on the disturbance is greater than the third threshold, the islanding phenomenon occurs in the inverter once counted.
  • detecting that the inverter islanding phenomenon occurs includes: if the counted number of times that the inverter islanding phenomenon occurs is greater than a fourth threshold, determining that the inverter islanding phenomenon occurs. In this way, the islanding phenomenon of the inverter can be determined only when the islanding phenomenon of the inverter is confirmed for many times, so as to prevent misjudgment.
  • the method further includes: if the duration of the inverter in the voltage source mode is greater than or equal to the second threshold, controlling the inverter to switch from the voltage source mode to the current source mode. If the inverter is in the voltage source mode for a long time and the islanding of the inverter is still detected, it means that the inverter does not transmit the islanding, and the inverter is controlled to switch from the voltage source mode to the current source mode, which can achieve continuous power supply.
  • controlling the inverter to switch from the current source mode to the voltage source mode includes: when detecting that the voltage of the first target port jumps , judge whether the interval between the time when the inverter switches to the voltage source mode last time and the time when the voltage jump occurs is greater than the fifth threshold; if the interval is greater than the fifth threshold, control the inverter to switch from the current source mode to the voltage source source mode. In this way, frequent switching of the inverter between the current source mode and the voltage source mode can be avoided, so as to ensure the normal operation of the system.
  • the method further includes: when the inverter is in a voltage source mode and it is detected that the voltage of the second target port is greater than a sixth threshold, controlling the inverter to not output power; wherein the second The target port is the port where any inverter is connected to the power supply. In this way, the inverter can be prevented from being damaged due to excessive voltage of the second target port.
  • an embodiment of the present application provides a distributed power system, including a control device and multiple distributed power supply units, and the multiple distributed power supply units are all connected to an AC power grid; wherein each distributed power supply unit includes a Connect the inverter of the power supply device, the input end of the inverter is connected to the power supply device, and the output end of the inverter is connected to the AC power grid.
  • a control device for controlling the inverter to work in a current source mode
  • the current source mode is that the inverter acts as a current source to convert the direct current generated by the power supply equipment into alternating current and output it to the alternating current grid
  • the first target port is detected
  • the inverter is controlled to switch from the current source mode to the voltage source mode; wherein, the first target port is the port where any inverter is connected to the AC power grid; the voltage jumps into the first target port.
  • the variation of the voltage within the first time period is greater than the preset value, and the voltage source mode is that the inverter acts as a voltage source to output voltage.
  • the voltage jump is specifically that the voltage of the first target port is greater than the first threshold, and the variation of the voltage of the first target port within the first time period is greater than a preset value.
  • control device is further configured to perform islanding detection on the inverter; when it is detected that an islanding phenomenon occurs in the inverter, the inverter is turned off.
  • control device is specifically configured to cyclically perform islanding detection on the inverter during a period when the inverter is in the voltage source mode for less than a second threshold; wherein, cyclically perform islanding detection on the inverter To: If the islanding phenomenon of the inverter was not detected in the last islanding detection, perform the islanding detection of the inverter again until the islanding phenomenon of the inverter is detected.
  • control device is specifically configured to use a phase-locked loop in the inverter to track the phase change of the voltage of the first target port, and inject positive feedback disturbance into the first target port;
  • the control device is specifically configured to use a phase-locked loop in the inverter to track the phase change of the voltage of the first target port, and inject positive feedback disturbance into the first target port;
  • control device is specifically configured to determine that the inverter islanding phenomenon is detected if the counted number of times that the inverter islanding phenomenon occurs is greater than a fourth threshold.
  • control device is further configured to control the inverter to switch from the voltage source mode to the current source mode if the duration of the inverter in the voltage source mode is greater than or equal to the second threshold.
  • control device is further configured to determine the time when the inverter switches to the voltage source mode last time and the time when the voltage jump occurs when detecting that the voltage of the first target port jumps. Whether the interval between them is greater than the fifth threshold; if the interval is greater than the fifth threshold, the inverter is controlled to switch from the current source mode to the voltage source mode.
  • control device is further configured to control the inverter not to output power when the inverter is in the voltage source mode and it is detected that the voltage of the second target port is greater than the sixth threshold; wherein, The second target port is the port through which the inverter is connected to the power supply device.
  • an embodiment of the present application provides a control apparatus, including: a processor configured to invoke a program in a memory to implement the first aspect or any control method in any possible implementation manner of the first aspect.
  • the present application provides a chip or a chip system, the chip or chip system includes at least one processor and a communication interface, the communication interface and the at least one processor are interconnected through a line, and the at least one processor is used for running a computer program or instruction, To perform the control method described in any one of the implementation manners of the first aspect.
  • the communication interface in the chip may be an input/output interface, a pin or a circuit, or the like.
  • the chip or chip system described above in this application further includes at least one memory, where instructions are stored in the at least one memory.
  • the memory may be a storage unit inside the chip, such as a register, a cache, etc., or a storage unit of the chip (eg, a read-only memory, a random access memory, etc.).
  • the embodiments of the present application provide a computer-readable storage medium, where a computer program or instruction is stored in the computer-readable storage medium, and when the computer program or instruction is run on a computer, the computer is made to execute any one of the first aspect.
  • an embodiment of the present application provides a computer program product, the program product includes a computer program, the computer program is stored in a readable storage medium, and at least one processor of an electronic device can read the computer program from the readable storage medium, at least A processor executes the computer program to cause the electronic device to perform the control method described in any one of the implementations of the first aspect.
  • FIG. 1 is a schematic structural diagram of a distributed power system according to an embodiment of the present application
  • FIG. 2 is a schematic diagram of the architecture of an island system provided by an embodiment of the present application.
  • FIG. 3 is a schematic diagram of an inverter output port voltage rising too high according to an embodiment of the present application
  • FIG. 4 is a schematic structural diagram of a distributed power system according to an embodiment of the present application.
  • FIG. 5 is a schematic flowchart of a control method provided by an embodiment of the present application.
  • FIG. 6 is a schematic flowchart of detecting whether the voltage of the first target port jumps according to an embodiment of the present application
  • FIG. 7 is a schematic structural diagram of a phase-locked loop provided by an embodiment of the present application.
  • FIG. 8 is a schematic diagram of a phase-locked loop chasing the phase by adjusting the frequency according to an embodiment of the present application
  • FIG. 9 is a schematic diagram of another phase-locked loop chasing the phase by adjusting the frequency provided by an embodiment of the present application.
  • FIG. 10 is a schematic flowchart of obtaining a voltage reference value according to an embodiment of the present application.
  • FIG. 11 is a schematic flowchart of a specific control method provided by an embodiment of the present application.
  • FIG. 12 is a schematic structural diagram of a chip according to an embodiment of the present application.
  • words such as “first” and “second” are used to distinguish the same or similar items with basically the same function and effect.
  • the first log and the second log are only for distinguishing the network logs in different time windows, and the sequence of the logs is not limited.
  • the words “first”, “second” and the like do not limit the quantity, and the words “first”, “second” and the like do not limit certain differences.
  • “at least one” means one or more, and “plurality” means two or more.
  • “And/or”, which describes the association relationship of the associated objects, indicates that there can be three kinds of relationships, for example, A and/or B, which can indicate: the existence of A alone, the existence of A and B at the same time, and the existence of B alone, where A, B can be singular or plural.
  • FIG. 1 is a schematic diagram of the architecture of a distributed power system.
  • the distributed power system includes a plurality of distributed power supply units, such as distributed power supply unit 101 to distributed power supply unit 10N, etc., where N is a natural number.
  • a plurality of distributed power supply units jointly supply power to the AC bus 100 and the local load 110 .
  • each distributed power supply unit includes an inverter for connecting the power supply equipment, the input end of the inverter is connected to the power supply equipment, and the output end of the inverter is connected to the AC power grid.
  • the power supply equipment may include: photovoltaic power generation equipment, wind power equipment, electric energy storage equipment, fuel cell equipment, and/or micro cogeneration equipment, etc.
  • the direct current output by the power supply equipment cannot be directly fed back to the alternating current power grid.
  • the inverter may be a power conditioning device composed of semiconductor switching devices, and is mainly used to convert direct current power into alternating current power.
  • the inverter may be composed of a boost circuit and an inverter bridge circuit, wherein the boost circuit is used to boost the DC voltage of the power supply equipment to the DC voltage required for the inverter output control, and the inverter bridge circuit It is used to convert the boosted DC voltage into an AC voltage of common frequency equivalently.
  • the inverter and the AC grid can be connected through a circuit breaker.
  • the inverter acts as a current source to control the current power input to the AC grid.
  • the distributed power system may fail due to various reasons.
  • the circuit breaker connected to the distributed power supply unit 10N disconnects the connection with the AC bus 100 from the grid connection point A, and the distributed power supply unit 10N and the local load 110 form an island system.
  • the inverter in the distributed power supply unit 10N has an islanding phenomenon.
  • the inverter needs to increase the output voltage to achieve power balance. For example, if the output power of the inverter is 20kw and the load power is 5kw, if the inverter is disconnected from the bus, which is called an island, and the power consumed by the load is 5kw, the inverter still cannot output 15kw.
  • the relationship between P and voltage U and current I, P UI, when the inverter works as a current source, and I is constant, the inverter needs to continuously increase the output voltage U to achieve power balance.
  • FIG. 3 shows a schematic diagram of the voltage of the inverter rising continuously with time when the inverter is islanded.
  • the horizontal axis is time
  • the vertical axis is voltage amplitude.
  • the output voltage of the inverter may be much higher than the rated voltage of the load, thereby causing damage to the load.
  • the output voltage of the inverter port cannot be greater than a certain value to protect the safety of local load equipment and personnel.
  • certain measures need to be taken to improve system security.
  • the amplitude of the voltage at the output port of the inverter is detected.
  • the inverter triggers protection and shuts down, thereby avoiding the risk caused by the high output voltage of the inverter.
  • the inverter may have a high voltage ride through (HVRT) phenomenon due to various reasons.
  • the high voltage ride through phenomenon can be understood as a phenomenon in which the voltage suddenly increases, but can return to normal in a short time.
  • the high voltage ride through phenomenon usually does not cause load damage etc.
  • the inverter will be shut down, and the inverter will be frequently shut down due to the occasional high-voltage ride-through phenomenon, which cannot provide a more continuous power supply for the load.
  • the embodiments of the present application provide a control method and a distributed power system.
  • the output voltage of the inverter is detected. If the detected output voltage of the inverter is greater than a threshold value , and the boost is fast, then the inverter is switched to a voltage source, still supplying power to the load, and the voltage of the voltage source is constant, which can protect the load and provide a more continuous power supply for the load. Further, after the inverter is switched to a voltage source, perform islanding detection on the inverter, and when it is confirmed that the inverter is islanded, shut down the inverter. If the inverter does not have islanding, the inverter can be installed. The inverter switches to the current source to supply power to the AC bus to achieve continuous power supply.
