A method for optimizing closing speed of vacuum circuit breaker

Abstract

The application discloses a vacuum circuit breaker closing speed optimization method, selecting a plurality of closing speeds in a closing speed range, calculating a pre-breakdown arc time interval of a vacuum circuit breaker under all closing phase angles corresponding to each selected closing speed according to the relationship between a pre-breakdown gap distance and a pre-breakdown voltage, calculating a bounce arc time interval of the vacuum circuit breaker under all closing phase angles corresponding to each selected closing speed according to a contact bounce recovery coefficient, calculating a closing arc total energy of the vacuum circuit breaker under all closing phase angles corresponding to each closing speed according to the pre-breakdown arc time interval and the bounce arc time interval, accumulating the closing arc total energy to obtain a closing arc total energy expectation value of the vacuum circuit breaker under each closing speed, and repeatedly iterating and executing the intelligent optimization algorithm to find the closing speed corresponding to the minimum closing arc total energy expectation value.

Description

Technical Field

[0001] This invention belongs to the field of circuit breaker technology, specifically relating to a method for optimizing the closing speed of a vacuum circuit breaker. Background Technology

[0002] Vacuum circuit breakers offer advantages such as being environmentally friendly, having a long lifespan, and low maintenance costs. Supported by the "dual carbon target" (carbon emission reduction and decarbonization), vacuum circuit breakers are widely used in medium and low voltage power systems and are continuously evolving towards higher voltage levels. From the initial design stage of vacuum circuit breaker production, the dynamic fusion welding of contacts during the energized closing process is a crucial issue.

[0003] Existing research indicates that pre-breakdown and contact bounce during the closing process of vacuum circuit breakers are the primary causes of contact dynamic fusion welding. During the energized closing process of a vacuum circuit breaker, a pre-breakdown arc and a continuous arc during bounce are generated sequentially. Both types of arcs heat the contact surface. If the total energy is too high, the contact surface may melt, or even weld the moving and stationary contacts together, making them inseparable. This not only significantly reduces the electrical life of the vacuum interrupter but also seriously affects the interruption of fault arcs, thereby endangering the safety and stability of the entire power system.

[0004] Currently, there is little research on methods to reduce the dynamic fusion welding of closing contacts in vacuum circuit breakers. Some methods aim to achieve the optimal closing speed by minimizing the sum of the pre-breakdown arc time and the bounce arc time. However, this method has limitations because it does not consider the time-varying nature of the arc current; that is, minimizing the sum of the pre-breakdown arc time and the bounce arc time does not necessarily mean a smaller total closing arc energy. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for optimizing the closing speed of a vacuum circuit breaker. This method can quickly and accurately find the optimal closing speed, minimizing the sum of the two types of arc energy. It is also widely applicable and can be promoted for use in various operating conditions, such as AC / DC, low, medium and high voltage power systems, and vacuum circuit breakers with different mechanical parameters.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0007] A method for optimizing the closing speed of a vacuum circuit breaker includes:

[0008] (1) Obtain the closing speed range of the vacuum circuit breaker, the relationship between the pre-breakdown gap distance and the pre-breakdown voltage, the contact bounce recovery coefficient, and multiple different closing phase angles;

[0009] (2) Select several closing speeds within the closing speed range, and calculate the pre-breakdown arc time interval of the vacuum circuit breaker under all closing phase angles corresponding to each selected closing speed according to the relationship between the pre-breakdown gap distance and the pre-breakdown voltage. Calculate the bounce arc time interval of the vacuum circuit breaker under all closing phase angles corresponding to each selected closing speed according to the contact bounce recovery coefficient.

[0010] (3) Based on the pre-breakdown arc time interval of the vacuum circuit breaker under all closing phase angles corresponding to each closing speed and the bounce arc time interval of the vacuum circuit breaker under all closing phase angles corresponding to each closing speed, calculate the total closing arc energy of the vacuum circuit breaker under all closing phase angles corresponding to each closing speed.

