Electric power system, power converter, direct current control equipment and control method thereof

Abstract

The invention discloses a power system, a power converter, a DC control device and a control method thereof. According to the embodiment of the invention, the power system can respond to the received activation signal through the DC control device in the DC string, controls the DC control circuit to start according to the preset starting mode, and monitors the change degree index of the specified electrical parameter of the DC control device. And in response to the change degree index being greater than a preset change index threshold, executing a preset risk feedback action, the change degree index being used for indicating the change degree of a specified electrical parameter of the DC control device, and the preset risk feedback action being used for feeding back that the DC control device has a reverse connection risk to the power converter. On the basis, the direct current control equipment can be utilized to find or assist the power converter to find the reverse connection risk in the power system provided with the direct current control equipment, and the problem that in the related technology, due to the lack of continuous reverse current, the detection of the reverse connection risk fails is solved.

Description

Technical Field

[0001] This application relates to the field of power generation technology, and more specifically, to a power system, a power converter, a DC control device, and a control method thereof. Background Technology

[0002] In power systems, DC strings are installed, and these strings contain multiple DC control devices. If the DC strings or their control devices are reverse-connected, it will affect the system. At best, it will prevent the connected DC string from generating electricity normally; at worst, it will damage hardware in the power system (such as power converters). Therefore, detecting the risk of reverse connection of DC control devices and DC strings is crucial in power systems. Related technologies typically detect reverse connection of DC strings by detecting the presence of reverse current flowing through them.

[0003] However, with current grid connection regulations emphasizing the shutdown of DC components within DC strings, more and more power systems are adding DC control devices to these components. In power systems with DC control devices, when a DC string is reverse-connected, the presence of the control device will cause a hiccuping phenomenon in that DC string, preventing the generation of a continuous reverse current. Therefore, how to detect the reverse connection risk in power systems with DC control devices has become an urgent problem to be solved. Summary of the Invention

[0004] This application provides a power system, a power converter, a DC control device, and a control method thereof. The various aspects involved in this application's embodiments are described below.

[0005] In a first aspect, a power system is provided, comprising: a power converter, including a DC terminal, a DC conversion circuit, an inverter circuit, and an AC terminal connected in sequence; a DC string, including multiple DC control devices, each DC control device including a DC control circuit, the input terminal of each DC control device being connected to a DC power supply, the output terminal of each DC control device being connected in series to the DC terminal, and all the multiple DC control devices being communicatively connected to the power converter; the power converter being used to broadcast an activation signal to the DC control devices in the DC string; the DC control devices being used to: in response to receiving the activation signal, control the DC control circuit to start according to a preset start-up mode, monitor the degree of change of a specified electrical parameter of the DC control device, and in response to the degree of change index being greater than a preset change index threshold, execute a preset risk feedback action, wherein the degree of change index is used to indicate the degree of change of the specified electrical parameter of the DC control device, and the preset risk feedback action is used to feedback to the power converter that the DC control device has a reverse connection risk.

[0006] In some embodiments, the execution of the preset risk feedback action includes: sending a specified risk flag to the power converter and stopping power output, wherein the specified risk flag is used to indicate that there is a reverse connection risk in the DC control device; and the power converter is used to determine, in response to receiving the specified risk flag, that there is a reverse connection risk in the DC control device that sent the specified risk flag.

[0007] In some embodiments, the DC control device is a shutdown device, and the DC control circuit includes a first controllable switch connected between the input terminal and the output terminal of the shutdown device. The shutdown device controls the first controllable switch to open to stop the power output.

[0008] In some embodiments, the DC control device is an optimizer, the DC control circuit includes a switching circuit, and the optimizer stops providing a drive signal to the switching circuit to stop the power output.

[0009] In some embodiments, the power converter is configured to determine that the DC string is reverse-connected in response to the fact that the proportion of DC control devices sending the specified risk identifier to the plurality of DC control devices is greater than a preset proportion value.

[0010] In some embodiments, the DC control device is an optimizer, and the execution of the preset risk feedback action includes: controlling the output current of the DC control circuit to be less than or equal to a preset current value, and controlling the input voltage of the DC control circuit to be stable at a preset voltage value; the power converter is used to detect whether there is a reverse current and, in response to the presence of a reverse current, determine that the DC string is reverse-connected, wherein the reverse current is generated based on the control related to the output current of the DC control circuit in the preset risk feedback action executed by the DC control device.

[0011] In some embodiments, controlling the DC control circuit to start according to a preset start-up method includes: controlling the DC control circuit to start slowly, and during the slow start-up process, controlling the input voltage setpoint of the DC control circuit to the preset voltage value and controlling the output current setpoint of the DC control circuit to the preset current value.

[0012] In some embodiments, the power converter is further configured to stop sending the activation signal to the plurality of DC control devices within the DC string in response to the reverse connection of the DC string.

[0013] In some embodiments, the degree of change index of a specified electrical parameter of the DC control device includes one or more of the following indices: a first degree of change index indicating the magnitude of the decrease in the input voltage of the DC control device within a preset duration after the DC control device receives the activation signal; a second degree of change index indicating the magnitude of the decrease in the output voltage of the DC control device within a preset duration after the DC control device receives the activation signal; and a third degree of change index indicating the magnitude of the increase in the output current of the DC control device within a preset duration after the DC control device receives the activation signal.

[0014] In a second aspect, a power converter is provided, comprising a DC terminal, a DC conversion circuit, an inverter circuit, and an AC terminal connected in sequence. The power converter is used for communication connection with multiple DC control devices in a DC string. The input terminal of each DC control device is used for connection to a DC power supply, and the output terminal of each DC control device is connected in series to the DC terminal. Each DC control device includes a DC control circuit. The power converter is configured to: broadcast an activation signal to the DC control devices in the DC string; wherein, when the activation signal is received by the DC control device, the DC control device is used to: control the DC control circuit to start according to a preset start-up mode, monitor the degree of change of a specified electrical parameter of the DC control device, and execute a preset risk feedback action when the degree of change index is greater than a preset change index threshold. The degree of change index is used to indicate the degree of change of the specified electrical parameter of the DC control device, and the preset risk feedback action is used to feedback to the power converter that the DC control device has a reverse connection risk.

[0015] Thirdly, a DC control device is provided, located within a DC string and communicatively connected to a power converter. The power converter includes a DC terminal, a DC conversion circuit, an inverter circuit, and an AC terminal connected in sequence. The input terminal of the DC control device is connected to a DC power supply, and the output terminal is connected to the DC terminal. The DC control device includes a DC control circuit and is configured to: in response to receiving an activation signal from the power converter, control the DC control circuit to start according to a preset startup mode; monitor the degree of change of a specified electrical parameter of the DC control device; and in response to the degree of change index exceeding a preset threshold, execute a preset risk feedback action. The degree of change index indicates the degree of change of the specified electrical parameter of the DC control device, and the preset risk feedback action provides feedback to the power converter that the DC control device has a reverse connection risk.

[0016] Fourthly, a control method for a power system is provided. The power system includes a power converter and a DC string. The power converter includes a DC terminal, a DC conversion circuit, an inverter circuit, and an AC terminal connected in sequence. The DC string includes multiple DC control devices, each DC control device including a DC control circuit. The input terminal of each DC control device is connected to a DC power supply, and the output terminal of each DC control device is connected in series to the DC terminal. All the multiple DC control devices are communicatively connected to the power converter. The control method includes: controlling the power converter to broadcast an activation signal to the DC control devices in the DC string; controlling the DC control devices to perform the following operations: in response to receiving the activation signal, controlling the DC control circuit to start according to a preset startup mode, monitoring the degree of change of a specified electrical parameter of the DC control device, and in response to the degree of change index being greater than a preset change index threshold, executing a preset risk feedback action; wherein the degree of change index is used to indicate the degree of change of the specified electrical parameter of the DC control device, and the preset risk feedback action is used to feedback to the power converter that the DC control device has a reverse connection risk.

