Balancing method for H-connection capacitor tower

Abstract

The application relates to the technical field of high-voltage capacitor towers, and particularly provides a balancing method for an H-type wiring capacitor tower, which comprises the following steps: acquiring an actual operation voltage of the H-type wiring capacitor tower, an unbalanced current corresponding to the actual operation voltage, and a high-voltage bridge arm design capacity and a low-voltage bridge arm design capacity; determining a bridge arm capacity increase / decrease direction according to a phase difference between the unbalanced current and the actual operation voltage; calculating an unbalance coefficient according to an amplitude of the unbalanced current, an amplitude of the actual operation voltage, the high-voltage bridge arm design capacity and the low-voltage bridge arm design capacity, and determining an adjusted capacity; and interchanging capacitor units in the low-voltage bridge arm based on the bridge arm capacity increase / decrease direction and the adjusted capacity to balance. The method can solve the problem that, in the related art, the balancing of a capacitor tower cannot simultaneously achieve high efficiency and high reliability.

Description

Technical Field

[0001] This invention relates to the field of high-voltage capacitor tower technology, and in particular to a balancing method for an H-type connected capacitor tower. Background Technology

[0002] High-voltage capacitor towers are an essential component of AC filters in converter stations. A single tower can contain up to 200 capacitors. Due to the non-linear characteristics of capacitor capacitance changing with voltage and the possibility of factory-specified capacity deviations, tower imbalance and excessively high unbalanced currents can easily occur, affecting the reliability of protection devices. Therefore, during high-voltage capacitor tower maintenance, it is necessary to detect the unbalanced current and perform bridge arm balancing (capacitor tower balancing) to ensure that the unbalanced current remains within a minimal range.

[0003] The relevant technologies mainly employ the following methods for balancing high-voltage capacitor towers: (1) First, use special equipment to measure the unbalanced current, and then have professionals propose a balancing scheme based on their own experience. This is inefficient and unreliable. Specifically, in actual field, the unbalanced current is usually tested by applying power frequency voltage to both ends of the capacitor tower. This method is severely affected by external magnetic fields, and the test error is large. Moreover, the balancing of the bridge arm mainly relies on the work experience of maintenance personnel and the trend of unbalanced current changes to adjust the position of the capacitor. The maintenance work is cumbersome, the process is repetitive, and there is a lot of uncertainty.

[0004] (2) First, use special equipment to measure, and then calculate the balancing scheme by traversal method. The maximum voltage of the special measuring equipment is usually less than 1000V, which is too different from the working voltage of more than 100kV. This may lead to low-voltage balancing and high-voltage operation failure, affecting reliability. In addition, the workload is large and the efficiency is low because measurement is required before each balancing.

[0005] (3) By applying high-frequency low-voltage or low-frequency high-voltage AC signals at both ends of the capacitor tower, the unbalanced current can be indirectly measured by the unbalanced voltage, which can reduce the influence of the power frequency magnetic field on the test results. However, this method adopts the idea of ​​low-voltage measurement and high-voltage use, without considering the nonlinearity of the capacitor capacitance with voltage change, which may lead to failure and low reliability.

[0006] There is currently no effective solution to the problem that capacitor tower balancing in related technologies cannot achieve both high efficiency and high reliability. Summary of the Invention

[0007] The present invention provides a balancing method for H-type connected capacitor towers, which at least solves the problem in related technologies that capacitor tower balancing is difficult to balance with high efficiency and high reliability.

[0008] This invention provides a method for balancing an H-type connected capacitor tower, comprising: obtaining the actual operating voltage of the H-type connected capacitor tower, the unbalanced current corresponding to the actual operating voltage, and the design capacitance of the high-voltage bridge arm and the design capacitance of the low-voltage bridge arm; determining the direction of bridge imbalance based on the phase difference between the unbalanced current and the actual operating voltage, and determining the direction of increase or decrease of bridge arm capacitance; calculating the imbalance coefficient based on the amplitude of the unbalanced current, the amplitude of the actual operating voltage, the design capacitance of the high-voltage bridge arm, and the design capacitance of the low-voltage bridge arm, and determining the adjustment capacitance; and swapping the capacitor units in the low-voltage bridge arm based on the direction of increase or decrease of bridge arm capacitance and the adjustment capacitance to balance the system.

