High-power capacitor power taking device based on parallel resonance compensation

Abstract

The utility model discloses a high-power capacitor electricity taking device based on parallel resonance compensation, which comprises a primary electricity taking capacitor C1, an isolation TV, a compensation capacitor C2 and a power supply module, and is characterized in that the primary electricity taking capacitor C1 and the isolation TV are poured inside a solid-sealed polar pole; two ends of the primary electricity taking capacitor C1 are respectively connected with the power transmission line and the primary side of the isolation TV; the compensation capacitor C2 is connected in parallel to the primary side of the isolated TV, and is connected in parallel with the primary side of the isolated TV for resonance to improve power and suppress impact overvoltage; the power supply module is connected with the isolation TV secondary side and the intelligent terminal. According to the utility model, the overvoltage of equipment can be effectively reduced, the space and the cost are reduced, the service life is prolonged, and the primary side and the secondary side are thoroughly separated in structural design.

Description

Technical Field

[0001] The utility model belongs to the technical field of intelligent primary-secondary integration of AC distribution networks, and relates to a high-power capacitor power-taking device based on parallel resonance compensation. Background Technique

[0002] With the upgrade of the equipment level of the distribution network, the improvement of the intelligent level of the equipment body, the integration of functions, and the gradual implementation of lightweight and low-power-consuming equipment, the 10kV pole-mounted switch power-taking PT (voltage transformer) has problems such as large volume, inconvenient installation, and ferromagnetic resonance, and has been widely criticized, and is gradually not suitable for the direction of new technologies. The capacitor power-taking technology has become the development direction of new technologies due to its advantages such as miniaturization, no ferromagnetic resonance, and easy integration.

[0003] At present, the capacitor power-taking technology is mainly divided into three types. The first is the method of directly connecting a capacitor in series with an isolated TV (PT voltage transformer). The second is the method of directly connecting a capacitor in series with an isolated TV and connecting a capacitor in parallel on the primary side of the isolated TV. The third is the method of using the principle of a high-voltage CVT (capacitive voltage transformer) and series compensation with a reactor.

[0004] For the power-taking capacitor power-taking device of the distribution network, due to the limitation of the primary side leakage current, the primary capacitor generally does not exceed 5NF. After being connected in series with the isolation TV for voltage division, the total power does not exceed 52W, and the isolation transformer can be divided into a maximum of 25W. Under the premise of the limitation of the primary capacitor C1, too high power will cause the voltage on the primary side to be too high, affecting long-term reliability. Coupled with the loss of the energy transmission efficiency of the TV, it is generally necessary to be used with a low-power FTU. Therefore, it is particularly important to improve the transmission efficiency. At present, the mainstream scheme adopted by the distribution network for power taking is the method of directly connecting the primary side capacitor in series with the isolation TV, that is, the first method. In this method, the primary part of the capacitor power-taking device is realized by connecting the primary high-voltage capacitor in series with the isolation TV. Under the impact overvoltage, a large overvoltage will be induced on both sides of the isolation TV. Therefore, under the action of voltages such as lightning strikes, a relatively large overvoltage is likely to be generated in the isolation TV winding. If used for a long time, the insulation may fail. If the insulation margin is not enough, it is extremely easy to cause damage. In order to ensure the reliability of the TV under lightning and impact overvoltages, protective devices are connected in parallel on the primary side. After adding the protective devices, due to the small distributed parameters of the protective devices, overvoltage is easily generated under impact, and the protective devices are easily damaged, and there are potential hazards to the long-term insulation life. In addition, the potential of the primary side of the isolation TV is relatively high. After coming out from the primary lead and contacting the switch housing, the primary and secondary sides are not separated, and there is a risk of electric leakage. In the second method, the capacitance value of the parallel capacitor is much larger than that of the primary capacitor, and the primary capacitor of the capacitor power-taking device is generally in the order of a few nF, and the compensation capacitor may be as high as dozens of nF. If the compensation capacitor is too small, a relatively large overvoltage will be generated. If the compensation capacitor is too large, the shunt will be serious. It is required that the compensation capacitor is relatively large (dozens of nF), and the energy transfer efficiency will inevitably be greatly reduced. Therefore, corresponding measures need to be taken. The third method is to add a reactor to improve the energy efficiency by means of series resonance, but the volume is relatively large and the cost is relatively high, which is not very suitable for the miniaturization of the deep integration of the distribution network and is not suitable for the batch application of the distribution network.

[0005] To sum up, the following points need to be improved in the existing capacitor power-taking devices: the attention and evaluation means of the reliability assessment brought by the new technologies in the distribution network aspect are slightly insufficient, and the overall reliability, especially the service life under long-term overvoltage, needs to be strengthened; in addition, the primary and secondary sides are not completely separated. The TV of the energy-taking device is placed inside the mechanism housing, and high-voltage leads need to be led out from the solid-sealed pole column. The high-voltage leads need to be contacted and connected inside the switch housing and wrapped with insulating sleeves. Improper process treatment will cause electric leakage breakdown; the adaptability to the distribution network is insufficient. Summary of the Utility Model

[0006] Based on the above analysis, the present utility model provides a high-power capacitor power-taking device based on parallel resonance compensation, which can effectively reduce the overvoltage of the equipment, reduce the space and cost, improve the service life, and at the same time achieve a complete separation of the primary and secondary sides in the structural design.