[0017] Fifthly, a control method for a power converter is provided. The power converter includes a DC terminal, a DC conversion circuit, an inverter circuit, and an AC terminal connected in sequence. The power converter is used for communication connection with multiple DC control devices in a DC string. The input terminal of each DC control device is used to connect to a DC power supply, and the output terminal of each DC control device is connected in series to the DC terminal. Each DC control device includes a DC control circuit. The control method includes: broadcasting an activation signal to the DC control devices in the DC string; wherein, when the activation signal is received by the DC control device, the DC control device is used to: control the DC control circuit to start according to a preset start-up mode, monitor the degree of change of a specified electrical parameter of the DC control device, and execute a preset risk feedback action when the degree of change index is greater than a preset change index threshold. The degree of change index is used to indicate the degree of change of the specified electrical parameter of the DC control device, and the preset risk feedback action is used to feedback to the power converter that the DC control device has a reverse connection risk.

[0018] Sixthly, a control method for a DC control device is provided. The DC control device is located within a DC string and is communicatively connected to a power converter. The power converter includes a DC terminal, a DC conversion circuit, an inverter circuit, and an AC terminal connected in sequence. The input terminal of the DC control device is connected to a DC power supply, and the output terminal of the DC control device is connected to the DC terminal. The DC control device includes a DC control circuit. The control method includes: responding to receiving an activation signal sent by the power converter, controlling the DC control circuit to start according to a preset startup mode; monitoring the degree of change of a specified electrical parameter of the DC control device; and responding to the degree of change index being greater than a preset change index threshold, executing a preset risk feedback action. The degree of change index is used to indicate the degree of change of the specified electrical parameter of the DC control device, and the preset risk feedback action is used to feedback to the power converter that the DC control device has a reverse connection risk.

[0019] In this embodiment, the power system can utilize a DC control device within a DC string to respond to an activation signal. This device controls the DC control circuit to start according to a preset startup method, monitors the degree of change of a specified electrical parameter of the DC control device, and executes a preset risk feedback action if the degree of change exceeds a preset threshold. The degree of change indicator indicates the extent of change of the specified electrical parameter of the DC control device, and the preset risk feedback action provides feedback to the power converter that the DC control device poses a reverse connection risk. This facilitates the use of DC control devices to detect or assist power converters in detecting reverse connection risks in power systems with installed DC control devices, overcoming the problem of detection failure due to the lack of continuous reverse current in related technologies. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of a power system in related technologies.

[0021] Figure 2 This is a schematic diagram of the structure of a power system provided in an embodiment of this application.

[0022] Figure 3 This is a schematic diagram of the structure of the shut-off device provided in the embodiments of this application.

[0023] Figure 4 This is a schematic diagram of the optimizer provided in the embodiments of this application.

[0024] Figure 5 yes Figure 4 The control block diagram of the optimizer in the diagram.

[0025] Figure 6This is a schematic diagram illustrating the changing characteristics of the electrical signal of the switch provided in the embodiments of this application.

[0026] Figure 7 This is a schematic diagram illustrating the changing characteristics of the electrical signal of the optimizer provided in the embodiments of this application.

[0027] Figure 8 This is a flowchart illustrating the fault detection method for a power system provided in an embodiment of this application. Detailed Implementation

[0028] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present application should fall within the scope of protection of the present application.

[0029] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0030] Power systems (such as photovoltaic power generation systems) are devices that convert new energy sources (such as solar energy) into direct current (DC) and then perform bidirectional power conversion between DC and alternating current (AC). They can be connected to the grid or supply power to AC loads. During the installation of power systems, wiring errors are inevitable, and a DC string (such as a photovoltaic string) may be reverse-connected. If a power system with a reverse-connected DC string is put into operation after installation, it will have adverse effects on the system. At best, it will prevent the connected DC string from generating electricity normally; at worst, it will damage the hardware in the power system (such as the power converter). For example, a reverse connection will cause reverse current to flow into the power converter, and a large reverse current over a long period of time may cause irreversible hardware damage to the power converter. Furthermore, a large reverse current can cause severe overheating and lead to accidental fires. Therefore, the detection of reverse connection risks in power systems is crucial.

[0031] Power systems typically include power converters and at least one DC string. In related technologies, the presence of reverse current in the DC string is usually detected by the power converter to determine if the DC string is reverse-connected. For ease of understanding, the following section will combine... Figure 1 This will be illustrated by example. Figure 1The diagram shows the flow of DC current generated by each DC string in the power system when the first DC string is reverse-connected. It should be understood that... Figure 1 The example described uses at least one DC string in the power system 100 as two DC strings, namely the first DC string 121 and the second DC string 122. However, this application does not limit the specific number of at least one DC string, which can be set as needed.

[0032] like Figure 1 As shown, the first DC string 121 and the second DC string 122 are connected in parallel to the DC terminal of the power converter 110. A DC string may include one or more DC modules. The DC modules may be photovoltaic modules (or photovoltaic panels), and each DC module may consist of multiple photovoltaic cells. PVn+ represents the positive terminal of the nth DC string, and PVn- represents the negative terminal of the nth DC string.

[0033] When the DC component generates DC current, the DC current flows out from PVn+ and enters the DC terminal of the power converter 110, finally flowing into PVn-, thus completing the current loop. Under normal circumstances, PVn+ is connected to the positive DC bus BUS+, and PVn- is connected to the negative DC bus BUS-. In the event of a reverse connection, PVn+ is connected to the negative DC bus BUS-, and PVn- is connected to the positive DC bus BUS+.

[0034] exist Figure 1 In the diagram, the first DC string 121 is a reverse-connected DC string, and the second DC string 122 is a positive-connected DC string. Therefore, PV1+ is connected to the negative DC bus BUS- terminal, PV1- is connected to the positive DC bus BUS+ terminal, PV2+ is connected to the positive DC bus BUS+ terminal, and PV2- is connected to the negative DC bus BUS- terminal. Figure 1 It can be seen that the current generated in the first DC string 121 flows in the opposite direction to the current generated in the second DC string 122, and the current generated in the first DC string 121 is a reverse current. Based on this, the risk of reverse connection in the first DC string 121 can be determined by detecting the reverse current in the first DC string 121.

[0035] However, with current grid connection regulations emphasizing the shutdown of DC components, more and more power systems are adding DC control equipment to their DC components. In power systems with DC control equipment, when a DC string is reverse-connected, the presence of the DC control equipment will cause the DC string to hiccup, resulting in a lack of continuous current.

[0036] This is because DC control equipment relies on the DC power from its corresponding DC components to operate. Therefore, to ensure the normal operation of the DC control equipment, the voltage of the DC components must be greater than or equal to the operating voltage required by the DC control equipment (for example, the operating voltage required by the DC control equipment might be 12V). However, in a power system with DC control equipment installed, if a DC string is reverse-connected, it is equivalent to short-circuiting that DC string. Based on this, if the DC control equipment is activated to connect that DC string to the power converter for power conversion, the voltage of that DC string drops to 0V due to the short circuit. The DC control equipment within that DC string will then lose power, reset, and shut down, causing the DC components corresponding to each DC control equipment to disconnect from the DC string, restoring the voltage to the open-circuit voltage, allowing the DC control equipment to power on again and enter standby mode. At this point, the DC control equipment within that DC string receives an activation signal from the component-level management controller again, and the DC control equipment will reactivate and conduct, causing the voltage of that DC string to drop to 0V again, thus repeating this cycle of restarting and shutting down.

