Polarity switching stability control method for single-pole source and load in bipolar direct current distribution network

Abstract

The application particularly relates to a polarity switching stability control method for a single-pole source load in a bipolar direct-current power distribution network, which comprises the following steps: constructing a corresponding polarity switching device based on the polarity switching demand of the single-pole source load in the bipolar direct-current power distribution network, and constructing a stable operation device with a capacitor adjustment function and a PWM adjustment function; performing a polarity switching operation on the single-pole source load through the polarity switching device; during the polarity switching process, first delaying the voltage change of the single-pole source load through the capacitor adjustment function of the stable operation device; if the voltage of the single-pole source load is out of limit, further stabilizing the voltage of the single-pole source load through the PWM adjustment function of the stable operation device; after the polarity switching of the single-pole source load is completed through the polarity switching device, stopping the operation of the polarity switching device and the stable operation device. The application can realize the polarity switching of the single-pole source load through the polarity switching device with low on-state loss, and can ensure the stable operation of the single-pole source load during the polarity switching process.

Description

Technical Field

[0001] This invention relates to the field of DC distribution network control technology, specifically to a method for stable control of polarity switching of unipolar source loads in bipolar DC distribution networks. Background Technology

[0002] Compared to AC distribution networks, DC distribution networks offer advantages such as fewer transformation stages, lower line losses, larger power supply capacity, and higher power supply reliability. DC distribution network topologies can be categorized into unipolar and bipolar types. Unlike unipolar DC distribution networks, bipolar DC distribution networks feature multiple voltage levels, multiple power supply circuits, and reliable grounding, offering more flexible power supply methods and higher reliability.

[0003] In a bipolar DC distribution network, alternating current (AC) is converted to direct current (DC) by passing through an AC-DC converter and a voltage balancer. Both power sources and loads can be connected to the network via bipolar or unipolar connections, with unipolar connections further divided into positive and negative connections. Uneven polarity distribution among unipolar sources and loads in a bipolar DC distribution network leads to voltage imbalance. This voltage imbalance increases network losses and negatively impacts economic efficiency.

[0004] The applicant discovered that switching the polarity of unipolar loads in a distribution network to achieve uniform distribution within the network helps suppress voltage imbalance. However, existing technologies do not consider the implementation of polarity switching devices, or they use power electronic devices with high conduction losses. Furthermore, to achieve polarity switching, mechanical circuit breakers with low conduction losses could be used for opening and closing, which necessitates consideration of the operational stability of the switched object during the switching process. Therefore, designing a method to achieve unipolar load polarity switching using a low conduction loss polarity switching device while ensuring the stable operation of the unipolar load during the polarity switching process is a pressing technical problem that needs to be solved. Summary of the Invention

[0005] To address the shortcomings of the prior art, the technical problem to be solved by this invention is: how to provide a stable control method for polarity switching of unipolar source loads in a bipolar DC distribution network, which can realize the polarity switching of unipolar source loads through a polarity switching device with low conduction loss, and can ensure the stable operation of unipolar source loads during the polarity switching process, thereby improving the effectiveness and stability of unipolar source load polarity switching in a bipolar DC distribution network, and providing a solution for suppressing voltage imbalance in a bipolar DC distribution network.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] Polarity switching stability control methods for unipolar source-load systems in bipolar DC distribution networks include:

[0008] S1: Based on the polarity switching requirements of unipolar source loads in bipolar DC distribution networks, construct a corresponding polarity switching device, as well as a stable operation device with capacitor regulation and PWM regulation functions.

[0009] S2: Perform the polarity switching operation of the corresponding single-polarity source charge through the polarity switching device;

[0010] S3: During polarity switching, the voltage change of the corresponding single-pole source load is first delayed by the capacitor regulation function of the stable operation device; if the voltage of the single-pole source load exceeds the limit, the voltage of the single-pole source load is further stabilized by the PWM regulation function of the stable operation device.

[0011] S4: After the polarity switching of the corresponding single-polarity source load is completed by the polarity switching device, the polarity switching device and the stable operation device are stopped.

