A power supply system and control method

Abstract

A power supply system and a control method, which can improve the reliability of handling fault ride-through. The power supply system comprises an inverter and a fault ride-through control device, the fault ride-through control device is configured to: detect a voltage of a grid connection point; in a case where it is detected that the voltage of the grid connection point is abnormal, send a fault ride-through start instruction to the inverter, the fault ride-through start instruction is configured to indicate that the voltage of the grid connection point is abnormal; the inverter is further configured to: receive the fault ride-through start instruction; execute a fault ride-through mode according to the fault ride-through start instruction, the fault ride-through mode comprises outputting a reactive current to the grid, the reactive current is configured to correct the voltage of the grid connection point.

Description

Technical Field

[0001] This application relates to the field of circuit technology, and more specifically, to a power supply system and control method. Background Technology

[0002] A power supply system, also known as a power plant, generates electrical energy, collects and boosts the voltage at the grid connection point, and then sends it into the power grid. A power supply system typically includes an inverter, which converts direct current (DC) to alternating current (AC). After the power supply system is connected to the grid, the inverter will issue active or reactive power commands according to the grid dispatch instructions when the grid is normal. When the grid experiences disturbances characterized by short-term low and overvoltage, the inverter must ensure continuous operation without disconnecting from the grid for a specified period and correct the abnormal voltage by providing reactive current to the grid; this process is called "fault ride-through."

[0003] Currently, when dealing with fault ride-through issues, the main approach is to rely on the inverter in the power supply system to determine whether to activate fault ride-through mode based on the relationship between its own port voltage and a threshold. However, there are many uncertainties in the operating states of the power supply system and the grid. For example, power differences within the power supply system can cause errors between the inverter terminal voltage and the grid connection point voltage, leading to unreliable triggering issues such as false triggering, failure to trigger, or repeated triggering of fault ride-through. Furthermore, after experiencing severe disturbances, the grid may not be able to recover to its pre-fault state in a short time, meaning the grid connection point voltage may remain abnormal. Consequently, the inverter will remain in fault ride-through mode, which could lead to grid dispatching being unable to manage the system or even disconnecting it from the grid. Summary of the Invention

[0004] This application provides a power supply system and control method that can determine whether the grid voltage is abnormal and reliably trigger the fault ride-through mode, thereby improving the reliability of fault ride-through handling.

[0005] In a first aspect, a power supply system is provided, comprising: an inverter for receiving direct current (DC) output from a power generation module, and after converting the DC to alternating current (AC), outputting electrical energy to the power grid through a grid connection point, wherein the grid connection point is a node that collects the electrical energy output by the power supply system; and a fault ride-through control device for: detecting the voltage of the grid connection point; and, upon detecting an abnormal voltage at the grid connection point, sending a fault ride-through start command to the inverter, wherein the fault ride-through start command indicates that the voltage at the grid connection point is abnormal; the inverter is further configured to: receive the fault ride-through start command; and, according to the fault ride-through start command, execute a fault ride-through mode, wherein the fault ride-through mode includes outputting reactive current to the power grid, wherein the reactive current is used to correct the voltage at the grid connection point.

[0006] By setting up fault ride-through control equipment in the power supply system, the fault ride-through control equipment directly detects the voltage at the grid connection point and sends a fault ride-through start command to the inverter, instead of the inverter side determining whether to start the fault ride-through mode. This enables accurate detection of grid anomalies and improves the reliability of fault ride-through handling.

[0007] In conjunction with the first aspect, in one possible implementation, the abnormal voltage of the grid connection point includes situations where the voltage of the grid connection point is higher than a first voltage threshold for a duration exceeding a first preset duration; or, the voltage of the grid connection point is lower than a second voltage threshold for a duration exceeding a second preset duration, wherein the first voltage threshold is greater than the second voltage threshold.

[0008] In conjunction with the first aspect, in one possible implementation, the fault ride-through start command is further used to instruct the inverter to adjust the magnitude of the reactive current according to the voltage at the grid connection point in the fault ride-through mode.

[0009] The fault ride-through start command is also used to indicate the grid connection point voltage detected by the fault ride-through control equipment, so that the inverter can calculate the reactive current based on the grid connection point voltage, thereby improving the accuracy of reactive current calculation and the reliability of fault ride-through handling.

[0010] In conjunction with the first aspect, in one possible implementation, the fault ride-through start command is further used to indicate the magnitude of the reactive current, so that the inverter determines the magnitude of the reactive current according to the fault ride-through start command.

[0011] The fault ride-through start command is also used to instruct the reactive current calculated by the fault ride-through control equipment, so that the inverter can determine the reactive current according to the fault ride-through start command, thereby improving the accuracy of the reactive current and the reliability of fault ride-through handling.

[0012] In conjunction with the first aspect, in one possible implementation, the fault ride-through mode is a first fault ride-through mode, the reactive current is a first reactive current, and the inverter is further configured to: detect the output voltage of the inverter; execute a second fault ride-through mode when the output voltage of the inverter is abnormal, the second fault ride-through mode including outputting a second reactive current to the grid, the second reactive current being used to correct the voltage at the grid connection point; determine whether a fault ride-through start command is received within a fourth preset time period after the execution of the second fault ride-through mode; specifically, the inverter is configured to: execute the first fault ride-through mode according to the fault ride-through start command if the fault ride-through start command is received within the fourth preset time period after the execution of the second fault ride-through mode; the inverter is further configured to: stop executing the second fault ride-through mode if the fault ride-through start command is not received within the fourth preset time period after the execution of the second fault ride-through mode.

[0013] Unlike fault ride-through schemes where the inverter is completely independent in starting, stopping, and controlling the fault, this scheme is led by a fault ride-through control device with the inverter assisting. The fault ride-through control device analyzes the voltage and generates fault ride-through start and stop commands.