[0009] As an optional approach, the direction of bridge imbalance is determined based on the phase difference between the unbalanced current and the actual operating voltage, thereby determining the direction of increase or decrease in bridge arm capacitance. This includes: when the phase difference between the unbalanced current and the actual operating voltage is +90°, the direction of increase or decrease in bridge arm capacitance is to decrease the single-arm capacitance of the high-voltage bridge arm on the first side and the single-arm capacitance of the low-voltage bridge arm on the second side, and to increase the single-arm capacitance of the low-voltage bridge arm on the first side and the single-arm capacitance of the high-voltage bridge arm on the second side, wherein the circuit reference positive direction of the H-type capacitor tower is from the first side to the second side; when the phase difference is -90°, the direction of increase or decrease in bridge arm capacitance is to increase the single-arm capacitance of the high-voltage bridge arm on the first side and the single-arm capacitance of the low-voltage bridge arm on the second side, and to decrease the single-arm capacitance of the low-voltage bridge arm on the first side and the single-arm capacitance of the high-voltage bridge arm on the second side.

[0010] As an optional approach, the imbalance coefficient is calculated based on the amplitude of the unbalanced current, the amplitude of the actual operating voltage, the design capacitance of the high-voltage bridge arm, and the design capacitance of the low-voltage bridge arm, and the adjustment capacitance is determined. This includes: calculating the imbalance coefficient based on the amplitude of the unbalanced current, the amplitude of the actual operating voltage, the design capacitance of the high-voltage bridge arm, and the design capacitance of the low-voltage bridge arm; and dividing the product of the imbalance coefficient and the design capacitance of the low-voltage bridge arm by four to obtain the adjustment capacitance.

[0011] As an alternative approach, the formula for calculating the aforementioned imbalance coefficient is as follows: ; In the formula, Indicates the imbalance coefficient. Indicates the design capacitance of the high-voltage bridge arm. Indicates the design capacitance of the low-voltage bridge arm. Indicates the magnitude of the unbalanced current. Indicates the power frequency angular frequency. This indicates the amplitude of the actual operating voltage.

[0012] As an optional approach, the capacitor units in the low-voltage bridge arm are interchanged to balance the load based on the aforementioned direction of increase / decrease in bridge arm capacitance and the aforementioned adjustment capacitance. This includes: determining the first-side capacitance adjustment condition and the second-side capacitance adjustment condition of the low-voltage bridge arm based on the aforementioned direction of increase / decrease in bridge arm capacitance and the aforementioned adjustment capacitance, wherein the first-side capacitance adjustment condition and the second-side capacitance adjustment condition use the same number of capacitor units to adjust; and exchanging the positions of the first-side low-voltage capacitor units that meet the first-side capacitance adjustment condition with the second-side low-voltage capacitor units that meet the second-side capacitance adjustment condition for balancing.

[0013] As an optional solution, based on the aforementioned direction of increase / decrease in bridge arm capacitance and the aforementioned adjustment capacitance, the first-side capacitance adjustment conditions and the second-side capacitance adjustment conditions of the low-voltage bridge arm are determined, including: when the aforementioned direction of increase / decrease in bridge arm capacitance is to increase the single-arm capacitance of the low-voltage bridge arm on the first side and decrease the single-arm capacitance of the low-voltage bridge arm on the second side, the aforementioned first-side capacitance adjustment condition is that after replacing all the low-voltage capacitor units of the aforementioned adjusted capacitor unit quantity on the first side with reference capacitor units, the single-arm capacitance of the low-voltage bridge arm on the first side increases, and the increase value is the aforementioned adjustment capacitance. The overall capacitance; the second-side capacitance adjustment condition is that after replacing all the low-voltage capacitor units of the second-side capacitor units with the reference capacitor units, the capacitance of the single arm of the low-voltage bridge arm on the second side decreases, and the decrease is the adjusted capacitance; wherein, the capacitance of the reference capacitor unit is the product of the low-voltage bridge arm design capacitance and the number of low-voltage series connections divided by the number of low-voltage parallel connections, the number of low-voltage series connections is the number of capacitor units in the series branches inside the single arm of the low-voltage bridge arm, and the number of low-voltage parallel connections is the number of series branches connected in parallel inside the single arm of the low-voltage bridge arm.

[0014] As an optional solution, the positions of the first-side low-voltage capacitor unit that meets the first-side capacitance adjustment conditions and the second-side low-voltage capacitor unit that meets the second-side capacitance adjustment conditions are interchanged, including: the positions of the first-side low-voltage capacitor unit located at the lower layer of the low-voltage bridge arm and the second-side low-voltage capacitor unit located at the lower layer of the low-voltage bridge arm are interchanged.

