Energy overreach protection method for controllable self-restoring energy dissipation device

Abstract

The embodiment of the present application relates to a kind of controllable self-restoration energy consumption devices energy over-limit protection method, comprising the following steps: S1, after first time input is completed, obtain the energy value L1 and time t1 of this time input injection;S2, judge whether the energy value L1 exceeds first energy threshold Q1, if exceeds, then execute step S3;If not exceed, then execute step S4;S3, lock the device;S4, if next time input is carried out, then calculate the effective energy value L n ′ of this time absorption after the input is completed;S5, judge whether the effective energy value L n ′ exceeds first energy threshold Q1, if exceeds, then execute step S3;If not exceed, then execute step S4.The technical scheme of the embodiment of the present application, by the split and combination of control switch, realize the switching of arrester controlled element, restrain system transient overvoltage with maximum utilization under the premise of guaranteeing equipment safety, improve the anti-disturbance ability of system, guarantee the safe and stable operation of power grid.

Description

Technical Field

[0001] This invention relates to the field of power system fault protection technology, and in particular to a method for energy over-limit protection of a controllable self-recovering energy dissipation device. Background Technology

[0002] The rapid development of ultra-high voltage direct current (UHVDC) transmission has effectively filled the power gap in load centers and reduced coal consumption, playing a vital role in promoting economic development and environmental protection in these areas. However, due to the relatively weak sending-end power grid, limited conventional power generation capacity, and low voltage withstand capability of wind turbines, when a receiving-end commutation failure disturbance occurs in the UHVDC transmission system, the rectifier station firing angle increases, and the bus voltage of the sending-end converter station decreases, causing wind turbines near the sending-end to enter a low-voltage ride-through state. During the commutation failure recovery period, the rectifier station firing angle decreases, and the large amount of surplus reactive power at the converter station will cause wind turbines and other surrounding grid equipment to experience varying degrees of overvoltage, leading to wind turbine disconnection. When some wind turbines disconnect due to high voltage, the power flow on the line becomes lighter, and capacitive reactive power compensation becomes excessive, further increasing the surrounding voltage and subsequently triggering a chain reaction of wind turbine disconnections. These overvoltage problems severely restrict the stable operation of the UHVDC transmission system.

[0003] Taking the Zhalute-Qingzhou UHVDC transmission project as an example, its transmission capacity is 10,000 MW, and its rated DC current is 6,250 A. It was put into operation in bipolar mode in 2017 and is an important energy transmission channel for Northeast China. It can effectively solve the problem of power curtailment in Northeast China, promote wind power consumption, and reduce wind curtailment rates. If a commutation failure or DC fault blockage occurs at the receiving end of the DC system, it will cause transient overvoltage on the AC bus of the sending end, the Zhalute converter station. Due to the limitations of the near-area grid system of the Zhalute converter station, in order to ensure that the AC bus overvoltage of the converter station does not exceed 1.3 pu, the transmission power of the Zhalute-Qingzhou DC system needs to be limited to below 6,800 MW, which is not conducive to the full utilization of the large DC energy channel.

[0004] When a bipolar DC fault occurs under high power conditions (bipolar commutation failure, bipolar blocking, bipolar line restart), the AC system and AC filter generate a large amount of excess reactive power during the DC power interruption, causing transient overvoltages exceeding the system control level (1.3 pu) at the Zhalute converter station, which is the main problem constraining DC power. Summary of the Invention

[0005] Based on the above-mentioned situation of the prior art, the purpose of this invention is to provide an energy over-limit protection method for a controllable self-recovering energy dissipation device, which improves equipment utilization, effectively solves the system overvoltage problem, further improves the system's fault ride-through capability, and enhances the safety and stability of the power grid system.

[0006] To achieve the above objectives, according to one aspect of the present invention, a method for energy over-limit protection of a controllable self-resetting energy dissipation device is provided. The controllable self-resetting energy dissipation device includes N parallel-connected fixed surge arrester elements, N parallel-connected controlled surge arrester elements, a trigger switch, and a bypass switch, where N is a natural number. The trigger switch and bypass switch are both connected in parallel to the controlled surge arrester elements and are switched off or on according to an activation command to activate or deactivate the controlled surge arrester elements. The method includes the following steps:

[0007] S1. After the first investment is completed, obtain the energy value L1 and time t1 of this investment.

[0008] S2. Determine whether the energy value L1 exceeds the first energy threshold Q1. If it does, proceed to step S3; if it does not, proceed to step S4.

[0009] S3. Lock the device;

[0010] S4. If another investment is made, the energy value L injected in this investment will be obtained after the investment is completed. n and time t n And based on this energy value L n and time t n And the energy value L from the previous injection. n-1 and time t n-1 Calculate the effective absorbed energy value L. n ';

[0011] S5. Determine the effective absorbed energy value L. n 'Whether the first energy threshold Q1 is exceeded. If it is exceeded, proceed to step S3; if it is not exceeded, proceed to step S4.'

[0012] Where n represents the number of investments starting from the second investment, and n≥2.