[0014] In conjunction with the first aspect, in one possible implementation, the fault ride-through control device is further configured to: send a fault ride-through release command to the inverter when the voltage at the grid connection point returns to normal, the fault ride-through release command indicating that the voltage at the grid connection point has returned to normal; the inverter is further configured to: receive the fault ride-through release command; and stop executing the fault ride-through mode according to the fault ride-through release command.

[0015] By setting up fault ride-through control equipment in the power supply system, the fault ride-through control equipment directly detects the voltage at the grid connection point and sends a fault ride-through release command to the inverter, instead of the inverter side determining whether to end the fault ride-through mode. This allows for accurate determination of whether the power grid has returned to normal, thus improving the reliability of handling fault ride-through.

[0016] In conjunction with the first aspect, in one possible implementation, before the inverter receives the fault ride-through clearance command, the inverter is further configured to: detect the output voltage of the inverter; and if the output voltage of the inverter exceeds a fifth voltage threshold, control the reactive current to be less than or equal to a first current upper limit value.

[0017] Before the inverter ends the fault ride-through mode, it can detect the inverter's output voltage. When the inverter's output voltage recovers to a certain value (i.e., greater than the fifth voltage threshold), it can control the upper limit of reactive current to be less than the first upper limit of current, thereby preventing the grid voltage recovery from overshooting and improving the reliability of fault ride-through handling.

[0018] In conjunction with the first aspect, in one possible implementation, the voltage of the grid connection point returning to normal includes: the duration for which the voltage of the grid connection point is lower than a third voltage threshold and higher than a fourth voltage threshold is greater than a third preset duration.

[0019] In conjunction with the first aspect, in one possible implementation, the fault ride-through control device is specifically used to sample and detect the voltage of the grid connection point according to a preset period.

[0020] In conjunction with the first aspect, in one possible implementation, the system further includes a relay route, wherein the fault ride-through control device is specifically used to send the fault ride-through start command to the inverter via the relay route.

[0021] In conjunction with the first aspect, in one possible implementation, the power supply system further includes a transformer unit, which receives the AC power output from the inverter and, after boosting the voltage, outputs the electrical energy to the grid connection point.

[0022] Secondly, a control method for a power supply system is provided. The power supply system includes: an inverter for receiving direct current (DC) output from a generator module and, after converting the DC to alternating current (AC), outputting electrical energy to the power grid through a grid connection point, wherein the grid connection point is a node that collects the electrical energy output by the power supply system; the method includes: a fault ride-through control device detecting the voltage of the grid connection point; the fault ride-through control device sending a fault ride-through start command to the inverter when it detects an abnormal voltage at the grid connection point, the fault ride-through start command indicating that the voltage at the grid connection point is abnormal; the inverter receiving the fault ride-through start command; and the inverter executing a fault ride-through mode according to the fault ride-through start command, the fault ride-through mode including outputting reactive current to the power grid, the reactive current being used to correct the voltage at the grid connection point.

[0023] By setting up fault ride-through control equipment in the power supply system, the fault ride-through control equipment directly detects the voltage at the grid connection point and sends a fault ride-through start command to the inverter, instead of the inverter side determining whether to start the fault ride-through mode. This enables accurate detection of grid anomalies and improves the reliability of fault ride-through handling.

[0024] In conjunction with the second aspect, in one possible implementation, the abnormal voltage of the grid connection point includes situations where the voltage of the grid connection point is higher than a first voltage threshold for a duration exceeding a first preset duration; or, the voltage of the grid connection point is lower than a second voltage threshold for a duration exceeding a second preset duration, wherein the first voltage threshold is greater than the second voltage threshold.

[0025] In conjunction with the second aspect, in one possible implementation, the fault ride-through start command is further used to instruct the inverter to adjust the magnitude of the reactive current according to the voltage at the grid connection point in the fault ride-through mode.

[0026] In conjunction with the second aspect, in one possible implementation, the fault ride-through start command is further used to indicate the magnitude of the reactive current, so that the inverter determines the magnitude of the reactive current according to the fault ride-through start command.

[0027] In conjunction with the second aspect, in one possible implementation, the fault ride-through mode is a first fault ride-through mode, the reactive current is a first reactive current, and the method further includes: the inverter detecting the output voltage of the inverter; the inverter executing a second fault ride-through mode when the output voltage of the inverter is abnormal, the second fault ride-through mode including outputting a second reactive current to the grid, the second reactive current being used to correct the voltage at the grid connection point; the inverter determining whether it receives a fault ride-through initiation command within a fourth preset time period after starting to execute the second fault ride-through mode; the inverter executing the fault ride-through mode according to the fault ride-through initiation command, including: if the fault ride-through initiation command is received within the fourth preset time period after starting to execute the second fault ride-through mode, executing the first fault ride-through mode according to the fault ride-through initiation command; the method further includes: if the fault ride-through initiation command is not received within the fourth preset time period after starting to execute the second fault ride-through mode, stopping the execution of the second fault ride-through mode.

[0028] In conjunction with the second aspect, in one possible implementation, the method further includes: the fault ride-through control device sending a fault ride-through release command to the inverter when the voltage at the grid connection point returns to normal, the fault ride-through release command indicating that the voltage at the grid connection point has returned to normal; the inverter receiving the fault ride-through release command; and the inverter stopping the execution of the fault ride-through mode according to the fault ride-through release command.

[0029] In conjunction with the second aspect, in one possible implementation, before the inverter receives the fault ride-through clearance command, the method further includes: the inverter detecting the output voltage of the inverter; and the inverter controlling the reactive current to be less than or equal to a first current upper limit value when the output voltage of the inverter exceeds a fifth voltage threshold.

