JP7095926B2 - How to improve single-phase self-adaptive reclosing of high-voltage AC transmission line on the inverter side - Google Patents

Description

The present invention relates to a standard for improving a single-phase self-adaptive reclosing of a high-voltage AC transmission line on the inverter side.

Single-phase self-adaptive reclosing technology can identify the nature of an AC overhead transmission line failure before the circuit breaker closes, so that the circuit breaker closes again after the momentary failure disappears and again in case of a permanent failure. Since it does not close, it improves the reliability of the power supply of the power supply system. For pure AC systems of synchronous power, domestic and foreign scholars have given various single-phase self-adaptive reclosing criteria, which can more accurately identify the nature of the failure. In recent years, DC power transmission technology has been widely used, and Japan is currently constructing the world's largest AC / DC hybrid system with the most complicated operating conditions. The electrical characteristics of an AC / DC hybrid system after a single-phase ground fault occurs on the inverter side are different from those of a pure AC system with a synchronous power supply. Specifically, in a pure AC system, the amplitude of the voltage recovered by cutting the phase after tripping due to a single-phase ground failure does not fluctuate, whereas in the high-voltage AC system on the inverter side, it is simple. The voltage amplitude recovered by cutting the phase after tripping due to a phase ground failure has a short time fluctuation due to the influence of phase switching failure and non-linear adjustment of the DC control system. This difference creates some single-phase adaptive matching criteria that apply to high-voltage AC transmission lines on the inverter side, making it impossible to pinpoint the nature of the failure. There is no literature showing a countermeasure for the problem that the conventional single-phase self-adaptive reclosing standard cannot be applied to the high-voltage AC transmission line on the inverter side.

Due to the above problems, the present invention provides an improvement standard for a single-phase self-adaptive reclosing line suitable for an inverter-side high-voltage AC transmission line. The technical proposal of the present invention is as follows.

Methods for improving single-phase self-adaptive reclosing that are compatible with inverter-side high-voltage AC transmission lines include the following steps.

(1) Acquire the inverter side current transformer bus voltage in real time using a current transformer.

(2) After a single-phase ground failure of the AC system on the inverter side occurs and a trip occurs, the voltage amplitude value U of the turbulent bus is calculated using the high-speed Fourier algorithm, and the difference between the peak value and valley value of U in half a cycle. Is calculated in real time and set to ΔU.

(3) Set the voltage of the current transformer bus to _UB , set the set value G to 4% UB, and compare _ΔU with G. If ΔU is greater than G, the single-phase self-adaptive reclosing cycle is closed, and if it is less than G, the single-phase self-adaptive reclosing path is opened to distinguish the nature of the failure.

(4) For AC overhead transmission lines without parallel reactors, the following single-phase adaptive reclosing criteria are adopted. In the case of a temporary failure, the recovery voltage amplitude is high, and in the case of a permanent failure, the recovery voltage amplitude is low, and the set value U _DZ is set.
U _DZ = K _k U _xl

In the above equation, K _k is the reliability coefficient, 1.2, U _xl is the fault phase induced voltage during two-phase operation under the maximum load condition, and if the measured voltage is larger than U _DZ , it is judged as a temporary fault. do.

For AC overhead transmission lines with parallel reactors, the following single-phase self-adaptive reclosing criteria are adopted. When a temporary failure occurs in the transmission line, the recovery voltage has a beat frequency characteristic, and the relationship in each beat cycle is as follows.
U _max -U _min = 2U ₁ ＞ U _xL / 2

In the above equation, U _max and U _min are the maximum and minimum recovery voltages for each beat cycle, respectively, and U _{x L} is the electromagnetic coupling voltage of the disconnected phase. In the event of a permanent failure of the transmission line, there is no recovery voltage beat frequency characteristic. The relationship in each beat cycle is as follows.
U _max -U _min = 0 << U _xL / 2

Set the set value U _DZ to U _xL / 2, calculate (U _max -U _min ) and compare it with the set value U _DZ to distinguish the nature of the failure.

The present invention employs the above technical scheme and has the following advantages. It provides an improved standard for single-phase self-adaptive reclosing suitable for high voltage AC transmission lines on the inverter side. For single-phase ground faults on the inverter side, the improved criteria ensure safe and stable operation of AC-DC interconnect systems by being able to accurately identify the nature of the fault.

It is a failure characteristic determination flowchart of the failure of the improvement standard of the single-phase self-adaptive reclosing of an overhead transmission line which does not use a parallel reactor. It is a failure characteristic determination flowchart of the failure of the improvement criteria of the single-phase self-adaptive reclosing of an overhead transmission line equipped with a parallel reactor. It is a figure which shows the structure of a Yun-Gguang UHVDC system. Parallel reactor This is the voltage amplitude of the switching bus at the time of temporary failure of the overhead transmission line. It is a figure which shows the amplitude of the switching bus voltage at the time of a permanent failure of an overhead transmission line by a parallel reactor. The amplitude of the switching bus voltage during a temporary failure of an overhead transmission line with parallel reactors. It is a figure which shows the amplitude of the switching bus voltage at the time of a permanent failure of an overhead transmission line equipped with a parallel reactor.

