AC lightning arrester and lightning arrester voltage equalization method

Abstract

An AC arrester, characterized in that it includes an arrester body, the arrester body includes a fixed element and a controlled element, and characterized in that the arrester also includes: a thyristor-controlled switch branch connected in parallel with the controlled element; a voltage-equalizing branch connected in parallel with the fixed element; and voltage equalization of the fixed element and the controlled element of the arrester body is achieved by adjusting the resistance of the voltage-equalizing resistor and the capacitance of the capacitor in the voltage-equalizing branch respectively. This prevents the arrester fixed element from having a high voltage division under steady-state conditions, which increases the leakage current.

Description

Technical Field

[0001] The present invention relates to the field of lightning arresters for grid-connected new energy units, and in particular to an alternating current lightning arrester and a lightning arrester voltage balancing method. Background Art

[0002] The development and utilization of renewable energy power generation has received increasing attention, and its expansion has also brought new topics and challenges to the operation of the power grid. It can be foreseen that renewable energy power generation will be an important part of the future power market, while new energy sources such as wind power and photovoltaics have been found to have a series of problems such as instability and poor technical performance in accessing the power grid. Multi-energy complementary new energy sites are mostly composed of photovoltaic power stations and wind turbines. The new energy units are mainly connected in parallel to the 35kV AC bus. When a system failure occurs and the bus voltage exceeds a certain voltage limit, the new energy units will be disconnected from the grid, which will have a very serious impact on the stability and security of the power grid system. In order to ensure the normal operation of the new energy units and the power grid, and to suppress the overvoltage of the AC incoming line fault as much as possible, an AC lightning arrester based on thyristor control is connected in parallel to the port of the new energy unit.

[0003] From the structural topology and working principle of the arrester, it can be seen that the arrester is subjected to AC working voltage for a long time in steady state. Due to the influence of the thyristor off-state resistance and the resistor and capacitor components in the thyristor trigger switch connected in parallel with the controlled element, the fixed element has a high voltage division and a high charge rate in steady state, which increases the leakage current and affects the stability of the arrester resistor under long-term working conditions. At present, there is no better way to improve the steady-state charge rate of the arrester with this topology. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides an AC arrester, comprising an arrester body, the arrester body comprising a fixed element and a controlled element, characterized in that the arrester further comprises:

[0005] a thyristor controlled switch branch connected in parallel with the controlled element;

[0006] A voltage balancing branch connected in parallel with the fixed element;

[0007] By adjusting the resistance of the voltage-equalizing resistor and the capacitance of the voltage-equalizing capacitor in the voltage-equalizing branch respectively, the voltage equalization of the fixed components and the controlled components of the arrester body can be achieved.

[0008] Preferably, the voltage balancing branch includes:

[0009] A voltage-equalizing resistor and a voltage-equalizing capacitor connected in parallel with each other;

[0010] The impedances of the voltage-equalizing resistor and capacitor are configured according to the expected resistance value and the expected capacitance value of the voltage-equalizing branch, respectively.

[0011] Preferably, the expected resistance value of the voltage-equalizing resistor in the voltage-equalizing branch is based on the off-state resistance value R of the thyristor in the thyristor-controlled switch branch. T and the damping ratio of the fixed element to the controlled element;

[0012] The expected capacitance value of the voltage-equalizing capacitor in the voltage-equalizing branch is based on the damping capacitor C in the thyristor-controlled switch branch. D And the damping ratio of the fixed element to the controlled element is determined.

[0013] Preferably, the thyristor controlled switch branch comprises:

[0014] Thyristor;

[0015] A saturable reactor connected in series with the thyristor;

[0016] And a resistor-capacitor structure connected in parallel with the thyristor.

[0017] Preferably, the lightning arrester further comprises:

[0018] A bypass switch connected in parallel with the controlled element.

[0019] Preferably, the fixed element and the controlled element respectively include a plurality of resistors connected in series.

