966 results about "Capacitance voltage" patented technology

The invention relates to the technical field of unit power failure detection, in particular to an AC power supply input power failure detection method and system. The AC power supply input power failure detection method comprises the following steps: comparing a characteristic voltage value with a preset threshold value; triggering a sampling frequency adjustment mechanism according to the preliminary detection signal, increasing the sampling rate according to the voltage fluctuation frequency by adopting an adaptive algorithm, and obtaining high-precision sampling data through real-time calculation; for the optimized power consumption control scheme, acquiring current system state data, coordinating quick response capability and low power consumption optimization through a state machine algorithm, and outputting a multi-stage interaction strategy signal; adjusting a dynamic threshold value of capacitance voltage division design according to the multi-stage interaction strategy signal, and predicting voltage fluctuation by adopting a Kalman filtering algorithm to obtain smoothed detection sensitivity data; and analyzing the misjudgment rate reduction degree through a threshold fine tuning algorithm in combination with the abnormal fluctuation characteristics and the partial pressure state, and outputting a final power failure detection result.

The invention discloses an intelligent self-adaptive suppression method for oscillation of a data-driven SVG (static var generator) grid-connected system. Obtaining the capacitor voltage of the direct current side of the SVG and the actual voltage and the actual current of the grid connection point of the SVG, and respectively calculating the active power output by the SVG and the voltage amplitude output by the SVG according to the actual voltage and the actual current; a current reference value is generated through a voltage outer loop; the active power output by the SVG, the voltage amplitude output by the SVG and the voltage of the direct current side of the SVG are input into a DeePC controller to be processed, and an additional current reference value is obtained; and then the current error is obtained by adding the current reference value output by the voltage outer loop and subtracting the actual current, and then the current error is input to the voltage inner loop for processing to obtain a modulation wave voltage amplitude signal. According to the method, the oscillation of the converter grid-connected system can be suppressed under the condition that the dynamic characteristics of the converter and the conditions of the power grid are changed, and the problems of insufficient fixed structure and parameter sensitivity of the traditional SVG are solved.

The present invention provides a method for cooperatively suppressing a common-mode voltage and current harmonics of coupled three-level inverters, comprising: based on amplitude and phase angle of reference voltage vector, determining sector and region in which the reference voltage vector is located; selecting four basic voltage vectors with low common-mode voltage amplitudes to synthesize the reference voltage vector; writing volt-second balance equation based on selected basic voltage vectors, and calculating duty cycles thereof; and based on sector and region in which reference voltage vector is located, set value of voltage difference across capacitors on direct current side, and actual value of voltage difference across capacitors on direct current side, (1) updating duty cycles of basic voltage vectors, to realize separate control of capacitor voltage; and (2) designing and converting switching sequence into PWM drive signal of power switch, to control the coupled three-level inverter to operate.

The invention discloses a construction method and a modulation method of a three-port multi-frequency MMC topology based on bridge arm multiplexing, and relates to the technical field of power electronics. The construction method comprises the steps that sub-modules of a traditional double-bridge-arm MMC are integrated and optimized into a three-bridge-arm structure through a current conversion branch, independent energy interaction of three ports is achieved through an auxiliary bridge arm, multi-frequency operation modes of power frequency, frequency division, direct current and the like are supported at the same time, and therefore the utilization rate of the bridge arm sub-modules is increased, and the energy utilization rate of the MMC is increased. And the overall size and the manufacturing cost of the converter are reduced. Based on three-port multi-frequency coordination control and power balance requirements, a modulation method of the topological structure is provided, a multi-frequency coordination modulation strategy is adopted, frequency offset is performed through an auxiliary bridge arm to reduce cross interference of port frequency, and output waveform quality is improved through multi-objective optimized capacitor voltage balance control. And meanwhile, direct-current side faults are effectively eliminated by means of the auxiliary bridge arm.

The invention discloses a particle swarm and non-linear programming hybrid optimization VSG adaptive control method and system, and relates to the technical field of virtual synchronous generator control, and the method comprises the steps: collecting a filter inductor current and capacitor voltage signal, outputting an instantaneous active power and a reactive power, constructing a small signal dynamic model of a VSG, and building a parameter mapping relation; setting a constraint range based on the parameter mapping relation in combination with a second-order oscillation modal stability criterion of the power system; constructing a hybrid optimization algorithm according to the constraint range, and outputting steady-state data; constructing a two-dimensional threshold criterion system, and cooperatively generating a voltage reference value through a speed regulator and a controller; the voltage reference value is compared with the actual output voltage, and the inverter output is driven through PI control and PWM modulation. The method has the beneficial effects that the parameter optimization precision is improved, the stability of the system is guaranteed, and the calculation efficiency of the algorithm is improved.

