Line voltage amplitude drop-based power transmission system commutation method, system and medium

Abstract

The application discloses a power transmission system commutation method and system based on line voltage amplitude drop, and a medium; relates to the technical field of power systems; line voltage data of a bus is sampled in real time, and the maximum drop percentage of line voltage commutation voltage of the bus is predicted; the maximum drop percentage of line voltage commutation voltage is used to implement early trigger control on the converter; according to the line voltage data of the bus, the maximum drop percentage of line voltage commutation voltage of the bus is predicted, and the maximum drop percentage of line voltage commutation voltage is used to implement early trigger control on the converter, and the subsequent trigger control is performed for the maximum drop percentage of line voltage commutation voltage (the fault phase); the line voltage directly affecting the commutation failure is directly measured, the drop of each phase line voltage is calculated in real time, and especially under the condition of inter-phase fault, the main body of commutation failure is more accurately predicted compared with the calculation result of the prior art, and the sensitivity of inter-phase fault discrimination is improved.

Description

Technical Field

[0001] This invention relates to the field of power system technology, and more specifically to a commutation method, system, and medium for power transmission systems based on line voltage amplitude drop. Background Technology

[0002] High-voltage direct current (HVDC) transmission plays a crucial role in my country's energy optimization and allocation due to its advantages in long-distance, high-capacity power transmission. The basic principle of HVDC transmission is as follows: at the sending end of the HVDC system, a converter rectifies the three-phase alternating current (AC) into direct current (DC). The electrical energy is then transmitted through the HVDC transmission line. At the receiving end of the HVDC system, a converter inverts the DC into three-phase AC, and the electrical energy is then sent to the AC system at the receiving end.

[0003] High-voltage direct current (HVDC) transmission converters typically employ six-pulse bridge converters for rectification and inversion. These converters use thyristor valves without self-turn-off capability as basic commutation elements, with each valve alternately conducting during normal operation. Due to the presence of reactance parameters in the circuit, the switching of current between two valves cannot be instantaneous and requires a certain amount of time, known as the commutation process. After the commutation process, if the valve that just exited conduction fails to regain its blocking capability within a certain period under reverse voltage, or if the commutation process is not completed, the valve will conduct again after the voltage reverses, a phenomenon known as commutation failure. Commutation failure is one of the most common fault types in HVDC transmission systems, usually occurring on the inverter side. Commutation failure leads to a sudden increase in DC current, impacting the converter valves and even causing DC blockage, seriously threatening the safe and stable operation of the power grid. Summary of the Invention

[0004] The technical problem this invention aims to solve is that the commutation failure prediction method based on the normalized sag voltage of three-phase AC voltage in engineering has a large error under phase-to-phase fault conditions, affecting the action speed of commutation failure prediction control. This invention aims to provide a commutation method, system, and medium for transmission systems based on line voltage amplitude sag; it improves upon existing commutation failure prediction technologies. This scheme predicts the maximum sag percentage of the bus line voltage commutation voltage based on the bus line voltage data, implements advance trigger control for the converter based on this percentage, and performs subsequent trigger control based on the maximum sag percentage of the line voltage commutation voltage (faulty phase), accurately predicting the main body of the commutation failure and improving the sensitivity of phase-to-phase fault detection.

[0005] This invention is achieved through the following technical solution:

[0006] This solution provides a commutation method for transmission systems based on line voltage amplitude drop, including:

[0007] Real-time sampling of bus line voltage data;

[0008] Predict the maximum percentage drop in the commutation voltage of the busbar based on the busbar line voltage data;

[0009] The converter is controlled to be triggered in advance based on the maximum percentage drop in line voltage and commutation voltage.

[0010] The working principle of this solution is as follows: The commutation failure prediction method based on the normalized drop voltage of three-phase AC voltage in engineering has a large error under phase-to-phase fault conditions, which affects the action speed of commutation failure prediction control. This solution improves the existing commutation failure prediction technology by predicting the maximum percentage drop of the bus line voltage commutation voltage based on the bus line voltage data, and implements advance trigger control of the converter based on the maximum percentage drop of the line voltage commutation voltage (faulty phase). Subsequent trigger control is performed based on the maximum percentage drop of the line voltage commutation voltage (faulty phase), which accurately predicts the main body of commutation failure and improves the sensitivity of phase-to-phase fault detection.

