High-voltage electricity-taking capacitor protection and harmonic suppression system and circuit thereof

Abstract

A high-voltage electricity-taking capacitor protection and harmonic suppression system and a circuit thereof belong to the field of intelligent control switch electricity taking of a distribution network, and the circuit is arranged between an isolation transformer and a feeder terminal unit (FTU) and comprises an input protection circuit used for suppressing input surge overvoltage and a fast pulse train, a harmonic filter circuit used for filtering harmonic waves, and an output protection circuit used for outputting the harmonic waves. The signal acquisition conditioning circuit is used for converting an alternating current signal into a direct current voltage signal, the control protection circuit is used for comparing the direct current voltage signal with a preset reference voltage, and the system further comprises a high-voltage capacitive voltage divider, an isolation transformer and a feeder terminal unit (FTU). The problem that harmonic interference, surge impact and overvoltage risks coexist in a high-voltage power taking system is effectively solved, and on the premise that the voltage signal measurement accuracy and the power supply continuity are ensured, the operation safety and reliability of rear-end FTU equipment are greatly improved.

Description

Technical Field

[0001] This invention relates to a high-voltage power supply capacitor protection and harmonic suppression system and its circuit, belonging to the field of 10kV distribution network intelligent control switch power supply. Background Technology

[0002] First, according to the "General Technical Conditions for High Voltage Switchgear and Control Equipment" GB / T 11022-2011, the main circuit power frequency withstand voltage test requirements are as follows: Phase-to-ground and phase-to-phase connections must withstand 42kV AC voltage for 1 minute; switch contacts and isolating contacts must withstand 48kV AC voltage for 1 minute, and flashover and breakdown must not occur during this process. In actual testing, the voltage input to the high-voltage equipment is increased by a voltage regulator controlling the step-up transformer. However, due to various factors, the test voltage often exceeds 48kV. This results in the voltage across the capacitors and transformer exceeding their normal operating voltage, and the high voltage will couple to the secondary circuit through the transformer. In this situation, some products may experience varying degrees of secondary equipment damage during type testing. Furthermore, overvoltage can also cause transformer temperature rise.

[0003] Secondly, in actual use, the equipment is susceptible to interference from external lightning strikes, and at the low-voltage end, there is a risk of surge damage. In traditional applications, a varistor is usually connected across the capacitor to prevent such hazards. However, in practice, it has been found that varistors do not always fully perform their protective function. For some fast pulse groups, due to their extremely rapid change rate, the varistor's response speed cannot keep up, resulting in an inability to effectively suppress the pulse group in time. This causes some pulse energy to accumulate on the capacitor, gradually building up a voltage across its terminals. This may affect the normal operation of the capacitor and even the entire circuit system, and may even damage the equipment.

[0004] Third, in actual 10kV distribution network systems, the presence of harmonics can severely interfere with the measurement process of feeder terminal units (FTUs), mainly in the following aspects: The impact of harmonics on voltage waveforms: Harmonics cause distortion of the actual voltage waveform, which is no longer a standard sine wave. When measuring equipment processes the distorted waveform according to conventional algorithms, it will misjudge the harmonic components as part of the normal voltage, thus causing the measurement results to deviate from the true value.

[0005] The impact of harmonics on transformers: Traditional power extraction devices typically use resonant transformers to isolate the physical connection between the high-voltage side and the low-voltage side of the FTU. Harmonic currents generate additional losses in the transformer windings and core, leading to a significant increase in core hysteresis and eddy current losses, and a sharp rise in core temperature. Prolonged exposure to high temperatures accelerates the aging of the transformer's insulation materials, degrades insulation performance, and increases the risk of short-circuit faults, significantly shortening the transformer's lifespan. This, in turn, affects the lifespan of the entire primary and secondary integrated equipment.

[0006] The impact of harmonics on power supply efficiency and safety: Harmonic currents not only reduce the operating efficiency of transformers, but may also affect the power supply efficiency and safety of FTUs. The presence of harmonics may lead to voltage resonance in the power grid, increase line losses, and affect the stability of the power system. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a high-voltage power extraction capacitor protection and harmonic suppression system and its circuit, thereby solving the technical problems of simultaneous harmonic interference, surge impact, and overvoltage risk in existing high-voltage power extraction systems.