  • FIG. 4 shows a schematic frame diagram of a distributed power system 400 according to an embodiment of the present application.
  • the distributed power system 400 includes distributed power supply units, and the distributed power supply units are connected to the AC bus 403 .
  • the distributed power supply unit includes an inverter 402 for connecting the power supply device 401 , the input end of the inverter 402 is connected to the power supply device 401 , and the output end of the inverter 402 is connected to the AC bus 403 through a circuit breaker.
  • the inverter 402 can work in a current source mode or a voltage source mode. It can be understood that the inverter works in the current source mode, and the inverter converts the direct current generated by the power supply equipment into alternating current and then outputs a stable current as a current source. It can be understood that the inverter works in the voltage source mode, and the inverter acts as a voltage source to output a stable voltage to the load.
  • the distributed power system 400 also includes a control module 405 .
  • the control module 405 may be implemented by means of software, hardware, or a combination of software and hardware.
  • the control module 405 may be provided in the inverter 402 , for example, the control module 405 may be a processor or a chip provided in the inverter 402 .
  • the control module 405 may also be independent of the inverter 402 , and the control module 405 controls the working mode of the inverter 402 through communication with the inverter 402 .
  • the distributed power system 400 also includes a voltage sampling unit 406 .
  • the voltage sampling unit 406 is used for sampling the voltage of each port.
  • the voltage sampling unit 406 may be disposed in the inverter 402, or may be independent of the inverter 402, which is not specifically limited in this embodiment of the present application.
  • the input terminal of the inverter 402 is connected to the power supply device 401
  • the output terminal of the inverter 402 is connected to the AC bus 404 through a circuit breaker
  • the first target port 404 is the connection of the inverter 402 to the AC bus. port.
  • the voltage sampling unit 406 can sample the voltage of the first target port 404, and send the sampled voltage of the first target port 404 to the control module 405, and the control module 405 can execute an adaptive control strategy according to the voltage of the first target port 404, For example, the control module 405 may control the inverter 402 to switch from the current source mode to the voltage source mode when detecting that the voltage of the first target port 404 jumps.
  • FIG. 4 uses a single distributed power supply unit as an example to illustrate a DC distributed power system provided by this embodiment of the present application. It can be understood that a distributed power system may include a plurality of distributed power supply units, each Each of the distributed power supply units may have the same or similar architecture as the distributed power supply unit shown in FIG. 4 .
  • the distributed power system consists of a hardware system and a software system
  • the hardware system may include: power supply equipment, inverters and circuit breakers
  • the software system may include the control module 405 .
  • the hardware system has the characteristics of strong electricity
  • the software system has the characteristics of weak electricity.
  • the voltage of the power system may be several hundred volts
  • the voltage of the control chip in the control module 405 may be several volts. If the chip in the control module 405 is directly connected to the distributed power system, when there is interference in the power system, it will also cause strong interference to the chip.
  • the DC power system is isolated from the control module 405.
  • the digital signal of the strong voltage in the power system is transmitted to the control module 405.
  • the strong voltage is 100V, and only the transmission number 100 is transmitted to the control module 405, so that the hardware system can be realized. Electrical isolation from software systems.
  • FIG. 5 is a schematic flowchart of a control method provided by an embodiment of the present application, and the method is applicable to the control module 405 in the distributed power system corresponding to FIG. 4 above. Include the following steps:
  • control module can control the inverter to work in the current source mode.
  • the inverter converts the DC power generated by the power supply equipment into AC power and outputs it to the AC grid, providing stable current to the AC grid and the load.
  • the inverter when the inverter works in the current source mode, the inverter can output a stable current of the same frequency and phase as the AC grid, and the voltages of the input port and the output port of the inverter can vary.
  • S502 When detecting that the voltage of the first target port jumps, control the inverter to switch from the current source mode to the voltage source mode.
  • the first target port is a port through which any inverter is connected to the AC power grid.
  • the port through which the inverter 402 is connected to the AC bus 4036 is the first target port 404 .
  • control module may sample the voltage of the first target port through the voltage sampling unit. It may be determined that the voltage of the first target port jumps. Wherein, the variation of the voltage within the first time period can be understood as the jumping amount of the voltage within a period of time.
  • the first duration and the specific value of the preset value may be set according to the actual application scenario, and are not limited.
  • the voltage of the first target port may also be determined that the voltage of the first target port jumps when the voltage of the first target port is greater than the first threshold and the variation of the voltage within the first time period is greater than a preset value.
  • the first threshold may be set according to an actual application scenario, which is not specifically limited in this embodiment of the present application.
  • the first threshold may be around 120% of the rated voltage of the load.
  • the control module may first detect whether the voltage of the first target port is greater than the first threshold, and if the voltage of the first target port is less than the first threshold, it means that the first target The voltage of the port usually does not cause damage to the load, and it can be considered that the voltage of the first target port does not jump. In this case, the inverter still works in the current source mode.
  • the voltage of the first target port is greater than the first threshold, it is further detected whether the variation of the voltage within the first duration is greater than the preset value, and if the variation of the voltage within the first duration is greater than the preset value, it can be considered that the first target port
  • the voltage jumps, and the inverter is controlled to switch from the current source mode to the voltage source mode.
  • FIG. 6 is a schematic flowchart of detecting whether the voltage of the first target port jumps according to an embodiment of the present application. As shown in FIG. 6 , it is determined whether the voltage of the first target port is greater than the first threshold, and the In the case where the voltage of the first target port is greater than the first threshold, it is determined whether the variation of the voltage of the first target port within the first time period is greater than the preset value, if the voltage of the first target port is greater than the first threshold, and the voltage is within the first If the variation within a period of time is greater than the preset value, it can be detected that the voltage of the first target port jumps, so the inverter is controlled to switch from the current source mode to the voltage source mode.
  • the voltage jump of the first target port may be caused by power failure of the power grid or high voltage ride-through of the power grid.
  • control the The inverter switches from current source mode to voltage source mode.
  • the inverter When the inverter works in the voltage source mode, the inverter outputs a stable voltage. In this way, the voltage of the first target port will not continue to rise, and the voltage of the first target port can be controlled within a safe range, so that there is no detection voltage. Before the cause of the abnormality, the local load can be protected and a relatively continuous power supply can be provided for the local load.
  • the inverter originally working in the current source mode is controlled to switch to the voltage source mode, and the inverter Voltage output as a voltage source.
  • the working mode of the inverter can be adjusted, and the output voltage of the inverter can be controlled within a safe range.
  • the load is protected, and a relatively continuous power supply can be provided for the load without causing loss of power generation.
  • S502 includes: when it is detected that the voltage of the first target port jumps, judging that the time when the inverter was last switched to the voltage source mode is the same as the time when the inverter switches to the voltage source mode last time. Whether the interval between the times when the voltage jump occurs is greater than the fifth threshold; if the interval is greater than the fifth threshold, the inverter is controlled to switch from the current source mode to the voltage source mode.
  • the interval between the time when the inverter was switched to the voltage source mode last time and the time when the voltage jump occurred is less than or equal to the fifth threshold, it can be understood that when the inverter was switched to the voltage source mode last time, there was no detection When a power failure occurs in the power grid, the distributed power system is in normal operation. Therefore, it is not necessary to switch the inverter from the current source mode to the voltage source mode, so as to avoid the damage to the inverter caused by frequent switching of the working mode of the inverter.
  • the time when the inverter was last switched to the voltage source mode was 10:25:18, and the time when the voltage of the first target port was detected to jump was 10:25:19, then the last time the inverter was switched
  • the interval between the time it is in voltage source mode and the time the voltage transition occurs is 1 second. If the fifth threshold is 100 milliseconds, and the interval is greater than the fifth threshold, the inverter can be controlled to switch from the current source mode to the voltage source mode.
  • the inverter may not be controlled to switch from the current source mode to the voltage source mode.
  • the value of the fifth threshold may be set according to the actual situation, which is not specifically limited in the embodiment of the present application.
  • the inverter when the interval between the time when the inverter switches to the voltage source mode last time and the time when the voltage jump occurs is greater than the fifth threshold, the inverter is controlled to switch from the current source mode to the voltage source mode In this way, frequent switching of the inverter between the current source mode and the voltage source mode can be avoided, so as to ensure the normal operation of the system.
  • the control method provided by this embodiment of the present application further includes performing islanding detection on the inverter where the voltage jump occurs, to determine the voltage that causes the first target port The reason for the jump.
  • S503 (not shown in the figure): perform islanding detection on the inverter.
  • the islanding detection of the inverter can be performed in the following ways:
  • Method 1 Determine whether an islanding phenomenon occurs in the DC distributed power system by detecting the voltage deviation value of the output port of the power supply equipment. Among them, if the islanding phenomenon does not occur, the inverter in the distributed power supply unit is also connected to the AC bus. Because the AC bus has a strong voltage support capability, the port voltage of the power supply equipment will be maintained at a relatively high level near the rated operating voltage of the system. within a small range. If the islanding phenomenon occurs, the inverter will be disconnected from the AC bus, and the voltage support capability of the large grid will be lost.
  • Method 2 The power supply equipment injects current disturbance into the output current, and the system equivalent impedance is calculated according to the fluctuation of the AC bus voltage and the disturbance current, and the islanding phenomenon is detected by the difference between the equivalent impedance of the grid-connected mode and the islanded mode system.
  • the inverter remains connected to the AC bus, and the system impedance includes the AC bus side impedance and the local load impedance. Since the AC bus side impedance and the local load impedance are connected in parallel, and the magnitude of the AC bus side impedance is very large Therefore, the total equivalent impedance of the system is small.
  • the inverter is in the island mode, the power supply device is disconnected from the AC bus. Since there is no parallel effect of the impedance on the AC bus side, the equivalent impedance is large. Therefore, when the equivalent impedance of the system is large, it can be judged that the islanding phenomenon occurs in the inverter.
  • Mode 3 Island detection is performed by using a phase locked loop (PLL) in the inverter.
  • PLL phase locked loop
  • FIG. 7 shows a schematic diagram of an architecture of a phase-locked loop.
  • the phase-locked loop includes: a phase detector (phase detector, PD), a loop filter (loop filter, LF) and Voltage controlled oscillator (voltage controlled oscillator, VCO).
  • the phase detector is used to distinguish the phase difference between the input signal Ui and the output signal Uo, and output the error voltage Ud.
  • the function of the loop filter is to filter out the high-frequency components and noise in the error voltage Ud to obtain the control voltage Uc of the voltage-controlled oscillator.
  • the voltage-controlled oscillator pulls the frequency fo of the output signal Uo to the loop.
