Direct current support capacitor signal sampling system for flexible direct current converter valve

Abstract

The invention discloses a direct current support capacitor signal sampling system for a flexible direct current converter valve, which is characterized by comprising a non-contact current transformer, a rectification loop, a charging loop, a low current relay, a signal sampling conditioning loop and a sampling loop, and is characterized in that the primary side of the non-contact current transformer is connected with a to-be-measured point of a main loop, and the secondary side of the non-contact current transformer is connected with a to-be-measured point of the main loop; a secondary side of the non-contact current transformer is connected with a common node of the low-current relay; a normally closed node of the low-current relay is connected with the charging loop through the rectifying loop; a normally open node of the low-current relay is connected with the sampling loop through the signal sampling conditioning loop; the charging end of the charging loop is connected with the sampling loop; the charging loop comprises a super capacitor, a discharging switch, a boosting chip and a controller, and the controller is configured to control the discharging switch to be closed when it is detected that the voltage value of the super capacitor exceeds a conduction threshold value. According to the signal sampling system provided by the invention, the accuracy of signal sampling can be improved.

Description

Technical Field

[0001] This application relates to the technical field of electronic circuits, and in particular to a signal sampling system for a DC support capacitor of a flexible DC converter valve. Background Art

[0002] In the power system, it is crucial to accurately measure and monitor the signals in the main circuit. Accurately measuring the operating data in the main circuit can help power system operators understand the operating status of the power grid in real time, so as to adjust the power distribution in a timely manner and ensure the stable operation of the power grid.

[0003] In the prior art, the sampling system faces many challenges, and the most significant one is the limitation brought by its system structure itself. Specifically, when the current in the circuit changes due to load fluctuations, power grid faults or other factors, this change will directly cause corresponding fluctuations in the voltage at the input end of the sampling system. This kind of fluctuation is not only difficult to predict, but also has a wide range of amplitudes and frequencies, bringing great challenges to the sampling circuit. Since the design of the sampling circuit is often based on the assumption of a stable input voltage, when the input voltage fluctuates, the ability of the sampling circuit to capture and process signals will be seriously affected, resulting in a significant decrease in the accuracy of the sampling results. Summary of the Invention

[0004] This application aims to provide a signal sampling system for a DC support capacitor of a flexible DC converter valve to solve the technical problem of how to improve the accuracy of the sampling system.

[0005] To solve the above technical problem, on the one hand, an embodiment of this application provides a signal sampling system for a DC support capacitor of a flexible DC converter valve, including a non-contact current transformer, a rectification circuit, a charging circuit, a low-current relay, a signal sampling and conditioning circuit, and a sampling circuit, where,

[0006] The primary side of the non-contact current transformer is connected to the point to be measured in the main circuit, and the secondary side of the non-contact current transformer is connected to the common node of the low-current relay; the normally closed node of the low-current relay is connected to the charging circuit through the rectification circuit; the normally open node of the low-current relay is connected to the sampling circuit through the signal sampling and conditioning circuit; the charging end of the charging circuit is connected to the sampling circuit;

[0007] The charging circuit includes a super capacitor, a discharge switch, a boost chip, and a controller; the input end of the super capacitor is respectively connected to the output end of the rectification circuit and one end of the discharge switch, the other end of the discharge switch is connected to the input end of the boost chip, and the output end of the boost chip is connected to the charging end of the charging circuit; the first control end of the controller is connected to the controlled end of the discharge switch, and the controller is configured to control the discharge switch to close when detecting that the voltage value of the super capacitor exceeds the conduction threshold.

[0008] As one of the preferred solutions, the rectification circuit includes a transient voltage suppression diode and a rectifier bridge, wherein one end of the transient voltage suppression diode is connected to the secondary side of the non-contact current transformer through the low-current relay, and the other end of the transient voltage suppression diode is connected to the rectifier bridge.

[0009] As one of the preferred solutions, the boost chip includes a switching transistor, a boost inductor, and a freewheeling diode. One end of the switching transistor is connected to the other end of the discharge switch, the other end of the switching transistor is respectively connected to the boost inductor and the freewheeling diode, and the boost inductor is connected in parallel with the freewheeling diode.

[0010] As one of the preferred solutions, the second control end of the controller is connected to the controlled end of the boost chip, and the controller is configured to control the boost chip to boost the voltage value to the preset voltage threshold when detecting that the voltage value of the super capacitor is lower than the preset voltage threshold.

