CN113067321B - Overvoltage protection device of unified power flow controller - Google Patents

Abstract

The invention discloses an overvoltage protection device of a unified power flow controller, which comprises first to fifth lightning arresters, a bypass circuit breaker and a resistor I, wherein the first to fifth lightning arresters are connected with the first to fifth lightning arresters respectively; the first lightning arrester is arranged on the valve side of the parallel transformer; the second lightning arrester is arranged on the alternating current side of the converter valve and is grounded through a resistor I; the third lightning arrester is connected in parallel to the valve side of the series transformer and is grounded through the fourth lightning arrester, and the neutral point of the third lightning arrester is connected with the neutral point of the series transformer; the fifth lightning arrester and the bypass breaker are bridged at two ends of the line side of the series transformer; the overvoltage protection device reduces the overvoltage of the unified power flow controller and improves the reliability and the economy of the unified power flow controller.

Description

A kind of overvoltage protection device of unified power flow controller

technical field

The invention relates to the field of flexible AC power transmission, in particular to an overvoltage protection device for a unified power flow controller.

Background technique

The modern power system is a complex AC-DC hybrid grid in which DC transmission and AC transmission coexist. There are many problems in the grid, such as the large geographical differences between the load center and the power generation center, which lead to the increasingly prominent problem of power flow distribution differences in transmission channels. The ability of the channel can not play well. At the same time, the difficulty and cost of new transmission channels in urban power grids are also increasing, and the difficulty of line reconstruction and expansion is also increasing. Traditional control methods are difficult to solve the above problems, which has become an important factor limiting power system transmission.

The unified power flow controller, also known as UPFC (Unified Power Flow Controller), can control the power flow of the line and improve the power transmission capacity of the line. The simplest UPFC consists of two converters connected through a common DC bus, one converter is connected to the AC system through a parallel transformer, and the other converter is connected to the AC line through a series transformer.

In the current overvoltage protection device of the UFC converter, two sets of surge arresters are used on the valve side of the series transformer, and a thyristor bypass switch and a low-voltage bypass circuit breaker on the valve side of the series transformer are added, so there is room for optimization. The overvoltage protection device proposed by the invention has optimized configuration, and improves the economy of the unified power flow controller while ensuring the safety of the unified power flow control.

Contents of the invention

Aiming at the areas that need to be improved in the prior art, the present invention proposes a converter overvoltage protection device for the unified power flow controller, which can effectively reduce the overvoltage protection level of the unified power flow controller, and ensure the safe operation of the unified power flow controller. , which improves the economy of the unified power flow controller.

In order to achieve the above object, the present invention adopts following technical scheme to realize:

An overvoltage protection device for a unified power flow controller, comprising: first to fifth arresters, a bypass circuit breaker and a resistor I; the first arrester is installed on the valve side of a parallel transformer; the second arrester is installed on the AC side of a converter valve, And grounded through resistance I; the third arrester is connected in parallel to the valve side of the series transformer, grounded through the fourth arrester, the neutral point of the third arrester is connected to the neutral point of the series transformer; the fifth arrester and bypass circuit breaker are connected in parallel across the series transformer Both ends of the line side.

Further, after the unified power flow controller detects that the converter valve on the series side is blocked, the bypass circuit breaker is closed immediately.

Further, the first to fifth arresters all use gapless zinc oxide arresters.

Further, the coordination principle of the parameters of the second, third and fifth arresters is: when the AC system fails, the energy is absorbed by the second and third arresters, and the energy absorbed by the fifth arrester is less than the set threshold.

Further, the operation impact protection level of the second arrester is less than 0.9 times of the DC operating voltage of the unified power flow controller.

Further, the selection principle of the resistor I is: the current flowing through the converter valve before the converter valve is blocked under the ground fault of the DC side of the unified power flow controller is limited to within 2 times the rated current of the converter valve.

The beneficial effects of the present invention are: adopting the overvoltage protection device of the present invention reduces the overvoltage of the unified power flow controller, and improves the economy of the unified power flow controller while ensuring the safe operation of the unified power flow controller.

Description of drawings

Figure 1 is a schematic diagram of the overvoltage protection device of the unified power flow controller.

Among them, 1-first arrester; 2-second arrester; 3-third arrester; 4-fourth arrester; 5-fifth arrester.

detailed description

Specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings.