[0007] The present utility model adopts the following technical solutions.

[0008] The first aspect of the present utility model proposes a high-power capacitive power extraction device based on parallel resonance compensation, which includes a primary power extraction capacitor C1, an isolation TV, a compensation capacitor C2, and a power supply module;

[0009] The primary power extraction capacitor C1 and the isolation TV are cast inside the solid-sealed pole column;

[0010] Both ends of the primary power extraction capacitor C1 are respectively connected to the power transmission line and the primary side of the isolation TV;

[0011] The compensation capacitor C2 is connected in parallel to the primary side of the isolation TV, and is in parallel resonance with the primary side of the isolation TV to improve power and suppress impulse overvoltage;

[0012] The power supply module is respectively connected to the secondary side of the isolation TV and the intelligent terminal.

[0013] Preferably, the primary power extraction capacitor C1 can also be independently encapsulated to achieve external power extraction.

[0014] Preferably, the parameters of the isolation TV satisfy the following formula:

[0015]

[0016] Wherein,

[0017] R1 is the resistance of the primary side winding of the isolation TV;

[0018] Lm(t) is the instantaneous value of the exciting inductance of the primary side of the isolation TV at time t;

[0019] L1(t) is the instantaneous value of the leakage inductance of the primary side of the isolation TV at time t;

[0020] C2 is the capacitance value of the compensation capacitor;

[0021] ω represents the angular velocity in the power system.

[0022] Preferably, the parameters of the isolation TV also satisfy the following formula:

[0023]

[0024] -5% ≤ T ≤ 5%;

[0025] Wherein, T is the deviation rate;

[0026] L1 is the actual value of the leakage inductance of the primary side when the voltage of the isolation TV is in the range of (80% - 120%) Un;

[0027] Lm is the actual value of the exciting inductance of the primary side when the voltage of the isolation TV is in the range of (80% - 120%) Un;

[0028] Un is the rated voltage of the primary line.

[0029] Preferably, the isolation TV uses 30Q120 silicon steel sheet as the core material, and matches the core cross-sectional area and core air gap length of the isolation TV, so that when the primary side voltage exceeds 1.3Un, the core magnetic flux density reaches more than 1.8T, and then the overvoltage on the secondary side of the isolation TV is suppressed by core saturation.

[0030] Preferably, the capacitance value of the C2 satisfies the following formula:

[0031]

[0032] In the formula, U2 is the overvoltage on the primary side of the TV, which is less than 5000V under impact;

[0033] C1 is the capacitance value of the primary power take-off capacitor.

[0034] Preferably, the isolation TV is cast inside the solid-sealed pole column. The power transmission line is connected to the primary side through the primary power take-off capacitor C1, and the secondary output is led out of the solid-sealed pole column through the secondary lead wire, and the output is connected to the external power supply module.

[0035] Preferably, the intelligent terminal includes an FTU, a backup power supply and a super capacitor.

[0036] Preferably, the power supply module is provided with three inputs and three outputs to receive the input of the isolation TV connected to the A, B, and C-phase power transmission lines and supply power to the FTU, the backup power supply and the super capacitor.

[0037] Compared with the prior art, the beneficial effects of the present utility model at least include:

[0038] Based on the problem that the reliability evaluation concerns and evaluation means brought by the new technologies in the distribution network aspect are slightly insufficient, the present utility model proposes a high-reliability and high-efficiency distribution network capacitor power take-off device, which can effectively reduce the overvoltage of the equipment, reduce the space and cost, and improve the service life. Specifically:

[0039] The present utility model can cast the primary power take-off capacitor C1 and the isolation TV together inside the solid-sealed pole column, and the power supply module is installed inside the shell. There is no need to introduce high-voltage leads into the shell, ensuring that the medium-voltage power supply part is inside the solid-sealed pole column, avoiding the intermediate connecting wires leading out of the solid-sealed pole column and directly contacting the shell bracket, avoiding the risk of high-voltage wires approaching the shell from the design, realizing complete isolation between the primary and secondary sides, separating the high-voltage and low-voltage parts from the design source, eliminating the possibility of high-voltage leakage, greatly improving the reliability of the power take-off device, and ensuring that there is no leakage risk during the long-term operation of the system.

