A high-voltage power-on capacitor protection and harmonic suppression system and circuit thereof

Abstract

The application relates to a high-voltage power-taking capacitor protection and harmonic suppression system and a circuit thereof, and belongs to the field of power distribution network intelligent control switch power taking. The circuit is arranged between an isolation transformer and a feeder terminal unit (FTU), and comprises an input protection circuit for suppressing input surge overvoltage and fast pulse group, a harmonic filter circuit for filtering out harmonics, a signal acquisition and conditioning circuit for converting an alternating current signal into a direct current voltage signal, and a control protection circuit for comparing the direct current voltage signal with a preset reference voltage. The system further comprises a high-voltage capacitor voltage divider, an isolation transformer and the feeder terminal unit (FTU). The application effectively solves the problem that harmonic interference, surge impact and overvoltage risk coexist in the high-voltage power-taking system, greatly improves the safety and reliability of the operation of the rear-end FTU equipment under the premise of ensuring the accuracy of voltage signal measurement and power supply continuity.

Description

TECHNICAL FIELD

[0001] The application is a high-voltage power supply capacitor protection and harmonic suppression system and a circuit thereof, and belongs to the technical field of 10kv distribution network intelligent control switch power supply. BACKGROUND

[0002] First, according to the provisions of the General Technical Conditions for High Voltage Switching Equipment and Control Equipment GB / T 11022-2011, the main circuit power frequency withstand voltage test requirements are as follows: the relative ground and phase-to-phase need to withstand 42kV AC voltage for 1 minute; the switch breaking point and the isolation breaking point need to withstand 48kV AC voltage for 1 minute, and no flashover and breakdown phenomenon occurs during the process. In actual testing, the voltage of the input high-voltage equipment is controlled by the voltage regulator to boost the booster. However, due to various factors, the voltage during testing is often higher than 48kV. This causes the power supply capacitor and the transformer to withstand a voltage higher than its normal operating voltage, and the high voltage is coupled to the secondary circuit through the transformer. In this case, some products may have varying degrees of secondary equipment damage during type testing. In addition, overvoltage conditions can also cause transformer temperature rise.

[0003] Second, in actual use, the device is easily disturbed by external lightning, and at the low-voltage end, there is a risk of surge hazards. In traditional applications, a varistor is usually connected across the capacitor to prevent such hazards. However, in actual operation, it is found that the varistor does not always fully play a protective role. For some fast pulse groups, due to their extremely fast change rate, the response speed of the varistor cannot keep up, resulting in the inability to effectively suppress the pulse group in time, and thus part of the pulse energy is continuously accumulated on the capacitor, causing a certain voltage to gradually accumulate across the capacitor, which may affect the normal operation of the capacitor and even the entire circuit system, and even cause damage to the device.

[0004] Third, in the actual 10kV distribution network system, the existence of harmonics can seriously interfere with the measurement process of the feeder terminal unit (FTU), mainly in the following aspects:

[0005] Influence of harmonics on voltage waveform: harmonics cause the actual voltage waveform to be distorted, and it is no longer a standard sine wave. When the measurement device processes the distorted waveform according to the conventional algorithm, it will misjudge the harmonic component as part of the normal voltage, resulting in a deviation of the measurement result from the true value.

[0006] Influence of harmonics on transformers: Traditional power taking devices usually use resonant transformers to isolate the physical connection between the high-voltage side and the FTU low-voltage side. Harmonic currents in the windings and core of the transformer will cause additional losses, resulting in a significant increase in hysteresis and eddy current losses of the core, and a sharp rise in core temperature. In a high-temperature environment for a long time, the insulation material of the transformer will accelerate the aging of the insulation material, and the insulation performance will decrease, which will easily cause short circuit fault and significantly shorten the service life of the transformer. And affect the service life of the whole primary and secondary fusion station set.

[0007] Influence of harmonics on power supply efficiency and safety: Harmonic currents not only reduce the operating efficiency of the transformer, but also affect the power supply efficiency and safety of the FTU. The existence of harmonics may cause voltage resonance of the power grid, increase line loss, and affect the stability of the power system. SUMMARY

[0008] In view of the deficiencies of the prior art, the purpose of the present application is to provide a high-voltage power taking capacitor protection and harmonic suppression system and circuit to solve the technical problem of coexistence of harmonic interference, surge impact and overvoltage risk in the existing high-voltage power taking system.

