Bus overvoltage system for AC filter bus charging and small filter commissioning and calculation method
By using bus overvoltage calculation methods and systems to analyze and control overvoltage during the AC filter bus charging and small filter operation, the threat of instantaneous overvoltage to equipment and systems is solved, and higher safety and reliability are achieved.
Patent Information
- Application Number
- CN202510256378.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-05
- Publication Date
- 2025-05-23
AI Technical Summary
During the AC filter bus charging and small filter operation, instantaneous overvoltage may occur, resulting in equipment damage or system failure, and the existing technology lacks effective overvoltage analysis and control.
Provide bus overvoltage calculation methods and systems for AC filter bus charging and small filter operation. By calculating overvoltage under different closing angles and residual voltage conditions, potential overvoltage phenomena are identified and corresponding control measures are taken.
By accurately predicting and analyzing overvoltages, we help engineers identify potential risks, take protective measures in advance, avoid equipment damage and safety accidents, optimize the equipment start-stop process, and improve system stability and equipment service life.
Smart Images
Figure CN120033812A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the electrical field, and in particular relates to a bus overvoltage system and a calculation method for charging an AC filter bus and putting a small filter into operation. Background Art
[0002] During the charging and commissioning of the filter bus, transient overvoltages may occur due to operations such as switch closing and filter switching. These overvoltages can damage the equipment and may even cause system failures. By calculating the overvoltage of the bus, it is possible to predict and analyze the overvoltage under different conditions, so that corresponding control measures can be taken to avoid overvoltages exceeding the tolerance range of the equipment and ensure safe operation of the system.
[0003] The choice of closing angle has a significant impact on the magnitude of overvoltage. By calculating the busbar overvoltage at different closing angles (0°, 90°, 180°), the appropriate closing time can be found to reduce the overvoltage generated at the moment of closing, thereby optimizing the start-stop process of the equipment and ensuring the stability of the power system.
[0004] When the AC filter is put into operation, if the voltage waveform is not properly controlled, it may cause a large voltage spike. By calculating the overvoltage with a preset step size, the overvoltage situation at different input times can be evaluated, and then technical means (such as adjusting the switching time, delaying input, etc.) can be used to avoid excessive transient voltage, thereby protecting the system and equipment. Summary of the invention
[0005] The purpose of the present invention is to overcome the above-mentioned deficiency of lack of overvoltage analysis and control, and to provide a bus overvoltage system and calculation method for AC filter bus charging and small filter operation. In order to achieve the above object, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for calculating bus overvoltage during AC filter bus charging and small filter operation, comprising the following steps: Select the required closing angle, with each preset angle as a step length, and set the AC filter bus residual voltage to -1.0pu or 1.0pu respectively. Calculate the overvoltage of the AC filter bus under the condition that the gap breakdown voltage is 0V; The range of the AC filter bus is selected as [-1.0 pu, 1.0 pu], and the overvoltage of the AC filter bus is calculated at closing angles of 0°, 90°, and 180° with a preset step size.
[0006] A further improvement of the present invention is that the required closing angle range is [0°, 315°].
[0007] A further improvement of the present invention is that the preset angle is 45°.
[0008] A further improvement of the present invention is that the preset step size is 0.2 pu.
[0009] A further improvement of the present invention is that when the AC filter bus is charged, all grounding switches on the loop are disconnected, the circuit breakers and disconnectors on the AC filter bus are disconnected, the disconnectors Q13 and Q14 on the 330kV bus are in a closed state, and the circuit breaker Q2 is closed.
[0010] A further improvement of the present invention is that when the small filter is put into operation, the isolating switch Q11 is closed first, and then the circuit breaker Q1 is closed.
[0011] A further improvement of the present invention is that the time constant of the circuit breaker arc is 1 ps.
[0012] A further improvement of the present invention is that the time constant of the isolating switch is 1 ns.
[0013] In a second aspect, the present invention provides a bus overvoltage system for charging an AC filter bus and commissioning a small filter, comprising a 330 kV bus, an AC filter bus and a filter; 330kV busbar connects voltage transformer cabinet and lightning arrester; The 330kV busbar and the AC filter busbar are provided with isolating switches Q13 and Q14, and a circuit breaker Q2 is provided between the isolating switches Q13 and Q14; A circuit breaker Q1 is provided between the AC filter bus and the filter, and an isolating switch Q11 is provided between the AC filter bus and the circuit breaker Q1.
[0014] A further improvement of the present invention is that the isolating switch Q11, the isolating switch Q13 and the isolating switch Q14 are all grounded.