The invention relates to the technical field of modular multilevel converters, and provides an MMC fault diagnosis method, system and device based on a sorting voltage-sharing algorithm. Comprising the steps that according to measurement data of the modular multilevel converter, a theoretical value and an actual value of bridge arm voltage of the modular multilevel converter are obtained through calculation, the theoretical value and the actual value are compared with a first alarm threshold value, and a corresponding bridge arm fault and a fault type are determined; calculating the number of fault sub-modules according to the bridge arm voltage actual value and the bridge arm voltage theoretical value; judging the switching number of the fault bridge arm sub-modules, and controlling and adjusting the bridge arm sub-modules to be switched on according to the fault type and the number of the fault sub-modules; and calculating a capacitor voltage minimum difference value, comparing the capacitor voltage minimum difference value with a second alarm threshold value, and determining a fault sub-module. According to the multi-tube fault diagnosis method, the problem that the fault positioning performance is poor under the light load working condition is solved, and the sub-module positioning performance in the full power range is improved.

The invention relates to the technical field of energy storage system grid-connected control, and particularly discloses a two-stage coupling type battery energy storage grid-connected converter model prediction control method and device, and the method comprises the following steps: S1, constructing a two-stage coupling type battery energy storage grid-connected converter single-machine two-order composite model; s2, according to the single-machine dual-order composite model, constructing a prediction equation of the output current and the capacitor voltage of the inverter; s3, constructing a unified cost function of the output current and the capacitor voltage of the inverter; s4, predicting the switch state combination of all the switch tubes, and calculating the value of a corresponding unified cost function; and S5, selecting the switch state combination with the minimum uniform cost function value as the optimal switch state of all the switch tubes, and carrying out on-off control on the switch tubes. According to the invention, through unified modeling and control optimization, the dynamic response capability and the voltage stabilization performance of the energy storage grid-connected converter are improved.

This invention discloses a method and system for suppressing capacitor voltage fluctuations in SiC MMC submodules, belonging to the field of electronic power technology. Based on the analysis results of the optimal broadband harmonic circulating current injection boundary and order for SiC MMC submodules, an optimized model for submodule capacitor voltage fluctuations is determined that simultaneously injects 2nd, 4th, and 8th harmonic circulating currents and 3rd harmonic voltages, which can fully utilize the higher control bandwidth characteristic of SiC MMC. By solving the optimized model for submodule capacitor voltage fluctuations, the amplitude and phase of the reference values ​​of the 2nd, 4th, and 8th harmonic circulating currents to be injected, as well as the amplitude and phase of the corresponding 3rd harmonic voltage, are determined. Then, by injecting 2nd, 4th, and 8th harmonic circulating currents and jointly injecting the 3rd harmonic voltage, broadband harmonic joint injection is achieved, reducing the capacitor voltage fluctuations of the submodule and realizing a method for suppressing capacitor voltage fluctuations in SiC MMC submodules with high suppression effect.

The invention is suitable for the technical field of resonant converters, and provides a starting control circuit and a resonant converter. The starting control circuit comprises a feedback module, a comparison selection module and a logical operation module, the comparison selection module is electrically connected with the feedback module and the logical operation module, the feedback module is used for being electrically connected with the output end of a resonant conversion circuit in the resonant converter, and the logical operation module is used for being electrically connected with a driving circuit in the resonant converter. According to the starting control circuit provided by the embodiment of the invention, the resonant capacitor voltage constraint threshold value which is gradually enlarged along with the starting process can be constructed, smooth establishment of resonant capacitor direct current bias is realized, the fluctuation amplitude of the resonant capacitor voltage is limited, the problem that the total bus voltage is applied to the resonant inductor in a traditional scheme is avoided, and the starting control circuit is suitable for a high-voltage power supply. Finally, the resonance current peak value in the starting stage is effectively suppressed, and the impact of current stress on core devices such as a switching tube and a resonance inductor is reduced.