[0012] Preferably, in step S1, the polarity switching device includes a first switching module and a second switching module with one end connected to the negative terminal of the corresponding unipolar source load, and a third switching module and a fourth switching module with one end connected to the positive terminal of the corresponding unipolar source load, and the ends of the first switching module, the second switching module, the third switching module and the fourth switching module that are away from the corresponding unipolar source load are connected to the bipolar DC distribution network.

[0013] When the first and third switching modules are turned on and the second and fourth switching modules are turned off, the corresponding unipolar source load is connected to the positive pole of the bipolar DC distribution network; when the second and fourth switching modules are turned on and the first and third switching modules are turned off, the corresponding unipolar source load is connected to the negative pole of the bipolar DC distribution network.

[0014] Preferably, each switching module includes a self-excited mechanical circuit breaker with a disconnecting switch and an RL parallel unit connected in series; the function of the self-excited mechanical circuit breaker with a disconnecting switch is to disconnect the corresponding unipolar source load from the bipolar DC distribution network and to reconnect the corresponding unipolar source load to the bipolar DC distribution network; the function of the RL parallel unit is to suppress the impulse current generated when the corresponding unipolar source load is reconnected to the distribution network.

[0015] Preferably, when no polarity switching operation is performed, the corresponding unipolar source load is connected to the bipolar DC distribution network via the polarity switching device, at which time the polarity switching device has low conduction loss; when a polarity switching operation is required, the polarity switching device realizes the polarity switching of the corresponding unipolar source load in the bipolar DC distribution network by changing the on / off state of the corresponding switching module.

[0016] Preferably, in step S1, the stable operation device includes a first capacitor C1 for releasing or absorbing electrical energy to delay the voltage change of the corresponding unipolar source charge, a half-bridge circuit and a conversion circuit for realizing the flow of electrical energy, a first resistor R1 for limiting the current, a control switch for controlling the on / off state of the line, and a PWM adjustment module.

[0017] Preferably, the stable operation device includes a first line and a second line respectively connected to the two poles of the corresponding unipolar source load, and the ends of the first line and the second line away from the corresponding unipolar source load are connected to the bipolar DC distribution network.

[0018] The first line has four control switches, M1, M2, M3, and M4, connected in series from the bipolar DC distribution network to the corresponding unipolar source load.

[0019] The half-bridge circuit is set between M1 and M2 to control the connection and disconnection of the first line and the second line;

[0020] The PWM adjustment module is connected to the control terminal of the half-bridge circuit;

[0021] The conversion circuit is located between M2 and M3, and includes a second resistor R2 connected in series on the first line and a second capacitor C2 whose two ends are respectively connected to the first line and the second line.

[0022] The first capacitor C1 and the first resistor R1 are disposed between M3 and M4, and the two ends of the first capacitor C1 are connected to the first line and the second line respectively, and the first resistor R1 is connected in series with the first line.

[0023] Preferably, the polarity switching device sends an acknowledgment signal Sc to the stable operation device, and the stable operation device sends a feedback signal Sf to the polarity switching device. First, after receiving the polarity switching command, the polarity switching device changes the acknowledgment signal Sc from 0 to 1. Then, after receiving the acknowledgment signal Sc with a value of 1, the stable operation device changes the feedback signal Sf from 0 to 1. Finally, after receiving the feedback signal Sf with a value of 1, the polarity switching device begins to execute the polarity switching operation of the corresponding single-polarity source load.

[0024] Preferably, in step S3, when M4 is turned on, the first capacitor C1 delays the change in the voltage of the unipolar source charge; if the voltage of the corresponding unipolar source charge is normal, then M1, M2 and M3 are all turned off, and the PWM regulation module does not run.