[0009] In order to achieve the above-mentioned purpose, the present application is realized by the following technical scheme: a high-voltage power taking capacitor protection and harmonic suppression circuit, comprising:

[0010] An input protection circuit is connected to the output end of the secondary side of the isolation transformer, used to suppress the input surge overvoltage and fast pulse group;

[0011] A harmonic filter circuit is connected to the output end of the input protection circuit, used to filter out high-order harmonics in the input signal;

[0012] A signal acquisition and conditioning circuit is connected to the output end of the harmonic filter circuit, used to convert the filtered alternating current signal into a direct current voltage signal representing its effective value;

[0013] A control protection circuit is connected to the output end of the signal acquisition and conditioning circuit, used to compare the direct current voltage signal with a preset reference voltage, and according to the comparison result, to decide whether to turn on or cut off the power supply to the feeder terminal device FTU.

[0014] Further, the input protection circuit includes a pressure sensitive resistor MOV1 and a plurality of transient suppression diodes TVS, the pressure sensitive resistor MOV1 is connected in parallel between the input circuits of the input protection circuit, and the plurality of transient suppression diodes TVS are connected in parallel and connected between the input circuits of the input protection circuit and the ground.

[0015] Further, the harmonic filter circuit is a Π-type second-order low-pass filter network, which is composed of at least two inductors and two capacitors.

[0016] Further, the filter network comprises a first inductor L1, a second inductor L2, a first capacitor C2 and a second capacitor C3, and the specific connection relationship is as follows:

[0017] The output end of the input protection circuit is connected to the second inductor L2 and the first inductor L1 in sequence, and is connected to the input end of the signal collection and conditioning circuit, the second capacitor C3 is connected between the node of the first inductor L1 and the second inductor L2 and the ground, and the first capacitor C2 is connected between the node of the first inductor L1 and the input end of the signal collection and conditioning circuit and the ground.

[0018] Further, the signal collection and conditioning circuit comprises a precision full-wave rectifier circuit U1 composed of an operational amplifier and its peripheral circuit, which is used to accurately rectify the alternating current signal filtered by the harmonic filter circuit and output the direct current voltage signal.

[0019] Further, the control protection circuit comprises a comparator, an opto-isolator U5 and a switching device, the comparator is used to compare the direct current voltage signal with a preset reference voltage, the input end of the opto-isolator U5 receives the output signal of the comparator, and the output end of the opto-isolator U5 is used to drive the switching device, and the switching device is connected in series in the loop for supplying power to the load in the rear stage.

[0020] Further, the comparator compares the direct current voltage signal received by the inverting input end with the reference voltage preset by the non-inverting input end in real time.

[0021] When the direct current voltage signal is greater than the reference voltage, the comparator outputs a first level signal to trigger the turn-off action of the control protection circuit, thereby driving the switching device to cut off the power supply to the feeder terminal unit FTU in the rear stage.

[0022] When the direct current voltage signal is less than the reference voltage, the comparator outputs a second level signal, the control protection circuit maintains the original state, the switching device remains conducting, and the feeder terminal unit FTU in the rear stage is normally powered.

[0023] Further, the switching device is one of an IGBT or a MOSFET.

[0024] A system adopting a high-voltage power-taking capacitor protection and harmonic suppression circuit, the system further comprises a high-voltage capacitor voltage divider, an isolation transformer and a feeder terminal unit FTU, the input end of the high-voltage capacitor voltage divider is connected to a high-voltage bus, the output end of the high-voltage capacitor voltage divider is connected to the primary side of the isolation transformer, the secondary side of the isolation transformer is connected to the input end of the high-voltage power-taking capacitor protection and harmonic suppression circuit, and the output end of the high-voltage power-taking capacitor protection and harmonic suppression circuit supplies power to the feeder terminal unit FTU.