The invention provides an input voltage anomaly detection method, a protection method and a control circuit. The control circuit comprises a voltage-current conversion circuit, the input end of which is coupled with the power switch for obtaining the terminal voltage of the power switch; the first capacitor is coupled to the output end of the voltage-current conversion circuit; the comparison circuit is used for comparing the first capacitor voltage with a reference signal and providing an input voltage anomaly detection signal; and a switch control circuit which controls the power switch based on the output of the comparison circuit and starts input voltage abnormality protection when the input voltage abnormality detection signal is valid. The control circuit provided by the invention can realize the anomaly detection of the input voltage based on the terminal voltage of the power switch, can reduce the use of pins, simplifies a peripheral circuit, reduces the system cost, and accelerates the protection response speed.

The invention discloses a three-level flexible excitation dynamic regulation and control method and system for a large-scale hydroelectric generating set, and relates to the technical field of flexible excitation control of the large-scale hydroelectric generating set, and the method comprises the steps: setting a DC bus voltage, and initializing a mapping relation between a capacitor voltage and an excitation output level; collecting operation parameters of a machine end, constructing a disturbance identification model and outputting a disturbance level; the excitation voltage output gear is set according to the disturbance level, the capacitor voltage difference is controlled, and dynamic voltage sharing is achieved by modulating the midpoint duty ratio. According to the method, through setting a bus target voltage and constructing excitation voltage output mapping, in combination with a disturbance level identification mechanism and a dynamic voltage-sharing strategy, closed-loop linkage of disturbance perception-voltage regulation-voltage difference control is realized. According to the method, the identification precision of the system on light disturbance and strong disturbance is effectively improved, the voltage stability and capacitance symmetry of the excitation system are enhanced, the overshoot risk is reduced, and the control robustness and safety of the system under extreme working conditions are improved.

The invention relates to an external phase shift angle determination method and system, a frequency conversion phase shift control method and a chip, and the method comprises the steps: obtaining an external phase shift angle based on a general solution of a time domain differential equation of a resonant inductor current and a resonant capacitor voltage of a DBSRC equivalent circuit and the symmetry of the DBSRC equivalent circuit; determining a first current value of the resonant inductor at the first moment and a second current value of the resonant inductor at the second moment; based on the first current value when the primary bridge circuit meets the ZVS soft switching requirement, obtaining a first relational expression of the external phase shift angle about the input voltage and the output voltage of the DBSRC and the switching frequency of the switching tube; based on a second current value when the secondary-side bridge circuit meets the ZVS soft switching requirement, obtaining a second relational expression of the external phase shift angle with respect to the input voltage, the output voltage and the switching frequency; according to the first relational expression, the second relational expression and the steady-state voltage value of the output end of the DBSRC, the expression of the external phase shift angle about the switching frequency, the steady-state voltage value and the input voltage is determined; the scheme is simple, the accuracy is high, and the portability is high.

The invention discloses an AI feedback system for monitoring opening and closing time of a switch in real time, which relates to the technical field of electrical variable measurement, and comprises a data acquisition module for acquiring three types of data in real time, pre-processing the data, marking the closing time by a central calculation processing module, comprehensively processing the data to obtain a copper scale interference model, and judging whether the copper scale interference model is interfered or not according to the copper scale interference model; the opening speed is adjusted, the opening moment is marked, the opening and closing time is calculated, and the early warning feedback module is called for early warning and AI feedback in case of abnormality. According to the method, multi-dimensional data are collected in real time to construct a copper scale interference model, when interference is detected, capacitor voltage is automatically increased to accelerate opening, compensation opening time is prolonged, equipment short circuit is avoided, the method is more real-time and self-adaptive compared with a traditional scheme, arc light and frequency parameters are comprehensively calculated, historical and real-time data are analyzed in combination with AI, early warning is carried out in the case of abnormity, and an adjustment strategy is optimized. Decision support is provided through a visual chart, whole-process intelligent management is achieved, and the safety and reliability of equipment are improved.

A multilevel power converter includes a plurality of switches, a first DC link capacitor, a second DC link capacitor, and one or more processors configured to: generate, for a duty cycle of the multilevel power converter, a pulse width modulated pulse pattern in accordance with a reduced common mode voltage scheme; modify the pulse width modulated pulse pattern to render a modified pulse pattern; and cause the plurality of switches to implement the duty cycle based at least in part on the modified pulse pattern to render a common mode voltage pulse to balance voltages at the first DC link capacitor and the second DC link capacitor.

The invention relates to a non-current sensor model prediction control method and system based on an LC filtering type voltage source inverter, and belongs to the field of inverter control. The designed sliding mode observer only needs capacitance parameters, and inductance and voltage observation errors have no influence on current observation errors. A capacitor current predicted value and a capacitor voltage predicted value are predicted by using the sliding mode observer, and the three-phase switching state of the inverter is regulated and controlled according to the predicted values. Therefore, the parameter robustness of the sliding-mode observer is high, and when the sliding-mode observer is used for controlling the inverter, the control precision is high.