[0011] The existing commutation failure predictive control uses a criterion that reduces the three-phase AC voltages of A, B, and C to a single index Uαβ. αβ The drop was determined to have caused a three-phase fault. αβ Direct measurement of line voltage—a key factor directly affecting commutation failure—is not yet feasible, especially under phase-to-phase fault conditions, where only the line voltage between the faulty phases drops. In this case, U... αβ The voltage drop is smaller than the actual commutation voltage drop (because it includes the normal phase voltage), resulting in insufficient fault detection sensitivity. This, in turn, affects the action speed of the commutation failure prediction control, which is detrimental to the safe and stable operation of the system.

[0012] This invention performs real-time detection of voltage drops in each phase, thereby improving the sensitivity of phase-to-phase fault detection.

[0013] A further optimized solution involves real-time sampling of the bus line voltage data; predicting the maximum percentage drop in the bus line voltage commutation voltage based on the bus line voltage data; including the following methods:

[0014] T1, continuously sampling the AB phase line voltage data of the AC bus on the inverter side of the high-voltage direct current transmission system at time intervals of Ts: first line voltage u ab1 Second line voltage u ab2 ;

[0015] T2, calculate the component voltage of the AB phase line voltage based on the AB phase line voltage data;

[0016] T3, Calculation of the amplitude U of the AB phase line voltage based on component voltage. abm ;

[0017] T4, calculated amplitude U of phase AB line voltage. abm And the standard amplitude U of the AB phase line voltage under normal conditions. abm_N Calculate the percentage drop in voltage amplitude ΔU between phase AB lines. abm ;

[0018] T5, repeat steps T1-T4 to calculate the percentage drop in amplitude ΔU of the BC phase line voltage. bcm And the percentage drop in the amplitude of the CA phase line voltage ΔU cam And calculate the maximum commutation voltage drop percentage ΔU max .

[0019] A further optimized solution is that the first line voltage u ab1 Second line voltage u ab2 Represented as:

[0020]

[0021]

[0022] Among them U abm It is the amplitude of the AB phase line voltage. It is the current phase, and f is the line voltage frequency, f = 50Hz.

[0023] A further optimized solution is that the calculation of the component voltages of the AB phase line voltage based on the AB phase line voltage data includes the following method:

[0024] The d-axis component U of the AB phase line voltage is calculated using the following formula. abd and q-axis component U abq :

[0025]

[0026] .

[0027] A further optimized solution is to calculate the amplitude U of the AB phase line voltage based on component voltage. abm Including methods:

[0028]

[0029] A further optimized solution is to calculate the amplitude U based on the AB phase line voltage. abm And the standard amplitude U of the AB phase line voltage under normal conditions. abm_N Calculate the percentage drop in voltage amplitude ΔU between phase AB lines. abm Including methods:

[0030]

[0031] A further optimization scheme is to calculate the maximum commutation voltage drop percentage ΔU according to the following formula. max :

[0032] ΔU max =max{ΔU abm ,ΔU bcm ,ΔU cam}

[0033] A further optimized solution is to implement advance triggering control of the converter based on the maximum percentage drop in line voltage and commutation voltage, including the following methods:

[0034] Implement converter advance trigger control, advance trigger angle α pre for:

[0035]

[0036] Where ΔU t The threshold for early triggering of control.

[0037] This solution also provides a transmission system commutation system based on line voltage amplitude sag, used to implement the aforementioned transmission system commutation method based on line voltage amplitude sag; including:

[0038] The sampling module is used to sample the line voltage data of the bus in real time;

[0039] The prediction module is used to predict the maximum percentage drop in the commutation voltage of the bus based on the line voltage data of the bus.

[0040] The control module is used to implement advance trigger control of the converter based on the maximum percentage drop in line voltage and commutation voltage.

[0041] This solution also provides a computer-readable medium having a computer program stored thereon, which, when executed by a processor, can implement the power transmission system commutation method based on line voltage amplitude drop as described above.

[0042] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0043] The present invention provides a method, system, and medium for commutation of power transmission systems based on line voltage amplitude drop, which improves upon existing commutation failure prediction technologies. It predicts the maximum percentage drop in bus line voltage commutation voltage based on bus line voltage data, implements advance trigger control on the converter based on this percentage, and performs subsequent trigger control based on the maximum percentage drop in line voltage commutation voltage (faulty phase). This accurately predicts the main body of commutation failure and improves the sensitivity of phase-to-phase fault detection. Attached Figure Description

[0044] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0045] Figure 1 This is a schematic diagram of the commutation method for a power transmission system based on line voltage amplitude drop.

