Method for realizing automatic power flow reversal function of flexible direct current power transmission project

Abstract

The application discloses a kind of flexible direct current transmission engineering automatic power flow reverse function implementation methods, comprising: power instruction includes positive power instruction and negative power instruction, positive power instruction mapping positive sending mode, negative power instruction mapping reverse sending mode;In positive sending mode, negative power instruction is sent to first unit control host, triggers power flow direction reversal, enters reverse sending mode;In reverse sending mode, positive power instruction is sent to first unit control host, triggers power flow direction reversal, enters positive sending mode;Wherein, first unit control host is the controlled end of first flexible direct current station.The beneficial effects of the present application are: by optimizing the value range of power instruction to positive and negative, when unit control host receives power instruction, it can automatically control flexible direct current station to reverse power flow according to the positive and negative of power instruction, so as to reduce the operation pressure of operation and maintenance personnel, improve the automatic flexibility of flexible direct current operation.

Description

Technical Field

[0001] This invention relates to the field of flexible DC transmission control technology, and in particular to a method for realizing the automatic power flow reversal function in flexible DC transmission projects. Background Technology

[0002] Flexible DC transmission (DC) features rapid power flow reversal, providing significant operational flexibility for the power grid. When a new DC project is put into operation, the DC substation needs to be connected to the electricity market spot trading system. The planned power flow curve will be dynamically adjusted according to market changes, potentially resulting in multiple power direction reversals within a single day. Currently, while operational flexible DC systems also possess power flow reversal capabilities, their programming relies on manual commands from maintenance personnel to execute power reversals. This means that power direction reversals are achieved manually by operators, making it impossible to automatically reverse power flow based on automatic power curves. This places immense pressure on maintenance personnel and carries a risk of error. Summary of the Invention

[0003] To address the aforementioned problems, this invention proposes a method for implementing automatic power flow reversal in flexible DC transmission projects, primarily resolving the issues raised in the background technology.

[0004] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0005] A method for implementing automatic power flow reversal function in a flexible DC transmission project includes: power commands including positive power commands and negative power commands, with positive power commands mapping to forward transmission mode and negative power commands mapping to reverse transmission mode; in forward transmission mode, sending a negative power command to the first unit control host to trigger power flow reversal and enter reverse transmission mode; in reverse transmission mode, sending a positive power command to the first unit control host to trigger power flow reversal and enter forward transmission mode; wherein, the first unit control host is the controlled end of the first flexible DC station.

[0006] The beneficial effects of this invention are as follows: by optimizing the range of power command values ​​to positive and negative values, when the unit control host receives the power command, it can automatically control the flexible DC station to reverse the power flow according to the positive or negative value of the power command, without the need for operation and maintenance personnel to issue control commands, thereby reducing the operational pressure on operation and maintenance personnel and improving the automatic flexibility of flexible DC operation. Attached Figure Description

[0007] Figure 1 This is a control schematic diagram of the Shiyang-Chonghuan bipolar DC transmission system disclosed in Embodiment 1 of the present invention;

[0008] Figure 2This is a control schematic diagram of the bipolar DC transmission system from Shiyang to Chonghuan and from Shiyang to Shajiao disclosed in Embodiment 2 of the present invention. Detailed Implementation

[0009] To make the objectives, technical solutions, and advantages of this invention clearer and more explicit, the content of this invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to this invention are shown in the accompanying drawings, not all of them.

[0010] Example 1

[0011] This embodiment proposes a method for implementing automatic power flow reversal in flexible DC transmission projects. By optimizing the range of power command values ​​to positive and negative values, when the unit control host receives the power command, it can automatically control the flexible DC station to reverse the power flow according to the positive or negative value of the power command, without the need for operation and maintenance personnel to issue control commands, thereby reducing the operational pressure on operation and maintenance personnel and improving the automatic flexibility of flexible DC operation.

[0012] The method includes:

[0013] The power command includes positive power command and negative power command. Positive power command is mapped to forward power mode, and negative power command is mapped to reverse power mode. In this embodiment, in order to realize the function of automatic power curve power flow online reversal, the power values ​​of the current automatic power curve are optimized to allow negative values. That is, forward power (from west to east) is positive and reverse power (from east to west) is negative. The existing two power curves can be optimized into one power curve.