[0015] As an alternative, if there are multiple options for the number of capacitor units to be adjusted under the first and second capacitance adjustment conditions, the smallest value shall be selected as the number of capacitor units to be adjusted for balancing.

[0016] As an optional solution, after swapping the positions of the first-side low-voltage capacitor unit that meets the first-side capacitance adjustment condition and the second-side low-voltage capacitor unit that meets the second-side capacitance adjustment condition, if the balancing is not completed, the number of capacitor units to be adjusted is increased, and the first-side low-voltage capacitor unit and the second-side low-voltage capacitor unit are swapped again.

[0017] As an optional solution, after swapping the capacitor units in the low-voltage bridge arm based on the above-mentioned direction of increase or decrease in bridge arm capacitance and the above-mentioned adjustment capacitance, the method further includes: if swapping the capacitor units in the low-voltage bridge arm still cannot achieve balance, swapping the capacitor units in the high-voltage bridge arm based on the above-mentioned direction of increase or decrease in bridge arm capacitance and the above-mentioned adjustment capacitance.

[0018] The balancing method for H-type capacitor towers provided by this invention can calculate the balancing scheme based solely on operational data and capacitor tower design data. This data can be directly read from the capacitor tower's operational records, eliminating the need for unbalanced current measurement. This avoids balancing failures caused by nonlinear changes in capacitance with voltage, achieving both high efficiency and high reliability in balancing. It solves the problem in related technologies where capacitor tower balancing struggles to achieve both high efficiency and high reliability. Attached Figure Description

[0019] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other embodiments based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart illustrating the steps of a balancing method for an H-type connected capacitor tower according to an embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram illustrating the protection of an H-type wired capacitor tower according to an embodiment of the present invention. Detailed Implementation

[0022] Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. While some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0023] High-voltage capacitor towers are an essential component of AC filters in converter stations. A single tower can contain up to 200 capacitors. Due to the non-linear characteristics of capacitor capacitance changing with voltage and the possibility of factory-specified capacity deviations, tower imbalance and excessively high unbalanced currents can easily occur, affecting the reliability of protection devices. Therefore, during high-voltage capacitor tower maintenance, it is necessary to detect the unbalanced current and perform bridge arm balancing (capacitor tower balancing) to ensure that the unbalanced current remains within a minimal range.

[0024] The present invention provides a balancing method for an H-type connected capacitor tower, including steps S101 to S104.

[0025] Step S101: Obtain the actual operating voltage of the H-type connected capacitor tower, the unbalanced current corresponding to the actual operating voltage, and the design capacitance of the high-voltage bridge arm and the design capacitance of the low-voltage bridge arm.

[0026] Step S102: Determine the direction of bridge imbalance based on the phase difference between the unbalanced current and the actual operating voltage, and determine the direction of increase or decrease in bridge arm capacitance.

[0027] Step S103: Calculate the imbalance coefficient based on the amplitude of the unbalanced current, the amplitude of the actual operating voltage, the design capacity of the high-voltage bridge arm, and the design capacity of the low-voltage bridge arm, and determine the adjustment capacity.

[0028] Step S104: Based on the above-mentioned direction of increase or decrease in bridge arm capacitance and the above-mentioned adjustment capacitance, the capacitor units in the low-voltage bridge arm are interchanged to balance the voltage.

[0029] H-type capacitor towers are mainly deployed in converter stations of high-voltage direct current (HVDC) transmission projects. They are standard equipment for AC filter banks, with rated operating voltages generally exceeding 100kV, and belong to ultra-high voltage, large-capacity power capacitor devices. The internal electrical circuit adopts an H-type AC bridge (bridge differential connection) topology, mainly undertaking system filtering and reactive power compensation functions, and is also a key carrier for capacitor imbalance protection in converter stations.

[0030] Please refer to the protection diagram of the H-type connected capacitor tower. Figure 2 As shown, when the capacitor towers are connected in a bridge circuit, the unbalanced current is... The value is 0 when a capacitor element breaks down. If it gets bigger, it will trigger protection.

[0031] Unbalanced current As shown in the following formula.