[0037] During the repeated restarting and hiccuping process, the time for gaining operating power (i.e., powering off) is short (e.g., less than 10ms), while the time for losing operating power (i.e., powering on, entering standby, and activating) is long (e.g., more than 1s). Therefore, the effective value of the overall continuous current of the reverse-connected DC string is very low, equivalent to not generating a continuous reverse current. Thus, the power converter cannot detect the risk of reverse connection of the DC string by the reverse current.

[0038] In summary, how to detect reverse connection risks in power systems with DC control equipment has become an urgent problem to be solved.

[0039] Through research on power systems equipped with components and controllers, the inventors discovered that in such power systems, although the reverse-connected DC strings do not generate continuous reverse current, the specified electrical parameters of the DC control devices in the reverse-connected DC strings exhibit unique changing characteristics when activated by an activation signal sent by a power converter (which has an internal component-level management controller (or MLPE master node)). Specifically, when the DC control devices in the reverse-connected DC strings are activated by an activation signal sent by the power converter, the changing characteristics of the specified electrical parameters of the DC control devices in the reverse-connected DC strings include one or more of the following: the input voltage on the DC control devices in the reverse-connected DC strings drops sharply, the output voltage on the DC control devices in the reverse-connected DC strings drops sharply, and the output current and voltage on the DC control devices in the reverse-connected DC strings increase.

[0040] In view of this discovery, embodiments of this application provide a power system in which a power converter can send activation signals to multiple DC control devices in a DC string. Upon receiving the activation signal, the DC control devices control a DC control circuit to start according to a preset startup mode, monitor the degree of change of a specified electrical parameter of the DC control device, and execute a preset risk feedback action if the degree of change index exceeds a preset threshold. The degree of change index indicates the degree of change of the specified electrical parameter of the DC control device, and the preset risk feedback action provides feedback to the power converter that the DC control device has a reverse connection risk. Based on this, it is advantageous to use the DC control device and the degree of change index of its specified electrical parameter to detect or assist the power converter in detecting reverse connection risks in power systems with installed DC control devices, overcoming the problem of detection failure due to the lack of continuous reverse current in related technologies.

[0041] To make it easier to understand, the following will be combined with... Figure 2 The power system provided in the embodiments of this application will be described in detail. For example... Figure 2 As shown, the power system includes a power converter 210 and a DC string 220.

[0042] The power converter 210 may include a DC terminal, a DC-DC conversion circuit, an inverter circuit, and an AC terminal. The DC terminal is used to connect to a DC power source, and the AC terminal is used to connect to the power grid or an AC load. The DC power source includes at least one photovoltaic panel. Optionally, the DC power source may also include a battery. The power converter 210 can be used to convert the DC power generated by the DC power source into AC power for use by the power grid or an AC load. Alternatively, the power converter 210 can also be used to convert AC power from the power grid into DC power for use by a DC load or a battery. The DC terminal of the power converter 210 may include one or more input ports, which may be photovoltaic (PV) ports or maximum power point tracking (MPPT) ports.

[0043] In some embodiments, the DC-DC conversion circuit may be m Boost converters (e.g., Boost converters) included within the power converter 210. Figure 2 (As shown), m is a positive integer greater than or equal to 1. Each Boost converter has one input port, which can also be called an MPPT port. Each MPPT port can be divided into multiple parallel PV ports inside the power converter 210, or each MPPT port can directly become a PV port inside the power converter 210. Each PV port can be connected to a DC string, or connected to two parallel DC strings through a bus terminal.

[0044] It should be noted that the number of photovoltaic modules in different DC strings connected to the same system can vary. If the DC end is an MPPT port, the series and parallel connection methods of DC strings connected to different MPPT ports are allowed to be inconsistent, and the power of the DC modules is also allowed to be inconsistent.

[0045] The number of DC strings 220 is one or more. That is, a power system can be connected to at least one DC string 220. For any one DC string in at least one DC string, it may include multiple DC components and multiple DC control devices. For example, in Figure 2 In this context, at least one DC string specifically includes a first DC string 211 to a k-th DC string 21k, where K is greater than or equal to 2, and each DC string can contain multiple DC components. Figure 2 The DC components in each DC string are numbered 1 to n, and each DC component is associated with a DC control device. The input terminals of the multiple DC control devices in each DC string are connected one-to-one with the multiple DC components. Figure 2 The output terminals of DC control devices 1 to n are connected in series to the DC terminal of power converter 210. That is, the positive output terminal of any DC control device is connected to the negative output terminal of the previous DC control device, and the negative output terminal of the DC control device is connected to the positive output terminal of the next DC control device, and finally connected to a DC terminal of power converter 210.

[0046] The power system 200 equipped with DC control equipment can also be called a power system equipped with an intelligent monitoring system. The DC control equipment can monitor the corresponding DC components and report the abnormality to the MLPE master node (or power converter 210) or actively execute the circuit breaker control of the DC control equipment to avoid the danger caused by the abnormality.

[0047] In this embodiment, the DC control device is a module-level power electronic device (MLPE). The DC control device can independently monitor, safely shut down, or fault-protect the corresponding DC module. It can collect electrical signals such as voltage and current from the corresponding DC module and transmit the data to the power converter 210 via a communication link. The DC control device may include a DC control circuit and a controller, which work together to monitor, regulate, and protect the electrical energy of the DC module. The DC control circuit, as a power execution unit, directly processes the main circuit's electrical energy; the controller, as an intelligent decision-making unit, generates control signals and manages the operating logic. This embodiment does not specifically limit the type of DC control device. For example, the DC control device can be a shutdown device, capable of module-level rapid shutdown to meet fire safety regulations. Alternatively, the DC control device can be an optimizer, capable of power optimization and rapid shutdown, improving power generation efficiency based on a module-level maximum power point tracking (MLPE-MPPT) algorithm and enabling remote shutdown.

[0048] The power converter 210 is communicatively connected to multiple DC control devices within each DC string in at least one DC string; in other words, the power converter 210 can communicate with all DC control devices in all DC strings of the power system 200. For example, the power converter 210 communicates with the DC control devices via power line communication (PLC). PLC communication uses power lines as the transmission channel to transmit analog or digital signals at high speed via carrier waves, and can be widely used in photovoltaic power generation systems equipped with intelligent monitoring systems. This communication method does not require rewiring, utilizes power lines, is easy to deploy, has a short construction period, low cost, high reliability, and the communication rate meets system requirements, providing a low-cost data communication platform for the power system 200.

[0049] The power converter 210 is used to manage all DC control devices in at least one DC string in the power system 200. For example, the power converter 210 can broadcast activation signals to all DC control devices in all DC strings in the power system 200. Alternatively, the power converter 210 can stop sending activation signals to all DC control devices in a faulty DC string.

[0050] The DC control device is configured to control the power transmission of the corresponding DC component to the power converter 210 based on the activation signal sent by the power converter 210. In other words, the DC control device does not continuously allow the corresponding DC component to generate and transmit power; it waits until the power converter 210 sends an activation signal and the DC control device receives the signal before allowing or regulating the corresponding DC component to generate power and transmit it to the power converter 210. If the DC control device does not receive an activation signal, it will remain in standby, off, or low-power state to prevent power transmission to the power converter 210.

[0051] In this embodiment of the application, the DC string in the power system includes multiple DC control devices. The power converter 210 is used (or configured to) broadcast an activation signal to the multiple DC control devices in the DC string. The DC control devices are used to: in response to receiving the activation signal, control the DC control circuit to start according to a preset start-up mode, monitor the degree of change of a specified electrical parameter of the DC control device, and in response to the degree of change index being greater than a preset change index threshold, execute a preset risk feedback action.