  • the frequency fi of the channel input signal Ui when both fo and fi are equal, the loop is locked.
  • the frequency and phase of the voltage-controlled oscillator can continuously track the change of the frequency of the input reference signal, making the loop Re-enter locked state.
  • the phase-locked loop in the inverter can be used to track the phase change of the voltage of the first target port, and the disturbance of positive feedback can be injected into the first target port.
  • the islanding phenomenon of the inverter is counted once. If the counted number of times that the inverter island phenomenon occurs is greater than the fourth threshold, it is determined that the inverter island phenomenon occurs.
  • the inverter works in the voltage source mode, if the inverter does not have an islanding phenomenon, it means that the inverter is not disconnected from the AC grid. In this case, the first target port outputs the voltage. The frequency is clamped by the grid, and no frequency greater than the third threshold will occur.
  • phase disturbance of positive feedback When the phase disturbance of positive feedback is injected into the voltage of the first target port, a reference value of the voltage will be generated, and the phase-locked loop will make the phase of the voltage of the original first target port catch up with the phase of the voltage reference value through frequency modulation, resulting in the first target
  • the frequency of the output voltage of the port is increasing.
  • the output voltage frequency is greater than the third threshold, it can be determined that the inverter has an islanding phenomenon.
  • the phase disturbance can be positive or negative.
  • the inverter when the inverter works in the voltage source mode, if a negative phase disturbance is superimposed on the voltage of the first target port, the phase of the obtained voltage reference value will move to the right , in this case, the phase-locked loop will chase the phase through frequency modulation, resulting in the frequency of the output voltage of the first target port getting smaller and smaller. Therefore, when the output voltage frequency is less than the preset value, it can be determined that the inverter has an islanding phenomenon.
  • the voltage can be analyzed based on the Parker transform dq coordinate system.
  • a phase-locked loop is used to obtain a value Theta corresponding to the first target port voltage ug-sample, and a value delta is superimposed on the basis of Theta.
  • the corresponding three-phase voltages of ug-sample in the abc stationary coordinate system are u a , u b and u c .
  • Theta+delta can be used to convert u a , ub and uc to two-phase voltages ud and u q in the dq coordinate system.
  • a virtual impedance is added to the voltage control loop of ud to obtain the voltage amplitude. If the amplitude is large, two current loops can be used to limit the amplitude. Set the current limiting reference values id-up-lmt-ref and id-dn-lmt-ref of the two current loops to be smaller; similarly, add a virtual impedance to the voltage control loop of u q to obtain the voltage amplitude, If the amplitude is large, two current loops can also be used to limit the amplitude.
  • the current limiting reference values id-up-lmt-ref of the two current loops and The id-dn-lmt-ref is set to a smaller value; then the clipped ud and u q are converted into three-phase voltages in the abc static coordinate system, and the inverter is used for pulse width modulation with the three-phase voltages. , PWM), so that the inverter can output a stable voltage at the first target port voltage as a voltage source.
  • the voltage frequency output by the first target port will change. Therefore, when the voltage frequency output by the phase-locked loop based on the disturbance is greater than the third threshold, it is possible to count the inverter islanding phenomenon once. If the counted number of times of islanding of the inverter is greater than the fourth threshold, it is determined that the islanding of the inverter is detected, and the semiconductor switch driving signal matching the hardware device of the inverter is further controlled to control the semiconductors in the inverter. disconnection of the switch.
  • the values of the third threshold and the fourth threshold may be set according to actual conditions, which are not specifically limited in the embodiments of the present application.
  • the fourth threshold when the fourth threshold is set to 0, it can be understood that an islanding phenomenon is detected, that is, it is determined that an islanding phenomenon occurs in the inverter, so that the islanding phenomenon in the inverter can be quickly detected.
  • the fourth threshold is set to a value greater than 0, it can be understood that the islanding phenomenon of the inverter is determined only after the islanding phenomenon is detected for many times, which can reduce the probability of misjudging the islanding phenomenon of the inverter.
  • islanding detection is performed on the inverter.
  • islanding detection is performed on the inverter, so as to determine whether the cause of the voltage jump of the first target port is the power failure of the power grid or the high voltage ride-through of the power grid. In the case of voltage jumps, the inverter is quickly controlled.
  • the time that the inverter is in the voltage source mode can be limited, for example, the duration of the inverter being in the voltage source mode is limited to be less than the first time.
  • Two thresholds During the period when the inverter is in the voltage source mode is less than the second threshold, islanding detection is performed on the inverter cyclically; wherein, islanding detection is performed on the inverter cyclically as follows: if the inverter is not detected during the last islanding detection If the islanding phenomenon occurs, perform islanding detection on the inverter again until the islanding phenomenon of the inverter is detected.
  • the inverter is controlled to switch from the voltage source mode to the current source mode. This is because if the islanding phenomenon of the inverter is not detected for a long time, usually because the inverter does not have islanding phenomenon, switch the inverter from the voltage source to the current source mode to avoid power failure in the grid. In this case, the islanding detection of the inverter is repeated to ensure the normal operation of the distributed power system.
  • the islanding phenomenon in the inverter may be detected within 40ms. If the islanding phenomenon of the inverter is not detected within 200ms, it can be judged that the voltage jump of the first target port is not caused by the power failure of the power grid. In this case, the inverter can be switched from the voltage source Switch to the current source mode to avoid repeated islanding detection of the inverter when the grid does not lose power, so as to ensure the normal operation of the distributed power system.
  • the value of the second threshold may be set according to the actual situation, which is not specifically limited in this embodiment of the present application.
  • FIG. 11 is a specific flowchart of a control method provided by an embodiment of the present application.
  • the inverter when the inverter is in the voltage source mode for a period less than the second threshold, the inverter is cyclically performed. Island detection. If the inverter is islanded, turn off the inverter. If the duration of the inverter in the voltage source mode is greater than or equal to the second threshold, the inverter is controlled to switch from the voltage source mode to the current source mode.
  • the inverter when the inverter is in the voltage source mode and it is detected that the voltage of the second target port is greater than the sixth threshold, the inverter is controlled not to output power .
  • the second target port is a port through which any inverter is connected to the power supply device.
  • the position of the second target port may correspond to 407 in FIG. 4 .
  • abnormal protection measures can be triggered. If the voltage of the second target port is too large, although the inverter works in the voltage source mode to protect the load, the power supply equipment input to the inverter If the voltage of the inverter is too large, it may cause damage to the inverter. Therefore, when the inverter is in the voltage source mode and it is detected that the voltage of the second target port is greater than the sixth threshold, the semiconductor switch in the inverter can be controlled to be turned off, so that the inverter does not output power.
  • the value of the sixth threshold may be set according to the actual situation, which is not specifically limited in this embodiment of the present application.
  • the sixth threshold may be the same as or related to the rated voltage of the inverter.
  • the distributed power system includes a plurality of distributed power supply units and a control unit.
  • a plurality of distributed power supply units are all connected to the AC power grid; wherein, each distributed power supply unit includes an inverter for connecting power supply equipment, the input end of the inverter is connected to the power supply equipment, and the output end of the inverter is connected to the power supply equipment. into the AC grid.
  • a control device for controlling the inverter to work in a current source mode
  • the current source mode is that the inverter acts as a current source to convert the direct current generated by the power supply equipment into alternating current and output it to the alternating current grid
  • the first target port is detected
  • the inverter is controlled to switch from the current source mode to the voltage source mode; wherein, the first target port is the port where any inverter is connected to the AC power grid; the voltage jumps into the first target port.
  • the variation of the voltage within the first time period is greater than the preset value, and the voltage source mode is that the inverter acts as a voltage source to output voltage.
  • control device is further configured to perform islanding detection on the inverter; when it is detected that an islanding phenomenon occurs in the inverter, the inverter is turned off.
  • control device is specifically configured to cyclically perform islanding detection on the inverter during a period when the inverter is in the voltage source mode for less than a second threshold; wherein, cyclically perform islanding detection on the inverter For: If the islanding phenomenon of the inverter is not detected in the last islanding detection, perform the islanding detection on the inverter again until the islanding phenomenon of the inverter is detected.
  • control device is specifically configured to use a phase-locked loop in the inverter to track the phase change of the voltage of the first target port, and inject positive feedback disturbance into the first target port;
  • the control device is specifically configured to use a phase-locked loop in the inverter to track the phase change of the voltage of the first target port, and inject positive feedback disturbance into the first target port;
  • control device is specifically configured to determine that the inverter islanding phenomenon is detected if the counted number of times that the inverter islanding phenomenon occurs is greater than a fourth threshold.
  • control device is further configured to control the inverter to switch from the voltage source mode to the current source mode if the duration of the inverter in the voltage source mode is greater than or equal to the second threshold.
  • control device is further configured to determine the time when the inverter switches to the voltage source mode last time and the time when the voltage jump occurs when detecting that the voltage of the first target port jumps. Whether the interval between them is greater than the fifth threshold; if the interval is greater than the fifth threshold, the inverter is controlled to switch from the current source mode to the voltage source mode.
  • control device is further configured to control the inverter not to output power when the inverter is in the voltage source mode and it is detected that the voltage of the second target port is greater than the sixth threshold; wherein, The second target port is the port through which the inverter is connected to the power supply device.
  • An embodiment of the present application further provides a control device, where the control device can execute the steps of the above control method.
  • the control device may be a processor, a chip or a chip system, or a virtual module running in the processor, chip or chip system.
  • FIG. 12 is a schematic structural diagram of a chip 120 according to an embodiment of the present application.
  • the chip 120 includes one or more (including two) processors 1210 and a communication interface 1230 .
  • the chip 120 shown in FIG. 12 further includes a memory 1240 , which may include read-only memory and random access memory, and provides operation instructions and data to the processor 1210 .
  • a portion of memory 1240 may also include non-volatile random access memory (NVRAM).
  • NVRAM non-volatile random access memory
  • memory 1240 stores the following elements, executable modules or data structures, or a subset thereof, or an extended set of them:
  • the corresponding operation is performed by calling the operation instruction stored in the memory 1240 (the operation instruction may be stored in the operating system).
  • the processor 1210 controls the operation of the terminal device, and the processor 1210 may also be referred to as a central processing unit (central processing unit, CPU).
  • Memory 1240 may include read-only memory and random access memory, and provides instructions and data to processor 1210 .
  • a portion of memory 1240 may also include non-volatile random access memory (NVRAM).
  • NVRAM non-volatile random access memory
  • the memory 1240, the communication interface 1230 and the memory 1240 are coupled together through the bus system 1220, where the bus system 1220 may include a power bus, a control bus, a status signal bus, and the like in addition to a data bus.
  • the various buses are labeled as bus system 1220 in FIG. 12 .
  • the above communication unit may be an interface circuit or a communication interface of the device for receiving signals from other devices.
