Continuous commutation failure suppression method based on current deviation control

Abstract

The invention discloses a continuous commutation failure suppression method based on improved current deviation control, and the method comprises the steps: starting from the operation characteristics of the current deviation control, analyzing the influence of a slope k and an output upper limit value on a system in the current deviation control; the slope k and the output upper limit value in the current deviation control are improved, so that the commutation failure resistance of the system is improved, but the fault recovery of the system is not facilitated. On the basis, an improved current deviation control commutation failure suppression scheme is provided, and the slope k and the output upper limit value of current deviation control are dynamically changed according to the voltage drop condition of the alternating current bus during the fault. And finally, a direct current power transmission model electromagnetic transient simulation platform is built in PSCAD / EMTDC to verify improved current deviation control, and the scheme can effectively improve the turn-off angle when a fault occurs, avoids continuous commutation failure of the system, and ensures safe operation of the power system.

Description

Technical Field

[0001] This invention relates to the field of DC power transmission technology, specifically to a method for suppressing continuous commutation failure based on current deviation control. Background Technology

[0002] High-voltage direct current (HVDC) transmission has significant advantages such as low transmission loss, high operating efficiency, and suitability for cross-regional energy distribution. However, due to the use of thyristors as converter devices, commutation failure can easily occur on the inverter side of grid-commutated HVDC transmission systems. Commutation failure can lead to adverse factors such as DC voltage drop, short-term surge in DC current, and waveform distortion, affecting the stable operation of the system.

[0003] Currently, most solutions for suppressing commutation failures in high-voltage direct current (HVDC) transmission projects focus on three aspects: control and protection, equipment addition, and topology modification. These solutions are mainly categorized into "first-time" and "subsequent" approaches, with an emphasis on modeling and predictive index optimization under complex AC / DC coupling scenarios, and on the continuous study of dynamic coupling mechanisms and discrete commutation processes [9-10]. However, with the continuous expansion of HVDC transmission scale and the increasing complexity of power grid structures, existing suppression methods still face many challenges. Commutation failures can still lead to system power oscillations, equipment overloads, and even cascading failures. Therefore, further in-depth research into commutation failure suppression technology and overcoming existing theoretical and technological bottlenecks is of significant practical importance for ensuring the safe and reliable operation of HVDC transmission systems.

[0004] To address the commutation failure problem caused by AC bus faults on the inverter side of high-voltage direct current (HVDC) transmission systems, this invention delves into the characteristics of current deviation control. By analyzing the impact of the slope *k* and output upper limit value in current deviation control on the system, a continuous commutation failure suppression strategy based on improved current deviation control is proposed. First, the analysis of the slope and output upper limit value in current deviation control shows that increasing these values ​​improves the system's commutation failure resilience but hinders fault recovery; conversely, decreasing these values ​​reduces the system's commutation failure resilience but aids in fault recovery. Based on this, an improved current deviation control commutation failure suppression scheme is proposed, dynamically adjusting the slope *k* and output upper limit value according to the AC bus voltage drop during a fault. Finally, simulations on the Yongfu HVDC transmission model in PSCAD / EMTDC verify that the improved current deviation control scheme effectively increases the turn-off angle during a fault and reduces the probability of continuous commutation failures. Summary of the Invention

[0005] In view of the above-mentioned problems, the present invention provides a method for suppressing continuous commutation failure based on current deviation control.

[0006] Therefore, the technical problem solved by this invention is: this invention provides a continuous commutation failure suppression scheme based on improved current deviation control, starting from the operating characteristics of current deviation control, and by analyzing the slope k and the upper limit of the output in current deviation control. The impact on the system is illustrated by increasing the slope k and the upper limit of the output in the current deviation control. This is beneficial for improving the system's ability to withstand commutation failures, but detrimental to the system's fault recovery; while reducing the slope k and the upper limit of the output... This reduces the system's ability to withstand commutation failures but helps with fault recovery. Based on this, an improved current deviation control commutation failure suppression scheme is proposed, which dynamically changes the slope k and the upper limit of the output current deviation control according to the AC bus voltage drop during a fault. This effectively increases the shut-off angle during faults and prevents the system from experiencing continuous commutation failures.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for suppressing continuous commutation failure based on current deviation control, comprising, Based on the CIGRE standard test model and current deviation control strategy, the impact of slope and upper limit of turn-off angle increment on commutation failure is analyzed. A commutation failure suppression scheme is proposed, which dynamically changes the slope and the upper limit of the turn-off angle increment based on the AC voltage drop. The proposed commutation failure suppression scheme was compared with the CIGRE HVDC standard test model scheme in micro single-phase grounding faults, major single-phase grounding faults, and major three-phase grounding faults to ensure the safe and stable operation of the DC transmission system.

