Power distribution network soft start method and device, nonvolatile storage medium and electronic equipment

Abstract

The invention discloses a power distribution network soft start method and device, a nonvolatile storage medium and electronic equipment. The method comprises the steps of determining a soft start strategy under the condition that a voltage is not established at a medium-voltage direct-current side of the multi-terminal alternating-current and direct-current hybrid power distribution network; under the condition that the soft start strategy is that soft start is executed through the distributed power supply, a first switch between the direct current side and the medium-voltage direct current side of the ACDC converter is controlled to be closed, and a second switch between the alternating current side of the ACDC converter and the alternating current power grid is kept to be disconnected; a third switch between the DCDC converter and the medium-voltage direct current side is controlled to be closed, and a fourth switch, connected with the distributed power supply, of the DCDC converter is controlled to be closed, so that the distributed power supply supplies power to the medium-voltage direct current side; and the second switch is controlled to be switched on until the first preset voltage value is reached. According to the invention, the technical problem that the related technology is not suitable for the soft start execution of the multi-terminal AC / DC hybrid power distribution network containing distributed energy grid connection is solved.

Description

Technical Field

[0001] The present application relates to the technical field of distribution networks, and in particular, to a soft start method, device, non-volatile storage medium and electronic device for a distribution network. Background Art

[0002] In the current new distribution network with integrated source-network-load-storage, the proportion of distributed energy is increasing day by day. On the other hand, the integration of AC and DC power grids is becoming increasingly close, and the application of AC-DC conversion devices is increasing. The device based on the Voltage Source Converter (VSC) is the core device of the existing AC-DC hybrid distribution network. Since the VSC has a support capacitor on the DC side, during the period from the device being uncharged to operating stably under the rated conditions, it is necessary to charge the DC capacitor to the rated voltage. If the charging strategy is improper, it will cause a large impact voltage and impact current, which may trigger a fault protection to cause a trip or even damage the device.

[0003] The starting charging methods provided in the related technologies are not suitable for the soft start of a multi-terminal AC-DC hybrid distribution network with distributed energy grid connection. In a multi-terminal AC-DC hybrid power distribution system, there are multiple AC-DC and DC-DC converters, and in addition, there is distributed energy (such as photovoltaic and wind power), so the whole system is relatively complex. For the soft start of the converter device and the soft start strategy, there are relatively high requirements, and the related technologies do not provide a soft start strategy applicable to distributed energy grid connection.

[0004] In view of the above problems, no effective solution has been proposed yet. Summary of the Invention

[0005] Embodiments of the present application provide a soft start method, device, non-volatile storage medium and electronic device for a distribution network, so as to at least solve the technical problem that the related technologies are not applicable to the soft start of a multi-terminal AC-DC hybrid distribution network with distributed energy grid connection.

[0006] According to one aspect of the embodiments of the present application, a soft start method for a distribution network is provided, including: determining a soft start strategy when the voltage on the medium-voltage DC side of a multi-terminal AC-DC hybrid distribution network has not been established. The multi-terminal AC-DC hybrid distribution network includes an AC-DC converter, a DC-DC converter, an AC power grid, and distributed power sources. The AC power grid is electrically connected to the medium-voltage DC side through the AC-DC converter, and the distributed power sources are electrically connected to the medium-voltage DC side through the DC-DC converter; when the soft start strategy is to perform soft start on the AC-DC converter and the DC-DC converter through the distributed power sources, controlling the first switch between the DC side of the AC-DC converter and the medium-voltage DC side to close, and keeping the second switch between the AC side of the AC-DC converter and the AC power grid open; controlling the third switch between the DC-DC converter and the medium-voltage DC side to close, and the fourth switch connecting the DC-DC converter and the distributed power sources to close, so that the distributed power sources supply power to the medium-voltage DC side; until the voltage of the first DC capacitor set in the DC-DC converter reaches the first predetermined voltage value, controlling the second switch to close, so that the AC power grid supplies power to the medium-voltage DC side.

[0007] Optionally, the second switch includes a first sub-switch and a second sub-switch. One end of the first sub-switch is connected to the AC power grid through a series charging resistor, the other end of the first sub-switch is connected to the AC side of the AC-DC converter, and the second sub-switch is connected in parallel with the charging resistor.

[0008] Optionally, the method further includes: when the soft start strategy is to perform soft start on the AC-DC converter and the DC-DC converter through the AC power grid, controlling the first sub-switch, the third switch, and the fourth switch to close, and keeping the second sub-switch open, so that the electric energy of the AC power grid charges the second DC capacitor set in the AC-DC converter through the charging resistor; when the voltage of the second DC capacitor reaches the second predetermined voltage value, controlling the second sub-switch to close, so that the electric energy of the AC power grid charges the second DC capacitor through the first sub-switch and the second sub-switch; when the voltage of the second DC capacitor reaches the third predetermined voltage value, controlling the first switch to close, where the third predetermined voltage value is greater than the second predetermined voltage value.

[0009] Optionally, after controlling the second sub-switch to close, the method further includes: controlling the AC-DC converter to perform DC voltage control processing, so that the voltage of the second DC capacitor increases at a predetermined rate of change.

[0010] Optionally, the first switch, the second switch, the third switch, and the fourth switch are respectively contactors or circuit breakers.