[0030] In conjunction with the second aspect, in one possible implementation, the voltage of the grid connection point returning to normal includes: the duration for which the voltage of the grid connection point is lower than a third voltage threshold and higher than a fourth voltage threshold is greater than a third preset duration.

[0031] In conjunction with the second aspect, in one possible implementation, the fault ride-through control device detects the voltage at the grid connection point by: the fault ride-through device sampling and detecting the voltage at the grid connection point according to a preset period.

[0032] In conjunction with the second aspect, in one possible implementation, the power supply system further includes a relay route, wherein when the fault ride-through control device detects an abnormal voltage at the grid connection point, it sends a fault ride-through start command to the inverter, including: the fault ride-through control device sending the fault ride-through start command to the inverter through the relay route.

[0033] In conjunction with the second aspect, in one possible implementation, the power supply system further includes a transformer unit, which receives the AC power output from the inverter and, after boosting the voltage, outputs the electrical energy to the grid connection point.

[0034] Thirdly, a fault-crossing control device is provided, which is capable of implementing the method executed by the fault-crossing control device in the second aspect or any possible implementation of the second aspect.

[0035] Fourthly, an inverter is provided that is capable of implementing the method performed by the inverter in the second aspect or any possible implementation of the second aspect. Attached Figure Description

[0036] Figure 1 This is a structural diagram of an application scenario applicable to the embodiments of this application.

[0037] Figure 2 This is a schematic diagram of the power supply system 200 according to an embodiment of this application.

[0038] Figure 3 This is a flowchart illustrating the fault traversal control method according to an embodiment of this application.

[0039] Figure 4This is a flowchart illustrating a fault traversal control method according to another embodiment of this application.

[0040] Figure 5 Is with Figure 4 A schematic diagram of the corresponding fault crossing process. Detailed Implementation

[0041] To facilitate understanding, several terms used in the embodiments of this application will be introduced first.

[0042] Active power refers to the electrical power required to maintain the normal operation of a power system, that is, the electrical power that converts electrical energy into other forms of energy. These other forms of energy include mechanical energy, light energy, and heat energy.

[0043] Reactive power refers to the power required to establish a magnetic field when components such as inductors and capacitors in a power system are working. It is mainly used for energy exchange between electric and magnetic fields in the power system, and does not manifest as external work.

[0044] Reactive current: refers to the current corresponding to reactive power.

[0045] Positive sequence voltage refers to the three-phase voltages arranged in the order A, B, and C, each maintaining its own phase angle. Specifically, phase A leads phase B by 120 degrees, phase B leads phase C by 120 degrees, and phase C leads phase A by 120 degrees. It should be understood that AC power systems are typically three-phase (A, B, C), and the positive, negative, and zero-sequence components of the power system are determined based on the order of these three phases.

[0046] Negative sequence voltage: This refers to the three-phase voltages arranged in reverse order of A, B, C, each maintaining its own phase angle. That is, phase A lags behind phase B by 120 degrees, phase B lags behind phase C by 120 degrees, and phase C lags behind phase A by 120 degrees.

[0047] Zero-sequence voltage: refers to the three phases (A, B, and C) being in the same phase.

[0048] The technical solutions in this application will now be described with reference to the accompanying drawings.

[0049] To facilitate understanding of the embodiments of this application, firstly, in conjunction with... Figure 1 Describe the application scenarios of this application. Figure 1 This is a structural diagram illustrating an application scenario applicable to the embodiments of this application. For example... Figure 1As shown, the power supply system 100 is used to supply power to the power grid. The power supply system 100 includes a power generation module 110 and a voltage conversion module 120. As an example, the power generation module 110 is used to generate direct current (DC). As an example, the power generation module 110 may include a photovoltaic (PV) module 111, which converts solar energy into electrical energy and outputs DC power. The voltage conversion module 120 includes an inverter 121 and a transformer unit 122. The inverter 121 converts the DC power output from the PV module 111 into alternating current (AC), and the transformer unit 122 boosts the DC power output from the inverter 121. Then, the high-voltage AC power is transmitted to the power grid through a grid connection point to supply power to the grid. The aforementioned grid connection point refers to the node where the electrical energy output from the power supply system 100 is collected.

[0050] In some examples, the power supply system 100 described above may not include the transformer unit 122.

[0051] Optionally, the power generation module 110 can also be a wind power generation system or other types of power generation systems.

[0052] Furthermore, the inverter 121 can also detect whether its own output voltage is abnormal. If an abnormality occurs, the inverter starts the fault ride-through mode and sends reactive current to the grid to correct the abnormal voltage.

[0053] In some examples, the transformer unit 122 described above may include a low-voltage / medium-voltage transformer and a medium-voltage / high-voltage transformer. The low-voltage / medium-voltage transformer is used to convert low-voltage AC power into medium-voltage AC power and output the medium-voltage AC power to the medium-voltage / high-voltage transformer. The medium-voltage / high-voltage transformer is used to convert the medium-voltage AC power into high-voltage AC power and then send the high-voltage AC power into the power grid through the grid connection point.

[0054] It should be understood that Figure 1 The power supply system 100 described above is only for illustrating the application scenario of the embodiments of this application and is not intended to limit this application. The power supply system 100 described above can also be modified appropriately, or the power supply system 100 can also include other devices, functional modules or units, or reduce some devices, functional modules or units.

[0055] It should be understood that the embodiments of this application do not limit the connection relationship of the circuit. In practical applications, Figure 1 There may be other devices connected to the various components.