[0025] Preferably, in step S3, if the voltage drops or rises above the threshold, M2 and M3 are switched to the on state, and the PWM adjustment module controls the half-bridge circuit to alternately open and close at a certain frequency. For the load, M1 is switched to the on state, at which time the bipolar DC power from M1 is converted into a PWM wave, and then transmitted to the corresponding unipolar load after filtering, so as to support the load to operate near the rated voltage. For the power supply, in order to avoid unnecessary losses, M1 is kept in the off state. At this time, the power supply charges the first capacitor C1 and the second capacitor C2, causing the capacitor voltage to rise, while the electrical energy stored on the capacitor is released through the half-bridge circuit, causing the capacitor voltage to drop. After the PWM adjustment module adjusts this process, the power supply voltage can be stabilized near the rated voltage.

[0026] Preferably, in step S4, after the polarity switching device completes the polarity switching of the corresponding unipolar source load, the confirmation signal Sc turns to 0, and the polarity switching device stops operating; the feedback signal Sf turns to 0, M1, M2, M3 and M4 are disconnected, the PWM adjustment module does not operate, and the stable operation device stops operating; at this time, the corresponding unipolar source load is connected to the bipolar DC distribution network and is in normal operating condition.

[0027] The polarity switching stability control method for unipolar source-load in a bipolar DC distribution network of the present invention has the following beneficial effects:

[0028] This invention performs polarity switching of a single-pole source load through a polarity switching device. First, it delays the voltage change of the corresponding single-pole source load through the capacitor regulation function of the stabilizing operation device. When the voltage of the single-pole source load exceeds the limit, it further stabilizes the voltage of the single-pole source load through the PWM regulation function of the stabilizing operation device. This enables the polarity switching of the single-pole source load and ensures the stable operation of the single-pole source load during the polarity switching process. This improves the effectiveness and stability of the polarity switching of the single-pole source load in the bipolar DC distribution network and provides a solution for suppressing voltage imbalance in the bipolar DC distribution network.

[0029] Since the polarity switching operation requires a very short time, voltage stability can generally be ensured during this period by capacitor regulation. At the same time, in order to ensure the normal operation of the source load, a PWM regulation function is added to act as a short-term connection intermediary in emergency situations, ensuring voltage stability at both ends of the source load, thereby further improving the effectiveness and stability of unipolar source load polarity switching in bipolar DC distribution networks.

[0030] The polarity switching device of this invention uses a self-excited oscillating mechanical circuit breaker with an isolating switch to disconnect the unipolar source load from the bipolar DC distribution network and reconnect the unipolar source load to the bipolar DC distribution network. The parallel RL unit suppresses the impulse current generated when the corresponding unipolar source load reconnects to the distribution network, enabling the polarity switching device to have low conduction losses when the unipolar source load is normally connected to the grid. The cooperation of the four switching modules effectively realizes the polarity switching of the unipolar source load, thereby improving the effectiveness of unipolar source load polarity switching in the bipolar DC distribution network. Attached Figure Description

[0031] To make the objectives, technical solutions, and advantages of the invention clearer, the invention will now be described in further detail with reference to the accompanying drawings, wherein:

[0032] Figure 1 The logic block diagram is shown for the polarity switching stability control method of unipolar source load in a bipolar DC distribution network.

[0033] Figure 2 A flowchart of a polarity switching stability control method for unipolar source-load in a bipolar DC distribution network;

[0034] Figure 3 This is a circuit topology diagram of a polarity switching device;

[0035] Figure 4 A polarity switching device controls a single-pole load to be connected to the power grid in a positive polarity configuration.

[0036] Figure 5 A polarity switching device controls a single-pole load to connect to the power grid in the form of a negative pole;

[0037] Figure 6 A circuit topology diagram (including the overall topology) for a device that is operating stably. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but only to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0039] It should be noted that similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the figures, or the orientation or positional relationship commonly used when the product is in use. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance. In addition, the terms "horizontal," "vertical," etc., do not indicate that the component is required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted. In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0040] The following detailed explanation illustrates the specific implementation methods:

[0041] Example:

[0042] This embodiment discloses a polarity switching stability control method for unipolar source-load in a bipolar DC distribution network.

[0043] like Figure 1 and Figure 2 As shown, the polarity switching stability control method for unipolar source-load in a bipolar DC distribution network includes:

[0044] S1: Based on the polarity switching requirements of unipolar source loads in bipolar DC distribution networks, construct a corresponding polarity switching device, as well as a stable operation device with capacitor regulation and PWM regulation functions.