The invention relates to the technical field of converter control, in particular to a novel four-level efficient grid-connected system and a control method, and the method comprises the steps: determining the target output power, the target input power, the actual output power and the actual input power of a converter based on a 4L-HCC converter; determining a phase angle and an output voltage amplitude based on a preset virtual synchronous machine control strategy, and converting to obtain a corresponding three-phase reference voltage; performing HCC internal capacitor voltage control on the converter, establishing a corresponding loss function, and determining a reference wave change range corresponding to each switching device on the converter based on actual setting; the corresponding reference wave signal with the minimum loss function derivative is calculated; and carrying out phase shift pulse width modulation on the converter, taking high-frequency triangular waves with different phases as carriers, comparing the calculated reference wave signals with the carriers, calculating the duty ratio of each switching device of the converter and a switch driving signal, and driving each switching device of the converter.

The application provides a transient frequency conversion control method of a converter and an electronic device. The method comprises the following steps: determining the working state of the converter, wherein the working state comprises a light load working state and a heavy load working state; if it is determined that the working state switches between the light load working state and the heavy load working state, starting a transient frequency conversion control strategy to adjust the switching frequency of the converter, wherein the transient frequency conversion control strategy is used to adjust the duration of the freewheeling stage in the switching cycle of the converter; after the working state of the converter switches, and the clamping capacitor voltage sampling value of the converter v c satisfies a preset condition, exiting the transient frequency conversion control strategy to restore the switching frequency of the converter to normal. The dynamic response speed of the converter is effectively improved, and the overshoot and drop of the output voltage when the converter is subjected to a step load are reduced.

The invention provides a direct-current capacitance determination method for a flexible interconnection device of a three-port intensive low-voltage power distribution network, the flexible interconnection device comprises three alternating-current ports and a direct-current port, each alternating-current port is connected with a power grid through an alternating-current feeder line, and the direct-current port comprises a plurality of direct-current capacitors; the method comprises the following steps: respectively determining active power and reactive power of three alternating-current feeder lines, and respectively determining current and modulation voltage of three alternating-current ports according to the active power and the reactive power of the three alternating-current feeder lines; according to the current and the modulation voltage of the three alternating current ports, determining a current instantaneous value of a direct current capacitor without a current direct current component in a fundamental wave period; determining the capacitance value of the direct current capacitor according to the capacitor voltage ripple limit value and the current instantaneous value of the direct current capacitor; the scene of multiple alternating current ports is considered, and the adjusting effect of the power flow is improved.

The invention discloses a flexible direct current power transmission system receiving end alternating current fault ride-through control method and system, and relates to the technical field of power transmission and distribution grids, the capacitor voltage value of each energy self-balancing sub-module is obtained in real time, the capacitor voltage value associated with each bridge arm is averaged, the average module voltage of each bridge arm is obtained, and the average module voltage of each bridge arm is calculated; adjusting each energy self-balancing sub-module according to the capacitor voltage value and each average module voltage, and when an AC fault signal is received, determining a trigger instruction corresponding to each bridge arm according to each average module voltage and a preset converter valve control model, and the associated energy self-balancing sub-modules are regulated and controlled by adopting the trigger instructions. The technical problem that when a large amount of surplus power occurs in an existing system, a large-size energy release device needs to be configured for energy release, and the manufacturing cost of the system is increased is solved.

In an MMC-type power conversion device, a control device calculates an evaluation value representing the degree of variations in voltage of capacitors of individual converter cells. When this evaluation value exceeds a threshold value, the control device controls the converter cells as follows: (i) when current in a positive direction flows through a first converter cell with a voltage of the capacitor greater than a mean value, reducing an output time of positive voltage, (ii) when current in a negative direction flows through the first converter cell, increasing an output time of positive voltage, (iii) when current in the positive direction flows through a second converter cell with a voltage of the capacitor smaller than a mean value, increasing an output time of positive voltage, or (iv) when current in the negative direction flows through the second converter cell, reducing an output time of positive voltage.

