A frequency protection system and reclosing

Abstract

The utility model relates to frequency protection technical field discloses a kind of frequency protection system and reclosing, and frequency protection system is applicable to small reclosing, system includes: power supply circuit is used to provide working voltage;Frequency detection circuit is used to collect power grid frequency signal and convert it into digital square wave signal that can be identified by processing circuit;Processing circuit is used to receive digital square wave signal, whether power grid frequency is abnormal by algorithm calculation and judge, when power grid frequency is abnormal, control signal is sent to small reclosing.The utility model is strong in adaptability, accurately matches the demand of small reclosing " miniaturization, low cost", without relying on traditional big size, high power consumption special frequency acquisition chip, simplifies system architecture, saves installation space and cost;Frequency detection is accurate and efficient, and frequency detection circuit converts power grid frequency signal into digital square wave signal that processing circuit can identify, reduces signal interference and distortion, lays foundation for processing circuit accurate calculation frequency.

Description

Technical Field

[0001] This utility model relates to the field of frequency protection technology, specifically to a frequency protection system and a reclosing device. Background Technology

[0002] With the widespread adoption of distributed power sources (such as residential photovoltaic systems and small-scale energy storage) and the diversification of electricity loads, the probability of grid frequency fluctuations has increased significantly. Frequency anomalies can not only damage loads such as motors and precision electronic equipment, but also cause regional power supply instability. Therefore, configuring frequency protection functions for small reclosers has become an important requirement for improving the safety of low-voltage power distribution. Traditional frequency protection circuits generally use dedicated frequency acquisition chips, which have the disadvantages of large size and high power consumption, and are not compatible with the design goals of "miniaturization, low cost, and low power consumption" of small reclosers. Utility Model Content

[0003] This invention provides a frequency protection system and a reclosing device to solve the problem of how to achieve frequency protection for small reclosing devices.

[0004] In a first aspect, this utility model provides a frequency protection system suitable for small reclosing circuit breakers. The system includes: a power supply circuit, a frequency detection circuit, and a processing circuit. The power supply circuit is connected to both the processing circuit and the frequency detection circuit, and is used to provide the operating voltage. The frequency detection circuit is connected to the processing circuit, and is used to collect the power grid frequency signal and convert it into a digital square wave signal that can be recognized by the processing circuit. The processing circuit receives the digital square wave signal, calculates and determines whether the power grid frequency is abnormal through an algorithm, and sends a control signal to the small reclosing circuit breaker when the power grid frequency is abnormal.

[0005] This invention boasts strong adaptability, precisely matching the "miniaturization and low cost" requirements of small reclosers. It eliminates the need for traditional, bulky, high-power dedicated frequency acquisition chips, simplifying the system architecture and saving installation space and costs. Power supply is stable and reliable; the power circuit provides a suitable operating voltage for the processing and frequency detection circuits, and features wide voltage compatibility and low temperature rise characteristics, preventing power supply issues from affecting system operation and ensuring long-term stability. Frequency detection is accurate and efficient; the frequency detection circuit converts the grid frequency signal into a digital square wave signal recognizable by the processing circuit, reducing signal interference and distortion, laying the foundation for accurate frequency calculation by the processing circuit. Protection response is timely; the processing circuit quickly determines whether the grid frequency is abnormal through algorithms, and immediately sends a control signal to the small recloser when an abnormality is detected. This effectively prevents damage to loads such as motors and precision electronic equipment due to frequency abnormalities, while also preventing regional power supply instability and improving the safety of low-voltage power distribution.

[0006] In one optional embodiment, the power supply circuit includes: a surge suppression circuit, an overcurrent protection circuit, a rectifier circuit, a first step-down circuit, a high-frequency transformer, and a voltage regulator. The surge suppression circuit is connected to the power grid and is used to absorb instantaneous high-voltage surges input from the power grid. The overcurrent protection circuit is connected to the power grid and is used to limit the current amplitude of the circuit under overload or short-circuit conditions and to cut off abnormal power supply paths to protect circuit components. The rectifier circuit is connected to the overcurrent protection circuit and is used to convert the AC voltage input from the power grid into a unidirectional pulsating DC voltage. The first step-down circuit is connected to the rectifier circuit and employs a primary-side feedback design to eliminate the need for a secondary-side feedback component, converting the high-voltage DC output from the rectifier circuit into a low-voltage DC output. The voltage regulator is connected to the first step-down circuit and is used to modulate the low-voltage DC output before outputting it.

