A method and device for commutation failure suppression in a weak ac system

Abstract

The application discloses a kind of weak AC system commutation failure inhibition method and device, using the AC voltage fluctuation generated in the switching process of conventional AC filter to determine the system strength state of weak AC system, so as to determine the minimum angle of arc extinguishing angle according to the system strength state of weak AC system, by timely adjusting arc extinguishing angle to not less than minimum angle, so as to achieve the purpose of inhibiting commutation failure, without configuring dynamic reactive compensation device, the commutation failure inhibition of weak AC system can be realized on the original conventional DC equipment and arc extinguishing angle control method, solve the technical problem that the existing way of preventing weak AC system commutation failure needs to configure dynamic reactive compensation device, not only increase the technical difficulty, also increase cost, not suitable for popularization and application.

Description

Technical Field

[0001] This invention relates to the field of AC / DC system technology, and in particular to a method and apparatus for suppressing commutation failure in a weak AC system. Background Technology

[0002] When two valves of the inverter in the converter station are commutating, if the commutation process is not completed, or if the valve that was supposed to be turned off fails to restore its blocking capability during the reverse voltage period after being turned off, it will immediately turn on again when the voltage applied to the valve is positive, resulting in a commutation failure. This phenomenon is called commutation failure.

[0003] Commutation failure in conventional DC transmission is a major concern, especially in weak systems, as it can affect the normal operation of the DC transmission system. When commutation failure occurs, especially when there are consecutive commutation failures, the conventional DC transmission power will be interrupted, thereby affecting the safe and stable operation of the AC systems at both the sending and receiving ends.

[0004] Commutation failure typically occurs when there is a significant voltage drop in the external environment, especially in weak AC systems. Faults in remote AC systems can cause a substantial voltage drop at the converter station bus, leading to commutation failure. Currently, in weak AC systems, dynamic reactive power compensation devices such as STATCOM are typically required to prevent commutation. This not only increases technical complexity but also costs, making it unsuitable for widespread application. Summary of the Invention

[0005] This invention provides a method and apparatus for suppressing commutation failure in weak AC systems, which addresses the problem that existing methods for preventing commutation failure in weak AC systems require the configuration of dynamic reactive power compensation devices, which not only increases technical difficulty but also costs, making them unsuitable for widespread application.

[0006] In view of this, the first aspect of the present invention provides a method for suppressing commutation failure in a weak AC system, comprising:

[0007] Real-time acquisition of the first effective value of AC voltage at the AC bus of the converter station;

[0008] Obtain the effective value of the second AC voltage at the AC bus of the converter station after the AC filter is put into or removed;

[0009] Calculate the voltage fluctuation value of the AC filter to be switched on or off based on the first AC voltage effective value and the second AC voltage effective value;

[0010] Calculate the system strength characterization value of the weak AC system based on the voltage fluctuation value;

[0011] The minimum angle for extinguishing the arc at the converter station is calculated based on the system strength characteristics.

[0012] The arc-extinguishing angle of the converter station is adjusted in real time to be no less than the minimum angle.

[0013] Optionally, the formula for calculating the voltage fluctuation value when the AC filter is switched on or off is as follows:

[0014]

[0015] Where δ is the voltage fluctuation value when the AC filter is switched on or off, U ac1 U is the effective value of the first AC voltage. ac2 This is the effective value of the second AC voltage.

[0016] Optionally, the formula for calculating the system strength characteristic value of a weak AC system is:

[0017]

[0018] Where K is the system strength characteristic value of the weak AC system, Q0 is the capacity of a single AC filter, and P is the DC transmission power.

[0019] Optionally, the formula for calculating the minimum arc extinction angle of the converter station is:

[0020]

[0021] Where, γ min γ is the minimum angle for the extinction angle of the converter station. mins γ is the minimum arc extinction angle for the operation of a weak AC system. maxs K1 represents the maximum arc extinction angle of the weak AC system, K2 represents the upper limit of the system's strength and weakness characteristics, and K2 represents the lower limit of the system's strength and weakness characteristics.

[0022] Optionally, the upper limit of the system strength characterization value is 2.5, and the lower limit of the system strength characterization value is 1.5.

[0023] A second aspect of the present invention provides a commutation failure suppression device for a weak AC system, comprising:

[0024] The first acquisition module is used to acquire the effective value of the first AC voltage at the AC bus of the converter station in real time.

[0025] The second acquisition module is used to acquire the effective value of the second AC voltage at the AC bus of the converter station after the AC filter is put into or cut off.