[0011] Optionally, the distributed power sources are new energy power generation devices.

[0012] According to another aspect of the embodiments of the present application, a soft start device for a distribution network is provided, including: a strategy determination module, configured to determine a soft start strategy when the voltage on the medium-voltage DC side of a multi-terminal AC-DC hybrid distribution network is not established. The multi-terminal AC-DC hybrid distribution network includes an AC-DC converter, a DC-DC converter, an AC power grid, and distributed power sources. The AC power grid is electrically connected to the medium-voltage DC side through the AC-DC converter, and the distributed power sources are electrically connected to the medium-voltage DC side through the DC-DC converter; a first control module, configured to, when the soft start strategy is to perform soft start on the AC-DC converter and the DC-DC converter through the distributed power sources, control the first switch between the DC side of the AC-DC converter and the medium-voltage DC side to close, and keep the second switch between the AC side of the AC-DC converter and the AC power grid open; a second control module, configured to control the third switch between the DC-DC converter and the medium-voltage DC side to close, and the fourth switch between the DC-DC converter and the distributed power sources to close, so that the distributed power sources supply power to the medium-voltage DC side; a third control module, configured to control the second switch to close until the voltage of the first DC capacitor provided in the DC-DC converter reaches a first predetermined voltage value, so that the AC power grid supplies power to the medium-voltage DC side.

[0013] According to another aspect of the embodiments of the present application, a non-volatile storage medium is provided. The non-volatile storage medium stores multiple instructions, and the instructions are suitable for being loaded and executed by a processor to perform the distribution network soft start method according to any one of the above.

[0014] According to another aspect of the embodiments of the present application, an electronic device is provided, including: one or more processors and a memory. The memory is used to store one or more programs. When the one or more programs are executed by the one or more processors, the one or more processors implement the distribution network soft start method according to any one of the above.

[0015] According to another aspect of the embodiments of the present application, a computer program product includes a computer program, and when the computer program is executed by a processor, the steps of the distribution network soft start method according to any one of the above are implemented.

[0016] In an embodiment of the present application, a soft start strategy is determined when there is no established voltage on the medium-voltage DC side of a multi-terminal AC-DC hybrid distribution network. The multi-terminal AC-DC hybrid distribution network includes an AC-DC converter, a DC-DC converter, an AC power grid, and distributed power sources. The AC power grid is electrically connected to the medium-voltage DC side through the AC-DC converter, and the distributed power sources are electrically connected to the medium-voltage DC side through the DC-DC converter. When the soft start strategy is to perform soft start on the AC-DC converter and the DC-DC converter through the distributed power sources, control the first switch between the DC side of the AC-DC converter and the medium-voltage DC side to close, and keep the second switch between the AC side of the AC-DC converter and the AC power grid open. Control the third switch between the DC-DC converter and the medium-voltage DC side to close, and the fourth switch connecting the DC-DC converter and the distributed power sources to close, so that the distributed power sources supply power to the medium-voltage DC side. Until the voltage of the first DC capacitor set in the DC-DC converter reaches the first predetermined voltage value, control the second switch to close, so that the AC power grid supplies power to the medium-voltage DC side. The purpose of using the distributed power sources inside the system to start the entire distribution network and ensure a smooth transition from the zero-voltage state to the normal operating state is achieved, and the technical effect of realizing the soft start of the multi-terminal AC-DC hybrid distribution network by using the distributed power sources is realized. Furthermore, the technical problem that the related technology is not applicable to the soft start of the multi-terminal AC-DC hybrid distribution network with distributed energy grid connection is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation of the present application. In the drawings:

[0018] Figure 1 is a flowchart of an optional distribution network soft start method provided according to an embodiment of the present application;

[0019] Figure 2 is a first topology diagram of an optional distribution network soft start method provided according to an embodiment of the present application;

[0020] Figure 3 is a second topology diagram of an optional distribution network soft start method provided according to an embodiment of the present application;

[0021] Figure 4 is a third topology diagram of an optional distribution network soft start method provided according to an embodiment of the present application;

[0022] Figure 5 is a first connection schematic diagram of an optional distribution network soft start method provided according to an embodiment of the present application;

[0023] Figure 6 It is the first voltage change schematic diagram of an optional soft start method for a distribution network provided by an embodiment of the present application;

[0024] Figure 7 It is the second connection schematic diagram of an optional soft start method for a distribution network provided by an embodiment of the present application;

[0025] Figure 8 It is the second voltage change schematic diagram of an optional soft start method for a distribution network provided by an embodiment of the present application;

[0026] Figure 9 It is the first process schematic diagram of an optional soft start method for a distribution network provided by an embodiment of the present application;

[0027] Figure 10 It is the second process schematic diagram of an optional soft start method for a distribution network provided by an embodiment of the present application;

[0028] Figure 11 It is the schematic diagram of an optional soft start device for a distribution network provided by an embodiment of the present application. Detailed implementation manners

[0029] In order to enable those skilled in the art to better understand the solution of 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 in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present application.