[0007] This utility model adopts a power supply circuit designed with a primary-side feedback wide input voltage range and a transformer-isolated AC / DC conversion chip, achieving the advantages of a wide operating voltage range and low temperature rise. It solves the defects of power supply circuit design that requires optocouplers for secondary-side feedback, which has complex circuit design, narrow normal operating voltage range, and high temperature rise leading to reduced product reliability.

[0008] In one optional embodiment, the frequency detection circuit includes: a second step-down circuit and a square wave circuit, wherein the second step-down circuit is connected to the power grid and the square wave circuit, and the second step-down circuit is used to reduce the high voltage signal input from the power grid to a low voltage signal that can be stably processed by the square wave circuit; the square wave circuit is connected to the processing circuit, and the square wave circuit is used to convert the output signal of the second step-down circuit into a digital square wave signal that can be recognized by the processing circuit.

[0009] This invention relates to a frequency detection circuit design that uses a sampling resistor for voltage reduction and a transistor for square wave recognition. The circuit is simple and overcomes the shortcomings of dedicated frequency acquisition chip designs, such as complex circuit design, large size, and high power consumption.

[0010] In one optional embodiment, the step-down circuit includes: a first resistor, a second resistor, and a third resistor, wherein a first terminal of the first resistor is connected to the power grid, a second terminal of the first resistor is connected to the first terminal of the second resistor, a second terminal of the second resistor is connected to a square wave circuit, and a second terminal of the second resistor is grounded through the third resistor.

[0011] In one optional implementation, the square wave circuit includes: a fourth resistor and a transistor, wherein the first end of the fourth resistor is connected to the power supply circuit, the second end of the fourth resistor is connected to the first end of the transistor; the second end of the transistor is grounded, and the control terminal of the transistor is connected to the second step-down circuit.

[0012] In one alternative implementation, the processing circuitry includes an MCU chip.

[0013] This invention uses a sampling MCU chip as the core algorithm to calculate and judge frequency. It has the advantages of simple circuit and high reliability, and solves the defects of dedicated frequency acquisition chip design, such as slow frequency data update, which cannot fully meet the requirements of circuit breaker fast protection.

[0014] In one optional implementation, the frequency protection system further includes a human-machine interface circuit, wherein the human-machine interface circuit is connected to the processing circuit and is used to provide feedback on the system's operating status.

[0015] In one alternative implementation, the human-machine interface circuit includes at least one indicator circuit, wherein the indicator circuit is connected to the processing circuit and is used to provide feedback on a working state of the system.

[0016] In one alternative implementation, the indicator circuit includes a light-emitting diode (LED).

[0017] Secondly, this utility model provides a reclosing system, including: a frequency protection system according to the first aspect and any optional embodiment thereof. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a first configuration diagram of a frequency protection system according to an embodiment of the present utility model; Figure 2 This is a composition diagram of the power supply circuit according to an embodiment of the present utility model; Figure 3 This describes the specific circuit structure of the power supply circuit according to an embodiment of the present utility model; Figure 4 This is a second configuration diagram of the frequency protection system according to an embodiment of the present utility model; Figure 5 This describes the specific circuit structure of the frequency detection circuit according to an embodiment of the present utility model; Figure 6 This is a schematic diagram of an MCU chip according to an embodiment of the present utility model; Figure 7 This is a flowchart of the frequency detection circuit of the MCU chip control frequency detection circuit according to an embodiment of the present utility model; Figure 8 This is a second configuration diagram of the frequency protection system according to an embodiment of the present utility model; Figure 9 This describes the specific circuit structure of the indicator circuit according to an embodiment of the present utility model. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0021] It is understood that before using the technical solutions disclosed in the various embodiments of this utility model, users should be informed of the types, scope of use, and usage scenarios of the personal information involved in this utility model in an appropriate manner in accordance with relevant laws and regulations, and user authorization should be obtained.