[0020] Based on the same inventive concept, the present invention provides a voltage equalization method for an AC lightning arrester, comprising:

[0021] When the arrester is in a steady-state condition, the thyristor is controlled to be in an off state by using the thyristor-controlled switch branch, and the damping ratio of the fixed element and the controlled element in the arrester body, the off-state resistance value of the thyristor in the thyristor-controlled switch branch, and the damping capacitance value in the thyristor-controlled switch branch are obtained;

[0022] Determining an expected resistance value of a voltage grading branch connected in parallel with the fixed element based on the damping ratio and the off-state resistance value;

[0023] Determining an expected capacitance value of a voltage grading branch connected in parallel with the fixed element based on the damping ratio and the damping capacitance value;

[0024] By adjusting the voltage-equalizing resistance value and the voltage-equalizing capacitance value in the voltage-equalizing branch, the voltage-equalizing branch reaches the expected resistance value and the expected capacitance value, so as to realize voltage equalization of the fixed components and the controlled components in the arrester body.

[0025] Preferably, the expected resistance value is calculated as follows:

[0026]

[0027] Where: m is the number of resistors in series with the fixed element; n is the number of resistors in series with the controlled element; RT : is the off-state resistance of thyristor T.

[0028] Preferably, the expected capacitor is calculated as follows:

[0029]

[0030] Where: m: the number of resistors in series with the fixed element; n: the number of resistors in series with the controlled element; C D : is the capacitance value of the damping capacitor in the thyristor controlled switch branch.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] An AC arrester, characterized in that it includes an arrester body, the arrester body includes a fixed element and a controlled element, and characterized in that the arrester also includes: a thyristor-controlled switch branch connected in parallel with the controlled element; a voltage-equalizing branch connected in parallel with the fixed element; and voltage equalization of the fixed element and the controlled element of the arrester body is achieved by adjusting the resistance of the voltage-equalizing resistor and the capacitance of the capacitor in the voltage-equalizing branch respectively. This prevents the arrester fixed element from having a high voltage division under steady-state conditions, which increases the leakage current. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a topological diagram of the arrester of the present invention. DETAILED DESCRIPTION

[0034] In order to better understand the present invention, the content of the present invention is further described below in conjunction with the accompanying drawings and examples.

[0035] Embodiment 1:

[0036] An AC arrester, such as Figure 1 As shown, the arrester comprises a lightning arrester body, the lightning arrester body comprises a fixing element and a controlled element, and is characterized in that the lightning arrester further comprises:

[0037] a thyristor controlled switch branch connected in parallel with the controlled element;

[0038] A voltage balancing branch connected in parallel with the fixed element;

[0039] By adjusting the resistance of the voltage-equalizing resistor and the capacitance of the voltage-equalizing capacitor in the voltage-equalizing branch respectively, the voltage equalization of the fixed components and the controlled components of the arrester body can be achieved.

[0040] Among them, when the lightning arrester is in a steady-state condition, the thyristor is controlled to be in a disconnected state (referred to as the off state) through the thyristor-controlled switch branch. When a fault occurs in the converter valve, the DC system and / or the AC system, the thyristor is controlled to close through the thyristor-controlled switch branch to achieve the diversion of the fault current.

[0041] Preferably, the voltage balancing branch includes:

[0042] A voltage-equalizing resistor and a voltage-equalizing capacitor connected in parallel with each other;

[0043] The impedances of the voltage-equalizing resistor and capacitor are configured according to the expected resistance value and the expected capacitance value of the voltage-equalizing branch, respectively.

[0044] Preferably, the expected resistance value of the voltage-equalizing resistor in the voltage-equalizing branch is based on the off-state resistance value R of the thyristor in the thyristor-controlled switch branch. T and the damping ratio of the fixed element to the controlled element;

[0045] The expected capacitance value of the voltage-equalizing capacitor in the voltage-equalizing branch is based on the damping capacitor C in the thyristor-controlled switch branch. D And the damping ratio of the fixed element to the controlled element is determined.

[0046] Preferably, the thyristor controlled switch branch comprises:

[0047] Thyristor;

[0048] A saturable reactor connected in series with the thyristor;

[0049] And a resistor-capacitor structure connected in parallel with the thyristor.

[0050] Preferably, the lightning arrester further comprises:

[0051] A bypass switch connected in parallel with the controlled element.

[0052] When the arrester is in a steady-state condition, the bypass switch is controlled to be in an open state (referred to as the off state). When a fault occurs in the converter valve, the DC system and / or the AC system, the bypass switch is controlled to be closed to further divert the fault current.

[0053] Preferably, the fixed element and the controlled element respectively include a plurality of resistors connected in series.