[0030] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so that the embodiments of the present application described here can be implemented in an order different from those illustrated or described here. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units does not necessarily need to be limited to those clearly listed steps or units, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0031] For the convenience of description, some nouns or terms related to the embodiments of the present application are described below:

[0032] The multi-terminal AC / DC hybrid distribution network is a new type of distribution system that integrates AC and DC power resources, loads and energy storage devices. It flexibly connects different types of power networks and distributed energy through multiple ports to achieve efficient and intelligent power conversion and distribution.

[0033] Voltage source converter (VSC), also known as converter, is a core device in power electronics technology. It is mainly used to convert voltage source type electric energy and realize the conversion between AC and DC. The support capacitor is located on the DC side of the converter. During the startup and operation of the converter, the support capacitor can store charge and provide a stable DC voltage to support the normal operation of the converter. In the conversion from AC to DC or DC to AC, a stable DC voltage is the key to maintaining the quality of the converter output power. The DC side support capacitor needs to be charged smoothly at startup to avoid shock.

[0034] Soft start refers to the process of smoothly increasing current or voltage through control strategies during the equipment startup process to reduce the impact at the moment of startup, protect power electronic equipment and grid stability, and ensure that the converter smoothly transitions from a static state to normal operation.

[0035] ACDC (AC to DC Converter) is a power electronic converter that converts AC power into DC power. It plays a bridging role in multi-terminal AC / DC hybrid distribution networks, connecting the AC grid and the DC network, and supporting energy exchange between distributed energy and the main grid.

[0036] DCDC (DC to DC Converter) converter is used for voltage conversion between DC power, regulating DC power in hybrid distribution networks, supporting distributed energy such as photovoltaic and wind power to be directly integrated into the DC system, and realizing efficient energy utilization and flexible scheduling of the power grid.

[0037] According to an embodiment of the present application, a method embodiment for soft starting of a distribution network is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0038] Figure 1 is a flow chart of an optional distribution network soft start method provided according to an embodiment of the present application, such as Figure 1 As shown, the method comprises the following steps:

[0039] Step S102, when the voltage on the medium-voltage DC side of the multi-terminal AC-DC hybrid distribution network is not established, determine the soft-start strategy. The multi-terminal AC-DC hybrid distribution network includes an AC-DC converter, a DC-DC converter, an AC power grid, and distributed power sources. The AC power grid is electrically connected to the medium-voltage DC side through the AC-DC converter, and the distributed power sources are electrically connected to the medium-voltage DC side through the DC-DC converter;

[0040] It can be understood that the voltage not yet established on the medium-voltage DC side is in a zero-voltage state, and a soft-start strategy is required to stably establish DC voltage support. In the multi-terminal AC-DC hybrid distribution network, an AC-DC (AC to DC) converter and a DC-DC (DC to DC) converter are integrated to achieve seamless power exchange between the AC power grid and the DC power grid, and power regulation at different voltage levels within the DC power grid.

[0041] As a bridge connecting the AC power grid and the medium-voltage DC side, the main function of the AC-DC converter is to convert alternating current into direct current and provide stable DC power for the medium-voltage DC side. In the distribution network, when connecting an AC power source (such as a traditional power plant or an AC power grid) to a DC network (such as a network containing distributed energy).

[0042] The DC-DC converter is mainly used within the DC power grid to regulate the DC voltage and achieve interconnection and energy conversion between DC power sources at different voltage levels. In the multi-terminal AC-DC hybrid distribution network, it connects the distributed power sources to the medium-voltage DC side, converts the direct current of the distributed power sources (such as photovoltaic, wind power, etc.) to a voltage level suitable for the medium-voltage DC side, ensures that the distributed power sources can be smoothly connected to the grid, and at the same time can adapt to the dynamic requirements of the grid, provide or absorb power, and enhance the flexibility and reliability of the distribution network.

[0043] The connection between the AC power grid and the AC-DC converter, and the connection between the distributed power sources and the DC-DC converter jointly construct a multi-terminal AC-DC hybrid distribution network, which can handle AC and DC power sources simultaneously and achieve efficient integrated management of power sources, grids, loads, and energy storage. Through the coordinated operation of the AC-DC and DC-DC converters, the flow direction and form of power can be flexibly adjusted to meet the requirements in different scenarios, while ensuring the high quality of power and the stability of the power grid.

[0044] Optionally, the scenarios applicable to this embodiment include, but are not limited to, the topological structure of a multi-terminal AC-DC hybrid distribution network with distributed DC grid connection (i.e., distributed power sources), which may include multiple AC-DC converters and DC-DC converters.

[0045] Figure 2 It is the first topological diagram of an optional distribution network soft-start method provided according to an embodiment of the present application. Figure 2It is a dual - end power supply + distributed DC grid - connected topology, showing a dual - end power supply system. One end is connected to the S1, S2 AC grid, and the other end is connected to distributed DC power sources such as photovoltaic or wind power. It includes ACDC converters (i.e., VSC1 and VSC2) and DCDC converters (i.e., DCT1) for converting AC and DC power to achieve bidirectional power flow. The distributed DC power source is connected through the DCDC converter, which can supply power to the system and also absorb power from the system for charging. N represents the neutral point, ACB represents the switch on the AC side, and DCB represents the switch on the DC side. In Figures 2 to 4 different labels (any 0, 1, 2, 3, 4) can be assigned to ACB and DCB to distinguish different connection objects.