[0022] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0023] To address the problems of large size, high power consumption, and complex architecture in traditional frequency protection circuits, and to meet the design goals of "miniaturization, low cost, and low power consumption" for small reclosing circuits, this embodiment provides a frequency protection system suitable for small reclosing circuits. Figure 1 As shown, the system includes: power supply circuit 1, frequency detection circuit 2, and processing circuit 3.

[0024] like Figure 1 As shown, the power supply circuit 1 is connected to the processing circuit 3 and the frequency detection circuit 2 respectively, and the power supply circuit 1 is used to provide the working voltage.

[0025] Specifically, the power supply circuit 1, as the core of the entire frequency protection system, is electrically connected to the processing circuit 3 and the frequency detection circuit 2 through low-impedance wires to ensure stable transmission of the power supply signal. Considering that the small recloser may be used in low-voltage power distribution scenarios with different voltage levels, the power supply circuit 1 is designed with a wide voltage input range and can convert the AC power from the grid into two independent stable DC operating voltages. One voltage supplies power to the core chip of the processing circuit 3, and the other voltage supplies power to the sampling element and signal conditioning element in the frequency detection circuit 2. At the same time, the power supply circuit 1 integrates overvoltage protection (OVP), overcurrent protection (OCP), and surge suppression modules, which can effectively resist the damage to subsequent circuits caused by grid voltage fluctuations or instantaneous impacts, and ensure the long-term reliable operation of the system.

[0026] like Figure 1 As shown, the frequency detection circuit 2 is connected to the processing circuit 3. The frequency detection circuit 2 is used to collect the power grid frequency signal and convert it into a digital square wave signal that can be recognized by the processing circuit 3.

[0027] Specifically, the frequency detection circuit 2 serves as the "sensing front end" of the power grid frequency signal. One end is connected to the power grid phase line (to prevent the high voltage of the power grid from directly intruding into the system), and the other end interacts with the processing circuit 3 to realize signal interaction. Its working process is as follows: First, the power grid voltage signal is stepped down and isolated for sampling to obtain a low-voltage AC signal that is synchronized with the power grid frequency. Then, the low-voltage AC signal is converted into a digital square wave signal with steep edges and stable amplitude (the square wave frequency is consistent with the power grid frequency).

[0028] like Figure 1 As shown, the processing circuit 3 is used to receive digital square wave signals, calculate and determine whether the power grid frequency is abnormal through an algorithm, and send a control signal to the small reclosing device when the power grid frequency is abnormal.

[0029] Specifically, the processing circuit 3, acting as the "decision center" of the frequency protection system, employs a low-power MCU (microcontroller, such as the STM32L series chip, which balances computational performance and low power consumption). Its main functions include signal reception, frequency calculation, anomaly detection, and control signal output. First, the processing circuit 3 receives the digital square wave signal transmitted by the frequency detection circuit 2 through a timer capture interface, calculates the real-time grid frequency, and obtains the signal period by measuring the time interval between two adjacent rising (or falling) edges of the square wave. Then, it calculates the current grid frequency using the formula frequency = 1 / period. Second, the processing circuit 3 internally stores a normal threshold range for the grid frequency and compares the real-time calculated grid frequency with the threshold to determine if there is a frequency anomaly. When a grid frequency anomaly is detected, the processing circuit 3 immediately triggers the protection logic and outputs a control signal. This control signal is transmitted to the actuator of the small reclosing device, driving the small reclosing device to quickly open, cutting off the connection between the abnormal grid and the load, preventing damage to loads such as motors and precision electronic equipment due to frequency anomalies, and preventing the anomaly from spreading and causing regional power supply instability.

[0030] In some alternative implementations, such as Figure 2 As shown, the power supply circuit 1 includes: a surge suppression circuit 11, an overcurrent protection circuit 12, a rectifier circuit 13, a first step-down circuit 14, and a voltage regulator 15. Each module, through optimized signal links and architecture design, forms a complete energy conversion and protection system from grid input to downstream circuit power supply, meeting the voltage adaptation requirements of a wide range of scenarios while reducing overall size and energy consumption.

[0031] like Figure 2 As shown, the surge suppression circuit 11 is connected to the power grid and is used to absorb instantaneous high-voltage surges input from the power grid.