[0045] S2: Perform the polarity switching operation of the corresponding single-polarity source charge through the polarity switching device;

[0046] In this embodiment, the polarity switching device sends an acknowledgment signal Sc to the stable operation device, and the stable operation device sends a feedback signal Sf to the polarity switching device. First, after receiving the polarity switching command, the polarity switching device changes the acknowledgment signal Sc from 0 to 1. Then, after receiving the acknowledgment signal Sc with a value of 1, the stable operation device changes the feedback signal Sf from 0 to 1. Finally, after receiving the feedback signal Sf with a value of 1, the polarity switching device begins to execute the polarity switching operation of the corresponding single-polarity source load.

[0047] Specifically, Figure 2 When Sc is 0, it means the polarity switching device has neither received a switching command nor is the source load in the switching process; when Sc is 1, it means the polarity switching device has received a switching command or the source load is in the switching process. When Sf is 0, it means the stable operation device has not received an acknowledgment signal Sc with a value of 1; when Sf is 1, it means an acknowledgment signal Sc with a value of 1 has been received. Both the acknowledgment signal Sc and the feedback signal Sf are initialized to 0 in the initial stage of device operation to ensure accurate subsequent information exchange. The purpose of setting signal variables is to enable the polarity switching device and the stable operation device to communicate through these two signals, thereby executing the on / off switching of each switch correctly according to the set procedure.

[0048] S3: During polarity switching, the voltage change of the corresponding single-pole source load is first delayed by the capacitor regulation function of the stable operation device; if the voltage of the single-pole source load exceeds the limit, the voltage of the single-pole source load is further stabilized by the PWM regulation function of the stable operation device.

[0049] S4: After the polarity switching of the corresponding single-polarity source load is completed by the polarity switching device, the polarity switching device and the stable operation device are stopped.

[0050] This invention performs polarity switching of a single-pole source load through a polarity switching device. First, it delays the voltage change of the corresponding single-pole source load through the capacitor regulation function of the stabilizing operation device. When the voltage of the single-pole source load exceeds the limit, it further stabilizes the voltage of the single-pole source load through the PWM regulation function of the stabilizing operation device. This enables the polarity switching of the single-pole source load and ensures the stable operation of the single-pole source load during the polarity switching process. This improves the effectiveness and stability of the polarity switching of the single-pole source load in the bipolar DC distribution network and provides a solution for suppressing voltage imbalance in the bipolar DC distribution network.

[0051] Since the polarity switching operation requires a very short time, voltage stability can generally be ensured during this period by capacitor regulation. At the same time, in order to ensure the normal operation of the source load, a PWM regulation function is added to act as a short-term connection intermediary in emergency situations, ensuring voltage stability at both ends of the source load, thereby further improving the effectiveness and stability of unipolar source load polarity switching in bipolar DC distribution networks.

[0052] Combination Figure 3 As shown, the polarity switching device includes a first switching module and a second switching module, one end of which is connected to the negative terminal of the corresponding unipolar source load, and a third switching module and a fourth switching module, one end of which is connected to the positive terminal of the corresponding unipolar source load. The ends of the first switching module, the second switching module, the third switching module and the fourth switching module that are away from the corresponding unipolar source load are connected to the bipolar DC distribution network.

[0053] Each switching module includes a self-excited mechanical circuit breaker with a disconnecting switch and an RL parallel unit connected in series. The function of the self-excited mechanical circuit breaker with a disconnecting switch is to disconnect the corresponding unipolar source load from the bipolar DC distribution network and to reconnect the corresponding unipolar source load to the bipolar DC distribution network. The function of the RL parallel unit is to suppress the impulse current generated when the corresponding unipolar source load is reconnected to the distribution network.

[0054] like Figure 4 As shown, when the first and third switching modules are turned on and the second and fourth switching modules are turned off, the corresponding unipolar load is connected to the positive pole of the bipolar DC distribution network (the same applies to switching unipolar power supplies).