Using the following four failure calculation examples of the Yun-Gguang UHVDC system model, the specifics of the present invention when a temporary and permanent ground failure occurs in an AC line without a parallel reactor and an AC line with a parallel reactor. Introducing a typical implementation method.

Calculation example 1: Yun-Guang UHVDC The single AC transmission line on the inverter side of the high voltage DC system is 100km long and does not have a parallel reactor, and its A phase has a temporary single-phase ground failure. When it occurred, the failure position was at the midpoint of the line. The failure time was 1.0s, the failure lasted 0.1s, the phase A breaker tripped at 1.06s, and the failure disappeared at 1.1s. The implementation process of the improved single-phase self-adaptive reclosing criteria is as follows.

(1) The inverter-side current transformer bus voltage was acquired in real time using a current transformer.

(2) After a single-phase grounding failure of the AC system on the inverter side occurs and a trip occurs, the voltage amplitude value U of the transmutation bus is calculated using the high-speed Fourier algorithm, and the amplitude curve is shown in FIG. In the figure, the circle points are the peak points and the triangles are the value points. The difference between the peak value U and the valley value of the current transformer bus voltage amplitude value was calculated as ΔU.

(3) Yun-Gguang UHVDC The rated voltage of the AC system on the high-voltage DC inverter side was 525kV, the set value G was 21kV, and ΔU was compared with G. If ΔU is greater than G at the initial stage of a single-phase trip, it is used as a single-phase self-adaptive reclosing reference. As the phase switching process recovers, ΔU gradually decreases. When ΔU was smaller than G, the single-phase self-adaptive reclosing criterion was opened. In Figure 4, the starting criteria for single-phase self-adaptive reclosing are indicated by arrows.

(4) The nature of the failure was distinguished using a criterion based on the phase retrieval voltage amplitude value off. In this model, the maximum load current for fault bypass is 4.41 kA, the maximum zero sequence current during two-phase operation is 0.85 kA, and the line parameters can be calculated as U _xl = 49.9 kV, K _k 1.2, U _DZ . = 59.88kV. The recovery voltage of the disconnected phase is measured at 66.1 kV, which is higher than U _DZ . Therefore, the nature of the failure could be determined to be a temporary failure. The judgment result matched the simulation conditions.

Calculation example 2: The one-circuit AC transmission line on the inverter side of the Yun-Gguang UHVDC high-voltage DC system is 100 km long, has no parallel reactor, and has a permanent single-phase ground failure in its A phase. The failure position was the midpoint. The failure occurrence time is 1.0s, the transition resistance is 2Ω, and the A-phase circuit breaker trips in 1.06 seconds. The implementation process of the improved single-phase self-adaptive reclosing method is as follows.

(1) The voltage of the current transformer on the inverter side was acquired in real time using a current transformer.

(2) After a single-phase grounding failure of the AC system on the inverter side occurs and the trip occurs, the voltage amplitude value U of the transmutation bus is calculated using the high-speed Fourier algorithm, and the amplitude curve is shown in FIG. In the figure, the circle points are the peak points and the triangles are the value points. The difference between the peak value U and the valley value of the current transformer bus voltage amplitude value was calculated as ΔU.

(3) Yun-Gguang UHVDC The rated voltage of the AC system on the high-voltage DC inverter side was 525kV, the set value G was 21kV, and ΔU was compared with G. If ΔU is greater than G at the initial stage of a single-phase trip, it is used as a single-phase self-adaptive reclosing reference. As the phase switching process recovers, ΔU gradually decreases. If ΔU is less than G, the single-phase self-adaptive reclosing criterion is opened. In FIG. 5, the starting criteria for single-phase self-adaptive reclosing is indicated by arrows.

(4) The nature of the failure was distinguished using a criterion based on the phase retrieval voltage amplitude value off. In this model, the maximum load current for fault bypass is 4.41 kA, the maximum zero sequence current during two-phase operation is 0.85 kA, and the line parameters can be calculated as U _xl = 49.9 kV, K _k 1.2, U _DZ . = 59.88kV. The recovery voltage of the disconnected phase is measured as 3.7 kV, which is higher than U _DZ . Therefore, the nature of the failure could be determined to be a permanent failure. The judgment result matched the simulation conditions.

Calculation example 3: One circuit AC transmission line on the inverter side of the Yun-Guang UHVDC high-voltage DC system is 358 km long and has parallel reactors at both ends, and a temporary single-phase ground failure occurs in its A phase. The failure position is 322km from the current transformer line, the failure occurrence time is 1.0s, the transition resistance is 2Ω, and the A-phase circuit breaker trips in 1.06 seconds. The failure disappeared in 1.1s. The implementation process of the improved single-phase self-adaptive reclosing method is as follows.