[0056] To improve the reliability of detecting and managing grid fault ride-through, embodiments of this application provide a power supply system and a control method. The power supply system includes a fault ride-through control device, which can detect the voltage at the grid connection point and, in the event of an anomaly at the grid connection point, send a control command to the inverter to initiate a fault ride-through mode. This solution can improve the reliability of handling fault ride-through. The solution in this application embodiment will now be described in detail with reference to the accompanying drawings.

[0057] Figure 2 This is a schematic diagram of the power supply system 200 according to an embodiment of this application. Figure 2 As shown, the power supply system 200 includes a power generation module 110, a voltage conversion module 220, and a fault ride-through control device 230. The voltage conversion module 220 includes an inverter 210 and a transformer unit 122. The functions of the power generation module 110 and the transformer unit 122 are... Figure 1 The same or similar items are not repeated here.

[0058] In some examples, the power supply system 200 may not include the transformer unit 122.

[0059] The fault ride-through control device 230 can be used to: detect the voltage at the grid connection point; and send a fault ride-through start command to the inverter 210 when an abnormal voltage is detected at the grid connection point. The fault ride-through start command is used to indicate that the voltage at the grid connection point is abnormal.

[0060] It should be understood that the grid connection point refers to the node that collects or boosts the electrical energy output from the power supply system 200. If the voltage at the grid connection point is abnormal, it indicates that the grid voltage is abnormal, that is, the grid voltage has been disturbed.

[0061] In some examples, the fault ride-through control device 230 is specifically used to sample and detect the voltage at the grid connection point according to a preset period.

[0062] Inverter 210 is used to: receive fault ride-through start command; and execute fault ride-through mode according to the fault ride-through start command. The fault ride-through mode includes outputting reactive current to the grid, which is used to correct the voltage at the grid connection point.

[0063] In some examples, a relay route 240 may be provided between the fault ride-through control device 230 and the inverter 210, through which the fault ride-through control device 230 can communicate with the inverter 210. For example, the fault ride-through control device 230 sends a fault ride-through start command to the inverter 210 through the relay route 240.

[0064] Optionally, inverter 210 can be connected to transformer unit 122 via AC cable. Inverter 210 and relay router 240 can be connected via optical fiber.

[0065] Optionally, a voltage sensor and / or a power sensor may be installed at the grid connection point to convert the three-phase voltage and three-phase current at the grid connection point to a measurable range.

[0066] In this embodiment of the application, by setting up a fault ride-through control device in the power supply system, the fault ride-through control device directly detects the voltage at the grid connection point and sends a fault ride-through start command to the inverter, instead of the inverter side determining whether to start the fault ride-through mode. This enables accurate detection of whether the power grid is abnormal and improves the reliability of handling fault ride-through.

[0067] Optionally, the fault ride-through control device 230 described above can also be called a station-level controller, that is, a control device installed in the power station. The fault ride-through control device 230 can analyze the grid connection point voltage in real time and generate fault ride-through start and stop commands, as well as other types of fault ride-through control commands. It should be understood that the fault ride-through control device 230 described above can be installed independently or integrated into other devices, and this application does not limit this.

[0068] In some examples, abnormal voltage conditions at the grid connection point include: the voltage at the grid connection point being higher than a first voltage threshold for a duration exceeding a first preset duration; or, the voltage at the grid connection point being lower than a second voltage threshold for a duration exceeding a second preset duration, where the first voltage threshold is greater than the second voltage threshold. The magnitudes of the first voltage threshold, the second voltage threshold, the first preset duration, and the second preset duration can be determined based on practical experience.

[0069] As an example, assuming the first voltage threshold is 0.8kV, the second voltage threshold is 0.6kV, and the first and second preset durations are both 10ms, then when the grid connection point voltage is detected to be higher than 0.8kV for a duration greater than 10ms or lower than 0.6kV for a duration greater than 10ms, it is determined that an abnormality has occurred in the grid connection point voltage.

[0070] In some examples, the primary basis for setting the first and second voltage thresholds includes the following:

[0071] i) It can effectively distinguish the voltage from that during normal operation mode, avoiding misjudgment;

[0072] ii) It has a certain degree of anti-interference capability and can control the influence of detection errors or external power fluctuations;

[0073] iii) Take into account the difficulty of identifying inverters and fault ride-through control devices.

[0074] In some examples, assuming the voltage at the grid connection point during normal grid operation is taken as the voltage reference value, the first voltage threshold can be set to 110%–120% of the voltage reference value, and the second voltage threshold can be set to 80%–90% of the voltage reference value. For example, the first voltage threshold is 115% of the voltage reference value, and the second voltage threshold is 85% of the voltage reference value.

[0075] Optionally, the fault ride-through start command described above can also be used to determine the magnitude of the reactive current. In one example, the fault ride-through start command is further used to instruct the inverter 210 to adjust the magnitude of the reactive current according to the voltage at the grid connection point in the fault ride-through mode. Alternatively, the fault ride-through control device 230 can control the inverter 210 to determine the magnitude of the reactive current according to the voltage at the grid connection point. As an example, the fault ride-through start command is also used to indicate the magnitude of the voltage at the grid connection point, and the inverter 210 is specifically used to: calculate the magnitude of the reactive current according to the magnitude of the voltage at the grid connection point; and output the reactive current to the grid. Specifically, the inverter 210 can calculate and convert the difference between the magnitude of the grid connection point voltage and the voltage reference value into the magnitude of the reactive current to be output to the grid, so as to output the reactive current to correct abnormal voltage.

[0076] In another example, the fault ride-through start command is also used to indicate the magnitude of the reactive current. Specifically, the fault ride-through control device 230 can calculate the magnitude of the reactive current that needs to be output to the grid and indicate the magnitude of the reactive current to the inverter 210 via the fault ride-through start command. The inverter 210 can directly output the reactive current to the grid according to the fault ride-through start command to correct abnormal voltage.