The invention belongs to the field of storage, and discloses a high-energy-efficiency mixed-precision charge domain in-storage computing architecture and a working method thereof. Comprising a single-slope analog-to-digital converter, a sparsity perception input alignment module, a multi-bit input accumulation module, a controller and an accumulation module, wherein the single-slope analog-to-digital converter consists of an index calculation array, a mantissa calculation array, a shared ramp voltage generator and a bidirectional counter. According to the invention, serial input binary coding based on capacitor voltage is suitable for floating point and integer multiply-accumulate operation with flexible bit width; according to the invention, a shared single-slope analog-to-digital converter (SS-ADC) is introduced to realize maximum index search and index difference calculation; according to the method, a sparsity perception calculation scheme is provided, low-importance input-weight pairs are filtered out through an adjustable threshold value, and invalid power consumption is reduced; according to the method, a multi-bit input accumulation method is further combined, and an ADC redundancy optimization quantization and normalization process is utilized, so that the overall energy efficiency is improved.

The present disclosure provides a switched-capacitor voltage converter, a chip, and an electronic device. In the switched-capacitor voltage converter, a first branch, a second branch, a third branch, and a fourth branch are electrically connected between an input terminal and a ground terminal of the switched-capacitor voltage converter, and are further electrically connected to an output terminal of the switched-capacitor voltage converter. Transistors in the first branch and the second branch are configured to be simultaneously turned on or turned off and of different sizes, and transistors in the third branch and the fourth branch are configured to be simultaneously turned on or turned off and of different sizes. When the output terminal of the switched-capacitor voltage converter is electrically connected to a small load, the transistors in the branches may be controlled to be turned off, such that loss of the switched-capacitor voltage converter is effectively reduced.

The invention discloses a power control method, system, equipment and medium for a modular multilevel converter, and belongs to the technical field of power electronics and power system application, and the method comprises the steps: collecting the bridge arm current, the sub-module capacitor voltage, the DC bus voltage and the AC side power of the modular multilevel converter; calculating a power error according to the AC side power and a power reference value, and calculating a sub-module capacitor voltage error according to the sub-module capacitor voltage and a voltage reference value; constructing a Lyapunov function comprising a plurality of control targets, wherein the Lyapunov function comprises a power error term, a sub-module capacitor voltage error term, a circulating current suppression term and a total energy balance term; and determining a control law on the basis that the Lyapunov function meets a stability condition, and controlling the modular multilevel converter according to the control law. According to the method, the coupling control problem of multi-terminal direct current system power distribution and sub-module energy balance is considered and improved.

The invention belongs to the technical field of power electronic conversion, and particularly discloses an MMC-STATCOM system direct optimization model prediction control method and system, and the method comprises the steps: respectively calculating a differential mode voltage and a common mode voltage between an upper bridge arm and a lower bridge arm of each phase; third harmonic voltage is injected into the upper bridge arm and the lower bridge arm of each phase to obtain upper bridge arm voltage and lower bridge arm voltage of a newly-added third voltage component of each phase; and based on the obtained voltage of the upper and lower bridge arms of the newly added three-time voltage component, determining the input number of the sub-modules of the upper and lower bridge arms of each phase by adopting a nearest level approximation modulation strategy, and determining the input sub-module of each bridge arm according to the capacitor voltage sequence of each sub-module of the bridge arms and the current direction. According to the method, on the basis of keeping a discrete control structure, direct injection of third harmonic voltage under an MPC framework is achieved, and higher real-time performance and expandability are achieved.

The invention discloses a voltage and current synchronous measurement method for a high-voltage power supply of a fusion device, which is suitable for accurately sampling and monitoring voltage and current signals of each key node of the high-voltage power supply of the fusion device. According to the method, firstly, a resistance-capacitance voltage division technology is adopted, a front-end high-voltage attenuation network is constructed by utilizing high-precision resistors and capacitors, and stable voltage division and linear attenuation of high-voltage signals are achieved; then, electrical isolation is realized through a small-signal voltage and current transformer, and multi-channel synchronous acquisition of voltage and current signals is completed respectively. Then, the ADC module adopts two multi-channel AC sampling special electric energy metering chips to realize ten-channel synchronous acquisition of high voltage and current signals. And finally, the FPGA receives, processes and analyzes the acquired data in real time, and transmits a result to an upper computer monitoring platform. According to the method, the synchronism, the precision and the anti-interference performance of a fusion power supply high-voltage measurement system are remarkably improved, and reliable data support is provided for safe and stable operation of a fusion device.