[0008] To achieve the above objectives, the present invention provides a high-voltage power tapping capacitor protection and harmonic suppression circuit, comprising: The input protection circuit, whose input terminal is connected to the secondary output terminal of the isolation transformer, is used to suppress input surge overvoltage and fast pulse group; The harmonic filter circuit has its input terminal connected to the output terminal of the input protection circuit, and is used to filter out high-order harmonics in the input signal. The signal acquisition and conditioning circuit has its input terminal connected to the output terminal of the harmonic filter circuit, and is used to convert the filtered AC signal into a DC voltage signal that represents its effective voltage value. The control and protection circuit has its input terminal connected to the output terminal of the signal acquisition and conditioning circuit. It is used to compare the DC voltage signal with a preset reference voltage and, based on the comparison result, decide whether to connect or disconnect the power supply to the downstream feeder terminal unit (FTU).

[0009] Furthermore, the input protection circuit includes a varistor MOV1 and multiple transient suppression diodes (TVS). The varistor MOV1 is connected in parallel between the input circuits of the input protection circuit, and the multiple transient suppression diodes (TVS) are connected in parallel between the input circuits of the input protection circuit and ground.

[0010] Furthermore, the harmonic filter circuit is a Π-type second-order low-pass filter network, consisting of at least two inductors and two capacitors.

[0011] Furthermore, the filter network includes a first inductor L1, a second inductor L2, a first capacitor C2, and a second capacitor C3, with the following specific connection relationships: The output terminal of the input protection circuit is connected in sequence to the second inductor L2 and the first inductor L1, and is connected to the input terminal of the signal acquisition and conditioning circuit. The second capacitor C3 is connected between the node of the first inductor L1 and the second inductor L2 and ground, and the first capacitor C2 is connected between the node of the first inductor L1 and the input terminal of the signal acquisition and conditioning circuit and ground.

[0012] Furthermore, the signal acquisition and conditioning circuit includes a precision full-wave rectifier circuit U1 composed of an operational amplifier and its peripheral circuits. The precision full-wave rectifier circuit U1 is used to precisely rectify the AC signal filtered by the harmonic filter circuit and output the DC voltage signal.

[0013] Furthermore, the control and protection circuit includes a comparator, an opto-isolator U5, and a switching device. The comparator is used to compare the DC voltage signal with a preset reference voltage. The input terminal of the opto-isolator U5 receives the output signal of the comparator, and its output terminal is used to drive the switching device. The switching device is connected in series in the circuit that supplies power to the downstream load.

[0014] Furthermore, the comparator compares the DC voltage signal received at its inverting input terminal with a preset reference voltage at its non-inverting input terminal in real time. When the DC voltage signal is greater than the reference voltage, the comparator outputs a first level signal, triggering the shutdown action of the control protection circuit, thereby driving the switching device to cut off the power supply to the downstream feeder terminal unit (FTU). When the DC voltage signal is less than the reference voltage, the comparator outputs a second level signal, the control and protection circuit maintains its original state, the switching device remains on, and the power supply to the downstream feeder terminal unit (FTU) is normal.

[0015] Furthermore, the switching device is either an IGBT or a MOSFET.

[0016] A system employing a high-voltage capacitor protection and harmonic suppression circuit is disclosed. The system further includes a high-voltage capacitor divider, an isolation transformer, and a feeder terminal unit (FTU). The input terminal of the high-voltage capacitor divider is connected to the high-voltage bus, and its output terminal is connected to the primary side of the isolation transformer. The secondary side of the isolation transformer is connected to the input terminal of the high-voltage capacitor protection and harmonic suppression circuit, and the output terminal of the high-voltage capacitor protection and harmonic suppression circuit supplies power to the feeder terminal unit (FTU).