[0008] As a preferred embodiment of the continuous commutation failure suppression method based on current deviation control described in this invention, the analysis of the influence of the slope and the upper limit of the turn-off angle increment on commutation failure is performed. In the CIGRE standard test model, the operating characteristic curve of current deviation control is a ramp function, where the current deviation... I dc With shut-off angle compensation The following operational relationship exists between them: In the formula: This represents the maximum current deviation. This is the upper limit value for current deviation control output. When the current deviation value exceeds... At that time, the shut-off angle compensation value output by the controller Remain unchanged; The slope of the ramp function is expressed as: k = .

[0009] As a preferred embodiment of the continuous commutation failure suppression method based on current deviation control described in this invention, the proposed commutation failure suppression scheme includes dynamically changing the slope according to the drop amplitude of the AC voltage. and the upper limit of the shut-off angle increment When a minor single-phase or three-phase fault occurs in the system, the zero-sequence voltage U0 is lower than the threshold U. 0m , The calculation module outputs values ​​based on and Change, selector selection As the controller output.

[0010] As a preferred embodiment of the continuous commutation failure suppression method based on current deviation control described in this invention, the proposed commutation failure suppression scheme includes, when a severe single-phase ground fault occurs in the system, the zero-sequence voltage U0 is higher than a threshold U. 0m The controller is Multiplying the current by a coefficient q and adding an increment mU0, the result is used as the controller output. The more severe the single-phase fault, the larger the zero-sequence voltage, and the larger the corresponding increment mU0. This also means a stronger ability to handle commutation failures. Based on this, the improved current deviation control equation can be obtained as follows: In the formula, q is the adjustment coefficient.

[0011] As a preferred embodiment of the continuous commutation failure suppression method based on current deviation control described in this invention, the comparison of micro single-phase grounding faults, severe single-phase grounding faults, and severe three-phase grounding faults includes comparing two control schemes based on an electromagnetic transient simulation platform for DC transmission models built in PSCAD / EMTDC. Option 1: Use the CIGRE HVDC standard test model; Option 2: Use the current deviation control scheme described above, and set q and m to 0.8 and 2 respectively.

[0012] As a preferred embodiment of the continuous commutation failure suppression method based on current deviation control described in this invention, the comparison of micro single-phase grounding fault, major single-phase grounding fault, and major three-phase grounding fault includes, in the case of micro single-phase grounding fault, assuming a single-phase grounding fault occurs at the inverter-side converter bus via a 0.86H inductor, with a fault time of 1s and a fault duration of 0.5s, and comparing the original control strategy with three DC power control strategies under the current conditions.

[0013] As a preferred embodiment of the continuous commutation failure suppression method based on current deviation control described in this invention, the comparison of micro single-phase grounding fault, major single-phase grounding fault, and major three-phase grounding fault includes, in the case of major single-phase grounding fault, assuming a single-phase grounding fault occurs at the inverter-side converter bus via a 0.025H inductor, with a fault time of 1s and a fault duration of 0.5s, and comparing the original control strategy with three DC power limiting strategies under the current conditions.

[0014] As a preferred embodiment of the continuous commutation failure suppression method based on current deviation control described in this invention, the comparison of micro single-phase ground fault, heavy single-phase ground fault, and heavy three-phase ground fault includes, in the case of heavy three-phase ground fault, H inductor ground fault, fault time 1s, fault duration 0.5s, in which case the original control strategy and three DC power limiting strategies are compared.

[0015] The present invention provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the continuous commutation failure suppression method based on current deviation control.

[0016] The present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the continuous commutation failure suppression method based on current deviation control.

[0017] The beneficial effects of this invention: This invention, through the current deviation control operating characteristics in the CIGRE standard test model, illustrates the slope k and the upper limit of the output in current deviation control. The impact on the system is discussed, and an improved current deviation control scheme for continuous commutation failure in DC transmission systems is proposed, increasing the slope k and the upper limit of the output in the current deviation control. This is beneficial for improving the system's ability to withstand commutation failures, but detrimental to the system's fault recovery; conversely, reducing the slope k and the upper limit of the output value... This will reduce the system's ability to withstand commutation failures, but it will help the system recover from faults. The effectiveness of this solution in suppressing commutation failures can reduce continuous commutation failures, avoid DC system blockage, and provide a certain reference for the improvement of actual DC system control. It has good engineering application value. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a diagram illustrating an improved current deviation control structure for a continuous commutation failure suppression method based on current deviation control, provided as an embodiment of the present invention.