[0040] The compensation capacitor C2 of the present utility model is connected in parallel to the primary side of the isolation TV, and based on formula (1)-

[0041] (2) Resonate in parallel with the primary side of the isolated TV. At the same time, based on formula (3), by taking power from the capacitor and connecting a compensating capacitor in parallel to the primary side of the isolated TV, the impulse overvoltage of the isolated TV winding is reduced. From the source, the amplitude of the lightning overvoltage of the isolated TV is decreased. And by resonating in parallel the compensating capacitor with the excitation and leakage magnetic flux of the secondary isolated TV, the energy loss is suppressed, and the lightning impulse overvoltage on the primary side of the isolated TV is reduced, improving the system reliability on the premise of ensuring high-power output.

[0042] For the excitation inductance and leakage inductance of the isolated TV of the present utility model, they basically maintain a low change at (80% - 120%) Un (rated voltage), preventing detuning under the working voltage. And to prevent the secondary side and the subsequent power supply module of the isolated TV from being burned out after the overvoltage of the primary system, by adjusting the cross-sectional area of the iron core and the length of the air gap of the iron core, when the primary side voltage exceeds 1.3Un, the magnetic flux density of the iron core quickly reaches above 1.8T. By matching ferromagnetic materials such as silicon steel sheet 30Q120, the overvoltage on the secondary side of the isolated TV is suppressed through the saturation of the iron core.

[0043] The compensating capacitor C2 of the present utility model resonates in parallel with the excitation inductance of the isolated TV to improve the transmission power. According to formula (3), the capacitance value of C2 is compensated to reduce the overvoltage on the primary side under a single impulse to below 5000V to ensure the safety and reliability of the system. But to ensure a power of more than 10W, it is also required to satisfy formulas (1) and (2), with a deviation rate within 5%. On the premise of high power, the volume of the isolated TV is reduced, the space and equipment costs are decreased, and the reliability of the device is improved.

[0044] In the present utility model, the secondary power module composed of the primary power-taking capacitor C1, the isolated TV, the compensating capacitor C2 and the rectifying circuit in the power supply module can accept the incoming and outgoing lines of any one of A, B, and C phases for three-phase energy injection. One module can collect multiple paths of power, reducing the number of devices, greatly saving space and reducing the usage cost. Brief Description of the Drawings

[0045] Figure 1 is the schematic diagram of the overall system of the high-power capacitor power-taking device based on parallel resonance compensation in the present utility model;

[0046] Figure 2 is the schematic diagram of the high-power capacitor power-taking device based on parallel resonance compensation in the present utility model;

[0047] Figure 3 is the schematic diagram of the equivalent circuit of the high-power capacitor power-taking device based on parallel resonance compensation in the present utility model;

[0048] Figure 4 is the structural diagram of the high-power capacitor power-taking device based on parallel resonance compensation in the present utility model;

[0049] Figure 4 The reference numerals in the figure are: 1, vacuum circuit breaker; 2, epoxy resin layer; 3, low-power current transformer; 4, primary conductor; 5, insulating pull rod; 6, voltage sensor; 7, primary power-taking capacitor; 8, isolating TV and compensating capacitor C2;

[0050] Figure 5 It is a schematic diagram of power supply module energization of the high-power capacitor power-taking device based on parallel resonance compensation in the present utility model. Specific embodiments

[0051] To make the objectives, technical solutions and advantages of the present utility model clearer, the technical solutions of the present utility model will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present utility model. The embodiments described in this application are only a part of the embodiments of the present utility model, rather than all the embodiments. Based on the spirit of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present utility model.

[0052] As Figure 1 shown, the present utility model provides a high-power capacitor power-taking device based on parallel resonance compensation, which can be used for internal power-taking, that is, encapsulating the primary and secondary deep fusion pole-mounted switch (such as Figure 1 the solid-sealed pole shown); it can also be used for external power-taking, that is, the primary power-taking capacitor C1 is independently encapsulated in an external hanging form. Taking internal power-taking as an example: it includes a primary power-taking capacitor C1, an isolating TV, a compensating capacitor C2 and a power supply module;

[0053] The primary power-taking capacitor C1 and the isolating TV are integrally cast inside the solid-sealed pole. The isolating TV is led out of the solid-sealed pole through the secondary lead and connected to the power supply module, so that the medium-voltage part is completely cast in the solid-sealed pole, ensuring that the medium-voltage power supply part is inside the solid-sealed pole, and the low voltage of about 27V is introduced into the FTU device without being led out to the operating mechanism housing with an insulating wire. The primary power-taking capacitor C1 and the isolating TV are connected in series for voltage division. The isolating TV transforms the medium voltage into a low voltage of about 27V and inputs it into the power supply module inside the housing, avoiding the risk of high-voltage wires approaching the housing, completely realizing the separation of the primary and secondary, and eliminating the possibility of high-voltage leakage from the design source, greatly improving the overall reliability;

[0054] Both ends of the primary power-taking capacitor C1 are respectively connected to the transmission line and the primary side of the isolating TV. The energy is transmitted from the primary power-taking capacitor C1 to the isolating TV and then supplied to the subsequent protection device through the power supply module; further preferably, the primary power-taking capacitor C1 can be a ceramic or thin-film capacitor;

[0055] The compensating capacitor C2 is connected in parallel to the primary side of the isolating TV. Through parameter matching according to formulas (1), (2), and (3), the capacitance value of the compensating capacitor C2 is in parallel resonance with the exciting reactance + leakage reactance of the primary side of the isolating TV, and the impact overvoltage is suppressed.