[0046] Figure 2 This is a schematic diagram comparing the results of the real-time phase-by-phase calculation of AC voltage sag in this invention with those of the traditional voltage sag calculation. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0048] Example 1

[0049] This embodiment provides a commutation method for transmission systems based on line voltage amplitude drop, including:

[0050] Step 1: Real-time sampling of bus line voltage data;

[0051] Step 2: Predict the maximum percentage drop in bus line voltage commutation voltage based on the bus line voltage data;

[0052] Real-time sampling of bus line voltage data; prediction of the maximum percentage drop in bus line voltage commutation voltage based on the bus line voltage data; including methods:

[0053] T1, continuously sampling the AB phase line voltage data of the AC bus on the inverter side of the high-voltage direct current transmission system at time intervals of Ts: first line voltage u ab1 Second line voltage u ab2 ;

[0054] T2, calculate the component voltage of the AB phase line voltage based on the AB phase line voltage data;

[0055] T3, Calculation of the amplitude U of the AB phase line voltage based on component voltage. abm ;

[0056] T4, calculated amplitude U of phase AB line voltage. abm And the standard amplitude U of the AB phase line voltage under normal conditions. abm_NCalculate the percentage drop in voltage amplitude ΔU between phase AB lines. abm ;

[0057] T5, repeat steps T1-T4 to calculate the percentage drop in amplitude ΔU of the BC phase line voltage. bcm And the percentage drop in the amplitude of the CA phase line voltage ΔU cam And calculate the maximum commutation voltage drop percentage ΔU max .

[0058] First line voltage uu ab1 Second line voltage u ab2 Represented as:

[0059]

[0060]

[0061] Among them U abm It is the amplitude of the AB phase line voltage. It is the current phase, and f is the line voltage frequency, f = 50Hz.

[0062] Calculate the component voltages of the AB phase line voltage based on the AB phase line voltage data, including the following methods:

[0063] The d-axis component U of the AB phase line voltage is calculated using the following formula. abd and q-axis component U abq :

[0064]

[0065]

[0066] Calculation of the amplitude U of phase line voltage AB based on component voltage. abm Including methods:

[0067]

[0068] The calculated amplitude U of the AB phase line voltage abm And the standard amplitude U of the AB phase line voltage under normal conditions. abm_N Calculate the percentage drop in voltage amplitude ΔU between phase AB lines. abm Including methods:

[0069]

[0070] The maximum commutation voltage drop percentage ΔU is calculated using the following formula. max :

[0071] ΔU max =max{ΔU abm ,ΔUbcm ,ΔU cam}

[0072] Step 3: Implement advance triggering control for the converter based on the maximum percentage drop in line voltage and commutation voltage, including the following methods:

[0073] Implement converter advance trigger control, advance trigger angle α pre for:

[0074]

[0075] Where ΔU t The threshold for early triggering of control.

[0076] Example 2

[0077] This embodiment provides a power transmission system commutation system based on line voltage amplitude sag, used to implement the power transmission system commutation method based on line voltage amplitude sag in Embodiment 1; including:

[0078] The sampling module is used to sample the line voltage data of the bus in real time;

[0079] The prediction module is used to predict the maximum percentage drop in the commutation voltage of the bus based on the line voltage data of the bus.

[0080] The control module is used to implement advance trigger control of the converter based on the maximum percentage drop in line voltage and commutation voltage.

[0081] Example 3

[0082] This embodiment provides a computer-readable medium having a computer program stored thereon. The computer program, when executed by a processor, can implement the power transmission system commutation method based on line voltage amplitude drop as described in Embodiment 1.

[0083] Example 4

[0084] This embodiment uses the method described in Embodiment 1 to calculate and solve the fault voltage data of an actual high-voltage direct current (HVDC) transmission project. The data comes from a real-world engineering case involving an AB-phase inter-phase fault that caused a HVDC transmission commutation failure. In this case, the existing commutation failure prediction control uses criterion U... αβ Insufficient sensitivity prevents fault detection, thus failing to prevent commutation failure.