[0046] Figure 3 It is the second topology diagram of an optional distribution network soft - start method provided according to an embodiment of the present application. As Figure 3 shown, it is a star - shaped structure + distributed DC grid - connected topology, which is connected to multiple AC grids (S1, S2, S3).

[0047] Figure 4 It is the third topology diagram of an optional distribution network soft - start method provided according to an embodiment of the present application. As Figure 4 shown, it is a ring - shaped structure + distributed DC grid - connected topology, which can transmit power in any direction along the ring network, enhancing the flexibility of power distribution. The ring - shaped structure also promotes the balanced distribution of power, reduces the impact of single - point failures, and improves the reliability and efficiency of the entire distribution network.

[0048] Step S104, when the soft - start strategy is to perform soft - start on the ACDC converter and DCDC converter through the distributed power source, control the first switch between the DC side and the medium - voltage DC side of the ACDC converter to close, and keep the second switch between the AC side and the AC grid of the ACDC converter open;

[0049] It can be understood that for the soft - start method through the distributed power source, ensure that the first switch between the DC side of the ACDC converter and the medium - voltage DC side of the distribution network is closed, and at the same time, keep the second switch between the AC side of the ACDC converter and the AC grid open. The AC grid does not participate in the charging process temporarily. Use the distributed power source to charge the DC capacitor, and avoid large - current impact at the start moment by designing the switch operation sequence, reducing potential damage to the system and the grid.

[0050] Step S106, control the third switch between the DCDC converter and the medium - voltage DC side to close, and the fourth switch between the DCDC converter and the distributed power source to close, so that the distributed power source supplies power to the medium - voltage DC side;

[0051] It can be understood that the third switch is located between the DCDC converter and the medium-voltage DC side. Closing it means that the DCDC converter starts to be directly connected to the power system on the medium-voltage DC side. The fourth switch is the part connecting the DCDC converter and the distributed power source. When the fourth switch is closed, the current path between the distributed power source and the DCDC converter is established, and the distributed power source starts to supply power to the DCDC converter. This enables the distributed power source to input electrical energy into the medium-voltage DC side through the DCDC converter, providing the necessary DC voltage for the startup of the entire AC-DC hybrid distribution network. The distributed power source can serve as the electrical energy source during the startup phase to charge the DC capacitor of the DCDC converter, thereby gradually establishing the voltage required on the medium-voltage DC side.

[0052] In an alternative embodiment, the first switch, the second switch, the third switch, and the fourth switch are respectively contactors or circuit breakers.

[0053] It can be understood that both contactors and circuit breakers are electrical devices in the power system, used for connecting and disconnecting circuits. Contactors are usually used for frequent circuit operations and can connect and disconnect circuits without overload. Circuit breakers have the function of protecting the circuit and can automatically disconnect the circuit in case of overcurrent or short-circuit faults to prevent equipment damage and ensure personal safety.

[0054] Step S108: Until the voltage of the first DC capacitor set in the DCDC converter reaches the first predetermined voltage value, control the second switch to close so that the AC grid supplies power to the medium-voltage DC side.

[0055] It can be understood that the charging state of the first DC capacitor in the DCDC converter is detected. The first DC capacitor can be regarded as the support capacitor in the DCDC converter. Until its voltage reaches the preset threshold (the first predetermined voltage value), then the connection between the AC grid and the medium-voltage DC side is allowed to be established.

[0056] Optionally, Figure 5 is the first connection schematic diagram of an optional distribution network soft startup method provided by an embodiment of the present application. As Figure 5 shown, S1p and S1n are respectively the switches on the distributed energy access side (i.e., the fourth switch), which can be contactors or circuit breakers; Sdcp1 and Sdcn2 are respectively the switches on the medium-voltage DC side (i.e., the third switch), which can be contactors or circuit breakers.

[0057] Figure 6 is the first voltage change schematic diagram of an optional distribution network soft startup method provided by an embodiment of the present application. As Figure 6 shown, in as Figure 5After S1p and S1n in the figure are closed and new energy is grid-connected, at time 0, the capacitor voltage rises according to a ramp. When it reaches time t0, the capacitor voltage Udc reaches Uset (i.e., the first predetermined voltage value), and the soft start is completed, and the normal working state can be entered.

[0058] In an alternative embodiment, the method further includes: when the soft start strategy is to perform soft start on the ACDC converter and the DCDC converter through the AC power grid, controlling the first sub-switch, the third switch, and the fourth switch to be closed, and keeping the second sub-switch open, so that the electric energy of the AC power grid charges the second DC capacitor provided in the ACDC converter through the charging resistor; when the voltage of the second DC capacitor reaches the second predetermined voltage value, controlling the second sub-switch to be closed, so that the electric energy of the AC power grid charges the second DC capacitor through the first sub-switch and the second sub-switch; when the voltage of the second DC capacitor reaches the third predetermined voltage value, controlling the first switch to be closed, where the third predetermined voltage value is greater than the second predetermined voltage value.