[0055] like Figure 5 As shown, when the second and fourth switching modules are turned on and the first and third switching modules are turned off, the corresponding unipolar load is connected to the negative pole of the bipolar DC distribution network (the same applies to switching unipolar power supplies).

[0056] When no polarity switching operation is performed, the corresponding unipolar source load is connected to the bipolar DC distribution network via the polarity switching device. At this time, the polarity switching device has low conduction loss. When a polarity switching operation is required, the polarity switching device changes the on / off state of the corresponding switching module to realize the polarity switching of the corresponding unipolar source load in the bipolar DC distribution network.

[0057] The polarity switching device of this invention uses a self-excited oscillating mechanical circuit breaker with an isolating switch to disconnect the unipolar source load from the bipolar DC distribution network and reconnect the unipolar source load to the bipolar DC distribution network. The parallel RL unit suppresses the impulse current generated when the corresponding unipolar source load reconnects to the distribution network, enabling the polarity switching device to have low conduction losses when the unipolar source load is normally connected to the grid. The cooperation of the four switching modules effectively realizes the polarity switching of the unipolar source load, thereby improving the effectiveness of unipolar source load polarity switching in the bipolar DC distribution network.

[0058] Combination Figure 6As shown, the stable operation device includes a first capacitor C1 for releasing or absorbing electrical energy to delay the voltage change of the corresponding unipolar source charge, a half-bridge circuit and a conversion circuit for realizing the flow of electrical energy, a first resistor R1 for limiting the current, a control switch for controlling the on / off state of the line, and a PWM adjustment module.

[0059] Specifically, the stable operation device includes a first line and a second line that are respectively connected to the two poles of the corresponding unipolar source load, and the ends of the first line and the second line that are furthest from the corresponding unipolar source load are connected to the bipolar DC distribution network.

[0060] The first line has four control switches, M1, M2, M3, and M4, connected in series from the bipolar DC distribution network to the corresponding unipolar source load.

[0061] The half-bridge circuit is set between M1 and M2 to control the connection and disconnection of the first line and the second line;

[0062] The PWM adjustment module is connected to the control terminal of the half-bridge circuit;

[0063] The conversion circuit is located between M2 and M3, and includes a second resistor R2 connected in series on the first line and a second capacitor C2 whose two ends are respectively connected to the first line and the second line.

[0064] The first capacitor C1 and the first resistor R1 are disposed between M3 and M4, and the two ends of the first capacitor C1 are connected to the first line and the second line respectively, and the first resistor R1 is connected in series with the first line.

[0065] In this embodiment, M1, M2, M3, and M4 can be common fully controllable power electronic devices, such as MOSFETs. Since M2, M3, and M4 need to achieve bidirectional switching so that the device can be used for both power supplies and loads, two N-channel enhancement-mode MOSFETs with their source terminals connected in series are used.

[0066] The function of the control switch M1 is to control whether the half-bridge circuit is connected to the power distribution network. M1 is turned on only when the PWM regulation module for a single-pole load is running. The purpose of setting this switch is to avoid unnecessary losses to the power distribution network.

[0067] The function of control switch M2 is to control whether the path between the half-bridge circuit and the conversion circuit is open. M2 is only open when the PWM adjustment module is running.

[0068] The function of control switch M3 is to control whether the PWM regulation module participates in stabilizing the source-load voltage. M3 is turned on only when the PWM regulation module is running. The purpose of setting M2 and M3 is to reduce the change in capacitor energy in the conversion circuit when the PWM regulation module is not running, which is beneficial to the next adjustment.

[0069] The function of the control switch M4 is to control whether the first capacitor C1 participates in delaying voltage changes. M4 is turned on only when the stable operation device is running.

[0070] The function of the half-bridge circuit is to turn the power electronic devices on and off at a certain frequency under the control of the PWM adjustment module, thereby outputting a PWM wave.

[0071] The first resistor R1 has a small resistance value, and its function is to limit the current value of the circuit it is in, so that it is not too large and will damage the control switch (i.e., MOSFET).

