Balance test method and leveling method for capacitor bank of extra-high voltage direct current converter station

Abstract

The invention provides a balance testing method and a leveling method for an extra-high voltage direct current converter station capacitor bank, and belongs to the technical field of alternating current filter capacitor bank maintenance. The balance test method comprises the following steps: removing a low-voltage side lead of the capacitor bank and a lead of a current transformer in the capacitor bank; an AC filter high-voltage end grounding knife switch to which the capacitor bank belongs is closed, so that the high-voltage side of the capacitor bank is grounded; applying a test voltage between the low-voltage side of the capacitor bank and the grounding grid, and obtaining a test current value between an upper bridge arm middle connection point and a lower bridge arm middle connection point of the capacitor bank; obtaining an unbalance value of the capacitor bank according to the test voltage value, the test current value and an unbalance protection constant value of the capacitor bank; and if the unbalance value is smaller than the qualified value, the balance test of the capacitor bank passes. A high-voltage side lead of the capacitor bank does not need to be dismounted, a high-voltage side test wire does not need to be hooked during test, and the requirements of operation on special vehicles and the strength and danger of climbing operation are greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of AC filter capacitor bank maintenance, and in particular relates to a balance test method and a leveling method for a capacitor bank of an ultra-high voltage DC converter station. Background Art

[0002] A large number of AC filters are configured in the converter station of the UHV DC transmission project to compensate for the reactive power consumed by the converter valve during operation, and also to filter out the harmonics of the DC system. The capacitor bank is one of the main electrical components of the AC filter. When the capacitor bank is replaced due to failure, defect, etc., it is necessary to perform a balance test on the capacitor bank. Only when the balance test is passed can it be officially put into operation.

[0003] However, the capacitor bank is several meters high, and the current balancing test method requires the simultaneous removal of the leads of each bridge arm in the capacitor bank to completely disconnect the capacitor bank from the power grid, which is labor-intensive. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a balance testing method and a leveling method for a capacitor bank of an ultra-high voltage direct current converter station.

[0005] In order to solve one, part or all of the above technical problems, the technical solution adopted by the present invention is:

[0006] A balance test method for a capacitor bank of a UHV DC converter station, comprising:

[0007] Remove the leads on the low-voltage side of the capacitor bank and the leads of the current transformer in the capacitor bank;

[0008] The grounding switch at the high-voltage end of the AC filter to which the capacitor bank belongs is closed to ground the high-voltage side of the capacitor bank;

[0009] Apply a test voltage between the low-voltage side of the capacitor bank and the grounding grid, and obtain a test current value between the middle point of the upper bridge arm and the middle point of the lower bridge arm of the capacitor bank;

[0010] Obtain the unbalance value of the capacitor bank according to the test voltage value, the test current value and the unbalance protection setting value of the capacitor bank;

[0011] If the unbalanced value is less than the qualified value, the balance test of the capacitor bank passes.

[0012] Furthermore, the unbalance value is Where I1 is the test current value, I0 is the capacitor bank unbalance protection current setting value, U n is the rated voltage value of the AC filter, and U1 is the test voltage value.

[0013] Furthermore, when the capacitor bank unbalance protection setting is a ratio, Where K1 is the constant value of the unbalanced current ratio of the capacitor bank, K2 is the transformation ratio of the current transformer at the end of the AC filter, K3 is the transformation ratio of the unbalanced current transformer in the capacitor bank, I n It is the rated primary phase current value of the AC filter.

[0014] Furthermore, the test voltage is provided by a voltage regulator, and the test current value is obtained by an ammeter connected to a middle point of an upper bridge arm and a middle point of a lower bridge arm of the capacitor group.

[0015] Furthermore, the test voltage is 400V-500V.

[0016] Furthermore, the qualified value is 20%.

[0017] A leveling method for a capacitor bank of a UHV DC converter station is implemented by using the balance test method, comprising:

[0018] Obtaining the initial unbalance value of the capacitor bank;

[0019] Swap a capacitor with a larger capacitance value in the lower high-voltage side bridge arm of the capacitor bank with a capacitor with a smaller capacitance value in the lower low-voltage side bridge arm of the capacitor bank;

[0020] Obtain the unbalanced value of the capacitor bank after the capacitors are swapped. If the unbalanced value is less than the qualified value, the leveling is terminated.