[0011] As one of the preferred solutions, the signal sampling and conditioning circuit includes a resistor circuit, an AD627 amplifier, and an RC filter circuit. The input end of the resistor circuit is connected to the normally open node of the low-current relay, the positive input end of the AD627 amplifier is connected to the output end of the resistor circuit, the negative input end of the AD627 amplifier is connected to the output end of the AD627 amplifier through a feedback resistor, and the output end of the AD627 amplifier is connected to the input end of the RC filter circuit.

[0012] As one of the preferred solutions, the resistor circuit includes a first resistor and a second resistor, wherein the first resistor and the second resistor are connected in parallel.

[0013] As one of the preferred solutions, the RC filter circuit includes a resistor and a capacitor. The input end of the RC filter circuit is connected to one end of the resistor, the other end of the resistor is connected in series with one end of the capacitor, and the other end of the capacitor is connected to the sampling circuit.

[0014] As one of the preferred solutions, the sampling circuit includes an analog-to-digital converter, a buffer, and a timer. Among them, the input end of the analog-to-digital converter is connected to the output end of the signal sampling and conditioning circuit, the output end of the analog-to-digital converter is connected to the input end of the buffer, the output end of the timer is connected to the controlled end of the analog-to-digital converter, and the timer is configured to generate a sampling trigger signal according to a preset time point, and control the analog-to-digital converter to perform sampling at the preset time point through the sampling trigger signal.

[0015] As one of the preferred solutions, the non-contact current transformer includes a sensor and a signal processing circuit. Among them, the input end of the sensor is connected to the point to be measured, the output end of the sensor is connected to the input end of the signal processing circuit, and the output end of the signal processing circuit is connected to the common node of the low-current relay.

[0016] As one of the preferred solutions, the third control end of the controller is connected to the controlled end of the low-current relay, and the controller is configured to control the low-current relay to close the normally open node and disconnect the normally closed node when detecting that the voltage value of the super capacitor exceeds the conduction threshold; when detecting that the voltage value of the super capacitor is lower than the turn-off threshold, control the low-current relay to disconnect the normally open node and close the normally closed node.

[0017] Compared with the prior art, the beneficial effects of the embodiments of the present application are at least one of the following:

[0018] 1) The present application measures the current signal in the main circuit in a non-contact manner on the primary side of the current transformer, avoiding the error caused by direct contact measurement.

[0019] 2) The present application converts the AC signal output by the current transformer into a DC signal, which provides convenience for subsequent digital signal processing because digital systems are usually easier to process DC signals.

[0020] 3) The present application uses the rectified DC signal to charge the energy storage element (such as a super capacitor) to store electrical energy. This function can provide a stable power output when needed, providing reliable electrical energy support for subsequent circuits such as the sampling circuit.

[0021] 4) By switching the connection state of the current transformer, the system can flexibly switch between the charging mode and the sampling mode. In the charging mode, the secondary side of the current transformer is connected to the rectification circuit; in the sampling mode, it is connected to the signal sampling and conditioning circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1It is a schematic diagram of a signal sampling system in one embodiment of the present application. Detailed implementation manners

[0023] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The purpose of providing these embodiments is to make the disclosure content of the present application more thorough and comprehensive. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present application.

[0024] In the description of the present application, the terms "first", "second", "third", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", "third", etc. may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise stated, the meaning of "plurality" is two or more.

[0025] In the description of the present application, it should be noted that, unless otherwise clearly defined and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two components. The terms "vertical", "horizontal", "left", "right", "up", "down" and similar expressions used herein are only for the purpose of illustration, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the present application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0026] In the description of the present application, it should be noted that, unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the specification of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0027] An embodiment of the present application provides a signal sampling system for a DC support capacitor of a flexible DC converter valve. Specifically, please refer to Figure 1 , Figure 1Schematic diagram of a signal sampling system in one embodiment of the present application, including: a current transformer 1, a rectification circuit 2, a charging circuit 3, a low-current relay 4, a signal sampling and conditioning circuit 5, and a sampling circuit 6, where,

[0028] The primary side of the current transformer is used for non-contact measurement of the first current signal in the main circuit, and the secondary side of the current transformer is used for outputting the second current signal after converting the first current signal;