[0025] The beneficial effects of the present application are:

[0026] The present application innovatively adopts the protection strategy of the cooperation of the pressure sensitive resistor MOV1 and the multi-stage transient suppression diode TVS, and through the optimized PCB layout (i.e. arranging the protection device close to the input capacitor), a multi-stage discharge channel is constructed, the MOV1 is responsible for absorbing high energy surges, and the TVS tube with extremely fast response speed is specially used for clamping the nanosecond level fast pulse group, solving the problem of the accumulation of interference energy on the capacitor due to the slow response of the protection device in the traditional scheme, when the external surge interference causes the line voltage to instantaneously rise above the breakdown voltage of the TVS tube, both can quickly introduce the surge current into the ground, providing comprehensive and efficient protection for the subsequent precision measurement circuit and power conversion circuit, greatly improving the reliability and life of the system.

[0027] The present application precisely sets the cutoff frequency in the high harmonic range by adopting the Π type second-order low-pass filter network composed of specific inductance and capacitance, ensures that the collected alternating voltage signal waveform is pure and undistorted, and at the same time, the passive filter topology itself has extremely low power consumption, completely does not affect the stability and efficiency of the power supply for the FTU and other secondary devices.

[0028] The present application uses the precise full-wave rectifier circuit U1 composed of high-precision operational amplifier and its peripheral circuit, realizes accurate linear collection of small amplitude voltage signals, combines the real-time voltage monitoring of the comparator, so that the system has a microsecond level fast response capability to abnormal conditions such as overvoltage, and transmits the protection control signal through the opto-isolator, realizes the electrical isolation between the high-voltage side and the low-voltage side, not only prevents high-voltage interference from entering the low-voltage control unit, but also ensures that the protection action does not affect the stability of the front-end sampling circuit. The entire measurement and protection circuit is carefully designed and has ultra-low power consumption characteristics, its own energy consumption is much lower than the output capacity of the power supply capacitor, ensuring that while providing uninterrupted and safe power supply for the FTU, all protection functions are completed. BRIEF DESCRIPTION OF DRAWINGS

[0029] Other features, objects and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments, made with reference to the accompanying drawings:

[0030] Figure 1 It is a hardware circuit structure schematic diagram of the high-voltage power supply capacitor protection and harmonic suppression circuit according to the embodiment of the present application;

[0031] Figure 2 It is a process schematic diagram of direct current voltage signal generation, transmission and comparison of the high-voltage power supply capacitor protection and harmonic suppression circuit according to the embodiment of the present application;

[0032] Figure 3Structure diagram of high-voltage power supply capacitor protection and harmonic suppression system according to embodiment two of the present application.

[0033] The reference signs are as follows: 1, input protection circuit; 2, harmonic filter circuit; 3, signal acquisition and conditioning circuit; and 4, control protection circuit. DETAILED DESCRIPTION

[0034] In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the present application is further described below in combination with specific embodiments. Embodiment one

[0036] As shown in Figure 1 and Figure 2 , the present application provides a high-voltage power supply capacitor protection and harmonic suppression circuit technical solution, which comprises:

[0037] The input protection circuit 1 has an input end connected to the secondary side output end of an isolation transformer, and is used to suppress the input surge overvoltage and fast pulse group; the harmonic filter circuit 2 has an input end connected to the output end of the input protection circuit 1, and is used to filter out high-order harmonics in the input signal; the signal acquisition and conditioning circuit 3 has an input end connected to the output end of the harmonic filter circuit 2, and is used to convert the filtered alternating current signal into a direct current voltage signal representing the effective value of the voltage; and the control protection circuit 4 has an input end connected to the output end of the signal acquisition and conditioning circuit 3, and is used to compare the direct current voltage signal with a preset reference voltage, and according to the comparison result, to decide whether to turn on or turn off the power supply to the feeder terminal unit FTU in the rear stage.

[0038] Embodiment one

[0039] This embodiment describes the composition of each circuit and the connection relationship of the internal devices thereof, and the specific connection is as follows:

[0040] 1. Input protection circuit 1

[0041] The input protection circuit 1 comprises a varistor MOV1 and three transient voltage suppression diodes TVS (GD1, GD2, GD3):

[0042] The varistor MOV1 is connected in parallel between the input live wire L and the zero line N of the input protection circuit 1, and is mainly used to absorb surge overvoltage (such as lightning surge) with large energy and long duration; the three transient voltage suppression diodes TVS are connected in parallel and then connected between the input live wire L and the ground GND, and are specially used to clamp fast pulse group (EFT) interference by using the extremely fast response speed of nanoseconds.