[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention can accurately predict the overvoltage that may be generated by the filter bus during charging and commissioning by calculating the overvoltage under different closing angles and different residual voltage conditions. This can help engineers better understand the overvoltage phenomenon that may occur in actual operation, so as to prepare countermeasures in advance to prevent equipment damage. The present invention can identify under which conditions a large overvoltage shock may occur in the power grid system through detailed analysis of overvoltage. This allows the design of electrical equipment to more specifically enhance protection measures (such as adding overvoltage protection devices, adjusting withstand voltage design, etc.) to avoid equipment damage or safety accidents caused by overvoltage. The present invention can optimize the closing strategy of the filter by analyzing the overvoltage results under different closing angles and voltage residual pressures. For example, the amplitude of the overvoltage can be reduced by selecting the most suitable closing angle, thereby reducing the probability of overvoltage. By adjusting the parameters during commissioning, the impact on the system and equipment can be further reduced. The present invention can reduce the test and debugging time in actual operation by calculating and simulating overvoltage in advance. Designers can find potential problems in the simulation and analysis stages to avoid complex debugging and improvements due to overvoltage problems in the later stage. This can improve the efficiency of the design and reduce unnecessary debugging work. In summary, the present invention can effectively overcome the shortcomings of traditional methods in terms of lack of overvoltage analysis and control, and can not only improve the safety and reliability of systems and equipment, but also optimize the operation of electrical systems, increase equipment service life and reduce maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 is a system diagram of the present invention; Figure 2 This is a schematic diagram of the overvoltage of the AC filter bus when the A phase closing angle is 0° and the bus residual voltage is -1.0pu; Figure 3 This is a schematic diagram of the overvoltage of the AC filter bus when the A phase closing angle is 180° and the bus residual voltage is 1.0pu; Figure 4 It is a schematic diagram of the relationship between the overvoltage amplitude of phase A and the closing angle; Figure 5 It is a schematic diagram of the relationship between the minimum bus overvoltage amplitude and the bus residual voltage; Figure 6 It is a schematic diagram of the relationship between the maximum bus overvoltage amplitude and the bus residual voltage; Figure 7 It is a schematic diagram of the relationship between the overvoltage of phase A and the closing angle; Figure 8 It is a schematic diagram of the relationship between the difference between the minimum value and the instantaneous value of the overvoltage amplitude of phase A and the residual voltage of the line; Fig. 9 Schematic diagram of the relationship between the difference between the maximum value and instantaneous value of the overvoltage amplitude of phase A and the line residual voltage. DETAILED DESCRIPTION
[0017] In order to further understand the content of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the embodiments are only for explaining the present invention and are not intended to limit it.
[0018] See also Figure 1 The bus overvoltage system for AC filter bus charging and small filter operation includes 330kV bus, AC filter bus and filter. The 330kV bus is connected to the voltage transformer cabinet and the arrester; the 330kV bus and AC filter bus are equipped with disconnectors Q13 and Q14, and a circuit breaker Q2 is set between the disconnectors Q13 and Q14; a circuit breaker Q1 is set between the AC filter bus and the filter, and a disconnector Q11 is set between the AC filter bus and the circuit breaker Q1.
[0019] The switching operation when charging the AC filter bus is to disconnect all grounding switches on the circuit and all circuit breakers and disconnectors on the AC filter bus, and the disconnectors Q13 and Q14 on the 330kV bus are closed, and finally the circuit breaker Q2 is closed to charge the AC filter bus. Since the arc extinguishing capability of the circuit breaker is higher than that of the disconnector, the time constant of the circuit breaker arc is set to 1ps, and the disconnector is set to 1ns.
[0020] The closing angle (cosine function) range is selected as [0°, 315°], with a step size of 45° (based on phase A), and the overvoltage of the AC filter bus is calculated under the conditions that the bus residual voltage is -1.0pu or 1.0pu (corresponding to the phase voltage of 190.5kV) and the breakdown voltage of the gap is 0V. Theoretically, when the closing angle is 0° or 180°, the bus residual voltage is -1.0pu or 1.0pu (corresponding to the phase voltage of 190.5kV), and the breakdown voltage of the gap is 0V, which is theoretically the most severe working condition and will obtain the maximum amplitude of VFTO. Therefore, the main report only shows the overvoltage waveforms of the AC filter bus under the two conditions of the A phase closing angle of 0°, the bus residual voltage of -1.0pu and the A phase closing angle of 180°, and the bus residual voltage of 1.0pu, as shown in the figure. Figure 2 and Figure 3 shown.