[0052] The preset startup method can be predetermined by the DC control device based on the type of its internal DC control circuit; however, this application does not specifically limit this. For example, when the DC control device is a shut-off device, its internal DC control circuit may include a controllable switch for startup, and the preset startup method may be to directly close the switch to directly start the DC control circuit. As another example, when the DC control device is an optimizer, its internal DC control circuit may include a switching circuit for startup, and the preset startup method may be to control the switching circuit to start slowly, thereby starting the DC control circuit. The switching circuit can be understood as a switching circuit formed by two or more controllable switches, and a slow startup can be achieved by providing a drive signal to the switching circuit.

[0053] The degree of change index is used to indicate the degree of change of a specified electrical parameter of a DC control device. The specified electrical parameter of the DC control device can be, for example, one or more of the following: the output voltage of the DC control device, the input voltage of the DC control device, and the output current of the DC control device. Specifically, the degree of change index can be used to indicate the degree of change of the specified electrical parameter of the DC control device within a preset time period after the DC control device receives an activation signal.

[0054] The preset risk feedback action is a pre-defined control action in the DC control equipment. This action is only executed when the change in a specified electrical parameter of the DC control equipment exceeds a preset threshold. The preset risk feedback action is used to report a reverse connection risk to the power converter.

[0055] In the power system provided in this application embodiment, the power converter can send activation signals to multiple DC control devices in the DC string. Upon receiving the activation signal, the DC control device controls the DC control circuit to start according to a preset startup mode, monitors the degree of change of a specified electrical parameter of the DC control device, and executes a preset risk feedback action if the degree of change exceeds a preset threshold. Based on this, it is beneficial to use the DC control device and the degree of change of its specified electrical parameters to discover or assist the power converter in discovering the reverse connection risk in the power system with the DC control device installed, overcoming the problem of detection failure of reverse connection risk due to lack of continuous reverse current in related technologies.

[0056] The embodiments of this application do not specifically limit the preset risk feedback action. For example, the preset risk feedback action may be to send some indication signals to the power converter to feedback that there may be a reverse connection risk. Alternatively, the preset risk feedback action may be to change the electrical parameters of the DC control device itself, so as to provide feedback on the possible reverse connection risk through the detectability of the change in the output of its own electrical parameters.

[0057] As an example, performing a preset risk feedback action may include: sending a specified risk flag to the power converter and stopping power output. The specified risk flag can be understood as an indication signal used to indicate that the DC control device has a reverse connection risk. Based on this, the power converter can determine the reverse connection risk in the following specific way: the power converter, in response to receiving the specified risk flag, determines that the DC control device that sent the risk flag has a reverse connection risk.

[0058] Among them, the DC control equipment includes stopping power output during the execution of preset risk feedback actions. This is to prevent the reverse connection risk from lowering the input voltage of the DC control equipment and causing the auxiliary power source to fail when a reverse connection risk is detected in the DC control equipment, thereby avoiding the hiccup phenomenon mentioned above.

[0059] This embodiment of the application, by specifically configuring the DC control device to send a designated risk flag and stop power output to the power converter and execute a preset risk feedback action, can not only promptly avoid auxiliary power failure caused by reverse connection risk, but also directly feed back the reverse connection risk to the power converter through the DC control device. Furthermore, it reduces the control logic required by the power converter to determine the reverse connection risk, thus simplifying the implementation and reducing costs. In addition, this method can specify the control granularity of reverse connection risk to the DC control device, thereby enabling more timely detection of reverse connection risks and preventing damage to the power system.

[0060] In some embodiments, the power converter can also determine whether the DC string is reverse-connected based on a specified risk flag. Specifically, the power converter can determine that the DC string is reverse-connected in response to the proportion of DC control devices sending the specified risk flag to multiple DC control devices in the DC string (i.e., all DC control devices in the DC string) being greater than a preset proportion value. The preset proportion value can be determined as needed; for example, it can be 50%. Therefore, the reverse-connection detection scheme provided in this application embodiment is equivalent to the power converter determining that the DC string has a reverse-connection risk only when the DC controllers in the DC string exceeding the preset proportion value return the specified risk flag to the power converter after receiving an activation signal.

[0061] This method of determining the reverse connection risk of DC strings avoids false detections of reverse connection risks caused by defects in individual DC components, thereby further improving the detection accuracy of reverse connection risks of DC strings.

[0062] This application does not specifically limit the method by which the DC control device stops power output. The method by which the DC control device stops power output is related to the type of DC control device and its internal DC control circuitry.

[0063] As an example, DC control equipment is Figure 3 The switch shown includes a DC control circuit comprising a first controllable switch Q1 connected between the input and output terminals of the switch. The input terminal of the switch is used to connect to a DC power supply; therefore, the first controllable switch Q1 controls the on / off state between the DC power supply and the switch. Based on this, the switch can control the first controllable switch Q1 to open, thereby stopping power output.

[0064] This application does not specifically limit the type of the first controllable switch Q1. As an example, the first controllable switch Q1 is a semiconductor switch. For example, the first controllable switch Q1 can be any of the following switches: MOSFET switch, GaNFET switch, GaN HEMT switch, or SiC MOSFET switch.

[0065] By controlling the power output of the shutdown device in this way, the response speed of stopping power output can be improved, so that the power output of the shutdown device can be cut off as soon as a specified risk indicator is generated, thus avoiding the auxiliary power source being pulled down.

[0066] As yet another example, the DC control device is as follows: Figure 4 The optimizer is shown. The optimizer's power supply is the connected DC component, and it needs to track the maximum power point voltage of the DC component; therefore, the outer loop of the input voltage is sampled. In some embodiments, the optimizer's control block diagram can be as follows: Figure 5As shown, it includes an outer voltage loop and an inner current loop. Both the outer voltage loop and the inner current loop of the optimizer are PI controllers.

[0067] The optimizer's functional background includes: 1) The optimizer uses the corresponding DC component as a power source, and its output can serve as the input voltage support for the power converter. 2) Within its own capabilities, the optimizer can control its input voltage to reach any value. 3) The optimizer has its own MPPT algorithm to track the maximum power point. The optimizer achieves the above functions by: 1) Performing input voltage closed-loop control to ensure the input voltage remains consistent with the input voltage setpoint. 2) Performing maximum power point tracking, tracking the maximum power point according to the power converter implementation method, and using the tracked voltage value as the input voltage setpoint for input voltage closed-loop control.

[0068] See details Figure 4 The DC control circuit in the optimizer includes a switching circuit. The switching circuit can be used to control whether the corresponding DC component outputs power, and also to allow the optimizer to transfer the power from the corresponding DC component to the power converter according to the maximum power point tracking algorithm. For example... Figure 4 As shown, the switching circuit may include a second controllable switch Q2, a third controllable switch Q3, and a fourth controllable switch Q4. One end of the second controllable switch Q2 is connected to one end of the corresponding DC component, and the other end is connected to an inductor L in series. f and inductor L plc Between the optimizer's output terminal (i.e., the DC control device's output terminal) and the second controllable switch Q2, the second controllable switch Q2 controls whether the power from the corresponding DC component is transferred to the optimizer's output terminal. One end of the third controllable switch Q3 is connected to the other end of the second controllable switch Q2, and the other end of the third controllable switch Q3 is connected to the other end of the DC component. As the core switch for the optimizer's boost converter, the switching action of the third controllable switch Q3 directly determines the inductance L. f Current variation and optimizer output voltage V out The adjustment of inductance L. f The current in the circuit is the output current of the optimizer. One end of the fourth controllable switch Q4 is connected to the inductor L. f and inductor L plcOne end is connected to the other end of the DC component. The fourth controllable switch Q4 is a synchronous rectifier diode, and its drive signal is usually automatically generated by the self-driven chip based on the state of the third controllable switch Q3, thus requiring no software intervention. As a synchronous rectifier MOSFET and freewheeling diode, the fourth controllable switch Q4 provides a freewheeling path when the third controllable switch Q3 is turned off. This provides a temporary, low-impedance loop for the current in the inductor, allowing it to continue flowing instead of being abruptly interrupted when the third controllable switch Q3 is suddenly turned off. Based on this, the optimizer can stop providing drive signals to the switching circuit to stop power output. In other words, when the optimizer generates a specified risk indicator, it can perform waveform blocking control on the switching circuit within the optimizer to stop power output.