The invention discloses a flexible interconnection and mode smooth switching method for a distributed power generation system, and relates to the technical field of distributed power generation, and the method comprises the steps: building a droop control relation through continuously collecting DC voltage and current for a source side rectifier of each power generation unit; in a normal mode, the output current of the back-to-back rectifier and the voltage of an intermediate capacitor are collected, the same phase of the current and the load current is kept by using phase locking control, and voltage regulation is realized by combining a dq coordinate model; when a fault of a source side rectifier is detected, an alternating current reference value is generated based on intermediate capacitor voltage deviation and is input into a single current loop controller for voltage stabilization, and meanwhile, a phase advance, adaptive gain and integral saturation resistance mechanism is introduced, so that quick response and stable operation are ensured; in the mode switching process, normal control quantity and fault control quantity are subjected to weighted fusion, and dynamic consistency is achieved through pole matching and reference pre-alignment; the intermediate capacitor voltage fluctuation is significantly reduced, the recovery time is shortened, and the system stability and reliability are improved.

The invention provides a touch key test method and device, equipment and a storage medium. The method comprises the following steps: constructing a test environment according to a preset test condition; in the test environment, performing a touch test on the touch key to obtain a response current, a response voltage, a touch full scale value and charging and discharging time of the touch key; determining a capacitance test value of the touch key according to the capacitance current, the capacitance voltage, the touch full scale value, the capacitance charging and discharging time and a preset touch threshold value; determining a baseline threshold according to the capacitance test value; subtracting the baseline threshold from the capacitance test value to obtain a test response value; determining a first test grade of the touch key according to the capacitance test value, and determining a second test grade of the touch key according to the test response value and a preset noise range; and generating test response data according to the capacitance test value, the test response value, the first test grade and the second test grade.

The invention provides a network construction type converter control method suitable for multiple power grid intensities, and belongs to the field of new energy grid-connected stability. The method comprises the steps that the actual output power of an inverter is calculated according to inverter side capacitor voltage and grid-connected current; the actual output power of the inverter and the power reference value control an output internal potential amplitude reference value and an internal potential phase angle through the virtual synchronous generator; subtracting the voltage drop of the grid-connected current on the virtual impedance from the internal potential amplitude reference value to obtain a virtual internal potential; inputting the virtual internal potential as a reference voltage into a voltage and current double-loop controller, inputting a grid-connected current into a proportional differential controller, subtracting the output of the proportional differential controller from the output of the voltage and current double-loop controller, inputting an obtained result into an inverter through an SPWM modulator, and controlling the inverter; the invention also provides a control system of the network-forming converter. Grid-connected current proportional differential feedback is introduced, the inner loop control bandwidth is kept constant in the dynamic change process of the power grid strength, and power-voltage loop harmful coupling is eliminated.

The invention provides a multifunctional low-power-consumption power distribution terminal power supply system which comprises a filtering and rectifying unit. The charging and discharging management unit is integrated with an intelligent charging and discharging control algorithm, performs charging and discharging management on the charging process of the capacitor and the battery, and switches to a battery discharging mode to provide a starting power supply when the voltage of the capacitor is insufficient; wherein the intelligent charging and discharging control algorithm is an algorithm based on the combination of a fuzzy logic control algorithm and a dynamic threshold adjustment strategy; the PWM control unit is used for outputting voltage by adopting a pulse width modulation technology and automatically reducing the power to the lowest level in a non-working state; and the CPU control unit is used for controlling the normal operation of the charging and discharging management unit and the PWM control unit, and monitoring the working states of the three-stage rectification topological structure, the grading protection circuit and the high-precision acquisition circuit in real time through a built-in intelligent monitoring algorithm. Stable, reliable, efficient and low-power-consumption power supply support can be provided for the power distribution terminal, and further development of an intelligent power grid is promoted.

The invention relates to the technical field of modular multi-level converter health management, and discloses a modular multi-level converter sub-module capacitance value online monitoring method and system, which are used for improving the accuracy of capacitance value monitoring. The capacitance value on-line monitoring method for the sub-module of the modular multilevel converter comprises the following steps: monitoring capacitance voltage information and bridge arm current signals of the sub-module; determining an initial input window of the sub-module based on the capacitor voltage information; determining an optimal input duration interval of the initial input window based on an error relationship between the duration of the preset input window and the capacitance value of the corresponding capacitor; eliminating abnormal durations which are lower than the lower limit of the optimal duration interval or higher than the upper limit of the optimal duration interval in the initial input window to obtain a target input window; and extracting the capacitor voltage at the target starting moment and the target cut-off moment of the target input window and the corresponding target bridge arm current, and calculating the capacitance value of the target capacitor.