[0014] In forward power mode, a negative power command is sent to the first unit control host to trigger the power flow direction to reverse and enter reverse power mode;

[0015] In reverse power mode, a positive power command is sent to the first unit control host to trigger the power flow direction to reverse and enter forward power mode.

[0016] In this embodiment, taking "Shiyang to Chonghuan" as an example, the first flexible DC station refers to the Chonghuan flexible DC station, and the first unit control host is the control host at the Chonghuan flexible DC station.

[0017] More preferably, before sending the power command, a zero-value command is sent to the first unit control host. The zero-value command maps to zero-power operation. In this embodiment, before the power flow reversal, the currently sent power command should be reduced to 0MW, that is, there must be at least one planned point of zero-power operation, indicating that the power flow reversal is about to occur.

[0018] In the case of power reversal in the next unit after full transmission, in the forward transmission mode, the first unit control host is on the constant power side and directly executes the positive power command; in the reverse transmission mode, the second unit control host is on the constant power side and the first unit control host is on the constant voltage side. The first unit control host transmits the negative power command to the second unit control host, which then executes the negative command.

[0019] The second unit control host is the controlled end of the second flexible DC station, and... Figure 1 Taking the "Shiyang to Chonghuan" bipolar system as an example, the second flexible DC station refers to the Shiyang flexible DC station, and the second unit control host is the control host at the Shiyang flexible DC station. It should be noted that this invention uses a bipolar DC transmission system as an example, referring to a DC line with two poles connecting the power source and the load. In fact, this invention can also be applied to a unipolar system. Therefore, in this embodiment, the first unit control host can be considered as the two control hosts in the Chonghuan flexible DC station that control the two poles respectively. Similarly, the second unit control host can be considered as the two control hosts in the Shiyang flexible DC station that control the two poles respectively. Clearly, in the bipolar system of this embodiment, there are two first unit control hosts and two second unit control hosts.

[0020] In forward power mode, when the value of the power command being run by the first unit control host is ≥0, if the first unit control host receives a negative power command, it determines whether the absolute value of the negative power command is greater than the threshold value. If not, an alarm is triggered and execution is refused. If so, a power flow direction reversal remote control command is immediately triggered. The power flow direction reversal remote control command is also used to send the negative power command to the second unit control host and alarm "Automatic power curve triggers power reversal". After the power flow direction reversal remote control command is triggered, the power direction is reversed.

[0021] In reverse transmission mode, when the value of the power command being run by the second unit control host is ≤0, if the second unit control host receives a positive power command sent from the first unit control host, it determines whether the absolute value of the positive power command is greater than the threshold value. If not, an alarm is triggered and execution is refused. If so, a power flow direction reversal remote control command is immediately triggered, and an alarm "Automatic power curve triggered power reversal" is triggered. After the power flow direction reversal remote control command is triggered, the power direction is positive. The threshold value is 0.015pu (22.5MW for independent units and 45MW for dual units) to ensure that the control mode can be switched. The positive power command / negative power command is less than 0.1pu.

[0022] While triggering the power flow direction reversal remote control command, a positive power command or a negative power command is issued with a delay of t, where t≤100ms, to ensure that the power flow direction adjustment is completed.

[0023] The first unit control host and the second unit control host adjust the power direction after the power flow direction is reversed by the remote control command, and adjust the power according to the positive power command / negative power command. When the value of the positive power command / negative power command is greater than the threshold value, the power flow is reversed.

[0024] When the adjusted power value reaches the power command value, the power flow reversal is complete.

[0025] In this embodiment, taking "Shiyang to Chonghuan" as an example, in the forward transmission mode, the power value of curve 1 (Shiyang to Chonghuan planned curve) should be ≥0; in the reverse transmission mode, the power value of curve 1 (Shiyang to Chonghuan planned curve) should be ≤0. The specific power values ​​of the planned curves are shown in Table 1.

[0026] Table 1 Power values ​​of the planned curve for the Lion Yang's delivery of Chong Huan

[0027]

[0028] As shown in Table 1, starting from 12:00, the automatic power control operates in the Shiyang-Chonghuan forward power transmission mode. At 12:10, the planned power value of the Shiyang-Chonghuan power transmission curve is 0. The automatic power control function detects a power value of -100MW at 12:15 and believes that a power flow reversal (forward power transmission to reverse power transmission) is about to occur. At 12:10, a power value of -100MW is sent to the unit control host. After receiving the -100MW instruction, the unit control host automatically triggers the power flow direction reversal. At 12:15, the power is executed to -100MW. At this time, it is already in the Shiyang-Chonghuan reverse power transmission mode.