[0069] By controlling the optimizer to stop power output in this way, the response speed of stopping power output can be improved, so as to cut off the optimizer's power output as soon as the optimizer generates a specified risk indicator, and avoid the auxiliary source being pulled down.

[0070] As mentioned earlier, the preset risk feedback action can be to change the electrical parameters of the DC control device itself, so as to provide detectable feedback on the potential reverse connection risk through the change in the output of its own electrical parameters. As an example, if the DC control device is an optimizer, the preset risk feedback action performed by the DC control device includes: controlling the output current of the DC control circuit to be less than or equal to a preset current value, and controlling the input voltage of the DC control circuit to stabilize at a preset voltage value. It should be understood that the prerequisite for the DC control device to perform the preset risk feedback action is that the degree of change of a specified electrical parameter of the DC control device is greater than a preset change threshold. At this point, it is equivalent to the DC control device determining that the DC component it is connected to has a reverse connection risk. Based on this, controlling the input voltage of the DC control circuit to stabilize at the preset voltage value can be achieved by, during the soft start-up process of the DC control circuit, controlling the duty cycle of the DC control circuit to not increase when the input voltage drops to the preset voltage value, thus ensuring that the input voltage stabilizes at the preset voltage value. One way to control the output current of the DC control circuit to be less than or equal to the preset current value is to reduce the duty cycle of the DC control circuit when the output current of the DC control circuit is pulled up to exceed the preset current value due to the risk of reverse connection during the soft start-up process of the DC control circuit, until the output current of the DC control circuit does not exceed the preset current value.

[0071] The preset current or voltage value can be set according to requirements. The preset current value is used to limit excessive reverse current while ensuring that the subsequent power converter can detect the reverse current. For example, the preset current value is 3A. The preset voltage value is used to prevent the auxiliary power source from failing due to a power failure of the DC control equipment. For example, the preset voltage value can be 85% of the open-circuit input voltage of the DC control equipment.

[0072] Based on the aforementioned preset risk feedback action performed by the DC control device, in this embodiment, the power converter is used to detect whether a reverse current exists and, in response to the presence of a reverse current, determines that the DC string is reverse-connected. The reverse current is generated based on the control related to the output current of the DC control circuit during the preset risk feedback action performed by the DC control device. Alternatively, the preset risk feedback action performed by the DC control device includes controlling the output current of the DC control circuit to be less than or equal to a preset current value, during which a corresponding reverse current can be generated within the DC string, and the power converter can detect this reverse current.

[0073] By setting the preset risk feedback action executed by the optimizer to control the output current and input voltage of the DC control circuit within it to preset current and voltage values ​​respectively, it can help generate a reverse current that can be detected by the power converter. This can overcome the problem of failure to detect reverse connection risk caused by the lack of stable reverse current, and further improve the detection accuracy of reverse connection risk of DC string.

[0074] In some embodiments, the optimizer performs a preset risk feedback action: controlling the output current and input voltage of its internal DC control circuit to preset current and voltage values, respectively, during the startup process of the DC control circuit in the optimizer according to a preset startup mode. Specifically, controlling the DC control circuit to start according to the preset startup mode may include: controlling the DC control circuit to start slowly, and during the slow startup process, controlling the input voltage setpoint of the DC control circuit to a preset voltage value and controlling the output current setpoint (or inductor current limit setpoint) of the DC control circuit to a preset current value.

[0075] To further enhance power system security, in some embodiments, the power converter is also configured to stop sending activation signals to multiple DC control devices within the DC string in response to reverse connection of the DC string. In other words, once the power converter determines that there is a risk of reverse connection in the DC string, it will no longer activate any DC control devices within the DC string. This method provides protection without affecting the power generation of other normal DC strings, ensuring the robustness of photovoltaic power generation.

[0076] Optionally, the power converter is also configured to send a reverse connection warning signal to the user to provide a warning to the user that the first DC string in the power system is reverse connected, thereby facilitating the user to perform maintenance as soon as possible and further improving the safety of the power system.

[0077] As mentioned above, the degree of change index can specifically be used to indicate the degree of change of a specified electrical parameter of the DC control device within a preset duration after the DC control device receives the activation signal. Furthermore, the specified electrical parameter of the DC control device can be, for example, one or more of the following: the output voltage of the DC control device, the input voltage of the DC control device, and the output current of the DC control device. Based on this, in some embodiments, the degree of change index of the specified electrical parameter of the DC control device includes one or more of the following indices: a first degree of change index for indicating the magnitude of the decrease in the input voltage of the DC control device within the preset duration after the DC control device receives the activation signal; a second degree of change index for indicating the magnitude of the decrease in the output voltage of the DC control device within the preset duration after the DC control device receives the activation signal; and a third degree of change index for indicating the magnitude of the increase in the output current of the DC control device within the preset duration after the DC control device receives the activation signal.

[0078] As an example, the degree of change index of a specified electrical parameter of a DC control device includes a first degree of change index. Based on this, the DC control device is specifically configured to: execute a preset risk feedback action in response to the first degree of change index being greater than a first preset change index threshold; otherwise, not execute the preset risk feedback action.

[0079] As another example, the variation index of a specified electrical parameter of the DC control device includes a second variation index. Based on this, the DC control device is specifically configured to: execute a preset risk feedback action in response to the second variation index being greater than a second preset variation index threshold; otherwise, not execute the preset risk feedback action.

[0080] As another example, the variation index of the specified electrical parameters of the DC control device includes a third variation index. Based on this, the DC control device is specifically configured as follows: in response to the third variation index being greater than a third preset variation index threshold, a preset risk feedback action is executed; otherwise, the preset risk feedback action is not executed.

[0081] As another example, the variation index of a specified electrical parameter of a DC control device includes a first variation index and a second variation index. Based on this, the DC control device is specifically configured to: execute a preset risk feedback action in response to the first variation index being greater than a first preset variation index threshold, and the third variation index being greater than a third preset variation index threshold; otherwise, not execute the preset risk feedback action. By determining whether to execute the preset risk feedback action based simultaneously on the variation characteristics of the input voltage and output current of the DC control device, the detection accuracy of reverse connection risk can be further improved.

[0082] As another example, the variation index of specified electrical parameters of the DC control device includes a first variation index, a second variation index, and a third variation index. Based on this, the DC control device is specifically configured as follows: in response to the first variation index being greater than a first preset variation index threshold, the second variation index being greater than a second preset variation index threshold, and the third variation index being greater than a third preset variation index threshold, a preset risk feedback action is executed; otherwise, the preset risk feedback action is not executed. By simultaneously determining whether to execute the preset risk feedback action based on the variation characteristics of the DC control device's input voltage, output voltage, and output current, the detection accuracy of reverse connection risk can be further improved.

[0083] In this embodiment, both the first and second preset change index thresholds are preset voltage thresholds, and these thresholds can be different. The third preset change index threshold can be a preset current threshold. This application does not specifically limit the first, second, or third preset change index thresholds, as long as they reflect an electrical signal change value corresponding to the risk of reverse connection of the DC string in the DC control equipment.

[0084] To facilitate understanding, the following example 1 illustrates the control strategy for detecting reverse connection risk in a power system when the DC control device is a shutdown device.

[0085] Example 1: The control strategy for detecting reverse connection risk in a power system when the DC control device is a switch-off device includes the following three steps.

[0086] First, the master node broadcasts the activation of all shutdown devices in that frequency band.