  • the communication unit is an interface circuit or a communication interface used by the chip to receive or transmit signals from other chips or devices.
  • the methods disclosed in the above embodiments of the present invention may be applied to the processor 1210 or implemented by the processor 1210 .
  • the processor 1210 may be an integrated circuit chip with signal processing capability. In the implementation process, each step of the above-mentioned method can be completed by an integrated logic circuit of hardware in the processor 1210 or an instruction in the form of software.
  • the above-mentioned processor 1210 may be a general-purpose processor, a digital signal processor (digital signal processing, DSP), an application specific integrated circuit (ASIC), an off-the-shelf programmable gate array (field-programmable gate array, FPGA) or Other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components.
  • a general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
  • the steps of the method disclosed in conjunction with the embodiments of the present invention may be directly embodied as executed by a hardware decoding processor, or executed by a combination of hardware and software modules in the decoding processor.
  • the software modules may be located in random access memory, flash memory, read-only memory, programmable read-only memory or electrically erasable programmable memory, registers and other storage media mature in the art.
  • the storage medium is located in the memory 1240, and the processor 1210 reads the information in the memory 1240, and completes the steps of the above method in combination with its hardware.
  • the instructions stored by the memory for execution by the processor may be implemented in the form of a computer program product.
  • the computer program product can be pre-written in the memory, or it can be downloaded and installed in the memory in the form of software.
  • a computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the procedures or functions according to the embodiments of the present application are generated in whole or in part.
  • the computer may be a general purpose computer, a special purpose computer, a computer network, or other programmable device.
  • Computer instructions may be stored in or transmitted from one computer-readable storage medium to another computer-readable storage medium, for example, the computer instructions may be transmitted from a website site, computer, server, or data center over a wire (e.g. coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (eg, infrared, wireless, microwave, etc.) to another website site, computer, server, or data center.
  • a wire e.g. coaxial cable, fiber optic, digital subscriber line (DSL)
  • wireless e.g, infrared, wireless, microwave, etc.
  • the computer-readable storage medium can be any available medium that can be stored by a computer or a data storage device such as a server, data center, etc. that includes one or more available media integrated.
  • Useful media may be magnetic media (eg, floppy disks, hard disks, magnetic tapes), optical media (eg, DVDs), or semiconductor media (eg, solid state disks, SSDs), and the like.
  • Embodiments of the present application also provide a computer-readable storage medium.
  • the methods described in the above embodiments may be implemented in whole or in part by software, hardware, firmware or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium.
  • Computer-readable media can include both computer storage media and communication media and also include any medium that can transfer a computer program from one place to another.
  • the storage medium can be any target medium that can be accessed by a computer.
  • the computer readable medium may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium intended to carry or in an instruction or data structure
  • the required program code is stored in the form and can be accessed by the computer.
  • any connection is properly termed a computer-readable medium.
  • coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave
  • coaxial cable, fiber optic cable , twisted pair, DSL or wireless technologies such as infrared, radio and microwave
  • Disk and disc as used herein includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and blu-ray disc, where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.
  • CD compact disc
  • DVD digital versatile disc
  • floppy disk floppy disk
  • blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.
  • the above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention. should be included within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

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Abstract

本申请实施例提供一种控制方法和分布式电力系统，涉及控制技术领域，分布式电力系统包括多个分布式供电单元，多个分布式供电单元均接入交流电网，方法包括：控制逆变器工作于电流源模式，电流源模式为逆变器作为电流源将电源设备产生的直流电转换成交流电输出至交流电网；检测到第一目标端口的电压发生跳变时，控制逆变器从电流源模式切换为电压源模式。这样，可以在安全范围内对逆变器输出电压进行控制，从而在没有检测电压出现异常的原因之前，能对本地负载进行保护，且可以为本地负载提供较为连续的供电。

Description

一种控制方法和分布式电力系统 技术领域