[0029] The input end of the rectification circuit is connected to the secondary side signal line of the current transformer, and is used for converting the second current signal into a DC signal;

[0030] The input end of the charging circuit is connected to the output end of the rectification circuit, and is used for storing the DC electrical energy of the DC signal;

[0031] The common node of the low-current relay is connected to the secondary side signal line of the current transformer, the normally closed contact of the low-current relay is connected to the rectification circuit, and the normally open node of the low-current relay is connected to the signal sampling and conditioning circuit, and is used for switching the connection state of the current transformer;

[0032] The signal sampling and conditioning circuit is used for converting the second current signal into a voltage signal;

[0033] The input end of the sampling circuit is connected to the output end of the signal sampling and conditioning circuit, and is used for converting the voltage signal into a digital signal.

[0034] The energy acquisition requirement of the signal sampling system of the present application ensures its effective operation under different current conditions. Specifically, the start-up current range of the signal sampling system is set to 50A to 700A. When the current exceeds 50A, the device can start and output at least once within 5 minutes; when the current is greater than 150A, continuous real-time online monitoring can be achieved. This enables the system to handle both intermittent working scenarios and meet the requirements of continuous monitoring.

[0035] The start-up current range of the sampling system of the present application is precisely set between 50A and 700A. This range ensures that the device can be effectively started under various current conditions and obtain energy from the current. The wide start-up current range provides the ability to adapt to different load conditions, enabling the device to be applied to a variety of practical scenarios, such as different branches of the power system, various equipment on industrial production lines, and electrical systems in residential and commercial buildings. At the same time, this design also takes into account the robustness and reliability of the system, ensuring stable operation under various working conditions, thereby improving the practicality and application scope of the sampling system.

[0036] When the current in the monitored circuit (i.e., the main circuit) is greater than 150A, the sampling system can immediately enter the real-time online monitoring mode. In this mode, the system can continuously collect and process data without waiting for a specific startup interval or entering the low-power mode.

[0037] The power supply of the signal sampling system of this application is non-contact. The core lies in using a current measurement transformer (CT) for non-contact power supply to improve the volume efficiency, independence, and reliability of the sampling system. The current transformer (CT) of this application is made of permalloy material, which has the characteristics of high magnetic permeability and low loss and is very suitable for current measurement. The high magnetic permeability of permalloy means that the CT can capture the magnetic field changes in the main circuit more effectively, thus measuring the current more accurately. The low-loss characteristic ensures that the CT will not generate too much heat during long-term use, maintaining its stability and reliability.

[0038] The outer diameter of the CT is 76mm, the inner diameter is 70mm, and the thickness is 9mm. This compact size design enables the CT to be easily installed on the working current path of the capacitor without occupying too much space. The number of turns on the secondary side is 1000 turns, which ensures that the CT can efficiently convert the large current in the main circuit into a small current signal for subsequent processing.

[0039] The CT works based on the principle of electromagnetic induction. When there is current flowing in the main circuit, a magnetic field will be generated in the iron core of the CT. This magnetic field will generate an induced electromotive force in the secondary coil of the CT, thereby converting the large current in the main circuit into a small current signal on the secondary side. This process is non-contact and lossless, does not interfere with the normal operation of the main circuit, and at the same time provides accurate current measurement data. The CT is directly installed on the working current path of the capacitor, so that the current of the capacitor can be directly measured to ensure the accuracy and real-time nature of the data.

[0040] The common node of the low-current relay of this application is connected to the secondary side of the CT, so that the output signal of the CT can be switched as needed. The normally closed node is connected to the charging circuit. When the relay is in the initial state, the secondary side signal of the CT is connected to the charging circuit to charge the super capacitor. The normally open node is connected to the acquisition conditioning circuit. When the relay is closed, the secondary side signal of the CT is connected to the acquisition conditioning circuit for data acquisition and processing.

[0041] In the stable state, the power consumption of the sampling system is designed to consume only 50mA current at 5V voltage. The low-power design reduces the requirements for the power supply, extends the service life of the sampling system, and improves the energy efficiency of the overall system. This characteristic enables the sampling system to work for a long time in battery-powered or energy-constrained application scenarios, such as power line monitoring in remote areas or status monitoring of mobile devices.