[0032] Considering that miniature reclosers are mostly used in low-voltage power distribution scenarios, where the power grid is prone to instantaneous high-voltage surges due to lightning strikes, start-up and shutdown of high-power equipment, etc., this circuit can quickly absorb surge energy of different amplitudes through multi-dimensional protection logic design. For medium and low amplitude surges, energy dissipation is achieved through an instantaneous response mechanism; for high amplitude surges, energy is guided to ground through a discharge path to prevent surge signals from intruding into subsequent circuits. At the same time, the circuit adopts a compact layout design, which does not require excessive additional installation space and is highly compatible with the size constraints of miniature reclosers.

[0033] like Figure 2As shown, the overcurrent protection circuit 12 is also connected to the power grid side and is connected in series between the surge suppression circuit 11 and the subsequent rectifier circuit 13, undertaking the protection against circuit overload and short circuit faults. When the circuit experiences overload current due to a fault in the downstream module (such as chip short circuit or component breakdown), or when a direct short circuit occurs, this circuit can detect the current abnormality in a very short time, limit the current amplitude through its own state switching, and cut off the abnormal power supply path at the same time to prevent excessive current from burning out the power supply circuit 1 and the downstream processing circuit 3 and frequency detection circuit 2.

[0034] like Figure 2 As shown, the rectifier circuit 13 is connected to the overcurrent protection circuit 12. The rectifier circuit 13 is used to convert the AC voltage input from the power grid into a unidirectional pulsating DC voltage.

[0035] To address the potential grid voltage fluctuations that small reclosing circuits may encounter, this circuit is designed with a wide voltage input adaptation mode, capable of stably handling AC input voltages of varying amplitudes. During operation, it converts the alternating voltage of the grid into a pulsating DC voltage with a fixed polarity through unidirectional conduction logic, while filtering out reverse components in the AC voltage to ensure a stable output DC signal direction. Furthermore, the conversion efficiency of the rectifier circuit 13 has been optimized to reduce energy loss during voltage conversion, meeting low-power design requirements. The output pulsating DC voltage also provides a stable input basis for subsequent buck circuits, preventing the bucking effect from being affected by unstable input signals.

[0036] like Figure 2 As shown, the first step-down circuit 14 is connected to the rectifier circuit 13. The first step-down circuit 14 adopts a primary-side feedback design to eliminate the secondary-side feedback element and converts the high-voltage DC output of the rectifier circuit 13 into low-voltage DC.

[0037] Employing a primary-side feedback design, compared to traditional step-down schemes that rely on secondary-side feedback components, this design eliminates the need for secondary-side components used for voltage sampling and signal feedback. This significantly simplifies the circuit architecture, reduces the number of components, and consequently compresses the circuit's footprint, perfectly meeting the size requirements of compact reclosers. During voltage conversion, the circuit indirectly regulates the output voltage amplitude by monitoring the primary-side voltage signal in real time, ensuring a stable output of the preset low-voltage DC even if the input high-voltage DC fluctuates. Simultaneously, the circuit possesses dynamic power consumption adjustment capabilities, automatically adjusting its operating mode under light load conditions to reduce energy consumption, further aligning with the low-power design goals of compact reclosers.

[0038] like Figure 2 As shown, the voltage regulator 15 is connected to the first step-down circuit 14, and the voltage regulator 15 is used to output the low-voltage DC after amplitude modulation.

[0039] Because the processing circuit 3 and the frequency detection circuit 2 have different requirements for operating voltage (e.g., the processing circuit 3 requires a low-amplitude stable voltage, while the frequency detection circuit 2 requires a slightly higher amplitude voltage), the voltage regulator 15 adopts a multi-channel independent output design, which can modulate the low-voltage DC output from the first step-down circuit 14 into multiple stable DC voltages with different amplitudes. During the amplitude modulation process, the circuit significantly reduces the ripple and fluctuation of the output voltage through a high-precision voltage regulation mechanism, avoiding interference with the frequency calculation accuracy of the processing circuit 3 or affecting the signal acquisition effect of the frequency detection circuit 2 due to voltage instability. In addition, the voltage regulator 15 has a built-in safety protection function. When the circuit experiences abnormal conditions such as overheating or overvoltage, it can automatically cut off the output to protect the sensitive circuit components in the downstream stage. Finally, the amplitude-modulated stable DC voltage is transmitted to the corresponding circuit module through a low-loss transmission path to ensure the continuous and stable operation of each module.