[0011] (4) The total energy of the closing arc of the vacuum circuit breaker at each closing speed corresponding to all closing phase angles is accumulated to obtain the expected value of the total energy of the closing arc of the vacuum circuit breaker at each closing speed;

[0012] (5) Using an intelligent optimization algorithm, repeatedly execute steps (2) to (4) up to a set number of times to find the closing speed corresponding to the minimum expected value of the total energy of the closing arc. The closing speed corresponding to the minimum expected value of the total energy of the closing arc is the optimal closing speed of the vacuum circuit breaker.

[0013] Further, based on the pre-breakdown arc time interval of the vacuum circuit breaker at each closing speed corresponding to all closing phase angles and the bounce arc time interval of the vacuum circuit breaker at each closing speed corresponding to all closing phase angles, the total closing arc energy of the vacuum circuit breaker at each closing speed corresponding to all closing phase angles is calculated using the following formula:

[0014]

[0015] In the formula, W a W represents the total energy of the closing arc. y Pre-breakdown arc energy; W t For the energy of the bouncing arc; t y The time interval for the pre-breakdown arc; t t For the time interval of the bouncing arc; U a For arc voltage; i a This is the short-circuit arc current.

[0016] Furthermore, the method for determining the relationship between the pre-breakdown gap distance and the pre-breakdown voltage of the vacuum circuit breaker includes:

[0017] Obtain the pre-breakdown gap distance corresponding to different pre-breakdown voltages;

[0018] The relationship between the pre-breakdown gap distance and the pre-breakdown voltage of the vacuum circuit breaker is obtained by fitting the pre-breakdown gap distance corresponding to different pre-breakdown voltages.

[0019] Further, the step of calculating the pre-breakdown arc time interval of the vacuum circuit breaker for each selected closing speed corresponding to all closing phase angles based on the relationship between the pre-breakdown gap distance and the pre-breakdown voltage includes:

[0020] Calculate the pre-breakdown arc time interval of the vacuum circuit breaker for each closing speed and corresponding closing phase angle. The calculation formula is as follows:

[0021]

[0022] In the formula, U d For the vacuum circuit breaker to withstand voltage at the break point; U m U represents the voltage amplitude that the vacuum circuit breaker contacts withstand; f represents the frequency; U y U represents the insulation strength of the vacuum circuit breaker. y =g(d) represents the relationship between the pre-breakdown gap distance and the pre-breakdown voltage of the vacuum circuit breaker; d is the contact gap distance of the vacuum circuit breaker; d0 is the vacuum circuit breaker in U d The maximum pre-breakdown gap distance; t0 is the time corresponding to different closing phase angles;

[0023] by|U d |≥U y The pre-breakdown arc time interval is calculated, and the pre-breakdown time interval is corrected by the following formula to obtain the pre-breakdown arc time interval of the vacuum circuit breaker at each closing speed and corresponding closing phase angle.

[0024]

[0025] In the formula, I is the effective value of the periodic component of the short-circuit current; ψ is the phase angle of the power supply voltage at the instant the short circuit occurs. The phase angle by which the current lags behind the voltage. τ is the decay time constant of the DC component.

[0026] Methods for correcting the pre-breakdown time interval include:

[0027] Determine whether the pre-breakdown time interval is a single segment or multiple segments;

[0028] If the pre-breakdown time interval is a segment [t] y1 , t y2 If ], then no correction is needed for the interval [t]. y1 , t y2 This refers to the pre-breakdown arc time interval of the vacuum circuit breaker at each closing speed corresponding to a closing phase angle;

[0029] If the pre-breakdown time interval is multiple segments [t] y1 , t y2 ]U[t y3 , t y4 ], then first we need to deal with i d Solve for (t) if [t] y2 , t y3 [i is always true within the interval] d If (t)≠0, then the start time of the first segment of the pre-breakdown time interval is taken as the start time, and the end time of the last segment of the pre-breakdown time interval is taken as the end time. That is, the pre-breakdown arc time interval of the vacuum circuit breaker corresponding to each closing speed and a closing phase angle after correction is [t]. y1 , t y4 ]; If in [t y2 , t y3 There exists a time t within the interval. y5 make i d If (t) = 0, then the zero point of this short-circuit current is taken as the end time of the previous segment of this pre-breakdown time interval. That is, the pre-breakdown arc time interval of the vacuum circuit breaker corresponding to each closing speed and a closing phase angle after correction is [t]. y1 , t y5 ]U[t y3 , t y4 ].