[0056] Further preferably, the specific parameter matching analysis is as follows:

[0057] The power grid power-taking capacitor adopts the method of connecting a capacitor in series with the isolating TV. Since there is a limit on the power-taking current on the primary side, the primary power-taking capacitor C1 generally does not exceed 5 nF. After being connected in series with the isolating TV and dividing the voltage, the total power does not exceed 52 W, and the isolating transformer can be divided into a maximum of 25 W. Excessive power will cause a relatively large voltage on the primary side, affecting long-term reliability. Coupled with the loss of the energy transmission efficiency of the TV, the final output power is only about a dozen watts at most (the actual power is much less than this value). If the energy loss is not controlled, only low-power FTUs (limiting some functions) can be used. To ensure that normal FTUs can also be powered normally, it is particularly important to improve the transmission efficiency. At present, the scheme adopted for power grid power-taking is to directly connect the primary-side capacitor in series with the isolating TV or EVT. In order to ensure the reliability of the TV against lightning and impact overvoltage, protective devices need to be connected in parallel on the primary side. However, the lifespan of the protective devices is limited. If they are struck by lightning for a long time, the lifespan will be greatly reduced. In the present utility model, a capacitor C2 is connected in parallel to the primary side of the isolating TV, which can greatly suppress the amplitude of lightning and impact overvoltage. In order to improve the energy transmission efficiency, the capacitance value of C2 needs to be matched in parallel resonance with the exciting inductance and leakage inductance of the isolating TV. Assuming that the primary power-taking capacitor C1 = 5000 pF, according to formula (3), the compensating capacitor C2 = 70000 pF (14 times that of the primary C1 capacitor), with a capacitance value of 45.5 kΩ, then the exciting reactance of the isolating TV is 45.5 kΩ, and the exciting inductance of the isolating TV is about 145 H, which can ensure the reliability of the system and the power is stable above 10 W. These parameters are different from the conventional design. In the conventional design, the exciting inductance and leakage inductance of the isolating TV are relatively large. The key point of the present utility model is that after the exciting inductance and leakage inductance of the isolating TV are reduced to a certain extent, if the isolating TV is used, the efficiency is extremely low and high-power transmission cannot be guaranteed. Therefore, it needs to be used in resonance with the parallel capacitor C2. Further, the leakage inductance and leakage inductance cannot be ignored. It is equivalent to the secondary capacitor C2 being in parallel resonance with the exciting inductance + leakage inductance, and relatively accurate requirements are put forward for each parameter to ensure high-power transmission.

[0058] The exciting inductance and leakage inductance of the isolation TV at the rated voltage are in parallel resonance with the compensation capacitor C2. To improve the service life of the equipment, the capacitance value of the capacitor connected in parallel on the primary side of the isolation TV is matched with the exciting inductance and leakage inductance of the transformer according to formula (2). At the same time, the larger the capacitance value, the better. According to formula (3), the larger the capacitance value, the lower the secondary voltage division under impact. This requires that the exciting inductance and leakage inductance of the isolation TV should not be too large, and the change of the exciting inductance and leakage inductance within the voltage fluctuation range (±20%) should not exceed a certain limit value. It is matched according to formula (1) to ensure high-power output. Therefore, the values of the exciting inductance and leakage inductance need to be strictly limited within the allowable range.

[0059] Based on the above analysis, the present invention proposes the requirement for the deviation rate (formula (1)). Combining with the accuracy of the compensation capacitor C2 itself, the exciting inductance value of the compensation capacitor C2 and the primary side of the isolation TV is obtained, and the isolation TV is designed accordingly.

[0060] Due to the air gap opening, the efficiency of the isolation TV itself is not high, and the exciting inductance and leakage inductance of the isolation TV will also fluctuate with the voltage. The operation of this system is based on the parameter matching of formula (1) and the parallel resonance method. It is realized by the secondary adjustment of the capacitance value of the compensation capacitor C2 according to formula (2). If the exciting inductance and leakage inductance of the isolation TV fluctuate greatly, the entire power-taking device may be seriously detuned, and the power-taking efficiency will be greatly reduced. To limit the detuning, the deviation rate is defined as

[0061]

[0062] Among them,

[0063] L1 is the actual value of the leakage inductance on the primary side of the isolation TV;

[0064] Lm is the actual value of the exciting inductance on the primary side of the isolation TV.

[0065] R1 is the resistance of the primary side winding of the isolation TV;

[0066] C2 is the capacitance value of the compensation capacitor;

[0067] ω represents the angular velocity in the power system;

[0068] To control the power-taking efficiency and overall reliability of the entire power-taking device, the parameters of the isolation TV are controlled during design to ensure that within the voltage fluctuation range of ±20%, the deviation rate is controlled within ±5%, which can ensure normal power supply efficiency and reliable energy transmission.