[0026] The fluctuation calculation module is used to calculate the voltage fluctuation value of the AC filter when it is switched on or off based on the first AC voltage effective value and the second AC voltage effective value.

[0027] The system strength index calculation module is used to calculate the system strength characterization value of a weak AC system based on the voltage fluctuation value.

[0028] The minimum arc extinction angle calculation module is used to calculate the minimum arc extinction angle of the converter station based on the system strength characteristics.

[0029] The arc extinction angle adjustment module is used to adjust the arc extinction angle of the converter station to no less than the minimum angle in real time.

[0030] Optionally, the formula for calculating the voltage fluctuation value when the AC filter is switched on or off is as follows:

[0031]

[0032] Where δ is the voltage fluctuation value when the AC filter is switched on or off, U ac1 U is the effective value of the first AC voltage. ac2 This is the effective value of the second AC voltage.

[0033] Optionally, the formula for calculating the system strength characteristic value of a weak AC system is:

[0034]

[0035] Where K is the system strength characteristic value of the weak AC system, Q0 is the capacity of a single AC filter, and P is the DC transmission power.

[0036] Optionally, the formula for calculating the minimum arc extinction angle of the converter station is:

[0037]

[0038] Where, γ min γ is the minimum angle for the extinction angle of the converter station. mins γ is the minimum arc extinction angle for the operation of a weak AC system. maxs K1 represents the maximum arc extinction angle of the weak AC system, K2 represents the upper limit of the system's strength and weakness characteristics, and K2 represents the lower limit of the system's strength and weakness characteristics.

[0039] Optionally, the upper limit of the system strength characterization value is 2.5, and the lower limit of the system strength characterization value is 1.5.

[0040] Compared with the prior art, the commutation failure suppression method and apparatus for weak AC systems provided by the present invention have the following advantages:

[0041] The present invention provides a method for suppressing commutation failure in weak AC systems. This method utilizes the AC voltage fluctuations generated during the switching process of a conventional AC filter to determine the strength of the weak AC system. Based on the strength of the weak AC system, the minimum angle of the arc extinction angle is determined. By adjusting the arc extinction angle to be no less than the minimum angle in a timely manner, the purpose of suppressing commutation failure is achieved. This method can suppress commutation failure in weak AC systems without the need for a dynamic reactive power compensation device. It solves the technical problem that existing methods for preventing commutation failure in weak AC systems require the configuration of a dynamic reactive power compensation device, which not only increases the technical difficulty but also the cost, making it unsuitable for widespread application.

[0042] The commutation failure suppression device for weak AC systems provided by this invention is used to execute the commutation failure suppression method for weak AC systems provided by this invention. Its principle and the technical effects achieved are the same as those of the commutation failure suppression method for weak AC systems provided by this invention, and will not be described again here. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a flowchart illustrating a method for suppressing commutation failure in a weak AC system provided in this invention.

[0045] Figure 2 This is a schematic diagram of the commutation failure suppression device for a weak AC system provided in this invention. Detailed Implementation

[0046] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] For easier understanding, please refer to Figure 1 This invention provides an embodiment of a method for suppressing commutation failure in a weak AC system, comprising:

[0048] Step 101: Obtain the effective value of the first AC voltage at the AC bus of the converter station in real time.

[0049] It should be noted that, in this embodiment of the invention, the effective value of the AC voltage at the AC bus of the converter station is obtained by an AC voltage measuring device installed at the AC bus of the converter station, and is denoted as the first effective value of the AC voltage U. ac1 .

[0050] Step 102: Obtain the second effective value of AC voltage at the AC bus of the converter station after the AC filter is put into or removed.

[0051] It should be noted that when the AC filter is put into operation or removed, the effective value of the AC voltage at the AC bus of the converter station is obtained through the AC voltage measuring device and recorded as the second effective value of AC voltage U. ac2 .

[0052] Step 103: Calculate the voltage fluctuation value of switching on or off the AC filter based on the first AC voltage effective value and the second AC voltage effective value.

[0053] It should be noted that, based on the first AC voltage effective value U ac1 The second AC voltage effective value U ac2 The voltage fluctuation at the AC bus of the converter station after the AC filter is put into or removed can be calculated using the following formula:

[0054]

[0055] Where δ is the voltage fluctuation value when the AC filter is switched on or off, U ac1 U is the effective value of the first AC voltage. ac2 This is the effective value of the second AC voltage.

[0056] Step 104: Calculate the system strength characterization value of the weak AC system based on the voltage fluctuation value.