[0021] Table 1 Bus overvoltage amplitude
[0022] The voltage reference value of each phase in Table 1 is the effective value of the phase voltage 190.5kV, and the voltage in brackets is the 330kV bus phase A voltage. When the closing angle is in the positive half cycle and the bus residual voltage is -1.0 pu or the closing angle is in the negative half cycle and the bus residual voltage is 1.0 pu, the bus overvoltage amplitude is large. Taking phase A as an example, the relationship between its overvoltage amplitude and closing angle is as follows: Figure 4 As shown in Figure 4, when the closing angle is 0°, the 330kV bus A phase voltage reaches the maximum value. At this time, the overvoltage maximum value on the AC filter bus is large; similarly, when the closing angle is 180°, the overvoltage minimum value is small. It can be found from Figure 4 that when the closing angle is 90° or 270°, that is, when the 330kV bus A phase voltage passes through the zero point, the difference between the maximum and minimum overvoltage values is the smallest, and the interference caused by the AC filter bus overvoltage is the smallest.
[0023] The bus residual voltage range is selected as [-1.0 pu, 1.0 pu], and the overvoltage of the AC filter bus is calculated at closing angles of 0°, 90°, and 180° (phase A) with a step size of 0.2 pu. The overvoltage amplitude of the AC filter bus is shown in Table 2.
[0024] Table 2 AC filter bus overvoltage
[0025] In order to more intuitively find the relationship between bus overvoltage and bus residual voltage, the relationship between phase A overvoltage amplitude and bus residual voltage is plotted as shown in the figure. Figure 5 and Figure 6 As shown. Figure 5 and Figure 6 It can be found that when the closing angle is 0°, that is, when the 330kV bus voltage A phase reaches the positive peak, the AC filter bus residual voltage has little effect on the maximum value of its overvoltage amplitude; similarly, when the closing angle is 180°, the bus residual voltage has little effect on the minimum value of the overvoltage amplitude. This is because the amplitude of VFTO is the superposition of multiple refracted and reflected traveling waves. When the 330kV bus A phase voltage reaches the maximum, the forward traveling wave dominates the voltage amplitude, so the bus residual voltage has little effect on the overvoltage amplitude. It can be found from the figure that when the closing angle is 90°, the minimum value of the overvoltage amplitude first increases and then decreases with the bus residual voltage, and the amplitude is closest to 0 near the residual voltage of 0; when the closing angle is 90° or 180°, the maximum value of the overvoltage amplitude first decreases and then increases with the bus residual voltage, and the amplitude is closest to 0 near the residual voltage of 0. Therefore, when the 330kVA phase bus voltage passes through zero, phase A is closed and the bus overvoltage is minimal. The same applies to phases B and C.
[0026] When the isolating switch Q13 and the isolating switch Q14 are closed, the circuit breaker Q2 is also closed to complete the charging of the large group AC filter bus. At this time, if the small group filter needs to be switched, the switching operation is to first close the isolating switch Q11 and then close the circuit breaker Q1. Calculate the bus overvoltage when the isolating switch Q11 is closed. Since the arc extinguishing ability of the isolating switch is poor, its arc resistance at the same time is greater than that of the circuit breaker, so the time constant of the time-varying resistance corresponding to the isolating switch is set to 1ns.
[0027] The closing angle (cosine function) range is selected as [0°, 315°], with a step size of 45° (based on phase A), and the overvoltage of the AC filter bus is calculated under the conditions that the bus residual voltage is -1.0pu or 1.0pu (corresponding to the phase voltage of 190.5kV) and the breakdown voltage of the gap is 0V. Theoretically, when the closing angle is 0° or 180°, the bus residual voltage is -1.0pu or 1.0pu (corresponding to the phase voltage of 190.5kV), and the breakdown voltage of the gap is 0V, which is the most severe working condition in theory, and the maximum amplitude of VFTO will be obtained. Therefore, the main report only shows the conditions of the closing angle of phase A being 0°, the bus residual voltage being -1.0pu and the closing angle of phase A being 180°, and the bus residual voltage being 1.0pu.
[0028] Table 3 AC filter bus overvoltage amplitude (to be subtracted from the instantaneous value of each phase)
[0029] When the small filter group is switched on, the AC filter bus acts as a power source, and the voltage on it is 330kV AC power. Therefore, the overvoltage on the AC filter bus is superimposed on the instantaneous value of each phase voltage, as shown in brackets in Table 3. When drawing the relationship between the overvoltage and the closing angle of phase A, the instantaneous value is subtracted from the overvoltage amplitude, and the results are compared, as shown in Figure 3. Figure 7 As shown. It can be found that as the closing angle gradually approaches 90° and 270°, the maximum value of overvoltage decreases and the minimum value increases, indicating that the busbar is better able to withstand overvoltage; conversely, the maximum value of overvoltage increases and the minimum value decreases, indicating that the busbar is worse able to withstand overvoltage. When the residual voltage is 1.0pu, both the maximum and minimum values of overvoltage are greater than when the residual voltage is -1.0pu; when the residual voltage is -1.0pu, both the maximum and minimum values of overvoltage are less than when the residual voltage is 1.0pu, indicating that the overvoltage will change upward or downward with the overall residual voltage.