[0069] Based on formula (2) and the requirement that the deviation rate is controlled within ±5%, combined with the 10% accuracy of the compensation capacitor C2 itself, the principle of the capacitance power-taking device of the present invention is as Figure 2As shown, the leakage reactance of the isolated TV is X1, the line resistance is R1, the excitation reactance is Xm, the secondary leakage reactance is X2, the line resistance is R2, the power module and the terminal are equivalent to RL, and the schematic diagram of the primary side is as follows: Figure 3 As shown, the secondary leakage reactance X2', line resistance R2', power module and terminal load are equivalent to RL'. Due to the parallel resonance of matching C2, the excitation inductance Lm is small, and the open core design is generally adopted. The leakage inductance L1 cannot be ignored, so the parallel resonance relationship between the compensation capacitor C2 and the excitation inductance and leakage inductance of the primary side of the isolation TV is:

[0070]

[0071] in,

[0072] R1 is the primary side winding resistance;

[0073] Lm(t) is the instantaneous value of the excitation inductance of the primary side of the isolated TV at time t;

[0074] L1(t) is the instantaneous value of the leakage inductance of the primary side of the isolated TV at time t;

[0075] C2 is the capacitance of the compensation capacitor;

[0076] ω represents the angular velocity in the power system;

[0077] Based on formulas (1) and (2), the parameters of the isolated TV are matched to achieve parallel resonance between the compensation capacitor C2 and the primary side of the isolated TV:

[0078] The excitation inductance and leakage inductance of the primary side of the isolated TV obtained by matching according to the relationship (2) are theoretical values, which are difficult to achieve in practice. Therefore, the present invention comprehensively considers that the excitation inductance of the isolated TV is difficult to keep constant under the voltage of (0-100%) Un. Based on the formula (1), it is only necessary to ensure a certain deviation rate T within the normal working voltage range of (80%-120%) Un. The accuracy of C2 itself is about 10%. A compensation point is reserved for C2 in the design to facilitate compensation. It is further proposed to match C2 according to the formula (3). When the excitation inductance and leakage inductance of the primary side of the isolated TV are finally obtained and the coil is wound, the excitation inductance and leakage inductance are controlled so that the actual values ​​of the excitation inductance and leakage inductance are under (80%-120%) Un, and the deviation rate T is within ±5%. Then, high power output can be achieved, and the primary side has a lower impulse overvoltage (5000V), which meets high reliability. The output power can be controlled to be stable by controlling the deviation rate within ±5%, so as to prevent detuning under the working voltage and reduce the energy efficiency of the system.

[0079] The utility model suppresses the impulse overvoltage by compensating the capacitance of capacitor C2:

[0080] The capacitance value of the compensation capacitor C2 is matched with the primary capacitance value C1 of the system, and the equivalent parameters of the isolation TV, etc. and the subsequent power supply module are matched through formula (2); under impact, the device circuit is equivalent to the direct series connection of C1 and C2, and the overvoltage U2 on the primary side of the TV is equivalent to formula (3).

[0081]

[0082] It can be seen from formula (3) that by adjusting the capacitance value of C2, the secondary overvoltage U2 can be made less than 5000V (generally, the insulation on the secondary side is above 5000V).

[0083] In the present utility model, a compensation capacitor is connected in parallel to the primary side of the isolation TV for power taking by capacitance to reduce the impulse overvoltage of the winding through the method of formula (3), thereby reducing the overvoltage amplitude of the isolation TV at the source. Since the energy taken by the capacitance power taking device itself is relatively low, shunting will inevitably occur after connecting the parallel compensation capacitor, further reducing the energy efficiency. In order to ensure the output requirement of high power (about 10W), the present utility model further adopts the method of parallel resonance, that is, the excitation and leakage inductance of the isolation TV are in parallel resonance with the compensation capacitor C2, improving the output efficiency of the energy.

[0084] In actual products, it is necessary to accurately measure the excitation inductance Lm and the leakage inductance L1 to match the capacitance value of C2. Since the service life of primary equipment is at least 20 years, the service life of all components integrated with the cast solid pole column shall not be less than 20 years. It is advisable to select a highly reliable ceramic capacitor C2 to be integrally cast with the isolation TV.

