Method and device for monitoring state of high-voltage parallel capacitor under high-frequency harmonic working condition

Abstract

The invention discloses a state monitoring method and device for a high-voltage parallel capacitor under a high-frequency harmonic working condition, and the device comprises a high-frequency and power-frequency current sensor and a voltage sensor which have the characteristics of high sensitivity and broadband, and are used for measuring current and voltage signals under the high-frequency harmonic working condition. Electrical parameters of the high-voltage parallel capacitor are collected through the current sensor and the voltage sensor; transmitting the monitoring data of the electrical parameters to a data processing terminal in real time by adopting a wireless signal synchronization technology; and performing real-time analysis on the monitoring data, and establishing a simplified evaluation model of the running state of the high-voltage parallel capacitor in combination with electrical parameters so as to judge the health state of the capacitor and perform fault early warning. The electrical parameters are monitored in real time according to the set threshold value, potential faults are recognized in time, an alarm is given out, the equipment fault rate is effectively reduced, and the monitoring precision and reliability of the high-voltage parallel capacitor in the high-frequency harmonic and power frequency environment are improved.

Description

Technical Field

[0001] The present invention relates to power system monitoring technology, and in particular to a state monitoring method and device for high-voltage shunt capacitors under high-frequency harmonic conditions. Background Art

[0002] As an important reactive power compensation device in the power system, high-voltage shunt capacitors are widely used in power transmission and distribution networks to improve the power factor of the system, reduce line losses, and improve voltage quality. With the continuous growth of power demand and the increasing complexity of power equipment, the power system has put forward higher requirements for the operating performance and reliability of high-voltage shunt capacitors. However, during the long-term operation of capacitors, they are affected by various factors such as electrical, thermal, and mechanical factors, and may experience aging, failure, and other problems, which in turn affect the safety and stability of the entire power system.

[0003] At present, the research on high-voltage shunt capacitors at home and abroad mainly focuses on its design, manufacturing and operating characteristics. Traditional monitoring methods rely on regular manual inspections and simple electrical parameter measurements. This method is not only inefficient, but also difficult to reflect the operating status of the capacitor in real time and unable to detect potential fault hazards in time. With the development of smart grid and Internet of Things technologies, intelligent monitoring technology based on real-time monitoring and data analysis has gradually become a research hotspot.

[0004] In recent years, many researchers have begun to explore capacitor status monitoring methods based on sensor technology. These methods usually collect the electrical parameters of the capacitor in real time by installing current sensors and voltage sensors, and conduct comprehensive analysis based on environmental factors. However, existing monitoring systems often have problems such as unstable data transmission, insufficient anti-interference ability, and low monitoring accuracy, which makes it difficult to meet the application requirements of high-voltage shunt capacitors in complex power environments.

[0005] In addition, with the prevalence of high-frequency harmonics, the effectiveness of traditional monitoring methods in high-frequency environments is limited, resulting in inaccurate monitoring results. Therefore, it is particularly important to develop an efficient and stable high-voltage shunt capacitor condition monitoring system that can accurately measure electrical parameters in high-frequency harmonic and power frequency environments and combine non-electrical parameters for comprehensive evaluation.

[0006] In summary, the state monitoring technology for high-voltage shunt capacitors is in urgent need of innovation to improve the operational safety and reliability of the power system. This invention aims to build an efficient monitoring system by introducing advanced sensor technology, wireless communication technology and intelligent data analysis methods to achieve real-time monitoring, fault diagnosis and state evaluation of high-voltage shunt capacitors, thereby providing strong guarantee for the safe operation of the power system. Summary of the invention

[0007] In order to address the deficiencies in the prior art, the purpose of the present invention is to provide a state monitoring method for high-voltage shunt capacitors under high-frequency harmonic conditions. The method can effectively cope with the monitoring challenges in high-frequency harmonic environments, and improve the accuracy and reliability of capacitor monitoring by acquiring the electrical parameters of the capacitor in real time.