[0030] Further, the step of calculating the bounce arc time interval of the vacuum circuit breaker for each selected closing speed at all closing phase angles based on the contact bounce recovery coefficient includes:

[0031] The specific calculation method is as follows: Calculate the bounce arc time interval of the vacuum circuit breaker for each closing speed and corresponding closing phase angle.

[0032] The differential equation of motion of the moving contact after the p-th collision is as follows:

[0033]

[0034] In the formula, m is the mass of the moving part of the moving contact; x is the displacement of the moving contact after the closing collision; t is the time after the collision; K is the stiffness coefficient of the contact spring; x0 is the pre-compression length of the overtravel spring; x2 is the displacement of the overtravel spring due to the continued movement of the mechanism after the contact collision; v is the closing speed; x c For overtravel compression distance; F x The electromagnetic attraction force generated by the current flowing through the equivalent coil portion of the longitudinal magnetic contact sidewall; F c The electromagnetic repulsion between the contacts is caused by the contraction of the electric arc; μ0 is the permeability of vacuum (4π × 10⁻⁶).-7 H / m; n is the equivalent number of coil turns of the contact structure; R is the outer diameter of the contact; r is the inner diameter of the coil; D is the distance between the centers of the contacts; k is the electromagnetic repulsion coefficient; i d (t) represents the short-circuit current;

[0035] The initial conditions for the motion differential equation of the moving contact after the p-th collision are as follows:

[0036]

[0037] In the formula, β is the contact bounce recovery coefficient;

[0038] Combining the equations of motion and their initial conditions, the fourth-order Runge-Kutta method is used to solve the equations of motion, obtaining the curve of displacement x as a function of time after the p-th closing collision of the moving contact, which is the spring-opening time interval after the p-th collision of the moving contact; when the calculated spring-opening time interval after the q-th collision is less than the set value, the calculation is stopped, and the first q spring-opening time intervals are summed to obtain the spring-jumping arc time interval of the vacuum circuit breaker.

[0039] Furthermore, the intelligent optimization algorithm is a particle swarm optimization algorithm or a genetic algorithm.

[0040] Compared with the prior art, the present invention has at least the following beneficial effects:

[0041] This invention provides a method for optimizing the closing speed of a vacuum circuit breaker. When calculating the total arc energy of the pre-breakdown arc and the bounce arc during the closing process, the randomness of the closing phase angle of the non-phase-controlled switch is considered. Based on the pre-breakdown arc time interval and the bounce arc time interval of the vacuum circuit breaker at all closing phase angles corresponding to each closing speed, the total closing arc energy of the vacuum circuit breaker at each closing speed is calculated. The total closing arc energy of the vacuum circuit breaker at each closing speed is accumulated to obtain the expected value of the total closing arc energy of the vacuum circuit breaker at each closing speed. Finally, an intelligent optimization algorithm is used to iteratively perform the calculation, selecting the optimal closing speed with the goal of minimizing the expected value of the total closing arc energy. In other words, this invention optimizes the closing speed by reducing the total arc energy of the pre-breakdown arc and the bounce arc during the closing process. Compared with traditional optimization methods that reduce the total arc time during closing, the optimized speed obtained by this invention is more accurate. Furthermore, since the computational load is too large when using the exhaustive method for optimization calculation, this invention uses an intelligent optimization algorithm as a calculation tool to optimize the closing speed, which greatly reduces the amount of optimization calculation and allows the optimal closing speed to be obtained more quickly and conveniently.

