Adaptive reclosing method for distribution network based on distributed generation characteristic signal injection

Abstract

The present invention discloses a distribution network adaptive reclosing method based on the injection of distributed power source characteristic signals. The method comprises the following steps: after a line fault occurs, the protection device operates to trip the power supply side switch adjacent to the fault point, and the distributed power source of the faulty line is disconnected from the grid; the distributed power source injects a characteristic signal; the distributed power source identifies whether a fault exists based on the imbalance of the phase-to-phase impedance of the characteristic signal, and when the fault exists, the duration of the distributed power source output characteristic signal is set to T1; when the fault does not exist, the duration of the distributed power source output characteristic signal is set to T2; the protection device detects the characteristic signal, and when the reclosing action conditions are met, the tripped line switch is reclosed. The present invention can realize accurate judgment of the nature of the fault, improve the popularity and action accuracy of cable line and hybrid line reclosing, avoid secondary impact caused by reclosing on the fault, and effectively improve power supply reliability.

Description

Technical Field

[0001] The invention relates to the technical field of relay protection, in particular to a distribution network adaptive reclosing method based on distributed power source characteristic signal injection. Background Art

[0002] With the construction of new power systems and the advancement of photovoltaic construction in the whole county, a large number of distributed power sources are connected to the distribution network, which has brought a large number of flexible and controllable converter equipment to the distribution network system, and has had a huge impact on the relay protection of the distribution network. At the same time, it also brings new ideas for the distribution network relay protection from the traditional "passive" to the "active" fault detection.

[0003] At present, overhead lines in distribution networks are equipped with reclosing functions. When a transient fault occurs, the line reclosing function can restore the system power supply. However, when a permanent fault occurs, the reclosing function may cause an impact on the power equipment. For cable lines, reclosing function is generally not used. Considering that there are many permanent faults, the line will be disabled even if a transient fault occurs, resulting in power outages for users during the load transfer process. Therefore, it is necessary to manage the reclosing function of the distribution network line in a refined manner, accurately identify whether the fault is a transient fault or a permanent fault, and determine whether reclosing function is required based on the fault type. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a distribution network adaptive reclosing method based on distributed power source characteristic signal injection.

[0005] The technical solution adopted by the present invention to achieve the above-mentioned purpose is: a distribution network adaptive reclosing method based on distributed power source characteristic signal injection, comprising the following steps:

[0006] When a line fails, the protection device trips the power supply side switch adjacent to the fault point, and the distributed power supply of the faulty line is disconnected from the grid;

[0007] Distributed power injection characteristic signal;

[0008] The distributed power supply identifies whether a fault exists based on the unbalanced degree of the phase impedance of the characteristic signal. When a fault exists, the duration of the distributed power supply output characteristic signal is set to T 1 ; When the fault does not exist, the duration of the distributed power output characteristic signal is set to T 2 ;

[0009] The protection device detects the characteristic signal and recloses the tripped line switch when the reclosing action conditions are met.

[0010] The characteristic signal adopts a three-phase high-order harmonic voltage signal, and the amplitude is (2% to 5%) Un , where U n is the rated voltage.

[0011] The distributed power generation injection characteristic signal adopts a fast start method: when the distributed power generation is disconnected from the grid, the grid-connected circuit breaker is not tripped, only the control pulse is blocked, the power frequency power output is stopped, and after a delay T n Then output characteristic signal.

[0012] After the distributed power source injects the characteristic signal, the grid-connected circuit breaker is tripped.

[0013] The distributed power supply injection characteristic signal is specifically:

[0014] A single distributed power source is selected to start injecting characteristic signals, and other distributed power sources are not injected with characteristic signals.

[0015] The distributed power supply identifies whether a fault exists based on the unbalanced degree of phase impedance of the characteristic signal, specifically:

[0016]

[0017]

[0018]

[0019] Among them, Z ab , Z bc , Z ca is the characteristic signal phase impedance, k set is the imbalance threshold;

[0020] When formulas (1), (2), and (3) are all satisfied, it is determined that the fault does not exist; otherwise, it is determined that the fault exists.

[0021] The k set Take 0.1.

[0022] The T 1 The value ranges from 20ms to 50ms.

[0023] The T 2 The value range is 100ms to 200ms.

[0024] The reclosing action conditions are:

[0025] The characteristic signal is greater than the minimum detection threshold U set1 , and the duration reaches T 2 ; At the same time, the power frequency voltage is less than the no-voltage threshold U set2 .

[0026] The present invention has the following advantages and beneficial effects:

[0027] After the line fault protection device trips, the distributed power source injects characteristic signals of different time scales based on the fault persistence, and the protection device detects the characteristic signals and recloses the line after the fault disappears to restore power supply. This can effectively improve the popularity and action accuracy of reclosing, avoid secondary impact caused by reclosing on faults, and improve power supply reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is an application system architecture diagram of the method of the present invention;

[0029] Figure 2 It is a method flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0031] The invention discloses a distribution network adaptive reclosing method based on distributed power source characteristic signal injection, which can effectively improve the power supply reliability of the distribution network. Figure 1 Taking the system architecture diagram as an example, the workflow is explained.

[0032] 1) The injection start delay of distributed generation 1, 2, and 3 is set to 1s, 2s, and 3s, respectively.

[0033] 2) After a fault occurs in the line at point F, the protection device P1 operates to trip the power supply side switch A adjacent to the fault point.