[0020] Figure 2 The current deviation control characteristic curve is provided for a continuous commutation failure suppression method based on current deviation control in one embodiment of the present invention.

[0021] Figure 3 This diagram illustrates the operating characteristics of a DC system using different schemes of a continuous commutation failure suppression method based on current deviation control, as provided in an embodiment of the present invention.

[0022] Figure 4 This is a schematic diagram of the changes in various electrical quantities during a single-phase grounding fault via a 0.086H inductor, which is provided as an embodiment of the present invention for a continuous commutation failure suppression method based on current deviation control.

[0023] Figure 5 This is a schematic diagram of the changes in various electrical quantities during a single-phase grounding fault via a 0.025H inductor, as provided in an embodiment of the present invention, for a continuous commutation failure suppression method based on current deviation control.

[0024] Figure 6 This is a schematic diagram of the changes in various electrical quantities during a three-phase inductive grounding fault via a 0.24H current deviation control-based continuous commutation failure suppression method, as provided in an embodiment of the present invention.

[0025] Figure 7 A comparison diagram of single-phase grounding faults provided by a continuous commutation failure suppression method based on current deviation control in an embodiment of the present invention.

[0026] Figure 8 A comparison diagram of three-phase grounding faults provided by an embodiment of the present invention for a continuous commutation failure suppression method based on current deviation control. Detailed Implementation

[0027] To make the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0028] Example 1, referring to Figures 1-8 This is one embodiment of the present invention, which provides a method for suppressing continuous commutation failure based on current deviation control, comprising: S1: On the CIGRE HVDC standard test model, single-phase ground faults via 0.5H and three-phase ground faults via 0.3H were set, with a fault time of 2 seconds and a duration of 0.5 seconds. Three schemes were used and compared with the original control scheme: Original scheme: current deviation control slope k is 2.973, upper limit is 16°; Scheme 1: current deviation control slope k is set to 2.123, upper limit remains unchanged; Scheme 2: current deviation control slope k is set to 0.4955, upper limit remains unchanged; Scheme 3: current deviation control upper limit is set to 24°, slope k remains unchanged. The operating results of different schemes are attached. Figure 3 .

[0029] Analysis Appendix Figure 3 It can be seen that after adopting Scheme 1, the number of commutation failures increased significantly compared to the original scheme. However, the AC voltage value was the highest among all schemes during the fault recovery process, which is beneficial for system recovery. Scheme 2 and Scheme 3 enhanced the system's ability to resist commutation failures during faults by increasing the slope k of the current deviation control and the upper limit of the output value to a certain extent, respectively. However, the AC bus was too low during the recovery process, which was not conducive to system recovery.

[0030] S2: This invention proposes an improved current deviation control commutation failure suppression scheme: dynamically changing the slope k and the upper limit of the turn-off angle increment based on the AC voltage drop amplitude. As per the instructions attached. Figure 2 As shown, the upper limit of the turn-off angle increment for the improved current deviation control is: (5) The slope k can be expressed as: (6) Improved current deviation control characteristic expression: (7) Extensive simulations revealed that this scheme was less effective at suppressing commutation failure during severe single-phase ground faults. This was primarily due to: ① the presence of a zero-crossing offset in the commutation voltage during a single-phase ground fault, resulting in a smaller turn-off angle compared to a three-phase fault, thus increasing the likelihood of commutation failure; ② from... Figure 2 It can be seen that the phase voltage fluctuated significantly within a short period of time during the fault, causing... Severe fluctuations occur, affecting the current deviation control slope k and the upper limit of the turn-off angle increment. This also causes significant fluctuations, affecting the output shut-off angle compensation. It is difficult to maintain stability. Therefore, the suppression scheme for single-phase ground faults still needs improvement.

[0031] Based on this, in order to increase the system's resilience to commutation failure during a single-phase ground fault, when the AC bus zero-sequence voltage amplitude exceeds the threshold U, 0m At that time, through the output of equation (4) Multiply by a coefficient q and give based on the zero-sequence voltage magnitude An additional increment yields: (8) In the formula, m is a constant greater than 0, and U0 is the amplitude of the zero-sequence voltage of the AC bus.