[0032] ; In the formula, j represents the imaginary unit. Indicates the power frequency angular frequency. represents the actual operating voltage, C1 represents the single-arm capacitance of the high-voltage bridge arm on the first side, C2 represents the single-arm capacitance of the high-voltage bridge arm on the second side, C3 represents the single-arm capacitance of the low-voltage bridge arm on the first side, and C4 represents the single-arm capacitance of the low-voltage bridge arm on the second side.

[0033] When C1C4>C2C3, leads the voltage by approximately 90°, and when C1C4<C2C3, lags the voltage by approximately 90°, so the direction of unbalance can be determined according to the phase of the unbalanced current, and then the direction of adjustment can be determined. When leading by 90°, it is necessary to decrease C1 and C4 and increase C2 and C3; When lagging by 90°, it is necessary to increase C1 and C4 and decrease C2 and C3.

[0034] In order to balance the capacitor tower, the following relationship shall be satisfied in design: C1=C2=C m , C3=C4=C n ; where C m represents the designed capacitance of the high-voltage bridge arm, and C n represents the designed capacitance of the low-voltage bridge arm.

[0035] If there is a deviation in the capacitance of the bridge arm, then C1C4=k C m C n , C2C3=g C m C n , since the deviation of the bridge arm capacitance is very small, that is, k→1, g→1, the following holds: ; ; where I d represents the amplitude of the unbalanced current, U represents the amplitude of the actual operating voltage, represents the unbalance coefficient.

[0036] Since C1 and C2 correspond to the high-voltage bridge arms, which are usually provided with high insulators below, the above method provided by the present application preferentially adjusts the capacitor units in C3 and C4 corresponding to the low-voltage bridge arms for balancing. This embodiment will further describe the balancing by swapping capacitor units later.

[0037] Compared to adjustments based on experience, the method provided in this invention provides quantitative calculations, resulting in higher efficiency. Compared to methods using dedicated equipment for on-site measurements, the method provided in this invention calculates the balancing scheme solely based on operational data and capacitor tower design data. This data can be directly read from the capacitor tower's operational records, eliminating the need for unbalanced current measurement. The method used in this invention employs data from actual operating voltages, avoiding balancing failures due to nonlinear changes in capacitance with voltage. This method solves the problem in related technologies where capacitor tower balancing struggles to balance high efficiency and high reliability.

[0038] As an optional solution, step S102, determining the direction of bridge arm capacitance increase / decrease based on the phase difference between the unbalanced current and the actual operating voltage, includes: when the phase difference between the unbalanced current and the actual operating voltage is +90°, the direction of bridge arm capacitance increase / decrease is to decrease the single-arm capacitance of the high-voltage bridge arm on the first side and the single-arm capacitance of the low-voltage bridge arm on the second side, and to increase the single-arm capacitance of the low-voltage bridge arm on the first side and the single-arm capacitance of the high-voltage bridge arm on the second side, wherein the circuit reference positive direction of the H-type capacitor tower is from the first side to the second side. When the phase difference is -90°, the direction of bridge arm capacitance increase / decrease is to increase the single-arm capacitance of the high-voltage bridge arm on the first side and the single-arm capacitance of the low-voltage bridge arm on the second side, and to decrease the single-arm capacitance of the low-voltage bridge arm on the first side and the single-arm capacitance of the high-voltage bridge arm on the second side. The circuit reference positive direction can be referenced... Figure 2 As shown, C1 and C3 are located on the first side, and C2 and C4 are located on the second side.

[0039] A phase difference of +90° or -90° is a preferred reference value provided in this embodiment. In practical applications, any value close to this preferred reference value is acceptable. For example, phase differences of +85°, +86°, +89°, etc., can all be processed with reference to the +90° case, and phase differences of -91°, -93°, -95°, etc., can all be processed with reference to the -90° case.

[0040] As an optional approach, step S103, calculating the imbalance coefficient based on the amplitude of the unbalanced current, the amplitude of the actual operating voltage, the design capacitance of the high-voltage bridge arm, and the design capacitance of the low-voltage bridge arm, and determining the adjustment capacitance, includes: calculating the imbalance coefficient based on the amplitude of the unbalanced current, the amplitude of the actual operating voltage, the design capacitance of the high-voltage bridge arm, and the design capacitance of the low-voltage bridge arm; dividing the product of the imbalance coefficient and the design capacitance of the low-voltage bridge arm by four to obtain the adjustment capacitance.