[0017] The beneficial effects of this invention are: This invention innovatively employs a protection strategy that combines a varistor MOV1 with a multi-stage transient voltage suppressor (TVS) diode. Through optimized PCB layout (placing the protection devices close to the input capacitor), a multi-stage discharge channel is constructed. The MOV1 is responsible for absorbing high-energy surges, while the extremely fast-responding TVS diode is specifically used to clamp nanosecond-level fast pulse groups. This solves the problem in traditional solutions where the protection devices cannot respond in time, leading to the accumulation of interference energy on the capacitor. When external surge interference causes the line voltage to rise instantaneously above the breakdown voltage of the TVS diode, both can quickly divert the surge current to ground, providing comprehensive and efficient protection for subsequent precision measurement circuits and power conversion circuits, significantly improving the reliability and lifespan of the system.

[0018] This invention employs a Π-type second-order low-pass filter network composed of specific inductors and capacitors to precisely set the cutoff frequency within a range that effectively filters out high-order harmonics, ensuring that the acquired AC voltage signal waveform is pure and distortion-free. At the same time, this passive filter topology itself has extremely low power consumption and does not affect the stability and efficiency of the power supply capacitor for secondary equipment such as FTU.

[0019] This invention utilizes a high-precision operational amplifier and its peripheral circuitry to form a precision full-wave rectifier circuit U1, achieving precise linear acquisition of minute amplitude voltage signals. Combined with a comparator for real-time voltage monitoring, the system possesses a microsecond-level rapid response capability to abnormal conditions such as overvoltage. Furthermore, by transmitting protection control signals through an opto-isolator, electrical isolation between the high-voltage and low-voltage sides is achieved. This prevents high-voltage interference from entering the low-voltage control unit and ensures that protection actions do not affect the stability of the preceding sampling circuit. The entire measurement and protection circuit is meticulously designed with ultra-low power consumption characteristics; its own energy consumption is far lower than the output capacity of the power-taking capacitor, ensuring uninterrupted and safe power supply to the FTU while completing all protection functions. Attached Figure Description

[0020] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the hardware circuit structure of the high-voltage power tapping capacitor protection and harmonic suppression circuit according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the DC voltage signal generation, transmission, and comparison process of the high-voltage capacitor protection and harmonic suppression circuit according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the high-voltage power tapping capacitor protection and harmonic suppression system according to Embodiment 2 of the present invention.

[0021] The attached diagrams are labeled as follows: 1. Input protection circuit; 2. Harmonic filter circuit; 3. Signal acquisition and conditioning circuit; 4. Control and protection circuit. Detailed Implementation

[0022] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments. Specific implementation method one: like Figure 1 and Figure 2 As shown, the present invention provides a high-voltage power tapping capacitor protection and harmonic suppression circuit technical solution, which includes: Input protection circuit 1, whose input terminal is connected to the secondary output terminal of the isolation transformer, is used to suppress input surge overvoltage and fast pulse groups; harmonic filter circuit 2, whose input terminal is connected to the output terminal of input protection circuit 1, is used to filter out high-order harmonics in the input signal; signal acquisition and conditioning circuit 3, whose input terminal is connected to the output terminal of harmonic filter circuit 2, is used to convert the filtered AC signal into a DC voltage signal representing its effective voltage value; control protection circuit 4, whose input terminal is connected to the output terminal of signal acquisition and conditioning circuit 3, is used to compare the DC voltage signal with a preset reference voltage, and based on the comparison result, decide to connect or disconnect the power supply to the downstream feeder terminal unit (FTU).

[0024] Example 1: This embodiment describes the composition of each circuit and the connection relationship of its internal components. The specific connections are as follows: 1. Input protection circuit 1: The input protection circuit 1 includes a varistor MOV1 and three transient voltage suppressor diodes (TVS) (GD1, GD2, GD3): The varistor MOV1 is connected in parallel between the input live wire L and the neutral wire N of the input protection circuit 1. It is mainly used to absorb surge overvoltages with large energy and long duration (such as lightning surges). The three transient suppression diodes TVS are connected in parallel between the input live wire L and ground GND. They are used to clamp fast pulse group (EFT) interference by utilizing their nanosecond-level extremely fast response speed.