[0057] It should be noted that after obtaining the voltage fluctuation value, the system strength characterization value is calculated based on the voltage fluctuation value. The formula for calculating the system strength characterization value is:

[0058]

[0059] Where K is the system strength characteristic value of the weak AC system, Q0 is the capacity of a single AC filter, and P is the DC transmission power.

[0060] Step 105: Calculate the minimum angle of the converter station's arc extinction angle based on the system strength characteristics.

[0061] It should be noted that the minimum angle for calculating the extinction angle of the converter station based on the system strength characteristics is as follows:

[0062]

[0063] Where, γ min γ is the minimum angle for the extinction angle of the converter station. mins γ is the minimum arc extinction angle for the operation of a weak AC system. mins The value is 17°, γ maxs γ is the maximum arc extinction angle for the operation of a weak AC system. maxs The value is 60°, K1 is the upper limit of the system strength characterization value with a value of 2.5, and K2 is the lower limit of the system strength characterization value with a value of 1.5.

[0064] Step 106: Adjust the arc-extinguishing angle of the converter station to no less than the minimum angle in real time.

[0065] It should be noted that the arc extinction angle is directly related to the commutation failure on the inverter side. When the AC voltage on the inverter side decreases, it is often because the angle is too small, resulting in commutation failure. Therefore, after the AC filter is put into operation or cut off, the minimum arc extinction angle of the converter station is calculated according to the above method, and the arc extinction angle of the converter station is adjusted in real time to be no less than the minimum angle, thereby avoiding commutation failure of the inverter in the converter station.

[0066] The present invention provides a method for suppressing commutation failure in weak AC systems. This method utilizes the AC voltage fluctuations generated during the switching process of a conventional AC filter to determine the strength of the weak AC system. Based on the strength of the weak AC system, the minimum angle of the arc extinction angle is determined. By adjusting the arc extinction angle to be no less than the minimum angle in a timely manner, the purpose of suppressing commutation failure is achieved. This method can suppress commutation failure in weak AC systems without the need for a dynamic reactive power compensation device. It solves the technical problem that existing methods for preventing commutation failure in weak AC systems require the configuration of a dynamic reactive power compensation device, which not only increases the technical difficulty but also the cost, making it unsuitable for widespread application.

[0067] For easier understanding, please refer to Figure 2 This invention provides an embodiment of a commutation failure suppression device for a weak AC system, comprising:

[0068] The first acquisition module is used to acquire the effective value of the first AC voltage at the AC bus of the converter station in real time.

[0069] The second acquisition module is used to acquire the effective value of the second AC voltage at the AC bus of the converter station after the AC filter is put into or cut off.

[0070] The fluctuation calculation module is used to calculate the voltage fluctuation value of the AC filter when it is switched on or off based on the first AC voltage effective value and the second AC voltage effective value.

[0071] The system strength index calculation module is used to calculate the system strength characterization value of a weak AC system based on the voltage fluctuation value.

[0072] The minimum arc extinction angle calculation module is used to calculate the minimum arc extinction angle of the converter station based on the system strength characteristics.

[0073] The arc extinction angle adjustment module is used to adjust the arc extinction angle of the converter station to no less than the minimum angle in real time.

[0074] The formula for calculating the voltage fluctuation value when the AC filter is switched on or off is as follows:

[0075]

[0076] Where δ is the voltage fluctuation value when the AC filter is switched on or off, U ac1 U is the effective value of the first AC voltage. ac2 This is the effective value of the second AC voltage.

[0077] The formula for calculating the system strength characteristic value of a weak AC system is:

[0078]

[0079] Where K is the system strength characteristic value of the weak AC system, Q0 is the capacity of a single AC filter, and P is the DC transmission power.

[0080] The formula for calculating the minimum arc extinction angle of a converter station is:

[0081]

[0082] Where, γ min γ is the minimum angle for the extinction angle of the converter station. mins γ is the minimum arc extinction angle for the operation of a weak AC system. maxs K1 represents the maximum arc extinction angle of the weak AC system, K2 represents the upper limit of the system's strength and weakness characteristics, and K2 represents the lower limit of the system's strength and weakness characteristics.

[0083] The upper limit of the system strength characterization value is 2.5, and the lower limit of the system strength characterization value is 1.5.