[0054] Embodiment 2:

[0055] Based on the same inventive concept, the present invention also provides a lightning arrester voltage equalization method, comprising:

[0056] When the arrester is in a steady-state condition, the thyristor is controlled to be in an off state by using the thyristor-controlled switch branch, and the damping ratio of the fixed element and the controlled element in the arrester body, the off-state resistance value of the thyristor in the thyristor-controlled switch branch, and the damping capacitance value in the thyristor-controlled switch branch are obtained;

[0057] Determining an expected resistance value of a voltage grading branch connected in parallel with the fixed element based on the damping ratio and the off-state resistance value;

[0058] Determining an expected capacitance value of a voltage grading branch connected in parallel with the fixed element based on the damping ratio and the voltage grading capacitance value;

[0059] By adjusting the voltage-equalizing resistance value and the voltage-equalizing capacitance value in the voltage-equalizing branch, the voltage-equalizing branch reaches the expected resistance value and the expected capacitance value, so as to realize voltage equalization of the fixed components and the controlled components in the arrester body.

[0060] Preferably, the expected resistance value is calculated as follows:

[0061]

[0062] Where: m is the number of resistors in series with the fixed element; n is the number of resistors in series with the controlled element; R T : is the off-state resistance of thyristor T.

[0063] Preferably, the expected capacitor is calculated as follows:

[0064]

[0065] Where: m: the number of resistors in series with the fixed element; n: the number of resistors in series with the controlled element; C D : is the capacitance value of the damping capacitor in the thyristor controlled switch branch.

[0066] Embodiment 3:

[0067] This arrester is a typical large-capacity multi-column parallel arrester. It changes the residual voltage by controlling the number of resistors in series, thereby limiting the overvoltage at the ports of new energy units under different system faults. The primary side of the arrester is mainly composed of fixed components, controlled components, and control switches (composed of thyristor trigger switches and bypass switches). Its topological structure is shown in Figure 1 , where the fixed element and the controlled element are also called the arrester body. Its working principle is that when the new energy unit is in a steady-state condition, the arrester is subjected to AC voltage for a long time, and only leakage current flows through the arrester element; when an overvoltage fault occurs in the new energy unit, the fast switch in parallel with the controlled element is closed to reduce the residual voltage of the arrester, consume surplus power, and suppress the overvoltage of the parallel unit. After the fault is crossed, the arrester returns to its initial state.

[0068] Metal oxide resistors will gradually age and even eventually cause thermal collapse when charged for a long time during normal operation, which is the main factor determining the life of the arrester. The speed of aging depends on the long-term system operating voltage and the long-term charge of the resistor. In order to ensure the life of the resistor, its long-term operating voltage must be limited. The charge rate refers to the ratio of the long-term operating voltage peak to the operating voltage λ.

[0069] The arrester topology introduced in this patent is as follows Figure 1As shown, MOA1: fixed element, MOA2: controlled element, K1: thyristor trigger switch, K2: bypass switch; T: thyristor, Lv: saturated reactor, R D : Damping resistance, C D : Damping capacitor.

[0070] 1. Design principles

[0071] It is known that this type of arrester is connected in parallel to the port of the new energy unit, and the fixed component working voltage U1, the controlled component voltage U2, and the bus working voltage Ub have the following voltage relationship:

[0072] U1+U2=U b (1)

[0073] The voltage division of the fixed element and the controlled element is determined by the number of resistors connected in series. Assume that the impedance of the fixed element of the arrester is Z MOV1 , the number of series resistors m, the impedance of the controlled element Z MOV2 , the number of series resistors n.

[0074]

[0075]

[0076]

[0077] Where:

[0078] R MOV1 : Fixed component resistance;

[0079] R MOV2 : Resistance of the controlled element.

[0080] The design principles are as follows:

[0081] λ1=U1 / U a1 =U2 / U a2 =λ2≤λ o (5)

[0082] Where:

[0083] λ1: fixed component charge rate;

[0084] λ2: charging rate of the controlled element;

[0085] U a1 : Fixed element action voltage;

[0086] U a2 : Action voltage of controlled element;

[0087] λ o : Maximum value of the arrester charging rate.

[0088] The long-term charge rate of the arrester must be lower than λ o In order to ensure the stability of metal oxides.

[0089] 2. Voltage division optimization method

[0090] Depend on Figure 1 It can be seen that the controlled element needs to be connected in parallel with the control switch. K2 is a bypass switch, which is open circuit under steady-state conditions and has no effect on the voltage division of the arrester body components. K1 is a thyristor trigger switch. Under steady-state voltage, the thyristor T is not conducting and works in the off state for a long time, showing a high resistance state to the outside. The damping resistor R D can be ignored, the damping capacitor C D In the AC system, it shows capacitive impedance to the outside. From the above, we can know that the off-state resistance R of thyristor T T With the damping capacitor C D It will affect the steady-state voltage division of the arrester.