[0087] Second, at the instant the master node broadcasts the activation of the shutdown device (this instant can be understood as the preset time within which the shutdown device receives the activation signal), if a DC string is reverse-connected, the electrical signal change characteristics of the shutdown device within it will be as follows: the input and output voltages of the shutdown device will drop sharply, and the output current of the shutdown device will increase. The shutdown device will then consider that the PV string may be reverse-connected, actively report a reverse connection warning to the master node, and immediately control the first switch in the shutdown device to turn off, preventing the input voltage of the shutdown device from being pulled down and causing the auxiliary power supply to fail. The electrical signal change characteristics of the shutdown device are, for example, as follows: Figure 6 As shown.

[0088] Third, once the power converter master node detects that a certain percentage (e.g., more than 50%) of the shutdown devices in a DC string report a reverse connection warning, it will no longer activate all shutdown devices under the corresponding BOOST of that DC string, and will also issue a warning to the user.

[0089] To facilitate understanding, the following examples 2 and 3 illustrate the control strategy for detecting reverse connection risk in a power system when the DC control device is an optimizer.

[0090] Example 2: The control strategy for detecting reverse connection risk in the power system when the DC control device is an optimizer includes the following three steps.

[0091] First, the master node broadcasts and activates all optimizers for that frequency band.

[0092] Second, the moment the master node broadcasts the activation of the optimizer, the optimizer begins a slow start (duty cycle starts from 0% and continues until the voltage limit is reached). During this process, if one of the DC components or DC strings is reverse-connected, i.e., the DC string corresponding to that component is short-circuited, as the optimizer's slow start duty cycle increases, the optimizer's electrical signal characteristics change as follows: the optimizer's input voltage drops sharply, and the optimizer's output current increases. At this point, it is considered that the DC string may be reverse-connected, and a reverse connection warning is actively reported to the master node. Simultaneously, the optimizer corresponding to that DC string is immediately blocked to prevent the optimizer's input voltage from being pulled down, causing the auxiliary power source to fail. The characteristics of the optimizer's electrical signal change are, for example, similar to... Figure 6 Similar. The difference is that the output voltage variation characteristics of the optimizer may be different from... Figure 6 different.

[0093] Third, if the master node finds that a certain percentage (more than 50%) of the optimizers in a DC string report reverse connection warnings, it will no longer activate all the shutdown devices under the BOOST corresponding to that DC string, and will also issue a warning to the user.

[0094] Example 3: The control strategy for detecting reverse connection risk in the power system when the DC control device is an optimizer includes the following four steps.

[0095] First, the master node broadcasts and activates all optimizers for that frequency band.

[0096] Second, the moment the power converter master node broadcasts the activation of the optimizer, the optimizer begins a slow start (the duty cycle starts from 0% and continues until the voltage limit value is reached). During the slow start period (i.e., during the slow start process), the "input voltage setpoint" of the optimizer control loop is fixed at 85% of the open-circuit input voltage, while the optimizer limits the "inductor current limit setpoint" (i.e., the output current setpoint) to 3A.

[0097] Third, during the soft start process, if one of the DC components or DC strings is reverse-connected, meaning the corresponding DC string is short-circuited, the optimizer's electrical signal changes as the soft start duty cycle increases: the optimizer's input voltage drops sharply, and the optimizer's output current increases; after the input voltage drops to the "input voltage setpoint," the optimizer's PI controller starts to function, limiting the duty cycle to prevent further increases, ensuring the input voltage remains stable near the "input voltage setpoint"; when the optimizer's output current exceeds its "inductor current limit setpoint," the optimizer's PI controller will control the duty cycle to decrease until the optimizer's output current does not exceed the inductor current limit setpoint. This method ensures that the power converter's input voltage is not pulled down and effectively prevents the PV output current from rising excessively in reverse connection. The characteristics of the optimizer's electrical signal are as follows: Figure 7 As shown.

[0098] Fourth, the power converter detects whether there is reverse current in each DC string. If a DC string has reverse current, it is considered that the string is reverse-connected. All shutdown switches under the corresponding BOOST will no longer be activated, and a warning will be issued to the user.

[0099] It should be noted that Examples 1-3 are only for the purpose of facilitating understanding of the solution in this application and should not be construed as limiting the scope of this application. This application can also reasonably recombine the solutions described above, and such recombination should also be included within the protection scope of this application.

[0100] In addition, this application embodiment also provides a power converter, which includes a DC terminal, a DC conversion circuit, an inverter circuit, and an AC terminal connected in sequence. The power converter is used to communicate with multiple DC control devices in a DC string. The input terminal of each DC control device is used to connect to a DC power supply, and the output terminal of each DC control device is connected in series to the DC terminal. The DC control device includes a DC control circuit. The power converter is configured to broadcast an activation signal to the DC control devices in the DC string. When the activation signal is received by the DC control device, the DC control device is used to: control the DC control circuit to start according to a preset start-up mode, monitor the degree of change of a specified electrical parameter of the DC control device, and execute a preset risk feedback action when the degree of change index is greater than a preset change index threshold. The degree of change index is used to indicate the degree of change of the specified electrical parameter of the DC control device, and the preset risk feedback action is used to feedback to the power converter that there is a reverse connection risk of the DC control device.

[0101] In some embodiments, the power converter is configured to: in response to receiving a specified risk identifier, determine that the DC control device that sent the risk identifier has a reverse connection risk, wherein the specified risk identifier is used to indicate that the DC control device has an input reverse connection risk.

[0102] In some embodiments, the power converter is further configured to: determine that the DC string is reverse-connected in response to the fact that the proportion of DC control devices sending a specified risk identifier is greater than a preset proportion value.

[0103] In some embodiments, the power converter is further configured to: detect whether a reverse current exists and, in response to the presence of a reverse current, determine that the DC string is reverse-connected, wherein the reverse current is generated based on the control related to the output current of the DC control circuit in a preset risk feedback action performed by the DC control device.

[0104] In some embodiments, the power converter is further configured to: stop sending activation signals to multiple DC control devices within the DC string in response to sending a DC string reverse connection.

[0105] In addition, this application embodiment also provides a DC control device, which is located within a DC string and is communicatively connected to a power converter. The power converter includes a DC terminal, a DC conversion circuit, an inverter circuit, and an AC terminal connected in sequence. The input terminal of the DC control device is used to connect to a DC power supply, and the output terminal of the DC control device is connected to the DC terminal. The DC control device is configured to: in response to receiving an activation signal sent by the power converter, control the DC control circuit to start according to a preset start-up mode, monitor the degree of change of a specified electrical parameter of the DC control device, and in response to the degree of change index being greater than a preset change index threshold, execute a preset risk feedback action. The degree of change index is used to indicate the degree of change of the specified electrical parameter of the DC control device, and the preset risk feedback action is used to feedback to the power converter that there is a reverse connection risk in the DC control device.

[0106] In some embodiments, performing a preset risk feedback action includes: sending a specified risk flag to the power converter and stopping power output, wherein the specified risk flag is used to indicate that there is a risk of reverse connection of the DC control device.

[0107] In some embodiments, the DC control device is a shutdown device, and the DC control circuit includes a first controllable switch connected between the input terminal and the output terminal of the shutdown device. The shutdown device controls the first controllable switch to open to stop power output.

[0108] In some embodiments, the DC control device is an optimizer, and the DC control circuit includes a switching circuit. The optimizer stops providing drive signals to the switching circuit to stop power output.

[0109] In some embodiments, the DC control device is an optimizer, and the preset risk feedback action includes: controlling the output current of the DC control circuit to be less than or equal to a preset current value, and controlling the input voltage of the DC control circuit to be stable at a preset voltage value.

[0110] In some embodiments, controlling the DC control circuit to start according to a preset start-up method includes: controlling the DC control circuit to start slowly, and during the slow start-up process, controlling the input voltage setpoint of the DC control circuit to a preset voltage value and controlling the output current setpoint of the DC control circuit to a preset current value.