[0042] Furthermore, in calculating the total arc energy of the pre-breakdown arc and the bouncing arc during the closing process, this invention is based on the short-circuit current expression in the relevant national standards. When calculating the pre-breakdown arc energy, the characteristics of arc extinction when the arc current crosses zero are considered. When calculating the bouncing arc energy, the electromagnetic force generated by the arc current flowing through the contacts is considered, making the optimal closing speed obtained by this invention more accurate.

[0043] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the specific embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0045] Figure 1 This is a flowchart of a method for optimizing the closing speed of a vacuum circuit breaker according to the present invention;

[0046] Figure 2 This is a graph showing the real-time withstand voltage and voltage withstand capability of a vacuum circuit breaker.

[0047] Figure 3 It is a historical search trajectory map obtained using the particle swarm optimization algorithm;

[0048] Figure 4 This is a diagram of the convergence process obtained using the particle swarm optimization algorithm. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, 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.

[0050] As a specific embodiment of the present invention, such as Figure 1 As shown, a method for optimizing the closing speed of a vacuum circuit breaker specifically includes the following steps:

[0051] (1) Obtain the closing speed range of the vacuum circuit breaker, the relationship between the pre-breakdown gap distance and the pre-breakdown voltage, the contact bounce recovery coefficient, and multiple different closing phase angles.

[0052] Specifically, the method for obtaining the relationship between the pre-breakdown gap distance and the pre-breakdown voltage of a vacuum circuit breaker is as follows:

[0053] Obtain the pre-breakdown gap distance corresponding to different pre-breakdown voltages;

[0054] The relationship between the pre-breakdown gap distance and the pre-breakdown voltage of the vacuum circuit breaker is obtained by fitting the pre-breakdown gap distance corresponding to different pre-breakdown voltages.

[0055] (2) Select several closing speeds within the closing speed range. Based on the relationship between the pre-breakdown gap distance and the pre-breakdown voltage, calculate the pre-breakdown arc time interval of the vacuum circuit breaker under all closing phase angles corresponding to each selected closing speed. Based on the contact bounce recovery coefficient, calculate the bounce arc time interval of the vacuum circuit breaker under all closing phase angles corresponding to each selected closing speed.

[0056] Specifically, the step of calculating the pre-breakdown arc time interval of the vacuum circuit breaker for each selected closing speed corresponding to all closing phase angles based on the relationship between the pre-breakdown gap distance and the pre-breakdown voltage includes:

[0057] Calculate the pre-breakdown arc time interval of the vacuum circuit breaker for each closing speed and corresponding closing phase angle. The calculation formula is as follows:

[0058]

[0059] In the formula, U d For the vacuum circuit breaker to withstand voltage at the break point; U m U represents the voltage amplitude that the vacuum circuit breaker contacts withstand; f represents the frequency (50Hz); U y The function U represents the insulation strength (i.e., pre-breakdown voltage) of a vacuum circuit breaker. y =g(d) represents the relationship between the pre-breakdown gap distance and the pre-breakdown voltage of the vacuum circuit breaker, determined experimentally, also known as the withstand voltage curve of the vacuum circuit breaker to be optimized; d is the contact gap distance of the vacuum circuit breaker; d0 is the withstand voltage curve of the vacuum circuit breaker at U d The maximum pre-breakdown gap distance; t0 is the time corresponding to different closing phase angles;

[0060] by|U d |≥U y The pre-breakdown arc time interval is calculated. Since the arc will be extinguished at zero after the pre-breakdown occurs, the pre-breakdown time interval calculated above needs to be corrected by combining the following short-circuit current formula to obtain the pre-breakdown arc time interval of the vacuum circuit breaker for each closing speed and corresponding closing phase angle.

[0061]

[0062] In the formula, I is the effective value of the periodic component of the short-circuit current; ψ is the phase angle of the power supply voltage at the instant the short circuit occurs. The phase angle by which the current lags behind the voltage. τ is the decay time constant of the DC component. According to section 4.101.3 of GB1984-2014 High Voltage AC Circuit Breakers, the standard DC component time constant is taken as 45ms.