[0025] The input protection circuit 1, through the coordinated operation of MOV and TVS, forms a multi-level protection system against interference of different frequencies and energy levels. It can effectively limit instantaneous surge voltages of several kilovolts within a safe range, with a response time of less than 50 nanoseconds, providing a solid safety guarantee for the components in the subsequent circuits.

[0026] 2. Harmonic filter circuit 2: The harmonic filter circuit 2 is a Π-type second-order low-pass filter network. The filter network includes a first inductor L1, a second inductor L2, a first capacitor C2, and a second capacitor C3, with the specific connection relationship as follows: The output terminal of the input protection circuit 1 is connected to the second inductor L2 and the first inductor L1 in sequence, and then connected to the input terminal of the signal acquisition and conditioning circuit 3 to form a two-stage inductor filter. The second capacitor C3 is connected between the node of the first inductor L1 and the second inductor L2 and ground, and the first capacitor C2 is connected between the node of the first inductor L1 and the input terminal of the signal acquisition and conditioning circuit 3 and ground to form a two-stage capacitor filter. This Π-type second-order low-pass filter network can efficiently filter out high-order harmonic components mixed in the input signal, while reducing the impact on the power frequency fundamental signal, thereby improving the purity and quality of the voltage waveform. It effectively eliminates the negative impact of harmonic interference on the subsequent signal acquisition and measurement accuracy, laying a solid foundation for accurate voltage measurement.

[0027] 3. Signal Acquisition and Conditioning Circuit 3: The signal acquisition and conditioning circuit 3 includes a precision full-wave rectifier circuit U1 composed of an operational amplifier and its peripheral circuits. The precision full-wave rectifier circuit U1 is used to precisely rectify the AC signal filtered by the harmonic filter circuit 2 and output the DC voltage signal.

[0028] By using a precision full-wave rectifier circuit U1 based on a high-precision operational amplifier, high linearity and distortion-free rectification of AC voltage signals is achieved, completely overcoming the nonlinear dead zone problem of traditional diode rectification. It can accurately extract and convert weak voltage signals and output a DC signal that can accurately reflect the true effective value of the grid voltage, greatly improving the accuracy and reliability of system monitoring.

[0029] 4. Control and protection circuit 4: The control and protection circuit 4 includes a comparator, an opto-isolator U5, and a switching device. The comparator is used to compare the DC voltage signal with a preset reference voltage. The input terminal of the opto-isolator U5 receives the output signal of the comparator, and its output terminal is used to drive the switching device. The switching device is connected in series in the circuit that supplies power to the downstream load. The switching device is either an IGBT or a MOSFET.

[0030] The control and protection circuit 4 integrates voltage comparison, electrical isolation, and power control functions, forming the core of the system's intelligent protection. It achieves real-time voltage monitoring through a high-speed comparator, ensuring extremely fast response to overvoltage anomalies. The introduction of an opto-isolator safely isolates the high-voltage side from the low-voltage side, preventing fault propagation and ensuring the integrity of signal transmission. Finally, through efficient semiconductor switching devices, it achieves fast and reliable control of the power supply status of the downstream load, providing intelligent power-off protection.

[0031] In summary, this invention, through the organic coordination of various functional circuits, synergistically achieves multiple functions such as harmonic suppression, surge protection, and overvoltage shutdown. While ensuring that the power-taking capacitor provides continuous and stable power to the FTU equipment, it significantly improves the robustness of the entire power-taking system in the face of complex power grid interference and abnormal operating conditions, thereby effectively ensuring the safety of core electrical equipment and extending the service life of the equipment.

[0032] Example 2: Based on the circuit structure of Embodiment 1, this embodiment uses a comparator to continuously monitor the DC 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 operating voltage state of the high-voltage side power-taking capacitor. Based on this comparison result, power is supplied to the feeder terminal unit (FTU). The specific comparison process is as follows: 1. Overvoltage trigger protection mechanism: When the mains voltage rises abnormally, the DC voltage signal increases accordingly 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 a high level). This signal serves as a shutdown command, triggering the logic processing unit of the subsequent control and protection circuit 4. When the opto-isolator U5 receives this command, it converts it into an isolated control signal, driving the switching device (IGBT / MOSFET) to switch from the on state to the off state.