[0111] In some embodiments, the degree of change index of a specified electrical parameter of the DC control device includes one or more of the following indices: a first degree of change index for indicating the magnitude of decrease of the input voltage of the DC control device within a preset duration after the DC control device receives the activation signal; a second degree of change index for indicating the magnitude of decrease of the output voltage of the DC control device within a preset duration after the DC control device receives the activation signal; and a third degree of change index for indicating the magnitude of increase of the output current of the DC control device within a preset duration after the DC control device receives the activation signal.

[0112] The above text combined Figures 2 to 7 The device embodiments of this application have been described in detail below, in conjunction with... Figure 8 The method embodiments of this application are described in detail below. It should be understood that the description of the method embodiments corresponds to the description of the apparatus embodiments; therefore, any parts not described in detail can be referred to the foregoing apparatus embodiments.

[0113] like Figure 8 The diagram illustrates a power system control method provided in an embodiment of this application. It should be understood that this method is applied to the power system described above. The power system includes a power converter and a DC string. The power converter includes a DC terminal, a DC conversion circuit, an inverter circuit, and an AC terminal connected in sequence. The DC string includes multiple DC control devices, each including a DC control circuit. The input terminal of each DC control device is connected to a DC power supply, and the output terminal of each DC control device is connected in series to the DC terminal. All the multiple DC control devices are communicatively connected to the power converter.

[0114] See details Figure 8 The fault detection method for power systems includes steps S810-S820.

[0115] In step S810, the control power converter broadcasts an activation signal to the DC control device in the DC string.

[0116] In step S820, the DC control device is controlled to perform the following operations: in response to receiving an activation signal, the DC control circuit is controlled to start according to a preset startup mode, the change degree index of a specified electrical parameter of the DC control device is monitored, and in response to the change degree index exceeding a preset change index threshold, a preset risk feedback action is executed. Here, the change degree index is used to indicate the degree of change of the specified electrical parameter of the DC control device, and the preset risk feedback action is used to report to the power converter that the DC control device has a reverse connection risk.

[0117] In some embodiments, performing a preset risk feedback action includes: sending a specified risk flag to the power converter and stopping power output, wherein the specified risk flag is used to indicate that there is a reverse connection risk in the DC control device; the control method further includes: controlling the power converter to determine that there is a reverse connection risk in the DC control device that sent the risk flag in response to receiving the specified risk flag.

[0118] In some embodiments, the control method further includes: controlling the power converter to determine DC string reverse connection in response to the fact that the proportion of DC control devices sending a specified risk identifier to a plurality of DC control devices is greater than a preset proportion value.

[0119] In some embodiments, the DC control device is an optimizer, and the execution of the preset risk feedback action includes: controlling the output current of the DC control circuit to be less than or equal to a preset current value, and controlling the input voltage of the DC control circuit to be stable at a preset voltage value; the control method further includes: controlling the power converter to detect whether there is a reverse current and, in response to the presence of a reverse current, determining that the DC string is reverse connected, wherein the reverse current is generated based on the control related to the output current of the DC control circuit in the preset risk feedback action of the DC control device.

[0120] In some embodiments, controlling the DC control circuit to start according to a preset start-up method includes: controlling the DC control circuit to start slowly, and during the slow start-up process, controlling the input voltage setpoint of the DC control circuit to a preset voltage value and controlling the output current setpoint of the DC control circuit to a preset current value.

[0121] In some embodiments, the control method further includes: controlling the power converter to stop sending activation signals to multiple DC control devices within the DC string in response to a reverse connection of the DC string.

[0122] In addition, this application embodiment also provides a control method for a power converter. The power converter includes a DC terminal, a DC conversion circuit, an inverter circuit, and an AC terminal connected in sequence. The power converter is used to communicate with multiple DC control devices in a DC string. The input terminal of each DC control device is used to connect to a DC power supply, and the output terminal of each DC control device is connected in series to the DC terminal. The DC control device includes a DC control circuit. The control method includes: broadcasting an activation signal to the DC control devices in the DC string; wherein, when the activation signal is received by the DC control device, the DC control device is used to: control the DC control circuit to start according to a preset start-up mode, monitor the degree of change of a specified electrical parameter of the DC control device, and execute a preset risk feedback action when the degree of change index is greater than a preset change index threshold. The degree of change index is used to indicate the degree of change of the specified electrical parameter of the DC control device, and the preset risk feedback action is used to feedback to the power converter that there is a reverse connection risk of the DC control device.

[0123] In some embodiments, the control method includes: in response to receiving a specified risk identifier, determining that the DC control device sending the risk identifier has a reverse connection risk, wherein the specified risk identifier is used to indicate that the DC control device has an input reverse connection risk.

[0124] In some embodiments, the control method includes: determining that the DC string is reverse-connected in response to the fact that the proportion of DC control devices sending a specified risk identifier is greater than a preset proportion value among a plurality of DC control devices.

[0125] In some embodiments, the control method includes: detecting whether a reverse current exists and, in response to the presence of a reverse current, determining that the DC string is reverse-connected, wherein the reverse current is generated based on control related to the output current of the DC control circuit in a preset risk feedback action performed by the DC control device.

[0126] In some embodiments, the control method includes: in response to sending a DC string reverse connection, stopping the transmission of activation signals for a plurality of DC control devices within the DC string.

[0127] In addition, this application embodiment also provides a control method for a DC control device. The DC control device is located within a DC string and is communicatively connected to a power converter. The power converter includes a DC terminal, a DC conversion circuit, an inverter circuit, and an AC terminal connected in sequence. The input terminal of the DC control device is used to connect to a DC power supply, and the output terminal of the DC control device is connected to the DC terminal. The control method includes: in response to receiving an activation signal sent by the power converter, controlling the DC control circuit to start according to a preset start-up mode; monitoring the degree of change of a specified electrical parameter of the DC control device; and in response to the degree of change index being greater than a preset degree of change index threshold, executing a preset risk feedback action. The degree of change index is used to indicate the degree of change of the specified electrical parameter of the DC control device, and the preset risk feedback action is used to feedback to the power converter that there is a reverse connection risk in the DC control device.

[0128] In some embodiments, performing a preset risk feedback action includes: sending a specified risk flag to the power converter and stopping power output, wherein the specified risk flag is used to indicate that there is a risk of reverse connection of the DC control device.

[0129] In some embodiments, the DC control device is an optimizer, and the preset risk feedback action includes: controlling the output current of the DC control circuit to be less than or equal to a preset current value, and controlling the input voltage of the DC control circuit to be stable at a preset voltage value.

[0130] In some embodiments, controlling the DC control circuit to start according to a preset start-up method includes: controlling the DC control circuit to start slowly, and during the slow start-up process, controlling the input voltage setpoint of the DC control circuit to a preset voltage value and controlling the output current setpoint of the DC control circuit to a preset current value.

[0131] This application also provides a machine-readable storage medium for storing a program. This program causes a computer to execute the methods described in the various embodiments of this application.

[0132] This application also provides a computer program product. The computer program product includes a program. The program causes a computer to perform the methods described in various embodiments of this application.

[0133] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any other combination. When implemented in software, it can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this disclosure are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a machine-readable storage medium or transmitted from one machine-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another via wired (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The machine-readable storage medium can be any available medium accessible to a computer or a data storage device such as a server or data center that integrates one or more available media. The available media can be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., digital video discs (DVDs)), or semiconductor media (e.g., solid-state drives (SSDs)).

[0134] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments of this disclosure 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 disclosure.