本申请涉及控制技术领域，尤其涉及一种控制方法和分布式电力系统。
背景技术
作为再生能源与电网之间的能量交换装置，逆变器已经广泛应用于包括风力发电、光伏发电和波浪发电等新能源分布式电力系统中。分布式电力系统通常由新能源发电装置、逆变器、本地负载及电网组成，逆变器和电网共同向本地负载供电。在逆变器并网运行时，逆变器作为电流源控制输入电网的电流功率。当电网由于故障或者线路切除等原因与逆变器断开与电网的连接时，逆变器与本地负载相连。在失去了电网的电压和频率的支撑后，逆变器输出电压可能远高于额定电压，导致本地负载的损坏等问题。因此，当逆变器输出端口电压上升过高时，需要对逆变器输出端口电压进行控制，提升系统安全性。
目前，常用的控制方法为主动控制法，例如，通过检测逆变器输出端口电压的幅值，当电压幅值超过预先设定的阈值时，逆变器触发保护并停机。
然而在上述控制方法中，不能为本地负载提供较为连续的供电。
发明内容
本申请实施例提供一种控制方法和分布式电力系统，当判断电压出现异常时，将逆变器的工作模式进行调整，可以在安全范围内对逆变器输出电压进行控制，从而在没有检测电压出现异常的原因之前，能对本地负载进行保护，且可以为本地负载提供较为连续的供电。
第一方面，本申请实施例提供一种控制方法，应用于分布式电力系统，所述分布式电力系统包括多个分布式供电单元，多个分布式供电单元均接入交流电网；其中，每个分布式供电单元包括用于连接电源设备的逆变器，逆变器的输入端连接电源设备，逆变器的输出端接入交流电网；方法包括：控制逆变器工作于电流源模式，电流源模式为逆变器作为电流源将电源设备产生的直流电转换成交流电输出至交流电网；检测到第一目标端口的电压发生跳变时，控制逆变器从电流源模式切换为电压源模式；其中，第一目标端口为任一个逆变器接入交流电网的端口；电压发生跳变为第一目标端口的电压在第一时长内的变化量大于预设值，电压源模式为逆变器作为电压源进行电压输出。
这样，在逆变器作为电流源向交流母线供电的过程中，检测逆变器的输出电压，若检测到逆变器输出电压大于阈值，且升压较快，则将逆变器切换为电压源，仍然向负载供电，且电压源的电压恒定，可以实现对负载的保护，且可以为负载提供较为连 续的供电。进一步地，在逆变器切换为电压源后，执行对逆变器的孤岛检测，确认逆变器发生孤岛现象时，关停逆变器，若逆变器没有发生孤岛现象，则可以将逆变器切换为电流源向交流母线供电，实现连续供电。
在一种可能的实现方式中，电压发生跳变具体为，第一目标端口的电压大于第一阈值，且第一目标端口的电压在第一时长内的变化量大于预设值。这样，若第一目标端口的电压小于第一阈值，说明第一目标端口的电压通常不会对负载带来损害，可以认为第一目标端口的电压没有发生跳变，在这种情况下，逆变器仍工作于电流源模式，能够实现逆变器连续供电。
在一种可能的实现方式中，控制逆变器从电流源模式切换为电压源模式之后，还包括：对逆变器进行孤岛检测；检测到逆变器发生孤岛现象时，关闭逆变器。这样，在对逆变器输出电压进行控制之后，对逆变器进行孤岛检测，从而判断导致第一目标端口电压发生跳变的原因是电网掉电还是电网发生高压穿越，这样在第一目标端口电压发生跳变的情况下，对逆变器进行较好地控制。
在一种可能的实现方式中，对逆变器进行孤岛检测，包括：在逆变器处于电压源模式的时长小于第二阈值期间，循环对逆变器进行孤岛检测；其中，循环对逆变器进行孤岛检测为：若上一次孤岛检测时未检测到逆变器发生孤岛现象，再次对逆变器进行孤岛检测，直到检测到逆变器发生孤岛现象。这样，可以在第二阈值内，循坏对逆变器进行孤岛检测，防止出现误判。
在一种可能的实现方式中，对逆变器进行孤岛检测，包括：利用逆变器中的锁相环跟踪第一目标端口的电压的相位变化，以及向第一目标端口注入正反馈的扰动；在锁相环基于扰动输出的电压频率大于第三阈值时，计数一次逆变器发生孤岛现象。
在一种可能的实现方式中，检测到逆变器发生孤岛现象包括：若计数得到的逆变器发生孤岛现象的次数大于第四阈值，确定检测到逆变器发生孤岛现象。这样，可以在多次确认逆变器发生孤岛现象时，才判定逆变器发生孤岛现象，防止出现误判。
在一种可能的实现方式中，方法还包括：若逆变器处于电压源模式的时长大于或等于第二阈值，控制逆变器从电压源模式切换为电流源模式。如果逆变器处于电压源模式较长时间，仍为检测到逆变器发生孤岛，则说明逆变器没有发送孤岛，控制逆变器从电压源模式切换为电流源模式，可以实现连续供电。
在一种可能的实现方式中，检测到第一目标端口的电压发生跳变时，控制逆变器从电流源模式切换为电压源模式，包括：检测到第一目标端口的电压发生跳变时，判断逆变器上次切换为电压源模式的时间与电压发生跳变发生的时间之间的间隔是否大于第五阈值；若间隔大于第五阈值，控制逆变器从电流源模式切换为电压源模式。这样，可以避免频繁地将逆变器在电流源模式和电压源模式下进行切换，保证系统正常运行。
在一种可能的实现方式中，方法还包括：在逆变器处于电压源模式，且检测到第二目标端口的电压大于第六阈值时，控制逆变器不进行功率输出；其中，第二目标端口为任一个逆变器接入电源设备的端口。这样，可以防止第二目标端口电压过高对逆变器造成损坏。
第二方面，本申请实施例提供一种分布式电力系统，包括控制装置和多个分布式 供电单元，多个分布式供电单元均接入交流电网；其中，每个分布式供电单元包括用于连接电源设备的逆变器，逆变器的输入端连接电源设备，逆变器的输出端接入交流电网。
控制装置，用于控制逆变器工作于电流源模式，其中，电流源模式为逆变器作为电流源将电源设备产生的直流电转换成交流电输出至交流电网；以及，在检测到第一目标端口的电压发生跳变时，控制逆变器从电流源模式切换为电压源模式；其中，第一目标端口为任一个逆变器接入交流电网的端口；电压发生跳变为第一目标端口的电压在第一时长内的变化量大于预设值，电压源模式为逆变器作为电压源进行电压输出。
在一种可能的实现方式中，电压发生跳变具体为，第一目标端口的电压大于第一阈值，且第一目标端口的电压在第一时长内的变化量大于预设值。
在一种可能的实现方式中，控制装置，还用于对逆变器进行孤岛检测；检测到逆变器发生孤岛现象时，关闭逆变器。
在一种可能的实现方式中，控制装置，具体用于在逆变器处于电压源模式的时长小于第二阈值期间，循环对逆变器进行孤岛检测；其中，循环对逆变器进行孤岛检测为：若上一次孤岛检测时未检测到逆变器发生孤岛现象，再次对逆变器进行孤岛检测，直到检测到逆变器发生孤岛现象。
在一种可能的实现方式中，控制装置具体用于，利用逆变器中的锁相环跟踪第一目标端口的电压的相位变化，以及向第一目标端口注入正反馈的扰动；在锁相环基于扰动输出的电压频率大于第三阈值时，计数一次逆变器发生孤岛现象。
在一种可能的实现方式中，控制装置，具体用于若计数得到的逆变器发生孤岛现象的次数大于第四阈值，确定检测到逆变器发生孤岛现象。
在一种可能的实现方式中，控制装置，具体还用于若逆变器处于电压源模式的时长大于或等于第二阈值，控制逆变器从电压源模式切换为电流源模式。
在一种可能的实现方式中，控制装置，具体还用于检测到第一目标端口的电压发生跳变时，判断逆变器上次切换为电压源模式的时间与电压发生跳变发生的时间之间的间隔是否大于第五阈值；若间隔大于第五阈值，控制逆变器从电流源模式切换为电压源模式。
在一种可能的实现方式中，控制装置，还用于在逆变器处于电压源模式，且检测到第二目标端口的电压大于第六阈值时，控制逆变器不进行功率输出；其中，第二目标端口为逆变器接入电源设备的端口。
第三方面，本申请实施例提供一种控制装置，包括：处理器，用于调用存储器中的程序，以实现第一方面或第一方面任意可能的实现方式中的任一控制方法。
第四方面，本申请提供一种芯片或者芯片系统，该芯片或者芯片系统包括至少一个处理器和通信接口，通信接口和至少一个处理器通过线路互联，至少一个处理器用于运行计算机程序或指令，以进行第一方面任意的实现方式中任一项所描述的控制方法。
其中，芯片中的通信接口可以为输入/输出接口、管脚或电路等。
在一种可能的实现中，本申请中上述描述的芯片或者芯片系统还包括至少一个存储器，该至少一个存储器中存储有指令。该存储器可以为芯片内部的存储单元，例如， 寄存器、缓存等，也可以是该芯片的存储单元(例如，只读存储器、随机存取存储器等)。
第五方面，本申请实施例提供一种计算机可读存储介质，计算机可读存储介质中存储有计算机程序或指令，当计算机程序或指令在计算机上运行时，使得计算机执行如第一方面的任意一种实现方式中描述的控制方法。
第六方面，本申请实施例提供一种计算机程序产品，程序产品包括计算机程序，计算机程序存储在可读存储介质中，电子设备的至少一个处理器可以从可读存储介质读取计算机程序，至少一个处理器执行计算机程序使得电子设备执行第一方面的任意一种实现方式中描述的控制方法。
应当理解的是，本申请实施例的第二方面至第六方面与本申请实施例的第一方面的技术方案相对应，各方面及对应的可行实施方式所取得的有益效果相似，不再赘述。
附图说明
图1为本申请实施例提供的一种分布式电力系统的架构示意图；
图2为本申请实施例提供的一种孤岛系统的架构示意图；
图3为本申请实施例提供的一种逆变器输出端口电压上升过高的示意图；
图4为本申请实施例提供的一种分布式电力系统的架构示意图；
图5为本申请实施例提供的一种控制方法的流程示意图；
图6为本申请实施例提供的一种检测第一目标端口的电压是否发生跳变的流程示意图；
图7为本申请实施例提供的一种锁相环的架构示意图；
图8为本申请实施例提供的一种锁相环通过调整频率来追赶相位的示意图；
图9为本申请实施例提供的另一种锁相环通过调整频率来追赶相位的示意图；
图10为本申请实施例提供的一种获取电压参考值的流程示意图；
图11为本申请实施例提供的一种控制方法的具体流程示意图；
图12为本申请实施例提供的一种芯片的结构示意图。
具体实施方式
为了便于清楚描述本申请实施例的技术方案，在本申请的实施例中，采用了“第一”、“第二”等字样对功能和作用基本相同的相同项或相似项进行区分。例如，第一日志和第二日志仅仅是为了区分不同时间窗内的网络日志，并不对其先后顺序进行限定。本领域技术人员可以理解“第一”、“第二”等字样并不对数量进行限定，并且“第一”、“第二”等字样也并不限定一定不同。
需要说明的是，本申请中，“示例性的”或者“例如”等词用于表示作例子、例证或说明。本申请中被描述为“示例性的”或者“例如”的任何实施例或设计方案不应被解释为比其他实施例或设计方案更优选或更具优势。确切而言，使用“示例性的”或者“例如”等词旨在以具体方式呈现相关概念。
本申请中，“至少一个”是指一个或者多个，“多个”是指两个或两个以上。“和/或”，描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表 示：单独存在A，同时存在A和B，单独存在B的情况，其中A，B可以是单数或者复数。
下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行描述，显然，所描述的实施例仅仅是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。
图1为分布式电力系统的架构示意图，如图1所示，分布式电力系统包括多个分布式供电单元，例如分布式供电单元101至分布式供电单元10N等，N为自然数。多个分布式供电单元共同向交流母线100和本地负载110供电。
其中，每个分布式供电单元包括用于连接电源设备的逆变器，逆变器的输入端连接电源设备，逆变器的输出端接入交流电网。
其中，电源设备可以包括：光伏发电设备、风电设备、电力储能设备、燃料电池设备和/或微型热电联产设备等。
由于电源设备输出的是直流电，电网是交流电，因此电源设备输出的直流电不能直接反馈到交流电网，需要逆变器将直流电逆变为交流电后反馈到电网,该过程可以称为并网发电。