[0008] The technical solution adopted by the present invention to solve the problem is as follows:

[0009] The first aspect of the present invention relates to a method for monitoring the status of a high-voltage parallel capacitor under high-frequency harmonic conditions, comprising the following steps: Step 1: Using high-frequency and industrial frequency current sensors and voltage sensors, the current sensors and voltage sensors have high sensitivity and wide-band characteristics, and are used to measure current and voltage signals under high-frequency harmonic conditions; Step 2: Collecting electrical parameters of the high-voltage parallel capacitor through the current sensors and voltage sensors, including current amplitude, phase, frequency and voltage amplitude; Step 3: Using wireless signal synchronization technology, the monitoring data of the electrical parameters are transmitted to a data processing terminal in real time; Step 4: Analyzing the monitoring data in real time, and establishing a simplified evaluation model for the operating status of the high-voltage parallel capacitor in combination with the electrical parameters to determine the health status of the capacitor and fault warning.

[0010] Preferably, in step 4, the simplified evaluation model for the operating state of the high-voltage shunt capacitor includes an equivalent series resistor and an ideal capacitor.

[0011] Preferably, in step 4, the values ​​of the equivalent series resistance and the ideal capacitor are both functions of time, and the voltage across the capacitor is expressed as:

[0012]

[0013] Among them, u c (t) is the instantaneous value of the capacitor voltage, u c0 is the instantaneous value of the ideal capacitor voltage, u esr is the instantaneous value of the equivalent series resistance voltage, v c0 is the initial value of the ideal capacitor voltage, C is the ideal capacitor capacitance, i c (t) is the instantaneous value of current, R esr is the equivalent series resistance value;

[0014] According to the operating characteristics of the modular multilevel converter MMC, the voltage across the capacitor is rewritten as:

[0015]

[0016] Among them, u ci (t) is the capacitor voltage of the i-th submodule, S iis the access status of the submodule. The value of capacitor access is 1, and the value of capacitor exit is 0. ci0 is the initial capacitor voltage of the i-th submodule, i arm_u is the bridge arm current;

[0017] Where i arm_u It can be expressed as:

[0018]

[0019] Among them, I sm is the AC current amplitude, θ I is the initial phase of the AC current, I 2ω is the secondary cycle amplitude, θ I2ω is the initial phase of the secondary cycle.

[0020] Preferably, in step 4, the equivalent of the high-voltage parallel capacitor adopts the idea of ​​discretization, and the time interval from t1 to t2 is 0.01 seconds in step length, and the voltage difference between t1 and t2 is expressed as:

[0021]

[0022] Δu ci =u ci (t2)-u ci (t1)

[0023]

[0024] I ER =(i arm_u (t2)-i arm_u (t1))·S i

[0025] Among them, I EC and I ER is the equivalent current coefficient, u ci (t2) is the capacitor voltage of the ith submodule at time t2, u ci (t1) is the capacitor voltage of the i-th submodule at time t1, i arm_u (t2) is the bridge arm current at time t2, i arm_u (t1) is the bridge arm current at time t1;

[0026] Perform discretization calculations:

[0027]

[0028] in x K =t1+Kh(K=0,1,2,3,4).

[0029] Preferably, in step 4, the equivalent resistance and capacitance values ​​are only related to the capacitor voltage across the capacitor and the current flowing through the capacitor, wherein the capacitor voltage and the current flowing through the capacitor are respectively acquired by a current sensor and a voltage sensor, and a binary first-order equation is constructed to solve the equivalent resistance and capacitance values:

[0030]

[0031] Among them I EC1 ,I ER1 is the equivalent current coefficient of the first submodule, I EC2 ,I ER2 is the equivalent current coefficient of the second submodule, Δu c1 is the capacitor voltage difference of the first submodule, Δu c2 is the capacitor voltage difference of the second submodule.

[0032] Preferably, in step 4, the simplified evaluation model gives a capacitor failure warning according to the capacitance deviation:

[0033] For internal fuse capacitors, for capacitors with a capacity of 334kvar or above, when the capacitance decreases by more than 1%-3%, the system will alarm and exit operation; for capacitors with a capacity of 334kvar, when the capacitance decreases by more than 5%, the system will alarm and exit operation; for capacitors with a capacity of 200kvar and below, when the capacitance decreases by more than 10%, the system will alarm and exit operation.

[0034] Preferably, the wireless signal synchronization technology adopts wireless communication protocols such as Zigbee, Wi-Fi or Bluetooth.