[0033] This series of actions quickly cut off the power supply circuit to the downstream feeder terminal unit (FTU), effectively preventing the FTU from being damaged due to overvoltage and achieving microsecond-level rapid active protection.

[0034] 2. Normal power supply maintenance mechanism: When the grid voltage is within 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 a low level) to indicate 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 conducting state. The power supply circuit is unobstructed, which can ensure that the power is continuously and stably delivered to the feeder terminal unit (FTU) and ensure its normal operation.

[0035] This comparison mechanism achieves fully automated intelligent control from continuous monitoring and accurate judgment to rapid execution. The entire process requires no software intervention and is implemented entirely by hardware circuitry, resulting in extremely fast response and high reliability. The overvoltage protection point of the system can be flexibly adjusted by setting an appropriate reference voltage value according to different needs. Furthermore, the comparator-based digital output ensures crisp and clean protection actions, effectively avoiding the critical oscillation problems that may occur in analog circuits, and ensuring the consistency and reliability of protection for downstream equipment. Specific Implementation Method Two: like Figure 3 As shown, a system employing a high-voltage capacitor protection and harmonic suppression circuit is disclosed. The system further includes a high-voltage capacitor divider, an isolation transformer, and a feeder terminal unit (FTU). The input terminal of the high-voltage capacitor divider is connected to the high-voltage bus, and its output terminal is connected to the primary side of the isolation transformer. The secondary side of the isolation transformer is connected to the input terminal of the high-voltage capacitor protection and harmonic suppression circuit. The output terminal of the high-voltage capacitor protection and harmonic suppression circuit supplies power to the feeder terminal unit (FTU).

[0037] Specifically, the high-voltage capacitor divider serves as the front end for high-voltage sensing and energy extraction in the system. Its input is directly connected to the 10kV (or 35kV) high-voltage bus. It consists of multiple high-voltage resistant capacitors connected in series. Utilizing the principle of capacitor voltage division, it obtains a voltage that is proportionally reduced but still at a dangerous level from the high-voltage bus.

[0038] Isolation transformer: As the core safety isolation and secondary voltage reduction unit of the system, its primary winding is connected to the output of the high-voltage capacitor divider, receiving medium and high voltage. This device can achieve electrical isolation, completely blocking the direct electrical connection between the high-voltage side and the low-voltage side, forming the first safety barrier; it can also perform voltage conversion, further reducing the voltage output of the voltage divider to a completely safe low-voltage AC level suitable for downstream circuit processing. High-voltage power extraction capacitor protection and harmonic suppression circuit (i.e., the core circuit of this invention): As the intelligent management and protection center of the system, its input terminal is connected to the secondary side (secondary winding) of the isolation transformer to receive safe low-voltage AC power after isolation and step-down. This circuit integrates the functions of real-time monitoring, harmonic purification, surge protection, intelligent judgment and automatic control. It can continuously monitor the energy quality from the power grid and decide whether to deliver it to the load. Feeder Terminal Unit (FTU): As the power receiving load and protected object of the system, it is a key device for distribution network automation. Its power input terminal is connected to the controlled output terminal of the high-voltage power extraction capacitor protection and harmonic suppression circuit.

[0039] This system constructs a triple safety system of "isolation + protection + intelligent shutdown" through high-voltage capacitor voltage division and two-stage isolation by isolation transformer, combined with multiple protections of the downstream circuit. This fundamentally ensures the safety of personnel and equipment. Furthermore, the system highly integrates power supply, isolation, protection, and power distribution functions, providing an ideal integrated power solution for "primary and secondary integrated" intelligent devices (such as circuit breakers), which is in line with the development trend of miniaturization and integration of power equipment.