[0072] When stabilizing the voltage of a unipolar load, the first capacitor C1 functions as follows: it discharges electrical energy and reduces its own voltage (capacitor regulation function), and filters (PWM regulation function); when stabilizing the voltage of a unipolar power supply, it absorbs electrical energy and increases its own voltage (capacitor regulation function), and undertakes the function of capacitor charging and discharging voltage regulation (PWM regulation function).

[0073] The second capacitor C2 serves as a filter when stabilizing the voltage of a unipolar load; when stabilizing the voltage of a unipolar power supply, it serves as a capacitor for charging, discharging, and voltage regulation.

[0074] In the specific implementation process, when M4 is turned on, the first capacitor C1 delays the change in the voltage of the unipolar source charge; if the voltage of the corresponding unipolar source charge is normal, then M1, M2 and M3 are all turned off, and the PWM regulation module does not run.

[0075] If the voltage drops or rises above the threshold, control M2 and M3 turn on, and the PWM adjustment module controls the half-bridge circuit to alternately turn on and off at a certain frequency. For the load, control M1 turns on, at which time the bipolar DC power from M1 is converted into a PWM wave, and then transmitted to the corresponding unipolar load after filtering to support the load to operate near the rated voltage. For the power supply, to avoid unnecessary losses, M1 is kept off. At this time, the power supply charges the first capacitor C1 and the second capacitor C2, causing the capacitor voltage to rise, while the electrical energy stored in the capacitors is released through the half-bridge circuit, causing the capacitor voltage to drop. After the PWM adjustment module adjusts this process, the power supply voltage can be stabilized near the rated voltage.

[0076] After the polarity switching device completes the polarity switching of the corresponding unipolar source load, the confirmation signal Sc turns to 0, and the polarity switching device stops operating; the feedback signal Sf turns to 0, M1, M2, M3 and M4 are disconnected, the PWM adjustment module does not operate, and the stable operation device stops operating; at this time, the corresponding unipolar source load is connected to the bipolar DC distribution network and is in normal operating condition.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A polarity switching stability control method for a single-pole source load in a bipolar direct current power distribution network, characterized by, Comprise: S1: based on the polarity switching requirement of single pole source load in bipolar direct current distribution network, the corresponding polarity switching device is constructed, and the stable operation device with capacitor adjustment and PWM adjustment function is provided; In step S1, the polarity switching device includes a first switching module and a second switching module connected to the negative pole of the corresponding single pole source load, and a third switching module and a fourth switching module connected to the positive pole of the corresponding single pole source load, and the first switching module, the second switching module, the third switching module and the fourth switching module are connected to the bipolar direct current distribution network at the end away from the corresponding single pole source load; When the first switching module and the third switching module are turned on, and the second switching module and the fourth switching module are disconnected, the corresponding single pole source load is connected to the positive pole of the bipolar direct current distribution network; when the second switching module and the fourth switching module are turned on, and the first switching module and the third switching module are disconnected, the corresponding single pole source load is connected to the negative pole of the bipolar direct current distribution network; S2: the polarity switching operation of the corresponding single pole source load is performed through the polarity switching device; S3: during the polarity switching process, the voltage change of the corresponding single pole source load is delayed through the capacitor adjustment function of the stable operation device first; if the voltage of the single pole source load is out of limit, the voltage of the single pole source load is further stabilized through the PWM adjustment function of the stable operation device; S4: after the polarity switching of the corresponding single pole source load is completed through the polarity switching device, the polarity switching device and the stable operation device are controlled to stop running.

2. The method for the polarity switching stability control of the single-pole source and load in the bipolar direct current power distribution network according to claim 1, characterized in that: Each switching module comprises a self-oscillation mechanical circuit breaker with isolating switch and an RL parallel unit connected in series with each other; the function of the self-oscillation mechanical circuit breaker with isolating switch is to disconnect the connection between the corresponding single pole source load and the bipolar direct current distribution network and to make the corresponding single pole source load reconnected to the bipolar direct current distribution network; the function of the RL parallel unit is to suppress the inrush current generated when the corresponding single pole source load is reconnected to the distribution network.