The invention proposes an overvoltage protection device for a unified power flow controller, including: first to fifth arresters, a bypass circuit breaker and a resistor I; the first arrester is installed on the valve side of the parallel transformer; the second arrester is installed on the converter valve AC side, and grounded through resistor I; the third arrester is connected in parallel to the valve side of the series transformer, grounded through the fourth arrester, and the neutral point of the third arrester is connected to the neutral point of the series transformer; the fifth arrester is connected in parallel with the bypass circuit breaker across the line side of the series transformer.

Wherein, after the unified power flow controller detects that the converter valve on the series side is blocked, the bypass circuit breaker is closed immediately.

Wherein, the first to fifth arresters all adopt gapless zinc oxide arresters.

Wherein, the coordination principle of the parameters of the second, third and fifth arresters is: when the AC system fails, the energy is absorbed by the second and third arresters, and the energy absorbed by the fifth arrester is less than the set threshold. The fifth arrester is used to limit the lightning intrusion wave overvoltage.

Wherein, the operation impact protection level of the second arrester is less than 0.9 times of the DC operating voltage of the unified power flow controller.

Wherein, the selection principle of the resistor I is: limit the current flowing through the converter valve before the converter valve is locked under the ground fault of the DC side of the unified power flow controller to within 2 times of the rated current of the converter valve.

Fig. 1 shows a preferred embodiment of the overvoltage protection device of the unified power flow controller. The main equipment of the unified power flow controller includes parallel transformers, parallel converters, series converters and series transformers. Both the parallel transformer and the series transformer adopt a double-winding structure. One side of the parallel transformer is connected in parallel to the AC system, and the other side is connected to the parallel converter. The parallel converter includes a converter valve and a bridge arm reactor. One side of the series transformer is connected to the AC line, and the other side is connected to the series converter. The series converter and the parallel converter adopt the same parameters and structure. The rated voltage of the grid side of the parallel transformer is 110kV, the rated voltage of the valve side is 20.8kV, the neutral point resistance of the parallel transformer is 5000 ohms; the rated voltage of the line side of the series transformer is 38kV, the rated voltage of the valve side is 20.8kV, and the neutral point resistance of the series transformer is 5000 ohm. The rated voltage of the DC side of the unified power flow controller is 20kV, and the line voltage level connected in series to the unified power flow controller is 110kV.

The first arrester is connected in parallel to the valve side of the parallel transformer, and the operating impact level of the first arrester is 56kV; the second arrester is connected in parallel to the AC side of the converter valve, using a star connection, the neutral point is grounded through the resistor I, and the operating impact of the second arrester is The protection level is 36kV, and the resistance value of the resistance I is 50 ohms; the third arrester is connected in parallel to the valve side of the series transformer, adopts a star connection, the neutral point is connected with the neutral point of the transformer, and is grounded through the fourth arrester, and the third arrester operates the shock The protection level of the fourth surge arrester is 45kV, and the operation impact protection level of the fourth arrester is 30kV; the fifth arrester and bypass circuit breaker are connected in parallel at both ends of the line side of the series transformer, the operation impact protection level of the fifth arrester is 90kV, and the bypass circuit breaker bypass The road time is not more than 40ms. The first to fifth arresters are all gapless zinc oxide arresters.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the present invention can still be Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention shall be covered by the scope of the claims of the present invention.

Claims (5)

1. A kind of overvoltage protective device of unified power flow controller, it is characterized in that, comprises: the first ~ the 5th lightning arrester, bypass circuit breaker and resistance I; The first lightning arrester is installed in parallel transformer valve side; The second lightning arrester is installed in The AC side of the converter valve is grounded through the resistor I; the third arrester is connected in parallel to the valve side of the series transformer, grounded through the fourth arrester, and the neutral point of the third arrester is connected to the neutral point of the series transformer; the fifth arrester and bypass circuit breaker Parallel connection across the two ends of the line side of the series transformer; the coordination principle of the parameters of the second, third and fifth arresters is: when the AC system fails, the energy is absorbed by the second and third arresters, and the energy absorbed by the fifth arrester is less than the set Set the threshold. 2. The overvoltage protection device according to claim 1, wherein the bypass circuit breaker is closed immediately after the unified power flow controller detects that the converter valve on the series side is blocked. 3 . The overvoltage protection device according to claim 1 , wherein the first to fifth arresters are all gapless zinc oxide arresters. 4 . 4. The overvoltage protection device according to claim 1, wherein the operation impact protection level of the second arrester is less than 0.9 times of the DC operating voltage of the unified power flow controller. 5. The overvoltage protection device as claimed in claim 1, characterized in that, the selection principle of the resistance I is: the current flowing through the converter valve before the converter valve is blocked under the DC side grounding fault of the unified power flow controller is limited to Within 2 times of the rated current of the converter valve.

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