[0021] If the unbalanced value after the swap increases compared to the initial unbalanced value, the capacitors in the two lower bridge arms are swapped with the goal of increasing the capacitance value of the bridge arm on the high voltage side of the lower capacitor bank and reducing the capacitance value of the bridge arm on the low voltage side of the lower capacitor bank until the unbalanced value is less than the qualified value;

[0022] If the unbalanced value after the swap is lower than the initial unbalanced value, the capacitors in the two lower bridge arms are swapped with the goal of reducing the capacitance value of the bridge arm on the high-voltage side of the lower capacitor group and increasing the capacitance value of the bridge arm on the low-voltage side of the lower capacitor group until the unbalanced value is less than the qualified value.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The capacitor bank balance test method provided by the present invention only needs to remove the lead wires on the low-voltage side of the capacitor bank, and the high-voltage side of the capacitor bank does not need to be removed. The grounding grid is connected to the test loop by using the grounding knife switch at the high-voltage end of the AC filter. The present invention does not need to remove the high-voltage side lead wires of the capacitor bank, nor does it need to hang the high-voltage side test wires during the test, which greatly reduces the demand for special vehicles for the operation and the intensity and danger of the high-altitude operation.

[0025] The capacitor bank leveling method provided by the present invention completes the leveling by adjusting the capacitors in the two bridge arms of the lower layer of the capacitor bank according to the unbalance value obtained during the balance test, without the need to disassemble the capacitors in the upper layer, thereby reducing the intensity and danger of the height operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0027] Figure 1 : Electrical schematic diagram of the AC filter and capacitor bank of the present invention;

[0028] Figure 2 : Schematic diagram of the test of Example 1 of the present invention. DETAILED DESCRIPTION

[0029] In order to better understand the present invention, the content of the present invention is further clearly described below in conjunction with the embodiments and the accompanying drawings, but the protection content of the present invention is not limited to the following embodiments. In the following description, a large number of specific details are provided to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details.

[0030] like Figure 1 The figure shows the electrical schematic diagram of the AC filter, where C1 is a capacitor bank. The capacitor bank is an H-bridge structure consisting of four bridge arms, the two bridge arms on the upper layer form the upper bridge arm, and the two bridge arms on the lower layer form the lower bridge arm. The current transformer T1 set between the upper and lower bridge arms can measure the unbalanced current during the operation of the capacitor bank.

[0031] After repairing or replacing a capacitor bank with defects or faults, a balance test is required to check the quality of the repair work, ensure that the unbalanced current of the capacitor bank meets the requirements, and provide a basis for the equipment to be put into operation. Based on this, Example 1 of the present application provides a balance test method for a capacitor bank of a UHV DC converter station.

[0032] Example 1: See Figure 2 The purpose of this embodiment is to provide a balance test method for a capacitor bank of a UHV DC converter station. The balance test method comprises:

[0033] S101, disconnect the low-voltage side lead of the capacitor bank and the lead of the current transformer in the capacitor bank;

[0034] S102, AC filter high voltage end grounding switch ( Figure 2 K1) in the capacitor bank is closed to ground the high voltage side of the capacitor bank;

[0035] S103, applying a test voltage between the low-voltage side of the capacitor bank and the grounding grid, and obtaining a test current value between a middle point of an upper bridge arm and a middle point of a lower bridge arm of the capacitor bank;

[0036] S104, obtaining an unbalanced value of the capacitor bank according to the test voltage value, the test current value and the unbalanced protection setting value of the capacitor bank;

[0037] S105. If the unbalanced value is less than the qualified value, the balance test of the capacitor bank passes.

[0038] like Figure 2 As shown, the test voltage is provided by the voltage regulator, and the test current value is obtained by the ammeter connected to the middle point of the upper bridge arm and the middle point of the lower bridge arm of the capacitor bank. The preferred test voltage is 400V-500V, and the preferred qualified value is 20%. Compared with the current transformer T1, the ammeter used in the test adopts a precision ammeter, which can improve the test accuracy on the one hand, and detect the smaller test current generated under the test voltage on the other hand.

[0039] The unbalance value in step S4 is Where I1 is the test current value, I0 is the capacitor bank unbalance protection current setting value, U n is the rated voltage value of the AC filter, and U1 is the test voltage value.

[0040] When the capacitor bank unbalance protection setting is a ratio, Where K1 is the unbalanced current ratio of the capacitor bank, K2 is the current transformer at the end of the AC filter ( Figure 2 T2) ratio, K3 is the unbalanced current transformer ratio ( Figure 2 Middle T1), I n It is the rated primary phase current value of the AC filter.

[0041] When the balance test of the capacitor group fails, the capacitor group needs to be leveled. Based on this, Example 2 of the present application provides a leveling method for a capacitor group of a UHV DC converter station.