[0030] The line residual voltage range is selected as [-1.0 pu, 1.0 pu], and each 0.2 pu is used as a step size. The overvoltage of the AC filter bus is calculated under the conditions of closing angles of 0°, 90° and 180° (phase A). The overvoltage amplitude of the AC filter bus is shown in Table 4.
[0031] Table 4 AC filter bus overvoltage amplitude
[0032] Since there is a 330kV power frequency voltage on the AC filter bus at this time, when drawing the relationship between the A-phase overvoltage amplitude and the bus residual voltage, the overvoltage amplitude minus the instantaneous value of the A-phase voltage is used as the vertical coordinate, such as Figure 8 and Fig. 9 As shown. It can be found from the chart that when the closing angle is 0°, that is, when the AC filter bus voltage phase A reaches the positive peak, the AC filter bus residual voltage has little effect on its maximum overvoltage amplitude; similarly, when the closing angle is 180°, the bus residual voltage has little effect on the minimum overvoltage amplitude. This is because the amplitude of VFTO is the superposition of multiple refracted and reflected traveling waves. When the 330kV bus phase A voltage reaches its maximum, the forward traveling wave dominates the voltage amplitude. Therefore, the bus residual voltage has little effect on the overvoltage amplitude. Figure 8 and Fig. 9 It can be found that when the closing angle is 90°, the minimum value of the overvoltage amplitude increases first and then decreases with the bus residual voltage, and the amplitude is closest to 0 near the residual voltage of 0; when the closing angle is 90° or 180°, the maximum value of the overvoltage amplitude decreases first and then increases with the bus residual voltage, and the amplitude is closest to 0 near the residual voltage of 0. Therefore, when the bus voltage of phase A of the AC filter passes through zero, the small filter group is switched on, and the bus overvoltage is minimized, and the same is true for phases B and C.
[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.
Claims
1. The bus overvoltage calculation method for AC filter bus charging and small filter operation is characterized by: The following steps are involved: Select the required closing angle, with each preset angle as a step length, and set the AC filter bus residual voltage to -1.0pu or 1.0pu respectively. Calculate the overvoltage of the AC filter bus under the condition that the gap breakdown voltage is 0V; The range of the AC filter bus is selected as [-1.0 pu, 1.0 pu], and the overvoltage of the AC filter bus is calculated at the closing angles of 0°, 90°, and 180° with a preset step size.
2. The bus overvoltage calculation method for AC filter bus charging and small filter operation according to claim 1 is characterized in that: The required closing angle range is [0°, 315°].
3. The bus overvoltage calculation method for AC filter bus charging and small filter operation according to claim 1 is characterized in that: The default angle is 45°.
4. The bus overvoltage calculation method for AC filter bus charging and small filter operation according to claim 1 is characterized in that: The default step size is 0.2 pu.
5. The bus overvoltage calculation method for AC filter bus charging and small filter operation according to claim 1 is characterized in that: When the AC filter bus is charged, disconnect all grounding switches in the loop, disconnect the circuit breaker and disconnector on the AC filter bus, the disconnector Q13 and disconnector Q14 on the 330kV bus are in the closed state, and close the circuit breaker Q2.
6. The bus overvoltage calculation method for AC filter bus charging and small filter operation according to claim 1 is characterized in that: When the small filter is put into operation, first close the isolating switch Q11 and then close the circuit breaker Q1.
7. The bus overvoltage calculation method for AC filter bus charging and small filter operation according to claim 1 is characterized in that: The time constant of the circuit breaker arc is 1ps.
8. The bus overvoltage calculation method for AC filter bus charging and small filter operation according to claim 1 is characterized in that: The time constant of the isolating switch is 1ns.
9. A bus overvoltage system for AC filter bus charging and small filter operation, based on the bus overvoltage calculation method for AC filter bus charging and small filter operation as described in any one of claims 1 to 8, characterized in that: Including 330kV busbar, AC filter busbar and filter; [Fengrun 1] 330kV busbar connects voltage transformer cabinet and lightning arrester; The 330kV busbar and the AC filter busbar are provided with isolating switches Q13 and Q14, and a circuit breaker Q2 is provided between the isolating switches Q13 and Q14; A circuit breaker Q1 is provided between the AC filter bus and the filter, and an isolating switch Q11 is provided between the AC filter bus and the circuit breaker Q1.
10. The bus overvoltage system for charging the AC filter bus and commissioning the small filter according to claim 9, characterized in that: The isolating switch Q11, the isolating switch Q13 and the isolating switch Q14 are all grounded.