[0059] It can be understood that the AC power grid is used to charge the DC capacitors in the ACDC converter and the DCDC converter. Control the first sub-switch, the third switch, and the fourth switch to be closed, while keeping the second sub-switch open. Allow the electric energy of the AC power grid to charge the second DC capacitor in the ACDC converter through the charging resistor R, and the current path of the DCDC converter is also established at this stage, but it is not directly connected to the AC power grid, avoiding the large current impact at the initial stage of startup. When the voltage of the second DC capacitor reaches the second predetermined voltage value, it means that the charging enters the next stage. At this time, control the second sub-switch to be closed, and the connection between the AC power grid and the ACDC converter is further strengthened. The electric energy directly charges the second DC capacitor through the first sub-switch and the second sub-switch, skipping the charging resistor R, and the charging rate is accelerated. When the voltage of the second DC capacitor reaches the third predetermined voltage value, control the first switch to be closed. The third predetermined voltage value is greater than the second predetermined voltage value and is close to or has reached the voltage level required for normal operation. At this time, the charging process ends, and the entire system can smoothly transition to the normal working state.

[0060] By controlling the switch in stages, the charging process is divided into multiple controllable stages, effectively avoiding the large current impact at the moment of startup, ensuring the smoothness of system startup, reducing the instantaneous stress on power electronic devices, and extending the service life of the devices. During the charging process, through the use of the charging resistor R, the charging current is effectively limited, avoiding the impact on the system caused by the sudden change of the current. As the voltage gradually increases, the role of the charging resistor gradually decreases until it completely exits, and this process ensures the stability and safety of the system during the startup stage.

[0061] Optionally, Figure 7It is the second connection schematic diagram of an optional soft start method for a distribution network provided by an embodiment of the present application. As Figure 7 shown, there are three circuit connections with similar results between the AC power grid and the ACDC converter. Taking one of them as an example for illustration, Ra is the charging resistor, S1a belongs to the second sub-switch and is in parallel with Ra, S2a belongs to the first sub-switch and is in series with Ra, and Sdcp3 and Sdcn4 are respectively switches (i.e., the first switches) on the medium-voltage DC side, which can be contactors or circuit breakers. a, b, and c are used to distinguish different electrical connectors.

[0062] In an optional embodiment, after controlling the second sub-switch to close, the method further includes: controlling the ACDC converter to perform DC voltage control processing so that the voltage of the second DC capacitor increases at a predetermined change rate.

[0063] It can be understood that in order to ensure that the voltage of the second DC capacitor can increase in a controlled manner until it reaches the predetermined operating voltage level. After the second sub-switch is closed, it means that the AC power grid has established a direct current path with the ACDC converter, and it gradually rises at a preset change rate (ramp rate) until it reaches the predetermined third predetermined voltage value. The DC voltage control processing can ensure the stable rise of the capacitor voltage and avoid the impact on the system caused by the sudden change of the voltage.

[0064] Figure 8 It is the second voltage change schematic diagram of an optional soft start method for a distribution network provided by an embodiment of the present application. As Figure 8 shown, the soft start process on the AC side of the ACDC converter is as Figure 8 shown. At time 0, S2a, S2b, and S2c are closed, and the capacitor of the converter is charged through the charging resistor R. The period from 0 to t1 is the uncontrolled charging stage and reaches the voltage Uset1 (i.e., the second predetermined voltage value). At time t1, the switches S1a, S1b, and S1c are closed, and the DC capacitor voltage rises in a ramp. At time t2, it reaches the voltage Uset2. The period from t1 to t2 is the controllable charging stage. After t2, the soft start ends, and the entire system can enter the formal working state.

[0065] Through the above step S102, when the voltage on the medium-voltage DC side of the multi-terminal AC-DC hybrid distribution network is not established, a soft-start strategy is determined. The multi-terminal AC-DC hybrid distribution network includes an AC-DC converter, a DC-DC converter, an AC power grid, and distributed power sources. The AC power grid is electrically connected to the medium-voltage DC side through the AC-DC converter, and the distributed power sources are electrically connected to the medium-voltage DC side through the DC-DC converter; step S104, when the soft-start strategy is to perform soft start on the AC-DC converter and the DC-DC converter through the distributed power source, control the first switch between the DC side of the AC-DC converter and the medium-voltage DC side to close, and keep the second switch between the AC side of the AC-DC converter and the AC power grid open; step S106, control the third switch between the DC-DC converter and the medium-voltage DC side to close, and the fourth switch connecting the DC-DC converter and the distributed power source to close, so that the distributed power source supplies power to the medium-voltage DC side; step S108, until the voltage of the first DC capacitor set in the DC-DC converter reaches the first predetermined voltage value, control the second switch to close, so that the AC power grid supplies power to the medium-voltage DC side. It can achieve the purpose of using the distributed power source inside the system to start the entire distribution network and ensure a smooth transition from the zero-voltage state to the normal operation state, realizing the technical effect of using the distributed power source to achieve soft start of the multi-terminal AC-DC hybrid distribution network, and further solving the technical problem that the related technology is not applicable to soft start of the multi-terminal AC-DC hybrid distribution network with distributed energy grid connection.

[0066] Based on the above embodiments and optional embodiments, the present application proposes an optional implementation method, two main methods for the soft-start configuration and strategy of the multi-terminal AC-DC hybrid distribution network with distributed energy grid connection: all VSCs are started through the AC side and the distributed power source side of the DCDC side.

[0067] Figure 9 is the first flowchart of an optional distribution network soft-start method provided according to an embodiment of the present application. As Figure 9 shown, in the initial stage of the soft-start configuration, all VSCs (Voltage Source Converters), that is, the AC-DC converters are not energized, and the system is in an inactive state.