[0029] At 12:25, the power value of the Shiyang-Chonghuan planned curve was 0. The automatic power control function detected a power value of 100MW at 12:30 and determined that the power flow was about to reverse (reverse transmission to forward transmission). At 12:25, a power value of 100MW was sent to the unit control host. After receiving the 100MW instruction, the unit control host automatically triggered the power flow direction reversal. At 12:30, the power was executed to 100MW. At this time, it was in the Shiyang-Chonghuan forward transmission mode.

[0030] Example 2

[0031] This embodiment proposes a method for implementing the automatic power flow reversal function in flexible DC transmission projects, including:

[0032] The power command includes positive power command and negative power command. Positive power command is mapped to forward power mode, and negative power command is mapped to reverse power mode. In this embodiment, in order to realize the function of automatic power curve power flow online reversal, the current automatic power curve power value is optimized to allow the existence of negative values, that is, forward power (from west to east) is positive and reverse power (from east to west) is negative.

[0033] In forward power mode, a negative power command is sent to the first unit control host to trigger the power flow direction to reverse and enter reverse power mode;

[0034] In reverse power mode, a positive power command is sent to the first unit control host to trigger the power flow direction to reverse and enter forward power mode.

[0035] In this embodiment, taking "Shiyang to Chonghuan" and "Shiyang to Shajiao" as examples, the first flexible DC station refers to the Chonghuan flexible DC station, and the first unit control host is the control host at the Chonghuan flexible DC station.

[0036] Even better, a zero-value command is sent to the first unit control host before the power command is sent, and the zero-value command maps to zero-power operation.

[0037] In the case of power reversal in dual units under distribution mode, in the forward distribution mode, the first unit control host and the third unit control host are constant power sides and directly execute positive power commands; in the reverse distribution mode, the second unit control host and the fourth unit control host are constant power sides, the first unit control host is constant voltage side, the first unit control host transmits negative power commands to the second unit control host and the third unit control host, and the second unit control host and the third unit control host execute the negative commands.

[0038] Among them, the fourth unit control host is another controlled end of the second flexible DC station, and the first unit control host and the third unit control host are the controlled ends of the first flexible DC station and the third flexible DC station, respectively. In this embodiment, using Figure 2 Taking the "Shiyang to Chonghuan" and "Shiyang to Shajiao" lines as examples, the first flexible DC station refers to the Chonghuan flexible DC station, the second flexible DC station refers to the Shiyang flexible DC station, and the third flexible DC station refers to the Shajiao flexible DC station. Therefore, the first unit control host is the control host at the Chonghuan flexible DC station, the third unit control host is the control host at the Shajiao flexible DC station, and the second and fourth unit control hosts are both the control hosts at the Shiyang flexible DC station. It should be noted that this invention uses a bipolar DC transmission system as an example, referring to a DC line with two poles connecting the power source and the load. Therefore, in this embodiment, the first unit control host is the control host at the Chonghuan flexible DC station, the third unit control host is the control host at the Shajiao flexible DC station, and the second and fourth unit control hosts can be considered as two control hosts at the Shiyang flexible DC station that control the two poles respectively.

[0039] The first unit control host corresponds to the second unit control host, and the third unit control host corresponds to the fourth unit control host.

[0040] In forward power mode, when the value of the power command being executed by the first unit control host and the third unit control host is ≥0, if the second unit control host receives a negative power command and the value of the power command currently being executed by the fourth unit control host is ≤0, then the second unit control host and the fourth unit control host are triggered to reverse the power flow direction and an alarm "Automatic power curve triggered power reversal" is triggered, and the power direction is reverse power flow.

[0041] In reverse transmission mode, when the power command value of the second unit control host and the fourth unit control host is ≤0 and the power direction is reverse transmission, if the second unit control host receives a positive power command and the power command value of the fourth unit control host is ≥0, the second unit control host and the fourth unit control host are triggered to reverse the power flow direction and alarm "Automatic power curve triggered power reversal", the power direction is forward transmission; the threshold value is 0pu.

[0042] While triggering the power flow direction reversal remote control command, a positive power command or a negative power command is issued with a delay of t, where t≤100ms, to ensure that the power flow direction adjustment is completed.