[0043] The input protection circuit 1 cooperates with MOV and TVS to form a multi-level protection system for different spectrum and energy interference, which can effectively limit the instantaneous surge voltage of thousands of volts within a safe range, and the response time is less than 50 nanoseconds, thereby providing a solid safety guarantee for the elements on the rear circuit.

[0044] 2, harmonic filter circuit 2:

[0045] The harmonic filter circuit 2 is a Π type second-order low-pass filter network, which comprises a first inductor L1, a second inductor L2, a first capacitor C2 and a second capacitor C3, and the specific connection relationship is as follows:

[0046] The output end of the input protection circuit 1 is connected to the input end of the signal acquisition and conditioning circuit 3 in sequence after being connected to the second inductor L2 and the first inductor L1, forming two-stage inductor filtering, the second capacitor C3 is connected between the node of the first inductor L1 and the second inductor L2 and the ground, and the first capacitor C2 is connected between the node of the first inductor L1 and the input end of the signal acquisition and conditioning circuit 3 and the ground, forming two-stage capacitor filtering;

[0047] The Π type second-order low-pass filter network can efficiently filter out the high-order harmonic components mixed in the input signal, while reducing the influence on the fundamental wave signal, thereby improving the purity and quality of the voltage waveform, effectively eliminating the negative influence of harmonic interference on subsequent signal acquisition and measurement accuracy, and laying a solid foundation for accurate voltage measurement.

[0048] 3, signal acquisition and conditioning circuit 3:

[0049] The signal acquisition and conditioning circuit 3 comprises a precision full-wave rectifier circuit U1 composed of an operational amplifier and its peripheral circuit, and the precision full-wave rectifier circuit U1 is used for accurately rectifying the alternating current signal filtered by the harmonic filter circuit 2 and outputting the direct current voltage signal.

[0050] Through the precision full-wave rectifier circuit U1 based on a high-precision operational amplifier, high-linearity and distortionless rectification of the alternating voltage signal is realized, the nonlinear dead zone problem existing in the traditional diode rectification is completely overcome, and weak voltage signals can be accurately extracted and converted, thereby outputting a direct current signal that can accurately reflect the real effective value of the power grid voltage, and the accuracy and reliability of system monitoring are greatly improved.

[0051] 4, control protection circuit 4:

[0052] The control protection circuit 4 comprises a comparator, a photoelectric isolator U5 and a switching device, the comparator is used for comparing the direct current voltage signal with a preset reference voltage, the input end of the photoelectric isolator U5 receives the output signal of the comparator, and the output end is used for driving the switching device, the switching device is in series in a loop for supplying power to a rear-stage load, and the switching device is one of an IGBT or a MOSFET.

[0053] The control protection circuit 4 integrates voltage comparison, electrical isolation and power control functions, constitutes an intelligent protection core of the system, realizes real-time voltage monitoring through a high-speed comparator, ensures extremely fast response speed to overvoltage abnormalities, safely isolates the high-voltage side from the low-voltage side through the photoelectric isolator, prevents fault diffusion and guarantees the integrity of signal transmission, finally realizes fast and reliable control of the power supply state of the rear-end load through an efficient semiconductor switching device, and provides intelligent power-off protection.

[0054] In conclusion, the present application realizes multiple functions such as harmonic suppression, surge protection and overvoltage shutdown through the organic cooperation of various functional circuits, significantly improves the robustness of the entire power supply system in dealing with complex interference and abnormal working conditions of the power grid, effectively guarantees the safety of the core power equipment and prolongs the service life of the equipment.

[0055] Embodiment 2:

[0056] In this embodiment, the comparator continuously monitors the direct current voltage signal output by the signal acquisition and conditioning circuit 3 and compares it with a preset reference voltage provided by a precision reference source, to reflect the actual working voltage state of the high-voltage side power supply capacitor, and according to the comparison result, the power supply of the feeder terminal device FTU is realized, and the specific comparison process is as follows:

[0057] 1. Overvoltage trigger protection mechanism:

[0058] When the grid voltage abnormally rises, the direct current voltage signal increases and exceeds the preset reference voltage threshold, the comparator will immediately detect this overvoltage state, and its output state will quickly flip, outputting a first level signal (such as high level), which is used as a shutdown instruction to trigger the logic processing unit of the subsequent control protection circuit 4, and when the photoelectric isolator U5 receives this instruction, it is converted into an isolated control signal to drive the switching device (IGBT / MOSFET) to change from the on state to the off state.