[0041] The formula for calculating the above imbalance coefficient is expressed as follows: ; In the formula, Indicates the imbalance coefficient. Indicates the design capacitance of the high-voltage bridge arm. Indicates the design capacitance of the low-voltage bridge arm. Indicates the magnitude of the unbalanced current. Indicates the power frequency angular frequency. This indicates the amplitude of the actual operating voltage.

[0042] Adjusting the capacitance is represented by C. n λ / 4.

[0043] As an optional solution, step S104, which involves swapping capacitor units in the low-voltage bridge arm for balancing based on the aforementioned direction of increase / decrease in bridge arm capacitance and the aforementioned adjustment capacitance, includes: determining a first-side capacitance adjustment condition and a second-side capacitance adjustment condition for the low-voltage bridge arm based on the aforementioned direction of increase / decrease in bridge arm capacitance and the aforementioned adjustment capacitance, wherein the first-side capacitance adjustment condition and the second-side capacitance adjustment condition use the same number of capacitor units to adjust; and swapping the positions of the first-side low-voltage capacitor units that meet the first-side capacitance adjustment condition with the second-side low-voltage capacitor units that meet the second-side capacitance adjustment condition for balancing.

[0044] Prioritize adjusting the low-voltage bridge arm. Compared to the high-voltage bridge arm, the low-voltage side equipment has lower ground voltage, insulation level, and working height, significantly reducing the safety risks of electric shock and falls from heights.

[0045] There's no need to calculate the number of adjustment units separately for each side; only one set of adjustment units N needs to be determined, and then units that meet the capacity conditions on both sides can be selected separately. This simplifies the workload and computational complexity of preliminary parameter calculations and unit selection. It is convenient for manual calculation of balancing schemes and also adaptable to automated program calculations, resulting in high efficiency in generating balancing schemes.

[0046] Individually disassembling and adding / removing capacitor units requires repeated disassembly of wiring and fasteners, which is a complicated process. However, the method provided in this embodiment adopts a unit position interchange mode, which only changes the installation position of the unit. The component body, wiring terminals, and fixing brackets do not need to be disassembled or modified, reducing repetitive labor, effectively reducing the workload of each balance, improving maintenance efficiency, reducing disturbance to the mechanical structure and electrical connection parts of the equipment, and reducing mechanical wear and connection failure rate.

[0047] As an optional solution, based on the aforementioned direction of increase / decrease in bridge arm capacitance and the aforementioned adjustment capacitance, the first-side capacitance adjustment conditions and the second-side capacitance adjustment conditions of the low-voltage bridge arm are determined, including: when the aforementioned direction of increase / decrease in bridge arm capacitance is to increase the single-arm capacitance of the low-voltage bridge arm on the first side and decrease the single-arm capacitance of the low-voltage bridge arm on the second side, the aforementioned first-side capacitance adjustment condition is that after replacing all the low-voltage capacitor units of the aforementioned adjusted capacitor unit quantity on the first side with reference capacitor units, the single-arm capacitance of the low-voltage bridge arm on the first side increases, and the increase value is the aforementioned adjustment capacitance. The overall capacitance; the second-side capacitance adjustment condition is that after replacing all the low-voltage capacitor units of the second-side capacitor units with the reference capacitor units, the capacitance of the single arm of the low-voltage bridge arm on the second side decreases, and the decrease is the adjusted capacitance; wherein, the capacitance of the reference capacitor unit is the product of the low-voltage bridge arm design capacitance and the number of low-voltage series connections divided by the number of low-voltage parallel connections, the number of low-voltage series connections is the number of capacitor units in the series branches inside the single arm of the low-voltage bridge arm, and the number of low-voltage parallel connections is the number of series branches connected in parallel inside the single arm of the low-voltage bridge arm.

[0048] Accordingly, when the direction of the increase or decrease of the bridge arm capacitance is to decrease the single-arm capacitance of the low-voltage bridge arm on the first side and increase the single-arm capacitance of the low-voltage bridge arm on the second side, the capacitance adjustment condition on the first side is that after replacing all the low-voltage capacitor units of the adjusted number of capacitor units on the first side with reference capacitor units, the single-arm capacitance of the low-voltage bridge arm on the first side decreases, and the decrease is the adjusted capacitance; the capacitance adjustment condition on the second side is that after replacing all the low-voltage capacitor units of the adjusted number of capacitor units on the second side with reference capacitor units, the single-arm capacitance of the low-voltage bridge arm on the second side increases, and the increase is the adjusted capacitance.