[0077] It should be understood that the processing instructions and calculation functions executed by the inverter 210 in this embodiment can be executed by the controller located in the inverter 210.

[0078] Optionally, the inverter 210 can also detect whether its own output voltage is abnormal. If an abnormality occurs, it can determine whether to activate the fault ride-through mode. However, the inverter 210's own commands have a lower priority than the commands sent by the fault ride-through control device. That is, if the operating mode determined by the inverter 210 itself is different from the operating mode indicated by the command received from the fault ride-through control device, then the inverter 210 needs to execute the command sent by the fault ride-through control device. The aforementioned operating modes include normal operating mode and fault ride-through mode.

[0079] In some examples, assuming the fault ride-through mode triggered by the fault ride-through control device 230 is the first fault ride-through mode, and its corresponding reactive current is the first reactive current, and the fault ride-through mode triggered by the inverter 210 is the second fault ride-through mode, and its corresponding reactive current is the second reactive current, then the inverter 210 is also used to: detect the output voltage of the inverter 210; if the output voltage of the inverter 210 is abnormal, execute the second fault ride-through mode, the second fault ride-through mode including outputting a second reactive current to the grid, the second reactive current being used to correct the voltage at the grid connection point; determine whether a fault ride-through start command is received within a fourth preset time period after the start of the second fault ride-through mode; if a fault ride-through start command is received within the fourth preset time period after the start of the second fault ride-through mode, execute the first fault ride-through mode according to the fault ride-through start command; if no fault ride-through start command is received within the fourth preset time period after the start of the second fault ride-through mode, stop executing the second fault ride-through mode and execute the normal operation mode.

[0080] It should be understood that the aforementioned fourth preset duration can be determined based on practice, and this application does not impose any limitations on it.

[0081] This can be understood as follows: the initiation of fault ride-through mode for inverter 210 requires consideration of two conditions simultaneously: first, inverter 210 detects an abnormal voltage; second, it receives a fault ride-through start command from fault ride-through control device 230 within a specified time. If condition one is met, inverter 210 can temporarily initiate the first fault ride-through mode. However, if no fault ride-through start command is received within the specified time, inverter 210 needs to stop the first fault ride-through mode. Upon receiving a fault ride-through start command, inverter 210 can determine the magnitude of the reactive current based on the command and initiate the second fault ride-through mode.

[0082] In the first fault ride-through mode, the inverter 210 determines the magnitude of the reactive current based on its own detected output voltage. In the second fault ride-through mode, the inverter 210 determines the magnitude of the reactive current based on the magnitude of the grid connection point voltage or the magnitude of the reactive current indicated by the fault ride-through start command.

[0083] In this embodiment, unlike the fault ride-through scheme where the inverter is completely independent in starting, stopping, and controlling, the fault ride-through control device takes the lead and the inverter cooperates. The fault ride-through control device analyzes the voltage and generates fault ride-through start and stop commands.

[0084] Optionally, the fault ride-through control device 230 is also used to send other fault ride-through related instructions to the inverter 210. For example, the fault ride-through control device 230 is also used to: send a fault ride-through release instruction to the inverter 210 when the voltage at the grid connection point returns to normal, the fault ride-through release instruction indicating that the voltage at the grid connection point has returned to normal; the inverter 210 is also used to: receive the fault ride-through release instruction; and stop executing the fault ride-through mode according to the fault ride-through release instruction.

[0085] In some examples, after detecting an abnormality in the grid connection point voltage, the fault ride-through control device 230 can continue to monitor whether the grid connection point voltage has returned to normal. After detecting that the grid connection point voltage has returned to normal, the fault ride-through control device 230 sends a fault ride-through release command to the inverter 210. After receiving the fault ride-through release command, the inverter 210 deactivates the fault ride-through mode, loads the power output setting value before the fault ride-through occurred, the fault ride-through transient process ends, and it returns to normal operating mode.

[0086] Optionally, the above-mentioned fault crossing cancellation command can also be called the fault crossing stop command.

[0087] Optionally, the fault ride-through control device 230 determines the situation in which the grid connection point voltage returns to normal by: the duration during which the voltage at the grid connection point is lower than the third voltage threshold and higher than the fourth voltage threshold is greater than the third preset duration.

[0088] The third voltage threshold, the fourth voltage threshold, and the third preset duration can be determined in practice, and this application embodiment does not limit them.

[0089] It should be understood that the first and second voltage thresholds mentioned above are fault ride-through initiation thresholds, and the third and fourth voltage thresholds are fault ride-through exit thresholds. In some examples, the first voltage threshold is greater than the third voltage threshold, and the second voltage threshold is less than the fourth voltage threshold.

[0090] In some examples, before the inverter 210 receives the fault ride-through release command, the inverter 210 is also used to: detect the output voltage of the inverter 210; and control the reactive current to be less than or equal to the first current upper limit value if the output voltage of the inverter 210 exceeds the fifth voltage threshold.

[0091] The fifth voltage threshold and the first current upper limit can be determined based on practice, and this application embodiment does not limit them.

[0092] It can be understood that the fault ride-through recovery logic of inverter 210 includes two steps: first, detecting the inverter's own voltage and setting the upper limit of the output reactive current; second, only after receiving the fault ride-through release command does it completely end the fault ride-through mode.

[0093] In this embodiment of the application, before the inverter ends the fault ride-through mode, the inverter output voltage can be detected. When the inverter output voltage recovers to a certain value (i.e., greater than the fifth voltage threshold), the upper limit of the reactive current can be controlled to be less than the first upper limit of the current, thereby preventing the voltage recovery of the grid from overshooting and improving the reliability of fault ride-through processing.