[0068] As Figure 7 shown in the connection method, close the AC side switches S2a, S2b, S2c (the first sub-switches) of each AC-DC converter, and close all DC switches (including the third switch and the fourth switch) connected to the DC-DC converter to prepare a circuit path for subsequent charging operations.

[0069] After the AC switches S2a, S2b, and S2c are closed, the AC grid starts to charge the capacitors in the VSC through the charging resistors Ra, Rb, and Rc. This stage is an uncontrollable charging process, and the capacitor voltage Udc rises to a preset first voltage threshold Uset1 (i.e., the second predetermined voltage value).

[0070] The starting resistors of each VSC (i.e., the ACDC converter) are connected in parallel, and the switches S1a, S1b, and S1c (i.e., the second sub-switches) are closed. When the capacitor voltage reaches Uset1, the switches S1a, S1b, and S1c connected in parallel with the starting resistors are closed, and the capacitor charging enters the controllable stage.

[0071] Subsequently, the VSC is unlocked, and constant DC voltage control is started to ensure that the capacitor voltage gradually rises to the second voltage threshold Uset2 (i.e., the third predetermined voltage value).

[0072] In the controllable charging stage, the DC voltage command of the VSC rises according to the set slope to achieve a smooth transition of the voltage.

[0073] When the capacitor voltage reaches Uset2 (i.e., the third predetermined voltage value), the soft start process is completed, and the system enters the normal operating state. The first switch between the ACDC converter and the medium-voltage DC side is closed.

[0074] Figure 10 is the second process schematic diagram of an optional soft start method for a distribution network provided according to an embodiment of the present application. As Figure 10 shown, the system is not energized in the initial stage, and all relevant switches are in the off state.

[0075] Close all the DC switches (i.e., the first switches) at the DC side outlets of all VSCs (i.e., the ACDC converters).

[0076] Close all the DC switches of the DCDC converter (including the third and fourth switches), and all the other VSC AC switches (i.e., the second switches) are in the off state to avoid the direct participation of the AC network.

[0077] Using distributed energy as the power source, controllable charging is carried out by increasing the voltage at a specified slope until the set first predetermined voltage value Uset is reached.

[0078] When the DC capacitor voltage Udc of the DCDC converter reaches Uset1, the soft start strategy starts to consider connecting the AC network.

[0079] As Figure 7 shown, simultaneously close the second switches S1a, S1b, S1c and S2a, S2b, S2c of each ACDC converter. The AC grid starts to connect to the AC side of the ACDC converter, indicating that the soft start process of the system is completed and it transitions to the normal operating state.

[0080] The above optional embodiments achieve at least the following effects: For a multi-terminal AC-DC hybrid distribution network with distributed energy DC grid connection, a hardware device configuration for soft start is proposed, as well as an overall switching action and soft start strategy; a start strategy with the AC grid as the power source point, and a "black start" strategy that directly starts from the distributed power source without connecting to the AC grid as the power source point. For a multi-terminal AC-DC hybrid distribution network with distributed energy DC grid connection, two soft start methods from the uncharged state are proposed, with less impact on the overall system. For a multi-terminal AC-DC hybrid distribution network with distributed energy DC grid connection, the proposed soft start strategy fully considers starting from the AC grid and starting from distributed energy, integrating the advantages of both. At the same time, the two methods are also complementary, improving the working range of the multi-terminal AC-DC hybrid distribution network under adverse grid conditions.

[0081] It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. And although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0082] In this embodiment, a distribution network soft start device is also provided. This device is used to implement the above embodiments and preferred embodiments, and those that have been described will not be repeated. As used below, the terms "module" and "device" can be a combination of software and / or hardware that can achieve a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, implementation in hardware, or a combination of software and hardware is also possible and contemplated.

[0083] According to an embodiment of the present application, an apparatus embodiment for implementing the distribution network soft start method is also provided. Figure 11 It is a schematic diagram of an optional distribution network soft start device provided according to an embodiment of the present application, as Figure 11 shown. The above distribution network soft start device includes: a strategy determination module 1102, a first control module 1104, a second control module 1106, and a third control module 1108. The device will be described below.

[0084] The strategy determination module 1102 is used to determine a soft start strategy when the voltage on the medium-voltage DC side of the multi-terminal AC-DC hybrid distribution network is not established. Among them, the multi-terminal AC-DC hybrid distribution network includes an AC-DC converter, a DC-DC converter, an AC grid, and a distributed power source. The AC grid is electrically connected to the medium-voltage DC side through the AC-DC converter, and the distributed power source is electrically connected to the medium-voltage DC side through the DC-DC converter;

[0085] The first control module 1104, connected to the policy determination module 1102, is configured to control the closing of the first switch between the DC side of the ACDC converter and the medium-voltage DC side and keep the second switch between the AC side of the ACDC converter and the AC power grid open when the soft-start policy is to perform soft start on the ACDC converter and the DCDC converter through a distributed power source.

[0086] The second control module 1106, connected to the first control module 1104, is configured to control the closing of the third switch between the DCDC converter and the medium-voltage DC side and the closing of the fourth switch between the DCDC converter and the distributed power source, so that the distributed power source supplies power to the medium-voltage DC side.