[0084] The commutation failure suppression device for weak AC systems provided by this invention utilizes the AC voltage fluctuations generated during the switching process of conventional AC filters to determine the strength of the weak AC system. Based on this strength, the minimum arc-extinguishing angle is determined. By adjusting the arc-extinguishing angle to a value not less than the minimum angle, commutation failure is suppressed. This method eliminates the need for dynamic reactive power compensation devices and can achieve commutation failure suppression in existing conventional DC equipment and arc-extinguishing angle control methods. It solves the problem that existing methods for preventing commutation failure in weak AC systems require dynamic reactive power compensation devices, which not only increase technical difficulty but also cost, making them unsuitable for widespread application.

[0085] The commutation failure suppression device for weak AC systems provided by this invention is used to execute the commutation failure suppression method for weak AC systems provided by this invention. Its principle and the technical effects achieved are the same as those of the commutation failure suppression method for weak AC systems provided by this invention, and will not be described again here.

[0086] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for suppressing commutation failure in a weak AC system, characterized in that, include: Real-time acquisition of the first effective value of AC voltage at the AC bus of the converter station; Obtain the effective value of the second AC voltage at the AC bus of the converter station after the AC filter is put into or removed; Calculate the voltage fluctuation value of the AC filter to be switched on or off based on the first AC voltage effective value and the second AC voltage effective value; Calculate the system strength characterization value of the weak AC system based on the voltage fluctuation value; The minimum angle for extinguishing the arc at the converter station is calculated based on the system strength characteristics. The arc-extinguishing angle of the converter station is adjusted in real time to be no less than the minimum angle. The formula for calculating the system strength characteristic value of a weak AC system is: Where K is the system strength characteristic value of the weak AC system. Where P is the capacity of a single AC filter and P is the DC transmission power. The voltage fluctuation value for switching the AC filter on or off.

2. The method for suppressing commutation failure in a weak AC system according to claim 1, characterized in that, The formula for calculating the voltage fluctuation value when the AC filter is switched on or off is as follows: in, To adjust the voltage fluctuation value of the AC filter, This is the effective value of the first AC voltage. This is the effective value of the second AC voltage.

3. The method for suppressing commutation failure in a weak AC system according to claim 1, characterized in that, The formula for calculating the minimum arc extinction angle of a converter station is: in, This is the minimum angle for the converter station to extinguish its arc. This represents the minimum arc extinction angle for operation of a weak AC system. This represents the maximum arc extinction angle for a weak AC system. This represents the upper limit of the system's strength or weakness. This represents the lower limit of the system's strength or weakness.

4. The method for suppressing commutation failure in a weak AC system according to claim 1, characterized in that, The upper limit of the system strength characterization value is 2.5, and the lower limit of the system strength characterization value is 1.

5.

5. A commutation failure suppression device for a weak AC system, characterized in that, include: The first acquisition module is used to acquire the effective value of the first AC voltage at the AC bus of the converter station in real time. The second acquisition module is used to acquire the effective value of the second AC voltage at the AC bus of the converter station after the AC filter is put into or cut off. The fluctuation calculation module is used to calculate the voltage fluctuation value of the AC filter when it is switched on or off based on the first AC voltage effective value and the second AC voltage effective value. The system strength index calculation module is used to calculate the system strength characterization value of a weak AC system based on the voltage fluctuation value. The minimum arc extinction angle calculation module is used to calculate the minimum arc extinction angle of the converter station based on the system strength characteristics. The arc extinction angle adjustment module is used to adjust the arc extinction angle of the converter station to a minimum angle in real time. The formula for calculating the system strength characteristic value of a weak AC system is: Where K is the system strength characteristic value of the weak AC system. Where P is the capacity of a single AC filter and P is the DC transmission power. The voltage fluctuation value for switching the AC filter on or off.

6. The commutation failure suppression device for a weak AC system according to claim 5, characterized in that, The formula for calculating the voltage fluctuation value when the AC filter is switched on or off is as follows: in, To adjust the voltage fluctuation value of the AC filter, This is the effective value of the first AC voltage. This is the effective value of the second AC voltage.

7. The commutation failure suppression device for a weak AC system according to claim 5, characterized in that, The formula for calculating the minimum arc extinction angle of a converter station is: in, This is the minimum angle for the converter station to extinguish its arc. This represents the minimum arc extinction angle for operation of a weak AC system. This represents the maximum arc extinction angle for a weak AC system. This represents the upper limit of the system's strength or weakness. This represents the lower limit of the system's strength or weakness.

8. The commutation failure suppression device for a weak AC system according to claim 7, characterized in that, The upper limit of the system strength characterization value is 2.5, and the lower limit of the system strength characterization value is 1.5.

Images