[0042] Preferably, in an embodiment of the present application, the rectification circuit includes a transient voltage suppression diode and a rectifier bridge. Among them, one end of the transient voltage suppression diode is connected to the secondary side of the non-contact current transformer through the low-current relay, and the other end of the transient voltage suppression diode is connected to the rectifier bridge.

[0043] Among them, the TVS diode is a component used to protect electronic circuits from transient overvoltages (such as surges, lightning overvoltages, etc.). It can respond quickly when an overvoltage occurs, limit the instantaneous high voltage within a safe range, and protect other components in the circuit from damage.

[0044] The rectifier bridge is composed of four diodes, forming a bridge structure. When an AC signal is input, the diodes will conduct and cut off alternately according to the polarity of the signal, thereby converting the AC signal into a DC signal. The main function of the rectifier bridge is to convert AC power into DC power. In the rectification circuit, the rectifier bridge receives the second current signal (usually an AC signal) from the current transformer and converts it into a DC signal for subsequent circuits to use.

[0045] In the rectification circuit, the TVS diode and the rectifier bridge work together to achieve the following functions:

[0046] 1) The TVS diode responds quickly when a transient overvoltage occurs, protecting the rectifier bridge and other circuit components from damage;

[0047] 2) The rectifier bridge converts the AC signal into a DC signal, providing a stable DC power supply for subsequent circuits;

[0048] 3) By integrating the TVS diode and the rectifier bridge, the rectification circuit can maintain stable operation under various current conditions, improving the reliability and stability of the entire sampling system.

[0049] Preferably, in an embodiment of the present application, the boost chip includes a switching tube, a boost inductor, and a freewheeling diode. One end of the switching tube is connected to the other end of the discharge switch, the other end of the switching tube is respectively connected to the boost inductor and the freewheeling diode, and the boost inductor is connected in parallel with the freewheeling diode.

[0050] Preferably, in an embodiment of the present application, the second control end of the controller is connected to the controlled end of the boost chip, and the controller is configured to control the boost chip to boost the voltage value to the preset voltage threshold when it detects that the voltage value of the super capacitor is lower than the preset voltage threshold.

[0051] Specifically, the controller is used to monitor the voltage state of the supercapacitor in real time. Specifically, the controller continuously monitors the voltage value of the supercapacitor and compares it with a preset voltage threshold.

[0052] When it is unfortunately detected that the voltage value of the supercapacitor drops below the preset voltage threshold, the controller sends a clear control signal to the controlled end of the boost chip. This signal is an instruction for the boost chip to start the boost operation, aiming to boost the current voltage value of the supercapacitor to the preset voltage threshold.

[0053] After receiving this instruction, the boost chip uses its internal circuit design and working principle to gradually and stably boost the voltage of the supercapacitor to the required preset voltage threshold. This process ensures that the supercapacitor can always be maintained within a suitable voltage range, thus guaranteeing the stability and reliability of the entire system.

[0054] Preferably, in an embodiment of the present application, the signal sampling and conditioning circuit includes a resistor circuit, an AD627 amplifier, and an RC filter circuit. Among them, the input end of the resistor circuit is connected to the normally open node of the low-current relay, the positive input end of the AD627 amplifier is connected to the output end of the resistor circuit, the negative input end of the AD627 amplifier is connected to the output end of the AD627 amplifier through a feedback resistor, and the output end of the AD627 amplifier is connected to the input end of the RC filter circuit.

[0055] Preferably, in an embodiment of the present application, the resistor circuit includes a first resistor and a second resistor, and the first resistor and the second resistor are connected in parallel.

[0056] Specifically, in order to convert the current signal on the secondary side of the current transformer (CT) into a voltage signal, two 1Ω high-precision resistors are connected in parallel in the design of the present application. This configuration not only improves the measurement accuracy and reliability but also ensures the stability of signal conversion.

[0057] Among them, two 1Ω high-precision resistors are selected in parallel to increase the redundancy of the system while ensuring the measurement accuracy. The equivalent resistance after parallel connection is 0.5Ω, which means that when the current on the secondary side of the CT flows through, a larger voltage drop will be generated, making it easier to be measured and processed. According to Ohm's law (V = I×R), when the current on the secondary side of the CT passes through the parallel resistors, a corresponding voltage signal will be generated. For example, if the current on the secondary side of the CT is 1A, the voltage generated on the 0.5Ω equivalent resistor will be 0.5V. This conversion method is simple and direct, and can accurately convert the current signal into a voltage signal. Using high-precision resistors can reduce measurement errors and improve the accuracy of signal conversion. This is because the resistance value change range of high-precision resistors is very small, and even after temperature changes or long-term use, the resistance value can remain stable. The design of the parallel resistors increases the redundancy and reliability of the system. Even if one of the resistors fails (such as open circuit or short circuit), the other resistor can still continue to work, thus ensuring the continuous operation of the system and the accuracy of measurement.