[0087] The third control module 1108, connected to the second control module 1106, is configured to control the closing of the second switch until the voltage of the first DC capacitor set in the DCDC converter reaches the first predetermined voltage value, so that the AC power grid supplies power to the medium-voltage DC side.

[0088] In a soft-start device for a distribution network provided by an embodiment of the present application, by setting the policy determination module 1102, the first control module 1104, the second control module 1106, and the third control module 1108, the purpose of starting the entire distribution network by using the distributed power source inside the system and ensuring a smooth transition from the zero-voltage state to the normal operation state is achieved, and the technical effect of realizing soft start of a multi-terminal AC-DC hybrid distribution network by using a distributed power source is realized. Furthermore, the technical problem that the related technology is not applicable to soft start of a multi-terminal AC-DC hybrid distribution network with distributed energy grid connection is solved.

[0089] It should be noted that the above-mentioned respective modules can be implemented by software or hardware. For example, for the latter, it can be implemented in the following manner: the above-mentioned respective modules can be located in the same processor; or, the above-mentioned respective modules are located in different processors in any combination.

[0090] Here, it should be noted that the above-mentioned policy determination module 1102, the first control module 1104, the second control module 1106, and the third control module 1108 correspond to steps S102 to S108 in the embodiment. The examples and application scenarios implemented by the above-mentioned modules and the corresponding steps are the same, but are not limited to the content disclosed in the above-mentioned embodiment. It should be noted that the above-mentioned modules can run in a computer terminal as part of the device.

[0091] It should be noted that the optional or preferred implementation manners of this embodiment can refer to the relevant descriptions in the embodiment, and will not be elaborated here.

[0092] The above-mentioned distribution network soft start device may further include a processor and a memory. The policy determination module 1102, the first control module 1104, the second control module 1106, the third control module 1108, etc. are all stored in the memory as program units, and the corresponding functions are implemented by the processor executing the above program units stored in the memory.

[0093] The processor includes a kernel, and the kernel retrieves the corresponding program units from the memory. One or more kernels can be set. The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of, for example, read-only memory (ROM) or flash RAM (flash RAM), and the memory includes at least one storage chip.

[0094] An embodiment of the present application provides a non-volatile storage medium, on which a program is stored, and when the program is executed by a processor, a distribution network soft start method is implemented.

[0095] An embodiment of the present application provides an electronic device, which includes a processor, a memory, and a program stored on the memory and executable on the processor. When the processor executes the program, the following steps are implemented: in the case where the voltage on the medium-voltage DC side of the multi-terminal AC-DC hybrid distribution network is not established, determine a soft start strategy, where the multi-terminal AC-DC hybrid distribution network includes an AC-DC converter, a DC-DC converter, an AC power grid, and distributed power sources. The AC power grid is electrically connected to the medium-voltage DC side through the AC-DC converter, and the distributed power sources are electrically connected to the medium-voltage DC side through the DC-DC converter; in the case where the soft start strategy is to perform soft start on the AC-DC converter and the DC-DC converter through the distributed power sources, control the first switch between the DC side of the AC-DC converter and the medium-voltage DC side to close, and keep the second switch between the AC side of the AC-DC converter and the AC power grid open; control the third switch between the DC-DC converter and the medium-voltage DC side to close, and the fourth switch between the DC-DC converter and the distributed power source to close, so that the distributed power source supplies power to the medium-voltage DC side; until the voltage of the first DC capacitor set in the DC-DC converter reaches the first predetermined voltage value, control the second switch to close, so that the AC power grid supplies power to the medium-voltage DC side. The device herein can be a server, a PC, etc.

[0096] The present application also provides a computer program product which, when executed on a data processing device, is adapted to execute a program initialized with the following method steps: in the case where no voltage is established on the medium-voltage DC side of a multi-terminal AC-DC hybrid distribution network, determine a soft start strategy, wherein the multi-terminal AC-DC hybrid distribution network includes an AC-DC converter, a DC-DC converter, an AC power grid, and distributed power sources. The AC power grid is electrically connected to the medium-voltage DC side through the AC-DC converter, and the distributed power sources are electrically connected to the medium-voltage DC side through the DC-DC converter; in the case where the soft start strategy is to perform soft start on the AC-DC converter and the DC-DC converter through the distributed power sources, control the first switch between the DC side of the AC-DC converter and the medium-voltage DC side to close, and keep the second switch between the AC side of the AC-DC converter and the AC power grid open; control the third switch between the DC-DC converter and the medium-voltage DC side to close, and the fourth switch connecting the DC-DC converter and the distributed power sources to close, so that the distributed power sources supply power to the medium-voltage DC side; until the voltage of the first DC capacitor provided in the DC-DC converter reaches a first predetermined voltage value, control the second switch to close, so that the AC power grid supplies power to the medium-voltage DC side.

[0097] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0098] The present application is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for realizing the functions specified in Figure 1 one or more of the flows or multiple flows and / or blocks Figure 1 one or more of the blocks or multiple blocks.

[0099] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device, and the instruction device realizes the functions in the flowFigure 1 one process or multiple processes and / or blocks Figure 1 the functions specified in one block or multiple blocks.