[0063] Methods for correcting the pre-breakdown time interval include:

[0064] Determine whether the pre-breakdown time interval is a single segment or multiple segments;

[0065] If the pre-breakdown time interval is a segment [t] y1 , t y2 If ], then no correction is needed for the interval [t]. y1 , t y2 This refers to the pre-breakdown arc time interval of the vacuum circuit breaker at each closing speed corresponding to a closing phase angle;

[0066] If the pre-breakdown time interval is multiple segments [t] y1 , t y2 ]U[t y3 , t y4 ], then first we need to deal with i d Solve for (t) if [t] y2 , t y3 [i is always true within the interval] d If (t)≠0, then the start time of the first segment of the pre-breakdown time interval is taken as the start time, and the end time of the last segment of the pre-breakdown time interval is taken as the end time. That is, the pre-breakdown arc time interval of the vacuum circuit breaker corresponding to each closing speed and a closing phase angle after correction is [t]. y1 , t y4 ]; If in [t y2 , t y3 There exists a time t within the interval. y5 make i d If (t) = 0, then the zero point of this short-circuit current is taken as the end time of the previous segment of this pre-breakdown time interval. That is, the pre-breakdown arc time interval of the vacuum circuit breaker corresponding to each closing speed and a closing phase angle after correction is [t]. y1 , t y5 ]U[t y3 , t y4 ].

[0067] This invention considers the zero-crossing arc extinction characteristic of the arc current when solving the pre-breakdown arc time interval of the vacuum circuit breaker, which makes the solved pre-breakdown arc time interval of the vacuum circuit breaker more consistent with reality, thereby improving the accuracy of speed optimization.

[0068] Specifically, the step of calculating the bounce arc time interval of the vacuum circuit breaker for each selected closing speed under all closing phase angles based on the contact bounce recovery coefficient includes:

[0069] The specific calculation method is as follows: Calculate the bounce arc time interval of the vacuum circuit breaker for each closing speed and corresponding closing phase angle.

[0070] For vacuum circuit breakers with an overtravel spring at the moving contact end and whose closing motion direction is opposite to the direction of gravity;

[0071] The differential equation of motion of the moving contact after the p-th collision is as follows:

[0072]

[0073] In the formula, m is the mass of the moving part of the moving contact (above the overtravel spring); x is the displacement of the moving contact after the closing collision; t is the time after the collision; K is the stiffness coefficient of the contact spring; x0 is the pre-compression length of the overtravel spring; x2 is the displacement of the overtravel spring due to the continued movement of the mechanism after the contact collision; v is the closing speed; x c For overtravel compression distance; F x The electromagnetic attraction force generated by the current flowing through the equivalent coil portion of the longitudinal magnetic contact sidewall; F c The electromagnetic repulsion between the contacts is caused by the contraction of the electric arc; μ0 is the permeability in vacuum (4π×10⁻⁶). -7 H / m); n is the equivalent number of coil turns of the contact structure; R is the outer diameter of the contact; r is the inner diameter of the coil; D is the distance between the centers of the contacts; k is the electromagnetic repulsion coefficient, generally taken as 1. i d (t) represents the short-circuit current;

[0074] The initial conditions for the motion differential equation of the moving contact after the p-th collision are as follows:

[0075]

[0076] In the formula, β is the contact bounce recovery coefficient;

[0077] Combining the equations of motion and their initial conditions, the fourth-order Runge-Kutta method is used to solve the equations of motion, obtaining the curve of displacement x as a function of time after the p-th closing collision of the moving contact, which is the spring-opening time interval after the p-th collision of the moving contact; when the calculated spring-opening time interval after the q-th collision is less than a set value (e.g., 10μs), the calculation is stopped, and the first q spring-opening time intervals are summed to obtain the spring-jumping arc time interval of the vacuum circuit breaker.

[0078] This invention considers the electromagnetic force generated when the arc current flows through the contacts when solving the bounce arc time interval of a vacuum circuit breaker, including electromagnetic attraction and electrodynamic repulsion. This makes the solved bounce arc time interval of the vacuum circuit breaker more consistent with reality, thereby improving the accuracy of speed optimization.