[0094] In the embodiments of this application, the fault ride-through control device can measure and analyze the grid connection point voltage and generate a fault ride-through start or stop command. The inverter can integrate its own terminal voltage and the start or stop command of the fault ride-through control device to complete the current control during the fault ride-through process, so as to avoid unreliable triggering problems caused by various uncertainties in the grid operation status and / or power supply system operation status, realize reliable triggering of fault ride-through, and ensure that the power supply system does not disconnect from the grid and continues to operate when the grid experiences faults or disturbances.

[0095] The following will combine Figure 3 The fault ride-through control method of the power supply system in this application is described in detail.

[0096] Figure 3 This is a flowchart illustrating the fault ride-through control method for the power supply system in an embodiment of this application. For example... Figure 3 As shown, the control method includes the following: S310, the fault ride-through control equipment detects the grid connection point voltage in the power supply system to determine whether the grid connection point voltage is abnormal.

[0097] In a specific example, if the voltage at the power station's grid connection point in the power supply system is higher than the first voltage threshold or lower than the second voltage threshold within a preset time period (e.g., 10ms), the fault ride-through control device determines that the grid connection point voltage is abnormal. At this time, the power supply system needs to ensure that it does not disconnect from the grid within the specified time period and correct the abnormal voltage to complete the fault ride-through process.

[0098] S311, in the event of an abnormal voltage at the grid connection point, the fault ride-through control device sends a fault ride-through start command to the inverter.

[0099] Specifically, the fault ride-through start command is used to indicate an abnormal voltage. Optionally, the fault ride-through command can also perform at least one of the following functions: (1) indicating the magnitude of the grid connection point voltage, that is, the fault ride-through control device implicitly tells the inverter the magnitude of the reactive current to be output to the grid. (2) indicating the magnitude of the reactive current output by the inverter to the grid.

[0100] S312, the inverter starts the fault ride-through mode according to the fault ride-through start command.

[0101] Specifically, the inverter determines the amount of reactive current that needs to be output to the grid based on the fault ride-through command, and activates the fault ride-through mode to output reactive current to the grid.

[0102] For example, the inverter determines the abnormal voltage value at the grid connection point based on the grid connection point voltage. The difference between this abnormal voltage value and the voltage reference value is then calculated and converted into the amount of reactive current that needs to be output to the grid. This reactive current is then used to correct the abnormal voltage, completing the fault ride-through logic. The voltage reference value refers to the voltage at the grid connection point during normal operation.

[0103] For example, the inverter can directly determine the amount of reactive current that needs to be output based on the fault ride-through start command, and then output that reactive current to the grid.

[0104] In the embodiments of this application, the fault ride-through control device can detect the voltage at the grid connection point in real time, determine whether the voltage is abnormal based on the voltage at the grid connection point, and generate a corresponding fault ride-through command, so that the inverter can reliably trigger the fault ride-through according to the fault ride-through command, thereby improving the speed and reliability of handling grid faults or disturbances.

[0105] Figure 4 This is a flowchart illustrating a fault traversal control method according to another embodiment of this application. Figure 5 Is with Figure 4 The corresponding state diagram of the fault crossing process. The following is combined with... Figure 4 and Figure 5 This section describes the detailed process of handling fault ride-through in a power supply system.

[0106] S410, in its initial state, the fault-crossing device detects the grid connection point voltage.

[0107] Specifically, the fault ride-through device can sample the three-phase voltage and current at the grid connection point according to a period T, and extract the positive-sequence, negative-sequence, and zero-sequence voltage components or the positive-sequence, negative-sequence, and zero-sequence current components. As an example, the sampling period T is 0.833 ms.

[0108] In its initial state, the inverter can output corresponding active or reactive power according to the dispatch instructions issued by the power grid. At the same time, the inverter can also sample its own output voltage to determine whether there are any abnormalities in its output voltage.

[0109] At time S411, T1, the power grid experiences a disturbance of a certain magnitude.

[0110] At time S412, T2, the fault ride-through control device determines that the grid connection point voltage is abnormal and sends a fault ride-through start command.

[0111] In a specific example, if the fault ride-through control device detects that the grid connection point voltage is higher than a first voltage threshold or lower than a second voltage threshold for a duration exceeding a preset time, it determines that the grid connection point voltage is abnormal and sends a fault ride-through start command to the inverter. This fault ride-through start command is used to indicate that the grid connection point voltage is abnormal, and can also be used to indicate the magnitude of the grid connection point voltage or the magnitude of the reactive current that needs to be output to the grid. If it is determined that the grid connection point voltage is not abnormal, the fault ride-through control device maintains normal operation, continuously monitoring the positive-sequence, negative-sequence, and zero-sequence voltages and currents at the grid connection point.

[0112] In some examples, the magnitude of reactive current is calculated by converting the difference between the reference voltage value and the measured voltage value at the grid connection point into an increment of reactive current (including positive and negative sequence). The reference voltage value can refer to the voltage at the grid connection point during normal operation.

[0113] Optionally, the process involves multiplying the percentage deviation between the voltage reference value and the measured voltage value by a pre-set constant coefficient K to obtain the percentage increment of the injected current during fault ride-through. The reactive current to be injected for voltage correction during fault ride-through is calculated in this manner.

[0114] In some examples, the fault-crossing control device can broadcast a fault-crossing start command over a southbound network.

[0115] At time S413 and T3, the inverter detects its own output voltage, determines that the output voltage of the inverter is abnormal, and starts the second fault ride-through mode.

[0116] In some examples, if the inverter detects an abnormal voltage, it will activate a second fault ride-through mode and output a second reactive current; otherwise, it will operate normally.

[0117] S414, the relay router receives the fault traversal start command sent by the fault traversal device and broadcasts it to its subordinate inverters.