[0100] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process. Thus, the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one process or multiple processes and / or blocks Figure 1 the functions specified in one block or multiple blocks.

[0101] In a typical configuration, a computing device includes one or more processors (CPUs), an input / output interface, a network interface, and a memory.

[0102] The memory may include non-permanent memory in the computer-readable medium, in the form of random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash memory (flash RAM). The memory is an example of a computer-readable medium.

[0103] Computer-readable media includes permanent and non-permanent, removable and non-removable media that can store information by any method or technology. The information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassette tapes, magnetic disk storage or other magnetic storage devices, or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include transitory computer-readable media, such as modulated data signals and carrier waves.

[0104] It should also be noted that the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, commodity or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, commodity or device. Without further limitation, an element defined by the statement "comprising one..." does not exclude the presence of additional identical elements in the process, method, commodity or device comprising the element.

[0105] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0106] The above are only the embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

Claims

1. A soft start method for a distribution network, characterized in that Including: When the voltage is not established on the medium-voltage DC side of the multi-terminal AC-DC hybrid distribution network, determine a soft-start strategy, where the multi-terminal AC-DC hybrid distribution network includes an AC-DC converter, a DC-DC converter, an AC power grid, and a distributed power source. The AC power grid is electrically connected to the medium-voltage DC side through the AC-DC converter, and the distributed power source is electrically connected to the medium-voltage DC side through the DC-DC converter; When the soft-start strategy is to perform soft start on the AC-DC converter and the DC-DC converter through the distributed power source, control the first switch between the DC side of the AC-DC converter and the medium-voltage DC side to close, and keep the second switch between the AC side of the AC-DC converter and the AC power grid open; Control the third switch between the DC-DC converter and the medium-voltage DC side to close, and the fourth switch connecting the DC-DC converter and the distributed power source to close, so that the distributed power source supplies power to the medium-voltage DC side; Until the voltage of the first DC capacitor set in the DC-DC converter reaches a first predetermined voltage value, control the second switch to close, so that the AC power grid supplies power to the medium-voltage DC side.

2. The method according to claim 1, wherein The second switch includes a first sub-switch and a second sub-switch, where one end of the first sub-switch is connected to the AC power grid through a series charging resistor, the other end of the first sub-switch is connected to the AC side of the AC-DC converter, and the second sub-switch is connected in parallel with the charging resistor.

3. The method according to claim 2, characterized in that, The method further includes: When the soft-start strategy is to perform soft start on the AC-DC converter and the DC-DC converter through the AC power grid, control the first sub-switch, the third switch, and the fourth switch to close, and keep the second sub-switch open, so that the electric energy of the AC power grid charges the second DC capacitor set in the AC-DC converter through the charging resistor; When the voltage of the second DC capacitor reaches a second predetermined voltage value, control the second sub-switch to close, so that the electric energy of the AC power grid charges the second DC capacitor through the first sub-switch and the second sub-switch; When the voltage of the second DC capacitor reaches a third predetermined voltage value, control the first switch to close, where the third predetermined voltage value is greater than the second predetermined voltage value.

4. The method according to claim 3, characterized in that, After controlling the second sub-switch to close, the method further includes: Control the AC-DC converter to perform DC voltage control processing, so that the voltage of the second DC capacitor increases at a predetermined rate of change.

5. The method according to any one of claims 1 to 4, characterized in that, The first switch, the second switch, the third switch, and the fourth switch are respectively contactors or circuit breakers.

6. The method according to any one of claims 1 to 4, characterized in that, The distributed power source is a new energy power generation device.

7. A soft start device for a distribution network, characterized in that, Including: A strategy determination module, configured to determine a soft start strategy when the medium-voltage DC side of a multi-terminal AC-DC hybrid distribution network has not established a voltage. The multi-terminal AC-DC hybrid distribution network includes an AC-DC converter, a DC-DC converter, an AC power grid, and distributed power sources. The AC power grid is electrically connected to the medium-voltage DC side through the AC-DC converter, and the distributed power sources are electrically connected to the medium-voltage DC side through the DC-DC converter; A first control module, configured to, when the soft start strategy is to perform soft start on the AC-DC converter and the DC-DC converter through the distributed power sources, control a first switch between the DC side of the AC-DC converter and the medium-voltage DC side to close, and keep a second switch between the AC side of the AC-DC converter and the AC power grid open; A second control module, configured to control a third switch between the DC-DC converter and the medium-voltage DC side to close, and a fourth switch connecting the DC-DC converter and the distributed power sources to close, so that the distributed power sources supply power to the medium-voltage DC side; A third control module, configured to, until the voltage of a first DC capacitor provided in the DC-DC converter reaches a first predetermined voltage value, control the second switch to close, so that the AC power grid supplies power to the medium-voltage DC side.

8. A non-volatile storage medium, characterized in that, The non-volatile storage medium stores multiple instructions, and the instructions are adapted to be loaded and executed by a processor to perform the distribution network soft start method according to any one of claims 1 to 6.

9. An electronic device, characterized in that, Comprising: One or more processors and a memory, the memory is used to store one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors implement the distribution network soft start method according to any one of claims 1 to 6.

10. A computer program product, comprising a computer program, characterized in that, The computer program, when executed by a processor, implements the steps of the distribution network soft start method according to any one of claims 1 to 6.

Images