[0135] In the several embodiments provided in this disclosure, 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 disclosure 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] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure 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 disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A power system, characterized in that, include: A power converter includes a DC terminal, a DC conversion circuit, an inverter circuit, and an AC terminal that are connected in sequence. A DC string includes multiple DC control devices, each DC control device including a DC control circuit. The input terminal of each DC control device is used to connect to a DC power supply, and the output terminal of each DC control device is connected in series to the DC power supply. All of the multiple DC control devices are communicatively connected to the power converter. The power converter is used to broadcast an activation signal to the DC control equipment in the DC string; The DC control device is configured to: in response to receiving the activation signal, control the DC control circuit to start according to a preset start-up mode, monitor the degree of change of a specified electrical parameter of the DC control device, and in response to the degree of change index being greater than a preset change index threshold, execute a preset risk feedback action, wherein the degree of change index is used to indicate the degree of change of the specified electrical parameter of the DC control device, and the preset risk feedback action is used to provide feedback to the power converter that the DC control device has a reverse connection risk.

2. The power system according to claim 1, characterized in that, The execution of the preset risk feedback action includes: sending a specified risk flag to the power converter and stopping power output, wherein the specified risk flag is used to indicate that there is a risk of reverse connection input to the DC control device; The power converter is used to determine, in response to receiving the specified risk identifier, that the DC control device that sent the specified risk identifier has a reverse connection risk.

3. The power system according to claim 2, characterized in that, The DC control device is a shutdown device, and the DC control circuit includes a first controllable switch. The first controllable switch is connected between the input terminal and the output terminal of the shutdown device. The shutdown device controls the first controllable switch to open, thereby stopping the power output.

4. The power system according to claim 2, characterized in that, The DC control device is an optimizer, and the DC control circuit includes a switching circuit. The optimizer stops providing drive signals to the switching circuit to stop the power output.

5. The power system according to claim 2, characterized in that, The power converter is used to determine that the DC string is reverse-connected in response to the fact that the proportion of DC control devices sending the specified risk identifier is greater than a preset proportion value.

6. The power system according to claim 1, characterized in that, The DC control device is an optimizer, and the execution of the preset risk feedback action includes: controlling the output current of the DC control circuit to be less than or equal to a preset current value, and controlling the input voltage of the DC control circuit to be stable at a preset voltage value; The power converter is used to detect whether there is a reverse current and, in response to the presence of a reverse current, determines that the DC string is reverse-connected. The reverse current is generated based on the control related to the output current of the DC control circuit in the preset risk feedback action performed by the DC control device.

7. The power system according to claim 6, characterized in that, The step of controlling the DC control circuit to start according to a preset start-up method includes: controlling the DC control circuit to start slowly, and during the slow start-up process, controlling the input voltage setpoint of the DC control circuit to the preset voltage value and controlling the output current setpoint of the DC control circuit to the preset current value.

8. The power system according to claim 5 or 6, characterized in that, The power converter is also configured to stop sending the activation signal to the plurality of DC control devices within the DC string in response to the reverse connection of the DC string.

9. The power system according to claim 1, characterized in that, The degree of change of the specified electrical parameters of the DC control equipment includes one or more of the following indicators: A first degree of change index used to indicate the magnitude of the decrease in the input voltage of the DC control device within a preset time period after the DC control device receives the activation signal; A second degree of change index is used to indicate the magnitude of the decrease in the output voltage of the DC control device within a preset time period after the DC control device receives the activation signal; A third indicator of the degree of change in the output current of the DC control device during a preset period after the DC control device receives the activation signal.

10. A power converter, characterized in that, The power converter includes a DC terminal, a DC conversion circuit, an inverter circuit, and an AC terminal connected in sequence. The power converter is used for communication with multiple DC control devices in a DC string. The input terminal of each DC control device is connected to a DC power supply, and the output terminal of each DC control device is connected in series to the DC terminal. Each DC control device includes a DC control circuit. The power converter is configured as follows: Broadcast an activation signal to the DC control devices in the DC string; When the activation signal is received by the DC control device, the DC control device is used to: control the DC control circuit to start according to a preset start-up mode, monitor the degree of change of a specified electrical parameter of the DC control device, and execute a preset risk feedback action when the degree of change index is greater than a preset change index threshold. The degree of change index is used to indicate the degree of change of the specified electrical parameter of the DC control device, and the preset risk feedback action is used to feed back to the power converter that the DC control device has a reverse connection risk.

11. A DC control device, characterized in that, The DC control device is located within the DC string and is communicatively connected to the power converter. The power converter includes a DC terminal, a DC conversion circuit, an inverter circuit, and an AC terminal connected in sequence. The input terminal of the DC control device is connected to the DC power supply, and the output terminal of the DC control device is connected to the DC terminal. The DC control device includes a DC control circuit and is configured as follows: In response to receiving an activation signal from the power converter, the DC control circuit is controlled to start according to a preset startup mode, monitor the degree of change of a specified electrical parameter of the DC control device, and in response to the degree of change index being greater than a preset change index threshold, execute a preset risk feedback action, wherein the degree of change index is used to indicate the degree of change of the specified electrical parameter of the DC control device, and the preset risk feedback action is used to feedback to the power converter that the DC control device has a reverse connection risk.

12. A control method for a power system, characterized in that, The power system includes a power converter and a DC string. The power converter includes a DC terminal, a DC conversion circuit, an inverter circuit, and an AC terminal connected in sequence. The DC string includes multiple DC control devices. Each DC control device includes a DC control circuit. The input terminal of each DC control device is used to connect to a DC power supply. The output terminal of each DC control device is connected in series to the DC terminal. All of the multiple DC control devices are communicatively connected to the power converter. The control method includes: The power converter is controlled to broadcast an activation signal to the DC control devices in the DC string; The DC control device is controlled to perform the following operations: in response to receiving the activation signal, the DC control circuit is controlled to start according to a preset start-up mode, the degree of change of a specified electrical parameter of the DC control device is monitored, and in response to the degree of change being greater than a preset change threshold, a preset risk feedback action is executed. The degree of change index is used to indicate the degree of change of a specified electrical parameter of the DC control device, and the preset risk feedback action is used to provide feedback to the power converter that the DC control device has a reverse connection risk.

13. A control method for a power converter, characterized in that, The power converter includes a DC terminal, a DC conversion circuit, an inverter circuit, and an AC terminal connected in sequence. The power converter is used for communication with multiple DC control devices in a DC string. The input terminal of each DC control device is connected to a DC power supply, and the output terminal of each DC control device is connected in series to the DC terminal. The DC control device includes a DC control circuit. The control method includes: Broadcast an activation signal to the DC control devices in the DC string; When the activation signal is received by the DC control device, the DC control device is used to: control the DC control circuit to start according to a preset start-up mode, monitor the degree of change of a specified electrical parameter of the DC control device, and execute a preset risk feedback action when the degree of change index is greater than a preset change index threshold. The degree of change index is used to indicate the degree of change of the specified electrical parameter of the DC control device, and the preset risk feedback action is used to feed back to the power converter that the DC control device has a reverse connection risk.

14. A control method for a DC control device, characterized in that, The DC control device is located within the DC string and is communicatively connected to the power converter. The power converter includes a DC terminal, a DC conversion circuit, an inverter circuit, and an AC terminal connected in sequence. The input terminal of the DC control device is connected to the DC power supply, and the output terminal of the DC control device is connected to the DC terminal. The DC control device includes a DC control circuit, and the control method includes: In response to receiving the activation signal sent by the power converter, the DC control circuit is controlled to start according to the preset start-up mode, monitor the degree of change of the specified electrical parameters of the DC control device, and in response to the degree of change index being greater than the preset change index threshold, a preset risk feedback action is executed. The degree of change index is used to indicate the degree of change of a specified electrical parameter of the DC control device, and the preset risk feedback action is used to provide feedback to the power converter that the DC control device has a reverse connection risk.

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