[0035] A second aspect of the present invention relates to a high-voltage parallel capacitor device under high-frequency harmonic conditions, comprising a current sensor and a voltage sensor, a signal conditioning and data acquisition module, a wireless transmission module and a data processing terminal;

[0036] Current sensors and voltage sensors for measuring current and voltage in the high-frequency and power-frequency range;

[0037] A signal conditioning and data acquisition module, used for processing and converting the signals collected by the current sensor and the voltage sensor;

[0038] A wireless transmission module, used to transmit the processed data to a data processing terminal via a wireless network;

[0039] The data processing terminal includes data analysis software and a user interface for real-time display of the capacitor's operating status and generation of health status reports.

[0040] A third aspect of the present invention relates to a terminal, comprising a processor and a storage medium; the storage medium is used to store instructions; the processor is used to operate according to the instructions to execute the steps of the method in the first aspect of the present invention.

[0041] A fourth aspect of the present invention relates to a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method in the first aspect of the present invention.

[0042] Compared with the prior art, the present invention has the following beneficial effects: the present invention adopts high-frequency and industrial frequency current sensors and voltage sensors to collect the electrical parameters of the capacitor in real time, can effectively monitor the current and voltage changes in the 2-50th harmonic frequency range, monitors the electrical parameters in real time according to the set threshold, promptly identifies potential faults and issues alarms, adopts wireless communication modules to transmit data in real time, reduces the installation complexity and maintenance costs brought by traditional wired connections, and significantly improves the status monitoring capability and operation reliability of high-voltage parallel capacitors. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a flow chart of a method for monitoring the state of a high-voltage shunt capacitor under high-frequency harmonic conditions; DETAILED DESCRIPTION

[0044] The present invention adopts the following technical solution: a high-voltage parallel capacitor state monitoring system and a monitoring method thereof, which are intended to effectively improve the operation monitoring capability of high-voltage parallel capacitors in high-frequency harmonic and power frequency environments to ensure the stability and safety of the power system. Specifically, the technical solution of the present invention includes multiple key components and steps to form a complete monitoring system that can achieve comprehensive and real-time monitoring of high-voltage parallel capacitors. The monitoring system of the present invention is mainly composed of high-frequency and power frequency current sensors, voltage sensors, signal conditioning modules, data processing modules, wireless communication modules and fault warning modules.

[0045] Step 1: Use high-frequency and industrial frequency current sensors and voltage sensors, which have high sensitivity and wide-band characteristics, and are used to measure current and voltage signals under high-frequency harmonic conditions. Step 2: Collect the electrical parameters of the high-voltage parallel capacitor through the current sensor and voltage sensor, including current amplitude, phase, frequency and voltage amplitude; Step 3: Use wireless signal synchronization technology to transmit the monitoring data of the electrical parameters to the data processing terminal in real time; Step 4: Analyze the monitoring data in real time, and establish a simplified evaluation model for the operating status of the high-voltage parallel capacitor in combination with the electrical parameters to determine the health status of the capacitor and fault warning.

[0046] In step 1, the high-frequency and industrial frequency current sensors used in the present invention have high sensitivity and wide-band characteristics, and can perform accurate measurements within the 2-50th harmonic frequency range. The sensor adopts advanced electromagnetic induction principles, can capture current changes in real time, and convert them into electrical signal outputs. The design of the sensor takes into account the particularity of the high-voltage environment, and has good insulation performance and anti-interference ability, ensuring that it can still work stably under the operating conditions of the high-voltage parallel capacitor.

[0047] The current sensor mainly includes energy extraction coil, sampling coil, power module, sampling module, wireless communication module, etc. A current sensor is configured on each capacitor to monitor the current. After obtaining the operating current, the power frequency and high-frequency harmonic analysis calculation are performed, and the monitoring information is uploaded in response to the call from the monitoring system background.

[0048] The current sensor communicates with the upper data collection unit and transmits information via wireless communication at a frequency of 433MHz. The fundamental wave measurement accuracy is ±0.5% and the measurement range is 20A to 100A.

[0049] The power coil inputs the AC current into the power module through electromagnetic induction, and the stable DC output by the power module supplies power to the entire product; the signal source is the sampling coil through which the measured current passes through the inner hole, and after passing through the signal conditioning unit, it is converted into a signal that is suitable for the AD signal acquisition range, and then the data in the AD channel is processed by the processor. After the processing is completed, the data is stored in the internal storage space, waiting for the call command from the upper collection unit. When this product receives the call command, the amplitude and angle of the power frequency current collected by the AD and the amplitude and angle of the high-frequency current calculated by the FFT algorithm will be sorted out through the wireless transceiver system according to the communication protocol between the units. After the sorting is completed, the wireless transceiver system uploads the data to the collection unit through a specific frequency;

[0050] The specific module hardware design is as follows:

[0051] (1) Power module: A wire carrying alternating current passes through the inner hole of the power coil. The power coil generates electromotive force through electromagnetic induction and supplies it to the power module through the power input terminal. After sorting, the power module outputs direct current to power all modules of this product.