[0043] The first unit control host and the third unit control host reverse the power direction after the remote control command is triggered according to the power flow direction, and adjust the power according to the positive power command / negative power command. When the value of the positive power command / negative power command is greater than the threshold value, the power flow reversal is triggered.

[0044] This embodiment takes "Shiyang to Chonghuan" and "Shiyang to Shajiao" as examples. In the forward transmission mode, the power value of curve 1 (planned curve of Shiyang to Chonghuan) should be ≥0 and curve 2 (planned curve of Shiyang to Shajiao) should be ≥0. In the reverse transmission mode, the power value of curve 1 (planned curve of Shiyang to Chonghuan) should be ≤0 and curve 2 (planned curve of Shiyang to Shajiao) should be ≤0. The specific power values ​​of the planned curves are shown in Table 2.

[0045] Table 2 Power values ​​of the planned curve from Shihyang to Chonghuan, from Shihyang to Shajiao

[0046] 1. Lion Ocean's plan to send Chonghuan's curve 100 100 0 -100 -100 0 100 200 2. Lion Ocean Sends Shajiao Plan Curve 50 50 0 -80 -80 0 100 100 Operating mode Zhengsong Zhengsong Zhengsong Send back Send back Send back Zhengsong Zhengsong

[0047] Starting at 12:00, the automatic power control operates in the forward power transmission mode from Shiyang to Chonghuan (Shajiao). At 12:10, the planned power value of curve 1 (Shiyang to Chonghuan) and curve 2 (Shiyang to Shajiao) is 0. The automatic power control function detects that at 12:15, the power values ​​of curve 1 are -100MW and curve 2 are -80MW, indicating that a power flow reversal (forward power transmission to reverse power transmission) is about to occur. At 12:10, curve 1 sends a power command of -100MW to the unit 1 control host, and curve 2 sends a power command of -80MW to the unit 2 control host. After receiving the negative commands, the unit control host automatically triggers the power flow direction reversal and triggers the control mode switch. At 12:15, the power of unit 1 reaches -100MW and the power of unit 2 reaches -80MW. At this time, it is already in the reverse power transmission mode from Shiyang to Chonghuan (Shajiao).

[0048] At 12:25, the power values ​​of curves 1 and 2 are both 0. The automatic power control function detects that the power values ​​of curves 1 and 2 at 12:30 are 100MW, and assumes that the power flow is about to reverse (reverse transmission to forward transmission). At 12:25, a power value of 100MW is sent from curve 1 to the control host of unit 1, and a power value of 100MW is sent from curve 2 to the control host of unit 2. After receiving the positive power command, the unit control host automatically triggers the power flow direction reversal and triggers the control mode switch. At 12:30, the power of unit 1 reaches 100MW, and the power of unit 2 reaches 100MW. At this time, it is in the forward transmission mode of Shiyang to Chonghuan (Shajiao).

[0049] Even better, the symbols of the power commands received by the first unit control host and the third unit control host at the same time are verified. If the symbols of the two power commands are inconsistent, the first unit control host and the third unit control host will reject the import of the two power commands, thereby avoiding abnormal situations.

[0050] The above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made based on the essence of the content of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for implementing automatic power flow reversal function in a flexible DC transmission project, characterized in that, include: The power command includes a positive power command and a negative power command. The positive power command is mapped to the forward transmission mode, and the negative power command is mapped to the reverse transmission mode. Before the power command is sent, a zero value command is sent to the first unit control host. The zero value command is mapped to zero power operation. In forward power mode, a negative power command is sent to the first unit control host to trigger the power flow direction to reverse and enter reverse power mode; In reverse power mode, a positive power command is sent to the first unit control host to trigger the power flow direction to reverse and enter forward power mode. The first unit control host is the controlled end of the first flexible DC station; In the event of a power reversal in the next unit during full transmission, in the positive transmission mode, the first unit control host is on the constant power side and directly executes the positive power command; in the reverse transmission mode, the second unit control host is on the constant power side, and the first unit control host is on the constant voltage side. The first unit control host transmits the negative power command to the second unit control host, which then executes the negative power command; wherein, the second unit control host is the controlled end of the second flexible DC station; In the forward power mode, when the value of the power command being run by the first unit control host is ≥0, if the first unit control host receives a negative power command, it determines whether the absolute value of the negative power command is greater than the threshold value. If not, an alarm is triggered and execution is refused. If yes, a power flow direction reversal remote control command is immediately triggered. The power flow direction reversal remote control command is also used to send the negative power command to the second unit control host and alarm "Automatic power curve triggered power reversal". After the power flow direction reversal remote control command is triggered, the power direction is reversed. In the reverse transmission mode, when the value of the power command being run by the second unit control host is ≤0, if the second unit control host receives a positive power command sent from the first unit control host, it determines whether the absolute value of the positive power command is greater than the threshold value. If not, an alarm is triggered and execution is refused. If yes, a power flow direction reversal remote control command is immediately triggered and an alarm "Automatic power curve triggered power reversal" is triggered. After the power flow direction reversal remote control command is triggered, the power direction is positive. While triggering the power flow direction reversal remote control command, the positive power command or the negative power command is sent with a delay of t, where t≤100ms; The first unit control host and the second unit control host reverse the power direction after the remote control command is triggered according to the power flow direction, and adjust the power according to the positive power command / the negative power command. When the value of the positive power command / the negative power command is greater than the threshold value, the power flow reversal is triggered. When the adjusted power value reaches the value of the power command, the power flow reversal is completed.