[0091] When the controlled element is connected in parallel with K1, assuming the working voltage of the arrester fixed element is U1′ and the working voltage of the controlled element is U2′, the following derivation can be obtained.

[0092]

[0093]

[0094] Known

[0095]

[0096] therefore

[0097] U1′>U1 (9)

[0098]

[0099] When K1 exists, the partial pressure of the fixed element increases and λ1 increases.

[0100] In order to reduce the steady-state charge rate of the fixed part, a resistor R is connected in parallel to the fixed element. q and capacitor C q ,like Figure 1 To minimize the voltage divider effect caused by K1, the resistor R q and capacitor C q The resistance value should be based on the thyristor off-state resistance R T With the damping capacitor C D For matching, the following relationship exists.

[0101]

[0102] Thus, the following deduction is made:

[0103]

[0104] Substituting equations (2) and (11) into equation (12), we can obtain

[0105]

[0106] Parallel resistance R q and capacitor C q The steady-state voltage division effect of this type of arrester due to the introduction of the control switch is reduced, and the steady-state charge rate of the fixed components is reduced.

[0107] Obviously, the described embodiments are only some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0108] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0109] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0110] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0111] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0112] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. An AC lightning arrester, characterized in that: The invention comprises a lightning arrester body, wherein the lightning arrester body comprises a fixing element and a controlled element, and is characterized in that the lightning arrester further comprises: a thyristor controlled switch branch connected in parallel with the controlled element; A voltage balancing branch connected in parallel with the fixed element; By adjusting the resistance of the voltage-equalizing resistor and the capacitance of the voltage-equalizing capacitor in the voltage-equalizing branch respectively, the voltage of the fixed components and the controlled components of the arrester body can be equalized; The voltage balancing branch comprises: A voltage-equalizing resistor and a voltage-equalizing capacitor connected in parallel with each other; The impedance of the voltage-equalizing resistor and capacitor are configured according to the expected resistance value and expected capacitance value of the voltage-equalizing branch, respectively; The expected resistance value of the voltage-equalizing resistor in the voltage-equalizing branch is determined according to the off-state resistance value of the thyristor in the thyristor-controlled switch branch and the damping ratio between the fixed element and the controlled element; The expected capacitance value of the voltage-equalizing capacitor in the voltage-equalizing branch is based on the damping capacitor C in the thyristor-controlled switch branch. D and the damping ratio of the fixed element to the controlled element; The thyristor controlled switch branch comprises: Thyristor; A saturable reactor connected in series with the thyristor; and a resistor-capacitor structure connected in parallel with the thyristor; The lightning arrester further comprises: A bypass switch connected in parallel with the controlled element; The fixed element and the controlled element respectively include a plurality of resistor sheets connected in series.

2. A voltage equalization method for an AC lightning arrester, characterized in that: Applied to the arrester as claimed in claim 1, characterized in that it comprises: When the arrester is in a steady-state condition, the thyristor is controlled to be in an off state by using the thyristor-controlled switch branch, and the damping ratio of the fixed element and the controlled element in the arrester body, the off-state resistance value of the thyristor in the thyristor-controlled switch branch, and the damping capacitance value in the thyristor-controlled switch branch are obtained; Determining an expected resistance value of a voltage grading branch connected in parallel with the fixed element based on the damping ratio and the off-state resistance value; Determining an expected capacitance value of a voltage grading branch connected in parallel with the fixed element based on the damping ratio and the damping capacitance value; By adjusting the voltage-equalizing resistance value and the voltage-equalizing capacitance value in the voltage-equalizing branch, the voltage-equalizing branch reaches the expected resistance value and the expected capacitance value, so as to realize voltage equalization of the fixed components and the controlled components in the arrester body; The expected resistance value is calculated as follows: Where: m is the number of resistors in series with the fixed element; n is the number of resistors in series with the controlled element; R T : is the off-state resistance of thyristor T; The expected capacitance value is calculated as follows: Where: m: the number of resistors in series with the fixed element; n: the number of resistors in series with the controlled element; C D : is the capacitance value of the damping capacitor in the thyristor controlled switch branch.

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