[0052] (2) Signal source: The wire carrying the measured current passes through the inner hole of the sampling coil. The sampling coil induces current through electromagnetic induction and inputs it into the sampling module through the signal input terminal on the board;

[0053] (3) Sampling module: The sampling module converts the signal input into a voltage signal within the AD range, and after signal conditioning through a high-precision signal amplifier, the conditioned signal is sent to the AD calculation channel of the processor;

[0054] (4) Main processor: When the signal enters the AD channel, the fundamental current value of the signal source output is first calculated based on the ratio of the reference voltage to the voltage signal and Ohm's law. Then, the fundamental angle and the amplitude and angle of the 2nd to 50th harmonics are calculated using the FFT algorithm based on the fundamental current value. The current amplitude and angle at the industrial frequency and the amplitude and angle of the high-frequency harmonics are calculated, and the call command from the upper-level convergence unit is waited for. When the call command from the upper-level convergence unit is received, the calculated data is sent through the wireless transceiver system.

[0055] (6) Wireless transceiver system: The communication module uses APC340, which is a highly integrated, low-power half-duplex wireless data transmission module. It embeds a high-speed, low-power single-chip microcomputer and a high-performance spread spectrum RF chip SX1276 / 8. It also uses efficient cyclic interleaving error correction and detection coding. Its anti-interference and sensitivity are at the top level in the industry. It can also provide multiple frequency channels and can modify various parameters such as serial port rate, transceiver frequency, transmission power, RF rate, etc. online.

[0056] In the software design, the main functions are to process and convert the collected data and communicate with the upper unit through the wireless transceiver system. The data collection and processing is to wait for the reception of the acquisition synchronization signal, and at the same time collect and calculate the precise frequency of the measured signal, so as to realize the synchronous acquisition of current and voltage and the subsequent FFT calculation and processing. Once the synchronization signal is received, the AD is immediately started to collect data, and 512 points are collected for each power frequency cycle. After the collection is completed, the FFT discrete Fourier transform is performed to calculate the positive and negative sequence components of the 1st to 50th harmonics, and save them, waiting for the data call command from the upper unit. The communication processing with the upper unit is that after the data collection is completed, the processor will perform the calculation processing. When the processor completes the data processing, it waits for the call command sent by the upper unit. When the call command sent by the upper unit is received, the information data is uploaded through the wireless transceiver system.

[0057] The voltage sensor suitable for high frequency and industrial frequency is used to realize the real-time voltage monitoring of the capacitor during steady-state operation, and the voltage data is uploaded and wirelessly synchronized with the current sensor through wireless communication technology. The voltage sensor is mainly responsible for the collection and transmission of voltage data in the monitoring system; the voltage sensor uses the secondary winding of the discharge coil for power supply, and continuously collects the capacitor voltage signal through the high-speed processor. After processing and analyzing the collected signal, the voltage data is sent to the upper unit through the 433M wireless frequency. At the same time, the FSK function of the 433M wireless is used to realize the synchronous collection of current and voltage with the capacitor current sensor, so as to provide the upper unit with the calculation of various parameters of the capacitor.

[0058] Hardware design:

[0059] (1) Power module design:

[0060] Module selection: Adopt LH05-23B05R2 from Goldensun, which has wide range input: AC85-305V, output: 5VDC / 1A, operating temperature range: -40℃ to +80℃, suitable for outdoor work most of the time.

[0061] Module design: After the AC220V power supply is taken out from the secondary winding, it is connected in parallel with X capacitors at both ends of the input line to eliminate differential mode interference, and Y capacitors are connected in parallel between the input line and the ground line to eliminate common mode interference. Then, it is input into the LH05-23B05R2 we use, which can output DC 5V to provide power for other modules of this product;

[0062] (2) Measurement module design:

[0063] Signal module design: When there is voltage input at the signal input end, the voltage signal is rectified by the TR31140C rectifier transformer, passes through two high-precision operational amplifiers, and then enters the AD channel of the processor;

[0064] (3) Main control module design:

[0065] Data calculation design: When the signal enters the AD channel, the fundamental voltage value output by the signal source is first calculated based on the ratio of the reference voltage to the voltage signal and the transformation ratio of the rectifier transformer. Then, the fundamental angle and the amplitude and angle of the 2nd to 50th harmonics are calculated using the FFT algorithm based on the fundamental voltage value.