[0040] In some optional implementations, the specific circuit structure of power supply circuit 1 is as follows: Figure 3 As shown, surge suppression circuit 11 consists of varistor RV1. Overcurrent protection circuit 12 consists of wire-wound resistor RX1. Rectifier circuit 13 consists of diode D1. First step-down circuit 14 consists of primary-side feedback conversion chip U1, capacitors C30, C1, C4, C5, C11, C14, C9, resistors R6, R7, R8, R9, R10, R33, R35, diodes D3, D4, D5; and high-frequency transformer T1. Voltage regulation is achieved by chip U4.

[0041] In some alternative implementations, such as Figure 4 As shown, the frequency detection circuit 2 includes: a second step-down circuit 21 and a square wave circuit 22.

[0042] like Figure 4 As shown, the second step-down circuit 21 is connected to the power grid and the square wave circuit 22. The second step-down circuit 21 is used to reduce the high voltage signal input from the power grid to a low voltage signal that can be stably processed by the square wave circuit 22.

[0043] Specifically, the second step-down circuit 21 smoothly reduces the high-voltage AC voltage signal from the grid side to a low-voltage signal range that the square wave circuit 22 can stably receive and process. The low-voltage signal after step-down must be strictly synchronized with the grid frequency (i.e., the signal period and phase are consistent with the grid), providing a precise frequency reference for subsequent square wave conversion.

[0044] like Figure 4 As shown, the square wave circuit 22 is connected to the processing circuit 3. The square wave circuit 22 is used to convert the output signal of the second step-down circuit 21 into a digital square wave signal that can be recognized by the processing circuit 3.

[0045] Specifically, the square wave circuit 22 converts the low-voltage AC signal (usually a sine wave signal) output by the second step-down circuit 21 into a digital square wave signal that can be directly recognized by the processing circuit 3. That is, through the waveform shaping mechanism, the smooth sine wave signal is converted into a square wave signal with steep edges and clear high and low levels. The frequency of the square wave is completely consistent with the frequency of the input low-voltage AC signal (i.e., the power grid frequency), and the amplitude of the high and low levels of the square wave matches the digital signal recognition standard of the processing circuit 3, so as to avoid the processing circuit 3 being unable to recognize the signal due to level mismatch.

[0046] In some alternative implementations, such as Figure 5 As shown, the step-down circuit includes: a first resistor R185, a second resistor R194 and a third resistor R184. The first end of the first resistor R185 is connected to the power grid, and the second end of the first resistor R185 is connected to the first end of the second resistor R194. The second end of the second resistor R194 is connected to the square wave circuit 22, and the second end of the second resistor R194 is grounded through the third resistor R184.

[0047] like Figure 5 As shown, the second step-down circuit 21 adopts a pure resistor network design, specifically including a first resistor R185, a second resistor R194, and a third resistor R184. It achieves safe voltage reduction of the high-voltage signal through the combined effect of voltage division and current limiting. Its connection relationship and functional logic are as follows: When the high-voltage AC signal from the grid side first passes through the first resistor R185, most of the voltage is shared by it, while simultaneously limiting the current amplitude flowing into the subsequent circuit, preventing excessive current from impacting the square wave circuit 22. The second resistor R194 further divides and adjusts the signal output from the first resistor R185, making the signal amplitude precisely close to the adaptation range of the square wave circuit 22 (e.g., a few volts to tens of volts), ensuring the stability of subsequent signal conversion. The third resistor R184 and the second resistor R194 form a voltage division ratio relationship. By adjusting their impedance ratio, they can flexibly adapt to the voltage reduction requirements under different grid voltage scenarios (e.g., stabilizing the amplitude range of the output signal when the grid voltage fluctuates). Simultaneously, the grounding design can quickly discharge small interference currents in the circuit, reducing the impact of noise on the low-voltage signal. This pure resistive voltage reduction structure requires no complex magnetic components or active devices. It has fewer components, a compact layout, and significantly reduces the circuit size. It is also inexpensive, perfectly meeting the design goals of small reclosing circuits.