[0034] 3) Distributed power sources 1, 2, and 3 of the faulty line are disconnected from the grid.

[0035] 4) After being disconnected from the grid, distributed power source 1 detects that there is no characteristic signal on the system, and after a delay of 1 second, it starts to inject the characteristic signal; distributed power sources 2 and 3 detect that there is a characteristic signal on the system and will not start again.

[0036] Select a single distributed power source to start injecting characteristic signals, and other distributed power sources do not inject characteristic signals. Specifically:

[0037] For overhead lines, one distributed power source is selected as the injection source in each partition; for cable lines, one distributed power source is selected as the injection source in each bus section;

[0038] On the same loop line, the injection start delay T of different distributed power sources n Different, different T n The level difference ΔT between them is greater than the difference in off-grid time between different distributed power sources, and T n Greater than the fault arc extinction time;

[0039] The distributed power generation detects characteristic signals on the system. When any phase has a characteristic signal, the distributed power generation will no longer start injection, and the distributed power generation that has already started injection will continue to inject.

[0040] 5) The distributed power source identifies whether a fault exists based on the unbalanced degree of the phase impedance of the characteristic signal. When a fault exists, the duration of the distributed power source output characteristic signal is set to T 1 ; When the fault does not exist, the duration of the distributed power output characteristic signal is set to T 2 .

[0041] Distributed power supply based on characteristic signal phase impedance Z ab , Z bc , Z ca The imbalance degree can be used to identify whether a fault exists. The calculation formula is:

[0042]

[0043]

[0044]

[0045] When equations (1), (2), and (3) are all satisfied, it is determined that the fault does not exist; otherwise, it is determined that the fault exists. set is the imbalance threshold, usually set to 0.1.

[0046] If the fault is a permanent fault, the characteristic signal detected by the protection device lasts for T 1 , at this time the reclosing switch is locked.

[0047] T 1 The setting of T should take into account the fault tolerance of the inverter and the reliable detection of the protection device, and the value is 20ms~50ms. 2 The setting should be considered with T 1 The obvious difference and the impact of characteristic signals on load, the value is 100ms~200ms.

[0048] 6) When the protection device detects the characteristic signal and the following reclosing action conditions are met, the tripped line switch is reclosed:

[0049] ①The characteristic signal is greater than the minimum detection threshold U set1 , and the duration reaches T 2 ;

[0050] ②The power frequency voltage is less than the no-voltage threshold U set2 .

[0051] Among them, the characteristic signal adopts three-phase high-order harmonic voltage signal, and the amplitude is generally (2%~5%)U n , Un is the rated voltage, which is 57.735V in this embodiment.

[0052] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A distribution network adaptive reclosing method based on distributed power source characteristic signal injection, characterized in that: The following steps are involved: When a line fails, the protection device trips the power supply side switch adjacent to the fault point, and the distributed power supply of the faulty line is disconnected from the grid; Distributed power injection characteristic signal; The distributed power source identifies whether a fault exists based on the unbalanced degree of the interphase impedance of the characteristic signal. When a fault exists, the duration of the distributed power source output characteristic signal is set to T1; when a fault does not exist, the duration of the distributed power source output characteristic signal is set to T2; The protection device detects the characteristic signal and recloses the tripped line switch when the reclosing action conditions are met; The distributed power supply identifies whether a fault exists based on the unbalanced degree of phase impedance of the characteristic signal, specifically: Among them, Z ab , Z bc , Z ca is the characteristic signal phase impedance, k set is the imbalance threshold; When formulas (1), (2), and (3) are all satisfied, it is determined that the fault does not exist; otherwise, it is determined that the fault exists.

2. A distribution network adaptive reclosing method based on distributed power source characteristic signal injection according to claim 1, characterized in that: The characteristic signal adopts a three-phase high-order harmonic voltage signal, and the amplitude is (2% to 5%) U n , where U n is the rated voltage.

3. The method for adaptive reclosing of a distribution network based on distributed power source characteristic signal injection according to claim 1, characterized in that: The distributed power generation injection characteristic signal adopts a fast start method: when the distributed power generation is disconnected from the grid, the grid-connected circuit breaker is not tripped, only the control pulse is blocked, the power frequency power output is stopped, and after a delay T n Then output characteristic signal.

4. A distribution network adaptive reclosing method based on distributed power source characteristic signal injection according to claim 3, characterized in that: After the distributed power source injects the characteristic signal, the grid-connected circuit breaker is tripped.

5. The method for adaptive reclosing of distribution network based on distributed power source characteristic signal injection according to claim 3, characterized in that: The distributed power supply injection characteristic signal is specifically: A single distributed power source is selected to start injecting characteristic signals, and other distributed power sources are not injected with characteristic signals.

6. The method for adaptive reclosing of a distribution network based on distributed power source characteristic signal injection according to claim 1, characterized in that: The k set Take 0.

1.

7. The method for adaptive reclosing of a distribution network based on distributed power source characteristic signal injection according to claim 1, characterized in that: The value of T1 is 20ms to 50ms.

8. The method for adaptive reclosing of distribution network based on distributed power source characteristic signal injection according to claim 1, characterized in that: The value of T2 is 100ms to 200ms.

9. The method for adaptive reclosing of distribution network based on distributed power source characteristic signal injection according to claim 1, characterized in that: The reclosing action conditions are: The characteristic signal is greater than the minimum detection threshold U set1 , and the duration reaches T2; at the same time, the power frequency voltage is less than the no-voltage threshold U set2 .

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