[0118] At time S415 and T5, the inverter receives the fault ride-through start command and starts the first fault ride-through mode according to the fault ride-through start command.

[0119] In some examples, if the inverter receives a fault ride-through start command, it initiates the first fault ride-through mode according to the fault ride-through start command and outputs reactive current.

[0120] In some examples, the inverter can continue to detect its own output voltage and limit the upper limit of the output reactive current when the output voltage recovers above a certain value to prevent voltage recovery overshoot.

[0121] In some examples, if the inverter does not receive a fault ride-through command within a certain period of time and is currently in the second fault ride-through mode, the second fault ride-through mode needs to be canceled, the inverter needs to return to normal operation, and the power output setting value before the disturbance needs to be applied.

[0122] In some examples, the inverter does not activate the second fault ride-through mode and is in normal operation mode. However, if a fault ride-through start command is received, the first fault ride-through mode is activated, and reactive current is supplied to the grid according to the fault ride-through start command.

[0123] S416, repeat steps S411 to S415 according to the cycle until time T7 after multiple cycles, when the power grid disturbance or fault is cleared.

[0124] As one possible way to clear grid disturbances, some generator units and / or line faults are disconnected and taken out of operation.

[0125] At time S417 and T8, the fault ride-through control device determines that the grid connection point voltage has returned to normal and sends a fault ride-through release command to the inverter.

[0126] In some examples, the fault ride-through control device can issue a fault ride-through release command if any of the following conditions are met: 1. The fault ride-through control device detects that the grid connection point voltage has returned to the normal range; 2. The fault ride-through control device receives a fault ride-through release command from the superior power grid dispatching authority.

[0127] In some examples, the fault-crossing control device can broadcast a fault-crossing release command over the southbound network.

[0128] At time S418 and T9, the relay router receives the fault crossing clearance command and broadcasts the fault crossing clearance command to its subordinate inverters.

[0129] S419, the inverter cancels the fault ride-through mode and returns to the operating state before the fault, and the fault ride-through transient process ends.

[0130] In this embodiment, the fault ride-through control device takes the lead and the inverter cooperates. The fault ride-through control device analyzes the voltage and generates a fault ride-through command or a cancellation command, thereby reliably starting the fault ride-through mode and improving the reliability of fault ride-through.

[0131] In the embodiments of this application, the inverter coordinates with the fault ride-through control device. During the beginning and end stages of a fault disturbance, the inverter quickly suppresses the disturbance amplitude and prevents control overshoot through its own detection and action. During the disturbance, it follows the instructions of the fault ride-through control device, thus achieving both the timeliness and stability of the fault ride-through control.

[0132] As used in this specification, the terms "component," "module," "system," etc., are used to refer to computer-related entities, hardware, firmware, combinations of hardware and software, software, or software in execution. For example, a component can be, but is not limited to, a process running on a processor, a processor, an object, an executable file, an execution thread, a program, and / or a computer. As illustrated, applications running on computing devices and computing devices can both be components. One or more components may reside in a process and / or an execution thread, and components may be located on a single computer and / or distributed among two or more computers. Furthermore, these components can be executed from various computer-readable media on which various data structures are stored. Components can communicate, for example, via local and / or remote processes based on signals having one or more data packets (e.g., data from two components interacting with another component between a local system, a distributed system, and / or a network, such as the Internet interacting with other systems via signals).

[0133] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0134] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0135] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0136] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0137] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0138] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0139] The above description is merely a specific embodiment of this application, but the scope of protection of this application 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 this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A power supply system, characterized in that, include: An inverter is used to receive direct current (DC) output from a power generation module and, after converting the DC to alternating current (AC), outputs the electrical energy to the power grid through a grid connection point, which is a node that collects the electrical energy output from the power supply system. Fault ride-through control equipment is used for: Detect the voltage at the grid connection point; If an abnormal voltage is detected at the grid connection point, a fault ride-through start command is sent to the inverter. The fault ride-through start command is used to indicate that the voltage at the grid connection point is abnormal. The inverter is also used for: Receive the fault-crossing start command; According to the fault ride-through initiation command, the fault ride-through mode is executed, which includes outputting reactive current to the power grid, and the reactive current is used to correct the voltage at the grid connection point; The fault ride-through mode is the first fault ride-through mode, the reactive current is the first reactive current, and the inverter is further used for: Detect the output voltage of the inverter; In the event of an abnormal output voltage of the inverter, a second fault ride-through mode is executed. The second fault ride-through mode includes outputting a second reactive current to the grid, which is used to correct the voltage at the grid connection point. Determine whether the fault-crossing start command is received within a fourth preset time period after the second fault-crossing mode is started; The inverter is specifically used to: execute the first fault ride-through mode according to the fault ride-through start command when the fault ride-through start command is received within a fourth preset time period after the second fault ride-through mode is started; The inverter is also configured to: stop executing the second fault ride-through mode if it does not receive the fault ride-through start command within a fourth preset time period after starting to execute the second fault ride-through mode.

2. The system according to claim 1, characterized in that, The abnormal voltage at the grid connection point includes the following situations: The voltage at the grid connection point is higher than the first voltage threshold for a duration exceeding a first preset duration; or, The duration for which the voltage at the grid connection point is lower than the second voltage threshold exceeds the second preset duration, and the first voltage threshold is greater than the second voltage threshold.

3. The system according to claim 1, characterized in that, The fault ride-through start command is also used in the fault ride-through mode to instruct the inverter to adjust the magnitude of the reactive current according to the voltage of the grid connection point.

4. The system as described in claim 1, characterized in that, The fault ride-through start command is also used to indicate the magnitude of the reactive current, so that the inverter determines the magnitude of the reactive current according to the fault ride-through start command.