[0066] Data upload design: After the data is calculated, the calculated data will be sorted according to the communication protocol between the upper and lower levels, and wait to be called after the sorting is completed;

[0067] (4) Communication module design:

[0068] Module selection and design: The communication module uses APC340, which is a highly integrated, low-power half-duplex wireless data transmission module. It is embedded with a high-speed, low-power microcontroller and a high-performance spread spectrum RF chip SX1276 / 8. It also uses efficient cyclic interleaving error correction coding. Its anti-interference and sensitivity are at the top level in the industry. It can also provide 71 / 120 channels with multiple frequencies and can modify various parameters such as serial port rate, transceiver frequency, transmission power, RF rate, etc. online. The communication frequency of this product uses 433MHz communication frequency, which is characterized by long transmission distance, strong penetration ability, outstanding diffraction ability, and no need to apply for frequency band.

[0069] The software design mainly completes the data collection and processing, communication with the upper unit and other functions. After the processor completes the initialization and sets the peripheral device functions, two threads are started: 1. Data collection and processing is to wait for the reception of the acquisition synchronization signal, and at the same time collect and calculate the precise frequency of the measured signal, so as to realize the synchronous acquisition of current and voltage and the subsequent FFT calculation and processing. Once the synchronization signal is received, AD is immediately started for data collection, and 512 points are collected for each power frequency cycle. After the collection is completed, FFT discrete Fourier transform is performed to calculate the positive and negative sequence components of the 1st to 50th harmonics, and save them, waiting for the data call command of the upper unit; 2. Wait for the wireless synchronization and data reporting commands sent by the upper unit, and respond to them in turn.

[0070] Step 2 includes a signal conditioning module and a data processing module, wherein the main function of the signal conditioning module is to process the signals from the current sensor and the voltage sensor. The signal conditioning module includes components such as filters, amplifiers, and analog-to-digital converters, which can effectively remove noise signals, enhance signal strength, and convert analog signals into digital signals for subsequent data processing. The design of the signal conditioning module ensures the high accuracy and stability of the data and avoids measurement errors caused by signal interference. The data processing module is the core of the entire monitoring system and is responsible for analyzing the collected electrical parameters. The module calculates the capacitance of the high-voltage parallel capacitor by collecting voltage and current electrical parameters in real time, and generates an evaluation report on the operating status of the capacitor. The data processing module also has data storage and historical data query functions, which facilitates subsequent analysis and decision-making.

[0071] In step 3, in the wireless communication module, in order to realize real-time data transmission, the wireless signal synchronization technology of the monitoring system of the present invention adopts wireless communication protocols such as Zigbee, Wi-Fi or Bluetooth. The wireless communication module supports multiple communication protocols and can stably transmit data under high voltage environment. The module adopts spread spectrum modulation and efficient error correction coding technology to ensure the reliability of data transmission in harsh environment. The wireless signal synchronization technology can send data to the monitoring center in real time, so that the operation and maintenance personnel can obtain the operating status information of the capacitor at any time.

[0072] In step 4, the fault warning module is responsible for monitoring the safety of the system and can identify potential faults in a timely manner according to the set threshold. When the electrical parameters exceed the preset range, the fault warning module will immediately sound an alarm and send the alarm information to the terminal device of the operation and maintenance personnel through the wireless communication module. The design of the fault warning module greatly improves the safety of the system, can effectively reduce the equipment failure rate, and extend the service life of the capacitor. The capacitance deviation warning determination of the high-voltage parallel capacitor is based on the existing high-voltage parallel capacitor related standards and specifications.