[0058] Preferably, in an embodiment of the present application, the RC filter circuit includes a resistor and a capacitor. Among them, the input end of the RC filter circuit is connected to one end of the resistor, the other end of the resistor is connected in series with one end of the capacitor, and the other end of the capacitor is connected to the sampling circuit.

[0059] The converted voltage signal is first input into the AD627 instrumentation amplifier for amplification. The amplified signal is then filtered through an RC filter circuit to remove high-frequency noise and interference, and improve the purity and reliability of the signal.

[0060] Among them, AD627 is a high-precision, low-noise instrumentation amplifier with excellent linearity and stability, which can effectively enhance the amplitude of the signal and make it more suitable for subsequent processing and analysis. In addition, AD627 also has the characteristics of high input impedance and low output impedance, which can reduce signal loss and interference during transmission.

[0061] The RC filter circuit consists of a resistor and a capacitor, which is a simple and effective filtering method that can remove high-frequency noise and interference in the signal according to the required cut-off frequency. In this design, the RC filter circuit is used to retain the required low-frequency components (i.e., the effective value of the current signal), while removing high-frequency noise and interference. This filtering method helps to improve the purity and reliability of the signal.

[0062] After amplification and filtering, the signal becomes more stable and accurate. At this time, the signal is sent to the sampling circuit for data acquisition. The sampling circuit usually includes components such as an analog-to-digital converter (ADC) and a microprocessor (such as an MCU or DSP), which are used to convert the analog signal into a digital signal and perform further analysis and processing. In this way, the sampling system can obtain accurate and reliable current data to support efficient power monitoring and fault diagnosis.

[0063] Preferably, in an embodiment of the present application, the sampling circuit includes an analog-to-digital converter, a buffer, and a timer. Wherein, the input end of the analog-to-digital converter is connected to the output end of the signal sampling conditioning circuit, the output end of the analog-to-digital converter is connected to the input end of the buffer, the output end of the timer is connected to the controlled end of the analog-to-digital converter, and the timer is configured to generate a sampling trigger signal according to a preset time point, and control the analog-to-digital converter to perform sampling at the preset time point through the sampling trigger signal.

[0064] Specifically, the analog-to-digital converter (ADC) is the core component of the sampling circuit and is responsible for converting the continuous analog voltage signal into a discrete digital signal. This conversion process is based on a preset sampling rate and resolution.

[0065] Among them, the sampling rate refers to the number of times the ADC samples the analog signal per second. The higher the sampling rate, the more signal details can be captured, but at the same time, higher processing power and storage space are required. When selecting the sampling rate, it is necessary to balance the signal bandwidth, noise level, and requirements for subsequent digital processing. The resolution represents the minimum voltage change that the ADC can distinguish. The higher the resolution, the finer the voltage range that the ADC can convert, and thus the more accurately it can represent the changes in the analog signal.

[0066] The ADC usually converts the analog signal into a digital signal through three steps: sampling, quantization, and encoding. In the sampling stage, the ADC obtains the value of the analog signal at specific time intervals. The quantization process divides the continuous analog signal amplitude into several discrete levels, and each level corresponds to a digital value. Finally, the ADC maps each quantization level to the corresponding binary code for subsequent digital processing and storage.

[0067] The buffer plays a role of electrical isolation and signal buffering in the sampling circuit. It can protect the ADC from the impact of transient voltage or current from the input signal, and at the same time provide a stable signal source for the ADC to perform sampling.

[0068] Among them, electrical isolation means that the buffer reduces the transmission of interference and noise by isolating the direct electrical connection between the input signal and the ADC. This helps to improve the accuracy and stability of sampling. Signal buffering means that the buffer can store and amplify the input signal to ensure that the ADC can receive a stable and clear signal during sampling. This helps to reduce sampling errors caused by signal fluctuations or attenuation.