(1) The inverter-side current transformer bus voltage was acquired in real time using a current transformer.

(2) After a single-phase grounding failure of the AC system on the inverter side occurs and the trip occurs, the voltage amplitude value U of the transmutation bus is calculated using the high-speed Fourier algorithm, and the amplitude curve is shown in FIG. In the figure, the circle points are the peak points and the triangles are the value points. The difference between the peak value U and the valley value of the current transformer bus voltage amplitude value was calculated as ΔU.

(3) Yun-Gguang UHVDC The rated voltage of the AC system on the high-voltage DC inverter side is 525kV, the set value G is 21kV, and ΔU is compared with G. If ΔU was greater than G in the early stages of a single-phase trip, it was used as a single-phase self-adaptive reclosing criterion. As the phase switching process recovered, ΔU gradually decreased. When ΔU was smaller than G, the single-phase self-adaptive reclosing criterion was opened. In FIG. 6, the starting criteria for the single-phase self-adaptive reclosing cycle are indicated by arrows.

Calculation example 4: One circuit AC transmission line on the inverter side of the Yun-Guang UHVDC high-voltage DC system is 358 km long and has parallel reactors at both ends, and a permanent single-phase ground failure occurs in its A phase. The location of the failure is 322km from the current bus. The failure time was 1.0s, the transition resistance was 2Ω, and the A-phase circuit breaker tripped in 1.06 seconds. The implementation process of the improved single-phase self-adaptive reclosing method is as follows.

(1) The voltage of the current transformer on the inverter side was acquired in real time using a current transformer.

(2) After a single-phase grounding failure of the AC system on the inverter side occurs and the trip occurs, the voltage amplitude value U of the transmutation bus is calculated using the high-speed Fourier algorithm, and the amplitude curve is shown in FIG. In the figure, the circle points are the peak points and the triangles are the value points. The difference between the peak value U and the valley value of the current transformer bus voltage amplitude value was calculated as ΔU.

(3) Yun-Gguang UHVDC The rated voltage of the AC system on the high-voltage DC inverter side was 525kV, the set value G was 21kV, and ΔU was compared with G. If ΔU was greater than G in the early stages of a single-phase trip, it was used as a single-phase self-adaptive reclosing criterion. As the phase switching process recovers, ΔU gradually decreases. When ΔU was smaller than G, the single-phase self-adaptive reclosing criterion was opened. In Figure 7, the starting criteria for single-phase self-adaptive reclosing are indicated by arrows.

Claims (1)

A method for improving the single-phase self-adaptive reclosing of high-voltage AC transmission lines on the inverter side, including the following steps.
(1) Acquire the inverter side current transformer bus voltage in real time using a current transformer.
(2) After a single-phase grounding failure of the AC system on the inverter side occurs and a trip occurs, the voltage amplitude value U of the turbulent bus is calculated using the high-speed Fourier algorithm, and the difference between the peak value and valley value of U in half a cycle. Is calculated in real time, set to ΔU, and
(3) Set the voltage of the turbulent bus to UB, set the set value G to 4% UB, compare ΔU with G, and if ΔU is larger than G, close the single _- phase self _- adaptive reclosing cycle. , If smaller than G, open the single-phase self-adaptive reclosing cycle to distinguish the nature of the failure,
(4) In the case of an AC overhead transmission line without parallel reactors, the following single-phase adaptive reclosing criteria are adopted, the amplitude of the recovery voltage is high in the case of a temporary failure, and the recovery voltage in the case of a permanent failure. Recover to the phenomenon that the amplitude is low, set the set value U _DZ , and
U _DZ = K _k U _xl
In the above equation, K _k is the reliability coefficient, and 1.2 is _{U xl} , which is the fault phase induced voltage during two-phase operation under the maximum load condition. death,
For AC overhead transmission lines with parallel reactors, the following single-phase self-adaptive reclosing criteria are adopted, and in the event of a temporary failure of the transmission line, the recovery voltage has a beat frequency characteristic and at each beat cycle. The relationship is as follows:
U _max -U _min = 2U ₁ ＞ U _xL / 2
In the above equation, U _max and U _min are the maximum and minimum recovery voltages for each beat cycle, respectively, and U _{x L} is the electromagnetic coupling voltage of the disconnected phase, resulting in a permanent failure of the transmission line. When it occurs, there is no recovery voltage beat frequency characteristic, and the relationship at each beat cycle is as follows:
U _max -U _min = 0 << U _xL / 2
Inverter side height characterized by setting the set value U _DZ to U _xL / 2, calculating (U _max -U _min ) and comparing it with the set value U _DZ to distinguish the nature of the failure. How to improve single-phase self-adaptive reclosing of voltage-AC transmission lines.

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