[0032] Combined with the instructions Figure 1 As can be seen, the input in this embodiment is U a U b U c Three-phase voltage and current deviation value I d The fundamental amplitude of the three-phase voltage is obtained using the SOGI method. Then, the voltage drop is calculated by taking the minimum value of each phase voltage amplitude. , , After further processing using equations (2) and (3), we obtain , k, finally through The calculation module obtains the shut-off angle compensation value. On the other hand, the magnitude of the zero-sequence voltage is calculated to determine whether further adjustments are needed. Incremental compensation is performed, and the specific increment is determined based on the zero-sequence voltage value. Finally, the value is selected. or To serve as the final output of the controller When a minor single-phase or three-phase fault occurs in the system, the zero-sequence voltage U0 is lower than the threshold voltage U. 0m , The calculation module outputs values ​​based on and Change, selector selection As the controller output. When a severe single-phase ground fault occurs in the system, the zero-sequence voltage U0 exceeds the threshold U0m, and the controller... The output of the controller is obtained by multiplying the current deviation by a coefficient q and adding an increment mU0. The more severe the single-phase fault, the larger the zero-sequence voltage, and the larger the corresponding increment mU0, resulting in a stronger ability to handle commutation failures. Based on this, the improved current deviation control equation can be obtained: (9) In the formula, q is the adjustment coefficient, and its specific value can be adjusted according to the actual situation.

[0033] S3: To verify the effectiveness of this scheme in suppressing continuous commutation failures, an electromagnetic transient simulation platform for the Yongfu DC transmission model was built in PSCAD / EMTDC, and two control schemes were compared: Scheme 1: using the CIGREHVDC standard test model; Scheme 2: using the improved current deviation control scheme described in this invention, with q and m set to 0.8 and 2 respectively.

[0034] During a single-phase ground fault, the changes in the main electrical quantities are shown in the attached description. Figure 4 As shown, when a minor fault occurs on the receiving-end AC bus, compared to Scheme 1, the number of commutation failures in the DC system is reduced after using Scheme 2. However, the current deviation control output value is basically the same as that of Scheme 1. This is because the severity of the fault is less and the AC voltage drop is smaller. Furthermore, Scheme 1 experienced two commutation failures during the recovery process after the fault was cleared, resulting in significant changes in DC power and current.

[0035] During a single-phase ground fault, the changes in the main electrical quantities are shown in the attached description. Figure 5 As shown, due to the small grounding inductance, a relatively severe grounding fault occurred during actual operation. Under Scheme 1 control, the system experienced four commutation failures after the fault, leading to significant changes in electrical quantities such as DC transmission power and DC current, impacting the system and even posing a risk of DC blocking. Under Scheme 2 control, only two commutation failures occurred, effectively reducing the number of failures. Furthermore, due to the severe single-phase grounding fault, the zero-sequence voltage was high during the fault and exceeded the set threshold; therefore, the output of the improved current deviation control was... Due to the effect of current deviation control, the turn-off angle during the fault period is slightly higher than that during normal operation. Although the turn-off angle fluctuates to some extent during this process, it effectively suppresses the subsequent commutation failure.

[0036] During a three-phase ground fault, the changes in the main electrical quantities are shown in the attached description. Figure 6 As shown, when a severe three-phase fault occurs in the system, Scheme 2 still has a good effect on suppressing commutation failure, and the recovery process of each electrical quantity during the fault and recovery process is basically similar to that of a single-phase fault.

[0037] To further verify the effectiveness of this scheme in suppressing continuous commutation failures, simulations were conducted under different fault conditions: the grounding inductance varied in steps of 0.1H within the range of 0.1~1H; the fault onset time was 2~2.006s with a step size of 0.001s; and the fault duration was 0.5s. (See attached diagram.) Figure 7 and Figure 8To compare the commutation failure suppression effects of different control methods, Scheme 2 showed better suppression of commutation failure compared to Scheme 1, indicating that the improved current deviation control scheme can more effectively reduce the risk of commutation failure and ensure the safe and stable operation of the DC transmission system.

[0038] The specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

[0039] This embodiment also provides an electronic device applicable to a continuous commutation failure suppression method based on current deviation control, comprising: a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to implement the continuous commutation failure suppression method based on current deviation control as proposed in the above embodiment.

[0040] This embodiment also provides a storage medium storing a computer program that, when executed by a processor, implements a continuous commutation failure suppression method based on current deviation control as proposed in the above embodiment.

[0041] The storage medium proposed in this embodiment belongs to the same inventive concept as the method for suppressing continuous commutation failure based on current deviation control proposed in the above embodiments. Technical details not described in detail in this embodiment can be found in the above embodiments, and this embodiment has the same beneficial effects as the above embodiments.