[0049] When the capacitor cells in the high-voltage bridge arm are interchanged to balance the voltage, the capacitance of the reference capacitor cell is the product of the high-voltage bridge arm design capacitance and the number of high-voltage series connections, divided by the number of high-voltage parallel connections.

[0050] Among them, the number of low-voltage series connections, the number of low-voltage parallel connections, the number of high-voltage series connections, and the number of high-voltage parallel connections are all design data for capacitor towers.

[0051] As an optional solution, the positions of the first-side low-voltage capacitor unit that meets the first-side capacitance adjustment conditions and the second-side low-voltage capacitor unit that meets the second-side capacitance adjustment conditions can be interchanged. This includes: interchangering the positions of the first-side low-voltage capacitor unit located at the lower layer of the low-voltage bridge arm with the second-side low-voltage capacitor unit located at the lower layer of the low-voltage bridge arm. Prioritizing the interchange of capacitor units at the lower layer of the low-voltage bridge arm can reduce the risks of working at heights and improve on-site safety; reduce operational difficulty, simplify the work process, and improve balancing efficiency; and avoid disturbing upper-level equipment, reducing the incidence of secondary failures.

[0052] As an alternative, when there are multiple options for the number of capacitor units to be adjusted under the first and second capacitance adjustment conditions, the smallest value should be selected as the number of capacitor units to be adjusted for balancing. Prioritizing the smallest adjustment number helps reduce workload, improve overall balancing efficiency, reduce equipment disturbance, lower the risk of secondary failures, reduce the probability of human error, and ensure work quality.

[0053] As an optional solution, after swapping the positions of the first-side low-voltage capacitor unit that meets the first-side capacitance adjustment condition and the second-side low-voltage capacitor unit that meets the second-side capacitance adjustment condition, if the balancing is not completed, the number of capacitor units to be adjusted is increased, and the first-side low-voltage capacitor unit and the second-side low-voltage capacitor unit are swapped again.

[0054] After the initial swap of the low-voltage bridge arm capacitor units, if the test results indicate that the balance requirements have not been met, the number of capacitor units to be adjusted can be gradually increased, and the unit swapping operation can be carried out again using the original swapping rules. On the one hand, this can achieve gradual capacity adjustment, effectively avoid over-adjustment, reduce trial and error costs, and optimize overall operation and maintenance efficiency; on the other hand, it can adapt to different degrees of imbalance, enhancing the versatility of the solution and the adaptability to operating conditions.

[0055] As an optional solution, after swapping the capacitor units in the low-voltage bridge arm based on the above-mentioned direction of increase or decrease in bridge arm capacitance and the above-mentioned adjustment capacitance, the method further includes: if swapping the capacitor units in the low-voltage bridge arm still cannot achieve balance, swapping the capacitor units in the high-voltage bridge arm based on the above-mentioned direction of increase or decrease in bridge arm capacitance and the above-mentioned adjustment capacitance.

[0056] The technical principle of exchanging capacitor units in the high-voltage bridge arm based on the above-mentioned direction of increasing or decreasing bridge arm capacitance and the above-mentioned adjustment of capacitance is the same as the technical principle of exchanging capacitor units in the low-voltage bridge arm based on the above-mentioned direction of increasing or decreasing bridge arm capacitance and the above-mentioned adjustment of capacitance. It can be understood by reference, and will not be repeated here in this embodiment.

[0057] For example, if the number of capacitors connected in series in C3 and C4 is S and the number of capacitors connected in parallel is P, then the design capacitance of the capacitor unit in C3 and C4 (referencing the capacitance of the capacitor unit) is C. u =C n *S / P, the process is as follows:

[0058] (1) Set the number of capacitor units to N.

[0059] (2) Find the capacitance of the capacitor unit in C3 and select capacitor unit C. 31 C 32 ..., C3N Its capacitance satisfies the condition: if it is replaced with a capacitance of C u After the capacitor unit, C3 is increased by C n λ / 4.

[0060] (3) Find the capacitance of the capacitor unit in C4, and select capacitor unit C. 41 C 42 ..., C 4N Its capacitance satisfies the condition: if it is replaced with a capacitance of C u After the capacitor cell is removed, C4 reduces C. n λ / 4.

[0061] (4) Capacitor unit C 31 -C 3N With capacitor unit C 41 -C 4N Swapping their positions constitutes the adjustment plan.