[0059] This series of actions quickly cuts off the power supply loop to the rear-stage feeder terminal device FTU, thereby effectively preventing the FTU from being damaged due to overvoltage, and realizing microsecond-level fast active protection.

[0060] 2. Normal power supply maintenance mechanism:

[0061] When the grid voltage is in the normal range, the DC voltage signal is always lower than the preset reference voltage. At this time, the comparator outputs a second level signal (such as low level), indicating that the system is in a safe state. The control protection circuit 4 maintains the original state under this signal, and the opto-isolator U5 outputs an enable signal to keep the switching device in a fully on state. The power supply circuit is unobstructed, which can ensure that the power is continuously and stably transmitted to the feeder terminal device FTU, and the normal operation is ensured.

[0062] The comparison mechanism realizes automatic intelligent control from continuous monitoring, accurate judgment to rapid execution. The whole process does not need software program intervention, and is completely realized by hardware circuit. The response speed is extremely fast, the reliability is extremely high, the overvoltage protection point of the system can be flexibly adjusted by setting appropriate reference voltage value according to different needs. Moreover, the digital output based on the comparator makes the protection action crisp and neat, effectively avoiding the critical oscillation problem that may be caused by analog circuit, and ensuring the consistency and reliability of the protection of the rear-end equipment. Specific implementation method two:

[0064] As shown in Figure 3 A system adopting high-voltage power supply capacitor protection and harmonic suppression circuit, the system further comprises a high-voltage capacitor voltage divider, an isolation transformer and a feeder terminal device FTU, the input end of the high-voltage capacitor voltage divider is connected to a high-voltage bus, and the output end thereof is connected to the primary side of the isolation transformer. The secondary side of the isolation transformer is connected to the input end of the high-voltage power supply capacitor protection and harmonic suppression circuit, and the output end of the high-voltage power supply capacitor protection and harmonic suppression circuit supplies power to the feeder terminal device FTU.

[0065] Specifically, the high-voltage capacitor voltage divider: as the high-voltage sensing and energy extraction front end of the system, the input end thereof is directly connected to a 10kV (or 35kV) high-voltage bus. It is composed of a plurality of high-voltage capacitors connected in series, and a voltage proportional to the high-voltage bus is obtained by using the capacitor voltage division principle.

[0066] Isolation transformer: as the core safety isolation and secondary voltage reduction unit of the system, the primary side (primary winding) thereof is connected to the output end of the high-voltage capacitor voltage divider, and receives the received medium and high voltage. The device can realize electrical isolation, completely block the electrical direct connection between the high-voltage side and the low-voltage side, and form the first safety barrier; it can also convert the voltage output by the voltage divider to a completely safe low-voltage alternating current level suitable for processing by the rear-end circuit;

[0067] The high-voltage power taking capacitor protection and harmonic suppression circuit (i.e. the core circuit of the application): as the intelligent management and protection center of the system, the input end thereof is connected to the secondary side (secondary winding) of the isolation transformer to receive safe low-voltage alternating current after isolation and voltage reduction, the circuit integrates the functions of real-time monitoring, harmonic purification, surge protection, intelligent judgment and automatic control, and can continuously monitor the energy quality from the power grid and determine whether to deliver it to the load;

[0068] The feeder terminal unit FTU: as the power receiving load and protection object of the system, it is the key equipment of power distribution network automation, and the power input end thereof is connected to the controlled output end of the high-voltage power taking capacitor protection and harmonic suppression circuit.

[0069] The system constructs a triple safety system of "isolation + protection + intelligent shutdown" through two-stage isolation of high-voltage capacitor voltage division and isolation transformer and combined with multiple protection of the rear circuit, fundamentally guarantees the safety of personnel and equipment, and the system highly integrates the functions of power taking, isolation, protection and power distribution, provides an ideal integrated power supply solution for "primary and secondary fusion" intelligent equipment (such as circuit breakers), and meets the development trend of miniaturization and integration of power equipment.

[0070] The above shows and describes the basic principles and main features of the application and the advantages of the application, and it is obvious for those skilled in the art that the application is not limited to the details of the above exemplary embodiments, and the application can be implemented in other specific forms without departing from the spirit or basic characteristics of the application. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, the scope of the application is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the application. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0071] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description manner of the specification is only for the sake of clarity, those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be properly combined to form other embodiments that those skilled in the art can understand.