逆变器可以是由半导体开关器件组成的电力调整装置，主要用于把直流电力转换成交流电力。例如，逆变器可以由升压回路和逆变桥式回路构成，其中，升压回路用于把电源设备的直流电压升压到逆变器输出控制所需的直流电压，逆变桥式回路则用于把升压后的直流电压等价地转换成常用频率的交流电压。
如图1所示，在分布式电力系统实际运行中，逆变器和交流电网之间可以通过断路器连接。在逆变器并网运行时，逆变器作为电流源控制输入交流电网的电流功率。但是在实际运行过程中，由于种种原因，分布式电力系统可能会发生故障。
示例性的，如图2所示，与分布式供电单元10N连接的断路器从并网点A点断开与交流母线100的连接，分布式供电单元10N和本地负载110构成了孤岛系统，在这种情况下，可以理解为分布式供电单元10N中的逆变器发生孤岛现象。
当逆变器发生孤岛现象时，由于逆变器的输出功率通常大于负载的功率，为了平衡逆变器多出负载需要的功率，逆变器需要提高输出电压，以达到功率平衡。例如，若逆变器输出功率为20kw，负载功率为5kw，若逆变器断开与母线的连接，称为孤岛，负载消耗的功率为5kw，则逆变器还有15kw无法输出，根据功率P与电压U和电流I的关系，P＝UI，逆变器作为电流源工作时，I恒定，则逆变器需要不断调高输出电压U，以实现功率平衡。
示例性的，图3示出了一种逆变器发生孤岛时，逆变器的电压随着时间不打断升高的示意图。图3中横轴为时间，纵轴为电压幅值。
可以理解的是，随着逆变器输出电压的不断升高，逆变器的输出电压可能远高于负载的额定电压，从而对负载造成损坏。
因此，在一些并网标准中，规定逆变器端口的输出电压不能大于一定值，以保护本地负载设备和人员的安全。当逆变器的输出电压上升过高时，需要采取一定的措施提升系统安全性。
例如，检测逆变器输出端口电压的幅值，当电压幅值超过预先设定的阈值时，逆变器触发保护并停机，从而避免逆变器输出电压过高造成的风险。
然而，实际应用中，逆变器由于种种原因可能发生高压穿越(high voltage ride through，HVRT)现象，高压穿越现象可以理解为电压突然升高，但较短时间又可以恢复正常的现象。高压穿越现象通常不会造成负载损坏等。但是在上述实现中，只要逆变器输出电压高于阈值，就关停逆变器，则逆变器偶然发生高压穿越现象，就会被频繁的关停，不能为负载提供较为连续的供电。
有鉴于此，本申请实施例提供控制方法和分布式电力系统，在逆变器作为电流源向交流母线供电的过程中，检测逆变器的输出电压，若检测到逆变器输出电压大于阈值，且升压较快，则将逆变器切换为电压源，仍然向负载供电，且电压源的电压恒定，可以实现对负载的保护，且可以为负载提供较为连续的供电。进一步地，在逆变器切换为电压源后，执行对逆变器的孤岛检测，确认逆变器发生孤岛现象时，关停逆变器，若逆变器没有发生孤岛现象，则可以将逆变器切换为电流源向交流母线供电，实现连续供电。
示例性的，图4示出了本申请实施例的一种分布式电力系统400的框架示意图。如图4所示，分布式电力系统400包括分布式供电单元，分布式供电单元接入交流母线403。
具体地，分布式供电单元包括用于连接电源设备401的逆变器402，逆变器402的输入端连接电源设备401，逆变器402的输出端通过断路器接入交流母线403。
其中，逆变器402可以工作于电流源模式或电压源模式。逆变器工作于电流源模式可以理解为，逆变器将电源设备产生的直流电转换成交流电后作为电流源输出稳定电流。逆变器工作于电压源模式可以理解为，逆变器作为电压源向负载输出稳定电压。
分布式电力系统400还包括控制模块405。其中，控制模块405可以通过软件、硬件或者软件与硬件结合等方式实现。具体实现中，控制模块405可以设置在逆变器402中，例如控制模块405可以为设置在逆变器402中的处理器或芯片。控制模块405也可以独立于逆变器402，控制模块405通过与逆变器402的通信，实现对逆变器402的工作模式的控制。
分布式电力系统400还包括电压采样单元406。电压采样单元406用于采样各端口的电压。电压采样单元406可以设置在逆变器402中，也可以独立于逆变器402，本申请实施例对此不作具体限定。
如图4所示，逆变器402的输入端与电源设备401连接，逆变器402的输出端通过断路器接入交流母线404，第一目标端口404为逆变器402接入交流母线的端口。电压采样单元406可以采样第一目标端口404的电压，并将采样得到的第一目标端口404的电压的发送给控制模块405，控制模块405可以根据第一目标端口404电压执行适应的控制策略，例如，控制模块405可以在检测到第一目标端口404的电压发生跳变时，控制逆变器402从电流源模式切换为电压源模式。
需要说明的是，图4以单个分布式供电单元为例对本申请实施例提供的一种直流分布式电力系统进行了说明，可以理解为，分布式电力系统可以包括多个分布式供电单元，每个分布式供电单元均可以与图4所示的分布式供电单元架构相同或相似。
可能的理解方式中，该分布式电力系统由硬件系统和软件系统组成，硬件系统可以包括：电源设备、逆变器和断路器，软件系统可以包括控制模块405。硬件系统具有强电的特征，软件系统具有弱电的特征，例如，电力系统的电压可能为几百伏，控制模块405中控制芯片的电压可能为几伏。如果直接将控制模块405中的芯片与分布式电力系统进行连接，当电力系统中存在干扰时，对芯片也会造成很强的干扰，因此可选地，可以使用线圈或者变压器之类的方式将直流电力系统和控制模块405进行隔离，例如把电力系统中强电电压的数字信号传递到控制模块405，例如强电电压为100V，只将传递数字100传递到控制模块405，这样可以实现硬件系统和软件系统的电气隔离。
下面结合图4的分布式电力系统，对本申请实施例的控制方法进行介绍。图5为本申请实施例提供的一种控制方法的流程示意图，该方法适用于上述图4对应的分布式电力系统中的控制模块405。包括以下步骤：
S501：控制逆变器工作于电流源模式。
在正常供电时，控制模块可以控制逆变器工作于电流源模式，逆变器作为电流源将电源设备产生的直流电转换成交流电输出至交流电网，向交流电网和负载提供稳定的电流。
可以理解的是，当逆变器工作于电流源模式时，逆变器可以输出与交流电网同频同相的稳定的电流，而逆变器输入端口和输出端口的电压可以是变化的。S502：检测到第一目标端口的电压发生跳变时，控制逆变器从电流源模式切换为电压源模式。
本申请实施例中，第一目标端口为任一个逆变器接入交流电网的端口。以图4中的分布式供电单元为例，逆变器402接入交流母线4036的端口为第一目标端口404。
本申请实施例中，控制模块可以通过电压采样单元采样第一目标端口的电压，一种可能的实现方式中，当第一目标端口的电压在第一时长内的变化量大于预设值时，可以确定第一目标端口的电压发生跳变。其中，电压在第一时长内的变化量可以理解为电压在一段时间内的跳变量。第一时长以及预设值的具体值可以根据实际应用场景设定，不作限制。
另一种可能的实现方式中，也可以在第一目标端口的电压大于第一阈值，且电压在第一时长内的变化量大于预设值时，确定第一目标端口的电压发生跳变。第一阈值可以根据实际应用场景设定，本申请实施例不作具体限定。例如，第一阈值可以为负载额定电压的120％左右。
例如，控制模块在检测第一目标端口的电压是否发生跳变时，可以先检测第一目标端口的电压是否大于第一阈值，若第一目标端口的电压小于第一阈值，则说明第一目标端口的电压通常不会对负载带来损害，可以认为第一目标端口的电压没有发生跳变，在这种情况下，逆变器仍工作于电流源模式。若第一目标端口的电压大于第一阈值，进一步检测电压在第一时长内的变化量是否大于预设值，如果电压在第一时长内的变化量大于预设值，可以认为第一目标端口的电压发生跳变，控制逆变器从电流源模式切换为电压源模式。
示例性的，图6为本申请实施例提供的一种检测第一目标端口的电压是否发生跳 变的流程示意图，如图6所示，判断第一目标端口的电压是否大于第一阈值，在第一目标端口的电压大于第一阈值的情况下，判断第一目标端口电压在第一时长内的变化量是否大于预设值，若第一目标端口的电压大于第一阈值，且电压在第一时长内的变化量大于预设值，则可以检测到第一目标端口的电压发生跳变，因此控制逆变器从电流源模式切换为电压源模式。
可以理解的是，在采样第一目标端口的电压和确定该电压是否发生跳变的过程中，可能会存在信号或噪声干扰。在这种情况下，若只是检测到第一目标端口的电压大于第一阈值时，就确定第一目标端口的电压发生跳变，这样可能会引起误判。因此，为避免发生误判，可以在第一目标端口的电压大于第一阈值，且电压在第一时长内的变化量大于预设值时，检测到第一目标端口的电压发生跳变。
第一目标端口的电压发生跳变，可能是电网掉电或电网发生高压穿越导致的。在不能确定具体是哪种原因导致第一目标端口的电压发生跳变时，为防止第一目标端口电压过高对负载造成损坏，可以在检测到第一目标端口的电压发生跳变后，控制逆变器从电流源模式切换为电压源模式。
当逆变器工作于电压源模式时，逆变器输出稳定电压，这样，第一目标端口电压不会再继续上升，可以将第一目标端口电压控制在安全范围内，从而在没有检测电压出现异常的原因之前，能对本地负载进行保护，且可以为本地负载提供较为连续的供电。
综上，本申请实施例中，当检测到任一个逆变器接入交流电网的端口的电压发生跳变时，控制原本工作于电流源模式的逆变器切换为电压源模式，逆变器作为电压源进行电压输出。这样，当判断逆变器端口电压出现异常时，将逆变器的工作模式进行调整，可以在安全范围内对逆变器输出电压进行控制，从而在没有检测电压出现异常的原因之前，能对负载进行保护，且可以为负载提供较为连续的供电，不会对发电量造成损失。
在图5对应的实施例的基础上，一种可能的实现方式中，S502包括：在检测到第一目标端口的电压发生跳变时，判断逆变器上次切换为电压源模式的时间与电压发生跳变发生的时间之间的间隔是否大于第五阈值；若间隔大于第五阈值，控制逆变器从电流源模式切换为电压源模式。
若逆变器上次切换为电压源模式的时间与电压发生跳变发生的时间之间的间隔小于或等于第五阈值时，可以理解为上次逆变器切换为电压源模式时，没有检测到电网发生掉电，分布式电力系统是正常运行的，因此可以不用将逆变器从电流源模式切换为电压源模式，避免频繁切换逆变器的工作模式对逆变器造成损害。
示例性的，若逆变器上次切换为电压源模式的时间为10时25分18秒，检测到第一目标端口的电压发生跳变的时间为10时25分19秒，则上次切换为电压源模式的时间与电压发生跳变发生的时间之间的间隔为1秒。若第五阈值为100毫秒，则该间隔大于第五阈值，则可以控制逆变器从电流源模式切换为电压源模式。
示例性的，若逆变器上次切换为电压源模式的时间为12时4分18秒，检测到第一目标端口的电压发生跳变的时间为12时4分19秒，则上次切换为电压源模式的时 间与电压发生跳变发生的时间之间的间隔为1秒。若第五阈值为200毫秒，则该间隔小于第五阈值，则可以不控制逆变器从电流源模式切换为电压源模式。
本申请实施例中，第五阈值的取值可以根据实际情况设定，本申请实施例对此不作具体限定。
本申请实施例中，在逆变器上次切换为电压源模式的时间与电压发生跳变发生的时间之间的间隔大于第五阈值时，控制逆变器从电流源模式切换为电压源模式，这样，可以避免频繁地将逆变器在电流源模式和电压源模式下进行切换，保证系统正常运行。
在图5对应的实施例的基础上，在检测到第一目标端口的电压发生跳变，并控制逆变器从电流源模式切换为电压源模式后，可以进一步确定第一目标端口的电压发生跳变的原因，从而可以基于跳变原因对逆变器进行控制以实现对系统更好的保护。例如，在控制逆变器从电流源模式切换为电压源模式后，本申请实施例提供的控制方法还包括对发生电压跳变的逆变器进行孤岛检测，来确定导致第一目标端口的电压发生跳变的原因。
可选的，S502之后还可以包括：
S503(图中未示出)：对逆变器进行孤岛检测。
S504(图中未示出)：检测到逆变器发生孤岛现象时，关闭逆变器。
示例性的，对逆变器进行孤岛检测可以采用下述几种方式：