[0048] In some alternative implementations, such as Figure 5 As shown, the square wave circuit 22 includes: a fourth resistor R195 and a transistor Q187. The first end of the fourth resistor R195 is connected to the power supply circuit 1, and the second end of the fourth resistor R195 is connected to the first end of the transistor Q187. The second end of the transistor Q187 is grounded, and the control terminal of the transistor is connected to the second step-down circuit 21.

[0049] Specifically, the square wave circuit 22 adopts a switching conversion structure with transistor Q187 as the core, and works with the fourth resistor R195 to achieve efficient conversion of low voltage signal to digital square wave. Its connection relationship and working logic are as follows: The fourth resistor R195 serves as the load resistor and pull-up resistor of transistor Q187. When transistor Q187 is in the off state, the fourth resistor R195 can pull the potential of the first terminal to the high level of the power supply circuit 1, ensuring the stability of the high level amplitude of the output signal; the second terminal of transistor Q187 is directly grounded, forming the low level reference point of the switching circuit; the gate (control terminal) of transistor Q187 is connected to the output node of the second step-down circuit 21 (i.e., the connection point of the second resistor R194 and the third resistor R184), and receives the low voltage AC signal after step-down processing.

[0050] Specifically, the operation of transistor Q187 is as follows: When the low-voltage signal output by the second step-down circuit 21 is in the positive half-cycle, the gate receives a positive voltage, transistor Q187 conducts, and the first terminal is grounded through the second terminal, outputting a low level; when the low-voltage signal is in the negative half-cycle, the gate voltage is lower than the conduction threshold, transistor Q187 is turned off, and the first terminal is connected to power supply circuit 1 through the fourth resistor R195, outputting a high level. Through this alternating "conduction-turn-off" switching, transistor Q187 converts the input sinusoidal low-voltage signal into a digital square wave signal synchronized with the grid frequency (alternating high and low levels, with a period consistent with the grid frequency). The high-speed switching characteristics of transistor Q187 ensure that the edges of the square wave signal are steep, avoiding signal distortion, while the current-limiting effect of the fourth resistor R195 protects transistor Q187 from overcurrent damage. The overall circuit structure is simple, the response is fast, and it can accurately capture subtle changes in the grid frequency, providing a reliable digital signal source for the frequency calculation of processing circuit 3.

[0051] In some alternative implementations, the processing circuit 3 includes an MCU chip. The MCU chip is as follows: Figure 6 As shown, port P1 is the circuit required by the MCU.

[0052] The process of frequency detection by the MCU chip controlling the frequency detection circuit 2 is as follows: Figure 7 As shown, Figure 7 The specific process is as follows: 1. Start the process, initialize the PA0 port, and configure it as a GPIO input mode; 2. Initialize the T21 timer, set it to falling edge capture mode, operating frequency 1MHz, and enable the T21_CH0 (PA0) port function; 3. Enable T21 capture interrupt; 4. Start timer T21; 5. Trigger interrupt handling (detection of falling edge of square wave), latch CNT value to capvalue0; 6. Calculate the frequency and duty cycle based on capvalue0, and the process ends.

[0053] In some alternative implementations, such as Figure 8 As shown, the frequency protection system also includes a human-machine interface circuit 4, which is connected to the processing circuit 3 and is used to provide feedback on the system's operating status.

[0054] Specifically, the human-machine interface circuit 4 establishes a stable signal connection with the processing circuit 3 (i.e., the core control unit of the system, such as the MCU circuit). This connection is not only a physical electrical connection, but also a "real-time information transmission channel" at the logical level. During operation, the processing circuit 3 continuously collects information such as power grid frequency data and its own operating status (such as power supply stability and module cooperation status), and converts this information into standardized control signals, which are then transmitted to the human-machine interface circuit through a preset signal link. At the same time, the human-machine interface circuit 4 has signal receiving and parsing capabilities, and can accurately identify the control signals sent by the processing circuit 3, ensuring the accuracy and synchronization of status feedback and avoiding misjudgments of status due to signal delay or misinterpretation.