[0079] (3) Based on the pre-breakdown arc time interval of the vacuum circuit breaker at each closing speed and the bounce arc time interval of the vacuum circuit breaker at each closing speed and the corresponding closing phase angle, calculate the total closing arc energy of the vacuum circuit breaker at each closing speed and the corresponding closing phase angle. The calculation formula is as follows:

[0080]

[0081] In the formula, W a W represents the total energy of the closing arc. y Pre-breakdown arc energy; W t For the energy of the bouncing arc; t y The time interval for the pre-breakdown arc; t t For the time interval of the bouncing arc; U a The arc voltage is taken as a constant of 20V based on previous research on arc characteristics, and this value does not affect the accuracy of optimizing the closing speed; a This is the short-circuit arc current.

[0082] (4) The total closing arc energy of the vacuum circuit breaker at each closing speed is accumulated under all closing phase angles to obtain the expected value of the total closing arc energy of the vacuum circuit breaker at each closing speed.

[0083] (5) Steps (2) to (4) are iteratively executed repeatedly using an intelligent optimization algorithm up to a set number of times (e.g., 100 times) to find the closing speed corresponding to the minimum expected value of the total energy of the closing arc. The closing speed corresponding to the minimum expected value of the total energy of the closing arc is the optimal closing speed of the vacuum circuit breaker. Preferably, the intelligent optimization algorithm is a particle swarm optimization algorithm or a genetic algorithm.

[0084] The present invention will be further described in detail below with reference to a specific implementation example.

[0085] (1) As Figure 1 This is the overall flowchart of the method of the present invention. First, the closing speed range of the vacuum circuit breaker to be optimized is obtained by repeatedly debugging the vacuum circuit breaker to be optimized. Then, a pre-breakdown experiment is performed on the vacuum circuit breaker to be optimized to obtain the functional relationship between the pre-breakdown voltage and the breakdown gap distance. The contact bounce recovery coefficient of the circuit breaker to be optimized is measured, and then a set of random closing phase angles is generated.

[0086] (2) Based on the above conditions, an optimization calculation program is written using the particle swarm optimization algorithm to optimize the closing speed. The program needs to calculate the pre-breakdown arc time interval and the bounce arc time interval of the vacuum circuit breaker. The specific calculation method has been explained above and will not be repeated here. The following uses a certain closing speed and a certain closing phase angle as an example to explain the specific solution process of the expected value of the total closing arc energy of the vacuum circuit breaker at the corresponding closing phase angle under the given closing speed.

[0087] like Figure 2 The figure shows the withstand voltage curve, bearing pressure curve, and short-circuit current curve of the break at a certain closing speed and a certain closing phase angle. From the figure and the method for calculating the pre-breakdown arc time interval of the vacuum circuit breaker, it can be known that the pre-breakdown time interval is [t1, t2] ⊆ [t3, t4]. However, since the short-circuit current does not cross zero within the time interval [t2, t3], the corrected pre-breakdown arc time interval of the vacuum circuit breaker is [t1, t4].

[0088] From the figure and the solution method of the bounce arc time interval of the vacuum circuit breaker, it can be known that the bounce arc time interval of the vacuum circuit breaker is [t4, t5].

[0089] Based on the pre-breakdown arc time interval and the bounce arc time interval of the vacuum circuit breaker obtained above, the total closing arc energy at this closing speed and closing phase angle is calculated using the formula for calculating the total closing arc energy of the vacuum circuit breaker. Then, the total closing arc energy at other closing phase angles at this closing speed is calculated using the same method. Finally, summing these values ​​yields the expected value of the total closing arc energy of the vacuum circuit breaker at this speed.

[0090] (3) Figure 3 and Figure 4The figures show the historical search trajectory and convergence curve of the closing speed optimization obtained using the method of this invention for a 35kV vacuum circuit breaker with a short-circuit current of 10kA. As can be seen from the figures, the expected value of the total closing arc energy reaches its minimum when iterating to the 62nd generation, and it no longer decreases until the 100th generation. Therefore, it is considered that the optimization result has converged at this point, and the corresponding closing speed is the optimal closing speed, which is 1.2 m / s.