方式一：通过检测电源设备输出端口的电压偏差值来判断直流分布式电力系统是否出现孤岛现象。其中，若没有发生孤岛现象，则分布式供电单元中的逆变器还与交流母线连接，由于交流母线具有很强的电压支撑能力，因此电源设备的端口电压会维持在系统额定工作电压附近较小的范围内。若发生孤岛现象，则逆变器断开与交流母线的连接，失去大电网的电压支撑能力。在这种情况下，当电源设备发出的电量大于本地负载消耗的电量时，则系统电压会逐步增大，当分布式发电单元发出的电量小于本地负载消耗的电量时，则系统电压会逐步减小。因此，当系统电压超出预设的上限值或下限值时，则可以判断系统已失去大电网的支撑作用，逆变器发生孤岛现象。
方式二：通过电源设备在输出电流中注入电流扰动，根据交流母线电压的波动和扰动电流计算出系统等效阻抗，通过并网模式和孤岛模式系统等效阻抗的差异实现孤岛现象的检测。例如，当系统处于并网模式时，逆变器与交流母线保持连接，系统阻抗包括交流母线侧阻抗和本地负载阻抗，由于交流母线侧阻抗和本地负载阻抗并联且交流母线侧阻抗的幅值非常小，因此系统总等效阻抗较小。当逆变器处于孤岛模式时，电源设备断开与交流母线的连接，由于没有了交流母线侧阻抗的并联效果，等效阻抗较大。因此，当系统等效阻抗较大时，可以判断逆变器发生孤岛现象。
方式三：利用逆变器中的锁相环(phase locked loop，PLL)进行孤岛检测。
锁相环可以快速且准确地检测出电网信号并且跟踪电网信号的频率和相位。示例性的，图7示出了锁相环的一种架构示意图，如图7所示，锁相环包括：鉴相器(phase detector，PD)、环路滤波器(loop filter，LF)和压控振荡器(voltage controlled oscillator，VCO)。
其中，鉴相器用来鉴别输入信号Ui与输出信号Uo之间的相位差，并输出误差电 压Ud。环路滤波器的作用是滤除误差电压Ud中的高频成分和噪声，得到压控振荡器的控制电压Uc，在Uc的作用下，压控振荡器将输出信号Uo的频率fo拉向环路输入信号Ui的频率fi，当fo和fi二者相等时，环路被锁定。当环路已处于锁定状态时，如果输入参考信号的频率和相位发生变化，通过环路的控制作用，压控振荡器的频率和相位能不断跟踪输入参考信号频率的变化而变化，使环路重新进入锁定状态。
本申请实施例中，可以利用逆变器中的锁相环跟踪第一目标端口的电压的相位变化，并向第一目标端口注入正反馈的扰动，在锁相环基于扰动输出的电压频率大于第三阈值时，计数一次逆变器发生孤岛现象。若计数得到的逆变器发生孤岛现象的次数大于第四阈值时，确定检测到逆变器发生孤岛现象。
可能的理解方式中，当逆变器工作于电压源模式时，如果逆变器没有发生孤岛现象，则说明逆变器没有从交流电网断开，在这种情况下，第一目标端口输出电压的频率由电网钳位，不会发生频率大于第三阈值的情况。
当向第一目标端口电压注入正反馈的相位扰动后，会生成电压的参考值，则锁相环路会通过调频来使原第一目标端口电压相位追赶电压参考值的相位，导致第一目标端口的输出电压的频率越来越大。当输出电压频率大于第三阈值时，可以判断逆变器发生孤岛现象。其中，相位扰动可以是正值，也可以是负值。
一种实现中，如图8所示，当逆变器工作于电压源模式时，若在第一目标端口电压中叠加正值的相位扰动，则得到的电压参考值的相位会向左移动，在这种情况下，锁相环会通过调频去追赶相位，若逆变器发生孤岛现象，则第一目标端口的输出电压的频率越来越大。
另一种实现中，如图9所示，当逆变器工作于电压源模式时，若在第一目标端口电压中叠加负值的相位扰动，则得到的电压参考值的相位会向右移动，在这种情况下，锁相环会通过调频去追赶相位，导致第一目标端口的输出电压的频率越来越小。因此，当输出电压频率小于预设值时，可以判断逆变器发生孤岛现象。
下面结合图10对向第一目标端口电压注入正反馈的相位扰动后，锁相环工作的具体过程进行示例性介绍。
如图10所示，若在第一目标端口电压中叠加正值的相位扰动后，可以基于派克变换dq坐标系对电压进行分析。
具体地，在采样到第一目标端口电压ug-sample大于第一阈值时，利用锁相环得到对应于第一目标端口电压ug-sample的值Theta，并在Theta的基础上叠加值delta。
其中，ug-sample在abc静止坐标系下对应的三相电压为u a，u b和u c。可以利用Theta+delta将u a，u b和u c转换为dq坐标系下的两相电压u d和u q。
在u d的电压控制环路中加入虚拟阻抗，得到电压幅值，如果幅值较大，可以利用两个电流环进行限幅，其中，为防止交流母线的电压反灌到逆变器，可以将两个电流环的限流参考值id-up-lmt-ref和id-dn-lmt-ref设置较小；相似的，在u q的电压控制环路中加入虚拟阻抗，得到电压幅值，如果幅值较大，也可以利用两个电流环进行限幅其中，为防止交流母线的电压反灌到逆变器，可以将两个电流环的限流参考值id-up-lmt-ref和id-dn-lmt-ref设置较小；再将限幅后的u d和u q转换为abc静止坐标系下三相电压，利用该三相电压对逆变器进行脉冲宽度调制(pulse width modulation， PWM)，使得逆变器作为电压源在第一目标端口电压可以输出稳定的电压。
并且，对逆变器进行了PWM，第一目标端口输出的电压频率将发生变化，因此，可以在锁相环基于扰动输出的电压频率大于第三阈值时，计数一次逆变器发生孤岛现象。若计数得到的逆变器发生孤岛现象的次数大于第四阈值时，确定检测到逆变器发生孤岛现象，进一步控制与逆变器硬件装置相匹配的半导体开关驱动信号，控制逆变器中半导体开关的断开。
本申请实施例中，第三阈值与第四阈值的取值可以根据实际情况设定，本申请实施例对此不作具体限定。
可以理解的是，第四阈值设置为0时，可以理解为检测到一次孤岛现象即判定逆变器发生孤岛现象，这样可以快速检测出逆变器发生孤岛现象。第四阈值设置为大于0的值时，可以理解为检测到多次孤岛现象才判定逆变器发生孤岛现象，这样可以减少误判逆变器发生孤岛现象的概率。
综上，本申请实施例中，在控制逆变器从电流源模式切换至电压源模式后，对逆变器进行孤岛检测。当检测到逆变器发生孤岛现象时，关闭逆变器。这样，在对逆变器输出电压进行控制之后，对逆变器进行孤岛检测，从而判断导致第一目标端口电压发生跳变的原因是电网掉电还是电网发生高压穿越，这样在第一目标端口电压发生跳变的情况下，对逆变器进行快速地控制。
可能的实现方式中，当控制逆变器从电流源模式切换为电压源模式后，可以对逆变器处于电压源模式的时间进行限制，例如，限制逆变器处于电压源模式的时长小于第二阈值。在逆变器处于电压源模式的时长小于第二阈值期间，循环对逆变器进行孤岛检测；其中，循环对逆变器进行孤岛检测为：若上一次孤岛检测时未检测到逆变器发生孤岛现象，再次对逆变器进行孤岛检测，直到检测到逆变器发生孤岛现象。
若逆变器处于电压源模式的时长大于或等于第二阈值，控制逆变器从电压源模式切换为电流源模式。这是因为，如果较长时间没有检测到逆变器发生孤岛现象，通常是因为逆变器没有发生孤岛现象，将逆变器从电压源切换至电流源模式，避免在电网没有发生掉电的情况下，重复对逆变器进行孤岛检测，从而保证分布式电力系统的正常运行。
示例性的，若第二阈值为200ms，若逆变器发生了孤岛现象，则可能在40ms内就可以检测出逆变器发生孤岛现象。若在200ms之内都没有检测逆变器发生孤岛现象，则可以判断第一目标端口的电压跳变不是由于电网发生掉电而产生的，在这种情况下，可以将逆变器从电压源切换至电流源模式，避免在电网没有发生掉电的情况下，重复对逆变器进行孤岛检测，从而保证分布式电力系统的正常运行。
可以理解的是，第二阈值的取值可以根据实际情况设定，本申请实施例对此不作具体限定。
示例性的，图11为本申请实施例提供的一种控制方法的具体流程示意图，如图11所示，在逆变器处于电压源模式的时长小于第二阈值期间，循环对逆变器进行孤岛检测。若逆变器发生孤岛现象，关闭逆变器。若逆变器处于电压源模式的时长大于或等于第二阈值，控制逆变器从电压源模式切换到电流源模式。
在上述任一实施例的基础上，一种可能的实现方式中，在逆变器处于电压源模式， 且检测到第二目标端口的电压大于第六阈值时，控制逆变器不进行功率输出。
其中，第二目标端口为任一个逆变器接入电源设备的端口。示例性的，第二目标端口的位置可以对应图4中的407。这样，可以在第二目标端口407电压大于第六阈值时，触发异常保护措施，若第二目标端口电压过大，逆变器虽然工作于电压源模式，保护负载，但电源设备输入到逆变器的电压过大，可能会对逆变器造成损坏。因此，可以在逆变器处于电压源模式，且检测到第二目标端口的电压大于第六阈值时，控制逆变器中半导体开关断开，从而使得逆变器不进行功率输出。
其中，第六阈值的取值可以根据实际情况设定，本申请实施例对此不作具体限定。例如，第六阈值可以与逆变器的额定电压相同或相关。
上面结合图4-图11，对本申请实施例的方法进行了说明，下面对本申请实施例提供的适用上述方法的分布式电力系统进行描述，该分布式电力系统包括多个分布式供电单元和控制装置，多个分布式供电单元均接入交流电网；其中，每个分布式供电单元包括用于连接电源设备的逆变器，逆变器的输入端连接电源设备，逆变器的输出端接入交流电网。
控制装置，用于控制逆变器工作于电流源模式，其中，电流源模式为逆变器作为电流源将电源设备产生的直流电转换成交流电输出至交流电网；以及，在检测到第一目标端口的电压发生跳变时，控制逆变器从电流源模式切换为电压源模式；其中，第一目标端口为任一个逆变器接入交流电网的端口；电压发生跳变为第一目标端口的电压在第一时长内的变化量大于预设值，电压源模式为逆变器作为电压源进行电压输出。
在一种可能的实现方式中，控制装置，还用于对逆变器进行孤岛检测；检测到逆变器发生孤岛现象时，关闭逆变器。
在一种可能的实现方式中，控制装置，具体用于在逆变器处于电压源模式的时长小于第二阈值期间，循环对逆变器进行孤岛检测；其中，循环对逆变器进行孤岛检测为：若上一次孤岛检测时未检测到逆变器发生孤岛现象，再次对逆变器进行孤岛检测，直到检测到逆变器发生孤岛现象。
在一种可能的实现方式中，控制装置具体用于，利用逆变器中的锁相环跟踪第一目标端口的电压的相位变化，以及向第一目标端口注入正反馈的扰动；在锁相环基于扰动输出的电压频率大于第三阈值时，计数一次逆变器发生孤岛现象。
在一种可能的实现方式中，控制装置，具体用于若计数得到的逆变器发生孤岛现象的次数大于第四阈值，确定检测到逆变器发生孤岛现象。
在一种可能的实现方式中，控制装置，具体还用于若逆变器处于电压源模式的时长大于或等于第二阈值，控制逆变器从电压源模式切换为电流源模式。
在一种可能的实现方式中，控制装置，具体还用于检测到第一目标端口的电压发生跳变时，判断逆变器上次切换为电压源模式的时间与电压发生跳变发生的时间之间的间隔是否大于第五阈值；若间隔大于第五阈值，控制逆变器从电流源模式切换为电压源模式。
在一种可能的实现方式中，控制装置，还用于在逆变器处于电压源模式，且检测到第二目标端口的电压大于第六阈值时，控制逆变器不进行功率输出；其中，第二目 标端口为逆变器接入电源设备的端口。
本申请实施例还提供的一种控制装置，控制装置可以执行上述控制方法的步骤。以该控制装置可以为处理器、芯片或芯片系统，或运行在处理器、芯片或芯片系统中的虚拟模块。
示例性的，以控制装置为芯片为例，图12为本申请实施例提供的芯片120的结构示意图。芯片120包括一个或两个以上(包括两个)处理器1210和通信接口1230。
在一种可能的实施例中，如图12所示的芯片120还包括存储器1240，存储器1240可以包括只读存储器和随机存取存储器，并向处理器1210提供操作指令和数据。存储器1240的一部分还可以包括非易失性随机存取存储器(non-volatile random access memory，NVRAM)。
在一些实施方式中，存储器1240存储了如下的元素，可执行模块或者数据结构，或者他们的子集，或者他们的扩展集：