[0085] As Figure 4 shown, the solid pole column internally includes a vacuum circuit breaker 1, an epoxy resin layer 2, a low-power current sensor 3, a conductor 4, an insulating pull rod 5, a voltage sensor 6, a primary power-taking capacitor C17, an isolation TV and a compensation capacitor C2 8, components such as a primary-side matching capacitor, etc. The voltage sensor 6 can sample at the upper and lower break points of the circuit breaker, and can sample the phase sequence and zero-sequence voltage simultaneously. The current sensor 3 samples at the lower break point and can sample the phase sequence and zero-sequence current simultaneously. The primary power-taking capacitor C17 can sample at the upper break point or the lower break point. Since the voltage on the primary side of the isolation TV and the compensation capacitor C2 8 is relatively high, they are integrally cast with the primary power-taking capacitor C17 inside the solid pole column, avoiding the high-voltage connecting wires in the middle from being led out of the solid pole column and directly connecting to and contacting the housing bracket, separating the high-voltage and low-voltage parts from the design source and ensuring no leakage risk during the long-term operation of the system. The isolation TV 8 converts the energy obtained by the primary power-taking capacitor C17 into low-voltage power of about 27V and then leads it out of the solid pole column through the secondary lead wire and connects it to the power supply module.

[0086] Parameter matching for suppressing the overvoltage on the secondary side of the isolation TV:

[0087] Through the above parallel resonance compensation solution, the present utility model can ensure the energy efficiency and further reduce the impact overvoltage on the primary side of the isolated TV. A further implementation solution is that the leakage inductance plus the exciting inductance on the primary side of the isolated TV is in parallel resonance with the compensation capacitor. Since the capacitance value of the compensation capacitor is relatively large (tens of nF), the exciting inductance is small, and the leakage inductance is high. Compared with the conventional isolated TV, if no resonance measures are added, the energy efficiency of such a core itself is extremely low, and the turns ratio parameter is uncontrollable. Therefore, it needs to be used together with the compensation capacitor to transfer energy efficiency normally. To prevent overvoltage in the primary system, a self-protection design is carried out: the secondary side and the subsequent power supply module of the isolated TV are not burned out. By adjusting the cross-sectional area of the iron core and the length of the iron core air gap, when the primary side voltage exceeds 1.3Un, the magnetic flux density of the iron core quickly reaches above 1.8T. If ferromagnetic materials such as silicon steel sheet 30Q120 are matched, the overvoltage on the secondary side of the isolated TV is suppressed through the saturation of the iron core, protecting the secondary equipment.

[0088] During specific implementation, based on formula (3), to suppress the impact overvoltage of the system, the capacitance value of the compensation capacitor C2 is 14 times or more of the capacitance value of the primary power-taking capacitor C1.

[0089] The compensation capacitor C2 of the present utility model is in parallel resonance with the exciting inductance of the isolated TV to improve the transmission power. Assuming that the primary power-taking capacitor C1 = 5000PF and the compensation capacitor C2 = 70000PF (14 times the primary C1 capacitor), with a capacitance value of 45.5kΩ, the exciting inductive reactance of the isolated TV is 45.5kΩ, and the exciting inductance of the isolated TV is about 145H, which can ensure the reliability of the system and the power is stable above 10W.

[0090] Further preferably, the power supply module is respectively connected to the secondary side of the isolated TV and the intelligent terminal. The isolated TV inputs energy into the power supply module, and the power supply module rectifies, protects, and stabilizes the voltage to provide a stable DC power supply to the intelligent terminal, such as the FTU power management module.

[0091] Further preferably, the power supply module is provided with three inputs and three outputs to receive the inputs from the isolated TVs connected to the A, B, and C phase transmission lines and supply power to the FTU, the backup power supply, and the super capacitor.

[0092] The power supply module can supply 1 - 3 isolated TV inputs, and one module can collect multiple channels, greatly reducing the number of devices, saving the use space, and reducing the use cost. Moreover, the primary power-taking capacitor C1 and the isolated TV are cast inside the solid-sealed pole column together, and the power supply module is installed inside the housing, without the need to introduce high-voltage leads into the housing, without long-term safety hazards.

[0093] The power supply module can accept any one to three-phase inputs of A, B, and C. Conventional power-taking generally requires taking the power of phases A and C. For example, the power supply module includes 1 - 3 rectifier circuits and a power control module;

[0094] The intelligent terminal includes an FTU, a backup power supply, and a super capacitor;

[0095] The rectifier circuit includes functions such as rectification, filtering, voltage regulation, and protection. The rectifier circuit rectifies the 1-3 phase alternating current input by the isolated TV8 into about 24V direct current. The rectifier circuit also further adds a TVS circuit to protect against surges, transients, and other transient overvoltages.

[0096] In the power supply module, the input power enters the rectifier circuit after being protected by the TVS. The rectified DC small signal divides the power (energy) into three paths through the power control module. One path directly supplies power to the subsequent FTU, one path charges the backup power supply, and one path charges the super capacitor, giving priority to ensuring reliable power supply for the terminal. The numbers listed in this article are only for a more detailed description of a situation. For example, when the rectifier circuit outputs 10W of power to the power control module, the power control module supplies 6W to devices such as the intelligent terminal FTU of the intelligent terminal, and the other 4W charges the backup power supply and the super capacitor.