[0091] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, 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, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for optimizing closing speed of a vacuum circuit breaker, characterized by, The method comprises the following steps: (1) obtaining the closing speed range of a vacuum circuit breaker, the relationship between the pre-breakdown gap distance and the pre-breakdown voltage of the vacuum circuit breaker, the contact bounce recovery coefficient and a plurality of different closing phase angles; (2) selecting a plurality of closing speeds in the closing speed range, calculating the pre-breakdown arc time interval of the vacuum circuit breaker corresponding to each selected closing speed and all closing phase angles according to the relationship between the pre-breakdown gap distance and the pre-breakdown voltage, and calculating the bounce arc time interval of the vacuum circuit breaker corresponding to each selected closing speed and all closing phase angles according to the contact bounce recovery coefficient; (3) calculating the total closing arc energy of the vacuum circuit breaker corresponding to each closing speed and all closing phase angles according to the pre-breakdown arc time interval of the vacuum circuit breaker corresponding to each closing speed and all closing phase angles and the bounce arc time interval of the vacuum circuit breaker corresponding to each closing speed and all closing phase angles; (4) accumulating the total closing arc energy of the vacuum circuit breaker corresponding to each closing speed and all closing phase angles to obtain the expected value of the total closing arc energy of the vacuum circuit breaker corresponding to each closing speed; (5) repeatedly iterating steps (2) to (4) a set number of times by using an intelligent optimization algorithm to find the closing speed corresponding to the minimum expected value of the total closing arc energy, wherein the closing speed corresponding to the minimum expected value of the total closing arc energy is the optimal closing speed of the vacuum circuit breaker.

2. The method for optimizing closing speed of vacuum circuit breaker according to claim 1, characterized in that, The calculation formula for calculating the total closing arc energy of the vacuum circuit breaker corresponding to each closing speed and all closing phase angles according to the pre-breakdown arc time interval of the vacuum circuit breaker corresponding to each closing speed and all closing phase angles and the bounce arc time interval of the vacuum circuit breaker corresponding to each closing speed and all closing phase angles is as follows: wherein W a is the total energy of the closing arc; W y is the pre-breakdown arc energy; W t is the bounce arc energy; t y is the pre-breakdown arc time interval; t t is the bounce arc time interval; U a is the arc voltage; i a is the short circuit arc current.

3. The method for optimizing closing speed of vacuum circuit breaker according to claim 1, characterized in that, The method for determining the relationship between the pre-breakdown gap distance and the pre-breakdown voltage of the vacuum circuit breaker comprises the following steps: obtaining the pre-breakdown gap distance corresponding to different pre-breakdown voltages; fitting the pre-breakdown gap distances corresponding to the different pre-breakdown voltages to obtain the relationship between the pre-breakdown gap distance and the pre-breakdown voltage of the vacuum circuit breaker.