5. The system as described in claim 1, characterized in that, The fault ride-through control device is also used for: When the voltage at the grid connection point returns to normal, a fault ride-through release command is sent to the inverter. The fault ride-through release command is used to indicate that the voltage at the grid connection point has returned to normal. The inverter is also used for: Receive the fault crossing cancellation command; According to the fault crossing cancellation command, the execution of the fault crossing mode is stopped.

6. The system according to claim 5, characterized in that, Before the inverter receives the fault ride-through release command, the inverter is also configured to: Detect the output voltage of the inverter; If the output voltage of the inverter exceeds the fifth voltage threshold, the reactive current is controlled to be less than or equal to the first current upper limit value.

7. The system according to claim 5, characterized in that, The restoration of normal voltage at the grid connection point includes: The duration during which the voltage at the grid connection point is lower than the third voltage threshold and higher than the fourth voltage threshold is greater than the third preset duration.

8. The system according to claim 1, characterized in that, The fault ride-through control device is specifically used to sample and detect the voltage of the grid connection point according to a preset period.

9. The system according to claim 1, characterized in that, The system also includes a relay route, and the fault ride-through control device is specifically used to send the fault ride-through start command to the inverter through the relay route.

10. The system according to claim 1, characterized in that, The fault ride-through control device is a station-level controller.

11. The system according to any one of claims 1 to 10, characterized in that, The power supply system also includes a transformer unit, which receives the AC power output from the inverter and, after boosting the voltage, outputs the electrical energy to the grid connection point.

12. A control method for a power supply system, characterized in that, The power supply system includes an inverter and a fault ride-through control device, wherein: The inverter is used to receive the DC power output from the power generation module, and after converting the DC power into AC power, output the electrical energy to the power grid through the grid connection point, which refers to the node that collects the electrical energy output by the power supply system. The method includes: The fault ride-through control device detects the voltage at the grid connection point; When the fault ride-through control device detects an abnormal voltage at the grid connection point, it sends a fault ride-through start command to the inverter. The fault ride-through start command is used to indicate that the voltage at the grid connection point is abnormal. The inverter receives the fault ride-through start command; The inverter executes the fault ride-through mode according to the fault ride-through start command. The fault ride-through mode includes outputting reactive current to the grid, and the reactive current is used to correct the voltage at the grid connection point. The fault ride-through mode is a first fault ride-through mode, the reactive current is a first reactive current, and the method further includes: The inverter detects the output voltage of the inverter; When the inverter's output voltage becomes abnormal, the inverter executes a second fault ride-through mode, which includes outputting a second reactive current to the grid to correct the voltage at the grid connection point. The inverter determines whether it receives the fault ride-through start command within a fourth preset time period after starting to execute the second fault ride-through mode; The inverter executes the fault ride-through mode according to the fault ride-through start command, including: If the fault crossing start command is received within a fourth preset time period after the second fault crossing mode is started, the first fault crossing mode is executed according to the fault crossing start command; The method further includes: If the fault-traversal start command is not received within a fourth preset time period after the second fault-traversal mode is started, the execution of the second fault-traversal mode shall be stopped.

13. The method according to claim 12, characterized in that, The abnormal voltage at the grid connection point includes the following situations: The voltage at the grid connection point is higher than the first voltage threshold for a duration exceeding a first preset duration; or, The duration for which the voltage at the grid connection point is lower than the second voltage threshold exceeds the second preset duration, and the first voltage threshold is greater than the second voltage threshold.

14. The method according to claim 12, characterized in that, The fault ride-through start command is also used in the fault ride-through mode to instruct the inverter to adjust the magnitude of the reactive current according to the voltage of the grid connection point.

15. The method as described in claim 12, characterized in that, The fault ride-through start command is also used to indicate the magnitude of the reactive current, so that the inverter determines the magnitude of the reactive current according to the fault ride-through start command.

16. The method as described in claim 12, characterized in that, The method further includes: When the voltage at the grid connection point returns to normal, the fault ride-through control device sends a fault ride-through release command to the inverter. The fault ride-through release command is used to indicate that the voltage at the grid connection point has returned to normal. The inverter receives the fault ride-through release command; The inverter stops executing the fault ride-through mode according to the fault ride-through cancellation command.

17. The method according to claim 16, characterized in that, Before the inverter receives the fault ride-through release command, the method further includes: The inverter detects the output voltage of the inverter; When the inverter's output voltage exceeds a fifth voltage threshold, the inverter controls the reactive current to be less than or equal to a first current upper limit value.

18. The method according to claim 16, characterized in that, The restoration of normal voltage at the grid connection point includes: The duration during which the voltage at the grid connection point is lower than the third voltage threshold and higher than the fourth voltage threshold is greater than the third preset duration.

19. The method according to claim 12, characterized in that, The fault ride-through control device detects the voltage at the grid connection point, including: The fault ride-through device samples and detects the voltage at the grid connection point according to a preset cycle.

20. The method according to claim 12, characterized in that, The power supply system also includes a relay route. When the fault ride-through control device detects an abnormal voltage at the grid connection point, it sends a fault ride-through start command to the inverter, including: The fault ride-through control device sends the fault ride-through start command to the inverter through the relay route.

21. The method according to claim 12, characterized in that, The fault ride-through control device is a station-level controller.

22. The method according to any one of claims 12 to 21, characterized in that, The power supply system also includes a transformer unit, which receives the AC power output from the inverter and, after boosting the voltage, outputs the electrical energy to the grid connection point.

23. A fault ride-through control device for a power supply system, characterized in that, The fault-crossing control device is used to perform the method of any one of claims 12 to 22 performed by the fault-crossing control device.

24. An inverter for a power supply system, characterized in that, The inverter is used to perform the method performed by the inverter according to any one of claims 12 to 22.

Images