[0042] Based on the above description of the implementation methods, those skilled in the art can clearly understand that the present invention can be implemented using software and necessary general-purpose hardware, and of course, it can also be implemented using hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk, or optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of the various embodiments of the present invention.

[0043] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A continuous commutation failure suppression method based on current deviation control, characterized by: Comprising, According to the CIGRE standard test model, the current deviation control strategy analyzes the slope and the influence of the upper limit of the turn-off angle increment on the commutation failure; A commutation failure suppression scheme is proposed, which dynamically changes the slope and the upper limit of the turn-off angle increment according to the drop amplitude of the alternating voltage; The proposed commutation failure suppression scheme and the CIGRE HVDC standard test model scheme are compared in micro single-phase ground fault, heavy single-phase ground fault and heavy three-phase ground fault, to ensure the safe and stable operation of the DC power transmission system.

2. A continuous commutation failure suppression method based on current deviation control as claimed in claim 1, characterized by: The analysis of the influence of the slope and the upper limit of the turn-off angle increment on the commutation failure, In the CIGRE standard test model, the operating characteristic curve of current deviation control is a ramp function, in which the current deviation I dc and the off-angle compensation amount have the following operating relationship: In the formula: is the maximum current deviation, is the upper limit of the current deviation control output, and when the current deviation value exceeds , the off angle compensation value output by the controller remains unchanged; The slope of the ramp function is expressed as: k = 1 / t .

3. A continuous commutation failure suppression method based on current deviation control as claimed in claim 2, characterized by: The proposed commutation failure suppression scheme includes dynamically changing the slope according to the magnitude of the AC voltage drop and the upper limit of the angle increment When the system experiences a minor single-phase fault and a three-phase fault, the zero-sequence voltage U0 is lower than the threshold value U 0m , The calculation module output value changes according to and The selector selects as the controller output.

4. A continuous commutation failure suppression method based on current deviation control as claimed in claim 3, characterized by: The proposed commutation failure suppression scheme includes, when a serious single-phase ground fault occurs in the system, zero sequence voltage U0 is higher than threshold value U 0m , the controller multiplies coefficient q and adds an increment mU0 on the basis of , and takes it as the output of the controller. The more serious the single-phase fault is, the larger the zero sequence voltage is, and the larger the corresponding increment mU0 is. The lower the ability of commutation failure is, and the stronger the current deviation control equation is improved, according to which the equation is as follows: In the formula, q is the adjustment coefficient.

5. A continuous commutation failure suppression method based on current deviation control as claimed in claim 4, characterized by: The comparison of the micro single-phase ground fault, the heavy single-phase ground fault and the heavy three-phase ground fault includes building a DC power transmission model electromagnetic transient simulation platform in PSCAD / EMTDC, and using two control schemes for comparison: Scheme one: using the CIGRE HVDC standard test model; Scheme two: using the current deviation control scheme, taking q and m as 0.8 and 2 respectively.

6. A continuous commutation failure suppression method based on current deviation control as claimed in claim 5, characterized by: The comparison of the micro single-phase ground fault, the heavy single-phase ground fault and the heavy three-phase ground fault includes that in the micro single-phase ground fault, it is assumed that a single-phase ground fault occurs at the inverter side of the converter bus through a 0.86H inductor, the fault time is 1s, the fault lasts for 0.5s, and the original control strategy and three DC power control strategies are used for comparison under the current condition.

7. A continuous commutation failure suppression method based on current deviation control as claimed in claim 6, characterized by: The comparison of the micro single-phase ground fault, the heavy single-phase ground fault and the heavy three-phase ground fault includes that in the heavy single-phase ground fault, it is assumed that a single-phase ground fault occurs at the inverter side of the converter bus through a 0.025H inductor, the fault time is 1s, the fault lasts for 0.5s, and the original control strategy and three DC power control strategies are used for comparison under the current condition.

8. A continuous commutation failure suppression method based on current deviation control as claimed in claim 7, characterized by: The comparison of the micro single-phase ground fault, the heavy single-phase ground fault and the heavy three-phase ground fault includes that in the heavy three-phase ground fault, the H inductor is grounded, the fault time is 1s, the fault lasts for 0.5s, and the original control strategy and three DC power control strategies are used for comparison under the current condition. 9.A computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the computer device is configured to perform the method according to any one of claims 1-8 when the computer program is executed by the processor. The processor executes the computer program to realize the steps of the continuous commutation failure suppression method based on the current deviation control in any one of claims 1 to 8.

10. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to realize the steps of the continuous commutation failure suppression method based on the current deviation control in any one of claims 1 to 8.

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