在本发明实施例中，通过调用存储器1240存储的操作指令(该操作指令可存储在操作系统中)，执行相应的操作。
处理器1210控制终端设备的操作，处理器1210还可以称为中央处理单元(central processing unit，CPU)。存储器1240可以包括只读存储器和随机存取存储器，并向处理器1210提供指令和数据。存储器1240的一部分还可以包括非易失性随机存取存储器(non-volatile random access memory，NVRAM)。例如应用中存储器1240、通信接口1230以及存储器1240通过总线系统1220耦合在一起，其中总线系统1220除包括数据总线之外，还可以包括电源总线、控制总线和状态信号总线等。但是为了清楚说明起见，在图12中将各种总线都标为总线系统1220。
以上通信单元可以是一种该装置的接口电路或通信接口，用于从其它装置接收信号。例如，当该装置以芯片的方式实现时，该通信单元是该芯片用于从其它芯片或装置接收信号或发送信号的接口电路或通信接口。
上述本发明实施例揭示的方法可以应用于处理器1210中，或者由处理器1210实现。处理器1210可能是一种集成电路芯片，具有信号的处理能力。在实现过程中，上述方法的各步骤可以通过处理器1210中的硬件的集成逻辑电路或者软件形式的指令完成。上述的处理器1210可以是通用处理器、数字信号处理器(digital signal processing，DSP)、专用集成电路(application specific integrated circuit，ASIC)、现成可编程门阵列(field-programmable gate array，FPGA)或者其他可编程逻辑器件、分立门或者晶体管逻辑器件、分立硬件组件。可以实现或者执行本发明实施例中的公开的各方法、步骤及逻辑框图。通用处理器可以是微处理器或者该处理器也可以是任何常规的处理器等。结合本发明实施例所公开的方法的步骤可以直接体现为硬件译码处理器执行完成，或者用译码处理器中的硬件及软件模块组合执行完成。软件模块可以位于随机存储器，闪存、只读存储器，可编程只读存储器或者电可擦写可编程存储器、寄存器等本领域成熟的存储介质中。该存储介质位于存储器1240，处理器1210读取存储器1240中的信息，结合其硬件完成上述方法的步骤。
在上述实施例中，存储器存储的供处理器执行的指令可以以计算机程序产品的形式实现。计算机程序产品可以是事先写入在存储器中，也可以是以软件形式下载并安 装在存储器中。
计算机程序产品包括一个或多个计算机指令。在计算机上加载和执行计算机程序指令时，全部或部分地产生按照本申请实施例的流程或功能。计算机可以是通用计算机、专用计算机、计算机网络、或者其他可编程装置。计算机指令可以存储在计算机可读存储介质中，或者从一个计算机可读存储介质向另一计算机可读存储介质传输，例如，计算机指令可以从一个网站站点、计算机、服务器或数据中心通过有线(例如同轴电缆、光纤、数字用户线(DSL))或无线(例如红外、无线、微波等)方式向另一个网站站点、计算机、服务器或数据中心进行传输。计算机可读存储介质可以是计算机能够存储的任何可用介质或者是包括一个或多个可用介质集成的服务器、数据中心等数据存储设备。可用介质可以是磁性介质，(例如，软盘、硬盘、磁带)、光介质(例如，DVD)、或者半导体介质(例如固态硬盘solid state disk，SSD)等。
本申请实施例还提供了一种计算机可读存储介质。上述实施例中描述的方法可以全部或部分地通过软件、硬件、固件或者其任意组合来实现。如果在软件中实现，则功能可以作为一个或多个指令或代码存储在计算机可读介质上或者在计算机可读介质上传输。计算机可读介质可以包括计算机存储介质和通信介质，还可以包括任何可以将计算机程序从一个地方传送到另一个地方的介质。存储介质可以是可由计算机访问的任何目标介质。
作为一种可能的设计，计算机可读介质可以包括RAM，ROM，EEPROM，CD-ROM或其它光盘存储器，磁盘存储器或其它磁存储设备，或目标于承载的任何其它介质或以指令或数据结构的形式存储所需的程序代码，并且可由计算机访问。而且，任何连接被适当地称为计算机可读介质。例如，如果使用同轴电缆，光纤电缆，双绞线，数字用户线(DSL)或无线技术(如红外，无线电和微波)从网站，服务器或其它远程源传输软件，则同轴电缆，光纤电缆，双绞线，DSL或诸如红外，无线电和微波之类的无线技术包括在介质的定义中。如本文所使用的磁盘和光盘包括光盘(CD)，激光盘，光盘，数字通用光盘(DVD)，软盘和蓝光盘，其中磁盘通常以磁性方式再现数据，而光盘利用激光光学地再现数据。上述的组合也应包括在计算机可读介质的范围内。以上所述，仅为本发明的具体实施方式，但本发明的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本发明揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本发明的保护范围之内。因此，本发明的保护范围应以所述权利要求的保护范围为准。
以上所述，仅为本发明的具体实施方式，但本发明的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本发明揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本发明的保护范围之内。因此，本发明的保护范围应以所述权利要求的保护范围为准。
以上所述，仅为本发明的具体实施方式，但本发明的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本发明揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本发明的保护范围之内。因此，本发明的保护范围应以所述权利要求的保护范围为准。

Claims (16)

  1. 一种控制方法，其特征在于，应用于分布式电力系统，所述分布式电力系统包括多个分布式供电单元，所述多个分布式供电单元均接入交流电网；其中，每个所述分布式供电单元包括用于连接电源设备的逆变器，所述逆变器的输入端连接所述电源设备，所述逆变器的输出端接入所述交流电网；
    所述方法，包括：
    控制所述逆变器工作于电流源模式，所述电流源模式为所述逆变器作为电流源将所述电源设备产生的直流电转换成交流电输出至所述交流电网；
    检测到第一目标端口的电压发生跳变时，控制所述逆变器从所述电流源模式切换为电压源模式；其中，所述第一目标端口为任一个所述逆变器接入所述交流电网的端口；所述电压发生跳变为所述第一目标端口的电压在第一时长内的变化量大于预设值，所述电压源模式为所述逆变器作为电压源进行电压输出。
  2. 根据权利要求1所述的方法，其特征在于，所述控制所述逆变器从所述电流源模式切换为电压源模式之后，还包括：
    对所述逆变器进行孤岛检测；
    检测到所述逆变器发生孤岛现象时，关闭所述逆变器。
  3. 根据权利要求2所述的方法，其特征在于，所述对所述逆变器进行孤岛检测，包括：
    在所述逆变器处于所述电压源模式的时长小于第二阈值期间，循环对所述逆变器进行孤岛检测；其中，所述循环对所述逆变器进行孤岛检测为：若上一次孤岛检测时未检测到所述逆变器发生孤岛现象，再次对所述逆变器进行孤岛检测，直到检测到所述逆变器发生孤岛现象。
  4. 根据权利要求2或3所述的方法，其特征在于，所述对所述逆变器进行孤岛检测，包括：
    利用所述逆变器中的锁相环跟踪所述第一目标端口的电压的相位变化，以及向所述第一目标端口注入正反馈的扰动；
    在所述锁相环基于所述扰动输出的电压频率大于第三阈值时，计数一次所述逆变器发生孤岛现象。
  5. 根据权利要求4所述的方法，其特征在于，所述检测到所述逆变器发生孤岛现象包括：
    若计数得到的所述逆变器发生孤岛现象的次数大于第四阈值，确定检测到所述逆变器发生孤岛现象。
  6. 根据权利要求2-5任一项所述的方法，其特征在于，还包括：
    若所述逆变器处于所述电压源模式的时长大于或等于所述第二阈值，控制所述逆变器从所述电压源模式切换为所述电流源模式。
  7. 根据权利要求1-6任一项所述的方法，其特征在于，所述检测到第一目标端口的电压发生跳变时，控制所述逆变器从所述电流源模式切换为电压源模式，包括：
    检测到所述第一目标端口的电压发生跳变时，判断所述逆变器上次切换为所述电 压源模式的时间与所述电压发生跳变发生的时间之间的间隔是否大于第五阈值；
    若所述间隔大于所述第五阈值，控制所述逆变器从所述电流源模式切换为电压源模式。
  8. 根据权利要求1-7任一项所述的方法，其特征在于，还包括：
    在所述逆变器处于所述电压源模式，且检测到第二目标端口的电压大于第六阈值时，控制所述逆变器不进行功率输出；其中，所述第二目标端口为所述逆变器接入所述电源设备的端口。
  9. 一种分布式电力系统，包括控制装置和多个分布式供电单元，所述多个分布式供电单元均接入交流电网；其中，每个所述分布式供电单元包括用于连接电源设备的逆变器，所述逆变器的输入端连接所述电源设备，所述逆变器的输出端接入所述交流电网；
    所述控制装置，用于控制所述逆变器工作于电流源模式，其中，所述电流源模式为所述逆变器作为电流源将所述电源设备产生的直流电转换成交流电输出至所述交流电网；以及，在检测到第一目标端口的电压发生跳变时，控制所述逆变器从所述电流源模式切换为电压源模式；其中，所述第一目标端口为任一个所述逆变器接入所述交流电网的端口；所述电压发生跳变为所述第一目标端口的电压在第一时长内的变化量大于预设值，所述电压源模式为所述逆变器作为电压源进行电压输出。
  10. 根据权利要求9所述的分布式电力系统，其特征在于，所述控制装置，还用于对所述逆变器进行孤岛检测；检测到所述逆变器发生孤岛现象时，关闭所述逆变器。
  11. 根据权利要求10所述的分布式电力系统，其特征在于，所述控制装置，具体用于在所述逆变器处于所述电压源模式的时长小于第二阈值期间，循环对所述逆变器进行孤岛检测；其中，所述循环对所述逆变器进行孤岛检测为：若上一次孤岛检测时未检测到所述逆变器发生孤岛现象，再次对所述逆变器进行孤岛检测，直到检测到所述逆变器发生孤岛现象。
  12. 根据权利要求10或11所述的分布式电力系统，其特征在于，所述控制装置具体用于，利用所述逆变器中的锁相环跟踪所述第一目标端口的电压的相位变化，以及向所述第一目标端口注入正反馈的扰动；在所述锁相环基于所述扰动输出的电压频率大于第三阈值时，计数一次所述逆变器发生孤岛现象。
  13. 根据权利要求12所述的分布式电力系统，其特征在于，所述控制装置，具体用于若计数得到的所述逆变器发生孤岛现象的次数大于第四阈值，确定检测到所述逆变器发生孤岛现象。
  14. 根据权利要求10-13任一项所述的分布式电力系统，其特征在于，所述控制装置，具体还用于若所述逆变器处于所述电压源模式的时长大于或等于所述第二阈值，控制所述逆变器从所述电压源模式切换为所述电流源模式。
  15. 根据权利要求9-14任一项所述的分布式电力系统，其特征在于，所述控制装置，具体还用于检测到所述第一目标端口的电压发生跳变时，判断所述逆变器上次切换为所述电压源模式的时间与所述电压发生跳变发生的时间之间的间隔是否大于第五阈值；若所述间隔大于所述第五阈值，控制所述逆变器从所述电流源模式切换为电压源模式。
  16. 根据权利要求9-15任一项所述的分布式电力系统，其特征在于，所述控制装置，还用于在所述逆变器处于所述电压源模式，且检测到第二目标端口的电压大于第六阈值时，控制所述逆变器不进行功率输出；其中，所述第二目标端口为所述逆变器接入所述电源设备的端口。
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