[0097] Such as Figure 5 shown, further preferably, the power supply module can also be provided with an output control module, and the intelligent terminal can also feedback commands to the output control module; the output control module is used to receive commands from devices such as the intelligent terminal FTU, and realizes functions such as charging and discharging of the backup power supply, starting and stopping of battery activation, low battery warning, AC input power loss warning, battery charge and discharge management, overload protection, battery reverse connection protection, and short circuit protection by controlling the power module. If the input power of the rectifier circuit is insufficient, priority is given to ensuring the priority operation of devices such as the intelligent terminal FTU of the intelligent terminal, and charging of the backup power supply and the super capacitor is stopped. For example, when the power of the rectifier circuit input power control module is only 6W, this 6W of power is all supplied to the FTU intelligent terminal device of the intelligent terminal, and the backup power supply and the super capacitor stop charging. When the power threshold reaches the first set value, such as 7W, only then, by controlling the power control module, 1W is allocated to charge the backup power supply and the super capacitor.

[0098] When the output power of the rectified power supply exceeds the set threshold, power protection is started, and the output power of the power control module is controlled within a limited range. For example, when the input power of the rectifier circuit is greater than 15W, overload protection is started to limit the output power of the power control module within 15W to ensure the safety of the subsequent terminal devices. After the voltage of the backup power supply reaches the limit value, devices such as the intelligent terminal FTU control the output control module to control the power module to stop charging the battery. When the battery voltage is lower than the set value, a low voltage warning indication is sent, and charging of the battery is started; if the voltage of the backup power supply is higher than the voltage of the super capacitor, the FTU controls the battery to charge the super capacitor. The super capacitor serves as a remote backup power supply and automatically switches in when the battery fails. This adds a reliable guarantee for the power supply.

[0099] The functions of the above rectification circuit, control power module, and output control module can be specifically implemented using existing mature hardware circuits, which will not be elaborated in this article.

[0100] The process of high-power capacitor power extraction in this utility model is as follows:

[0101] After connecting a primary power extraction capacitor C1 in series on the primary side of the isolation TV, high-voltage power input (such as 10 kV) is taken from the power transmission line. After being converted into low voltage (several tens of volts) by the secondary side of the isolation TV, the low-voltage power output is transmitted to the power supply module.

[0102] After rectifying and filtering the low-voltage power into 27 V or the direct current required by the system by the power supply module, power is output to the intelligent terminal, realizing power supply to the device by directly drawing power from the line.

[0103] In order to protect the isolation TV from impact overvoltage, a compensation capacitor C2 is connected in parallel on the primary side of the isolation TV. Through precise parameter matching using formulas (1), (2), and (3), it is in parallel resonance with the magnetizing reactance and leakage reactance on the primary side of the isolation TV, and suppresses the impact overvoltage on the primary side. On the premise of ensuring system reliability, the output power reaches high power (10 W and above).

[0104] The high-efficiency power extraction device described above can be used for the built-in power extraction method, that is, encapsulated inside the pole-mounted switch with deep integration of primary and secondary; it can also be used for the external power extraction method, that is, the primary power extraction capacitor C1 is independently encapsulated. All those similar to the content of this utility model are within the scope of protection.

[0105] Compared with the prior art, the beneficial effects of this utility model at least include:

[0106] Based on the problem that the reliability evaluation concerns and evaluation means brought by new technologies in the distribution network are slightly insufficient, this utility model proposes a high-reliability and high-efficiency distribution network capacitor power extraction device, which can effectively reduce equipment overvoltage, reduce space and cost, and improve service life. Specifically:

[0107] This utility model can pour the primary power extraction capacitor C1 and the isolation TV together inside the solid-sealed pole column, and the power supply module is installed inside the housing. There is no need to introduce high-voltage leads into the housing, ensuring that the medium-voltage power part is inside the solid-sealed pole column, avoiding the middle connecting wire leading out of the solid-sealed pole column and directly contacting the housing bracket. From the design, it avoids the risk of high-voltage lines approaching the housing, realizes complete isolation between primary and secondary, separates the high-voltage and low-voltage parts from the design source, eliminates the possibility of high-voltage leakage, greatly improves the reliability of the power extraction device, and ensures that there is no leakage risk during long-term operation of the system.

[0108] This utility model connects the compensation capacitor C2 in parallel on the primary side of the isolation TV, and is based on formula (1)-

[0109] (2) Resonate in parallel with the exciting reactance and leakage reactance on the primary side of the isolated TV. At the same time, based on formula (3), by connecting a compensating capacitor in parallel to the primary side of the capacitive power-taking isolated TV, the impulse overvoltage of the isolated TV winding is reduced, and the amplitude of the lightning overvoltage of the isolated TV is reduced at the source. Through the parallel resonance of the compensating capacitor and the exciting and leakage reactances of the secondary isolated TV, the energy transmission is improved, and the lightning impulse overvoltage on the primary side of the isolated TV is reduced, thereby improving the system reliability on the premise of improving the energy transmission efficiency.