[0062] (5) Let the adjusted capacitances be C3' and C4', as shown in the following formula: ; ; In the formula, w and v represent deviations, and |w| << 1, |v| << 1.

[0063] The unbalanced current after adjustment is: ; Balance is achieved when the adjusted unbalanced current is within the preset value range.

[0064] (6) If the balance target cannot be achieved by simply exchanging the capacitor units in C3 and C4, the capacitor units in C1 and C2 should also be exchanged.

[0065] (7) The smaller the value of the number of capacitor units N, the less workload there is, the lower the number of capacitor unit layers selected, and the lower the difficulty of the work.

[0066] It should be noted that the term "comprising" and its variations used in the embodiments of this invention are open-ended, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". The modifications of "one" and "a plurality" mentioned in the embodiments of this invention are illustrative and not restrictive, and those skilled in the art should understand that unless explicitly indicated otherwise in the context, they should be understood as "one or more". The descriptions of terms such as "first", "second", etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of indicated technical features.

[0067] The user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in the embodiments of this invention are subject to strict compliance with relevant laws, regulations, and regulatory requirements in their collection, storage, use, processing, transmission, provision, and disclosure, and adhere to the principles of legality, legitimacy, necessity, and good faith. The acquisition of relevant information and data is premised on the user's explicit consent or other legitimate reasons, and a clear and convenient authorization management approach is provided to the user, allowing the user to independently choose to consent, withdraw consent, or refuse to provide relevant information. For functions that rely on user information, if the user does not authorize or withdraws authorization, the corresponding technical function cannot be implemented, and the technical solution of this invention is not applicable in this scenario.

[0068] The steps described in the method embodiments provided by the present invention can be performed in different orders and / or in parallel. Furthermore, the method embodiments may include additional steps and / or omit the steps shown. The scope of protection of the present invention is not limited in this respect.

[0069] The term "embodiment" in this specification refers to a specific feature, structure, or characteristic described in connection with an embodiment that may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily imply the same embodiment, nor does it imply independence or alternativeity from other embodiments. The various embodiments in this specification are described in a related manner, with reference to each other for similar or identical parts. In particular, for apparatus, device, and system embodiments, since they are substantially similar to method embodiments, the description is relatively simple, and relevant details are referred to in the description of the method embodiments.

[0070] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of protection. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A balancing method for an H-type connected capacitor tower, characterized in that, include: Obtain the actual operating voltage of the H-type connected capacitor tower, the unbalanced current corresponding to the actual operating voltage, and the design capacitance of the high-voltage bridge arm and the design capacitance of the low-voltage bridge arm. The direction of bridge imbalance is determined by the phase difference between the unbalanced current and the actual operating voltage, thereby determining the direction of increase or decrease in bridge arm capacitance. The imbalance coefficient is calculated based on the amplitude of the unbalanced current, the amplitude of the actual operating voltage, the design capacitance of the high-voltage bridge arm, and the design capacitance of the low-voltage bridge arm, and the adjustment capacitance is determined accordingly. Based on the direction of increase or decrease in the bridge arm capacitance and the adjustment capacitance, the capacitor units in the low-voltage bridge arm are interchanged to balance the load.

2. The method according to claim 1, characterized in that, The direction of bridge imbalance is determined based on the phase difference between the unbalanced current and the actual operating voltage, thus determining the direction of increase or decrease in bridge arm capacitance, including: When the phase difference between the unbalanced current and the actual operating voltage is +90°, the direction of increasing or decreasing the bridge arm capacitance is to decrease the single-arm capacitance of the high-voltage bridge arm on the first side and the single-arm capacitance of the low-voltage bridge arm on the second side, and to increase the single-arm capacitance of the low-voltage bridge arm on the first side and the single-arm capacitance of the high-voltage bridge arm on the second side. The circuit reference positive direction of the H-type connected capacitor tower is from the first side to the second side. When the phase difference is -90°, the direction of increase or decrease of the bridge arm capacitance is to increase the single-arm capacitance of the high-voltage bridge arm on the first side and the single-arm capacitance of the low-voltage bridge arm on the second side, and to decrease the single-arm capacitance of the low-voltage bridge arm on the first side and the single-arm capacitance of the high-voltage bridge arm on the second side.