[0073] The simplified evaluation model for the operating status of high-voltage shunt capacitors includes an equivalent series resistor and an ideal capacitor. The values ​​of the equivalent series resistor and the ideal capacitor are functions of time, where the voltage across the capacitor is expressed as:

[0074]

[0075] Among them, u c (t) is the instantaneous value of the capacitor voltage, u c0 is the instantaneous value of the ideal capacitor voltage, u esr is the instantaneous value of the equivalent series resistance voltage, v c0 is the initial value of the ideal capacitor voltage, C is the ideal capacitor capacitance, i c (t) is the instantaneous value of current, R esr is the equivalent series resistance value;

[0076] According to the operating characteristics of the modular multilevel converter MMC, the voltage across the capacitor is rewritten as:

[0077]

[0078] Among them, u ci (t) is the capacitor voltage of the i-th submodule, S i is the access status of the submodule. The value of capacitor access is 1, and the value of capacitor exit is 0. ci0 is the initial capacitor voltage of the i-th submodule, i arm_u is the bridge arm current;

[0079] Where i arm_u It can be expressed as:

[0080]

[0081] Among them, I sm is the AC current amplitude, θ I is the initial phase of the AC current, I 2ω is the secondary cycle amplitude, θ I2ω is the initial phase of the secondary cycle.

[0082] The equivalent of high-voltage parallel capacitors adopts the idea of ​​discretization. The time interval from t1 to t2 is 0.01 seconds in step length. The voltage difference between time t1 and t2 is expressed as:

[0083]

[0084] Δu ci =u ci (t2)-u ci (t1)

[0085]

[0086] I ER =(i arm_u (t2)-i arm_u (t1))·S i

[0087] Among them, I EC and I ER is the equivalent current coefficient, u ci (t2) is the capacitor voltage of the ith submodule at time t2, u ci (t1) is the capacitor voltage of the i-th submodule at time t1, i arm_u (t2) is the bridge arm current at time t2, i arm_u (t1) is the bridge arm current at time t1;

[0088] Perform discretization calculations:

[0089]

[0090] in x K =t1+Kh(K=0,1,2,3,4).

[0091] Preferably, in step 4, the equivalent resistance and capacitance values ​​are only related to the capacitor voltage across the capacitor and the current flowing through the capacitor, wherein the capacitor voltage and the current flowing through the capacitor are respectively acquired by a current sensor and a voltage sensor, and a binary first-order equation is constructed to solve the equivalent resistance and capacitance values:

[0092]

[0093] Among them I EC1 ,I ER1 is the equivalent current coefficient of the first submodule, I EC2 ,I ER2 is the equivalent current coefficient of the second submodule, Δu c1 is the capacitor voltage difference of the first submodule, Δu c2 is the capacitor voltage difference of the second submodule.

[0094] The simplified evaluation model gives capacitor failure warning based on capacitance deviation:

[0095] For internal fuse capacitors, for capacitors with a capacity of 334kvar or above, when the capacitance decreases by more than 1%-3%, the system will alarm and exit operation; for capacitors with a capacity of 334kvar, when the capacitance decreases by more than 5%, the system will alarm and exit operation; for capacitors with a capacity of 200kvar and below, when the capacitance decreases by more than 10%, the system will alarm and exit operation.

[0096] Compared with the prior art, the present invention has the following beneficial effects: the present invention adopts high-frequency and industrial frequency current sensors and voltage sensors to collect the electrical parameters of high-voltage parallel capacitors in real time, can effectively monitor the current and voltage changes in the 2-50th harmonic frequency range, monitors the electrical parameters in real time according to the set threshold, promptly identifies potential faults and issues alarms, adopts wireless communication modules to transmit data in real time, reduces the installation complexity and maintenance costs brought by traditional wired connections, and significantly improves the status monitoring capability and operation reliability of high-voltage parallel capacitors.

Claims

1. A method for monitoring the state of a high-voltage shunt capacitor under high-frequency harmonic conditions, characterized in that: The following steps are involved: Step 1: Use a high-frequency and industrial frequency current sensor and voltage sensor, wherein the current sensor and voltage sensor have high sensitivity and wide-band characteristics and are used to measure current and voltage signals under high-frequency harmonic conditions; Step 2: Collecting electrical parameters of the high-voltage shunt capacitor through the current sensor and the voltage sensor, including current amplitude, phase, frequency and voltage amplitude; Step 3: Using wireless signal synchronization technology, the monitoring data of the electrical parameters are transmitted to the data processing terminal in real time; Step 4: Analyze the monitoring data in real time, and establish a simplified evaluation model for the operating status of the high-voltage shunt capacitor in combination with electrical parameters to determine the health status and fault warning of the capacitor.