[0040] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0041] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A high-voltage power extraction capacitor protection and harmonic suppression circuit, wherein the circuit is located between the isolation transformer and the feeder terminal unit (FTU), characterized in that: It includes: The input protection circuit (1) has its input terminal connected to the secondary output terminal of the isolation transformer, and is used to suppress the input surge overvoltage and fast pulse group; The harmonic filter circuit (2) has its input terminal connected to the output terminal 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 its input terminal connected to the output terminal of the harmonic filter circuit (2) and is used to convert the filtered AC signal into a DC voltage signal that represents its effective voltage value. The control and protection circuit (4) has its input terminal connected to the output terminal of the signal acquisition and conditioning circuit (3) and is used to compare the DC voltage signal with the preset reference voltage and, based on the comparison result, decide whether to connect or disconnect the power supply to the downstream feeder terminal unit (FTU).

2. The high-voltage power tapping capacitor protection and harmonic suppression circuit according to claim 1, characterized in that: The input protection circuit (1) includes a varistor MOV1 and multiple transient suppression diodes TVS. The varistor MOV1 is connected in parallel between the input circuits of the input protection circuit (1), and the multiple transient suppression diodes TVS are connected in parallel between the input circuits of the input protection circuit (1) and ground.

3. The high-voltage power tapping capacitor protection and harmonic suppression circuit according to claim 1, characterized in that: The harmonic filter circuit (2) is a Π-type second-order low-pass filter network, consisting of at least two inductors and two capacitors.

4. The high-voltage power tapping capacitor protection and harmonic suppression circuit according to claim 3, characterized in that: The filter network includes a first inductor L1, a second inductor L2, a first capacitor C2, and a second capacitor C3, with the following specific connection relationships: The output terminal of the input protection circuit (1) is connected in sequence to the second inductor L2 and the first inductor L1, and is connected to the input terminal of the signal acquisition and conditioning circuit (3). The second capacitor C3 is connected between the node of the first inductor L1 and the second inductor L2 and ground, and the first capacitor C2 is connected between the node of the first inductor L1 and the input terminal of the signal acquisition and conditioning circuit (3) and ground.

5. The high-voltage power tapping capacitor protection and harmonic suppression circuit according to claim 1, characterized in that: The signal acquisition and conditioning circuit (3) includes a precision full-wave rectifier circuit U1 composed of an operational amplifier and its peripheral circuits. The precision full-wave rectifier circuit U1 is used to precisely rectify the AC signal filtered by the harmonic filter circuit (2) and output the DC voltage signal.

6. The high-voltage power tapping capacitor protection and harmonic suppression circuit according to claim 5, characterized in that: The control and protection circuit (4) includes a comparator, an opto-isolator U5, and a switching device. The comparator is used to compare the DC voltage signal with a preset reference voltage. The input terminal of the opto-isolator U5 receives the output signal of the comparator, and its output terminal is used to drive the switching device. The switching device is connected in series in the circuit that supplies power to the downstream load.

7. The high-voltage power tapping capacitor protection and harmonic suppression circuit according to claim 6, characterized in that: The comparator compares the DC voltage signal received at its inverting input terminal with the preset reference voltage at its non-inverting input terminal in real time. When the DC voltage signal is greater than the reference voltage, the comparator outputs a first level signal, triggering the shutdown action of the control protection circuit (4), thereby driving the switching device to cut off the power supply to the downstream feeder terminal unit (FTU). When the DC voltage signal is less than the reference voltage, the comparator outputs a second level signal, the control protection circuit (4) maintains its original state, the switching device remains on, and the power supply to the downstream feeder terminal unit (FTU) is normal.

8. The high-voltage power tapping capacitor protection and harmonic suppression circuit according to claim 6, characterized in that: The switching device is either an IGBT or a MOSFET.

9. A system employing the high-voltage power extraction capacitor protection and harmonic suppression circuit described in any one of claims 1-8, characterized in that: The system also includes a high-voltage capacitor divider, an isolation transformer, and a feeder terminal unit (FTU). The input of the high-voltage capacitor divider is connected to the high-voltage bus, and its output is connected to the primary side of the isolation transformer. The secondary side of the isolation transformer is connected to the input of the high-voltage power supply capacitor protection and harmonic suppression circuit. The output of the high-voltage power supply capacitor protection and harmonic suppression circuit supplies power to the feeder terminal unit (FTU).

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