[0055] In some alternative implementations, the human-machine interface circuit 4 includes at least one indicator circuit, wherein the indicator circuit is connected to the processing circuit 3 and is used to provide feedback on a working state of the system.

[0056] Optionally, such as Figure 9 As shown, the indicator circuit includes: a light-emitting diode.

[0057] This embodiment provides a reclosing circuit, including: the frequency protection system of the above embodiments and any optional implementation thereof.

[0058] Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A frequency protection system, characterized in that, The frequency protection system is suitable for small reclosing circuit breakers. The system includes: a power supply circuit, a frequency detection circuit, and a processing circuit. The power supply circuit is connected to the processing circuit and the frequency detection circuit respectively, and the power supply circuit is used to provide the working voltage. The frequency detection circuit is connected to the processing circuit. The frequency detection circuit is used to collect the power grid frequency signal and convert it into a digital square wave signal that can be recognized by the processing circuit. The processing circuit is used to receive digital square wave signals, calculate and determine whether the power grid frequency is abnormal through an algorithm, and send a control signal to the small reclosing device when the power grid frequency is abnormal.

2. The frequency protection system according to claim 1, characterized in that, The power supply circuit includes: a surge suppression circuit, an overcurrent protection circuit, a rectifier circuit, a first step-down circuit, a high-frequency transformer, and a voltage regulator, wherein... The surge suppression circuit is connected to the power grid and is used to absorb instantaneous high-voltage surges input from the power grid. The overcurrent protection circuit is connected to the power grid. The overcurrent protection circuit is used to limit the current amplitude of the circuit under overload or short circuit conditions and cut off abnormal power supply paths to protect circuit components. The rectifier circuit is connected to the overcurrent protection circuit, and the rectifier circuit is used to convert the AC voltage input from the power grid into a unidirectional pulsating DC voltage. The first step-down circuit is connected to the rectifier circuit. The first step-down circuit adopts a primary-side feedback design to eliminate the secondary-side feedback element and converts the high-voltage DC output from the rectifier circuit into low-voltage DC. The voltage regulator is connected to the first step-down circuit, and the voltage regulator is used to output the low-voltage DC after amplitude modulation.

3. The frequency protection system according to claim 1, characterized in that, The frequency detection circuit includes: a second step-down circuit and a square wave circuit, wherein... The second step-down circuit is connected to the power grid and the square wave circuit. The second step-down circuit is used to reduce the high voltage signal input from the power grid to a low voltage signal that can be stably processed by the square wave circuit. The square wave circuit is connected to the processing circuit, and the square wave circuit is used to convert the output signal of the second step-down circuit into a digital square wave signal that can be recognized by the processing circuit.

4. The frequency protection system according to claim 3, characterized in that, The step-down circuit includes: a first resistor, a second resistor, and a third resistor, wherein, The first end of the first resistor is connected to the power grid, and the second end of the first resistor is connected to the first end of the second resistor. The second end of the second resistor is connected to the square wave circuit, and the second end of the second resistor is grounded through the third resistor.

5. The frequency protection system according to claim 3, characterized in that, The square wave circuit includes: a fourth resistor and a transistor, wherein... The first end of the fourth resistor is connected to the power supply circuit, and the second end of the fourth resistor is connected to the first end of the transistor. The second terminal of the transistor is grounded, and the control terminal of the transistor is connected to the second step-down circuit.

6. The frequency protection system according to claim 1, characterized in that, The processing circuit includes an MCU chip.

7. The frequency protection system according to claim 1, characterized in that, Also includes: Human-machine interface circuit, in which, The human-machine interface circuit is connected to the processing circuit, and the human-machine interface circuit is used to provide feedback on the system's operating status.

8. The frequency protection system according to claim 7, characterized in that, The human-machine interface circuit includes: at least one indicator circuit, wherein, The indicator circuit is connected to the processing circuit, and the indicator circuit is used to provide feedback on the operating status of the system.

9. The frequency protection system according to claim 8, characterized in that, The indicator circuit includes a light-emitting diode.

10. A reclosing circuit breaker, characterized in that, include: The frequency protection system according to any one of claims 1-9.

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