Claims

1. A high voltage power supply capacitor protection and harmonic suppression circuit, the circuit is arranged between an isolation transformer and a feeder terminal unit (FTU), characterized in that: It includes: The input protection circuit (1) is connected to the output end of the secondary side of the isolation transformer, and is used to suppress the input surge overvoltage and fast pulse group; The harmonic filter circuit (2) is connected to the output end of the input protection circuit (1), and is used to filter out high-order harmonics in the input signal; The signal acquisition and conditioning circuit (3) is connected to the output end of the harmonic filter circuit (2), and is used to convert the filtered alternating current signal into a direct current voltage signal representing the effective value of the voltage; The control protection circuit (4) is connected to the output end of the signal acquisition and conditioning circuit (3), and is used to compare the direct current voltage signal with a preset reference voltage, and according to the comparison result, to determine whether to turn on or turn off the power supply to the feeder terminal unit FTU; Wherein, the input protection circuit (1) includes a varistor MOV1 and a plurality of transient voltage suppression diodes TVS, the varistor MOV1 is connected in parallel between the input circuits of the input protection circuit (1), and the plurality of transient voltage suppression diodes TVS are connected in parallel and then connected between the input circuit of the input protection circuit (1) and the ground; The harmonic filter circuit (2) is a Π type second-order low-pass filter network, which is composed of at least two inductors and two capacitors; The signal acquisition and conditioning circuit (3) includes a precision full-wave rectifier circuit U1 composed of an operational amplifier and its peripheral circuit, which is used to accurately rectify the alternating current signal filtered by the harmonic filter circuit (2) and output the direct current voltage signal.

2. A high voltage capacitive protection and harmonic suppression circuit according to claim 1, characterized in that: The filter network includes a first inductor L1, a second inductor L2, a first capacitor C2 and a second capacitor C3, and the specific connection relationship is as follows: The output end of the input protection circuit (1) is connected to the input end of the signal acquisition and conditioning circuit (3) in sequence through the second inductor L2 and the first inductor L1, and the second capacitor C3 is connected between the node of the first inductor L1 and the second inductor L2 and the ground, and the first capacitor C2 is connected between the node of the first inductor L1 and the input end of the signal acquisition and conditioning circuit (3) and the ground.

3. A high voltage capacitive protection and harmonic suppression circuit according to claim 1, characterized in that: The control protection circuit (4) includes a comparator, an optoelectronic isolator U5 and a switching device, the comparator is used to compare the direct current voltage signal with a preset reference voltage, the input end of the optoelectronic isolator U5 receives the output signal of the comparator, and the output end of the optoelectronic isolator U5 is used to drive the switching device, and the switching device is connected in series in the circuit for supplying power to the load.

4. A high voltage capacitive protection and harmonic suppression circuit according to claim 3, characterized in that: The comparator compares the direct current voltage signal received by the inverting input end with the preset reference voltage of the non-inverting input end in real time; When the direct current voltage signal is greater than the reference voltage, the comparator outputs a first level signal, triggers the turn-off action of the control protection circuit (4), and then drives the switching device to cut off the power supply to the feeder terminal unit FTU; When the direct current voltage signal is less than the reference voltage, the comparator outputs a second level signal, the control protection circuit (4) maintains the original state, the switching device remains conducting, and the feeder terminal unit FTU is normally powered.

5. A high voltage capacitive protection and harmonic suppression circuit according to claim 3, wherein: The switching device is one of IGBT or MOSFET.

6. A system employing the high voltage power supply capacitor protection and harmonic suppression circuit of any one of claims 1-5, characterized by: The system further comprises a high-voltage capacitor voltage divider, an isolation transformer and a feeder terminal unit (FTU), wherein an input end of the high-voltage capacitor voltage divider is connected to a high-voltage bus, an output end of the high-voltage capacitor voltage divider is connected to a primary side of the isolation transformer, a secondary side of the isolation transformer is connected to an input end of the high-voltage power-taking capacitor protection and harmonic suppression circuit, and an output end of the high-voltage power-taking capacitor protection and harmonic suppression circuit supplies power to the feeder terminal unit (FTU).

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