2. The condition monitoring method according to claim 1, characterized in that: In step 4, the equivalent of the high-voltage parallel capacitor adopts the idea of ​​discretization, and the simplified evaluation model of the operating state includes an equivalent series resistor and an ideal capacitor.

3. The condition monitoring method according to claim 1 or 2, characterized in that: In step 4, the values ​​of the equivalent series resistance and the ideal capacitor are both functions of time, and the voltage across the capacitor is expressed as: Among them, u c (t) is the instantaneous value of the capacitor voltage, u c0 is the instantaneous value of the ideal capacitor voltage, u esr is the instantaneous value of the equivalent series resistance voltage, v c0 is the initial value of the ideal capacitor voltage, C is the ideal capacitor capacitance, i c (t) is the instantaneous value of current, R esr is the equivalent series resistance value; According to the operating characteristics of the modular multilevel converter MMC, the voltage across the capacitor is rewritten as: Among them, u ci (t) is the capacitor voltage of the i-th submodule, S i is the access status of the submodule. The value of capacitor access is 1, and the value of capacitor exit is 0. ci0 is the initial capacitor voltage of the i-th submodule, i arm_u is the bridge arm current; Where i arm_u It can be expressed as: Among them, I sm is the AC current amplitude, θ I is the initial phase of the AC current, I 2ω is the secondary cycle amplitude, θ I2ω is the initial phase of the secondary cycle.

4. The condition monitoring method according to claim 3, characterized in that: In step 4, the equivalent of the high-voltage parallel capacitor adopts the idea of ​​discretization, and the time interval from t1 to t2 is 0.01 seconds in step length. The voltage difference between time t1 and t2 is expressed as: Δu ci =u ci (t2)-u ci (t1) I ER =(i arm_u (t2)-i arm_u (t1))·S i Among them, I EC and I ER is the equivalent current coefficient, u ci (t2) is the capacitor voltage of the ith submodule at time t2, u ci (t1) is the capacitor voltage of the i-th submodule at time t1, i arm_u (t2) is the bridge arm current at time t2, i arm_u (t1) is the bridge arm current at time t1. Perform discretization calculations: in x K =t1+Kh(K=0,1,2,3,4).

5. The condition monitoring method according to claim 4, characterized in that: In step 4, the equivalent resistance and capacitance values ​​are only related to the capacitor voltage across the capacitor and the current flowing through the capacitor, wherein the capacitor voltage and the current flowing through the capacitor are respectively acquired by a current sensor and a voltage sensor, and a binary first-order equation is constructed to solve the equivalent resistance and capacitance values: Among them I EC1 ,I ER1 is the equivalent current coefficient of the first submodule, I EC2 ,I ER2 is the equivalent current coefficient of the second submodule, Δu c1 is the capacitor voltage difference of the first submodule, =u c2 is the capacitor voltage difference of the second submodule.

6. The condition monitoring method according to claim 5, characterized in that: In step 4, the simplified evaluation model gives a capacitor failure warning based on the capacitance deviation: For internal fuse capacitors, for capacitors with a capacity of 334kvar or above, when the capacitance decreases by more than 1%-3%, the system will alarm and exit operation; for capacitors with a capacity of 334kvar, when the capacitance decreases by more than 5%, the system will alarm and exit operation; for capacitors with a capacity of 200kvar and below, when the capacitance decreases by more than 10%, the system will alarm and exit operation.

7. The condition monitoring method according to claim 1, characterized in that: The wireless signal synchronization technology adopts wireless communication protocols such as Zigbee, Wi-Fi or Bluetooth.

8. A high-voltage parallel capacitor device under high-frequency harmonic conditions based on the condition monitoring method described in any one of claims 1 to 7, comprising a current sensor and a voltage sensor, a signal conditioning and data acquisition module, a wireless transmission module and a data processing terminal; characterized in that: Current sensors and voltage sensors for measuring current and voltage in the high-frequency and power-frequency range; A signal conditioning and data acquisition module, used for processing and converting the signals collected by the current sensor and the voltage sensor; A wireless transmission module, used to transmit the processed data to a data processing terminal via a wireless network; The data processing terminal includes data analysis software and a user interface for real-time display of the capacitor's operating status and generation of health status reports.

9. A terminal comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to execute the steps of the method according to any one of claims 1-7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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