3. The method according to claim 1, characterized in that, The imbalance coefficient is calculated based on the amplitude of the unbalanced current, the amplitude of the actual operating voltage, the design capacity of the high-voltage bridge arm, and the design capacity of the low-voltage bridge arm. The adjustment capacity is then determined, including: The imbalance coefficient is calculated based on the amplitude of the unbalanced current, the amplitude of the actual operating voltage, the design capacitance of the high-voltage bridge arm, and the design capacitance of the low-voltage bridge arm. The product of the imbalance coefficient and the design capacitance of the low-voltage bridge arm is divided by four to obtain the adjustment capacitance.

4. The method according to claim 3, characterized in that, The formula for calculating the imbalance coefficient is expressed as follows: ； In the formula, Indicates the imbalance coefficient. Indicates the design capacitance of the high-voltage bridge arm. Indicates the design capacitance of the low-voltage bridge arm. Indicates the magnitude of the unbalanced current. Indicates the power frequency angular frequency. This indicates the amplitude of the actual operating voltage.

5. The method according to claim 1, characterized in that, Based on the direction of increase or decrease in the bridge arm capacitance and the adjustment capacitance, the capacitor units in the low-voltage bridge arm are interchanged to balance the voltage, including: Based on the direction of increase or decrease of the bridge arm capacitance and the adjustment capacitance, the first side capacitance adjustment condition and the second side capacitance adjustment condition of the low voltage bridge arm are determined, wherein the first side capacitance adjustment condition and the second side capacitance adjustment condition adopt the same number of capacitor units for adjustment. The positions of the first low-voltage capacitor unit that meets the first-side capacitance adjustment condition and the second low-voltage capacitor unit that meets the second-side capacitance adjustment condition are interchanged for balancing.

6. The method according to claim 5, characterized in that, Based on the direction of increase or decrease in the bridge arm capacitance and the adjusted capacitance, the first-side capacitance adjustment conditions and the second-side capacitance adjustment conditions of the low-voltage bridge arm are determined, including: When the direction of increasing or decreasing the capacitance of the bridge arm is to increase the capacitance of the low-voltage bridge arm on the first side and decrease the capacitance of the low-voltage bridge arm on the second side, The first-side capacitance adjustment condition is that after replacing all the low-voltage capacitor units of the first-side capacitor unit adjustment quantity with reference capacitor units, the single-arm capacitance of the low-voltage bridge arm of the first side increases, and the increase value is the adjusted capacitance. The second-side capacitance adjustment condition is that after replacing all the low-voltage capacitor units of the second-side capacitor unit adjustment quantity with the reference capacitor unit, the single-arm capacitance of the low-voltage bridge arm on the second side decreases, and the decrease value is the adjusted capacitance. Wherein, the capacitance of the reference capacitor unit is the product of the design capacitance of the low-voltage bridge arm and the number of low-voltage series connections, divided by the number of low-voltage parallel connections. The number of low-voltage series connections is the number of capacitor units in the series branches inside a single low-voltage bridge arm, and the number of low-voltage parallel connections is the number of series branches connected in parallel inside a single low-voltage bridge arm.

7. The method according to claim 5, characterized in that, The first low-voltage capacitor unit that meets the first side capacitance adjustment condition and the second low-voltage capacitor unit that meets the second side capacitance adjustment condition are interchanged, including: the first low-voltage capacitor unit located at the lower layer of the low-voltage bridge arm and the second low-voltage capacitor unit located at the lower layer of the low-voltage bridge arm are interchanged.

8. The method according to claim 5, characterized in that, When there are multiple options for the number of capacitor units to be adjusted under the first-side capacitance adjustment condition and the second-side capacitance adjustment condition, the smallest value is selected as the number of capacitor units to be adjusted for balancing.

9. The method according to claim 5, characterized in that, After swapping the positions of the first-side low-voltage capacitor unit that meets the first-side capacitance adjustment condition and the second-side low-voltage capacitor unit that meets the second-side capacitance adjustment condition, if the balancing is not completed, increase the number of capacitor units to be adjusted and swap the first-side low-voltage capacitor unit and the second-side low-voltage capacitor unit again.

10. The method according to claim 1, characterized in that, After the capacitor cells in the low-voltage bridge arm are interchanged based on the direction of increase or decrease of the bridge arm capacitance and the adjustment capacitance, the method further includes: If the capacitor units in the low-voltage bridge arm still cannot be balanced by swapping them, the capacitor units in the high-voltage bridge arm are swapped based on the direction of increase or decrease in the bridge arm capacitance and the adjustment capacitance.

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