[0069] The timer is used to control the start and end of the sampling process. It ensures that the ADC samples at the correct time intervals, thereby enabling continuous and regular digital processing of the analog signal.

[0070] Among them, the triggering mechanism means that the timer can be set to external triggering or internal triggering. External triggering allows an external signal to control the start and end of sampling and is suitable for scenarios that require synchronous sampling. Internal triggering automatically triggers the sampling process according to a preset time interval.

[0071] Accuracy and stability mean that the accuracy and stability of the timer are crucial for the accuracy of sampling. A high-precision timer can ensure the consistency of the sampling interval, thereby avoiding signal distortion or confusion caused by time errors.

[0072] The overall working process of the sampling circuit is as follows:

[0073] 1) Signal input: The analog voltage signal enters the sampling circuit through the input terminal;

[0074] 2) Buffering and isolation: The buffer performs electrical isolation and signal buffering on the input signal;

[0075] 3) Timing trigger: The timer triggers the ADC to sample according to a preset time interval;

[0076] 4) Digital processing: The ADC samples, quantizes, and encodes the buffered analog signal, converting it into a digital signal;

[0077] 5) Data output: The converted digital signal is output through the output terminal to the subsequent digital processing system or storage device.

[0078] Preferably, in an embodiment of the present application, the non-contact current transformer includes a sensor and a signal processing circuit, wherein the input terminal of the sensor is connected to the measurement point, the output terminal of the sensor is connected to the input terminal of the signal processing circuit, and the output terminal of the signal processing circuit is connected to the common node of the low-current relay.

[0079] Specifically, according to the principle of electromagnetic induction, when there is a current flowing through the point to be measured, a changing magnetic field will be generated around the sensor. The sensor uses this magnetic field change to indirectly measure the magnitude and direction of the current. For Hall effect sensors, they use the deflection of Hall elements in the magnetic field to generate a voltage output proportional to the current.

[0080] Preferably, in an embodiment of the present application, the third control terminal of the controller is connected to the controlled terminal of the low-current relay, and the controller is configured to control the low-current relay to close the normally open node and disconnect the normally closed node when detecting that the voltage value of the supercapacitor exceeds the conduction threshold; when detecting that the voltage value of the supercapacitor is lower than the turn-off threshold, control the low-current relay to disconnect the normally open node and close the normally closed node.

[0081] Specifically, when the acquisition work starts, the relay closes. At this time, the normally open node closes, and the secondary side signal of the CT is connected to the acquisition conditioning circuit, starting the data acquisition and processing process. After completing the data acquisition, the control system releases the relay to restore it to the initial state. At this time, the normally closed node closes again, and the secondary side signal of the CT is connected to the charging circuit, and the 2-farad (F) supercapacitor is charged through the rectifier circuit. This design ensures that the CT can be flexibly switched under different working modes, supporting both data acquisition and ensuring continuous energy supply. When acquiring data, the CT provides the required electrical energy for the acquisition conditioning circuit; when not acquiring data, the CT charges the supercapacitor to prepare for the next data acquisition.

[0082] Compared with the prior art, the beneficial effects of the embodiments of the present application are at least one of the following:

[0083] 1) In the present application, the current signal in the main circuit is measured non-contactingly on the primary side of the current transformer, avoiding the errors caused by direct contact measurement.

[0084] 2) The present application converts the AC signal output by the current transformer into a DC signal, which facilitates subsequent digital signal processing because digital systems usually handle DC signals more easily.

[0085] 3) The present application uses the rectified DC signal to charge the energy storage element (such as a supercapacitor) to store electrical energy. This function can provide a stable power output when needed, providing reliable electrical energy support for subsequent circuits such as the sampling circuit.

[0086] 4) In the present application, by switching the connection state of the current transformer, the system can flexibly switch between the charging mode and the sampling mode. In the charging mode, the secondary side of the current transformer is connected to the rectifier circuit; in the sampling mode, it is connected to the signal sampling conditioning circuit.