[0085] The calculation and comparison results are as follows Figure 2 As shown. By Figure 2 It can be seen that after the A / B phase-to-phase fault occurs, the line voltage U ab The real-time phase-separation calculation results immediately dropped, with a maximum drop of about 15%, while the line voltage U bc and Uca The decline was relatively small. Existing indicator U αβ Essentially, it is about U ab U bc and U ca Based on a comprehensive assessment, its voltage drop falls between the most severe and the least severe of the three. In fact, the line voltage waveform directly affects the commutation of high-voltage direct current transmission. Compared to traditional methods, this method can quickly and directly identify the line voltage U. ab The sharp drop in price facilitates the rapid implementation of subsequent commutation failure control measures.

[0086] This solution enables direct measurement of line voltage, a key factor directly affecting commutation failure. It can calculate the voltage drops of phases AB, BC, and CA in real time, based on the sampling frequency. The results are more accurate than existing technologies, especially under phase-to-phase fault conditions, thus facilitating the prevention and control of commutation failure. The proposed criteria have clear physical meaning, and the calculation process requires no additional equipment, making it easy to implement in engineering.

[0087] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A commutation method for power transmission systems based on line voltage amplitude drop, characterized in that, include: Real-time sampling of bus line voltage data; Predict the maximum percentage drop in the commutation voltage of the busbar based on the busbar line voltage data; The converter is controlled to be triggered in advance based on the maximum percentage drop in line voltage and commutation voltage. The method includes real-time sampling of bus line voltage data; predicting the maximum percentage drop in bus line voltage commutation voltage based on the bus line voltage data; including: T1, with time intervals Ts, continuously samples the AB phase line voltage data of the AC bus on the inverter side of the high-voltage direct current transmission system: first line voltage u ab1 Second line voltage u ab2 ; T2, calculate the component voltage of the AB phase line voltage based on the AB phase line voltage data; T3, Calculation of the amplitude U of the AB phase line voltage based on component voltage. abm ; T4, calculated amplitude U of phase AB line voltage. abm And the standard amplitude U of the AB phase line voltage under normal conditions. abm_N Calculate the percentage drop in voltage amplitude of phase AB lines. ; T5, repeat steps T1-T4 to calculate the percentage drop in the amplitude of the BC phase line voltage. And the percentage drop in the amplitude of the CA phase line voltage. And calculate the maximum percentage drop in commutation voltage. ; The method of implementing advance triggering control of the converter based on the maximum percentage drop in line voltage commutation voltage includes: implementing advance triggering control of the converter, and the advance triggering angle. for: ； in The threshold for early triggering of control.

2. The power transmission system commutation method based on line voltage amplitude drop according to claim 1, characterized in that, The first line voltage u ab1 Second line voltage u ab2 Represented as: ； U abm It is the amplitude of the AB phase line voltage. It is the current phase, and f is the line voltage frequency, f=50Hz.

3. The power transmission system commutation method based on line voltage amplitude drop according to claim 2, characterized in that, The method for calculating the component voltages of the AB phase line voltage based on the AB phase line voltage data includes: The d-axis component U of the AB phase line voltage is calculated using the following formula. abd and q-axis component U abq : 。 4. The power transmission system commutation method based on line voltage amplitude drop according to claim 3, characterized in that, The calculated amplitude U of the AB phase line voltage based on component voltage is... abm Including methods: .

5. The power transmission system commutation method based on line voltage amplitude drop according to claim 4, characterized in that, The calculated amplitude U of the AB phase line voltage abm And the standard amplitude U of the AB phase line voltage under normal conditions. abm_N Calculate the percentage drop in voltage amplitude of phase AB lines. Including methods: .

6. The power transmission system commutation method based on line voltage amplitude drop according to claim 1, characterized in that, The maximum percentage drop in commutation voltage is calculated using the following formula. : .

7. A power transmission system commutation system based on line voltage amplitude drop, characterized in that, A method for implementing a power transmission system commutation method based on line voltage amplitude drop as described in any one of claims 1-6; comprising: The sampling module is used to sample the line voltage data of the bus in real time; The prediction module is used to predict the maximum percentage drop in the commutation voltage of the bus based on the line voltage data of the bus. The control module is used to implement advance trigger control of the converter based on the maximum percentage drop in line voltage and commutation voltage.

8. A computer-readable medium having a computer program stored thereon, characterized in that, The computer program, when executed by a processor, can implement the power transmission system commutation method based on line voltage amplitude drop as described in any one of claims 1-6.

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