[0013] Furthermore, step S3 also includes:

[0014] After the device is locked and cooled to a first predetermined time T, return to step S1.

[0015] Furthermore, the initial investment is carried out based on the following steps:

[0016] Check if the input is valid; if valid, proceed with the first input.

[0017] Furthermore, the effective absorbed energy value L is calculated according to the following formula. n ':

[0018] L n '=L n-1 -K·Δt+L n

[0019] Where K is the energy absorption capacity of the surge arrester to recover per unit time, and Δt is the interval between two adjacent energy impacts.

[0020] Furthermore, in step S4, if no further activation is performed, the surge arrester is allowed to cool down naturally.

[0021] Furthermore, it also includes:

[0022] If Q1≤L1≤Q2, then T=T1;

[0023] If L1≥Q2, then T=T2;

[0024] Where Q2 is the second energy threshold, Q2>Q1, T2>T1.

[0025] Furthermore, it also includes:

[0026] If Q1≤L n If '≤Q2, then T=T1;

[0027] If L n If '≥Q2, then T=T2;

[0028] Where Q2 is the second energy threshold, Q2>Q1, T2>T1.

[0029] Furthermore, the first energy threshold and the second energy threshold satisfy:

[0030] Q2 = Q1 · 120%.

[0031] In summary, this invention provides a method for energy over-limit protection of a controllable self-recovering energy dissipation device, comprising the following steps: S1, after the first input is completed, obtaining the energy value L1 and time t1 of this input; S2, determining whether the energy value L1 exceeds a first energy threshold Q1; if it exceeds, proceeding to step S3; if it does not exceed, proceeding to step S4; S3, locking the device; S4, if the next input is to be performed, obtaining the energy value L1 of this input after the next input is completed. n and time t n And based on this energy value L n and time t n And the energy value L from the previous injection. n-1 and time t n-1 Calculate the effective absorbed energy value L. n S5. Determine the effective absorbed energy value L. nIf the first energy threshold Q1 is exceeded, proceed to step S3; otherwise, proceed to step S4. The technical solution of this invention, by controlling the opening and closing of the switch, enables the switching of the controlled components of the surge arrester, thereby maximizing the utilization rate of the system's transient overvoltage while ensuring equipment safety, improving the system's anti-disturbance capability, and ensuring the safe and stable operation of the power grid. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the controllable self-recovering energy dissipation device provided in an embodiment of the present invention;

[0033] Figure 2 This is a flowchart of the energy over-limit protection method of the controllable self-recovering energy dissipation device according to an embodiment of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0035] The technical solutions of the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. An embodiment of the present invention provides a method for energy over-limit protection of a controllable self-recovering energy dissipation device. Figure 1 The diagram shows the principle of a controllable self-recovering energy dissipation device, such as... Figure 1 As shown, the controllable self-recovering energy dissipation device includes N parallel-connected fixed surge arrester elements, N parallel-connected controlled surge arrester elements, a trigger switch, and a bypass switch, where N is a natural number. The trigger switch and bypass switch are both connected in parallel to the controlled surge arrester elements and are switched on or off according to an activation command to activate or deactivate the controlled surge arrester elements. Upon receiving an activation command from the DC control system, the activation and deactivation functions of the controlled surge arrester elements are realized by controlling the opening and closing of the trigger switch and bypass switch.

[0036] Figure 2 The flowchart of the energy over-limit protection method of the controllable self-recovering energy dissipation device according to an embodiment of the present invention is shown. The method includes the following steps:

[0037] S1. After the first input is completed, obtain the energy value L1 and time t1 of this input. The first input is based on the following steps: check whether the input is valid; if valid, then perform the first input. After the controllable self-recovering energy dissipation device control system is powered on, it checks whether the input is valid by self-checking the initial state of the surge arrester. If invalid, no input logic is executed; if valid, then perform the first input.

[0038] S2. Determine whether the energy value L1 exceeds the first energy threshold Q1. If it does, proceed to step S3; if it does not, proceed to step S4.

[0039] S3. Lock the device. After the device is locked, allow it to cool for a first predetermined time T, then resume normal operation of the device and return to step S1.

[0040] S4. If another investment is made, the energy value L injected in this investment will be obtained after the investment is completed. n and time t n And based on this energy value L n and time t n And the energy value L from the previous injection. n-1 and time t n -1 Calculate the effective absorbed energy value L. n Where n is the number of inputs starting from the second input, n≥2. Calculate the effective absorbed energy value L according to the following formula. n ':

[0041] L n '=L n-1 -K·Δt+L n

[0042] Where K is the energy absorption capacity of the surge arrester to recover per unit time, and Δt is the interval between two adjacent energy impacts.

[0043] If no further action is taken, wait for the surge arrester to cool down naturally. Then, return to this step and reassess.

[0044] S5. Determine the effective absorbed energy value L. n 'Whether the first energy threshold Q1 is exceeded. If it is exceeded, proceed to step S3; if it is not exceeded, proceed to step S4.'