[0110] For the exciting reactance and leakage reactance of the isolated TV of the present utility model, they basically maintain a low change at (80% - 120%) Un (rated voltage), preventing detuning under the working voltage. And to prevent overvoltage in the primary system, the secondary side and the subsequent power supply module of the isolated TV are reliable. By adjusting the cross-sectional area of the iron core and the length of the air gap of the iron core, when the primary side voltage exceeds 1.3Un, the magnetic flux density of the iron core rapidly reaches above 1.8T. By matching ferromagnetic materials such as silicon steel sheet 30Q120, the overvoltage on the secondary side of the isolated TV is suppressed through the saturation of the iron core.

[0111] The compensating capacitor C2 of the present utility model resonates in parallel with the exciting reactance of the isolated TV to improve the transmission power. According to formula (3), the capacitance value of C2 is compensated to reduce the overvoltage on the primary side under impulse to below 5000V, which can ensure the safety and reliability of the system. However, to ensure a power of more than 10W, it is also required to satisfy the resonance of formula (2), and formula (1) requires the deviation rate to be within 5%. On the premise of high power, the volume of the isolated TV is reduced, the space and equipment cost are reduced, and the reliability of the device is improved.

[0112] In the present utility model, the secondary power module composed of the primary power-taking capacitor C1, the isolated TV, the compensating capacitor C2, and the rectifying circuit in the power supply module can accept the energy injection from any one of the incoming and outgoing lines of phases A, B, and C to three-phase. A single module can be connected to multiple injections, reducing the number of devices, greatly saving space, and reducing the usage cost.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present utility model and are not intended to limit them. Although the present utility model has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the specific implementation manners of the present utility model can still be modified or equivalently replaced, and any modification or equivalent replacement without departing from the spirit and scope of the present utility model shall be covered by the protection scope of the claims of the present utility model.

Claims

1. A high-power capacitor power supply device based on parallel resonance compensation, comprising a primary power supply capacitor C1, an isolation TV, a compensation capacitor C2 and a power supply module, characterized in that: The primary power supply capacitor C1 and the isolation TV are cast inside the solid-sealed pole; The two ends of the primary power-taking capacitor C1 are connected to the transmission line and the primary side of the isolated TV respectively; The compensation capacitor C2 is connected in parallel to the primary side of the isolated TV, and is connected in parallel with the primary side of the isolated TV to resonate to increase the power and suppress the impact overvoltage; The power module is connected to the secondary side of the isolated TV and the smart terminal respectively.

2. A high-power capacitor power supply device based on parallel resonance compensation according to claim 1, characterized in that: The primary power supply capacitor C1 can also be packaged independently to achieve external power supply.

3. A high-power capacitor power supply device based on parallel resonance compensation according to claim 1, characterized in that: The parameters of the isolated TV satisfy the following formula: in, R1 is the primary winding resistance of the isolated TV; Lm(t) is the instantaneous value of the excitation inductance of the primary side of the isolated TV at time t; L1(t) is the instantaneous value of the leakage inductance of the primary side of the isolated TV at time t; C2 is the capacitance of the compensation capacitor; ω represents the angular velocity in the power system.

4. A high-power capacitor power supply device based on parallel resonance compensation according to claim 3, characterized in that: The parameters of the isolated TV also satisfy the following formula: -5％≤T≤5％； Where, T is the deviation rate; L1 is the actual value of the primary side leakage inductance when the isolation TV voltage is in the range of (80% to 120%) Un; Lm is the actual value of the primary side excitation inductance when the isolation TV voltage is in the range of (80% to 120%) Un; Un is the rated voltage of the primary circuit.

5. A high-power capacitor power supply device based on parallel resonance compensation according to claim 4, characterized in that: The isolation TV uses silicon steel sheet 30Q120 as the core material, and matches the core cross-sectional area and core air gap length of the isolation TV, so that when the primary side voltage exceeds 1.3Un, the core flux density reaches above 1.8T, thereby suppressing the overvoltage on the secondary side of the isolation TV through core saturation.

6. A high-power capacitor power supply device based on parallel resonance compensation according to claim 4, characterized in that: The capacitance value of C2 satisfies the following formula: Where, U2 is the overvoltage on the primary side of TV, which is less than 5000V under impulse; C1 is the primary power supply capacitance value.

7. A high-power capacitor power supply device based on parallel resonance compensation according to claim 1, characterized in that: The isolation TV is cast inside the solid-sealed pole, and the transmission line is connected to the primary side through the primary power-taking capacitor C1. The secondary side output is led out of the solid-sealed pole through the secondary lead, and the output is connected to the external power module.

8. A high-power capacitor power supply device based on parallel resonance compensation according to claim 1, characterized in that: The intelligent terminal includes an FTU, a backup power supply and a super capacitor.

9. A high-power capacitor power supply device based on parallel resonance compensation according to claim 8, characterized in that: The power module is provided with three inputs and three outputs to receive isolated TV inputs connected to the A, B, and C phase transmission lines to supply power to the FTU, the backup power supply, and the supercapacitor.

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