2. The method for implementing the automatic power flow reversal function in flexible DC transmission projects as described in claim 1, characterized in that, The threshold value is 0.015 pu, and the ratio of the positive power command to the negative power command is less than 0.1 pu.

3. A method for implementing automatic power flow reversal function in a flexible DC transmission project, characterized in that, include: The power command includes a positive power command and a negative power command. The positive power command is mapped to the forward transmission mode, and the negative power command is mapped to the reverse transmission mode. Before the power command is sent, a zero value command is sent to the first unit control host. The zero value command is mapped to zero power operation. In forward power mode, a negative power command is sent to the first unit control host to trigger the power flow direction to reverse and enter reverse power mode; In reverse power mode, a positive power command is sent to the first unit control host to trigger the power flow direction to reverse and enter forward power mode. The first unit control host is the controlled end of the first flexible DC station; In the case of power reversal in dual units under distribution mode, in the positive transmission mode, the first unit control host and the third unit control host are constant power sides and directly execute the positive power command; in the reverse transmission mode, the second unit control host and the fourth unit control host are constant power sides, the first unit control host is constant voltage side, the first unit control host transmits the negative power command to the second unit control host and the third unit control host, and the second unit control host and the third unit control host execute the negative power command; The third unit control host is another controlled terminal of the first flexible DC station, while the second unit control host and the fourth unit control host are controlled terminals of the second and third flexible DC stations, respectively. The first unit control host corresponds to the second unit control host, and the third unit control host corresponds to the fourth unit control host.

4. The method for implementing the automatic power flow reversal function in flexible DC transmission projects as described in claim 3, characterized in that: In the forward power mode, when the value of the power command being executed by the first unit control host and the third unit control host is ≥0, if the second unit control host receives a negative power command and the value of the power command currently being executed by the fourth unit control host is ≤0, then the second unit control host and the fourth unit control host are triggered to reverse the power flow direction and an alarm "Automatic power curve triggered power reversal" is triggered, and the power direction is reverse power flow. In the reverse transmission mode, when the power command value of the second unit control host and the fourth unit control host is ≤0 and the power direction is reverse transmission, if the second unit control host receives a positive power command and the power command value of the fourth unit control host is ≥0, then the second unit control host and the fourth unit control host are triggered to reverse the power flow direction and an alarm "Automatic power curve triggered power reversal" is triggered, and the power direction is forward transmission. While triggering the power flow direction reversal remote control command, the positive power command or the negative power command is sent with a delay of t, where t≤100ms; The first unit control host and the third unit control host adjust the power direction after the power flow direction is reversed by the remote control command, and adjust the power by the positive power command / the negative power command. When the value of the positive power command / the negative power command is greater than the threshold value, the power flow reversal is triggered.

5. The method for implementing the automatic power flow reversal function in flexible DC transmission projects as described in claim 4, characterized in that, The threshold value is 0pu.

6. The method for implementing the automatic power flow reversal function in flexible DC transmission projects as described in claim 4, characterized in that, The symbols of the power commands received by the first unit control host and the third unit control host at the same time are verified. If the symbols of the two power commands are inconsistent, the first unit control host and the third unit control host reject the import of the two power commands.

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