[0042] Embodiment 2: The purpose of this embodiment is to provide a leveling method for a capacitor bank of a UHV DC converter station. The leveling method comprises:

[0043] S201, using steps S101-S104 in embodiment 1 to obtain an initial unbalanced value of the capacitor bank;

[0044] S202, swapping a capacitor with a larger capacitance value in the lower high-voltage side bridge arm of the capacitor bank with a capacitor with a smaller capacitance value in the lower low-voltage side bridge arm of the capacitor bank;

[0045] S203, obtaining the unbalanced value of the capacitor bank after the capacitors are interchanged, and if the unbalanced value is less than the qualified value, the leveling is terminated; otherwise:

[0046] S204. If the unbalanced value after the swap increases compared with the initial unbalanced value, the capacitors in the two lower bridge arms are swapped by increasing the capacitance value of the bridge arm on the lower high-voltage side of the capacitor group and decreasing the capacitance value of the bridge arm on the lower low-voltage side of the capacitor group until the unbalanced value is less than the qualified value; if the unbalanced value after the swap decreases compared with the initial unbalanced value, the capacitors in the two lower bridge arms are swapped by decreasing the capacitance value of the bridge arm on the lower high-voltage side of the capacitor group and increasing the capacitance value of the bridge arm on the lower low-voltage side of the capacitor group until the unbalanced value is less than the qualified value.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in the field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for balancing a capacitor bank in a UHV DC converter station, characterized in that: include: Remove the leads on the low-voltage side of the capacitor bank and the leads of the current transformer in the capacitor bank; The grounding switch at the high-voltage end of the AC filter to which the capacitor bank belongs is closed to ground the high-voltage side of the capacitor bank; Apply a test voltage between the low-voltage side of the capacitor bank and the grounding grid, and obtain a test current value between the middle point of the upper bridge arm and the middle point of the lower bridge arm of the capacitor bank; Obtain the unbalance value of the capacitor bank according to the test voltage value, the test current value and the unbalance protection setting value of the capacitor bank; If the unbalanced value is less than the qualified value, the balance test of the capacitor bank passes.

2. The method for balancing a capacitor bank in a UHV DC converter station according to claim 1, characterized in that: The unbalance value is Where I1 is the test current value, I0 is the capacitor bank unbalance protection current setting value, U n is the rated voltage value of the AC filter, and U1 is the test voltage value.

3. The method for balancing a capacitor bank in a UHV DC converter station according to claim 2, characterized in that: When the capacitor bank unbalance protection setting is a ratio, Where K1 is the constant value of the unbalanced current ratio of the capacitor bank, K2 is the transformation ratio of the current transformer at the end of the AC filter, K3 is the transformation ratio of the unbalanced current transformer in the capacitor bank, I n It is the rated primary phase current value of the AC filter.

4. The method for balancing a capacitor bank in a UHV DC converter station according to claim 1, characterized in that: The test voltage is provided by a voltage regulator, and the test current value is obtained by an ammeter connected to the middle point of the upper bridge arm and the middle point of the lower bridge arm of the capacitor group.

5. The method for balancing a capacitor bank in a UHV DC converter station according to claim 1, characterized in that: The test voltage is 400V-500V.

6. The method for balancing a capacitor bank in a UHV DC converter station according to claim 1, characterized in that: The qualified value is 20%.

7. A method for leveling a capacitor bank of a UHV DC converter station, implemented by using the balancing test method according to any one of claims 1 to 6, characterized in that: include: Obtaining the initial unbalance value of the capacitor bank; Swap a capacitor with a larger capacitance value in the lower high-voltage side bridge arm of the capacitor bank with a capacitor with a smaller capacitance value in the lower low-voltage side bridge arm of the capacitor bank; Obtain the unbalanced value of the capacitor bank after the capacitors are swapped. If the unbalanced value is less than the qualified value, the leveling is terminated. If the unbalanced value after the swap increases compared to the initial unbalanced value, the capacitors in the two lower bridge arms are swapped with the goal of increasing the capacitance value of the bridge arm on the high voltage side of the lower capacitor bank and reducing the capacitance value of the bridge arm on the low voltage side of the lower capacitor bank until the unbalanced value is less than the qualified value; If the unbalanced value after the swap is lower than the initial unbalanced value, the capacitors in the two lower bridge arms are swapped with the goal of reducing the capacitance value of the bridge arm on the high-voltage side of the lower capacitor group and increasing the capacitance value of the bridge arm on the low-voltage side of the lower capacitor group until the unbalanced value is less than the qualified value.

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