[0087] The embodiments described above merely represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation to the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A DC support capacitor signal sampling system for a flexible DC converter valve, characterized in that It includes a non-contact current transformer, a rectification circuit, a charging circuit, a low-current relay, a signal sampling and conditioning circuit, and a sampling circuit. Among them, the primary side of the non-contact current transformer is connected to the point to be measured of the main circuit, and the secondary side of the non-contact current transformer is connected to the common node of the low-current relay; the normally closed node of the low-current relay is connected to the charging circuit through the rectification circuit; the normally open node of the low-current relay is connected to the sampling circuit through the signal sampling and conditioning circuit; the charging end of the charging circuit is connected to the sampling circuit; the charging circuit includes a super capacitor, a discharge switch, a boost chip, and a controller; the input end of the super capacitor is respectively connected to the output end of the rectification circuit and one end of the discharge switch, the other end of the discharge switch is connected to the input end of the boost chip, and the output end of the boost chip is connected to the charging end of the charging circuit; the first control end of the controller is connected to the controlled end of the discharge switch, and the controller is configured to control the discharge switch to close when detecting that the voltage value of the super capacitor exceeds the conduction threshold.

2. The DC support capacitor signal sampling system for a flexible DC converter valve according to claim 1, characterized in that, The rectification circuit includes a transient voltage suppression diode and a rectifier bridge. Among them, one end of the transient voltage suppression diode is connected to the secondary side of the non-contact current transformer through the low-current relay, and the other end of the transient voltage suppression diode is connected to the rectifier bridge.

3. The DC support capacitor signal sampling system for a flexible DC converter valve according to claim 1, wherein The boost chip includes a switching tube, a boost inductor, and a freewheeling diode. One end of the switching tube is connected to the other end of the discharge switch, the other end of the switching tube is respectively connected to the boost inductor and the freewheeling diode, and the boost inductor is connected in parallel with the freewheeling diode.

4. The DC support capacitor signal sampling system for a flexible DC converter valve according to claim 3, characterized in that, The second control end of the controller is connected to the controlled end of the boost chip, and the controller is configured to control the boost chip to boost the voltage value to the preset voltage threshold when detecting that the voltage value of the super capacitor is lower than the preset voltage threshold.

5. The DC support capacitor signal sampling system for a flexible DC converter valve according to claim 1, wherein The signal sampling and conditioning circuit includes a resistor circuit, an AD627 amplifier, and an RC filter circuit. Among them, the input end of the resistor circuit is connected to the normally open node of the low-current relay, the positive input end of the AD627 amplifier is connected to the output end of the resistor circuit, the negative input end of the AD627 amplifier is connected to the output end of the AD627 amplifier through a feedback resistor, and the output end of the AD627 amplifier is connected to the input end of the RC filter circuit.

6. The DC support capacitor signal sampling system for a flexible DC converter valve according to claim 5, characterized in that, The resistor circuit includes a first resistor and a second resistor. Among them, the first resistor and the second resistor are connected in parallel.

7. The DC support capacitor signal sampling system for a flexible DC converter valve according to claim 5, wherein The RC filter circuit includes a resistor and a capacitor. Among them, the input end of the RC filter circuit is connected to one end of the resistor, the other end of the resistor is connected in series with one end of the capacitor, and the other end of the capacitor is connected to the sampling circuit.

8. The DC support capacitor signal sampling system for a flexible DC converter valve according to claim 1, wherein The sampling circuit includes an analog-to-digital converter, a buffer, and a timer. Among them, the input end of the analog-to-digital converter is connected to the output end of the signal sampling and conditioning circuit, the output end of the analog-to-digital converter is connected to the input end of the buffer, the output end of the timer is connected to the controlled end of the analog-to-digital converter, and the timer is configured to generate a sampling trigger signal according to a preset time point, and control the analog-to-digital converter to perform sampling at the preset time point through the sampling trigger signal.

9. The DC support capacitor signal sampling system for a flexible DC converter valve according to claim 1, characterized in that, The non-contact current transformer includes a sensor and a signal processing circuit. Among them, the input end of the sensor is connected to the point to be measured, the output end of the sensor is connected to the input end of the signal processing circuit, and the output end of the signal processing circuit is connected to the common node of the low-current relay.

10. The DC support capacitor signal sampling system for a flexible DC converter valve according to claim 1, characterized in that, The third control end of the controller is connected to the controlled end of the low-current relay, and the controller is configured to control the low-current relay to close the normally open node and disconnect the normally closed node when detecting that the voltage value of the super capacitor exceeds the conduction threshold; and control the low-current relay to disconnect the normally open node and close the normally closed node when detecting that the voltage value of the super capacitor is lower than the turn-off threshold.

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