[0045] The first specified time T can be set according to the following conditions: if Q1≤L1≤Q2, then T=T1; if L1≥Q2, then T=T2; where Q2 is the second energy threshold, Q2>Q1, and T2>T1. Also, if Q1≤L1≤Q2, then T=T1. n If '≤Q2, then T=T1; if L nIf Q2 ≥ Q1, then T = T2; where Q2 is the second energy threshold, Q2 > Q1, and T2 > T1. The first and second energy thresholds, for example, satisfy: Q2 = Q1 * 120%. In this embodiment of the invention, in step S2, it is assumed that the absorbed energy is L1, and it is determined whether L1 is greater than or equal to 200 MJ (the rated absorbed energy of the device is 200 MJ). If it is greater than the rated absorbed energy, it is directly blocked. If the surge arrester absorbs energy greater than or equal to 200 MJ and less than 240 MJ (including 20% ​​hot reserve energy), the device's unusable time is determined to be 7.5 hours based on the surge arrester's heat dissipation curve; if the surge arrester absorbs energy greater than or equal to 240 MJ, the device's unusable time is determined to be 10 hours based on the surge arrester's heat dissipation curve. Similarly, if 200 MJ ≤ L1, the device's unusable time is determined to be 10 hours based on the surge arrester's heat dissipation curve. n If L < 240MJ, then the device is unavailable for time T = T1, where T1 is determined to be 7.5h based on the surge arrester's heat dissipation curve; if L n If the surge arrester has a surge charge of ≥240MJ, then the device will be unavailable for a period of time T = T2, where T2 is determined to be 10 hours based on the surge arrester's heat dissipation curve.

[0046] In summary, the embodiments of the present invention relate to an energy over-limit protection method for a controllable self-recovering energy dissipation device, comprising the following steps: S1, after the first input is completed, obtaining the energy value L1 and time t1 of this input; S2, determining whether the energy value L1 exceeds a first energy threshold Q1; if it exceeds, proceeding to step S3; if it does not exceed, proceeding to step S4; S3, locking the device; S4, if the next input is to be performed, obtaining the energy value L1 of this input after the next input is completed. n and time t n And based on this energy value L n and time t n And the energy value L from the previous injection. n-1 and time t n-1 Calculate the effective absorbed energy value L. n S5. Determine the effective absorbed energy value L. n If the first energy threshold Q1 is exceeded, proceed to step S3; otherwise, proceed to step S4. The technical solution of this invention, by controlling the opening and closing of the switch, enables the switching of the controlled components of the surge arrester, thereby maximizing the utilization rate of the system's transient overvoltage while ensuring equipment safety, improving the system's anti-disturbance capability, and ensuring the safe and stable operation of the power grid.

[0047] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for energy over-limit protection of a controllable self-recovering energy dissipation device, characterized in that, The controllable self-recovering energy dissipation device includes N parallel-connected surge arrester fixed elements, N parallel-connected surge arrester controlled elements, a trigger switch, and a bypass switch, where N is a natural number; The trigger switch and bypass switch are both connected in parallel to the controlled element of the surge arrester, and are turned off or on according to the activation command to activate or deactivate the controlled element of the surge arrester; the method includes the following steps: S1. After the first investment is completed, obtain the energy value L1 and time t1 of this investment. S2. Determine whether the energy value L1 exceeds the first energy threshold Q1. If it does, proceed to step S3. If the time limit is not exceeded, proceed to step S4; S3. Lock the device; S4. If another investment is made, the energy value L injected in this investment will be obtained after the investment is completed. n and time t n And based on this energy value L n and time t n And the energy value L from the previous injection. n-1 and time t n-1 Calculate the effective absorbed energy value L. n ′; S5. Determine the effective absorbed energy value L. n Check if the first energy threshold Q1 is exceeded; if it is, proceed to step S3. If the time limit is not exceeded, proceed to step S4; Where n is the number of investments starting from the second investment, n≥2; Calculate the effective absorbed energy value L using the following formula. n ′: L n ′=L n-1 -K·Δt+L n Where K is the energy absorption capacity of the surge arrester to recover per unit time, and Δt is the interval between two adjacent energy impacts.

2. The method according to claim 1, characterized in that, Step S3 further includes: after the device is locked, it is cooled to a first predetermined time T, and then the process returns to step S1.

3. The method according to claim 1, characterized in that, The first investment is carried out based on the following steps: Check if the input is valid; if valid, proceed with the first input.

4. The method according to claim 1, characterized in that, In step S4, if no further activation is performed, the surge arrester is allowed to cool down naturally.

5. The method according to claim 2, characterized in that, Also includes: If Q1≤L1≤Q2, then T=T1; If L1≥Q2, then T=T2; Where Q2 is the second energy threshold, Q2>Q1, T2>T1.

6. The method according to claim 2, characterized in that, Also includes: If Q1≤L n If '≤Q2, then T=T1; If L n If '≥Q2, then T=T2; Where Q2 is the second energy threshold, Q2>Q1, T2>T 1。 7. The method according to claim 5 or 6, characterized in that, The first energy threshold and the second energy threshold satisfy: Q2 = Q1 · 120%.

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