3. The method of claim 2, wherein the polarity switching of the single-pole source and load in the bipolar DC power distribution network is stable controlled. When the polarity switching operation is not performed, the corresponding single pole source load is connected to the bipolar direct current distribution network through the polarity switching device; when the polarity switching operation needs to be performed, the polarity switching device changes the on-off state of the corresponding switching module to realize the polarity switching of the corresponding single pole source load in the bipolar direct current distribution network.

4. The method of claim 1, wherein the method further comprises: determining the polarity of the single-pole source load; and switching the polarity of the single-pole source load to the opposite polarity. In step S1, the stable operation device comprises a first capacitor C1 for discharging or absorbing electric energy to delay the voltage change of the corresponding single pole source load, a half-bridge circuit and a conversion circuit for realizing the flow of electric energy, a first resistor R1 for limiting current, a control switch for controlling the on-off state of the line, and a PWM adjustment module.

5. The method of claim 4, wherein the polarity switching of the single-pole source and load in the bipolar DC power distribution network is stable controlled. The stable operation device comprises a first line and a second line connected to the two poles of the corresponding single pole source load respectively, and the ends of the first line and the second line away from the corresponding single pole source load are connected to the bipolar direct current distribution network; M1, M2, M3 and M4 are connected in series on the first line from the bipolar direct current distribution network to the corresponding single pole source load; The half-bridge circuit is arranged between M1 and M2, and controls the on-off of the first line and the second line; The PWM adjustment module is connected to the control end of the half-bridge circuit; The conversion circuit is arranged between M2 and M3, and comprises a second resistor R2 connected in series on the first line and a second capacitor C2 connected to the first line and the second line respectively. The first capacitor C1 and the first resistor R1 are arranged between M3 and M4, and the two ends of the first capacitor C1 are connected with the first line and the second line respectively, and the first resistor R1 is connected in series with the first line.

6. The method of claim 1, wherein the method further comprises: determining the polarity of the single-pole source load; and switching the polarity of the single-pole source load to the opposite polarity. In step S2, the polarity switching device sends a confirmation signal Sc to the stable operation device, and the stable operation device sends a feedback signal Sf to the polarity switching device; first, the polarity switching device receives the polarity switching command, and changes the confirmation signal Sc from 0 to 1; Then, the stable operation device receives the confirmation signal Sc with the value of 1, and changes the feedback signal Sf from 0 to 1; finally, the polarity switching device receives the feedback signal Sf with the value of 1, and starts to perform the polarity switching operation corresponding to the single-pole source load.

7. The method of claim 5, wherein the polarity switching of the single-pole source and load in the bipolar DC power distribution network is stable controlled. In step S3, M4 is turned on, and the first capacitor C1 delays the change of the voltage of the single-pole source load; if the voltage corresponding to the single-pole source load is normal, M1, M2 and M3 are all turned off, and the PWM adjustment module does not operate.

8. The method of claim 7, wherein the polarity switching of the single-pole source and load in the bipolar DC power distribution network is stable controlled. In step S3, if the voltage drops or rises to more than the threshold value, M2 and M3 are controlled to be turned on, and the PWM adjustment module controls the half-bridge circuit to be opened and closed alternately at a certain frequency; for the load, M1 is controlled to be turned on, at this time, the bipolar direct current from M1 is converted into a PWM wave, and then transmitted to the corresponding single-pole load after filtering, so as to support the load to operate near the rated voltage; for the power supply, M1 is kept off, at this time, the power supply charges the first capacitor C1 and the second capacitor C2 to make the capacitor voltage rise, and the electric energy stored on the capacitor is released through the half-bridge circuit to make the capacitor voltage drop.

9. The method of claim 8, wherein the polarity switching of the single-pole source and load in the bipolar DC power distribution network is stable controlled. In step S4, after the polarity switching device completes the polarity switching of the corresponding single-pole source load, it stops operating; at the same time, M1, M2, M3 and M4 are turned off, the PWM adjustment module does not operate, and the stable operation device stops operating; at this time, the corresponding single-pole source load is connected to the bipolar direct current power distribution network and is in a normal operating state.

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