4. The method for optimizing closing speed of vacuum circuit breaker according to claim 1, wherein, The method for calculating the pre-breakdown arc time interval of the vacuum circuit breaker corresponding to each selected closing speed and all closing phase angles according to the relationship between the pre-breakdown gap distance and the pre-breakdown voltage comprises the following steps: calculating the pre-breakdown arc time interval of the vacuum circuit breaker corresponding to each closing speed and one closing phase angle respectively, and the calculation formula is as follows: wherein U d is the voltage withstand of the vacuum circuit breaker contact; U m is the voltage withstand amplitude of the vacuum circuit breaker contact; f is the frequency; U y is the insulation strength of the vacuum circuit breaker contact; U y = g(d) is the relationship between the pre-breakdown gap distance and the pre-breakdown voltage of the vacuum circuit breaker; d is the gap distance between the contacts of the vacuum circuit breaker; d0 is the maximum pre-breakdown gap distance of the vacuum circuit breaker at U d ; t0 is the time corresponding to different closing phase angles; By |U d |≥U y The pre-breakdown arc time interval is calculated, and the pre-breakdown arc time interval of the vacuum circuit breaker corresponding to each closing speed under the closing phase angle is obtained by correcting the pre-breakdown arc time interval in combination with the following formula: where I is the effective value of the short-circuit current periodic component; ψ is the phase angle of the power supply voltage at the instant of short-circuit occurrence; is the phase angle of the current lagging behind the voltage, τ is the decay time constant of the direct current component, The method for correcting the pre-breakdown time interval comprises the following steps: determining whether the pre-breakdown time interval is one segment or multiple segments; If the pre-breakdown time interval is a segment [t y1 ,t y2 ], no correction is needed, and the interval [t y1 ,t y2 ] is the pre-breakdown arc time interval of the vacuum circuit breaker corresponding to each closing speed and closing phase angle; If the pre-breakdown time interval is multi-section [t y1 ,t y2 ]∪[t y3 ,t y4 ], first, i d (t) needs to be solved, if there is always i y2 (t)≠0 in the interval [t y3 ,t d ], the starting time of the first section of the pre-breakdown time interval is taken as the starting time, and the cutoff time of the last section of the pre-breakdown time interval is taken as the cutoff time, that is, the pre-breakdown arc time interval of the vacuum circuit breaker under each closing speed corresponding to a closing phase angle is[t y1 ,t y4 ]; if there is a time t y5 in the interval [t y2 ,t y3 ] such that i d (t)=0, then the short-circuit current zero point is taken as the termination time of the previous section interval of the pre-breakdown time interval, that is, the pre-breakdown arc time interval of the vacuum circuit breaker under each closing speed corresponding to a closing phase angle is[t y1 ,t y5 ]∪[t y3 ,t y4 ].

5. The method for optimizing closing speed of vacuum circuit breaker according to claim 4, wherein, The method for calculating the bounce arc time interval of the vacuum circuit breaker corresponding to each selected closing speed and all closing phase angles according to the contact bounce recovery coefficient comprises the following steps: calculating the bounce arc time interval of the vacuum circuit breaker corresponding to each closing speed and one closing phase angle respectively, and the specific calculation method is as follows: The motion differential equation of the moving contact after the pth collision is as follows: where m is the mass of the moving contact moving part; x is the displacement of the moving contact after the closing collision; t is the time after the moving contact collision; K is the stiffness coefficient of the contact spring; x0 is the pre-compression length of the over-travel spring; x2 is the displacement of the over-travel spring compression due to the mechanism continuing to move after the contact collision; v is the closing speed; x c is the over-travel compression distance; F x is the electromagnetic attraction force generated by the current flowing through the equivalent coil part of the longitudinal magnetic contact side wall; F c is the electromagnetic repulsion force generated between the contacts due to the arc contraction; μ0 is the magnetic permeability in vacuum, 4π×10 -7 H / m; n is the equivalent coil turns of the contact structure; R is the outer diameter of the contact; r is the inner diameter of the coil; D is the distance between the contact center and the contact center; k is the electromagnetic repulsion force coefficient; i d (t) is the short-circuit current; The initial conditions of the motion differential equation of the moving contact after the pth collision are as follows: In the formula, β is the contact bounce recovery coefficient. In combination with the motion differential equation and initial conditions of the motion differential equation, the fourth-order Runge-Kutta method is used to solve the motion differential equation to obtain a curve of displacement x of the moving contact with respect to time after the pth closing collision of the moving contact, that is, to obtain a bounce-off time interval after the pth collision of the moving contact; when the bounce-off time interval after the qth collision is less than a set value, the calculation is stopped, and the bounce-off time intervals of the first q collisions are summed to obtain the bounce arc time interval of the vacuum circuit breaker.

6. The method for optimizing closing speed of vacuum circuit breaker according to claim 1, wherein, The intelligent optimization algorithm is a particle swarm optimization algorithm or a genetic algorithm.

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